Sean Carroll
Appearances
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
In his own telling of the story, his greatest moment, his happiest moment was when he realized that if the way that we would say it in modern terms, if you were in a rocket ship, accelerating at 1G, at one acceleration due to gravity, if the rocket ship were very quiet, you wouldn't be able to know the difference between being in a rocket ship and being on the surface of the Earth.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Gravity is sort of not detectable or at least not distinguishable from acceleration. So number one, that's a pretty clever thing to think. But number two, if you or I had that thought, we would have gone, huh, we're pretty clever. He reasons from there to say, okay, if gravity is not detectable, then it can't be like an ordinary force, right? The electromagnetic force is detectable.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
We can put charged particles around, positively charged particles and negatively charged particles respond differently to an electric field or to a magnetic field. He realizes that what his thought experiment showed, or at least suggested, is that gravity isn't like that. Everything responds in the same way to gravity. How could that be the case?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And then this other leap he makes is, oh, it's because it's the curvature of space-time, right? It's a feature of space-time. It's not a force on top of it. And the feature that it is is curvature. And then finally, he says, okay, Clearly, I'm going to need the mathematical tools necessary to describe curvature. I don't know them, so I will learn them.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And they didn't have MOOCs or AI helpers back in those days. He had to sit down and read the math papers, and he taught himself differential geometry and invented general relativity.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
It's certainly not simple, actually. It's a profound insight. That's why I said I think we should give... Minkowski more credit than we do. He's the one who really put the finishing touches on special relativity.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Again, many people had talked about how things change when you move close to the speed of light, what Maxwell's equations of electromagnetism predict and so forth, what their symmetries are. So people like Lorentz and Fitzgerald and Poincaré, there's a story that goes there. And in the usual telling, Einstein sort of puts the capstone
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
He's the one who says, all of this makes much more sense if there just is no ether. It is undetectable. We don't know how fast. Everything is relative, thus the name relativity. But he didn't take the actual final step, which was to realize that the underlying structure that he had invented is best thought of as unifying space and time together.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I honestly don't know what was going through Minkowski's mind when he thought that. I'm not sure if he was so mathematically adept that it was just clear to him, or he was really struggling it and he did trial and error for a while. I'm not sure.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Oh, yeah, all the time. I mean, we, of course, make our lives easy by ignoring two of the dimensions of space. So instead of four-dimensional space-time, we just draw pictures of one dimension of space, one dimension of time, the so-called space-time diagram.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But, you know, I mean, maybe this is lurking underneath your question, but even the best physicists will draw, you know, a vertical axis and a horizontal axis, and they'll go space-time. But deep down, that's wrong because you're sort of preferring one direction of space and one direction of time. And it's really the whole two-dimensional thing that is space-time.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
The more legitimate thing to draw on that picture are rays of light, are light cones. From every point, there is a fixed direction at which the speed of light would represent. And that is actually inherent in the structure. The division into space and time is something that's easy for us human beings.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
It's the difference between X and Y when you draw axes on a piece of paper. So there's really no difference? There's almost no difference. There's one difference that is kind of important, which is the following. If you have a curve in space, I'm going to draw it horizontally because that's usually what we do in space-time diagrams.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
If you have a curve in space, you've heard the motto before that the shortest distance between two points is a straight line. If you have a curve in time, which is, by the way, literally all of our lives, right? We all evolve in time. So you can start with one event in space-time and another event in space-time.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
What Minkowski points out is that the time you measure along your trajectory in the universe is precisely analogous to the distance you travel on a curve through space. And by precisely, I mean it is also true that the actual distance you travel through depends on your path, right? You can go a straight line, shortest distance, and curvy line would be longer.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
The time you measure in space-time, the literal time that takes off on your clock, also depends on your path. It depends on it the other way. So that the longest time between two points is a straight line. And if you zig back and forth in space-time, you take less and less time to go from point A to point B. How do we make sense of that, the difference between the observed reality and the
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I'm a huge believer in objective reality. I think that objective reality is real. But I do think that people are a little overly casual about the relationship between what we observe and objective reality in the following sense.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Of course, in order to explain the world, our starting point and our ending point is our observations, our experimental input, the phenomena we experience and see around us in the world. But in between... There's a theory. There's a mathematical formalization of our ideas about what is going on.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And if a theory fits the data and is very simple and makes sense in its own terms, then we say that the theory is right. And that means that we should attribute some reality to the entities that play an important role in that theory, at least provisionally until we come up with a better theory down the road.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yes and no. It depends on exactly how careful we're being. So here is a bunch of things I think are correct here. If you imagine there is a black hole spacetime, so like the whole solution Einstein's equation, and you treat you and me as what we call test particles. So we don't have any gravitational fields ourselves. We just move around in the gravitational field.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And that's obviously an approximation, okay? But let's imagine that. And you stand outside the black hole and I fall in. And as I'm falling in, I'm waving to you, you know, because I'm going into the black hole, you will see me. move more and more slowly. And also the light from me is redshifted. So I kind of look embarrassed because I'm falling into a black hole. And there is a limit.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
There's a last moment that light will be emitted from me, from your perspective, forever, okay? Now you don't literally see it because I'm emitting photons more and more slowly, right? Because from your point of view, right? So it's not like I'm equally bright. I basically fade from view in that picture. Okay. So that's one approximation.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
The other approximation is I do have a gravitational field of my own. And therefore, as I approach the black hole, the black hole doesn't just sit there and let me pass through. It kind of moves out to eat me up because its net energy mass is going to be mine plus its. Okay. But roughly speaking, yes. I don't like to go to the dramatic extremes because that's where the approximations break down.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But if you see something falling into a black hole, you see its clock ticking more and more slowly.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
We don't. I mean, how would we? Because it's always possible that right at the last minute it had a change of heart and starts accelerating away, right? If you don't see it pass in, you don't know. And let's point out that as smart as Einstein was, he never figured out black holes, and he could have. It's kind of embarrassing.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
It took decades for people thinking about general relativity to understand that there are such things as black holes, because basically Einstein comes up with general relativity in 1915. Two years later, Carl Schwarzschild derives the solution to Einstein's equation that represents a black hole, the Schwarzschild solution.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
No one recognized it for what it was until the 50s, David Finkelstein and other people. And that's just one of these examples of physicists not being as clever as they should have been.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
It is absolutely hard to imagine, and the black hole is very different in many ways from what we're used to. On the other hand, I mean, the real reason, of course, is that between 1915 and 1955, there's a bunch of other things that are really interesting going on in physics, all of particle physics and quantum field theory. So many of the greatest minds were focused on that.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But still, if the universe hands you a solution to general relativity in terms of curved spacetime, and it's kind of mysterious, certain features of it, I would put some effort into trying to figure it out.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
It's best to think of a black hole as not an object so much as a region of spacetime, okay? It's a region with the property, at least in classical general relativity. Quantum mechanics makes everything harder, but let's imagine we're being classical for the moment. It's a region of spacetime with the property that if you enter, you can't leave.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Literally, the equivalent of escaping a black hole would be moving faster than the speed of light. They're both precisely equally difficult. You would have to move faster than the speed of light to escape from the black hole. So once you're in, that's fine. In principle, you don't even notice when you cross the event horizon, as we call it. The event horizon is that point of no return.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
where once you're inside, you can't leave. But meanwhile, the space-time is sort of collapsing around you to ultimately a singularity in your future, which means that the gravitational forces are so strong, they tear your body apart and you will die in a finite amount of time.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
The time it takes, if the black hole is about the mass of the sun, to go from the event horizon to the singularity takes about one millionth of a second.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Well, you've raised a crucially difficult point. So that's why I keep needing to distinguish between black holes according to Einstein's theory of general relativity, which is book one of space, time, and geometry, which is perfectly classical, and And then come the 1970s, we start asking about quantum mechanics and what happens in quantum mechanics.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
According to classical general relativity, the information that makes up you when you fall into the black hole is lost to the outside world. It's there. It's inside the black hole, but we can't get it anymore. In the 1970s, Stephen Hawking comes along and points out that black holes radiate. They give off photons and other particles to the universe around them.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And as they radiate, they lose mass and eventually they evaporate. They disappear. So once that happens, I can no longer say the information about you or a book that I threw in a black hole or whatever is still there. It's hidden behind the black hole because the black hole has gone away.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So either that information is destroyed, like you said, or it is somehow transferred to the radiation that is coming out, to the Hawking radiation. The large majority of people who think about this believe that the information is somehow transferred to the radiation and information is conserved. That is a feature both of general relativity by itself and of quantum mechanics by itself.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So when you put them together, that should still be a feature. We don't know that for sure. There are people who have doubted it, including Stephen Hawking for a long time. But that's what most people think.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And so what we're trying to do now in a topic which has generated many, many hundreds of papers called the black hole information loss puzzle is figure out how to get the information from you or the book into the radiation that is escaping the black hole.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Right now, we are nowhere close to observing Hawking radiation. Here's the sad fact. The larger the black hole is, the lower its temperature is. So a small black hole, like a microscopically small black hole, might be very visible. It's given off light.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But something like the black hole at the center of our galaxy, three million times the mass of the sun or something like that, Sagittarius A star, that is so cold and low temperature that its radiation will never be observable. Black holes are hard to make. We don't have any nearby. The ones we have out there in the universe are very, very faint.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So there's no immediate hope for detecting Hawking radiation. Allegedly, we don't have any nearby. As far as we know, we don't have any nearby. Could tiny ones be hard to detect? Somewhere at the edges of the solar system, maybe? So you don't want them to be too tiny or they're exploding, right? They're very bright and then they would be visible.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But there's an absolutely regime where black holes are large enough not to be visible because the larger ones are fainter, right? Not giving off radiation, but small enough to not been detected through their gravitational effect. Yeah. Psychologically, just emotionally, how do you feel about black holes? Do they scare you? I love them. I love black holes.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But the universe, weirdly, makes it hard to make a black hole, right? Because you really need to squeeze an enormous amount of matter and energy into a very, very small region of space. So we know how to make... stellar black holes. A supermassive star can collapse to make a black hole. We know we also have these supermassive black holes at the center of galaxies.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
We're a little unclear where they came from. I mean, maybe stellar black holes that got together and combined, but that's one of the Exciting things about new data from the James Webb Space Telescope is that quite large black holes seem to exist relatively early in the history of the universe. So it was already difficult to figure out where they came from. Now it's an even tougher puzzle.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I think that's fair. Yeah. It's always interesting when something is difficult, but happens anyway, right? I mean, the probability of making a black hole could have been zero. It could have been one, but it's this interesting number in between, which is kind of fun. Are there more intelligent alien civilization than there are supermassive black holes? Yeah.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I have no idea, but I think your intuition is right that... It would have been easy for there to be lots of civilizations and then we would have noticed them already. And we haven't. So absolutely the simplest explanation for why we haven't is that they're not there.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
How easy is it to make life?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I mean, I get it. I get exactly what you're thinking. I think it's a perfectly reasonable attitude to have before you confront the data. I would not have expected Earth to be special in any way. I would have expected there to be plenty of very noticeable extraterrestrial civilizations out there. Um,
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But even if life finds a way, even if we buy everything you say, how long does it take for life to find a way? What if it typically takes 100 billion years? Then we'd be alone.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I don't believe that very strongly. Look, I'm not going to place a lot of bets here. I would not, I'm both pretty up in the air about whether or not life itself is all over the place. It's possible when we visit other worlds, other solar systems, there's very tiny microscopic life ubiquitous, but none of it has reached some complex form. It's also possible there's just, there isn't any.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
It's also possible that there are intelligent civilizations that have better things to do than knock on our doors. So I think we should be very humble about these things we know so little about.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
That is absolutely possible. I'm actually putting less credence on that one just because you need it to happen every single time, right? If even one... I mean, this goes back to von Neumann pointing out... John von Neumann pointed out that you don't need... to send the aliens around the galaxy. You can build self-reproducing probes and send them around the galaxy.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And you might think, well, the galaxy is very big. It's really not. It's some tens of thousands of light years across. And billions of years old. So you don't need to move at a high fraction of the speed of light to fill the galaxy.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Just spread out. Yes. And what you should do, this is, so if you want the optimistic spin, here's the optimistic spin. People looking for intelligent life elsewhere often tune in with their radio telescopes, right? At least we did before Arecibo was decommissioned.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
That's not a very promising way to find intelligent life elsewhere because why in the world would a super intelligent alien civilization waste all of its energy by beaming it in random directions into the sky? For one thing, it just passes you by, right? So if we're here on Earth, we've only been listening to radio waves for a couple hundred years, okay?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So if an intelligent alien civilization exists for a billion years, they have to pinpoint exactly the right time to send us this signal. It is much, much more efficient to send probes And to park, to go to the other solar systems, just sit there and wait for an intelligent civilization to arise in that solar system. This is kind of the 2001 monolith hypothesis, right?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I would be less surprised to find a sort of quiescent alien artifact in our solar system than I would to catch a radio signal from an intelligent civilization.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I just want to integrate over time. A probe can just sit there and wait, whereas a radio wave goes right by you.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Couldn't I be like the elected leader of the alien civilization?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I think we would figure out that language thing pretty quickly. I mean, maybe not... as quickly as we do when different human tribes find each other, because obviously there's a lot of commonalities in humanity, but there is logic and math and there is the physical world. You can point to a rock and go rock, right? I don't think it would take that long.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I know that Arrival, the movie, based on a Ted Chiang story, suggested that the way that aliens communicate is going to be fundamentally different, right? But also they had precognition and other things I don't believe in. So I think that if we actually find aliens, that will not be our long-term problem.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Well, again, if it's intelligent and technologically advanced. The more short-term question of if we get some spectroscopic data from an exoplanet, so we know a little bit about what is in its atmosphere. How can we judge whether or not that atmosphere is giving us a signature of life existing? That's a very hard question that people are debating about.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I mean, one very simple-minded but perhaps interesting approach is to say small molecules don't tell you anything because even if life could make them, something else could also make them. But long molecules, that's the kind of thing that life would produce.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
You know, I think, I mean, I'm in favor of this kind of humility, this intellectual humility that we won't know because we should be prepared for surprises. But I do always keep coming back to the idea that we all live in the same physical universe. And if... Well, let's put it this way.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
The development of our intelligence has certainly been connected to our ability to manipulate the physical world around us. And so I would guess, without 100% credence by any means, but my guess would be that any advanced kind of life would also have that capability. Both dolphins and octopuses are potential counterexamples to that.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But I think in the details, there would be enough similarities that we would recognize it.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Well, it goes back to this question that we were talking about with the information and how it gets out. In quantum mechanics, certainly, arguably even before quantum mechanics comes along in classical statistical mechanics, there's a relationship between information and entropy. Entropy is my favorite thing to talk about that I've written books about and will continue to write books about.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So Hawking tells us that black holes have entropy. And it's a finite amount of entropy. It's not an infinite amount. But the belief is, and now we're already getting quite speculative, the belief is that the entropy of a black hole is the largest amount of entropy that you can have in a region of spacetime. It's sort of the most densely packed that entropy can be.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And what that means is there's sort of a maximum amount of information that you can fit into that region of space and you call it a black hole. And interestingly, you might expect if I have a box and I'm gonna put information in it, And I don't tell you how I'm gonna put the information in, but I ask, how does the information I can put in scale with the size of the box?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
You might think, well, it goes as the volume of the box because the information takes up some volume and I can only fit in a certain amount. And that is what you might guess for the black hole, but it's not what the answer is. The answer is that the maximum information as reflected in the black hole entropy scales as the area. black holes event horizon, not the volume inside.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So people thought about that in both deep and superficial ways for a long time, and they proposed what we now call the holographic principle, that the way that space-time and quantum gravity convey information or hold information is not different bits or qubits for quantum information at every point in spacetime.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
It is something holographic, which means it's sort of embedded in or located in or can be thought of as pertaining to one dimension less of the three dimensions of space that we live in. In the case of the black hole, the event horizon is two-dimensional, embedded in a three-dimensional universe.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And the holographic principle would say all of the information contained in the black hole can be thought of as living on the event horizon rather than in the interior of the black hole. I need to say one more thing about that, which is that this was an idea. The idea I just told you was the original holographic principle
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
put forward by people like Gerard de Tuft and Leonard Susskind, a super famous physicist. Leonard Susskind was on my podcast and gave a great talk. He's very good at explaining these things. Mindscape podcast, everybody should listen. That's right, yes. And you don't just have physicists on. I don't.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But anyway, what I was trying to get at was Suskind and also at Tuft were a little vague. They were a little hand-wavy about holography and what it meant. Where holography, the idea that information is sort of encoded on a boundary, really came into its own was with Juan Maldacena.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
in the 1990s and the ADS-CFD correspondence, which we don't have to get into that into any detail, but it's a whole full-blown theory. It's two different theories. One theory in n dimensions of spacetime without gravity, and another theory in n plus 1 dimensions of spacetime with gravity. And the idea is that this n-dimensional theory is...
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
casting a hologram into the n plus one dimensional universe to make it look like it has gravity. And that's holography with a vengeance. And that's an enormous source of interest for theoretical physicists these days.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yeah, I mean, it's a good question. One of the things that quantum field theory indirectly suggests is that there's not that much information in you and me compared to the volume of space-time we take up. As far as quantum field theory is concerned, you and I are mostly empty space. And so we are not information dense, right?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
The density of information in us or in a book or a CD or whatever, a computer RAM is is indeed encoded by volume, like there's different bits located at different points in space, but that density of information is super-duper low.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So we're just like the speed of light or just like the Big Bang, for the information in a black hole, we are far away in our everyday experience from the regime where these questions become relevant. So it's very far away from our intuition. We don't really know how to think about these things. We can do the math, but we don't feel it in our bones.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So you can just write off that weird stuff happens in a black hole. Well, we'd like to do better, but we're trying. I mean, that's why we have an information loss puzzle, because we haven't completely solved it. So here's just one thing to keep in mind.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Once spacetime becomes flexible, which it does according to general relativity, and you have quantum mechanics, which has fluctuations in virtual particles and things like that, the very idea of a location in space-time becomes a little bit fuzzy, right? Because it's flexible and quantum mechanics says you can't even pin it down.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So information can propagate in ways that you might not have expected. And that's easy to say, and it's true, but we haven't yet come up with the right way to talk about it that is perfectly rigorous.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
You do, you do. But I'll point out one other thing. It's information dense, but it's also very, very high entropy. So a black hole is kind of like a very, very, very specific random number, right? It takes a lot of digits to specify it, but the digits don't tell you anything. They don't give you anything useful to work on.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So it takes a lot of information, but it's not of a form that we can learn a lot from.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Well, the black hole, I said that the black hole is the highest density of information, but it's not the highest amount of information because the black hole can evaporate.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And when it evaporates, and people have done the equations for this, when it evaporates, the entropy that it turns into is actually higher than the entropy of the black hole was, which is good because entropy is supposed to go up. But it's much more dilute, right? It's spread across a huge volume of space-time. So in principle...
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
All that you made the black hole out of, the information that it took, is still there, we think, in that information, but it's scattered to the four winds.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
No one's been there.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Again, this is a theoretical prediction. But I'll say one super crucial feature of the black holes that we know and love, the kind that Schwarzschild first invented. There's a singularity, but it's not at the middle. the black hole. Remember, space and time are parts of one unified space-time. The location of the singularity in the black hole is not the middle of space, but our future.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
It is a moment of time. It is like a big crunch. You know, the Big Bang was an expansion from a singularity in the past. Big crunch probably doesn't exist, but if it did, it would be a collapse to a singularity in the future. That's what the interiors of black holes are like. You can be fine in the interior, but things are becoming more and more crowded.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Space-time is becoming more and more warped, and eventually you hit a limit, and that's the singularity in your future. I wonder what time is like on the inside of a black hole. Time always ticks by one second per second. That's all it can ever do. Time can tick by differently for different people. And so you have things like the twin paradox, where two people initially are the same age.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
One goes off near the speed of light and comes back. Now they're not. You can even work out that the one who goes out and comes back will be younger because they did not take the shortest distance path. But locally, as far as you and your wristwatch are concerned, time is not funny.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Your neurological signals in your brain and your heartbeat and your wristwatch, whatever's happening to them is happening to all of them at the same time. So time always seems to be ticking along at the same rate.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
You would not be you anymore.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
It depends on what you mean by preserved. It's there in the microscopic configuration of the universe. It's exactly as if I took a regular book, made a paper, and I burned it. The laws of physics say that all the information in the book is still there in the heat and light and ashes. You're never going to get it. It's a matter of practice, but in principle, it's still there.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
From outside the black hole, it doesn't matter because they're inside the black hole.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But also, by the way, just in relativity, special relativity, forget about general relativity, it's enormously tempting to say, okay, here's what's happening to me right now. I want to know what's happening far away right now. The whole point of relativity is to say there's no such thing as right now when you're far away. And that is doubly true for what's inside a black hole.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So you're tempted to say, well, how fast is their clock ticking? Or how old are they now? Not allowed to say that according to relativity.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
As far as we know, nothing dramatic happens. We're not anywhere close to being confident that we know what's going on here yet. So there are good unanswered questions about whether time is fundamental, whether time is emergent. whether it has something to do with quantum entanglement, whether time really exists at all, different theories, different proponents of different things.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But there's nothing specifically about holography that would make us change our opinions about time, whatever they happen to be.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Time just goes along for the ride, as far as we know, yeah.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yeah, I mean, that might be a reflection of our ignorance right now, but yes.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
It does depend on what they would say. I think that there are colleagues of mine who think that we're pretty close to figuring out how information gets out of black holes, how to quantize gravity, things like that. I'm more skeptical that we are pretty close. I think that there's room for a bunch of surprises to come. So in that sense, I suspect I would be surprised.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
The biggest and most interesting surprise to me would be if quantum mechanics itself were somehow superseded by something better. As far as I know, There's no empirical evidence-based reason to think that quantum mechanics is not 100% correct. But it might not be. That's always possible. So, and there are, again, respectable friends of mine who speculate about it.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So that's something I would, that's the first thing I would want to know.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I mean, maybe. The point is that black holes are mysterious for various reasons. So yeah, if our best theory of the universe is wrong, that might help explain why.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yeah, you know, that would be less surprising to me because I've already written papers about that. We don't... have, again, strong reason to think that the interior of a black hole leads to another universe. But it is possible, and it's also very possible that that's true for some black holes and not others. This is stuff we don't know. It's easy to ask questions we don't know the answer to.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
The problem is the questions that are easy to ask that we don't know the answer to are super hard to answer. Because these objects are very difficult to test and to explore. The regimes are just very far away. So either literally far away in space, but also in energy or mass or time or whatever.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yeah, you know, I'm always interested in, since my first published paper, taking these wild speculative ideas and trying to test them against data. And the problem is, when you're dealing with wild speculative ideas, they're usually not... well-defined enough to make a prediction, right? Like it's kind of a, I know what's gonna happen in some cases, I don't know what's gonna happen in other cases.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So we did the following thing. As I've already mentioned, the holographic principle, which is meant to reflect the information contained in black holes, seems to be telling us that information, there's less information, less stuff that can go on than you might naively expect. So let's upgrade naively expect to predict using quantum field theory.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Quantum field theory is our best theory of fundamental physics right now. Unlike this holographic black hole stuff, quantum field theory is entirely local. In every point of space, something can go on and then you add up all the different points in space, okay? Not holographic at all.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So there's a mismatch between the expectation for what is happening even in empty space in quantum field theory versus what the holographic principle would predict. How do you reconcile these two things?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So there's one way of doing it that had been suggested previously, which is to say that in the quantum field theory way of talking, it implies there's a whole bunch more states, a whole bunch more ways the system could be than there really are. And I'll do a little bit of math, just because there might be some people in the audience who like the math. If I draw...
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
two axes on a two-dimensional geometry, like the surface of the table, right? You know that the whole point of it being two-dimensional is I can draw two vectors that are perpendicular to each other. I can't draw three vectors that are all perpendicular to each other, right? They need to overlap a little bit. That's true for any numbers of dimensions.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But I can ask, OK, how much do they have to overlap? If I try to put more vectors into a vector space than the dimensionality of the vector space, can I make them almost perpendicular to each other? And the mathematical answer is, as the number of dimensions gets very, very large, you can fit a huge extra number of vectors in that are almost perpendicular to each other.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
In this case, what we're suggesting is the number of things that can happen in a region of space is correctly described by holography. It is somewhat overcounted by quantum field theory, but that's because the quantum field theory states are not exactly perpendicular to each other.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I should have mentioned that in quantum mechanics, states are given by vectors in some huge dimensional vector space, very, very, very, very large dimensional vector space. So maybe the quantum field theory states are not quite perpendicular to each other. If that is true, that's a speculation already, but if that's true, how would you know? What is the... experimental deviation.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And it would have been completely respectable if we had gone through and made some guesses and found that there is no noticeable experimental difference because, again, these things are in regimes very, very far away. We stuck our necks out. We made some very, very specific guesses as to how this weird overlap of states would show up in the equations of motion for particles like neutrinos.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And then we made predictions on how the neutrinos would behave on the basis of those wild guesses. And then we compared them with data. And what we found is we're pretty close, but haven't yet reached the detectability of the effect that we are predicting.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
In other words, well, basically one way of saying what we predict is if a neutrino, and there's reasons why it's neutrinos, we can go into if you want, but it's not that interesting. The neutrino comes to us from across the universe, from some galaxy very, very far away.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
There is a probability as it's traveling that it will dissolve into other neutrinos because they're not really perpendicular to each other as vectors as they would ordinarily be in quantum field theory. And that means that if you look at neutrinos coming from far enough away with high enough energies, they should disappear.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Like if you see a whole bunch of nearby neutrinos, but then further away, you should see fewer. And there is an experiment called IceCube, which is this amazing testament to the ingenuity of human beings, where they go to Antarctica. And they drill holes and they put photo detectors on a string a mile deep in these holes. And they basically use all of the ice in a cube.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I don't know whether it's a mile or not, but it's like a kilometer or something like that, some big region. That much ice is their detector. And they're looking for flashes when a cosmic ray or a neutrino or whatever hits an ice molecule, water molecule in the ice. Flashes in the ice. Yes, they're looking for flashes in the ice.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But isn't there some crazy, I mean, what does the detector of that look like? It's a bunch of strings, many, many, many strings with 360-degree photo detectors. That's really cool. It's extremely cool. They've done amazing work and they find neutrinos. They're looking for neutrinos. Yeah. The whole point is most cosmic rays are protons. Because why?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Because protons exist and they're massive enough that you can accelerate them to very high energies. So high energy cosmic rays tend to be protons. They also tend to hit the Earth's atmosphere and decay into other particles. So neutrinos, on the other hand, punch right through, at least usually, right, to a great extent. So not just Antarctica, but the whole Earth.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And occasionally, a neutrino will interact with a particle here on Earth. And this neutrino is going through your body all the time, from the sun, from the universe, et cetera. And so if you're patient enough and you have a big enough part of the Antarctic ice sheet to look at, the nice thing about ice is it's transparent. So you've built yourself. Nature has built you a neutrino detector.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
There's not that much ice, right? Yeah. So there's more ice in Antarctica than anywhere else. Right. So anyway, you can go and you can get a plot from the Ice Cube experiment. Yeah. how many neutrinos there are that they've detected with very high energies. And we predict in our weird little holographic guessing game that there should be a cutoff.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
You should see neutrinos as you get to higher and higher energies, and then they should disappear. If you look at the data, their data gives out exactly where our cutoff is. That doesn't mean that our cutoff is right. It means they lose the ability to do the experiment exactly where we predict the cutoff should be.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But why is there a limit? Oh, just because there are fewer and fewer high-energy neutrinos. So there's a spectrum, and it goes down. What we're plotting here is number of neutrinos versus energy. It's fading away. And they just get very, very few.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And let me just mention the name of Oliver Friedrich, who was a postdoc who led this. He deserves the credit for doing this. I was a co-author and a collaborator. I did some work, but he really gets the lion's share.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
There's a very interesting things that happens once you're a theoretical physicist, once you become trained. You're a graduate student, you've written some papers and whatever. Suddenly you are the world's expert in a really infinitesimally tiny area of knowledge, right? And you know not that much about other areas. there's an overwhelming temptation to just drill deep, right?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Just keep doing basically the thing that you started doing. But maybe that thing you started doing is not the most interesting thing to the world or to you or whatever. So you need to separately develop the capability of stepping back and going, okay, now that I can write papers in that area, now that I'm sort of trained enough in the general procedure,
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
What is the best match between my interests, my abilities, and what is actually interesting? And honestly, I've not been very good at that over my career. My process traditionally was I was working in this general area of particle physics, field theory, general relativity, cosmology, and I would sort of...
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
try to take things other people were talking about and ask myself whether or not it really fit together. Like my, my two, so I guess I have three papers that I've ever written. that have done super well in terms of getting cited and things like that. One was my first ever paper that I get very little credit for. That was my advisor and his collaborator set that up.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
The other two were basically my idea. One was right after we discovered that the universe was accelerating. So in 1998, observations showed that not only is the universe expanding, but it's expanding faster and faster. So that's attributed to either Einstein's cosmological constant or some more complicated form of dark energy, some mysterious thing that fills the universe.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And people were throwing around ideas about this dark energy stuff. What could it be? And so forth. Most of the people throwing around these ideas were cosmologists. They work on cosmology. They think about the universe all at once. I, you know, since I like to talk to people in different areas, I was sort of more familiar than average
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
with what a respectable working particle physicist would think about these things. And what I immediately thought was, you know, you guys are throwing around these theories. These theories are wildly unnatural. They're super finely tuned. Like any particle physicist would just be embarrassed to be talking about this. But rather than just...
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
scoffing at them, I sat down and asked myself, okay, is there a respectable version? Is there a way to keep the particle physicists happy, but also make the universe accelerate? And I realized that there is some very specific set of models that is relatively natural. And guess what? You can make a new experimental prediction. on the basis of those. And so I did that.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
People were very happy about that.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
The fact that dark energy pervades the whole universe and is slowly changing, that should immediately set off alarm bells because particle physics is a story of length scales and time scales that are generally, guess what? Small, right? Particles are small. They vibrate quickly. And you're telling me now I have a new field and its typical rate of change is once every billion years, right?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Like that's just not natural, right? And indeed, you can formalize that and say, look, even if you wrote down a particle that evolved slowly over billions of years, if you let it interact with other particles at all, that would make it move faster. Its dynamics would be faster. Its mass would be higher, et cetera, et cetera. So there's a whole story.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Things need to be robust and they all talk to each other in quantum field theory. So how do you stop that from happening? And the answer is symmetry. You can impose a symmetry that protects your new field from talking to any other fields, okay? And this is good for two reasons. Number one, it can keep the dynamics slow. So you can't tell me why it's slow. You just made that up.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But at least it can protect it from speeding up because it's not talking to any other particles. And the other is it makes it harder to detect. Naively, experiments looking for fifth forces or time changes of fundamental constants of nature like the charge of the electron, these experiments should have been able to detect these dark energy fields.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And I was able to propose a way to stop that from happening. The detection. The detection, yeah. Because a symmetry could stop it from interacting with all these other fields and therefore makes it harder to detect. And just by luck, I realized, because it was actually based on my first ever paper, there's one loophole.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
If you impose these symmetries, so you protect the dark energy field from interacting with any other fields, there's one interaction that is still allowed that you can't rule out. And it is a very specific interaction between your dark energy field and photons, which are very common. And it has the following effect. As a photon travels through the dark energy, the photon has a polarization.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
up, down, left, right, whatever it happens to be. And as it travels through the dark energy, that photon will rotate its polarization. This is called birefringence. And you can kind of run the numbers and say, you know, you can't make a very precise prediction because we're just making up this model.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But if you want to roughly fit the data, you can predict how much polarization rotation there should be. A couple of degrees, okay? Not that much. So that's very hard to detect. People have been trying to do it. Right now, literally, we're on the edge of either being able to detect it or rule it out using the cosmic microwave background. And there is just, you know, truth in advertising.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
There is a claim on the market that it's been detected, that it's there. It's not very statistically significant. If I were to bet, I think it would probably go away. It's a very hard thing to observe. But maybe as you get better and better data, cleaner and cleaner analysis, it will persist and we will have directly detected the dark energy. So if we just take this tangent of dark energy,
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Well, two ways. One way is those people would have had to say the same thing when we discovered the planet Neptune. Because it's exactly analogous. Where we have a very good theory, in that case, Newtonian gravity in the solar system. We made predictions. The predictions were slightly off for the motion of the outer planets.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
You found that you could explain that motion by positing something very simple. One more planet. In a very, very particular place. And you went and looked for it, and there it was, right? That was the first successful example of finding dark matter in the universe. It's a matter that we can't see. Neptune was dark. Yeah. There's a difference between dark matter and dark energy, right?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Dark matter, as far as we are hypothesizing it— is a particle of some sort. It's just a particle that interacts with us very weakly. So we know how much of it there is. We know more or less where it is. We know some of its properties. We don't know specifically what it is. But it's not anything fundamentally mysterious. It's a particle. Dark energy is a different story.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So dark energy is indeed uniformly spread throughout space. And has this very weird property that it doesn't seem to evolve as far as we can tell. It's the same amount of energy in every cubic centimeter of space from moment to moment in time. That's why far and away the leading candidate for dark energy is Einstein's cosmological constant.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
The cosmological constant is strictly constant, 100% constant. The data say it had better be 98% constant or better. So 100% constant works, right? And it's also very robust. It's just there. It's not doing anything. It doesn't interact with any other particles. It makes perfect sense. Probably the dark energy is the cosmological constant.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
The dark matter, super important to emphasize here, you know, it was hypothesized at first in the 70s and 80s, mostly to explain the rotation of galaxies. Today, the evidence for dark matter is both much better than it was in the 1980s and from different sources. It is mostly from observations of the cosmic background radiation or of large-scale structure.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So we have multiple independent lines of evidence, also gravitational lensing and things like that, many, many pieces of evidence that say that dark matter is there. And also that say that the effects of dark matter are different than if we modified gravity. So that was my first answer to your question is dark matter, we have a lot of evidence for.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But the other one is, of course, we would love it if it weren't dark matter. Our vested interest is 100% aligned. with it being something more cool and interesting than dark matter, because dark matter is just a particle. That's the most boring thing in the world.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
bigger than the galaxy, sadly. We think that in the galaxy, dark matter is lumpy, but it's weaker, its effects are weaker. But on the scale of large-scale structure and clusters of galaxies and things like that, yes, we can show you where the dark matter is.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
The super cool explanation would be modifying gravity rather than inventing a new particle. Sadly, that doesn't really work. We've tried. I've tried. That's my third paper that was very successful. I tried to unify dark matter and dark energy together. That was my idea. That was my aspiration, not even an idea. I tried to do it. It failed even before we wrote the paper.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I realized that my idea did not help. It could possibly explain away the dark energy, but it would not explain away the dark matter. And so I thought it was not that interesting actually. And then two different collaborators of mine said, has anyone thought of this idea? Like they had thought of exactly the same idea completely independently of me.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I said, well, if three different people found the same idea, maybe it is interesting. And so we wrote the paper. And yeah, it was very interesting.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So here is what we know about dark matter and dark energy. They become important in regimes where gravity is very, very, very weak, right? That's kind of the opposite from what you would expect if you actually were modifying gravity. Like there's a rule of thumb in quantum field theory, et cetera, that new effects show up when the effects are strong, right?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
We understand weak fields, we don't understand strong fields. But okay, maybe this is different, right? So what do I mean by when gravity is weak? The dark energy shows up late in the history of the universe. Early in the history of the universe, the dark energy is irrelevant. But remember, the density of dark energy stays constant. The density of matter and radiation go down.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So at early times, the dark energy was completely irrelevant compared to matter and radiation. At late times, it becomes important. That's also when the universe is dilute and gravity is relatively weak. Now think about galaxies, okay? A galaxy is more dense in the middle, less dense on the outside.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And there is a phenomenological fact about galaxies that in the interior of galaxies, you don't need dark matter. That's not so surprising because the density of stars and gas is very high there and the dark matter is just subdominant. But there's generally a radius inside of which you don't need dark matter to fit the data, outside of which you do need dark matter to fit the data.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So that's, again, when gravity is weak, right? So I asked myself... Of course, we know in field theory, new effects should show up when fields are strong, not weak. But let's throw that out of the window. Can I write down a theory where gravity alters when it is weak? And we've already said what gravity is. What is gravity? It's the curvature of spacetime.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So there are mathematical quantities that measure the curvature of spacetime. And generally, you would say, like, I have an understanding Einstein's equation, which I explained to the readers in the book, relates the curvature of spacetime to matter and energy. The more matter and energy, the more curvature.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So I'm saying, what if you add a new term in there that says the less matter and energy, the more curvature? No reason to do that except to fit the data, right? So I tried to unify the need for dark matter and the need for dark energy. That would be really cool if that was the case. Super cool, right? It'd be the best. It'd be great.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yeah, it does. I agree. Again, that's why it is a little bit, I tear my hair out when people who are not physicists think, you know, accuse physicists, like you say, of sort of losing the plot because they need dark matter and dark energy. I don't want dark matter and dark energy. I want something much cooler than that. I've tried. But you got to listen to the equations and to the data. Yeah.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Well, by the way, this is not awesomeness. This is impact. Impact. Right? Sure. There's no correlation between awesomeness and impact. Right. Some of my best papers fell without a stone. A tree falls in the forest. Yeah. Yeah. The first paper was called Limits on a Lorentz and Parity Violating Modification of Electromagnetism or Electrodynamics.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So we figured out how to violate Lorentz invariance, which is the symmetry underlying relativity. And the important thing is we figured out a way to do it that didn't violate anything else and was experimentally testable. So people love that. The second paper was called Quintessence and the Rest of the World. So quintessence is this dynamical dark energy field.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
The rest of the world is because I was talking about how the quintessence field would interact with other particles and fields and how to avoid the interactions you don't want. And the third paper was called, is cosmic speed up due to gravitational physics? Something like that. So you see the common theme.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I'm taking, you know, what we know, the standard model of particle physics, general relativity, tweaking them. In some way, and then trying to fit the data. And trying to make it so it's experimentally validated. Ideally, yes. That's right. That's the goal.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Quantum mechanics is a harder one. You know, I wrote a textbook on general relativity and I started it by saying general relativity is the most beautiful physical theory ever invented. I will stand by that. It is less fundamental than quantum mechanics. But quantum mechanics is a little more mysterious. So It's a little bit kludgy right now.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
If you think about how we teach quantum mechanics to our students, the Copenhagen interpretation, it's a god-awful mess. No one's going to accuse that of being very beautiful. I'm a fan of the many-worlds interpretation of quantum mechanics, and that is very beautiful in the sense that fewer ingredients, just one equation, and it could cover everything in the world.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
It depends what you mean by beauty, but I think that the answer to your question is quantum mechanics can start with extraordinarily austere, tiny ingredients and in principle lead to the world, right? That boggles my mind. It's much more comprehensive. General relativity is about gravity, and that's great. Quantum mechanics is about everything. and seems to be up to the task.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And so I don't know, is that beauty or not? But it's certainly impressive.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
In classical mechanics, I have a particle here, a particle there. I described them separately. I can tell you what this particle is doing, what that particle is doing. In quantum mechanics, we have entanglement, right? As Einstein pointed out to us in 1935. And what that means is there is a single state for these two particles.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
There's not one state for this particle, one state for the other particle. And indeed, there's a single state for the whole universe called the wave function of the universe, if you want to call it that. And it obeys one equation and is our job then to sort of chop it up, to carve it up, to figure out how to get tables and chairs and things like that out of it.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I'm a big boy, I can take it.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
You know, the classic experiment to explain quantum mechanics to people is called the Stern-Gerlach experiment. You're measuring the spin of a particle, okay? And in quantum mechanics, the spin is just a spin. It's the rate at which something is rotating around in a very down to earth sense. The difference being is that it's quantized.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So for something like a single electron or a single neutron, it's either spinning clockwise or counterclockwise. Those are the only two, let's put it this way, those are the only two measurement outcomes you will ever get. There's no, it's spinning faster or slower. It's either spinning one direction or the other. That's it, two choices, okay?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
According to the rules of quantum mechanics, I can set up an electron, let's say, in a state where it is neither purely clockwise or counterclockwise, but a superposition of both. And that's not just because we don't know the answer. It's because it truly is both until we measure it. And then when we measure it, we see one or the other.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So this is the fundamental mystery of quantum mechanics is that how we describe the system when we're not looking at it is different from what we see when we look at it. So we teach our students in the Copenhagen way of thinking is that the act of measuring the spin of the electron causes a radical change in the physical state. It spontaneously collapses from being a superposition
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
of clockwise and counterclockwise to being one or the other. And you can tell me the probability that that happens, but that's all you can tell me. And I can't be very specific about when it happens, what caused it to happen, why it's happening, none of that. That's all called the measurement problem of quantum mechanics.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So many worlds just says, look, I just told you a minute ago that there's only one way function for the whole universe. And that means that you can't take too seriously just describing the electron. You have to include everything else in the universe. In particular, you clearly have to interact with the electron in order to measure it.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So whatever is interacting with the electron should be included in the wave function that you're describing. And look, maybe it's just you. Maybe your eyeballs are able to perceive it, but okay, I'm going to include you in the wave function. And if you do that, let's be, you know, since you have a very sophisticated listenership, I'll be a little bit more careful than average.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
What does it mean to measure the spin of the electron? We don't need to go into details, but we want the following thing to be true. If the electron were in a state that was 100% spinning clockwise, then we want the measurement to tell us it was spinning clockwise. We want your brain to go, yes, the electron was spinning clockwise, right?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Likewise, if it was 100% counterclockwise, we want to see that, to measure that. The rules of quantum mechanics, the Schrodinger equation of quantum mechanics is 100% clear that if you want to measure it clockwise when it's clockwise and measure it counterclockwise when it's counterclockwise, then when it starts out in a superposition,
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
What will happen is that you and the electron will entangle with each other. And by that, I mean that the state of the universe evolves into part saying the electron was spinning clockwise and I saw it clockwise. And part of the state is it's in a superposition with the part that says the electron was spinning counterclockwise and I saw it counterclockwise. Everyone agrees with this.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Entirely uncontroversial, straightforward consequence of the Schrodinger equation. And then Niels Bohr would say, and then part of that wave function disappears. And we're in the other part. And you can't predict which part it will be, only the probability. Hugh Everett, who was a graduate student in the 1950s, was thinking about this, says, I have a better idea.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
part of the wave function does not magically disappear. It stays there.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
The reason why that idea, Everett's idea, that the whole wave function always sticks around and just obeys the Schrodinger equation was not thought of years before is because naively you look at it and you go, okay, this is predicting that I will be in a superposition, that I will be in a superposition of having seen the electron be clockwise and having seen it be counterclockwise.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
No experimenter has ever felt like they were in a superposition. You always see an outcome, okay? Everett's move, which was kind of genius, was to say, the problem is not the Schrodinger equation. The problem is you have misidentified yourself in the Schrodinger equation. You have said, oh, look, there's a person who saw counterclockwise. There's a person who saw clockwise.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I should be that superposition of both. And Everett says, no, no, no, you're not. Because the part of the wave function... in which the spin was clockwise, once that exists, it is completely unaffected by the part of the wave function that says the spin was counterclockwise. They are apart from each other. They are uninteracting. They have no influence.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
What happens in one part has no influence in the other part. So Everett says the simple resolution is to identify yourself as either the one who saw spin clockwise, or the one who saw spin counterclockwise. There are now two people. Once you've done that experiment, the Schrodinger equation doesn't have to be messed with. All you have to do is locate yourself correctly in the wave function.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
That's many worlds.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Where do they go? The short answer is... The worlds don't exist in space. Space exists separately in each world. So, I mean, there's a technical answer to your question, which is Hilbert space, the space of all possible quantum mechanical states. But physically, you know, we want to put these worlds somewhere. That's just a wrong intuition that we have.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
There is no such thing as the physical spatial location of the worlds because space is inside the worlds.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
They are existing separately and simultaneously.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Without locations in space.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
The real answer to that, the honest answer is... The equations predict it. If you can't visualize it, so much worse for you. The equations are crystal clear about what they're predicting.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
You know, I don't think it's that hard. It wasn't that hard for me. You know, I don't mind the idea that when I make a quantum mechanical measurement, there is later on in the universe, multiple descendants of my present self who got different answers for that measurement. I can't interact with them.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Hilbert space, the space of all quantum wave functions was always big enough to include all of them. I'm going to worry about the parts of the universe I can observe. So let's put it this way. Many worlds comes about by taking the Schrodinger equation seriously.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
The Schrodinger equation was invented to fit the data, to fit the spectrum of different atoms and different, you know, emission and absorption experiments. And it's perfectly legitimate to say, well, okay, you're taking the Schrodinger equation, you're extrapolating it. You're trusting it, believing it beyond what we can observe. I don't want to do that, right?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
That's perfectly legit, except, okay, then what do you believe? Come up with a better theory. You're saying you don't believe the Schrodinger equation. Tell me the equation that you believe in. Turns out, and people have done that, turns out it's super hard to do that in a legitimate way that fits the data. And many worlds is a really clean.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Absolutely the most austere, clean, no extra baggage theory of quantum mechanics.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yes. In fact, let me put it this way. The single best reason in my mind is To be skeptical about many worlds is not because it doesn't make sense or it doesn't fit the data or I don't know where the worlds are going or whatever. It's because to make that extrapolation, to take seriously the equation that we know is correct in other regimes, requires new philosophy.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
requires a new way of thinking about identity, about probability, about prediction, a whole bunch of things. And it's work to do that philosophy, and I've been doing it, and others have done it, and I think it's very, very doable. But it's not... straightforward. It's not a simple extrapolation from what we already know. It's a grand extrapolation very far away.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And if you just wanted to be sort of methodologically conservative and say, that's a step too far. I don't want to buy it. I'm sympathetic to that. I think that you're just wimping out. I think that you should have more courage, but I get the impulse.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
That's right. All of quantum mechanics, all different versions, require a kind of arrow of time. It might be different in every kind. But the quantum measurement process is irreversible. You can measure something, it collapses, you can't go backwards. If someone tells you the outcome, if I say I've measured an electron, its spin is clockwise. And they say, what was it before I measured it?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
You know there was some part of it that was clockwise, but you don't know how much, right? And many worlds is no different. But the nice thing is that the kind of arrow of time you need in many worlds is exactly the kind of arrow of time you need anyway. for entropy and thermodynamics and so forth. You need a simple, low entropy initial state. That's what you need in both cases.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
As far as we know, so according to many worlds, the wave function of the universe, all the branches of the universe at once, all the worlds, does contain all the information. Calling it a memory is a little bit dangerous because it's not the same kind of memory that you and I have in our brains because our memories rely on the arrow of time.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And the whole point of the Schrodinger equation or Newton's laws is they don't have an arrow of time. built in. They're reversible. The state of the universe not only remembers where it came from, but also determines where it's going to go in a way that our memories don't do that.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Can you do this? We can, but the act of forming a memory increases the entropy of the universe. It is an irreversible process also, right? You can walk on a beach and leave your footprints there. That's a record of your passing. It will eventually be erased by the ever-increasing entropy of the universe.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Oh, yeah. It depends on the level of precision you're trying to ask that question. The universe contains the information about where the universe was, but you and I don't. We're nowhere close.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Well, it depends on, again, exactly what you're asking. There are some simple questions, like what was the temperature of the universe 30 seconds after the Big Bang? We can answer that. That's amazing that we can answer that to pretty high precision. But if you want to know where every atom was, then no.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
We have no idea. I think that that's a super important question that I can imagine making progress on. But right now, I'm more or less maximally uncertain about what the answer is. You think black holes will help? No. Potentially? Not that much. Quantum gravity will help, and maybe black holes will help us figure out quantum gravity, so indirectly, yes.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But we have the situation where general relativity, Einstein's theory, unambiguously predicts there was a singularity in the past. There was a moment of time... When the universe had infinite curvature, infinite energy, infinite expansion rate, the whole bit.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
That's just a fancy way of saying the theory has broken down and classical general relativity is not up to the task of saying what really happened at that moment. So it is completely possible there was in some sense a moment of time before which there were no other moments.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And that would be the Big Bang, even if it's not a classical general relativity kind of thing, even if quantum mechanics is involved, maybe that's what happened. It's also completely possible there was time before that, space and time, and they evolved into our hot Big Bang by some procedure that we don't really understand.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Well, I think that if there is a first moment of time... That would be very good evidence or that would fit hand in glove with the idea that time is emergent. If time is fundamental, then it tends to go forever because it's fundamental.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
That's my life. My life is asking pothead questions. Some of them, the answer is that's not the right way to think about it.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
It's absolutely legit to ask questions, but you have to be comfortable with the possibility that the answer is there's no such thing as outside our universe. That's absolutely on the table. In fact, that is the simplest, most likely to be correct answer that we know of.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yeah, if the universe is the totality of everything, it would not have an outside.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Because that is our experience. That's the world we grew up in, right? The universe doesn't need to obey those rules. It's such a weird thing. When I was a kid, that used to keep me up at night. What if the universe had not existed? Right.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
There's one pitfall that I'll just mention because there's a move that is made in these theoretical edges of cosmology that I think is a little bit mistaken, which is to say, I'm going to think about the universe on the basis of imagining that I am a typical observer, This is called the principle of typicality or the principle of mediocrity or even the Copernican principle.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Nothing special about me. I'm just typical in the universe. But then you draw some conclusions from this. And what you end up realizing is you've been hilariously presumptuous because by saying I'm a typical observer in the universe, you're saying typical observers in the universe are like me. And that is completely unjustified by anything. Right.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So I'm not telling you what the right way to do it is, but these kinds of questions that are not quite grounded in experimental verification or falsification are ones you have to be very careful about.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I think that specifically the question, why is there something rather than nothing, does not have the kind of answer that we would ordinarily attribute to why questions. Because typical why questions are embedded in the universe. And when we answer them, we take advantage of the features of the universe that we know and love.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But the universe itself, as far as we know, is not embedded in anything bigger or stronger, and therefore it can just be.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Sure.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
You know, my own podcast listeners, Mindscape listeners, tease me because they know from my AMA episodes that if you ever start a question by asking, do you think it's possible that? The answer is going to be yes. That might not be the answer that you care about, but it's possible, sure. As long as you're not, you know... adding two even numbers together and getting an odd number.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
You want to know is there a reasonable non-zero credence to attach to this. I don't think that there's any... philosophical knockout objection to the simulation hypothesis. I also think that there's absolutely no reason to take it seriously.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yeah, I think they will create better and better simulations. I think the philosopher David Chalmers has done what I consider to be a good job of arguing that we should treat things that happen in virtual reality and in simulated realities as just as real as the reality that we experience.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I also think that as a practical matter, people will realize how much harder it is to simulate a realistic world than we naively believe. So this is not a my lifetime kind of worry.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I want to eliminate the phrase AGI.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
My intuition is basically that artificial intelligence is different than human intelligence. And so the mistake that is being made by focusing on AGI, among those who do, is an artificial agent, as we can make them now or in the near future, might be way better than human beings at some things. way worse than human beings at other things.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And rather than trying to ask how close is it to being a human-like intelligent, we should appreciate it for what its capabilities are. And that will both be more accurate and help us put it to work and protect us from the dangers better, rather than always anthropomorphizing it.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I don't think that there are many limits in principle. I'm a physicalist about consciousness and awareness and things like that. I see no obstacle to, in principle, building an artificial machine that is indistinguishable in thought and cognition from a human being. But we're not trying to do that, right? What a large language model is trying to do is to predict text. That's what it does.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And it is leveraging the fact that we human beings, for very good evolutionary biology reasons, attribute intentionality and intelligence and agency to things that act like human beings. As I was driving here... to get to this podcast space, I was using Google Maps and Google Maps was talking to me, but I wanted to stop to get a cup of coffee. So I didn't do what Google Maps told me to do.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I went around a block that it didn't like. And so it gets annoyed, right? It says like, no, why are you doing? It doesn't say exactly in this, but you know what I mean? It's like, no, turn left, turn left, and you turn right. It is impossible as a human being not to feel a little bit sad that Google Maps is getting mad at you. It's not. It's not even trying to. It's not a large language model.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
There's no aspirations to intentionality, but we attribute that all the time. Dan Dennett, the philosopher, wrote a very influential paper on the intentional stance. The fact that it's the most natural thing in the world for we human beings to attribute more intentionality to artificial things than are really there. Which is not to say it can't be really there.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But if you're trying to be rational and clear thinking about this, the first step is to recognize our huge bias. towards attributing things below the surface to systems that are able to, at the surface level, act human.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Well, I don't think it will happen naturally. I think it could happen. Again, I'm not against the principle. But again, the way that large language models came to be and what they're optimized for is wildly different than the way that human beings came to be and what they're optimized for.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So I think we're missing a chance to be much more clear-headed about what large language models are by judging them against human beings, again, both in positive ways and negative ways.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yeah. So that's why I think that there's a set of hugely interesting questions to be asked about the ways in which large language models actually do represent the world. Because what is clear is that they're very good at acting human. The open question in my mind is, is the easiest, most efficient, best way to act human to do the same things that human beings do? Or are there other ways?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And I think that's an open question. I just heard a talk by Melanie Mitchell at Santa Fe Institute, an artificial intelligence researcher. And she told two stories about two different papers, one that someone else wrote and one that her group is following up on. And they were modeling Othello. Othello, the game was a little rectangular board, white and black squares.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So the experiment was the following. They fed a neural network the moves that were being made in the most symbolic form, like E5. Just means that, okay, you put a token down E5. So it gives a long string. It does this for millions of games, right? Real legitimate games.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And then it asks the question, the paper asks the question, okay, you've trained it to tell what would be a legitimate next move from not a legitimate next move. Did it in its brain, in its little large language model brain, I don't even know if it's technically a large language model, but a deep learning network, did it come up with a representation of the Othello board? Well, how do you know?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And so they construct a little probe network that they insert and ask it, what is it doing right at this moment, right? And the answer is that the little probe network can ask, would this be legitimate or is this token white or black or whatever? Things that in practice would amount to it's invented the Othello board.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And it found that the probe got the right answer, not 100% of the time, but more than by chance, substantially more than by chance. So they said, there's some tentative evidence that this neural network has discovered the Othello board just out of data, raw data, right?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But then Melanie's group asked the question, okay, are you sure that that understanding of the Othello board wasn't built into your probe? And what they found was like at least half of the improvement was built into the probe, you know, not all of it. Right. And look, A, Othello board is way simpler than the world.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So that's why I just think it's an open question whether or not the – I mean, it would be remarkable either way to learn that large language models that are good at doing what we train them to do are good because they've built the same kind of model of the world that we have in our minds. or that they're good despite not having that model. Either one of these is an amazing thing.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I just don't think the data are clear on which one is true.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Look, and I think that's perfectly fair. I also was... I will say pleasantly, but I don't know whether it's pleasantly or unpleasantly, but factually surprised by the recent rate of progress. Clearly, some kind of phase transition percolation has happened, right? And the improvement has been remarkable, absolutely amazing. That I have no arguments with.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
That doesn't yet tell me the mechanism by which that improvement happened. Constructing a model much like a human being would have is clearly one possible mechanism, but part of the intellectual humility is to say maybe there are others.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Probably the best way to start to try to explain it is special relativity, which came first, 1905. It was the culmination, right, of many decades of people putting things together. But it was Einstein in 1905. In fact, it wasn't even Einstein. I should give more credit to Minkowski. in 1907.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yeah, 100%. I think this is one of the biggest... things that physics can help with and it's an obvious kind of low-hanging fruit situation where the heat generation, the inefficiency, the waste of existing high level computers is nowhere near the efficiency of our brains. It's hilariously worse. And we kind of haven't tried to optimize that hard on that frontier.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I mean, your laptop heats up when you're sitting on your lap, right? It doesn't need to, your brain doesn't heat up like that. So clearly there exists in the world of physics, the capability of doing these computations with much less waste heat being generated. And I look forward to people doing that, yeah. Are you excited for the possibility of a nuclear fusion? I am cautiously optimistic.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Excited would be too strong. I mean, it'd be great, right? But if we really tried solar power, it would also be great.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Put them in space. Sure, you can go in space, yeah. Space is bigger than the Earth. Yeah, just solar panels everywhere.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I like it. We already have fusion. It's called the sun.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Sending it down is the hard part, absolutely.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
There are constraints, right? There's a certain amount of energy, a certain amount of damage we can do to the environment before it is not worth it anymore. So yeah, I think that's a new question. In fact, it's kind of frustrating because we get better and better at doing things efficiently. But we invent more things we want to do faster than we get good at doing them efficiently.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So we're continuing to make things worse in various ways.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So Einstein in 1905 figured out that you could get rid of the ether, the idea of a rest frame for the universe, and all the equations of physics would make sense, with the speed of light being a maximum. But then it was Minkowski, who used to be Einstein's professor in 1907, who realized the most elegant way of thinking about
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Look, I'm with you. Between nuclear and bioweapons, it is a little bit surprising that we haven't caused enormous devastation. Of course, we did drop two atomic bombs on Japan, but compared to what could have happened or could happen tomorrow… It could be much worse.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yeah, but that's exactly what you would say right before we went too far.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I think it's a fascinating topic. I mean, that's why I'm thinking about these things these days rather than the papers that I was describing to you before. You know, all of those papers I described to you before are guesses. Like, what if the laws of physics are different in the following way? And then you can work out the consequences.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
At some point in my life, I said, like, what is the chance I'm going to guess right? You know, Einstein guessed right. Steven Weinberg guessed right. But there's a very small number of times that people guessed right. Whereas with this emergence of complexity from simplicity, I really do think that we haven't understood the basics yet. I think we're still kind of pre-paradigmatic.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
There have been some spectacular discoveries. People like Jeffrey West at Santa Fe and others have really given us true insights into important systems. But still, there's a lot of the basics I think are not understood. And so searching for the general principles is what I like to do. And I think it's absolutely possible that
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I mean, to be a little bit more substantive than that, I think this is kind of a cliche. I think the key is information. And I think that what we see through the history of the universe as you go from simple to more and more complex is really subsystems of the universe figuring out how to use information. to do whatever, to survive or to thrive or to reproduce.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I mean, that's the sort of fuel, the leverage, the resource that we have, for a while anyway, until the heat death, but that's where the complexity is really driven by.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So for those of the listeners who don't know, viewers, cellular automata come from imagining a very simple configuration. For example, a set of ones and zeros. along a line. And then you met a rule that says, okay, I'm gonna evolve this in time. And generally the simplest ones start with just each block of three ones and zeros have a rule that they will determinously go to either one or a zero.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
this idea of Einstein's was to blend space and time together into space-time, to really imagine that there is no hard and fast division of the four-dimensional world in which we live into space and time separately. Einstein was at first dismissive of this. He thought it was just like, oh, the mathematicians are over-formalizing again. But then he later realized that
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And you can actually classify all the different possibilities, a small number of possible cellular automata of that form. And what was discovered by various people, including Stephen Wolfram, is some of these cellular automata have the feature that you start from almost nothing, like 000010000, and you let it rip. and it becomes wildly complex, okay? So this is very provocative, very interesting.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
It's also not how physics works at all, because as we said, physics conserves information. You can go forward or backwards. These cellular automata do not. They're not reversible in any sense. You've built in an arrow of time. You have a starting point, and then you evolve.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So what I'm interested in is seeing how, in the real world, with the real laws of physics and underlying reversibility, but macroscopic irreversibility from entropy in the arrow time, et cetera, how does that lead to complexity? I think that that's an answerable question. I don't think that cellular automata are really helping us in that one. So what is in that...
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Well, entropy is hard to localize. It's a property of systems, not of parts of systems, right? Having said that, we can do approximate answers to the question. The answer is black holes are huge in entropy. Let's put it this way. The whole observable universe that we're in had a certain amount of entropy before stars and planets and black holes started to form. 10 to the 88th.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I can even tell you the number, okay? The single black hole at the center of our galaxy has entropy. 10 to the 90th. Single black hole at the center of our galaxy has more entropy than the whole universe used to have not too long ago. So most of the entropy in the universe today is in the form of black holes.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
The interesting thing to me is that if you start with a system that is isolated from the rest of the universe, and you start it at low entropy, there's almost a theorem that says if you're very, very, very low entropy, then the system looks pretty simple because there's low entropy means there's only a small number of ways that you can rearrange the parts to look like that.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So if there's not that many ways, the answer is going to look simple. But there's also almost a theorem that says when you're at maximum entropy, the system is going to look simple because it's all smeared out. If it had like interesting structure, then it would be complicated, right? So entropy in this isolated system only goes up. That's the second law of thermodynamics.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But complexity starts low, goes up, and then goes down again. Sometimes people mistakenly think that complexity or life or whatever is fighting against the second law of thermodynamics, fighting against the increase of entropy. That is precisely the wrong way to think about it. We are surfers riding the wave of increasing entropy. We rely on increasing entropy to survive.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
That is part of what makes us special. This table maintains its stability mechanically. By which I mean there's molecules, they have forces on each other, and it holds up. You and I aren't like that. We maintain our stability dynamically by ingesting food, fuel, right? Food and water and air and so forth. Burning it, increasing its entropy. We are non-equilibrium quasi-steady state systems.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
if space-time is a thing, it can have properties. And in particular, it can have a geometry. It can be curved from place to place. And that was what let him solve the problem of gravity. He had previously been trying to fit in What we knew about gravity from Newtonian mechanics, the inverse square law of gravity, to his new relativistic theory, it didn't work.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
We are using the fuel the universe gives us in the form of low entropy energy to maintain our stability.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I think it is, and I think we don't. It's possible to have it. I don't think we yet have it. Because, you know, in part because complexity is not a univalent thing. There's different ideas that go under the rubric of complexity. One version is just a comalgor of complexity, right? If you have a configuration or a string of numbers or whatever, can you compress it?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
so that you have a small program that will help with that. That's the common rule of complexity. But that's the complexity of a string of numbers, okay? It's not like the complexity of a problem right, computational complexity, the traveling salesman problem, or factoring large numbers. That's a whole different kind of question that is also about complexity.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So we don't have a sort of unified view of it.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yeah, absolutely.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yeah.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
We're working on various things. The glib thing that I'm trying to work on right now with a student is complexogenesis. How does complexity come to be if all the universe is doing is moving from low entropy to high entropy?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
It's a good name. Yeah, I like the name. I just got to write the paper.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Well, I think it comes in stages, right? So I think that if you go from the – I'm, again, a physicist. So biologists studying evolution will talk about how complexity evolves all the time, the complexity of the genome, the complexity of our physiology, right? But they take for granted that life already existed and entropy is increasing and so forth. I want to go back to the beginning.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
and say the early universe was simple and low entropy and entropy increases with time and the universe sort of differentiates and becomes more complex. But that statement, which is indisputably true, has different meanings because complexity has different meanings. So sort of the most basic primal version of complexity is what you might think of as configurational complexity.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
That's what Komogorov gets at. How much information do you need to specify the configuration of the system? then there's a whole nother step where subsystems of the universe start burning fuel, right? So in many ways, a planet and a star are not that different in configurational complexity. They're both spheres with density high at the middle and getting less as you go out.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But there's something fundamentally different because the star only survives as long as it has fuel, right? I mean, then it turns into a brown dwarf or a white dwarf or whatever. But as a star, as a main sequence star, It is an out of equilibrium system, but it's more or less static, right?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Like if I spill the coffee mug and it falls, in the process of falling, it's out of equilibrium, but it's also changing all the time. A specific kind of system is where it looks sort of macroscopically stationary, like a star, but underneath the hood, it's burning fuel to beat the band in order to maintain that stability. So as stars form, that's a different kind of complexity that comes to be.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So the final leap was to say gravity is the curvature of space-time. And that statement is basically general relativity.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Then there's another kind of complexity that comes to be, roughly speaking, at the origin of life. Because that's where you have information really being gathered and utilized by subsystems of the universe. And then arguably, there's any number of stages past that. I mean, one of the most obvious ones to me is… We talk about simulation theory, but you and I run simulations in our heads.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
They're just not that good, but we imagine different hypothetical futures, right? Bacteria don't do that. So that's the kind of information processing that is a form of complexity. So I would like to understand all these stages and how they fit together. Yeah, imagination. Yeah, mental time travel.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
There's an argument to be made that literally what separates human beings from other species on Earth is our ability to imagine counterfactual hypothetical futures.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Everyone has their own favorite little feature, but that's why I said there's an argument to be made. I did a podcast episode on it with Adam Bully. It developed slowly. I did different podcasts. Sorry to keep mentioning podcast episodes I did, but Malcolm McIver, who is an engineer at Northwestern, has a theory about one of the major stages in evolution is when fish first climbed on the land.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I mean, of course, that is a major stage of evolution, but in particular, there's a cognitive shift. Because when you're a fish swimming under the water, the attenuation length of light in water is not that long. You can't see kilometers away. You can see meters away. And you're moving at meters per second.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So all of the evolutionary optimization is make all of your decisions on a timescale of less than a second. When you see something new, you have to make a rapid fire decision what to do about it. As soon as you climb onto land, you can essentially see forever, right? You can see stars in the sky. So now a whole new mode of reasoning exists.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yes.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
opens up where you see something far away and rather than saying look up table i see this i react you can say okay i see that thing what if i did this what if i did that what if i did something different and and that's you know the birth of imagination eventually you've been critical on panpsychism yes you've noticed that right can you make the case for panpsychism and against it
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I had David Chalmers, who's one of the world's great philosophers, and he is panpsychism curious. He doesn't commit to anything, but he's certainly willing to entertain it. Philip Goff, who I've had, who's a great guy, but he is devoted to panpsychism. In fact, he is almost single-handedly responsible for the upsurge of interest in panpsychism in the popular imagination.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And the argument for it is supposed to be that there is something fundamentally uncapturable about about conscious awareness by physical behavior of atoms and molecules. So the panpsychist will say, look, you can tell me maybe someday through advances of neuroscience and what have you, exactly what happens in your brain and how that translates into thought and speech and action.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
What you can't tell me is what it is like to be me. You can't tell me what I am experiencing when I see something that is red or that tastes something that is sweet. You can tell me what neurons fire, but you can't tell me what I'm experiencing. That first-person inner subjective experience is simply not capturable by physics.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I know, that's hard. That's a little bit of a joke there, right? Because we all give Einstein a lot of credit. But then we also... partly based on fact, but partly to make ourselves feel better, tell ourselves a story about how later in life, Einstein couldn't keep up.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And therefore, this is an old argument, of course, but then the therefore is supposed to be, I need something that is not contained within physics to account for that. And I'm just going to call it mind. We don't know what it is yet. We're going to call it mind. And it has to be separate from physics. And then there's two ways to go.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
If you buy that much, you can either say, okay, I'm going to be a dualist. I'm going to believe that there's matter and mind and they are separate from each other and they are interacting somehow. Or that's a little bit complicated and sketchy as far as physics is going to go. So I'm going to believe in mind, but I'm going to put it prior to matter. I'm going to believe that mind comes first.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And the consciousness is the fundamental aspect of reality and everything else, including matter and physics, comes from it. That would be at least as simple as physics comes first, right? Now, the physicalist, such as myself, will say, I don't have any problem explaining what it's like to be you or what you experience when you see red. It's a certain way of talking, right?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
about the atoms and the neurons, et cetera, that make up you. Just like the hardness or the brownness of this table, these are words that we attach to certain underlying configurations of ordinary physical matter. Likewise, sadness and redness or whatever are words that we attach to you to describe what you're doing.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
When it comes to consciousness in general, I'm very quick to say I do not claim to have any special insight on how consciousness works other than I see no reason to change the laws of physics to account for it.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I almost never use the word illusion. Illusion means that there's something that you think you're perceiving that is actually not there. Like an oasis in the desert is an illusion. It has no causal efficacy. If you walk up to where the Oasis is supposed to be, you'll say you were wrong about it being there. That's different than something being emergent or non-fundamental, but also real.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Like this table is real, even though I know it's made of atoms. That doesn't remove the realness from the table. I think the consciousness and free will and things like that are just as real in tables and chairs.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
There were younger people doing quantum mechanics and quantum field theory and particle physics, and he was just sort of unable to really philosophically get over his objections to that. And I think that that story about the latter part is completely wrong, like almost 180 degrees wrong. I think that Einstein understood quantum mechanics as well as anyone, at least up through the 1930s.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
It leads you to draw incorrect conclusions about the world.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Sure, but your understanding of the world in a way that gives you power over it and influence over it is decreased rather than increased by believing in that oasis. That is not true about consciousness or this table.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But that's different than imagining that humans are flying. Right. In terms of counterfactuals in the future, absolutely. Imagination is crucially important. But that's not an illusion. That's just a... Oh, okay.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Well, I think there's like part of that idea that is perfectly respectable and part of it that is perfectly nonsensical. And I'm not even going to try to steal away the nonsensical part. The real part to me is what is called structural realism. So We don't know what the world is at a deep fundamental level, right? Let's put ourselves in the minds of people living 200 years ago.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
They didn't know about quantum mechanics. They didn't know about relativity. That doesn't mean they were wrong about the universe that they understood. They had Newton's laws, right? They could predict what time the sun was going to rise perfectly well. In the progress of science, the words that would be used to give the most fundamental description
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
of how you were predicting the sun would rise changed because now you have curved space-time and things like that, right? And you didn't have any of those words 200 years ago. But the prediction is the same. Why? Because that prediction, independent of what we thought the fundamental ontology was, the prediction pointed to something true about our understanding of reality.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
To call it an illusion is just wrong. I think. We might not know what the best, most comprehensive way of stating it is, but it's still true.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
No, I think that was completely an illusion. I think it was a very, very reasonable illusion to be under. There are illusions. There are, you know, substantive claims about the world that go beyond predictions that we can make and verify, which later turned out to be wrong. And the existence of God was one of them.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I think that his philosophical objections to it are correct. So he should actually have been taken much more seriously about that. And what he did, what he achieved in trying to think these problems through is to really basically understand the idea of quantum entanglement, which is kind of important these days when it comes to understanding quantum mechanics.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
If those people at that time had abandoned their belief in God and replaced it with a mechanistic universe, they would have done just as well at understanding things, right? Again, because there are so many things they didn't understand, it was very reasonable for them to have that belief. It wasn't that they were dummies or anything like that.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But that is, as we understand the universe better and better, some things stick with us, some things get replaced.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Naturalism is just the idea that all that exists is the natural world. There's no supernatural world. You can have arguments about what that means, but I would claim that the argument should be about what the word supernatural means, not the word natural. The natural world is the world that we learn about by doing science.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
The poetic part means that you shouldn't be too, I want to say, fundamentalist about what the natural world is. As we went from Newtonian spacetime to Einsteinian spacetime, Something is maintained there. There is a different story that we can tell about the world. And that story in the Newtonian regime, if you want to fly a rocket to the moon, you don't use general relativity.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
You use Newtonian mechanics. That story works perfectly well. The poetic aspect of the story is that there are many ways of talking about the natural world. And as long as those ways latch on to something real and causally efficacious about the functioning of the world, then we attribute some reality and truth to them.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
It's doing double duty a little bit, so that's why it's confusing. The more obvious respectable duty it's doing is that tables are real. Right. Even though you know that it's really a quantum field theory wave function, tables are still real. They're a different way of talking about the underlying deeper reality of it.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
The other duty it's doing is that we move beyond purely descriptive vocabularies for discussing the universe onto normative and prescriptive and judgmental ways of talking about the universe. This painting is beautiful. That one is ugly. This action is morally right. That one is morally wrong. These are also ways of talking about the universe. They are not fixed by the phenomena.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
They are not determined by our observations. They cannot be ruled out by a crucial experiment. But they're still valid. They might not be universal. They might be subjective. But they're not arbitrary. And they do have a role in describing how the world works.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
No, I don't think that's what it is. I think that what we mean by aesthetics or morality are we're attaching categories, properties, to things that happen in the physical world. And there is always going to be some subjectivity to our attachment and how we do that. And that's okay. And the faster we recognize that and deal with it, the better off we'll be.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Now, it's true that in the 40s and 50s, he placed his efforts in hopes for unifying electricity and magnetism with gravity that didn't really work out very well. All of us try things that don't work out. I don't hold that against him. But in terms of IQ points, in terms of trying to be a clear-thinking physicist, he was really, really great.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
That will absolutely be helpful in explaining why certain people have certain moral beliefs. It won't justify those beliefs as right or wrong.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
That's a very pothead question, Lex, but that's okay. We'll do it as possible. The answer is yes. I think that there's no, I think that we're part of the physical world and the natural world. So physicalism would have been just as good a word to use as naturalism, maybe even a more accurate word, but it's a little bit more off-putting.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So I do want a snappier, more attractive label than physicalism. Are there limits to science? Sure. We just talked about one, right? Science can't tell you right from wrong. You need science to implement your ideas about right and wrong. If you are functioning on the basis of an incorrect view of how the world works, you might very well think you're doing right, but actually be doing wrong.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But all the science in the world won't tell you which action is right and which action is wrong.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But there's an instrumentalist view here. You have to first decide what your goals are, and then science can help you achieve those goals. If your goals are horrible, science has no problem helping you achieve them. Science is happy to help out.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I don't. I'm really terrible at that. My strategy for finding time is just to ignore interruptions in emails. But it's a different time every day. Some days it never happens. Some weeks it never happens.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Right. No, I get that. Yeah, I do. And yeah, it's just like everyone has their foibles or whatever. So I'm not able to do that. Therefore, I have to just figure it out on the fly.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yeah, get behind a computer. And my way of doing it, so my wife, Jennifer, is a science writer. But it's interesting because our techniques are entirely different. She will think about something, but then she will free write. She'll just sit at a computer and write. Like, I think this, I think this.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And then that will be vastly compressed, edited, rewritten or whatever until the final thing happens. I will just sit there silently thinking for a very long time. And then I will write what is almost the final. So a lot of it happens. There might be some scribbles for an outline or something like that, but a lot of it is in my brain before it's on the page.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yeah, quanta and fields, which is actually mostly about quantum field theory and particle physics. That's coming out in May. And that is, I'm letting people in on things that no other book lets them in on. So I hope it's worth it. It's a challenge because there's a lot of equations.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
There's a lot of equations. Book two goes further in those directions than book one did. So it's more cool stuff. It's also more mind-bending. It's more of a challenge. Book three that I'm writing right now is called Complexity and Emergence. Oh, wow. And that'll be the final part of the trilogy.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Well, but, you know, I'm not trying to be cutting edge. In other words, I'm not trying to speculate in these books. Obviously, in other books, I've been very free about speculating. But the point of these books is to say things that 500 years from now will still be true. And so there are some things we know about complexity and emergence, and I want to focus on those.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And I will mention, I'm happy to say, this is something that needs to be speculated about, but I won't pretend to be telling you what one is the right one.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I try. I mean, look, these three books, the Biggest Ideas books, are absolutely an experiment. They're going to appeal to a smaller audience than other books will. But that audience should love them. Like, my 16-year-old self would have been so happy to get these books, I can't tell you.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yeah, no, these are great questions. And I've sort of struggled and changed my techniques over the years. It's over a five-year-old podcast. I might be approaching six years old now. I started out over-preparing when I first started. I had a journey that I was going to go down. Many of the people I talked to are academics or thinkers who write books, so they have a story to tell.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I could just say, okay, give me your lecture, and then an hour later, stop, right? Yeah. So the mistake is to sort of anticipate what the lecture would be and to ask the leading questions that would pull it out of them. What I do now is much more. Here are the points here, like the big questions that I'm interested in. And so I have a much sketchier approach.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yeah, that's a great question. I think that if you want to make the case for Einstein's greatness, which is not hard to do, there's two things you point at. One is in 1905, his famous miracle year, he writes three different papers on three wildly different subjects, all of which would make you famous just for writing that one paper. Special relativity is one of them.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
outline to start and then try to make it more of a real conversation. I'm helped by the fact that it is not my day job. So I strictly limit myself to one day of my life per podcast episode on average. Some days take more. And that includes not just doing the research, but inviting the guests, recording it, editing it, publishing it. So I need to be very, very efficient at that, yeah.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
You enforce constraints for yourself in which creativity can emerge. That's right. That's right. And look, sometimes if I'm interviewing a theoretical physicist, I can just go in. And when I'm interviewing an economist or a historian, I have to do a lot of work.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yes, on both counts. Some people have so many things to talk about that you don't know where to start or finish, right? Others have a message. And one thing I discovered over the course of these years is the correlation with age. Like, there are brilliant people, and I try very hard on the podcast to sort of get all sorts of people, right, different ages and things like that.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And bless their hearts, the most brilliant young people are not as practiced at wandering past their literal research. They have less mastery over the field as a whole, much less how to talk about it. Whereas certain older people just have their patent answers, and that's kind of boring.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So you want somewhere in between the ideal person who has a broad enough scope that they can wander outside their specific papers they've written. But they're not overly practiced, so they're just giving you their canned answers.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
That's a great one. Again, it's evolved over time. So the Ask Me Anything episodes were first, when I started doing them, they were only for Patreon subscribers to both listen to and to ask the questions. But then I actually asked my Patreon subscribers, would you like me to release them publicly? And they overwhelmingly voted yes. So I do that. So the Patreon supporters ask the questions.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Everyone can listen. And also at some point, I really used to try to answer every question. But now there's just too many. So I have to pick. And that's fraught with peril. And my personal... standard for picking questions to answer is, what are the ones I think I have interesting answers to give for, right?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
So that both means if it's kind of the same old question about special relativity that I've gotten 100 times before, I'm not going to answer it because you can just Google that. It's easier. There are some very clear attempts to ask an interesting question that honestly just I don't have an answer to. Like, I read this science fiction novel. What do you think about it?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I'm like, well, I haven't read it, so I can't help you there. What's your favorite color? I could tell you what it is, but it's not that interesting. I try to make it a mix. It's not all physics questions, not all philosophy questions. I will talk about food or movies or politics or religion if that's what people want.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I keep suggesting that people ask me for relationship advice, but they never do. I don't think I've heard one. I'm willing to do it. I'm a little reluctant because I don't actually like giving advice. Um, but I do, but I'm happy to talk about those topics.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I want to, you know, I want to give several hours of, of, of talking and I want to try to say things that I haven't said before and keep it interesting. Keep it rolling. If you don't like this question, wait for the next one.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Brownian motion is another one, which is just, you know, the little vibrations of tiny little dust specks in the air. But who cares about that? What matters is it proves the existence of atoms. He explains Brownian motion by imagining their molecules in the air and deriving their properties. Brilliant.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Rarely, but occasionally, people will ask me a super insightful philosophy question. Like, I hadn't thought of things in exactly that way. And I try to be, you know, I try to recognize that. A lot of times, It's the opposite where it's like, okay, you're clearly confused and I'm going to try to explain the question you should have asked.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Right.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But the hard questions, I don't know. I don't actually answer personal questions very much. The most personal I will get are questions like, what do you think of Baltimore? That much I can talk about. Or how are your cats doing? Happy to talk about the cats in infinite detail. But very personal questions I don't get into.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yeah, no, very happy to talk about politics. I try to be clear on what is professional expertise, what is just me babbling, what is my level of credence in different things, where you're allowed to disagree, whether if you disagree, you're just wrong. And people can disagree with that also. But I do think, and I'm happy to go out on a limb a little bit.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I'm happy to say, look, I don't know, but here's my guess, right? I just did a whole solo podcast, which was exactly that. And it's interesting. Some people are like, oh, this was great. And there's a whole bunch of people like, why are you talking about this thing that you are not the world's expert in?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yeah, it's interesting because when people... react against you by saying, you are being arrogant about this. 99.999% of the time, all they mean is I disagree. That's all they really mean, right? You know, like at a very basic level, people will accuse atheists of being arrogant. And I'm like, you think God exists and loves you and you're telling me that I'm arrogant.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I think that all of this is to say, Just advice. When you disagree with somebody, try to specify the substantive disagreement. Try not to psychologize them, right? You know, try to say, oh, you're saying this because of this. Maybe it's true. Maybe you're right. But if you had an actual response to what they were saying, that would be much more interesting.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And then he basically starts the world on the road to quantum mechanics with his paper on – which, again, is given a boring label of the photoelectric effect – What it really was is he invented photons. He showed that light should be thought of as particles as well as waves. And he did all three of those very different things in one year. Okay.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And I once wrote a blog post. I think it was called The Grid of Disputation. And I had a two-by-two grid. And it's, are you someone I agree with or disagree with? Are you someone who I respect or don't? Right? And all four quadrants are very populated. And so what that means is there are people who I like. and I disagree with.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And there are people who agree with me and I have no respect for at all. The embarrassing allies quadrant, that was everyone's favorite. So, and I just think being honest, right? Like trying to be honest about where people are, but if you actually want to move a conversation forward, forget about whether you like or don't like somebody, explain the disagreement, explain the agreement.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But you're absolutely right. I completely agree. Like as a society, we are not very good at disagreeing. We instantly go to the insults.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Let's put it this way. When I teach courses... There's no more satisfying subject to teach than general relativity. And the reason why is because it starts from very clear, precisely articulated assumptions, and it goes so far, right? And, you know, when I give my talk, you can find it online. I'm probably not going to give it again. The book, one of the biggest ideas talk, right?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Was building up from, you don't know any math or physics. An hour later, you know, Einstein's equation for general relativity. And the punchline is the equation is much smarter than Albert Einstein because Albert Einstein did not know about the Big Bang. He didn't know about gravitational waves. He didn't know about black holes, but his equation did.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
And that's, I mean, that's a miraculous aspect of science more generally, but general relativity is where it manifests itself in the most absolutely obvious way.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Tragedy. He should have gotten maybe four Nobel Prizes, honestly. That one. He certainly should have got – the photoelectric effect was 100% worth the Nobel Prize because – and people don't quite get this – Who cares about the photoelectric effect? That's like this very minor effect. The point is his explanation for the photoelectric effect invented something called the photon.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
But the other thing that gets him genius status is, like you say, general relativity. So this takes 10 years from 1905 to 1915. He wasn't only doing general relativity. He was working on other things. He wrote, he invented a refrigerator. He did various interesting things. And he wasn't even the only one working on the problem.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
That's worth the Nobel Prize. Max Planck gets credit for this in 1900, explaining blackbody radiation by saying that when a little electron is jiggling in an object at some temperature, gives off radiation in discrete chunks rather than continuously. He didn't quite say that's because radiation is discrete chunks, right? It's like having a coffee maker that makes one cup of coffee at a time.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
It doesn't mean that liquid comes in one cup quanta, right? It's just that you are dispensing it like that. It was Einstein in 1905 who said light is quanta, and that was a radical thing. So that clearly, that was not a mistake. But also special relativity clearly deserved the Nobel Prize and general relativity clearly deserved the Nobel Prize.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Not only were they brilliant, but they were experimentally verified, like everything you want. So separately, you think?
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Yeah, absolutely.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
Whatever the explanation there. Edwin Hubble never won the Nobel Prize for finding the universe was expanding.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I think the Nobel Prize has enormous problems. I think it's probably a net good for the world because it brings attention to good science. I think it's probably a net negative for science because it makes people want to win the Nobel Prize.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
There were other people who suggested relativistic theories of gravity. But he really applied himself to it. And I think as your question suggests, the solution was not a matter of turning a crank. It was something fundamentally creative.
Lex Fridman Podcast
#428 – Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens
I appreciate it. Thanks very much for having me on. Now that you're a big deal, still having me on. Thank you, Sean.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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That's B-A-B-B-E-L dot com slash mindscape. Rules and restrictions may apply. And how deterministic is this whole RNA goes through the ribosome and becomes protein process? I mean, I have this feeling that the world at this nanoscale is a lot more chaotic and jumpy than what I'm used to visualizing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
This reminds us, of course, that you started as a physicist, like all the great biologists. Well, I don't know. I think there are lots of biologists who have nothing to do with physicists. But is it... The other question I had is... every cell in my body has a ribosome in it, a single one. Thousands of ribosomes. Thousands of ribosomes. Oh, okay, good.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
And are all of those ribosomes identical to each other or do different cells have different versions?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
Okay.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
What about between species? Are our ribosomes the same as in a mollusk?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
Hello, everyone. Welcome to the Mindscape Podcast. I'm your host, Sean Carroll. Is it possible that listening to the Mindscape Podcast will help you live forever? As we like to say here at Mindscape, sure, it is possible. It is not especially likely.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
And you mentioned regulation, which I take it to be sort of like gene regulation. I mean, there's sort of external factors that can turn knobs.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
But it's not necessarily unlikely that listening to a podcast like this, or more generally, just doing things to keep your mind active, not just active doing the same thing over and over again, but doing different kinds of things, thinking about things in new ways, being exposed to new ideas and ways of thinking—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
If I started with a stem cell, for example, in a human being and let it develop into some specialized component cell, would its ribosome also be altered along the way? Or is it more or less the same?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
How close are we, if the ribosome is a million atoms, to knowing what all those atoms are and being able to just put it on a computer and simulating it?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
can help you live just a little bit longer, as well as of course more down-to-earth things like eating less food and exercising and stuff like that. It's a fascinating subject, right? We human beings, not only are we going to have only finite lifespans, but arguably we are the only species that knows that we have finite lifespans, that we are aware of our own mortality.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
Okay, very good. You know, it's funny. You must know Bonnie Bassler, the biologist at Princeton? Oh, yes. I don't know her personally, but of course I do offer. I once invited her to give a colloquium at Caltech, and I was struck by one of the graduate students after the colloquium said, it's depressingly easy in biology to come up with good questions we don't know the answers to in physics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
Yes, you know.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
Well, I would say exactly the opposite. I would say that biology is behind because it is harder, because it's messy, right? There's only so many elementary particles.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
And so I could kind of guess or envision how you go from thinking about ribosomes and molecular biology to death, because we need the constant success of these dynamical processes in our bodies to be working very, very efficiently and nearly flawlessly over the course of decades.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
So it's perfectly natural that we human beings would like to extend it, right? On the one hand, We have an instinct built in. We want to survive and live. On the other hand, we also have a death sentence built in. And of course, science has already done a lot to extend lifespans, mostly through better health and nutrition and safety and things like that. But it's interesting.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
But let me not just guess, let me just ask you, what is your path from thinking about ribosomes to writing a book about why we die?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
The average human lifespan has absolutely increased, but the maximum human lifespan has not increased very much. People live to be around 120 at most, and that's as true now as it was 100 or 200 years ago. And we think that we understand roughly why that's true. There's a lot going on in our bodies that is not only not meant to let us live forever, but is meant to not let us live forever.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
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291 | Venki Ramakrishnan on the Biology of Death and Aging
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
There you go. That's perfectly okay. That's completely a good moral stance. I can back you up on that. Let's get a feeling, let's work our way into this understanding about why essentially all higher organisms have death kind of programmed into them, right? It is part of their design in some sense. You know, my impression is unicellular organisms never die of old age.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
I mean, how could they, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
We basically have an expiration date on each of us. And we don't like to have that expiration date. So science and technology are trying to think about ways to make us live longer and longer. It's difficult because there's not a single switch inside. It's not like there's one thing going on that says, yeah, you're going to do this much stuff and then you're going to die.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
So, okay, but now you've sort of changed my mind in different directions. So you're pointing out that even unicellular organisms can die of old age, because I hadn't quite appreciated, but now that you mention it, I had heard before that when a unicellular organism splits, the two copies are not exactly identical. There is some differentiation between them. But then...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
even complicated multicellular organisms, there's many layers to the death process in some sense. So I guess what I'm striving toward is, is there some difference in how we think about death when you go from unicellular to multicellular life? Is that from the very early stages?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
There's so many systems interacting with each other from the molecular biology level, the level of individual DNA strands and things like that, up to the various systems that are bigger systems in our cells and our organs that are keeping us working together coherently, right? So reducing aging, extending lifespans turns out to be a very difficult problem.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
So who better to talk to about it with than today's guest, Venky Ramakrishnan, is a Nobel Prize-winning... molecular biologist. He won the Nobel Prize for his work understanding the ribosome. And so for irresistible reasons, I couldn't help but talk about the ribosome quite a bit in this podcast.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
It does make it sound like we could, not we personally, but our bodies could do this more efficiently to our actual grown-up selves, right? Like we're spending all of this effort to make sure the baby is brand new, but our cells allow our own bodies to age and die, which I guess has a kind of obvious evolutionary explanation. Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
And there's this well-known puzzle, but I think it's a solvable puzzle. Why don't larger animals get cancer more often? I mean, after all, they have more cells in them. So if there's a rate of a cell becoming cancerous, it should happen all the time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
Venky was part of a group of people who helped sort of figure out the function and structure of the ribosome. If you've ever been told that there's information in DNA that contains your genome, and then it gets transcribed into RNA and then the RNA figures out how to make proteins.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
Yeah, it doesn't quite suggest a cure for cancer, right? Because we'd have to change all of the DNAs and all of our cells. No, no.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
That's exactly true, but the thing that takes the information from the RNA and makes the proteins, the actual assembly area, is the ribosome. The ribosome is the thing that makes the proteins given the template that the RNA provides. So it's super important. It's a kind of a really important part of everything that we think about in biology as it is practiced here on Earth.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
It's a harsh mistress, evolution. So you mentioned the telomere shortening. I think that's probably the thing that pops up in my mind most clearly when people say, Things happen as you grow older that there's aging going on in individual cells. Is that the main thing, or are there many different kind of things that add up to aging?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
And here's the guy who helped figure out, people knew it existed, but he helped figure out how it works. And it's not surprising that once you do that, you turn your attention to this even grander question of aging, because of course, copying DNA, copying genetic information from cell to cell, turns out to be something that ages, right? That process can only go on so far.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
And it does sound, on the one hand, as if any one of these aspects, like we could target or we could learn how to delay or fix or repair, whatever it is. But there's just so many of them that it really is a quintessentially complex system where all the parts matter.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
As we'll talk about, even single-celled organisms can die of old age in a very real sense. When they divide, they don't divide completely equally. They divide sort of into an older part and a younger part, and the older part can die. So we talk about a lot of stuff.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
Well, it certainly does give me the impression that simply getting a blood transfusion with the blood of young children is not going to make me younger. Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
I remember.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
Venky has a new book called Why We Die and How We Live, The New Science of Aging and Longevity, where he talks not just about the molecular biology, but about lots of things, about the systems, larger scale biology, but also the technology, ideas for possibly extending life, and the philosophy. What does it mean to us that we're all going to die? Well worth checking out the book.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
Well, I want to get to that, but just one tiny question on the mouse. It wasn't just a blood transfusion the mouse got. It literally was sharing blood with a younger mouse, and that sounds like a big difference. Yes.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
Do you have any feelings about what might be the best science fiction-y but plausible way of slowing, stopping, reversing aging? I mean, I know that we don't have any silver bullets here, and we have a lot of hype, like you said. What are the more respectable ways to think about that very ambitious goal?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
If you're in the London area, it will also be well worth checking out Venky and others at New Scientist Live, which is going to happen in London from Saturday, October 12th through Monday, October 14th, 2024. It's a great event, plenty of good talks and demonstrations and things like that. I've spoken there before. Sadly, I can't be there this year, but I highly encourage you to go.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
What exactly is involved in cellular reprogramming? That sounds hard.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
And whether or not you can do that, you can listen to this episode. So let's go. Thank you, Ramakrishnan. Welcome to the Mindscape Podcast. Thank you. It's a pleasure to be here. We're going to talk about the new book that you have out. It's still this year, I think, 2024, on why we die. That's a cheerful topic to think about, I know. The subtitle is not so bad.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
Okay. I mean, I have a lot of cells, so it sounds like a complicated process, but worth looking into. In the meantime, is there anything more down to earth that an individual can do to slow down their own aging? Sure. So it turns out
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
It's too bad. It's just not the answer I want to hear. I don't want to restrict my caloric intake. Oh, right.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
Yeah, the subtitle is always where, you know, you tell the truth. But I can't help but start with the ribosome. You won the Nobel Prize for thinking about it. And I think I kind of have this impression the ribosome is an underrated part of human cellular molecular biology. So why don't you tell us what that is and why you think that little system is so interesting?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
I'm happy to sleep. I'm willing to exercise. I'm sad that I have to cut my calories, but I'll take all of these under advisement.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
Get to work, you folks. I guess let's wrap up with the philosophical questions, because one of the things I liked about the book is that you're totally willing to discuss these bigger picture questions. Like we already said, the fact that human beings are perhaps unique in appreciating not just the reality of death, but their own individual mortality.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
I mean, have you put a lot of thought into how that affects who we are? Is death important not only to our biology, but to the meaningfulness of our lives?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
I like the idea implicit in what you just said that doing a podcast keeps you young because you have to talk to all sorts of different kinds of people and shake up your brain in different ways.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
And I think the same thing goes for the audience, too. Listening to Mindscape will keep you young. I hope so, yeah. That's a great thought to end on. So thank you, Ramakrishnan. Thanks so much for being on the Mindscape podcast.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
So it reminds me a little bit of astronomy, which is where I grew up, in the sense that, you know, back in the day, you would get this little set of data about the brightness of a star over time, and astronomers would spin this amazingly detailed story about what must be happening. And without an image, like, oh, there's a disk, and it's accreting and things like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
And you're stuck in the same situation. At least we were stuck a few decades ago when it comes to molecular biology. Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
So can we at this point basically take a photograph or an image of something as, it's a million atoms, but it's still pretty tiny, a ribosome?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
Exactly. I mean, when you first saw something approaching an image from an electron microscope or whatever of a ribosome... Because we're using crystallography.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
I mean, we're very used to seeing images of molecular structures that have been drawn by a human being, right? Because we've worked out what the structure is, so we draw, we've seen pictures of double helices, etc. Right. When you see the actual image, are you more struck by, wow, that is exactly what I expected? Or no, no, no, it's just my visualization was kind of off.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
291 | Venki Ramakrishnan on the Biology of Death and Aging
And so the story that we're told is that the DNA in a modern organism, DNA is a good storage unit, right? It's relatively stable. And then it zips open, transfers the info over to the RNA, and then the RNA walks over to the ribosome and makes some proteins. Is that still basically the story?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
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294 | Addy Pross on Dynamics, Stability, and Life
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294 | Addy Pross on Dynamics, Stability, and Life
That's B-A-B-B-E-L dot com slash mindscape. Rules and restrictions may apply. So dynamic kinetic stability, DKS, those are our buzzwords here. I like it. But in the thermodynamic case, it is clear to me what is the fuel for making this happen, right? You have some free energy, like whether it's from the sun or whether it's from glucose that we consume as living beings or what have you. What is it?
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294 | Addy Pross on Dynamics, Stability, and Life
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
Do you have an end?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
Hello, everyone, and welcome to the Mindscape Podcast. I'm your host, Sean Carroll. In physics, we're very used to talking about balls rolling down hills. This is one of our paradigmatic examples of a physical system that you can study to death.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
So this sounds like, I know this is a distraction, but it sounds like it would be super interesting to roboticists. Isn't this a much better way to build a robot with flexible materials that can sort of become rigid upon command rather than just building them out of metal and plastic that break and can't be repaired?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
It took nature a long time to do it, to be fair. That's true. That's true. So let me try to get a... if it's possible, visual representation of what's going on here. I know what a fountain looks like. In these chemical fountains or these DKS states, what is it that the eye or the audience should picture going on, like in a test tube or whatever the context is?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
And it's very familiar in your everyday life that if a ball rolls down a hill and it comes down to the valley at the bottom of the hill, eventually it will stop there. It might roll around a little bit, bump into some things, but it will come to rest. And if you just took your first year physics course straightforwardly to heart, it would say that that shouldn't happen because energy is conserved.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
We certainly haven't made things in the lab that would really qualify as completely ab initio life. But I take it that we have made these DKS states, these dynamically kinetically stable states. And so I'm just saying, is there a pattern? Is it spatially uniform or does it look pretty?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
Well, good. So I think that links us up to life once again. So I take your point that we are examining what is in effect a new state of matter, this dynamic, kinetically stable kind of stuff. And there seems to be an obvious connection to how life is and presumably began. But for those of us who are not experts, fill us in on that. maybe the conventional wisdom about how life began.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
I know there are different schools of thought about replication and metabolism and things like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
If a ball rolls down the hill one way, it will roll up the hill the other way to exactly the height that it started at originally because of conservation of energy. Of course, no one's really worried about this. We know that in the real world there is friction, there is dissipation, there's air resistance. The ball makes noise and that generates heat and things like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
So the energy is dissipated into the environment and it makes perfect sense to us that the ball ends up on the bottom of the hill. Why am I telling you this? Because physicists have a way of thinking about structures that persist for extended periods of time. Stable structures, in other words. The ball rolling down a hill and getting to the bottom of the valley is a paradigmatic example.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
Yeah, that makes perfect sense to me because in the discussions of metabolism first and replication first, it always was clear to me that you would eventually need both, whichever one came first. And there was this looming problem of how to link them up together. How did an RNA molecule build an engine or how did an engine start replicating itself?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
And that seemed like just as hard as getting either one of them to start.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
Somewhere in the audience right now. They're there. Or maybe here. Maybe it's one of the two of us. But, you know, it could be an audience member. So you're saying that that is not something we have – we're zeroing in on the right idea for that, you think?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
That ball is going to stay there unless someone picks it up or some other force comes along and moves it. In a world with friction... you can distinguish between the total energy of a system and what is called the free energy of the system, the energy that is available to do work. And that free energy is degraded, is used up by friction, entropy-increasing processes in general.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
Maybe it's worth saying a little bit about the relationship of ideas like entropy, organization, simplicity, complexity, things like that. It's something that I've talked about in the podcast quite a bit, but there's definitely this naive feeling that if all the universe does is increase in entropy, how could something organized like life ever come into existence?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
And I know that that's not a very good argument, but it's at least a little bit of a worry in the
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
So that ball rolling down to the bottom of the hill reaches a state of minimum free energy. There's nothing more that it can do but sit there. And that's how we understand stability. This... to no one's surprise, is not a good way of thinking about living beings. In particular, it's not a good way of thinking about the origin of life.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
That I absolutely agree with you there. I'm wondering if there's a way to help us understand when these DKS states happen. We all know what a fountain looks like, and you turn it on and you make it go. But apparently, from what you're saying, the whole idea of dynamically, kinetically stable states is a relatively recent one.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
Is there a trick, or is there some particular thing you have to do to make that occur?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
You and I, as organic creatures in our own right, individuals, are not minima of potential energy or even free energy. We are not sitting at the bottom of some metaphorical hill. Unlike the ball sitting at the bottom of the hill, we are internally quite dynamic.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
I do want to dig in a little bit more to this idea of simply out-reproducing your competitors. It sounds similar to an idea that we talked about recently with Blaise Aguera-Iarcas, who I think you also communicated with. And he has a computer program where it can do all these different things, and when it stumbles across reproduction and computation, that little bit takes over the whole space. And
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
Am I right in thinking you're advocating something similar, that once you have the right kind of DKS state and it learns to reproduce, that will start to take over?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
Good. So I guess then I would like to better understand stability then. I mean, there's stability because you've been mentioning stability and it has a lot of aspects like you've already pointed out. I am pretty darn stable, but is that what matters, my body? Or is it, you know, is the gene being passed down through generations and its stability what matters?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
Even if we try our best to sit still, still our breathing, slow down our heart rate, there's a billion little processes going on in our cells. The ATP is being generated. Blood is rushing from place to place. There's a lot going on. On slightly longer timescales, all of our atoms and molecules are going to be replaced. They're going to be a ship of Theseus kind of situation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
So just so I know what the jargon means, is my body a DKS system?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
going on where one by one, the actual bits of matter that make up you and me mostly get replaced, not 100%, but to a very great degree, maintaining the kind of pattern that we have. So this is a very different kind of thing than just minimizing the energy or the free energy of the system.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
So is this the moment where we should talk about how DNA is overrated?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
Today's guest, Adi Pras, is a chemist by training who became interested quite a while ago in the origin of life. And he wrote a book called What is Life? How Chemistry Becomes Biology, where he focuses on a particular idea that he and his collaborators have developed called dynamic kinetic stability.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
It's a way for a configuration of stuff to be stable, or at least pretty stable, but not because it's kind of mechanically stable, like the ball at the bottom of the hill, or even thermodynamically stable, like a box of gas in its equilibrium configuration,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
But a dynamically, kinetically stable system, DKS, as they call it, is one that is constantly renewed by resources from the outside world in order to maintain a stable configuration. And as we'll talk about in the podcast, it's a little bit different from the physics version of this, where you're constantly getting new energy from the outside world and
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
Yeah, maybe we can put these in terms similar to what—we had Chris Adami on the podcast not too long ago, and he wrote a book about information in biology and makes the claim that every biological organism has a huge amount of mutual information with its environment, not necessarily because it's thinking about the environment, but because it is adapted to survive in that particular environment.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
And this is exactly the point you were making earlier. Right.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
And is this a kind of teleology? I think you were hinting at that earlier. I mean, I think that I would certainly agree, but maybe I'm wrong with a conventional biological view that evolution is not typically forward thinking. It's not trying to solve a problem that hasn't arisen yet. It's just trying to survive in the present moment. Are you asking us to think beyond that paradigm?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
And I guess it makes sense that if you can begin to see glimmers of self-awareness in these persistent DKS systems, self-awareness broadly construed, then maybe it's not so surprising that you see self-awareness more narrowly construed and maybe even the beginnings of cognition and consciousness and things like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
In what Addy is talking about, you're constantly getting new chemicals from the outside world, new molecules, and running through them. And he makes the case that this kind of process is absolutely key to understanding the origin of life. The first sort of proto-living organisms were these dynamically, kinetically stable patterns of in chemical reactions, which developed the ability to reproduce.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
Okay, I mean, maybe can you say a little bit more explicitly about consciousness itself? I mean, consciousness, as you know, has just been something people have wondered about for a long time. Philosophers sometimes try to make it almost inexplicable. Where do you come down?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
I guess it makes perfect sense that a greater capacity to gather information about the environment and then process it helps you survive, right? That's not at all surprising. But then there's presumably some... competition or constraints or trade-offs because you don't want to see something new out there in the world and then be frozen with option paralysis by saying, what do I do?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
And then once you can reproduce, you can take over, right? You might not be individually as robust as the rest of the world, but you can reproduce. So you can make a whole bunch of copies of yourselves, and those copies of yourselves can adapt to their environments. They can learn about things. So there's a whole new way of surviving and persisting.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
I'm going to think about it, right? So these are always, in the real world, these are always sort of satisficing things where we do just well enough to get by rather than perfectly optimizing what's going on.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
And it's a somewhat deflationary view of consciousness in the sense that, if I'm understanding correctly, even bacteria have a tiny bit of awareness of themselves and their environments. And all we human beings are doing, we're just much better at it than the bacteria are. I think so.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
And as he emphasizes, persisting is what it's all about when it comes to existing in the world. So this is an interesting episode. It connects to other things that we've talked about, to the recent episode with Blaise Aguero y Arcas, to previous episodes with Stuart Bartlett and others about the origin of life with Sarah Walker.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
Well, it's a good sort of wrapping up point because that picture of mental aspects and biological aspects both playing a role is parallel kind of to the picture of the genome and the structure in the cell both playing a role. I mean, the lesson overall is that information flows and control systems are not one way in biology. It's back and forth.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
We all are just a part of the holistic cycle at the end of the day. That's a good place to end on. Eddie Pross, thanks so much for being on the Mindscape podcast.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
We don't understand the origin of life yet, but what we know is that it involves a whole bunch of different things, a whole bunch of different aspects. are going to be involved. And I think this new kind of stability is one of them. And at the end, we'll even talk about how consciousness comes into that game. So stay tuned for that. Let's go. So Eddie Prost, welcome to the Mindscape Podcast.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
Thank you, Sean. Great to be here. So let's start very, very broadly. We're going to work our way into some cool ideas, I know. But one of the topics that we need to discuss is what is life? You wrote a book with that title, right? What is your definition of what life is?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
Well, that's an interesting way to put it because I think, and you also mentioned stability and instability as both crucial features, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
I mean, as a physicist, if I didn't know that life existed, I know that's a difficult thought experiment to pull off, but I would think that probably most things in the universe either are sort of moving, like a planet orbiting the sun in a uniform way, or they come to rest, right? But life has this ability to sort of turn on its motion and turn it off, and that's kind of remarkable.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
Absolutely, yeah. And just to flesh that out a little bit, because I think this is something the audience might be interested in, you know, when you talk about the thermodynamic sense, I would even extend that to the more general physical sense, right? If you have some system that has an energy that depends on various parameters, and there's a minimum energy that it can have...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
then it's automatically stable because if you nudge it away from that minimum energy, it wants to come back. It'll oscillate around, right? And maybe, do you tell me whether I'm on the right track here? Are you saying that we've kind of been blinded by that? Like that's too easy? There might be other ways to really be stable than that simple energetic picture?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
In fact, I bet it has to be free energy. It has to be energy in a nice, useful form. Yes, correct. Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
294 | Addy Pross on Dynamics, Stability, and Life
This is at least related to the idea of, or at least similar to the idea of non-equilibrium steady states in thermodynamics, right? Where you have something that is relying on the use of low entropy energy that is then being dissipated, but its overall form is somehow stable over time. You're talking about something similar to that, but sort of an adjacent idea.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
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303 | James P. Allison on Fighting Cancer with the Immune System
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303 | James P. Allison on Fighting Cancer with the Immune System
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
And do tumors spread just because the cells in the tumor sort of get carried around by the blood system? It's a little more complicated than that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
And my understanding is that you started as a chemist, an actual chemist, more than a sort of biologist or medical person.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
Not enough, yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
Hello, everyone, and welcome to the Mindscape Podcast. I'm your host, Sean Carroll. Cancer is one of the most terrible things we have to deal with in human life. It's a potentially fatal disease, of course. You know, we're all going to die someday. That's something that maybe we can make our peace with. But unlike many other diseases, cancer seems arbitrary in ways that are hard to pin down.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
Well, I was going to ask, do the T cells in our body develop new receptors? Do they learn on the job, or does the body make new T cells?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
So the cell is sort of doing its own annual checkup at all times.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
It can happen to anyone. It can happen at any stage of your life. Young people can get it as well as old people. When you reach a certain stage of your life, like I have, not only do you have to worry about checking for it yourself, but you know people who have had cancer and even who have died because of it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
This is where my, uh, simple physics brain, uh, rebels at the complexity of all the networks inside the human body. It's kind of an amazing edifice.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
Well, there's a lot of stars, but stars are pretty similar to each other. There's 10 of the 22 stars out there, but, uh, you know, they're, they're not that different. There's no lock and key in there. I mean, I guess that's my question, that your talk about receptors reminds me of people who are trying to study smell and how we're sensitive to different kinds of molecules.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
Is it a similar kind of thing going on?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
And so the job of a T cell is to understand what the normal healthy cells are like and target anything that is not that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
But they do a pretty good job, like you said, and yet we still get cancer. So there's some reason why, I guess in principle, they can attack cancers, but they don't do as well as they could.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
So it's very natural that as a species, we put a lot of effort into figuring out what is going on, how to stop this. It turns out to be really, really difficult, as maybe you know.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
That helps because I did have the question, you know, do tumors or do cancer cells defend themselves? You know, they don't pass on their genes in some sense, but I guess the answer is, but they're versions of or made of ordinary cells which do have defense mechanisms.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
Today's conversation is going to be with one of the world's leaders in the field of fighting cancer, James Allison, who won the Nobel Prize a few years ago in physiology and medicine for one of the ways, one of the various techniques that we can use to attack cancer once it starts. The idea being rather than going in and just zapping the cells with radiation or chemicals or whatever...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
One impression I get from reading about these or talking to people is that everything is about switches, turning things on and off. Once you realize that every cell has the same DNA in it, I guess it makes sense because they do very different things, but it's all a matter of which parts of them are playing a role at this particular moment.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
How much, you know, it sounds like with the receptor stuff on the wall of the T cell, that's right down to the level of atomic and molecular structure, right? Is it very different how we're studying that now than when we're in like 1980s or whenever it was? Like, has the technology changed things?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
We don't mind a little bit of details here. You're allowed, like, if you really want to go into details, we'll go with you a little later.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
that we can use immunotherapy. In other words, we learn how to cajole the body's own existing immune system to fight the cancer tumors. And if this can work, it works in some cases, doesn't work in others yet. This is what we're studying and we'll talk about in the episode.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
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303 | James P. Allison on Fighting Cancer with the Immune System
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
I do love the idea that even before you really had any direct evidence of what it looked like, you could sit back and think, well, what should it look like to do the job that it does? In some sense, that's what people did for DNA, too.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
Well, are we at the level now where we take pictures of not just T cells, but the actual receptors that are on them?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
But it's not just a more kind of organic, natural way to fight the disease, but then the person who has had the therapy has that extra layer of protection against getting cancer going forward. You haven't just killed that tumor or most of that tumor. You've built up the body's defense systems. So, of course, that is, for real world purposes, a fascinating and important development.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
Pretty good. I mean, is this part of the sort of CRISPR revolution of gene editing?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
But I was actually going to ask about the role of simulations. I mean, in physics and astronomy, of course, that's what we do all the time. We simulate things. We test them against the data. I've always had the impression that in biology, the state of the art was that biological things are too complicated to do that and too specific and too individual.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
So we have to actually test the pharmaceutical in a living thing rather than just putting it on a computer.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
So we have this basic security force in our body of the T cells roaming around looking for interlopers. You mentioned a little bit about this already, but why is it that they aren't better at attacking cancer and how can we make them better? That seems to be the project, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
For science purposes, of course, it's also fascinating because, man, the body, very, very complicated, very, very complex networks of reactions and cells and proteins and molecules and all that going on. We learn a lot about it because we are motivated for reasons of making people healthier, but what we learn is also equally fascinating.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
So what is our goal as immunotherapists? Are we trying to teach the T cells to ignore some of these problems?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
Okay. I mean, I read a little bit about the T cells before talking to you, but I didn't read anything about myeloid cells. Maybe you should tell me something about that. It sounds like they're important.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
So we'll talk about how we got here, where we're going, and how I think the impression I get as an interested outsider is real progress is being made on one of the trickiest problems out there. So let's go. So James Allison, welcome to the Mindscape Podcast. Thank you. Glad to be here. I guess this is a big topic, right? I mean, you do research on cancer therapies and things like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
What are the myeloid cells? What's their role when everything is going well?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
And they have this spinoff effect that they can basically communicate the existence of a tumor to the T-cells?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
Right, if things are going badly. And isn't there also, this is my very vague understanding popping up, but you can get in trouble if you make too many T cells.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
And by the therapy, I mean, it sounds like what we're doing is sort of trying to regulate the amount and the sensitivity of these different cells in our immune system, presumably by giving people drugs?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
Let's start at the very lowest level here. We've all heard of cancer. It's bad. Something about cells dividing and going crazy. How do you think about what cancer is, broadly speaking?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
Right. I mean, I know that one of the most terrible things you can hear when you have cancer is that it has spread, right? It's spread around the body. So it sounds like maybe this kind of therapy will be more amenable to even dealing with that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
So I guess that answers my next question. How much is this in the clinic now? Is there a pill that you can take? Is this growing?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
And that's better than chemotherapy as we know it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
That is amazing. But so my immediate reaction is that 20%, 50, 55% numbers are on the one hand, super impressive. On the other hand, why not a hundred percent? What do we got to do?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
I guess the question I have is, is it the same phenomenon when we talk about different kinds of cancer? I mean, there's obviously a wide variety. I know some therapies work better than others. Is it accurate to call it one thing?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
And do I get, my impression is, or my guess would be that this kind of therapy might also have the benefit that can, you know, Thinking of vaccines as an analogy, it sticks around in the body and might help prevent what's coming next.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
Okay, so we're running to the end of the podcast, but so I'll ask one slightly crazier question. I mean, all these ideas about networks and switches and nonlinearities, I'm a complexity scientist, among other things. It just makes me think of the study of complex systems.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
But is your work and the work of other people trying to do what you do, is it just so focused on cancer and immunology that you don't have time to...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
Never satisfied. Well, you know, one of the goals of the podcast is to give young, curious people food for thought about areas that are exciting and changing very rapidly right now. You've certainly done that for us.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
It's exciting times. Absolutely. Jim Allison, thanks so much for being in the Mindscape podcast.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
That's a, that's a bass guitar that I'm very, very, very bad at. If, if we had more time or if you want to take another five minutes, I was going to say like, tell us the Willie Nelson story. Come on. It's so good.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
Congratulations on being the recipient of a miracle. It sounds like you deserved it there. All right. Once again, Jim Allison, thanks very much for being on the Mindscape podcast.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
Thanks.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
That's interesting. Actually, I don't think I knew that, that the rate of mutation in the tumor gets much larger. So as the tumor is growing, you're not just fighting one kind of cell.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
You already mentioned that it's a little bit surprising to you that the body lasts as long as it does and works as well as it does. I mean, I see that, and I also see someone else saying it's kind of amazing to me that bodies haven't learned to fight cancer better since it's all over the place.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
It doesn't matter. But some animal species are pretty good at avoiding cancer. It does seem to be possible. Do we understand that?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
This is very vague to me. Isn't there some paradox that larger animals you might expect to get cancer more easily because there's more cells, but in fact they get it more rarely?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
That's true. But mice, happily, we're able to give cancer to because that's where we do a lot of our tests.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
So how much do we know about, I know this is not, you sort of just very nicely explained why this is not what you care most about, but how much do we know about how tumors start? And is it just a myriad of various different reasons, or is there some central understanding?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
And you're obviously going to tell us about immunotherapies, but maybe put that in the context of other kinds of therapies. I mean, we've all heard of chemotherapy, radiation therapy, et cetera.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | James P. Allison on Fighting Cancer with the Immune System
Why are they good at killing cancer cells?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
287 | Jean-Paul Faguet on Institutions and the Legacy of History
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
287 | Jean-Paul Faguet on Institutions and the Legacy of History
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
287 | Jean-Paul Faguet on Institutions and the Legacy of History
So that I'm not afraid to participate in conversations. And here's a special holiday treat for our listeners. Right now, get up to 60% off your Babbel subscription, but only for our listeners at babbel.com slash mindscape. Get up to 60% off at babbel.com slash mindscape. That's B-A-B-B-E-L dot com slash mindscape. Rules and restrictions may apply. Right. So you start asking why it's different.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
287 | Jean-Paul Faguet on Institutions and the Legacy of History
One of the things you've looked at a lot is the legacy of colonialism, people coming in and pushing other people around, how that affects things. Before we get into your work, what is the conventional wisdom about that? Is the thought that where there is some colonial past that makes development faster or slower or better or worse?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
287 | Jean-Paul Faguet on Institutions and the Legacy of History
Yeah, I think that makes perfect sense. I'm glad that the field has gotten to that point. I mean, it's certainly not an argument about whether or not colonialism is good or bad, if only because there's a moral argument there, right? Like people should determine themselves.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
287 | Jean-Paul Faguet on Institutions and the Legacy of History
But we can still, as social scientists, ask, okay, what are the specific long-term legacy impacts of having that colonial background?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
287 | Jean-Paul Faguet on Institutions and the Legacy of History
Hello, everyone. Welcome to the Mindscape Podcast. I'm your host, Sean Carroll. Colonialism is an idea that is bandied about in the discourse these days, usually with the subtext that colonialism is bad. It is bad for the powerful, rich country to impose its will on some smaller, less well-equipped to defend itself part of the world.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
287 | Jean-Paul Faguet on Institutions and the Legacy of History
I mean, it's almost inevitable when you start looking more closely, you're going to find all sorts of little structures that were glossed over by the big picture that had been put forward, right? Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
287 | Jean-Paul Faguet on Institutions and the Legacy of History
So let's go deeper. Let's go to Colombia. I mean, let's go back to the 16th century, which is kind of amazing that we can ask questions about the impact of the 16th century on what was going on today. So what was going on in Colombia back in the 1500s?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
287 | Jean-Paul Faguet on Institutions and the Legacy of History
Please, we're here to go on.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
287 | Jean-Paul Faguet on Institutions and the Legacy of History
But, you know, it wasn't always thus that colonialism was thought of as bad. Maybe in the United States it has a bad rep. We started out as colonies and we needed to have a revolutionary war to overthrow the yoke of the British Empire.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
287 | Jean-Paul Faguet on Institutions and the Legacy of History
But there are other countries where they want to make an argument that by going into other parts of the world that are less enlightened, less developed, less rich than they are— They can bring an element of civilization, or they can spread laws or institutions. And even if it wasn't quite fair all the time, it wasn't all peaches and cream, maybe there's some lingering good effect.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
287 | Jean-Paul Faguet on Institutions and the Legacy of History
And so, yeah, I mean, I guess they could have defeated them if they had tried their best. But for whatever reason that we don't quite understand, because the history is written by the winners, we're not exactly sure why they didn't try their best.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
287 | Jean-Paul Faguet on Institutions and the Legacy of History
Okay. And so that means what? I mean, I guess it's tempting to think that now the Spanish rule over Colombia, but it's more complicated than that. I mean, they're not actually, there's not enough Spanish to really rule over Colombia.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
287 | Jean-Paul Faguet on Institutions and the Legacy of History
Now, let me not be ambiguous here. Colonialism is bad. I think it is bad. I think you could easily argue that it's bad purely on sort of moral ethical grounds. There should be a right of self-determination of countries. You can help them, but maybe you can help them without taking them over would be my perspective.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
287 | Jean-Paul Faguet on Institutions and the Legacy of History
And did most of the Spanish conquistadores imagine going back to Spain at some point? Were they purely just trying to extract and leave, or were they setting up a new life?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
287 | Jean-Paul Faguet on Institutions and the Legacy of History
But fortunately for the modern social scientist, there were not enough of them to comprehensively take over the whole country. So we have a situation where some locations had this system, which is basically slave labor, right? And some were left more or
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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But as a scientist, you also want to be careful and nuanced and empirically based and say, OK, maybe some bad things happened in the past under the name of colonialism or whatever. Were they entirely bad? Or were there aspects that actually were good? Was civilization actually brought? Or was literacy or better roads or something like that to a different part of the world? Well, guess what?
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Right. And so that's something that we who grew up and are familiar with the United States are just not quite familiar with. Like the U.S. government governs the whole country one way or the other.
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So the wonderfully ambitious, audacious question you want to ask is, can you go back into the historical record, look at where the Spanish were in control, where they weren't, and compare that to what things look like today? I mean, it would not be super surprising if the answer were, there's no relation. It's been hundreds of years since this has happened, but that's not exactly what we find.
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You can do some of that. You can ask these questions. The answers are that it's complicated. Lots of things go into these questions, and so there's no clean and crisp answer to be had.
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And it's interesting because I mean, I can't it's probably unfair. I can't help but think of the United States. Right. Where to a very good approximation. States that had slavery are less economically developed, you know, have worse universities, worse health care than states that did not have slavery or which abolished slavery relatively quickly. So I guess the moral is that it's complicated.
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But it's also a very difficult question to ask because if you talk about the different experiences of different countries, different countries have a lot of ways in which they're different geographically, in terms of resources, in terms of the culture and the institutions that are already there before the colonizers come in. So it's going to be hard to get very specific answers.
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I do want to note that if it were true, a trade of eternal salvation for a few decades of indentured servitude would actually be a good trade.
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Right. Exactly. OK. So – but it's very interesting. So the – You're explaining what's going on here in the sense that it's not the indentured servitude that led to better outcomes centuries later. But in order to get that system off the ground, you had to lay some groundwork in terms of institutions and infrastructure that actually did kind of linger on for a long time.
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Today's guest, Jean-Paul Foguet, is a political economist at the London School of Economics with a particular emphasis on Latin America. But he's interested in how different countries have developed over time and the legacy of history in playing out to the extent where we are today, right? We have all sorts of things going on in the world. Different countries are different from each other.
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Yeah, I mean, that's a very good point. So it's not necessarily that the colonialist institutions were better. It's that they were able to survive because the other areas were kind of run to the ground. Exactly. That's exactly right.
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And as a careful scientist, of course, I want to raise my hand and say, well, how do you know that the areas in which you're getting better institutions and better development weren't just better places to live? I mean, maybe there's a confounding variable that explains both without giving colonialism the causal power here.
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How much does it matter what the situation was 50 years ago, 100 years ago, 500 years ago, for that matter? How much is there a lingering historical impact, whether it's from colonialism or anything else? And I think that this is a great topic to talk about here on Mindscape for a couple of reasons. One is that the questions are super important and difficult to answer.
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We think we each have experience growing up in whatever country we grew up in. When you talk about the successes of government or of other social institutions, it's too easy to generalize from an n equals one kind of data set, right? You know your experience, and you want to— go from that to theorize about how things must be more generally. But science isn't like that.
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And then the answer is that when you control for all these things, yes, the encomienda did have a noticeable effect on modern development outcomes.
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Well, I mean, I'm sure there's many more things to say about this, but I don't want to miss the opportunity to also switch to your Bolivia paper, which is in some senses completely different. But in some sense, there is absolutely a similarity of sort of both spirit and answer.
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So in the case of Bolivia, we're asking a much more modern question and not even about, well, about political parties, I guess, is the short way of saying it.
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So even if it was not a democracy, even in those moments when Bolivia was a dictatorship, we still had these political parties.
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So I'm sorry, but it seems like they're kind of. two mysteries. One mystery is how that political system, party system, I got to be careful, it's not the political system that survived, it's the party system that survived. The party system, yes, exactly. And so both how it survived for so long and then why it collapsed are kind of both interesting questions.
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You got to actually dig into the data and you have to be able to compare differences from place to place. And that's exactly what Jean-Paul's work allows us to do. And the other thing that is fascinating about it is the methodology. You know, I love how good social scientists are at striving against the difficulties that you have in not being able to do controlled experiments.
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Like social scientists are not going to found a country and give it some terrible history just so they can actually figure out the impacts of that history hundreds of years later. So we'll talk about two specific case studies here. And as I said, Jean-Paul specializes in Latin America, South America. So we'll talk mostly about Colombia.
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So the pre-2003 party system did reflect that kind of familiar European left-right divide, but Bolivia didn't.
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As compared to Colombia, for instance? Oh, it's three. Three percent. Okay. Three percent. Very different.
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where there is a long colonial history going back to the 1500s and the Spanish conquistadores. And the great thing about this in terms of modern day social science is that some areas of what we now call Colombia were in fact governed by the Spanish, others were not. So you can ask the question, did that legacy of colonial domination in early Colombia in the 1500s, does it still manifest today?
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So in modern Bolivia, are there political parties just organized along different cleavages?
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agree or at least work with people you don't agree with everything about. I mean, the idea of a political party, especially in a presidential system like ours, where only two can be viable at any one time, is asking a lot. I mean, why should, like you said, why should our opinions about economics line up, correlate with our opinions about cultural issues or international relations?
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Are there still differences from place to place? And the answer, interestingly enough, is yes, and there are many positive results of that colonial history era in Colombia. The areas where there were Spanish conquistadores doing—the technical term is encomiendas. That's what these little areas were called where the Spanish had their fiefdoms.
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It's economic at the end of the day.
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Absolutely. I mean, and in the U.S., I can't help once again connecting it to polarization in the U.S. I mean, it seems, and I've had other previous podcast guests talk about this, that back in the day, you know, the parties had more overlap, right? There were more socially conservative Democrats. There were more Rockefeller Republicans who were sort of socially liberal.
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And for whatever, a collection of reasons dealing with geography and technology and politics— they're more effectively sorted now, right? It's clear what the differences is between the parties. And even if it's still mostly a political one versus an identity one, it still makes it harder to work together, to imagine that what we have here is a common project.
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We just differ on some strategic details.
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They set up infrastructures and institutions that helped those areas still get better, still improve historically over the five centuries to come. But of course, there's also downsides. There's also plenty of historical examples where it doesn't work. So that's why social science is complicated and physics is much better.
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Yeah, and presidential elections, FDR, and then decades later, Reagan on the other side could win 48 states, right? Yeah. You can't imagine that now.
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And I think you're, I mean, this is, you didn't quite say it, but with the example of Bolivia, where you had a system that worked pretty well for a while and then suddenly collapsed because it was unstable and the pressures built up. I can imagine that the success of the American presidential system, you know, sort of we lucked out a little bit.
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And now that they have sorted into two very, very different parties, it's going to be harder. Does this... Would you make the argument that there is something simply objectively better about a more parliamentary system when – because it sort of gives the possibility of a 10 percent third party still having viability in a way that in the United States is just impossible?
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The other example we'll look at is in Bolivia, a much more recent phenomenon, where there was a political party system that was weirdly persistent in Bolivia from, let's say, the second half of the 20th century. It's weird because Bolivia was not stable or persistent at all.
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Well, that's what makes it very interesting to me. I see lots of benefits of both a parliamentary system and proportional representation for people. But since I haven't lived under those systems, I wonder about... the hidden worries. The good thing about the American system is supposed to be checks and balances, right?
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We can have different control over the legislature, the courts, the presidency, and when the country is literally split, maybe that's a good thing. Whereas like you say, if you have the system where suddenly you have a big majority in parliament, there's not a lot that can stop you from implementing your agenda for better or for worse.
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There was constant economic fluctuations and coups, and there were votes and then dictatorship for a while and back and forth. But the same kind of political parties seemed to persist. And then they collapsed. They collapsed in the early 21st century. So Jean-Paul asks, why is that?
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And I won't give away all the answers right here, but the answers are kind of relevant for political issues going on in other countries right now, including the U.S., Western Europe, and elsewhere. It's a wonderful little exploration of the dynamics, the complicated, rich, super-duper fascinating dynamics of human beings trying to govern themselves. It's a miracle we do it at all.
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There's probably some mathematical theorem to the effect that there is no system that works well all the time.
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Okay, I know that it's late, but I can't let you go because one more question, mildly relevant. We just had an election, quote unquote, in Venezuela, right? like days before we're talking about this, and I'm sure that it's going to be on the mind of some of our listeners. Now, it seems like less of an interesting social science problem and more just like corruption and autocracy problem.
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1988.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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There are a lot of kind of pessimistic lessons from this podcast, but that's the one optimistic lesson, that we human beings, despite all the weirdness, we do manage to govern ourselves a little bit. Maybe by being good scientists, we can learn how to do it better. So with that, let's go.
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For what it's worth, and maybe not that much, I'm not going to push this too hard, but Kieran Healy, who was a sociologist, previous Mindscape guest, did the fun thing of, in the Venezuelan, reported vote totals. He took the number that was reported as voting for a single party and just divided it by the total number of votes. And so you get a fraction. Okay, that's fine.
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Between zero and one, it's not that bad. But the fraction, which you would ordinarily expect to be like, you know, 0.5438, whatever it is, the fraction is 0.54300000000. Which means that what happened is someone took the vote total, multiplied it by 54.2, and made up the reported vote total from that, rather than... That makes sense. A regular number. So I don't know.
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It's certainly not going to hold up in a court of law. And maybe it actually just is a coincidence. But the chance of being coincidence is you can quantify it, right? One part in 10 to the 5 or something like that.
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All right, so I'm going to let you go, but very last question, very simple, using all of the powers of your political science, developmental, economics knowledge, how is democracy in the United States doing? Is it going to last?
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Jean-Paul Foguet, welcome to the Mindscape Podcast.
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Yeah, me neither. So I guess we've got to keep working to keep it a little bit better than that.
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Yeah. Well, you know, something about crisis, forging virtue or something like that, I think we'll have to see whether we can rise to the occasion or not. But you've given us a lot to think about. Jean-Paul Foguet, thanks so much for being on the Mindscape podcast.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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Bye.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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Now, we're going to get into a couple of papers you've written recently. And I love the fact that we're going to get into sort of the nitty gritty of what it means to be a modern social scientist. It's very different than being a physicist where we build a piece of equipment and then smash things together, whatever. But let's start with very, very broad issues to get the audience kind of grounded.
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While reading your papers, I can't help but come away wondering, how is it that human beings are ever able to govern themselves? Do you get that feeling by doing this work at all?
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Well, and the history matters. And I get the impression that a lot of pundits and commentators, probably not professional academics, but they like to look at what's happening in their country and then propose theoretical explanations for it. But this idea of looking at different eras, looking at different countries, that actually is hard work.
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One thing I got to ask about, because we recently had Duran Asamoglu on the podcast, and he is someone who has been... Yeah, he's fantastic, but he's also been thinking hard about this idea of institutions and exclusive institutions and inclusive institutions and... Or extractive, I should say, versus inclusive institutions.
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And one of your goals is to kind of go a little bit more deeply than that.
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Well, it's interesting that you think of that as somewhat Marxist. I mean, I guess I'm very much an outsider here, but when I hear Marxist, again, in the non-USSR sense of the word, I think of kind of economic class determinism. And I think that in what you're saying and in what Daron's saying, ideas matter a lot, right? Yeah.
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And that kind of sort of feedback interplay mechanism is very much in line with the attitude of the Santa Fe Institute, where I first ran into you and where you are sitting right now, even though I'm in Baltimore while we're having this discussion.
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And a particular kind of idea that you've emphasized is the role of culture in development, that it's not purely economic determinism, that human beings have attitudes that we get from psychology, from our other fellow human beings in a society, and those also help influence the development of institutions and their success.
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That's B-A-B-B-E-L dot com slash mindscape. Rules and restrictions may apply. And by dyad, we just mean two individuals relating to each other? Or could it be an individual in a larger structure or what?
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Well, that's very interesting. Does it have any implications for how we think about something like voting theory, where usually we're just imagining we have a bunch of individuals with preferences and trying to decide how to aggregate them?
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Hello, everyone. Welcome to the Mindscape podcast. I'm your host, Sean Carroll. Here at Mindscape, we don't have that many hard and fast rules, but we do have some tendencies, some preferences, some inclinations, let's say. And one of them is we don't do politics that much in the conventional sense. We don't invite...
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Good. And that makes perfect segue into this idea that we want politics to be about more than just election day and voting, but about other forms of participation. Is there a particular kind of angle that you care about most? Is it organization, protest? I don't know. What are the kinds of organization and participation that we're interested in?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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And it does sound a little bit like work.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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So how do you think about the current state of political participation? I mean, here in the United States, people don't even vote most of the time, much less, you know, join a committee and try to make some political change happen. Is participation in political activity on the rise? Is it falling? Is it high or low compared to our peer countries?
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political candidates on to debate Republican versus Democratic talking points or whatever. But we are interested in the ideas of politics, right? In political science, in the theory of democracy, things like that. And sometimes the distinction between those two things, the dirty, get your hands messy,
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And do we overestimate the impact of white conservative evangelicals because when they do political activism, they do it qua being white conservative evangelicals rather than just, you know, because they have different interests in different things?
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realization of politics in the actual world and the theory of politics, the grand ideas that lay behind everything, that distinction is not 100% airtight, right? It's a little bit of an artificial distinction, in fact. And so sometimes the best way to get into the ideas behind politics and democracy, which I'm extremely interested in, is to dig into the reality. But
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It seems, and I don't know, you're the expert here, so you'll tell me, it seems that much of the story you just told is different now than when I was a kid, you know, when Jimmy Carter was president. The first evangelical president was Jimmy Carter, right? He was, but yet it wasn't, I didn't even know.
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I was beginning to follow politics at the time, but I didn't sort of, he was certainly Christian, but it didn't have the resonance that it has now in terms of being a political identity. Sure. And then the moral majority in Jerry Falwell came on the scene. So am I right to think that this discourse has changed quite a bit over the past few decades?
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to look at some actual cases of these kinds of ideas in action to improve how you think about them. This is no different than in physics, doing an experiment and collecting the data. It's not all about theorizing. So that's what we're going to do today. Today's guest is Hari Hahn, who's a professor here at Johns Hopkins. In fact, she is the director of the SNF Agora Institute here at Hopkins.
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And how does this, this is a big question, but how does this tie in with what I perceive to be more polarization now on the political level than we ever had before?
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I mean, I remember reading recent studies saying that there are people who now call themselves evangelical Christians, even though they don't ever go to church, don't even know anything about the Bible, but they know that those are their political fellow travelers, so that's how they start to think of themselves.
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Very, very messy. I know. But also, I mean, the question I was going to ask next, you've already basically told me is unanswerable, which is how many evangelicals are there? Like, how big is this block of like-minded people as a percentage of the U.S.?
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of which I'm a faculty affiliate, I'm proud to say. The Agora Institute is all about studying democracy and how it works. And Hari's work over the years has been about the aspect of democracy which goes beyond making a decision about your preferences and then voting, right? It's not just about Election Day. It's about all the work that's
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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But those are fractions within that group. What is the percentage of Americans who are evangelicals in some sense or another?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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That's a big number. That's a powerful group. It is a big number.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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OK. And then, as you've already alluded to, there is this phenomenon called Donald Trump who came on the scene, not as an especially obvious paragon of religious virtue, but entered into a strong alliance with that political segment. So there's got to be a lot of theorizing that I don't know about by professional political scientists trying to understand what makes that alliance work.
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Well, and to be fair, it seems effective, right? Like if I were, I'm not, but if I were an evangelical Christian who was most focused on getting my agenda put into practice, then I could imagine holding my nose and voting for someone who didn't really embody the same values as me, but would get that agenda into practice.
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that goes into changing people's minds, making people think about politics, getting people active, getting people organized, right? All of that part of democracy that goes above and beyond just waiting for election day and then casting your vote. And her latest book is an even more specific example of this. It's called Undivided, The Quest for Racial Solidarity in an American Church.
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I guess the weird thing is that most of the interviews you hear are not people holding their nose. They seem pretty enthusiastic about it.
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Well, it goes back to this huge debate that was in 2016 after Trump first won whether or not we should understand the surprising number of Trump voters in many people's minds as a result of economic anxiety or something more resentment-based, racial resentment or resentment against immigrants or just people's powerlessness in society. Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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OK, so now just to drive home the point that political science is very, very complicated and there's always exceptions to everything. There's a ballot initiative in Cincinnati, issue 44, that caught your attention. So tell the audience about that.
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OK, so that doesn't sound political right away, but of course it is because everything is political. As Hari will tell us in the podcast, this book started with a really weird election result in a part of the country in Cincinnati, Ohio, which. You know, Cincinnati is a city.
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So to be clear, this is a—the word megachurch means there's like tens of thousands of parishioners who go there—
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Completely different from the church that I went to as a kid was a declining Episcopalian parish in Trenton, New Jersey with a few dozen people maybe. Yeah.
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If you listen to previous podcasts with people like Will Wilkinson, you know there are no Republican cities in the United States anymore. So it's mostly Democratic. But Ohio as a whole in 2016 went for Donald Trump in the presidential election against Hillary Clinton. And Cincinnati went for Clinton, the city of Cincinnati, as opposed to the whole state of Ohio, but not by a huge amount.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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Do we understand what is so attractive or effective about these bigger churches?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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Okay, good. And this particular church, Crossroads, it's multiracial?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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Right, okay. But the person who started this program, Undivided, which is a program within Crossroads, the church, was a black pastor?
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But there was this particular ballot initiative, which was very democratic, liberal coded. It was about universal preschool. And it won by a huge amount, by way more than Clinton beat Trump in those districts where the vote was being held. And so political scientists are going to say, what is going on?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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Yeah. And you should tell us about Undivided. One thing that I wanted to make sure the audience heard was you compare it to DEI programs, right? Diversity, equity and inclusion. And I like all those words. I'm in favor of diversity, in favor of equity, in favor of inclusion. But you do not hold back to say typically those programs just don't work. And yet somehow this one does.
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And the audience, because it's a completely audio podcast, the audience cannot see both Hari and I sort of rolling our eyes.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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And when Hari went in to figure out what had gone on in those districts, she kept running into an organization or an idea called Undivided, which was sponsored by a church, indeed a Christian evangelical megachurch called Crossroads in Cincinnati. And Christian evangelical megachurch, those words make you think right-wing, Republican,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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All right. Lay it on us. What did they do that was so different and effective? And also, how did they know to do something so different? Was it just a single person figured it out or were they coming at it from a different angle?
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And OK. And so when it came down to actually so that's you told us a little bit about process. And so what were the what would it be like to be in that program other than sitting and watching YouTube videos and clicking on, you know, yes, I should report it when this person gets harassed?
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But this church has advocated for this very left-wing slash democratic-sounding policy. What's going on there? How did these people come to the conclusion that they should act to do this? Why did they make that policy choice, etc.? And I think that the—well, we're going to talk about the specifics. We're going to talk about the background and the specifics of this incident.
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But hopefully, even though we didn't draw out too much of it explicitly, you the listeners will be able to draw some lessons about this for much broader questions. If you think that democracy is about more than just making up your mind about who to vote for and then voting, but it's actually about participating.
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Well, no, I love that for a lot of reasons. Going way beyond DEI, I mean, there's an obvious issue with a certain kind of bureaucratic mindset, right? Which is we're going to consider everything that can possibly happen and, like you say, tell you the right way to respond to that case.
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And again and again and again, there's a failure because the thing that actually happens isn't quite what you anticipated and the laws, the rules don't apply. So... The general philosophy seems to be instead of doing that, I don't know, can we be so grandiose as to say focus on the underlying values that lead you to make the right decision rather than here's the decision you should make?
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But it sounds like they are helping people get a sense of agency and responsibility. And that's just a much more positive thing to get than a list of right and wrong things.
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It's about getting other people to think in ways that you think would make the country you live in or the city you live in a better place. The kind of lessons we learn from this study are very broad applicability. It's not just about churches. It's not just about universal preschool. It's about how do you work and live and function together in a democratic society.
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And one of the things I loved about it that you mentioned in the book is that despite the fact that this was about racial justice, etc., they, I don't know whether this was sort of baked in from the start or arose later, but they didn't try to make people less racist.
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they sort of found people who were not that invested in being racist and gave them a way to do things that would make the world better.
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How important was the religious aspect in all of this? I mean, would they point to parts of the Bible that were reinforcing the message?
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So lots of lessons for all of us, I hope. Let's go. Ari Han, welcome to the Mindscape Podcast.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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And so how much of a direct connection was there between the Undivided program and the results of Issue 44, the preschool lunch program in Cincinnati or preschool?
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So you already started answering this then, but what are the lessons for other people in other places? Cincinnati, as awesome as it is, is one little city in the United States. Does this kind of program scale more broadly? It seems like individual contact matters a lot.
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So let's get a general overview before we go into the specific new book you've written, which is very fascinating. But it is something that grows out of previous work you've done. So as a political scientist, that covers a lot of ground. What do you think of as your specialty within political science?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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Sorry, which has become less common?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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Yeah, and to wildly generalize here, it sounds like there's a theory in which these structures are more effective if they grow up kind of organically modeled on real-world complex networks rather than some top-down intelligent design system.
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All right. We'll organize a Santa Fe workshop on this. We have to do it. It would be great. Okay. I guess let's close up then with bringing the lens out and being grandiose again. There have been claims out there in more pessimistic sectors that democracy is hard to make work
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unless one group, one ethnic or racial or whatever group just dominates everybody else and then they're voting within themselves. But a true patchwork of different kinds of cultures and ethnicities is harder to make work. Does this study make you a little bit more optimistic about those questions?
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I mean, it's easy to start projects. It's fun to start projects. It's sometimes hard to follow them through and finish them. That's true in every endeavor of human life. But you've given us a little bit of hope. I hope that people read the book and think about how it can apply to other circumstances. So Hari Han, thanks so much for being on the Mindscape podcast.
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Yeah, no, that's great. So to sort of rephrase, like there's this cheap and easy view of democracy that every so often we vote for our favorite candidate and then we get back to our lives. But you're aiming at a need to be a little bit more engaged than that.
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I mean, maybe talk a little bit about what to me has become much more obvious over the past 10 years, which is what a challenging and counterintuitive idea democracy is. You know, not just that we let people vote and whoever is the majority has a say, but that the rest of the polity goes along like that. It turns out that's asking a lot of people.
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majority rule you know through elections that happens every four years or whatever so well yeah and putting it that way brings into stark relief the fact that it's kind of an abstract ask right i mean people people want results yeah you're saying let's instead buy a process that sounds difficult to get them to buy into
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Well, and maybe this is also too simplistic, but what I detect in the modern world is a lot of people yelling at people they disagree with for being wrong and then wondering why they haven't changed their minds.
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Like the actual sort of dirty work of building a coalition that might win an election is not even paramount in people's minds a lot of the time, much less something that they effectively move toward.
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Is it related to the fact that – well, let's put it this way. I predict with very high confidence that a certain tiny fraction of my listeners will complain about this episode because it's about politics. And they think that anything about politics is sort of lowered in their estimate. Like politics is just bad. Politics is not pure. It's sort of grungy and whatever. And to me, this sort of –
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betrays like an unwillingness to do the hard work, right? Like politics is about compromise and working with people you don't like. And that's, I want to say it's a feature, not a bug. I don't know. Yeah.
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293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
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293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
I'm sure that most audience members have figured this out, but so exogenous is some influence coming in from outside, endogenous is the dynamics within the system. Yes, thank you, definitely. Yeah, and you're saying that classical economic theory, if you restrict yourself to the endogenous influences— because it's looking for equilibrium points, nothing should ever change with time, right?
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I mean, it can deal maybe with exogenous things, the meteor hitting, but it predicts pretty strongly that things settle down. Is that right, or is that an exaggeration?
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293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
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That's B-A-B-B-E-L dot com slash mindscape. Rules and restrictions may apply. But there are business cycle theories, no? Yeah, yes, and no.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Ah, okay, okay. That's very interesting. I mean, it's fascinating to me. We talked on the podcast about complexity and complexity economics before. The centrality of departures from equilibrium hadn't quite sunk into me before. And it...
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reminds me of things going on in physics over the past 20 years, because, of course, we have statistical mechanics and thermodynamics, and all the classical theory is about equilibria, and, you know, you settle down fairly quickly.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
There have been some attempts to do non-equilibrium stat mech, but it's really only in the past couple decades that people have taken those dynamical processes seriously and talked about fluctuations and, you know, unlikely events and fat tails and things like that. And so could I think of it as adding time scales into the problem?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
I mean, maybe I reach equilibrium, but maybe it just takes me a long time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
This is very helpful to me because the 2008 financial crisis is obviously something that many economists have talked about to death, and I could never quite decide whether the— everyone agrees that people did a bad job of predicting it, anticipating it even, but it was unclear whether or not it was the specific models being used were inadequate or the whole approach was inadequate.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
And you seem to be coming down on the very approach was inadequate.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
One thing that I noticed, I think I saw this table in your book. If you look at the historical dates when, let's say, the stock market changed by a relatively large fraction, one thing I can't help but notice is they're almost all downward. It's not an equal distribution of fluctuations upward and downward. Is that something that makes sense to you?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Hello, everyone, and welcome to the Mindscape Podcast. I'm your host, Sean Carroll. Usually in these intros to the episodes, I will start with some big picture kind of question, narrow it down a little bit, and then eventually introduce the speaker who we're going to talk to during the course of the episode. It's ideas first and speaker second.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Is there a simple – I mean I can guess at a sort of physics-y phase transition kind of thing. Like the economy generally grows, but as it grows, it's also exploring new configurations and suddenly it finds a lower energy minimum and it sort of crashes down and then starts growing again.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
And the episode that we have here today is also that, but let me do the intro first. in the opposite direction, because we have a very special speaker here today, Doan Farmer. His name is pronounced Doan. He says it's like the name Owen, but with a D in front of it, even though it's spelled like D-O-Y-N-E. Apparently some amalgamation of Irish and Southeastern U.S. pronunciations.
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293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Very, very much. It does make me think that this is a good connection between complexity and chaos, which are two different things, but they're related to each other. Part of the spiel and chaos theory is that small deviations get you very different futures. that does seem to be related to this inability for things to settle down. But I can't quite put it together in my head.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Well, I guess, yeah, that's what I'm striving to understand this a little bit better. I mean, part of me wants to say, okay, let's back up. The thing you just said about two frequencies or two periods, that makes perfect sense to me. If we have a double pendulum, right? If we have one pendulum hanging off another one, that is a paradigmatic example of a chaotic system. Hard to predict. But...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
if I have a little bit of friction, the double pendulum will eventually settle down into an equilibrium. And part of me wants to think that the economy, if it didn't have any outside shocks, would have a little bit of friction and settle down. But you're telling me different, and I'm trying to understand how that goes.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Sure.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
But he came to fame, in some sense, back in the 1980s, when a book was written called The Eudaemonic Pie, Those of you who are of a certain age will remember this book. It was about something that Doane and his friends from graduate school pulled off in the 1970s to win in Vegas.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
So, of course, that pole by itself is not in equilibrium. It's at an unstable equilibrium, right? That's right. So is that—I mean, that would change my mind about a lot of things, if you're arguing that the equilibria discovered by classical economics are secretly unstable and small perturbations would tend to grow. Well, the economists know that.
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You've all heard of different stories of people trying to beat the house, beat the casinos in Las Vegas, either through counting cards or through high-tech apparatuses. And Doane and his friends, they were first. They did it first, at least the first in the high-tech world.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Got it. Okay.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Yeah, no, that's extraordinarily helpful. So basically, rather than the naive picture I had in mind, where there is an equilibrium and there's dissipation and you settle into it, there's an unstable equilibrium and things around us are gradually changing. Like you said, the economy is growing. We discover new things, new resources or technologies or whatever.
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So of course, there's constant jiggles at the unstable equilibrium and there's nonlinear feedback and they will want to grow unless we correct. And that correction is going to be kind of a, back-and-forth process that is intrinsically dynamic.
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293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Okay, good. I understand a lot better now. So let's try to figure out what we should be doing instead of those benighted ordinary economists. I mean, how does the statement of bounded rationality play into this? I mean, clearly it's a statement that the assumption of perfect rationality is too strong, but then how can you implement that in your better way of thinking?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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Dolan himself programmed what we would now call a wearable digital computer, arguably the first of its kind, that fit into a shoe so that you couldn't see it. And they were not counting cards or anything like that. They were playing roulette. They were using a little bit of physics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
And if you're a roulette player, you know that the roulette croupier throws the ball around the roulette wheel and it spins several times. It spends some time spinning. So you could actually, in principle, time how fast that ball is moving and time the motion of the wheel and at least probabilistically, even though you wouldn't get it exactly right every time, have a better than average chance of
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Right. And so just to clarify again to the audience members who've never made a model of anything of this sort, the difference would be in a standard economic model, you would have things like supply and demand and inflation rate or whatever. And here you have individual variables in your computer simulation representing the states and aspirations of a million different agents.
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293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Well, in the mainstream models, I guess they have no individuals in them, if I understand correctly, like the role of the individual is just to be absorbed into the collective notion of supply and demand.
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or better than typical chance, I should say, of getting the right answer to where the ball was going to fall. And they figured out that through their mechanism, they could get a substantial increase in the odds of winning. And in fact, they did win. The winnings were not very large. I have to confess to that. Hardware problems, software problems kept coming in the way.
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And one of the advantages of this approach, as I understand it from your book, is that the agents in your model can take on specializations in a certain way. I mean, you use the analogy that the economy is kind of like a metabolism, the metabolism of civilization.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Listeners of Mindscape will get a $75 sponsored job credit to get your jobs more visibility at Indeed.com slash Mindscape. Just go to Indeed.com slash Mindscape right now and support our show by saying you heard about Indeed on this podcast. That's Indeed.com slash Mindscape. Terms and conditions apply. Need to hire? You need Indeed.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
And at some point, they got a They got worried that the casinos were going to throw them in a dark alley and beat them up or something like that. But the proof of principle was there, and it launched Doan on a career. He went back to grad school in physics, actually, started thinking about chaos theory.
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293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
And you even have some prediction that turned out correctly about how different industries that were able to specialize more would find efficiencies and lower prices.
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293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
It was sort of straightforward Newtonian mechanics for the roulette wheel, but chaos theory was the new thing at the time. He was a founding member of the Chaos and Dynamical Systems Collective, which helped really put the physics of chaos theory on a firm footing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
And he then became more and more interested in thinking about how to apply insights from chaos theory to predicting the future, because the world is a messy place and there's all sorts of chaotic, complex things going on. He founded a company called to play the financial markets and did very, very well at that. Better than average, let's put it that way once again.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Well, biologists who think about evolution have long wondered about the development of complexity over the course of biological time. Why is it that organisms seem to become more complex? And one possible answer is they find new efficiencies. And I guess you're doing the economic version of that.
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293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Yeah. What is the role of innovation here? Does innovation count as an endogenous happening or an exogenous one?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Of course, it almost is inevitable that he became involved with the Santa Fe Institute and the sciences of complexity. And given his previous interest, the particular kind of complexity that Doane became interested in is complexity economics. So now we finally get to the topic of today's podcast. Don has a new book coming out called Making Sense of Chaos, A Better Economics for a Better World.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
I think it's often the case that if you go back to some of the classic papers in a field, they were much more thoughtful and nuanced than the sort of high contrast version that survives into subsequent generations.
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293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Exactly. So one thing you've mentioned a few times is this idea that we now have access to giant computers, right? We can do agent-based modeling. We can have a million different... agents, and even if the actual society we want to model has a few hundred million, surely a million is a pretty good sampling, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
But you sort of hinted at the idea that therefore you get results that I couldn't derive analytically, that I couldn't figure out without doing the model. That would make me sad. I'm a pencil and paper kind of person. How well do we know that we just haven't yet been able to derive some of these results? Well,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
And he's arguing, as we've talked to other speakers about, that thinking like a complex systems scientist is just so much more suited to thinking about the economy than traditional economic models. And I've talked to a bunch of economists, a bunch of complexity theorists before. I think that...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
So when you say we, as in the complexity economists, I presume, I mean, trying to be as fair as possible, how does that fit into the larger economics profession? I know that I'm completely biased in the economists I talk to because I hang out at SFI. But at the major departments, you're at Oxford. It's not exactly a small backwoods place. Are people respecting this new approach to economics?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
After this conversation, I have a much better understanding of why that statement is true, of why thinking like a complex systems scientist is very, very helpful in understanding the economy in particular. And this is not just ivory tower theorizing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Yeah, you have to actually have a result, have some success, then people will listen to you, not just because you think it's cool. That's true in any academic field, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Well, speaking of those results, I mean, it's one thing to say, oh, yes, the 2008 crash, I could have predicted that. It makes sense to me. How quantitative can we be about the next crash? I'm a little bit worried from what you said that it's almost inevitable that there will be one.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Well, I guess for the 2008 crash, you mentioned, everyone has mentioned the crucial role played by novel financial instruments. Is that something, I don't know if complexity economics helps us here, but is that something that we can sort of be more cognizant of the dangers of ahead of time?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
The British government asked Doane and his collaborators in his group at Oxford University to help understand what the economic impact of the COVID pandemic would be. And they did their little complexity theory models. And again, it worked really well, especially compared to traditional models.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
So, you know, as in many ways in the world of complex systems science, I think that we're on the cusp of really getting better at this. I think that we have breakthroughs right ahead of us. This is revolutionary science. This is the middle of a paradigm shift where all sorts of problems in the world are going to have light shed on them
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
So you're trying to convince central banks and planners and prognosticators to take this approach proactively?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
So you're investigating possible worlds in your computer. Yeah, exactly. And I should say SEC is Security and Exchange Commission for those non-Americans listening to us. Okay, I mean, I guess maybe the last thing to ask about, one more big picture question about complexity. One of the worries about...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
people who are enthusiastic about complex systems, such as ourselves, is that there's no there there. There's the economy, and there's biology, and there's the internet, and these are very different things. To what extent have your investigations into the economy actually been helped by thinking about complex systems for their own sake or analogous systems that are not economics?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
You've already given us some examples with biology.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
They would not have me.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
by thinking about not just the specific phenomenon under consideration, but more broadly as a complex systems thinker. And I think that this conversation with Joan Farmer helps convince us that that's what's going to be happening. So let's go.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Thank you.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Don Farmer, welcome to the Mindscape podcast. Welcome. I'm very happy to be here. So you're writing about complexity economics in your latest book. I will encourage all the readers, all the listeners rather, to go back and check out all of your previous adventures, which are colorful and fun.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
But today we're going to think about complexity economics, which leads me to ask, like, is there simplicity economics? Isn't all of economics pretty complex right off the bat?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
293 | Doyne Farmer on Chaos, Crashes, and Economic Complexity
Great. So of course, there is a lot of complexity out there. I mean, maybe let's ask the question this way. Can conventional non-complexity economics get anywhere by oversimplifying things? Are you, in other words, adding to something that we already know by taking the complexity seriously?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
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302 | Chris Kempes on the Biophysics of Evolution
It's a tiny little tube-like thing, so it's not a spherical centimeter-long thing, but That's very creepy to me. I don't want any centimeter-long bacteria climbing around anywhere near where I am. And I bring this up because I did – Chris Kempis, today's guest, introduced me to the possibility during this podcast. I had never heard about it.
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302 | Chris Kempes on the Biophysics of Evolution
I mean, that might be a good example of, I had a recent podcast with our mutual friend, Brandon Abunu, and we were talking about fitness landscapes and seascapes and so forth. The fitness landscape changes over time. So, you know, at one point the direction to go in was to build a brain and only later that you'd need to make an optic nerve.
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302 | Chris Kempes on the Biophysics of Evolution
And so you're stuck kind of in a little valley where only certain things are possible.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
While we're at this very high level of abstraction, we'll get our hands dirtier in just a second. But the other thing that I liked very much in one of the papers that I've read of yours, the idea of competing constraints, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
Like there's one constraint that makes you want to grow bigger, another one that makes you want to stay small, and you can almost quantitatively predict what is the smallest kind of organism you could get, what is the largest kind, what is the optimum size, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
But it shows sort of two sides of a certain coin for a bacterium that is about the size of a coin. One is what we will be talking about in the podcast are the existence and usefulness of physical constraints on biological organisms and their evolution. So biological organisms are embedded in the physical world.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
This is more like an end of the podcast kind of question, but does this mean that if we discover advanced interstellar life, alien life, that we shouldn't be too surprised if there's some commonality of forms in the morphology?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
Good, okay.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
It makes the Star Trek budget help under control, right? All you need is to slap some prostheses on a human being and you get an alien. Yeah. You know, physicists, of course, like to look at toy models and spherical cows and so forth to put their theories to the test. So let's think about bacteria. They seem to be simple unicellular organisms that we can really do some math on, perhaps.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
Well, tell the audience about bacteria. Like, one amazing thing is the range of sizes that we get in bacteria. This always knocks my socks off.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
And just to get, again, our non-biologically literate audience up to speed, the bacteria don't have nuclei, they're eukaryotes, and they're friends with the archaea, which are the other kinds of prokaryotes, right? Yes.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
They obey the laws of physics, and therefore they need to use good old sensible, allowed physical mechanisms to survive, to metabolize, to eat, to move, all of these things. it should be unsurprising that the existence of the laws of physics will provide constraints on what kind of architectures and morphologies and sizes are allowed in the realm of living organisms.
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302 | Chris Kempes on the Biophysics of Evolution
But the DNA, they're just wandering around, bouncing back and forth inside the bacteria.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
And so despite the fact that four orders of magnitude in the size, that is to say a factor of 10 to the four, that's pretty big. It's a large range, but there is a lower limit and an upper limit. And this is where you're going to earn your keep, right? Telling us why the physical constraints help us understand those limits.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
And of course, you can apply this idea, you can actually do it quite quantitatively and specifically, to simple organisms like bacteria. And under some very reasonable assumptions, you can derive the smallest size of a bacterium possible and the largest size of a bacterium possible. And these thio margarita guys are way larger than the largest size possible.
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302 | Chris Kempes on the Biophysics of Evolution
Knowing that our audience is raised on watching movies like Ant-Man and so forth, we have to say, why can't you just make the cell wall smaller?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
Of course, that turns out because they violate some of the assumptions you made. They're actually not like one big blob. They're almost like sausage links kinds of things glued together to make a long tube to grow to that centimeter size. But it's both an illustration to me of the power of physical constraints in biology because you can't do anything.
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302 | Chris Kempes on the Biophysics of Evolution
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302 | Chris Kempes on the Biophysics of Evolution
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302 | Chris Kempes on the Biophysics of Evolution
But aside from the possibility of novel molecular structures, we are running up against, I'm going to have to take back what I said earlier, we're running up against quantum mechanics because it's the size of the atoms that ultimately sets what we can do here, right?
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302 | Chris Kempes on the Biophysics of Evolution
Change the mass of the electron. Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
Yeah, people have done that in the context of the anthropic principle. Maybe not exactly that, but they've definitely asked whether you could have the chemistry. Okay, I guess that makes perfect sense. an organism at all, an organism that has its own DNA and could be produced by itself, there's probably a minimal size you can get away with.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
You got to obey the laws of physics, but also the cleverness of biology and figuring out ways around what you thought were physical constraints. So in today's conversation, we're talking to Chris Kempis, who is a faculty member at the Santa Fe Institute, a biophysicist, I think that's safe to say, or a physical biologist, maybe.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
There's certain, you know, ingredients you can't do without. But why is there a maximum size to bacteria?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
And the theme running through Chris's work is applying these physical constraints to life in all of its forms. So starting from viruses to bacteria, but we will also be talking about the transition from prokaryotes to eukaryotes, right? The existence of nuclei and other substructures in cells that are characteristic of eukaryotic life.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
Well, this sounds like something that you could calculate mathematically, and then as scientists, you're going to go compare with the data.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
It's very much, I love that example of how science works, right? Like you have a theory, you compare it with the data, you realize I could have had a better theory or a different theory all along, but I'm learning something by looking at what nature actually does.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
And then the transition to multicellularity and even a little bit about larger macroscopic animals and their constraints. We live in a world governed by the laws of physics. Don't forget that. And those laws of physics will matter
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
Is there any relationship between Jeremy England's work on the statistical mechanics of self-replication? I've had him on the podcast years ago.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
Interesting. Okay, good. But this doesn't sound like we're done yet. It doesn't sound like this field is completely I's dotted and T's crossed.
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302 | Chris Kempes on the Biophysics of Evolution
for even for biology occasional reminder here at mindscape we have a patreon community that you are welcome to join just go to patreon.com slash sean m carroll and you can leave uh oh actually we're changing yeah we're changing the the funding mechanism i'm not changing it apple is forcing patreon to do it so anyway there's gonna be a monthly subscription fee
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302 | Chris Kempes on the Biophysics of Evolution
Well, this is good because it's definitely nudging us in a certain direction. That other overly-sized bacterium you talked about before, you mentioned that it has these storage vacuoles inside. It seems as if when you get big, it begins to become helpful to become complex, at least have more structure inside you than the ordinary bacterium does. And of course, we know famously—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
Eventually, we're going to make eukaryotes. We're going to make cells by marrying or, I don't know, shotgun marriage of the archaea and the bacteria to get cells with nuclei in them. So is that something? That seems like an out-of-context problem. It's like you're changing all the rules once you make a eukaryote because it's a transition to a whole other kind of thing.
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to Mindscape if you want to be a supporter, but it's not going to be that much money. I actually got to do that updating now. And then you can be the kind of person who asks questions for the Ask Me Anything episodes, and you get ad-free versions of the podcast and a feeling of belonging that is useful to everyone in our troubled times. So with that, let's go. So
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302 | Chris Kempes on the Biophysics of Evolution
This is good because it's not like teleological. It's not like something is making it more complex. It's that the cell, given what it wants to do, is being faced with a problem, and extra layers of structure are going to help it solve that problem.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
And this might actually help push me in the direction of greater understanding towards something that's puzzled me ever since I realized that even though the bacteria got embedded in the archaea to make eukaryotes and eukaryotes have nuclei, it's not the bacteria that are the nuclei. The nuclei are a whole separate thing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
But if it's because it's pressing up against some limit at its current level of complexity and it needs to become more complex, maybe it's not surprising that it's becoming more complex in multiple ways. It's getting a nucleus and it's getting mitochondria.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
And we're still in this realm of what we say eukaryotes. They're much more complex in some way than the prokaryotes, but they're still unicellular organisms, so we can compare them, right? I mean, one of the things you did was say what kind of scaling remains true as you go from prokaryotes to eukaryotes, and then what things kind of break down and become different?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
Chris Kempis, welcome to the Mindscape Podcast. Thanks, Sean. Really glad to be here. So you're a faculty at the Santa Fe Institute, where I'm fractal faculty. So I guess my boundary area might be larger compared to my volume than you, as just a regular faculty member, since I'm fractal. But in both cases, we're supposed to be thinking about complexity.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
So when you say words like, just to be nice to the audience, metabolic power scaling shifts from prokaryotes to eukaryotes, what would that mean? What are some synonyms for that?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
So in a eukaryote, you still need more power when you're bigger, but you need less than your extra bigness.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
Is there a simple way to connect that to the existence of a nucleus and some mitochondria?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
And it seems to me that even though SFI studies lots of different things, life, living organisms are kind of the paradigmatic example of a complex system, right? Much of what I hear people talking about when they talk about complexity, like clearly they're either thinking about life or inspired by living beings. Is that a fair kind of thing?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
I can't help but mention as a slight aside that there's a lot of really cool work being done on artificial life, like simulated life in a computer, origin of life, or evolution and things like that. And generally, the word metabolism is not there at all, right? These are just running programs, and they have all the food that they want.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
But clearly, if we're going to find some more ultimate endgame understanding, the constraints of metabolism in the real world are kind of going to be a big deal.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
Good. That was just an aside. I don't want to get sidetracked by that. Every modern podcast ends up talking about AI at some point, so it's an attractor. It's a constraint. We did it. We checked the box. We did it, yeah. But we have looming in front of us the next big evolutionary major transition, right, from unicellular organisms to multicellular organisms. Let me just first ask—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
How clear is it what qualifies as a major evolutionary transition? Is it just that, you know, when you see it, is there a theory of major evolutionary transitions? Or is it just like, well, we look at the data and we have to explain what we see?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
I like it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
Okay, that makes perfect sense as to why a theory of individuality would be extremely relevant here. That's good. So, okay, multicellularity itself, one might have guessed, if one were completely ignorant of these things, that maybe... eukaryotes that have more complexity inside were more willing or able to become multicellularity because they sort of had more degrees of freedom.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
But my impression that actually in the data, either one is possible. It's just that the eukaryotes kind of won out empirically.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
Well, we did have a podcast with Will Ratcliffe. I don't know if you know his work. I know Will very well, yeah. I mean, he's doing the experiment where he's stressing these yeasts and they decide that becoming multicellular is a good life survival strategy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
And that does seem like something that a eukaryote would pull off more readily than a prokaryote. Yes, yes, I think so.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
It's an interesting perspective because, of course, there's many ways of defining this. I kind of don't care what the definition is, obviously. What matters is what the things do. But that's a very kind of interactionist perspective you just gave.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
No, that's good. I don't want to be eukaryocentric. I want to give the prokaryotes their props. It's too easy to be in the situation that we're in. But the callback to Radcliffe's work in the multi... What is it called? Multi, right? Multi... Cellular evolutionary, long-term evolution experiment. Yes, yeah. Like we said, they kind of put constraints, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
There's a new physical external thing, and that's very analogous to what you say was going on in the actual origin of multicellularity back in the snowball Earth times.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
It's about how the system adapts to the world rather than a sort of completely internal definition in terms of hierarchy and organization and parts and wholes and things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
So it's all because life got hard.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
Life got hard and multicellularity was the solution. But, of course, we had to get to the point where we were pushing the boundaries of what the single-celled things could do before that became – we had to develop our single-celled technology well enough so that we were able to take advantage of a new modality in the multicellular world. Exactly. Yeah, exactly. Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
And then, okay, I presume, I can just sort of imagine that all sorts of new options open up once you become multicellular. I guess the differentiation is key, right? Different cells serving different purposes. On the one hand, you can't have that if you're unicellular. On the other hand, you don't need to have that if you're multicellular. So that had to be a new innovation also. Right.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
That absolutely makes sense. But there is an extra layer of complexity here because, you know, in a car, the tires and the roof are doing different jobs, but they're also just made of completely different things. In the multicellular organism, all the cells start off kind of from the same basic material. So it's not a top-down plan with different kinds of stuff.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
It's that the different cells in a multicellular organism work learn how to respond to their environments and therefore become something different, which is kind of amazing to me.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
So I do presume that the kinds of logic that we talked about at the very beginning of the podcast, where there are constraints that give you smallest things and largest things. I presume these can be applied to mammals just as well as to bacteria.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
Good, very good. I think that that inspires me to wind up the podcast with what is probably a completely unfair question.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
If the harsh conditions, well, let's not say harsh, changing external conditions on snowball Earth prodded little unicellular eukaryotes to come together and start being multicellular, it's arguably... One could say that changing technological conditions on Earth right now are creating very different conditions for life to exist and thrive and so forth.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
So I would guess that this opens up the possibility for dramatically, well, a new kind of major transition in individuality.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
Good. Okay, so to get down to business, I noticed that you opened a paper you wrote a few years ago with the provocative statement that, quote, organisms are subject to the laws of physics. These are bold words, Chris. Does everyone agree with this? Is this going to be a major constraint?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
Well, we would, it's completely, that's why I was thinking this is an unfair question, but we would like a theory. We would like to be able to predict, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
You know, if we do change the conditions in some ways, like, could you, in retrospect, maybe someone could have been able to predict that some small set of livestock animals would become a huge fraction of the biomass, given that human beings were technologically dominant?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
Well, I guess it is one kind of interesting thing that people should keep in mind about constraints and how things evolve with respect to them. Even if there is some tendency to move in some direction and there's a constraint that prevents you from moving too far, it doesn't mean that everything runs right up to the limit.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
There is very often an equilibrium distribution that allows for some variety in there.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
And maybe one more reminder that we are not in equilibrium. We're in a state of flux, the modern world right now.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
We'll see where we go. Chris Kempis, thanks very much for being on the Mindscape podcast. This was great. Thank you, Sean. Great being here.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
I'm unsurprisingly going to be sympathetic to this perspective, but I guess I can see why one might not bother with that perspective. I mean, the variety of living organisms is so incredibly large. When you think about what evolution has accomplished with all the species, etc., it seems it could do anything.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
And here you are saying, but yes, you know, the center of mass of the organism will follow Newton's laws of gravitation or something like that. And I guess a typical biologist might say, so what? Like, that's not much of a constraint.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
And the good news here is that by the laws of physics, we really don't need to worry that much about quantum field theory, et cetera, right? It's more or less classical Newtonian stuff.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
And just so—I think maybe people might get this mixed up a little bit. I mean, the constraints we're talking about are not necessarily external constraints like being fit into a box or something like that, right? I mean, there's sort of constraints on what you can do. I don't know. I should always—I always start in these podcasts by, like, making statements and then saying, is that right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
I should phrase them as questions, right? Should we think about being fit into box or is there some, do you mean something slightly different by the words physical constraints?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
Welcome to the Mindscape Podcast. I'm your host, Sean Carroll. Have you all heard about the centimeter-long bacterium? I had not heard about this until this podcast, as you will discover, but just a couple years ago, scientists found a kind of bacterium called Thiomargarita magnifica, which can grow up to a centimeter in length, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
302 | Chris Kempes on the Biophysics of Evolution
And is this pointing in the direction of explaining examples of convergent evolution, like dolphins look more or less like fish because given what they're trying to do and the constraints of the laws of physics, that's what an efficiently swimming thing is going to look like?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
You sopped to the historians out there. Now, you know, for the physics enthusiasts, what are the specific problems? You mentioned the hierarchy problem. That sounds like politics, not physics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Indeed is your matching and hiring platform with over 350 million global monthly visitors, according to Indeed data, and a matching engine that helps you find quality candidates fast. What I like about Indeed is the instant match feature that shows you the best possible candidates right away before you do any busy work.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Right. But OK, I'm going to be a little bit unfair to you. I mean, you use words like what the mass should be. Yeah, of course. And things like that. I mean, how do you know what the mass should be? What gives us that expectation?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
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289 | Cari Cesarotti on the Next Generation of Particle Experiments
That's B-A-B-B-E-L dot com slash mindscape. Rules and restrictions may apply. Okay, good. So that's the hierarchy problem. There's probably a bunch of other problems there. Dark matter is the obvious one.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
And do you worry that much about neutrinos and their masses? Those are actual discoveries that we made over the last 25 years.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Hello, everyone. Welcome to the Mindscape Podcast. I'm your host, Sean Carroll. In science, when things are going well, there is an interplay between theory and experiment. Experimenters notice something about the world. Theorists rush to offer an explanation or many explanations for those phenomena. The experimenters go out and test the predictions of the theory. They discover even new things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Well, okay, let's indulge ourselves there a little bit and try to figure out if we can explain why you can't give neutrinos masses the same way you give electrons or quarks masses.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Or talk about left-handed and right-handed fields. Go for it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Good.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Well, it was goodly technical. I like it. But maybe we can boil it down. So in the standard model for the other particles, for the other fermions, we know they have a right-handed part and a left-handed part. And then the Higgs sort of glues them together and gives them mass.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
For the neutrino, we know they have a left-handed part.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
and the right-handed part is not necessarily there, but you need it to make mess, or you can be more tricky.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
The theorists are called in again, and it keeps going back and forth. But occasionally, in fact, I would say almost never, but sometimes, one can be the victim of one's own success. And that is the story of modern particle physics. In the 50s, 60s, 70s, we were just splashed with all sorts of experimental results that were very puzzling, very interesting, very intriguing, very hard to explain.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Right. Okay, so very good. So along with the hierarchy problem, neutrino masses, we can come up with theories that explain them, but they're pointing toward things that we haven't yet found. This is what motivates people like you to continue on the search for new particle physics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Good. Very good. And the last thing I wanted to mention were muons. You've already mentioned them. I'm not sure if this counts in your mind, but the muon is basically the heavier cousin of the electron. And then there's the tau, which is the heavier cousin of that. And one can ask, why are there three copies of all these particles? Is that one of the puzzles we worry about?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
And so what's the answer to all these questions? I mean, I know that supersymmetry was out there.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
You would reveal it on this podcast, I'm pretty sure.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
I would be in your acceptance speech. I think we'd have to share it, honestly. But okay, for a long time, the particle physics community was very excited about supersymmetry. Yes. And they were hoping to see it at the Large Hadron Collider, etc. Maybe enthusiasm has cooled for that, but not completely gone away? What is your take?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
We put together a theory, the standard model of particle physics. And then something happened that almost never happens in science, which is that we kept collecting data. The experimenters have not slowed down. They've not gotten worse at their job. They're probing the universe in regimes where we have not yet probed it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
So if we were having this conversation 20 years ago, you might have been very excited about your supersymmetric grand unified theory that was going to predict, that was going to solve the hierarchy problem and give you the right dark matter and explain neutrino masses and evidence for it would be existing at the LHC. And that did not happen.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
But you can see why it's a little frustrating. I mean, the puzzles that you've talked about sound like, to me, a very good motivation for the need for new physics out there. And we could have found it all at the Large Hadron Collider.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
And we didn't. And it's not that we disproved the theories, right? I mean, supersymmetry could still be right or whatever. It's just that they're hiding from us.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
But the new data is still in line with the standard model, with the theory that we put together back in the 60s and 70s. The capstone of this, of course, was the discovery in 2012 of the Higgs boson, something that was predicted to exist back in the 1960s, with more or less the same properties that we'd predicted it should have back in the 1960s.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Is there still room for the Large Hadron Collider itself to discover new things?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
And it's even possible following what you sort of alluded to that the LHC has discovered something new, but we haven't quite analyzed it in the right way to notice.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Good. Well, that's good. This is going to keep you employed for a little while. That's nice.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
So let's allow ourselves then to be starry-eyed and optimistic and imagine that we're going to build new particle accelerators to go beyond what the LHC does. Maybe to soften us up, could you explain sort of the fundamental difference between colliding protons and other hadrons together versus colliding electrons and other leptons together?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Despite that success, there are plenty of reasons to think the Standard Model is not the final answer. Of course, it doesn't include gravity as a fully quantum mechanical theory, but also what is the dark matter? Why are there so many particles? Why do they have the numbers that they have? Why is there more matter than antimatter?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
There you go.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
I think that's Feynman's fault, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
A whole bunch of questions that are looming over the Standard Model. Or to think of it as a physicist would think about it, there are clues that there must be deeper stuff going on than the Standard Model of particle physics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
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289 | Cari Cesarotti on the Next Generation of Particle Experiments
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
And despite this wonderful ability of experimentalists to come up with new experiments looking beyond where they've looked before, it's hard to keep that project up in fundamental particle physics. It's expensive. The timescales are very, very slow. It's a different kind of problem. Every science has its own idiosyncrasies.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
It would seem that... We're in a discovery kind of mood right now. I mean, precision sounds like it's good for studying things we've already discovered, but now we would like to discover some new particles, no?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
So in other words, there's so many predictions made by the standard model of particle physics that you can test them all. And if any one of them is discrepant, you determine that there must be new physics, even though maybe you don't know what it is. But then the theorists will have a field day writing papers about what it could be.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
And are there plans or at least sort of ideas on the drawing board for building either higher energy proton colliders or electron colliders?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
But in biology, if you're working with a little C. elegans roundworm, you can... go in there and change its genome and make it do something that has literally never been done before, at least as witnessed by human beings. In particle physics, it is very, very difficult. to do an experiment that probes into a regime where human beings have never probed before.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
If you were a betting person, putting aside the muon collider, the muon collider we're going to get to, that's the payoff here. But what is the leading candidate for building the next collider other than the muon collider?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Listeners of Mindscape will get a $75 sponsored job credit to get your jobs more visibility at Indeed.com slash Mindscape. Just go to Indeed.com slash Mindscape right now and support our show by saying you heard about Indeed on this podcast. That's Indeed.com slash Mindscape. Terms and conditions apply. Need to hire? You need Indeed.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
I love how, Carrie, you use the idea of being on shell as just a common adjective that people would know.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Okay, I noticed that the United States is not included in there. Have we basically dropped out?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
And just so for sort of cultural enrichment purposes, Fermilab, which was the home of the Tevatron, which was for a long time before the LHC came on, the highest energy particle, et cetera, out there. The Tevatron is now just shut down. It's in mothballs, right? They don't keep running it even though the next thing is turned on.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
You need a lot of money, a lot of engineering know-how, and at this day and age, you need a lot of political will. It's a more than one country kind of international collaboration to get this going. So the question is, the Large Hadron Collider was super successful as a machine. They found the Higgs boson, Nobel Prizes were given out.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Okay, and then we have the possibility of a collider using muons, which is kind of a compromise. Like muons are heavier than electrons, but they're simple, unlike protons. So is that a good way to go?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Well, that's because you have not yet told the audience that the typical muon decays in about two milliseconds.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Sorry, microseconds.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
So you have a millionth of a second to make a muon, to hopefully make more than one muon, make a whole bunch of them, gather them up and accelerate them around a ring that is kind of big and then collide them together. That's the challenge.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Make no small plans, as a famous Chicagoan once said. How do you make all these muons? Let's get into the nitty-gritty of pretending we're experimentalists. We can do that because we don't need to worry about all the details.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
I would like one more Nobel Prize to be given out to the actual experimenters who were responsible for that, but we'll see whether that happens. The question is where to go next. What are we going to do? We're in this weird position, a theory that fits the data, but we know or we strongly, strongly think that it's not the final theory.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
That sounds scary already, yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
So there's different programs on the board, different proposals for what to do. The folks at CERN, which is the home of Large Hadron Collider, would love to build a larger hadron collider or electron collider or something like that on their site. There are people in China who want to build an ultra high energy machine. We're not sure what we're going to do next.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
And they're all negatively charged. So not only are they in a puffy cloud, but they're repelling each other.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
So is this something that we have the technology to do or do we have ideas to do it? Is this an ongoing research program?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
And then, okay, we're probably pretty good at the actual accelerating. I mean, that's something that we have been doing for a while.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Today's guest, Kari Cesarotti, is a particle theorist. So she works on building models of new kinds of particle physics that could then go out and be tested. But she's especially interested in literally the experiments you can do and figuring out what are the best experiments possibly that you can do. So rather than...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Don't have that time, no.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
And I remember... this might literally have been before you were born, but I remember Chris Quigg talking about a muon collider many years ago. Chris Quigg, former Mindscape guest, as well as a physicist. And there was something called the Ring of Death, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Because the muons, once they're in the circle, keep decaying and giving off neutrinos and other particles, which then go off and kill all the cows in the field around the particle accelerator.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Is this something that I should be worried about, or is that more or less something we have under control?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
They go right through you.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
I mean, there might be a public relations problem here. If you say, don't worry, we can wiggle the neutrinos so the deadly dose of radiation is spread out over a wider area.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Okay.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
I'm going to trust that OSHA is on top of this. But all right, so I wanted to get the challenges on board, and I think we've done a good job with that, unless there's any other secret challenges that we need to...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Sitting back in the armchair and thinking about quantum gravity and the emergence of spacetime, as some people are wont to do, she wants to make predictions and then go test them in a very, very detailed way. And the particular way that she is most fond of is colliding muons together. Muons were discovered back in the 1930s by Carl Anderson. There's a brief moment.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Well, and maybe again, just for cultural enrichment purposes for the audience, there's a kind of physicist whose job it will be to figure out, okay, how do we build a detector that can distinguish the actual muon collisions giving us new physics from sort of the background radiation and things like that? And then...
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There's another kind of physicist who's in there with a soldering iron and building the machine. And there's another kind of physicist, I think like you, who is saying, okay, here's a model that makes a prediction that we could actually test in a machine like this.
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289 | Cari Cesarotti on the Next Generation of Particle Experiments
Well, it will take a while to do it so we can get the youngsters excited about this, right?
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289 | Cari Cesarotti on the Next Generation of Particle Experiments
And okay, but let's switch to why this is worth all of the hassle. What's so great about a muon collider?
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In the 1930s, when Carl Anderson, a physicist at Caltech, had discovered half of the known particles in existence, because before Anderson, there was only electrons, protons, and neutrons. And then he discovered the positron, the antiparticle, the electron, as well as the muon and the antimuon. And the muon was the particle that led I.I. Robbie to say, who ordered that?
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And you used two words in there that sort of sound prosaic, but are super important, which is compact and energy efficient. Maybe that's the words. But, you know, compact, who cares how much space it takes? Don't you have space? And energy efficient, like, can you just plug it in? Why is that a big constraint?
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It was not clear what purpose it served. It was not part of the atom or anything like that. Of course, today, there's plenty of things that are not part of our everyday human existence, but they're there, out there as particles. Muons are heavier cousins of the electrons, so they have a lot of benefits that electrons have and protons have. They're kind of a happy medium in between them.
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289 | Cari Cesarotti on the Next Generation of Particle Experiments
Yeah, that makes a perfectly good argument. I noticed you didn't say that you were actually in favor of shutting down or turning the LHC, giving it less power to help the Ukrainians, but you understood why people would be, which is, that's good. That's how physicists have to think, right? Because no one else is going to do it for us.
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289 | Cari Cesarotti on the Next Generation of Particle Experiments
So you mentioned Fermilab there. Does this mean that the US, like, I don't really honestly care in some sense where it's built, Australia, India, these are all fine places. But is the US one of the places that is contemplating building a muon collider?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Massive, like the proton, but easy to control, like the electron. So why not build a machine? Well, sadly, the muons decay in about a microsecond.
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289 | Cari Cesarotti on the Next Generation of Particle Experiments
That causes some technological challenges, and it's plausible that we are right now at the verge of being able to address those technological challenges, opening up the possibility of building a muon collider and testing physics beyond the standard model of particle physics in a way we've never been able to do before. Carrie's going to give us the sales pitch for doing that.
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Yeah, I think it's a very good point. And it's not just that one style is better than the other, but a diversity of styles is very helpful, especially in a situation where we don't know exactly what we will see at this next generation.
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289 | Cari Cesarotti on the Next Generation of Particle Experiments
And I remember seeing an interview with a scientist from CERN who made the perfectly reasonable point that we're not building particle colliders that often. We built the LHC. It's going to take a long time to build the next one. And there's a very real danger that we forget how to do it, right? That there's a lot of implicit knowledge that just sort of ages out if we don't do this regularly.
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289 | Cari Cesarotti on the Next Generation of Particle Experiments
Right.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
And good. Let's bring it wind up sort of by bringing it back to the physics goals here. Are there things that a muon collider would be specifically good at discovering if they happen to be out there?
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289 | Cari Cesarotti on the Next Generation of Particle Experiments
I hope you come away convinced that this would be a wonderful idea. So let's go. Keri Cesarotti, welcome to the Mindscape Podcast.
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Your day job is writing papers, thinking about models of physics beyond the standard level. We're recording this during the day, so I guess this is part of your job. So it's the end of the podcast. We can let our hair down. Do you have a specific favorite model that you have personally worked on or thought up that might be amenable to testing in some way?
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I want the audience to know what it's like to be a working theoretical particle physicist.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
So sorry, we know of the good old Z boson. There's only one of them. It's a neutral spin one particle. And you're saying a different neutral spin one particle with a different mass, but doing kind of similar things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
So the standard model of particle physics, this is what people like you and I think about a lot these days. Let me ask like a silly question to start. Do you think that the standard model is beautiful or is it kind of an ugly duckling as theories go?
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289 | Cari Cesarotti on the Next Generation of Particle Experiments
So your calendar for the working particle physicist that includes three cups of coffee, two existential crises, it also has to include a sense of absolute grandiosity that we can figure all of this out, that it's something that is amenable to our understanding.
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289 | Cari Cesarotti on the Next Generation of Particle Experiments
With very good reasons, it sounds like. Carrie Cesarotti, thanks so much for being on the Mindscape Podcast.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Well, let's just be nice to our historian listeners or whatever and explain what a gauge boson is and why you say they go into a bucket.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
And the standard model, that's the label. It's such a boring label. I mean, it gives you the impression that it's just the model we have today and tomorrow we're going to change it. But there's a little bit more stability here.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
Actually, that's something worth amplifying on because maybe we don't always make it clear to folks, but the difference between a model and maybe a theory or a framework, right? I mean, we have quantum field theory as a very broad framework and then this very specific thing of the standard model.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
And the standard model of particle physics, as we call it, it does a pretty good job of accounting for what we see.
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Tell us, tell us what that exactly means. Why is that frustrating and how good is the job?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
But we, it's a weird thing, right? I mean, we have a theory that fits so much data and yet we're convinced it's not right. Like why don't we just declare victory and, you know, do on do biology?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
You're younger.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
And I think that, you know, in certain corners of the Internet anyway, there's a big Internet out there. There's a lot of corners to it. But there are people who worry. They would almost give you the impression that the slowing down of discoveries in fundamental physics is somehow physicists' fault. Like you're not doing it right. And I try to explain that's not really it.
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289 | Cari Cesarotti on the Next Generation of Particle Experiments
Do you have a favorite way of conceptualizing this?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
289 | Cari Cesarotti on the Next Generation of Particle Experiments
But there still are looming questions. And you used maybe the perfect word here when you said there are subtle questions, right? It's not like here is a picture in our experiment that we can't explain. It's like we have a feeling there are deeper explanations and there are reasons to go look for them.
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292 | Jonathan Birch on Animal Sentience
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292 | Jonathan Birch on Animal Sentience
That's B-A-B-B-E-L dot com slash mindscape. Rules and restrictions may apply. There have been, of late, broadly speaking, a few declarations on consciousness, Cambridge Declaration, the New York Declaration, both of which pointing in the direction. I think there were some overlapping signatories. I think you're one of the signatories of one of them.
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292 | Jonathan Birch on Animal Sentience
And in both cases, as far as I understand it, there's a Cambridge declaration in 2012. The New York declaration was just last year, 2023. At least the point seemed to be to nudge... 2024. Oh, was it 2024? Okay, good. This very year.
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292 | Jonathan Birch on Animal Sentience
Yeah. pushing people in the direction of taking seriously the possibility of animals having some notion of consciousness. What struck me about those, I mean, maybe you can just talk about them in general terms, but what struck me was the... they seem to give off an aura of consensus. Like we know this is true, which is something that in philosophy I so rarely come across.
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
Is that because there actually is consensus or because the people who organized these particular declarations are all of a mind on this issue?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
I feel bad when I drive in a way other than what Google Maps tells me to do, and it seems to be upset with me, right? So if we're thinking about it very, very carefully, we can have fun using words like personalities and being anthropomorphic with our pets, but maybe we want to be a little bit more rigorous. So you might want to ask... What kinds of animals are conscious, right?
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292 | Jonathan Birch on Animal Sentience
And maybe this is, I don't know, tell me about the journey here. Did thinking about that to help convince you that sentience is a better thing to focus on just because it's a little bit better defined or were you already on that train?
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292 | Jonathan Birch on Animal Sentience
Well, I'm completely on board with the idea that if you're going to have a declaration, the whole point of the declaration is to get a little bit of attention to it. And yeah, consciousness is going to be a more attention-grabbing word to the popular audience. Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
So, okay, let's focus in on sentience then. If it is about experiencing a sensation, what does that mean? How do we know when one is experiencing a sensation?
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292 | Jonathan Birch on Animal Sentience
I think we do, but this gets into the issue of the first person versus the third person way of thinking about things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
So I guess what I'm getting at then is how will we ever know? Or even how do we get more informed feelings about this or opinions about this? Is it by looking at the behavior of the crab? Do we dive into their connectome and their nervous system? Or is there something under a different methodology?
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292 | Jonathan Birch on Animal Sentience
Consciousness is a big topic in some of these debates. You instantly run into the problem that we don't agree on what consciousness is. Different people are going to have different standards for that. We might agree that rocks are not conscious, but maybe panpsychists will even argue for that. Most of us will agree that humans are conscious somewhere in between.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
In the case of the crab, just because that is something you talked about, I mean, what is the evidence that there is sentience there? It does skitter away if it's being approached by a predator, I suppose, but how much does that mean?
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292 | Jonathan Birch on Animal Sentience
Maybe there's a threshold or maybe there's a series of many thresholds. One way to make this a little bit more careful is to switch the conversation from consciousness, which is a little bit unclear what it means, to sentience. Sentience is sort of the ability to have a feeling of what it is like to be something, the ability to experience feelings and sensations, okay?
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292 | Jonathan Birch on Animal Sentience
Yeah, so this is what I've been struggling with since thinking about that example that you gave. Clearly what we—well, let's put it this way. If we have two magnets sitting on a table and we push one magnet toward the other, the other magnet, depending on how it's aligned, will either move away or come closer, right? That's not sentience or consciousness or anything.
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292 | Jonathan Birch on Animal Sentience
That's clearly just the laws of physics playing out. But if we are really strongly in an anthropomorphizing mode, we could tell stories about, oh, this magnet doesn't like the other one and it's skittering away. So that's what we want to avoid, right? That's the trap we don't want to fall into.
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And so the Crabbe evidence is saying that there's a bit of...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
So it does seem like it would be hard, you already have sort of said this, but it would be hard just on the basis of behavior, right? I mean, if I put the magnet on a wavy surface. There's going to be some competition back and forth between the push of the magnetic field and the pull of the gravitational field, but I'm still not thinking that the magnet is doing any integrating.
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292 | Jonathan Birch on Animal Sentience
Good. Okay, good. So those words are important. We're attributing sentience to ... it relies on some internal representation.
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292 | Jonathan Birch on Animal Sentience
And I think I'm not trying to be too skeptical here, but I do think I could imagine the crab doing exactly those behaviors without really having an integrated evaluative model of the world. It's just sort of being pushed in one way and pushed in the other way. So do we really need to go into the crab's neurons to be sure?
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292 | Jonathan Birch on Animal Sentience
Especially feelings and sensations that we would characterize as having a valence, a good sensation, or a bad one, a positive one, or a negative one. That's a little bit more well-defined. And then we can go ahead and ask which kinds of animals are sentient. And also the public policy question, what should we do about it?
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292 | Jonathan Birch on Animal Sentience
That sounds interesting.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
So before they're actually doing it, you want them to think about it.
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292 | Jonathan Birch on Animal Sentience
Yeah, no, I think I like very much the idea of the anticipatory question, because like you said, if there is some action that is clearly being taken because it's very hard to even use words that are not laden with human meaning. I want to say, you know, not anticipating, but imagining, right? But I don't want to attribute imagination necessarily to the bees, but they clearly are representing.
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292 | Jonathan Birch on Animal Sentience
How should we act if we believe that certain kinds of creatures are sentient? For as much as we tend to cutely anthropomorphize our pets, there's also a temptation to sort of ignore the possibility of sentience in animals that are not like us.
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292 | Jonathan Birch on Animal Sentience
You're better at this. You know what words I'm allowed to use. They're clearly representing a situation that hasn't happened yet, and that's something that the simple physical systems are not doing. Maybe even clearly is going too strong, but apparently.
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I did an interesting podcast with Adam Bully, who is a young collaborator of Thomas Sudendorf, I guess, in the vein of thinking about mental time travel and imagining the future and things like that.
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And they were trying to make the case that this is something that is uniquely human, the ability to literally imagine ourselves in a future environment that is kind of hypothetical, conjectural, contrary to fact. But there has to be some evolutionary journey for us to get there, right?
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292 | Jonathan Birch on Animal Sentience
I mean, do you have feelings about the importance of that to being human, to being conscious, to being sentient, the sort of counterfactual reasoning?
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292 | Jonathan Birch on Animal Sentience
I'm trying to figure out, is it really that different from counterfactual reasoning? I mean, is it not the rat in the maze?
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292 | Jonathan Birch on Animal Sentience
It is very common to cook crabs and lobsters by boiling them alive, and they thrash around a little bit, but you say, well, that's just an instinctive reflex reaction. That's not experiencing pain in the same way that we are. So regardless of what your opinions about it are, we should be able to think about this. rationally, coolly, calmly, okay? It's hard because we get very emotional.
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292 | Jonathan Birch on Animal Sentience
Right, possible futures.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
Is there any evidence for something like that in invertebrates?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
And it's always hard. It's a challenge. This is why I always say that physics is much easier than this kind of science. Because we see a behavior, and we know if we were doing that behavior, how we would explain why we did it. And then we're impressed when we see some other species do it. But maybe they're just using a different mechanism than we are, and we shouldn't be as impressed.
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292 | Jonathan Birch on Animal Sentience
And you never know whether we should be super impressed or less impressed.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
It is. It is absolutely suggestive. I'm sort of in my countervailing brain. I'm thinking of all these videos of dogs separated by a treat by some little piece of glass, and they just can't figure out. All you need to do is walk around the glass and get the treat.
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Well, maybe let's talk about what we know about the evolutionary journey to sentience or even to consciousness. I mean, is there some understanding of why it was useful for these different species to develop these capacities?
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Some people see the little lobster thrashing around and feel something deep inside, a sense of revulsion. Others just do it as a matter of course, and how do you have a rational conversation about that? Well, here we are to try to do that. Today's guest is Jonathan Birch, who is a philosopher. who's written a new book that just came out. Well, I'll tell you whether it came out or not.
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292 | Jonathan Birch on Animal Sentience
So, I mean, maybe it's useful to go through some organisms and ask how we should think about sentience. Or maybe prior ask this. Is there some, in your mind, even if not in the consensus of the field, can you identify where sentience started? What is the most primitive organism that could plausibly be associated with this?
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292 | Jonathan Birch on Animal Sentience
The common ancestor of those groups sounds like it would be very, very far back.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
Yeah, okay. So if sentience is evolutionarily useful, which it's easy enough to imagine that it would be, there's no reason why it wouldn't evolve in parallel in different branches, right?
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292 | Jonathan Birch on Animal Sentience
The book is called The Edge of Sentience, Risk and Precaution in Humans, Other Animals, and AI, because soon we're going to be building artificial systems that have many of the characteristics of things we would call sentience. So the book, The Edge of Sentience, just came out in the UK, will come out in the US in a little while, but also is available for free online.
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The octopus especially, right? There's a lot to keep track of if you're an octopus.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
So you would not think of single-celled organisms as sentience candidates?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
For plants, they're obviously multicellular organisms, but is the thought, even if it's a vague and tentative thought, that because they don't move around in the way that animals do, there wasn't any need for them to generate that self-image, that modeling ability?
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292 | Jonathan Birch on Animal Sentience
Maybe this is a tangential or distracting question, but I forgot to ask at the beginning, do you think of yourself as a physicalist or a panpsychist, or what is your deep take on what consciousness is?
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292 | Jonathan Birch on Animal Sentience
There's a PDF that you can just go to, and I'll, in the show notes, put the URL there. Oxford University Press is graciously letting everyone read this book because Jonathan is someone who wants to have an impact in the public debate. government thought about what it means to be a sentient creature and how we should deal with that. This is a set of issues where I don't think we're done yet, right?
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But it is perfectly plausible. And in this case, I think you make a convincing case that it doesn't matter for the specific set of questions that you're answering, that you're asking.
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292 | Jonathan Birch on Animal Sentience
Okay, so let me ask you, should we drop crabs into pots of boiling water?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
So let's just be super clear, because we're trying to be careful philosophers here. There's a question to be asked about whether it is ethical to kill and eat other sentient creatures. And maybe that's an important, interesting question, but you seem to be highlighting a different question, which is the suffering that we inflict upon these creatures.
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292 | Jonathan Birch on Animal Sentience
So there's room in your world for saying, we can eat the crab, but there's no reason to sort of egregiously make it suffer.
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292 | Jonathan Birch on Animal Sentience
I tend to agree with you there, but again, since it's my job to play the devil's advocate, are we really sure that any reasonable ethical stance would have that? I mean, how much do you rely on some specific notion of what is ethical to do to another sentient creature?
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292 | Jonathan Birch on Animal Sentience
I don't think that we have the consensus. I don't think we figured everything out. That's why we got to talk about it. Here we are to do just that. So let's go. So Donathan Birch, welcome to the Mindscape podcast.
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292 | Jonathan Birch on Animal Sentience
How do we try to compare the suffering of a crab to the suffering of a human being? I mean, maybe we don't have to. We're not usually... faced with crab-based trolley problems, but maybe we would like to be able to.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
I mean, maybe we're letting ourselves off the hook here just by talking about crabs. Talk a little bit about how in the modern way of farming, etc., we cause a lot of suffering. Yeah.
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292 | Jonathan Birch on Animal Sentience
And you've been, I mean, I should phrase it as a question. How involved have you been with actual policymaking, specifically in the UK where you live?
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292 | Jonathan Birch on Animal Sentience
So you're talking about issues that in philosophy contexts are often brought up, but often the word that we're talking about is consciousness. And you're focusing on the word sentience, which is a little bit different. So maybe explain to us what it is, how it's different, why you're thinking about that.
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292 | Jonathan Birch on Animal Sentience
Yeah, no, absolutely. I guess we naturally tend to be vertebrate chauvinists, being as we're part of them.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
And then there's an even bigger leap to artificial sentience in the sense of on a computer or even maybe in a robot that we build. How close are we to being able to build an artificial creature that has the complexity of C. elegans or something like that?
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292 | Jonathan Birch on Animal Sentience
I'm a big fan, yeah.
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292 | Jonathan Birch on Animal Sentience
Let's be a little bit more explicit for the non-experts out there. So we understand, or at least we've mapped out the connectome of C. elegans, which is literally how all the neurons are wired together. And there's only like 300 some. But you imply that we don't actually know what the individual neurons do. Neurons have structure. They're not just bits.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
So something like the open worm project, which I have on my phone, I haven't, I haven't looked at it for a long time. Uh, what do they try to emulate what the neurons do?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
Just so we have a vague impression of how difficult this is, you see elegans, we understand the connectome, which is like 300-some neurons. How big is the connectome of a crab or an octopus? Do you know?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
Yeah, but those are just the neurons. The neurons connect to each other, so there's some growth very, very quickly with the number of neurons.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
Okay, but we're skirting around the sort of other end of the simulation question, which is something like a large language model, which can mimic how human beings talk and respond to stimuli in some ways very accurately. Do you have any worry that a large language model would count as sentient by some criteria? Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
Maybe explain what a global workspace is in this context.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
You know, we see these videos of the robot dogs from Boston Dynamics that can walk around and do amazing feats of agility. It doesn't seem that hard. Maybe it's already been done to put a large language model in the robot dog and train it to sort of avoid pain and seek some rewards or something like that. How close would that be to being sentient?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
Well, I don't know. I've seen these videos of a cat walking into a store in the city and it's sort of limping so that the people feel sorry for it and give it food and then it walks away and it's fine. So at least there's some emulation going on there at that level.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
This does seem like a job for philosophy in some sense, right? I mean, philosophers... clearly are going to play an important role in this because it's not just that we all agree that there is something called sentience and we're trying to find evidence for it. We're defining it as well as finding it along the way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
So it seems like the paradigmatic case of a need for cooperation between scientists, philosophers, and policymakers.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
Are you more or less optimistic that philosophy has been helpful here and will continue to be?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
Yeah, I think this is a domain where a lot of discourse is driven by... People's feelings, their emotions, their non-reflected opinions about things. So I'm very glad to see some more careful thought put into these hard, very, very hard questions.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
Sounds like a good thing to do. Jonathan Burge, thanks so much for being on the Mindscape podcast.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
So in other words, something you mentioned about awareness, I forget whether I'm imposing that word on you or whether you used it, but so conscious experience in some sense is something that I need to know I'm experiencing, whereas sentience is a little bit broader. I could sort of feel something and experience it unconsciously. That would still count?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
So sentience is then broader than consciousness. We might imagine that there are critters that are sentient but not conscious.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
Okay. I think I'm finally getting it. So in other words, one of the advantages, the biggest advantage of sentience over consciousness as a concept to focus on is that it's better defined and consciousness sort of means different things in different contexts.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
And let's look ahead a little bit, sort of tease the audience. Why should we care about sentience? What is the impact of having a nuanced understanding of what that means?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
And eventually we're going to have to ask these questions about artificial intelligences.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
Hello, everyone, and welcome to the Mindscape Podcast. I'm your host, Sean Carroll. Sometimes on the podcast, I will refer to our two cats, Ariel and Caliban. They are born at the same time, you know, twins, I guess if you can say, but they're, of course, part of a bigger litter. Brother and sister with very different personalities.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
Okay, good. So we will get there. But I couldn't figure out, you've written a whole nice book about this, but in my brain, all these issues are kind of jumbled together. So I'm going to apologize ahead of time if I just kind of throw things out there and ask for your response to them. But let's home in, let's go back to this issue of sentience versus consciousness. You said one
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
thing that really struck me in a video I watched, which is that a crab does not have an inner monologue. A crab does not sort of narrate its own life. Presumably it doesn't. I mean, so I guess number one, are we sure that it doesn't? And number two, what does that say about conscious sentience or whatever?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
How much do we know about the inner monologue? I'm not sure that I have an inner monologue so much as an inner cacophony. Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
Do we have any idea? This is going beyond what we're talking about here, but you've fascinated me. Do we have any idea what's going on in the brain when we're sitting silently having an inner monologue?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
If you met Ariel and Caliban and interacted with them, even if you didn't see them, you would instantly know which one was which. There's a danger there, though, if we want to be a little bit more careful, a little bit more rigorous in using a word like personality, right? We tend to anthropomorphize our pets, other objects in the world. We anthropomorphize our GPS Google Maps system.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
And this is something which at least arguably is uniquely human. Does my cat have an inner monologue?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
292 | Jonathan Birch on Animal Sentience
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Let's help the audience understand the idea of benchmark hacking, because that's probably a cool but important one. I mean, what's a benchmark and how do you hack it?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
going to be in our human-level intelligence and agency, but well beyond that, superhuman, godlike creatures that we're going to have to deal with. I am myself not of that opinion. I do not think that that is actually what is going on. But just like the landing explorers, AIs do have different capacities than we do. They're trained, of course. They're designed.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
But on the science side, the physicist or social science side, the people who are interested in these models that create the sets of data you have, there's also, as I understand it, a lot of worry about degeneracy or overdetermination or underdetermination where very different physical models could give you essentially the same kind of graph or network. How big of a problem is that?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Well, this is because what you do for a living matters a lot to the real world and to money and things like that, unlike the foundations of quantum mechanics that I do. I don't need to worry about people being overly concerned with the results. They're all willing to give me a hard time anyway. Okay, so I have this sort of philosophical, mathematical problem. I don't know.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
I mean, if I have a graph, a big graph, so some nodes, some edges that are relationships, and I have a different graph, are there measures of similarity between them? Like if I add one node to the graph, is it a completely different graph? Or is there a metric I could put on there? How much is that even understandable?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
They're made to, in many ways, act very human. But they're really not. They're thinking in a different way. They're capable of some things much better than we are and other things not nearly as good as we are. So how do we think about this?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
That makes sense. In fact, because that because I was going to ask about when you have a big graph and you somehow coarse grain it. Right. Or, you know, you group subgroups into single nodes. You want to somehow have the feeling that it's still representing the same thing, even though you've thrown away a lot of information.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Yeah, I do know. Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
This world in which interacting with AIs, interacting with computerized systems more broadly is going to be a crucially important part of how we live our lives. Today's guest is Tina Eliassi-Rod, who is a computer scientist whose work spans the space. And this is why I really like it. From very technical stuff, just, you know, how do you better detect things?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Okay. I mean, I guess I'm spoiled by caring about what probably in your world would be the simplest possible case, because I think about the emergence of space from some set of quantum entanglements or something like that. And it sounds all very fancy and highbrow, but
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Basically, something is entangled with something else if it's next to it, and there's this very similar spatial or a very simple-minded spatial coherence. But, of course, in social networks, I can be connected to people anywhere, and that makes it a more complicated problem.
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301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
And so I mean, how good are we these days at detecting real clusters, communities, figuring out what's going on just from knowing about a graph and the connections between the nodes?
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301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Right. But you started with an example of being given recommendations by Amazon or whatever, and sometimes the algorithm fails because it's not picking up our individual idiosyncrasies. It's just giving us the most popular thing. Right. Is that tie in to the well-known problem of polarization or extremization of network recommendations?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Like everyone is pushed to some slightly more extreme set of YouTube videos or Reddit posts or whatever?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
I guess that makes perfect sense. So like the point is, if Amazon wants to recommend things to me, it's not maximizing the chance that I want this, it's maximizing its profit.
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301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
certain nodes or communities in an abstract network that you have embedded as some sort of data, but then also the human side of how you deal with this stuff, how these computer systems, how these AIs are going to affect our lives and we're going to affect them all the way up to human AI co-evolution.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Oh, wow, okay, yeah. I had not quite gotten that far, right. Right.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Well, we are part of the world and we create the world and it reflects back on us, right? I mean, it reminds me a little bit of discussions about extended cognition theories where you count your calculator and your pad of paper and whatever is part of your brain because you keep information there, you do calculations, et cetera.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
And so our environment and who we are is being increasingly populated by these artificial algorithms that we put out there.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
So I didn't see this article. What's your actual opinion? Is there any chance that that would help?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
We should also reveal to the audience that Tina has the good or bad fortune of being married to a philosopher.
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301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
So, yeah, so the evolution, I mean, I was going to get that later, but it's so good. We have to talk about it now. Co-evolution of humans and AI. And my guess was when I heard that phrase, we were thinking more about cultural evolution. evolution, right? Memes more than genes. But of course, they're interconnected with each other.
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301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Now that you say it, it's obvious because our cultural effects of our behavior, our behavior affects how we pass genes on to the next generation. So AI is going to be affecting the population genome of human beings.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Once we build these systems and then we interact with them and then we use them to decide how to go shopping or decide how to find a romantic partner, guess what? That affects who we are, how we live our lives, and the survival strategies we're going to have to move forward in this very brave new world. Again, many positive aspects here. There are things that, you know,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Are we good enough that we could at least imagine some kind of new equilibria that we get into when we're tightly coupled with our AIs that, you know, there is some happier state of being we could at least aim for if we're working together well? Or is it too much in flux these days to know much about that?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
But utility is tricky. I was talking with ChatGPT or whatever the other day, and I was trying to get it to imagine And maybe I didn't try too hard. I didn't really put that much effort into it. But I was trying to imagine a character in a fictional narrative who was very insulting and who would give out some good insults. And I said, what are some good insults that I could give out?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
But it wouldn't tell me. It's like, oh, no, you shouldn't give out insults. You should talk to people politely. It's clearly programmed not to go down that road.
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301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
We don't want to do, we don't want to bother doing or it's hard to do for us as human beings that we can outsource to the AIs. There are other ways in which it's very dangerous. The biases, the bad things that we have in our own brains can be inherited by the AIs and they can have new failure modes that we human beings don't have.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
And I know, I mean, this is probably related to the big worry that a lot of people have had about bias in AI algorithms. I mean, if you've trained AI, Well, if you train AI on human discourse and human beings are biased, then of course the algorithm is going to be biased. It's not because the computer is biased. It's because you've trained it on data that is.
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301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
And is that something that your tools can help us deal with?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Well, and human beings, I mean, this is an ongoing cultural flashpoint. So, I mean, there's a lot of different opinions about it. But human beings might at some point think of something to say that we know is inappropriate. And then we're smart enough or we have enough controls that we don't say it.
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301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Is that a kind of thing that it makes sense to try to implement in the context of a large language model?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Oh, that's very interesting. Is that actually true or is that like a feeling that people have?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
It's a world that is changing super duper rapidly, obviously, as a lot of research is coming in and a lot of influences are out there. It's not all about necessarily writing the best program. Some people who are very good at writing programs want to optimize for making the best money, right?
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301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Well, it's interesting because one of the things we discover, you discover, we in the royal we, thinking about these very, very large data sets is a sort of sometimes you can predict even more than maybe you thought you'd be able to. I mean, I want to ask you about this paper that you wrote about using sequences of life events to predict human lives. That sounds interesting, but also maybe scary.
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301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Yeah, that's okay.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
And we have to take that into consideration when we consider what to do, how to regulate, how to control, how to optimize for our own actual goals, rather than just seeing what happens next and living with the consequences. So the more informed we are about what the possibilities are and how to deal with them, the more we'll be able to do that. So let's go.
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301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
What does it mean in artificial symbolic language? Like literally a human language or it's like some logical encoding?
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301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
And what's the answer? Are we likely to die if we're 38 years old? How do we don't?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Right.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
How important is it to extract causality from these relationships? Like maybe riskier-minded people just become electricians.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
And so it's like, no, I ain't going there.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
There are some issues there. Yeah, no, absolutely. But I guess, I mean, it's interesting. Is it too much to draw a general lesson that... By looking at these large data sets, we might find simpler indications of what we're looking for than we expected. You might have said, okay, how many calories is somebody ingesting is the important thing to look at.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
But then you look at the data and you learn, no, what is their job? That's what's the important thing to look at.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Tina Eliassi-Rod, welcome to the Mindscape Podcast.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Hello, everyone, and welcome to the Mindscape Podcast. I'm your host, Sean Carroll. There's a kind of history myth that sometimes gets promulgated in, I don't know, elementary schools, maybe, or just folk tales we tell each other. According to which, when the first European explorers landed in the New World...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
So human beings, of course, are examples of complex systems themselves. But this raises the larger question of human beings will eventually die for whatever reason. Complex systems have their lifespans, right? Or maybe they're infinite. I don't know. But they can also change dramatically and die. And that's something else you're interested in trying to tease out in a general way.
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301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Normally, I like to start the conversation with someone talking about the most basic stuff, the things everyone knows about. For your stuff, I kind of feel like going in reverse order. We'll end with the fun stuff about AI and democracy and things like that, but let's start with...
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301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Yeah, I mean, I guess that's a good example. I hadn't quite thought of the vaccine thing yet. The traditional example that I hear for sort of a social phase transition is opinions about gay marriage, right, where it was universally against. It somewhat rapidly changed to generally for.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
But this is – the vaccine stuff is more subtle, right, because it's not that the whole society has gone against them but about half or whatever, right? There's this political polarization and there's sort of more than one –
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
consensus being built up is that is that just my impression or is there some idea that the modern informational ecosystem lets us have these sub larger sub communities where they have their own sets of beliefs different from other communities yeah i think it's the second one in that like in the past when you did have people that tend to be on the fringe they would people wouldn't hear them
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301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
understanding graphs and networks and things like that, especially using neural networks to understand things that human brains can't quite wrap their minds around. So what is the most general way of stating what it is that you're trying to understand when it comes to thinking about graphs and networks?
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301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
So I like the hypothesis that the vagueness of the proposition makes it harder to have a phase transition. How would we test that hypothesis? Is that something that we can sort of sift through the data and figure out whether or not that's on the right track?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Everything's a vector. It's okay. It's all in your algebra.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
So, I mean, one thing about complex systems is they can survive a long time. Like the human body, you know, fends off attacks pretty well because it's complex enough to catch things. The other thing is that they can sort of go into this wild negative – positive feedback loop, I guess, and crash, right? Like the economy or something like that.
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301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
So is this something – maybe this question is too vague, but is – Are we learning general purpose lessons about complex systems concerning what features they need to be stable versus what features they need to be delicate?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Okay, so I guess, you know, and one of the important applications here that you have talked about explicitly is democracy, right? Democracy is a complex system and democracies do fail sometimes. And I guess one way of putting the worry is that, or at least the interest, is that the introduction of AI as a new feature in some sense, opens the possibility of a new instability.
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301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
It could lead to sort of a runaway disaster that destroys democracy, not to put it in too alarmist terms.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Well, is that true? I mean, maybe it is true. I'm certainly willing to believe that's true. But again, I always worry about comparing eras, right? Because I was a different person in the 70s, and the 70s were also a different time. But I don't know what things are common between different eras and things are not.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Like, did we really want to think more back in the 1970s than we did in the TikTok era? I don't know.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Yeah. Okay, good. So this is another aspect. So, okay. That's actually nice. Despite not really trying to, I think that I see a bunch of threads coming together here. Like, uh, Technology broadly, not just AI, is giving us new ways to fulfill our own objective functions. Maybe it's a dopamine hit or whatever. But its objective function might not be ultimately our flourishing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
So there's an absolutely danger mode there.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
You've co-evolved with your network. That makes perfect sense to me. Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Exactly. Exactly right. So, okay. So you've said many things about this already, but I just want to get it as clear as possible. The trust, the community of trust idea that is so central to a democracy is one of the things that is in danger of being undermined by AI, right? Like you probably saw the story about Instagram having its AI accounts.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
The sassy black lesbian lady who was programmed by a bunch of people who are neither black nor lesbian and just pure AI. And that one was admitted, right? Like they said that was AI. And do you personally worry that people are just going to mostly become friends with non-existent human beings in the long term?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
So how do we get that? What do we do? This sounds very scary, but I'm not quite sure what to do about it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
But the problem with that, of course, is that the value of getting an education is also susceptible to this loss of trust. I don't know if you saw the recent – people were getting upset because there was a poll that showed that young men were becoming less and less interested in going to college.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
But then someone else pointed out that if you go into the crosstabs, if you look at other questions that were asked, there's actually no relationship between male and female versus going to college. It's all about Republican versus Democrat.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
It's a Simpsons paradox kind of thing where most of the young Republicans are male, and those are the ones who have become very polarized against wanting to go to college. So that's a – That's part of the problem you've been talking about, right? Like there's a whole new epistemic community out there that is forming and it seems to be solidifying over time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Do you think that AI and associated technologies can be a force for good in education?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Do you yourself use ChatGPT or something equivalent to help figure things out, to learn about things?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
You don't trust it. I certainly don't trust it. But sometimes I did realize that there was a good use case because I was trying to understand... You know, in mathematical things, they will often tell you true things, but you don't understand what the point of it is. Right. And I was trying to understand type three von Neumann algebras.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
And so I asked and I got chat GPT to explain to me not just what the definition was, but why it was important in this particular case. And that was actually very helpful. Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
That's the problem. There's too much. Like you just said, there's too much junk out there. In some sense, if you get technical enough that it knows about it, but not so technical, all the stuff that's been written about it is sensible. Like, no one's going to make up stuff about type 3 von Neumann algebras. What would be the point? Exactly.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Yeah, I think that the weird thing is we're trying to use it for creative work, whereas the most obvious use case is for the least creative things that we don't want to do.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
All right. It's all very complex, and it's evolving, and there's a lot of degrees of freedom. So Tina Eliassi-Rod, thanks very much for helping us all figure it out.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
So for the audience who wasn't there, what Tina is not telling you is that we spent 10 minutes before the podcast struggling with our Apple products to make the recording work, but we still use them. So, you know, I guess take whatever lessons from that. Okay, but I guess in the current era, the issue is you have...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Too much data, or at least in principle, one would like to imagine having too much data. There's like so much stuff, right? Is a large part of the worry like how to pick and choose what to pay attention to, what to draw connections between?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
The indigenous folks saw them and thought, oh, my goodness, these are gods coming to visit us and we need to worship them and they're too powerful to deal with. Turns out nothing like that is actually true. This is a story that the Europeans made up after the fact to make themselves look good, justify some of the things that happened.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
So thinking though, like purely like a mathematician or a computer scientist, faced with these big networks, how should we think about them? What are the tools that we use to tease out what are the important relationships?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Nowadays, we are being faced with a new set of visitors from another world, namely artificial intelligences, whether it's large language models or some other kind of constructed program that in many ways can act human, but has a different set of capacities and we're learning to deal with them.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Uh-oh.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
So it's interesting because it seems like an attempt to go from syntax to semantics in some sense, right? You're going from structure to meaning, broadly speaking.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
Well, or as you were giving the example, I was thinking, I don't interact with my romantic partner on social media that much because we interact in real world. Like we don't need that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
And unlike the myth of the European explorers landing in the Western Hemisphere, today there are a bunch of people who quite literally who are very willing to say that these are gods coming to deal with us. I know there's also plenty of skepticism out there, but there are people who think not only that AIs are gods,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
301 | Tina Eliassi-Rad on Al, Networks, and Epistemic Instability
I mean, allow for the existence of noise in these descriptions and see how your answers change.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
based only on macroscopic data, coarse-grained data, limited data, whatever you want to call it, compressed data about the system that you're thinking about. And we'll get into exactly what that means. Let me first, though, point out there's a question here. Is the existence of such higher-level patterns robust? Is it a generic feature?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
Like, is it true that for almost anything, the underlying laws of physics could have been— that you would get some emergent higher-level descriptions, that it would be possible to make predictions with vastly incomplete data? Or is that very, very special? Is there some feature or set of features about the specific rules that we have in nature around us that helps us predict?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
by allowing us to discuss it at this higher emergent level? I do not know the answer to that one. It would be really nice to have some theorems or some demonstrations about when emergence happens and when it doesn't, not just if this happens, then emergence is possible, but in the space of all possible underlying theories, how many of them What proportion? What fraction?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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How likely is it that you will have any kind of higher level emergent theory? I truly don't know the answer to that one at all. I can speculate. But that's up to future researchers to figure that out. OK. So that's the general idea.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
The general idea of emergence is you have a lower level, you have a higher level, they're related in some way, and part of the relationship is that the higher level uses less data. It does not require that you know everything that there is to know about the lower level, and you can talk about each level for its own sake, in its own terms, using its own vocabulary.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
So there's a couple of problems associated with this very natural setup. One is that when people actually do this, they are very vague. People are vague. It's very frustrating to me, as I said in the intro. I don't. I don't mind disagreeing about the substance of how you think the world works. That's fine.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
But this is a strange part of philosophy and science where people are almost intentionally vague about what exactly it is they mean, or at least... Maybe they're not intentionally vague, but they're satisfied with using terminology that is just not that clear what is meant when they say it. And I don't see any reason for that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
I would like to be clear in what I'm trying to say whether or not people agree with it. So very often in descriptions of emergence, one of the aspects that you'll find is that people say that the higher level – properties or higher level behaviors or dynamics are novel or new or surprising or cannot be derived from the microscopic level. What does any of that mean?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
Or at least if it does mean something, if we think it means something, what precisely does it mean? Is it subjective? When you say something is surprising or novel about a higher level theory that is not there, not obvious from the point of view of the lower level theory, well, what if it's not surprising to me? Yeah. Could it be surprising to one person and not surprising to somebody else?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
Likewise, even if you say the behavior cannot be derived even though it is implicitly there from the underlying theory, what do you mean it can't be derived? Like I haven't derived it yet. There are some things which I haven't derived yet but maybe in the future I will derive. Is emergence sort of time-dependent? Once you are able to derive it, it's no longer emergent anymore? No.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
So this was a big motivating factor in writing the paper that Achuth Parola and I wrote, the idea of removing all subjective judgment-like words. I do think that these ideas are related to real objective features. It's just a matter of spelling out explicitly what those real objective features are. Thank you very much.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
One paper that is a classic in the discussion of emergence, at least among physicists, is Phil Anderson, the condensed matter physicist who passed away a few years ago, wrote a paper in the 70s called More is Different.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
And his point in the More is Different paper is, as I said before, if he's a condensed matter physicist and he's trying to study superconductivity or something like that, as he often did, he doesn't need to know. All the microscopic specific details about things. He doesn't need to know about the Higgs boson or the top quark to study superconductivity.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
You don't even necessarily need to know about – well, you certainly don't need to know about quarks and gluons. Maybe you don't even know about atoms at a certain level of abstraction, OK? But in that paper – so people – Take that paper, the title of which is More is Different. And they – I think – I don't like to be unfair.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
But I think they read the title and I don't think they read the paper because from the title you get the impression, well, once you have many things and they're coming together and they're interacting in a certain way – Different things happen, right? Things that you would not maybe have predicted from the underlying stuff. But Anderson is very clear.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
Welcome to the Mindscape Podcast. I'm your host, Sean Carroll. Longtime Mindscape listeners know that the idea of emergence emerges over and over again. And in various contexts, for example, you might hear someone claim that consciousness is not a new fundamental category, but rather an emergent category from underlying physics. And
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
He says multiple times, and I'm sort of sympathetic to his way of writing it because I've done this before myself where I know I'm saying something that is going to be misunderstood. So I say it as clear as possible multiple times. Anderson says very clearly reductionism is true.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
That is to say when he's studying his superconductors or whatever, he has no doubt that there is a way of describing what's going on that is at a lower level, that is in terms of atoms and forces and quantum field theory and whatever. His – and what happens at the higher level is 100 percent compatible with that and indeed in principle 100 percent predicted by it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
He is not denying that in any possible way. What he's denying is not reductionism but what he calls constructivism. He's denying that the right way to study the behaviors of superconductors or higher level things is to start thinking at the lower level. That's, I think, pretty undeniable.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
Like certainly if you go much further than superconductors up to biology or economics, there's zero insight gained by studying the lower level description in terms of particle physics, right? We have the core theory. We have a very successful micro understanding of the world in the everyday life regime, the standard model of particle physics plus gravity, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
That's not very helpful when you want to study biology. But that's zero reason to think, following Anderson's perspective, that biology is somehow not in principle entailed by the standard model of particle physics plus general relativity. Anyway, all of this is to say that people need to be clear about what their words mean.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
When I had my debate with Philip Goff over panpsychism, et cetera, a few – I guess it's over a year ago now. I said that the one thing – I gave advice to people. I said if you're talking to a panpsychist – The one question you have to ask them is, OK, you're imagining that consciousness is everywhere or everything is consciousness.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
You're promoting some view of consciousness that it is something more than just a convenient way of talking about the collective behavior of underlying particles and fields. Fine. Does your understanding of panpsychist consciousness imply that we need to modify the underlying laws of physics? Or, as we know them now, or is it completely compatible with those? Either one is worth discussing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
I'm happy to discuss the possibility we don't need to do it. I'm happy to discuss the possibility we do need to do it. But tell me whether we need to do it or not. And Philip's answer was, you know, no, I don't have to tell you that. I'm not really there. Maybe it is, maybe it isn't. And in some sense, that's fine.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
It's fine to not have your theory developed well enough that you can answer every possible question. But then don't claim that your theory is very good. My point is that this is a very, very fundamental basic feature of your theory of consciousness. Is it compatible with the known microscopic laws of physics or not? That's super duper important. That's not like, oh, we'll figure that out someday.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
But meanwhile, we have a very successful theory. If you haven't figured that out, you do not have a successful theory. And this is part of the quasi-intentional vagueness that rubs me the wrong way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
The other thing that gets in the way of talking about emergence is that even when they're not being vague, people do use the word differently depending on where they come from, what they were exposed to in the early point of their education and so forth. And this is perfectly fair because the meaning of the word has sort of grown and changed over time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
This is a useful idea of emergence in the sense that we're talking about it here. It's talked about a lot both in science context and in philosophy context. But it's also a little frustrating. It's frustratingly vague about what exactly is meant. Part of this is because different people use it to mean different things. Part of it is because different people want it to mean different things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
And that's just a reason to try to be explicit about what you mean, not just use the word emergence and then assume everyone is going along with you, but to just say what kind of emergence you're talking about. If you look up or you talk to philosophers or you look up in philosophy references, the word emergence came into popularity from a group of people who are known as the British emergentists.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
I believe that John Stuart Mill was actually in some sense the founder of this perspective, and it's a way of thinking about consciousness especially. I mean, it could be It could be spread more widely to other kinds of ideas, but they cared about consciousness. People like C.D.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
Broad and Samuel Alexander and so forth talked about the emergence of consciousness, and they were emphasizing in their view that there really was something truly new. at the emergent level.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
So if I understand correctly, the perspective of the British emergentists, they were on the side of things that said the kind of emergence they care about is something where you could not predict the higher level behavior just on the basis of the underlying theory.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
Of course, they had no idea that we would have such an effective underlying theory like we have now, but still the perspective is perfectly OK. And these days we use emergence sometimes to mean that and sometimes to mean something much more down to earth just like what Phil Anderson meant, OK? And both ways are fine but they are very, very different especially in their philosophical implications.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
So … Once again, I would advocate being clear about this. And finally, I guess I should say, just to be super clear because not everyone is a physicist or philosopher, the word emergence absolutely has a connotation of something happening or playing out over time, right? The emergence of a chick from its egg or the emergence of worms from the ground after it rains or something like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
Zero about what I'm talking about in this solo podcast is about that kind of emergence. Our kind of emergence is a relationship between two theories, a micro theory and a macro theory, and that relationship is supposed to be true at all times, okay? It's not the—when we say, you know, consciousness emerges—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
that that particular phrase does not refer to the fact that things come to be conscious over time. That might also be true, but that's not what we mean by consciousness emerging in this discussion that we're having right now. OK.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
Given that there are all these different definitions, different ways of talking, and I'm trying to get people to be clear, let me be clear about the fact that there is a very famous and somewhat useful distinction between strong emergence and weak emergence. You've heard of this distinction probably. If you've heard of emergence discussions at all, it's the first thing people talk about.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
And again, I think the British emergentists came first and they would be in the realm of what we call strong emergence. And only later did the idea of weak emergence become so obviously useful that they started calling it emergence also. There's a famous paper by philosopher Mark Bedow that is simply entitled Weak Emergence.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
I don't know if that's the first time the idea of weak emergence was sort of explicitly used. spelled out in the philosophy community, but certainly been a very influential paper since then. And Badao's point is that you might have a situation where there's a microscopic theory and a macroscopic theory.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
And it might be true that the higher level properties, the way that we talk about the macroscopic theory is not obvious from just thinking about the microscopic theory. But But in principle, in his version of weak emergence, the idea is that it does arise from the lower level dynamics. And the nice thing about Badao's paper is that he operationalizes this idea.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
So when you say, OK, the higher level dynamics arises from… the lower level dynamics. What exactly do you mean by that? That's the kind of tedious thing we're going to be talking about during this whole podcast. What exactly do you mean by that? And he answered it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
And part of it is because people are not clear about what it is that they actually are meaning. In particular, the thing that gets me is I just really would like clarity when some people talk about higher-level emergent things about whether or not they are imagining that the existence of these higher-level emergent things— violates or demands a modification of the lower level laws of physics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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He said, what I mean by arises from is that in principle, I could take the description of the system I'm talking about, I could cast it in the language of the lower level of the microscopic theory, and then I could put it on a computer. That's the step that he did that was really very useful.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
He said rather than using philosophy words like governing or supervening or determining or whatever, which are fine, but then you have to sort of negotiate what you mean by them. He was very down to earth. He said, look, if I really believe I have a theory of the atoms in let's say a crumpled up piece of paper I'm throwing up in the air.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
295 | Solo: Emergence and Layers of Reality
I could put the state of the crumpled up piece of paper and the dynamical laws of a lower level theory on a computer, run the simulation, and the simulation would make a prediction and it would be correct. That's what he means by weak emergence. So we may or may not be able to derive the higher level description from the lower level ones.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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But in principle, it's there as is made clear by the idea of the possibility of putting on a computer and asking. As opposed to this, we have strong emergence. Strong emergence is where the higher level properties are not only not obvious, but they are fundamentally new. They are even in principle not predictable from the lower level.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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There's another famous paper by David Chalmers, former Mindscape guest. where he talks about both strong and weak emergence and he's very clear in the sense that he says that the higher level properties in strong emergence are not deducible even in principle from the lower level properties.
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And this in principle thing is very important because a lot of people – one of the ways, one of the favorite ways to be vague about emergence is to blur the distinction between what is in principle impossible and what is merely kind of difficult, OK?
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So he's saying that in strong emergence, even in principle, even by putting it on a computer, you could not figure out what was happening in the macro theory. So that's fine. That's a relatively clear conception. But there's an obvious problem with it. Not a problem with it, but a puzzle that arises when you take that conception seriously.
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And this puzzle is sometimes but not very often confronted, which is the following. If you say I have a lower level theory. I have a theory of atoms and how they bump into each other and how they combine chemically and whatever. And I also have a higher level theory of like a conscious person with a brain and the brain is made of atoms. Okay.
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then in principle I think I could imagine taking the state of the brain, the person or whatever it is, and putting it on a computer and making a prediction based on the lower level theory. So are you saying that the lower level theory is wrong? I think that people don't want to say that.
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It's very, very rare that strong emergentists will actually say, yes, I'm saying the lower-level theory is just wrong in the domain where you have a person with a brain. I think what they would like to say is that the lower-level theory is just incomplete, right? right, that somehow there's wiggle room in the lower level theory.
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So when you apply it to a person who has a brain, there were gaps, there were lacunae in the lower level description that are filled in by some higher level strongly emergent properties. And I think that's just wrong.
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I think that in the case of a good lower level theory, if the higher level theory is supposed to literally describe a system that is made of lower level things, the lower level theory says something. And you're either going to agree with that or disagree with it.
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And therefore, if you disagree with it, if you think that there is strong emergence going on, then the lower level theory was never the right lower level theory in the first place. So the problem in this sense with strong emergence is just that it raises the possibility that it's not a deep feature of the world. It's just that you made a mistake when you invented that lower level theory, right?
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Maybe, maybe not. That's what we're going to talk about. So our goals are first to distinguish between these various varieties of probability. weak emergence. So even aside from the weak versus strong dichotomy, there's a lot going on just in the world of weak emergence.
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Maybe it does, maybe it doesn't. But I do think that as a respectable thinker about these things, we should be clear about what exactly is going on. And so I'm not interested so much in policing the definition. I'm not here to say what the right definition of emergence is.
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And I think that one of the stumbling blocks to clear communication here is that people haven't really been clear about the different subdivisions of weak emergence. And I want to do that in a way that doesn't use these sort of subjective judgmental words like novelty or derivability or whatever.
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And then the other goal is to explain how strong emergence could be a real thing without just reducing it in some simple sense to the microscopic theory or your idea of what the microscopic theory is was just wrong, right? Is there any way you could have some version of strong emergence and still think that in its own domain the microscopic theory is perfectly right?
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And I want to offer that yes, there's a potential answer yes to that question. Now, because I've gotten feedback, polite feedback from some people who've looked at the paper, I want to be very clear that that's all we're trying to do. We're trying to figure out the different varieties of emergence, okay? That's why the title of the paper is What Emergence Can Possibly Mean.
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There is another, maybe arguably more important thing to do, which is to ask questions. When does emergence happen and how can you discover it? That is to say, given some microscopic theory, can you figure out whether there are higher level emergent ways of talking about it? And if so, can you literally construct what those higher level ways are? People do work on this.
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Former Mindscape guests like Anil Seth or David Krakauer have written interesting papers about exactly this problem. Super-duper important, super-duper interesting, not what we're talking about. So you're welcome to be interested in that problem, but it's just not the fish that we're trying to fry here today. Okay.
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So how are we going to do this? How are we going to figure out the different ways that there could be some kind of emergence and that we can define what we mean very clearly without using fuzzy subjective language? The short answer is we're going to think like physicists. That is to say we're going to imagine that there are systems that we're interested in, and those systems have two elements.
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But I do think that it's important to clarify all the possible ways in which we might profitably talk about something being emergent without first judging what exactly is going on. And indeed, this is a longstanding ambition of mine. I finally got a chance to write a paper about it with Achuth Parola, who's a student here at Johns Hopkins. We wrote a paper called What Emergence Can Possibly Mean.
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They have states that you can be in. In classical mechanics, you have constituents with positions and momenta. In quantum mechanics, you have wave functions. In biology, maybe you have cells or organisms. There's some space of states. And then you have some dynamical rules for how those states evolve with time.
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And the idea is that if you give me the state of the system, maybe the microstate, maybe some macrostate, whatever, you can use the rules to make predictions about what will happen next. And the rules need not be either super precise or even deterministic. Maybe the rules are there's a volcano and it will erupt a certain fraction of the time or something like that, right?
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There's a probability per unit year that it will erupt. That's fine. That's a theory. We're not demanding that your theories be perfect. We're just saying that they exist.
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We're making one assumption that is non-trivial, which is that the theories are what is called Markovian, where this is sort of a slight abuse of terminology because Markovian is usually invoked as a concept when you have non-deterministic theories. We're going to include deterministic theories as well.
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The idea of Markovian is just that the theory makes a prediction for what will happen next based on the state at a current time. It doesn't need to know the past history of the system and what it was doing to make a prediction about what comes next. If you have a baseball flying through the air, you can predict where it will go from knowing how it left the bat, its position and its velocity.
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But if you look halfway through and you tell me its position and velocity halfway through its trajectory, you can predict its future without knowing. It's past, okay? That's because the dynamics are Markovian. I don't think this is a real restriction because I think that there's sort of a matter of convenience here.
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I could always define a space of states to include enough information about the past right now to make that Markovian version of the theory perfectly adequate, okay? So I don't think this is a restriction on what we're looking at, but I just wanted to flag that as something that we do actually assume, it makes the later discussion much, much simpler.
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And then with this setup, we have spaces of states and we have an evolution law over time. So we're not worrying about complicated questions in quantum gravity about the emergence of time or anything like that. Time is fundamental for us, okay? Then the basic idea of emergence is pretty straightforward.
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First, there is a map, the emergence map from the micro theory to the macro theory, which will be throwing away information. The map will be coarse-graining. It will be many to one. There are many different microstates that map onto the same macrostate, okay? That's not the only thing you can have if you have two different theories. There are certainly examples in physics where you have
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two different theories that are secretly equivalent to each other, right? So one state in one version of the theory maps onto one state in the other one. That's fine. You can have that. I'm just saying that that's not under our definition of emergence. You throw away information in the emergence map.
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So you map from a collection of many, many atoms in a piece of paper to just the crumpled up ball of paper. You throw away an enormous amount of information when you make that map. There are many different... individual microscopic states that could amount to that kind of ball of wadded up paper, okay?
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And then secondly, you retain the ability to predict even though you've thrown away all that information. That's the other aspect of emergence, that the macroscopic theory by itself has sensible dynamics. I don't need to know about the atoms to throw the ball in the air and to catch it, okay? So those are the elements you have.
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You have a microscopic theory with its space of states and its evolution law. You have a macroscopic theory with its space of states and its evolution law. And technically, what we're saying is that there are two maps. One is the map from microstates to macrostates. The other is the map of the state at one time to the state at a future time.
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This is actually the second title of the paper. The original title when we were working on it was called Emergence Without Judgments. That was supposed to represent our frustration at people who tried to define emergence but used words that were themselves ill-defined, like novelty or surprise or things like that.
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And the requirement that all of this setup describe emergence be that the diagram commutes. That is math speak for saying that I can start in the micro theory at some time. I can evolve it forward in time using the laws of physics. And then I can do the emergence map to a macro state.
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Or I can start with a microscopic state, immediately map it to a macroscopic state, and then evolve it forward in time with its laws of physics, and I will get to the same place. I will get to the same future state of the macroscopic system. That's what it means for the diagram to commute. We can walk through the diagram. The diagram has four...
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nodes in it, microscopic state at time one, macroscopic state at time one, microscopic state at time two, macroscopic state at time two, and it has arrows, upward arrows for the time evolution, arrows going left to right for the coarse graining emergence map, and the diagram commutes. You can chase through those arrows either way.
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So that's what it means for us roughly to get emergence one way or another. Now, something we're not going to pursue but is very interesting is – and I'm not – so I'm not even sure this is a thing. I'm not sure this is like important or it's just obvious.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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But in many examples of emergence, not only can you throw away an enormous amount of information in this coarse-graining emergence map, but the info you do throw away tends to be Sorry, the info that you keep, I should say, the opposite of the info you throw away, the information that is still there in the macroscopic description tends to be observable from the macroscopic point of view. right?
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So if I have the little ball of wadded up pieces of paper, not only is what I need to know about it, roughly its position and roughly its macroscopic momentum, but I can see those things by looking at them, right? That's conceptually not exactly the same thing.
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It is, as a practical matter, super important to the fact that higher level emergent theories are useful, but I just don't really know if it's sort of obviously always going to be the case or if we just get lucky? It's certainly the case that there are things that are not observable that might be useful to me in predicting the future, right?
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If I have a theory of volcanoes erupting, it might be useful to me to be able to observe microscopic features of what's going on within the volcano that give me much more precise ability to predict rather than just a certain rate of eruption. But I can't observe those. That's not part of my macroscopic theory.
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If I could read someone's mind, if I could look into the state of their neurons and know what they were going to do next, that would be super useful. But the laws of physics don't let me do that, okay?
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So there's some feature of some relationship between what is observable at the macro level and what you need to build a decent immersion theory that is fascinating to me, but I don't have anything to say about. I'm just letting you know that it's out there. Okay.
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With this setup, micro theory, macro theory, space of states, emergence map, evolution laws, we can start classifying all the different kinds of emergence. And we are being so general that some of what we call emergence won't be called emergence by anyone else. So we had in our paper something called type zero emergence or featureless emergence.
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So one way or the other, what we're trying to do is just to bring super-duper clarity to this. And Today's podcast episode is about exactly talking about this, going over what we did in the paper, and more generally commenting on how emergence goes.
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And that's where you have literally nothing but what I just gave you. So there's no extra structure. So later on for other kinds of emergence, we're going to be talking about locations of things in space, right? Things are going to have structure in space and they're going to interact locally. That's going to be very important. But you notice I didn't say anything about that.
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I didn't say that there were holes made of parts, holes, W-H-O-L-E-S, right? Very often in discussions of emergence, you will instantly leap to a discussion of little things coming together to constitute big things. But I didn't use any of those words when I said micro-theory, macro-theory.
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So it's about the theories and their spaces of states and at the level of Type 0 emergence, there's no talk of parts, holes, spatial structure, or anything like that. Roughly speaking, I have one example that is very important, very close to my heart of Type 0 emergence, which is the classical limit of quantum mechanics. Arguably, there are other limits.
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There's other examples of general relativity mapping onto Newtonian gravity or something like that. But basically, what you have is some very rich description at the fundamental level, like quantum mechanics says you have these wave functions for many, many particles. But let's just look at one particle, okay? Let's not worry about entanglement or anything like that.
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When we learn about quantum mechanics in class— we are told how to take the classical limit of a big heavy quantum object. If a quantum mechanical object is very massive, then you can make its uncertainty in both position and velocity relatively small, right?
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So that's where you get a classical limit and you literally take the average value within the wave function of the position and of the velocity and you show using Ehrenfest's theorem that those average values, those expectation values of position and velocity will satisfy the classical equations of motion.
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So in this case, you have a very, very explicit emergence map from a wave function to classical point-in-phase space, position and velocity. And it is clearly a many-to-one map because all the information you're keeping is the location of the center, the expectation value of the position and of the velocity or the momentum.
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So you may or may not agree on some of my judgment calls along the way, but hopefully the classification system for different kinds of emergence will be useful to anybody, no matter what kind of emergence you actually think exists.
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You're losing, you're throwing away a lot of specific details about the shape. of the wave function. As long as it's relatively localized, there's more than one way to be relatively localized. There's many, many ways to be relatively localized, but you don't care. All you care is where the sort of centroid of that wave function is. So to us, that is absolutely emergence. The classical limit
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is an emergent description from quantum mechanics. And notice that it is not valid in all regimes, right? Whenever you have a situation where quantum mechanics is necessary, like if you talk about the double slit experiment, right, where you send a wave function through two slits and they interfere with each other, that is outside the classical limit. So That's fine.
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All of these emergence maps are generally going to be well-defined in some domain of applicability. That's perfectly legit. So no one else calls the classical limit of quantum mechanics emergence, but we specifically and intentionally do so because we want to start with things that are easy to understand, right?
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Start with things that are unambiguous, that are perfectly clear what is going on while still building up to what ordinary people would – use or have in mind when they invoke the idea of emergence. So we didn't, in type zero emergence, what we called featureless emergence, make use of the whole being made out of parts.
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A quantum particle, an electron, that classically is described by a position and a velocity and quantum mechanically is described by a wave function, doesn't have the property that somehow that position and velocity are made up of little bits of wave function, right? That's just not how it works. But still, there's a many-to-one map, which is a more general idea.
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But okay, admittedly, more often we're talking about situations where the big macroscopic things are made up of many different little microscopic things. When we take the piece of paper and we crumple it up, the idea of emergence there is that the piece of paper is made of atoms, okay?
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Now, I should, of course, mention that for contemporary listeners, those that are listening to the podcast soon after it was released, we are in the aftermath, less than the week away, of a presidential election in the United States, which was held last week, where Donald Trump beat Kamala Harris to become the president-elect. This is a big deal.
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And the emergence map takes many, many different configurations of the atoms and combines them into a single configuration of the piece of paper. So if we move on to type 1 emergence, which we call local emergence, that's exactly what we have. Local emergence, you will not be surprised to hear, relies on a notion of locality.
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That is to say there is space, three-dimensional space, typically for you and me, but physicists will let their imaginations wander a little bit. But OK, three-dimensional space. And there's a notion of locality. Things have space. locations in three-dimensional space, and locality refers both to what you are and how you interact, or at least I should say it can refer to both of those things.
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So the word locality is sort of doing double duty here, and I think it's important to be careful. It means both that objects have extent and position in space in a way which, by the way, they kind of don't in quantum mechanics, right? The wave function is defined all over space or in field theory for that matter.
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But once you get to classical particle dynamics, etc., things have locations in space. And they also interact locally in space, or they can interact locally in space, which is a way of saying that billiard balls bump into each other. They bump into each other not when they have the same velocities or opposite velocities, but when they are near or at the same position in space.
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That's what it means for interactions to be local. In quantum field theory, interactions are local. The field at any one point is affected by values of the field only right there at that point or at least really, really nearby. specifically derivatives of the values of the field in space can affect what the field does. But there's no direct influences from far away.
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You can have something happen far away in field theory, either classical field theory or quantum field theory. You poke a field, Let's say your field is a very down-to-earth thing, like the surface of water on a pond, okay? You throw a stone into the pond and little waves ripple out in all directions.
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The waves can travel quite a way, but what's happening is that the wave at one point in space is affecting the point right next to it. And those effects just accumulate over space and time to give you the impression of waves rippling out in all directions. That is local interactions.
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Even though it's not exactly what we're talking about here, let me be super careful because I know there's a lot of quantum mechanics fans out there in the Mindscape audience. In quantum mechanics as we know it in something like the core theory, the dynamics are local at the level of the Schrodinger equation. So what we call the unitary dynamics of quantum field theory are perfectly 100% local.
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Said in yet other ways, when we are not measuring the theory, when it's just doing its thing without its wave function collapsing, That's all 100 percent local. Non-localities come in when you measure the system and that's of course Bell's theorem and entanglement and EPR and all that fun stuff. All that's great. None of it we're going to be talking about in this discussion today.
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So in local emergence, We have a situation where macroscopic objects are made up of collections of microscopic objects, okay? So locality is doing a lot of work. Locality is respected in both the microscopic theory and the macroscopic theory. Pieces of paper are made up of atoms, organisms are made of cells, whatever you want to say.
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And people have asked and I did contemplate whether or not it would be appropriate to devote a solo episode to that. The emergence episode was sort of in my brain for a while. So I was planning on that. But and I knew that Trump absolutely had a chance to win. That's what it means to be a coin flip in an election. But I decided not to. I decided not to devote this episode to talking about that.
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All of these are different versions of big things being made up of little things. And local emergence, type one emergence, respects that. If you want to be a little bit more specific, famous examples are, let's say, the center of mass motion of planets in the solar system, right? So, and I bring this one up specifically because it goes back to Isaac Newton, right?
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When Isaac Newton first wrote down his law of gravity and he's thinking about in the Principia Mathematica how to derive the motions of the planets around the Sun, Isaac Newton was pretty smart. He didn't just say let's idealize a planet as a point. He knew that planets had size and so he put in the work to show that as long as the planet is spherically symmetric,
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its behavior in a gravitational field reduces to the behavior of a single particle with the appropriate mass and location of the center of mass and momentum of the center of mass. So when we talk about the motion of the planets in the sky or in the solar system. We don't need to track all of the planets, all of the particles of which all these planets are made of.
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The Earth has something like 10 to the power of 50 atoms in it. Newton didn't know that. We still don't care about it for purposes of flying a rocket to the moon or anything like that. We can reduce this description of many, many, many, many particles to a relatively small number of variables, the position and velocity of the center of mass of the various planets.
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And again, some people would say that doesn't even count as emergence because it's too easy to understand. It's too simple. I think, maybe this is my physics background talking, that having some examples where you do understand things perfectly is actually good, not bad. A more standard example is, of course, the emergence of fluids from what we call kinetic theory or atomic theory, right?
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The air in the room around you is made of atoms and molecules. You don't need to know that the air is made of atoms and molecules. In order to predict what's going to happen to the air, you would do a very, very good job if you knew the density, the pressure, the velocity, and the temperature of the air at each point in space. You might...
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very quickly worry, there's a reasonable worry but not a difficult worry, that even though there's a lot of atoms around you, right, a lot of molecules in the air, the fluid description of the air has an infinite number of variables because there's an infinite number of points of space and there's a value for
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these collective variables, the density and pressure and so forth at every point in space. They are smooth, continuous fields. Doesn't that look like not a coarse graining map? Doesn't that look like we've increased the amount of information? But that's a little bit fake because if you wanted to do the Mark Waddell thing and put the thing on a computer, you would actually discretize space.
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You would put the space around you and think of it as a lattice. So in other words, rather than specifying pressure and density, et cetera, at literally every point in space, you would divide up space into little tiny boxes, maybe a millimeter across or a nanometer across or whatever. there's still going to be a large number of atoms in those little boxes.
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And in those little boxes, you go from all the atoms to just a small number of variables, pressure density, velocity, temperature, okay? So for all practical purposes, you are actually greatly decreasing the number of variables. And there you get a description, which is a useful... example to contrast with the center of mass motion example.
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And this is why the fluids coming from particles or atoms is a more common example of emergence because the higher level description, the emergent description, talks a different language. than the lower level description does.
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I mean I do think it's a huge deal. I think that Trump winning is a blow to anyone who is against racism and corruption and in favor of democracy and the international order and economic stability and things like that. Just as one little tiny thing among many, we now have an incoming vice president who has proclaimed in a speech that universities are the enemy.
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When you have particles that make up the Earth and you just reduce them to their center of mass motions, at both the microscopic level and the macroscopic level, you have particles obeying Newton's laws, okay? In the atoms going to fluids or to gases example, at the lower level you have particles and at the higher level you have fluids. That's a different kind of thing, okay?
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So it's a fun example of emergence. But it's still – and nothing in the definition that we gave said that the kind of theory you have at the macroscopic level has to be the kind of theory you had at the microscopic level. They can be completely different looking theories. Some people would still say that the fluids coming from atoms is too cheap of an example. It's too easy.
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And the reason why is because we know exactly what the map is. We have a formula. We have equations for saying given some collection of atoms doing certain things, here's what the pressure is. Here's what the emergent temperature and density and velocity are. And the existence of such a simple relation, such a simple explicitly write-downable emergence map rubs some people the wrong way.
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Like I just said, I actually think it's a feature, not a bug.
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It is all still, by the way, remarkable that it exists, that you can throw away all of that information, throw away what all the atoms in the air around you are doing and only keep track of some macroscopic variables. So why is it like that? As I already said, I don't know why it's like that. I'm not going to tell you why it's like that. It was not part of our paper.
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But I just do want to pause to kind of take a breath and reflect on the fact that the lower-level laws that we have in the world allow for the existence of these higher-level patterns, these emergent laws of physics. I don't know exactly why it's like that. I do think it has something to do with— the locality of the underlying laws.
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And in some very real sense, quantum mechanics is less local than classical mechanics, but still there are things called positions in space. And there are things, there's a feature in quantum mechanics or classical mechanics, there's a sense in which things interact when they are at or near the same position in the space. And those features of physics as we know it
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are so built in to how we think about the world that we sometimes forget it didn't have to be that way. If I imagine that I have a certain set of what physicists call degrees of freedom, whether they be atoms or values of a field at different points in space, the degrees of freedom are the things you have to specify to tell me what point you're at in the state space of the theory, okay?
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So if we imagine we have some very large set of degrees of freedom and we imagine relatively generic laws of physics in the space of all possible laws of physics that we could invent, very, very few of those laws of physics have any notion of locality built into them at all.
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Locality means that if I have an atom here, it's going to interact with its nearest neighbors, but not with all of the gajillion atoms somewhere else, okay? That's a huge restriction on what can happen in the world. And one of the things that I'm interested in from my—wearing my fundamental physicist hat is why are the laws of nature like that?
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So you might imagine that I am not in favor of the incoming administration. But I decided not to devote this podcast to it for a couple of reasons. One is that it is still fairly recent and I have talked about related things and I'm not sure I have anything really new and interesting to say right now. I know that there's always a rush to judgment to say, well, this is the reason why that happened.
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Did that notion of locality arise dynamically somehow, or was it just built in? This rubs up against questions of what are the laws of physics? Are you Humean or anti-Humean, etc.? In a very real sense, honestly, I almost hate to bring this up, but it's a kind of fine-tuning of the laws of physics, the existence of locality itself, in the sense that generic laws of physics wouldn't be like that.
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And, you know, look, maybe the answer is just the world is like that. The world has space. Space exists. There's never any option for it to be anything other than that. But I would like to, you know, think a little bit more deeply about that. OK, that was all a little bit of an aside. All I'm trying to do is give you some examples about the most straightforward kind of emergence.
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And this is definitely weak emergence. What we're calling type one emergence. is indisputably weak by the conventional characterization. But notice that we never mentioned derivability or anything like that. You know, we never said that the higher level laws could or could not be derived. We just said that they existed, and that's all that you need to have this kind of type 1 local emergence.
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Having said that, we should admit that some examples of type 1 local emergence are more straightforward than others. So in the paper, we suggested a subcategorization into what we called direct emergence versus incompressible emergence. Type Ia and Type Ib, if you want to call them that, okay?
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So direct emergence is basically the case that we've already talked about, either center of mass motion or atoms to fluids, where you have a very explicit formula that gives you the emergence map. And again, we didn't want to say that having a formula was the important thing because maybe we don't have a formula now, but we invent it. OK.
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But what we can say relatively objectively is whether or not the map from microstates to macrostates is algorithmically simple. or algorithmically complex in the sense of Komolgorov complexity.
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You know, you've probably heard of this idea of Komolgorov complexity, that you have all the possible computer programs that would output a certain string, and the Komolgorov complexity of the string is the length of the shortest computer program that does this. A couple times recently, we've mentioned Charlie Bennett's version of logical depth, which is
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not the length of the program, but the time it takes to run the program to predict that. And you could use either one for this particular purpose. The idea is, do you have to work hard to specify the map from the microstates to the macrostates, or can you state it in a very short, compact expression? So you get direct emergence, like fluids from atoms, when the map is algorithmically simple.
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Incompressible emergence is when you have to work hard to specify the map, the emergence map from microstates to macrostates. So arguably, I don't have a knockdown version of an incompressible emergence, but I do want to be open to the possibility. The example that Mark Medow uses in his paper is the Game of Life, Conway's Game of Life.
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John Conway, the mathematician, famously had this cellular automaton, a two-dimensional cellular automaton with on and off sites in a square lattice and rules for the sites propagating over time. And what you find in the Game of Life is that There are certain very specific configurations of sights being on and off that persist over time.
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You can get a glider that has a certain shape and it moves up and to the left or up and to the right depending on how you've pointed it. You can get a glider gun, a configuration that sort of produces gliders and spits them out as well as many other more complicated things.
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And roughly speaking, the only way to tell me whether you have a glider or a glider gun or whatever is to give me the explicit expression for what sights are turned on and what sights are turned off. It's not like a little integral formula that you can just write down and plug it in.
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So I think arguably that's a case of what we're calling incompressible emergence, where there is a higher level way of talking. It's not super good because I don't know how comprehensive the higher level language of gliders and glider guns would be in talking about the dynamics, but it's there.
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If only they had listened to me first. Or to be sort of doomerist about it and saying, oh, no, let's just tear our hair out about how bad it's going to be. Or to be prescriptivist, like here's what we have to do right now. I'm very sympathetic to all of these impulses. I have them myself. But I don't need to foist them on you, OK? I do think it's OK to think about these things.
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And the only way to specify it that I know is to just give the explicit formula in an incompressible map from microstates to macrostates. So to me, that idea of whether or not the map from the micro theory to the macro theory is algorithmically simple or complex is a better thing to keep in mind than whether or not the macroscopic behavior is surprising or novel or unexpected or whatever.
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Those seem to me to be in the eye of the beholder, whereas the comorbid complexity of the map is something that in principle you could figure out what it actually is. which reminds me that I should also draw a distinction for those real emergence fans out there.
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There is a distinction in emergence talk, which is not quite the strong versus weak emergence distinction, but it is the epistemological versus ontological distinction. distinction, okay? So epistemological emergence would be, well, you have a higher level theory, which is just a way of talking about, a way of knowing things about and describing lower level things,
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versus ontological emergence is, oh, no, there really are new things at the higher level, right? Ontology being the discussion of what really exists. To me, I don't quite vibe with this distinction because I'm on the train of people like Dan Dennett, who talked about real patterns, also James Ladyman, another former Mindscape guest, and He and Don Ross have done a lot of exploration of an idea.
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It's not original to them, but they've been championing it for a while called structural realism, where the idea is that what really exists out there in the world, we don't know, right? We don't know the fundamental theory of everything yet, and therefore you might worry it's impossible to say that anything is real.
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You know, we used to think that atoms are real, but now maybe they're just manifestations of a wave function. Does that mean that atoms don't really exist? Ladyman and Ross in structural realism more generally say, no, there are patterns in the behavior that are preserved as you go from a higher level theory to a lower level theory. And those patterns are real and they count as really existing.
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So ontological structural realism I should label this as. So what this does is it licenses you to do exactly what you want to do and should do, which is to say tables and chairs are real.
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To me, if your definition of reality is not broad enough to encompass tables and chairs, then I think you're probably barking up the wrong tree or at least you haven't chosen the most useful definition of reality.
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And structural realism and the real patterns point of view from Dennett both point you in a direction of saying there's absolutely something real about these higher level emergent things. They might be epistemologically useful, but they're also ontologically worth taking seriously.
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So I'm not dwelling on that distinction between epistemological and ontological, but I'm just letting you know that to me this is ontological emergence that we're talking about. OK. So that's the easy part. Those are the easy parts of emergence. And we only have two more categories left and there's a lot of – they're action-packed.
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But I do think that it's very helpful to think in the terms that we introduce in this paper. So – The next category, given that type 1 emergence was local emergence, you're not going to be surprised that type 2 emergence is non-local emergence. And we had to think a lot.
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to really decide what it means, what we're supposed to do going forward. I don't think that the second Trump administration is going to be like the first one. I think it'll be worse in any number of ways, but we'll have to actually see and respond accordingly. The other reason is because I absolutely believe that we have to fight against encroachments on rights and democracy and so forth.
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It took us a bit of discussing and writing things down and noodling about what exactly it means to say that there is non-locality in type. the emergence idea? Is it that the objects are not local or is it that the rules are not local or what is going on? This is something that, and so the short answer is both. You can have objects at your higher level of emergence that are not locally defined.
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That is to say, they are not simply made up of little locally collected pieces of your microscopic theory. Or you could have – and or you could have influences between objects in your higher level that sort of extend over space in ways that ordinary physical things like billiard balls pumping into each other do not. Right. And this is real. This is something that absolutely is plausible.
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Like certainly in biology or in the social sciences where very often both your microscopic theory – microscopic theory doesn't mean to be fundamental physics. You can absolutely have a case where your microscopic theory is, for example, human beings. And your macroscopic theory is political structures or the economy or something like that, right?
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So we want our conception of emergence to be rich enough to include all of those different possibilities. We're not, you know, physics chauvinists here. And so it might be very often true in biology or the social sciences that we have very important emergent entities that are not localized in space or time. Maybe, you know, the U.S. Constitution, right? Now, the U.S.
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Constitution is written on a piece of paper, but the Constitution itself doesn't have a location in space. You know, a contract or an obligation more generally is not localized in space, but it might play a super important explanatory role at some higher emergent level, right? he didn't do this because there's a contract that says that he can't do it, you know?
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That's the idea of the higher level immersion theory is supposed to be able to tell you what happens in some reliable way, and therefore the pieces of it are going to have some causal power. And if they do, in other words, the existence of something or non-existence of it affects what happens, okay? And if they do, they're part of that higher level theory. And Very often they're just not local.
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If you think that consciousness is in some sense emergent, there's not one neuron in your brain where the consciousness is located. It's not even exactly right to say it's localized in your brain, although we could have a discussion about that. Simon Dedeo, who's another former Mindscape guest, read our paper and gave us a wonderful example of this sort of non-local emergence.
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that is as close to fundamental physics as I think we can get, which is the jerk. This is the jerk in the mathematical sense. Sometimes you'll be told that the first derivative of position with respect to time is the velocity. The second derivative is the acceleration. The third derivative is the jerk. And then there are higher level derivatives with snap, crackle, pop derivatives.
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I swear to God, these are the words that are attached to the higher derivatives of position with respect to time. But if you know anything about Newton's laws of classical mechanics, F equals ma is the second law, force is mass times acceleration. So it's a nice feature of classical mechanics that the state space requires you to give me positions and velocities.
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it does not require you to give me accelerations because accelerations are given to you by a formula, F equals ma. And once you know the position and velocity, and you figured out the acceleration from F equals ma, that is enough to determine the entire future evolution. of the system. That's what Laplace's demon does.
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We can't just resign ourselves to the worst things that can possibly happen. But part of that fight is keeping going. preserving those aspects of our lives that make life worth living. As always on these podcasts, I will essentially mention the importance of considering our lives as more than merely survival.
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So what you notice in that discussion is the jerk, the third derivative of position with respect to time, nowhere appears. It is not part of your fundamental description. You could figure it out. You could calculate it. Once someone gave you the positions and velocities and you used F equals ma to predict the future evolution, you could calculate what the jerk was.
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But it didn't play any causal role. The causal role was already filled up by the other things, the position and the velocity and the acceleration. But what Simon points out in a nice little paper that he wrote is that you can feel the jerk as a person in a car or an elevator. The jerk is the rate of change of acceleration.
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So you not only feel acceleration, but you would swear to God you could feel that acceleration was changing, right? What is going on there? Why are you able to have jerk as a part of your useful description of the higher level world? It could even play some causal role.
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And the answer is, roughly speaking, because it's non-local emergence, because you at the higher level are kind of averaging over things that happen at slightly different points of time, right? You know, the reason why you think that you know what the jerk is is because your consciousness, conscious experience of the world is not really instantaneous. It has some…
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length of time over which you're sort of integrating what you're feeling, and then you can tell people, you can report back on what you have experienced. And from our point of view, you could, if you wanted to, trade in that finite discrete interval of time for a finite discrete region of space.
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Because at the fundamental level, if you're trying to map this higher level description onto what's going on fundamentally, everything that happens to you in the elevator or in the car or whatever is determined by what happens in your past light cone.
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So whatever you count as a moment before, there is a region of space that is not that big but is pretty big in which if you knew everything that happened, it would completely determine what you call the jerk going forward. But it does it in a non-local way. You need to know not just what happens at what point in space but what is happening over a certain region of space.
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So when you go from the microscopic theory of just Newton's laws or whatever to the macroscopic theory of your human experience, there's a bit of non-locality that has seeped in. And I think that's a wonderful example of exactly this kind of type 2 non-local emergence. it doesn't happen that much.
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It doesn't happen in any real noticeable way if both your microscopic theory and your macroscopic theory, I should say, if both your lower level theory and your higher level theory are still pretty low level. So the jerk example is because your higher level theory was human beings, which are very high level.
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If your lower level theory is the standard model of particle physics and your higher level theory is some theory of atoms and electrons in a superconductor, that's not very far removed, right? Your so-called higher level theory is still pretty low level theory. And in that case, the speed of light really is a fundamental limitation.
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And so you're not going to get emergent non-locality in that case. So emergent non-locality basically has the possibility of being relevant when you're coarse-graining so much that the speed of light is just not a limitation. As far as you and I are concerned, when I see you in a room a few meters away, I'm basically seeing you now. Right?
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I'm not, you know, technically I'm seeing you in the past because it takes time for light to get to me. But on the time scales that I personally move around and react to things and think about things, I'm seeing you instantaneously.
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And of course, depending on one's situation in the world, that can be easier or harder to do, right? Easier said than done for some people. But I do think that we have to remember that there's more to life than politics. I think politics is important. I think that people who think that politics is sort of distracting or annoying are part of the problem. But it's not everything.
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So because we all move so much more slowly than the speed of light, in a fairly reasonably sized region of the universe, the speed of light is not there and we can think non-locally that non-local effects can be very relevant to how we talk about the world. So...
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It's an interesting sort of changeover from emergence at the super micro to the merely slightly micro level versus emergence at the micro level to the truly macro level. Now, why are we bothering about this? Why do we really distinguish between type 2 emergence and type 1 emergence?
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Because the possibility of type 2 emergence, non-local emergence, opens up an interesting possibility that wasn't there in local emergence. And we didn't give an especially fascinating name or label to this possibility, but we called them filter functions.
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We should have worked harder on giving the name because maybe it would be an idea that would catch on better if we had come up with a snappier label for it. The idea of the filter function is this. Imagine you have some microdynamics that appears to you to be local and perfectly well understood. the standard model of particle physics, the core theory, for example.
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But let's imagine that you are convinced that when the global configuration, that is to say the state of the universe or the state of some non-trivially sized part of the universe, is a certain way, then the dynamics that you thought were good enough at the microscopic level fail.
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That is to say, new features kick in at the macro level, but only for certain configurations that are global, that you need to give me information spread out over space to specify. So when we do particle physics, for example— When we do experiments to learn about the standard model of particle physics, what kind of experiments are we doing? You know, we're typically at a particle collider.
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You know, we're at the Large Hadron Collider. We're smashing particles together. It all happens in a very tiny region of space with relatively few particles colliding to each other, okay? So we've developed the ideas of the core theory in a fairly simple set of circumstances, small regions of spacetime, small number of particles.
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The possibility exists that how electrons behave is different if that electron is in a human brain versus when it is in a particle accelerator, when it is in the detector, the Atlas detector at the Large Hadron Collider or something else. This is not what you expect from the core theory. This is changing the core theory. We're being very, very explicit about it.
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But we're saying that you could do all of the experiments you want in this sort of localized small number of particles regime and never notice the new dynamics. So the idea of the filter function is there is an equation telling you how the particles or how the constituents of your micro theory behave. And there's a set of terms in that equation that refer to what happens locally.
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In other words, there's a set of terms that say, you know, in some region of space, I care about the particles bumping into me or whatever. I don't care about what happens far away. And then the filter function says, plus there are additional terms that do care about the global configuration. There are things that affect the dynamics of electrons. And again, I'm saying this hypothetically.
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And politics is existing in some part in order to carve out space for the other things that are actually super-duper important. And for me, one thing that is— Bringing meaningfulness and purpose to life is the ongoing quest to better understand our universe.
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I don't think this is true. I'm just allowing for the possibility. But there could be things that affect the dynamics of electrons when the broader context the electron is in has the form of a human brain. that are not noticeable if that broader context is not there.
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So in type 2 non-local emergence, you have the possibility of new dynamical considerations that you would not have noticed by simply speaking the language and doing the experiments that you thought were appropriate for your micro theory. So to be clear, you're not changing the micro theory. What you're doing is you're explaining why the micro theory was incomplete.
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These new dynamics governed by the filter function were always there and they could in principle be captured in terms of the micro theory, So you're not adding new ontology. You're not adding new consciousness particles or whatever. Let's say the microtheory is the core theory. It's the same quantum fields that you had all along.
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They just have certain dynamical properties that were not evident from the sort of microscopic perspective, so it's natural to miss them. we tend to only probe a certain domain and then extrapolate. And in quantum field theory, we have good reason to do that. We can give you an argument why, based on things like locality, that is more than good enough.
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But in the space of all possible theories, maybe quantum field theory is not right. OK, maybe there are true differences. So if that's true, if that possibility is realized in nature, this fits into our type two dynamics, type two emergence. We're not introducing new stuff. We're introducing new dynamics for the old stuff. But the new dynamics depends on global, non-local considerations.
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So you might have missed it. So we're trying to explain how you could simultaneously think that you believe everything that particle physicists are telling you about the behavior of quantum fields, and yet we need a theory that changes those dynamics in certain situations like human brains, okay?
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So again, I think that this is possible, but I don't think it's actually true in the case where your lower level is literally fundamental physics and the core theory, because I think that locality, the constraints of locality there are very strong, I think that non-local emergence is much more plausible when your micro theory is already a little bit macro. But we're open to the possibility.
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So if someone who believes in strong emergence wants to take up that challenge, we have an equation. We have an equation that tells you how, in principle, you could modify the core theory to allow for this kind of dynamics. And we encourage you to speak the language of that equation, OK?
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So I think we need a balance of political struggle and discussion and work and concentration and for that matter play and enjoyment concerning the rest of existence. So there is a role for an entirely abstract, not very directly useful kind of discussion like this one. because we can do both. We're not tied to only fighting the political struggle or being ivory tower academics.
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Now in the paper, Atuth and I mentioned that this could – this possibility could open up the idea of counterfeit downward causation. Downward causation is the idea that there are things that happen in a higher level theory that play a causal role in the lower level theory, OK? That you need to know about something that sounds purely emergent, OK?
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in order to completely explain something that is going down at the microscopic level.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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And in what we call type two non-local emergence, you can think that's what's happening because you have an electron that is in a human brain, and maybe you're smart enough to do an experiment that actually showed that this electron behaves differently in a human brain than in a rock or in a particle accelerator, okay? So that would look like downward causation.
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That would look like the existence of a brain has been affecting the motion of the electron. But in our definition of type two emergence, and by the way, there will be a type three where this is not true, but in what we're calling type two emergence, this kind of downward causation is merely counterfeit.
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And the reason why is because the micro level theory, and indeed, you know, good theories more generally are causally closed. they are sufficient to describe what happens perfectly well in their own domain of applicability. There is a rule that I talk about in the big picture where I say you shouldn't bounce willy-nilly between levels of description. The levels are independent, okay?
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Like if you have a good macro description of some emergent phenomena, the whole point is it shouldn't rely on what's going on at the microscopic level. and vice versa. What's going on at the microscopic level shouldn't rely on the macro theory. So that doesn't mean you don't have both descriptions, but you should only talk one language at a time.
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So for example, I hate to bring up this example, but one might ask, why are the Philadelphia 76ers off to a truly awful start in this basketball season 2024-25? Which they are, sadly. This is dwelling on my mind and bringing me down. What kind of explanation could you offer for a bad start? Well, maybe it's because there's too many new faces, right?
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They let a lot of the players go from the previous year and they have a lot of new people. They're still working hard to incorporate them into the offense and the defense, the schemes, okay? Or you could say maybe it's because of injuries. You know, Joel Embiid has been injured. Tyrese Maxey just got injured.
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Paul George, all their best players have struggled with injuries in this short beginning to the season. That's another possible explanation. And you can very legitimately debate which of these factors is more important or maybe they both matter. Maybe there's a third thing we haven't thought of. That's a perfectly sensible debate to have. There's another possible answer you could give.
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Why are the Sixers off to a truly awful start? Well, it's because of the initial conditions of the universe and the laws of physics, right? That's an answer you could give. That's the answer you could give to any question of the form. Why is this particular thing the way it is right now? Because of the initial conditions of the universe and the laws of physics. That's not a wrong answer.
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The initial conditions of the universe plus the laws of physics really do, in some tangible sense, explain why the current situation is what it is. All I'm trying to say is you shouldn't mix them together. Once you've chosen to speak the language of the microscopic theory and you've said, why are the sixes not doing well?
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Well, because of the initial conditions of the universe plus the laws of physics plus this coarse graining map that fits the record of the basketball team into that language. You don't also say because of injuries or because there's too many new faces or something like that. That is over-attributing.
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what is going on because in principle from the initial conditions of the universe and the laws of physics you can derive the fact that they are injured or they have too many new faces or whatever you only get to give the explanation once and so that's the reason why it is counterfeit downward causation because in this type 2 picture there are higher level non-local influences but ultimately you can give a perfectly good lower level explanation
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We're grownups who can do all of those things at once. And this is part of that. This is part of the reminder, the urge to keep our lives moving forward, even as we're
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you can explicitly include those influences in the microscopic theory. You don't need to invoke the higher level. You don't need to talk about influences at the emergent level exerting causal influence on the micro level. So examples of downward causation, if you look them up, You might find something like why is a certain hydrocarbon molecule in a certain physical location of the world?
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And people will say, well, if you realize that what you're actually talking about is a little hydrocarbon molecule in a gas tank of a car, then you can give an explanation for why that molecule is there based on ideas of the internal combustion engine and the modern economy and the need to get from place to place in a suburban environment or whatever. And they would go so far as to claim –
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that unless you give that explanation, you have not answered the question. You've not actually accounted for why that molecule is where it is without using these higher-level emergent ideas. To me, I think that's just a mistake. I think that's just wrong. I think that you can, in principle—not in practice, obviously—but in principle, you can perfectly account for the location of that molecule
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purely at the micro level, right? There's no one saying in the context of Type II emergence that you can't account for the dynamics that led that molecule to be there purely in terms of the local dynamics of the underlying core theory. right? You have a much more efficient, informative explanation at the macro level. That's a very common thing.
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That's the wonderful thing about emergence is that you can have these explanations based on far fewer pieces of information than you need at the micro level. But that's not the same as saying you needed it. It might be more convenient. you can talk either language you want. One language might be better for the purposes that you have in front of you.
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temporarily depressed about the political state of the world and you know who knows maybe it'll help us sleep a little bit better give us some ideas uh i'd love to hear feedback as always on the solo podcasts uh it's me talking out loud in some sense um in a way that about something i think i know something about but there's certainly more questions to be answered so let's go so
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Using one description or another might be useful relative to certain purposes, but it isn't demanded. So I think that at that level, if we're talking a type two language, where the microscopic states, the microscopic entities are in principle all you need, but they might have some global influences on their dynamics that you missed by doing microscopic experiments.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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Still, you don't need to actually talk the higher level emergent language in order to account for what happens at the microscopic level. So within type 2 or non-local emergence, you can have apparent downward causation because global properties matter, but it's not honest. You could have given a complete account purely within the causally closed micro theory.
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And having said all that, of course, you will be completely unsurprised to hear there's one final type of emergence that we talk about, which is labeled type 3 or augmented emergence. I think this is what people have in mind when they talk about strong emergence. I think sometimes when they talk about strong emergence, they're really just talking about what we call type 2.
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Sometimes they're talking about what we're going to call type 3. That's why we have these extra specifications so people can be clear when they're talking to each other. The idea of augmented type 3 emergence is to admit that the microtheory really is simply incomplete.
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In other words, that there are regimes of applicability for the microtheory and a regime of applicability for the macrotheory, and one is not a subset of the other. There are places where the macro theory works, where the micro theory is just wrong in its own terms. But it's not just that you made a mistake.
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We're using the same kind of filter function language we introduced in type 2 to help provide an understanding of why you might have believed the micro theory in the first place. In the domain where you test and get empirical information about the micro theory, the micro rules work and these new macro influences don't play a role.
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But in actual type 3 emergence, we allow for the existence of truly new ontological entities that are strictly global. Maybe you think that way about consciousness. Maybe consciousness is just not ever reducible, even in principle, to the to-ings and fro-ings of microscopic particles. Maybe there's something extra about it, consciousness juice or something, the spirit, the soul, the geist.
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Or maybe in a slightly more subtle way, you think that there's a teleological aspect to the laws of nature, right? Maybe you think that, yeah, when you look at particles bumping into each other, it all looks random.
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But in fact, to explain the origin and evolution of life, you need to include an extra effect having to do with certain things are more likely than others if they ultimately lead to some biological happenings down the road. That would be a truly new thing, right? a truly non-local aspect of reality. So in type 3, these new things, these augmentations of the micro theory are real.
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They do affect the micro dynamics, but they only do so when the micro configurations are under certain global conditions. So again, when an electron is part of a brain, is it affected by these new ontological features? That's what the filter function is supposed to tell you. The filter function is there both in type 2 and type 3.
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The difference is that in type 2, the filter function says when you're in a brain, you turn on new interactions between the existing microscopic lower-level features. In type 3, when the filter function turns on, you allow for new influences that are simply not describable in terms of the microscopic features.
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consciousness, the spirit, or whatever, or the teleologically, the future goal of the universe. So that's supposed to help explain, that's supposed to help reconcile the way in which the microscopic theory is not complete It is not correct in some sense, but you might have been tricked into thinking that it was correct because that's where you probed it, right?
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I personally do not think that anything like type 3 emergence happens when the lower level theory is—particle physics is the core theory, okay? When we are talking about lower levels that are really fundamental physics as they are currently understood, we have very, very good reason— to think that the dynamics are truly local.
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But the thing that we're trying to do in this paper is be as explicit and clear as possible as to how that expectation could go wrong. So again, when people say consciousness is strongly emergent, etc., That's not my way of thinking, but it's a free country and I could be wrong. I want people to pursue other possibilities. What I object to is just needless vagueness.
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I think that people can be explicit about the ways in which these things come together. to pass. And so I think that, again, we have an equation in our paper which gives you a template for showing how truly new ontological features of the world could become relevant, but only globally.
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That would be a case where the core theory of particle physics did not completely and correctly account for how human beings behave. That is obviously a logical possibility. But if you want to explore it, you've got to do more than wave your hands. You've got to be explicit about how the equations change. We have given you a template for changing those equations.
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So I think that's a good place to end up because I've been very, very explicit about what I think is the way the world actually works. But I don't know everything. I could certainly be wrong about some things. I think that in these very difficult questions, it's perfectly good to be open-minded.
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Hopefully, we will have given people a little bit of a roadmap, a little bit of an example of knowing what to look for, right? I mean knowing what it would mean to have these things be relevant to our best understanding of society.
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consciousness or life or anything else and maybe a bit of vocabulary to distinguish between other options that are a little bit less dramatic than that i know that thinking this through has helped me anyway um whether or not our jargon catches on or not i can be a lot more clear when i'm talking to other people about what i mean by different kinds of emergence so what more can we ask from that with that uh thanks for listening thanks for supporting mindscape talk to you next time
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These days, I am busily working on volume three of the Biggest Ideas in the Universe series, and its subtitle is going to be called Complexity and Emergence. So as you might imagine, I've been thinking about these things. Complexity and Emergence, to some extent, is a grab bag title.
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I'm going to be doing lots of things like thermodynamics and cosmology, which are related to those subjects, but then also digging into what it means to say something is emergent, something is complex. The theme of those books is always to be uncontroversial, non-speculative to actually do the things that people will agree on and continue to agree on for hundreds of years from now.
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So I won't be going into the specific kind of categorization I talk about today. But I did open the book. I do open the book, will open the book with a thought experiment that is worth keeping in mind. You can do it as a real experiment if you want or as just a thought experiment. Very simple. Take a piece of paper, crumple it up into a ball and
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a piece of paper you don't really care about what's written on it, hold it in your hand and then toss it into the air a short distance so that you can catch it. Okay? Imagine having done that or actually doing it. It doesn't really matter. Hopefully you know what it would be like to do that.
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I want to claim that you have just demonstrated one of the most remarkable and important features of the natural world as we experience it. In fact, you've demonstrated something that relies on several very important features of the natural world, just so we keep them in mind. One of them is gravity is a weak force, right?
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The entire gravitational field of all of the mass of the Earth is pulling down on that little ball, and your arm is able to toss it in the air, even though you are much tinier than the Earth. That's because your arm's forces come from electrochemical reactions, which are enormously stronger than gravity on a particle-by-particle basis.
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That might very well be a non-accidental important feature of the world. There's something called the weak gravity conjecture. that suggests that gravity has to be the weakest force and it has to do with entropy and quantum gravity and that's very interesting. We're not going to talk about it today. Another interesting feature that you have implicitly demonstrated is that the world is predictable.
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that there are laws of physics, right? When you throw that ball into the air, you are able to use your brain to figure out, to predict where it's going to come down. It does not just randomly go up into the air, right? It does not randomly go right or left. There is a pattern. There's a predictability to how the world works. Obviously, a crucially important feature. of reality.
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And for that matter, the world is intelligible, right? It's not just that there is a pattern to how the ball goes up and down, but that you can figure out what that pattern is and use it to make the catch. Good for you. All of these are worth book-length treatments and have received them all by themselves.
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But what we're going to talk about is something that is so intrinsic in how we think about the world that we take it for granted. Namely, these days, when you think about what that piece of paper is, it's made of molecules which are made of atoms, which are made of elementary particles, which are described by the rules of quantum field theory.
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Many times in the podcast, we've mentioned the idea of Laplace's demon.
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Now you can be specific about whether or not you're in the classical approximation or you really want to do the whole quantum field theory if you want to, but one way or the other, the idea of Laplace's demon is that if you knew exactly the state of that piece of paper plus the environment that it was bumping into, then the laws of physics would tell you, would allow you to predict how it would behave, okay?
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You would have the position and momentum of all the atoms that were in the piece of paper and you could tell how it would go up and would go down. You're not Laplace's demon. You're never going to be Laplace's demon. We all know that. You don't know all those positions and velocities. You have vastly incomplete information about the specific microscopic state of the atoms in that piece of paper.
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And nevertheless, you are perfectly capable of saying what it's going to do when you throw it up into the air. That's kind of amazing, OK? It's not just that – well, it is, but it's not just that you can throw away some of the information contained in the microscopic description of the system, but that we know exactly what information we can throw away.
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All you basically need to know is something about the center of mass of that little ball of paper that you have crumpled up. And maybe something about the environment that it's in, if it's windy or something like that. But relatively few pieces of information give you a very good handle on what's going to happen in the macroscopic world. That is emergence at work. It is one example of emergence.
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Some people would not even define that as emergence. Like I said, it's a contentious definition that we can battle over. But to me, it's exactly what I'll be talking about here or one of the examples I'll be talking about. The idea is that there are multiple levels of description of the world. This was a theme in my earlier book, The Big Picture, where I talked about poetic naturalism.
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There's only one world, but there are many ways to talk about it. So in this case, there is a micro level or a lower level, as we usually talk about it. That's the level where we can describe the piece of paper as a collection of atoms or elementary particles or whatever you want to do.
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And then there is a higher level, a macro level, where you have pieces of paper and you have people and they have hands and they can throw the pieces of paper up in the air and catch them, OK? And the crucially, amazingly, wonderful, non-trivial fact – about the world is that you don't need to know about the lower level to navigate the higher level.
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You don't need to know anything about the atoms of which the paper was made. In fact, people could do this exercise of taking a piece of paper, crumpling it up, throwing it up in the air and catching it long before they knew. about atoms and molecules, etc.
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This higher or emergent level, where you just had the macroscopic things like the paper and you and so forth, is really descriptive all by itself. it captures something real, something that Daniel Dennett, former Mindscape guest, called real patterns in the underlying dynamics of the system.
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To me, that's the basis of emergence, the idea that you have something that has many, many things going on, but you don't need to keep track of all the things going on in order to make useful predictions. There are certain kinds of predictions you can make,
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That's B-A-B-B-E-L dot com slash mindscape. Rules and restrictions may apply. And am I right that these formative years where you were looking for vinyl records, was that in Germany?
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Because Germany obviously has been in the vanguard of electronic music and experimental music.
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It does, it's very different, different world.
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Were you already in love with classical music at this time?
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Okay, very good. Let's do our best to give the audience an idea of what your music sounds like, given that if we try to actually play some music for them, there are rights issues and lawyers will come in. So I will link to that, absolutely. But how would you describe your own approach within this eclectic musical universe?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Let me just interrupt to ask for an explanation of tonal versus the alternative.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Hello, everyone. Welcome to the Mindscape Podcast. I'm your host, Sean Carroll. Sometimes I wonder what Henry David Thoreau would have thought of the modern world. Thoreau, among other things, wrote Walden about his experience sort of escaping from the hustle and bustle of modern life back in the mid-19th century.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
I think it kind of makes sense. You know, probably a lot of people have seen those videos where people play the same three chords, right? You know, the root, the fourth, and the fifth, and it fits half the songs they've ever heard in their lives, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
But in your schools, this was looked down upon.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Our modern life is a lot more hustly and bustly than that, not just in terms of what we're doing, but in terms of what we're hearing and seeing. All of the buzzing, blooming confusion around us is amplified in our modern world of electronics and streaming and cell phones and so forth. What is the role of something like classical music in an environment like that?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
It sounds like an amazingly familiar kind of story, not just in music, but in art, literature, maybe even like science and politics, where there's some super successful paradigm, tonal music, and so successful that it just gets done to death and people react against it. And maybe they go too far reacting against it. So there becomes more room for experimenting in some perpendicular direction.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Yeah. And it's part of the historic aspect of it, right? Like when you write a piece of music, the audience has heard other pieces of music, right? They've heard some of these things and they put it in that context, whether consciously or otherwise.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
So would you, and again, this is labels and I know they're never perfect, but again, the audience has to go out and find the music for themselves. So until then, would you count yourself as a minimalist composer?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Popular music famously can interrupt into your attention, right? It can be catchy, it can be loud, it can be fast-paced, and maybe you hear it in the background or in a store and you get a little bit of it and you recognize the song and it contributes to the atmosphere. But at least the stereotype of classical music is you're supposed to sit and listen to it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
But it is a little bit in there. Are there explicitly geometric or mathematical ideas that go into your head when you're composing a piece of music?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Well, I have two different, completely uneducated ideas about music that I'm going to take advantage of you being here to run by you, and you can tell me whether I'm right or wrong. One... dealing with what we were just talking about, is that a lot of the pleasure of music comes from some competition between anticipation and novelty, right? There's a rhythm.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
If you have no rhythm, if you have no structure at all, it's kind of not musical. But of course, if it's just repeating exactly the same thing over and over again, it's not musical either. So finding that sweet spot is a lot of the part of success story.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Okay.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
You're supposed to give your attention over to this intricately constructed, careful piece of music. Do we really have time for things like that anymore? Some people do, of course, but maybe fewer people than did before. Someone who has very, very successfully pushed against this worry about modern classical music is today's guest, Max Richter.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Do you think of different elements of your music as characters in a drama?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
quite hard to explain it but there's a sort of feeling of like trying to it's sort of world building a little bit yeah okay that's great that quality so you did mention um borrowing suspended chords from the baroque and and i should tell the audience you've done a whole album of reimagining vivaldi yes i have yeah that's yeah This episode of Mindscape is sponsored by BetterHelp.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Visit betterhelp.com slash mindscape today to get 10% off your first month. That's betterhelp, H-E-L-P, dot com slash mindscape. And so it leads me to ask – so here's my other crazy theory, and this is even crazier. The first one was kind of obvious. In biology or in physics, we sometimes talk about a fitness landscape. We have all different sorts of –
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
ways that DNA can be arranged, or fields or particles can be arranged, and they have different energies and different possibilities of survival. And the idea is that there's kind of isolated peaks where everything is good and happy, and then in the valleys in between them you're unstable.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
So, for example, elephants are very successful, ants are very successful, but something that was halfway in between an elephant and an ant would not be successful, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
So my crazy theory is that music is the same way, that there are different kinds of music that are individually successful and that there's reasons for internal coherence and so forth that they are successful and you can try to blend them, but it's never quite the same.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
So there will always be orchestral music and there will always be pop music and there will always be jazz and there will always be talking to each other, but a little bit different. That's my theory. What do you think?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Max is a classical composer in a very real sense, but someone who has completely embraced the modern world rather than trying to fight against it. You can go to his Wikipedia page and find that he has passed one billion streams for his music and over a million album sales. Very, very good by the... Standards of Modern Classical Music. But he's a composer who works in a variety of media.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
And is this, you know, among people who might be thought of as classical composers of your generation, do some of them completely reject the historical perspective? Or is it very common for people to kind of be quoting and in conversation with their predecessors?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Well, we already mentioned the audience reaction in real time when you're doing a performance. But it seems like your new album, tell us about your new album, because the quote that comes with it is, it is an open conversation with the audience.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
He has solo albums. He does commissions for classical ensembles. He also works with the ballet and scores, TV shows and films, films like Arrival, TV shows like The Leftovers on HBO, Black Mirror from the UK. And he's even been very successful at crafting little pieces of music that can be used as ringtones on your phone.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
The idea of spatial structures seems to be very common, whether it's like a landscape or, you know, you mentioned different patterns out there in the world, walking to a room and so forth. But at the end of the day, it's sound that you're making. How much of that connection is personal versus like, oh, here is the theory of why these sounds kind of fit into this spatial structure?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
You know, I had a music teacher in junior high school who was the one who explained to us that if you just listen to a pop song, there are things called verses and choruses and instrumental sections and guitar solos and drum solos. And that had, very embarrassed to say that it never really occurred to me, not being a, you know, practicing performer of music myself.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
I just, like you say, I just sort of, enjoyed the thing, the song, as a gestalt. And this idea of structure warmed my proto-physicist heart. Then I could see layers there that I hadn't seen before. But I suspect a lot of musicians and composers don't realize the extent to which the audience doesn't appreciate some of the structural bells and whistles that they have.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
So I love this ability to stretch from the ability to do a major performance at the Sydney Opera House, but also really vibe with how people are living today. And in this conversation, we get to what this kind of music means today, you know, how it fits in with the history of music and
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
But that was interesting because you use the phrase speaks very directly and plainly. But a lot of the music is instrumental, right? And when you describe it, it's clear that... In your mind, there are often, you know, words or themes or things that could be expressed verbally that are attached to it. How close is that connection there when you say like a certain piece is about the Iraq war?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
But I wouldn't know that if I were just listening to it, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
And I guess now that I'm just thinking of this right now, so I might be embarrassed to say this, but it makes me think of Bruce Springsteen's song, Born in the USA. I don't know if you know it, but the music is sort of anthemic, right? And, you know, it makes you feel given the title that this is some patriotic anthem or whatever, but the words are telling a very different story.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
And so many people don't get that because they don't listen to the words.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Yeah. So the other thing you say about In a Landscape is that it asks the audience to consider the dualities in their own life. And that was just sort of pregnant with meaning there. I didn't want to unpack it for you. So what are the dualities we're thinking about here?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
how it fits in with how people listen to music right now, how the process of composing and creativity goes, and how it can be the case that music that is essentially non-vocal, right, almost purely instrumental music, he's done some vocal music things, but most of his music is just the instruments doing their part. How can that have a message? How can that have a theme?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Well, the listening does matter, and here is the topic I'm most interested in hearing your thoughts about. I once had a friend who was a musician who would come over to our house, and if I had music playing in the background, he would ask me to turn it off. He did not want there to be any music if you could not sit silently and listen to it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
But I guess there's layers, there's different approaches here. Where do you come down on the, if there's music at all, you'd better be paying close attention to it question?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Well, usually that's what the artist intends, but you do have this famous record called Sleep, not really a record, a piece. Tell the audience about that, because I just love the whole concept.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
How can that resonate with what we're thinking about something in the modern world? He has a new solo album called In a Landscape. It's a solo album, so it's just him constructing all the sounds recorded in his new home studio that he and his partner have put together.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Wow.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
But the eight hours is not chosen as a random number. It is meant to allow you to put the music on while you are sleeping at night.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
And maybe in some sense, a more truthful acknowledgement of the fact that music, like anything else, is just one aspect of the life that is going on all around us. So rather than insisting that you stop everything else and pay attention, work it into the fabric.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
And it's sort of a back and forth between these constructed pieces of music in a more or less traditional sense and little bits of found sounds, everyday life, the human world, the natural world, all fitting it together in a new way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Well, and the other manifestation of that, which I truly love, is that rather than being annoyed or frustrated that in the smartphone era someone might use your music as a ringtone, you leaned into that. You said, all right, here's a bunch of ringtones for you.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Well, there's a difference between greatness and grandiosity, right? Yeah. And for, well, it reminds me of, again, completely randomly, very recently, someone pointed out that The most reproduced example of visual art in the history of the world is probably, do you want to guess? I don't know, actually. The portrait of Abraham Lincoln on the U.S. penny. Really?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Just because there's so many pennies out there, right? Of course, right. Okay, fair enough. So little bits of art all around. Why not make it good? Yeah, exactly. Exactly. And is it true that for sleep, you thought a little bit about sleep, about the neuroscience of sleep, about what's going on in people's brains when they're asleep?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
It gives us hope, this kind of interview you're just about to hear, that classical music is not going away, that it can be super vibrant and absolutely part of the world moving forward. So with that, let's go. Max Richter, welcome to the Mindscape podcast.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Former guest of the podcast.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
When you say the word subsonic, do you mean literally too low to hear? We don't know we're experiencing it?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
So has anyone done the obvious follow-up study of seeing what happens to people's brains while they're listening to your composition and they're sleeping?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Okay, good.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Throw it out there. I'm sure we have some neuroscience grad students who are looking for a good PhD project. That might just be it. Okay, the other thing I wanted to talk about, I can't let you go without asking, you know, I always have these sort of
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
craft questions like what is it like to be a composer uh in the way that you're doing it i mean i i hate asking this question but it's the standard one where do you get your ideas for a tune is it random do you like sit down and think okay now i will come up with a melody or a harmony um it it's i i
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
writing going on all the time well that's a fascinating thing to say because i've never heard a musical composer say that but i've heard many many fiction writers say that right once they get characters they go places that they had no idea Yeah, exactly.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
I do think that I am one of those people who always has music bouncing around in their heads, but it's music that has been written and recorded by other people. So I think that it would be very hard for me to break out of that and make something new, having been exposed to so many really good pieces of music already in my life.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
I do appreciate you coming on. I understand that you are preparing for a world tour. And what is that about? What is that like? I mean, I think of world tours as being done by performers, and I think of you as a composer, but of course, you're a bit of both.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
And then in that process, once you go from, well, sorry, let me just back up and be very down to earth. Do you then go to the piano or do you have other instruments you go to or do you go to a piece of paper and start writing a score?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
And that always leaves you with many more ideas and paths, ideas sketched out and paths walked down than you can possibly fit into the final piece, right? Do those stay with you when you hear a piece of music that you have composed, you recall all the things you didn't do?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
describes the territory and there's another you know there's a million other universes out there with all the different versions right have you or anyone else done a an album or a piece around that idea like you know here the paths not walked down for this final thing that we end up with
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
OK, and then for someone like you, you're established. You've made a name for yourself, to say the least. Do you hand over the music to performers? Or is it, I don't know, how does it work?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
I guess that is true. I forgot to ask about this process of collaborating with a movie or TV director or what have you. I mean, that sounds very different to me than sitting down and writing a solo album or, you know, sorry, the word went out of my head, a commissioned symphony.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Are you presented with basically the film without a soundtrack and you start filling in?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
I mean, the theme that seems to come through over and over again is that music is not independent of the rest of our sensoria, right? The rest of what we are experiencing and related to in our everyday lives.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
All right, last question then. Any advice for the teenagers in the audience who have made the somewhat foolhardy decision to try to make a living being a composer of music or a performer for that matter?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
This is great. This is good advice for no matter what you're growing up to be, I think.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Good. Perfect. I like ending on the optimistic note and that was a perfect place to stop. So Max Victor, thanks so much for being on the Mindscape podcast.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
So what about the actual mechanics here? Are you playing piano? I know that you have electronic instruments in your music.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
And you've, correct me if I'm wrong, not done a world tour before. You've done plenty of individual performances, but this is like the Rolling Stones going on tour.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Yeah, so exciting, intimidating, different?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Well, I was going to ask about that. I mean, how much do you feel you are feeling the emotions or reactions of the audience in real time? How much does that come across?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
I once went to a concert at Walt Disney Concert Hall, which I think is on your tour, right? So I went to a recital by Andres Schiff playing piano. And I don't know whether this is going to affect you or not, but the acoustics are very, very good in that hall. And for some reason, it was the time of year where everyone started coughing in the audience.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
And it got so bad because once one person starts coughing, everyone else catches on, that Schiff actually stopped playing and stormed off of the stage. He did.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
He did.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Well, that's a great segue because I want to give the audience a chance to just think about the idea of classical music. One of the ideas of classical music is that you don't clap when you're still in the middle of a chain of pieces that are connected together. I mean, how do you think about... What is your definition of classical music? Let's ask it that way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Right.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
That would be great. It's never going to happen. I don't think we're too fond of putting things into boxes, right? It does help us think about things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
Well, I grew up enjoying bands like Emerson, Lake and Palmer, who would play the occasional Prokofiev or Holster or whatever. And there's also always been classical orchestras doing kind of gimmicky covers of popular music. But from what you're saying, it sounds like there's a bit more seriousness to the erasure of the boundaries.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
I guess, yeah, I've never really thought of that impact, but that feeds into the idea that the boundaries should come down. There's no reason why someone can't make a playlist with Taylor Swift followed by something classical.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
288 | Max Richter on the Meaning of Classical Music Today
And you also, the other thing about your music, so that the audience knows, is that you do, you're pretty eclectic in terms of instrumentation. And not only... conventionally understood instruments, but ambient sounds, electronic instruments, et cetera. I mean, what role do those things play, would you say?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Tarun says, I've thought of the principle of conservation of information as meaning that Laplace's demon would be able to perfectly retrodict the past based on the current state of every particle, even though in practice that knowledge is unobtainable. However, in a previous AMA, you said that even in principle, that knowledge is unobtainable due to quantum uncertainty.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
In what sense then is information conserved? Well, I could have grouped this with a previous question. When we talk about Laplace's demon, we often do exactly what I did before, which is to say, let's simplify our lives and imagine the world is classical, okay? That's the world in which Laplace actually invented Laplace's demon, and in that world, Laplace's demon is very simple to explain.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Quantum mechanics comes along, and it has the idea of measurement. in it, which classical mechanics didn't, and the measurements are unpredictable. So if you have quantum mechanics complete with measurements, and you say that those measurements are truly unpredictable, let's just say that for the moment, then Laplace's demon doesn't exist.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Then there is no quantum mechanical Laplace's demon, full stop. That's it. People will nevertheless say information is conserved, but secretly they mean as long as you're not doing a measurement, okay? There's yet another footnote saying that in something like pilot wave theories or many worlds, there's a sense of which information is still conserved, but you don't have access to it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It changes some of the fundamental presuppositions of society or the economy or whatever, and some bad actors can rush in there and take advantage of that and scoop up a lot of wealth to the detriment of other people, and it can be exploitative and so forth until we finally figure it out, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But okay, you still don't have access to it, so I don't see what good that is doing you. More importantly, for the purposes of understanding the language used by modern physicists who keep saying, who keep banging on about the conservation of information, they are intentionally excluding the collapse of the wave function when they talk about that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So when you include that, information is just not conserved. Redmond says, while I believe human activity is warming the planet, the notion that governments can make the climate great again strikes me as laughably hubristic, with a backfire of some sort as likely as success. After decades of talk, the temperature is still rising.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Would not limited funds be better spent on adaptation rather than prevention? No. Limited funds would not be better spent on adaptation rather than prevention. There's a whole bunch of things going on here. Number one, like you say, after decades of talk, the temperature is still rising. That's because talk does not lower the temperature.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Action lowers the temperature, and as a planet, we have not taken the right actions to do it. The amazingly good thing about the climate is, roughly speaking, there's a simple thing happening with a simple solution. Of course, there are also very complicated things happening, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The atmosphere is a complex system, and you can sort of drive yourself batty getting into the details of exactly what's going on. But interestingly, amazingly, there is kind of a robust, simple underlying thing. We are putting greenhouse gases into the atmosphere. They are heating up the globe, and the temperature is going up. That's it, right? Everything else is downstream of that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There's many other things going on. There's melting going on. There's changes in the frequencies of storms and whatever. Patterns of wind are shifting. But roughly speaking, there's one cause for all of this. And therefore, we can fix it. We can just stop putting those greenhouse gases into the atmosphere, and we're choosing not to do it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It is absolutely the simplest thing, most straightforward thing, and we're just choosing not to do it. We're getting a little bit better, right? We are getting a little bit better. We're shifting to less harmful energy sources and so forth. So maybe it will be good. We've had several conversations on the podcast about the optimistic side. of climate change.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And so that's absolutely something that we can do. Would limited funds be better spent on adaptation? No, absolutely not. For one thing, those funds would be enormously larger than the funds that we just, I mean, it's actually not that difficult to stop spewing greenhouse gases into the environment compared to picking up and moving, what, a billion people?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Until we finally go, oh, okay, now we need to switch things and change things up to be a little bit more equitable, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
to get away from areas that are going to be devastatingly hurt by climate change. You know, if you're in the United States, you can sort of get along by saying, yeah, how bad would it be? It's already bad in regions like India and more generally in the global south, where they're both closer to the warm parts of the earth and less well-equipped to deal with these things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And so the suffering is already beginning. Indeed, as I'm recording this here in the United States, we just had a hurricane that did tremendous damage to Asheville, North Carolina, among other places. And, you know, as hopefully everyone knows, you cannot do a one to one map between this certain hurricane and global climate change.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But you can do a map between the tendency to have more hurricanes and more severe ones and global climate change. And the reason why I'm mentioning this one is because Asheville, North Carolina, was literally used as an example of a place that will not be harmed by climate change before the storm hit, OK?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So it would be nice if we could use those kinds of insights, those kinds of considerations from what did we learn from other situations where things were complex and changing and hierarchical and they were both top-down and bottom-up influences when things are rapidly changing and they're going to be different than they were before, but maybe some of those
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You can't say ahead of time that, you know, here's where to go if you don't want to be affected by climate change. You just don't know. It's just so much easier to fix the problem than to try to let the problem get worse and worse and worse and hope that you can avoid its worst consequences. I think that's a very easy choice.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Gary Miller says, if we find signs of technologically advanced alien life in the next 30 years, what signs do you think we would most likely see? Would they be light signals, spacecraft, artifacts, whatever? I think that we probably won't, is my bet. But if we did, I'm still a fan of the artifact way of doing things. The monolith hypothesis for you 2001 fans out there.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And the reason why is simply, to use the technical term, integration time. So if you send out a spacecraft to visit – if you are the aliens, OK, and you are exploring the galaxy and you send out a spacecraft to like visit another star system and then come back and tell people what you've learned, you're only going to spend a short period of time there, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
If you send a radio signal, it's literally moving through the other star system at the speed of light, right? Whereas if you send an artifact, if you send a machine that will just sit and park itself, it can wait for potentially millions or billions of years for life to come to existence and then become more technologically advanced in that system.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So if you're a smart alien civilization, the smart way to get to know other civilizations, extraterrestrials from your point of view, in the universe is to plant little listening stations or maybe speaking stations all throughout the galaxy. So even though I don't think it's likely to happen, I think that that's the kind of way it would be most likely to happen.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Franketh Rag Kernow says, I recently stumbled upon a video of Richard Gott, who is showing a glass model of a branching inflationary multiverse. One of the branches looped back to form the main stem. Richard was explaining that a closed time loop in one of the branches could mean that the multiverse caused itself, thus avoiding the singularity of the Big Bang. How does this work?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I was under the impression that branches cannot interact. Well, yes. So two things. Number one, the branches that Richard Gott are talking about are not quantum multiverse branches. They're not Everettian branches. It's just sort of a different part of spacetime. You know, Gott is a very clever guy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
His most influential work has been in relatively down-to-earth studies of large-scale structure and things like that. But he's a creative person who has some wacky ideas out there. And this is one of his wacky ideas. It's one that never really caught on. He was focused on the idea that conventional cosmology has a singularity at the beginning. Can we get rid of it somehow?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And he has this idea of time loops, closed time like curves at the beginning of time. It doesn't really fit in with what we know about cosmology and gravity and things like that, so not a lot of people jumped on that bandwagon. And furthermore, you know, the existence of the Big Bang Singularity is probably not true.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You know, singularity is a feature of classical general relativity, and classical general relativity doesn't apply in those circumstances. So we don't know what happened at the beginning of the universe, which is why we're welcome to think of different possibilities.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I think lots of different possibilities are on the table, but I'm just not that focused on smoothing things out but still talking classically. I think that quantum mechanics is going to be very, very important in understanding what happened at what we think of as the Big Bang.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Murray Cantor says, you were quoted in a recent special issue of Quantum Magazine on treating spacetime as a continuous approximation to a deeper underlying structure. You were quoted as saying spacetime emerged from this behavior of the underlying system. Please expand on this and share your thoughts on what might be the structure of this deeper reality. Right.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
universal recurrent features will be important. So again, I don't know what they are. I don't know exactly how to go about doing this. This is an absolutely rich field of endeavor that there are people who do study it. And I'm a kibitzier here. I'm just watching from the sidelines. But I do think that it is a very valuable perspective to keep in mind.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
If you want more details on this that I'm about to give you right now, there was an early solo episode from years ago, I don't know, five years ago, on finding gravity within quantum mechanics. I want to be clear, I don't read the articles quoting me very much, right? So I don't know exactly what I said in the issue of quanta, which is very worth looking at.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I saw other parts of it that are very well done. So anyone out there, I recommend they check out Quanta's special interactive feature on emergent spacetime. But it's not – I would not say that I'm imagining spacetime to be a continuous approximation to a deeper underlying structure.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I mean, that's not strictly speaking false, but it's not the way that I would say it because it gives the impression of like a discrete kind of lattice, you know, imagining that space-time is made out of little blocks of a certain fixed size glued together in some way, or there's a certain minimum distance or something like that, none of which is what I have in mind.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I'm thinking of quantum mechanics, okay? So Hilbert space in quantum mechanics is smooth. It is not discrete. It could be finite dimensional or infinite dimensional. And I think it's very interesting to think of it as finite dimensional, at least for the part of the universe that we observe. And that's what I've been thinking about.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But it is not the same as having like a little lattice underlying space-time itself. So I want to clarify that one thing. So what I'm imagining, though, is that there is some quantum wave function, some quantum state with some Hamiltonian, and there is an emergent description of that system that looks like spacetime.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So emergence is a story of finding a coarse-grained, higher-level way of talking about the underlying theory where there's sort of variables that have an independent—not an independent— Variables that can be defined from the underlying fundamental variables, which you don't need to know all the microscopic information for, but have a sort of existence of their own.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
They can propagate, they can evolve, etc., in ways that are self-contained. The vocabulary doesn't exist, which is why I keep stumbling here. You don't want to say independent or autonomous because the higher level emergent variables are defined by the lower level variables. But you don't need to know about the lower level variables to understand what the emergent theory does. That's the idea.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So the question is, can you start with that underlying quantum, purely quantum description, and extract the classical spacetime from it? So we've written a couple papers that, you know, point in directions that try to do that. I would not say it's anywhere near far along. There's all sorts of questions we don't know the answer to. The whole thing might fail any moment.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But I do think it's a very promising way forward, and I'm hoping that more people start thinking about it. Gavin McQuillan says, You know what? No. I think all the conventional advice works. But, of course, you have to adapt the conventional advice to the context that you're in. So when you say—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
your path into higher education, I'm not sure whether you mean as a student or like because you want to become a faculty member in higher education. Those are two very different things. But in either, so let's go for the commonalities here.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Kyle Stevens says, you often refer to brute facts in physics to which there is no further explanation. Is there any a priori reason we should prefer brute facts to either an infinite or circular explanatory chain? No, I don't really think so. For one thing, I worry a little bit about the whole idea of an explanatory chain. I'm not quite sure that that is the kind of thing that you have in
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You know, I think that the single mistake people make when they're in college or getting their training to be professors someday is of doing what is asked of them And that's it. Like, you know, maybe having fun, going to parties or being on an extracurricular activity or whatever. But academically, they're doing what is asked of them rather than taking the initiative.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I just always advise to my students, you know, take more courses than you need to. Read more about the subject matter than is required in the course. Learn about the material in ways other than just what the course is doing for you, whether it's online or whatever. Take the initiative. Try to learn it because you want to learn it, not just because the course is forcing you to do so.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Wander outside your chosen area. Go to seminars or colloquia in other departments other than your own. Expose yourself to a very wide variety of possibilities, and then stand up and learn about them intentionally, not just because you're required to do so.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Whenever we, you know, it's the nature of the linear passage of time, but we are forced to make deep decisions about what to do for our lives at a moment when we are far too young to know much about the space of possibilities about what to do. So learning about what that space of possibilities is and moving into it with purpose and intentionality is the best possible thing you can do.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And I don't think that changes in any way because of new technologies or new systems of education being introduced. Brendan Barry says, I really enjoyed your conversation with Kari Cesarati. However, there was one statement that I'm questioning. Kari stated if you were to build a 10 TeV muon collider, which sounds less than the LHC because that's 14, but...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Protons are composite, so a 10 TeV muon collider would be comparable to the physics for the average collision you can get out of something like a 70 or 80 TeV, if not more, proton-proton machine. So that 100 TeV number that you might hear thrown around by China and CERN would be comparable to a 14 TeV muon collider.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I understand that with a proton-proton collider, you don't get the full energy of the protons in a collision event. However, won't there be some collision events where two colliding partons possess significant portions of the total proton's momentum?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
In other words, while the average hard collision energy for a 100 TeV proton collider may be 14 TeV, won't some events be closer to the 100 TeV energy? This is a great question. This is clearly a physics-informed question. I love it. So just so everyone is on the same page here, protons are composite particles, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
They have not only the three quarks that you know and love inside a proton, two up quarks and a down quark. But there's a whole bunch of virtual quarks, quark-anti-quark pairs, popping in and out of existence. And there's a whole bunch of gluons, virtual gluons, popping in and out of existence.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So when you smash two protons together, the things that actually collide and produce a spray of new particles are not the whole big floppy bag of protons. They are the individual pieces inside, which Richard Feynman called partons. Murray Gell-Mann was very mad at Richard Feynman for calling that. He thought they should have just called them quarks.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But the gluons are also partons, so Feynman did know what he was doing a little bit. So the things that collide in a proton-proton collision have less energy— than the proton as a whole because that energy is spread out over all these partons. So even though you're colliding at 14 TeV at the Large Hadron Collider, it's not really a 14 TeV worth of energy in each collision that's spread out.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So the question from Brendan is, well, but if the things are moving around inside the proton, some are going to be moving coincidentally toward each other from one proton and the other proton, some will be moving away. Won't you get some higher energy collisions? And the short answer is no. You have to do this calculation more carefully than I'm about to intuitively do it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But the point is that inside the proton, the kind of typical average effective velocity of a parton is not that big, right? I mean, the whole proton has a mass of about 1 GeV, which is one thousandth of a TeV in the units we're using here. And we're talking about 10 TeV and 100 TeV collisions.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
modern physics or modern ontologies trying to understand the fundamental nature of reality. That's sort of a more classical way of thinking about things. I think instead in terms of emergence and different theories offering multiple vocabularies for talking about the same underlying things going on in the world. And it's not that I insist that there are brute facts.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So the typical momentum or energy of one of those partons is very, very tiny compared to the overall collision energy that you're getting. And what that means is that there will be fluctuations around the average energy, but they're going to be very tiny. They're not going to be relevant. You're not going to go from a typical, you know, 1 TeV worth of energy in a collision up to 100 TeV.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
because of this. Just not going to happen. Or let's say it could happen, but the probability is really, really tiny. The fraction of events with that energy are going to be very, very tiny.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And then it's not going to help that you have a lot of energy in those very tiny fraction of collisions because the kinds of discoveries that are made at a proton-proton collider are not like, oh, here's an event that must be a new particle. you make discoveries by having many, many, many events, or at least enough of them that you can see them above the background noise, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The Higgs boson, you can see the plots. It's a bump around a background. So if you add one or two extra events out there near the tail of the distribution, it's not a statistically significant thing. So number one, you're not going to get super high energies. Number two, when you do get high energies, there are not going to be that many of them and you can't do much with them.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Having muons, which are elementary particles and you know exactly what their energies are, is a much more careful way of knowing that you're seeing truly high energy things. Floris Queek says, can you explain how to think of the geometry of the universe before electroweak symmetry breaking? As nothing had any mass yet everything was moving at the speed of light, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So no rest frames, no proper time. How do I wrap my head around this concept? I think probably the first step to wrapping your head around this concept is to distinguish between the geometry of spacetime and what stuff does within spacetime. So as I was literally just teaching my class the other day, the speed of light is not special because of light.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The speed of light is special because it's the speed limit in the universe. It's the thing that remains invariant in special relativity or general relativity. Every observer measures the speed of light to be the same thing. And it provides structure on spacetime by distinguishing present, future, past, and inaccessible, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
If you're too far away from one point in spacetime to get there other than moving faster than the speed of light, you can't get there. That's space-like separated. That's inaccessible. The question is, given that there is a speed limit in the universe, does anything move at that speed limit? And the answer is yes.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And one way of thinking about what moves at that speed limit is massless particles or certain kind of massless waves, if you want to think of it that way. And those include electromagnetic waves and gravitational waves. They move at the maximum speed limit. So we call it massless. the speed of light, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Things that are massive, like electrons, protons, et cetera, move slower than the speed of light. So they move slower than the speed limit. But even if there was nothing around, even if there were no particles in the universe, there would still be that speed limit.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Of course, there's always general relativity, so there's always curved spacetime and propagating gravitational waves, so that would make it a physically real thing, this speed of light limit that we would just call the speed of gravity if there were no light around. So before the electroweak symmetry breaking, the particles that we know about were all massless.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
We don't – neutrinos are a special case. So forget about the neutrinos. They may or may not be. We don't understand where their masses come from. But the other particles that we know about at that scale were indeed moving close to the speed of light. So it's not true that there's no rest frames.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
A rest frame can be defined by a physicist defining a rest frame, whether or not there's any stuff that is at rest with respect to that rest frame. Furthermore, if I have a box full of photons, okay, I literally have a box, a bunch of light particles bumping around inside the box, all those particles are moving at the speed of light. But there is an average amount of energy, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It's just it seems obvious to me that there are, right? And here's the argument. The world could have been different. The world could have been different dimensions of space-time or different forces of nature. It might not have been quantum mechanical at all. It could have been completely classical. It could have been discrete. It could have been continuous.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There is still a mass for the whole box. I imagine that the size of the box... have no energy. I'm imagining this as a thought experiment. There's an energy that I get from the combination of all the energy of the photons inside the box, and there's a rest frame for that box, okay? There's a rest frame.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There's a frame in which the average amount of photons going to the left and the average amount of photons going to the right are equal to each other. In other frames, they wouldn't be the same. So there was a fluid, a plasma, whatever you want to call it, in the early universe that defined a rest frame with respect to that. I'm trying to be comprehensive here.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So I'm saying there needn't have been that. There still would be the concept of rest frames. But in fact, there was a fluid of particles, each individual particle moving the speed of light, but the fluid was not moving at the speed of light. Just like the speed of the air around you is not equal to the speed of the individual air molecules. It's an average over all of them.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So I don't think it should be that hard to wrap your head around that particular concept. You've just got to get used to the idea of spacetime having a structure independent of what happens to be in that spacetime in any one moment. David Maxwell says, mattering in proportion to their wave function squared.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
As branches get thinner, their significance lessens when considering your effects on future use. It feels wrong to conclude that I'm less important than any previous me, but I can't pinpoint why. How do we think about a system of thinning worlds and not infer something negative about the existential meaningfulness of the future? I think there's two things going on here. I like the question.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It's sort of a clever... taking seriously of the idea of the significance of individual worlds lessening over time. But there are two things to say. One is that the – if you just take literally the idea that as the world's branch and then each individual branch matters less, you also have to take seriously the idea that there are more branches.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The total amount of meaningfulness didn't decrease when the worlds branched any more than the amount of cake decreases when you cut the cake into slices, right? It's just divided up slightly differently. So what matters for the future is exactly the same, whether you're in one world or in many worlds.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The other is that from the perspective of any one person in any one of those worlds, they have thinned out in the sense that the amplitude associated with their branch of the wave function has gone down, but the whole world has thinned out. It's very analogous to thinking about conservation of energy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Why does it seem like the whole world has the same amount of energy even if it's branched into multiple copies and its overall contribution to the energy of the wave function of the universe is much, much less? Well, you have branched and everything else is branched and you're all multiplied by this small number.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There are many different possible worlds as far as we currently know. Maybe... There is some argument that no one has ever thought of. People have certainly tried, but they have done a pitifully bad job of coming up with an argument to say that the world around us is in some sense uniquely the world as it could have been, right? That's a tough argument.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So the amount that you matter to the rest of the stuff in the world around you is just as big as it ever was because relatively it hasn't changed that much. So I see no reason to be existentially worried about the branching of the wave function.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Massimo Tori says, could you clarify why Calabi-Yau manifolds are the preferred choice in superstring theory for describing the six compactified extra dimensions? What specific properties make them so suitable for this role? I'm not the superstring theory expert to answer this question, but this is, I think, a pretty basic one. The basic idea is just that they solve Einstein's equation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There's one subtlety here. because Einstein's equation relates the curvature of space-time to the amount of energy density in it. And how much energy density is in the extra dimensions of space-time? That sounds like a hard question. But the simplest kind of model is to say there is zero energy density in the extra dimensions of space-time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
That doesn't mean that there's zero energy density in the universe. It just means that the energy density that we have comes in the form of particles whose wavelengths are much larger than the size scale of the extra dimensions. So basically a photon that you see in your room carries energy, but its wavelength is much, much larger than the size of the extra dimensions.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And so from the perspective of the extra dimensions, it carries zero energy. The energy is not spread across the extra dimensions. It's only spread across your three dimensions, okay? So back in the 80s, when they started thinking about string theory, they looked for solutions to the equations where there's zero energy in the extra dimensions.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And then Einstein's equations become a little bit simpler. You're just setting a certain condition on the curvature tensor of the extra dimensions. R mu nu equals zero for those experts out there. And Calabi-Yau manifolds are curled up kinds of manifolds with R mu nu equals zero. They're the kinds of things that can easily plug in to the string theory equations and get a solution.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
These days, since the 90s, so not just these days, but for a while now, they've been thinking more generally about what are called flux compactifications, where you actually do have energy density threading the extra dimensions. And that opens up a whole new... landscape, literally, of possibilities. This is where the string theory landscape comes from.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Once you have d-brains and fluxes that might affect the geometry of the extra dimensions, you have a lot more possibilities going on. So these days we would not think of Calabi-Yau manifolds as the only possible compactification spaces. They're still there. There's still a possibility, but there are many, many, many possibilities. Linio Miziara says, No, absolutely not.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
In fact, it's very much the opposite. Typically, when you branch the wave function of the universe, you do not affect every symphony ever created. When you measure the spin of an electron in your laboratory in the basement of your physics department— and you get either spin up or spin down, you're not affecting Beethoven's Fifth Symphony in any way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There are now two branches of the wave function in which that symphony is exactly the same. Likewise, again, typically, all the laws of physics are the same. Everything is more or less the same except for that one measurement outcome. And to be super duper careful, everything that might directly be affected by that measurement outcome.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
kind of thing to imagine having an argument for, given all the weird specificities of the world. I mean, you're telling me that the ratio of the mass of the electron to the mass of the muon is somehow inevitable? It couldn't have been anything else? So, I mean, maybe it needed to be that. Early days of string theory in the 1980s, that's what people hypothesized.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But most things in the universe are not affected by that measurement outcome. GS says, in past podcasts, I believe you said that you are a Humean, or at least you lean more toward it than anti-Humeanism, but didn't go into much detail as to why you felt this way. Could you share more of your reasoning behind being more of a Humean as opposed to an anti-Humean?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Yeah, I think that when you try to think about what the world is made of, the fundamental ontology of reality, I tend to favor the picture that gets the most for the least, right? I tend to say, like, what can we get by with as minimal ingredients out of which everything else emerges? There is kind of a personality that comes into this. You know, some people— are very happy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I want to almost say that they prefer to assign new elements of reality to sort of every kind of phenomenon that they see around them. So electrons are real, but consciousness is also real. Life is also real and not just real in the sense of an emergent higher level reality, but a fundamental reality to them. I am not that kind of person.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I want to see, I think it's just more productive to say, oh, here's a very tiny set of ingredients. and we can explain everything else in terms of them. So when it comes to the laws of physics, if you say like, okay, here is Einstein's equation, for example, we were just talking about it. Law of physics that explains how the universe's spatial space-time geometry evolves throughout history.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There's two attitudes to take towards that law. One is the Humean view, which is that you just have spacetime. What exists is spacetime, and different points in spacetime are related to each other in different ways. And there's a pattern.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
If you know what spacetime has done over time, you discern that all this geometric relations between different points in spacetime and different curves through it, et cetera, look, they seem to obey this equation, which is Einstein's equation. In other words, the Humean says the laws of physics are a convenient way of summarizing what the actual universe is doing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The antihumian says, no, the laws of physics are the reason why the universe does that. The laws of physics play a role. The laws of physics bring the universe into existence somehow. So it's not just that the universe exists and the laws of physics summarize what it does. It's that laws of physics exist separately and in addition to the physical universe. That's the antihumian view.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And to that, I want to say, well, what's the difference? How would I experimentally tell the difference between these two scenarios? Maybe you think the Humean view is just incoherent somehow, but I haven't heard any— convincing argument to that effect. So I want to know, like, how do I know that these laws of physics actually exist?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I get the temptation to say that they exist, because otherwise you're stuck saying, well, isn't it a big coincidence that the universe just happens to obey these laws all the time? And I think that that's just a situation where our intuitions are getting the better of us. We don't have any strong way of saying that the universe should or should not obey some rules.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
All we can say is that as a matter of fact, it does. I don't think that that means that there are somehow existing these rules in some ontologically robust sense. Where are these rules? What are they— What would be the difference between them creating the universe and the universe just existing all by itself? I have very similar feelings about mathematical realism.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I tend against mathematical realism for exactly the same way. What are the causal influences that these extra things seem to have? What are the influences of the number two or Einstein's equation on the universe over and above summarizing what the universe does? I can't perceive anything, therefore I go Humean in these ways of thinking.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But of course, what they seem to have found is, oh, actually, no, there's many, many ways that it could be. And that's not at all unique to string theory. That's true in every other attempt to unify physics that has made any progress at all. So if that's true, that there are different possible worlds, then there is a brute fact about the fact that we're in this world.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Benjamin Zand says, my question is, how do we know the laws of physics and the physical constants are the same everywhere in the observable universe? Is this an assumption or can they be confirmed by observation? It's not an assumption. It's, you know, science doesn't really generally work by assumptions. It works by hypotheses. You make a hypothesis. You say maybe things are this way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Then you test the hypothesis against the data that you have. Sometimes those tests are rather indirect. Sometimes they're super direct. But for the constants of nature, we say, you know, OK, so first start, let's imagine that we have— Something like Einstein's equation that uses Newton's gravitational constant and the speed of light, and we imagine those are constant everywhere.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But then we also say, let's imagine they're not constant everywhere. How would things be different? How would we test that? How could we invent a theory where that is true? So for the constants of nature that we know, we absolutely have done an enormous number of tests to make sure that they're not different other places. Think of it this way. Here's the rule of thumb.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
If there is some assumption that you could undo in physics and then you could test the impact of undoing that assumption, and if you tested it and found that your test had located some difference in the usual way of doing things, and by making that discovery you become a super famous scientist and win all the Nobel Prizes, then probably people have done it. Already.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So for things like the speed of light, the mass of the electron, Newton's gravitational constant, it would be super duper important physics discovery to actually detect them changing over time. So of course people have tested that and there's all sorts of ways to test it. My favorite way is big bang nucleosynthesis. You know, when the universe was one minute old, it was a nuclear reactor.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It was fusing hydrogen and protons and neutrons together to to make helium and other elements. And that rate of nuclear reaction depends on the masses and charges of all the elementary particles in a very specific way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And so you can make a prediction, and then you go back and test the prediction, and the model that works is the one where the constants of nature had basically the same values back then as they do now. Norman Wickner says, is the wave function defined on all of the universes, those that exist after multiple splits at once, or is there a different wave function defined on each?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Would a wave function of all the universes be a simple weighted linear combination of wave functions of each universe? Roughly speaking, yes. I think that that's not usually the vocabulary that Everettians use. The usual vocabulary is there's just one wave function. period. That one wave function includes all of the universes, okay? The word universe is sloppy here.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It goes back to the early 70s and Bryce DeWitt calling it the many worlds interpretation of quantum mechanics, but it's okay. It's all right to use it. It's better, we think, to call them branches of the wave function because that makes them clear that they exist inside the wave function. When people want to know where are all these other universes located, That's a category error.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
As I say in my paper on why there is something rather than nothing, people have tried to say that – and I also – I wrote a tiny little paper recently that you can find it on the web on physics and the principle of sufficient reason. The principle of sufficient reason is this idea from Leibniz that everything that happens – happens for a reason.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
That is a mistake in reasoning because there's not a physical location for the other universes. Space and time exist within the universes, within each branch. It's not that the branches are located somewhere in space-time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But within the approximation where you have branching that is sort of clear and clean and you can say, all right, here's one branch of the wave function, there's another branch, et cetera, then it is true, yes, that the whole wave function is just a linear combination, weighted linear combination of the wave function of each branch.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Mehran Mizrahi says, in a prior episode you mentioned in relation to spin that those are the only options that we've seen. We can imagine others. We've never found a fundamental particle with any spin other than that. Nima Arkani-Hamed in his Cornell lectures in 2007 made a much stronger statement that quantum field theory constrains the possible menu to only these five values.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Plus there can be only one spin zero and one spin two. Is he correct what mechanism creates this constraint? So you have to be careful when you talk about spins because there's sort of two different things going on. One is the total amount of spin and the other is the projection of that amount onto some axis, right? Like spin is like a vector.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It's not quite a vector because it's spin one half rather than spin one. But it could be spin one half, I should say. But it's kind of like a vector that has a length. But then when you measure it, you're projecting it onto some axis. So if you have a spin one half particle, the total spin, and we simply say spin one half, but there are two possible projections.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
They're separated by an amount equal to one. All of these numbers are secretly multiplied by Planck's constant h-bar, but we set h-bar equal to one so we don't notice. So spin one half, the actual amount of spin is one half times h-bar, we just say a half. So it could be spin plus a half, i.e. spin up, or it could be spin minus a half.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
When you have a spin one particle, when you measure its spin, you can get plus one, zero, or minus one. That's the amount of spin in the z direction. If you had a spin 3 halves particle, you could have plus 3 halves, plus 1 half, minus 1 half, or minus 1. If you had a spin 2 particle, you could have plus 2, 1, 0, minus 1, minus 2, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So that's where the number 5 comes from in Nima's statement, because in quantum field theory as we currently understand it, in terms of fundamental particles, not composite particles, so you have a nucleus with whatever spin you want, but in fundamental particles, The maximum total spin is two, okay? And the spin, like Nima said, there's only one spin two particle. It's the graviton.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There are good reasons not to have multiple spin two particles. And so the five he's referring to is the five possible spin projections of a spin two graviton. Plus two, one, zero, minus one, minus two. Now, I don't know the origin of the statement that there can be only one spin zero. I don't even think that's true.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There's generally, certainly the standard model of particle physics has more than one spin zero particle, so I don't think he said that. It has one spin zero Higgs boson, as we say, but that's a complex doublet. So complex numbers mean there's a real and imaginary part. Doublet means there's two of them.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So there's actually four spin zero particles in the standard model, but three of them are eaten by the W plus, W minus, and Z bosons. So we have one spin zero left over, but we could have more than. one spin zero particle. There are reasons to think we only have one spin two particle, the graviton. Anyway, you're asking about what are those reasons?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Everything that exists has a reason or cause for it existing. And I tried to make the argument, you know, in physics, no, that's, I mean, there could be a cheap kind of trivial construal of what that means, which is just everything obeys the laws of physics. Okay, sure, everything obeys the laws of physics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So there's a whole set of reasons and it's complicated. I'm not going to go into great detail here, but it's a good question because it reminds us that when theoretical physicists build quantum field theories, particle physics theories, there are enormous numbers of constraints that they have to satisfy. The most basic constraint is that the energy needs to be bounded below.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There needs to be a minimum amount of energy in your quantum field theory. There needs to be, in other words, a vacuum state, a state for which the total energy is the minimum possible value. The reason for that is more or less an empirical one. If that weren't true, if you could get arbitrarily large energies, negative energies, then you would get arbitrarily large negative energies.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Whatever state you are in right now would decay into the lower energy state plus some particles. It would decay infinitely fast in some unregularized way of thinking about things, but super fast in any possible way of thinking about things. So you want a stable vacuum state. That's one very important thing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And if you just start throwing fields around and you don't work very hard, you will end up with a quantum field theory that allows you to have particles with negative energies. And that means that your vacuum state is not stable. If you have one particle that has a negative energy, you can get an arbitrarily large negative energy just by creating a lot of those particles, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So that's one constraint on what you can do. Another constraint is that you don't want to have particles moving faster than the speed of light, right? And that might sound easy to do, but in fact if you just start writing down random quantum field theories with high spin particles, the fact that your spin is so large means that every kind of particle comes with many different components.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And it's going to be the case that if one of those components moves slower than the speed of light, then another one moves faster. Or if one is positive energy, another one is negative energy. Things like that. So I'm not going through all the different possibilities, but just to let you know that there are a lot of constraints in particle physics on what you can possibly do.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And one of those constraints adds up to the fact that spins are two or less overall. Ken Wolf says, But if that level of minute manual control is required by all of us in perpetuity, is that not just a sign that the government has helped itself to too many opportunities to derange people's lives without their consent?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I know your question started out really good and then kind of ran off the rails there at the end, Ken. I don't know what we're talking about with deranging people's lives without their consent. But I do think that it's perfectly accurate to characterize what Hari was saying as involving – real participation in democracy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I mean, the lesson is that democracy is not something you show up for at the ballot box once every four years. It's an ongoing process. Why should that be surprising? I think that's a very natural thing. It might be a worry that people become too busybody-ish, etc. It's the typical—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But if it's supposed to be something deeper that says there's a reason why the laws of physics are the way they are, I'm skeptical that that's possibly true because there are other ways the laws of physics could have been, and at some point you just say this is the way it is rather than that way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Homeowners Association problem where people start controlling what other people can do in their houses and that's something you need to fight back against, yes.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But the very idea that the authority for governing a country with hundreds of millions of people in it is vested in the people themselves, it should not be surprising that that idea leads you to say that those people need to do some work, right? That work might involve educating themselves. It might involve talking to other people.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It might involve listening to other people, sharing their opinions back and forth, doing work to convince people. Yeah, that's absolutely going to happen. That's what life in a democracy is like. It might be more efficient to have just one person who makes all the decisions, but we have other values in addition to efficiency.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The one person making all the choices system never actually works out well for the majority in the long run. Eric Stromquist says, a few months ago, I saw you on Robinson Earhart's podcast, where you gave the anthropic principle as an example of a piece of philosophy that physicists tend to handle poorly. What is the right application of the anthropic principle?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I've always taken it to mean that because the values of some properties of fear are fine-tuned for our existence, we are justified in inferring that an ensemble actually exists, be it of universes, planets, or whatever, where different ensemble members have different values of the fine-tuned properties and where we necessarily exist and an ensemble member doesn't.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
having values that allow our existence. Well, there's two things. Number one, I don't exactly think that that's the right way of stating the anthropic principle. It's very close. I would tweak it a little bit. I would not say that because some values of properties appear fine-tuned, we're justified in inferring that an ensemble actually exists. I think that's too much.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
That is granting ourselves too much. I would say that the hypothetical existence of an ensemble could be a perfectly good explanation for why some properties in our observed universe appear fine-tuned. It's just a selection effect. That's like the sort of most weak, asking the least of us version of the anthropic principle.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
If there is an ensemble, we're going to find ourselves in the part of the ensemble where we can exist, right? How can you possibly disagree with that? People manage to find ways of disagreeing with that, even though it's perfectly true right here in the solar system, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There's different parts of the solar system where it would be very difficult for life to exist, parts where it's very easy for life to exist. Lo and behold, we find ourselves in a part of the solar system where it is easy for life to exist. The anthropic principle at work, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But I wouldn't necessarily, if the Earth were clouded over in perpetuity and we didn't know about the rest of the solar system, I wouldn't necessarily say that we have to infer the existence of the rest of the solar system. We hypothesize it and then we wait to see if there is better evidence that comes along that makes it, lets us make choices between the alternatives.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So my own personal argument is not so much that I don't want there to be an infinite or circular explanatory chain. I'm not even sure what the circular explanatory chain would mean. That might not be fair, but if there was an infinite chain, That's fine. I just don't think it's true. It's not that I think that there's some logical impossibility about it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You know, there's no rule in physics that says the universe has to give us answers quickly and cheaply. Like sometimes we might just have to live in uncertainty for a while. Okay, but In cosmological applications of the anthropic principle, not the uncertainty principle, that's something different. Here's the second point. Physicists often want to do more than that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
They want to say, if you have a certain kind of ensemble, then I want to be able to make a prediction for what typical observers will measure, right? This is what Steven Weinberg did back in the late 80s for the cosmological constant, what let him predict that a typical observer in an ensemble where different people saw different values of the cosmological constant
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
that they should observe something that is a small but not zero number, and that eventually turned out to be right, that prediction, right? So in some sense, maybe he was on the right track. We still debate that. That kind of thing where you're actually making a prediction is harder to get right, and I don't think that we do get it right. So –
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
When I say that physicists don't get it right, I don't mean that philosophers do get it right. So your first question is, what is the right application of the anthropic principle? I don't know. I don't think that we've thought it through very, very carefully. I take very seriously the very basic critique that you and I are not typical observers in the universe. universe.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
We know that we're not typical for all sorts of reasons. So why should we be so clueless as to forget all of our specificity and then pretend that we're typical and then remember it again and try to make a prediction? There's got to be a better way of doing it than that. And I don't know what that good way is. That's why I'm encouraging philosophers to think about it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I'm thinking about it myself, but I don't have the final answer yet. I don't know exactly how we should do this. People like Nick Bostrom, former Mindscape guest, have thought about it and written books about it. I just find their answers completely unconvincing. I think we've got to do better. I'm going to group two questions together.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
One is from Brian Gunnison who says, how does theoretical physics research contribute to real world applications and technological advancements considering that historically breakthroughs like Einstein's theory of relativity led to GPS technology and quantum mechanics enabled the development of modern electronics?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Can we quantify the impact given that approximately 28,000 physicists are employed in the US alone with theoretical physicists comprising about 10% of this workforce? Can we expect anything else soon? And then Rufus Knapp says, I was thinking about Oppenheimer the other day, and the question occurred to me, what areas of cutting edge theoretical physics currently require a security clearance?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So I think that there's a lot going on here. And one very tiny footnote, it is not accurate to say that Einstein's theory of relativity led to GPS technology. The correct thing to say is that to get GPS right, you either need to understand relativity, so people invent the technology, but then it would have been giving the wrong answers if they didn't know about relativity.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But maybe that's not even a big – kind of problem. If you didn't know about relativity, you would do the experiment. You would put satellites up there, you would realize it was giving you the wrong answer, and you would figure out how to correct for it. The problem would be you wouldn't know why. You wouldn't know why it was going wrong, right? Relativity provides that answer.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I just don't think that's how philosophy and physics work. Have you thought about a gift for yourself this year, one that has the power to help you grow, learn, and become a better version of you? Give yourself the gift of language by getting Babbel. Babbel is the language learning app that gets you talking with quick 10-minute lessons handcrafted by over 200 language experts.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But it's not like once you knew relativity, suddenly you could invent GPS. It's just that you could invent GPS that works correctly, okay? Quantum mechanics has led directly to modern electronics and other things, so I think that's a better example there. But we need to distinguish a couple things. One is the difference between fundamental physics and sort of higher level emergent physics, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There's a set of people working on quantum field theory and particle physics and gravity and cosmology and things like that who are doing fundamental physics. Those people get a lot of the airtime in the public sphere, but they are not the majority of physicists, not even the majority of theoretical physicists, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Most physicists are working on atomic physics and condensed matter physics and plasmas and biophysics and all sorts of things that are much more down to earth. So when you want to ask, you know, what good is physics doing for technology, you have to distinguish between those two sets of people.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And as I've said various times before, there was a time when the people doing fundamental physics had a huge impact on applications to technology. But that time was before 1950. Going back to, you know, Sachi Carnot and building steam engines, it was very clear that fundamental physics had a technological application, not to mention Newton and Galileo, etc., right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
All the way up to nuclear physics and people like Oppenheimer, right? When we were discovering radioactivity and nuclear fission and fusion, no question that those kinds of fundamental physics cutting-edge discoveries were important for technological progress.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Since the 1950s, roughly speaking, you know, you can argue about details, but since then, we have constructed a theory of fundamental physics that works well enough for all technological applications, right? We discovered new particles, like, okay, now we know about the top quark. How can we put that to work in a technological application? And the answer is we can't.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The top quark has no technological applications. Maybe someday someone will invent one, but you have to really be impressed by how difficult that would be to invent a technological application of the top quark for the simple reason that top quarks disappear in a tiny fraction of a second.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
the difference between physics pre-1950s and fundamental physics, pre-1950s and fundamental physics post-1950s, is that pre-1950s we were learning more and more about the behavior of the particles all around us. right? Nuclei and electrons and things like that existed all around us even before we understood them.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And by learning more about them, we learned more about how to manipulate them and create technology. The progress in fundamental physics since the 1950s has not been understanding electrons better. It hasn't even really been in understanding nuclei better. It's been in discovering new particles and new aspects of quantum physics
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
field theory and understand symmetry breaking and things like that, inflationary cosmology, dark matter, whatever, which are great, which are super important. It's what I do for a living. I am very impressed by the importance of these areas, but they're not going to lead to technological advancements because they're talking about things that are not around us. And if you make them, they disappear.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So it's like exactly made for not being technologically very, very relevant.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Meanwhile, of course, the vast majority of theoretical physicists are working on things that do have something to say about the materials that are all around us, whether you're working on superconductivity or atomic transitions that are relevant to lasers and so forth, or biophysical things about molecules that are relevant to DNA.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Hello, everyone. Welcome to the October 2024 Ask Me Anything edition of the Mindscape Podcast. I'm your host, Sean Carroll. So we're in the middle of the semester here at Johns Hopkins, teaching and writing papers and all that stuff. And I wondered the other day about how do I remember how to actually pull off doing these AMAs, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Babbel gets you talking a new language in just three weeks. Whenever I'm going to visit a country where I don't speak the language, Babbel gives me a leg up in learning the basics so that I'm not afraid to participate in conversations. And here's a special holiday treat for our listeners.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
These are not what we call fundamental physics, but they're absolutely physics, and they absolutely will have important technological and medical, for that matter, applications going forward. So to Rufus's question, what areas of cutting-edge theoretical physics currently require a security clearance? Not fundamental physics, not string theory or loop quantum gravity or anything like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But there are other areas. Quantum information theory, maybe? To be super direct about the answer, it never is true that an area of cutting-edge theoretical physics requires a security clearance. It might be that the kind of physics that you're doing allows you to get a security clearance and therefore know about some project, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So I can absolutely do quantum information theory without a security clearance, but the
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
government might be building some especially good quantum computer for which I would need a security clearance while doing theoretical physics but quantum information theory is just the Schrodinger equation at the end of the day okay we know the Schrodinger equation you're not inventing new fundamental physics you're putting it to work
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And putting it to work is a very, very good thing to do, just like superconductivity or whatever. So the areas of cutting-edge theoretical physics that might require security clearance are those that involve particles we already know about, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I mean, here at Johns Hopkins, we run something called the Applied Physics Lab, which is a giant laboratory that does a lot of research that requires a security clearance.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
If you look up, I think I mentioned this before, but if you look up lists of universities ranked by the amount of grant money they get from the United States, Johns Hopkins is number one, has been number one for many, many years. And a lot of people think it's because of the medical school, which is part of it, but mostly it's because of the applied physics lab.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But mostly applied physics is not fundamental, cutting edge, emergent space time kind of physics, to put it that way. Dan Butler says, when talking about many worlds, sometimes you talk about discrete events like atomic decay or the detection of a photon being the cause of the branching process.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But other times you talk about how it's all just a smooth wave function evolving smoothly under the Schrodinger equation. Do you think of branching as a discrete or continuous process? Yeah, it's absolutely smooth in the sense that the wave function of the universe evolves smoothly. Branching, remember, is a higher level emergent phenomenon, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Right now, get up to 60% off your Babbel subscription, but only for our listeners at babbel.com slash mindscape. Get up to 60% off at babbel.com slash mindscape. That's B-A-B-B-E-L dot com slash mindscape. Rules and restrictions may apply. Tim Falzone says, which philosophers do you think have had the most profound insights into the nature of complexity?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
We human beings find it convenient to talk about the wave function of the universe by splitting it into branches. So it's an approximation. The branches are approximately orthogonal to each other, but they're not exactly. They go from being not orthogonal at all, then under a measurement process they become pretty darn orthogonal.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Again, super duper duper close to being orthogonal to each other, so more than good enough for government work. But it is, strictly speaking, a smooth process that is just an approximation that we human beings use to discuss the universe in easily understood ways.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Hail Zeus says, when you are asked to review a physics article for a prominent peer-reviewed journal, how do you approach completing the review? I find it interesting that articles by different authors in the same journal can at times reach rather different conclusions or even directly contradict each other, yet both are published.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I would appreciate your thoughts on what role reviewers play in this process or even what you think a journal editor's responsibility is in such situations. I think it's a great question. I think that, number one, the general public is— very misinformed about what referees do and how reviewing works.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And number two, professional scientists aren't especially in agreement about how that process should work. You know, I think of reviewing or refereeing as more or less a filter, right? And it filters out the weakest things, the things that are obviously mistakes, or should, it tries to. Refereeing is not perfect, you Neither journal editors nor referees get everything right.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So just because something appears in a journal that has been peer-reviewed doesn't mean it's reliable. It increases your credence that it's reliable, but that credence shouldn't be 100%. It certainly doesn't mean it's interesting or that it's right. You know, you can be
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You can be correct but not right, by which I mean you can have some equations and you can solve them and you can solve them correctly, but the thing you're talking about doesn't apply to the real world, right? So I have a theory of dark matter that says it's this kind of particle. Someone else has a theory of dark matter that says it's a completely different particle.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
We both do calculations within our specific models. We both publish papers. One of us is right in the sense maybe, hopefully, that one of us is right in describing the world. The other one is not. But they're both, you know, correct within the – I forget. I'm mixing up the words right and correct here. But within the model, within the set of assumptions, the calculations are legit.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But that doesn't mean it describes the world correctly. It would be too high a bar. to say that the referee needs to perceive the reality of the cosmos before they can accept a paper. So plenty of papers are accepted provisionally under the model that they're looking at. And also some issues are just controversial, right? Some issues, the field as a whole doesn't know the answer to them.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And so you will get published papers that have contradictory results. That's part of the process. You know, this is the theme of today's episode is that science, they process, right? It's not a set of true-false statements that are handed down by God, okay? It's not a set of experiments that just tell us the right thing once and for all and then we move on.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
We make hypotheses, we test them, we try to figure out whether we correctly made the predictions based on those hypotheses. Sometimes we did, sometimes we didn't. We interpret what we've done, other people interpret it differently. It's a mess. but it takes time and the process eventually makes progress. I personally, in the process of refereeing, I like to be forgiving.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I end up rejecting a lot of papers because they're just bad or wrong, I think. But I tend to think that if something is saying something interesting, look, I just... accepted a paper whose literally its whole job was to argue against something that I had argued about. I'm trying to hide the specifics here, but I had written a paper.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Is the science of complexity theory ahead of philosophy at this point, or are there useful exchanges between science and philosophy in the area? I think it's growing, actually. This is a very, very good question, and I thought about it, and I don't think I've done a good job of coming up with it. great philosophers who have really given profound insight into the nature of complexity.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Someone else wrote a paper saying, no, you absolutely cannot think this way. It's wrong. And I recommended that it be accepted because it was—even though I disagree with the conclusions of the paper— I thought that the arguments presented were very interesting and worth considering and that issues are difficult. So maybe I'm wrong, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So I like to be forgiving when accepting papers in terms of the conclusions as long as they are well argued and plausible and, you know, something that I could imagine. Well, you know, maybe someday I will realize that I was wrong about this and I want that point of view out there in the published literature so people can think about it. I think that should be the standard.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Kyle Cabasares says, who or what gave you the inspiration to start writing your textbook, Spacetime and Geometry, early in your academic career as opposed to later? I noticed that the lecture notes that were eventually transformed into the textbook were on archive back in 1997. Yeah, what happened with the book was when I was still a postdoc at MIT, so my first ever postdoc.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
A postdoc is a three-year position, usually something like that, and then you try at the end of the postdoc to apply for faculty jobs. Sometimes you succeed, sometimes you don't. If not, you apply for another postdoc, okay? So I was in the last year of my postdoc at MIT and applied for faculty jobs and also new postdocs.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And one of the professors at MIT in the physics department went on leave and was supposed to come back, and he said, nope, I'm not coming back. That happens sometimes. So he was supposed to teach general relativity, and they were out a professor, and so they asked me to teach general relativity as a postdoc.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Now, in fact, Ted Pine and I, Ted Pine, of course, all Mindscape listeners know as the guitarist and composer for the Mindscape theme music. When he composed it, it was not the Mindscape theme music. This is, you know, his band did this back in the 90s, and I just borrowed it because I knew that he wouldn't sue me for infringement, and I liked the songs.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So Ted was a graduate student with me in the astronomy department at Harvard, and the two of us led a course. We taught a course for our fellow graduate students in general relativity. We both took general relativity from Nick Warner, who was at MIT at that time, is now a scientist at USC.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And he taught this wonderful course in general relativity, and we loved it so much that we volunteered to teach it to our own graduate friends at the astronomy department at Harvard. The reason being that typically in those days, the GR course at Harvard was very bad, and the GR course at MIT was very good, and it was a schlep to go from the astronomy department at Harvard to MIT.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So my fellow astronomy grad students just would not have taken general relativity, which would have been a shame, so we taught it. So I was more or less ready to go because we had lecture notes. What Ted and I did was we hand wrote lecture notes and then we Xeroxed them and handed them out to the class. So we had, you know, a whole couple hundred pages of lecture notes in general relativity.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
based on Nick Warner's lecture notes, but we put our own spins on them in various ways. And then when the opportunity came to teach general relativity, normally you shouldn't teach a course all by yourself when you're a postdoc because you're trying to get papers written, trying to do research, and trying to get a faculty job.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I think this is one of the areas in which philosophy might be lagging a little bit behind the science. You know, in many ways, the, well, let me just mention the Santa Fe Institute recently is in the process of collecting the great papers in the history of complexity, right? Most of them are from the 20th century. I think they had a cutoff of 2000, but there aren't many from the 1800s.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But I was so prepared for it, and they asked nicely, and it was after the application season had gone by, right? So I'd already applied for second postdocs and whatever before I started teaching general relativity. And I ended up going to the Institute for Theoretical Physics in Santa Barbara. So I said yes, and I taught it. And I was young and energetic at the time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So not only did I rewrite our lecture notes in my own way, but I typed them all up, right? So I had these latex lecture notes, and I handed them out before teaching the class. We'll never do that again. That's something you do when you're young and energetic. Sorry about that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And then, you know, yeah, so someone pointed out that after the course, people who liked the lecture notes were Xeroxing them and sharing them around. So I just cleaned them up a little bit and put them on the internet. So they're on the archive from 1997.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So then, you know, once that happens and then you become a professor, which I did in 1999, once you have a set of lecture notes, that's halfway to a book. And so people started knocking on my door and say, like, you want to make it into a book? So I talked to different publishers and eventually in a moment of weakness, I said yes. So I turned it into a book.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I wasn't really in any way thinking about, oh, this is early in my career. This is going to hurt my career. It absolutely did hurt my career. It was the single dumbest thing I did in terms of getting tenure at the University of Chicago because you don't want to let them know that you're interested in doing things other than writing research papers.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And writing a textbook definitely is something other than writing a research paper. But if you forget about short-term careerist motives, I think it was a very good thing to do. I did it. I had more time then than I have now to do it. So I might not have done it if I had waited until longer in my career. And I was young and I would do things a little bit differently now.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But mostly I think that it was a good job. So I'm happy I did it. Peter Newell says, many worlds seems to imply that there were fewer branches of the wave function in the past and more in the future. This sounds like an arrow of time to me. Is this arrow of time somehow the same as the entropic arrow of time? Yes, I think it is. Anyway, you're right.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There were fewer branches of the wave function in the past, more in the future. And... Again, we define branches of the wave function in ways that are convenient to us human beings, so it turns out to be difficult to quite objectively define how many branches there are, how many branches you should say there are, because it depends on what purposes you're asking these questions for, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But roughly speaking, in the conventional way of thinking about many worlds— The arrow of time comes from an assumption about the past state of the universe. Things were relatively unentangled back then. David Wallace, a former Mindscape guest, is the world's expert on this, so you should look up his writings about it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Things were relatively unentangled back then, become more entangled as you go toward the future, and there's more and more branching. why were things in that special state in the early universe? It's exactly the same question as why the early universe had low entropy at early times. We don't know the answer to either one of those questions, but we know they're the same basic question.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Henry Jacobs says many worlds pluralism being a good Bayesian compatibilism all these things seem to be cut from the same or similar cloth. They are all theories that entertain many possibilities albeit not equally. Do you recognize this pattern in your interests and does it extend farther than those examples. Yeah, I think that's a perfectly legit characterization of how I like to think.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I like my individual ontologies to be very simple and minimal, but I also like to be able to live in uncertainty, to recognize that there are different possibilities that are worth pursuing. I don't want to tell everyone how to live their individual lives. I want people to be able to make their own choices, and I want to think that those choices are valid.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
If you want to enjoy smooth jazz, fine for you. You're able to do that. I want people to be able to live together, respecting each other's different choices and lifestyle arrangements, etc. Likewise, you know, I think it might be a bit of a stretch for many worlds. I think that many worlds, what I care about is not that there are many worlds.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
complexity science. And they're publishing them in four books. And there's an introduction by David Krakauer, a former Mindscape guest. It was a 100-page introduction which goes over, surveys the history of the field and draws connections between all these different papers. And you can buy that as a separate little book. So this is my plug.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
What I care about is that the fundamental ontology is very, very simple. That's the overriding interest that I have in physics theories. But the pluralism about values, the being a good Bayesian about propositions about the world comes down to imagining the possibility that various different things are true
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
or correct, or valuable, or whatever you want to say, and that we're not absolutely sure what they are. That is absolutely a big part of my way of thinking about how we should go through life. Chillin' like a leovillion. that's probably my favorite handle of any Patreon supporter ever, asks the following.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The quark model sounds a bit like a collection of spin one-half fields for which up to three particles can occupy a given state rather than the usual zero or one for fermions because of the Pauli exclusion principle.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There is a color charge taking one of three values that provides an additional quantum number to distinguish the states, but you can never isolate a quark and determine if its color is the same or different from another's. The gluon fields basically exist to guarantee symmetry among color assignments.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Would such fields behave fundamentally differently from the quark-gluon model if not forbidden by the spin statistics theorem? So I don't think, yeah, so I take the question to say that maybe there's some extension of the Pauli exclusion principle that says rather than ordinary fermions, where there's only one or zero fermion in every quantum state.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Maybe there's a different kind of particle where there could be zero, one, two, or three particles in the same quantum state. And maybe that could somehow recover the ordinary quark model.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It's very close to one of the motivations for the early quark model, which is that when Gelman and his friends started thinking about quarks and then they were able to predict the existence of collections of quarks, baryons, collections of three quarks that had never been observed, right? one of the—well, actually, I shouldn't say had never been observed.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
He did predict the existence of baryons that had never been observed, but also he made sense of baryons that already had been observed, and I'm not going to historically remember which was which, okay? So forgive me for that. But there was one particle called the—I think it was the delta, the delta plus plus. To make sense of that particle—it's a baryon—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
To make sense of that particle in the quark model, you had to imagine three quarks, all the same, so all up quarks we would say in the current lingo, all the same quark in all the same spin. So they're spinning parallel to each other because you want to have all the charge in the spin three halves particle overall, so you had to add up the spins.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You should buy that separate little book if you're at all interested in this stuff. It does a great job great job of sort of not only telling you about the history, but connecting different ideas that you didn't realize were otherwise there.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So you had basically in that particle, you know, unless you could play games, and this is why science is hard, and this is why it's not definitive, right? You could say, okay, well, I have three spins, three quarks with the same aligned spin, but maybe they're in a higher excited state or something like that, so they're not really exactly in the same state.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But certainly the simplest, most direct thing to say, and maybe they knew this from measurements of the mass of the particle, I don't really know— But certainly the simplest thing to say would be all of the three quarks are in exactly the same quantum state with their spins aligned. OK, the same kind of quark, same spin, et cetera. That is ruled out by the Pauli exclusion principle.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You can't even have two in the same state, much less three. So they said, and I think this is the motivation, maybe there's a new quantum number. Let's call it color. The word color didn't come along until later, but maybe there's another quantum number that takes three possible values.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So these three quarks, each of which look like they're in the same quantum state in the delta plus plus baryon, actually are in different states because they take on different colors, okay? And that turns out to be correct. So that's the ordinary way of doing things with the Pauli exclusion principle remaining unchanged.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It was only later, not much later, because people are very clever and they were thinking around, people like Yoshiro Nambu and others started asking, well, could color, this new quantum number – again, it wasn't called color at the time – but could this new quantum number – be the basis for some new symmetry, an SU3 symmetry, and could that provide the force that holds the particles together?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And Nambu's original model wasn't on the right track, but eventually Gelman and Harold Fritsch figured out how to make it work, and we invented QCD. So that all works. It works fine. There's no reason, you know, there's no empirical experimental reason to overthrow it and replace it with something better. But you're allowed to imagine trying to replace it with something better.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And there's absolutely a connection between the growth of complexity as something we think about and the growth of computers as both something to think about and as a tool for thinking about things, right? So I don't think that philosophy has studied complexity for as long as it might have.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
In this case, for this new idea that you're proposing, if I understand it correctly, the challenge would be to get the SU gauge bosons to come out right. So it's not at all obvious that if you generalize the exclusion principle to allow for zero, one, two, three, or four fermions in the same state, that that should be associated with a gauge symmetry in any sense.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
much less one that has essentially identical properties to good old quantum chromodynamics, SU3. You know, SU3 QCD has been tested experimentally to quite high precision, and roughly speaking, it passes all the tests with flying colors. So I suspect that if you tried to mess with something that sounded foundationally different...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Either it would somehow secretly turn out to be the same as QCD, just using different language, or it would give very different predictions and it would be hard to match what we know. Nate Wadoops says, So also imagine a gravitational wave or field sensor that is sensitive enough to detect an individual particle and determine which slit the particle went through.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Which of the following would you expect? A. Particle detection via gravity is sufficient to produce two stripes on the screen, or B.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
the gravity sensor just sees waves passing through the slits unless something else first detects which slit the particle passed through, or C, a sufficiently sensitive gravity-based sensor is theoretically impossible, thus rendering the question nonsensical, or D, something else.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
A, if I'm imagining I'm granting you the thought experiment license to imagine that your gravitationally based particle detector is sensitive enough. Whether or not that could be feasible in the real world is, you know, it's not actually practically feasible, no, because gravity is too weak. We cannot detect the gravitational field of a single particle.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But maybe you make your particles really massive, right? Or maybe you make the slits very far apart and you imagine very, very sensitive gravity detectors. This is an engineering problem. This is a technological problem, not one of principle of physics, so I'm granting you the ability to use gravity to measure which slit the particle goes through. So that would count as a measurement.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The gravitational field of the particle is just as much a measurement as the electric field of the particle, etc. So absolutely, yes, you would ruin the interference pattern by doing that measurement. Anonymous says, what are ways that your quirky preferences for thinking about math differ from other people's quirky preferences? E.g.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
some people like MTW bend over backwards to geometrically visualize covectors, or I'm more of an algebra guy and don't see what the fuss is about. Yeah, there's a rough division of mathematicians into geometers and algebraists, right? People who like drawing pictures and looking at shapes, people who like writing equations and filling in the blanks in those equations. I'm closer to a geometer.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I like pictures more than equations, but I'm not an extremist about either one. I recognize the need for equations. There's nothing like a good equation. I did once have an ambition, it's still kind of an ambition, to write a really good physics paper or even math paper proving a theorem of some sort where there were no equations. It was just done by geometric demonstration.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I don't know if there are any, you know, early modern philosophers who really thought that much about complexity.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
That would be very fun. The closest I ever came was a paper that I wrote with Alan Guth and Eddie Fari and Ken Olam back in the 90s on restrictions on closed time-like curves in 2 plus 1 dimensions. In that paper, the fundamental demonstration was just drawing pictures. In fact, it was drawing pictures of geodesics or at least piecewise geodesic curves in anti-de Sitter space.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But to set it up, you need to have a lot of equations. So we had a lot of equations in that paper. It was very far from this pristine ideal of just drawing a picture. But I think that everything is valuable. You know, again, this is the pluralist in me coming out. So even though I like pictures better than equations, I'm not going to disparage the use of a good equation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Whereas Ted Pine, my colleague who I just mentioned, he was absolutely an equation guy. Like if you ask him what a tensor is, he would say, you know, he would visualize an equation with some slots and he'd say, yeah, you put the vectors into these slots and it gives you out a scalar quantity. And I'm thinking more geometrically than that, but I get the importance.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I think that, you know, as much as I am a cheerleader for philosophy, I think that complexity is a case where scientists of various sorts, computer scientists, economists, people like that, have been leading the charge to sort of think about what complexity is, and the philosophers have some catching up to do. Emergence might be one counterexample to that, or exception, I should say, to that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Azure Propagation says, I appreciate Mindscape for taking a down-to-earth approach and just letting experts talk about the details they find exciting. But I think there's also pressure to select for exciting guests and topics. I was wondering if you had considered inviting on a grad student or a postdoc just to talk shop.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I think it would be quite interesting to get a very authentic, deglamorized, day-in-the-life image of what it means to be an academic. Yeah, I mean, this is an interesting suggestion. I've certainly thought about things like that. I have had some people who are postdoc level or beginning assistant professor level on the show. There's no pressure to select for exciting guests and topics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There is an interest that I have in learning new things. And talking about things that I think are exciting and new, right? Yeah, that's sometimes not new. Like when we're talking about the ribosome with Venki Ramakrishnan, that's old stuff in some sense, but it's new to me. So that counts as new as far as I'm concerned. And I do try to have a variety of different age groups.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
If you think about the last three guests, there is Kari Cesarotti, who is a postdoc doing physics. There is Hari Han, who is a mid-career successful political scientist. And then there is Venky, who is a Nobel Prize winning senior biochemist. OK, so we do try to get different groups.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
layers there different kinds of career moments and I do try it's actually remarkably interesting how people are reluctant to give me the day to day thing I think that they're trained to not talk about that so like when I talk to an experimentalist I always want to get a feeling for what the lab is like and
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And they never want to give it to me, not that they reject or object to giving it to me, but they skip to the answers, right? And I want to know more about the details about how they got there, but I need to get better at pulling that out of people. But I will also say, look, very, very honestly, It's a skill to be a good podcast guest.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And it's a skill that people learn over time, not by training to be a good podcast guest, but just by giving talks, talking to journalists, giving talks at different levels, some popular level talks, some technical talks, maybe even appearing as a podcast guest, you know.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You might have super brilliant young people who are grad students or postdocs who are not very good at being podcast guests, you know. And the— Very often for me, I'm asking people to be on the podcast who I actually haven't talked to in any detail in the real world before. It's the first time I'm meeting them.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So for my purposes of making sure that you all get a good podcast, it's a little bit safer for me to talk to older people because it is more likely, again, never 100% likely, but more likely that they have a slightly more polished way of getting to the point of what they are talking about. But talking about the day in the life, yeah, I mean that would be a risky thing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It could easily degenerate into sort of – especially if it was someone who was very close to my intellectual area. It's tricky. Yeah. to talk at a level, to talk in a way that addresses the concerns of people who are not at that exact specialty within science, right? So as I mentioned to Kari before we had our conversation, I have to play dumb. I'm the interviewer.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I have to say, what is a quark, even though I know what a quark is. So it's a tricky thing. I suspect the average attempt to for me and a younger person to sit around and shoot the shit about the day in the life of what we do would be less compelling than you think it is. I think that it would be better to have someone who thought about discussing that stuff in a careful way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Philosophers have thought about emergence very, very carefully for a long time now, And I tend to disagree with some of the things that are popular to be said in the philosophical community about that, but at least they've been thinking about it. Back to the British emergentists wrote and maybe John Stuart Mill even wrote about these things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It matters to think about it a lot, you know? If you talk to a basketball player about how to play basketball, some of them are no good at explaining it. They're super good at playing basketball or hitting a baseball or whatever. But being able to talk about something in an interesting way is a different skill set than being able to do it. And so you've got to look for the people who can do both.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Elias Aspin says, why are you a sports fan? And bonus question, why those teams? I think I am missing the fan gene. It's just never been very interesting to me to watch others doing sports, much less to root for one team over another. Of course, many people around me do enjoy spectator sports, so in a sense I realize that I'm the weird one. I'd be interested in your thoughts.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Why is it interesting to watch other people play basketball? Yeah, well, I'm going to take the pluralist line here. You're certainly welcome to ask why it is interesting, but you're under no obligation to find it interesting. That's not at all something that you should feel guilty about.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Honestly, you know, whenever someone has a hobby, whenever someone has a leisure time activity that you don't get, whether it's watching sports or cooking or going on vacations or whatever— Count your blessings because as long as you have other things, but like every individual thing that you like to do takes time and money and things like that, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So if you can save yourself a little bit of anxiety, sports is like the worst, right? If you like travel, then you can just go to nice places and enjoy them. Sports, usually your team is not going to win the championship, right? Most sports fans' seasons end in disappointment. You're just setting yourself up.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
for disappointment because only one team can win the championship out of let's say the 30 in the nba as a philadelphia sports fan i'm especially knowledgeable about this fact that you have to set yourself up for disappointment we've been doing better in the past decade or so not in basketball but in in baseball and football at least which i don't care about as much So why do I like it?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Hard to say. I do think basketball is also the sport that I played the most. So I appreciate it a little bit. I was never super good at it, but I was adequate. I could hold my own, right? And when you play against people who are even a little bit better than you, like – I'm on an intramural basketball team in graduate school.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And when we played with people who were mediocre players on the Harvard basketball team, which is not a very high level basketball team, But they so completely annihilated us, or at least like one person on each of our pickup teams would just dominate everything because they were so much faster, so much more skilled. And they're like Ivy League basketball players.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Again, it's very different than how I've thought about those things. But the closest that I could come to a name that you deserve, Tim, for your question here is actually Charles Bennett, who is certainly not a professional philosopher. He is a computer scientist, theoretical computer scientist, complexity theorist.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
They're not as good as the good college basketball players who are not as good as the pros, et cetera. So there's just an appreciation for the levels of skill that exist here. Yeah. And there's something – again, I'm not an expert on this, so a good psychologist who studies it would know more than I do.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But there's something primal about rooting, about competition, right, about organized competition in the form of a game. We did talk a little bit with Ti Nguyen, the philosopher, a while back about gamification and how it – It sparks people's interest in things, whether it's sports and you're being a spectator or whether you're playing something on your phone, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You're playing solitaire on your phone. The gamification, the existence of a reward, the goal that is explicitly stated, the ability to accumulate points and make progress and eventually achieve the reward, this all speaks to something primal within us. It's also – I'm very pleased that it is – controlled, right? It sort of replaces violent conflict in some very real sense.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It's completely arbitrary. You know, you're asking why those teams rather than others. It's because I grew up with those teams. In the 1970s, when I was a kid, I lived just outside Philadelphia, so rooted for the Philadelphia teams, the Phillies, the Sixers, the Eagles, and I just kept rooting for them.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
My favorite was definitely the Sixers because they had Dr. J, Julius Irving, who was just the most entertaining basketball player of all time to watch play. And they did exactly, you know, the sort of heroic journey where they kept coming close and couldn't quite make it. You know, in 1977 and then in 1980 and in 81, 82, they came very close to winning the championship.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And couldn't quite make it until they broke through in 1983. So, you know, very cathartic when they finally did win. And happily for me, the Internet has allowed me to become, to remain a fan, a very, very embedded fan in my hometown basketball team, even though I lived all over the country in the meantime. So I get enjoyment out of it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You know, I follow who the teams are, what are the trades that we've made. Basketball I like especially because there's only five players on the team at any one time. They're not wearing big bulky uniforms and they're all asked to do the same thing. It's not like baseball where everyone is specialized. The pitcher and the catcher and the first baseman are entirely different roles.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
there's slightly different roles in basketball, but everyone has to shoot the ball, pass the ball, rebound the ball, etc., you know, and you can see them, you can see their individual differences, you can get to know the people, they have personalities, some of them are jerks, some of them are awesome people. We just, a couple of days ago, when I was recording this, Dikembe Mutombo passed away.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
He was a Basketball player, famously good, tall defender, not a very fluid scorer, but he was a wonderful shot blocker and also a very vibrant personality. He played for the 76ers for just two years, but one of those years is when they made the NBA Finals in 2001. So he has— He has a warm place in the hearts of many Philadelphia sports fans.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And he also – he was born in Africa and he devoted his post-basketball career to being a humanitarian in Africa. He was building hospitals with the money that he made and he was using his star power to – get other people to give money to make Africa a better place. And that just warms your heart. You know, it's not that athletes are better people than others.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
famous for his work in quantum computation, no-cloning theorems, teleportation, things like that. He's a brilliant guy, and he's thought a lot about complexity, and he has written an influential paper that, in fact, we recently read in the complexity reading course that Janan Ismail and I are doing here at Johns Hopkins, where he introduced the idea of logical depth and
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Some of them are really bad people, but some of them are good people. And when you're rooting for people because you want them to block a shot, and then later in life they turn out to actually be really good human beings, that makes you feel good. It's a microcosm in a controlled... planned way of the in and outs of life, right? Of struggles to succeed, of setting goals and trying to achieve them.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And it's completely arbitrary. If I had been growing up in a different city, I would have rooted for a different team. That's fine. Right now, the team I root for is the Sixers. And until they do something really terrible, I'm going to root for them. And now the martini question. Rue Phillips says, what are your favorite alcoholic spirits, including any brands?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Do you drink any neat or on the rocks or do you always go for the cocktail? Yeah, sadly, I'm in a part of my life where I got to start cutting down on the drinking a little bit. I'm still allowed to do it. It's still quite healthy. But, you know, one is not as young as one used to be. So most of my drinking these days is wine. But I do enjoy cocktails and I also enjoy spirits neat upon occasion.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You know, I have this. It's not even gizmo. It's just a styrofoam container, but it lets me make spherical ice cubes that are perfectly clear. So it's a little way of freezing ice cubes in a spherical mold that pulls out all the bubbles to a reservoir below. So a typical ice cube, you know, if you just make an ice cube, it's filled with bubbles and it's sort of cloudy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I can make perfectly clear spherical ice cubes. So it's very cool. to have, you know, a glass of scotch or bourbon or whatever poured over the spherical ice cubes. I'm very proud of that. So I take, you know, pleasure in these little tiny aesthetic touches. But I do prefer a good cocktail to just drinking spirits neat.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You know, when I first, I didn't first discover whiskey, scotch whiskey and related American whiskeys like bourbon and rye. until, I remember, it was literally at a physics conference. It was at, in the 90s, in Ambleside, England, a Cosmo, maybe the first Cosmo conference.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I remember it because it was in, Ambleside is in the Lake District in England, so it's technically in England, but it's close to Scotland, so it's in the Lake District, is up there. So there's a lot of Scotch drinking going on, and the conference organizers planned an event for keeping the conference goers entertained, which was a whiskey tasting.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
In the middle of a semester while I'm trying to like teach and things like that. So the answer is I have not figured this out. I have not figured out how to do it. But maybe one strategy is to make the introductions shorter, to spend less time in the intro. So I'm going to do that. I will mention very quickly that pluralism works. is one of the themes of today's AMA.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So they invited—I mean, I'm sure they paid, or maybe they didn't pay because the company thought that they would get income from it down the road. But J&B is a major scotch manufacturer of blended scotches— And a representative from J&B came and gave us a whiskey tasting demonstration. And so we were all tasting whiskeys. And what a blended scotch is, is individual single malt scotches.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So an individual distillery will make what is called a single malt, a very specific, very unique kind of whiskey. And then a blend will try to mix and match them to make something that fits a certain flavor profile. And the guy was very entertaining. He had a thick Scotch accent. He explained that J&B brags about having 41 different single malts in there.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And he's like, yeah, maybe five of them matter. The others are just so we can say we have 41 malts in our blend. And he was very specific about, you know, like a very, very peaty, smoky thing like a Laphroaig. He insisted you have to drink it either with water or over ice. You can't just drink it straight.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Of course, I thought that this was an insult and would only ever drink it straight until I did discover later that, in fact, it's better if it's over ice or with a little bit of water. Yeah, he was just correct. He knew what he was talking about. You shouldn't try to be macho when you're trying to decide how to enjoy your spirits. So good Scotch whiskey.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
you might have heard of Comolgorov complexity. So if you have a string of bits, the Comolgorov complexity is roughly the length of the shortest computer program that will output that string of bits. Logical depth is the number, roughly, very, very roughly, I'm trying to get to other questions here, but it's roughly the number of computations you need to go through.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And I like—I do—I still am macho in liking the peatiest ones when it comes to Scotch, the Laphroaig and the Lagavulin and the Talisker. There's some very good Glenmorangies. Glenmorangie—or Glenmorangie, I think it's pronounced—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
They have a special place in whiskey lovers' esteem because the guy who's in charge of making the whiskeys there is some kind of mad scientist who takes the scotch and puts it in different kinds of barrels, right? So there's scotch you get that was aged in sherry barrels and other scotch that is aged in bourbon barrels and whatever. And so you get all sorts of—it actually does work, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It sounds like it could be awful, but it's a different way to enjoy scotch than sort of the straight-up-in-your-face Laphroaig way of doing things. And I'm not so stuck up that I can't enjoy a good American whiskey. I have struggled to enjoy Irish whiskeys and Canadian whiskeys, even though I have Irish heritage. I like a good bourbon or rye more than Canadian or Irish whiskeys, I have to say.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I have a bottle of French whiskey, which is, you know, it's a— conversation piece because it's French whiskey, but the French are good at other things besides whiskey. I did discover that I love Armagnac more than Cognac. Cognac is good, but Armagnac is just as good, if not better, and way cheaper. And it's kind of much more fun to search the world for a good Armagnac, a good bargain.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So that's a lot of fun. But as I said, this is all preliminary to say that cocktails are more interesting to me. I find it—I struggle in many restaurants or cocktail bars because they're all about, like, fruitiness or sweetness. They put sugar and orange juice in their cocktails. I'm just not about that. Spirit forward would be the way that I would describe my favorite way of doing cocktails.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So I go for the classics. I go for martinis, Manhattans, Negronis. Um, occasional explorations of sidecars or corp survivors or things like that. Um, and honestly, the martini is my favorite. Um, A Manhattan is good, but it's a little, you know, it's more like a dessert than a dinner kind of cocktail. A martini, I don't know what it is. It somehow gets it exactly right.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And as I'm sure you have heard, even if you're not a martini person, there are great controversies in the world of martinis about how to make them. The basic idea of a martini is gin or vodka, mostly, a little bit of dry vermouth. So that's the green vermouth bottles if you're in the store buying them.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And then some sort of garnish in the form of either olives or a little – what is called a twist, a little bit of the peel of a lemon or something like that. And then how you make it. What are the ratios of vodka or gin to – so all the things you can argue about. How much vodka or gin you should use versus how much vermouth. Should you use vodka or gin? Should you shake it or should you stir it?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
What is the best kind of garnish? How should you serve it? All of these are controversies that people rage over at great length. As a pluralist, knock yourself out. Do whatever you want. But also I have my favorites, and so I will tell you what my favorites are in terms of the answers to all these questions. Number one, it's absolutely gin, not vodka. Like, what are you thinking?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I'm going to pretend that my opinions are just the objective truth for the rest of this answer. So you can translate back into my actual pluralist leanings. But what is the point of a vodka martini? I mean, vodka is great as like a little cold shot when you're enjoying, I don't know, black bread and anchovies or something like that on a Siberian winter. Shot of vodka is a great thing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I remember very clearly in Las Vegas going to a Russian restaurant and having a vodka tasting. So a vodka flight, right? Like five little glasses with a tiny amount of vodka in each of them. The point being that vodka tries to be flavorless in some approximation, but it doesn't succeed and it sort of intentionally doesn't succeed.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So you could have a very short program, right? But it just, you run it forever before you get the output. that has small of complexity, Bennett is highlighting the number of steps that you have to do in such a program to actually output that string of bits, and that's the logical depth. And he makes an argument that this is what matters to complexity, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So different vodkas actually do taste different, and the feel of them is different, and the little tiny bit of flavor is different depending on what it's made from and so forth. So if you're doing a vodka tasting with different vodkas right in front of you, you absolutely can tell the difference between them. At least I can, and I don't have the most sensitive palate out there.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But it's still very, very subtle. Like if I'm going to have vodka, there's two reasons to have vodka. One is to have that little shot and just enjoy the pristine purity of the vodka, maybe in some environment that calls out for that. Or you're just trying to get drunk, right? You're like mixing vodka with orange juice or whatever because it's not very flavorful and you can drink a lot of it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And I've never been interested in that whatsoever. But in a cocktail, the whole point of the cocktail is that different spirits with different flavors are interacting with each other. And vodka doesn't do that much interacting because there's not that much there. It just serves as a basis to feed you the alcohol if it's mixed with something else. So for a martini, I absolutely want gin.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Gin is, roughly speaking, and I know the real gin connoisseurs will not agree with this characterization, but roughly speaking, it's alcohol plus flavor. It's vodka plus flavor, where the flavor comes in the form of various botanicals, okay? So in a typical gin, most of the botanicals, the dominant flavor is from juniper,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But you mix and match all sorts of different botanicals, lemon peels and thyme and whatever to make your particular kind of gin. And so different gins are actually very different because the botanicals are very noticeable in a good gin. My local – shout out to local Baltimore folks here. You should go to the Remington Bottle.com. which is a little local liquor store near where I live.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And the guy is like this old couple who owns it, and they're very into it, right? So it's exactly what you want in a local store or establishment where the people who own it are very passionate about what they do, and they can tell you everything. They can speak at great length about everything they sell. So he knew that I bought gin, and so he suggested to me this gin. What is it called?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It's Tom's Gin, but it's like Old Tom's or something like that. But it's this... Again, mad scientist, in this case in Vermont, who ages gin in bourbon barrels. this is just bizarre because those are two very different places in spirit, flavor, space, gin and bourbon, right? And so the gin is not clear that comes out this way. It's slightly brownish color.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It looks like watered-down bourbon, but it tastes like somewhere in between gin and bourbon. And I'm both delighted by it and haven't yet figured out how to use it in a cocktail. So I'm challenged by that one. Old Tom's, I think it is. Anyway, the gins are very different. If you're into gin or into martinis, it is absolutely worth doing your own little gin tasting.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
This is what matters to being different in some sense than just a simple thing repeated over and over again. that you have to like carefully do things in a complex system to put them together in exactly one way rather than some other way. So it takes a lot of steps to do that. This sounds like a very basic kind of simple idea, but it's actually very deep.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Buy five bottles of gin, invite some friends over, taste them all, and figure out which is the one that you like the best. OK, so that's one question. I mean, I guess I should say what the answer is, but I'll come back to an even better answer. So the tentative answer is I kind of like, you know, a classic Bombay Sapphire, but St.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
George's is a smaller organization that makes a bunch of good gins, and their terroir gin is probably my favorite basic gin, St. George's terroir, if you can find that. OK.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
others that are very good there's a baltimore gin that is actually remarkably good the shot tower gin the shot tower is a famous tower in baltimore where they made shot 200 years ago in the sense of uh the shots that you put into your musket right so you need little lead pellets and you let them roll down a spiral inside a tall tower to cool off and so that's the shot tower and somehow they named the gin after that i don't think it's made at the shot tower but it's actually quite good um
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There's a bunch of other good gins. Monkey 47 is great, a little bit expensive, but it's very, very individual. So I truly don't think it makes sense to talk about what is the best gin. I think it makes sense to talk about what is the gin that you like, okay? And then... ratio of gin to vermouth, I think you should be able to taste the vermouth.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There's this weird thing that is overcome, and again, it's because I like the interplaying of the spirits, but there's this weird thing that the drier the martini, the better. And dry just means less vermouth. So, you know, famously there's a competition to come up with ways of describing the least amount of vermouth, which is silly because the least amount of vermouth is zero.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So you can just say, I don't want any vermouth, I just want to drink cold gin. Good for you if that's what you want to do. It's not a martini, but good for you if that's what you want to do. So like some people will say, I wave the vermouth bottle over the martini glass, or, you know, I bow in the direction of France because France is where the vermouth is made.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Gin is funny because gin is a very British drink, a spirit kind of alcohol. It's from England, but the martini is not from England. Martinis, they'll kick you out of a pub in England if you order a martini. It's an American drink. It combines a British thing in gin with a French thing in vermouth. So I like to be able to taste the vermouth.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I think the interplay of the vermouth and the gin is part of what makes a great martini. And I would put it at like three to one or four to one ratio of gin to vermouth. In fact, I don't carefully measure it. I'm just making it for myself. But I think that that's the ratio I would serve to somebody else. Then do you shake or do you stir it? And I go back and forth on this.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Again, this is — interestingly, there's arguments on both sides, shaking versus stirring. The argument that it's what James Bond does is not a good argument at all. James Bond was intentionally uncouth in a whole bunch of ways, and people don't get it. People have been ruined by the movies to think that James Bond is a role model of sophistication. But in many ways, he was kind of a —
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
unsophisticated guy. That's why he wore those sports wristwatches with a tuxedo. You should never do that. That is not a cool thing to do. And shaking, not stirring your martini is not necessarily a good thing, but there are arguments for it. So there is, again, a completely bogus argument, which is that if you shake the martini in the shaker, you'll bruise the gin somehow.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It makes connections not only with computer science, but with like origin of life type questions, with larger questions about complex systems generally. And it's one of the better contributions to the very – messy literature about how best to define complexity. So I think people like that have been the leading theorists of complexity.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
That's completely made up. You're not going to bruise the gin. Shake to your heart's content. The actual things that matter are the benefit of stirring is that the gin remains clear, right? You do not introduce tiny little bubbles into the gin.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And part of the aesthetic pleasure of the martini, once you pour it, is that perfectly clear crystal, almost invisibility to the combination of the gin and the vermouth. So cloudy martini is not quite as aesthetically pleasing as... the clear martini. But the argument for shaking it is that you cool it off much more efficiently.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Like stirring it is just harder to bring it down to a low temperature. And to me, other than getting the gin and the vermouth right, the coldness of the martini is the absolutely most important thing. A good martini should be as cold as possible for it to be. I've been in places that I won't mention any states, but Texas, where you can order a martini and they will serve it at room temperature.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I'm like, oh, my God, what are you even thinking about? Make your martini cold. Steak they're good at. Martinis they're not so good at in certain states of the United States. So I actually shake these days because I'm willing to give up the aesthetic pleasure of the clarity because eventually the bubbles go away anyway. I would rather have the martini be cold.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And then it's the garnish, and then I revert back to pluralism. Sometimes a twist, sometimes a regular olive, sometimes feeling a little playful, have an olive with garlic or jalapeno or blue cheese inside. All that is fine. I'm not going to be strict about that. But all that is to say I've recently perfected my martini by stepping a little bit outside of the advice I just gave you.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I discovered at the Remington Bottle, this little fun little liquor store, a Japanese gin. And in whiskey circles, Japanese whiskey is highly esteemed. The Japanese are really good at making whiskey. I have tried it, and I don't quite like it as much as the best American bourbons or Scottish Scotch whiskeys, so I'm not a connoisseur of Japanese whiskey whiskey.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But gin, I thought, okay, I'll give it a shot, because gin is about the botanicals, right? It's a very basic spirit that you then— give some oomph to by choosing the botanicals. And that sounds to me like something that Japanese people are good at, right? The subtlety of flavor profiles, et cetera. And so it turns out there's a bunch of different kinds of Japanese gin.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And the one that I got and fell in love with is called Etsu, E-T-S-U. And there's a little bit of tea leaves in there, as well as other botanicals, as well as the juniper and others. So it's a sort of Japanese take on the typical British way of making gin. And number one, it's amazing all by itself. Like it really, really works. I was skeptical, but it totally works.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And number two, at a different local Baltimore place that sells all sorts of different kinds of bitters. Parentheses, bitters are a type of – they're alcoholic by themselves, but they're like not that much alcohol. They're all about the flavors. So it's like gin, if you reduced the amount of actual – whiskey of background spirit down to almost nothing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So it's an intense kind of flavorful—I'm missing the right vocabulary words here, but there's a whole universe of different kinds of bitters, and you can have bitters with different kinds of flavors. So there's like straightforward bitters, like Angostura is the standard thing, but there's also orange-flavored bitters, and then you go crazy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
People like Jeffrey West have been very, very successful at applying complexity. Sam Bowles and David Krakauer and others we've had on the podcast. So I do think that the philosophers have some catching up to do. I mean, that's one—I've said this before—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There's chocolate bitters and pecan bitters, and there's all sorts of Italian Amari that are bitters-like but have different flavor profiles, some very astringent. They're almost like mouthwash and others, you know, quite smooth and delightful. So I found a little tiny bottle of what are called Woodland Bitters from the Portland Bitters Company.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And it gives you a flavor of being in an evergreen forest, right? You know, that very typical scent of evergreen trees all around you on a crisp fall evening, right, in the form of bitters.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And so if you make a martini, three to one gin to vermouth with this etsu gin, which has the little bit of tea leaf flavor in it, and then you add two drops of the woodland bitters, and it gives you this tiny feeling of evergreen trees. And then you shake it and you pour it. And you don't want olives with this one because the olives are a little bit overwhelming. And this is very, very subtle.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So you want the twist. So you want a little bit of the lemon peel in there. You twist it over the glass and dump it in. That's it. That is my favorite martini right now. That is the martini I envision myself drinking when I'm drinking martinis from here for the rest of my life. I don't see how you can get better than this martini.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Of course, in practice, as a pluralist, I will keep trying different things. I'm always trying different things, even though I suspect they're not as good as my best. I can't order this martini when I'm out. No one else makes it. It's my martini. But I will serve it to others, and I'm going to push it on others. We've made friends with the local bartender at our local restaurant here.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
We made friends with the owners and chefs also. So we had a little cocktail tasting at our house with the bartender, and we were trading recipes, and I was— I was showing off my martini. And sadly, the bartender, he's a great guy. He's not really a martini guy. He likes other kinds of things, which is fine. But he did understand why, if you liked martinis, this would be the martini to like.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
One of the reasons why I'm changing my own research focus these days from cosmology and particle physics and gravity to things like complexity is there's so much good work to be done. There's so many low-hanging fruit questions yet to be answered. So I'm going to try to do that myself. Benjamin Barbrell says, How to set these statements about entropy straight?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
A. Entropy is the result of a coarse-graining process, the log of the number of microstates per macrostate, and therefore depends on a subjective choice of macrostates. B. Entropy is responsible for such things as the thermodynamic arrow of time. It should never have an observer-independent definition. And C. The universe knows precisely its microstate, therefore its entropy is always zero.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Well, there's a couple things going on here. One is, of course, there's more than one definition of entropy. There's many definitions of entropy, and that's perfectly okay. That's not a mistake. It's not that some people are using the wrong definition. It's that which version of entropy you care about depends on what situation you're thinking about, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So this definition that Benjamin says in A, which is the one that is engraved on Boltzmann's tombstone, that you have a coarse graining into macrostates, and then you take the logarithm of the number of microstates per macrostate. So the low entropy means there aren't many microstates that look that way. High entropy means there are many microstates that look that way, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
That is what is relevant for statements about the arrow time in cosmology. That is the relevant empirical fact is that the coarse-grained information we have about the early universe does not have that many microstates that look that way. And we have been since growing into coarse-grained macrostates
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Strength in diversity, taking seriously other perspectives, sometimes sticking by your guns when there's a true or correct answer, but other times recognizing that we don't know all the answers and letting other people have their feelings about things. That's one thing that shows up again and again in the questions this month, whether it is refereeing scientific papers or mixing cocktails.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
that have more and more microstates associated with them, and that is why entropy tends to increase. So in B, you are worried about it having an observer-independent definition, and in C, you're worried about Laplace's demon knowing precisely the microstate. But these are both very related things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Laplace's demon, who knows everything about the microstate of the universe, doesn't know about entropy, doesn't know about the arrow of time. Laplace's demon just knows everything in the universe. The reason why we think there is an arrow of time, forgetting for the moment about quantum mechanics and the messiness there, but it doesn't really matter, so I'm happy to forget about it for right now.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Or rather, I should say, it's not really a different story, so I'm happy to forget about it right now. If you believe in classical deterministic microphysics, then there is no arrow of time if you know the microstate of the universe. But we don't.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And it is simply a fact that human beings and other intelligent creatures have very, very strong correlations in what they can observe about the universe. It's not that two different people observe completely different macroscopic information about things, right? We coarse-grain in the real world in very consistent ways. So it's observer-dependent in a very weak sense.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The coarse-graining of the set of all possible microstates is observer-dependent in the weak sense that, yes, we choose what to call the macrostates. We observers do that. but that's entirely okay because exactly what we're trying to explain is something that is experienced by those observers. The arrow of time, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
When an ice cube melts in a glass of water, if I were able to observe all the molecules in their exact Newtonian position and momentum microstates, I wouldn't say that any information had come or gone or been lost or there's any arrow of time. I'm just following the microstates. The reason why I experience an arrow of time is because I don't observe those microstates.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So the fact that I need to use some coarse graining to define the arrow of time and to define entropy is completely okay. We're using an observer-defined thing to explain an observer-defined experience. Renan Boschetti says, he seeks a clarification of your point of view regarding AI and consciousness. I've been hearing you say the phrase, in principle, AI can be conscious. I can't see why not.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Consciousness is an emergent property of nervous systems, says Renan. That is, when neurons do what they do, consciousness emerges. It seems clear that it is only possible because we are this system, i.e., we are the neurons in fields, and field oscillations. It is an emergent property of this system that when these excitations happen in this very particular way, these fields feel, present qualia.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
We can describe exactly how it happens, that's all. Well, just like when simulating an electromagnetic field in a computer, it can capture in a certain regime its mathematical behavior, Nobody ever claimed there is an electromagnetic field in the computer. Why do people claim there could be consciousness in the computer?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I clearly see a fundamental limitation for AI on consciousness in the way we do it now, i.e. without recreating the real patterns in the electromagnetic field in reality as an initial ansatz, which turns out to be what perception is made of. Am I missing something? Well, I don't know if you're missing something or not.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I mean, you could be right, but it's generally not the way that I think about consciousness or the way other people think about consciousness. What you are saying would be completely true if consciousness were some kind of substance, right? If there were a consciousness field that interacted with our neurons in a certain way to make us conscious—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There are different ways to do it correctly. Reminder that the questions in the AMA are asked by Patreon supporters of the Mindscape podcast. Sometimes I'm getting emails from people who say literally, I know that AMA questions are asked by Patreon supporters, but I'm not a Patreon supporter. Here's my question anyway. Please don't do that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
then you could absolutely make an argument that says that's not going to happen for a computer because it's not a nervous system. It's made of chips or whatever. It's not made of neurons and other kinds of cells. But I don't think that is what is going on in consciousness. I think that when we talk about consciousness, we're talking about a certain kind of pattern.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
A certain kind of behavior, a certain kind of way of conceptualizing at a very high level, emergent level, the sort of informational relationships between different parts of a brain or something like that. In other words, forget about the word consciousness. Think about the word computation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
One of the great things about computations is that they're independent of the substrate that is computing them. Two plus three equals five, whether you do it on an abacus or on your fingers or on your computer or on your watch or whatever. Consciousness, to me and to most people like it, who think about these things, is like that. It is a higher level structure.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It is not dependent on some specific kind of material substrate. Again, that could be wrong, but that is the basic idea. Okay, so I'm going to group together two questions. One is from Ilya Lvov. who says energy conservation is a consequence of time translation variance.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
This, to the best of my understanding, means that the laws of physics at t0 are the same as at t1, not that they are the same forward and backward in time. Energy is not conserved in quantum measurement. Hereby, it follows that quantum measurement changes laws of physics over time. What is this change?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And the second question is from Sandro Stucchi, who says, in the September AMA, you mentioned your blog post, Energy is Not Conserved, where you explain that it's been well understood since at least the 1920s that energy is not conserved in general relativity and why that isn't a problem.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But Noether's theorem says energy conservation is a consequence of the time translation symmetry of the laws of physics. What gives? Are the laws of physics not symmetric under time translation after all? So both of these questions are about energy conservation and their relationship to time translation invariance. And they deal with subtleties in Noether's theorem.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Emmy Noether famously proved this wonderful theorem that really set the stage for a lot of modern talk about gauge theories and charges and conserved quantities and so forth.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And the way that we usually informally state the theorem is that when there is a symmetry of nature, at least a continuous symmetry, we can talk about discrete symmetries or some subtleties there, but think about a continuous symmetry of nature. Like time translation invariance, which as we say is the laws of physics or the situation or whatever are the same over time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
spatial translations, rotations, things like that. Noether's theorem says whenever there's such a symmetry, there is an associated conserved quantity, okay? There's something that doesn't change over time. Energy is associated with time translation of variance. Momentum is associated with spatial translations. Angular momentum associated with rotations.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Electric charge is associated with gauge transformations, etc. Okay, but there are two subtleties here. One is, what do we mean by the laws of physics remaining invariant? So to Sandro's question, in the blog post about energy not being conserved in general relativity, as I actually encourage you to read the blog post, it says something that is relevant to what I said earlier about entropy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
the word energy has different definitions in different contexts, okay? So general relativity as a theory is completely time translation invariant. There's no special time in the universe according to general relativity. Therefore, by Neurodress theorem, there should be a conserved quantity, and there is. There is a conserved quantity that you can call the energy of the universe.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
We get more than enough questions from the Patreon supporters. And I do actually think that they're a pretty good representative sample of the questions we would get anyway. I don't think we're introducing a lot of biases by taking the questions from the Patreon supporters. And it's a nice little benefit you can get. The set of people who ask questions is a small subset of the Patreon supporters.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It's absolutely clear how to get it in general relativity. The problem is that that if you're in a closed universe, that quantity is simply zero. it doesn't matter what is happening in the universe. As long as you're in a closed universe, then you can show mathematically that no matter what's going on inside, that energy is going to be zero. So it's not a very informative fact.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It doesn't separate out certain kinds of universes from other kinds of universes. And if you're not in a closed universe, if you're in an open universe, then it's actually, it becomes harder to define what this quantity is because it depends on what's happening infinitely far away
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And in an open universe, there is an infinitely far away, but it's changing with time because the universe is expanding or something like that. Therefore, even though this thing exists, the Hamiltonian of the universe, if you want to call it that, it is not what we sort of intuitively feel in our bones as energy. It exists. You can define it, but it's not what we usually think of.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So as I say in the blog post, what we usually think of in cosmology as energy is not the energy of the gravitational field itself. which is an important contribution to the formula in general relativity, it's just the energy of the stuff inside the universe. So the matter, the radiation, the dark matter, the dark energy, all that stuff has energy and you can add it up.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But if you do that, that quantity would be conserved if the universe were not expanding. Because then conditions that the stuff in the universe are experiencing would be time translation invariant. If the universe is not expanding, the amount of stuff is the same from moment to moment.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It can change from one kind of stuff to another, but it's still starting from the same point and just doing its transformations. Whereas, because we've now defined energy in a way that does not include the gravitational field, the fact that in an expanding universe, gravity is changing over time, the universe is expanding, right? Things are getting more dilute as time goes on.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
That means that relevant to the stuff in the universe, things are not the same. from moment to moment in time. They are more dense in the past, less dense in the future, et cetera. And therefore, Noether's theorem, by the standards of Noether's theorem, there is no time translation of variance in an expanding universe, because the universe is changing. That's it. Simple as that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Now, you might say, well, I don't want to define energy that way. You are welcome to define it however you like. Knock yourself out. It's a free country. To Ilya's question, it's even a more subtle aspect of Noether's theorem, which is that she proves her theorem using what is called the principle of least action.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
This is—in fact, you can prove it classically, and then you can go and show that in quantum mechanics there's a version of it that still works. But the principle of least action is based on the idea that we can consider the space of all possible paths or trajectories for some physical system— And then we can imagine the transformations that are enacted by a symmetry on those paths.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And you can see this. It's in one of the biggest ideas in the universe videos if you want the details for it. I ended up not going into the details in the book of the biggest ideas because it was just like a little too technical for a book that was already way technical enough. But the point is that –
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It's an assumption of Noether's theorem, not just that you have time translation variance for energy, but that you can define the laws of physics you care about in terms of the principle of least action.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Most people just support anyway. Those people could include you. If you want to become a Patreon supporter of Mindscape, you can go to www.patreon.com slash Sean M. Carroll. And you get the ability to ask the AMA questions. You get the ability to listen without ads. And you get little reflection audio commentaries by me after every podcast. Thank you very much.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The principle of least action says there is a quantity called the action that I can assign to any possible trajectory the system could imaginably have, and the one it physically does have in classical mechanics is the one where that action is the lowest, okay? But quantum measurement doesn't fit into that paradigm. Quantum measurement doesn't have a principle of least action.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Quantum measurement is ill-defined, for one thing, okay? But to the extent that it's defined, it's sudden and unpredictable, and you're just asserted that there is something called the Born Rule and the collapse postulate, okay? You collapse onto a definite state of whatever observable you were looking at, and you have a probability for doing that collapse.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But none of that is based on having an action principle or minimizing that action or anything like that. So Noether's theorem simply doesn't apply. There you go. So in both cases, you have to read the fine print on what the theorem is trying to tell you. That's often good advice anyway. Benny Spess says, I was recently reading about the development of matrix mechanics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
As I understand it, Heisenberg was concerned with manipulating properties we can measure, not whatever the underlying reality might be. The text indicated that the uncertainty principle derives from the fact that matrices do not commute. Is this just stating that the order in which you measure position and momentum matters?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Or does the noncommutativity imply a fundamental limit on what we can know about the system regardless of measurement? I think I had to translate—I'm sorry, but I had to translate your questions from English into math. I think I'm going to agree with the second version rather than the first one.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It's not just stating that the order in which you measure position and momentum matters, although it's true that the order in which you measure position and momentum does matter because they don't commute. That is true, but the word just is making me hesitant to agree with or to say yes to that question.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The only reason I'm not quite saying yes to the second question, does the noncommutativity imply a fundamental limit on what we can know about the system regardless of measurement, is because it's not about what we can know. It really isn't. It's about what states exist.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
When you say a limit on what we know, you're leaving open the door, at least implicitly, to the idea that there is some fact about the system and we can just never know it. That's not what the uncertainty principle is trying to say. It is— The phrase at the end, regardless of measurement, is on the right track. The uncertainty principle is not about measurements.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It has implications for measurement outcomes, but it's not about measurements, and it's not about what we can know. It's about what quantum states exist. And so if you say the uncertainty principle is delta x times delta p is greater than h-bar, h-bar is Planck's constant, delta x is the uncertainty that you would get in a measurement,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
from measuring x, the position, delta p is the uncertainty you would get in a measurement from measuring the momentum p, well even if you don't measure it that's a statement about quantum states. The statement is that there are no quantum states that have precisely defined positions and momenta, okay? There's always going to be.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The quantum states that exist can never have completely predictable measurement outcomes for those things. But again, that's a feature. The fact that that's a statement about measurement is only how we— get there, how we observe it, how we find out about it, it's true whether or not you ever do the measurement. It has nothing to do with the process of measuring.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Heisenberg's Uncertainty Principle has nothing to do with the idea that when you measure something, you're going in there with photons or with your fingers or anything, and you are disturbing it with your energy or momentum. That has zero to do with the Uncertainty Principle. It has to do with what states could possibly describe that system, whether you're observing it or not.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Grant Stone says, is the concept of self-locating uncertainty something that you see as being broadly applicable to questions of how subjective observers should assign credences? You wrote a paper on deriving the Born rule in many worlds where you used this epistemic separability principle for this purpose.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It seems to me that the implication of this logic working for quantum mechanics should be that any process which can be modeled from one perspective as a deterministically involving in time— but looks uncertain from a perspective of an observer, which is part of that process, would have the credences of the observer quantified in the same way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Is there something special about the kind of branching in quantum mechanics with the states becoming orthogonal after decoherence? So I got a little lost. Sorry, Grant, in the middle of the questions. I'm not sure I'm going to be answering exactly what you asked, but I'll give it a shot.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
For those of you who don't know, I wrote this paper with Chip Siebens a while back, Deriving the Born Rule for Quantum Mechanics. which says that the probability of getting a measurement outcome is given by the associated wave function squared. And we derived it in the context of many worlds, in the context of Everettian quantum mechanics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And it started, the whole project started because there's a standard argument that you can't do that, and Chip knew that argument and gave it to me, and we sort of battered it back and forth, and we came up with a reason why actually you could do it. And The idea is based on actually Lev Weidman who first pointed this out. He's another physicist.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And when you have branching in Everettian quantum mechanics, there will be a moment after the wave function of the universe has branched where there are two versions of the observer. let's say it's spin up and spin down, there's an observer on the spin up branch, an observer on the spin down branch, and neither one of them knows which branch they're on.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
They could try to look very, very quickly, but the branching always happens faster, okay, as a matter of empirical fact. So that's a condition of self-locating uncertainty. Neither one of those two observers knows—they might know everything there is to know about the universe. They know the entire wave function of the universe, but they don't know where they are in it, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Listeners of Mindscape will get a $75 sponsored job credit to get your jobs more visibility at Indeed.com slash Mindscape. Just go to Indeed.com slash Mindscape right now and support our show by saying you heard about Indeed on this podcast. That's Indeed.com slash Mindscape. Terms and conditions apply. Need to hire? You need Indeed.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So I do think that that's something special about the kind of branching in quantum mechanics, okay? It's not because the states are orthogonal, although that's true, that's important, that's a part of it. The relevant fact is there are two copies of the person, right? That's where self-locating uncertainty is kind of unavoidable.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You know, self-locating uncertainty in general is the idea you know everything in the original about the universe, but there's multiple copies of people like you, and you don't know which one you are. So that might be relevant to a multiverse. It might be relevant to a recurrent universe. It might be relevant to just a good old classical universe that is so big, maybe infinitely big.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
that there are things that happen over and over again, including copies of you elsewhere in space. But all of those possibilities are highly speculative and might not be there if you're an Everettian, then this actually happens in quantum mechanics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So I do think that it's an idea that can be relevant to other circumstances, but in Everettian quantum mechanics, that's the condition where the situation where it is sort of absolutely inevitable to happen. And then Chip and I made the argument that how do you resolve that self-locating uncertainty? Well, you're allowed to do whatever you want. Again, free country.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And finally, I realized that I have been giving a little bit of incorrect information about the subreddit. So there is someone, some nice person, not me, set up a subreddit devoted to me and my stuff, okay? And I keep saying that it's reddit.com slash r slash Sean M. Carroll, but it's not. It's slash Sean Carroll with no M in there. So there's a Sean Carroll subreddit. Subreddit.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But there's a uniquely sensible way to do it, and that way ends up giving you the Born Rule. By the way, I've said this before, but just for people who remain a little bit unhappy with the derivation of the Born Rule in Everett, when people talk about deriving the Born Rule, the Born Rule is the probabilities of the wave function squared, right? They don't care.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
They're not primarily concerned with the fact that the probability is given by the wave function squared. that's kind of obvious. Like even though that's what you say you're deriving, there's nothing else it could have been. It's not like, well, it could have been equal to the wave function or the logarithm of the wave function or whatever. The wave function itself is a complex number.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It can't be a probability, right? So you might already guess that's something you should square to get a non-negative, non-imaginary number. And indeed, it turns out there's a theorem, Gleason's theorem, that, you know, among other things, it reminds you that The set of numbers given by the wave function squared for different measurement outcomes is a set of numbers that are between 0 and 1.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
and they add up to one, and their sum is constant over time. In other words, it's exactly what you want for a probability. So once you think that you will get a probability distribution out of many worlds, the fact that it is the wave function squared is the easiest thing in the world. There's nothing else it could have been, right? If you'd said the wave function to the fourth...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
OK, that's not conserved over time. So even though it is numbers between zero and one, they would not necessarily add up to one. They're not conserved over time, etc. But people worry that maybe there just isn't any association of probability with Everettian branches at all. And to me, the existence of self-locating uncertainty says, no, there clearly is.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Like there's so obviously a probability distribution that we need to deal with, the self-locating uncertainty. Which one am I? And so kind of the last holdout for people who don't think you can derive the Born rule in Everett is to say, well, yes, there's uncertainty, but I refuse to – apply probability distribution to it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
That's something that someone like David Albert would say, for example, or probably Tim Modlin. The only way you can get out of Everett working completely is to say, I refuse to believe that there is any way to assign a correct probability distribution, even though the wave function squared is a pretty obvious thing to do. So anyway, that's why I think it's all in pretty good hands, actually.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Visit betterhelp.com slash mindscape today to get 10% off your first month. That's betterhelp, H-E-L-P dot com slash mindscape. Ben Linus says I've been thinking about human willpower. Some people have a remarkable drive to push beyond others. Yet it seems we all give up at some point. Why do some people develop successful strategies to go further than others?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Is this simply a mental muscle that needs to be trained? I think it's a little weird that you are specifically thinking about willpower in terms of a drive to push beyond others. Willpower can be for all sorts of things. You can accomplish things that aren't necessarily better than someone else is accomplishing. Maybe you just want to do your push-ups every morning or something like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Who cares if other people are doing it or not? I'm not caring about pushing beyond others. I'm just trying to be a little bit healthier, right? But aside from that, again, I'm not an expert on human psychology or anything like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The only thing that I have to offer here is the kind of interesting fact about willpower and similar human things is that they're a relationship between our present self and our future self, right? How often have you— eaten, I don't know, ice cream or something like that and regretted it later. I mean, maybe never. That's good for you in that case.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But willpower is the ability to avoid doing something that in the moment you are kind of tempted to do. Stay in bed, eat the ice cream, whatever it is. Why? Because you think that there is a payoff down the road, right? That there is a future reward that you're going to get from this. And I do think it's fascinating how the human mind carries out this kind of calculation, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And it's not as active as... It's like a little bit active, but every episode of the podcast gets a post that you can talk about things there. You can also talk about things on the Patreon page or on the podcast page. But you can also just ask other questions or just talk to other members. I chime in there occasionally, but not very often because... It's the semester.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Why isn't the human mind much better at willpower? Why isn't it optimized to make our future selves very happy? And I am sure that psychologists have thought about this. It's not a novel theory. consideration by any means, but I don't know what the story is there. We human beings, as we talked about with Adam Bully a while back, we human beings have a complicated relationship with time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It's both super duper important to who we are and how we live, and it's also something that we need to think about and exert our willpower to try to successfully navigate and even master. So I'm not actually offering any very useful answers to your questions, Ben, but I do think it's an interesting thing to think about. I think it's going to be a theme in today's AMA.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I picked out a bunch of questions where I have to say, like, I don't know what the answer is, but this is a good question. So food for thought for those of you who are listening out there in podcast land. Varun Narasimachar says, Recently, there have been reports of savvy provocateurs expressing veiled threats to prominent personalities in language barely within legal free speech protection.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Although disturbing, this phenomenon has gotten me curious about the fascinating world of legal technicalities of free speech. Would you consider inviting an expert on such matters to discuss both the legal theory for its own sake and the messy praxis of protecting and regulating free speech? Yeah, it's a very important question. I completely agree that it is messy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The only super-duper strong opinion I have about free speech discussion is that if anyone says, oh, it's all very simple, just do it this way, they're not worth listening to. They have not thought it through very carefully or they're just not very interested in all the nuances. I tend myself to be very, very protective of free speech as long as it means –
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
If someone wants to say something and someone else wants to listen, they are welcome to do that. No one has free speech on my Blue Sky account. I can block them, right? There's no demand that I need to listen to them. That is not part of free speech. But otherwise, I'm very, very open.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
If someone wants to invite some terrible, terrible person to a university to give a talk, I think they should have the ability to do that. Both the speaker and the inviter have the right to do that. But, yeah, I don't know who would be a good person to invite.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
We did have one such discussion with Theresa Bejan, who's a political theorist and also a political historian at Oxford, and we had a very interesting discussion on the origins of free speech back—I don't know if it's the origins of free speech. I shouldn't put it that way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Part of the prehistory of free speech was in the American colonies, in Rhode Island in particular, and the importance of the notion of civility there. And civility didn't exactly mean back then what it means now, so it was an interesting thing to dig into. But I don't know exactly who would be good to talk to about that, but I do think it's an interesting thing— to get right.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The reason why I don't know of anyone who's going to talk to about it is because it becomes too kind of polarized and simplistic, right? It's the reason why we don't have political candidates generally here on Mindscape. It's not because they're not interesting or smart people. It's just because there are agendas, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I need to teach courses, and I love my students, and they need to get first priority. Students and Mindscape listeners, it's you all who get priority here. So with that, let's go. OK, I need to start out by saying that originally in the beginning of the podcast, there was a question, the AMA.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There are things that they are trying to bring about other than thinking about the true nature of reality. And here at Mindscape, we're mostly thinking about the true nature of reality.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So I'm happy to talk about the true nature of a certain modern political reality, but I have to do it in a way where I'm convinced that the person is most interested in getting at the truth rather than achieving some goal one way or another. Perry Romanowski says, How do you come up with fresh ideas to explore in a field that feels like all the major discoveries have already been made?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
For instance, in physics, there seem to be only a few remaining mysteries, but it doesn't seem like there are many promising avenues that could lead to groundbreaking changes in how we understand the world. I work in chemistry, particularly in the cosmetic industry, and it sometimes feels like there isn't much left to discover.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
How do you stay engaged with your discipline and find inspiration for ideas that might lead to something truly novel? Well, I do think that in every area of science, there are still major discoveries to be made, okay? But it's not that they're all equally easy. So this goes back to something I just said.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
One of the reasons why I'm not thinking that much about cosmology or gravity is because the low-hanging fruit has been picked. We do have—I mean, this is a success story, not a failure story. We have really good theories—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
of particle physics, of gravity, and cosmology, and that makes it hard to make progress, because it's not like we have 20 experimental results that we don't have an explanation for. When you're in that kind of situation, like we were in the 1950s and 60s in particle physics, then it's playtime for theorists, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Trying to come up with theoretical explanations for all these wonderful experimental results. Likewise in chemistry, I can imagine that it depends on exactly what area of chemistry you're in. But in certain simple areas of chemistry, maybe you have a pretty good basic picture and it's hard to come up with something truly fundamentally new.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The obvious thing to do, what I did, is to start thinking about things where we don't have a wonderful theoretical understanding of things, right? Where There are data that are coming in that are hard to explain, that are interesting and surprising. And the theoretical ideas we do have are not yet completely mature and fleshed out.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So I think you have to, you know, I don't know when you say you work in the cosmetic industry, I don't know what your job is. I don't know the extent to which you have freedom to pick what you work on. And I also don't know enough about cosmetic chemistry to say whether or not there are any areas where Everything is still sort of chaotic and up for grabs.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But those areas, the ones where things are still chaotic and up for grabs, are the ones where the biggest discoveries will be made. Let me mention, just because there's reasons to go into all these different things, that it's also super frustrating— to work in those areas.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
When you have a mature field, it might be hard to make a super important breakthrough, but it's much easier to make an incremental progress. It's much easier to have a well-defined problem, ask a question and answer it, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
When you're in these sort of more chaotic pre-paradigmatic areas, that's when you, maybe you'll make a breakthrough, but maybe you'll just waste your time for years and years and years. That's kind of the trade-off that you have to think about. Eric Runquist says, you often use chairs as a basic example of an emergent phenomenon. At a fundamental physics level, there's no such thing as chairs.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And if you eliminated conscious creatures like us who reify the experience of certain patterns of matter into chairs, it would cease to be a valid category with which to describe reality. Is that right? And if so, if space and time were also emergent, would the same logic apply to them? So no, that is not right. That's not anyway the way that I think about it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
In my way of thinking about emergent phenomena, whether or not there are conscious creatures never has anything to do with it whatsoever. It might, as we said before, in the case of Heisenberg's uncertainty principle, it might be very useful to conscious creatures when there are emergent phenomena. But the fact that a phenomenon is emergent is an objectively true one.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And it has to do with whether or not you can make predictions about what happens in the world based on dramatically incomplete information. But the information you have refers to these higher-level emergent phenomena. When someone says, you know, we have 12 guests coming. How many chairs do we need? you don't need to know the microphysical state of the world to answer that question, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You don't need to know the position of every atom and molecule in your neighborhood to answer that question because the idea of chairs has causal power. You know that if you're going to have 12 guests total, you're going to need 12 chairs, right? There's a high-level emergent
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
conversation, a vocabulary, a theoretical structure that makes sense even though you don't know all the details about the microstate. And the existence of that higher level way of talking is completely independent of the existence of conscious creatures. Of course, as I just said, it's super useful to conscious creatures to know about that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It is an unmistakable fact about the world that we conscious creatures don't immediately apprehend the deepest level of reality. We apprehend much more directly some higher level way of viewing reality. But that's not what the layer is about. It's just the fact that it's useful to us. And therefore, space and time exactly the same way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I was answering a question about spirits, that is to say alcoholic beverages, not spirits like Halloween and cocktails and things like that. And I warmed my subject matter maybe a little bit more than many people will care about. So I have moved that subject. to the very end of the podcast, for those of you who are not martini-pilled, as it were. And we can dive into more regular subjects.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And this is Dan Dennett's point in his famous paper about real patterns, which we talked about in the conversation with Dan. The word real in the phrase real patterns is doing something there, right? A chair is part of a real pattern. It doesn't have to do with subjective experiences of human beings.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
A chair is a chair is a chair, whether or not there's any human beings sitting in it or thinking about it. Gilbert Rodriguez says, For example, I've read that we find fundamentally incompatible concepts or unexpected resolutions funny. But I feel like this is also a mark of good science, e.g. particle wave duality.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Another theory suggests humor is a mechanism for pent-up emotions or tension through emotional relief. But a good physics paper makes unexpected connections that feel inevitable almost cathartic. I have in fact been brought to the brink of tears in my math classes upon understanding some beautiful equation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Math, philosophy, and physics seem to rely on all the same elements that humor does, even beyond paradox and emotion. There's obviously an isomorphism between science and humor. But what makes it an isomorphism and not an identity, i.e., how are they fundamentally different? Good. So this is one of the questions that I promised early on I don't have a good answer to.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I just thought it was a great question. I think it's not quite obvious that there's an isomorphism between science and humor. And I think that you're sort of hinting at that. They're clearly different in some important way. And the most obvious way in which they're different is the— you know, if you want to call it the teleology, the function, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Maybe there are some aspects of the practice of science that parallel certain aspects of the practice of humor, but the goal is a completely different thing. You know, maybe a good mathematical equation brings you to tears. I get that. I can see that. But that's not the purpose of the mathematical equation. The purpose of the joke is to make you laugh.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The purpose of the mathematical equation is to capture some logical truth. The purpose of the scientific theory and the process to get to that scientific theory is to provide some understanding of the physical world. So I would argue that the most obvious and important difference is that they're oriented toward different goals. For humor, the emotional reaction is the point.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
For science and math, the emotional reaction follows along because of how human beings respond to the point. Matt Becker says, I'm curious how Einstein's field equations are used to predict the age of the universe. What observational evidence is being extrapolated to make such predictions and what variable in the equations is causing the singularity?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Well, there's a simple version of this and a more complicated version. The simple version is you model the universe as a very, very simple thing. You say the universe is completely homogeneous and isotropic. That is to say, it's the same looking in every direction. That's isotropic. And it's the same at every point. That's homogeneous.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And that simplifies, and you say that about, sorry, you say that about space, not about time, okay? So you're drawing a distinction between space and time, which is fine. It's not a feature of the deep down equations. It's a feature of the specific arrangement of matter in the universe. And also, it need not be true. It's not actually, you know, demanded on us by any principle.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It's just a fact that in our universe, that's a pretty good approximation, especially when you look at very large scales and average out the number of galaxies and stuff like that. So once you've done that, it turns out that if the universe is homogeneous and isotropic, then at every moment of time you have three-dimensional space, and it's completely characterized by its overall curvature.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It'll be there at the end if you listen all the way. So Anonymous asks a priority question. Priority questions, remember, are ones where the Patreon supporters get to ask one priority question in their lifetime. I haven't dealt with loopholes about if they upload their consciousness to a computer, but that hasn't happened yet. So we're thinking about ordinary biological lifetimes here.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Its overall curvature can be positive, negative, or zero. So it's a number between minus infinity and infinity. That's a very simple thing to have. And then what happens to that space is it expands. So you have another quantity which is the scale factor. The scale factor tells you the relative size of the universe, of the spatial universe, at different moments of time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So you put this all together and Einstein's equation gives you, or reduces to, what we call the Friedmann equation. named after Alexander Friedman, an early cosmologist, and it relates the change of the scale factor over time, which is given by the Hubble constant, a dot over a, if a is the scale factor and dot is a time derivative, the Hubble expansion parameter.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
is a way of characterizing the rate of growth of the scale factor. And the Friedman equation relates that to the curvature of space and to the energy density within space. So the fundamental thing you do as a starting out cosmologist is you learn the Friedman equation and you solve it. So you say, oh, the curvature is such and such, or the density of matter is matter or radiation or dark energy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And with those inputs, you solve the Friedmann equation for how the universe expands. And then, of course, in the real world, when you're a slightly more sophisticated cosmologist, you actually measure these things. You go, oh, here's how much radiation we have. Here's how much matter. Here's how much dark energy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And then you can use your solution to the Friedmann equation to extrapolate it backward in time. And that's how you get a 14 billion year old universe. So that is your theoretical prediction. You say general relativity plus our current knowledge about the universe gives us this prediction. The Hubble constant is also important.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The current rate of expansion plus the stuff in the universe makes a prediction for how old the universe is. And then you can test that, right? It was already a pretty good success decades and decades ago. when we realized that the ages of the stars in the universe are of the same order of magnitude as the age of the universe predicted by the Friedman equation, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It could have been that the stars were a thousand times older than our prediction from general relativity for the age of the universe, and that would have been a severe problem. In fact, it looked like for a while that the ages of the oldest stars were a little bit longer than the age of the universe as a whole. This problem went away when we found the dark energy in 1998.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
If you include the dark energy or the cosmological constant, all else being equal, you make the universe a little bit older. than you would have otherwise. And so now it all fits together very, very beautifully. So you both make the theoretical prediction, you test it. Right now, it's more or less bang on, working very, very well.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Sergei says in your last AMA, you said there is this thing called the Electoral College which messes everything up. There's a whole bunch of attempts to suppress votes or disenfranchise people in different ways or to mount legal challenges when the votes come in. It seems like you would rather have a straight up majority vote for president.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Let's imagine that in November, Trump wins the majority vote, but Kamala wins the Electoral College and any challenge from him is shot down by the current Supreme Court. Would you then say that the current setup is robust and worked as expected? Or would you still prefer changes in the electoral and maybe judicial process, assuming this was in the realm of possibility?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It has nothing to do with who wins, okay? I don't care who wins or who doesn't win. The system is stupid, and I would like a less dumb system. Yes, I would like that. there was, you know, historically the electoral college here in the United States was put in for dumb reasons.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And I will do my best to answer that one question. So Anonymous asks, should I go back to school and pursue a formal physics education and or job? The pros of this are that I spend all my time already reading about physics and science in general. It is definitely my primary interest. The cons are that I'm too old. This is I'm quoting. This is not me talking. This is the anonymous questioner.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It was largely because slave states wanted to make sure that they had a little bit more representation than they otherwise would get. But maybe you could invent ex post facto some kind of justification for it if you thought that having people vote for electors who then were sort of responsible, educated people who then debate who they were going to vote for for president.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The Electoral College would actually do the voting. Maybe that would be a justifiable system. That's certainly not the system, right? That's not even close to the system. In fact, the electors are pledged to vote for certain people. So it's the opposite of the system we have. And, you know, the current system does absolutely zero good at all.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It does great harm because it means that vast parts of the country are completely ignored in nationwide elections because they're either all red or all blue. It's only a very tiny sliver of states that get a lot of attention in presidential elections. So I don't care who wins. I don't care what the process is. I would like just a majority vote.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Chipsy says, do you think something like an ideological Turing test is a useful tool for helping people to think and argue better? Basically, such a test challenges someone to explain an idea they disagree with in terms that a person who actually believes that idea would fully agree with.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It is intended to demonstrate to yourself and to your debate partners that you understand what they actually believe rather than arguing against a weaker distorted version. If both sides in debate can articulate the other side's arguments convincingly, then they are more likely to have a fruitful exchange. Yeah, I'm a big believer in things like this.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I definitely think that if you're having a reasonable argument, okay, you know, people, gimmicks and strategies to make sure that debates and disagreements are carried out fairly are easy to game by bad actors, right? By people who aren't being sincere, people who don't have any good arguments, etc. But let's put that aside. Okay.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
let's imagine that you have a sincere disagreement with someone who you respect, and maybe you're both open to thinking about things in new ways, then you should be looking for ways to understand each other better. And absolutely, the ability to articulate what the other person is saying is crucially important. It's a strategy for doing those things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It doesn't necessarily make you more sympathetic. Like sometimes you can come up with a way of—you can figure out what to say in the terms that the people who actually disagree with you would say them, and you realize, oh my goodness, this is a terrible argument, right? But at least you're trying to understand it from the perspective of those people. And I would say it's not just true for—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
disagreements between people. This is true for any time you're trying to understand why somebody would believe something, even if that is a historical figure. Why would Aristotle have ever said this particular thing, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
That's a very useful mental exercise for people to go through, trying to understand the context, the reason why people are saying things in terms, like you say, they would agree with. Mikkel Pickle says, the conversations this month have been fantastic. I was especially motivated to spend time in self-examination after listening to Hari Han on making multicultural democracy work.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
In particular, I've been repeating your statement that being okay with losing the vote is a big part of what makes democracy work. But now I think we should have added, believing that you will have another chance and personally identifying as a member of the democratic enterprise. What else do you think is essential, if anything? Yeah, these are good questions.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I'll be behind everyone else and I'll be leaving a promising career. If I try this out and fail, I'll have been gone so long it would be essentially impossible to return." For background, I graduated at 19 from a top college with honors. Now I'm a 32-year-old songwriter. I wrote some hit songs and brought my dream home in LA with enough left over to live comfortably while I pay for tuition.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You know, I do think that personally, my... reason for being a supporter of democracy is mostly a moral one, mostly a normative one. You know, sometimes people want to say, well, let's add requirements to who can vote, like they have to be able to pass a citizenship test or something. And I think that to me, that's missing the point.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The point is not that we think that the democratic process is going to lead to the smartest decisions. We think that it's going to represent the interests of the people who are doing the voting. Now, it fails at that in a lot of cases because people don't always vote in their own interest. People don't always understand who is going to stand up for their interests, et cetera.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But they should have the right, in my view, to be able to say that. What makes it work is some – the most important thing that makes it work is the buy-in. right? It's—we agree that, okay, we are going to abide by the will of the majority, or some version of the majority in a more Republican system, right? That's fine.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But whatever process we have to—this is part of, like, the physics of democracy thinking. In ordinary physics, we often coarse-grain or renormalize, right? We have a bunch of spins, and we calculate the expectation value of the spins in a certain block, and we assign a single spin to that block.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And the nice thing about physics is that you know, or maybe you know or you don't, but the correct way to coarse-grain is fixed by the physics, right? It's the way that leads to some higher-level emergent phenomena without knowing all the microstates. And some ways of coarse-graining will work and some ways won't. So in democracy, we choose how we coarse-grain, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
We have a large number of people all with their individual interests and preferences, and we're choosing by identifying a voting system and a governmental system how to sort of coarse-grain those up into a small number of people making a relatively compact number of decisions.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So some methods for voting systems and for representation systems will be better than others, and you should have a discussion about how to do that. But anyway, whatever that method is, I think the buy-in on the part of the voters is important. I think that you have to have a citizenry which overall thinks that democracy is a good idea.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Everyone says democracy is a good idea because they want their point of view to be represented. But you have to have people who say democracy is a good idea even when it's the other points of view that end up carrying the day. There needs to be some fairness. There needs to be some minimal requirements. That's why we have a Bill of Rights and things like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You have to protect people's interests against the— feeling of the mob in the moment, absolutely sure. But overall, you have to be able to take some policy defeats if you're in a democracy. I do think that second, you need some responsibility, right? You need some responsibility as a voter to be informed, to basically know what is going on.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
We live in a country, I live in a country in the United States where voting is not mandatory, right? Some places it's mandatory, but Half the people, more than half the people in most elections just don't vote at all. I think that's okay. It's okay not to vote. That's fine.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I wish more people did vote, but I wish that the people who did vote had a better idea of what was going on, had a more realistic view of what different candidates stood for, what different policy choices, what their effects would be, all that stuff. It's not something I would ever mandate. It's not something I would ever put into law, but we can encourage it, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The people around me are celebrities and celebrity types, uninspiring, unintelligent, and most importantly, not curious about the world. Their primary concern is being perceived as high status. It's very unfulfilling, but then again, so are a lot of jobs. My dad says the only thing less likely than being a hit songwriter is being a hit physicist. He's probably right.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And finally, I think that you need an understanding of what it means to be active in a democracy. And what I mean by that is so much of our current discourse these days is just pointing at the other people who you disagree with and saying that they're wrong. And that maybe they are wrong, OK, on both sides. This is one of the issues that is a both sides issue. Not every issue is.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But on both sides, people just like to highlight the worst parts of the people they disagree with and mock them. And that doesn't grow your coalition, really. That doesn't help people understand why your perspective is better than the other perspective. You actually have to persuade people to be on your side. And so few people seem to be interested in that part of democracy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
That's one of the things that is making it harder and harder for democracy to work in the modern world. Part of the responsibility is voting. Part of the responsibility is bringing people into agreement. with you, right? Not just saying that they're wrong or they're right, but changing their minds or helping them make up their minds if they're not yet decided.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So I think we're going to come back to this in a later question, but democracy is work when you do it right. It's not something that happens once every four years. It's kind of a responsibility that is a good one to have. It's better than living in a dictatorship, but it's a responsibility worth taking seriously.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Nicholas Latart-Bersionic says, when you look into a telescope today, what comes to your mind first, the thought of the cosmologist or that of the philosopher? I love the idea that I'm looking into telescopes today. I have not looked into a telescope in quite a while. I was never really, by the way, a real telescope looker. You know, I was interested in cosmology from a very young age.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And so family and friends who didn't understand what I really was interested in, they roughly had the idea that I liked things in the sky, the stars, space, or whatever. So I, you know, got a telescope as a present one Christmas, et cetera. And I tried to use it, but it was never really my thing. I'm interested in the equations. I'm interested in the ideas and the concepts.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And you don't see equations when you look through the telescope. But anyway, I did spend a lot of time looking through telescopes, especially as an undergraduate astronomy major. I worked as an observatory assistant among various other part-time jobs. But these days, when I metaphorically—I understand, Nicholas, that you're not really worried about that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Curious what you would do in this situation. So as I often say for personal advice kinds of questions, I can't actually give you the advice you want. This is a situation, if you're trying to imagine changing your career in some dramatic way, where there are no certainties, right? There are only probabilities, and the things you do don't make some good outcome possible.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Your question is, am I thinking about the universe primarily as a cosmologist or a philosopher? And the answer is neither one. You know, the answer is my whole shtick is to appreciate that those are not two separate categories. It's not that, you know, now that I'm half in the physics department and half in the philosophy department that I am—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
somehow more of a philosopher than I was before, that I have switched. My interest is still the same, understanding how nature works. That is my interest. I have changed, but the change is appreciating the ways in which thinking like a philosopher helps that goal, helps move us toward better understanding how the universe works. So
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
When I look through the metaphorical telescope, it is not as a cosmologist or philosopher. It is as someone who wants to understand the world better, given any tools that I can lay my hands on to move closer to that goal. Steve NZ says, how does it feel to be someone whose opinions are sought out by thousands of people all over the world?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Your views are sought on such diverse subjects as cosmology, history, particle physics, pizza cats, relationships, life, the universe, and everything. When you were, say, 17 or 18 planning your career, did you ever think you would be where and what you are today? That's a good question. You know, I don't want to exaggerate the extent to which my opinions are sought after.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And also, I don't want to exaggerate The compliment that the world pays you by being a person whose opinions are sought after, just look at the other people whose opinions are sought after. Let's just say it's a wide spectrum. There's some very admirable people whose opinions are sought after, some less admirable ones whose opinions are taken seriously. way too seriously.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So it's easy to be humble about that part of it. And also, you know, I appreciate that, yes, people ask me questions about pizza and cats and martinis and things, but that's part of, you know, just expanding the space a little bit when they really, you know, most of the questions, as you'll notice in the AMAs, are about physics and philosophy, right? Which makes perfect sense.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
If I just started a pizza podcast, I don't think it would be very, very popular. I would enjoy it. But anyway, it's hard when you're 17 or 18 to have any idea. So if I take the question to be, what was I planning when I was 17 or 18? Look, when I was 17 or 18, I wanted to be a physics major or astronomy major at university. Um, and I didn't know much about what came after that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Like I vaguely knew that you go to graduate school. Okay. But I came from a family where there's no academics, right. And you know, there's no, there's not a lot of books in the house that I had growing up. Uh, I went to a large public school. You know, it wasn't usual that they sent people off to eventually get PhDs and become professors. It did happen, but it didn't happen all the time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So I didn't have any guidance. And even when I was an undergraduate at Villanova, which was a wonderful place in many ways, but there was no graduate school there in physics or astronomy. So the professors were good, but no one there did theoretical cosmology or particle physics or gravity like I wanted to do.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And there wasn't other graduate students or any graduate students for me to get sort of wisdom from. So I just stumbled from moment to moment. I remember it took me a while just to learn that I could afford to go to graduate school, because when you go to graduate school in physics, for example, you get a stipend, right? So you either are a research assistant or a teaching assistant.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So they will list when you— we didn't have the internet in these days, right? So there was this book put out by the American Institute of Physics that listed all the graduate programs that said who was there, what research they were doing, and things like that. And it also listed the tuition. And I would look at the tuition and go, yeah, there's no way I can pay that. This is impossible.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
entirely certain or bad outcome entirely certain, they raise or lower the probabilities of things. So to do something risky and uncertain is just a very deeply personal decision that you're going to have to make for yourself. What I can do is talk about some of what those probabilities are. One thing is that, you know, being a physicist is hard, like you said.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And my professors did help me out in explaining that, oh, no one pays the tuition in graduate school. Nobody pays graduate school tuition. It It's covered somehow or another through hook or by crook. And I certainly didn't understand that there was a system of postdocs and whatever. So anyway, all this is to say, zero intention of becoming a public figure in any way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I did maybe imagine writing books some days. I didn't have a podcast plan in mind when I was 17 years old. But writing books always seemed like that would be a fun thing to do. In fact, if anything— My regret is that I didn't take those more outlandish plans more seriously, more early.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It would have been even worse for my career than what it was, but I would have gotten a head start, which is always a good thing. So short answer, no. I didn't think I would be in precisely this place today, but I didn't have a great idea of where I would be either.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You know, I knew that there were people like Stephen Hawking and Steven Weinberg and Ed Witten who were doing great things in physics. I had that vague idea. You know, these are the people who were big names at the time, and I kind of wanted to be like them in some rough way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And, you know, Stephen Hawking and Steven Weinberg, of course, did wonderfully good things in writing books and reaching out to a wider audience. Neither one of them quite ever had a podcast, though, so I have that. I have that over them. Ed asks, I saw this on Britannica.com and I have doubts about its veracity. Is any of this true? Quote,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
meaning that humans are able to see more and more of the universe with the passing of time. While humans will never be able to see the entire universe from Earth, only the relatively small bubble of the observable universe, the sphere of observation is ever expanding. You know, this is something that is gesturing toward the truth in a little awkward way, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So the observable universe expanding the light year per year is not—that's not it. That's quantitatively not quite right. But the observable horizon, our ability to look backward in time and see some things in the universe, is getting bigger because the universe is getting older. And the thing that bounds our observable horizon is that when you look back in time, you're
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You run into the cosmic microwave background. You run into the moment in time when the universe was opaque. And every year, that moment gets to be one year in the past, okay? One year further into the past, and therefore you can see a little bit farther. Because the universe is expanding and changing its size in between now and then, it's not exactly a one-to-one map. years to light years.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
That's why the quantitative thing isn't quite right. And of course, this depends on the future history of the universe. But right now, yes, it is true. We are seeing more and more of the universe. When you think of it, though, you know, if you live 100 years, that gives you an extra 100 years of time in between you and the Big Bang.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
That's not a big number compared to the 14 billion years that is roughly speaking actually already there. So it's not a very large effect. Robert Ruxandrescu says, back in 2021, after my COVID infection, my sense of smell and taste were severely affected. At some point, I had no taste or smell. They recovered a little, but in a terrible way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Everything tasted really bad, especially eggs, onions, any type of meat, even bread. It seems like a spectrum of my taste, the sour taste, was destroyed, and everything tasted and smelled really weird, usually like rotten meat. Considering that you've mentioned things about cooking and wines quite a bit, how would such an event affect your life?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Just a little, a lot, would it be absolutely terrible? Would you be able to deal with this for the rest of your life? I'm not going to be able to give honest answers here because I think that these things are hard to predict. The literal question is, how would it affect my life? I can predict that I would be really disturbed by this if my sense of taste went away.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I don't know if it's as unlikely as being a hit songwriter. It's less unlikely. to become a practicing physicist than to become a professional basketball player, for example, but it's still pretty unlikely.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But how I would deal with it, how I would cope with it is hard to say. I like to think— that I would shift focus, you know, my loci of pleasures from things that used to give me pleasure to other new things that could give me pleasure, right? Maybe I would finally become a better musician than I am now. But you don't know. Like, maybe I would just become bitter and grumpy all the time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So I don't want to predict how good I would be at handling this kind of thing. I do think, you know, look, different people have different inputs, sensory inputs or whatever. Jennifer, my wife, is what is called a super taster. So she has a very, very sensitive palate, which is good in some ways, bad in other ways. You know, she's able to pick out notes in wine and everything, but...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There's other things like broccoli, okay, which to me and to most people is crunchy but unobjectionable. To her is inedibly bitter, right? She tastes bitter notes in there that other people just don't taste. Tomatoes, raw tomatoes, she can't eat. They make her throw up because of the effect it has. And so that's okay. You just don't eat those things. You eat other things, right? Um,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
If everything about your sense of smell and taste went wrong, that would definitely disturb me a lot, I'm happy to admit, but I don't know how I would go about dealing with it. I would try to be zen about the whole thing and look for pleasures elsewhere, but I can't promise you I would succeed. Sometimes we're more successful at those aspirations than others.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Joshua Hillerup says, a lot of people, including on some episodes of your podcast, have talked about why politics in the US are so polarized right now. What I don't understand is why it's polarized on a federal level so close to 50-50. Why do you think that is instead of, say, 70-30 in favor of one party or the other? You know, I think this is a sneakily good question in the sense that there are
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
answers to it that are not that hard to find, but I'm not sure those answers are right. So the simple answer is you're trying to win elections, right? There's something called the median voter theorem in voting theory, which says that the place you want to be as a political candidate is as close to the median voter as you can be. What that means is if you have a single spectrum of opinions—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The rule of thumb is that—that I always say, I haven't seen the statistics in years and years, but the rule of thumb for someone who gets a PhD from a top program is that maybe one in four graduates are going to become— faculty members with tenure at some university at some point, which is usually what those people want to do.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
and you're reducing complicated political feelings just to that single spectrum, and they line up from left to right, you want to be in the middle of that in terms of actual numbers of people, because if you are moving to the left or right of the middle, then your opponent can move just a little bit to the other side of you, and they will always get more than 50% of the vote.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
This assumes a lot of things, the median voter theorem. It assumes that there is a single spectrum you can line everyone up on. It assumes that candidates have well-defined locations on that spectrum. It assumes that all people do is to vote for the person that is closer to them on the spectrum. All of these assumptions are false, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But nevertheless, we call it a theorem because it does follow from the axioms. That's what theorems are supposed to be. Now, if you look at the people who actually run for president, it is perfectly clear that the median voter theorem doesn't work, that the actual candidates do not both try to stick as close as possible to the center, right? And why? Well, there's many different reasons.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
One is that we have a party system, and the party system is an almost inevitable result of the Constitution of the U.S., which gives so much— power to a single president who is popularly elected as opposed to giving power to the parliament or whatever. So given that we have a party system, the party carries a lot of the work of choosing candidates and defining positions.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And what you end up with is people who more or less represent their party, and then the two parties are not going to be right there at the median voter level. Because it's not just a matter of getting people to prefer you, you have to get them to vote for you, right? So you have to make people enthusiastic.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You have to get them out of their seats and into the voting booth, which means you just can't be the milquetoasty centrist candidate all the time. Now, so all that makes kind of sense, right? Even though we do have political parties, etc., it makes sense from reasoning analogous to the median voter theorem that the parties should divvy up the vote about 50-50.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
That's the simple answer that I don't think is quite right. It's too close to 50-50, honestly, especially when so many voices in either party are not really representative of moderation in any way. So I think that part of this is because there's, well, so I don't know what the 50-50 answer is. I would like to know more about that. I do have some understanding of the polarization.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You know, back in the day, as we learned from Will Wilkinson and Ezra Klein and other people, Back in the day, there was simply less alignment between different sets of political questions in individual people. You might have people who were very typical voters, who were very liberal on one issue and very conservative on other issues.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And first you have to get into a good graduate school, et cetera, et cetera. Physics, science, like all other careers, involve a certain amount of strategizing about balancing what you want to do personally versus what is good for your career personally, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And then what has happened over time is that both individual people and the political parties have kind of lined up, right? So if you were— conservative in one thing, then you're probably conservative in something else, and likewise for being liberal in United States sort of nomenclature. There's analogous nomenclature all over the world.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So that makes it easier to just think of people in the other party as the enemy. Right. And that sort of drives people apart. There is, you know, remember the very first episode of Mindscape was with Carol Tavris, a social psychologist, and she and her co-author in the book that we talked about. where mistakes were made, but not by me, they have something called, what is it called?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The pyramid of choice, if I'm remembering. It was a long time ago that we talked about this. But the pyramid of choice is this. There's two people, and they are both faced with a question, the same question. And to both of them, it's like, okay, I don't really care what the answer is. 50-50, you know, it could go one way or it could go the other way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But imagine that for whatever reason, these two people choose different answers to this question. there is a psychological feature of human beings that we do want our beliefs and choices to sort of be right. And that means not only right externally, but also in agreement with other things that we believe. So as soon as you make the choice, you start justifying it, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You start saying, oh, yes, that was clearly the right choice. And then so you can see they trace in the book how it's called the pyramid of choice because you can see like these two people who started out with exactly identical opinions but just by random quantum fluctuations ended up making different decisions become less and less alike.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
They sort of move apart because they're both internally justifying that original decision that they made. I suspect something like this is going on at the national level to sort of push people apart now that they're – interests and political opinions line up, and now that elections in the U.S. have become more national because of technology and things like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I don't know how that explains the 50-50 split, which is still baffling to me, but I'm sure that there's probably a perfectly good explanation out there. So if anyone knows what it is, let us know. Clement Goers says, if you could ask an all-powerful genius one question that can only be answered with yes or no, what would your question be and why?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So this is one of those questions I'm going to read out loud, but I'm not going to answer. I want to talk about the idea of the question. So I'm not... I'm not into questions like this. I think that this question represents a different way of conceptualizing human knowledge than the way that I have, right? I had a good analogy for this. What was the analogy?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
When I first read the question, I came up with a good analogy. But it was something like... You know, if you could only eat one part of the pizza, the crust or the cheese or whatever, which part would it be? It's kind of missing out on the point of pizza, right? Pizza is my mind because we just were talking about it a second ago.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It's the grouping and the interplay of the different ingredients that matters. For knowledge— It's the whole story that matters, right? Like if I want to know, this is not the question I would pick, but let's say, you know, I want to know, did the universe begin at the Big Bang? And so I asked the all-powerful genius and they said, yes, it did.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
If it goes well for you, if you're the kind of person who would be a successful physicist, it is generally true that the kinds of things that you are passionate about doing
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
As opposed to, you know, having a prehistory or something like that, right? Because we honestly don't know the answer to that question. So that's very valuable information. It's sort of half of the possibility space has now been eliminated, right? But it's entirely dissatisfying.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It's a slight help in our future research programs that we now no longer have to consider certain models and can only consider other models. But we still have a huge number of models to be considered, right? So it's one bit of information. And that's just not how science or knowledge works. And I— I think it's a feature of science and knowledge. They don't work that way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It's a journey that builds up a story piece by piece, and all of the story matters. So sorry, Clement, if I'm kind of being a jerk and not answering your question in the spirit in which you intended it. But I think it's emblematic. I mean, I get lots of questions, not quite like this, but along these lines. You know, what question would you have for—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Albert Einstein or to ask God or, you know, who would you want to invite to your dinner party of historical features? Like, none of these are my kind of question, I got to say. I just don't think like that. The journey matters as well as the individual achievements along the way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Marie Rouskew says, what, in your opinion, are the main properties making a model theory or an equation, etc., beautiful? That's a good question. And you know, I haven't deeply theorized about this. People have sat down and really tried to think about, you know, what makes a model theory or equation beautiful. I'm happy to use the language.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
line up fairly comfortably with the kinds of things that would lead to success and jobs and things like that if there is huge tension between the kind of physics you want to do and the kind that would actually make you employable then that's a very big barrier that you're going to have to try to overcome or contemplate whether or not it's worth overcoming i don't think that being too old
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You know, I'm happy to say that general relativity is the most beautiful physical theory ever invented. So why is that? What is it that makes it more beautiful? Let's say more beautiful than the Schrodinger equation of quantum mechanics, which is beautiful in its own right, or the Lagrangian of the standard model of particle physics, which is kind of not beautiful.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It has beautiful aspects, but most people would say it's kind of clunky. Why is that? Well, look, in the standard model, there's a lot of seemingly arbitrary choices, right? There are symmetries. What are the symmetries? Oh, there's an SU2 and a U1 and an SU3. Why those symmetries? There's some discrete symmetries.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There's some partial symmetries that are like approximately good but not perfectly good. There are three generations of fermions, but why not four? Why not two? And you can go on and on. And it just seems arbitrary and kind of— ad hoc, and that feeds into something, the feeling that we get that it's kind of ugly. Also, it's kind of long.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It's like a lot of separate things going on in the standard model of particle physics. Oh, look, there's the gluon, there's the Higgs field, there's the neutrinos, etc. Whereas general relativity is There's Einstein's equation. You can read about it in Space, Time, and Motion, because I did its volume one, or I did a whole solo podcast explaining Einstein's equation. And it's elegant.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It's elegant in that it's very simple, it's very short, and it explains a huge amount. It was invented almost by pure thought by Albert Einstein, circa 1915. Pure thought, there was some empirical input to it, like the principle of equivalence and relativity itself, so the speed of light being constant, mattered.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But it wasn't like we were doing enormous numbers of gravitational experiments that forced us to general relativity. Einstein was trying to come up with a very simple, beautiful reconciliation of relativity with the existence of gravity. And he kind of did it. And now over 100 years later, we have not improved on his idea.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Whereas the standard model of particle physics is not something you would have come up with by pure thought. Every single bit of input there mattered. You know, I start when I give my talk on volume two of the biggest ideas in the universe, where I do talk about the standard model a little bit, quantum field theory, etc.,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I have a list of concepts that played a very big role in constructing the standard model, and I give a couple of names who helped us establish each concept, and it fills up the whole slide with small print, okay? There's many, many, many, many names, all of which had something to add to that, and it's all necessary, and it's all because of individual specific features of the real world.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So it is impressive without being elegant or beautiful. So something in there about the elegance or the beauty is it's simple, and once you see it, it seems almost inevitable. How could it possibly have been any other way? As a scientist, of course, you have to keep in mind that it could have been another way, okay? Simplicity is not what decides whether things are true or false.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Simplicity, elegance, beauty help us look for hypotheses, which then we test against the data, and that's what tells us whether something is true or false. Ned Grady says, I've heard recently a continually accelerating observer experiences radiation in a vacuum. But if the observer is in a vacuum, relative to what are they accelerating? Yes, you've heard correctly.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
is a problem. I mean, it depends on how old you are. I would say that if you were 70, maybe it becomes more difficult to learn these things. 32 years old is not too old to learn physics. I don't think your brain has stopped being plastic enough to learn these things. You have to convince people. And I've known people who have entered grad school in their 30s, in their mid-30s.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You've heard about Unruh radiation. William Unruh, who's still around, still at the University of British Columbia. did a wonderful thing in the 1970s after Stephen Hawking showed that black holes evaporate, Unruh did what every good physicist dreams of doing, which is to sort of distill that idea down to its essence. And, you know, he asked, like, what is the simplest version of this?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
What is the spherical cow? And he discovered that if you have a constantly observing particle detector— in empty flat space-time, Minkowski space, no matter energy or anything, then in the quantum field theory vacuum, that particle detector that is constantly accelerating will tell you that it's detecting particles.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
That turns out that the mathematical demonstration of that is very, very closely related to the derivation of Hawking radiation. In fact, I'm working with a graduate student right now.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
He, Chris Shalhoub, who's the grad student, is doing almost all the work, but we are writing a paper that looks at what particle detectors detect when they fall into black holes in what we like to think is an unprecedentedly careful way, and we found some interesting results there. So hopefully that will be out soon. But anyway, so that's Unruh radiation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And what you're asking is, how do we know they're accelerating? Well, that goes back to Galileo. You don't need Einstein for this. The idea of relativity, if you're either Galileo or Einstein, is that there is no preferred location in the universe. And there is no preferred velocity in the universe. But there is a preferred acceleration, namely zero.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The demonstration of this is just that if you're in a sealed spaceship and you can't look outside, you do not know where you are. You can't look outside. You do not know how fast you're moving. You don't feel that motion because you and the spaceship are all moving together. But you absolutely know if you're accelerating.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
If you're accelerating, you're pushed against the wall or the floor of the spaceship. And if you're not accelerating, you're not. So there is a preferred set of trajectories in space-time called the inertial trajectories, those that feel no acceleration. And you are accelerating relative to those.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Paul says much has been discussed in recent times regarding the impact of AI technology on work and removing the mundane aspects of life. Much less has been said about the possible impact on our hobbies, sports and the arts. How do you see AI impacting these aspects of life that many of us hold dear? Well, I think it'll be a mixed bag.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I already confessed above that predicting the actual specific outcomes of these large-scale shifts in technological capacity is very hard to do, so I'm not going to claim to get it on the bullseye here. There's sort of the optimistic scenario and the pessimistic scenario, right? The optimistic scenario is it enables people— to do hobbies at an unprecedented level.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And I know that some people are sort of scared by this, and I think that's bad. You know, we had Grimes on the podcast a while back. The thing that I was really interested in talking about is just that You know, it's possible now with a computer. It wasn't even AI at the time. We didn't talk that much about AI. She wanted to talk about AI more than I was interested in.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So she saw it better than I did that AI would have a big impact on this. But this was a couple years ago. And just the existence of computers and synthesizers and drum machines makes it really much easier for a person without any real musical skill or training to write and create a song. You know? I think that's great. I think that's a wonderful thing. Not that many people do it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It is absolutely possible. But it's hard. It's like one more little barrier. If you think about all of the things that make it difficult to get a faculty job in physics, like... Maybe you're not talented enough. Maybe you are talented enough, but you got stuck with a bad advisor. Maybe you got stuck with a good advisor, but somehow you just didn't come up with the good research programs.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I mean, some people do it, but it's not like, you know, before you had to learn to play the piano or the guitar or something, and now you need to learn less, but still you need to, like, learn something. And it turns out that most people are just not that into creating new songs for themselves, which is fine. So the optimistic scenario for AI is that it makes it even easier, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Is that you can tell the AI, look, I've had this drum track and this set of key changes, chord changes in a certain key. Write a melody that will go along with it, and it will do it. And maybe that just inspires people who might not put in all the effort to learn an instrument in the usual way to explore creative avenues to an unprecedented extent.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Again, I don't know whether it will happen, but it's certainly possible. You see people already who are making movies using AI. And that's just something that would be very, very hard to do with a pocket camera to make a sort of professional-level film. You still can't even with the AI, but it's very conceivable that you could once AIs get better.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Now, I'm putting aside – I should have said it at the start. I'm putting aside here all of the very, very important and real-world worries about AI. Number one, using up a huge amount of natural resources. Number two, polluting the environment. Number three, stealing from other artists, etc.,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Those are very good issues, but that's not the question that Paul asked, so I'm not addressing that one right now. The pessimistic side would be that people become couch potatoes, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Like that rather than putting in the work to learn to play the guitar or the keyboards or whatever or learn to set up a shot with proper lighting and sound design in a movie, we just, you know, let the AI do it, right? It's the WALL-E theory of the impact of AI on our lives.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You know, I don't—I get that that's a little bit of a worry, but I don't really think that's going to be a huge thing either. I'm sure that when movies came along, people said this would completely kill off live theater performances. And maybe it diminished the role that live theater performances have in our lives, but they still exist. They're still out there. People still do it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
High schoolers still put on musicals, right? Yeah. I think that people will still do art the old-fashioned way, even when newfangled ways come along. So overall, I would tend to be optimistic. I would tend to fall on the side that the AI will give us some tools that we didn't otherwise have, and it will still allow us to do things the old way if that's what we want to do.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
To make that optimistic scenario come out, it is going to require thought. thought and care and, believe it or not, regulation and rules, because this is what Daron Asamoglu warned us about. If we don't do that, then it's just going to be an extractive capitalist institution, not going to be something that allows for a flourishing of human creativity.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Maybe you got sick in the middle of grad school. There's many things that can go wrong, many things that can basically lower your probabilities for getting the job. Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Anders says, you've said you don't like smooth jazz. At what point do you think preference becomes snobbery? Well, I think it's revealing you would even associate those two things. You know, if I said I don't like 12-tone classical music, you would not think that that was snobbery. It is true that smooth jazz is something that people are snobbish about. But I don't
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
ever think that liking or disliking a certain kind of art is snobbery. That's just your personal preference. Some people like more accessible kinds of art. Some people like less accessible kinds of art. Some people aren't very artistically inclined at all. This is all perfectly fine as far as I'm concerned. Snobbery is a reference to how you think about other people's interests in art.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
If someone says they like country music and not classical music, and you look down upon them because of that, that would be snobbery. And I'm not into that either. So if someone else likes smooth jazz, knock yourself out. That's completely okay with me. Matthew Wright says, last month you left us on a real cliffhanger.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You just managed to trap Puck, the wild cat you've been taking care of, for a trip to the vet, but the vet visit itself had not yet happened. How did it end up going? I did. So in the call for AMA questions, what exactly was the – it was a month ago, so I don't remember the things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Anyway, let's jump forward because I know that different people out there inside Patreon and outside Patreon have different amounts of background on Puck, our stray cat. As I am recording this AMA right now, Puck is sitting next to me. He's about five feet away. We're upstairs in our house here. So we trapped Puck.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
being a little bit older is another thing that lowers the probability because you have that extra work to do of convincing other people that you're serious about it, that you, you know, despite the fact that for the last 10 years you've not been in grad school when you could have been, nevertheless, doing physics is what inspires you and you're passionate about and so forth.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
took him to the vet, discovered Puck was a he, which we weren't sure about, did the operation that he needed. He got all of his shots. He got the fleas removed, et cetera. And we were told that he needed to come back for a booster shot. I forget which one it is. Maybe the feline HIV shot, but it can't be HIV because that's human immunodeficiency.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
deficiency virus but you know there's a there's a shot you need to get if you're a cat and you need to get one shot and then a booster three weeks later so we suspected because puck is like not super genius level but he's pretty clever at avoiding things and so we figured we only had one chance ever to trap him
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So when that worked and we trapped him, we took him to the vet, we figured, okay, three weeks, we're just going to keep him inside for three weeks. We have a big room, like a playroom that we can give up in the house, put him in the playroom, feed him, kitty litter box, the whole bit. And what we suspected was that after those three weeks, we would sort of let him out again.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Like we'd take him back to the vet, do that, let him out again. Um, I will put up pictures, at least for the Patreon subscribers, you'll see pictures of Puck in his room. The truth is he just made himself at home right away. We were thinking that he would try to escape, that he would meow and express unhappiness, that he would, you know, like scratch at the windows or whatever.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
He hasn't done that. Puck has sort of realized there's soft blankets here and there's food all the time and it's
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
warm and dry and comfortable and he has made himself at home he is very very happy right now um and he's he's not uh he doesn't want to be touched doesn't want to be petted but he will come right up to you sniff your fingers you know nod and say okay you're all right i know who you are he will follow me around in the room and uh when i come into the um room to do the podcast that that's next to his room and he will follow me in as he is right now sitting next to me listening to me podcasting
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So therefore, because he is just clearly up there, he's looking at me. Hi there, Puckster. He's clearly much more at home and safer in here than he would be outside. Now we're thinking maybe we should just keep him inside. That raises the whole new challenge of socializing him to be friends with Ariel and Caliban. Ariel and Caliban were here first.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
They get veto power, and bless their hearts, they are not sociable kitty cats. They do not want any strangers in the house. So that has not happened yet. We've been keeping all the cats apart. But even though Ariel and Caliban don't like intruders or interlopers, they're at heart good-natured, OK? And we live in a house where there's enough room.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There's different rooms where they can all spend time apart if that's what they want to do. So we are optimistic that we will adjust all the cats to being friends with each other. Now, then the second question, the biggest question is how the three cats get along. The second one is, will we let Puck outdoors again? Um, Part of Puck, I'm sure, is going to want to go back outdoors again.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So maybe you can do that. Maybe you can convince people. Like I said, I've known people who've been in grad school and gotten PhDs at later stages in life and But it is one more thing to try to overcome. Having said that, physics is awesome. You know, thinking about the fundamental nature of reality as your day job and getting paid for it is a pretty amazing thing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But like we said, it is less safe out there. We have a yard, but he doesn't stay in the yard. He crosses the street and things like that. It's super dangerous out there. There are falcons in our neighborhood and foxes and things like that. So part of us wants to just keep him inside. Whether he will be happy with that or not, I'm not sure.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Like I said, so far he has shown zero communication to us that he would rather be outside, but we'll see how that goes once he gets the run of the house. So updates to come as they are warranted. Josh B. says, imagine an intergalactic advanced alien civilization in terms of technology, virtually unlimited source of energy and societal organization, little to no scarcity of resources.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
In what way would you imagine their society being organized in terms of hierarchy and division of labor? So I don't believe in the question, honestly. When you say virtually unlimited source of energy, little to no scarcity of resources, that can't happen. I know that people like to imagine this, but I think that they're fooling themselves.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I think that they're imagining, well, how much could I personally possibly want in life? I can imagine a civilization where everyone has that much or more. But you know what? Human nature being what it is, what I suspect is that people will want more things. I want my own galaxy, right? Who's to say? Well, if you say, well, okay, we don't have that much. You can't have your own galaxy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
That is scarcity right there. If you don't believe that will happen, look at what actual super rich people do. They buy a lot of stuff. Some are more modest than others, sure. Some are very showy about it. But there's— a whole bunch of people who have a lot of resources already and still want a lot more, you know? I think that, again, it's a journey, not a destination kind of thing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So whatever the organization of the society is going to be, I suspect it will not be dramatically different than ours simply because scarcity has been overcome. I do think that we can overcome poverty. I do think that if we, we could do that right now here on Earth, right? If we put our minds to it, We could absolutely distribute resources in such a way that no one was truly, truly badly off.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
We choose not to do that for whatever reason, and we can talk about that. And I suspect that those reasons are deeply ingrained in human nature. Therefore, I would not be surprised if even when a society is much more advanced and wealthier, there are still vast disparities and there's still a lot of poverty out there. I don't want that to be the case.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And indeed, you know, to be fair, we have made a certain amount of progress in reducing the amount of poverty in the world. But that's a tricky thing to measure because what you're comparing against is unclear, et cetera, et cetera. But I can't say that if society reaches a level or an alien society is already at the level,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
where they have enormous, enormous resources, that that would somehow mean that things are more equitable or less hierarchical. I would like to think things like that are true. I have zero reason to expect it in the real world. Connor Schaffran says, what do you think is the most misunderstood concept in modern cosmology, and why do you think it's so challenging for people to grasp?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
What I can't judge is how good you are at it, anonymous priority question asker. So I can't give you any honest opinion about that. But...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
This is a hard question, not because there's no good answers, but because there's too many good answers, depending on what you mean by the set of people who are misunderstanding it, right? I think that, you know, there's a surprising number of people on the street who barely know the universe is expanding. They don't have a grasp of cosmology yet.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
up to the level of the typical Mindscape listener, much less that of a professional cosmologist, etc. So different sets of people are going to have different misconceptions. You know, I'll just name one popular one, which is that if the universe is expanding, if you already know that, then you think that it should be expanding into something.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And it's perfectly clear why that misconception exists, because whenever we visualize things, we visualize them inside the three-dimensional space that is around us. So our intuition says that things that are expanding are expanding into the space that is around them.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And Einstein, using mathematical techniques developed by Riemann and others, going back to Gauss, et cetera, figured out that the four-dimensional geometry of spacetime can be expanding or can be dynamical more generally without being embedded in any bigger thing. And to add to that, if you're a careful scientist, if someone says, what is the universe expanding into?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
We can say, as far as we know, it's not expanding into anything, but it's conceivable that it is. We have zero reason to think that it is, and we have perfectly good theories that fit the data without it doing that, but maybe it is. And in some sense, there's various theories of extra dimensions in which something like that is actually happening. So I do think that, generally speaking, cosmology...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
If you are good at it, if you are the kind of person who, if you get into grad school, will do the work, will impress your advisor and other faculty members, they will write you good letters, you will get papers written that other people pay attention to and move the field forward in some tangible way, then it's all good.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
has some misconceptions because its regime of applicability is just very, very far away from the intuition that we've built up as ordinary human beings living our everyday lives. It shouldn't be surprising. It's okay for things to be misunderstood. All you should do is work harder to understand them better. Aaron Munger says, how can information be preserved with quantum indeterminacy?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Shouldn't it also work backward in time as well, and therefore make it impossible to determine a past state? It's not quantum indeterminacy. I don't really like that word. I'm not sure what that refers to. But there is, in the real world, an arrow of time associated with quantum mechanics, namely... wave functions collapse toward the future, not toward the past.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And indeed, the process of wave function collapse does not preserve information. That is true. When people talk about, you know, in the context of black holes or whatever, information being preserved, they mean other than the measurement process in quantum mechanics. This is the weird thing about quantum mechanics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There's one set of rules for when things are not being measured, another set of things for when they are being measured. So when they are not being measured, the rules that we understand them in quantum mechanics tell us that quantum states preserve information. But measurements seem to not preserve information. There we go.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Again, it depends on your favorite view of quantum mechanics and Everettian quantum mechanics. The universe as a whole, the wave function of the universe, does preserve information, but we don't have access to it. We have access to one branch at a time. And the time asymmetry comes from the fact that the early universe was special.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
That is exactly the same origin as the thermodynamic time asymmetry. I think we'll talk about that a little bit later in the AMA. So therefore, in fact, if someone says I have a quantum spin, I'm going to measure it. Oh, look, it's spin up. Tell me what its state was before I measured it. You can't. all you know is that there was a greater than zero contribution from spin-up, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You don't know whether it's 50-50 or 70-30 or 99-1 or whatever. All you know is there was some spin-up part, and probabilistically you got that. So you cannot infer the past from the present in quantum mechanics, given the information that is actually available to observers. Going to group two questions together.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Peter Kraus says, Roger Penrose has said in an interview that the cosmic microwave background has a nearly perfect blackbody spectrum, which would indicate a thermal equilibrium state, which in turn would indicate high entropy. Therefore, he assumes gravity to balance out with very low entropy so that the past hypothesis can be maintained. Hopefully I didn't misunderstand something.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
What is your take on this? And Bits Plus Atoms says, I heard Brian Greene interview Roger Penrose. And Penrose says, paraphrased, an intensity versus frequency graph of the CMB is almost identical to the Planck curve representing blackbody radiation. That curve represents thermal equilibrium for a system.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Then you're going to get a faculty job and you're going to be a physicist, right? I can't tell you the probability that that's going to happen. If it does, well, I want to say you'll be very happy. But of course, It also depends, personally. Some people are very happy with those kinds of jobs.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
This would suggest that at the birth of the CMB, the universe was in a state of thermal equilibrium, but it wasn't. The overall low entropy of the universe is due to the negative contribution of gravity.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I know you don't put high credence on Penrose's cyclical cosmology approach, but are his statements about CMB gravity correct in terms of the contributions to the early low entropy of the universe? You know, I think that Penrose—I give Penrose a huge amount of credit for this. I think that Roger Penrose was the first—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
at least big-name physicist, to really, really appreciate the importance of the low entropy of the early universe near the Big Bang. He was saying this in the 70s. When inflation came along, he pointed out that inflation did not help solve this problem, and he's been consistent on that ever since. I didn't hear this interview that he did.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Probably Peter's interview is the same one as Bits Plus Atoms heard. I don't like this way of phrasing it. I think that this is a frequent way of talking about the early universe that is, in my mind— almost intentionally obscurantist, okay? And here's what I mean. The early universe had low entropy. That's just a fact.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Now, it is also a fact that if you take the spectrum of the cosmic microwave background, it looks like a black body. and black bodies are usually associated with high entropy states. Therefore, you might be temporarily confused, okay? But the confusion is very, very easy to resolve. It's because the black bodies that you're used to measuring have a self-gravity
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
That is to say the gravitational force enacted by one part of the object on another part of the object that is completely negligible, right? If you have like an oven that is glowing like a blackbody, you can ignore the gravity of one part of the oven on the other part of the oven, right? So gravity is just completely ignorable. In the early universe, it's not.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Gravity is super-duper important in the early universe, and gravity is a force of nature. Therefore... This idea that the early universe looks like it has high entropy because it looks like a black body is just a bad idea, just a wrong idea. You never should have had that idea, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So somehow acting like it's a big puzzle, that we have this tension here, like the tension is super-duper resolvable. And furthermore, it's absolutely not true that gravity has negative entropy. That's not what is going on at all. That's just false. So I don't know whether Roger misspoke or it was mistranslated in the interview or whatever.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It's that gravity could, is allowed to, contribute a huge amount of positive entropy. And in the early universe, it just doesn't. Because everything is smooth. The gravitational field is more or less the same from place to place.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Some people realize that, ah, I just wanted to, like, sit around and think about the universe, but instead I have to, like, teach and apply for grants and supervise students and, you know, go to committee meetings. And, yeah, this is just like any other job, right? Every job has its aspects that you do because they need to be done, not because they're what you're there to do.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Whereas a high entropy state would look either like a black hole or a set of black holes or a highly expanded universe, like our future of the universe where everything is very far apart from everything else. All of those would be high entropy. And gravity is just not in any of those configurations, so it's not contributing the entropy that it could contribute.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So I think that the safe thing to say is just that the actual entropy of the early universe is low. That's a true statement. This idea that it's broken up into gravity entropy and other entropy— is not anything very well defined. I mean, maybe talking in those terms will help you come up with a new theory of it. That's great.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But it's just not, it's very, very hand wavy and suggestive, not anything rigorously defined at all. Darren Ho says, If the laws of physics govern, why would that necessarily be true? Don't the particles have to interact according to the forces of nature such that there could be such a thing that prevents such a configuration from ever happening? Is that not what entropy tells us cannot happen?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Good. I'm very glad you're asking this question because you are channeling many physicists in the 1870s. In the 1870s, we had the second law of thermodynamics saying that entropy will increase in closed systems. we're beginning to have a grasp on statistical mechanics from Maxwell and Boltzmann and others. And in statistical mechanics, the second law is not a law.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It's just a probabilistic statement. It's very, very likely for entropy to increase.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
people rejected that people or at least had trouble with that they thought that they had a law in their hands but you know experimentally you never have a law right you can never it's the black swan problem you can never verify that not only has it never happened but it never will happen that entropy spontaneously goes down all you can do is see a bunch of cases where it goes up and generalize that in your head and say oh i think maybe it always goes up
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And someone else says, no, it only goes up 99.99999999% of the time, so you've never seen it. You have not experimentally distinguished those. You should be open to that possibility if there's a good reason to be. There is a subtlety with the apple example. If you have the right ingredients to make an apple out of randomly distributed atoms, so you have the right
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
amount of hydrogen and carbon and oxygen and so forth, it's not absolutely necessary that over time it will come to be an apple. It depends on the configuration that it is in. You want there to be the right energy, right? There better be enough energy in there to be an apple.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But there is a principle called ergodicity, which says that in a certain kind of physical system with many moving parts, the system will basically, over time— explore every part of configuration space that it is allowed to explore. By allowed, we mean we're not going to violate energy conservation or things like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But, you know, physics is no different than that. The only other thing that I will say – I'm sure this has not been a super-duper helpful answer to your question, but I'm surprised that you say that the people you hang around with are uninspiring, unintelligent, and not curious about the world.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But other than that, a typical system, not all systems are ergodic, but we think that typical systems are, they will explore every possibility. So it's not, even though we talk about randomness, and we talk about a probability, that's all from the fact that we just don't know exactly the microscopic state of the system.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Even if you put aside questions of randomness and probability, under sufficiently controlled circumstances, you can prove that the system will do everything the system can possibly do given enough time. The time scale is what is called the Poincare recurrence time after Henri Poincare, and it is of order e to the power s, where s is the entropy of the system. So that is a huge time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You know, notice I don't even have units correct in there because it doesn't matter because e to the s is going to be such a huge number. It doesn't matter whether you measure it in years or microseconds. But eventually it will happen. That number is less than infinity. So we think that the apple will spontaneously come together. Sorry if you have trouble believing that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Again, very far away from our everyday experience. P. Walder says, you have published extensively on the arrow of time and the associated increase in disorder in the universe. Sarah Walker and Lee Cronin's assembly theory promotes a perspective on complexity accumulation, which seems to challenge the centrality of the second law of thermodynamics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Do you feel there is merit in assembly theory and how the second law of thermodynamics may or may not be key to the origin of life explanations? So I do, there's two things. So Sarah Walker, former Mindscape guest, and Lee Cronin and other collaborators had this idea called assembly theory, which they put forward as a way of understanding how complex structures come to be in the universe.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Very much thinking in the back of their minds about complex molecules and ultimately life, but in principle, any kind of complex structure. And what they point out is that once you have different pieces, different tiny pieces that can be put together in big pieces in many different ways, the space of combinatoric possibilities becomes very, very large, very, very quickly.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
People like Stuart Kaufman have pointed this out a very long time ago. So that's a well-known thing. So you're not going to explore all of the combinatorial possibilities. The human genome has 3 billion base pairs in it, okay? You're not even coming anywhere close in the history of the universe to exploring all the different ways to arrange 3 billion base pairs.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So instead, you have some way of exploring a bit of that space. And the assembly theory idea is that we focus on the ways that you can build up slightly more complex things from very simple things, and then repeat that to put slightly more complex things together, and you have a history of assembly. So you're not just randomly putting together your base pairs or whatever.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I was in LA for 16, 17 years, and I found plenty of people who were super-intelligent, super-inspiring, and super-curious about the world. Maybe they were not, you know, the highest level celebrities, but there are people in L.A. who are absolutely creative, absolutely curious about things, whether it's screenwriters, songwriters, movie directors. You know, it's a...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You have a particular trajectory over time that leads to particular places in the space of possible configurations. Now, all this seems perfectly reasonable and interesting and potentially useful. None of it, in my mind, has any conflict with the second law of thermodynamics. So I have mixed feelings about assembly theory.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
On the one hand, I think that the approach to thinking about complexity and its accumulation is potentially very, very promising. By all means, let's think about it and take it seriously, and maybe that helps. Because again, there's a lot we don't know about complex systems, and it would be nice to know more, and maybe this is a helpful tool for doing that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
On the other hand, the advocates of this theory seem very happy to give in to the temptation to say this is somehow incompatible with what we know about physics. I have seen zero evidence that it is in any way compatible with what we know about physics. To me, if anything, it's a perfectly natural consequence of what we know about physics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So I kind of like where they get to and don't always like the rhetoric that they use along the way. Qubit says, The short answer is I don't see a big difference. I think that both of those would very plausibly be wrong, okay? There's a difference in what they are, and there's more of a difference than people think.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Because when you say living in an artificial but realistic world, that's a big ask. You toss it out. Not you, Cupid. One tosses that out, we'll put our simulated consciousness or whatever in a complicated and tricky than people give it credit for. That's at least as hard as building the artificial consciousness in the first place, okay, which we're not close to doing right now.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Putting it in a robot and having the robot be in the real world is much more straightforward and achievable than doing an entirely artificial world. But granting that, just because I want to make sure that people understand that distinction, I don't think that there's necessarily any obvious moral distinction between these two scenarios.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Now having said that, I also want to emphasize that who knows? You know, as a moral constructivist, I think that morality comes from a way of sort of systematizing our preferences and intuitions about how to live good lives in the world. It's not an objectively true thing that we find by experiment. or by proving theorems, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So when you get to these kinds of thought experiments that are super far away from anything that we have in our intuition or experience, I'm open to different people disagreeing about where to go, as long as they all agree that we should be cautious and not too wedded to our conclusions, because we're trying to extrapolate
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It's like we've always lived within a five-block-wide part of the world, part of a city, and we're trying to extrapolate what things like are on a different continent or a different planet entirely. Not that we shouldn't try, but we shouldn't get overly wedded to whatever comes up, whatever our imagination comes up with. Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Sid Huff says, what is your take on the recent dramatic rise in sports betting? I've read perspectives that range from a great way to generate even more interest in sports to another nail in the coffin of America. Do you think that on balance it is a good thing, a bad thing, or something in between? I have to say I think it's bad because at the end of the day, I'm an empiricist.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
place full of creative, inspirational types of people. They might not be the ones you're hanging out with. So maybe there's a much easier switch that you can do in your life to just sort of find more like-minded people who are close to the area that you're already in, somehow combine your interest in being ambitious about thinking about the world with the job that you're already in the middle of.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I look at the data. it is causing a lot of harm. So anyway, for those of you who are not in the U.S. or whatever, who just don't pay attention to sports, when I was your age, you were not allowed to bet on sports except for maybe in Nevada, okay? You literally had to go to Nevada to place a bet on a sporting event. And the major sports leagues were very, very, very concerned about—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
corrupting the games by letting players or coaches or whatever be involved in betting on them. Pete Rose, who was a great talented baseball player who recently died, was found out that he bet on baseball games while he was a player and a manager, and then he was banned from baseball and prohibited from going into the Hall of Fame.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Since then, in recent years, they have realized that there's a lot of money to be made in sports betting. And so they have allowed it into their games. I think I say they, but at least all the major sports in the United States have welcomed betting on their sports. If you watch a... broadcast of a game.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
They will give you updates on the betting lines during the game, during the broadcast, you know. And with the internet, it's just much easier to place these bets in perfectly legal ways. And the data are coming in and they're saying, yeah, people are ruining their lives. They're going bankrupt. They're not managing their bankrolls well, and so on.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So I'm torn here because I'm a big believer in letting people live their lives as they want to live their lives. I want people to be allowed to bet on sports. I do not think it should be illegal. But there have to be some guardrails if, as a matter of fact, this is ruining people's lives at an unsustainable rate, right? I don't know what those guardrails are going to be.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I think that somehow we have to make it impossible to bet too much or something like that or to lose too much, right? Everyone thinks they're going to win. Most of them are not. That's the way the numbers work, one way or another. So I think that we haven't figured out how to do it right. I hope that we can do it, but I think that we need to be a little bit more responsible about how it's done.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Robert Grenice says, I'm reading Tom Chivers' book, Everything is Predictable. He is a Bayesian apologist and makes the case for its superiority over statistical analyses focused on a p-value. I know that you are also a proponent of Bayes and wonder if it still applies in physics, which has a lot of raw data. So the question is, do you use both approaches?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And how do you decide which is best in a given situation? Yeah, I think it's actually changed. It's interesting. Someone should do a study on how the way that scientists think about statistics has changed in the last few decades. When I was a graduate student, no one talked about Bayes' theorem or Bayesian analysis.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And while I was a postdoc and junior professor, the data sets that were being looked at became increasingly bigger and more sophisticated, and we needed better statistical tools for thinking about them. And people discovered—some people already knew, of course, all along, but the wider communities discovered—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Bayesian analysis, and they became rather annoyingly evangelical about them, you know, browbeating you if you didn't use Bayesian statistics. I think it's just Bayesian statistics are correct. I think it's just the right way to do it. You don't always need to do it. So the alternative to being a Bayesian is to be a frequentist, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
To say, what we're talking about when we talk about probabilities is a summary or a shorthand for an infinite time frequency. You can imagine doing the same thing over and over and over again, and there's going to be a certain number of times it turns out A, a certain number of times it turns out B. The ratios of those give you the probabilities. And Bayesians don't say that at all.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
They don't, they're not... forced to think about doing things an infinite number of times. If you say, I think the probability that Donald Trump will win the presidential election is 60%, no one has the nightmare scenario of running that an infinite number of times in their head, okay? It's a credence that you put on things. And so the Bayesians focus their attention on the likelihoods
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You know, I wish that it were easier to change your career every 20 years, right? You can do it. You can change your career every 20 years if you wanted to. 20 years is enough time to establish yourself, accomplish something, and move on. It's not what we standardly do. And part of that is just because success in a career is cumulative in some ways, right? You prove yourself worthy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
under different hypotheses, certain experimental outcomes are more likely or less likely. And that's supposed to be objectively computable as opposed to the priors that are your initial beliefs. And that turns out to be super important, right? If you have data that is, if you have two theories, theory one and theory two,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
and you have data that is more likely to be predicted by Theory 2 than by Theory 1, is that good evidence that Theory 2 is true and you should just disregard Theory 1? Well, no, not if your prior was that Theory 1 was much, much, much more likely, right? And this feeling can be made very quantitative. You can show very, very explicitly
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
that this can save you from incorrect conclusions in medical studies or something like that, because there are things that are less likely a priori, but if they were true, then you get certain data. But when you get that data, it's still not enough. to overcome the fact that they're just a priori less likely, right? So Bayesian analysis, I think, is just right.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It rubs people the wrong way a little bit sometimes, because the priors are subjective. If you have enough data, that doesn't matter anymore, and the priors go away. Plus, reasonable people often have priors that are actually pretty close to each other, despite the philosophical disagreements about whether they need to be or not.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Matt Grinder says, I listened to your interview with Philip Goff on panpsychism, and I agree with you that any theory of consciousness cannot contradict the laws of physics. So would the following be a way out for the panpsychist?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Every time a particle changes state by wave function collapse, a calculation must be made for the particle to decide what to do next, and this calculation involves a qualia. Over time, the calculations via qualia would have to agree with the Born rule. This seems to me not to contradict any laws of physics. Is it just an add-on to physics? Yeah, this is something that is absolutely conceivable.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
People have conceived it. David Chalmers, former Mindscape guest, and his collaborator Kelvin McQueen wrote a paper that really looked at exactly this possible idea. I would say a few things. Number one, it absolutely is a change in the laws of physics because the laws of physics as we know them now don't say that. I should say I don't say it's a change of laws of physics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
We don't know the laws of physics. I should say it's a change in what we take the laws of physics right now to be, okay? Because right now we do not say that the probabilities depend on quality in any way. If you say, yes, they do, you are suggesting that the laws of physics are different than what we think they are. It's hard to make it work.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It's hard to make it work for whatever you're saying, precisely because, long story short, like you say, over time the calculation would have to agree with the Born rule. Well, what does that mean? Like if... If the qualia are pushing it all, you know, you have a bunch of spins that are 1 over square root of 2 spin up and 1 over square root of 2 spin down.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
If somehow your qualia are making you get spin up every time, then there's some catch-up procedure later where you get a bunch of extra spin downs. Like, it's hard to make work. that way. Number one. Number two, zero evidence for anything like that in anything that we've ever seen in either physics or neuroscience.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And number three, it would be of zero help in solving the hard problem of consciousness. The hard problem is specifically about experience, not behavior. And you're saying, this theory is saying, Things behave slightly differently than you would have predicted by conventional physics. So what? I mean, great. They're behaving differently.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
That doesn't help you explain this thing about consciousness that proponents of the hard problem say cannot possibly be reduced to behavior. So this is why I don't spend a lot of time worrying about this stuff other than answering AMA questions.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It becomes easier and easier to convince your colleagues that what you're doing is worthwhile. and so forth. So what I want to say, the romantic part of me wants to say, go for it, do it, leave songwriting and become a physicist. But I am also ruthlessly practical about these things. So if you do it, do it with your eyes open, knowing what the prospects are.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Joseph Eli says, assuming many worlds is actually the true fundamental theory of quantum mechanics, how long do you think it will take for it to become the status quo? Do you envision one large discovery that convinces the physics community all at once, or a slow process of competing theories being falsified?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Furthermore, do you think that important discoveries in physics are potentially being hindered by a lack of support for many worlds? Yeah, you know, compatible with what I said earlier about yes-no questions from oracles in physics, there's not going to be one large discovery that convinces the physics community all at once. I don't even know what kind of discovery that would be.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But, you know, there almost never is one large discovery. Usually, when we discover things in physics, they do accumulate, and it's accumulation on both the theory side and the experimental side. There are certainly examples of times when there has been one large discovery. You know, the accelerating universe in 1998 is an example.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But you have to remember the physics community was primed for that, okay? We were already talking about the possibility. Most people didn't think it was true, but we knew it was a possibility that there was dark energy accelerating the universe. We knew what it could be. We knew that it would solve various problems if it was true.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So the time was right for one big discovery to instantly be accepted. Usually it's not like that. Usually you have to go back and forth. a little bit. When Einstein invented general relativity, people didn't believe it right away.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
When they did the experimental measurements of deflection of light by the sun during the total solar eclipse, they had had some time to mull it over and they were ready to go, oh yeah, okay, that's it. It was not really, you know, a complete unexpected shift. So I don't think anything like that would happen in quantum mechanics either.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And it's not even—I don't even think it's a slow process of competing theories being falsified. I think that very often theories just sort of gradually fade away because they are found to be less useful, less fruitful, less well-defined than other theories, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You can always fix up your theory by tweaking it, by adding epicycles or whatever, but eventually it just becomes boring and not very productive. So
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I think that it is absolutely possible that many worlds will be accepted by the vast, vast majority of the physics community, but it'll be a gradual process and it will be because many worlds proves to be the best way of thinking about quantum mechanics, both for known features like the apparent collapse of the wave function, the measurement problem, the Born rule, and also potential future insights.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So this is the last part of your question. I 100% think that important discoveries in physics are potentially being hindered by a lack of support for many worlds. People, by choosing not to think hard about the difficulties of quantum mechanics at the foundational level, are leaving money on the table, leaving meat on the bone, however you want to say it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
That's one of the reasons why I do it, because, you know, you want to look where other people aren't looking. You don't want to just look under the lamppost. Krzysztof Randowski says, Roughly speaking, no. I mean, technically I've considered doing things like that, but it seems like not the best use of my time and energy. The podcast is already here. The podcast exists.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There are full transcripts of every podcast. So really making a book out of them would just be like, number one, picking my favorites, which is very hard to do because that means that some people are going to be informed that they are not my favorites. Number two, editing them. Number three, getting a publisher and putting them into a book. rights to reproduce them.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Zach McKinney says, building on your reflections from the end of episode 290. So Zach is referring to the fact, for those of you who are not Patreon supporters, uh,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Like, I didn't have anyone who appears on the podcast sign a form saying that I could use their interviews for whatever I want. So it would be a thing, and I don't want to do that thing. I mean, maybe I would do it if I had infinite times and resources, but I would rather do other things with the time I have. In the meantime, hopefully everyone can find the transcripts.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I think a remarkable number of people—I Don't ever know that there are transcripts to all the Mindscape podcasts on the webpage, but they're there. The original version for starting the Patreon was so that I could pay to get transcripts made. And that still works. That is still going on. Sam Hartzog says, why aren't most multicellular organisms warm-blooded, aka endotherms?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Intracellular processes should be taking in energy and doing work to maintain a low entropy internal state. Shouldn't that kind of thing result in waste heat more often than not, making endothermy the most natural way to make a living? Well, look, you're not asking the right person this question, okay? So I'm certainly going to advocate that you not take my answer at a high confidence level.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Let's put it that way. I can say some things that I think are true as food for thought kinds of things, but you should ask an expert about this. Yes, there is waste heat generated in any animal, cold-blooded or warm-blooded. That is a very generic feature of thermodynamics. You should expect that to happen. But that's different than what we think of as being warm-blooded or cold-blooded.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
At the end of every episode, after every episode, I do a little reflections, like what I thought about the episode, sometimes closely related to what we just talked about, other times spinning off into some completely different direction. But, you know, little five-minute reflections on every – episode of the podcast, and those are posted for Patreon supporters exclusively.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Warm-blooded versus cold-blooded is more about regulation of temperature, right? Warm-blooded animals are not just their blood is warm. It's that their blood is kept at a relatively high temperature. It's a homeostatic temperature. kind of thing made for certain reasons, that happens for certain reasons inside the organism.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So not knowing a lot about biology, I'm guessing that there are trade-offs in resource allocation, right? It costs energy to maintain your body temperature at a certain temperature. Is it worth it? You get some benefits from doing that. Some heat is generated, but clearly, I mean, look, cold-blooded organisms are not going out of their way to refrigerate themselves. That's not what they're doing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
They're just not going out of their way to heat themselves. Cold-blooded organisms respond more dramatically to changes in the environmental temperature than warm-blooded organisms do. So maybe for some reason it's just not worth it for them to put those resources into that particular homeostatic maintenance. The other thing to keep in mind is that organisms are not intelligently designed, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There are accidents of... history of evolution that lock you into certain choices. And so when you find that certain animals do things a certain way, it may or may not be the best way to do things. It's a satisficing question. You do things well enough to get along and survive. You don't necessarily do things in the completely optimal way. Rob Gebeler says, No. Short answer is no.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I know that people have talked about this. Roger Penrose talks about adjacent ideas to this. But to me, it's like clearly sliding around the meaning of some of the terms in Gödel's theorem. Gödel's theorem says, and again, even this is a simplification, but very roughly it says, I have a system with some axioms and some way of turning those axioms into theorems.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And there are going to be some propositions that are true but not provable if the system is consistent, okay? So I cannot prove them, but I can't disprove them either, right? And okay, that's fine. That's not what the brain is. The brain is not an axiomatic system. I don't know.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Penrose sometimes acts as if you should—he doesn't think it's an axiomatic system either, I think, but he acts as if he thinks that you should think it is and then goes to an effort to fix it somehow because he thinks that human creativity is something that is incompatible with this kind of reasoning because of Gödel's theorem. I don't think that at all.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I just don't think that's a good model for what the brain is doing. The brain is not trying to prove theorems. The brain is trying to haphazardly and heuristically model the world around it, right? So I've never—like, people often bring up the possibility that there are some truths— that human minds are just never going to be able to reach. I see zero evidence for this.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And if there are any such truths, we're not close to reaching them. I see no evidence that we're bumping into any barriers. Some things are hard. Some questions are hard. But I am always much more impressed by how far we've gotten in understanding things than depressed about the possibility there are some places we won't get to.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Alex says, could you explain how measurement of one component of spin, e.g. the Z component, affects the results of measuring some other component of the spin, like the X component? Sure. This is, I mean, I explained this in some detail, both in Something Deeply Hidden and in Quanta and Fields. So it is out there, but it is a fundamental fact I'm happy to talk about again.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So Zach is referring to the reflections on the episode with Hari Hahn, and he says, what hypotheses, if any, would you make with respect to extrapolating Dr. Hahn's observations about the potential advantages of nestled or fractal structures within institutions? to the governance of emerging technologies such as AI or neurotechnology?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And it's very analogous to the uncertainty principle that we mentioned before. You know, the uncertainty principle from Heisenberg's original formulation is about position and momentum, x and p. And one way of coming to a derivation of the uncertainty principle is to realize that in quantum mechanics, unlike in classical mechanics, position and momentum are not independent variables.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Indeed, they are not features of the state at all. They are observables. They can give you different answers. But the point is that the wave function in quantum mechanics is a function of just position. It's not separately a function of position and momentum. There's a separate thing called the wave function in momentum space, but it is derivable from the wave function in position space.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
The wave function in momentum space contains exactly the same information as the wave function in momentum space. It's just that the information is encoded differently in the form of the wave function. It's exactly the same thing for the spin, to get back to your question. The state of a quantum spin is a element of a two-dimensional Hilbert space.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And what that means is there are two basis vectors, and the quantum state is a superposition of these two basis vectors, a component in one direction plus a component in the other direction. And I have freedom to change the basis, right? And in any vector space, I have a freedom to change around my basis vectors. They're complex vectors, not real valued vectors.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So that's the thing you have to be careful about, but we're putting that aside for right now. And the short answer is, one way of choosing the basis vectors for your spin is spin up in the z-direction and spin down in the z-direction. So in Hilbert space, spin up and spin down are orthogonal to each other. They're not pointing opposite, they're pointing perpendicular, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Because those are the two states to be in, and you're in one or the other. And so that is the entirety of the Hilbert space. Alpha times spin up plus beta times spin down. So where does the spin in the x-direction come from? If you have the x-direction, maybe you can measure spin left or spin right, right? How does that fit in? you can derive it from spin up and spin down.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It's just a change of basis. Indeed, it's just a rotation of the basis by 45 degrees. So spin plus x, I'm not going to get the signs right here, so forgive me, but roughly speaking, spin plus x is 1 over the square root of 2, spin up plus spin down in the z direction. Spin minus x is 1 over square root of 2, spin up minus spin down in the z direction. So they're just related to each other.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And what it means is if you measure a spin in the up direction and you get up, so in the z-direction I should say, and you get up, you instantly know its wave function in the x-direction and you instantly know that it's maximally uncertain.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You instantly know that it is 1 over the square root of 2 plus x plus 1 over the square root of 2 minus x. So 50-50 chance if you were to measure in the x-direction to get either spin left or spin right. Shane Blazier says, I just watched Meta, aka what used to be called Facebook, reveal their prototype augmented reality glass, and they look really interesting.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
In particular, do you see in Dr. Han's work any insights regarding the optimal balance and interplay between top-down and bottom-up approaches to the regulation of rapidly evolving high-impact technologies, both within and across organizations and jurisdictions? I do think that these kinds of considerations are super important in exactly this area. I'm not
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
It seems clear to me that this type of device will become mainstream by allowing us to be remotely present with loved ones. interact with virtual screens without looking at a phone, and more naturally interact with AI. I'm curious if you have any thoughts on this new product category, specifically how it may improve science communication with things like interactable 3D content.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You know, my track record for predicting the adoption of technology is not especially good. I don't think you should give especially high credence to my opinions here. I'm a little skeptical on the glasses, OK? The glasses, you know, you have to take into account human beings, human beings. Many of them, a majority of them, I don't know, don't like wearing glasses.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I used to wear glasses when I was a kid, and then I got contact lenses, and eventually I got LASIK, because it's just more convenient not to have to put glasses on. And I spend a lot of my day looking at a screen. Here I am right now reading questions off of my laptop, okay? But I want to separate that from my everyday life. I don't want to be looking at screens all the time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I absolutely see the benefits that could happen from wearing these glasses and having them augmented, augmented vision and AI or not AI. And they absolutely have attractive looking use cases. But I don't actually, if I had to guess, I would say 100 years from now, you're not going to see greater than 50% of Americans wearing glasses. augmented reality glasses all the time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I do still have a soft spot for virtual reality more generally. You don't even need the whole headset. You can just do it on your computer screen, right? Video games, in a very real sense, are that. Well, immersive video games are that. And I can very easily imagine... We get much more realistic things to replace Zoom meetings or things like that, where you have some virtual reality kind of thing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Jennifer used to run a lecture series in Second Life. She would interview people. I think this was affiliated with someone. Who was it affiliated with? I'm forgetting now. But she would interview people in Second Life, which was an early VR platform. I think it's still out there. People would have their avatars and everything, and they'd sit down in a fake room,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
in a virtual auditorium and people could come in and listen and so forth. And it was a lot of fun. It didn't quite catch on because it was clunky, but I can imagine something like that happening. But that's a step away from having it be glued to your face all the time or most of the time. That's my personal prediction.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Beau Parizeau says, how would you explain why neutrons, the one massively electrically non-interacting particle we know about for sure, are not a candidate for dark matter? Plenty of reasons. So this is actually a very simple question to answer.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I'm happy to answer it, but I wanted to answer it even though many other people could do so because it's a good excuse for driving home the kind of constraints cosmologists have to deal with. when it comes to inventing candidates for dark matter. It's not an anything-goes kind of situation. The very simple reason why neutrons can't be dark matter is because they're not stable.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
They decay away in a matter of minutes. Dark matter has been there for 14 billion years, so neutrons do not qualify. There you go. That's the simple answer. But the thing is, that's not the only answer. That's not the only reason why it doesn't work. Another reason is that neutrons are strongly interacting. They affect each other very much.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
That means that their dynamics in a galaxy or something like that would be different than that of dark matter particles. Even though they're electrically neutral, they can bump into atoms. They can even bump into photons because they're made of charged quarks inside. So they're not completely transparent like we want a good dark matter particle to be.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
They would fit into what is called strongly interacting dark matter, which was—it had a moment for a while where people were thinking about it, but I think overall it doesn't fit the data quite as well. And finally, most importantly, when you do find a stable, electrically neutral, non-interacting particle out there, you have to get the right abundance of it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
specifically, personally, an expert on how best to alleviate harms and governing emerging technologies that are intrinsically complex. But I do think that exactly, this is one of exactly the motivations for thinking of complexity as a field of study. For thinking of robust universal principles that are recognizable between different kinds of complex structures.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
We think that there's about five times as much dark matter as ordinary matter in the universe by energy budget. So you need a theory for the production of those particles that gets you the right abundance. And that's often the hardest thing to do. I mean, neutrons, if there was an equal number of neutrons and antineutrons, they would have just decayed away a long time ago.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
There would not be nearly enough of them to be the dark matter. So anyway, lots of reasons, lots of things that cosmologists know about the universe make neutrons not a good candidate and reemphasize how difficult it is to find a good candidate.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Wes Payne says, in your excellent mini lecture on tensors at the end of the July 2024 AMA, you mentioned the polarizing effects that gravitation by Mr. Thorne and Wheeler has on students. This is a textbook, a famous book by Mr. Thorne and Wheeler. I'm just wondering, what do you think of it? Did you fall in love forever, toss the book out and never read it again or something else?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
I would say something else. You know, I first came across Mr. Thornton Wheeler as an undergrad where I didn't know a lot of GR, but I wanted to. And so I did take a look at it. It didn't teach me GR. Let's put it that way. It did ruin at least one book bag that I had, one backpack. It was so heavy that my cheapo backpack fell apart carrying Mr. Thornton Wheeler around campus.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But, you know, it is a style, and it's an intimidating style. So I think that it could possibly be used as a textbook for teaching with a professor who told you exactly which parts of it to read. You know, it's 1,000-plus pages. Just reading from the start, you would be tearing your hair out before you ever got to Einstein's equation, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Stylistically, in addition to being long, you know, it has a very— a very noticeable style that warms the hearts of some people and throws others off. And I'm in between. You know, I get the style. I appreciate the style, just like I get Steven Weinberg's style and I get Bob Wald's style. These are all different styles. They all serve a purpose.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
And, you know, there's a reason why I wrote a general relativity textbook myself. It's because I don't think that any of these styles, for me, would have been a good way to learn general relativity for the first time. They're all, you know, look, Misner and Thorne and Wheeler and Weinberg and Wald all know better about general relativity than I ever will.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But they all have such an idiosyncratic way of thinking about it that it doesn't sort of serve the common purpose. They're better for research reference books than for textbooks. So I actually decided to write a book that was –
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
purely devoted to being a pedagogical treatise, to teach people general relativity in a way that also didn't make any quirky assumptions about what is too hard or what is too easy. I'm like, I'm going to tell you what you need to know, not too much about what you don't need to know. I'm going to tell it to you straight. I'm not going to hide the hard parts, but I will try to make it clear.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
That was the philosophy behind my book, and I don't think that any of these other books did that very well, so that's why I did it. Anyway, that was not your question, but I hope that answers the spirit of your question. Arnie says, I don't know if the odds are 1 billion to 1 or 1 trillion to 1, but why not utilize cryonics? All you've got to lose is money. Am I being ridiculous?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So I presume that you mean why not have your body frozen after you're dead to maybe be revitalized sometime in the future. So one thing is I think the odds are much lower than 1 trillion to 1. I think that pretty clearly with the current state of the art, after you're dead, you're dead. And cryonics does not preserve you in any sensible way. You're losing money. Yes, you are losing money.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You're dead, so you don't care. But maybe that money could be put to other uses other than a scam company that is pretending to keep your body frozen for a long time. So I don't think you're being ridiculous. You know, I get the calculation. If there's some chance that they will be able to revive you down the road, that would be an awfully good reward.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
But I don't think the chance is non-negligible enough to make it worth considering. Edward A. Morris says, Would you be skeptical of this conclusion, or would you take it as an unsurprising confirmation of the Everettian view that since individual mutations can be caused by quantum events with non-zero weights in the wave function, the conjunction was guaranteed to happen in some branch?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
Because when you have a new technology, we also talked, we hit on this quite substantially in the episode with Daron Asimoglu. When you have a new technology, you can't really predict what's going to happen. what exactly it's going to bring about, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
No, I would be skeptical of that conclusion because there's no guarantee that The exact way that human beings are needs to exist in any branch of the Everettian wave function, right? Or the selection effect, if there's some kind of anthropic selection that we're only going to find ourselves in branches where human life can exist.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
You need to be exactly clear about what you mean by human life, etc. I'm not very firm on this, so don't take me completely solidly here. As I said before, I think I should have ordered these questions better. But as I think we're going to get to later in the AMA, I don't think we understand how to use the anthropic principle exactly well.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | October 2024
So in cases like this, I don't think that my answers are very firm. But I think that as a methodological matter, appealing to unlikely branches of the wave function should literally be your last resort. You know, the Bayesian prior on that one is very, very small in my mind. There's almost always going to be a larger prior for there's some reason for this, we just haven't figured it out yet.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Hello, everyone. Welcome to the Mindscape Podcast. I'm your host, Sean Carroll. Welcome to a new year by the conventional calendar, of course, 2025, but also this first podcast episode of 2025 is episode 300. And looking back on previous episodes that ended with 00, that is to say 100 and 200, I did some solo episode of some sort to celebrate the little milestone.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And, of course, Patreon supporters get ad-free versions of the podcast. They get to ask questions for the AMAs and occasional other benefits, like I asked them what solo episode should I do. And I did have some ideas, and I took suggestions also. And the idea that I had that eventually won out by the vote, and I think it's a perfectly good one, is, is time real?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And what's super important about that is that we don't know the final answer yet. So going beyond the theory we have right now actually matters. And therefore, stances you take towards different existing things in the universe might suggest different ways of going forward. So in the post-Newtonian world, it at least makes sense to think of time in a different way than we thought of it before.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
You know, before we thought of time as playing some role in the reality of the universe, right? The universe evolves with time. That's the most fundamental thing about the universe. If there were no time evolution, if the it's almost as if the universe is not something you could talk about, right? The universe wouldn't have any sensible thing to say because you say, well, you look at something.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Well, you look at looking as something that unfolds in time, isn't it? You didn't look before, now you're looking. So we're so embedded in the evolution of time that it's necessary somehow to how we talk about and how we conceptualize the universe, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
The shift then is from thinking of time as something that really has to do with the unfolding of reality to time which is more like a coordinate, a label, a way of finding out where you are, specifying where you are in this four-dimensional reality. And so this raises a new question that didn't exist before, and some of you longtime listeners will know where I'm going here.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
The arrow of time, the directionality of time becomes important. The arrow of time was not an issue for Aristotle or for pre-Newtonian thinkers in general, and it took quite a while for post-Newtonian thinkers. thinkers to realize that it was an issue.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
I believe that the phrase the arrow of time is due to Arthur Eddington, who is a 20th century physicist and astronomer, astrophysicist, mathematical astrophysicist, let's put it that way, because Newton's laws, these wonderful rules that govern the rigid motion of the universe, the evolution of the universe over time, don't pick out a direction. to time, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And this is one of the reasons why in the 19th century there was so much struggle to come to grips with the second law of thermodynamics, which does have an arrow of time built in. The second law says that entropy doesn't decrease with time. It either increases or remains constant in closed, isolated systems. That clearly distinguishes between the past and future.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Entropy was lower in the past, will be higher in the future. That makes a difference between the past and future, even though the underlying Newtonian laws don't. So how do you reconcile those two facts? This is a new problem. It's a problem that didn't exist before Newton's equations came along. I'm not going to dwell that much on the arrow of time here.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Some of you who are not old, old-time listeners might not know that I wrote a whole book about the subject. My first trade book was called From Eternity to Here, The Quest for the Ultimate Theory of Time. So I talk about the arrow of time, cosmology, presentism, eternalism, time travel, all of those things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
I'll give you the very short version right now because it will actually become relevant later on because today we're interested in is time itself fundamental, not why does time have an arrow. Maybe these questions are not disentanglable, right? Maybe they have something to do with each other. So entropy is defined by Ludwig Boltzmann in the following way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
He says you look at a system, either you literally look at it or you imagine knowing something about it, and you get incomplete information. If you think that some system is actually made of atoms but you don't personally see the atoms … You see, oh, I have a table. It has a certain size and mass and things like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
There could be many, many different arrangements of the atoms that look like that table or whatever other macroscopic system you're looking at. And the entropy is a way of counting how many ways there are to organize or arrange the microscopic constituents into the macroscopic thing you're looking at.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Now, just to not keep you in suspense, yes, the answer is yes, time is real. But there are people in modern physics and philosophy who question whether time is real. In fact, I once wrote a paper almost as a joke, but I mean, the title was a joke. The paper was not a joke, I don't like to think, but the title was, What If Time Really Exists?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
When the entropy is low, that means that the macroscopic information you have is enough to pretty much pin down what the microscopic arrangement is. There aren't that many ways to arrange the underlying atoms. Like if you have all the air in the room around you, but you knew that all the air, for whatever reason,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
was confined to a cubic centimeter over there in the corner and it was vacuumed everywhere else, that is a low entropy configuration. You know a lot about where the atoms are. I just told you. Whereas if I tell you that the air is uniformly spread throughout the room, that doesn't tell you a lot about the individual atoms. Individual atoms could be here or there.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
There's many different ways to arrange them. to make the whole thing look uniform overall. So that's high entropy. And the second law says the universe starts with low entropy and it gets larger as time goes on. That is an arrow of time. There's a huge question for cosmology, which is why did the universe start with low entropy? That's going to be a question that cosmologists should keep in mind.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
We're not going to primarily worry about that right here and right now. Now there's a big leap that can be made, and I am in favor of making it, which is the following. The laws of physics at the microscopic level, as far as we know them, do not have an arrow of time. The macroscopic world has an arrow of time. In fact, it has... apparently various different arrows of time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
There are various different ways in which the past and future are distinguishable from each other. Most obviously, you remember the past. You have records of it. You predict the future. And in fact, you can affect the future by the choices that you make right here in ways that you cannot affect the past by the choices you make right here and right now.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So those are two arrows, the arrow of memory or recording, the arrow of causality and influence. There's also the psychological arrow of time. There's an aging arrow of time, et cetera. The big claim that I'm going to endorse is that all of these arrows of time are basically just different manifestations of what we call the thermodynamic. arrow of time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
The thermodynamic arrow is just the fact that entropy tends to increase over time. So there's a huge amount of work to be done by scientists and philosophers to understand whether or not that claim is correct and to understand why entropy increasing has anything to do with things like why we're all born young and then grow older, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And I think it can be done, but it's an amount of work to be done, not going to do it actually today. I talk a little bit about it in From Eternity to Here and elsewhere. It's something I'm fascinated by in many deep ways. But for our present purposes, let's just take it on board. The reason why there's an apparent arrow of time is because entropy is increasing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So the reason why you have a feeling that you're moving through time is because entropy is increasing. You can kind of see if you squint— If you're not too hardcore about it, you can imagine why that would be true. Why do you have memories of the past and not the future? Well, the entropy was lower in the past.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
That means that we know that in the early universe there were fewer possible configurations of the underlying stuff the universe is made out of. Therefore, you can use information in the present universe to draw conclusions about the path you took.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
to get from the past to here in ways that it's not possible to do with the future because there's no future boundary condition of either high or low entropy that anyone really knows about. And given that memory aspect, you can also imagine understanding the causal aspect. Because we have memories and records of the past, we can't change them.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
because it has become so common in physics to not only say, well, maybe time is not fundamental, maybe time isn't even real, maybe it's an illusion, but to also pat yourself on the back for thinking this is a profound thought, even though many, many other people have already had this thought also. I don't think time is an illusion. I think it is absolutely real. It might not be fundamental.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
We think that we can actually infer what did happen in the past. But because we can't do that toward the future, we can imagine different possible actions that I take right now having different possible consequences in the future.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So psychologically, you're always carrying with you not only who you are in the here and now, but a memory of who you were just a moment ago, and also a set of possible people you can be in the future. And those are different, right? There's an imbalance there because of the arrow of time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And so that's what gives you the feeling of moving through time or of, if you want to put it that way, time moving you along. It's because you're constantly updating. your impression of who you were, and your guesses about who you're going to be next in this asymmetric way. Obviously, there's a lot more to be said about that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
We've said a little bit before in the podcast, you know, the conversation we had with Janan Ismail talked about that and others. Dean Buonomano, it's a rich, rich subject. Okay. Not what we're talking about today. We want to talk today about... time itself, not the arrow of time, right? Two separate things, very, very important.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
When I say that entropy underlies the arrow of time, sometimes people like mangle some words together and claim that I'm saying that entropy is time or something like that, right? Entropy explains the arrow of time, which is a feature that time has. It doesn't explain time itself. Time is a thing in the Newtonian view, which is more or less inherited by subsequent theories.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Time is a label, a coordinate, et cetera. There's some updates there, as we'll talk about in a second. But time could exist without an arrow, right? There's a fact about our observed universe that time has an arrow, but you can still talk about time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
time and time evolution and things like that even if the arrow didn't exist if you just have a pendulum swinging back and forth in a frictionless universe so it swings back and forth forever time is passing the pendulum is changing but there's no arrow if you took a movie of that and you played it backward it would look perfectly sensible there's no difference between the evolution toward the past or toward the future
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So it's that that we're trying to think about now, the actual existence of time itself, not the fact that it has an arrow. Anyway, two things do come along in the 20th century that kind of are relevant to this question, relativity and quantum mechanics. You shouldn't be surprised that both relativity and quantum mechanics have something to say about the fundamental nature of time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Obviously, relativity. has a lot to say about the fundamental nature of time. It's what says that time is not universal, right? In Newton's world, the existence of space and the existence of time were separately given to us. In Einstein's world, all we're given is four-dimensional space-time, and how we divide that up into space and time is up to us to some extent.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Now, in special relativity that comes along in 1905, space-time itself is still flat. Minkowski space, there's no gravity. There is only one actual space-time that you're supposed to be thinking about. And so there's a set of different ways to divide it up that are all different but all kind of natural. This is what we mean when we talk about reference frames in special relativity.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
You know, when you have just a piece of paper and you're doing two-dimensional spatial Euclidean geometry, there's a natural set of coordinates you can use, Cartesian coordinates. You draw perpendicular axes. You label them x and y. Now, you could rotate them or label the origin or whatever, but perpendicular Cartesian coordinates are natural things to use when you have a flat piece of paper.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
As we've often stressed on the podcast, one should think of things that are emergent as nevertheless real. You know, the table in front of me is real, even though there are no tables in the standard model of particle physics. The idea of a table is an approximate higher level description that has a lot of causal and explanatory power. Maybe time is like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Likewise, in flat Minkowski special relativity spacetime, there's a natural set of ways to divide spacetime into space and time. Different observers will do it differently, but for each observer, there's a natural way to do it. Inertial frames, global reference frames, whatever you want to call them. When general relativity comes along 10 years later in 1915,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Now you're saying that spacetime is curved and it's curved in wild ways. It's curved in ways that can change arbitrarily from point to point – not arbitrarily but by a lot from point to point, from moment to moment. And now this was also true in special relativity but you didn't care as much.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Now in general relativity, you cannot help but face up to the fact that you could slice space-time in an infinite number of ways into space and time. Sometimes in general relativity, people talk about many-fingered time. I think this is a Wheelerism. I think this goes back to John Wheeler, but I'm not exactly sure. It could have been somebody else.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
The point being that if you take the universe in general relativity and you take a slice, a slice through the universe that you label, here's what I'm going to call one moment in time. And you say, all right, how do I march it forward in time? You are allowed, in general relativity, to march it forward faster in some places than others.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Many fingers is the different rates at which time is moving, in some sense, according to your coordinate system, which is entirely arbitrary. Clocks, physical clocks that actually measure time always measure one second per second.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
But in general relativity, since there is no natural coordinate system that everyone can agree on, the freedom to choose how you measure space and time is in your face, and therefore you can choose whatever coordinates you want. No one can blame you, right? Certain coordinates might be more convenient than others, but you're allowed to do whatever you want.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So in general relativity, the freedom to divide space-time into space and time is quite unmissable. You cannot help but talk about it. And you know what? Honestly, I'm going to say that doesn't have any huge ramifications for the fundamental nature of time. other than the very, very huge ramification that time is part of space-time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
But in terms of time being a label, being a coordinate, being part of the fundamental description of reality, it's still all there. I mean, you would say it's really space-time, not time, but other than that little update, the basic way of thinking that you inherited from classical mechanics still works pretty well. Now, let's be honest.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
If it weren't for quantum mechanics, I wouldn't be saying that. I'd be saying that the relativity revolution was absolutely huge— It was conceptually very, very important to how we think about reality, etc., etc. But as much as I love relativity, in terms of the amount of conceptual updating you need to do, relativity is nothing compared to quantum mechanics. So it's still a classical theory.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
You need to improve your way of thinking a little bit. But many of the basic ideas that you inherited from Isaac Newton can just be translated and you can still use them in relativity. The notion of time, the nature of time itself, goes through more or less unchanged. Not everyone agrees about that. I think they should agree.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
But famously, people like Julian Barber, a physicist, wants to say that general relativity changes our notion of time so much that time is an illusion, really, in general relativity. As I said before, I'm not sympathetic to that point of view. I'm not going to explicate here why he says that or why he shouldn't say that, but putting it on the table, he wrote a book.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
You're welcome to read the book about that. That's not where we're going right here. We're going into quantum mechanics because, of course, we are. Quantum mechanics is where it gets tricky, the notion of what time is. It needn't get tricky, but where it's really, really going to get tricky is where we try to marry together quantum mechanics with gravity to do quantum gravity.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
But sometimes people want to label things that are just emergent as illusions or somehow not real, right? This becomes much more popular in the popular imagination when it comes to things like consciousness or free will or what have you. They want to say, well, it's just an illusion. It's not what you think it is. To me, you know, look, who cares about the definitions, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
You know, sometimes people will say, well, wait a minute, we don't understand quantum gravity. How can we say anything about quantum gravity? It's true. We don't fully understand quantum gravity, but we understand a lot about quantum mechanics and we understand a lot about gravity. So there's a lot that we expect to be true.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
about quantum gravity, and either it is, and we should try to understand it, or the reality of the situation is even more profound, and we need to try to understand that. So I think it does absolutely pay off to try to think about how the combined implications of quantum mechanics and general relativity tell us something new and interesting about the nature of time. Okay.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So at the most fundamental level, You probably know, you know, I've talked about this a lot before. So quantum mechanics is tricky because you need to not only say, oh, there's a wave function and it evolves with time, but you also need some rules for what happens when you measure the wave function. It collapses, there's probabilities, et cetera, et cetera.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
I'm going to advocate something like the many worlds approach where that collapse of the wave function is only apparent because observers live on different branches of the wave function. They don't see the whole thing. Other people will advocate different points of view. I'm, again, not interested in that particular conundrum right now. I will just put on the table it is easiest for me to talk.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
for the rest of this episode as if Many Worlds is true, not because of the worlds. You know, I don't know how often I've said this, but I do want to emphasize I don't care about the worlds in Many Worlds. I mean, they're there. I think that it makes absolute perfect sense to believe that they exist and to think about them. But that's not why I believe in it or don't believe in it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
It's just a prediction of the Schrodinger equation and the formalism of quantum mechanics. And I take that the lesson of Everett to be that if you properly interpret what the wave function is, it can just obey the Schrodinger equation and it fits all the data.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
OK, so that's where I go from for many worlds is that it fits all the data without adding anything to either the ontology of the theory or the dynamics of the Schrodinger equation. So we'll talk that language. We'll talk the language that what quantum mechanics is is some quantum state evolving with time according to the Schrodinger equation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Now, when you say the words of Schrodinger equation, you have to be a little bit careful here because sometimes people think that means literally the equation that Schrodinger first wrote down in 1925 or 1926, which is now sometimes called the non-relativistic Schrodinger equation. So Schrodinger was literally interested in the wave function of an electron in an atom.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
or something like that, right? He knew about relativity. As my old quantum field theory professor, Sidney Coleman, liked to say, Schrodinger was no dummy. And he actually invented a relativistic version of his equation first, but it didn't fit the data. It didn't work. You needed to be a little bit more clever than they were at the time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
You can call it that if you want as long as you're clear about what you mean. I think it's a bad choice, though, if you want to actually get across to people what it is you're trying to say. You know, I disagreed with Dan Dennett about this. He said he's an illusionist about consciousness. I said, does that mean you think consciousness is an illusion? He said, no, of course not.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So the non-relativistic version that he came up with worked better in the non-relativistic regime. So that's what we know as the Schrodinger equation. Of course, today we know you can also have a relativistic version of the Schrodinger equation, and there's complications involved with quantum field theory, etc. But that's not where we're going today either.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Basically, all I want to do is to say that the Schrodinger equation, as far as time is concerned— isn't that different from Newtonian physics, right? It's a nicer equation in many ways. The technical reason that it's nicer is because it is linear. What does that mean?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
That means that the fundamental thing that is evolving over time, according to the Schrodinger equation, is the wave function or the quantum state. For today's purposes, you can call either one. You can use either terminology to... to talk about the state of a quantum mechanical system.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So the wave function for a single particle is just a complex number at every possible position it could have, and you square that number to get the probability of observing it there.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
For more complicated things with many particles or many fields or whatever, you assign a complex number to every possible configuration of all those different things, and you square that to say what would the configuration look like probably if you were to observe it. Or you could just more abstractly talk about a vector in Hilbert space.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
There's all sorts of different mathematically equivalent ways of talking about the quantum state of a system. But it's precisely analogous in this way of thinking to the classical state of the system. The classical state of a system is the position and velocity of every object, every constituent of whatever system you have, and it tells you everything you need to know.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Likewise, the quantum state tells you everything you need to know. The crucial difference is you can't measure. quantum state without disturbing it. So that's a whole thing to go into. Maybe some other, I think I have gone into that, right, in previous podcasts, previous solo episodes. Okay. But the linearity is what I'm trying to get to here of the Schrodinger equation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
The linearity means that you can think of the Schrodinger equation as a box. You feed into the box the current state of of the quantum system, the wave function or whatever you want to call it, and the Schrodinger equation spits out the rate of change of that quantum state, okay? It's a way of saying, given what the state is, how fast is the state changing?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And the relationship, that function, you give me the state, I tell you how fast it's changing, is linear. If you gave me two states and you added them together and you plugged into the function, it would give you the sum of the two different changes, okay? This reflects the fact that the quantum state is a vector.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
You can add states together in ways that you can't add classical states together, okay? If I have a classical system of two particles—no, forget that. Let me say one particle, okay? Let me imagine I have one particle. And so I have one particle in three-dimensional space. The classical state of that particle gives me its position and its momentum or its velocity.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
I just think it means that it's not what you think it is. And I just think that it's a very bad marketing strategy to call that illusionism about consciousness. Because an illusion has the connotation, the word illusion, of being a fake, being something that isn't really happening.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
If I take two different possible states of a classical particle, okay, so two different instances of here's the position, here's the velocity, it doesn't mean anything to add them together. I can't add together two different positions of particles.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
You might think, well, I could just draw axes and make little vectors and add them together, but the resultant vector would entirely depend on where I put the origin of my coordinates. Points in space do not naturally have a vector structure. You cannot add two points together in space.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
This is a deep, deep, super important, frankly, underappreciated feature of quantum mechanics, that when you have two wave functions, you can add them together. You can scale them by real numbers. They have all the properties of vectors. And the reason why that makes sense is because the Schrodinger equation is linear. If you have one
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
quantum state evolving over time and you have another quantum state evolving over time, they both solve the Schrodinger equation individually, then the sum of those two quantum states also solves the Schrodinger equation. This is a wonderful feature that we will take advantage of in just a second.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
But for the moment, all I care about is what the Schrodinger equation is telling you is something very, very analogous to what Newton's laws of motion are telling you. Newton's laws say you give me the classical state of the system, I will tell you how it changes in time. The Schrodinger equation says you give me the wave function of a system, I will tell you how it changes in time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
There's no difference between those two things. But this linearity... honestly makes things much easier. So Newtonian mechanics is not necessarily linear. You might have one particle being affected by all sorts of other particles in all sorts of complicated ways, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
The Schrodinger equation has less freedom in what can happen because it's this linear system, which means it's very, very restricted in what can happen. Let me just pause as an aside here. You've heard about chaos theory, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Chaos theory says that if I have two different possible states a system can be in that are almost the same but a little bit different, then they can evolve in ways that are very, very different. You can step on a butterfly and completely change the weather patterns a month later. Tiny perturbations of initial conditions can lead to huge differences later.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
One practically synonym for chaos theory is nonlinear dynamics. Because the whole point of chaos theory is those tiny little initial differences can be amplified. They can grow bigger. That's what chaos theory is all about. That's a feature of nonlinearities. Nonlinearities let you amplify tiny little changes.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
When a magician saws a person in half in the box and it looks like that is what is really happening, the reason why that's an illusion is because nobody actually did get sawed in half. It's not just there's an emergent sawing in half. It's like no one really got sawed in half at all. It's just fake.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
But linear systems, which are much simpler, have the feature that tiny initial differences become tiny later differences. The differences don't grow exponentially or anything like that. There is no chaos in the evolution of a quantum mechanical wave function.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Quantum chaos, which is a topic that people talk about, absolutely exists, but it only appears in the classical limit of the quantum mechanical evolution. The Schrodinger equation itself doesn't have any chaos in it. Okay. Why am I telling you this?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Well, because there is a feature of classical dynamics, especially when you think of general relativity as an example of classical dynamics, that is kind of important to the nature of time, which is that in classical mechanics, time can end. you can hit something called a singularity, right? In general relativity, for example, the universe could collapse in the future.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
We don't think it will, but maybe it will. We used to think that it was quite plausible. Now it's less plausible. Now we know that the universe is accelerating, but it still could happen. The future is hard to predict, part of the arrow of time, right? So...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
If you just follow the equations of Einstein's general theory of relativity, you could reach a moment of time in which the theory breaks down. in which the physical quantities representing reality become infinitely big and the equations stop making sense. That's what a singularity is. And so time itself can end. It's a boundary to space-time and therefore to time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And singularities are not actually these rare things that it's hard to make in general relativity. They're kind of generic. There seems to be a singularity in our past if you believe what general relativity is telling you. You shouldn't believe what general relativity is telling you, of course, because general relativity is a classical theory. But that's my point.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
I mean, it's a pretty big milestone. We have a lot more than 300 episodes because many episodes don't get numbers. The AMAs don't get numbers. Holiday messages don't get numbers, special episodes, et cetera. But still, having 300 even numbered episodes is pretty darn good. We've been doing it for a while, longer than I might have guessed at the very beginning.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
In classical theories like general relativity, it would make perfect sense to talk about the beginning of time or the end of time because you can reach singularities. If you look at quantum mechanics, as given to you by the Schrodinger equation, time cannot end. The Schrodinger equation says time keeps marching on, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
I once cheekily labeled this fact the quantum eternity theorem because, well, it's a long story, but I did this in the context of my debate with William Lane Craig. But the point is, if all you knew about the universe was the Schrodinger equation and there was any time evolution at all, okay? So you picked an initial condition that would change over time, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And I don't think that that's what's going on with consciousness or free will or time for that matter. But there's still plenty of good questions, forgetting about the nomenclature, whatever we're going to call it, plenty of good questions about the fundamental nature of time. Is it fundamental or is it emergent?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Then it's easy to prove that it changes forever into the future and it was changing forever into the past. That's the quantum eternity theorem. There are no singularities in the Schrodinger evolution of a wave function because everything is linear. There's no way for things to blow up and become infinite. It's a theorem, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
If you talk to people, even very, very good professional physicists out there, they won't always say those words. They won't always agree with what I just said. They should agree, but, you know, you have to be very, very clear about what assumptions you're working with because we're sort of casually introducing the idea that someday we will include gravity into our quantum theory.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So what I said was 100% absolutely correct. If you believe that some version of the Schrodinger equation is correct— and you believe that the universe is evolving in time at all, then the Schrodinger equation predicts it will evolve forever to the past and to the future. But if you instead start with some classical picture and imagine quantizing it,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
then you can get yourself into the belief state where you think your classical variables are representing singularities. They can't if you think purely quantum mechanically. But of course, since we don't perfectly well understand quantum gravity, anything is possible. right? So there's a theorem that if the Schrodinger equation is true, time evolution happens forever.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
If it happens at all, it happens forever. But maybe the Schrodinger equation or even a relativistic version of it is not true. Maybe quantum gravity needs something beyond that, okay? Those are all on the table because we don't fully understand quantum gravity. That's fine.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Nevertheless, since we do understand the Schrodinger equation, even if we don't understand quantum gravity, and remember, the Schrodinger equation in its, I say remember, that's a bad habit that physicists have, telling people to remember things they might never have heard before. So let me back up.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Schrodinger equation, you do remember because I already said it, the Schrodinger equation is just the quantum version of Newton's laws of motion, okay? So it doesn't matter what the system is.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
All different systems have a version of the Schrodinger equation, just like all different systems for F equals ma, Newton's second law of motion, all different systems have some specification of what are the forces, what are the masses, and then you do the math. Likewise, for the quantum mechanical version, Every system has some version of the Schrodinger equation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
You know, that box, you give me the state, I tell you how fast it's changing. The way that that is accomplished, according to the Schrodinger equation, is by calculating what is called the Hamiltonian of the system. So you giving me the Hamiltonian in quantum mechanics is exactly analogous to you telling me what forces there are in classical mechanics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Because when you have a table in front of you or when you have the air molecules in this room and you say, I have a higher level emergent description… you know what the microscopic description is, right? There's some full microscopic description in terms of atoms or molecules or quantum fields or what have you. And you can talk about how the higher level emergent thing is related to that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
If I know the Hamiltonian, which is basically a way of thinking about the energy contained in the quantum state, the Schrodinger equation tells me how fast it will evolve, okay? So even though Schrodinger himself was interested in electrons in atoms, there is a version of the Schrodinger equation for every system we can think of in conventional quantum mechanics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
For systems with many particles, for quantum field theories, there's a version of the Schrodinger equation because there's a version of the Hamiltonian equation. You can have versions of the Schrodinger equation representing perfectly relativistic Lorentz invariant dynamics, okay? The Schrodinger equation has a time variable in it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
It tells you how the system is changing with time, and therefore people think, well, it can't be compatible with relativity because relativity says I can choose different time variables. That's fine. There's no actual incompatibility there. The Schrodinger equation is just saying, yes, you can pick different time variables, so pick one, and then I will tell you how the system evolves with time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So you pick a time variable. The Schrodinger equation says, here's the Hamiltonian and the state variables. with respect to that time variable, I will tell you how it evolves with respect to that time variable. So I'm just emphasizing here that talking about the Schrodinger equation is in no way a restriction.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
It's a perfectly general idea whether you're single particles, quantum fields, gravity, whatever it is. No current version of physics has some improvement to the Schrodinger equation that it needs to contemplate. Maybe there will be someday. That's always possible. But the Schrodinger equation is the state of the art right now in terms of quantum dynamics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And people, in fact, have thought about improving the Schrodinger equation. I don't think they've actually succeeded, but people definitely thought about it. So anyway, where does that put us?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
In quantum mechanics, if all we're caring about is the Schrodinger equation and quantum states, that is the many worlds perspective, even though I don't care about the worlds, like I said, it's just the perspective that says that's all there is to quantum mechanics, states and the Schrodinger equation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
All we need to know is what is the state, what is the Hamiltonian that makes it go, and then we can do it, okay? And because of this feature, that time lasts forever, once you have Schrodinger evolution, you have two options to what can happen to the quantum state over very, very, very long periods of time. The two options were it eventually comes back to where it started, or it doesn't.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Those are the two options. And this is also, because the Schrodinger equation isn't that different from classical mechanics, this is also a feature of classical mechanics. This is something called the Poincaré recurrence theorem.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Henri Poincaré, mathematician and physicist from contemporaneous with Einstein, did a lot of work that was very relevant to relativity, but also practically invented chaos theory, arguably, did a lot of work in classical mechanics. Generally, And Poincaré was thinking about the solar system, where you have a bunch of planets orbiting the Sun. And forget about the fact that the Sun itself can move.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
If you're telling me that time is emergent, What is it emerging from? What is the more fundamental thing? What is the microscopic theory? What is the nature of this thing we call time? Why does it exist? Is that even a question that we have any right to ask or any hope of an answer for? So that's what I want to talk about today.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Fix the Sun as if it were infinitely massive. Let all the planets go around it. The planets go around at different rates, right? Mercury's year is shorter than the Earth's year, which is shorter than Saturn's year, etc. So from moment to moment, you can look at the positions of the planets. They'll all be different relative to each other.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And one question you can ask is, if they're in a certain configuration relative to each other now, will all the planets return to the same configuration sometime in the future? You know, one Earth year later, they certainly won't because Mercury will have gone around several times and Saturn will not even have gone around once. But can you wait long enough so they all line up once again?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And a moment's thought tells you, yes, that should eventually happen, basically because there's only a finite number of choices, right? It's an infinite number of choices for where the planets can be because they move on smooth trajectories. We're talking about classical mechanics now. But it's a bounded set of trajectories, right? Every planet is moving on an ellipse, OK?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
We're also ignoring the influences from one planet to another. So they're moving on perfect ellipses like Kepler would have liked, OK? So the planets are moving on ellipses. They just do the same ellipse over and over and over again, even if their different orbital periods might be incommensurable. In other words, one orbit is not some integer multiple of the other.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Poincaré was able to show that because, you know, there might be irrational numbers relating the orbital periods of the different planets. So being a clever mathematician, he said, what I really care about is not will they line up exactly where they started. But if you give me a tiny number epsilon, will all the planets line up to within epsilon of where they started?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And will that be true no matter how tiny you made your number epsilon? And what he's able to show is yes, indeed. For a very, very tiny number epsilon, the planets will line up in exactly the same configuration within a precision of epsilon eventually in the future. basically because their orbits are bounded. There's not that many places they can go. This is called the Poincaré recurrence theorem.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
I believe, although I'm not 100% sure, that the Poincaré recurrence theorem came after Friedrich Nietzsche started talking about a universe that eternally recurred. Nietzsche did talk about that, but he talked about it for different reasons. I used to know this. It's in From Eternity to Here. If you read that book, the stories are in there and in the correct chronological order. Okay.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So under certain circumstances, a classical mechanical system will evolve for a long time and it will return to where it started. It might take a very long time. Poincaré showed that typically it takes a very long time. That's absolutely going to be true, but it will eventually happen. You will return again and again and again infinitely often to where you started.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
However, what if you have a comet? What if you have a comet that is not on a bound orbit, right? A comet that is not on an ellipse, but on a hyperbolic orbit that is just zooming into the solar system, passing by and then zooming back out. That case does not recur. If you include the comet in your coordinates that are telling you what the solar system looks like,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
There are absolutely indications in fundamental physics that time is not fundamental, but it's very, very uncertain. So, you know, the good news is the short answer to does time exist is yes, it does. Okay, but if it's emergent, what is emergent from? That we don't know. We don't know whether time is fundamental or emergent. If it is emergent, we don't know how that works.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
the comet doesn't recur all by itself. It just goes from minus infinity to infinity. It never is in the same place twice, okay? So that's obviously an apparent exception to the Poincare recurrence theorem. What's going on? What's going on is that the space of states is not bounded, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So Poincaré, again, being a careful mathematician, showed that if you have a bounded phase space, a bounded space of states, under the rules of classical mechanics, you will eventually recur. But if you have an unbounded phase space, then you don't necessarily recur. So an unbound orbit, like a comet moving on a hyperbolic trajectory, the system will not return to where it started again.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Why am I telling you this? Well, because the same thing is all true. All the same things are true in quantum mechanics if the Schrodinger equation is telling you all that is going on. You can have either recurrent evolution of the quantum state or non-recurrent evolution. Does the state eventually come back to where it started? Or does it wander off into ever different states?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
places, configurations, whatever you want to call them, toward the infinite past and the infinite future. And in fact, you can figure out fairly simply, just like in classical mechanics, the question is, is phase space bounded or unbounded? It becomes basically the same question in quantum mechanics, but now it is, is Hilbert space bounded or unbounded?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Hilbert space is the space of all possible distinct quantum wave functions. And really what we mean by bounded or unbounded in this sense is, is Hilbert space finite dimensional or infinite dimensional? Remember, Hilbert space is a space of vectors. So it's a space of things that are, well, it can be described by axes that are orthogonal to each other. The number of axes is typically very large.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Very, very often in quantum mechanics we think about infinite dimensional Hilbert spaces, but sometimes we think about finite dimensional Hilbert spaces. And those finite versus infinite have nothing to do with the dimensionality of space as we know it. So a single spin, like the spin of an electron, is described by a two-dimensional Hilbert space. That is a small number, finite number.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
The position of a single electron is described by an infinite dimensional Hilbert space, simply because there are an infinite number of different dimensions, sorry, an infinite number of different locations that the electron can be in. There's only a finite number of spin measurements you can do. It's either up, spin up, or spin down. That's it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
There's only two of them, thus two-dimensional Hilbert space. As I have talked about before in various places, so I don't need you to have heard it before, but there are reasons to think that we should be taking seriously the possibility that Hilbert space of the real world is finite dimensional. This is not at all obvious. It's not even necessarily true. That's why I'm phrasing it carefully.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
There are reasons to think it. The reasons are basically because there is gravity, right? If it weren't for gravity, if gravity didn't exist, if you just had like the standard model of particle physics or quantum electrodynamics or whatever, quantum field theory generally says that the dimensionality of Hilbert space is infinite.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
I think some people have sort of convinced themselves that we're pretty close to knowing how it works, and I think that they're not quite being honest with themselves. So... We're going to dig into that today.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Like I said, even for a single electron all by itself, the dimensionality of Hilbert space is infinite. quantum field theory is basically you can think of as describing not just one particle, but zero particles, n particles for any n, numbers of particles changing back and forth to each other.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So of course, you could have an infinite dimensional, you generally will have an infinite dimensional Hilbert space there as well. One way of thinking about that is take a little box, take a region of space, not a physical box with walls, but just imagine boundaries that are like a cube or something in some region of space and ask yourself,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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how many possible things can happen in that region of space, okay? It sounds like an infinite number of things. I put one particle in there, two particles in there, three particles. In quantum field theory language, I can excite the field a little bit or a lot or really a lot and so forth. There's an infinite number of things I could think about.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So without gravity, Hilbert space would very naturally appear to us as infinite dimensional. An infinite number of things can happen inside a box. Hopefully you can kind of predict where this is going with gravity. There's a cutoff. There's a new limitation on what I can do, which is if I try to put too much stuff in my box, it collapses into a black hole.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And the black hole has a size, and if that size is bigger than the box, then I have violated the rules of the game, okay? There's only a certain amount of energy. I can put into any region in a theory with gravity while it is literally still fit inside that region that I have just invented.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So that's a very hand-wavy argument, but it translates into thinking that in quantum mechanics, there's only a finite dimensional Hilbert space describing any region of spacetime. Now, this is where it gets, again, more subtle, okay? There could be an infinite number of regions of spacetime.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
This is something I'm actually thinking about myself at a research level these days, and either for that reason or just independently, the podcast will be a little bit more technical than usual. I'm going to try to keep it soft and gentle, try to explain everything, but we're going to get into some of the weeds. And technical, I mean in a physics sense here.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So the Hilbert space of the real world, the quantum mechanical space of states of reality, could be infinite dimensional, even if there's only a finite number of things that can happen in any region. As long as there's an infinite number of regions, then there's still an infinity there.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
But we think that in our real world, there are plausible reasons to think that there is an observable universe that is finite in size, not just finite right now, but finite forever. There is a horizon around us because of the acceleration of the universe that's a finite size.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
In fact, we know what the size is, you know, of order 10 billion light years across, where you can never see what's happening outside. that horizon around us because of the acceleration of the universe, because of the dark energy pushing everything apart, that makes the observable universe finite in size.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So it is very natural to imagine, although we don't know any of this for certain, but it's very natural to imagine that the quantum mechanical Hilbert space, the space of states, for our observable universe is finite dimensional. Now is the whole universe finite dimensional or not in quantum mechanical description? We honestly don't know. Sorry to be vague about that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
I'm just trying to be – I'm trying to both sort of tell you what the plausible things are but also to be clear about what we don't know yet. So basically what I'm trying to say is when you're thinking about the Schrodinger equation and the evolution of the universe, it's perfectly respectable – to think about either finite dimensional Hilbert spaces or infinite dimensional Hilbert spaces.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
That is to say, recurrent evolution, as in Poincaré, a quantum system that will come back to itself infinitely often, or non-recurrent evolution, evolution that will just keep evolving forever and ever. Hopefully, the implications are sinking in. If you pause the podcast right now and think about what I just said for the last 10 minutes, there's an implication here. I said two things. One is,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
the Schrodinger equation says that if the universe evolves with time at all, it will evolve forever into both the past and the future. And then I said it is plausible that the Hilbert space of the universe, the space of quantum mechanical states, is finite dimensional.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And finally, in between saying those two things, I said that if the Hilbert space is finite dimensional, there will be recurrences, eventually. It will last a very, very long time. For the reasonable numbers, given the size of our universe, our observable universe, etc., there is something called the Poincaré recurrence time. And classically, it's very straightforward to define.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Quantum mechanically, it depends on how close you're defining your states to be to each other. But roughly speaking, for realistic numbers, the Poincaré recurrence time for our observable universe is of order 10 to the power 10 to the power 122 years. Where do we get that from? It's a long story involving the cosmological constant and the horizon and the entropy that Hawking calculated, etc.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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I mean, you know that I'm a big believer that philosophy has a lot to offer physics and vice versa. But in particular questions, in my individual humble opinion, either physics or philosophy is doing a better job at taking certain questions seriously.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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But the point is it's a very, very big number. The universe right now is approximately 10 to the 10 years old. The recurrence time for observable universe is supposed to be 10 to the 10 to the 122 years. That's very, very much longer than that. But it's finite. 10 to the 10 to the 122 is still a finite number, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And therefore, the recurrence theorem says you will eventually come back to where you started. And this remarkable fact was pointed out not long after—was emphasized, I guess—not long after we realized the universe is accelerating— in a paper by Lisa Dyson, Matthew Kleban, and Leonard Susskind, Leonard Susskind, former Mindscape guest.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
They pointed out that, you know, the universe has a finite recurrence time. That's bad. Why is that bad? Well, one way of thinking about it is to go back to entropy again. Remember Boltzmann said that low entropy states are those that have a tiny number, relatively tiny number of arrangements of constituents that look that way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
High entropy states have many, many arrangements, correspond to many, many arrangements. And in some sense, what the Poincare recurrence theorem is telling you, this is not exactly the same result. I should be more careful here. There is a further thing that one might want to talk about, which is ergodicity.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Ergodicity is the idea that when you take your initial state and you set it off to follow the equations of motion, it will eventually fill up all of the allowed configurations or possibilities or states or whatever it is. That can't be exactly true because, for example, energy is conserved. Electric charge is conserved.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
There are conserved quantities that limit what are the allowed states you can be in. But ergodicity is within those constraints, the state wanders all around the space of possibilities and fills it up. And quantum mechanically, there are also analogous constraints there, but there's sort of a similar thing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Given all the allowed states, you will eventually reach them, and for very similar reasons that the Poincare recurrence theorem says. So the recurrence theorem says, given any individual state you start with, you eventually come back to it. The ergodicity idea is that you will get to all the possible states, OK?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So if the entropy tells you how many states look a certain way and you eventually go to every possible state if you're in a finite bounded space of possibilities, then you spend the vast majority of your time in what look like high entropy states. because most of the microstates are in high entropy macro configurations, right? That's kind of what it means to be high entropy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Things like the measurement problem in quantum mechanics, the ontology problem in quantum mechanics, the nature of the time asymmetry in the universe, etc. I think that philosophy and foundations of physics have done a better job than good old conventional physics. The nature of time, I don't think that's true. I think that philosophers have thought a lot about the nature of time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So if you just have a system that evolves forever, but in a bounded space of possibilities, most of the time it will look like high entropy. That is to say, thermal equilibrium. In the case of the universe, that corresponds to empty space, what we call de Sitter space, nothing going on whatsoever. The universe is completely emptied out.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
That turns out, for subtle quantum gravity reasons, to be the high entropy configuration of the universe. That's not surprising, by the way, because that is where we are going to, right? Entropy is increasing, the universe is expanding, it's emptying out, eventually it will be perfectly empty. That is the high entropy state that we're eventually getting to.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
But then, because you're evolving forever and there's only a finite number of things you can do, you don't stay high entropy forever. There will be occasional fluctuations downward in entropy. This is exactly what Boltzmann himself pointed out in the 1890s when he was trying to solve the problem of the arrow of time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
It wasn't called that problem yet, but he was trying to understand why the second law had a direction. And he suggested, you know, if you start in equilibrium and you just wait long enough, you will eventually fluctuate downward into a state of very, very low entropy. And then you will relax back upward into a state of high entropy again. Maybe that— Boltzmann said, is our universe.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Actually, what he said was, is our Milky Way galaxy. He didn't even say the word Milky Way. He said, is our galaxy. We didn't know at the time in the 1890s that there were any other galaxies. But Boltzmann was smart enough to know that in thermal equilibrium, life could not exist.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So he used what is essentially anthropic reasoning to say that you would have to wait around in a finite universe until you fluctuate into a low entropy state and then back.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Now, longtime listeners certainly know where this is going and where this was – it was sort of pointed out in a correct but not the most elegant way by Dyson, Klebman and Susskind that there's a lot of thermodynamically crazy evolutions that you will eventually see if you go forever in a universe with a bounded universe. phase space or Hilbert space or whatever.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
It was sharpened in a follow-up paper by Andreas Albrecht and Lorenzo Sorbo that quoted, that coined the term Boltzmann brains. The idea being that if all you were doing was waiting for an intelligent observer to appear, you don't need the rest of the universe to appear.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Among all those possible states you could be in – and remember, you will eventually visit all of them because there's a finite number of states effectively and an infinite amount of time for you to try all of them out – the most observers will find themselves in an otherwise empty universe. Indeed, maybe not even with the body, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Just their brains, enough to look around and go, ha, thermal equilibrium, and then die, okay? That's the Boltzmann brain problem. And succinctly stated, the Boltzmann brain problem is if you are in an eternal universe, which is what the Schrodinger equation predicts, right? The universe will last forever to the past and the future.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And the universe evolves forever in some bounded space of possibilities. Then when you look for any particular configuration you care about, either a person or a galaxy or universe or whatever, you will find the lowest, sorry, the highest entropy possible version of that thing you are looking for. So what is the highest entropy possible universe that can have an observer in it?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
I think that they have not kept up or put any emphasis on the best ideas we have from physics about whether time is fundamental or emergent. There's plenty of room for philosophy to offer some help to the physicists because the physicists, frankly, are very confused, but there's not a lot of activity. in actually doing that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
An observer that is in thermal equilibrium other than — a universe that is in thermal equilibrium other than just that one observer, or maybe even just the brain of that observer. That's the Boltzmann brain problem. Boltzmann himself did not point out this problem. Maybe he could have. It was actually Arthur Eddington that sort of first explained a version of it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So it's Eddington's brains, really, that we're talking about here. But that was understood to be a problem. I'm not going to talk about the Boltzmann brain problem in any great details here. But this is basically what I... So, sorry, let me just finish the story. So Albrecht and Sorbo said, you know, following Dyson, Klebin, and Susskind, they said this is clearly a worry about...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
our favorite cosmological model. The cosmological model suggested to us by the data, and, you know, it's absolutely not set in stone, but it's just the simplest interpretation of what we see, is that there is a cosmological constant. It will last forever. Do a little quantum mechanics to that. There's a finite number of states we can have in our universe.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
You should cycle through them in perpetuity forever, and therefore most of us should be Boltzmann brains. That's a problem. And so indeed, in that paper that I mentioned very quickly earlier, the paper I wrote called What If Time Really Exists, I simplified that issue down to its essence, you know, forgetting about the cosmological constant and real cosmology or anything like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
If you have time evolution... governed by the Schrodinger equation in the most straightforward normal way with a finite dimensional Hilbert space, you will have some version of the Boltzmann brain problem. Now, you can argue about whether or not the Boltzmann brain problem is a bad problem or not. I think it is a bad problem.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And therefore, I think that observers would not have any right to trust their own deductions about what the universe is like in that kind of large-scale cosmology. And that's Problematic for all sorts of reasons, okay? So therefore, I said in the What If Time Really Exists paper, we know something deep about the universe.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
It can't be a finite dimensional Hilbert space and ordinary Schrodinger revolution. There you go. Even though we don't know much about quantum gravity, right, even though we don't know lots of different things, that is apparently not a viable alternative for a fundamental picture of how things work in the universe. And I still think that's right. So, I mean, that narrows it down.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So remember, I want to say it again very, very specifically so you know what the assumptions are here. Ordinary Schrodinger revolution, finite dimensional Hilbert space. Those two things all by themselves give you a Boltzmann brain problem, irrespective of any details about quantum gravity, etc. So one of those two things has to go, okay? It could be either one. We don't know.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
But that is an important implication for the nature of time. You know, the simplest way for time to exist is for time to be eternal, and the... implication of the cosmological constant is at least our observable universe has a finite dimensional Hilbert space. So you might have thought that was a nice model. It seems not to quite work. Okay.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So maybe if some philosophers of physics are out there and listening, this is a nudge in that direction. So even though I'm not going to give you like a nice, compact, happy moral of the story at the end of the day, because we don't know what the answer is, there's plenty of food for thought, I think, in this subject.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And this is what led me to—so the Boltzmann brain problem is something I think was very important. And Kim Boddy, who was a graduate student at Caltech at the time, she and I worked on a paper about the Higgs boson, believe it or not.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
You might know that an interesting thing about the Higgs boson is given its mass and given other things we know about particle physics, the thing about the Higgs boson is it's a field, the Higgs field, filling all of space. There is symmetry breaking because the Higgs field gets an expectation value, as we call it. A zero expectation value is what most fields have. There's a value in empty space.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
On average, if you measure the value of the field, it will be zero. The Higgs field is not zero. Because of its potential energy, it gets a value 200 and some GeV, I think it is, even in empty space. So that is a vacuum state of the theory that has a lower energy than if the field were at zero.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
That's what causes the spontaneous symmetry breaking, gives masses to other particles, all the fun that is associated with the Higgs boson. People have asked, is that value of the Higgs boson the only allowed vacuum state? And of course, we don't know because a lot of things we don't know, but you can extrapolate.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And under very, very reasonable circumstances, it turns out that we're at least on the edge of having another vacuum. Vacuum state for the Higgs boson with a much larger expectation value and even lower energy. OK, so what that means is it's hard to visualize in your brain without me being able to plot the graph.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
But it could be that we right now in the real world live in what is called a false vacuum state. Vacuum state in physics just means state of lowest energy. False vacuum is a state that appears to be the lowest energy, but somewhere else out there in field space, in the space of possibilities, there's an even lower energy state.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And then you can imagine a transition—it might be very slow, very rare, but it would eventually happen—where a bubble of the true vacuum forms, and then it grows and takes over the whole universe. As Sidney Coleman, again, my quantum field theory professor, said long ago in a paper that he wrote, this would be the ultimate ecological catastrophe.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
If a bubble of true vacuum appeared in our universe and grew and hit us, we would all die because from our point of view, all the local laws of physics would change. So – The current knowledge of the Higgs boson puts us on the ragged edge of disaster in terms of that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
It suggests that maybe there could be another vacuum out there and maybe we could transition into it and maybe that would be the end of all life on Earth and indeed in our observable universe, OK? Now, that would be bad, I think, because I like the universe, at least compared to the alternatives. But it would get us out of the Boltzmann brain problem, OK? That is to
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And before we move on, let me just mention one other thing that I should have been mentioning all along. I don't know. I've been bad about this. But many of you know we still have the Mindscape Big Picture Scholarship. This is a college scholarship for either high school students or current college students can apply at bold.org. That's B-O-L-D.org.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So what to do for a solo episode to start things out? I mean, in some sense, I've already been talking too much. I did the Hits and Misses holiday message, which went on for a long while. I did a previous solo episode about emergence not too long ago. But OK, there's a tradition. And when there's a tradition, we might as well stick to it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So Kim and I wrote a paper, you know, can the Higgs boson save us from the menace of the Boltzmann brains? And the idea would be if the Higgs would eventually undergo a transition to a better vacuum state, that would make our current state of the universe only have a finite lifetime, not long enough to make Boltzmann brains. And then we'd be safe from it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
It'd be bad for other reasons, but at least we'd be safe from that empirical problem. Okay. For – we submit the paper. The paper was good. We did a good job. We submit the paper. And the referees, like instead of worrying about our calculations, dealing with the Higgs boson and the false vacuum, worried about the Boltzmann brain problem. They're like, yeah, I don't believe that problem.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
It's not a big deal, which is frustrating. Like, OK, you can believe that, but other people think it's a problem. But that made us think, you know, we should just write another paper saying – I think maybe I thought this first and I shanghaied Kim into joining me and then Jason Pollock, who was another student, also joined us at some point.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And I said, you know, we should just write a paper saying here's why the Boltzmann brain problem really is a problem, OK? And eventually I wrote a paper by myself called Why Boltzmann Brains Are Bad. But that was only after we finished this paper, Kim and Jason and I, because step one in saying here's why Boltzmann brains are bad was to say here's why there are Boltzmann brains.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Let us rehearse the problem, right? Rehearse the idea that there can be quantum fluctuations that would create brains that would be observers that are cognitively unstable, et cetera, et cetera. And what we realized is that the traditional argument for Boltzmann brains was not convincing. It depends what you mean by the traditional argument for Boltzmann brains.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
If you go back to Boltzmann or to Eddington pre-quantum mechanics days and you just have a box of gas or some equivalent of a box of gas, then the Boltzmann brain argument is entirely convincing in my mind. In quantum mechanics, it's more subtle, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And the reason why people were talking about Boltzmann brains, the hand-wavy argument, is that the equilibrium state that you get for de Sitter space, for a space with a non-zero vacuum energy, the state of the universe that we think that we are headed toward,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
As we said, that has a horizon, a la Hawking, just like a black hole has a horizon, and has a temperature, just like a black hole has a temperature. And so empty space has a temperature, which is not zero, and therefore there should be thermal fluctuations.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
There should be random motions that give rise to brains and planets and universes and whatever, if only you waited long enough, much like a classical box of gas. And so what Kim and Jason and I realized after banging our heads against it for a while is actually that's just wrong. And that's just not thinking correctly about how quantum mechanics works.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
You can just search within Bold for Mindscape or go to bold.org slash scholarships slash Mindscape. And the idea is we give money to college students who want to pursue these sort of academic-y, intellectual, less practical side of deep questions. The big picture is what we're interested in. And huge thanks to all the Mindscape supporters out there who've been giving money.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
You can have a quantum mechanical state that you say is a thermal state, a state of thermal equilibrium. But the quantum mechanical thermal state is a very different kind of thing than a classical thermal state. A classical thermal state is based on your ignorance. You have a box of gas and you say, oh, it's in a thermal state. It's in thermal equilibrium. What does that mean?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
It means that in the box of gas, all the different molecules and atoms and whatever, they each have some specific position and velocity, but you don't know what they are. So you assign them a probability distribution, and it's the maximum entropy probability distribution, and that's the thermal probability distribution. But that's not what happens in quantum mechanics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
In quantum mechanics, you have a wave function, or more generally, you have a mixed quantum state, which can be like a probabilistic sum of different wave functions. So we have all the technology to deal with that. That's what you learn in your quantum mechanics classes. So you know what a thermal state looks like in quantum mechanics. But it's not the same character.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
It has the same observational consequences. If you have a quantum mechanical thermal state and you measure it, you will see different outcomes because it's quantum mechanics, right? You will see a distribution of possible outcomes for the positions and velocities of the particles just because it's quantum mechanics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
But when you're not measuring it, it's a very different kind of thing than the classical thermal state because classically there is an actual microstate where things are moving. The atoms are moving around. You might not know what the actual microstate is, but it exists, right? Quantum mechanically, that's not the story. Quantum mechanics isn't like statistical mechanics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
The quantum state corresponding to a thermal state is completely static. It is not changing over time. If you measure it over and over again multiple times, you will get different answers, again, because quantum mechanics. But in an empty universe, there's no one there to measure it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
You need to think about the state for its own sake, not what measurement outcomes you would get if you were to look at the state. And the state for its own sake isn't changing over time. It's static. It's stationary. Nothing's happening.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So we made the argument that, in fact, when the universe does expand and sort of empty out and become empty de Sitter space with a temperature, so it is a thermal state, but it is not a fluctuating temperature. state. There's nothing happening from moment to moment that could pop into existence, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
When we talk in quantum field about virtual particles popping into existence, that's colorful language. That's not what actually is happening. You know, in the proton, for example, people show these pictures of what it looks like inside a nucleon. And you see all these quarks and gluon fields fluctuating in and out. That's completely wrongheaded. That's not what is actually happening.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
The quantum state of a proton is exactly the same from moment to moment in time. And the same thing is true with empty space. If no one's measuring it, there's nothing happening. There's nothing fluctuating. There's nothing coming into existence. And certainly not Boltzmann brains or whole civilizations or whole universes, anything like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Now how does this get reconciled with the recurrence theorem? Well, the idea is that the universe is not a closed system in this case, right? There's a horizon around us, and therefore features of our universe sort of leak out. They leave us, right? Our universe is not a closed system.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
It is finite-dimensional Hilbert space, but it is connected to an apparently infinite-dimensional Hilbert space representing the entire rest of the universe. Now again, that may or may not be true, so Kim and Jason and I were very, very clear.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
If what is going on is that our observable universe is described by a finite dimensional Hilbert space that is embedded in a larger infinite dimensional Hilbert space, then it can just settle down. Our universe can go into a completely—can sort of asymptote to a completely stationary state. where there are no dynamical fluctuations.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
to the scholarship fund. We've been doing very, very well. This year we're planning to give two scholarships worth $20,000 each, which is considerable. That's going to help some students quite a lot. And I'm going to ask for even more contributions because we're going to keep doing this every year is my goal. And the deadline for contributing for this year is January 20.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And so we distinguish between dynamical fluctuations and Boltzmann fluctuations and things like that. But nothing would happen. No actual brain would ever pop into existence. And therefore, under those circumstances, there is no Boltzmann brain problem. If the whole Hilbert space is infinite dimensional, Boltzmann brains would not dynamically pop into existence, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
That paper, we also got published. We did get that one published. It... It also went through referee problems because people just don't like the Boltzmann brain problem, but eventually it sailed through. Okay, so let's take a step back and see where we are because we're trying to think about the nature of time here, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So we've been talking about the possibility that time is fundamental, that it's right there in the Schrodinger equation, taking it seriously. And what we're finding is an interesting thing that will continue to be true is
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
which is that whether or not time acts in a certain way, in a way that is compatible with the universe as we know it, also depends on how space behaves, or more generally, the space of possibilities. If you just have the Schrodinger equation and time is fundamental, then time is eternal.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And then if the space of possibilities is bounded, aka Hilbert space is finite dimensional, then you run into troubles with the Boltzmann brain problem, with recurrences and fluctuations and so forth. if the space of possibilities is unbounded, then time evolution can go eternally in a way that, at least in principle, maybe, plausibly, could be compatible with the universe we see.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
In some ways, the paper I wrote with Jennifer Chen back in 2004 on a double-headed arrow of time, a universe that was statistically symmetric to the far, far, far past and the far, far, far future is an implementation of this kind of idea. We were sort of semi-classical in the way that we talked about it with baby universes and so forth, but it's the same basic strategy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And the reason why it works is because in the specific version of the, in the specific understanding of the more or less realistic idea that we live in an accelerating universe which will eventually settle down into a static state, you don't have fluctuations in that static state, so you don't need to worry about the Boltzmann brain problem. Okay. So that's good.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
That's a helpful connection between the space of possibilities in space and matter and energy and those things and the possible behavior of time. But guess what? Not everyone agrees.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So in particular, we wrote the paper saying, look, you're free of the Boltzmann brain problem if you settle down to a stationary state, because quantum mechanically, it's not like a thermal state in classical mechanics where secretly things are moving beneath your notice. It's that things truly are static.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Other people say, well, no, even if the quantum state is static, quantum mechanics is very subtle, and things can still happen in the universe even if the quantum state is not changing over time. Okay, that's a dramatic thing, and I still to this day have not correctly wrapped my mind around it. I don't even know if it's true or not.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
This is exactly the thing that is sort of on the table, whether we can understand this correctly. In the specific example considered here, it was Seth Lloyd, a quantum information person, a very successful physicist at MIT, who wrote a paper responding to ours saying, no, no, no. even if the state of the universe is static, there still can be things that happen. So what does that mean?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Well, remember, and I'm going to try to simplify the technicalities here a little bit, the actual way that Seth talked about it was using the decoherent histories formalism. This is a way of thinking about the evolution of quantum systems by talking about Under what circumstances can we think about an evolving quantum system as describing a set of individually coherent histories?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Sorry, the application, you can always contribute. There's no deadline for that. The deadline for applying, if you are an actual student who wants the money, is January 20th. So we're still looking for applications, and the winners are going to be announced February 20th. So that's very, very exciting.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Coherent in the sort of informal sense, not the formal sense. Actually, you want them to be decoherent in the formal sense. You want them to separate from each other. The standard example here is the double slit experiment. You know, when a single electron passes through slits and interferes on the other side, then that is an example of two histories.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
The electron goes through one slit, the electron goes through the other slit that don't decohere from each other. They will interfere later on. They still sort of are part of the same world, OK? And therefore, people like Griffiths and Omnus and Hartle and Gelman have developed this formalism to say you cannot actually separately calculate probabilities
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
for the question, did the electron go through the left-hand slit or the right-hand slit? They both are there. They're not separate probabilities. They interfere with each other later on. Whereas, if you observe...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
which slit the electron goes through, then decoherence happens, and now you don't have interference on the other side of the double slit experiment, and now you can attach probabilities to whether or not the electron went through the left-hand side or the right-hand side, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So there's a whole formalism built up about this, and this is what Lloyd used when he talked about his objections to our paper, but I don't think you need to really dig into it, although we'll bring it up again. The point is that
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Once again, quantum states have this feature that two different states can be added together to get a third state, and if the two states you started with solve the Schrodinger equation, then the state that you get by adding them will solve the Schrodinger equation, okay? So very roughly speaking, what Seth pointed out is that even if your overall quantum state is static,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
you can think of it as the sum of various states that are not static, that are changing with time. If you think about, you know, waves going up and down, you can imagine two waves, each of which individually are changing with time, but their sum remains constant, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
If that's not quite obvious to you, think about a constant function, a function between 0 and 1 that just takes on the value 1, and subtract a wave from it. So take another function that is wiggling and then changing with time, take 1 minus that function, So then your wave function plus one minus your wave function is just one, which is just the constant.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
I deeply appreciate all the efforts out there from the Mindscape listeners to help the next generation ask these big questions and hopefully even answer some of them. So with that, let's go. Time is one of those ideas that we've had around long before we had physics, right? We have used time, we've measured time, but it has been adapted into physics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So you have two individually changing things that can add up to a constant. And what Seth points out is that I can take a static quantum state and I can divide it into a set of histories of things happening, things changing over time. And when I add them all up, I get that static quantum state.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
But, he says, I'm allowed to think of it as a superposition of many things actually happening dynamically, including Boltzmann brains popping into existence, etc. And then there's a lot of math involved with, you know, OK, showing that that's realistic and so forth.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
In fact, this is a version of something that Faye Dauker and Adrian Kent pointed out a long time ago and was a was a inspiration for the paper that I wrote on quantum urology with Ashmeet Singh. And Dauker and Kent called it the set selection problem. So mathematically, what Seth Lloyd says is completely correct. You know, you can't argue with the equations in this case.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
It's trying to understand what the equations are saying, okay? So it is simply a true fact that you can take a quantum state that is not changing over time and express it as a set of histories of things that are changing over time. The question is, should you consider those changing histories as really happening? And I will give you two arguments that you should not. Seth says you should.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
I'm going to give you two arguments that you should not. One argument is it would be terrible if it were true. When I expressed the original version of the Boltzmann brain problem that sort of came about through work of Dyson, Klepp, and Susskind, then Albrecht and Sorbo,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
What they were thinking was that in the thermal state that you get at the end of cosmic evolution or the long-term limit of cosmic evolution in the presence of vacuum energy, There's a temperature and a temperature – they were thinking that the temperature implies fluctuations just like classically it would and therefore there's a probability for things happening that depends on that temperature.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And what Kim Boddy and Jason Pollock and I pointed out is that that's not true in the precise way they were thinking of it because it's a different kind of temperature, OK? There's not actual thermal fluctuations associated with it. And so what Lloyd is saying about even in a static state, you can have dynamical histories that sort of constitute that static state.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
That would be true whether or not there was a temperature. That's true even in the vacuum state of empty space without a cosmological constant, Minkowski space, right? You can have literally the emptiest possible quantum state. a universe with nothing in it, no vacuum energy, no particles, no vibrations of any sort, everything is absolutely static.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And you can express that as the sum of all sorts of things happening, changing over time. That's just a feature of quantum mechanics that follows from exactly the same logic that Seth Lloyd used. You can think of it this way, and he actually pointed this out in his paper. The simple harmonic oscillator, right? One little quantum system that we think we understand.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
The ground state of the simple harmonic oscillator, an oscillator that is sitting there doing nothing to the extent that it possibly can in quantum mechanics, can be decomposed as the sum of various things changing over time. And what that means is that if you take this attitude that all of those histories that you're inventing to sum up to make an overall static quantum state, if they count...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
as really happening in some sense, and this is where the philosophy comes in, what counts as really happening, right? If they count as really happening, then essentially everything you can conceive of is happening, even in empty space, all the time. Civilizations are arising and falling in the vacuum of a quantum field theory, okay? So is that what you want to believe is true?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Like this is a terrible argument. This isn't a very convincing technical argument, but I'm just trying to push forward the implications of this view. If you say I can take a static quantum state— and decompose into a sum of dynamical changing quantum states, and I treat every one of them as really happening and truly real, then that has wild implications for what you think is truly real.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Then you sort of get time evolution, even though you're in just empty space and nothing is naively happening at all. So maybe that should bother you, maybe it shouldn't, but you have to come to grips with it anyway.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
A slightly more respectable technical objection is, yes, I can take a static quantum state, I can divide it up, express it as many different dynamical states that just happen to be dynamical in the right way to add up to no dynamics. That's what he's proposing doing. But there's more than one way to do that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
In fact, there are an infinite number of ways to do that, and this is what Daucher and Kent pointed out. There's a set selection problem. You can, in the context of the decoherent histories formalism, if you have a set of histories, a single set, so you say I'm going to look at this history, that history, this other history, and it's a complete set.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
It includes everything that could possibly happen. Then the point of decoherent histories is if those histories decoher from each other, if they don't interfere, okay, then you can assign probabilities to them. And you can say, yes, 20%, this will be the history you see, 70%, something else, and so forth. But you can't assign probabilities between different sets of histories.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So if you take the static wave function and express it as a sum of things, you can do that in many, many different ways. And there's no guidance whatsoever as to what is the right way. If you can do it one way, you can do it any number of other ways. And they should all, by the rules that you've just invented, be counting as equally real. Do you really want that?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
It certainly removes any possibility that quantum mechanics ever predicts anything or that assigns a probability to anything because literally almost everything happens all the time in almost every quantum state. I don't think that's what we want quantum mechanics to do. So somehow I firmly believe that can't be the right interpretation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
That can't be the right way to think about what these equations are telling us. But we need to... Come to grips. We need to figure out. This is not an unanswered question. This is something I'm thinking about, other people are thinking about. How do you decide what actually happens in that non-evolving quantum state, okay? I will tell you my guess.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Physics, when I say modern physics, sometimes people mean modern physics as in 20th century. I mean like Isaac Newton and after, okay? I think that Isaac Newton, classical mechanics, and the people around him like Galileo and Descartes and so forth, they really codified physics in a way that was very, very different than what came before. And the notion of time came along, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
My guess is that it has something once again to do with the arrow of time. I think that... I think that has to do with emergence, in other words. You know, when do things really happen? I think that, again, this is very hand-wavy because we don't understand it completely, but there is a classical limit of quantum mechanics, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And sometimes you're taught the classical limit is just like when things are big, they behave classically. But that's leaving out a little bit of the discussion. In quantum mechanics, when things are big, like a planet, they can behave classically, but they don't have to behave classically.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
I can take a wave function of a planet like the Earth, and I can mathematically construct a wave function that puts the Earth in a superposition of being here and on the other side of the sun, and some of it is in the Andromeda galaxy and so forth, okay? Highly non-classical behavior, even though the Earth is a very big thing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
What of course happens, at least from this many worlds perspective, is that the Earth keeps interacting with the rest of the universe and it decoheres and branches. And on each individual branch, the Earth looks more or less like a classical object, like we know and love and live on.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So you get the branch where the Earth is here, the branch where the Earth is on the other side of the sun, the branch where it's on in Alpha Centauri and so forth, okay, or the Andromeda Galaxy. And so that process of decoherence and branching relies on the arrow of time, relies on dissipation, relies on the fact that the whole state is very far from thermal equilibrium.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And so my rough feeling is that that aspect, the aspect of entropy increasing, dissipation happening, decoherence occurring, is missing from this point of view that says I can take a quantum state that is perfectly static and just divide it up into many different histories and then consider them all to be real. I think that...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Those histories that you're considering are not ones that are living in any classical emergent reality. And maybe that's a quasi-anthropic argument. I don't know. Like maybe the point is that you can't get observers in those trajectories. I honestly don't know. That's what I'm saying. We need to think about it. And so now I can get into the even deeper reason why we need to think about this.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So the issue that I've just raised is, do things happen in static quantum states? And one way of saying this is, can time emerge when it is not fundamental? So, so far we've been talking about ideas or theories or frameworks in which time is truly fundamental. It's right there in the Schrodinger equation, and the quantum state is changing over time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And we ran up into this issue that, okay, maybe if there's an unbounded space of possibilities, even though there's time evolution, the local, visible, observable part of your universe settles down to a static quantum state. And then we ask, well, OK, but things are still happening in that static quantum state. Are Boltzmann brains or whole civilizations randomly fluctuating into existence?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
We had time before Isaac Newton. We still have time after. But the meaning of it changed a little bit. And I think that because a lot of people who are not professional physicists still think about time in the everyday sense, the pre-Newtonian sense, one of the things you have to do to understand time is to reconcile what physicists mean when they use the word.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So, OK, this is an important question, but it is right up next to another important question, which is what if time isn't fundamental in the first place? And why would you ever think that? Well, what would you think that is because of quantum gravity. So again, we don't understand quantum gravity perfectly well, but we understand a little bit about quantum mechanics, a little bit about gravity.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
We can lump them together and see what happens. So you just like follow your nose and imagine that general relativity is like any other classical theory. Let's try to quantize it, see what happens. And this was done years ago, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
In fact, the famous equation that pops out of this perspective is called the Wheeler-DeWitt equation, named after John Wheeler and Bryce DeWitt, who cooked up this equation, I don't know, in the 60s or 70s or something like that. It was literally just, you know, take general relativity as a classical theory, quantize it the same way you would quantize anything else.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And what you find is that those features of general relativity that we talked about before, that time is not absolute, right? That time is a little bit loosey-goosey in general relativity, that you can slice your universe in all sorts of different ways. This is something that the fancy language for is called diffeomorphism invariance.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
You can choose to coordinate your spacetime manifold in an infinite number of possible ways, and they're all equally good. That's the diffeomorphism invariance. And what that means is that time kind of has a different form. feeling a different status in general relativity.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And like I said, at the classical level that is a technicality that you have to be aware of, but it's not truly changing your view of the theory. You solve Einstein's equation and you get on with your life. At the quantum level it becomes really important precisely because the ordinary Schrodinger equation treats time as fundamental.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
The ordinary Schrodinger equation says you give me the quantum state, I apply the Hamiltonian to it, and what that tells me is the rate of change of the quantum state with respect to time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
In general relativity, this symmetry, this diffeomorphism invariance, takes that statement and says what actually happens in quantum gravity is you give me the quantum state, I apply the Hamiltonian to it, and it doesn't change with time. That is to say, the ordinary Schrodinger equation says Hamiltonian acting on quantum state is the time derivative of the quantum state.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
The Wheeler-DeWitt equation says Hamiltonian acting on the quantum state equals zero. So there is no time variable in the Wheeler-DeWitt equation. The Hamiltonian annihilates the state is the way that we technically say it. h psi equals zero is the Wheeler-DeWitt equation. So time has disappeared.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
You know, in the Schrodinger equation, we have d by dt, the derivative with respect to t, time of the quantum state. And according to the naive version of quantum gravity, that should vanish. There's technicalities there. strictly speaking true if you have a compact spatial universe, but versions of it should be true even if you don't. So we're not going to get into those details.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
with what ordinary people mean when they use the word. One way of thinking about it is, what exists, right? We're asking, does time really exist? Well, if you didn't know anything about physics or philosophy, etc., and someone said, what exists, what would you say?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So this feature, so in other words, just to let it sink in, when we were taking the attitude that time is fundamental, that it's right there in the Schrodinger equation, and we weren't worrying about specific things that we might think are true about quantum gravity and so forth, we said, well, maybe you eventually evolve to a state that's not evolving with time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Okay, maybe the universe sort of approaches asymptotically some equilibrium state and it just stays there. And now we're saying, okay, now we are taking seriously some implications of the straightforward, naive version of quantum gravity, And it says that there isn't any time evolution at all, not just eventually but just as a fact.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
This seems naively to be in contradiction with the world that we live in, right? I mean I look around. There's clocks. I think that time is part of my life and the Wheeler-DeWitt equation says no, it's not, not really. So this is called the problem of time in quantum gravity. The problem of time is different than the arrow of time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
The arrow of time exists even classically, and there's the question of the arrow of time. Why is it there? Where did it come from? Et cetera, et cetera. The problem of time is specific to quantum gravity, and it just is the question, why is there time at all if the fundamental equation of quantum gravity doesn't have any time in it? That's the problem of time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And of course, obviously, for obvious reasons, people have thought about this a lot. You know, this is not something that we're newly approaching here. And guess what the motto is? The motto is, well, time must be emergent. This is something that has been stated in people thinking about quantum gravity for many decades now.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
That if you take – if the Wheeler-DeWitt equation is on the right track, then time should somehow be emergent. I mean is the Wheeler-DeWitt equation on the right track? It's hard to say. I think that there's arguments either way. Clearly, quantizing general relativity in the most naive way is not the entire story of quantum gravity. It doesn't work. It blows up. It gives you nonsensical results.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
But maybe like in some big infrared effective field theory kind of sense, every version of what's going on at small scales, whether it's strings or loops or whatever, should sort of smear out and look like general relativity quantized at the end of the day. and therefore something like the Wheeler-DeWitt equation should hold. After all, it just really depends on
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
But I do worry about doing too many solo episodes because I'm not an expert in that many things. I don't want to do a solo episode just on me ranting about things. I think it's OK to admit that one is not an expert on everything or even one doesn't have interesting things to say about every issue out there.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
the symmetry that the theory has, this diffeomorphism invariant symmetry. So maybe that should be robust, even if we don't understand all the details of quantum gravity. But because we don't understand the details, you have to keep an open mind. That's why I'm sort of laying out all the different possibilities.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
I think the typical answer, I mean, people would include different things, whether you believe in angels or something like that might be controversial. But most people would say that the world exists. The world in some sense consists of space where things are located, and there's a whole bunch of things in space, tables and chairs and planets and people, etc.,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Maybe time is fundamental, as we were just talking about before, but maybe, a la the Wheeler-DeWitt equation, it is not, and we have to get it to be emergent. So what would that mean? How could time emerge if the fundamental equation... of science, of physics, is the wave function of the universe never evolves with time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Well, happily, quantum mechanics giveth and quantum mechanics taketh away, and so it took away time from us, but it gives us something that we already discussed, this fact that quantum states are vectors and can be added together. And by itself, that might not seem like a big help, but the point is that you can imagine that in quantum mechanics everything is relational.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
In other words, that time is not out there, it is not absolute, it is not an external parameter saying how things are evolving from moment to moment. Rather, In this point of view, time is just a statement about the relations between different things going on in the universe. In other words, we might try to—sometimes people glibly say time is what clocks measure, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
This point of view that I'm trying to explain here is an operationalization of that. It's really taking seriously the claim that time is what clocks measure. You can, in other words, have a quantum state that is not changing with respect to any absolute out there existing time. But within the quantum state, there can be things that you call clocks.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
And they can be in superpositions of many different possible clock readings. And those superpositions of different possible clock readings are maybe entangled with the rest of the universe so that when the clock reads something or in the part of the quantum state where the clock has a certain reading, that counts as that is what time it is for the rest of the universe.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
That's the basic idea for time trying to emerge somehow. And the question is, can you make it work? So the way I like to think of it is this way. The way I like to sort of warm up to why this might be a plausible thing. In quantum mechanics, states are vectors. Quantum states can be added together.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
If I take the universe as a whole or any sufficiently big quantum system, imagine I take two different configurations of the universe, two different quantum states the universe might be in. and I add them together.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
You might think from your experience adding vectors together, like if you add a vector that's pointing in one direction and a vector that's pointing in another direction, you get a third vector, the sum of them. But you can't go backward, right? Like you can't say, okay, here's the sum of two vectors. What are the two vectors I added to originally to get them out, right? If I say I have
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
two and I have three. These are vectors in one-dimensional space, right? I have the vector two and I have the vector three. I add them together to get the vector five. That's fine, but if I say I have the vector five and I added two vectors together to get it, what were the two vectors? You have no way of knowing. Was it two and three? Was it six and minus one?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
You know, there's an infinite number of possibilities. However, it turns out that our intuition is not very good on this score because our intuition is built up in, you know, one-dimensional, two-dimensional, three-dimensional vector spaces. In the huge, huge, huge dimensional vector spaces that describe quantum states...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Space, if you want to be a little bit physics-y about it, it's a three-dimensional manifold, and the things that are in it, physics tries to understand, describes them in terms of mass and motion and location and what have you. And then in that pre-Newtonian picture, The reality of the world is that three-dimensional space plus everything in it, and time is something that happens.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
It turns out that when your vector spaces get very big, almost all vectors are perpendicular to each other. You give me two random vectors, I take their dot product, their overlap, and it'll be very, very, very close to zero unless I worked really, really hard. And this is something that is a little bit counterintuitive. Let's put it this way. If I take, you know, a box of gas...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
with a bunch of atoms in it or a bunch of photons or something like that. And I consider it as a true quantum mechanical system, so I have the quantum state of that. Here is a true fact. If I add a single particle, like a single electron or a single photon or whatever to that box of gas, there's many, many, many, many particles in it. I add just one particle to it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Classically, I have not changed the state very much, right? The overall mass and pressure and things like that have not been changed very much because I just added one particle. Quantum mechanically, the quantum state that I get by adding that one particle is perpendicular to the state that I started with. They are orthogonal to each other.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So quantum states very, very rapidly and easily become perpendicular to each other, orthogonal, as we like to say in quantum mechanics. And so that at least gives us hope. for picking them out from each other, for reverse engineering from the sum of two states back to the original ones we added together.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
If we have some basis, some set of preferred directions in this vector space, and I know that the states I'm adding together are sort of perpendicular to each other, then I can try to reverse engineer what they weren't. Okay, so that's a bit of math. Sorry about that, that I wanted to let you know about.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So you might think when you add together two different quantum states of the same system, you just lose a lot of information, it becomes mush. But at least in principle, maybe under the right circumstances, you can figure out what are the two states I added together, especially if you have some extra criteria, right? Like you're looking for classical states.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
If I take two quantum states that are, you know, behaving relatively classically, like a well-localized sensible wave function, if I generally take two well-localized wave functions, the wave function I get is not well-localized. If I take a wave function where a particle is located near x and a different wave function where a particle is located near y far away, I
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Those two are separately classical-looking particles localized. But I add them together, and now the particle's not localized. There's part of it near x, part of it near y, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So if I say, well, I know that the two states that I added together both look classical, and here's what the result looks like, a little lump near x and a little lump near y, I can go, oh, yeah, okay, you added together a classical-looking state with a particle near x and a classical-looking state with a particle near y. I can figure that out. I can disentangle them, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
Good, keep that in mind, and now consider an ordinary time-evolving system, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
So imagine a quantum system that is changing with time, you know, forget about emergent time, et cetera, just have the ordinary Schrodinger equation, take a quantum state, plug it in, let it evolve with time, and now imagine recording, solving the Schrodinger equation, and writing down what the state looks like at t equals zero, and t equals one and t equals two, et cetera.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
I mean, maybe one, two, maybe these are measured in nanoseconds or something, right? Like very, very quick snapshots of the quantum state of the system at slightly different moments of time, right? So I could do that. Here's what I could do in quantum mechanics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
300 | Solo: Does Time Exist?
I could take all these different quantum states, which represent this big system at different moments of time, and I can just add them together. I'm not saying that the universe does this. I'm saying I can do this. I could imagine that time-evolving state, take snapshots of it at discrete moments of time, every nanosecond, and then I add them together.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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And I have to be vague here because it's not very specified. The world changes from moment to moment, and time is how we talk about that change. Here is what the world is at this particular time. At a certain later time, the world is something different. You could imagine saying words like time is change or time brings about change.
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And I get one state, okay, because I can add them together. I'm allowed to add quantum states together. I'm allowed to have one state. And they're all distinguishable because all the different states are going to be more or less orthogonal to each other.
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I've basically taken all of the information that was contained in a single quantum state evolving with time and encoded it in a single quantum state that is not evolving in time, right? By taking snapshots of the time-evolving state at different moments and then adding them together into one big state.
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And if I'm in a nice situation where things are more or less classical looking, et cetera, maybe I can even go backwards. Maybe I can even take that one big state and extract all of the behaviors of the state at different moments of time and then arrange them in the right order, okay? So I have basically encapsulated time evolution into a single state that itself is not evolving with time.
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And all I'm saying here is that I'm trying to convince you that we can imagine in quantum mechanics in a way that you can't imagine in classical mechanics. You can imagine time being emergent.
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In the sense that I could have a quantum state that is not evolving with time but really I can think cleverly of a way of expressing that quantum state as if it were a quantum system that is really evolving in time because it's really the sum of those time steps in that evolution. The question is how to make that work, how to operationalize it, okay?
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And again, all this is stuff people have been thinking about for a long time. So one of the classic papers here was written in 1983 by Don Page and William Wooters. It's well enough known that it's now called the Page and Wooters Mechanism. And they did a very simple thing, very, very nice, simple thing. They basically said, okay— Imagine I have a quantum system.
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They were inspired by the Wheeler-DeWitt equation, but they didn't look at that explicitly. They just said, imagine I have a quantum system that doesn't evolve with time. It's psi is just static. Psi is the wave function of the universe, the quantum state. It's not changing over time. But imagine that I can decompose the quantum Hilbert space, the space of all possibilities.
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I can break it up into two subsystems, which is very, very plausible, very, very easy to do in a wide variety of circumstances. And they say, so I have one subsystem that I'm going to call the clock subsystem. And the other subsystem is the rest of the universe subsystem. OK, so the rest subsystem. And basically, if the whole system is not evolving with time.
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Then they can set it up so that the clock subsystem has different possible values. You know, when you observe a quantum system, you get different possible answers. And so, I mean, let's imagine that whatever this subsystem is, it's clock-like. It's something that we can measure, like literally looking at your wristwatch and looking at what time it is.
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And they show that what very naturally happens is that there is entanglement between the clock subsystem and the rest of the universe. with the property that there is an emergent time evolution to the rest of the universe. That the, if you think about arranging the clock states, the states of the clock subsystem in order 0, 1, 2, 3, etc.,
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Then those are separately entangled with states of the rest of the universe, the state of the rest of the universe at time zero, the state of the rest of the universe at time one, the state of the rest of the universe at time two, where this is not real time. This is emergent time. It's not fundamental time. It's real, as we said at the very, very beginning. But it's emergent.
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It's emergent because it's literally what is being read off from measuring the clock subsystem, okay? So at every value of the clock subsystem, the rest of the universe looks like it has evolved to that time. And there's some technical details there. It really looks like Hamiltonian evolution, etc. It's kind of marvelous. It's kind of wonderful.
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It's, again, unclear exactly what the best set of words to use is, but conceptions like that are evolved. The world is three dimensions plus stuff. Time tells us about how that stuff changes, evolves, becomes different from moment to moment. Now, Newton comes along, Isaac Newton, classical mechanics, Principia Mathematica, etc. And he invents these equations, right? The equations are very strict.
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So it at least is plausible that time emerges in quantum mechanics in exactly that way.
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There's a whole other tradition of, you know, rather than taking this abstract quantum mechanics for its own sake point of view, taking quantum gravity seriously and giving variables that describe the universe that might be the scale factor of the universe or the value of some scalar field and using those as clocks. So the game to play in quantum cosmology is,
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the study of quantum mechanics applied to the whole universe, is to pick out a clock and let that be an emergent time variable, okay? And this is something that in principle is doable. And I think that's the state of the art, honestly. I mean, there's been improvements over time, as it were. People have done some technical details. I mean the Page and Wooter's paper is pretty simple.
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They make a lot of assumptions to simplify their lines, which is completely legit. And people have complicated those assumptions over time and looked at it more carefully and great. And this is still – I think the – cutting edge of how we think about the emergence of time in quantum mechanics to this day. Now, but I don't, what can I say? People haven't looked at this seriously enough.
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It's one of those cases where We live in a universe that is very classical. Like we know what the universe is like in some ways. So we know what answer we want to get when we look at quantum mechanics and we say, you know, please correctly describe the universe. And what that leads to is a bit of carelessness, a bit of sloppiness.
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Like we say, well, maybe if you think about it this way, you get the right answer. And people go, oh, yeah, OK. Yeah, that looks plausible. They move on with their lives. Because there's other things about the universe we don't understand, right? Why does the Higgs boson have the mass it does? Why is there more matter than antimatter?
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And those seem like pressing problems, whereas, you know, how does time emerge seems like, well, it must happen, and here's a somewhat plausible story about it, so we'll accept that and move on. And I don't think they've really... come to grips with it as seriously as they should. One exception is Andy Albrecht, the same guy who with Lorenzo Sorbo wrote about Boltzmann brains back in the day.
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Andy and I are very sympathetic in terms of what we think are interesting physics and cosmology problems. So we end up working on the same thing. very frequently. So Andy wrote a paper with Albrecht and Iglesias on what he called the clock ambiguity.
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And there was a previous paper he wrote, and I'm not going to get the title right, but it was something like A Theory of Everything or A Theory of Anything. So here's the issue.
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Don Page and Bill Wooters said, I can get time to emerge in a quantum state that is not actually evolving in time by dividing the quantum system into the clock subsystem and the rest of the universe, then the rest of the universe appears to evolve with respect to the reading on the clock. And Albrecht and Iglesias say, okay, sure, what if I divide up the space of the quantum states differently?
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So you chose a way to divide up the space of quantum states into clock plus rest of the universe. I could take a different subsystem to be my clock. I could make the clock subsystem be part of yours but part of something else, right? There's literally an infinite number of ways to divide up. It's literally like slicing a pie, right? I can slice any one pie in principle an infinite number of ways.
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And what they argued is – and here – this is something one could agree or disagree with. It's not – people have not taken it seriously enough. So I don't think that the dust has settled even though the first paper was, I don't know, 20 – over 20 years ago.
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What they argued was that they could essentially slice up the Hilbert space of possibilities in enough different ways that they could get the clock and the rest of the universe to do whatever you want. It's reminiscent of this thing where in the static state where Dauker and Kent are complaining about, I could—
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It's a deterministic clockwork universe. And the equations at their most fundamental relate the configuration of stuff in the universe at one moment in time to the configuration of stuff in the universe at a different moment in time. So there's a relationship between what the world is at one moment and what the world is at all other moments. Of course, there always was a relationship.
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express a static state as a set of time-dependent histories in an infinite number of ways. I can get whatever I want. And Albrecht and Glacius are saying same thing with the sort of Page and Wooter's emergent time mechanism. I can get time to emerge in any way I want. And what that means is I can basically get the effective laws of physics for the rest of the universe to be whatever I want.
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And they're not changing the laws of physics. Like in this picture, the laws of physics are supposed to be given to you. And all you're doing is taking a solution to the Wheeler-DeWitt equation, to h psi equals zero, this quantum gravity replacement for the Schrodinger equation, or specific version of the Schrodinger equation, I should say.
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And you're supposed to say, you know, here's what this means in terms of an emergent time evolution. And Albrecht and Iglesias are saying, I can get what, well, time evolution means laws of physics, I guess is what I'm trying to say here is, right? It's not just that things change with time. They change in a particular way.
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And that way is supposed to be a reflection of the underlying laws of physics. And Albrecht and Iglesias says you can get time to emerge in a sufficiently large number of different ways that in exactly the same quantum state, you can talk about it as if the laws of physics are whatever you want them to be. That's a problem, right? That's what they call the clock ambiguity.
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This freedom of dividing the quantum space of possibilities, the Hilbert space, into subsystems is, of course, exactly the problem of quantum mereology that I've talked about many times. But I was always talking about it in the vastly simpler case where you imagine that time really is fundamental. that the Schrodinger equation is describing time evolution.
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And we're using, in the paper that I wrote with Ashmeet Singh about quantum meteorology, how to divide... Hilbert space up into subsystems, we absolutely took advantage of the fact that time evolution was real and is fundamental, and we could use that to say, okay, certain ways of dividing the Hilbert space up make sense and certain ones don't, okay?
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Here, where you don't have real time evolution, your freedom is vastly greater, and you can just divide things up however you want. So that's it. That's the state of the art right now. This is what I'm trying to get you to. I don't know whether time can be emergent or not. There's other wrinkles here. As you might tell, my voice is running out. I'm at the tail end of a cold. It's that time of –
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year. I can't talk for too much longer. But there's other wrinkles here. One other very interesting wrinkle is an idea called the thermal time hypothesis, which was proposed by Alan Cohn and former Mindscape guest Carlo Rovelli. They are using, they're saying, well, what if the universe is in a thermal state and they can sort of use features of the thermal state to get an emergent time parameter?
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But I think it has exactly the same sets of issues here. So here is the upshot of this. If time is supposed to be emergent in the sense that the real true quantum state of the universe is not changing with time, but we think that we can divide the universe into clocks, subsystems, and the rest of the universe, there is the worry that there's too much freedom in that.
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And that as a result of all that freedom, there's actually no answers, no sensible answers to how time really emerges in that particular system. Okay, so that is the state of the art right now. And I will tell you my guess. And this is, you know, now this is what I'm doing for a living.
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When I'm not doing podcasts and things or writing books, when I do physics research, this is one of the things I'm thinking about very seriously. which is, again, I've already given it away, but it's that we need to take decoherence, classicality, and the arrow of time more seriously.
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You know, the world is not rearranged, sort of scattered and completely randomly constituted from moment to moment in time. There's always, long before Isaac Newton, some notion of continuity and even some rules of thumb about how things change from moment to moment. But when Newton comes along, you really have this rigidity happening.
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So the game that is being played here is quantum mechanics gives us a lot of freedom to divide up the space of possibilities in different ways, and that freedom is too much, say, Albrecht and Iglesias. That's the clock ambiguity.
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And my suggestion is, well, yes, but some of those ways are not going to give rise to nice emergent classical descriptions of space and the things in it and the evolution of those things in it, okay? So again, the lesson being maybe the way that time emerges depends on the way that space emerges, and in particular in a way that allows you to get a classical or semi-classical description.
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And this, by the way, opens an interesting possibility. I don't know if that's true. That's like a guess, okay? Or let's call it a conjecture. That sounds more science-y. It opens an interesting possibility. I said before that if time is fundamental, then you have two choices. The Hilbert space, the space of possibilities, is finite, dimensional, or bounded.
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And in that sense, you're in trouble because of Boltzmann brains and recurrences and fluctuations. If it's unbounded, you have at least a possibility of getting an empirically adequate description, a description of cosmology that matches the universe we see because you can have time evolving forever but not come to the same place over and over again.
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That's one possibility I think is absolutely alive and on the table. Maybe time is just fundamental. Maybe it's just there. That's absolutely worth taking seriously. The other one is the time is emergent. It is not fundamental. And then I think the hope would be the following. What if the space of possibilities is bounded? OK, so the Hilbert space is finite dimensional.
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The problem before was that if you have real time evolution and that time evolution is eternal, if you have a bounded space of possibilities, you will explore all of it and you'll explore all of it again and again. And that's bad. But if time is not fundamental, then the space of possibilities can be finite dimensional.
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And maybe the way that time emerges basically says there's only a finite number of ticks of the clock, right? Okay? The emergent clock doesn't tick forever. It doesn't go forever. There really would be a beginning to time and an end to time. Or maybe it's cyclic. That's also a possibility. But at least it's finite in scope. Okay? So maybe you can escape.
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the menace of the Boltzmann brains or recurrences, etc., if time is emergent and there's only a finite number of ticks of the clock. And maybe that helps explain why the Big Bang is so special, right? It's a boundary. Maybe this is a way of having the Big Bang truly be the beginning of the universe and
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And it raises the specter or the possibility or the prospect, however you want to put it, that not only was the Big Bang the beginning, it was time equals zero, but there is also a last moment of time because time is only emergent anyway. And the whole space of possibilities is finite dimensional. So somewhere in the future, we will reach the end. And you might go, well, what will that be like?
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this deterministic aspect to the evolution of the universe over time.
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Will we hit a wall? Will we hit a singularity? And the conjecture would be, no, that's not what it is like. Rather, we just approach equilibrium, right? It's very much a fading away rather than a burning out, the universe ending with a whimper, not a bang in that sense. So in that case, if that's all anything close to true, you don't notice anything because nothing is happening.
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Of course, the most vivid version of this is in the Laplace's Demon Thought Experiment from Pierre-Simon Laplace, much later, circa 1800, where he tries to say that, well, he imagines saying that if a vast intelligence knew everything about the universe, the complete state of the universe at one moment of time, that is to say, more specifically, the positions and velocities of everything in the universe at one moment of time,
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Like the set of things that happen— gradually cease to become interesting as you approach the later moments in the history of emergent time. So that's the other way I think it can work. There's basically two possibilities I think are alive.
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One is that time is fundamental and eternal and the space of possibilities is infinitely big and we seem to live in a universe with time evolution because the universe is always evolving and there's always an arrow of time. The other possibility that makes sense to me is that the space of possibilities is finite. Time is emergent.
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And for some reason that I have no understanding of whatsoever right now, the way that it emerges begins with a very, very special low entropy state and then sort of expands and cools the way that our Big Bang did to some finite period of time in the future. Maybe the reason why it does that is because that's the way to get –
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semi-classical anthropically allowed descriptions or something like that? I honestly don't know, but that is something we're thinking about. So, you know, this is not connected very strongly to how we would teach quantum mechanics to undergraduates, right? Like you teach the simple harmonic oscillator and you treat it as a spherical cow, right? You imagine the spherical harmonic
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The simple harmonic oscillator is all by itself in the universe. But the sort of lesson, the moral of this story is the rest of the universe matters, that we need to take into consideration the way that you measure things, the way you experience things, what you mean by time passing and all that stuff. And all that sort of relies on—
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The idea that there is a classical limit, that there are individual branches of the wave function in which we can coherently talk about stuff happening that more or less resemble classical evolution. Is that really necessary? Is it the only way to go? I truly don't know. I think these are very, very good open questions. So time, something we don't have a complete 100% understanding of. Is it real?
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Yes. Does it exist? Yes. Is it fundamental? Is it emergent? Even if we think we completely understand the equations of quantum mechanics, we don't yet know the answers to those questions. That is both kind of sad because we've had 100 years to figure it out since the advent of quantum mechanics and we haven't done it yet, but it's also heartening.
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Sometimes it's better just to listen to other people, which is why we have the format of Mindscape as we have it. But I do have some things that I know something about. So I couldn't decide. So what I did is I went on to Patreon, where we have our wonderful Patreon supporters for Mindscape. You yourself could be a Patreon supporter if you just go to patreon.com slash Sean M. Carroll.
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It's always fun when there are big unanswered questions yet to be addressed. So that's what we're trying to do. If I do it, I will let you know. I will update you. Thanks for spending this time with me, whether it be fundamental or emergent. And here's to a hopeful 2025. Take care. Bye-bye. Bye-bye.
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then given Newton's equations, you could tell exactly what the universe would be in the future and what it had been in the past. Laplace's demon doesn't exist. None of us is Laplace's demon. It's just a way of making vivid the idea of determinism, of making very clear what it implies.
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And even though it's not necessary, this existence of deterministic laws of evolution suggests thinking about the universe in a new way. It suggests a four-dimensional perspective because what the universe is at any one moment is so clearly unambiguously and rigidly related to any other moment.
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You can think of time as a location, as a way of finding yourself in a universe that you could think of as four-dimensional. Of course, Einstein and relativity made that almost necessary to think of the universe as space-time, as four-dimensional.
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because the way that we slice up spacetime into space and time is not absolute, as Newton assumed it was, but rather relative to how you move through the universe. But even before relativity comes along, the existence of deterministic equations of motion lets you imagine that the whole of reality should be thought of as the four-dimensional thing, the four-dimensional system.
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This is the eternalist point of view on time rather than the presentist point of view on time, which says that only the current moment is actually real. A lot of us start the new year saying that we will learn a new language, but it's hard to actually commit to it. Babbel makes it easy to learn one in less time than you think.
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That's babbel.com slash mindscape. Rules and restrictions may apply. For today's purposes, we're not going to debate presentism versus eternalism. I'm actually quite, you know, I'm an eternalist by inclination, but I don't really care.
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I think that whether you're a presentist or eternalist about the universe, that is to say, do you believe that only the present moment is real or that all moments are equally real? is in a very plausible sense a matter of taste, right? There's no experiment you can do to show, even in principle, to show that eternalism is right or presentism is right. But it's an attitude.
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It is a way of thinking about all of the universe, and attitudes matter. They suggest ways forward. You know, this is always true about theories of physics. It's very often true that different theories of physics can be formulated in completely equivalent ways, right? But when you formulate them in one way or another, it might suggest ways of going beyond those theories.
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303 | AMA | February 2025
They have ways of thinking about this. They know what the issues are. And the thing is, you don't simply—these words that we use when we talk about these in ordinary language don't map exactly onto what real cosmologists actually do. The point is that cosmologists have a model. They don't just use words like, ah, the universe is expanding, the universe is accelerating.
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I'm just going to say, look, what I mean by real is it plays some causal role in the universe. It helps me understand what will happen. As I've given the example many times before, if someone says there is a table in the room over here and there are chairs around that table, then instantly certain things appear in my mind like, oh, so we could go sit at the chairs around the table.
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You say, I have Einstein's equation in general relativity. Under assumptions of homogeneity and isotropy, this turns into a differential equation for the scale factor of the universe, the relative size of the universe at different times, called the Friedmann equation. And the Friedmann equation depends on the sources of matter and energy and curvature in the universe.
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the amount of ordinary matter, dark matter, radiation, vacuum energy, et cetera. And with all of these ingredients, the specification of what those ingredients are, how much matter, how much radiation, et cetera, at any one moment of time allows you to predict what the observed relationship should be between a redshift and a distance.
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303 | AMA | February 2025
And then you match the data to the observations and you figure out, aha, the data will match the observations if 70% of the universe is dark energy, vacuum energy, 30% is matter, and 10 to the minus 4 is radiation, something like that. Now, when we explain this to people, they don't want to hear that. They want to hear the universe is accelerating or the universe is not accelerating.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And that's true. Those are accurate statements. The universe is accelerating right now. But the way that you actually get there is this very careful procedure of matching data with theoretical predictions. Ken Wolf says, I recall you saying that you are not fond of the old-fashioned cocktail because it depends too much on sweetness for its flavor.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Is there any whiskey or scotch-based cocktail that you do like, or is anything more than a splash of water simply not acceptable? Well, look, everything's acceptable. I hope I've been clear about that. You can do whatever you like. I have my own preferences. If you include American whiskeys like bourbon and rye, then certainly I love lots of cocktails with whiskeys. I'm a huge fan of Manhattan's.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
among other things. I don't know exactly what the definition of whiskey is as opposed to other spirits. So I don't know, you know, is brandy whiskey? Is cognac whiskey? I think typically not, but they're comparable. They're similar in certain ways to bourbon or rye. Scotch is notoriously a spirit that is hard to turn into cocktails, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It's so unique and it's so flavorful on its own that either drinking a neater over an ice cube is how I would generally go. Kelly Hoogland says, what do you think the average person misunderstands the most about artificial intelligence and large language models?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
For me, I've heard a lot of buzz about how ChatGPT is much more water and energy intensive than a standard Google search, a fact which people are now using as a moral argument against people using it at the individual level.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I feel like this completely misses the mark and is analogous to shaming someone for forgetting to bring their own grocery bag and turning a blind eye to corporations profit maximizing behavior. In my opinion, this is a greater misunderstanding than the fear that AGI is going to take over and start ruling us.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Maybe that's possible, but, you know, plenty of people do shame each other for not bringing their own grocery bags. This is just a feature of human nature. It's not a great feature of human nature. I'm on your side about deploring it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But when we see individual behavior, we find that very judgeable in a way that the invisible corporate or systemic or government, for that matter, behavior behind the scenes does. tends to be a little bit more invisible, going back to the shooting the United CEO kind of thing, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I mean, how do you relate, how do you compare the crime of shooting an individual person on the street to the crime of denying a whole bunch of people health care, right? One is much more visceral. and visible.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
In the case of AIs and large language models, I do think that there is some tribalism going on, some choosing of sides, because there's a whole bunch of reasons why you might be either skeptical or outright hostile to AIs. One reason is the way that they have been deployed by corporations, right? Google searches or Microsoft products are now full of AI when nobody asked for it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
We could put our beverages onto the table and it would hold them up. right? So that information that is useful about dealing with the world, predicting what will happen, anticipating what comes next, strategizing between different alternative things, actions we could take and things like that, that's what I mean by real, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Another reason is if you're an artist or a writer or for that matter, any other number of professions that have their livelihoods in danger of being stolen away by AI. Or like you say, there's the worry about resource usage in various ways. And these are very different objections, right? Like these are not the same objection, but we get aligned.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
We care about one of these objections and we start relying on other ones just to build our case because we've already decided what side we're on. And then we just collect evidence to make our side happy. I think that the question of using up resources is a very tricky one. I mean, it is clear that As a whole, on the aggregate, AI and other – the label AI is a little not exactly appropriate here.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
People are using computing power for all sorts of things. But computing power broadly construed uses up an enormous amount of resources, uses up an enormous amount of electricity and water and things like that. I've seen plenty of people complain about this.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I have not seen much of a sensible breakdown of how much an individual attempt to query ChatGPT about what is the best way to make a noodle dish with ground pork or something like that. Does that really... use up an enormous amount of electricity compared to something else? I honestly don't know. I'm saying that I haven't seen it carefully compared to other things that we do, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
This is just, again, another very basic human flaw. We like to think about total amounts rather than rates, but the rate is what matters. What is the rate of an individual person's use of AI in terms of electricity and water consumption versus other uses of AI?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You know, people in California work very hard to not run their faucets too much because there's a water shortage, but the enormous fraction of water is used by agriculture, not by people running their faucets.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
That's not to say that people should waste water running their faucets, but it's just very hard to get accurate information about the actual scope of the problem versus the thing that you feel you personally can have a handle over. I think that the real danger of AI is neither one of these things, is neither power usage or AGI taking over and ruling us.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It's that we start handing over really crucial functions of society and technology to algorithms we don't perfectly well understand. Right. And that is going to lead to very down-to-earth mundane failure modes that I can foresee happening in the future.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So I think that there are very legitimate worries about this technology, but they don't always match up to the worries that people spend a lot of time talking about. Rue Phillips says, did Google's quantum chip willow really tell us anything about the multiverse? Is there any measurable connection between quantum computing and many worlds?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
If someone lied, if there were no table in there, or if the table were an illusion, if it were a hologram, then it would not be real because I would mistake what the implications are of that statement. So I don't think it's that controversial or hard, of course, around the edges, making things perfectly definite can be tricky, but I just try to be clear about what I mean when I use those words.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I should have grouped this clearly with the earlier question, so no. There's no measurable connection between quantum computing and many worlds. There is arguably a connection between quantum computing and wave function realism. I think someone like David Deutsch would say that, in fact, he has said, I don't need to think it, he has said that hidden variable theories, which are also real,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
wave function realist theories and also say that the wave function strictly and only obeys the Schrodinger equation, Deutsch would say these are just Everett in disguise because you have the whole wave function. It's going to branch. It obeys the Schrodinger equation. There's going to be decoherence. All of those things are true.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And he would say that the advocates of pilot wave theories then add these hidden variables and say, OK, yes, but this is what's real. And he just doesn't believe that that makes any sense. So I don't really think that anyone who advocates any currently popular theory interpretation or foundational approach to quantum mechanics would be surprised that quantum computers work.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And therefore, you know, to be fair, I don't think that we have gained any information that changes our credences about these different approaches. Anonymous says, have you considered doing 23andMe or similar services? You've mentioned that you don't know much about your ancestry. Could be interesting to learn. Maybe there's a physicist somewhere in there.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It also provides a lot of useful medical info. So no, not really. I'm not that curious about my ancestry, and I'm very worried about handing over my genetic information to faceless corporations.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I mean, in fact, it became clear that 23andMe in particular had worked out quite an amazing gimmick because they are taking all of this data from people who have handed over their data to them, and they're using it to do—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
pharmacological experiments and things like that you know they're basically ordinarily the corporation would have to pay the person to get the data that they needed but 23andMe figured out a way that the people paid them for the privilege of giving them their data and I don't think that was a very good bargain.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Of course, genetic tests can provide a lot of useful medical info, but if I ever thought that that was something I needed to do, I would just try to do it on an individual level with a doctor, not with a corporation like 23andMe. Not that it's bad to have done it, but that's the bargain that I would personally make. Ilya Lvov says, thank you for your solo episode on emergence.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
In it, you provided the definition of emergence as the operations micro theory goes to macro theory and time zero goes to time one commuting with each other. Doesn't this by definition rule out strong type three emergence? Isn't the point of the strong emergence that the macro theory predicts brand new outcomes that the micro theory starts being wrong at a certain scale?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Yes, that is completely true. So if you think that strong emergence can happen, then that simple idea of the commuting diagram between time and the emergence map would fail. And in the paper, we say that very explicitly. I still think it is useful to start with that conception because it's easy to understand.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I know that out there in emergence land or in the land of people who talk about emergence, there is a strong constituency of that resists any version of emergence that is understandable. They think that emergence is only an interesting concept in those cases where you can't understand what's going on. And I resist that. I don't think that's true.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
In some cases, you can certainly understand what's going on. And they would say, therefore, that's not emergence. I would say it's a kind of emergence. Let's understand this first. And then let's add on the weird stuff that you want to add for the strong emergence later. That's my personal preference.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Miron Mizrahi says, I'm guessing that you and Jennifer are reasonably frequent flyers. Do you have any specific approach you take to packing? Do you have sets of travel gear or do you just pack the same things you use every day? For example, I have a full toiletries bag just for travel. Any packing routines? Are you a light or heavy packer? I think I'm a medium packer.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Nicholas Sharosky says, given your stance on poetic naturalism and emergence, would you say that when describing a sunset, both person A, who says shorter blue and violet wavelengths are scattered by rarely scattering, and person B, who says the light dances, transforming the sky into a fiery canvas, are using sufficiently accurate and useful vocabularies to be considered real.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
How does this align with your notion of emergence, where different levels of reality and their descriptions must remain compatible? Does the poetic vocabulary of person B, in your view, fall short of the scientific one of person A in capturing reality, or is it equally valid? I don't think it's equally valid. I think they're both completely valid, right? But that doesn't mean equal, you know?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
They're trying to do different things. If I said, could you explain— physically, why the sunset looks more red than blue, and someone gave me the answer, the light dances transforming the sky into a fiery canvas, I would not give them full credit on an exam, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Likewise, if I said, give me a poetic description of the feelings that this sunset evokes in you, if you started talking about Rayleigh scattering, I would not give you a full marks on that exam either. I think it's relative to the kind of thing you're trying to achieve.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Now there's the additional factor that in these two cases, the kinds of things you're trying to achieve, a scientific understanding of photon scattering versus a poetic description of the feelings that are invoked by the sunset, have different standards of success, right? Science, the scientific kind of description there is much more precise and rigorous and testable and quantifiable.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And the more poetic description is a little bit harder to judge whether it's successful or not. That doesn't stop them from both being accurate or both being real. They're just trying to do two different things. Nico Bersianek says, my question is about quantum field theory. When an observer travels in space, for example, do they cross quantum fields?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Is there a way to verify to measure that we're traversing through all or some quantum fields by moving or, on the contrary, fields are always anchored to the observer? Certainly in the way that we think about quantum field theory and what quantum field theory means, the fields exist everywhere. That's what it means to be a field.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
A field is the answer to a question, at this point in space, what is the value of the field? For every single point in space, a field has a value. The electric field has a value at every point in space. It might be zero. So you might say there's no electric field here, but you don't actually mean the electric field doesn't exist there.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
What you mean is the value of the electric field is zero there. Just like when you have a function of y as a function of x, if that function happens to cross through y equals zero, you don't say the function stops existing, you just say that its value is zero. If the temperature is zero degrees Fahrenheit, you don't say there's no temperature. you just say the value is zero.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Same thing with quantum fields. They exist everywhere. They're not pulled along or traveling along. You absolutely do pass through them in the sense that you pass through space and the fields are everywhere in space. I don't know how to pronounce this.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It is true that we travel a decent amount. We're trying to cut down a little bit for various reasons on the amount of travel we do. It was definitely noticeable after the pandemic. that we'd gotten out of practice traveling. I do, in fact, have a travel kit with the toiletries and things like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Timlo, P-T-M-I-L-O, Private Milo maybe, says, is your objection to the potential for large language models to exhibit more generalized and extrapolation-heavy intelligence based on deeper principles, or is it more intuitive? That is, is there anything in information theory that tells us it is impossible for locally generated interpolations of tokens to uncover patterns and sequences that
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
that are indecipherable from conventional human-like extrapolation successes. Well, I don't think it's based on deeper principles in the sense that it's a proof that you're asking about. In fact, I'm open to the possibility that large language models could construct, you know, sorry, let's back up.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The large language model is optimized to give sensible-sounding answers to human beings asking questions of it. Now, it may very well turn out that in that black box of many, many layers of deep learning, the way the LLM does that is essentially to invent intelligence, to invent a model of the world, invent sort of counterfactual reasoning, invent all those things. I'm open to that possibility.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
However, number one, I don't see why that would necessarily be the case because that's not how you've programmed the LLM. It would have to be a case where the optimization procedure was just so successful that the LLM founded itself despite the fact that that's not what it was trained to do. And number two, in the data, I see no evidence of that happening, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It's not that LLMs don't become better and better. They're clearly becoming better and better. But they aren't perfect, and they make mistakes, and they make failures. And my point has always been the types of failures they make are precisely the type you would expect if they were not being real human intelligence, if they were not causally mapping the world and inventing counterfactual reasoning.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So I am very open to new evidence coming in that changes my mind. That'd be super duper interesting if it were true. I just haven't seen it yet. Ed says, I know you're not an AI expert, but you have had a number of AI expert guests, so you likely have a better handle on it than I do.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Do you have a sense as to whether there's a fundamental difference between the theory of operation of an AI LLM and that of an autocorrect feature on my phone? Is it just a massively scaled up version of this thing that is always failing to guess the next word I want, or is it doing the same thing in some utterly different way? I think it's both. It's a little bit half and half there.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Certainly, there's a spiritual connection between LLMs and autocorrect. I mean, autocorrect is not a separate kind of technology, right? Autocorrect is next token prediction. And in a very real sense, LLMs are... very, very, very souped up next token prediction. It's not just the next token. They're predicting more than that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And, you know, I have a tiny little checklist, like you need the travel kit, you need your phone, you need your computer, you need chargers, right? You need all different cables. that we carry around everywhere we go, passport and things like that. Otherwise, I don't have much of a routine.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
They have some memory of what they've been talking about and things like that. They have very important, crucial distinctions between a simple autocorrect kind of thing. But there is that spiritual connection. So I think that there's both a similarity and a difference there. Jesse Rimler says, I'm currently reading the wonderful new David Bentley Hart book, All Things Are Full of Gods.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It's a thoughtful and engaging philosophical treatise on consciousness and materialism written as a platonic dialogue. Hart is religious, and I generally disagree with him. I'm guessing you would too. but it does make me think about the areas where non-materialists can find argumentative purchase.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Do you think that the irreducible experience of consciousness is one of those brute facts that allows otherwise rational thinkers the wiggle room to play around with non-scientific ideas? If I understand what you're asking, no, I do not think that. I'm not sure what the word irreducible means in the phrase the irreducible experience of consciousness. there is an experience of consciousness.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
How do I know it's not reducible? I don't even know necessarily what reducible means. I worry that it means different things to different people. I've been very, very clear about what I think consciousness is. I think that people obey the laws of physics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And I think that we talk about people using a higher level emergent vocabulary, which absolutely includes all the interior first person consciousness talk. I don't think that there's any fundamental difference between that and the exterior talk that we use about how people are moving or talking or thinking or whatever.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So I think that there is some temptation to treat consciousness as different precisely because it is first person. There is something unique about my consciousness from my perspective, sure. But I want to understand the world comprehensively and fundamentally, and I think that by far the leading way to do that is to not treat me as all that special, including my consciousness.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It's just a higher-level emergent way of talking about the collective behavior of atoms and electrons and photons in my brain. Polina Vino says... Computable analysis is a kind of analysis that is compatible with computability theory.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
For example, we have the computable intermediate value theorem, the assertion that if f is a computable continuous function and f of a less than c less than f of b for computable reals a, b, and c, then there's a computable d with f of d equals c. Does that make sense?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I try to travel light, but if you're going to go to the gym while you're there but also go to a fancy dinner and also just be casually walking around the city, then there's already three pairs of shoes you need in some sense. So it can be hard sometimes. I don't have any special – clues or tips or anything like that. I'm not an expert traveler.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You have a function and you know the function at some argument is less than c and that is less than the function for b, then in between it had to go through c. That does make some intuitive sense. The idea is that these computable theorems do not say anything about numbers that cannot be expressed in terms of an algorithm.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Do you think that this type of analysis has any place in physics research such as in the effort to make relativity and quantum mechanics compatible? For example, maybe limiting mathematical results used in computations to only those that discuss computable functions and values could expose where we helped ourselves to conclusions about things we can't even express. Well, it's possible.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It's absolutely possible, but I don't see how exactly that could happen. For one thing, let's be clear. Relativity, in the sense of special relativity, Einstein in 1905, is 100% compatible with quantum mechanics. That's where quantum field theory comes from.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
General relativity, which is Einstein's theory of gravity, has not yet been quantized, or to put it slightly more carefully, we do not yet have a quantum mechanical theory that in the classical limit achieves all of the predictions that general relativity does, okay? But okay, but that's still a problem.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You're suggesting that a particular kind of focus on a particular subset of math might be helpful, computable analysis. It might be. That's just too vague of a suggestion to me to really think about. It's like, you know, there's a lot of cool math out there, right? Category theory is something that is very exciting among mathematicians right now.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
We talked about it with Emily Real on the podcast some time back. And a lot of people are very optimistic this is going to help us understand some deep questions of physics. The proof of the pudding is in the tasting. You know, it's great to be excited by cool math, but you can't just say, I think maybe this is going to help solve some problems. You've got to solve the problems.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I'm sorry, that's just how it works, you know. In order to get people excited, you have to kind of show them the money. You have to give them the killer app. Schleyer says, your discussion with Stone Farmer touched on the fact that our economic system averages growth around two or three percent per year, which I believe means a doubling in size every few decades.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It's surprising to me there isn't more work being done to come up with an economic system that can thrive and persist but not grow. Why don't we inevitably need that given finite resources? Do you have thoughts on why this isn't a significant focus of economists or others who study complex systems? Well, I do think that this kind of thing is a focus.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I mean if you mean how could we make a transition to a fixed economy rather than a growing one, that's not much of a focus of economists because I don't think that most economists think it's either – plausible or desirable. I mean, for one thing, at the very, very most basic level, the population of the Earth is growing, right? So there are more people.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Remember it. Keep it in mind. Not act like it's business as usual. One of the biggest things that Trump and his allies have going for them is the idea on the part of everyone else that it's just another political squabble. But it's really – Not. It's worse than that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
If you had an economy that didn't grow, that would be less and less resources per person, and no one's going to vote for that. But even if you do live in a country where the population is not noticeably growing, people like to think that their descendants might be better off than they are, right? That is something that is... very much a goal of a lot of people.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I think at a down-to-earth level, there are reasons why growth and indeed a little amount of inflation are useful. Just to give you one very, very easy to understand one, is helpful if I want to—different things. Maybe I want to buy a house, but maybe I also want to start a company, right? For various reasons, I might want to take out a loan.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
That is borrowing so that I have money right now against the promise of a future payment. A tiny bit of inflation will ease the burden of paying back that loan in the future and therefore make me more likely to take out the loan and therefore, in a well-functioning economy, makes it a little bit easier to make progress and have everything be active and churning and new things going on.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I'm not one of these people who dwells in great detail on the most efficient way to pack. For that, you know, yeah, you got to go somewhere else. Sorry about that. This episode of Mindscape is sponsored by BetterHelp. When it comes to relationships, we often hear about the red flags we should avoid. But what if we focus more on looking for the green flags in friends and partners?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Now, of course, this is a tricky thing because you don't want too much inflation. That means that everyone's savings disappear. So there's a very, very fine line to be drawn there. And of course, getting it right is what economists talk about all the time. I do think that...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It's just wrong to think that things would be easier if we fixed everything at a constant value of GDP and just tried to keep it completely stable like that. It's hard to make it stable. For one thing, there are fluctuations up and down. So if the overall trend is growing, then the downward fluctuation is relatively benign.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Whereas if the overall trend is flat, then a downward fluctuation can be pretty devastating. So maybe there are good reasons why you don't want that, and maybe that's why it's not a significant focus.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Zach McKinney says, inspired by your episode with Eddie Pross, if you were to consider and model functional democracy as a dynamic kinetically stable system, then what are the inputs or conditions that you would hypothesize are needed to maintain kinetic stability?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So I'm answering this question because I have no idea what the answer is, but I think it's a super important question in some version or another. So I'm not – I don't understand – the specific idea of dynamic kinetic stability well enough to say that that's the right kind of model to use. I mean, it's a little bit specific to chemistry, honestly.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But the more general idea, if you remove the word kinetic and just say, you know, dynamic stability, that's a very general idea. Lots of things are sort of stable in the aggregate, stable at a macro level, like a human being is certainly mostly stable, right? Like I don't change my configuration dramatically from moment to moment, but only because I take in fuel from the outside and then...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
throw away entropy and energy back to the world. The biosphere as a whole does that. Waterfalls, you know, the great red spot on Jupiter, many different things. So you want a functioning democracy, or any kind of functioning country for that matter, to be something like that, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I mean, the individual human beings are allowed to move, but the overall shape of the country maintains some coherence. and you also want it to be stable. So, I mean, just like the economics question above, you want perturbations to fluctuate rather than to grow, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Stable to a physicist means if I poke it, there's a system that I poke, so I do a little perturbation, I change something about it, Does the perturbation sort of oscillate back and forth or does it grow bigger and bigger? If it grows bigger and bigger, then it's unstable and that's bad. So that's a positive feedback loop, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
When a tiny deviation in one direction keeps growing in that direction. Doane Farmer's point is that it is often in the economy, very typical to have these unstable positive feedback loops and the complexity economics perspective is supposed to help with that. I think there's been much less study about that at any quantitative level for political science, for democracy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
There's been a lot of sort of qualitative political science and historical work on the stability of democracies or the lack of stability sometimes. But thinking about it in terms of physics systems or chemistry systems has not been done a lot. I would like to see more of that. I'm going to do more of it myself, and I'll let you know if I come up with anything good. I haven't quite yet.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Tim Giannizos says, a great hits and misses episode. You mentioned that your paper about the origins of the arrow of time avoids making an assumption about a single low entropy beginning. But does it just make a different assumption that the natural state of the universe is empty to sitter space? So two things. Number one, no, it does not make that assumption.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It says we make an argument, a very hand-wavy argument to be sure. But the argument is, if you're not in empty de Sitter space, you approach it. It's basically the cosmic no hair theorem proven by Bob Wald back in the 1980s. And then there's a reason for that. The reason for that is that in the presence of a positive cosmological constant, de Sitter space is the highest entropy state.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So that's the whole point, part of the whole point of our paper, which is that you have to start somewhere. By start, you don't mean the initial condition of the universe, but you have to have a condition for the universe at some moment of time, and then you try to evolve it both forward and backward. And our point was you don't have to tune that condition at all.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It can be very, very natural, very, very generic. And you can think of that as either saying, well, I'm going to pick the most generic state, and it would indeed be empty decider space. Or you can think about saying, I want to allow for other things, but guess what? Those other things evolve into decider space. You get the same answer either way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Eric Hogan says, in the solo episode about time, you talked about stuff fluctuating into existence, maybe even the universe itself. It isn't clear to me what you imagine that such a universe producing fluctuation would look like. Would a super dense expanding bang instantaneously appear from nothing? Or would white holes grow from radiation and spit out stars?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Would the dead rise from the ground and ungrow into babies? Would galaxies dissolve into smooth gas clouds just in time for the big crunch, just by chance? If it was time symmetrical, would it even make sense to call one of the two histories a fluctuation? So I'm not sure exactly what you're referring to. This is entirely my fault about the stuff fluctuating into existence.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
For the universes fluctuating into existence, if I said something like that, I did not mean... the entire universe fluctuating into existence. That is not something that I particularly have contemplated. I don't even know what that means. If there was no universe, what is there to do fluctuating? We did have a
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
In this scenario I was just talking about, the one from the Arrow of Time paper with Jennifer Chen, we had the idea of baby universes, where you have a pre-existing universe that can undergo a fluctuation inside itself that would cause a little tiny bit of universe to pinch off and go its own way. There we have a picture of what it would look like.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It would look like, well, let me emphasize the important point here. The amount of baby universe you need to pinch off is very, very tiny. It's just a little Planck scale-sized thing. You don't need to undergo the entire history of the universe backwards. It's not anything like that at all. What it would look like is a number of particles, photons or whatever.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I'm not sure what the most likely thing would be. would actually be, but a bunch of particles come in by random fluctuation and collide with each other in a small region of space, enough to make what looks to the outside like a black hole, but actually inside is a baby universe pinching off.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And then that thing that looks like a black hole then radiates away, and that whole process looks more or less symmetric, right? Bunch of particles come together, make a black hole, black hole evaporates into a bunch of particles. But the set of particles there is enormously smaller than what you would need to make a big universe-sized thing like us.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The reason why that's viable is because of inflation. Because inside the baby universe, you can use the laws of physics, take advantage of the property that a closed universe has zero total energy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So if that closed universe is full of an inflaton field, it can expand to an arbitrary size, and that inflaton field can turn into ordinary matter and radiation and create many, many, many, many more particles than you actually needed to make the baby universe in the first place.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
If what you're referring to is some self-contained universe, then I would not use the vocabulary of fluctuating into existence. For a baby universe that comes from a pre-existing space-time, I think that language is appropriate. For the universe as a whole, if you mean a universe that just has a beginning, then I would just say it's a universe that has a beginning.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I would not say that it's fluctuating into existence out of nothingness or anything like that. Johann Yartelius says, can a molecule be earmarked? There's this factoid, or perhaps trueoid, that with every breath we breathe, we get an oxygen atom once breathed by Julius Caesar. Now, from a probability point of view, I'm sure this makes mathematical sense.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But if one would want to test it, how would one do so? Is the likelihood larger that a water molecule, for instance, stays closer to where it met me, or is the dispersion equal? If I wanted to register individual molecules to see if that particular molecule returns to some given point, i.e. a water molecule passing through my faucet again, could I do so, and if so, how?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So to the actual question, can you earmark the molecule, Not really, is the answer. It depends on what you mean. I mean, you can always take that molecule and attach it to another molecule. But if you're talking about an oxygen atom or a water molecule, they're sufficiently small that if you attach them to large other molecules, you're going to completely change their dynamics, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
They might not even float in the air anymore. But individual molecules is an interesting physics point. Let's start with an individual atom. An individual oxygen atom—oxygen atoms can be in different states, but by different states what we mean is the electrons in those oxygen atoms can have different energy levels, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
As we talked about earlier, when you're in a higher energy level for an electron in an atom, you tend to relax, you tend to decay down to the lowest allowed energy level. And so typically oxygen atoms are going to be in their lowest allowed energy levels. And all oxygen atoms that are in the same lowest energy level are indistinguishable from each other.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
They are literally indistinguishable particles in the quantum field theory sense of the term. So there's no marker, there's no way to say this is this oxygen molecule, that one is that oxygen molecule, or atom I should say. But even as you get to molecules, Molecules are more complicated. They have more moving parts, so it becomes slightly easier for more things to happen.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Molecules can vibrate and stuff like that. But if we're talking about things as simple as a water molecule, there's not an interesting set of vibrations that it can have, and even those vibrations decay away, so they all look alike. So no, you cannot really watermark the molecules.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It's true that if Julius Caesar breathes a breath, the atoms that he's just breathed out will, for the moment, mostly be near him. They're not going to instantaneously spread through the universe or spread even through the Earth's atmosphere, right? So when people make these statements, they are absolutely not just using numerology about how many atoms there are.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
they need to make statements about how quickly the Earth's atmosphere mixes, how quickly a test particle, if you have one particle in the air that is floating randomly, well, you know what the temperature of the air is, you know what the typical velocity is, and it's doing a random walk, it's bumping into other molecules.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So you can ask the question, how long does it take to sort of randomly go throughout the whole Earth's atmosphere? And the answer is less than 2,000 years. So that's why there is some quantitative sensibility to that kind of statement, even if you can't actually look at the individual molecules.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
DMI says, is the feeling that only the present we see is real, even though nothing in the physics equations makes it more fundamental than any other slice of spacetime, could that be the same kind of illusion that gives us the feeling that only the branch of the wave function we see is real, even though nothing in Schrodinger's equation makes it more fundamental than any other branch?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Kind of, I guess. I like the analogy and I'm trying to decide whether or not I think it's a completely accurate analogy or not. The wave function case is actually easier in this particular example because even though the wave function itself is very abstract, it is indisputable that if you believe any of the usual Everettian story, any individual agent is located on one and only one branch.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
of the wave function, and that's the branch they see, and that's the branch they naturally attribute reality to. And that's true across time, right? Not just for a moment, but in future moments as well. Whereas for the presentism question, you have to say, well, you have to distinguish between the agent at one moment and the agent at another moment, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
At any individual moment, the agent only sees a little bit of their immediate environment, but they attribute reality in the casual presentist kind of way of doing it to a whole slice of the universe very far away from what they see. So my worry about saying it's a perfectly good analogy is that there is more extrapolation in the presentism case, right? It's more model dependent.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It is more relying on the fact that I'm not only considering what I see around me right now, but I'm also treating everything at this one moment of time as equally real. And of course, everyone knows that relativity is a huge challenge to presentism because different people moving at different velocities would extend their present moment of time differently.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So how in the world can it be true that only one slice is real? Of course, the sophisticated presentists have answers to that. Since I'm not a presentist, I've never put any work into understanding what those answers are. Joan Beluda says, priority question. If you could get the definitive true answer to any open-ended question, what would that question be?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Well, this comes down to the question of whether or not the ultimate laws of physics are in fact deterministic or not. You know, Laplace's demon is a thought experiment meant to illustrate the implications of determinism in classical physics. That's the whole point.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The answer would be complete and thorough in a scientific paper. Yeah, it's a boring answer, but I guess I would say what is the correct theory of everything? You know, what is the correct theory of gravity and space and time and all the forces and quantum mechanics and all that? Just tell that to me.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I think that hopefully a scientific paper will be long enough to explain it in language I can understand. I don't know. I'm not expecting anyone to give me that paper anytime soon, but, you know, that would be pretty awesome if it happened.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Alexander Knirkel says, is there a theoretical mechanism how, when time emerges separately from space, the whole of space-time still ends up exhibiting this high degree of symmetry?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Lorentz invariance, or diffeomorphism invariance, all these different ways in which relativity convinces us, this is me, Sean, talking now, not Alexander, all the different ways that relativity teaches us that space and time are unified into spacetime. How does that come out of this?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And then Alexander continues, naively, I would expect that an emergent time parameter would not magically fall in place to form a nice representation of these exact symmetries. with the rest of space-time, and all the fields being in representation of these as well, but instead stick out like a sore thumb? So I think this is a very good question, a very, very important question.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
We don't know how this is supposed to work. So I think that there's two kind of competing intuitions going on here. One is... If I started with a theory in which time and space were clearly different, I just told you what was going on in space and separately had an equation telling you how things evolve in time, why in the world would that knit together?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So you build up by evolving in time, here's space, here's space at a moment later, here's space a moment later. And by space I mean not just space itself, but everything in space, the whole configuration of the universe. And I build up a bunch of these, okay? And then I say, okay, I've knitted together a four-dimensional spacetime.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Is it true that we have these symmetries like Lorentz invariance that we know and love from relativity? From that perspective, I agree. It would seem weird, right? That you would just magically have this invariance where I could now completely switch to a different perspective and get and slice spacetime differently and get just as good, the same laws of physics basically.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The point of Laplace's demon is that the information needed to predict what comes in the future is implicitly present in the moment right now. If you had the complete 100% comprehensive state of the universe. You never do, so that's just a thought experiment just to try to teach you what determinism really means. In quantum mechanics, for all intents and purposes, in the observable universe,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But there's another intuition, which is let's say that I have a theory that does have this invariance, that is Lorentz invariant, that does have the symmetries of relativity built into it. I am 100 percent allowed to pick a reference frame.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
to pick a decomposition of space-time into space and time to, within the terms of that decomposition, describe what's going on in space and write down equations telling me how it evolves in time. And so there's no obstacle to building entirely symmetric descriptions in a language that is manifestly not symmetric.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And so we're asking the question, you know, under what conditions does this step-by-step, moment-by-moment building up lead us to something that shares all the symmetries of relativity? And the answer is I don't know. I mean, there's something very nice about the symmetries of relativity. So I'm not in any sense convinced that they couldn't come out generically under some scheme.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But I don't actually know. I know people have tried, by the way. At least I am aware of the existence of various papers about the emergence of Lorentz invariance from not obviously Lorentz invariant descriptions. Divimorphism invariance is a very different thing. That's almost automatic. That's basically coordinate invariance. It's hard to not be divimorphism invariant. Or let me put it this way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Divimorphism invariance, which for those of you who don't know, is basically coordinate invariance. It's basically saying I can choose whatever coordinates I want, but there's sort of an active and a passive version of that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Changing the coordinates and leaving the underlying system invariant is one way of saying it, but then keeping the coordinates and moving the system is another way of saying it. That kind of sounds more impressive. But... In my mind, diffeomorphism invariance is a real thing, but it's a real thing that is a label that gets attached to descriptions of theories, not to theories.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So I can describe Newtonian gravity in a 100% diffeomorphism invariant way. I don't because it's just more convenient to— treat space and time differently, explicitly, to pick coordinates on time and coordinates on space separately. But I don't have to do that because it's a description statement, not a theory statement. Whereas Lorentz invariance is a theory statement.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Some theories are Lorentz invariant and some are not, so I would treat those differently. Anyway, yes, I would love to know whether or not Lorentz invariance under some very simple assumptions naturally emerges, and I don't know the answer to that one. Brendan Hall says, To what extent would you agree with this sentiment? You know, I get it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I think that you're correct that leisure is now more isolated from our fellow people. Arguably, computers have done that and smartphones even more than TV has. On the other hand, it's given us a whole bunch of enjoyment and entertainment that we didn't used to have. How do I weigh those two things against each other? I truly don't know. My own feeling is that probably TV is a net good.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I don't really want to go back 200 years to a place where I have to, like, learn to play the piano and sing to get my entertainment in the evening. But I have no objective way of actually doing that comparison. Nikola Ivanov says, it seems to me that there are different types of vacua that you discussed in podcasts.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The desider vacuum from your podcast on the nature of time, the vacuum at a black hole horizon, which gives rise to Hawking radiation, and the vacuum that gives rise to the cosmological inflation and the Big Bang. Can you please explain their characteristics and differences, if any? Yeah, that's a completely fair question.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
We use, as very often in science or in physics in particular, the same word to mean different things. The overall definition of vacuum to a physicist is, given some theory, what is the lowest energy state of that theory? So in ordinary theories, classical theories, empty space is the lowest energy state, and that matches on to our intuitive idea of what the vacuum is supposed to be, empty space.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
the laws of physics are not deterministic, okay? And I need to like put all those words in there with emphases about the observable universe for all intents and purposes, etc., because maybe there is a deterministic theory underlying what's going on. Both Bohmian mechanics or pilot wave theories and also many worlds in two very different ways are ultimately deterministic theories.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Once you have quantum field theory, it's a little bit trickier. So once you have both quantum field theory especially and also gravity, so that you have space-time curvature, then it can be trickier. So we talk about not only the vacuum locally, That is to say, here I am in some finite region of space and time, and I look around and there's nothing there. And I can describe what is going on.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
There's always something going on in quantum field theory in the sense that there is some state that describes the state of the quantum fields around me, but it's the minimum energy state as seen by me locally. I call that the vacuum. But then we also have this situation where there is a global situation. There's a black hole or cosmology or whatever.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And we can say overall, what is the lowest energy state? And usually, I'm tempted to say always, but usually those look the same in the limit of when you go Well, sorry, let me say it this way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Usually when I have some global vacuum state, that is to say the lowest energy state with a non-zero cosmological constant, so de Sitter space, or with a black hole nearby, right, then if I just choose to look only at... a very, very small region of space and time, it will just look like empty space to me.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
This is one of the lessons of the paper that I finally did just publish with Chris Shalhoub, a graduate student, where we look at Hawking radiation and what it looks like to different kind of observers. The point is, long story short, but you need to operationalize that question. What do you actually do when you want to say, I'm detecting Hawking radiation? What kind of detector do you have?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
How long do you turn it on for? And all these questions. Quantum field theory is tricky. If you try to operationalize what you mean by the vacuum by saying, okay, I have a detector and I turn it on and off, the detector needs to be coupled, interacting with the quantum fields that you're trying to measure, and therefore turning it on and off tends to create particles.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And even though you think you're in the vacuum, you're still detecting particles. That's one way of thinking about various effects in quantum field theory. Anyway, the point is that you can have different global vacuum states depending on the geometry of spacetime, but locally they should look all more or less the same. The differences become subtle like if you, you know, Let's put it this way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
If our universe continues to expand and has a positive cosmological constant and lasts that way forever, we will enter the de Sitter vacuum state, and that has a non-zero temperature. So we say that Minkowski space, that is to say space-time without a cosmological constant, it has its vacuum state. and its temperature is zero.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
If you have a thermometer there and just let it equilibrate with the vacuum, it will say zero degrees. Whereas in de Sitter space, there's a non-zero temperature. The thermometer you put there comes to equilibrium at a non-zero temperature.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But that temperature is so extraordinarily, incredibly low, the wavelength of a typical photon that is observed, that is being measured, is as big as the universe. So if you're confined to a tiny little region of space, you're never going to detect those photons. To you, it's going to look like empty space. So there is some commonality in all these different notions of vacuum state.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
George Candelopoulos says, Can you explain how matter and information are linked in these contexts? You know, I think it's a little bit casual, to be honest. I don't think there's a hard and fast set of rules there. Physicists are just as prone to speaking casually as anyone else, especially when they hope and think that the people around them will get what they are trying to say.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But in both of them, it is impossible for an actual observer in the actual universe to predict what is going to happen next. So it might depend on exactly what kind of Boltzmann—sorry, what kind of Laplace's demon you have in mind. Laplace's demon in Everett could predict the wave function of the entire universe, but there will be different observers observing different things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But I do think that part of it is that as we dig more and more deeply into quantum mechanics and quantum gravity and emergent space time and things like that, the fundamental stuff out of which the universe is made is a little bit less tangible than you might have thought. You know, in Newtonian, when Newton wrote the Principia, if you said, what is the universe made of?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
He would have said, well, some particles, right? He even thought light was particles, corpuscles. But he's mostly thinking of, you know, the Earth is a particle, or at least is made of particles. He didn't know about atoms, but, you know, he could imagine it was made of matter and things like that. And all that stuff existed in space. And it's all things you can see and touch.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Whereas if, like me, you're trying to show how gravity can emerge from quantum information, well, you can very well ask quantum information about what? But the answer is some abstract, d-dimensional factor of Hilbert space. You know, what help is that? It doesn't seem as material as a particle moving through space. It is, by the way, just as material.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It's just we're learning better what material means. And that's why... At a philosophical level, what used to be called materialism as a philosophy of nature is these days much more likely to be labeled physicalism as a philosophy of nature, because it's a little bit misleading to refer to the ultimate stuff of reality as matter. It's more abstract than that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Not that it's any fundamentally less existent or anything like that, but we're not as familiar with it from our everyday lives. And what matters to us about it is the information that it contains. So physicists tend to talk that way just to go along with what their theories are telling them. Stevie CPW says, do you invest in the stock market?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And if yes, what is your investing strategy or philosophy? Close to no. You know, I probably should. I don't have enough money to be a major player in the stock market. Let's put it that way. I do have some retirement savings from working for many years at universities. And mostly I put those into index funds. That is to say, just follow the S&P 500 or whatever.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I've had plenty of smart people tell me that is the best investing strategy, at least unless you are the owner of some high-speed trading firm or something like that. So no, I do not have anything interesting to say about my investing strategy or philosophy. Sorry. T says, What do we mean when we refer to something occurring, say, one second after the Big Bang?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Just to remind you very quickly, I can't possibly remember everything, but Trump fired a bunch of inspectors general the moment he got into office. These are government employees whose job it is to make sure there is minimal fraud and corruption. So we're getting rid of them because fraud and corruption are going to be kind of an important catchphrase. He fired a bunch of federal prosecutors, U.S.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I really struggle to understand the idea of measuring one second in that context, especially given the extreme and novel conditions of the universe at that time. There was no cesium, or for that matter, no atoms even born, much less having the opportunity to decay yet. Right.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So, you know, in some sense this question is related to the one about measuring the expansion or acceleration of the universe. It is true that no one had a wristwatch available one second after the Big Bang or any atomic version of a wristwatch. But time was passing and things were happening according to what we call the laws of physics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
That's going to be inevitable, and those observers themselves will never be able to predict what will happen. In a hidden variable model, if that were plausible and fit the data, then presumably Laplace's demon would know what exactly was going to happen. So it depends on what you mean by quantum fluctuations and what you mean by Laplace's demon. Steve Bonner says, priority question.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So the laws of physics tell us how quickly things happen as a function of time. And the way that we do it is we go back and forth. We build a model. So we have Einstein's general theory of relativity. We have some conjecture as to what the matter sources were and the energy sources were at those times. So we talk about what happened as a function of time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
That equation we referred to earlier, the Friedmann equation of general relativity, is literally an equation for the scale factor as a function of time. So it is true that time is measured by clocks. But that's not all time is. Time exists as a parameter in our best physical descriptions of the world. And in that role, it absolutely has true meaning, even one second after the Big Bang.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Which brings us to our last question here from William Kittlestad. asking a priority question. What does science, math, economic theory, Warren Buffett, Bill Gates, and Marie Antoinette say when the wealth separation curve goes 100% vertical, which is fast approaching? Wealth separation is proceeding at a mathematically unsustainable pace. The increasing concentration among a
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So I know that's your priority question, but there weren't any question marks in there, but that's okay. I can talk about it. I do think it's a worry. I honestly do. I don't think most people listening will be surprised to hear that is my personal opinion. I don't know the exact numbers here because I'm not following it that carefully.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But something like 20 years ago, the richest people in the world had less than $10 billion. And now there are several people who have hundreds of billions of dollars just a few decades later. Why in the world should that be the case? One can make a case that it should be the case, either a consequentialist case or a moral case.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You could say letting certain people get all that money is part of incentivizing them to be innovative and create new things and dot, dot, dot. You've heard the story before. Or you can have a more libertarian moral case that just says they have a right to earn money and you don't have a right to take it and they've been very good at earning money. To me, neither one of these is very convincing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I'm a big believer. Like I've said it many times, I have no problem with rich people or with being rich. I wish everyone were a rich person. That would be my ideal world. I just think that when there is inequality, we should tax them. We used to tax them much more effectively in the 1950s. the top marginal tax rate was 90% for income tax in the United States.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And now it's in the 30s or something like that? I'm not exactly sure. And not to mention all sorts of other things like inheritance taxes and capital gains taxes and so forth, generally lower than they have historically been. I think we could do a lot of good with, I think, two things. I think we could do a lot of good with the revenue that might be generated by a fair tax system.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And number two, and this is something that has only become super noticeable relatively recently, we're putting too much power in the hands of a small number of people. I mean, I don't know if William knew this when he asked the question. I forget exactly when
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The deadline was, but we are seeing a small number of super rich people basically take over the US government right now, up to and including getting information about social security numbers and payment histories for everyone the government deals with, which is basically every person in the country. That's bad.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I've always wondered why cosmologists say we need to explain why the baryons in the current universe are almost all matter. If there were nearly equal parts matter and antimatter in the early universe, but randomly just a tad more matter, then after annihilation, that small amount is what you would see today.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And it's all done in ways that are completely illegal and a strict reading of what you're supposed to do. It's not even real government agencies that are doing this. And we have a system that is letting it happen. And it kind of— causes one to shake one's head. And the real question is, how do we get people who voted for this to realize the terrible damage that is being done by it?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You know, it doesn't do that much good to shake your fist in impotent outrage. We have to gather people together and get them on the right side of thinking about these things. We can't just say that they're idiots. We have to Talk to them, understand why they would have done this.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Is it because they didn't know what they were voting for, despite the fact that it was very clearly said that this is what was going to happen? Or did they actually want it? And if they did want it, what are the reasons why they would want this terrible thing? And I don't know the answer to those questions. Yeah. Yeah, I don't know the answer to those questions.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I think it's absolutely worth thinking about. So we have built a system, short answer, in which those things are allowed to happen. I think that they're bad. I think that all the good things about capitalism, et cetera, can happen without people having nearly that much wealth and power as they do.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And I say this as someone who doesn't believe everyone should have exactly the same amount of wealth or power. I remember John Rawls, the philosopher who wrote The Theory of Justice, and he has this economic political system that he proposed that by most lights is incredibly redistributive. He has what is called the Difference Principle.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
where he says in a well-functioning society, the amount of economic inequality should only be tolerated insofar as it benefits or advantages the least well-off, okay? So in other words, you're not allowed to invent a system where the worst-off people become a little worse off, even if better-off people become better off. That was his idea. So this is like super-duper egalitarian, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And there was a... An attempt at refuting this by Rawls's Harvard colleague Robert Nozick called the Wilt Chamberlain example. And the Wilt Chamberlain example, this is like the early 70s when this discussion was going on. So Nozick says – and it's interesting he chose Wilt Chamberlain because they were both in Boston. I don't know why they chose the enemy of the Celtics. But anyway –
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It looks to us like a lot, but we have no idea how much total matter and antimatter there was to start with. Given any amount of observed residual matter or antimatter, couldn't we come up with an initial combined mass sufficiently large to explain it all as just a small, statistically insignificant imbalance?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The Will Chamberlain example says, look, Will Chamberlain is better at playing basketball than you or I are. People are entertained by watching him play basketball. They would like to give money to Will Chamberlain in order to play basketball so they can see him play, and this brings them pleasure.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And as a result of this, Will Chamberlain has more money than anybody else, and everyone else has a little bit less money. Isn't this incompatible with the difference principle? So number one, this is like a bizarre example to use, right? He's not choosing a captain of industry here. He's choosing a basketball player. But number two, I actually talked to John Rawls about this.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And I said, what is your take on this? And he was just so exasperated. He's like, let people watch basketball and let people get rich and then tax them. Give them income taxes. And then not 100% of what they earned, but some fraction of it and use that to do good things. This should not be hard. It should not be hard to do better than we're doing right now. Apparently, it is hard.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I don't know what to do about it, but we got to keep trying to do things about it. I guess that's as good a place to conclude as any. Thanks, as always, for listening, for supporting the Mindscape podcast. Always appreciate the support I get. Talk to you next time. Bye-bye.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Well, hopefully you'll not be surprised to learn that cosmologists have thought about this quite a bit. And you have to be careful. Of course, generally, well, let's say one thing. In fact, what cosmologists believe is that there was almost exactly an equal amount of matter and antimatter, but not exactly.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And you can work out from the equations and from what you observe how much more matter you needed than antimatter in the early universe. And the answer is about one extra proton per billion protons. So for every 10 to the 9 protons and antiprotons, there was 10 to the 9 plus 1 protons for every 10 to the 9 antiprotons. But that's not equal, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So could you explain it just as an initial condition? Sure. I don't think you can explain it just as a fluctuation, because you have to say a fluctuation of what? You would need some theory of the early universe. Sometimes you have a theory of the early universe, like you have theories like inflation, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So in inflation, there is a predictive theory for where the baryons and the antibaryons come from, and you can calculate that. what the fluctuations should be, they're much, much smaller than one part in a billion, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
One part in a billion is actually a huge difference by the scales that we're talking about here, because there are quantum fluctuations, but every—sorry, there really are not quantum fluctuations. It depends on models of physics that we don't yet have complete handles on, okay? So you could—what you want to do
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
is to create some theory of the initial conditions where there's an imbalance where, sorry, there's not an imbalance in the initial condition, but there's dynamically a preference for, you know, decaying into baryons or antibaryons. And you can invent that. Models of leptogenesis and things like that do that kind of thing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It's a little bit tricky because even in the standard model of particle physics, baryon number is not conserved. B minus L, baryon number minus lepton number is conserved. So if that quantity is exactly zero, it stays zero. But you can still create or destroy individual baryons. And in fact, we also think that gravity does not conserve baryon number at all.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And that hurts you for this particular question because if you started with an imbalance, but it's super-duper high energies, there was copious violation of baryon number, then you would tend to equilibrate. You would tend to get rid of the excess number of baryons over anti-baryons. So, you know, we don't know what the final answer is.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
We certainly don't know what the initial conditions are, but cosmologists are thinking about all of these things. And, you know, the thing is, it's not just like we don't know why there's more matter than antimatter and this makes us sad, right? That's not the motivation. The motivation is this is a clue that the universe is giving us. There's more matter than antimatter. Okay.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
attorneys, especially ones who have been working on the various felony cases against him at the federal level. He either fired or sent home or convinced to leave a bunch of people at the National Security Council, the director of the federal – Aviation administration, people at the State Department, people in the foreign aid office, there's a 90-day pause on all foreign assistance.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
does that tell us something about the laws of physics that we don't know? So, you know, it's nice to have those little puzzles out there in the universe for us to think about. Helen Edwards says, I love all the interviews you've been doing in some form or another on life, how to think about agency, multiple scales, computation, information, etc.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Where has your intuition got to on whether AI could ever be alive? And how are you conceptualizing information and computation as a common root of synthetic versus organic systems? Well, computation and—sorry, information and computation, absolutely a central part of the commonality between synthetic and organic systems.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I don't think that my main conception has shifted very much vis-a-vis whether AI could ever be alive. Namely— Sure, it could be. I'm 100% willing to imagine that it is being.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I think that as I know more and more about what it means to be alive, I'm more and more appreciative of the differences between what we are doing these days in the realm of AI and what it would be to create a truly living artificial organism.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
As I've said many times before, so I'm not going to rehearse now, but real living beings are quasi-stable systems that take in free energy from the environment and use that free energy to survive, to persist, to self-repair. We do metabolism. We eat and we excrete and we get on with lives and we're constantly increasing the entropy of the universe.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You can't turn us on and off like you can turn on and off a computer in quite the same way. We have built-in instructions from billions of years of natural selection that lead us to want to survive and to eat and things like that. were much more self-sufficient than the typical AI system would be. None of these are complete obstacles, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
None of these are things that you couldn't build into an artificial system, which is why I think that that's completely possible. It's just not where we're putting most of our effort right now, right? If you want to optimize for
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
a machine that will create human-sounding sentences and paragraphs on topics that you ask it questions about, then there are much easier ways to do that than to build a full-blown artificial living being. And that's exactly what people are doing. OK, I'm going to group together two questions. One is from Matthew Cushman, who says, a question from my son Aaron in high school.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Suppose there were a small toy universe a few meters in diameter. Alternatively, it could be a region of our universe encased in a reflective impermeable barrier. The only thing in this universe is an apple. Otherwise, it's static. What would the long-term fate of the universe be?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Aaron's theory is that it must eventually end up as photons bouncing around at high temperature due to conservation of energy. And Claudio says, imagine a device, let's say a sphere in which the interior is isolated from the rest of the universe in an absolute way. No radiation or matter of any kind can penetrate. It's even isolated from the CMB, the cosmic microwave background.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Could such a device, if feasible, be used to study the cosmological constant and questions such as the heat depth of the universe? It's always interesting to me when... In one month, in one particular AMA session, questions that had never come up before but are closely related to each other just pop into existence.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So here we have two people asking about tiny little universes or tiny little – tiny little compared to the size of the universe, our actual universe, I suppose. Tiny little regions of the universe that are isolated from everything else. What happens inside? So for Matthew slash Aaron's question, let's just –
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
get one thing on the table very quickly, which is the slight unrealisticness of the question. So there's two different versions, if you remember Aaron's question, either a small toy universe a few meters in diameter or a region of our universe encased in reflective impermeable barrier.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So there aren't really any reflective impermeable barriers, at least not ones that would last literally forever, right? Because they're made of matter. Just like for the previous question about the matter-antimatter asymmetry, there are questions about physics at super early times and super high energies we don't know the answer to.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Not all foreign assistance, I shouldn't say that. Israel and Egypt are still getting their assistance, but everywhere else, cut off. Ukraine, elsewhere, heartbreaking stories of people trying to, you know, U.S. workers in Africa and elsewhere working to save people in various ways, just having their funds cut off.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
There's also questions about physics at super long times and low energies. We don't know the answer to. Both of them involve, among other things, is baryon number conserved, which is a way of saying, are protons stable, right? Maybe they are. We think that they're not. Most physicists think that they're not, but we've never seen one decay.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
We think, among other things, if you just have ordinary matter, there is a possibility, a sort of probability per unit time, that if you waited long enough would always become real, that the ordinary matter collapses into a black hole. right? And then it would just evaporate away. And that's true for your impermeable barrier also.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Even if that doesn't happen, the protons in your barrier could decay themselves, and that would be bad. So it's hard to imagine truly impermeable barriers. It's also hard to imagine small toy universes a few meters in diameter for exactly the reason that Einstein was shocked back in 1917 when he started thinking about cosmology. And he realized that in general relativity,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Universes tend to either expand or contract. You can't keep the universe fixed, in other words. So that's fine. I'm going to roll with the question. I know what you mean. But I just want people to know that in a world with physics as we currently know it, imagining a small universe that just sits there stationary forever is harder than you think. OK?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So we're going to do it anyway, but it's harder than you think. OK. So there's an apple. in our region, what happens to it? Well, again, what happens to the apple depends on laws of physics that we don't know the answer to. The apple, we think, has a probability per unit time of spontaneously collapsing to make a black hole. And then that black hole would gradually radiate via Hawking radiation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Even if that doesn't happen, the protons and neutrons in the black hole probably also have a probability of decaying into other things if baryon number is not conserved. So I think, as far as our best guesses about physics are concerned, that Aaron's theory is mostly correct.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
because either the protons and neutrons directly decay in the apple, or, and part of the decay, like when the proton decays, it will emit a positron, which will annihilate the electrons in the apple, and mostly you'll be ending up with photons. Now, if it does decay into a black hole and that black hole turns into photons, details are going to start to matter.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
How small is this region of space that you have invented? Because it's always possible for those photons to recombine to make another black hole, right, which would then decay again. And in fact, there's going to be some equilibrium distribution where it's mostly photons. The vast majority of things are photons.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But there's a probability that a tiny little black hole pops into existence and then radiates away again. Okay. Okay. Now for Claudio's question, it's a little bit different. Claudio is asking whether or not you could do science in this region. Could you study the cosmological constant in questions such as the heat-death of the universe in the sealed-off sphere? Well, in principle, yes.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
There was this weird event where there was a memo that went out that said all federal grants are hereby suspended for a while. That would be just enormously destructive to the country. You know, grants, maybe the word is bad. I don't know. Maybe people don't understand what the word means. It's not like a present.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
In practice, no. In principle, the cosmological constant, which is equivalent to the energy density of empty space, has an effect on the geometry of spacetime here in our solar system? If that's what you're getting at, then the answer is yes, it absolutely does.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So for example, the orbit of Mercury, which famously was a test of general relativity, because general relativity predicts that Mercury's elliptical orbit precesses a little bit more than Newtonian gravity predicts. the cosmological constant adds a contribution to the predicted precession of the orbit of Mercury.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But when you plug in the numbers, that extra addition is so incredibly tiny that breathing on Mercury is probably at least as effective, okay? The numbers actually matter here, and with things like the cosmological constant or the heat depth of the universe, size matters. The cosmological constant has effects that build up over space and time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So if you have a small region of space, in principle there's an effect of the cosmological constant, but that's exactly the wrong place to look for a noticeable effect. That's why in practice when we try to constrain the cosmological constant we are generally doing cosmology experiments.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Okay, Pete Faulkner says, in your December 2024 AMA, in response to a question about black holes, you mentioned that details like a black hole's size, composition, and the observer's velocity significantly impact the experience of someone falling into a black hole.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
This seems to contrast with my understanding of the no-hair theorem, which suggests that black holes are fundamentally characterized by just mass, angular momentum, and electric charge. Could you explain how these seemingly conflicting perspectives are reconciled? Sure, it's the difference between falling in and staying outside. It's as simple as that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
If I throw a bunch of things into a black hole, then from the perspective of someone outside, the details of what I've thrown in completely disappear. I mean, things that are just visible, like I throw in a red ball or a blue ball, that literally disappears. It's now behind the black hole. I just don't know.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Things like the lumpiness, the spatial configuration, would initially distort the shape of the black hole, but the black hole would quickly radiate away any such distortions in the form of gravitational radiation. So the black holes settle down from the perspective of an outside observer. But if you're falling into the black hole, you could still see what I threw in.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You know, if I threw in a ball and you don't know whether it's red or blue, But if you fall in fast enough after the ball, you can just catch up to it and look at it. So it's completely consistent. It's just you're asking two different questions from two different points of view. Robo says, I liked your solo episode 295 on emergence.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
From the start, I was listening for some description that corresponds to my naive idea that the term emergence refers to the way that lower level states and their dynamics interact on a meta level to generate macro relationships, even if those relationships or influences do not arise from the theory of the micro level. An example from recent experience is Albrecht's law.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It's money that is used to do important things like get science done among other things. So then another memo went out saying – no, the previous memo had been rescinded because they realized how bad it would be. But then the presidential spokesperson, the White House press secretary said the substance of the memo is still true even though we rescinded the memo itself.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Intelligent people, when assembled into an organization, will tend toward collective stupidity. Does your idea of type 3 or type 2 emergence encompass this kind of concept, or am I off track even thinking of this as emergence? You're not off track thinking of it as emergence.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I think that anything which starts with either individuals and goes to groups or starts with atoms and goes to individuals, these are examples of emergence. If you can describe the group in terms that don't require specific information about all the elements of the group, then you're doing emergence in some way or the other.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I don't know whether Albrecht's Law is really true or it's just kind of a joke, right? I'm not exactly sure about that. But I don't think it's fancy emergence in the sense that I think it would be completely predictable on the basis of a competent theory of individuals, right? Like, why are the individuals tending towards stupidity?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Like, they react to other individuals in certain ways, and you kind of could have predicted it. Maybe you didn't. but you could have. Just like in principle, if I knew everything about atomic physics and chemistry, I could predict liquids and solids and superconductivity and all those things, right? In practice, it might be very hard, but it's absolutely implicit in the underlying theory.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So emergence is great because you don't need to know the underlying theory. I can learn about solids and liquids without knowing about atoms, but that doesn't make them incompatible somehow. And in principle— which is a very, very important phrase in this game. I could tell you about solids and liquids just based on the underlying stuff of which they are made.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Gray Monroe asks a priority question. What are your thoughts on the relevance of many worlds quantum mechanics to theories on the origin of life? Many worlds suggests rare branch of the wave function where functioning life, let's call it a Boltzmann cell, emerges by chance.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
These cells could seed their universe with the first replicating organism bypassing the challenge of explaining the origins of the first complex cell. Should we seriously consider the possibility that we live in such a world? You know, sure, you're welcome to consider that possibility.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I would, as usual, even though I think that many worlds is probably the best theory we have of quantum mechanics, I don't really care about the other worlds. Like, it's just not the reason why I care about it. The reason why I care about many worlds is because it gets the predictions for our world right.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And in our world, what you predict are various quantum probabilities in exactly the same way in many worlds as you do anywhere else, that the probability of something happening is proportional to the wave function squared. The thing about intelligent life is we know it exists because we are it by most definitions of intelligence. So it happened.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And if you want to say, well, the probability of it happening, there's some bottleneck, maybe the first cell, maybe some other point along the way. The probability was really, really, really, really low. OK, well, but it happened. We're in the part where it happened.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So either it happened because there's a single world and we just got lucky, or it happened because there are multiple worlds and there's an anthropic selection and we're going to find ourselves in the world where it could have happened. The difference between those two things makes no difference, as far as I can tell, to theories of the origin of life, etc.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Getting lucky versus anthropic selection have all exactly the same empirical content as far as our world is concerned. So I wouldn't point to many worlds as helping that much there. It might help you, like,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
feel better about the fact that something unlikely happened because since we need to conditionalize on life existing, we don't need to conditionalize on other things like the mass of the Higgs boson or whatever, but we wouldn't be having this conversation if life didn't exist.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So if there are many, many universes, each one of which it's rare to find life, but one of them was bound to do it, that might help you feel better about the fact that we are in that world. But I don't think it really helps you in terms of investigating the details about how life came to be. There's still an empirical question. Is it easy or hard? What is the probability?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
If this doesn't make any sense to you, join the club. It doesn't make any sense to anyone else either. Science has been dramatically affected. This is my own bailiwick. All grant reviews at National Science Foundation and National Institutes of Health and elsewhere have been suspended indefinitely.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Many Worlds doesn't help you answer those questions. Daniel Schirmer says, if the rotation of the sun was slowed down, could that cause the orbit of the Earth to decay? I heard the Earth would get closer to the sun if the sun's rotation slowed down. How much closer would the Earth get to the sun if the sun was spinning half as fast as it currently does?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So you hopefully will not be surprised to hear I have no idea how much closer the Earth would get to the sun if the sun was spinning half as fast as it currently does. I'm not even at all sure that it's true. that the orbit of the Earth would decay in a noticeably different way if the Sun will slow down. Or I guess what I should say is I'm not sure whether it would decay at all.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It does decay because of various effects that are much, much more important than the rotation of the Sun, like the orbit of Jupiter, is more important than the rotation of the Sun for things like this. And the orbit of Jupiter doesn't matter that much. So the only thing I really have to say about this question is any of these effects are going to be really, really, really small.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Isaac Newton did pretty darn well in understanding the orbits of planets and things by treating everything like a point particle that wasn't rotating at all. So that must be a pretty good approximation. Craig Stevens says, I learned in college that photons may be absorbed by atoms if they have the right energy and move a valence electron from one energy level to a higher one.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Then when the energy, sorry, when the electron moves back down to the lower level, another photon is emitted. Is there a way that photons can be absorbed and not re-emitted? Or are they constantly bouncing from one atom to another or moving through empty space forever? I think that the answer is no, there is not such a way. But I mean, of course, it depends on what you're allowing yourself to do.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
If you put the elect—so here, let me say what I think is true, and then we can decide what you meant by the question. When you have an atom— that has an electron. Let's just take a hydrogen atom, right? Let's make it very simple. So you have one proton, which is the nucleus. You have one electron. And there are energy levels, okay? And there is a bottom energy level.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
There's the ground state energy, the minimum energy state of the electron. And as far as ordinary quantum mechanics goes, so we're ignoring... baryon number violation, proton decay, all that stuff, right? All that crazy stuff.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
In ordinary undergraduate quantum mechanics, if you have a hydrogen atom with its electron in the ground state and you ignore the rest of the world, then it will stay there forever, okay? It's a stable state. It's not going to do anything. It just sits there. If you excite it, so you send a photon in and you prod the electron to a higher energy state, the higher energy states are unstable.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
They just are. You can predict, this is a classic undergraduate homework set, You can predict, based on what that energy is, the probability per unit time of the electron decaying back down to the ground state and emitting a photon. So if you wait arbitrarily long, the probability approaches one, that that electron will go back down to its ground state.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I have a grant proposal in, hoping to fund some research into quantum gravity and cosmology, but that has been put on hold. If it ever comes back, who knows? That's a minor inconvenience for me. The more important thing is that they're not paying salaries to people like postdocs and grad students at the National Science Foundation, for example.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
If you want to ask why that happens, why is it necessary, why can't the electron just stay there, then there are many possible answers, depending on what kind of answer you're looking for. My favorite answer, which is not the one anyone else gives, but it's because entropy increases. Why is that?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Well, because you go from a system that has one proton and one electron to a system that has one proton, one electron, and one photon. There are more ways to have that system arranged than just the one proton and the one electron. So emitting more and more photons increases the entropy of the universe in general. So that's likely to happen and unlikely to unhappen.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It cannot happen because you can aim a photon, right? It's just the numbers are small enough that you can control what's going on. But in general, the way to think about it is the electron will want to dissipate any extra energy it has to go down to the ground state, and it does that dissipation by emitting photons, either single or more than one photon sometimes.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And because conversing is the key to really understanding each other in new languages, Babbel is designed using practical, real-world conversations. What I love about Babbel is you can either dive in deeply and truly get fluent, or you can just master some of the basics before going on a trip. So let's get more of you talking in a new language.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But spatial locality was used to separate types of emergence. Couldn't the analogous thing be done for spatial locality, where knowledge about other locations is contained at each location, making the dynamic local? Is there some crucial difference between time and space that I am missing? Yes, there is a very crucial difference between time and space that you are missing. This is subtle.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You know, we all know that Einstein came along and said that in some sense, time and space are both part of a single underlying space-time. You want to say that, and you want to appreciate it, and you want to take it on board in your precious belief set. But you also want to understand that there are still differences between time and space.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The single biggest difference, I would say, there's a lot of differences, but the single biggest one is time. given information about the universe at one moment in time, you can, in principle, in classical mechanics, predict what it will be like at other moments of time, right? That's Laplace's demon that we were just talking about. There is no analogous statement for space, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So the table I have right in front of me right now, it has atoms in it. The atoms have a certain density, right? And knowing the density of atoms, the number, you know, the amount of grams per cubic centimeter at one location of the table does not help me predict what the density of matter is like a few centimeters away, because the table might end, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
For the grad students, I am told it is not such a big deal because if you're a NSF fellow, if you have a fellowship from the National Science Foundation, they allocate your yearly salary in one lump sum at the beginning of the year, and then the university doles it out monthly or whatever, so they should be okay, at least until next year. Postdocs don't have it that good.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
There's a sharp line where the table is to the left and it's not to the right. There's a discontinuity in the density of matter. But if I think about, so over space, there's just complete difference from place to place. There's no determination from what happens at one point to what happens at the other point. But there is a determination in time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
If I say, okay, there's a certain amount of energy density here at one moment of time, what's it going to be like a minute later? It depends on details, but probably it's going to be the same number, right? The table's not really moving. So there is this rigidity, there's this predictability from moment to moment in time that simply isn't there in space.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And this has to do with the fact that there is only one dimension of time. This allows for that fact to happen. Mathematically, it has to do with the hyperbolic nature of the underlying differential equations. But there are three dimensions of space, so you don't quite have that same rigid control. So...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Yes, in practice, for the reasons that we care about here, time and space are pretty different. There's predictability in time, not predictability in space. Anonymous says, I've noticed you almost never swear on the podcast. I'm curious if this is in order to be professional, or is that how you are in daily life as well? I think that in daily life, I swear more than I do on the podcast, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I'm not afraid of swearing. I'm happy to do it. But yeah, I don't know whether you want to call it professional or not, but I do try to respect the audience and try to care about what the audience is. some members of the audience would probably like it better if I swore more. Some would not like it better.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I'm going to play it cautious and just try to be as accommodating for the largest number of people that I can. So when I give a talk, when I'm giving a colloquium or something like that, there's no swearing going on. When I give a public lecture, there might be children in the audience, there might be adults who just don't like it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So there is a certain standard of behavior that one adopts that I'm perfectly happy to do. One can always violate the rules in strategic ways, right? For emphasis, If you want to make a point especially hard, if there's a guest that I'm interviewing and they swear a blue streak, you know, then sometimes that's going to happen. Ti Nguyen was definitely like that, for example.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
There have been others. I remember when I was an undergraduate and I took a class, a philosophy class, actually, and the professor had, you know— He missed the first class.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So because he was traveling, he was at a conference and he came back for the second class and he was talking about, you know, he was sort of getting to know us and just sort of schmoozing or whatever before launching into the substance of the course. And he was talking about being in New Orleans and he ended up in this place in New Orleans and there was no beer being served.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And he was upset about this. He was like, come on, I'm in New Orleans. Where's the fucking beer? Yeah. And years later, because I got to know him pretty well, he explained that that was entirely preplanned, that he very intentionally tries to swear in every first class meeting of every class he teaches. Why? Because if he happens to swear in week five, it does not seem like such a big deal.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You know, he's sort of already set the stage. This is just human relations. This is just accurately gauging what you're trying to do, what the impact of how you talk and what you say is. If you want to get grandiose about it, think about the conversation we had with Derek Guy about how to dress. You can dress however you want, sure. You can talk however you want.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
They have a monthly salary, if they're NSF-funded, that is just not coming. They're not getting paid. Postdoc life is not easy, right? You are bouncing around. You have a three-year job, typically, at most, and then you have to go somewhere else. You're living paycheck to paycheck, and those paychecks are not coming, so this is going to be catastrophic for them personally.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You can present yourself however you want. You're totally welcome to do that. It's a free country. But you can't be naive. You can't just say, not only do I want to dress and talk and present myself however I want, but I don't want anyone else to react badly about it, to judge me, to think less or more of me based on how I talk or how I dress or whatever. That you don't have a right to.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You can talk and dress however you want, but people are going to react to it one way or another. We all live in a world where there are other people judging us all the time. Maybe you don't care. That's fine. You don't have to care. But if you do care, you should be cognizant of what it is. So I just want the podcast to be as pleasant and enjoyable for as many people as possible.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And I talk like I do—I talk in the podcast like I do when I'm being a physics professor, more or less. Soonest Mended says, in the recent solo podcast on time, you argue that presentism versus eternalism question is important not because one or the other being true would change the predictions of physics, but because believing one or the other might influence future avenues of research in physics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Are there examples of other such questions where choosing a particular orientation has led to a research breakthrough that would otherwise have been unlikely or impossible? I don't know of a perfect example off the top of my head, to be honest. I know exactly what you mean.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So there's various places in physics where we have multiple ways of talking about exactly the same processes or phenomena or whatever. A classic example, especially for those of you who have read volume one of The Biggest Ideas in the Universe, Space, Time, and Motion, is the difference between Lagrangian classical mechanics and Hamiltonian classical mechanics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
This is to say, for those of you who have not read that wonderful book that I can absolutely recommend to you, you can formulate the laws of physics either in sort of the good old-fashioned Laplace's demon way, which is to say, give me the complete state of the system now, give me the equations of motion, I will tell you what happens next. The Laplacian paradigm, we called it in the book.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And that is how Hamiltonian mechanics works. Lagrangian mechanics is based on what's called the principle of least action. You may have heard about it. And it says, don't tell me exactly the state of the system to start. Tell me the configuration of the system. Tell me the positions, but not the velocities, for example, of the system.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
but then also tell me the configuration of the system at some other time. And I'm going to search through all possible ways to connect the configuration at the early time to the configuration at the late time. I'm going to choose the one that minimizes a certain number called the action. So you can show that the actual behavior of systems under these two ways of talking are completely equivalent.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But the actual procedure you go through to get them is very, very different. In a slightly more advanced version of this, these days we talk about the ADS-CFT duality and other dualities in quantum field theory. A duality is exactly this. A duality is two different ways of talking about exactly the same underlying physics, two different equivalent ways of talking.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Of course, it's also catastrophic for US science as a whole. Why in the world would the best people from outside the US think of coming here with all of this obvious chaos and dysfunction that we are exhibiting to the rest of the world? Anyway, I could go on for hours about this. I don't want to do that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
In quantum mechanics, we have the Schrodinger picture and the Heisenberg picture. There's a whole bunch of different examples where you have multiple ways of doing things. I don't know whether there are examples where choosing a particular orientation has led to a research breakthrough. Probably yes, but I don't know off the top of my head.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But absolutely it's true that choosing a particular orientation changes how you naturally think about things, right? It changes the sort of natural ways to – modify the theory or think about different theories. Anyway, I don't have any perfect examples of that off the top of my head right now.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But for presentism versus eternalism, you know, if you, you know, presentists, I should say, I'm an eternalist myself. So I think of the whole shebang, right? I think of, you know, the whole universe all at once and try to figure out what rules it obeys and things like that. Someone like Tim Maudlin, former Mindscape guest, is a presentist.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
He really thinks that the laws of physics not only describe patterns in the evolution of the universe, but bring them about. He's not only a presentist, but an anti-Humian when it comes to laws of physics, as we talked about with Tim, but also previously with Ned Hall, etc. So Barry Lower and I talked about that also.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So that does lead these individuals, myself, Tim Maudlin, et cetera, to propose different theories of understanding. You know, Tim is not happy with many worlds. He's much happier with Bohmian mechanics. I'm kind of appalled by Bohmian mechanics. Which one of us is right will hopefully be decided by data and things like that in the future.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But in the meantime, since we don't know the answer, our orientations are absolutely going to affect what we're most likely most positively predisposed toward. Robert F. asks a priority question.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
My father always wanted to understand the answer to the question, if mass, a large object, follows the curvature of the fabric of space, wouldn't then there be some kind of small measurable background heat due to friction of its motion through space? So yes and no. Strictly speaking, no.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
There's not friction due to the motion of objects through space because the idea that you have that there should be friction comes from a very higher level, non-fundamental description of reality, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
If I push a tire down the road, there is friction because the tire is made of atoms and the road is made of atoms and the air through which it moves is made of atoms and there are photons bouncing off the tire. And in all of these invisible ways, there's noise and friction and dissipation and energy gets lost from the tire.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But there's one other thing I just can't help but mention because I'm sure that the people of the future are just going to think there's no way that that actually happened. We had fires in Los Angeles not long ago, devastating fires. I used to live in L.A. and I know many people who either – had to evacuate. Some came very close to losing their houses.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And so you perceive that as a kind of frictional force that eventually slows down the tire. If I have an elementary particle or a single object moving through the universe, space itself is not made of atoms in the same sense that the tire or the road is made of atoms. There isn't any way for that object to sort of give off energy to the medium around it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The medium around it is as empty as it's possible to be. So strictly speaking, no. There's no friction of that kind because the medium we're talking about is a much more basic element of reality, it's not this collective thing that you get by taking many, many atoms and jiggling them together.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Having said all that, there's one kind of tiny caveat, which is that if you move an object back and forth, rather than just like letting it move through space, actually, sorry, let me back up because I realized I missed a chance to explain something. I can prove that an object moving through space does not slow down. The proof is the following.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
There's no such thing as a reference frame for velocity in relativity. There's no preferred velocity to the universe. So slow down compared to what? Said in other words, if there was only one object in the universe, I could always describe that object in its rest frame, in the frame in which it's not moving at all. And there it's just not moving, so there's no need for it to give off—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
energy and slow down. And if it just stays there perfectly ordinarily in its rest frame, then in some frame that is moving with respect to it at constant velocity, you will always see it moving at constant velocity. Okay, that's one way of saying it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Which is why if instead I'm shaking it back and forth, rather than just having it move at a constant velocity, then it's a different story, because then it is coupled to gravity. Everything is coupled to gravity. There's a gravitational field for this massive object that you're shaking back and forth, and there it will emit gravitational waves.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It might also emit photons or something like that, electromagnetic waves. Because every object creates gravity, if it's moving on a non-uniform trajectory, it can lose energy by emitting through gravitational waves. Indeed, when you get a detection of gravitational waves at a gravitational wave observatory like LIGO, Why do you do it?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Well, it's because two black holes were orbiting each other, or a black hole and a neutron star, and they're orbiting, so they're circling around each other, so that's more or less like being shaken back and forth, and they're emitting gravitational waves, and those gravitational waves are what you ultimately observe.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The energy loss due to that emission of gravitational waves is what causes the black holes to spiral together and eventually coalesce. There you go. Taylor Gray says, I'm currently reading former Mindscape guest Matt Strassler's book, Waves in an Impossible Sea. The book states that the faster you go past a magnet in the magnetic field, the more you will detect the electric field.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
What mechanism, for lack of a better term, makes this so? Again, this is a question that the satisfactoriness of the answer is going to depend on your prior exposure to physics. Let me give you the highest level answer right away, which is that according to the theory of relativity, the electric and magnetic fields are just two different aspects of the same underlying field.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Others who are not very close to me, but did lose their houses. Many people were significantly, severely affected by these fires. And the response to the fires on the part of the local government was not great. I'm not going to defend it. I think that the California governments, both locally and the state, most of whom are completely run by Democrats, didn't do a great job of preparing for
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Exactly in the same way, not exactly exactly, but very, very analogous to how time and space are two different aspects of the same underlying space-time. The electric field and the magnetic field are two different aspects of the underlying electromagnetic field, if you want to put it that way. Very, very roughly, the sort of spatial components are the magnetic field.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The temporal, time-like components are the electric field. But that's not exactly right, but it has something to do with it. The point is that when you do a Lorentz transformation—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
which is to say, if you go from one reference frame, like we were just talking about with the large object, you go from one reference frame to another, which you can do by either moving yourself or by moving the magnet or the charged particle or some other electromagnetic phenomenon. Either you move it or you move you, it doesn't matter.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You are now shifting, rotating the different parts of the electromagnetic field into each other so that... Exactly for the same reason why moving at a constant velocity means that you define the division of spacetime into time and space slightly differently than a person who is not moving in the original reference frame.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Now you also define what part of the electromagnetic field is electric and what part of it is magnetic slightly differently. So this was a crucial feature of, of course, the empirical, the historical development of relativity. It was first these wonderful experiments done in the mid-1800s that culminated in Maxwell's theory of electromagnetism that showed that
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
that empirically you could make an electric field by moving a magnet and vice versa, that eventually led to different transformation laws, Lorentz and Fitzgerald and so forth, and Poincare, and Einstein eventually unifying the whole bit.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So the very short answer is the electric magnetic fields are two different aspects of the same single underlying electromagnetic field, and they are transformed into each other by changing your frame of reference.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Alex West says, with the general release of AI, have you noticed any fluctuations or trends in both the quality and quantity of peer-reviewed papers and more personally emails from the next Einsteins? Well, that's a good question. For peer-reviewed papers, no, I certainly have not.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It's a weird thing to me because in my kind of field, the most active people, you know, the people who are most respected in the field basically know each other, and you know what people are doing, and you recognize their names when they write papers, and people write a few papers a year. Some are more prolific than others.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But there are these other fields where apparently there exist people who just write, I don't know, 100 papers a year, which is essentially impossible. It's not the field's fault because that's not typical in that field, but you can get away with doing that. I can't even read 100 papers a year. But obviously there's a lot of churn here.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
People are leaning on other co-authors to do writing or they're just taking something they've already written and rewriting it 10 different times and submitting it as an extra paper, etc. But that's not my world. In that world, AI might be very, very helpful if all you're trying to do is maximize the number of papers you submit somewhere and publish them in junk journals or whatever.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
That I don't really follow, so I wouldn't know. In the field that I'm in, I don't think that I've noticed anything at all as a result of AI, except that people are writing papers about AI, which makes perfect sense. As to the next Einstein thing, when I read this question at first, I thought, no, I don't think that there has been an uptick or a change in quality.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
a fire that was quite this bad. Some of it is there are unpredictable natural disasters. Some of it is you weren't ready for it, right? So that there's plenty of blame to go around. But Donald Trump somehow got it into his head that it was simply because there was water to fight the fires and the California government didn't want to turn on the faucet.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And I think that there's an explanation for that psychologically. You know, the people who think of the next Einstein, they don't want to hand over credit to AI, right? They don't want to say, well, you know, the AI and I put this together. They want to say that their own personal genius is responsible for this.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But having thought of it and having a few days gone by, it is possible that I'm getting more of those emails. I've always gotten a lot. Arguably, the numbers are small, but it's possible that I'm getting more now. And so maybe they're just not telling me and they are indeed helping themselves to a little bit of AI help when making up their theories of everything. Look, life is short.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I don't spend a lot of time paying attention to those papers. So as soon as I can tell that the email is from someone who has a new theory of everything, all they need is for me to fill in the math, that gets filed pretty quickly.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Janderson or some version of Letters and Numbers says, in your recent solo episode number 300, you present a way time might be modeled as emerging from the universal wave function. Am I right in assuming that this method could also be used to produce any number of other dimensions of space and time perhaps?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Well, the particular method that I was talking about, the idea, doesn't really work with space. It doesn't really make sense. What you're trying to do is take advantage of the fact that there is two features of quantum mechanics, number one, entanglement, and number two, superposition.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So by entanglement, to get time to emerge, you take advantage of that by saying that there is some clock subsystem that that is entangled with the rest of the universe, okay, and then superpositions that you can take different states corresponding to different configurations at different times and just adding them together in an overall static wave function.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But space is just a different kind of thing. Like we said, that evolution through time that is characteristic of the time dimension doesn't happen in the same way in space. So it really is a different kind of thing. Ultimately, probably you want to have everything be unified, but that's tricky to do for a number of reasons.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So in the specific approach that I was talking about in that podcast, time is just a very different kind of thing than space. Ben Lloyd asks a priority question. I need your help with something. This might seem weird, but my biggest fear by far is that at some point everything will end forever. I'm not really scared that our civilization will likely not be able to survive the heat death.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
My main fear is that the universe will end. Nothing interesting will be able to happen anywhere forever, and no multiverse scenarios that would contradict what would turn out to be true. Luckily, many theories or hypotheses make it so that interesting things would happen forever. For example, inflation is the dominant theory for explaining the early universe and how it evolved.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And many prominent proponents of inflation often say that eternal inflation is almost inevitable once you get inflation. In eternal inflation, there would be continuously new universes forever. The next biggest competing theories to inflation are cyclic models, etc.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I've always needed this sort of existential comfort, but more than that, I need to believe things that have evidence and things that could be true. That's why I'm not religious. Anyway, what do you think of this? Do you align more with my view? I really don't align with your view.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You know, I think that I can't let my life here on Earth be vastly affected by things that are going to happen long after the last star stops burning. This is something that I can imagine, but not something that affects my life in any way. I am entirely at peace with the idea that the universe might someday end. Maybe the last living creatures in such a universe will be sad, and that I understand.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
and let the water come down to Los Angeles to be used to fight the fires. This is entirely nonsense. There were times when the water ran out, but it was just because the capacity of the local firefighting infrastructure wasn't up to it because the fires were so bad. There were multiple fires, and they were very, very bad.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
That makes perfect sense. But we are so enormously far away from that that no, it doesn't really affect me very much.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And in fact, it's sort of important to not let it affect you too much if you're a scientist or philosopher, because then it will point you towards sort of giving more credence to certain theories than might otherwise be appropriate, even though you don't have a lot of evidence really for them.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Hello, everyone. Welcome to the February 2025 Ask Me Anything edition of the Mindscape podcast. I'm your host, Sean Carroll. This month's AMA is going to be mercifully short on politics. We're mostly talking about science and other fun things. But, you know, politics still goes on and we're aware of it. And I'm a big believer that you kind of
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Funky Town says, for the first few decades of my life, I lived, first two decades of my life, I lived in a very small bubble with limited knowledge of the universe's workings and a huge emphasis on religion and the Bible as final truth. For the last decade of my life, I found myself diverging from my original worldview and considering myself a little more enlightened.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The biggest struggle for me during this time is trying to understand the feelings and experiences I had in my earlier years and rationalizing them. Is there a physical explanation for the responses someone has that are considered religious experiences, especially if that has been something they have been immersed in during their entire upbringing?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
For example, I went to a service recently for the first time in years and had a very emotional response despite not putting much stock into the belief anymore. Yeah, you know, I think that I'm not an expert in exactly the neurological or even psychological explanation for these responses, but to me they seem completely unsurprising.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You know, when I walk into a beautiful cathedral or hear really good church music, it is emotionally affecting. Why wouldn't it be? Forget about the existence of God. These things, these cathedrals, these pieces of music were designed by human beings to evoke an emotional response, right? That's why they were designed the way they were.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So I have no trouble believing that the physical trappings of a church or the aesthetic trappings of the art or the music, or for that matter, the sort of ritualistic trappings of the steps you go through when you're at a church service, have important resonance to us.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
That is as unsurprising to me as saying, oh, I went to a music, a rock concert, and a bunch of people seem to be having a really good time and dancing around. Isn't that surprising? It's not really surprising to me. Robert Grenise says, when the universe reaches maximum entropy, heat death, does time end as well? With no more entropy, the arrow of time would cease to have meaning, wouldn't it?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Well, as I've said many times before, but it's been a while so I'll say it again, time is separate from the arrow of time. Just like space exists without an arrow of space, time can exist without an arrow of time. Time, as we conceptualize it in physics, can absolutely be part of the best description of the universe while not having a directionality one way or the other.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So just like there is a distance between me and the sun, even if there are not a bunch of rulers or meter sticks lying between me and the sun to actually measure it, there will be time in the universe once you reach thermal equilibrium.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
If I have, you know, a glass of water and there's an ice cube in it and the ice cube melts, and the water is now more or less in equilibrium at room temperature with the room around it, I can still sensibly talk about how long it's been there. Time is still passing. DI says, how does one stay realistically optimistic within the next four years in the United States?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And so firefighters did run out of water, but it wasn't because, as Trump believed, there was plenty of water up in— Washington and Oregon and Northern California that could be sent down to Los Angeles, but the Democrats didn't choose to do it. That is entirely wrong. There's no water transport from Washington or Oregon to California.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Any suggestions for small yet socially meaningful actions each one of us can take? Short answer is not really. I mean, I have suggestions, but I don't necessarily think my suggestions are very good. Different people will respond differently. Different people are going to have different ways of coping. Some people are going to be happy about the next four years.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But if you're the kind of person who is concerned, worried, anxious about the next four years... I do think that it's important to mix trying to do something about it with also trying to live the rest of your life, as I said at the beginning in the intro of the podcast. Doing something about it means politics one way or the other.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It could mean campaigning or something like that, but it also could just mean talking to people. You know, at the end of the day, democracy is not just about putting up more posters. It's about changing people's minds to agree with you. You know, you have to actually communicate with people and give them the sales pitch that your point of view is better.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I think that people on both sides of the divide are not very good at that. But if you could talk to some people who are not closed-minded and not just insult them for not agreeing with you, but actually provide them reasons that it would be better to agree with you, then you've done a little bit to make the country a better place. Meanwhile, take care of yourself. Learn interesting things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Listen to good podcasts. Keep trying to get better ourselves at understanding the world, both in political ways and in scientific ways. It's an ongoing process. We're not going to declare victory and like, okay, now the world is good. We're going to try to keep on, in little tiny ways, making it better.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Sid Huff says, Jan 11, a former Mindscape guest in a recent episode of Robinson's podcast, stated that astrophysicists don't really care what goes on inside a black hole. The event horizon is the black hole. We simply don't care what's going on inside. Why would she say this? Why wouldn't she and other astrophysicists want to know?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Well, astrophysicists are human beings, and a human being might want to know what's going on the inside. What Jana means is that for the purposes of astrophysics, it doesn't matter what's going on inside the black hole. That has to do with the no-hair theorem we were just talking about earlier.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Once you throw that stuff in the black hole, and once the black hole settles down, it is entirely defined by what's going on at its event horizon. Astrophysics is not affected by what's going on inside. That's all that she meant. Randall Bessinger says, do you have any views on the current brouhaha and the atheist skeptical movement on the trans issue?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I'm not quite sure what kind of views you want me to think about here. I mean, I'm definitely on one side of this issue in the sense that I think that trans people are people and should be treated as such. And
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It's absolutely true that a certain segment of the atheist skeptic movement has just wandered into really bad territory at being very actively anti-trans in a way that seems very illiberal and immoral, honestly, and bigoted to me. As to why that's the case, it's a trickier question. I think that there's a lot of psychology going on here.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
There is plenty of water transport from Northern California down to Los Angeles, but it was working fine. There was no problems with that. But he got it in his head. This is what happens. He's a very not smart person. And he got into his head that all you have to do is turn on the faucet. So he literally ordered the U.S.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And so I'll just – again, I'm not a professional psychologist, not a professional sociologist for that matter, but I will point to one thing that seems to strike me about these things. Well, to two things. One very quick thing is – as soon as something is called a movement, it's in trouble.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You know, whether it's the atheist movement, the skeptical movement, the effective altruism movement, or whatever, when you have an idea, like atheism, God does not exist, that's an idea. When it becomes a movement, all sorts of bad things can happen, right? You know, now, okay, there's people, you're in the movement or you're out the movement, there's good ways of behaving, there's
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
all sorts of possibilities for things to go wrong, and they typically do. So that's one very broad thing. The other thing is that in that particular movement that we're talking about of atheism and skepticism, there is the huge danger that you are in a movement that is in large part devoted to patting itself on the back for being more rational than the rest of the world, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You people think that there's a giant man in the sky who is judging you, but I am too rational to believe that. And I'm in favor of being rational. I think that's a good thing, trying to be rational. But it sets you up for making the mistake when someone says that something that you're doing is –
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
not rational or not correct or not nice of not listening to that kind of criticism because you've already decided that you're more rational, right? And so people become defensive. And in fact, there's a backfire effect where they double down on whatever it is they are believing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I think that this is not specific to atheism and skepticism actually, but in progressive liberal circles more generally, there's a certain slice of people who feel nostalgic for the days when in their minds it was all just about the economy and class struggle, right? And they thought of themselves as fighting for the workers and the underprivileged and whatever.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And now it's about identity politics and like these black people and these trans people and whatever. They are all leaving the message that they thought was supposed to be the message. And you see the difference is that the people we're talking about here could think of themselves as the underdog when it was all about fighting for the lesser well-off.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But now you're telling me there are other groups that are disadvantaged that I'm not in. Maybe even you're implying that my group is causing the disadvantage. You know, you're kind of criticizing me. A lot of people in these communities, like the most irrational response you can get from them is to call them racist or bigoted or whatever.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Army Corps of Engineers to find some dams in central California and turn on the faucet. So they found two dams associated with reservoirs in the Central Valley. And open them. Just let them go. Now, they're not going to Los Angeles. These dams are not connected to an aqueduct or a pipeline that brings water. When you open the dams, the reservoirs just empty into the rivers.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
No matter what the evidence for it is, they're like, you can't believe I'm that kind of person. I'm a rational person. I'm not that. And, you know, that leads them to some dark places when they try to justify that. So I don't know how much of the effect is caused by that particular syndrome, but I do think it's real.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And of course, there's plenty of people in the atheist skeptical movement such as it is that are very supportive of trans people. A lot of trans people are atheists, right? So it's complicated. I wouldn't want to oversimplify it. I do think that it's much easier to preach rationality than to practice it, especially when it comes to potential criticisms of one's own worldview and behaviors.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Eric Stromquist says, this may be a long shot, but have you read The Problem of Molecular Structure is Just the Measurement Problem by Franklin and Seifert in the British Journal for the Philosophy of Science last year? They argue that the favorite eigenstates of collections of electrons and nuclei are superpositions of all enantiomers and isomers.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
These are chemistry words, I don't understand, by the way. Not the chiral molecules or individual isomers studied by chemists, which have less symmetry. They look at Everett, Bohm, and GRW and conclude that Everett and Bohm can explain classical molecular structure, but only due to the action of decoherence in each case. However, decoherence doesn't save GRW.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
No, I'm not familiar with that at all. Ordinarily, if I were not familiar with it, I would just skip over the question. But it's an interesting issue. I really want there to be experimental tests you can do to decide between these different theories. There are experimental tests you can do to decide between objective collapse models like GRW and Bohm slash Everett.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
As far as I know, there aren't any tests to distinguish between Bohm and Everett. But I'm open-minded about still looking. You know, there's arguments that Bohm and Everett should give the same result, but there's also arguments, in fact, there's arguments from both sides that the other side just doesn't make sense, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So if you talk to either Bohmians or Everettians, who are more or less made up their minds, and you ask them the reason why they don't like the other one, it's typically because they don't think the other one does the job of being a well-defined theory that fits the data. and of course they think that theirs does.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So anyway, none of this is specifically about electrons and orbitals and in molecules and so forth, but just to say that I can imagine something like that being true. So I've not read the paper, but I can imagine that in a theory like GRW, which is one where there's a random chance that the wave function of a particle will spontaneously localize every moment or whatever,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
you could show that something, some feature of chemistry or solid state materials physics or something like that just doesn't work under these models. So I'm all in favor of doing that. It would be very, very hard to distinguish between Bohm and Everett on that account because Bohm and Everett have the same equation for the wave function. The wave function is just obeying the Schrodinger equation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But I still am holding out hope for some subtle difference that will let us test these ideas experimentally. Will says, I have moments when the suffering and unfairness of the world feels just too much to bear.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
When one sees children killed by bombs or suffering from horrible incurable diseases or learns about life in crushing dictatorships or poverty, one yearns for some cosmic justice that those who suffered will be made whole one day and that all the suffering wasn't just a hideous waste. These are the moments when I would be most inclined to religion, probably as a form of wishful thinking.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
When you have these moments, what do you turn to? Are there philosophers or ideas that you find helpful in this regard? Not specifically philosophers or ideas. I do think that just truly taking on the philosophy of
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
of naturalism, of, you know, the world is not guided by any external forces, it just obeys the laws of physics, and appreciating that those laws of physics and the initial conditions or whatever include an enormous amount of information that we don't have access to, and therefore there will be things happen that we don't like and can't predict and can't do anything about, I think it is possible just to accommodate oneself to those true facts about the universe.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
We're all going to die. Probably life itself will someday cease. I have plans for the future, some of which will turn out and some of which will not. I've had plans in the past that did not turn out. It doesn't make it any easier in the moment. You know, when a close friend of yours is sick or passes away, that doesn't make it any less tragic and hurtful when that happens. But
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And this is something that is part of a plan because the Central Valley is the home of an enormous amount of agriculture. And during the summer months when the drought is usually bad and the crops are most needy, you need that water. You don't need it in January or February in the farmlands of the Central Valley. So this did absolutely nothing. It's literally pouring water into the ocean.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But the fact that things like that will happen are things that you can come to grips with long before they actually do. And I don't think it's a matter of like this philosopher or this idea really helps you with that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I think that there's some combination of that understanding of the world and the kind of psychological accommodation or orientation that lets you approach that with clear eyes and do the best we can, accepting that they will make us sad when they happen. Robert Ruxendrescu says, we usually talk about electrons having their spins entangled, but why not positions?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Why can't we have electrons A and B entangled such that if I measure A and find it at coordinates one, two, three, then I immediately know that B is at coordinates minus one, minus two, minus three. You can. Sure. No problem at all. In fact, that's a very, very common form of entanglement. We don't even talk about it that much because it's just so common.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But, you know, the example that I often use is imagine a particle like the Higgs boson. Picking the Higgs boson just because it has no spin, so we're not worried about spin at all. It decays. It decays into an electron and a positron. And the prediction, according to the Schrodinger equation, is that if you ask in what direction will the electron be moving?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The answer is the wave function spreads out in all directions. It is equally likely, because there was no spin for the original Higgs boson, so there was no orientation, no special direction of space was picked out, equal probability to observe the electron moving in any one position, likewise in any one direction.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Likewise for the positron, equal probability to observe it moving in any one direction. But when you observe one, then you know where the other one is because momentum is conserved. You know exactly what the coordinates has to be for the other particle that you didn't observe. There you go. And that's entanglement.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Indeed, that is more or less what EPR actually talked about in the famous Einstein-Podolsky-Rosen paper about entanglement. The idea of doing it with spins came later. It might have been John Bell, actually, who originally popularized the idea of doing it with spins. I'm not sure about that. David Summers says, I finally got around to watching Oppenheimer.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
In your opinion, how valid was the concern that the atmosphere could ignite when detonating an atomic bomb? Was it irresponsible to carry out the test given the available information at the time? Well, I can certainly say that the movie overhyped that particular worry. The worry did exist, or rather, let's put it this way, the possibility had been raised.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
There was never a time when someone did a calculation and they said, oh, this will ignite the atmosphere, okay? Rather, people suggested, like, is it possible that this will ignite the atmosphere? Should we worry about that? And they did the best they could. They tried to calculate it, and they found out that the answer was no. It would not ignite the atmosphere, so they moved on.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Now, it's completely legitimate to say, okay, but there was a chance, there was a chance it would ignite the atmosphere, and how exactly confident were they that it wouldn't happen, right? Isn't that kind of important?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
That's very true, and it's something I'm actually very interested in and not completely clear about in my own brain, how to deal with these things that you think are very, very unlikely but hugely consequential if they happen.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
One of the aspects to keep in mind is lots of things, other than setting off a nuclear test, have the property that they could, in principle, cause some tremendous calamity to happen, and you don't know what the probability is, okay? When I wrote my book on the Higgs boson, the particle at the end of the universe, that was a worry, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And so it was all so that Donald Trump could, on his social media site, put up a little photograph of water pouring out and going, see, I opened the faucet and if I had been president— these fires in LA never would have happened, literally what he said. It's inexplicably dumb. It's also evil and incompetent, but just the dumbness is what really gets you. So what do we do?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The worry was that by turning on the LHC, the Large Hadron Collider, we would destroy the Earth eventually. And I said, look, every time you open a jar of spaghetti sauce, pasta sauce, there is a possibility that some random mutation brought to life a terrible mutated pathogen that you are now releasing into the world and will kill all life on Earth by opening that jar of pasta sauce. Unlikely.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But it's possible, and what you're doing is you're risking all of human existence by opening that jar. Is this an argument to not do it? And I think that the answer is no. It is not an argument to not do it. Lots of things are possible, but we still have to get through the day.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
That's not a very well-formulated, rigorous philosophical theory of getting through the day, but getting through the day is actually kind of important. So I think that I would like to actually understand that better. Paul Hess says, in the many worlds interpretation, what happens when I use a quantum computer?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Is there one world where I get the right answer and some other number of worlds where I instead get errors? Is the thickness of the world where I get the right answer a function of how carefully I isolate the qubits? Well, you know, as I said this before, there's not a lot of difference between what happens in a quantum computer in many worlds and any other interpretation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The success of quantum computers does—so I think that it's possible in my mind, although I don't know for sure, that there could be a principal argument made that quantum computing is an argument in favor of wave function realism. OK, the idea that the wave function really has a physical reality to it because it's becoming entangled, it's interfering, blah, blah, blah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
All these things are happening. Now, the people who are not wave function realists find this entirely unpersuasive. In fact, many people who are not wave function realists, epistemic people when it comes to the foundations of quantum mechanics, actually are in the field of quantum information. So I don't understand how they reconcile that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But putting that aside, if you think that you are a wave function realist, there's nothing in the quantum computer that differentiates Everett from Bohm, from GRW, objective collapse models, Penrose, whatever, right? That's the same kind of predictions you go along the way. The only difference is, and maybe this is what you have in mind, when you do the final measurement,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
in a quantum computer because a quantum computation generally starts by putting in some qubits into the algorithm and running it through the algorithm and you get out some qubits and then you measure them, okay? So there's a measurement process and the measurement process is governed by the Born rule. The probability of getting an outcome is the wave function squared.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And it might very well be the case that the kind of calculation you've done tells you that you will, you know, factor a large number with really, really high accuracy, 99% confidence or something like that. And so in the traditional single-world interpretation, you would say there's a chance I get the right answer, there's a chance I get the wrong answer.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
In Everett, you would say there's a world in where I get the right answer and a world in which I get the wrong answer. And of course, to make sense of it, you have to believe that the Born Rule still works. So if most of the amplitude is on the right answer, then you interpret that as saying that the probability of me getting the right answer is given by the amplitude squared.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So again, I don't think that Everettian attitude towards quantum mechanics says much or is much informed by the success or workings of quantum computers. Nanu says, I recently had the pleasure to read your paper, Reality as a Vector in Hilbert Space, and truly enjoyed it. I read it over and over again.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I was wondering what was going through your head when you realized that reality is a vector in Hilbert space. You know, I don't – I feel bad sometimes because people ask me questions just like we had the question just a second ago about like what philosopher or what idea helps you through this.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I think I just think differently than other people do maybe or at least I think differently than other people want me to think. Because there seems to be this feeling like that there should be epiphanies and moments. You go like, this is the moment I realized something. Or I read this book and this book helped me realize something.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I mean, half the country voted for this. Half the country who chose to vote voted for this. We all knew it was going to happen. Like I said, it's been a little bit faster and more dramatic than we expected. But yeah, we live in a democracy, and this is what people wanted. And we have to both live with it and fight against it at the same time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Or this person is very brilliant and I would, you know, here's the list of people I would like to talk to who are dead. But I really like to talk to them because they're brilliant people. I just don't think that way, honestly. Like it's much more gradual and process-oriented in my head. There was not a moment when I realized that reality is a vector in Hilbert space. It kind of creeps up on you.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You think about quantum mechanics and you try to understand quantum mechanics. And then you think about interpretations of quantum mechanics and you decide that the Everett interpretation is a good one. And you realize that the Everett interpretation is really not about many worlds. It's about just the wave function, the vector in Hilbert space always obeying the Schrodinger equation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And then you say, well, okay, what are the data that define a quantum mechanical theory? Like what do you have to put into it? And you ask people and they tell you, oh, we have to give an algebra of observables and all these things. But then you think about it and you realize, no, you really don't.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It might be convenient and it might be important if you are devoted to some notion of locality in your theory. So in quantum field theory, we often care about algebras of observables and things like that. Local observables is usually implicitly taken for granted there.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But really, you understand that the quantum theory simply is a theory of a vector in Hilbert space obeying the Schrodinger equation. You come to that understanding gradually. So nothing was going through my head in that moment because that moment didn't exist. Many, many things went through my head along the way to it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And I hope that things keep going through my head and I come to new understandings. And it's going to be a very, I don't want to say scattershot process, but there's always a process. It's a give and take. You go back and forth. Things become clear, less clear, et cetera. And that's how life goes, at least for me. Colin Johnson says, You know, um...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I hope you don't mind if I say that this is an absolutely impossible question to answer. Like, there's no such thing as the measure on how much of baseline reality we currently perceive. Let's put it this way. When I look at this table in front of me, this poor table is going to get overused as an example, but I could tell you facts about the table.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I could tell you its approximate size, its color, its shape, and things like that. But there's, who knows, 10 to the 26 atoms in this table. And I'm not telling you nearly that much information. So on a scale of 1 to 10 of how much I'm perceiving of baseline reality, I'm kind of perceiving 1 plus epsilon, where epsilon is 10 to the minus 26, or something like that. I'm not seeing neutrinos.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So for the next few hours, we're going to live with it by thinking about other things. The rest of life goes on. The rest of the universe goes on. At other moments, we can resist and think about how to improve the political situation. But meanwhile, we can also think about bigger, more eternal questions. So that's what we're going to do for a little bit.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I'm not seeing most of the photons. Most of the photons emitted from the table aren't headed toward my eyeballs, right? They're going in other directions. So, yeah, most of reality I'm not perceiving. Not to mention the fact that I'm in a room, which is an infinitesimally tiny fraction of the whole space of reality. I don't even have my window open, so I can't even see the outside world right now.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So that's okay. We directly perceive a very, very, very tiny slice of reality. And the interesting thing is that it's enough to do pretty well, right? To have a pretty good handle on how reality works, a causal map, as Judea Pearl would have said, about if I poke something in one way, what its response is going to be, despite the fact that I know very, very little.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The miracle of emergence, that's what it's all about. TJ McMorrow says, in several podcasts, you've distinguished between the concept of complex and complicated systems. In some of those episodes, you and your guests have discussed ways of defining or at least describing complex systems. I'm wondering whether it's more straightforward to define complicated systems.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I recently learned about the notion of Kolmogorov complexity, and it seems like a pretty good measure of how complicated a system is. In plain English, both seem to roughly mean how much information is required to write down the full rules of the system. Is that a reasonable connection to make? You know, I'm in favor in these kinds of questions of not saying that there's a right answer.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You know, there's many different aspects to what you mean by complexity and complicated. I think it's a wrong strategy to say, here is a word, like complex or complicated. Let's try to decide what it means. That seems to imply that, like, the meaning of the word pre-exists, our use of the word out there in the numinous ether or something like that, and it doesn't quite...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
jive with how I think it actually is work, actually does happen. I think that what happens is we can ask that there, we use a word, we use the words long before we rigorously define them. And then when it comes to rigorously defining them, we realize, oh, actually, there are different aspects that we're using the same word to convey.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So in the case of complexity or complicatedness, I'm not even going to differentiate between them for these particular discussions. There is something called Komogorov complexity, the length of the shortest program that would output the system or the string of digits that you're talking about.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Scott Aronson and I, when we wrote our coffee cup paper, defined something we called apparent complexity, which is the commonwealth complexity of the coarse-grained version of the image or the system you're talking about. Both of those are just descriptions of either a string of bits or of some configuration of matter in space.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But there are many more things you would like to attribute complexity to, including processes, right? Charlie Bennett defined an idea called logical depth, which is not the length of the program that would output the string but the time it would take to run the program that would output the string. There's other measures of complexity having to do with calculations or computations, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
As always, the AMA episodes are brought to you by Patreon supporters of Mindscape. You could become a Patreon supporter by going to patreon.com slash Sean M. Carroll and pledging a bit of money for every podcast. I need to switch it for every month. That's what we're going to be doing now for every month. And as a reward, you get ad-free versions of the podcast. You also get to ask questions.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
How long does it take to solve the traveling salesman problem? But when it comes to physically moving things in the world, things that have many parts like a human body, okay, the complexity of the human body is not simply encapsulated by the distribution of its parts through space.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
We talk about the processes that go on in the human body, the creation of ATP and the traveling of white blood cells that Jim Allison talked about through the body to fight diseases and things like that. So it should be the least surprising thing in the world that there are different ways to quantify what we call complexity.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And the word complicated is generally not a technical term that people use in this context. So when I say that complexity and complicated are different, what I really just mean is that we have an informal notion when things are complicated. we have several different formal notions of when things are complex.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And if you really want to be careful, you should tell me what version of complexity you're referring to when you say something is complex. Matthew Fritz says, is the Dirac equation just a special case of the Schrodinger equation? I remember learning that the Dirac equation is the first successful relativistic treatment of quantum mechanics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But you generally talk about the Schrodinger equation as being the equation of quantum mechanics. Yes, that is completely true. I am completely right about this one, even though there's sort of a lingering set of places where you could hear the wrong answer about this. So the story is, of course, in fact, people don't usually tell the story. The story is that Schrodinger knew about relativity.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
When he wrote down his equation, the Schrodinger equation, he wrote down a non-relativistic equation. But he knew about relativity perfectly well. He first tried to write down a relativistic equation. And he came up with, I'm pretty sure he came up with basically what we now call the Klein-Gordon equation. which is a relativistic wave equation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It just doesn't fit the data if you try to solve it for electron energy levels, etc. So he eventually found his non-relativistic equation. And what happened was Klein and Gordon tried to find a relativistic equation. So did Dirac. They were aiming at different things. Dirac was aiming at the electron, which has spin. It is now what we call a fermion.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Klein and Gordon, their equation turns out to describe scalar fields, scalar particles, which were not known to actually exist at the time, but theorists could talk about them. But they're both perfectly relativistic. Neither one of them is a generalization or replacement for the Schrodinger equation. They're very useful in physics, but for a completely different purpose.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The Dirac equation and the Klein-Gordon equation are both classical equations of motion for fields. The Klein-Gordon equation is the classical equation of motion for a spinless field. The Dirac equation is the classical equation of motion for a spin-1 field that has electric charge.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Okay, so it includes both the electron, spin up and spin down, and the positron, spin up and spin down, the particle and its antiparticle. So Dirac thought that he was generalizing the Schrodinger equation, but it turns out that that's not what he was doing, okay? So the correct interpretation, and people sort of hang on to that mistake.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
These AMA questions are asked by the Patreon supporters. And every month, every episode and every regular interview episode, not so those are AMAs, but every regular episode, I do a little reflection audio thinking of talking about how I responded to the interview that we just had, the discussion we just had. And that's for the Patreon supporters.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It sounds good when you say, well, there was Schrodinger, and he had the non-relativistic thing, and then Dirac came along and he made it relativistic. The relativistic thing is quantum field theory. That's what the relativistic thing is. But even in quantum field theory, you start with the classical field, And Dirac and Klein and Gordon gave us equations for those classical fields.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And then you quantize it. And there's different ways of quantizing the field. And one way is precisely analogous to what Schrödinger did for a single electron, namely to invent a wave function that is a function of the field rather than a function of the particle. And that wave function obeys an equation, and that equation is called the Schrodinger equation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The Schrodinger equation is completely general in terms of does it describe non-relativistic things, relativistic things? Yes. There are different versions of the Schrodinger equation that apply to any of those individual circumstances. Indeed, there's a version of the Schrodinger equation that applies to a single qubit, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
A single degree of freedom that is either spin up or spin down, which is not a field at all. For every quantum system, there is a Schrodinger equation, even for the relativistic ones. Supine Otter asks a priority question, continuing in the spirit of asking someone who doesn't like tattoos about tattoos.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You previously suggested your favorite equations to ink on one's body, but for the visually inclined, can you recommend the physics-related diagrams or images that are most meaningful, satisfying, or beautiful to you and would make a great tattoo? It's a good question, a perfectly legit question.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I'm going to probably not give you a great answer just because, well, anyone who gets a tattoo shouldn't listen to me about what tattoo to get. And not because I don't like tattoos, because they shouldn't listen to anyone about what tattoo to get. They should... Think of it themselves, right? I mean, do you care about thermodynamics? Do you care about general relativity?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Do you care about quantum mechanics or whatever? These would all suggest different tattoos you could get. I mean, you could be playful. You could get a tattoo of Schrodinger's cat, right, of being both awake and asleep at the same time. you could get a tattoo of a space-time diagram.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You know, there's some very nice Penrose diagrams, like the Penrose diagram for the eternal Schwarzschild black hole is a very nice little diagram, pretty simple. You could shade it in if you wanted to make it look a little more complicated or something like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I mean, honestly, leaf through books and papers by Roger Penrose, because he is not only a great mathematician and physicist, he's a great artist as well. And he always has these amazing diagrams in his papers. So if you're a relativity kind of person, I would definitely recommend looking through Penrose's work for striking images, because they're definitely there.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
have to be aware of it and respond to it and think about it and take it seriously while also living the rest of your life. So I'm perfectly happy to be talking about non-political stuff for the AMA, but I do want to note what's going on. I always think about the audience hundreds of years in the future who are wondering what we were thinking back now.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And you could go either, you know, more whimsical, like the Schrodinger cat thing, or Laplace's demon. Get a tattoo of Laplace's demon. I don't know what Laplace's demon looks like, but you know what I mean. Feynman diagrams, particles interacting, you know, Feynman diagrams can get pretty complicated. They don't have to be simple ones. So I think there's all sorts of different possibilities.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
If nothing immediately strikes you, I like the idea of leafing through some technical physics papers. Even if you don't understand what the papers are about, maybe you can understand like the area they're in. Are they in quantum cosmology? You know, you can read the papers by Hartle and Hawking. See if there's any images in there that strike your fancy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And that would be something that would be pretty unique. David Whitaker says the universe is expanding and the stars and everything else are moving away from us at an increasing rate even. But they can't all be moving away from us or we'd be at the center of the universe.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So that could be you if that's how you want to roll. If not, that's also cool. We love you all. Let's go. Cooper starts us off with a priority question. Remember, the priority questions are something that all the Patreon supporters get to ask once in their lives, and I will do my best to answer that one question. We have too many questions to answer all of them.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And if they are moving away from us, but everything started together immediately before the Big Bang, why is everything not traveling outwards at the same speed? The great thing about this question is that the second part answers the first part. If everything was traveling outwards at the same speed, that would indeed be an indication that we were at the middle of the universe. But it's not.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So forget about moving. Forget about visualizing everything moving away from everything else. Think about, you know, the universe itself. In fact, what I like to do is to literally imagine you're outside on a clear night, and you are gifted with perfect vision, including for very, very distant galaxies, okay? So we're not using any analogies. We're just trying to visualize the real universe.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And imagine that you have Doppler imaging in your eyeballs, so you can see how fast the different galaxies are moving away from you. And you notice that galaxies that are relatively nearby are moving away from you relatively slowly. Galaxies that are far away are moving away from you faster, okay? So they're moving away from you at different speeds. what does that mean?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
That means that if you think about the people who are in, who are living in one of the nearby galaxies, they see you moving away from them in one direction, and the galaxies that to you are further away are moving away from them in the other direction. Indeed, they see the same kind of pattern that you do. They see everyone moving away from them in
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
in a pattern which is the further away they are, the faster they're moving. So this precise behavior where everything is moving away from everything else with the property that further away things are moving away faster is exactly what you need to not have a center so that everything is created equal. Everyone sees the same basic kind of thing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
This is both what is predicted by general relativity and what is actually observed in the universe. Anonymous says, imagine a future where the NBA moves to a virtual format and all players are linked to an avatar via a brain chip. All avatars are the same height and strength.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Do you think the majority of current players would stay in the NBA or are there probably lots of more skilled, smart basketball players out there who simply aren't large or genetically fortunate enough to compete? I think that it depends on whether you're talking about the very short term or the very long term.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I think in the very long term, if everything is virtual and everyone's physical abilities are essentially equal, then I think that—I'm guessing, this is an empirical question you'd have to test, but my guess is that the distribution of basketball talent is kind of uncorrelated. with height and physical speed and things like that, and you get all sorts of people doing very well.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It's basically playing a video game, right? There's not any, as far as I know, correlation with height and strength with ability to play video games, okay? But if you did this and did it next year, then I think what you would find is that the current
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
very good basketball players would still be the very good basketball players because they've been training for a very long time to do exactly this and in ways that other people haven't. If you're a casual basketball player, you haven't been put in the work compared to an actual NBA player. Some NBA players would not turn out to be very good. They're
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
There are some who are just coasting by on their physical gifts and they would not do that well. But I think a lot of the actual basketball players to stay and flourish in the modern NBA, you have to be pretty talented and dedicated. You know, there's always going to be exceptions.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I remember just because of a similarity in names, there was a center in the NBA back in the 80s named Joe Barry Carroll. No relationship to me, but his important talent was he was tall. That was it. So his nickname, Joe Barry Carroll, was nicknamed Just Barely Cares. Because he was really not interested in putting in the work, getting better.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
He was just standing out there and being tall, and he earned a lot of money doing that. I think it's harder to do that now, maybe, than it was in the 80s. Josh Flowers asks a priority question. Okay. You know, in principle, sure.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I mean, you have to be careful when you're talking about distances of objects in astronomy because there is no fixed reference frame, okay, with respect to which we're supposed to measure these distances.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
As Einstein taught us, if you're moving close to the speed of light, the distance that you think you would have measured if you had not been moving close to the speed of light might be very different. It's length contracted, as we say.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But the good news is that, in fact, the amount of velocity that typical astronomical objects have, galaxies and stars and planets and things like that, is small compared to the speed of light.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Even though there is not absolutely a reference frame in physics, there is approximately a rest frame in the universe where stars and galaxies typically move at about one one-thousandth the speed of light with respect to each other. So the Doppler effect is actually just not very big. There are circumstances in which it matters. In fact, there's a phenomenon called the finger of God.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And the finger of God is this. If you have a cluster of galaxies, okay? So you have a cluster of galaxies and... That means you have a bunch of galaxies, and they're orbiting the common center, which means that some of them will be in the—you're measuring two things. You know, this is back in the day. You aren't measuring the distances directly.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You're measuring the redshift and using that to infer a distance to the galaxy. And then you can accurately measure its position on the sky, right? You know, its angular position on the sky. So your inferred distance measure to the galaxies is contaminated by the fact that the galaxies are moving.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
In fact, this month we had a very large number, and I feel very bad. There's a lot of good questions that didn't get chosen, so sorry about that. But Cooper's priority question says, the episode with Jeff Lichtman was fantastic and has really stuck with me.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You're measuring the redshift and some of that, not most of it, just a small amount, but some of it is from the Doppler effect. And that Doppler effect that affects the redshift and therefore your inferred distance only is added to the distance measure radially, that is to say in the direction of your line of sight.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The angular distance you just measure by taking a picture of the galaxies on the sky. So you have accurate measure of where the galaxies are in the sky and a distorted measure of where they are along your line of sight. So you take what should be a relatively spherical blob of galaxies in a cluster, and when you plot it in what you think is position in space, it is elongated in the direction of u.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It's the finger of God that the joke was, this is a finger of God pointing at you saying, you are wrong, because you have small errors in your measure of distance.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Now, this was a thing back in my day, in the early days of my cosmological career, because measuring galaxies and their redshifts and their distances was a painstaking process, and we didn't have a lot of them, and therefore the ones we had were relatively nearby.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
as you go to further and further clusters of galaxies, et cetera, the relative importance of this Doppler effect becomes less and less because the overall recession velocity becomes more and more dominant.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So these days, this kind of thing is not that important in terms of making maps of galaxies, and even its existence is perfectly well understood, and there are statistical techniques for compensating for that mistake. So yes, these differences exist. No, they're not very big. Yes, even the small differences are things that we know about and are able to compensate for.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
His comment about how understanding something requires compressing it in some way and how the brain perhaps cannot be compressed in that way is something I keep thinking about. It's as if the only way to understand a brain is to be a brain, sort of like how perfectly simulating a universe requires something the size of the universe. Did this comment of Jeff's leave an impression on you as well?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Alex Reinhart says, why do you think that complexity science concepts have caught on in a popular way, especially chaos theory, but also things like economic examples and flocking, but aren't captured in most STEM university educations? This is just my perception. Yeah, I think your perception is kind of right. And I think that there's a couple of things going on.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I guess the biggest thing is David Krakauer and I disagreed with this about this when we were talking. So you can go back and hear our conversation. He's the world's expert on complexity. But I kind of think that complex systems science is still pre-paradigmatic.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
That is to say, we don't have a fixed curriculum, a fixed set of examples, a fixed path from not knowing anything to hear the basic things you should know and hear the applications of them, right? In physics or economics or chemistry or whatever, we kind of agree on what is the first course you should take, the second course you should take, and you build up an agreed upon set of knowledge.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
With complexity, it's still more of a grab bag. There's very interesting results out there. There are some things that seem to be common across different kinds of complex systems, but it's less clear what exactly the standard set of knowledge is supposed to be. It's more scattered across different domains, different disciplines, and therefore harder for it to get into a standardized curriculum.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
We're getting there. There's a couple of very interesting textbooks that now exist on complex systems theory, and maybe it will become more popular. But also, you know, the way that complex systems—I never know whether to call it complexity or complex systems, and therefore the accent on the first word is always unpredictable for me.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Complex systems science is an interdisciplinary science by its very nature. It's you know, what can be a complex system? A biological organism can be a complex system. The economy can be a complex system. The internet is a complex system. A language is a complex system. What department is this supposed to be in, right? You know, who is supposed to be learning this and teaching it?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So what you get is different departments doing little bits of it, and it hopefully in some areas does have an impact, but there's no standard. There's no consensus. And I think that Maybe that will change. You know, I keep trying to teach a course in complex systems in the physics department at Johns Hopkins.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It is not like they're trying to prevent me, but other courses that are more pressing keep coming up. So I'm teaching quantum mechanics next year. That's got to be taught. Someone's got to teach quantum mechanics, and so I'm going to be doing it to the undergraduates.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
We do have a new faculty member at Hopkins, Matthew Wyart, who is a true complex systems statistical mechanics expert, and he's going to be teaching things. So I do think that, you know, maybe it's seeping its way in. These things take time. Academia is very slow, very slow to change and to adapt to new ideas.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Bjorn Haig says, you seem to be able to disagree with people so gently, clearly, and unobtrusively. How do you do it? Are you even aware of this being a skill of yours? Yeah, I would disagree. This is a skill of mine. I don't think this is a skill. That's not the way that it comes across to me.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Don't feel the need to say much if it did not." No, it did leave an impression, but I've thought about things like that before. I think that there are important differences between levels of understanding. You can understand something a little bit or better, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I get very frustrated with people sometimes, and I do disagree with them maybe a bit too harshly or shrilly than really I do. I try. to disagree gently and constructively. It's not about being unobtrusive or even gentle so much as clear is important, to be clear about why you disagree and to be constructive about it, to try to understand why we're disagreeing, maybe move forward.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But I would say that there are different kinds of disagreement, right? There are people who are worth disagreeing with, and there are people who are not worth disagreeing with. I do try very hard to not spend too much time disagreeing with the people who are not worth disagreeing with. I mean, I disagree with them maybe,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But if they're not going to change their minds or their thoughts are just not very interesting or good, then I'm not going to spend a lot of time engaging with them. I'm trying to engage with people who I disagree with in a way that potentially they could change my mind or I could change theirs or at least we could learn something important from each other.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
That's the criterion that I try to have for guests on Mindscape. It doesn't always work, you know. There's – Podcasts has to happen every week, and I choose a lot of different people, but basically what I'm looking for is somebody I can learn from. Even if it's something that I already know a lot about, I can learn little details, and the audience maybe can learn a lot.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And if it's something that I disagree with somebody, but I want to know why they think that, right? So I'm choosing to engage with people I disagree with but can learn from, and so that kind of naturally makes it a more pleasant experience. I do think this might not be true, but I think that...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It's weird to me to see people on the outside of academia be less able to disagree with each other politely and constructively than people inside academia. If you just asked me if I hadn't thought about it that much and you just asked, do professors disagree with each other sort of loudly and emotionally, I would say, yeah, they really get into it and they disagree pretty badly.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
still almost all the time, not all the time, but almost all the time, professors, intellectuals, scholars, people who are in academia, they disagree, and they go out and, you know, have a drink with each other and talk about it. They keep talking about it forever, for decades, right? This is very, very standard. It's not 100% by any means, but it happens all the time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And I think that a lot of people outside just, if they're disagreeing, then that person is an enemy And they shouldn't be engaged with in any way. And that's a little alien to me. It makes me sad when I see things like that. Folkman says, I just finished reading the big picture, which I found excellent.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It's very similar to the discussion about emergence and higher-level macroscopic, coarse-grained understandings versus lower-level microscopic understandings. So I might not understand everything about a brain, but I understand some things about it. Or think about something that is a little bit less problematic to get all the nuances down. I understand how to drive a car.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
On the question of free will, it almost seems as if your definition results in a situation where entropy is reversed or inverted.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Multiple potential macro states resulting from the decision you actually make, you have free will so you can make many different decisions with distinctly different outcomes, correspond to only one microstate, which results from the deterministic chugging forward of the microscopic configurations based on the laws of physics. What are your thoughts on this interpretation?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Does this have any interesting implications for the arrow of time and related concepts? So I'm not exactly sure what you have in mind here. I'm not sure that it came through to me perfectly clearly, but I don't think that your interpretation is on the right track. Let's forget for the moment about quantum mechanics, okay? Quantum mechanics introduces true indeterminism into our observed world.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So that's something that in detail – at the detail level, we have to keep in mind. But even in classical mechanics, if classical physics were true at the base level, you would still have a world – I think you could imagine a world that looks pretty similar to the one we live in where we're made of atoms and the atoms are jiggling around and doing different things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And the point is, in that world, when you have emergence at a level of, you know, there's a higher level where you've coarse-grained over a lot of individual details, and at the lower level there's deterministic microscopic dynamics, it will often be the case that the higher-level dynamics are stochastic, and the best possible thing you can do is make a prediction about probabilities, even though the lower-level dynamics are completely deterministic.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
if I have a theory of, you know, when a volcano is going to erupt, the details will depend on a lot of microscopic facts that I don't know the answer to, right? But the point is that what that means is there are two, actually many more, but let's say particularly two microstates that are in the same macrostate that lead to very different behavior at the macro level.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So there's a microstate of the volcano. I look at the volcano. I do all the tests I can, but I cannot measure every single atom in it. So there's details about the pressure and the temperature that I don't exactly know. Certain microstates of the volcano are going to explode any minute now. other microstates of the volcano are going to last years without exploding, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So that's okay at the- at the emergent level. That's not a failure of emergence. It just means that the emergent theory tells you the probability that the volcano is going to erupt. And I think the same thing is true with people and with free will.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
My macrostate description of a person obviously doesn't include an enormous amount of information about the details of what's going on in their brains, right? So it may very well be the case that the microphysics of what's going on in their brains completely determines what they're going to do next. But that information is not available to me. I don't have that information.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I don't even have that information about myself, much less about other people. So what happens is in the macro state that I use to describe a person, there are various different possibilities about what will happen in the future. And 100% compatible with everything I know, there are different possible future choices. We call these decisions or –
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Yeah, choices, decisions, things that your free will is doing. And free will is just a label we put on them. And I know that some people don't want to put that label. That's fine. I don't care. Don't put it on. I'm just trying to correctly describe what goes on in the world.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Henry Jacob says that so many people support Luigi Mangione, which blew my mind, suggests that a lot of people are consequentialists. Do you agree with this inference? So Luigi Mangione is the one who killed the CEO of UnitedHealthcare, which did indeed – Start a lot of conversation there on the old internet and elsewhere.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I don't understand everything that is going on in the car, right? That would require a lot more information. But I can still understand enough to be able to drive the car. And I think the same thing is true with brains. We can understand some things about how they work or we can focus in on some aspects of them.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I think that here in the United States, for those of you who don't live here right now, we have problems with our healthcare system. And a lot of the problems in the United States in general are simply the result of the fact that very important –
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
functions of everyday life are outsourced to corporations who are trying to make as much money as possible, not trying to make our lives better as possible. The whole idea of capitalism and Adam Smith is that under certain circumstances, the interests of corporations trying to make money and the interests of the consumers or the workers can align with each other, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You can actually have a situation where it's win-win for everybody. But that's not inevitable. It doesn't necessarily happen. Sometimes the corporations can just leech off money from people because they have figured out a way to do it. It doesn't make anyone's life better except they make money. And The insurance industry here in the United States is a classic example of that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And so it's in a regime or it's in a context where emotions run very high because you're literally talking about people's lives, people's health. The healthcare companies deny life-saving care to people. And so people are rightfully angry about this. And so Luigi Mangione took it out. I don't know the details. I don't follow this kind of thing very carefully. But
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
He was someone who was upset about the situation. I think that there were personal issues involved also and he basically assassinated the CEO of a healthcare company. And there was – among things that I see on the internet, there was a remarkable amount of cheering him on after the fact with the very basic justification that –
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Look, this healthcare CEO in fact was responsible for many more than one deaths in a very tangible way. And I think that there's a couple things going on. Consequentialism might be part of it. So Henry is suggesting, well, you can kill one person but then you're saving many other people. So it's sort of a trolley problem kind of thing and maybe that's OK.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I don't actually think that that's really what's at the heart of the support for something like this. I think it's just more visceral, right? People feel powerless. People feel like bad things are happening and they can't do anything with it. And this is when people think about turning to violence. It's not a good sign, I don't think.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So the complete understanding might involve something at the Laplace's demon level of perfect information at some microscopic level that we might never obtain. But we can get better and better at understanding bits of it and aspects of it. And I think that's perfectly good.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I'm not in favor of assassinating the CEOs of healthcare companies. I think it's bad for all sorts of reasons. That would be a long list of reasons why it's bad. But aside from the consequentialism argument, the other argument that I think is perfectly legit is to say we count different kinds of deaths differently in terms of being upset by them, thinking of them as illegitimate, et cetera.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
takes a gun and walks up on the street and shoots somebody, then we all agree that's bad. But if someone sits behind a desk and judges that a person doesn't deserve to get health care, that's just business as usual, right? That's just how the system works.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And I'm entirely on board with arguing that we should think about these kinds of deaths in more similar ways rather than in the very, very different ways that the system currently does think about them. Doesn't mean I think we should go around assassinating people. I'm kind of a believer in the rule of law, not in vigilante justice.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But I do think that taking seriously accusations against people and corporations whose actions end in deaths of ordinary citizens is something we absolutely should be able to do. Not that I really know how to bring it about, but that's true for many political or social or economic ideas. Kevin's Disobedience asks a priority question.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I'm a contractor by trade, but a year ago I decided I wanted to teach myself particle physics after work. In short, I quickly realized I needed to go back and relearn at least some basic classical mechanics before moving on to relativity and quantum mechanics. So I'm slowly working through a high school textbook again.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But after reading dozens of popular books, the thing that impresses me the most about physics is physicists mastering the old and new stuff to work on the cutting edge. So my question is, would graduate level problem sets on, say, geometric optics or thermodynamics be simple to you now or would involve a quick refresher?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I guess I'm curious how much of the technical education one retains and in what form. I hope that's clear. It is clear.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So putting aside all the details that might come up in your mind in the preamble to the question, the question is, you know, once you're a professional physicist, can you go back to the stuff you did as undergrad or graduate at the problem set level, and is it all now easy, or do you have to, like, work just as hard? Well, there's two things involved.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
One thing is sometimes these problem sets in, you know— thermodynamics or E and M or quantum mechanics or whatever, just involve a lot of work, right? You know, sometimes there were a lot of all-nighters back then when I was in grad school, but it just, the amount of calculations you have to do is just large no matter who you are, no matter how much knowledge you have, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You got to do that integral, you got to solve that differential equation, you got to diagonalize that matrix, whatever it is, okay? So some of it is irreducible, the amount of work you have to do. So that's one thing. The other thing is, of course, hopefully you do get better at seeing how to solve these problems. Sometimes I will see online, I'll see a final exam or a problem set in a course.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Martin Leitner says, I was wondering how photosensitive organic molecules like chlorophyll implants or the receptors in our eyes are able to react to a range of frequencies. I was taught that an electron needs a very specific frequency to get excited. Similarly, how can two electrons and two atoms that are not perfectly stationary...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
that is being taught somewhere else, and I haven't taken it for many years, and I read it and I go, oh my God, I would never be able to solve that. But then I sit and think about it and go, actually, yeah, no, I could do it. I just haven't thought about it for a long time. And I think that it's a combination.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You do forget some of the details that you might have recently learned if you're taking the class, But I think that, in fact, the purpose of the education, this is a slight exaggeration, but a lot of the purpose of the education is to sort of know where to look. Like, oh, OK, this particular problem requires taking a Fourier transform, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Or this particular problem is a perturbation theory problem. Like the angle of attack and, you know, what books you have to turn to to figure out what equations you need and that kind of thing. Rather than the actual solution to the problem or even the actual step-by-step way to solve the problem, it's more like what kind of problem is this? What kind of tools are you going to need to do this?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
That kind of stuff is taught to you and it's not necessarily what you think is being taught to you, but it's what sticks with you decades later. So... I would say that specifically it would not be simple for me to answer a question like graduate level statistical mechanics or something like that necessarily. But it would be much simpler now than it was back when I was doing it the first time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Anders says, so it turns out that Schrödinger was a pedophile. He groomed a 14-year-old girl and got her pregnant when she was 17. He also attempted a relationship with a 12-year-old girl and called her the love of his life. How do we handle situations when unquestionably brilliant men are monsters? Should we mention it in the textbooks and when lecturing?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Should we rename lecture halls and remove statues of them? I think, you know, I chose this question to talk about because I don't think the answer is easy. I think it's a complicated one. I don't think there's a cut and dry solution here. I do think that we shouldn't hide it when people who are great for one reason are pretty terrible for another reason.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And I think that for Schrodinger, that's a perfectly plausible answer. conclusion to draw from his actions. I don't think we should rename the Schrodinger equation. You know, I think of these labels, I think of names of equations and things like that as labels, not as honors.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Sure, Schrodinger is someone we remember in part because his name is on an equation, but it's also just the Schrodinger equation. That label, the Schrodinger equation, has transcended Schrodinger the person a long time ago. But in terms of like honoring them by statues and things like that, that's a more difficult question. I think that –
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
ever exchange photons given that the Doppler effect will alter the frequency? Well, there's a lot going on here and I'm actually not the best person to ask about what is going on in the receptors in our eyes or things like that. But I think part of it is there are many different frequencies.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
On the one hand, the argument would be we're honoring them for the good work they did. The other argument would be like shouldn't we be honoring good people rather than bad people, not just people who achieve things no matter how bad they are? I think – I don't know the answer to those questions. I do think we should be upfront about it. I think there is a certain –
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
temptation to think that because somebody did a great thing in science or, for that matter, in art or politics or sports or literature or whatever, that there are heroes and we should honor them, right? And that I'm much more skeptical about. I think that that's always a dangerous thing because you're honoring someone who you don't know. Personally, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
If you want to honor the thing they did, that's fine. But then to just transfer that into honoring the person as a whole when you really don't know that person as a whole is a very dangerous move. So I'm in favor of teaching the history accurately and letting people go where they will from that. Natalie Standing asks a priority question. I'm a 52 year old with a passion for reading about physics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I've been captivated by your books and those by Brian Green. They never fail to blow my mind. Though I didn't excel in school, particularly in mathematics, I find myself fascinated by the discipline. I would love to deepen my knowledge of this beautiful language. Could you recommend some starting points or resources to help me on this journey?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
well, you know I'm going to recommend my own books, right? That's where I'm going to start. But let me say, books are for some people. Videos are for other people. Classroom discussions are for other people. Different people are going to learn different ways. You've got to find the way that works for you. Some people are mostly happy just reading the texts.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Other people need to work out problems and things like that. Again, find what works for you. Part of the goal of my... hopefully eventually completed trilogy on the biggest ideas in the universe is to provide some insight into those more quantitative aspects of modern physics that popular level books don't cover, whether it's classical mechanics, quantum mechanics, or complexity and emergence.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So to me, that's like hopefully a very good starting point for exactly what you're thinking about, the biggest ideas in the universe. Leonard Susskind also has a series of books, The Theoretical Minimum. It's a little more straightforwardly course-like laid out. In the biggest ideas, I try to sort of mix and match things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I don't go in the traditional order because I'm very, very explicitly not teaching a course, right? It's about— people picking up the books and reading them. So it's a slightly different angle, but a very similar spirit of showing you the equations and helping you learn about them. None of those books are quite at the level of a textbook. So ultimately, if you really want to learn this stuff,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So indeed, in the cartoon model of an atom or a molecule, there are electrons in orbitals with very, very specific energies. So you might think that unless you hit that energy right on, you're not going to be able to excite that particular electron. But typically, the photons that are moving around doing the exciting are not in what we call energy eigenstates.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Well, what do you mean by really want to learn this stuff, right? If you want to learn it at the level of a professional physicist, you have to start at the beginning. You have to learn classical mechanics and calculus and differential equations and waves and E&M and basic quantum mechanics and statistical mechanics and then on your way up.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
There is a famous slash infamous web page put up by Gerard de Tuft, who is a Nobel Prize winning brilliant physicist, called How to Be a Good Theoretical Physicist. And he lists – I've always thought maybe I should do a – my own version of this because it lists every course you need to take.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And he points to specific resources, both online and textbooks that will take you all the way up through quantum field theory and particle physics and condensed matter physics and so on. But he also has all the steps along the way, including things like foreign languages and the mathematics and so forth. The problem is that a Tufts idea of what you need to know is rather expansive.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So it's incredibly intimidating. Like you look at the list and you're like, I'm never going to get through all this. And, you know, maybe that's what you need to be in a Tufts level theoretical physicist, but maybe some of us want to just aim at being a, a working class hack theoretical physicist, and that would be good enough.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So you can maybe pick and choose a little bit, but ultimately, yeah, you're going to have to buy some textbooks, I think. Maybe buy is the wrong word, because at this point, there's so much stuff online, whether it's online courses, which I really am a fan of, or online lecture notes or whatever. I don't have specific recommendations there, but go to edX and Coursera.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
These are online course sites. Or go to Khan Academy or whatever and just find courses you can sign up for. And many of them are archived, so the videos are there. You don't need to take them at some specific pace. You can just do it whenever you want, which is great.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Christoph Radomski says, in Space Time in Motion, you mentioned that you, being a science consultant in Marvel's Thor, had something to do with Jane Foster's mention of an Einstein-Rosen bridge. Are you also responsible for Tony Stark's mentioning quantum fluctuations at Planck scale triggering Deutsch proposition in Avengers Endgame? No, that one was not mine.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
There were other science consultants on Endgame. I think, I'm not 100% sure, but I think that former Mindscape guest Clifford Johnson was one of them, and it might be from him. I mean, that particular statement of Tony Stark's is kind of word salad nonsense. All the individual terms make sense, but the particular way they are arranged in order doesn't, which is, that's fine. You know, it's just...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And here in February 2025, this is literally a pivotal moment of history. And it would be weird to pretend that it was just a normal moment. We're less than two weeks into Donald Trump's second term as president, and it has been even worse of a fiasco than his biggest enemies might have predicted. The combination of ruthlessness and incompetence is quite shocking, and so it's important to
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It could have been better like if they had more science consulting going on. It could easily have been massaged into a statement that both made sense and to serve the dramatic purposes in the moment. But despite the fact that these movies cost a lot of money to make and spend a lot of time being made, there's always kind of a rush.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
People don't have time to sit back and go like, OK, how exactly should we get this one particular line? Should we get the technobabble right so that it makes sense? So, no, I am not responsible for that one. Sorry.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Gary Miller says, But if you read this question aloud to your entire audience and agree that any one person's vote doesn't matter, you risk alienating a large group of people from voting. It seems like democracy depends on people believing something untrue that their vote matters. Is this an inherent problem with democracy?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Well, there's certainly some problem with democracy that you have two choices. Either you let voting be voluntary, which happens in most places, and then some people don't do it. Or you make it mandatory and then you're going to have voters who are hilariously under-informed. And in fact, that still happens when the voting is voluntary. Right.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
That is to say, they don't have perfectly precise, well-defined energies. That's part of the fun of quantum mechanics. in exactly the same way that an electron itself, which if we imagine that it is exactly in a perfectly definite state of energy, it will then not be in a perfectly definite state of position. We think of the electron as being in a superposition of many different positions.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So I don't think there's any perfect solution to these questions. You know, I don't think it's right to think of democracy as trying to be a method for making the best decisions. It's trying to be a method of giving people a voice. And of course, any one person's voice is small in countries that are as large as ours.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I think an underappreciated problem with democracy is just that nations are big now. I mean, 200 years ago, we didn't have 300 million people in the country, and the voices mattered a little bit more. So there's a lot of things going on here. We talked about this with Herb Gintis, among other things, and it's a reflection of – a more general issue in philosophy, in moral philosophy or whatever.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So Immanuel Kant would tell you you should act if you want to act morally in such a way so that your actions may be the basis for a general principle, right? In other words, the golden rule, basically the golden rule. The categorical imperative is a slightly philosophized-up version of the golden rule. It says act the way you want everyone else to act, right? But why?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Why should I do that if it's not actually true that everyone else will act the way that I'm supposed to act? Why should I be acting in that way? Now, of course, counterfactually, if everyone acts the way they want everyone else to act, then they will all inform themselves and they will vote, et cetera, et cetera.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So even if that doesn't happen, should we act because we want it to happen in the way that we would be acting if it were happening? That's the question. And the answer is not obvious. The answer is not obvious at all. I mean, Herb Gintas's answer was something like it's kind of tribal affiliation signaling, right? We don't vote thinking that our vote will be the tiebreaker.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
We vote thinking that we are expressing ourselves. We are saying, here is who I stand for, where I want the country or the municipality to go, things like that. And it's rational in a way that is different than how we pretend it's rational. We pretend it's rational because we're choosing who is going to lead us, and collectively that happens.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But at the individual level, the rationality is about belonging to a group, not about making a decision. Does that hang together? I really don't know. You know, I do think that there's a give and take between our individual actions and how we influence others. So therefore, I am very much in favor of both voting and encouraging other people to vote.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Chris A. says, why is developing a quantum description of gravity so difficult? A lot of very smart people have been trying very hard for nearly 100 years. So what is it about the problem that makes it so intractable? It's a great question, you know, one that does get talked about, but maybe deserves to be talked about more. And I think that there are two kinds of problems. This is not just me.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I'm not just making this up. There is a standard understanding that there are two kinds of problems with quantizing gravity. There are technical problems and there are conceptual problems. The technical problems are just that, according to the ordinary ways we have of doing quantum field theory, which is what you should need to do in gravity since gravity
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Einstein's general theory of relativity is a classical field theory. In quantum field theory, we have rules for taking a classical field theory and quantizing it. And in the case of gravity, these rules don't work. The straightforward way of saying this is that it's not a renormalizable theory, which is to say that if you try to extend your quantum field theory version of gravity,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
to arbitrarily high energies, you kind of get nonsense. You lose the ability to predict what is actually going to happen, okay? I'm sort of hesitating because there's a technical way of saying this. I'm not sure if it's worth saying, but essentially to make any one prediction requires an infinite number of input parameters in the theory. That's the consequence of non-renormalizability.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
these photons are typically going to be in superpositions of many different energies. So the energy has to be pretty close to the right answer to poke the electron around in the right way. But there's probably some uncertainty around that exact right answer. And as long as the electron's energy is within that uncertainty band, you have a probability of making this happen.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Now, you may have heard me say that we have this thing called effective field theories, right? If you don't want to extend your field theory to arbitrarily high energies, then we can just say we have a cutoff, we have an energy scale above which we don't care, and make a theory about what happens below that scale. And that you can do for gravity, and it works in a wide variety of circumstances. But
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
If you think that what we're actually after, at some point, you care about what does happen even at arbitrarily high energies. So the effective field theory technique lets you have a functioning theory, an effective theory, below a certain energy scale. But that doesn't mean you don't care what happens above the energy scale.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And when you start including gravity, maybe you do care what happens at energy scale. So gravity is just sort of not a successful quantum field theory by the standard measures. So in other cases where we had like the Fermi theory of the weak interactions, Enrico Fermi came up with this theory where neutrons could decay into protons, electrons, and antineutrinos, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
That's a non-renormalizable theory also, just like gravity is. But it turns out it wasn't the right theory. It was only a theory that works below a certain energy scale. And above that energy scale, you have to invoke W bosons and the weak interactions and things like that. and you get the standard model of particle physics, which is a renormalizable theory.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So you might hope to find a renormalizable theory that reduces to gravity at low energies. No one has been able to do that. They tried. Okay. Well, actually, sorry, that's not true. String theory is exactly an example of this. In fact, maybe it's worth saying that, you know, to a lot of people who wonder why string theory is so popular, this is really the reason. At the end of the day,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
That's why string theory is so popular because you think that you really are looking for a theory that is complete. Indeed, the phrase that is used is an ultraviolet complete theory, a theory that works up to arbitrarily high energy scales. And I'm even underselling the problem with gravity because it's not just that gravity itself is non-renormalizable and gives you infinities at high energies.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But the infinities depend super sensitively on not just how gravity operates but how every other field in the world operates because everything couples to gravity.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So the naive feeling is if you just try to come up with a quantum theory of gravity that's well-defined, you need an infinite conspiracy between what the gravitational field is doing at high energies and what all the other fields are doing at high energies. It turns out string theory gives you that infinite conspiracy because it's just one thing, a string, that's vibrating in different ways.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And you can show that not only are there no infinities, sorry, not only is it renormalizable, but it's finite. There's not even an infinity you have to remove in string theory. You just get a finite answer. No other approach to quantum gravity that anyone has been working on has that nice property.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So as many other problems as string theory has, as long as it has that nice property, it's going to be a popular approach to quantizing gravity. The other set of problems are the conceptual problems. When we're quantizing gravity, we don't even know what it is we're quantizing because space-time itself is on the table.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Remember, all of quantum mechanics is about probabilities for these things happening. And likewise, yes, the electrons are going to be moving back and forth. They're going to have Doppler effects in the photons that they emit and absorb. But that's sort of helping them, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Among one—one among a large number of avatars of this particular problem is what is called the problem of time. This is what we were talking about in the solo episode recently. If you naively plug away, treat general relativity like a field theory, quantize it, you get an equation called the Wheeler-DeWitt equation, which says that the wave function of the universe doesn't evolve with time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But it does evolve with time. I'm looking around. My immediate environment is evolving with time. So what's up with that? So these are conceptual problems, not just technical problems. It's not just I hit infinity. It's just that I'm getting nonsensical answers to the questions because I don't have any firm ground to stand on. In ordinary quantum field theory, at least I have space-time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It's there. It's sitting there. It's rigid, and I know what it is, and I have some fields vibrating on it. In quantum gravity, space-time itself, is part of the quantum description and it's much harder to know where to start because that's a unique situation. There's no other versions of physics theories in which space-time itself is part of the dynamical playground.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So yeah, we don't know what time is. We don't know how Lorentz invariance evolves. We don't know what it is we're supposed to be predicting. You have the wave function of the universe. Okay, what does it mean? How do you turn it into a prediction for something? No one knows. the once and for all answers to any of these questions. So yeah, gravity is special.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Gravity is different as far as we can tell. Nate Wadoops says, the volume of a sphere is proportional to radius cubed. And the area of a sphere is proportional to radius squared. So it seems intuitively obvious that there are too few Planck squared units on the surface of a sphere to capture all the information contained in the much more numerous Planck cubed units of volume within the sphere.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But much better informed people than me believe in the holographic principle where something like that happens. Can you help me understand where my intuition has gone wrong here? No, I think that your intuition is completely fine. It's absolutely the case. Everyone knows that there are fewer Planck areas on the surface of a sphere than there are Planck volumes in the volume of a sphere.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
That's very well known. The whole point of the holographic principle is those Planck volumes in the volume of the sphere are not independent from each other. right? That's the whole point of a hologram. A real-world hologram is a two-dimensional thing that if you shine light on it in the right way, you see a three-dimensional image.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But the different parts of the three-dimensional image are not independent from each other. They're all derived from only two dimensions worth of information. So that's the whole trick in the holographic principle. You don't, in holography, have the ability to separately choose what is going on everywhere within the volume of spacetime.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
In the sense that if you have many different molecules and they, you know, molecular energy levels are generally tightly compressed. There's a lot of them. So it's not just like the one or two that you see in the cartoon of the hydrogen atom and so forth, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Now, how does that actually play out in practice is a little bit unclear, but people are working on it. It's clearest in the ADS-CFT correspondence, but even there, it's not 100% clear. So still work in progress. Yeah. Sandro Stucki says, in your January solo on the existence of time, you sketch an argument for why Boltzmann brains are not a problem once one considers quantum physics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You said that this is because thermal quantum states are static, but I could not quite follow how that solves the problem. How can the universe settle into a static state if Hilbert space is finite? Doesn't recurrence forbid that? Yeah, no, you're absolutely 100% correct. So I don't know whether maybe I mumbled through it and wasn't clear.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The whole point is that this scenario where the universe settles down and asymptotes to a static state and there are no fluctuations and no Boltzmann brains, that only works if Hilbert space is infinite dimensional. Now you have to be careful because we think that the Hilbert space of our observable universe is finite dimensional. But that's okay.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Maybe there's something outside our observable universe and maybe there's infinite more Hilbert space out there. That's what you would need to make this scenario work. We don't know if that's true or not. So if it turns out to be true that Hilbert space is truly finite dimensional, then this argument is off the table.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Then indeed you would expect recurrences, fluctuations, Boltzmann brains, all of that stuff going on. Kirsten Johnson says, do you think the holographic principle might have anything to say about why neural networks work as well as they do? I guess that depends on what you mean by the holographic principle.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The holographic principle, strictly speaking, is supposed to be a statement about quantum gravity. It's not supposed to be a statement about anything else. It's not, you know, a principle that is widely extendable to all sorts of different circumstances.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It's something that becomes evident when you have quantum mechanics plus gravity, and in particular, when you have pretty strong gravity, like a horizon or something like that, when... you have black hole, or you have anti-de Sitter space, de Sitter space, a cosmological horizon, then holography becomes relevant.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Even with quantum gravity, in other circumstances like the solar system, holography is completely negligible. It's completely irrelevant. You can just talk about ordinary gravity. So there's no reason why if you don't have either gravity or quantum mechanics going on, like you don't in a neural network, the holographic principle should have anything to say about anything.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So if you have the molecules moving or the photons moving, so there's not only some uncertainty in energy but some shift in energy because of the Doppler effect, it is more likely that some of the photons are going to be in the right band to do the action.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Now, it's possible that there is something analogous to the holographic principle or something similar or formally comparable to it that is relevant to neural networks. That's completely possible, and I just don't know. But the neural networks that you and I know and love are firmly within the regime of classical mechanics, and gravity is very, very weak.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So strictly speaking, the holographic principle isn't relevant. Marie Roscu says... When there are different types of ways to look at things, values and perspectives, can or should there be different types of democracy? Maybe. In principle, yes. I think it depends on details there. It does remind us of a...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Really, really important fact about democracy, which is that it's hard to understand why democracy should work at all because it revolves around people with different interests, different values and perspectives coming together to work in a cooperative way and sometimes saying, I didn't get my way that time. That's OK. I will live to fight again next time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And so what it means is that you're allowed to disagree about some values and perspectives, but you must share some other values and perspectives. You need to share the value of supporting democracy, right, which I think is increasingly rare. A lot of people just would rather be governed by – a cabal, a small number of people, a strongman, an oligarchy, whatever you want to call it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
They think that putting ourselves in the hands of a small number of competent people is preferable to democratic rule. And they would be able to say that quite explicitly. And so not everybody thinks that democracy is a good idea. It's conceivable to me that different kinds of people would agree on slightly different conceptions about how democracy should work. And therefore, yes,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Possibly, in principle, there could be different types of democracy. Some might be more direct, some might be more representative, different numbers of people might be involved, different ways of choosing the representation, representation, representation, and so on. Like all of these could be very different and that might be appropriate for different circumstances.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I suspect that—and I don't know this for sure, so you should talk to a real biologist—but I suspect that in the eye, when there is an electrochemical receptor that fires, the probability of that happening per photon, I suspect, is pretty small. I don't know that, but we have a lot of photons in the world. I think that there is some controversy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Hussein says, in your last AMA, you emphasized the importance of an objective mainstream media that aspires to provide factual recounting of world events, stating that it's important for a healthy society and informed public. However, over the last 16 months, my faith in the mainstream media has significantly eroded. This is largely due to the media's coverage of the genocide in Gaza.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Do you see the same disconnect between the media's coverage of Gaza? And if so, how do you reconcile this glaring disconnect between the reality on the ground and what the media has portrayed? The past 16 months have left me feeling dejected at the notion of an objective American media.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Well, I think we have to first distinguish at the abstract level between two things, the importance of an objective mainstream media and then the effectiveness of the actual media we have, right? Those are two different questions. Even if you are depressed by what you consider to be the performance of those media outlets that try to be objective, that's a perfectly legitimate feeling to have.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But that doesn't mean, therefore, we don't need an objective mainstream media. We need it more than ever. We need— both objectivity and competence and effectiveness, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I completely agree that the Israel and Gaza conflict, it's not the only example, but is an example of something where there are certain sort of standards and guardrails and expectations within what we think of as the objective mainstream media that prevents a lot of stories from being told. That's a problem. That's something that you should work to try to fix. We should work to try to fix.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But it's not going to be solved by saying, forget about objectivity in media. Let's just have individual different media outlets that tell us what we want to hear, right? That is not actually going to solve anybody's problems. Those things should exist. That's fine. Can exist. But we also need something that is common to everybody.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
One of the huge problems in what is going on in the United States right now is that not only are really terrible things happening at the upper level of governments, but half of the country has no idea that these terrible things are happening because they're not told by their media outlets. And that is a problem. Anonymous says, It's not so much a matter of easier or harder.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
There's challenges in both cases. In both cases, it's super important to know your audience, right? I mean, my books, my popular books are generally pitched at a slightly higher level than other people's popular books because I'm not, you know, I'm not really, I would like to sell, I have to say this very carefully, I would like to be the best seller of the world.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I would like to sell a billion copies of my books, but I am not optimizing to do that. I am not writing a book specifically because I think it will sell the most copies. I want to write the book I want to write, and then I want people to buy it, okay? Those are two separate things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I want to write the book that is something that I can be proud of, and people who want what I have to offer will get something out of it, okay? And that's a variety of things. That might be textbooks, that might be popular books, that might be kind of in-between books like The Biggest Ideas. In terms of the challenges, you know, for textbooks, textbooks are very functional, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
They're very purposeful. It's not simply a matter of pleasure and distraction that you read them. You want to learn a skill from the textbook. I think that one of the reasons why my general relativity book has become relatively popular is because there's a lot of general relativity books on the market.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
many of them—I'm trying to say this very politely—they're not meant to teach people general relativity, or at least they're not trying as hard as they could to teach people general relativity. They're trying to get it right, to sort of put forward some body of knowledge that the author thinks is important.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But when you write a textbook, you have to take into account who's reading it, where they're coming from, what they already know, etc., etc. And there might be things that you think are really cool, but putting them in your textbook isn't actually helpful to the audience members. So optimizing for actually teaching the subject is the very simple strategy that I had in mind.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
For the quantum mechanics textbook that I'm working on very, very slowly, but it's still going on, it's a slightly different thing. Again, there's many, many quantum mechanics textbooks on the market, and some of them do actually try their best to be optimized for pedagogy. But I think there the subject matter is the issue.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Now that I'm thinking about it, there's some uncertainty about, you know, is the eye sensitive enough to detect a single photon? And maybe the answer is sometimes it is, sometimes it isn't, depending on what's going on. But anyway, I think the basic lesson here is there's a lot of uncertainty in quantum mechanics, and this is an example where that actually helps us out.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
For general relativity, everyone more or less agrees on the subject matter. For quantum mechanics, and this has nothing to do with interpretations or many worlds or anything like that, the actual quantum mechanics, the actual thing you're supposed to teach, so undergraduates are empowered to go solve problems and solve equations and so forth, people disagree on what that is.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
How important is it to talk about entanglement? Or how important is it to talk about measurement? How important is it to talk about two-state systems or quantum information research? rather than just solving the Schrodinger equation over and over again for different explicit potentials and things like that. People disagree about these things. And so I'm going to try to, I have a strategy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
We're going to see how it works. You know, I'm teaching it, which is always very, very helpful. So it's really a matter of effectiveness in a very, very tangible way. So the difficulty of writing a textbook is just being as clear and useful as possible. The usefulness is something that I would emphasize there. For a popular book, there's a lot more freedom, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The objective of doing it is much less predefined. You can write books for inspiration, for education, to be thought-provoking, to synthesize a whole bunch of different things. There's all sorts of different reasons why you write a popular book. But you still have the challenge of trying to match what you think is cool and interesting with what the audience might be interested in.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Obviously, for the popular book, you don't need to worry about getting all those equations right. But for the textbook where you do have all those equations, the thing is that the equations are either right or wrong, right? You can actually test them as kind of tedious. You better check, you know, when you have problem sets or things like that that you suggest in your book.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You better check that they're doable and they're sensible and all your derivations are correct and you're free of typos, all that stuff. becomes very, very relevant, less so in a popular book. But in a popular book, you really should think carefully about why am I saying this at all? Why do I have a chapter on this? Is this really necessary? Could I do it better?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Could I talk about something completely different? Just because it is so much less constrained, it can be trickier to choose how to do it well. Ved Kumar says, priority question. I recently finished your biggest ideas in the universe series and I found it helpful in my understanding of foundational physics. It prompted a thought on the quantum measurement problem I wanted your feedback on.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
The idea involves trying to entangle a superposition into a classical and quantum system while requiring information conservation and considering the implications. A useful case of this is trying to pass a data sequence, which will be a superposition of several definite sequences all equal in length, onto a classical and quantum computer.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Both computers will contain bits and qubits equal in quantity to the length of a definite sequence. So the question goes on. I'm going to stop reading there. But I do not understand what is going on in this question. I know it's a priority question, so I have to address it. But I am not at all clear about the setup that is being proposed to be judged.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Cole Giusto says, in the big picture, you emphasize that emergent phenomena are still real even if they're not fundamental. How do you differentiate important ontological disagreements from semantics? In what way do you think real has a definite meaning that is worth arguing for? You know, whether it's worth arguing for or not, I think that's a bit of a judgment call, right? And very often...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
when you say entangle a superposition into a classical and quantum system, that makes no sense to me. I mean, I'm sure it could make sense if I understood what you had in mind. Maybe there are some equations or something like that. But entanglement is a purely quantum thing. There's no such thing as—or, yeah, entangle a superposition. I don't even know what entangle a superposition means.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I know what it means to entangle quantum states, and quantum states— are in superpositions from certain points of view, not in superpositions from other points of view, but classical systems are neither entangled nor in superpositions, so I really don't know what's going on. Sorry about that. I can't really be very helpful. Stephen Moradi has a priority question.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I like everyone's using up their priority questions. That's good. You put some thought into what you want these to be. I've heard people say that there is no chaos in quantum processes.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Could you elucidate the difference between a three-body classical gravitational interaction with a three-body electrostatic quantum interaction, given that both are deterministic and interact via inverse square forces? This is a subtle thing, this statement that there is no chaos in quantum processes. I mean, the world is quantum and there is chaos in the world.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
So therefore, clearly, in some sense, there is chaos in quantum mechanics. But on the other hand, chaos is a result. Chaos is a statement about sensitive dependence on initial conditions, right? Tiny deviations in the initial conditions lead to large deviations in the final answer. How can that happen at the down and dirty level of equations?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
It happens because of nonlinearities, because small deviations in the state of the system can feed back onto each other through nonlinear terms in the equations of motion. In quantum mechanics, the equation of motion is, you guessed it, the Schrodinger equation. And the Schrodinger equation is resolutely linear as a function of the wave function.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
There's no wave function squared terms in the Schrodinger equation. So if the question you're asking is, Is there sensitive dependence on initial conditions in the evolution of the quantum state according to the Schrodinger equation? The answer is no. There never is. It's a linear equation of motion.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But within all the different things that can pop out of the Schrodinger equation, one of the things is the classical limit. So you can have a classical limit, and it makes absolutely no difference whether we're talking about gravity or electromagnetism. They're exactly the same in this sense.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
In either case, there can be a classical limit where there is chaos, where there is nonlinear classical equations of motion that arise as the limit of quantum mechanics. How can nonlinear equations of motion arise as the limit of linear equations of motion?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Well, the classical limit is subtle, and it involves the combined effect of many, many different parts of the quantum mechanical wave function. So basically, you have... many, many different modes or whatever you want to call them of the wave function, either interfering constructively or destructively to give you a classical trajectory.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
And that emergent classical trajectory can indeed obey chaotic dynamics. The whole thing is very subtle. I'm not trying to undersell it. There was a whole subject for a while where people were trying to bang their heads against this question. How can there be quantum chaos? And the answer is you need to take the classical limit.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Paul Torek says, on the memory arrow of time and the causal arrow, you said, because we have memories and records of the past, we can't change them. But I'm tempted to turn the explanation around. If you can, at time t1, select an event so you can't, at t1, have a record of the event. Sorry, I inserted a word there.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
arguments about whether or not something is real aren't worth arguing for. I don't want to argue about it, honestly. I just want to be clear about what I mean. So if someone wants to say the tables and chairs are not real, I'm not going to expend my precious time here on this earth convincing them that they're wrong.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
If you can at time t1 select an event, you can't at time t1 have a record of the event. So it seems that either lack of influence is a precondition or else a co-condition of records. In Janan Ismail's book, How Physics Makes Us Free, she offers a united explanation of both arrows of time, influence, and records.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Local macroscopic changes to the present state of the world propagate asymmetrically into the past and future. So who's right about the direction of explanations here? Or is this a case where, depending on what the audience already understands, the explanation can go either way?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I do think there's a unified explanation here, and I might have been, or the specific language that I used might have been chosen sloppily here. When I say because we have memories of records of the past, we can't change them, what I mean is because we have what we think of as reliable memories and records of the past, we know we can't change them.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
But our knowledge of the fact that we can't change them is different than the fact we can't change them. I don't love the language of – macroscopic changes to the present state of the world propagating asymmetrically into the past and the future. I'm not quite sure what it means that they propagate. But of course, you can invent a meaning for it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
I'm not saying that it's meaningless, but I'm saying that you have to be very clear. There's more words that would need to be stated to go into what exactly is being said. But anyway, I don't think there's any... weirdness or mysteriousness or true disagreement here. The overall unmistakable fact is you have some macroscopic incomplete information about the present.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
You have some hypothetical information about the past in the form of a low entropy boundary condition. You have no information about the future. There's no boundary condition that you are imposing there. And given those three ingredients, you will get an asymmetry both of memory and causality.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
303 | AMA | February 2025
Ryan Hibbs says, the light we see from stars represents the object as it was in the past due to the speed of light and the further away the object is, the faster it's moving away from us. How do we know from just this data that expansion is accelerating and not that expansion just used to be faster in the past than it is in the present? You know, I mean, cosmologists aren't dummies, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
We are all driven by searching for something better. But when it comes to hiring, the best way to search for a candidate isn't to search at all. Don't search, but match with Indeed. If you need to hire, you need Indeed.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But the short answer is how do you know that your axioms are consistent? That is kind of the point. Gödel has proven you actually can't prove the consistency of the axioms within the system itself. And you might have a feeling that they are consistent, but that's not a proof of anything at all. And even a computer can sort of – guess at things that are not proven false.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I suspect that consciousness is something like that, that you have it or you don't, and you might have it in degrees, but there's not a new thing toward the future that we're going to aim for someday. And in terms of Gary's question, he's asking whether conscious experience requires subjectiveness as a feature of nature. So I don't know.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So I'm not quite sure why we need to modify the laws of physics to make any of this happen. Anyway, the other idea is that consciousness must be purely non-physical. Now, that I don't... Again, I have a tough time making a steel man argument for that because I'm not—well, because I find all the arguments for it very, very weak. You know, the zombie argument or the Mary's room argument or whatever.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I think that they're pretty straightforwardly shown why they don't work. So it would have to be my steel man argument for consciousness requiring something nonphysical— would ultimately end of the day just come down to consciousness being very difficult to understand. Therefore, we're going to have to go beyond what we already understand about the physical underpinnings of the natural world.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
That's not a crazy argument, right? I mean, but it's not really an argument about consciousness. It's an argument about epistemology, about how well we know what goes on in the world. What is the future theory of the world going to be like?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I would grant the plausibility of an argument that says, look, in the space of all possible future theories, I just don't see that many that rely on the laws of physics as we understand them and account for consciousness, okay? Like, I don't believe that, but I can see that that is an argument, and maybe that would ultimately lead you to want to mess with the collapse of the wave function.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Kyle Kabasares says, I'm curious what your thoughts are on neural link implants. Would you ever consider getting one implanted within yourself if it were verifiably safe and could enhance your ability to do your research? So first note, you shouldn't call them neural link
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You know, there is this company that was founded by Elon Musk called Neuralink that is trying to input – to implant brain-computer interfaces inside people's brains. But it's not the only company that is doing that, and it's not even the company that is anywhere near furthest ahead as far as I can tell right now. So there's a burgeoning area of brain-computer interfaces.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Some of them are what we call invasive. drilling a hole in your head and putting something inside, but mostly these days people don't want to do that, so they're looking at non-invasive BCIs, brain-computer interfaces, and that's, you know, some obvious shortcomings to do it that way, but it's way safer, so that's what's going on. Would I consider it done to myself?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Yeah, I mean, there are many, many worries that one would have about that, but there are many, many worries about automobiles or, you know... nuclear power, or a whole bunch of different things. Fire, there's many, many worries about. So sometimes one can control the dangers in an acceptable way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And I think that, in fact, I will go further, and I will say that probably eventually everyone will have some kind of brain-computer interface. We haven't been able to talk directly about the technology of brain-computer interfaces that much here on Mindscape, but we did talk with Nita Farharani in what I thought was a very good podcast about the dangers to privacy of brain-computer interfaces.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I do think that they're coming, and I think that probably, as is often the case with new technologies, as Duran Asamoglu explained to us, they will initially very plausibly not be to the benefit of many people. They'll be to the benefit of a small number of people, and other people will suffer, but then eventually we will equilibrate, and hopefully everyone will be better off.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You know, Doris Tsao and I had this conversation, but we didn't have that much time to get into some of the nitty-gritty about it. As most of you know, who've been listening to me on the podcast, I don't think that there's anything over and above the known laws of physics, of atoms and molecules and forces, so forth, so forth. Yeah.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I think that's the optimistic scenario. BG167 says, of the papers you've published, are there any that would deserve Nobel Prize nominations if their conjectures were confirmed in experiment? And do you think that the Nobel Committee generally chooses wisely in the physics category?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Second question first, I do think the Nobel Committee generally does a pretty good job, at least in the areas that I understand. I can nitpick. I do think that the Foundations of Quantum Mechanics is an area where the Nobel Committee could do more recognizing. It gave the prize to the people who tested Bell inequalities, so that was totally deserved. That's great.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
They never gave a prize to John Bell, right? He died. Because back in those days, the foundations of quantum mechanics were not thought to be all that important. Even today, the theory side of those foundations is very underrepresented. And I don't just mean people working on, like, many worlds or whatever. Nobel Prize-winning discoveries do tend to involve experimentally testable ideas, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Short-term experimentally testable ideas. Stephen Hawking never won the Nobel Prize. And Roger Penrose winning the Nobel Prize was actually a bit of a surprise. They sort of bent the rules to include the existence of black holes as Roger Penrose's Nobel Prize-worthy finding. Yeah, you know, okay, fine. I'm not going to argue about that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But in quantum information theory and quantum foundations, people like Charlie Bennett or Wojtek Zurek, Yakir Aronov, there's a bunch of physicists who've done very important work on quantum mechanics, which I think deserve the Nobel Prize. But anyway, that's not the point. I think that generally they do a pretty good job. The one other prize I think is really just calling out to be given would be
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
the experimenters behind the Large Hadron Collider who helped find the Higgs boson, right? We gave it to the theorists but not to the experimenters. It's very complicated because the Nobel Committee has decided no more than three people can win it at any one time. And there were thousands and thousands of people involved. So I don't know how they will –
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
finesse that one, but I do think that it is deserving. In terms of my papers that I've published, you know, one can get lucky with the Nobel Prize. There's plenty of examples of completely worthy, good Nobel Prizes that were given out to people who basically got lucky. They didn't even know what they were doing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Penzias and Wilson, who discovered the cosmic microwave background, are the best examples of that. They were not looking for the cosmic microwave background. They were looking for other things, but they found it. Perfectly okay. They found it. The prize is not given for having the most IQ points. It's given for finding things, for really discovering something true about nature.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So I don't think that any paper that I've written that makes verifiable experimental predictions is like super duper clever in the way that general relativity or quantum mechanics was super duper clever. But I could get lucky.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I do have papers out there that predicted different models like violating Lorentz invariance or how dark energy could interact with gravity or with other particles, I should say. Sorry about that. Which if I get super duper lucky, that could show up. Whether that would actually merit a Nobel Prize for me, I'm a little dubious of that. Let's just put it that way. But I have made predictions.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
and so forth, the core theory that describes the stuff of which we are made. But of course at the higher emergent levels, all sorts of unanticipated features might arise. So I'm not sure exactly—I should have pushed Doris a little bit more on whether or not she was claiming to go beyond that or not.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Any one of them is unlikely to come true. But if they do come true, I'll become famous. That would be great. I would love it, prizes or not. Tyler Haley says, I have a friend who is currently getting his master's in physics and he told me something I'm having trouble getting my head around. He said that light interacts with matter but matter doesn't really interact with light.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
He uses the example that you can't push a photon but a photon can push you. Can you make out what he means? He's a well-read student and clearly understands interactions are two-way events so I think he's getting at something a bit deeper. Well, I think he's just getting – he's just wrong. That's what I think. I can push photons all the time. I can put a photon through a prism.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I can bounce photons off a mirror, right? I can detect photons in a CCD camera. I don't see any problem with pushing photons in a very real way. I really am not sure what your friend is getting at. There is a true statement you can make that is sort of grammatically similar to this statement, which is that photons interact with charged particles, but photons are not themselves charged particles.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So photons directly interact with electrons and protons and so forth, but they don't directly interact with each other. That doesn't sound exactly what your friend is getting at, but that's a true statement that I would trust. Okay, Jeff Davis says, there are a lot of unsolved problems in cosmology, the Hubble tension, the nature of dark matter, formation of supermassive black holes, etc.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Predictions are hard, especially about the future, but I wonder which you find most puzzling and most likely to require new physics to solve, and which are you most optimistic about being solved in the nearer term? in our lifetime, for example. I would be pretty optimistic about all of these being solved in my lifetime. I hope my lifetime goes on long enough for all those to be solved.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But these are three very different puzzles, Hubble tension, nature of dark matter, formation of supermassive black holes. Hubble tension is a relatively new problem, and it might just go away via better observations or better understanding of our current observations. We had Adam Rees on the podcast.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
He's done an amazingly good job of establishing that to the best of our current understanding, the Hubble tension is a real thing. It's not just a silly mistake. If it's a mistake, it's a very, very subtle and interesting mistake, and they haven't been able to find it yet.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But it still could be out there, and as I've often said, the Hubble tension is not something for which there's any obvious solution. It's not like, oh, if I just add simple ingredient X, everything fixes itself. And so that decreases our credence that there is some complicated theoretical solution. That increases our credence that it is in fact some issue with the observations.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But the non-zero credence is there for both, so I really don't know what's going to happen. For the nature of dark matter, on the other hand, we've had it for decades, and we have lots of ideas, lots of good theoretical ideas that could explain it. We just don't know which one is true. So at any moment, we could get lucky and find the dark matter, and that would be it. But we might not get lucky.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But of course she's an actual neuroscientist, not a particle physicist, so she might not think in those terms at all. I think that the definition of consciousness involves subjectivity, like you have to be a subject to have consciousness, but I don't really think that it's an intrinsic feature of nature in any sense.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
We don't know. The formation of supermassive black holes, my suspicion is, is a much easier problem than these other ones. Supermassive black holes seem to form in the early universe a little bit sooner than most experts have expected. But, you know, it's a complicated problem. And I think that we're at the
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Stage now where we're throwing big supercomputer simulation resources at it, and we're getting data from JWST and other sources so we know more about the conditions under which these supermassive black holes form. So I'm relatively optimistic that that one will be figured out fairly soon.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Gregory Kusnick says, in the August AMA, you said something along the lines of, if God exists, he's powerful enough to make me believe in him. The corollary is that he can just as easily convince you of his non-existence or indeed of any other consistent proposition that suits his purpose. It seems to me this quickly gets us into the realm of cognitive instability.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
If a theory posits the existence of a being powerful enough to arbitrarily manipulate evidence, then there's no coherent way to assign a credence to that theory. Am I way off base here? I don't think that you're quite right, but I think that the point is that the word God is not by itself a theory.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You know, I've given talks where I've pointed out that theism as a general idea is by itself not well-defined. So to have a theory that you could assign credence to, you can't just say God exists. You can't even just say... there is a powerful being, okay, a being powerful enough to arbitrarily manipulate evidence, you also need to specify some details about how that being actually behaves.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Does that being have goals, right? Does that being have feelings, you know, wants, desires? So when I say that God is powerful enough to make me believe in him, I'm specifically referring to a version of God that is pretty close to the standard, traditional, monotheistic view of a being that is omnipotent, but also omniscient and omnibenevolent.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
A God that cares about me and wants me to believe true things. That would give me evidence that God would not just try to trick me. Eric Wonlick says, Um, I don't know is the short answer. I, I, I, you need to specify whether or not I can like get into the tank and then just see how long I can take it. Or do I need to specify ahead of time how long I want to be in the tank?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I am not very good at this kind of thing. I know from previous experience with, uh, sensory deprivation tanks and things like that, uh, I have a little bit of claustrophobia in this case. It's not really about being in small, um, areas, but about not being able to move. Like, that bugs me.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I think it's a higher level emergent thing that happens under the right circumstances because of the collective behavior of ordinary atoms and particles and other non-conscious things. NJTPL says, which one do you think is more weird slash interesting, dark matter or dark energy? Well, dark matter is certainly more dynamic, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
There's something primally irrational in me that the inability to move, and you did specify in the question, I cannot do anything with my hands or leave the tank. So that does, at a visceral level, bug me. And, you know, at some level, one has to just accept that one is old and one's skin has blemishes and scars and wrinkles, right? And so...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
even though I can't give you a specific answer in periods of time, I don't think I would actually vote for a very long period of time spent in the tank. Sorry, if it were a period of time spent in isolation in a house where I could walk around and eat and read books, even though I couldn't talk to people or check the internet, then I'd be willing to spend much, much longer.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Marie Rouskew says, on the topic of to pick the right problems to work on, how do you persuade someone, either a person or a group, what is the right problem or shift their focus to it? I mean, in general, not necessarily in physics. I face the issue that my team won't usually focus on anything like, sorry, on anything else than the easiest or the most likable thing of all the things to solve.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Yeah, that's a very good question. I actually don't know the answer to that. I haven't quite faced that problem. I mean, maybe in some ways I have. There's been times when I've had, you know, my team, my group of grad students, postdocs and whatever, and I would say, you know, we really should think about this issue. And they would go, hmm, that sounds hard and not do it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But, you know, part of me is believing that maybe they're just right, you know. Part of me says I'm the old person here. I should just tell them what to do and they should listen to me. But another part says, you know, don't be that advisor who thinks they always know what is best. So I think that, you know, there's nothing better than honesty in these situations.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
If you have a good reason why you think it would be worth it to do this harder thing, then tell them what the reason is. See if you can actually articulate the rational reason why they should do this very difficult thing, spend all their time working on this difficult problem. And maybe if you can't be very persuasive there, maybe the reasons aren't quite as good as you thought.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Stuart Hain says, in your discussion with Nate Silver, there was a mention of a 50-50 risk to lose everything or have two times plus epsilon framed in terms of utility. Viscerally, I would not risk everything for two times plus epsilon on a 50-50 bet, even though the odds say I should. This made me think that utility may not scale linearly. Any thoughts on this?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Is utility more like a log function in shape? Well, a function of what is what you have to ask. So economists know perfectly well that utility does not scale linearly with something like wealth or money or whatever, right? If you are poor and destitute on the street, $1,000 is worth a lot more to you than if you already are a billionaire. OK, that's a very, very well understood thing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And I think that it is kind of like a log function. But of course, the actual curve is going to depend on psychology and individual idiosyncrasies and things like that. So you have to make assumptions, some assumptions to get there. But the point of Nate Silver's examples is that this is not a 50-50 bet for two times the money.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
two times plus epsilon the money, it is for two times plus epsilon the utility, whatever that is, okay? So you take what utility you have for a certain amount of money and you compare getting zero of it or getting twice as much of it. That's the game you're supposed to be playing here. So you're right, the utility is not linear in money, but that's okay.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Economists worry about utility, not about money. Ari Moody says, if extraterrestrials were advanced enough to send a signal to us, would we be able to even recognize it as an ET message? Wouldn't it be more like me trying to converse with ants? Well, I think there's a couple things here.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
As I think I've already said, I do think that, you know, we have crossed, we human beings have crossed some cognitive threshold, some phase transition that lets us think symbolically and in terms of language and written symbols and transmitted symbols that is probably pretty universal. It would be my guess.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
We don't know exactly what either one of these things are, but in the case of dark energy, the thing that makes the universe accelerate, we have an overwhelmingly plausible candidate, namely Einstein's cosmological constant. And the cosmological constant is the least likely least intricate thing you can imagine. It's literally just one number. It is the energy density of empty space.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I don't place huge credence on this guess because we have no data about it, but I'm willing to think that that just like utility does not scale linearly with money, ability to think does not scale linearly with evolutionary time, okay? I don't think that even if human beings evolved for another billion years, they wouldn't be as much...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
They wouldn't have as many transitions in what it meant to think as we have had between now and a billion years ago, okay? We will be better at thinking because we better at computation and we'll figure out clever ways to solve problems, but I still think we'll be Turing complete. We'll be solving problems like a good Turing machine, just a much more efficient one.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So I see no reason to think that a message from ET would be impossible for us to decipher as if we were ants. The ants you can't converse with because ants just can't converse using symbolic languages. More importantly, though, if these really are super smart extraterrestrials, I would give them enough credit to think that they would send us a signal we could read.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
If it's true that there are various higher forms of consciousness or cognition to which we humans don't have access, then either these ETs don't want to communicate with us or they understand what level we're at and they're going to send us a signal that is comprehensible to us.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Cooper says, do physicists have crackpots that tend to focus on them personally, like how people have a stalker, or do crackpots tend to blast out their papers to entire departments? Not generally entire departments, but certainly large lists of people. Some Crackpots do kind of have stalkerish tendencies.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You know, I have a certain set of Gmail filters that when I get emails from some people, they get deleted right away. And I've never regretted that policy. Sometimes I go back into the trash and come across a message by accident. I go, oh, yeah, OK, that guy. But more often, crackpots will look for any feedback they can get. So yeah, they're going to send it to lots of people.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
In fact, recently, I was trying to compile an email list of people to identify for some email I want to send out to a broad group of people. And one of the best sources of email addresses was emails I was getting from crackpots. The crackpots have done a lot of research to find out who are the good people doing work on physics or philosophy or whatever it is. So yeah, many...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Many crackpots are kind of notorious in certain communities. Nate Heller says, in your emerging journey into complexity research, are you planning to focus solely on identifying universal law-like patterns akin to those in fundamental physics, or do you also intend to explore specific classes of systems and particular types of data? Well, you know, one does what makes one progress.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
My predilections are absolutely to look for unifying ideas across many systems. So I would love to understand robust features of complex systems that are true for very, very different kinds of complex systems. My favorite kinds of things to understand would be true for both the human brain and the world economy. Even those are two very, very different kinds of systems.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But one takes what one can get. And if it turns out that I discover or think about something interesting that only applies to one kind of specific complex system, I'm going to think about that. We'll see where it goes. You don't get to pick where the research takes you ahead of time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Kyle Stevens says, if eternal inflation and the infinite cosmological multiverse are true, would it then be possible to coarse grain at a large enough scale to replicate all of the subatomic behavior of our universe, e.g., where our observable universe contributes only some fraction to a subatomic particle at some massive scale?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And we've measured it. We know what it is. If the dark energy is the cosmological constant, no more observations we ever do will teach us anything more about it. Observations we do of other things might teach us about the theory that helps predict the number, but the actual knowledge about the dark energy itself would just be that number.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Well, you know, anything's possible, but probably not in this particular case. And the reason is one of timescales. You know, a feature of, let's just say, a human body, okay? You have a lot of atoms in your body, and you are big compared to those atoms.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But those atoms are all bumping into each other and they're literally like attached to each other and they're interacting and trading electrons and creating new molecules and all this stuff. And the fact that the interactions happen and they happen quite rapidly is kind of important. It is kind of a big deal. On cosmological scales, things are very far apart.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And that doesn't mean just everything slows down, but it becomes literally impossible to for things to interact with each other. Given the fact that we have a positive vacuum energy, distant galaxies are going to move apart from each other and never interact.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
If you have a cosmological multiverse, maybe you have some kind of fractal structure to the universe on very large scales, but that fractal describes parts of space-time that never interact with each other.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So again, to the best of our current way of thinking about things, there is zero sense in which the large complicated universe is just a bigger and slower version of the small interacting universe inside matter as we know it. Hugen says, what are your credences about Claudia de Ram's theory of gravity that decreases faster than inverse square at a distance?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You know, to be honest, it's pretty low. This refers to a podcast we did with Claudia de Ram about modified gravity, massive gravity, and various extra-dimensional models that try to modify gravity both for the purposes of better understanding what is possible and impossible, but specifically for possible cosmological application to the accelerating universe and so forth.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Look, I think that it's unlikely that that approach is right, but let me be very clear. I think that it is unlikely that any known approach is right to explaining dark matter, dark energy, things like that, because there's many approaches, and they're all kind of speculative. I mean, I guess the one...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
counter example to that is I think that the dark energy itself is probably a cosmological constant. I would give more than 50% credence to that. I would not give more than 50% credence to any specific model of dark matter. I think that I would put huge credence on the idea that dark matter exists, but there's many different theories of it, and we don't really know which one is on the right track.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So the fact that I give small credence to it is not a way of saying I think it's not worth thinking about. These are high-risk, high-gain kind of operations. You make a speculative idea. And this goes back to the question about my papers earlier. I would put the same exact low credence or I would put a lower credence on some of my ideas, maybe a marginally higher credence on some of them.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But you take your shot, right? You say, oh, here's an interesting idea. I don't think it's probably right, but it's possibly right. And we'll let the data decide. What is right? And if I'm right, it's very, very important, right? That's the bucket into which I would put Claudia's work and her collaborators.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Tim Converse says, Theory seems to have preceded observation in cases like the Higgs boson and black holes. What is this corresponding story for cosmic inflation? Was there any theoretical reason to expect a quickly expanding early universe, or do we just need that theory to explain our observations that space is isotropic and flat?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Now if the dark energy turns out to be dynamical somehow, if it's not a constant energy density but a slowly changing energy density, then there's lots of different possibilities that open up. The dark energy could be dynamically interesting or it could just be kind of dynamically dynamical but boring.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Here definitely the observations came first, and in particular the fact, the observational fact, that our universe looks pretty smooth and isotropic and geometrically flat. These were known for quite a long time, relatively long time. It wasn't until the 1970s that it was very specific. It was Jim Peebles and Robert Dickey who pointed out that these features are puzzling, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So first people guessed them, and then they observed that, yeah, the guesses are more or less right. And then Peebles and Dickey point out that, you know, actually, they're a little unstable, you know, these features of the universe. If you deviated from them a little bit, those deviations would grow in time. So they're not really as natural as you might have thought they are.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And these were dubbed the horizon and flatness problem. And so Dickey and Peebles gave—sorry, I think it was Dickey who gave some lectures at— Cornell, where Alan Guth was a postdoc at the time, and Guth went to those lectures. That's where he heard about these cosmological problems. Guth was trained as a particle physicist, and he was mostly thinking about particle physics and symmetry breaking.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And in particular, he was thinking about magnetic monopoles. There's this idea that magnetic monopoles should be predicted by... theories that were very popular at the time, grand unified theories, and they're predicted in a much larger number than was consistent with the observations. So Guth was mostly thinking about how to get rid of the monopoles.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And when he invented inflation as a way to get rid of the monopoles, he instantly realized that it would also solve, potentially solve, the horizon and flatness problems that Dickey and Peoples had. So that was definitely a case where the theory came after the observations. Now,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
it was a unanticipated side bonus to realize quite quickly after that that the right kind of inflationary scenario would also explain the density perturbations in our universe, the tiny perturbations in early times that eventually grow into stars and galaxies and things like that. That was unanticipated when Guth was first thinking about it, but people quickly realized it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And so that was a case where the theory came before the observations.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Jeremy Dittman says in Mitchell Waldrop's book on the Santa Fe Institute and the search for a theory of complexity, a section on Chris Langton describes his epiphany connecting complexity and dynamical systems as living in the transition between order and chaos, akin to the phase transition from a solid to a liquid as well as to computational classes moving from halting to undecidable to non-halting.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And all of these analogies were connected with Wolfram cellular automata classes, class four being the interesting one. From your perspective, are these concepts likely to be fundamental parts of a theory of complexity or attractive poetic analogies that don't get us very far? Or worse, are they distractors that miss the point? I will say attractive poetic analogies.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It could interact with other fields of nature and that would be super duper interesting, of course. But I think that those possibilities are a little bit less likely than just the simple cosmological constant. Whereas dark matter we know is dynamical. It collects in galaxies and clusters. It has an effect on the evolution of the universe.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So as we said just a little bit ago, I think complexity, the development of complexity over cosmic time proceeds in stages and is a story that seems to me to be understood in terms of information utilization, using the resource of information that is granted to us by the low entropy of the early universe.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And the interesting features of complexity to me have to do with structure in the system and how that structure allows it to utilize information, to gather information, to store information, to take that information and use it to decide what to do next in some slightly anthropomorphic language. None of that is really there in these cellular automata models or these edge of chaos models.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Or fractals is another example, right? So all of these, and I think that the, I'm not saying anything weird here. I think that the modern take on complexity is, is more about adaptive systems and hierarchies and information utilization and less about the boundary between chaos and order.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Those are fun analogies and cool things to look at, but they are missing really important parts of the complexity story, I think. Dan Cohen says, in Quanta and Fields, you explain that it is the exclusion principle that keeps solids solid and stops matter from being compressed and not the electromagnetic force. If that is so, why doesn't the exclusion principle count as a force? It does.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Go ahead. Count it. In fact, I say this in Quanta and Fields. If you read closely enough, I explain that we have a sort of traditional way of listing four fundamental forces of nature, strong and weak nuclear forces, electromagnetism, and gravity. But that's just human language. okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
We have realized through the development of quantum field theory that the fundamental ontology of the world is not divided into matter and forces. It is all quantum fields, and the quantum fields interact in certain ways. The thing that is universal between the strong and weak nuclear forces, electromagnetism, and gravity is that they are gauge theories. There's a symmetry underlying them that
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
that helps us account for the specific fields that exist and the way that those fields interact with each other. But there are other things like the Higgs boson. Is the Higgs boson, it's a boson, just like the photon is, or like the graviton, et cetera. Does the Higgs boson carry a force? The answer is, sure. If you want it to, if you want to call it that, it does something.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It's a field and we know how that field interacts, no problem. If you want to call it a force, go ahead. The exclusion principle makes matter solid. It is literally why when I push my hand on the table in front of me here, the table pushes back. Okay. Sometimes we call that a force. In a neutron star or a white dwarf, we talk about the degeneracy pressure.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So the evolution of galaxies and structures and things like that. So it seems overwhelmingly likely that there's more going on in the dark matter world than the dark energy world. Not 100% likely, but it seems very most likely. And again, the dark matter is dynamical, but it could be dynamical in a relatively boring way. It could just be some cold particles that don't interact with each other.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And indeed, I think they talk about the Pauli force. because these electrons don't want to be in the same quantum states, or these neutrons. It's just a word. It's a word that turns out not to be fundamental, the word force. The idea of what a force is does not map cleanly onto the fundamental nature of reality. That's okay. It's still pretty evocative.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
We know what we mean, usually, so we use it, and you can decide whether something like the exclusion principle counts as a force or not. Fran Pla says, yummy French canelés you posted on Instagram. So for those of you who don't know, I do have an Instagram account. I essentially never use it. Like once every six months, I'll post something there. But we did go to France a little while back.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And in Bordeaux, they have this local delicacy called the canelé. It's all over the place, but Bordeaux is the center of it. You can't get out, you can't escape Canelés if you're in Bordeaux. You arrive at the hotel and they give you Canelés. You go to breakfast and they give you Canelés. You're on the street and you go by a Canelés store.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
They're these beautiful little pastries with a kind of a hard crust and a custardy inside that are very, very yummy, flavors of vanilla and rum. which don't sound very French, but Bordeaux was a major port back in the days when the trade from the West Indies started. So Bordeaux was in the receiving end of all these exotic flavors like vanilla and rum, and so that's why they feature in Canelés.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Anyway, I learned how to make them. Very proud of myself. And Fran is asking... Kudos to you because I've read that canelés are very hard to make. To connect with the fantastic episode number 103 with Kenji Lopez-Alt, what, in your opinion, is the most rewarding thing about cooking? And are you experimenting and rebelling on recipes more since that episode? Yeah, you know, I do like cooking.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I've always liked cooking. I've never been very expert at it. I will let others decide whether I'm any good at it, but I will absolutely say that I'm not very expert at it in the following sense. I can't whip together good dishes out of random ingredients that happen to be laying around. I'm pretty good at following recipes. I'm quite good at following recipes.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So I can make yummy things if someone gives me a good recipe for them. I don't have this intuitive quasi-magical ability that truly good chefs have to whip up something more spontaneously or change ingredients or whatever. I am at least pleased to learn that there are other people like me. You know, there's this—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
There's this – I forget where I was reading it on the internet, but people were complaining about a certain genre of reviews online for recipes. People post their recipes online. Other people review them, give them stars. Apparently, there's a subgenre which consists of taking the recipe –
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
changing an ingredient to something completely different and then complaining that the recipe they made wasn't very good. Like, literally, this was a recipe for carrot cake. I don't like carrots very much, so I used kale instead of carrots, and it came out not tasting very good. Two stars, right? So it's not just me that doesn't really know how to make this work.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But anyway, it's not so much since talking to Kenji, but more since moving to Baltimore. We now have a bigger house, a bigger kitchen, and you know, I'll be very honest here, a somewhat more domestic cast of mind than we used to have living in our townhouse in LA. So I am trying to learn to cook more. I've... I use that as an excuse to buy gizmos, which I like doing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So I have a nice cast iron wok that I bought from Made In, for example, that I love very much. A really good sharp Japanese chef's knife. Those little instant read thermometers that you stab into things. And it's funny because, you know, what you realize by doing this, and I just like gizmos and gadgets in general, but... For the most part, you realize, holy smokes, this is super useful.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
That fits the data quite well as long as you can have a theory of why it has the abundance that it does. Or there's all sorts of intricacies it could have. I mean, this is something that I myself have worked on quite a bit, different ways that dark matter can interact with other dark matter particles or with ordinary matter or with large long-range forces, things like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
How in the world did I ever get by without an instant read thermometer? It's one of the most useful things in the world. So I don't know whether my ability to actually cook yummy things has improved upon, but I am having fun trying to do it once or twice a week, trying to actually cook something. This is my lifestyle ambition these days.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Mike Gottlieb says, oh, and I should say to anyone who's interested, In the canelés in particular, they are notoriously hard to make in the sense that if you go online and read about making canelés, you will get intimidated because two things. Number one, you're told you must make them in copper molds. This is the way they are traditionally made in Bordeaux.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Individual molds made out of copper because their heat-conducting properties are very, very good. And number two, even though copper molds are very good at conducting heat, they're also very sticky. So the traditional Bordeaux thing to do is to coat the interior of the copper mold with a mixture of beeswax and butter. Okay, so number one, this is hilariously expensive.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Like the one copper mold to make one canelé costs like 35 bucks, and a canelé is like a tiny thing. So it can get very expensive very quickly if you make a dozen canelés. That's a big... investment you have to put there, especially if you don't know if it's going to work. And number two, it's a pain to like get beeswax pellets and then melt them and then coat the thing, whatever and whatever.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So I did find a recipe that was very helpful that assured me that a good copper steel canelé pan that makes 20 or 12 canelés at the same time works perfectly well. That's what I used. They came out great. Don't buy the hype about the copper molds and the beeswax.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I predict that someday, if I'm like 85 years old and retired from writing books and doing physics and living a life of leisure where I get to like indulge all of my leisure time desires, I'm going to get the copper molds and I'm going to get the beeswax and I'm going to, you know, devote myself to making the world's perfect canelés. But for now, the copper steel works perfectly well.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Mike Gottlieb says, what's your take on the declining replacement population numbers in developed countries? I could not possibly care less about that. I mean, number one, because the world population is still growing. We talked about this on more than one different podcast. The world population is growing, but the rate of growth is going down.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So experts predict that the world population will peak at some foreseeable time in the future. But it'll still be bigger than it is now by quite a bit. And when I was your age, we worried that there were too many people on the Earth and the population was growing exponentially. Nothing grows exponentially other than the universe. So that was a silly worry to have.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But, you know, what is the right number of people to have in the world? I have no idea what number that is. And so I have zero worry that 10 billion people is not enough. OK, that's just not a worry that I have. The fact that it's in developed countries rather than elsewhere, you know, I hope that all countries become developed sooner rather than later.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
All of those are very much alive. There's no evidence for them, really, but our evidence is sufficiently weak that there's still plenty of room for it in the future that we could actually hopefully discover it. Have you thought about a gift for yourself this year, one that has the power to help you grow, learn, and become a better version of you?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And then maybe, yeah, families stop having babies and the population goes down. I would predict that that would also be temporary, right? I predict that there would be a new equilibrium that is reached. The world right now is not an equilibrium. Society is not an equilibrium. Technology is changing. Our lifestyles are changing. How we live on the land and— in the ecosystem is changing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So we're not close to whatever the future equilibrium is going to be. If it turns out the future equilibrium has a billion people on the earth, I'm perfectly happy with that. We're nowhere close to that right now. So my list of problems to worry about, that is not in the top 1,000. Don McKenzie says, Good.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I don't have a very good credence for either one of these, and it's not because I shouldn't. It's just because I don't, because I am not really sure what counts as a computation. There are different definitions of what a computation is. Someone like Seth Lloyd, quantum information theorist, has a very broad definition of what is computation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So he's going to be the kind of person who says the universe is a computer. He's written a kind of interesting popular level book arguing that the universe is a quantum computer. But to get there, you basically have to say that what I mean by a computer is just anything that evolves in time, especially if it evolves according to some sort of simple rules, some kind of
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
thing that you could cast as an algorithm, right? In that case, lots of things are computers, but that's just so broad that I'm not quite sure what the usefulness of it is, right? The Earth is a computer, sure. The Moon is a computer, sure.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But there's another, there are other, more than one, there's multiple other sets of meanings one could attach to this that take seriously more the definition of a useful computation. in which case you have something about certain variables evolving in a certain kind of way. Some systems are, like we mentioned before, Turing-complete and some are not.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So I would very much like to have a very clear view on when something should count as a computer and when it shouldn't. I don't have that view right now. The claim that life is a computation is plausible to me, because if I do think that what is interesting about life considered as a complex system is that it has learned to take advantage of information processing in a
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
what one might profitably define to be a computation. So to me, these are good questions, not ones I have very strong feelings on right now. Russell McClellan says, in the Feynman lectures on physics in 1964, Feynman said, it is important to realize that in physics today, we have no knowledge of what energy is. Is this still true today in 2024? Wow, I have no idea.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I have no idea what Feynman was talking about in that quote. Usually, when Feynman says one of these provocative things, I can translate it into something I understand. But I truly don't know what he is talking about here. Maybe what he means is the following.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
There's this thing that happens in—because I know he does talk about the following fact, that energy is something that we like to think is usually conserved. It's roughly speaking conserved. There's footnotes and counterexamples or— exceptions there.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I have talked about both energy not being conserved in quantum measurement and energy not being conserved in the expansion of the universe, but let's put aside those. Let's just think about ordinary stuff here on Earth in the lab where we think energy is going to be largely conserved. There's a worry that you say, oh, it's meaningless to say there's this thing called energy that is conserved.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Energy is not a fluid, right? Energy is not a substance that moves from place to place. It's a characteristic. It's something that is dependent on other quantities of a system, like its position in space and its velocity and things like that. It's the reason why I say it's meaningless to say there's a conserved thing called energy is you have to tell me what it is.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You have to say this thing is conserved and I'm going to call it energy, right? When Einstein says E equals MC squared, he's saying there's a whole nother contribution to energy that we didn't tell you about before. Even when an object is sitting still, it has energy, it's rest energy, MC squared. So the worry that Feynman does talk about is that we can always come up
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
with a conserved quantity just by adding more and more terms, adding more and more contributions to this thing that we call the energy. But I'm not, I certainly would not translate that into saying we have no knowledge of what energy is, if only because we have Noether's theorem.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Emmy Noether proved that when you have a symmetry of some continuum theory of physics, that symmetry will be associated with a conserved quantity. And energy is the conserved quantity associated with time translation invariance.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
The fact that the laws of physics are invariant with respect to what time you apply them, they're the same laws at every moment in time, that implies that energy is conserved. I think that's a perfectly good definition of what energy is. It's the thing that is conserved because of time translation invariance. So I don't think it was true in 1964 or today. Sorry.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Ronald Gorin says, I still read science fiction and my favorite stories are the genre of space opera. So after rereading Space, Time and Motion and finally beginning to truly grok the concepts inside, I was dismayed by a line in chapter six, the section Simultaneity and its Discontents, which states it is safer for physics and for fiction to just exclude faster than light travel entirely.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So that's a quote from me and I would stand by it. Anyway, Ronald says, I just finished a new release by C.J. Chera that seemed to do an excellent job of dealing with the vagaries of time in FTL travel. I can see where far-flung star empires might not be feasible, but it certainly seems to work at smaller distances in this book.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Any hope of working FTL into fiction so I can enjoy my space operas again? Sorry about that may just be the answer, and that's okay. So, no, I don't want to just say sorry about that in this case. What I want to say is If you want to imagine there's faster than light travel, your job is not done.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Because in the context of ordinary relativity theory as we know it, particles either move slower than the speed of light or at the speed of light. You can imagine new kinds of particles, new kinds of substances, tachyons, that only move faster than the speed of light, okay? We have zero evidence that those things exist in the real world, but you can imagine them.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
However, once you imagine them, once you imagine particles that are allowed to move faster than the speed of light, the feature of relativity that says that different...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Reference frames, different ways of putting coordinates on space and time, and in some sense all such frames are equally good, means that if you can have a particle going faster than the speed of light, you can have a particle going backward in time. And so the worry that I was referring to in that chapter was faster-than-light travel seems to indicate time travel.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And that's true in the context of relativity as we know it. So the point is you can't just say faster than light travel. You can't just say, oh, I can go three times faster than the speed of light. You know, in whose reference frame? That's a meaningless statement.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And if you can go faster than the speed of light at all, you can go infinity times or even minus three times as fast as the speed of light, and that's problematic. However, OK, so you just change the rules. You change relativity. Relativity is not right. Imagine that the fundamental positive relativity, that there is no background state of rest in the universe, is wrong.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So imagine that there is some field in the universe that actually does define a universal rest frame. People, including myself, have written physics papers about this possibility. Maybe it's true. And so maybe relativity is incomplete.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And in some incomplete theory, there is a preferred reference frame, and there's a new rule that says the actual speed that is the maximum at which you can go is 10 times the speed of light. So there is a maximum speed, but it's not the speed of light as we know it. It's a bigger thing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You could imagine that, but all I'm saying is you have a lot of work to do to figure out a theory that accommodates that without leading to disaster. Paul Cousin says, I just read your paper, Reality as a Vector in Hilbert Space. It was super cool and exciting, especially the introduction to your work on quantum mereology.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
That's B-A-B-B-E-L dot com slash mindscape. Rules and restrictions may apply. Kim Burke says, Measurements on orthogonal axes will be random. It always sounds like the quantum state specified is an attribute of the particle alone, but it strikes me this cannot be true.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So I haven't taken a course in quantum field theory yet, so I'm not sure to be equipped for your paper with Ashmeet Singh. Could you tease me about what you've been able to achieve? Yeah, so the paper with Ashmeet on quantum meteorology does not require any quantum field theory at all, okay? So don't worry about that. It's pure quantum mechanics all the way down.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But, you know, if I'm honest, it is super technical quantum mechanics. I kind of tried to make it less technical, but I didn't really succeed. The paper is kind of long, and there's a lot of equations there, and... It's intricate, so that's what it is. But what we're trying to achieve is the following quite modest goal, which is this.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
If someone gives you a quantum mechanical system, a theory of a quantum mechanical system, so what I mean by that is what is called the Hamiltonian theory. If any of you know the Schrodinger equation, if you know what I taught you in the book, Quanta and Fields, or in the solo episode, et cetera, the Hamiltonian is what powers the Schrodinger equation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
The Hamiltonian is an operator which asks of a quantum state, what is your energy? And typically the answer will be, well, I am a superposition of many different energies and here they are, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And so different physical systems, you know, here's an atom, there is a crystal, there is the gluon field, different physical systems have different Hamiltonians, and that defines what they do, how they evolve with time. So the quantum muriology question is, how do you know how to divide a big quantum system into subsystems?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
in particular such that at least one of those subsystems seems to match up with our classical behavior that we know and love. You know, again, we said... Quantum mechanics is a superset of classical mechanics. I don't need to know quantum mechanics to predict how the Moon will go around the Earth, okay? So I can have a classical limit that describes the Moon going around the Earth.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
To do that, I ignore various other things like the photons bumping off of the Moon and so forth, right? So I have the system I care about, the Moon. I also have the environment, like all the photons in the solar system. That's a division. That's what mereology is about, the relationship between wholes and parts. So usually, we go backwards. We say, I have photons. I have the moon.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I'm going to add them together to make the whole system. The quantum mereology question is, how do you go backwards? How do you go from the whole system and say, ah, identify this as the classical behaving system. Identify that as the environment.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And we, Ashmeet and I, came up with a couple of criteria for doing that, minimizing entanglement, minimizing the spread of the wave function so that it looks relatively classical and so forth. And I think that you should be able to get the basic features of the paper, even if you don't have any quantum field theory at all. We don't even really talk about quantum field theory.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
We're all working with discrete finite dimensional systems. Spencer Hargis says, when Kurt Jamagal asked you to blow his mind, you tantalizingly floated the idea—I was on a podcast, the Theory of Everything podcast—you tantalizingly floated the idea that the laws of physics could have evolved.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Do you suspect there's a replicator involved here which might have gotten started a little like abiogenesis, the origin of life, or the brain fuck programs of Blaise Aguera? If so, what would this replicator correspond to? What is the fitness it's trying to maximize? So no, in the particular scenario that I have in mind, I'm not imagining there's a replicator of any such sort.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Other people have suggested things like that. I mean, something kind of like that happens in eternal inflation in the cosmological multiverse. If you have a landscape of different possibilities, inflation can populate a multiverse where the laws of physics are very different.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
More directly, Lee Smolin has come up with an idea where inside black holes you pinch off a new universe with slightly different constants of nature. Now that's much less well-defined because in the string theory case you have microscopic dynamics that predict the existence of a multiverse. Those dynamics might not be right, but at least the theory is there. Smolin is just hypothesizing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Hello everyone, and welcome to the September 2024 Ask Me Anything edition of the Mindscape Podcast. I'm your host, Sean Carroll. Being as it's September, of course, for us university-bound folks, that means the semester has started, the school year has started again. As I'm recording this, I haven't quite yet started teaching. That'll be tomorrow, but it is already the vibe in the air.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
He's saying maybe this happens, wouldn't it be cool, okay? In that case, in Smolin's case, in some sense you are passing down information from one universe to another. That is not what I have in mind. What I have in mind is more a situation where the early universe is kind of a mess where there's no interpretation of it in terms of space and time and fields.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Time maybe, but at least not space and fields and locality and things like that. And the conjecture is, and we're working on this, but the conjecture is that out of that quantum mechanical mess emerges individual branches of the wave function. And on each branch, you sort of home in on a certain set of laws of physics, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So they don't evolve in the sense of changing from moment to moment in time. They evolve in the sense of emerging or coalescing out of some primordial chaos. That would be the idea. Michael Wall says, are the different dark matter theories mutually exclusive or is there compatibility in overlapping parameter space among some of them? Oh no, yeah, they're not exclusive at all.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
An experimenter isolated from and unaware of the first measurement would have no way of measuring what state the particle was in, or distinguishing it from a random unmeasured particle which remains in a superposition of states with respect to all axes. Can a particle have a state which is in principle unmeasurable? It strikes me
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So every dark matter theory gives you two things. It gives you the dark matter candidate. So what is the particle or black hole or whatever that is the dark matter? And then number two, it gives you a theory of the abundance of that dark matter. Where did it come from? Why do you get the certain amount of dark matter? Indeed, the first of these turns out to be way easier than the second.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It's easy to come up with an example of a neutral, stable, invisible particle. It's very hard to get the right abundance. There's a lot of constraints there. But most of the successful theories don't really pin down the abundance to any hyper-specific number. Like, there's usual free parameters in there where if they were a little bit different, you would get a very different abundance.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And therefore, it's simpler and therefore common to imagine that if you have a dark matter candidate that is the right one, it is the only right one, essentially, right? If it's axions, then all the dark matter is axions. If it's WIMPs, then all the dark matter are WIMPs. But it's not hard at all to imagine there's actually a cocktail, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Indeed, in some sense, since we know that neutrinos are massive, neutrinos are a part of the dark matter, right? We think that they're a small part of the dark matter. For one thing, the neutrinos we know and love would be hot dark matter, which does not fit the data. And for another, we can count them, and it's more or less, you know, an energy density of 10 to the minus 4 or something like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Not nearly enough of what we need to be all the dark matter we see. But they're there. So, you know, there is in fact—if there's also WIMPs, let's say, then the dark matter cocktail is, you know, 25% of the energy density of the universe is WIMPs and 10 to the minus 4 of it is neutrinos. But it could easily be that—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
15% of the energy density is WIMPs, and 10% is axions, and then 10 to the minus 4 is neutrinos, or anything like that. Since no one of these candidates seems like inevitable, having more than one be interestingly comparable to each other seems even less likely, but who knows? We can keep an open mind about that. Ilya Lavov says, your chat with Blaise Aguero was great.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Blaise was extremely well-spoken while academically rigorous, and he and his team seemed to have achieved a deep and important scientific result very quickly. Do you have any commentary on the fact that Blaise and his work were based in Google rather than in academia? Is this fact even worth any commentary? Sure, it's worth some commentary. I mean, the zeroth order commentary is, that is awesome.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It is great. I would like to live in a world where high-level academic research does not only happen at universities. Indeed, we clearly don't live in that world because there are research centers and think tanks, etc., like the Santa Fe Institute, but also the Perimeter Institute, the Institute for Advanced Study, and so forth. But also in commercial enterprises.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Famously, back in the heyday of Bell Labs, they were a Nobel Prize-producing factory devoted to pure research with the idea that important ideas would eventually come out, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
that the quantum state of the particle only makes sense in relation to the apparatus on which it was measured, i.e., is actually a statement about the correlation between two systems. Am I on the right track or missing something? I would not put it the way you're putting it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Plenty of important ideas happened, not just because corporate enterprises gave money to pie-in-the-sky research, but even because they said our applied research might be helped out if we step back and think about deep ideas. You know, Claude Shannon inventing information theory wasn't just playing around with equations.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
He was saying, what is the best way to send a signal over a transatlantic cable, right? So a lot of these are driven by applications. Most of Blazegara's work is in AI and in applications that literally show up on your smartphone. So Google is good enough to let people do some fraction of their work on more pie-in-the-sky stuff, and he takes advantage of that. So I think it is great.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But I guess the final thought there would be I don't think there's anything about that work that would necessitate or even go along especially well with being at Google. I think the people at universities could have done it just as well. Just so happens that they didn't. Plenty of other good work is done in universities. So the more, the merrier.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Jameson says in one of Leonard Susskind's books on quantum mechanics, as well as in a few other popular science books by other authors, he says that quantum logic is different than classical logic. Is it true that the quantum mechanics actually changes the laws of logic, or is that overstated?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So it is absolutely not true that quantum mechanics changes the laws of logic, but there is nevertheless kind of a sense in which there is something called quantum logic that is different than classical logic. It's just that both obey the rules of logic. The difference is that they are applied to different systems, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Classical logic, if you want to call it that, is traditionally interpreted as Boolean logic. You have bits of information. They are on or off, yes or no, zero or one. Quantum information deals with the manipulation of qubits. Qubits are little vectors in two-dimensional complex Hilbert spaces. And you can do a little math and show that's equivalent to being a point on a sphere.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
These are called the Bloch sphere, B-L-O-C-H. The Bloch sphere is the space of states of a qubit. And so a sphere, a two-dimensional sphere, has an infinite number of points on it, right? Because it's a smooth sphere. But even if you ignore that, you need to give me two numbers, two coordinates to tell me where you are on that sphere. And they are real-valued numbers, not integers.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And in fact, I think that there is something very, very profound going on here, but it's sort of backwards from what you're shocked by. You're asking, can a particle have a state which is in principle unmeasurable? I would say it this way. In quantum mechanics, Every state is in principle unmeasurable. That's the weirdness of quantum mechanics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So there's more information in a qubit than a bit. And of course you also know that qubits can be entangled, etc. So the rules of logic are the same in both cases, but the system that you're manipulating to do your computations is different. That's all. Now I will also say that—so that's the—let's put it this way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
That is the respectable interpretation of the phrase quantum logic is different than classical logic, and certainly Lenny Susskind understands this perfectly well. There is a disreputable interpretation of that phrase, which is the following. In classical logic, there is only true and false. But in quantum logic, there is neither true or false. You can be in a superposition of true or false.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And therefore, certain things like the law of the excluded middle are no longer true. Because if you have an electron in a box, it is not true that it's on the left-hand side or the right-hand side. It's neither and both at the same time. That's just like purposefully annoying imprecision. That is not getting you new insight.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
That is just talking about quantum states as if they were classical yes-no things and then acting surprised that they're not. Of course they're not. There's no such thing as the electron on the left-hand side of the box or the right-hand side of the box, but there is such a thing as what is the wave function of the electron.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
If you stop talking about these observational outcomes and start talking about what the system actually is, you find that all of your conventional rules of logic are perfectly fine. Sam Davies says, So congratulations, Sam. That's a big leap and one that will help make the world a better place, I think. So good for you. He says, Well, yeah, that's the beginning of the semester.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I should be thinking about this, right? You know, look, I'm generally bad at this. I'm generally a believer that the best way to learn—to become a better teacher— is not to have someone give you advice on how to do it. There's a bunch of things to do to become a better teacher rather than to teach well, if you see the difference.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You're the one who has to decide how to teach well, but I can give you advice on how to help decide how to teach well. Number one, of course, watch what other people do. So if you're reading a book or watching a lecture or listening to a lecture or something like that, pretend you were giving the lecture or writing the book. Imagine what you would say next.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
See what is actually said by this person who you think is good at it, and then say, well, if the thing that you would have said is always the same as what they said, then good for you. You're doing well. But in the more likely event that they're different— analyze that. Think about why they're doing something different. Did they pause to tell a historical anecdote?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
In classical mechanics, you have states of systems and you can measure them. And you can measure them, you can be sloppy about it and measure it badly or disturb the system, but you can also imagine being very, very precise about them and measure it without disturbing the system.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Did they repeat an important lesson more than once? Did they stop to give the bigger picture kind of thing? Did they give a little philosophical, whatever it is, you know? Did they do more examples than you would have done? Maybe you have a better way of doing it, but at least ask yourself, is there a reason why they were doing it that way? But even more importantly,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I think that becoming a better teacher or speaker or writer or almost anything involves a synergy between two things. Number one, paying attention to what you are doing. And number two, caring about doing it better, right? So a lot of people, you know, if they need to teach or to write or whatever, they have some sort of minimal—what is the word that the economists use? Satisfaction.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
That's not quite it, but, you know, something close to that. Rather than optimizing and being perfect, there's a minimal level of competence that they're happy with, and once they reach that, they stop. Okay? So not being— content to stop with merely adequate is the huge step to becoming a better teacher. And what that means is ask people how you're doing. Like, I don't know, did that make sense?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Do you understand what I'm saying? Ask for feedback. Sometimes they'll give it to you, sometimes they won't. If I maybe, you know, it's the end of a long podcast, I will say something a tiny bit self-aggrandizing here. I had told the story before, but I once gave a talk
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
A popular physics talk, I think it was in the Higgs boson days, and a friend of mine I was chatting with afterward, and I said, so, you know, how could I have done better? Like, what did you think of the talk? What are the parts that were not clear? And she said, you know, I know lots of people who give talks, and you give the best talks, but you're the only one who asks me how I could do better.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And I said, well, maybe those things are correlated, right? There's no such thing as the perfect talk. You can always do better. So thinking about how you're doing, thinking about how you can do it better, asking for actual input from other people on how you can do it better, these are all super important.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So I'm not going to teach you like how to explain things, but maybe I can give advice for figuring out how to explain things and then you can do it. Okay, and then the final question of this month's AMA comes from David Maxwell. Watch any review of the new Google Pixels, and you'll hear the reviewer ask the question, what even is a photo? Often followed by, what even is reality?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Whereas in quantum mechanics, even the gentlest of measurements can extremely disturb the system because wave functions collapse onto specific values of whatever it is you have measured. And so what that collapse means is that if the particle, the system, is in some unknown state, there is literally nothing you can do to measure it and tell you what state it was in before the measurement.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Every person is asking this question. Kids are asking this question. Will generative AI help philosophy become a permanent feature of common human thinking, and can we give it a nudge? Well, wow, I would love it if that were going to be the case. Sadly, I'm going to give a slightly deflationary spin on this question. You know, philosophy starts by asking these questions. What even is a photo?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
What even is reality? But it doesn't end there. And I think that one of the various huge barriers to philosophy becoming a permanent feature of common human thinking is the casual impression that philosophical questions are ones where they're worth spending five or ten minutes bullshitting about. but not actually deserving of serious, careful investigation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So philosophy starts with these questions, but then it's been thinking about these questions for thousands of years. And it has some opinions. It doesn't have the definitive once and for all answers. Maybe those are not going to come for another 10,000 years. I don't know. But we've learned a lot about how to talk about these questions.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And I think that there's a huge difference between an advertisement for Google Pixels raising a philosophical question and nudging the people watching that advertisement to actually think in a recognizably philosophically careful way. right? That's a whole nother level of importance. I'm doing my little part, you know, I'm in favor of thinking in a philosophically careful way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I have a podcast that a few thousand people listen to. Maybe I can nudge them into acknowledging or getting the impression that philosophy can occasionally be useful, among other ways of thinking. and maybe they'll spread that word to their friends. But it doesn't mean just going like, hey man, what's reality?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It means perhaps getting some informed opinions, some actual careful previous art, and reading it and getting to know it. Like what have other people thought about what reality is? What is a photo? I do think it's important, I made the joke on Blue Sky the other day, that this is the moment for epistemologists to finally step forward. because we can now manipulate photos in any way we want.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So the idea that a photograph is a semi-reliable piece of evidence for something that actually happened in the world is just no longer going to be true. It was true for two centuries. It was never perfectly true, because you could always manipulate photos, going back to Arthur Conan Doyle. But
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It gets so easy now that the value of photos for establishing claims that might be contested becomes essentially zero. How do you know when you have enough evidence to believe a claim about something that happened? It's a good epistemology question. So it's time for professional philosophers to do their job. And I think that that's not only true for epistemology, but
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I also think it's true for ethics, moral philosophy. We're going to be editing genes. We're going to have artificial intelligence, which is giving the impression of being conscious. There's going to be plenty of opportunities for real, serious philosophical questions being given an airing in the public sphere. I hope— that both the public and the philosophy profession are up to the challenge.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
We will see. Thanks very much for supporting Mindscape. Thanks once again for listening. Talk to you next time. Bye bye.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You know what state it's in after the measurement, very plausibly. That's what happens with the spin of the particle going through a magnet, right? I send it spin going through the magnet if it goes up, now I know that it's in spin up. If it goes down, I know it's in spin down. But I don't know what state it was in before.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
This is a fundamental time asymmetry in quantum mechanics that you can worry about. Personally, I think that it's the same origin as the thermodynamic time asymmetry, and it's nothing really to worry about, but it's an interesting feature there. So I think that there are quantum states of particles. The thing to be impressed by is that we can prepare quantum states, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You can't measure a quantum state if you don't know what it is, but you can prepare a system so that you do know what it is, and then you can do the measurements on it. And of course, as always worth saying, maybe we don't understand quantum mechanics perfectly well, so we'll change our minds down the road, but that is the conventional story as we currently understand it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Joseph Ellie says, or Eli, says, I watched a clip recently of Brian Green on Joe Rogan talking about the interplay between science and religion.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Brian offered one of the most surprisingly sympathetic views of religion I have heard from a presumably atheist scientist, examining religion more from an anthropological and evolutionary point of view and judging its usefulness in our lives based on its ability to help us understand ourselves deeply and figure out how we interact with the world and what is important to us in a way that a completely scientific worldview may never quite achieve.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I'm interested to hear your thoughts on this, specifically on if you think religion can or should be thought of as a valuable tool for living a meaningful life, rather than being a source for true facts about the world. In other words, do you think that religion or something like it can still have a place in a modern naturalistic worldview?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
these questions are very hard to answer because people don't agree on what the word religion means. And especially when you say religion or something like it, that's a pretty broad bushel of ideas, right? Religion or something like it. In my book, The Big Picture, I try to make a case for naturalism, which is generally thought to be in conflict with religion and
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I've been, you know, on campus, the students are back, they're getting oriented, we've had welcome events for the different departments, and... I gotta say, I love it. It's just so romantic and beautiful.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But some religions claim to be naturalistic, right? You can buy books on naturalistic religion or religious naturalism, for that matter. And, you know, good for them. But at some point, if— what are you doing with this word, religion, if it also applies to things that completely atheistic people would believe?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
In the book, in the big picture, I say, look, it would be very, very surprising given the fact that for thousands of years, the deepest, most profound ruminations by human beings on the the human condition and what it meant to be a good person and our place in the world were all carried out within a religious tradition, to find that those reflections were completely worthless, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I would be very surprised if all of those reflections were completely worthless. I think there's something to be said for thinking carefully about the Sermon on the Mount or the Ten Commandments. The difference is I don't think that there's any authority that those things have because they come from religious sources. You know, you can think carefully about the Ten Commandments.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
That doesn't mean you have to agree with them, right? You can say, oh, that's a good idea, but oh, that's not a good idea. And then by doing that, you're invoking standards that are from outside the religious tradition or the religious perspective. So I'm all in favor of being inspired by religion to think about things in new ways, to be a
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
just like I'm in favor of being inspired by literature or philosophy or art or whatever, right? Why not be inspired by religion? But I don't think there's anything special about religion that gives it a place or religious thought or religious traditions that give them a privileged place in thinking about these questions. I don't think it's necessary to think in a religious way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And the only downside is that I can't help in this day and age of being reminded that we underplay that romance, the romance of a bunch of people coming together to learn new things and to share that knowledge, right? To learn new things in the sense of doing research, right? also learn new things in the sense of going to classes, think about these ideas.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
or even that because something comes from a religious set of ideas, it is somehow presumed to be more insightful about these very deep questions. Spencer says, So I personally don't understand how it could be possible to maintain the idea that there is no complete theory of the universe, for the simple reason that in some sense the universe itself is a complete theory of the universe, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
We just haven't discovered everything there is to know about the universe. But the universe is doing something. Whatever it's doing, that's the theory, right? In a language that we haven't yet quite grasped with. That's not to say there can't be an infinite number of fields or particles or whatever. That might very well be true.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Indeed, one of the big selling points of string theory, one of the ones that is completely ignored by the sort of popular level anti-string theory contingent, is that when you think about ultraviolet processes, when you think about, for those of you who have not heard me talk about this stuff or read Quanta and Fields, my most recent book, ultraviolet just means high energy, short distance, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
The regimes of particle physics and field theory that we can ignore in the effective field theory framework. So when you scatter particles in the deep ultraviolet above the Planck scale, Our naive expectation, or not completely naive, our expectation is that gravity becomes important, including all of the interactions between gravity and everything else, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So this is why—and the infinities that you generally get from a non-renormalizable quantum field theory like general relativity— It blows up, not only are there infinities when you naively quantize gravity, but the infinities depend not only on the graviton, but on all the other particles as well.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So this is why a lot of people are very, very skeptical about approaches like loop quantum gravity that try to quantize gravity without including all the other particles. How in the world are you going to get the right answer when everything matters in that ultraviolet regime?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And the miracle of string theory is that indeed there are effectively an infinite number of different kinds of particles, but they are organized. They are organized into the vibrational modes of the strings. And all the infinities happily cancel each other in string theory in an apparently miraculous way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And so you have an answer to this question of how is it possible to quantize gravity in a sensible way despite the fact that you need to know everything about all the fields in nature. String theory says we know everything about all the fields in nature. They're all vibrations of a string, OK?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So but anyway, that's just an aside to get to the fact that maybe there are effectively an infinite number of fields out there. That does not mean that there's no theory of it, right? There's an infinite number of integers, but we have a pretty good theory of the integers. It might just be like that. Qubit says, Well, there's a couple things going on here that we have to get straight.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
One is the approach that I've been investigating on space from Hilbert space gets you general relativity at the end of the day in the classical infrared limit. If it didn't, we wouldn't be interested in it. In fact, I shouldn't even say that it gets you general relativity. It plausibly gets you general relativity, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You know, we make fun of the idea of the dorm room conversations, but dorm room conversations are super important, I think, in our lives. And For whatever reasons, for lots of different reasons that I'm not going to go into right now, we tend to sort of be a little bit more small-minded about how we think about education these days.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
We don't understand enough about the approach to say that it actually succeeds in doing that. But that's what we're aiming for because general relativity is the theory that you want to get because we have tested gravity and it acts like general relativity in the infrared. And once that is true, then it's not that you have the quote that you have here at the end of the question is,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Isn't it plausible that your approach leads to a completely new type of force that doesn't rely on an additional particle like the graviton? It's not a new type of force. It's gravity. That's the force. And it's not an additional particle. It's the particle that you get by quantizing gravity in the infrared.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So no matter what your approach is, whether it's emergent spacetime or loop quantum gravity or string theory, as long as you obey the rules of quantum mechanics and you get general relativity in the infrared limit, you will have gravitons. That doesn't mean that you start with gravitons, right? That doesn't mean that gravitons are fundamental in any sense.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Indeed, if you think about things, and this is what people doing condensed matter physics do all the time, if you think about non-fundamental systems like solids or gases or whatever, you can quantize them. And instead of getting photons, like you get by quantizing the electromagnetic field, you can get sound waves, which you then quantize to get phonons, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Sound waves aren't fundamental, but there's still quantized excitations in the fields and their perturbations that give rise to sound waves rippling through the medium, okay? That's what gravitons could be. Gravitons might not be fundamental, but they're still going to be there if you have quantum mechanics and general relativity.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Mikkel Pickle says, have you come across a, quote, use it till you find a better one, unquote, method for addressing very small risk of very bad outcome? Is it a hard problem? It is a hard problem, but we are apparently faced with more than one in the world right now.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
As an alternative, have you come across a method or do you have a recommendation for addressing multiple small risk big consequences problem at one time? Perhaps the consideration changes when you have more than one in the world that seems like a small but existential risk. Yeah, I don't have a once and for all perfect methodology that I favor for these questions.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I think this is a super interesting question that I have not seen anyone give a convincing answer to. Obviously, this is in part inspired by the Nate Silver conversation. And there was something in Silver's book that I thought was actually very interesting that we didn't quite get an opportunity to talk about.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
dealing with these very small probability events, he didn't quite advocate, but at least he discussed the idea that rather than trying to think of what is the probability of this unlikely event happening, think of what the range of plausible probabilities are.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
what is the lowest probability you would put on this, and what is the highest probability that you would put on this, and sort of deal with living in that range of uncertainty, okay? If you realize that, you know, oh, maybe I think the probability is 1%, but it could be as low as 10 to the minus 20, then maybe your thinking changes a little bit, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Either pro-education people who try to emphasize the practical benefits of it, getting jobs, technological innovation, whatever it is, or the anti-education people who think that universities are overly politicized, by which they often mean that they don't have their own politics and they don't approve of that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I don't think that's a sufficient answer to the question, but it is an interesting change of perspective I hadn't thought of. Two other things I'll just throw out there as things to keep in mind when thinking about these problems. One is that it's too easy in my mind to assign a small probability to an unlikely event.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
and forget about all the other unlikely events that have similar probabilities, right? When you're talking about something as a probability of 10 to the minus 8, which is a very small chance, right? One in 100 millionth of a chance. But it has huge consequences. The world would end or whatever, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
what are other things that might happen with exactly that probability or even more probability than that? Maybe some of them would be positive effects, right? So at least that doesn't, again, that's not helpful. It's not a complete algorithm for dealing with these, but it is something to very much keep in mind.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And the other is sometimes, I think, again, oftentimes when we're dealing with these existential worries, that is to say worries or problems that could destroy all of life on Earth, many of them have the feature that it's not just that they seem unlikely, but that they would creep up on us, right? That they don't just... not exist today and then suddenly tomorrow they destroy all life on Earth.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
That would be something I would be quite worried about because you can't sort of shift in midstream, right? But for a lot of these worries, they would actually creep up on us. You would take that very tiny probability of them happening that you started with and say, oh, you know, look, the probability is going up. We can see exactly how this is happening now. Let's try to do something about it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And then I think that I'm much more willing to take risks if those are the probabilities we're talking about, because then we can be more clear as we gather more data about what the correct actions to take might be. Alan Lubell says, Thanks.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So to just be clear, so everyone knows what I take this question to be, the question to be is that, okay, there's some diet that might not be what you would ordinarily eat, but you're guaranteed, maybe not guaranteed is too strong, but on average, you would get 20 years extra lifespan, and it would be healthy lifespan, okay? You would actually be, you know, functioning at a high level.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It's not just like you're sitting in the, in the bed all day with, with a aging body, but you actually have 20 more productive years. Yeah, I think that, I'd like to think that I would do that. There's always – the human condition is to struggle with short-term pleasures versus long-term investments in your happiness.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And so we don't have enough blatant, straightforward celebration of the idea of learning for its own sake, learning about the universe, learning about ourselves. So I don't have anything profound to say about this, but I do think that we shouldn't forget that more high-minded aspect of learning, of being at a university. It's a very, very special place.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But I suppose I could try to do that because even though I get a lot of pleasure out of eating and eating a variety of foods in particular, not just the same thing every day – I also get pleasure out of other things like thinking about things and writing books and traveling and stuff like that, which I could do 20 years more of. So yeah, I think I would be tempted to try to do that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
If it were the pizza diet, just pizza and ice cream and Doritos, then I would definitely do it. Then I would do it no problem at all. Maybe I could get rid of the Doritos. Those are more of a childhood craving that I used to have. Happily or unhappily, I see very, very, very, very small credence that eating just red meat, salt, and water would increase your lifespan.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It might do lots of things to you. Increasing your lifespan is very unlikely to be one of them. Nikola Ivanov says, Yeah, they're exactly the same kind of thing. They are mathematical constructs to describe something that is really happening. So when you say they're mathematical constructs, that's not the same as saying they don't exist.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
There is something, there's some effect that is being described. And you invented these mathematical constructs to help you calculate and think about what those effects are. The real effect, whether it's the true vacuum state or scattering interactions of particles, is that there are many quantum fields that interact with each other in ways that we don't have straightforward ways of calculating.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I think it was last month's AMA, we talked a little bit about the amplitudes program for calculating scattering of particles in quantum field theories. The aspiration there is to jump over the idea of virtual particles and go right to the answer in some simpler way. So virtual particles are a tool that we use to think about these things that we're calculating.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
They're a metaphor in some sense, but they are absolutely having an effect, okay? It's just the language that we use is a little bit colorful sometimes to describe how we calculate what that effect is. And that's true whether it's the vacuum or the physical interactions of scattering particles. Captain Brick says, I have a question about Bayesian reasoning.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You've mentioned a couple of times that you should never set your priors to one because that would mean no evidence could change your mind. I don't see why I shouldn't have my prior set to one, but then given some evidence update my credence to close to zero. What is so special about the prior one? Yeah, this is a good question. I could probably be more clear about explaining this.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Let's imagine that we only have two choices, right? A or not A. Those are the only choices that we have. These are the two propositions that we are going to try to attach credences to. We could go through Bayes' theorem and you could show that if the credence on A was equal to 1, then updating according to Bayes' theorem would never change you from 1. That is a true fact.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But it is easier to think about the alternative, right? If you set your credence on A to 1, then the fact that not A and A are the complete set of possibilities and are mutually exclusive means that your credence for not A has to be 0, right? Right? Has to be exactly zero.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Universities, colleges, high schools, and whatever it is, you know, a very special place where your job is to learn new things. And of course, we can't neglect the fact that in this day and age, it's easier to keep learning forever, if you want to do that, with books, with the internet, with podcasts, with online courses, with a whole bunch of different things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And if you visualize Bayes' rule in your mind, the updated probability for a proposition is proportional to the prior probability of that proposition. And the great thing about numbers that are proportional to zero is that they're all zero.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So it's easier to see why if you have something for which your credence is zero, it can never change because Bayes' theorem just sets the new probability to be a number times the old probability. And that number is never infinity. So it's going to be a finite number times 0. That's still going to be 0.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So if your only two options are a and not a, and the probability of not a is 0, no amount of evidence will make the probability of not a anything other than 0. And therefore, the probability of a will remain 1. That's why evidence will never help you if you're in that degenerate case.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Brzozowski says, do you think that artificial intelligence can potentially experience pain or emotions or are they tied to our biology? I think I'm probably halfway in between the two allowed answers here. I see zero obstacle to some kind of artificial intelligence experiencing pain and emotions. I think I'm a physicalist about consciousness and all of those things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
There's no reason why we cannot entirely reproduce the full spectrum of thoughts and conscious experiences that human beings have in an artificial context. However, having said that, I think that modern work on artificial intelligence and simulations of people and things like that vastly underestimates the importance of our biology.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I think not only are our brains embedded in our bodies and constantly receiving sensory inputs and things like that, But we're also, you know, running for a certain – there's a certain metabolism that we have in our bodies, right? We need food. We need light from the sun or whatever. These needs are generally not baked into modern approaches to artificial intelligence.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You know, there's no reason to give an AI program hunger, right? Now, again, there's no reason why we can't do it either. But I think that my impression from knowing a little bit about what we do in modern AI research is that people write computer programs and they let the computer programs run, right? We're not embedding them in bodies that have needs and desires and –
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
things built in by the course of biological evolution that act like feelings and goals. Go way back to the podcast we did with Antonio Damasio. The feelings that he keeps emphasizing are exactly that, are these feedbacks that we're getting from our biology that have a huge role in how our brains actually work. So
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
My suspicion is that if you want to get something that is honestly close to what human beings experience as pain or emotions, you're going to have to somehow mimic or simulate or even just reproduce the biological aspects of our thinking, not just the computational aspects. This episode of Mindscape is sponsored by BetterHelp.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So, you know, we can't be too practical-minded about all these different things. It's okay to have a little song in our hearts about the adventure of learning more about our universe and sharing what it is that we have learned. So this AMA, of course, like all AMAs, is supported by Patreon supporters of Mindscape. You too can be a Patreon supporter.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Halloween is approaching and it's time to think about what is it that scares us. But what about those fears that don't involve zombies and ghosts? For those, therapy is a great tool for facing our fears and finding ways to overcome them. Because sometimes the scariest thing is not facing our fears in the first place and holding ourselves back.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
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Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Visit betterhelp.com slash mindscape today to get 10% off your first month. That's betterhelp, H-E-L-P, dot com slash mindscape. Alex Thu says, recently my wife took an interest in natal charts, N-A-T-A-L, which appear to be an extension of astrological interpretations of life.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Natal charts seemingly offer high fidelity information about one's personality based on relative, planetary, and solar positioning at the time and location of one's birth. While neither of us seriously believe in astrology's predictive powers, the results of our and our family's natal chart readouts were uniquely specific and familiar. The results were uncanny.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Listeners of Mindscape will get a $75 sponsored job credit to get your jobs more visibility at Indeed.com slash Mindscape. Just go to Indeed.com slash Mindscape right now and support our show by saying you heard about Indeed on this podcast. That's Indeed.com slash Mindscape. Terms and conditions apply. Need to hire? You need Indeed.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
My question is, to what extent do you find that physical phenomena in the universe can have real effects of life on Earth, particularly on more abstract concepts such as personality? Certainly, moon phases affect tides, which affects various forms of life interaction, but to what extent can such dynamics play on moods, perspectives, beliefs, etc. ?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Essentially none is the short answer to this question for two reasons. Number one, people have done studies on this. Just recently a study came out.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Whenever you are careful about it, whenever you're doing, you know, double-blind, blah, blah, blah, blah studies, there's zero relationship between astrological charts, including natal charts or whatever, and anything to do with how human beings behave or their personalities or anything.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It is far too easy to ex post facto hear some prediction or some reading or whatever and go, oh yeah, that kind of sounds like me, right? It's very well known that that is something that human beings are very bad at. That is not something we can judge. When you try to control it and be a good scientist, all the effects go away.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But the other thing is, and this is much more important to how I think about it, there's just no room for these effects in how physics works, right? The moon indeed is close enough to the Earth that its gravitational field affects tides. But there's plenty of other things here on Earth that have a much bigger impact on human beings than tides do.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
The temperature in the room that you're in is much more important than the tides. I mean, unless you really think that you can sit in the room a thousand miles away from the ocean and sort of suss out what level the tides are at just by thinking about it very carefully— which, by the way, you can't. I'm just teasing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Just go to patreon.com slash Sean M. Carroll and pledge a little bit. For those of you who don't know, Patreon, because of pressure from Apple and the Apple App Store, is going to have to change its model for charging people. So we're going to have to change from a... pay a dollar per episode model to you pay a certain number of dollars per month model.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It's completely implausible that even the tides caused by the moon have any important impact on our development, especially since, as you probably know, human beings being conceived— growing up inside the womb and then being born takes a few months, takes nine months. So it's not like the tides, which go up and down every day, have any single push on that kind of thing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And other planets and stars and things like that are just wildly far away. We know that there aren't any long-range forces that we're missing in our description of the world, at least not any that are anywhere near strong enough to affect human life, behavior, growth, development, anything like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So both on the basis of my priors about the laws of physics and by thinking about the experiments that have actually been done, I put next to no credence on the idea that natal charts are telling you anything about who you are. OK, now I'm going to group together a whole bunch of questions, but I'm not going to group them together.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I've just arranged things so that I will discuss common topics all at once. So this has to do, unsurprisingly, with the recent podcast with Blaise Aguera y Arcas. It's a very provocative podcast and people have a lot of questions. The questions are often very close to each other, but they're not the same.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So rather than reading them all first and then trying to answer, I will read them and try to answer one by one, but it will be easier to answer the later questions because I will have covered similar things earlier. So Sandro Stucki says, I really enjoyed your episode with Blaise Aguera y Arcas. Early on in your discussion, he noted that life doesn't seem exactly encouraged by thermodynamics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
There's something mysterious there. I was hoping his work would shed some light on this, but BFF seems to be completely irreversible with an arrow of time built in. Do you think that we can nevertheless learn something about the connection between entropy and life from his experiments?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Well, I don't think that we can learn much realistic about the connection between entropy and life from his experiments. So let's just back up and talk in a general way about what's going on here. When Blaze does a computer simulation, the simulation with the program that he's running is embedded in the physical world, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It's not separate from the physical world, but you have to plug in the computer to make it happen. So it is not a closed system. It is an open system that has free energy being put into it, and that enables it to do certain manipulations, which, like Sandro says, are irreversible, right? It's not like you can go back and figure out exactly where you came from.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
When you add 2 plus 2 to get 4, if someone gives you 2 plus 2, they can tell you the answer is 4, but if someone gives you 4, you don't know what you added together. It could be 5 minus 1, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So that is a different thing than thinking about the fundamental laws of physics, which more or less do conserve energy and do have a reversible character at the deepest possible levels, as we discussed in the podcast. However, that's less of a barrier than you might think because, of course— you very often talk about aspects of the world where you have open systems, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You know, like I said, that computer is part of the physical world. And if you restrict your attention to subsystems of the world that are not closed systems, you can get effective dynamics. You can get a theory that whether it's an emergent higher level thing or even just, you know, a theory of chemistry.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Like if you talk to chemists, chemists will often have irreversible processes that they study. And what's really going on from the physicist's point of view is that those processes are giving off radiation, right? Giving off infrared or even longer wavelength light because they're dissipative. They're losing energy to the environment. And the chemists are just not keeping track
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I'm hoping that it's not going to be too much of a big deal. You know, back when I started Mindscape, I wasn't completely sure I'd be doing it every week. So I wanted to charge by the episode rather than by the month. But six years in, I've been doing it every week. So I think that charging by the month makes perfect sense.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
of those photons that are being given off. So they're just keeping track of the molecules and they will find what appear in their worlds to be irreversible processes. Of course, we know that it's compatible with deeper down reversible laws, but that's not what they see because they're not studying the whole system. In some very weak sense, that's what's going on in these computer simulations.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You would like, I would like, to embed any result that you get from these computer simulations in a more full theory that did care about entropy and dissipation and the fundamentally reversible theory. nature of the laws of physics that we understand. But okay, they didn't do that yet. That's perfectly okay.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Now, there's another connection between entropy and life, which is a little bit less down and mechanistic there. So putting aside the fact that we have the second law of thermodynamics, etc., there is still the question of the statistical mechanics of these systems that he's looking at. So forgetting about dissipation and photons, there's still probabilistic questions we can ask.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Blaze was trying to make a claim or at least a conjecture, let's put it that way, that given his kind of setup where you had many different copies of these little programs and they interacted in certain ways, um, if- there's two different questions you can ask.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
One is, in the space of all possible configurations of that system, which of them, uh, have- are doing many computations and are- have little, uh, subsets that reproduce themselves? And the answer is very, very tiny. Very, very few configurations actually look that way in the set of all possible configurations.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Instead of all possible random programs, most of them aren't going to have those properties. But, he said, that tiny subspace is an attractor. Now, an attractor in the world of dynamical systems is a subspace where many different trajectories flow to it, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And if you live in the world of reversible dynamics, like frictionless dynamics to a physicist, you can easily prove there are no attractors because there's a theorem, Liouville's theorem, that says that the volume of a space is conserved in such systems.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But if you have a dissipative system, if you have an open system that is not the entire closed, isolated universe, then you can have attractors and you see attractors all the time. So there can be tiny subspaces of the whole state space of the system, which are unlikely to be chosen if you just choose something randomly, but can be very likely to be an ultimate destination of the evolution.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
When you do become a Patreon supporter, which is very easy to do, you get to participate by asking the questions that I eventually answer in the AMAs. I don't answer all of them. I try to answer the ones I have something interesting to say about. As always, many apologies to those who don't get their questions answered. And we also have, after every episode, I do a little reflections audio.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
of that system. So that was his conjecture. His conjecture was that some kind of computation is an attractor in this dynamical system sense. And so that's a kind of relationship between entropy and his computational work. And I don't know if the conjecture is true. I think it's very interesting. I don't even think that the conjecture is quite well formulated yet.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And I certainly don't know how to address it. But I think that's a super interesting question there that I would like to know more about. Connor says your last episode with Blaise Gary Yarkas was one of my favorite ever. At one point, you brought up how there doesn't seem to be any obvious energy or entropy or dissipation in their simulated world.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But biological life arises from the dissipation of the sun's free energy. Is it surprising that there could be life in their simulation without apparent energy dissipation? What is going on here? So hopefully you see that what I just said, DeSandro's question, will help us also with Conor's question. Yes, there isn't any obvious energy or entropy or dissipation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It's not supposed to be a model of the fundamental laws of physics. It's not even supposed to be a model of chemistry, okay? So I've seen some people, not in mindscape land, but elsewhere responding to Blaise's paper, saying things like, but this isn't really chemistry. This isn't really life. To which I want to say, like, Yeah. Or they say things like, it doesn't answer all the questions we have.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Yeah. Of course it doesn't answer all the questions we have. That's not usually how science works. You know, maybe sometimes you get lucky, but usually you work in steps. So this is not in any sense a realistic model of biology or chemistry or anything like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It's taking one aspect of biology, the idea of information containing subsystems replicating themselves with small variations due to mutations and so forth, and asking, can that arise without it being put in? I've seen a whole nother bunch of people saying, well, this has already been looked at in work on artificial life and things like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But generally, and I don't know if this is always true, but certainly generally, again, as we mentioned in the podcast, that work starts with something lifelike and watches it evolve. um, is usually not about the origin of this, um, reproduc- reproductive behavior from true random initial conditions.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I mean, there could be counter examples to that, but I know- and I know of like one or two, but there's- there's not that many. So anyway, to Connor's question, is it surprising that there could be life in the simulation without apparent energy dissipation? As we talked about in the previous question, there is effective energy dissipation. There is irreversible dynamics, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So in that sense, it is not surprising to me that there could be something lifelike in their simulation. Dennis says, I liked a lot of the recent podcast with Blaise Aguera-Yarkas. At the beginning, he claims that in his experiment, replication emerges from nothing without being put in the system from the start.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
That seems like cheating, considering that there is a copy instruction in the base language. This point is even kind of acknowledged later, but not as a weakening of the original claim. More generally, do you think that starting from a programming language to make computation emerge is a weak point of this approach? So again, as I alluded to before, it's not a weak point of the approach.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So I record just a few minutes of me talking about what I thought about the episode that we just had. That's exclusive just for Patreon supporters. And so we appreciate it when you join on Patreon. But if you don't join, you're still a listener, that's still good too. Plenty of other places to talk about Mindscape episodes.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It's a feature of the approach. I don't mean feature as opposed to bug as a positive feature. It's just a fact about this approach. This approach is not supposed to be realistic chemistry. It's not supposed to exactly answer all the questions you have about the origin of life. There is no analog here of a nucleotide, right? in a DNA molecule or anything like that, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It's an entirely different kind of thing. It's trying to ask, does computation and replication, do computation and replication naturally emerge from random initial conditions in certain kinds of circumstances? So of course, yes, this programming language does allow for copy as an instruction, but it doesn't copy, it doesn't naturally copy the whole program, and that's what you're looking for. So
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
They absolutely are dealing with a context where it is possible to get the answer that you were hoping to get. And indeed, they get the answer they were hoping to get. But baby steps. It's going to be a long journey before we go from this to understanding how actual life actually formed.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But I will say, like, you know, just so I can be a little bit more substantively positive, I think the hope is—well, one of the hopes might be the following, that if it's true that there is some sense in which computation is an attractor, even in this very, very toy model spherical cow example that they do on the computer, maybe that makes you think that some kind of life is more ubiquitous in the universe than you thought.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Maybe it is evidence that given that the laws of physics we know allow for life because we're here, we're life, we're consistent with the laws of physics. If there's some attractor behavior to this kind of computational model, then maybe biology, chemistry, geology are more likely to make it happen than you might think.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I think that the evidence for that is pretty weak right now, but it's something we can absolutely think about more carefully. Adam Rotmill says, I enjoyed the podcast with Blaze on computational life using BFF. Also started Sarah Walker's book, Life as No One Knows It, along similar lines.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
How do you think these computational approaches compare to the way Daniel Dennett references Conway's Game of Life in Freedom Evolves? Has the newer paradigm changed? I don't know too much about the Game of Life, to be honest. I mean, I know what the Game of Life is, but there's been a lot of research on it at a detailed level that I have not kept up on.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So as far as I know, there's two statements. One statement that I know is true, which is that the Game of Life, Conway's Game of Life, for those of you who don't know, you probably do know, it's this sort of grid cellular automaton, a two-dimensional cellular automaton with white and black lines. squares that interact with their nearest neighbors in definite ways.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
There's a whole subreddit slash Sean M. Carroll, believe it or not, where you can talk about Mindscape episodes. And I am always very happy to have so many people supporting the show. So with that, let's go. 🎵 Mark V asks a priority question.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And you can build reproducing things like gliders and you can build things that make an infinite number of gliders and so on. And it has been proven that this particular cellular automaton is Turing complete.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
That is to say you can construct a configuration in the game of life that will be able to be a Turing machine, that will be able to compute any computable function just as well as anything else. So that is known. What I don't know is how robust that configuration is, right? In other words, precisely this question of is that an attractor in the space of the dynamics?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I have no idea whether anyone has looked at that question in the Game of Life. it's incredibly plausible to me that you can construct a Turing machine in the game of life, but they're very, very fragile. And if you bump into a little bit, it breaks, right? And it never arises from random initial conditions. The game of life is not that robust by itself.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Like all the interesting stuff is not that robust. If you put random configurations down, usually they peter out, okay? They usually don't start reproducing interesting things in them. Now, I don't know if There's some subset of conditions that are not completely random but for which computation happens naturally. That's something that I'm not up on.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Nate Wadoops says, the episode with Blaise Aguera-Iarcas was outstanding. It got me wondering why we, got me wondering, we only see very limited forms of self-replication emerge from Conway's Game of Life.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
For example, we often see patterns that crawl across the grid, but the soup generally converges pretty quickly to either a static image or to something that repeats after a small number of steps. Do you have any thoughts on what sorts of extensions to the rules of Conway's Game of Life might enable more interesting phenomena to emerge from a substrate of cellular automata?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Yeah, so that's a good question. So that's exactly what I was getting at before. Like generally you converge to boring things in the game of life. And so one open question, and it's okay to have open questions. It's not a flaw in the paper you wrote because you didn't answer every possible open question.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
figure out how likely it is that the kind of behavior you saw with the BFF simulations will also exist in these other simulations. It seems completely plausible to me that the game of life is on one side of a divide, and that divide separates automata in which computation almost never spontaneously arises.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
On the other side, there's a set of automata and programming languages or whatever where computation almost always arises from random initial conditions. But that's all work to be done. That's why it's so much fun, because we don't know the answers to these questions.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Daniel Bagley says, I'm having trouble with what seems to be a teleological perspective coming from Blaze in your most recent episode. If life is computation and it was created via instructions, doesn't that imply agency or teleology? Who or what encoded instructions in the matter and information that comprises life? This seems to open the door for creationism.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Well, I hate to disappoint you, Daniel, but the door has been open to creationism for a very long time. It has been the dominant paradigm for thousands of years. We're just crawling out from under it. And we should go wherever we go, you know, whether it opens doors or not, whatever is the best theory that we can invent. However, it is absolutely not teleological in the relevant sense.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Of course, as we said, this is an experiment done on a computer and someone built the computer, someone designed the programming language, someone set up the experiment that we're running. All very, very true. That's going to be necessary in any simulation we ever do. It's going to be set up by human beings, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
There's zero thought that that implies that our physical universe was set up by some higher intelligence. That's just a different kind of question. This model that they have is supposed to be a version of laws of physics. Certainly not our laws of physics. Absolutely not. We've already talked about the fact that their computer algorithm is irreversible rather than reversible, for example.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But there's other differences as well. And the fact that we have laws of physics does not imply that those laws were passed by a legislature or that they were invented by some cosmic autocrat or anything like that. And it doesn't matter. You know, we have to lead where the science takes us. And we have to figure out why it is that life arose.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Priority questions, for those who don't know, are those where once in your lifetime, every Patreon supporter gets to ask a question that I will definitely try to answer. There's so many questions I can't answer all of them, but the priority questions, I'm going to give it my best shot.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And, you know, if ultimately someday we decide that it must have been because God did it, then I will live with that. I think that my credence on that is very, very, very tiny. But I'm absolutely willing to decide that if that's where the evidence eventually points.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
John Haig says, with the Blaze Aguirre-Yarcos podcast fresh in our minds, I have a question concerning the Briggs-Rauscher oscillating reaction. This reaction oscillates on average about 10 times. The oscillating color cycle goes from clear to amber to dark blue and then back to clear again, always ending on the dark blue stage.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Do you believe and or think, Blaze would believe, that each oscillation is one complete complex life cycle and that each new oscillation is a form of replication? If so, how would you define death and rebirth? If not, could it all just be one life cycle with 10 stages of morphogenesis?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So yeah, if you don't know, this idea, the BR oscillation, Briggs-Rauscher oscillating reaction, this is a chemical reaction that people who study complexity sometimes get very excited about. And it's kind of interesting because you have this system. I'm not super expert on it because I don't think it's that exciting, to be honest, as I will just explain. But you have this chemical reaction.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And, you know, many chemical reactions will happen. And then at the end of the day, you equilibrate, right? Everything is smooth and more or less constant everywhere. This kind of chemical reaction goes through these oscillations. And you see patterns. And the patterns are unpredictable where exactly they will appear. But there's like stripes. And the stripes sort of curl around each other.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And they oscillate in color. They change color. So it looks kind of unpredictable and kooky and kind of structured and complex. But there's not really any information being processed there. It's actually all pretty simple.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Honestly, even though the picture looks complex, you know, it's not something where you could consider mutations or learning or any of the kinds of things that we associate with what I would associate with important aspects of life. You know, think back, as I like to keep reminding us of prior podcasts, Stuart Bartlett.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
we had a very interesting conversation about what he called Leufe, which I think is a terrible way of pronouncing this neologism L-Y-F-E, where he and Michael Wong tried to say, look, what matters is not finding the right definition of life. It's acknowledging that life has many different aspects to it, and some of those aspects might appear in systems without the other ones, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So Mark asks, imagine a scenario where Sean Carroll is born in a distant future, long after the possibility of detecting other galaxies, the cosmic microwave background, and similar phenomena have vanished. However, society has preserved uninterrupted records of earlier observations.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So metabolism and reproduction are some of those aspects, but so are learning and adaptation. And those kinds of things don't exist in this Briggs-Rauscher reaction. So I think it's a cool reaction, but I would not call it life in honestly any sense whatsoever. That's my view.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
OK, that is enough for the moment about the origin of replication and computation. We can move on. Ahmed Hindawi says, what are your thoughts on an election system where each voter assigns a score between minus 1 and 1 to every candidate, perhaps with increments of 0.1? In this system, voters wouldn't need to normalize their scores to any specific value. I see two potential advantages.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Number one, moderate candidates could gain support from across the political spectrum, potentially outperforming more extreme polarizing candidates. And number two, it could increase voter turnout. Even if a voter is indifferent to candidate X, they might still be motivated to give candidate Y a negative score to offset someone else's positive vote.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
A potential downside is that this system is more complex than a simple single choice ballot. Yeah, this is a known system called range voting or score voting. And I think that it, in theory, has a lot of advantages. For those voting theory aficionados out there, it avoids Arrow's theorem.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Kenneth Arrow proved a famous theorem that said that no voting system under certain reasonable assumptions can keep everybody happy—not keep everybody happy, of course. If you lose the election, you're not happy, but can satisfy certain conditions that you would want a fair voting system to satisfy, like no one person is a dictator. If you—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
How would you think about cosmology when direct observations are no longer possible and only historical records remain? Would it be any different if society had not preserved those records, but instead they were suddenly rediscovered? I think that there's sort of two issues here.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
prefer A to B and B to C, prefer A to C, things like that. But one of the assumptions of Arrow's theorem is that it's an ordinal system, that is to say you rank or vote yes or no for candidates rather than a cardinal system, as it would be called, where cardinal means you can assign numbers, right? And this is exactly what range voting or score voting does.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And I think that there's even been papers written saying that people will be unhappy when you have an election because not everyone's candidate wins. But people are at least unhappy in range voting kind of systems. So I think it's a good idea overall.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It's still subject to the worry that people are insincere, that people try to strategically vote, you know, if there's someone who they think – well, so here – with range voting, here is the typical worry. You might have three candidates. One is the best, and you give them a plus one. One is the worst, and you give them a minus one. And one you're indifferent to, so you want to give them a zero.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Your sincere score would be giving them a zero. Okay. But there's two worries you have. One is maybe your least favorite candidate is actually popular. So you want to maximize the difference between your least favorite candidate and everybody else, especially if your second favorite candidate is more popular than your first favorite candidate. So you might be...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
pushed towards exaggerating your preference, increasing the score of your second favorite candidate to increase the distance between them and your least favorite one. But also there's the backwards worry. If the second favorite candidate is popular and so is your favorite candidate, you might be tempted to lower your score for your second favorite candidate. It's always going to be true.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
that you should give your favorite candidate the highest score and your worst candidate the lowest score. But apparently there's some research, I'm not sure if this is completely reliable or not, but empirically, apparently people, when they have this voting system, do tend to try to be honest, to try to give fair scores to people rather than voting strategically.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I mean, maybe that's just because these systems are not very common, so people haven't learned to game the system. And also maybe it's not so bad to game the system. Maybe that's perfectly okay. Anyway, I do think that it would be better than our current system.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
One is an issue about the scientific method and the other is an issue about how you would reconstruct truths about cosmology in a data-impoverished universe. As far as the scientific method is concerned, I don't think it's that much different about the scientific method if you didn't have the CMB and other galaxies and stuff like that and you just had… historical records.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But our current system in the United States, most jurisdictions have what is called first-past-the-post or winner-take-all kind of elections where whoever gets the most votes wins, right? Everyone who does voting theory wins. thinks that that's the worst possible system. Except for, as Ahmed says, it is a simplest system, first past the post.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And therefore, people worry that if you have more complicated systems, people just won't vote or won't vote correctly. Or especially, you know, I remember... There was a California election, the one that Arnold Schwarzenegger won, where you had like over 100 people on the ballot. So you're going to give all of them scores? No.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You need to have some way to either have a primary or something like that. But overall, yeah, I do think that it's worth trying. You have to figure out how to improve the current system. It might help voters. third party candidates.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I think that the United States presidential system, where you have one president, and that person has a lot of power, and they're basically voted on directly rather than by the assembly, like in a parliamentary system, then in that kind of system, you will always have enormous preference for a two party system, because it's just hard to, it's not like where you
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
have a parliamentary system and there can be coalitions or something like that. You vote for the president, right, directly. That's always going to favor a two-party system. And indeed, in the United States, there's always been two parties that have been dominant. But maybe you could have in the primaries or something like that, quirkier outcomes or
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
More moderation if you didn't just do first past the post. In the most recent British elections, which they do have a parliamentary system, but they do have first past the post, which means that it basically turns up the contrast knob, right? If you have 100 districts...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And in every district, 51% vote for candidate X and 49% vote for candidate Y. The country is pretty evenly split, but the parliament is 100% candidate X, right, or party X. So that's not really a good way to – make things most representative of the feelings in the country. That probably would still be the case if all you did was have range voting or score voting or something like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But there's other ways that you can have more proportional representation. So I do think that modern voting systems have become – modern polarization and things like that have become – big enough problems that even though systems might be more complex, they are still worth trying out. And places have tried ranked choice voting and things like that with actual success, as far as I can tell.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So definitely worth considering. George Hampton says, I was re-listening to your July AMA while walking in the grocery store and while answering a question about John Moffat's theory. In your story about your undergrad studies, you said it was 40 years ago. We can admit it. I'm a bit older than you and just turned 60, and I've been thinking and saying things like that for a while.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
If you thought that the historical records had good reason to be accurate and their implications were compatible with what you did see around you, then I would see no reason to doubt them, or at least put high credence on them and then prepare to change your mind later. it's pretty analogous to what actually happens in the universe.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
My question is, how do you feel about approaching 60 and growing older? It's been surprising to me how much I've been reflecting on my life and the world in general, and I'm wondering if you have been having similar feelings. Yeah, I've definitely been having similar feelings. And it's a cliche, and it's predictable, and it's going to happen anyway.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
For those of you who are young out there, it is definitely something on your mind when you grow older. In a very real physical sense, one does not bounce back from minor injuries in one's 50s as one did in one's 20s. And there are more of them. And your trips to the doctor become a little bit more action-packed. than they are when you're young.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I'm in pretty good health right now, but you know, there are things that I have, like I have to take vitamin C supplements now, which I never had to do. Very minor thing, but it's something, right? It's a reminder that the number of things you're going to have to take as time goes on only increases. And in a more existential way,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I'm at an age where, absent some dramatic increase in human longevity science, I have had more years behind me than I have ahead of me, right? There's this feeling you have when you're young that... you're preparing for life, right? You're learning things, you're getting good at things, and then you're going to someday put all these new skills to work.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And later in life, you have to think, you know, look, I got a finite amount of time left. I got to figure out exactly what I want to get done. I got to prioritize. And what I want to get done, that doesn't mean necessarily like, you know, work, writing books or whatever.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Like sometimes what you want to get done is to travel or to have a good time or to enjoy your family life or your pets or good food or whatever it is. But I do absolutely think it shifts your perspective a little bit to grow older. This is not a novel... insight on my part in any way. But it is true for those young people out there. It will happen to you too.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Redmond says, I favor a low bar on suffrage. Suffrage means the right to vote. And Redmond says, a GEDW2, DD214, rent receipt, or other indicia of minimum participation in society. So for those of you who are not Americans or acronym freaks, GED is a high school equivalency diploma. W-2 is the form you get for when you get paid for the income taxes.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
DD-214 is a discharge from the military, things like that. And Redmond says, why should the village idiot and town drunk get to vote? So the answer is because the village idiot and the town drunk are people too. They have absolutely just as much right to vote as anyone else does.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
In terms of photons, we do see the cosmic microwave background, but that's the surface of last scattering. That is the transition moment in the history of the universe when it became transparent after having been opaque in all previous times, which means that all of the information about previous times as far as at least light and direct visual observations are concerned, is invisible.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I think there's a fundamental mistake that some people make about the purpose of democracy, or at least what I think the purpose of democracy should be. You know, we had the conversation with Henry Farrell some time back about how democracies can be useful as ways of making decisions.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You know, they're cognitive democracy, democracy as a way to find an equilibrium, sort of analogously to how markets work for economics. But that's not really the moral or ethical case for democracy. The moral or ethical case is people should have a voice that when you have a government, you know, again, not saying anything new or insightful here.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
When you give some subset of your society the right to make decisions for the society as a whole, where does that right come from? From the people being governed is the theory of democracy. People have the right to speak for their own interests. It's not an IQ test. It's not something where only the intelligent or only the productive or whatever get to participate.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Every human being who is above a certain age and a citizen of the country should get the right to participate. And I buy that ethical argument. I'm entirely in favor of it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
George says, you did an episode a couple years ago that roughly ended with a suggestion that someone should consider doing a careful analysis of cosmologists' psychological profiles and how they might inform said cosmologists' tastes for cosmological models. In your field and in the wild, have you noticed or do you have a hunch about any of those potential patterns yourself?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Maybe along the lines of messy office equals bigger, more diverse universe, clean office equals neater, more predictable universe, and so forth. Well, so no, I have not done anything, I have not noticed anything nearly that straightforward. which is exactly why I think that someone should do a careful analysis of it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It's far too easy to have your own personal, informal, not careful analysis be swayed by some particular vivid examples rather than being fair to the whole data set, right? And also, my prediction is not that if there is any connection between personality and scientific theory preference, it would be anything like that straightforward. What I'm thinking of is—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Things like whenever we pick scientific theories, when we don't know the right answer, when we don't have the correct theory in front of us and we have different options, especially when those different options are ill-defined, when we don't exactly know all the details of what the options are going to be. When someone says, for example, dark matter versus modified gravity,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Well, that's great, but what modified gravity? How exactly are you modifying gravity? What dark matter candidate? Where exactly does it come from and how does it behave, right? So even what you call a model is ill-defined. But you have preferences, and this is well known that scientists will prefer different hypothetical models, even though they completely admit that we don't know yet.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
They will have preferences, and those preferences are based on different criteria, and the criteria cannot be objectively weighted against each other. Maybe one theory is very simple to write down, but you really kind of have to stretch to make it cover the data. Another theory is more complicated, but it fits the data very well.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
One theory is very elegant in its own right, but doesn't fit in with other theories very well that we understand. You know what I mean? Some theories postulate entities that we don't see. Some don't. Okay, so there's many different things, fruitfulness and things like that. Thomas Kuhn, long after he wrote The Structure of Scientific Revolutions, wrote an attempt to—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
defend himself from charges of that he was a relativist, that he thought that, you know, Kuhn and the structure of scientific revolutions argue that there are non-epistemic factors that go into scientists' preference for one theory or another. And people read this as saying that it was arbitrary, and he later wrote that, no, it is not arbitrary, but it's just not an algorithm, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
We can't see what happened before the surface of last scattering, which is about 380,000 years after the Big Bang, right? There is one exception to that because we do have data from primordial nucleosynthesis. which happens just a few seconds or minutes after the Big Bang. But that's not as detailed as maybe you would like.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It's not just perfectly mapped from here are the data, here are the theories, here's what scientists will agree on. There's judgment that comes into it, and there's different factors that come into that judgment, and those different factors will be weighted differently. Foundations of quantum mechanics is another example where you can come up with your own different things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
my issue or my suggestion, my conjecture was that, um, the way that different people weight these different factors might be correlated in interesting ways with their personality profiles. I have no idea whether that is true. Um,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It was Lee Smolin, former Mindscape guest, who pointed out that people who think that computers can someday become conscious are more likely to support the Everett interpretation of quantum mechanics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And I thought that was extremely insightful, not because those two issues are directly correlated, but they're co-correlated with a third thing, which is how happy are you to take like a very, very simple basic structure and extrapolate it very, very far? right, and have confidence that eventually the extrapolation will work.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
That is what happens both in physicalist theories of consciousness, where you say, I don't understand consciousness yet, but I really do have a good amount of credence in the underlying physical construction of the world, so I suspect that when we understand consciousness, we will understand it from a physicalist point of view. And likewise for many worlds, where you say, look, the
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
whole thing about quantum mechanics is very weird. No matter what choice you pick, I'm going to pick the choice that is the simplest model and just believe its predictions, even if those predictions involve metaphysical surprises that I wouldn't otherwise have sought out, like all these other universes.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So I think that there is a psychological makeup in how physicists and philosophers, for that matter, go about preferring theories that we haven't yet established one way or the other. Robert Ruxandrescu says, does causality really exist fundamentally, or is it just a way of talking about events that happen from our limited perspective?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I'm thinking about the Humean view of laws of physics and the idea that causes and effects are emergent properties, and if so, can we really say that we cause things to happen when we make a decision to perform an action? It's more like we witness a movie and are tricked into thinking there's causality involved when it's really not.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Well, I think, if I understand what you're getting at, I think this is the classic... example of somehow being reluctant to think that emergent things are real. But as soon as you use the word we, you're already attributing reality to some certain kind of emergent things, namely human beings, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
There is a way of thinking about the universe in which there is just the most fundamental level, and Laplace's demon would understand it perfectly well, and that's the only way of talking about the universe. But nobody really talks that way. No human being really talks that way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
If you believe that tables and chairs are real, if you believe that people are real, then there's no reason why you shouldn't think that causes are real. Causes, as I've often said, are not—the idea of a cause is not a concept that is anywhere to be found in the fundamental laws of physics, as far as we know. But likewise, neither are cats. But I think the cats exist.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You get really sort of a couple of data points from primordial nucleosynthesis. But the point is, we take what data we have and we try to fit it to a model. It's not that you just observe everything you want to observe ever in science. You have to have a comprehensive story, and then you have to match it to whatever data you do have. sometimes that will be very, very hard.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
They just exist at a higher level of abstraction, and so does cause and effect. There's no discrepancy there. There's no inconsistency there. Massimo Tori says, I recently read an article by Ethan Siegel titled New Theoretical Calculation Solves the Muon G-2 Puzzle.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
In the article, he discusses the observed discrepancy between the measured value of the muon's magnetic moment and the value predicted by the standard model. This discrepancy had been seen as a potential indication of new physics beyond the standard model.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
However, this difference appears to be the result of a flaw in the technique used to calculate the theoretical value of G-2 rather than a flaw in the standard model itself.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
While I understand that the muon interacts with other fields, such as quark fields, I'd assume that these interactions would occur only through the electromagnetic or weak force given that the muon is a lepton and interacts via these forces alone. However, the revised calculation explicitly considers the contribution of the strong force as described by QCD.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Would you clarify why the strong force would play a role in determining the muon's magnetic moment? Sure, this I can do. In fact, I'm pretty sure I did a solo episode about this. There's a solo episode. See, if I did any research before I did my AMAs, I would have done this ahead of time. Maybe I can just do this in real time as I'm recording this. I will look for my solo episode.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Yes, episode 144 was a solo episode called Are We Moving Beyond the Standard Model? And I discussed some of these purported discrepancies, most of which involved muons, and the most promising one of which was, well, I shouldn't say it's the most promising, it's probably not, but a promising one of which was the so-called G-2 puzzle of the muon.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And G-2 is a way of saying the magnetic moment of the muon. The muon is a spinning particle that So it has a magnetic field. How symmetric is that magnetic field versus how distorted is it? That's a thing that you can measure and you can predict it on the basis of the standard model. And the point is that if the muon were just a point particle all by itself, g, the magnetic moment, would be two.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And it's not. There's little corrections to that. Why? Because quantum field theory. Because a muon traveling all by itself, just like any other fundamental particle, will be constantly interacting with other fields around it. And you can think about those interactions as being described by Feynman diagrams, right? The particle is just moving, but then it spits off a photon.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So the muon going along spits off a photon, then reabsorbs it. That is a Feynman diagram that contributes to the following process. Muon becomes a muon. So the muon is just traveling along through space. But there's all these buzzing fields around it, which we discuss using Feynman diagrams. There are also diagrams where the muon spits out a photon and eventually reabsorbs it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But there are higher loop diagrams where that photon, along its trajectory, will split itself into a particle and an antiparticle and then reabsorb them, right? So there's a two-loop diagram where muon becomes muon plus photon. Photon becomes, let's say, quark and antiquark. which then get reabsorbed to become a photon again, and then reabsorbed into the muon.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Even though we have the CMB and nucleosynthesis, we still can't see what happened before the Big Bang. We don't even know if anything happened before the Big Bang. That does not stop us from thinking about it. So I think a similar kind of situation would hold if you were in a universe where the galaxies and the CMB themselves had disappeared.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Quarks and anti-quarks can be produced in the motion of a photon, in what we call the propagator of a photon, because quarks are charged particles. And they are also strongly interacting particles. So eventually, you will have every particle of the standard model interacting with every other particle. They might not be direct interactions, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
There's no direct interaction between muons and quarks or gluons. But there are indirect interactions mediated by these higher loop diagrams. That's where the muon magnetic moment comes from. And it is a beastly calculation to do it because, number one, you need more than one loop. And whenever you get more than one loop in a Feynman diagram, it becomes hard to do.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But number two, you have the strong interactions. As soon as you make quarks or gluons— then those particles interact strongly. So that quark-antiquark pair that can be produced by the traveling photon will themselves scatter gluons back and forth and other quark-antiquark pairs. And that turns out to be hard to actually calculate. And it's not just photons spitting off of the muon.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You can have Z bosons or whatever. So... The fact that the muon is a bit heavier and interacts with the Z and the Higgs more than the electron does means it's a more noticeable feature of the muon's magnetic moment, which is why it's the muon that is being looked at for this discrepancy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But all the way back when I did this solo episode, which was in 2021, right, over three years ago, it was already clear that one of the possible discrepancies was in that theoretical calculation. We had an experiment that came up with a measured value for the muon g minus 2. And we had two different ways of doing a theoretical calculation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
One, which was a lattice calculation, where you try to discretize spacetime, put it on a computer. And the other one was with the little Feynman diagrams, pencil and paper. But of course, they also use computers to do those integrals and so forth. And I forget which one it was, but one of them agreed with the experiment and one of them disagreed.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So it was a very obvious kind of loophole that if the two theories don't—theoretical predictions don't agree with each other, then you shouldn't be surprised that one of them disagrees with the experiment.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And, you know, for the last 50 years, it's always been a smart bet to say if you think you have an anomaly that points to new physics, it will probably go away unless it's like super strong and absolutely unmistakable. So it's still possible that it's out there. But, yeah, this is a very plausible explanation for that apparent experimental anomaly.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Thies Janssen says, your ideas about space being emergent from entanglement seem to have a lot in common with the basic assumptions from Penrose's conformal cyclic cosmology. You mentioned that you were not very interested in CCC. Without diving deeper into the ideas, you don't find it very convincing. That surprises me. Why is that? Well, lots of reasons.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I don't see what the connection is, honestly, from space emerging from entanglement with the conformal cyclic cosmology. But My lack of interest in CCC just stems from the model all by itself for two reasons. Number one, it's not really physics. It's magic. Penrose says, you know, you have the certain assumption about what the very early universe looked like, which by itself is plausible.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
The other one is, what could you possibly infer without those wonderful observations that we have? And probably not that much. You know, you could certainly make the case that there's still an arrow of time, I presume, in this hypothetical future universe.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And then there is the future of the universe. The far future of our cosmology will look like empty space with a positive cosmological constant. And you can do a mathematical redefinition to sort of match this early condition to the late condition. But it's not a physical definition. redefinition. It's not a physical thing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It's not, you know, the physical conditions in the early universe are super different than the physical conditions in the late universe. So Penrose just sort of conjectures that one turns into the other, and that is just not predicted by any known laws of physics. He just made it up, okay? Now, maybe there are unknown laws of physics that would make it happen.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
That's great, but it's super speculative and not based on anything really that fits in with anything else that we understand. And number two, I don't even think it solves the important problem. You know, I think that the, the important problem as I see it, for these theories of initial conditions is why was the entropy low? Why is there an arrow of time?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Why is there an asymmetry between past and future? And Penrose's answer, the CCC answer, is it's just there. It's put in by hand. There is an eternally persisting arrow of time from the far past to the far future. And again, That might be right. That might be the correct answer. But it is highly unsatisfying to me.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
As we were just saying a second ago, in the realm of theories that are a little bit ill-defined, people's personal preferences are relevant to their judgments about what's likely to be true. To me, CCC might very well be true, but it would be a highly unsatisfying answer to why the initial conditions of the universe look the way they do.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Jonathan Good says, how likely are sterile neutrinos as an answer to the majority of dark matter? Well, they're possible. You know, I would say that, again, we were just talking about different criteria we use for understanding theories that are not completely fully baked yet. Dark matter has overwhelming evidence that it exists, and we know some of its properties.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It's cold, and it's largely non-interacting, and we know approximately how much of it there is, okay? That's not a lot to go on, but it's a little bit to go on. And what you want to do is sort of minimize the number of miracles that need to occur. Or sometimes we say you want to minimize the number of invocations of the tooth fairy in your theory.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So the reason why weakly interacting massive particles are so popular, have been popular for a very long time for dark matter, is that they're involved in a completely different problem other than dark matter. They're involved in whatever happens at the electroweak scale, the hierarchy problem, the Higgs boson, whatever.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
If it's literally the future of our universe, then there will be an arrow of time for a while before we eventually reach equilibrium and the arrow of time ceases to exist. So the cosmologists in that era, epoch, might hypothesize that there had to be a lower entropy beginning in order to give you an arrow of time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
These are all things – in other words, you could have a fully comprehensive theory that explained the hierarchy problem, the mass of the Higgs, and also the dark matter, and that would be great. In particular, in a very quantitative way, there is what is called the weak miracle, or the wimp miracle, which is that if you just have a particle that naturally –
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
annihilates and scatters with a strength similar to what we think is there for the weak interactions of particle physics, you will tend to get approximately the right density of dark matter. So you don't need to invoke a miracle. There's plenty of models where there are stable particles with the right density. That's exactly what you want.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But we've looked for the WIMPs and we haven't found them yet. Maybe we will, but we haven't found them yet, which is sort of depressing. The other popular candidate are axions. And again, the reason why axions are popular, it's not because you naturally get the right density of dark matter, but the axions solve another problem. They solve what is called the strong CP problem.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Why is the CP symmetry respected by the strong interactions but not the weak interactions? And axions are part of an explanation for that. So you like that. You like it when the particle explains something else. And even though axions don't necessarily have the right density to be the dark matter, you can give them the right density to be the dark matter without too much effort.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
There's a free parameter that you can pick so that it would naturally have the dark matter density, and there you go. So people are happy about that. But we haven't seen axions either. We haven't looked for them nearly as hard.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And then if it's neither of those, I think that the next couple of candidates that you would take seriously are sterile neutrinos, which are neutrinos not like the ones we already have in the standard model, but neutrinos that don't feel the weak interactions at all. That's why they're called sterile. And on the one hand, on the other hand, black holes. Why are these two examples so good?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Well, they're things that are very closely related to things that exist. Black holes do exist. But the problem with black holes as dark matter is it's very hard to get the right abundance of black holes with the right masses so that we haven't already ruled them out. It's very hard to get the right abundance at all.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You need to invent some very weird physics in the early universe to get enough black holes to be dark matter. And then you want them to be not too heavy or not too light, not too heavy you haven't already noticed, not too light they already evaporated away, right? So it's a very weird set of circumstances, but it's allowed and it's nice because black holes are known to exist.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Likewise, the sterile neutrinos might be involved with some theories of neutrino masses, right? So like the axions, they might be related to some known problem. It's just not very obvious they should have the right abundance to be the dark matter. So we don't know. I have not followed the latest wrinkles in what people think about their favorite dark matter models.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I think the dark matter is out there, but since I'm now old, as we've already discussed, model building in particle physics is not how I choose to spend the rest of my time, unless I really invent something that is absolutely genius. Stay tuned for that. You'll be the first to know, I promise. Beetroot says, as a European, I'm watching with anxiety your presidential elections.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And then they might even come up with something roughly resembling what we think of as the Big Bang. I don't know. They might alternatively come up with other scenarios that are not Big Bang-like. But the point is that...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I'm very preoccupied that the Democratic Party and supporting social media channels are not highlighting enough the implications of Project 2025, but instead are fixated on every blunder of Trump, which is basically everything he says or does. I've taken a deep look into the Project 2025 paper.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
What really concerns me is that it's a battle plan to end democracy in the United States and turn it into a Christian nationalistic autocracy. Do you have an opinion about the Democratic strategy and this specific aspect? Well, yeah, from my internal perspective, it's more or less the opposite of what you say, which I don't know if that's a good thing or a bad thing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So for people who don't know or for people who are listening to this 500 years from now, we are in the middle of a – not in the middle of, near the end of, a couple months from the end of a presidential election between Donald Trump and Kamala Harris, the Republican candidate and the Democratic candidate.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And a Republican think tank, the Heritage Foundation, published this document, Project 2025, which would be a roadmap for policies they would like to implement. And it's a little bit sketchy because it wasn't an official Trump campaign document.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But if you look at it, like everyone who was involved in writing it, not everyone, slight exaggeration, but there's a huge overlap between people who wrote that document and people who either have advised Trump or previously worked in his previous administration. So it's more or less them coming out on the open and having a wish list. This is what we would like to do if we get back into power.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And it's full of very specific strategies for doing these things. And the interesting thing is that it was put out at a time when, as most listeners know, Joe Biden, the current president, was still the Democratic candidate. Since then, he has stepped down and Kamala Harris got nominated. And Biden was not doing very well in the polls. And the Republicans...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
basically thought they were going to win. And so they put out, they were basically giving red meat to the base, as we say. They were, you know, telling everyone on their side already what awesome things they were going to do in a way that was completely horrifying to people on the other side, the Democrat Party. And, you know, a lot of it is, you know, beetroot is not wrong.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
cosmologists, astronomers, other kinds of scientists, archaeologists, paleontologists, etc., are very good at figuring out quite detailed features of our universe from relatively small amounts of information, of direct observational data. So I think they would get pretty far. Kalan says, I know you are a sports fan from following the podcast.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
A lot of it is both accumulating and then consolidating power in ways that are not very democratic, small d, democratic. So if you actually read the list of policies in Project 2025 to the median American voter, they are horrified. In my mind, the Democratic Party has done an amazingly effective job at publicizing the existence of this policy document. That's a very hard thing to do.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I don't know how they succeeded, honestly, in getting as many people to know what Project 2025 is. That seems to me to be a kind of inside baseball kind of thing. But somehow they have turned it into a target. I think they've turned it into a target pretty effectively. Whether it will work or not, I don't know. But there's a long way to go. I'm not going to make a prediction about the election.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It's going to be close. There's this thing called the Electoral College, which messes everything up. There's a whole bunch of attempts to suppress vote or disenfranchise people in different ways or to mount legal challenges when the votes come in. So we have a long way to go. But I do think that in that particular single aspect of highlighting the dangers of Project 2025 –
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
the Democratic Party has done better than I would have expected. Jacob says, you've often emphasized that curiosity should drive scientific inquiry rather than just practical applications. In your view, which specific area of physics is most likely to yield the next breakthrough that will have significant impact on everyday life?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Well, I'm not going to answer this with the specific answer because I don't have one. I don't know exactly what area of physics it will be. Also, I suspect that if it is, I suspect that what it will be will be an interdisciplinary area of physics. So computational physics or biological physics or something like that. Biological physics in particular, like I don't know what you counted.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
If you learn how to build a robot out of DNA – which is a very plausible thing that people are trying to do right now. Does that count as physics? Maybe, I don't know. It's probably not. But who cares? What matters is the impact it will have. What I can say, the reason why I am answering the question is I do not think that it will be what we call fundamental physics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I do not think that improving our understanding of particle physics and gravity and things like that will have a significant impact on everyday life. the room for significant impacts on everyday life has moved up to the emergent level, the level of biophysics and biology itself. Material science could very well have an impact, certainly building better computers, building better batteries.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
There's all sorts of ways in which physics can have an impact on everyday life, but it's still going to be constructed from the same set of particles and forces that we have known in the core theory for quite a while.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Pauline Guerri says, I've gotten used to thinking of probabilities as subjective, which implies that questions such as, what was the probability the nuclear war would happen in 1962, don't make much sense, even though they're related to coherent questions such as, what did smart people think at the time? My question is, does many worlds change that?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It seems like the proportion of the wave function associated with worlds in which the nuclear war erupted is an objective thing. but are split branches of the wave function a good approximation of all the ways things could have gone? So I see where you're going, but I think that Many Worlds does not change this in any very important way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
However, do you ever feel like your views on eternalism or determinism detract from your enjoyment of sports? Personally, I kind of feel like the excitement isn't there as much if there is some already determined fact of the matter as to who's going to win. Sports is all about competition, but if determinism or eternalism are true, well, the competition is just kind of epistemic.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I think that the much more interesting question, the much more relevant notion of probability is... given what classical macroscopic observers were aware of at the time, what is the best they could do in talking about what the probability would have been? You know, I went to Villanova University as an undergraduate.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And while I was there, Villanova beat Georgetown in the NCAA basketball championship game. And they were highly, highly underdogs. They were not favored to win, the Villanova Wildcats. Everyone thought Georgetown would win. And one way this has been stated is if they played that game again 10 times, Georgetown would have won 9 times out of 10 or 99 times out of 100. I think those are subjective.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It's hard to exactly measure things like that and call them probabilities in any objective way. But they're real and relevant and important. And I think quantum mechanics has nothing to do with it. It's very, very— I don't know this for sure, but it's very, very possible that given the classical configuration of the world that eventually led Villanova to beating Georgetown—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So there is quantum uncertainty there, and there are going to be branches of the wave function in which Georgetown wins, but those branches might typically have weights of something like 10 to the minus 20 or something like that. It's not going to be anywhere close to what you normally think of as your probability arising just from good old classical uncertainty.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So it's not a good enough approximation to all the ways things could have gone in the sense you're asking. Now I'm going to group some questions together. Connor Kostick says, I enjoyed listening to you and David Wallace discuss Schrodinger's cat. And it seemed to me that the approach articulated in your conversation would also address the apparent conundrums of the two-slit experiment.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Is that right? Then Tejas Damania says... Thank you very much. And finally, Luke Gendrow says, it seems to me that a lot of the fundamental mysteries we're still confronted with are related to the uncertainty principle in some way, or at the very least it comes up a lot when talking about them. Are there any legitimate theoretical attempts to refute or abandon the uncertainty principle?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And if so, could you give some idea of their flavor? If not, could you describe why the proof is strong enough for there not to be? So these sound like different questions. I do get it, okay? Connor is asking about the double slit experiment and conundrums there. Tejas is asking about quantum computers thought of from the many worlds perspective, and Luke is asking about the uncertainty principle.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But the reason why I'm grouping them together is I kind of am tempted to give a similar kind of answer to all of them, which is that there are mysteries and then there are mysteries. And this is something that is very important when talking about quantum mechanics in particular, because we motivate...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Sure, I don't know who's going to win, and neither do the players, but it's not up for grabs, so to speak." I guess this is just a psychological difference. I have zero feeling that if the future of the universe is determined, which of course it's not because there's quantum mechanics, but if it's fairly determined, then I should have less enjoyment about sports.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
thinking about quantum mechanics by talking about mysteries, by talking about puzzles or paradoxes or things like that. But then, you know, is the electron a wave or a particle, right? Things like this, questions that seem difficult to answer because you can say here is the argument, you should think of it as a particle. Here's the argument, you should think of it as a wave.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But sometimes we then figure out the answer to those puzzles and we know what the answer is, okay? So These are all cases in which I would argue we know the answers. These are not actual existing mysteries that we need to keep banging our heads against. Sometimes we answer questions. So Connor asks about the apparent conundrums of the double slit experiment. Those are...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
We know what the answers are to those apparent conundrums. It's a motivation for taking quantum mechanics seriously, but quantum mechanics gives completely unambiguous predictions for what happens in the double slit experiment. The only conundrum is there is no classical way of explaining what you see. But there's absolutely a quantum mechanical way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You can do it in many worlds perfectly well, but you can also do it in Bohmian mechanics, or for that matter, in the Copenhagen interpretation of quantum mechanics. You get the same answers for what you observe in the double-slit experiment. So straightforwardly, yes, the approach we articulated does address the apparent conundrums of the double-slit experiment, but don't
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
think that people are worried about the double slit experiment. It's again, just a motivation to take quantum mechanics seriously, not an ongoing puzzle within quantum mechanics. Tejas asked about what is, what is happening in a Hadamard gate when it's putting a bit in a superposition. you know, the many worlds perspective on this is that you should think about putting a bit in a superposition.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You should think about the quantum state, the wave function or the vector in Hilbert space or whatever you want to call it. And the quantum computer is not a reality selector. The quantum computers as an example of a physical system which obeys the Schrodinger equation, again, in the many worlds version of things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And because many worlds is really just saying that there are quantum states that obey the Schrodinger equation. So quantum computers are no different than that. At the end of the quantum computation, which is just again a vector evolving according to the Schrodinger equation, you measure it. And that measurement in the many worlds language is described by decoherence.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You bring the output of the quantum computation into entanglement with its environment and you branch the wave function to different places where you got different answers. So again, there's no mystery there once you accept some particular version of quantum mechanics. Likewise, finally, for Luke's question with the uncertainty principle.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It's true that back in 1927, people were worried about the implications of the uncertainty principle, but they quickly realized that those implications were true. All versions of quantum mechanics have the uncertainty principle as a bedrock feature of it. The uncertainty principle is not an axiom or an assumption, it's a theorem that you derive from the axioms of quantum theory.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So today, most people, certainly anyone who believes many worlds or Bohmian mechanics or etc., accepts the uncertainty principle as just true. It's not really very problematic, right? Now, of course, it's possible that quantum mechanics is wrong, but that's hard to imagine.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Plenty of people from Einstein since have been trying to come up with better theories than quantum mechanics, but none of them have succeeded yet. So I think we just should accept the uncertainty principle. John Eastman says, you say that the doomsday argument fails.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
The doomsday argument, for those who want to, who haven't heard of it, is an argument that doomsday for the human race is not that far off in the future, in some way of measuring, based on statistics and the fact that the past of the human race is not that far in the past, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I mean, this goes hand in hand with my compatibilist views on free will, compatibilism between determinism and the existence of free will. To me the existence of free will is an epistemic matter, right? None of us is Laplace's demon, you may have heard me say before. And therefore we go through life not knowing what the future is going to hold. And that's fine.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It would be unlikely to find ourselves in the first 10 to the minus 5 of the whole history of the universe, of the whole history of humanity, right? or even 10 to the minus 3 of the whole history of humanity. So therefore, probably, the whole history of humanity is not stretched into the future very far. That's the doomsday argument.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So you say the doomsday argument fails because you are not typical, but consider the chronological list of the n humans who will ever live. Almost all the humans have fractional position encoded by an algorithm of size log2n bits. This implies their fractional position has a uniform probability density function on the interval 0 to 1, so the doomsday argument proceeds.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Surely it is likely that you are one of those humans. No, I can't agree with any of this, really, to be honest. I mean, sure, you can encode the fractional position with a certain... string of a certain length, n, okay, great. Sorry, the log2 n is the length of the string. Yes, that is true. There's absolutely no justification to go from that to a uniform probability density function.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
In fact, I am absolutely sure that I am not randomly selected from a uniform probability distribution on the set of all human beings who ever existed. Because most of those human beings don't have the first name Sean, right? There you go. I am atypical in this ensemble. But where did this probability distribution purportedly come from? And why does it get set on human beings, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Why not living creatures? Or why not people with an IQ above a certain or below a certain threshold? Or why not people in technologically advanced societies? You get wildly different answers, right? If you depend—if you put— different, if you have different, what are they called, reference classes for the set of people in which you are purportedly typical. Multi-celled organisms, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You know, so that's why it's pretty easy to see that this kind of argument can't be universally correct, because there's just no good way to decide the reference class. People try. Nick Bostrom, former Mindscape guest, has put a lot of work into this, wrote a book on it, and we talked about it in our conversation, but I find all the efforts to put that distribution on completely unsatisfying.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
The one possible counterexample would be—possible counterexample—would be if we were somehow in equilibrium, right? If somehow there was some feature of humanity where every generation was more or less indistinguishable from the previous generation. Then within that equilibrium era, if there was a finite number of people, you might have some justification for choosing that as your reference class.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But we are clearly not in equilibrium. Things are changing around us very, very rapidly. So no era in modern human history is the same as the next era. No generation is the same. There's no reason to treat them similarly in some typicality calculation. Artem Vorostov says, I was listening to your lovely podcast with Philip Goff, and the following question emerged in my mind.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Do you believe that consciousness could emerge in a purely Newtonian world? In other words, is quantum mechanics and or general relativity essential for such emergence? Consciousness can be an essential component of quantum mechanics with known or inconceivable laws of evolving, and its role can be to choose the branch in the linear combination of Newtonian on big scales branches.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
That's actually an important part of what makes the universe interesting. I think that I mean, think about it this way. Imagine that you were betting on something trivial like the outcomes of coin tosses, OK? Just for fun, you and your friends were tossing coins and betting on the outcomes. And imagine, for the sake of a thought experiment, that you found that interesting.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So again, I do not know what consciousness is or what it requires. I see absolutely zero reason why it couldn't emerge in a purely Newtonian world. It's true that things happen in our brains that are fundamentally stochastic because of the rules of quantum mechanics. But there's very little that happens in your brain that actually depends on a single quantum mechanical event, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Maybe you can come up with one, but most things are big and squishy and biological and therefore described pretty well by classical mechanics. So in some sense, consciousness does emerge in a purely Newtonian world, not 100%. But I think that that is completely plausible. So I'm happy to be surprised by this, by future research, but I see no reason right now.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Steve Welton says, I enjoyed your podcast with David Goyer and I'm a big fan of the Foundation series and the novels by Isaac Asimov. In his books, Asimov describes the laws of robotics, which are intended to protect humans and humanity, which are hardwired into the positronic brains of the androids. Do you have any thoughts on the future serious applications of these or similar laws?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I'm a little surprised there isn't more discussion about the subject in the mainstream other than predictions on the likelihood of AI doom. For fun, what would you suggest for the top three to four laws if we were on the verge of creating sentient androids?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Well, I will just note that if you read, if any of you out there have read The Robot Stories by Asimov, he proposes the three laws of robotics. I'm not going to remember the three laws. Sorry about that. But it's, you know, don't allow humans to come to harm unless, or don't allow harm to come to yourself unless it would allow humans to come to harm, those kinds of things. It's trying to
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Be fail-safes, be preventative from the robots doing bad things. Let them do as many good things as they can without doing any bad things. But every story in the robot series of stories is about the laws failing, is about pressure being put on the first law versus the second law and them being incompatible and things like that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And I think that that's not just dramatically interesting, but kind of a feature of this kind of attempt to be too general. I think that if we're actually going to have... Well, I should say... There's been a lot of discussion of this kind of thing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I don't think that Asimov's laws per se are a central feature in these discussions, but there's been a lot of discussion about how to make AI and robots ethical or how to make their values align. It's Google alignment problem in AI, and that's what this exactly refers to. But I suspect that the right way to do it is going to be much more specific than general. You know, when...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
you know, if you try to have a law in a robot brain that says, you know, make human beings happy, then you run the risk that they will, you know, strap humans down to tables and give them drugs that will make them happy. And that's not the intended consequence that you want. And I think that the solution to that is don't give such vague open-ended instructions to the robots.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Be very, very specific about what you want them to do. So I therefore— have to apologize, they do not have the top three or four laws that we should give to sentient androids. Chris Gunter says, suppose you were advising Marvel on a new storyline regarding Magneto, the master of electromagnetism, and he wanted to expand his electromagnetic powers in a novel way that sounds physics-y.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Now, instead of that, say that someone tossed a coin out of your view and wrote down, recorded the outcomes, and then you revealed the outcomes one at a time, and you bet on that, right? In one case, the event hasn't happened yet, but you don't know, and you don't know what the outcome is going to be. In the other... case, the event has happened yet, but you don't know. To me, it's identical.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
What would you suggest? So again, I'm not going to give a perfect answer to this, or at least a straightforward answer. I will tell you my thoughts about Magneto, which was that Originally, I was never a big X-Men guy when I was in my comic reading days as a youngster. My comics were Green Lantern, Doctor Strange, and Thor. Those are my favorites. Occasionally, the Fantastic Four, I suppose.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But I knew about the X-Men. There were just too many X-Men, and they kept changing who was in the team and what they could do, so I never really got into it. But Magneto was famously one of the antagonists, and in the films, he's been a big part of it. And his power is manipulating, as Chris says, electromagnetism.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And when I was a kid, I thought that was a lame power, especially if it's just magnetism. Like there aren't that many magnets out there, right? But of course, if it's electromagnetism, which really it is supposed to be, then that turns out to be super powerful. And in the movies, you know, anytime there's metal, Basically, Magneto can do whatever he wants with metal.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So you have to – if you're trying to imprison him, he has to be in plastic or glass or something like that. But the truth is that once you've expanded his powers to be electromagnetic – any manipulation of electromagnetic fields – That's basically anything.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
He's basically omnipotent almost at the human scale because everything that happens in chemistry and biology is mediated by electromagnetic fields. The very stability of matter is mediated by electromagnetic fields. Not an individual, I mean, individual atoms have structure because of the Pauli exclusion principle a little bit,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But the size of the orbitals of the electrons in the atoms is entirely determined by electromagnetism. Certainly all the bonds of different atoms into molecules is determined by electromagnetism. So the idea that you could actually imprison Magneto in a plastic or glass cage is ridiculous. He could just make any matter made of atoms and molecules dissolve as soon as he wanted to.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
He could instantly kill any human being if he wanted to, or even more interestingly, he could make human beings think different thoughts by changing the neurons firing in their brains, right? So you don't have to go very far to imagine that if Magneto were anywhere near realistic, he'd be far and away the most powerful antagonist you could imagine having.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Henry Jacob says, when you coarse grain a system, it seems analogous to block diagonalizing a matrix into a macro scale and micro scale component. This would mean the system is actually the product of two systems. However, most of the coarse grainings I've seen, e.g. in thermodynamics, are not of this form. It seems like we are simply ignoring the off-diagonal terms. Am I right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And if so, is there a penalty? Well, I'm not exactly sure what the matrix is that you have in mind. I think that the way to put it – again, I'm not sure that I'm going to be addressing your concern here, but – If you have a matrix, so again, for the non-mathy people out there, this is an array of numbers. Let's say it's a square matrix. So it's n by n numbers.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And these matrices appear in physics all the time. The metric tensor in general relativity is a matrix. The Hamiltonian or any other operator in quantum mechanics is also a matrix.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And if you have a form where near the diagonal of the matrix you have a lot of non-zero entries, and away from the diagonal the entries are all zero, then that gives you an enormous simplification over what the matrix is trying to do. So... Anyway, to get what I was saying, that is a form of coarse graining, but it is certainly not the only form.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It doesn't actually change my enjoyment of the situation whatsoever. You know, when the NBA, the National Basketball Association, does its lottery for which teams get to pick first in the upcoming draft, they do all of the actual lottery choosing ahead of time, and they put the answers in envelopes, and all you're watching on the TV screen is them being revealed.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
In the case of thermodynamics, for example, I don't know what matrix it would be that you are coarse graining. I'm not exactly sure what you have in mind. But it is absolutely true that when you want to coarse grain in a useful way to move away from the matrix language and just think more physically, You want to do two things.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Number one, you want to coarse grain so that the – so coarse graining just means you're throwing away information. Rather than having – keeping track of every single atom in a system, you just have some macroscopic features like pressure and temperature and density and things like that. That's a coarse graining.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So you map the microstates that have all the molecules and atoms and what they're doing – to macro states where you only have incomplete information. That's what coarse graining means. And you want that to be useful in some way, which means, number one, that the coarse grained system has its own dynamics, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
That you can predict what it will do next, at least to a certain approximation, based on the information that is left after you've done the coarse graining. But number two, it sort of plays nicely with other coarse-grained systems. So a baseball is a coarse-grained system. A bat is a coarse-grained system.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And you can tell by giving me the behavior of the bat and the behavior of the baseball what's going to happen to the system, right? So there's enough predictive power in the interactions that you have interesting non-trivial dynamics there.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
If you coarse grain badly, then you might have, rather than a baseball and a bat, you might have like the top half of the baseball and the top half of the bat and call that a single subsystem. There's no useful dynamics for that system, right? Like Daniel Dennett talks about this in his real patterns idea, if you go back to the We did the podcast with Dan and we talked about real patterns.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It makes a difference how you choose to throw away information and how you choose to keep it. So it's not like we're just ignoring things willy-nilly. We're ignoring things that empirically don't need to be kept to do the job that we want to do. Matthew Wright says, in your interview with Doris Tsao, at one point you said, I'm going to go off script here.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I presume that was mostly a figure of speech, but it got me wondering about the extent to which the podcasts are scripted. Do you plan out most of your questions in advance and do the guests know more or less what you'll be asking them or is it more off the cuff? It's basically in between that. I certainly don't plan out questions in advance, but I do have a few talking points that I want to hit.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I mean, most of these guests have done work. I think all of them have done work that I think is interesting to talk about. And so I try my best to have some understanding of what work they've done. And the big worry is that the guest has something really interesting to say, and I don't ask a question that lets them say it. You know, that's what you want to avoid. So you don't want to be a lecture.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I certainly never tell them ahead of time what questions I'm going to ask because I don't know, but I don't even give them, like, an outline or anything like that. I might say, like, okay, you have a book coming out. We're going to talk about that. But no more than that. So you're right.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And when I said going to go off script here, that was more or less to mean I'm going to go off the whole topic I thought we were talking about, right? You know, for Doris, you know, the topic was – starting with the visual cortex and moving our way up to bigger questions about consciousness.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
but it is just as exciting to me as if they were somehow conjuring that number in real time. Okay, I'm going to group a few questions together, which we do sometimes. Andy Chaumont says, we've been observing the cosmos for less than 100,000 years.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But, you know, there's a lot of other topics that we could have talked about, and we ended up talking about some of them. You know, I do think that if I critique my own abilities as a podcaster and an interviewer, I could be better at letting the conversation wander around to places where I didn't anticipate ahead of time. I'm a So I keep trying to become better at that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But then, again, the problem with letting the conversation wander, you might end up in an interesting place, but you might then leave out things you know are interesting that the guest has to say. So I actually do need enough structure to be able to say what I think is their most interesting stuff. Brian Rahm asks a priority question.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
In a podcast earlier this year, you offered a moving appreciation of both the writing and the science of the great sci-fi author, Werner Wenge, who, by the way, I think I mispronounced his name back then. Maybe I'm still mispronouncing it. Sorry about that. Who had just recently passed away.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
My initial request is for you to expand on those brief comments of the art and science that have contributed to his legend. You could also invite someone who knew and worked closely with him. And speaking for myself and his legions of other super fans, now bereft in the certain knowledge that the fate of mankind, in the Unfinished Zones of Thought series will forever remain unknown.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Maybe you can find a guest who might know something of his plans for the series' conclusions. So I'm going to be very, very disappointing here in my answer to this priority question. I don't know that much about Werner Wenge's work. I've read one book by him. I talked about that in a podcast earlier this year when we were talking about the singularity and phase transitions and so forth.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But my knowledge otherwise is very superficial. So I am not the one to expand on those comments. I basically gave you all the comments that I could. I appreciate his work very, very much. He was a thoughtful guy, clearly, who was one of the science fiction authors who sort of –
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
The job of science fiction is not to predict the future, but there is a variety of good science fiction which tries to take very seriously what the future could be. You know, there's all sorts of good science fiction, like Star Wars is perfectly good science fiction, but it's not trying to be in any sense telling you what the future is going to be like. It's basically...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
some kind of combination of a Western and a Roman gladiator epic moved to outer space, right? It's not trying to envision the implications of any major change in technology or society. But Vinge's work and other people's work is much like that, you know, really thinking through the implications of coming changes.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Although we've made tremendous progress in the last 500 years in terms of understanding the nature of the universe, how can we actually trust our observations? What if our attempts to understand reality are like ants attempting to understand Seinfeld? Paul Turek says,
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And so, again, not to predict that this is going to be what it's like, but to let us anticipate what the possibilities are. And I think that's super important. So he was one of the greatest at that. Let me just say that. That's probably the best I can do. Ken Wolfe says...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Years ago, I read a book by George Lakoff and Rafael Nunez called Where Mathematics Comes From, How the Embodied Mind Brings Mathematics Into Being. They had an interesting take on Euler's identity, where E, the natural logarithm, raised to the power of I, the square root of minus 1, times pi plus one equals zero.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
They seem to more or less reject the idea that there's anything really profound about this identity. Instead, it was simply a function of the way we plot the imaginary component of complex numbers as the y-axis on the same graph paper we use for Euclidean geometry. Are they onto something? Are they missing something? Are they onto something and missing something?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I think they're missing something, honestly. Or maybe, to be more generous, they are both onto something and missing something. You know, it reminds me a little bit, because we were just talking about the uncertainty principle, of the following claim that you will hear, and I think maybe in my youth I even made this claim myself. The uncertainty principle is completely trivial.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It's just a feature of Fourier transforms. Yeah. It's just a restatement of the fact that the axes of the momentum basis are at 45 degrees to the axes of the position basis. Okay. Those are all true statements. Even if those statements are meaningless to you, the audience member, those are true mathematical statements.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But it is absolutely untrue that the uncertainty principle is somehow a triviality. The derivation of the uncertainty principle is a triviality once you have set up an enormous amount of work to understand what position and momentum are.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
from the quantum mechanical viewpoint, that there are certain kind of sets of operators, that they're canonically conjugate to each other, blah, blah, blah, blah, blah, on a vector space rather than simply coordinates on phase space as they are in classical mechanics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So it's an absolutely profound change of perspective that once you make that change of perspective, this particular mathematical result is kind of trivial, okay? So it's that kind of thing. e to the i pi is minus one. Is trivial once you understand what all those symbols mean. But really, you know, you're inventing trigonometry.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You know, there's a lot of things like what a cosine and a sine are that go into that kind of identity. How there is a natural way of coordinate-izing the set of complex numbers using trigonometry is, you know, highly non-trivial. But then once you do it, once you set it up, then it's all trivial, right? So that's the sense in which they're both onto something and missing something.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
The end result, given all the groundwork that you've laid, is very trivial. But all that groundwork is highly non-trivial. Kilngod says, here is my odd thought that could explain dark matter in the cosmological constant. We know vacuum energy is created from virtual particles. What if creating virtual particles also results in antigravitons? Well, there's no such thing as an antigraviton.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
That's just not a thing that exists, just like there's no such thing as antiphotons. I know that physicists sometimes say for every particle there's an antiparticle, but that's just kind of not true, at least not in the usual way of thinking about antiparticles.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
There's two different kinds of gravitons, just like there's two different kinds of photons, one that are helicity plus one and helicity minus one. Same thing is true for gravitons, so different spins of the gravitons, but they're not in any sense antiparticles to each other. It's generally speaking charged particles that have antiparticles.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
If you have a charge minus one particle like the electron, you're guaranteed to have a charge plus one particle antiparticle like the positron. But particles like gravitons and photons carry no conserved quantities that could be negative, so they don't really have antiparticles. Jeff Babon says, it's been very interesting listening to your views on entropy and the heat depth of the universe.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I'm a biochemist and so run experiments every day where local entropy decreases, whether it's growing bacteria, synthesizing DNA, or translating proteins. This is fine because they are not closed systems and all of those processes require an input of external energy. My question is about dark energy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
If it's constantly adding energy to the universe, does that mean the universe is not a closed system? And is it conceivable that it could be harnessed to decrease local entropy in a region of space forever? So a couple things going on here. One is that you gotta be careful about entropy versus energy, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
The universe could very well be a closed system and still have dark energy becoming more and more over time. I wrote a blog post once then you can look up Google energy is not conserved. And you will find my blog post explaining that there's this particular example of a way of defining energy, which is take the energy density per cubic centimeter and multiply it by the number of cubic centimeters.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And that gives you a number that is not conserved in cosmology. That's not because dark energy is weird. It's not conserved if your universe has nothing in it but photons also. Every photon loses energy as space expands. What's really going on is that there's an interplay between the energy of the stuff, the photons or the dark energy or whatever, and the curvature of space-time.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And that interplay is a little subtle. There's just as many rules in cosmology as there is in a flat space-time where there is energy conservation, but the rule is a slightly different rule than you thought it was. So the universe can be closed even with dark energy, and none of that has anything to do with entropy, except very indirectly. The entropy of the universe is increasing
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And Gary Miller says, at the end of your conversation with Doris Tsao, you each suggested you agreed on the emergent nature of consciousness in complex systems, but she seemed to feel that subjectiveness is necessarily a fundamental feature of reality. We'd love to hear more on your take on that. Does a conscious experience require subjectiveness as a feature of nature?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
That's the law, the second law of thermodynamics. But how it increases depends on details, and the existence of dark energy is an important detail. And the specific detail is that the future of the universe will be empty space with nothing in it but the cosmological constant, if the dark energy is the cosmological constant, which, as I've said, I think it probably is.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Scott asks a question where he says, I've been reading about the possibility of electroweak vacuum decay. If a vacuum decay were to happen inside a black hole, would the expanding bubble be contained by the black hole? Are vacuum decays more likely to happen inside a black hole due to the high energy densities?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So the idea here is that you may have heard that there's something called the Higgs boson. The Higgs boson is the particle which is an excitation in a field, the Higgs field. And the thing about the Higgs field that is different than all the other fields that we know for sure exist in the universe is that it has a non-zero vacuum expectation value.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So what that means is the Higgs field, when you have a field, like the electromagnetic field or the electron field or the quark field or whatever, It is natural to imagine that the lowest energy state is when the value of the field is zero. And that's typically true, but it's not true for the Higgs.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
For the Higgs field, the Higgs field could be zero, but that is a higher energy state than the Higgs field living at some large value, which is what it actually has. The Higgs field plays this important role in the electroweak theory, in the unification of electricity and magnetism with the weak nuclear force.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So it is possible that the value that the Higgs field has, even though it is lower energy density than it would at zero, is still not the lowest energy density that it could have. If that's true, it opens up the possibility of vacuum decay. There could be a little bubble, a very, very, very, very tiny bubble where the Higgs field takes on a much larger value than it currently has.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But once it does that, it is lower energy than the Higgs field in the world in which we live in. So the universe likes lower energy. So that bubble, if it ever forms, would grow at a tremendously fast rate, basically the speed of light or very close to the speed of light. And if this happens all over the place, it would wipe out our universe, basically speaking.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
All of the laws of physics would change. We would all die. And we would not even see it coming. It would just happen almost instantaneously. So the question is from Scott, could this happen inside a black hole? And would the expanding bubble be contained by the black hole? Yes and yes. It could happen. Would it happen more? Is it more likely to happen?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I think that depends on details that I don't really know that- that are not known, let's put it that way, but it's possible that it's more likely to happen, but it would stay inside the black hole. If you think about black holes from a sophisticated point of view, what is a black hole? A black hole is a region of space-time from which nothing can escape because of the speed of light.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So all of these, these are very loosely grouped. I didn't need to group them, but I wanted to sort of comment on the commonality of trying to understand what consciousness is and And I'm always very quick to say I do not understand what consciousness is. Not that it is un-understandable, but it is hard to understand.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You would have to move faster than the speed of light to escape from the black hole. The bubble of true vacuum that is nucleated in this electric weak vacuum decay scenario expands at a certain velocity relative to some reference frame, and that velocity is constrained by the speed of light. The bubble cannot grow faster than the speed of light. Therefore, the bubble cannot escape the black hole.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
This is actually pretty clear if you have read... Space, time, and motion, my first installment in the Biggest Ideas in the Universe series, where you have pictures of what it looks like inside a black hole, the space-time diagram, where the singularity is in the future.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And if you have a little bubble that is confined to the interior of its light cone, its future light cone will hit that singularity everywhere. There's nowhere where we'll escape to the outside world. So don't worry. And worry about black holes all you want, but don't worry that they're going to nucleate electroweak vacuum decay. Okay, I'm going to group a couple of questions together.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Tim Giannitsos says, great conversation with Doris Tsao about consciousness. You mentioned that you can tell if something is conscious because of how it behaves, i.e. they are aware of certain things, update mental states, etc., And Rue Phillips says, Yeah. So again, I'm going to try to emphasize here, I don't know the answer to questions like this.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I don't even pretend to have a vague theory about questions like this. I do think that consciousness is likely to be a bit of a spectrum rather than a sharp phase transition. There can be sharp phase transitions in nature, and so I could be wrong about that. There could be some You know, let's put it this way.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
In the theory of random graphs, okay, a random graph is you have some dots which are going to be nodes, and then you randomly assign edges between some of the nodes and not other nodes. And there are, as you get very, very large numbers of nodes, and you increase the number of edges between them, there's a phase transition that happens in the percolation phase transition.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
For a small number of edges, the components are mostly disconnected, right? You've connected two nodes together, but they remain disconnected from everything else, probably. And for a large enough number of edges, it will be the case that almost all nodes are connected together, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
For some fixed number of nodes, as you increase the number of edges, there's that kind of percolation phase transition. So maybe something like that is responsible or necessary for consciousness. I'm just throwing it out there as an example because I don't think it's true.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I think that it's probably more likely that you gradually develop the capacities, which when they're fully developed, we recognize as consciousness.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It is a thing that we scientists are still working on, and it is not my area of expertise. So you shouldn't trust anything that I have to say. about consciousness. Having said that, I can give you my completely uneducated or mildly educated opinions about it. And these questions are about, you know, what if there is higher levels of consciousness, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I don't even want to give the impression that, you know, Tim says that I said, and as you know from longtime listeners know, I can't remember what I said in most of these podcast conversations, that you can tell something is conscious because of how it behaves. I'm not at all claiming that that's necessarily the case. In practice, I think that you can—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
pretty clearly delineate certain conscious things from certain unconscious things by doing that, but there could also be edge cases, difficult cases, counterexamples, so forth, anything like that. So I don't really know whether anything intricate enough to exhibit those behaviors is conscious, nor do I know what the fundamental requirements are. Sorry about that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
JC says, what went on with the wild cat you were feeding? Still around. So yes, good timing to ask this question. The wild cat is Puck. Puck visited us on our back porch and we sort of adopted him or her or them. Puck might be non-binary for all purposes. We don't know whether Puck is a boy or a girl. But it was almost a year ago that Puck started hanging out and we've been very...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
We've been very dedicated to making life comfortable for Puck. But what we didn't do, what we knew we had to do was take Puck to the vet to get shots, maybe to get spayed or neutered or whatever. You don't want more stray cats out there than you need. That's for sure. So there's a certain responsibility there. that we take on because we're taking care of Puck.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And part of that is you got to take Puck to the vet. And the downside was, you know, you have to trap Puck. Puck doesn't want to go to the vet. Puck doesn't know what it means. You cannot use symbolic language and explain to the kitty that this is for their own good, even though It's something new and scary. So you have to trap the kitty, which we did.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
We bought a little trap and we were worried that Puck was too smart to fall for the trap. No need to worry about that. It was actually pretty easy to trap Puck. But as I speak, as I'm recording this, Puck is in the room next to me in a little bathroom. chilling until we take them to the vet tomorrow to get examined. And then once that happens, we will release Puck back out into the wild.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I mean, Puck is clearly not going to be a happy cat if they're confined inside, so We'll keep it with a sort of hybrid indoor-outdoor lifestyle. I mean, hopefully, as time goes on, Puck will be more and more acclimated to us. But the worry, I started saying the worry is, the worry is Puck doesn't like us anymore, right? Because we trapped Puck and are taking them to the big bad vet.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So hopefully that's not true. We're trying to be very nice, giving Puck all the treats and saying that Puck is a pretty little kitty. So we'll see how that goes.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Kevin's Disobedience says, if we've understood quantum mechanics perfectly, do you think it would be ideal to teach quantum mechanics before classical mechanics and then have second-year students derive simple macroscopic systems from quantum field theory, or will it always be better to work backwards and quantize our intuitions?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Good question, perfectly legit question, but I think that it will always be better to quantize our intuitions for the following reason. It's a question of emergence, right? There is a of quantum mechanics that looks like classical mechanics. Quantum mechanics is a broader, wider range of applicability than classical mechanics does.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
What if there is something even beyond consciousness that we don't have yet and that we're just completely clueless about. So Andy says, you know, what about, what if our attempts to understand reality are like ants attempting to understand Seinfeld? And Paul says, what about an AGI that has this higher level of consciousness? I don't think that that's a thing.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Any system that can be described classically could also be described quantum mechanically. But... there are some systems that you don't need quantum mechanics to talk about. I'm emphasizing this because it gets fuzzy sometimes. Sometimes you get the impression for big things, they obey the rules of classical mechanics. For small things, they obey the rules of quantum mechanics.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Everything obeys the rules of quantum mechanics. It's just that for small things, you need... to use quantum mechanics, whereas for large things you have the option of using classical mechanics. And classical mechanics is in many ways much easier. I can describe a single particle or an object, a particle-like object, just using a couple numbers, right? Position and velocity.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Whereas a quantum mechanical object needs a wave function, so in principle an infinite number of numbers. Furthermore, the specific realm in which classical mechanics applies to the world is the realm of our everyday experience. It is much more intuitive, much more easily graspable.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So there's no reason not to point to classical mechanics and teach that first and then generalize it later to quantum mechanics. I think that's a very natural thing to do.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Otherwise, you know, if you didn't think that was true, then rather than teaching math in usual ways, you would start with category theory or some other very highly abstract logical theory and derive all of the implications in logical order. But that's not necessarily the best pedagogical strategy.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Schleyer says, is it fair to think of complexity in the universe as having increased in a relatively small number of steps? Specifically, for like 10 billion years, there were just clumps of stuff, and then suddenly there was life. Then 3 billion years later, suddenly there was complex life.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Is it wrong to think of these things as the most meaningful increases in the complexity of the universe that we know of? Yeah, I think that's basically right. I mean, at least let's put it this way. That is basically my view. So I've been thinking about the process of complexogenesis, how complexity comes to be in the universe. And I absolutely do think that it's a series of phase transitions.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And I even think that, and this I'm much more tentative about, but I think that tentatively, those phase transitions can be thought of as more and more sophisticated uses of information. You know, there's a way of thinking about information, a physicist's way of thinking about information, such that low entropy systems contain a lot of information.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
They contain a lot of information in the sense that you know a lot about the system if it's low entropy and you know it's macrostate because there's not that many microstates it could be in. If you have a high entropy system, there's many, many microstates that look that way, so you have less information about it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And as the universe expands and entropy grows, you're basically using up that resource that you had in the low entropy past, and you're able along the way to use that information in more and more specific ways. First, just to sort of locate yourself in the universe. You know, here's a star or a planet, there's not. But then you can find food in the universe, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
That's a more sophisticated use of information. And then you can sort of start thinking about things. That's a yet more sophisticated use of information. So that's a vague picture. And sort of firming that up is something that I'm trying to think about how to do in a quantitative way. Tariq says, my question is related to the matter-antimatter asymmetry.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Matter-antimatter should have been created in equal quantities in the early universe, and the assumption is that unless there was an asymmetry in that process that led to matter dominating, everything should have just annihilated.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Were the matter-antimatter particles created in the early universe the same type of particles we see today, or was it a special type of particle, antiparticle, that decayed into the conventional particles we know of?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Why is it that if matter and antimatter particles were created in the quantities that would have been present in the early universe, that they couldn't have interacted in chaotic ways, even if they were created in equal quantities, such that we could have regions dominated by matter and regions dominated by antimatter, but separated by vast regions of empty space where most everything did annihilate?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I do not think that there are higher levels. I do believe completely that there's a possibility of better consciousness, being more conscious or, you know, being more aware of things, certainly being more rational, being better able to think about the world. That's completely 100% plausible to me. But I do think that there's a phase transition.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Well... There's a couple questions in there. You're cheating, Tariq, because you're supposed to only ask one question, but that's okay. We'll sort of group them together. You know, we don't know what the particles were in the early universe.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
They might be exactly the particles that we know and love today, but there's plenty of theories according to which, you know, theories of unification and so forth, according to which the fundamental fields of the world were rearranged into different groupings in the early universe that we would recognize now as different particles.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
or that there were other fields that are just too massive and unstable for us to notice now, but played an important role in the early universe. So we don't know any of these things. Even the claim that there should have been equal amounts of matter and antimatter, I don't know if that's true or not. I don't know who decides what should have been true in the early universe.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It's a simple, obvious starting point, but we don't know for sure that it's right. I think that there are arguments in the standard model of particle physics. Here's a slightly not well-advertised fact.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
In the standard model of particle physics, we've never experimentally seen violation of what we call baryon number, the number of baryons, which is basically the number of quarks minus the number of antiquarks, right? Quarks never turn into antiquarks or vice versa, or they don't even turn into non-quarks as far as we know.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But the standard model predicts that there should be baryon number-violating transitions. They're called sphalerons, and you can look them up. But they're supposed to be so very, very rare in the current universe that you would never notice them. But maybe they were frequent in the early universe. And so even if that's true, even if you started with unequal numbers of baryons and antibaryons—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
they would have equilibrated. They would go back and forth and end up with roughly the same numbers. There's loopholes to that argument, so don't take it too seriously, but there's various arguments that indeed it would have been natural, let's put it that way, from our current perspective to have equal numbers of particles and antiparticles. So today we don't.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
We have more particles than antiparticles. One of the schemes for generating that asymmetry is indeed something like you outline. There's something called leptogenesis, which arises from production of a certain kind of neutrino more than its antiparticle. And then those massive neutrinos, like super heavy neutrinos, which then decay.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
These leptons, neutrinos, decay into particles and antiparticles asymmetrically, and then the standard model processes turn some of those leptons into baryons. Maybe that's what happened, but we honestly don't know. It's a puzzling thing because, you know, when I was a starting out cosmologist, 80s and 90s, a lot of people were thinking about baryogenesis, and it's tantalizingly close to
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
to the kind of work that is experimentally testable, right? I mean, it's not, you know, weird multiple universes or anything like that. You're messing with the standard model of particle physics or nearby phenomena and asking what happens. But I think people sort of have lost a little bit of interest just because it turns out to be harder to connect it to observations than people thought.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So we don't know is the short answer for why there is that asymmetry. Your specific scenario about sort of chaotic interactions I think is just ruled out by the data, right? The data say that the early universe was pretty smooth, roughly similar numbers of particles and antiparticles in every cubic centimeter.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And as I said, even if you started out with different numbers of particles and antiparticles, they would tend to equilibrate in the early enough universe. So as a matter of fact, we look at our universe today, like look at the cosmic microwave background, there's no big empty regions, which would separate regions of matter and antimatter.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
There's a threshold that we pass when we enter into a world of subjectivity and self-awareness And some things don't have that and some things do. It's not a sharp transition. You can get more and more of it. But I don't think that there are layers to it. I think it's there or it's not there, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
All the matter, all the particles and antiparticles that existed back then were bumping into each other. So we think that all the other galaxies that we're looking at today are matter. The whole universe that we see is just more matter than antimatter. Brent Meeker says, my friend and I are having an argument about black hole Hawking radiation and Unruh radiation. I'm just glad to hear that.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I think more people should have arguments about this kind of thing. Susskind and Lindsay describe an observer hovering above the event horizon and then refer to his acceleration as creating a Rindler horizon and Unruh radiation, which they then go on to equate with the Hawking radiation of that black hole.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
They then also conclude that if the observer were freely falling into the black hole, he would not observe any radiation. Lindsay writes, a freely falling observer would not detect a horizon or temperature without violating the principle of equivalence.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
This seems wrong to me since it would imply that if he were orbiting the black hole out beyond the near field, then he would see no radiation, yet he must. Hawking radiation is not a subjective experience relative to one accelerated observer, it's a real loss of energy radiated away, whether or not anyone is there to see it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And sufficiently far away, there's no difference between a stationary observer and an orbiting observer, so which view is right? I'm glad you're asking this question. I apologize to the folks listening for whom there's a bit of technicality in there that was hard to follow. I'll try to clear it up.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But I've worried about this question a lot, and I've been recently talking to a graduate student at Harvard, Chris Shalhoub, who has been tackling this question in a very careful, quantitative way. And I think he has an answer, and I think the answer makes sense to me, so I can lay it on you. I don't think I'm giving away any secrets. The idea... Let me just explain the idea of Unruh radiation.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So you probably... Most of you have heard of Hawking radiation. Black holes give off radiation with a black body spectrum with a temperature that you can calculate.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
There's an analogous and much simpler phenomenon called Unruh radiation that Bill Unruh invented after Hawking invented Hawking radiation because Unruh was trying to sort of simplify it down to the most common denominator, which is what physicists like to do. So Unruh pointed out that if you have...
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Flat spacetime, so no black holes, no gravity for that matter, just the vacuum state of flat spacetime, empty space, okay? So if you have a detector sitting there, it would, if you turn it on and let it equilibrate, et cetera, it would not detect any particles. It's in empty space. But now you ask that what happens if you have a detector that is accelerating, right?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
at accelerating at a constant velocity. Don't ask me why it's, sorry, a constant acceleration, I should say. Don't ask me why it's accelerating, maybe it has a rocket engine or whatever, but we assume that whatever is making it accelerate does not actually interfere with the experiment. And the experiment is, you have a detector, you have a particle detector looking for particles.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Now, you're still in empty space, okay? There's no difference in the quantum state of the universe whether your particle detector is stationary or accelerating. But there is a difference, Unruh showed, in what the detector detects. An accelerating detector detects particles in what you thought was empty space.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And that is a feature of the relationship between the particle detector and the quantum vacuum. And you can even, and Unruh does this, you can analogize the fact that the detector is moving at a constant acceleration is kind of like sitting stationary outside a black hole horizon. There is also a horizon called the Rindler horizon for the accelerating observer.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
There's more or less of it, but there's not sort of a series of different discrete transitions that you go through. I could be completely wrong about that. Like I said, this is not something that I have any theorems about or even very highly educated opinions about. But the slight analogy is with actual rationality and computation, where you do have this idea of Turing completeness.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So there's a close mathematical connection there. Indeed, in my general relativity textbook, sort of as a bonus chapter at the end, I talk about quantum field theory in curved spacetime, and I do this example of unruh radiation. It's much simpler than doing Hawking radiation, which is more complicated.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So anyway, there's a rough tension because if you're standing outside the black hole and you look at it, you're supposed to see thermal radiation. If you fall into the black hole, you're supposed to see nothing because you wave your hands about the principle of equivalence or something like that. But there's an expectation you're supposed to see nothing. So what's really going on?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
What happens, roughly speaking, if I'm to vastly oversimplify, is that you don't have enough time to observe Hawking radiation when you're falling into the black hole. When you're falling past the event horizon, think of it this way. We say that when you're far outside, you see Hawking radiation with a certain temperature. But what is that temperature?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Temperatures of radiation are associated with wavelengths of radiation. For any given temperature, there is a wavelength at which most of the radiation is coming out, a typical wavelength for the thermal radiation. For a black hole, the typical wavelength of the thermal radiation is roughly the size of the black hole. It's the Schwarzschild radius of the black hole, roughly speaking.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So very low frequency, long wavelength, photons are coming out. And basically what happens as you fall in, your speed increases. you would imagine that you're seeing these photons to be blue shifted, okay? But really what is going on is that if you have a detector that is sensitive to certain wavelengths, it is sensitive to more and more blue photons.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
But there just aren't that many blue photons, and it's sensitive to blue photons, short wavelength photons, because there's only a short period of time you have before you cross the event horizon. So essentially, your sensitivity window blue shifts away from where the radiation is. And even though there is radiation, you end up not seeing it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So there actually is a consistent story, I think, that you can tell. Chris is still writing his paper, so forgive me if there's elaborations to come on that view. Eugene says computer scientists mostly assume that p is not equal to np, which means that there's a variety of problems for which exponential time is required to compute answers on a Turing machine.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
For quantum algorithms, the equivalent of p is called bqp. You've mentioned that there is some support for the idea that locality is not fundamental in our universe, e.g. from the holographic principle.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
If locality is not fundamental or computation is not bounded by the limitations of gravity, are there implications for the existence of computational engines that do not require exponential time on a wider class of problems? Or is this a nonsense question? No, this is a super good question, Eugene. This is a very, very important question. There's various interesting ways.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Scott Aronson, former Mindscape guest, is literally the world's expert on this kind of thing. But there's various interesting ways in which if you change the laws of physics by a little bit, you have ended up granting yourself powers to answer hard questions faster. Like if you have a time machine, for example, you can answer hard questions faster than you thought you would.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So you have complexity classes in the presence of closed-time light curves. So what you're asking is, do you change complexity classes in the presence of non-locality? And the general answer that you would expect if it's sort of generic non-locality is yes, that you have more power than you thought you would. It's the non-generic cases that matter.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So in holography, for example, in the ADS-CFT correspondence, where you have a boundary theory and a bulk theory, that's holographic. It is non-local. It's non-local because anything that is happening in the bulk is described non-locally on the boundary and vice versa, okay? But nevertheless, if you consider the bulk by itself or the boundary by itself, you have two local theories—
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
You have an idea, going back not that far actually, but to people like Alan Turing, that there are machines that can calculate any function that is calculable. And they have very specific definitions of what you mean by calculable, etc., But it's, again, either there or it's not. Like once you've crossed that threshold, you don't get better and better at it.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So there's a non-local relationship between the two theories, but each theory is perfectly local. So neither theory actually gives you the capacity to do calculations any faster than you thought you would. Nevertheless, maybe there's other kinds of non-localities. Maybe there's something more subtle. Maybe the quantum gravity is actually giving you some other kinds of powers.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I do think that it's probably not an accident that it is so hard to solve NP problems. I should have said this earlier. P versus NP. P are problems that are easy to solve, okay? It only takes polynomial time. That's what the P stands for, which means if you have N inputs, then the difficulty of the problem, the number of steps it would take, the time it would take, scales as N to some power, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
all the details are kind of fuzzy and don't matter. But roughly speaking, these are easier than exponentially hard problems, problems that it takes, you know, e to the number of inputs to solve in some algorithm that you could write down. NP problems are problems where you can check the solution very easily, but you are not guaranteed to be able to find the solution very easily.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Now, the guaranteed is playing a big role there. It's actually hard to know, given a problem, whether it is NP or whether it is polynomial, whether it's P. Let me put it that way. You can take a problem where you know it's easy to solve, easy to verify a solution. but it's hard to know whether it is difficult to actually find the solution.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So just a classical illustrative example of easy to check versus hard to solve is, if I take two very, very large numbers, and I multiply them together to get a third even larger number, and someone hands you just the larger number and says, factor it into two smaller numbers. Okay, if someone just says factor it, that's very hard to do, as far as we currently know.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It's hard to exactly quantify precisely how hard it is to do, but it's hard. Whereas if someone says, I think it's these two numbers that got multiplied together, then you can easily multiply them and check, right? It's much easier to check the numbers. So OK, would nonlocality help us with this? Like I said, various forms of different changes in the laws of physics do help you.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
So I bet that there is some idea that generic changes would help you. But I also feel that in the real world, those changes seem to be not within our grasp. So I'm suspecting that in the real world that will continue to be the case, that there's not going to be in practice any nonlocality from quantum gravity helping us to solve NP problems.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Emmett Francis says, you've done well convincing me this isn't the case, but I'm curious, what is your best steel man argument for consciousness being linked to the collapse of wave functions? Well, I think that there's two aspects here. It depends on whether you think that consciousness requires something non-physical or not.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Because I think that if wave function collapse is somehow related to consciousness, wave function collapse, whether it is done by conventional quantum mechanics or not, is still a perfectly physical thing, right? There are wave functions. They're physical, they collapse.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I mean, well, you can get better and better at it quantitatively. You can get faster and faster, more and more accurate, but you're not learning a new thing. You're still computing that function, okay?
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
It's not entering a new element into your ontology of the world, some purely mental aspect that is affecting the wave function collapse. If I have wave function collapses that are describable by some perfectly physical theory, then the only way to make them connected to consciousness is to somehow say that consciousness requires a certain kind of dynamics. I think that's what Roger Penrose thinks.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
I honestly do not get it. I can repeat his argument, but I don't think it's a steel man argument because I think it's pretty weak, you know, his argument. And again, Scott Aronson has vividly explained why this is not a good argument, but it's roughly speaking based on Gödel's theorem. This is why he writes The Emperor's New Mind, and, you know, it's about Gödels and machines and intelligence.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
And the idea is that Gödel has proven that an insufficiently powerful formal system— I'm going to paraphrase, apologies to the experts out there, but there are true things that you can't prove if you assume that the system that you're looking at is consistent in some way. And Penrose says, but I'm a mathematician. I can see the truth. of these statements even though I can't prove them.
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
AMA | September 2024
Therefore, I'm better than a computer. I'm not at least a sort of computer that obeys the kind of formal system logic that Gödel was thinking about. And that's why he needs to go beyond the ordinary laws of physics and he does so in a way that invokes the collapse of the wave function. So the short – there's various longer responses to that.
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Ryan Hibbs says, the light we see from stars represents the object as it was in the past due to the speed of light and the further away the object is, the faster it's moving away from us. How do we know from just this data that expansion is accelerating and not that expansion just used to be faster in the past than it is in the present? You know, I mean, cosmologists aren't dummies, okay?
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They have ways of thinking about this. They know what the issues are. And the thing is, you don't simply—these words that we use when we talk about these in ordinary language don't map exactly onto what real cosmologists actually do. The point is that cosmologists have a model. They don't just use words like, ah, the universe is expanding, the universe is accelerating.
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You say, I have Einstein's equation in general relativity. Under assumptions of homogeneity and isotropy, this turns into a differential equation for the scale factor of the universe, the relative size of the universe at different times, called the Friedmann equation. And the Friedmann equation depends on the sources of matter and energy and curvature in the universe.
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the amount of ordinary matter, dark matter, radiation, vacuum energy, etc. And with all of these ingredients, the specification of what those ingredients are, how much matter, how much radiation, etc., at any one moment of time, allows you to predict whether what the observed relationship should be between a redshift and a distance.
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And then you match the data to the observations and you figure out, aha, the data will match the observations if 70% of the universe is dark energy, vacuum energy, 30% is matter, and 10 to the minus 4 is radiation, something like that. Now, when we explain this to people, they don't want to hear that. They want to hear the universe is accelerating or the universe is not accelerating.
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And here in February 2025, this is literally a pivotal moment of history. And it would be weird to pretend that it was just a normal moment. We're less than two weeks into Donald Trump's second term as president, and it has been even worse of a fiasco than his biggest enemies might have predicted. The combination of ruthlessness and incompetence is quite shocking, and so it's important to
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And that's true. Those are accurate statements. The universe is accelerating right now. But the way that you actually get there is this very careful procedure of matching data with theoretical predictions. Ken Wolf says, I recall you saying that you are not fond of the old-fashioned cocktail because it depends too much on sweetness for its flavor.
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So if someone wants to say the tables and chairs are not real, I'm not going to expend my precious time here on this earth convincing them that they're wrong. I'm just going to say, look, what I mean by real is it plays some causal role in the universe. It helps me understand what will happen.
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Is there any whiskey or scotch-based cocktail that you do like, or is anything more than a splash of water simply not acceptable? Well, look, everything's acceptable. I hope I've been clear about that. You can do whatever you like. I have my own preferences. If you include American whiskeys like bourbon and rye, then certainly I love lots of cocktails with whiskeys. I'm a huge fan of Manhattan's.
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among other things. I don't know exactly what the definition of of whiskey is as opposed to other spirits. So I don't know, you know, is brandy whiskey? Is cognac whiskey? I think typically not, but they're comparable. They're similar in certain ways to bourbon or rye. Scotch is notoriously a spirit that is hard to turn into cocktails, right?
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It's so unique and it's so flavorful on its own that either drinking a neat or over an ice cube is how I would generally go. Kelly Hoogland says, what do you think the average person misunderstands the most about artificial intelligence and large language models?
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For me, I've heard a lot of buzz about how ChatGPT is much more water and energy intensive than a standard Google search, a fact which people are now using as a moral argument against people using it at the individual level.
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I feel like this completely misses the mark and is analogous to shaming someone for forgetting to bring their own grocery bag and turning a blind eye to corporations profit maximizing behavior. In my opinion, this is a greater misunderstanding than the fear that AGI is going to take over and start ruling us.
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Maybe that's possible, but plenty of people do shame each other for not bringing their own grocery bags. This is just a feature of human nature. It's not a great feature of human nature. I'm on your side about deploring it, but when we see individual behavior, we find that very judgeable in a way that the invisible corporate or systemic behavior
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or government for that matter, behavior behind the scenes tends to be a little bit more invisible. Going back to the shooting the United CEO kind of thing, right? I mean, how do you relate, how do you compare the crime of shooting an individual person on the street to the crime of denying a whole bunch of people healthcare, right? One is much more visceral and visible.
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In the case of AIs and large language models, I do think that there is some tribalism involved going on, some choosing of sides, because there's a whole bunch of reasons why you might be either skeptical or outright hostile to AIs. One reason is the way that they have been deployed by corporations, right? Google searches or Microsoft products are now full of AI when nobody asked for it.
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Another reason is if you're an artist or a writer or, for that matter, any other number of professions that have their livelihoods in danger of being stolen away by AI. Or, like you say, there's the worry about resource usage in various ways. And these are very different objections, right? Like these are not the same objection, but we get aligned.
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As I've given the example many times before, if someone says there is a table in the room over here and there are chairs around that table, then instantly certain things appear in my mind like, oh, so we could go sit at the chairs around the table. We could put our beverages onto the table and it would hold them up. right?
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We care about one of these objections and we start relying on other ones just to build our case because we've already decided what side we're on. And then we just collect evidence to make our side happy. I think that the question of using up resources is a very tricky one. I mean, it is clear that as a whole on the aggregate, AI and other, the label AI is a little not exactly appropriate here.
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People are using computing power for all sorts of things, but computing power broadly construed uses up an enormous amount of resources, uses up an enormous amount of electricity and water and things like that. I've seen plenty of people complain about this.
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I have not seen much of a sensible breakdown of how much an individual attempt to query ChatGPT about what is the best way to make a noodle dish with ground pork or something like that. Does that really... use up an enormous amount of electricity compared to something else? I honestly don't know. I'm saying that I haven't seen it carefully compared to other things that we do, right?
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This is just, again, another very basic human flaw. We like to think about total amounts rather than rates, but the rate is what matters. What is the rate of an individual person's use of AI in terms of electricity and water consumption versus other uses of AI?
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You know, people in California work very hard to not run their faucets too much because there's a water shortage, but the enormous fraction of water is used by agriculture, not by people running their faucets.
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That's not to say that people should waste water running their faucets, but it's just very hard to get accurate information about the actual scope of the problem versus the thing that you feel you personally can have a handle over. I think that the real danger of AI is neither one of these things, is neither power usage or AGI taking over and ruling us.
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It's that we start handing over really crucial functions of society and technology to algorithms we don't perfectly well understand. Right. And that is going to lead to very down-to-earth mundane failure modes that I can foresee happening in the future.
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So I think that there are very legitimate worries about this technology, but they don't always match up to the worries that people spend a lot of time talking about. Rue Phillips says, did Google's quantum chip willow really tell us anything about the multiverse? Is there any measurable connection between quantum computing and many worlds?
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I should have grouped this clearly with the earlier question, so no. There's no measurable connection between quantum computing and many worlds. There is arguably a connection between quantum computing and wave function realism. I think someone like David Deutsch would say that, in fact, he has said, I don't need to think it, he has said that hidden variable theories, which are also real,
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So that information that is useful about dealing with the world, predicting what will happen, anticipating what comes next, strategizing between different alternative things, actions we could take and things like that, that's what I mean by real, right?
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wave function realist theories and also say that the wave function strictly and only obeys the Schrodinger equation, Deutsch would say these are just Everett in disguise because you have the whole wave function. It's going to branch. It obeys the Schrodinger equation. There's going to be decoherence. All of those things are true.
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And he would say that the advocates of pilot wave theories then add these hidden variables and say, OK, yes, but this is what's real. And he just doesn't believe that that makes any sense. So I don't really think that anyone who advocates any currently popular theory interpretation or foundational approach to quantum mechanics would be surprised that quantum computers work.
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And therefore, you know, to be fair, I don't think that we have gained any information that changes our credences about these different approaches. Anonymous says, have you considered doing 23andMe or similar services? You've mentioned that you don't know much about your ancestry. Could be interesting to learn. Maybe there's a physicist somewhere in there.
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It also provides a lot of useful medical info. So no, not really. I'm not that curious about my ancestry, and I'm very worried about handing over my genetic information to faceless corporations. I mean, in fact, it became clear that 23andMe in particular had worked out quite an amazing gimmick
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because they are taking all of this data from people who have handed over their data to them, and they're using it to do pharmacological experiments and things like that. Basically, ordinarily, the corporation would have to pay the person to get the data that they needed. But 23andMe figured out a way that the people paid them for the privilege of giving them their data.
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I don't think that was a very good bargain. Of course, genetic tests can provide a lot of useful medical info, but if I ever thought that that was something I needed to do, I would just try to do it on an individual level with a doctor, not with a corporation like 23andMe. Not that it's bad to have done it, but that's the bargain that I would personally make.
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Ilya Lvov says, thank you for your solo episode on emergence. In it, you provided the definition of emergence as the operations micro theory goes to macro theory and time zero goes to time one commuting with each other. Doesn't this by definition rule out strong type three emergence?
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If someone lied, if there were no table in there, or if the table were an illusion, if it were a hologram, then it would not be real because I would mistake what the implications are of that statement. So I don't think it's that controversial or hard, of course, around the edges, making things perfectly definite can be tricky, but I just try to be clear about what I mean when I use those words.
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Isn't the point of the strong emergence that the macro theory predicts brand new outcomes that the micro theory starts being wrong at a certain scale? Yes, that is completely true. So if you think that strong emergence can happen, then that simple idea of the commuting diagram between time and the emergence map would fail. And in the paper, we say that very explicitly.
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I still think it is useful to start with that conception because it's easy to understand. I know that out there in emergence land or in the land of people who talk about emergence, there is a strong constituency of that resists any version of emergence that is understandable. They think that emergence is only an interesting concept in those cases where you can't understand what's going on.
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And I resist that. I don't think that's true. In some cases, you can certainly understand what's going on. And they would say, therefore, that's not emergence. I would say it's a kind of emergence. Let's understand this first. And then let's add on the weird stuff that you want to add for the strong emergence later. That's my personal preference.
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Nicholas Sharosky says, given your stance on poetic naturalism and emergence... Would you say that when describing a sunset, both person A, who says shorter blue and violet wavelengths are scattered by Rayleigh scattering, and person B, who says the light dances transforming the sky into a fiery canvas, are using sufficiently accurate and useful vocabularies to be considered real?
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How does this align with your notion of emergence where different levels of reality and their descriptions must remain compatible? Does the poetic vocabulary of person B, in your view, fall short of the scientific one? I don't think it's equally valid. I think they're both completely valid, right? But that doesn't mean equal, you know? They're trying to do different things.
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If I said, could you explain... physically, why the sunset looks more red than blue, and someone gave me the answer, the light dances transforming the sky into a fiery canvas, I would not give them full credit on an exam, okay? Likewise, if I said, give me a poetic description of the feelings that this sunset evokes in you, if you started talking about Rayleigh scattering, I would not give you
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a full marks on that exam either. I think it's relative to the kind of thing you're trying to achieve. Now there's the additional factor that in these two cases, the kinds of things you're trying to achieve, a scientific understanding of photon scattering versus a poetic description of the feelings that are invoked by the sunset, have different standards of success, right?
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Science, the scientific kind of description there is much more precise and rigorous and testable and quantifiable. And the more poetic description is a little bit harder to judge whether it's successful or not. That doesn't stop them from both being accurate or both being real. They're just trying to do two different things. Nico Bersianik says, my question is about quantum field theory.
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When an observer travels in space, for example, do they cross quantum fields? Is there a way to verify, to measure, that we're traversing through all or some quantum fields by moving, or on the contrary, fields are always anchored to the observer? Certainly in the way that we think about quantum field theory and what quantum field theory means, the fields exist everywhere.
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That's what it means to be a field. A field is the answer to a question, at this point in space, what is the value of the field? For every single point in space, a field has a value. The electric field has a value at every point in space. It might be zero. So you might say there's no electric field here, but you don't actually mean the electric field doesn't exist there.
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What you mean is the value of the electric field is zero there. Just like when you have a function of y as a function of x, if that function happens to cross through y equals zero, you don't say the function stops existing, you just say that its value is zero. If the temperature is zero degrees Fahrenheit, you don't say there's no temperature. You just say the value is zero.
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Miron Mizrahi says, I'm guessing that you and Jennifer are reasonably frequent flyers. Do you have any specific approach you take to packing? Do you have sets of travel gear or do you just pack the same things you use every day? For example, I have a full toiletries bag just for travel. Any packing routines? Are you a light or heavy packer? I think I'm a medium packer.
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Same thing with quantum fields. They exist everywhere. They're not pulled along or traveling along. You absolutely do pass through them in the sense that you pass through space and the fields are everywhere in space. I don't know how to pronounce this.
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Timlo, P-T-M-I-L-O, Private Milo maybe, says, is your objection to the potential for large language models to exhibit more generalized and extrapolation-heavy intelligence based on deeper principles, or is it more intuitive? That is, is there anything in information theory that tells us it is impossible for locally generated interpolations of tokens to uncover patterns and sequences that
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that are indecipherable from conventional human-like extrapolation successes. Well, I don't think it's based on deeper principles in the sense that there's a proof that you're asking about. In fact, I'm open to the possibility that large language models could construct, you know, sorry, let's back up.
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The large language model is optimized to give sensible sounding answers to human beings asking questions of it. Now, it may very well turn out that in that black box of many, many layers of deep learning, the way the LLM does that is essentially to invent intelligence, to invent a model of the world, invent sort of counterfactual reasoning, invent all those things. I'm open to that possibility.
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However, number one, I don't see why that would necessarily be the case because that's not how you've programmed the LLM. It would have to be a case where the optimization procedure was just so successful that the LLM founded itself despite the fact that that's not what it was trained to do. And number two, in the data, I see no evidence of that happening, right?
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It's not that LLMs don't become better and better. They're clearly becoming better and better. But they aren't perfect, and they make mistakes, and they make failures. And my point has always been the types of failures they make are precisely the type you would expect if they were not being real human intelligence, if they were not causally mapping the world and inventing counterfactual reasoning.
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So I am very open to new evidence coming in that changes my mind. That'd be super duper interesting if it were true. I just haven't seen it yet. Ed says, I know you're not an AI expert, but you have had a number of AI expert guests, so you likely have a better handle on it than I do.
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Do you have a sense as to whether there's a fundamental difference between the theory of operation of an AI LLM and that of an autocorrect feature on my phone? Is it just a massively scaled up version of this thing that is always failing to guess the next word I want, or is it doing the same thing in some utterly different way? I think it's both. It's a little bit half and half there.
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Certainly, there's a spiritual connection between LLMs and autocorrect. I mean, autocorrect is not a separate kind of technology, right? Autocorrect is next token prediction. And in a very real sense, LLMs are... very, very, very souped up next token prediction. It's not just the next token. They're predicting more than that.
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It is true that we travel a decent amount. We're trying to cut down a little bit for various reasons on the amount of travel we do. It was definitely noticeable after the pandemic. that we'd gotten out of practice traveling. I do, in fact, have a travel kit with the toiletries and things like that.
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They have some memory of what they've been talking about and things like that. They have very important, crucial distinctions between a simple autocorrect kind of thing. But there is that spiritual connection. So I think that there's both a similarity and a difference there. Jesse Rimler says, I'm currently reading the wonderful new David Bentley Hart book, All Things Are Full of Gods.
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It's a thoughtful and engaging philosophical treatise on consciousness and materialism written as a platonic dialogue. Hart is religious, and I generally disagree with him. I'm guessing you would too. but it does make me think about the areas where non-materialists can find argumentative purchase.
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Do you think that the irreducible experience of consciousness is one of those brute facts that allows otherwise rational thinkers the wiggle room to play around with non-scientific ideas? If I understand what you're asking, no, I do not think that. I'm not sure what the word irreducible means in the phrase the irreducible experience of consciousness. there is an experience of consciousness.
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How do I know it's not reducible? I don't even know necessarily what reducible means. I worry that it means different things to different people. I've been very, very clear about what I think consciousness is. I think that people obey the laws of physics.
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And I think that we talk about people using a higher level emergent vocabulary, which absolutely includes all the interior first person consciousness talk. I don't think that there's any fundamental difference between that and the exterior talk that we use about how people are moving or talking or thinking or whatever.
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So I think that there is some temptation to treat consciousness as different precisely because it is first person. There is something unique about my consciousness from my perspective, sure, But I want to understand the world comprehensively and fundamentally. And I think that by far the leading way to do that is to not treat me as all that special, including my consciousness.
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It's just a higher level emergent way of talking about the collective behavior of atoms and electrons and photons in my brain. Polina Vino says, computable analysis is a kind of analysis that is compatible with computability theory.
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For example, we have the computable intermediate value theorem, the assertion that if f is a computable continuous function and f of a less than c less than f of b for computable reals a, b, and c, then there's a computable d with f of d equals c. Does that make sense?
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You have a function and you know the function at some argument is less than c and that is less than the function for b, then in between it had to go through c. That does make some intuitive sense. The idea is that these computable theorems do not say anything about numbers that cannot be expressed in terms of an algorithm.
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And I have a tiny little checklist, like you need the travel kit, you need your phone, you need your computer, you need chargers, right? You need all the different cables that we carry around everywhere we go, passport and things like that. Otherwise, I don't have much of a routine.
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Do you think that this type of analysis has any place in physics research, such as in the effort to make relativity and quantum mechanics compatible? For example, maybe limiting mathematical results used in computations to only those that discuss computable functions and values could expose where we helped ourselves to conclusions about things we can't even express. Well, it's possible.
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It's absolutely possible, but I don't see how exactly that could happen. For one thing, let's be clear. Relativity, in the sense of special relativity, Einstein in 1905, is 100% compatible with quantum mechanics. That's where quantum field theory comes from.
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General relativity, which is Einstein's theory of gravity, has not yet been quantized, or to put it slightly more carefully, we do not yet have a quantum mechanical theory that in the classical limit achieves all of the predictions that general relativity does, okay? But okay, but that's still a problem.
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You're suggesting that a particular kind of focus on a particular subset of math might be helpful, computable analysis. It might be. That's just too vague of a suggestion to me to really think about. It's like, you know, there's a lot of cool math out there, right? Category theory is something that is very exciting among mathematicians right now.
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We talked about it with Emily Real on the podcast some time back. And a lot of people are very optimistic this is going to help us understand some deep questions of physics. The proof of the pudding is in the tasting. You know, it's great to be excited by cool math, but you can't just say, I think maybe this is going to help solve some problems. You've got to solve the problems.
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I'm sorry, that's just how it works, you know. In order to get people excited, you have to kind of show them the money. You have to give them the killer app. Schleyer says, your discussion with Stone Farmer touched on the fact that our economic system averages growth around 2% or 3% per year, which I believe means a doubling in size every few decades.
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It's surprising to me there isn't more work being done to come up with an economic system that can thrive and persist but not grow. Why don't we inevitably need that given finite resources? Do you have thoughts on why this isn't a significant focus of economists or others who study complex systems? Well, I do think that this kind of thing is a focus.
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I mean if you mean how could we make a transition to a fixed economy rather than a growing one, that's not much of a focus of economists because I don't think that most economists think it's either – plausible or desirable. I mean, for one thing, at the very, very most basic level, the population of the Earth is growing, right? So there are more people.
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I try to travel light, but if you're going to go to the gym while you're there but also go to a fancy dinner and also just be casually walking around the city, then there's already three pairs of shoes you need in some sense. So it can be hard sometimes. I don't have any special – clues or tips or anything like that. I'm not an expert traveler.
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If you had an economy that didn't grow, that would be less and less resources per person, and no one's going to vote for that. But even if you do live in a country where the population is not noticeably growing, people like to think that their descendants might be better off than they are, right? That is something that is a very much a goal of a lot of people.
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I think at a down-to-earth level, there are reasons why growth and indeed a little amount of inflation are useful. Just to give you one very, very easy to understand one, is helpful if I want to—different things. Maybe I want to buy a house, but maybe I also want to start a company, right? For various reasons, I might want to take out a loan.
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That is borrowing so that I have money right now against the promise of a future payment. A tiny bit of inflation will ease the burden of paying back that loan in the future and therefore make me more likely to take out the loan and therefore, in a well-functioning economy, makes it a little bit easier to make progress and have everything be active and churning and new things going on.
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Now, of course, this is a tricky thing because you don't want too much inflation. That means that everyone's savings disappear. So there's a very, very fine line to be drawn there. And of course, getting it right is what economists talk about all the time. I do think that...
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It's just wrong to think that things would be easier if we fixed everything at a constant value of GDP and just tried to keep it completely stable like that. It's hard to make it stable. For one thing, there are fluctuations up and down. So if the overall trend is growing, then the downward fluctuation is relatively benign.
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Whereas if the overall trend is flat, then a downward fluctuation can be pretty devastating. So maybe there are good reasons why you don't want that, and maybe that's why it's not a significant focus.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Zach McKinney says, inspired by your episode with Eddie Pross, if you were to consider and model functional democracy as a dynamic kinetically stable system, then what are the inputs or conditions that you would hypothesize are needed to maintain kinetic stability?
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So I'm answering this question because I have no idea what the answer is, but I think it's a super important question in some version or another. So I'm not – I don't understand – the specific idea of dynamic kinetic stability well enough to say that that's the right kind of model to use. I mean, it's a little bit specific to chemistry, honestly.
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But the more general idea, if you remove the word kinetic and just say, you know, dynamic stability, that's a very general idea. Lots of things are sort of stable in the aggregate, stable at a macro level, like a human being is certainly mostly stable, right? Like I don't change my configuration dramatically from moment to moment, but only because I take in fuel from the outside and then...
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throw away entropy and energy back to the world. The biosphere as a whole does that. Waterfalls, you know, the great red spot on Jupiter, many different things. So you want a functioning democracy, or any kind of functioning country for that matter, to be something like that, right?
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I mean, the individual human beings are allowed to move, but the overall shape of the country maintains some coherence. and you also want it to be stable. So, I mean, just like the economics question above, you want perturbations to fluctuate rather than to grow, right?
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Stable to a physicist means if I poke it, there's a system that I poke, so I do a little perturbation, I change something about it, Does the perturbation sort of oscillate back and forth, or does it grow bigger and bigger? If it grows bigger and bigger, then it's unstable, and that's bad. So that's a positive feedback loop, right?
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I'm not one of these people who dwells in great detail on the most efficient way to pack. For that, you know, yeah, you got to go somewhere else. Sorry about that. This episode of Mindscape is sponsored by BetterHelp. When it comes to relationships, we often hear about the red flags we should avoid. But what if we focus more on looking for the green flags in friends and partners?
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When a tiny deviation in one direction keeps growing in that direction. Don Farmer's point is that it is often in the economy very typical to have these unstable positive feedback loops. And the complexity economics perspective is supposed to help with that. I think there's been much less study about that at any quantitative level for political science, for democracy.
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There's been a lot of sort of qualitative political science and historical work on the stability of democracies or the lack of stability sometimes. But thinking about it in terms of physics systems or chemistry systems has not been done a lot. I would like to see more of that. I'm going to do more of it myself and I'll let you know if I come up with anything good. Haven't quite yet.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Tim Giannitsos says, a great hits and misses episode. You mentioned that your paper about the origins of the arrow of time avoids making an assumption about a single low entropy beginning. But does it just make a different assumption that the natural state of the universe is empty to sitter space? So two things. Number one, no, it does not make that assumption.
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It says we make an argument, a very hand-wavy argument to be sure, but the argument is if you're not in empty de Sitter space, you approach it. It's basically the cosmic no hair theorem proven by Bob Wald back in the 1980s. And then there's a reason for that. The reason for that is that in the presence of a positive cosmological constant, de Sitter space is the highest entropy state.
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So that's the whole point, part of the whole point of our paper, which is that you have to start somewhere. By start, you don't mean the initial condition of the universe, but you have to have a condition for the universe at some moment of time, and then you try to evolve it both forward and backward. And our point was you don't have to tune that condition at all.
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It can be very, very natural, very, very generic. And you can think of that as either saying, well, I'm going to pick the most generic state, and it would indeed be empty decider space. Or you can think about saying, I want to allow for other things, but guess what? Those other things evolve into decider space. You get the same answer either way.
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Eric Hogan says, in the solo episode about time, you talked about stuff fluctuating into existence, maybe even the universe itself. It isn't clear to me what you imagine that such a universe producing fluctuation would look like. Would a super dense expanding bang instantaneously appear from nothing? Or would white holes grow from radiation and spit out stars?
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Would the dead rise from the ground and ungrow into babies? Would galaxies dissolve into smooth gas clouds just in time for the big crunch, just by chance? If it was time symmetrical, would it even make sense to call one of the two histories a fluctuation? So I'm not sure exactly what you're referring to. This is entirely my fault about the stuff fluctuating into existence.
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For the universes fluctuating into existence, if I said something like that, I did not mean the entire universe fluctuating into existence. That is not something that I particularly have contemplated. I don't even know what that means. If there was no universe, what is there to do fluctuating? We did have a...
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In this scenario I was just talking about, the one from the Arrow of Time paper with Jennifer Chen, we had the idea of baby universes, where you have a pre-existing universe that can undergo a fluctuation inside itself that would cause a little tiny bit of universe to pinch off and go its own way. There we have a picture of what it would look like.
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It would look like, well, let me emphasize the important point here. The amount of baby universe you need to pinch off is very, very tiny. It's just a little Planck scale-sized thing. You don't need to undergo the entire history of the universe backwards. It's not anything like that at all. What it would look like is a number of particles, photons or whatever.
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I'm not sure what the most likely thing would be. would actually be, but a bunch of particles come in by random fluctuation and collide with each other in a small region of space enough to make what looks to the outside like a black hole, but actually inside is a baby universe pinching off.
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And then that thing that looks like a black hole then radiates away, and that whole process looks more or less symmetric, right? Bunch of particles come together, make a black hole, black hole evaporates into a bunch of particles. But the set of particles there is enormously smaller than what you would need to make a big universe-sized thing like us.
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The reason why that's viable is because of inflation. Because inside the baby universe, you can use the laws of physics, take advantage of the property that a closed universe has zero total energy. So if that closed universe is full of an inflaton field, it can expand to an arbitrary size,
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and that an inflaton field can turn into ordinary matter and radiation and create many, many, many, many more particles than you actually needed to make the baby universe in the first place. If what you're referring to is some self-contained universe, then I would not use the vocabulary of fluctuating into existence.
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For a baby universe that comes from a pre-existing space-time, I think that language is appropriate. For the universe as a whole, if you mean a universe that just has a beginning, then I would just say it's a universe that has a beginning. I would not say that it's fluctuating into existence out of nothingness or anything like that. Johann Yartelius says, can a molecule be earmarked?
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There's this factoid or perhaps truoid that with every breath we breathe, we get an oxygen atom once breathed by Julius Caesar. Now, from a probability point of view, I'm sure this makes mathematical sense. But if one would want to test it, how would one do so? Is the likelihood larger that a water molecule, for instance, stays closer to where it met me, or is the dispersion equal?
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If I wanted to register individual molecules to see if that particular molecule returns to some given point, i.e. a water molecule passing through my faucet again, could I do so, and if so, how? So to the actual question, can you earmark the molecule, not really is the answer. It depends on what you mean. I mean, you can always take that molecule and attach it to another molecule.
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But if you're talking about an oxygen atom or a water molecule, they're sufficiently small that if you attach them to large other molecules, you're going to completely change their dynamics, right? They might not even float in the air anymore. But individual molecules is an interesting physics point. Let's start with an individual atom.
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An individual oxygen atom—oxygen atoms can be in different states, but by different states what we mean is the electrons in those oxygen atoms can have different energy levels, OK? As we talked about earlier, when you're in a higher energy level for an electron in an atom, you tend to relax, you tend to decay down to the lowest allowed energy level.
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And so typically oxygen atoms are going to be in their lowest allowed energy levels. And all oxygen atoms that are in the same lowest energy level are indistinguishable from each other. They are literally indistinguishable particles in the quantum field theory sense of the term.
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So there's no marker, there's no way to say this is this oxygen molecule, that one is that oxygen molecule, or atom I should say. But even as you get to molecules, Molecules are more complicated. They have more moving parts, so it becomes slightly easier for more things to happen. Molecules can vibrate and stuff like that.
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But if we're talking about things as simple as a water molecule, there's not an interesting set of vibrations that it can have, and even those vibrations decay away, so they all look alike. So no, you cannot really watermark the molecules. It's true that if Julius Caesar breathes a breath, the atoms that he's just breathed out will, for the moment, mostly be near him.
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They're not going to instantaneously spread through the universe or spread even through the Earth's atmosphere, right? So when people make these statements, they are absolutely not just using numerology about how many atoms there are.
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they need to make statements about how quickly the Earth's atmosphere mixes, how quickly a test particle, if you have one particle in the air that is floating randomly, well, you know what the temperature of the air is, you know what the typical velocity is, and it's doing a random walk, it's bumping into other molecules.
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So you can ask the question, how long does it take to sort of randomly go throughout the whole Earth's atmosphere? And the answer is less than 2,000 years. So that's why there is some quantitative sensibility to that kind of statement, even if you can't actually look at the individual molecules.
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DMI says, is the feeling that only the present we see is real, even though nothing in the physics equations makes it more fundamental than any other slice of spacetime? Could that be the same kind of illusion that gives us the feeling that only the branch of the wave function we see is real, even though nothing in Schrodinger's equation makes it more fundamental than any other branch?
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Kind of, I guess. I like the analogy and I'm trying to decide whether or not I think it's a completely accurate analogy or not. The wave function case is actually easier in this particular example because even though the wave function itself is very abstract, it is indisputable that if you believe any of the usual Everettian story, any individual agent is located on one and only one branch.
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You can easily switch therapists anytime at no extra cost. So discover your relationship green flags with BetterHelp. Visit betterhelp.com slash mindscape today to get 10% off your first month. That's betterhelp, H-E-L-P dot com slash mindscape. Scott Collins says, could Laplace's demon predict a Boltzmann brain? Put another way, are random quantum fluctuations theoretically predictable?
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of the wave function, and that's the branch they see, and that's the branch they naturally attribute reality to. And that's true across time, right? Not just for a moment, but in future moments as well. Whereas for the presentism question, you have to say, well, you have to distinguish between the agent at one moment and the agent in another moment, right?
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At any individual moment, the agent only sees a little bit of their immediate environment, but they attribute reality in the casual presentist kind of way of doing it to a whole slice of the universe very far away from what they see. So my worry about saying it's a perfectly good analogy is that there is more extrapolation in the presentism case, right? It's more model dependent.
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It is more relying on the fact that I'm not only considering what I see around me right now, but I'm also treating everything at this one moment of time as equally real. And of course, everyone knows that relativity is a huge challenge to presentism because different people moving at different velocities would extend their present moment of time differently.
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So how in the world can it be true that only one slice is real? Of course, the sophisticated presentists have answers to that. Since I'm not a presentist, I've never put any work into understanding what those answers are. Joan Beluda says, priority question. If you could get the definitive true answer to any open-ended question, what would that question be?
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The answer would be complete and thorough in a scientific paper. Yeah, it's a boring answer, but I guess I would say what is the correct theory of everything? You know, what is the correct theory of gravity and space and time and all the forces and quantum mechanics and all that? Just tell that to me.
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I think that hopefully a scientific paper will be long enough to explain it in language I can understand. I don't know. I'm not expecting anyone to give me that paper anytime soon, but, you know, that would be pretty awesome if it happened.
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Alexander Knirkel says, is there a theoretical mechanism how, when time emerges separately from space, the whole of space-time still ends up exhibiting this high degree of symmetry?
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Lorentz invariance, or diffeomorphism invariance, all these different ways in which relativity convinces us, this is me, Sean, talking now, not Alexander, all the different ways that relativity teaches us that space and time are unified into spacetime. How does that come out of this?
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And then Alexander continues, naively, I would expect that an emergent time parameter would not magically fall in place to form a nice representation of these exact symmetries. with the rest of space-time, and all the fields being in representation of these as well, but instead stick out like a sore thumb? So I think this is a very good question, a very, very important question.
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We don't know how this is supposed to work. So I think that there's two kind of competing intuitions going on here. One is... If I started with a theory in which time and space were clearly different, I just told you what was going on in space and separately had an equation telling you how things evolve in time, why in the world would that knit together?
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So you build up by evolving in time, here's space, here's space at a moment later, here's space a moment later. And by space, I mean not just space itself, but everything in space, the whole configuration of the universe. And I build up a bunch of these, okay? And then I say, okay, I've knitted together a four-dimensional spacetime.
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Is it true that we have these symmetries like Lorentz invariance that we know and love from relativity? From that perspective, I agree. It would seem weird, right? That you would just magically have this invariance where I could now completely switch to a different perspective and get and slice spacetime differently and get just as good, the same laws of physics basically.
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But there's another intuition, which is, let's say that I have a theory that does have this invariance, that is Lorentz invariant, that does have the symmetries of relativity built into it. I am 100% allowed to pick a reference frame.
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to pick a decomposition of space-time into space and time to, within the terms of that decomposition, describe what's going on in space and write down equations telling me how it evolves in time. And so there's no obstacle to building entirely symmetric descriptions in a language that is manifestly not symmetric.
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Well, this comes down to the question of whether or not the ultimate laws of physics are in fact deterministic or not. You know, Laplace's demon is a thought experiment meant to illustrate the implications of determinism in classical physics. That's the whole point.
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And so we're asking the question, you know, under what conditions does this step-by-step, moment-by-moment building up lead us to something that shares all the symmetries of relativity? And the answer is I don't know. I mean, there's something very nice about the symmetries of relativity. So I'm not in any sense...
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convinced that they couldn't come out generically under some scheme, but I don't actually know. And people have tried, by the way. At least I am aware of the existence of various papers about the emergence of of Lorentz invariance from not obviously Lorentz invariant descriptions. Divimorphism invariance is a very different thing. That's almost automatic. That's basically coordinate invariance.
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It's hard to not be divimorphism invariant, or let me put it this way. Divimorphism invariance, which for those of you who don't know, is basically coordinate invariance. It's basically saying I can choose whatever coordinates I want, but there's sort of an active and a passive version of that.
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Changing the coordinates and leaving the underlying system invariant is one way of saying it, but then keeping the coordinates and moving the system is another way of saying it. That kind of sounds more impressive. But in my mind, diffeomorphism invariance is a real thing, but it's a real thing that is a label that gets attached to descriptions of theories, not to theories.
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So I can describe Newtonian gravity in a 100% diffeomorphism invariant way. I don't because it's just more convenient to treat space and time differently, explicitly, to pick coordinates on time and coordinates on space separately. But I don't have to do that because it's a description statement, not a theory statement. Whereas Lorentz invariance is a theory statement.
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Some theories are Lorentz invariant and some are not, so I would treat those differently. Anyway, yes, I would love to know whether or not Lorentz invariance under some very simple assumptions naturally emerges, and I don't know the answer to that one.
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Brendan Hall says I've convinced myself recently that TV and subsequent technologies for passive entertainment have worsened the quality of our lives by making leisure more isolated from our fellow people. To what extent would you agree with this sentiment? You know, I get it. I think that you're correct that leisure is now more isolated from our fellow people.
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The point of Laplace's demon is that the information needed to predict what comes in the future is implicitly present in the moment right now. If you had the complete 100% comprehensive state of the universe. You never do, so that's just a thought experiment just to try to teach you what determinism really means. In quantum mechanics, for all intents and purposes, in the observable universe,
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Arguably, computers have done that and smartphones even more than TV has. On the other hand, it's given us a whole bunch of enjoyment and entertainment that we didn't used to have. How do I weigh those two things against each other? I truly don't know. My own feeling is that probably TV is a net good.
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I don't really want to go back 200 years to a place where I have to, like, learn to play the piano and sing to get my entertainment in the evening. But I have no objective way of actually doing that comparison. Nikola Ivanov says, it seems to me that there are different types of vacua that you discussed in podcasts.
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The desider vacuum from your podcast on the nature of time, the vacuum at a black hole horizon, which gives rise to Hawking radiation, and the vacuum that gives rise to the cosmological inflation and the Big Bang. Can you please explain their characteristics and differences, if any? Yeah, that's a completely fair question.
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We use, as very often in science or in physics in particular, the same word to mean different things. The overall definition of vacuum to a physicist is, given some theory, what is the lowest energy state of that theory? So in ordinary theories, classical theories, empty space is the lowest energy state, and that matches on to our intuitive idea of what the vacuum is supposed to be, empty space.
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Once you have quantum field theory, it's a little bit trickier. So once you have both quantum field theory especially and also gravity, so that you have space-time curvature, then it can be trickier. So we talk about not only the vacuum locally, That is to say, here I am in some finite region of space and time, and I look around and there's nothing there, and I can describe what is going on.
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There's always something going on in quantum field theory in the sense that there is some state that describes the state of the quantum fields around me, but it's the minimum energy state as seen by me locally. I call that the vacuum. But then we also have this situation where there is a global situation. There's a black hole or cosmology or whatever.
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And we can say, overall, what is the lowest energy state? And usually, I'm tempted to say always, but usually those look the same. In the limit of when you go... Well, sorry, let me say it this way.
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Usually when I have some global vacuum state, that is to say the lowest energy state with a non-zero cosmological constant, so de Sitter space, or with a black hole nearby, right, then if I just choose to look only at... a very, very small region of space and time, it will just look like empty space to me, okay?
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Um, this is one of the lessons of the paper that I finally did just publish, um, with Chris Shalhoub, a graduate student, where we look at Hawking radiation and what it looks like to different kind of observers, uh, The point is, long story short, but you need to operationalize that question. What do you actually do when you want to say, I'm detecting Hawking radiation?
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What kind of detector do you have? How long do you turn it on for? And all these questions. Quantum field theory is tricky.
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If you try to operationalize what you mean by the vacuum by saying, okay, I have a detector and I turn it on and off, the detector needs to be coupled, interacting with the quantum fields that you're trying to measure, and therefore turning it on and off tends to create particles. And even though you think you're in the vacuum, you're still detecting particles.
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That's one way of thinking about various effects in quantum field theory. Anyway, the point is that you can have different global vacuum states depending on the geometry of spacetime, but locally they should look all more or less the same. The differences become subtle, like if you, you know, Let's put it this way.
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If our universe continues to expand and has a positive cosmological constant and lasts that way forever, we will enter the desider vacuum state. And that has a non-zero temperature. So we say that Minkowski space, that is to say space-time without a cosmological constant, it has its vacuum state. and its temperature is zero.
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the laws of physics are not deterministic, okay? And I need to like put all those words in there with emphases about the observable universe for all intents and purposes, et cetera, because maybe there is a deterministic theory underlying what's going on. Both Bohmian mechanics or pilot wave theories and also many worlds in two very different ways are ultimately deterministic theories, right?
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If you have a thermometer there and just let it equilibrate with the vacuum, it will say zero degrees. Whereas in de Sitter space, there's a non-zero temperature. The thermometer you put there comes to equilibrium at a non-zero temperature.
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But that temperature is so extraordinarily, incredibly low, the wavelength of a typical photon that is observed, that is being measured, is as big as the universe. So if you're confined to a tiny little region of space, you're never going to detect those photons. To you, it's going to look like empty space. So there is some commonality in all these different notions of vacuum state.
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George Kendallopoulos says, priority question. In everyday life, we think of matter as physical stuff, stuff like objects we can touch, and information as things like data or knowledge. But in theoretical physics, these ideas seem to be deeply connected, especially in ideas like black holes and the holographic principle. Can you explain how matter and information are linked in these contexts?
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You know, I think it's a little bit casual, to be honest. I don't think there's a hard and fast set of rules there. Physicists are just as prone to speaking casually as anyone else, especially when they hope and think that the people around them will get what they are trying to say.
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But I do think that part of it is that as we dig more and more deeply into quantum mechanics and quantum gravity and emergent space time and things like that, The fundamental stuff out of which the universe is made is a little bit less tangible than you might have thought. You know, in Newtonian, when Newton wrote the Principia, if you said, what is the universe made of?
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He would have said, well, some particles, right? He even thought light was particles, corpuscles. But he was mostly thinking of, you know, the Earth is a particle, or at least is made of particles. He didn't know about atoms, but, you know, he could imagine it was made of matter and things like that. And all that stuff existed in space. And it's all things you can see and touch.
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Whereas if, like me, you're trying to show how gravity can emerge from quantum information, well, you can very well ask quantum information about what? But the answer is some abstract d-dimensional factor of Hilbert space. You know, what help is that? It doesn't seem as material as a particle moving through space. It is, by the way, just as material.
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It's just we're learning better what material means. And that's why... At a philosophical level, what used to be called materialism as a philosophy of nature is these days much more likely to be labeled physicalism as a philosophy of nature because it's a little bit misleading to refer to the ultimate stuff of reality as matter. It's more abstract than that.
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Not that it's any fundamentally less existent or anything like that, but we're not as familiar with it from our everyday lives. And what matters to us about it is the information that it contains. So physicists tend to talk that way just to go along with what their theories are telling them. Stevie CPW says, do you invest in the stock market?
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And if yes, what is your investing strategy or philosophy? Close to no. You know, I probably should. I don't have enough money to be a major player in the stock market. Let's put it that way. I do have some retirement savings from working for many years at universities. And mostly I put those into index funds. That is to say, just follow the S&P 500 or whatever.
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I've had plenty of smart people tell me that is the best investing strategy, at least unless you are the owner of some high-speed trading firm or something like that. So no, I do not have anything interesting to say about my investing strategy or philosophy. Sorry.
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But in both of them, it is impossible for an actual observer in the actual universe to predict what is going to happen next. So it might depend on exactly what kind of Boltzmann—sorry, what kind of Laplace's demon you have in mind. Laplace's demon in Everett could predict the wave function of the entire universe, but there will be different observers observing different things.
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t says what do we mean when we refer to something occurring say one second after the big bang i really struggle to understand the idea of measuring one second in that context especially given the extreme and novel conditions of the universe at that time there was no cesium or for that matter no atoms even born much less having the opportunity to decay yet Right.
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So, you know, in some sense this question is related to the one about measuring the expansion or acceleration of the universe. It is true that no one had a wristwatch available one second after the Big Bang or any atomic version of a wristwatch. But time was passing and things were happening according to what we call the laws of physics.
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So the laws of physics tell us how quickly things happen as a function of time. And the way that we do it is we go back and forth. We build a model. So we have Einstein's general theory of relativity. We have some conjecture as to what the matter sources were and the energy sources were at those times. So we talk about what happened as a function of time.
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That equation we referred to earlier, the Friedmann equation of general relativity, is literally an equation for the scale factor as a function of time. So it is true that time is measured by clocks. But that's not all time is. Time exists as a parameter in our best physical descriptions of the world. And in that role, it absolutely has true meaning, even one second after the Big Bang.
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Which brings us to our last question here from William Kittlestad. asking a priority question. What does science, math, economic theory, Warren Buffett, Bill Gates, and Marie Antoinette say when the wealth separation curve goes 100% vertical, which is fast approaching? Wealth separation is proceeding at a mathematically unsustainable pace.
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The increasing concentration among a handful of uber oligarchs has created a class of relatively nimble humans and core who So I know that's your priority question, but there weren't any question marks in there, but that's okay. I can talk about it. I do think it's a worry. I honestly do. I don't think most people listening will be surprised to hear that is my personal opinion.
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I don't know the exact numbers here because I'm not following it that carefully. But something like 20 years ago, the richest people in the world had less than $10 billion. And now there are several people who have hundreds of billions of dollars just a few decades later. Why in the world should that be the case?
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One can make a case that it should be the case, either a consequentialist case or a moral case. You could say letting certain people get all that money is part of incentivizing them to be innovative and create new things and dot, dot, dot. You've heard the story before.
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Or you can have a more libertarian moral case that just says they have a right to earn money and you don't have a right to take it and they've been very good at earning money. To me, neither one of these is very convincing. I'm a big believer. Like I've said it many times, I have no problem with rich people or with being rich. I wish everyone were a rich person. That would be my ideal world.
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Remember it. Keep it in mind. Not act like it's business as usual. One of the biggest things that Trump and his allies have going for them is the idea on the part of everyone else that it's just another political squabble. But it's really – Not. It's worse than that.
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I just think that when there is inequality, we should tax them. We used to tax them much more effectively in the 1950s. the top marginal tax rate was 90% for income tax in the United States. And now it's in the 30s or something like that? I'm not exactly sure.
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That's going to be inevitable, and those observers themselves will never be able to predict what will happen. In a hidden variable model, if that were plausible and fit the data, then presumably Laplace's demon would know what exactly was going to happen. So it depends on what you mean by quantum fluctuations and what you mean by Laplace's demon. Steve Bonner says, priority question.
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And not to mention all sorts of other things like inheritance taxes and capital gains taxes and so forth, generally lower than they have historically been. I think we could do a lot of good with – I think two things. I think we could do a lot of good with the revenue that might be generated by a fair tax system.
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And number two, and this is something that has only become super noticeable relatively recently, we're putting too much power in the hands of a small number of people. I mean I don't know if William knew this when he asked the question. I forget exactly when –
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the deadline was, but we are seeing a small number of super rich people basically take over the US government right now, up to and including getting information about social security numbers and payment histories for everyone the government deals with, which is basically every person in the country. That's bad.
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And it's all done in ways that are completely illegal and a strict reading of what you're supposed to do. It's not even real government agencies that are doing this. And we have a system that is letting it happen. And it kind of causes one to shake one's head. And the real question is, how do we get people who voted for this to realize the terrible damage that is being done by it?
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You know, it doesn't do that much good. to shake your fist in impotent outrage. We have to gather people together and get them on the right side of thinking about these things. We can't just say that they're idiots. We have to talk to them, understand why they would have done this.
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Is it because they didn't know what they were voting for, despite the fact that it was very clearly said that this is what was going to happen? Or did they actually want it? And if they did want it, what are the reasons why they would want this terrible thing? And I don't know the answer to those questions. Yeah, I don't know the answer to those questions.
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I think it's absolutely worth thinking about. So we have built a system, short answer, in which those things are allowed to happen. I think that they're bad. I think that all the good things about capitalism, et cetera, can happen without people having nearly that much wealth and power as they do.
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And I say this as someone who doesn't believe everyone should have exactly the same amount of wealth or power. I remember John Rawls, the philosopher who wrote The Theory of Justice, and he has this economic political system that he proposed that by most lights is incredibly redistributive. He has what is called the difference principle.
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where he says, in a well-functioning society, the amount of economic inequality should only be tolerated insofar as it benefits or advantages the least well-off, okay? So in other words, you're not allowed to invent a system where the worst-off people become a little worse off, even if better-off people become better off. That was his idea. So this is like super-duper egalitarian, right?
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And there was a... An attempt at refuting this by Rawls's Harvard colleague Robert Nozick called the Wilt Chamberlain example. And the Wilt Chamberlain example, this is like the early 70s when this discussion was going on. So Nozick says – and it's interesting he chose Wilt Chamberlain because they were both in Boston. I don't know why they chose the enemy of the Celtics. But anyway –
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The Will Chamberlain example says, look, Will Chamberlain is better at playing basketball than you or I are. People are entertained by watching him play basketball. They would like to give money to Will Chamberlain in order to play basketball so they can see him play, and this brings them pleasure.
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I've always wondered why cosmologists say we need to explain why the baryons in the current universe are almost all matter. If there were nearly equal parts matter and antimatter in the early universe, but randomly just a tad more matter, then after annihilation, that small amount is what you would see today.
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And as a result of this, Will Chamberlain has more money than anybody else, and everyone else has a little bit less money. Isn't this incompatible with the difference principle? So number one, this is like a bizarre example to use, right? He's not choosing a captain of industry here. He's choosing a basketball player. But number two, I actually talked to John Rawls about this.
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And I said, what is your take on this? And he was just so exasperated. He's like, let people watch basketball and let people get rich and then tax them. Give them income taxes. And then not 100% of what they earned, but some fraction of it and use that to do good things. This should not be hard. It should not be hard to do better than we're doing right now. Apparently, it is hard.
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I don't know what to do about it, but we got to keep trying to do things about it. I guess that's as good a place to conclude as any. Thanks, as always, for listening, for supporting the Mindscape podcast. Always appreciate the support I get. Talk to you next time. Bye-bye. Bye-bye.
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It looks to us like a lot, but we have no idea how much total matter and antimatter there was to start with. Given any amount of observed residual matter or antimatter, couldn't we come up with an initial combined mass sufficiently large to explain it all as just a small, statistically insignificant imbalance?
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Well, hopefully you'll not be surprised to learn that cosmologists have thought about this quite a bit. And you have to be careful. Of course, generally, well, let's say one thing. In fact, what cosmologists believe is that there was almost exactly an equal amount of matter and antimatter, but not exactly.
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And you can work out from the equations and from what you observe how much more matter you needed than antimatter in the early universe. And the answer is about one extra proton per billion protons. So for every 10 to the 9 protons and antiprotons, there was 10 to the 9 plus 1 protons for every 10 to the 9 antiprotons. But that's not equal, right?
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So could you explain it just as an initial condition? Sure. I don't think you can explain it just as a fluctuation, because you have to say a fluctuation of what? You would need some theory of the early universe. Sometimes you have a theory of the early universe, like you have theories like inflation, right?
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So in inflation, there is a predictive theory for where the baryons and the antibaryons come from, and you can calculate that. what the fluctuations should be, they're much, much smaller than one part in a billion, okay?
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One part in a billion is actually a huge difference by the scales that we're talking about here, because there are quantum fluctuations, but every—sorry, there really are not quantum fluctuations. It depends on models of physics that we don't yet have complete handles on, okay? So you could—what you want to do
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is to create some theory of the initial conditions where there's an imbalance where, sorry, there's not an imbalance in the initial condition, but there's dynamically a preference for decaying into baryons or antibaryons. And you can invent that. Models of leptogenesis and things like that do that kind of thing.
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It's a little bit tricky because even in the standard model of particle physics, baryon number is not conserved. B minus L, baryon number minus lepton number is conserved. So if that quantity is exactly zero, it stays zero, but you can still create or destroy individual baryons. And in fact, we also think that gravity does not conserve baryon number at all.
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Just to remind you very quickly, I can't possibly remember everything, but Trump fired a bunch of inspectors general the moment he got into office. These are government employees whose job it is to make sure there is minimal fraud and corruption. So we're getting rid of them because fraud and corruption are going to be kind of an important catchphrase. He fired a bunch of federal prosecutors, U.S.
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And that hurts you for this particular question, because if you started with an imbalance, but it's super-duper high energies, there was copious violation of baryon number, then you would tend to equilibrate. You would tend to get rid of the excess number of baryons over antibaryons. So, you know, we don't know what the final answer is. We certainly don't know what the initial conditions are.
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But cosmologists are thinking about all of these things. And, you know, the thing is it's not just like we don't know why there's more matter than antimatter and this makes us sad. Right. Right? That's not the motivation. The motivation is this is a clue that the universe is giving us. There's more matter than antimatter. Okay.
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Does that tell us something about the laws of physics that we don't know? So, you know, it's nice to have those little puzzles out there in the universe for us to think about. Helen Edwards says, Computation and—sorry, information and computation, absolutely a central part of the commonality between synthetic and organic systems.
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I don't think that my main conception has shifted very much vis-a-vis whether AI could ever be alive, namely— Sure, it could be. I'm 100% willing to imagine that it is being.
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I think that as I know more and more about what it means to be alive, I'm more and more appreciative of the differences between what we are doing these days in the realm of AI and what it would be to create a truly living artificial organism.
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As I've said many times before, so I'm not going to rehearse now, but real living beings are quasi-stable systems that take in free energy from the environment and use that free energy to survive, to persist, to self-repair. We do metabolism. We eat and we excrete and we get on with lives and we're constantly increasing the entropy of the universe.
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You can't turn us on and off like you can turn on and off a computer in quite the same way. We have built-in instructions from billions of years of natural selection that lead us to want to survive and to eat and things like that. We're much more self-sufficient than the typical AI system would be. None of these are complete obstacles, right?
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None of these are things that you couldn't build into an artificial system, which is why I think that that's completely possible. It's just not where we're putting most of our effort right now, right? If you want to optimize for
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a machine that will create human-sounding sentences and paragraphs on topics that you ask it questions about, then there are much easier ways to do that than to build a full-blown artificial living being. And that's exactly what people are doing. OK, I'm going to group together two questions. One is from Matthew Cushman, who says, a question from my son Aaron in high school.
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Suppose there were a small toy universe a few meters in diameter. Alternatively, it could be a region of our universe encased in a reflective impermeable barrier. The only thing in this universe is an apple. Otherwise, it's static. What would the long-term fate of the universe be?
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attorneys, especially ones who have been working on the various felony cases against him at the federal level. He either fired or sent home or convinced to leave a bunch of people at the National Security Council, the director of the federal – Aviation administration, people at the State Department, people in the foreign aid office. There's a 90-day pause on all foreign assistance.
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Aaron's theory is that it must eventually end up as photons bouncing around at high temperature due to conservation of energy. And Claudio says, imagine a device, let's say a sphere in which the interior is isolated from the rest of the universe in an absolute way. No radiation or matter of any kind can penetrate. It's even isolated from the CMB, the cosmic microwave background.
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Could such a device, if feasible, be used to study the cosmological constant and questions such as the heat depth of the universe? It's always interesting to me when in one month, in one particular AMA session, questions that had never come up before but are closely related to each other just pop into existence.
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So here we have two people asking about tiny little universes or tiny little... Tiny little compared to the size of the universe, our actual universe, I suppose. Tiny little regions of the universe that are isolated from everything else. What happens inside? So for Matthew slash Aaron's question, let's just...
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get one thing on the table very quickly, which is the slight unrealisticness of the question. So there's two different versions, if you remember Aaron's question, either a small toy universe a few meters in diameter or a region of our universe encased in reflective impermeable barrier.
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So there aren't really any reflective impermeable barriers, at least not ones that would last literally forever, right? Because they're made of matter. Just like for the previous question about the matter-antimatter asymmetry, there are questions about physics at super early times and super high energies we don't know the answer to.
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There's also questions about physics at super long times and low energies. We don't know the answer to. Both of them involve, among other things, is baryon number conserved, which is a way of saying, are protons stable, right? Maybe they are. We think that they're not. Most physicists think that they're not, but we've never seen one decay.
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We think, among other things, if you just have ordinary matter, there is a possibility, a sort of probability per unit time, that if you waited long enough would always become real, that the ordinary matter collapses into a black hole. right? And then it would just evaporate away. And that's true for your impermeable barrier also.
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Even if that doesn't happen, the protons in your barrier could decay themselves, and that would be bad. So it's hard to imagine truly impermeable barriers. It's also hard to imagine small toy universes a few meters in diameter for exactly the reason that Einstein was shocked back in 1917 when he started thinking about cosmology. And he realized that in general relativity,
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Universes tend to either expand or contract. You can't keep the universe fixed, in other words. So that's fine. I'm going to roll with the question. I know what you mean. But I just want people to know that in a world with physics as we currently know it, imagining a small universe that just sits there stationary forever— is harder than you think, okay?
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So we're going to do it anyway, but it's harder than you think. Okay. So there's an apple in our region. What happens to it? Well, again, what happens to the apple depends on laws of physics that we don't know the answer to. The apple, we think, has a probability per unit time of spontaneously collapsing to make a black hole. and then that black hole would gradually radiate via Hawking radiation.
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Even if that doesn't happen, the protons and neutrons in the black hole probably also have a probability of decaying into other things if baryon number is not conserved. So I think, as far as our best guesses about physics are concerned, that Aaron's theory is mostly correct.
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because either the protons and neutrons directly decay in the apple, or, and part of the decay, like when the proton decays, it will emit a positron, which will annihilate the electrons in the apple, and mostly you'll be ending up with photons. Now, if it does decay into a black hole and that black hole turns into photons, details are going to start to matter.
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How small is this region of space that you have invented? Because it's always possible for those photons to recombine to make another black hole, right, which would then decay again. And in fact, there's going to be some equilibrium distribution where it's mostly photons. The vast majority of things are photons.
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Not all foreign assistance. I shouldn't say that. Israel and Egypt are still getting their assistance, but everywhere else, cut off. Ukraine, elsewhere. Heartbreaking stories of people trying to – U.S. workers in Africa and elsewhere working to – save people in various ways just having their funds cut off.
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But there's a probability that a tiny little black hole pops into existence and then radiates away again. Okay. Okay. Now for Claudio's question, it's a little bit different. Claudio is asking whether or not you could do science in this region. Could you study the cosmological constant in questions such as the heat-death of the universe in the sealed-off sphere? Well, in principle, yes.
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In practice, no. In principle, the cosmological constant, which is equivalent to the energy density of empty space, has an effect on the geometry of spacetime here in our solar system? If that's what you're getting at, then the answer is yes, it absolutely does.
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So for example, the orbit of Mercury, which famously was a test of general relativity, because general relativity predicts that Mercury's elliptical orbit precesses a little bit more than Newtonian gravity predicts. the cosmological constant adds a contribution to the predicted precession of the orbit of Mercury.
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But when you plug in the numbers, that extra addition is so incredibly tiny that breathing on Mercury is probably at least as effective, okay? The numbers actually matter here, and with things like the cosmological constant or the heat depth of the universe, size matters. The cosmological constant has effects that build up over space and time.
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So if you have a small region of space, in principle, there's an effect of the cosmological constant, but that's exactly the wrong place to look for a noticeable effect. That's why, in practice, when we try to constrain the cosmological constant, we are generally doing cosmology experiments.
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Okay, Pete Faulkner says, in your December 2024 AMA, in response to a question about black holes, you mentioned that details like a black hole's size, composition, and the observer's velocity significantly impact the experience of someone falling into a black hole.
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This seems to contrast with my understanding of the no-hair theorem, which suggests that black holes are fundamentally characterized by just mass, angular momentum, and electric charge. Could you explain how these seemingly conflicting perspectives are reconciled? Sure, it's the difference between falling in and staying outside. It's as simple as that.
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If I throw a bunch of things into a black hole, then from the perspective of someone outside, the details of what I've thrown in completely disappear. I mean, things that are just visible, like did I throw in a red ball or a blue ball, that literally disappears. It's now behind the black hole. I just don't know.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Things like the lumpiness, the spatial configuration would initially distort the shape of the black hole, but the black hole would quickly radiate away any such distortions in the form of gravitational radiation. So the black holes settle down from the perspective of an outside observer. But if you're falling into the black hole, you could still see what I threw in.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You know, if I threw in a ball and you don't know whether it's red or blue, But if you fall in fast enough after the ball, you can just catch up to it and look at it. So it's completely consistent. It's just you're asking two different questions from two different points of view. Robo says, I liked your solo episode 295 on emergence.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
There was this weird event where there was a memo that went out that said all federal grants are hereby suspended for a while. That would be just enormously destructive to the country. You know, grants, maybe the word is bad. I don't know. Maybe people don't understand what the word means. It's not like a present.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
From the start, I was listening for some description that corresponds to my naive idea that the term emergence refers to the way that lower level states and their dynamics interact on a meta level to generate macro relationships, even if those relationships or influences do not arise from the theory of the micro level. An example from recent experience is Albrecht's law.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Intelligent people, when assembled into an organization, will tend toward collective stupidity. Does your idea of type 3 or type 2 emergence encompass this kind of concept, or am I off track even thinking of this as emergence? You're not off track thinking of it as emergence.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I think that anything which starts with either individuals and goes to groups or starts with atoms and goes to individuals, these are examples of emergence. If you can describe the group in terms that don't require specific information about all the elements of the group, then you're doing emergence in some way or the other.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I don't know whether Albrecht's Law is really true or it's just kind of a joke, right? I'm not exactly sure about that. But I don't think it's fancy emergence in the sense that I think it would be completely predictable on the basis of a competent theory of individuals, right? Like, why are the individuals tending towards stupidity?
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Like, they react to other individuals in certain ways, and you kind of could have predicted it. Maybe you didn't. But you could have. Just like in principle, if I knew everything about atomic physics and chemistry, I could predict liquids and solids and superconductivity and all those things, right? In practice, it might be very hard, but it's absolutely implicit in the underlying theory.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So emergence is great because you don't need to know the underlying theory. I can learn about solids and liquids without knowing about atoms. But that doesn't make them incompatible somehow. And in principle— which is a very, very important phrase in this game. I could tell you about solids and liquids just based on the underlying stuff of which they are made.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Gray Monroe asks a priority question. What are your thoughts on the relevance of many worlds quantum mechanics to theories on the origin of life? Many worlds suggests rare branch of the wave function where functioning life, let's call it a Boltzmann cell, emerges by chance.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
These cells could seed their universe with the first replicating organism bypassing the challenge of explaining the origins of the first complex cell. Should we seriously consider the possibility that we live in such a world? you know, sure, you're welcome to consider that possibility.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I would, as usual, even though I think that many worlds is probably the best theory we have of quantum mechanics, I don't really care about the other worlds. Like, that's just not the reason why I care about it. The reason why I care about many worlds is because it gets the predictions for our world right.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And in our world, what you predict are various quantum probabilities in exactly the same way in many worlds as you do anywhere else, that the probability of something happening is proportional to the wave function squared. The thing about intelligent life is we know it exists because we are it by most definitions of intelligence. So it happened.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And if you want to say, well, the probability of it happening, there's some bottleneck, maybe the first cell, maybe some other point along the way. The probability was really, really, really, really low. OK, well, but it happened. We're in the part where it happened.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It's money that is used to do important things like get science done among other things. So then another memo went out saying – no, the previous memo had been rescinded because they realized how bad it would be. But then the presidential spokesperson, the White House press secretary said the substance of the memo is still true even though we rescinded the memo itself.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So either it happened because there's a single world and we just got lucky or it happened because there are multiple worlds and there's an anthropic selection and we're going to find ourselves in the world where it could have happened. The difference between those two things makes no difference, as far as I can tell, to theories of the origin of life, etc.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Getting lucky versus anthropic selection have all exactly the same empirical content as far as our world is concerned. So I wouldn't point to many worlds as helping that much there. It might help you, like,
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
feel better about the fact that something unlikely happened because since we need to conditionalize on life existing, we don't need to conditionalize on other things like the mass of the Higgs boson or whatever, but we wouldn't be having this conversation if life didn't exist.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So if there are many, many universes, each one of which it's rare to find life, but one of them was bound to do it, that might help you feel better about the fact that we are in that world. But I don't think it really helps you in terms of investigating the details about how life came to be. There's still an empirical question. Is it easy or hard? What is the probability?
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Many Worlds doesn't help you answer those questions. Daniel Schirmer says, if the rotation of the sun was slowed down, could that cause the orbit of the Earth to decay? I heard the Earth would get closer to the sun if the sun's rotation slowed down. How much closer would the Earth get to the sun if the sun was spinning half as fast as it currently does?
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So you hopefully will not be surprised to hear I have no idea how much closer the Earth would get to the sun if the sun was spinning half as fast as it currently does. I'm not even at all sure that it's true. that the orbit of the Earth would decay in a noticeably different way if the Sun will slow down. Or I guess what I should say is, I'm not sure whether it would decay at all.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It does decay because of various effects that are much, much more important than the rotation of the Sun, like the orbit of Jupiter. is more important than the rotation of the Sun for things like this. And the orbit of Jupiter doesn't matter that much. So the only thing I really have to say about this question is any of these effects are going to be really, really, really small.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Isaac Newton did pretty darn well in understanding the orbits of planets and things by treating everything like a point particle that wasn't rotating at all. So that must be a pretty good approximation. Craig Stevens says, I think that the answer is no, there is not such a way. But I mean, of course, it depends on what you're allowing yourself to do.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
If you put the elect—so here, let me say what I think is true, and then we can decide what you meant by the question. When you have an atom that has an electron, let's just take a hydrogen atom, right? Let's make it very simple. So you have one proton, which is the nucleus, you have one electron, and there are energy levels, okay? And there is a bottom energy level.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
There's the ground state energy, the minimum energy state of the electron. And as far as ordinary quantum mechanics goes, so we're ignoring baryon number violation, proton decay, all that stuff, right? All that crazy stuff.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
In ordinary undergraduate quantum mechanics, if you have a hydrogen atom with its electron in the ground state and you ignore the rest of the world, then it will stay there forever, okay? It's a stable state. It's not going to do anything. It just sits there. If you excite it, so you send a photon in and you prod the electron to a higher energy state, the higher energy states are unstable.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
if this doesn't make any sense to you, join the club. It doesn't make any sense to anyone else either. Um, science has been dramatically affected. This is my own Bailiwick, you know, um, all grant reviews at National Science Foundation and National Institutes of Health and elsewhere have been suspended indefinitely.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
They just are. You can predict, this is a classic undergraduate homework set, You can predict, based on what that energy is, the probability per unit time of the electron decaying back down to the ground state and emitting a photon. So if you wait arbitrarily long, the probability approaches one, that that electron will go back down to its ground state.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
If you want to ask why that happens, why is it necessary, why can't the electron just stay there, then there are many possible answers, depending on what kind of answer you're looking for. My favorite answer, which is not the one anyone else gives, but it's because entropy increases. Why is that?
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Well, because you go from a system that has one proton and one electron to a system that has one proton, one electron, and one photon. There are more ways to have that system arranged than just the one proton and the one electron. So emitting more and more photons increases the entropy of the universe in general. So that's likely to happen and unlikely to unhappen.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It cannot happen because you can aim a photon, right? It's just the numbers are small enough that you can control what's going on. But in general, the way to think about it is the electron will want to dissipate any extra energy it has to go down to the ground state, and it does that dissipation by emitting photons, either single or more than one photon sometimes.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Babbel is gifting our listeners 60% off subscriptions at babbel.com slash mindscape. Get up to 60% off at babbel.com slash mindscape, spelled B-A-B-B-E-L dot com slash mindscape. That's babbel.com slash mindscape. Rules and restrictions may apply. Thomas DeWitt says, The Markovian assumption, saying it is not an important assumption because, for example...
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Memories could be introduced at a given time step that have information about the past, while the system remains Markovian. But spatial locality was used to separate types of emergence. Couldn't the analogous thing be done for spatial locality, where knowledge about other locations is contained at each location, making the dynamic local?
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Is there some crucial difference between time and space that I am missing? Yes, there is a very crucial difference between time and space that you are missing. This is subtle. You know, we all know that Einstein came along and said that in some sense, time and space are both part of a single underlying space-time.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You want to say that, and you want to appreciate it, and you want to take it on board in your precious belief set, but you also want to understand that there are still differences between time and space. The single biggest difference, I would say, there's a lot of differences, but the single biggest one is...
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I have a grant proposal in hoping to, you know, fund some research into quantum gravity and cosmology, but that has been put on hold. If it ever comes back, who knows? Uh, That's a minor inconvenience for me. The more important thing is that they're not paying salaries to people like postdocs and grad students at the National Science Foundation, for example.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Given information about the universe at one moment in time, you can, in principle, in classical mechanics, predict what it will be like at other moments of time, right? That's Laplace's demon that we were just talking about. There is no analogous statement for space, okay? So the table I have right in front of me right now, it has atoms in it. the atoms have a certain density, right?
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And knowing the density of atoms, the number, the amount of grams per cubic centimeter at one location of the table does not help me predict what the density of matter is like a few centimeters away because the table might end, right? There's a sharp line where the table is to the left and it's not to the right. There's a discontinuity in the density of matter.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But if I think about, so over space, there's just complete difference from place to place. There's no determination from what happens at one point to what happens at the other point. But there is a determination in time. If I say, okay, there's a certain amount of energy density here at one moment of time, what's it going to be like a minute later?
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It depends on details, but probably it's going to be the same number, right? The table's not really moving, right? So there is this rigidity, there's this predictability from moment to moment in time that simply isn't there in space. And this has to do with the fact that there's only one dimension of time. This allows for that fact to happen.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Mathematically, it has to do with the hyperbolic nature of the underlying differential equations. But there are three dimensions of space, so you don't quite have that same rigid control. So... Yes, in practice, for the reasons that we care about here, time and space are pretty different. There's predictability in time, not predictability in space.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Anonymous says, I've noticed you almost never swear on the podcast. I'm curious if this is in order to be professional, or is that how you are in daily life as well? I think that in daily life, I swear more than I do on the podcast, okay? I'm not afraid of swearing. I'm happy to do it.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But yeah, I think, I don't know whether you want to call it professional or not, but I do try to respect the audience and try to care about what the audience is. some members of the audience would probably like it better if I swore more. Some would not like it better. I'm going to play it cautious and just try to be as accommodating for the largest number of people that I can, okay?
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So when I give a talk, when I'm giving a colloquium or something like that, there's no swearing going on, right? When I give a public lecture, there might be children in the audience, there might be adults who just don't like it. So there is a certain standard of behavior that one adopts that I'm perfectly happy to do. One can always violate the rules in strategic ways, right? For emphasis,
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
If you want to make a point especially hard, if there's a guest that I'm interviewing and they swear a blue streak, then sometimes that's going to happen. Ti Nguyen was definitely like that, for example. There have been others. I remember when I was an undergraduate and I took a class, a philosophy class actually, and the professor had – He missed the first class.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So because he was traveling, he was at a conference and he came back for the second class and he was talking about, you know, he was sort of getting to know us and just sort of schmoozing or whatever before launching into the substance of the course. And he was talking about being in New Orleans and he ended up in this place in New Orleans and there was no beer being served.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
For the grad students, I am told it is not such a big deal because if you're a NSF fellow, if you have a fellowship from the National Science Foundation, they allocate your yearly salary in one lump sum at the beginning of the year, and then the university doles it out monthly or whatever, so they should be okay, at least until next year. Postdocs don't have it that good.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And he was upset about this. He was like, come on, I'm in New Orleans. Where's the fucking beer? And years later, because I got to know him pretty well, he explained that that was entirely pre-planned, that he very intentionally tries to swear in every first class meeting of every class he teaches. Why? Because if he happens to swear in week five, it does not seem like such a big deal.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You know, he's sort of already set the stage. This is just human relations. This is just accurately gauging what you're trying to do, what the impact of how you talk and what you say is. If you want to get grandiose about it, think about the conversation we had with Derek Guy about how to dress. You can dress however you want, sure. You can talk however you want.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You can present yourself however you want. You're totally welcome to do that. It's a free country. But you can't be naive. You can't just say, not only do I want to dress and talk and present myself however I want, but I don't want anyone else to react badly about it, to judge me, to think less or more of me based on how I talk or how I dress or whatever. That you don't have a right to.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You can talk and dress however you want, but people are going to react to it one way or another. We all live in a world where there are other people judging us all the time. Maybe you don't care. That's fine. You don't have to care. But if you do care, you should be cognizant of what it is. So I just want the podcast to be as pleasant and enjoyable for as many people as possible.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And I talk like I do. I talk in the podcast like I do when I'm being a physics professor, more or less.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Soonest Mended says, in the recent solo podcast on time, you argue that presentism versus eternalism question is important not because one or the other being true would change the predictions of physics, but because believing one or the other might influence future avenues of research in physics.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Are there examples of other such questions where choosing a particular orientation has led to a research breakthrough that would otherwise have been unlikely or impossible? I don't... know of a perfect example off the top of my head, to be honest. I know exactly what you mean.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So there's various places in physics where we have multiple ways of talking about exactly the same processes or phenomena or whatever. A classic example, especially for those of you who have read volume one of The Biggest Ideas in the Universe, Space, Time, and Motion, is the difference between Lagrangian classical mechanics and Hamiltonian classical mechanics.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
This is to say, for those of you who have not read that wonderful book that I can absolutely recommend to you, you can formulate the laws of physics either in sort of the good old-fashioned Laplace's demon way, which is to say, give me the complete state of the system now, give me the equations of motion, I will tell you what happens next. The Laplacian paradigm, we called it in the book.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And that is how Hamiltonian mechanics works. Lagrangian mechanics is based on what's called the principle of least action. You may have heard about it. And it says, don't tell me exactly the state of the system to start. Tell me the configuration of the system. Tell me the positions, but not the velocities, for example, of the system.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
They have a monthly salary, if they're NSF-funded, that is just not coming. They're not getting paid. Postdoc life is not easy, right? You are bouncing around. You have a three-year job, typically, at most, and then you have to go somewhere else. You're living paycheck to paycheck, and those paychecks are not coming, so this is going to be catastrophic for them personally.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But then also tell me the configuration of the system at some other time. And I'm going to search through all possible ways to connect the configuration at the early time to the configuration at the late time. I'm going to choose the one that minimizes a certain number called the action. So you can show that the actual behavior of systems under these two ways of talking are completely equivalent.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But the actual procedure you go through to get them is very, very different. In a slightly more advanced version of this, you know, these days we talk about the ADS-CFT duality and other dualities in quantum field theory. A duality is exactly this. A duality is two different ways of talking about exactly the same underlying physics, two different equivalent ways of talking.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
In quantum mechanics, we have the Schrodinger picture and the Heisenberg picture. There's a whole bunch of different examples where you have multiple ways of doing things. I don't know whether there are examples where choosing a particular orientation has led to a research breakthrough. Probably yes, but I don't know off the top of my head.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But absolutely it's true that choosing a particular orientation changes how you naturally think about things, right? It changes the sort of natural ways to – modify the theory or think about different theories. Anyway, I don't have any perfect examples of that off the top of my head right now.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But for presentism versus eternalism, you know, if you, you know, presentists, I should say, I'm an eternalist myself. So I think of the whole shebang, right? I think of, you know, the whole universe all at once and try to figure out what rules it obeys and things like that. Someone like Tim Maudlin, former Mindscape guest, is a presentist.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
He really thinks that the laws of physics not only describe patterns in the evolution of the universe, but bring them about. He's not only a presentist, but an anti-Humian when it comes to laws of physics, as we talked about with Tim, but also previously with Ned Hall, etc. So Barry Lower and I talked about that also.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So that does lead these individuals, myself, Tim Maudlin, et cetera, to propose different theories of understanding. You know, Tim is not happy with many worlds. He's much happier with Bohmian mechanics. I'm kind of appalled by Bohmian mechanics. Which one of us is right will hopefully be decided by data and things like that in the future.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But in the meantime, since we don't know the answer, our orientations are absolutely going to affect what we're most likely most positively predisposed toward. Robert F. asks a priority question.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
My father always wanted to understand the answer to the question, if mass, a large object, follows the curvature of the fabric of space, wouldn't then there be some kind of small measurable background heat due to friction of its motion through space? So yes and no. Strictly speaking, no.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
There's not friction due to the motion of objects through space because the idea that you have that there should be friction comes from a very higher level, non-fundamental description of reality, right?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Of course, it's also catastrophic for US science as a whole. Why in the world would the best people from outside the US think of coming here with all of this obvious chaos and dysfunction that we are exhibiting to the rest of the world? Anyway, I could go on for hours about this. I don't want to do that.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
If I push a tire down the road, there is friction because the tire is made of atoms and the road is made of atoms and the air through which it moves is made of atoms and there are photons bouncing off the tire. And in all of these invisible ways, there's noise and friction and dissipation and energy gets lost from the tire.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And so you perceive that as a kind of frictional force that eventually slows down the tire. If I have an elementary particle or a single object moving through the universe, space itself is not made of atoms in the same sense that the tire or the road is made of atoms. There isn't any way for that object to sort of give off energy to the medium around it.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
The medium around it is as empty as it's possible to be. So strictly speaking, no. There's no friction of that kind because the medium we're talking about is a much more basic element of reality, it's not this collective thing that you get by taking many, many atoms and jiggling them together.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Having said all that, there's one kind of tiny caveat, which is that if you move an object back and forth, rather than just like letting it move through space, actually, sorry, let me back up because I realized I missed a chance to explain something. I can prove that an object moving through space does not slow down. The proof is the following.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
There's no such thing as a reference frame for velocity in relativity. There's no preferred velocity to the universe. So slow down compared to what? Said in other words, if there was only one object in the universe, I could always describe that object in its rest frame, in the frame in which it's not moving at all. And there it's just not moving. So there's no need for it to give off...
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
energy and slow down. And if it just stays there perfectly ordinarily in its rest frame, then in some frame that is moving with respect to it at constant velocity, you will always see it moving at constant velocity. Okay, that's one way of saying it.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Which is why if instead I'm shaking it back and forth, rather than just having it move at a constant velocity, then it's a different story, because then it is coupled to gravity. Everything is coupled to gravity. There's a gravitational field for this massive object that you're shaking back and forth, and there it will emit gravitational waves.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It might also emit photons or something like that, electromagnetic waves. Because every object creates gravity, if it's moving on a non-uniform trajectory, it can lose energy by emitting through gravitational waves. Indeed, when you get a detection of gravitational waves at a gravitational wave observatory like LIGO, Why do you do it?
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Well, it's because two black holes were orbiting each other, or a black hole and a neutron star, and they're orbiting, so they're circling around each other, so that's more or less like being shaken back and forth, and they're emitting gravitational waves, and those gravitational waves are what you ultimately observe.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
The energy loss due to that emission of gravitational waves is what causes the black holes to spiral together and eventually coalesce. There you go. Taylor Gray says, I'm currently reading former Mindscape guest Matt Strassler's book, Waves in an Impossible Sea. The book states that the faster you go past a magnet in the magnetic field, the more you will detect the electric field.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But there's one other thing I just can't help but mention because I'm sure that the people of the future are just going to think there's no way that that actually happened. We had fires in Los Angeles not long ago, devastating fires. I used to live in L.A. and I know many people who either – had to evacuate. Some came very close to losing their houses.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
What mechanism, for lack of a better term, makes this so? Again, this is a question that the satisfactoriness of the answer is going to depend on your prior exposure to physics. Let me give you the highest level answer right away, which is that according to the theory of relativity, the electric and magnetic fields are just two different aspects of the same underlying field.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
exactly in the same way, not exactly exactly, but very, very analogous to how time and space are two different aspects of the same underlying space-time. The electric field and the magnetic field are two different aspects of the underlying electromagnetic field, if you want to put it that way.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
very, very roughly the sort of spatial components or the magnetic field, the temporal time-like components or the electric field. But that is not exactly right, but it has something to do with it. The point is that when you do a Lorentz transformation,
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
which is to say, if you go from one reference frame, like we were just talking about with the large object, you go from one reference frame to another, which you can do by either moving yourself or by moving the magnet or the charged particle or some other electromagnetic phenomenon. Either you move it or you move you, it doesn't matter.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You are now shifting, rotating the different parts of the electromagnetic field into each other so that... Exactly for the same reason why moving at a constant velocity means that you define the division of spacetime into time and space slightly differently than a person who is not moving in the original reference frame.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Now you also define what part of the electromagnetic field is electric and what part of it is magnetic slightly differently. So this was a crucial feature of, of course, the empirical, the historical development of relativity. It was first these wonderful experiments done in the mid-1800s that culminated in Maxwell's theory of electromagnetism that showed that
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
that empirically you could make an electric field by moving a magnet and vice versa, that eventually led to different transformation laws, Lorentz and Fitzgerald and so forth, and Poincare, and Einstein eventually unifying the whole bit.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So the very short answer is the electric magnetic fields are two different aspects of the same single underlying electromagnetic field, and they are transformed into each other by changing your frame of reference.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Alex West says, with the general release of AI, have you noticed any fluctuations or trends in both the quality and quantity of peer-reviewed papers and more personally emails from the next Einsteins? Well, that's a good question. For peer-reviewed papers, no, I certainly have not.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It's a weird thing to me because in my kind of field, the most active people, you know, the people who are most respected in the field basically know each other, and you know what people are doing, and you recognize their names when they write papers, and people write a few papers a year. Some are more prolific than others.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But there are these other fields where apparently there exist people who just write, I don't know, 100 papers a year, which is essentially impossible. It's not the field's fault because that's not typical in that field, but you can get away with doing that. I can't even read 100 papers a year. But obviously there's a lot of churn here.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Others who are not very close to me but did lose their houses. Many people were significantly, severely affected by these fires. And the response to the fires on the part of the local government was not great. I'm not going to defend it. I think that the California governments, both locally and the state, most of whom are completely run by Democrats, didn't do a great job of preparing for
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
People are leaning on other co-authors to do writing or they're just taking something they've already written and rewriting it. 10 different times and submitting it as an extra paper, etc. But that's not my world. In that world, AI might be very, very helpful if all you're trying to do is maximize the number of papers you submit somewhere and publish them in junk journals or whatever.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
That I don't really follow, so I wouldn't know. In the field that I'm in, I don't think that I've noticed anything at all as a result of AI, except that people are writing papers about AI, which makes perfect sense. As to the next Einstein thing, when I read this question at first, I thought, no, I don't think that it has been an uptick or a change in quality.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And I think that there's an explanation for that psychologically. You know, the people who think of the next Einstein, they don't want to hand over credit to AI, right? They don't want to say, well, you know, the AI and I put this together. They want to say that their own personal genius is responsible for this.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
but having thought of it and having a few days gone by, it is possible that I'm getting more of those emails. I've always gotten a lot. Arguably, the numbers are small, but it's possible that I'm getting more now, and so maybe they're just not telling me, and they are indeed helping themselves to a little bit of AI help when making up their theories of everything. Look, life is short.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I don't spend a lot of time paying attention to those papers. So as soon as I can tell that the email is from someone who has a new theory of everything, all they need is for me to fill in the math, that gets filed pretty quickly.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Janderson or some version of Letters and Numbers says, in your recent solo episode number 300, you present a way time might be modeled as emerging from the universal wave function. Am I right in assuming that this method could also be used to produce any number of other dimensions of space and time perhaps?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Well, the particular method that I was talking about, the idea, doesn't really work with space. It doesn't really make sense. What you're trying to do is take advantage of the fact that there is two features of quantum mechanics. Number one, entanglement, and number two, superposition.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So by entanglement to get time to emerge, you take advantage of that by saying that there is some clock subsystem that is entangled with the rest of the universe, and then superpositions that you can take different states corresponding to different configurations at different times and just adding them together in an overall static wave function. But space is just a different kind of thing.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Like we said, that evolution through time that is characteristic of the time dimension doesn't happen in the same way in space. So it really is a different kind of thing. Ultimately, probably you want to have everything be unified, but that's tricky to do for a number of reasons.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So in the specific approach that I was talking about in that podcast, time is just a very different kind of thing than space. Ben Lloyd asks a priority question. I need your help with something. This might seem weird, but my biggest fear by far is that at some point everything will end forever. I'm not really scared that our civilization will likely not be able to survive the heat death.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
My main fear is that the universe will end. Nothing interesting will be able to happen anywhere forever, and no multiverse scenarios that would contradict what would turn out to be true. Luckily, many theories or hypotheses make it so that interesting things would happen forever. For example, inflation is the dominant theory for explaining the early universe and how it evolved.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
A fire that was quite this bad. You know, some of it is there are unpredictable natural disasters. Some of it is you weren't ready for it, right? So that there's plenty of blame to go around. But Donald Trump somehow got it into his head that it was simply because there was water to fight the fires and the California government didn't want to turn on the faucet.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And many prominent proponents of inflation often say that eternal inflation is almost inevitable once you get inflation. In eternal inflation, there would be continuously new universes forever. The next biggest competing theories to inflation are cyclic models, etc.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I've always needed this sort of existential comfort, but more than that, I need to believe things that have evidence and things that could be true. That's why I'm not religious. Anyway, what do you think of this? Do you align more with my view? I really don't align with your view.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You know, I think that I can't let my life here on Earth be vastly affected by things that are going to happen long after the last star stops burning. This is something that I can imagine, but not something that affects my life in any way. I am entirely at peace with the idea that the universe might someday end. Maybe the last living creatures in such a universe will be sad, and that I understand.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
That makes perfect sense. But we are so enormously far away from that that no, it doesn't really affect me very much.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And in fact, it's sort of important to not let it affect you too much if you're a scientist or philosopher, because then it will point you towards sort of giving more credence to certain theories than might otherwise be appropriate, even though you don't have a lot of evidence really for them.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Funky Town says, for the first few decades of my life, I lived, first two decades of my life, I lived in a very small bubble with limited knowledge of the universe's workings and a huge emphasis on religion and the Bible as final truth. For the last decade of my life, I found myself diverging from my original worldview and considering myself a little more enlightened.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
The biggest struggle for me during this time is trying to understand the feelings and experiences I had in my earlier years and rationalizing them. Is there a physical explanation for the responses someone has that are considered religious experiences, especially if that has been something they have been immersed in during their entire upbringing?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
For example, I went to a service recently for the first time in years and had a very emotional response despite not putting much stock into the belief anymore. Yeah, you know, I think that I'm not an expert in exactly the neurological or even psychological explanation for these responses, but to me they seem completely unsurprising.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You know, when I walk into a beautiful cathedral or hear really good church music, it is emotionally affecting. Why wouldn't it be? Forget about the existence of God. These things, these cathedrals, these pieces of music, were designed by human beings to evoke an emotional response, right? That's why they were designed the way they were.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So I have no trouble believing that the physical trappings of a church or the aesthetic trappings of the art or the music, or for that matter, the sort of ritualistic trappings of the steps you go through when you're at a church service, have important resonance to us.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
That is as unsurprising to me as saying, oh, I went to a music, a rock concert, and a bunch of people seem to be having a really good time and dancing around. Isn't that surprising? It's not really surprising to me. Robert Grenise says, when the universe reaches maximum entropy, heat death, does time end as well? With no more entropy, the arrow of time would cease to have meaning, wouldn't it?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Well, as I've said many times before, but it's been a while, so I'll say it again, time is separate from the arrow of time. Just like space exists without an arrow of space, time can exist without an arrow of time. Time, as we conceptualize it in physics, can absolutely be part of the best description of the universe while not having a directionality one way or the other.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So just like there is a distance between me and the sun, even if there are not a bunch of rulers or meter sticks lying between me and the sun to actually measure it, there will be time in the universe once you reach thermal equilibrium.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
and let the water come down to Los Angeles to be used to fight the fires. This is entirely nonsense. There were times when the water ran out, but it was just because the capacity of the local firefighting infrastructure wasn't up to it because the fires were so bad. There were multiple fires, and they were very, very bad.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
If I have, you know, a glass of water and there's an ice cube in it and the ice cube melts, and the water is now more or less in equilibrium at room temperature with the room around it, I can still sensibly talk about how long it's been there. Time is still passing. DI says, how does one stay realistically optimistic within the next four years in the United States?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Any suggestions for small yet socially meaningful actions each one of us can take? Short answer is not really. I mean, I have suggestions, but I don't necessarily think my suggestions are very good. Different people will respond differently. Different people are going to have different ways of coping. Some people are going to be happy about the next four years.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But if you're the kind of person who is concerned, worried, anxious about the next four years, I do think that it's important to mix trying to do something about it with also trying to live the rest of your life, as I said at the beginning in the intro of the podcast. Doing something about it means politics one way or the other.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It could mean campaigning or something like that, but it also could just mean talking to people. At the end of the day, democracy is not just about putting up more posters. It's about changing people's minds to agree with you. You have to actually communicate with people and give them the sales pitch that your point of view is better.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I think that people on both sides of the divide are not very good at that. But if you could talk to some people who are not closed-minded and not just insult them for not agreeing with you but actually provide them reasons that it would be better to agree with you, then you've done a little bit to make the country a better place. Meanwhile, take care of yourself. Learn interesting things.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Listen to good podcasts. Keep trying to get better ourselves at understanding the world, both in political ways and in scientific ways. It's an ongoing process. We're not going to declare victory and like, okay, now the world is good. We're going to try to keep on, in little tiny ways, making it better.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Sid Huff says, Jan 11, a former Mindscape guest in a recent episode of Robinson's podcast, stated that astrophysicists don't really care what goes on inside a black hole. The event horizon is the black hole. We simply don't care what's going on inside. Why would she say this? Why wouldn't she and other astrophysicists want to know?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Well, astrophysicists are human beings, and a human being might want to know what's going on the inside. What Jana means is that for the purposes of astrophysics, it doesn't matter what's going on inside the black hole. That has to do with the no-hair theorem we were just talking about earlier.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Once you throw that stuff in the black hole, and once the black hole settles down, it is entirely defined by what's going on at its event horizon. Astrophysics is not affected by what's going on inside. That's all that she meant. Randall Bessinger says, do you have any views on the current brouhaha in the atheist skeptical movement on the trans issue?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And so firefighters did run out of water, but it wasn't because, as Trump believed, there was plenty of water up in— Washington and Oregon and Northern California that could be sent down to Los Angeles, but the Democrats didn't choose to do it. That is entirely wrong. There's no water transport from Washington or Oregon to California.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I'm not quite sure what kind of views you want me to think about here. I mean, I'm definitely on one side of this issue in the sense that I think that trans people are people and should be treated as such. And it's absolutely true that a certain segment of the atheist skeptic movement has been
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
just wandered into really bad territory at being very actively anti-trans in a way that seems very illiberal and immoral, honestly, and bigoted to me. As to why that's the case, it's a trickier question. I think that there's a lot of psychology going on here.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And so I'll just, you know, again, I'm not a professional psychologist, not a professional sociologist for that matter, but I will point to one thing that seems to strike me about these things. Well, to two things. One very quick thing is as soon as something is called a movement, it's in trouble, right?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You know, whether it's the atheist movement, the skeptical movement, the effective altruism movement, or whatever, when you have an idea, like atheism, God does not exist, that's an idea. When it becomes a movement, all sorts of bad things can happen, right?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You know, now, okay, there's people, you're in the movement or you're out the movement, there's good ways of behaving, there's all sorts of possibilities for things to go wrong, and they typically do. So that's one very broad thing.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
The other thing is that in that particular movement that we're talking about of atheism and skepticism, there is the huge danger that you are in a movement that is in large part devoted to patting itself on the back for being more rational than the rest of the world, right? You people think that there's a giant man in the sky who's judging you, but I am too rational to believe that.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And I'm in favor of being rational. I think that's a good thing, trying to be rational. But it sets you up for making the mistake when someone says that something that you're doing is— not rational or not correct or not nice of not listening to that kind of criticism because you've already decided that you're more rational, right? And so people become defensive.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And in fact, there's a backfire effect where they double down on whatever it is they are believing. I think that this is not specific to atheism and skepticism actually, but in progressive liberal circles more generally, there's a certain slice of people who feel nostalgic for the days when in their minds it was all just about the economy and class struggle, right?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And they thought of themselves as fighting for the workers and the underprivileged and whatever. And now it's about identity politics and like these black people and these trans people and whatever. They are all leaving the message that they thought was supposed to be the message.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And you see the difference is that the people we're talking about here could think of themselves as the underdog when it was all about fighting for the lesser well-off. But now you're telling me there are other groups that are disadvantaged that I'm not in. Maybe even you're implying that my group is causing the disadvantage. You know, you're kind of criticizing me.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
There is plenty of water transport from Northern California down to Los Angeles, but it was working fine. There was no problems with that. But he got it in his head. This is what happens. He's a very not smart person. And he got into his head that all you have to do is turn on the faucet. So he literally ordered the U.S.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
A lot of people in these communities, like the most irrational response you can get from them is to call them racist or bigoted or whatever. No matter what the evidence for it is, they're like, you can't believe I'm that kind of person. I'm a rational person. I'm not that. And that leads them to some dark places when they try to justify that.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So I don't know how much of the effect is caused by that particular syndrome, but I do think it's real. And of course, there's plenty of people in the atheist skeptical movement such as it is that are very supportive of trans people. A lot of trans people are atheists, right? So it's complicated. I wouldn't want to oversimplify it.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I do think that it's much easier to preach rationality than to practice it, especially when it comes to potential criticisms of one's own worldview and behavior. Eric Stromquist says, this may be a long shot, but have you read The Problem of Molecular Structure is Just the Measurement Problem by Franklin and Seifert in the British Journal for the Philosophy of Science last year?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
They argue that the favorite eigenstates of collections of electrons and nuclei are superpositions of all enantiomers and isomers. These are chemistry words, I don't understand, by the way. Not the chiral molecules or individual isomers studied by chemists, which have less symmetry.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
They look at Everett, Bohm, and GRW and conclude that Everett and Bohm can explain classical molecular structure, but only due to the action of decoherence in each case. However, decoherence doesn't save GRW. No, I'm not familiar with that at all. Ordinarily, if I were not familiar with it, I would just skip over the question. But it's an interesting issue.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I really, really want there to be experimental tests you can do to decide between these different theories. There are experimental tests you can do to decide between objective collapse models like GRW and Bohm slash Everett. As far as I know, there aren't any tests to distinguish between Bohm and Everett. But I'm open-minded about still looking.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You know, there's arguments that Bohm and Everett should give the same result, but there's also arguments—in fact, there's arguments from both sides that the other side just doesn't make sense, right?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So if you talk to either Bohmians or Everettians who are more or less made up their minds and you ask them the reason why they don't like the other one, it's typically because they don't think the other one does the job of being a well-defined theory that fits the data. And of course they think that theirs does.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So anyway, none of this is specifically about electrons and orbitals and in molecules and so forth. But just to say that I can imagine something like that being true. So I've not read the paper, but I can imagine that in a theory like GRW, which is one where there's a random chance that the wave function of a particle will spontaneously localize every, uh, every moment or whatever.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You could show that something, some feature of chemistry or solid state materials physics or something like that just doesn't work under these models. So I'm all in favor of doing that. It would be very, very hard to distinguish between Bohm and Everett on that account because Bohm and Everett have the same equation for the wave function. The wave function is just obeying the Schrodinger equation.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Army Corps of Engineers to find some dams in central California and turn on the faucet. So they found two dams associated with reservoirs in the Central Valley. And open them. Just let them go. Now, they're not going to Los Angeles. These dams are not connected to an aqueduct or a pipeline that brings water. When you open the dams, the reservoirs just empty into the rivers.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But I still am holding out hope for some subtle difference that will let us test these ideas experimentally. Will says, I have moments when the suffering and unfairness of the world feels just too much to bear.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
When one sees children killed by bombs or suffering from horrible incurable diseases or learns about life in crushing dictatorships or poverty, one yearns for some cosmic justice that those who suffered will be made whole one day and that all the suffering wasn't just a hideous waste. These are the moments when I would be most inclined to religion, probably as a form of wishful thinking.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
When you have these moments, what do you turn to? Are there philosophers or ideas that you find helpful in this regard? Not specifically philosophers or ideas. I do think that just truly taking on the philosophy of
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
of naturalism, of, you know, the world is not guided by any external forces, it just obeys the laws of physics, and appreciating that those laws of physics and the initial conditions or whatever include an enormous amount of information that we don't have access to, and therefore there will be things happen that we don't like and can't predict and can't do anything about, I think it is possible just to accommodate oneself to those true facts about the universe.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
We're all going to die. Probably life itself will someday cease. I have plans for the future, some of which will turn out and some of which will not. I've had plans in the past that did not turn out. It doesn't make it any easier in the moment. You know, when a close friend of yours is sick or passes away, that doesn't make it any less tragic and hurtful when that happens. But
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But the fact that things like that will happen are things that you can come to grips with long before they actually do. And I don't think it's a matter of like this philosopher or this idea really helps you with that.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I think that there's some combination of that understanding of the world and the kind of psychological accommodation or orientation that lets you approach that with clear eyes and do the best we can, accepting that they will make us sad when they happen. Robert Ruxendrescu says, You can, sure, no problem at all. In fact, that's a very, very common form of entanglement.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
We don't even talk about it that much because it's just so common. But the example that I often use is imagine a particle like the Higgs boson, picking the Higgs boson just because it has no spin, so we're not worried about spin at all. It decays, it decays into an electron and a positron.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And the prediction, according to the Schrodinger equation, is that if you ask in what direction will the electron be moving? The answer is the wave function spreads out in all directions.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It is equally likely, because there was no spin for the original Higgs boson, so there was no orientation, no special direction of space was picked out, equal probability to observe the electron moving in any one position, likewise in any one direction. Likewise for the positron, equal probability to observe it moving in any one direction.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But when you observe one, then you know where the other one is because momentum is conserved. You know exactly what the coordinates has to be for the other particle that you didn't observe. There you go. And that's entanglement. Indeed, that is more or less what EPR actually talked about in the famous Einstein-Podolsky Rosen paper about entanglement. The idea of doing it with spins came later.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It might have been John Bell, actually, who originally popularized the idea of doing it with spins. I'm not sure about that. David Summers says, I finally got around to watching Oppenheimer. In your opinion, how valid was the concern that the atmosphere could ignite when detonating an atomic bomb? Was it irresponsible to carry out the test given the available information at the time?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Well, I can certainly say that the movie overhyped that particular worry. The worry did exist, or rather, let's put it this way, the possibility had been raised. There was never a time when someone did a calculation and they said, oh, this will ignite the atmosphere, okay? Rather, people suggested, like, is it possible that this will ignite the atmosphere? Should we worry about that?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And this is something that is part of a plan because the Central Valley is the home of an enormous amount of agriculture. And during the summer months when the drought is usually bad and the crops are most needy, you need that water. You don't need it in January or February in the farmlands of the Central Valley. So this did absolutely nothing. It's literally pouring water into the ocean.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And they did the best they could. They tried to calculate it, and they found out that the answer was no. It would not ignite the atmosphere, so they moved on. Now, it's completely legitimate to say, okay, but there was a chance, there was a chance it would ignite the atmosphere, and how exactly confident were they that it wouldn't happen, right? Isn't that kind of important?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
That's very true, and it's something I'm actually very interested in and not completely clear about in my own brain, how to deal with these things that you think are very, very unlikely, but hugely consequential if they happen.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
One of the aspects to keep in mind is lots of things, other than setting off a nuclear test, have the property that they could, in principle, cause some tremendous calamity to happen, and you don't know what the probability is, okay? When I wrote my book on the Higgs boson, the particle at the end of the universe, that was a worry, right?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
The worry was that by turning on the LHC, the Large Hadron Collider, we would destroy the And I said, look, every time you open a jar of spaghetti sauce, pasta sauce, there is a possibility that some random mutation brought to life a terrible mutated pathogen that you are now releasing into the world and will kill all life on Earth by opening that jar of pasta sauce. unlikely, but it's possible.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And what you're doing is you're risking all of human existence by opening that jar. Is this an argument to not do it? And I think that the answer is no, it is not an argument to not do it. Lots of things are possible, but we still have to get through the day.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
That's not a very well-formulated, rigorous philosophical theory of getting through the day, but getting through the day is actually kind of important. So I think that I would like to actually understand that better. Paul Hess says, in the many worlds interpretation, what happens when I use a quantum computer?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Is there one world where I get the right answer and some other number of worlds where I instead get errors? Is the thickness of the world where I get the right answer a function of how carefully I isolate the qubits? Well, you know, as I said this before, there's not a lot of difference between what happens in a quantum computer in many worlds and any other interpretation.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
The success of quantum computers does—so I think that it's possible in my mind, although I don't know for sure, that there could be a principal argument made that quantum computing is an argument in favor of wave function realism. OK, the idea that the wave function really has a physical reality to it because it's becoming entangled, it's interfering, blah, blah, blah.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
All these things are happening. Now, the people who are not wave function realists find this entirely unpersuasive. In fact, many people who are not wave function realists, epistemic people when it comes to the foundations of quantum mechanics, actually are in the field of quantum information. So I don't understand how they reconcile that.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But putting that aside, if you think that you are a wave function realist, there's nothing in a quantum computer that differentiates Everett from Bohm from GRW, objective collapse models, Penrose, whatever, right? That's the same kind of predictions you go along the way. The only difference is, and maybe this is what you have in mind, when you do the final measurement,
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
in a quantum computer because a quantum computation generally starts by putting in some qubits into the algorithm and running it through the algorithm and you get out some qubits and then you measure them. Okay, so there's a measurement process and the measurement process is governed by the Born rule. The probability of getting an outcome is the wave function squared.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And it might very well be the case that the kind of calculation you've done tells you that you will factor a large number with really, really high accuracy, 99 percent confidence or something like that. And so in the traditional single-world interpretation, you would say there's a chance I get the right answer, there's a chance I get the wrong answer.
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And so it was all so that Donald Trump could, on his social media site, put up a little photograph of water pouring out and going, see, I opened the faucet and if I had been president— These fires in LA never would have happened, literally what he said. It's inexplicably dumb. That's the – it's also evil and incompetent but just the dumbness is what really gets you. So what do we do?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
In Everett, you would say there's a world in where I get the right answer and a world in which I get the wrong answer. And of course, to make sense of it, you have to believe that the Born Rule still works. So if most of the amplitude is on the right answer, then you interpret that as saying that the probability of be getting the right answer is given by the amplitude squared.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So again, I don't think that Everettian attitude towards quantum mechanics says much or is much informed by the success or workings of quantum computers. Nanu says, I recently had the pleasure to read your paper, Reality as a Vector in Hilbert Space, and truly enjoyed it. I read it over and over again.
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I was wondering what was going through your head when you realized that reality is a vector in Hilbert space. You know, I don't – I feel bad sometimes because people ask me questions just like we had the question just a second ago about like what philosopher or what idea helps you through this.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I think I just think differently than other people do maybe or at least I think differently than other people want me to think. Because there seems to be this feeling like that there should be epiphanies and moments. You go like, this is the moment I realized something. Or I read this book and this book helped me realize something.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Or this person is very brilliant and I would, you know, here's the list of people I would like to talk to who are dead. But I really like to talk to them because they're brilliant people. I just don't think that way, honestly. Like it's much more gradual and process-oriented in my head. There was not a moment when I realized that reality is a vector in Hilbert space. It kind of creeps up on you.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You think about quantum mechanics and you try to understand quantum mechanics. And then you think about interpretations of quantum mechanics and you decide that the Everett interpretation is a good one. And you realize that the Everett Interpretation is really not about many worlds. It's about just the wave function, the vector in Hilbert space always obeying the Schrodinger equation.
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And then you say, well, okay, what are the data that define a quantum mechanical theory? Like what do you have to put into it? And you ask people and they tell you, oh, we have to give an algebra of observables and all these things. But then you think about it and you realize, no, you really don't.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It might be convenient and it might be important if you are devoted to some notion of locality in your theory. So in quantum field theory, we often care about algebras of observables and things like that. Local observables is usually implicitly taken for granted there. But really, you understand that—
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
The quantum theory simply is a theory of a vector in Hilbert space obeying the Schrodinger equation. You come to that understanding gradually. So nothing was going through my head in that moment because that moment didn't exist. Many, many things went through my head along the way to it. And I hope that things keep going through my head and I come to new understandings.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And it's going to be a very, I don't want to say scattershot process, but there's always a process. It's a give and take. You go back and forth. Things become clear, less clear, et cetera. That's how life goes, at least for me. Colin Johnson says, You know, um... I hope you don't mind if I say that this is an absolutely impossible question to answer.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Like, there's no such thing as the measure on how much of baseline reality we currently perceive. Let's put it this way. When I look at this table in front of me, this poor table is going to get overused as an example. But I could tell you facts about the table. I could tell you its approximate size, its color, its shape, and things like that.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But there's, who knows, 10 to the 26 atoms in this table. And I'm not telling you nearly that much information. So on a scale of 1 to 10 of how much I'm perceiving of baseline reality, I'm kind of perceiving 1 plus epsilon, where epsilon is 10 to the minus 26, or something like that. I'm not seeing neutrinos. I'm not seeing most of the photons.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I mean half the country voted for this, half the country who chose to vote. voted for this. We all knew it was going to happen. Like I said, it's been a little bit faster and more dramatic than we expected. But yeah, we live in a democracy and this is what people wanted. And we have to both live with it and fight against it at the same time.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Most of the photons emitted from the table aren't headed toward my eyeballs, right? They're going in other directions. So yeah, most of reality I'm not perceiving. Not to mention the fact that I'm in a room, which is an infinitesimally tiny fraction of the whole space of reality. I don't even have my window open, so I can't even see the outside world right now. So that's okay.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
We see that we directly perceive a very, very, very tiny slice of reality. And the interesting thing is that it's enough to do pretty well, right? To have a pretty good handle on how reality works, a causal map, as Judea Pearl would have said, about if I poke something in one way, what its response is going to be, despite the fact that I know very, very little.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
The miracle of emergence, that's what it's all about. TJ McMorrow says, in several podcasts, you've distinguished between the concept of complex and complicated systems. In some of those episodes, you and your guests have discussed ways of defining or at least describing complex systems. I'm wondering whether it's more straightforward to define complicated systems.
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I recently learned about the notion of Kolmogorov complexity, and it seems like a pretty good measure of how complicated a system is. In plain English, both seem to roughly mean how much information is required to write down the full rules of the system. Is that a reasonable connection to make? You know, I'm in favor in these kinds of questions of not saying that there's a right answer.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You know, there's many different aspects to what you mean by complexity and complicated. I think it's a wrong strategy to say, here is a word, like complex or complicated. Let's try to decide what it means. That seems to imply that, like, the meaning of the word pre-exists our use of the word out there in the numinous ether or something like that. And that doesn't quite...
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
jive with how I think it actually is work, actually does happen. I think that what happens is we can ask that there—we use a word, we use the words long before we rigorously define them, and then when it comes to rigorously defining them, we realize, oh, actually, there are different aspects that we're using the same word to convey that
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So in the case of complexity or complicatedness, I'm not even going to differentiate between them for these particular discussions, there is something called Komogorov complexity, the length of the shortest program that would output the system or the string of digits that you're talking about.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Scott Aronson and I, when we wrote our coffee cup paper, defined something we called apparent complexity, which is the Komogorov complexity of the coarse-grained version. of the image or the system you're talking about. Both of those are just descriptions of either a string of bits or of some configuration of matter in space.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So for the next few hours, we're going to live with it by thinking about other things. The rest of life goes on. The rest of the universe goes on. At other moments, we can resist and think about how to improve the political situation. But meanwhile, we can also think about bigger, more eternal questions. So that's what we're going to do for a little bit.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But there are many more things you would like to attribute complexity to, including processes, right? Charlie Bennett defined an idea called logical depth, which is not the length of the program that would output the string but the time it would take to run the program that would output the string. There's other measures of complexity having to do with calculations or computations, right?
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How long does it take to solve the traveling salesman problem? But when it comes to physically moving things in the world, things that have many parts like a human body, okay, the complexity of the human body is not simply encapsulated by the distribution of its parts through space.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
We talk about the processes that go on in the human body, the creation of ATP and the traveling of white blood cells that Jim Allison talked about through the body to fight diseases and things like that. So it should be the least surprising thing in the world that there are different ways to quantify what we call complexity.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And the word complicated is generally not a technical term that people use in this context. So when I say that complexity and complicated are different, what I really just mean is that we have an informal notion when things are complicated. we have several different formal notions of when things are complex.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And if you really wanted to be careful, you should tell me what version of complexity you're referring to when you say something is complex. Matthew Fritz says, is the Dirac equation just a special case of the Schrodinger equation? I remember learning that the Dirac equation is the first successful relativistic treatment of quantum mechanics.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But you generally talk about the Schrodinger equation as being the equation of quantum mechanics. Yes, that is completely true. I am completely right about this one, even though there's sort of a lingering set of places where you could hear the wrong answer about this. So the story is, of course, in fact, people don't usually tell the story. The story is that Schrodinger knew about relativity.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
When he wrote down his equation, the Schrodinger equation, he wrote down a non-relativistic equation. But he knew about relativity perfectly well. He first tried to write down a relativistic equation. And he came up with, I'm pretty sure he came up with basically what we now call the Klein-Gordon equation. which is a relativistic wave equation.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It just doesn't fit the data if you try to solve it for electron energy levels, etc. So he eventually found his non-relativistic equation. And What happened was Klein and Gordon tried to find a relativistic equation. So did Dirac. They were aiming at different things. Dirac was aiming at the electron, which has spin. It is now what we call a fermion.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Klein and Gordon, their equation turns out to describe scalar fields, scalar particles, which were not known to actually exist at the time, but theorists could talk about them. But they're both perfectly relativistic. Neither one of them is a generalization or replacement for the Schrodinger equation. They're very useful in physics, but for a completely different purpose.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Hello, everyone. Welcome to the February 2025 Ask Me Anything edition of the Mindscape podcast. I'm your host, Sean Carroll. This month's AMA is going to be mercifully short on politics. We're mostly talking about science and other fun things. But, you know, politics still goes on, and we're aware of it. And I'm a big believer that you kind of—
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
As always, the AMA episodes are brought to you by Patreon supporters of Mindscape. You could become a Patreon supporter by going to patreon.com slash Sean M. Carroll and pledging a bit of money for every podcast. I need to switch it for every month. That's what we're going to be doing now for every month. And as a reward, you get ad-free versions of the podcast. You also get to ask questions.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
The Dirac equation and the Klein-Gordon equation are both classical equations of motion for fields. The Klein-Gordon equation is the classical equation of motion for a spinless field. The Dirac equation is the classical equation of motion for a spin-1 field that has electric charge.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Okay, so it includes both the electron, spin up and spin down, and the positron, spin up and spin down, the particle and its antiparticle. So Dirac thought that he was generalizing the Schrodinger equation, but it turns out that that's not what he was doing, okay? So the correct interpretation, and people sort of hang on to that mistake.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It sounds good when you say, well, there was Schrodinger, and he had the non-relativistic thing, and then Dirac came along and he made it relativistic. The relativistic thing is quantum field theory. That's what the relativistic thing is. But even in quantum field theory, you start with the classical field, And Dirac and Klein and Gordon gave us equations for those classical fields.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And then you quantize it. And there's different ways of quantizing the field. And one way is precisely analogous to what Schrödinger did for a single electron, namely to invent a wave function that is a function of the field rather than a function of the particle. And that wave function obeys an equation, and that equation is called the Schrodinger equation.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
The Schrodinger equation is completely general in terms of does it describe non-relativistic things, relativistic things? Yes. There are different versions of the Schrodinger equation that apply to any of those individual circumstances. Indeed, there's a version of the Schrodinger equation that applies to a single qubit, right?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
A single degree of freedom that is either spin up or spin down, which is not a field at all. For every quantum system, there is a Schrodinger equation, even for the relativistic ones. Supine Otter asks a priority question, continuing in the spirit of asking someone who doesn't like tattoos about tattoos.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You previously suggested your favorite equations to ink on one's body, but for the visually inclined, can you recommend the physics-related diagrams or images that are most meaningful, satisfying, or beautiful to you and would make a great tattoo? It's a good question, a perfectly legit question.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I'm going to probably not give you a great answer just because, well, anyone who gets a tattoo shouldn't listen to me about what tattoo to get. And not because I don't like tattoos, because they shouldn't listen to anyone about what tattoo to get. They should... Think of it themselves, right? I mean, do you care about thermodynamics? Do you care about general relativity?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Do you care about quantum mechanics or whatever? These would all suggest different tattoos you could get. I mean, you could be playful. You could get a tattoo of Schrodinger's cat, right, of being both awake and asleep at the same time. you could get a tattoo of a space-time diagram.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You know, there's some very nice Penrose diagrams, like the Penrose diagram for the eternal Schwarzschild black hole is a very nice little diagram, pretty simple. You could shade it in if you wanted to make it look a little more complicated or something like that.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I mean, honestly, leaf through books and papers by Roger Penrose, because he is not only a great mathematician and physicist, he's a great artist as well. And he always has these amazing diagrams in his papers. So if you're a relativity kind of person, I would definitely recommend looking through Penrose's work for striking images, because they're definitely there.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
These AMA questions are asked by the Patreon supporters. And every month, every episode, and every regular interview episode, not so those are AMAs, but every regular episode, I do a little reflection audio talking about how I responded to the interview that we just had, the discussion we just had, and that's for the Patreon supporters. So that could be you if that's how you want to roll.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And you could go either, you know, more whimsical, like the Schrödinger cat thing, or Laplace's demon. Get a tattoo of Laplace's demon. I don't know what Laplace's demon looks like, but you know what I mean. Feynman diagrams, particles interacting, you know, Feynman diagrams can get pretty complicated. They don't have to be simple ones. So I think there's all sorts of different possibilities.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
If nothing immediately strikes you, I like the idea of leafing through some technical physics papers. Even if you don't understand what the papers are about, maybe you can understand the area they're in. Are they in quantum cosmology? You can read the papers by Hartle and Hawking. See if there's any images in there that strike your fancy, and that would be something that would be pretty unique.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
David Whitaker says, the universe is expanding and the stars and everything else are moving away from us at an increasing rate even, but they can't all be moving away from us or we'd be at the center of the universe. And if they are moving away from us, but everything started together immediately before the Big Bang, why is everything not traveling outwards at the same speed?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
The great thing about this question is that the second part answers the first part. If everything was traveling outwards at the same speed, that would indeed be an indication that we were at the middle of the universe. But it's not. So forget about moving. Forget about visualizing everything moving away from everything else. Think about the universe itself.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
In fact, what I like to do is to literally imagine you're outside on a clear night. and you are gifted with perfect vision, including for very, very distant galaxies, okay? So we're not using any analogies. We're just trying to visualize the real universe. And imagine that you have Doppler imaging in your eyeballs, so you can see how fast the different galaxies are moving away from you.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And you notice that galaxies that are relatively nearby are moving away from you relatively slowly. Galaxies that are far away are moving away from you faster, okay? So they're moving away from you at different speeds. What does that mean?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
That means that if you think about the people who are in, who are living in one of the nearby galaxies, they see you moving away from them in one direction, and the galaxies that to you are further away are moving away from them in the other direction. Indeed, they see the same kind of pattern that you do. They see everyone moving away from them in
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
in a pattern which is the further away they are, the faster they're moving. So this precise behavior where everything is moving away from everything else with the property that further away things are moving away faster is exactly what you need to not have a center so that everything is created equal. Everyone sees the same basic kind of thing.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
This is both what is predicted by general relativity and what is actually observed in the universe. Anonymous says, imagine a future where the NBA moves to a virtual format and all players are linked to an avatar via a brain chip. All avatars are the same height and strength.
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Do you think the majority of current players would stay in the NBA or are there probably lots of more skilled, smart basketball players out there who simply aren't large or genetically fortunate enough to compete? I think that it depends on whether you're talking about the very short term or the very long term.
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I think in the very long term, if everything is virtual and everyone's physical abilities are essentially equal, then I think that—I'm guessing, this is an empirical question you'd have to test, but my guess is that the distribution of basketball talent is kind of uncorrelated virtually. with height and physical speed and things like that, and you get all sorts of people doing very well.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It's basically playing a video game, right? There's not any, as far as I know, correlation with height and strength with ability to play video games, okay? But if you did this and did it next year, then I think what you would find is that the current
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
very good basketball players would still be the very good basketball players because they've been training for a very long time to do exactly this and in ways that other people haven't. If you're a casual basketball player, you haven't been put in the work compared to an actual NBA player. Some NBA players would not turn out to be very good. They're
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
If not, that's also cool. We love you all. Let's go.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
There are some who are just coasting by on their physical gifts, and they would not do that well. But I think a lot of the actual basketball players, to stay and flourish in the modern NBA, you have to be pretty talented and dedicated. You know, there's always going to be exceptions.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I remember just because of a similarity in names, there was a center in the NBA back in the 80s named Joe Barry Carroll. No relationship to me, but his important talent was he was tall. That was it. So his nickname, Joe Barry Carroll, was nicknamed Just Barely Cares. Because he was really not interested in putting in the work, getting better.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
He was just standing out there and being tall, and he earned a lot of money doing that. I think it's harder to do that now, maybe, than it was in the 80s. Josh Flowers asks a priority question. Do measurements made in light years need to be adjusted to account for velocity changes between a photon's initial reference frame and its destination reference frame? You know, in principle, sure.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I mean, you have to be careful when you're talking about distances of objects in astronomy because there is no fixed reference frame, okay, with respect to which we're supposed to measure these distances.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
As Einstein taught us, if you're moving close to the speed of light, the distance that you think you would have measured if you had not been moving close to the speed of light might be very different. It's length contracted, as we say.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But the good news is that, in fact, the amount of velocity that typical astronomical objects have, galaxies and stars and planets and things like that, is small compared to the speed of light.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Even though there is not absolutely a reference frame in physics, there is approximately a rest frame in the universe where stars and galaxies typically move at about one one-thousandth the speed of light with respect to each other. So the Doppler effect is actually just not very big. There are circumstances in which it matters. In fact, there's a phenomenon called the finger of God.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And the finger of God is this. If you have a cluster of galaxies, okay? So you have a cluster of galaxies and... That means you have a bunch of galaxies and they're orbiting the common center, which means that some of them will be in the—you're measuring two things. You know, this is back in the day. You're measuring the distances directly.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You're measuring the redshift and using that to infer a distance to the galaxy. And then you can accurately measure its position on the sky, right? You know, its angular position on the sky. So your inferred distance measure to the galaxies is contaminated by the fact that the galaxies are moving. You're measuring the redshift.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And some of that, not most of it, just a small amount, but some of it is from the Doppler effect. And that Doppler effect that affects the redshift and therefore your inferred distance only affects is added to the distance measure radially, that is to say, in the direction of your line of sight. The angular distance you just measure by taking a picture of the galaxies on the sky.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Cooper starts us off with a priority question. Remember, the priority questions are something that all the Patreon supporters get to ask once in their lives, and I will do my best to answer that one question. We have too many questions to answer all of them. In fact, this month we had a very large number, and I feel very bad.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So you have accurate measure of where the galaxies are in the sky and a distorted measure of where they are along your line of sight. So you take what should be a relatively spherical blob of galaxies in a cluster, and when you plot it in what you think is position in space, it is elongated in the direction of uke.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It's the finger of God that the joke was, this is a finger of God pointing at you saying, you are wrong, because you have small errors in your measure of distance.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Now, this was a thing back in my day, in the early days of my cosmological career, because measuring galaxies and their redshifts and their distances was a painstaking process, and we didn't have a lot of them, and therefore the ones we had were relatively nearby.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
as you go to further and further clusters of galaxies, et cetera, the relative importance of this Doppler effect becomes less and less because the overall recession velocity becomes more and more dominant.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So these days, this kind of thing is not that important in terms of making maps of galaxies and even its existence is perfectly well understood and there are statistical techniques for compensating for that mistake. So yes, these differences exist. No, they're not very big. Yes, even the small differences are things that we know about and are able to compensate for.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Alex Reinhart says, why do you think that complexity science concepts have caught on in a popular way, especially chaos theory, but also things like economic examples and flocking, but aren't captured in most STEM university educations? This is just my perception. Yeah, I think your perception is kind of right. And I think that there's a couple of things going on.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I guess the biggest thing is David Krakauer and I disagreed with this about this when we were talking. So you can go back and hear our conversation. He's the world's expert on complexity. But I kind of think that complex systems science is still pre-paradigmatic.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
That is to say, we don't have a fixed curriculum, a fixed set of examples, a fixed path from not knowing anything to hear the basic things you should know and hear the applications of them, right? In physics or economics or chemistry or whatever, we kind of agree on what is the first course you should take, the second course you should take, and you build up an agreed upon set of knowledge.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
With complexity, it's still more of a grab bag. There's very interesting results out there. There are some things that seem to be common across different kinds of complex systems, but it's less clear what exactly the standard set of knowledge is supposed to be. It's more scattered across different domains, different disciplines, and therefore harder for it to get into a standardized curriculum.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
There's a lot of good questions that didn't get chosen, so sorry about that. But Cooper's priority question says, the episode with Jeff Lichtman was fantastic and has really stuck with me. His comment about how understanding something requires compressing it in some way and how the brain perhaps cannot be compressed in that way is something I keep thinking about.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
We're getting there. There's a couple of very interesting textbooks that now exist on complex systems theory, and maybe it will become more popular. But also, you know, the way that complex systems Complex systems, I never know whether to call it complexity or complex systems, and therefore the accent on the first word is always unpredictable for me.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Complex system science is an interdisciplinary science by its very nature. It's, you know, what can be a complex system? A biological organism can be a complex system. The economy can be a complex system. The internet is a complex system. A language is a complex system. What department is this supposed to be in, right? You know, who is supposed to be learning this and teaching it?
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So what you get is different departments doing little bits of it. And it hopefully in some areas does have an impact. But there's no standard. There's no consensus. And I think that maybe that will change. You know, I keep trying to teach a course online. in complex systems in the physics department at Johns Hopkins.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It is not like they're trying to prevent me, but other courses that are more pressing keep coming up. So I'm teaching quantum mechanics next year. That's got to be taught. Someone's got to teach quantum mechanics, and so I'm going to be doing it to the undergraduates.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
We do have a new faculty member at Hopkins, Matthew Wyart, who is a true complex systems statistical mechanics expert, and he's going to be teaching things. So I do think that, you know, maybe it's seeping its way in. These things take time. Academia is very slow, very slow to change and to adapt to new ideas.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Bjorn Haig says, you seem to be able to disagree with people so gently, clearly, and unobtrusively. How do you do it? Are you even aware of this being a skill of yours? Yeah, I would disagree. This is a skill of mine. I don't think this is a skill. That's not the way that it comes across to me.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I get very frustrated with people sometimes, and I do disagree with them maybe a bit too harshly or shrilly than really I do. I try. to disagree gently and constructively. It's not about being unobtrusive or even gentle so much as clear is important, to be clear about why you disagree and to be constructive about it, to try to understand why we're disagreeing, maybe move forward.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But I would say that There are different kinds of disagreement, right? There are people who are worth disagreeing with and there are people who are not worth disagreeing with. I do try very hard to not spend too much time disagreeing with the people who are not worth disagreeing with. I mean I disagree with them maybe.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But if they're not going to change their minds or their thoughts are just not very interesting or good, then I'm not going to spend a lot of time engaging with them. I'm trying to engage with people who I disagree with in a way that potentially they could change my mind or I could change theirs or at least we could learn something important from each other.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It's as if the only way to understand a brain is to be a brain. Sort of like how perfectly simulating a universe requires something the size of the universe. Did this comment of Jeff's leave an impression on you as well? Don't feel the need to say much if it did not. No, it did leave an impression, but I've thought about things like that before.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
That's the criterion that I try to have for guests on Mindscape. It doesn't always work, you know. There's – Podcast has to happen every week, and I choose a lot of different people, but basically what I'm looking for is somebody I can learn from. Even if it's something that I already know a lot about, I can learn little details, and the audience maybe can learn a lot.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And if it's something that I disagree with somebody, but I want to know why they think that, right? So I'm choosing to engage with people I disagree with but can learn from, and so that kind of naturally makes it a more pleasant experience. I do think this might not be true, but I think that...
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It's weird to me to see people on the outside of academia be less able to disagree with each other politely and constructively than people inside academia. If you just asked me if I hadn't thought about it that much and you just asked, do professors disagree with each other sort of loudly and emotionally, I would say, yeah, they really get into it and they disagree pretty badly.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But still almost all the time, not all the time, but almost all the time, professors, intellectuals, scholars, people who are in academia, they disagree and they go out and have a drink with each other and talk about it. They keep talking about it forever, for decades, right? This is very, very standard. It's not 100 percent by any means, but it happens all the time.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And I think that a lot of people outside just – if they're disagreeing, then that person is an enemy. And they shouldn't be engaged with in any way. And that's a little alien to me. It makes me sad when I see things like that. Folkman says, I just finished reading the big picture, which I found excellent.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
On the question of free will, it almost seems as if your definition results in a situation where entropy is reversed or inverted.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Multiple potential macro states resulting from the decision you actually make, you have free will so you can make many different decisions with distinctly different outcomes, correspond to only one microstate, which results from the deterministic chugging forward of the microscopic configurations based on the laws of physics. What are your thoughts on this interpretation?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Does this have any interesting implications for the arrow of time and related concepts? So I'm not exactly sure what you have in mind here. I'm not sure that it came through to me perfectly clearly, but I don't think that your interpretation is on the right track. Let's forget for the moment about quantum mechanics, okay? Quantum mechanics introduces true indeterminism into our observed world.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So that's something that in detail – at the detail level, we have to keep in mind. But even in classical mechanics, if classical physics were true at the base level, you would still have a world I think you could imagine a world that looks pretty similar to the one we live in where we're made of atoms and the atoms are jiggling around and doing different things.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And the point is, in that world, when you have emergence at a level of, you know, there's a higher level where you've coarse-grained over a lot of individual details, and at the lower level there's deterministic microscopic dynamics, it will often be the case that the higher-level dynamics are stochastic, and the best possible thing you can do is make a prediction about probabilities, even though the lower-level dynamics are completely deterministic.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I think that there are important differences between levels of understanding. You can understand something a little bit or better, right? It's very similar to the discussion about emergence and higher-level macroscopic, coarse-grained understandings versus lower-level microscopic understandings. So I might not understand everything about a brain, but I understand some things about it.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
if I have a theory of, you know, when a volcano is going to erupt, the details will depend on a lot of microscopic facts that I don't know the answer to, right? But the point is that what that means is there are two, actually many more, but let's say particularly two microstates that are in the same macrostate that lead to very different behavior at the macro level.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So there's a microstate of the volcano. I look at the volcano, I do all the tests I can, but I cannot measure every single atom in it. So there's details about the pressure and the temperature that I don't exactly know. Certain microstates of the volcano are going to explode any minute now. Other microstates of the volcano are going to last years without exploding, okay?
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So that's okay at the emergent level. That's not a failure of emergence. It just means that the emergent theory tells you the probability that the volcano is going to erupt. And I think the same thing is true with people and with free will. My macro state description of a person –
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
obviously doesn't include an enormous amount of information about the details of what's going on in their brains, right? So it may very well be the case that the microphysics of what's going on in their brains completely determines what they're going to do next, but that information is not available to me. I don't have that information.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I don't even have that information about myself, much less about other people. So what happens is in the macro state that I use to describe a person, there are various different possibilities about what will happen in the future. And 100% compatible with everything I know, there are different possible future choices. We call these decisions or –
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Yeah, choices, decisions, things that your free will is doing. And free will is just a label we put on them. And I know that some people don't want to put that label. That's fine. I don't care. Don't put it on. I'm just trying to correctly describe what goes on in the world.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Henry Jacob says that so many people support Luigi Mangione, which blew my mind, suggests that a lot of people are consequentialists. Do you agree with this inference? So Luigi Mangione is the one who killed the CEO of UnitedHealthcare, which did indeed – Start a lot of conversation there on the old internet and elsewhere.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I think that here in the United States, for those of you who don't live here right now, we have problems with our healthcare system. And a lot of the problems in the United States in general are simply the result of the fact that very important –
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
functions of everyday life are outsourced to corporations who are trying to make as much money as possible, not trying to make our lives better as possible. The whole idea of capitalism and Adam Smith is that under certain circumstances, the individual interests of corporations trying to make money and the interests of the consumers or the workers can align with each other, right?
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You can actually have a situation where it's win-win for everybody. But that's not inevitable. It doesn't necessarily happen. Sometimes the corporations can just leech off money from people because they have figured out a way to do it. It doesn't make anyone's life better except they make money. And The insurance industry here in the United States is a classic example of that.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And so it's in a regime or it's in a context where emotions run very high because you're literally talking about people's lives, people's health. The healthcare companies deny life-saving care to people. And so people are rightfully angry about this. And so Luigi Mangione took it out. I don't know the details. I don't follow this kind of thing very carefully. But
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Or think about something that is a little bit less problematic to get all the nuances down. I understand how to drive a car. I don't understand everything that is going on in the car, right? That would require a lot more information. But I can still understand enough to be able to drive the car. And I think the same thing is true with brains.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
He was someone who was upset about the situation. I think that there were personal issues involved also and he basically assassinated the CEO of a healthcare company. And there was – among things that I see on the internet, there was a remarkable amount of cheering him on after the fact with the very basic justification that –
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Look, this healthcare CEO in fact was responsible for many more than one deaths in a very tangible way. And I think that there's a couple things going on. Consequentialism might be part of it. So Henry is suggesting, well, you can kill one person but then you're saving many other people. So it's sort of a trolley problem kind of thing and maybe that's OK.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I don't actually think that that's really what's at the heart of the support for something like this. I think it's just more visceral, right? People feel powerless. People feel like bad things are happening and they can't do anything with it. And this is when people think about turning to violence. It's not a good sign, I don't think.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I'm not in favor of assassinating the CEOs of health care companies. I think it's bad for all sorts of reasons. That would be a long list of reasons why it's bad. But aside from the consequentialism argument, the other argument that I think is perfectly legit is to say we count different kinds of deaths differently in terms of being upset by them, thinking of them as illegitimate, et cetera.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
takes a gun and walks up on the street and shoots somebody, then we all agree that's bad. But if someone sits behind a desk and judges that a person doesn't deserve to get health care, that's just business as usual, right? That's just how the system works.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And I'm entirely on board with arguing that we should think about these kinds of deaths in more similar ways rather than in the very, very different ways that the system currently does think about them. Doesn't mean I think we should go around assassinating people. I'm kind of a believer in the rule of law, not in vigilante justice.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But I do think that taking seriously accusations against people and corporations whose actions end in deaths of ordinary citizens is something we absolutely should be able to do. Not that I really know how to bring it about, but that's true for many political or social or economic ideas. Kevin's disobedience asks a priority question.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I'm a contractor by trade, but a year ago I decided I wanted to teach myself particle physics after work. In short, I quickly realized I needed to go back and relearn at least some basic classical mechanics before moving on to relativity and quantum mechanics.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So I'm slowly working through a high school textbook again, but after reading dozens of popular books, the thing that impresses me the most about physics is physicists mastering the old and new stuff to work on the cutting edge. So my question is, would graduate-level problem sets... on say geometric optics or thermodynamics be simple to you now or would involve a quick refresher?
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
We can understand some things about how they work or we can focus in on some aspects of them. So the complete understanding might involve something at the Laplace's demon level of perfect information at some microscopic level that we might never obtain. But we can get better and better at understanding bits of it and aspects of it. And I think that's perfectly good.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I guess I'm curious how much of the technical education one retains and in what form. I hope that's clear. It is clear. So putting aside all the details that might come up in your mind in the preamble to the question, The question is, you know, once you're a professional physicist, can you go back to the stuff you did as undergrad or graduate at the problem set level?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And is it all now easy or do you have to, like, work just as hard? Well, there's two things involved. One thing is sometimes these problem sets in, you know, thermodynamics or E&M or quantum mechanics or whatever just involve a lot of work, right? Sometimes there were a lot of all-nighters back then when I was in grad school.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
The amount of calculations you have to do is just large no matter who you are, no matter how much knowledge you have, right? You got to do that integral. You got to solve that differential equation. You got to diagonalize that matrix, whatever it is, okay? So some of it is irreducible, the amount of work you have to do. So that's one thing.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
The other thing is, of course, hopefully you do get better at seeing how to solve these problems. Sometimes I will see online, I'll see a final exam or a problem set in a course. that is being taught somewhere else, and I haven't taken it for many years, and I read it and I go, oh my God, I would never be able to solve that.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But then I sit and think about it and go, actually, yeah, no, I could do it. I just haven't thought about it for a long time. And I think that it's a combination. You do forget some of the details that you might have recently learned if you're taking the class,
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But I think that in fact, the purpose of the education, this is a slight exaggeration, but a lot of the purpose of the education is to sort of know where to look. Like, oh, okay, this particular problem requires taking a Fourier transform, right? Or this particular problem is a perturbation theory problem.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
like the angle of attack and what books you have to turn to to figure out what equations you need and that kind of thing. Rather than the actual solution to the problem or even the actual step-by-step way to solve the problem, it's more like what kind of problem is this? What kind of tools are you going to need to do this?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
That kind of stuff is taught to you, and it's not necessarily what you think is being taught to you, but it's what sticks with you decades later. So... I would say that specifically it would not be simple for me to answer a question like graduate level statistical mechanics or something like that necessarily. But it would be much simpler now than it was back when I was doing it the first time.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Anders says, so it turns out that Schrödinger was a pedophile. He groomed a 14-year-old girl and got her pregnant when she was 17. He also attempted a relationship with a 12-year-old girl and called her the love of his life. How do we handle situations when unquestionably brilliant men are monsters? Should we mention it in the textbooks and when lecturing?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Should we rename lecture halls and remove statues of them? I think, you know, I chose this question to talk about because I don't think the answer is easy. I think it's a complicated one. I don't think there's a cut and dry solution here. I do think that we shouldn't hide it when people who are great for one reason are pretty terrible for another reason.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And I think that for Schrodinger, that's a perfectly plausible argument. conclusion to draw from his actions. I don't think we should rename the Schrodinger equation. You know, I think of these labels, I think of names of equations and things like that as labels, not as honors.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
sure, you know, Schrodinger is someone we remember in part because his name is on an equation, but it's also just the Schrodinger equation. That label, the Schrodinger equation, has transcended Schrodinger the person a long time ago. But in terms of, like, honoring them by statues and things like that, that's a more difficult question.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Martin Lightner says, I was wondering how photosensitive organic molecules like chlorophyll implants or the receptors in our eyes are able to react to a range of frequencies. I was taught that electron needs a very specific frequency to get excited.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You know, I think that on the one hand, the argument would be we're honoring them for the good work they did. The other argument would be like shouldn't we be honoring good people rather than bad people, not just people who achieve things no matter how bad they are. I think – I don't know the answer to those questions. I do think we should be upfront about it.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I think that there is a certain temptation to think that because somebody did a great thing in science or for that matter in art or politics or sports or literature or whatever, that there are heroes and we should honor them. And that I'm much more skeptical about. I think that that's always a dangerous thing because you're honoring someone who you don't know personally.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
If you want to honor the thing they did, that's fine. But then to just transfer that into honoring the person as a whole when you really don't know that person as a whole is a very dangerous move. So I'm in favor of teaching the history accurately and letting people go where they will from that. Natalie Standing asks a priority question. I'm a 52-year-old with a passion for reading about physics.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I've been captivated by your books and those by Brian Green. They never fail to blow my mind. Though I didn't excel in school, particularly in mathematics, I find myself fascinated by the discipline. I would love to deepen my knowledge of this beautiful language. Could you recommend some starting points or resources to help me on this journey?
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
well, you know I'm going to recommend my own books, right? That's where I'm going to start. But let me say, books are for some people. Videos are for other people. Classroom discussions are for other people. Different people are going to learn different ways. You've got to find the way that works for you. Some people are mostly happy just reading the texts.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Other people need to work out problems and things like that. Again, find what works for you. Part of the goal of my... hopefully eventually completed trilogy on the biggest ideas in the universe is to provide some insight into those more quantitative aspects of modern physics that popular level books don't cover, whether it's classical mechanics, quantum mechanics, or complexity and emergence.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Similarly, how can two electrons and two atoms that are not perfectly stationary ever exchange photons given that the Doppler effect will alter the frequency? Well, there's a lot going on here, and I'm actually not the best person to ask about what is going on in the receptors in our eyes or things like that. But I think part of it is there are many different frequencies.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So to me, that's like hopefully a very good starting point for exactly what you're thinking about, the biggest ideas in the universe. Leonard Susskind also has a series of books, The Theoretical Minimum. It's a little more straightforwardly course-like laid out. In the biggest ideas, I try to sort of mix and match things.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I don't go in the traditional order because I'm very, very explicitly not teaching a course, right? It's about— people picking up the books and reading them. So it's a slightly different angle, but a very similar spirit of showing you the equations and helping you learn about them. None of those books are quite at the level of a textbook. So ultimately, if you really want to learn this stuff,
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Well, what do you mean by really want to learn this stuff, right? If you want to learn it at the level of a professional physicist, you have to start at the beginning. You have to learn classical mechanics and calculus and differential equations and waves and E&M and basic quantum mechanics and statistical mechanics and then on your way up.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
There is a famous slash infamous web page put up by Gerard de Tuft, who is a Nobel Prize winning brilliant physicist, called How to Be a Good Theoretical Physicist. And he lists, I've always thought that maybe I should do my own version of this, because Atuf lists every course you need to take.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
have to be aware of it and respond to it and think about it and take it seriously while also living the rest of your life. So I'm perfectly happy to be talking about non-political stuff for the AMA, but I do want to note what's going on. I always think about the audience hundreds of years in the future who are wondering what we were thinking back now.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And he points to specific resources, both online and textbooks, that will take you all the way up through quantum field theory and particle physics and condensed matter physics and so on. But he also, you know, has all the steps along the way, including things like foreign languages and the mathematics and so forth. The problem is that a Tufts idea of what you need to know is rather expansive.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So it's incredibly intimidating. Like you look at the list and you're like, I'm never going to get through all this. And, you know, maybe that's what you need to be in a Tufts level theoretical physicist. But maybe some of us want to just aim at being a a working-class hack theoretical physicist, and that would be good enough.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So you can maybe pick and choose a little bit, but ultimately, yeah, you're going to have to buy some textbooks, I think. Maybe buy is the wrong word because at this point, there's so much stuff online, whether it's online courses, which I really am a fan of. or online lecture notes or whatever. I don't have specific recommendations there, but go to edX and Coursera. These are online course sites.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Or go to Khan Academy or whatever and just find courses you can sign up for. And many of them are archived, so the videos are there. You don't need to take them at some specific pace. You can just do it whenever you want, which is great.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Christoph Radomski says, in Space Time in Motion, you mentioned that you, being a science consultant in Marvel's Thor, had something to do with Jane Foster's mention of an Einstein-Rosen bridge. Are you also responsible for Tony Stark's mentioning quantum fluctuations at Planck scale triggering Deutsch proposition in Avengers Endgame? No, that one was not mine.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
There were other science consultants on Endgame. I think, I'm not 100% sure, but I think that former Mindscape guest Clifford Johnson was one of them, and it might be from him. I mean, that particular statement of Tony Stark's is kind of word salad nonsense. All the individual terms make sense, but the particular way they are arranged in order doesn't, which is, that's fine. You know, it's just...
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So indeed, in the cartoon model of an atom or a molecule, there are electrons in orbitals with very, very specific frequencies. energies. So you might think that unless you hit that energy right on, you're not going to be able to excite that particular electron. But typically, the photons that are moving around doing the exciting are not in what we call energy eigenstates.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It could have been better like if they had more science consulting going on. It could easily have been massaged into a statement that both made sense and to serve the dramatic purposes in the moment. But despite the fact that these movies cost a lot of money to make and spend a lot of time being made, there's always kind of a rush.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
People don't have time to sit back and go like, OK, how exactly should we get this one particular line? Should we get the technobabble right so that it makes sense? So, no, I'm not responsible for that one. Sorry. Gary Miller says, I believe that who I vote for president has no impact on who gets elected.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Even if I convinced 10 or 100 friends to vote the same as me, there would still be no impact on who gets elected for president. But if you read this question aloud to your entire audience and agree that any one person's vote doesn't matter, you risk alienating a large group of people from voting. It seems like democracy depends on people believing something untrue that their vote matters.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Is this an inherent problem with democracy? Well, there's certainly some problem with democracy that you have two choices. Either you let voting be voluntary, which happens in most places, and then some people don't do it. Or you make it mandatory, and then you're going to have voters who are hilariously under-informed. And in fact, that still happens when the voting is voluntary.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So I don't think there's any perfect solution to these questions. You know, I don't think it's right to think of democracy as trying to be a method for making the best decisions. It's trying to be a method of giving people a voice. And of course, any one person's voice is small in countries that are as large as ours.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I think an underappreciated problem with democracy is just that nations are big now. right? I mean, 200 years ago, we didn't have 300 million people in the country, and the voices mattered a little bit more. So there's a lot of things going on here. We talked about this with Herb Gintis, among other things, and it's a reflection of a more general issue in philosophy in
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
you know, moral philosophy or whatever. So Immanuel Kant would tell you you should act if you want to act morally in such a way so that your actions may be the basis for a general principle, right? In other words, the golden rule, basically the golden rule. The categorical imperative is a slightly philosophized up version of the golden rule.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It says act the way you want everyone else to act, right? But why? Why should I do that if it's not actually true that everyone else will act the way that I'm supposed to act? Why should I be acting in that way? Now, of course, counterfactually, if everyone acts the way they want everyone else to act, then they will all inform themselves and they will vote, et cetera, et cetera.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So even if that doesn't happen, should we act because we want it to happen in the way that we would be acting if it were happening? That's the question. And the answer is not obvious. The answer is not obvious at all. I mean Herb Gintas' answer was something like it's kind of tribal affiliation signaling, right? We don't vote thinking that our vote will be the tiebreaker.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
We vote thinking that we are expressing ourselves. We are saying, here is who I stand for, where I want the country or the municipality to go, things like that. And it's rational in a way that is different than how we pretend it's rational. We pretend it's rational because we're choosing who is going to lead us, and collectively that happens.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But at the individual level, the rationality is about belonging to a group, not about making a decision. Does that hang together? I really don't know. I do think that there's a give and take between our individual actions and how we influence others. So therefore, I am very much in favor of both voting and encouraging other people to vote.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Chris A. says, why is developing a quantum description of gravity so difficult? A lot of very smart people have been trying very hard for nearly 100 years. So what is it about the problem that makes it so intractable? It's a great question, one that does get talked about, but maybe deserves to be talked about more. And I think that there are two kinds of problems. This is not just me.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
That is to say, they don't have perfectly precise, well-defined energies. That's part of the fun of quantum mechanics. in exactly the same way that an electron itself, which if we imagine that it is exactly in a perfectly definite state of energy, it will then not be in a perfectly definite state of position. We think of the electron as being in a superposition of many different positions.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I'm not just making this up. There is a standard understanding that there are two kinds of problems with quantizing gravity. There are technical problems and there are conceptual problems. The technical problems are just that according to the ordinary ways we have of doing quantum field theory, which is what you should need to do in gravity since gravity
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Einstein's general theory of relativity is a classical field theory. In quantum field theory, we have rules for taking a classical field theory and quantizing it. And in the case of gravity, these rules don't work. The straightforward way of saying this is that it's not a renormalizable theory, which is to say that if you try to extend your quantum field theory version of gravity,
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
to arbitrarily high energies, you kind of get nonsense. You lose the ability to predict what is actually going to happen, okay? I'm sort of hesitating because there's a technical way of saying this. I'm not sure if it's worth saying, but essentially to make any one prediction requires an infinite number of input parameters. in the theory. That's the consequence of non-renormalizability.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Now, you may have heard me say that we had this thing called effective field theories, right? If you don't want to extend your field theory to arbitrarily high energies, then we can just say we have a cutoff, we have an energy scale above which we don't care, and make a theory about what happens below that scale. And that you can do for gravity, and it works in a wide variety of circumstances.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But if you think that what we're actually after— At some point, you care about what does happen even at arbitrarily high energies. So the effective field theory technique lets you have a functioning theory, an effective theory below a certain energy scale. But that doesn't mean you don't care what happens above the energy scale.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And when you start including gravity, maybe you do care what happens at energy scale. So gravity is just sort of not a successful quantum field theory by the standard measures. So in other cases where we had like the Fermi theory of the weak interactions, Enrico Fermi came up with this theory where neutrons could decay into protons, electrons, and antineutrinos, right?
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
That's a non-renormalizable theory also, just like gravity is. But it turns out it wasn't the right theory. It was only a theory that works below a certain energy scale. And above that energy scale, you have to invoke W bosons and the weak interactions and things like that. and you get the standard model of particle physics, which is a renormalizable theory.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So you might hope to find a renormalizable theory that reduces to gravity at low energies. No one has been able to do that. They've tried. Okay. Well, actually, sorry, that's not true. String theory is exactly an example of this. In fact, maybe it's worth saying that, you know, to a lot of people who wonder why string theory is so popular, this is really the reason. At the end of the day,
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
That's why string theory is so popular because you think that you really are looking for a theory that is complete. Indeed, the phrase that is used is an ultraviolet complete theory, a theory that works up to arbitrarily high energy scales. And I'm even underselling the problem with gravity because it's not just that gravity itself is non-renormalizable and gives you infinities at high energies.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But the infinities depend super sensitively on not just how gravity operates but how every other field in the world operates because everything couples to gravity.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So the naive feeling is if you just try to come up with a quantum theory of gravity that's well-defined, you need an infinite conspiracy between what the gravitational field is doing at high energies and what all the other fields are doing at high energies. It turns out string theory gives you that infinite conspiracy because it's just one thing, a string, that's vibrating in different ways.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
these photons are typically going to be in superpositions of many different energies. So the energy has to be pretty close to the right answer to poke the electron around in the right way. But there's probably some uncertainty around that exact right answer. And as long as the electron's energy is within that uncertainty band, you have a probability of making this happen.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And you can show that not only are there no infinities, sorry, not only is it renormalizable, but it's finite. There's not even an infinity you have to remove in string theory. You just get a finite answer. No other approach to quantum gravity that anyone has been working on has that nice property.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So as many other problems as string theory has, as long as it has that nice property, it's going to be a popular approach to quantizing gravity. The other set of problems are the conceptual problems. When we're quantizing gravity, we don't even know what it is we're quantizing, OK? Because space-time itself is on the table.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
One among a large number of avatars of this particular problem is what is called the problem of time. This is what we were talking about in the solo episode recently. If you naively plug away, treat general relativity like a field theory, quantize it, you get an equation called the Wheeler-DeWitt equation, which says that the wave function of the universe doesn't evolve with time.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But it does evolve with time. I'm looking around. My immediate environment is evolving with time. So what's up with that? So these are conceptual problems, not just technical problems. It's not just I hit infinity. It's just that I'm getting nonsensical answers to the questions because I don't have any firm ground to stand on. In ordinary quantum field theory, at least I have space-time.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It's there. It's sitting there. It's rigid, and I know what it is, and I have some fields vibrating on it. In quantum gravity, space-time itself, is part of the quantum description and it's much harder to know where to start because that's a unique situation. There's no other versions of physics theories in which space-time itself is part of the dynamical playground.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So yeah, we don't know what time is. We don't know how Lorentz invariance evolves. We don't know what it is we're supposed to be predicting. You have the wave function of the universe. Okay, what does it mean? How do you turn it into a prediction for something? No one knows. the once and for all answers to any of these questions. So yeah, gravity is special.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Gravity is different as far as we can tell. Nate Wadoops says, the volume of a sphere is proportional to radius cubed, and the area of a sphere is proportional to radius squared. So it seems intuitively obvious that there are too few Planck squared units on the surface of a sphere to capture all the information contained in the much more numerous Planck cubed units of volume within the sphere.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But much better informed people than me believe in the holographic principle where something like that happens. Can you help me understand where my intuition has gone wrong here? No, I think that your intuition is completely fine. It's absolutely the case. Everyone knows that there are fewer Planck areas on the surface of a sphere than there are Planck volumes in the volume of a sphere.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
That's very well known. The whole point of the holographic principle is those Planck volumes in the volume of the sphere are not independent from each other. Right. They are. That's the whole point of a hologram. A real world hologram is a two dimensional thing that if you shine light on it in the right way, you see a three dimensional image.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But the different parts of the three dimensional image are not independent from each other. They're all derived from only two dimensions worth of information. So that's the whole trick in the holographic principle. You don't, in holography, have the ability to separately choose what is going on everywhere within the volume of spacetime.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Remember, all of quantum mechanics is about probabilities for these things happening. And likewise, yes, the electrons are going to be moving back and forth. They're going to have Doppler effects in the photons that they emit and absorb. But that's sort of helping them, right?
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Now, how does that actually play out in practice is a little bit unclear, but people are working on it. It's clearest in the ADS-CFT correspondence, but even there, it's not 100% clear. So still work in progress. Sandro Stucky says, in your January solo on the existence of time, you sketch an argument for why Boltzmann brains are not a problem once one considers quantum physics.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You said that this is because thermal quantum states are static, but I could not quite follow how that solves the problem. How can the universe settle into a static state if Hilbert space is finite? Doesn't recurrence forbid that? Yeah, no, you're absolutely 100% correct. So I don't know whether maybe I mumbled through it and wasn't clear.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
The whole point is that this scenario where the universe settles down and in asymptotes to a static state and there are no fluctuations and no Boltzmann brains, that only works if Hilbert space is infinite dimensional. Now, you have to be careful because we think that the Hilbert space of our observable universe is finite dimensional. But that's OK.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Maybe there's something outside our observable universe, and maybe there's infinite more Hilbert space out there. That's what you would need to make this scenario work. We don't know if that's true or not. So if it turns out to be true that Hilbert space is truly finite dimensional, then this argument is off the table.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Then, indeed, you would expect recurrences, fluctuations, Boltzmann brains, all of that stuff going on. Kirsten Johnson says, Do you think the holographic principle might have anything to say about why neural networks work as well as they do? I guess that depends on what you mean by the holographic principle.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You know, the holographic principle, strictly speaking, is supposed to be a statement about quantum gravity. It's not supposed to be a statement about anything else. It's not, you know, a principle that is widely extendable to all sorts of different circumstances.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It's something that becomes evident when you have quantum mechanics plus gravity, and in particular, when you have pretty strong gravity, like a horizon or something like that, when you black hole, where you have anti-de Sitter space, de Sitter space, a cosmological horizon, then holography becomes relevant.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Even with quantum gravity, in other circumstances like the solar system, holography is completely negligible. It's completely irrelevant. You can just talk about ordinary gravity. So there's no reason why if you don't have either gravity or quantum mechanics going on, like you don't in a neural network, the holographic principle should have anything to say about anything.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Now, it's possible that there is something analogous to the holographic principle or something similar or formally comparable to it that is relevant to neural networks. That's completely possible, and I just don't know. But the neural networks that you and I know and love are firmly within the regime of classical mechanics, and gravity is very, very weak.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
In the sense that if you have many different molecules and they, you know, molecular energy levels are generally tightly compressed. There's a lot of them. So it's not just like the one or two that you see in the cartoon of the hydrogen atom and so forth, right?
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So strictly speaking, the holographic principle isn't relevant. Marie Roscu says... When there are different types of ways to look at things, values and perspectives, can or should there be different types of democracy? Maybe. In principle, yes. I think it depends on details there. It does remind us of a...
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Really, really important fact about democracy, which is that it's hard to understand why democracy should work at all because it revolves around people with different interests, different values and perspectives coming together to work in a cooperative way and sometimes saying, I didn't get my way that time. That's OK. I will live to fight again next time.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And so what it means is that you're allowed to disagree about some values and perspectives, but you must share some other values and perspectives. You need to share the value of supporting democracy, right, which I think is increasingly rare. A lot of people just would rather be governed by – a cabal, a small number of people, a strongman, an oligarchy, whatever you want to call it.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
They think that putting ourselves in the hands of a small number of competent people is preferable to democratic rule. And they would be able to say that quite explicitly. And so not everybody thinks that democracy is a good idea. It's conceivable to me that different kinds of people would agree on slightly different conceptions about how democracy should work. And therefore, yes,
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Possibly, in principle, there could be different types of democracy. Some might be more direct, some might be more representative, different numbers of people might be involved, different ways of choosing the representation, representation, representation, and so on. Like all these could be very different and that might be appropriate for different circumstances.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Hussein says, in your last AMA, you emphasized the importance of an objective mainstream media that aspires to provide factual recounting of world events, stating that it's important for a healthy society and informed public. However, over the last 16 months, my faith in the mainstream media has significantly eroded. This is largely due to the media's coverage of the genocide in Gaza.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Do you see the same disconnect between the media's coverage of Gaza? And if so, how do you reconcile this glaring disconnect between the reality on the ground and what the media has portrayed? The past 16 months have left me feeling dejected at the notion of an objective American media.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So if you have the molecules moving or the photons moving, so there's not only some uncertainty in energy but some shift in energy because of the Doppler effect, it is more likely that some of the photons are going to be in the right band to do the action.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Well, I think we have to first distinguish at the abstract level between two things, the importance of an objective mainstream media and then the effectiveness of the actual media we have, right? Those are two different questions. Even if you are depressed by what you consider to be the performance of those media outlets that try to be objective, that's a perfectly legitimate feeling to have.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But that doesn't mean, therefore, we don't need an objective mainstream media. We need it more than ever. We need— both objectivity and competence and effectiveness, right?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I completely agree that the Israel and Gaza conflict, it's not the only example, but is an example of something where there are certain sort of standards and guardrails and expectations within what we think of as the objective mainstream media that prevents a lot of stories from being told. That's a problem. That's something that you should work to try to fix. We should work to try to fix.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But it's not going to be solved by saying forget about objectivity in media. Let's just have individual different media outlets that tell us what we want to hear, right? That is not actually going to solve anybody's problems. Those things should exist. That's fine. Can exist. But we also need something that is common to everybody.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
One of the huge problems in what is going on in the United States right now is that not only are really terrible things happening at the upper level of governments, but half of the country has no idea that these terrible things are happening because they're not told by their media outlets. And that is a problem.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Anonymous says, how does writing a textbook intended for a particular audience compare to writing a book intended for a broader audience? I'm curious on what challenges arise when writing those books. Is one easier than the other? It's not so much a matter of easier or harder. There's challenges in both cases. In both cases, it's super important to know your audience, right?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I mean, my books, my popular books are generally pitched at a slightly higher level than other people's popular books because I'm not, you know, I'm not really, I would like to sell, I have to say this very carefully, I would like to be the best seller of the world. I would like to sell a billion copies of my books, but I am not optimizing to do that. I am not writing a book specifically
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
because I think it will sell the most copies. I want to write the book I want to write, and then I want people to buy it, okay? Those are two separate things. I want to write the book that is something that I can be proud of, and people who want what I have to offer will get something out of it, okay?
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I suspect that—and I don't know this for sure, so you should talk to a real biologist—but I suspect that in the eye, when there is an electrochemical receptor that fires, the probability of that happening per photon, I suspect, is pretty small. I don't know that, but we have a lot of photons in the world. I think that there is some controversy.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And that's a variety of things that might be textbooks, that might be popular books, that might be kind of in between books like The Biggest Ideas. In terms of the challenges, you know, for textbooks, textbooks are very functional, right? They're very purposeful. It's not simply a matter of pleasure and distraction that you read them. You want to learn a skill from the textbook.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I think that one of the reasons why my general relativity book has become relatively popular is because there's a lot of general relativity books on the market. many of them, I'm trying to say this very politely, they're not meant to teach people general relativity, or at least they're not trying as hard as they could to teach people general relativity.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
They're trying to get it right, to sort of put forward some body of knowledge that the author thinks is important. But when you write a textbook, you have to take into account who's reading it, where they're coming from, what they already know, etc., etc., etc.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And there might be things that you think are really cool, but putting them in your textbook isn't actually helpful to the audience members. So optimizing for actually teaching the subject is the very simple strategy that I had in mind. For the quantum mechanics textbook that I'm working on very, very slowly, but it's still going on, it's a slightly different thing.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Again, there's many, many quantum mechanics textbooks on the market, and some of them do actually try their best to be optimized for pedagogy. But I think there the subject matter is the issue. For general relativity, everyone more or less agrees on the subject matter.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
For quantum mechanics, and this has nothing to do with interpretations or many worlds or anything like that, the actual quantum mechanics, the actual thing you're supposed to teach, so undergraduates are empowered to go solve problems and solve equations and so forth, people disagree on what that is. How important is it to talk about entanglement or how important is it to talk about measurement?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
How important is it to talk about two-state systems or quantum information or rather than just solving the Schrodinger equation over and over again for different explicit potentials and things like that. People disagree about these things. And so I'm going to try to—I have a strategy. We're going to see how it works. You know, I'm teaching it, which is always very, very helpful.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So it's really a matter of effectiveness in a very, very tangible way. So the difficulty of writing a textbook is just being as clear and useful as possible. The usefulness is something that I would emphasize there. For a popular book, there's a lot more freedom, right? The objective of doing it is much less predefined.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You can write books for inspiration, for education, to be thought-provoking, to synthesize a whole bunch of different things. There's all sorts of different reasons why you'd write a popular book. But you still have the challenge of trying to match what you think is cool and interesting with what the audience might be interested in.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Obviously, for the popular book, you don't need to worry about getting all those equations right. But for the textbook where you do have all those equations, the thing is that the equations are either right or wrong, right? You can actually test them as kind of tedious. You better check, you know, when you have problem sets or things like that that you suggest in your book.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
You better check that they're doable and they're sensible and all your derivations are correct and you're free of typos, all that stuff. becomes very, very relevant, less so in a popular book. But in a popular book, you really should think carefully about, why am I saying this at all? Why do I have a chapter on this? Is this really necessary? Could I do it better?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Could I talk about something completely different? Just because it is so much less constrained, it can be trickier to choose how to do it well. Ved Kumar says, priority question. I recently finished your biggest ideas in the universe series and I found it helpful in my understanding of foundational physics. It prompted a thought on the quantum measurement problem I wanted your feedback on.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
The idea involves trying to entangle a superposition into a classical and quantum system while requiring information conservation and considering the implications. A useful case of this is trying to pass a data sequence, which will be a superposition of several definite sequences, all equal in length, onto a classical and quantum computer.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Now that I'm thinking about it, there's some uncertainty about, you know, is the eye sensitive enough to detect a single photon? And maybe the answer is sometimes it is, sometimes it isn't, depending on what's going on. But anyway, I think the basic lesson here is there's a lot of uncertainty in quantum mechanics, and this is an example where that actually helps us out.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Both computers will contain bits and qubits equal in quantity to the length of a definite sequence. So the question goes on. I'm going to stop reading there, but I do not understand what is going on in this question. I know it's a priority question, so I have to address it, but I am not at all clear about the setup that is being proposed to be judged. Um,
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
When you say entangle a superposition into a classical and quantum system, that makes no sense to me. I mean, I'm sure it could make sense if I understood what you had in mind. Maybe there are some equations or something like that. But entanglement is a purely quantum thing. There's no such thing as—or, yeah, entangle a superposition. I don't even know what entangle a superposition means.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I know what it means to entangle quantum states and quantum states— are in superpositions from certain points of view, not in superpositions from other points of view, but classical systems are neither entangled nor in superpositions, so I really don't know what's going on. Sorry about that. I can't really be very helpful. Steven Moradi has a priority question.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I like everyone's using up their priority questions. That's good. You put some thought into what you want these to be. I've heard people say that there is no chaos in quantum processes.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Could you elucidate the difference between a three-body classical gravitational interaction with a three-body electrostatic quantum interaction, given that both are deterministic and interact via inverse square forces? This is a subtle thing, this statement that there is no chaos in quantum processes. I mean, the world is quantum and there is chaos in the world.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
So therefore, clearly, in some sense, there is chaos in quantum mechanics. But on the other hand, chaos is a result. Chaos is a statement about sensitive dependence on initial conditions, right? Tiny deviations in the initial conditions lead to large deviations in the final answer. How can that happen at the down and dirty level of equations?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
It happens because of nonlinearities, because small deviations in the state of the system can feed back onto each other through nonlinear terms in the equations of motion. In quantum mechanics, the equation of motion is, you guessed it, the Schrodinger equation. And the Schrodinger equation is resolutely linear as a function of the wave function.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
There's no wave function squared terms in the Schrodinger equation. So if the question you're asking is, Is there sensitive dependence on initial conditions in the evolution of the quantum state according to the Schrodinger equation? The answer is no, there never is. It's a linear equation of motion.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But within all the different things that can pop out of the Schrodinger equation, one of the things is the classical limit. So you can have a classical limit and it makes absolutely no difference whether we're talking about gravity or electromagnetism. They're exactly the same in this sense.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
In either case, there can be a classical limit where there is chaos, where there is non-linear classical equations of motion that arise as the limit of quantum mechanics. how can nonlinear equations of motion arise as the limit of linear equations of motion?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Cole Giusto says, You know, whether it's worth arguing for or not, I think that's a bit of a judgment call, right? And very often... arguments about whether or not something is real aren't worth arguing for. I don't want to argue about it, honestly. I just want to be clear about what I mean.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Well, the classical limit is subtle and it involves the combined effect of many, many different parts of the quantum mechanical wave function. So basically you have many, many different modes or whatever you want to call them of the wave function. either interfering constructively or destructively to give you a classical trajectory.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
And that emergent classical trajectory can indeed obey chaotic dynamics. The whole thing is very subtle. I'm not trying to undersell it. There was a whole subject for a while where people were trying to bang their heads against this question. How can there be quantum chaos? And the answer is you need to take the classical limit.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Paul Torek says, on the memory arrow of time and the causal arrow, you said, because we have memories and records of the past, we can't change them. But I'm tempted to turn the explanation around. If you can, at time t1, select an event, so you can't, at t1, have a record of the event, Sorry, I inserted a word there.
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
If you can at time t1 select an event, you can't at time t1 have a record of the event. So it seems that either lack of influence is a precondition or else a co-condition of records. In Janan Ismail's book, How Physics Makes Us Free, she offers a united explanation of both arrows of time, influence, and records.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
Local macroscopic changes to the present state of the world propagate asymmetrically into the past and future. So who's right about the direction of explanations here? Or is this a case where, depending on what the audience already understands, the explanation can go either way?
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Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I do think there's a unified explanation here, and I might have been, or the specific language that I used might have been chosen sloppily here. When I say because we have memories of records of the past, we can't change them, what I mean is because we have what we think of as reliable memories and records of the past, we know we can't change them.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
But our knowledge of the fact that we can't change them is different than the fact we can't change them. I don't love the language of – macroscopic changes to the present state of the world propagating asymmetrically into the past and the future. I'm not quite sure what it means that they propagate. But of course, you can invent a meaning for it.
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
I'm not saying that it's meaningless, but I'm saying that you have to be very clear. There's more words that would need to be stated to go into what exactly is being said. But anyway, I don't think there's any weirdness or mysteriousness or true disagreement here. The overall unmistakable fact is you have some macroscopic, incomplete information about the present. You have some...
The Mel Robbins Podcast
Why 80% of Autoimmune Diseases Happen to Women & Solutions From a Renowned MD
hypothetical information about the past in the form of a low entropy boundary condition. You have no information about the future. There's no boundary condition that you are imposing there. And given those three ingredients, you will get an asymmetry, both of memory and causality.