Sarah Walker
Appearances
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But you think the book has a finite size.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I don't. I mean, not that I believe in infinities, but I don't, I think the size of the book is growing.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Oh, there you go. Oh, we're being recursive.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think life obeys universal principles. I think there is some deep underlying explanatory framework that will tell us about the nature of life in the universe and will allow us to identify life that we can't yet recognize because it's too different.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Well, you couldn't have been asking this at the origin of life, right? Because obviously like you wouldn't have existed at the origin of life, but like the question of intelligence and artificial general, like those questions did not exist then. And so, and they in part existed because the universe invented a space for those questions to exist through evolution, right?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It will, but there will be other questions we can't anticipate now that we'll be asking.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Right. Or like, like the theory of like gravitation, for example, like when we invented that theory, like we only knew about the planets in our solar system. Right. And now, you know, many centuries later, we know about all these planets around other stars and black holes and other things that we could never have anticipated. So, and then we can ask questions about them.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
You know, like we wouldn't have been asking about singularities and like, can they really be physical things in the universe several hundred years ago? That question couldn't exist.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So do you think the universe has an end? If you think it's a book with an end?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think universes inside universes is maybe possible.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
The universe is a huge place.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Oh, I'm not a many worlds person.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
No. Are you? How many Lex's are there?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Do some of them wear yellow jackets?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah. But, yeah, I mean, that's consistent with many worlds, right? Because, like, there's this constant branching. But it doesn't really have a directionality to it. I don't know. Many worlds is weird.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So my interpretation of reality is, like, if you folded up, like, all that bifurcation of many worlds and you just fold it into the structure that is you and you just said you are all of those many worlds – And, like, that sort of, you know, like, your history, like, converged on you. But, like, you're actually an object exists that's, like, that, you know, was selected to exist.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And you're self-consistent with the other structures. So, like, the quantum mechanical reality is not the one that you live in. It's this very deterministic classical world. And you're carving a path through that space. But I don't think... that you're constantly branching into new spaces. I think you are that space.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
No, it's random at the bottom, right? But like this randomness that we see at the bottom of reality that is quantum mechanics, I think like people have assumed that that is reality. And what I'm saying is like all those things you see in many worlds, all those versions of you, just collect them up and bundle them up. And like, they're all you. And what has happened is,
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
You know, like elementary particles don't have, they don't live in a deterministic universe, the things that we study in quantum experiments. They live in this fuzzy random space. But as that structure collapsed and started to build structures that were deterministic and evolved into you, you are a very deterministic macroscopic object.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
You know, all the sort of classic definitions people want to use just don't work. They don't work in all cases. So Carl Sagan had this wonderful essay on definitions of life where I think he talks about aliens coming from another planet. If they saw Earth, they might think that cars were the dominant life form because there's so many of them on our planet.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And you can look down on that universe that doesn't have time in it, that random structure. And you can see that all of these possibilities look possible, but they're not possible for you because you're constrained by this giant causal structural history. So you can't live in all those universes.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
You'd have to go all the way back to the very beginning of the universe and retrace everything again to be a different you.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So it's the fact that you're a deterministic structure living in a random background. And also all of that selection bundled in you allows you to select on possible futures. So that's where your will comes from. And there's just always a little bit of randomness because the universe is getting bigger.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And, you know, like this idea that the past is and the present is not large enough yet to contain the future. Right. The extra structure has to come from somewhere. And some of that is because outside of those giant causal structures that are things like us, it's fucking random out there. And it's scary.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And we're all hanging on to each other because the only way to hang on to each other, like the only way to exist is to like cling on to all of these causal structures that we happen to co-inhabitate existence with and try to keep reinforcing each other's existence.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But free will is totally consistent with that.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Well, it's also – it's not just the randomness. There's two features. One is randomness helps generate some novelty and some flexibility. But it's also that, like, because you're the structure that's deep in time, you have this combinatorial history that's you. And I think about time and assembly theory not as linear time but as combinatorial time.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So if you have all of this structure that you're built out of, you – in principle, you know, your future can be combinations of that structure. You obviously need to persist yourself as a coherent you. So you want to optimize for a common, like a, a future in that combinatorial space that still includes you most of the time for most of us.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And, and when you make those kinds of, and then that gives you a space to operate in and that's your sort of horizon where your free will can operate. And your free will can't be instantaneous.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So for like example, like I'm sitting here talking to you right now, I can't be in the UK and I can't be in Arizona, but I could plan, I could execute my free will over time because free will is a temporal feature of life to be there, you know, tomorrow or the next day if I wanted to.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think those were already decided a while ago. I don't think free will is ever instantaneous.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And like humans are inside them and you might want to exclude machines. But any definition, you know, like classic biology textbook definitions would also include them. And so, you know, he wanted to draw a boundary between these kind of things by trying to exclude them. But they were naturally included by the definitions people want to give.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Or you being Lex. Whatever you want to call it.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah. It exists. I think that's the hardest question.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It is the same. I try to fold all of the questions into that question because I think that one's really hard. And I think the nature of existence is really hard.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Right. So, well, I think there's sort of two questions embedded here. I think the one that we can't answer by answering life is why certain things exist and others don't. But I think the sort of ultimate question, the sort of like prime mover question of why anything exists, we will not be able to answer.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Oh, there's nothing outside the universe. So I have a very – I am a very – like I am like the most physicalist that like anyone could be. So like for me, everything exists in our universe. And like I like to like think it like everything exists here. So even when we talk about the multiverse, I don't – like to me, it's not like there's all these other universes outside of our universe that exist.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
The multiverse is a concept that exists in human minds. And it allows us to have some counterfactual reasoning to reason about our own cosmology, and therefore it's causal in our biosphere to understanding the reality that we live in and building better theories. But I don't think that the multiverse is something... And also math.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I don't think there's a platonic world that mathematical things live in. I think mathematical things are here on this planet. I don't think it makes sense to talk about things that exist outside of the universe. If you're talking about them, you're already talking about something that exists inside the universe and is part of the universe and is part of what the universe is building.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I mean, what else would there be?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And you can say that, and that's an interesting philosophy. But again, this is sort of like pushing on the boundaries of the way that we understand things. I think it's more constructive to say the fact that I can talk about those things is telling me something about the structure of where I actually live and where I exist.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Well, it may not be true. It may be something that allows me to build better theories I can test to try to understand something objective.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And in fact, what he ended up pointing out is that all of the definitions of life that we have, whether it's life as a self-reproducing system or life eats to survive or life requires compartments, whatever it is, there's always a counter example that challenges that definition. This is why viruses are so hard or why fire is so hard.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah. So there's no such thing as experimental Platonism. But if you think math is an object that emerged in our biosphere, you can start experimenting with that idea. And that to me is really interesting.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Like to think about, well, people, I mean, mathematicians do think about math sometimes as an experimental science, but to think about math itself as an object for study by physicists rather than a tool physicists use to describe reality, it becomes the part of reality they're trying to describe to me as a deeply interesting inversion.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I love the way it makes me feel.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah. So I think I love, yeah, I love the way it makes me feel to have ideas that I think are novel. And I think that the dual side of that is the painful process of trying to communicate that with other human beings to test if they have any kind of reality to them.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
uh and i also love that process i love trying to figure out how to explain really deep abstract things that i don't think that we understand and trying to understand them with other people and i also love the shock value of uh you like this kind of idea we were talking about before of like being on the boundary of like what we understand and so people can kind of see what you're seeing but they
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I love the shock value that, like, people have, like, that immediate moment of recognizing that there's something beyond the way that they thought about things before.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And being able to deliver that to people, I think, is one of the biggest joys that I have is just, like, maybe it's that sense of mystery, like, to share that there's something beyond the frontier of how we understand and we might be able to see it.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yes. And I think my greatest wish in life is to somehow contribute to an idea that transforms the way that we think. I have my problem I want to solve, but the thing that gives me joy about it is really changing something. And ideally getting to a deeper understanding of how the world works and what we are.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It's the only way to do anything.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so we've had a really hard time trying to pin down from a definitional perspective exactly what life is.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Did you see this in the jungle?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, but it can't erase it. It's just restructuring it. And I think the other thing that is really vivid to me about this example that you're giving is how much death is necessary for life. So I worry a bit about notions of immortality and whether immortality is a good thing or not. So I have sort of a broad conception that life is the only thing the universe
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
generates that actually has even the potential to be immortal. But that's as like this sort of process that you're describing where life is about memory and historical contingency and construction of new possibilities. But when you look at any instance of life, especially one as dynamic as what you're describing, it's a constant birth and death process.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But that birth and death process is like the way that the universe can explore what possibilities can exist and Not everything, not every possible human or every possible ant or every possible zombie ant or every possible tree will ever live. So it's, you know, it's an incredibly dynamic and creative place because of all that death.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, it does. I think the thing that's perplexing for me about these kind of examples is, you know, effectively the ant's dead, but it's staying alive now because it's piloted by this fungus. And so that gets back to this, you know— thing that we were talking about a few minutes ago about how the boundary of life is really hard to define.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So, you know, anytime that you want to draw a boundary around something and you say, this feature is the thing that makes this alive, or this thing is alive on its own, there's not ever really a clear boundary.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And these kind of examples are really good at showing that because it's like the thing that you would have thought is the living organism is now dead, except that it has another living organism that's piloting it. So the two of them together are are alive in some sense, but they're, you know, now in this kind of weird symbiotic relationship that's taking the sand to its death.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think we have to get rid of the notion of an individual as being relevant. And this is really difficult because, you know, a lot of the ways that we think about life, like the fundamental unit of life is the cell. Individuals are alive. But we don't think about how how gray that distinction is. So, for example, you might consider
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
you know, self-reproduction to be the most defining feature of life. A lot of people do actually like, you know, one of these standard different definitions that a lot of people may feel like to use in astrobiology is life as a self-sustaining chemical system capable of Darwinian evolution, which I was once quoted as agreeing with. And I was really offended because I hate that definition.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think it's terrible. And I think it's terrible that people use it. I think like every word in that definition is actually wrong as a descriptor of life.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, I know. If you want to make me angry, you can pretend I said that and believed it.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, they're all interesting words. Um, And, you know, together they sound really smart and they sound like they box in what life is, but you can use any of the words individually and you can come up with counterexamples that don't fulfill that property. The self-sustaining one is really interesting thinking about humans, right? Like we're not self-sustaining. We're dependent on societies.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so, you know, I find it paradoxical that, you know, it might be that societies, because they're self-sustaining units, are now more alive than individuals are. And that could be the case, but I still think we have some property associated with life. I mean, that's the thing that we're trying to describe. So that one's quite hard. And in general, you know, no organism is really self-sustaining.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
They always require an environment. So being self-sustaining is coupled in some sense to the world around you. We don't live in a vacuum. So that part's already challenging. And then you can go to chemical system. I don't think that's good either. I think there's a confusion because life emerges in chemistry, that life is chemical. I don't think life is chemical.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think life emerges in chemistry because chemistry is the first thing the universe builds where it cannot exhaust all the possibilities because the combinatorial space of chemistry is too large.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Oh, sure. Or maybe. I don't know.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Where the – very precisely, it's not the first thing it creates. Obviously, like, it has to make atoms first. But it's the first thing. Like, if you think about, you know, the universe originated, atoms were made in, you know, Big Bang nuclear synthesis and then later in stars and then planets formed and planets become engines of chemistry. They start exploring what kind of chemistry is possible.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Okay. And the combinatorial space of chemistry is so large that even on every planet in the entire universe, you will never express every possible molecule. I like this example actually that Lee gave me, which is to think about taxol. It has a molecular weight of about It's got, you know, a lot of atoms, but it's not astronomically large.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And if you tried to make one molecule with that molecular formula and every three-dimensional shape you could make with that molecular formula, it would fill 1.5 universes. So with one unique molecule. That's just one molecule. So chemical space is huge.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I think it's really important to recognize that because if you want to ask a question of why does life emerge in chemistry, well, life emerges in chemistry because life is the physics of how the universe selects what gets to exist. And those things get created along historically contingent pathways and memory and all the other stuff that we can talk about.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But the universe has to actually make historically contingent choices in chemistry because it can't exhaust all possible molecules.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Oh, if it's not chemical. So I think some of the things that have evolved on our biosphere, I would call as much alive... as chemistry, as a cell, but they seem much more abstract. So for example, I think language is alive, I think, or at least life. I think memes are, I think- You're saying language is life.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Life maybe not, maybe not alive, but I don't, I actually don't know where I stand exactly on that. I've been thinking about that a little bit more lately, but mathematics too. And it's interesting because people think that math has this platonic reality that exists outside of our universe. And I think it's a feature of our biosphere and it's telling us something about the structure of ourselves.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I find that really interesting because when you would sort of internalize all of these things that we noticed about the world and you start asking, well, what did these look like if I was, you know, something outside of myself observing these systems that we're all embedded in, what would that structure look like?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I think we look really different than the way that we talk about what we look like to each other. Yeah.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think it's the fact that it's open-ended in some sense. It's another open-ended combinatorial space and the recursive properties of it allow creativity to happen. which is what you see with the revolution in the last century with Gödel's theorem and Turing. And there's clear places where mathematics notices holes in the universe.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Definitely not chemical. I mean, chemistry is one substrate.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Well, specifically it's Darwinian evolution.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I think Darwinian evolution is a problem, but the reason that that definition is a problem is not because evolution is in the definition, but because the implication is that evolution you know, that most people would want to make is that an individual is alive.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And the evolutionary process, at least the Darwinian evolutionary process, most evolutionary processes, they don't happen at the level of individuals. They happen at the level of populations. So again, you would be saying something like what we saw with the self-sustaining definition, which is that populations are alive, but individuals aren't because populations evolve and individuals don't.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And obviously, maybe you're alive because your gut microbiome is evolving, but Lex as an entity right now is not evolving by canonical theories of evolution. In assembly theory, which is attempting to explain life, evolution is a much broader thing. So
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yes. You're constructing yourself all the time. Assembly theory is about construction and how the universe selects for things to exist.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
That's fine too. But, but this again gets back to, so, um, so I think what all of the, you know, like we can nitpick at definitions. I don't think it's like incredibly helpful to do it, but the reason for, for me.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, it is fun. It is really fun. And actually I do, I do think it's useful in the sense that when you see the way, the you either have to keep forcing in your like sort of conception of life you want to have, or you have to say, all these definitions are breaking down for a reason. Maybe I should adopt a more expansive definition that encompasses all the things that I think and our life.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so for me, I think life is the process of how information structures matter over time and space. And an example of life is what emerges on a planet and, you know, yields an open-ended cascade of generation of structure and increasing complexity. And this is the thing that life is. And any individual is just a particular instance of these lineages that are, you know, structured across time.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so we focus so much on these individuals that are these short temporal moments in this larger causal structure that actually is the life on our planet. And I think that's why these definitions break down because they're not general enough. They're not universal enough. They're not deep enough. They're not abstract enough to actually capture that regularity.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, it's like Aristotle focusing on heavy things falling because they're earth-like and things floating because they're air-like. It's the wrong thing to focus on.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think we're missing most of what we are. So one of the issues, I've been thinking about this really viscerally lately. It's weird when you do theoretical physics because I think it literally changes the structure of your brain and you see the world differently, especially when you're trying to build new abstractions.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I mean, I think you're always on the edge of it, but I think what is amazing about being a scientist and trying to do things rigorously is it keeps your sanity. So I think if I wasn't a theoretical physicist, I would be probably not sane. But what it forces you to do is hold the fire, like you have to hold yourself to the fire of like,
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
these abstractions in my mind have to really correspond to reality. And I have to really test that all the time. And so I love building new abstractions and I love going to those like incredibly creative, you know, spaces that people don't see as part of the way that we understand the world now.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But ultimately I have to make sure that whatever I'm pulling from that space is something that's really usable and really like relates to the world outside of me. That's what science is.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah. So the issue is we evolve perception to see reality a certain way, right? So for us, space is really important and time feels fleeting. And I had a really wonderful mentor, Paul Davies, most of my career. And Paul's amazing because he gives these like little seed thought experiments all the time.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Like, you know, something he used to ask me all the time was when I was a postdoc, this is kind of a random tangent, but was like, you know, how much of the universe could be converted into technology if you were thinking about like, you know, long-term futures and stuff like that. And it's like a weird thought experiment, but like there's a lot of deep things there.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I do think a lot about the fact that We're really limited in our interactions with reality by the particular architectures that we evolved. And so we're not seeing everything. And in fact, our technology tells us this all the time because it allows us to see the world in new ways by basically allowing us to perceive the world in ways that we couldn't otherwise.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so what I'm getting at with this is I think that living objects are actually huge. Like they're some of the biggest structures in the universe, but but they are not big in space, they are big in time. And we actually can't resolve that feature. We don't interact with it on a regular basis.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So we see them as these fleeting things that have this really short temporal clock time without seeing how large they are. When I'm saying time here, I really like the way that people could picture it is in terms of causal structure.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So if you think about the history of the universe to get to you and you imagine that that entire history is you, that is the picture I have in my mind when I look at every living thing.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Doesn't everyone?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Well, you know what the trick is? The reason they're hard to write is because it's compressing a very deep idea into a short amount of space. And I really like doing that intellectual exercise because I find it productive for me.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, I like language. I think it's really fun to play with.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I would like to try this, but I think I use language in certain ways that are non-canonical, and I do it very purposefully. And it would be interesting to me how AI would interpret it.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
The universe is far larger in time than it is in space.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And this planet is one of the biggest things in the universe.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Technosphere. I think the modern technosphere is the largest object in time in the universe that we know about.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I mean the global integration of life and technology on this planet.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But I don't think of them as separate. They're like very integrated with the structure that generated them. So you can almost imagine it like time is constantly bifurcating and it's generating new structures. And these new structures are, you know, locally constructing the future.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so things like you and I are very close together in time because we didn't diverge like very early in the history universe. It's very recent. And I think this is one of the reasons that we can understand each other so well and we can communicate effectively.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I might have some sense of what it feels like to be you, but other organisms bifurcated from us in time earlier, this is just the concept of phylogeny, right? But if you take that deeper and you really think about that as the structure of the physics that generates life, and you take that very seriously, all of that causation is still bundled up Uh, yeah.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It's hard to use words to visualize what's in minds. I have such a hard time with this sometimes. Actually, I was thinking in the way over here. I was like, you know, you have pictures in your brain, and then they're hard to put into words. But I realized I always say I have a visual, but it's not actually I have a visual. It's I have a feeling.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Because oftentimes I cannot actually draw a picture in my mind. for the things that I say, but sometimes they go through a picture before they get to words. But I like experimenting with words because I think they help paint pictures.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, I think so. And I think this is one of the reasons that we have such an ability to abstract as humans because we are so gigantic that like the space that we can go back into is really large. So like the more abstract you're going, like the deeper you're going in that space.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yes. And this is why the definition of life cannot be the individual. It has to be these lineages because they're all connected. They're interwoven and they're exchanging parts all the time.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, I think life is very high dimensional. And in fact, I think you can be alive in some dimensions and not in others. Like if you could project all the causation that's in you, in some features of you, you know, very little causation is required and like very little history. And in some features, a lot is. So it's quite difficult to take this really high dimensional perspective.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
very deep structure and project it into things that we really can understand and say like this is the one thing that we're seeing because it's not one thing.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Billions of years, yeah.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It's crazy that there's billions of years inside all of us.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Because it's creative, but with us, obviously, like not independently of us. And also because of this sort of lineage view of life. And I think about life often as a planetary scale phenomena, because that's sort of the natural boundary for all of this causation that's bundled in every object in our biosphere. And so for me, it's just sort of the current boundary of how far life
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
on our planet has pushed into the things that our universe can generate. And so it's the furthest thing. It's the biggest thing. And I think a lot about the nature of life across different scales. And so, you know, we have cells inside of us that are alive and we feel like we're alive, but we don't often think about the societies that we're embedded in.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
as alive or a global scale organization of us and our technology on the planet as alive. But I think if you have this deeper view into the nature of life, which I think is necessary also to solve the origin of life, then you have to include those things.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah. This is the hard thing about solving the problem of life, I think, is how many things you have to integrate into building a unified picture of this thing that we want to call life. And a lot of our theories of physics are built on building...
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
deep regularities that explain a really broad class of phenomenon i think we haven't really traditionally thought about life that way uh but i think to get it at some of these hardest questions like looking for life on other planets or the original life you really have to think about it that way and so most of like my professional work is just trying to understand like every single thing on this planet that might be an example of life which is pretty much everything and then trying to figure out like what's the deeper structure underlying that
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, Schrodinger really tried to... to do what physicists try to do, which is explain things. And his attempt was to try to explain life in terms of non-equilibrium physics, because he thought that was the best description that we could generate at the time. And so he did come up with something really insightful, which was to predict the structure of DNA as an aperiodic crystal.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And that was for a very precise reason that, you know, that was the only kind of physical structure that could encode enough information to actually specify a cell. We knew some things about genes but not about DNA and its actual structure. when he proposed that. But in the book, he tried to explain life as kind of going against entropy.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so some people talked about it as like Schrodinger's paradox, how can life persist when the second law of thermodynamics is there? But in open systems, that's not so problematic. And really the question is, why can life generate so much order? And we don't have a physics to describe that. And it's interesting, you know, generations of physicists have thought about this problem.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Oftentimes it's like when people are retiring, they're like, oh, now I can work on life. Or they're like more senior in their career and they worked on other more traditional problems. And there's still a lot of impetus in the physics community to think that non-equilibrium physics will explain life. But I think that's not the right approach.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I don't think ultimately the solution to what life is, is there. And I don't really... think entropy has much to do with it unless it's entirely reformulated.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yes. From randomness.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
No. Physics hardly even acknowledges that the universe is random at its base. Yeah, absolutely. you know, he, he formulated laws that had initial conditions and, um, fixed dynamical laws. And that's been sort of become the standard canon of how people think the universe works and how we need to describe any physical system is with an initial condition and a law of motion.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I think that's not actually the way the universe really works. I think it's a good approximation for the kind of systems that physicists have studied so far. And I think it will radically fail, um, in the long term at describing reality at its more basal levels. I'm not saying there's a base.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I don't think that reality has a ground, and I don't think there's a theory of everything, but I think there are better theories, and I think there are more explanatory theories, and I think we can get to something that explains much more than the current laws of physics do.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, you know, like in physics right now, it's really popular to talk about theories of everything. So string theory is supposed to be a theory of everything because it unifies quantum mechanics and gravity. And, you know, people have their different pet theories of everything.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And the challenge with a theory of everything, I really love this quote from David Krakauer, which is a theory of everything is a theory of everything except those things that theorize.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, but it's also weird because if a theory of everything explained everything, it should also explain the theory. So the theory has to be recursive. And none of our theories of physics are recursive. So it's a weird concept.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I don't think so. I think you can build a theory acknowledging that you're an observer inside the universe.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think so. I mean, I don't think, there's always going to be the paradox of another meta level you could build on the meta level, right? So like if you assume this is your universe and you're the observer outside of it, you have some meta description of that universe, but then you need a meta description of you describing that universe, right? So, you know, this is one of,
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
The biggest challenges that we face being observers inside our universe and also, you know, why the paradoxes and the foundations of mathematics and any place that we try to have observers in the system or a system describing itself show up. But I think it is possible to build a physics system.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
that builds in those things intrinsically without having them be paradoxical or have holes in the descriptions. And so one place I think about this quite a lot, which I think can give you sort of a more concrete example, is the nature of what we call fundamental. So we typically define fundamental right now in terms of the smallest indivisible units of matter.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So again, you have to have a definition of what you think material is and matter is. But right now, what's fundamental are elementary particles. And we think they're fundamental because we can't break them apart further.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And obviously we have theories like string theory that if they're right, would replace the current description of what's the most fundamental thing in our universe by replacing it with something smaller. But we can't get to those theories because we're technologically limited.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so if you look at this from a historical perspective and you think about explanations changing as physical systems like us learn more about the reality in which they live, we once considered atoms to be the most fundamental thing. And, you know, it literally comes from the word indivisible.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And then we realized atoms had substructure because we built better technology, which allowed us to quote unquote, see the world better and resolve smaller features of it. And then we built even better technology, which allowed us to see even smaller structure and get down to the standard model. particles.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And we think that there might be structure below that, but we can't get there yet with our technology. So what's fundamental, the way we talk about it in current physics is not actually fundamental. It's the boundaries of what we can observe in our universe, what we can see with our technology. And so if you want to build a theory that's about us and about what
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
What's inside the universe that we can observe, not what's at the boundary of it. You need to talk about objects that are in the universe that you can actually break apart to smaller things. So I think the things that are fundamental are actually the constructed objects.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
They're the ones that really exist and you really understand their properties because you know how the universe constructed them because you can actually take them apart. You can understand the intrinsic laws that built them. But the things at the boundary are just at the boundary. They're evolving with us, and we'll learn more about that structure as we go along.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But really, if we want to talk about what's fundamental inside our universe, we have to talk about all these things that are traditionally considered emergent, but really just structures in time that have causal histories that constructed them and are really actually what our universe is about.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I don't see one.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think so, yeah. I think for me, the frontier in modern physics, where the new physics lies is not in high energy particle physics. It's not in quantum gravity. It's not in any of these sort of traditionally sold, this is going to be the newest, deepest insight we have into the nature of reality. It is going to be in studying the problems of life.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
and intelligence and the things that are sort of also our current existential crises as a civilization or a culture that's going through an existential trauma of inventing technologies that we don't understand right now.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Well, humans have always been afraid of our technologies though, right? So it's kind of a fascinating thing that every time we invent something we don't understand, it takes us a little while to catch up with it.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, we love being traumatized.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
We want to learn more. And then when we learn more, it traumatizes us. You know, I never thought about it this before, but I think this is one of the reasons I love what I do is because it traumatizes me all the time. That sounds really bad. But what I mean is like, I love the shock of like realizing that like coming to understand something in a way that you never understood it before.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think it seems to me when I see a lot of the ways other people react to new ideas that they don't feel that way intrinsically. But for me, that's like, that's why I do what I do. I love that feeling.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, I'm trying to embody that because I think you have to live the physics to understand it. But there's a great quote about Einstein. I don't know if this is true or not, that he once said that he could feel a light beam in his belly. And I think – but I think like you got to think about it though, right?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Like if you're a really deep thinker and you're really thinking about reality that deeply and you are part of the reality that you're trying to describe, like you feel it. You really feel it.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yes. It's a constant, constant descent into madness.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, you know you don't know.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I rely on other people to tell me. Actually, this is very funny because I have these conversations with my students often. They're worried about going crazy.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
The origin of life is like this boundary that the universe can only cross if If a structure that emerges can reinforce its own existence, which is self-reproduction, autocatalysis, things people traditionally talk about, but it has to be able to maintain its own existence against this sort of randomness that happens in chemistry and this randomness that happens in the quantum world.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And like it's in some sense the emergence of like a deterministic structure that says, you know, I'm going to exist and I'm going to keep going. But, you know, pinning that down is really hard. We have ways of thinking about it in assembly theory that I think are pretty rigorous.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And one of the things I'm really excited about is trying to actually quantify in an assembly theoretic way when the original life happens. But the basic process I have in mind is, is a system that has no causal contingency, no constraints of objects basically constraining the existence of other objects or allowing the existence of other objects.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so that sounds very abstract, but you can just think of a chemical reaction can't happen if there's not a catalyst, for example, or a baby can't be born if there wasn't a parent. So there's a lot of causal contingency that's necessary for certain things to happen. So- You think about this sort of unconstrained, random system. There's nothing that reinforces the existence of other things.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So the sort of resources just get washed out in all of these different structures, and none of them exist again. Or they just, you know, they're not very complicated if they're in high abundance. And some random events allow some things to start reinforcing the existence of a small subset of objects.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And if they can do that, you know, like just molecules basically recognizing each other and being able to catalyze certain reactions, there's this kind of transition point that happens where,
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
where unless you get a self-reinforcing structure, something that can maintain its own existence, it actually can't cross this boundary to make any objects in high abundance without having this sort of past history that it's carrying with us and maintaining the existence of that past history.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And that boundary point where objects can't exist unless they have the selection and history in them is what we call the original life. And pretty much everything beyond that boundary is holding on for dear life to all of the causation and causal structure that's basically put it there. And it's carving its way through this possibility space into generating more and more structure.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And that's when you get the open-ended cascade of evolution. But that boundary point is really hard to cross. And then what happens when you cross that boundary point and the way objects come into existence is also like really fascinating dynamics because, you know, like as things become more complex, the assembly index increases. I can explain all these things.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Sorry, you can tell me what you want to explain. I mean, explain what people will want to hear. Sorry, I have like a very vivid visual in my brain and it's really hard to articulate it.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I know. It's so hard. It's going from like a feeling to a visual to language is so stifling sometimes.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yes. So self-reproduction has this property, right? Like if the system can make itself, then it can persist in time, right? Because all objects decay. They all have a finite lifetime. So if you're able to make a copy of yourself before you die, before the second law eats you or whatever people think happens, then that structure can persist in time.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Right. But things that can copy themselves are very rare.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so what ends up happening is that you get structures that enable the existence of other things. And then somehow, only for some sets of objects, you get closed structures that are self-reinforcing and allow that entire structure to persist.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Right, so this is the classic idea.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And that's what we're trying to figure out is what are the causal constraints that close the loop. So there is this idea that's been in the literature for a really long time that was originally proposed by Stuart Kaufman as really critical to the origin life called autocatalytic set. So autocatalytic set is exactly this property. We have A makes B, B makes C, C makes A, and you get a closed system.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But the problem with the theory of autocatalytic sets is an incredibly... brittle as a theory and it requires a lot of ad hoc assumptions. Like you have to assume function. You have to say this thing makes B. It's not an emergent property, the association between A and B. And so the way I think about it is much more general. If you think about
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
um these histories that make objects it's kind of like the structure of the histories becomes um collapses in such a way that these things are all in the same sort of causal structure and that causal structure actually loops back on itself to be able to generate some of the things that make the higher level structures. Lee has a beautiful example of this actually in molybdenum.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It's like the first non-organic autocatalytic set. It's a self-reproducing molybdenum ring, but it's like molybdenum. And basically, if you look at the molybdenum, it makes a huge molybdenum ring. I don't remember exactly how big it is. It might be like 150 molybdenum atoms or something. But
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But if you think about the configuration space of that object, you know, it's exponentially large, how many possible molecules. So, like, why does the entire system collapse on just making that one structure? If you start from, like, you know, molybdenum atoms that are maybe just, like, a couple of them stuck together. And so what they see in this system is there's a few intermediate stages.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So there's, like, some random events where the chemistry comes together and makes these structures large. And then once you get to this very large one, it becomes a template for the smaller ones, and then the whole system just reinforces its own production.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It's a... No, but I think it goes to the deepest roots of like when he started thinking about origins of life. So I like, I mean, I don't know all his history, but like what he's told me is he started out in crystallography. And, you know, there are some things that he would just, you know, like people would just take for granted about chemical structures that he was like deeply perplexed about.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Like, just like, why are these like really intricate structures
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
really complex structures forming so easily under these conditions and he was really interested in life um but he started in that field so he's just carried with him these sort of deep insights from these systems that seem like they're totally not alive and just like these metallic chemistries um into actually thinking about the deep principles of life so i think he already uh
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And he already knew a lot about that chemistry. And he also, you know, assembly theory came from him thinking about how these systems work. So he had some intuition about what was going on with this molybdenum ring.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
They knew about them for a long time, but they didn't know that the mechanism of why that particular structure form was autocatalytic feedback. And so that's what they figured out in this paper. And I actually think that paper is revealing some of the mechanism of the origin-life transition because really what you see –
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Like the origin of life is basically like you should have a combinatorial explosion of the space of possible structures that are too large to exhaust. And yet you see it collapse on this, you know, really small space of possibilities that's mutually reinforcing itself to keep existing. That is the origin of life.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think it's a small space. But chemistry is very large. There might be a lot of them out there, but we don't know.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah. I mean, there's also all kinds of other weird properties that happen around this kind of phase boundary. So this other project that I have in my lab is focused on the origin of chirality, which is, you know, thinking about, so chirality is this property of molecules that they can come in mirror image forms. So like, just like chirality means hand. So you're
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Your left and right hand are what's called non-superimposable because if you try to lay one on the other, you can't actually lay them directly on top of each other. And that's the property of being a mirror image.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So there's this sort of perplexing property of the chemistry of life that no one's been able to really adequately explain that all of the amino acids in proteins are left-handed and all of the bases in RNA and DNA are right-handed. And yet the chemistry of these proteins building block units, amino acids, and nucleobases is the same for left and right-handed.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So you have to have like some kind of symmetry breaking where you go from these chemistries that seem entirely equivalent to only having one chemistry take over as the dominant form. And for a long time, I had been really, I actually did my PhD on the origin of chirality. I was working on it as like a symmetry breaking problem in physics. This is how I got started in the origin of life.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And then I left it for a long time because I thought it was like one of the most boring problems in the original life, but I've come back to it because I think there's something really deep going on here related to this like combinatorial explosion of the space of possibilities. But just to get to that point, like this feature of this handedness has been the main focus, but...
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
people take for granted the existence of chiral molecules at all, that this property of having a handedness. And they just assume that it's just a generic feature of chemistry. But if you actually look at
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
molecules, if you look at chemical space, which is like the space of all possible molecules that people can generate, and you look at small molecules, things that have less than about 7 to 11 heavy atoms, so things that are not hydrogen, almost every single molecule in that space is achiral, like doesn't have a chiral center. So it would be like a spoon of
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
spoon doesn't have it like it's the same as its mirror image it's not like a hand that's different than its mirror image but if you get to like this threshold boundary above that boundary almost every single molecule is chiral so you go from a universe where almost nothing has a mirror image form there's no mirror image universe of possibilities to this one where every single structure has pretty much a mirror image version and what
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
we've been looking at in my lab is that it seems to be the case that the original life transition happens around the time when you start accumulating. You push your molecules to a large enough complexity that chiral molecules become very likely to form. And then there's a cascade of molecular recognition where chiral molecules can recognize each other.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And then you get this sort of autocatalytic feedback and things self-reinforcing.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
No, it's a super interesting feature. I think chirality breaks symmetry in time, not space. So we think of it as a spatial property, like a left and right hand. But if I choose the left hand, I'm basically choosing the future of that system for all time because I've basically made a choice between the ways that that molecule can now react with every other object in its chemical universe.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Oh, I see. And so you're actually like, when you have this splitting of making a molecule that now has another form it could have had by the same exact atomic composition, but now it's just a mirror image isometry, you're basically splitting the universe of possibilities every time.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
In two, but molecules can have more than one chiral center, and that's not the only stereosometry that they can have. So This is one of the reasons that Toxol fills 1.5 universes It's all of these spatial permutations that you do on these objects that actually makes the space so huge.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So the point of this sort of chiral transition that I'm putting out is chirality is actually a signature of being in a complex chemical space. And the fact that we think it's a really generic feature of chemistry and it's really prevalent is because most of the chemistry we study on Earth is a product already of life.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And it also has to do with this transition in assembly, this transition in possibility spaces. Because I think there's something really fundamental going on at this boundary that you don't really need to go that far into chemical space to actually see life in terms of this depth in time, this depth in symmetries of objects in terms of like chiral symmetries or this assembly structure.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But getting past this boundary that's not very deep in that space requires life. It's a really weird property, and it's really weird that so many abrupt things happen in chemistry at that same scale.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Well, it's efficient for things to eat other things that are already alive because they don't have to go all the way back to the, Base chemistry.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I actually think it's a gift that we don't have much time.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I like invention as a word for them. I think that's good.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
No, I think the origin of life is a continual process. That's why. I'm interested in the first transition and solving that problem because I think it's the hardest, but I think it's happening all the time.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I like sight as an invention because I think having sensory perception and trying to comprehend the world, to use anthropocentric terms, is like a really critical feature of life. And I also, it's interesting the way that sight has complexified over time, right? So like if you think of the original life, nothing on the planet could see. Mm-hmm. Right. So like for a long time, life had no sight.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And then, you know, like photon receptors were invented. And then when multicellularity evolved, those cells eventually grew into eyes. And we had the multicellular eye. And then it's interesting when you get to societies like human societies that we invent even better technologies of seeing like telescopes and microscopes, which allow us to see deeper into the universe or at smaller scales.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So I think that's pretty profound the way that sight has transformed the ability of life to literally see the reality in which it's existing in. Yeah. I think consciousness is also obviously deeply interesting. I've gotten kind of obsessed with like octopus. I don't like, I, they're just so weird.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And the fact that like they evolved complex nervous systems kind of independently is like, seems very alien. Yeah.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Oh, I've seen videos of that. It's so gross when the babies come out. Did you see that? Yes. Like in person, like the babies coming out?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It's so gross. It's one of the grossest things I've ever seen.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I guess if I was one of those frogs, I would think that was the most beautiful event I'd ever seen. Although like human childbirth is not that beautiful either.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Well, we come into the world so violently. It's just like, it's amazing.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
You know what? This actually makes me think of one that's not up there, which I do find really incredibly amazing, is the process of the germline cell in humans. you know, in organisms, like basically like every living thing on this planet at some point in its life has to go through a single cell. And this whole issue of like development, like the developmental program is kind of crazy.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Like how do you build you out of a single cell? How does a single cell know how to do that? Like, you know, pattern formation of a multicellular organism obviously like evolves with DNA, but there's a lot of stuff happening there about when cells take on certain morphologies and things that people don't understand, like the actual shape formation mechanism.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And a lot of people study that and it's, and there's a lot of advances being made now in that field. I think it's pretty shocking though that like how little we know about that process. And often it's left off of people's lists. It's just kind of interesting. Embryogenesis is fascinating.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah. And the genes in all the cells are the same, right? So like the differentiation has to be something that's like much more about like the actual like, you know, expression of genes over time and like how they get switched on and off and also the physical environment of like the cell interacting with other cells. And there, there's just a lot of stuff going on.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Probably, yes. I think most of the things about understanding anything about what we are are embedded in time.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I know. So predictable. It's turning into a deterministic universe.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, always was, but it won't be in the future.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah. I think the, uh, first thing is, you know, that like the observation that, uh, Life seems to be the only thing in the universe that builds complexity in the way that we see it here. And complexity is obviously like a loaded term. So I'll just use assembly instead because I think assembly is more precise.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But the idea that like, you know, all the things on your desk here from your computer to the pen to, you know, us sitting here don't exist anywhere else in the universe as far as we know. They only exist on this planet. And it took a long evolutionary history to get to us.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
is a real feature that we should take seriously as one that's deeply embedded in the laws of physics and the structure of the universe that we live in. Standard physics would say that all of that complexity traces back to the infinitesimal deviations and like the initial state of the universe that there was some order there.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I find that deeply unsatisfactory and what assembly theory says that's very different is that The universe is basically constructing itself. And when you get to these common editorial spaces like chemistry, where the space of possibilities is too large to exhaust them all, you can only construct things along historically contingent paths.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Like you basically have causal chains of events that happen. to allow other things to come into existence. And that this is the way that complex objects get formed is basically on scaffolding on the past history of objects, making more complex objects, making more complex objects.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
That idea in itself is easy to state and simple, but it has some really radical implications as far as what you think objects is the nature of the physics that would describe life. And so what assembly theory does formally is try to measure the boundary in the space of all things that, you know, chemically could exist, for example, like all possible molecules.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Where is the boundary above which we should say these things are too complex to happen outside of an evolutionary chain of events, outside of selection? And we formalized that with two observables. One of them is the copy number of the object. So how many of the object did you observe? And the second one is what's the minimal number of recursive steps to make it?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So if you start from elementary building blocks like bonds for molecules and you put them together and then you take things you've made already and build up to the object, what's the shortest number of steps you had to take? And what Lee's been able to show in the lab with his team is that for organic chemistry, it's about 15 steps.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And then you only see molecules that, you know, the only molecules that we observe that are past that threshold are ones that are in life. And in fact, one of the things I'm trying to do with this idea of like trying to actually quantify the origin of life as a transition is in like a phase transition assembly theory is actually be able to explain why that boundary is where it is.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Because I think that's actually the boundary that life must cross. So the idea of going back to this thing we were talking about before about these structures that can reinforce their own existence and move past that boundary, 15 seems to be that boundary in chemical space. It's not a universal number. It will be different for different assembly spaces.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But that's what we've experimentally validated so far.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It's 15 or so for the experimental data, yeah.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
That's when you have to have that feature in order to observe molecules in high abundance in that space.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Recursive. Yeah. So you can think of objects in assembly theory as basically recursive stacks of the construction steps to build them. So they're like, it's like you take this step and then you make this object and you make it this object and make this object and then you get up to the final object. But that object is all of that history rolled up into the current structure.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
You can't take the long way.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
The long way doesn't exist.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
No, if you look at objects and you, so we define something we call the assembly universe and the assembly universe is ordered in time. It's actually ordered in the causation, the number of steps to produce an object. And so all objects in the universe are in some sense exist at a layer that's defined by their assembly index. And the size of each layer is growing exponentially.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So what you're talking about, if you want to look at the long way of getting to an object, as I'm increasing the assembly index of an object, I'm moving deeper and deeper into an exponentially growing space. And it's actually also the case that the sort of typical path to get to that object is also exponentially growing with respect to the assembly index.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so if you want to try to make a more and more complex object and you want to do it by a typical path, that's actually an exponentially receding horizon. And so most objects that come into existence have to be causally very similar to the things that exist because they're close by in that space and they can actually get to it by an almost shortest path for that object.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, imagine yourself- A copy number greater than one. Yeah, I mean, basically we live, the more complex we get, we live in a space that is growing more exponentially large. And the ways of getting to objects in the space are also growing exponentially large.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so we're this kind of recursively, like, stacked structure of, like, all of these objects that are clinging on to each other for existence. And then they, like, grab something else and are allowed, like, able to bring that thing into existence because it's kind of similar to them.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
There is a- There is a transition.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think it's actually abrupt. I've never been able to say that in my entire career before. I've always gone back and forth about whether the original life was kind of gradual or abrupt. I think it's very abrupt.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It snaps. Okay, but- We'll be poetic today. But no, I think there's like a lot of random exploration. And then there's like, and then the structure, the possibility space just collapses on the structure kind of really fast. that can reinforce its own existence because it's basically fighting against non-existence.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I don't know. We can make songs out of all of these.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So there was this website. I forgot what it was. But it's like a neural network that just generates a human face. And it's like this person does not exist. I think that's what it's called, right? So you can just click on that all day. And you can look at people all day that don't exist. All of those people exist in that space of things that don't exist.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, so the struggle of the quote, the struggle for existence is, you know, that goes all the way back to Darwin's writing about natural selection, right? So like the whole idea of survival of the fittest is everything struggling to exist, this predator-prey dynamic. And the fittest survive. And so the struggle for existence is really what selection is all about. And that's true.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
We do see things that do exist competing to continue to exist. But each time that, like, if you think about this space of possibilities and the You know, each time the universe, you know, generates a new structure or like an object that exists generates a new structure along this causal chain. It's generating something that exists that never existed before.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And each time that we make that kind of decision, we're excluding a huge piece of possibilities. And so actually like as this process of increasing assembly index, it's not just that like the space that these objects exist in is exponentially growing, but there are objects in that space that are exponentially receding away from us.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So they're becoming exponentially less and less likely to ever exist. And so existence excludes a huge number of things.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, it is in part an accident because I think some of the structure that gets generated is driven a bit by randomness. I think a lot of it, you know, so, you know, one of the conceptions that we have in assembly theory is, you know, the universe is random at its base. You can see this in chemistry, like unconstrained chemical reactions are pretty random.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And then, and also quantum mechanics, you know, there's lots of places that give evidence for that. And deterministic structures emerge by things that can causally reinforce themselves and maintain persistence over time. And so we are some of the most deterministic things in the universe.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so, like, we can generate very regular structure and we can generate new structure along a particular lineage. But the possibility space at the sort of tips, like the things we can generate next, is really huge. So there's some stochasticity in what we actually, you know, generate. instantiate as like the next structures that get built in the biosphere.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It's not completely deterministic because the space of future possibilities is always larger than the space of things that exist now.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So I said before, right now, I think the original life is a continuous process on Earth. I think this idea of combinatorial spaces that our biosphere generates, not just chemistry, but other spaces, often cross this threshold where they then allow themselves to persist with a particular regular structure over time. So language is another one where the space of
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
you know, possible configurations of the 26 letters of the English alphabet is astronomically large, but we use with very high regularity certain structures. And then we associate meaning to them because of the regularity of like how much we use them, right?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So meaning is an emergent property of the causation and the objects and like how often they recur and what the relationship of the recurrence is to other objects.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Well, this is why you can play with language so much, actually. So words don't really carry meaning. It's just about how you lace them together.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Obviously, as a speaker of a given language, you don't have a lot of room with a given word to wiggle, but you do have a certain amount of room to push the meanings of words. Yeah. And I do this all the time, and you have to do it with the kind of work that I do, because if you want to...
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
to discover an abstraction, like some kind of concept that we don't understand yet, it means we don't have the language. And so the words that we have are inadequate to describe the things. This is why we're having a hard time talking about assembly theory, because it's a newly emerging idea.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so I'm constantly playing with words in different ways to try to convey the meaning that is actually behind the words, but it's hard to do.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yes. Lots of wiggle.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Do you wiggle?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
No, I like playing with words a lot. You know, it's very funny because I know you talked about this with Lee, but people are so offended by the writing of the paper that came out last fall. And it was interesting because the ways that we use words were not the way that people were interacting with the words.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I think that was part of the mismatch where we were trying to use words in a new way because we were trying to describe something that hadn't been described adequately before, but we had to use the words that everyone else uses for things that are related.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so it was really interesting to watch that clash play out in real time for me, being someone that tries to be so precise with my word usage, knowing that it's always going to be vague.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I use it as an experimental platform for that reason.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Like, you know, the rant, like how things, you know, it's like usually based on interest, but I think it would be really nice if you got like 10% of your Twitter feed was random stuff sampled from other places. That'd be kind of fun. True.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yes. Oh, that would be fantastic.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah. Usually it takes a lot of clicking to find that out. Yeah. So it'd be better if it was sorted. Yeah.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
This goes into like the, you know, like, are you on the boundary of insane or not? But, you know, when you think about the structure of the physics of what we are that deeply, it really changes your conception of things. And, you know, going to this idea of the universe...
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
you know, being kind of small in physical space compared to how big it is in time and like how large we are, it really makes me question about whether there's any other structure that's like this giant crystal in time, this giant causal structure like our biosphere slash technosphere is anywhere else in the universe.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But I think the universe is expanding, right? It's expanding in space, but in assembly theory, it's also expanding in time. And actually, that's driving the expansion in space. And expansion in time is also driving the expansion in the sort of combinatorial space of things on our planet. So that's driving the sort of pace of technology and all the other things.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So time is driving all of these things, which is a little bit crazy to think that the universe is just getting bigger because time is getting bigger. But the sort of visual that gets built in my brain about that is the structure that we're building on this planet is packing more and more time in this very small volume of space, right?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Because our planet hasn't changed its physical size in 4 billion years, but there's a ton of of causation and recursion and time, whatever word you wanna use, information packed into this. And I think this is also embedded in sort of the virtualization of our technologies or the abstraction of language and all of these things. These things that seem really abstract are just really deep in time.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so what that looks like is you have a planet that becomes increasingly virtualized And so it's getting bigger and bigger in time, but not really expanding out in space. And the rest of space is like kind of moving away from it. Again, it's a sort of exponentially receding horizon.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I'm just not sure how far into this evolutionary process something gets, if it can ever see that there's another such structure out there.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Virtual as sort of a play on virtual reality. and like simulation theories. But virtual also in a sense of, you know, we talk about virtual particles in particle physics, which, you know, they are very critical to doing calculations about predicting the properties of real particles, but we don't observe them directly. So what I mean by virtual here is virtual reality for me
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
things that appear virtual, appear abstract, are just things that are very deep in time, in the structure of the things that we are. So if you think about you as a four billion year old object, the things that are part of you, like your capacity to use language or think abstractly or have mathematics are just very, you know, like deep temporal structures.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
That's why they look like they're informational and abstract. is because they're existing in this temporal part of you, but not necessarily spatial part.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
There's a couple ideas that are embedded here. So one of them comes again from Paul. He wrote this book years ago about the eerie silence and why we're alone. And he concluded the book with this idea of quintelligence or something, but this idea that really advanced intelligence would basically just
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
build itself into a quantum computer and it would want to operate in the vacuum of space because that's the best place to do quantum computation. And it would just like run out all of its computations indefinitely, but it would look completely dark to the rest of the universe. And I don't think as typical, like I don't think that's actually like the right physics because
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But I think something about that idea, as I do with all ideas, is partially correct. And Freeman Dyson also had this amazing paper about how long life could persist in a universe that was exponentially expanding. And his conception was like if you imagine analog life form, it could run slower and slower and slower and slower and slower as a function of time.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so it would be able to run indefinitely even against an exponentially expanding universe because it would just run exponentially slower. And so I guess part of what I'm doing in my brain is putting those two things together along with this idea that we are building, you know, like if you imagine with our technology, we're now building virtual realities, right?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Like things we actually call virtual reality, which required, you know, four billion years of history and a whole bunch of data to basically embed them in a computer architecture. So now you can put like you know, an Oculus headset on and think that you're in this world, right? And what you really are embedded in is in a very deep temporal structure.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so it's huge in time, but it's very small in space. And you can go lots of places in the virtual space, right? But you're still stuck in like your physical body and like sitting in the chair. And so, you know, part of it is it might be the case that sufficiently evolved technology
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Biospheres kind of virtualize themselves, and they internalize their universe in their sort of temporal causal structure, and they close themselves off from the rest of the universe.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
No, I don't either. So that's kind of my fear. So I'm not sure I'm agreeing with what I say. I'm just saying like this is one sort of conclusion. And, you know, like in my most sort of like – it's interesting because I don't do psychedelic drugs.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But when people describe to me like your thing with the faces and stuff and like I have, you know, had a lot of deep conversations with friends that have done psychedelic drugs for intellectual reasons and otherwise. But I'm always like, oh, it sounds like you're just doing theoretical physics. Like that's what brains do on theoretical physics. Yeah.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So I live in these like really abstract spaces most of the time. But there's also this issue of extinction, right? Like extinction events are basically pinching off an entire like causal structure, the one of these like, I'm going to call them time crystals. I don't like know what, but there's like these very large objects in time pinching off that whole structure from the rest of it.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so it's like, if you imagine that sort of same thing in the universe, I, you know, I once thought that sufficiently advanced technologies would look like black holes.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah. So there might be lots of aliens out there. Maybe that's an explanation for all the singularities. They're all pinched off causal structures that virtualize their reality and kind of broke off from us.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah. But the other way I think about it is there is probably hopefully life out there. So like I do work on life detection efforts in the solar system and I'm trying to help with the Habitable Worlds Observatory mission planning right now and working with like the biosignatures team for that, like to think about exoplanet biosignatures. So like I have some optimism that we might find things.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But there are the challenges that we don't know the likelihood for life, which is what you were talking about. So if I get to a more grounded discussion, what I'm really interested in doing is trying to solve the origin of life. So we can understand how likely life is out there.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So I don't think that the, I think that the problem of discovering alien life and solving the original life are deeply coupled and in fact are one in the same problem. And that the first contact with alien life will actually be in an original life experiment. But that part I'm super interested in. And then there's this other feature that I think about a lot, which is
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
our own technological phase of development as sort of like, what is this phase in the evolution of life on a planet? If you think about a biosphere emerging on a planet and evolving over billions of years and evolving into a technosphere, when a technosphere can move off planets, And basically reproduce itself on another planet. Now you have biospheres reproducing themselves.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Basically, they have to go through technology to do that. And so there are ways of thinking about sort of the nature of intelligent life and how it spreads in that capacity that I'm also really excited about and thinking about. Yeah. And all of those things for me are connected.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
We have to solve the origin of life in order for us to get off planet because we basically have to start life on another planet. And we also have to solve the origin of life in order to recognize other alien intelligence. All of these things are literally the same problem.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I totally agree with this, like that visual I really love and I think we live in a universe that like generates life and purpose. And like it's part of the structure of just the world. And so maybe like this sort of lonely view I have is, I never thought about it this way till you were describing that. I was like, I want to live in that universe. And I'm like a very optimistic person.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I love building visions of reality that are positive. But I think for me right now in the intellectual process, I have to tunnel through this This particular way of thinking about the loneliness of being like separated in time from everything else, which I think like we also all are because time is what defines us as individuals.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Part of what I mean is you have to go through ideas you don't necessarily agree with to work out what you're trying to understand. And I'm trying to be inside this structure so I can really understand it. And I don't think I've been able to... I'm so deeply embedded in what we are intellectually right now that I don't have an ability to see these other...
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
ones that you're describing, if they're there.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But yeah, I worry about it. Yeah.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I mean, just think about us with microbial life, right? Like we used to once be cells. And for most of human history, we didn't even recognize cellular life was there until we built a new technology, microscopes, that allowed us to see them. Right, so it's kind of weird, right?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
They're close, they're everywhere.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, super close, super close. Like, yeah, I mean, everything on this planet is like, it's like pretty much the same thing. Like the space of possibilities is so huge. It's like, we're virtually identical.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, this is kind of cool. I'll answer the question in a second, but it's just maybe like this idea of flickering lights and intelligence is interesting to me because I, you know, like we have such a human centric view of alien intelligences that a lot of the work that I've been doing with my lab is just trying to take inspiration from non-human life on earth.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so I have this really talented undergrad student that's basically building a model of alien communication based on fireflies. So one of my colleagues, Orit Peleg, she's totally brilliant, but she goes out with GoPro cameras and films in high resolution, all these firefly flickering. And she has this theory about how their signaling evolved to maximally differentiate the flickering pattern.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So she has a theory basically that predicts this species should flash If this one's flashing like this, this other one's going to do it at a slower rate so that, you know, like they can distinguish each other living in the same environment.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so this undergrad's building this model where you have like a pulsar background of all these like giant flashing sources in the universe and an alien intelligence, you know, wants to signal it's there. So it's flashing like a firefly. And I just like I like the idea of thinking about non-human aliens. So that was really fun.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
That's what... Yeah, well, I think there's some ways we might be able to differentiate that signal. I'm still thinking about this part of it. So one is like if you have pulsars and they all have a certain spectrum to their pulsing patterns... And you have this one signal that's in there that's basically tried to maximally differentiate itself from all the other sources in the universe.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It might stick out in the distribution. Like there might be ways of actually being able to tell if it's an anomalous pulsar, basically. But I don't know if that would really work or not. So still thinking about it.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think the question there is about whether life can be described in terms of matter and physical things, or whether there is some Other feature that's not physical that actually animates living things. So for a long time, people maybe have called that a soul. It's been really hard to pin down what that is. So I think the vitalist idea is really that it's kind of a dualistic interpretation.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Like, you know, like, they have ears and things. Like, it's such, like, a weird, grotesque aesthetic. But, like, it's totally bizarre. But what I meant – like, I have a visceral experience when I walk into my closet. I have, like, a lot of –
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It's like I do assembly theory every morning when I walk in my closet because I really like a very large, combinatorial, diverse palette, but I never know what I'm going to build in the morning.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I have trouble getting rid of some stuff. It depends on what it is. If it's vintage, it's hard to get rid of because it's kind of hard to replace. It depends on the piece. Yeah. Yeah.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It's a physical manifestation of my personality.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think it's an interesting feature of our species that we allow, we get to express ourselves through what we wear, right? Like if you think about all those animals in the jungle you saw, like they're born looking the way they look and then they're stuck with it for life.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah. And it's highly dynamic. I mean, you can be dynamic if you want to. Very few people are, there's a certain bravery, but it's actually more about confidence. willing to play with style and play with aesthetics. And I think it's interesting when you start experimenting with it, how it changes the fluidity of the social spaces and the way that you interact with them.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Do you feel like that every morning? No.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
You're like, this is a life commitment.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah. Well, see, this is the thing though, right? It simplifies your thought process in the morning. So like I have other ways I do that. I park in the same exact parking spot when I go to work on the fourth floor of a parking garage because no one ever parks on the fourth floor. So I can, I don't have to remember where I park my car. But I really like aesthetics and playing with them.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So I'm willing to spend part of my cognitive energy every morning trying to figure out what I want to be that day.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And even this one could have been really different because like, you know, it's not just the sort of jacket and the shoes and like, and the hairstyle. It's like the jewelry and the accessories. So like any outfit is a lot of small decisions.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah. Yellow's my daughter's favorite color. And I never really thought about yellow much, but she's been obsessed with yellow. She's seven now. And I don't know. I just really love it.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I'm playing with yellow a lot lately. Like this is not even the most yellow because I have black pants on, but I have worn outfits that have probably five shades of yellow in them.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, it's interesting. It's not – I mean, I am attracted to style and aesthetics because I think they're beautiful, but it's much more because I think it's fun to play with. And so I will get to the beauty thing, but I guess I want to just explain a little bit about my motivation in this space because it's really an intellectual thing for me.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And, you know, Stuart Brand has this great infographic about the layers of like human society. And I think it starts with like the natural sciences and like physics at the bottom and it goes through all these layers and it's like economics and then like fashion is at the top is like the fastest moving thing. part of human culture.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I think I really like that because it's so dynamic and so short and it's temporal longevity, uh, contrasted with like studying the laws of physics, which are like, you know, like the deep structure reality that I feel like I like bridging those scales tells me much more about the structure of the world that I live in.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
That there's sort of the material properties, but there's something else that animates life that is there when you're alive and it's not there when you're dead. And materialists kind of don't think that there's anything really special about the matter of life and the material substrates that life is made out of. So they disagree on some really fundamental points.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Are you embodying this?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
You wouldn't know how to be you. I know this is amazing though, isn't it? Amazing. You have the choice to do it. But one of my favorite, just on the question of beauty, one of my favorite fashion designers of all time is Alexander McQueen. And he was really phenomenal.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But like his early – and actually, I kind of used like what happened to him in the fashion industry as a coping mechanism with our paper when – like the Nature paper in the fall when everyone was saying it was controversial and how terrible that like – But controversial is good, right? But when Alexander McQueen first came out with his fashion lines, he was mixing horror and beauty.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And people were horrified. It was so controversial. It was macabre. It looked like there were blood on the models. That's beautiful.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah. No, I mean, his stuff is amazing. His first runway line, I think, was called Nealism. Okay. I don't know if you could find it. You know, I mean, he was really dramatic. He carried a lot of trauma with him. There you go. That's, yeah. Yeah. But he changed the fashion industry. His stuff became very popular.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Right, right. But this gets at the question, like, is that horrific or is it beautiful? And I think, you know, he ended up committing suicide. And actually, he left his death note on the descent of man. So he was a really deep person.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, it sure does. So I think it's the intellectual pursuit, right? Like it's not, so this is like very highly intellectual. And I think it's a lot like how I play with language is the same way that I play with fashion or the same way that I play with ideas in theoretical physics. Like there's always this space that you can just push things just enough.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So they're like, they look like something someone thinks is familiar, but they're not familiar. And yeah, and I think that's really cool.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
What do you mean it doesn't have function?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Oh, evolutionarily, maybe, but then beauty becomes a signal of other things, right? So it's really not like, and then beauty becomes an adaptive trait. So it can change with different, like, you know, maybe some people, some species would think, well, you thought the frog having babies come out of its back was beautiful. And I thought it was grotesque.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Like there's not a universal definition of what's beautiful. It is something that is dependent on your history and how you interact with the world. And I guess what I like about beauty, like any other concept, is when you turn it on its head. So maybe the traditional conception of why women wear makeup and they dress certain ways is because they want to look beautiful and pleasing to people.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I just like to do it because It's a confidence thing. It's about embodying the person that I want to be and about owning that person. And then the way that people interact with that person is very different than if I didn't have that, like if I wasn't using that attribute as part of, and obviously that's influenced by the society I live and like what's aesthetically pleasing things.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But it's interesting to be able to turn that around and not have it necessarily be about the aesthetics, but about the power dynamics that the aesthetics create.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Well, the point is you're saying it's an adaptive trait for like sexual selection or something. And I'm saying that the adaptation that beauty confers is far richer than that. And some of the adaptation... is about social hierarchy and social mobility and just plain social dynamics. Like, why do some people dress goth? It's because they identify with a community and a culture associated with that.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And they get, you know, and that's a beautiful aesthetic. It's a different aesthetic. Some people don't like it.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yes, exactly. It's the same kind of- Yes, and I think too few people think about the way that they, the aesthetics they build for themselves in the morning and how they carry it in the world and the way that other people interact with that because they put clothes on and they don't think about clothes as carrying function.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think one thing that I feel like I notice much more viscerally than I feel like I hear other people describe is that the representations in our mind and the way that we use language are not the things like... Actually, I mean, this is an important point going back to what Gertl did, but also this idea of signs and symbols and all kinds of ways of separating them. There's like the word, right?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And then there's like what the word means about the world. And we often confuse those things. And what I feel very viscerally, I almost sometimes think I have some kind of like synesthesia for language or something. And I just like don't interact with it like the way that other people do. But for me, words are objects and the objects are not the things that they describe.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
They have like a different ontology to them. Like they're physical things and they carry causation and they can create meaning, but they're not. They're not what we think they are. And also like the internal representations in our mind, like the things I'm seeing about this room are probably, you know, like they're small projection of the things that are actually in this room.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I think we have such a difficult time moving past the way that we build representations in the mind and the way that we structure our language to realize that those are approximations to what's out there and they're fluid and we can play around with them and we can see deeper structure underneath them that I think like we're missing a lot.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, I think the entire universe is just a giant mystery. I guess that's what motivates me as a scientist. And so oftentimes when I look at open problems like the nature of life or consciousness or what is intelligence or are there souls or whatever question that we have that we feel like we aren't even on the tip of answering yet, I think we have a lot more work to do to really understand that.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, for sure. I love this essay by Poincaré about like mathematical creativity, where he talks about this sort of like frothing of all these things. And then like somehow you build theorems on top of it and they become kind of concrete. But like, and I also think about this with language.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It's like, there's a lot of stuff happening in your mind, but you have to compress it in this few sets of words to try to convey it to someone. So it's, It's a compactification of the space. And it's not a very efficient one. And I think just recognizing that there's a lot that's happening behind language is really important.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think this is one of the great things about the existential trauma of large language models, I think, is the recognition that language is not the only thing required. Like there's something underneath it. Not by everybody.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, I was just gonna say it's like a playground.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I love doing that in everything I do, but especially with language.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, it's literally my favorite thing to do.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah. So I, you know, a lot of my sort of like what happens in my mind when I'm thinking about ideas is I've been presented with this information about how people think about things. And I try to go around to different communities and hear the ways that different, whether it's like, you know, hanging out with a bunch of artists or philosophers or scientists thinking about
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
things, like they all think about it different ways. And then I just try to figure out like, how do you take the structure of the way that we're talking about it and turn it slightly? So you have all the same pieces that everybody sees are there, but the description that you've come up with seems totally different.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So they can understand that there's like, they understand the pattern you're describing, but they never heard the structure underlying it described the way that you describe it.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah. I mean, the first couple sentences of that paper disturbed people a lot. And I think they were really carefully constructed in exactly this kind of way.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Oh, it was really fun. But I think it's interesting because... I do, you know, sometimes I'm very upfront about it. I say I'm going to use the same word in probably six different ways in a lecture. And I will.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, for sure. I mean, this is part of the sort of brilliant thing about our collaboration is, you know, complementary skill sets. So I love playing with the abstract space of language. And it's a really interesting playground when I'm working with Lee because... he thinks at a much deeper level of abstraction than can be expressed by language.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And the ideas we work on are hard to talk about for that reason.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
the answers to these questions. So it's not magic, it's just the unknown. And I think a lot of the history of humans coming to understand the world around us has been taking ideas that we once thought were magic or supernatural and really understanding them in a much deeper way that we learn what those things are. And they still have an air of mystery even when we understand them.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think it's a very poor language. A lot of people think it's a really great one, but I think it has some nice properties. But I think the feature of it that is compelling is this kind of idea of universality, that if you have a language, you can describe things in any other language.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I don't think that they're outside our human languages. I think they define the boundary of the space of human languages. They allow us to explore things within that space, which is also fantastic. But I think there is a set of ideas that takes, and Stephen Wolfram has worked on this quite a lot and contributed very significantly to it.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I really like some of the stuff that Stephen's doing with his physics project, but don't agree with a lot of the foundations of it. But I think the space is really fun that he's exploring. you know, there's this assumption that computation is at the base of reality. And I kind of see it at the top of reality, not at the base, because I think computation was built by our biosphere.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It's something that happened after many billion years of evolution. And it doesn't happen in every physical object. It only happens in some of them. And I think one of the reasons that we feel like the universe is computational is because it's so easy for us as things that have the theory of computation in our minds.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And actually, in some sense, it might be related to the functioning of our minds and how we build languages to describe the world and sets of relations to describe the world. But it's easy for us to go out into the world and build computers. And then we mistake our ability to do that with assuming that the world is computational. And I'll give you a really simple example.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
This one came from John Conway. I one time had a conversation with him, which was really delightful. He was really fun. But he was pointing out that if you string lights in a barn, you can program them to have your favorite one-dimensional CA, and you might even be able to make them be capable of universal computation. Is universal computation a feature of the string lights?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
No, it's probably not. It's a feature of the fact that you as a programmer had a theory that you could embed in the physical architecture of the string lights. Now, what happens, though, is we get confused by this kind of distinction between us as agents in the world that actually can transfer things that life does onto other physical substrates with what the world is.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so, for example, you'll see people, you know, doing studying the mathematics of chemical reaction networks and saying, well, chemistry is Turing universal or studying the laws of physics and saying the laws of physics are Turing universal. But any time that you want to do that, you always have to prepare an initial state.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
You have to, you know, you have to constrain the rule space and then you have to actually be able to demonstrate the properties of computation. And all of that requires an agent or a designer to be able to do that.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
There's no sort of bottom to our understanding.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think that's the intuition that people have derived from it. The intuition I get from cellular automata is that the flat space of an initial condition in a fixed dynamical law is not rich enough to describe an open-ended generation process. And so the way I see cellular automata is they're embedded slices in a much larger causal structure.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And if you wanna look at a deterministic slice of that causal structure, you might be able to extract a set of consistent rules that you might call a cellular automata, but you could embed them as much larger space. That's not dynamical and is about the causal structure and relations between all of those computations. And that would be the space cellular automata live in.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I think that's the space that Stephen is talking about when he talks about his rule he added in these hypergraphs of all these possible computations. But I wouldn't take that as my base reality because I think, again, computation itself, this abstract property computation, is not at the base of reality.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
One Rulliad to rule them all.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Well, it's interesting. So Stephen came to a workshop we had in the Beyond Center in the fall, and the workshop theme was mathematics. Is it evolved or eternal? And he gave a talk about the Rulliad, and he was talking about how a lot of the things that we talk about in the Beyond Center, like does reality have a bottom? If it has a bottom, what is it?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
We'll have you to one sometime.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah. So we had one that was called Infinite Turtles or Ground Truth. And it was really just about this issue. But the thing that was interesting, I think Stephen was trying to make the argument that fundamental particles aren't fundamental. Gravitation is not fundamental. These are just and computation is fundamental.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think that no tradition, vitalists included, is ever fully wrong about the nature of the things that they're describing. So a lot of times when I look at different ways that people have described things across human history, across different cultures, there's always a seed of truth in them.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I remember pointing out to him, I was like, well, computation is your turtle. And I think it's a weird turtle to have.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It's totally fine to have a turtle. Everyone has a turtle. You can't build a theory without a turtle. So it depends on the problem you want to describe. And actually, the reason I can't get behind... Steven's ontology is I don't know what question he's trying to answer. And without a question to answer, I don't understand why you're building a theory of reality.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Well, I started working on the origin of life. And I think what my challenge was there was no one knew what life was. And so you can't really talk about the origination of something if you don't know what it is. And so the way I would approach it is if you want to understand what life is, then proving that physics is solving the origin of life.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So there's the theory of what life is, but there's the actual demonstration that that theory is an accurate description of the phenomena you aim to describe. So again, they're the same problem. It's not like I can decouple origin of life from what life is. It's like that is the problem.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
um and i the the point i guess i'm making about having a question is no matter what slice of reality you take what regularity of nature you're going to try to describe there will be there there will be an abstraction that unifies that structure of reality um hopefully um and and that will have a fundamental layer to it right because you have to explain something in terms of something else.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But so if I want to explain life, for example, then my fundamental description of nature has to be something I think that has to do with time being fundamental. But if I wanted to describe, I don't know, the sort of interactions of matter and light, you know, I have elementary particles be fundamental.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
If I want to describe electricity and magnetism in the 1800s, I have to have waves be fundamental, right? So like you are in quantum mechanics, like it's a wave function that's fundamental because that's the sort of explanatory paradigm of your theory, right? So I guess I don't know what problem saying computation is fundamental solves.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I think it's really important to try to look for those because if there are narratives that humans have been telling ourselves for thousands of years, for thousands of generations, there must be some truth to them. We've been learning about reality for a really long time, and we recognize the patterns that reality presents us. We don't always understand what those patterns are.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Well, I think that the issue is general relativity and quantum mechanics are expressed in mathematical languages. Mm-hmm. And then computation is a mathematical language. So you're basically saying that maybe there's a more universal mathematical language for describing theories of physics that we already know. That's an important question.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I do think that's what Stephen's trying to do and do well. But then the question becomes, does that formulation of a more universal language for describing the laws of physics that we know now tell us anything new about the nature of reality? Or is it a language? Yeah.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
The language itself is never the fundamental thing. It's whatever it's describing.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think if assembly theory is an accurate depiction of the physics of life, it should shed a lot of light on those problems. And in fact, I sometimes wonder if the problems of consciousness and intelligence are at all different than the problem of life generally.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I'm of two minds of it, but I in general try to, you know, like the process of my thinking is trying to regularize everything into one theory. So pretty much every interaction I have is like, oh, how do I fold that into? And like, so I'm just building this giant abstraction that's basically trying to take every piece of data I've ever gotten in my brain into a theory of what life is.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And consciousness and intelligence are obviously some of the most interesting things that life has manifest. And so I think they're very telling about some of the deeper features about the nature of life.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Like this use of flavors, the same as you meant when you were talking about flavors of alien life.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah. But we were talking about in terms of colors and like very nondescript. But the way that you just talked about flavors now is more in like the space of consciousness and intelligence. It was kind of like much more specific.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Quantifying flavors.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so I think it's really important to pay attention to that. So I don't think the vitalists were actually wrong. And a lot of what I talk about in the book, but also I think about a lot just professionally, is the nature of our definitions of what's material and how science has come to invent the concept of matter.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Depending on what you want to explain, as I was saying before, you have to assume something's fundamental. And so because people can't explain consciousness, there's a temptation for some people to want to take consciousness as fundamental and assume everything else is derived out of that. And then you get some people that want to assume consciousness preceded life.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I don't find either of those views particularly illuminating. Because I don't want to assume a feminology before I explain a thing. And so what I've tried really hard to do is not assume that I think life is anything.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Except hold on to sort of the patterns and structures that seem to be the sort of consistent ways that we talk about this thing and then try to build a physics that describes that. And I think that's a really different approach than saying, you know, consciousness is this thing, you know, we all feel and experience about things.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I would want to understand the regularities associated with that and build a deeper structure underneath that and build into it. I wouldn't want to assume that thing and that I understand that thing, which is usually how I see people talk about it.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, so I think if you're thinking about this sort of thinking about living things as these giant causal structures or these objects that are deep in time or whatever language we end up using to describe it, it seems to me that consciousness is about The fact that we have a conscious experience is because we are these temporally extended objects.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So consciousness and the abstraction that we have in our minds is actually a manifestation of all the time that's rolled up in us. And it's just because we're so huge that we have this very large inner space. That we're experiencing. And it's also separated off from the rest of the world because we're this separate thread in time.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so our consciousness is not exactly shared with anything else because nothing else occupies the same part of time that we occupy. But I can understand something about you maybe being conscious because you and I didn't separate. that far in the past in terms of our causal histories.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And that some of those things actually really are inventions that happened in a particular time in a particular technology that could learn about certain patterns. and help us understand them. And that there are some patterns we still don't understand.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So in some sense, we can even share experiences with each other through language because of that sort of overlap in our structure.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It's not merely temporal separateness. It's about the depth in that time. So it's the reason that my conscious experience is not the same as yours is because we're separated in time. The fact that I have a conscious experience is because I'm an object that's super deep in time. So I'm huge in time.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And that means that there's a lot there that I am basically in some sense, a universe onto myself because my structure is so large relative to the amount of space that I occupy.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think there's a horizon, and I don't know how to articulate this yet. It's a little bit like the horizon at the origin of life, where the space inside a particular structure becomes so large that it has some access to a space that's not... That doesn't feel as physical. It's almost like this idea of counterfactuals.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So I think like the past history of your horizon is just much larger than can be encompassed in like a small configuration of matter. So you can like pull this stuff into existence. This property is maybe a continuous property, but there's something really different about human level physical systems and human level ability. to understand reality.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I really love David Deutsch's conception of universal explainers, and that's related to the theory of universal computation. And I think there's some transition that happens there. But maybe to describe that a little bit better, what I can also say is what intelligence is in this framework. So you have these objects that are large in time,
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
they were selected to exist by constraining the possible space of objects to this particular, like all of the matter is funneled into this particular configuration of object over time. And so these objects arise through selection, but the more selection that you have embedded in you, the more possible selection you have on your future. And so the
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And if we knew how to measure those things, or we knew how to describe them in a more rigorous way, we would realize that the material world matter has more properties than we thought that it did. And one of those might be associated with the thing that we call life. Life could be a material property and still have a lot of the features that the vitalists thought were mysterious.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
selection and evolution we usually think about in the past sense, where selection happened in the past. But objects that are high density configurations of matter that have a lot of selection in them are also selecting agents in the universe. So they actually embody the physics of selection and they can select on possible futures.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I guess what I'm saying with respect to consciousness and the experience we have is that there's something very deep about that structure and the nature of how we exist in that structure that has to do with how we're navigating that space and how we generate that space and how we continue to persist in that space.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I mean, I think they already do, but not in the way I hear popularly discussed. So there are obviously signatures of intelligence and... and a part of a ecosystem of intelligent systems. But I don't know that individually, you know, I would assign all the properties to them that people have.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It's a little like, so, you know, we talked about the history of eyes before and like how eyes scaled up into technological forms. And language has also had a really interesting history and got much more interesting, I think, once we started writing it down. And then, you know, inventing books and things.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But like, you know, every time that we started storing language in a new way, you know, we were kind of existentially traumatized by it.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So like, you know, the idea of written language was traumatic because it seemed like the dead were speaking to us even though they were deceased and books were traumatic because, you know, like suddenly there were lots of copies of this information available to everyone and it was going to somehow dilute it. And large language models are kind of interesting because they don't feel as static.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
They're very dynamic. But if you think about language in the way I was describing before as language is this very large in time structure. And before it had been something that was distributed over human brains as a dynamic structure. And occasionally we store components of that structure. very large dynamic structure in books or in written language.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Now we can actually store the dynamics of that structure in a physical artifact, which is a large language model. And so I think about it almost like the evolution of genomes in some sense where, you know, there might've been like really primitive genes in the first living things and they didn't store a lot of information or they were like really messy things.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And then by the time you get to the Eukarya Excel, you have this really dynamic genetic architecture that's rewritable and has all of these different properties. And I think large language models are kind of like the genetic system for language in some sense, where it's allowing a sort of archiving that's highly dynamic.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And I think it's very paradoxical to us because obviously in human history, we haven't been used to conversing with anything that's not human. But now we can converse basically with a crystallization of human language in a computer.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
That's a highly dynamic crystal because it's a crystallization in time of this massive abstract structure that's evolved over human history and is now put into a small device.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think there's not, I mean it very purposefully because a particular instantiation of a language model trained on a particular data set becomes a crystal of the language at that time it was trained. But obviously we're iterating with the technology and evolving it.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Right. It's a societal level technology, right? We've actually put collective intelligence in a box.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I actually, I don't like the sort of language we use around that. And I think the language really matters. So I don't know how to talk about how much smarter one human is than another, right? Like usually we talk about abilities or particular talents someone has.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And, you know, going back to, you know, David Joyce's idea of universal explainers, like, you know, adopting the view that, you know, we're the first, you know, kinds of structures our biosphere has built that can understand the rest of reality. We have this universal comprehension capability. You know, he makes an argument that, you
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Basically, we're the first things that actually are capable of understanding anything. It doesn't matter. It doesn't mean an individual understands everything, but like we have that capability. And so there's not a difference between that and what people talk about with AGI.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
In some sense, AGI is a universal explainer, but it might be that a computer is much more efficient at doing, I don't know, prime factorization or something than a human is, but it doesn't mean that it's necessarily smarter or has a broader reach of the kind of things that can understand than a human does. And so I think we really have to think about, is it a level shift
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah. So I think about, I always like to use examples from physics, so I'll probably do that. It's just my go-to place. But in the history of gravitational physics, for example, in the history of motion, when Aristotle came up with his theories of motion, he did it by the material properties he thought things had.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Or is it we're enhancing certain kinds of capabilities humans have in the same way that we can enhance eyesight by making telescopes and microscopes? Are we enhancing capabilities we have into technologies and the entire global ecosystem is getting more intelligent? Or is it really that we're building some super machine in a box that's going to be smart and kill everybody?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
That sounds like a science, it's not even a science fiction narrative, it's a bad science fiction narrative. I just don't think it's actually accurate to any of the technologies we're building or the way that we should be describing them. It's not even how we should be describing ourselves.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Well, these are human questions, right? I don't think they're necessarily questions that we're going to outsource to an artificial intelligence. I think what is happening and will continue to happen is there's a co-evolution between humans and technology that's happening. And we're coexisting in this ecosystem right now, and we're maintaining a lot of the balance. And for
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
The balance to shift to the technology would require some very bad human actors, which is a real risk, or some sort of... I don't know, some sort of dynamic that favors... Like, I just don't know how that plays out without human agency actually trying to put it in that direction.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So, like, I think the things that are, you know, terrifying are, you know, the ideas of deep fakes or, you know, like... You know, all the kinds of issues that become legal issues about artificial intelligence technologies and using them to control weapons or using them for, you know, like child pornography or. Or like faking out that someone's loved one was kidnapped or killed.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
There's all kinds of things that are super scary in this landscape and all kinds of new legislation needs to be built and all kinds of guardrails on the technology to make sure that people don't abuse it need to be built. And that needs to happen. And I think one function of sort of the artificial intelligence doomsday space
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
sort of part of our culture right now is it's sort of our immune response to knowing that's coming. And we're overscaring ourselves. So we try to act more quickly, which is good. But I just, you know, it's about the words that we use versus the actual things happening behind the words.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think one thing that's good is when people are talking about things different ways, it makes us think about them. And also when things are existentially threatening and We want to pay attention to those.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So there was a concept of things falling to Earth because they were solid-like and things raising to the heavens because they were air-like and things moving around the planet because they were celestial-like.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But the ways that they're existentially threatening and the ways that we're experiencing existential trauma, I don't think that we're really going to understand for another century or two, if ever. And I certainly think they're not the way that we're describing them now.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, it's just what we do to ourselves. Yeah.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Yeah, for sure.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Well, I think people are going to have romantic relationships with them. And I also think that some people will be convinced already that they're conscious. But I think in order... What does it take to convince... convince people that something is conscious, I think that we actually have to have an idea of what we're talking about.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
We have to have a theory that explains when things are conscious or not that's testable, right? And we don't have one right now. So I think until we have that, it's always going to be this sort of gray area where some people think it hasn't, some people think it doesn't, because we don't actually know what we're talking about that we think it has.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It is a tricky one. I mean, that's why it's called the hard problem of consciousness, because it's hard. And, you know, it might even be outside of the purview of science, which means that we can't understand it in a scientific way.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
There might be other ways of coming to understand it, but those may not be the ones that we necessarily want for technological utility or for developing laws with respect to, because the laws are, you know, the things that are going to govern the technology.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But then we came to realize that thousands of years later and after the invention of many technologies that allowed us to actually measure time in a mechanistic way and track planetary motion, and we could roll balls down inclined planes and track that progress, we realized that if we just talked about mass and acceleration, we could unify all motion in the universe.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Oh, that's interesting. I think it depends on the culture though, because I mean, some cultures already think like everything's imbued with, you know, a life essence or kind of conscious.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
No, they don't. They're probably not building the most advanced technologies.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so what do you think the risks are there, that the conscious things will get angry with us and fight back?
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Oh, okay. Yeah, I think we do that quite a lot. Anyway, without I mean, I don't I mean, it goes back to your and I don't know how to feel about this. But, you know, like we talked already about the predator prey thing that like in some sense, you know, being alive requires eating other things that are alive.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And even if you're a vegetarian or, you know, like try to have like you're like you're still eating living things like.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But I don't like thinking about them as like our technologies as a separate species. Because this again goes back to this sort of levels of selection issue. And if you think about humans individually alive, you miss the fact that societies are also alive. And so I think about it much more in the sense of
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
An ecosystem is not the right word, but we don't have the right words for these things of like – and this is why I talk about the technosphere. It's a system that is both human and technological. It's not human or technological. And so –
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
This is the part that I think we're really good for the like, and this is driving in part a lot of the sort of attitude of like, I'll kill you first with my nuclear weapons. We're really good at identifying things as other. We're not really good at understanding when we're the same or when we're part of an integrated system that's actually functioning together in some kind of cohesive way. Right.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Um, but, uh, but that's how societies solve problems. What it looks like for an individual is really different than the societal level outcomes. And the fact that like, there is, uh, I don't want to call it cognition or computation. I don't know what you call it, but like, there is a process playing out in the dynamics of societies that we are all individual actors in.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And like, we're not part of that, you know, like it requires all of us acting individually, but like this higher level structure, uh, is playing out some things and like things are getting solved for it to be able to maintain itself. And that's the level that our technologies live at. They don't live at our level.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
They live at the societal level and they're deeply integrated with the social organism, if you want to call it that. And so I really get upset when people talk about the species of artificial intelligence. I'm like, you mean we live in an ecosystem of all these kinds of intelligent things and these animating technologies that we're in some sense, helping to come alive.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
in a really simple description. So we didn't really have to worry about the fact that my cup is heavy and the air is light. The same laws describe them if we have the right material properties to talk about what those laws are actually interacting with. And so I think the issue with life is we don't know how to think about information in a material way.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
We are generating them, but it's not like the biosphere eliminated all of its past history when it invented a new species. All of these things get scaffolded. And we're also augmenting ourselves at the same time that we're building technologies. I don't think we can anticipate what that system's going to look like.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
The planet is one living thing.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Is it still just the- Still the same causal chain.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It's like when the first cell split into two. That's what I was talking about. When a planet reproduces itself, the technosphere emerges enough understanding. It's like this recursive, like the entire history of life is just recursion, right? So you have an original life event. It evolves for 4 billion years, at least on our planet. It evolves the technosphere.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
The technologies themselves start to become- having this property we call life, which is the phase we're undergoing now. It solves the origin of itself, and then it figures out how that process all works, understands how to make more life, and then can copy itself onto another planet so the whole structure can reproduce itself.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so the original life is happening again right now on this planet in the technosphere with the way that our planet is undergoing another transition, just like at the original life when geochemistry transitioned to biology, which is the global. For me, it was a planetary scale transition. It was a multi-scale thing that happened from the scale of chemistry all the way to planetary cycles.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It's happening now all the way from individual humans to the internet, which is a global technology and all the other things. Like there's this multi-scale process that's happening and transitioning us globally. And it is really like, it's a dramatic transition. It's happening really fast. And we're living in it.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I hope so. I think so.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I don't really like the Kardashev scale. And it goes back to like, I don't like a lot of the narratives about life because they're very like, you know, survival of the fittest, energy consuming, this, that, and the other thing. It's very like, I don't know, sort of old world, you know, like conqueror mentality.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I mean, I think it does require life to use new energy sources in order to expand the way it is. So that part's accurate. But I think this sort of process of life being the mechanism that the universe creatively expresses itself, generates novelty, explores the space of the possible, is really the thing that's most deeply intrinsic to life.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so, you know, these sort of energy-consuming scales of technology I think is missing the sort of actual feature that's most prominent about any alien life that we might find, which is that it's literally… our universe, our reality, trying to creatively express itself and trying to find out what can exist and trying to make it exist.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And so we haven't been able to build a unified description of what life is or the kind of things that Evolution builds because we haven't really invented the right material concept yet.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But this is why I'm okay with having a finite lifetime. And, you know, one of the reasons I'm okay with that, actually, goes back to this issue of the fact that we're resource-bound. We live in a... You know, like, we have a finite amount of material, whatever way you want to define material. I think, like, for me, you know, material is time. Material is information.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
But we have a finite amount of material. If time is a generating mechanism, it's always going to be finite because... The universe is, you know, like it's a resource that's getting generated, but it has a size, which means that all the things that could exist don't exist. And in fact, most of them never will.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
So death is a way to make room in the universe for other things to exist that wouldn't be able to exist otherwise. So if the universe over its entire temporal history wants to maximize the number of things, wants is a hard word, maximize is a hard word, all these things are approximate, but It wants to maximize the number of things that can exist.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
The best way to do it is to make recursively embedded stacked objects like us that have a lot of structure and a small volume of space and to have those things turn over rapidly so you can create as many of them as possible.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
Hopefully. Hopefully our universe is teeming with life.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I think we're in our 20s. 20% of the 20s? No, like age-wise, let's say. We're in our 20s, but the lifespan is going to keep getting longer.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
You know why I use that, though? I'll tell you why. Why my brain went there is because anybody that gets an education in physics has this sort of trope about how all the great physicists did their best work in their 20s. And then you don't do any good work after that. And I always thought it was kind of funny because for me, physics is not complete.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
It's not nearly complete, but most physicists think that we understand most of the structure of reality. And so I think I actually, I think I put this in the book somewhere, but like this idea to me that societies would discover everything while they're young is very consistent with the way we talk about physics right now. But I don't think that's actually the way that things are going to go.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
And you're finding that people that are making major discoveries are getting older in some sense than they were. And our lifespan is also increasing. So I think there is something about age and your ability to learn and how much of the world you can see that that's really important over a human lifespan, but also over the lifespan of societies. And so I don't know how big the frontier is.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
I don't actually think it has a limit. I don't believe in infinity as a physical thing, but I think as a receding horizon, I think because the universe is getting bigger, you can never know all of it.
Lex Fridman Podcast
#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens
That number had to come from somewhere.