Lex Fridman Podcast
#455 – Adam Frank: Alien Civilizations and the Search for Extraterrestrial Life
Sun, 22 Dec 2024
Adam Frank is an astrophysicist studying star systems and the search for extraterrestrial life and alien civilizations. Thank you for listening ❤ Check out our sponsors: https://lexfridman.com/sponsors/ep455-sc See below for timestamps, transcript, and to give feedback, submit questions, contact Lex, etc. Transcript: https://lexfridman.com/adam-frank-transcript CONTACT LEX: Feedback - give feedback to Lex: https://lexfridman.com/survey AMA - submit questions, videos or call-in: https://lexfridman.com/ama Hiring - join our team: https://lexfridman.com/hiring Other - other ways to get in touch: https://lexfridman.com/contact EPISODE LINKS: Adam's Website: https://adamfrankscience.com Adam's X: https://x.com/adamfrank4 Adam's Instagram: https://instagram.com/adamfrankscience Adam's Books: The Little Book of Aliens: https://amzn.to/3OTX1rP Light of the Stars: https://amzn.to/4iMKC6C The Blind Spot: https://amzn.to/4gOCe4K The Constant Fire: https://amzn.to/3ZVnxX4 SPONSORS: To support this podcast, check out our sponsors & get discounts: Encord: AI tooling for annotation & data management. Go to https://encord.com/lex Eight Sleep: Temp-controlled smart mattress cover. Go to https://eightsleep.com/lex Shopify: Sell stuff online. Go to https://shopify.com/lex NetSuite: Business management software. Go to http://netsuite.com/lex BetterHelp: Online therapy and counseling. Go to https://betterhelp.com/lex Notion: Note-taking and team collaboration. Go to https://notion.com/lex LMNT: Zero-sugar electrolyte drink mix. Go to https://drinkLMNT.com/lex AG1: All-in-one daily nutrition drinks. Go to https://drinkag1.com/lex OUTLINE: (00:00) - Introduction (14:22) - Planet formation (19:32) - Plate tectonics (26:54) - Extinction events (31:04) - Biosphere (34:02) - Technosphere (38:17) - Emergence of intelligence (44:29) - Drake equation (48:43) - Exoplanets (51:28) - Habitable zones (54:30) - Fermi Paradox (1:03:28) - Alien civilizations (1:12:55) - Colonizing Mars (1:25:11) - Search for aliens (1:41:37) - Alien megastructures (1:47:43) - Kardashev scale (1:52:56) - Detecting aliens (1:59:38) - Warp drives (2:05:45) - Cryogenics (2:09:03) - What aliens look like (2:17:48) - Alien contact (2:28:53) - UFO sightings (2:40:38) - Physics of life (3:06:29) - Nature of time (3:22:53) - Cognition (3:27:16) - Mortality
The following is a conversation with Adam Frank, an astrophysicist interested in the evolution of star systems and the search for alien civilizations in our universe. And now a quick few second mention of each sponsor. Check them out in the description. It's the best way to support this podcast.
Let me say as a side note that I had to put a bunch of podcast episodes on hold to focus deeply on preparing for conversations with world leaders. So I apologize to include more sponsors on this episode than usual. They really wanted me to mention them this year, and I'm not sure when I'm going to do another episode.
We were going to do eight episodes this month, but instead I think we're doing two. We'll see. Every single day, every single hour changes the plan, changes the situation, changes my life. So please be patient with me. There are no sponsor reads in the middle, so you can skip this long and beautiful list. But I do try to make them interesting in case you do listen, and I hope you do.
In either case, please still check out the sponsors. Buy their stuff. It is the best way to support this podcast. The sponsors are Uncord for your ML stack, Eight Sleep for naps, Shopify for e-commerce, NetSuite for business, BetterHelp for the mind, Notion for notes, Element for electrolytes, and AG1 for nutrition.
If you want to get in touch with me for whatever reason, go to lexfreeman.com contact. Perhaps you could tell from my voice, on top of everything else, I'm also sick. What a wonderful, beautiful, challenging life this is, and I'm grateful for every second of it. All right, and now on to the full arteries. Let's go.
This episode is brought to you by Encord, a platform that provides data-focused AI tooling for data annotation, curation, and management, and for model evaluation. For example, if you are an independent private or government agency that is running
the drones that is flying all over New Jersey and the tri-state area, you might be doing the same kind of data annotation and collection, curation and management that Encore excels at. Also, if you're an extraterrestrial species performing the same, I wonder what kind of computation tools alien civilizations have.
At the physics level, computation is fundamentally a part of the fabric of the universe. So every advanced civilization would or surely would discover how to leverage that computation, how to organize that computation, how to access and communicate with that computation.
Anyway, think of it, if you have a swarm of drones and you are the ruler of an alien civilization and want to collect some data about New Jersey, you are going to have to do some great machine learning. And great machine learning is not just about the algorithms. It is so much more about the data.
So whoever you are running the drone program over New Jersey, go try out Encore to curate, annotate, and manage your AI data at Encore.com. That's Encore.com. By the way, in all seriousness, I will probably talk about drones in New Jersey soon. I think it's a fascinating mystery. Is it China? Is it aliens? Is it the U.S. government? Is it private companies within the U.S. government?
Is it other nation states? Are nuclear weapons involved? And what are the mechanisms that ensure that the U.S. government is transparent about communicating what they discover? These are essential questions. Okay, on to A-Sleep. This episode is brought to you by A-Sleep and it's pod 4 ultra. You know, sleep makes me think about the night. And I've been watching a lot of war movies.
I've been watching a lot of war reporting. I've been watching a lot of conversations with soldiers and I've been talking to soldiers. And there's something about the night. There's something about the quiet night that serves as the break from the hell of war. That's a song from the Second World War. A song about a soldier writing to a woman he loves. That's just it.
Just like a man's search for meaning in the darkest hours of war. Those are the things that keep the flame of the heart going. Talking about these topics makes it difficult for me to then talk about eight sleep and the technology and the comfort of good night's sleep Somewhere in America.
That's one of the things you discover when you travel, especially travel to a country that's participating in war. That the basic comforts, the basic securities, the basic dreams and hopes and the ways of life are taken away. And still, the human spirit persists. Anyway, this is supposed to be an ad read. Go to asleep.com slash Lex.
Use code Lex to get up to $600 off your Pod 4 Ultra purchase when bundled. That's asleep.com slash Lex. This episode is also brought to you by Shopify, a platform designed for anyone to sell anywhere with a great looking online store. I've been reading a lot about the long history of the Silk Road, especially before and after the Mongol Empire and Genghis Khan.
I've been reading a lot about Genghis Khan and the influence he had on revolutionizing the trade network. A lot of networks, the trade of not just goods, but information of knowledge, of languages, of ideas, of religions, of peoples. And it's fascinating how roads of that nature, trade, first and foremost, can break down the barriers that divide peoples. I suppose it all starts with incentives.
People are people and they have stuff they don't need and they want to sell it and other people have stuff they want and they're willing to buy it. And those incentives at scale overpower any kind of emotional, psychological, historical hatreds and all those kinds of things. It's funny, the little incentives and the mechanisms of capitalism, at its best, can heal the wounds of war.
Of course, it can also fuel the military-industrial complex, which is the fuel of war. Oh, the double-edged sword. Anyway, take the Silk Road and fast forward to today and we have Shopify that you can sign up to for $1 per month trial period at Shopify.com slash Lex. That's all lowercase. Go to Shopify.com slash Lex to take your business to the next level today.
This episode is also brought to you by NetSuite, an all-in-one cloud business management system. When I think about NetSuite and all the different administrative modules and the language, standardized language, that allows them to communicate with each other, I think about all the empires throughout history that were able to create remarkable administrative systems.
The Byzantine Empire, the Roman Empire, the Mongol Empire, as I mentioned. None of it works without paperwork. You know, bureaucracy, rightfully so, gets a bad rap. But at its best, bureaucracy is necessary to manage the affairs of large organizations. You know, humans aren't very good at working with each other when they scale beyond a thousand people. So you need great administrative systems.
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I am a person who loves conversation. And not small talk. The fake niceties that alleviate social frictions. I'm not for that. I'm in for diving deep through conversation. And I think that is something that I just can't quite do yet. And I would say not even close. It is an assistant. It is not a therapist. So...
The distinction, the difference is quite fascinating to analyze, to watch, to try to sort of elucidate and articulate clearly. Yeah, so I'm a big fan of talking to a human to explore your own mind. And BetterHelp is a very easy, accessible way of doing that. Check them out at betterhelp.com slash Lex and save in your first month. That's betterhelp.com slash Lex.
This episode is brought to you by Notion, a note-taking system service app that I use and you should use, especially if you're on a large team, to collaborate on all kinds of stuff, including notes and project management, wikis, all that kind of stuff. Nuclear weapons have been on my mind quite a bit. And I think about the Manhattan Project.
And I think about the amount of incredible, rapid organization that was involved in that project. Just think about the coordination. The coordination of brilliant people working on separate parts of an incredibly complicated project where all of it has to be secret. So many of the people working on it may not even be aware of the bigger picture of it or the different modules involved.
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My daily zero sugar and delicious electrolyte mix. Did you know that salt... in ancient Rome was a currency also referred to as white gold. How crazy is that things like salt or cinnamon or frankly gold and silver are things that all of us humans imbue with value for a time and even do horrific things to each other in order to attain more of it. The human greed for salt.
So dark and so fascinating we humans are. Anyway, on a basic level, just thirst. Something I've experienced in the Amazon jungle. Thirst for water. And for that, you need electrolytes too, not just water. Water and salt, plus magnesium and potassium. That is the basic thing you want the most when it is gone. And I got the chance, the gift, to experience it.
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You wrote a book about aliens. So the big question, how many alien civilizations are out there?
Yeah, that's the question, right? The amazing thing is that after two and a half millennia of people yelling at each other or setting each other on fire occasionally over the answer, we now actually have the capacity to answer that question. So in the next 10, 20, 30 years, we're going to have data relevant to the answer to that question.
We're going to have hard data finally that will, one way or the other, you know, even if we don't find anything immediately, we will have gone through a number of planets. We'll be able to start putting limits on how common we are. life is. The one answer I can tell you, which was an important part of the problem, is how many planets are there, right?
And just like people have been arguing about the existence of life elsewhere for 2,500 years, people have been arguing about planets for the exact same amount of time, right? You can see Aristotle yelling at Democritus about this. You can see they had very wildly different opinions about how common planets were going to be and how unique Earth was. And that question got answered, right?
Which is pretty remarkable that in a lifetime you can have a 2,500-year-old question. The answer is they're everywhere. There are planets everywhere. And it was possible that planets were really rare. We didn't really understand how planets formed. And so if you go back to, say, the turn of the 20th century –
There was a theory that said planets formed when two stars passed by each other closely and then material was gravitationally squeezed out. In which case, those kinds of collisions are so rare that you would expect one in a trillion stars to have planets. Instead, every star in the night sky has planets.
So one of the things you've done is simulated the formation of stars. How difficult do you think it is to simulate the formation of planets, like simulate your solar system through the entire evolution of the solar system? This is kind of a numerical simulation sneaking up to the question of how many planets are there.
That actually we're able to do now. There is, you can run simulations of the formation of planetary system. So if you run the simulation, really where you wanna start is a cloud of gas, these giant interstellar clouds of gas that may have a million times the mass of the sun in them. And so you run a simulation of that. It's turbulent. The gas is roiling and tumbling.
And every now and then you get a place where the gas is dense enough that gravity gets hold of it and it can pull it downward. So you'll start to form a protostar. And a protostar is basically the young star of this ball of gas where nuclear reactions are getting started. But it's also a disk. So as material falls inward, because everything's rotating,
As it falls inward, it'll spin up and then it'll form a disc. Material will collect in what's called an accretion disc or a protoplanetary disc. And you can simulate all of that. Once you get into the disk itself and you wanna do planets, things get a little bit more complicated, because the physics gets more complicated.
Now you gotta start worrying about dust, because actually dust, which is just, dust is the wrong word, it's smoke, really. These are the tiniest bits of solids. They will coagulate in the disk to form pebbles, right? And then the pebbles will collide to form rocks, and then the rocks will form boulders, et cetera, et cetera. That process is super complicated.
But we've been able to simulate enough of it to begin to get a handle on how planets form, how you accrete enough material to get the first proto-planets or planetary embryos, as we call them. And then the next step is those things start slamming into each other. to form, you know, planetary-sized bodies. And then the planetary bodies slam into each other.
Earth, the moon came about because there was a Mars-sized body that slammed into the earth and basically blew off all the material that then eventually formed the moon.
And all of them have different chemical compositions, different temperatures? Yeah.
Yeah, so the temperature of the material in the disk depends on how far away you are from the star. So it decreases, right? And so there's a really interesting point. So like, you know, close to the star, temperatures are really high. And the only thing that can condense, that can kind of freeze out, is going to be stuff like metals.
So that's why you find mercury is this giant ball of iron, basically. Yeah. And then as you go further out stuff, you know, the gas gets cooler and now you can start getting things like water to freeze, right? So there's something we call the snow line, which is somewhere in our solar system out around between Mars and Jupiter.
And that's the reason why the giant planets in our solar system, Jupiter, Saturn, Uranus, and Neptune all have huge amounts of ice in them or water and ice. Actually, Jupiter and Saturn don't have so much, but the moons do. The
there's oceans right that we've got a number of those moons have got more water on them than there's water on earth do you think it's possible to do that kind of simulation to have a stronger and stronger estimate of uh how likely an earth-like planet is can we get the physics simulation done well enough to where we can start estimating like what are the possible earth-like things that could be generated
Yeah, I think we can. I think we're learning how to do that now. So, you know, one part is like trying to just figure out how to how planets form themselves and doing the simulations like that, that cascade from dust grains up to planetary embryos. That's hard to simulate because it's both you got to do both the gas and you got to do the dust and the dust colliding and all that physics.
Um, once you get up to a planet sized body, then, you know, you kind of have to switch over to almost like a different kind of simulation. They're often what you're doing is you're doing, you know, sort of, you're assuming the planet is this sort of spherical ball. And then you're doing what, you know, like a one D a radial calculation. And you're just asking like, all right.
How is this thing going to, what is the structure of it going to be? Like, am I going to have a solid iron core or am I going to get a solid iron core with that liquid iron core out around it like we have on Earth? And then you get, you know, a silicate, kind of a rocky mantle and then a crust.
All of those details, those are kind of beyond being able to do full 3D simulations from ab initio, from scratch. We're not there yet. How important are those details, like the crust and the atmosphere, do you think? Hugely important. So I'm part of a collaboration at the University of Rochester where we're using the giant laser. Literally, this is called the Laboratory for Laser Energetics.
We got a huge grant from the NSF to use that laser to, like, slam tiny pieces of silica to understand what the conditions are like at, you know, the center of the earth, or even more importantly, the center of super earths. Like the most common, this is what's wild. The most common kind of planet in the universe we don't have in our solar system. Which is amazing, right?
So we've been able to study enough or observe enough planets now to get a census. You know, we pretty, you know, we kind of have an idea of what, who's average, who's weird. And our solar system's weird because the average planet has a mass between somewhere between a few times the mass of the Earth. to maybe, you know, 10 times the mass of the earth.
And that's exactly where there are no planets in our solar system. So, um, the smaller ones of those we call super earths, the larger ones we call sub Neptunes. And they're anybody's guess. Like we don't really know what happens to material when you're squeezed to those pressures, which is like millions, tens of millions of times the pressure on the surface of the earth.
So those details really will matter of what's going on in there because that will determine whether or not you have, say, for example, plate tectonics. We think plate tectonics may have been really important for life on earth, for the evolution of complex life on earth.
So it turns out, and this is sort of the next generation where we're going with the understanding the evolution of planets in life. It turns out that you actually have to think hard about the planetary context for life. You can't just be like, oh, there's a warm pond, you know, and then some interesting, you know, chemistry happens in the warm pond.
You actually have to think about the planet as a whole and what it's gone through in order to really understand whether a planet is a good place for life or not.
Why do you think polytectonics might be useful for the formation of complex life?
There's a bunch of different things. One is that, you know, the Earth went through a couple of phases of being a snowball planet. Like, you know, we went into a period of glaciation where pretty much the entire planet was under ice. The oceans were frozen. You know, early on in Earth history, there was barely any land.
We were actually a water world, you know, with just a couple of Australia-sized planets. cratons, they called them, protocontinents. So those, we went through these snowball earth phases. And if it wasn't for the fact that we had kind of an active plate tectonics, which had a lot of volcanism on it, we could have been locked in that forever.
Like once you get into a snowball state, a planet can be trapped there forever, which is, you know, maybe you already had life form, but then because it's so cold, you may never get anything more than just microbes, right?
So what plate tectonics does, because it fosters more volcanism, is that you're going to get carbon dioxide pumped into the atmosphere, which warms the planet up and gets you out of the snowball Earth phase. But even more, there's even more really important things.
I just finished a paper where we were looking at something called the hard steps model, which is this model that's been out there for a long time that purports to say intelligent life in the universe will be really rare. And it made all these assumptions about the Earth's history, particularly the history of life and the history of the planet, or have nothing to do with each other.
And it turns out, as I was doing the reading for this, that Earth probably early on had a more mild form of plate tectonics. And then somewhere about a billion years ago, it ramped up. And that ramping up changed everything on the planet. Because here's a funny thing. The Earth used to be flat. You know what I mean by that, right? So all the flat earthers out there can get excited for one sec.
Clip it. Yeah.
what i mean by that is that there really weren't many mountain ranges right the beginning of i think the term is orogenesis mountain building the true himalayan style giant mountains didn't happen until this more robust form of plate tectonics where the plates are really being driven around the planet and that is when you get the crusts hitting each other and they start pushing you know into these himalayan style mountains the weathering of that
The erosion of that puts huge amounts of nutrients, things that microbes want to use, into the oceans and then what we call the net primary productivity, the bottom of the food chain, how much sugars they are producing, how much photosynthesis they're doing. shot up by a factor of almost a thousand, right?
So the fact that you had plate tectonics supercharged evolution in some sense, you know, like we're not exactly sure how it happened, but it's clear that the amount of life, the amount of living activity that was happening really got a boost from the fact that suddenly there was this new vigorous form of plate tectonics.
So it's nice to have turmoil in terms of temperature, in terms of surface geometries, in terms of the chemistry of the planet, turmoil.
Yeah, that's actually really true because what happens is if you look at the history of life, that's a really, you know, it's an excellent point you're bringing up. If you look at the history of life on earth, we get, uh, you know, a biogenesis somewhere around at least 3.8 billion years ago. And that's the first microbes. They kind of take over enough that they really do.
You get a biosphere, you get a biosphere that is actively changing the planet. But then you go through this period they call the boring billion where like it's a billion years and it's just microbes. Nothing's happening. It's just microbes. I mean, microbes are doing amazing things. They're inventing fermentation. Thank you very much. We appreciate that.
But it's not until sort of you get probably these continents slamming into each other. You really get the beginning of continents forming and driving changes. that evolution has to respond to, that on a planetary scale, this turmoil, this chaos is creating new niches as well as closing other ones. And biology, evolution has to respond to that.
And somewhere around there is when you get the Cambrian explosion, is when suddenly every body plan, evolution goes on an orgy, essentially. So yeah, it does look like that chaos or that turmoil was actually very helpful to evolution.
I wonder if there's some... extremely elevated levels of chaos, almost like catastrophes behind every leap of evolution. You're not going to have leaps. In human societies, we have an Einstein that comes up with a good idea, but it feels like on an evolutionary time scale, you need
some real big drama going on for the evolutionary system to have to come up to a solution to that drama, like an extra complex solution to that drama.
Well, I think what's... I'm not sure if that's true. I don't know if it needs to be like an almost extinction event, right? Because it's certainly true that we have gone through... almost extinction events where we've had five mass extinctions. But you don't necessarily see that there was this giant evolutionary leap happening after those.
With the comet impact, the KT boundary, certainly lots of niches opened up And that's why we're here, right? Because, you know, our ancestors were just little basically rodents, rats living under the footsteps of the dinosaurs. And it was that common impact that opened the route for us. But it wasn't, I mean, that still took another, you know, 65 million years.
It wasn't like this thing immediately happened. But what we found with this hard steps paper, because the whole idea of the hard steps paper was It was one of these anthropic reasoning kinds of things where Brandon Carter said, oh, look, the intelligence doesn't show up on Earth until about, you know, almost close to when the end of the sun's lifetime.
And so he's like, well, there should be no reason why the sun's lifetime and the time for evolution to produce intelligence should be the same. Uh, and so therefore, and he goes through all this reasoning, anthropic reasoning, and, and, and he ends up with the idea that like, oh, it must be that the odds of getting intelligence are super low. And so that's the hard steps, right?
So there was a series of steps in evolution that were, you know, very, very hard. And because of that, you can calculate some probability distributions, um, and everybody loves a good probability distribution and they went a long way with this, but it
When you look at it, of course, the timescale for the sun's evolution and the timescale for evolution on life are coupled because life and the timescale for evolution of the earth is coupled is about the same timescale as the evolution is the sun. It's billions of years. The earth evolves over billions of years and life and the earth co-evolve.
That's what Brandon Carter didn't see is that actually evolution. The fate of the Earth and the fate of life are inextricably combined. And this is really important for astrobiology, too. Life doesn't happen on a planet. It happens to a planet. So this is something that David Grinspoon and Sarah Walker both say. And, you know, I agree with this. It's a really nice way of putting it.
So, you know, plate tectonics, the evolution of oxygen, of an oxygen atmosphere, which only happened because of life. These things, you know, these are things that are happening where life and the planet are sort of sloshing back and forth.
And so rather than to your point about do you need giant catastrophes, maybe not giant catastrophes, but what happens is as the Earth and life are evolving together, windows are opening up, evolutionary windows. Like, for example, life put oxygen into the atmosphere. When life invented this new form of photosynthesis about two and a half billion years ago,
that broke water apart to work, to do its chemical shenanigans. It broke water apart and pushed oxygen into the atmosphere. That's why there's oxygen in the atmosphere. It's only because of life. That opened up huge possibilities, new spaces for evolution to happen. But it also changed the chemistry of the planet forever.
So the introduction of oxygen photosynthesis changed the planet forever, and it opened up a bunch of windows for evolution that wouldn't have happened otherwise. Like, for example, you and I, we need that amount of oxygen. Big-brained creatures need an oxygen-rich atmosphere because oxygen is so potent for metabolism.
So you couldn't get intelligent creatures 100 million years after the planet formed.
So really, on a scale of a planet, when there's billions, trillions of organisms on a planet, they can actually have planetary scale impact. So the chemical shenanigans of an individual organism when scaled out to trillions can actually change a planet.
Yeah, and we know this for a fact now. So there was this thing, Gaia theory, that was James Lovelock introduced in the 70s. And then Lynn Margulis, the biologist, Lynn Margulis together. So this Gaia theory was the idea that Planets pretty much take, or sorry, life takes over a planet.
Life hijacks a planet in a way that the sum total of life creates these feedbacks between the planet and the life such that it keeps the planet habitable. It's kind of a homeostasis, right? I can go out like right now outside, it's 100 degrees, right? And I go outside, but my internal temperature is going to be the same.
And I can go back to, you know, Rochester, New York in the winter, and it's going to be, you know, zero degrees, but my internal temperature is going to be the same. That's homeostasis. The idea of Gaia theory was that life, the biosphere, exerts this pressure on the planet or these feedbacks on the planet that even as other things are changing...
the planet will always stay in the right kinds of conditions for life. And now when this theory came out, it was very controversial. People were like, oh my God, you know, what are you smoking weed? You know, and like, there were all these guy and festivals with guy and dances. And so, you know, it became very popular in the new age community.
But Lovelock, actually, they were able to show that, no, this has nothing to do with the planet being conscious or anything. It was about these feedbacks that the biology, the biosphere can exert these feedbacks. And now that's become, whether or not, we're still unclear whether there are true Gaian feedbacks in the sense that the planet can really exert complete control.
But it is absolutely true that the biosphere is a major player in Earth's history. So the biosphere fights for homeostasis on Earth. So, okay, what I would say right now is I don't know if I can say that scientifically. I can certainly say that the biosphere does a huge amount of the regulation of the planetary state and over billions of years has strongly modified the evolution of the planet.
So whether or not a true guy in feedback would be exactly what you said, right? The biosphere is this somehow, and Sarah Walker and David Grinspoon and I actually did a paper on this about the idea of planetary intelligence or cognition across a planetary scale. And I think that actually is possible. It's not conscious, but there is a kind of cognitive activity going on.
The biosphere, in some sense, knows what is happening because of these feedbacks. So it's still unclear whether we have these full Gaian feedbacks, but we certainly have semi-Gaian feedbacks. If there's a perturbation on the planetary scale, temperature, you know, insulation, how much sunlight's coming in, the biosphere will start to have feedbacks that will damp that perturbation.
Temperature goes up, the biosphere starts doing something, temperature comes down.
Now, I wonder if the technosphere also has a Gaian feedback or elements of a Gaian feedback such that the technosphere will also fight to some degree for homeostasis. Open question, I guess.
Well, I'm glad you asked that question because that paper that David and Sarah and I wrote, what we were arguing was is that over the history of a planet, right, when life first forms, you know, 3.8 billion years ago, it's kind of thin on the ground, right? You've got the first species, you know, these are all microbes.
And they have not yet, they're not going to, enough of them to exert any kind of these Gaian feedback. So we call that an immature biosphere. But then as time goes on, as life becomes more robust and it begins to exert these feedbacks, keeping the planet in the place where it needs to be for life, we call that a mature biosphere, right?
And the important thing, and we're going to, I'm sure later on we're going to talk about definitions of life and such. There's this great term called autopoiesis. That Francisco Varela, the neurobiologist Francisco Varela came up with. And he said, you know, one of the defining things about life is this property of autopoiesis, which means self-creating and self-maintaining.
Life does not create the conditions which will destroy itself, right? It's always trying to keep itself in a place where it can stay alive. So the biosphere, from this guy in perspective, has been autopoietic for billions of years. Now, we just invented this technosphere in the last couple of hundred years. And what we were arguing in that paper is that it's an immature technosphere, right?
Because right now, with climate change and all the other things we're doing, the technosphere right now is sort of destroying the conditions under which it needs to maintain itself. So the real job for us, if we're going to last over... you know, geologic timescales.
If we want a technosphere that's going to last tens of thousands, hundreds of thousands, millions of years, then we've got to become mature, which means to not undermine the conditions, to not subvert the conditions that you need to stay alive. So as of right now, I'd say we're not autopoietic.
Well, I wonder if we look across thousands, tens of thousands, hundreds of thousands of years, that perturbations, the technosphere should create perturbations as a way for developing greater and greater defenses against perturbations. Which sounds like a ridiculous statement, but basically go out and play in the yard and hurt yourself to strengthen the, or like drink water from the pond.
From the pond, yeah, right. Get sick a few times.
To strengthen the immune system. Yeah.
Well, you know, it's interesting with the technosphere, we can talk about this more, but like, you know, we're just emerging as a technosphere in terms of as a interplanetary technosphere, right?
That's really the next step for us is to, David Grinspoon talks about, I love this idea of anti-accretion, like this amazing thing that for the first time, you know, over the entire history of the planet, stuff is coming off the planet. It used to be everything just fell down, all the meteorites fell down, but now we're starting to push stuff out.
The idea of planetary defense or such, we are actually going to start exerting perturbations on the solar system as a whole. We're going to start engineering if we make it. I always like to say that if we can get through climate change, the prize at the end is the solar system. So we will be changed, literally engineering the solar system.
But what you can think of right now with what's happening with the Anthropocene, the great acceleration that is the technosphere, is the creation of it, that is a giant perturbation on the biosphere, right? And what you can't do is, the technosphere sits on top of the biosphere. And if the technosphere undermines the biosphere for its own conditions of habitability, then you're in trouble, right?
I mean, the biosphere is not going away. There's nothing we could do. The idea that we have to save the Earth is a little ridiculous. The Earth is not a furry little bunny that we need to protect. But it's the conditions for us, right? Humanity emerged out of the Holocene, the last 10,000 years interglacial period. We can't tolerate very different kinds of Earths.
So that's what I mean about a perturbation.
Before we forget, I got to ask you about this paper. Right. Pretty interesting. There's an interesting table here about hard steps. Abiogenesis, glucose fermentation to purific acid, all kinds of steps, all the way to homo sapiens, animal intelligence, land ecosystems, endoskeletons, eye precursor, so formation of the eye. Yeah. Complex multicellularity. That's definitely one of the big ones.
Yeah, so interesting. I mean, what can you say about this chart? There are all kinds of papers talking about what the difficulty of these steps are.
Right. And so this was the idea. So what Carter said was, you know, using anthropic reasoning, he said there must be a few very hard steps for evolution to get through to make it to intelligence, right? So there's some steps are going to be easy. So every generation, you know, you roll the dice and yeah, it won't take long for you to get that step, but there must be a few of them.
And he said you could even calculate what, how many there were, five, six, In order to get to intelligence. And so this paper here, this plot, is all these different people who've written all these papers. And this is the point, actually. You can see all these papers that were written on the hard steps. Each one proposing a different set of what those steps should be.
And there's this other idea from biology of the major transitions in evolution, MTEs, that those were the hard steps. But what we actually found was... that none of those are actually hard. The whole idea of hard steps, that there are hard steps, is actually suspect. So what's amazing about this model is it shows how important it is to actually work with people who are in the field, right?
So Brandon Carter was a brilliant physicist, the guy who came up with this. And then lots of physicists and astrophysicists like me have used this But the people who actually study evolution and the planet were never involved, right? And if you went and talked to an evolutionary biologist or a biogeophysicist, they'd look at you when you explained this to them and they'd be like, what?
Like, what are you guys doing? Turns out none of the details or none of the conceptual structure of this matches with evolution. what the people actually study the planet and its evolution.
Is it mostly about the fact that there's not really discrete big steps? It's a gradual, continual kind of process?
Well, there's two things. The first most important one was that the planet and the biosphere have evolved together. That's something that every, you know, most biogeophysicists completely accept. And it was the first thing that Carter kind of rejected. He said, like, no, that's probably not possible.
And yet, you know, like if he'd only sort of had more discussions with this other community would have seemed like, no, there are actually windows that open up. And then the next thing is this idea of whether a step is hard or not.
Because for a hard, what you mean by a hard step is that, like I said, every time there's a generation, every time there's the next generation born, you're rolling the dice on whether this mutation will happen. And the idea of something being a hard step, there's two ways in which something might even appear as a hard step and not be, or actually not be a hard step at all.
One is that you see something that has occurred in evolution that has only happened once, right? So let's take the opposite. You see something that's happened multiple times, like wings, lots of examples of wings over lots of different evolutionary lineages. So that's clearly not a hard, making wings is not a hard step.
There are certain other things that people say, no, that's a hard step, oxygen, you know, the oxygen photosynthesis. But they are so, they tend to be so long ago that we've lost all the information. There could be other things in the fossil record that, you know, went, made this innovation, but they're just gone now. So you can't tell. So there's information loss.
The other thing is the idea of pulling up the ladder that somebody, you know, some species makes the innovation, but then it fills the niche and nobody else can do it again. So yeah, it only happened once, but it happened once because basically the creature was so successful, it took over and there was no space for anybody else to evolve it.
So yeah, so the interesting thing about this was seeing how... How much, once you look at the details of life's history on Earth, how it really shifts you away from this hard steps model. And it shows you that those details, as we were talking about, like, do you have to know about the planet? Do you have to know about plate tectonics? Yeah, you're going to have to.
I mean, to be fair to Carter on the first point, it makes it much more complicated if life and the planet are co-evolving. Because it would be nice to consider the planet as a static thing that sets the initial conditions. And then we can sort of, from an outside perspective, analyze...
planets based on the initial conditions they create and then there's a binary yes or no will it create life but if they co-evolve it's just a really complex dynamical system where everything is becomes much more difficult from the perspective of SETI of looking out there and trying to figure out which ones are actually producing life.
But I think we're at the point now, so now there may be other kinds of principles that actually, because, you know, co-evolution actually has its own, not deterministic, you're done with determinism, right? But complex systems have patterns, complex systems have constraints, and that's actually what we're going to be looking for, are constraints on them.
And so, you know, and again, nothing against Carter was a brilliant idea, but it just goes to show, you know, there's this great XTC. I'm a theoretical physicist, right? And so I love simplified. Give me a simplified model with, you know, a dynamical equation, some initial conditions. I'm very happy.
But there's this great XTC comic where like, you know, somebody is working something out on the board and this physicist is looking over and saying, oh, oh, I just I just wrote down an equation for that. I solved your problem. Do you guys even have a journal for this? And the subtitle is why everybody hates physicists. Yeah. So sometimes that approach totally works.
Sometimes physicists can be very good at like zooming in on what is important and casting the details aside so you can get to the heart of an issue. And that's very useful sometimes. Other times it obfuscates, right? Other times it clouds over actually what you needed to focus on, especially when it comes to complexity. Yeah.
uh speaking of simplifying everything down to an equation uh let's return back to the question of how many alien civilizations are out there and uh talk about the drake equation yeah can you uh explain the drake equation you know people have various uh feelings about the drake equation uh you know it can be abused but basically it was the the story actually is really interesting so frank drake in uh 1960 does the first ever astrobiological experiment he
gets a radio telescope, points it at a couple of stars and listens for signals. That was the first time anybody done any experiment about any kind of life in the history of humanity. And he does it and he's kind of waiting for everybody to make fun of him. And still he gets a phone call from the government says, hey, we want you to do a meeting on interstellar communications, right?
So he's like, okay. So they organize a meeting with like just eight people. A young Carl Sagan is going to be there as well. And like the night before, Drake has to come up with an agenda. How do you come up with an agenda for a meeting on a topic that no one's ever talked about before, right? And so he actually breaks what he does.
What's so brilliant about the Drake equation is he breaks the problem of how many civilizations are out there into a bunch of sub-problems. And he breaks it into seven sub-problems. Each one of them is a factor in an equation that when you multiply them all together, you get the number of civilizations out there that we could communicate with. So the first term is the rate at which stars form.
The second term is the fraction of those stars that have planets, F sub p. The next term is the number of planets in the habitable zone, the place where we think life could form. The next term after that is the fraction of those planets where actually an abiogenesis event, life forms, occurs. The next one is the fraction of planets on which you start to get intelligence.
After that, it's the fraction of planets where that intelligence goes on to create a civilization. And then finally, the last term, which is the one that we really care about, is the lifetime. How long you have a civilization, now how long does it last? Well, you say we humans. We humans, right?
Because we're standing, we're staring at the, you know, multiple guns pointing at us, you know, nuclear war, climate change, AI. So, you know, how long in general does civilizations last? Now, each one of these terms, what was brilliant about what he did was what he was doing was he was quantifying our ignorance.
By breaking the problem up into these seven sub-problems, he gave astronomers something to do. And so this is always with a new research field. You need a research program or else you just have a bunch of vague questions. You don't even know really what you're trying to do. So the star people could figure out how many stars were forming per year.
The people who were interested in planets could go out and find techniques to discover planets, et cetera, et cetera.
I mean, these are their own fields. Essentially, by creating this equation, he's launching new fields.
He gave astrobiology, which wasn't even a term then, a roadmap. Like, okay, you guys go do this. You go do that. You go do that. And it had such far-reaching effect on astrobiology because it did break the problem up in a way that gave useful sort of marching orders for all these different groups. Like, for example, it's because of the Drake equation in some sense that
people who were involved in SETI pushed NASA to develop the technologies for planet hunting. There was this amazing meeting in 1978, two meetings, 1978 and 1979, that were driven in some part by the people who were involved in SETI, Getting NASA together to say, look, okay, look, how, you know, what's the roadmap for us to develop technologies to find planets?
So, yeah, so, you know, the Drake equation is absolutely foundational for astrobiology, but we should remember that it's not a law of nature, right? It's not something that's it's not equals MC squared. And so you can see it being abused in some sense. People, you know, it's generated a trillion papers. Some of those papers are good. I've written some of those and some of those papers are bad.
You know, I'm not sure where my paper fits in on those. I'm saying, you know, one should be careful about what you're using it for. But in terms of understanding the problem that that astrobiology faces, this really broke it up in a useful way.
We could talk about each one of these, but let's just look at exoplanets. Yeah. So that's a really interesting one. I think when you look back, you know, hundreds of years from now, what is it, in the 90s when they first detected the first?
Yeah, 92 and 95. 95 to me was really, that was the discovery of the first planet orbiting a sun-like star. To me, that was the water, the dam being broken.
I think that's one of the greatest discoveries in the history of science. I agree. I agree. Right now, I guess nobody's celebrating it too much because you don't know what it really means. But I think once we almost certainly will find life out there, it will obviously allow us to generalize across... the entire galaxy, the entire universe.
So if you can find life on a planet, even in the solar system, you can now start generalizing across the entire universe.
You can. All you need is one. Like right now, it's an any, you know, our understanding of life. We have one example. We have N equals one example of life. So that means we could be an accident, right? It could be that we're the only place in the entire universe where this weird thing called life has occurred. Get one more example and now you're done.
Because if you have one more example, you don't have to find all the other examples. You just know that it's happened more than once. And now you are, from a Bayesian perspective, you can start thinking like, yeah, this life is not something that's hard to make.
Well, let me get your sense of estimates for the Drake equation. You've also written a paper expanding on the Drake equation, but what do you think is the answer?
So the paper, there was this paper we wrote, Woody Sullivan and I, in 2016, where we said, look, we have all this exoplanet data now, right? So the thing that exoplanet science and the exoplanet census I was talking about before have nailed is, F sub P, the fraction of stars that have planets, it's one. Every fricking star that you see in the sky hosts a family of worlds.
I mean, it's mind boggling because every one of those, those are all places, right? They're either, you know, gas giants, probably with moons. So the moons are places you can stand and look out. Or they're like terrestrial worlds where even if there's not life, there's still snow falling and there's oceans washing up on shorelines.
It's incredible to think how many places and stories there are out there. So, right, the first term was F sub P, which is how many stars have planets. The next term is how many planets are in the habitable zone. Right? On average. And it turns out to be 1 over 5. Right? So, you know, we're on 0.2. So that means you just count five of them. Go out at night and go 1, 2, 3, 4, 5.
One of them has an Earth-like planet, you know, in the habitable zone. Like, whoa! So what defines a habitable zone? Habitable zone is an idea that was developed in 1958 by the Chinese-American astronomer Xu Sheng. And it was, it was a brilliant idea. It said, look, this is there, you know, I can do this simple calculation.
If I take a planet and just stick it at some distance from a star of what's the temperature of the planet, what's the temperature of the surface. So now you're all, you're going to ask, you give it a standard kind of, you know, earth-like atmosphere and ask, okay, Could there be liquid water on the surface, right? We believe that liquid water is really important for life.
There could be other things that's happening. Fine. But you know, if you were to start off trying to make life, you'd probably choose water as your solvent for it. So basically the habitable zone is the
band of orbits around a star where you can have liquid water on the surface you could take a you know glass of water pour it on the surface and it would just pool up it wouldn't freeze immediately which would happen if your planet is too far out and it wouldn't just boil away if your planet's too close in so that's the formal definition of the habitable zone so it's a nice strict definition there's probably way more going on than that but this is a place to start
Right.
Well, we should say it's a place to start. I do think it's too strict of a constraint. I would agree. We're talking about temperature where water can be on the surface.
There's so many other ways to get the aforementioned turmoil where the temperature varies, whether it's volcanic interaction of volcanoes and ice and all of this on the moons of plants that are much farther away, all this kind of stuff. Yeah.
Well, for example, we know in our own solar system, we have say Europa, the moon of Jupiter, which has got a hundred mile deep ocean under 10 miles of ice, right? That's not in the habitable zone. That is outside the habitable zone. And that may be the best place. It's got more water than Earth does. All of its oceans are, you know, it's twice as much water on Europa than there is on Earth.
So, you know, that may be a really great place for life to form. And it's outside the habitable zone. So, you know, the habitable zone is a good place to start and it helps us. And there's reason, there's reasons why you do want to focus on the habitable zone because like Europa, I couldn't, I won't be able to see from across telescopic distances across light years.
I wouldn't be able to see life on Europa because it's under 10 miles of ice. So with the important thing about planets in the habitable zone is that we're thinking they have atmospheres. Atmospheres are the things we can characterize for across 10, 50 light years. And we can see biosignatures as we're going to talk about.
So there is a reason why the habitable zone becomes important for the detection of extrasolar life.
But for me, when I look up at the stars, it's very likely that there's a habitable planet or moon in each of the stars, habitable defined broadly.
Yeah, I think that's not unreasonable to say. I mean, especially since the formal definition, you get one in five, right? One in five is a lot. There's a lot of stars in the sky. So yeah, saying that in general, when I look at a star, there's a pretty good chance that there's something habitable orbiting it is not a unreasonable scientific claim.
To me, it seems like there should be alien civilizations everywhere. Why the Fermi Paradox? Why haven't we seen them?
Okay. The Fermi Paradox. Let's talk about... I love talking about the Fermi Paradox because there is no Fermi Paradox. Dun, dun, dun, dun. Yeah. So the Fermi Paradox, let's talk a little about the Fermi Paradox and the history of it. So Enrico Fermi, it's 1950. He's walking with his friends at Los Alamos Nuclear Weapons Lab to the cantina. And there had been this...
cartoon in the new yorker they all read the new yorker uh and the cartoon was trying to explain why there had been this rash of uh uh garbage cans being disappearing in new york and this cartoon said oh it's ufos because this is already you know it's 1950 the first big ufo craze happened in 47 so they'd all they were laughing about this as they're walking and they started being physicists started talking about interstellar travel interstellar propulsion blah blah blah you know conversation goes on for a while conversation turns to something else you know
they've gone to other things about 40 minutes later over lunch, Fermi blurts out, well, where is everybody? Right. Typical Fermi sort of thing.
He'd done the calculation in his head and he suddenly realized that, look, if one, if they're, you know, if intelligence is common, that even traveling at sub light speeds, a, a civilization could cross, you know, kind of hop from one star system to the other and spread out across the entire galaxy in a few hundred thousand years. And he realized this. And so he was like, why aren't they here now?
And that was the beginning of the Fermi paradox. It actually got picked up as a formal thing in 1975 in a paper by Hart, where he actually kind of went through this calculation and showed and said, well, there's nobody here now. Therefore, there's nobody anywhere that, you know. Okay, so that is what we will call the direct Fermi paradox. Why aren't they here now?
But something happened where people, after SETI began, where people started to, there was this idea of the great silence. People got this idea in their head that like, oh, we've been looking for decades now for signals of extraterrestrial intelligence and we haven't found any. Therefore, there's nothing out there. So we'll call that the indirect Fermi paradox.
And there absolutely is no indirect Fermi paradox for the most mundane of reasons, which is money. There's never been any money to look. SETI was always done by researchers who were kind of like scabbing some time, you know, some extra time from their other projects to, you know, look a little bit better. You know, at the sky with a telescope. Telescopes are expensive.
So Jason Wright, one of my collaborators, he and his students did a study where they looked at the entire search space for SETI. You know, and imagine that's an ocean. All the different stars you have to look at, the radio frequencies you have to look at, how when you look, how often you look. And then they summed up all the SETI searches that had ever been done. They went through the literature.
And what they found was if that search space, if the sky is an ocean and you're looking for fish, how much of the ocean have we looked at? And it turns out to be a hot tub. That's how much of the ocean that we've looked up. We've dragged a hot tub's worth of ocean water up, and there was no fish in it. And so now are we going to say, oh, well, there's no fish in the ocean, right?
So there is absolutely, positively no indirect Fermi Paris. We just haven't looked. Um, but we're starting to look, so that's what's, you know, finally we're starting to look. That's what's exciting. The direct Fermi paradox. There are so many ways out of that, right? There's a book called 77 solutions to the Fermi paradox that it just, you know, you can pick your favorite one.
It just doesn't carry a lot of weight because there's so many ways around it. We did an actual simulation, my group, Jonathan Carroll, one of my collaborators, we actually simulated the galaxy and we simulated probes moving at sublight speed from one star to the other, gathering resources, heading to the next one.
And so we could actually track the expansion wave across the galaxy, have one IABiogenesis event, and then watch the whole galaxy get colonized or settled. And it is absolutely true that that wave crosses, you know, Hart was right, Fermi was right, that wave crosses very quickly. But civilizations don't last forever, right? So one question is, when did they visit?
When did they come to Earth, right? So if you give civilizations a finite lifetime, let them last 10,000, 100,000 years, what you find is you now have a steady state. Civilizations are dying, they're coming back, they're traveling between the stars. What you find then is you can have big holes opened up. You can have regions of space where there is nobody. For, you know, millions of years.
And so if that, if we're living in one of those bubbles right now, then maybe we were visited, but we were visited a hundred million years ago. And there was a paper that Gavin Schmidt and I did that showed that if there was a civilization, whether it was like dinosaurs or aliens that was here a hundred million years ago, there's no way to tell. There's just there's no record left over.
The fossil record is too sparse. The only way maybe you could tell is by looking at the isotopic strata to see if there was anything reminiscent of an industrial civilization. But the idea that, you know, you'd be able to find, you know, iPhones or toppled buildings after 100 million years is there's no way.
So if there was an alien camp here. Yeah. An alien village, a small civilization. Right. Maybe even a large civilization.
Even a large civilization, even if it was a large. A hundred million years ago. And it lasted 10,000 years, fossil record's not going to have it. Yeah, yeah. The fossil record is too sparse, right? Most things don't fossilize. And 10,000 years is a blink in the eye of geological time.
So Gavin called this the Silurian hypothesis after the Doctor Who episode with the lizard creatures, the Silurians. But that paper got a lot of press. But it was an important idea. And this was really Gavin's. I was just helping with the astrobiology. To recognize that, yeah, we could have been visited a long time ago. There just would be no record. Yeah. It's kind of mind blowing.
It's really mind blowing. And it's also a good reminder that we've been intelligent species have been here for a very short amount of time.
Very short amount of time. Yeah. This is not to say that there was like, so whenever I gave, you know, I like what I was on Joe Rogan for exactly this paper. And I had to always emphasize, we're not saying there was a Silurian, you know, but we're just saying that if there was. That's why I love Gavin's question. Gavin's question was just like, how could you tell, right?
It was a very beautifully scientific question. That's what we were really showing is that you really, you know, unless you did a very specific kind of search, which nobody's done so far, that, you know, there's not an obvious way to tell that there could have been civilizations here earlier on.
I've actually been reading a lot about ancient civilizations and it just makes me sad how much of the wisdom of that time is lost. Yeah. And how much guessing is going on, whether it's in South America, like what happened in the jungle?
Yeah, like the Amazon, like the Amazon problem. That was, you know, the conquisters came and wiped everybody out. And especially just even like the plague may have decimated. So yeah, how much of that civilization? And there's a lot of theories.
And, you know, because of archaeology only looks at cities, they don't really know the origins of humans. And there's a lot of really interesting theories. And they're, of course, controversial. And there's a lot of controversial people in history. in every discipline, but archaeology is a fascinating one because we know so little. They're basically storytellers.
You're assembling the picture from just very few puzzle pieces. It's fascinating. It makes me, it's humbling and it's sad that there could be entire civilizations ancient civilizations that are either almost entirely or entirely lost.
Yeah. Well, like the, the, the indigenous peoples of North America, there could have been like millions and millions. You know, we get this idea that like, oh, you know, this, the Europeans came and it was empty, you know, but it was, may have only been empty because the plague had swept up from the, you know, from the, what happened in Mesoamerica.
So, and yeah, and they didn't really build cities, but they had, they, I mean, they, they didn't build wooden or stone cities. They built wooden cities, you know,
Everybody seems to be building pyramids, and they're really damn good at it. What does that have to do with a pyramid?
Why does that apply?
What archetype in our brain is that? And it is also really interesting, speaking of archetypes, is that independent civilizations formed, and they had a lot of similar kind of dynamics, like human nature, when it builds up hierarchies in a certain way, builds up myths and religions in a certain way, it builds pyramids in a certain way, it goes to war, all this kind of stuff, independently emerges.
Fascinating. Santa Fe Institute, the stuff the Santa Fe Institute does on this as complex systems, the origin of hierarchies and such, very cool. Yeah, Santa Fe folks.
Complexity in general is really cool. Really cool. What phenomena emerge when a bunch of small things get together and interact. Going back to this paper, a new empirical constraint on the prevalence of technological species in the universe, this paper that expands on the Drake equation. What are some interesting things in this paper?
Well, so the main thing we were trying to do with this paper is say, look, we have all of this exoplanet data, right? It's got to be good for something, especially since two of the terms that have been nailed down empirically are two terms in the Drake equation. So F sub P, that's the second term, fraction of stars that have planets.
And then N sub E, the average number of planets in the habitable zone. Those are the second and third term in the Drake equation. So what that means is all the astronomical terms have been nailed. And so we said like, okay, how do we use this to do something with the Drake equation? And so we realized is, well, okay, we got to get rid of time, the lifetime thing. We can't say anything about that.
Um, but if we let that, if we don't ask how long do they last, but instead ask what's the probability that there've been any civilizations at all, no matter how long they lasted. I'm not asking whether they exist now or not. I'm just asking in general, um, about probabilities to make a technological civilization anywhere and at any time in the history of the universe.
And that we were able to constrain. And so what we found was basically that there have been 10 billion trillion habitable zone planets in the universe. And what that means is those are 10 billion trillion experiments that have been run.
Um, and the only way that we're the only time that this is, you know, this whole process from, you know, uh, a biogenesis to a civilization has occurred is if every one of those experiments failed. Right. So therefore you could put a, a probability you could, we called it the pessimism line. right?
We don't really know what nature sets for the probability of making intelligent civilizations, right? But we could set a limit using this. We could say, look, as if the probability per habitable zone planet is less than 10 to the minus 22, one in 10 billion trillion, then yeah, we're alone. If it's anywhere larger than that, then we're not the first. It's happened somewhere else.
And to me, that was mind-blowing. It doesn't tell me there's anybody nearby. The galaxy could be sterile. It just told me that like, you know, unless nature's really against, it has some bias against civilizations. We're not the first time this has happened. This has happened elsewhere over the course of cosmic history.
10 billion trillion experiments. Yeah. That's a lot of experiments. That's a lot, right? A thousand is a lot. Yeah. A hundred is a lot. Yeah. If, uh, we normal humans saw a hundred experiments and, uh, We knew that at least one time there was a successful human civilization built. I mean, we would say for sure in 100, you'll get another one.
Yeah, yeah. So that's why, I mean, that's why. So this, you know, these kinds of arguments, you have to be careful of what they can do. But what it really, I felt like what this paper showed was that, you know, the burden of proof is now on the pessimists, right? So that's why we called it the pessimism line.
Throughout history, there's been alien pessimists and alien optimists, and they've been yelling at each other. That's all they had to go with, right? And like with Giordano Bruno in 1600, they burned the guy at the stake for being an alien optimist. But nobody really knew what pessimism or optimism meant. We sort of thought this was like the plank length.
This was sort of the plank length of astrobiology. It gave you an actual number. That, you know, if you could somehow calculate what the probability, you know, of forming a technological civilization was, this thing sort of shows you where the limit is. As long as you're above 10 to the minus 22, then you actually, absolutely, it has occurred in the history.
Other civilizations have occurred in the history of the universe.
So to me, at least, the big question is F-E, which is basically abiogenesis. How hard is it for life to originate on a planet? Because all the other ones seem... Very likely. Everything seems very likely. The only open question to me is, like, how hard is it for life to originate?
There's lots of ways to, again, you know, we don't know unless we look. And, you know, you had Sarah walk around not too long ago. You know, she's very interested in origins of life. So, you know, lots of people are working on this. But I think it's hard looking at the history of the Earth. You know, and again, this is, you can do Bayesian arguments on this. Um, but yeah, it's forming life.
I don't think it's hard getting, getting like basic biology started. I don't think it's hard. It's still wild. It's an amazing process that actually I think requires some deep rethinking about how we conceptualize what life is and what life isn't. That's one of the things I like about Sarah's work.
Um, we're, we're pursuing on a different level, uh, about the life as that, the only process or the only system that uses information. Um, but still, regardless of all those kinds of details, uh, life is probably easy to make. That's, that's my, that's my gut feeling.
Yeah. I mean, day by day, this changes, right? for me, but as you see, once you create bacteria, it's off to the races. You're gonna get complex life. As long as you have enough time, I mean, that boring billion, but I just can't imagine a habitable planet not having a couple billion
despair yeah a couple million years to spare you know there is a mystery there about why did it take so long like with the cambrian explosion but that may be again about these windows that like you couldn't happen until until the window the planet and the the life had evolved together enough that they together kind of opened the window for the the next step um you know i i
intelligent life and how long intelligent is civil technological civilizations i think there's a big question about how long those last and how you know i'm hopeful you know um but uh but in terms of just like i think life is absolutely going to be common in the you know pretty common in the universe yeah i think it's absolutely like i think uh again if i were to bet everything uh even in advanced civilizations are common so the to me then the the only explanation is the l
our galaxy is a graveyard of civilizations.
Yeah, because, you know, you think about it, we've only been around, I mean, as a technical, truly, you know, when we think about, in Drake's definition, you had to have radio telescopes. That's been 100 years. You know, and if we got another 10,000, 100,000 years of history, that would be, for us, that'd be pretty amazing, right?
But that still, that wouldn't be long enough to really pop up the number of civilizations in the galaxy. So you really need it to be, like, hundreds of millions of years. And that raises a question which I am... very interested in, which is how do we even talk about, I call it the billionaire civilization, right?
How do we even begin to hypothesize or think about in any kind of systematic way what happens to a technological civilization across hundreds of millions to a billion years?
How do you even simulate the trajectories that civilizations can take across that kind of time scale? When all the data we have is just for the 10,000 years or so, 20,000 years that humans have been building civilizations. And then just, I don't know what you put it at, but maybe 100 years that we've been technological.
Yeah, and we're ready to blow ourselves to bits or drive ourselves off the planet. Yeah, no, it's really interesting. But there's got to be a way. I think that's really a frontier. So you had David Kipping on not too long ago.
And David and I did a paper, and Caleb Sharf, David really drove this, where it was a Bayesian calculation to sort of ask the question, if you were to find a detection, if you were to find a signal or a techno signature, would that come from a civilization that was younger your age or older? Yeah. And you could see, I mean, this is not hard to do, but it was great.
The formalism, the formalism was hard, you know, it's kind of intuitive, but the formalism was hard to show that, yeah, they're older, you know, probably much older. So that means you really do need to think about like, okay, how do billion year civilizations manifest themselves? What signatures will they leave? And yeah, can you even, I mean, what's so cool about it?
It's so much fun because you gotta, like, you have to, you have to imagine the unimaginable, right? Like, you know, would you still, I mean, obviously biological evolution can happen on, you know, on those kinds of timescales. So you wouldn't even really be the same thing you started out as, but social forms, what kind of social forms can you imagine that would be continuous over that?
Or maybe they wouldn't be continuous. You'd get, they drop out, you know, they destroy themselves and then they come back. So maybe it's, you know, it's a trunk or a punctuated evolution. I mean, but we got to sort of, this is the fun part. We have to sort of work this out. Well, I mean, one way to approach that question is like,
what are the different ways to achieve homeostasis as you get greater and greater technological innovation? So like if you expand out into the universe and you have up to Kardashev scale, what are the ways you can avoid destroying yourself? Just achieve stability while still growing. And I mean, that's an interesting question. I think it's probably simulatable.
Could be. I mean, you know, agent-based modeling, you could do it with that. So, you know, our group has used agent-based modeling to do something like the Fermi paradox. That was agent-based modeling. But you can also do this. People at Santa Fe have done this. Other groups have done this to use agent-based modeling to track the formation of hierarchies.
the formation of stable hierarchies the so i think that i think it's actually very doable but um understanding the kind of assumptions and principles that are going into it and what you can extract from those that is what is sort of the frontier do you think if humans colonized mars