Sara Walker: The Origin of Life on Earth and Alien Worlds | Lex Fridman Podcast #198

1. 0:00 – 1:53

   Introduction

   1. LFLex Fridman0:00

      The following is a conversation with Sara Walker, an astrobiologist and theoretical physicist at Arizona State University and the Santa Fe Institute. She's interested in the origin of life, how to find life on other worlds, and in general, the more fundamental question of what even life is. She seeks to discover the universal laws that describe living systems on Earth and elsewhere using physics, biology, and computation. Quick mention of our sponsors: Athletic Greens, NetSuite, Blinkist, and Magic Spoon. Check them out in the description to support this podcast. As a side note, let me say that my hope for this podcast is to try and alternate between technical and non-technical discussions, to jump from the big picture down to specific detailed research, and back to the big picture, and to do so with scientists and non-scientists. Long-term, I hope to alternate between discussions of cutting edge research in AI, physics, biology, to topics of music, sport, and history, and then back to AI. AI is home. I hope you come along with me for that, uh, wild oscillating journey. Some people message me saying to slow down since they're falling behind on the episodes of this podcast. To their disappointment, I have to say that I'll probably do more episodes, not less, but you really don't need to listen to every episode. Just listen to the ones that spark your curiosity. Think about it like a party full of strangers. You don't have to talk to everyone. Just walk over to the ones who look interesting and get to know them. And if you're lucky, that one conversation with a stranger might change the direction of your life. And it's a short life, so be picky with the strangers you talk to at this metaphorical party. This is the Lex Fridman Podcast, and here is my conversation with Sara Walker.

2. 1:53 – 9:46

   Origin of life

   1. LFLex Fridman1:53

      How did life originate on Earth? What are the various hypotheses for how life originated on Earth?

   2. SWSara Walker2:00

      Yeah, so I guess you're asking a historical question, which is always a good s- place to start thinking about life. Um, so there's a lot of ideas about how life started on Earth. Um, probably the most popular is what's called the RNA world scenario. Um, so this idea is probably the one that you'll see most reported in the news, um, and is based on the idea that there are, um, molecules in our bodies, um, that, uh, relay genetic information, and we know those as DNA obviously, but there's also sort of an intermediary called RNA, ribonucleic acid, um, that also plays the role of proteins. And, um, people came up with this idea in the '80s that maybe that was the first genetic material because it could play both roles of being genetic and performing catalysis. And then somehow that idea got reduced to this idea that there was a molecule that emerged on early Earth and underwent Darwinian evolution, and that was the start of life. Um, so there's a lot of assumptions, um, packed in there that we could unpack, um, but that's sort of the leading hypothesis. There's also other ideas about life starting as metabolism, and so that's more connected to the geochemistry of early Earth-

   3. LFLex Fridman3:16

      Mm-hmm.

   4. SWSara Walker3:17

      ... um, and would be kind of more focused on this idea that you get some kind of catalytic cycle of molecules that can reproduce themselves and form some kind of metabolism, and then life starts basically as self-organization, and then you have to explain how evolution comes later.

   5. LFLex Fridman3:31

      Right, so that's the difference between sort of, uh, energy and genetic code, so like e- energy and- and information? Are those the two kinda-

   6. SWSara Walker3:38

      Yeah.

   7. LFLex Fridman3:39

      ... distinctions there?

   8. SWSara Walker3:39

      Yeah, I think that's a good way of putting it. It's, um, it's kind of funny 'cause I think most of the people that think about these things are really disciplinary biased. So, the people that tend to think about genetics come from a biology background, and they're really evolution focused, and so they're worried about where does the information come from and how does it change over time, but they're talking about information in a really narrow way where they're talking about a genetic sequence. And then most of the people that think about, um, metabolism, origins of life scenarios tend to be people like physicists or geochemists that are worried about what are the energy sources and what, you know, like what kinds of organization can you get out of those energy sources.

   9. LFLex Fridman4:14

      Okay, so w- which one is your favorite?

   10. SWSara Walker4:15

       I don't like either.

   11. LFLex Fridman4:17

       (laughs)

   12. SWSara Walker4:17

       (laughs)

   13. LFLex Fridman4:17

       Okay. All right, can we talk about them for a little bit longer though? Uh... (laughs)

   14. SWSara Walker4:20

       Yeah. No, that's fine. (laughs)

   15. LFLex Fridman4:22

       (laughs) Uh, so okay, so there's, uh, early Earth. What was that like? Was there... Just mostly covered by oceans? Was there heat sources, energy sources? So if we, uh, talk about the metabolism view of the origin of life, like where was the source of energy?

   16. SWSara Walker4:38

       Probably the most popular view for where the origin of life happened on Earth is hydrothermal vents because they had sufficient energy. Um, and so we don't really know a lot about, um, early Earth. Um, we have s- you know, some ideas about when oceans first formed and things like that, but the time of the origin of life is kind of, um, not well understood or pinned down, and the conditions on Earth at that time are not well known. Um, but a lot of people do think that there was probably hydrothermal vents which are really hot, um, chemically active regions, say, on the sea floor in modern times, um, which also would have been present on early Earth, um, and they would have provided energy and organics, um, and basically all of the right conditions for, um, the origins of life, which is one of the reasons that we look for these hydrothermal systems when we're talking about life elsewhere too.

   17. LFLex Fridman5:27

       Okay. And for the genetic code, the idea is that the RNA is the first... Like why would RNA be the first moment you can say it's life? I guess the idea is it could both have persistent information and then it can also do some of the work of like, what? Creating a self-sustaining organism?

   18. SWSara Walker5:49

       Yeah, that's the basic idea. So the idea is you have in an RNA molecule, you have a sequence of characters, say. So you can treat it like a string in a computer, um, and it can be copied so information can be propagated, um, which is important for evolution, uh, because evolution happens by having inheritance of information. So for example, you know, like my eyes are brown because my mother's eyes were brown. Um, so you need that copying of information, but then, um...You also have the ability to perform catalysis, which means that that RNA molecule is not inert in that environment, but it actually interacts with something. It could potentially mediate, say, a metabolism that could then fuel the actual reproduction of that molecule. So, in some ways people think that RNA gives you, um, you know, the most bang for your buck in a single molecule (laughs) . And therefore, um, you know, it gives you all the features that you might think are life. Um, and so th- this is sort of where this RNA world conjecture came from, is because of those two properties.

   19. LFLex Fridman6:54

       Isn't it amazing that RNA came to be, in general? Isn't it-

   20. SWSara Walker6:59

       Yes, that is amazing.

   21. LFLex Fridman7:01

       Okay. So, so we're not talking down about RNA. We're, we're still-

   22. SWSara Walker7:03

       No, no, no. I love RNA.

   23. LFLex Fridman7:04

       Okay.

   24. SWSara Walker7:04

       It's one of my favorite molecules.

   25. LFLex Fridman7:06

       It's just not-

   26. SWSara Walker7:06

       I think it's beautiful.

   27. LFLex Fridman7:07

       It's just not step one.

   28. SWSara Walker7:08

       But... Uh, yeah. I think, I think the issue... It's not even the RNA world is a problem. And actually if you really, um, dig into it, um, the RNA world is not one hypothesis. It is a set of hypothesis. Hypotheses, sorry. And they range from a molecule of RNA spontaneously emerged on the early Earth and started evolving, which is kind of like the hardest RNA world scenario, which is the one I cited and I get a little, um, uh, animated about, 'cause it seems so blatantly wrong to me. But, but that's a separate story. And then the other one is actually something I agree with, which is that a- you can say there was an RNA world because RNA was the first genetic material for life on Earth.

   29. LFLex Fridman7:50

       Right.

   30. SWSara Walker7:50

       So, an RNA world could just be the earliest organisms that had genetics in a modern sense, didn't have DNA evolved yet, they had RNA. All right? And so that's sort of a softer RNA world scenario in the sense that it doesn't mean it was the first thing that happened.
3. 9:46 – 14:57

   Did aliens seed life on Earth?

   1. SWSara Walker9:46

      (laughs) .

   2. LFLex Fridman9:46

      ... in a second. But first let me ask for the other alternative, which is panspermia.

   3. SWSara Walker9:51

      Right.

   4. LFLex Fridman9:52

      So, that's the idea, the hypothesis that life exists elsewhere in the universe and got to us through like an asteroid-

   5. SWSara Walker9:59

      Yes.

   6. LFLex Fridman9:59

      ... or planetoid or some, uh, according to Wikipedia, space dust, whatever the heck that is (laughs) . Uh, it sounds fun.

   7. SWSara Walker10:06

      (laughs) .

   8. LFLex Fridman10:06

      But basically it rode along-

   9. SWSara Walker10:07

      Yeah.

   10. LFLex Fridman10:08

       ... whatever kind of rock, and got to us. Do you think that's at all a possibility?

   11. SWSara Walker10:15

       Sure. So, I think the reason that most origin of life scientists are interested in the origin of life on Earth and say not the origin of life, um, you know, on Mars and then panspermia, you know, the exchange of life between planets being the explanation, is once you start removing the origin of life from Earth you know even less about it than you do if you study it on Earth. Although I think there are ways of reformulating the problem. This is why I said earlier, like, "Oh, you mean the historical origin of life problem? You don't mean the problem of how does life arise in the universe and what the universal principles are?" Because there's this historic problem, how did it happen on early Earth, and there's a more tractable general problem of how does it happen. Um, and how does it happen is something we can actually ask in the lab. How does it, how did it, how did it happen on early Earth is, um, a much more detailed and nuanced question, and requires detailed knowledge of what was happening on early Earth that we don't have. Um, and I'm personally more interested in general mechanisms. So, to me it doesn't matter if it happened on Earth or it happened on Mars. Um, it just matters that it happened. We have evidence it happened. Um, the question is, did it happen more than once in our universe? And so the reason I don't find panspermia as a particularly... I think it's a fascinating, um, hypothesis. I definitely think it's possible. Um, and, um, and I in particular think it's possible once you get to the stage of life where you have technology, because then you, you obviously can spread out into the cosmos. Um, but it's also possible for microbes because we know that, um, certain microorganisms can survive the journey in space and we, you know, they can live in a rock and go between Mars and Earth. Like, people have done experiments to try to prove that could work. Um, so in that scenario it's super cool 'cause then you get planetary exchange. But say we go find, we go look for life on Mars and it ends up being exactly the same life we have on Earth, biochemically speaking. Then we haven't really discovered something new about the universe.

   12. LFLex Fridman12:06

       Mm-hmm.

   13. SWSara Walker12:07

       What kind of aliens are possible? Were there other origin of life events? If we find, if all the life we ever find is the same origin of life event in the universe it doesn't help me solve my problem.

   14. LFLex Fridman12:16

       But it's possible that that would be a sign that you could separate the environment from the-... basic ingredients.

   15. SWSara Walker12:24

       Yes, that's true.

   16. LFLex Fridman12:25

       So, like, you can have, like, a life gun-

   17. SWSara Walker12:27

       (laughs)

   18. LFLex Fridman12:27

       ... that you shoot throughout the universe and then, uh, like, once you shoot it... It's like The Simpsons with the makeup gun. That was a great episode. Uh, when you shoot this life gun, it'll s- it'll find the earths. It'll, like, get sticky.

   19. SWSara Walker12:42

       Yeah.

   20. LFLex Fridman12:42

       It'll, it'll stick to the earths. And, and that kind of reduces the barrier of, um, like, the time it takes, the, the luck it takes to actually from nothing, from the basic chemistry, from the basic physics of the universe for the life to spring up.

   21. SWSara Walker12:58

       Yeah, I think this is actually super important to just think about, like, does life getting seeded on a planet have to be geochemically compatible with that planet? So, you're suggesting, like, we could just shoot guns in space and like-

   22. LFLex Fridman13:11

       Yeah.

   23. SWSara Walker13:12

       ... life could go to Mars and then it would just live there and be happy there. Um, but that's actually an open question. So, one of the things I was gonna say in response to your question about whether the origin of life happened once or multiple times is, for me personally right now in my thinking, all this, this changes on a weekly basis, but, um, is that I think of life more as a planetary phenomena. So, I think the origin of life-

   24. LFLex Fridman13:32

       Okay.

   25. SWSara Walker13:32

       ... because, um, because life is so, um, intimately tied to planetary cycles and planetary processes, and this goes all the way back through the history of our planet, that the origin of life itself grew out of geochemistry and became coupled and controlled geochemistry. And, and when we start to talk about life existing on the planet is when we have evidence of life actually influencing properties of the planet. Um, and so, so if life is a planetary property, um, then going to Mars is not a trivial thing because you basically have to make ours, m- Mars more Earth-like. Um, and so in some sense, um, like when I think about sort of long-term vision of humans in space, for example, uh, really what you're talking about when, when you're saying, "Let's send our civilization to Mars," is you're not saying, "Let's send our civilization to Mars." You're saying, "Let's reproduce our planet on Mars." Like, the information from our planet actually has to go to Mars and make Mars more Earth-like, which means that you're now having a reproduction process. Like a cell reproduces itself to propagate information in the future, planets have to figure out how to reproduce their con- conditions, including geochemical conditions, on other planets in order to actually reproduce life in the universe. Which is kind of a little bit radical, but I think, um, for long-term sustainability of life on a planet, that's absolutely essential.

   26. LFLex Fridman14:47

       Okay. So, if we were to think about life as a planetary phenomena, and so life on Mars would b- be best if it's way different than life on Earth,

4. 14:57 – 26:36

   What is life?

   1. LFLex Fridman14:57

      we have to ask the very basic question of, what is life?

   2. SWSara Walker15:03

      I actually don't think that's the right question to ask. It took me a long time to get there, right? So I-

   3. LFLex Fridman15:07

      Let me cross it out.

   4. SWSara Walker15:08

      Yeah, (laughs) cross it off your list. It's wrong. Uh, no.

   5. LFLex Fridman15:11

      Next question.

   6. SWSara Walker15:12

      Um, no. No, no, no. I mean, I think it has an answer, but I think the pro- part of the problem is, um, you know, most of the places in science where we get really stuck is because we don't know what questions to ask.

   7. LFLex Fridman15:22

      Right.

   8. SWSara Walker15:22

      Um, and so you can't answer a question if you're asking the wrong question. Um, and I think, uh, the way I think about it is obviously I'm interested in what life is, so I'm being a little cheeky when I say that's the wrong question to ask. That's exactly, like, the, the question that's, like, the core of my existence. But, um, but I think the way of framing that is, what is it about our universe that allows features that we associate life to be there? Um, and so really what, I guess when I'm asking that question, what I'm after is an explanatory framework for what life is, right? And so most people, they try to go in and define life and they say, "Well, life is, uh, say, a self-reproducing chemical system capable of Darwinian evolution." That's a very popular definition for life. Um, or life is something that metabolizes and eats. Um, that is not how I think about life. What I think about life is there are principles and laws that govern our universe, um, that we don't understand yet, um, that have something to do with, um, how information interacts with the physical world. I don't know exactly what I mean even when I say that, um, because we don't know these rules. Um, but it's a little bit like, um... I like to use analogies if you give me time to be, like, a little long-winded for a second, even in essay. Um, but, um, but sort- sort of like if you look at the history of physics, for example. This is like... So, we are in the period of the development of thought on our planet where we don't understand what we are yet, right? Um, there was a period of thought in the history of our planet where we didn't understand what gravity was. Um, and we didn't understand, for example, the planets in the heavens, you know, were actually planets or that they operated by the same laws that we did. Um, and so there has been this sort of progression of getting a deeper understanding of explaining basic phenomena like... I'm not gonna drop the cup. I'll drop the water bottle. There you go. Okay, that fell, right? (laughs) But why did that fall? Um, (laughs) it's th- this is why I'm a theorist, not an experimentalist. (laughs)

   9. LFLex Fridman17:19

      (laughs) That could have gone wrong in so many ways.

   10. SWSara Walker17:20

       I know it could have, especially if I did the cup and it smashed. Anyway. (laughs)

   11. LFLex Fridman17:24

       (laughs)

   12. SWSara Walker17:25

       Um, so, um, so if you think, uh, you take this view that there's sort of some missing principles, I associate them, uh, to information. And what it, what the sort of feeling there is there's some missing explanatory framework for how our universe works. And if we understood that physics, it would explain what we are. Um, it might also explain a lot of other features we don't associate to life. Um, and so it's a little like, um, people accept the fact that gravity is a universal phenomena, um, but when we wanna study gravity, we study things like large-scale, um, you know, galactic structures or black holes or planets. Um, if we wanna understand information and how it operates in the physical world, we study intelligent systems or living systems because they are the manifestation of that physics. Um, and the fact that we can't see that clearly yet or we don't have that explanatory framework I think is just because we haven't been thinking about the problem deeply enough. But I feel like if you're explaining something, you're deriving it from some more fundamental property. And of course, um, I have to say I'm wearing my, my physicist hat, so I have a, a huge bias of liking simple, elegant explanations of the universe that, um...... you know, really are compelling. But I think, um, one of the things that I've sort of maybe in some ways rejected my training as a physicist is that most of the elegant explanations that we have so far don't include us in the universe. And I can't help but think there's something really special about what we are, and there have to be some deep principles at play there. Um, and so, so that's sort of my perspective on it. Now when you ask me what life is, I have some ideas of what I think it is, but I think that we haven't gotten there yet because we haven't been able to see that structure. And it's a, and, and just to go back to the gravity example, it's a little like, you know, in ancient times they didn't know... I was talking about stars and heavens and things, they didn't know those were, um, you know, governed by the same principles as that darned experiment.

   13. LFLex Fridman19:19

       Mm-hmm.

   14. SWSara Walker19:19

       Here's where I was going with it. Once you realize, like Newton did, that, you know, heavenly motions and earthly motions are governed by the same principles, and you unify terrestrial and celestial motion, you get these more powerful ideas. Um, and I- I- I think where life is, is somehow unifying these abstract ideas of computation and information with the physical world, with matter, and realizing that there's some explanatory framework that's not physics and it's not computation, but it's something that's deeper.

   15. LFLex Fridman19:49

       So, answering the question of what is life requires deeply understanding something about the universe as information processing, the universe as computation?

   16. SWSara Walker19:59

       Sort of.

   17. LFLex Fridman19:59

       It's something about-

   18. SWSara Walker20:00

       Yeah. (laughs)

   19. LFLex Fridman20:00

       Like would, uh, once you come up with an answer to what is life, will the words information and computation be in the paragraph that answer?

   20. SWSara Walker20:08

       No, I don't think so.

   21. LFLex Fridman20:09

       Ah, damn it. Okay.

   22. SWSara Walker20:10

       I know. It doesn't help, does it? I know, I, I hate, actually I hate this about what I do because it's so hard to communicate, right? With words. Like when you have words that are, um, ideas that have historically described one thing and you're trying to describe something people haven't seen yet-

   23. LFLex Fridman20:25

       Right.

   24. SWSara Walker20:25

       ... and the words just don't fit.

   25. LFLex Fridman20:27

       So what, uh, what's wrong? Is it too ambiguous, the word information? We could switch to binary if you want.

   26. SWSara Walker20:33

       (laughs) Yeah. No, I don't think it's binary either.

   27. LFLex Fridman20:35

       Okay.

   28. SWSara Walker20:35

       Um, I think information is just loaded. I use it... So the other way I might talk about it is the physics of causation, but I think that's worse because causation is even more loaded word than, um, information. So sometimes-

   29. LFLex Fridman20:46

       So causation is fundamental, you think?

   30. SWSara Walker20:48

       I do, yeah. And, um, in some sense I think the physics... So this is the really radical part. In some sense like when I really think about it sort of most deeply, uh, what I think life is, is actually the physics of existence. What gets to exist and why. Um, and you know, for simple elementary particles that's not very complicated because the interactions are simple, but for things like, um, you know, you and me and human civilizations, um, you know, what comes next in the universe is really dependent on what came before. And there's a huge space of possibilities of things that can exist. And when I say information and causation, what I mean is, why is it that, uh, cups evolved in the universe and not some other object that could deliver water and not spill it? (laughs) Um, I don't know what you would call it. Uh, maybe it wouldn't be a cup, but um, but it's a huge... I- I- It's, um, you know, uh, you know, people talk about the space of things that could exist as being actually infinitely large, right? I don't know if I believe in infinity, um, but I do think that there is something very interesting about the problem of what exists and its relationship to life.
5. 26:36 – 31:04

   Cellular automata

   1. LFLex Fridman26:36

      There's a guy named Stephen Wolfram.

   2. SWSara Walker26:38

      Mm-hmm.

   3. LFLex Fridman26:38

      There's a concept called cellular automata. So, there's, um, there's some mysteries in these, um, systems that are computational in nature, that have maybe echoes of the kind of mysteries we should need to solve to understand what is life.

   4. SWSara Walker26:57

      Mm-hmm.

   5. LFLex Fridman26:59

      So, if we could talk, take a computational view of things, do you think there's something compelling to reducing everything down to computation, like the universe as computation, and then trying to understand life? So, throw away the biology, throw away the chemistry, throw away even the physics that you, you learn in undergrad and graduate school, and more look at these simple little systems. Whether it's cellular automata or whatever the heck kind of computational systems that operate on simple local rules and then create complexity, uh, as they evolve. Is, is it, uh, at all, do you think, productive to focus on those kinds of systems to get an inkling of what is life? And if it is, do you, do you think it's, it's possible to come up with some kind of laws and principles about what makes life in those computational systems?

   6. SWSara Walker27:56

      So, I like cellular automata. I think they're good toy models. Um, but mostly like where I've thought about them and used them is to actually, um, let's say, poke at sort of the current conceptual framework that we have and see where the flaws are. Um, so I think like the part that you're talking about, that people find intriguing, is that if you have like a fairly simple rule and you specify some initial condition, and you run that rule and that initial condition, you could get really complex patterns emerging.

   7. LFLex Fridman28:26

      Yeah.

   8. SWSara Walker28:26

      And, ooh, doesn't that look life-like? Um... (laughs)

   9. LFLex Fridman28:29

      Yeah.

   10. SWSara Walker28:29

       Yeah.

   11. LFLex Fridman28:31

       Well, it's like really surpri- isn't it really surprising?

   12. SWSara Walker28:32

       It is really surprising, and they're beautiful, um, and I, I think they have a lot of nice features associated to them. Um, I think the things that I find... Yeah, so, so I, I do think, um, as a proof of principle, that you can get complex things emerging from simple rules, they're great. Um, as a sort of proof of principle about some of the ways that we might think of computation as being sort of a fundamental principle for dynamical systems and maybe they, the evolution of the universe as a whole, they're a great model system. As an explanatory framework for life, I think, um, they're a bit problematic for the same reason that, uh, the laws of physics are a bit problematic. Um, and the clearest way I can articulate that is, like cellular automata are actually cast in sort of a conceptual framework for how the universe should be described that goes all the way back to Newton, in fact, with this idea that we can have a fixed law of motion which exists sort of... it's given to you. (laughs) Um, you know, the great programmer in the sky gave you this equation or this rule, and then you just run with it. Um, and the rule doesn't have... So, a good feature of the rule is it doesn't have specified in the rule information about the patterns it generates. So, you wouldn't want, for example, the. My cup or my water bottle or, you know, me sitting here to be specified in the laws of physics. That would be ridiculous 'cause it wouldn't be a very simple explanation of all the things happening. It'd have to explain everything. So... And cellular automata have that feature, um, and the laws of physics have that feature, um, but, but, you know, you also need to specify the initial condition. Um, and it also s- it basically means that everything that happens is sort of a consequence of that initial condition. And I think this kind of framework is just not the right one for biology. Um, and part of the way that it's easiest to see this is, um, a lot of people talk about self-reference being important in life. The fact that, um, you know, like the genome has information encoded in it. That information gets read out. Um, it specifies something about the architecture of a cell. Um, the architecture of the cell includes the genome, so the genome has basically self-referential information. Self-reference obviously comes up in, um, computational law because it's kind of foundational, um, to Turing's work and what Godel did with the incompleteness theorems and things. So, there's a lot of, um-... parallels there and, and people have talked about that

6. 31:04 – 40:50

   The laws of physics may change with time

   1. SWSara Walker31:04

      at depth. Um, but the other way of kind of thinking about it in terms of like a more physics-y way of talking about it is that what it looks like in biology is that the rules or the laws depend on the state. This is typical-

   2. LFLex Fridman31:16

      Mm-hmm.

   3. SWSara Walker31:16

      ... in computer science. This is obvious to you.

   4. LFLex Fridman31:18

      Mm-hmm.

   5. SWSara Walker31:18

      You know, the update rule depends on the state of the machine, right? But in, you know, you don't think about, um, uh, you know, that being sort of the dynamic in physics. It's, you know, the rule is given to you and then it, you know, it's a, it's a very special subclass say of computations if, you know, you don't ever change the update. Um, but in biology, it seems to be that the state and the law change together as a function of time and we don't have that as a paradigm in physics. Um, and so a lot of people talk about this as being kind of a perplexing feature, that maybe there are certain scenarios where the laws of physics or the laws that govern a particular system actually change as a function of the state of that system.

   6. LFLex Fridman31:56

      That's trippy.

   7. SWSara Walker31:57

      Yeah. (laughs)

   8. LFLex Fridman31:57

      So yeah, the, the, the hope of physics, it's a hope I guess though, but often stated as a underlying assumption is that the law is, uh, static.

   9. SWSara Walker32:08

      Right.

   10. LFLex Fridman32:10

       Okay. And you just-

   11. SWSara Walker32:10

       And even having laws that vary in time and not even as a function of the state is very radical when you- when-

   12. LFLex Fridman32:16

       The time in general, like-

   13. SWSara Walker32:18

       Yeah.

   14. LFLex Fridman32:18

       ... you, you wanna remove time from the equation as much as possible?

   15. SWSara Walker32:22

       Yeah. I, I do. Um, there's some interesting things in this, like w- when we think sort of deep, more deeply about the actual physics that we're trying to propose governs life, um, with me with collaborators and then also other people that think about similar things, that time might actually be fundamental and there really is an ordering to time. Um, and that events in the universe are unique because they have a particular, you know, they, they happen, like an object in the universe requires a certain history of events in order to exist, which therefore suggests that time really does have an ordering. I'm not talking about the flow of time and our perception of time, just the ordering of events.

   16. LFLex Fridman32:53

       Causation of things.

   17. SWSara Walker32:54

       Yes. Causation. There's that word again.

   18. LFLex Fridman32:56

       So causation, that's which...

   19. SWSara Walker32:58

       (clears throat)

   20. LFLex Fridman32:58

       When you say time, you mean causation?

   21. SWSara Walker32:59

       Yes.

   22. LFLex Fridman33:00

       In your proposed model of the physics of life, the, the fundamental thing would be causation?

   23. SWSara Walker33:08

       Yes.

   24. LFLex Fridman33:08

       If you were to bet your money on, on one particular horse or whatever.

   25. SWSara Walker33:12

       Yes.

   26. LFLex Fridman33:13

       And then space is emergent?

   27. SWSara Walker33:15

       Yes.

   28. LFLex Fridman33:16

       So everything is emergent except time?

   29. SWSara Walker33:19

       Kind of, yeah. Or causation.

   30. LFLex Fridman33:21

       And laws-
7. 40:50 – 46:09

   Nobel Prize for the origin of life

   1. LFLex Fridman40:50

      so let's look into the future.

   2. SWSara Walker40:53

      I try that every day, it never works. (laughs)

   3. LFLex Fridman40:56

      So say a Nobel Prize is given in physics, maybe chemistry, for discovering the origin of life.

   4. SWSara Walker41:05

      Mm-hmm.

   5. LFLex Fridman41:06

      No, not, but not the historical origin.

   6. SWSara Walker41:09

      No.

   7. LFLex Fridman41:09

      Some kind of thing that we're talking about. What exactly would... (sighs) What do you think, um, that like what do you think that person, maybe you, did to get that Nobel Prize? Like what- what would they have to have done? 'Cause you could do a bunch of experiments that go like with an aha moment. Like you- you rarely get the Nobel Prize or for like you've solved everything, we're done. (laughs)

   8. SWSara Walker41:36

      Right.

   9. LFLex Fridman41:37

      It's like some inkling of some deep truth.

   10. SWSara Walker41:40

       Right.

   11. LFLex Fridman41:41

       Like what do you think that would actually look like? Would it be an experimental result? Uh, I mean, it will have to have some kind of experimental, maybe validation-

   12. SWSara Walker41:49

       Yes. Yes.

   13. LFLex Fridman41:49

       ... component. So what- what would that look like?

   14. SWSara Walker41:52

       This is an excellent question. I wanna... (laughs) Sorry, I got, I gotta make a quick point which is just a slight tangent. But you know, like when people ask about the origin of mass, you know, and like looking for The Higgs mechanism and things, they never are like, "We need to find the historical origins of life in the early..." You know, although those things are related, right? So, um, so this problem of origins of life in the lab I think is really important. But The- The Higgs is a good example because you had theory to guide it. So somehow you need to have an explanatory framework, um, that can say that we should be looking for these features, um, and explain why they might be there, and then be able to do the experiment and demonstrate that it matches with the theory. But it has to be something that is outside sort of the paradigm of what we might expect based on what we know, right? So this is a really sort of tall order. Um, and I think, um... I mean, I- I guess the way people would think about it is like, you know, if you had a bacteria that climbed out of your test tube or something and it was like, you know, moving around on the surface, that would be ultimate validation. You saw the origin of life in- in an experiment. But I don't think that's quite what we're looking for. I think what- what we're looking for is evidence of when information that originated within the bounds of your experiment and you can demonstratively prove emerged spontaneously in your experiment wasn't put in by you, actually started to govern the- the future dynamics of that system and specify it, and you could somehow relate those two features directly. So you know that the program specifying what's happening in that system is actually internal to that system.... like, say you have a chemical thing in a box.

   15. LFLex Fridman43:32

       Well, i- i- (sighs) so that's, that's one Nobel Prize-winning experiment, which is like, information, in some fundamental way, originated within the constraints of the system without you injecting anything. But another experiment is you injected something-

   16. SWSara Walker43:49

       Yeah.

   17. LFLex Fridman43:50

       ... and got out information.

   18. SWSara Walker43:52

       Yes.

   19. LFLex Fridman43:52

       So like, you injected, I don't know, like, uh, like some sugar and like something, (laughs) something that doesn't necessarily feel like in- it should be information. Um, but-

   20. SWSara Walker44:03

       Yeah. So actually no. I mean, sugar is information, right? So part of the argument here is that every physical object i- is-

   21. LFLex Fridman44:11

       Right.

   22. SWSara Walker44:11

       Well, it's information, but it's a set of causal histories and also a set of possible futures. So there is an experiment, um, that I've talked a lot about, uh, with Lee Cronin, but also with Michael Lockman and Chris Kempes, who are at Santa Fe, about this idea that sometimes we talk about as like seeding assembly. Um, which is-

   23. LFLex Fridman44:28

       Mm-hmm.

   24. SWSara Walker44:28

       ... you take a high, high complexity, like a, um, an object that exists in the universe because of a long causal history, and you seed it into a system of lower causal history. And then suddenly you see all of this complexity being generated. So I think another validation of the physics would be, say you engineer an organism by, by purposefully introducing something where you understand the relationship between the causal history of the organism and the, say, very complex chemical set of ingredients you're adding to it. And then you can predict the future evolution of that system to some, um, statistical, uh, set of constraints and, and possibilities for what it will look like-

   25. LFLex Fridman45:09

       Hmm.

   26. SWSara Walker45:09

       ... in the future. You know, I'm a physical structure, obviously. Like I, I'm composed of atoms. Um, the configuration of them and the fact that they happen to be me, um, is because I'm not actually my atoms. I am a informational pattern that keeps repatterning those atoms into Sarah. Um, and I have also associated to me s- uh, like a space of possible things that could exist (laughs) that I can help mediate come into existence because of the information in my history. Um, and so when you understand sort of that time is a real thing embedded in a physical object, um, then it becomes possible to talk about how histories, when they interact... And a history is not a unique thing, it's a set of possibilities.

   27. LFLex Fridman45:59

       Mm-hmm.

   28. SWSara Walker45:59

       When they interact, how do they specify what's coming next? And then where does the novelty come from in that structure? 'Cause some of it is kind of things that haven't existed in the past can't exist in the future.

8. 46:09 – 57:28

   Is consciousness fundamental to the universe?

   1. SWSara Walker46:09

   2. LFLex Fridman46:09

      Mm-hmm. Let me ask about this entity that you call Sarah.

   3. SWSara Walker46:12

      Yes.

   4. LFLex Fridman46:13

      M-

   5. SWSara Walker46:14

      I talk to myself (laughs) about myself in third person sometimes. I don't know why. (laughs)

   6. LFLex Fridman46:18

      (laughs) Uh, so maybe this is a good time to bring up consciousness.

   7. SWSara Walker46:22

      Sure.

   8. LFLex Fridman46:23

      (laughs)

   9. SWSara Walker46:24

      It's been here all along. (laughs)

   10. LFLex Fridman46:26

       Well, has it? So, I mean, that's-

   11. SWSara Walker46:29

       At least in this conversation, I think I've been conscious most of it, but maybe I haven't.

   12. LFLex Fridman46:32

       Well, yeah. Speak f- so speak for yourself. You're, (laughs) you're, you're projecting your consciousness onto me. You don't know if I'm conscious or not. Is-

   13. SWSara Walker46:40

       No, I don't.

   14. LFLex Fridman46:40

       ... um-

   15. SWSara Walker46:41

       You're right.

   16. LFLex Fridman46:41

       ... is that, uh, y- y- you talked about the physics of existence. You talked about the emergence of, um, of causali- uh, sorry. You talked about causality and time being fundamental to the universe. W- where does consciousness fit into all of this? Like, uh, do you, do you draw any kind of inspiration or value with the idea of panpsychism that maybe th- one of the things that we ought to understand is the physics of consciousness? Like, one of the missing pieces in the physics view of the world is understanding the physics of consciousness. Or like that word has so many concepts underne- underneath it, but let's put it on a... Let's put consciousness as a label on a black box of mystery that we don't understand. Do you think that black box holds the key to, uh, finally answering the question of the physics of life?

   17. SWSara Walker47:40

       The problems are absolutely related. I think, um, most... And I'm interested in both because I'm just interested in what we are. And to me, the most interesting feature of what we are is our minds and the way they interact with other minds. Like, minds are the most beautiful thing that exists in the universe, so how did they come to be? Um-

   18. LFLex Fridman47:55

       I'm sorry to interrupt. So when you say we, you mean humans?

   19. SWSara Walker47:58

       I mean humans right now, but I, but that's because I'm a human. Or at least-

   20. LFLex Fridman48:01

       But you, you, you-

   21. SWSara Walker48:01

       ... I think I am.

   22. LFLex Fridman48:02

       ... think there's something special to this particular-

   23. SWSara Walker48:05

       No, no, no, no, no. Um, no. Um, I don't... I'm not a human-centric thinker.

   24. LFLex Fridman48:11

       But are you one entity? You said a bunch of stuff came together to make a Sarah. Like do you, do you think-

   25. SWSara Walker48:16

       Oh. Do, um-

   26. LFLex Fridman48:17

       ... of yourself as one entity or are you just a bunch of different components? Like is there any value to understand the physics of Sarah? Like, or are you just a bunch of different things that are like a nice little temporary side effect that you-

   27. SWSara Walker48:30

       Uh, yeah. You, you could think of me as a bundle of information that just-

   28. LFLex Fridman48:33

       Yeah.

   29. SWSara Walker48:33

       ... became temporarily aggregated into-

   30. LFLex Fridman48:34

       Yeah, locally.
9. 57:28 – 1:00:03

   Life is the most deterministic part of physics

   1. SWSara Walker57:28

      me something.

   2. LFLex Fridman57:28

      Let- let's continue the deep analysis of your tweets.

   3. SWSara Walker57:31

      (laughs)

   4. LFLex Fridman57:33

      You, you, you said that determinism, in a tweet, "Determinism and randomness play important roles in understanding what life is."

   5. SWSara Walker57:40

      Yeah.

   6. LFLex Fridman57:40

      So let me ask on this topic of free will, what is determinism? What is randomness? And why the heck do they have anything to do with understanding life?

   7. SWSara Walker57:50

      Yeah. And you threw free will in there. You're just throwing all the, the stuff in the bag. Um-

   8. LFLex Fridman57:55

      Are, are they not related, determination and randomness?

   9. SWSara Walker57:56

      No, no. They are, they are related. The- no, no (laughs) . Sorry, I was being unfair.

   10. LFLex Fridman58:00

       You didn't even capitalize the tweet, by the way. It was all lowercase.

   11. SWSara Walker58:03

       I must've been angry (laughs) .

   12. LFLex Fridman58:05

       Oh, that was-

   13. SWSara Walker58:05

       (laughs)

   14. LFLex Fridman58:05

       Was ang- can you analyze the emotion behind that?

   15. SWSara Walker58:08

       (laughs) No, I actually, I-

   16. LFLex Fridman58:08

       Just frustration? Or it's hope?

   17. SWSara Walker58:09

       Yeah, maybe. So, I already argued that I don't think that can happen without that s- whole causal history. And so I guess in some sense, um, the determinism, for me, arises because of the causal history.

   18. LFLex Fridman58:22

       Mm-hmm.

   19. SWSara Walker58:23

       Um, and I'm not really sure actually about whether the universe is random or deterministic. I just had this sort of intuition for a long time, I'm not sure if I agree with it anymore, but it's still kind of lingering and I don't know what to do with this question. But it seems to me, you know, so there's- you asked the question, "What is life?" But you could also, "Why life? Why does life exist? What, what does the universe need life for?" Not that the universe has needs, but, you know, we have to anthropocentrize things sometimes to talk about them.

   20. LFLex Fridman58:50

       Mm-hmm.

   21. SWSara Walker58:50

       Um, and I had this feeling that if it was possible for a cup, or a desk ornament, or a phone on Mars to spontaneously fluctuate into existence, the universe didn't need life to create those objects. It wasn't necessary for their existence. It was just a random fluke event. And so somehow to me it seems that it can't be that those things form by rando- random processes. They actually have to have a set of causes that accrue and form those things, and they have to have that history. And so it seems to me that, that life was s- somehow deeply related to the question of whether the underlying rules of our universe had randomness in them, or they were fully deterministic. And in some ways you can think about life as being the most deterministic part of physics, um, because it's where the causes are, um, precise in some sense. Um-

   22. LFLex Fridman59:39

       Or more- more stable? So like, uh, I'm try-

   23. SWSara Walker59:40

       Most stable, yes. Most reliable.

   24. LFLex Fridman59:43

       Uh, uh, uh... most reliable?

   25. SWSara Walker59:43

       Yeah.

   26. LFLex Fridman59:43

       For, for our- m- for how we- for the tools of physics. But what, um-

   27. SWSara Walker59:48

       Right, well, so-

   28. LFLex Fridman59:49

       Where's the randomness come from, then, if... Okay, so you, you were at, uh, speaking with, uh-

   29. SWSara Walker59:54

       I've gone in a tangent, so I'm not sure where we are in the q- yeah.

   30. LFLex Fridman59:57

       All-
10. 1:00:03 – 1:08:20

    Free will

    1. LFLex Fridman1:00:03

       So, free will.

    2. SWSara Walker1:00:05

       Yes.

    3. LFLex Fridman1:00:05

       You believe-

    4. SWSara Walker1:00:07

       Yes.

    5. LFLex Fridman1:00:07

       ... at this current time that you have free will.

    6. SWSara Walker1:00:09

       I believe my whole life I have free will. What is illusion? No, I'm just kidding (laughs) .

    7. LFLex Fridman1:00:13

       (laughs)

    8. SWSara Walker1:00:13

       I still believe it.

    9. LFLex Fridman1:00:14

       You still believe it? So, uh, at the same time you think that in your conception of the universe, causality seems to be pretty fundamental.

    10. SWSara Walker1:00:23

        That's right.

    11. LFLex Fridman1:00:23

        Which kinda wants the universe to be deterministic. So, how the heck-

    12. SWSara Walker1:00:29

        Because I'm a determin-

    13. LFLex Fridman1:00:29

        ... do you think you have a free will, and yet you value causality?

    14. SWSara Walker1:00:34

        Um, because I depart from the conception of physics that you can write down an initial condition and a fixed law of motion and that will describe everything.

    15. LFLex Fridman1:00:45

        Oh.

    16. SWSara Walker1:00:45

        There's no incompatibility if you are willing to reject that assertion.

    17. LFLex Fridman1:00:49

        So where is the randomness? Where is the magic that gives birth to the free will? Is it the randomness of the laws of physics?

    18. SWSara Walker1:00:57

        No, free- um, in, in my mind what free will is, is the fact that I, I as a physical system have causal control over certain things. I don't have causal control over everything, but I have a c- a certain set of things. And I'm also, um, you know, as I described, sort of a nexus of a particular set of histories that exist in the universe and a particular set of futures that might exist, um, and those futures that might exist are in part specified by my physical configuration as me. Um, and therefore, you know, it may not be free will in the traditional sense. I don't even know what people mean when they're talking about free will, honestly. It's like the whole discussion's really muddled. But in the sense that I am a causal agent, if you wanna call it that, that exists in the universe, and there are certain things that happen because I exist as me, then yes, I have free will.

    19. LFLex Fridman1:01:45

        No, but...Do you, Sarah, have a choice about what's going to happen next?

    20. SWSara Walker1:01:51

        Oh, I see. Um...

    21. LFLex Fridman1:01:53

        Like, if the univ- c- could I have... If I run this universe back-

    22. SWSara Walker1:01:56

        Yes, I think so.

    23. LFLex Fridman1:01:57

        You have a choice? Where does the choice come from? Is it-

    24. SWSara Walker1:02:00

        I think that's really just the physics of consciousness. So, one of the things I didn't say about that, and I don't know, maybe this is me just being hopeful, um, because I- I- maybe I just want to have free will, but I don't think that we can rule out the possibility because I don't think that we understand enough about any of these problems. But I think one of the things that's interesting for me about this sort of inversion of the question of consciousness that I propose is, one of the features that, that we do is we have imagination, right? And people don't think about imagination as a physical thing, but it is a physical thing.

    25. LFLex Fridman1:02:30

        Mm-hmm.

    26. SWSara Walker1:02:30

        It exists in the universe, right? Um, and so I'm, like, really intrigued by the fact that, say, humans for, you know, and another physical system could do this too, it's not special to humans, but, uh, you know, for centuries imagined flying machines and rockets, and then we finally built them, right? So they were, they were represented in our minds and on the pages of things that we drew for hundreds of years before we could build those physical objects in the universe. Um, but certainly, the existence of rockets is, in part, um, causally, uh, you know, caused by the fact that we could imagine them. Um, and so, um, so there seems to be this property that some things don't exist, they've never physically existed in the universe, but we can imagine the possibility of them existing and then cause them to exist, maybe individually or collectively. Um, and I think that property is related to what I would say about having choice or free will because the- that set of possibilities, that thing, those set of things that you can imagine is not constrained to your local physical environment and history. And this is what's a little bit different about intelligence as we see it in humans and AI that we want to build than biological intelligence, because biological intelligence is predicated completely on the history of things as seen in the past. But something happened with the neural architectures that evolved in multicellular organisms that they don't just have access to the past history of their particular, you know, set of events, but they can imagine things that haven't happened, aren't on their timeline, and a- as long as they're consistent with the laws of physics, make them happen.

    27. LFLex Fridman1:03:59

        So, (laughs) this is fascinating. In some sense-

    28. SWSara Walker1:04:02

        It's trippy physics, but it exists, so there you go.

    29. LFLex Fridman1:04:05

        I mean, in some sense, if you look at, like, uh, general relativity and gravity morphing space time, in that same way maybe whatever the physics of consciousness might be, it might be morphing... that's like what free will is.

    30. SWSara Walker1:04:18

        Yes.
11. 1:08:20 – 1:22:57

    How to detect alien life

    1. SWSara Walker1:08:20

    2. LFLex Fridman1:08:20

       Can we talk about aliens?

    3. SWSara Walker1:08:22

       Anytime. (laughs)

    4. LFLex Fridman1:08:25

       (laughs) Uh, so one, I think, one interesting way to sneak up on the question of what is life is to ask, "What should we look for in alien life?" You know, if we were to look out into our galaxy and into the universe and come up with a framework of how to detect alien life, what should we be looking for? Is there a, like, set of rules? Uh, like, it's both the tools and the tools that are- serve as sensors for certain kind of properties of life. So, what should we look for in alien life?

    5. SWSara Walker1:09:05

       Yeah. So, we have a paper actually coming out on Monday which is a collaboration. Um, it's- it's actually really Lee Cronin's lab, but my group worked with him on it, and we're working on the theory, which is this idea that we should look for life, um, as high-assembly objects. What we mean by that is, um, which is actually observationally measurable, and this is one of the reasons that I started working with Lee on these ideas, is because being a theorist, it's easy to work in a vacuum. It's very hard to connect abstract ideas about the nature of life to anything that's experimentally tractable.

    6. LFLex Fridman1:09:35

       Mm-hmm.

    7. SWSara Walker1:09:36

       Um, but what his lab has been able to do is develop this method where they look at a molecule and they break it apart into all its component parts, and so you say you have some elementary building blocks and you can build up all the ways of putting those together to make the original object-

    8. LFLex Fridman1:09:52

       Mm-hmm.

    9. SWSara Walker1:09:52

       ... and then you look for the shortest path in that space, um, and you say that's sort of the assembly number associated to that object. Um, and if that number's higher, it assumes that a longer causal, causal history is necessary to produce that object, or more information is necessary to specify the creation of that object in the universe. Now, that kind of, uh, idea at a superficial level has existed for a long time. That kind of idea as a physical observable of molecules is completely novel, and what his lab has been able to show is that if you look at a bunch of samples of non-biological things and biological things, there's this kind of threshold, um, of assembly where all- as far as the experimental evidence is, and also your intuitive- intuition would suggest, that bio- non-biological systems don't produce things with high assembly number. Um, so this goes back to the idea, like, a protein is not gonna spontaneously fluctuate into existence on the surface of Mars. It requires an evolutionary process and a biological architecture to produce a protein. You generalize that argument, you know, a complex molecule or, or a cup or a desk ornament, um, in this sort of abstract idea of assembly spaces as being, um, the causal history of objects, and you can talk about the shortest path from elementary objects to an object given a elementary set of operations, and you can experimentally measure that with a mass spec. And that's basically sort of the idea.

    10. LFLex Fridman1:11:16

        That's incredible. That's really fascinating. I can't get out of my head... I've started imagining LEGOs-

    11. SWSara Walker1:11:20

        Yeah.

    12. LFLex Fridman1:11:20

        ... and all the LEGOs I've ever built and how many steps, what is the shortest path to, to the final-

    13. SWSara Walker1:11:25

        Right, right.

    14. LFLex Fridman1:11:26

        ... the final-

    15. SWSara Walker1:11:26

        Right.

    16. LFLex Fridman1:11:26

        ... little LEGO castles. (laughs)

    17. SWSara Walker1:11:28

        So, the idea- so, yeah, so then, like, asking about going to look for alien life, the idea is, you know, most of the instruments that NASA builds, for example, or any of the space agencies looking for life in the universe are looking for chemical correlates of life, right?

    18. LFLex Fridman1:11:41

        Right.

    19. SWSara Walker1:11:42

        But here we have something that is based on properties of molecules. It's not a chemical correlate. It's agnostic. It doesn't care about the molecule. It cares about what is the history necessary to produce this molecule. Um, how complex is it in terms of how much time is needing, how much information is required to produce it?

    20. LFLex Fridman1:12:00

        So, when you observe a thing on another planet, you're essentially... the process looks like reverse engineering, trying to figure out what is the shortest path to create that thing?

    21. SWSara Walker1:12:11

        Yeah. So most... yeah. And I would say most, like most examples of biology or technology don't take the shortest path, right? But the shortest path is a bound on how hard it is for the universe to make that.

    22. LFLex Fridman1:12:21

        Yeah. And s- and I guess what, what you and Lee are saying that there's a heuristic that's a good metric for, uh, like better perhaps than chemical correlates.

    23. SWSara Walker1:12:31

        Yes.

    24. LFLex Fridman1:12:32

        Okay.

    25. SWSara Walker1:12:32

        Because it doesn't- it's not contingent on looking for the chemistry of life on Earth on other planets. And it also has a deeper explanatory framework associated to it as far as the kind of theory that we're trying to develop associated to what life is. And I think this is one of the problems I have in my f- my field personally, in astrobiology, is people observe something on Earth, say oxygen in the atmosphere or an amino acid i- in a cell, and then they say, "Let's go look for that on another planet. (laughs) Uh, let's look for oxygen on exoplanets or let's look for amino acids on Mars." And then they assume that's a way of looking for life. Um, a- and it- it... or even phosphine on Venus, but, you know, like, there's all these examples of let's look for one molecule. A molecule is not life. Life is a, a system that patterns particular structures into matter. That's like its- that's what it is, and it doesn't care what molecules are there. It's something about the patterns and, and that structure and that history. Um, and if you're looking for a molecule, you're not testing any hypotheses about the nature of what life is. It doesn't tell me anything if we discover oxygen on an exoplanet about what kind of life is there. It's just oxygen on an exoplanet. It's not... there, there's n- I, I guess I think, like, when you think about the question, are we alone in the universe, that's a pretty fricking deep question. (laughs) It should have a fricking deep answer.

    26. LFLex Fridman1:13:51

        Mm-hmm.

    27. SWSara Walker1:13:51

        It shouldn't just be there's a molecule on an exoplanet. Wow, we solved the problem. It should tell us something meaningful about our existence. And I feel like we've fallen short on how we're searching for life in terms of actually searching for things like us in this kind of deeper way.

    28. LFLex Fridman1:14:07

        But how do you do that initial kind of, say I'm walking down the street and I'm looking for that double take test of like, like what the hell is that?

    29. SWSara Walker1:14:17

        Yeah.

    30. LFLex Fridman1:14:17

        Like that, that initial, like how do we look for the possibility of weirdness, the possibility of high assembly number?

Episode duration: 1:59:27