#433 – Sara Walker: Physics of Life, Time, Complexity, and Aliens

Sara Walker is an astrobiologist and theoretical physicist. She is the author of a new book titled “Life as No One Knows It: The Physics of Life’s Emergence”. Please support this podcast by checking out our sponsors: – Notion: https://notion.com/lex – Motific: https://motific.ai – Shopify: https://shopify.com/lex to get $1 per month trial – BetterHelp: https://betterhelp.com/lex to get 10% off – AG1: https://drinkag1.com/lex to get 1 month supply of fish oil Transcript: https://lexfridman.com/sara-walker-3-transcript EPISODE LINKS: Sara’s Book – Life as No One Knows It: https://amzn.to/3wVmOe1 Sara’s X: https://x.com/Sara_Imari Sara’s Instagram: https://instagram.com/alien_matter PODCAST INFO: Podcast website: https://lexfridman.com/podcast Apple Podcasts: https://apple.co/2lwqZIr Spotify: https://spoti.fi/2nEwCF8 RSS: https://lexfridman.com/feed/podcast/ YouTube Full Episodes: https://youtube.com/lexfridman YouTube Clips: https://youtube.com/lexclips SUPPORT & CONNECT: – Check out the sponsors above, it’s the best way to support this podcast – Support on Patreon: https://www.patreon.com/lexfridman – Twitter: https://twitter.com/lexfridman – Instagram: https://www.instagram.com/lexfridman – LinkedIn: https://www.linkedin.com/in/lexfridman – Facebook: https://www.facebook.com/lexfridman – Medium: https://medium.com/@lexfridman OUTLINE: Here’s the timestamps for the episode. On some podcast players you should be able to click the timestamp to jump to that time. (00:00) – Introduction (10:40) – Definition of life (31:18) – Time and space (42:00) – Technosphere (46:25) – Theory of everything (55:06) – Origin of life (1:16:44) – Assembly theory (1:32:58) – Aliens (1:44:48) – Great Perceptual Filter (1:48:45) – Fashion (1:52:47) – Beauty (1:59:08) – Language (2:05:50) – Computation (2:15:37) – Consciousness (2:24:28) – Artificial life (2:48:21) – Free will (2:55:05) – Why anything exists

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Lex Fridman?

  The following is a conversation with Sarah Walker, her third time on this podcast. She is an astrobiologist and theoretical physicist interested in the origin of life and in discovering alien life on other worlds. She has written an amazing new upcoming book titled Life as No One Knows It: The Physics of Life's Emergence. This book is coming out on August 6th, so please go preorder it now. It will blow your mind. 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.

• 0:39Lex Fridman?

  We got Notion for notes, Motif for LLM deployment, Shopify for e-commerce, BetterHelp for mental health, and AG1 for delicious, delicious multivitamin drink. Choose wisely, my friends. Also, if you want to get in touch with me or to work with our amazing team, go to lexfridman.com/contact. And now onto the full ad reads. No ads in the middle. I try to make these interesting, but if you skip them, please still check out the sponsors. I enjoy their stuff. Maybe you will too. This episode is brought to you by Notion, a note-taking and team collaboration tool. I've been using it recently for note-taking on academic papers, specifically machine

• 1:22Lex Fridman?

  learning papers, and there's a lot of machine learning papers. And it's straight up just a great note-taking tool. But beyond that, it's a great collaboration tool for the note-taking process and the whole project management lifecycle. So it combines note-taking wikis, project management, and then there's an AI assistant that can summarize everything and anything, and you can ask it questions across all of those things. So it's not just for a single document, across all the documents. And obviously, people are collaborating on those documents, so you can ask questions. What did this person do? What is the status of this project? So on, so forth. It's just a really nice integration of LLMs. This is the fun about the question with LLMs.

• 2:06Lex Fridman?

  How do you leverage the obvious power that they possess to be useful?

• 2:12Lex Fridman?

  To whatever tasks we do, like what is the actual product here? And so Notion leverages them extremely well where the product is team collaboration on notes, wikis and project management. So really well done. Love to support people that do a great job of building a great software product. Try Notion AI for free when you go to notion.com/lex. That's all lowercase notion.com/lex to try the power of Notion AI today. This episode is brought to you by a new sponsor, Motific. It's a SaaS platform that helps businesses deploy LLMs and in general generative AI

• 2:52Lex Fridman?

  that are customized with RAG, Retrieval Augmented Generation, on organizational data sources. Obviously, these kinds of data sources are often super sensitive and that's where Motific comes in. They help companies with security and compliance. A little background here, since I had to do the deep dive myself a while back. Motific is created by Cisco, specifically Cisco's Outshift Group. And Outshift is doing cutting edge R and D stuff in Cisco. So Cisco has very, very, very long track record and reputation of working with giant businesses and helping them out in not messing stuff up. When you're dealing with sensitive data and when you're dealing with businesses that

• 3:36Lex Fridman?

  make a lot of money and already have products that bring in a lot of money and a lot of people rely on, you don't want to mess stuff up. I think specifically this task of taking organizational data that's private to the company, that has to remain very secure, it's very sensitive data, using the power of LLMs and search via the RAG framework on that data is super, super powerful. I think companies that do this well and quickly, which is what Motific helps with,

• 4:18Lex Fridman?

  will win because the productivity gains, nobody knows, but I don't think there's a ceiling. So it pays off to play with LLMs, but do so in a secure way. Visit Motific AI to learn more. That's M O T I F I C dot AI.

• 4:39Lex Fridman?

  This episode is also brought to you by Shopify, a platform designed for anyone to sell anywhere with a great looking online store. I have a site set up, luxstreamer.com/store. Has a few shirts on it, took a few minutes to set up. Super easy. They integrate third-party apps. I did that for the on-demand printing, so I don't have to think about any of that. All you do is upload the design, the shirts are sold and shipped. It's kind of an interesting experiment for me to understand how people look at you when you have a T-shirt with nothing on it and a T-shirt with something on it, especially if that something is recognizable. So if I have a Jimi Hendrix or Pink Floyd shirt, or Johnny Cash or Metallica shirt, there's going to be certain people that look at me with recognition and respect.

• 5:24Lex Fridman?

  And almost like they want to start a conversation with me. When I have a T-shirt, like a black T-shirt with nothing on it, that kind of look doesn't happen. If I went out more, I would take a notebook and actually make this a little bit more rigorous. But anyway, there's definitely a noticeable social effect that happens when you have a T-shirt with a cool thing on it. So I'm really happy with all the creators that are using Shopify to sell cool T-shirts. I wish there was a better discovery process, though. I'm always in search of buying cool T-shirts. Like I just, on Instagram, I think there was an advertisement for a set of T-shirts for classic movies.

• 6:08Lex Fridman?

  And that was really badass, but I scrolled past it and I regret it. See, that's like a piece of advertisement that actually works. But I wish there was a way to not take me from the scrolling experience, or maybe a way to bookmark it really naturally. There's already a natural sort of skepticism about advertisement, but here it worked. So like when advertisement is done well, it works. I just wish I saved it. But anyway, hopefully they use Shopify to sell shirts. If they don't, they should. And if you're thinking of selling shirts, use Shopify also. Sign up for a $1 per month trial period at Shopify.com/lex. That's all lowercase. Go to Shopify.com/lex to take your business to the next level today.

• 6:53Lex Fridman?

  This episode is brought to you by BetterHelp, spelled H E L P, help. They figure out what you need to match you with a licensed therapist in under 48 hours. Individuals, couples, the whole thing. What are my favorite couples' therapies in film? I feel like Breaking Bad had good ones. That's a series, but I'm trying to think of in a movie. That's a cool setting because I've been thinking about interviewing directors and actors more and more. And the setting of a couples' therapy is really interesting. It's a really interesting dynamic between a man and a woman and a therapist,

• 7:32Lex Fridman?

  and them trying to sort of make explicit the implicit drama that's been boiling over in their relationship. Obviously, the therapist one-on-one relationship is really interesting on film. Good Will Hunting with Robin Williams. Man, what a great, great performance. I miss that guy so much. What a truly special human being. Anyway, back in the real world, therapy, even when there's no camera, is really important for shining the light on the young in shadow. 350 million plus messages, 34,000 licensed therapists, 4.4 million people who have gotten help through BetterHelp.

• 8:17Lex Fridman?

  Check them out at betterhelp.com/lex and save on your first month. That's betterhelp.com/lex. This episode is also brought to you by AG1, an all-in-one daily drink to support better health and peak performance. I drink it every day, multiple times a day sometimes. Usually after a run, like I'm gonna go for a run in a little bit. It's already that Texas heat. It's warming up. It's warming up. It's creeping up on the 100-degree weather, and I love it. I don't care. The hotter it is, the tougher the run, the more of a mental test it is. And what I do is I speed up, take that feeling of discomfort,

• 8:56Lex Fridman?

  and allow myself to sit in it and visualize that feeling of discomfort fading. Sort of from a third-person perspective, it's just a feeling. And a feeling can be controlled. A feeling can be ignored. A feeling can be morphed from the negative to the positive. So for me, it's not just a meditative practice of letting go of all feelings and focusing on the breath. For me, It is also being able to control that discomfort and letting go of that discomfort. The feeling and the notion of discomfort, even when on the surface, there should be a lot of physical discomfort, because physical discomfort is first and foremost, a construction

• 9:38Lex Fridman?

  of the mind. It's not real. It's not real. As long as you believe it's not real, it's not real. And that's what I do. But when I get back home, extremely exhausted and uncomfortable, having overcome that challenge, I put an AG1 in the freezer for like 30 minutes. It has this great consistency. And then after a shower, I just take the drink and celebrate having overcome something difficult. They'll give you one month's supply of fish oil when you sign up at drinkag1.com/lex. This is the Lex Preven Podcast. To support it, please check out our sponsors in the description.

• 10:20Lex Fridman?

  And now, dear friends, here's Sarah Walker.

• 10:40Lex Fridman?

  You open the book, Life as No One Knows It, The Physics of Life's Emergence, with the distinction between the materialists and the vitalists. So what's the difference? Can you maybe define the two?

• 10:52Sara Walker?

  I think the question there is about whether life can be described in terms of matter and, you know, physical things, or whether there is some other feature that's not physical, that actually animates living things. So for a long time, people maybe have called that a soul. It's been really hard to pin down what that is. So I think the vitalist idea is really that it's kind of a dualistic interpretation, that there's sort of the material properties, but there's something else that animates life that is there when you're alive and it's not there when you're dead. And materialists kind of don't think that there's anything really special about the matter of life and the

• 11:37Sara Walker?

  material substrates that life is made out of. So they disagree on some really fundamental points.

• 11:43Lex Fridman?

  Is there a gray area between the two? Like, maybe all there is is matter, but there's so much we don't know that it might as well be magic. That like, whatever that magic that the vitalists see. Meaning like, there's just so much mystery that it's really unfair to say that it's boring and understood. And as simple as quote unquote physics.

• 12:09Sara Walker?

  Yeah, I think the entire universe is just a giant mystery. I guess that's what motivates me as a scientist. And so oftentimes, when I look at open problems like the nature of life or consciousness, or, you know, what is intelligence, or are there souls, or whatever, whatever question that we have that we feel like we aren't even on the tip of answering yet, I think, you know, we have a lot more work to do to really understand the answer to these questions. So it's not magic, it's just the unknown. And I think a lot of the history of humans coming to understand the world around us has been taking ideas that we once thought were magic or supernatural and really understanding them in a much deeper way.

• 12:52Sara Walker?

  That we learn what those things are. And they still have an air of mystery, even when we understand them. There's, there's no, there's no sort of bottom to our understanding.

• 13:03Lex Fridman?

  So do you think the vitalists have a point? That they're more eager and able to notice the magic of life?

• 13:12Sara Walker?

  I think that no tradition, vitalists included, is ever fully wrong about the nature of the things that they're describing. So a lot of times when I look at different ways that people have described things across human history, across different cultures, there's always a seed of truth in them. And I think it's really important to try to look for those, because if there are narratives that humans have been telling ourselves for thousands of years, for thousands of generations, there must be some truth to them. You know, we've been learning about reality. For a really long time, and we recognize the patterns that reality presents us. We don't always understand what those patterns are. And so I think it's really important to pay attention to that. So I don't think the vitalists were actually wrong.

• 13:54Sara Walker?

  And a lot of what I talk about in the book, but also I think about a lot just professionally, is the nature of our definitions of what's material and how science has come to invent the concept of matter. And that some of those things actually really are inventions that happened in a particular time and a particular technology that could learn about certain patterns and help us understand them. And that there are some patterns we still don't understand. And if we knew how to measure those things, or we knew how to describe them in a more rigorous way, we would realize that the material world, matter, has more properties than we thought that it did.

• 14:37Sara Walker?

  And one of those might be associated with the thing that we call life. Life could be a material property and still have a lot of the features that the vitalists thought were mysterious.

• 14:46Lex Fridman?

  So we may still expand our understanding what is incorporated in the category of matter that will eventually incorporate such magical things that the vitalists have noticed.

• 14:57Sara Walker?

  Yeah.

• 14:58Lex Fridman?

  Like life.

• 14:59Sara Walker?

  Yeah, so I think about, I always like to use examples from physics, so I'll probably do that to like, like, it's just my, it's my go-to place. But, you know, in, in the history of gravitational physics, for example, in the history of motion, you know, like, when Aristotle came up with his theories of motion, he did it by the material properties he thought things had. So there was a concept of things falling to earth because they were solid-like, and things raising to the heavens because they were air-like, and things moving around the planet because they were celestial-like. But then we came to realize that thousands of years later, and after the invention of many technologies that allowed us to actually measure time in a mechanistic way and track

• 15:40Sara Walker?

  planetary motion, and we could, you know, roll balls down incline planes and track that progress, we realized that if we just talked about mass and acceleration, we could unify all motion in the universe in a really simple description. So we didn't really have to worry about the fact that my cup is heavy and the air is light, like the same laws describe them. If we have the right material properties to talk about what those laws are actually interacting with. And so I think the issue with life is we don't know how to think about information in a material way. And so we haven't been able to build a unified description of what life is, or the kind

• 16:19Sara Walker?

  of things that evolution builds, because we haven't really invented the right material concept yet.

• 16:27Lex Fridman?

  So when talking about motion, the laws of physics appear to be the same everywhere out in the universe. You think the same is true for other kinds of matter that we might eventually include life in?

• 16:43Sara Walker?

  I think life obeys universal principles. I think there is some deep, underlying explanatory framework that will tell us about the nature of life in the universe, and will allow us to identify life that we can't yet recognize, because it's too different.

• 17:01Lex Fridman?

  You write about the paradox of defining life. Why does it seem to be so easy and so complicated at the same time?

• 17:08Sara Walker?

  You know, all the sort of classic definitions people want to use just don't work. They don't work in all cases. So Carl Sagan had this wonderful essay on definitions of life, where I think he talks about aliens coming from another planet. If they saw Earth, they might think that cars were the dominant life form, because there's so many of them on our planet. And like, humans are inside them, and you might want to exclude machines. But any definition, you know, like, classic biology textbook definitions would also include them. And so, you know, he wanted to draw a boundary between these kind of things by trying to exclude them, but they were naturally included by the definitions people want to give. And in fact, what he ended up pointing out is that all of the definitions of life

• 17:50Sara Walker?

  that we have, whether it's life is a self reproducing system, or life eats to survive, or life requires compartments, whatever it is, there's always a counter example that challenges that definition. This is why viruses are so hard, or why fire is so hard. And so we've had a really hard time trying to pin down, from a definitional perspective, exactly what life is.

• 18:16Lex Fridman?

  Yeah, you actually bring up the zombie ant fungus. I enjoyed looking at this thing. As an example of one of the challenges, you mentioned viruses, but this, this is a parasite. Look at that.

• 18:27Sara Walker?

  Did you see this in the jungle?

• 18:28Lex Fridman?

  Infects ants. Actually, one of the interesting things about the jungle, everything is ephemeral. Like, everything eats everything really quickly. So if you, if an organism dies, that organism disappears.

• 18:43Sara Walker?

  Yeah.

• 18:44Lex Fridman?

  It's a machine that doesn't have, I wanted to say doesn't have a memory or a history, which is interesting, given your work on history in defining a living being. The jungle forgets very quickly. It wants to erase the fact that you existed very quickly.

• 19:01Sara Walker?

  Yeah, but it can't erase it. It's just restructuring it. And I think the other thing that is really, you know, vivid to me about this example that you're giving is how much death is necessary for life. So I, I worry a bit about notions of immortality and whether immortality is a good thing or not. So I have sort of a broad conception that life is the only thing the universe generates that actually has even the potential to be immortal. But that's as like this sort of process that you're describing where life is about memory and historical contingency and construction of new possibilities. But when you look at any instance of life, especially one as dynamic as what you're describing, it's a constant birth and death process. But that birth and

• 19:45Sara Walker?

  death process is like the way that the universe can explore what possibilities can exist. And not everything, not every possible human or every possible ant or every possible zombie ant or every possible tree will ever live. So it's, you know, it's an incredibly dynamic and creative place because of all that death.

• 20:08Lex Fridman?

  So does this thing, this is a parasite that needs the ant. So is this a living thing or is this not a living thing? So this is

• 20:16Sara Walker?

  Yeah.

• 20:17Lex Fridman?

  It just pierces the ant. I mean, it

• 20:19Sara Walker?

  Right.

• 20:20Lex Fridman?

  And I've seen a lot of this, by the way, organisms working together in the jungle, like ants protecting a delicious piece of fruit. So they need the fruit, but like if you touch that fruit, they're going to, like, the forces emerge. They're fighting you. They're defending that food

• 20:37Sara Walker?

  Right.

• 20:38Lex Fridman?

  to the death. It's just, nature seems to find mutual benefits, right?

• 20:42Sara Walker?

  Yeah, it does. I think the thing that's perplexing for me about these kind of examples is effectively the ant's dead, but it's staying alive now because it's piloted by this fungus. And so that gets back to this thing that we were talking about a few minutes ago about how the boundary of life is really hard to define. So any time that you want to draw a boundary around something and you say, this feature is the thing that makes this alive, or this thing is alive on its own, there's not ever really a clear boundary. And these kind of examples are really good at showing that because it's like the thing that you would have thought is the living organism is now dead, except that it has another living organism

• 21:22Sara Walker?

  that's piloting it. So the two of them together are alive in some sense, but they're now in this kind of weird symbiotic relationship that's taking the ant to its death.

• 21:32Lex Fridman?

  So what do you do with that in terms of when you try to define life?

• 21:36Sara Walker?

  I think we have to get rid of the notion of an individual as being relevant. And this is really difficult because a lot of the ways that we think about life, like the fundamental unit of life is the cell, individuals are alive. But we don't think about how gray that distinction is. So for example, you might consider self reproduction to be the most defining feature of life. A lot of people do actually like one of these standard different definitions that a lot of people may feel like to use in astrobiology is life is a self sustaining chemical system capable of Darwinian evolution, which I was once quoted as agreeing with. And I was really offended because I hate that definition.

• 22:18Sara Walker?

  I think it's terrible. And I think it's terrible that people use it. I think like every word in that definition is actually wrong as a descriptor of life.

• 22:25Lex Fridman?

  Life is a self sustaining chemical system capable of Darwinian evolution. Why is that? That seems like a pretty good definition.

• 22:31Sara Walker?

  Yeah, I know. If you want to make me angry, you can pretend I said that.

• 22:35Sara Walker?

  And believed it.

• 22:36Lex Fridman?

  So self sustaining, uh, chemical system, Darwinian evolution. What is self sustaining? What's, what's, what's so frustrating? I mean, which aspect is frustrating to you, but it's also those are very interesting words.

• 22:48Sara Walker?

  Yeah, they're all interesting words. Um, and you know, together they sound really smart and they sound like they box in what life is. But you can use any of this, any of the words individually and you can come up with counter examples that don't fulfill that property. The self sustaining one is really interesting, thinking about, um, humans, right? Like, we're not self sustaining, we're dependent on societies. And so, you know, I find it paradoxical that, you know, it might be that societies, because they're self sustaining units, are now more alive than individuals are. And that could be the case, but I still think we have some property associated with life. I mean, that's the thing that we're trying to describe. So that one's quite hard. And in general, you know, no organism is really self sustaining. They always require an environment.

• 23:32Sara Walker?

  So being self sustaining is coupled in some sense to the world around you. Uh, we don't live in a vacuum. Um, so, so that part's already challenging. And then you can go to chemical system. I don't think that's good either. I think there's a confusion because life emerges in chemistry, that life is chemical. I don't think life is chemical. I think life emerges in chemistry because chemistry is the first thing the universe builds, where it cannot exhaust all the possibilities, because the combinatorial space of chemistry is too large.

• 24:07Lex Fridman?

  Well, but is it possible to have a life that's not a chemical system?

• 24:09Sara Walker?

  Yes.

• 24:10Lex Fridman?

  Uh, there's a guy I know named Lee Cronin, has been on a podcast a couple of times, who just got really pissed off listening to this. He probably just got really pissed off hearing that. I hope people somehow don't know he's a chemist.

• 24:22Sara Walker?

  Yeah, but he would agree with that statement.

• 24:24Lex Fridman?

  Would he? I don't think he would. I don't think he would. He would broaden the definition of chemistry until it would include everything.

• 24:31Sara Walker?

  Oh, sure.

• 24:32Lex Fridman?

  Okay, so you're.

• 24:33Sara Walker?

  Or maybe, I don't know.

• 24:34Lex Fridman?

  But wait, but you said that universe, that's the first thing it creates is chemistry.

• 24:38Sara Walker?

  Where the, very precisely, it's not the first thing it creates, obviously, like, it has to make atoms first, but it's the first thing. Like, if you think about, you know, the universe originated, uh, atoms were made in, you know, big bang, nuclear synthesis, and then later in stars, and then planets formed, and planets become engines of chemistry. They start exploring what kind of chemistry is possible. And. The combinatorial space of chemistry is so large that even on every planet in the entire universe, you will never express every possible molecule. I like this example, actually, that Lee gave me, which is to think about Taxol. It has a molecular weight of about 853. It's got, you know, a lot of atoms, but it's not astronomically large.

• 25:23Sara Walker?

  And if you tried to make one molecule with that molecular formula in every three-dimensional shape you could make with that molecular formula, it would fill 1.5 universes in volume. So with one unique molecule, that's just one molecule. So, chemical space is huge. And I think it's really important to recognize that because if you want to ask a question of why does life emerge in chemistry? Well, life emerges in chemistry because life is the physics of how the universe selects what gets to exist. And those things get created along historically contingent pathways and memory and all the other stuff that we can talk about.

• 26:05Sara Walker?

  But the universe has to actually make historically contingent choices in chemistry because it can't exhaust all possible molecules.

• 26:11Lex Fridman?

  What kind of things can you create that's outside the combinatorial space of chemistry? That's what I'm trying to understand.

• 26:18Sara Walker?

  Oh, if it's not chemical. So I think some of the things that have evolved on our biosphere, I would call as much alive as chemistry, as a cell, but they seem much more abstract. So, for example, I think language is alive. I think, or at least life, I think memes are, I think.

• 26:39Lex Fridman?

  You're saying language is life.

• 26:40Sara Walker?

  Yeah.

• 26:41Lex Fridman?

  Language is alive. Oh, boy. I'm gonna have to explore that one.

• 26:45Sara Walker?

  Life, maybe not, maybe not alive, but I don't, actually, I don't know where I stand exactly on that. I've been thinking about that a little bit more lately. But mathematics, too. And it's interesting because people think that math has this platonic reality that exists outside of our universe. And I think it's a feature of our biosphere and it's telling us something about the structure of ourselves. And I find that really interesting because when you would sort of internalize all of these things that we noticed about the world and you start asking, well, what do these look like if I was, you know, something outside of myself observing these systems that we're all embedded in, what would that structure look like? And I think we look really different than the way that we talk about what we look like to each other.

• 27:30Lex Fridman?

  What do you think a living organism in math is? Is it one exoteric system or is it individual theorems or is it?

• 27:37Sara Walker?

  I think it's the fact that it's open-ended in some sense. It's another open-ended combinatorial space and the recursive properties of it allow creativity to happen, which is what you see with, you know, like the revolution in the last century with Gödel's theorem and Turing and, you know, there's, there's clear places where mathematics notices holes in the universe.

• 28:05Lex Fridman?

  So it seems like you're sneaking up on a different kind of definition of life, open-ended, large combinatorial space.

• 28:12Sara Walker?

  Yeah.

• 28:13Lex Fridman?

  Room for creativity.

• 28:14Sara Walker?

  Definitely not chemical. I mean, chemistry is one substrate.

• 28:19Lex Fridman?

  Strictly to chemical.

• 28:20Sara Walker?

  Yeah.

• 28:21Lex Fridman?

  Okay, what about the third thing, which I think will be the hardest because you probably like it the most is evolution or selection.

• 28:28Sara Walker?

  Well, specifically, it's Darwinian evolution.

• 28:30Lex Fridman?

  Darwinian.

• 28:31Sara Walker?

  And I think Darwinian evolution is a problem, but the reason that that definition is a problem is not because evolution is in the definition, but because the implication is that, you know, that most people would want to make is that an individual is alive. And the evolutionary process, at least the Darwinian evolutionary process, most evolutionary processes, they don't happen at the level of individuals. They happen at the level of populations. So again, you would be saying something like what we saw with the self-sustaining definition, which is that populations are alive, but individuals aren't because populations evolve and individuals don't. And obviously, like, maybe you're alive because, you know, your gut microbiome is evolving, but Lex is an entity right now is not evolving by canonical

• 29:15Sara Walker?

  theories of evolution. In assembly theory, which is attempting to explain life.

• 29:21Sara Walker?

  Evolution is a much broader thing, so.

• 29:24Lex Fridman?

  So then, an individual organism can evolve under assembly theory?

• 29:27Sara Walker?

  Yes, you're constructing yourself all the time. Assembly theory is about construction and how the universe selects for things to exist.

• 29:34Lex Fridman?

  What if you formulate everything like a population is a living organism?

• 29:37Sara Walker?

  That's fine, too. But, but this again gets back to, so, um, so I think what all of, you know, like, we can nitpick at definitions. I don't think it's like incredibly helpful to do it, but the reason for, for me.

• 29:49Lex Fridman?

  It's fun.

• 29:50Sara Walker?

  Yeah, it is fun. It is really fun. And actually, I do, I do think it's useful in the sense that when you see the ways that they all break down, you either have to keep forcing in your like sort of conception of life you want to have, or you have to say, all these definitions are breaking down for a reason. Maybe I should adopt a more expansive definition that encompasses all the things that I think and are life. And so for me, I think life is the process of how information structures matter over time and space. And, and an example of life is what emerges on a planet and yields an open-ended cascade of generation of structure and increasing complexity. And this is the thing that life is.

• 30:33Sara Walker?

  And any individual is just a particular instance of these lineages that are, you know, structured across time. Um, and so we focus so much on these individuals that are these short temporal moments in this larger causal structure that actually is the life on our planet. And I think that's why these definitions break down, because they're not general enough. They're not universal enough. They're not deep enough. They're not abstract enough to actually capture that regularity.

• 31:01Lex Fridman?

  Because we're focused on those, that little ephemeral thing.

• 31:05Sara Walker?

  Yeah.

• 31:05Lex Fridman?

  That we call human life.

• 31:07Sara Walker?

  Aristotle focusing on, you know, heavy things falling because they're earth-like and, you know, things floating because they're air-like. It's the wrong thing to focus on.

• 31:18Lex Fridman?

  So what exactly are we missing by focusing on such a short span of time?

• 31:23Sara Walker?

  I think we're missing most of what we are. So one of the issues, I've been thinking about this like really viscerally lately. It's weird when you do theoretical physics because I think it like literally changes the structure of your brain and you see the world differently, especially when you're trying to build new abstractions.

• 31:39Lex Fridman?

  Do you think it's possible if you're a theoretical physicist that like it's easy to fall off the cliff and go descend into madness?

• 31:46Sara Walker?

  I mean, I think you're always on the edge of it, but I think what is amazing about being a scientist and trying to do things rigorously is it keeps your sanity. So I think if I wasn't a theoretical physicist, I would, I would be probably not sane. But what it forces you to do is hold the fire, like you have to hold yourself to the fire of like, these abstractions in my mind have to really correspond to reality and I have to really test that all the time. And so I love building new abstractions and I love going to those like incredibly creative, you know, spaces that people don't see as part of the way that we understand the world now. But ultimately, I have to make sure that whatever I'm pulling

• 32:28Sara Walker?

  from that space is something that's really usable and really like relates to the world outside of me. That's what science is.

• 32:35Lex Fridman?

  So we were talking about what we're missing when we look at a small stretch of time and a small stretch of space.

• 32:42Sara Walker?

  Yeah. So the issue is we evolve perception to see reality a certain way, right? So for us, space is really important and time feels fleeting. And I, you know, I had a really wonderful mentor, Paul Davies, most of my career. And Paul's amazing because he gives these like little seed thought experiments all the time. Like, you know, something he used to ask me all the time was when I was a postdoc, this is kind of a random tangent, but was like, you know, how much of the universe could be converted into technology if you were thinking about like, you know, long-term futures and stuff like that. And it's like a weird thought experiment, but like, there's a lot of deep things there. And I do think a lot about the fact that we're really limited in our interactions with reality by the particular architectures that we evolved.

• 33:27Sara Walker?

  And so we're not seeing everything. And in fact, our technology tells us this all the time because it allows us to see the world in new ways by basically allowing us to perceive the world in ways that we couldn't otherwise. And so what I'm getting at with this is I think that living objects are actually huge. Like, they're some of the biggest structures in the universe, but they are not big in space, they are big in time. And we actually can't resolve that feature. We don't interact with it on a regular basis. So we see them as these fleeting things that have this really short temporal clock time without seeing how large they are. When I'm saying time here, I really like the way that people could picture it is in terms of causal structures. So if you think about the history of the universe to get to you,

• 34:12Sara Walker?

  and you imagine that that entire history is you, that is the picture I have in my mind when I look at every living thing.

• 34:22Lex Fridman?

  So you have a tweet for everything. You tweeted-

• 34:26Sara Walker?

  Doesn't everyone?

• 34:28Lex Fridman?

  You have a lot of poetic, profound tweets. Sometimes-

• 34:31Sara Walker?

  Thank you.

• 34:32Lex Fridman?

  They're puzzles that take a long time to figure out.

• 34:36Sara Walker?

  Well, you know what it is? The trick is, the reason they're hard to write is because it's compressing a very deep idea into a short amount of space. And I really like doing that intellectual exercise because I find it productive for me.

• 34:47Lex Fridman?

  Yeah, it's a very interesting kind of compression algorithm, though.

• 34:51Sara Walker?

  Yeah, I like language. I think it's really fun to play with.

• 34:53Lex Fridman?

  Yeah, I wonder if AI can decompress it. That'd be-

• 34:57Sara Walker?

  I think I would like to try this, but I think I use language in certain ways that are non-canonical, and I do it very purposefully. And it would be interesting to me how AI would interpret it.

• 35:09Lex Fridman?

  Yeah, your tweets would be a good Turing test-

• 35:11Sara Walker?

  There you go.

• 35:11Lex Fridman?

  For superintelligence. Anyway, you tweeted that things only look emergent because we can't see time. So if we could see time, what would the world look like? You're saying you'll be able to see everything that an object has been, every step of the way that led to this current moment. And all the interactions that required to make that evolution happen. You would see this gigantic tail.

• 35:44Sara Walker?

  The universe is far larger in time than it is in space.

• 35:49Lex Fridman?

  Yeah.

• 35:50Sara Walker?

  And this planet is one of the biggest things in the universe.

• 35:55Lex Fridman?

  Also, the more complexity, the bigger.

• 35:57Sara Walker?

  Yeah, so like, yeah, tech technosphere. I think the the modern technosphere is the largest object in time in the universe that we know about.

• 36:06Lex Fridman?

  And when you say technosphere, what do you mean?

• 36:08Sara Walker?

  I mean, the global integration of life and technology on this planet.

• 36:14Lex Fridman?

  So all the things, all the technological things were created?

• 36:16Sara Walker?

  Mm hmm. But I don't think of them as separate. They're like very integrated with the structure that generated them. So you can almost imagine it like time is constantly bifurcating and it's generating new structures. And these new structures are, you know, locally constructing the future. And so things like you and I are very close together in time because we didn't diverge like very early in history. Universe is very recent. And I think this is one of the reasons that we can understand each other so well and we can communicate effectively. And I might have some sense of what it feels like to be you. But, you know, other organisms bifurcated from us in time earlier. This is just the concept of phylogeny, right?

• 37:00Sara Walker?

  But if you take that deeper and you really think about that as the structure of the physics that generates life.

• 37:08Sara Walker?

  And you take that very seriously, all of that causation is is still bundled up in the objects we observe today. And so, so you and I are are close in this temporal structure. But we're also, we're so close because we're really big and we only are very different. And sort of like the most recent moments in the time that's like embedded in us.

• 37:35Sara Walker?

  It's hard to use words to visualize what's in minds.

• 37:40Sara Walker?

  I have such a hard time with this sometimes. I'm like, I like, I actually, I was thinking in the way over here. I was like, I like, you know, you have pictures in your brain and then they're hard to put into words. But I realized I always say I have a visual, but it's not actually I have a visual. It's I have a feeling because oftentimes I cannot actually draw a picture in my mind for the things that I say. But sometimes they go through a picture before they get to words. But I like experimenting with words because I think they help paint pictures.

• 38:07Lex Fridman?

  Yeah, it's again, some kind of compressed feeling that you can query to get a sense of the bigger visualization that you have in mind. It's just got a really nice compression.

• 38:20Lex Fridman?

  But I think the idea of this object that in it contains all the information about the history of identity that you see now, just trying to visualize that is pretty cool.

• 38:31Sara Walker?

  Yeah.

• 38:32Lex Fridman?

  It's, I mean, obviously the mind breaks down quickly as you step seconds and minutes back in time.

• 38:39Sara Walker?

  For sure.

• 38:41Lex Fridman?

  I guess it's just a gigantic object.

• 38:46Sara Walker?

  Yeah.

• 38:47Lex Fridman?

  We're supposed to be thinking about.

• 38:48Sara Walker?

  Yeah, I think so. And I think this is one of the reasons that we have such an ability to abstract as humans, because we are so gigantic that like the space that we can go back into is really large. So like the more abstract you're going, like the deeper you're going in that space.

• 39:03Lex Fridman?

  But in that sense, aren't we fundamentally all connected?

• 39:06Sara Walker?

  Yes. And this is why the definition of life cannot be the individual. It has to be these lineages because they're all connected, they're interwoven and they're exchanging parts all the time.

• 39:15Lex Fridman?

  Yeah. So that maybe there's certain aspects of those lineages that can be lifelike. They can be characteristics that can be measured like with the Solvay theory that have more or less life. But they're all just fingertips of a.

• 39:28Sara Walker?

  Yeah.

• 39:29Lex Fridman?

  Of a much bigger object.

• 39:30Sara Walker?

  Yeah, I think life is very high dimensional. And in fact, I think you can be alive in some dimensions and not in others. Like if you could, if you could project all the causation that's in you in some, in some features of you, you know, very little causation is required and like very little history. And in some features, a lot is. So it's quite difficult to take this really high dimensional, very deep structure and project it into things that we really can understand and say like, this is the one thing that we're seeing because it's not one thing.

• 40:06Lex Fridman?

  It's funny, we're talking about this now and I'm slowly starting to realize, one of the things I saw when I took ayahuasca afterwards, actually. So the actual ceremony is four or five hours, but afterwards you're still riding whatever the thing that you're riding. And I got a chance to afterwards hang out with some friends and just shoot the shit in the, you know, in the forest. And I get to see their faces.

• 40:35Lex Fridman?

  And what was happening with their faces and their hair is I would get this interesting effect. First of all, everything was beautiful and I just had so much love for everybody. But I could see their past selves like behind them. It was this effect where I guess it's a blurring effect of where like if I move like this, the faces that were just there are still there and it would just float like this, these behind them, which will create this incredible effect. But it's also another way to think about that is I'm visualizing a little bit of that object of the thing they wore just a few seconds ago.

• 41:18Sara Walker?

  Yeah.

• 41:19Lex Fridman?

  It's a cool little effect.

• 41:20Sara Walker?

  That's very cool.

• 41:21Lex Fridman?

  And now it's like giving it a bit more profundity to the effect that was just beautiful aesthetically, but it's also.

• 41:30Lex Fridman?

  Beautiful from a physics perspective because that is a past self. I get a little glimpse at the past selves that they were. But then you take that to its natural conclusion, not just a few seconds ago, but just to the beginning of the universe. And you can probably get to that.

• 41:48Sara Walker?

  Millions of years, yeah.

• 41:49Lex Fridman?

  Get down that lineage.

• 41:50Sara Walker?

  It's crazy that there's billions of years inside all of us.

• 41:53Lex Fridman?

  All of us.

• 41:54Sara Walker?

  Yeah.

• 41:55Lex Fridman?

  And then we connect, obviously.

• 41:56Sara Walker?

  Yeah.

• 41:57Lex Fridman?

  Not too, not too long ago.

• 41:58Sara Walker?

  Yeah.

• 42:00Lex Fridman?

  You, you mentioned just the technosphere and you also wrote that the most alive thing on this planet is our technosphere.

• 42:06Sara Walker?

  Yeah.

• 42:07Lex Fridman?

  Why is it technology we create a kind of life form? Why do you, why are you seeing it as life?

• 42:12Sara Walker?

  Because it's creative, but with us, obviously, like not independently of us. And also because of this sort of lineage view of life. And I, I think about life often as a planetary scale phenomena. Cause that's sort of the natural boundary for all of this causation that's bundled in every object in our biosphere. And so for me, it's just sort of the current boundary of how far life on our planet has pushed into the things that our universe can generate. And so it's the furthest thing. It's the biggest thing. And I think a lot about the nature of life across different scales.

• 42:51Sara Walker?

  And so, uh, you know, we have cells inside of us that are alive and we feel like we're alive, but we don't often think about the societies that we're embedded in as alive or a global scale organization of us and our technology on the planet as alive. Um, but I think if you have this, uh, deeper view into the nature of life, uh, which I think is necessary also to solve the origin of life, then you have to include those things.

• 43:20Lex Fridman?

  All of them. So you have to simultaneously think about.

• 43:23Sara Walker?

  Every scale.

• 43:24Lex Fridman?

  At every single scale.

• 43:25Sara Walker?

  Yeah.

• 43:26Lex Fridman?

  The planetary and the bacteria level.

• 43:28Sara Walker?

  Yeah. This is the hard thing about solving the problem of life, I think, is how many things you have to integrate into building a sort of a. A unified picture of this thing that we want to call life. And a lot of our theories of physics are built on building deep regularities that explain a really broad class of phenomena. And I think we haven't really traditionally thought about life that way. But I think to get at some of these hardest questions, like looking for life on other planets or the origin of life, you really have to think about it that way. And so, most of like my professional work is just trying to understand like every single thing on this planet that might be an example of life, which is pretty much everything. And then trying to figure out like, what's the deeper structure underlying that?

• 44:12Lex Fridman?

  Yeah. Schrodinger wrote that living matter, while not alluding to laws of physics as established up to date, is likely to involve other laws of physics hitherto unknown. So to him.

• 44:26Sara Walker?

  I love that quote.

• 44:29Lex Fridman?

  There was a sense that at the bottom of this are new laws of physics that could explain this thing that we call life.

• 44:38Sara Walker?

  Yeah. Schrodinger really tried to do what physicists try to do, which is explain things. And he, his attempt was to try to explain life in terms of non-equilibrium physics because he thought that was the best description that we could generate at the time. And so, he did come up with something really insightful, which was to predict the structure of DNA as an aperiodic crystal. And that was for a very precise reason that, you know, that was the only kind of physical structure that could encode enough information to actually specify a cell. We knew some things about genes, but not about DNA and its actual structure when he proposed that.

• 45:21Sara Walker?

  But in the book, he tried to explain life is kind of going against entropy. And so, some people talked about it as like Schrodinger's paradox. How can life persist when the second law of thermodynamics is there? But in open systems, that's not so problematic. And really, the question is, why can life generate so much order? And we don't have a physics to describe that. And it's interesting, you know, generations of physicists have thought about this problem. Oftentimes, it's like when people are retiring, they're like, oh, now I can work on life. Or they're like more senior in their career and they've worked on other more traditional problems. And there's still a lot of impetus in the physics community to think that non-equilibrium physics will explain life. But I think that's not the right approach.

• 46:05Sara Walker?

  I don't think ultimately the solution to what life is is there. And I don't really think entropy has much to do with it unless it's entirely reformulated.

• 46:15Lex Fridman?

  Well, because you have to explain how interesting water, how complexity emerges from the soup.

• 46:20Sara Walker?

  Yes, from randomness.

• 46:22Lex Fridman?

  From randomness. Physics currently can't do that.

• 46:24Sara Walker?

  No, physics hardly even acknowledges that the universe is random at its base.

• 46:30Sara Walker?

  We like to think we live in a deterministic universe and everything's deterministic. But I think that's probably, you know, an artifact of the way that we've written down laws of physics since Newton invented modern physics and his conception of motion and gravity, which, you know, he formulated laws that had initial conditions and fixed dynamical laws. And that's been sort of become the standard canon of how people think the universe works and how we need to describe any physical system is with an initial condition and a law of motion. And I think that's not actually the way the universe really works. I think it's a good approximation for the kind of systems that physicists have studied so far.

• 47:12Sara Walker?

  And I think it will radically fail in the long term at describing reality at its more basal levels. But I'm not saying there's a base. I don't think that reality has a ground. And I don't think there's a theory of everything. But I think there are better theories and I think there are more explanatory theories. And I think we can get to something that explains much more than the current laws of physics do.

• 47:35Lex Fridman?

  When you say theory of everything, you mean like everything, everything?

• 47:38Sara Walker?

  Yeah, you know, like in physics right now, it's really popular to talk about theories of everything. So string theory is supposed to be a theory of everything because it unifies quantum mechanics and gravity. And, you know, people have their different pet theories of everything. And the challenge with a theory of everything, I really love this quote from David Krakauer, which is a theory of everything is a theory of everything, except those things that theorize.

• 48:01Lex Fridman?

  Oh, you mean removing the observer from the thing?

• 48:03Sara Walker?

  Yeah, but it's also, it's also weird because if a theory of everything explained everything, it should also explain the theory. So the theory has to be recursive. And none of our theories of physics are recursive. So it's just, it's a weird concept.

• 48:17Lex Fridman?

  Yeah, but it's very difficult to integrate the observer into a theory.

• 48:20Sara Walker?

  I don't think so. I think you can build a theory acknowledging that you're an observer inside the universe.

• 48:26Lex Fridman?

  But doesn't it become recursive in that way? And that's, you're saying it's possible to make a Theory that's okay with that?

• 48:33Sara Walker?

  I think so. I mean, I don't think there's always gonna be

• 48:38Sara Walker?

  the paradox of another meta level you could build on the meta level, right? So like, if you assume this is your universe and you're the observer outside of it, you have some meta description of that universe, but then you need a meta description of you describing that universe, right? So, you know, this is one of the biggest challenges that we face, being observers inside our universe and also, you know, why the paradox is and the foundations of mathematics and any place that we try to have observers in the system or a system describing itself show up. But I think it is possible to build a physics that builds in those things intrinsically without having them be paradoxical or have holes in the descriptions. And so, one, one place I think about this quite a lot,

• 49:22Sara Walker?

  which I think can give you sort of a more concrete example is, is the nature of like what we call fundamental. So, we typically define fundamental right now in terms of the smallest indivisible units of matter. So again, you have to have a definition of what you think material is and matter is. But right now, the, you know, what's fundamental are elementary particles. And we think they're fundamental because we can't break them apart further. And obviously, we have theories like string theory that if they're right, would replace the current description of what's the most fundamental thing in our universe by replacing with something smaller. But we can't get to those theories because we're technologically limited. And so, if you, if you look at this from a historical perspective

• 50:08Sara Walker?

  and you think about explanations changing as physical systems like us learn more about the reality in which they live. We once considered atoms to be the most fundamental thing. And, you know, it literally comes from the word indivisible. And then we realized atoms had substructure because we built better technology, which allowed us to quote unquote, "see the world better" and resolve smaller features of it. And then we built even better technology, which allowed us to see even smaller structure and get down to the standard model particles. And we think that there's, might be structure below that, but we can't get there yet with our technology. So what's fundamental? The way we talk about it in Current physics is not actually fundamental.

• 50:53Sara Walker?

  It's the boundaries of what we can observe in our universe, what we can see with our technology. And so if you want to build a theory that's about us and about what's inside the universe that we can observe, not what's at the boundary of it, you need to talk about objects that are in the universe that you can actually break apart to smaller things. So I think the things that are fundamental are actually the constructed objects. They're the ones that really exist and you really understand their properties because you know how the universe constructed them, because you can actually take them apart. You can understand the intrinsic laws that built them. But the things at the boundary are just at the boundary. They're evolving with us and we'll learn more about that structure as we go along. But really, if we want to talk about what's fundamental inside our universe, we have

• 51:37Sara Walker?

  to talk about all these things that are traditionally considered emergent, but really just structures in time that have causal histories that constructed them and are really actually what our universe is about.

• 51:51Lex Fridman?

  So we should focus on the construction methodology as the fundamental thing. Do you think there's a bottom to the smallest possible thing that makes up the universe?

• 52:01Sara Walker?

  I don't see one.

• 52:02Lex Fridman?

  And it'll take way too long. It'll take longer to find that than it will to understand the mechanism that created life.

• 52:09Sara Walker?

  I think so, yeah. I think for me, the frontier in modern physics, where the new physics lies, is not in high-energy particle physics, it's not in quantum gravity, it's not in any of these sort of traditionally sold, this is going to be the newest, deepest insight we have into the nature of reality. It is going to be in studying the problems of life and intelligence and the things that are sort of also our current existential crises as a civilization or a culture that's going through, you know, an existential trauma of inventing technologies that we don't understand right now.

• 52:42Lex Fridman?

  Existential trauma and the terror we feel that that technology might somehow destroy us, us meaning living, intelligent living organisms.

• 52:51Sara Walker?

  Right.

• 52:52Lex Fridman?

  Yet we don't understand what that even means.

• 52:53Sara Walker?

  Well, humans have always been afraid of our technologies though, right? So it's kind of a fascinating thing that every time we invent something we don't understand, it takes us a little while to catch up with it.

• 53:02Lex Fridman?

  I think also in part, humans kind of love being afraid.

• 53:06Sara Walker?

  Yeah, we love being traumatized.

• 53:08Lex Fridman?

  It's weird.

• 53:09Sara Walker?

  We want to learn more and then when we learn more, it traumatizes us.

• 53:14Sara Walker?

  You know, I never thought about it this before, but I think this is one of the reasons I love what I do is because it traumatizes me all the time. That sounds really bad. But what I mean is like, I love the shock of like realizing that, like coming to understand something in a way that you never understood it before. I think it seems to me when I see a lot of the ways other people react to new ideas that they don't feel that way intrinsically. But for me, that's like, that's why I do what I do. I love, I love that feeling.

• 53:42Lex Fridman?

  But you're also working on a topic where it's fundamentally ego destroying because you're talking about like, life. It's humbling to think that we're not, the individual human is not special.

• 53:55Sara Walker?

  Yeah.

• 53:57Lex Fridman?

  And you're like, very viscerally exploring that.

• 54:00Sara Walker?

  Yeah. I'm trying to embody that. Because I think you have to live the physics to understand it. But there's a great quote about Einstein. I don't know if this is true or not, that he once said that he could feel like a beam in his belly. And I think, but I think like, you gotta think about it though, right? Like, if you're a really deep thinker and you're really thinking about reality that deeply, and you are part of the reality that you're trying to describe, like, you feel it. You really feel it.

• 54:28Lex Fridman?

  That's what I was saying about, you're always like, walking along the cliff. If you fall off, you're falling into madness.

• 54:35Sara Walker?

  Yes. It's a constant, constant descent into madness.

• 54:38Lex Fridman?

  The fascinating thing about physicists and madness is that you don't know if you've fallen off the cliff.

• 54:43Sara Walker?

  Yeah, I know, you don't know.

• 54:44Lex Fridman?

  That's the cool thing.

• 54:46Sara Walker?

  I rely on other people to tell me. Actually, this is very funny, because like, I have these conversations with my students often, like, they're worried about going crazy. I have to like, reassure them that like, one of the reasons they'll stay sane is by trying to work on concrete problems.

• 55:00Lex Fridman?

  Going crazy or waking up? I don't know which one, which one it is.

• 55:05Sara Walker?

  Yeah.

• 55:06Lex Fridman?

  So what do you think is the origin of life on Earth? And how can we talk about it in a productive way?

• 55:13Sara Walker?

  The original life is like this boundary that the universe can only cross if a structure that emerges can reinforce its own existence, which is self-reproduction, autokatalysis, things people traditionally talk about. But it has to be able to maintain its own existence against this sort of randomness that happens in chemistry and this randomness that happens in the quantum world. And like, it's in some sense, the emergence of like a deterministic structure that says, you know, I'm going to exist and I'm going to keep going. But, you know, pinning that down is really hard. We have ways of thinking about it in assembly theory that I think are pretty rigorous. And one of the things I'm really excited about is trying to actually quantify in an

• 55:58Sara Walker?

  assembly theoretic way when the original life happens. But the basic process I have in mind is like a system that has no causal contingency, no constraints of objects, basically constraining the existence of other objects or forming or allowing the existence of other objects. And so that sounds very abstract, but like you can just think of like a chemical reaction can't happen if there's not a catalyst, for example, or a baby can't be born if there wasn't a parent. So there's a lot of causal contingency that's necessary for certain things to happen. So you think about this sort of unconstrained, random system, there's nothing that reinforces the existence of other things.

• 56:42Sara Walker?

  So, so the sort of resources just get washed out in all of these different structures and none of them exist again. Or they just, you know, they're, they're not very complicated if they're in high abundance. And some random events allow some things to start reinforcing the existence of a small subset of objects. And if they can do that, you know, like just molecules basically recognizing each other and being able to catalyze certain reactions, there's this kind of transition point that happens where

• 57:17Sara Walker?

  Unless you get a self-reinforcing structure, something that can maintain its own existence, it actually can't cross this boundary to make any objects in high abundance without having this sort of past history that it's carrying with us and maintaining the existence of that past history. And that boundary point where objects can't exist unless they have this selection and history in them is what we call the original life. And pretty much everything beyond that boundary is holding on for dear life to all of the causation and causal structure that's basically put it there. And it's carving its way through this possibility space into generating more and more structure. And that's when you get the open-ended cascade of evolution.

• 58:02Sara Walker?

  But that boundary point is really hard to cross. And then what happens when you cross that boundary point? And the way objects come into existence is also like really fascinating dynamics because, you know, like as things become more complex, the assembly index increases. I can explain all these things. Sorry, you can tell me what you want to explain. I mean, explain or what people will want to hear. This, sorry, I have like a very vivid visual in my brain and it's really hard to articulate it.

• 58:28Lex Fridman?

  Got to convert it to language.

• 58:29Sara Walker?

  I know. It's so hard. It's like, it's going from like a feeling to a visual to language is so stifling sometimes.

• 58:37Lex Fridman?

  I have to convert it.

• 58:38Sara Walker?

  Yeah.

• 58:39Lex Fridman?

  From language to a visual.

• 58:41Sara Walker?

  Yeah.

• 58:41Lex Fridman?

  To a feeling.

• 58:42Sara Walker?

  Yeah.

• 58:43Lex Fridman?

  I think it's working.

• 58:44Sara Walker?

  I hope so.

• 58:45Lex Fridman?

  I really like the self-reinforcing objects. I mean, this is.

• 58:49Sara Walker?

  Yeah.

• 58:50Lex Fridman?

  Just so I understand, one way to create a lot of the same kind of object is make them self-reinforcing.

• 58:57Sara Walker?

  Yes. So self-reproduction has this property, right? Like if a system can make itself, then it can, it can persist in time, right? Because all objects decay. They all have a finite lifetime. So if you're able to make a copy of yourself before you die, before the second law eats you or whatever people think happens, then that structure can persist in time.

• 59:20Lex Fridman?

  So that's a way to sort of emerge out of a random soup, out of randomness of soup.

• 59:25Sara Walker?

  Right. But things that can copy themselves are very rare.

• 59:28Lex Fridman?

  Yeah.

• 59:29Sara Walker?

  And so what ends up happening is that you get structures that enable the existence of other things. And then somehow.

• 59:42Sara Walker?

  Only for some sets of objects, you get closed structures that are self-reinforcing and allow that entire structure to persist.

• 59:49Lex Fridman?

  Right, so the one object A reinforces the existence of object B, but you know, object A can die.

• 59:58Sara Walker?

  Yeah.

• 59:58Lex Fridman?

  So you have to like, close that loop.

• 1:00:00Sara Walker?

  Right, so this is the classic idea.

• 1:00:02Lex Fridman?

  It's just all very unlikely statistically, but you know, that's sufficiently, um, it's, you're saying there's a chance.

• 1:00:11Sara Walker?

  There is a chance.

• 1:00:12Lex Fridman?

  It's a probability, and then, but once you solve that, once you close the loop, you can create a lot of those objects.

• 1:00:17Sara Walker?

  And that's what we're trying to figure out, is what are the causal constraints that close the loop? So there is this idea that's been in the literature for a really long time, that was originally proposed by Stuart Kaufman, is really critical to the origin life, called autocalytic set. So autocalytic set is exactly this property, we have A makes B, B makes C, C makes A, and you get a closed system. But the problem with the theory of autocalytic sets is incredibly brittle as a theory, and it requires a lot of ad hoc assumptions, like you have to assume function, you have to say this thing makes B, it's not an emergent property, the association between A and B. And so, the way I think about it is much more general, if you think about, um, these

• 1:00:57Sara Walker?

  histories that make objects, it's kind of like, the structure of the histories becomes, collapses in such a way that these things are all in the same sort of causal structure, and that causal structure actually loops back on itself to be able to generate some of the things that make the higher level structures. Lee has a beautiful example of this, actually, in molybdenum, it's like the first non-organic autocalytic set, it's a self-reproducing molybdenum ring, uh, but it's like, like molybdenum, and, and basically, like, if you look at the molybdenum, it makes a huge molybdenum ring, I don't remember exactly how big it is, it might be like 150 molybdenum atoms or something, but if you think about the configuration space of that object, you know,

• 1:01:42Sara Walker?

  it's exponentially large, how many possible molecules, so like, why does the entire system collapse on just making that one structure? If you start from like, you know, molybdenum atoms that are maybe just like, a couple of them stuck together, and so, what they see in this system is there's a few intermediate stages, so there's like, some random events where the chemistry comes together, makes these structures, and then, once you get to this very large one, it becomes a template for the smaller ones, and then the whole system just reinforces its own production.

• 1:02:08Lex Fridman?

  How did Lee find this molybdenum?

• 1:02:14Sara Walker?

  If I knew how Lee's brain work, I think I would understand a little more about the universe, but I.

• 1:02:20Lex Fridman?

  This is not an algorithmic discovery. It's a.

• 1:02:22Sara Walker?

  No, but, um, but you, I think it goes to the deepest roots of like when he started thinking about origins of life. So I like, I mean, I don't know all his history, but like what he's told me is, um, he started out in crystallography. Um, and you know, there are some things that he would just, you know, like people would just take for granted about chemical structures, um, that he was like deeply perplexed about, like, just like, why are these like really intricate, really complex structures forming so easily under these conditions? And he was really interested in life, um, but he started in that field. So he's just carried with him these sort of deep insights from these systems that seem like they're totally not alive and just like these metallic chemistries, um, into actually

• 1:03:06Sara Walker?

  thinking about the deep principles of life. So I think he already, uh, he already knew a lot about that chemistry and he also, um, you know, assembly theory came from him thinking about how these systems work. Uh, so he had some intuition about what was going on with this molybdenum ring.

• 1:03:26Lex Fridman?

  The molybdenum might be able to be the thing that makes a ring.

• 1:03:30Sara Walker?

  They knew about them for a long time, but they didn't know that the mechanism of why that particular structure formed was autocratic feedback. Um, and so that's what they, they figured out in this, this paper. And I actually think that paper is revealing some of the mechanism of the origin of life transition, cause really what you see, like the origin of life is basically like, you should have a combinatorial explosion of the space of possible structures, um, that are too large to exhaust. And yet you see it collapse on this, you know, really small space of possibilities that's mutually reinforcing itself to keep existing.

• 1:04:06Sara Walker?

  That is the origin of life.

• 1:04:08Lex Fridman?

  There's some set of structures that result in this autocatalytic feedback.

• 1:04:13Sara Walker?

  Yeah.

• 1:04:14Lex Fridman?

  And is it, what is it, tiny, tiny, tiny, tiny percent?

• 1:04:18Sara Walker?

  I think it's a small space, but chemistry is very large.

• 1:04:23Lex Fridman?

  And so like.

• 1:04:24Sara Walker?

  There might be a lot of them out there, but we don't know.

• 1:04:27Lex Fridman?

  And one of them is the thing that probably started life on Earth.

• 1:04:30Sara Walker?

  That's right.

• 1:04:30Lex Fridman?

  Or many, many starts.

• 1:04:32Sara Walker?

  Yes.

• 1:04:32Lex Fridman?

  And it keeps starting, maybe.

• 1:04:33Sara Walker?

  Yeah. I mean, there's also all kinds of other weird properties that happen around this kind of phase boundary. So this other project that I have in my lab is focused on the origin of chirality, which is, you know, thinking about, so chirality is this property of molecules that they can come in mirror image forms. So like, just like chiral it means hands. So your, your left and right hand are what's called non-superimposable, because if you try to lay one on the other, you can't actually lay them directly on top of each other. And that's the property being a mirror image. So there's this sort of perplexing property, the chemistry of life, that no one's been able to really adequately explain, that all of the amino acids in proteins are left-handed and all

• 1:05:18Sara Walker?

  of the bases in RNA and DNA are right-handed. And yet, the chemistry of these, these building block units, amino acids and nucleobases is the same for left and right-handed. So you have to have like some kind of symmetry breaking, where you go from these chemistries that seem entirely equivalent, to only having one chemistry take over as the dominant form. And for a long time, I had been really, I actually did my PhD on the origin of chirality. I was working on it as like a symmetry breaking problem in physics. This is how I got started in the origin of life. And then I left it for a long time because I thought it was like one of the most boring problems in the origin of life. But I've come back to it because I think there's something really deep going on here related to this like combinatorial explosion of the space of possibilities.

• 1:06:02Sara Walker?

  But just to get to that point, like this feature of this handedness has been the main focus, but people take for granted the existence of chiral molecules at all, that this property of having a handedness, and they just assume that, you know, like, it's just a generic feature of chemistry. But if you actually look at molecules, if you look at chemical space, which is like the space of all possible molecules that people can generate, and you look at small molecules, things that have less than about seven to 11 heavy atoms, so things that are not hydrogen, almost every single molecule in that space is a chiral, like, doesn't have a chiral center. So it would be like

• 1:06:44Sara Walker?

  a spoon. A spoon doesn't have a, like, it's the same as its mirror image. It's not like a hand, that's different than its mirror image. But if you get to, like, this threshold boundary, above that boundary, almost every single molecule is chiral. So you go from a universe where almost nothing has a mirror image form, there's no mirror image universe of possibilities, to this one where every single structure has pretty much a mirror image version. And what we've been looking at in my lab is that it seems to be the case that the origin of life transition happens around the time when you start accumulating, you push your molecules to a large enough complexity that chiral molecules become very

• 1:07:29Sara Walker?

  likely to form. And then there's a cascade of molecular recognition where chiral molecules can recognize each other. And then you get this sort of autocatalytic feedback and things self-reinforcing.

• 1:07:39Lex Fridman?

  So is chirality in itself an interesting feature, or just an accident?

• 1:07:44Sara Walker?

  No, it's a super interesting feature. I think chirality breaks symmetry in time, not space. So we think of it as a spatial property, like a left and right hand. But if I choose the left hand, I'm basically choosing the future of that system for all time, because I've basically made a choice between the ways that that molecule can now react with every other object in its chemical universe.

• 1:08:05Lex Fridman?

  I see.

• 1:08:06Sara Walker?

  And so you're actually, like, when you have this splitting of making a molecule that now has another form it could have had by the same exact atomic composition, but now it's just a mirror image isometry, you're basically splitting the universe of possibilities every time.

• 1:08:21Lex Fridman?

  Yeah, in two.

• 1:08:23Sara Walker?

  In two, but molecules can have more than one chiral center and that's not the only stereosommetry that they can have. So this is one of the reasons that taxol fills 1.5 universes of space. It's all of these spatial permutations that you do on these objects that actually makes the space so huge. So the point of this, this sort of chiral transition that I'm, I'm putting out is, is chirality is actually a signature of being in a complex chemical space. And the fact that we, we think it's a really generic feature of chemistry and it's really prevalent is because most of the chemistry we study on earth is a product already of life. And it also has to do with this transition and assembly, this transition in possibility spaces, because I, I think there's something really fundamental going

• 1:09:02Sara Walker?

  on at this boundary, that you don't really need to go that far into chemical space if you can, to actually see life in terms of this depth in time, this depth in, in symmetries of objects, in terms of like chiral symmetries, or this assembly structure. But, but getting past this boundary, that's, that's not very deep in that space, requires life. It's a, it's a really, is a really weird property. And it's really weird that so many abrupt things happen in chemistry at that same scale.

• 1:09:35Lex Fridman?

  So would that be the, the greatest invention ever made on earth in its evolutionary history? So I really like that formulation of it. Nick Lane has a book called Life Ascending, where he lists the 10 great inventions of evolution. The origin of life being first, and DNA, the hereditary material that encodes the genetic instructions for all living organisms, then photosynthesis, the process that allows organisms to convert sunlight into chemical energy, producing oxygen as a byproduct, the complex cell, eukaryotic cells, which contain nucleus and organelles that arose from simple bacterial cells, sex, sexual reproduction,

• 1:10:17Lex Fridman?

  movement, so just the ability to move under which you have the predation, the predators and ability of living organisms to find food.

• 1:10:25Sara Walker?

  I like that movement's in there, that's cool.

• 1:10:26Lex Fridman?

  Yeah, but a movement includes a lot of interesting stuff in there, like predator-prey dynamic.

• 1:10:31Sara Walker?

  Right.

• 1:10:31Lex Fridman?

  Which, not to romanticize, a nature is metal. That seems like an important one. I don't know, it's such a computationally powerful thing to have a predator and prey.

• 1:10:44Sara Walker?

  Well, it's efficient for things to eat other things that are already alive because they don't have to go all the way back to the. Base chemistry.

• 1:10:52Lex Fridman?

  Well, that, but maybe I just like deadlines, but it creates an urgency. You're gonna get eaten.

• 1:10:57Sara Walker?

  You gotta live.

• 1:10:58Lex Fridman?

  Yeah, like survival is not just the static.

• 1:11:01Sara Walker?

  Oh, I see.

• 1:11:02Lex Fridman?

  Against, you're like.

• 1:11:03Sara Walker?

  Yeah.

• 1:11:04Lex Fridman?

  The, the, the dangers against which you're trying to survive are also evolving. This is just much faster way to explore the space of possibilities.

• 1:11:16Sara Walker?

  I actually think it's a gift that we don't have much time.

• 1:11:18Lex Fridman?

  Yes. Sight, the ability to see, so the increasing complexifying of sensory organisms. Consciousness and death. The concept of programmed cell death. These are all inventions.

• 1:11:35Sara Walker?

  Yeah.

• 1:11:35Lex Fridman?

  Along the line.

• 1:11:36Sara Walker?

  I like invention as a word for them. I think that's good.

• 1:11:39Lex Fridman?

  Which are the more interesting inventions to you? The origin of life, because you kind of are not glorifying the origin of life itself. There's a, there's a.

• 1:11:48Sara Walker?

  No, I think the origin of life is a continual process. That's why I'm interested in the first transition and solving that problem because I think it's the hardest. But I think, I think, I think it's happening all the time.

• 1:11:57Lex Fridman?

  When you look back at the history of Earth, like, what are you impressed happened?

• 1:12:01Sara Walker?

  I like sight.

• 1:12:05Sara Walker?

  As an invention, uh, cause I think having sensory perception and trying to comprehend the world, to use anthropocentric terms is like a really critical feature of life. And I also, it's interesting, the way that sight has complexified over time. Right? So like, if you think at the origin of life, uh, nothing on the planet could see. Right? So like, for a long time, life had no sight. Um, and then, you know, like photon receptors were invented. And then when multicellular already evolved, those cells eventually grew into eyes. And we had the multicellular eye.

• 1:12:47Sara Walker?

  And then it's interesting when you get to societies, like human societies, that we invent even better technologies of seeing, like telescopes and microscopes, uh, which allow us to see deeper into the universe or at smaller scales. Um, so I think, I think that's pretty profound, the way that sight has transformed the ability of life to literally see, uh, the reality in which it's existing in.

• 1:13:16Sara Walker?

  I think consciousness is also obviously deeply interesting. I've gotten kind of obsessed with like octopus. I don't like I they're just so weird. And the fact that like they evolved complex nervous systems kind of independently is like seems very alien.

• 1:13:34Lex Fridman?

  Yeah, there's a lot of alien like organisms. That's another thing I saw in the jungle.

• 1:13:40Sara Walker?

  Yeah.

• 1:13:41Lex Fridman?

  Just things that are like, okay, they make one of those, huh? It just feels like there's.

• 1:13:45Sara Walker?

  Any examples?

• 1:13:47Lex Fridman?

  There's a frog that's as as thin as a sheet of paper. And I was like, what? And it gives birth through like pores like.

• 1:13:55Sara Walker?

  Oh, I've seen videos of that. It's so gross when the babies come out. Did you see that? Like, like in person, like the baby.

• 1:14:02Lex Fridman?

  Oh, no, no. I saw the without the.

• 1:14:05Sara Walker?

  Have you seen videos of that? It's so gross. It's one of the grossest things I've ever seen.

• 1:14:09Lex Fridman?

  Well, so gross is just the other side of beautiful. Yes, it's like, oh, wow, that that's that's possible.

• 1:14:17Sara Walker?

  I guess if I was one of those frogs, I would think that was the most beautiful event I'd ever seen. Although like human childbirth is not that beautiful either.

• 1:14:24Lex Fridman?

  Yeah, it's all about our perspective.

• 1:14:27Sara Walker?

  Well, we come in the world so violently. It's just like, it's amazing.

• 1:14:32Lex Fridman?

  I mean, the world is a violent place.

• 1:14:33Sara Walker?

  Yeah.

• 1:14:34Lex Fridman?

  So again, another it's just another side of the coin.

• 1:14:38Sara Walker?

  You know what? This actually makes me think of one that's not up there, which I do find really incredibly amazing is

• 1:14:47Sara Walker?

  is the process of like the germ line cell in, you know, in organisms, like basically like every living thing on this planet at some point in its life has to go through a single cell. And this whole issue of like development, like the developmental program is kind of crazy. Like, how do you build you out of a single cell? How does a single cell know how to do that? Like, you know, pattern formation of a multicellular organism obviously like evolves with DNA. But there's a lot of stuff happening there about when cells take on certain morphologies and things that people don't understand, like the actual shape formation mechanism. And a lot of people study that and it's and there's a lot of advances being made now in that field. I think it's pretty shocking, though, that like how little we know about that process.

• 1:15:31Sara Walker?

  And often it's left off of people's lists. It's just kind of interesting. Embryogenesis is fascinating.

• 1:15:36Lex Fridman?

  Yeah, because you start from just one cell.

• 1:15:39Sara Walker?

  Yeah. And the genes in all the cells are the same, right? So like the differentiation has to be.

• 1:15:46Sara Walker?

  Something that's like much more about like the actual like,

• 1:15:51Sara Walker?

  you know, expression of genes over time and like how they get switched on and off. And also the physical environment of like the cell interacting with other cells. And there, there's just a lot of stuff going on.

• 1:16:02Lex Fridman?

  Yeah, the computation, the intelligence of that process.

• 1:16:05Sara Walker?

  Yes.

• 1:16:06Lex Fridman?

  Might be like the most important thing to understand. And we just kind of don't really think about it.

• 1:16:11Sara Walker?

  Right.

• 1:16:12Lex Fridman?

  We think about the final product.

• 1:16:13Sara Walker?

  Yeah.

• 1:16:15Lex Fridman?

  Maybe the, the key to understanding the organism is understanding that process, not the final product.

• 1:16:21Sara Walker?

  Probably yes. I think most of the things about understanding anything about what we are embedded in time.

• 1:16:27Lex Fridman?

  Of course you would say that.

• 1:16:28Sara Walker?

  I know. So predictable.

• 1:16:32Sara Walker?

  It's turning into a deterministic universe.

• 1:16:34Lex Fridman?

  It always has been, always was like the meme.

• 1:16:38Sara Walker?

  Yeah, always was, but it won't be in the future.

• 1:16:41Lex Fridman?

  Well, that's before we talk about the future, let's talk about the past. The assembly theory.

• 1:16:45Sara Walker?

  Yes.

• 1:16:45Lex Fridman?

  Can you explain assembly theory to me? I listened to Lee talk about it for many hours and I understood nothing. No, I'm just kidding. I just wanted to take another, you've been already talking about it, but just, just, just another, just, what from a big picture view is the assembly theory way of thinking about our world, about our universe?

• 1:17:12Sara Walker?

  Yeah. I think the first thing is, you know, that like the observation that

• 1:17:21Sara Walker?

  life seems to be the only thing in the universe that builds complexity in the way that we see it here. And complexity is obviously like a loaded term, so I'll just use assembly instead. Cause I think assembly is more precise.

• 1:17:34Sara Walker?

  But the idea that like, you know, all the things on your desk here, from your computer to the pen, to, you know, us sitting here don't exist anywhere else in the universe as far as we know. They only exist on this planet. And it took a long evolutionary history to get to us. Is a real feature that we should take seriously as one that's deeply embedded in the laws of physics and the structure of the universe that we live in. Standard physics would say that, you know, all of that complexity traces back to the. Infinitesimal deviations and like the initial state of the universe that there was some order there. I find that deeply unsatisfactory. And what assembly theory

• 1:18:16Sara Walker?

  says that's very different is that the universe is basically constructing itself. And when you get to these commonestorial spaces like chemistry, where the space of possibilities is too large to exhaust them all, you can only construct things along historically contingent paths. Like you basically have causal chains of events that happen to allow other things to come into existence. And that this is the way that complex objects get formed is basically on scaffolding on the past history of objects making more complex objects, making more complex objects. That idea in itself is easy to state and

• 1:19:01Sara Walker?

  simple, but it has some really radical implications as far as what you think is the nature of the physics that would describe life. And so what assembly theory does formally is try to measure the boundary in the space of all things that, you know, chemically could exist, for example, like all possible molecules. Where is the boundary above which we should say, these things are too complex to happen outside of an evolutionary chain of events, outside of selection. And we formalize that with two observables. One of them's the copy number of the object. So how many of the object did you observe? And the second

• 1:19:39Sara Walker?

  one is what's the minimal number of recursive steps to make it? So if you start from elementary building blocks, like bonds for molecules, and you put them together, and then you take things you've made already and build up to the object, what's the shortest number of steps you had to take? And what Lee's been able to show in the lab with his team is that for organic chemistry,

• 1:20:05Sara Walker?

  It's about 15 steps and then you only see molecules that, you know, the only molecules that we observe that are past that threshold are ones that are in life. And in fact, one of the things I'm trying to do with this idea of like trying to actually quantify the origin of life as a transition in like a phase transition assembly theory is actually be able to explain why that boundary is where it is. Because I think that's actually the boundary that life must cross. So the idea of going back to this thing we were talking about before about these, these structures that can reinforce their own existence and move past that boundary, 15 seems to be that boundary in chemical space. It's not a universal

• 1:20:46Sara Walker?

  number. It will be different for different assembly spaces. But that's what we've experimentally validated so far. And then

• 1:20:53Lex Fridman?

  So literally 15, like the assembly index is 15?

• 1:20:56Sara Walker?

  It's 15 or so for the experimental data. Yeah.

• 1:20:58Lex Fridman?

  So that's when you start getting the self reinforcing?

• 1:21:02Sara Walker?

  That's when you have to have that feature in order for to observe molecules in high abundance in that space.

• 1:21:09Lex Fridman?

  So copy number is the, the number of exact copies. That's what you mean by high abundance and assembly index or the complexity of the object is how many steps it took to create it recursive?

• 1:21:20Sara Walker?

  Recursive. Yeah. So you can think of objects in assembly theory as basically recursive stacks of the, the construction steps to build them. So they're like, it's like, you take this step and then you make this object and you make it this object and make this object and then you get up to the final object. But that object is all of that history rolled up into the current structure.

• 1:21:40Lex Fridman?

  What if you took the long way home?

• 1:21:41Sara Walker?

  You can't take the long way.

• 1:21:43Lex Fridman?

  Why not?

• 1:21:44Sara Walker?

  The long way doesn't exist.

• 1:21:45Lex Fridman?

  It's a good song though. What do you mean the long way doesn't exist? If I do, if I do a random walk from A to B, I'll eventually, if I started A, I'll eventually end up at B and that random walk would be much shorter than, longer than the short.

• 1:22:00Sara Walker?

  Now, if you look at objects and you, so that we, we define something we call the assembly universe and the assembly universe is ordered in time. It's actually ordered in the causation, the number of steps to produce an object. And so all objects in the universe are in some sense existed a layer that's defined by their assembly index. And the size of each layer is growing exponentially. So what you're talking about, if you want to look at the long way of getting to an object, as I'm increasing the assembly index of an object, I'm moving deeper and deeper into an exponentially growing space. And it's actually also the case that the sort of typical path to get to that object is also exponentially growing with respect

• 1:22:43Sara Walker?

  to the assembly index. And so if you want to try to make a more and more complex object and you want to do it by a typical path, that's actually an exponentially receding horizon. And so most objects that come into existence have to be causally very similar to the things that exist because they're close by in that space and they can actually get to it by an almost shortest path for that object.

• 1:23:04Lex Fridman?

  Yeah, the almost shortest path is the most likely and like by a lot.

• 1:23:09Sara Walker?

  By a lot.

• 1:23:10Lex Fridman?

  Okay, so if you see a high copy number.

• 1:23:12Sara Walker?

  Yeah.

• 1:23:13Lex Fridman?

  A copy number greater than one.

• 1:23:15Sara Walker?

  Yeah, I mean, basically, we live, the more complex we get, we live in a space that is growing exponentially large. And the ways of getting to objects in the space are also growing exponentially large. And so we're this kind of recursively like stacked structure of like, all of these objects that are clinging on to each other for existence. And then they like grab something else and are like able to bring that thing into existence because it's kind of similar to them.

• 1:23:45Lex Fridman?

  But there is a phase transition. There is a

• 1:23:47Sara Walker?

  There is a transition.

• 1:23:48Lex Fridman?

  There is a place where you would say, oh, that's life.

• 1:23:51Sara Walker?

  I think it's actually abrupt. I've never been able to say that in my entire career before. I've always gone back and forth about whether the original life was kind of gradual or abrupt. I think it's very abrupt.

• 1:23:59Lex Fridman?

  Poetically, chemically, literally, with snaps, okay, that's very beautiful.

• 1:24:03Sara Walker?

  It snaps. We'll be poetic today. But no, I think there's like a lot of random exploration. And then there's like, and then the structure, the possibility space just collapses on the structure kind of really fast. That can reinforce its own existence because it's basically fighting against non-existence.

• 1:24:20Lex Fridman?

  Yeah, you tweeted, "The most significant struggle for existence in the evolutionary process is not among the objects that do exist, but between the ones that do and those that never have the chance to." This is where selection does most of its causal work.

• 1:24:39Lex Fridman?

  The, the objects that never get a chance to exist.

• 1:24:43Sara Walker?

  Yeah.

• 1:24:44Lex Fridman?

  The struggle between the ones that never get a chance to exist and the ones that, okay. What, what's that line exactly?

• 1:24:49Sara Walker?

  I don't know, we can make songs out of all of these.

• 1:24:51Lex Fridman?

  What are the objects that never get a chance to exist? What does that mean?

• 1:24:54Sara Walker?

  So there was, there was this website, I forgot what it was, but it's like, it's like a, a neural network that just generates a human face. And it's like, this person does not exist. I think that's what it's called, right? So you can just click on that all day and you can look at people all day that don't exist.

• 1:25:09Lex Fridman?

  Yeah.

• 1:25:09Sara Walker?

  All of those people exist in that space of things that don't exist.

• 1:25:13Lex Fridman?

  Yeah, but there's a, the real struggle.

• 1:25:17Sara Walker?

  Yeah, so the struggle of the quote, the struggle for existence is, you know, that goes all the way back to Darwin's writing about natural selection, right? So like, the whole idea of survival of the fittest is everything's struggling to exist, this predator prey dynamic. Um, and, and the fittest survive. And so the struggle for existence is really what selection is all about. But you're, and that's true. We do see things that do exist, competing to continue to exist. But each time that, like, if you think about this space of possibilities and, you know, each time the universe, you know, generates a new structure, or like, a, an, an object

• 1:25:58Sara Walker?

  that exists generates a new structure along this causal chain, it's generating something that exists that never existed before. And each time that we make that kind of decision, we're excluding a huge space of possibilities. And so actually, like, as this process of increasing assembly index, it's not just that, like, the space that these objects exist in is exponentially growing, but there's, there are objects in that space that are exponentially receding away from us. So they're becoming exponentially less and less likely to ever exist. And so existence excludes a huge number of things.

• 1:26:36Lex Fridman?

  Just because of the accident of history, how it ended up.

• 1:26:40Sara Walker?

  Yeah, it, it is in part an accident, because I think, I think some of the, the structure that gets generated is, is driven a bit by randomness. Um, I think a lot of it, you know, so, uh, you know, one of the conceptions that we have in assembly theory is, you know, the universe is random at its base. You can see this in chemistry, like unconstrained chemical reactions are pretty random. And then, and also. Quantum mechanics, you know, like there's less places that that give evidence for that. And deterministic structures emerge by things that can causally reinforce themselves and maintain persistence over time. And so we are some of the most deterministic things in the universe.

• 1:27:21Sara Walker?

  And so like, we can generate very regular structure and we can generate new structure along a particular lineage, but the possibility space at the sort of tips, like the things we can generate next is really huge. So there's some stochasticity in what we actually, you know, instantiate as like the next structures that get built in in the biosphere. It's not completely deterministic because the space of future possibilities is always larger than the space of things that exist now.

• 1:27:50Lex Fridman?

  So how many instantiations of life is out there, do you think? So how how often does this happen? What we see happen here on Earth? How often is this process repeated throughout our galaxy, throughout the universe?

• 1:28:06Sara Walker?

  So I I said before, like, right now, I think the origin of life is a continuous process on Earth. Like, I think this this idea of like, combinatorial spaces that are biosphere generated, it's not just chemistry, but other spaces, often cross this threshold where they then allow themselves to persist with particular regular structure over time. So language is is another one where, you know, like, the space of, you know, possible configurations of the 26 letters of the English alphabet is astronomically large, but we use with very high regularity certain structures. And then we associate meaning to them because of the regularity of like, how much we use them, right? So meaning is an emergent property of the causation and the objects and like, how often they recur and what the relationship of the recurrence is to other objects.

• 1:28:51Lex Fridman?

  Meaning is the emergent property. Okay, got it.

• 1:28:54Sara Walker?

  Well, this is why you can play with language so much, actually. So words don't really carry meaning, it's just about how you lace them together.

• 1:29:00Lex Fridman?

  Yeah, but from where does?

• 1:29:02Sara Walker?

  But you don't have a lot of room, obviously, as a speaker of a given language, you don't have a lot of room with a given word to wiggle, but you do have, you do have, you have a certain amount of room to push the meanings of words.

• 1:29:15Lex Fridman?

  Yeah.

• 1:29:15Sara Walker?

  And, and I do this all the time, and you have to do it with the kind of work that I do, because if you want to discover an abstraction, like some kind of concept that we don't understand yet, it means we don't have the language. And so the words that we have are inadequate to describe the things. This is why we're having a hard time talking about assembly theory, because it's a newly emerging idea. And so, so I'm constantly playing with words in different ways to try to convey the meaning that is actually behind the words, but it's hard to do.

• 1:29:51Lex Fridman?

  So you have to wiggle within the constraints.

• 1:29:53Sara Walker?

  Yes, lots of wiggle.

• 1:29:57Lex Fridman?

  The great orators are just good at wiggling.

• 1:30:00Sara Walker?

  Do you wiggle?

• 1:30:03Lex Fridman?

  I'm not a very good wiggler, no. This is the problem, this is part of the problem.

• 1:30:07Sara Walker?

  No, I like playing with words a lot. You know, it's very funny, because, you know, like, I know you talked about this with Lee, but like, people are so offended by the writing of the paper that came out last fall. And it was, it was interesting, because the ways that we use words were not the way that people were interacting with the words. And I think that was part of the mismatch, where we were trying to use words in a new way, because we were trying to describe something that, you know, hadn't been described adequately before, but we had to use the words that everyone else uses for things that are related. And so it was really interesting to watch that clash play out in real time. For me, being someone that tries to be so precise with my word usage, knowing that it's always going to be vague.

• 1:30:50Lex Fridman?

  Boy, can I relate. It's like.

• 1:30:54Lex Fridman?

  What is truth? Is truth the thing you meant when you wrote the words? Or is truth the thing that people understood when they read the words?

• 1:31:02Sara Walker?

  Oh, yeah.

• 1:31:02Lex Fridman?

  I think that compression mechanism into language is a really interesting one. And that's why Twitter is a nice exercise.

• 1:31:09Sara Walker?

  I love Twitter.

• 1:31:10Lex Fridman?

  You get to write a thing and you think a certain thing when you write it. And then you get to see all these other people interpret it all kinds of different ways.

• 1:31:20Sara Walker?

  I use it as an experimental platform for that reason.

• 1:31:23Lex Fridman?

  I wish there was a higher diversity of interpretation mechanisms applied to tweets. Meaning like, all kinds of different people would come to it. Like some people that see the good in everything and some people that are ultra cynicals. A bunch of haters and a bunch of lovers and a bunch of-

• 1:31:41Sara Walker?

  Maybe they could do better jobs with presenting material to people. Like, you know, the rant, like, like how things, you know, it's like usually based on interest. But I think it would be really nice if you got like 10% of your Twitter feed was random stuff sampled from other places. That'd be kind of fun.

• 1:31:56Lex Fridman?

  I also would love to filter just like been the response to tweets by like, the people that hate on everything.

• 1:32:06Sara Walker?

  Yes.

• 1:32:07Lex Fridman?

  The people that are-

• 1:32:07Sara Walker?

  Oh, that would be fantastic.

• 1:32:09Lex Fridman?

  The people that are like super positive about everything. And that they'll just kind of, I guess, normalize their response. Cause then it'd be cool to see if the people that are usually positive about everything are hating on you. Or like totally don't understand or completely misunderstood.

• 1:32:24Sara Walker?

  Yeah, usually takes a lot of clicking to find that out. Yeah, so it'd be better if it was sorted, yeah.

• 1:32:29Lex Fridman?

  The more clicking you do, the more damaging it is to the soul.

• 1:32:34Sara Walker?

  Yeah, it's like instead of like, well, you could have the blue check, but you should have like, are you a pessimist? An optimist?

• 1:32:40Lex Fridman?

  There's a lot of colors.

• 1:32:43Lex Fridman?

  A whole rainbow of checks. And then you realize there's more categories than we can possibly express in colors.

• 1:32:50Sara Walker?

  Yeah, of course. People are complex.

• 1:32:55Lex Fridman?

  That's our best feature. I don't know how we got to the wiggling required, given the constraints of language, because I think we started about me asking about alien life, which, which is, how many different times did the face transition happen elsewhere? Do you think there's other alien civilizations out there?

• 1:33:22Sara Walker?

  This goes into like the, you know, like, are you on the boundary of insane or not? But, you know, when you think about the, the structure of the physics of what we are that deeply, it really changes your conception of things. And, you know, going to this idea of the universe,

• 1:33:41Sara Walker?

  you know, being kind of small in physical space compared to how big it is in time and like how large we are, it really makes me question about whether there's any other structure that's like this giant crystal in time, this giant causal structure like our biosphere slash technosphere is anywhere else in the universe.

• 1:34:02Lex Fridman?

  Why not?

• 1:34:03Sara Walker?

  I don't, I don't know.

• 1:34:05Lex Fridman?

  Just because this one is gigantic, doesn't mean there's other gigantic ones.

• 1:34:09Sara Walker?

  But, but I think when the universe is expanding, right, it's expanding in space, but in assembly theory, it's also expanding in time. And actually, that's driving the expansion in space. And that expansion in time is also driving the expansion in the sort of combinatorial space of things on our planet. So that's driving the sort of, you know, pace of technology and all the other things. So time is driving all of these things, which is a little bit crazy to think that the universe is just getting bigger because time is getting bigger. But like, the sort of visual that gets built in my brain about that is like, the structure that we're building on this planet is packing more and more time in this very small volume of space, right? Because our planet hasn't changed its physical size in

• 1:34:54Sara Walker?

  four billion years, but there's like a ton of causation and recursion and time, whatever word you want to use, information packed into this. And I think this is also, you know, embedded in sort of the virtualization of our technologies or the abstraction of language and all of these things, these, these, these things that seem really abstract are just really deep in time. And so, so what that looks like is you have a planet that becomes increasingly virtualized. And so it's getting bigger and bigger in time, but not really expanding out in space. And the rest of space is like, kind of moving away from it. It's again, it's a sort of exponentially receding horizon. And I'm just not sure how far into this evolutionary

• 1:35:38Sara Walker?

  process, something gets, if it can ever see that there's another such structure out there.

• 1:35:44Lex Fridman?

  What do you mean by virtualized in that context?

• 1:35:46Sara Walker?

  Virtual as sort of a play on virtual reality, and like simulation theories. But virtual also in a sense of, you know, we talk about virtual particles in, in particle physics, which, you know, they, they are very critical to doing calculations about predicting the properties of real particles, but we don't observe them directly. So what I mean by virtual here is virtual reality, for me, things that appear virtual, appear abstract, are just things that are very deep in time, in the, in the structure of the things that we are. So if you think about you as a four billion year old object, the things that are part of you, like your capacity to use language, or think abstractly, or have mathematics,

• 1:36:31Sara Walker?

  are just very, you know, like, deep temporal structures. That's why they look like they're informational and abstract, is because they're like, they're existing in this temporal part of you, but not necessarily spatial part.

• 1:36:43Lex Fridman?

  Just because I have a four billion year old history, why does that mean I can't hang out with aliens?

• 1:36:48Sara Walker?

  There's a couple of ideas that are embedded here. So one of them comes again from Paul. He wrote this book years ago about, you know, like the eerie silence and why we're alone. And he concluded the book with this idea of quintelligence or something, but like this idea that like, really advanced intelligence would basically just build itself into a quantum computer, and it would want to operate in the vacuum of space, because that's the best place to do quantum computation. And it would just like, run out all of its computations indefinitely, but it would look completely dark to the rest of the universe. And I don't think, as, as typical, like, I don't think that's actually like, the right physics, but I think something about that idea, as I do with all ideas, is partially correct. And Freeman Dyson also had this amazing paper about how long life could persist

• 1:37:32Sara Walker?

  in a universe that was exponentially expanding. And his conception was like, if you imagine analog life form. It could run slower and slower and slower and slower and slower as a function of time. And so it would, it would be able to run indefinitely even against an exponentially expanding universe because it would just run exponentially slower. And so I guess part of what I'm doing in my brain is putting those two things together along with this idea that we are building, you know, like if you, if you imagine with our technology, we're now building virtual realities, right? Like things we actually call virtual reality, which required, you know, four billions of years of history and a whole bunch of data to basically embed them in a computer architecture.

• 1:38:16Sara Walker?

  So now you can put like, you know, an Oculus headset on and think that you're in this world, right? And what you really are embedded in is in a very deep temporal structure. And so it's huge in time, but it's very small in space and you can go lots of places in the virtual space, right? But you're still stuck in like your physical body and like sitting in the chair. And so, you know, part of it is, it might be the case that sufficiently evolved biospheres kind of virtualize themselves and they internalize their universe in their sort of temporal causal structure and they close themselves off from the rest of the universe.

• 1:38:53Lex Fridman?

  I just don't know if a deep temporal structure necessarily means that you're closed off.

• 1:38:57Sara Walker?

  No, I don't either. So that's kind of my fear. So I'm not, I'm not sure I'm agreeing with what I say. I'm just saying like, this is one sort of conclusion and you know, like in my most sort of like, it's interesting because I don't do psychedelic drugs. But when people describe to me like your thing with the faces and stuff and like I have, you know, had a lot of deep conversations with friends that have done psychedelic drugs for intellectual reasons and otherwise. But I'm always like, oh, it sounds like you're just doing theoretical physics. Like that's what brains do on theoretical physics. So I live in these like really abstract spaces most of the time. But there's also this, this issue of extinction, right? Like extinction events are basically pinching off an entire like causal structure, the one of these like, I'm going to call them time crystals.

• 1:39:41Sara Walker?

  I don't like know what, but there's like these very large objects in time, pinching off that whole structure from the rest of it. And so it's like, if you imagine that sort of same thing in the universe, I, you know, I once thought that sufficiently advanced technologies would look like black holes.

• 1:39:55Lex Fridman?

  They would be just completely imperceptible.

• 1:39:57Sara Walker?

  Yeah. Um, so, so there might be lots of aliens out there. Maybe that's the explanation for all the singularities. They're all pinched off causal structures that virtualize their reality and kind of broke off from us.

• 1:40:07Lex Fridman?

  Black holes in every way. So like, um, untouchable to us or unlikely to be detectable by us.

• 1:40:16Sara Walker?

  Right.

• 1:40:16Lex Fridman?

  With whatever sensory mechanisms we have.

• 1:40:18Sara Walker?

  Yeah. But the other way I think about it is, um, is there is probably hopefully life out there. So like, I do work on life detection, uh, efforts in the solar system and I'm trying to help with the habitable worlds observatory mission planning right now, um, and working with like the biosignatures team for that, like to think about exoplanet biosignatures. So like, I have some optimism that we might find things.

• 1:40:43Sara Walker?

  But there are the challenges that we don't know the likelihood for life, like, which is what you were talking about. So if I get to a more grounded discussion, what I'm really interested in doing is trying to solve the origin of life. So we can understand how likely life is out there. So I don't think that the, I think that the problem of discovering alien life and solving the origin of life are deeply coupled and in fact are one and the same problem. And that the first contact with alien life will actually be in an origin of life experiment. But, but that part I'm super interested in. And then there's this other feature that I think about a lot, which is

• 1:41:23Sara Walker?

  our own technological phase of development as sort of like, what is this phase in the evolution of life on a planet? If you think about a biosphere emerging on a planet and evolving over billions of years and evolving into a technosphere.

• 1:41:39Sara Walker?

  When a technosphere can move off planet and basically reproduce itself on another planet, now you have biospheres reproducing themselves.

• 1:41:50Sara Walker?

  Basically, they have to go through technology to do that. And so there are ways of thinking about sort of the nature of intelligent life and how it spreads in that capacity that I'm also really excited about and thinking about.

• 1:42:05Sara Walker?

  And all of those things for me are connected. Like, we have to solve the origin of life in order for us to get off planet because we basically have to start life on another planet. And we also have to solve the origin of life in order to recognize other alien intelligence. Like, all of these things are like literally the same problem.

• 1:42:20Lex Fridman?

  Right. Understanding the origin of life here on Earth is a way to understand ourselves and to, uh, understanding ourselves is a prerequisite for being able to detect other intelligent

• 1:42:32Lex Fridman?

  civilizations. I, for one, take it for what it's worth, on ayahuasca, one of the things I did is zoom out, like aggressively, like a spaceship. And it would always go quickly through the galaxy and from the galaxy to this, uh, representation of the universe. And at least for me, from that perspective, it seemed like it was full of alien life. Not just alien life, but, uh, intelligent life.

• 1:43:02Sara Walker?

  I like that.

• 1:43:03Lex Fridman?

  And conscious life. So like, I don't know how to convert it into words. It's more like a feeling, like you were saying. A feeling converted to a visual to, uh, convert it to words. So I had a visual with it, but really it was a feeling that it was just full of this vibrant energy that I was feeling when I'm looking at the people in my life.

• 1:43:27Sara Walker?

  Yeah.

• 1:43:27Lex Fridman?

  And full of gratitude, but that same exact thing is everywhere in the universe.

• 1:43:33Sara Walker?

  Right.

• 1:43:34Lex Fridman?

  So.

• 1:43:34Sara Walker?

  I totally agree with this, like, that visual I really love. And I think we live in a universe that, like, generates life and purpose and like it's, it's part of the structure of just the world.

• 1:43:49Sara Walker?

  And so maybe like this sort of lonely view I have is, uh, I never thought about it this way until you were describing that. I was like, I want to live in that universe. And I'm like a very optimistic person and I love. I love building visions of reality that are positive, but I think for me right now in the intellectual process, I have to tunnel through this, this particular way of thinking about the loneliness of being like separated in time from everything else, which I think like we also all are because time is what defines us as individuals.

• 1:44:18Lex Fridman?

  So part of you is drawn to the trauma of being alone.

• 1:44:21Sara Walker?

  Yeah.

• 1:44:21Lex Fridman?

  In a physics.

• 1:44:23Sara Walker?

  Yeah, but also part of what I mean is like you have to go through ideas you don't necessarily agree with to work out what you're trying to understand. And I'm trying to be inside the structure so I can really understand it. And I don't think I've been able to like, like I'm so deeply embedded in what we are intellectually right now that I, I don't have an ability to see these others, these other ones that you're describing if they're there.

• 1:44:48Lex Fridman?

  Well, one of the things you kind of described that you already spoke to, you call it the great perceptual filter.

• 1:44:53Sara Walker?

  Yeah.

• 1:44:54Lex Fridman?

  So there's the, the famous great filter, which is basically the idea that there's some really powerful moment in every intelligent civilization that where they destroy themselves.

• 1:45:09Sara Walker?

  Yeah.

• 1:45:10Lex Fridman?

  That explains why we have not seen aliens. And you're saying that there's something like that in the temporal history of the creation of complex objects that at a certain point they've become an island, an island too far to reach based on the perceptions.

• 1:45:26Sara Walker?

  I hope not, but yeah, I worry about it. Yeah.

• 1:45:28Lex Fridman?

  But that's basically meaning there's something fundamental about the universe where if the more complex you become, the, the harder it will be to perceive other complex.

• 1:45:38Sara Walker?

  Yeah. I mean, just think about us with microbial life, right? Like we used to once be cells. And for most of human history, we didn't even recognize cellular life was there until we built a new technology, microscopes that allowed us to see them. Right? So that's kind of, it's kind of weird, right? Like, like things that.

• 1:45:54Lex Fridman?

  And they're close to us.

• 1:45:56Sara Walker?

  They're close. They're everywhere.

• 1:45:57Lex Fridman?

  But also in the history of the development of complex objects, they're pretty close.

• 1:46:01Sara Walker?

  Yeah, super close, super close. Like, yeah, I mean, everything on this planet is like, it's like pretty much the same thing. Like, like the space of possibilities is so huge. It's like we're virtually identical.

• 1:46:15Lex Fridman?

  So how many flavors? Or kinds of life do you think are possible?

• 1:46:21Sara Walker?

  I'm like trying to imagine all the little flickering lights in the universe like in the way that you were describing it. That was kind of cool.

• 1:46:26Lex Fridman?

  It was so, I mean, it was, it was exactly that. It was like lights.

• 1:46:30Sara Walker?

  Yeah.

• 1:46:31Lex Fridman?

  The way you maybe see a city, but a city from like up above, you see a city with the flickering lights, but there's a coldness to the city.

• 1:46:40Sara Walker?

  Yeah.

• 1:46:41Lex Fridman?

  There's some, you know, that, you know, humans are capable of good and evil. And you could see like, there's a complex feeling to the city. I had no such complex feeling about seeing the lights of all the galaxies, whatever, the billions of galaxies.

• 1:46:55Sara Walker?

  Yeah, this is kind of cool. I'll answer the question in a second, but it's just maybe like this idea of flickering lights and intelligence is interesting to me because I, you know, like we have such a human centric view of alien intelligences that a lot of the work that I've been doing with my lab is just trying to take inspiration from uh, non-human life on earth. And so I have this really talented undergrad student that's basically building a model of alien communication based on fireflies. So one of my colleagues, Orat Peleg, is, she's totally brilliant, but she, she goes out with like GoPro cameras and like, you know, films in high resolution, all these firefly flickering. And she has like this theory about how their signaling evolved to like maximally differentiate

• 1:47:40Sara Walker?

  the flickering pattern. So like she has a theory basically that predicts, you know, like this species should flash like this. If this one's flashing like this, this other one's going to do it at a slower rate so that the, you know, like they can distinguish each other, living in the same environment. And so this undergrad's building this model where you have like a pulsar background of all these like giant flashing sources in the universe. And an alien intelligence, you know, wants to signal it's there. So it's flashing like a firefly. And I just like, I like the idea of thinking about a non-human alien. So that was really fun.

• 1:48:11Lex Fridman?

  The mechanism of the flashing unfortunately is like the diversity of that is very high and we might not be able to see it. That's what.

• 1:48:17Sara Walker?

  Yeah. Well, I think there's some ways we might be able to differentiate that signal. I'm still thinking about this part of it. So one is like, like if you have pulsars and they all have a certain spectrum to their pulsing patterns. And you have this one signal that's in there that's basically tried to maximally differentiate itself from all the other sources in the universe. It might stick out in the distribution. Like there might be ways of actually being able to tell if it's, it's an anomalous pulsar, basically. But I don't know if that would really work or not. So still thinking about it.

• 1:48:46Lex Fridman?

  You tweeted, if one wants to understand how truly combinatorially and compositionally complex our universe is, they only need step into the world of fashion.

• 1:48:55Sara Walker?

  Yeah.

• 1:48:56Lex Fridman?

  It's bonkers how big the construct, constructible space of human aesthetics is. Can you explain? Can we explore the space of human aesthetics?

• 1:49:07Sara Walker?

  Yeah, I don't know. I've been kind of obsessed with the, I never know how to pronounce it, is Schiaparelli, like, you know, like, like, they, they have ears and things like, it's such like a, like a weird grotesque aesthetic, but like, it's, it's totally bizarre. But what I meant, like, I, like, I have a visceral experience when I walk into my closet. I have like, a lot of.

• 1:49:28Lex Fridman?

  How big is your closet?

• 1:49:29Sara Walker?

  It's pretty big. It's like, I do assembly theory every morning when I walk in my closet because I have, I like, I really like a very large combinatorial diverse palette, but I never know what I'm going to build in the morning.

• 1:49:41Lex Fridman?

  Do you get rid of stuff?

• 1:49:42Sara Walker?

  Sometimes.

• 1:49:44Lex Fridman?

  Or do you have trouble getting rid of stuff like?

• 1:49:45Sara Walker?

  I have trouble getting rid of some stuff. It depends on what it is. If it's very, if it's vintage, it's hard to get rid of because it's kind of hard to replace. It depends on the piece. Yeah.

• 1:49:55Lex Fridman?

  So you have, your closet is that, is that one of those temporal time crystals that?

• 1:50:00Sara Walker?

  Yeah.

• 1:50:00Lex Fridman?

  They just, you get to visualize the entire history.

• 1:50:03Sara Walker?

  It's a physical manifestation of my personality.

• 1:50:06Lex Fridman?

  Right. So, so why is that a good visualization of the, the combinatorial and compositionally complex?

• 1:50:15Sara Walker?

  I think it's an interesting feature of our species that we allow, we get to express ourselves through what we wear. Right? Like, if you think about all those animals in the jungle you saw, like, they're born looking the way they look, and then they're stuck with it for life.

• 1:50:29Lex Fridman?

  That's true. I mean, it is one of the loudest, clearest, most consistent ways we signal to each other.

• 1:50:35Sara Walker?

  Yeah.

• 1:50:35Lex Fridman?

  The clothing we wear.

• 1:50:36Sara Walker?

  Yeah. And it's highly dynamic. I mean, you can be dynamic if you want to. Very few people are there's a certain bravery, but it's actually more about confidence. Willing to play with style and like and play with aesthetics. And I think it's interesting when you start experimenting with it. How it changes the fluidity of the social spaces and the way that you interact with them.

• 1:51:01Lex Fridman?

  But there's also commitment, like you have to wear the outfit all.

• 1:51:05Sara Walker?

  I know, I know. It's a big commitment. Do you feel like that every morning?

• 1:51:10Lex Fridman?

  I wear, that's why.

• 1:51:11Sara Walker?

  You're like, this is a life commitment.

• 1:51:14Lex Fridman?

  All I have is suits and a black shirt and jeans. Those are the two outfits.

• 1:51:18Sara Walker?

  Yeah. Well, see, this is the thing though, right? It simplifies your thought process in the morning. So like, I have other ways I do that. I park in the same exact parking spot when I go to work on the fourth floor of a parking garage, because no one ever parks on the fourth floor. So I can, I don't have to remember where I park my car. But I really like aesthetics and playing with them. So I'm willing to spend part of my cognitive energy every morning, trying to figure out what I want to be that day.

• 1:51:42Lex Fridman?

  Did you deliberately think about the outfit you're wearing today?

• 1:51:46Sara Walker?

  Yep.

• 1:51:47Lex Fridman?

  Was there backup options? Were you going back and forth between?

• 1:51:49Sara Walker?

  Three or four. But I really like.

• 1:51:52Lex Fridman?

  Were they drastically different?

• 1:51:53Sara Walker?

  Yes.

• 1:51:55Lex Fridman?

  So, okay.

• 1:51:56Sara Walker?

  And then even this one could have been really different because like, you know, it's not just the, the sort of jacket and the shoes and like, and the hairstyle, it's like the jewelry and the accessories. So like any outfit is, is a lot of small decisions.

• 1:52:11Lex Fridman?

  Well, I think your current outfit is like a lot of shades of yellow. There's like a theme. It's nice. It's really, I'm grateful that you did that. It's like, it's its own art form.

• 1:52:23Sara Walker?

  Yeah, yellow is my daughter's favorite color and I never really thought about yellow much, but she's been obsessed with yellow. She's seven now. And I don't know, I just really love it.

• 1:52:31Lex Fridman?

  I guess you can pick a color and just make that the constraint and then just go with it.

• 1:52:36Sara Walker?

  I'm playing with yellow a lot lately. Like this is not even the most yellow because I have black pants on, but I have, I've worn outfits that have probably five shades of yellow in them.

• 1:52:45Lex Fridman?

  Wow.

• 1:52:47Lex Fridman?

  What uh, what do you think beauty is? We seem to, so underlying this idea of playing with aesthetics is we find certain things beautiful.

• 1:52:56Sara Walker?

  Yeah.

• 1:52:57Lex Fridman?

  What is it that humans find beautiful? And why do we need to find things beautiful?

• 1:53:03Sara Walker?

  Yeah, you know, it's interesting. It's not, I'm not, I mean, I am attracted to, to, to style and aesthetics because I think they're beautiful, but it's much more because I think it's fun to play with.

• 1:53:17Sara Walker?

  And so, um, so I will get to the beauty thing, but I like, I guess I want to just explain a little bit about my motivation in this space because it's really an intellectual thing for me. And, you know, Stuart Brand has this great infographic about the layers of like human society. And I think it starts with like the natural sciences and like physics at the bottom and it goes through all these layers and it's like economics and then like fashion is at the top is like the fastest moving part of human culture. And I think I really like that because it's so dynamic and so short and it's temporal longevity contrasted with like studying the laws of physics, which are like, you know, like the deep structure of reality that I feel like, like bridging those scales tells

• 1:54:00Sara Walker?

  me much more about the structure of the world that I live in.

• 1:54:04Lex Fridman?

  That said, there's certain kinds of fashions, like a dude in a black suit with a black tie seems to be less dynamic.

• 1:54:14Sara Walker?

  Yeah.

• 1:54:14Lex Fridman?

  It seems to persist through time.

• 1:54:16Sara Walker?

  Are you embodying this?

• 1:54:18Lex Fridman?

  Yeah, I think so. I, I, I think, I think it's just.

• 1:54:22Sara Walker?

  I'd like to see you wear yellow wax.

• 1:54:25Lex Fridman?

  I wouldn't even know what to do with myself. I would freak out. I wouldn't know how to act in the world.

• 1:54:30Sara Walker?

  You wouldn't know how to be you, yeah. I know, this is amazing though, isn't it? Amazing, like you have the choice to do it. But, but one of my favorite, um, just on the question of beauty, one of my favorite fashion designers of all time is Alexander McQueen. And he, he was really phenomenal, but like his early, and actually I kind of, I kind of used like what happened to him in the fashion industry as a coping mechanism with our paper when. Uh, like the nature paper in, in the, the fall, when everyone was saying it was controversial and how terrible that like, you know, like, but controversial is good, right? But like when Alexander McQueen, you know, first came out with his fashion lines, he was mixing horror and beauty. Um, and people were horrified. It was so controversial, like they, like it was macabre. He had like, you know, like it looked like there were blood on the models and like, um.

• 1:55:15Lex Fridman?

  That's beautiful. We're just looking at some pictures here.

• 1:55:17Sara Walker?

  Yeah, no, I mean, his stuff is amazing. Um, his first, uh, like runway line, I think was called nihilism. I don't know. I don't know if you could find it. Um, you know, I mean, he was really dramatic. Uh, he, he carried a lot of trauma with him. Uh, there you go. That's, yeah. Uh, yeah.

• 1:55:35Lex Fridman?

  Wow.

• 1:55:36Sara Walker?

  Um, but he changed the fashion industry. His stuff became very popular.

• 1:55:40Lex Fridman?

  That's, that's a good outfit to show up to a party.

• 1:55:42Sara Walker?

  Right, right. But this gets at the question, like, is, is that horrific or is it beautiful? Um, and I think, you know, he, he had a traumatic, he, he ended up, um, uh, committing suicide. And actually he left his death note on the descent of man. Um, so he was, he was a really deep, uh, person.

• 1:56:02Lex Fridman?

  So, I mean, great fashion certainly has that kind of depth to it.

• 1:56:05Sara Walker?

  Yeah, it sure does. Uh, so I think it's the intellectual pursuit, right? Like it's not, um, so this is like very highly intellectual. And I think it's a lot like how I play with language is the same way that I play with fashion or the same way that I play with ideas in theoretical physics. Like there's always this space that you can just push things just enough. So they're like, they look like something someone thinks is familiar, but they're not familiar.

• 1:56:29Sara Walker?

  And yeah, and I think that's really cool.

• 1:56:31Lex Fridman?

  It seems like beauty doesn't have much function, right? But, but it seems to also have

• 1:56:40Lex Fridman?

  a lot of influence on the way.

• 1:56:42Sara Walker?

  It has tons of function. What do you mean it doesn't have function?

• 1:56:44Lex Fridman?

  I guess sexual selection incorporates beauty somehow, but why? Because beauty is a sign of health or something? I don't even.

• 1:56:53Sara Walker?

  Oh, evolutionarily, maybe, but then beauty becomes a signal of other things, right? So it's really not like, and then beauty becomes an adaptive trait. So it can change with different speed, like, you know, maybe some people, some species would think, well, you thought the frog having babies come out of its back was beautiful and I thought it was grotesque. Like, there's not a universal definition of what's beautiful. It is something that is dependent on your history and how you interact with the world. And I guess what I like about beauty, like any other concept, is when you turn it on its head. So, you know, maybe the traditional conception of, you know, why women wear makeup and they dress

• 1:57:34Sara Walker?

  certain ways is because they want to look beautiful and, you know, pleasing to people. And I just like to do it because it's a confidence thing. It's about embodying the person that I want to be and about owning that person. And then that, the way that people interact with that person is very different than if I didn't have the, like, if I wasn't using that attribute as part of... And obviously, that, that's influenced by the society I live and like, what's aesthetically pleasing things. But it's interesting to be able to turn that around and not have it necessarily be about the aesthetics, but about the power dynamics that the aesthetics create.

• 1:58:11Lex Fridman?

  But you're saying there's some function to beauty in that way, in the way you're describing, and the dynamic it creates in the social interaction.

• 1:58:18Sara Walker?

  Well, well, the point is, you're saying it's an adaptive trait for like sexual selection or something. And I'm saying that the adaptation that beauty confers is far richer than that. And some of the adaptation is about social hierarchy and social mobility and just plain social dynamics. Like, why do some people dress goth? It's because they identify with a community and a culture associated with that. And they get, you know, and that's a beautiful aesthetic. It's a, it's a different aesthetic. Some people don't like it.

• 1:58:46Lex Fridman?

  So it has the same richness as does language?

• 1:58:49Sara Walker?

  Yes.

• 1:58:50Lex Fridman?

  It's the same kind of...

• 1:58:51Sara Walker?

  Yes. And I think, I think too few people think about the way that they, the aesthetics they build for themselves in the morning and how they carry it in the world and, and the way that other people interact with that because they put clothes on and they don't think about clothes as carrying function.

• 1:59:09Lex Fridman?

  Let's jump from beauty to language. There's so many ways to explore the topic of language. You called it, you said that language is... Parts of language or language in itself and the mechanism of language is a kind of living life form. You've tweeted a lot about this in all kinds of poetic ways. Let's talk about the computation aspect of it. You tweeted, "The world is not a computation, but computation is our best current language for understanding the world. It is important we recognize this so we can start to see the structure of our future languages that will allow us to see deeper than computation allows us." So what's the use of language in helping us understand and make sense of the world?

• 1:59:52Sara Walker?

  I think one thing that I feel like I notice much more viscerally than I feel like I hear other people describe is that the representations in our mind and the way that we use language are not the things like, actually, I mean, this is an important point, going back to what Gödel did, but also this idea of signs and symbols and all kinds of ways of separating them. There's like the word, right? And then there's like what the word means about the world. And we often confuse those things. And what I feel very viscerally, I almost sometimes think I have some kind of like synesthesia for language or something and I just like don't interact with it like the

• 2:00:36Sara Walker?

  way that other people do. But for me, words are objects and the objects are not the things that they describe. They have like a different ontology to them. Like they're physical things and they carry causation and they can create meaning, but they're not, they're not, they're not what we think they are. And also like the internal representations in our mind, like the things I'm seeing about this room are probably, you know, like they're small projection of the things that are actually in this room. And I think we have such a difficult time moving past the way that we build representations in the mind and the way that we structure our language to realize that those are approximations to what's out there and they're fluid and we can play around with them and we can see

• 2:01:18Sara Walker?

  deeper structure underneath them that I think like we're missing a lot.

• 2:01:23Lex Fridman?

  Yeah, but also the life of the mind is in some ways richer than the physical reality.

• 2:01:29Sara Walker?

  Sure.

• 2:01:30Lex Fridman?

  What's going on in your mind? It might be a projection

• 2:01:33Sara Walker?

  Right.

• 2:01:34Lex Fridman?

  Actually here, but there's also all kinds of other stuff going on there.

• 2:01:38Sara Walker?

  Yeah, for sure. I love this essay by Poincaré about like mathematical creativity, where he talks about this sort of like frothing of all these things. And then like somehow you build theorems on top of it and they become kind of concrete. But like, and I also think about this with language. It's like, there's a lot of stuff happening in your mind, but you have to compress it in this few sets of words to try to convey it to someone. So it's, it's a compactification of the space. And it's not a very efficient one. And I think just recognizing that there's a lot that's happening behind language is really important. I think this is, this is one of the, the great things about the existential trauma of large language models, I think, is the recognition that language is not the only thing required.

• 2:02:23Sara Walker?

  Like there's something underneath it, not by everybody.

• 2:02:27Lex Fridman?

  Can you just speak to the feeling you have when you think about words? So is there, like, what's the magic of words to you? Is it like, do you feel it almost sometimes feels like you're playing with it?

• 2:02:42Sara Walker?

  Yeah, I was just gonna say it's like a playground.

• 2:02:44Lex Fridman?

  But you're almost like, I think one of the things you enjoy, maybe I'm projecting, is deviating, like using words in ways that not everyone uses them. Like slightly sort of deviating from the norm, a little bit.

• 2:02:58Sara Walker?

  I love doing that in everything I do, but especially with language.

• 2:03:02Lex Fridman?

  But not so far that it doesn't make sense.

• 2:03:04Sara Walker?

  Exactly.

• 2:03:05Lex Fridman?

  So you're always like tethered to reality, to the norm, but like are playing with it. Like basically fucking with people's minds a little bit. I mean, like, you know, in so doing, creating a different perspective on the thing that's been previously explored in a different way.

• 2:03:24Sara Walker?

  Yeah, it's literally my favorite thing to do.

• 2:03:26Lex Fridman?

  Yeah. Like use words as one way to make people think.

• 2:03:31Sara Walker?

  Yeah, so I, you know, a lot of my sort of, like, what happens in my mind when I'm thinking about ideas is I've been presented with this information about how people think about things. And I try to go around to different communities and hear the ways that different, whether it's like, you know, hanging out with a bunch of artists or philosophers or scientists thinking about things, like they all think about it different ways. And then I just try to figure out like,

• 2:03:59Sara Walker?

  How do you take the structure of the way that we're talking about it and turn it slightly? So you have all the same pieces that everybody sees are there, but the description that you've come up with seems totally different. So they can understand that there's, like, they understand the pattern you're describing, but they never heard the structure underlying it describe the way that you describe it.

• 2:04:20Lex Fridman?

  Is there words or terms you remember that disturbed people the most? Maybe the positive sense of disturbed? There's assembly theory, I suppose, is one.

• 2:04:34Sara Walker?

  Yeah, I mean, the first couple of sentences of that paper disturbed people a lot. And I think they were really carefully constructed in exactly this kind of way.

• 2:04:41Lex Fridman?

  What was that? Let me look it up.

• 2:04:43Sara Walker?

  Oh, it was really fun. But I think it's interesting because I do, you know, sometimes I'm very upfront about it. I say I'm going to use the same word in probably six different ways in a lecture, and I will.

• 2:04:59Lex Fridman?

  You write, "Scientists have grappled with reconciling biological evolution with immutable laws of the universe defined by physics. These laws underpin life's origin, evolution, and..."

• 2:05:09Sara Walker?

  I think you went through this with Lee when he was here, too.

• 2:05:11Lex Fridman?

  "...the development of human culture." Well, he was, I think, your love for words runs deeper than these.

• 2:05:19Sara Walker?

  Yeah, for sure. I mean, this is part of the, the sort of brilliant thing about our collaboration is, you know, complementary skill sets. So I love playing with the abstract space of language, and it's a really interesting playground when I'm working with Lee because he thinks at a much deeper level of abstraction than can be expressed by language. And the ideas we work on are hard to talk about for that reason.

• 2:05:50Lex Fridman?

  What do you think about computation as a language?

• 2:05:52Sara Walker?

  I think it's a very poor language. A lot of people think it's a really great one, but I think it has some nice properties. But I think the, the feature of it that, you know, is compelling is this kind of idea of universality that, like, you can, if you, if you, if you have a language, you can describe things in any other language.

• 2:06:11Lex Fridman?

  Well, for me, one of the people who kind of revealed...

• 2:06:15Lex Fridman?

  The expressive power of computation, aside from Alan Turing, is Stephen Wolfram, through all the explorations of cellular automata type of objects that he did in a new kind of science and afterwards. So what do you get from that? The kind of computational worlds that are revealed through even something as simple as cellular automata. It seems like that's a really nice way to explore languages that are far outside our human languages and do so rigorously and understand how those kinds of complex systems can interact with each other, can emerge, all that kind of stuff.

• 2:06:57Sara Walker?

  I don't think that they're outside our human languages. I think they define the boundary of the space of human languages. They allow us to explore things within that space, which is also fantastic. But I think there is a set of ideas that takes, and Stephen Wolfram has worked on this quite a lot, and contributed very significantly to it. And I really like some of the stuff that Stephen's doing with his physics project, but don't agree with a lot of the foundations of it. But I think the space is really fun that he's exploring. There's this assumption that computation is at the base of reality. And I kind of see it at the top of reality, not at the base, because I think computation

• 2:07:40Sara Walker?

  was built by our biosphere. It's something that happened after many billion years of evolution. And it doesn't happen in every physical object. It only happens in some of them. And I think one of the reasons that we feel like the universe is computational is because it's so easy for us as things that have the theory of computation in our minds. And actually, in some sense, it might be related to the functioning of our minds and how we build languages to describe the world and sets of relations to describe the world. But

• 2:08:18Sara Walker?

  It's easy for us to go out into the world and build computers. And then we mistake our ability to do that with assuming that the world is computational. And I'll give you a really simple example. This one came from John Conway. I one time had a conversation with him, which was really delightful. He was really fun, but he was pointing out that if you, you know, string lights in a barn, you know, you can, you can program them to have your favorite one dimensional CA. And you might even be able to make them, you know, do like be capable of universal computation. Is universal computation a feature of the string lights?

• 2:08:59Lex Fridman?

  Well, no.

• 2:09:00Sara Walker?

  No, it's probably not. It's a feature of the fact that you, as a programmer, had a theory that you could embed in the physical architecture of the string lights. Now, what happens, though, is we get confused by this kind of distinction between us as agents in the world that actually can transfer things that life does onto other physical substrates with what the world is. And so, for example, you'll see people, you know, doing, studying the mathematics of chemical reaction networks and saying, well, chemistry is turning universal or studying the laws of physics and saying the laws of physics are turning universal. But anytime that you want to do that, you always have to prepare an initial state. You have to, you know, you have to constrain the rule space.

• 2:09:41Sara Walker?

  And then you have to actually be able to demonstrate the properties of computation. And all of that requires an agent or a designer to be able to do that.

• 2:09:50Lex Fridman?

  But it gives you an intuition. If you look at a one D or two D cellular automata, it gives you, it allows you to build an intuition of how you can have complexity emerge from very simple beginnings, very simple initial conditions.

• 2:10:04Sara Walker?

  I think that's the intuition that people have derived from it. The intuition I get from cellular automata is that the flat space of an initial condition in a fixed dynamical law is not rich enough to describe an open ended generation process. And so, the way I see cellular automata is they're embedded slices in a much larger causal structure. And if you want to look at a deterministic slice of that causal structure, you might be able to extract a set of consistent rules that you might call a cellular automata, but you could embed them as much larger space. That's not dynamical and is about the causal structure and relations between all of those computations. And that would be the space cellular automata live in. And I think that's the space that. Stephen is talking about when he talks about his ruliad and these hypergraphs of

• 2:10:47Sara Walker?

  all these possible computations, but I wouldn't take that as my base reality because I think, again, computation itself, this abstract property computation, is not at the base of reality.

• 2:10:58Lex Fridman?

  Can we just linger on that ruliad?

• 2:11:01Sara Walker?

  Yeah. One ruliad to rule them all.

• 2:11:04Lex Fridman?

  Yeah. So what, this is part of Wolfram Physics Project. It's what he calls the entangled limit of everything that is computationally possible. So what's your problem with the ruliad?

• 2:11:18Sara Walker?

  Well, it's interesting. So Stephen came to a workshop we had in the Beyond Center in the fall, and the workshop theme was mathematics, is it evolved or eternal? And he gave a talk about the ruliad, and he was talking about how, you know, a lot of the things that we talk about in the Beyond Center, like, does reality have a bottom? You know, if it has a bottom, what is it? You know, like, what's the...

• 2:11:41Lex Fridman?

  I need to go...

• 2:11:42Sara Walker?

  Well, have you done one sometime?

• 2:11:44Lex Fridman?

  This is great. Does reality have a bottom?

• 2:11:48Sara Walker?

  Yeah. So we had one that was, it was called, "Infinite Turtles or Ground Truth," and it was really just about this issue. But the thing that was interesting, I think Stephen was trying to make the argument that, you know, fundamental particles aren't fundamental, gravitation is not fundamental, you know, these are just turtles, and computation is fundamental. And I just, I remember pointing out to him, I was like, "Well, computation is your turtle." And I think it's a weird turtle to have.

• 2:12:18Lex Fridman?

  First of all, isn't it okay to have a turtle?

• 2:12:20Sara Walker?

  It's totally fine to have a turtle. Everyone has a turtle. You can't build a theory without a turtle. It's just, so it depends on the problem you want to describe. And I'd, actually, the reason I can't get behind Stephen's ontology is I don't know what question he's trying to answer. And without a question to answer, I don't understand why you're building a theory of reality.

• 2:12:40Lex Fridman?

  And the question you're trying to answer is...

• 2:12:43Sara Walker?

  What life is.

• 2:12:44Lex Fridman?

  What life is, which, another simpler way of phrasing that is, how did life originate?

• 2:12:50Sara Walker?

  Well, I started working on the origin of life, and I think what my challenge was there was no one knew what life was, and so you can't really talk about the origination of something if you don't know what it is. And so the way I would approach it is if you want to understand what life is, then proving that physics is solving the original life. So there's the theory of what life is, but there's the actual demonstration that that theory is an accurate description of the phenomena you aim to describe. So again, they're the same problem. It's not like I can decouple original life from what life is. It's like, that is the problem. And the point I guess I'm making about having a question is no matter what slice of reality

• 2:13:33Sara Walker?

  you take, what regularity of nature you're going to try to describe, there will be an abstraction that unifies that structure of reality, hopefully. And that will have a fundamental layer to it, right? Because you have to explain something in terms of something else. But so if I want to explain life, for example, then my fundamental description of nature has to be something I think that has to do with time being fundamental. But if I wanted to describe, I don't know, the sort of interactions of matter and light, you know, I have elementary particles be fundamental.

• 2:14:13Sara Walker?

  If I want to describe electricity and magnetism in the 1800s, I have to have waves be fundamental, right? So like you are in quantum mechanics, like it's a wave function that's fundamental because that's the sort of explanatory paradigm of your theory. So I guess I don't know what problem saying computation is fundamental solves.

• 2:14:40Lex Fridman?

  Doesn't he want to understand how does the basic law of quantum mechanics and general relativity emerge?

• 2:14:48Sara Walker?

  Yeah.

• 2:14:48Lex Fridman?

  And how does time?

• 2:14:49Sara Walker?

  Right. So I think-

• 2:14:50Lex Fridman?

  Then that doesn't really answer an important question for us.

• 2:14:52Sara Walker?

  Well, I think the issue is general relativity and quantum mechanics are expressed in mathematical languages. And then computation is a mathematical language. So you're basically saying that maybe there's a more universal mathematical language for describing theories of physics that we already know. That's an important question, and I do think that's what Stephen's trying to do and do well. But then the question becomes, does that formulation of a more universal language for describing the laws of physics that we know now tell us anything new about the nature of reality? Or is it a language?

• 2:15:28Lex Fridman?

  Anti-oral languages are fundamental, can't be fundamental.

• 2:15:32Sara Walker?

  The language itself is never the fundamental thing. It's whatever it's describing.

• 2:15:37Lex Fridman?

  So one of the possible titles you were thinking about originally for the book is the hard problem of life. Sort of reminiscent of the hard problem of consciousness. So you're saying that assembly theory is supposed to be answering the question about what is life? So let's go to the other hard problems. You also say that's the easiest of the hard problems is the is the hard problem of life.

• 2:16:03Lex Fridman?

  So what do you think is the nature of intelligence and consciousness? We think something like assembly theory can help us understand that.

• 2:16:19Sara Walker?

  I think if assembly theory is an accurate depiction of the physics of life, it should shed a lot of light on those problems. And in fact, I sometimes wonder if the problems of consciousness and intelligence are at all different than the problem of life generally.

• 2:16:40Sara Walker?

  And I'm not, I'm, I'm of two minds of it, but I, I in general try to, you know, like the process of my thinking is trying to regularize everything into one theory. So pretty much every interaction I have is like, oh, how do I fold that into? And like, so I'm just building this giant abstraction that's basically trying to take every piece of data I've ever gotten in my, in my brain into a theory of what life is.

• 2:17:06Sara Walker?

  And consciousness and intelligence are obviously some of the most interesting things that life has manifest. And so I think they're very telling about some of the deeper features about the nature of life.

• 2:17:18Lex Fridman?

  It does seem like they're all. Flavors of the same thing. But it's interesting to wonder like, at which stage that's something that we would recognize as life in a sort of canonical, silly, human way. And something that we would recognize as intelligence. At which stage does that emerge? Like, at which assembly index does that emerge? And which assembly index is consciousness? Something that we would canonically recognize as consciousness.

• 2:17:46Sara Walker?

  Is this the use, like, this use of flavors? The same as you meant when you were talking about flavors of alien, like, alien life?

• 2:17:52Lex Fridman?

  Yeah, sure, yeah. I mean, it's same as the flavors of ice cream and the flavors of fashion.

• 2:17:58Sara Walker?

  Yeah, like, but we were talking about in terms of colors and like, very nondescript. But the way that you just talked about flavors now was more in like, the space of consciousness and intelligence. It was kind of like, much more specific.

• 2:18:07Lex Fridman?

  It'd be nice if there's a formal way of expressing.

• 2:18:11Sara Walker?

  Quantifying flavors.

• 2:18:13Lex Fridman?

  Quantifying flavors.

• 2:18:14Sara Walker?

  Yeah.

• 2:18:14Lex Fridman?

  It seems like

• 2:18:18Lex Fridman?

  I would order it life, consciousness, intelligence, probably. As like, the order in which things emerge. And they're all just the same.

• 2:18:27Sara Walker?

  They're the same.

• 2:18:28Lex Fridman?

  We're using the word life differently here. I mean, life, sort of, when I'm talking about what is a living versus a non-living thing at a bar with a person. I'm already like, four, five drinks in, that kind of thing.

• 2:18:42Sara Walker?

  Just that.

• 2:18:44Lex Fridman?

  Like, we're not, we're not being too philosophical. Like, here's the thing that moves and here's the thing that doesn't move. And, uh, but maybe consciousness precedes that. It's a weird dance there. We're like, is life precede consciousness or consciousness precede life? And I think that, understanding of what life is in the way you're doing, will help us disentangle that.

• 2:19:10Sara Walker?

  Depending on what you want to explain, as I was saying before, you have to assume something's fundamental. And so, because people can't explain consciousness, there's a temptation for some people to want to take consciousness as fundamental and assume everything else is derived out of that. And then you get some people that want to assume consciousness preceded life. And I don't, I don't find either of those views particularly illuminating. I think, because I don't, I don't want to assume a feminism before I explain a thing. And so what I've tried really hard to do is, is not assume that I think life is anything, except hold on to sort of the patterns and structures that seem to be the sort of consistent

• 2:19:51Sara Walker?

  ways that we talk about this thing and then try to build a physics that describes that. And I think that's a really different approach than saying, you know, consciousness is this thing, you know, we all feel and experience about things. I would want to understand the regularities associated with that and build a deeper structure underneath that and build into it. I wouldn't want to assume that thing and that I understand that thing, which is usually how I see people talk about it.

• 2:20:16Lex Fridman?

  The difference between life and consciousness?

• 2:20:19Sara Walker?

  Yeah.

• 2:20:19Lex Fridman?

  Which, which comes first?

• 2:20:21Sara Walker?

  Yeah, so I think if you're thinking about this sort of thinking about living things as these giant causal structures or these objects that are deep in time or whatever language we end up using to describe it. It seems to me that consciousness is about the fact that we have a conscious experience is because we are these temporally extended objects. So consciousness and the abstraction that we have in our minds is actually a manifestation of all the time that's rolled up in us. And it's just because we're so huge that we have this very large inner space that we're experiencing that's not, and it's also separated off from the rest of the world

• 2:21:04Sara Walker?

  because we're the separate thread in time. And so our consciousness is not exactly shared with anything else because nothing else occupies the same part of time that we occupy. But I can understand something about you maybe being conscious because you and I didn't separate that far in the past in terms of our causal histories. So in some sense, we can even share experiences with each other through language because of that sort of. Overlap in our structure.

• 2:21:33Lex Fridman?

  Well, then if consciousness is merely temporal separateness, then that comes before life.

• 2:21:41Sara Walker?

  It's not merely temporal separateness, it's about the depth in that time. So it's

• 2:21:45Lex Fridman?

  Yes.

• 2:21:46Sara Walker?

  The reason that my conscious experience is not the same as yours is because we're separated in time. The fact that I have a conscious experience is because I'm an object that's super deep in time. So I'm huge in time. And that means that there's a lot there that I am basically, in some sense, a universe on to myself because my structure is so large relative to the amount of space that I occupy.

• 2:22:07Lex Fridman?

  But it feels like that's possible to do before you get anything like bacteria.

• 2:22:13Sara Walker?

  I think there's a horizon, and I don't know how to articulate this yet. It's a little bit like the horizon at the origin of life where the space inside a particular structure becomes so large that it has some access to a space that's not

• 2:22:29Sara Walker?

  that doesn't feel as physical. It's almost like this idea of counterfactuals.

• 2:22:35Sara Walker?

  So I think like the the past history of your horizon is just much larger than can be encompassed in like a small configuration of matter. So you you can like pull this stuff into existence. This property is maybe a continuous property, but there's something really different about

• 2:22:54Sara Walker?

  human level, physical systems and human level ability to understand reality. I really love David Dicke's conception of universal explainers and like, and that's related to the theory of universal computation.

• 2:23:09Sara Walker?

  And I think there's some transition that happens there. But maybe, maybe to describe that a little bit better, what I can also say is like what intelligence is in this this framework. So you have these, these, these objects that are, you know, large in time. They were selected to exist by constraining the possible space of objects to this particular, like all of the matter is funneled into this, this particular configuration of object over time. And so these objects arise through selection. But the more selection that you have embedded in you, the more possible selection you have on your future. And so, so selection and evolution, we usually think about in the past sense, where selection happened in the past.

• 2:23:55Sara Walker?

  But objects that are High-density configurations of matter that have a lot of selection in them are also selecting agents in the universe. So they actually embody the physics of selection, and they can select on possible futures. And I guess what I'm saying with respect to consciousness and the experience we have is that there's something very deep about that structure and the nature of how we exist in that structure that has to do with how we're navigating that space and how we generate that space and how we continue to persist in that space.

• 2:24:29Lex Fridman?

  Is there shortcuts we can take to artificially engineering living organisms, artificial life, artificial consciousness, artificial intelligence? So maybe just looking pragmatically at the LLLs we have now, do you think those can exhibit qualities of life, qualities of consciousness, qualities of intelligence in the way we think of intelligence?

• 2:24:57Sara Walker?

  I mean, I think they already do, but not in the way I hear popularly discussed. So they're obviously signatures of intelligence and a part of an ecosystem of intelligent systems. But I don't know that individually, you know, I would assign all the properties to them that people have. It's a little like, so, you know, we talked about the history of eyes before and like how eyes scaled up into technological forms. And language has also had a really interesting history and got much more interesting, I think, once we started writing it down and then, you know, inventing books and things. But like, you know, every time that we started storing language in a new way, you know, we're kind

• 2:25:42Sara Walker?

  of existentially traumatized by it. So like, you know, the idea of written language was traumatic because it seemed like the dead were speaking to us, even though they were deceased. And books were traumatic because, you know, like suddenly there were lots of copies of this information available to everyone and it was going to somehow dilute it. And large language models are kind of interesting because they don't feel as static, they're very dynamic. But if you think about language in the way I was describing before, is language is this very large in time structure. And before it had been something that was distributed. Over human brains as a dynamic structure. And occasionally, we store components of that very large dynamic structure in books or in written language.

• 2:26:26Sara Walker?

  Now, we can actually store the dynamics of that structure in a physical artifact, which is a large language model. And so I think about it almost like the evolution of genomes in some sense, where, you know, there might have been like really primitive genes in the first living things, and they could, they didn't store a lot of information, or they were like really messy. And then me, you know, like you, by the time you get to the eukaryocel, you have this really dynamic genetic architecture that's readwritable, right? And like, and has all of these different properties. And I think large language models are kind of like the genetic system for language in some sense, where it's, it's allowing and a sort of archiving that's highly dynamic. And I think it's very paradoxical to us, because obviously, in human history, we haven't

• 2:27:10Sara Walker?

  been used to conversing with anything that's not human. But now, we can converse, basically, with a crystallization of human language in a computer. That's a highly dynamic crystal, because it's a crystallization in time of this massive abstract structure that's evolved over human history, and is now put into a small device.

• 2:27:34Lex Fridman?

  I think crystallization kind of implies that a limit on its capabilities.

• 2:27:40Sara Walker?

  I think there's not, I mean it very purposefully, because a particular instantiation of a language model, trained on a particular data set, becomes a crystal of the language at that time it was trained. But obviously, we're iterating with the technology and evolving it.

• 2:27:53Lex Fridman?

  I guess the question is, when you crystallize it, when you compress it, when you archive it, you're archiving some slice of the collective intelligence of the human species.

• 2:28:04Sara Walker?

  That's right.

• 2:28:05Lex Fridman?

  And the question is, like, how powerful is that?

• 2:28:09Sara Walker?

  Right. It's a societal level technology, right? We've actually put collective intelligence in a box.

• 2:28:13Lex Fridman?

  Yeah. I mean, how much smarter is the collective intelligence of humans versus a single human? And that's-

• 2:28:23Lex Fridman?

  That's the question of AGI versus human level intelligence, superhuman level intelligence versus human level intelligence. Like, how much smarter can this thing, when done well, when we solve a lot of the

• 2:28:36Lex Fridman?

  complexity, computation complexities, maybe there's some data complexities and how to really archive this thing, crystallize this thing really well.

• 2:28:44Sara Walker?

  Yeah.

• 2:28:45Lex Fridman?

  How powerful is this thing going to be? Like, what's your?

• 2:28:47Sara Walker?

  I think, I actually, I don't like the sort of language we use around that, and I think the language really matters. So I don't know how to talk about how much smarter one human is than another. Right? Like, usually we talk about abilities or particular talents someone has. And, you know, going back to, you know, David Dratch's idea of universal explainers, like, you know, adopting the view that,

• 2:29:18Sara Walker?

  you know, we're the first, you know, kinds of structures our biosphere has built that can understand the rest of reality. We have this universal comprehension capability.

• 2:29:29Sara Walker?

  You know, he makes an argument that basically we're the first things that actually are capable of understanding anything. It doesn't matter, it doesn't mean an individual understands everything, but like, we have that capability. And so there's not a difference between that and what people talk about with AGI. In some sense, AGI is a universal explainer. But, you know, like, it might be that a computer is much more efficient at doing, you know, I don't know, prime factorization or something than a human is. But it doesn't mean that it's necessarily smarter or has a broader reach of the kind of things that can understand than a human does. And so I think we really have to think about, is it a level shift?

• 2:30:13Sara Walker?

  Or is it we're enhancing certain kinds of capabilities humans have in the same way that we can enhance eyesight by making telescopes and microscopes? Are we enhancing capabilities we have into technologies? And the entire global ecosystem is getting more intelligent? Or is it really that we're building some super machine in a box that's going to be smart and kill everybody? Like, that sounds like a science, like, it's not, it's not even a science fiction narrative. It's a bad science fiction narrative. I like, I just don't think it's actually accurate to any of the technologies we're building or the way that we should be describing them. It's not even how we should be describing ourselves.

• 2:30:45Lex Fridman?

  So, the benevolent story is, is a benevolent system that's able to transform our economy, our way of life by just, you know, ten X-ing the GDP of countries.

• 2:30:59Sara Walker?

  Well, these are human questions, right? I don't think they're necessarily questions that we're gonna like outsource to an artificial intelligence. I think what is happening and will continue to happen is there's a co-evolution between humans and technology that's happening. And we're coexisting in this ecosystem right now, and we're maintaining a lot of the balance. And for the balance to shift to the technology would require some very bad human actors, which is a real risk, or some sort of, um, I don't know, some sort of dynamic that favors, like, I, I just don't know how that plays out without human agency actually trying to put it in that direction.

• 2:31:42Lex Fridman?

  It could also be how rapid the rate.

• 2:31:45Sara Walker?

  The rapid rate is scary. So like, I think the things that are, you know, terrifying are, um, you know, the ideas of deep fakes, or, um, you know, like, you know, all the, the kinds of issues that become legal issues about artificial intelligence technologies, um, and using them to control weapons, or, uh, using them for, you know, like, child pornography, or, you know, like, or like, you know, faking out that someone's, um, you know, loved one was kidnapped or killed, and it, you know, like, and ransom, like, there's all kinds of things that are super scary in this landscape, and all kinds of new legislation needs to be built, and all kinds of, um, guardrails on the technology to make sure that people don't abuse it need to be built.

• 2:32:30Sara Walker?

  And that needs to happen. And I think one function of sort of the artificial intelligence, uh, doomsday.

• 2:32:39Sara Walker?

  Sort of part of our culture right now is it's sort of our immune response to knowing that's coming. And we're over scaring ourselves, so we try to act more quickly, which is good. But I, I, I just, you know, it's, it's about the words that we use versus the actual things happening behind the words. I think one thing that's good is when people are talking about things different ways, it makes us think about them. And also when things are existentially threatening, we want to pay attention to those. But the ways that they're existentially threatening and the ways that we're experiencing existential trauma, I don't think that we're really going to understand for another century or two, if ever. And I certainly think they're not the way that we're describing them now.

• 2:33:21Lex Fridman?

  Well, creating existential trauma is one of the things that makes life fun, I guess.

• 2:33:28Sara Walker?

  Yeah, it's just what we do to ourselves.

• 2:33:30Lex Fridman?

  It gives us really exciting, big problems to solve.

• 2:33:34Sara Walker?

  Yeah, for sure.

• 2:33:35Lex Fridman?

  Do you think we will see these AI systems become conscious or convince us that they're conscious? And then maybe we'll have relationships with them, romantic relationships?

• 2:33:47Sara Walker?

  Well, I think people are going to have romantic relationships with them. And I also think that some people will be convinced already that they're conscious. But I think in order, you know, what does it take to convince, convince people that something is conscious? I think that we actually have to have an idea of what we're talking about, that it's con- like, it's like, we have to have a theory that explains when things are conscious or not, that's testable, right? And we don't have one right now. So I think until we, we have that, it's always going to be this sort of gray area where some people think it has it and some people think it doesn't, because we don't actually know what we're talking about that we think it has.

• 2:34:25Lex Fridman?

  So do you think it's possible to get out of the gray area and really have a formal test for consciousness?

• 2:34:30Sara Walker?

  For sure.

• 2:34:31Lex Fridman?

  And, and for life, as you were-

• 2:34:33Sara Walker?

  For sure.

• 2:34:34Lex Fridman?

  As we've been talking about for some of it.

• 2:34:36Sara Walker?

  Yeah.

• 2:34:36Lex Fridman?

  Consciousness is a tricky one.

• 2:34:38Sara Walker?

  It is a tricky one. I mean, that's why it's called the hard problem of consciousness, because it's hard. And, you know, it might even be outside of the purview of science, which means that we can't understand it in a scientific way. There might be other ways of coming to understand it, but that, those may not be the ones that we necessarily want for technological utility, or for developing laws with respect to, because the laws are, are- You know, the things that are going to govern the technology.

• 2:35:04Lex Fridman?

  Well, I think that's actually where the the hard problem of consciousness, a different hard problem of consciousness is that I fear that humans will resist. That's the last thing they will resist is calling something else conscious.

• 2:35:21Sara Walker?

  Oh, that's interesting. I think it depends on the culture, though, because, I mean, some cultures already think like everything's imbued with, you know, a life essence or kind of conscious.

• 2:35:31Lex Fridman?

  I don't think those cultures have nuclear weapons.

• 2:35:34Sara Walker?

  No, they don't. They're probably not building the most advanced technologies.

• 2:35:37Lex Fridman?

  The cultures that are primed for destroying the other, constructing a very effective propaganda machines of what the other is, the group to hate, are the are the cultures that I worry would.

• 2:35:53Sara Walker?

  Yeah, I know.

• 2:35:54Lex Fridman?

  Would would be very resistant to label something to sort of acknowledge the consciousness latent in a thing that was created by us humans.

• 2:36:06Sara Walker?

  And so what do you think the risks are there that the conscious things will get angry with us and fight back?

• 2:36:12Lex Fridman?

  No, that that would that we would torture and kill conscious beings.

• 2:36:15Sara Walker?

  Oh, yeah, I think we do that quite a lot. Anyway, without, I mean, I don't, I mean, it goes back to your, and I don't know how to feel about this, but, you know, like, we talked already about the predator prey thing that, like, in some sense, you know, being alive requires eating other things that are alive. And even if you're a vegetarian or, you know, like, try to have, like, you're like, you're still eating living things.

• 2:36:42Lex Fridman?

  So maybe part of the the story of Earth will involve a predator prey dynamic between humans and human creations.

• 2:36:53Sara Walker?

  Yeah.

• 2:36:53Lex Fridman?

  And all of that is part of the.

• 2:36:55Sara Walker?

  But I don't like thinking about them as like our technologies as a separate species because this, again, goes back to this sort of levels of selection issue. And, you know, if you think about humans individually alive, you miss the fact that societies are also alive. And so I think about it much more in the sense of. An ecosystem is not the right word, but we don't have the right words for these things of like, and this is why I talk about the technosphere. It's a system that is both human and technological. It's not human or technological. And so, this is the part that I think we're really good for the like, and this is driving in part a lot of the

• 2:37:38Sara Walker?

  sort of attitude of like, I'll kill you first with my nuclear weapons. We're really good at identifying things as other. We're not really good at understanding when we're the same, or when we're part of an integrated system that's actually functioning together in some kind of cohesive way. So even if you look at like, you know, the division in American politics or something, for example, it's important that there's multiple sides that are arguing with each other, because that's actually how you resolve society's issues. It's not like a bad feature. I think like some of the sort of extreme positions and like the way people talk about it are maybe not ideal. But, but that's how societies solve problems. What it looks like for an individual is really different than the societal level outcomes and the fact that like, there is, I don't want to call it cognition or

• 2:38:23Sara Walker?

  computation, I don't know what you call it, but like, there is a process playing out in the dynamics of societies that we are all individual actors in, and like, we're not part of that, you know, like, it requires all of us acting individually, but like, this higher level structure is playing out some things and like, things are getting solved for it to be able to maintain itself. And that's the level that our technologies live at. They don't live at our level. They live at the societal level and they're deeply integrated with the social organism, if you want to call it that. And so, I really get upset when people talk about the species of artificial intelligence. I'm like, you mean, we live in an ecosystem of all these kind of intelligent things and these animating technologies that were

• 2:39:07Sara Walker?

  You know, in some sense, helping to come alive. We are, we are generating them, but it's not like the biosphere eliminated all of its past history when it invented a new species. All of these things get scaffolded. And we're also augmenting ourselves at the same time that we're building technologies. I don't think we can anticipate what that system's going to look like.

• 2:39:24Lex Fridman?

  So in some fundamental way, you always want to be thinking about the planet as one organism.

• 2:39:29Sara Walker?

  The planet is one living thing.

• 2:39:30Lex Fridman?

  What happens when it becomes multi-planetary? Is it still just the-

• 2:39:35Sara Walker?

  Still the same causal chain.

• 2:39:36Lex Fridman?

  Same causal chain.

• 2:39:37Sara Walker?

  It's like when the first cell split into two. That's what I was talking about when the, when a planet reproduces itself, the technosphere emerges enough understanding. It's, it's, it's like this recursive, like the entire history of life is just recursion, right? So you have an original life event. It evolves for four billion years, at least on our planet. It evolves a technosphere. The technologies themselves start to become having this property we call life, which is the phase we're undergoing now. It solves the origin of itself and then it figures out how that process all works, understands how to make more life, and then can copy itself onto another planet. So the whole structure can reproduce itself. And so the original life is happening again right now on this planet in the technosphere

• 2:40:22Sara Walker?

  with the way that our planet is undergoing another transition, just like at the original life, when geochemistry transitioned to biology, which is the global, for me, it was a planetary scale transition. It was a multi-scale thing that happened from the scale of chemistry all the way to planetary cycles. It's happening now, all the way from individual humans to the internet, which is a global technology and all the other things. Like there's this multi-scale process that's happening and transitioning us globally. And it is really like, it's a dramatic transition. It's happening really fast.

• 2:40:51Lex Fridman?

  And you think-

• 2:40:52Sara Walker?

  And we're living in it.

• 2:40:54Lex Fridman?

  You think this technosphere that we created, this increasingly complex technosphere will spread to other planets?

• 2:40:59Sara Walker?

  I hope so. I think so.

• 2:41:01Lex Fridman?

  You think we'll become a type two Cartershev civilization?

• 2:41:05Sara Walker?

  I don't really like the Cartershev scale. And it goes back to like, I don't like a lot of the narratives about life because they're very like, you know, survival of the fittest, energy consuming this, that and the other thing. It's very like, I don't know, sort of old world, you know, like conqueror mentality.

• 2:41:22Lex Fridman?

  What's the alternative to that exactly?

• 2:41:24Sara Walker?

  I mean, I think it does require life to use new energy sources in order to expand the way it is. So that part's accurate. But I think this sort of process of life, like being the mechanism that the universe creatively expresses itself, generates novelty, explores the space of the possible is really the thing that's most deeply intrinsic to life. And so, you know, these sort of energy consuming scales of technology, I think is missing the sort of actual feature that's most prominent about any alien life that we might find, which is that it's literally our universe, our reality, trying to creatively express itself and trying to find out what can exist and trying to make it exist.

• 2:42:09Lex Fridman?

  See, but past a certain level of complexity, unfortunately, maybe you can correct me, but we're built, all complex life on Earth is built on a foundation of that predator prey dynamic.

• 2:42:19Sara Walker?

  Yes.

• 2:42:20Lex Fridman?

  And so like, I don't know if we can escape that.

• 2:42:22Sara Walker?

  No, we can't. But this is why I'm okay with having a finite lifetime. And you know, one of the reasons I'm okay with that, actually, goes back to this issue of the fact that we're resource bound. We live in a, you know, like we have a finite amount of material, whatever way you want to define material, I think, like for me, you know, material is time, material is information, but we have a finite amount of material. If time is a generating mechanism, it's always going to be finite because the universe is, you know, like it's a resource that's getting generated, but it has a size.

• 2:42:57Sara Walker?

  Which means that all the things that could exist don't exist. And in fact, most of them never will. So death is a way to make room in the universe for other things to exist that wouldn't be able to exist otherwise. So if the universe over its entire temporal history wants to maximize the number of things, wants is a hard word, maximize is a hard word. All of these things are approximate, but wants to maximize the number of things that can exist. The best way to do it is to make recursively embedded stacked objects like us that have a lot of structure and a small volume of space and to have those things turn over rapidly so you can create as many of them as possible.

• 2:43:31Lex Fridman?

  So there for sure is a bunch of those kinds of things throughout the universe.

• 2:43:35Sara Walker?

  Hopefully. Hopefully our universe is teeming with life.

• 2:43:38Lex Fridman?

  This is like early on in the conversation, you mentioned that we really don't understand much. Like there's mystery all around us.

• 2:43:47Sara Walker?

  Yes.

• 2:43:48Lex Fridman?

  If you had to like bet money on it, like what percent? So like, say a million years from now, the story of science

• 2:43:58Lex Fridman?

  and human understanding, understanding that started on Earth is written. Like what chapter are we on? Are we like, is this like 1%, 10%, 20%, 50%, 90%? How much do we understand? Like the big stuff, not, not like the details of like, like big, important questions.

• 2:44:23Sara Walker?

  Yeah.

• 2:44:23Lex Fridman?

  And ideas.

• 2:44:25Sara Walker?

  I think we're in our twenties and

• 2:44:28Lex Fridman?

  20% of the 20?

• 2:44:30Sara Walker?

  No, like age wise, let's say we're in our twenties, but the lifespan is going to keep getting longer.

• 2:44:35Lex Fridman?

  You can't do that.

• 2:44:36Sara Walker?

  I can. You know why I use that though? I'll tell you why. Why my brain went there is because, you know, anybody that gets an education in physics, you know, has this sort of trope about how all the great physicists did their best work in their twenties. And then you don't do any good work after that. And I always thought it was kind of funny because for me physics is

• 2:45:01Sara Walker?

  Is not complete. It's not nearly complete, but most physicists think that we understand most of the structure of reality. And so I, I think I actually, I think I put this in the book somewhere, but like this idea to me that societies would discover everything while they're young is very consistent with the way we talk about physics right now. But I don't think that's actually the way that things are going to go. And you're finding that people that are making major discoveries are getting older in some sense than they were, and our lifespan is also increasing. So I think there is something about age and your ability to learn and how much of the world you can see that's really important

• 2:45:42Sara Walker?

  over a human lifespan, but also over the lifespan of societies. And so I don't know how big the frontier is. I don't actually think it has a limit. I, I don't believe in infinity as a physical thing, but I think as a receding horizon, I think because the universe is getting bigger, you can never know all of it.

• 2:46:01Lex Fridman?

  Well, I think it's about 1.7%.

• 2:46:06Sara Walker?

  1.7? Where did that come from?

• 2:46:09Lex Fridman?

  It's a finite, I don't know, I just made it up. But it's like-

• 2:46:12Sara Walker?

  That number had to come from somewhere.

• 2:46:13Lex Fridman?

  Certainly, I think seven is the thing that people usually pick.

• 2:46:17Sara Walker?

  7%?

• 2:46:18Lex Fridman?

  So I, I wanted to say 1%, but I thought it'd be funnier.

• 2:46:22Sara Walker?

  Yeah.

• 2:46:23Lex Fridman?

  To add a point, you know, so humor, inject a little humor in there. So the seven is for the humor, one is for how much mystery I think there is out there.

• 2:46:32Sara Walker?

  99% mystery, 1% known.

• 2:46:34Lex Fridman?

  In terms of like really big, important questions.

• 2:46:37Sara Walker?

  Yeah.

• 2:46:38Lex Fridman?

  It's like the list, say there's going to be like 200 chapters, like the stuff that's going to remain true.

• 2:46:43Sara Walker?

  But you think the book has a finite size.

• 2:46:47Lex Fridman?

  Yeah, yeah.

• 2:46:48Sara Walker?

  And I don't. I mean, it, not that I believe in infinities, but I don't, I think the size of the book is growing.

• 2:46:56Lex Fridman?

  Well, the fact that the size of the book is growing is one of the chapters in the book.

• 2:47:01Sara Walker?

  Oh, there you go. Oh, we're being recursive.

• 2:47:06Lex Fridman?

  I think you have to, you can't, you can't have an ever-growing book.

• 2:47:10Sara Walker?

  Yes, you can.

• 2:47:11Lex Fridman?

  I mean, you just, I mean, I don't even, because then-

• 2:47:14Sara Walker?

  Well, you couldn't have been asking this at the origin of life, right? Because obviously, like, you wouldn't have existed at the origin of life. But like, the question of intelligence and artificial general, like, those questions did not exist then. And so, and they, in part, existed because the universe invented a space for those questions to exist. Through evolution.

• 2:47:35Lex Fridman?

  But like, I think that question will still stand a thousand years from now.

• 2:47:39Sara Walker?

  It will, but there will be other questions we can't anticipate now that we'll be asking.

• 2:47:43Lex Fridman?

  Yeah, and maybe we'll develop the kinds of languages that will be able to ask much better questions.

• 2:47:48Sara Walker?

  Right, or like, like the theory of, like, gravitation, for example. Like, when we invented that theory, like, we only knew about the planets in our solar system. Right, and now, you know, many centuries later, we know about all these planets around other stars, and black holes, and other things that we could never have anticipated. So, and then we can ask questions about them. You know, like, we wouldn't have been asking about singularities, and like, can they really be physical things in the universe several hundred years ago? That question couldn't exist.

• 2:48:15Lex Fridman?

  Yeah, but it's not, I still think those are chapters in a book. Like, I don't get a sense from that.

• 2:48:22Sara Walker?

  So, do you think the universe has an end?

• 2:48:25Sara Walker?

  If you think it's a book with an end?

• 2:48:27Lex Fridman?

  I think the number of words required to describe how the universe works has an end, yes.

• 2:48:36Lex Fridman?

  Meaning, like, I don't care if it's infinite or not.

• 2:48:39Sara Walker?

  Right.

• 2:48:39Lex Fridman?

  As long as the explanation is simple, and it exists.

• 2:48:43Sara Walker?

  Oh, I see.

• 2:48:44Lex Fridman?

  And I think there is a finite explanation for each aspect of it. The consciousness, the life.

• 2:48:51Sara Walker?

  Yeah.

• 2:48:53Lex Fridman?

  I mean, very probably, there's like some-

• 2:48:57Lex Fridman?

  The black hole thing is like, what's going on there?

• 2:49:00Sara Walker?

  I know.

• 2:49:00Lex Fridman?

  Where's that going?

• 2:49:01Sara Walker?

  So fun about here.

• 2:49:02Lex Fridman?

  Like, where do they, what? And then, you know, why the Big Bang? Like, what?

• 2:49:07Sara Walker?

  Right.

• 2:49:07Lex Fridman?

  It's probably there's just a huge number of universes and it's like universes inside universe.

• 2:49:13Sara Walker?

  I think universes inside universes is maybe possible.

• 2:49:17Lex Fridman?

  I just think it's, it, um, every time we assume this is all there is. It turns out there's much more.

• 2:49:26Sara Walker?

  The universe is a huge place.

• 2:49:27Lex Fridman?

  And we mostly talked about the past and the richness of the past, but the future, I mean, with, um, with many worlds, interpretation of quantum mechanics. So.

• 2:49:36Sara Walker?

  Oh, I'm not a many worlds person.

• 2:49:37Lex Fridman?

  You're not.

• 2:49:38Sara Walker?

  No. Are you? How many Lexes are there?

• 2:49:41Lex Fridman?

  Depending on the day. Well.

• 2:49:43Sara Walker?

  Do some of them wear yellow jackets?

• 2:49:45Lex Fridman?

  At the moment, at the moment you asked the question, there was one. Uh, at the moment I'm answering it, there's now in, in near infinity, apparently. I mean, the future is, is the future is bigger than the past, yes?

• 2:49:58Sara Walker?

  Yes.

• 2:49:58Lex Fridman?

  Okay.

• 2:49:59Sara Walker?

  I think so.

• 2:49:59Lex Fridman?

  But in the past, according to you, it's already gigantic.

• 2:50:02Sara Walker?

  Yeah, but yeah, I mean, that's consistent with many worlds, right? Cause like, there's this constant branching, so, but it doesn't really have a directionality to it. It's, it's a, I don't know, many worlds is weird. So my interpretation of reality is like, if you folded up like all that bifurcation of many worlds and you just fold it into the structure that is you and you just said you are all of those many worlds. And like, that's sort of, you know, like, like your history, like converged on you, but you're like, you're, you're actually an object exists that's like, that, you know, was selected to exist and you're self-consistent with the other structures. So like, the quantum mechanical reality is, is not the one that you live in. It's this very deterministic, uh, classical world. And you're carving a path through that space, but I don't think.

• 2:50:49Sara Walker?

  That you're constantly branching into new spaces. I think you are that space.

• 2:50:53Lex Fridman?

  Wait, so to you at the bottom, it's deterministic? I thought you said the universe.

• 2:50:57Sara Walker?

  No, it's random at the bottom, right? But like this randomness that we see at the bottom of reality that is quantum mechanics. I think like people have assumed that that is reality. And what I'm saying is like, all those things you see in many worlds, all those versions of you, just collect them up and bundle them up. And like, they're all you. And what has happened is, you know, like elementary particles don't have, they don't live in a deterministic universe, the things that we study in quantum experiments. They live in this fuzzy, random space. But as that structure collapsed and started to build structures that were deterministic and evolved into you, you are a very deterministic microscopic, macroscopic object. And you can look down on that universe that doesn't have time in it, that random structure.

• 2:51:42Sara Walker?

  And you can see that all of these possibilities look possible, but they don't look, they're not possible for you because you're constrained by this giant, like causal structural history. So you can't live in all those universes. You'd have to go all the way back to the very beginning of the universe and retrace everything again to be a different you.

• 2:52:03Lex Fridman?

  So where's the source of the free will for the macro object?

• 2:52:07Sara Walker?

  It's the fact that you're a deterministic structure, living in a random background. And also, all of that selection bundled in you allows you to select on possible futures. So that's where your will comes from. And there's just always a little bit of randomness because the universe is getting bigger. And, you know, like, this idea that the past is in the present is not large enough yet to contain the future. The extra structure has to come from somewhere. And some of that is because outside of those giant causal structures that are things like us, it's fucking random out there.

• 2:52:43Sara Walker?

  And it's scary and we're all hanging on to each other because the only way to hang on to each other, like the only way to exist is to like cling on to all of these causal structures that we happen to co-inhabitate existence with and try to keep reinforcing each other's existence.

• 2:52:58Lex Fridman?

  All the selection bundled in.

• 2:53:00Sara Walker?

  And us, but, but free will is totally consistent with that.

• 2:53:03Lex Fridman?

  I don't know what I think about that. That's complicated to imagine. Just that little bit of randomness is enough. Okay.

• 2:53:10Sara Walker?

  Well, it's also, it's not just the randomness. There's two features. One is randomness helps generate some novelty and some flexibility, but it's also that like, because you're, you're the structure that's deep in time, you have this combinatorial history that's you. And I think about time and assembly theory, not as linear time, but as combinatorial time. So if you have all of this structure that you're built out of, you, in principle, you know, your future can be combinations of that structure. You obviously need to persist yourself as a coherent you. So you want to optimize for a common, like a, a, a future in that combinatorial space that still includes you, um, most of the time for most of us.

• 2:53:55Sara Walker?

  And, um, and when you make those kinds, and then that gives you a space to operate in, uh, and that's your sort of horizon where your free will can operate. And your free will can't be instantaneous. So for like example, like I'm sitting here talking to you right now, I can't be in the UK and I can't be in Arizona, but I could plan, I could execute my free will over time because free will is a temporal feature of life, uh, to be there, you know, tomorrow or the, or the next day if I wanted to.

• 2:54:24Lex Fridman?

  But what about like the instantaneous decisions you're making? Like to, I don't know, to put your hand on the table. That's.

• 2:54:32Sara Walker?

  I think those were already decided a while ago. I don't think that, that, I don't think free will is ever instantaneous.

• 2:54:38Lex Fridman?

  But on a longer time horizon.

• 2:54:40Sara Walker?

  Yep.

• 2:54:41Lex Fridman?

  There's some kind of steering going on.

• 2:54:46Lex Fridman?

  Who's doing the steering?

• 2:54:47Sara Walker?

  You are.

• 2:54:49Lex Fridman?

  And you being this macro object that's encompasses.

• 2:54:54Sara Walker?

  Or you being Lex.

• 2:54:57Sara Walker?

  Whatever you want to call it.

• 2:55:00Lex Fridman?

  There you are, assigning words to things once again.

• 2:55:04Sara Walker?

  I know.

• 2:55:05Lex Fridman?

  Why does anything exist at all?

• 2:55:09Lex Fridman?

  You've kind of taken that as a starting point.

• 2:55:12Sara Walker?

  Yeah.

• 2:55:13Lex Fridman?

  Exists.

• 2:55:13Sara Walker?

  I think that's the hardest question.

• 2:55:16Lex Fridman?

  Isn't it just hard questions stacked on top of each other?

• 2:55:18Sara Walker?

  It is.

• 2:55:19Lex Fridman?

  Wouldn't it be the same kind of question of what is life?

• 2:55:22Sara Walker?

  It is the same. Well, that's sort of like, I try to fold all of the questions into that question because I think that one's really hard. And I think the nature of existence is really hard.

• 2:55:31Lex Fridman?

  You think actually like answering what is life will help us understand existence? Maybe, maybe there's, it's turtles all the way down. It'll just, understanding the nature of turtles will help us kind of march down, even if we don't have the experimental methodology of reaching before the Big Bang.

• 2:55:49Sara Walker?

  Right. So, well, I think there's, there's sort of two questions embedded here. I think the one that we can't answer by answering life is why certain things exist and others don't. But I think the sort of ultimate question, the sort of like prime mover question of why anything exists, we will not be able to answer.

• 2:56:09Lex Fridman?

  What's outside the universe?

• 2:56:11Sara Walker?

  Oh, there's nothing outside the universe. So I have a very, I am a very, like, I am like the most physicalist that like anyone could be. So like for me, everything exists in our universe. And it, and like, I like to like, think like, everything exists here. So even when we talk about the multiverse, I don't like, to me, it's not like there's all these other universes outside of our universe that exist. The multiverse is a concept that exists in human minds here. And it allows us to have some counterfactual reasoning to reason about our own cosmology. And therefore it's causal in our biosphere to understanding the reality that we live in and building better theories.

• 2:56:54Sara Walker?

  But I don't think that the multiverse is something like, and also math. Like, I don't think there's a platonic world that mathematical things live in. I think mathematical things are here. On this planet, like, I don't think it makes sense to talk about things that exist outside of the universe. If you're talking about them, you're already talking about something that exists inside the universe and is part of the universe and is part of like what the universe is building.

• 2:57:17Lex Fridman?

  It all originates here. It all exists here in some.

• 2:57:20Sara Walker?

  I mean, what else would there be?

• 2:57:22Lex Fridman?

  There could be things you can't possibly understand outside of all of this.

• 2:57:27Sara Walker?

  Right, but and you can say that, and that's an interesting philosophy. But again, this is sort of like pushing on the boundaries of like the way that we understand things. I think it's more constructive to say the fact that I can talk about those things is telling me something about the structure of where I actually live and where I exist.

• 2:57:42Lex Fridman?

  Because it's more constructive doesn't mean it's true.

• 2:57:46Sara Walker?

  Well, it may not be true. It may be something that allows me to build better theories I can test to try to understand something objective.

• 2:57:54Lex Fridman?

  And in the end, that's a good way to get to the truth.

• 2:57:58Sara Walker?

  Exactly.

• 2:57:59Lex Fridman?

  Even if you realize.

• 2:58:00Sara Walker?

  So I can't do.

• 2:58:01Lex Fridman?

  You were wrong in the past.

• 2:58:02Sara Walker?

  Yeah. So there's no such thing as experimental platonism. But if you think math is an object that emerged in our biosphere, you can start experimenting with that idea.

• 2:58:13Sara Walker?

  And that, to me, is really interesting. Like, to think about, well, people, I mean, mathematicians do think about math sometimes as an experimental science, but to think about math itself as a as object for study by physicists rather than a tool physicists use to describe reality, it becomes the part of reality they're trying to describe, to me, is a deeply interesting inversion.

• 2:58:35Lex Fridman?

  What to you is most beautiful about this kind of exploration of the physics of life that you've been doing?

• 2:58:42Sara Walker?

  Um, I love the way it makes me feel.

• 2:58:48Lex Fridman?

  And then you have to try to convert the feelings into visuals and the visuals into words?

• 2:58:53Sara Walker?

  Yeah. So I think I love, um, yeah, I love the way it makes me feel to have ideas that I think are novel. And I think that the dual side of that is the painful process of trying to communicate that with other human beings to test if they have any kind of reality to them. And I also love that process. I love trying to figure out how to explain really deep abstract things that I don't think that we understand and trying to understand them with other people. And I also love the shock value of. You like this kind of idea we were talking about before of like being on the boundary of like what we understand. And so people can kind of see what you're seeing,

• 2:59:37Sara Walker?

  but they haven't ever saw it that way before. And I, I, I love the shock value that like people have, like that immediate moment of recognizing that there's something beyond the way that they thought about things before. And being able to deliver that to people, I think is one of the biggest joys that I have is just like, I maybe it's that sense of mystery, like to share that there's something beyond the frontier of how we understand, and we might be able to see it.

• 3:00:00Lex Fridman?

  And you get to see the humans transformed.

• 3:00:03Sara Walker?

  Yeah.

• 3:00:04Lex Fridman?

  By your idea.

• 3:00:04Sara Walker?

  Yes. And I think my, my greatest wish in life is to somehow contribute to an idea that some, that transforms the way that we think. Like, you know, I have my problem I want to solve, but like the thing that gives me joy about it is really changing something. And ideally getting to a deeper understanding of how the world works and what we are.

• 3:00:31Lex Fridman?

  Yeah, I would say, understanding life at a deep level.

• 3:00:35Sara Walker?

  Yeah.

• 3:00:36Lex Fridman?

  Is probably one of the most exciting problems, one of the most exciting questions. So I'm glad you're trying to answer just that and doing it in style.

• 3:00:48Sara Walker?

  It's the only way to do anything.

• 3:00:51Lex Fridman?

  Thank you so much for this amazing conversation. Thank you for being you, Sarah. This was awesome.

• 3:00:56Sara Walker?

  Thanks, Lex.

• 3:00:58Lex Fridman?

  Thanks for listening to this conversation with Sarah Walker. To support this podcast, please check out our sponsors in the description. And now, let me leave you with some words from Charles Darwin. "In the long history of humankind, and animal kind too, those who learned to collaborate and improvise most effectively have prevailed." Thank you for listening and hope to see you next time.