Alien Debate: Sara Walker and Lee Cronin | Lex Fridman Podcast #279

1. 0:00 – 2:08

   Introduction

   1. LCLee Cronin0:00

      I don't know what it's like to be an alien. I would like to know.

   2. LFLex Fridman0:03

      Two alien civilizations coexisting on a planet, what's that look like exactly?

   3. LCLee Cronin0:07

      When you see them and they see you, you're assuming they have vision, they have the ability to construct in 3D and in time. That's a lot of assumptions we're making.

   4. SWSara Walker0:16

      What human-level intelligence has done is quite different. It's not just that we remember states that the universe has existed in before, it's that we can imagine ones that have never existed and we can actually make them come into existence.

   5. LFLex Fridman0:29

      So you can travel back in time sometimes?

   6. SWSara Walker0:32

      Yes.

   7. LCLee Cronin0:33

      You travel forward in time to travel back?

   8. SWSara Walker0:35

      Yes.

   9. LFLex Fridman0:37

      The following is a conversation with Sarah Walker and Lee Cronin. They have each been on this podcast once before individually and now, for their second time, they're here together. Sarah is an astrobiologist and theoretical physicist. Lee is a chemist and, if I may say so, the real life manifestation of Rick from Rick and Morty. They both are interested in how life originates and develops, both life here on earth and alien life, including intelligent alien civilizations out there in the cosmos. They are colleagues and friends who love to explore, disagree, and debate nuanced points about alien life. And so we're calling this an alien debate. Very few questions to me are as fascinating as, what do aliens look like? How do we recognize them? How do we talk to them? And how do we make sense of life here on earth in the context of all possible life forms that are out there? Treating these questions with the seriousness and rigor they deserve is what I hope to do with this conversation and future ones like it. Our world is shrouded in mystery. We must first be humble to acknowledge this, and then be bold in diving in and trying to figure things out anyway. This is a Lex Fridman podcast. To support it, please check out our sponsors in the description. And now, dear friends, here's Sarah Walker and Lee Cronin.

2. 2:08 – 16:14

   Aliens

   1. LFLex Fridman2:08

      First of all, welcome back, Sarah.

   2. SWSara Walker2:10

      Thank you.

   3. LFLex Fridman2:10

      Welcome back, Lee. You guys, I'm a huge fan of yours. You're incredible people. I should say thank you to Sarah for wearing, uh, really awesome boots. We'll probably overlay a picture later on. But why, why the hell didn't you dress up, Lee? No, I'm just kidding.

   4. LCLee Cronin2:22

      This is me dressed up.

   5. LFLex Fridman2:23

      You were saying that you're pink.

   6. LCLee Cronin2:25

      Yeah.

   7. LFLex Fridman2:25

      Like, your thing is pink, my thing is black and white, the simplicity of it.

   8. LCLee Cronin2:30

      Yeah.

   9. LFLex Fridman2:30

      Where's the pink? When, when did the pink, when did it hit you that pink is your color?

   10. LCLee Cronin2:34

       I became pink about, I don't know actually, maybe 2017. You kn- did you know me, uh, when we first-

   11. SWSara Walker2:42

       I think I met you pre-pink.

   12. LCLee Cronin2:44

       Yeah, yeah. So about, about 2017, I think. I just decided I was boring and I needed to make a statement. And red was too bright, so I went pink. Salmon pink.

   13. LFLex Fridman2:53

       Well, I think you were always pink, you just found yourself in 2017. (laughs)

   14. LCLee Cronin2:59

       (laughs)

   15. SWSara Walker2:59

       There's an amazing photo of him where there's, like, everybody in their black gown and he's just wearing the pink pants. It's on the internet somewhere.

   16. LCLee Cronin3:03

       Oh, that was at Wageningen University, 100-

   17. SWSara Walker3:05

       It's totally nuts. (laughs)

   18. LCLee Cronin3:06

       100-year anniversary, they got me to give the plenary and they didn't, they didn't find an outfit for me so they're all wearing these silly hats and these gowns, and there was me dressed up in pink looking like a complete idiot.

   19. LFLex Fridman3:16

       We're definitely gonna have to find that picture and overlay it.

   20. LCLee Cronin3:19

       (laughs)

   21. SWSara Walker3:19

       (laughs)

   22. LFLex Fridman3:19

       Big full screen, slow motion. All right, let's talk about aliens. We'll find places we disagree and places we agree. Life, intelligence, consciousness, universe, all of that. Let's start with a tweet from Neil deGrasse Tyson stating his skepticism about aliens wanting to visit earth. "How egocentric of us to think that space aliens, who have mastered interstellar travel across the galaxy, would give..." Uh, pardon the French, "uh, would give a shit about humans on Earth?" So let me ask you, would aliens care about visiting earth, observing, communicating with humans? Let's take a perspective of aliens, maybe Sarah, uh, first. Are we interesting in the whole spectrum of life in the universe?

   23. SWSara Walker4:11

       I'm completely biased. At least as far as I think right now, we're the most interesting thing in the universe. Um, so I would expect, um, based on the intrinsic curiosity that we have, and how much I think that's deeply related to the physics of what we are, that other intelligent aliens would wanna seek out examples of the phenomena they are to understand themselves better. And I, I think that's kind of a, a natural thing to want to do. And I don't think there's any kind of judgment on it being a lesser being or not. It's like saying you have nothing to learn by talking to a baby. Uh, you have lots to learn probably more than you do talking to somebody that's 90. So, um, yeah, so I think they absolutely would.

   24. LFLex Fridman4:51

       So whatever the phenomena is that is human, there will be an inkling of the same kind of phenomena within alien species, and they would be seeking that same?

   25. SWSara Walker5:00

       I think there's gotta be some features of us that are universal. And I think the ones that are most interesting, and I hope I live in an interesting universe, are the ones that are driven by our curiosity and the fact that our intelligence allows us to do things that the universe wouldn't be able to do without things like us existing.

   26. LFLex Fridman5:22

       We're gonna define a lot of terms. One of them is interesting.

   27. SWSara Walker5:26

       Yes. (laughs)

   28. LFLex Fridman5:26

       Uh, that's, that's a very interesting term to try to define. Uh, Lee, what, what do you think? Are humans interesting for aliens?

   29. LCLee Cronin5:33

       Well, let's take it from our perspective. We wanna go find aliens as a species quite desperately. So if we put the shoe on the other foot, of course we're interesting. But I'm wondering, um, and assuming that we're at the right technological capability to go searching for aliens, then that's interesting. So what I mean is, if there needs to be a massive leap in technology that we don't have, how will aliens prioritize coming to earth and other places? But I th- I do think...... that they would come and find us, 'cause they'd wanna find out about our culture, what things are universal. It- what about, I mean, I'm a chemist, so I would say, "Well, is the chemistry universal," right? Are- are the creatures that we're gonna find making all this commotion, are they made of the same stuff? Um, what does their science look like? Um, are they off-planet yet? Um, I guess there's... So I- I think that Neil deGrasse Tyson is being slightly pessimistic, and maybe trying to play the tune that the universe is vast and it's not worth them coming here. I don't think that, but I just worry that maybe we- we don't have the ability to talk to them. We don't have the universal translator. We don't have the right physics. But, sure, they should come. We are interesting. I wanna know if they exist. It would make it easier if they just came. (laughs)

   30. LFLex Fridman6:50

       (laughs) So, again, I'm gonna use, uh, your tweets like it's Shakespeare and analyze it. So Sara tweeted, uh, "Thinking about aliens thinking about aliens." So how much do you think aliens are thinking about other aliens, including humans? So you said we humans want to visit, like, we're longing to connect with aliens. Why is that? Can you introspect that? Is that an obvious thing that we should be... Like, what are we hoping to understand by meeting aliens exactly? A- asking as an introvert, it's like, I ask myself this all the time, why- why go out on a Friday night to meet people? What are you hoping to find?
3. 16:14 – 23:56

   What is life?

   1. LFLex Fridman16:14

      Okay, so let's talk about life. What is life? What is non-life? Wh- what is the line between life and non-life? And maybe at any point, we can pull in ideas of assembly theory.

   2. SWSara Walker16:27

      Mm-hmm.

   3. LFLex Fridman16:27

      Like, how do we start to try to define life? And for people, uh, listening, so Sarah, uh, identifies as a physicist, and Lee identifies as a chemist. Of course, they are very interdisciplinary in nature, in general, but, um... So, what is life? Sarah?

   4. SWSara Walker16:48

      (laughs)

   5. LFLex Fridman16:48

      (laughs)

   6. SWSara Walker16:48

      Yeah.

   7. LFLex Fridman16:49

      I love asking that question 'cause it's so absurdly big.

   8. SWSara Walker16:52

      I know. I love it. Um, it's my absolute favorite question in the whole universe. Um, so I think I have three ways of describing it right now, um, and I like to say all three of them 'cause people latch onto different facets of them. And so the whole idea of, of what Lee and I are trying to work on is not to try to define life, but to try to find a more fundamental theory that explains what- the phenomena we call life. And then it should explain certain attributes, and you end up having a really different framing than the way people usually talk. So the way I, I talk about it three different ways. Um, life is how information structures matter across space and time. Um, life is, uh... I don't know. This one's from you actually, simple machines constructing more complex machines. Um, and the other one is the physics of existence, so to speak, which is life is the mechanism the universe has to explore the space of what's possible. Um, that's my favorite.

   9. LCLee Cronin17:43

      So, can I... yeah, yeah, can I add onto that?

   10. SWSara Walker17:46

       Yes.

   11. LFLex Fridman17:46

       Oh, c- can you say the physics one again? Uh, the-

   12. SWSara Walker17:49

       Oh, the-

   13. LFLex Fridman17:49

       ... physics of existence.

   14. SWSara Walker17:51

       Yeah, the physics of existence.

   15. LCLee Cronin17:52

       Yeah.

   16. SWSara Walker17:52

       I- I don't know what to call it. You know, like, if you think of all the things that could exist, only certain things do exist, and I think life is basically the universe's mechanism of bringing things into physically existing in the, in the moment now.

   17. LCLee Cronin18:05

       Yeah.

   18. LFLex Fridman18:06

       Yeah. And what's, what's another one? Lee?

   19. LCLee Cronin18:08

       Oh, we were debating this the other day. So, if you think about universe that has nothing in it-... that's kind of hard to conceive of, right? Because, and this is where the physicists really go wrong, like, think of a universe with nothing in it. They can't. And you think it's-

   20. LFLex Fridman18:21

       Non-existence is really hard to think about.

   21. LCLee Cronin18:22

       Non-exis- yeah. And then if you think of a universe with everything in it, that's really hard, and- and you just- you just have this white blob, right? It's just everything. But the fact we have dec- discrete stuff in the universe beyond, say, planets. So you've got st- stars, space, planet, stuff, right? The boring stuff. Well, I would define life or say that life is where there are architectures, any architectures, and we should stop fixating on what the- bill is building the architectures to start with, and the fact that the universe has discrete things, and it is completely mind-blowing. If you think about it for one second, the fact there's any objects at all that- and th- there's- because for me, the pr- the o- o- object is a proxy for a machine that built it, some information, um, being moved around, actuation, sensing, getting resource, and building these objects. So for me, everyone's been obsessing about the machine, but I'm like, "Forget the machine. Let's see the objects." The, you know, and I think in a way that assembly theory, we realized maybe a few months ago that assembly theory actually does account for the soul in the objects, not mystically like, say, Sheldrake's morphic resonance or Leibniz's mo- uh, monadology seeing souls in things. But when you see an object, and I've said this before, but this object is evidence of thought, and then there's a lineage of those objects. So I think what is fascinating is that, um, you put it much more elegantly, but- but the barrier between life and non-life is accruing enough memories to then actuate. So- so what that means is there are contingency, there are things that happen in the universe get trapped. These memories then have a causal effect on the future. And then when you get those concentrated in a machine and you're actually able, in real time, able to integrate r- r- m- the past, the present with the future and do stuff, that's when you are most alive.

   22. LFLex Fridman20:22

       Uh, you being the machine?

   23. LCLee Cronin20:23

       Yes.

   24. LFLex Fridman20:24

       Wait a minute. W- why is the object, so one- one of the ways to define life, uh, that Sarah said, is simple machines creating complex machines. So there's a million questions there. So how- how the hell does a simple machine create a complex machine? First of all-

   25. LCLee Cronin20:41

       By mutation. So th- this is what we were talking about at the beginning, is you have the minimum replicator, so a molecule.

   26. SWSara Walker20:46

       Mm-hmm.

   27. LCLee Cronin20:46

       So this is what I was trying to convince Sarah of the mechanism to get there years ago, I think, but then you've been building on it and saying, you have a small- you have a molecule that can copy itself, but then that, b- there has- there has to be some variability, otherwise it's not gonna get more functional. So you need about add bits on. So you have a minimum molecule that can copy itself, but then it can add bits on, and that can be copied as well, and those add-ons can give you additional function, um, uh, e- uh, to be able to acquire more stuff to exist. So existence is weird, but the fact that there is existence is why there is life. And that's why I realized a few days ago that there must be, that's why alien life must be everywhere, because there is existence.

   28. LFLex Fridman21:28

       Is there like a conservation of cheeky stuff happening? So, like, how can you keep injecting more complex things? Like, um, doesn't the machine that creates the object need to be as or more comp- more powerful than the things it creates? So how can you get complexity from simplicity?

   29. LCLee Cronin21:51

       So the way you get complexity from simplicity is that you, I would, listen, I'm just making this up, but this is kind of my notion that you have a large volume of stuff, so you're able to get, um, seeds, if you like, random cues from the environment. So you just use those objects to basically write on your tape, ones and zeros, whatever. And that is- that is necessarily rich, complex, okay? But it has a low assembliness, but even though it has a high assembly number, we can talk about that. But then when you start to then integrate that all into smaller volume, as over time, and you become more autonomous, you then make the transition. I don't know what you think about that.

   30. SWSara Walker22:34

       I think the easiest way to think about it is actually, which I know is a concept you hate, but I also hate, which is entropy, but people are more familiar with entropy than what we talk about in assembly theory. Um, and also the idea that, like say physics as we know it, um, involves objects that don't exist across time or as we would say low memory objects. Um, so one of the- the key distinctions that- that is-
4. 23:56 – 46:24

   Assembly theory

   1. LFLex Fridman23:56

      Let's step back and- and start at the beginning. What is assembly theory? Lee sent me some slides. There's a b- there's a big sexy paper coming out probably, maybe, I don't know. Uh-

   2. LCLee Cronin24:07

      We've almost finished it.

   3. SWSara Walker24:10

      Almost, almost finished it.

   4. LFLex Fridman24:11

      That's like a s- that's also a summary of science. We're almost done. (laughs)

   5. SWSara Walker24:14

      Yes.

   6. LCLee Cronin24:15

      Well, no, no, we're almost done. I think we're-

   7. LFLex Fridman24:16

      It's the- the history of science summarized.

   8. LCLee Cronin24:17

      We are ready to start an interesting discussion with our peers. (laughs)

   9. LFLex Fridman24:21

      Right.

   10. SWSara Walker24:22

       Yeah.

   11. GUGuest24:22

       (laughs)

   12. LFLex Fridman24:22

       You're the machine that created the object and we'll see where the object takes us.

   13. SWSara Walker24:25

       Yeah.

   14. LFLex Fridman24:26

       All right. So what i- what is assembly theory?

   15. SWSara Walker24:28

       Um, yeah. Well, I think- I think the easiest way for people to understand it is to think about, um, assembly in molecules. Although the theory is very general, it doesn't just apply to molecules. And this was really Lee's insight, so it's kind of funny that I'm explaining it. But, um-

   16. LCLee Cronin24:42

       I'll- I'll mark you.

   17. SWSara Walker24:43

       But... Okay. All right.

   18. LCLee Cronin24:44

       (laughs)

   19. SWSara Walker24:44

       I'm ready. I'm ready. I'm ready. You have to tell me where I get the check mark- marks minus but...

   20. LCLee Cronin24:47

       It's your theory as well, so. (laughs)

   21. SWSara Walker24:48

       Yeah, I know. But ima- imagine a molecule, um, and then- and then you can, you know, break the molecule apart into elementary building blocks, they happen to be bonds, and then you can think of all the ways, for molecular assembly theory, you can think of all the ways of building up the original molecule. So there's all these paths, um, that you can assemble it, and the sort of rules of assembly is you can use pieces that have been generated already. Um, so it has this kind of recursive property to it. Um, and so that's where kind of memory comes into assembly theory. And then the assembly index is the shortest path in that space. So it's supposed to be the minimal amount of history that the universe has to undergo in order to assemble that particular object. And the reason that this is significant is we figured out how to measure that, um, with a mass spec, um, in the lab, and we had this conjecture that if that minimal number of steps was sufficiently large, it would indicate that you required a machine or a system that had information about how to assemble that specific object, because the combinatorial space of possibilities is getting exponentially large as the assembly index is increasing.

   22. LFLex Fridman25:49

       So just, sorry to interrupt, but so that means there's a- a sufficiently high assembly index that, if observed in an object, is an indicator that something life-like created it? Or is the object itself life-like?

   23. SWSara Walker26:07

       Um, both. But you might wanna make the distinction that a water bottle is not life, but it would still be a signature that you were in that domain of physics, and that I might be alive. So, um...

   24. LFLex Fridman26:19

       So there would be s- potentially a lot of arguments about where the line, at- at which assembly index, uh, does interesting stuff start to happen?

   25. SWSara Walker26:28

       The point is, we can make all the arguments but it should be experimentally observable, and- and Lee can talk more about that part of it. But the- the point I wanna make about it is there was always this intuition that I had that there should be some complexity threshold in the universe above which you would start to say whatever physics governs life actually becomes operative. And I think about it a little bit like we have Planck's constant, which, you know, like- and we have the fine structure constant, and then this sort of assembly threshold is basically another sort of, uh, potentially constant of nature. It might depend on specific features of the system, right? But, um, which we debate about sometimes. But, um, but then when you're past that, you ha- you have to have some other explanation than the current explanations we have in physics, 'cause now you're in high memory, um-

   26. LCLee Cronin27:14

       Yeah.

   27. SWSara Walker27:14

       ... uh, things actually require time for them to exist, and time becomes a physical variable.

   28. LFLex Fridman27:19

       So the- the path to the creation of the object is the memory?

   29. LCLee Cronin27:23

       Yeah.

   30. LFLex Fridman27:23

       So you need to consider that...
5. 46:24 – 58:06

   Math

   1. LFLex Fridman46:24

      So what- what is, uh, what is math exactly? It's a, uh, a nice simplification, a- a- a simple description of what?

   2. LCLee Cronin46:38

      So we have a computer scientist, a physicist, and a chemist here.

   3. LFLex Fridman46:40

      (laughs) Walk into a bar.

   4. LCLee Cronin46:42

      I think- I think the chemist is gonna define math, and you guys can correct me.

   5. SWSara Walker46:45

      Go for it.

   6. LCLee Cronin46:46

      I would say-

   7. SWSara Walker46:47

      Lay- lay- lay it on us, Lee.

   8. LCLee Cronin46:48

      (laughs)

   9. SWSara Walker46:49

      (laughs) We're ready. (laughs)

   10. LCLee Cronin46:51

       I think the ability to, um, to label objects and, uh, and place them into classes and then do operations on those objects is what math is.

   11. LFLex Fridman47:01

       So, on that point, what does it mean to be object first versus information first? So what- what's the difference between object and information when you get to that low fundamental level?

   12. LCLee Cronin47:12

       Well, I might change my view. So I'm stuff first, the stuff.

   13. LFLex Fridman47:16

       Mm-hmm.

   14. LCLee Cronin47:16

       And then when stuff becomes objects, it has to invent information, and then the information acts on more stuff and becomes more object. So I think there is a transition to information that occurs when you go from stuff to object.

   15. LFLex Fridman47:29

       No, wait.

   16. SWSara Walker47:29

       It must mean time, though ...

   17. LFLex Fridman47:31

       Information is em- emergent then?

   18. LCLee Cronin47:33

       Not emergent, information is actionable memories from the universe. So when- when memories become actionable, that's information.

   19. LFLex Fridman47:44

       But there's always memory, but it's not actionable.

   20. LCLee Cronin47:48

       Yeah, and then it's not information. Great.

   21. LFLex Fridman47:49

       And actionable is what you can create...

   22. LCLee Cronin47:52

       You can use it. If you can't use it, then it's not information. If you can't transmit it, if you- if it doesn't have any-

   23. LFLex Fridman47:58

       If a tree...

   24. LCLee Cronin47:58

       ... causal consequence...

   25. LFLex Fridman47:59

       ... falls in the forest... I don't understand. Why is that not information? (laughs)

   26. LCLee Cronin48:03

       It's not information, it's- it's, um, it's, uh...

   27. LFLex Fridman48:06

       Stuff.

   28. LCLee Cronin48:07

       It's stuff happening, but it's not- it's not caus- Yeah, it- yeah, we can... This is cool.

   29. LFLex Fridman48:12

       But it's happening.

   30. LCLee Cronin48:13

       No, no, but yeah, but- that's-
6. 58:06 – 1:22:59

   Communication with aliens

   1. LFLex Fridman58:06

      you mentioned that there's no way to communicate with aliens until there's overlap in the causal graph. Communication includes being able to see them? And like what are we... This is- the question is, um, is communication any kind of detection? And if so, what do aliens look like as you get more and more overlap on the causal graph?

   2. LCLee Cronin58:33

      Well, you're assuming... Let's assume that ali- so when you see them and they see you, you're assuming they have vision, they have the ability to construct in 3D and in time. That's a lot of assumptions we're making.

   3. LFLex Fridman58:45

      Well, detection. All right, let's step back. So yes, okay, you're right. So when, in the English language when we say the word see, we mean visually. They show up to a party and it's like, "Oh, wow, that's an alien."

   4. SWSara Walker58:56

      (laughs)

   5. LFLex Fridman58:56

      That's visual, that's 3D, that's... Okay. Um, and that's also assuming scale, uh, spatial scale of something that's visible to you. So it can't be microscopic or it can't be so big that you don't even realize that's an entity. Okay. Um, but other kinds of detection too.

   6. LCLee Cronin59:14

      I would make it more abstract and go do- I was thinking this morning about how to rewrite the Arecibo message in assembly theory, and also to abandon binary. 'Cause I don't think aliens necessarily... Uh, why should they have binary?

   7. LFLex Fridman59:27

      Well, they have some basic elements with which to- to do information exchange. So why-

   8. LCLee Cronin59:32

      But let's make it more fundamental and more universal. So we need to think about, what is a universal way of making a memory? And then we should re-encode Arecibo in that way.

   9. LFLex Fridman59:43

      W- uh, what's more basic than zeros and ones?

   10. LCLee Cronin59:45

       Well, it's really difficult to get out of that causal chain because we're so... So let's raise the idea of zero for a moment. It took human beings a long time to come up with the idea of zero. Now- now you got the idea of zero, you can't throw it away. It's so useful.

   11. LFLex Fridman59:57

       To discover the idea of zero?

   12. LCLee Cronin59:58

       Yeah. To discover or invent.

   13. LFLex Fridman1:00:00

       I don't know. But it took a long time, so it was, uh, in- invented. That's right.

   14. LCLee Cronin1:00:05

       Yeah, I think zero was invented. So exactly. So it's not a given that aliens know what zero is. So it's a massive-

   15. LFLex Fridman1:00:11

       They just have the one.

   16. LCLee Cronin1:00:12

       ... a massive assumption.

   17. LFLex Fridman1:00:13

       It's a useful- it's a useful discovery. They're- you're saying if you break the causal chain, there might be some other more efficient way of representing things.

   18. LCLee Cronin1:00:20

       That's why I wanna meet 'em and ask 'em. (laughs)

   19. LFLex Fridman1:00:23

       For a shortcut.

   20. LCLee Cronin1:00:24

       Yeah.

   21. LFLex Fridman1:00:24

       But you won't be able to, um, ask 'em until-

   22. LCLee Cronin1:00:27

       Well, so I- I interrupted you and I think you're making a good point, and I was just gonna say, well, look-

   23. LFLex Fridman1:00:31

       Thank you.

   24. LCLee Cronin1:00:31

       (laughs) Sorry.... rather than saying-

   25. LFLex Fridman1:00:35

       Please, internet, tweet at him for the rude interruptions.

   26. LCLee Cronin1:00:37

       (laughs)

   27. LFLex Fridman1:00:37

       Oh, go ahead. I'm sorry.

   28. LCLee Cronin1:00:38

       No, it's okay. Um, maybe it's changed. How do we... So, oh, I don't know what it's like to be an alien. I would like to know.

   29. LFLex Fridman1:00:47

       What is the full spectrum of what aliens might look like to us? Now that we've laid this all on-

   30. LCLee Cronin1:00:55

       yup.

Episode duration: 4:05:22