StarTalk Radio - The Origins of Life with Sara Imari Walker

Episode Date: October 15, 2024

What is life? Neil deGrasse Tyson and co-host Chuck Nice tackle assembly theory, artificial life, and the origin of lifeforms in the universe as we revise the definition of life with astrobiologist and theoretical physicist Sara Imari Walker.NOTE: StarTalk+ Patrons can listen to this entire episode commercial-free here: https://startalkmedia.com/show/the-origins-of-life-with-sara-imari-walker/Thanks to our Patrons Bill Williamson, Amanda, Charles Waggoner, Jason Wiatr, Don Lane, Biren Amin, Jean C Roy, david accetta, STAHLGEIST, joshua george, Danny, daniel oliveira, Matthew Szwajda, Gabe Magallanes, Mike Jespersen, Elias, and Jon O for supporting us this week. Subscribe to SiriusXM Podcasts+ on Apple Podcasts to listen to new episodes ad-free and a whole week early.

So Chuck, I don't know if we answered all those profound questions, but we certainly went there. We certainly did. What is life as we know it? Is that understood? And if it is or isn't, what is life as we don't know it? Right. And as long as we're talking about life, is AI alive? Is AI life itself?

Right. Yes. Right. It better not be, because soon it will be asking for a raise and all kinds of rights and oh, it's going to be a mess. Coming up, life in a nutshell and outside of a nutshell on StarTalk. Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now. Collide. StarTalk begins right now.

This is StarTalk. Neil deGrasse Tyson, your personal astrophysicist, got with me, of course, Chuck Knight. Chuck, baby. Hey, Neil, what's happening? Lord Chuck Knight. Oh, thank you, yes. All right, my co-host, professional comedian, stand-up comedian. Yes. And not always the same thing, a professional comedian and stand-up comedian. And actor. And actor. I've seen you in some TV commercials. Acting like a comedian. You know what?

Almost dropped my sandwich when I saw that. I'm actually going to do a sandwich commercial next. All right, no, good that you're out there. Yeah, you know, got to keep it moving. And we can say we knew you when. You're going to know me then, too. So Gotta keep it moving. And we can say, we knew you when. You gonna know me then, too. So, wonderful topic today. Yeah.

Oh my God, love it. Love me this topic. It's a rich, rich topic. So, there's always been this concept of life as we know it. Right. And never caught on as an acronym, LOCKEY, life as we know it. I wonder why. Such a mellifluous acronym, LOCKEY. Never caught on. Life as we know it. I wonder why. Such a mellifluous acronym.

Never caught on. Life as we know it. It's like carbon-based. All the usual things that you throw into the mix. And there's been some effort lately to think about life as we don't know it. Oh, now, I like that. It's far more intriguing. And that seems to me opens up all manner of possibilities.

Absolutely. Outside of the box that we've put ourselves in. Right. So we have a world's expert. We have Sarah. You have three names, Sarah, as do I. Sarah Amari Walker. That's me.

And which one do we go by? Sarah. Sarah, okay, we'll do that. Oh, thanks for making it simple. I try. We appreciate Sarah. Sarah, okay. We'll do that. Oh, thanks for making it simple. I try. We appreciate that. I really try. So Sarah, you're an astrobiologist and physicist, theoretical physicist.

So you're coming to this life question not from the normal trackings of a biologist. Because who else would you think to bring to the table when you're talking about life if not a biologist? Absolutely. But now you're going to bring some physics into the equation, and I love me some physics. Yeah, me too. The buck stops at physics, okay? There's an old saying, there's no understanding of biology without chemistry.

Right. And there's no understanding of chemistry without physics. There you go. Somehow your subject of expertise lords over the bar. Lords over the bar. I don't know how this happened. So what brought you to the question of life? Yeah, I'm really interested in fundamental laws of nature and where we might find new ones.

So I think this is the main motivator for me, is to think about life being explained by some universal physics we don't know yet. Whoa. Okay, that's... Whoa. That's... Damn, Sarah's... Whoa. Damn, Sarah coming in hot.

The only way I know to go. Sarah is not playing around, buddy. Didn't even warm up to that one. I'm telling you. It's like, why don't you take a couple of warm-up tosses? All right, we clocked that one at 97 miles an hour. That's fantastic. So I can't think of a department, a traditional department in a university that would serve this cause. And now I learn you're deputy director of the Beyond Center?

Yes. That's audacious. Now you guys are the people that make the meat, right? The Beyond Meat? No, we don't make meat. Yeah, it's okay. No, we don't do anything like that. We're actually,

it's like the full name of the center is the Beyond Center for Fundamental Concepts in Science. So we're actually an exploratory center based at Arizona State, and we think about deep problems. Arizona State University. Yep.

Not just in the state of Arizona. No, not, yeah, Arizona State University. So you're on the faculty there. Mm-hmm, that's right. Excellent. ASU, they have really good astro folk there, too. Okay. Yeah, no, I know ASU. All right. They have really good astrophoic there, too. Okay. Yeah. Yes. No, I know ASU.

All right. Yeah. Yeah. And so this Beyond Center, are you co-founder of that? No, the founder is Paul Davies, but I'm the deputy director. We know Paul Davies. Yeah. An astrophysicist from way back.

Yeah. Yeah. I like hanging out with cosmologists. And the Beyond Center is in the cosmology wing on ASU on the campus. Okay, I was looking at at least one of your research papers, you have collaborators, some of whom are based in the Santa Fe Institute, which is also one of these beyond. Yes.

I mean, they specialize in, here's what everybody's thinking, but we're going to put a foot outside that circle. Now let's go beyond. Let's go beyond. Right. right right so you're teaming up with other beyond people yes i like hanging out with people that think outside the box they're my favorite kind of people in fact the stomach stuff i've been working on is not just the box this box is a three-dimensional object right she's thinking beyond the tesseract. Oh, wow. Look at that. Now I have pretty shapes in my head. I like this. So tell me, I know there might've been adjustments over the decades, but today, what is the commonly held definition of life itself? The way that I consider it is that

we actually don't need to define life. We need to figure out a theory that helps us derive the properties of life. So we should be able to predict features of life anywhere it should occur in the universe. So that's been my approach. It's very, you know, theoretical physicist, need to build theories, need to explain regularities of nature.

She's got theoretical physics bad. I love it. I do. It's bad in you. It's never coming out. Yeah, it's a little fever with you. You got a little fever. You got a little theoretical fever.

Yeah, I do. So, I mean, basically you're like, let's not worry about identifying. Let's find out what creates the identification. Yes. In the first place. Yes. Wow.

How do you go about doing that? So I started, you know, in a true theorist fashion, I had probably like seven or eight working definitions, but I was trying I started, you know, in a true theorist fashion, I had probably like seven or eight working definitions, but I was trying to find, you know, what's the commonality under them. But a lot of them were about something to do with information structuring matter was kind of the early way I was thinking about it. Wow. Okay. I got you because then that gets you all the way down to single cells because even they are carrying information. So if you get to the root of the information and what creates the information,

then it may not even be a cell that you're working with. It could be something outside of that. Yep, and a cell is a good example because it's very complex and we don't think they can form outside of evolution. So the way that we talk about these ideas now, which is what I'm really excited about, is this theory, assembly theory.

I've been working on with my collaborator, Lee Cronin. Assembly theory. Assembly theory. It's a theory. As a theorist should do. Yeah, so assembly theory's key conjecture about the nature of life is life is the only physics that can generate complex objects. Interesting. Like a cell. Right. Or

a microphone. Or a comedian. We're not that complex, unfortunately. We're the simplest of, unfortunately. He's very simple. We're the simplest of all life. Wait, so you are declaring that rocks and crystals and things is not complex. So therefore, while you could, in principle, create those out of your modeling or out of your theories,

that's not your target of interest. So the nature of how we define complexity is it doesn't happen spontaneously. It requires evolution. So there are some kinds of rocks and minerals that do require, say, technology to precisely engineer defects in a crystal, like if you want a perfect diamond or something.

Right, exactly. So there would be rocks maybe that pass the boundary of life, but they would be something life created or engineered so i'd love this because you're you you you poured out the mold and you said let me start from scratch and if you start from scratch you're not biased by any pre-existing construct for what is or could or should be. Right. Now you can make almost anything that has complexity. Yes.

And the space of complexities is then what you will study. Yes. And that space is huge. So as an astronomical example, I like to use this molecule taxol as an example. It's molecular weight's about 853. Taxol? What do we do with that? Taxol is an anti-cancer drug. It's just one molecule that's been created in a tree somewhere.

That's a fat molecule. It's a fat molecule. It's a big molecule. But if you wanted to make- How many atoms are in that molecule? Approximately. Hundreds? Gobs and gobs.

Gobs. I think it's like a couple hundred. Yeah. On that order. Yeah. A hundred to 200. But if you wanted to make one molecular structure of the same molecular formula, like every single three-dimensional conformation,

it would fill a volume of about one and a half universes. Just one molecular formula. One molecule per centimeter cubed. This is how big chemical space is. The reason it's hard to make complex objects is there's so many of them. So evolution is necessary to select in that space. Uh-huh. So we can't have a universe and a half full of just taxol.

It would be very boring. Right. We live in a universe with lots of different complex objects. Wait, I have to, let me repeat what I think you said. Yeah. That the complexity of, what's it called again? Taxol. Taxol.

It's not a special molecule either. I just picked one out of a hat. Okay. Yeah, we all have these in our hat, don't we? Exactly. Yeah, I'm carrying around a hat with lots of Taxol in it. So, more like a ski mask. If I think I understand you, the complexity of this molecule

is such that if you explored all molecules that could be that complex, there's not enough room in the universe to hold it. That's right. So clearly, that molecule's existence comes from some prior requirement or urging.

For that configuration. For that configuration. Yes, that's exactly right. That's fair. Yes, that's exactly right. So let me ask you this then, because now I'm a little, you'll have to forgive my ignorance,

but I'm the only non-scientist here, thank God. So I can say stupid- God had nothing to do with that. Okay, but go on. That's a very complex molecule. Okay. Okay. Where exactly does spontaneity and selection cross and how do you identify which is which which is

which is a progression and which is a cross yeah so you know the kinds of very simple molecules that might happen on a planet you know can happen spontaneously or if you're thinking like lego or easier for people than chemistry if you have like a tray tray with a bunch of Lego in it and you shake it, you're going to get some Lego sticking together and making simple shapes. So those would be spontaneous objects. But you're not going to be able to shake it long enough to have Hogwarts castle spontaneously emerge out of it. That would require a process of evolution and refinement.

And a wand. And a wand, yeah. No magic though. The universe doesn't have magic. At least not in this scenario so she's covering her business she's like

you know what she's in a beyond institute she's like I am a theorist she's in a beyond institute you gotta leave her move to the bathroom for the wand

go ahead well I like you know magic for me is yet to be you know regularized in theoretical physics so there still always has to be other things

for us to do. Any sufficiently advanced technology is indistinguishable from magic. That's right. Or the laws of physics. Wow. Okay. So go ahead, back to you can't get to the place where you could shake it and then have Hogwarts.

So if you do shake it and some stick together, those are like the amino acids? Yes. Gotcha. Because we did that with the Miller-Urey experiment. That's right. Where he just throws some basic. Can you explain that, please? Everybody knows that Miller-Urey.

Clearly they don't. Okay. And by the way, of course I know. I'm just talking about the people out there. No, they do. I mean, there may be someone listening. Please regale us of the Miller experiment. Yeah, so Stanley Miller was a PhD student.

I think he published a paper in 1953, so it was a long time ago. But basically, he put a bunch of molecules that might have been available on the early Earth in a flask and put some lightning in his flask and tried to model. As a source of energy. Yes, as a source of energy. And he had a reducing environment. And then he got amino acids out of it. Reducing means you remove oxygen that's taken out. Yeah, as a source of energy. And he had a reducing environment. And then, you know, he got amino acids out of him. Reducing means you remove oxygen that's taken out. Yeah.

And so he made amino acids. And, you know, people were so shocked by this at the time. They thought little aliens were crawling out of, you know, life forms would be crawling out of the test tube in a couple weeks. But that's not what happened. Right. Unfortunately. Yeah. The reducing environment is that we think the early Earth did not have free oxygen.

Right. So he's trying to, if life's formed on earth under these conditions. Well, you got to create the conditions under which it formed. So out of the ooze, nothing crawled out. Nothing crawled out. If you run the experiment long enough, you basically get what we call a tar in prebiotic chemistry, which is just an undifferentiated mess of a whole bunch of organic molecules

that we can't identify. Okay. Prebiotic chemistry means what? Prebiotic chemistry means chemistry that could plausibly happen on the early earth in the absence of life. Before you have life. Before you have life. So it's organic chemistry. Yeah. Yeah, I like the word organic chemistry better because

prebiotic kind of makes it sound like it's predisposed to become biological, but there's no teleology. There's no direction. It also makes it sound like something you take before a meal. Yeah. That's true. People do confuse it with probiotic all the time. Exactly. Oh my gosh. All that probiotic chemistry. Yeah.

I'm Ali Khan Hemraj and I support StarTalk on Patreon. This is StarTalk with Neil deGrasse Tyson. So I'd like the basic principles that are being invoked here. Very, very simple basic principles. Okay, so now you shake the Legos, some stick together. Now what?

Now selection needs to happen to get to something like Hogwarts, which means that some parts have to start being abundant in the environment and then reused to build further structure. And these become your building units, your building units. Yes. Your bricks. That's right. Yes. To build the edifice. Yes. And you say selection because they are selected to succeed? Is that the idea? Yes. And also because selection is excluding that

huge space of other possibilities. You have to. Otherwise you're lost in space. That's right. I don't even want to know how many possible configurations there are of the Legos in the Lego Hogwarts set. It's like 2000 Lego. If you imagine all the things you could build out of that, it's crazy. It's three universes.

So now, since you're looking for life outside of this, let's consider in the selection that- Life outside of what? I'm saying outside of the life that we know. Oh, yeah. Right. You're looking for life outside. Other planets, even. outside of the life that we know.

Oh, yeah. Right. You're looking for life. Other planets, even. So let's go back to the primordial soup of another planet, and we have the shaken Legos, okay? But are there circumstances that may be led to selection for the development here that may be different there creating something different entirely could that possibly be the case yes i think so so i think assembly theory would predict yes because the possibility space of the chemistry is so large and what we've actually

been able to do is to find a threshold that we expect life to emerge which is what you described as the spontaneous to selection dynamics and it actually has you know for the physics nerds out there it has like properties of a phase transition right so you go from spontaneous like random configurations of objects to selected ones that have this historical pathway the phase transition is all the molecules are this way and then like a moment later they're in a whole other way. Configuration. Yeah. So, but we live this. Yeah. Right. Okay.

It's our fancy word for it, but when water becomes ice. Ice. Ice is not water. That's a phase, right. That's a phase transition. When water becomes steam. It's a phase transition. There you go.

And so we actually generalize that term even in the early universe. If everything is this way and then something happens and then it's another way we just call it a phase transition gets us through we geek out on that yeah yeah we physicists love phase transitions anything can happen through a phase transition right and uh like spooky things fun things yes dangerous things yes so i shake the legos some of them stick together they're the le Lego counterpart to amino acids. This was done in the Miller-Urey experiment. It's amino acids, which are the building blocks of protein,

the building blocks of life as we know it. All right. On another planet, you shake it. We're thinking it'll also make amino acids. So this becomes a unit of life. Let's call it that. Or your AT, what's at what's the assembly theory at we call we talk about assembly index is the number of steps to make an object so that's a step yeah that's a step okay if that's the same step everywhere yeah then that greatly

limits what comes after because you're not starting not everything is possible in that early first unit yeah this is a great point. The interesting thing there is how varied geochemistry is on different planets. And actually, even if you look at amino acids, there's hundreds of them that we've identified in meteorites. Right, and not all of them. Not all of them are in biology. Right.

So if you find them in meteorites, it means they're out there. They're out there. They're being made. They're being made. But they're not here. Or even if they come here, we're not using them. Right. They don't serve a purpose here. Right, Jack. Okay, being made. They're being made. But they're not here. Or even if they come here, we're not using them. Right.

They don't serve a purpose here. Right, Jack. Okay, go on. That's the point. Yeah, so I don't think that we should have an expectation that all the steps on the pathway to something as complex as cell would be the same. Because maybe the first few are similar, but as you build up the complexity of the chemistry, there's so many paths you could take, so many kinds of molecules, that there should be a point where planets start to diverge in what kind of biochemistry evolves out of the geochemistry so let's okay aliens can be really weird that's what i was gonna that's what i was gonna get to it's like it sounds to me like a like a virus could be an alien like highly effective like lots of information carrying out like a you know purpose

uh procreating you know i mean it when you if if you can look for something like that how do you even begin to uh narrow the search once you start looking out there yeah so the great thing about assembly theory is we can actually measure how assembled a group of molecules is quantitatively. Quantitatively, we have predictions that we can make from the theory, but we can test

them in the lab. We have a way of measuring the complexity of a molecule independent of knowledge of what the molecule is. We can just do it with a mass spectrometer. Okay. See, this is physics, badass physics coming in the doorway here. We like measurements.

They ground us in reality. Evolutionary steps, sometimes we think of them that way, can involve added complexity. So what are you doing that's different from that? So evolutionary theory as we have it now works really well for biology on Earth, but it doesn't help us understand life on other planets or solve the original life

because we don't know where life comes from to begin with. So we need- Because you have a sample of one. Yeah, we have a sample of one. It's a big problem. We need a deeper explanation of evolution in order to explain how evolutionary systems that we recognize as biology emerge in the first place. Is there any chance that it could just be a mistake?

You know, that might be true, but then it's not very interesting from the perspective of theoretical physics because there's nothing to explain. Okay. Oh, good answer. Yeah. I mean, it doesn't stop the search, though. No. That's a good answer. It's not very interesting at that point.

All right, so let's make sure we're on the same page here. When I think of how a biologist would define life, which has been, there's been variations on that over the decades. But what comes to mind is it's something that has a metabolism, so it uses energy from its environment. It reproduces and it evolves in a darwinian way yeah you have things to add to that subtract from that i don't or can you juxtapose both what do you what do you call what he just said in from your where you are what is that and then where are you different so so one definition that people like to use, which encapsulates what you're saying as fundamental pieces of it, is life is a self-sustaining chemical system capable of Darwinian evolution. It's quite a mouthful.

That's what he just said, though. Yeah, it is. Exactly. It totally is. So there's a lot of problems, actually, from my perspective with that definition. One of them is whether you regard life to be self-sustaining. So viruses are an example. People don't know whether to place them as life or not because they're not self-sustaining on their own.

And in fact, when we're doing, you know, chemical evolution in the laboratory, like trying to study molecules, you know, we don't know how to call them alive because they're not self-sustaining because graduate students are pipetting. They require the graduate student. Pipetting, that's a verb. I know the pipette is a little thing. Put your little glass straw in there. Yeah, you got to move the molecules from one tube to the next to do artificial selection. So why do you do it? You say, I am crushing your head.

Okay, sorry. Right, so there's many, or my favorite example is like you know a parasite that um you know sits in the the brain of an ant and you know pilots the ant right right so i talk about that example in my book i love that parasite by the way it's so crazy but is that is that a living is that a life form because it's actually you know it's a symbiont right so or actually a parasite um so this idea of self-sustaining is kind of very problematic for a lot of reasons. I don't actually think life is defined by chemistry.

So this is again, getting a deeper physical principles. Wow. So I include technology. Yeah, first shots fired. Yeah, okay. Yeah. So my definition, or well, my understanding of life, I don't have a definition.

My understanding of life is life is the things that can only be produced by evolution and selection. And technology is also an example of that. And that's not chemical. Right. And also this idea of it being self-reproducing. I mean, there are plenty of humans that can't self-reproduce.

Actually, no human can individually self-reproduce. Right. I've been trying. Yeah. But there's plenty of things. I've been trying. Yeah. But a mule, things. I've been trying.

But a mule, for example, is certainly alive. Can't reproduce. Yeah, and those are kind of odd examples because we bred them, but even if you think of a bee in a colony, most of the bees can't reproduce alone. Are they not alive? Because they're part of a social network?

Traditional definitions of life have issues. Lots of issues. Every single word. Plus, there are stars that have metabolisms and they live out their lives and die

and then they explode and send their materials to other gas clouds that make other stars. Right. So they do reproduce. And there's some heritability there

because of the elements that get made in one star generation. The DNA in one star goes in another. Yep, that's right. So are stars alive? Right? We can ask that question. Yes, star generation. The DNA in one star goes in another. Yeah, that's right. So are stars alive, right? We can ask that question.

Yes, we could. We can ask any question. So why even have a definition at all? So I think definitions are useful heuristics in the absence of having a more fundamental understanding. And so one of my favorite sort of analogies that people in my field make is like, how would you define water before you knew atomic theory?

You would describe it as like a clear liquid. It might be a liquid at room temperature, but you wouldn't really understand what water is until you understand what atoms are and how they combine to make H2O. And that's sort of where we are with definitions of life. We can kind of describe effectively its properties, but we don't have-

Kind of like a macroscopic. Yeah. You know what you're looking at. You just don't know really what it is. Yeah, that's exactly right. Right. You just don't know really what it is. Yeah, that's exactly right. Right. And I want to know really what it is. I want to know at the same level that we understand our other theories of physics, like gravity or quantum mechanics.

You have disentangled the definition of life. Yeah. From people's biases. That's right. Like a chef. Yeah. I'm cooking the primordial soup. When they deconstruct a dish. Deconstruct a dish. Yeah. And you see the primordial soup. When they deconstruct the dish.

Deconstruct the dish. Yeah, you see all the, and you're like, what the hell is that? I know, right? I had eggplant parmesan, the eggplant's here, the cheese is over there.

I'd say, dude, what am I paying you to do? Exactly. The parmesan shows up on Tuesday. All right, so let's get back to this. Any good theory, in fact, I'm a theory snob. Okay.

Forgive me. I love that. No, it's okay. I'm also a theory snob. No, no, theory snob. Please tell me about your theory. But I want to know what your definition of theory snob is. I'm not sure that's a very good theory at all.

That's not the kind of theory that we would let into this club. Oh, dear. Who sponsored you? Sorry. I'm sorry. If you have an idea that you're still testing, then we should call it a hypothesis. And once it's tested and verified and supported by multiple people and not just your lab in the Beyond Institute or Beyond Center, then it can elevate to the level of a theory, which gives us the thermodynamics theory,

quantum theory, relativity theory. But it's not Sarah's theory until it's multiply supported. Yes. I would call it Sarah's hypothesis and your colleagues, your hypothesis. Ooh. Am I allowed, will you grant me that? I'll grant you that. I think there are clear reasons why we call it a's hypothesis and your colleagues, your hypothesis. Am I allowed? Will you grant me that? I'll grant you that. I think there are clear reasons why we call it a theory. And for me, what theories are is our explanatory paradigms, like their actual frameworks that have brought us to a certain pattern.

But you all got to predict something that we have found. What have you predicted that we have found? We have predicted that there should be a threshold above which only molecules produced by life should reside. And we've tested that experimentally. Wait, wait, wait. Wait, wait. Wait, wait. I missed that.

The universe can generate simple molecules. It can't generate complex molecules without evolution and selection. That suggests a boundary. This is the Lego experiment. Yes. Right. A boundary that just random chemistry can explore, but it can't go beyond. Oh.

And we've tested that with living and non-living samples. And even some that NASA sent, and this was done by Lee Cronin's lab, they sent him samples and they blinded them. And they tried to, like, you know, a blinded sample is one that you don't know the identity of the sample. And they tried to really trick them. They sent them Murchison meteorite, which is one of the most complex, inorganic, non-biological samples in the solar system. And it's still classified, the experimental approach still classified it correctly as non-living and what we saw was only the living samples had an assembly index value this number of minimal steps above 15 which is not a magic number it's just an experimentally confirmed number so so you're suggesting that nowhere in

the universe without some other driving force on the system would give you a complexity higher than this? About 15, but that was for a specific set of chemical kinds of bonds that can form. So we don't know if 15 is a universal number. It might be different in a different planet with different geochemistry. But the threshold is there is the point. So that was the first prediction that we've made that we've tested. And also the other thing that we have that hasn't come out yet is actually constructing phylogenetic trees. Come out and it hasn't been published yet.

Hasn't been published yet. Constructing phylogenetic trees with no genomic information, just molecular information. Taking that stuff down to molecules. Molecules. Molecules contain their history. Wow. But I think your point is really important about a theory. And obviously, like, this theory is still under development, but I think theories have played a really important role

in the history of physics in terms of trying to unify a broad set of phenomena that we thought were different. Initially, I would just call them hypotheses. Yeah, I think... That would then later be elevated to theory once it has been verified. Yeah, you should kind of drop it down to hypothesis, because then when it's elevated, we can

call it Sarah's theory. I don't want it to be called Sarah's theory, though. What do you mean I don't want it to be called Sarah's theory. What do you mean you don't want it to be called Sarah's theory? What it does is speaking as a, as an educator, what it does is it protects the usage of the word theory for things that are experimentally objectively true. Right. Right. Otherwise you get people in Congress. I quote, true right right otherwise you get people in congress i quote we should teach evolution only as a theory uh and therefore teach other theories as well but evolution it was trying to get god in

there oh god and so so which we're susceptible right yeah if a theory is something that's sort of in progress and we don't not really sure yet and then it gets shown to be false people will say well we're waiting for the day that relativity theory is shown to be false that's not going to happen yeah right so i know i understand that i think working from the scientist side of it it's really interesting because i think also i've noticed that you know distinguishing between a model and a theory is hard that's another one yeah yeah yeah so these are this is on some level it's semantic yeah semantic just it makes my job easier if we get the semantics we want your job to be easy don't mess with my job so again you're telling me left to its own devices the universe can construct molecules of complexity level 15 in your units of complexity paradigm.

Yes. Okay. After that, what does it require? It requires a system that has some constraints on what kind of molecules get produced. That favors one kind or another. Favors selection. Selection. There's that word again.

We're back to that. Okay. We got you. So. And memory. Whereas getting to a complexity level of 15 does not require that. That's right. And so a key component of passing that threshold is actually storing memory in the system because you have to remember the steps.

So you can get to it every time, right? That's right. Oh, otherwise it's just randomly getting there. That's right. Oh my gosh. Yeah, that makes sense. Oh yeah. So you still have to know what getting there. That's right. Oh my gosh. Yeah, that makes sense. Oh yeah. So you have to know what not to do

in order to know what to do. So you're saying this meteorite and this meteorite can both get to complexity level 15 because they both formed in the void of the early universe, of the early solar system, but without a driving force. Yeah, without something to remember molecules that the meteorite has made in the past

and then build further complexity on top of that. Can't do it. So now you need a system to store information and DNA can do that. Yes. Famously. Yes. Well, I guess there's no way to know. I was going to say, is DNA because like all of everything

around us, you know, that's organic. We all share this, right? So is that optimized in any way for life? Do we look at that as a model that is optimized? I like that. Yeah. Because the Murchison meteorite doesn't contain living molecules.

That's right. All right. So if you're going to get what anyone would call life, why doesn't it select the same path because this is a question that's come up uh my colleagues in geology posed the question and i didn't have a good answer it was an intriguing question they look at multiple planets and they're finding the same rock this comes directly out of what you're saying they find the same rocks even though it's a completely different planet.

Yeah. Same rocks, that is, they understand the rock chemistry of what they bought. The composition and the like. There's basalt there, there's basalt here. Okay, that came out of a volcano. Volcanoes here, volcanoes there.

Why can't life have the same consistency that geology does? It's because of the complexity. Well, see, you have an answer for that. Yeah. You come out of your assembly theory with an answer to that. Yeah. Yeah.

That's right. Can you assemble something like DNA that isn't DNA? Yes. That would... Oh! Oh! Oh! Watch out!

Hello! Okay. Sorry. You buried the Hello. Okay. Sorry. You buried the lead. Okay. Sorry. Oh, my God. Okay.

Sorry. All right, all right. That's amazing. What, pray tell, can store information for you and go beyond your 15 steps? And do you have this thing locked up? I have to say, I'm a serious non-experimentalist, so I haven't built these things myself. But even in the space of just synthetic biology,

people have alternatives to DNA and RNA, which are the usual. Let me just remind people, synthetic biology is basically genetically modified organisms. Right. Right, that's what that is. It's got this new branding, but that's what. Yeah. We started out thinking about it as GMOs.

Because nobody wants to stay genetically modified. Yeah, so synthetic biology. Yeah, so there's all kinds of different, they're called XNAs, alternative nucleic acids, basically, that people have studied. So those are real molecules that people have validated in the lab and actually work in living cells.

But what we're trying to get at that's a bit deeper than that with assembly theory is actually looking at the iteration of chemical space and trying to predict what molecules could be. And right now where we're doing that most significantly is for drug design. That makes sense. And predicting pharmaceutical drugs. And there are some approaches also, if you're talking about validation of a theory, there

are some places where we've been able to predict molecules and actually synthesize them. Knowing that they'd be stable. Yeah. So for example, one place that's really interesting is looking at non-addictive opioids. So if you want to make an opioid, you want to keep the opioid groups, like those parts of the molecule, and then make it non-addictive, you actually have to look at molecules that are

not addictive and then try to combine their features. Well, you get them together and then you figure out how you make the non-addictive molecule bind in such a way that you get the result of the opioid without. Yep, so you can look at the steps to making both kinds of molecules and then you can combine those steps

to look at other kinds of molecules. It's freaking crazy. Okay, so how, so. This is what solving alien life will give you, new drugs. Oh, we're going to get to aliens in a minute. That's good. Let me tell you something. That's good. Make sure you lead with that when we're going to get to amines in a minute. That's good. Let me tell you something.

That's good. Make sure you leave with that when you're going for your grants. It is part of the strategy, actually. It's a good one. How do molecules behave? So give me an example of something that can encode, store information that is not DNA. Well, you can store information in RNA and protein. Those are already in cells. But there's one I like is,

and I actually don't know if people have stored information in it, it's called PNA. It's peptide nucleic acid. I like that because it's kind of a cross between a protein and DNA. Right. All right. And so most of the places where people study these kind of alternative nucleic acids is just in synthetic biology labs.

But there's a whole host of them that you could use. Just the same way that you can store information in DNA, you could just write a sequence of bases in one of these kind of molecules. Minerals are more fun though. Trying to store information in a mineral is pretty crazy. Whoa. So, okay, that's pretty wild.

Now, why would you be storing information in the mineral? Miner minerals are really important in origin of life chemistry and we think that they were actually the first templates for information to actually pattern chemistry in specific ways and they retain you know they have an aperiodic pattern to them which means they can contain a lot of information and they actually was perfectly periodic yep there's hardly any information that's right right yeah so this goes all the way back to has hardly any has hardly any information. Right. Because everything is regular. Yeah.

Right, so if it varies but then repeats, you can stick something in there and repeat it and remember it. Yes. Okay. Fascinating. Yeah, so minerals might have been the templates for the first genetic information, actually. Gotcha, gotcha. Gotcha. Gotcha.

So now we want to look for aliens. How did what you do inform that? So the current way that we're informing it, I think that's most significant, is this ability to look for complexity in the universe as a biosignature instead of looking for specific molecules that life on Earth generated. And we can do that with a mass spectrometer. So we can just fly to another body in our solar system

and try to infer whether there's high assembly molecules there. Whether or not it's crawling out of a beaker. Doesn't make a difference. Well, we haven't seen that yet. And we haven't seen little critters crawling around on Enceladus' plumes or on Mars or anything. So I think we need better tools. In your universe of complexity,

it is a measure of the complexity of information. And artificial intelligence is a level of complexity that's even beyond what we think of as biological. How do you rate artificial intelligence as it's currently expressed in our world on your scale of... So I definitely think artificial intelligence is life, but I also, I know, shocking, huh?

What? But I also think your microphone... Why was I programmed to feel pain? life, but I also, I know, shocking, huh? What? But I also think your microphone. Why was I programmed to feel pain? Oh, did you feel pain from that? I'm so sorry. I didn't mean to induce pain. Often, you know, like, yeah, there's a lot of shock value to things I say.

So I guess I induce pain a lot. That's a very shocking statement. Why? Why do you feel that way though? Well, so I think you want to make a distinction between what you might call life and what you might call alive. This actually comes derived from the theory

and the way I've been thinking about life for a long time. The things I would qualify as life are anything that requires evolution and selection to produce them. Artificial intelligence do not exist on a planet unless there are billions of years of evolution to make intelligent beings like us that are capable of engineering them. In that sense, they are life. The universe is not creating AI.

There are no large language models on Mars unless we put them there. So therefore, we are the remembered molecular complexity to create that. Yes, we're like the minerals imprinting on the genomic information of AI. That makes sense. I gotta say, I didn't want to actually agree with this,

but now I'm thinking of perhaps in a world, maybe even our own, where we're a couple hundred years in the future, or we have somehow mucked things up to the point where we're not going to be here. So we then turn to artificial intelligence, imprint it with the ability to do everything that we do. It continues to evolve in our absence. And then somebody comes and finds us, but not this organic life. It finds us in the form of what we left behind, which was artificial intelligence.

Okay, well, you've been smoking before. I have a more optimistic view of it, though. I did create a whole story out of that. And it wasn't very optimistic, but go ahead. I think when people envision that future, they don't envision us still being here. But cells are inside our bodies and part of the evolutionary structure we are. They've been here for billions of years.

I don't think artificial intelligence or our technology is going to replace us. It's going to become part of a larger integrated system of technology and biology that's co-evolving on the planet. I agree with that as a beginning. But I think, unfortunately, our nature is our penchant and proclivity for self-destruction, which will leave artificial intelligence behind. You're a glass is half empty, I'm a glass is half full kind of person. Let's take it to the next level. Go ahead. Okay.

Go ahead. Actually, I have the answer to the half empty, half full question. Excellent. Drink it. What is the answer? That's a profound question. No, to me, it's no longer profound. If you have a vessel and you're adding liquid to it and it reaches the halfway point, it's

half full. If you have a vessel and you're removing the mechanism, it's half empty. It's half empty. So it depends on where you start. No, it depends. The rate of change, in calculus, would be the first derivative of the volume of liquid that's in it. Right.

Is that positive or negative? And then it's half full or half empty. History matters. Yes, exactly. It's very assembly theoretic and very evolved. See, I just got a compliment. You did. I got the compliment.

All right. So let's take it up a notch. If we are all simulated by some alien juvenile in a basement. Yeah. Well, they just simulated you to think and say that. Sure. In that full-up variant. Or simulated in a surrounding where it would lead you to say that,

even you being sentient and capable of making deductions. That's right. A simulation would say something like that. Oh, that's exactly what you would say. That was very good. That was good. That was good. That was good. So,

a simulation is zeros and ones on a chip creating information that's stored in zeros and ones and manipulated and maneuvered. Is that alive?

So, simulation... Are you alive in a simulation? Oh. I don't think that we're living in a simulation. And the sort of key evidence there is you just talked about the simulation having to run in a chip, which means it needs a physical hardware. And there's always a physical substrate underlying any simulation, as far as we understand.

So, there's always a physical reality at the bottom. Why isn't the simulation empowering you to discover molecules that comprise your body? It does. It does actually, because you can have AI-driven exploration of chemical space, for example. So that's a clear place where a simulation

is driving exploration and making things physical that aren't physical in the absence of a simulation. Exactly, because we joke about, or we talk about, if this whole world is simulated, it would be really inefficient to simulate parts that no sentient being

is absorbing at any given moment. So you'd only simulate where you need to simulate what is necessary. At the time that it's needed. So if I want to dig to the center of the earth, I don't need to make it until I'm getting to the center of the earth. And you simulate it as I'm doing it. And so the simulation is creating the molecules that I'm measuring as having complexity. I think we see observational evidence of that and just with our technologies.

And I think that's really important. And I think there it's explanatory, but when you say the universe is a simulation, I don't think it gives you any additional explanatory power. I find it to be a useless hypothesis. Well, that's, I know what you're saying because then everything is resolved. It's like I say, she just called me useless.

No, no, I'm just kidding. No, what I say to that is it doesn't make a difference because at the end of the week, I still owe Visa, you know, $210.

So what difference does it make if the whole universe is a simulation if at the end of the week, I still owe Visa $210? And you can still write down laws of physics that describe your universe. That's what I'm saying. It does make a difference. It's all the same. Oh, I understand. You're saying the distinction is not interesting

if you can't make the distinction. That's right. So I think simulations being an emergent property that the universe creates, the one that happens through evolution is interesting and then asking

about the physical nature of simulations and why life generates them. That's interesting. Saying the universe is a simulation kicks the can way too far back

for me to give any explanatory power to what we're talking about. Oh, so because you can't figure it out it don't mean nothing. That's exactly right. Don't you know

you're in a room with theoretical physicists? That's exactly right you're in a room with theoretical physicists that's exactly like that's my card we'll grant you your complexity okay in your assembly theory thank you you're unanimous of you i know we grant it star talk grants you Do I get a badge for this or something? I'll find something here. I love this. Or I'm like knighted.

So in that, does it say anything about free will? We've had a few episodes on that subject with some leading thinkers in the area. Indeed. Can you say anything about it?

Yeah, I have a lot to say on it, but I think the sort of most important thing is I think you can have free will and be consistent with the laws of physics as we understand them. And the reason for that- You can have free will. You can. Because people were arguing that you couldn't. Yes. Because the laws of physics are commanding everything you say, think, and do.

That's right. Yeah. And then the flip side of it is like, you know, the universe is totally random and then you have absolute freedom, right? So it's not that you have total or, you know, free will is a trade-off between the sort of control and the freedom. And I think what happens is when you have these evolved structures that are building complexity, they become really constrained by their history, but they still have some freedom in terms of the kind of complexity they can generate. And this becomes sort of deeply intrinsic to what they are. So they are deterministic in some sense,

but there's still some freedom for them to actually make action. Normally when we think of free will, we think of I'm deciding. Right. But really, if you come at it from a molecular point of view, it's whatever the molecule is going to make.

And it'll work within the space of options it has available. Yeah, free will is executed over time, right? So this is also the thing. It's not instantaneous. We don't have free will to be in Arizona right now. Right. But we could be there tomorrow. So I think a key point that we're missing is it's not like you have instantaneous command over what the atoms in your bottom are doing,

but you can make decisions over time. And even your decisions are determined by what came before. So they're executed over a period of time. Yes. Just the fact that, you know, well, I'm a comedian.

Well, I didn't just wake up one day and go, I'm a comedian. It has precedent. It has precedent. Right. So that makes sense. Assembly theory makes some really radical conjectures about the future being larger than the past.

And so there's also some freedom in terms of, because of this idea of building complexity, the future is always more complex and larger in sort of the space of possibility. Because it's not here, though. Yes. I get this. And it helps that we have an expanding universe.

Yes, it does. Exactly. No, this is exactly right. The universe is getting bigger every minute. To accommodate this. Exactly. Cool. No, this is exactly right. The universe is getting bigger every minute. To accommodate this. Exactly. Cool. What does this say about entropy?

So, yeah. Oh. Entropy requires. Oh, I want to hear this. You're not going to like this. Hold on. Hold on. He's going to pop corn out.

Let me get my popcorn out. He's going to. After all that we've been through, we got to entropy now. I got to hear what's. Entropy wants disorder as a direction in which systems move that's right um so but the the reason that that happened like we describe things that way is because of the way we label states like entropy depends on a couple key features one is like you as an observer labeling the particular configurations and the other one being able

to talk about an ensemble of systems that are identically prepared and there's some statistical trend and what is happening in the biosphere is complexity is increasing it's kind of like an entropic tendency but it's actually over configurations like the combinatorial space and so i don't really actually think the second law is telling us that things are- Second law of thermodynamics. Yes, second law of thermodynamics is necessarily telling us that things are trending toward disorder. I think there's a deeper law underlying that that can also account for the structure of what we see in life. But- Of course, there's still entropy on the bed.

Physics would say we're getting, it's only for closed systems that you evolve towards higher. But of course the universe might be an open system. No, no, but I'm saying, but earth is clearly not a closed system. That's right. We have sunlight coming in. That's right. And so we've credited that infusion of energy as a pump for the development of complexity

that wouldn't otherwise be there. Right, like if there were no sun, none of this crap would be here. But you know, one of the things that's been really hard from the perspective of theoretical physics as it's written now, not like what new laws might be present in biology to explain is that it looks like what life is doing

is changing the nature of the underlying state space as we talk about it in physics as it's going along. So it's hard to define something like entropy when you can't count the same things at every instance in time. So you want a second and a half law of thermodynamics that applies to the observed universe. The second law of thermodynamics is an approximate law. I think we all know this is a statistical statement. I would like an exact law.

Ooh. Wow. You are very demanding, I've got to tell you. You are not messing around. No. Theoretical physicists don't mess around. Wow. Wow.

Okay. Screw you, Newton. It's all his fault. And you put all of this in a book. In a book. There's a book. Yeah, man. Oh, my gosh. Life as no one knows it.

Except for you. I still don't know it either. I'm still one of the no ones. I love it. Life as no one, including the author, but it's the whole foundations of that thinking. Yes. And I'm glad it doesn't just live in this conversation. Yeah. Because it lives in the pages of this thinking. Yes. And I'm glad it doesn't just live in this conversation. Yeah.

Because it lives in the pages of this book. So this came out just recently? That's right. Summer 2024. Oh, good for you.

Yeah, yeah. Congratulations. Thank you. Congratulations. Your first book? It is my first book. Excellent. Wonderful.

Excellent. And at the rate you're going, more books should be on there. Are you kidding me? We just wrote one today. We wrote one just now. Are you kidding me? We just wrote one today. We wrote one just now. Are you kidding me?

No, so I look forward to what becomes of this branch of thinking. I'm hoping we will do an experiment where an alien crawls out of it. I'm going to say I'm not with you. Just going to go on the record and say no. You don't want the alien crawling out. No, thank you. No, thank you. Nothing crawling out of anything. Nothing crawling out of anything.

But the understanding that would come with that would be so great. That I want you to find. That I want you to find. That's a pure scientist saying, but we'll learn. Exactly. You know? Right. I think there's a famous quote from Kurt Vonnegut who says,

the last word ever spoken by any human is between two scientists. And one says to the other, let's try the experiment the other way. There you go. That's it. That makes perfect sense. They're all excited about it. It's the last word ever spoken. Yeah.

It's going to be you. I'm a theorist. I'm not doing experiments. Oh, that's right. Oh, okay. All right. See, this be you. I'm a theorist. I'm not doing an experiment. See, this is another reason to be a theorist. Yeah, you know how to do the last experiment. All right. Well, this has been a delight.

Thank you for sharing your expertise and your wisdom and your knowledge coming from beyond. Literally. Beyond. I saw what you did there. Yeah. Yeah. That was cool. Yeah.

Very good. And you got to keep us surprised. Yeah. Of new developments. It's a fascinating frontier And you got to keep us surprised. Yeah. Of new developments. Fascinating frontier. I got to give it to you. And do you have a pipeline into NASA as they set up experiments to look for life? Because we just had Funky Spoon.

Dr. David Grinspoon. Oh, I love David. He's great. Yeah, David Grinspoon. We just had him a few days ago. Oh, really? Yeah, and so he's guiding NASA's search for life. And if you have something to tell him, you better

tell him quick. Yeah, yeah, I could tell him. But actually what I'm trying to do now is prepare data because when you're talking about artificial intelligence, people are also trying to use it for life detection and we don't have good data to train models on. Right. Right. It's not like a large language model for aliens. That's right. We don't have one. Right, right, right.

Awesome. All right. That's a lot of fun. Thanks. That was great. Let me see if I can put some cosmic perspective on this. On this? Yeah, yeah, yeah. Always, throughout time, throughout the history of civilization, somebody had to think out of the box. Somebody does it first.

And they always look a little weird to everybody else. They look a little strange. And most people who do that are just wrong. Let's be honest about this. There's a trash bin of people who stepped out of the box thinking they had new insights into the nature of reality, and they did not. So how do you find the ones that work, that move where we all are and how we think? It needs to be subject to experiment and observation. It can't just live in your head and make sense to you and no one else. So for me, watching these new steps to think about life, to bring a little bit of dose of physics, theoretical physics into the equation

to me is an important first step and I look forward to where this will take us just short of the alien falling out of the box. Don't stop short of the possibility that the alien can help save us from ourselves.

That is a cosmic perspective. This has been another episode of Star Talk, taking you to places that we hadn't been the day before. Sarah Delight, thank you. Thank you guys.

Thanks for coming to my office here at the Hayden Planetarium. It was really fun. In New York City, the American Museum of Natural History. All the way up from Arizona.

Yes. So tell folks at ASU, I said hi. I will. We love way up from Arizona. Yes. So tell folks at ASU I said hi. I will. We love them all down there. Yeah, in the heat. Do you know Tempe, Arizona is one quarter of a mile from the surface of the sun? Yeah, that's funny. I knew that. That's an old joke.

It hit 120 degrees this past summer, right? Yeah, that's typical. Yeah. Oh, yeah. Yeah. All right. Sometimes we can't even fly planes. It's so hot. Oh, because there's not enough air density coming through the thing. That's right. Wow. There's some good physics for you. Yeah. Yeah. It's not just the temperatures, the density of the air. Right. Yeah.

Or you need a longer runway or something. Yeah. Yeah. We got to call it quits there. Chuck, always good to have you, man. Always a pleasure. And again. Thank you so much. My congratulations and good luck on life as no one knows it. Not even the author. That's what makes this especially intriguing.

Hopefully someone will know it one day. One day. One day. All right. Dark Talk here. Keep looking up.