The Origins of Life with Sara Imari Walker

Summary

StarTalk Radio Episode Summary: "The Origins of Life with Sara Imari Walker"

Release Date: October 15, 2024

In this enlightening episode of StarTalk Radio, astrophysicist and beloved host Neil deGrasse Tyson delves deep into the profound question of the origins of life with esteemed astrobiologist and theoretical physicist, Sara Imari Walker. Joined by co-host Chuck Nice, the conversation seamlessly blends scientific inquiry with engaging banter, offering listeners a comprehensive exploration of what constitutes life beyond traditional definitions.

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1. Introduction to the Conversation

The episode begins with Neil and Chuck setting the stage for a discussion that transcends conventional biological perspectives. They introduce Sara Imari Walker, highlighting her unique approach that integrates physics into astrobiology.

Neil deGrasse Tyson [02:41]: "What is life as we know it? Is that understood? And if it is or isn't, what is life is. We don't know it."

This opening sets the tone for a conversation that challenges listeners to rethink life beyond carbon-based biology.

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2. Assembly Theory and Defining Life

Sara introduces her groundbreaking Assembly Theory, which proposes that life is characterized by the ability to generate complex objects through evolution and selection, rather than mere chemical interactions.

Sara Imari Walker [08:20]: "Assembly theory's key conjecture about the nature of life is life is the only physics that can generate complex objects."

She emphasizes that complexity arising without a guiding process like evolution is virtually impossible, distinguishing living systems from non-living matter.

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3. Complexity as a Biosignature

A significant portion of the discussion centers on using molecular complexity as a biosignature in the search for extraterrestrial life. Sara explains how Assembly Theory allows scientists to measure the complexity of molecules independently of their specific structures, facilitating the identification of life beyond Earth.

Sara Imari Walker [23:03]: "We have a way of measuring the complexity of a molecule independent of knowledge of what the molecule is. And we can just do it with a mass spectrometer."

This approach provides a novel methodology for missions like those undertaken by NASA to detect life on other planets by analyzing the molecular makeup of samples.

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4. Challenges with Traditional Definitions of Life

The conversation critiques traditional biological definitions of life, which often hinge on characteristics like metabolism, reproduction, and evolution. Sara points out the limitations of these definitions, especially when considering non-Earth-like life forms.

Sara Imari Walker [25:03]: "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."

She uses examples like viruses and socially structured organisms such as bees to illustrate the ambiguity in classifying life based solely on these traits.

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5. Artificial Intelligence and the Future of Life

An intriguing segment explores the classification of artificial intelligence within the framework of Assembly Theory. Sara posits that AI represents a form of life due to its complexity and ability to evolve through data-driven processes.

Sara Imari Walker [42:22]: "I definitely think artificial intelligence is life."

Neil and Chuck engage with this idea, debating the implications of AI as a living entity and its potential role in the future of intelligent systems.

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6. Entropy, Complexity, and the Second Law of Thermodynamics

Sara delves into the relationship between entropy and complexity, challenging the traditional interpretation of the Second Law of Thermodynamics. She suggests that while entropy describes a trend towards disorder in closed systems, the emergence of life introduces a dynamic where complexity can increase locally within an open system.

Sara Imari Walker [52:07]: "The 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."

This nuanced perspective offers a fresh lens through which to view the interplay between life and the fundamental laws of physics.

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7. Practical Applications and Future Research

Towards the end of the episode, Sara discusses the practical applications of Assembly Theory, particularly in drug design and synthetic biology. She highlights how understanding molecular complexity can lead to the development of non-addictive opioids and other pharmaceutical advancements.

Sara Imari Walker [38:16]: "So 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."

She also touches on the importance of preparing data for AI-driven life detection, emphasizing the need for robust datasets to train models effectively.

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8. Concluding Thoughts and Future Directions

Neil deGrasse Tyson wraps up the episode by reflecting on the significance of integrating theoretical physics into the study of life's origins. He underscores the importance of subjecting new theories to experimental validation to advance our understanding of the universe.

Neil deGrasse Tyson [57:09]: "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."

Sara expresses optimism about the future of Assembly Theory and its potential to revolutionize how we search for and understand life, both terrestrial and extraterrestrial.

Sara Imari Walker [54:58]: "Hopefully someone will know it one day."

---

Key Takeaways

• Assembly Theory offers a novel framework for defining life based on molecular complexity and evolution-driven processes.
• Traditional biological definitions are insufficient for identifying all forms of life, especially extraterrestrial.
• Molecular complexity serves as a promising biosignature in the search for life beyond Earth.
• Artificial Intelligence may represent a new form of life characterized by its own complexity and evolutionary capabilities.
• The interplay between entropy and complexity is more nuanced than previously understood, particularly in open systems like Earth.
• Practical applications of Assembly Theory extend to fields like drug design and synthetic biology, with significant implications for future research.

---

Notable Quotes

• Neil deGrasse Tyson [02:41]: "What is life as we know it? Is that understood? And if it is or isn't, what is life is. We don't know it."

• Sara Imari Walker [08:20]: "Assembly theory's key conjecture about the nature of life is life is the only physics that can generate complex objects."

• Sara Imari Walker [23:03]: "We have a way of measuring the complexity of a molecule independent of knowledge of what the molecule is. And we can just do it with a mass spectrometer."

• Sara Imari Walker [42:22]: "I definitely think artificial intelligence is life."

• Sara Imari Walker [52:07]: "The 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."

• Neil deGrasse Tyson [57:09]: "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."

---

This episode serves as a thought-provoking exploration of life's origins, pushing the boundaries of traditional science to encompass new theories that could redefine our understanding of life in the universe. Sara Imari Walker's insights provide a foundational perspective for future research and the ongoing quest to uncover the mysteries of life beyond our planet.

Keep Looking Up!

Transcript

[Sarah Imari Walker]

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[Neil DeGrasse Tyson]

So Chuck, I don't know if we answered all those profound questions, but we certainly went there.

[Chuck Nice]

We certainly did.

[Neil DeGrasse Tyson]

What is life as we know it? Is that understood? And if it is or isn't, what is life is. We don't know it. Right. And as long as we're talking about.

[Chuck Nice]

Life is AI a lot is AI life itself.

[Neil DeGrasse Tyson]

Right?

[Chuck Nice]

Yes.

[Neil DeGrasse Tyson]

Right.

[Chuck Nice]

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.

[Neil DeGrasse Tyson]

Coming up, life in a nutshell. And outside of the nutshell on StarTalk. Welcome to StarTalk, your place in the universe where science and pop culture collide. START Talk begins right now. This is STARTalk. Neil DeGrasse Tyson, your personal astrophysicist got with me, of course, Chuck Knight.

[Chuck Nice]

Chuck, Mail. What's happening?

[Neil DeGrasse Tyson]

Lord Chuck. Nice.

[Chuck Nice]

Thank you. Yes.

[Neil DeGrasse Tyson]

All right. My co host, professional comedian. Standup comedian.

[Chuck Nice]

Yes, and not always the same thing. A professional comedian and standup comedian.

[Neil DeGrasse Tyson]

An actor.

[Chuck Nice]

An actor.

[Neil DeGrasse Tyson]

I seen you in some TV commercial.

[Chuck Nice]

Acting like a comedian, you know, almost.

[Neil DeGrasse Tyson]

Dropped my sandwich when I saw that.

[Chuck Nice]

There's. I'm actually going to do a sandwich commercial next. Yeah.

[Neil DeGrasse Tyson]

All right. No, good, good that you're out there.

[Chuck Nice]

Yeah. You know, gotta, gotta keep it moving.

[Neil DeGrasse Tyson]

And we can say we knew you.

[Chuck Nice]

When and you gonna know me then too.

[Neil DeGrasse Tyson]

So wonderful topic today. 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.

[Chuck Nice]

Right.

[Neil DeGrasse Tyson]

And never caught on as an acronym LOCKY life as we know it.

[Chuck Nice]

I wonder why such a mellifluous acronym.

[Neil DeGrasse Tyson]

AWKY never caught on Life as we know, it's like carbon based. You know, all the usual things that you throw into the mix. And there's been some effort lately.

[Chuck Nice]

Okay.

[Neil DeGrasse Tyson]

To think about life as we don't know it.

[Chuck Nice]

Ooh, now I like that. Is far more intriguing.

[Neil DeGrasse Tyson]

And that seems to me, opens up all manner of possibilities.

[Chuck Nice]

Absolutely.

[Neil DeGrasse Tyson]

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

[Sarah Imari Walker]

That's me.

[Neil DeGrasse Tyson]

And which one do we go by?

[Sarah Imari Walker]

Sarah.

[Neil DeGrasse Tyson]

Sarah. Okay, we'll do that.

[Chuck Nice]

Oh, thanks for making it simple.

[Sarah Imari Walker]

I tried.

[Chuck Nice]

We appreciate that.

[Sarah Imari Walker]

I really tried.

[Neil DeGrasse Tyson]

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?

[Chuck Nice]

Absolutely.

[Neil DeGrasse Tyson]

But now you're going to bring some physics into the equation. And I love me some physics.

[Sarah Imari Walker]

Yeah, me too.

[Neil DeGrasse Tyson]

The buck stops at physics.

[Chuck Nice]

Okay.

[Neil DeGrasse Tyson]

There's an old saying. There's no understanding of biology without chemistry, and there's no understanding of chemistry without physics.

[Chuck Nice]

There you go. Somehow your subject of expertise be lords over. The lords over. I don't know how this happened.

[Neil DeGrasse Tyson]

So what brought you to the question of life?

[Sarah Imari Walker]

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.

[Chuck Nice]

Whoa.

[Neil DeGrasse Tyson]

Okay, that's.

[Chuck Nice]

Whoa. Damn, Sarah. Coming in hot.

[Sarah Imari Walker]

The only way I know to go.

[Chuck Nice]

Sarah is not playing around, buddy.

[Sarah Imari Walker]

No.

[Neil DeGrasse Tyson]

Didn't even warm up to that one.

[Chuck Nice]

I'm telling you, it's like, why don't you take a couple of warmup tosses? All right. We clock that one at 97 miles an hour. That's fantastic.

[Neil DeGrasse Tyson]

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.

[Sarah Imari Walker]

Yes, the Beyond.

[Neil DeGrasse Tyson]

That's audacious.

[Chuck Nice]

Now, you guys are the people that make the meat, right?

[Neil DeGrasse Tyson]

The Beyond Meat.

[Sarah Imari Walker]

Oh, no, we don't make meat.

[Chuck Nice]

That was the joke.

[Sarah Imari Walker]

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 Arizona State University. Yep.

[Neil DeGrasse Tyson]

Not just in the state of Arizona.

[Sarah Imari Walker]

No, not. Yeah, Arizona State University.

[Neil DeGrasse Tyson]

So you're on the faculty there?

[Sarah Imari Walker]

Yeah, that's right.

[Neil DeGrasse Tyson]

Asu. They have really good astro folk there too.

[Chuck Nice]

Okay.

[Neil DeGrasse Tyson]

Yeah, no, I know asu. All right. Yeah, yeah. And so this beyond center, are you co founder of that?

[Sarah Imari Walker]

No, the founder is Paul Davies, but I'm the deputy director.

[Neil DeGrasse Tyson]

We know Paul Davies. Yeah. An astrophysicist, like from way back.

[Sarah Imari Walker]

Yeah, yeah. I like hanging out with cosmologists. So. And the beyond center is in the cosmology, like it's in the cosmology wing on asu, on, like on the campus.

[Chuck Nice]

Okay.

[Neil DeGrasse Tyson]

And 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.

[Chuck Nice]

Let's go beyond.

[Neil DeGrasse Tyson]

Let's go beyond. Right, right. So you're teaming up with other beyond people.

[Sarah Imari Walker]

Yes, I like hanging out with people that think outside the box. They're my favorite kind of people.

[Neil DeGrasse Tyson]

In fact, the some of the stuff I've been working on is not just the box because box is a three dimensional object.

[Chuck Nice]

Right.

[Neil DeGrasse Tyson]

She's thinking beyond the tesseract.

[Chuck Nice]

Oh.

[Neil DeGrasse Tyson]

Oh, wow.

[Chuck Nice]

Look at that.

[Sarah Imari Walker]

Now I have pretty shapes in my head. I like this.

[Neil DeGrasse Tyson]

So tell me, I know there might have been adjustments over the decades, but today what is the commonly held definition of life itself?

[Sarah Imari Walker]

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 in nature.

[Neil DeGrasse Tyson]

She's got theoretical physics bad.

[Chuck Nice]

I love it.

[Neil DeGrasse Tyson]

It's bad in you.

[Sarah Imari Walker]

It's never coming out.

[Chuck Nice]

Yeah, yeah. It's a little fever with you. You got a little fever? You got a little theoretical fever.

[Sarah Imari Walker]

Yeah, I do.

[Chuck Nice]

So I mean, basically you're like, let's not worry about identifying, let's find out what creates the identification.

[Sarah Imari Walker]

Yes.

[Neil DeGrasse Tyson]

In the first place.

[Sarah Imari Walker]

Yes.

[Chuck Nice]

Wow.

[Neil DeGrasse Tyson]

How do you go about doing that?

[Sarah Imari Walker]

So 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.

[Neil DeGrasse Tyson]

Wow.

[Chuck Nice]

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 in what creates the information, then it may not even be a cell that you're working with. It could be something outside of that.

[Sarah Imari Walker]

Yep. And the cell's 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.

[Neil DeGrasse Tyson]

Assembly theory.

[Sarah Imari Walker]

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.

[Chuck Nice]

Interesting.

[Sarah Imari Walker]

Like a cell.

[Chuck Nice]

Right.

[Sarah Imari Walker]

Or a microphone or a comedian.

[Chuck Nice]

We're not that complex, unfortunately. He's very simple. We're the simplest of all life.

[Neil DeGrasse Tyson]

Yeah. Wait, so you are declaring that rocks and crystals and things, it's 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.

[Sarah Imari Walker]

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 or. So there would be rocks maybe that pass the boundary of life, but they would be something life created or engineered.

[Neil DeGrasse Tyson]

So I 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 preexisting construct for what is or could or should be. Right now you can make almost anything that has complexity.

[Sarah Imari Walker]

Yes.

[Neil DeGrasse Tyson]

And the space of complexities is then what you will study.

[Sarah Imari Walker]

Yes. And that space is huge. So as an astronomical example, you know, I like to use this molecule, Taxol, as an example. It's molecular weights about 853.

[Neil DeGrasse Tyson]

Taxol. What do we do with that?

[Sarah Imari Walker]

Taxol is an anti cancer drug. It's just one molecule that's been created in a tree. It's a fat molecule. It's a fat molecule. It's a big molecule. But if you wanted to make.

[Neil DeGrasse Tyson]

How many atoms are in that molecule? Approximately? I mean, hundreds or thousands of.

[Sarah Imari Walker]

It's like a couple hundred.

[Neil DeGrasse Tyson]

Yeah. So on that order. Yeah.

[Sarah Imari Walker]

Or 100 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 centimeter, 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.

[Chuck Nice]

Uh huh.

[Sarah Imari Walker]

So you like we can't have a universe and a half full of just Taxol. It'll be very boring.

[Neil DeGrasse Tyson]

Right.

[Sarah Imari Walker]

We live in a universe with lots of different complex options.

[Neil DeGrasse Tyson]

Wait, I have to. Let me repeat what I think you said, that the complexity of what's it called again?

[Chuck Nice]

Taxol.

[Sarah Imari Walker]

Taxol.

[Neil DeGrasse Tyson]

Taxol.

[Sarah Imari Walker]

It's not a special molecule either. I just picked one out of a hat.

[Neil DeGrasse Tyson]

Yeah, we all have these in our hat, don't we?

[Chuck Nice]

Exactly, yeah. I'm carrying around the hat with lots of Taxol in it, so more like.

[Neil DeGrasse Tyson]

A ski mask if I think I understand you.

[Sarah Imari Walker]

Yeah.

[Neil DeGrasse Tyson]

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.

[Sarah Imari Walker]

That's right.

[Neil DeGrasse Tyson]

So clearly that molecule's existence comes from some prior requirement or urgent configuration for that configuration. Right?

[Sarah Imari Walker]

Yes, that's exactly right.

[Neil DeGrasse Tyson]

That's fair.

[Sarah Imari Walker]

Yes, that's exactly right.

[Chuck Nice]

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.

[Neil DeGrasse Tyson]

Had nothing to do with that. Okay, but go on.

[Chuck Nice]

That's a very complex molecule. Okay. Anyway. Okay, where exactly does spontaneity and selection cross and how do you identify which is which? Which is.

[Sarah Imari Walker]

Oh I love.

[Chuck Nice]

Which is a progression and which is a cross.

[Sarah Imari Walker]

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 are easier for people than chemistry. If you have like a 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.

[Chuck Nice]

And a wand.

[Sarah Imari Walker]

And a wand, yeah. No magic though. The universe doesn't have magic, at least not in this scenario. So.

[Chuck Nice]

She covered her best. She's like you know what?

[Neil DeGrasse Tyson]

She's in a Beyond Institute. I am a theorist, but she's in a beyond.

[Sarah Imari Walker]

Is.

[Chuck Nice]

You got to leave her moving for.

[Neil DeGrasse Tyson]

The room for the wand.

[Chuck Nice]

Go ahead.

[Sarah Imari Walker]

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.

[Neil DeGrasse Tyson]

Any sufficiently advanced technology is indistinguishable from magic.

[Sarah Imari Walker]

That's right. Yeah. Or the laws of physics.

[Neil DeGrasse Tyson]

Good.

[Chuck Nice]

Wow. Okay, so go ahead back to. You can't get to the place where you could shake it and then have Hogwarts. So.

[Neil DeGrasse Tyson]

So if you do shake it and some stick together, those are like the amino acids.

[Sarah Imari Walker]

Yes. God, yes.

[Neil DeGrasse Tyson]

Because we did kind. We did that with the Miller Urey experiment.

[Sarah Imari Walker]

That's right.

[Neil DeGrasse Tyson]

Where he just throws some basic.

[Chuck Nice]

Oh, can you explain that, please?

[Neil DeGrasse Tyson]

Everybody knows that Miller.

[Chuck Nice]

Clearly they don't. Okay. And by the way, of course, I know. I'm just talking about the people out there. I mean, there may be someone regardless.

[Neil DeGrasse Tyson]

Of the Miller experiment.

[Sarah Imari Walker]

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, you know, 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.

[Neil DeGrasse Tyson]

Source of energy.

[Sarah Imari Walker]

Yes. As a source of energy. And he had a reducing environment. And then, you know, he got amino acids remove.

[Neil DeGrasse Tyson]

Oxygen is taken out.

[Sarah Imari Walker]

Yeah. And so he made amino acids and, you know, people were so shocked by this at the time. They thought little aliens were being crawling out of, you know, life forms would be crawling out of the test tube in a couple of weeks. But that's not what happened.

[Chuck Nice]

Right.

[Sarah Imari Walker]

Unfortunately.

[Neil DeGrasse Tyson]

Now the reducing environment is that we think the early Earth did not have free oxygen.

[Chuck Nice]

Oxygen.

[Neil DeGrasse Tyson]

Right. So. So he's trying to. If. If life's formed on Earth under these.

[Chuck Nice]

You got to create the conditions under which it formed.

[Neil DeGrasse Tyson]

So what? So out of the ooze, nothing crawled out.

[Sarah Imari Walker]

Nothing crawled out. If you run the experiment long enough, you basically get what we call a tar. In prebiotic chemistry, which an undifferentiated mess of a whole bunch of organic molecules that we can't identify.

[Neil DeGrasse Tyson]

Prebiotic chemistry means what?

[Sarah Imari Walker]

Prebiotic chemistry means chemistry that could plausibly happen on the early Earth in the absence of life.

[Neil DeGrasse Tyson]

Before you have life.

[Sarah Imari Walker]

Before you have life.

[Neil DeGrasse Tyson]

So it's organic chemistry, right?

[Sarah Imari Walker]

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.

[Chuck Nice]

It makes it sound like something you take before a meal.

[Sarah Imari Walker]

Yeah, that's true. People do confuse it with probiotic all the time. Oh my gosh, all that probiotic chemistry.

[Neil DeGrasse Tyson]

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[Neil DeGrasse Tyson]

So, all right, so I like the basic principles that are being invoked here. Very, very simple basic principles. Okay, so now you have you shake the Legos, some stick together. Now what?

[Sarah Imari Walker]

Now selection needs to happen to get to something like Hogwarts, which means that some parts have to start being, you know, abundant in the environment and then reused to be build further structure.

[Neil DeGrasse Tyson]

And these become your units of your building. Units.

[Sarah Imari Walker]

Yes, your bricks. That's right, yes.

[Neil DeGrasse Tyson]

To build the edifice.

[Sarah Imari Walker]

Yes.

[Chuck Nice]

And you say selection because they are selected to succeed, Is that the idea?

[Sarah Imari Walker]

Yes. And also because selection is excluding that huge space of other possib. So you have to.

[Neil DeGrasse Tyson]

Otherwise you're lost in space.

[Sarah Imari Walker]

That's right, yeah. 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.

[Neil DeGrasse Tyson]

It's three universities.

[Chuck Nice]

So now since you're looking for life outside of this, let's consider in the selection, life outside of what I'm saying, outside of the life that we know.

[Neil DeGrasse Tyson]

Oh yeah, right, right.

[Sarah Imari Walker]

You're looking for life, other planets even.

[Chuck Nice]

So let's go back to the primordial soup of another planet and we have the shaken Legos. Okay, but are there circumstances that maybe led to selection for the development here that may be different there creating something different entirely? Could that possibly be the case?

[Sarah Imari Walker]

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 define a threshold that we expect life to emerge, which is what you described as this 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.

[Neil DeGrasse Tyson]

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. So we live this.

[Sarah Imari Walker]

Yeah, right.

[Neil DeGrasse Tyson]

Okay. It's our fancy word for it. But when water becomes ice.

[Chuck Nice]

Ice that's.

[Neil DeGrasse Tyson]

Ice is not water. That's a phase Transit. When water becomes steam, it's a phase transit.

[Chuck Nice]

There you go.

[Neil DeGrasse Tyson]

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.

[Sarah Imari Walker]

Gets us through and we geek out on that. We physicists love phase transitions.

[Neil DeGrasse Tyson]

Anything can happen through a chase transition.

[Chuck Nice]

That's right.

[Neil DeGrasse Tyson]

And like, spooky things, fun things, dangerous things. So I shake the legos. Some of them stick together. They're the 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 AI, Your what's at.

[Sarah Imari Walker]

What's the assembly theory at? We call it. We talk about assembly indexes, the number of steps to make an oxygen.

[Neil DeGrasse Tyson]

Okay, so that's a step. Yeah, that's a step.

[Sarah Imari Walker]

Okay.

[Neil DeGrasse Tyson]

If that's the same step everywhere, then that greatly limits what comes after. Because you're not starting. Not everything is possible in that early first unit.

[Sarah Imari Walker]

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.

[Neil DeGrasse Tyson]

Right. And not all of them, not all.

[Sarah Imari Walker]

Of them are in biology.

[Neil DeGrasse Tyson]

Right. So if you find them in meteorites, it means that they're out there.

[Chuck Nice]

They're out there, they're being made.

[Neil DeGrasse Tyson]

They're being made, but they're not here. Or even if they come here, we're not using them.

[Chuck Nice]

Right. They don't serve a purpose here.

[Neil DeGrasse Tyson]

Right, exactly. Okay, that's the point.

[Sarah Imari Walker]

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, you know, 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.

[Chuck Nice]

So let's. Okay.

[Sarah Imari Walker]

Aliens can be really weird.

[Chuck Nice]

That's what I was going to. That's what I was going to 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, you know, purpose procreating, you know, I mean, when you, if, if you can look for something like that, how do you even begin to narrow the search once you start looking out there?

[Sarah Imari Walker]

Yeah. So the great thing about assembly theory is we can actually measure how assembled a group of molecules is with quantitatively, actually. With. Yeah, quantitatively we have predictions that we can make from the theory, but we can test them in the lab. And so we have a way of measuring the complexity of a molecule independent of knowledge of what the molecule is. And we can just do it with a mass spectrometer.

[Neil DeGrasse Tyson]

Okay.

[Chuck Nice]

See this is, this is some, this.

[Neil DeGrasse Tyson]

Is physics coming in the doorway here. All right.

[Sarah Imari Walker]

We like measurements. They ground us in reality.

[Neil DeGrasse Tyson]

Right. Evolutionary steps, sometimes we think of them that way is, can involve added complexity. So why, what is, what are you doing that's different from that?

[Sarah Imari Walker]

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 origin of life because we don't know where life comes from to begin with. So we need.

[Neil DeGrasse Tyson]

Because you have a sample of one.

[Sarah Imari Walker]

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.

[Chuck Nice]

Is there any chance that it could just be a mistake?

[Sarah Imari Walker]

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.

[Neil DeGrasse Tyson]

Oh, good answer.

[Chuck Nice]

Yeah. I mean, it doesn't stop the search though.

[Neil DeGrasse Tyson]

But you're right, that's a good answer.

[Chuck Nice]

It's not very interesting at that point.

[Neil DeGrasse Tyson]

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.

[Sarah Imari Walker]

Yeah.

[Neil DeGrasse Tyson]

You have things to add to that, subtract from that.

[Sarah Imari Walker]

I don't.

[Chuck Nice]

Laura, can you juxtapose both. What do you call what he just said from your. Where you are, what is that? And then where are you different?

[Sarah Imari Walker]

So, so one definition that people like to use which encapsulates what you're saying as like fundamental pieces of it, is life is a self sustaining chemical system capable of Darwinian evolution. It's quite a mouthful that is what.

[Chuck Nice]

He just said though.

[Sarah Imari Walker]

Yeah, it is exactly what he Said it totally is. So, you know, 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. 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, you know, like they require the graduate student. So pipetting, that's a verb.

[Chuck Nice]

Yeah, like pipette.

[Neil DeGrasse Tyson]

It's a little thing. Yeah.

[Chuck Nice]

Puts a little glass straw in there.

[Neil DeGrasse Tyson]

Yeah, yeah.

[Sarah Imari Walker]

So, yeah, you got to move. You got to move the molecules from one tube to the next to do artificial selection.

[Chuck Nice]

Why you do it? You say, I am crushing your head.

[Sarah Imari Walker]

Okay, sorry. So. So there's many. Or my favorite example is like, you know, a parasite that, you know, sits in the brain of an ant and, you know, pilots the ant. Right, right. So I talk about that example in.

[Chuck Nice]

My book, actually Parasite, by the way.

[Sarah Imari Walker]

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. 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.

[Chuck Nice]

Wow.

[Sarah Imari Walker]

So I include technology. Yeah.

[Neil DeGrasse Tyson]

First shots fired.

[Sarah Imari Walker]

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. 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, but there's plenty of.

[Chuck Nice]

Things I've been trying.

[Neil DeGrasse Tyson]

Yeah, but a mule, for example.

[Sarah Imari Walker]

Yeah, exactly.

[Neil DeGrasse Tyson]

Is certainly alive. Can't reproduce.

[Chuck Nice]

Can't reproduce.

[Sarah Imari Walker]

Yeah. And those are kind of odd examples because we bred them. But even if you think of like a bee in a colony. Right. Like most of the bees can't reproduce alone. Are they not alive because they're part of a social network? So a.

[Neil DeGrasse Tyson]

The traditional definition of life have issues, lots of issues.

[Sarah Imari Walker]

Every single word.

[Neil DeGrasse Tyson]

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. So they do reproduce.

[Sarah Imari Walker]

And there's some heritability there because of the elements that get made in one star generation, DNA.

[Neil DeGrasse Tyson]

And one star goes into another generation. So our stars alive. Right. We can ask that question.

[Sarah Imari Walker]

Yes, we could. So you can ask any question.

[Neil DeGrasse Tyson]

So why even have a definition at all?

[Sarah Imari Walker]

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, you know, 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 like a macroscopic.

[Chuck Nice]

Yeah, you know what you're looking. You know what you're looking at. You just don't know really what it is.

[Sarah Imari Walker]

Yeah, that's exactly right.

[Chuck Nice]

Right.

[Sarah Imari Walker]

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.

[Neil DeGrasse Tyson]

Or quantum mechanics, you have disentangled the definition of life.

[Chuck Nice]

Yeah.

[Neil DeGrasse Tyson]

From people's biases.

[Sarah Imari Walker]

That's right.

[Chuck Nice]

Like a chef.

[Sarah Imari Walker]

Yeah. Like when they say they're cooking the primordial soup.

[Neil DeGrasse Tyson]

No, when they deconstruct. When they deconstruct the dish.

[Chuck Nice]

Yeah. And you see all the. And you're like, what the hell is that? I know, right?

[Neil DeGrasse Tyson]

I had eggplant parmesan. The eggplant dude, what am I paying you to do?

[Chuck Nice]

Exactly. The Parmesan shows up on Tuesday.

[Neil DeGrasse Tyson]

All right, so let's get back to this. Any good theory. In fact, I'm a theory snob. Okay, Excellent. Forgive me.

[Sarah Imari Walker]

I love that. No, it's okay. I'm also a theory snob.

[Neil DeGrasse Tyson]

No, no, Theory snob.

[Chuck Nice]

Tell me I'm holding on theory.

[Sarah Imari Walker]

But I want to know what your definition of theory snob is.

[Chuck Nice]

Yeah, 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. No, dear. Who sponsored you? Sorry.

[Neil DeGrasse Tyson]

No, I guess 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. I would call it Sarah's hypothesis. And your colleagues your hypothesis. Am I allowed? Will you grant me that?

[Sarah Imari Walker]

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.

[Neil DeGrasse Tyson]

That have brought something that we have found. What have you predicted that we have found?

[Sarah Imari Walker]

We have predicted that there should be a threshold above which only molecules produced by life should reside. And we've tested that experimentally.

[Neil DeGrasse Tyson]

Wait, wait, wait, wait, wait, wait, wait, I missed that.

[Sarah Imari Walker]

The universe can generate simple molecules, it can't generate complex molecules without evolution and selection. That suggests a boundary.

[Neil DeGrasse Tyson]

This is the Lego experiment.

[Sarah Imari Walker]

Yes. 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 confuse 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 nonliving. 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.

[Neil DeGrasse Tyson]

So, so you're suggesting that nowhere in the universe without some other driving force behind the system would give you a complexity higher than this, about 15.

[Sarah Imari Walker]

But that was for a specific set of chemical like 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.

[Chuck Nice]

Is there is the point.

[Sarah Imari Walker]

So that was the first prediction that we've made that we've tested. And also the other thing that we have that hasn' come out yet is actually constructing phylogenetic trees.

[Neil DeGrasse Tyson]

Hasn't been published yet.

[Sarah Imari Walker]

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.

[Chuck Nice]

Wow.

[Sarah Imari Walker]

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. I would just.

[Neil DeGrasse Tyson]

Initially, I would just call them hypothesis.

[Sarah Imari Walker]

Yeah.

[Neil DeGrasse Tyson]

I think that would then later be elements elevated to theory once it has been verified.

[Chuck Nice]

Yeah, you should drop it down the hypothesis, because then when it's elevated, we can call it Sarah's theory.

[Sarah Imari Walker]

I don't want it to be called Sarah's theory, though.

[Neil DeGrasse Tyson]

What do you mean you don't want.

[Chuck Nice]

It to be called Sarah's theory?

[Neil DeGrasse Tyson]

Of course it does. What it does is, speaking as an educator, what it does is it protects the usage of the word theory for things that are experimentally, objectively true.

[Chuck Nice]

Right.

[Neil DeGrasse Tyson]

Otherwise you get people in Congress, I quote, we should teach evolution only as a theory and therefore teach other theories as well.

[Chuck Nice]

But evolution, it was trying to get God in there.

[Neil DeGrasse Tyson]

And so we're susceptible. If a theory is something that's sort of in progress and we're 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.

[Sarah Imari Walker]

That's not going to happen. 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 distinguishing between a model and a theory is hard.

[Neil DeGrasse Tyson]

That's another one.

[Sarah Imari Walker]

Yeah.

[Neil DeGrasse Tyson]

So this is, on some level, it's semantic, but it's semantic just. It makes my job easier if we.

[Sarah Imari Walker]

Get the semantics right. We want your job to be easy.

[Neil DeGrasse Tyson]

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.

[Sarah Imari Walker]

Yes.

[Neil DeGrasse Tyson]

Okay. After that, what does it require?

[Sarah Imari Walker]

It requires a system that has some constraints on what kind of molecules get produced.

[Neil DeGrasse Tyson]

That favors one kind or another, favors selection.

[Chuck Nice]

Select.

[Sarah Imari Walker]

There's that word again.

[Chuck Nice]

We're back to that.

[Neil DeGrasse Tyson]

Okay, gotcha. So, memory. Whereas getting to a complexity level of 15 does not require that.

[Sarah Imari Walker]

That's right. And so a key component of passing that threshold is actually storing memory in the system, because you have to remember.

[Neil DeGrasse Tyson]

The steps so you can get to it every time, right?

[Sarah Imari Walker]

That's right.

[Neil DeGrasse Tyson]

Oh, otherwise it's just randomly getting.

[Chuck Nice]

That's right. Right.

[Neil DeGrasse Tyson]

Oh, my gosh.

[Chuck Nice]

Yeah. That makes sense.

[Neil DeGrasse Tyson]

Oh, yeah.

[Chuck Nice]

So you have to know what not to do in order to know what to do.

[Neil DeGrasse Tyson]

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.

[Sarah Imari Walker]

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.

[Neil DeGrasse Tyson]

So now you need a system to store information.

[Sarah Imari Walker]

That's right.

[Neil DeGrasse Tyson]

And DNA can do that.

[Sarah Imari Walker]

Yes, famously. Yes.

[Chuck Nice]

So. 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.

[Neil DeGrasse Tyson]

I like that. You know, because the Murchison meteorite doesn't contain living molecules.

[Sarah Imari Walker]

That's right.

[Neil DeGrasse Tyson]

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. 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 composition and the like. There's basalt there. There's basalt here. Okay. That came out of a volcano. Volcano's here, volcano's there. Why can't life have the same consistency that geology does?

[Sarah Imari Walker]

It's because of the complexity.

[Neil DeGrasse Tyson]

Well, see that? You have an answer for that.

[Sarah Imari Walker]

Yeah.

[Neil DeGrasse Tyson]

You come out of your assembly theory with an answer to that.

[Sarah Imari Walker]

Yeah, yeah, yeah, that's right.

[Neil DeGrasse Tyson]

Can you assemble something like DNA that isn't DNA? That would be. Yes, that would.

[Chuck Nice]

Watch out. Hello?

[Neil DeGrasse Tyson]

Okay, sorry, you buried the lead.

[Chuck Nice]

Okay, sorry.

[Neil DeGrasse Tyson]

Okay.

[Chuck Nice]

Oh, my God.

[Neil DeGrasse Tyson]

Okay. Sorry. Okay. All right, all right.

[Chuck Nice]

So that's amazing.

[Neil DeGrasse Tyson]

What, pray tell, can store information for you and go beyond your 15 steps?

[Chuck Nice]

Do you have this thing locked up?

[Sarah Imari Walker]

That is what I have to say. I'm a theorist, not an experimentalist, so I have. I haven't built these things myself, but there. I mean, even in the space of just synthetic biology, people have alternatives to DNA and rna, which are the usual.

[Neil DeGrasse Tyson]

Let me just remind people, synthetic biology is basically genetically modified organisms. Right. That's what that is. It's got this new branding, but that's what we started out thinking about it.

[Chuck Nice]

As GMOs, because nobody wants to genetically modify it anymore.

[Neil DeGrasse Tyson]

Yeah. So synthetic biology. Yeah.

[Sarah Imari Walker]

So there's all kinds of different. They're called xnas, like alternative nucleic acids, basically. That people have studied. So. So those are real molecules that people 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, there are some approaches also, if you're talking about validation of a theory, there are some places where we've able. Been able to predict molecules and actually synthesize them and then knowing that they'd be stable. Yeah. So, for example, one place is really interesting is looking at non addictive opioids. So if you want to make an opioid, you want to keep the opioid groups like that, 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.

[Chuck Nice]

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.

[Sarah Imari Walker]

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.

[Chuck Nice]

Freaking crazy.

[Neil DeGrasse Tyson]

Great. So, so how.

[Sarah Imari Walker]

So this is what solving alien life will give you. New drugs.

[Neil DeGrasse Tyson]

Oh, we're gonna get to aliens in a minute. That's good.

[Chuck Nice]

Let me tell you something that's good. Make sure you lead with that when you're going for your grants.

[Sarah Imari Walker]

It is part of the strategy, actually.

[Chuck Nice]

It's a good one.

[Neil DeGrasse Tyson]

How do molecules behave? So give me an example of something that can encode store information that is not DNA.

[Sarah Imari Walker]

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 information in. It is called pna. It's peptide nucleic acid. I like that because it's kind of a cross between a protein and DNA.

[Chuck Nice]

Right.

[Neil DeGrasse Tyson]

All right.

[Sarah Imari Walker]

And so, so most of the places where people study these kind of alternative nucleic acids is just, you know, in synthetic biology labs. But there, 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.

[Chuck Nice]

Whoa. So, okay, that's pretty wild. Now why would you be storing information in the mineral.

[Sarah Imari Walker]

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.

[Neil DeGrasse Tyson]

Because it was perfectly periodic.

[Sarah Imari Walker]

Yep.

[Neil DeGrasse Tyson]

There's hardly any information.

[Sarah Imari Walker]

That's right.

[Neil DeGrasse Tyson]

Right.

[Sarah Imari Walker]

Yeah. So this goes all the way back.

[Neil DeGrasse Tyson]

To has hardly any information.

[Sarah Imari Walker]

Right.

[Neil DeGrasse Tyson]

Because everything is regular.

[Sarah Imari Walker]

Yeah.

[Neil DeGrasse Tyson]

Right. So if it varies but then repeats, you can stick something in there and repeat it and remember it.

[Sarah Imari Walker]

Yes.

[Neil DeGrasse Tyson]

Okay.

[Chuck Nice]

Fascinating.

[Sarah Imari Walker]

Yeah. So minerals might have been the templates for the first genetic information actually.

[Chuck Nice]

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[Neil DeGrasse Tyson]

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[Chuck Nice]

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[Neil DeGrasse Tyson]

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[Chuck Nice]

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[Neil DeGrasse Tyson]

So now we want to look for aliens. How did what you do inform that.

[Sarah Imari Walker]

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. And instead of looking for specific molecules that life on Earth generated, and we can do that with a mass spectrometer. So we can just, you know, fly to another body in our solar system and try to infer whether there's high assembly molecules there.

[Chuck Nice]

Right.

[Neil DeGrasse Tyson]

Whether or not it's crawling out of.

[Chuck Nice]

A beaker doesn't make a difference or.

[Sarah Imari Walker]

Well, we haven't seen that yet, so. And we haven't seen little critters crawling around on, you know, Enceladus plumes or on Mars or anything. So I think we need. We need better tools.

[Neil DeGrasse Tyson]

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.

[Sarah Imari Walker]

So I definitely think artificial intelligence is life, but I also. I know. Shocking, huh? Shocking. But I also think you're my.

[Chuck Nice]

Why was I programmed to feel painful pain?

[Sarah Imari Walker]

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.

[Chuck Nice]

That's a very shocking statement. Why. Why do you feel that way, though?

[Sarah Imari Walker]

Well, so I think you want to make a distinction between what you might call life and what you might call alive. And this actually comes derived from the theory and the way I've been thinking about life for a long time. So the things I would qualify as life or anything that requires evolution and selection to produce them and artificial intelligence do not exist on a planet unless there are billions of years of evolution to make intellig like us that are capable of engineering them. So in that sense, they are, like, not creating AI. There are no large language models on Mars unless we put them there. Interesting.

[Neil DeGrasse Tyson]

So therefore we are the remembered molecular complexity to create that.

[Sarah Imari Walker]

Yes. We're like the minerals imprinting on the genomic information of the AI.

[Chuck Nice]

Makes sense. I got to 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 gonna 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.

[Neil DeGrasse Tyson]

Okay, what have you been smoking before?

[Sarah Imari Walker]

I have a more optimistic video.

[Neil DeGrasse Tyson]

Just created a whole story out there.

[Chuck Nice]

I did create a whole story out of that and it wasn't very optimistic. But go ahead.

[Sarah Imari Walker]

I think when people envision that future, they don't envision us still being here. But you know, like cells are inside our bodies and part of like 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.

[Chuck Nice]

I agree with that as a beginning. But I think unfortunately our nature.

[Sarah Imari Walker]

Oh, when we get off.

[Chuck Nice]

And proclivity for self destruction which will leave artificial intelligence behind.

[Sarah Imari Walker]

You're a glass is half empty. I'm a glass half full kind of person. I guess.

[Neil DeGrasse Tyson]

Take it to the next level.

[Chuck Nice]

Go ahead.

[Neil DeGrasse Tyson]

Okay, go ahead. Actually, I have the answer to the half empty half full question.

[Sarah Imari Walker]

Excellent.

[Chuck Nice]

Drink it.

[Sarah Imari Walker]

What is the answer? That's a profound question.

[Chuck Nice]

No, no, no.

[Neil DeGrasse Tyson]

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.

[Chuck Nice]

Removing liquor from it, it's half empty.

[Neil DeGrasse Tyson]

It's half empty.

[Chuck Nice]

So it depends on where you start.

[Neil DeGrasse Tyson]

No, it depends the rate of change. So it's the like in calculus it'd be the first derivative of the volume of liquid that's in it. Is that positive or negative? And then it's half full or half empty.

[Sarah Imari Walker]

History matters.

[Neil DeGrasse Tyson]

Yes, yes, exactly.

[Sarah Imari Walker]

It's very assembly theoretic and very evolved.

[Chuck Nice]

Wow.

[Neil DeGrasse Tyson]

See, I just got a compliment.

[Chuck Nice]

You did?

[Neil DeGrasse Tyson]

Don't worry, I caught the compliment. Okay. All right, so let's take it up a notch. If we are all simulated by some alien juvenile in a basement. Well, they just simulated you to think and say that.

[Sarah Imari Walker]

Sure.

[Chuck Nice]

In that full up variant or simulated a surrounding where it would lead you to say that even you being sentient and capable of making the ducks.

[Sarah Imari Walker]

A simulation would say something like that.

[Neil DeGrasse Tyson]

Oh, it's exactly what you would say.

[Chuck Nice]

That was very good.

[Neil DeGrasse Tyson]

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?

[Sarah Imari Walker]

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 is always under. There's always a physical substrate underlying any simulation that as far as we understand. So there's always a physical reality at the bottom.

[Neil DeGrasse Tyson]

Why isn't the simulation empowering you to discover molecules that comprise your body?

[Sarah Imari Walker]

It does. It does, actually, because you can have AI driven exploration of chemical space, for example. So that's a clear place where simulation is driving exploration and making things physical that aren't physical. In the absence of a simulation.

[Neil DeGrasse Tyson]

Exactly. Because we joke about what 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.

[Chuck Nice]

Time that it's needed.

[Neil DeGrasse Tyson]

So if I want to dig to the center of the Earth, I don't.

[Chuck Nice]

Need to make it until I'm digging to the center.

[Neil DeGrasse Tyson]

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.

[Sarah Imari Walker]

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.

[Chuck Nice]

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 220, and you.

[Sarah Imari Walker]

Can still write down laws of physics that describe your universe? No, that's what I'm saying.

[Chuck Nice]

It doesn't make a difference. It's all the same.

[Neil DeGrasse Tyson]

Oh, I understand it. You're saying the distinction is not interesting if you can't make the distinction.

[Sarah Imari Walker]

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.

[Chuck Nice]

Oh, so because you can't figure it out, it don't mean nothing.

[Sarah Imari Walker]

That's exactly right. Don't you know you're in a room with theoretical physicist. That's exactly like. That's my card.

[Neil DeGrasse Tyson]

We'll grant you your complexity.

[Sarah Imari Walker]

Okay.

[Neil DeGrasse Tyson]

In your assembly theory. Thank you, universe.

[Chuck Nice]

I'm magnanimous of you.

[Sarah Imari Walker]

I know.

[Neil DeGrasse Tyson]

We grant you startalk grants you assembly theory.

[Sarah Imari Walker]

Can I get a badge for this or something?

[Neil DeGrasse Tyson]

I'll find something here. I love this. So.

[Sarah Imari Walker]

Or I'm like knighted.

[Neil DeGrasse Tyson]

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.

[Chuck Nice]

Indeed.

[Neil DeGrasse Tyson]

Can you say anything about it?

[Sarah Imari Walker]

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.

[Neil DeGrasse Tyson]

Because people were arguing that you couldn't. Because the laws of physics. Physics are commanding everything you say they can do.

[Sarah Imari Walker]

That's right.

[Neil DeGrasse Tyson]

Yeah.

[Sarah Imari Walker]

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. Generate. And so. 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.

[Neil DeGrasse Tyson]

Normally, when we think of free will, we think of. I'm deciding.

[Chuck Nice]

Right.

[Neil DeGrasse Tyson]

But really, if you come in from a molecular point of view, it's whatever the molecule is going to make, and it will work within the space of options it has available.

[Sarah Imari Walker]

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, but we could be there tomorrow. So I, I think this, you know, 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.

[Chuck Nice]

And even your decisions Are determined by what came before. So they're executed over a period of time.

[Sarah Imari Walker]

Yes.

[Chuck Nice]

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.

[Neil DeGrasse Tyson]

It has precedent.

[Chuck Nice]

It has precedent. Right. So that makes sense.

[Neil DeGrasse Tyson]

Yeah.

[Sarah Imari Walker]

Assembly theory makes some really radical conjectures about, like, 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.

[Chuck Nice]

But that's because it's not here, though.

[Neil DeGrasse Tyson]

Yes, I get this. And it helps that we have an expanding universe if you want to put together.

[Sarah Imari Walker]

No, this is exactly right. The universe is getting bigger every minute.

[Neil DeGrasse Tyson]

We accommodate this. Cool. What does this say about entropy?

[Sarah Imari Walker]

Yeah.

[Neil DeGrasse Tyson]

Oh, entropy requires.

[Chuck Nice]

Oh, I want to hear this.

[Sarah Imari Walker]

You're not going to let.

[Chuck Nice]

Hold on, hold on.

[Neil DeGrasse Tyson]

He's getting his popcorn out.

[Chuck Nice]

Let me get my popcorn out.

[Neil DeGrasse Tyson]

He's going to.

[Chuck Nice]

After all that we've been through, we got the entropy. Now I got to get.

[Neil DeGrasse Tyson]

Entropy wants disorder as a direction in which systems move.

[Sarah Imari Walker]

That's right. But the reason that we describe things that way is because of the way we label states. Entropy depends on a couple key features. One is 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 trends. 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.

[Neil DeGrasse Tyson]

Second law of thermodynamics.

[Sarah Imari Walker]

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.

[Neil DeGrasse Tyson]

You know, physics would say we're getting. It's only for closed systems that you evolve towards a higher.

[Sarah Imari Walker]

But of course, the universe might be an open system.

[Neil DeGrasse Tyson]

No, no. But I'm saying. But Earth is clearly not a closed system.

[Sarah Imari Walker]

That's right.

[Neil DeGrasse Tyson]

We have sunlight coming in.

[Sarah Imari Walker]

That's right.

[Neil DeGrasse Tyson]

And so we've credited that infusion of energy as a pump for the development of complexity that wouldn't otherwise be there.

[Chuck Nice]

Right. Like, if there were no sun, none of this crap would be here.

[Sarah Imari Walker]

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.

[Neil DeGrasse Tyson]

So you want a second and a half law of thermodynamics that applies to the observed universe.

[Sarah Imari Walker]

The second law of thermodynamics is an approximate law. I think we all know his statistical statement. I would like an exact law.

[Chuck Nice]

Ooh. Wow. You are very demanding, I gotta tell you. You are not messing around.

[Sarah Imari Walker]

Yeah. Theoretical physicists don't mess around.

[Chuck Nice]

Wow.

[Neil DeGrasse Tyson]

Wow. Okay.

[Chuck Nice]

Screw you, Newton.

[Sarah Imari Walker]

It's all his fault.

[Neil DeGrasse Tyson]

And you put all of this in a book? In a book. Oh, my gosh. Life as no one knows it except for you.

[Sarah Imari Walker]

I still don't know it either. I'm still one of the no ones.

[Chuck Nice]

I love it.

[Neil DeGrasse Tyson]

Life has no one, including the author. But it's the whole foundations of that thinking.

[Sarah Imari Walker]

Yes.

[Neil DeGrasse Tyson]

And I'm glad it doesn't just live in this conversation because it lives in the pages of this book. So this came out just recently?

[Sarah Imari Walker]

That's right.

[Neil DeGrasse Tyson]

Just summer 2024.

[Chuck Nice]

Oh, good for you.

[Neil DeGrasse Tyson]

Yeah. Yeah.

[Chuck Nice]

Congratulations.

[Neil DeGrasse Tyson]

Thank you. Congratulations. Your first book.

[Sarah Imari Walker]

It is my first book.

[Neil DeGrasse Tyson]

Excellent.

[Chuck Nice]

Wonderful.

[Neil DeGrasse Tyson]

Excellent. And at the rate you're going, more books?

[Chuck Nice]

Are you kidding me? We just wrote one today. We wrote one just now. Are you kidding me?

[Neil DeGrasse Tyson]

No. So I look forward to what becomes of this branch of thinking.

[Sarah Imari Walker]

I'm hoping we will do an experiment where an alien crawls out of it.

[Chuck Nice]

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.

[Sarah Imari Walker]

But the understanding that would come with that would be so great.

[Neil DeGrasse Tyson]

That's a pure scientist saying. But we'll learn.

[Chuck Nice]

Exactly. You know. Right.

[Neil DeGrasse Tyson]

I think this 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.

[Chuck Nice]

There you go. That's it. That makes perfect sense.

[Neil DeGrasse Tyson]

They're all excited about it. It's the last words ever spoken.

[Chuck Nice]

Yeah.

[Neil DeGrasse Tyson]

It's going to be you. It's going to start you.

[Sarah Imari Walker]

I'm a theorist. I'm not doing any theorist. All right, See, this is another reason to be a the. Yeah, you don't have to do the last experiment.

[Neil DeGrasse Tyson]

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.

[Chuck Nice]

Yeah, I saw what you did there.

[Neil DeGrasse Tyson]

Yeah, that's cool. Yeah, very good. And you gotta keep us appraised of new developments.

[Chuck Nice]

Fascinating frontier. I gotta give it to you.

[Neil DeGrasse Tyson]

And do you have a pipeline into NASA as they set up experiments to look for life? Cause we just had funky spoon, Dr. Fun, David Grinspoon.

[Sarah Imari Walker]

I love David.

[Chuck Nice]

He's great.

[Neil DeGrasse Tyson]

Yeah, David Grinspoon. We just had him a few days ago.

[Sarah Imari Walker]

Oh, really?

[Neil DeGrasse Tyson]

Yeah. And so he's guiding NASA's search for life. And if you have something to tell him, you better tell him quick.

[Sarah Imari Walker]

Yeah, yeah, I could tell him, but actually what I'm trying to do now is prepare data because 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.

[Chuck Nice]

Right, right.

[Neil DeGrasse Tyson]

It's not like a large language model for aliens.

[Sarah Imari Walker]

That's right. We don't have one.

[Neil DeGrasse Tyson]

Right, right, right.

[Chuck Nice]

Awesome.

[Neil DeGrasse Tyson]

All right.

[Chuck Nice]

That's a lot of fun. Thanks.

[Neil DeGrasse Tyson]

Okay, let me. Let me see if I. I can put some cosmic perspective on this.

[Chuck Nice]

On this.

[Neil DeGrasse Tyson]

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 physical, 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 crawling 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. There's been another episode of Star Talk taking you to places that we hadn't been the day before. Sarah, Dwight, thank you.

[Sarah Imari Walker]

Thank you, guys.

[Chuck Nice]

Thanks.

[Neil DeGrasse Tyson]

Thanks for coming to my office here at the Hayden Planetarium.

[Sarah Imari Walker]

It was really fun.

[Neil DeGrasse Tyson]

In New York City, the American Museum of Natural History. All the way up from Arizona.

[Sarah Imari Walker]

Yes.

[Neil DeGrasse Tyson]

So tell folks at ASU I said hi.

[Sarah Imari Walker]

I will.

[Neil DeGrasse Tyson]

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? Did you know?

[Chuck Nice]

Yeah. That's funny.

[Sarah Imari Walker]

I knew that.

[Neil DeGrasse Tyson]

That's an old joke. It hit 120, 20 degrees this past summer, right?

[Chuck Nice]

Yeah.

[Sarah Imari Walker]

That's typical.

[Neil DeGrasse Tyson]

Yeah. Oh, yeah. Yeah.

[Chuck Nice]

All right.

[Sarah Imari Walker]

Sometimes we can't even fly planes, it's so hot.

[Neil DeGrasse Tyson]

Oh, because not enough air density coming through the thing.

[Sarah Imari Walker]

That's right.

[Chuck Nice]

Wow.

[Sarah Imari Walker]

There's some good physics for you.

[Neil DeGrasse Tyson]

Yeah, yeah. It's not that. It's not just the temperature, it's the density.

[Chuck Nice]

Right. Yeah.

[Neil DeGrasse Tyson]

Or you need a longer Runway or something.

[Sarah Imari Walker]

Yeah.

[Neil DeGrasse Tyson]

Yeah. We got to call it quits there, Chuck. Always good to have you, man.

[Chuck Nice]

Always a pleasure and again, thank you so much.

[Neil DeGrasse Tyson]

Mike. Congratulations and good luck on life as no one knows it, not even the author. That's what makes this especially intriguing.

[Sarah Imari Walker]

Hopefully someone will know it one day.

[Neil DeGrasse Tyson]

One day. One day. All right, start talk here. Keep looking up.

[Chuck Nice]

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