WEBVTT - Ep77 "What is Life?" 0:00:05.280 --> 0:00:09.639 What is life? How do you define what things are 0:00:10.039 --> 0:00:13.120 living and what things are dead. You might look at 0:00:13.160 --> 0:00:17.919 a running cheetah and say that thing is clearly living, 0:00:18.040 --> 0:00:20.479 and you look at a chunk of granite rock and 0:00:20.480 --> 0:00:22.919 you say, okay, that thing is not living. But where 0:00:22.920 --> 0:00:26.400 do we draw the line? And when we land on 0:00:26.520 --> 0:00:31.960 other planets someday, what can we realistically expect aliens are 0:00:31.960 --> 0:00:36.280 going to look like? Will we even recognize strange forms 0:00:36.320 --> 0:00:39.559 of life or will we only have the capacity to 0:00:39.680 --> 0:00:43.919 recognize things that are very close to earthly life? And 0:00:43.960 --> 0:00:46.720 what does any of this have to do with Frankenstein 0:00:47.040 --> 0:00:51.279 or ancient Greek philosophers or the possibility of finding a 0:00:51.440 --> 0:00:53.280 cell phone on Mars. 0:00:55.920 --> 0:00:58.280 Welcome to Intercosmos with me David Eagleman. 0:00:58.440 --> 0:01:01.200 I'm a neuroscientist in a all third at Stanford, and 0:01:01.280 --> 0:01:04.559 in these episodes we dive deeply into our three pound 0:01:04.640 --> 0:01:08.160 universe to uncover some of the most surprising aspects of 0:01:08.200 --> 0:01:11.000 our lives. In today's episode, we're not only going to 0:01:11.040 --> 0:01:14.520 dive into our three pound universe, but into the larger 0:01:14.800 --> 0:01:18.120 universe that surrounds us to think about the question of 0:01:18.280 --> 0:01:23.840 what is life? So what do we mean when we 0:01:23.880 --> 0:01:27.160 say something is alive. This is one of the oldest 0:01:27.240 --> 0:01:31.120 questions that biologists have been asking, and it's a strangely 0:01:31.680 --> 0:01:34.200 tough one. So today we're going to take a run 0:01:34.240 --> 0:01:37.920 at this question from a completely different angle, from the 0:01:38.360 --> 0:01:42.560 point of view of theoretical physics. Joining me today will 0:01:42.600 --> 0:01:46.040 be physicist Sarah Walker, who with her colleagues is working 0:01:46.080 --> 0:01:50.000 to ask the question of what is life through a 0:01:50.120 --> 0:01:53.200 very different lens, And we're going to get into questions 0:01:53.240 --> 0:01:57.000 like what we might expect when we discover life elsewhere 0:01:57.000 --> 0:02:00.240 in the universe, and how we can prepare ourselves to 0:02:00.480 --> 0:02:04.400 even know what to look for. But first I want 0:02:04.440 --> 0:02:07.920 to say that this question about what is life is 0:02:08.000 --> 0:02:11.720 one that humans have been asking for about as long 0:02:11.760 --> 0:02:14.880 as we can tell. So in the fourth century BCE, 0:02:15.160 --> 0:02:19.240 you had Greek philosophers like Plato and Aristotle writing about this. 0:02:19.520 --> 0:02:23.720 For example, Aristotle wrote a book called de Anima, or 0:02:23.880 --> 0:02:26.720 on the Soul, and he says, look to be a 0:02:26.760 --> 0:02:31.800 living thing, you possess a soul. And Plato, his mentor, 0:02:31.919 --> 0:02:34.519 was on the same train, talking about a world soul 0:02:35.040 --> 0:02:40.000 that differentiates between living beings and inanimate matter. But you 0:02:40.080 --> 0:02:44.320 had people being more specific too. For example, several decades 0:02:44.360 --> 0:02:49.560 before Plato and Aristotle, the Greek philosopher Empedocles proposed a 0:02:49.680 --> 0:02:54.160 theory of life based on the interaction of four elemental 0:02:54.240 --> 0:02:59.560 forces earth, air, water, and fire. He suggested that life 0:02:59.600 --> 0:03:02.960 is created through just the right combinations of these elements, 0:03:03.440 --> 0:03:05.880 and this is one of the earliest attempts to understand 0:03:05.960 --> 0:03:10.600 life as a combination of natural forces, offering a way 0:03:10.919 --> 0:03:17.280 of distinguishing between living things and inert matter. And another 0:03:17.360 --> 0:03:21.200 Greek Hippocrates, he started to lay the early foundations for 0:03:21.320 --> 0:03:25.440 the biological study of life by focusing on the human body. 0:03:25.560 --> 0:03:28.440 And what he said is there's a balance of four 0:03:28.840 --> 0:03:32.680 humors that are critical to life. You've got blood and 0:03:32.800 --> 0:03:35.440 phlem and yellow bile and black bile. 0:03:35.720 --> 0:03:37.040 So this was not correct, but. 0:03:37.040 --> 0:03:41.280 It started giving the earliest shape to this biological idea 0:03:41.360 --> 0:03:46.320 that life depends on balancing a certain physical state, and 0:03:46.360 --> 0:03:51.160 that's he suggested what separates the living body from non 0:03:51.200 --> 0:03:54.680 living matter. And people started to get more specific about things, 0:03:54.720 --> 0:03:56.640 a little closer to the way that we think about 0:03:56.640 --> 0:04:02.040 them now. For example, Epicurus suggested that all things, including 0:04:02.080 --> 0:04:07.000 living beings, are composed of atoms moving through the void. 0:04:07.200 --> 0:04:11.600 So for the epicureans life is the result of particular 0:04:11.800 --> 0:04:17.200 combinations of atoms, and death is just the dissolution of 0:04:17.320 --> 0:04:21.760 these atomic arrangements. So the difference between living and non 0:04:21.800 --> 0:04:26.440 living matter lies in the specific arrangement of the atoms. 0:04:26.600 --> 0:04:29.680 And then Lucretius in Rome some centuries later wrote a 0:04:29.680 --> 0:04:33.120 poem called on the Nature of Things, and he built 0:04:33.120 --> 0:04:36.480 on this idea, and he said, living beings are distinguished 0:04:36.480 --> 0:04:41.600 from non living things by their particular atomic configurations and 0:04:41.680 --> 0:04:46.040 the ability to move and reproduce. And by the way, 0:04:46.080 --> 0:04:50.200 even though I know Western thinkers the best, this question 0:04:50.279 --> 0:04:53.320 of what his life was being wrestled with around the world. 0:04:53.360 --> 0:04:57.000 So I know that in China in the fourth century BCE, 0:04:57.760 --> 0:05:02.480 the Taoist text called wang Xi reflected on the nature 0:05:02.560 --> 0:05:06.279 of life and existence. It looked at how life emerged 0:05:06.279 --> 0:05:10.400 from the interplay of natural forces, like what they called chi, 0:05:10.440 --> 0:05:13.680 which was their notion of life energy. And in first 0:05:13.720 --> 0:05:18.559 century India you have Iravedic texts discussing life in terms 0:05:18.640 --> 0:05:24.680 of the balance among three doshas, Vada, Pitta, and Kafa. 0:05:24.800 --> 0:05:27.039 This is all stuff that's not so relevant except for 0:05:27.160 --> 0:05:30.720 ritual purposes. But the idea that was being pursued was 0:05:30.760 --> 0:05:37.000 that somehow life is sustained by the equilibrium of different forces. Okay, 0:05:37.120 --> 0:05:38.560 so the point I want to make here is that 0:05:38.600 --> 0:05:42.120 the question of what is life is not a new question. 0:05:42.400 --> 0:05:45.240 And there's a sense in which all these thinkers and 0:05:45.320 --> 0:05:50.360 books they foreshadow later biological thought by asking this question 0:05:50.480 --> 0:05:55.599 what animates matter? What makes it alive? And we see 0:05:55.640 --> 0:05:59.159 the same question reflected all over literature. The most obvious 0:05:59.200 --> 0:06:03.320 example is Mary Shelley is Frankenstein, and you may know 0:06:03.400 --> 0:06:07.440 that tells the story of Victor Frankenstein, who's a scientist 0:06:07.520 --> 0:06:12.600 who sets out to create life by reanimating dead tissue. 0:06:12.720 --> 0:06:17.279 And the creature he brings to life is assembled from corpses, 0:06:17.839 --> 0:06:22.840 but becomes a sentient, feeling being, And so readers are 0:06:22.960 --> 0:06:27.120 challenged and thinking about the boundaries between living and non 0:06:27.160 --> 0:06:30.760 living matter. And this sort of mythology reaches back hundreds 0:06:30.800 --> 0:06:34.640 of years earlier. For example, Jewish folklore has the story 0:06:34.680 --> 0:06:38.280 of the Golum, which is a creature who is shaped 0:06:38.279 --> 0:06:41.480 out of clay, and when someone writes something on his head, 0:06:41.480 --> 0:06:44.520 he comes to life as a protector, and if you 0:06:44.600 --> 0:06:47.839 remove a letter from the word, he becomes inanimate again. 0:06:48.440 --> 0:06:52.040 And the myth of the Golam inspired ideas from Frankenstein 0:06:52.160 --> 0:06:57.160 to movies that deal with artificial beings like ex Machina, 0:06:57.320 --> 0:07:00.280 where you've got a robot that gets artificially intell gin 0:07:00.360 --> 0:07:06.160 and becomes something that we might call alive. So this question, 0:07:06.400 --> 0:07:09.240 what is the boundary between life and death? This is 0:07:09.240 --> 0:07:12.560 a question that has long been on the forefront of 0:07:12.600 --> 0:07:16.680 the human mind. But of course there's a deeper question also, 0:07:16.800 --> 0:07:20.600 not just about human life, but about all the life 0:07:20.600 --> 0:07:23.040 forms we find on this planet. Because when we look 0:07:23.080 --> 0:07:27.360 around the animal kingdom, we find all kinds of very 0:07:27.680 --> 0:07:35.440 strange life forms, like platypuses or jellyfish or sephonophores. Anyway, 0:07:35.480 --> 0:07:36.960 we look at these things and we think, wow, those 0:07:37.000 --> 0:07:41.280 are really strange. And then we look to plants and 0:07:41.320 --> 0:07:44.920 we say, well, they seem like to qualify as life also. 0:07:45.720 --> 0:07:48.720 And then we look at single celled bacteria, which we 0:07:48.720 --> 0:07:52.440 didn't even know existed until very recently in history, when 0:07:52.760 --> 0:07:56.640 lewand Hook made a microscope and found these little creatures 0:07:57.080 --> 0:08:01.800 which you called animacules, which we now call uni cellular organisms. Anyway, 0:08:02.000 --> 0:08:04.480 we look at those, we say, you know, that seems 0:08:04.520 --> 0:08:08.040 like life too, But what do these all have in common? 0:08:08.360 --> 0:08:11.720 Well, of course, the weird part of the story is. 0:08:11.680 --> 0:08:14.640 That when you look at what we are made out of, 0:08:14.920 --> 0:08:19.000 and what jellyfish and house plants and bacteria are made 0:08:19.040 --> 0:08:22.560 out of, it's the exact same stuff. It's the exact 0:08:23.000 --> 0:08:26.360 same stuff that makes our molecules, that makes their molecules, 0:08:26.600 --> 0:08:29.480 and by the way, the same stuff that makes rocks 0:08:29.520 --> 0:08:32.640 and oceans and so on. You got carbon and nitrogen 0:08:32.720 --> 0:08:34.960 and oxygen and calcium and the rest of the atoms. 0:08:35.480 --> 0:08:40.080 But it's all non living stuff that makes us. Somehow, 0:08:40.600 --> 0:08:43.920 life is built out of a bunch of non life. 0:08:44.200 --> 0:08:46.280 Now you may know that. In nineteen fifty two, a 0:08:46.320 --> 0:08:49.560 scientist named Stanley Miller showed that if you put a 0:08:49.559 --> 0:08:53.960 bunch of inorganic compounds together, like you put methane and 0:08:53.960 --> 0:08:56.839 ammonia and hydrogen and water, and then you zap that 0:08:57.000 --> 0:09:01.000 with electricity, you get amino ad acids, which are the 0:09:01.040 --> 0:09:04.560 building blocks of proteins. And this was such a striking 0:09:04.600 --> 0:09:09.080 result because it showed the way that molecules we see. 0:09:08.880 --> 0:09:11.000 In living things, like the amino. 0:09:10.760 --> 0:09:14.720 Acids, could emerge from dead stuff if you just have 0:09:14.840 --> 0:09:17.800 the right kind of atmosphere. And I wasn't alive in 0:09:17.800 --> 0:09:20.760 the nineteen fifties. But I imagine the mood was really 0:09:20.800 --> 0:09:25.360 optimistic that from there it would be a straightforward run 0:09:25.480 --> 0:09:28.560 to see how all the pieces and parts would come 0:09:28.600 --> 0:09:33.000 together to build life. But here we are over seventy 0:09:33.040 --> 0:09:36.520 years later, and we still don't know how the story 0:09:36.600 --> 0:09:40.440 comes together. But the problem is actually worse than that, 0:09:41.080 --> 0:09:46.280 because almost everything that we as biologists ask about life 0:09:46.960 --> 0:09:50.200 has to do with life on Earth, where everything is 0:09:50.240 --> 0:09:54.000 built on atoms like carbon and on big molecules like 0:09:54.120 --> 0:09:59.800 DNA and RNA, which carry the information to build creatures. 0:09:58.800 --> 0:10:00.080 Small and large. 0:10:00.240 --> 0:10:04.960 But there's no necessity that life elsewhere in the cosmos 0:10:05.280 --> 0:10:08.120 will be built of the same stuff and in the 0:10:08.120 --> 0:10:10.960 same way. And here's the way to think about this. 0:10:11.400 --> 0:10:14.640 In high school biology, we all learned that we call 0:10:14.720 --> 0:10:19.360 something alive if it's organized into cells or even a 0:10:19.360 --> 0:10:23.280 single cell, and it has to have metabolism, meaning it 0:10:23.320 --> 0:10:27.000 converts energy into stuff that it can use, and it 0:10:27.040 --> 0:10:31.360 can regulate its internal environment and grow and develop and 0:10:31.400 --> 0:10:34.439 reproduce and respond to things. And it has to have 0:10:34.480 --> 0:10:37.880 some sort of programming code like genetic material that says 0:10:37.920 --> 0:10:41.040 how to build new ones and so on. But no 0:10:41.080 --> 0:10:45.040 matter how carefully people try to define this they always 0:10:45.040 --> 0:10:49.840 get into gray areas like viruses which can reproduce but 0:10:49.960 --> 0:10:53.000 only inside the cells of a host, and they don't 0:10:53.000 --> 0:10:57.240 have metabolism or respond to stimuli on their own. So 0:10:57.480 --> 0:10:59.800 do you call them living or non living? 0:10:59.840 --> 0:11:00.000 Well? 0:11:00.080 --> 0:11:00.600 Who knows. 0:11:01.280 --> 0:11:04.160 And currently we're seeing all kinds of advances in biotech 0:11:04.559 --> 0:11:08.600 which are creating synthetic life forms, which raises all kinds 0:11:08.640 --> 0:11:13.160 of strange questions about what criteria should define life. But 0:11:13.240 --> 0:11:17.240 I think the problem isn't even about blurry boundaries between 0:11:17.360 --> 0:11:21.320 living and non living. The problem is that the criteria 0:11:21.400 --> 0:11:25.560 we use in biology textbooks, it's not really thinking big 0:11:25.679 --> 0:11:30.200 enough when we consider life in other forms elsewhere in 0:11:30.240 --> 0:11:32.600 the cosmos. And you may know that there's a lot 0:11:32.640 --> 0:11:36.720 of effort going into finding signatures of other life forms 0:11:36.760 --> 0:11:40.000 and the cosmos. And generally when people imagine meeting some 0:11:40.120 --> 0:11:43.880 alien civilization, they generally think, oh, it probably looks. 0:11:43.640 --> 0:11:44.600 Sort of like us. 0:11:44.640 --> 0:11:47.360 You got two eyes, even if those eyes are bigger, 0:11:47.640 --> 0:11:49.800 and it's got a head, even if the head's a 0:11:49.840 --> 0:11:53.280 little bigger, and maybe it's got pointy ears. And we 0:11:53.400 --> 0:11:56.080 say take me to your leader, and they say, okay, 0:11:56.160 --> 0:11:58.679 follow me. But this all may lead us to have 0:11:58.720 --> 0:12:03.560 a very difficult time recognizing other kinds of life in 0:12:03.600 --> 0:12:08.080 the cosmos if what we're looking for is a Hollywood 0:12:08.120 --> 0:12:11.960 actor with some green makeup. So what if we really 0:12:12.000 --> 0:12:14.880 expanded our thinking on this, What if we really thought 0:12:14.920 --> 0:12:18.719 about other ways that we could define or at least 0:12:18.800 --> 0:12:23.280 detect life. So I wanted to see how other people 0:12:23.360 --> 0:12:25.880 might be thinking about this question, And for that I 0:12:25.960 --> 0:12:29.480 wanted to look beyond earth biologists. When you're looking for 0:12:29.520 --> 0:12:31.880 someone who has a very big view of things, you 0:12:32.000 --> 0:12:37.760 generally look to physicists. Now, physicists have not always been 0:12:37.840 --> 0:12:41.880 interested in the question of life, although one of the 0:12:41.920 --> 0:12:45.600 most famous little books entitled What Is Life was a 0:12:45.679 --> 0:12:49.880 nineteen forty three series of lectures by Irwin Schrodinger, the 0:12:50.120 --> 0:12:51.079 quantum physicist. 0:12:51.640 --> 0:12:54.320 But generally the question of. 0:12:54.240 --> 0:12:57.320 Life seems like the wrong sort of level of question 0:12:57.520 --> 0:12:59.440 for a lot of physicists. And that's why I was 0:12:59.440 --> 0:13:02.840 so pleased to come across the book of Sarah Walker, 0:13:02.880 --> 0:13:05.560 who's a theoretical physicist. 0:13:05.040 --> 0:13:06.640 At Arizona State University. 0:13:07.040 --> 0:13:10.280 She wrote a book called Life as No One Knows It, 0:13:10.520 --> 0:13:12.640 and she looks at the question of how she could 0:13:13.160 --> 0:13:17.600 measure life so that we would know when we find it. 0:13:18.200 --> 0:13:20.760 So I called her up to hear her take on this, 0:13:21.320 --> 0:13:28.360 and here is Sarah Walker. Okay, So, Sarah, I want 0:13:28.400 --> 0:13:31.679 to get into this issue about how physicists think about 0:13:31.760 --> 0:13:35.880 things differently than biologists do. And you give this lovely 0:13:36.200 --> 0:13:39.760 analogy in your book about how a physicist thinks about 0:13:39.840 --> 0:13:41.560 let's say gravity, So. 0:13:41.480 --> 0:13:42.200 Tell us about that. 0:13:43.000 --> 0:13:43.200 Yeah. 0:13:43.240 --> 0:13:45.440 I like using gravity as a good example because it's 0:13:45.440 --> 0:13:47.840 pretty familiar to us, and we kind of accept gravity 0:13:47.880 --> 0:13:51.880 as a real objective feature of reality, and forget that 0:13:51.960 --> 0:13:54.920 people had to actually invent our concepts of gravity. The 0:13:54.960 --> 0:13:58.000 whole process of doing that was really trying to understand 0:13:58.600 --> 0:14:04.400 regularities that unify behavior across a huge diversity of objects. 0:14:04.440 --> 0:14:06.079 And so the kind of things that were of interest 0:14:06.120 --> 0:14:09.320 to early physicists were balls, rolling down, inclined planes, and 0:14:09.360 --> 0:14:11.080 planetary motion in the heavens. 0:14:11.280 --> 0:14:12.680 And you know what they. 0:14:12.559 --> 0:14:16.280 Realized was if they chose a sufficiently abstract representation, they 0:14:16.320 --> 0:14:19.120 could talk about those things in the same language. And 0:14:19.520 --> 0:14:21.800 prior to that, in human history, we had no idea 0:14:21.920 --> 0:14:24.640 that planetary motion was governed by the same principles that 0:14:24.720 --> 0:14:27.480 keep us on this planet. Right, So it was a 0:14:27.600 --> 0:14:30.480 huge conceptual leap made by our species, and it was 0:14:30.520 --> 0:14:32.640 really one about trying to find the right kind of 0:14:32.680 --> 0:14:37.160 representation that could describe a huge diversity of forms. And 0:14:37.200 --> 0:14:39.680 this is why it gets interesting when we're talking about biology, 0:14:39.720 --> 0:14:43.200 because in biology we have a plethora of diverse kinds 0:14:43.240 --> 0:14:46.320 of forms of life on this planet. And a critical 0:14:46.440 --> 0:14:48.440 question if you want to talk about whether there are 0:14:48.440 --> 0:14:51.360 governing laws or principles of life, is is there some 0:14:51.480 --> 0:14:55.040 simple unifying description that could unify all of that diversity 0:14:55.080 --> 0:14:56.840 of life on Earth and not just explain what we 0:14:56.880 --> 0:14:58.960 see her on this planet, but also on other planets, 0:14:58.960 --> 0:15:00.840 which is one of the key questions I'm interested in. 0:15:01.440 --> 0:15:03.640 So we're going to get into that question of what 0:15:04.080 --> 0:15:06.480 is life? How would a physicists think about life? But 0:15:06.560 --> 0:15:08.480 how did you get interested in that question? 0:15:09.840 --> 0:15:13.240 I wanted to be a cosmologist or a particle physicist. 0:15:13.320 --> 0:15:14.320 When I was an undergrad. 0:15:14.440 --> 0:15:17.760 I fell in love with theoretical physics and its ability 0:15:17.800 --> 0:15:21.040 to describe nature abstractly and the fact that the human 0:15:21.080 --> 0:15:23.120 mind could come up with descriptions of nature we could 0:15:23.160 --> 0:15:25.960 go test, so things like gravitational waves that we had 0:15:26.000 --> 0:15:27.880 no knowledge about, we could go out and look for 0:15:28.080 --> 0:15:30.040 just because the theory predicted them, and then learn new 0:15:30.080 --> 0:15:33.080 things about reality or neutrinos or another example. Right, these 0:15:33.080 --> 0:15:34.960 are not things that are like, you know, privy to 0:15:35.000 --> 0:15:35.960 our daily perception. 0:15:36.080 --> 0:15:36.240 Right. 0:15:36.280 --> 0:15:38.480 We didn't evolve capacity to sense these things. Yet we 0:15:38.520 --> 0:15:40.560 can build theories that allow us to build technology to 0:15:40.600 --> 0:15:43.720 sense them. And so I was deeply intrigued by that 0:15:43.800 --> 0:15:46.880 whole process and that whole sort of conception of nature 0:15:46.880 --> 0:15:51.240 that you know, underlies what physicists do, you know, at 0:15:51.240 --> 0:15:54.480 this sort of edge of developing new descriptions of reality. 0:15:55.240 --> 0:15:59.280 And it was the case that through my undergrad education 0:15:59.480 --> 0:16:01.920 I just really decided I want to be a theoretical physicist. 0:16:01.960 --> 0:16:03.640 When I got to graduate school, I was like dead 0:16:03.680 --> 0:16:07.800 set on it. And my PhD advisor, Marcelo Gleister, a 0:16:07.840 --> 0:16:11.480 really fantastic thinker, was just you know, later in his 0:16:11.560 --> 0:16:13.760 career as a cosmologist and thought, you know, wanted to 0:16:13.800 --> 0:16:15.880 be great if I did some projects I'm origins life. 0:16:16.400 --> 0:16:19.600 And so I was pretty resistant at first because because 0:16:19.640 --> 0:16:21.640 of you know, kind of what you were indicating initially, 0:16:21.640 --> 0:16:24.880 Like physics and biology are usually traditionally seen as totally separate, 0:16:24.920 --> 0:16:27.160 and in some sense physicists look down on biology as 0:16:27.200 --> 0:16:29.880 a lesser problem than the kind of grand sweeping things 0:16:30.280 --> 0:16:33.040 that physicists study. So it just wasn't on my radar 0:16:33.160 --> 0:16:36.920 from my education that there would really be fundamental problems 0:16:36.920 --> 0:16:38.440 of the kind I was interested in. And I always 0:16:38.520 --> 0:16:41.360 loved biological sciences, but like, I really loved this idea 0:16:41.360 --> 0:16:45.640 of deep, abstract, unifying principles and really understanding at a core, 0:16:46.840 --> 0:16:51.560 you know, the nature of physical reality. And so what 0:16:51.720 --> 0:16:53.800 really sold me on the original life and why I 0:16:53.840 --> 0:16:55.840 decided to dedicate my career to it is I realized 0:16:55.920 --> 0:16:59.480 it was like a major open question, and major in 0:16:59.480 --> 0:17:02.800 the sense it wasn't just that we didn't, you know, 0:17:02.840 --> 0:17:04.240 have the right tools to answer the question. 0:17:04.240 --> 0:17:05.760 We didn't even know what questions to ask. 0:17:05.880 --> 0:17:08.320 And these places where we have these sort of conceptually 0:17:08.359 --> 0:17:12.080 open you know, like like nobody knows how to think 0:17:12.119 --> 0:17:14.200 about it, Like those are the spaces that I love 0:17:14.280 --> 0:17:15.760 to be in because those are the ones where you 0:17:15.760 --> 0:17:18.520 really have this opportunity to do something new and also 0:17:19.000 --> 0:17:21.320 like to maybe discover something kind of deep that we 0:17:21.359 --> 0:17:22.040 didn't know before. 0:17:22.640 --> 0:17:24.639 So the way that a biologist thinks about what is 0:17:24.720 --> 0:17:27.280 life is we look and we see all these cells, 0:17:27.400 --> 0:17:31.560 we see cell processeds, and we discovered DNA and things 0:17:31.640 --> 0:17:33.840 like that and we think, Okay, we're going to make 0:17:33.920 --> 0:17:36.520 a theory about life, but how do you, as a 0:17:36.560 --> 0:17:39.440 theoretical physicist start tackling the problem? 0:17:40.720 --> 0:17:41.639 It was interesting. 0:17:41.760 --> 0:17:44.800 So my first, like, I really, what I'm interested in 0:17:45.119 --> 0:17:49.119 is how does non living matter transition to living matter? 0:17:49.480 --> 0:17:51.800 And in order to answer that question, you need to 0:17:51.840 --> 0:17:53.920 have some sense of what you mean when you say 0:17:53.920 --> 0:17:56.359 something is life or something is alive, or something as 0:17:56.440 --> 0:18:00.399 living matter. And so I've always been very questioned driven. 0:18:00.600 --> 0:18:02.080 I think a lot of people that ask the what 0:18:02.200 --> 0:18:05.439 is life question, that's their question. But the way I 0:18:05.520 --> 0:18:08.720 approach it is that question is in service of solving 0:18:08.760 --> 0:18:11.879 this other very big open question in science, which is 0:18:11.880 --> 0:18:14.320 where does life come from in the first place? And 0:18:14.440 --> 0:18:16.920 so I was actually early in my career I was 0:18:16.920 --> 0:18:19.480 steered away even by some biologists from working on the 0:18:19.480 --> 0:18:21.520 original life because they thought I could learn more about 0:18:21.560 --> 0:18:25.800 biology by studying biological forms as we already understand them. 0:18:26.240 --> 0:18:30.320 And I intrinsically felt that there was something really new 0:18:30.520 --> 0:18:33.480 and different to learn about the original life transition itself. 0:18:34.119 --> 0:18:36.960 And so the sort of traditional approach, as I said, 0:18:37.000 --> 0:18:38.680 has been to ask what is life and then try 0:18:38.680 --> 0:18:40.760 to answer that question directly, And I just don't think 0:18:40.760 --> 0:18:43.640 that that's actually useful exercise in these sort of more 0:18:43.640 --> 0:18:46.680 fundamental aspects or getting at the frontiers of detecting life 0:18:46.680 --> 0:18:49.560 elsewhere or origins of life, because what we end up 0:18:49.600 --> 0:18:53.199 doing is kind of having these descriptors life life is, 0:18:53.560 --> 0:18:57.879 you know, requires metabolism to sustain itself, Life needs genetics 0:18:57.960 --> 0:19:00.280 or these things that are very anthropercentric and base dating 0:19:00.320 --> 0:19:02.480 examples as we know it and might you know, and 0:19:02.560 --> 0:19:05.000 those examples don't apply to like the earliest life on 0:19:05.040 --> 0:19:07.200 Earth as far as we know, because we don't know 0:19:07.240 --> 0:19:09.240 if it had a genetic system or not, for example. 0:19:10.040 --> 0:19:12.760 So we need deeper descriptions to go further than the 0:19:12.760 --> 0:19:16.119 biology we know. And that's what I got interested in, 0:19:16.200 --> 0:19:18.240 and that needs to be driven by really having a 0:19:18.280 --> 0:19:21.399 compelling question that you're trying to answer to focus your effort. 0:19:21.400 --> 0:19:22.240 How you build theory. 0:19:22.760 --> 0:19:25.080 Okay, so you asked the question of how does non 0:19:25.160 --> 0:19:29.600 living stuff become living stuff? And how did you how 0:19:29.600 --> 0:19:30.359 did you go about it? 0:19:30.359 --> 0:19:32.119 How did you start making progress on a question like that? 0:19:32.760 --> 0:19:36.560 Yeah, so obviously I didn't know a lot about biology 0:19:36.600 --> 0:19:38.600 and chemistry when I started. You can pick up a 0:19:38.600 --> 0:19:41.480 lot reading and talking to people, but it wasn't it's 0:19:41.480 --> 0:19:43.199 not my training, it's not my field of expertise. I 0:19:43.200 --> 0:19:46.399 would I will always stay upfront. I have all of 0:19:46.400 --> 0:19:49.000 the cognitive biases of somebody that was trained in physics. 0:19:49.040 --> 0:19:51.000 I really tried to fight them. 0:19:51.359 --> 0:19:53.840 But you know, I'm very aware of my disciplinary training, 0:19:53.880 --> 0:19:55.760 and part of the reason I'm so aware of it 0:19:55.800 --> 0:19:58.360 is walking into origins of life as a PhD student. 0:19:58.760 --> 0:20:01.359 Almost everybody there comes from a different discipline, right, Like 0:20:01.400 --> 0:20:03.320 there's the organic chemists and they have a camp of 0:20:03.320 --> 0:20:06.280 how they think about it. There's the genetics and molecular 0:20:06.320 --> 0:20:08.920 biologists and they have a camp about how they think 0:20:08.920 --> 0:20:11.520 about the problem. And there's the physicists and they have 0:20:11.560 --> 0:20:13.760 a camp of how they think about the problem. And 0:20:13.840 --> 0:20:16.000 so each discipline or your perspective kind of had a 0:20:16.080 --> 0:20:19.280 hypothesis that was informed by their discipline but not the others. 0:20:20.400 --> 0:20:23.159 And so I really tried to abandon all of that 0:20:24.440 --> 0:20:26.960 and just really try to focus on what the fundamental 0:20:27.040 --> 0:20:29.680 nature of the problem was. But obviously, starting from physics, 0:20:29.680 --> 0:20:31.720 I wanted to start with, like, why can physics not 0:20:31.800 --> 0:20:36.919 explain the origin of life? And that led to focus 0:20:37.200 --> 0:20:40.000 focus on information and causation because it seems to be 0:20:40.240 --> 0:20:44.600 the case that in living systems information is causal. So 0:20:44.720 --> 0:20:47.160 for example, you know there's people listening to this right now, 0:20:47.160 --> 0:20:48.440 I could say raise your hand. 0:20:49.200 --> 0:20:50.520 Some of you may raise your hands. 0:20:50.680 --> 0:20:53.439 I'm raising my hand right, And so we're separated in 0:20:53.560 --> 0:20:56.200 space and time, and there's causation there, right, and it's 0:20:56.200 --> 0:21:00.280 carried by words which are you know, very abstract, but 0:21:00.440 --> 0:21:02.439 there must be some kind of physicality to them if 0:21:02.480 --> 0:21:04.960 they have some causation in the world with sort of 0:21:04.960 --> 0:21:08.800 my thinking. And obviously there's also like in genomes we 0:21:08.840 --> 0:21:11.480 talk about them carrying information, etcetera. So this language of 0:21:11.520 --> 0:21:14.640 information is all over biology. And so the first problem 0:21:14.680 --> 0:21:17.840 I identified, which I wrote this paper with my postdoc 0:21:17.880 --> 0:21:22.439 advisor Paul Davies in twenty thirteen called the Algorithmic Origins 0:21:22.440 --> 0:21:26.320 of Life, was the original life transition must have something 0:21:26.359 --> 0:21:29.640 to do with a transition in causation and information. 0:21:29.240 --> 0:21:30.200 And physical systems. 0:21:31.080 --> 0:21:33.679 And I've used that kind of as the paradigm of 0:21:33.720 --> 0:21:35.359 most of my career. Actually all of my work is 0:21:35.400 --> 0:21:38.080 training answer a question I posed in that paper. And 0:21:38.160 --> 0:21:40.880 so now I've settled on this new approach that I'm 0:21:40.960 --> 0:21:43.760 very excited about because of the connection between deep connection 0:21:43.800 --> 0:21:47.199 between theory and experiment called assembly theory, which is an 0:21:47.240 --> 0:21:51.919 attempt to understand how information really is the sort of 0:21:52.720 --> 0:21:55.520 underlying mechanism for the existence of some objects, but doing 0:21:55.560 --> 0:21:56.760 it in a much more physical way. 0:21:57.040 --> 0:21:57.320 Cool. 0:21:57.359 --> 0:21:59.479 So, just before we get into assembly theory, so give 0:21:59.560 --> 0:22:04.280 us an exams example of information and causation. Give us 0:22:04.320 --> 0:22:06.920 an example. How do you think about that in terms 0:22:06.920 --> 0:22:07.359 of life. 0:22:07.560 --> 0:22:12.120 Yeah, an example might be something like a technological artifact 0:22:12.119 --> 0:22:15.320 like a cell phone. We don't expect them to spontaneously 0:22:15.600 --> 0:22:18.200