The laws of the universe are unable to explain these origin mysteries — Paul Davies: Full Interview

[00:00:00] Paul Davies: My name is Paul Davies. I'm a theoretical physicist and cosmologist by profession. I'm a regents professor at Arizona State University, where I'm also the director of the Beyond Center for Fundamental Concepts in Science. I've written over 30 books. The most recent is What's Eating the Universe and Other Cosmic Questions, and before that, The Demon in the Machine, which is all about the nature of life. This Big Think interview is brought to you by [00:00:28] Speaker 2: Pangram. Navigating an internet filled with AI-generated content is a frustrating experience. It is becoming harder to separate real from fake and human from machine. Pangram is the most trusted AI detector, backed by rigorous public research. Pangram can tell you how much of what you're reading is AI-generated. If there's an image you think was made by AI, Pangram can detect that too. To regain trust over what you read and see, go to www.pangram.com. And now, back to the interview. [00:01:08] Paul Davies: There are really three origin mysteries, I like to say. There's the origin of the universe, the origin of life, and the origin of consciousness. Now, most of my career I've been working in cosmology, and I would say that we actually understand the origin of the universe pretty well. The origin of consciousness is a really tough one because we don't even know how to frame the questions. We don't know the right conceptual structure to apply when it comes to the nature of consciousness. I think it's still deeply mysterious. The origin of life is a tough one, but we're sort of on the case, and I can imagine that within a few decades we might have a pretty good understanding. There's always a danger of getting hung up on the words and the definitions. There's a very famous definition of life which is based on the definition of pornography. I know it when I see it. But if you want a snappy definition, one that's quite popular at the moment, is that life is chemistry plus information. You know, it's not like life is some sort of magic matter, or it's got some extremely rare ingredients. If you take a human being and break them down to their molecular structure, and then try and sell the components on the open market, you wouldn't get more than a few cents for the stuff that we're made of. You know, there's nothing very special or rare inside our bodies. So, it's not what we're made of, not the hardware. It is really what we do, our behavior. And that's where we're in the realm of what we might call software. So, I would express it this way: I'd say it's hardware and software. These are parallel narratives. They're not in conflict. But I would say that the software aspect has really been rather neglected until recently when it comes to trying to understand the origin of life. But it's clear that to have a full understanding of life, we have to integrate those two. I think we are very far from having done that. And the question of what is life, of course, is not a new one. It's not just part of the scientific era. It goes back thousands of years in the history of philosophy, because living things do stand out. And they struck the early Greek philosophers as being something really special. For example, Aristotle had a thought about how to connect living organisms with the wider scheme of things. And his view, the nature of causation was such that one could really attribute lifelike properties not just to living organisms themselves, but to the universe as a whole. That is, when you drop a stone, it falls to the ground. Why is that? Not as we would think today because of the force of gravity, but because it had a natural place down there. It was trying to get to its natural place. And so, in that sense, it was goal-oriented. And if we go back 100-150 years, there was this notion that, well, you know, maybe life requires some additional force or elan vital as what it was expressed in French, something to animate the matter. That you might have complex matter, but you need to sort of have some other type of essence which would infuse it and would make it come alive and do its amazing things. And so that was known as vitalism. And over the years, it came to be associated with a number of other things in physics, like electricity perhaps, or maybe radioactivity, you know, or some mysterious force that we didn't yet fully understand. And those ideas, I think, became pretty thoroughly discredited. Now, Darwin had a brilliant theory of how life evolves once it gets going on planet Earth, how it has evolved over billions of years to give us the complexity of the biosphere that we see today. But he wouldn't be drawn on how life got started in the first place. So addressing the question of what is life, you're never to be come up against this question, well, how does non-life turn into life? You know, what is that extra special thing it acquires on that pathway? Darwin said, it's a wonderful quote, "it's mere rubbish at this time talking of the origin of life." One might as well talk about the origin of matter. But by about the 1920s, there was increasing interest in what we might call the chemical pathway. I think it's pretty obvious that life is based on chemistry. So what sort of chemical magic took place to conjure life into being in the first stages? And there were attempts to cook up life in the lab. In the early 1950s, the chemist Harold Urey managed to interest a young student, Stanley Miller, in attempting to recreate the conditions on the early Earth. They didn't really know what those conditions were, but they had a guess that there would be certain gases in the atmosphere and water and lightning and so on. And so Miller did this early experiment in which he put a number of gases in a flask and sparked electricity through it for a week and was gratified to find that the building blocks of proteins called amino acids, simple molecules, were made in this process and there was sort of brown sludge in the bottom of the flask. And so that really looked like that was on the pathway to life. But again, you see, this lacked a definition of life. It was an attempt to define life in terms of its chemical components, not in terms of what it does. So I would say that that was addressing the problem of the hardware of life, but not the software. And if we fast forward to today, I think this is still a very deep problem. If you want to focus a definition of life just on the hardware just on its chemical components will be made a bit of progress. Not much, I might say, from that early Miller-Urey experiment that people have gone on to do more of these prebiotic experiments, but they haven't got very far down that pathway to life. Now quantum mechanics, with its brilliant start in 1925, went on within a very few years to explain the nature of matter all the way from subatomic particles up to stars. And Irving Schrodinger, he was one of the founders of quantum mechanics, wrote a book called What is Life? And in his book, Schrodinger drew attention to the fact that life is, as I've stated it earlier, chemistry plus information, that the information content of life was key to how it operates. He was also very clear that for the stability of that information, one had to use quantum mechanics. He came up with a metaphor, which is a rather beautiful one. He said that this biological information would have to be stored in something like an aperiodic crystal. What does that mean? Well, a crystal is, of course, familiar to everybody. It's a very simple thing. It's a very stable structure. I think of a salt crystal. It's just a geometrically repeating pattern of atoms. No problem about that, except that that can't store very much information because it's just too simple. So he wanted something that had the stability of a crystal, but would not just have that simple periodicity, but could have a vast number of alternative arrangements and permutations of its components. So he had this idea of an aperiodic crystal. Didn't know at the time what that molecule might be, but it took Crick and Watson's famous analysis of DNA to declare that that was the life molecule. And now we would say it contains the Book of Life. It encodes the information that is necessary to build the organism in that aperiodic crystal called DNA. I think the concept of information is absolutely critical to understanding the distinction between life and non-life. People use this term information in a very informal way in daily life. And we have, after all, information technology. And so what is it and why is it that this thing called information is the key to life? A pretty good general definition of information is reduction in uncertainty. I'll just give you a simple example. You might flip a coin and may come down heads, may come down tails. You don't know which, but if you look and find out that uncertainty 50/50 is reduced, you are certain heads. And that means you've acquired a bit of information. And I use that word advisedly because the technical definition is indeed one bit. It's short for a binary digit. And so the information from inspecting a flip coin is one bit of reduction in your uncertainty. And you can build upon that. And that's a way of quantifying information. And there's an entire branch of science and engineering information theory, which is just based on that rather austere definition. But when it comes to life, it's very clear that there's something else involved. Because if we think, for example, of bacteria, you could take out its DNA. This is routinely done. You can edit that DNA and put it back and get the bacterium to do something a bit different. But if you take out its DNA and just scramble it, just shuffle the base pairs of that DNA and put it back so that it's just gobbledygook, then the bacterium is in effect dead. I've got the same amount of information in the DNA, but it's not going to do anything. And it will slowly just decompose. In other words, it's like a book. If you take the words in that book and then just shuffle them randomly, and then you'd have a book with the same information content, but it wouldn't mean anything. And that's the point about life. The information in the DNA, and I might say it's only a small part of the total information content of living organisms. There's a whole lot of what we call epigenetic information outside of DNA as well. But if you take the whole thing, it is so effective because it means something. So that's the software component that's been refined over billions of years. So it's an operating system. And when a bacterium divides and makes a new organism, when it replicates, it has to upload that information, that program into the progeny for the whole thing to function. So this is the way that life works. And without the instructions, it isn't life. It's just complex chemistry. So how did that come to exist in the first place? How did that genetic code arise? It's, you know, it's a pretty clever, sophisticated sort of thing. Was there a simpler precursor code? If you go back four billion years, were there organisms using a doublet code instead of a triplet code? Were there less amino acids? But how did that notion of coded information come about in the first place? I think that is, for me, the point about the origin of life is how did the molecules, the complex molecules that make up life, write their own code, their own computer code? Because that's what it amounts to. How did that happen? I think that's a deep mystery. I don't think we've got anywhere close to understanding that particular step. But for me, if I think about, you know, what was the critical point at which you say it's alive in that pathway from just complex chemistry to a truly living thing? It's at the point that you get that abstract mathematical code appearing. We don't know how that that happened, but that would be the point for me at which you would say it's the origin of life. So if I stand back and look at the magic of life, the way it is performing its amazing feats, then it just seems to me that the correct words that come to my mind are information management. It's the way that the information is not just a head count of bits, not just the content, but the way that information is managing or organizing or supervising what life does. And so that information has to be in a context. It's got to be embedded in a bigger system. It has to have that biological functionality on that larger scale. That's a very hard thing for physicists to think about because we're used to understanding what goes on in the world in terms of forces and interactions and so on by thinking locally, you know, what is happening at a particular point. Give you an example, you might shoot a proton at a nucleus and shatters the nucleus. And then how do we describe what goes on in that interaction? Well, it's in terms of the forces concentrated in that nuclear volume. We wouldn't appeal to the entire lab when trying to figure out what's going on. But when it comes to biology, you have to look at the organism as a whole. It's the collective organization of the whole thing. And that's the difficulty. It's trying to understand how information embedded in the organism, stored in the DNA and in other features of the organism as well, can be deployed in a manner that supervises that overall organization. There are many, many examples that I could cite, but that's the gist of it. It's what is that semantic or meaningful or contextual information that is information plus. It's not just a matter of bits. So I've said several times that the information content of life, the book of instructions, if you like, and the information management is in much more than the DNA. And so we have this term genetics and that gene is a particular sequence of letters in DNA. And we can think of that as genetic information. But it's very clear that there is a lot of other information, which is called epigenetic. It just means outside of the genome. The question is, where is this information stored? There's networks of genes that switch each other on and off. And so these networks are one place that information can be stored. There's another way, which is the DNA just doesn't sort of sit there like you see in the textbooks. It's all folded up in complex patterns. And those patterns themselves can store information. But the question is really whether information outside of the genome can survive from one generation to the next. Can it be inherited? Back in the 19th century, when it became clear that life has evolved over billions of years of years, there were rival theories about how this might happen. And one of these is, of course, well known as Darwin's theory of random variation and natural selection. But the other was due to the French biologist and Lamarck. And Lamarck had the idea that maybe characteristics that organisms acquired during their lifetime could somehow be passed on to their progeny. And to give you a sort of trivial example, giraffes long necks, you know, they're stretching to get food higher and higher. So maybe a giraffe that had to stretch its neck even higher during its lifetime and sort of acquired an elongated neck as a result would then pass it on to its progeny. So its babies would have longer necks an average. In other words, the characteristics you acquire during a lifetime would be passed on. And that theory fell out of favor. It seems very easy to find counter examples. Think, for example, of a blacksmith acquiring huge muscles by sort of hammering away every day. Does the blacksmith have babies born with big muscles? Well, the answer is no. It looks like the blacksmith's genes, if you like, are sort of fixed early on and passed on to the offspring and have nothing to do with the activity of the blacksmith in his lifetime. And this is a rather controversial subject. It's called epigenetic inheritance. Now, it's very clear it could work at the cellular level. You know, a skin cell can make a skin cell and a liver cell can make a liver cell and so on. So its identity, they have identical DNA, but the identity, the gene expression is different in these different cells and yet it can be passed on. But can you have intergenerational epigenetic inheritance? What I mean by that, that is it possible for an organism to pass on some of the information, not in its genes, but in the body as a whole, pass that on to its progeny. Very controversial, clearly happens in plants. But what about people? You know, is it the case that what you do in your lifetime might affect your children, whether they be taller or shorter or thinner or fatter or, you know, even their behavior? Is that possible? There's a little bit of evidence that it might be, but it's contentious. As you might imagine, anything involving human beings becomes a very contentious issue. And then the problem is the mechanism. How would that be passed on through the eggs and the sperm? Is it possible that they could carry with them something other than the DNA, some chemical or structural information that would affect how the children develop? And it seems like an open question. I can be convinced. I know of some experiments with mice that show that it is possible, even through the male line, the sperm, for the progeny to be influenced in some way by the experiences of the fathers in that case. So it's easy to think of ways in which this might happen. There's some amazing experiments by Michael Levin and his colleagues at Tufts University using planaria. They're very popular because it's called a head and a tail. And if you chop a worm in two, the head grows a tail and the tail grows a head. So you've then got two worms for the price of one. And you can go on doing that, sort of chopping them up. In fact, you can chop a worm like that up into, you know, a hundred different sections. And somehow these sections remember which was the front and which was the back, and they grow into a hundred different worms. And that's all very amazing. Now you can chemically manipulate them such that you can make two-headed worms and two-tailed worms. But now you ask the question, what happens if you chop a two-headed worm in half? Does that reconstitute the original worm, two worms now with a head and tail? No, it turns out that the two-headed worm makes two more two-headed worms. In other words, it's like a new lineage. And so in a lab across town, you can have a whole population of two-tailed worms, and in your lab you've got a whole population of two headed worms. You might think these are different species, but they have identical DNA. So this shows that the morphology, the actual, the phenotype is the technical term that biologists use for these worms, depends on much more than the DNA content. It's that information is somehow stored, possibly electrically, possibly chemically. It's not really understood, somehow stored and can reconstitute the worms into that particular shape afterwards. So that's a clue that in just focusing on genes, we're missing a big [00:21:30] Speaker 2: part of the picture. Chapter Two: Life, Entropy, and the Laws Were Missing [00:21:42] Paul Davies: There was a famous scientist called Rolf Landauer who uttered the phrase "information is physical" and it stuck in my mind and the minds of a lot of other people inasmuch as we can talk about information in the abstract just as you go to a computer sciences department, you talk to a software engineer and they're writing all this computer code and they talk about it as if it's a separate thing. But of course, it always has to be instantiated in material, some sort of material substrate. And so information isn't something that can just sort of float around in the ether on its own, doing its own thing. It's got to be instantiated in matter. So then we come up against this very interesting thing that matter does what matter has to do. It's got laws of physics that describe how it should behave, and we can't say just because it's encoding information, it's going to behave differently. These laws are mathematical relationships and that's a really important point to get across. So when physicists talk about laws, they don't just mean ways of thinking about the world, they mean organizing principles which are mathematical relationships. And to give you a simple example, you might want to play chess on your computer. The shapes on the screen move around according to the laws of chess. Or does that mean that down among the circuitry you've got the laws of physics sort of squabbling with the laws of chess? You know, well, who's going to win here? Of course, it's perfectly consistent. It's just that the laws of physics, we come back to this, they operate locally. The standard laws of physics we understand are local effects. The laws of chess have to do with the overall organization of the shapes on the screen and the rules of the game and so on. And so we're dealing here with trying to understand if we want to reconcile, if we're talking about life or consciousness, we want to reconcile laws which describe the global or the context or the overall arrangement of things with the local laws at the bottom. Some people think that the mystery of life is all about the second law of thermodynamics and it's going against the trend from order to chaos. Here, living organisms go the other way, they create order out of order. And that has suggested to some non-scientists that there's some sort of mystical mysterious extra ingredient or a life force or some something sort of spiritual or the guiding hand of a deity or something which is bringing these effects about. And that's a total misunderstanding of the laws of thermodynamics. I must emphasize that living organisms are open systems. The second law, strictly stated, says that in a closed system, the entropy can never go down. But living organisms are not closed systems. There's a throughput of energy and material from their environment. And if you like, a good way of putting it is that they can export their entropy or their chaos into the wider environment. So, when we eat food, this helps us maintain our own internal order, but we're breaking the food down. And in acquiring the food in the first place, we're creating a lot of sort of chaos and disorder in the surrounding environment. I should say that this is not deeply mysterious. My refrigerator can perform a similar feat, because one of the best expressions of the second law of thermodynamics is that heat flows from hot to cold spontaneously. Now, my refrigerator, of course, does exactly what I've said is against the second law of thermodynamics. It takes heat from inside the refrigerator and pumps it out into the kitchen, which is taking heat from cold region and putting it out into the hot region, going against the trend of the second law of thermodynamics. But it can do that because I'm paying the electricity bills for it to happen. You see, it's not happening spontaneously. If you take the system as a whole that includes the electricity supply and the generator across town, all of that means that the entropy goes up. But locally, it can go down. We can think of living organisms as just sort of little entropy wells, if you like, that can achieve this going against the second law, but at the expense of the wider environment. Another way of thinking about life and the second law of thermodynamics is that information is like negative entropy, that if you gain information about something, you're reducing the amount of chaos or disorder. And one of the founders of thermodynamics, James Maxwell came up with a curious idea in a letter to a friend in which he imagined a box of gas with a membrane in the middle and a little hole in that membrane. And then one of those molecules would go through the hole and go to the other side of the box and vice versa. And in equilibrium, there'd be a traffic in both directions that would balance out. But now imagine he said that you had a little creature, later came to be called a demon, who could operate a shutter mechanism and could see the molecules coming along. And supposing the demon saw a fast-moving molecule coming from one side of the box and would think, "Yes, I'll open the shutter and let that one go through," but the slow-moving molecules would be rejected. Then over time, there'd be an accumulation of fast-moving molecules on the other side of the membrane, which in terms of temperature would mean a higher temperature. The molecules jiggling faster means it's hotter on that side. So the demon would be able to create a temperature difference between the two sides in complete violation of the second law of thermodynamics. It says heat goes from hot to cold. This is an example of it being pushed in the other direction, not by paying electricity bills for a refrigerator, which does the same, but by using the information about the molecular motions. So what this suggests is that information is a type of fuel. It's something which could be used to, in principle, create a little engine, you create a temperature difference and then you could run a motor after a temperature difference, using it entirely from the power of information, that information is a fuel. Now the interesting thing is that nature discovered Maxwell demons billions of years ago because our bodies are full of them. They're sort of chuntering away inside us. There are pumps and levers and all sorts of little mechanisms, little engines and so on, that are carrying out these operations, playing the margins of the second law of thermodynamics. I must emphasize, they don't violate the second law of thermodynamics, but they come very close to what we might regard as the perfection, very close to the theoretical limit permitted by the second law of thermodynamics. So life has refined this information processing or information as fuel, right down to the point of having lots of legions of these little molecular machines, which are effectively Maxwell demons carrying out the business of life. And the universe as a whole is undoubtedly on a one-way slide to a higher and higher entropy state, less and less useful sources of energy, and that's a cosmological story. So life is not going against the trend of the second law of thermodynamics, it's simply playing the margins of it. And if I might just back up and say that we talked earlier about Schrodinger. Schrodinger wrote this remarkable book, What is Life? And in it, he said, we must be prepared to find a new kind of physical law operating in it. The operative word there is kind, not just a new physical law. In other words, he wasn't saying, well, there's all the laws of physics we know, and there'll be one that we haven't discovered yet that will explain life. It would be a new kind of law. And I've taken that very seriously during my career, and I think that it does need a new kind of law. It doesn't just need another force or something of that sort. What it needs is a new way of, a new concept of law. And it's something which I've already hinted at, that the way information and matter, the hardware and the software, the way they interact in living organisms, we don't have any sort of law-like framework on a general basis for describing that. We do need something that would put that biological information in context. That is, I've explained how a gene is a set of instructions for a particular molecular system to do something, like make a protein. It has biological functionality. We have to relate the global context of the organism to the local instruction set. If we talk about law of gravitation or something, why does an object fall? It's because the gravitational field at this point is acting on it. It's a local thing. When we're talking about living organisms, somehow we have taken into account the organization of the entire system, the context of the assemblage. And we've got to embed that in some sort of new type of physical law. I think we're not going to do this just by inventing new local laws. We've got to have a new way of thinking about laws. Laws of physics at the bottom level, with some higher level laws of organization at the top level. And we've got to mesh these two in some way that people have tried. I mean, I'm not saying this is a lost cause in lots of attempts to describe what's often called top-down causation. What's happening at the global level is affecting what's happening at the local level. You can write down equations and things, and some of these are moderately successful. But I don't think we've really understood at a truly fundamental level how the higher levels of organization and the lower levels of the laws of physics really mesh together in a fundamental way, in a general sense. There's some ideas sloshing around. I won't get into them. They're a bit technical. This is all very tentative. But I think we're never going to fully explain life without having that new kind of physical law as Schrödinger was asking for. [00:32:30] Speaker 2: Chapter 3: Are We Alone? The Search for a Second Genesis [00:32:35] Paul Davies: Part of the problem about coming up with the definition of life and the origin of life is that we're guided almost entirely by life on Earth. And so we can look at what were the conditions on the early Earth, and what are the conditions necessary to sustain life on Earth today. Now we don't know that these were the same things. It may be that the origin of life requires one set of conditions, but for it to thrive it's a different set of conditions. We know life can move around. You know, maybe early Mars was a better place for life to get going, but early Earth was a better place for it to flourish. But because life, primitive microbial life can go from Mars to Earth in impact ejecta, that's no problem. Starts on Mars, flourishes on Earth. We don't really know. So when we're going to look for life beyond Earth, there's a tendency to think, well, we should look for Earth-like planets. When I was a student, I was really interested in the idea of life beyond Earth. But in those days, one might have professed an interest in looking for fairies. It was considered self-evident that there couldn't be any life beyond Earth, because life is so complex it would have happened only once. And Francis Crick, for example, who discovered the structure of DNA, said life seems almost a miracle, so many of the conditions necessary for it to get going. So the prevailing view a few decades ago was that life is a bizarre freak accident, a chemical fluke of such improbability that you'd only get it once in the whole universe. And then over the decades, the pendulum sort of swung. And so now very distinguished scientists are prepared to say that the universe is teeming with life. But I often criticize that by saying, well, when I was a student, nobody took that seriously, now you're all saying it's teeming with life, what's changed? And the answer that I often get is, oh, well, we know that life can now live under a much wider range of circumstances than when I was a student. It used to be taught that even hardy microbes couldn't survive temperatures above, you know, 50 or 60 degrees Celsius. Then it was found that there are organisms living in hot springs at much higher temperatures than that. And the same goes for other physical conditions, extremes of cold, extremes of chemical pollution, extremes of salinity. And so the collective noun for these organisms that survive under these conditions is extremophiles. And so people point to that and they say, well, now we know that life can survive under such a wide range of conditions, that greatly increases the amount of real estate out there that we might search to find life. And it's true that it may be by a factor of 10 or something that there are more places that we could look. But if the odds against life forming from non-life are one in a trillion trillion, you know, an extra factor of 10 isn't going to help you very much. I would like a demonstration or of the discovery, just one other sample of life. One microbe here on Earth that is life, but not as we know it, would do it. Two samples of life on Earth surely means that there would be life everywhere. Everyone has their favorite place to look. I like to think of Mars as the best possibility. But there's a lot of emphasis on the frigid outer moons of the Soda system, Europa and Enceladus. That's a moon of Saturn. It's got an icy crust and underneath it is a liquid ocean. The icy crust has cracks in it and spewing out of these cracks are gases. And the Cassini mission flew through this plume and detected organic molecules. Now organic doesn't necessarily mean living. Organic molecules are complex carbon molecules. They may be a product of living organisms or they may just be a product of complex carbon chemistry. How can you tell the difference? How would we know whether there is anything spewing out in this plume that was maybe once living and got mashed up or is maybe still living? What you'd like to do is have an instrument to put on board a spacecraft that will fly through that plume, collect the material spearing out and would deliver a verdict on whether it's living or not. We don't know quite what that instrument would be. What would be a definitive sign of life? Or for that matter, what would distinguish between something that was living and is now broken down into components? So that's death, if you like. That would be a death meter. Do we have a death meter? Something that could say, "Yes, it's dead, but it was living." Versus, "No, it isn't quite living yet." Versus, "It is alive." And that immediately gets you into some very interesting questions. We tend to obviously dwell on death for human beings and the loss of consciousness and people worry about, you know, is there some sort of existence after death and so on. But I'd like to be a bit more scientific, boil it down to something much simpler to think about. If we take, say, a bacterium. If you cool a bacterium down to, say, liquid nitrogen temperatures, it becomes dormant. There are bacteria which have been trapped in ice, for example, and can be sort of resuscitated after millions of years or trapped in salt crystals or in a fridge. They're not dead, but they're not living either. And I think of it a little bit like a clock. Well, it's a stopped clock, still a clock. It still has the potential to tell the time if you get it started again. But if it's a stopped clock, it's not a dead clock, it's a dormant clock. And the same thing with bacteria, that they're not dead when they're frozen. They're simply dormant and they can come alive again in the full expression. But now that raises a further question because it's entirely possible that life has traveled from Earth to Mars or Mars to Earth inside impact ejecta. We know Mars and Earth are hit from time to time by comets and asteroids that splatters rocks all around the solar system, and organisms can hitch a ride in these rocks and travel from Mars to Earth or Earth to Mars. Now, obviously, that is possible. We don't know if it's happened, but it seems entirely likely that it would have done. The biggest hazard in interplanetary space is not the cold because these microbes would become dormant. It is, in fact, the radiation. So, sitting inside a rock in space, a dormant bacterium is going to be bombarded by cosmic rays and some radiation from the rock itself, and so it's going to sustain damage during its journey. And supposing it's a million years before it finally hits the Earth, will it come alive again? How much damage can it sustain before it's gone beyond the point of no return? The point I'm trying to make is that, is a bacterium alive or dead? You can cool it down and stop it working, and it can sustain a certain level of damage, but at some particular point it won't start up again, and then you might pronounce it to be dead. But now let's consider a more complicated case like Titan. It's a moon of Saturn, and Titan's very cold. It would be unlikely to have life as we know it, but it's full of organic molecules. It's like a petrochemical smog in its atmosphere. We can imagine that it's been carrying out like a sort of cosmic Miller-Urey experiment. It's been cooking up prebiotic chemistry for four billion years, four and a half billion years. And so, you know, did it succeed in making life, even if it wouldn't be life quite as we know it? And how would we know? Imagine you sent some sort of life meter to Titan, and it went down through the atmosphere, and it then delivered a verdict. It might say, well, we didn't find any life on Titan, but it did get 93.4% of the way to life, or it only got, you know, 5% of the way to life. You know, what would you make of that? Well, what I just said seems sort of ridiculous. We don't have, it's hard enough to come up with a definition of life. We don't really have a definition of almost life. We couldn't tell by looking that it was nearly there, you know, give it another billion years, and it might make life. We don't even know how to think about that. And there's a very good metaphor. Richard Dawkins, the biologist, wrote a book called Climbing Mountain Probable, and it addresses the question of life started out very simple, just microbes, and today we have the whole complex biosphere, and some people find that miraculous. But the way he likes to describe it is that it's like climbing a mountain, and each step might be very improbable that you get more complexity, more order, and so on. But that's what natural selection does. It acts like a ratchet locking in the efficient, more complex order, and killing off the ones that doesn't work so well. And so laboriously, you climb up this mountain probable step by step by step. Well, of course, it didn't start with microbes. There's a mountain probable that starts with chemistry. You've got to climb all the way from simple chemistry to complex chemistry to living chemistry, the chemistry of living matter. How do you climb that mountain probable in that prebiotic sense? And is there any way of measuring what would be the elevation up mountain probable? Can we look at a particular complex chemical mixture and give it a probability and say how close it has come to actually forming life? Well, I don't think we can. You see, I think we lack, not only lack a definition of life, we lack a definition of even how close you might be getting to life. And more to the point, we don't even know whether the pathway from non-life to life was just some sort of seamless upward march of complexity, starting out simple over millions and millions of years, getting more and more complex, more and more complex, until suddenly you would say, well, now I guess we would call this really complex thing living, or whether it's more like a phase transition, like a gas bursting into flame, that you would go along this pathway, it would get more and more complex, and suddenly there'd be a jump. And you would say it sprung into life at that particular point. And then if we had a life meter that could say where you are on that pathway, has that jump happened, then it will be worth sending that meter out into the universe to look for somewhere else where that jump may have occurred. But we haven't got to that stage yet, we don't know how to build a life meter, because we don't really know how to understand this pathway, and the threshold of life, and what will constitute almost life. So, astrobiologists love looking for earth-like planets beyond the solar system, and that's very natural. But the most earth-like planet we know is earth itself, and so that raises the question about whether, if life arises readily under earth-like conditions, might it have happened more than once right here on our home planet? How do we know it didn't? Has anybody actually looked? And it turns out that nobody's really taken very seriously the idea that life could have arisen on earth many times over. Now, it could be that life started 500 times on earth and only one form of life has survived to the present day. But can we be absolutely sure that there is no other sample of life on earth hiding somewhere in some little niche beyond the reach of known life? Could it be that descendants from another genesis four billion years ago are still here in our biosphere today? This is a very speculative idea, sometimes called the shadow biosphere, that alongside the biosphere that we know and love, intermingled among the organisms, the microorganisms that are all around us might be some microorganisms from another genesis event. This would be not just a different branch on the known tree of life, but a different tree entirely. How could we tell? How would we know if such things are out there? How would we have spotted them? And it turns out the answer, when you look at this very carefully, is no, we probably wouldn't have noticed them. They could be there all around us. So it could be that there's a second sample of life, alien life if you like, right under our noses, or even in our noses, and nobody has really made an effort to look. Now there's a counter argument that people like to make, which is that once one form of life gets going, it sort of appropriates all the resources and changes the conditions in order to sustain its own existence so that this would act against the survival of any other type of organism. The classic example is when photosynthesis was discovered by life, I don't know, two and a half, three billion years ago, and then it led to the build-up of oxygen in the atmosphere. We tend to think of oxygen as a good thing, and it is for you and me, but it's a terrible corrosive poison. And when it first appeared, it threatened to wipe out life totally. It was a pollutant, and it was only that life was able to, some life was able to adapt and actually turn a sin into a virtue and use that oxygen as an energy source, that we are where we are today with an oxygen-rich atmosphere. But the build-up of oxygen has led to more than allowing life to become more energy-rich and more complex. It's also changed the nature of rocks, for example. Contrast the earth with Mars, Mars, you look at Mars, it's noticeably red because that red is really rust. And so Mars doesn't have this recycling mechanism, it doesn't have plate tectonics, it doesn't have plates that move around and volcanoes that change, it has volcanoes, but it doesn't manage to recycle all of these elements and so on. So there's a feedback loop between the life on Earth and the cycles that drive life on Earth and each affects the other. It's very unclear how often you would come across a planet quite like the Earth, which has these interlocking cycles, the biological and the geological and the atmospheric, all working together to change each other and sustain each other, which is done, not just for a short duration, but literally over billions of years. So these cycles have co-evolved. It may be a very special set of circumstances. It may be that it is a rare Earth, to use a title of a famous book. It could be it's a rare Earth. And I think most people have the idea of searching for alien beings as flesh and blood, organisms, you know, weird looking animals that you might find on another planet. But it's very clear that if there are technological civilizations out there, that they will very soon, if they got to our level of development, begin to outsource their intellectual heavy lifting. I prefer to call them design systems. Artificial is a bad term. I think of it as designed intelligence. We've got Darwinian intelligence, very slow. It's taken billions of years to get to this point. And then designed intelligence can be very rapid. And once you embed the design principles in the designed intelligence, once AI gets the design principles for the next generation, and so on, it very rapidly takes off. I can imagine an AI system in the not-too-distant future that would use components from living organisms, you know, from neural tissue being incorporated, and people are still doing this even now, incorporating those into some larger system. And that we're going to lose this distinction between, is it living, is it non-living? And it really just boils down to, is it designed, and is it designing the next generation, and so on. So if we ever do Contact ET, and I'm pretty skeptical, but if we ever do it, it's overwhelmingly likely not to be some sort of, you know, Hollywood-style flesh and blood being. But it's going to be something we might want to call AI, but we lack a term for what this super-intelligent, multi-generation designed system might be. But it's clear that, just from the way we're going, it's clear that this entity would have godlike features, that we would be dealing with something which would be probably well beyond our level of understanding. And if we combine AI with quantum computing, so that's where it gets really interesting and really profound, so we've got QAI, quantum artificial intelligence, or quintelligence, as Frank Wilczek calls it, then all bets are off. Because now we're dealing with an entity that can explore not only all of the possibilities that we can explore in our own minds, but all possible quantum alternatives, all possible worlds. So we're dealing with some sort of entity that is intelligent or conscious, or it might be an agent of some sort, which has an infinitely greater range of possibilities and experiences and processes that it can operate than we do. And if we're dealing with the ET that has civilization that's been going for 500 million years or something, it's overwhelmingly likely it's going to be dominated by these godlike, totally mysterious, awesome entities. [00:52:14] Speaker 2: Chapter 4: The Goldilocks Enigma Is the universe fine-tuned for life? [00:52:20] Paul Davies: So now, putting on my physicist hat and looking at the universe as a whole, I'm struck by the nature of physical laws. The fact that the universe is ordered in a very precise mathematical manner, and that these underlying laws are not only beautiful and powerful and represent mathematical relationships that enable the universe to run in such an efficient way, but they're also consistent with the existence of life. And so this is a subject that often goes under the name of the "anthropic principle", it's a very bad name, but what it basically means is the following: that if you take the various laws of physics and the initial conditions for the universe, the way the Big Bang went bang, and if you say, well suppose we change something a little bit, say you wanted to make all electrons a little bit heavier, or the weak nuclear force a little bit weaker, you know, can you, could you muck around with those things in such a way as to still have life? And it turns out that the answer is no, that some of the laws of physics are so exquisitely sensitive that the tiniest change would wreck the prospects of life, those changes would be literally lethal. Now obviously we can't do the real experiment, but we can do the mathematical experiment, we can figure out how would the world change, gravity was a bit stronger, or if the electrical forces were a bit weaker or something. And when you do that, you'll find that some rather small changes would wreck the chances of life. For example, it might prevent complex nuclei from forming, you might end up with a universe that consists entirely of neutrons, or entirely of just hydrogen, with no carbon, the life-giving element. So you can look at all those things and conclude that the universe, that the laws of nature in the universe as a whole seem to be, and this is where it gets, the terminology gets a bit controversial, seem to be fine-tuned for life. People talk about the fine-tuning argument. Now, fine-tuning doesn't necessarily mean that there was a designer who deliberately picked those values in order that there should be life. But what it does mean is that if those numbers were a bit different, there wouldn't be any life, and we wouldn't be here having this conversation. So what are we to make of this? I call this the Goldilocks enigma, that the universe looks like it's just right for life. So we have really three possible explanations for Goldilocks. We've got it's just a fluke, it happened that way, and there's nothing special about life anyway. There was a designer, or a god, who sort of made the universe, fine-tuned it in order that life should arise. And the other response that you can take to this is the multiverse explanation, that the universe is just right for life, because it wasn't just one universe. There's an infinite number of them, and it starts out sort of random, that the big bangs, lots of bangs going off scattered throughout space and time, and each one comes with its own set of laws. And so in some of these universes, gravity will be a bit stronger, and in some, the electrons will be a bit heavier, and so on. And in the vast, vast majority of those universes, there won't be life, and so there's no one around to bemen the fact that they're not Goldilocks universes. But here and there, just by the laws of chance, you're going to find that there will be a Goldilocks universe, and in that universe, there will be living creatures like ourselves, who arise and reflect on what does it all mean. And so, those three ideas are out there, and that discussion continues to take place, and really, it boils down to, at this stage, a matter of personal choice. But there is actually Davis's fourth way. I've been talking about the laws of physics in the traditional way of sort of fixed, immutable mathematical relationships, I said, stamped on the origin of the universe, you know, at the outset, like the maker's mark. So in other words, the laws are fixed. But, you know, maybe that's a simplistic way of looking at it. It's the way that physicists have looked at the laws ever since Newton, as immutable, eternal, universal mathematical relationships. But maybe we should think in terms of flexi-laws, or something that's a bit more malleable. This is where it does get rather subtle, because is there any way in which the emergence of life and mind can be connected in some way, some causal way, with the nature of the laws that gives rise to them? Is there like a feedback loop between observers, like ourselves, and the laws that enable the emergence of observers? And you think, well, if the laws are fixed, that's ridiculous. But earlier, in a very rough analogy, we were talking about the earth, the way that life on earth, there's feedback loops, the physical nature of our planet, of planet earth, and the life upon it, are connected together. So the existence of life affects the way the earth behaves, and so on. Is there some sort of cosmic feedback loop, so the existence of life affects the laws that then give rise to that life? And at first sight, you would think that that's completely impossible. But actually, there is a loophole, and that loophole arises in quantum mechanics, quantum physics. And the reason is, because I've been saying, well, the laws, the traditional way is that the laws are fixed at the beginning. But actually, because quantum mechanics is based on the notion of uncertainty, people have heard of Heisenberg's Uncertainty Principle, and what it means is even if you set up very precisely a quantum system, an atom in a certain state now, you can't be certain how it's going to be in one second time. But that uncertainty goes back in time as well. It's a fallacy to suppose that there is a fixed history connecting the Big Bang origin of the universe with the world today. And about 30 years ago, John Wheeler, the physicist, discovered that you could do an experiment called the Delayed Choice Experiment, in which you decide now what it shall have been in the past. So in quantum mechanics, something like a photon can be described as a particle, or it can be described as a wave, depending on the circumstances. And you, the experimenter, can choose. I will do an experiment that will disclose the wave-like nature. Or I shall do an experiment that will disclose the particle-like nature. But it turns out, if you ask the question, well, was it a particle or a wave one nanosecond ago, even before your choice, it would have been what you decided in the present moment, because quantum fuzziness engulfs the past. Now, you're not sending information back in time. You're not changing the past. The past is ambiguous. So we know some things about the past, but not everything. So if something we do today resolves an ambiguity in the past, then it's not backward causation, but it is a way in which what happens now is linked to what happens in the past. No doubt that this is the case in quantum physics. You can decide now what reality shall have been in the past. If we extend that from was it a wave, was it a particle, to are the laws of physics themselves part of this quantum landscape? Was it this law of physics? Was it that law of physics? Now we begin to see that there's a nexus, a way in which the existence of life and mind can gain some sort of patches over the nature of the laws that have emerged in the universe, by having flexibility in the laws and having this sort of quantum retroaction effect in this very subtle way. So it's very easy to misunderstand what I'm saying. I'm not saying that we now have changed the past to ensure our own existence, but there is a consistency. There's a feedback loop that operates in quantum physics. So that's number four. So you've now got, it's just an accident. God did it. There's an infinite number of universes with life very rare, but popping up somewhere. Or there's a way in which life and the universe form part of a common existence loop. And that idea, I should say, is not my idea. It's the one I favor. It was the idea that John Wheeler, the physicist, favored many years ago, he was a big influence on me. And he was the one who came up with this delayed choice experiment. And it was sort of a springboard for his idea that participants in the universe, that is, beings who have minds and choices and can do experiments and make measurements in quantum physics could be part of the whole existence story. And I find that very appealing. [01:01:41] Speaker 2: Four times a year, we print a magazine worth putting your phone down for. Big Think's premium print magazine is built with custom artwork and expert insight from the world's biggest thinkers. No AI slap, no rage bait, just big ideas for curious people. Support the media you want to see in the world. Go to bigthink.com/join to become a member today.