Caltech theoretical physicist Sean M. Carroll talks about his new book The Big Picture: On the Origins of Life, Meaning, and the Universe Itself. (Dutton, 2016)
Caltech theoretical physicist Sean M. Carroll talks about his new book The Big Picture: On the Origins of Life, Meaning, and the Universe Itself. (Dutton, 2016)
Steve Mirsky: Welcome to Scientific American's Science Talk, posted on May 12, 2016. I'm Steve Mirsky. On this episode…
Sean M. Carroll: You can be a naturalist and sort of be a hardcore naturalist, who says the only thing that is real are elementary particles, or the fundamental stuff of nature. I think the tables and chairs are real, and the argument for saying the tables and chairs are real leads you to also say that things like consciousness and free will are also real. They are useful ways of talking about the universe.
Mirsky: That's Sean M. Carroll. He's a theoretical physicist at Cal Tech whose research interests range from cosmology to the foundations of quantum mechanics, time's arrow, and the emergence of complexity. He is also the author of popular books such as The Particle at the End of the Universe and From Eternity to Here. In the movie version, Burt Lancaster and Deborah Kerr just try to count the number of grains of sand on the beach.
Sean Carroll's latest book is The Big Picture: On the Origins of Life, Meaning, and the Universe Itself – you know, fluffy stuff. It's published by Dutton, an imprint of Penguin Random House. Sean was in New York City on May 9th. I visited with him at the offices of his publisher.
Let me start with what I hope will be a brief anecdote. I was at a party and I hear these two people talking about this guy who used to have a TV show where he would talk to dead people for their family members. And I interjected obnoxiously and said, "You know that every atom in your body was created in a star?" Well, not every atom was created in a star, but you know where I'm going with –
Carroll: I know what you're talking about, yeah.
Mirsky: Right. "The heavier elements were created in a star maybe billions of years ago, and that's what you're made out of." And they both said, "Really?" And I said, "Yeah." I said, "You still want to talk to dead people? I mean, isn't that kind of trivial compared to the reality?" And they both looked at me and said, "Yeah. We still do want to talk to dead people. That's more interesting to us."
Carroll: It is true. It's a very – and I think it's very natural, right? I mean, I don't want it to be the case that when I die that's the end of me. If someone said, "Oh, you have, like, another few million years after that to live sort of a different kind of existence," I might take them up on that offer. But the evidence points otherwise. We're seeing what we get right around us. That's what we are. We're made of atoms. Those atoms are going to continue on, but our existence as a complex life form will eventually come to an end, and therefore let's make the most of what we've got.
Mirsky: And a lot of your book is just how to think clearly about things. I mean, that's really what the whole foundation of the book is. And in the book you talk about the fact that if you want something to be true, that's something you really have to watch out for when you're examining your evidence.
Carroll: Right. Yeah, I made the decision – and I agonized over it a little bit – but to talk at somewhat of a length about not only what we think is true about the universe, but how to go about deciding what is true about the universe. Some very obvious things about how science works, but also Bayesian inference and probabilities, and also, like you mentioned, cognitive biases. The fact that we as human beings are not perfectly rational all the time and we need to correct against that. And the funny thing is you tell people this and inevitably the answer, the response is, "Yes, I know many people who are irrational in that way." [Laughs] And almost no one says, "Why, yes, I am always irrational that way myself. I should work to do better at it."
So, I personally try to do better at it, but who knows what biases we have that we don't uncover in ourselves.
Mirsky: Right. That's a really interesting problem. I mean, it's almost impossible to know where your own –
Carroll: You can know you have them, but pinpointing them and seeing them in action is a trickier thing.
Mirsky: I mean, there are ways to actually test for your implicit biases now –
Mirsky: – but even if they're revealed to you, you might not accept it.
Carroll: Sometimes they get worse. Sometimes you become defensive about it. There is the backfire effect. If you're – if you have a strongly held belief and you are shown evidence that it is false, you come away from that demonstration believing in it more strongly than you did before.
Mirsky: Right. You know the famous video of the guy in the gorilla suit moving towards the basketball players –
Carroll: Absolutely, yes.
Mirsky: – and you're asked to count how many passes of the basketball happen among all the players, and almost nobody notices the guy in the gorilla suit moving through. And I showed that to my dad, and afterwards he told me how many passes he counted. And I said, "Did you notice the guy in the gorilla suit?" and he said, "What are you talking about?"
Mirsky: And I showed him the video again and he refused to believe it was the same video.
Carroll: Wow. Yeah. That's – it's a – that's the other thing, that not only do we have these biases and blind spots and heuristics, but the defense mechanisms against it are amazing. In the book I talk a little bit about the Capgras delusion, which is a mental illness you can get if you actually have brain damage, where you recognize people in exactly the way you did before and all the memories and associations you have with them, but you have zero emotional connection. So, one woman had this problem and her husband – she recognized this person as "I recognize him as my husband" and so forth but felt no affection or love for him anymore. So, her brain invented the workaround that this must be an imposter who is impersonating her husband and looks exactly like him.
Mirsky: This – it's amazing what your brain will resort to to make things the way either you want them to or the way that you feel at ease with them.
Carroll: Yeah. And it makes sense in retrospect if you think that we're not simple rational beings, we're not logical computers or anything like that. Our conscious selves are stitched together from all of these unconscious modules in our brain that are churning along doing their own individual jobs, and it's kind of a babbling parliament of voices inside our heads. And what comes out is only a tiny fraction of what's happening inside.
Mirsky: So, you're a theoretical physicist. Why are you writing about mental issues?
Carroll: Right. Well, it's all part of the universe, is the simple answer. My previous books have been specifically about topics in physics, but this time I wanted to take a step back and ask questions about how all of the different ways we have of describing the universe fit together. So, some ways we have of describing the universe are physic-centered – you know, talking about particles and forces and quantum mechanics. But we also talk about it in terms of macroscopic things like tables and chairs, biological things like cells and organisms, or human level things – you know, emotions and aspirations and desires. And they're all, I strongly believe, ways of describing the same underlying stuff. So, even though you don't need to know particle physics to do biology or psychology, your theories of biology or psychology better be compatible with particle physics. And your theories of psychology better be compatible with biology and so on.
There's an enormous amount of very exciting and challenging work to be done to both invent these different theories and fit them together, but I think we can see the outlines of how it will all happen.
Mirsky: And what are those outlines?
Carroll: Well, it's what in the book I label poetic naturalism. Naturalism is the simple idea that there's one world, the natural world. Even if there's a multiverse, we call it all a single world. There's nothing else that the universe needs. The universe just goes on by itself; it doesn't need to be sustained or created from outside.
And the poetic aspect of it is that we should take seriously all of these different ways that we have of talking about the natural world. So, you can be a naturalist and sort of be a hardcore naturalist, who says the only thing that is real are elementary particles, or the fundamental stuff of nature. I think the tables and chairs are real, and the argument for saying the tables and chairs are real leads you to also say that things like consciousness and free will are also real. They are useful ways of talking about the universe.
So, the act of choosing the best way to talk about the universe is in some context a fundamentally poetic one. It is narrating the story of our lives in a useful way.
Mirsky: In some sense there's no need for there to be a narrative about the history of the universe.
Carroll: Right. But what we find in the real world is that there are insights into what happens in the universe that can be gained by looking at the world in all of these various different ways. And what is more than that, some of these ways are not scientific. Right? When we talk about the world, we don't only describe what happens. Sometimes we're a little judgy. We say, "This is a good part of the world. This is a bad part of the world. A beautiful part. A not so beautiful part." And that's not objectively there in the external reality; that's something that we human beings bring to it.
Mirsky: You have this great line on – it's on page 54. And I made a point to bring it up. "The Big Bang itself is a mystery in that –" and then you say, "We shouldn't think of it as the singularity at the beginning of time. It's better understood, the Big Bang, as that moment early on when the universe was incredibly hot and dense, but we really don't know how to describe it." I mean, that's not something you get from when you watch a program on the Discovery Channel about the Big Bang.
Carroll: Yeah, it's not. Some of the work I'm doing in the book is cleaning up some of the myths that my fellow scientists – and I – have propagated because it makes our life a little bit easier. But sometimes it's important to get it right. So, it is absolutely possible that the Big Bang is the beginning of the universe, but the truth is we don't know. The truth is the level of trust we have in our scientific theories at that moment in the history of the universe is not that good. So, it's also perfectly possible that there was space and time before the Big Bang, out of which our universe came from some way or another. There are increasing amounts of attention being paid to models of cosmology that have exactly that feature.
So, since in the book I really do want to say that there are some things we honestly do understand, that we rely on and that are still going to be – believed to be true a thousand or a million years from now, it behooves me to pay special attention to those parts that we're not sure about, and to sort of not gloss over our uncertainties there. The Big Band is something we're very uncertain about.
Mirsky: You gave a talk that I was at a few years ago at a conference in Flagstaff. I don't remember seeing the green cheese moon in the book.
Carroll: I didn't do that. Yes.
Carroll: I remember – so, I used this example: Is the moon made of green cheese? And I thought it was a great example of trying to explain how even the wildest scientific theories have some non-zero chance of being right, no matter how much evidence we gather against them, because science just never goes to either 100 percent or zero percent probability; it just gets very big or very small.
So, maybe the moon is made of green cheese. Well, we've been there and it's not. Well, maybe just under the surface it's made of green cheese. But the density isn't right. Well, maybe this is very dense green cheese. You know, you can just go back and forth.
I thought it was great and I know that you enjoyed it very much. This has been so wildly misunderstood that I've given up on using that analogy. People are like, "You don't understand the moon is not made of green cheese?" They really just refuse to get that one. So, I have just learned my lesson. [Laughs]
Mirsky: But, I mean, I brought it up, so we do have to discuss just a little bit about how you use that example to talk about what is possible, that you don't have to go to the moon and take samples to know that it's not made out of cheese.
Carroll: Yeah. That's right. And the real lesson of that was supposed to be the fact that part of the reason you're so sure the moon is not made out of green cheese is you have prior background beliefs, both about the creation of the solar system and about the nature of cheese, and they do not fit together in such a way so that it's a plausible hypothesis. Cheese comes from milk that comes from sheep and cows, and so forth.
So, that is just going to be true no matter what beliefs about the universe we are talking about, and that's okay. It's inevitable. We always have background beliefs, what in this book I call a planet of belief, a set of beliefs that we have about the universe that are supposed to fit together in a comfortable way.
Mirsky: You get these people come up to you and tell you about their ideas about the universe and the creation and –
Carroll: They do that, yes.
Mirsky: Right. And you mentioned that you were on a plane going to Bozeman for a conference and you were reading some research papers on the connection between statistical physics and the origin of life. And this guy sitting next to you looks over and says, "Oh, I know that work well." And so, you're pretty sure you're going to get –
Carroll: The alarm bells go off. Right.
Mirsky: Right. I mean, just in the last couple of weeks I was given a book, a self-published book about the origins of the universe and the evolution of the universe until now and the purpose of everything. And it's just nuts. But the guy sitting next to you on the plane was not nuts, and you say, "Okay, what do you think the origin of life is and the purpose of life?" And he said, "Oh, it's easy. The purpose of life is to hydrogenate carbon dioxide." And all of a sudden, you knew you were not sitting not to a nut.
Carroll: It's a different kind of nut. Yeah, that's right. [Laughs]
Mirsky: A different kind of nut.
Carroll: Yeah, this was Mike Russell, who turns out to be a very well-respected worker in the origin of life – IBO Genesis, as it's called. Mike is a scientist at JPL – Jet Propulsion Laboratory, which is near Cal Tech, where I work. And he is one of the leaders in a respectable but minority group of people in IBO Genesis in what is called the "Metabolism First" crowd.
So, the thing about life is it's complicated. No one needs to be taught that. And so, there are many different things that need to come together to get life off the ground. One of them is just compartmentalization. You need a difference between inside the cell and outside the cell. That sounds hard, but it turns out to be easy. Chemistry does that – doesn't really seem like much of a barrier.
The other things are replication and metabolism – among other things; there's even more than that. But you need to be able to carry genetic information down through the generations – that's replication. And you need to sort of feed off of stuff in the environment. You need to bring in energy and expel waste and so forth – that's metabolism.
So, there's a debate about which came first – chicken or egg – metabolism or replication. And the replication people first are in the lead right now. They champion what is called the RNA world hypothesis, where it seems very likely that RNA, which is the molecule that carries information from DNA to proteins, could have been first. DNA stores information but doesn't make proteins or do catalysis or anything like that. Proteins do all these useful functions but they don't store information. RNA can do a little of both, so it's a very logical choice for what happened first.
But the metabolism people say, "That's like building the computer that runs your Prius without putting an engine in it first. You need something to get you to go before you have instructions on what to do." So, they think metabolism is crucial and it's harder than you might think. Complicated series of chemical reactions need to be put into place. And on the basis of thinking about that, Mike Russell made a prediction for the existence of a certain kind of underwater geological formation, which after he made the prediction came out to be true. They found it in the example of the lost city formation in the Atlantic Ocean.
So, who knows which one is right? They're probably both right. Probably when we understand things better there will be aspects of both stories. At some point you need both metabolism and replication. I think that we're beginning to see the beginnings of a really scientific attack on this problem of how life started.
Mirsky: But again, the reason it's in your book is because you're considering the sweep of everything that – I mean, literally everything.
Carroll: Well, that's right. I don't – it's a weird thing, because in some ways obviously the book with its subtitle – On the Origins of Life, Meaning, and the Universe Itself – is kind of hilariously overambitious, right?
Mirsky: And it's very similar to the subtitle of the book that I was given by the guy who is –
Mirsky: – not a theoretical physicist and had no business writing that book.
Carroll: It's a fine line. And in fact, the – so, the title of the book is The Big Picture. The subtitle I wanted was What Is and What Matters. I thought that was sort of elegant and artistic, but I was told it was not search engine optimized, so we went with the buzzwords instead.
At the same time, there's another sense in which my book is very humble and not very ambitious, because the truth is I don't tell you what the origin of the universe is, what the origin of life is, or what the meaning of life is. What I attempt to defend is the proposition that there is this background framework of naturalism in which these questions can be addressed.
So, what I do is if you're going to think that naturalism is true, if the universe doesn't need help from the outside to exist of be sustained or keep going, then there's various things that seem like puzzles within that framework. Why did life start to exist? How did consciousness come to be? Why does the universe itself exist? And so, I really wanted to sort of go through all of these potential puzzles within naturalism and give my best case for why I think that they ultimately will be resolved.
Mirsky: You go through an exercise in how to gauge the likelihood that something is true, and then how you can recalculate when new information comes in.
Carroll: Yeah. There's an informal idea that has been discovered various times over the course of history – David Hume, for example, uses very similar logic. I mean, basically, you have a set of beliefs, or a set of what I call in the book credences, as philosophers would call it. So, to some proposition you say, "Well, there's a 10 percent chance I think that's true; there's a 99.9 percent that's true." You shouldn't – according to the rules – ever say there's a zero percent chance or a 100 percent chance, because you can always be wrong about things. And then, when you learn new things about the universe, when new data comes in, new information, or even new insights, you update your credences. If the thing that you're learning is very favorable and compatible and natural under some proposition, your credence in that proposition should go up.
So, this was formalized by this wonderful fellow named Reverend Thomas Bayes and is now known as Bayesian inference. And in the statistics in scientific communities this is thought of as a way to deal with probability, to deal with probability theory. And there are many, many debates over what probability really is that I didn't want to get into in the book. But more broadly, it's just a way of keeping track of how much belief we should have in this or that proposition.
So, I used frivolous examples in the book. If you're a poker player that is playing against someone else, and you don't know exactly what cards they have but you have different credences that they have a pair or three of a kind or whatever, you can do all the Bayesian updating in great quantitative detail and it works very well. But when it comes to theories of the world – dark matter, modified gravity, evolution of the universe, any of these things – we are always doing that process. We always have these credences. We learn new information. We update accordingly.
Mirsky: You say "trivial example in the book," but the example in the book is this guy who's wondering if this girl's going to go out with him. And –
Carroll: It's kind of important. Yes. [Laughter]That's right. And so, even in your love life… I was very happy that there's an item in the index of my book that says, "Love, Bayesian analysis of." I think that every book should have that item in their index.
Mirsky: That's really good stuff. The book is so sweeping that I honestly don't know where to go next. What would you like to talk about?
Carroll: Well, it's – there's a lot of stuff in the book that is very familiar to me: quantum mechanics, field theory, particle physics, cosmology type stuff. But then, at the exact opposite end there is stuff that I'm certainly not an expert in. And there's philosophy in there, but actually, I know that better than I know the biochemistry in the book when you're talking about the ATP molecules and how they're synthesized and ATP synthase. I didn't know any of that two years ago when I started contemplating this book.
But I did know – or, I had the conviction with high credence – that if naturalism must be true, then given what I know about entropy and the laws of thermodynamics, there must be a way that the energy we get from the sun can ultimately be traced to how I contract my muscles to lift up a glass of wine at night. And so, I set myself that task – like, follow the path of a photon from the sun to contracting the muscle fibers in my arm. And it works. You can do it. And I was just delighted to be able to figure that out.
Mirsky: Yeah, you do trace that entire process. You remind me – there's this section of the book where you talk about some people think that every particle has consciousness. Was it pan-?
Carroll: The idea, yes.
Mirsky: And I remember about ten years ago it hit me that for a photon that was created at the Big Bang – which now we agree we're not really clear on – but anyway, no time has passed.
Carroll: That's right.
Mirsky: And it kind of freaked me out a little bit.
Carroll: [Laughs]Photons don't carry clocks. That is correct.
Mirsky: So – and it's impossible to do this, but if the photon had consciousness, it would – well, it couldn't because it's still in the same instant of its creation.
Carroll: Yeah. So, this is – I think this is a very interesting path to go down because I actually give credit in some sense to the people who buy into panpsychism, even though I don't buy into it at all myself. But I admire the courage of their convictions because they're not sidestepping the hard questions. It starts from a starting point that seems very reasonable. It's the idea that, okay, we agree that we're made of atoms and particles and forces. And we agree that our brains are made of these particles, for example. And we agree that in the process of thinking and being conscious our brains play an important role. Okay? They – whether or not they're the whole story, certainly our brains are important.
But then, there – there's a divide. Some people like me want to say that your brains are the whole story, and when we talk about being conscious and having experiences we're just describing what is happening in our brains in a certain way. And there are others who think that that story is incomplete, that there's no way at a deep level that a collection of atoms can truly have an experience, can know what it is like to see the color red for the first time, for example. There must be something over and above the physical description of the atoms of the brain.
They don't necessarily want to go all the way to Descartes, who believed that there is an immaterial soul that was completely separate. So, they say, "Well, maybe the actual particles in your atoms have mental properties as well as physical properties. You can completely describe the physical situation but you haven't described everything because there is some sort of conscious perception that is over and above the physical properties."
Now, you might want to explore that, and that's perfectly respectable. But then, one question that the skeptic could ask is "If the particles in your brain have mental properties, what were those properties doing before life existed?" For most of the history of the universe, billions of years, these particles are just floating around with mental properties that weren't doing anything. So, they take that criticism seriously and they say, "Well, maybe they were doing something. Maybe there was some primitive, very, very proto kind of consciousness that even exists in individual particles and atoms."
So, at that point I would say, "Ha, ha, ha – therefore it's wrong." Right? Because that's clearly silly. But to their credit, they're at least running with that idea and seeing where it takes them.
Mirsky: Yeah. Years ago I was talking to a Nobel Laureate in physics – I'm sorry, I can't remember who – but he had isolated an electron. So, it was all by itself. And I asked him – not because I believe any of this stuff, but I just wanted to see what he'd say – I said, "Do you think that electron was lonely?" And he didn't brush it off.
Carroll: Didn't laugh. Right.
Mirsky: So, I just remember that – and that's an indication of being willing to at least momentarily consider all these different things, which I think is important.
Carroll: And I think there's – there is – very common among scientists, physicists, biologists, et cetera, to sort of resist using language of intentionality and emotions when we talk about inorganic things. Right? The anthropomorphic fallacy. I actually use such language more than average in this book, and there's a reason why. And I'm thinking now that the book is in print and so forth maybe I was too subtle about my reason why; maybe I should have been more obvious. I think that we make the mistake – there's an old story about Sidney Morgenbesser, the Columbia philosopher, that he went to a talk by B.F. Skinner, the behaviorist philosopher, and Skinner was saying how we make the mistake in psychology of we should just look at what people do; we shouldn't look at their inner mental states. And Morgenbesser says, "I get what you're saying. What you're saying is we shouldn't anthropomorphize human beings." [Laughter]
And the point is I think that rather than saying, "No, we shouldn't use language of intentionality to describe inorganic things," we're all inorganic things at some level. We're all made of the same atoms. Right? The question is not there's this legitimate notion of intentionality when you talk about people or animals and it becomes illegitimate everywhere else; we should be interrogating when it's legitimate. Does it make sense? Why can we use that language even for people? And if that's true, then maybe sometimes we can use it for non-people as well.
Mirsky: Just recently I interviewed Franz de Waal about his new book, Are We Smart Enough to Know How Smart Animals Are?
Carroll: I'm a big fan, yeah.
Mirsky: And he talks about some of this same thing. Anthropomorphism was really to be avoided in all costs in his world of research, and Jane Goodall kind of changed that. And it's good to change it because you get to a whole different way of thinking about the subjects that we're dealing with. And he also talks so much about this – the question of how you know what you think you know –
Carroll: Right. Right, right.
Mirsky: – When you're dealing with these other beings. And I was thinking about it when I was reading your book. You have the Chinese room –
Carroll: Thought experiment. Yeah.
Mirsky: – Experiment, thought experiment. And basically, you're interacting with another human being in a language you don't understand just by putting papers back and forth through a slot in the wall. And I was thinking how much that's like trying to do research on animal intelligence.
Carroll: That's right. Or, the reason why the Chinese room was first proposed by John Searle – he wasn't thinking about theories of consciousness; he was thinking about artificial intelligence. And his point was that it is literally impossible to imagine a computer, an artificial intelligence, truly having understanding or consciousness. Because even if it could mimic those properties, as Alan Turing set up the imitation game – right? – even if you couldn't tell by asking questions of a computer whether it was artificial or a human being, Searle says, "But it's still not really understanding. It's just mindlessly pushing around symbols."
And from a physicalist point of view to a poetic naturalist, there is nothing but pushing around particles and symbols. Right? That's all that anything does. So, the question is when does it talk – when does it make sense, when is it useful or helpful to speak in the language of understanding and intentionality, whether it's a human being or a box full of Chinese symbols or an alien or a computer.
Mirsky: You mentioned Morganbesser. You have a different Morganbesser in the book, and maybe that's a good place to wrap up.
Carroll: I had to limit my number of Morganbesser anecdotes because he was a wonderful – I never met him, to my great regret, but many of my friends tell wonderful stories. So, the other quote that is in the book when I talk about why there is something rather than nothing, the conventional, eternal question that people debate about. And I try to deflate the question a little bit in the book. I think that it might be that the answer is just, "Well, that's the way it is." And I quote the Stanford Encyclopedia of Philosophy as saying, "Well, why not? Why shouldn't there be something?" And –
Mirsky: I think you say, "Well, that's the correct answer."
Carroll: I think that's the correct answer. Why not? It might be the correct answer.
And so, Morganbesser's answer was "If there were nothing, still you'd be complaining." [Laughs]And that sort of catches the essence of it. Maybe why this universe exists at all isn't really the question that is getting at scratching our explanatory itches.
Mirsky: But if a tree falls in the forest and you're not there to hear it, can you complain about the noise?
Carroll: Yeah, exactly. [Laughs]The physics says the noise is there, but what I care about is whether I can complain about it.
SMirsky: The Nobel prize winner whose name escaped me when I spoke with Carroll was 1989 physics laureate Hans Dehmelt, who I'm happy to report is still carrying on the Krebs cycle at the age of 93. That's it for this episode. Get your science news at our website, www.scientificamerican.com, where you can check out the full five-minute appearance of our space and physics editor Clara Moskowitz on Hardball with Chris Matthews on May 11. Seems that Hillary Clinton promised to open up the files on UFOs in Area 51 if she becomes president. Clara explained to Chris that if that info gets declassified, it will not require Donald Trump to plan a much, much, much, much, much higher wall.
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