Sean Carroll: The Nature of the Universe, Life, and Intelligence | Lex Fridman Podcast #26

1. 0:00 – 15:00

   The following is a…

   1. LFLex Fridman0:00

      The following is a conversation with Sean Carroll. He's a theoretical physicist at Caltech, specializing in quantum mechanics, gravity, and cosmology. He's the author of several popular books, one on the arrow of time called From Eternity to Here, one on the Higgs boson called Particle at the End of the Universe, and one on science and philosophy called The Big Picture: On the Origins of Life, Meaning, and the Universe Itself. He has an upcoming book on quantum mechanics that you can pre-order now called Something Deeply Hidden. He writes one of my favorite blogs on his website, preposterousuniverse.com. I recommend clicking on the Greatest Hits link that lists accessible interesting posts on the arrow of time, dark matter, dark energy, the Big Bang, general relativity, string theory, quantum mechanics, and the, uh, big meta questions about the philosophy of science, God, ethics, politics, academia, and much, much more. Finally, and perhaps most famously, he's the host of a podcast called Mindscape that you should subscribe to and support on Patreon. Along with The Joe Rogan Experience, Sam Harris's Making Sense, and Dan Carlin's Hardcore History, Sean's Mindscape podcast is one of my favorite ways to learn new ideas or explore different perspectives on ideas that I thought I understood. It was truly an honor to meet and spend a couple hours with Sean. It's a bit heartbreaking to say that for the first time ever, the audio recorder for this podcast died in the middle of our conversation. There's technical reasons for this having to do with phantom power that I now understand and will avoid. It took me one hour to notice and fix the problem. So, much like the universe is 68% dark energy, roughly the same amount from this conversation was lost, except in the memories of the two people involved and in my notes. I'm sure we'll talk again and continue this conversation on this podcast or on Sean's. And of course, I look forward to it. This is the Artificial Intelligence Podcast. If you enjoy it, subscribe on YouTube, iTunes, support it on Patreon, or simply connect with me on Twitter @lexfriedman. And now, here's my conversation with Sean Carroll. What do you think is more interesting and impactful, understanding how the universe works at a fundamental level or understanding how the human mind works?

   2. SCSean Carroll2:29

      You know, uh, of course, this is a crazy, meaningless, unanswerable question in some sense-

   3. LFLex Fridman2:33

      Yeah.

   4. SCSean Carroll2:33

      ... because they're both very interesting and there's no absolute scale of interestingness that we can rate them on. There's the glib answer says, "The human brain is part of the universe," right? And therefore, understanding the universe is more fundamental than understanding the human brain.

   5. LFLex Fridman2:47

      But do you really believe that once we understand the fundamental way the universe works at the particle level, the forces, we would be able to understand how the mind works?

   6. SCSean Carroll2:55

      No, certainly not.

   7. LFLex Fridman2:56

      All right.

   8. SCSean Carroll2:56

      We cannot understand how ice cream works just from understanding-

   9. LFLex Fridman2:59

      Yeah.

   10. SCSean Carroll2:59

       ... how particles work, right? So I'm a big believer in emergence. I'm a big believer that there are different-

   11. LFLex Fridman3:05

       Mm-hmm.

   12. SCSean Carroll3:05

       ... ways of talking about the world beyond just the most fundamental microscopic one. You know, w- when we talk about tables and chairs and planets and people, we're not talking the language of particle physics and cosmology. So, but understanding the universe, you didn't say, "Just at the most fundamental level," right?

   13. LFLex Fridman3:24

       Mm-hmm.

   14. SCSean Carroll3:24

       So understanding the universe at all levels is, is part of that. I do think, you know, to be a little bit more fair to the question, there probably are general principles of complexity, biology, information processing, memory, knowledge, creativity that go beyond just the human brain, right?

   15. LFLex Fridman3:45

       Mm-hmm.

   16. SCSean Carroll3:45

       And, and maybe one could count understanding those as part of understanding the universe. The human brain, as far as we know, is the most complex thing in the universe. So there's, it's certainly absurd to think that by understanding the fundamental laws of particle physics you get any direct insight on how the brain works.

   17. LFLex Fridman4:02

       But then there's this step from the fundamentals of particle physics to information processing-

   18. SCSean Carroll4:08

       Yeah.

   19. LFLex Fridman4:08

       ... which a lot of physicists and philosophers maybe a little bit carelessly take when they talk about artificial intelligence. Do you think of, um, the universe as a kind of a computational device?

   20. SCSean Carroll4:21

       No.

   21. LFLex Fridman4:22

       (laughs)

   22. SCSean Carroll4:22

       To be like the honest answer there is no. Uh, there's a sense in which the universe processes information, clearly. There's a sense in which the universe is like a computer, clearly. But in some sense, I, I think I, I tried to say this once on my blog and no one agreed with me, but the universe is more like a computation than a computer, because the universe happens once. A computer is a general-purpose machine, right? That you can ask it different questions, even a pocket calculator, right? And it's set up to answer certain kinds of questions. And the universe isn't that. So information processing happens in the universe, but it's not what the universe is.

   23. LFLex Fridman4:59

       Because-

   24. SCSean Carroll4:59

       And I know your MIT colleague, Seth Lloyd, feels very differently about this, right?

   25. LFLex Fridman5:03

       (laughs) But you're thinking of, uh, the universe as a closed system.

   26. SCSean Carroll5:07

       I am.

   27. LFLex Fridman5:07

       So, so what, what makes a computer more like a, like a PC, uh, l- like a computing machine is that there's a human that every once ... c- comes up to it and moves the mouse around.

   28. SCSean Carroll5:18

       Yeah.

   29. LFLex Fridman5:19

       So input-

   30. SCSean Carroll5:19

       Gives it input.
2. 15:00 – 30:00

   The question I'd like…

   1. SCSean Carroll15:00

      (laughs) And if there had been billions, we would have noticed already. To... For there to be literally, like, a small number, like, you know, Star Trek, there's, you know, a dozen intelligent, uh, civilizations in our galaxy, but not a billion. Uh, that, that's weird. That, that, that's sort of bizarre to me. It's easy for me to imagine that there are zero others because there's just a big bottleneck to making multicellular life or technological life or whatever. It's very hard for me to imagine that there's a whole bunch out there that, that have somehow remained hidden from us.

   2. LFLex Fridman15:32

      The question I'd like to ask is what would intelligent life look like? The... What I mean by that question and where it's going is what if, um, intelligent life is just fundament- list- is in some very big ways different than o- the one that has, uh, on, that has on Earth?

   3. SCSean Carroll15:51

      Yeah.

   4. LFLex Fridman15:51

      That there's all kinds of intelligent life that operates at different scales of both size and temporal.

   5. SCSean Carroll15:57

      Right. That's a great possibility because I think we should be humble about what intelligence is, what life is. We don't even agree on what life is, much less-

   6. LFLex Fridman16:04

      Right.

   7. SCSean Carroll16:04

      ... what intelligent life is, right? So that, that's an argument for humility is saying there could be intelligent life of a very different character, right?

   8. LFLex Fridman16:13

      Mm-hmm.

   9. SCSean Carroll16:13

      Like, you could imagine that dolphins are intelligent but never invent space travel 'cause they live in the ocean and they don't have thumbs, right? So they never invent technology, they never invent smelting. Maybe the universe is full of intelligent species that just don't make technology, right? That, that's compatible with the data, I think. And, and I think maybe, maybe what you're pointing at is even more out there versions of intelligence, you know, intelligence in, uh, intermolecular clouds or on the surface of a neutron star or in between the galaxies in giant things where the equivalent of a heartbeat is 100 million years.

   10. LFLex Fridman16:54

       Right.

   11. SCSean Carroll16:56

       On the one hand, yes, we should be very open-minded about those things. On the other hand, we all, all of us share the same laws of physics. There might be something about the laws of physics, even though we don't currently know exactly what that thing would be, that makes meters and years the right length in time scales for intelligent life. Maybe not.

   12. LFLex Fridman17:20

       Hmm.

   13. SCSean Carroll17:20

       But, you know, we're made of atoms. Atoms have a certain size. We orbit stars. Stars, stars have a certain lifetime. It's not impossible to me that there is a sweet spot for intelligent life that we find ourselves in, so I'm open-minded either way. I'm open-minded either being humble and there's all sorts of different kinds of life or no, there's a reason we just don't know it yet why life like ours is the kind of life that's out there.

   14. LFLex Fridman17:42

       Yeah, I'm of two minds too, but I, I often wonder if our brains is just designed to, uh, quite obviously to operate and see the world in th- on these time scales, and we're almost blind and, and the tools we've created for detecting things are blind-

   15. SCSean Carroll18:00

       Yeah.

   16. LFLex Fridman18:01

       ... to the kind of observation needed to see intelligent life at other scales.

   17. SCSean Carroll18:04

       Well, I'm totally open to that, but... So here's another argument I would make. You know, we, we have looked for intelligent life, but we've looked at, for it in the dumbest way we can, right?

   18. LFLex Fridman18:14

       Yes.

   19. SCSean Carroll18:14

       By turning radio telescopes to the sky.

   20. LFLex Fridman18:16

       Yeah.

   21. SCSean Carroll18:16

       And-Why in the world would a super advanced civilization randomly beam out radio signals wastefully in all directions into the universe? That just doesn't make any sense. Especially because in order to think that you would actually contact another civilization, you would have to do it forever. You'd have to keep doing it for millions of years. That sounds like a, a waste of resources. If you thought that there were other solar systems with planets around them where maybe intelligent life didn't yet exist, but might someday-

   22. LFLex Fridman18:48

       Mm-hmm.

   23. SCSean Carroll18:48

       ... you wouldn't try to talk to it with radio waves. You would send a spacecraft out there, and you would park it around there, and it would be like, from our point of view, it would be like 2001, where there's an, you know, uh, an monolith.

   24. LFLex Fridman19:00

       Monolith.

   25. SCSean Carroll19:01

       So there could be an artifact. In fact, it, the other way works also, right? There could be artifacts in our solar system, uh, that are, uh, have been put there by other technologically advanced civilizations, and that's how we will eventually contact them, uh, and we ha- just haven't explored the solar system well enough yet to find them. The reason why we don't think about that is 'cause we're young and impatient, right?

   26. LFLex Fridman19:21

       Right.

   27. SCSean Carroll19:21

       Like, it would take more than my lifetime to actually send something to another star system and wait for it and then come back. So, but, uh, if, if we start thinking on hundreds of thousands of years or million-year timescales, that's clearly the right thing to do.

   28. LFLex Fridman19:34

       Are you excited by the thing that Elon Musk is doing with SpaceX in general? Space, but the idea of space exploration, even though your, or your species is young and impatient?

   29. SCSean Carroll19:45

       Yeah. No, I do think that space travel is crucially important, long term, even to other star systems, and I think that many people overestimate the difficulty because they say, "Look, if you travel 1% the speed of light to another star system, we'll be dead before we get there," right? And I think that it's much easier, and therefore, when they write their science fiction stories, they imagine we go faster than the speed of light 'cause otherwise-

   30. LFLex Fridman20:10

       Yeah.
3. 30:00 – 34:34

   Yeah. …

   1. LFLex Fridman30:00

      In fact, I was a little disillusioned when I realized that academia is very siloed.

   2. SCSean Carroll30:06

      Yeah.

   3. LFLex Fridman30:07

      And so the question is...How, w- at your own level, how do you prepare for these conversations? How do you think about these conversations? How do you open your mind enough to m- have these conversations? And then maybe a little bit broader, how can you advise other scientists to have these kinds of conversations? Not at the podcast, uh, the fact that you're doing a podcast is awesome, the other people get to hear them.

   4. SCSean Carroll30:30

      Oh, yeah. Yeah.

   5. LFLex Fridman30:31

      But, it's also good to have it with op mics, in general.

   6. SCSean Carroll30:34

      Right. It's a good question, but a tough one to answer. I think about, you know, a guy I know who's a personal trainer, and he was asked on a podcast, "How do we, you know, psych ourselves up to do a workout? How do we make g- that discipline to go and work out?" And he's like, "Why are you asking me? Like, I can't stop working out."

   7. LFLex Fridman30:51

      (laughs)

   8. SCSean Carroll30:52

      "Like, I don't need to psych myself up." So, and likewise, you know, you ask me, like, "How do you get to like have interdisciplinary conversations and all sorts of different things with all sorts of different people?" I'm like, "That's- that's what makes me go," right?

   9. LFLex Fridman31:04

      (laughs)

   10. SCSean Carroll31:04

       Like that's, I- I couldn't stop doing that. I did that long before any of them were recorded. In fact, a lot of the motivation for starting recording it was making sure I would read all these books that I had purchased, right?

   11. LFLex Fridman31:15

       (laughs)

   12. SCSean Carroll31:15

       Like I had all these books I wanted to read.

   13. LFLex Fridman31:17

       Yeah.

   14. SCSean Carroll31:17

       Not enough time to read them, and now, if I have the motivation, 'cause I'm gonna, you know, interview Pat Churchland, I'm gonna finally read her b- her book, you know?

   15. LFLex Fridman31:26

       Hm.

   16. SCSean Carroll31:27

       And, it's absolutely true that academia's extraordinarily siloed, right? We don't talk to people. We- we rarely do. And in fact, when we do, it's punished. You know?

   17. LFLex Fridman31:37

       Right.

   18. SCSean Carroll31:37

       Like, the people who do it successfully generally first became very successful within their little siloed discipline-

   19. LFLex Fridman31:43

       Yep.

   20. SCSean Carroll31:43

       ... and only then did they start expanding out. If you're a young person, you know, I- I have graduate students, and I try to be very, very candid with them about this, that it's, you know, most graduate students do not become faculty members, right? It's a- it's a tough road. And so, live the life you want to live, but do it with your eyes open about what it does to your job chances, and the more broad you are, and the- the- the less time you spend hyper-specializing in your field, the lower your job chances are. That's just an academic reality. And it's terrible and I don't like it.

   21. LFLex Fridman32:18

       Yeah.

   22. SCSean Carroll32:18

       But it's a reality. And for some people, that's fine. Like there's plenty of people who are wonderful scientists who have zero interest in branching out and talking to things, to anyone outside their field. But it- it- it is, uh, disillusioning to me, some of the, you know, romantic notion I had of the intellectual/academic life is belied by the reality of it. The idea that we should reach out beyond our discipline, and that is a positive good, is just so rare in, uh, universities that it may as well not exist at all.

   23. LFLex Fridman32:53

       But, that said, even though you're saying you're doing it, like the personal trainer because he just can't help it, you're also an inspiration to others. Like, I could speak for myself, you know, I also have a career I'm thinking about, right?

   24. SCSean Carroll33:09

       Yeah.

   25. LFLex Fridman33:09

       And without your podcast, I may have not have been doing this at all. Right? So, um, it makes me realize that these kinds of conversations is kind of what science is about, uh, in many ways. What, the reason we write papers, this exchange of ideas, uh, is, uh, is much harder to do in disc- disciplinary papers, I would say.

   26. SCSean Carroll33:31

       Yeah. That's correct. Right.

   27. LFLex Fridman33:32

       And- and conversations are easier. So conversation is the beginning, and uh, in the field of AI, that's inter- it's- it's obvious that we should think outside of, uh, pure computer vision competitions on a particular data set. We should think about the broader impact of how this can be, y- y- you know, reaching out to- to physics, to psychology, to neuroscience and- and having these conversations. So that you're an inspiration, and so n- never-

   28. SCSean Carroll34:01

       Well thank you very much. That's very sweet, but...

   29. LFLex Fridman34:03

       You never know how the world changes. I mean, uh, the- the fact that this stuff is out there, and I've a huge number of people come up to me, grad students really loving the podcast, inspired by it, and they will probably have that, there'll be ripple effects when they become faculty and so on, so, we can end on a- on a balance between pessimism and optimism.

   30. SCSean Carroll34:25

       (laughs)

Episode duration: 34:49