Joe Rogan Experience #1352 - Sean Carroll

Joe Rogan 0:04 And here we go. Hello, Sean.

Sean Carroll 0:05 Hey, Joe. How's it going?

Joe Rogan 0:06 Thanks for being here again, man.

Sean Carroll 0:07 Sure.

Joe Rogan 0:07 I really appreciate it. So, uh, over the weekend, I got into your book. Whew.

Sean Carroll 0:13 Yes.

Joe Rogan 0:14 Yes.

Sean Carroll 0:14 (laughs)

Joe Rogan 0:14 It's great-

Sean Carroll 0:15 Thank you.

Joe Rogan 0:16 ... but, um, I mean, I really appreciate someone like you who's trying to break down quantum mechanics and quantum physics for someone like me. It's very hard to follow, and there was a lot of backing up and trying it again, and backing up and trying it again, and, like, just going over paragraphs and trying to figure out exactly what it means. But, uh, it's, it's really excellent and really perplexing at the same time.

Sean Carroll 0:40 Well, thank you. And you know, it, there are different styles when it comes to writing popular books, and I think there should be different styles. And my particular style is, look, it's not gonna be a breezy page-turner.

Joe Rogan 0:52 Right.

Sean Carroll 0:53 Uh, but if you read it carefully, like, there's no prerequisites. You don't have to come into it w- as an expert. What you have to come into it is someone who's willing to sit and think about every paragraph, and then hopefully it'll be rewarding and you'll truly understand what's going on after doing that.

Joe Rogan 1:07 Well, it is rewarding 'cause it is fascinating. And the history of quantum physics is also pretty fascinating 'cause I've always wondered, like, how did anybody even want to come up with this stuff? Like, these-

Sean Carroll 1:19 Yeah.

Joe Rogan 1:19 ... and the fact that it was so long ago, it was w- the beginnings of it were in the 19th century?

Sean Carroll 1:24 Well, 1900 is the typical, literally that year, the turn of the century when Max Planck first, uh, got the first hints of it. And then yeah, it was, took another 27 years to put it into final shape.

Joe Rogan 1:35 Now, for regular people that don't have a background of physics or that don't... This is, like, the whole idea behind it is so bizarre. It's like, why would anybody try to figure out something that... One of the things that you said that's really interesting is that you, quantum physics is used all the time.

Sean Carroll 2:00 Right.

Joe Rogan 2:00 It's used with exact calculations, but yet we don't really understand it.

Sean Carroll 2:08 Yeah. Yeah, no, that's the main message of the book, really, because (clears throat) physicists, of course, do quantum mechanics every day, whether it's, you know, straightforward quantum mechanics, quantum field theory, quantum information, quantum computing. Clearly we're pretty good at it, you know? Like, transistors and lasers depend on quantum mechanics. The sun shining, figuring th- that out depends on quantum mechanics. The Higgs boson, et cetera. So to claim that we don't understand quantum mechanics is a little bit weird, but then we have quotes from people like Richard Feynman saying, "Nobody understands quantum mechanics," right?

Joe Rogan 2:37 Yeah.

Sean Carroll 2:37 And so if he says that, then there's some authority behind it. And the reason is what we have is sci- sort of a black box, right? We, we say, you know, what, I think what I said in, uh, a New York Times article I wrote recently is physicists understand quantum mechanics in the same way that someone who owns a smartphone understands the smartphone. Like-

Joe Rogan 2:55 Ah.

Sean Carroll 2:55 ... they know how to use the apps. They can call people, they can make phone calls, they can take pictures. They don't know what's going on inside. And that's physicists with quantum mechanics. They, they use it, they can make very, very precise predictions, but if you ask them what is really going on, like, what is actually happening, what are all the details are like, "Yeah, no, that's not our job. Let's just stick to predictions."

Joe Rogan 3:16 But to someone like me, that's so terrifying because, like, the, the very nature of reality is being examined by people. Like, s- if, if it is a, a f- a smartphone, it's being examined by people like me-

Sean Carroll 3:30 Yeah. (laughs)

Joe Rogan 3:30 ... who don't really understand the smartphone. I have no idea what, what's going on inside a smartphone. I've no... I know some words that have, y- used to-

Sean Carroll 3:39 Yep.

Joe Rogan 3:39 ... describe RAM and processors and-

Sean Carroll 3:42 Probably electrons moving around-

Joe Rogan 3:43 Yeah.

Sean Carroll 3:43 ... in there, right? But, uh-

Joe Rogan 3:44 Yeah.

Sean Carroll 3:45 ... yeah, and I think, and s- in some sense, that's fine. Like, most of us don't need to know what's going on inside the smartphone to use it, but somebody (laughs) should know, right?

Joe Rogan 3:55 Yes.

Sean Carroll 3:55 And my argument in the book is, look, th- the, if 500 years from now when historians write the history of 20th century physics, they will say two things. Uh, one is, "My God, these people were so brilliant and creative to invent quantum mechanics, and then they were so afraid to really take it seriously and try to understand it." Like, they said like, "Stop asking questions about the meaning of reality and what the world is doing." In my mind, what physics is all about is understanding reality and what the world is doing. It's not just about making predictions. Making predictions is good, but we do that, uh, you know, mostly because we're curious about what the world is doing.

Joe Rogan 4:36 Well, for people outside the world of academia, when I read someone like you saying that you were discouraged from pursuing this, and y- you were literally told that you should be pursuing your work in cosmology and gravitation is, that's where it's at.

Sean Carroll 4:55 That's serious work, yeah.

Joe Rogan 4:56 Yeah. Th- that seems to me s- be so crazy. It's like, if anybody should be pursuing it, it should be people like you.

Sean Carroll 5:04 You know, I mean, I wanna be fair. So of course, 20th century physics was incredibly successful and, and there was... Part of the attitude was, look, we have to understand nuclear physics and particle physics. And, you know, a lot of it was the center of physics shifted from Europe to the US, and, and Europe is much more philosophical and, and, you know, willing to think about the deep ideas. And Americans are pretty pragmatic and wanna build things, right?

Joe Rogan 5:27 Mm-hmm.

Sean Carroll 5:27 In particular, at the time, they wanted to build nuclear weapons. And so the idea of just really putting aside deep philosophical issues and putting stuff to work was attractive. And it- and the other issue is, you know, okay, let's say we do demand that we understand quantum mechanics better. H- how do you do it? Like, what experiment is it there that you can do? As, as-

Joe Rogan 5:46 Right.

Sean Carroll 5:46 ... far as we know, the cookbook that we have, even though we don't understand it, works pretty well. Like, what, what could you type into your smartphone that would help you understand what's going on inside? It's kind of hard to figure out. So I think that those attitudes were wrong, but at least, you know, they're not completely crazy. It's not just that they, uh, were afraid of the truth or anything like that. And I also think that it is finally changing now. I think that there's slowly, slowly, slowly more people are appreciating that understanding quantum mechanics is important.

Joe Rogan 6:12 What, what do you attribute that to?

Sean Carroll 6:14 Um, a couple of things. One is (laughs) I mean, there's good news and bad news. Uh, part of the good news is technology has gotten better, so we're trying to build quantum computers, for example. And guess what? You know, some of the ad hoc rules that we had for doing quantum mechanics might not be up to the task. We need to understand the details a little bit better. Um, the other, sadder thing is that s- so much of fundamental physics is kind of stuck right now, right? We haven't (clears throat) ... we literally have not been surprised by a new experimental result in fundamental physics since the 1970s.

Joe Rogan 6:51 Whoa.

Sean Carroll 6:51 Uh, the one... there's one exception to that, which is the universe accelerating in 1998, which was the dark energy. Um, we've had amazing accomplishments in experimental and observational physics. We found the Higgs boson. We found the top quark. We found gravitational waves, the microwave background, many, many things. But they were all predicted decades ago, right?

Joe Rogan 7:11 Mm-hmm.

Sean Carroll 7:12 So progress is driven by being surprised, and it's been a long time since we've been surprised, so some people, including myself, say well, one of the things to do in that situation is to take a step back and reexamine the foundations. Maybe, maybe we can take a broader look and think that we're walking down the wrong path.

Joe Rogan 7:29 Now, for people that don't have any background in physics, there, there's a, uh, a bit of an issue with, uh, public perception. And one of the things about public perception is films like What The Bleep?!

Sean Carroll 7:41 Yeah. (laughs)

Joe Rogan 7:42 That sort of throw this-

Sean Carroll 7:44 (laughs)

Joe Rogan 7:44 ... sort of cultish monkey wrench into the, you know... W- quantum physics is weird enough as it is-

Sean Carroll 7:52 Yeah.

Joe Rogan 7:52 ... without adding th- that movie was l- literally created by a channeler, right? I mean, wasn't-

Sean Carroll 7:58 A friend of mine, uh, David Albert, who is one of the leading philosophers of physics... And I should also give credit to philosophers here, because they have been taking quantum mechanics seriously longer than the physicists have, to be honest. Um, so David is one of many people who got a PhD in physics and then switched to philosophy because he cared about the foundations of quantum mechanics and no physics department would ever hire him, right?

Joe Rogan 8:16 That's hilarious.

Sean Carroll 8:17 And, uh, yeah, I tell the story-

Joe Rogan 8:18 He had to go in through the back door.

Sean Carroll 8:19 Yeah, I tell the story in the book, like, he wrote a bunch of influential papers as a graduate student, and then he went and said, uh, "I would like to, you know, make these papers my PhD thesis." And they said, "No, that's not really serious physics," and they punished him by making him write this incredibly technical mathematical paper on quantum field theory just to prove he could do it, and then he's like, "This... I don't wanna take this anymore. I'm switching fields." But anyway, he was in that film. He was in What The Bleep?! And they lied to him. They misrepresented themselves. They said, "We're doing a documentary about quantum mechanics," and they sat him down for three hours and asked him all these questions, you know, leading questions like, "Doesn't this mean that we're bringing reality into existence by looking at it?" And, and he's like, "No. That's not what it means. Let me explain to you." And then in the final film, there's like 30-second clips of him going, "Yes, that is a really important question." (laughs) Right?

Joe Rogan 9:10 Right. Mm-hmm.

Sean Carroll 9:11 Like, completely misrepresenting what he said.

Joe Rogan 9:13 Mm-hmm.

Sean Carroll 9:13 And so he went public after that and, uh, and complained about... and... uh, about the film, and he did... In a hilarious story, there was a, uh, event, some sort of convention put on in Santa Monica by supporters of the film that they thought it would be fun to get all of the people who were in the movie, In What The Bleep Do We Know?! and get them at... you know, and talk to them and charge people money to listen to them. But these people were not affiliated with the filmmakers, so they didn't know that David Albert had been completely misrepresented in the film, so they invited him. And he goes to this event in Santa Monica, and he gave a talk. You know, he, he decided... you know, he wondered, like, "Should I just go at all? But okay, I'll... why not? Let's reach a different audience." And he, he gave a talk, and he said, "Look, there's two things you can do when you are faced with fundamental puzzles of reality. One is you can face up to what the world is trying to tell you, and you can accept it and take it as what it is no matter what you like. The other is you can choose to tell a flattering story about yourself."

Joe Rogan 10:15 (laughs)

Sean Carroll 10:15 "And the people who made this movie have decided that the mysteries of quantum mechanics are really stories about how they are powerful and have influence over reality and so forth, but it's all nonsense." And the punchline is the audience loved it.

Joe Rogan 10:29 Ah.

Sean Carroll 10:29 They went nuts because what they wanted was a guru of some sort, and like-

Joe Rogan 10:32 Right.

Sean Carroll 10:32 ... he was just as good a guru (laughs) as anybody else.

Joe Rogan 10:35 Right, right.

Sean Carroll 10:35 So, you know, he had a better story to tell.

Joe Rogan 10:36 A reality-based guru.

Sean Carroll 10:37 Reality guru, yeah. Yeah.

Joe Rogan 10:39 Yeah.

Sean Carroll 10:39 Yeah. Yeah, so I think you're right. I mean, I think that quantum mechanics, I've said before, is, uh... of all the theories in the history of science, the most easily distorted and misrepresented in the popular mind.

Joe Rogan 10:50 Well, you've done an amazing job in this book of trying to boil it down for dummies like me, but (laughs) it's hard. It is, it is a complicated and insanely nuanced subject.

Sean Carroll 11:01 Yeah. (laughs)

Joe Rogan 11:02 And it's, it's one of those things where it, it... th- like, this many-worlds theory. Uh, j- just for one example, the, the... just the possibility that there is... like, explain that.

Sean Carroll 11:14 Sure.

Joe Rogan 11:14 Ex- explain... for, for people that don't understand what quantum mechanics even means, give them just, like, a little bit of that, and then-

Sean Carroll 11:22 Yeah.

Joe Rogan 11:22 ... explain many-worlds theory.

Sean Carroll 11:24 Yeah. Uh, good. This is what I'm here to do, so-

Joe Rogan 11:26 Thank you.

Sean Carroll 11:26 ... you know, an electron. Take an electron. Um, quantum mechanics should apply to the entire universe, but it becomes unmistakable when you look at little tiny things, right? So we always are talking about electrons or atoms and so forth. An electron has a position, and... well, sorry. Let me not even say that. That... even that was wrong. It's just so hard to correctly talk about quantum mechanics, right?

Joe Rogan 11:47 Right.

Sean Carroll 11:47 If you were Isaac Newton, before there was quantum mechanics, there was classical mechanics, and they... basically, quantum mechanics and classical mechanics are the only two big frameworks that have ever existed in physics. You know, classical mechanics was so good that everyone thought that was just right, and it was all a matter of filling in the details until quantum mechanics came along and changed things. In classical mechanics, an electron is a point. It has a position, a location in space, and it has a velocity. It's moving somewhere. And from that, you can predict what's gonna happen. Okay? Quantum mechanics says, "No, no, no."... the electron has a wave function. So i- there's a wave, you know, sometimes you hear this debate about, are, are things like electrons and photons particles or waves? The answer is that they are waves (laughs) . And the wave function has this weird property that when you're not looking at it, it's a wave, it's all spread out or it's localized somewhere, but it obeys an equation, the Schrodinger equation, so far so good, just like regular physics. There's a thing, the wave function, it obeys an equation, the Schrodinger equation, you can predict what's gonna happen next. But the weird thing about quantum mechanics is that there's a whole separate set of rules for what happens when you look at the thing, when you observe it, when you measure it.

Joe Rogan 12:56 That's where things get squirrelly-

Sean Carroll 12:58 Yes.

Joe Rogan 12:58 ... with people describing it, right?

Sean Carroll 13:00 Yes.

Joe Rogan 13:00 And that's where they wanna go woo-woo on you.

Sean Carroll 13:02 It's an opening to be woo-woo, right?

Joe Rogan 13:04 Yes.

Sean Carroll 13:04 When you say, like, "What do you mean (laughs) -"

Joe Rogan 13:06 Right.

Sean Carroll 13:06 "... observe something?" Like, does it have to be a conscious being? Could it be a video camera? You know, that's just weird, right?

Joe Rogan 13:12 Right. Right. Is it the act of measuring that changes things?

Sean Carroll 13:16 Well, this is the puzzle, okay? This is what is called the measurement problem of quantum mechanics, that the rules we teach our students at Caltech or anywhere else when we teach them quantum mechanics in their sophomore year of college, uh, the rules say when a system is observed, when it is measured, its state, its wave function changes dramatically, suddenly, and unpredictably.

Joe Rogan 13:42 Now, let me ask you this. How do we know this based on if, if you're measuring it and it changes, how do we know? Because we didn't measure it before. Like, what, what observations are we making that we understand the state of it before it's measured without measuring it?

Sean Carroll 13:57 Good. There's a couple of ways. So, um, let, let, let me make things even simpler. Forget about where the electron is located and think about the electron as spinning, right?

Joe Rogan 14:06 Okay.

Sean Carroll 14:07 The electron is spinning just like the Earth spins. It's really exactly like that. It's like a little spinning top, except when you measure the spin, you can sort of send the electron through a magnetic field and it will get deflected either up or down, depending on whether it's spinning spin up or spin down. You only ever get one of two answers. It's either going up or going down. It's nowhere in between. This is an empirical measured fact, okay? Um, so that's a part of quantum mechanics. That's, that's the quantum fact, that there's discrete set of possible answers to this question. Is it spinning clockwise or counterclockwise? Yes or no. It's just those two possibilities, nowhere in between. So if you're... if you have a magnetic field that is oriented vertically, send your electron through it, it gets deflected up. You say, "Oh, it's spin up." So now I've measured its spin. Now I know what its state is. If I send it through another magnetic field or- oriented vertically, it will always be deflected up every single time. We know what it is. We're gonna measure it. Measuring it, in this case, doesn't change it. It's in exactly that state. We know it, okay? Now, let's send it through a magnetic field that is oriented horizontally. So it's gonna be deflected either right or left. We know exactly what state it's in. It's spinning this way. But when you send it through that magnetic field that's oriented horizontally, it gets deflected left or right 50-50, unpredictably. There's no way we can predict it.

Joe Rogan 15:27 Mm-hmm.

Sean Carroll 15:27 And then once it is... So, okay, now it's been spinning up, you measured its spin left, let's say, send it through another magnet that is going vertically, and now it's 50-50 again. It could be spin up or spin down (laughs) . So somehow, even though we knew exactly what state it was in, we couldn't predict what would happen next. That is part of quantum mechanics.

Joe Rogan 15:47 So the act of sending it through these things where it makes it vertical or horizontal, in... What is, what is happening to it when it's going through these things?

Sean Carroll 15:56 So in quantum mechanics, what we say is that it's not that we don't know whether the electron is spinning clockwise or counterclockwise. Um, it can be in a super position of both. That's just the spin version of the position that the electron can be spread out in a, in a wave, right? It's r- it's truly not just that we are lacking some knowledge, it's that the knowledge really isn't there. And again, this is how we teach quantum mechanics in textbooks, and then I'm gonna correct it 'cause many worlds is much better-

Joe Rogan 16:26 Okay.

Sean Carroll 16:26 ... but this is the standard textbook version. There's a wave function, the wave function for a spin is it's either up or down or some combination, and then there's a rule that says when you measure the spin, you only get up or down. You don't see the wave function. Just like the cloud that you have for the electron's position, when you look at it, you see it at a location. So another way to get... to make the same argument is take a little piece of... I have a, a nice little, uh, image of this when I give talks, little piece of uranium, so it's a radioactive, uh, little chunk of metal, and you put it in a bubble chamber. So it is emitting radioactive particles and you detect the particles. You can see a little streak of, uh, of motion when the particle leaves the uranium, okay? Well, like I said, when you're not looking at it, this electron is supposed to obey an equation, the Schrodinger equation. And you can ask what the prediction is when a, when a radioactive nucleus decays and gives off an electron, what is its wave function gonna do? What is the wave function of the electron gonna be? And the answer is, it goes off in a spherical wave. It goes off in all directions at once.

Joe Rogan 17:32 Evenly.

Sean Carroll 17:33 Yeah. All directions evenly. But you never see that. You always see a line.

Joe Rogan 17:37 Is that roughly based on the shape of the piece of uranium? Does it vary?

Sean Carroll 17:41 No, because the electron gets, uh, from one individual nucleus of an atom, right? So the, the... what the ele- what the uranium is doing doesn't matter, it's just that one atom matters. And the easiest thing for the electron to do is just to go out in a sphere. It doesn't have to, it can go out in higher energy states, but the point is, it's not going out in a straight line. But when you look at it, you see a straight line, right? That's the fundamental mystery of quantum mechanics. That how we describe the thing when we're not looking at it is different than what we see when we look at it.

Joe Rogan 18:09 So when you're in pursuit of an understanding, a deeper understanding of, of quantum mechanics, w- you... when you... you're thinking about people from the 1900s that are just sort of basically g-... getting the first steps going to understand this stuff. When, when you're talking about this lack of funding and the lack of encouragement for people to pursue quantum mechanics, you strongly feel like there are answers to these questions.

Sean Carroll 18:39 Yeah, that's right.

Joe Rogan 18:39 That we just need better tools and a better understanding, better equations, more time.

Sean Carroll 18:45 Yeah. Me and Einstein think this, right? (laughs)

Joe Rogan 18:47 (laughs)

Sean Carroll 18:47 So, Einstein is one of the secret heroes of the book because he has this reputation as someone who just couldn't quite accept quantum mechanics. Uh, the title, Something Deeply Hidden, is a quote from Einstein, uh, when he was talking about when he was a kid and he had a compass, right? And he was given his first magnetic compass and he could rotate it this way and that way, and it always pointed north. And you and I would go, "Huh, that's cool." But he was Einstein. He's like, "Wow, this is amazing. Why, how does it know where north is," right?

Joe Rogan 19:12 Right.

Sean Carroll 19:13 And he said, "There must be something deeply hidden that explains why it's doing this mysterious thing." And he felt the same way about quantum mechanics, that it, we have, we gave these set of rules, which are called the Copenhagen Interpretation of Quantum Mechanics. One set of rules for when you're looking at it, one set of rules for when you're not. And Einstein was like, "Oh, come on. Clearly this is not the final answer to the nature of reality," right? He wanted to know God's thoughts. He's like, "I wanna know everything. We're not done yet. There must be more going on." And so many worlds is one of the proposed answers to what could be going on. It's not the only one. There's alternatives, but it's definitely my favorite. It's definitely the easiest one to, uh, to write down. Let's put it that way.

Joe Rogan 19:53 Okay, so hit us with this many worlds theory.

Sean Carroll 19:55 Okay. So think about this electron. You're gonna s- you, you say that it could be either spin up or spin down. It's a combination of both. That's its wave function. You measure it, you only ever see spin up or spin down. So Copenhagen says that's because the wave function suddenly changed, snapped into place when you observed it. Don't ask me what it means to observe something. That's not what Copenhagen lets you ask.

Joe Rogan 20:16 Okay.

Sean Carroll 20:17 Many worlds says what you're missing is two things. Number one, you are a quantum system.

Joe Rogan 20:24 Mm-hmm.

Sean Carroll 20:25 You are obeying the rules of quantum mechanics. You're made of atoms and electrons and so forth. You have a wave function too, okay? So you are secretly treating yourself as a classical thing when you make that measurement, but you really should be treating yourself quantum mechanically, right? That's one thing. And the other thing is, uh, something that Einstein invented, namely called entanglement. When quantum mechanics says there's a wave function for a system, it doesn't say there's a separate wave function for every particle, right? It says that there's only one wave function for the whole universe. So the way I like to say it is, imagine two particles come in and bounce off of each other. Either one has a wave function and it's, you know, unpredictable exactly what angle it's gonna go off at. So both of them, both of the particles that go off, you don't know where they're going, but because momentum is conserved, if they came in at equal velocities, they'll go out at equal velocities in opposite directions. If you measure one, then you know where the other one is going, right? That's entanglement. The observed state of one system can be related to the observed state of another system. So those are the two ingredients. You're a quantum system and quantum systems can be entangled with each other. So Hugh Everett, who was a graduate student when he invented this idea in the 1950s said, "Look, when you measure that electron, what happens physically?" Like forget about you're a person, you're conscious, all of that BS. Like you're a physical system. You obey the Schrodinger equation. You, you are a quantum mechanical system. You obey the laws of physics. So you look at the electron, your wave function changes. It used to be you're just a person doing whatever you do, but then after you look at the electron, you become entangled with it. And it splits. So there is one part of the wave function that says the electron was spinning clockwise and you measured it spinning clockwise. And there's another part of the wave function that says the electron was spinning counterclockwise and you saw it spinning counterclockwise. Now everybody knows this. Like that, that far, it's not controversial at all. That's clearly the prediction of the equations of quantum mechanics. But everyone else said, "Well, that means that I'm some weird combination of, I saw it spinning one way and I saw it spinning the other way, but I've never felt that way. When I look at real electrons, I see them one way or the other. That can't be right. That can't be the final answer. The wave function must somehow collapse." And Everett said, "No, what you're missing is there's now two separate worlds." Both of those part of the wave function are real, but they're different worlds. They will never interact with each other again. What happens in one part of the wave function will not affect what happens in the other part. So now there's a version of you that saw the electron spinning clockwise and there's another version of you that saw it spinning counterclockwise. And that's just taking seriously the prediction of quantum mechanics. It's not adding any extra stuff, any extra worlds, anything like that.

Joe Rogan 23:14 That is the part where my brain broke.

Sean Carroll 23:16 All right.

Joe Rogan 23:16 The, the idea that there's a you that observes it going clockwise and a y- a you that observes it going in a different direction, like that is so hard to understand.

Sean Carroll 23:27 (laughs)

Joe Rogan 23:27 Do you, would you apply this in your regular life? Like do you think, like when you go home and you say hi to your wife and you open up-

Sean Carroll 23:34 Yeah.

Joe Rogan 23:34 ... the refrigerator-

Sean Carroll 23:35 Yeah.

Joe Rogan 23:35 ... do you think of yourself as this quantum being that's e- existing in this super state?

Sean Carroll 23:41 So, I mean, there's a couple answers to that. One is, you know, sure. If I think about it, like I really do believe it. You know, I have a chapter in the book, which my editor resisted at, at, at first, but then he let me get away with it, which is a dialogue between, uh, a young philosopher and her father, who is a physicist. And the father is skeptical about all this philosophical nonsense, and she tries to explain how many worlds works to him. And at the end, you know, his last question is, you know, "Do you really believe this?" (laughs) He says, "You feeling taking this seriously?" And look, that's a perfectly atti- good question. It's a very respectable question because it is... Many worlds, it's not crazy or weird or bizarre, but it's certainly very, very far away from our everyday experience, right?

Joe Rogan 24:24 Right.

Sean Carroll 24:24 So what it's asking you to do is to say, I have these equations.... they are really, really good at fitting what I do observe in the world and making predictions. You know, I can build the Large Hadron Collider, et cetera. Um, I will take them seriously even for things that I can't directly observe, 'cause they're the best equations I have, right? Until a better set of equations come along, I will believe these equations. And the implication of that is, yeah, there's a whole bunch of worlds, like a huge number, like a real, you know, gi- humongously, unimaginably big number, maybe an infinite number, maybe finite, we don't know, of different copies of you and they're being created all the time. Uh, the good news is that it doesn't really affect how you go through life. It doesn't really, um, imply that you should behave any differently than you would if you just lived in one world.

Joe Rogan 25:16 But do you think of each choice that you make possibly changing everything about the world that you exist in? Do... how... are... are you... how are you looking at it?

Sean Carroll 25:27 (laughs) It's-

Joe Rogan 25:28 You know what I'm saying?

Sean Carroll 25:28 So, I do.

Joe Rogan 25:28 Because you... you are a guy who probably understands this as good as anybody that's alive. So as weird as this stuff sounds, to... to me, it sounds like an... I mean, it's almost impossible for me to comprehend. So I'm trying to filter it through-

Sean Carroll 25:42 Yeah.

Joe Rogan 25:42 ... your understanding of it.

Sean Carroll 25:44 Well, I think that-

Joe Rogan 25:44 He's taking his jacket off. We're getting serious here.

Sean Carroll 25:46 I know. It's getting hot in here.

Joe Rogan 25:47 (laughs)

Sean Carroll 25:48 Physics is heating us up. Um, yeah. I'm not... I'm not exactly sure how to say it the best. You know, um, it... it doesn't... it... it doesn't change who you are. It's certainly not true that you making a decision is what branches the wave function of the universe. I guess that's the right thing to say.

Joe Rogan 26:08 Good, 'cause I wanna stop all woo-

Sean Carroll 26:10 Yeah, you can't do that.

Joe Rogan 26:10 ... before it happens.

Sean Carroll 26:11 Everyone, you know, believe me-

Joe Rogan 26:12 Hit the brakes.

Sean Carroll 26:13 The joke about how certain political choices imply that we're living in the wrong branch of the wave function has been made many, many times, right?

Joe Rogan 26:19 Oh, okay.

Sean Carroll 26:19 But, uh, you... the... it's not that your choices create different universes. Different universes get created, and maybe you're different in them by a little bit. In fact, I... you know, I like to point out there is an app you can download if you have an iPhone called Universe Splitter, which will, uh, branch the wave function of the universe for you. And then if you agree ahead of time to do one thing in one branch and another thing in another branch, then there will be multiple copies of you who are living different lives. Then you can deal with that and your therapist however you like. But, uh-

Joe Rogan 26:47 But what is the application exactly doing?

Sean Carroll 26:50 What it's doing is, uh, basically a version of measuring the spin of-

Joe Rogan 26:54 It's called Universe Splitter?

Sean Carroll 26:55 ... an electron... Universe Splitter. It's only for iPhones.

Joe Rogan 26:57 Oh, I'm gonna grab this right now.

Sean Carroll 26:58 But, uh, yeah.

Joe Rogan 26:58 Sorry, Android people.

Sean Carroll 26:59 Yeah, sorry. It's not even a web page.

Joe Rogan 27:02 Okay.

Sean Carroll 27:02 It's only a... only an app. There's equivalent web pages, but...

Joe Rogan 27:04 Okay, I'm pulling it up right now.

Sean Carroll 27:05 Yeah, and what... so what you can do, basically it sends a signal to a lab that coincidentally is located in Geneva, Switzerland, but has nothing to do with the Higgs boson or anything like that. Um, they send a single photon down a pipe to what's called a beam splitter. So the wave function of the photon goes 50/50 it gets sent left, it gets sent right. And if you agree and so then it sends back whether you ended up in the branch of the wave function where it went left or where it went... There you go, 199. Come on.

Joe Rogan 27:33 Yeah, that's two bucks.

Sean Carroll 27:34 The power of changing the universe is in your hands.

Joe Rogan 27:36 I just... I downloaded it.

Sean Carroll 27:37 Good.

Joe Rogan 27:37 I got it. I paid for it. I got it right here.

Sean Carroll 27:39 Yeah.

Joe Rogan 27:39 All right.

Sean Carroll 27:40 So if you have any tough choices, uh, you can type in, like, you know, "I want to have pizza or I want to have Chinese food for dinner tonight."

Joe Rogan 27:47 Well, it says, "In one universe, I will take a chance. In the other one, I will play it safe." Oh, Jesus.

Sean Carroll 27:51 Yeah, but you can, uh... you can correct those. You can fill in whatever you want.

Joe Rogan 27:55 Really?

Sean Carroll 27:55 Yeah. That's the good part.

Joe Rogan 27:57 But what is... what is happening with this app?

Sean Carroll 27:58 I... I will ask her to marry me. I will not ask her to marry me.

Joe Rogan 28:01 Is this the-

Sean Carroll 28:01 Right? I mean, I will accept this job. I will go somewhere else.

Joe Rogan 28:03 ... equivalent of a quantum fortune cookie?

Sean Carroll 28:06 Yeah.

Joe Rogan 28:07 Yes.

Sean Carroll 28:07 But except that all possible fortunes (laughs) are obtained-

Joe Rogan 28:11 (laughs)

Sean Carroll 28:11 ... in different universes.

Joe Rogan 28:12 Ugh.

Sean Carroll 28:12 The bad news is you can't ever find out how things went in the other universes.

Joe Rogan 28:16 Oh, Christ.

Sean Carroll 28:16 You can't talk to the different universes.

Joe Rogan 28:18 That's the problem, right?

Sean Carroll 28:18 That's the problem, right.

Joe Rogan 28:19 So people will be paralyzed by analysis.

Sean Carroll 28:21 That's why it's... you should act the same as if you just live in one universe, 'cause you can never talk to the people in the other ones.

Joe Rogan 28:28 Mm-hmm. So but... now let's hit... hit the brakes on the woo again.

Sean Carroll 28:32 Yeah.

Joe Rogan 28:32 'Cause people would like to believe that there are... I mean, are there an infinite number of yous existing at the... at the... at the exact same time, making various choices which send you off into different directions?

Sean Carroll 28:48 So number one, we don't know if it's infinite number or just really big. But there's certainly a really, really big number. It's big enough to be, you know, big enough for whatever you want. But it's not everything. It's not... the theory does not say everything happens somewhere, right? The theory says the Schrodinger equation is obeyed. There's an equation that is obeyed. So electrons will never convert into protons because electrons are negatively charged and protons are positively charged. And nowhere in the Schrodinger equation can you violate the conservation of charge, right? So there's plenty of things that don't happen, but then there are plenty of things that do happen. And some things are more likely than others for you to experience. So again, it's... it's sort of a... uh, you know, it's a mind-bendy thing, but it's a straightforward prediction of the equations, and it doesn't affect our lives. It... it... there's no rule that says, you know, to be a moral person, to be a good utilitarian and make the world happy, knowing that the world... the wave function is branching into multiple copies, I should act differently somehow. It's... it's exactly the same as it would be in the ordinary world.

Joe Rogan 29:44 So y- y-... and you are the ordinary world no matter how copies... how many copies of you there are, or how many versions of you there are?

Sean Carroll 29:50 There's nothing... so when all these copies are being made, there's no essence of you that is traveling through one of the copies, right?

Joe Rogan 29:58 Right.

Sean Carroll 29:58 Like all these people are separate people. So I... I... I use the analogy, it's like identical twins. They were the same zygote or whatever, and now they're different people, okay? So that's the same thing. Like you're you now, and if you hit the button and branch the wave function, there'll be two different people, both of whom used to be you, but they're not the same person anymore 'cause different things happen to them.

Joe Rogan 30:19 Now when people think about the concept of quantum mechanics and the way you're talking about describing things in the micro and the macro, you think of your existence itself very similar-... in a very similar manner, the- the way you think of electrons, the way you think of things being quantum, is that you are a combination of all these quantum things.

Sean Carroll 30:45 Yeah.

Joe Rogan 30:45 So you don't operate in some sort of static state that's very, like, here and now, and, (knocks on desk) and, and carbon, and you could put it on a scale and it'll never change. There's constant versions of you.

Sean Carroll 30:58 Yeah, it's kind of like a whooshing, where, you know, more and more versions of you are being created all the time. And i- it's a, it's a interesting thing because even the best-trained physicists sort of think intuitively classically. Like, "Look, here's a table, there's a bottle," right?

Joe Rogan 31:13 Right. You have to.

Sean Carroll 31:14 And yeah, the, yeah, you have to. This is your-

Joe Rogan 31:15 Red light comes, hit the brakes.

Sean Carroll 31:16 And this is how we evolved, right?

Joe Rogan 31:18 Yes.

Sean Carroll 31:18 It's how our brains work, right? And th- like I said, you know, many-worlds is one respectable version of quantum mechanics. There are other respectable versions, more respectable than the textbook presentation. But they all- all the other ones somehow lean on our classical experience and the textbook version certainly does. It says, like, you're a classical person observing a quantum mechanical system and so forth. And Everett, when he was a graduate student, you know, he was- he had arguments across, uh, the ocean with people in Copenhagen, you know, who tried to push their way forward. And he's like, "W- who, why do you get to be classical and the electron has to be quantum?"

Joe Rogan 31:52 Mmm.

Sean Carroll 31:52 Like, "Why aren't you quantum?" Like, "Why isn't everything... What's so special about you, really?"

Joe Rogan 31:56 Right.

Sean Carroll 31:56 And he was trying to think of the quantum mechanics of the whole universe, right, where he was not a separate observer outside, because he's doing the whole universe all at once. And so everything had to be quantum. And I think that that's another thing that is pushing us to appreciate the foundations of quantum mechanics a little bit more, is that we're trying to understand quantum gravity, we're trying to understand quantum cosmology, the universe all at once obeying the rules of quantum mechanics, and the conventional Copenhagen theory is just not up to it.

Joe Rogan 32:23 When I was reading it, I was thinking... A- a thought came across my mind that it's almost like the human brain is a radio that's picking up a distant signal, but getting better and better at tuning into it all the time, and that we are thinking of ourselves in this very limited, primitive, biological way, because that's how we evolved. But slowly but surely, through people like you and through work on this stuff, we're gaining this more comprehensive view of what reality is itself, and that we're experiencing these stages of comprehension. And that- that's why, I mean, uh, you know, again, going off of what you're saying about your being, uh, potentially discouraged from pursuing these things, that's why this is so important, is like for most people, like myself, who don't have a background in this at all, the- the signal is so distant. But it seems like the more you folks study it and the- the clo- the more, the Large Hadron Collider and CERN and more of these experiments get done, the closer we get to just a better signal, just a little bit better signal. And we might be talking about generations from now.

Sean Carroll 33:33 Right, exactly. Yeah, but no, I like the analogy very much, because the human brain did not evolve to understand quantum mechanics, right?

Joe Rogan 33:40 Right.

Sean Carroll 33:40 It didn't understand, didn't evolve to understand science at all. Like, we're, uh, and, uh, some... My best friends are human beings, but we are wonderful bundles of impulses and heuristics and shortcuts and ways to rationalize our behavior and stuff like that. And the idea that we can aspire to be logical and to develop theories and reject them and to develop theories that are very, very far away from our everyday experience, uh, is a relative latecomer on the evolutionary scene, and we're still not really good at it. We're getting better at it. And th- this is part of it, you know? Quantum mechanics is the biggest challenge that we have in physics to our intuitive understanding of the world, and so there's a question, how should we try to understand it? How much of it should we lean on our intuitive understanding and how much should we just accept that the world is fundamentally super-duper different? And I think that's a perfectly good question. I'm not trying to prejudice the answer one way or the other. I mean, our experience is limited, but it's all we have, right? You know?

Joe Rogan 34:40 Yes.

Sean Carroll 34:40 We have to, we have to be based on that. And so some people wonder, is quantum mechanics just impossible to understand? Like, is the human brain not up to the task?

Joe Rogan 34:50 The current human brain, maybe.

Sean Carroll 34:51 The current human brain, sure. But I think that, no, I think that it, that's totally wrong. I think that, number one, quantum mechanics certainly is very understandable. And number two, I don't think that anything about nature is impossible to understand for the current human brain. I mean, maybe it is. There's no way of knowing for sure, but there's zero evidence that we will fail in our ambition to try to understand the universe. It's just hard and it takes time. Look, a hundred years ago, we didn't have quantum mechanics at all. Like, we've made enormous progress, and a hundred years is nothing, even in, uh, human life- human, uh, history, much less cosmological history. So don't be impatient.

Joe Rogan 35:26 (laughs)

Sean Carroll 35:27 Take time.

Joe Rogan 35:28 But it just seems to me that, that y- the- the human understanding of the world we live in is obviously radically changed over the last 500 years. And if we continue to exist in this current state or a slightly better state as things move on, it's going to get better. But quantum mechanics and quantum theory, to me, almost seems like an ant trying to understand the choices on Netflix. It's like those choices exist, but the- the ant really lacks all tool... I mean, without people like you-

Sean Carroll 36:02 Yeah.

Joe Rogan 36:02 ... espici- especially describing the computations and what's been done and what, what we currently understand, for a regular person with no background or even, uh, no knowledge of it, no, no, no one's ever explained it to them at all-

Sean Carroll 36:14 Yeah.

Joe Rogan 36:14 ... it's almost outside of the realm of our capacity for reasoning.

Sean Carroll 36:19 Nope, I gotta disagree.

Joe Rogan 36:20 Okay.

Sean Carroll 36:20 I think it's just hard.

Joe Rogan 36:21 Just hard.

Sean Carroll 36:21 I think there's a difference. I think that, and I could be wrong about this, but I think that, you know, there was a phase transition. There was some... You know how we talk in computer science about, um, a- a certain kind of computational machine being Turing-complete? I mean, maybe you don't know this, but this is something we s- we say.

Joe Rogan 36:38 Please explain that.

Sean Carroll 36:39 Tur- so a Turing machine, Alan Turing, the great, um-

Joe Rogan 36:42 Oh, okay.

Sean Carroll 36:42 ... um, computer scientist who broke codes and things like that-He also thought a lot about like what computation was and he invented the Turing Test for consciousness and stuff like that.

Joe Rogan 36:51 For AI, right?

Sean Carroll 36:51 And, uh, for AI, yeah.

Joe Rogan 36:53 Yeah.

Sean Carroll 36:53 And, but the Turing-complete is basically, there's a certain kind of computational device that can essentially do any computation that can be done. Like anything you c- you can ask if you can do this problem, then you can also do that problem, and there's sort of a maximal hardness to problems, and so a Turing machine can do that problem, if you give it enough time. And there's some problems that are undoable, so no machine can do those, but the doable ones can be done on a Turing-complete machine. So in some sense, uh, this is not a rigorous fact by any stretch, but I think there's an analogy with human reasoning. Like at some point, we're a little bit smarter than dogs and cats, um, but it's not just we're a little bit smarter, we're a different kind of smart. Like we did pass a threshold. We can use language. We can reason symbolically and abstractly. We can write things down and pass them down through generations. We can imagine futures in ways that they can't. So even though, you know, the number of neurons or the number of connections in our brain might not be that different between a human being and a chimpanzee, uh, it's a different kind of reasoning that has been opened up. We- we've been- become capable of this kind of thought. And I think that's enough. My, my idea is that we are smart enough to understand the laws of physics, whatever they turn out to be, quantum mechanics or something beyond quantum mechanics. And to the person on the street who's never learned anything about quantum mechanics, you know, it is so different from how you experience the world, that it seems bizarre and you do have to like read the same paragraph over and over again sometimes. But I think it is absolutely understandable if people make the effort. I don't think there's any person who, you know, can, uh, balance their checkbook but not understand quantum mechanics.

Joe Rogan 38:30 They just need to put the time in.

Sean Carroll 38:31 Yeah.

Joe Rogan 38:32 Put the time in and take your time, and go back.

Sean Carroll 38:34 And be open.

Joe Rogan 38:35 Yes.

Sean Carroll 38:35 Like don't as- the- the- the real thing that holds people back I think is ass- insisting ahead of time that they know how things work, right? That reality should work in a certain way.

Joe Rogan 38:44 Yes.

Sean Carroll 38:44 And you have to at least be open to the possibility that the way reality works is way different than what you had in mind. If you're open and you're willing to put in the work, you can understand it.

Joe Rogan 38:53 That's why I was curious as to how you apply it in your actual physical life, your-

Sean Carroll 38:57 Yeah.

Joe Rogan 38:57 ... knock on wood, ring a doorbell, you know, drive a car physical life.

Sean Carroll 39:03 Yeah, um, if I was thinking about quantum mechanics when I was driving my car, things would be much worse than- (laughs)

Joe Rogan 39:08 (laughs)

Sean Carroll 39:08 ... than they are. And that's because the classical world is a really good approximation. I mean, this is something I'm also-

Joe Rogan 39:14 Oh.

Sean Carroll 39:15 ... interested in.

Joe Rogan 39:15 (laughs)

Sean Carroll 39:16 Yeah, you know, that- that's- this is, uh, important. Emergence, right? I talked about this-

Joe Rogan 39:20 Mm-hmm.

Sean Carroll 39:20 ... in the last book, in The Big Picture. Um, think about this, when we- when we talk about the earth going around the sun, forget about quantum mechanics, just- just do classical mechanics, Isaac Newton, Earth orbiting the sun, okay? Um, we can predict that. We can write down the equations. We can tell you where the Earth was a million years ago or a million years in the future, right? But think about how amazing that is. The Earth is made of something like 10 to the 50th atoms, okay? In principle, to tell you what the Earth is doing, I should tell you what every one of those atoms is doing.

Joe Rogan 39:52 Mm.

Sean Carroll 39:52 Right?

Joe Rogan 39:52 Yes.

Sean Carroll 39:52 But I have no idea what every one of those atoms is doing. All I actually in the real world need to tell you to predict what the Earth is doing is to tell you w- the center of mass of the Earth, where it is and where it's moving. So only using an incredibly tiny amount of information, I can make incredibly precise and accurate predictions. I have this enormous handle over what the world's doing, ignoring almost all the data that there is about this persis- about the specific state of the world. So that's emergence. When you don't need to know almost anything about a system, you have certain very, very special high leverage pieces of information that you can use to make accurate predictions. So really, now that we know quantum mechanics, all of classical physics is like that. The fact that you can throw a baseball and know where it's gonna land and stuff like that, the fact that you can get a rocket to the moon or drive a car is because, without knowing quantum mechanics, is because Newton's laws of physics are a really, really good approximation that let you make predictions without knowing the quantum wave function of the car you're driving, right? And if you needed to know the quantum wave function of the car you were driving, you'll be hopeless. It's just, you know, computationally intractable. So the world appears to us in a way that it- that is very convenient in some ways. We- we need to know so little about the world to yet understand quite a bit of it. Uh, otherwise we couldn't get through the day.

Joe Rogan 41:13 The idea that everything is in motion is also very difficult for people to wrap their brain around. You see a stationary rock on the ground.

Sean Carroll 41:21 Yeah.

Joe Rogan 41:21 You- you think that rock is still, but it is not. Nothing is still.

Sean Carroll 41:27 You know, it's pretty still.

Joe Rogan 41:28 But it's a part of the Earth-

Sean Carroll 41:29 It's pretty still.

Joe Rogan 41:30 And Earth is spinning.

Sean Carroll 41:31 Sure, the Earth is spinning. That's- that's right.

Joe Rogan 41:32 So relatively, in terms of the universe, everything is in motion in some way, shape, or form.

Sean Carroll 41:38 Well, you know, this is a very- this is, you know, uh, uh, there's a lot going on here actually because on the one hand, Einstein teaches us, you know, when you say something is moving, you have to say with respect to what.

Joe Rogan 41:50 Right, right.

Sean Carroll 41:51 (laughs) Right?

Joe Rogan 41:51 Mm-hmm.

Sean Carroll 41:51 So if- if you're standing next to the rock, it's not moving with respect to you, right?

Joe Rogan 41:55 Mm-hmm.

Sean Carroll 41:55 If you're just st- stationary there. There's also what I- I try to squelch in the book, one of the misunderstandings about quantum mechanics is the idea of quantum fluctuations. The idea that an electron sitting in the- the orbit of an atom is really jiggling around there and you don't know exactly where it is. That's not what quantum mechanics says. Like if you're good ever ready in any way, uh, a good many worlds person, there's a wave function to the electron and the wave function is sitting there not moving. It's really not changing appreciably over time. If you were to observe the electron, you would see it somewhere and if you- to observe it multiple times, it would be in different places. So it looks to you like it's jiggling around, but when you're not looking at it, it's not jiggling. It's just sitting there quietly according to quantum mechanics.

Joe Rogan 42:36 So is this confusing description based on our limited ability to perceive?

Sean Carroll 42:42 It's actually based on the fact that we inevitably attach a notion of reality to what we do perceive, right?

Joe Rogan 42:48 Mm-hmm.

Sean Carroll 42:49 So in quantum mechanics, what we perceive is different than what really is. And that really bugs people. (laughs)

Joe Rogan 42:55 Yeah.

Sean Carroll 42:55 Because I just saw it. I mean, how much more real could it be, right? Um, the way that we describe, you know... I, I like to, I go on, on a rant in a whole chapter of the book, like, the Heisenberg uncertainty principle, that there's uncertainty to either your position or your velocity, you can't know both, uh, them at the same time. It's not that you can't know both of them at the same time, it's that neither one of them exists. (laughs)

Joe Rogan 43:18 Oh, Jesus.

Sean Carroll 43:18 Position and velocity are things you measure, they're not the elements of reality that quantum mechanics-

Joe Rogan 43:24 Mmm.

Sean Carroll 43:24 ... uses. And there's a difference there, and people don't like that. But by the way, I wanted to bring up, you know, a whole nother, um, aspect of the not moving thing, which I think is fascinating. And it's nothing to do with quantum mechanics, but it, it is a future frontier for physics, I think. Um, you know, we can look at the bottle of water and say, like, "It looks pretty stationary. It's not really changing." Um, I could also look at you, and you're sitting there pretty quietly, you're not really changing. But there's a tremendous difference because this is stationary, not moving, because all of its pieces are stationary and not moving. I mean, this is liquid, so it's not the best example. The table would be a better example. But you and I are sort of macroscopically stationary, trying to sit here more or less quietly. But inside, there's a lot of churn going on, right? There's, you know, a lot of, uh, cellular biology. There's, ATP is being created and destroyed, and, you know, signals are going from our brain and back and forth. And someone like Antonio Damasio, uh, the neuroscientist emphasizes this idea of homeostasis, that there is stuff going on beneath the surface, but it regulates our particular configuration so that we are more or less macroscopically stable. And, and re- amazingly, you know, human beings last for a century. Like, you know, we're born, and we, we, our bodily integrity lasts for 100 years, which is, which is kind of crazy. But it doesn't do that by in- having its individual parts remain quiet and stationary. It does that through the arrow of time and the growth of entropy and the fact that we eat food and get sunlight, and we use up enormous resources for the purpose of apparently maintaining our integrity. And I think that how that whole story works and fits together is something that physics doesn't understand very well, but will be important going forward.

Joe Rogan 45:09 The idea that there's an, an enormous number of you making various choices-

Sean Carroll 45:15 Yeah.

Joe Rogan 45:16 ... and that these various choices will ultimately affect how long you exist.

Sean Carroll 45:22 In some branches. So there is a weird thing called quantum immortality, which I think is a bad idea, and I don't like to talk about it. But people hear about it, so I, I sometimes need to mention it. Max Tegmark, who is a friend of mine and a very smart guy, popularized this idea. He said, "Look, what if..." And it's a little bit macabre. Sorry about this. A little bit, uh, you know, weird, the experiment. But imagine you're doing, you're playing quantum Russian roulette. So you have your universe-splitter, okay? You have your app on your iPhone, and you split the universe.

Joe Rogan 45:49 Mmm.

Sean Carroll 45:49 And if it goes one way, you don't do anything. If it goes the other way, uh, faster than you can react, a machine is activated that kills you instantly, okay? So you, you don't even know it. You don't even perceive it. You don't have any pain. You're just instantly dead. Um, and you do this over and over and over and over again. So in most branches of the wave function, you're dead. But in those, you're dead. You don't know anything. You don't, you don't feel like you're dead, you know. There's no ex- regret after the fact. The only version of you that survives is the one that was lucky enough to be in the branch where you didn't die every single time. So Tegmark's argument was that if you do this over and over again, and you survive, you should take that as good evidence that the many-worlds interpretation of quantum mechanics is correct (laughs) because-

Joe Rogan 46:35 (laughs)

Sean Carroll 46:35 ... in other versions, you probably just died, right? Um, I don't think that's quite right. I don't think that's a good way to go through your life. I think that the reason why we don't want to die is not just that we will experience pain, but that sort of prospectively, right now, the idea of being dead in the future bothers me, right?

Joe Rogan 46:55 Mm-hmm.

Sean Carroll 46:55 Like I, yeah, if someone said, you know, "You're going to die in this and that date," might be useful information, but, um, I would be sad, (laughs) right? If that date was soon. And I think the same thing is true in the quantum immortality experiment. It, I, I don't buy the move that says, "Well, in all the branches where you're dead, it doesn't matter 'cause you're dead. You don't feel anything." Like, I think that right now, it's okay for me to be bothered by the prospect that in many future worlds, I will not be there. So I, you know, I think that at the end of the day, once again, you should act in quantum mechanics just like you act in the regular world.

Joe Rogan 47:25 Are there competing theories to this, that, this many-worlds theory that you've embraced and then discarded?

Sean Carroll 47:32 Yeah.

Joe Rogan 47:32 Or, yeah?

Sean Carroll 47:33 Yeah, there are. So there's two big ones that are, that are quite popular. Um, one is more or less what Einstein had in mind, which are called hidden variable theories. So basically, you know, if you have, uh, an electron and you say, "Look, when I'm not looking at it, it's wave-like. When I look at it, it's like particle-like." Maybe it's both. Maybe there is a wave, and there is a particle. So in a hidden variable theory, there's a wave function just like there is in many-worlds. But there's also another set of variables saying there's really a location of the electron, right? Maybe I don't know where it is, but there really is an electron located somewhere. And that location of the electron is pushed around by the wave function, but it's a whole new part of reality. So there's not... So there, there's separate branching of the wave function and all that stuff, but that, none of that is reality. Where reality is, is where the particles are. And this is now called Bohmian mechanics. David Bohm, in the 1950s, developed the most, uh, respectable version of this. Um, it's sort of therapeutic if you don't like all the other worlds. It's basically, you know, the equations are the same as many-worlds, except there's new equations and new stuff. So it complicates the theory by adding new variables. Uh, but the good news is it says only one of the branches of the wave function is real. I don't need to worry about the other ones. The problem is it's very hard... My, my particular problem is it's very hard to-... reconcile these ideas with modern physics. Like, if you thought the world was made of individual particles, it would be, do okay. But these days, we use quantum field theory and quantum gravity and things like that, and those more modern ideas are harder to attach hidden variables to. So, hidden variables are, you know, an old idea, but, uh, they're, I think that they're hard to make work. The other idea, which is more dramatic and a little bit more fun is, every single electron has a wave function, and it seems to you that when you observe it, it collapses. But, but maybe what's really going on is the following, that there's a random probability every second that every electron will just spontaneously collapse. So it's all spread out, but its wave function just randomly loc- localizes to some particular region of space. Very, very rarely, like, if you have one electron and you wait for it to happen, it will happen like, once every 100 million years, okay? But if I have lots of electrons, like in a table, there's way more than 100 million electrons in this table. There's, there's, you know, billions and billions and billions of electrons. So somewhere in the table, all the time, an electron is localizing at one particular position, and because that electron is entangled with all the other electrons, the table maintains a location in space.

Joe Rogan 50:05 Mm-hmm.

Sean Carroll 50:06 And this is, uh, called spontaneous collapse, or GRW theory, after the initials of the people who invented the theory. And the great thing about GRW theory is that it's experimentally distinguishable from many-worlds, because it says that if I have a collection of atoms, even if I'm not observing it, even if I'm not entangling it, one of the wave functions should c- spontaneously localize occasionally, and that will heat it up. Energy is not conserved in this theory. So people are doing experiments to test this, so it's really, you know, legit experimental science.

Joe Rogan 50:35 D- m- atoms. C- uh, the current perception by the general public of atoms is that it's mostly empty space.

Sean Carroll 50:45 Yeah. That's a bad idea.

Joe Rogan 50:46 This is not, this is not true.

Sean Carroll 50:47 (laughs) Well, it-

Joe Rogan 50:48 Or not correct, or not-

Sean Carroll 50:50 It's certainly not what many-worlds says.

Joe Rogan 50:52 Right.

Sean Carroll 50:52 So this is, you know, there are two enormous problems with our current way of presenting quantum mechanics. One is the measurement problem, which is this question like, what do you mean look at it? What do you mean observe? Like, what, what, what actually happens? When does that happen? That's the measurement problem. But the other problem is what I unhelpfully call the ontology problem. (laughs) 'Cause ontology is the philosophy of being, of what is real, what is actually existing. So we just talked about hidden variable theories. So in Everett, what's real is the wave function. The wave function of the universe describes the universe exactly and, and completely. In many-world, in, uh, hidden variable theories, there's a wave function and there's also particles, so there's extra ontology, extra pieces of reality. So the question of, is the atom mostly empty space, depends on what you think is real. So the wave function of the electron fills the atom. So if you're a many-worlds person like me, you think what is real is the wave function. It fills up the atom, and the atom is not mostly empty space. The atom is the wave function, it has that size, right? You get the feeling that elec- that atoms are mostly empty space because you think that really, the electron is a point, and the wave function is just telling you where you might see it.

Joe Rogan 52:10 When you measure it.

Sean Carroll 52:11 When, well, yes. So many-worlds says there's no such thing as where it is, there's only a probability of seeing it. Everyone knows that, but people kind of deny it. They talk as if there really is a location of the electron, even if they should know better. So people who, generally people who say that atoms are mostly empty space are just being sloppy.

Joe Rogan 52:30 Mm-hmm.

Sean Carroll 52:31 They're just really thinking of the electron as a little tiny dot rather than a wave function. There is a, an exception to that, because there is a fourth version of quantum mechanics that is somewhat popular. I said three, I said many-worlds, hidden variables, and spontaneous collapse. There's another version that just says, "Look, the wave function has nothing to do with reality." In many-worlds, it's all of reality. In spontaneous collapse, it's all of reality, but it obeys different equations. In hidden variables, the wave function is part of reality, but there's also particles. In the other approach, which is called an epistemic approach to quantum mechanics, the wave function is just a way of talking about your personal knowledge of the world, your knowledge or lack of knowledge, your ignorance of the world. So your wave function's just a tool you use to make a prediction for what the experimental outcome is gonna be, right? And that's more or less what we teach our students, and this approach says, "Don't bother about reality." What we should concern ourselves with is the experiences of agents who make predictions and update their probability ex- expectations of the world. And so someone like that, if you ask them, you know, "How i- is an electron located in an atom?" Or, "How, is it, an atom mostly empty space?" I think if they're honest, they would say, "Don't ask th- those questions. Those are, no, we, we don't ask reality questions. We just ask what are you gonna see kinds of questions."

Joe Rogan 53:59 Mm-hmm.

Sean Carroll 53:59 But I think that some of the less honest ones will say, "Sure, an atom is mostly empty space 'cause an electron has a location somewhere, we just don't know what it is."

Joe Rogan 54:07 Why do they approach it in this, what you, uh, the way you're describing it, a sloppy way? Why, why do you think that is so common?

Sean Carroll 54:15 Well, you know, it is part of, um, the attitude that physicis- physicists have adopted, that we use quantum mechanics but we don't try very hard to understand it. So y- you know, you can talk to plenty of physicists on the street and they will tell you to your face that understanding reality is not their job, and I, I think that's terrible, but it, but-

Joe Rogan 54:38 Right.

Sean Carroll 54:38 ... they will say it. And so when you press them too much on questions like, you know, "Is the atom mostly empty space? You know, what happens when you make an observation?" They just kind of get uncomfortable and say, "No, you're asking the wrong questions. Let's ask questions about-"... what will we see at the Large Hadron Collider if we smash protons together, right? And those are perfectly good questions too, but I think that the what's really going on questions are also interesting. So because they don't care about these questions, they will often be sloppy in answering them, right? They don't... y- It is hard. Like, like, like you said, it's, it's hard when you read the book, it's hard when you write the book, it's hard when you think about these things as a professional physicist. It's, it's not natural, it's not easy, it's not intuitive. So even if you're a super-duper expert at solving the equations and making predictions, understanding what's going on is a whole another activity that a lot of physicists don't try very hard to do.

Joe Rogan 55:30 Now, how was all this stuff v-verified or argued? Like say, uh, here come... y- you're sitting down, you're having a conversation with someone who, uh, espouses a competing theory, how are you guys working this out?

Sean Carroll 55:45 Good. I think that, um, i- if everything were going along really, really well, we would be making experimental predictions and testing them. But I think the theorists have sort of dropped the ball here, um, in the sense that the theoretical physicists should have, since the 1930s, been developing these alternatives like many-worlds hidden variables, whatever, and make... using them to make predictions. Um, but we really haven't. They were neglected. They were backwater. There are few people, a few plucky souls, who, uh, really put their efforts into understanding these, many of them got pushed out into philosophy departments, um, but that's what we need to do. We need to, like, catch up on the last 70 years of lost time and work out what the implications are of these ideas. So it's in... The ball, I think, is in theorist's court. The experimenters are working hard. Experimenters are doing amazing things with lasers and, um, atoms and, and learning about how to manipulate quantum systems at a delicate level, but the theorists have not given them sharp experimental questions that they... that would really illuminate the foundations of quantum mechanics. So honestly what it is is a bunch of people get around the table and talk to each other. (laughs) And they're like, "Oh, I think that what happens when the wave function branches is this." So a typical question we'll try to address is... In ordinary quantum mechanics, we say, if I send the electron through one way or I send it through the elec- the other way, there's a 50/50 chance that I will see it go left or go right. And someone says, "What do you mean 50/50 chance?" Especially in many-worlds where there's a 100% chance there'll be a world where it goes left and a world where it goes right. How, what, what is the meaning of the phrase there's a 50/50 chance? What is the nature of probability in this game where everything is perfectly deterministic, right?

Joe Rogan 57:30 Mm-hmm.

Sean Carroll 57:30 So that's not the kinda question that you a-answer very easily by doing an experiment. You have to think about it.

Joe Rogan 57:35 Right.

Sean Carroll 57:36 So that's what... the kinda thing that we argue about.

Joe Rogan 57:38 Now how often do you guys get together?

Sean Carroll 57:40 Um, yeah, you know, it happens. Uh, there's conferences. It's a small community. Someone asked me just the other day, 'cause that... you know, the book came out, Something Deeply Hidden, last week and I'm... uh, been on book tour. So I was on a... I was being interviewed and someone said, "How many people do you think in the world are... would classify themselves as working on the foundations of quantum mechanics?" Um, maybe 100, something like that, not a very large number. Like, if you say how many people would classify themselves as particle physicists, there'll be tens of thousands of people.

Joe Rogan 58:09 I remember there's a woman who came to The Comedy Store the... after the last podcast that we did and she apparently is also working on it, and she was trying to explain it to me, her version of it, you know, after hearing your version of it. It was very similar, but I believe she was from Romania so she was struggling a little bit with English.

Sean Carroll 58:28 Ah, okay.

Joe Rogan 58:28 But she was so excited to discuss it. It's so fascinating when you see someone who's... Like, for the limited number of how many of you guys there are, and gals, there are out there, I mean, whatever the number is, when that spark gets ignited and other people start tuning into it. She was so excited that this was being discussed on a podcast and she wanted to talk to me about it-

Sean Carroll 58:53 Yeah.

Joe Rogan 58:53 ... to say, you know, "Please have more people on. Please talk about this more." You know, "We need support. We need, you know..." It's...

Sean Carroll 59:01 It, it is... It's... It does baffle me a little bit how difficult it is swimming uphill, um, to get more support for this kind of thing because it is just an enormous privilege to be able to call your job thinking about the fundamental nature of reality, right?

Joe Rogan 59:19 Yeah.

Sean Carroll 59:19 Like, you know, I gave... You know, my first book tour talk was last Tuesday and I had dinner the night before with, you know, several philosophers of physics in the New York area, if, you know... from Columbia and NYU, and every... And, and, you know, we're all friends and we could talk about, you know, our cats and our cars but every single word discussed at the table all night long was about the philosophy of physics. (laughs)

Joe Rogan 59:39 Is it because you guys work in isolation essentially and then when you get together you just... you're so pumped up to be discussing these things-

Sean Carroll 59:46 In part, yeah.

Joe Rogan 59:47 ... with like-minded souls?

Sean Carroll 59:47 You know, in, in part, yeah. I, I mean, I... there's no one else a- at... in the physics department at Caltech who cares about these issues. I mean, some of them care in the sense that they are happy that I'm doing it, but no one does it really-

Joe Rogan 59:58 But it's just you?

Sean Carroll 59:58 ... themselves. Yeah. Well, there's a couple other people in the philosophy department, uh, who care about this-

Joe Rogan 1:00:03 And a lot of-

Sean Carroll 1:00:03 ... but small.

Joe Rogan 1:00:04 ... folks, you were saying, get pushed into philosophy. And, uh-

Sean Carroll 1:00:06 Yeah.

Joe Rogan 1:00:06 ... why, why is that? I mean, is it just because it's so complex that it's so esoteric, there's so many people that just... they don't... the, the, the support for it's not there but the support for philosophy is more common in mainstream?

Sean Carroll 1:00:19 Yeah. You know, there's different kinds of support. One kind of support in academia is who do you hire, right? W- what, what areas do you want? Like, a physics department will generally say, "Yeah, we should have some people doing particle physics, some people doing astrophysics, some people doing condensed matter and solid state physics." And, and then... and then it becomes hard. Do we need people doing biophysics? Do we need people doing this? And by the time they get to the foundations of quantum mechanics, there's, there's usually very little support. Um, philosophers, their, their job is being patient and clarifying difficult conceptual questions. And so they get that quantum mechanics is fertile territory for philosophy. Like, it... You know, one of the big problems in philosophy compared to science is that many of the questions that they're asking cannot be tested experimentally, right?

Joe Rogan 1:01:09 Mm-hmm.

Sean Carroll 1:01:09 What is infinity-Well, you know, okay, (laughs) it's hard to do an experiment there.

Joe Rogan 1:01:14 Right.

Sean Carroll 1:01:14 But it's an important question, right?

Joe Rogan 1:01:15 Sure.

Sean Carroll 1:01:16 And so, you need patience, but also it's harder to make progress because it's easy to be trapped by your intuition, right? Like when it's just you thinking and trying to think hard and be rational and so forth, it's easy to fall into a trap of, "Well, this looks reasonable to me." And quantum mechanics doesn't look reasonable to anybody, so it's a wonderful corrective. It's a wonderful reality check when you think, "Well, reality has to be this way." And then someone can say, "Well, look at quantum mechanics, that's different than what you said."

Joe Rogan 1:01:43 So philosophy and quantum mechanics, they sort of, they- they- they share some sort of a border?

Sean Carroll 1:01:50 Yeah. Oh, yeah, absolutely. I mean, the things... So I- I- I was always, uh, a big fan of philosophy ever since I was an undergraduate and I discovered it for the first time. But when I was an undergraduate and my favorite philosophy classes were like the philosophy of morality or p- political philosophy, right? I took philosophy of science classes, but they seemed to be kind of dry to me because they were all about how scientific theories are constructed and chosen. You know, The Structure of Scientific Revolutions is the famous book that everyone reads. Uh, people like Thomas Kuhn and Paul Feyerabend and so forth. And, okay, that's interesting, but it's sort of meta science, right? It's like how science is done, not how the world works. And it wasn't until, you know, circa 2000 that I discovered that there are philosophers of physics who are kind of really doing physics. You know, they're not asking how physics works, they're asking how the world works, but they're asking in a way that is comfortably, uh, located in philosophy departments and right now not so much in physics departments.

Joe Rogan 1:02:49 There was a part of the book that- that shocked me because I had a ridiculous idea once, and this idea was not my idea. Apparently Laplace had a very similar idea as a thought experiment. I had an idea once that if one day there was a computer that was so powerful that it could accurately describe every single object on Earth that we would be able to figure out the past.

Sean Carroll 1:03:15 Yeah.

Joe Rogan 1:03:16 And Laplace was saying that not only that, but he proposed for the entire universe.

Sean Carroll 1:03:21 Right. (laughs)

Joe Rogan 1:03:21 Like every single object, electron, everything in the- an atom in the entire universe, that you would not only be able to show the past, but also predict the future.

Sean Carroll 1:03:30 That's right. So this is called Laplace's demon, although he never called it that. Pierre-Simon Laplace, uh, was a brilliant guy. He, he deserves to be much more well-known. So I base- I think I've mentioned him- his name in every book that I've ever written for totally different reasons. Uh, he helped invent probability as we currently understand it-

Joe Rogan 1:03:47 Hmm.

Sean Carroll 1:03:47 ... for example. Um, but yeah, so Isaac Newton came up with the rules of classical mechanics in the 1600s, but it wasn't until Laplace around the year 1800 that this implication of classical mechanics was realized. It's a clockwork universe, that the way classical mechanics works is if you tell me the state of a system right now at one moment, by which in classical mechanics you would mean the position and the velocity of every part, and you knew the laws of physics, and you had arbitrarily large computational capacity, Laplace said a vast intelligence, okay? Then to that vast intelligence, the past and future would be as determined and known as the present was because that's the clockwork universe. It's deterministic. Everything is fixed once you know the present moment. Now, quantum mechanics comes along and throws a spanner into the works a little bit. If you're a many worlds person, Laplace's demon is still possible. So if you know the wave function of the universe exactly and you have infinite calculational capacity, you could predict the past and the future with perfect accuracy, but what you're predicting is all of the branches of the wave function. So any individual person inside the wave function still experiences apparently random events, right? So you can't predict what will happen to you even if you can predict what will happen to the entire universe.

Joe Rogan 1:05:10 Whoo!

Sean Carroll 1:05:11 Yeah.

Joe Rogan 1:05:12 Sean Carroll.

Sean Carroll 1:05:12 (laughs)

Joe Rogan 1:05:13 My goodness, there's a lot of people pausing this podcast right now just shaking their head like...

Sean Carroll 1:05:18 You know, I wrote a little article that just appeared in Quanta Magazine, which by the way, if anyone here is a- is a science fan, Quanta Magazine is the best, um, online magazine for science these days. They have really, really good high level ar- um, articles about all sorts of things. And so I wrote an article called What is Probability 'cause, you know, again, this is a philosopher's kind of question.

Joe Rogan 1:05:39 Yeah.

Sean Carroll 1:05:39 Like, you know, physicists will just put it to use and get on with their lives. Philosophers will say, "Well, what do you really mean by probability?" Um, the traditional answer is if you're flipping a coin and you say it's 50/50, what you mean by that is that if you flipped it an infinite number of times, half the time it would be heads, half the time it would be tails. That's what you mean. It's called the frequentist idea of probability. But then what do you say like, "Well, what is the probability that, uh, Donald Trump wins re-election?" That's not gonna happen an infinite number of times. You're not gonna do the experiment. Or even better, what was the probability that Lee Harvey Oswald actually was the- the lone shooter of JFK? That already happened. That's in the past, right?

Joe Rogan 1:06:19 Right.

Sean Carroll 1:06:20 But we can easily say, "Well, I think it was an 80% chance that that's true," right? So this is called Bayesian probability where rather than thinking of an infinite number of things going on, you're assigning a degree of confidence to your lack of perfect knowledge, right? Like I don't know exactly-

Joe Rogan 1:06:35 That's a great way to describe it.

Sean Carroll 1:06:36 There's something... Yeah, there's something going on. I don't know what it is. So I assign a probability and- and that just like a frequency that, you know, there's the- the credence as we say that you assign to these different ideas is a positive number then all the credences add up to one because something happened. Um, so in quantum mechanics i- is- is probability more like frequentist probability or is it more like Bayesian probability? And the answer is it depends on what your favorite version of quantum mechanics is. In one of these spontaneous collapse theories, uh, it's very much like a frequency, like, you know, you just... Things happen randomly and it's purely objective. In something like many world- well, sorry, I should say in something like hidden variables-It's Laplace's demon all over again. So Laplace's demon doesn't work in a spontaneous collapse theory, because you, the laws of physics are not deterministic. You don't know when things are gonna collapse all by themselves. Um, in hidden variable theory, the hidden variables and the wave function evolve deterministically, but you don't know what the hidden variables are, so you can assign some probability to having them be different things. So, there's some ignorance involved. Many worlds is the coolest idea, because it's, it's kind of... And this is what i- is, is kind of hard to wrap your mind around. On the one hand, there is only the wave function. It describes the universe exactly. But imagine that I measure the spin of an electron, okay? So I, I, j- actually do know what the wave function's going to evolve into. It's gonna evolve into a 50/50 split of I observed it spinning up and I observed it spinning down. And then... But I only ever find myself in one side or the other. So, there is always a moment in between when the wave function splits and when I know about it. It splits much faster than I can know about it. The, the rate, the speed of a wave function branching is some incredibly tiny number, 10 to the -20 seconds or something like that. And the timescale of things happening in my brain is like 10 to the -3 seconds at best, okay? So, there will always be a time when there are two copies of me. One on the branch where the spin was up, one on the branch where the spin was down, but they're both identical. They don't know which branch they're on yet. So they need to be good Bayesians and say, "Well, what probability should I assign that I'm on one branch or the other?" And it turns out that the probabilities work exactly like the textbook quantum mechanics tells you probabilities should work out.

Joe Rogan 1:09:01 And how is that?

Sean Carroll 1:09:02 The wave function squared is the probabilities. So there's a-

Joe Rogan 1:09:05 The wave function squared-

Sean Carroll 1:09:05 Yeah. This is a rule called the Born rule, after Max Born, who was a physicist who invented it. So, I mean, read the book, of course, but, uh, like, like you said at the very start, the history of quantum mechanics is just so fascinating and hilarious. Schrodinger, Erwin Schrodinger of Schrodinger's cat fame, invented the idea of the wave function and wrote down the equation that it obeys, okay? But what he hoped was that if you had the wave function of an electron all by itself, if you solved his equation, it would sort of show that the wave function becomes localized, peaked at one location. The electron kind of acts like a point particle, and that's why we see particles. That was his hope. What actually happens when you solve the equation is that the electron spreads out all throughout the universe, so he was... his hope was dashed. And then he's like, "All right, I have this equation. What is it? Like, what does the wave function do?" And it was Max Born, a whole nother guy, who said, "What the wave function does is you square it, and that's the probability of seeing something somewhere." Like if the wave function looks like this, it's some spread out thing, there's very small probability over here and large probability over there, because the probability is the wave function squared. And Schrodinger said like, "Oh my God, that's awful. I'm sad I, I had anything to do with it." He regretted (laughs) being involved with this whole idea of probabilities and collapses and all that stuff.

Joe Rogan 1:10:24 Do you see an increased interest in this subject among students? I mean, is this... This seems like-

Sean Carroll 1:10:31 I do.

Joe Rogan 1:10:31 ... a very l- Yeah?

Sean Carroll 1:10:32 I do, but, you know, with things like that, it's always hard to, um, you know, protect against my own biases, right?

Joe Rogan 1:10:40 Right.

Sean Carroll 1:10:40 Like I say, you know, the people who are interested come to me, 'cause I-

Joe Rogan 1:10:43 Of course.

Sean Carroll 1:10:43 ... I keep talking about it, right?

Joe Rogan 1:10:45 Right.

Sean Carroll 1:10:45 Um, and maybe I'm, uh, you know, ruining their lives by getting them interested in it. Uh, you know, when I have real graduate students, I, I try not to let them work on topics like this too much. Like a little bit, you know, get their foot wet, but they gotta work on respectable stuff that will get them a job also.

Joe Rogan 1:11:00 That's interesting. So you're protecting them?

Sean Carroll 1:11:02 Oh, yeah. No, I, I have... I'm c- I really try. Uh, mixed success, of course, but I try very hard to be a good advisor in the sense that, you know, uh, you know, challenge them intellectually and get them to do interesting things, but in a way that will lead to a productive career. And part of that is get a job, right?

Joe Rogan 1:11:21 Yeah.

Sean Carroll 1:11:22 Like, you know, it, it... I, I'm not a believer in being such an idealist that you stop doing physics by the time you're out of graduate school, you know? Keep going.

Joe Rogan 1:11:29 Do you think it's possible to boil this down to a documentary that isn't filled with woo? Like a, a, a, a... Y- just a response to something like What the Bleep? Some sort of entertaining yet clear version of what you're saying?

Sean Carroll 1:11:46 I think so, yeah. You know, if there's any producers out there-

Joe Rogan 1:11:48 Yeah.

Sean Carroll 1:11:49 ... who wanna option my book, um-

Joe Rogan 1:11:50 Jump in, kids.

Sean Carroll 1:11:51 You know, I think it's... Especially these days when computer graphics are really good, right?

Joe Rogan 1:11:57 Mm-hmm.

Sean Carroll 1:11:57 And we can visualize things-

Joe Rogan 1:11:58 Yeah.

Sean Carroll 1:11:58 ... that we couldn't visualize before.

Joe Rogan 1:12:00 That would help.

Sean Carroll 1:12:00 Yeah. Th- and that was... I... In fact, I think that you got a copy of my book that didn't have any figures in it, right? Didn't you get the ARC?

Joe Rogan 1:12:06 I believe so, yeah. I got it-

Sean Carroll 1:12:07 And that makes it much harder.

Joe Rogan 1:12:07 Yeah.

Sean Carroll 1:12:07 The real, the real book has pictures in it. (laughs)

Joe Rogan 1:12:09 Oh, okay.

Sean Carroll 1:12:10 And so, that does make things harder.

Joe Rogan 1:12:11 When does it... When is that out? Or is it-

Sean Carroll 1:12:12 Yeah, I'm sorry. I should have brought a copy. It came out last week.

Joe Rogan 1:12:14 Is that out today?

Sean Carroll 1:12:15 Last week.

Joe Rogan 1:12:16 Oh, okay.

Sean Carroll 1:12:16 So it is out now. Um, we'll send you a copy and then it'll, it- that'll be better. But honestly, all of the pictures in the book were made by me using Adobe Illustrator, and this is not really my area of expertise, so it's not like high-level graphics. It's just fairly functional. Um, yeah, especially, you know, there's so much history in there. I had the idea... Before I actually wrote this book, I was seriously contemplating writing a novel about the Bohr-Einstein debates, uh, because they were nominally about the nature of quantum mechanics, but they were really about the nature of reality, right? And there's all sorts of... The history is interesting. You know, there were Nazis. We're talking about the 1930s, right? You know, Einstein fled Germany. Um, the personalities are very different. Niels Bohr. Niels Bohr is this amazing figure. I had David Albert on my podcast, on Mindscape, and, uh, the same David Albert who appeared in What the Bleep?, and we talked about quantum mechanics and the measurement problem. And, you know, he said... He put it r- really well. He said, like, "If there's a figure from history who I would like to have dinner with, it would be Niels Bohr." And because, like...He was certainly a very, an amazingly good physicist, very, very influential. But over and and over again, super duper smart people would get together and talk to Niels Bohr and come away spouting nonsense about the foundations of quantum mechanics. (laughs) So, somehow he had this magic charisma that worked in a bad direction to, like, make people just become crazy about quantum mechanics in a bad way. And, uh, and that's part of the reason why we haven't, uh, dug into the foundations of quantum theory for so long.

Joe Rogan 1:13:51 Why? What was it about him?

Sean Carroll 1:13:53 He was just incredibly charismatic in a, in a weird way 'cause he was a terrible writer. You know, there's this story where he-

Joe Rogan 1:14:00 (laughs)

Sean Carroll 1:14:00 ... Einstein wrote this paper about entanglement and spooky action at a distance, and Bohr responded to it. And everyone said ... you know, 'cause, uh, by this time, 1935, people were already bored with the foundations of quantum