Modern WisdomSEAN CARROLL | The Problem With Quantum Mechanics | Modern Wisdom Podcast 126
EVERY SPOKEN WORD
115 min read · 23,260 words- 0:00 – 15:00
In the 1920s, you…
- SCSean Carroll
In the 1920s, you know, Niels Bohr and Albert Einstein or Erwin Schrödinger and Werner Heisenberg could get together in the same room and talk about these things. Ten years later, they're all on different continents, right, or different countries, and they can't travel back and forth. And they didn't have the internet. So just the pace of progress was enormously slowed down. The focus of physicists shifted to very practical things, right? Building bombs and stuff like that. And then even if they did more impractical things like understanding particle physics and quantum field theory and all these other very pressing questions. So quantum mechanics, measurement problem kinds of questions were put on the back burner. And for that matter, it's not clear how to make progress on these questions, right? If you have a question about particle physics, you can take two particles and smash them together and do the experiment and see what happens. Eh, for the interpretations of quantum mechanics, as, as they used to be called, uh, it wasn't clear how you would ever know what the right answer was.
- CWChris Williamson
(wind blowing) I'm joined by Sean Carroll, theoretical physicist specializing in quantum mechanics, gravity and cosmology, research professor at the Department of Physics, the California Institute of Technology, and also the man behind the Mindscape podcast. Sean, welcome to the show.
- SCSean Carroll
Thanks very much for having me.
- CWChris Williamson
Super excited to have you on. Been a little while since we delved into physics on this show, so we're gonna have to get over a little bit of inertia, some audience and my inertia as well. And, uh, we'll, we'll kickstart everything back off again, right?
- SCSean Carroll
Inertia's part of physics. That's okay. We understand it.
- CWChris Williamson
You are the man. If there was ever a man to get over some inertia-
- SCSean Carroll
(laughs)
- CWChris Williamson
... it's you right there. Um, before we, before we even start talking about physics, Mindscape podcast that you... It's not been going super long, right? But you've had some insane guests, like Max Tegmark, Seth MacFarlane, the guy, the-
- SCSean Carroll
Yeah.
- CWChris Williamson
... the Family Guy creator-
- SCSean Carroll
(laughs)
- CWChris Williamson
... like the voice of Brian and Stewie Griffin. Like, that's insane.
- SCSean Carroll
Yeah. Yeah. No, it's been great. It's been like a year and a half. Uh, I've been very, very lucky in people saying it. Not everyone says yes. Um, but, uh, you know, I always wanted to be one, one of the things why I wanted to do the podcast was just so that I could talk to intelligent people about things other than physics. And, uh, I've gotten some, uh, great guests and all over the spectrum. So yeah, it's been fun.
- CWChris Williamson
Is that informing the direction of any sort of more writing that you're looking at? Are you p- are you tempted to branch out into anything after having these conversations?
- SCSean Carroll
I've always been tempted. You know, I've al- and I always do. So, um, you know, my previous book, The Big Picture, was very broad, a lot of, uh, philosophy, a lot of biology was in there. And my last book was pure physics. So the next book is not gonna be pure physics again. I wanna, you know, keep it, keep it mixing it up.
- CWChris Williamson
Oh, got you. So tell us about your last book, Something Deeply Hidden. Why'd you write it?
- SCSean Carroll
Well, it's a book about quantum mechanics, and the world does not need another book about quantum mechanics, uh, for its own sake. There's lots of books out there of varying degrees of usefulness. Uh, one of the things I did for the book, you can see the results right in chapter one, is I went to Amazon and typed in the word "quantum" into the search bar and looked at all of the books that had quantum in the title. Quantum healing and quantum leadership and quantum yoga.
- CWChris Williamson
(laughs)
- SCSean Carroll
And it just goes on. And none of them have, uh, the Schrödinger equation or any differential equations at all in them. So I didn't want to, you know, just be negative, but I think that a lot of even the good books on quantum mechanics have this attitude of saying like, "Quantum mechanics is really, really bizarre. It's mysterious. We'll never understand it. Look at how bizarre it is." And I wanted to kind of be the opposite. I wanted to kind of say, "Look, this is just science. It's perfectly understandable. Even if we don't understand it yet, there's no reason to think we can't understand it." And even though I have a favorite way of understanding it, what I really care about is the fact that it can be understood.
- CWChris Williamson
What does it mean for something to not be understood, but be understandable?
- SCSean Carroll
Well, you know, we think that there's plenty of puzzles in science, right? There are things we don't yet know. We don't know exactly how the moon came to be, right? Was it something colliding with the Earth or was it sort of a, the mutual formation of the moon and the Earth at the same time? But no one thinks this is impossible to understand, right? I mean, we'll, we'll, we'll get there. It's just a matter of, you know, getting the evidence and doing the theory, etce- et cetera. And I think that quantum mechanics has this weird unique status where it was put together in the 1920s with sort of a, a wall around it saying, "Don't ask questions about the deep things going on here." The way, what I like to say it is, physicists are extremely good at using quantum mechanics without understanding it. It's exactly like I'm good at using my smartphone to send text messages or take pictures, but I couldn't build one, right?
- CWChris Williamson
Mm-hmm.
- SCSean Carroll
And that's how quantum mechanics is for physicists. And I don't think that, uh, it needs to be. And I think that this is a, a huge, huge, uh, wrong turn that physics took, and we're trying to sort of correct the course right about now.
- CWChris Williamson
Hmm. So what, what is it about quantum mechanics that makes it so slippery?
- SCSean Carroll
It's that in the rules that we developed in the 1920s, and we still teach to our undergraduates today, quantum mechanics is unique in the following way. There's a set of rules for what physical systems are and how they evolve, just like every other theory of physics, when you're not looking at them. And then there's another set of rules that apply when you look at something, when you measure it, when you observe it. And no other theory of physics has anything like that. I mean, there's general relativity, Maxwell's equations for electromagnetism, Newtonian mechanics. Like, there's no set of rules that say what you see and what happens to a system when you measure it. And so why does quantum mechanics seem to need these extra rules? And this is what's called the measurement problem of quantum mechanics, and it's just been hanging around unanswered since the 1920s.
- CWChris Williamson
Could you break down the measurement problem? Could you explain it with, uh, some experimental examples?
- SCSean Carroll
Sure. You know what we teach our students is that if you take an electron, for example, right, y- you imagine the standard picture of a, an atom that we've all seen that has a little nucleus at the center and electrons are orbiting around it. So we know that can't be right, because electrons orbiting like that would give off light, would lose energy, would spiral in, and all atoms would collapse into a point if that picture were correct.
- CWChris Williamson
Okay.
- SCSean Carroll
So they came up with the idea, well, maybe the electron is not a particle. Maybe it's a wave, maybe it's spread out and the wave sort of has a minimum wavelength, just like when you pluck a violin string or something like that, there's different allowed wavelengths. And that's why the electron can't collapse because it's actually spread out. That's a great idea. Then we have an equation, the Schrodinger equation given to us by Erwin Schrodinger which says how the electron behaves, et cetera. Except that when we look at the electron, when we shoot an electron through a detector, it doesn't look like a big fuzzy wave, like, you know, an electromagnetic wave would look like. It looks like there's a track, like there's a trajectory, like it's a particle, like it's located somewhere. So that seems to imply just from, on the one hand we need the electron to be a wave so that atoms don't collapse, but on the other hand when we look at it, it looks like a particle, that we need two separate sets of rules. And in what's called the Copenhagen Interpretation, the standard interpretation of quantum mechanics put together in the 1920s, they sort of just leaned into that. They said, "Yes, there's a separate set of rules for what happens when you measure a quantum system." But what they didn't do is tell you what it means to measure a quantum system. Like does it have to be a person? Could it be a video camera? Could it be a cat?
- CWChris Williamson
Mm-hmm. Mm-hmm.
- 15:00 – 30:00
Mm-hmm. …
- SCSean Carroll
all scales. You and I are perfectly quantum mechanical, and there's a limit where things become big enough that you don't need quantum mechanics to describe what's going on.
- CWChris Williamson
Mm-hmm.
- SCSean Carroll
There's a good approximation given to us by classical mechanics. So it's not that... It would be indeed very, very weird if the rules of nature were different for big things than small things. And, uh, I'm sure we'll get to, at some point in the conversation, the many worlds, uh, formulation of quantum mechanics, which was invented by Hugh Everett, who was a graduate student in the '50s. And this is exactly one of the things that he complained about. You know, he was writing letters to Niels Bohr, et cetera, saying, "H- why in the world can you treat the observer as classical?" You know, we're made of atoms and things like that. We're made of things that obey the laws of quantum mechanics. Why don't we? We should take that seriously. And that's exactly what he showed how we could do.
- CWChris Williamson
So just before we get onto- t- t- to that, I'm right in thinking that there was a few people in your book that you quote as having been dissuaded from working on quantum mechanics, yourself included, right? Could you tell us some stories about that? I had, um, Sabine Hossenfelder on talking about politics in physics. And for the listeners who didn't catch that episode, it's- it's a while ago. It's back in the 30s, I think. The number 30, not in the 1930s.
- SCSean Carroll
Not the 1930s. That would be good.
- CWChris Williamson
That would be a sick podcast.
- SCSean Carroll
(laughs)
- CWChris Williamson
And, um, but, uh, and I- I totally didn't understand just how political and, um, subject to social bias and reputation and, you know, all of that stuff, uh, that the world of physics was. And the synopsis that Sabine sort of came up with that she finished was, "Well, if nothing else, today you have learned that politicians are p- that, uh, physicists are people too." And I was like, "Yeah. Yeah, I have."
- SCSean Carroll
(laughs)
- CWChris Williamson
So could you talk us through some of the- the sort of the politics of- of quantum physics?
- SCSean Carroll
Yeah. Um, you know, physicists are people too, and there's a lot of, uh, politics and reputation. All that stuff is very true. I don't like to, uh, use the word politics in this context because it has ramifications, like it has connotations elsewhere. Um, and furthermore, you know, it's very hard to get this right, because especially in theoretical physics, where we're saying, well, we know that our current theories are pretty good, but not perfect. We wanna get to better theories. Everyone has a different opinion about which theory might be better. We don't know the right answer yet. And so if someone's best favorite theory is not the one that is accepted by other people, they're gonna say, "Ah, those people just don't appreciate my theory. They're just being political-"
- CWChris Williamson
Mm-hmm. Mm-hmm.
- SCSean Carroll
"... and driven by, you know, groupthink and whatever." And maybe that's true, or maybe your theory is just not as good, right?
- CWChris Williamson
Mm-hmm. Mm-hmm.
- SCSean Carroll
So it's... Uh, I'm- I'm literally... I'm not saying that rhetorically. Maybe your theory is better, maybe it's not. And that's very, very hard to pick that out in an unbiased way, uh, especially in a situation like we're in right now or like we have been in quantum mechanics for many decades when the experiments don't clearly distinguish between one way of doing things and another way. So putting aside, like, politics and bias and stuff like that, it's certainly true that the course of physics is heavily influenced by influential people, right? It's, you know, someone who is a brand new graduate student and has a good idea, uh, an idea that is not in accord with the prevailing standards of the field is gonna have a much harder time than a famous Nobel Prize winner who everyone respects.And that's not crazy because there are m- a lot more people who are young graduate students who have really bad ideas, right?
- NANarrator
(laughs)
- CWChris Williamson
(laughs)
- SCSean Carroll
So (laughs) it's not just... Y- just by being unknown doesn't make you right. (laughs)
- CWChris Williamson
Yeah. Yeah.
- SCSean Carroll
So there's a filter. You know, physicists have a way of dealing with new ideas and just like everyone else in the world, they're, they're like, they take, pay attention to different ideas depending on where they're coming from and how plausible they sound and how well-articulated they are and so forth. Okay. Having said all of that, I do think that there, as I've said, there was this massive abandonment of the right set of questions to ask in the whole 20th century, um, by physicists. And part of it was... So there's so many different things going on. Part of it was just World War II happened, right? I mean, think about when this is and think about who it was. A lot of these smart people were Germans. A lot of them were Jewish. So e- in the 1920s, you know, Niels Bohr and Albert Einstein or Erwin Schrödinger and Werner Heisenberg could get together in the same room and talk about these things. 10 years later, they're all on different continents, right, or different countries and they can't travel back and forth and they didn't have the internet. So just the pace of progress was enormously slowed down. The focus of physicists shifted to very practical things, right? Building bombs and stuff like that. And then even if they did weren't practical, things like understanding particle physics and quantum field theory and all these other very pressing questions. So quantum mechanics, measurement problem kinds of questions were put on the back burner. And for that matter, it's not clear how to make progress on these questions, right? If you have a question about particle physics, you can take two particles and smash them together and do the experiment and see what happens. Eh, for the interpretations of quantum mechanics, as, as they used to be called, uh, it wasn't clear how you would ever know what the right answer was. And part of-
- CWChris Williamson
The barriers to entry are quite high.
- SCSean Carroll
Well, it's... The, the state of the art was so bad that the ideas that were being thrown around did sound more like literary interpretations than good old physical theories. The state of the art has gotten a lot better. Now we're actually talking about real, distinct, well-defined rigorous physical theories that we can distinguish between. But in the '40s and '50s, that just wasn't the case.
- CWChris Williamson
It's a shame. It's a, it seems to me a surprise as well that Einstein's side of the fence didn't win.
- SCSean Carroll
Yeah, exactly. So that is a surprise. You might think that Einstein has some kind of-
- CWChris Williamson
Kind of thought he would have been like the, you know, the, the Deontay Wilder of the, the big heavyweight champion of the world when it comes to, like, directing the physics community.
- SCSean Carroll
But he was also kind of a loner, right? He didn't collaborate a lot. Uh, he didn't have students very much. He moved to the Institute for Advanced Study in Princeton where he didn't teach classes. Uh, whereas someone like Niels Bohr was endlessly gregarious, worked with everyone, had an institute of his own where he invited everyone to hang out and so forth and would badger them and hector them into doing things. Uh, so there's a personality. This, I think this goes to Sabine's point. There... Just the fact that Niels Bohr and Albert Einstein were very different personalities affected the course of physics. And it became so bad that, you know, at some point the major journal within the physics community just stopped looking at, uh, papers on the foundations of quantum mechanics. Um, David Bohm, who was one of the best people working on this stuff, uh, was hounded by the House Un-American Activities Communi- uh, Committee for being a communist in the 1950s and was eventually... He had to flee to Brazil. Um, I mean, he had letters of recommendation from Einstein and Oppenheimer and he couldn't get a job in the United States, right?
- CWChris Williamson
Wow.
- SCSean Carroll
Uh, John Bell, who was a brilliant theorist who worked at CERN, uh, was a particle physicist by day and worked on the foundations of quantum mechanics at night and didn't tell anyone that he also worked on them.
- CWChris Williamson
(laughs)
- SCSean Carroll
His colleagues, you know, in the next door office didn't know that's what he was doing. And now his theorem is very famous and we all know about it. Uh, even today, I tell the story in my book, you know, I do a bunch of different things. Some fundo- foundations of quantum mechanics, some gravity and particle physics and stuff like that. And I'm told that when we're doing our grant renewals, don't talk about quantum mechanics, talk about cosmology or gravity. That's the serious stuff. That's what's gonna get us funded.
- 30:00 – 45:00
Could there not be…
- SCSean Carroll
- CWChris Williamson
Could there not be the case that one is up and one is down, it's not a case of them being either way, and when you observe, it just happens to be that?
- SCSean Carroll
Could be, but the quantum mechanics makes a prediction, right? It makes a prediction, uh, for when you see the particles come out of Higgs boson decay, there'll be 50/50 up and down for the electron, 50/50 up and down for the positron.
- CWChris Williamson
Okay. So it's not a case that it is one of those two and you just look at it and it is the one that it is. It's a case that it could be either of them, and the observation causes it to choose.
- SCSean Carroll
Well, you know, this is exactly the question that Einstein was worrying about, you know? So, so he makes the point that I can make these two particles... He was using different examples, but the, the underlying point is the same. I could take one of them and just let it fly off to another star system light years away, right? And then I could measure-... my particle here, and the entanglement doesn't fade away or get less and less as the particles become separated. So if you take quantum mechanics seriously-
- CWChris Williamson
Mm-hmm.
- SCSean Carroll
... says Einstein, "You're telling me that when I measure my particle here to be spin up or spin down, instantly, light-years away, the other particle changes to be oppositely oriented." That's his spooky action at a distance. That's what he's like, "How does it know fo- four light-years away at Alpha Centauri that I just measured the spin right here?" And he's like, and again, you know, his, his, his thing is, "Surely you don't believe-"
- CWChris Williamson
(laughs)
- SCSean Carroll
"... that's what it was." So he thinks, Einstein is convinced, that there was some fact of the matter about when you were gonna measure this electron, were you gonna get spin up or spin down? And therefore, there's some fact of the matter for the other one too. There, that there's something, something deeply hidden, right, that would predict with 100% probability what you're going to eventually observe. And what John Bell proved is that that can't happen unless there is some other kind of spooky action at a distance all along. So the spooky action at a distance is just absolutely part of quantum mechanics, like it or not.
- CWChris Williamson
Hmm. Am I right in thinking as well that that, the measurement of one versus another that was four light-years away would happen instantaneously? So that would-
- SCSean Carroll
That's the, that's the idea, yeah. That's right.
- CWChris Williamson
That's the prediction. Which also would ... I mean, does that break the lo- the maximum speed of something? Is it, is it-
- SCSean Carroll
S-
- CWChris Williamson
... actually a speed that something's happening-
- SCSean Carroll
Yeah.
- CWChris Williamson
... at the same time?
- SCSean Carroll
That's, that's a great question. You know, it's, uh, the answer seems to be that it violates the spirit of-
- CWChris Williamson
(laughs)
- SCSean Carroll
... the speed limit, but not-
- CWChris Williamson
I love the idea (laughs) of the spirit of it. It's like-
- SCSean Carroll
Right.
- CWChris Williamson
... this, this might be true, but it's unfair and we really shouldn't sanction it.
- SCSean Carroll
So, when you ... The thing is, when you measure the particle here, you know that if you get spin up, that's gonna be spin down. If you get spin down, that's gonna be spin up. So the state, the way that we describe the particle over there, does change instantly right away.
- CWChris Williamson
Outside of your light cone, right?
- SCSean Carroll
The thing is, outside of your light cone, faster than the speed of light. The thing is that the person over there doesn't know what answer you got.
- CWChris Williamson
(laughs) Until-
- SCSean Carroll
You measure it here.
- CWChris Williamson
... until, at the very least-
- SCSean Carroll
So as far as they're concerned-
- CWChris Williamson
(laughs)
- 45:00 – 1:00:00
Mm-hmm. …
- SCSean Carroll
mechanics seems mysterious and there's a lot of other things that seem mysterious, so maybe they're related somehow.
- CWChris Williamson
Mm-hmm.
- SCSean Carroll
Uh, and, you know, other theories of physics are, are put to bad uses also. So it's just sort of a bit of sloppiness that people necess- or inevitably, uh, give into. But the other thing is that physicists have done a bad job of trying to understand quantum mechanics. And for a long time, it... they've made it seem like the role of a human observer is somehow crucial to explaining what happens in quantum mechanics. Someone measuring things, right? Someone actually looking at systems. And that lets you insinuate that somehow you are bringing the world into existence just by looking at it. And that is very close to saying that you influence the world, that the ways in which you look at the world and the ways in which you interact with it can somehow change the world out there.
- CWChris Williamson
Mm-hmm.
- SCSean Carroll
So you, not only do you bring the world into existence by looking at it, but you can choose what kind of world to bring into existence.
- CWChris Williamson
Mm-hmm.
- SCSean Carroll
Now, none of that has anything to do with quantum mechanics. That's all just crazy talk, wishful thinking, woo-woo kind of nonsense. But the physicists should ser- share, uh, part of the blame for letting people talk that way because they've not been at all clear about what quantum mechanics really says.
- CWChris Williamson
People talk about m- manifesting realities and, uh, uh, and I think they use the measurement problem or I think they would call it like the observer effect or whatever, right?
- SCSean Carroll
Yeah.
- CWChris Williamson
To, to explain that stuff. There was (clears throat) another conversation I was having recently about online coaches, so online fitness and diet and nutrition coaches, and I was asking the... these guys, I was saying, "Why is the industry filled with so much kind of misinformation and so many charlatans and people like that?" And they said that it's because of, uh, a lack of obvious causality between-
- SCSean Carroll
Mm-hmm.
- CWChris Williamson
... what, what happens and then the results on the other side of it. And where you have this vacuum of a lack of information, it just allows people to just throw speculation in there, right?
- SCSean Carroll
Yeah.
- CWChris Williamson
It's like, "This sounds like a plausible narrative." And, uh, you know, if, if there is anything that I hope that the listeners can take away from today's conversation, it is that plausible narratives are probably not the world in which quantum physics operates.
- SCSean Carroll
(laughs)
- CWChris Williamson
Like, it's not because there's, like, a good guy and a bad guy. There's like... it's not that-
- SCSean Carroll
Yeah.
- CWChris Williamson
... like the Higgs boson was like the referee or something like that. Like, we, we, we love to personify these sorts of stories, right? Because it, it brings them onto our level, it brings them onto the level of a social being, but that's not what's happening.
- SCSean Carroll
Yeah. No, it's absolutely right. And, uh, as David Albert, who's a philosopher of physics once said, you know, when, when it comes to trying to understand the deepest mysteries of nature, if they don't make you uncomfortable, you're not doing it right.
- CWChris Williamson
(laughs)
- SCSean Carroll
Because, you know, of course, the world's most fundamental level is something very, very different than we experience in our everyday lives. So, uh, this is one of the things that, that, uh, is an important consideration when you compare many worlds to other possible interpretations of quantum mechanics. Many worlds is the simplest. It has the fewest equations, the fewest ideas, it generates what you see in a very natural way. But it's very far away from what we observe, right? It's so different in structure and language than, uh, the world of our everyday experience that it is perfectly legitimate to say, "I just don't believe that this very, very simple lean and mean theory really gets us to the world we see." So other alternatives to many worlds generally bring in a lot more extra stuff that is somehow latching on to the classical world that we experience, whether it's extra hidden variables or ways that particles behave or whatever. And it's not crazy to think that that might be the way to go, that there might... there might be something extra other than the pure bare bones formalism of quantum mechanics that gives us this classical world we see around us. But...... the, I would, for people like me, the Many Worlds version is just so simple and so compelling that it's worth taking that extra effort to map it on to the world we see. So we actually see it as sort of a, a feature, not a bug that Many Worlds is so alien and so different, because that's what the nature should be like at its deepest level.
- CWChris Williamson
Mm. So when people say to kind of close the door to hell that... or hopefully there is the observer effect and the measurement problem for, you know, people that are reading The Secret and manifesting-
- SCSean Carroll
Yeah.
- CWChris Williamson
... good, good energies and bad energies and, and stuff like that. Um, without observers in the universe, would everything continue just as it is?
- SCSean Carroll
Yeah, absolutely. I mean, not only that, but, uh, uh, a theory like Many Worlds or the, the respectable alternatives to it, hidden variable theories, dynamical collapse theories, there's a whole bunch of different alternatives. Um, the, the word observer plays no role.
- CWChris Williamson
(laughs)
- SCSean Carroll
You know, that, that was a useful approximation when we didn't understand quantum mechanics very well. What we talk about now are the actual equations telling us what's happening, you know, when a big system with many degrees of freedom interacts and becomes entangled with a small system that's in a super position, et cetera. So it was just the bad old days when the idea of observers or experiences were thought to be in any way related to quantum mechanics.
- CWChris Williamson
And that's just been grandfathered in?
- SCSean Carroll
Well, look, not everyone agrees, right? Uh, progress is slow, especially when there's not a killer experiment to show everyone they must get on the bandwagon.
- CWChris Williamson
(laughs)
- 1:00:00 – 1:01:30
That's awesome. Also, you're,…
- SCSean Carroll
released an episode with a philosopher, and I've had musicians and poker players and biologists, uh, and it's a lot, been a lot of fun for me.
- CWChris Williamson
That's awesome. Also, you're, you're pretty prolific on Twitter ali- as well, right?
- SCSean Carroll
Twitter, yep, SeanMCarroll. And again, that's, that's a link from my home page, but, uh, yeah, I really like Twitter. It's, uh, it's, it's for better or for worse, I used to be a prolific blogger on my website, and I still do that sometimes, but, uh, it's easier to get my point across in a quick tweet and then move on to do real work, uh, rather than write a respectable blog post. So I- I'm letting this side down, but I do try to say some interesting things on Twitter, yeah.
- CWChris Williamson
I like it. I like it. If you're a physicist who's able to get his message across in less than 360 characters or whatever it is, I think, yeah, you're doing a good job.
- SCSean Carroll
Yeah. (laughs)
- CWChris Williamson
Uh, ladies and gentlemen, it's been an absolute pleasure. You know what to do. The links to all of Sean's books plus his website and his Twitter and everything else will be linked in the show notes below. If you've got any questions, comments, or feedback, get at me @chriswilex on all social media, leave a comment in the YouTube channel, or just hassle Sean on Twitter and he'll, he'll give you a reply maybe if he's-
- SCSean Carroll
Maybe.
- CWChris Williamson
... if he's online.
- SCSean Carroll
You never know. Yeah. (laughs)
- CWChris Williamson
(laughs) Sean, thank you so much for your time. It's been great.
- SCSean Carroll
Thanks very much, Chris.
- NANarrator
(instrumental music)
Episode duration: 1:01:30
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