AMA | December 2023

0:00:00.2 Sean Carroll: Hello, everyone. Welcome to the December 2023 Ask Me Anything edition of the Mindscape Podcast. I'm your host, Sean Carroll. So I will confess that I thought that maybe we would have some more, anyway, questions this month that were instigated by the recent spicy, controversial podcast that we had. You know, I did that solo episode on artificial intelligence and indeed online that got a lot of responses, both very, very positive and very, very negative. And it just reminds me that I am not built, I'm not cut out for controversy on the internet, which is weird to me because I love academic controversy. I love talking to people who have thoughtful opinions about things but as I mentioned before, it is to those of you who are not in academia, or not in the good parts of academia anyway, there is a difference with how disagreement happens.

0:01:01.9 SC: Academic disagreements can get very heated, very personal, very irrational sometimes but for the most part, when you give a talk or you write a paper or whatever, people can entirely, absolutely, strongly disagree and yet do so in a way that is constructive, that is offering, here are the reasons for my disagreement, et cetera. That doesn't happen as much on the internet and it just makes me sad to get completely unhelpful kinds of disagreement, let's just put it that way. But also I got some very constructive comments, so that was very useful. Not that many questions about that stuff in the AMA though. Likewise, we had the even more controversial episode with Derek Guy talking about fashion and the theory and practice of it.

0:01:52.4 SC: There it was just much more hilarious because people reacted very negatively to it without... Before they even could possibly listen to it. I know that when you react to a podcast a minute after it has been posted, that probably you haven't actually listened to it. And again, the responses were remarkably not very thoughtful for that one. Again, we had very good responses, but there were a lot of like, oh, you've lost your way. What kind of nonsense is this? This is not why I'm here, cancel my subscription, that kind of thing, which I've gotten since the very beginning of doing Mindscape to the very beginning of talking in public. People have been disappointed in me that I have not talked about the things that they wanted me to talk about and I'm going to keep disappointing them but it doesn't just roll off my back. It does make me sad that we get those kinds of responses. That's too bad. I thought the episode was great and I hope that the people who listen to it actually learn something about the theory behind this kind of frivolous occupation that we call dressing well.

0:02:55.1 SC: What we did get this month, and as you'll see, is a bunch of questions about the usual topics, most especially quantum mechanics, which leads me to mention that I have a new course out through Wondrium/The Great Courses. Wondrium and The Great Courses is the same company, the company that used to be called The Teaching Company. I basically did a course on quantum mechanics based on my book, Something Deeply Hidden. So we'll talk both about quantum mechanics in general but also about the Many Worlds interpretation in particular. And there were some things I did for The Teaching Company course that I did not do in the book. There's a little bit on quantum computing, there's more on sort of ethics and the meaning of Many Worlds, things like that. A little bit on Immersion Spacetime and so forth. So it's 24 lectures, half an hour each slickly produced by the people at The Teaching Company.

0:03:48.1 SC: And I think the only difference... I'm not even sure I understand this, but I think the difference between The Teaching Company label and the Wondrium label is whether it's streaming or whether you buy the DVDs. So go to either Wondrium, that's W-O-N-D-R-I-U-M or The Great Courses. I've been saying The Teaching Company, The Great Courses and you can get the course, I think probably... I don't know whether it's still true by the time you'll hear this, but there was at some point a Black Friday sale. Anyway, so much knowledge for so little money that it's worth it no matter what they are charging for it. It's a different modality, right? Like some people like reading words on pieces of paper, some people like listening to audio, some people like watching videos, et cetera.

0:04:34.1 SC: So if you like watching the videos and seeing the explanations with nice slick animations and so forth, this could be the course for you. Likewise, I wanted to mention two other things, book-keeping things. One of course is that these Ask Me Anything episodes are sponsored by supporters on Patreon. Anyone can be a supporter on Patreon. You can just go to Patreon.com/seanmcarroll and chip in a dollar or whatever per episode of Mindscape. It's much easier than you think to just sign up for Patreon, give a little dollar here and there, not just to me but to other creators and so forth. It's a nice thing to do. You can always get Mindscape for free if you listen to the ads but if you're on Patreon, you get an ad-free version. You get to ask the AMA questions. You also get little reflection videos that I do after each episode. So a tremendous deal at Patreon.com/seanmcarroll.

0:05:30.9 SC: And the other thing to mention is the Mindscape Big Picture Scholarship which is still ongoing, which you can either donate to if you're at that stage of your life or apply for if you are a high school senior, which is at bold.org, that's B-O-L-D.org/scholarships/mindscape. And I think that we're already funded to give out one scholarship this year and we're very close to being able to give out two. So that would be awesome. So if you could kick in, we would go over the target to be able to give out two scholarships. That's $10,000 to someone who wants to go to college to study very difficult, big picture questions, which is what we're all about here. And if you want to apply for that scholarship, please do. The application deadline is December 15, 2023. And with that, I think that's all the book-keeping we got to do. So let's go.

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0:06:40.6 SC: Our first question is from Rue Phillips. I loved the graphic your wife put out recently showing the entertainment value versus scientific value of time travel movies. Movie making has always been fascinating for me, and I know you've been involved in multiple productions. I would love to hear from you about your favorite and least favorite movie making experiences. And if you feel generous about answering a follow up, I'm very curious what you would do differently if there was a new Pride and Prejudice adaptation. So what Rue is referring to is that Jennifer and I did our first written collaboration. We do have a talk that we gave together. We sort of tagged a team to talk on black holes at the Royal Institution in London.

0:07:18.4 SC: That was a lot of fun, but we've actually never written anything together. We've certainly commented on and helped edit and shape each other's individual writings, but we've never collaborated until now. We co-wrote a story for Ars Technica, which is where Jennifer is a staff writer. So you can go to Ars Technica, look for time travel. And what we did was we took 20 time travel movies and we ranked them, not ranked, but rated them, let's put it that way, on a zero to 10 scale on both how successful they were as movies, that's one axis of the plot, the other axis is how much sense they make as time travel. So that second axis means both, is the time travel more or less scientifically respectable but also, does it make logical sense?

0:08:11.0 SC: Even if you just disappear in a puff of smoke and reappear at a different time, which is not very scientifically respectable, you can still be internally consistent. Right? And that's the kind of logical points that we gave, and especially if you used time travel in a very deep and important way. Again, we didn't go for controversy here. We were trying to celebrate the movies that did it well. Twelve Monkeys does it exceptionally well. Interstellar got some points, but also lost some points for the weirdness at the end. And Star Trek: The Voyage Home does remarkably well on these, at least on the scientific time travel kind of axis. I also thought it was actually quite a good movie, so you can read about those rankings. We had a lot of fun with that. And of course, we get controversy. We don't look for the controversy. The controversy came in one part that we expected and one part that we didn't. One part that we expected was that neither one of us really liked the movie Primer. And I know this is going to raise people's hackles because it's a cult classic and the people who love that movie really, really love it.

0:09:17.8 SC: But we neither loved it that much as a story nor as a time travel logic thing. The time travel in Primer is extremely convoluted and there's a lot going on which I think gives people the impression that it's kind of deep, but I don't think it actually is very deep. I mean, it does use time travel to... That's very much the point of the movie. It's not just a little side device, obviously, so it gets points for that but at the end of the day, it does the usual kind of time travel logic mistakes about changing the past and not having things be perfectly consistent, et cetera. So sorry, Primer fans. We wanted to like it, really, but it didn't quite work out.

0:10:00.6 SC: The weird thing that I wasn't expecting is that in our list of 20 movies, we did not include Time Bandits. And people got very upset about that. And I will tell you right here, right now, we watched Time Bandits for this purpose. We thought it was going to be on our list but the thing is, Time Bandits doesn't really use time travel in any intimate way. Time travel is in the movie, that's true but it's just an excuse to sort of be a fantasy, escaping to different parts of the world by escaping to different moments in time. Right? It didn't actually have any commentary on affecting the past or going to the future or loops or anything like that. That wasn't actually there in Time Bandits.

0:10:44.4 SC: And in fact, by the end, it's just obviously over the top fantasy having nothing to do with time travel at all. So that's why we didn't do Time Bandits. Sorry, Time Bandits fans. Look, it's a list of things on the internet. What is the point of lists of things on the internet if not to disagree with them and put in your own opinions in the comments? You're welcome to do that. As far as the actual question that Rue is asking, I don't want to say what my least favorite movie making experiences are. I've absolutely had experiences where I did a certain amount of work, collaborated with a writer or a director or whatever, and it never came to anything. That's kind of frustrating sometimes, but that's very much the way that Hollywood works. I think I mentioned before, back in my youth, I had ambitions to maybe someday write a screenplay or collaborate or something like that but these days I don't think I would be interested in doing that anymore because it's just a weird business model that Hollywood has, where you put a tremendous amount of work into things, then you get literally nothing to show for it.

0:11:45.4 SC: And I'm not even talking about the recent spate of studios making the whole movie and then just not releasing them for some weird tax write-off purposes. I'm just talking about the very, very common thing where as a writer in Hollywood, you put a lot of work into a screenplay, you're paid to do it even, and then nothing ever comes of it. Very, very frustrating. In terms of favorite examples. Actually, I think my favorite experience there was on the TV show Bones. And again, I've talked about this before, but it was a long time ago. There was a wonderful episode written where Richard Schiff, who played Toby on The West Wing, played a physicist on Bones and his daughter got murdered. And I'm not going to give away any spoilers or anything like that, but he was a suspect. And part of the reason why he was a suspect is because they portrayed him as a slightly stereotypical physicist without a lot of social skills.

0:12:41.2 SC: So he didn't act as upset about his daughter getting killed as the investigators thought he should have but then he finally managed to capture his love for his daughter in a series of equations, almost like a little poem in the form of equations. And so I got to write the equations, and I got to write the blackboards, and I got to write some other lines of dialogue when the character was talking about physics and so forth, so the characters, Richard Schiff's character's most recent paper bore a tremendously close resemblance to a paper that I had recently written. Let's just put it that way. So that was fun. I actually got to be on set while they were filming it and everything. Much more involvement in TV than at the movie level.

0:13:24.2 SC: Movies are huge industrial efforts these days, right? So I've never been on a movie set, and the writers on a movie have much less effect on what you actually finally see as the product than they do in TV. TV is a writer's medium. Movies are more a director's medium, if not a studio's medium. So writers for TV are the ones who are important, which is just not true in the movie world. As far as Pride and Prejudice is concerned, my advice would be do not adapt Pride and Prejudice. It's already been done more or less perfectly by the BBC with Jennifer L and Colin Firth. You don't need to adapt Pride and Prejudice ever again. Next two questions. I'm going to group two together. One is by Ties Jansen, who says, in the past you mentioned or maybe in some way even recommended David Wallace's book, The Emergent Multiverse for a deeper dive into Everett and quantum mechanics but I get stuck, especially the parts beginning with, as you recall from your quantum mechanics textbooks. These are hard to understand for me because I never had one. There's a huge apparent required knowledge gap between your quantum mechanics books and this one.

0:14:34.9 SC: Can you recommend a way to bridge that gap? I don't mind to do some work for it, but I don't feel motivated to do unguided self-study with a Copenhagen quantum mechanics textbook. And then Chris Murray says the first Biggest Ideas book features an essentially complete description of what general relativity is, which, though unaccompanied by many of the tools needed to actually work with it, is tremendously insightful. Will the second book provide similarly complete descriptions of quantum mechanics or quantum field theory, or would that be too much? So I'm grouping these two questions together because they both involve the book that I just finished copy-editing, which is Quanta and Fields. That's going to be book two of the Biggest Ideas in the Universe series, it's going to come out in May 2024.

0:15:18.0 SC: And it is just like book one, the idea is to be popular science, to explain things to everyone who's interested, not just to professional physicists, but to show you all the equations. And it's interesting because for Ties' question, I don't know whether that will be a good background, but probably it's the best thing I can think of. Some linear combination of that book and the Susskind series, Lenny Susskind series on the theoretical minimum. He has a book on quantum mechanics.

0:15:51.1 SC: His book on quantum mechanics is more sort of traditional, right, straightforward. Here is how we would do quantum mechanics if you were learning quantum mechanics as an undergraduate, but without necessarily quite as much detail as if you were officially a physics student. So it's a little bit easier to get through. Whereas my book, because it tries... So Lenny has a whole book on quantum mechanics. My one little book is doing both quantum mechanics and quantum field theory. So all of quantum mechanics happens in just the first three chapters, and there's 12 chapters total. So most of it is quantum field theory. Which leads me to Chris' question, which is, is the level of detail, is the level of completeness the same in the quantum field theory book as it is in the general relativity book?

0:16:39.2 SC: Well, no, is the short answer. And I say this right at the beginning, I try to be very upfront about it. When you do relativity and classical mechanics, you can, even in a relatively short book, basically give all of the equations in complete detail. Like Chris said correctly, the goal is not to try to solve the equations. So that's okay but you should at least understand exactly what's in all the equations. In quantum field theory... Quantum field theory is just a much larger subject than general relativity is.

0:17:14.5 SC: General relativity, despite its intimidating reputation, is relatively self-contained and the number of ideas is relatively small, whereas quantum field theory is enormous. I mean, just the idea of a quantum field is more or less the same amount of content as the idea of general relativity but then you have to get in the different types of fields. You have spinor fields and gauge fields and scalar fields. You have to get into renormalization and effective field theory. You have to get into symmetries, gauge symmetries and group theory. You have to get into the different phases of quantum field theory. So you have Higgs phase and Coulomb phase and confined phase, and you have to do all of that stuff, not to mention explaining what Feynman diagrams are, interactions are and so forth.

0:18:00.4 SC: So there's a lot you have to do. There are a lot of equations. Honestly, the density of equations is maybe a little bit higher in book two than in book one, and the equations are correct ones, okay? But not every detail is there in the same way that it is in the relativity book. Just as one example, when you do fermions in quantum field theory. So a fermion is spin-one-half particles, particles that take up space and obey the Pauli exclusion principle, like electrons and quarks and neutrinos and so forth.

0:18:33.7 SC: If you were a student learning quantum field theory, there's a lot of effort that goes into understanding the mathematical structure of the fields representing fermions. So they are called spinor fields. They have certain indices. They behave a certain way under Lorentz transformations. They involve things like Pauli spin matrices and Dirac matrices. They anti-commute with each other at the mathematical level. None of that stuff is going to appear in the book but things like the mass term and the kinetic term and the interaction term for fermions with gauge fields and also things like the spin statistics connection and why particles with spin-one-half are fermions and take up space, all of those conceptual things are there.

0:19:23.1 SC: So the difference in book two is I really tried to focus in on the concepts to the extent that sometimes the best way to focus in on the concepts was to make the equations a little bit simpler in this book than they would be in an actual textbook. So for those of you who are experts out there, things like Fierz identities are not going to appear in this book but hopefully I really think that there's still enough notation in there that it will look weird and intimidating if you're not used to it. So I encourage people to give it a try. And if you do give it a try, you will actually come away knowing what is actually meant by things like gauge symmetry, renormalization, the Higgs mechanism, things like that. So it's a fine line that I'm trying to balance there in that book. We'll have to see whether it's successful or not.

0:20:19.5 SC: Robert Ruxin Drescu says for two or even three years, my sister didn't want to stop eating, and she didn't like walking or doing any physical work, not even for her health. She just ate and stood in bed speaking to people on the phone. Because of this, she got heavier and heavier, and her oxygen levels started to go down dramatically until we found her dead in her bed a few weeks ago. I could probably have saved her if I and my family would have put tremendous amount of effort into this. Also, she would have survived if violence would have been used. She said that for a handful of times she just didn't care if she lives and she just wants to eat. My question is this, how do you navigate these complex issues? How do you determine if you should use violence to save someone, for example, or if violence is simply unacceptable? So I'm really, really sorry to hear about this, Robert. I mean, Robert has been a longtime supporter of Mindscape and asks a lot of great questions in the AMAs over the years. This sounds like a really, really difficult thing to go through for everyone involved, so I'm sorry to hear about it, and I hope that you're doing okay. And the issues are complex.

0:21:28.9 SC: There's no simple answers here in my mind, and it depends on a lot of things that I don't know. So at some level, you have to navigate these things as a human being rather than hoping to find some clear, crisp, algorithmic answers. I think what it comes down to is autonomy and responsibility, right? I'm a big believer that different people, at least as long as they are responsible and in their right minds, should have the autonomy to do with their lives and their bodies and their brains what they want to do. For example, in a slightly different example, but a related one, it often is the case that when people get older, when they get very old, they want to do things that are maybe considered unacceptably risky by their children or their caretakers or whatever. And generally my perspective is that they should be allowed to do that. It's their lives, and they should be allowed to do it. The question, the reason why that becomes complicated is because sometimes it's not just risky, but genuinely self-destructive, these kinds of behaviors. And then it is perfectly reasonable to ask, is the person engaging in these self-destructive behaviors, are they actually of sound mind as well as body?

0:22:50.8 SC: Or are they struggling with some mental illness or something that could be cured by either medication or therapy or something like that. And I don't know. And I'm sure that it's hard for anyone to know the question like that. At a philosophical level the question is, who is responsible? When is a person... When do they deserve to have the right to make choices about themselves? Someone who is an addict, for example, a drug addict or someone who clearly has a kind of specific mental illness that leads them to be incapable of making decisions, then I can see other people intervening in some way. I'm not quite sure why the word violence is necessarily here, but certainly intervening in someone's life to save their lives, even if it's against their will is absolutely allowed under certain circumstances but under other circumstances I think that people have the right to decide. And even if that decision is to let themselves go or even end their lives, I think that that should be something that people have the right to do. But again, there's just no easy answers here. The only thing I would say is don't be too hard on yourself for whatever might have happened.

0:24:08.2 SC: It's not like you made a mistake. It's not like there was some clearly right thing to do and you didn't have the guts to do it. The point is that someone else, your sister, was making choices and the default should be to let people make their choices even if they're not the choices you want them to make. I can imagine circumstances under which it is useful and necessary to step in and intervene but those are the exceptions rather than the rules. So don't be too hard on yourself. Things happen. Sometimes terrible things happen, sometimes tragic things happen, sometimes preventable tragedies happen even if everyone is doing the right thing at every point along the way. So, sorry to hear that that had to happen. I hope that you sort of can sort through it and move on.

0:24:57.4 SC: Again, I don't think that you personally seems like did anything wrong whatsoever. Sid Huff says, you have noted that democracy in the United States is under threat. If worse came to worst and American democracy collapsed, would you and Jennifer consider moving to another country assuming appropriate professional opportunities presented themselves? I do think that American democracy is under serious threat. I think that we are not as a culture, as a nation, we're not taking that threat nearly seriously enough. I go on about it. I guess that's something to do. It's not very effective, but it's a little bit. So would we leave the country? It certainly wouldn't be my first choice. I could imagine doing it under certain circumstances but what I would rather do is stay and try to fix things, try to fight, try to make things better.

0:25:52.9 SC: I'm in a position where it's easier for me... It would be hard for us to pick up and move for various reasons, friends, house, job, all the usual things. We're very, very established at a certain part of our lives. We're not just picking up and moving kind of people right now, but we have the resources to imagine doing it, whereas other people don't even have those resources. And it seems not quite fair to me to abandon those people when times get tough. So I don't know what it would mean to resist and to keep fighting against it, et cetera but that would be my first desire, that would be my first inclination is to try to make things better. Democracies do come and go, and if they go, they could possibly be brought back.

0:26:34.8 SC: Again, I don't know how to do that, but I would like to think that I would try. Nick C says, there was a recent article in the Washington Post talking about how John Clauser, who recently won the Nobel Prize for quantum mechanics experiments, is a vocal climate denier, news which disappointed me quite a bit. From what I can tell, his objections are not terribly credible. I guess I'm curious for any thoughts you have on that particular situation or the general situation where professional physicists go on to become crackpots in other fields at what seems to me to be an above average rate compared to other scientists. Why does that happen? Well, I don't know why it happens.

0:27:12.6 SC: This is compatible with the perspective that I have previously suggested, that you shouldn't have heroes because people can be really good at certain things and really bad at other things. And I don't know whether physicists go on to become crackpots at a higher rate than average, but some of them do become crackpots. That's absolutely true. It shouldn't be completely surprising, let's put it that way. And the reason why it shouldn't be completely surprising is it would be a mistake to think there is something called general purpose smartness. There just isn't, there are different kinds of smartness, and common sense is one of them. An ability to judge different sources of evidence is another. An ability to do very, very precise, accurate physics experiments is a very different one than either one of those. So physics is perhaps the most hyper specialized of the sciences. It's the most advanced science, and I don't mean that as bragging. It's the easiest science as I've often said.

0:28:20.7 SC: The questions that physics asks are very deep and very profound, but they're also easier to address and make progress on than questions in biology or psychology or things like that. So as a result, you can be a super successful physicist with a rather narrow skill set. With being really, really good at one very particular thing, you can be a Nobel Prize-winning physicist. There's zero reason to think that that particular skill set should generalize to other hard problems. And as a result, you see plenty of people who are highly credentialed physicists whose opinion about issues that are not within physics are completely bonkers, and climate change is one of them. Climate change is absolutely one where the number of physicists who are very successful have found it more attractive to be saucy contrarians, than to actually just get the right answer, which is pretty darn clear at this point.

0:29:21.6 SC: So I don't know exactly whether physicists are more likely to do that than others, but I do think it makes sense that you can be a super successful physicist and also bonkers on other things. There are physicists who are believers in parapsychology or whatever. Physicists should be... Well, let's put it this way. I once had... I was talking when I was a postdoc about some philosophy question with one of my physics professors, and we were in my office, and there was I think it was like the Feynman lectures on physics was on my desk, and the professor was arguing me about this philosophy question and said, what would Richard Feynman say about philosophy? And I said, Look, I will take very, very seriously whatever Richard Feynman has to say about physics, about theoretical physics, quantum field theory, quantum mechanics in particular.

0:30:12.8 SC: I see zero reason to take seriously what Richard Feynman has to say about anything else at all. I'm sure that sometimes he's right, I'm sure that sometimes he's wrong, just like any other human being but the ability to be really, really, really good at quantum field theory does not give you any special expertise in anything else. Now, I absolutely realize I am opening myself up to being criticized because I talk about all sorts of things, right? And what I would say is, yes, I do talk about all sorts of things, just like Richard Feynman did. And Richard Feynman has every right, as does John Clauser, to talk about whatever they want. So do I. But you shouldn't believe what I have to say about climate change or politics or religion or what John Clauser says or what Richard Feynman says, just because we're physicists. If you believe or don't believe, do so because what we're saying makes sense and comports with the data and your understanding of the arguments and things like that. I'm going to keep talking about all sorts of things but you should think about it, not just believe what I say because I'm a physicist. Not that anyone ever has but just to point out, I am not asking you to do that.

0:31:25.9 SC: John Capstone asks a priority question. Remember that if you are a Patreon supporter, then you get to ask a priority question once per lifetime. I'm going to just trust that no one abuses the privilege and tries to sneak in with different names or anything like that. And with the priority questions, I will do my best to answer them. So John asks, imagine that a spin up particle is split into spin left and spin right components. The components interact with two quantum computers whose operation is then reversed so that when the spin components are brought together again, we recover the original spin up state. Is it true that the quantum computers cannot be acting as conscious observers measuring their respective spin components because if they did, then we would have ended up with a spin left and spin right particle rather than a spin up particle.

0:32:16.1 SC: So this is a somewhat... I'm not completely clear on the experimental setup here, so let me say things that I think are true. If you take a spin up particle, as John says, you can measure its spin. So its spin up along the Z axis, let's say but you measure its spin along the X axis. You measure it in some axis that is perpendicular to how it is originally oriented. So you will get it 50/50 split between spin left and spin right. And you can do that, and you have to be careful. You don't want to measure it, but you can split it. Okay? So you can send it through a magnetic field, and then you have a component that is going spin left, a component that's going spin right but you don't actually measure either one of them. You just know that that's what they're doing because you understand the rules of quantum mechanics.

0:33:01.6 SC: And then you send these spins into a quantum computer, and you process them. Now ordinarily that processing would involve, at some point, doing a measurement. And then when you do that measurement, the spin that you had will disappear in one of the two apparatuses that you just sent it through. You'll be in one branch of the wave function, the spin only would have gone into one quantum computer and not into the other. In the other branch, it would have gone into the other and not the first one. You can invent something that you're going to choose to call a quantum computer for which no measurement or decoherence or branching happens. So basically, that's just a fancy way of saying I have my wave function that has these two different parts to it, the spin left part and the spin right part. I'm going to let those things interact, but not become entangled with anything that they're dealing with. It is only if they never become entangled that I could ever bring them back together to get a spin up particle.

0:34:06.3 SC: So if they didn't become entangled with anything, then it's almost as if quantum mechanics is not relevant to what is happening, right? It has nothing to do with conscious observers. It is true that the correct thing to say is that these two things that you're choosing to call quantum computers, even though they're not really regular quantum computers, because regular quantum computers do involve measurements, these two things you're choosing to call as quantum computers did not measure their respective spin components, so has nothing to do with consciousness. They just didn't measure them. They didn't measure them as conscious observers. They didn't measure them as unconscious observers. Now, there's a more subtle question. Do you have to do measurements to be a conscious observer? Well, no one quite agrees on the definition of what a conscious observer is. I would argue that to be a conscious observer, you have to participate in the Arrow of Time. So you have to generate entropy in the universe to form memories and things like that. And therefore, in general, things that you recognize as conscious observers will be doing measurements, increasing the entropy of the universe, et cetera.

0:35:15.8 SC: Something that is completely pristine and reversible would not, in general, in my mind, count as a conscious observer. Schleyer says, in your reflections following the Weinersmith's podcast, you opined that living is good, life is good. Having more life elsewhere in the universe would be a good thing. Do you think of this as a base level subjective preference or does it reflect some underlying principle such as valuing complexity or joy? Well, I'll confess I do not think that this is any deep philosophical statement or it's certainly not an overarching absolute principle. It's just a vague feeling. I think that I personally prefer a universe with living creatures in it. I'm not going to say that we need to maximize the number of creatures or anything like that, but I like living. This is absolutely my subjective preference.

0:36:08.8 SC: There are people out there who wish there were no living creatures in the universe. I don't get it. I know that living creatures do both good things and bad things but overall, I would like there to be living creatures. Yeah. That is a hill that I will try to defend. Roland Weber says, in chapter six, spacetime of the Biggest Ideas in the Universe, Volume One, you write, here's an idea. Let's define the energy of an object in relativity to just be that zeroth component of the four momentum that felt like it was just dropping out of the sky. Why can we ignore the three spatial dimensions of the four momentum and just pick the time dimension here? Well, we're not ignoring the three spatial dimensions of the four momentum.

0:36:49.7 SC: Those three spatial dimensions have a name already, they are called the momentum. If you are doing pre-relativity physics, if you're doing Newtonian mechanics, Newton wouldn't have said this because he didn't know about these ideas but if you're doing Newtonian mechanics before Einstein came along, you would have said there is a three dimensional vector called momentum, and there is a scalar quantity, a zero dimensional number called energy. So you have four numbers. The one number of energy and the three numbers of momentum. All that happens in relativity is that those four numbers get combined together to make a four vector. And the way that they get combined together is that the energy is the zeroth component, the time-like component of the four momentum and the ordinary three dimensional momentum are the spatial components of the three momentum. It's not just the definition, it's not a definition in any sense. Well, in some sense it's a definition because of course, when you go to relativity, the actual formulas for energy momentum get changed a little bit. They get changed in a way that you wouldn't notice if you were moving slowly compared to the speed of light.

0:37:56.9 SC: But once you start moving near the speed of light, you begin to notice a lot. But they all reduce to the usual quantities when you have slow velocities with, of course, the tiny exception that there is an intrinsic energy to any object that is just sitting there, namely MC-squared. The rest energy of an object is MC-squared but that doesn't really matter in pre-relativity physics because it's just a constant. It doesn't really change with time or anything like that. In relativity, then you can change, you can turn that energy into other forms of energy. So that's why it turns out to be a sensible definition to make, even though it's a definition that is just a generalization to relativistic contexts of the definitions that you already had.

0:38:45.5 SC: Emmett Francis asks, do all non-rotating black holes have a spherical event horizon? Short answer is yes. Of course, there's always a longer answer. One part of the longer answer is what do you mean by the word spherical? In mathematics, we distinguish between topological spheres, which are just sort of a sphere, but you can deform it smoothly into any shape you want. So an oblate spheroid would still topologically be a sphere versus geometrically a sphere, which I swear to God this is true, the technical term is the round sphere. So a non-rotating black hole in three non-compact spatial dimensions, plus of course, the one time dimension will have a perfectly round spherical event horizon.

0:39:33.5 SC: If you let the black hole... And that's true whether it's charged or not charged, if you let the black hole spin, then it becomes an oblate sphere. So the event horizon is still topologically a sphere, but geometrically it's not round. By the way, I'm assuming that we're talking about the event horizon at one moment in time. The full event horizon is a surface in spacetime that is a null surface. It extends in time as well as space and light rays are exactly parallel to it in the right direction. But anyway, I think that probably what you're getting at is at any one moment of time in three plus one dimensions with all the dimensions large, then a non-rotating black hole will indeed have a spherical event horizon. And this is part of the no-hair theorem for black holes. Basically any black hole is completely, once it settles down and after it's made, it will be completely characterized by mass charge and spin. So if it's not spinning, it's just characterized by mass and charge. And the full metric is the short-shield metric for uncharged black holes, the Reissner-Nordström metric for charged black holes they both have spherical event horizons.

0:40:41.7 SC: I keep saying three plus one dimensions because there are weird things called black strings. If you have a compact extra dimension of space, then you can have a black hole whose event horizon is kind of like a cylinder in that extra dimension but those are subject to various instabilities, and it's a subtle question. So the rough answer to this question is yes, they are spherical. Yasus says according to my layman understanding about quantum field theory, the mass of a single particle is resulted by an interaction between an excitation of the Higgs field and an excitation of the electron field. It seems to me that Higgs field should have positive and negative excitations. If that's correct, theoretically, can there be a particle with negative mass as a result of the interaction between a negative excitation of the Higgs field?

0:41:30.4 SC: So, nope, there cannot be a particle with a negative mass but more importantly, there's a couple of misconceptions going on here, the mass... So for one thing, super duper important, and I talk about this a lot in the upcoming book because people get the wrong impression. In quantum field theory, there's no rule that says you need a Higgs boson particle or a Higgs field in empty space in order to get mass. If you think about the history of quantum field theory, the first really successful one was Dirac and quantum electrodynamics.

0:42:04.8 SC: Which later was even more successful after Feynman and Schwinger and Tominaga et cetera showed how to re-normalize it but there you have a theory that doesn't have any Higgs bosons in it. It's from the 1930s, and it has electrons and positrons, and they both have mass. There's no problem at all. What's up with that? The issue is that in the specific context of the Standard Model of Particle Physics, and in particular in the specific context of the weak interactions as they are understood in the Weinberg, Salam electroweak unified theory, there, there's a very special property, which is that left-handed particles and right-handed particles are treated differently. This is parity violation, which was unknown in the 1930s. And it turns out that when you have parity violation of this form, then you cannot have masses for the fermions without a Higgs mechanism, a Higgs boson in empty space. So Weinberg figured out how to fix that problem by adding the Higgs boson in but that's only because of the specifics of the Standard Model and in particular, the parity violation.

0:43:12.5 SC: So it's not true that just to get mass, you need a Higgs. To get mass in this particular theory, where left and right-handed particles have different symmetries, then you need the Higgs particle to get a mass. And the next thing is, it's not excitations in the Higgs field that give mass to other particles. It's the expectation value, not excitation. So an excitation is the vibrations over and above what we call the expectation value. The expectation value is just the average value of the field in empty space. So that's a positive number. It is unambiguously positive for the Higgs boson. A fluctuation of the expectation value would make it a little bit less positive or a little more positive, but still positive.

0:43:58.0 SC: And it's that expectation value that matters. An excitation of the Higgs field gives rise to Higgs boson particles, which play no role at all in getting masses for electrons and things like that. It's only the average background expectation value that matters. Sandra Stuckey says, science has its experiments, mathematics has its proofs but how do philosophers settle an argument or do they? Can you tell us a bit about the process by which philosophical communities you are part of make progress on important questions? Sure. They have arguments and logic and reason. I mean, the usual way that people settle arguments. Of course, philosophy is a very, very broad field. There are parts of philosophy that are very formal. Mathematical logic is part of philosophy, and there you literally have a proof, okay? With the rules of logic expressed in certain ways. There are questions in... Let's take something that we're all very familiar with here.

0:44:58.6 SC: The collapse of the wave function in quantum mechanics. Okay? And it is philosophers who really have insisted that this is not okay, the sort of traditional physics Copenhagen version of the collapse of the wave function, because it makes no sense. Because it's incomplete. Because it's just not well-defined. Maybe something like it is true, but it's not well specified. So a philosopher will say, look, here is where in your description of what happens in quantum mechanics, you have been unclear. Here is where you need to be more precise. You need to define what these words mean. It's an argument using reason and rationality, right? And of course, they might suggest a solution to that. The philosophers of physics are less good at solving these problems than pointing out when they exist. In questions like morals and ethics or epistemology or metaphysics, different kinds of fields will have different standards for what constitutes an argument.

0:45:55.5 SC: But very often you will see something like a formal syllogistic argument. Arguments by induction or by Bayesian reasoning or something like that, as well as good old deductions, if p, then q, therefore q kinds of things. Very often, these arguments are informal which is also true in math, by the way. We all know... Well, sorry. Mathematicians have established what it would mean to give an incredibly careful, precise, rigorous mathematical proof of something and they never do it. [chuckle] To be really actually precise is just incredibly unwieldy and mathematicians all know this. So even though the standards for rigor in a real math paper are much higher than in physics papers or whatever, they're still not anywhere close to the quintessence of formalization that, for example, Russell and Whitehead did in their book, Principia Mathematica, where they tried to establish the foundations of arithmetic and they didn't quite succeed perfectly but, okay, that's a different question.

0:47:06.7 SC: So, yeah. Just the usual way that we make progress on other kinds of arguments. What are your assumptions? What are your conclusions? Did you derive them carefully? Jesse Rimler says, in a recent AMA, you said that the economic system you prefer is regulated capitalism. You noted that a free market leads to more efficient pricing and innovation as opposed to the planned economies found in socialist systems. The defining feature of capitalism, one could argue, is not the free market, but private ownership of capital. Capitalist owners decide what to do with profits, employees rent themselves out for a wage and have little to no say about how a company operates. In this way, the capitalist model is fundamentally undemocratic. Of course, socialist systems have been state run, undemocratic or even totalitarian but another model in the socialist tradition is the worker owned cooperative.

0:47:52.2 SC: This setup extends democracy to the workplace, giving workers the ability to determine how profits are distributed and how to grow or innovate their companies. I'm curious about your reactions to these definitions and models. As far as definitions are concerned, you can define things however you want. It doesn't really matter to me. And also, I guess it rubs me a little bit the wrong way to say that capitalism is not democratic because there is private ownership of capital. It's democratic in the sense that there is private ownership of capital, but anyone can be a capitalist, right? Any person could privately own capital. There's no intrinsic discrimination in that kind of system. Of course, there's de facto discrimination because people are not born into equivalent circumstances in the world. And that is absolutely an issue that you could take... That is a fact that you could take issue with. That you could disagree with.

0:48:47.7 SC: But the idea that anyone can be a capitalist is what makes it democratic. Also, I don't care [chuckle] if it's democratic or not. I think that government should be democratic. For an economy, I want it to serve the purpose of the economy. I want everyone to be well-off to the extent that that is possible. So, but that's just all definitional issues. I think that you're raising a very interesting, good question about private ownership of capital versus collective ownership of capital. I'm open to the possibility that this is a good idea. I'm a little bit skeptical because I'm not sure that this is stable in some sense. This is always one of the big problems with socialist attempts to reformulate how the economy works, is that they tend to be a little utopian. They tend to say, well, if you have this kind of setup, then everybody will be happier.

0:49:40.3 SC: But the problem is they propose a setup... And again, I'm not saying this is true. I'm saying this is the thing to worry about that I would have to see established. They propose a kind of setup that is unstable to people taking over, right? It's unstable to inequality. You have some kind of equality built into your system, but the usual workings of the system drive it toward inequality in some way. I don't think it's fair to criticize socialism or communism just by pointing to the USSR or the Communist Party of China or other real world, 20th century implementations of things that called themselves communist, because I don't think that they were very true to the ideals that Karl Marx would have noticed but I am completely sympathetic to the critique that that kind of lack of fidelity to the original goals is more or less inherent in the system.

0:50:40.9 SC: That could just be a very natural kind of thing that any attempt to be a traditional communist society will end up in these kinds of anti-democratic unequal distributions of power and wealth. Again, I don't know that for sure, but that's what I would worry about. And again, I think that what matters to me much more is what the effects are. When it comes to economies, I am pretty consequentialist. When it comes to governments, I am less consequentialist. I think that my most important reasons for supporting democracy are more deontological. I think that people have the right to have a voice in the way their government is ran. I'm less sure that people have a right to own the company that they work for. Again, you could make the argument, but that's less obvious to me. And I think that... I'll just say it again.

0:51:32.7 SC: I said it many times. What we should do is we should tax the bejesus out of people. [chuckle] We should let people... And individuals are motivated. They're more motivated for their self-interest than for the greater good on average. Not always, but on average. And I think that an economy that is driven by that self-interest can be very, very effective. And then we let people earn a lot of money, and we take a lot of it back to redistribute it by the government. That seems like a relatively good system. That's certainly not exactly what we're doing right now. We're letting people keep a lot of the money far more than any individual really, really needs even to be quite successful. TJ McMorrow says, what is your view on the, I think, relatively fringe fields of econophysics, sociophysics and other projects which attempt to apply physics and/or physical principles more or less directly to domains well outside its standard purview?

0:52:24.7 SC: Well, I love these fields, [chuckle] I love it when they are done well. I am completely sympathetic to the idea that often they are not done well. Physicists have a completely earned reputation for thinking that they can waltz into other fields and clean up all their problems with just a few minutes of work and being spectacularly wrong about that feeling. Like I said before, there's nothing about being a successful physicist that gives you any special insight into other fields of endeavor. However, I do think that there are fields that there are... Not fields, but ideas, concepts that physicists do develop in the very, very simplified contexts that they care about, in the spherical cow contexts that can very well be a wider applicability.

0:53:17.3 SC: Whether it's ideas of entropy and friction and momentum or ideas of networks and interactions and energies or ideas of phase transitions and collective behavior and emergence. There are a lot of ideas that come from physics that could, in principle, be very applicable to other areas. Otherwise, I would not be working on a book called The Physics of Democracy, which is exactly what I'm working on. I think that it is absolutely the responsibility of anyone who wants to think in these terms, to be very, very careful that the usual simplifications and assumptions that physicists like to make, still hold in the context where they are considering things. They often don't, which is why you have to be more careful when you talk about economy or society or things like that in terms that physicists would recognize.

0:54:14.1 SC: Shahil Abdullah says, what is your opinion about cryonics? Do you see any legitimacy or future in it? Well, I don't think that there is any violation of the laws of physics involved in the idea that we could freeze somebody cryonically and wake them up later on. There are enormous challenges at a practical level and I think that we are nowhere close to actually addressing these challenges. So I think that current ideas, current literal attempts to cryonically freeze people in the hope of waking them up sometime in the future are complete quackery, [chuckle] complete scams, honestly but maybe in the future it could happen. Biology is something that lots of progress remains to be made. We're nowhere close to figuring it all out, how to do things. So I can easily see lots of progress along these lines in the future. I have no idea how fast it would happen.

0:55:08.9 SC: Andrew Goldstein says, do you have any noteworthy discussions you can share about the classes you've been teaching in the Physics of Democracy or the Philosophy of Physics? Well, I mean, yes and no. I've had lots of noteworthy discussions. I don't like to discuss the discussions that we have in class outside of class. The classes for those of you who are just tuning in, this year and last year at Johns Hopkins, I've been teaching small seminars for undergraduates. Last year I taught a seminar on the Physics of Democracy, another seminar on the Philosophy of Physics. This year I'm teaching a seminar on Philosophical Naturalism and another one on the Arrow of Time. So these are not lecture courses, these are courses where I might get up and talk about something, but mostly we're sitting around the table discussing things, and it's a different kind of thing.

0:55:58.6 SC: If I stand up and give a lecture, then I'm generally completely okay with having that lecture recorded or talked about or whatever. That's fine. That's me and I'm supposed to be prepared. But a seminar is where you're supposed to be responding in the moment, right? Without necessarily having thought about things ahead of time. You're supposed to be working through ideas. So generally, I don't think that those things should be recorded either formally or even talked about afterwards. So, not trying to avoid your question, Andrew, but I do think that I don't want to say anything too specific. I will say it's been a lot of fun. I think that this kind of course is just the quintessence of a university education to me.

0:56:41.3 SC: The idea is, sitting around a small number of people really grappling with something at a deep, careful level and talking with each other about it is just wonderful. It also doesn't work for everything. Certainly it's much more intrinsically successful on the philosophy side than on the physics side. On the physics side, we've had very good discussions. That movie... The article that Jennifer and I wrote about time travel in movies was inspired directly from the course that I'm teaching on the Arrow of Time, because for the course, we had some movie nights where we watched a couple of time travel movies and we discussed them and that was great fun. And that got us thinking about the whole thing but in physics, there's gonna be more material that you just have to lecture on or get across in some way.

0:57:30.4 SC: So, you can make it work. The seminars I did in the physics side of things have worked, but the philosophy ones have been a little bit more directly to the sweet spot of people discussing things and really being engaged with them. And it has been very interesting. I think the one thing that came out of the Philosophical Naturalism course... A few things came out of that. This is my attempt to teach an upper level philosophy course that nobody else is teaching, right? I mean, obviously I can do Philosophy of Physics, which I did last year, but I was trying to do something different that wasn't just secretly physics, right? In the philosophy department. So I did naturalism. Nobody teaches Philosophical Naturalism. This is not really a course that you can find online for the most part.

0:58:15.6 SC: There's probably some exceptions out there. I'm sure that there are, but it's not a standard part of the curriculum, which is arguably a little bit weird since if you go to the survey of philosophers beliefs, the large majority of them are naturalists. And I think that there are a lot of questions raised by naturalism. Some of you know that I organized a workshop a few years ago on moving naturalism forward, where rather than rehashing tired, old debates about naturalism versus theism or supernaturalism or other forms of non-naturalism, we sit down as naturalists and try to confront our own problems. And that was very much the spirit of this course that I'm teaching this year. So when you're a naturalist, okay, good. You're a naturalist. So what is good and evil [chuckle] to a naturalist? Do numbers exist? Where does consciousness come from?

0:59:08.3 SC: These are all questions that even naturalists need to address. And I honestly don't think that they kind of have nearly as well as they should have. And what I discovered among other things, is that it's a fun kind of course for the students, because it crosscuts other kinds of courses that they're taking. From week to week, we might be doing some epistemology or some ethics or some metaphysics or some philosophy of science, but they've done all those things individually in different courses 'cause they're all philosophy majors, but they've never put them all together in a sort of overarching way from start to finish. So I think that's very, very useful for the students. The other thing is, there are sort of traditional dichotomies in philosophy that I come to realize, yeah, they're real. They actually exist.

1:00:00.8 SC: So this is an oversimplification, but within naturalism, there is Kant versus Hume. Immanuel Kant versus David Hume. And they're kind of two personality opposites that show up in philosophical conclusions. A Humean in... Forget about... There's specific definitions of Humean in different contexts, but what I just mean is, the general idea that the world is a set of things. The world is a set of individual little events and things happening, and then we look at the world, we attribute patterns to those things, right? We say, oh. Here's an atom, here's an atom, here's another atom. They make a table. Here is a set of atoms that sort of persist over time in a certain pattern, that makes a person. There's no fundamental essence of personhood or tablehood or whatever. There's just this sort of emergent higher level pattern. David Hume was the quintessential emergentist.

1:00:54.8 SC: Whereas Kant, even though a naturalist, is much more sympathetic to essences and single right ways. In the case of morality and ethics, we talked about constructivism. And there's a distinction between Humean constructivism and Kantian constructivism. Humeans are likely to say, well, every person will construct an ethical system given their own moral inclinations and intuitions and so forth whereas a Kantian is gonna say, everyone constructs their own moral system, but there is only one right way to do it. Every rational person will agree. The Kantians are much more sympathetic to these absolutes, these essences, these single right answers, the Humeans are a little bit more approximate emergence. That's all okay.

1:01:40.8 SC: And it's interesting to see that kind of dichotomy, which arguably goes back to Plato and Aristotle with Plato and Kant being somewhat sympathetic and Aristotle and Hume being somewhat sympathetic but it's educational for me from learning the history of philosophy kind of perspective. Aaron Berger says, it has been over five years since you started Mindscape. How, if at all, have your goals for the podcast changed since the beginning? That's a good question. I would honestly say I think it's true that mostly they haven't. In fact, surprisingly little, they haven't. One of the things that I find hilarious about people who listen to the Derek Guy fashion podcast is that, I liked it better when it was nothing but physics. And if you go back to the original episodes of Mindscape, it was never nothing but physics. There was always musicians and actors and psychologists and things like that on the podcast. So I think that, yeah, it's almost surprising to me how little the goals of the podcast have changed.

1:02:48.8 SC: I mean, there's two sets of goals. One is to bring to a wider audience, real good thinkers in various ways. I don't always agree with the thinkers, but there is a public... What can I say? There is a public sphere of people who like to talk about ideas and not all of them are very good. [chuckle] And there are pundits and commentators and other podcasters who just have opinions about everything. And you can get these opinions. And some people are louder than others. Let's just put it that way. And I very specifically wanted to make sure that the people who I tried to bring on Mindscape were the careful thinkers. The people who really dig deeply and are experts in some field, not just the loudest talkers, not just the people who had opinions about everything.

1:03:42.1 SC: It's okay to be a loud talker, to be a person who has opinion about everything, as long as you have some specific area of expertise where you are really expert level, deep knowledge. And there's no necessary reason why such people should always be familiar to people in the public. How would they know, right? So that's my job as the podcaster. And I've said this before, but I'm in a happy, fortunate situation where I don't have to make my living being a podcaster. I don't need to optimize for monetary return. So I don't have to bring on the most famous people. The people whose names you would instantly recognize. Sometimes I do if they have something interesting to say, but many times I presume it's true that almost everyone who listens to Mindscape has not heard of all the people that I have on before.

1:04:37.8 SC: I hadn't heard of all of them before. I look around in different areas, I'm like, you know, man, we haven't done history in a while. Let's get a historian on. And I try to look for somebody interesting to get on. Of course, you get a lot of pitches from people who have books out, and that makes your life easier but many of the guests I have just are people I've found as an academic who are doing something interesting. So spreading the insights and what people have to say who are super duper experts, who the general public doesn't get to hear very often, is something that I definitely have as a goal. I want more people to hear people like Elizabeth Anderson, who they might not have ever heard of before. The other goal, of course, is that I want to talk to interesting people.

1:05:19.5 SC: And I've said this before also, but I have a long pile of books next to my nightstand that I would like to read and who has time to read all the books? I have time to read books, but not nearly as many books as I want to read. So I get to talk to experts. I get to look through their books. Some I read cover to cover, some I just skim through to get enough questions to ask, but I get to ask the author of these books or the author of these ideas, "What's going on?" And I get all my questions answered and things like that. So, it's both very useful to me and very useful to everyone else, somewhat useful to anyone else anyway. And I think that those are the goals, and those pretty much remain the goals.

1:05:55.8 SC: I hope that other people are enjoying it as much as I am. Jameson says, does eternalism mean that every moment in space-time is equally real, or does it also mean every moment is equally persistent? For example, the current moment has the distinguishing characteristic that is happening right now. Do all other moments also have this distinguishing characteristic? I don't even know what this would mean. Certainly the first part of the sentence is the right one. Every moment is equally real. That's what eternalism says. It doesn't even say, every moment in space-time. It means every moment in time. The lingo that people use here is in space-time, a point is an event. If you have a specific location in space and moment in time, you're an event. A moment in time is a slice through all of space-time. And you can talk about how slices through space-time are dependent on the observer or the coordinate system or whatever, fine but however you do it, however you slice space-time into moments of time, an eternalist will say they are all equally real.

1:07:00.2 SC: No moments of time are persistent at all. I mean, persistent literally means lasting through time, and that's not what moments of time do. So I do not think that every moment is equally persistent in any sense. The traditional wrong thing to say about eternalism is every moment exists simultaneously or every moment exists now. That is not what eternalism says. Eternalism just says, every moment is equally real. Past, present, or future. And then you say, Jameson, the current moment has the distinguishing characteristic that is happening right now. I think that that sentence is just ill-formed in some sense, because you're switching from a point of view of inside the moments happening to outside. Okay? When you say, the current moment, is that the current moment when you typed that sentence or the current moment when I'm reading this? Which current moment are you talking about?

1:07:58.4 SC: To an eternalist, every moment in time has the feature that at that moment it is happening then, and people who are living in that moment would say it is happening now but there's no distinguish... There's nothing to distinguish, I suppose I should say, any moment from any other moment. All the moments are created equal. Malcolm McGregor says, people talk a lot about the fine-tuning and physical constants as if they were variables to be set in a computer program before running a simulation of the universe. And that if the constants were only slightly different than the universe as we know, it would not exist but is it possible that if we knew the fundamental laws of nature, the values of the constants would be what they are as a natural consequence? And we would see that they could not be any other way in the same way that the value of pie comes about from the properties of a circle? So then saying, if the universe... Sorry. If the charge on the electron had a different value, then the universe would not exist, would be like saying if the value of pie was different, then circles would not exist.

1:08:58.7 SC: Well, it's possible. [chuckle] Longtime listeners know whenever you ask a physics question beginning with the phrase, "is it possible that," the answer is always going to be yes, it is possible. However, we have absolutely no reason to think that that particular possibility is true. We have a huge distinction conceptually between numbers that appear in the laws of nature, like Newton's constant of gravity or the fine-structure constant versus mathematical constants that are universal and everybody would agree on. It is very, very easy for us to imagine alternative worlds where the value of the fine-structure constant was a little bit different, where the mass of the neutron is a little bit less than the mass of the proton instead of vice versa.

1:09:40.3 SC: We cannot imagine a universe in which the value of pie, as conventionally defined, comes about to be any other value than it does. That's a very important difference. Now, so I'm gonna be negative toward that particular scenario that you're proposing, but let me be positive toward the underlying question here, which is, how should we be talking about the fine-tuning of physical constants? As you say, people talk about them as if they were variables to be set in a computer program. My personal belief, and this is a future research project that I have absolutely every intention of doing, I don't think that we talk about values that the constants of nature could and should have in anything like a sensible way. I do think that we have to do it in some sense. In the same sense that we have to talk about counterfactuals more generally.

1:10:41.4 SC: When we talk about the universe, we do more than simply say, "This happened and this happened and this happened." We say things like, "If things had been different, then this would've happened." That's the origin of talk of causation and reasons why things happened. Because in this other universe where X didn't happen, Y would not have happened, right? And so we should be allowed to talk about the fundamental physical constants in the same way. The problem is a little bit in ordinary counterfactuals and very much in the physical constants context, we don't have a good measure on the space of possibilities. It is not true that our universe is randomly chosen from some set of possible physical constants. We don't know whether there is some underlying reason why the physical constants were likely to have the value they did, or whether there is just some arbitrariness in the way the world works.

1:11:39.9 SC: Maybe there's some multiverse where different things look different in different parts of the universe or whatever. We just don't know. So we're in this weird situation where we need to talk about this idea and we have no idea how to do it. So I would like to improve that situation. Maybe it'll be impossible, but that's certainly a goal. Giorgio says, is the concept of time we know and love necessarily going to be the same as the parameter we often label as t with respect to which the wave function of the universe evolves? I love this question because the answer is no, it doesn't necessarily need to be the same thing. Maybe it turns out to be the same thing. So just to back up to make sure everyone's on the same page here, I have often said that the most fundamental equation we know about in physics is the Schrödinger equation.

1:12:32.1 SC: The wave function of the universe evolves with respect to some Hamiltonian that tells us what the energy of the wave function is. And the Hamiltonian times the wave function tells us the derivative. The time derivative. The rate of change of the wave function. So there is a parameter t called the time that appears right there in the Schrödinger equation but as you know, quantum gravity is a tricky subject. We don't know exactly how the real world that you and I experience emerges from that wave function of the universe. So is it possible that the time we measure on our clocks is different than the time that appears in that universal Schrödinger equation? Yes. It's absolutely possible. There are even hints from things like the AdS/CFT correspondence and string theory that the same underlying quantum evolution can correspond to two different very classical space times to very different classical space times where time's measured differently in one than in the other.

1:13:29.7 SC: So I don't know what the right answer here is, but I do think we should be open-minded about those possibilities. Michael Shillingford says, what accounts for objects being more than conventional or non-anthropocentric in your ontology. In Something Deeply Hidden, you say these things would exist even without humans, but I'm not sure the finer details. Well, at some level this is just a good question and a tricky one, and no one has the exact answer to it, when things should be said to exist. My rough answer comes from Daniel Dennett, former Mindscape guest, in his notion of real patterns. I'm not exactly sure that my understanding of Dennett's real patterns is the same as Dennett's understanding but my understanding is that you have a bunch of things happening in the universe. You have a physical system called reality, whatever it is, but you don't know everything about reality.

1:14:19.6 SC: You have incomplete information. There are certain circumstances in which you can say very informative, predictive things about the universe, even though you don't have complete information. So if I tell you I have a table, let's say I have a dining room table, then you would instantly infer that I could put a plate on that table and it would not fall through. Now, I did not tell you what every atom in the table was. You know from the idea of a table that it has certain properties. So the fact that there are things called tables is a persistent, higher level real pattern in the ontology of the world. There is nothing there that requires the existence of human beings or knowledge or consciousness or anything like that. There is a pattern that can be picked out. Now, whether or not there are people doing the picking out is a different question, but the existence of the pattern is absolutely real and objective and independent of human beings.

1:15:19.5 SC: Christian Rodarte says, priority question. If all matter has some rudimentary form of experience, do you think it's possible we could remember things that happened during the Big Bang, like baryogenesis? It's crackpot, but if creation myths and stories were symbolic of what happened during the Big Bang, it would be poetic. Well, like we said, if your question is, "Is it possible?" Yes, it's always possible. However, once again, in this case, I think it's completely implausible that all matter has a rudimentary form of experience. I think we have zero evidence for that, plenty of evidence against it. So, I don't know how to answer questions of the form, "If this false thing were true, what would happen?" If you want an answer to this question, you would have to talk to somebody who thinks that it is plausible that all matter has a rudimentary form of experience. And then maybe they have further consequences of that. To me, I get off the train right there. So I can't say much more about it. Jeff H asks, another priority question. As you fall toward a black hole, from your perspective, does time dilation cause Hawking radiation to blue shift asymptotically the closer you get? In other words, are black holes white holes in slow motion?

1:16:36.7 SC: Well, this is a good question, but the different parts of it have different statuses here. The, "in other words," has kind of thrown a monkey into the wrench. Black holes are not white holes in slow motion. That is just not true. A white hole is not just something that glows and gives off radiation. A white hole is literally and explicitly the time reverse of a black hole. So a black hole is something that you can fall into and never escape. A white hole is something you can escape from, but never fall into. A white hole has a singularity in the past, black holes have singularities in the future. So there's zero sense in which black holes are white holes in slow motion. Now, there is a tricky and complicated technical question about what you see as you fall into a black hole. In fact, I have a student working to improve our current understanding of this 'cause our current understanding is just not that good right now, to be honest.

1:17:31.2 SC: Roughly speaking, you don't see more and more high energy radiation as you fall into the black hole. What you see is almost nothing. You don't see anything special as you cross the event horizon of a black hole. Now, the details matter here and the details are tricky because if you're standing far away from the black hole, the typical wavelength of radiation you see is comparable to the short shield distance. The short shield radius of the black hole. So a small black hole will have short wavelength radiation, high temperature, a big black hole has long wavelength radiation, low temperature. And so when you're near the event horizon, if it's a big black hole, if it's much bigger than you, then you don't have enough time to observe radiation at all, right? Because the radiation is on wavelengths much larger than you and on timescales much longer than your falling into the black hole time.

1:18:28.9 SC: So it becomes a very non-trivial question. You can't just imagine standing at the event horizon and asking what you see. You're not allowed to stand at the event horizon. So what you instead have to do is some complicated thing where you literally model falling in on some trajectory with a particle detector and turning on the detector and turning off the detector and then making sure that what you're observing when you do that is actually from the black hole, not from the particle detector that you turned on and turned off. So it is a subtle question, but the short, quick answer is that as far as we know, you do not see asymptotically brighter and brighter, higher and higher energy radiation as you fall into the black hole. Pete Newton says, I've heard you say that the universe is approximately flat and expansion happens most in the large open spaces. All the systems I know of that undergo self-organization from protein folding to nuclear decay do it to be in a lower energy state. Finally, if you stretch a curve, it becomes flatter. So could dark energy be caused by the universe trying to flatten to be in a lower, more stable energy state?

1:19:37.9 SC: That's a clever idea, but the answer's no. That is not [chuckle] what is going on. There's a couple of things to keep in mind here. One is, the motto that systems undergoing self-organization go to a lower energy state is not quite right. Of course, energy is conserved in these processes, right? When you have protein folding, nuclear decay and so forth, the total energy before is exactly equal to the total energy after. What's really going on is dissipation. The system that you care about is giving off energy in the form of the parts of the system you don't care about, whether it's sound or heat, light or low energy photons, things like that.

1:20:21.7 SC: So that process is actually characterized by increasing entropy. It's the increasing entropy that is most important, not going to lower energy, 'cause energy is conserved. Now, the case of the expanding universe, the entropy is indeed increasing, but the idea that it is trying to flatten is not quite right. In fact, what it's trying to do is to empty out. That's true. And what the empty state will look like depends on the value of the vacuum energy. Depends on the value of the cosmological constant. What's important about our current universe is the value of the cosmological constant is very, very tiny on the scale of physical parameters that we might imagine. So therefore, the state that we are approaching looks pretty flat, but if the cosmological constant were large, which it absolutely could be, then even the empty space state of the universe would still have a large amount of curvature.

1:21:17.6 SC: Now, the final complication here, just to be completely honest, is that you have to distinguish between the geometry of space versus the geometry of space-time. Okay? When I say the universe is approximately flat, I'm talking about the geometry of space. In cosmology, where you look at the approximation where things are homogeneous and isotropic on very large scales, then there's this well known fact that if the geometry of space, the three-dimensional geometry of space is homogeneous and isotropic, then it's either going to be positively curved, negatively curved or flat. And the observations tend to tell us that it is flat or at least very close to flat. That is not to say that the geometry of space-time is flat because the expansion rate of the universe also contributes to the geometry of space-time. So at early times when the expansion rate was very large, space was flat, but space-time very much was not. At late times like now, space is still flat, space-time is much closer to being flat because it's become dilute and emptier as the universe has expanded.

1:22:32.7 SC: Astro Nobel says, we always distinguish four fundamental forces and many attempts have been taken to unify them. First by Kaluza and Klein with electromagnetism and gravitation, later by Weinberg and Salam, who successfully described the electroweak force. Why do we never speak about electricity and magnetism as separate fundamental forces and Maxwell is the one who succeeded to find a unified description for them? Well, we do. We do all the time. Buy my upcoming book [chuckle] on Quanta and Fields, and you'll read exactly those words. Maxwell's unification of electricity and magnetism was one of the first early examples of a successful unification in physics. We don't talk about them in exactly the same footing because that unification was what eventually led us to invent special relativity, to think of space-time in a relativistic way. And once you have relativity, once you are immersed in that way of thinking, then electricity and magnetism are automatically unified.

1:23:32.2 SC: You don't need to work hard. They just are different versions of the same underlying thing in exactly the same way that space and time are different versions of the same underlying thing. Whereas the unification that Weinberg and Salam did, or Kaluza and Klein are trying to do, they're all presuming relativity from the start and trying to do some particle physics-based unification from imagining that there's a single underlying symmetry that gives rise to these apparently different forces. So it's not because of relativity that these extra unification attempts are happening. That's a separate symmetry breaking kind of thing when and if they actually do work.

1:24:12.9 SC: GS says, what do you think the path to normalcy looks like for the American democracy? Even if a Democrat progressive candidate wins the 2024 election, it's clear not much progress can be made without control of the Senate and House of Representatives as well. This is a long question. So I edited some. I do encourage all questioners to make their questions short. They don't listen to me but I encourage you to do that. Anyway, the question continues, I'm honestly feeling very hopeless. So much real world harm has been done in just the last few years. And even if I vote in every election in the next decade, I feel like the odds are just stacked against those of us who want to live in a more fair, kind, and progressive society. Is the path to this society just to keep voting until all the obstacles mentioned above are overcome, even if that might take decades? If it even happens at all. Well, the short answer here is I wish I knew how to get American democracy back to normal, healthy functioning.

1:25:07.6 SC: I don't think it has anything directly to do with voting for Democrats or progressive candidates. You should do that. I am pretty democratic progressive myself. And as of right now, as of 2023, the Democratic Party is much more in favor of traditional, literal, lowercase d democracy than the Republican Party is but that's not the underlying issue. The underlying issue is that a lot of people in the United States aren't that much impressed with democracy. They think that there could be a better system. They think that their party being perpetually in charge would be better. I think that protecting the health of democracy does not come down to voting for this or that party, but for convincing other people in the country that democracy is a good thing. I think this is an aspect of living in a democracy which has been under-emphasized in recent years. We look at the results. We look at who is elected, what policies they have. We forget about the fact that the whole point of living in a democracy is the people who are citizens of the country are supposed to be the ultimate authority from which the government derives its authority. And so if you want people to do good things, you convince the people. It's good to vote, it's good to run for office if you wanna do that.

1:26:28.0 SC: It's good to campaign for your favorite people but you also have to talk to other citizens. You also have to convince people that it's okay to lose elections sometimes. A democracy only works if you're willing to lose elections. And I think this is not just about the United States, I think this is true for any burgeoning democracy. If you're a country that recently overthrew an autocracy or a monarchy or a dictatorship and you say, well, look. We've had an election and the people who won the election are now governing the country. We have a democracy. I would say, no, you don't. Not yet. You have a democracy when the party or person who is in power loses an election they wanted to win and hands over power to the opposition. That's when you have a functioning democracy. And I think that we need to think that's okay in some very real sense. We need to... People on all sides... I think people more one side than the other but people on all sides need to be willing to talk to each other, to listen to what each other has to say, to try to persuade other people 'cause that's the foundation of an actual working democracy.

1:27:41.0 SC: I have no specific ways of making that happen, but I do think that's what we should work toward. Soonest Men Did says, I know you don't have kids, but if you did, what are some big picture concepts that you would want to be sure to teach them? It's a little open-ended, this question. I'm not quite sure what kind of concepts you mean. Do you mean like conservation of energy, or do you mean how to be a good person? I'm not sure. I do think that how to be a good person is a more important concept than conservation of energy, and related to the question I just answered about democracy, I think that taking other people's desires and values into consideration as a person, listening to other people is perhaps one of the most important skills that we can have.

1:28:31.2 SC: Really accepting that other people can be different than us, and that's okay as long as they're not hurting us. As I'm recording this, there was just this little conversation on Bluesky earlier about Derek Parfit. Derek Parfit is a very famous philosopher who died a few years ago, and he was one of these people who sometimes you see and not just academia, but high achievement people in various forms, who was kind of a jerk. He was kind of a jerk to his loved ones and friends and family because he had a friend, I guess, a former relationship, a former loved one who was dying of cancer and went to visit him just to say goodbye, and he didn't have any time to talk to her, he said, I'm writing my book, leave me alone. I don't care that you're dying of cancer.

1:29:22.6 SC: And my response to that is, that's his choice. I don't wanna be him. If I had my kids, I would not wanna teach my kids to be like that, but I would wanna teach my kids to accept people like that, to not try to make every person just like yourself. I think that's one of the most important things we can teach people. I would also like to teach kids to be curious and be honest and have integrity and help others, and all sorts of different things, but different... The thing about human beings, even if they're kids are they're individual human beings, they're gonna do what they wanna do. At the end of the day, we have to give them a good environment and let them become who they're going to become. Rob Petro says, you seem incredibly productive. From the perspective of an academic who's interested in doing more public outreach and generating more high quality content for people interested in learning more about my field, I find the sheer amount of diversity and quality of the content you produce to be incredible. I'm curious if you have a specific strategy or method for getting things done?

1:30:28.2 SC: Well, thank you, Rob. I appreciate that but I don't feel incredibly productive myself. I feel that there's all these other things I wanna do that I don't have time to do. So that's the version of my feelings about my productivity that is foremost in my mind. But no, I don't have a method, I don't have a specific strategy. It reminds me of... For a few years back in LA, I was working with a personal trainer, I would go to the gym and there's a thing you signed up, so you get personal training lessons. And he's a very nice guy, and he would help me out. And he once told me the story of, he had a group of friends and they decided to, in general, do self-improvement and help each other do self-improvement. And so they asked him 'cause he's a personal trainer. They said, help us get motivated to go to the gym and work out all the time and exercise. And he gave what I thought was a very insightful answer, which is, he said, I'm the last person who should help you with this because I don't need motivation to go to the gym and work out and exercise, that's what I like to do, that's what I would do left to my own devices.

1:31:38.2 SC: I'm not the person who will help you overcome a reluctance. And I think about that when you ask this question because... And again, I'm very, very fortunate and privileged to be in the situation, but I do the things I like doing. I like doing scientific research, I like doing philosophical research, I like making the podcast, I like writing books, I like doing all sorts of things, giving talks, and I also like the fact that I get to do all of them. I wouldn't be happy if I were only doing one of these things. And I know a lot of people, they're sort of Bayesians of attraction where you try to do many things, but one of them works out the best for you and you end up doing nothing but that. I am just a different kind of person, I'm happiest when I can do a little bit of all these kinds of things, so I don't really need a strategy or method to get the things done that I get done. These are my hobbies. These are the things that bring me joy. These are the things that I would do left to my own devices.

1:32:39.6 SC: So I don't need to sort of strategize. I still feel bad when I'm late for a deadline or whatever, or I'm ill-prepared for a podcast, I feel bad all the time but I don't need to motivate myself to do these things because it's what I would rather be doing than most other things that I would do. So, if you're not like that, I'm not sure what to say. I guess the general strategy would be find a way to sort of optimize what you want to get done versus what you intrinsically like to do. Try not to swim against the current too much, that's my secret for getting things done. Define as the things you wanna get done, the things that you would like to be doing, and then you'll be a success at that. Geddy Lee Smolin says, I can't find exactly where, but I think you said something along the lines of, the laws of nature are patterns which we can learn about through hypothesis testing and observation. I don't remember exactly saying that, but that sounds like something I would say.

1:33:42.9 SC: Does this change if you're a Laplacian demon or omniscient being? Do the laws of physics become like the rules of a video game, immutable and hard-wired into the fabric of reality? Yes, actually they do. If you're Laplace's demon, then the way in which you think about the universe is very, very different. Remember I talked about those real patterns, about tables and chairs and things like that. Laplace's demon need not know that there is such a thing as a table or a chair, 'cause Laplace's demon knows all the information. Tables and chairs become interesting and important when you have incomplete information. So Laplace's demon only needs to know the most fundamental level of reality, and from that everything follows.

1:34:24.2 SC: And that's a very different way of thinking than you or I are thinking. I don't necessarily think if the implication of your question is that Laplace's demon or omniscient being would see the laws of nature as inevitable, then that I don't think is necessarily true at all. I think, again, we can imagine different laws of physics, different laws of nature, so Laplace's demon would know that the world works in this way and not in that way, but it would absolutely know what those rules are at the deepest possible level. Liam McCarty says, in your book, The Big Picture, you say the laws of physics underlying everyday life are completely known. In other words, the core theory is and will forevermore be correct in its domain of applicability, which encompasses everyday life. Might there be however complex dynamics that begin outside that domain and yet ultimately affect everyday life? Could a proverbial butterfly which flaps its wings in a domain beyond our current experimental reach cause a proverbial tornado in the domain within our reach?

1:35:28.9 SC: Guess what, Liam? You've asked a question of the form, is it possible that... And the answer is yes, it is possible that that might very well be. As usual, that is not where I would stop the questioning. What I would ask is, given what we know about the universe, how likely is it to be true that this kind of thing is there? And in The Big Picture and in other ways of talking about this, I do not simply say, the laws of physics underlying everyday life are completely known. I provide the reasons for thinking that. Namely that the fundamental laws of physics in the regimes that we're talking about seem to run according to the rules of quantum field theory. Indeed, quantum field theories, more or less the only rules that are possible, if you believe in things like special relativity, quantum mechanics, locality, things like that. And if the laws of quantum field theory are true in the ways that we currently understand them, then no, then complex dynamics that begin outside that domain will not ultimately affect everyday life. It is a conclusion that the laws of physics underlying everyday life are completely known, not an assumption or a guess or a suggestion.

1:36:46.5 SC: Given certain very strong beliefs that we have about how the world works, it follows that the laws of physics are completely known. So, that's okay. There's plenty of other things that we don't know. We don't know the laws of physics underneath the level of everyday life, we don't know non-physics laws like chemistry or biology or whatever, plenty of work still to be done in science and other areas of human endeavor. Roy Thomson asks, is there a symmetry or other proposed reason why the imbalance in matter and antimatter quarks and the imbalance in matter and antimatter leptons ended in an electrically neutral universe or local universe at least?

1:37:24.9 SC: Well, it's absolutely possible that there is a reason, it's also possible that it's an accident. So here is what we think we know, if space... Again, space not space-time, three-dimensional space is compact, so if space is a three-dimensional sphere or taurus or something like that, then the rules of electromagnetism say, there must be exactly zero net electric charge in the universe. The way you can think about that is if you have a single electric charge, there are lines of electric force that go out from that charge to infinity, and there's a rule, Gauss' law, that you can integrate up the electric field at infinity to figure out how much charge is inside. But if space is compact, then there is no such thing as infinity, there is just the whole universe. You have those electric lines of force, they would have to go and meet themselves somewhere else in the universe, and that would be an opposite charge, a positive charge if you started with a negative charge, et cetera. So in a closed universe, the electric charge has to be exactly zero.

1:38:32.9 SC: If it's not closed, if the universe is not closed, then it doesn't have to be exactly zero, it can be some other number, but there's no reason why that we can think of it shouldn't be zero either. So this is not generally thought of as a big puzzle as far as modern physics is concerned, but we don't know precisely the situation yet. XLRWRPO90 says, how do experimentalists get their hands on particles they haven't decohered with? Presumably they decohered with their apparatus before the experiment began. So I'm not exactly sure what this question is about, but let me, again, try to say some true things. One true thing is that we often in the universe work under the assumption that we are not entangled with other things, and that is an assumption, but it's a good assumption for good physical reasons, for example, you are not entangled with the chair you're sitting on, for example, you're sitting on it and you're interacting with it, but if there was some quantum state that entangled you with the chair, that would mean that different parts of your wave function were connected to different parts of the chair's wave function.

1:39:42.3 SC: Now, in principle, in the wave function of the universe, that very well might be true, but because both you and the chair are big macroscopic things, you would quickly also become entangled with the environment, and that means from an Everettian perspective that you would branch the universe and there'd be one branch of the universe where you and the chair were doing one thing, another branch where you and the chair were doing another thing, and on those individual branches there is no more entanglement between you and the chair.

1:40:12.7 SC: Now, an elementary particle is not a chair, it is not a big macroscopic object. So the question, how do experimentalists get their hands on particles they haven't decohered with... For one thing, I'm not even sure what the word decohered with means, the phrase decohered with. You don't decohere with something, a quantum state is either coherent or decoherent, so to decohere means become entangled with the environment. So probably what you mean is, how do you get your hands on particles that you're not entangled with? In that case, well, you start with a particle and then you measure it, and as soon as you measure it, you're no longer entangled, you have seen some experimental outcome. So for example, it's most clear if you just think about the spin of a particle and you wanna say... People will often say, start with the particle that is spin up. And you might very well ask, well, how do you know that the particle is spin up? The answer is, you measure it, you measure the spin, if it's down, you throw it away and try again, if it's up, now you have a particle that is spin up and you can do with it whatever you want.

1:41:17.7 SC: Tyler Smacker says, out of all the great progressive rock albums from the '60s and '70s, what are some of your favorites? You know, I thought about this when you asked the question, I'm not a great ranker of albums or anything like that, I have my favorites, but I don't insist that one is the best and et cetera. And I love progressive rock, but these guys generally did tend to have both high points and low points on the same album, so I'm gonna say something like Fragile is an obvious choice by Yes, but they have those dopey little solo parts of Fragile. Fragile had these group compositions and performances that were amazing, that were great, Heart of the Sunrise, Roundabout, South Side of the Sky, et cetera but then they also had... Apparently they were short of money and they had just replaced their keyboard player, they kicked out Tony Kaye, invited in Rick Wakeman, and they needed to pay for Rick Wakeman's new keyboards.

1:42:18.7 SC: So they needed to bang out an album as quickly as possible in order to pay for his keyboards, and it was quicker to let each band member record a little solo piece to fill up the album rather than to actually just write a song and record it. So that makes it a very kind of disappointing effort, especially because they had just recorded a cover version of Simon & Garfunkel's, America, which was an amazing cover version. They could have just put that on the album, I think anyway, if I'm remembering the timing correctly, so that would have been a perfect album, but they didn't do that. ELP's albums at the early days, I love all of them and they all have weak points, maybe Trilogy might be my favorite one there, I think that has the least of the sort of indulgent instrumentals, the key that Emerson loved so much. And the first King Crimson album, also a classic. Many, many classics back then, and I make no pretense to being up on what the kids are listening to these days. I'm sure there's just as good music coming out now as there was when I first started listening to music seriously in high school and college, but I don't know what it is, and I've got other things on my mind. There you go.

1:43:33.5 SC: Cubit says, you said that the preferred basis problem of many worlds disappears when thinking in terms of density matrices, since we only have to find the basis in which the density matrix of the other interest becomes diagonal, however, this cannot be the final answer when we talk about many worlds and the wave function of the universe simultaneously, in this case, there is no well-defined sub-system with respect to which we can trace the environment, and therefore the density matrix represents a pure state with seemingly only a single world. How do we find the preferred basis in this case? Apologies to people who are not experts on quantum mechanics for this question but it's especially interesting question that I think is worth a stab at answering it. The very short answer is, this is a really important problem, it's an open problem. And I write papers about it, so you can look up my paper with Ashmeet Singh on quantum mereology, where we talk about exactly this problem.

1:44:28.1 SC: How do you divide up the world into a system, an environment, so that you can find a preferred basis for just the system rather. So the basic physics idea here is that, again, since we're not Laplace's demon, we course-grain our descriptions of the universe, and one of the ways that we do this in quantum mechanics is to divide the world into systems that we keep track of and environments that we don't keep track of. Now, often in practice, this is just kind of obvious, right? Here's a cat, that's the system, but then all the photons of light in the room that are bouncing off the cat, those are the environment, we're not keeping track of all those. Okay? If you're doing Schrödinger's cat experiment.

1:45:09.3 SC: But you would like to do better than that. And especially if you're interested in the foundations of quantum mechanics, you like a principled algorithm for figuring out how to divide the quantum state into system and environment. And so Ashmeet and I proposed such an algorithm, the quantum mereology algorithm for doing exactly that. And basically, it's based on the idea that you want to find a decomposition such that the system can have a classical limit, so that it can behave fundamentally classically. And there's a set of criteria that you can put in to make that happen, and it ends up that the system looks kind of classical looking, the environment looks kind of environment looking with a bunch of easily manipulated low energy degrees of freedom.

1:45:50.7 SC: Now, just to be super clear, I certainly have never said that the preferred basis problem disappears because the preferred basis problem is a good problem. I think it's solved, but it doesn't disappear, and even when it's solved, it's not just find the basis in which the density matrix of interest becomes diagonal. The density matrix, for those of you who are not experts, is how we talk about the quantum state of a sub-system that is entangled with the rest of the world, okay.

1:46:23.2 SC: If two things are not entangled, you can talk about the wave function of the sub-system, but if they are entangled, the density matrix is the thing that keeps track of as much information as you can keep track of without knowing what the rest of the world is doing. And it will always be true that if you have an entangled system, so you have a density matrix that describes it, you can diagonalize that density matrix, you can find a basis in which the density matrix looks like a diagonal matrix. But that's not the point, that's just a trivial mathematical fact, the important physical fact is that you can figure out ahead of time that once the system becomes entangled with its environment, the system's density matrix will become diagonal in a pre-defined basis. So this is exactly Schrödinger's cat. Okay? This is the question, why when you look at the cat, is it always either the awake cat or the asleep cat, not one over square root of two awake plus asleep or one over square root of two awake minus asleep. The answer is because the states that define definite spatial configurations are the ones in which the density matrix will become diagonal, you know that ahead of time, you don't need to just have the density matrix and diagonalize it.

1:47:41.2 SC: Why do they become diagonal? Because the environmental degrees of freedom, the photons, et cetera, become entangled separately, they become entangled differently with the different macroscopic configurations of the cat or any other macroscopic system you may have. So this is all work, this is all stuff you have to figure out, and I don't think that the state of the art is complete and finished yet, but we kind of see the outline for how it will all be settled once we understand everything perfectly.

1:48:52.6 SC: Nomad666 says, I've been hearing about JWST's new data, and can you tell me what's going on with the mystery of the Hubble constant tension? Yeah, I actually just got lucky enough a couple of days ago to sit in a colloquium at Johns Hopkins by Adam Riess. Adam, of course is Nobel Prize-winning observational astronomer, former Mindscape guest, and last but not least, my colleague at Johns Hopkins. So we unfortunately had a last minute cancellation in the colloquium series and Adam agreed to step in and talk about the Hubble tension. The Hubble tension, which we talked about on the podcast with Adam, if you wanna go check that out, that's from a couple of years ago, but basically it's not gone away it's just gotten worse.

1:48:53.8 SC: And what I mean by worse is the following; the Hubble parameter, we call it the constant, but of course, we all know the Hubble constant changes over time. So it's a parameter in our cosmological model and it's a physical thing that we can measure. Okay? So these are two different aspects of the Hubble parameter. One is, you can just measure the velocities and distances to galaxies. And Hubble's law says velocity of distant galaxies is Hubble parameter times distance. So if you get a bunch of galaxies, you plot them on a straight line and you fit the slope, you've measured the Hubble parameter, good for you. But there's a whole other thing you can do, which is you can start with a model of the overall evolution of the universe. Our favorite model these days is the famous ΛCDM model, a model based on general relativity and scale-free density perturbations at early times or nearly scale-free plus matter radiation, dark matter, cosmological constant.

1:49:54.2 SC: And within that model, you have different parameters that pin down which version of the model you're looking at. What exactly is the density of dark matter, what exactly is the amplitude of density fluctuations, what is the current Hubble constant? Okay, the current Hubble parameter. And that model can be measured, its parameters can be pinned down by all sorts of different cosmological observations, such as the cosmic microwave background, large-scale structure, what we call Baryon oscillations, the different amount of structure in visible matter at different wavelengths, gravitational lensing, a whole bunch of different kinds of measurements. And so from that model fitting, you can ask, what is the value of the Hubble parameter that you need to best fit the model? And these two methods, one is the direct method using galaxies and cepheid variables and supernovae relatively nearby, the other are these kinds of global methods where you fit to the model. These two methods disagree. That's the Hubble tension. The direct measurement method gives you about 72 for the Hubble constant as a number, the cosmic microwave background measurements from the Planck satellite and elsewhere give you about 67. These are pretty close.

1:51:08.0 SC: And when I was your age, we didn't even know whether the Hubble constant was 50 or 100. So we had factors of two discrepancies and now we're on 10% discrepancies. But still compared to the error bars that we expect to have, the discrepancy is statistically significant at a level of more than five Sigma to you scientists out there, which is very, very significant. And Adam gave a very good talk where he just went through all of the ways that the local measurements, which is what he does for a living, could be wrong, all the sources of error, et cetera, and he made a persuasive case that they're not wrong, that we have various sources of possible error, we checked all of them. Basically, the measurements... So the new wrinkle that we have now that we didn't have when we did the podcast is some new measurements from the James Webb Space Telescope. So here's a little bit of in the weeds for you astronomy fans out there.

1:52:06.1 SC: So we're trying to measure the local value of the Hubble constant by looking at actual expansion of the universe in our neighborhood. Now, our neighborhood still means millions and millions of light years, okay? But it's just not the whole global universe at once kind of thing. So we're looking at pretty high redshifts compared to our Milky Way or something like that. Anyway, you use a kind of traditional cosmic distance ladder, the cosmic distance ladder is what you need to do because you can't measure distances directly, what you can do is look at a supernova in a distant galaxy, and supernovae are very good standardizable candles, so you know that all the different supernovae you can reduce to a common brightness given their like curve shape and things like that.

1:52:51.3 SC: What you don't know is exactly what that brightness is, but what you can try to do is find supernovae in galaxies where you also have what are called cepheid variable stars, stars that pulsate with a given period and luminosity. And over a century ago, Henrietta Leavitt showed that there is a relationship in cepheid variables between their period and their intrinsic luminosity. So again, they are standardizable candles, so you can figure out, you can relate the brightness of the cepheid variables to the brightness of the supernovae in the same galaxies.

1:53:53.2 SC: Now still, you don't know the absolute brightness of the cepheid variables, but there are some cepheid variables that are very nearby, and you can basically use parallax, literally the geometry, the fact that a nearby star moves a little bit in its apparent location on the sky when the earth is on one side of the sun versus the other side of the sun, so that's a direct geometric measure of the distance. So he goes from parallax to cepheids, to supernovae. And what JWST has done is improved our precision at measuring these cepheid variables among other things, but this is one of the things that Adam was excited about and was talking about.

1:54:05.1 SC: So it's kind of interesting. I'm a theoretical physicist, what do I know about this? So it's interesting to see the real good observers at work. You can take an observation of these cepheid variables with the Hubble Space Telescope, which was of course unprecedentedly good in its day, but sometimes you got a little bit of error because the cepheid variable you're looking at, the literal number of pixels that it took up in the camera overlapped with other nearby stars, it was hard because you're literally looking at stars in other galaxies, they're very far away, it could be sometimes hard to get non-overlapping completely separate pictures of the cepheid variables.

1:54:45.4 SC: So this was a known source of potential error. And now with JWST, you have higher resolution, so you can distinguish between the cepheid variable you care about and the other stars that are nearby. So apparently from what Adam says, you get the same answer either way, but of course, you're now more confident in your answer because you have removed that particular source of error. So he went through a list of 10 different possible sources of error, this was one of them, but there are many different sources, and he painted a good case that we know what we're doing. So I'm actually relatively willing to believe that the Hubble tension is a real tension. The question is how to resolve it, and there, there's basically two camps. If the Hubble tension is real, so if measuring or... Yeah, measuring the Hubble parameter by local measurements versus model fitting of the whole universe, if you really get different answers, there's two possibilities that obviously come to mind.

1:55:49.5 SC: One is, there's something subtle about the evolution of structure in the universe that we are getting wrong. In other words, within the known laws of physics, but when considering all of the tricky details of the origin of density perturbations and their evolution, something has gone wrong. So that we've measured the local Hubble constant correctly, but our figuring out what that parameter should be in the context of ΛCDM is somehow making a mistake. I have no idea what this mistake would be, I'm not an expert at that, but I think it's legitimately on the table. The other big obvious, exciting possibility is there's something wrong with the laws of physics, there are some new physics going on and people like my other Hopkins colleague, Marc Kamionkowski, have been very active in proposing models for what that could be. Maybe there was a temporary period of dark energy in the early universe over and above the dark energy we see today. Maybe there are some effects of magnetic fields in the early universe that we don't know about. Maybe the universe is tilted or something... Some kind of... There's neutrinos or hot dark matter, in addition to cold dark matter, all sorts of different possibilities are being looked at.

1:57:08.4 SC: None of them... None of the thousands of papers written, the proposed models for this have yet kind of stood up and said, yes, look, I am obviously the right answer. So, as far as I can see, this is still a good question. We're still thinking about it. That's what makes cosmology fun. Ernie Moskowitz says, I am a 96-year-old male fellow atheist in good health. My doctor says I will make 100. My atheism allows me to enjoy life with little fear of the end. Imagine you are a 96-year-old atheist, what advice would you give fellow nonagenarians? Sorry, Ernie, I'm not exactly sure whether you're asking me... What you are literally asking, what advice would I give to nonagenarians versus specifically what advice would I give to atheist nonagenarians, or maybe what you're asking is, as an atheist, what advice would I give to non-atheist nonagenarians?

1:58:06.1 SC: In any case, I'm probably not the guy to be giving advice to nonagenarians. I congratulate you on living such a long and fruitful life and on being a happy and fulfilled atheist. I'm not going to downplay the reality of mortality and how important it is. We're all mortal. It's gonna happen. And as naturalists, as atheists, we think that the life that we have is the whole shebang, there's not anything that comes after that. I mean, it sounds just glib and simple and unhelpful, but accept that and not only accept it but relish it is my advice, so much as I could possibly say. What we do here on earth is what matters, and some day that's gonna come to an end. It's absolutely possible... Not to get morbid about it, but it's possible, Ernie, that you will outlive me, 'cause I don't know how long I'm gonna live. We don't have that view of the future. So all of us need to be aware that we should both... We have to simultaneously, to live a good life, think about and imagine our future accomplishments and activities and make sure that what we have already done is pretty good, right?

1:59:33.2 SC: You can't live your life only planning for the future, but you can't live your life not planning for the future either. So I don't like to live in the past or the future or the present, I like to live in all of these simultaneously, that's what my eternalist sympathies lean me towards. So it's perfectly okay to look over your long 96-year-old life, it's also still perfectly okay to say, well, I got a few years left. Let's write a book. Let's learn how to play the piano. I don't know. Let's learn a foreign language. It's absolutely like four years or 10 or 14 years, whatever you get, that's a long time, you can do a lot. Learn quantum mechanics, look forward to your life, however much there is left as well as enjoying reminiscing about the life you've already lived. Anthony Knott says, suppose I set my credences according to the Born rule to be 90% spin up and 10% spin down for some particle that I'm going to measure, but I happen to be mistaken about how the state was prepared, the amplitudes are actually reversed. What could I observe on the many worlds interpretation that would clue me into the fact that I was wrong about the state?

2:01:31.4 SC: If I understand right, it can't come down to the frequency of outcomes. Actually, it can come down to the frequency of outcomes. The philosophy of many worlds is different, but the place you end up is exactly the same as in a Copenhagen-like interpretation. What I mean by that is, what many worlds says is that, if you literally do have a spin with a certain amplitude squared for spin up and a certain amplitude squared for spin down, both branches of the wave function will come into being according to the Schrödinger equation. You will have some self-locating uncertainty as to which branch you are on once that measurement has happened, and the argument that I make, and I made it with Chip Sebens, and there's other people who made similar arguments is you should assign a credence to being on the different branches, that is given by the amplitude squared, given by the Born rule.

2:01:34.5 SC: Now that's a philosophical justification for assigning those credences, but once they are assigned, everything is completely normal. So, as Chip and I say in our paper that you're encouraged to read, what about Bayesian theory confirmation, how does it work in this context? And the answer is, it works exactly the same way as it always works. If you have a spin that you think is 90% likely to be spin up and 10% spin down, do many measurements on it, and if you find that most of the measurements are spin down, then you should contemplate two possibilities. One is, you got the credences wrong for whatever reason, right? You're mistaken how the state was prepared or something like that, that is absolutely a possibility. Another possibility is that you had just got unlucky. And as a good Bayesian, the chance that you just got unlucky should go down the more you do this kind of experiment over and over again.

2:02:31.0 SC: So in that sense, at the end of the day, the accumulation of evidence does come down to the frequency of outcomes. Now, the thing that gets some people upset about this is there will be some people in the multiverse, in the whole wave function of the universe who will come to the wrong conclusion, they will decide that the Born rule isn't right even though it is for other observers. And the answer is yes, there's just gonna be... Some people will be unlucky. There is always the chance that some people will be unlucky, many worlds says it is definitely true, some people won't be unlucky, but it also says there's a lot more people than in a single stochastic universe. So to my mind, everything balances out and the progress of science and the updating of your credences goes in exactly the usual way.

2:03:20.1 SC: Going to combine two questions here. One is from James Allen who says, say I'm trying to examine in a Bayesian way, whether or not I might be a Boltzmann brain, would I give weight to the fact that I don't just have memories, but that they all seem coherent? Is a Boltzmann brain that remembers all of these episodes of Mindscape hosted by Sean Carroll and in English less probable than a Boltzmann brain that remembers those podcasts consisting of gibberish and half of them hosted by Ariel and Caliban? And Claudio says, my intuition tells me that a Boltzmann brain, if and when it appears won't persist as such for more than a small fraction of time, so why is it even a useful concept? Well, I think both of these questions start from the... Asking the wrong question. Okay? So the reason why the Boltzmann brain scenario seems a little weird to us is because we keep wanting to ask what is a typical observer like in a world dominated by Boltzmann brains? A typical Boltzmann brain is very different than you and me. Okay? There was an episode of Star Trek: Strange New Worlds that had a Boltzmann brain character in it.

2:04:26.5 SC: It was very, very bad scientifically. If we had done... Jennifer and I had done a little pie chart of that it would be... Sorry, two-dimensional space of that, it would be very high on entertainment value, very low on scientific value. Boltzmann brains typically randomly fluctuate into existence, exist for a very short period of time and then go away. So if the question you're asking is, what does a typical thing look like? Boltzmann brains look very, very different than you and me, no doubt. But there's another question that you could ask which is more relevant for questions of, who do I think I am in these universes? Which is not what is a typical brain or observer or agent look like? But rather, given that I am who I am, given that I have all of my body and all of my memories and things like that, what is the most likely prediction for the rest of the world?

2:05:24.1 SC: That's a question, you conditionalize on knowing everything you know about yourself. And that's the case where you get a very different answer if you believe in a Boltzmann brain cosmology versus a conventional one, because it's your implications for the rest of the world that are very, very different. If the universe is dominated by Boltzmann brains, there will be essentially Boltzmann brain-like fluctuations that look exactly like you, that have all the memories of all the podcasts you ever heard, all of the things that you're seeing in your room around you right now, et cetera but the rest of the world is in thermal equilibrium. And given that you are who you think you are, given you conditionalize on the macroscopic surveyable information that you have, the Boltzmann brain cosmology says that with enormous probability the rest of the world is in thermal equilibrium, and that all of those impressions of the world that you think you have of memories of podcasts and so forth, are not actually attached to podcasts you listened to, those memories just randomly fluctuated into your brain.

2:06:32.1 SC: Therefore, this is not a cognitively stable situation, this is not a situation where you have any right to believe the Boltzmann brain scenario, even if it's true. You never have justifiable reasons to accept that you're in a Boltzmann brain cosmology and be in a Boltzmann brain cosmology at the same time. My advice is therefore try to construct cosmological models that are not dominated by Boltzmann brains. John Wyman says, if I understand quantum field theory correctly, everything is a field and a particle is a vibration in the field. If so, this means the planet or cat or just a lot of vibrations in the field. Is that too simplified or just wrong? No, that is exactly right. If you wanna read more about it, read my upcoming book on quantum fields, and I will go in great detail to answer this question about why vibrations in quantum fields look like particles to you and me. It's kind of always bothered me even after I'd taken a year's worth of quantum field theory, it kind of was rushed over in the class, so I think it's a perfectly good question, but the answer is exactly yes to what you were asking.

2:07:39.8 SC: Gomezante asks a priority question. If quantum gravity is proven, what would it look like? In the classical sense, gravity is an attractive force, in the relativistic sense, it is a bending of space-time. Given that even at planetary levels, gravity is weak, what would that translate to its subatomic levels with all the noise that happens down there? Well, nobody knows. I'm sorry, I know it's a priority question, but the rephrasing of the question would be, what kind of quantum gravity model is going to be the right one? Because there are different proposals for what quantum gravity might have to say at the most microscopic level when it comes to questions like, what is space-time, what is the structure of quantum space-time? Things like that. Is time fundamental, is space fundamental?

2:08:27.2 SC: Are they really strings or causal networks or something like that, or loops? Nobody knows the answer to this. These are all questions that we talk about, so I wish I knew, I wish I could help you but this is how science works. You propose models, you try to figure out which one is right. In the case of quantum gravity, there are many models that are at least semi-plausible, none of them that we actually know to be right. Anonymous says, should all the universes created during eternal chaotic inflation be almost flat, having the observable part as being as old as ours stretched exponentially with no horizon problem, no magnetic monopoles, et cetera, then there's more to the question that I kind of edited out, but the basic question is about what we call the cosmological measure problem.

2:09:13.8 SC: So when inflation was first proposed, the idea was you have a tiny little part of the universe, it will be dominated by a temporary dark energy period that would accelerate the expansion, to beat the band, everything would stretch out and get flat and then it would re-heat and you would get a universe that looked like our hot Big Bang cosmology. And it was nice because the idea was that no matter what had happened before this period of inflation would stretch everything out and make it look the same. The idea of eternal inflation is that that process happens within some region of space, but in another region of space, there's a quantum fluctuation that keeps inflation going on, and that region will expand and some of it will cool, but other parts inflation will keep going on due to quantum fluctuations.

2:10:09.4 SC: And in this picture, you don't get a unique future for the universe, there are different patches of the universe where things can look very, very different. So that raises a new question that wasn't there in the original inflationary model, which is, how do you compare the relative importance of one kind of area versus another, and the answer is nobody knows because the numbers are infinite. There's gonna be an infinite number of things that look one way and infinite number of things that look the other way. People have tried, I'm not very convinced with any of the attempts to actually answer this question. And it's a very strange situation because inflation kind of works, it makes predictions for perturbations in the early universe and so forth that modern observational astronomers and late universe cosmologists just use as a black box. They make predictions on the basis of it, they test these predictions, they narrow down the parameter space, et cetera, et cetera, but this looming question about eternal inflation draws into question whether any of those predictions make any sense at all.

2:11:18.0 SC: So this is the measure problem and it doesn't get a lot of attention, but I think it's super-duper important. I also think it's solvable, even though I don't know what the solution is. I do think that it's completely plausible to me that there is just some right measure that will say most universes are almost flat, no horizon problem, et cetera. There's gonna be a small fraction of other universes in the appropriate measure that look weird, but they're a small fraction. So I don't know what the answer is, I'm optimistic that it's out there, I think this is a very good problem that deserves more attention than it gets. Asean Bodin says, I was wondering if you have any opinions on psychological egoism, the idea that human action is always motivated by self-interest. And what about apparent altruism? Well, I don't know a lot of expert level stuff about this particular perspective, although I would very strongly say that it is perfectly obvious that human action is not always motivated by self-interest. I find it hard to believe that anyone can actually have experience with actual human beings and believe that. [chuckle] It's also perfectly obvious that sometimes human action is motivated by self-interest, sometimes it's not.

2:12:33.5 SC: See, I don't see what's so hard about accepting that. That's why it's interesting to think about human psychology because it's not something so cut and dried as yes, it's always motivated by self-interest. You have to be able to accept nuance and complication in the world, you should expect that of human beings. Human beings are not intelligently designed, they grew up under the course of evolutionary history with all sorts of random accidents as well as selection pressures. Sometimes a band of humans can stick together and work in cooperation and that helps them survive, other times human beings can betray all their friends and that helps them survive, so the selection pressures are not at all obvious. I think that we should glory in and work to understand all the nuances and complications of human psychology rather than trying to boil them down to a simple motto. Chris says, what are the best arguments you've heard for consciousness being fundamental and how would you refute them? I don't wanna be unfair here, I don't know any good arguments for consciousness being fundamental. It is a point of view that some people have and they hold it very strongly and there's some very, very smart people who do that.

2:13:49.8 SC: Therefore, I think that these people are worth engaging with because as a good Bayesian, I think that even though I hold a certain point of view very, very strongly if there's a whole bunch of smart people who disagree with me, I have to carve out some credence that I'm wrong. But as far as actually hearing the arguments and being persuaded, hmm, maybe there's something there, no, I have had zero persuasion that there's any reason to think that consciousness is fundamental. So can't really help you with what the best arguments are. Nichol Kramer says, if you were put in charge of the grand renaming scheme for all of physics, what would your main choices be and why? For example, in your new great course, which we talked about at the very beginning of the intro here, you described the term wave function as a dumb, boring name. Likewise, I've heard you express similar misgivings about terms like dark energy and entanglement, similarly, what might be a clearer, less confusing or ambiguous term for the many worlds interpretation of quantum mechanics? Yeah, I actually haven't thought about these a lot, and I'll tell you why. I do think that some names are more clear than others. Names serve two purposes, one is that they're labels, right?

2:15:05.8 SC: You could call this just alpha, beta, gamma, you just give completely symbolic labels to all of these things, it helps you distinguish whether you're talking about alpha or beta but then also, names ideally would at least suggest what it is that is being talked about, okay? So wave function, for example, that's just a terrible name just because it's boring, not because it's inaccurate, but because it's boring. When they invented the idea of a wave function, when Schrödinger first wrote down his idea of what the wave function was, it was something that he used to make predictions for hydrogen atoms and things like that. We now think of it and even Schrödinger presumably came to think of it as the fundamental description of the state of reality, right? I would prefer to call it the quantum state or the state vector, because it's a vector in Hilbert space. Wave function just sounds like a temporary label that you put on something before you come up with the right one.

2:16:09.0 SC: But I also think that despite the fact that these labels don't always convey useful information, it's not the biggest deal in the world. I'm not that worried by the fact that these labels are not descriptive, that they're merely pointers, that they're merely labels. Once the label is accepted by the world, you gotta deal with it. I don't think that renaming things is a very useful use of our time, right? People have heard the word, it's better to just be clear about what the word means. Dark energy is kind of fine, it's not the best label, even dark matter is not the best label because the important thing about dark matter is not that it's dark, it's that it's invisible, it's that it's transparent, right? It neither glows, which is what makes it dark, nor does it absorb light. That's what's important, it's invisible matter, but that sounds even spookier than dark matter. At least in the case of dark matter, the word matter is distinguishing it from other things like radiation or vacuum energy. Dark energy, the word dark is just as misleading, but also the word energy is just nondescriptive, because matter also has energy and radiation also has energy. So it's not a very helpful term in that form, but again, it's accepted so people are gonna use it. Entanglement is worse for two reasons.

2:17:27.0 SC: One is that at the practical level, it really does make people think that there is some tangible connection, like a little string or a ribbon that is connecting two different entangled particles, which could not be further from the truth. And the other more conceptual one, and this is where I become a little idiosyncratic minority member. I don't think the right way to think about the world is as little individual subsystems which are or are not entangled. That makes entanglement seem like a mystery, why are these two different subsystems entangled with each other? How will we ever account for the mystery of entanglement? From my point of view, it's exactly the opposite, the world is a single state vector and entanglement only comes about because we insist on dividing the Hilbert space in which quantum states live into subsystems. And then some of them are gonna be entangled, some of them are not going to be, but it's not a mystery, it's your fault because you divided the world into subsystems 'cause that's easy for you to do. Only if you're already thinking classically and thinking of these subsystems as fundamental do you begin to think that entanglement is somehow mysterious or weird.

2:18:42.3 SC: As far as many worlds goes, people often do simply call it unitary quantum mechanics, that's what it is. It's the idea there's only one wave function and it evolves unitarily, that is to say smoothly according to the Schrödinger equation. But many worlds is fine, I call it that all the time, other people do, language is for people to communicate with each other and that's okay. Dan O'Neill says, have you ever considered writing a memoir? If you were to write one, how would you imagine weaving conceptual material like your intellectual interests into your life story? Nope, [laughter] I have not ever considered writing a memoir, not anything I'm going to do. I might write like when I get to be Ernie's age and I'm 96, maybe I'll write like a short article telling some funny stories about my life or something like that but even myself, I think that the ideas that I think about and talk about are way more interesting than the specific anecdotes that happened in my life along the way. So let's largely leave it at that as far as I'm concerned.

2:19:47.0 SC: Helen Edwards says, I am trying to reconcile views of the account of physics and free will. In reference to past guests, on the one hand and currently popular authors and their views... On the one hand Robert Sapolsky and Sabine Hossenfelder and her determinism in no free will, then there's Jenann Ismael and Dan Dennett who have amazingly reasoned views and conclude that we do have free will even in a deterministic universe. All outline their views so precisely yet I find they don't fully dispute each other. Yeah, I get your frustration and honestly I try to occasionally answer questions about free will but I don't like talking about it, because very, very often people are just disagreeing with each other's words and definitions. And I had a podcast discussion with Robert Sapolsky, I really like him as a person and as a scientist. He wrote his book, Determined, that just came out and I actually got some chapters to read ahead of time so that I could offer commentary.

2:20:50.0 SC: And his discussion of compatibilism was just not any good, he clearly, he was saying you shouldn't be a compatibilist because determinism is true. And the whole point of compatibilism is to say that free will is compatible with determinism. You can disagree with compatibilism but you can't sensibly argue that the fact of determinism is somehow a refutation of it because it's part of it. So I would rather and I did this when I appeared on Sam Harris' podcast and we talked about free will. I said, look, let's cut out the possibility of just having semantic arguments over definitions by agreeing not to use the phrase free will in our discussion. I do this all the time and no one ever goes along with me, so Sam did not go along, we talked about free will, it was boring, it was all about definitions. I think there's much more interesting things to talk about than what those definitions should be so I would rather talk about those.

2:21:51.9 SC: P Walder says, Robert Sapolsky once again, in an interview about his book Determined dismissed the many worlds view of quantum mechanics out of hand. The basis for his dismissal was this notion that many worlds allows for time running backwards, I don't recall you ever discussing this. Is he right? I don't know if he is right about... I don't know what he means by time running backwards, I don't even know what that would mean, time running backwards. With respect to what is it running backwards? I do think that there is a fact of our physical observable universe, which is that there is an entropy gradient, one end of time the entropy in our observable universe is lower than the other end of time. After the fact, ex post facto, we define time so that early moments are the ones where the entropy was lower, later moments are the ones where entropy is higher. If there was another... If someone chose to define a time coordinate which moved backward, good for them, they're still describing the same time physically, so I don't even know what that means to say time is running backwards. All I will say is there's an interesting again psychological fact about people who don't like free will, people who wanna argue against free will, which is that they... And I've said this before.

2:23:10.0 SC: They really get beholden, they fall in love with determinism. They think that the reason why free will isn't there is because the world is deterministic, and I have to point out the world is not deterministic. [laughter] Certainly not the world as it is observed by actual observers, by people, because there is such a thing as quantum mechanics. Sorry, you can't predict what's gonna happen because quantum mechanics says you just can't, that's the laws of physics as we currently understand them. And this is absolutely irrelevant to your picture of free will, if the laws of physics are stochastic versus deterministic that has zero impact on whatever you think about free will but for some reason that is entirely psychological, people who want to argue against free will think that it's their duty to downplay the lack of determinism in the laws of physics. They will say, "Oh, yes, there can be quantum fluctuations, but they're not very big." Well, they could be big and also, even if they were small, they're still not deterministic, it's just not right, why not say things that are true rather than things that are false? I don't know, I don't know why people are so in love with determinism when it's not true. Have a discussion about realities would be my advice to these people who are not me so they don't need to listen to my advice.

2:24:30.8 SC: Herbert Berkowitz says, the moon appears larger when it is near the horizon than when it is overhead. Since we know that its actual size doesn't change, this is known as the moon illusion, there's no scientific consensus to explain this phenomenon, although there are multiple theories. In your opinion, what makes this nut so hard to crack? Well, because this is a question for psychology, not for physics or astronomy, that's what makes it so hard to crack. At the level of physics and objective reality, you can easily just take photographs of the moon when it is near the horizon, high in the sky and you can compare their angular diameter, and it is the same as it more or less needs to be. So there's zero physics problem here at all but remember, the human brain is not a camera, okay? The human brain interprets what it sees, because it wants to keep us alive and we are subject to the pressures of evolution and the constraints of energy use and things like that, that's what makes all sorts of optical illusions possible.

2:25:30.9 SC: So the question is, why is this particular optical illusion something that the brain is so prone to? I have no idea, that is absolutely a job for psychologists. I'm going to group two questions, one is from Mark Kumary, who says, you have mentioned that space is almost surely not fundamental, while the jury is still out regarding time, although you are of the belief that time is likely fundamental. There appears to be some tension between this statement and special relativity, where we talk about space-time as being a single entity. After all, if space is emergent but time is fundamental, what is space-time, emergental? And Dodzod says, in a theory where space emerges from entanglement, is there a preferred reference frame, I.e., one that is stationary with respect to the entangled elements?

2:26:16.1 SC: So, of course, the short answer is we don't know what is going on here, once and for all, these are all conjectures, hypotheses that we're still dealing with. So the context is trying to understand how space-time, maybe just space, maybe both space and time, maybe just time emerges from some underlying quantum state. Sometimes this is stated, including by me, as emerging from entanglement, but as I just said, entanglement isn't the best word here. The better way of thinking of it is just a single quantum state without any pre-existing structure. How can you say that space emerges from that and what about time? And then it seems to be that in these attempts to do that, space and time are being treated differently, on a different footing. That is contrary to the spirit of relativity. And it's actually worse than that, because in my favorite versions of these questions, the number of degrees of freedom in the observable universe is finite.

2:27:19.6 SC: So we work with a finite dimensional Hilbert space, which essentially means it is impossible to be exactly Lorentz invariant, where Lorentz invariance is the statement of relativity that there is no preferred distinction between space and time. So, even though we don't know what the final answer is, I think it is absolutely possible that in the fundamental theory of everything there is a preferred notion of time versus space. And the fact that in the world we live in, space and time seem to be on an equal footing in that case would just be an approximation. This is very unpalatable to a lot of physicists and I absolutely get it, the idea that Lorentz invariance, the symmetry that Einstein put into special relativity to make it all work, that that might not be exact, that it might just be an approximation, that it might not be fundamental, this is worrisome to a lot of people. And I'm not devoted to it by any stretch of the imagination. Let me just say two things about it. One is that it would be great to have some experimental test of these ideas and the idea that Lorentz invariance is being violated is perhaps one of the most straightforward examples of a possible experimental test. So in that case, that sense it would be great. The other is that our universe has a preferred reference frame, the rest frame of the cosmic microwave background.

2:28:46.8 SC: This is typically described as not fundamental, it is a feature of the stuff in the universe, not of the underlying laws of physics, but there is still a question, where did it come from? Why do we have a frame of reference in the universe that is somehow picked out as special? This is something we don't know the answer to on the basis of the early universe or inflation or anything like that, we just kind of bake it in to the fundamental description that we have. So maybe it's not an accident that the universe has a preferred reference frame if the fundamental laws of physics do as well. That's just a completely wild speculation at this point, but it's something to keep in mind when we're developing better theories of fundamental physics.

2:29:32.4 SC: DC says, my understanding is that conservation laws are only true on a time-averaged basis, meaning that on a fine enough time scale, conservation can be absolutely savaged. PV=nRT, the ideal gas law, is a weekly emergent non-fundamental finding, a shortcut that blessedly saves us from the horrors of statistical mechanics. Are Einstein's field equations like that, in that on small enough time scales you can violate the equation? I don't think you're right, the conservation laws are true on a time-averaged basis. Certainly in typical physical situations like conservation of electrical charge, that is absolutely 100% obeyed all the time at the most microscopic basis, not just on a time-averaged basis.

2:30:18.6 SC: Conservation of energy and momentum is 100% absolutely obeyed by the unitary Schrödinger evolution of the wave function of the universe. Quantum measurements violate conservation of energy, but that's a more subtle thing and I think personally that in the wave function of the universe, everything is still conserved. Of course, it might be that in a more fundamental understanding we find that these are just time-averaged quantities, but certainly as far as current ideas of fundamental physics are concerned, these are exact, not just approximate. Plant-based Heisenberger says, I don't believe that humans have a separate soul from their bodies, I also sympathize with the idea that what makes you you is the pattern of matter that makes up your body and brain, not necessarily the ever-changing bits of physical matter that fills that pattern. With this in mind, I struggle to understand what someone means when they say they were born into the wrong body. What is the you that was put into the incorrect body? I understand the confusion here, but it's a purely linguistic one.

2:31:24.8 SC: You have to think deeply about what these words mean in these slightly more subtle contexts. So, yes, humans do not have a separate soul from their bodies, but that doesn't mean you don't have a soul, or you don't have a self, or you don't have a self-identity, right? What we're saying is that this idea that we've had for millennia that human beings have souls, or essences or selves is not fundamental, is not something that is part of your bedrock ontology. It is emergent out of a description that is more physicalist and made of atoms and things like that. But exactly like tables and chairs, as I keep saying, that doesn't mean it's an illusion or it's wrong, right? We do have patterns of atoms and molecules and energy that make us who we are, and we are somebody.

2:32:18.6 SC: We individuals have preferences, we have instincts, we have feelings and it can absolutely... It's not even very hard to imagine how it could be the case that someone has desires or instincts or feelings that they are a certain kind of way and an actual physical manifestation being a different kind of way. I see no difficulty whatsoever in a physicalist, non-essentialist view of human nature to imagine that psychologically some people feel happier and more natural in a different kind of body than what they were born into. And of course experimentally, it happens all the time in the data, so if your theory does not accommodate that, I think you should kind of try to update your theory so that it does.

2:33:06.2 SC: Ned Grady says, do you read the comments underneath AMA questions and give them any weight to your answers in your answers? Yes and no. Mostly no is the answer. The way that it happens is that on the Patreon webpage, I look to see all the comments at once, usually there's like pushing 200 comments, and I cut and paste them into a text file so that I can edit them, remove the ones I'm not gonna read, edit individual questions, et cetera, move them around sometimes. And that cutting and pasting does not always include all the comments on questions, it usually will include like the first comment, but then click to load more or something like that. So I don't see all the comments and therefore, if your comment is, "This is a really good question, you should answer it." I would take that into consideration, possibly, it doesn't get 100% weight, but I would count it in wondering whether or not that's a question I should answer but you should just include that as a separate comment. By all means, feel free to just leave a comment saying, oh, I liked X's comment, a question about this, you should definitely answer that one. And then I will absolutely take that into consideration.

2:34:21.5 SC: Matt Haberland says, if I understand correctly, there have been shifts between the use of frequentist and Bayesian techniques in scientific practice over time, and Bayesian techniques seem to be more popular now than they were during most of the 20th century. Would it be better if the Bayesian paradigm were preferred in all fields of science, or is there still a place for frequentist statistics? These are debates that go on by very knowledgeable people, and I'm not very familiar with those debates, so you should not take my opinion very strongly here but for what it's worth, my opinion is that frequentism is just a special case of Bayesianism. Bayesianism is a way to assign credences to different things you're unsure about, one way to do that is to imagine that that thing you're unsure about is a frequency of something happening over and over again. So roughly, I think that yes, Bayesian paradigm should always be preferred, but that doesn't mean that frequentist ideas shouldn't be used. They should be used in the proper context where that is the kind of Bayesian reasoning that is relevant. The Great Deceiver says, how can we ever hope to understand the universe without first understanding the thing through by which we understand the universe, I.e., the brain or mind?

2:35:37.0 SC: I don't see how it's that complicated, really, it's like saying, how can I understand this Wikipedia article without understanding the thing that brought it to me, namely my personal computer in front of me? I don't really have a deep idea of how the circuitry in my computer works, but I can still read the Wikipedia article perfectly fine. I think you should distinguish between the thing you're trying to understand and the thing by which you do understand it. I can drive a car to get somewhere without knowing how cars work, I can do science actually without knowing a lot about the scientific method and certainly, I can have thoughts without knowing too much about how the brain works.

2:36:11.2 SC: Varun Narasimhachar says, papers that critique your mechanism for an emergent space-time tend to attack the uniqueness of the emergent space-time. Do you hold uniqueness to be an important criterion or would you be happy to have a mechanism that induces the emergence of at least one such structure? Well, I tend to think there probably will be at most one space-time that will emerge from a different underlying structure, but I think that we are still trying to figure out what the criteria are for seeing a successful emergence. I do think that in our experience, because of how we're embedded in the world and the Arrow of Time that we have, et cetera, we have a very specific love for the classical limit.

2:36:53.8 SC: We talked earlier about real patterns, the classical limit being applicable is a quintessential example of a real pattern embedded in a very different picture, which is fundamentally quantum mechanical. So I think that if you looked for a classical limit and you looked for an entropy gradient, so there was an Arrow of Time, and you looked for something like locality in some number of dimensions, I bet there would not be more than one unique emergent space-time from any underlying quantum structure. I don't know that for sure, but these are my guesses. Callum says, in 2008, you wrote an essay entitled The Cosmic Origins of Time's Arrow, that briefly described your project with Jennifer Chen to produce a time-symmetric cosmology. Have you updated any part of that theory in the last 15 or so years that have elapsed on new scientific findings? Not very much, but I'm trying to. I'm trying to write an article right now that talks about some of the loose ends in that model. In particular, I'm very interested in whether the baby universe scenario that we relied upon is the only way to make it work. I think that the general idea of unbounded entropy and a time-symmetric large-scale cosmology is a very, very interesting and good one, promising one.

2:38:08.0 SC: But there could be different ways to implement it in realistic cosmologies. So if you could do that without baby universes, I would like to be able to do that, but I haven't quite decided whether or not that's possible. Dallius Kubilis says, can Gödel's incompleteness theorems as presented, for example, in Douglas Hofstadter's Gödel, Escher, Bach be applied to physics? If physics is based on theorems compatible with number theory, they can never be complete and consistent, even if they are updated according to new experiments. I don't think that's quite right, I don't think that you're correctly paraphrasing Gödel's incompleteness theorem. The incompleteness theorem says that a given formal axiomatic system can never prove its own consistency, that is one of the theorems, and another theorem says that there will always be statements you can make in that formal system that can neither be proven true or false if the system is consistent.

2:39:04.4 SC: So you can't prove whether it's consistent, and there are certain true statements you can't prove if it is consistent. So neither one of those statements has any obstacle whatsoever to physics, as far as I can tell. Physics assumes consistency and moves on with that, and if you have some theory of physics... By the way, I should back up. A theory of arithmetic or a theory of number theory, like Gödel's incompleteness theorem directly applies to, is very different than a theory of physics, right?

2:39:39.8 SC: A theory of number theory says how you add things together, a theory of physics says what quantities you add together to make different quantities, like momenta or something like that. It's a specific model within a general framework, so I don't think that the analogies between number theory and physical theories are even right from the start. But having said that, in any given physical theory, I can use the axioms to derive theorems and things like that. And either I'm gonna to find that they're inconsistent, in which case, clearly, I had the wrong axioms, or I'm gonna find that they agree or disagree with experiment. That's how physics goes on, it's not that it can't be consistent, it's that according to Gödel, it's that I can't prove that it's consistent, but that's okay, in physics I do lots of things that I can't prove they will always be right.

2:40:31.6 SC: Bits plus Adams says, in her book, How the Universe Got Its Spots, former Mindscape guest Janna Levin says, there was no chicken in the primordial soup but given the initial conditions of the universe and the deterministic nature of the wave function evolution in many worlds, isn't there a sense in which it contained all the chickens in every world? Yes, there is, but let's be... But the details matter here, and I'm actually thinking about this. In fact, in part inspired by the conversation I had with Slavoj ŽIžek on Robinson's podcast, which you can look up on the internet if you want.

2:41:09.9 SC: It's very plausible that the initial conditions of the wave function of the universe were extremely simple, in the sense that, in the sort of Kolmogorov complexity sense of simple, it doesn't require a lot of bits to specify what the wave function was. Our universe that we see around us right now is extremely complex, in the sense that it takes lots of bits but if information is conserved, how do you evolve from a simple initial condition to a complex later one? The answer in many worlds is that the overall universe is very simple, but we don't see the overall universe, we see some little slice of it, some branch of it. So think about a disc cut out of construction paper, a disc is very simple, but I could, with my scissors, cut out a very, very intricate subset of the disc. And that's what our universe is like, right?

2:42:02.8 SC: Our branch of the wave function of the universe is an intricate slice cut out of a very simple overall wave function. So would you say that that intricate little picture that I cut out was always there in the disc? I don't know, maybe, maybe not. The possibility of it was always there and likewise for the universe, the possibility of coming up with a branch of the wave function that has chickens in it was always there, but you can't really read off the details of the chicken from the actual wave function of the universe at early times. Chris Gunter says, do you have an intuitive explanation for the degeneracy pressure of Pauli's Exclusion Principle? What can we picture as pushing particles apart in, say, the pressure opposing gravity in a neutron star? The explanation I've always heard is about fermions flipping signs when swapped and allowing them to occupy the same state will allow them to cancel, but is there a more intuitive picture then because the math doesn't like it?

2:43:01.9 SC: Part of me wants to say that the correct explanations are always because the math doesn't like it, or more particularly because the physical theory that we have described using the vocabulary of math doesn't like it. Everything else is just a warm and fuzzy feeling, okay? The physical theory is what actually is telling you what's going on, so you kind of should try to learn to be happy with that. And I talk about the math behind it a little bit in Quanta and Fields, my upcoming books, you can check that out. But depends on... So since all we're after is a feeling of satisfaction, it's gonna depend on what you qualify as satisfactory in an explanation. The thing about fermions in quantum field theory is two fermions must have zero overlap between their quantum states, okay? So it's not just they can't be in exactly the same quantum state, they can't be in almost the same quantum state. So when I have two electrons in an atom, their two wave functions need to be exactly orthogonal to each other.

2:44:09.6 SC: That can happen by having the spatial part of the wave function be exactly the same, but the spins be opposite, that's why you get helium atoms and other noble gases and things like that. When you have two different atoms, what happens when you try to push them together is that the two electrons, let's say two hydrogen atoms, try to push them together, if they were exactly overlapping, those electrons would be in the same quantum state, that's not allowed. If they're almost overlapping, then the wave functions have a lot in common and that's still not really allowed. So you have to sort of imagine pulling them apart until you can deform them in a way so there's zero overlap between the wave functions without putting too much energy into the system.

2:44:55.3 SC: So there's a push and a pull, right? The atoms want to be close together because the total energy is lower if there's no difference between the things, but the Pauli Exclusion Principle won't allow that to happen so you have to look for the lowest energy state that is allowed by the requirement that the two wave functions have no overlap. If that has no explanatory value to you, then sorry, I don't know quite what to say. DMI says, would there be a difference between a bet that, "when an initial pure quantum state undergoes gravitational collapse to form a black hole, the final state at the end of the black hole evaporation will always be a pure quantum state." And a bet that, "information can escape from a black hole."

2:45:44.0 SC: Well, there's a slight difference in how those are stated, but I think morally they're the same. If what you're asking is when physicists say, can information escape from black holes, is what they mean that a pure state will evolve to another pure state even if it goes through black holes as an intermediate state, then yes, that is exactly what they mean. Tim Converse says, if we encountered an alien civilization that had advanced math and physics, how different do you think their math and physics could be from ours? For example, human mathematicians think the Riemann Hypothesis is interesting and central, is there any reason to think that interestingness is also objective and would be shared? Honestly, I think it's a very good question, I don't really know the answer, I could easily imagine it either way. Let's put it that way, I could imagine that aliens think in such a very different way that we haven't thought of ourselves because we think like we think, that their idea of what mathematics is is just entirely different. You know, Tim Maudlin who was a recent Mindscape guest, has this project where he reinvents all of topology based on lines rather than sets, and he's interested in relativity and the Arrow of Time and things like that, there's a reason for doing that.

2:46:57.6 SC: Emily Riehl who was another Mindscape guest from a while ago, has a way of... A different way. And it's not just her, but there's a group she's a part of that has an entirely different axiomatization of all of math that doesn't use set theory, but instead uses some constructions from category theory. Whether or not these end up with very different final sets of theorems, they have to be compatible with each other, but they could seem very, very different. So I could imagine that aliens would have even more different ideas about mathematics but I can also imagine that even though the aliens are very different, they're still in our same physical universe, they're still driven to care about the same things, triangles and circles are still very important, maybe they have more or less similar ideas about math.

2:47:43.3 SC: I think it's a very interesting empirical question that I don't really know how to judge. Eric DaVinci says, who is your Mount Rushmore of NBA basketball? It's a tough one, again, because I'm not a big ranker of things, I'm not a big lister of things, but if you force me to do it, this wasn't a priority question, but I like to mix up the questions, so here's a little bit of a breather. I think that the two best basketball players of all time are probably Michael Jordan and LeBron James, I think that's the sensible way to go there, and in fact, I would pretty easily put Michael Jordan first.

2:48:20.0 SC: And this is, even though it's pretty easy, it's not necessarily quantitative, that's the impression I have as someone who has watched both Michael Jordan and LeBron James play basketball a lot. At his peak when Michael Jordan was playing, if you were on the other side because I was never rooting for him, I was rooting for the Sixers, and they were playing against him, and even when he was playing somebody else, I was generally rooting for the underdog, which the other team always was. When Michael Jordan was playing, you really always had the impression that he was gonna win, that if he... He didn't always win, of course, but it just seemed like a weird, bizarre fluke when his team didn't win 'cause he was just so overwhelming and so central and so accomplished.

2:49:03.8 SC: With LeBron he's won a lot, he's scored a lot, et cetera, but you don't have that same impression, I literally watched the Sixers play the Lakers the other day, and the Sixers destroyed the Lakers, the Lakers are who LeBron is playing for now. And admittedly, he's an old man, he's very, very advanced in his age, LeBron, he's played more minutes in the NBA than any other human being ever has. But, look, to be honest, I barely noticed him, he scored some baskets, but he looked very human, very ordinary and Michael Jordan never looked ordinary to me. Still, given all of his accomplishments, I think you've gotta put LeBron on there.

2:49:45.0 SC: And then I think and it pains me as a Philadelphia 76ers fan, I think you've got to put Bill Russell on that list also. Not the most talented basketball player in some ways, but he just won, he won basketball games all the time, and at the end of the day, that's what matters. He was by far the most effective winner in the history of NBA basketball, and he also won the Olympics and in high school and in college and everything. He's the guy you wanted on your team when you wanted to win a game, and I think that should count for a lot. And then I think you have to put Wilt Chamberlain on the list also, because if you look in the record books the things Wilt did, no one else ever did. And in terms of statistics, in terms of scoring and rebounding and block shots and all of these things, he led the league in total number of assists one year.

2:50:36.2 SC: He was the most amazing physical specimen and athlete that NBA basketball has ever seen. So if there's four people on Mount Rushmore, then those are the four I would probably put on. Of course, my personal favorite basketball player was always Julius Erving, because Dr. J was the guy who got me interested in basketball from the start. And I think that modern ways of judging basketball players very much underrate Julius Erving. There's a reason why the Sixers went to the NBA Finals in half of the years when Dr. J was on their team, and have only been back once in the many decades since then.

2:51:18.0 SC: He was a winner also, and he did it in ways that were not always obvious, he scored, but he didn't score more than anybody else, he also had a lot of steals, a lot of assists, a lot of block shots. And you can play games in the basketball statistics databases like Basketball Reference, and you can look for things like what basketball players have in the history of the NBA or ABA averaged more than this number of blocks, steals, assists, points? And it's not hard to find criteria such that Dr. J is the only person who shows up on those lists. He was also endlessly entertaining and a wonderful person to have on your team, so I have a special place for him even though he's not top four of all time.

2:52:03.6 SC: Christian Dobo says, in last month's AMA, you said you find it incoherent when people who say free will is an illusion are still trying to make choices as well as trying to convince others about making choices as well. Can you help me point out this contradiction? In my mind, they are not saying the illusion of free will doesn't exist or that it is not central to our everyday behavior. Moreover, they say that lacking free will, the only thing that can actually change your mind is an outside influence like someone trying to convince you to do or to not do something. I don't even know what to say. For one thing, the only thing that can change my mind is an outside influence just seems wrong to me as someone who has changed my mind before, but let's put that aside.

2:52:47.8 SC: My point is, if you think that free will is an illusion, then you should also think that moral responsibility or praiseworthiness or blameworthiness is an illusion. If the only thing... Remember, compatibilists are perfectly happy to believe in the laws of physics and that human beings obey the laws of physics. What that means is there's a perfectly consistent and comprehensive way of talking about what happens in the world that never mentions human beings, free will, choices, anything like that. It's just atoms obeying the laws of physics. But the compatibilists say there is another way of also talking about the world where there are humans and they do make choices, and in that way of talking we can assign moral goodness and badness to the choices that they make. What I don't see is how you can say there are no choices, choices are just an illusion, but I'm still gonna say that some choices are good and some choices are bad. I think that's pretty obviously a contradiction to me. Robert Holmes says, do you have a list of criteria for distinguishing pseudoscience from real science? I'm especially interested in critiques of astrology, it has no established mechanism, but neither did gravity at first.

2:54:03.0 SC: Its predictions aren't 100% true, but no model in science ever is. So what sets astrology or other pseudosciences apart? Honestly, here I am again in a minority perspective here, I almost never go around calling things pseudoscience. I certainly don't go around worrying about some distinguishing criteria for saying this is science and this is pseudoscience. I'm perfectly happy to call it all science, I just say that some of it is bad science and some of it is good science. The problem with astrology is not that it's pseudoscience, that it doesn't fit some made-up criteria for what's really science. The problem is it's just crappy in making predictions, it is completely disconnected from other things we know about the universe and there's no reason to believe it's true. You can call it science if you want, I'm just not gonna call it worth my time. David Maxwell says, movies and games let us digitally create sights and sounds in increasingly realistic way, experiencing things we never could in reality. My childhood dreams of digital sense remains elusive, but if it happens in our lifetime, what new olfactory experiences might you dive into?

2:55:14.3 SC: So I have no idea what new olfactory experiences might be worth diving into, all I will say is that if you haven't already, you should go back and listen to the podcast I did with Ann-Sophie Barwich, who is a philosopher of smell. Philosopher/neuroscientist. She actually has a lab where she discusses these things. And I'll warn you ahead of time, smell is very, very tricky. Part of how we appreciate smell is extremely contextualized. One thing, one chemical can smell very pleasant in one context and very unpleasant in another context, so I don't know what will happen when we can digitally generate smells because we're also gonna have to digitally generate an entire context to put them in before we say whether they are pleasant or unpleasant.

2:56:00.2 SC: Larry Hertzberg says, you often mention David Lewis' approach to modal logic when discussing how philosophy deals with the topic of possibility, but I've never heard you mention Saul Kripke's popular alternative. Kripke's approach does not posit the existence of other equally real worlds containing counterpart objects that are really qualitatively similar to those in the actual world, rather he views possible world talk as just a convenient way to analyze the truth or falsity of counterfactual statements about actual objects based on our modal intuitions about the necessity or contingency of their properties.

2:56:34.2 SC: I was just wondering whether you're familiar with Kripke's approach, and if so, what do you think of it? I am only very, very tiny amount familiar with Kripke's approach, and from the little that I have heard, I'm actually more sympathetic to it than I am to Lewis' approach. Personally, I think that the idea of possible worlds is absolutely crucial for how we talk and reason about the one actual world, but I'm not a modal realist, I don't think of the other possible worlds are actual in any real sense. If that is also what Kripke is saying, then I am completely on board with what he says. The only reason I always refer to David Lewis is the philosophers I hear talking about these ideas, mostly talk about Lewis' version of it. So someone like Barry Loewer in particular, thinks of what he is doing as building on David Lewis' approach to modality and possible worlds.

2:57:27.4 SC: Lewis did get into details about physics and time and things like that, so that might be why the people who I talk to more often referenced Lewis than Kripke, but I'm not trying to implicitly judge one as superior to the other. Wade Dan says, is there a recognized group of accredited scientists who are proponents of a young earth and also anti-evolution that aren't openly religious? No, not that I know of, certainly. Well, so there's no recognized group of accredited scientists. I don't know what it means to be an accredited scientist. I do not know of any group of serious scientists who are proponents of young earth cosmologies, whether or not they're religious. Nick Gal says, my question has to do with the role of coarse-graining and what it does to our perception of complexity. Is it possible that the eventual decrease in complexity in our universe is only apparent due to the fact of the structural complexity of the cream mixing into coffee may continue to increase, but only at scales smaller than the course-grained cut off?

2:58:33.1 SC: Anything is possible, but we're thinking about... So this is in reference to the paper I've been working on with Scott Aronson, an update of our old paper on the origin and evolution of complexity in closed systems with cream mixing into coffee as our paradigmatic example. The set up that we care about is... The phrase closed systems in that title refers not just to systems that are isolated, but systems that obey deterministic underlying laws of physics, like we think classical mechanics is or unitary quantum mechanics is. So in that case, complexity must be something that arises from coarse-graining, because if you have deterministic reversible underlying laws, then the total amount of information contained in the state is constant over time, it doesn't go either up or down.

2:59:26.6 SC: So the complexity can't go either up or down. It is only once you combine reversible underlying laws plus some macroscopic coarse-graining that what we call the apparent complexity can go up and then go down. And that's exactly what happens. So the eventual decrease of complexity is, yes, it is apparent in some sense, but it is also real, both things are true, because in the real world, we actually do coarse-grain the universe, we do not see all of the microscopic things going on. Jim Spangler says, reading a blog post about Sam Bankman-Fried, I came across... He's the guy who got indicted or maybe convicted by now, I don't know, for the FTX cryptocurrency scandals. Reading a blog post about him, I came across a tweet he made back before his life fell apart and challenging the idea that Shakespeare was the greatest writer in the English language, he says, "The Bayesian priors are pretty damning, about half the people born since 1600 have been born in the past 100 years, but it gets much worse than that. When Shakespeare wrote, almost all Europeans were busy farming and very few people attended University, a few people were even literate, probably as low as 10 million people.

3:00:40.4 SC: By contrast, there are now upwards of a billion literate people in the Western sphere, what are the odds that the greatest writer would have been born in 1564? The Bayesian priors aren't very favorable. Now, notwithstanding the fact that literature is subjective, this strikes me as extremely bad reasoning, but I can't put my finger on why. What do you think? Well, I think that the fact that literature is subjective is relevant here. More relevant, clearly, overwhelmingly relevant is the fact that the idea of having a greatest writer in the English language is not very well defined, right?

3:01:54.1 SC: What do you mean, the greatest writer? Shakespeare certainly isn't the best selling writer, if it's not the Bible, then it's Agatha Christie or someone like that, right? But Shakespeare is arguably the most influential writer, he coined an enormous number of words, he set the stage as it were, pun not intended, for the way that we think about poetic language and drama in general, and characterization and things like that, he pioneered forms of historical plays and tragedies and comedies, et cetera. Any time you see a Comedy of Errors, whether it's the Marx Brothers or the Three Stooges or whoever, Shakespeare literally wrote the Comedy of Errors. There are reasons why the kinds of situations that arise in Othello and Hamlet and Romeo and Juliet are used over and over again in modern dramas, but guess what? If that's your definition of the greatest writer, the one who is the most influential in a good sense, then you shouldn't put a uniform prior on all the writers who have ever lived, it's much easier to be influential when you are born earlier.

3:02:31.4 SC: So I just think it's kind of silly, this kind of argument that is given in the quote because it starts from an ill-defined idea, the greatest writer of the English language, it then smuggles in an implicit assumption, namely that your prior should be uniform over every person who is born and then reaches a conclusion. So the logic there is just based on a whole bunch of sketchy assumptions. This is a big problem overall for people who consider themselves to be rational, it's not okay just to have some assumptions and draw conclusions from them, your conclusions are no stronger than your assumptions, and so you have to be very careful that your assumptions actually accurately track with the world. And there is a very human flaw that people have, which is they like their assumptions to be simple.

3:03:23.5 SC: They like them to be easy and clear and cut and dried, as we talked about with Thi Nguyen back a while ago, right? Clarity and simplicity are just really, really seductive to human beings, so the idea that we just take all human beings, give them an equal chance of being the greatest writer in the English language and then act shocked that the greatest writer was in the 1600s, it's natural, it's compelling, but it's actually not very rational at all.

3:03:52.7 SC: Jeffrey Segal says, the discussion of the reality of mathematics in the last AMA was interesting and made me wonder how justified some of our choices for mathematical solutions are. In engineering, complex numbers can be used to describe amplitude and phase, for example, but starting early, we're told that the real life solution for X squared equals four is plus two, and we should simply ignore the minus two alternative as not realistic. Is there a deeper philosophical rationale for this choice, do you have a Bayesian prior regarding how likely it is that we might someday discover that the minus two alternative could be interpreted in terms of the physical world?

3:04:31.1 SC: Well, I think that the deep underlying philosophical principle is that you were taught badly, there's no reason whatsoever to say that if X squared equals four is all you know, that you should ignore the minus two solution and stick with the plus two solution. What is probably going on is that you don't only know that X squared equals four, there is some context in which you're trying to understand something, right? Like if someone says, I have a number of pebbles in my hand, and I will tell you that the number of temples squared is four, then you can reasonably conclude that they have two pebbles in their hand, not minus two, because the space of possibilities is only whole numbers, natural numbers, I guess, 0, 1, 2, 3, et cetera, right?

3:05:16.8 SC: You can't have minus two pebbles in your hand. So there is a physical context in which some solutions are physically reasonable and some are not. But there is no a priori philosophical rationale that you should always choose positive roots to algebraic equations, to polynomial equations. That's just not a thing that you should ever rely on. Mike Meyers says, whether it's discussing current topics in physics or the history of physics, you seem to have a talent for recalling the names of significant individuals and their accomplishments, are you especially good with names, or does this mainly come from repeated exposure to these topics?

3:05:55.5 SC: I'm certainly not especially good with names, I'm as embarrassed as anyone or worse than average when it comes to remembering the names of people who I've met personally, and I'm hilariously bad at remembering the names of actors in movies and things like that, it's just not something my brain is very good at. I think probably what... To the extent that your very nice compliment has any relationship to reality, the point is that as someone who spends his time writing about these topics for a broad audience or talking about them for a broad audience, it is often the case that I'm interested in looking up some of the history for how things happened, right? Looking up, so exactly what happened when Isaac Newton came up with the ideas behind the Principia Mathematica or the real origins of Riemannian geometry and things like that.

3:06:53.1 SC: So I do a little historical digging. Like I actually read Riemann's paper on Riemannian geometry, which essentially nobody has ever read in the modern world where we use Riemannian geometry. If they did, they would realize that most of what we think of as Riemannian geometry was developed by Italian geometers after Riemann, but that's a different story. But it's reading these stories that makes the names stand out, it's not because I have any special facility for names, but by knowing a little bit about the actual history and the stories behind them, that brings the people to life and that helps you remember their names. I don't know if that's good advice overall, but I think that's where I get these names from.

3:07:34.6 SC: Dragon sighted D says, have you seen any candidates on the Democratic ticket that you think would be preferable to Biden in the primary? And if so, why? Either way, I'd appreciate your thoughts on the US Presidential Democratic primary. Happy to give you my thoughts. My thoughts are that Biden is gonna be the nominee unless some disaster happens. Disaster to Joe Biden, not to the world. He's gonna be the nominee. Deal with that.

3:08:02.7 SC: I completely understand an urge to challenge candidates in primaries, we have a weird system in the United States where because of this thing called the presidency, and because of our particular first-past-the-post voting systems, everything about the system encourages there to be two and only two political parties, and that dramatically narrows down the space of possible candidates who can get elected, especially for nationwide office. It's a very, very narrow spectrum, indeed. In a parliamentary system one where you had ranked choice voting or something like that, you might imagine the wider spectrum of possibilities, and by the way, the wider spectrum means not only more people with weird extreme views, but also more people in the center, right? The fact that you have to have two and only two parties means that to get nominated by the parties, you have to be a little bit away from the center rather than right in the middle of it.

3:09:08.0 SC: So anyway, I am entirely on board with complaints about the system, however, given the system that we have, something that you have to do as a grown-up member of a democratic society is choose between the actual candidates. It does not help you or the world or the country to say, well, here are the candidates on the ballot, I don't like any of them, therefore, I'm not gonna vote. That makes the world a worse place, I'm sorry. Again, you don't have to like the system, you don't have to approve of it, but until we change the system, you have to deal with it. And right now with overwhelming probability, absence some health crisis or something else like that, as of December 2023, the Democratic nominee is gonna be Joe Biden and the Republican nominee is gonna be Donald Trump, unless he literally gets thrown in jail or something like that. So work to change the system by all means, but the idea of running someone against Biden the primary is just sort of... It's not serious. It's wish-fulfillment fantasies, and I think that politics is a place to be serious, especially once the elections... Once the nominees are known.

3:10:20.1 SC: Paul Turic says, I'm still thinking about the episode with Katie Elliott, you dismissed the relationship between patterns, laws of nature, counterfactual... Sorry, you discussed, that's important, the relationships between patterns, laws of nature, counterfactuals and causality. Previously, you've said that causality requires more than just that events are related by laws of nature, emerging macroscopic asymmetries must be added, but where in these structures and explanations do counterfactuals come in? Are laws counterfactual and physical properties part of a theory building package deal as former Mindscape guest, Barry Loewer would have it?

3:10:56.0 SC: Yes, that is correct. Laws, counterfactuals and physical properties are part of a theory building package deal. The point is, once again, none of us is Laplace's demon, okay? None of us has exact knowledge of the world. If we did, if we had exact knowledge of the world and the laws of physics, sure, we would know everything that happens in the past, present and future, but we would never need to refer to ideas like causality or even laws of physics. We would just know everything, we would just know what actually happens, okay? Where all of these other things come in is because we have imperfect information because we don't know everything, so if you want to say the... My typical... I don't know why this is my favorite example. My favorite example of causality is, I was late because there was traffic, there was a traffic jam on the road.

3:11:47.9 SC: It's weird, it's partly from my Los Angeles past because I walk to work now that I'm in Baltimore, it's very convenient and traffic jams do not get in my way. But what does it mean to say, I was late because there was a traffic jam as opposed to saying I was late because of the wave function of the universe and the Schrödinger equation? That latter thing would be true, but it's completely uninformative. The former thing, I was late because there was a traffic jam, implicitly refers to counterfactuals. What do you mean when you say, I was late because there was a traffic jam, you mean had there not been a traffic jam, I would not have been late, otherwise your statement isn't really saying anything. You can't say, I was late because two plus two equals four, that's not something where had it been different, there was an obvious consequence. The, had it been different is playing a crucial role there.

3:12:39.2 SC: Again, I don't think that these ideas are fully settled yet, I think that this is why this kind of science and philosophy is still very, very interesting, but there's some very crucial role being played in how we ordinary human beings talk about the world by counterfactuals and the reason why this is very interesting to a physicist is what is a small deviation from the real world and what is a big deviation. Right? This is something the philosophers, I don't think have gotten completely clear about, and maybe some physics has something to offer there. Brandon says, some theologians seem to get bothered by the need to explain God's origin, and they compare that to a naturalist view that the universe does not necessarily need an explanation, I.e., it is eternal. They seem to think that's a double standard. To me, it appears reasonable to stop at the universe as a brute fact since it is within the natural world, whereas something outside the natural world like God, we need a bit of explaining.

3:13:37.8 SC: Are there other aspects to this concept I might be overlooking? Well, I guess I think about it differently than you are implicitly thinking about it here. For one thing, I don't think there's any connection with whether or not the universe needs an explanation and whether or not it's eternal. I can very easily imagine a self-contained, physically consistent story of the universe for which time has a beginning. I just don't see any problem with that whatsoever. That does not imply some extra kind of explanation. I do encourage you to read the paper I wrote about this. Why is there something rather than nothing? I try to be very clear about what my ideas are here, I talk about it also a little bit in The Big Picture, but the paper, why is there something rather than nothing, is a much more clear, complete statement of how I think about this. So I don't think that whether or not the universe had a beginning matters. The question is, what kinds of things demand explanations?

3:13:58.0 SC: I don't think that many things demand explanations, I think that explanations are convenient when they exist, I think that just like causality, just like we were just talking about, they're features of higher level emergent phenomena. The fundamental nature of reality in my mind simply is what it is, you will always reach a bed rock when you're talking about, oh, this is true because of that, that's true because of this other thing, you will reach a bottom and you'll say, this is how the universe is, it's not some other way.

3:15:01.9 SC: And that's true, whether or not God is part of your fundamental ontology, so I don't count the explanatory needs as either pro-theism or pro-naturalism, to be honest. I do think it's fair, you're kind of alluding to the idea that a theistic ontology is more complicated, it has both the natural world and God in it, whereas naturalism just has the natural world, that I think is fair. I think that's perfectly fair to say that naturalism is simpler. And then the question is, is it too simple? I would reject naturalism if it were simple, but it failed to account for things that we actually observed in the world. I don't think that's true, so I'm a naturalist, but that's how I think that the logic would work.

3:15:49.2 SC: Aaron Anathema says, I hear that neutrinos are notoriously difficult to detect because of their low mass, but photons have no mass, and I have two surprisingly effective photon detectors, my eyeballs. How does that work? Easy, I like this question. I like the easy questions, the answer is, the fact that neutrinos are notoriously difficult to detect has absolutely nothing to do with their low mass. Absolutely zero. You could have low mass particles that are very easy to detect, like photons, as you point out, or at ones that are very difficult to detect, like neutrinos or for that matter, gravitons or axions or other things like that. The reason is because the mass of a particle is a completely independent parameter from the coupling strength of a particle.

3:16:37.5 SC: The coupling strength and again, plug, I'm gonna talk about this a lot in my upcoming book, there are interactions between different kinds of particles that we can define in particle physics. So the electromagnetic interaction is what happens at a particle physics level when a charged particle, like an electron or positron or proton for that matter, either absorbs or it emits a photon, the force-carrying particle of electromagnetism. And in particle physics, we associate that with a strength, a certain coupling constant, and the same thing is true for neutrinos or for axions or gravitons or whatever. It's just that the coupling constants for neutrinos and gravitons are much, much smaller than the coupling constants for photons. So the photon coupling constant is already pretty small, it's the fine structure constant, 1/137, but for neutrinos, it's way, way tinier. Nothing to do with the mass. The coupling constant is an independent parameter.

3:17:38.2 SC: Douglas Dicky says, priority question. I have always assumed that complex numbers are used in quantum mechanics because ironically, the mathematics involved is more straightforward. In principle, I assume that it would be possible to develop a valid treatment of quantum mechanics without the square root of minus one, I, in sight. Is that correct? Yes, it's absolutely correct. Indeed, you can go further, there is absolutely nothing that is done with complex numbers that could not be done without complex numbers. They're just convenient. Complex numbers have the property that you can write them as a plus I, b, where a and b are real numbers, and I is the square root of minus one. And you combine that together to make Z, that's the complex number, but then there's a special property that there is a map from complex numbers to themselves, Z goes to the complex conjugate of Z. In the real number way of talking, that's I goes to minus I, so b picks up a minus sign in A plus I, b.

3:18:43.1 SC: So you can just by hand, by brute force, replace all of your Z's with A plus IB's, and then rather than having I, just invent a new rule that you have an ordered pair, A, B with the property that there's a map that sends A, B to a, minus B, and you can multiply them together in certain ways, and secretly you're just doing complex numbers, but you're never mentioning complex numbers. This would be ugly. It would not be much fun, but if you really didn't like the square root of minus one, you could absolutely do it. Ari Maude says, when the universe experiences heat death, am I right that fundamental particles still exist, just infinitely separated, and if so, would particle entablement... I think we meant entanglement there, it's typo. Entanglement still be possible after the universe's heat death?

3:19:34.9 SC: Well, yes and no. I think that this is a case where your intuition is getting the best of you, because the fact that the particles you're talking about, our excitations in quantum fields actually becomes important. As the heat death of the universe, in the universe like we think we're in with a non-zero vacuum energy, the universe asymptotically approaches its vacuum state. I guess that would be true even if vacuum energy were zero, but the status of the vacuum state is a little bit different. In the universe with the cosmological constant, the vacuum state has a non-zero temperature, it's called the Bunch-Davies vacuum, after the two physicists who first solved the equations. And so if you had a thermometer, you would actually detect a non-zero temperature. That means that you would detect a photon occasionally, rarely, but occasionally. The point is, you don't have a photon detector, you don't have the thermometer because it's in the vacuum, there's no you, there's no thermometers, there's no devices. So there's just a quantum mechanical state, and as I said, you asymptote to a quantum mechanical state which is the vacuum state, that means that there aren't any fundamental particles lying around, there is just a quantum mechanical vacuum state.

3:20:52.5 SC: You can ask, but what about particles that have left my observable universe, left the horizon? There, it's a little bit tricky whether or not they still become particles. When the universe reaches heat death, everything smears out, everything becomes closer to thermal equilibrium, and the notion of a particle becomes less and less obviously relevant. Let's put it that way. So I would just advise people, if you're not really into all of the math and getting it exactly right, and you just want a hand wavy way of thinking about this, think of the universe as emptying out and there being no more particles left around. Ron Graber says, in your recent solo podcast on Artificial Intelligence and AGI, you presented an argument that LLMs/GPTs do not model the world. Can you say more about what you've learned about how conscious beings like us do model the world? Put another way, if LLMs aren't on the path to AGI, in part because they don't model the world, what does our understanding of human general intelligence suggests that path will look like?

3:22:01.7 SC: Well, I guess the best thing I can do is point you to the podcast I did with Gary Marcus, maybe also, we talked about this with Melanie Mitchell or Stuart Russell. I don't remember exactly the details, but the idea is that you can imagine symbolic representations of the world. So in other words, you have the world here I'm looking around the room I'm sitting in right now, I say, oh look, there's something called a table, there's something called a coffee cup, there's something called a computer, a microphone, et cetera, and all of these have different relationships to each other. Coffee cups are often found sitting on tables, tables are solid and have certain sizes, all of these facts, right?

3:22:43.5 SC: And a model is just sort of this set of facts and the relationships between them, whereas something that an LLM does are not models of the world like that, but rather sentences. Now, it's interesting because it's completely conceivable that if you have a model of the world and then you said out loud every sentence you could think about that model, coffee cups are often found on tables, things like that, the information would be equivalent, maybe enough sentences essentially determine a model of the world, that is something you could conjecture. How would you test that conjecture, and what I try to argue in the podcast was one way of testing whether current generations of LLMs in fact, implicitly spontaneously generate a model of the world is not just to say, oh, the LLM sometimes make mistakes.

3:23:41.2 SC: 'Cause that's obviously true. They absolutely make mistakes. You have to ask what kinds of mistakes they make, do they make the kinds of mistakes that they naturally would if all they were doing was calculating probabilities of sentences and words or tokens or whatever you wanna call them, versus having a symbolic representation of the world? And with the examples that I gave, I try to argue that at least in that informal set of evidence, yes, the LLM seemed to be making exactly the kinds of mistakes that they would make if they were just trying to say what words would most naturally follow previous words rather than referring back to some symbolic representation of the world. I don't know a lot about how actually human general intelligence works. So that's a very good question. I'm not an expert in these things, I'm looking forward to how we learn more about them.

3:24:36.5 SC: My main goal in the podcast was to emphasize that LLMs aren't built to be general intelligence, and therefore, although it's remarkable how intelligent they can sound, we should still be suspicious whether or not they're actually generally intelligent and when you press them in exactly the areas that you imagine they would fail, they often fail. So I think that it makes perfect sense, that story. That's not to say that we can't eventually make general intelligence, Gary Marcus says we gotta work with symbolic approaches to AI along with connectionist language model kinds of models. Maybe that is the way forward. I honestly don't know. Nita says, on Episode 51 with Anthony Aguirre, you said that you don't put high credence in inflationary cosmology, only 50%. Why is that? And what's the creative alternative that would allow for distant regions in the CMB to have the same temperature at three degrees Kelvin?

3:25:37.9 SC: Well, I think 50% is an enormously big credence, honestly. The point in my mind is the place in cosmic history where inflation reportedly happens is way, way, way beyond anything of which we have direct experience. The energy scales, the timescales, just the part of the universe that we're talking about is entirely speculative. You're invoking new physical fields, new initial conditions, new phenomena, et cetera, et cetera, et cetera. And it kind of works, right? You kind of get the answers that you wanna get, it works remarkably well to the extent that I'm happy to put a 50% credence on it. But the other 50% is not some other creative alternative, the other 50% in my mind is something we haven't thought of yet. We're talking about the origin of the universe here. Why in the world would we think that we have a 99% credence of having the actual correct answer already in hand? I think that any good Bayesian would always put some credence on something we haven't thought of yet.

3:26:45.7 SC: When it comes to the first tenth of the mind is 30th of a second in the history of the universe, I think that credence should be pretty big. Michael Lesniak says... I'm gonna answer two more questions and they're both a little more frivolous because the holidays are coming. So Michael Lesniak says, being that Thanksgiving is my favorite holiday, I have to ask, do you enjoy the traditional Thanksgiving meal? And if so, what is your favorite part? Short answer is no, I do not enjoy the traditional Thanksgiving meal, I've just never been a fan of turkey. I like a good turkey sandwich with some lettuce and mayo and things like that, but the big roasted turkey, I've just never been a fan of. It's too easy to make it badly, I understand some people can make it well, but it's too easy to make it badly. It's usually kinda dry and flavorless, to be honest.

3:27:35.7 SC: I do like stuffing and I like gravy, not a big mashed potatoes guy. So overall, I can imagine a halfway decent Thanksgiving meal, but I certainly don't look forward to it in any particular way. It's telling that we don't make roasted turkey on many other days of the year. In fact, when we lived in Los Angeles, Jennifer and I had a tradition of going to Las Vegas over Thanksgiving and having Peking duck on Thanksgiving Day at Jasmine in The Bellagio. So we were eating poultry at least but a much, much tastier poultry than everyone else was having for their Thanksgiving turkey. Now that we're on the East Coast, this year we just gave up. We've been too exhausted with moving in and doing my job and things like that, so I didn't leave the house during the entire day of Thanksgiving week. The nice thing that Hopkins does is you get the whole week off.

3:28:24.4 SC: So, what I did was on the weekend before I went shopping and I bought a whole huge amount of food, and I spent the whole week cooking different things. So we had paella and we had pasta carbonara and a whole bunch of different things that I really enjoyed cooking. So that was much more fun to me than the traditional Thanksgiving meal. And then the final question is from Norman Rameon, who says, given the end of the year holidays are upon us, I have a cocktail question for you. What is your preferred ratio of gin or vodka to vermouth for a classic gin or vodka martini? Shaken or stirred? Favorite garnish? I've written and talked about this quite a bit, in fact, I had a holiday message podcast a few years ago that talked about cocktails, but I tried to be a little bit expensive about that, so it was less about the actual mechanics of cocktails.

3:29:15.4 SC: I have different opinions that are of different levels of firmness, and the overall opinion is whatever you like, right? I'm absolutely not a prescriptivist when it comes to cocktails, so when I give you my opinions, please interpret them as my feelings, not as objective truths. With that in mind, there's no such thing as a vodka martini, that's just an abomination. The whole point of a martini in particular, or of cocktails in general, is to enjoy a combination and an interplay and an interaction between different kinds of flavors. So there are two problems with how many people make martinis, one is, if one of those ingredients is vodka, vodka doesn't have much taste at all, if you sip vodka or you take little shots of vodka, small amounts pure vodka and you do a taste test with different kinds of vodka, then you absolutely can taste the difference between them, there's different mouth feel, different little tiny spices that leak into it, but they're very, very subtle, and you really have to be pure about it. Vodka is not supposed to be strongly flavored.

3:30:32.4 SC: So if you put it into a martini, you're putting vermouth in there, which is somewhat strongly flavored and you're not gonna get any interplay between vodka and vermouth, especially if you don't put much vermouth in there. Then you don't have a martini, you have a vodka transferral system, and it's basically good for getting drunk. So go nuts. Have your vodka, put in orange juice, get drunk, whatever you want. My preference is to have a subtle, interesting martini, which is a cocktail which relies on an interplay of flavors. So first one of those should be gin, because gin has flavors indeed. For those of you who don't know, roughly speaking, gin is flavored vodka. You can buy gin making kits, I have one. It's tremendous fun. So you get a bunch of botanicals. By flavoring, I don't mean like put food coloring in there, or high fruit, those corn syrup or something.

3:31:33.4 SC: You get botanicals, you get herbs, primarily juniper, if it's a traditional gin, but you get different kinds of botanicals and you can seep them, infuse them into vodka to make gin. And if you have your gin making kit, the good news is you can make your favorite kind of gin, and it's actually very good. It can be very tasty. The bad news is professional distilleries will, after they do that infusing, remove all the color, because generally, those botanicals are going to impart a slight color to your gin. So pure gin is actually slightly yellow and it's not actually very attractive looking, but it still tastes really good. And I'm not even much of a traditionalist about gin, you can get very, very good... My favorite traditional gin is St. George's Terroir gin, which I think is very good, mostly juniper, et cetera, but there are also Japanese gins. The Japanese are more playful about it, they have tea flavors and yuzu in there and everything, and it can be very, very good.

3:32:36.7 SC: And then a cocktail, again, is based on the interplay, and therefore you're gonna want some vermouth in there, there's this weird macho thing where people try to brag about how little vermouth they put in their cocktail, in their martini, which again, then you're just drinking gin or vodka, which is fine, but just do that.

3:32:57.1 SC: So I would like at least, let's say 20% of my... So that's a four to one ratio of gin to vermouth, and I'd be perfectly happy with a 3 to 1 ratio as well. Shaken or stirred literally makes no difference, it absolutely does not change the taste. There are aesthetic things. I guess there's one way that it changes the taste, which is that if you shake and stir for the same amount of time, shaking is probably more effective at cooling down the martini, and if one thing must be true about a martini is that it must be cold. The low temperature is crucial for a martini. I kind of got in trouble at a friend's house a little while ago, where they knew that I liked martinis and they were very excited about serving martinis, and they gave me a martini at room temperature, and I was not able to hide my disappointment, which was not very polite as a guest, I have to say. Sorry, I just couldn't help myself. Felt bad about that.

3:34:01.1 SC: Cold, cold, cold, cold is what you want a martini to be. And so, shaking works for that, but you can also... It can cloud up the martini a little bit. Again, it doesn't change the taste at all, but if you want that absolutely crystal clarity in your martini, stirring is better. PS, don't take advice on anything from James Bond, people forget that when Ian Fleming first wrote James Bond, he was not supposed to be the role model of sophistication, he was kind of not sophisticated. That's why he wears wrist watches that are sort of divers watches like Omegas and Rolexes, that's not what you're supposed to wear with your tuxedo. And these shaken martinis are not right either. So I actually stir my martinis most often, but I again, don't object if you want to shake them.

3:34:53.1 SC: As far as garnishes are concerned, this is crucially important, and where I am absolutely a pluralist, I will have olives, I will have onions, I will have... I think if it's an onion, then it's a gimlet or something like that, or a different name, but to me, it's still a martini. I will do a twist, and when I do have the olive sometimes they're with pimento, sometimes they're with garlic, sometimes even a jalapeno, it all depends on my mood. I think you should do them all, I think you should enjoy whatever you like. And in fact, that is holiday advice of more general applicability. Don't hurt other people, be nice to them, talk to them and listen to them. And within those constraints, enjoy yourself, have a good time, be who you are. Oh, I forgot to say at the beginning, we take the holidays off, so there is no January AMA and there is no Christmas Day Mindscape podcast. So if you only listen to the AMAs, you'll hear me again at the beginning of February, otherwise, I'll talk to you next week. Have a good holiday time period, however you might construe that in terms of celebration. Bye-bye.

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