AMA | November 2024

0:00:00.0 Sean Carroll: Hello, everyone. Welcome to the November 2024 Ask Me Anything edition of the Mindscape podcast. I'm your host, Sean Carroll, and I'm recording this a few days before, but it is scheduled to be released the day before the US Presidential election on November 5, 2024. So I got to say something about that. It's scheduled to be a historic event, no matter what the outcome is. And that's, you should be careful about proclaiming things like that. It's too easy to say that every single election is a historic event. In some sense, they are. You can look up the history books. Every election is recorded. Some of them are more momentous in their implications than others. And I think that this one, it's fair to say, has every expectation of being one of those momentous ones. We've already had historically unusual aspects of the election season.

0:00:54.3 SC: As many of Joe Biden, who is the president right now as I speak, ran for reelection and then dropped out sort of not quite at the last minute but later than one would expect, later than it had ever happened before. And it was a big controversy over whether he should do that or not. He's clearly getting old. We're all getting older. He is, I think, the oldest president ever or maybe he would have been if he had stayed around a few more years. I'm not sure. But he's getting up there and it was pretty clear that it was taking a toll on him. In terms of policy outcomes, I think it's very easy to argue that he's been doing a pretty darn good job. I would say excellent in some areas, terrible in other areas. But overall, by the standards of American presidents, he's been doing quite well. But there's more to life than the policy outcomes. We want a president who is capable of handling unexpected things and someone who is more completely in control of their faculties at all times is a good idea.

0:01:58.4 SC: So I was in favor of Biden dropping out. But I was super duper worried at the time that that would lead to chaos in terms of trying to find a replacement. I was completely wrong as Kamala Harris and her team worked with Biden to absolutely, with stunning speed, wrap up the endorsements of everybody important and basically secure the nomination. And that's been going great since then. Her campaign has been functioning at a super duper high level for something that is relatively quick to get off the ground. But of course, there is an opponent, Donald Trump. He is always the opponent, it seems. This is the third presidential election in a row where Donald Trump will be the Republican nominee. And so someone pointed out, just so you know how US Presidential elections work, anyone can be president. But in fact, the same kind of people tend to run over and over again. This is the first election since, I think I mentioned this on Blue Sky, since 1976 that does not involve as a either presidential or vice presidential nominee, either a Bush, a Biden or a Clinton, one way or another. So since 1976, it's Kamala Harris and Tim Walz versus Donald Trump and JD Vance.

0:03:23.4 SC: And we all know the worry about this. There's many, many worries about Donald Trump as a president or presidential candidate. But there's one big worry, which is the fate of democracy in the United States. It's almost a cliche. People are tired of talking about it. But you have to talk about it because democracy is not forever. And this is not some vague threat. Four years ago, Donald Trump was president. He lost an election and he tried very hard and very explicitly, not super competently, thank goodness. But he tried as hard as he knew how to hold on to power despite having lost the election up to and including egging on a mob that attacked the US Capitol. Not to mention filing fake lawsuits, pressuring local officials, inventing slates of fake electors to be members of the Electoral College if he was able to convince people to go along with him. Many, many ways he was very, very explicitly trying to overturn the results of a fair election.

0:04:34.5 SC: This should be, in any well-functioning system, entirely disqualifying for someone to run again. There are plenty of other reasons to not love Donald Trump. He's a terrible human being. He's deeply racist. He's a serial sexual assaulter. He is as corrupt as any previous chief executive we've ever had. He was an awful steward of the country in many ways. But all that is now beside the point compared to the fact that he is a would-be autocrat and in the second time around, if he were voted to be president again, he would probably be much more effective at trying to be an autocrat than he was before. If you think that democracy is a good system, then none of the other issues really matter. Maybe for some weird reason you think that Donald Trump's proposal to eliminate all income taxes and replace them with 500% tariffs on foreign goods is not the obvious economic catastrophe that it really would be. Maybe you think that. But still, it doesn't matter. He is not someone who is someone who's going to protect American democracy. He's going to work very hard to undermine American democracy. That's not hypothetical.

0:05:48.4 SC: He has done it, and he's promised to do it again very, very explicitly. And what's bad is that he's coming so close to succeeding. That's hard to take. And just so it's clear what is obvious to me and what is surprising to me, it's not so surprising that low-information voters can be manipulated. That's been true since democracy was invented. There's always been low-information voters. And I think I'm not even against that. I wish more voters were high-information and well-informed and understood their civic duties, et cetera, et cetera. But I'm kind of not the kind of person who thinks that we should force people who are uninterested in politics to be interested in it. I think that my sort of moral backing for democracy is that the people who have interests and want to have them heard by voting should have that opportunity. But what is a little bit new is that the media landscape allows low-information voters to be manipulated more effectively than ever. In some sense, low-information voters are more low-information than they ever have been. You can hear interviews with voters who only get their news from certain sources.

0:07:03.2 SC: You ask them factual questions about the world, and you get these hilariously wrong answers. But it's kind of not surprising. It's a matter of degree rather than of kind. It's something that has always happened. What's more remarkable to me, and probably this has always happened back in the days of democracy throughout history, but I'm not personally, I have not been as aware of it, is the extent to which the elites go along with these manifestly anti-democratic movements. Of course, that has to happen to some extent. I'm just amazed at how here in the United States how large the extent has been. And by elites we mean the officials of the Republican Party, one of the purportedly major parties here in the United States, business leaders throughout the country, and most interestingly, leaders in Silicon Valley in California who are leaders of the tech industry, which is so important to our country and the world and how human beings live these days. An amazing percentage of these people are entirely supportive of Donald Trump despite the fact that he is super obviously an anti-democratic menace.

0:08:12.4 SC: And when you look for explanations for that, why did the Republican Party completely fold like a cheap suit, why are Silicon Valley leaders supporting this guy who is not exactly the sharpest knife in the drawer, etcetera. I do like to look for explanations that don't cast my adversaries or the people I disagree with as cartoonish super-villains. Usually they think that they're decent people with good reasons for what they do. And even though they might also have bad reasons that they don't admit, it's interesting to ask what the reasons are. Obviously, greed and power are important. Business leaders tend to support people who will promise to cut their taxes. The business leaders are not always rational about this. Someone promises to cut your taxes, that sounds good, you get more money. But if those people also crash the economy, your longer-term outlook does not look as good. That's okay. That's completely consistent with getting support from those people because often those people are super-duper short-term in their thinking.

0:09:18.3 SC: The Republican officials did initially in the rise of Donald Trump resist him a little bit. Then they realized that a lot of people who were voters actually liked him and they completely became hypocrites. There's all sorts of quotes, including from his own vice presidential candidate about how terrible Donald Trump is until they realized they could get a little bit more power by going along with him. But I think also there is just a lack of true belief in the ideals of democracy among some of these sectors. And it can be traced more or less to a feeling of superiority. To some kind of Ubermensch syndrome there's just a bunch of people out there who think that honestly if they were in charge, the world would be a better place. They are just smarter than everybody else. And the fact that that means that other people don't get a voice in how things are run is entirely okay with them. People honestly think that they should be the ones who have the power. And they see the undermining of democracy as perfectly consistent with that perspective, as long as they are the ones who benefit from it.

0:10:32.4 SC: As you can tell, I'm not in favor of this. I think that a huge necessary ingredient to a successful democracy is people acknowledging that they individually should not rule the world. And indeed, no individuals or small cabal of individuals should rule the world or the country or whatever. That it is actually better to let people vote for what happens than even to have like super smart, super wise people be in charge. Very few people really buy that. Most people think I would rather have the right super smart, super wise people in charge than to let the masses determine what's going to happen. And of course, everyone thinks that they're the super smart and super wise people. So you see the instability. You see the easy way that democracy can undermine itself. And that is what we're seeing in action. I don't know what's going to happen tomorrow, as it were, on Election Day. Trump may lose. He may win.

0:11:33.0 SC: If he does lose, he will clearly, obviously not accept the result that's already been announced. We already saw it four years ago. We're going to see it again. They have basically advertised to the playbook for how they're going to deny whatever the election outcome is if it doesn't go their way. And despite the fact that they've advertised it, despite the fact that we saw it happen four years ago, it's still going to be supported by a bunch of people. The combination of ill-informed masses of voters plus arrogant elites is a long-term problem for democracy, even if Trump loses. And by the way, he might be the Republican nominee again four years from now if he loses. Or he might not be. But I don't think that Trump as an individual has any magic powers. We have absolutely illustrated, shown a light on a true flaw in American democracy, a true incapacity to deal with certain kinds of challenges. And that's a long-term problem.

0:12:40.4 SC: It's not going to go away, one or the other. Historically, this is no surprise. Historically democracies don't last forever. There's no guaranteed stability. It is absolute. There's plenty of weak points. There's plenty of failure modes for a democracy. And we live in one that's been going on for over two centuries, longer than the lifetime of any individual people. So plenty of people here in the US just think it is essentially impossible for a democracy to collapse 'cause it's been going on as long as they've been alive. That's not how things work, historically. I think you could at least make an argument that we should expect the United States' democracy not to last for the next 100 years, one way or another. I don't want to say that. I wish I could be more optimistic. This is not where I want to go. But I also feel that if we're going to try to push against this, it's important to have our eyes open and to think about how to do better. The optimistic spin is that there are plenty of people out there fighting.

0:13:43.5 SC: I don't know whether most people fighting against Donald Trump are fighting against Republicans and Trump versus fighting for democracy. Something I like to say sometimes just to drive it home to my Republican friends is, Donald Trump was a lifelong Democrat. He grew up in New York, where the Democratic Party was ascendant. He was never a Republican. As a business person, a developer in New York City, he was obviously a Democrat. And he even in his own ghostwritten books fantasized about running for president as a Democrat. And what I like to say is, if Donald Trump had somehow won the nomination for the Democratic Party for the presidential campaign, and he was running against a truly awful Republican nominee like, I don't know, Ted Cruz, someone who is just truly a loathsome Republican, not only would I vote for Ted Cruz over Donald Trump, I would give money to his campaign.

0:14:41.2 SC: I would volunteer to support him, not because I agree with any of his policies whatsoever, but because it is more important to have a functioning democracy than to temporarily have your policies implemented. And what is very, very sad is how few Republicans are willing to make that principled choice. But some of them are, and some people on the Democratic side feel the same way, that they would be willing to go along with policies they don't like to support the overall system of democratic governance, which is much more important for the next few centuries to guarantee that roughly the kinds of policies that we like will be implemented. So it's good to see the people out there fighting. I hope that they keep fighting. I don't know what's going to happen on Election Day. I don't know what's going to happen over the next few months after that. I don't know what's going to happen over the next few centuries. We are truly at a decision point, I think, historically.

0:15:40.5 SC: So all we can do is keep fighting and keep trying. After that, I got to say things like this is the Ask Me Anything episode of Mindscape, and it is supported by our Patreon supporters. I got to do the capitalist job here, I guess. You can be a Patreon supporter. Go to patreon.com/seanmcarroll and pitch in a few bucks for Mindscape. And then you get to ask the questions that we are answering here in the AMAs, as well as just generally feeling good about supporting Mindscape and getting ad-free versions of the podcast. As always, super duper gratitude to everyone out there who listens to Mindscape and who supports it. Never thought this would happen. What are we, five years in, six years in? The support has been wonderful. So another thing that makes me a little bit optimistic about the future. And with that, let's go.

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0:16:49.3 SC: Anonymous asks a priority question. Remember that Patreon supporters who are asking these AMA questions get once in their life to ask a priority question. I'll do my best to try to answer it. This one is the following.

0:17:01.4 SC: The LIGO experiment should have detected the dark matter particle flow nearby much easier than some gravitational event far out there in the cosmos. Discuss. Not really a question, more sort of imperatively phrased request. But I will be happy to discuss it. And the discussion is no. It should not have. And in fact, I'm going to argue that anyone should be able to think their way through this. Maybe not to the correct answer, but to the understanding of why the answer must be correct. Of course, all sorts of things in the universe create gravitational waves. This is a feature of general relativity that says that every source of matter and energy and momentum acts as a source of gravity. Now, there are details. A static source of matter does not create any gravitational waves, just like an electric charge sitting still does not create any electromagnetic waves, just creates a static field around it. But as long as the field, the matter sources are changing or energy sources, then you can in principle have gravitational waves. You have to change in a specific way. Gravitational waves are not created if something expands or contracts in a perfectly spherically symmetric way. That has to do with the geometry of the tensor field that makes gravitational waves.

0:18:20.3 SC: But it is what we call quadrupole motion that makes gravitational waves, stretching in one direction, squeezing in another direction. That's a very characteristic feature of gravitational dynamics. But when it comes to how noticeable a gravitational wave source is, guess what? Two things count. How luminous it is and how far away it is. Both of those things count. No one is arguing that it should be easier to see from here in Maryland a lighthouse in California than the sun, even though the sun is much, much further away, because the sun is also much, much brighter. That's not that difficult to wrap our brains around. These signals that are being seen by LIGO when two black holes coalesce are enormously big in gravitational luminosity.

0:19:14.2 SC: I mean, we're talking about black holes that are typically something like 10 times the mass of the sun and they are coalescing with each other. The amount of energy given out per second, and that last little bit of coalescence of the black holes is, I believe this is right, you would have to check me on the internet, but it's more than all of the photons being given out by all of the stars in the sky, including other galaxies, okay? It's an enormous amount of energy for a brief period of time, but you only need it for a brief period of time. Contrast that with dark matter flows nearby. They are much closer, that is absolutely true, but they are enormously, enormously weaker for all sorts of reasons. One reason is just that the rate of change is much, much slower. Gravitational waves from dark matter moving in the galaxy, well, how long does it take for the dark matter to change its configuration in any obvious way? I don't know, probably hundreds of thousands, millions of years is a typical time scale. Whereas what LIGO is sensitive to is things that are happening at fractions of a second, which is what happens when you have two black holes coalescing.

0:20:26.4 SC: But more importantly, the gravitational field is just pretty darn weak because the dark matter is spread out over a really large distance. The thing about black holes is that they maximize how much energy and therefore how much curvature of space-time there is in a very, very small region of space that makes the intensity of the gravitational waves being created much, much greater. So for many reasons, I'm telling you the big ones, but you can be more detailed and be more quantitative about it. For many reasons, if you compare the gravitational wave signal of wispy dark matter flows in our galaxy to those of colliding black holes in galaxies far away, the black holes win out by a lot. Aidan McLaughlin asks another priority question. He says, I'm an AI researcher in San Francisco. The consensus among us lab staff is that we'll have AI vastly smarter than humanity by 2029. Internally, we already see the start of a Manhattan Project-like nationalization. The research continues to move faster than we expected. The next US president may control God. Nobody outside the AI labs in the Pentagon takes this seriously. What are your thoughts? Well, as someone outside the AI labs in the Pentagon, I do not take this seriously.

0:21:42.5 SC: I take AI very seriously, and I take the dangers of AI quite seriously. But talk of God or smarter than human intelligence I think is just way off base. Even when it's done by people who are incredibly tech savvy, who really, really understand the technology behind AI and how fast it's accelerating. Because to me, it indicates a very, very poor understanding of human intelligence and/or of God. Now, understanding God is a tricky thing. As we know, different people define God differently. But we have put enormous effort in modern AI research into making things that sound intelligent, that sound human. But the underlying mechanisms, as we have talked about here on the podcast many times, for example, with Francois Chollet most recently, but with other people as well. I mean, I could do it much more often, but I figure I've done it enough. The message has come through, I hope, that the kind of reasoning is very, very different.

0:22:44.6 SC: And it's not about what IQ tests you can pass. I have no doubt that advances in AI will be able by 2029 to do better than human beings on standardized test kind of things. Maybe, maybe not, but I would be completely unsurprised if that was true. It's just that it doesn't map onto what it means to be a human being. As we've said on the podcast many times, human beings are embedded creatures with bodies, with biologies, with heritages passed down from billions of years of evolution, with desires, with goals, with feelings, as Antonio Damasio put it many years ago here on the podcast. Motivations, things we want to do, things we need to do. We get hungry, we get tired, etcetera. The embodiment of intelligence, as we've talked about with people like Andy Clark, is crucially important to what a human being is. And again, there's no barrier in principle to making something like that with artificial intelligence, but there's been no progress in doing that, no real progress in doing that.

0:23:56.4 SC: It's more than just putting it in a robot. Robots don't have motivations or feelings either. It's a whole different kind of thing that I personally haven't seen much or any progress on. Once again, I'm going to emphasize over and over again, it's a slightly subtle point, and I know people hate slightly subtle points. They would much like everything to be a simple motto. There's no barrier, no obstacle in principle to doing anything artificially in terms of intelligence or capacity or ability or feelings or motivations or emotions that we can do biologically and organically. But that's different than saying we're almost about to do it. Likewise, the whole business about God is just completely crazy pants talk in my personal opinion. It is just a wild extrapolation from an analogy. Human beings are smart and we have desires, and therefore if we... And we test that smartness by giving people standardized tests or whatever. So if AI gets good at standardized tests, it will be able to outwit us. We won't be able to just stop it from doing whatever it wants because it will engage us in dialogue, and it's so smart that we can never win in the discussion. But that's like wildly inappropriate metaphorical talk right there. That's just not applicable to what is happening.

0:25:19.3 SC: And I don't like that kind of talk because it obscures the actual real very, very true problems that we face with AI. There was just an article last week about how we're, certain places are turning over medical transcription tasks to AI. So you talk to a patient or you talk to a doctor, ordinarily you would write down what is being said. This seems like something that an AI could do pretty well, but guess what? They are constantly hallucinating. So it's not just a matter of they don't hear the word and leave a blank like you would when we transcribe this podcast here at Mindscape. It's that they make stuff up. And of course that's a fixable problem. I have no doubt that that's a fixable problem. My point is that the urge to be slightly more convenient and save just a little bit of time or money by turning over mission-critical tasks to technology that we do not understand, that's the danger of AI. The danger of AI is we're going to ask it to do things and therefore lose control over what is being done. It's not that we're creating God, it's that we're creating stupid small children and handing them dangerous weapons. That's the danger that I would worry about very, very much.

0:26:36.2 SC: James Swift says in the excellent discussion with Doyne Farmer, he says the classical economic models don't make business cycles unless they're getting kicked. But then later about his Asian models, he says we initialized the model in the steady state it was in before the pandemic started and then we hit it with the shocks. To me these sounded like the same thing. What am I missing? Well, I think you have to very carefully parse what Doan said. He said the classical economic models don't make business cycles unless they're getting kicked and therefore maybe his agent-based models can make business cycles without getting kicked. That doesn't mean that you shouldn't also kick them sometimes. No agent-based model of the economy will predict correctly when a pandemic is going to happen. That's just not there in the model. So when a pandemic happens, of course it's perfectly sensible to take your economic model, whatever it is, agent-based, complexity theory-based, standard equilibrium-based and kick it. So the question is not whether you should kick your model with an external shock to correctly model the effects of a pandemic. The question is can you capture some of the intrinsic variability in the real economy using some kind of model? And I'm certainly not an expert here.

0:27:50.5 SC: A real economist I'm sure could say this better. But the worry is that by concentrating so much on equilibrium conditions, classical economics turns off the fluctuations, turns off the very real variability. And so they have to sort of artificially tweak them to mimic that variability. And then there's an empirical question. Are the artificial tweaks good enough or do we need a deeper, better model? That's what Doan is proposing. Nick Gall says, my question regards what you mean by counterfeit downward causation, given your embrace of Dennett's concept of real patterns. In your recent paper, What Emergence Can Possibly Mean, you introduce an equation as a formalization of what you call type-2 nonlocal emergence. In your discussion of this type of emergence, you say the possibility of novel macroscopic interactions such as in this equation in type 2 emergence can lead to a kind of counterfeit downward causation. Why is this label counterfeit? So I'm actually, I got a few questions about this recent paper.

0:28:54.2 SC: I wrote a paper with Achyuth Parola, a student here at Johns Hopkins, called What Emergence Can Possibly Mean. This is the paper that I originally advertised, or I think, I'm pretty sure I mentioned it several months ago, under the... But it might have been in a different forum, so it might not have been here on the podcast. The original title was Emergence Without Judgments. So our goal was to sort of characterize what is meant by emergence without using words like novelty or surprise or truly new, words that we thought were a little bit vague in their specification. And we did that. We tried to do that anyway, that was the goal, but we also, I think even more importantly, tried to clarify the relationship between locality and collections of things at the very small scales, and non-local, more global interactions at large scales. Because it's these kinds of distinctions that can give rise, in certain cases, to things that you might think of as strong emergence, downward causation, stuff like that. I'm not answering most of these questions because I'm trying to plan a solo episode where I talk about it in some detail, so I don't want to be too redundant there.

0:30:04.3 SC: But I thought I would put this one question in there just to sort of signpost that, and I think I can... I would worry that in the solo episode I forget to answer this particular issue, so I'm going to try to answer it here. It depends, of course, on what you mean by downward causation. I am someone who believes that most discussions of downward causation are pretty loose and ill-defined, and that's very frustrating. The idea of downward causation is roughly speaking, that you have a microscopic level, a fundamental physics kind of level, or maybe not completely fundamental physics, but a lower level of description one way or the other. And then you also have a higher macroscopic emergent level. And downward causation says that features of the higher macroscopic level have some causal influence on what happens at the microscopic level. And we have a specific kind of emergence. I don't know how many kinds of emergence we talked about overall because there's subdivisions and things like that, but in one of our kinds we said that this might look like downward causation in the example we're talking about, but it's not really.

0:31:09.4 SC: Why is it not really? Because you don't need the higher level to discuss what is going on. If you go onto the Internet and Google examples of downward causation, either they're very, very vague, having to do with consciousness or something like that, or they try to be more down-to-earth and physical, but they completely fail to be examples of downward causation. So a snowflake forms, and snowflakes have six sides inevitably, or basically inevitably, and people say, like, you can't explain the appearance of this water molecule at this place in the snowflake without knowing this macroscopic fact that snowflakes have this six-sided symmetry. I think that's just entirely bogus, to be honest. Of course I can explain that. There's nothing in the motion of the water molecules that violates the microscopic laws of physics. If I just put the laws of molecular dynamics in there, I can explain perfectly well what every single water molecule is doing.

0:32:09.2 SC: It might not be the most convenient explanation for you and me. That's always true, but that has nothing special to do with strong emergence or downward causation or anything like that. So in the case of what we called type 2 emergence, non-local emergence, in the higher-level theory, there are entities or characteristics or properties or whatever you want to call them that depend non-locally on the lower-level stuff. And so that's something you can consider. We're not saying in our paper which kinds of emergence actually happen, we're just saying here's all the plausible ways we could imagine it happening. But in this case, it's still completely autonomous what happens at the lower level. If you didn't know about the higher level and you just took the lower-level theory, put it on a computer and ran it, you would get the right answer. So there can't truly be downward causation from the higher level because you don't need to know about it to get all the right answers. That's why we called it counterfeit downward causation. Casey Mahone says, could you please help me understand the quantum Zeno effect? I can try.

0:33:17.4 SC: This is something where it's much easier if you can draw pictures, the quantum Zeno effect, but it is so cool that I think it's worth trying. So the quantum Zeno effect is basically the following. Imagine you have a spin, for example, something that could be either spin up or spin down. And you have the following idea. I'm going to take this spin, I'm going to start it spin down, and I'm going to rotate it until it's spin up. So I'm going to rotate it by 180 degrees. And let's talk about degrees rather than radians, it's just more understandable for a wider variety of people. So I'm going to rotate it, but I'm not going to rotate it all at once. If I rotate a spin that is down into up, it would indeed become up after I did that. But instead I'm going to rotate it in N steps, capital N steps. Okay? And every step I'm going to rotate it by an amount, 180 degrees divided by N. Okay? So if I have a very large N, what I'm doing is rotating the spin many, many times. Click, click, click, click, click.

0:34:14.3 SC: But after N times, even though each individual rotation is very tiny, N is very large. The fact that N is large makes both the individual rotations tiny and the total number of rotations large, therefore I rotate it all the way, the whole 180 degrees. Okay? All that just makes perfect sense, everyone understands it. Now in quantum mechanics, we have a new thing we can do, which is we can measure the spin. So imagine that the spin starts down, we rotate it by 180 degrees divided by N. Let's call that epsilon, okay? I know that it's hard to envision these things. That's why it's easier if there's a picture, but epsilon is a tiny number. It's 180 degrees divided by N, and N is a very big number. So epsilon is a small angle by which we're rotating it. And epsilon times N equals 180 degrees. That's the idea. So if I measure the spin after one rotation, and then I rotate again, measure again, rotate again, measure again, that's my new procedure.

0:35:15.2 SC: The first time I just said, what if I just keep on rotating? Now I'm saying, I rotate, then I measure, then I rotate, then I measure. And the thing that I'm measuring is the spin along the z-axis, the spin along the axis that it started, spin down, and it's supposed to end up spin up. What happens is, after that first measurement, where I have rotated it away from perfectly down by an amount epsilon, some tiny little amount, the probability that I measure spin up is the wave function squared, which in this case will look like epsilon squared. And the probability that it's still spin down goes like one minus epsilon squared. And epsilon is a really tiny number. So the fact that it's squared, the probability, means that I take a small number and I square it, and I get an even smaller number. So the point is that if I do this, if I rotate a tiny amount, measure, tiny amount, measure, then I will have only a probability that it rotates is epsilon squared each time. The total number of rotations is epsilon. So at the end of the day, the total amount of rotating it has done is epsilon, is a tiny number.

0:36:33.2 SC: Even though I rotated the same amount of times that I would have rotated it to make it all the way flip around, if I hadn't done those measurements. In other words, this is the Zeno effect, because Zeno of Elea, the Greek philosopher who caused all this trouble by inventing these paradoxes about infinitely tiny motions. Basically, it's the watched pot never boiling. If I just keep measuring this slowly moving thing, my measurements can have the effect of preventing it from moving at all. That is the quantum Zeno effect, and it's been measured. You can do it in the laboratory. It's quantum mechanics. It all actually works. Robert Hoke says, should we adapt the rate of consumption of audio content based on comprehension like we do written content? The context is, when listening to your podcast, I often don't fully comprehend every topic that's discussed, either because I'm distracted or I just can't quite grasp the concept.

0:37:29.3 SC: In contrast, when I'm reading a book or article and I don't understand something, I spend time making sense of it, either by rereading the passage or looking up some of the info to connect the dots. I've noticed that I'm letting an increasing percentage of the podcast go by unabsorbed. The optimist in me says that just hearing the terminology as background noise while I'm distracted is equipping a future me to fully understand the topic the next time it comes up. The pessimist in me says I'm training myself to tolerate fragmented attention and lack of understanding, and it's an overall net negative. I would love to hear your thoughts on this, both as a podcaster and a consumer of information. Well, I think that this is a job for an expert. I think that you probably need some real psychology with some real empirical data behind them to answer it reliably, but my feeling is you absolutely can get something from listening to audio content without 100% comprehension. Just because, for example, as an example from how I live my life, sometimes one goes to seminars in areas one is not an expert in, and one does not understand everything that is said. But you do get something, even if you don't understand everything that is happening. For instance, you get an idea that certain phrases or certain questions, certain issues just keep popping up over and over again. And so if you heard them once, you're like, well, it's not what I'm really interested in.

0:38:57.3 SC: But if you hear them again and again, then suddenly you're like, oh, I guess this is kind of a big deal. I should try to comprehend this. I should try to wrap my brain around this one. But also, I think that you do understand something when you're listening, and that can help along the way. Now, having said all that, it's certainly not as good as listening very carefully and really chewing on things. In fact, I've found that when I was younger, I was a much faster reader than I am now. These days, if I'm reading, then there's only two options. One is I'm reading something that is not all that interesting, and I'm going to stop reading it fairly soon. The other option is I have something that's really interesting, and it keeps making me think about things, and I stop to think about them. So whenever I'm actually reading something, it takes me much longer these days to get through them. That's perfectly okay. I think that when listening to podcasts, even a podcast as reliably awesome as Mindscape, there will be things that engage you more and things that engage you less. It's perfectly okay to say, well, this one, I'm just going to kind of let babble on in the background.

0:40:02.4 SC: This other one, I'm going to either pause and think about it, or I'm going to come back another time, or I'm going to look at the transcripts. We have full transcripts on the webpage of every single podcast. Or I'm going to Google the guy. I do put some effort into making the show notes for every episode, where I link to the guest's webpage and their CV, if that's available, or their publications or whatever the books that they write. So there's usually plenty of resources to dig more deeply in there if you want to do. Life is short. At least life is finite, let's put it that way. So you have to make your choices about what to do, and I think that one of the perfectly legitimate uses of listening to podcasts just in the background is to let you have a more educated idea of what it is you would like to follow up on and not. I know that I've absolutely been introduced to things that I now think are central to my intellectual life that I wouldn't have originally just because I was either listening to a podcast I thought was reliably good, or I was taking a required class, or something like that. So I think that that is fine.

0:41:10.5 SC: Aliyah Dawn Johnson says, are some fields isn't this, she's talking about fields like in quantum field theory, not fields like in a university, different departments. Are some fields more closely related or even interconnected than other fields? I'm thinking about the gritty process of exactly how and when different symmetries broke in the early universe. Did they all break at once equally, or did some break earlier or later than others? The electric and magnetic fields, if we were to imagine their symmetry breaking in the way I'm thinking about this, would be more closely related than the electric and weak fields, and so on. Is that a reasonable way to think about this, or am I totally off? No, I think different fields absolutely interact with each other in very different ways. It depends on the ways they can interact. For example, photons only interact naturally with charged fields like quarks and electrons and things like that. Neutrinos and even neutrons and even other photons do not interact directly with photons.

0:42:12.4 SC: They can interact a little bit indirectly through loop diagrams in Feynman diagram language, through virtual particles, or for something like a neutron, neutrons have charged particles inside, so the photons can interact with those, but it's nothing like the very direct and strong interaction that you get between a photon and an electron or a proton. And sometimes it's just that fields interact differently because nature said so. The masses of just, for example, the electron and the muon come from the spontaneous symmetry breaking from the Higgs boson, and there is a constant of nature which says, how strongly does the Higgs boson interact with the electron? A different constant of nature that says, how strongly does the Higgs boson interact with the muon? And that difference, the fact that these two constants are different, is the entire reason why the electron and the muon have different masses in observational cases that we see in experiments. So yeah, fields can interact with each other completely differently.

0:43:13.5 SC: I will say very quickly that the electric and magnetic fields are not good examples of symmetry breaking. The electric and magnetic fields are the same field. They are just the sort of time-like and space-like aspects of one underlying electromagnetic field. So the electric and magnetic fields have broken symmetry with respect to the W and Z boson fields, and they're completely different fields than the gluon fields. Mathematically, all these fields are closely related to each other, but physically, they're separate things in the standard model of particle physics. Brett Slog says, what do you make of the Washington Post and the Los Angeles Times declining to endorse a candidate in this year's presidential election? In general, do you think editorial boards of newspapers should make political endorsements? I honestly don't care whether editorial boards of newspapers make political endorsements.

0:44:06.3 SC: I can see it either way. You can argue that there is a civic function served by people who are very presumably well-informed, the editors of major newspapers, coming down on one side or the other and making an endorsement in a race. It helps people who don't spend all their time reading politics stories decide what is going on. I would be entirely in favor of sometimes the newspapers, if they did do endorsements, saying, you know what? This year, it's a close call. We're just going to let you decide. That should absolutely be an option. It shouldn't be a forced choice kind of thing. What people object to in the recent cowardly decisions of the Washington Post and the Los Angeles Times is not just the fact that they're not making a particular endorsement in a presidential election. It is very, very specifically that in this case, the editorial boards of both newspapers made an endorsement. They voted at the editorial board meeting to endorse Kamala Harris for president.

0:45:08.3 SC: They wrote editorials saying, you should vote for Kamala Harris. And then the owners of the newspapers stepped in and squashed those editorials. That's what people are objecting to. We should have editorial and repertorial? I don't know. Journalistic, I guess. Independence at newspapers. The newspapers that serve the people should not be held at the whims of their wealthy owners, okay? It's the system we have. I don't know what to do about that system, but it's not the best possible system for how things work in a deliberative democracy. Sergey says, a semi-classical general relativity question. Does the de Sitter spacetime have a Hawking radiation atmosphere that reduces H relative to the classical square root of lambda over three? Here, H is capital H, the Hubble constant. Your paper about de Sitter space not really having true quantum fluctuations seemed to imply that this is not the case.

0:46:11.0 SC: Well, you have to think a little bit carefully. You'll be un-surprised to learn that you have to think in subtle ways about what is going on here. So for those who don't know, if you have an empty universe, like literally nothing in the universe other than vacuum energy, other than the cosmological constant, then you can solve Einstein's equation of general relativity, and basically you have three choices depending on the sign of the cosmological constant. Is it positive, is it negative or is it zero. If the cosmological constant is zero, you get Minkowski space, the flat space time that special relativity lives in. If it's positive, the vacuum energy, you get what is called De Sitter space, and if it's negative, you get anti-De Sitter space. So in the real world, we think that is positive, nevertheless theoretical physicists often like to play an anti-De Sitter space 'cause it have some nice mathematical properties. But the real world seems to be, if anything De Sitter space or at least going toward De Sitter space. The real word is not empty. In the past, it was even less empty, but in the future it's emptying out, so it's coming closer and closer to this idea of what is called De Sitter space.

0:47:14.6 SC: And mathematically, you just run through the equations. You find that much like a black hole has a horizon, de sitter space also has a horizon. It's not exactly the same situation. In the black hole there's a definite location in space where the horizon is. In de sitter space every observer has a horizon around them, but each observer's horizon is differently placed. It is centered on them. And that horizon is defined as the distance past, which you can never, nothing that is out there right now can ever affect you. You would need to be able to travel faster than the speed of light to reach not only you now, but even your future. Okay? You are completely causally disconnected from this thing very far away past the horizon. So, mathematically once again, you run through the same kind of calculations that Stephen Hawking did to show that there are particles emitted by a black holes horizon. And you show the same kind of thing is true for the de sitter horizon.

0:48:13.5 SC: There is a temperature. The horizon is very, very far away for real world applications and the temperature is very, very low. So this is completely negligible in the current universe, but maybe in the future it will be there. So you might want to ask, it's completely sensible to say like, are these particles? Is this radiation? Is this adding something over and above the vacuum energy that we started with? And the answer is no. It is basically priced into the vacuum energy we started with. When we say that there is... And this is kind of the point of that paper that you talk about that I wrote with Kim Body and Jason Pollock on the lack of dynamical fluctuations in de sitter space. The point is, if you just look at the quantum state, if you just write it down on a piece of paper and you don't probe it, so you're not an observer doing measurements or anything, you're just mathematically describing the universe all at once.

0:49:09.5 SC: There's nothing changing from moment to moment in that vacuum state. It's not true that particles pop in and out of existence. That is a colorful human-centered way that we like to talk about it, but is not what's actually happening. What's really happening is that there is the vacuum state. There is the lowest energy state that the quantum fields can be in, in this cosmological background. And the minimum energy configuration that that state is in has a total energy density, which is the vacuum energy that you started with. It gets a little subtle because of course you start with a classical vacuum energy or you imagine you start with a classical vacuum energy typically, and then you quantize it and you get quantum corrections. And those quantum corrections are infinitely big naively, so you have to re-normalize them. There's a whole song and dance going on there, but the short answer is, it doesn't really change the Hubble concept that you thought you had that was already taken into account when you set up the problem.

0:50:05.4 SC: Anonymous says, I'm curious how accurate you think journals are at selecting serious papers to publish and weeding out the nonsense. Is it 90%, 99%? Is there any precedent for some pivotal paper that was originally turned down by journals but later turned out to be true? My sense is that they're probably very accurate, but would be curious to hear any notable counter examples if they exist. I think there's lots of notable [laughter] counter examples actually. People did a study a little while ago that it had a slightly misleading conclusion, but I'll tell you what the conclusion was. Super duper important creative new papers in science are more likely than average to get rejected by journals when they're first submitted. And this, when you say this, this is like, ah, see I knew it, the hide bound establishment, blah, blah, blah, blah. But in fact it makes perfect sense.

0:50:58.6 SC: The nature of a creative new idea is that it is outside the box. It is not what people are used to thinking about. So journals are very, very good at judging the quality of mainstream type papers. If you just try to solve the equations of some model of inflation and make some predictions for the cosmic microwave background, or you calculate the rate of production of some new particle in a model, the journals are pretty good at catching mistakes of that kind. But if you really try to be creative, then it's hard to find referees who are up to the task of judging the new ideas fairly. So there's many, many examples of ideas that turned out to be super important and creative, but were rejected on a first pass. The other category besides mainstream papers, the journals are pretty good at evaluating are crackpot papers. [laughter], There's plenty of papers that are just completely nonsensical and usually journals are pretty good at figuring out whether something is pretty nonsensical.

0:51:57.3 SC: So this puts us in the weird bimodal case where the papers that are rejected are either completely nonsensical or super duper creative. [laughter] And again, most of the super duper creative papers do get in. I don't wanna say that, but there's a healthy fraction of them that the current system is not quite set up to deal with accurately. I don't know how to improve that particular aspect of it. And by the way, most attempts to improve that particular aspect of it amount to saying I would like a flood of crackpot Papers to be accepted as well.

0:52:28.7 SC: And I don't think that would actually be good for anybody. Steven Mariotti says, I know you like the explanation that the arrow of time is due to entropy increase and the low entropy at the big bang, which certainly should have high credence. As entropy is a macroscopic concept it seems to play a subtler role, if any, for quantum processes and indeed quantum processes are usually regarded as reversible. Something caught my ear during a past AMA where you said that in the many worlds interpretation you can get branching in the forward time direction, but not the reverse. E.g there is only one past for each branch. Does that not suggest an arrow of time at the quantum level that has nothing obviously to do with entropy. Well, it depends on what you mean by the word obviously there. [laughter], There absolutely is an arrow of time at the quantum level and forget about many worlds or anything like that. In the everyday textbook rules of quantum mechanics, there absolutely is an arrow of time. Wave functions collapse toward the future, not toward the past.

0:52:29.5 SC: If I have a quantum state right now, and I know exactly what it is, I can predict very, very reliably the probabilities of getting any measurement outcomes in the future. If I have a future quantum state on which a measurement was already done, I cannot in any reliable sense retrodict what the quantum state was before the measurement just on the basis of the outcome. If I have a quantum state that is 90% spin up and 10% spin down and I measure it and it's spin up, or if I have a quantum state that is 50% spin up and 50% spin down, or 10% spin up and 90% spin down. If all of them get measured to be spin up, I can't tell any difference between them in the future. So I can't retrodict in that way. Now many worlds has an explanation for this. In Copenhagen or the textbook view it is just a posit, it is an axiom of the theory time reversibility is violated by quantum mechanics in the textbook view.

0:54:26.3 SC: Many worlds only has one rule, which is the Schrodinger equation, and that is reversible. In the case of many worlds, the apparent time asymmetry comes from an initial condition. It's exactly the same source of time asymmetry that we get in thermodynamics. There's a special initial condition near the Big bang after which everything is perfectly ordinary, reversible evolution. And so that explains why in many worlds in practice, although not in principle, the world's branch toward the future, but not the past. It's ultimately because of what happened at the Big Bang, which we don't really agree on why it was like that. Ken Wolf says in an article, battles of precise mass, in a recent issue of foreign affairs, it was pointed out that the recent Iranian drone and missile attack on Israel cost about $80 million, but the successful defense against it cost over a billion dollars. Meanwhile, in the Red Sea, the US Navy is expending more munitions than it has since the second World War to fend off anti-ship drones.

0:55:32.6 SC: If the capabilities of drones continue to improve and the cost continues to drop, it seems like we are approaching a conventional version of the nuclear mutually assured destruction where there will simply be no practical defense. Does this sound likely and what would be the implications? Yeah, I think it sounds very likely. And I don't even wanna say that that's exactly the mechanism for it, but I would be completely unsurprised if 100 years from now there were a lot more relatively cheap and easily scalable offensive capabilities in military actions than there were defensive capabilities. Entropy increases, and offense is all about just increasing the entropy on the other side. It is too easy to come up with ways of doing that. And defense is about preventing someone from increasing your entropy. That's hard to do.

0:56:25.0 SC: The laws of physics are against you here. And so as technology gets better and better, the ability to blow things up and the inability to prevent them from being blown up is going to be a feature of future warfare. For drones in particular, I can easily imagine drones becoming quite deadly and very, very small. I can imagine them being pinpoint accurate in being able to assassinate individual people. I can imagine them being so small that you wouldn't notice them. They could be flying right in front of your face right now, but too small to see, and yet they could still be deadly. And this is not even to mention all sorts of biological or hybrid biomechanical ways of inflicting damage on people. So I don't know that that's true, but I think that's a perfectly natural way for the technology of warfare to advance.

0:57:13.7 SC: What are we gonna do about it? Look, what if you lived in a society where literally everyone carried a gun and could easily shoot people and kill them? Does not immediately follow that that would happen. That everyone would start shooting people. Maybe everyone would just be very polite [laughter] because they don't wanna get shot at. Like, what if you could just blow up a car that cut you off in traffic? Maybe that would stop people from cutting people off in traffic. But you know if you've ever met actual human beings that some idiots would still cut people off in traffic. Some people who lived in the world where everyone had a gun would either still be jerks and therefore get shot at or just decide to start shooting people for no good reason. So those people you have to do something about.

0:58:00.1 SC: I think that if state actors have the capacity to cheaply and easily inflict enormous damage on other nation states, we will need some kind of mutually assured destruction and we will need some kind of treaty understanding that if states start doing that, they get punished in some meaningful way. I'm not enough of an international relations specialist to tell you exactly how that's going to happen, but I think the short answer is, or the short lesson is, international relations and future diplomatic strategies are going to have to adapt to the vast possibility space of future technological advancements in sneaky, cheap and easy to produce offensive weapons capabilities. Jim Murphy says, what do you think the Sean Carroll who chose 50 zeros in something deeply hidden is doing now? I'm gonna erase the word chose from that sentence 'cause there's no choosing about it. But what Jim is referring to is when I wrote something deeply hidden, the book about many worlds in quantum mechanics, I did a little fun thing where I ran a quantum random number generator to generate a 50 digit number.

0:59:16.4 SC: So 50 numbers between zero and nine in a row. And if you believe the many world's interpretation, every single possible outcome exists in some world. And I printed that number in the book. So if you have a copy of the book, you know the label of the universe that you're in right now, okay? That there's a number in there that corresponds to our universe that we live in. And I mentioned in the book that if, again, if you believe many worlds, there is a world in which those numbers came across 0, 0, 0, 0, 50 of them in a row. Was it 50 or was it, I thought it was only 20. Now that I'm forgetting exactly, but it is big enough, big enough that most of the numbers look completely random. Some don't. Some are 0, 1, 2, 3, 4, 5, et cetera. Some are 0, 0, 0, 0. What do those people think?

1:00:02.7 SC: I think there's a high possibility that many of them would go, maybe my quantum random number generator is broken. I think that's the first thing that I would do. I would try to run it again and see if I got it again. There's always gonna be someone who runs it twice and gets the same answer twice. And so at some point, either they will change their mind and stop believing in many worlds, or they're gonna accept the fact that they find themselves in a very, very unlikely outcome. That is just inevitable. When you have a view of the world in which something is stochastic or random or probabilistic or unpredictable, you're not gonna get the most likely thing every time. You're gonna have to learn to deal with it. And sometimes because of that necessity, you might end up getting the wrong answer, never promised you a rose garden.

1:00:55.0 SC: Randall Bissinger says, what is your position on lying? Is it always bad? Sometimes okay, etcetera. Sam Harris pretty much says that it is a bad thing. Almost all of the time. A situation came up with my sister when volunteering at a grade school. A little girl was crying because of something that happened and another child tried to console her by saying the same thing happened to her. She later told my sister that it really didn't happen, but was trying to make the other child feel better. I thought it was okay, but my sister thought that lying was always bad. What do you think? Yeah, this is the classic consequentialist versus deontologist dilemma. Okay? Deontologists think that morality should be based on rules, right conduct. If you do this, you're doing the right thing. If you do that, you're doing the wrong thing.

1:01:41.9 SC: Whereas consequentialist think that your moral decision should be based on the consequences of them. It doesn't matter what you do, it matters what consequences your actions actually lead to, happiness, sadness, etcetera. Consequentialist are typically happy to lie if it makes people happier or makes the world a better place overall. Deontologist, you can absolutely be a deontologist who thinks that lying is fine, but the prohibition against lying is a classic deontological rule that a lot of people would accept. So there's the story of Immanuel Kant claiming, I don't know if he actually claimed this or people were accusing him that he should claim it, but if he were harboring a fugitive in his house and an angry mob came to the house to unjustly kill the fugitive, can Emanuel Kant say, no, they're not here. And he would have to say, Nope. Yep, they're hiding in my basement. 'Cause he's not allowed to lie 'cause he's a deontologist Emmanuel kant.

1:02:35.9 SC: No, I don't think that way at all. Like as I've said many times, I do not have or claim to have a fully fleshed out ethical system that I can lay down on you. But I have easy objections to both pure deontological approaches or pure consequentialist approaches. I think that we need some kind of hybrid way of doing these things and that's the overall meta ethical point. And I think that this is a good example of how you can't stick to these arbitrary rules. As good as they sound I think you just can't stick to them in every single case. The urge to make up the rules and stick to them. You know what it reminds you of is bureaucracy [laughter] It reminds you of like if you're in a university or I'm sure if you're in most corporations, there are rules about what you can do and what you can't do.

1:03:26.2 SC: And usually these rules are good. They're there for the right reasons. We're trying to do the right thing. When Hahrie Han was on recently, she mentions the fact that DEI efforts at universities are usually terrible. And they're not terrible because diversity, equity or inclusion are bad. It's because they're bureaucracies and they make up rules and the rules turn out not to be able to cover every conceivable case. And rather than being a human being who uses their judgment and tried to make the world better, people say, well, these are the rules. We have to stick by them even if they obviously are inapplicable or bad in this particular case. I think that lying is the same way. I absolutely am happy to imagine people lying to make the world a better place in small innocent ways. There's a danger that once you say that it opens the floodgates to lying for bad ways, for reasons that make the world worse, but that danger is always there anyway.

1:04:22.7 SC: So I'm not interested in saying, well, little girls should just cry because I can't tell them anything but the truth [laughter] just because I have these rules. Like that's just not the way I wanna live my life. No, Andrew Kosro says, imagine two strings as in strings of digits of numbers with the same logical depth. So you remember we talked about Charlie Bennett in the last AMA who invented this idea of logical depth as a way of quantifying the complexity of a string. The number of computer operations you'd have to go through to produce that string from a computer program. And so anyway, Andrew says, assume the programs output their bits in order and as soon as possible. We run the programs and record the number of computation steps used to output each bit. The first one uses a constant number of steps per bit, and the other is highly variable. Which would you consider more complex?

1:05:20.7 SC: So basically what Andrew is saying is you define logical depth as a feature of the string as a whole. Can we kind of refine it to ask whether or not we can attach complexity or something like that to individual digits within the string? I don't know is the short answer here. This would require more thought that I generally give AMA questions, which I tend to answer extemporaneously. I suspect this is not a well-defined thing. Because I suspect that if you found the different bits required different amounts of time, but then you changed bases from binary to decimal or something like that, or hexa decimal, you might get a completely different answer. So one crucial feature of all of these ways of quantifying complexity and similar attempts to quantify intuitive concepts is that you want them to be as independent as possible of the arbitrary choices you make along the way.

1:06:19.9 SC: I think this particular characterization would be hard to make independent of those arbitrary choices. Now, you might think that there's a big, big arbitrary choice we're making here when we talk about things like logical depth or Kolmogorov complexity, which is we are imagining computer programs that are supposed to be either short or only run for a short amount of time. But different computer programs are different and doesn't the computer program you use make a big difference? That's where we turn the mathematicians loose and they're able to prove that there's sort of a constant difference, like a difference that you know ahead of time is gonna be there and you can take care of versus the scaling of the argument of the time or the logical depth. I should say the time or the length of the computer program that outputs your string as a function of how big the string actually gets. So it's that scaling behavior that is both what you care about and also something that is universal and free of the independent choices that you made along the way.

1:07:20.8 SC: Tis Jansen says, as far as I know, matrix mechanics and wave mechanics are different mathematical ways to describe the same theory of quantum mechanics, where wave mechanics tends to be favored for it's easier and more intuitive. Still we can't figure out how to use it with Einstein's relativity to describe stuff in extreme gravity like black holes or near the big bang. Could using the different mathematical approach like matrix mechanics give us more insight in how to do it? Or are the problems the same no matter the mathematical approach? I think this is a great question actually. Just to fill you in a little bit, it's not quite true that wave mechanics is favored for being easier or more intuitive. Wave mechanics is favored as a way to teach people quantum mechanics in their undergraduate years exactly because it is easier and more intuitive.

1:08:08.5 SC: But matrix mechanics absolutely has its uses. And when you get into the more high powered areas of quantum field theory, et cetera, we generally use a hybrid. We literally talk about the Heisenberg picture and the Schrodinger picture. Heisenberg being the matrix guy, Schrodinger being the wave guy. And then we have the interaction picture, which is the combination of both. And in quantum field theory, the way that I presented quantum field theory in the new book Quanta and Fields, is from a Schrodinger kind of point of view where I discuss the wave function of all possible quantum fields, but as a way of actually doing quantum field theory calculations that turns out to be pretty ungainly, not very easy after all. And so people do a kind of Matrix mechanicsy approach to it. So you use whatever is convenient in the moment. But to answer the spirit of your question, I think that it is absolutely possible that two approaches to a theory that are mathematically equivalent to each other can naturally suggest different kinds of generalizations.

1:09:14.7 SC: If you work in terms of the principle of least action, you think one way. If you work in terms of the Schrodinger equation, maybe you think another way, likewise for matrix mechanics or density matrices or whatever. All sorts of different mathematical approaches that you can show are equivalent can lead you to different places. In classical mechanics, we have Hamiltonian mechanics, which is distinct from Lagrangian mechanics and they generalize in different ways. And that's good because we don't know the final laws of physics, we need to generalize what we know now. And I think that it's good to sort of be a master of many, many possibilities so that you can imagine many, many different ways to generalize given that we don't know what the answer is. Nicholas Chapman says, what is the physical basis behind gauge symmetry, if any? Or is it just a useful undoubted results in some useful theories e.g, the forces of nature? Global symmetries such as U [1] makes sense to me. U [1] symmetry means that interaction factors shouldn't depend on absolute phase values, but only on relative phases. But on what do gauge or local symmetries imply?

1:10:22.1 SC: Well, if you want to get an intuitive understanding of gauge symmetries, it's very, very close to, but I won't say it's exactly the same as, but it's very, very close to a kind of souped up generalized coordinate in variance. If you learn about geometry on a tabletop, you will often be taught Cartesian coordinates and sometimes you might be taught that I could rotate the coordinates or I could translate them in the X direction or the Y direction and nothing important changes. If you also want to be able to say, I want to completely change my coordinates to like spherical coordinates or something like that there's a lot more mathematical effort involved, but it's super duper useful. And indeed physical quantities still don't change when you make a dramatic change of coordinates.

1:11:11.0 SC: So for the mathematical setup of fields in nature, we have fields that are not just numbers at every point in space. Sometimes we have fields that are little vectors at every point in space or more complicated mathematical objects like matrices at every point in space. And this generalization of coordinate variance is basically choosing axis, a set of basis vectors at each point in space for the vector fields or the matrix fields or whatever it is we're talking about. And it's supernatural to say, I shouldn't care what direction my basis vectors point in, and indeed I shouldn't care about what direction they point in separately at each point in the world. That's all a gauge in variance is. It's the ability to separately choose my basis vectors for my geometrically sophisticated fields at every point in space and time. Now it's a completely empirical question what symmetries actually exist. Just 'cause it seems natural for there to be a symmetry doesn't mean that nature has such a symmetry.

1:12:18.9 SC: You have to go out and look. You have to say, oh look, there is an SU3 symmetry that leads to glue ons and the strong interactions and so forth. But the possibility of either one is completely natural to us when you think about all these basis vectors for all these fields at every point in space. Mark Kumeri says, what do you think has been the most incredible or surprising results in physics since the discovery of dark energy? I don't know. That's a good question. Dark energy was discovered in 1998, and I very often use it as an example, as the example of the last time there was a truly surprising experimental result in fundamental physics. Fundamental physics is what I do for a living, it's what I pay attention to.

1:13:00.9 SC: So I am almost sure that if you had a condensed matter physicist or an atomic physicist or a biophysicist or etcetera, and ask them these questions, they would give you very good interesting answers. I don't know, maybe it has something to do with graphene or something like that. But I am not the person to ask about that. I'm just not expert enough. In fundamental physics we haven't had a surprising experimental discovery. We've had super duper important experimental discoveries. We found the Higgs Boson, we found gravitational waves. All of the measurements of the detailed measurements of the Anisotropies of the cosmic microwave background came after the discovery of dark energy. So we've learned an enormous amount, but it hasn't really been super duper surprising. Maybe I think you can make a good case that the most surprising result is that there haven't been any surprising results, especially of course, at the Large Hadron Collider in Geneva.

1:13:56.8 SC: I did, I haven't looked at it in years, but I did do the responsible thing before the LHC turned on, and I wrote a blog post saying, here are my predictions. And I had a pretty decent, I had double digit possibility credence, 10% or more. I forget what the number was on finding nothing. But it was certainly a minority. It was not 50%. I certainly thought, and in addition to the Higgs Boson. I meant the Higgs boson was almost inevitable. It wasn't completely inevitable, but I think we all expected it. Either the Higgs boson or something much, much more surprising. Those are basically the only possible choices, but the least surprising, least informative possible thing to find was the Higgs Boson and nothing else. This was often referred to as the nightmare scenario and so far it is what we got. And we might always change our mind tomorrow or not change our mind, but be changed in our minds tomorrow by a new paper that comes out of the experimenters at the LHC. But so far we haven't seen anything else. And I was certainly one of the people who thought there were very good reasons to expect to see something else. I was not someone who thought that we knew it was gonna be super symmetry or something like that or that we knew it was gonna be large extra dimensions.

1:15:12.3 SC: I didn't know what it was gonna be. I put a healthy amount of probability or credence on something we haven't predicted yet. But I thought there'd be something. Yeah, I thought that those arguments were good and they turned out not to be good. So that was surprising to me. David Carl says, I remember you briefly mentioning liking poker. That's right, David. In fact, I've had several poker players on the podcast, Liv Boeree and, Maria Konnikova most, obviously many also recreational poker players I'm sure. He says, David says, I'd be interested in your experiences with the game. Did you play online, at home games or at casinos tournaments or cash game? Did you try to play game theory optimal or exploitative? Yeah, I played a little bit of all of those things.

1:16:00.2 SC: I was never super duper active. People get into poker. It's one of those things you get really into poker. I love reading poker books. I have a lot of poker books. I probably spent more time reading poker books than playing poker because it's the theory of it that interests me a lot. I'm not a degenerate gambler. I'm a happy gambler and at small stakes, let's say that. So yeah, home games online, again, very small stakes online became hard to do because it got flooded with bots, with things that would play not too imaginatively, but they wouldn't make mistakes according to their programming. And then it was hard to beat them. I did eventually figure out some of them you could beat. They're not advertised as bots. They're masquerading as people, but basically they had models of typical opponents.

1:16:46.1 SC: So if you acted it in ways that were different than their internal models suggested, you could beat them pretty regularly. But it wasn't all that much fun. I think my most fun is comes from either a home game or a live game at the casino. Casino games can vary a lot. It depends on who you're playing with. It's a complete draw of the cards, as it were. Luck of the draw. You don't know who you're playing with. And I certainly have done better playing tournaments than playing cash games. I'm not exactly sure why that's true. One aspect, there's a couple of differences in tournaments, usually you're more short stacked. So knowing when to make a dramatic move is more important. And also the size of your stack can change throughout the tournament. So knowing how to adapt is also very important, and I was relatively good at that.

1:17:34.4 SC: As far as game theory optimal or exploitative, to the extent that I can claim to have a well-defined strategy, it is more exploitative. I liked to see flops and have a chance to get a good hand and see, wait for people to make mistakes. [laughter] That's my favorite way of making money. I'm a little skeptical about people who claim to play game theory optimal. I'm not sure exactly that we know what that is. It's hard to figure it out. Poker with eight people or 10 people at a table is not a solved game.

1:18:09.0 SC: You have certain things you can in very specific circumstances, like when you're heads up, you can solve a lot of things. But in general, I suspect that that's harder to do than people think. Lounging like Alagongrioan says, that's probably a pseudonym. I don't like to guess when people have pseudonyms, but that sounds pseudonymous to me. The ever ready and quantum mechanics interpretation hinges on the idea that we should experience only one branch of the wave function. But why should that be so? Why don't I experience the whole wave function at once? Yeah, that's a perfectly legitimate question. And this is why philosophy matters for physics, in general and quantum mechanics in particular. The answer is you have to correctly define what you mean by I in the statement. Why don't I experience the whole wave function at once? And this is whatever it did basically.

1:18:58.5 SC: He said, when you have a decoherent wave function, so there's two different branches, there's no reason to take the physical system that represents you on one branch and the physical system that represents you on another branch and call them the same physical system. There are two subsets of a physical system, two aspects of it, if you like, that will never interact with each other. It makes sense to call the left side of your brain and the right side of your brain, both part of a single brain because they're interacting with each other to make some common whole, but you on one branch and you on the other branch never interact. You never have anything to do with each other. So it just doesn't make any sense to identify those two things as one person. They're two different people. And this reminds you that the question of how to identify people in a physical universe is a non-trivial one, even if it's a single Newtonian universe.

1:19:52.0 SC: So we have some hints from our experience, but we also have to map it onto the underlying best physics that we have to describe the world. Nickens says, soon to graduate with a physics master's. All of my medium of studies are becoming completely digital, where I start the day opening my laptop and end my day closing it. As a professor at a university do you also feel this shift in your career or personal life? And any opinions on what is the optimal balance to do science these days? Certainly a lot of my life is spent online either sending emails to people or recording podcasts or so forth. But the teaching and research experience is largely exactly what it was when I was an undergraduate. I mean, mostly this is my choice. I do not teach even, like right now I'm teaching one little seminar, graduate philosophy seminar and one physics lecture course, and the physics lecture course.

1:20:42.8 SC: I mean, the graduate philosophy seminar is obviously the classic paradigm of we're sitting around a table with 10 people or less and digging into the details of a text in front of us. It's exquisitely fun to do that. And it's one of the reasons why I love being cross appointed in a philosophy department. The physics lecture course is me standing in front of a blackboard lecturing and drawing on the blackboard. In fact, I was recently asked by the Johns Hopkins pr media relations, let's say, department. They said, we have this new feature on Instagram where we feature courses that we think are really innovative and fun with an interesting, interactive or experiential visual element. Would you like your course to be featured there? And I said very honestly, like, this is the most boring possible course to feature on Instagram, I'm sorry. I'm standing in front of the Blackboard lecturing.

1:21:39.6 SC: I don't use slides, I don't use PowerPoint or anything like that. It's just me talking to the students about the laws of physics. So I don't see any difference whatsoever. I'm trying to think, yeah, I haven't really had anything that technology has affected me very much in that particular way. That's not to say it doesn't affect other people quite a bit. I'm just an old fogey about that in particular. Tim Ginitos says, you've mentioned that physicists generally assume the world is Markovian, in that you can predict the state of the universe in a future moment, given only the present state without knowing, needing to know the whole history of the universe. Markov chains only settle to a steady distribution over states if they have certain properties, e.g irreversibility, positive recurrence, et mcetera, without which the distribution bounces around forever.

1:22:25.6 SC: Do we know if the universe has the properties to allow it into a steady state distribution in the distant future? Well, Know is a high barrier when it comes to physics. We don't know much at all with perfect certainty. We have a favorite theory. Our favorite theory cosmologically is Lambda CDM, that you have a vacuum energy, the cosmological constant lambda plus you have cold dark matter. In that case, you can figure out, you can just ask the theory, what is gonna go on in the future? And the answer is you will come to equilibrium. This is something that's been talked about for 150 years now, the heat death of the universe. The heat death of the universe was always a possibility, but there were other possibilities as well. Now, according to our best physics, best cosmology, it is the most likely possibility.

1:23:11.8 SC: So you can even specifically relate the cosmological constant to the second law of thermodynamics. I did this in a paper with Aiden Chatwin Davis, where we showed that something called the cosmic no-hair theorem, which says that the universe will empty out and approach de sitter space, which we talked about before can be shown to be mathematically equivalent to the second law of thermodynamics under certain assumptions. Which are, you can always improve. I'm hoping that people cite the paper and do better than we did, but that was our idea. So yeah, as far as we know, it will settle down into a steady state. Now, of course, there's lots of speculative ideas. Maybe you make baby universes, maybe the universe eventually re-collapses, maybe the vacuum energy goes away. So we certainly don't know for sure, and I wouldn't even put very high confidence on any one possibility. But that's the leading candidate right now.

1:24:03.8 SC: Kelly Hoaglund says, you've said in the past that it's not a good idea to assign 100% credence to anything because it doesn't allow you to change your opinion. I'm wondering if this is for the, if for this reason, whether or not you believe in unconditional love. PS I had a professor who once graded our assignment on a credence based system. Rather than just selecting A, B, C, or D, you assigned your credence of each one being correct. The catch is that if you put a credence of 100% and you turned out to be wrong, your score would go to negative infinity, which meant that your entire class grade went to negative infinity, which I think really meant that you just got a talking to after class. I'll ask the second question first. It wasn't really a question, but I kind of love this system of the credence based grading.

1:24:46.3 SC: But it's weird that I don't know if he's dividing by zero or something like that. I would just say if you have choices, A, B, C, and D, you get to assign numbers between zero and 100 that add up to 100 to each one of those four things. And then the actual credit you get is the number that you assign to the right answer. So if you think there's a 90% chance that it's A, and 5% chance it's B, 2% chance it's C, 3% chance it's D and it turns out to be D, you get 0.03 points. Or you get three points and then you add them up. I think that'd be perfectly sensible. There's no negative infinities there. For the first question, do I believe that there is unconditional love? I just don't think it applies.

1:25:31.8 SC: I think that the question about whether or not you are in love with somebody is not the kind of factual proposition about the world, to which we do ordinary Bayesian reasoning and update on the basis of new information and things like that. I think it's a more opinion value related thing, and I think that facts and values are actually different, so it doesn't really apply to that situation. Joseph Eli says, if you woke up tomorrow as NBA Commissioner, what changes would you want implemented? I, for example, would tear down and rebuild the NBA if that's what it took to get rid of teams tanking for better lottery odds. I think anytime a professional sports team is motivated to systematically lose games on purpose, it's a mockery of the sport and an insult to the fans. Though I completely understand why teams do it under the current incentive structure.

1:26:18.5 SC: Do you agree? And if not, what would you want to see changed? Yeah, I haven't thought carefully about this. My attitude towards sports fandom, I've noticed is different than some other people's. 'Cause some other people's think that they really think of themselves, even though they're just fans as the coach or the general manager or even the scout for the team, they're like, "I have to be completely honest with myself or, I would do this trade or whatever, or I'm not rooting for that player anymore." I recognize that I don't have a lot of power in these situations, and so I'm gonna root for the team that is there and I want them all to succeed because I want my team to win. That's how it is. So I don't spend a lot of time thinking about how I would change it since I have really no power to do so.

1:27:06.7 SC: I completely agree with your judgment that there should not be incentives to be bad. I also agree that if there are incentives to be bad, you can't blame teams for doing it. That's 100% okay. You shouldn't give them incentives. There is a perfectly good way to avoid that. I think it was Mike Zarren who proposed the idea called the wheel for drafting in professional sports leagues like the NBA. So the point is, for those of you who are not sports fans, typically, every year there is a draft for amateur players. Typically college players, maybe high school players, people who are not professionals to join the league. You could just say like, anyone can go to whatever team they want, that's a system. But then you would worry that there's a couple of glamor franchises or wealthier franchises that all the best teams would want to go to, all the best players would want to go to.

1:27:58.5 SC: So instead you have a draft to assign them in some systematic way. And it would also seem unfair if the teams that were already really good got to pick first and therefore get the best players. So the typical system is that the teams that are bad as judged by their record in the previous year, get to pick first. That seems very equitable and fair, except in a sport like basketball where you only have five players playing on the field at a time for each team individual superstardom is crucially important. You roughly speaking can't compete to win the championship unless you have one of the top five players in the league, maybe maybe top 10 at the outside. There's never 100% stricture there, but that is the absolutely good rule of thumb. And if you need a top 10 player and there's only 30 teams in the league, then there's a huge premium being put on getting those players.

1:28:53.5 SC: And one way to do it is to just be really bad for years in a row and you get to pick early in the draft and therefore get one of the best players. It doesn't always work because sometimes you pick badly or sometimes players get injured or whatever. There's nothing certain in this scheme, but that's how it is. And the bad part is that, again, if you need really good players to be competitive for the championship, you start the season with between a third and a half of the teams knowing ahead of time they don't really have a realistic chance of competing for the championship. So what else can they do? Well, they can compete to be the worst team and that can give them the best chance of getting a high draft pick. And this is called tanking, as in dunking into being dunked into a tank falling to the bottom. Although the imagery is usually people commanding a little squadron of tanks as in army tanks.

1:29:47.1 SC: And it is bad because it means that there's a lot of games during the regular season that are kind of meaningless. Like either two teams that both wanna lose, or one team that wants to win and one that wants to lose. What is the fun in watching those? And it's usually not, by the way, the players or the coaches who want to lose. Usually, not always, but usually the players out there on the court play their hearts out. But if the players are bad [laughter], then they're not gonna have a very good chance of winning. So it's the management of the team that throws that team out there without very good players, and they're going to get a lot of high draft picks. And again, perfectly legit for the teams to do this, if that's the incentive structure.

1:30:24.4 SC: My beloved Philadelphia 76ERs did that for a long time and it worked out pretty well for them, honestly. Now how do you get rid of that while still being fair? So this wheel idea was kind of an obvious thing in retrospect. You take a year, like whatever next year let's say, and say, okay, we're going to do drafting and reverse order of your records. So the worst team goes first up to the best team, but every year after that, we're just gonna go on a predetermined cycle. So every single team will cycle through in a 30 team league being 30th, 29th, 28th, etcetera, in a 30 year cycle. So every team will have a shot at being first, at being last, etcetera. And so there's absolutely no incentive in that case to be bad because your record does not get you a better draft pick.

1:31:16.9 SC: There's a lot of immediate objections to this, like, what if a really good team gets to have a really good player just by accident? And I kind of say to them the same thing that I would say to the version of myself that got all zeros in their quantum random number generator. Tough luck, [laughter], tough luck happens anyway in sports. But I do think that it is worth removing this perverse incentive that we have right now. The other very clever idea, I might not explain it very well because I haven't seen it many times. But unlike a sport like baseball where even if you're down by eight runs in the ninth inning, in principle, you can catch up. In principle, even though it's very unlikely you could go on a 10 run inning and win the game. And actually moments like that in baseball are some of the most interesting, fun, exciting times.

1:32:06.9 SC: In basketball if you're down by 20 with two minutes left, you don't have a lot of probability for coming back. So people put out their... They clean the bench even the last couple minutes are just not worth very much. So there's this idea called the Elam ending, E-L-A-M, which changes how the games end. And rather than playing to a predetermined time after a certain time, you play to either the team that is winning at that moment has to score earn more points like eight more points or something like that. Or, well, let's say it this way. There's the score that the winning team has. Add 8 to that, Whichever team gets to that score first wins. Okay? So in that case, in principle, there's not a clock running. So even the losing team, the team that's losing by 20, if they play really good defense and really good offense, could come back just like in baseball. And this has been tried, like in the all-star game and things like that. It's actually, it increases the excitement by a little bit. I think that the play-in for the playoffs was a good idea. I do think that, I don't know, if I wanted to be radical about it, I might be in favor of pushing back the three-point line, but the court's just not big enough. Like really what do you wanna do is increase the size of the basketball court, because players now are much bigger than they were back in the day when they invented the dimensions of the court itself.

1:33:28.6 SC: I would like to decrease the emphasis on the three pointer. And indeed, Daryl Morey, who was on the podcast a while back, and is one of the masterminds behind increased emphasis on the three-point shot, agrees with this. He's like, oh yeah, it's not good for the game that the three-pointer is so important. It's just that that's how the rules are set up to incentivize that. So we have to change that incentive structure a little bit. But I should think about it more. Or if I do become, Adam Silver, if you're listening, if you... Adam Silver's the current commissioner of the NBA, if he's close to retirement and looking for a successor, I would be happy to be considered for that job. And if I am considered, I will put much more effort into thinking about how to improve the game of professional basketball.

1:34:13.6 SC: Colin Small says, at what point in your studies or post studies did you first start disagreeing with beliefs or theories of scientists you deeply respected? It strikes me as quite monumental the time that you first feel confident enough in your own perspective to critically evaluate and push back against ideas put forth by those that you look up to. I certainly don't remember a moment when that happened. I kind of never was reluctant to do that. I mean, I don't think that you can be reluctant to do it, because if you read lots of different people or talk to lots of different people, they will disagree with each other. So you can't just blindly agree with all of them. You're gonna pick some of them to be in your mind, more trustworthy than others, et cetera. And so you're instantly faced with the idea that you're not gonna trust everything that your senior people say. So of course, you should critically evaluate and push back against ideas. Maybe you're good at it, maybe you're not good at it, but I think that just comes along with the territory pretty early on. So I don't remember a specific epiphany where that started to happen.

1:35:22.0 SC: Paul says, your interest in mechanical watches has been mentioned previously. What is in your collection and what are your yet to be obtained Grail watches? I'd like to think that for the foreseeable future, I'm done buying watches. I went through a phase when I was buying watches and I got rid of some of them. And now I have like a small, like eight watch collection. That's small to me. It's small to watch collectors. It is huge to an average person, like who has one watch or zero watches, but I think I've covered all the bases. I have a nice dress watch from Nomos. I don't know if you know Nomos. I tend to, without planning, like these German watches. Swiss watches are of course the classic mechanical watches, and they're great, and I love them, but there's this one town in Germany, Glashutte, that was the center of German watchmaking before the Iron Curtain came down. And then was reinvigorated after, sorry, yeah, before the Iron Curtain. I don't know what the metaphor should be.

1:36:22.6 SC: Before the second World War, Glashutte was the center of German watchmaking, and it became revived after the Berlin Wall fell. And it's the home of a whole bunch of very good watchmakers, the best of which is Lange & Sohne who makes watches I could never afford. That's okay. I can still admire them. Nomos is a much more affordable example. There's also Glashutte Original, Union Glashutte and a bunch of others. But anyway, I have a nice sporty watch with a chronograph. I have a couple of sort of interesting looking watches with different color dials. I have a blue one, red one, brown one. So depending on what I'm wearing, it can look good. I have the Nomos dress watch, which is, if you're super interested, what is it? It's an Orion neomatik with a black dial, which I like very much. And then I have a very rugged Casio G-Shock if I'm actually out there doing dangerous things. You don't know, I could be out there doing dangerous things and then sometimes you need a watch to go with me. So I'm pretty happy with my watch collection right now. I'm not really looking to spend much more money in that particular direction.

1:37:32.9 SC: Erminio Maganzini says, in your discussion with Addy Pross in 294, he mentions the kinetic state of matter as if it's a new thing. I remember it from school, and I'm pretty old. Was he talking about a new refined kinetic state of matter?

1:37:53.9 SC: Look, I don't know. Chemistry is among all the sciences, probably the one I'm least familiar with. So I'm not the one to ask. He's talking specifically about dynamic kinetic stability. And the stability here is super duper important. The idea there is something changing, and it's chemical changes. It's not just flows of things. So it's particularly not like a hurricane or a fountain or the great red spot of Jupiter or whatever. It's an ongoing chemical reaction for which the changes of the ongoing reactions are important. But macroscopically, it's a stable configuration of stuff. If that's already well known to people, then that's great. It seemed, from talking to him and from Googling around that it is a different kind of thing. I think that's a good characterization of it, but you'd have to look that up.

1:38:46.7 SC: Daniel Crespo says, I just listened to your episode with Don Farmer, where he mentions that they simulate millions of agents to make economic predictions. At this point, wouldn't it be possible to go one step further and create a digital twin of the whole US economy that would simulate all the real actors of the economy with all the available data about them? That model should be very accurate to test any new policy. So I suspect not actually, because I suspect that the reason... That the limitation on accuracy does not come from the number of agents. So when we simulate in astrophysics the evolution of our Milky Way galaxy, which has of order 100 billion stars, we don't put in 100 billion stars into the simulation. We might do some n-particle dynamics where n is a large number, but it's not one particle per star. Every particle "in the simulation" will typically track thousands or millions of stars.

1:39:42.9 SC: And the reason why is because that's fine. That's all the accuracy you need. If you think about what is happening, the limitations of accuracy do not come from the fine-grainedness of the simulation, but from getting the behavior of the individual particles right. That's what is difficult and unpredictable. So you could do a simulation that has 350 million agents in it, but are your agents doing what individual human beings do? I mean, think about how difficult it is to simulate a single human being very, very accurately. And you can get some things right, you know they wanna buy food or whatever, but that's where the limitation on accuracy generally comes, not from the number of people. So maybe someday we'll be able to do both, accurately simulate individuals and have enough of them to make a map of the US economy, but I don't think we're anywhere near that yet.

1:40:35.8 SC: Michael Kelly says, given that life is a symbiotic coordination of organisms from the gut biome to the entire ecosystem, what are your thoughts on the possibility that the purpose of intelligent life is to build the brain of a larger organism such as the earth itself? Well, my thoughts are that there is no such thing as the purpose of intelligent life. Sometimes I tell the joke handed to me by Michael Russell, who's a person who does research in the origin of life, that the purpose of life is to hydrogenate carbon dioxide. That's based on the idea that in the early chemistry of the Hadean Earth, there was a channel to do a chemical reaction that hydrogenated carbon dioxide. That took carbon dioxide, removed the oxygens from the carbon molecule and replaced them with hydrogen to make methane.

1:41:22.1 SC: And that required a complex chemical reaction that eventually led to proto-life. But it is just a joke. There's not actually a purpose. This is something that... Well, it's conventional in discussions of Darwinian evolution, that evolution is not forward looking. Evolution just blindly tries a lot of possibilities and then it selects on the basis of what has been effective. So things get better and better because the failed experiments are selected out, but it's not that evolution thinks about what would be best and then tries that out. That would be a kind of purposeful action. And as far as we know, neither biology nor physics have that. So I just think that it's not right to think about purpose as a concept in this particular context. There are purposes in the world. Those purposes are held by agents like you or me. I have purposes. So that's an emergent feature of the world.

1:42:19.7 SC: The atoms I'm made of do not have purposes. But at the level that I talk about where I'm in a person and I'm surrounded by macroscopic objects, purposefulness is very important in talking about and making sense of how I act in the world. But it's not a feature of the underlying basic dynamics. And I don't think it is right to talk about it at the level of evolution or even systems biology, let's put it that way.

1:42:46.2 SC: Anonymous says, do you think a PhD in physics is worth it to just learn about physics? I want to know the deep understanding of the universe that comes with a PhD, but I'm not so sure about actually becoming a physicist. I could be wrong, but it seems that the field is kind of stale. All the low hanging fruit has been plucked, and there will never be another Einstein.

1:43:04.2 SC: So there's two things going on here. The first part of the question and the second part. I completely disagree with the second part. I don't think the field is stale. I don't think all the low hanging fruit has been plucked. I don't think there will never be another Einstein. Well, there will never be another Einstein, just as Einstein was not another Newton or another Galileo. They're all different. The kinds of successes we will have in the future are different. Einstein was not that long ago. Einstein died in the 1950s. He was very much in the lifetimes of many people who are still alive today. So to pine and say like, oh, there'll never be another Einstein seems rather impatient from my point of view. And of course, as far as low hanging fruit being plucked, it depends on what subfield you're in.

1:43:49.7 SC: In fundamental physics right now, it does seem to be a situation where the obviously located low hanging fruit has been plucked, but there's plenty of other areas of physics like biophysics where that's very far from true. And also if we have a revolutionary new either theory or discovery, that opens up whole new orchards where there's more fruit waiting to be plucked. So you just never know about that. As far as the first part of the question, is it worth getting a PhD in physics just to learn about physics? I think that as a young person, getting a PhD in physics is an intrinsically valuable thing, no matter whether you go on to do physics or something else. I think the training is good. I think it trains you to think carefully about things, to discipline yourself, to work hard, as well as teaching you some very interesting and important substantive things about how the universe works.

1:44:41.6 SC: I wouldn't advocate doing it as an older person unless you wanted to become a professional physicist for two reasons. Number one, there are other ways to learn physics than to actually enter a PhD program. It is a way, but these days, with so many things online, so many books and so many resources, there are other ways to actually learn that stuff, especially if you're already established in some kind of career. And the other one is PhD programs are set up, like it or not, to train future physicists, to train you to get a job doing physics as a professional. And if that's not what you want to do, there will be many, many frustrations that you have because you're being forced to do things for certain reasons that just don't apply to you. So you'll get something out of it if you ended up doing it, but I wouldn't necessarily advocate it if that's not where you wanted to go.

1:45:34.5 SC: Taylor Gray says, can you elaborate why entanglement can't be summed up as simply being the state of the entire quantum field? As I understand it, there is an electron field that permeates all of space. Why can't we simply say that if we determine the spin of electron A, then we know the spin of electron B, because that is the state of the quantum field. Why does there have to be this spooky action at a distance? I guess what I'm trying to ask is why can't we just accept that entire quantum field can be entangled?

1:46:02.8 SC: Well, it is entangled. Entire quantum fields are entangled all the time, even in the vacuum, even in empty space, in quantum field theory, the value of a quantum field at one location in space is typically highly entangled with values of it nearby. Particles are different things. Particles are specific kinds of features in the quantum fields. Certain kinds of vibrations in the quantum field. And I can easily imagine a vibration in the quantum field near one location in space, and a vibration in the quantum field in a completely other location of space, and these two vibrations may or may not be entangled with each other. They represent two separate particles. So it's not that you can't say the entire quantum field is entangled, it's that that's not what you want to say. That's not what is actually describing the field when it is vibrating in the way that represents a collection of particles. You need to say something more. Just knowing the spin of electron in one position of the universe doesn't necessarily tell you anything else at all about electrons elsewhere in the universe. You might learn something if you separately know that they're entangled in a certain way, but they might not be in a perfectly general configuration.

1:47:14.2 SC: BG167 says, is the cosmic microwave background present at every point in space, and will it remain to be present everywhere in the universe?

1:47:22.6 SC: My uneducated guess is the answer depends on whether the universe is finite or not. Well, let's ignore the finiteness of the universe because we certainly have a finiteness of the observable universe, and the universe outside may or may not continue on forever. And if it does continue on forever, it may or may not continue to look the same, or it may look very, very different. So I have no idea what to say about that. Within the observable universe, again, in our best model of cosmology, yes, the CMB is present at every point in space, and what happens is it will in some sense remain that way forever, but it will dilute away. Individual photons get stretched along with the expansion of the universe, so they become redshifted in lower energy, and the number density of photons goes down as space expands. So in any one point in space, the probability of detecting a photon will go down, and eventually the photons become so low energy that they're essentially not there at all. For all intents and purposes, they're indistinguishable from non-existing. So for all intents and purposes, for all practical purposes, space will eventually completely empty out, but that's gonna take a very, very long time.

1:48:31.6 SC: Anonymous says, I was listening to Robinson's podcast and in an interview, David Builes, I don't know how to pronounce the name, B-U-I-L-E-S mentioned this, the following argument in favor of Presentist view of time. The fact that the laws of nature seem to be Markovian in the sense that the next state of the system is predicted wholly by the current state seems natural if the current time is the only thing that exists. The Eternalist view, on the other hand, lacks a similar reason for the Markovian state of affairs. I thought this was intriguing, but I don't know enough to see if it's convincing. Do you have any thoughts on this?

1:49:04.7 SC: Yeah. My thoughts may or may not be convincing. I heartily recognize that right from the start. There is a difference of attitude that different people have toward the laws of physics and the role that they play. We've talked about humeanism versus anti-humeanism, and it's part of a bigger set of questions about what you consider to be sort of natural or explicable or obvious or on the contrary, something that demands a better explanation. Like there are some people like David Albert, former Mindscape guest, who think that the low entropy of the Big Bang, the past hypothesis, doesn't require an explanation. It is simply a law of physics. It's simply a fact about the universe. And now that we've located that fact and have stated it, there's nothing more to be done.

1:49:50.5 SC: He doesn't see any motivation for coming up with a better cosmological explanation of why the early universe has low entropy. And I don't know what to say about whether or not you should feel that there's a better explanation or not. I can only say what I do feel. When it comes to laws of physics and the Markovian nature of the laws of physics, I think if you are a humean like I am, you can't be surprised that the configuration of the universe is one way or another. And your justification for not being surprised is that there was no preexisting probability that the universe should be one way or the other. So when someone says, I don't understand why there are laws of physics that relate the universe at one time to the universe at the next time, the eternalist answer or the humean answer is, well, why shouldn't there be? Where did you get an idea that it's easier for it to be one way or the other way? I just don't know where those intuitions are supposed to come from.

1:50:57.6 SC: There's intuitions that we get within the universe with the laws of physics taken for granted, but I don't know that we have any right to intuitions about how the organization of the universe should be. It's true that in the humean view, there just are these patterns that describe what happens from moment to moment that we call the laws of physics and you can imagine that they weren't there, but they are there. So they're there. That's all that we need to say.

1:51:22.1 SC: Mario Butay says, I just finished reading your great book, Something Deeply Hidden, and to explain that conservation of energy is preserved when the universe branches. Using an example I found helpful for my understanding of a bowling ball. After branching, there would be two bowling balls, however, with the branch of each multiplied by the weight of their corresponding branch. Within the context of that example, I feel that the concept of the weight of the branch has no physical manifestation as such, each branch would not look different to an observer within them. And looking for one would be just me trying to force the classical view. Is this the right way to understand the branch weight concept?

1:52:00.1 SC: Yes and no. I think that you're completely correct. When you're inside the branch, the weight of the branch that you're in is entirely invisible to you. There's no way of detecting it, no way of knowing it, because as you say, everything in the branch, including yourself, is multiplied by that weight. By weight we mean the amplitude of the wave function squared. So there's no observation you can do to actually figure out what it is. But the idea of the branch weight is super important because things will happen in the future. And that branch weight tells you what you should predict, what you should expect, what probabilities you should assign to different possible outcomes. So it's an important aspect of quantum mechanics going forward in time. But at any one moment, there's no way to measure it. Those two ideas are completely compatible with each other.

1:52:47.8 SC: I'm gonna group two questions together. Laurent Delamere says, do you believe it's worth it for governments to use public money for the colonization of Mars over the next 50 years when we hardly spend enough to limit climate change? People keep saying we can do both, but it doesn't feel that we are as interested into saving the planet now than dreaming about some extraterrestrial future available for very few and not until a very long time from today. And Paul Conti says, given the continued success of robotic space exploration, do you think there's also value in human space exploration? And do you believe that there should eventually be settlements on other worlds in the solar system such as the moon, Mars and asteroids, et cetera, so that human civilization does not have all its eggs in one basket, so to speak?

1:53:28.1 SC: So I think I kind of have a judicious middle position here. If you listen to the episode with Zach and Kelly Weinersmith, it was very clear that actually colonizing Mars is not only hard, but it's way, way harder than you might think. The number of difficulties that we truly have no good strategies for overcoming is intimidating, let's put it that way. It's easy to read a science fiction novel or watch a movie and imagine just flying to Mars and setting up camp. The reality is way, way more harsh than that. As someone said on I think it was blue sky, but I don't know exactly where. If you took the earth and you had a giant thermonuclear war where US and Russia and China were all throwing weapons at each other, and you had some bio-terrorism that unleashed a plague on earth, and you had big climate change that increased the average temperature from what it used to be by five degrees Celsius, the earth after all that, is still much more hospitable to human life than Mars is. Okay?

1:54:35.7 SC: So it's hard to imagine hurting the earth so badly that it becomes less hospitable to human life than Mars for obvious kind of reasons. That's not to say we can't make Mars hospitable to human life, but it's a way of calibrating exactly how hard it would be. So I don't think that we should fantasize about short or medium term escapes to other planets in the solar system. The earth is just right for human beings in all sorts of crucially important ways. At the same time, I think it'd be very, very shortsighted to say, well, we should not do anything until we solve preexisting problems. In many different ways, I'm a believer that you should make different amounts of effort towards all the possible problems that you have all at once. So I think that we can try to address climate change and explore space at the same time.

1:55:26.7 SC: I think we should try to explore space in responsible reasonable ways. We should not daydream about colonization in our lifetimes or anything like that, but we can make progress. We can learn, we can try things out. We can see where it goes, see what the obstacles are, see how to improve things, and eventually maybe sometime in the future things will be different. Well, it's useful to those people, our future descendants, if we lay some of that groundwork now. And I don't think that we should ever have a policy that you should only pick the single most important problem and focus everything on that. I think that's generally not a very good way of running a world.

1:56:04.8 SC: Qubit says, in your approach of space from Hilbert space, you choose time to be fundamental by starting with the Schrodinger equation. However, the Wheeler-Dewitt equation could in a similar way lead to space time from Hilbert space. Can you give the sales pitch for both choices? Why treat time fundamentally different from space?

1:56:23.4 SC: Well, we certainly don't know what the right approach is, okay? So I'm not saying that that's been figured out. I'm all in favor of different people pursuing different approaches. We chose to start with the Schrodinger equation because that's a pretty good equation to start with. You have to start somewhere, and any place you start is gonna throw out some successes of other starting points. The Wheeler-Dewitt equation for people who don't know, is what you get when you try to straightforwardly quantize general relativity, in particular, general relativity on a closed, compact universe. And what it basically says is, instead of the Schrodinger equation, HΨ=ID by dtΨ, which says, the energy contained in the quantum state tells you how fast it's changing with time. The Wheeler-Dewitt equation just says HΨ=0. That is to say the quantum state in general relativity for a closed universe is not evolving at all.

1:57:24.2 SC: And this leads to what is called the problem of time in canonical quantum gravity, that it's not clear how to recover ordinary notions of time evolution. Plenty of work has been done trying to recover ordinary notions of time evolution. It's usually packaged as the emergence of time in quantum gravity. And good for the folks who've done it. Plenty of interesting ideas have been put forward, but I don't find any of them super duper compelling. Like, I don't think we know the right answer to that particular thing. Either the Wheeler-Dewitt equation is not the way forward, or we need to be better than we are right now about showing how time emerges from it. And I think that time is pretty evident all around me right now. So I think it's at least legitimate to start with time. Most people in quantum gravity start with the Wheeler-Dewitt equation or start with something even worse or even less fundamental, let's put it that way. So I think just starting with the Schrodinger equation, seeing what happens is at least a perfectly legitimate strategy. So let's try it. That's the best I can give you for sales pitch. That's my honest feeling.

1:58:25.6 SC: Adam Small says, if you trained an LLM only on the knowledge that Einstein had right up to the point where he had the idea of general relativity, do you think it's possible that if you asked it to come up with a revolutionary physics theory that it could come up with general relativity? And if so, would that mean it was a genius and it should be able to come up with future revolutionary theories?

1:58:47.1 SC: No, I don't think it would. Again, I say over and over again, no one ever listens to me, but I say it over and over again. An AI could very plausibly be able to do that, but not an LLM. The whole point of LLMs is to take things that have already been said and predict the most likely thing to be said, okay? That they have some ability to sort of interpolate in between things that have already been said, but they're very bad at extrapolating to wildly new ideas. General relativity is the paradigmatic case of a wildly new, out of the blue idea, not something that was built up from preexisting ideas in any straightforward linear fashion. So LLMs are kind of the worst possible thing to imagine trying to use if what you wanna do is discover or suggest hypothesize general relativity. Again, other techniques might work, but I don't think that LLMs are the way to go for that particular use case.

1:59:54.1 SC: Rob Gebbler says, in what sense is a continuous fluid description, a coarse graining of a large number of discrete atoms or molecules? Intuitively it makes sense that if we zoom out of the particles, they will look more and more like a continuous fluid. But mathematically, we go from a finite to an infinite number of degrees of freedom.

2:00:12.5 SC: I hear where you're coming from, Rob. I think it's a very good question. There's a kind of simple mindless answer, which is that even though we talk about the coarse grain fluid as a continuum, and therefore in potentially an infinite number of degrees of freedom. If we were to actually solve the equation on a computer or something like that, we would discretize it. We would take an average of the fluid variables in some tiny region of space, a cubic millimeter or whatever. And then if you did your counting, you would find that the number of variables you're actually tracking in that discreet system is much, much smaller than the number of variables you would have to track if you kept track of all the atoms and molecules. So that's a down to earth practical answer. There's probably, although I haven't thought about it very carefully, also a principled philosophical answer about how even though the values of the fields are potentially infinite in number, the actual number of entities is smaller. You have a field rather than many, many, many particles. Okay? I don't know what that argument would go like, but I can imagine it existing. So I'm just throwing that out there.

2:01:21.3 SC: Julian Voidel says, priority question. I have too many questions, many of them are half baked and you are answering more than enough other interesting ones. So I want to use mine just to say a huge thank you for this podcast. I really enjoy it a lot.

2:01:34.8 SC: That is very sweet, Julian. Thank you very much. In case it's not obvious, I do appreciate the positive feedback. I like it. I get a lot of positive feedback. It makes me happy. I get a lot of negative feedback too. It makes me sad. I am old enough now that I'm used to having both, but they still both affect me. So I appreciate the positive notes there.

2:01:57.4 SC: Derek Stegeman says, priority question. I'm asking this for my 6-year-old child who wants to know after I told him about how black holes are created, how hot is it inside a black hole? I tried to research a useful answer myself, but I found only references to Hawking radiation and other concepts useful to determine a black hole's temperature from an outsider's perspective. But what temperature would a thermometer display after crossing the event horizon and continuing its journey toward the center of the black hole?

2:02:23.5 SC: This is a great question. Perfectly legitimate one. And let's distinguish between two things. You could detect the temperature inside a black hole simply because when you're inside, you still see radiation from outside. The event horizon in the black hole prevents radiation from going from in to out, but just like you can go from out to in, so can radiation. So you will see when you look around you all the stars in the sky, you'll see the cosmic microwave background. You'll see all that stuff and you can detect it. So I presume you don't mean that. I presume you mean let's imagine a hypothetical situation where we can ignore all that stuff and we can carry with us a detector that is sensitive enough to see the analog or precisely the Hawking radiation that is due to the black hole itself, not just coming in from the environment.

2:03:14.9 SC: That's a difficult question. I think I have the answer, believe it or not, you asked me at the right time. So I think I mentioned earlier, I'm finishing this paper with Chris Shalu, a student at Harvard on what Hawking radiation looks like when you fall into a black hole. There's this puzzle because if you're far away, you are supposed to see a thermal bath of particles from the black hole. What Hawking predicts as you fall in, presumably that should blue shift and look like it's higher energy photons or whatever. But as you cross the event horizon, you're supposed to see nothing. 'Cause the principle of equivalence says you don't notice when the event horizon is there. How do you reconcile those two things? And in principle, you could just calculate it, but actually calculating it turns out to be super duper hard.

2:03:58.5 SC: We think we've done it, okay? And the answer is, it's kind of funny. You don't have enough time to see Hawking radiation when you fall across the event horizon because you're gonna fall into the singularity before you have enough time to actually get an accurate temperature measurement. And you might say, well, I work really quickly. But the point is that the Hawking photons are very long wavelength. They're typically, the average Hawking photon has a wavelength that is similar to the short shield radius of the event horizon. And you don't have a lot of time when you fall into the black hole. The bigger the black hole, the more time you have, but also the longer wavelength the Hawking radiation is. So what you can do is you can turn on a detector and you can turn it off so you will have like a little window of time when you're sensitive to photons around you.

2:04:50.1 SC: The problem is, even in Minkowski space, even with a no black hole around it all, if you go through very carefully the physics of a detector, turning it on and turning it off in the vacuum of quantum field theory has a non-zero chance of saying, I've detected a particle. Okay? Unless you really keep it on for infinitely long, you never quite settle down. You've shaken up the detector by turning it on and turning it off again. Can't get rid of that. What you can do is say, okay, I can calculate, I can define an effective temperature, which is if I were not just in Minkowski space, but I was in Minkowski space, not in the vacuum, but in a thermal bath of particles. So I'm in Minkowski with some real temperature that we all agree is the temperature. I can ask in that quantum state, what would happen if I turned on and turned off my detector in a certain way with a certain protocol.

2:05:44.2 SC: And then I can say, if I don't have, if I'm not in Minkowski space, if I'm somewhere else, I can still say, what is the typical response I would get when turning on and turning off the detector in the same way? And what does it correspond to in terms of the temperature in Minkowski space that would give me the same response? I don't know if that made sense, but basically, whatever you're doing, you're falling into a black hole, you're measuring Hawking radiation, et cetera. You're asking yourself, what is the same kind of temperature I would have in Minkowski space to give me the response that I'm getting right here, right now? And the answer is, that number gradually increases as you come closer and closer to the event horizon of the black hole. And in fact, it continues to increase as you go inside, but it is very gradual.

2:06:31.9 SC: It doesn't blow up, it doesn't go to infinity. When you're at the event horizon, it's about twice the temperature that you would measure for the black hole to have when you're infinitely far away from it. So it's a little bit bigger, but it's not hugely bigger. Even as you go into close to the singularity, the effective temperature is a little bit bigger, but it's not too much bigger. So there is a version of Hawking radiation, even when you're inside the black hole but it is not detectable in a full way. It is only sort of analogous to, or related to, or equatable to a kind of temperature you would detect in Minkowski space and we can do that quantitatively.

2:07:12.6 SC: Anonymous says, I'm dealing with a really bad work environment right now. I'm getting a lot of advice based on strengthening my own resilience, sometimes framed as the wiser healthy approach. After all, people you don't get along with will be everywhere. My solution is to look for a new job because that approach actually lets me have and express limits to what I'm okay with and what I don't find acceptable or even healthy to be around every day. It feels unfair to me to call it having a healthy mindset, to ask someone to simply learn to tolerate a thing that is hurting them unless that thing is truly inescapable. Have you ever had someone try to tell you that your reaction or expectations were the issue when you try to deal with a problem? Why do people do that and what's a good way to navigate that?

2:07:55.5 SC: So, in all honesty, this is gonna be one of those questions where I have to say, this is a super good question, completely legitimate question to ask. There's no possible way for me to have enough detailed information about your situation to give you the right answer to it. All we can do is sort of sketch out different possibilities, and you have to try your best to be honest about what the situation is because both extremes are within the realm of possibility. One extreme is your job is fine, it's normal. There's ups and downs, and you're just overly sensitive to it and finding it tough to deal with the downs. The other extreme is, you're bending over backwards to be reasonable. You're trying to be a good person, but you have absolutely unreasonable expectations being put on you or people are just being complete assholes to you. Both of those happen in the real world. I can't judge what is your situation.

2:08:53.6 SC: So if you have done the hard work of trying to be as honest as possible about are you being reasonable? Are your expectations reasonable? Are you able to deal with the inevitable ups and downs of living in any working environment and yet you still are finding that it is intolerable, then the environment's bad and you should move on, that's completely okay. There's no rule you have to put up with too much bullshit in your life. There are practical limitations, like changing jobs is not easy. Changing departments within one job is not easy. I do think after living a long life that I have come to a place in my own life where I place a huge emphasis on having as little as possible of my personal energies put into dealing with assholes. If I can possibly avoid dealing with people who are just bad actors, then I will try to do that. I mean, that sounds like an obvious thing to do. It's not at all obvious, 'cause sometimes bad actors are really valuable. Maybe they're really smart and good collaborators. Maybe they're really powerful and can help you out. Maybe even though they're jerks, they're really knowledgeable about something and you can get something from dealing with them.

2:10:08.3 SC: Maybe they just are the boss in the what would otherwise be your dream job. Sometimes you have to deal with them. But I do think that we are too ready to deal with them. We are too accommodating for people who act that way. And it's perfectly okay to say, no, this is not what I want. You have to be realistic about what the alternatives are, and that's, again, something I don't really know anything about. But if you've done your best to adapt and you find that it is more work or harder on you psychologically than it's worth, then by all means move on.

2:10:45.5 SC: David Maxwell says, American politics has become polarized in a way that Australian politics has managed to avoid despite having relatively similar voting systems. I think a big reason is strong institutions. An electoral commission that is truly independent to avoid gerrymandering and a truly independent nonpartisan high court. But I think more important is mandatory voting. Something you briefly discussed with Andrew Lee from Australia some years back. No matter the candidates, everyone votes, which removes the turnout factor and evens out extremes by compelling the sensible majority to turn up. And while one might expect it to be an explosive issue, it never comes up in public discourse. I'd love to hear your thoughts on the structural factors that determine the success of a democracy beyond its basic design, including mandatory voting.

2:11:30.9 SC: Well, as I said before, on sort of moral or ethical grounds, I'm not in favor of mandatory voting. I would nevertheless be willing to go along with it if the practical benefits were actually shown to outweigh the disadvantages. So I'm open to the possibility. But I don't really have any good way of judging how big those practical benefits are. The number of examples is very small, and there are ways that Australia and the US differ from each other other than the mandatory voting, That's one of them, but there are other ways as well, and it's just very hard to disentangle. This is something that is a job left for a sensible, empirically minded political scientist to tackle.

2:12:13.8 SC: I don't find very convincing the idea that mandatory voting compels the sensible majority to turn up. I don't think majorities are sensible. I think that people who do vote are on average better informed than people who don't vote. So I just find that particular thing a little bit unlikely as the correct explanation. It might be that forcing people to vote decreases polarization, but it might just be that the US wasn't nearly as polarized as we are now 50 years ago. Maybe the timescale for Australia to become polarized is just delayed by 50 years. I don't know. There are various reasons we've talked about in podcast episodes here, why the US has particularly become polarized in recent years. And polarization is not intrinsically bad, although it does make progress difficult in some directions. So I would like to understand it better than I do. I am skeptical the mandatory voting would help, but I'm completely open to really strong empirical evidence that I'm wrong about that.

2:13:22.2 SC: The Ukrainian IT Army asks a priority question. Why is time a one way street and are we truly forever bound by its arrow? What is our best current understanding of the nature and direction of time?

2:13:35.1 SC: I don't know, Ukrainian IT army or making me not very convinced of the competence of the snooping done by the Ukrainian IT Army because I've written a lot about this. I'm just, I kid the Ukrainian IT Army. I wrote a whole book from Eternity To Here, about exactly this question. Why is time a one way street? I think that the hardest thing for people to wrap their minds around is if it weren't for the low entropy of the early universe, there wouldn't be an arrow of time. But there also wouldn't be like life and experience and memory or any of those things. All of those come along with the arrow of time. So the short answer to your question, some of you have heard this before, but the early universe near the Big Bang, 14 billion years ago, was from our macroscopic point of view in a very, very special kind of state. Very, very far from a generic randomly chosen arrangement of the degrees of freedom that make up the universe. We qualify, characterize that state by saying that it was low entropy. It is relatively orderly. It is an element of a relatively small collection of possible micro states of the degrees of freedom in the early universe and as the universe expands and the physical systems within the universe bump into each other and kind of randomly shake each other up, entropy increases.

2:14:58.5 SC: That's the fundamental time asymmetry that we know about. Entropy is increasing. Complex systems like you and me come to be along the way as entropy increases. That's something that I'm doing research on and other people have done research on. And as a consequence of entropy increasing, we have different epistemic access to the past as to the future. There's no future boundary condition or future handle we have on the universe, and therefore we have no memories or records of the future. Whereas the fact that the early universe started with low entropy gives us a way of interpreting artifacts in our current universe as records of the past, whether they're photographs or fossils or history books or memories or whatever. Can we escape it? Can we escape the tyranny of the arrow of time? No. Or let's put it this way, only by dying. The arrow of time is absolutely crucial to biology, to psychology, to how we conceptualize life, the universe and everything. So if there weren't an arrow of time, there'd be no beings sitting around talking about it. So we should be very happy that it is there.

2:16:12.7 SC: DI says, I've been discussing the issue of letting cats roam around indoors with two friends. One is a nurse and the other is a general clean freak. Their rationale against letting cats indoors is that kitties use their paws to cover up their waist, and then they walk all over the owner and the house. Yes, kitties lick themselves often and their saliva supposedly has some disinfecting properties, but you cannot be sure the kitty is always adequately sanitized. As a devoted cat owner, what's your take on this?

2:16:41.5 SC: Well, as you might not be surprised to hear, I am entirely unconvinced by this worry. This seems much more like a psychological worry than an empirically informed, legitimate concern. Whenever people point to ways in which our environments are dirty or we're not doing the right cleansing rituals or whatever, or let's shift the topic a little bit. There's a recent spate of articles saying that black plastic kitchen implements are bad. Kitchen implements, like, a ladle or whatever, or a spoon or a spatula. Because they're made out of plastics that often have recycled materials in them, recycled electronic materials in them that can be quite harmful to human beings. So you have your spatula, you're flipping your eggs, and some bad things get from the spatula to your eggs if the spatula is made of black plastic. Okay. That's a very plausible possibility. But the fact that the spatula has something bad in it isn't the important fact. The important fact is, does it have enough bad stuff in it, and does enough of that bad stuff get into your food to actually cause you harm?

2:17:52.5 SC: And that question has gone completely unanswered in these articles. They don't even gesture at answering this. There's all sorts of stuff in the universe. You are dirty. Your air that you're breathing is dirty. Your stuff that you track in when you come inside from going outside is dirty. The wind through your window is dirty. Other human beings are dirty. Cats are dirty. Dogs are dirty. For some definition of the word dirty, the question is, does it rise to the level of being bad for you? And as far as I can see, I see zero evidence that cats are bad for you or lead to diseases. We've had many, many, many hundreds of years of people owning cats and generally living happy healthy lives as far as the cats are concerned. Maybe there's data that says otherwise, but that's what I would need. I would need data that says, living with a cat lowers your life expectancy or lowers your quality of life while you're doing it because of this dirtiness or whatever, rather than just a feeling that they're not licking their paws clean enough.

2:18:58.0 SC: TK says, "Were you ever into horror movies? And if so, how did your experience change over time as you gained more knowledge about the physical world?" I was never really into horror movies specifically. That was never really my thing. I didn't avoid them, but I didn't seek them out either. So I don't have any deep answers for this one. But I can say that I was super into like parapsychology and ghost stories and things like that when I was a young kid. I was 100% ready to believe in ESP and cryptids or whatever. And then gradually, yeah, like you look at the evidence and you go, oh yeah, the evidence for that is pretty shaky. And by the way, there's something called Laws of physics that gets in the way. So it was a gradual thing. It was not a quick phase transition, but I did eventually change my views about that stuff. Moshe Feder says, "I'm old enough to remember the first public demonstrations of holography in the 1960s and '70s. And I have a good grasp of how a sheet of film can record a wavefront as an interference pattern that can then be used to reconstruct a virtual three-dimensional scene. The scene appears behind the film.

2:20:06.3 SC: Nothing is projected. But that hasn't been much help to me in understanding how information on a hypothetical two-dimensional surface at an imaginary boundary at the edge of the universe can in some sense project all of the universe's contents into a tangible, solid, three-dimensional reality throughout the universe's volume. Even if there's a mechanism to do that, how can the information across the unimaginably large two-dimensional surface stay in sync with the constantly changing contents of the volume's interior without violating the light speed limit on the transmission of information? Can you explain the holographic principle hypothesis in a way that can give me a better intuitive feel for it?"

2:20:46.0 SC: Maybe I can, maybe I can't. I'm gonna suspect that maybe I can't. I suspect, Moshe, that the problem is that you understand good old holography too well. The holographic principle in quantum gravity, the word holographic is just a colorful image. It's not supposed to be taken literally. There's not literally a hologram that someone shines light on to project the bulk of anti-de Sitter space or something like that. It's rather a what is called a duality in theoretical physics. It is a map between two theories saying that the content of one theory, both in terms of the states of that theory and the dynamical rules governing how the states change with time, are interchangeable, are equivalent to each other. You can exchange one set of states for another, and you can exchange the dynamics for each other. Those maps might not be complete, like maybe there's some states on one side that don't have equivalents on the other side, and that's an ongoing thing that people are trying to understand better, but that's the basic idea. And yes, there is some intuitive resistance that we have to that, 'cause if you have, let's say, three-dimensional space, and someone is telling you that everything that is going on in three-dimensional space is equivalently represented by something going on on a two-dimensional boundary, there just doesn't seem to be enough room for all that to happen.

2:22:13.0 SC: The hand-waving reconciliation there is that, yes, there's three-dimensional space, but not everything you might imagine that could happen in that three-dimensional space is actually possible. The things that can happen in the three-dimensional space are restricted. They're restricted by the fact that they have to be representable on the two-dimensional boundary. I will just give you one very, very cheap example of this, but maybe it'll give you the idea. In a region of space, if it weren't for gravity, okay, 'cause think about in the AdS/CFT example, that's the best understood example of holography. You have anti-de Sitter space in D spatial dimensions, so that's a theory with gravity, a cosmological theory. Then you have the boundary theory in D-1 spatial dimensions without gravity. Okay, so one side of the duality has gravity, the other side does not. In a theory without gravity, the following is true. If I take a region of space and there's a photon in there or whatever, and I say, how energetic can the photon be? Well, the answer is as energetic as it wants to be. I can get a very, very energetic photon. In quantum field theory, I describe photons of arbitrarily high energy, no problem at all. But in the bulk theory, in the theory with one more dimension if I take a region of that higher dimensional space and say how energetic can I have a photon inside a box, there is a limit.

2:23:41.3 SC: The limit comes from the fact that if I make the photon too energetic, I make a black hole. So once there is gravity in a theory, fewer things can happen in space, in regions of space than you might otherwise have thought, because some of the things you might have thought can happen instead lead to black holes. So that should at least nudge you in the direction of thinking that if we went through everything very, very carefully, there might be an alignment between the set of things that can happen in one higher dimension, but with gravity, and in one lower dimension without gravity. Rue Phillips asks, "This is the last AMA before the 2024 US presidential election. On this topic, my question is, we regularly see celebrities who have large followings, like Taylor Swift or Elon Musk, publicly endorse a candidate to try and influence their followers.

2:24:32.1 SC: We also have seen public endorsements from institutions like Scientific American endorsing Kamala Harris, and other institutions like the Washington Post and LA Times publicly decide not to endorse a candidate. What are your views on when it is reasonable to publicly endorse a candidate and when, or what kinds of institutions should always remain silent or neutral?" Yeah, this is a good question because something like Scientific American or Nature, I think also endorsed, is different than something like the New York Times or the Washington Post, which are supposed to be general purpose newspapers with opinion sections and the whole bit. For celebrities, I have zero worries or problems with any celebrity endorsing at any time.

2:25:13.0 SC: They're just individual human beings. I have zero worries about scientists endorsing or movie stars endorsing or athletes endorsing. The question is, do you wanna listen to them. Do you wanna actually weigh their endorsement in any non-trivial way? That's up to the recipient of the endorsement. And that is to say, not the person who's getting endorsed, but the person who's hearing about the endorsement. They can decide how much effort they wanna put into that. I don't think that celebrity endorsements mean a lot. If they did, Kamala Harris would be up for a landslide victory here in 2024. We'll have to see about that. I don't even think that newspapers and things like that, news magazines, mean a lot about endorsements. They might mean a lot for local races where, honestly, it's hard to know what the issues are, what the candidates are, et cetera. But for national races, just the typical amount of information flowing by is enormous if you're the kind of person who reads newspapers. And if you're not, then the endorsement is not going to reach you very effectively. The interesting question is for institutions, not only Scientific American in nature, but also like what about Johns Hopkins University? Should they endorse a candidate for president? Things that are not general purpose news politics, magazines or newspapers, I suspect that usually they should not. That is my feeling.

2:26:41.3 SC: I think that when someplace like Scientific American. I don't feel strongly about this, so maybe you could talk me out of it. But I think that when someplace like Scientific American endorses a presidential candidate, it comes across as, oh, there are some editors at Scientific American who have strong political feelings, and they're letting their political feelings be felt in their endorsements. Not because the justification they give is wrong. I'm completely on board with the justification that certain candidates, we all know who they are are heavily anti-intellectual, anti-science, bad for the planet, et cetera just for the reason that it's not the job of Nature or Scientific American to make those judgments. I'd be perfectly happy with Scientific American or Nature writing an article, a news article, about how bad certain policies might be for science or for the environment or whatever, then let people draw their own conclusions about what that means for who they want to vote for ultimately.

2:27:40.1 SC: I vaguely remember seeing an actual study, like I'm a big believer, as you might have noticed in the previous answers, of like running the data, getting the numbers in and actually seeing what happens rather than going by our vibes. I vaguely remember seeing a study saying that when Nature or Scientific American, when a science magazine endorses a political candidate, what happens is not that the number of supporters of the political candidate goes up but that the trust in the magazine goes down because they're doing something that is outside their bailiwick.

2:28:13.0 SC: Obviously, people with podcasts can endorse whoever they want, and I don't even need to say out loud who I'm endorsing in this particular election. Josh Dobbin says, "The conversation with Doyne Farmer was fascinating and felt like the kind of simple Eureka of a Kepler refining Copernicus, but for economics. Not perfect circles, but circular elliptical orbits, removing the kludgy epicycles needed to keep the idea of perfect circles as a foundational given. Obviously, if he is correct, eventually his results will have to force a paradigmatic shift in economics, just because they'll accrue an undeniable weight of success. My question is, how long does science these days tend to accept new, non-quacky paradigm shifts that prove themselves? Kepler never saw the adoption of his ideas in his lifetime.

2:29:00.4 SC: Are things much the same now with the inertia of dogma and academia, or can we expect if he's correct to see a move toward his approach in the coming decade?" This is a very good question, and I think that it depends on a lot. It depends on many things, but the one thing that is sort of worth highlighting is how constrained by empirical data a different field of investigation actually is. The less constrained by data you are, the harder it is to change people's minds about things because the data speaks louder than anything else. The paradigmatic case of a whole huge field changing its mind very, very rapidly was over the course of the first three decades of the 20th century, all of physics changed from classical mechanics to quantum mechanics.

2:29:49.3 SC: And that might not seem like very long, three decades, but really like it sped up. It's sort of like 1900, 1905, 1908, little tiny things that were kind of hinting. And then in the mid '20s, boom, we're suddenly changing our entire view of the nature of reality. And it happened very, very quickly and was accepted very, very quickly. There were not aside from some outliers, there were not many influential physics departments that continued to say classical mechanics is the better way to go than quantum mechanics. It takes a few years, but people do catch on relatively quickly. The reason is because you had no choice, because the data are there. Atoms are stable. Blackbody radiation is what it is. You can see the spectral lines, et cetera. What are you gonna do? How are you gonna resist? In something like economics, the connection between ideas and data is much, much looser.

2:30:43.5 SC: Ultimately, you want to be governed by the data, just like you do in physics. But there are so many things going on for exactly the reasons that don't highlights. There's a lot of chaos and complexity, et cetera. So it's harder to extract absolutely clear lessons from the data in economics than it is in physics. So I do think that you're right, that eventually, if his approach is right, it will have to win out. And the reason it will win out is because it just keeps doing better at fitting the data that will eventually win. But I can't tell you how long it will take. It might take a very long time, depending on exactly how well they can do at fitting that data in a convincing way.

2:31:24.9 SC: Sandro Stucchi says, "What makes for a good environment in quantum decoherence? Can anything outside the system being measured play the role of the environment? Is a simple photon enough to cause decoherence? Or does the environment have to resemble a heat bath with certain statistical properties?" I think what we have to remember here is that decoherence is a higher level emergent phenomenon. Decoherence is an approximate kind of thing in exactly the same way that the second law becomes approximate in statistical mechanics. It becomes overwhelmingly probable, but still there's the possibility of something going wrong. The reason why decoherence works is because many, many, many degrees of freedom in the environment become correlated, entangled, in fact, with the quantum system that you're measuring due to some sort of macroscopic amplification process, like the pointer on an experiment moving from one place to another or a cat running around in a superposition of awake and asleep. But does it happen with one photon? Well, it happens a little bit with one photon. It happens more with 10 photons and more than that with Avogadro's number of photons. So it's not a hard and fast thing. In fact, you can trip yourself up by saying, okay, let's count one photon as causing decoherence. But then recognizing that if the information that we entangled with was just entangled with one photon, maybe we can undo it.

2:32:52.5 SC: We can store that photon and then undo the purported decoherence in which case it's not really decoherence. You shouldn't have counted it that way in the first place. So you just have to keep in mind what are the purposes for which you are talking about decoherence in the first place. Philip Malenkowski says, "Last month was a Nobel Prize announcement month. What do you think about the physics prize? It caused quite a divide. Contributions were certainly valuable. This is the prize that was given to Hopfield and Hinton for machine learning advances. Contributions were certainly valuable but does a theory of neural network classifies physics what top do you think deserves future mobile prizes?" I was fine with it, honestly. I had some fun on social media kidding about it, saying that obviously all of computer science is now a subset of physics. That's fine. But the Nobel Prize is a weird thing. Like it shouldn't be that big a deal, the Nobel Prize. It's good to have a prize.

2:33:49.9 SC: It's good to recognize good work. It's good to bring visibility in the public to scientific advances that might not otherwise get visibility. But it's just some people in a room making a decision about something. And furthermore, the rules were laid down about which prizes to give, et cetera, over 100 years ago. They no longer, if they ever did, map on very accurately to how science is actually done. So I'm happy with a fairly expansive view of what counts as physics when these prizes are given out. I have no problem with that. I do think that there's all sorts of things in more traditional physics that are still very, very deserving of Nobel Prizes. An obvious one is in quantum mechanics and quantum computation and information.

2:34:36.2 SC: Peter Shor for the Shor algorithm for factoring numbers. David Deutsch, former Mindscape guest, did foundational work in defining quantum computers, quantum Turing machines, simple algorithms back in the early days. Charlie Bennett for quantum cryptography, quantum teleportation, things like that. And you would even arguably give something to, give one to someone like Wojciech Zurek for decoherence. But there's other people who might wanna win that too, so that's a trickier thing. Who is going to win it is always a good question. We have gotten enormous mileage in cosmology lately from observations of the cosmic microwave background to anisotropies. You could argue someone should win for that. Interestingly, my Johns Hopkins colleague, who is also named Charles Bennett, but has nothing to do with the Charlie Bennett of quantum computing fame. Charles Bennett of CMB anisotropy fame was one of the big names in the WMAP experiment.

2:35:35.3 SC: I think he would be a good candidate, for example, for CMB anisotropies, et cetera. I'm still a little sad that no one has won the Nobel Prize for discovering the Higgs Boson. A Nobel was given for the idea, the theoretical picture of the Higgs Boson was given to Higgs and François Englert. But the experimenters didn't get one, in part for the obvious reason that there's thousands of them. And it's hard to know who. I did suggest when I wrote The Particle at the End of the Universe that Lynn Evans, who was an experimentalist who really helped guide and plan the building of the Large Hadron Collider in the first place, would be a natural candidate.

2:36:13.9 SC: I don't know if anyone was listening there, but I think that would be great if that happened. And then there's more out there ideas. What about Jeffrey West, who is a former Mindscape guest who's done this wonderful work on allometric scaling? Or what about other work in biophysics by people like William Bialek or someone. I don't even know who the right ones would be, but I think biophysics is a very obvious area for future Nobel Prizes. So what about Christopher Jarzynski and Gavin Crooks for fluctuation theorems? The Jarzynski equality and the Crooks relation have completely revolutionized non-equilibrium statistical mechanics. I think that I would love it for them to win the Nobel Prize. So yeah, there's plenty of good traditional physics that could win the Nobel Prize as well. I'm looking forward to the decisions they make going forward. David Summers says, "How curious are you about the unobservable universe? On the one hand, someone scientifically minded might say, well, we'll never have any data, so no point thinking about it.

2:37:14.1 SC: On the other hand, it's unfathomably enormous, dwarfing the observable universe and seems like a cool mystery. Or does it? Is there any reason to think anything interesting is happening there that we can't already observe in our local vicinity?" I think that I get why people say, well, I can't observe it, therefore I don't care. But I think that there is a loophole in that argument. Namely, if our best explanation for what we do observe in our universe has implications for the universe we don't observe, then we should accept those implications with high credence.

2:37:49.1 SC: Obviously, the super obvious example of this is the many worlds interpretation of quantum mechanics. I try to tell people the other worlds are not the point. I don't care about the other worlds, but the theory predicts they're there and the theory is the best explanation for the data that we have in our world. Therefore I accept them. If you wanna sort of erase them somehow you have to change the theory. I'm happy to let you change the theory, but I don't know why you're doing it. And generally when you start changing the theory you start messing it up. In cosmology, of course, there's the possibility of anthropic explanations for things we observe about our observable universe. That's a lot hazier because the underlying mechanisms to make the cosmological multiverse are much less well-established than quantum mechanics in the Schrodinger equation. But it's, I think, perfectly valid to say something like the cosmological constant in our universe is not a mystery because the value that we observe for it is what you would expect to observe given the anthropic principle in a multiverse. That may or may not be correct. I'm not saying that is the correct explanation or even that the logic behind that explanation is correct, but it's a perfectly plausible explanation to consider even though it invokes parts of the universe that we don't observe.

2:39:04.4 SC: Vicki Ramsey says, "You've long since said that you believe more work is necessary in the foundations of quantum mechanics to achieve a fuller understanding of our universe. Planck's solution to the ultraviolet catastrophe is the ultimate foundations of the foundations of quantum mechanics. The quantum mechanical viewpoint would not have emerged but for the creation of Planck's H constant as a means of solving the ultraviolet catastrophe. As a choice of foundations of quantum mechanics project, do you think it a worthwhile venture for a person to attempt to derive a classical solution to the ultraviolet catastrophe as an alternative to Planck's solution." It's a free country, it's a free world, you're welcome to try whatever you want. Anyone's welcome to try whatever they want, but no, that particular strategy does not seem super promising to me. When I say that we need to understand the foundations of quantum mechanics, I'm not saying that we need to change quantum mechanics into something else. Quantum mechanics is super duper successful. It's just amazingly successful considering the wide variety of circumstances it's been applied to. I can imagine deeper theories that are different from each other and could compete to map onto quantum mechanics in some regime. That's more or less what you're doing with Everett versus pilot waves versus objective collapse models, et cetera. But at the end of the day those are all quantum mechanics.

2:40:26.5 SC: You need quantum mechanics to explain things like the double slit experiment where the wave function interferes with itself. That means that the wave function is a physical thing. It's not just a probability distribution. Probability distributions just add. They don't interfere with themselves. And once you have the wave function as a physical thing and the fact that observations don't show you the whole wave function, you basically have quantum mechanics. So you can fiddle with it around the edges but I don't think replacing it with something classical is an interesting way forward. Cooper says, "Do you know of any factors that drive the American electorate toward being so evenly tied? Is it just a strange accident of demographics of all the possible breakdowns between donkeys and elephants, perfectly tied seems like a special and therefore unlikely scenario, kind of like how a cosmological constant of zero would demand explanation?" I completely agree with the implication here, with the attitude, I should say, that it does demand explanation. Here in the US, for those of you who are not American listeners, the electorate is remarkably evenly divided between the Republican Party and the Democratic Party. And what's weird about that is a combination of things. One is that there's a sense in which it shouldn't be surprising.

2:41:43.2 SC: There is, as I mentioned on the podcast before, the Median voter theorem. If you think of voters just as spread out on one axis, on a one-dimensional plot, then two candidates, if you have a two candidate race, they will try to be as close to the middle as possible to catch that median voter and then everyone to either left or right of them. And therefore, you should expect both parties to actually be very similar to each other and the electorate to be evenly divided between them. So on the one hand, you have a theory that predicts that the electorate should be evenly divided. But clearly, very, very obviously, the assumptions of that theorem are not relevant to the real world. We do not have two parties which are almost exactly the same as each other. We do not have two candidates trying their best to be just the median voter in their opinions. We have pretty wildly different candidates. And yet the electorate is still more or less evenly divided. And so I do think there should be some structural explanations for this. And I've heard some people kind of guess at them or hypothesize. But I have no good ideas. I don't actually see what the mechanism here that is going on. It is true that due to the structure of the American system where you have a president and then you have separately a legislature, so it's not like a parliamentary system where the prime minister is part of the legislature.

2:43:10.3 SC: There's separate things in the US that does naturally lead to kind of a two-party system. And if you go back historically, it's always been two parties, roughly speaking. There have been attempts to make third parties. They never really succeed. And so it's always been almost 50-50 between two parties. But the degree to which it's 50-50 is still surprising to me. I still think that there should be better explanations for it than there are. I think that's a good open problem as far as I know. Again, probably a real political scientist could give you a much more interesting answer. Darren Ho says, "On last month's AMA, you mentioned that consciousness is not axiomatic and therefore does not succumb to Gödel's incompleteness theorems. But what about the laws of physics themselves? Aren't the laws of physics technically axiomatic and therefore either inconsistent among themselves or then that there is something true about our universe that is fundamentally unknowable or unprovable?" No, not at all. I think this is a semi-common misconception. The idea of an axiomatic formal system and what you can prove or not prove in it is a very, very specific idea, and it's just not what the laws of physics do. The laws of physics are a procedure.

2:44:20.3 SC: Let's just take a very simple idea of what the laws of physics do. They take the state of the universe at one moment of time and tell you what its derivative is, so they tell you what it's gonna be the next moment of time. So that's just an algorithm. That's a machine that says you give me the state now, I give you the state the next minute. That's very, very different than an axiomatic formal system. An axiomatic formal system doesn't chug forward in time. It says it's supposed to take the space of all propositions that are well-formed within the system and then divide them into, given Gödel's theorem, divide them into ones I can prove because they're true, ones I can prove that are false, and ones that I cannot either prove or disprove. That's just a different thing. And I don't know how to express this. It's just a whole different kind of operation. Proving theorems is not time evolution.

2:45:13.2 SC: It's just a different thing that you're trying to do with your equations. So the laws of physics take a state and just move it forward in time, and there's no obstacle to just keeping it moving forward in time. The Gödel's theorem just doesn't apply. It just isn't really relevant there. So there might be ways of deriving the laws of physics from some axioms or something like that. But who cares? You're only looking for those particular laws you're trying to derive. The fact that those axioms may have other statements that they can either prove or disprove is of no relevance to the fact that the laws of physics are chugging the universe forward in time.

2:45:55.0 SC: Blake Suer says, "I just finished listening to your interview with Adi Pras. I loved it. More Complexity theory, please. In the interview, Dr. Pras states that life's purpose is to persist. While this seems to be true, it seems to me that this is more likely an emergent phenomenon due to the second law. I always ask myself, why would nature bother with generating complexity? The answer seems most likely to me, that seems most likely to me, is that it's just nature increasing local order in the service of greater global entropy production, entropy gradient dissipation. What are your thoughts on this?" Two thoughts here. One is that this idea, there is an idea out there that is just wrong, that increasing entropy is somehow connected with gradient dissipation. That idea is just not right. It's pretty obviously not right. If you look at the early universe, there were very few gradients. It was very, very smooth. The gradients in the sense of things changing from place to place increased over time as the universe expanded. So there's a well formulated rigorous thing, which is the second law of thermodynamics. Then there's the kind of an informal observation that in certain circumstances that maps on to smoothing things out, which is fine. But in other circumstances, it does not map on to smoothing things out. So you shouldn't confuse the two ideas.

2:47:15.4 SC: Okay, the second thing is there is no law that says entropy has to increase as fast as possible. I don't even know what that means. I don't even know how fast it might be possible for entropy to increase. So, again, sometimes we sort of joke about it or we're loose and we have metaphorical language where we say, oh, this happened because it would increase entropy faster or something like that. But there's no law of nature like that, at least not that I know of. So I think it's true that sometimes you get complex systems that do indeed generate a lot of entropy. They burn through free energy. None of them is as good at it as the sun. The sun is really good at generating entropy, and it's not a very complex system. So I don't see the very close connection between complexity and increasing entropy.

2:48:07.3 SC: I think the way to think of it is something different, that along the way, from low entropy to high entropy, the space of all possible trajectories of physical systems in different regions of space have a chance of going through a region of complexity. And then they, as Adi Pras says, they can get into a kind of quasi-stable state along the way. It's the stability that matters here. It's the fact that once you're there, you stay there. This is also what we saw in Blaise Aguera Arcas's computational reproduction thing where you have a random computer program and you let it run and eventually it gets located in an attractor regime where it is self-reproducing and computational.

2:48:52.8 SC: But what matters there is the stability. There's no entropy at all. But it takes over. It sort of is robust against interventions from the environment. And so I think that all these ideas are related and it's interesting to think about them, but I don't think that they're figured out yet and I don't think it's anything nearly as simple as the universe is just trying its best to increase its entropy. Jonathan Laban says, "I have read that tiny primordial black holes would not be expected to result in significant observable interaction with normal matter and so are considered a candidate for explaining the dark matter. However, these explanations tend to gloss over the self-interaction among a group of black holes which must also be low to be a good dark matter candidate. Is it just that the cross-section of each individual would be so tiny that the rate of direct interaction would be rare despite them being black holes?" Yes, that is exactly it. Well, plus the fact that gravity is a pretty weak force.

2:49:51.9 SC: Indeed, a bunch of very, very tiny primordial black holes would interact more rarely than a bunch of weakly interacting massive particles would. If the black holes are bigger, then it's easier for them to interact. But if they're bigger, they're also much more dilute. You need fewer of them to make up the dark matter. Indeed, black holes are the densest that you can pack energy into a small region of space. So putting energy into black holes makes them kind of as small as they can be, as non-interacting as they can possibly be. It's hard to imagine something interacting even less than a certain amount of mass distributed in the form of black holes.

2:50:31.2 SC: Of course there are details there. We're glossing over a bunch of details. And black holes do have special properties, because they're so small. Once you get very close to them, the interactions can be important. It's just that they tend to be far away from each other. By the way, if primordial black holes are the dark matter, it's very possible, even likely, that they're like one solar mass each or something like that. If you get very, very tiny primordial black holes, they tend to evaporate. And then there's different windows of plausibility that are ruled out by different kinds of observational data.

2:51:05.7 SC: If I recall correctly, it's about a solar mass or maybe a Jupiter mass or something like that that is still allowed for primordial black holes. So it's not like they're elementary particle-sized. But anyway, I was gonna say that because they're sort of astrophysically-sized, these primordial black holes. They do interact with the world around them. They do interact with the gas and dust and stars and things like that. And there can be sort of nonlinearities that build up and are interesting. In fact, Priya Natarajan, who was a previous Mindscape guest, has written some interesting papers on how the dynamics of primordial black holes can maybe help explain the existence of supermassive black holes or the early galaxy formation or things like that. So I think that it's a very plausible... Well, If you have a way of making primordial black holes, which I think is actually very difficult, people have ideas about it.

2:52:00.0 SC: They seem a little kludgy to me personally. But once you make them, I think that they are a kind of interesting dark matter candidate. Samir says, "Listening to your recent podcast with Doyne Farmer, which is truly excellent, I was captivated by your comment about classical theories describing equilibria versus recent theories bringing transient perturbative dynamics into play. I'd love to hear more in-depth explanation about those comments. I would also like to know if emergent theories imply equilibrium and vice versa." Yeah, I would like to know that too and this is tough stuff. There's things you can show, and there's things you would like to show, and there's a whole bunch of things in between. It is a feature of economies that they're not perfectly stable.

2:52:48.4 SC: You might have prices that are stable, relatively stable over a relatively long period of time. But two things are happening. One is there are slow kind of secular variations like inflation. Prices do creep up over time and there's actually good arguments that that's a good thing. As long as the inflation is not too much and doesn't ruin your planning, having a little bit of inflation is actually a good thing if you want your economy to be growing at all. And if you want your economy to be not growing. I know there's a fantasy out there in some circles. There's Don't let the economy grow. Don't let there be any inflation. Just have everything constant.

2:53:23.9 SC: But there the lack of stability becomes very important and you tend to crash. It's very difficult. It's more difficult to maintain a stable economy at a constant rate of prices and wages and things like that than it is to maintain a stable economy at a slowly but controlled growth kind of phase. And the other thing besides these gradual changes, there are sudden changes. There are shocks up and down or maybe even like business cycles over a few years at a time. And you would like to explain those without well, you would like to explain them and you would also like to prevent them from growing out of control.

2:54:02.3 SC: And my impression from talking to Doyne is that that last thing is not very well understood within classical economic theories. So there's a couple things going on. One is there might just be oscillations that are okay. There might just be cycles that are part of the natural evolution of the systems, and they're inevitable, and you build them in and just try to understand them, and that's okay. That's definitely a conceptual possibility. The other is that these variations, either slow or fast, are unstable and can grow out of control, and what actually happens is that we intervene in the economy. You don't actually just let economies go without any intervention just for the sake of doing an experiment and collecting data because people's livelihoods depend on the economy. So the central banks or whatever step in and change the money supply and change the interest rates in the interest of keeping things relatively stable.

2:55:00.3 SC: That makes it hard to actually understand the intrinsic stability or instability of the system. So the example that Doyne uses and I think he mentioned it in the podcast, but I forget. But there's videos where he's doing it. If you have a long stick, like a meter stick or something like that, you can hold it vertically in the palm of your hand so that you're not holding it, not gripping the stick. You're just putting it in your palm and putting it upward. And it is naturally unstable. If you were perfectly solid and had it exactly vertically, it would stay there. But in the real world, it wiggles. But it's actually quite easy to sort of move your hand back and forth to stabilize the meter stick as long as long enough. It's easier to stabilize a meter stick than to stabilize a pencil. The length actually helps you. So there is a conjecture that maybe you can imagine sort of automatic wiggles. Like putting the wiggles in rather than just imagining putting them in because there is something you want to stabilize, but just putting them in automatically as a feature. Maybe that would lead to stability where it wouldn't otherwise exist. This is just entirely a wild conjecture on my part. I know there are physical systems with that property. I have no idea whether it would really apply to economies or not. And I don't know if economists know either. I'm not actually pointing to real models. I'm just speculating out of my hat.

2:56:27.4 SC: Kyle Cabasares says, "Halloween-themed physics question here. I've heard about both good ghosts and bad ghosts in the context of quantum field theory and that they have something to do with gauge invariance and degrees of freedom. Can you be a ghost buster and briefly explain their importance in QFT and what constitutes a good versus bad ghost?" Yeah, roughly speaking, if you have a quantum field. So let's say you have a scalar field, that means you just have a number at every point in space. That's what the field is, as opposed to vector fields, tensor fields, et cetera. Then you're going to write down the energy of the field. There will be a kinetic energy, how much it's changing in time, a gradient energy, how much it's changing in space. Those two things are typically fixed in terms of each other because of relativity, saying that space and time are related. So we just say the kinetic energy usually when we mean both the kinetic and the gradient energy.

2:57:22.6 SC: And then there's potential energy due to the value of the field itself, rather than its changing over space or time. And then there can be interactions with other kinds of fields. So that's a pretty typical thing and the first thing you're gonna do is write down an equation so that the energy is positive. If you let the energy get negative, arbitrarily negative, then you get, guess what? An instability, just like we were talking about. You would tend to make a whole bunch of negative energy particles as well as positive energy particles. And that's, you can make an infinite number of that combination.

2:57:58.3 SC: And so you would not have a stable vacuum state. That would be bad for all sorts of reasons. These negative energy particles are ghosts. There's one name for them. There's different ways of dealing with them in quantum field theory. So I'm giving you the simplest way of thinking about it. Negative energy particles are ghosts. They come from fields that have negative kinetic energies or something like that. And you might think, well, okay, it's not that hard to get rid of the ghosts. Just make sure your kinetic energies are positive. The problem comes when you have something more complicated than a scalar field. When you have a vector field, for example, a four-vector field, because we're in four dimensions of space-time, so you have a time-like component and three different space-like components for your vector. It turns out, at the very basic level, if you want to create a simple kinetic energy for a vector field, it's hard to make both the time-like part and the space-like part be positive energy. They tend to have opposite energies. So it tends to be that one of them is a ghost and one of them is not. And the solution is to pick a kinetic energy that only turns on one of those kinds of fields and not the other. Typically, if you're going to all the trouble of having a vector field, you might as well have the spatial vector be turned on and you squash the time-like part of the field because that would have been a ghost.

2:59:21.1 SC: And gauge invariance helps you do that. And enforcing gauge invariance sort of naturally gives you only the real well-behaved part of the field, not the ghost-like part of the field. So that's an example of the kind of ghost you would like to avoid in quantum field theory. You don't wanna write down a quantum field theory that naturally has negative energy particles. But then there is an extra complication. If you have gauge theories. So if you have theories like electromagnetism, electromagnetism actually is an avoidable problem. But in more complicated gauge theories, non-abelian gauge theories like QCD, which is based on SU3 symmetry group. It's difficult in the process of quantization to deal with the fact that there are different field configurations that look different but are actually physically identical because they're related by a gauge transformation. So you don't want to in a typical way of doing quantum field theory, you do a path integral. You have an action which adds up contributions from... Well, you have an action and then you have an integral over all possible pads that adds up E to the I times the action for that field. This is how Feynman told us to do quantum mechanics. And so you need a way to map out every possible field configuration. And in a Gauge theory, that's a little bit tricky because some field configurations are actually just two copies of the same field configuration because of gauge transformations.

3:00:53.9 SC: And so one way of doing this is actually to... And I'm skipping a lot of steps here. I'm sure that you don't wanna hear all the steps, believe me. But one way of doing this is to add a term to your path integral that basically fixes the gauge, that picks a particular choice of gauge so that you don't have to worry about having too many overcounting the gauge degrees of freedom. And it turns out kind of amazingly enough, that doing this is equivalent to adding some fake ghost fields to your theory. These are the good ghosts that you're referring to. They're usually called Faddeev-Popov ghosts in quantum field theory language. They are ways of thinking about these extra terms that you added to prevent yourself from overcounting the gauge invariance equivalent field configurations that turn up as negative energy or negative probability particles but they never appear in your detector. They only ever appear as virtual particles in the middle deep confinement diagrams. So roughly speaking, if you've read Quanta and Fields, you would be able to figure out that really these fields, these particles, these good ghost particles are kind of a mathematical trick. They're not real particles. They're not actually detectable or anything like that.

3:02:18.4 SC: They only appear on the inside of Feynman diagrams but they're a very useful calculational device for figuring out how scattering works in actual Gauge theories. Brian Gunnison says, "Blaise Aguirre-Yarkas et al wrote a paper on computational life. While reading Sara Imari Walker's latest book, previous Mindscape guest, I began to wonder if life is simply the replication of information. As a computer scientist, I see it as a creation and manipulation of abstractions that interact with reality, CPUs, robots, data, et cetera. My question is, are there any similarities between the nascent computing environment, Babbage, Turing, Torvalds, et cetera, and the physical, chemical, earthly environment four billion years ago, excluding panspermia? Panspermia being the idea that maybe life originated outside the earth and kind of fell on us and we inherited it." I'm sure there are similarities, yes. At that level of asking the question, there are similarities. But there's also huge differences. Anyone who studies the origin of life in detail will emphasize the importance of things like compartmentalization or metabolism. You need free energy to get things going. When you're in a computer simulation, you plug it in. You plug in the computer and your energy comes from there and that input is sort of not evident at the level of the code that you're running.

3:03:44.5 SC: It's evident at the level of the hardware on which you're running the code and that seems separate. In the early Earth, where life was forming, there's no separation of energy inputs and physical stuff doing the computing. So there's a difference as well as a similarity. I think what people would like to be able to do is understand how ordinary chemistry becomes computational at the origin of life, or for that matter was that at the origin of life? It's one of the things that had to happen. One of the things that has to happen for life to start is information starts being processed in a more subtle way than it does in an ordinary chemical reaction. How does that start? And how does that jibe with the metabolic requirements of early life and the reproductive requirements as well as just good old chemical stability and all of those things? This is one of the reasons why the origin of life problem is tricky 'cause there's so many aspects that need to happen at the same time. And it's like how... They probably didn't all just gang up at literally the same time. Probably one started first and then it was borrowed by another one and we don't know the order of these operations.

3:04:58.7 SC: So these ideas of computation and substrates and things like that are important but they are certainly not the entire story. Anonymous says, "What are your Halloween traditions, if any? What kind of candy do you give out and do the cats ever get costumes?" The cats certainly do not get costumes. Oh, my goodness. Our cats are not the kind of little critters that like getting dressed up. Let's put it that way. They have gotten dressed up. They have been to the vet sometimes and they've had things happen to them that necessitated wearing little outfits afterward to protect themselves from licking their wounds. And also when we took them across the country, when we traveled with them, we tried, we experimented with the idea of putting these coats on them that are supposed to calm them down.

3:05:54.0 SC: And finally, of course, we did put, when we did travel, the coats didn't work, but we did put these little harnesses on them that you can attach to a leash so that they couldn't escape. 'Cause when you go through security, you have to take the cat outta the cat carrier and carry it. This is a rule. And so Caliban was fine with this, but Ariel was totally ready to bolt in the airport. And so happily we had her on a little harness, but they don't like it. They don't like these clothes, they don't like the thunder coats, they don't like the harnesses, anything like that. So a Halloween costume just out of the question there. In terms of other traditions, we only just had our second Halloween here in the house.

3:06:35.6 SC: And in previous places that we've lived, there wasn't really Halloween kids walking around, knocking on doors kind of tradition. We were more in like town homes or apartments or things like that. So we're still figuring out our traditions. We give out good candy, I have to say. We got a good crowd this year, a lot of kids, but we're still figuring out exactly how much candy to buy. In the last two years we bought way too much. And I did try to be clever about the candy last year. It just turned out to be too much work to be clever. So this year, it was just Twix and Snickers and Kit Kats and Reese's, and the kids love that stuff. They're not into trying to be clever, to be perfectly honest.

3:07:18.4 SC: Another anonymous says, "You previously mentioned that you're not much of a gamer. Does this include chess? You strike me as the type who would both enjoy and excel at it. It has become so popular in recent years that you can instantaneously find another real person at your exact level who's ready to play within seconds at any time of day on chess.com. As an avid gamer myself, who plays everything from virtual reality to the latest and greatest, still nothing compares to the rush of a three minute blitz against a real person online in this simple game, I strongly recommend it." Yeah, I used to play chess. I know the rules. I haven't played chess in years. I was on the chess club in high school and I was not the best player, but I was pretty good by those standards, which were very, very low standards. But it never really caught my imagination in the way that the real aficionados get into it.

3:08:09.8 SC: I think just because the, of course, there's a huge variety of possible chess games that you can play, but there's so much history and so much investigation into how to play well that you can get better just by studying what has happened in the past. By studying the classic moves and the classic strategies and things like that. And ultimately, that doesn't hold my interest that much. Honestly, I would rather play poker than play chess exactly because of the random numbers that come into the poker game. They're very different games. Chess is a game of complete information. Poker is a game of incomplete information. And honestly, I find more interest in the games of incomplete information where you have to be able to judge probabilities and try to figure out what someone else might be doing. So love chess.

3:08:57.0 SC: It's great. It's just not exactly my game. Reese Johns says, "Would you prefer an elbow which dispensed limited world-class wine, or a tattoo of a plane ticket on your neck granting you limitless economy air travel anywhere in the world?" I don't want either one of those. Well, I certainly don't want an elbow that dispenses wine one way or the other. I think that the thought experiment would require a slightly more elegant solution to the problem of limitless world-class wine. But look, as I would rather be able to travel anywhere in the world, even on economy, than to have as much wine as I want. And the reason is just that expensive wine is outta my reach like the super duper expensive wine that is only for the very, very elite. And I know that I am never gonna have that wine, but I'm perfectly happy with that.

3:09:50.0 SC: I can afford the wine I want, basically. Whereas I can't afford to do all the traveling that I want. As a somewhat tall person economy air travel to distant corners of the globe is very uncomfortable. So I would really want business class tickets if I could possibly afford them. But otherwise the ability to travel is more important to me. Well, the money I would save by having free travel is more important to me than the money I would save by having better wine. How about that? Raman Van Fleet says, "Although I live in Europe myself, I've been very invested in the upcoming US election and I'm consuming a lot of news from US news outlets. I've noticed that despite most news outlets having a pretty clear bias toward one party or the other, they all spend way more time on Trump than they do on Harris. This is presumably because Trump news attracts more eyeballs compared to Harris. Am I being too cynical and thinking that owners of news outlets on both sides want Trump to win, and that even the more democratic outlets can help make that happen, for example, by suggesting Harris has a large lead, thereby incentivizing Trump supporters to go out and vote and/or giving democratic voters misplaced confidence in their candidate winning?"

3:11:03.9 SC: I think that this is a common suspicion among democratic partisans online that news outlets want Trump to win because he is box office. And it's true that news outlets like talking about Donald Trump more than they like talking about Kamala Harris. She is basically a normal democratic politician in most ways. Donald Trump is completely abnormal in almost every way, and he does weird things, and it gets a lot of news. It sucks up all of the media oxygen in the room.

3:11:38.4 SC: That's absolutely true. But I just think it's too cheap and easy to say that therefore they want him to win. That's a little bit different. They're going to report on him as long as he's around. That doesn't mean they want him to win. I do think that the major media, the political media, has entirely failed at their jobs over the past two election cycles, precisely because Donald Trump doesn't fit into the conventional categories because he's not what they're used to dealing with, and they don't know how to deal with him. They don't know how to deal with someone who simply lies all the time. Politicians all lie, they all lie, but they don't lie quite as much. And they don't make the outrageous statements that he does. They don't actually try to lead assaults on the US capitol like he does.

3:12:27.2 SC: They don't do the sort of blatant obvious corruption that he does. His daughter-in-Law is the boss of the Republican National Committee. Like this is the kind of nepotism that for an ordinary politician would look very bad. You can go down a long, long list of examples of things Donald Trump has done, which if an ordinary politician had done them would be like big news. And for him, somehow he just does so much of it that they don't know how to cover it. So I think that they have failed in that responsibility in a deep way, but it's not because they want him to win, it's because they have certain modalities of operating. They have certain traditions and assumptions, and those traditions and assumptions are just not rising to the occasion of the current moment. They have trouble speaking the truth, because there is this false idea that reporting objectively, that reporting just the truth rather than one's opinion is equivalent to just giving equal time to both sides.

3:13:33.5 SC: And philosophically speaking, that is obviously wrong. If the two sides are not equally truthful, then giving equal time to both sides is not the way to get to the truth. Some kind of fact checking, some kind of objective truth being monitored is necessary. You can't just take the view from nowhere and imagine that every politician is equally likely to say the truth and therefore we will just report it. I would put that at the top of my list of failures of the media rather than they actually want Trump to win. Gary Miller says, "My cat, sir Benjamin Frederick Fussel fluff, duke of Meadows, has a tail that he mostly experiences through sensations, but sometimes, he sees his tail and mistakes it for a flying fluff ball leading him to swat at it. I think of Benji as a cat system where his tail exists in a kind of super position, an indeterminate potential fluff ball until he sees it, at which point it becomes real to him.

3:14:32.5 SC: Could a quantum system be thought of in a similar way that is as a single system that creates its own interaction, which then gives rise to real objects that exist only in relation to the system, like the position of an electron?" Well, I don't wanna say anything bad about Benji, but no, that is not a good way of thinking about quantum systems. And this is something you will hear me and other people say, and we'll try to say it as clearly as possible. Classical systems can exist in states of uncertainty in the sense that you don't know what they are, but they are something. Quantum systems exist in states of uncertainty in the sense that they have a quantum state that does not correspond to any specific classical observable fact of the matter, but that is what they are. That's the difference.

3:15:23.9 SC: It's not that they really have a position and in a momentum, you just don't know what it is. It's that they really have a wave function representing different possible outcomes to measurements of position and momentum. For example, if you try to be careful about stating the Heisenberg Uncertainty principle, it's not a statement about measurement outcomes. It's not saying, when you measure the position and momentum of a particle, there must be some uncertainty, blah, blah, blah, blah, blah. It's that no quantum state can have the properties of definite position and definite momentum at the same time. It's a statement about quantum states, not a statement about observational outcomes. So maybe this is too pedantic for you and your cat, Gary, but if you want to get it right, I would really not try to reach for ordinary classical analogies for quantum mechanical reality, because it's a fundamentally different thing. The idea that there is something called a quantum state, which is a different thing than what you observe when you observe it.

3:16:27.8 SC: And by observing it, you change that quantum state. All of this is intrinsic to quantum mechanics. There's just not really any good classical analogies there, cat based or otherwise. Bob Toroid says, "Could you talk about quantum oscillations? Neutrinos famously do oscillate, but I heard so do quarks. Although I thought that they decayed not oscillate. I tried Wikipedia, but as soon as I read Eigen state, that's an explanation beyond me so far. Can you explain what's going on and why other particles don't?" I can try. Yeah. This is another one that's a subtle thing that it's easier to do if you show some pictures or some equations or something like that. I think neutrinos are the best example. So let's use neutrinos as an example, and then let's see where it generalizes and where it doesn't. We're keeping in mind here that all of these particles are fundamentally quantum mechanical, okay?

3:17:22.6 SC: So they can exist in superpositions, their quantum state can be a superposition of different things. And that superposition need not only be of position or momentum, but even of what kind of particle it is. So for neutrinos, there's two different things going on. The fundamental thing that every particle has is what we call a mass. The particle has a definite mass. Like an electron has a mass. A muon has a mass, a tau particle has a mass. Likewise, the electron neutrino has a mass, the muon neutrino has a mass, et cetera. And there's three different masses for the three different neutrinos corresponding to muon, tau and electron. But then there's also what is produced in a decay. So if a muon decays, what does it decay into? It decays into an electron, a neutrino and an anti-neutrino.

3:18:21.8 SC: And the muon-ness and the electron-ness are conserved. So how do you decay from a muon into an electron? The answer is you decay into a muon plus a muon neutrino, and an electron and an electron anti-neutrino. So the muon and the muon neutrino carry the muon-ness through the process. The produced electron and electron anti neutrino have electron number and negative electron numbers, so they cancel out. So both before and after, your muon number is one, your electron number is zero. That's how you know what electron, what kind of neutrino you've been making. But what I just told you is the simplest version of the story and what you might expect it to be true. But there's a subtlety that undoes something that I just said, because these three different kinds of neutrinos, mass one, mass two, mass three, and electron neutrino, muon neutrino, tau neutrino don't actually map onto each other.

3:19:24.1 SC: They don't actually line up. In other words, in the world of quantum mechanics, the thing that we call the electron neutrino, which is defined by the thing that gets produced along with the electron when the muon decays, okay, does not either have mass one, mass two or mass three. It's a combination of the mass one neutrino, mass two neutrino, mass three neutrino. So it's not really true that an electron neutrino has one mass, a muon neutrino has another mass, a tau neutrino has yet a different mass. There are three different mass eigenstates. What can I tell you? Those are what they're called massive neutrino types. There are three different massive neutrino types that are mixtures of the electron neutrino, muon neutrino, and tau neutrino or equally well, the muon neutrino is a mixture of the three different mass states. And likewise, the electron neutrino is, and the tau neutrino is.

3:20:20.6 SC: So when you produce an electron neutrino, you're producing a little combination of the mass one neutrino, mass two neutrino, mass three neutrino, and that combination has a wave function. And really that's what it is. There is a combination there. It has a wave function. You can solve the Schrodinger equation and see how it evolves over time. In practice, the way it evolves is that the probability were you to measure it, so it's a combination of mass one, mass two, mass three, were you to measure it, and you say, what do I have here? Do I have mass one? Do I have mass two? Do I have mass three? There's different probabilities as a function of time for what you will get. It might seem that it's a high chance of getting mass one at some time, high chance of getting mass two at some other time, et cetera.

3:21:07.0 SC: We refer to that time dependent probability as an oscillation of the neutrinos back and forth. And the reason why it happens for neutrinos and not other particles is typically, well, you need for particles to oscillate back and forth they need to have the same charge. They need to have the same electric charge. Otherwise, it would be super easy to figure out which one you had. And they need to be produced at the same time. And something kind of similar to that does happen with quarks indeed. But then the quarks also decay away very, very quickly. The neutrinos, they have nothing to decay into. So they just last for a long time. So it is possible for other particles to have this oscillation phenomenon. It's just that in neutrinos, it's sort of most obvious, most inevitable, most necessary to sort of face up to it to explain the data that you see.

3:21:55.3 SC: Leland Beaumont says, "Do future generations deserve proportional representation in democratic forums? And how might that be implemented?" I would say, oh my goodness, no, they do not. I do think that current generations should take into account the welfare of future generations, but I think that there is zero way of actually implementing the idea of future generations being represented. We don't know either how many of them there are, and we certainly don't know what their preferences are. Okay? So I get the goal of being nice to them, of not destroying the planet for the sake of future generations, but there's no way in which you would give them a vote, okay? That's just impossible to do. The only thing that you could even imagine doing is sort of declaring certain, currently existing people to be representing the interests of future people.

3:22:54.2 SC: And I would have basically zero confidence that they would do that accurately. Again, as I've said before, to me, the whole point of democracy is to give actual people the right to say their actual opinions, their actual preferences. That's what we get to do in democracy. It's not that someone else who is supposed to be smarter than them is telling them what they should think. And if those people don't even exist yet, they have no way of voting. So I can't really imagine giving them representation. David Robertson says, "Priority question, whom would you talk to given the chance?" This is not a very well-defined question. I presume this is one of those questions about like, who would I talk to from history or something like that. Is it, who would I talk to right now? Right now I'm in a pretty good position where I can talk to most of the people I like talking to.

3:23:44.7 SC: Indeed, I have a podcast where I talk to many of them quite directly. It would be nice to talk to people in positions of power to affect what they wanna do and whatever. But lots of people talk to them all the time and maybe those effects aren't very big. So if I interpret the question as who throughout history would I have wanted to talk to, then as I've said before, I don't have that much interest in learning about physics or something like that from prior generations of physicists. We know more physics now than they did. So what you would want to get out of from a historical figure is either historical or biographical information. That might be very, very interesting.

3:24:30.4 SC: There, I am greatly handicapped by the fact that I only speak English, not ancient Greek or something like that, or ancient Cantonese. So let's hypothesize in this wildly unrealistic thought experiment that I can have a universal translator and I can speak to whoever I want. There's lots of people, and I don't carry around any particular choice of people who I would love to talk to. I'll throw one idea out there that's a little bit hard to guess. I would love to talk to James the just. James the just is a historical figure from the Bible. He was Jesus's brother. Jesus of course had brothers and sisters. The Catholic church won't admit it. The Catholic church has come up with weird twisted explanations as to why the people who the Bible very clearly said were Jesus's brothers and sisters were really just family friends or whatever.

3:25:23.2 SC: But it's very clear from the Bible that Jesus did have brothers and sisters, and James, his brother, was a leader in the early Jerusalem Christians. They weren't called Christians at the time, but we call them that now. After Jesus died, his followers, the Jewish people who followed him tried to hold together and figure out what to do. And so you have these dramatic scenes in the Bible where Paul, who came along a little bit later, he was not friends with Jesus while Jesus was alive. But Paul had the idea that we should proselytize, we should spread the good news to all sorts of far-flung corners of the earth. And there were people in Jerusalem there who were like, no, we're fine as we are. This is a Jewish thing. This is not something we wanna spread far and wide.

3:26:11.5 SC: And the big hangup was circumcision. Paul knew that if you followed Jewish law, all the men have to be circumcised. And that was a tough sell to grownups in different cultures that were not already circumcised. So they had a big meeting, and finally they decided okay, fine, we can be Christians without demanding that people be circumcised. But James had a really good reputation. He was called James the just. People really looked up to him, and he was sort of the leader of this group of Jerusalem Christians. And I'm just curious about how it took off. In many ways, there was no signs in the very early days of Christianity that this is gonna take over half the world. And there must have been something there. There must have been something.

3:27:03.9 SC: Was it literally just the message, or was it that the people were especially persuasive? Or was it there were socio-political conditions that were ready? Or was it intellectual conditions that meant that Paganism was on his last legs? And I really don't know. And I would love to sort of have more information about that. And I think that a lot of the people who were there at the time to be able to give the information were kind of religious zealots who I wouldn't believe. But as far as I can tell, James the just, brother of Jesus was a fairly reasonable guy. I might be completely wrong about that 'cause you can't really believe these things you read in the Bible. They were passed down for many decades as oral traditions and are unreliable. But there's more historical objective evidence for the existence of James than there is for the existence of Jesus.

3:27:48.4 SC: So I'm pretty sure that he was out there, would be interested to see what he had to say. Dominic Behe says, "After months of trying not to think about the Celtics being NBA champions, the regular season is finally here. What do you think about the 76ers roster this year? Embiid and George missing the first two games already is not too promising, but I'm holding out hope. Do you have any other teams you're excited to check out on League Pass this season?" Yeah, so since Dominic asked this question, the 6ers have gone on to lose a couple more games. They did win one game, I guess. For those of you who don't know, the 76ers, my favorite basketball team, of course have Joel Embiid, who is one of the best players in the NBA. And over the course of the summer, they acquired the star free agent signing, who is Paul George, who used to play in the LA Clippers.

3:28:36.6 SC: And along with Tyrese Maxey, who is the young guard on the team. They have three players who serve very different roles, but all at an all-star level, which is the perfect recipe for NBA success. We've not been seeing that success early on in the season because both Joel Embiid and Paul George are injured and not been playing. And the team has not risen to the occasion yet. So I think it's far too early to draw any conclusions, especially when two of your best three players haven't played yet. But yeah, the early returns are not promising yet. This is one of the downsides when you completely overhaul your roster over the course of an off season. We have more new players on the 76ers than any other team in the NBA has from last year to this year.

3:29:21.8 SC: So the potential is absolutely there to do great things. The reality is not yet exhibited. We will have to see what happens. I am always optimistic, this is the way that I pursue my sports fandom is that I'm always optimistic even up until last second, but right now I'm waiting for that optimism to pay off in some tangible results. Philip Grant says, "In recent AMAs and in the podcast with Hahrie Han, we've had some good discussions about democracy and what it means to participate in it. My question is, should universities be run in a way that incorporates more democratic participation? And if so, should students have more of a democratic say, should faculty, should the community that hosts the university?" I don't know. Like I'm not actually an expert on university governance. I do think that faculty traditionally do have a pretty good amount of say in how universities are run.

3:30:15.9 SC: I also do get the impression that faculty power has been eroding over the past few decades. At Johns Hopkins where I am, there are little moves around the margin that clearly seem to be targeted at making power more concentrated in the administration and less concentrated in the faculty. And I think that's bad. I think that's kind of a blatant power grab. I think that the faculty should have more power over things. But not perfect power. Faculty, like I've been to faculty meetings. I don't want them in charge of lots of things. I think there's an absolutely a place for certain decision making power to be in the hands of the administration. That's perfectly okay. But we need some balance between the kinds of decisions that are like how do we fundraise to build a new dorm versus what kind of intellectual diversity do we want on the faculty?

3:31:10.1 SC: Okay. That's the kind of thing that faculty should have the most say in, the purely academic intellectual questions. Students should absolutely have a say. And I don't think that the community should have a direct say in how the university runs, but I absolutely think that the university and the community should be in constant contact and conversation about how to run, how to address questions of mutual interest. That makes perfect sense. But I think that does happen. At a well run university anyway, that does happen. I think that the students are the most interesting question because individual students, five years later, they're not gonna be there anymore. But the idea of students are always going to be there. So I remember when I was at Harvard as a graduate student, Henry Rosovsky I think was the provost, and he got in trouble for saying the students are temporary. The faculty are long term. Harvard is forever.

3:32:08.2 SC: Guess who didn't like that? The students, because when they're there for their four or five years, depending on undergrad, grad student or whatever, it's important to them what is going on in the university. So I do think that they should have a say, but it's a different kind of thing than the faculty and the administration. So I don't know how best to do that. I think that typically most universities have mechanisms for student voices to be heard. But I think this is an individual thing. I don't think you can just say in sweeping terms, there should be more or less student involvement. I think that each individual university has to work out the best way to hear the voices of the students. For example, in the faculty meetings that I'm on now, graduate students have asked to be able to go to the faculty meetings, or at least to send a representative to faculty meetings.

3:32:57.8 SC: And so we're having deep discussions about that. Look, the faculty are not bad natured. They want the graduate students to be happy and to have a say. But on the other hand, they don't want the graduate students to be listening in on discussions of who to hire on the faculty, because they'll blab about that. And you want some privacy in those things. The whole point of having a graduate student representative to the faculty meeting is to blab, is to go back and tell the other students what is going on. And there are some conversations that should be in confidence. So we're looking for ways to balance that, like how to have good back and forth conversations with the graduate students in both the physics and philosophy departments that I'm part of, without compromising the integrity and the privacy of certain discussions that need to happen.

3:33:48.2 SC: Like in the philosophy department, we literally talk about every graduate student and their progress. We don't want other graduate students listening to that. That doesn't seem quite appropriate. Simon Carter says, "How is the house? Have you had the roof repaired yet?" I had forgotten that I told people that, yeah, we need to repair our roof. Like, people shouldn't know that we need to repair our roof. That's a little bit too much information out there. But no, we haven't repaired it yet. It's a big task. I mean, it's not... I'm not gonna go up on the roof, do it myself. It's not that kind of task, but I have to pay for it. We have to pay for it. It's a lot of money. So we're saving up our shekels to get the roof repaired at some point. But in general, the house is great.

3:34:27.7 SC: We live in a house. This is a kind of a new thing. When I was, I don't know, between sixth grade and 12th grade as a kid, I lived in a house in a small suburban cookie cutter, ticky techy house kind of development. But since then, I've been living either in dorms or in city apartments, condos, townhouses. And now I'm back in a real house, like with a yard and everything. Just to give you one example, in our house, we have a fireplace, like a real working fireplace. It doesn't heat the house. That would be crazy. But we do use it once a week in the cold months. It's very, very nice to have a fire in the fireplace. So Jennifer in particular has gotten very excited about building fires and very good at it.

3:35:10.5 SC: And we figured out how to get wood delivered. And we have room in the backyard to have logs of wood stacked up there. And so very often, the logs of wood are bigger than we want to build a good fire in the fireplace. And so it is my job to split the logs. And this is something I did as a kid. 'Cause we actually had both a fireplace and a wood burning stove when I was growing up. So I used to split logs all the time. It's been a long time, let's put it that way. So I bought an axe and I was splitting the logs, and you know what? I was not very good at it, and I was frustrated. I'm like, I thought I used to be better at this. So I went online and looked for advice about how to split logs better.

3:35:54.4 SC: And I realized that I bought the wrong axe. I bought an axe that was more appropriate for chopping down saplings or something like that, rather than splitting logs. So I went back and I reinvested in a Maul. This is spelled M-A-U-L, which is like a giant heavy axe that is really meant for splitting logs. And man, I love that maul. That maul is great. I'm like so happy now splitting logs. It's so easy, it's fun. I wanna buy more wood just so I can split logs and then sell it back to the wood seller in a more convenient form. So in that sense, yes, we're really enjoying having a house, having a yard, things like that. We even got a new cat out of it. We weren't looking for that, we weren't looking for that little input. But the neighborhood has given us a kitty cat.

3:36:39.9 SC: So that's always good. Renan Bashatti says, "Consider this thought experiment. Imagine we figure out exactly the computation required to generate the subjective experience of a certain image as it happens in the brain. Since the subjective experience is a computation. Then we take the sufficient number of people to simulate this computation. Each one will receive a number on his or her smartphone, make the appropriate computation in an old calculator and output the result by sending a text message to its connections, which are also people receiving numbers in their phones. Will this system have the subjective experience of an image?" So this is very, very close to John Searle's famous Chinese room thought experiment. He had the idea of replacing neurons in the brain with card systems, some card catalog. It was a little bit vague 'cause no one knows exactly how neurons work. But the idea of instantiating the thoughts in a brain in a much more macroscopic and mindless system, just a set of rules.

3:37:41.7 SC: When a certain input comes in, you process it in a certain way. And then someone, I don't know whether it was Searle or someone else proposed almost exactly your thought experiment, Renan saying, but they used China as a, I don't know why it's always China that is chosen for this, but like, what if every Chinese person was given something? By the way, we don't have nearly enough people to do this. There are 85 billion neurons in the brain that is more than the number of people on the earth, but okay, you can imagine doing something like it anyway. Also, by the way, it's completely conceivable that things other than neurons are relevant to what goes on in our brain. There are glial cells and there's the whole rest of our body, et cetera. So putting that aside. To the actual substance of the question, I have no problem thinking that in principle, a system like this could have the subjective experience of an image.

3:38:37.3 SC: I think that the entire oomph behind this kind of thought experiment is to make you think that it couldn't just because it's so much bigger. It's so much different than what we're used to in a real human brain inside our heads. And part of that is that it's so much slower, I think that what is sometimes hidden in these thought experiments is that once you blow up the physical size, the timescales blow up as well. So what you and I would hear a sentence like you're hearing right now and process it relatively quickly, this kind of thing, which would presumably require a very overcrowded globe of the whole earth with a lot of cell phones going on and off all the time, it would take an enormously long period of time to do the equivalent of seeing an image and getting the subjective experience of it.

3:39:31.6 SC: And because of that, it is just very different than our informal notion of what happens. And therefore, we kind of react against it. We go like, oh, that wouldn't be exactly the same. Furthermore, it's not embedded in a larger context like a society. We don't imagine that there are other planets with equal numbers of people who are also talking to each other. So it's just a very different world. It's very difficult to make an exact connection and exact analogy between that kind of system and real human brains. But at the end of it, I think that thought is substrate independent. And I do think that in some sense, if you ignore all these incredibly important complications and specific problems, yes, that would have the subjective experience of an image. Edward Morris says, "In your very thought provoking discussion with Jonathan Birch, I was a little surprised that the question of when a human fetus becomes what he calls a sentient candidate never came up.

3:40:31.1 SC: Do you have any thoughts on this? And especially on whether or not it is relevant to the highly charged debate over late stage abortion policy?" I don't have that much thoughts on it, honestly. I will say that at least here in the United States where I'm somewhat knowledgeable, not very knowledgeable, but I have zero knowledge outside the United States, there really isn't a highly charged debate over late stage abortion policy. There is a debate and it is highly charged, but it's not a big deal because there are very, very, very, very few late stage abortions. Late stage meaning once you're in the third trimester of pregnancy or something like that. To a very good approximation, I'm not gonna say 100% because who knows, but to a very good approximation, abortions are even contemplated at that late stage, only in cases where the mother is basically likely to die if the pregnancy continues.

3:41:23.5 SC: So it's a very different kind of debate than early stage abortion, where the fetus is, it's not a question of the health of the mother necessarily, it's the question that this little bundle of cells is not really ascension's candidate, and therefore it's part of the mother's body, and then she should get to decide what happens with it. So I do think it's an interesting question. When at what point does a human fetus become a sentience candidate? But also there's like a lot going on in these debates. So let's just mention one factor, which is not directly relevant, but is sort of neighboring to relevance. In the discussion with Jonathan, we talked about sentience and with a focus on the idea of animal cruelty. I think Jonathan is trying to make the case, and he does this as a philosopher, but also in public policy circles.

3:42:17.6 SC: He makes the case that we need more protections against animal cruelty in the world. Now, this is a stance one can talk about, and it's a different stance than a slightly more, slightly going farther stance, which says, we should be vegetarians. We should not kill animals at all and eat them as food. And that's not as far going as saying that we should be vegans. We should not even use eggs or milk or anything like that as food. And Jonathan, I think very specifically chose not to go there, not to have those conversations because, well, there's at least two reasons he might have done it. One reason is that it becomes sort of more emotionally and politically charged when you go to those other conversations, but also because the philosophical case is a little weaker. If you think you shouldn't kill animals to eat them for food, you probably agree that you shouldn't be cruel to them when they're alive.

3:43:19.1 SC: But the converse is not necessarily true. So this, I think that the strongest case is for reducing the amount of animal cruelty in the world, the strongest case philosophically and politically. And so he's focusing on that. There's no reason not to focus on the thing that you can make the best argument for, And guess what? The status of human fetuses is something that's very, very hard to get right. There's a lot of considerations going out there. I mean, I'm a strong believer in abortion rights and a strong believer that women who are actually pregnant are the ones who should be able to make the decisions about this. Ideally in a perfect world, we can accept that and also have careful philosophical discussions about the development of human fetuses, et cetera. In practice, that's hard to do, but we should still aspire to do it.

3:44:09.6 SC: It's just not the conversation that we were having right there. I think we were choosing to get right, a very specific, a very important set of issues. Sid Huff says, "I'm reading a new science fiction book by Neil Stevenson, which raises an interesting moral dilemma. A multi-billionaire has developed and implemented a scheme to seed the atmosphere with sulfur. The sulfur creates sulfur dioxide high in the atmosphere, which in the story reflects sunlight, thereby countering the effects of greenhouse gases. He's convinced that governments will dither forever about global warming, so decides to try to fix the problem on his own, using his own resources. But of course, there may be side effects of his atmospheric tampering, which he understands, but believes is a price that must be paid if Earth is to be saved. If you are him, would you go ahead with the scheme?"

3:44:58.5 SC: I like this moral dilemma. It's a good moral dilemma. This is a legit dilemma. And the reason why it's legit is because I think the default, the sort of presumption should be if you live in a democratic society, either locally or globally, then even if you think that there's a good policy, you have to let the democratic process play out. If the planet does not say, let's mess with our atmosphere, if the people of the planet do not make that decision, your presumption should be, you shouldn't go and do it yourself. But sometimes those presumptions can be overridden. Sometimes, there are crises. Sometimes as an individual you have such a strong moral feeling that the wider community is doing the wrong thing, that you have to take matters into your own hands. Sometimes it's civil disobedience or whatever it might be.

3:46:00.4 SC: That's a very, very tricky question when you should do that kind of thing. I certainly don't have a perfectly well developed theory of when you should and when you shouldn't do it. I certainly don't have enough information to answer whether or not I would do it in this particular case. You would really need a very clear understanding of how much you knew about the effects and the side effects of this intervention, and whether or not it is better or more possible to pursue doing the intervention, but through more conventional channels. It's too easy to give up. Well, let's put it this way. If you actually got buy in from all the nations of the world to do this, that would be much better for you and for the planet than if you just went off and did it by yourself.

3:46:46.3 SC: Okay? So certainly, again, your first move should be to try to work within the existing channels, and then maybe you're faced with a dilemma if that fails. So the answer is, I don't know. I think this is a legitimate question that would depend on all sorts of details that I don't have access to right here. Hopefully, no one in the real world is actually faced with this particular dilemma going forward. Okay, final question of this month's AMA comes from Bob Richie who says, "I'm 76, retired, and politically well-informed, but not an activist. If Trump wins, I plan to unplug entirely from the news and social media and try to live blissfully unaware of what that monster does during his second term, as well as all the other disturbing news we get bombarded with. My goal would be to minimize angst and just enjoy music, science novels, good movies, meditation, et cetera, for the duration. What are your thoughts on this strategy?"

3:47:42.3 SC: I think your strategy is fine. I think it is... This is again, a very good question. I back loaded the AMA with questions I thought were very, very good and tricky ones here. There's two things going on. One is, it is a good thing to work to try to make the world a better place, to try to sacrifice a little bit of one's own self comfort and even wellbeing for the greater good. On the other hand, there are limits, especially when one reaches a certain age, and there is not an obligation to do those things. It's a good thing to try to make the world a better place, even at sacrifice to yourself. But I don't consider it a moral obligation to always do that. I think that it needs to be a balance.

3:48:34.9 SC: There needs to be a balance, both in sort of space and time. Like, if you have put a certain amount of effort into doing that kind of thing over your life, you have the right to set down your tools and relax a little bit. If everyone just spent time unplugging and listening to music and science and reading novels, that would probably be a good world to live in. I mean, the problem is that not everyone does, and some people do harm to the world. So I am happy to license any individual who says to themselves, look, I've had enough. For me, I'm just not up to continuing to struggle against this. Likewise, if people say like, I'm leaving the country, if we descend into direct dictatorial rule here in the United States, I get that. It would not be my strategy personally.

3:49:29.9 SC: I would prefer to stay behind and fight in whatever very minor ways I could. But I don't blame the people who don't wanna do that. I think that there's room for individual choice in these matters. Hopefully, we're not gonna be faced with this particular dilemma, but enjoying music, science novels, movies, meditation, et cetera, I can think of worse things to do than that. Hopefully, we can do that in a flourishing democratic society going forward. That's my optimistic hope. Anyway, thanks very much for listening. Thanks as always, for your support. From Mindscape, talk to you next time.