Modern Wisdom - #521 - Sabine Hossenfelder - Life's Mysteries, Explained By Physics

Episode Date: September 3, 2022

Sabine Hossenfelder is a theoretical physicist, research fellow at the Frankfurt Institute for Advanced Studies, quantum gravity researcher and an author.  There are a lot of big questions in the world, like does the past still exist? Do particles think? Was the universe fine tuned for us? Do we have free will? And are we living in a simulation? Given that we don't have answers yet, why not let a physicist have a crack at them? Expect to learn why physicists who say they know how the universe started aren't telling the truth, whether we can compute a human brain, why no one gets any younger, if maths is the ultimate basis of reality, why there might be copies of all of us out there in the universe, how your entire life could be the imagined history of a brain floating in space and much more... Sponsors: Get 15% discount on Craftd London’s jewellery at https://bit.ly/cdwisdom (use code MW15) Get a Free Sample Pack of all LMNT Flavours at https://www.drinklmnt.com/modernwisdom (discount automatically applied) Get 20% discount on the highest quality CBD Products from Pure Sport at https://bit.ly/cbdwisdom (use code: MW20) Extra Stuff: Buy Existential Physics - https://amzn.to/3Rqbk6F  Subscribe to Sabine's YouTube Channel - https://www.youtube.com/c/SabineHossenfelder Get my free Reading List of 100 books to read before you die → https://chriswillx.com/books/ To support me on Patreon (thank you): https://www.patreon.com/modernwisdom - Get in touch. Instagram: https://www.instagram.com/chriswillx Twitter: https://www.twitter.com/chriswillx YouTube: https://www.youtube.com/modernwisdompodcast Email: https://chriswillx.com/contact/  Learn more about your ad choices. Visit megaphone.fm/adchoices

Hello friends, welcome back to this show. My guest today is Sabina Hassenfelder. She's a theoretical physicist, research fellow at the Frankfurt Institute for Advanced Studies, Quantum Gravity Researcher, and an author. There are a lot of big questions in the world, like, does the past still exist? Do particles think, was the universe fine-tuned for us? Do we have free will? And are we living in a simulation?

Given that we don't have answers yet, why not let a physicist have a crack at them? Expect to learn why physicists who say that they know how the universe started aren't telling the truth, whether we can compute a human brain, why no one gets any younger. If maths is the ultimate basis of reality, why there might be copies of us all out there in the universe, how your entire life could be the imagined history of a brain floating in space, and much more. But now, ladies and gentlemen, Please welcome Sabina Hassenfelder. Sabina Hassenfelder welcome at the show. Hi Chris. You've got a quote at the start of your new book

that says it is far better to grasp the universe as it really is than to persist in delusion, however satisfying and reassuring. Some Carl Sagan. What's that mean to you? When I came across this, I just thought this captures exactly what I'm trying to express with the book. So it's very tempting to fall for some pleasant explanation and try not to look at the evidence. But I think in the end, it's better to actually look at the evidence, at least for me. So that's been my conclusion. Because otherwise, you always have this feeling that you're lying to yourself. Do you feel like your Twitter account is mostly you dashing the dreams of people who have

a non-evidence-based ideas about what might be happening in the world or in the world of physics? Well, except for the animal pictures, basically. But yeah, well, you know, partly the reason that I was writing this book is that I felt what I do on social media is a little bit too destructive, a little bit depressing almost. If there's some headline that claims, well, soon we'll be able to send information faster than the speed of light with the quantum internet or physicists have created negative mass or they're kind of stuffed. Then I'm the one who has to say, well actually, no, you can't do this and it doesn't work and no, we have not made contact with parallel universes, that kind of stuff. And I do think it's important, but it's a very one-sided picture of physics. It raises the impression

that physics just tells you what you can't do, what is impossible. And I think physics has another side where it opens new possibilities, it tells you what you can do. It brings up new ideas that you might not have thought about otherwise. Hmm, so rather than just playing defense all the time, there's the opportunity for you to put forward some ideas. Well, not my own ideas. I'm talking about stuff like the multiverse or, I mean, other ideas that have already, I would say, an almost established place in the public mind is ideas like the time slows down near black holes or wormholes or maybe tell the Potation.

Those are all ideas that came out of physics and I think it's really inspirational and I understand that people like it and they want to hear more about it. So I thought, well, write a book about all those big ideas. Speaking of ideas that have captured the public consciousness, the simulation hypothesis is something that's been thrown around an awful lot. What's your problem with the simulation hypothesis? So the simulation hypothesis is the idea that our reality is just a computer program basically. And once you buy into this, there needs to be some kind of programmer

who has written the code and God knows what this programmer is doing, maybe he is God. And so I think that as a talking point over glass of wine, that's well and fine, or maybe philosophers want to go on about it, that's also fine. But if you claim that it's actually based on science, that's when I get a problem. Because it's a pretty big claim about what it takes to reproduce our observations. And it's a claim that says, well, you can reproduce everything that we observe with an algorithm put on a computer. And I want to see

the algorithm, I make you show it to me because basically you just claim that you have a theory of everything. And that falls into the terror of the foundations of physics, which is where I work. And so I think philosophers who write about it and make statements like, oh, well, you don't have to think about the computational capacity of the computer because if there's some corner of the universe, when or when it's looking at the moment, you don't have to compute it. I'm like, yeah, well, you know, show me how you want to write this into the code. So I'm just not buying it.

I think those people are trying to write this into the code. So I'm just not buying it. I think those people are trying to get away too cheaply. Because it's a problem that's put forward as a philosophy problem, right? It's like an idea playing with interesting ways that the universe perhaps could exist. But I think your argument is that you need to drag that across into physics. It's not really a question of philosophy. so much as it is a question of physics. But it was put forward by a philosopher and it has certainly been discussed by philosophers. Like I think David, what's his name, Charmers has just written a book about it, which I haven't really read.

I've looked at it, but I would not pretend that I actually read the whole thing. And it's fine to discuss, you know, on this abstract basis, maybe one day there'll be someone who'll be able to write a code on some kind of computer, you know, on that level. But when you're making a claim that it is actually possible for we currently know about the laws of nature and what we know about computers, there's nothing that's pushing it too far. And I think that some people have made claims about it, like Elon Musk, for example, and Neil DeGrasse Tyson, is one of them who's made statements about it. I think they overemphasize how much of it is actually based on science.

And that's the point where I get a problem. Which bit is not based in science, the fact that we don't have the computing power or the algorithms to be able to do this? Well, we don't have the algorithms. We don't even know how to do it. Like, I mean, there are really basic problems with how do you describe a chaotic system? This is something just to stick with this example.

That climate forces have to cope with in reality and it's really difficult because as you probably know you have something like the Navier Stokes equation at scale and variant. So strictly speaking you can't just chop it off at the finite grid. What do you have to go into that? Well, what the Navier Stokes equation or finite? Yeah, I'm not familiar with either of those. Oh, the Navier Stokes equation is the equation that describes how fluids and gases behave. For example, the atmosphere, but also oceans water and that kind of stuff.

So it's like the central equation that you have to solve on a computer. If you want to describe the weather or the climate in the long run, and this equation has the property that it's scaling variant, which basically means it draws on all different scales, like the long ones and the very short ones. But if you want to calculate what happens for the globe, you can't actually on a computer, you can't really calculate it on all scales. So what you have to do is you put a grid on it. And the resolution of the grid depends on whether you want to do a calculation on a country basis or on the entire globe and for what time span. But typically

for climate models, it's right now, I think something on the order of several tenths of kilometers, and maybe for weather models, they can go down to one or a few kilometers. So I'm not a climate scientist. I hope this is roughly right. It should be kind of in that order of magnitude. But that's clearly not scale invariant. So you've modified the equations and that has consequences. So they're just situations which those models will not correctly predict and we know this climate scientists know this, what are people know it, it's a problem. And so people are talking about the simulation I put at this kind of we totally ignore the problem that we have with putting our reality on a computer. And that's only at the

scale of a world or perhaps even a country with the grid size or the pixel kind of the pixel equivalent of one square kilometer perhaps. So trying to make something that's plank length across an entire universe is significant. Okay, I understand. So if we can't simulate a universe, can we create one? Well, that's an interesting question. I made a video about this,

and I was trying to argue that if everything we know about the early stage of our universe is correct, that's a pretty big if, but let's just assume it is correct. Then the answer is, yes, quite possibly, one day we'll be able to make a universe and a lot of people thought I was joking because they know me as someone who usually says, no, you can't do this, this is all rubbish, don't believe it. And this was another reason why I wanted to write a book because I felt that I

maneuvered myself into a corner where I'm taking this very, this very negative, destructive point of view. How is it that it could be possible for us to create a universe but not simulate one? Well, well, that's a very good point. Yeah, well, it depends on the question what you mean by simulation. And what people normally talk about, they talk about a computer that has been programmed by someone. And that's something which you would not be able to do with this universe. You would just create the conditions under which it comes into existence. And then what, at least for we currently know

about how those things work, it would create a small bubble, basically, and that would pinch off from our universe. So it goes away. You don't control it, you don't program it. It probably inherits most of the conditions from our universe. And you can ever get into contact with it again.

Would you ever actually be able to know if you'd created one in that case? Well, that's a good question. You have to think about some observables that would be related to it and people have thought about some, unfortunately, it would look pretty much like a tiny black hole, so it might be very difficult to tell a part. But I should probably add, like, this is not something we're going to do in the next one flowers, and there may be 10,000 years.

It would require to put macroscopic size of materials, so estimates say something like 10 kilograms into a particular quantum state where that kind of stuff could happen. So it's theoretically possible. There's nothing in principle that stands in the way of one day doing it, but it's certainly not something that's going to happen in our lifetime. Okay, no new universe is just yet. So what about free will? That's something else that's going to happen in our lifetime. Okay, no new universe is just yet. So what about free will?

That's something else that's been popularized people like Dan Dennett and Sam Harris over the last few years. I actually had a friend who I spiraled into a three-week depression by sending him a video of Sam Harris explaining free will on Joe Rogan. And after that, he came out on the other side, actually being quite thankful for it,

but for those three weeks, I'm sorry Luke. What about physics relationship to free will? What have you come to believe about that? Yeah, I've been there, but it took me much longer than three weeks. So it's one of the reasons why my book has kind of a warning in the beginning, like some of the things that we're going to talk about are not easy. And I think that it's one of those points. But I also think that everyone who knows something about physics will stumble over this problem sooner or later. So let's just talk about it, and then you can get through it and come out on the other side.

And I hope that my book facilitates that. And so, yeah, I'm basically, I'm with some, I like his book, I mean, to begin with, it's a very short book, so I can really recommend it, you can throw it very quickly. I like the book except for the one paragraph that he has about physics, where I'm like, I think this wasn't quite right. It was something about the Planck scale, which, a book would have been better without that paragraph. But yeah, I mean, so that's this basic problem that for all we know about the fundamental laws of nature, they are a combination of

determinism, where the future is predicted by what happened in the past, and then every once in a while there's some random event that comes from quantum mechanics but you can't influence it because nothing influences it's entirely random. And now whether you think that this rules out free will or doesn't depends on what you mean by free will. So this is why there is so much debate about it. So the way that I've tried to approach the problem in my book is by just first explaining what we know about the loss of nature, which is what just said, this combination of determinism with the occasional random quantum jump. And then you can ask, well, does this mean that free will does not exist? What do you make out of this? Now,

personally, my conclusion from this is just, well, free will doesn't exist. What do you make out of this? Now personally, my conclusion from this is just, well, free will doesn't exist. Let's get over with it and think about ourselves in a different way. But of course, you can try to come up with different definitions for free will. And this is something that David Arbor's has done, for example, and all the people have put forward slightly different definitions. And this is all fine with me so long as we know that we're talking about different things. Hmm. What is it that's happening at the quantum level that's causing this random chance? Because as far as I was aware, it means that had you have gone back and run the same period

of time again, that something different could have happened. But I thought that given the initial conditions, everything is predetermined from there, but it seems like you're saying there is a genuine role of the dice here, which could one times come up with a one, and the next time come up with a three of some kind. If you take quantum mechanics seriously, the way that we use it right now, that's exactly what happens. Of course, you can't actually go back and time and run it again. So there's a slight problem with that. But at least the way that the theory works, there are occasionally those measurement events for which you can't predict the outcome. You can only predict the probability of getting a particular outcome. And those are generally random. They are indeterministic.

So quantum mechanics is an indeterministic theory. But of course quantum mechanics may fundamentally not be correct. It may just be an approximation to something else that's going on and that's something else might be deterministic again. And then as you certainly know, there are also the many words in deportation which tries to do away with the measurement update entirely. So then you only have the deterministic evolution left. So it's somewhat controversial. But yeah, I mean, I think for what the discussion about free will is concerned, it doesn't really matter. You know, you either have a deterministic evolution with the occasional random event or you have a deterministic evolution without the occasional random event. But in both cases, I find it difficult to make sense of free will. Yes, because am I right in thinking the many

worlds is where you branch off each time that something occurs? Is that right? Yeah, basically. So when in, in the standard interpretation, which is often called the Copenhagen interpretation, you make a measurement, you collapse the wave function into one definite outcome, but you don't know exactly what, which outcome. So that's the indeterminism. In the many words interpretation, you don't collapse the wave function. You just say, well, now there are two universes or three or four or five, depending on how many possible outcomes there would have been. And each of them happens in its own universe. Yeah. So what that would mean is that each universe is deterministic because you are following down

the path of one. If you continue to go down that, that would mean that that is the only way that that could have come out. And all of the others are also deterministic. Is that right? No, actually what's deterministic is the entirety of all universes. But if you are in one of those universes,

it'll still look indeterministic. And this is exactly what we see. It looks indeterministic. Ah this is exactly what we see, right? It looks indeterminist. Ah, I see. So is it right? You often hear that if we had known the initial conditions of all of the matter at the beginning of the Big Bang, we could have accurately predicted everything that was going to occur for the rest of time going forward. Is that not true? Well, in the many words interpretation, it would be true for the collection of all those parallel worlds. In our universe, if you collapse the wave function, it's not true because you get

this, you get this random quantum element. And it's not necessarily the case that those quantum But those quantum events remain small. They can certainly grow into macroscopic differences. And this is what Shrewdinger tried to illustrate with his famous cat thought experiment. So he was trying to say, look, it could be that you have a cat that's either dead or alive depending on whether or not the natum decays. And so what it basically does is that it amplifies this indeterministic outcome from a tiny macroscopic quantum thing, which is this atomic nucleus, to a big thing, which is a cat, but it could be you, or could be the entire planet, you know, if you, I don't know, you blow

up a bomb or something like that. Going back to the beginning of the universe then, what are people getting wrong with the way that they currently look at the big bang, the origins of the universe? What are the claims that you've been beating over the head on Twitter or elsewhere? Yes, so the problem is that we have a fairly well-established theory of how the universe evolves and yeah, there are some nighly bits with dark matter and dark energy, but let's leave this aside for the moment. So we have Einstein's theory of general relativity that tells us how the universe as a whole changes

in time if we know the matter content, matter energy content. So we can use this to extrapolate the present state back in time by using those equations. And so what happens is that at some point those equations just break down. And we end up with a state at which the energy density and also the curvature of the universe was infinitely large. So this is what's called the big bang. And now the problem is that most physicists me included think that this is probably not what actually happened. It just means that those equations break down and we would have to use a better theory

so that would be a quantum theory of gravity, but we don't have it. So how did the universe begin? Well, we don't know because we don't have this theory. Now, of course, a lot of physicists are unhappy with this state of affairs. And what they try to do is that they kind of modify the equations at an early time and then they attach a different story to the beginning of the universe. So instead of a big bang, you might instead have a big bounce, like this is something which is popular in certain cycles.

So you have a previous universe which collapses, and then it starts to expand against the response in the middle. And those bounces could repeat, and then you get a cyclic universe, but it doesn't have to be the case in some scenarios. It's just single bounce. but it could be other things. You know, and other people have claimed that we came out of a black hole and it could have been a higher dimensional black hole, so it could have five dimensions, or it could have been some kind of collision between higher dimensional

membranes or something with a gas of strings, or some people say maybe it didn't have any geometry, but it was just some kind of network so there are all kinds of stories and the problem I have with those stories is that they make a simple story more complicated which isn't something that a scientist should do. So I think the honest answer can give as physicists to the question how did the universe begin is we don't know. What is the fundamental problem that physicists are bouncing up against, or coming up against, bounce might be the wrong word, with all of these extravagant stories that they're trying to tell about what might

have happened before the big bang or to create the big bang. What is the fundamental problem? Is it there's something from nothing? That's actually an even more difficult problem. No, it's got something to do with the type of theory that we currently use, which is this combination of description of the state of a system at one moment in time. It's normally called an initial state, but someone confusingly could also be at the final time. So this is just one specification of the state at one moment in time. And then we have some equation by which we can tell

from this one initial state what happens at any other time. And so the way that it works for the universe is that we take an initial state in the early phase of the universe. It can't be exactly at the big bang because as I said, this is a singularity. So it doesn't work, but it could be something after this. And then you apply your evolution law.

So in this simple case, that's just Einstein's equations. And then you can calculate how the universe should look like today. And you can compare this to observations. And if it works, you say bingo, okay, good theory. And now if you look at all those other explanations, basically what you do is you attach a more complicated story before this.

And this is something which you can always do. It's allowed by our theories, but it makes the theory completely ambiguous because there are many different ways that you can do it. And it's something that the scientific method actually doesn't allow, which is why I think it's a problem that we can't really resolve with the theories that we currently have. It's possible that at some point we'll come up with a different type of theory that might be able to overcome this limitation, but at least for now, I think

we're stuck with it. It seems to me like there's a lot of problems or theoretical physics is kind of bouncing off the limit of a bunch of the current theories that we have. I had Michio Kaku on the show speaking to him and it seemed like his explanations. There's always caveats here and there. There's always something that's like, well, we don't quite know about this, but it's sort of a best guess. And we've got this, but we need to add 11 dimensions in in order to make it work. And there's a lot of assumptions. Like, I'm, you know, I appreciate I'm bro sighing my way through this, right? But it seems like the, the, the, it seems unsubstantial or insubstantial at the moment, what we have to describe the universe and that

this is causing people to retrofit stories around what's happening in order to be able to make the theories work. Yes, right. And all of this is entirely unnecessary to actually explain what we observe. So that's the problem with it. So you get those multiple stories that can all be made to fit to the current observations. And then if you turn it around, it has the consequence that you can't use observations to tell those stories apart. Interesting one. Talking about how the universe began, what about how it's going to end?

Do we big crunch, big freeze? What's the other one? Big heat? Is there a heat death? Big grip, yeah. The heat death is also one of them, yeah. Okay, how are we going to end? How's it all going to finish? Yeah, I'm afraid the answers again, we don't know. In this case, it's I think it's easier to understand. So if we're trying to say how the universe is going to end, we have to extrapolate the current state of the universe into the future, possibly over trillions of years. And the problem is that there could be some physical processes that are just very rare and or they are so small that we

haven't been able to measure them. One example could be that the cosmological constant is not actually constant, but it might very, very slightly been changing. And now over over trillions of years or something like this, this could be the decisive factor for the fate of the universe. And it's just something that we we can never rule out. So basically what happens is that if we extrapolate the current state into the future, the uncertainty just blows up and in the end you can't say anything. So it's kind of an interesting mind game, I guess, to try to figure out, assuming that nothing else happens. The cosmological content

is actually constant and there are no other processes that we haven't yet heard of and so on and so forth. You can try to speculate what's going to happen, but I would say it don't take it too seriously. If nothing was to change, if there's no spooky alterations hiding in the future, what do you think would be most likely to expect in that case? I think if I remember correctly, at least in the current standard model of cosmology, it would be the heat death. So it's because the cosmological constant speeds up the expansion of the universe. So galaxies become more distant to each other and then the stars gradually die and they collapse to black holes, everything

will be dark and the black holes evaporate and you have this leftover gas of elementary particles and that's pretty much it. But I mean if you have another theory like Roger Penrose for example has this idea of a cyclic universe, then the whole thing eventually transitions into a new kind of big bang. So I know this is making this a little bit vague, but I mean, he has some mathematics to show for. And I think it's not entirely crazy. I actually have quite some sympathy for it, but I'm not really sold on it, I guess. Would you say speaking of mathematics and Roger Penrose's work is mathematics like the ultimate language or the basis of reality?

Is that what everything is built on? Yeah, that's a very interesting question. Believe it or not, I've actually thought about this for quite some bit. Well, it's certainly the case that currently it's the best thing that we have. And I think it'll continue to be the best thing for quite some time. We haven't fully exploited its potential, especially when it comes to a chaotic or complex system that we just talked about. We've barely begun to understand how the mathematics works. But how are we to tell if that's the best thing ultimately? Like we've barely just begun to understand nature and to try to formulate our hypotheses about it in forms of mathematics. Maybe in a hundred thousand

years somebody will come up with something better than mathematics. What else could there be? I don't understand what could be better than mathematics. there be, I don't understand what could be better than mathematics. Well, yeah, I guess that's the problem, right? Maybe we're just not smart enough. So I certainly hope that given time, there will be a more sophisticated species on this planet, and God knows what they will come up with. But one thing that I've played with is that it is, in principle, possible to do science without using mathematics as an intermediary. And we actually do this when we do computer simulations

to some extent. So the way that we currently do computer simulations is that we take the mathematics that we have extracted from observations and then we formulated in terms of an algorithm and we put that on a computer. So we use mathematics as this middle man to get the simulation. But strictly speaking, you don't actually need this, you could try to find another system that mimics the thing you want to describe directly. And actually, this is being done in quantum simulations.

So there are, well, one thing, there are certain types of quantum computers that are based on this idea. But more generally, you can simulate certain, the properties of certain fundamental particles. For example, the Hicks is one example that people have looked at, but also things like Moderna particles and so on. You can simulate them in condensed meta systems.

And now, again, this is using mathematics as an intermediary, yes, but strictly speaking, you don't need it. You could just say, well, I take the simulation in and by itself, and I just try to figure out what it tells me about this other system. So you can map reality directly to reality. And I think that's kind of a different way to do science that we haven't explored further enough. And maybe that's the way that we will be able to go beyond mathematics at some point. But this is like really, really far out there, wildest speculation. Is it true that other alien civilizations would have had to have discovered mathematics

as well? Often hear about mathematics being a universal language of the universe and stuff like that. Is there any legs to that? It seems very plausible to me, but how we to know, we haven't spoken to any alien species. So I mean, it's certainly the case that mathematics is kind of universal description of certain regularities. And so it seems plausible to me that this probably would have been the case, but I guess we'll have to wait until we meet those aliens to find out. I suppose if you were to think about any alien sat on its little green planet and it was

to look up at the sky at night and it would say there is a point of light in the sky. There is another point of light in the sky. There is another point of light in the sky. Like, I guess inferred from that is, look, that is the fundamental basis of counting, right? There's, you've got some mathematics in front of you. And I guess everything else from there all the way up to equals mc squared is just more of counting counting stuff and manipulating it. Yeah, that's how the argument normally goes. But again, I mean, this is kind of very strongly based on an hour experience of the world. So how are we to tell that not aliens would see reality to you completely differently.

You mentioned earlier on about the cosmological constant, which is part of this, is used to justify the fine-shoon theory of the universe, the fact that you have this unbelievable sort of knife edge, that a bunch of different characteristics of this universe, gravity, strong-week nuclear force, cosmological content. And I'm right in thinking that if any one of these was even ever so slightly different that basically we probably wouldn't exist and the likelihood of it occurring seems super, super low. And therefore people say, look, this is obvious that the universe has been fine-tuned

for life, but that's also super contested. Can you go into the fine-tuning theory for me? Yeah, so this is an argument which has been made for a long time and it works pretty much the way that you just summarized it. You take those constants that we have in the fundamental laws of nature, I think that 26 of them depends on how you count. You know, a lot of those constants are just zero for, you know we know the mass of the photon. And then you can argue over, it doesn't count as a constant if it's zero. So, you know, a splitting house.

But, yes, so you can ask stuff like, if the cosmological constant was a little bit larger, or if it was a little bit smaller, what would happen? And, or you can ask about the fine structure constant, that's the strength of the electromagnetic interaction alpha. So what would happen if we made this a little bit larger or smaller, or the gravitational consonants on the fourth. And in a lot of those cases, the answers, something would go badly wrong. SARS wouldn't be able to shine, or the galaxies

would never be able to form. Everything would collapse to black holes, or the entire universe might collapse immediately, or it would be impossible to form any kind of complex molecules that we think are necessary for life and people have gone through a lot of examples of that type. And some have taken this as an opportunity to say, well, that looks really unlikely that something like this would have happened by chance,

there must have been a creator. And then on the other side, there are physicists who say, well, this seems very unlikely to have been the case. Therefore, there must be a multiverse. So, two sides of the same coin, so to say, though they're both exactly opposite to some extent. So, they come out of the same idea, which is that it seems like there's something in need of an explanation, which is why are seems like there's something in need of an explanation, which

is why are the constants of nature exactly those. Now, the problem with this entire argument is that we have no way of quantifying the probability of this happening. So, if you tell me, well, it seems really unlikely, I would ask you, well, how do you know? I mean, it's not like you can collect a sample and ask, how often does that happen? Because we have only this one set of constants of nature. And we have no way of telling how likely or unlikely it would

have been. So typically these arguments work with some kind of statement about what is or isn't a small change in the constants of nature. But this, you can also question also question like how small is small? And why is this too small and why not this other thing? And so I think this is all it'll be fine. And I'm totally unconvinced by any of those arguments. There's also the curious fact that in the past couple of years you wouldn't believe it, but everyone's in a wider sexually progress on these matters. Some physicists have come up with

possible combinations of the constants of nature that are very different from the ones that we have now universe, but that still seem to allow for complex chemistry to happen. So physicists don't really talk about life, but it seems quite plausible that these other combinations of the constants of nature would also allow for complex chemistry and possibly even life. So, I think this argument is really just wrong and people should stop talking about it. Well, it's cool to think that there's another combination out there that would allow complex

life to evolve, because that, I mean, that would do a way with the fine-tune theory overall, right, that you have another version of this that could work. And I really like the idea that even though, if we were to look, I think it's the cosmological constant that's a very small number, or there's a couple of others, is it like the weak nuclear forces, an unbelievably small number compared with some other numbers that are in the bunch of constants. But when you talk about how much you want to change that by, as you said, who is to define what would be

a larger or a small change, who is to define whether that's a larger or a small number? And then when you talk about something being fine tuned, by design, you're talking about something being moved by small amounts, but if you're talking about something being moved by small amounts. But if you're the person that's already creating before that, a decision on what big and small is, then it's just you making, I guess,

like a value judgment or a pre-designed judgment on whether or not you think it should change. Yeah, that's one way to look at it. Normally, physicists draw their arbitrarily, say, if a change is of size one, then that's large. And everything that's below that order becomes very subjective. But then you can say, is it smaller than one over 100,

or is it smaller than one over 1,000? That would be small. But of course, you could just have started with, as you say, one over a thousand or something and then measure everything relative to that. And so this is exactly where this argument that physicists put forward becomes circular. What's your view on Boltzmann brains? I learned about these last year that there's potentially other versions of us floating out there in the ether and that me and you in this entire conversation might just be the brief flickering of some brain a million trillion billion miles away from here, and I might just be imagining it all.

Yeah, so indeed it might not have been a whole version of you, but maybe just your brain, which has the illusion that it's talking to me. Yes, so that's one thing which comes out of statistical mechanics if you take it too seriously. So basically, the idea is that if the universe goes on forever, which as we already discussed previously is likely to happen if you just extrapolate the current state into the future, then all kinds of combinations of fundamental parties that are in the universe should happen at some point. Provided the laws of nature for full of certain property, which is called ergodic which I'll come back to in a second. And then it can happen

that just coincidentally, you know, the elementary particles combine to form some particular molecule and it takes a really long time, you know, we're talking trillions and trillions of years. And then you wait a little bit longer and they combine to form something like that's like a cell and if you wait long enough It would form a brain and in fact if you just wait long enough it'll form any possible brain brains that will think all possible sorts But the downside of this is that the larger the thing the shorter it'll persist because it's surrounded by all this randomness which comes from the interaction of the other molecules which

have not spontaneous or similar to a large thing. So the shorter the thing lives the more likely it is. And this is what gives rise to this idea of the Boltzmann brains. So somewhere at the end of the universe in the very, very far future, there are all those brains spontaneously assembling themselves. Just thinking one thought, oh, hello, I'm here, or hello, I'm talking to Sabina, then they fall apart again. And I see you laughing. And yeah, it seems a little bit ridiculous. seems a little bit ridiculous. But the thing is that if you take this seriously, what we know about the fundamental laws of nature and about statistical mechanics, then you kind of have

to bite into this sour apple. I think that's a German idea, but I hope it translates. And so a lot of people think this is just silly, but I think it actually tells us something about the laws of nature. Because if you want to prevent this from happening, then we can conclude that the laws of nature can't be agotic. And that's a statement about the properties of those fundamental laws. There are actually some indications I should add that gravity or quite possibly the strong nuclear force might not be agotic.

And so I think that this is an interesting factual. So it's not quite as silly as it sounds as at first. Why would forces change within the same universe just because they're far away? Oh, no, the forces don't change. So the argument is that this statement that all possible combinations of fundamental particles happen at some time. This is only correct for loss of nature that have certain properties. So and this is this agodicity.

And this is basically what it means. So if the theories is agodic, then all these possible things will happen at some point. But this is not the case for all possible interactions that you can think of. In particular, if you have some interactions that are very strongly bound, which the strong nuclear forces,

it makes it highly implausible. But you take, you put some particles together and they get stuck in a bounce day. It likes the strong nuclear force binds together quarks in a proton or something like this. Why should everything that can happen, also actually happened at some point? Why can't they just remain stuck together forever?

And so this kind of interaction runs you into problems like this. And to be fair, Boltzmann, when he was thinking about this, didn't know anything about the strong nuclear force. It probably just wasn't a problem that didn't occur to him. Does that mean that it's wrong to say that mean you would be having this conversation further away? Is that the exact same model that people are using that if the universe outside of the observable universe is infinite, then it means that mean you are having this conversation a million different times in a million different ways. Well, the way that I would put it is that it's either

that or the laws of nature are not aggotic and then we learn something from it. Interesting. What do you mean you talk about knowledge and humans being predictable? What do you mean there? Interesting. What do you mean you talk about knowledge and humans being predictable? What do you mean there? Actually, David Deutsch talks about this. So I went and interviewed David Deutsch, which was very interesting. And he has this argument that knowledge can't be predictable because if you could predict the knowledge from what we already know, then it wouldn't be new knowledge, which makes sense. from what we already know, then it wouldn't be new knowledge, which makes sense. And I think it's also something that we see happening in physics, but also in other disciplines of science, is that any kind of new theory that we develop, it requires this intuitive leap.

It requires something new. You can't just strictly speaking deduce it from what came previously. So what you see a lot is that in hindsight, physicists often make up some kind of story for how they came to this conclusion. It was deduced from what they had previously heard and so on and so forth. But it seems to me that it's always like an element of magic between somewhere, you know, where there's this inside which comes in. And I think this is what David is getting at. I should say though that this is like something

at the at a very high emergent level. You could, on the level that we are talking about it. You could make an argument that fundamentally, if you're talking about course and clearance and the loss that they behave by, it might well have been deterministic. It just that for practical purposes, we would never have been able to predict it. Do you think, does that mean that knowledge is discovered or created? Well, I guess both, right? So sometimes, sometimes of knowledge you discover, others you create. I know people discuss this a lot when it comes to mathematics, but I've always been kind of a little bit ambiguous about it.

I don't see that it has to be one or the other. It could well be both. Got you. When it comes to consciousness as well, obviously we've spoken about free will, spoken about simulation. Is it possible for us to compute consciousness? That's a very good question.

As you probably know, Roger Penrose takes the point of view that it's not possible. He has an argument that's based on Gurdles' theorem, and I have an interview with him in my book about it. I'm not really convinced by this argument, but then, you know, he's a Nobel Prize winner and I'm not, so maybe you should listen to him and not to me. This is why I have the interviews in my books that you don't just hear what I think. So he thinks there's an uncomputable element to consciousness. And so the loss of nature that we currently use, they are computable. And I think this is one of the reasons why he thinks that there's something about quantum mechanics, which we don't yet fully understand.

And so he has put forward some alternative theories to quantum mechanics where he thinks this element of consciousness comes in. So I think it's interesting. I'm not convinced that it's quite right, but then maybe there's something worthwhile to it. So if he's right, then it would mean that artificial intelligence, at least in the way that we can currently formulate it in terms of algorithms run on computers, would never be really conscious. Yeah, well, I think that's maybe about 10 years ago,

or when did super intelligence come out? 2014, Nick Boss from Spok something like that. When that came out and I read that, I was adamant that the artificial general intelligence apocalypse was going to be with us within 10 or 15 years. And it seems like the AI safety community, the discussion around the A AI in general has kind of switched a little bit in that time.

It's not like I've got my finger on the pulse of the coolest stuff in the development of it, but just from my sort of perspective. And it seems now like well-defined problems as things that artificial intelligence is getting incredibly good at. And poorly defined problems basically haven't made much progress at all as far as I can see and it's the poorly defined problems that are precisely where the general from AGI would come from and I think that it seems like some of the what did they call embosterodamas, some of the Bostradamus concerns the pre-apocalyptic people, it seems like that's changed. It seems like the narrative around this sort of discussion has changed precisely

because of the fact that we're having more and more difficulty in computing this stuff. Yeah, it's very interesting. They're also increasingly running into resource limits, it's my understanding, like those running power. Yeah, computing power, energy. And then there's the problem that, you know, the stuff with the, what are they called, hyperparameters that have to be found out somehow. And, oh, those neural networks that are typically used for artificial intelligence, they have what's called hyper parameters that have to be chosen so the network can properly learn. And that's a little bit of black magic, like where do those hyper parameters come from? And there's a lot of discussion, at least that's my understanding, and like you, I don't

really work on this, I'm just following it from the outside that because of this black magic it's kind of irreproducible what what they achieve because you don't know how did they come up with those parameters how often did they try it how often did they fail and so there's now a move in the community, whether trying to make this more transparent, so that it's easier to figure out what was actually done. Hmm. Part of me feels grateful, I think,

that giving a self-reprogramming superintelligent AGI, a little bit more time to come around, while we could perhaps get some more wisdom Self-reprogramming super intelligent AGI, a little bit more time to come around while we could perhaps get some more wisdom to come along with the technology. That seems like a pretty good idea to me. Even if it's not by choice, it's simply by programming language restriction and our own lack of ability to write whatever it is

that we need to write. Part of that feels like probably a good thing. I think overall, I think that technology outstrips wisdom and the fact that we're hitting some real roadblocks is interesting. Am I right in thinking that Moore's Law, the computing power doubles every two years on average, that that's actually beginning to slow as well. I've heard this too, but then I've heard other people objecting to it. And so I'm really not a technology person. So I'm not entirely sure who to trust.

But yeah, so the death of Moore's law has been proclaimed a few times already. So at this point, I'm not really sure to trust. There's also this entire problem that with the word economy after the pandemic and all the supply chain Issues it might not you know, it might be an anomaly in the data So it's maybe maybe a little bit unfair. Yes, of course that makes sense. How come how come nobody gets any younger? Why aren't why aren't any of us getting any younger? Yeah, so that's an interesting question

In that we've we believe we figured out part of the answer. So in physics this goes under the problem of the era of time. Why does time seem to look different in one direction than in the other. And we believe we understand part of it. Part of it is just that certain chains of events are very likely to happen, whereas others are unlikely. So things are likely to break, disorder is likely to increase, but it's very unlikely that things spontaneously, unbreak, and it's very unlikely for orders, spontaneously to decrease, which is just another way of saying that entropy normally increases.

But this of course brings up the question like if entropy constantly increases, why was it small in the past to begin with? And the way that we currently deal with it is that we just say whether the universe was born with a small entropy and we have no idea why and that makes everything work. And that's true. But we have no idea why and that makes everything work and then that's true, but we have no idea why this was the case. And it's again, it's a question about the initial state, which we already discussed when we were talking about the beginning of the universe. So it's one of those issues where we can't we don't even know how to answer the question. It's one of the, it's a question that Penrose is actually trying to answer with his psychotic universe. Hmm.

And how do you envision from a physics perspective, how do you envision time? Is everything happening at once? Well, at least in our current theories, time is the dimension. So of course, if you map out space and time, then it's not that everything is happening at once. It's just that the whole thing together is one mathematical construct that just sits there. It's not that there is one particular moment, which we call the present moment, that is special in any regard.

I mean, it's special in our perception, but then you could say in our perception, each moment is special at some moment in time. So in that sense, they're all equal, if that makes sense. Would this be kind of the same as saying, because I'm stood in this spot right now, this is the spot which is special to me, but if I was stood in a slightly different spot, that would be in terms of the three dimensions, right, of space. and time is sort of an equally arbitrary choice of now and then now and then now again. Yeah, it's very similar except that in space you can go back and forth worse in time you can't. Why is that the case?

There is an arrow of time that it has directionality at all. Well, that's what I just said. We have only half of the answer, right? So if you're asking, like, why can't you go back in time? It's because you were already there. And so if you were allowed to do it a second time, then that could lead to all kinds of cause the paradox. This is the usual problem with time trouble. I'm afraid so that it's not going to happen. Well, if you say so. Look, Sabina Hassanfelder, ladies and gentlemen,

if people want to keep up to date with the stuff that you're doing, you've got your YouTube channel, which is blowing up now, and your Twitter and your new book, where should they go? Um, well, just Google my name, because it's not a very common name, and you'll find more out about me than you ever wanted to know. Sabina, I appreciate you. Thank you. Thank you. you