Instant Genius - Katie Mack: How will the Universe end?

Episode Date: August 24, 2020

The end of the Universe may be a common feature in science fiction, but this one isn’t a crisis that can be averted by a team of superheroes. The Universe really will come to an end one way or another, and we have an idea how – five ideas, actually. In this week’s episode of the Science Focus Podcast, astrophysicist Dr Katie Mack talks to us about the future of the cosmos. She dives into these five possible apocalypses, from the Universe gradually fading out to the ‘quantum bubble of death’. Let us know what you think of the episode with a review or a comment wherever you listen to your podcasts. Subscribe to the Science Focus Podcast on these services: Acast, iTunes, Stitcher, RSS, Overcast Read the full transcription [this will open in a new window] This podcast was supported by brilliant.org, helping people build quantitative skills in maths, science, and computer science with fun and challenging interactive explorations. Listen to more episodes of the Science Focus Podcast: Dr Jacob Bleacher: Why do we need to go back to the Moon? Colin Stuart: The most mysterious objects in the Universe Professor Fay Dowker: What is the problem of quantum gravity? Dr Erin Macdonald: Is there science in Star Trek? Dr Becky Smethurst: How do you actually find a black hole? Mark McCaughrean: How do you launch a successful space mission? Hosted on Acast. See acast.com/privacy for more information. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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then every point around it would also change value, and it would create a bubble of this kind of space with different laws of physics, different mix of particles and so on, that would then expand out at the speed of light and destroy everything because it would put it into this different kind of space, this what's called a true vacuum with different laws of physics. You're listening to the Science Focus podcast from the BBC Science Focus magazine team, with the UK's best-selling science and technology monthly,

available in print and in several digital formats throughout the world. Find out more at ScienceFocus.com or look out for us in your app store. Hello, I'm Alexander McNamara, online editor at BBC Science Focus. The end of the universe may be a common feature in science fiction, but this one isn't a crisis that can be averted by a team of superheroes or indeed super-scientists. Inevitably, at some point in the long-distant future, the universe really will come to an end one way or another. And we actually have an idea how. Five ideas, in fact.

In this week's episode, astrophysicist Dr. Katie Mack talks to online assistant Sarah Regby about the future of the cosmos. She dives into these five possible apocalypses, from the universe gradually fading out to the ominous sounding quantum bubble of death. First of all, could you give us a quick description of what your book is about, please? Yeah, my book is about the end of the universe. So in the book, I go through several different possibilities for how the universe might end and talk about how we are trying to figure that out in physics and astronomy and what it would look like if you were there to see it. Why does the universe have to end at all? Why can we not keep on as we are? It seems to be doing pretty well to me. Yeah, yeah. Well, for a long time, there was an idea.

that maybe the universe could just be in a steady state and, you know, unchanging forever. But once the Big Bang was discovered, once it was found that the universe started out in this sort of hot, dense state and has been expanding since then, it became clear that the universe changes and evolves over time. And then the number of possibilities for it remaining sort of reasonably pleasant decreased rapidly. Now it's at the point where we can see that the universe is expanding and we can see that, in fact, the universe is expanding faster and faster all the time. And when you get to that point, it's just the natural evolution is toward something where things that exist in the universe now will all be destroyed at some point in the future.

And there are a few different possibilities for how that can happen. But the idea that everything's just going to kind of keep going as is, does not, not work in the kind of universe we live in. Do we have any idea of when this is going to happen? I'd like to get this out of the way at the start. Is this something that's going to happen within a reasonable human time scale? There's no reasonable expectation that it's something that wouldn't be in the very, very, very far distant future.

So technically, there's a lot we don't understand about the universe and things could happen unexpectedly, and in one of the possible end-of-universe scenarios I talk about in the book, vacuum decay is based on a random process that in principle could happen at any time, but based on our understanding of how that physics works, we wouldn't expect it to occur any time within the next 10 to the power of 100 years. And even then, we're not sure if it's possible at all. So, you know, people do get worried about, you know, oh, it could happen in any moment. There are a lot of things that could technically happen at any moment that we don't worry about. And this one we very much should not worry about. But for the most part, we're talking

about things that are so many trillions and trillions of years in the future that it's hard to even come up with words to explain that sort of time scale. Right. So if it's not something that, you know, we even expect necessarily humans will even be around for, Why do you think it's important for us to care about what's going to happen at the end of the universe? I don't know if it's important that we care, but I think that we do. I think that it's just part of human nature that we are interested in where we came from and we're interested in where we're going. And we, in this case, to mean the bigger picture, the much larger universe.

But I think that we are interested in our environment and in our story and in how we fit into the story of the cosmos, into the whole narrative of existence. And so it's something that I think we're just basically curious about. And there are reasons why, as a physicist, it's an interesting thing to study because you, by extrapolating a theory to its ultimate conclusion, to stretching it to the limits, it does help you learn something about the theory, about how the physics works. because it's a useful exercise to go through in any theory or model of the universe. So it's a useful thing to do from a physics perspective to do these sort of thought experiments

and to extrapolate. But I think just as people, we just want to know this stuff. Fair enough. So there are, in your book, you cover five different ways that the universe can end. Could you just give us a very, very brief. outline of what those five different ways are. Sure, sure. So the first one I talk about is the big crunch.

This is the idea that the current expansion of the universe might at some point reverse and everything could come crashing back together, creating conditions very much like the sort of hot primordial soup we came out of initially. That one's unlikely now based on our understanding of how the universe is expanding and speeding up in its expansion. So that leads us to the next one. the heat death, which is the one that we think is probably most likely if you talk to physicists and cosmologists. The heat death is, it sounds a counterintuitive to call it

the heat death. I'll explain what the heat there refers to, but it's also sometimes called the big freeze. It's where the universe continues expanding and expanding faster and faster indefinitely into the future. And what that does is it kind of just dilutes everything and it makes galaxies move farther and farther apart from each other, and everything gets more and more separated and isolated. And you end up with each galaxy sort of in its own sort of sphere of darkness where it can't see other galaxies. And at some point, stars burn out and black holes evaporate and matter decays,

and you just end up in this sort of cold, dark, empty, lonely universe. And the only thing left in that universe is like a tiny amount of sort of waste, heat from creation. So this sort of, all this left is this extremely low level radiation. That's just the leftover, leftover sort of detritus from everything that ever was. And that's called the heat death. And that's the saddest story. But it does seem to be the kind of consensus model based on just extrapolating our current expansion into the future. And then the other three are sort of more speculative ideas that for various reasons people talk about in the cosmology literature. So one of them is called the big rip where whatever is making the universe expand faster right now.

We call that dark energy, depending on what kind of dark energy it is. It could be something that doesn't just separate galaxies apart and make them more isolated, but could actually pull the stars off of galaxies. become more powerful over time and start disrupting structures in the universe at some time in the future. And it would pull galaxies apart. It would pull planets away from their stars. And eventually, at the sort of final moments, it would destroy planets and stars and atoms and rip apart of space itself. And that's something that is not the most favored idea, but it's a, it's something that we can't rule out based on the data yet. But all we can say about it really is

that we're fairly sure it can't happen within the next 200 billion years or something like that. So, you know, as we get better data, we'll probably just push that number back and back. But we may not ever be able to say for certain that dark energy won't get weird at the end and destroy the universe that way. And then the next one is called vacuum decay. And this is the one I mentioned that could technically it happen at any moment. But again, don't worry about it. It almost certainly won't.

it's where there's a sort of instability built into the universe and it means that the universe is vulnerable to a kind of quantum event occurring somewhere in space that would create a bubble of a different kind of space that would expand through the universe at about the speed of light and destroy everything in its path and that's a that's a fun one to me because it it combines some interesting ideas in particle physics and cosmology, and it's just this very sudden, unexpected thing where at some moment the universe would basically just cease to exist. You know, there would just be this bubble, it would destroy everything, that everything's done. So that's an interesting one and my personal favorite, because it's the most dramatic.

And then the final one I talk about is really a set of different ideas that all have in common, kind of cycling cosmology. So I call that scenario bounce, but it's really just any kind of idea where you have an end of the universe that then transitions to a new beginning and so on over and over again, or even just once, maybe something that has, there was a previous universe before ours that led to our universe or at the end of our universe, there will be a new one, some kind of idea like that. And there are several possibilities for that, some where you have kind of a big crunch that leads to a big bang, somewhere you have a heat death that leads to a new big bang. So there's a variety of ways you can get to that. But those ones are

interesting because in principle, in certain models, you could have some information passing from the previous stage to the next one. And so it brings up a kind of way that something could live on past the end of the universe, which to many is an appealing idea. Wow. So the There's a sort of rebirth of the universe in that sense. Yeah, yeah. I mean, it would be a different universe, you know, and probably there would be no trace of anything of us. But the idea that there could be is intriguing, I think,

to a lot of people, including a lot of physicists. Right. So I sort of think of the big crunch, the big rip and the big bounce as all being kind of related in a sense. Would you say that's right? in the sense that they're all sort of based on the dramatic motions of the cosmos to me it sort of sounds like they all are a result of the way that the universe is expanding and moving at the minute yeah yeah sort of like what you know given that we know how we're expanding at the minute

what's going to happen is it going to is it going to come back on itself is it going to rip or is it so what is the mechanism that would sort of determine whether the universe would sort of turn back on itself and into the big crunch or whether it would, you know, rip or bounce? Yeah, so it all, for the, really for the heat death and the big rip and the big crunch, the thing that's governing the possibilities there is, is dark energy. So, you know, we don't know what dark energy is. All we know is that as of about five billion years ago, the expansion of the universe is speeding up. And there's nothing in sort of ordinary matter or energy that could do that.

And so dark energy is some component of the universe that makes space expand faster, that sort of counteracts the gravity of everything that's kind of trying to pull matter in, pull space back in. And so because we don't know what dark energy is, we don't know for sure how it's going to act in the future, our sort of baseline assumption is that dark energy is just a cosmological constant. It's just a property of the cosmos that space has this sort of stretchiness built into it. And that leads you to a heat death where the universe expands faster and faster and just fades away eventually.

But if dark energy is something more dynamical, more interesting that changes over time in some interesting way, then you could end up with something where dark energy gets more powerful and rips the universe apart or changes nature, you know, changes direction and pulls the universe back together. Maybe that could lead to some kind of balance as well. Although some of the balance models have sort of extra components or extra things involved to make those things, that stuff happen. But yeah, so dark energy is the big kind of question in trying to figure out what's going on with the future expansion of the universe.

And then when it comes to vacuum decay, the big question there is trying to better understand particle physics and how that works in our universe, because that's what would break down and create this change in how, you know, the new kind of space would be a kind of space where particle physics acts differently. And that would be the thing that would destroy everything, basically.

I'd just like to go back to dark energy for a moment. So if that's the sort of mediating factor, the thing that we don't know enough about, how are we going about learning about dark energy? And like, do we have any good theories about what it could be at the minute? Well, yeah. I mean, aside from a cosmological constant, there's the other idea is that dark energy is what's called a scalar field, which is a kind of a field that has some value all throughout space. we've only we only have evidence of scalar fields

existing in physics in one other contexts and that's the Higgs field that's associated with the Higgs boson which is this particle that the Large Hadron Collider discovered, it has something to do with how particles get mass so a kind of stuff

called a scalar field we're pretty sure that those things can exist in nature and if dark energy is something like that then it could be something that's changing over time that does, you know, weird things to the universe. And we also have reasonably, maybe there was a scalar field that was involved in the very early universe for a very rapid

expansion phase called inflation. So there's a theoretical construct for what dark energy could be if it's not just a property of space. But as for figuring out, you know, the properties of dark energy, there's, there aren't that many possibilities to do that. it's actually quite hard to study because whether it's a cosmological constant or a scalar field, it's something that seems to be totally uniform throughout space, invisible, untouchable, and all it does is make the universe expand faster. And so that's not an easy thing to study. You can't capture that in the lab.

And so the tools we have to study it are the expansion rate of the universe, which we study by looking at very, very distant objects, which we're seeing as they were in the past and seeing how they're moving through the universe. And then by looking at how things like clusters of galaxies built up over time by looking again deep into the past. And those kinds of things allow us to study the effect that dark energy has had on the cosmos over time,

and that gives us some clues as to how it works. There are also some possibilities that if it is, some kind of new aspect of physics like a, like a scalar field, there are certain versions of that that could interact with things in laboratories. So there are some laboratory experiments that are looking for specific kinds of dark energy or things associated with dark energy. So there are some laboratory possibilities, but it is a hard thing to study. And right now our best tools are things like galaxy surveys. And there are some of those that are coming up that will help us who much better study the evolution of the cosmos over time.

So what do you look for in a galaxy survey? So you look at as many galaxies as you can find, and you try and measure how they're moving, how old they are, how far away they are, and so on, as a way to kind of trace out the expansion history of the universe. So there's a new instrument being built, the Vera Rubin Observatory, that's going to carry out a survey called the LSST,

and that will be studying something like billions of galaxies through the universe. And it's a survey of galaxies in the whole, the part of the sky that the telescope can see. And it will be telling us a lot more about just how matter is distributed through our cosmos. Then there are other tools we have like studying the cosmic microwave background, which is the sort of afterglow of the Big Bang. And by looking at that, we can learn something about the early universe, we can learn something about the components of the universe, and that can also give us some more clues about dark energy and how it's behaved over time as well. I think in your book, you described the cosmic microwave background as being a way to look directly at the big bang. Is that right?

Yeah, yeah, yeah. So it's a wild thing. When we look out into the cosmos, when we look at very distant objects, we're looking back in time because the light from those distant objects took a long time to get to us. So if we look at a galaxy that's billions of light years away, then it took the light billions of years to get to us. And if we look farther and farther away, then we see parts of the universe that are so far away that it could take 13.8 billion years for the light to get to us. That's how old the universe is. And so if we think that the universe started as this hot, dense, sort of space filled with sort of roiling plasma, which is what, which is sort of what the Big Bang theory is built on, that the universe was hot and dense in its early times. But hot and dense everywhere, it wasn't just a single point. It was the whole universe was hot and dense at some early time. Then it sends the reason that if we look anywhere in the universe, if we look far enough away, we will see parts of the world.

universe that are so far in the past that they are still on fire. From our perspective, they're still in that hot, dense phase. And so we can actually look out into the cosmos and see that primordial fire from which all of our cosmos was born. And the light that we see in every direction, if we look far enough way, is this leftover light from the Big Bang, the light directly coming from that fire to us traveling across billions of light years to come. come to us. So we're seeing the final stages of that primordial fire when we look out into the cosmos. And I think that's, I think that's amazing that we can see that. Let's go back to the heat death of the universe. So how that's related to thermodynamics,

isn't it? Yeah, yeah. So, yeah, technically you don't get to a heat death until you get to the maximum entropy state of the cosmos. So entropy is a, sort of a measure of disorder, you know, so the more disorder something is, the higher the entropy. Okay, so there's this very strict rule in physics called the second law of thermodynamics, and what this says is that over time in any closed system, and we think in the universe as well, the entropy can only increase. And this is why, you know, you can't have a perfectly efficient machine. You'll always lose a little bit of energy to friction or something. can't have a perpetual motion machine because entropy increases, there's always a little more

disorder, you always lose a little bit of energy to waste heat or something like that. And so if that's the case in the universe, which it seems to be, then over time, all of the processes in the universe will be a little bit inefficient and things will degrade and decay and sort of fall apart. And so in the far, far, far future of the universe, you get closer and closer to the maximum entropy of the cosmos. So you get to the point where entropy can no longer increase because everything is degraded, everything is dissipated into pure waste heat, all of the energy is disordered. And when you get to that point, when you have the maximum entropy state, then that is truly the heat death, because that means that basically nothing can happen anymore. Because if entropy has to increase, that's just a totally,

solid law of physics, that entropy can only increase, then you can't get to maximum entropy and then do something that would create more entropy. So at that point, you know, there can be little random fluctuations or something that might, you know, rearrange energy a little bit, and then it would come back, you know, to this maximum entry state, but you can't do anything productive. You can't build anything anymore. You can't even, like, You can do technical calculations that say you can't even think anymore. Like, there's just everything will be, you know, totally disordered. And that's the heat death.

Is that the same as saying that the universe will be the same temperature everywhere? Yeah, it'll be a uniform temperature. There might be, you know, random fluctuations here and there that would settle out again. But, yeah, everything would be this uniform temperature. and it's a calculable temperature of kind of the background of the universe after it reaches maximum entropy. It's a very small number. So why is that the most likely explanation for what's going to happen to our universe? Well, we think that's the most likely just because if you take the kind of expansion we're having now,

where the universe is expanding and it's speeding up and its expansion, then what that does is it kind of separates everything out, and every sort of galaxy can only go through its own evolution with stars dying and things like that, and then things will decay. And that's just part of, it's just kind of, it'll all sort of decay into entropy in its own space. And then once everything in each region decays, then all that's left is you actually get a tiny, tiny bit of radiation. from the cosmic horizon, which is sort of the region around each point out to which the information can't pass anymore.

But there's a kind of horizon that occurs in a space that's expanding faster and faster all the time. And that kind of horizon has a little bit of radiation associated with it. And that ends up being all that's left in the universe is just this tiny little bit of radiation that's basically, you know, just waste heat more or less. Right, so that's something to look forward to. Yeah. Yeah, it's a bit of a sad ending.

There are some interesting theories about how you could have random fluctuations that could lead to a new big bang or even weird little entities fluctuating out of this empty heat-death universe. So there are some interesting theories about strange things that can happen. If you just have a universe that's basically empty, but you leave it alone for an infinite amount of time, all the weird things can occur. And so in the book, I talk about some of the stranger hypotheses in there. So can you give us some example? Yeah. So there's this really weird sort of thought experiment that's been around for a while where if you, if you,

think that if you want to have a universe that sort of where you you kind of randomly fluctuate out of a heat death universe and create a new big bang, if that's an idea that you want for the origin of the cosmos, which would make sense if you want a universe where you have an end of universe and the new beginnings here and there and branching out of some larger space, then the problem with that is that you can calculate that that's a very unlikely thing to happen, right? To have that random fluctuation of a whole new universe, it's, it's, very improbable. Much more probable is that only just like one galaxy would randomly fluctuate out of the sort of soup. And more, more probable even than that, it's just one planet would

fluctuate out of it. And then more probable than even than that, just just one person or, or even more probable because it requires getting fewer particles together would be just a single brain like a single human brain that thinks that it's living in an entire universe with the whole past that had a big bang and cosmic evolution and everything like that. And this is actually a problem in physics that because that single human brain is more probable to occur than the entire universe, you can't say for sure that we are not just imagining all of cosmic history. It's this really bizarre problem. It's called the Boltzmann brain problem. And it's not a problem because we actually think these things would happen, but it's a problem

because it's hard to figure out how these probabilities make sense if you calculate that that's something more likely to happen than the universe existing. Does it be like problems like that, do they? No, no, no. So it means that we have to be really careful with how we suppose a universe might come out of this kind of state. And you have to, if you set up a system where it's more likely that we're just imagining the cosmic history than that cosmic history actually existed, then you've probably set up a bad problem in physics. And so it's one of these things that, the physicists worry about when when constructing possible models of the universe. Now I'd like to talk a bit more about vacuum decay. You mentioned earlier that it's the result of an instability in the universe, which brings about what you call in the book a quantum bubble of death, which I think that's what makes

it my favorite theory. So what exactly is this instability? Right. So, okay, so I mentioned before the Higgs field, which is a, it's kind of an energy field that pervades all of space. And the Higgs boson is this particle that was discovered at the Large Hadron Collider that is somehow associated with this Higgs field. Now, the Higgs boson was called by some of the God particle because the Higgs field was associated with how particles got mass in the early universe. and so, you know, sort of the creation of matter in some way has something to do with the Higgs particle through the Higgs field. But the Higgs field is really the important thing, not the particle itself.

But because we've detected the particle, we can learn something about the Higgs field by measuring the mass of the particle and how it interacts with other particles and so on. And unfortunately, what we seem to be learning about the Higgs field is that it looks like, based on current data, it has a vulnerability. to changing its value. So the Higgs field, it's this energy field that pervades all of space, has some value associated with it, some sort of number. And the value the Higgs field has determines how particle physics works, how particles work together, the masses of the particles, which particles even exist, how the forces of nature work together.

And in the very early universe, the Higgs field had a different value, and there were a different mix of particles, different kinds of forces of nature. and you know atoms and molecules and things couldn't exist at that time because the laws of physics just weren't set up that way. When the Higgs field changed to the value it has now, that allowed the, you know, creation of protons and neutrons, electrons and molecules and all of these things, right? So if the Higgs field were to change again, that would be very bad for us as creatures built out of, you know, atoms and molecules. because we want our particles to hold together. We want physics to work the way it does.

So unfortunately, the data currently point to the idea that the current value of the Higgs field is not sort of the value that the universe would in some sense prefer, that there is some other value that if you disturb the Higgs field enough, it would switch to that other value and be more stable there, which means that if you could somehow cause the Higgs field to change value at one point in space, then every point around it would also change value and it would create a bubble of this kind of space with different laws of physics, different mix of particles and so on, that would then expand out at the speed of light and destroy everything because it would put it into this different kind of space, this, it's called a true vacuum with different laws of physics.

Now, fortunately, disturbing the Higgs field seems to be something that we cannot do, that even, you know, astrophysical events cannot do. That doesn't seem to be plausible, but... I'm not sure we'd want to either. No, we wouldn't want to, certainly. But I'm just saying, like, don't worry about particle colliders. They can't do this. People do worry about that. Don't worry about that.

But what can do that, what can switch the Higgs field to this other value is quantum tunneling, which is a... a process that happens all the time with subatomic particles. We find quantum tunneling in laboratories where a particle might be on one side of a barrier and then suddenly appear on the other side, and that's just something that happens in quantum mechanics. And we even use this in our electronics and things like flash memory. We use it for certain kinds of microscopes. We make use of the fact that quantum tunneling happens as a way to kind of slowly leak particles

into the machines and so on. Like there are, quantum tumbling is a thing that totally happens all the time in physics. And unfortunately, it could also happen to something like the Higgs field.

And if it did, if the Higgs field quantum tunneled to its different, to a different state somewhere in the cosmos, then that would also create this cascade that would create this bubble

that would expand and destroy everything. And because, Because quantum tunneling is not something that we can deterministically predict, we can't say exactly when it'll happen or where, that means that it's just a random event that we can't say when or if it might occur. But we can put a time scale on it because there are sort of probabilities associated with that. And so we can say that it's very, very unlikely to occur within the next 10 to the power of 100 years or maybe 500. So that's a long time. It's much longer than the age of the universe.

We probably don't have to worry about it. But it's intriguing because we don't know when it would happen if it were going to happen. We don't know for sure if it could happen because the calculations that lead to the idea that vacuum decay is even possible are based on assuming that we understand particle physics in all its detail. And we know that there's aspects of particle physics that we don't understand yet. So there might be something that comes into this picture and changes it entirely. But it's an intriguing possibility, and it is something that physicists worry about when thinking about, you know, how were, what kinds of assumptions we're making about particle physics and about cosmology. And it's one of those things that makes you really just sort of stuck and re-evaluate your whole place in the universe, doesn't it?

Yeah. Yeah, I mean, yeah, it is. I mean, even just knowing that the Higgs field changed in the past, changed the mix of particles in the past, you know, we are very unimportant to the cosmos, and it can do things to how physics works that we have no control over. You know, and it is, there is something humbling about discovering all of these, you know, giant forces in the universe for which we are totally unimportant and, you know, in principle could affect us in some very big way. I remember the first time I heard about this and my friend just said to me something like

so there's this theory that there could be this you know this instability in the universe and it could suddenly create this like expanding bubble which destroyed everything in its path and it's travelling at light speed so you'd never even know it was coming and in a way that's kind of terrifying but also

yeah I mean if you don't know it's coming and I mean it's an all right way to go I suppose I mean you don't even feel it because if it's coming at the the speed of light, like your nerve impulses don't travel that fast. You wouldn't notice. Like, it's kind of inconsequential. Nobody's going to miss you. There's no tragic aftermath. It's just, it would just be done. The universe is just done. Like, oh, well, that's it. So now I'd like to talk about the song that you were mentioned in by the musician Hosier.

Yeah. So here's this song that came out. When was it? Was it last year or the year before? It was last February. Last February, yeah. So he's got this song called No Plan. And he talks about the end of the universe. So can you tell us a bit about how that came about? Yeah.

Well, so I've known him for a while through, like, we've been friends through Twitter and stuff, which is amazing because I've always been a huge fan of his music. You know, he's incredibly talented. And one of the very strange things about Twitter is that sometimes you get to know people who you massively admire and you have to kind of be cool about it. But, yeah, so we became friends a while back. And then he was working on this album and we'd been talking about, you know, physics and stuff sometimes. And he mentioned that he has this song about the end of the universe and that he'd been kind of like watching these lectures I did about. the end of the universe and stuff, and he asked if he could put my name in the song. And I was like,

sure. That sounds good to me. And yeah, and so he put my name in the song, and the song is about the heat death, basically. I guess as a metaphor for, you know, love or something. But it's, I mean, it's a very cool song. It's a very, you know, sort of, I don't know, apocalyptic, of a song. I like it a lot. But anyway, so he put my name in the song and then and then he went around doing concerts, you know, for the, for the album. And he would introduce the song and, like, talk about my work and then talk about, like, and give like a short lesson on the heat death of the universe, which was awesome because it's like, you know, real cosmology at a concert. And then, and then he would even, he asked me at some point for, for a quote for, to put, like,

some text on the screen behind him when he was doing arena shows. So then he's doing these shows where he's singing the song and there's like words behind him of me talking about like how the how the heat death, you know, leads to this dark, empty universe. It's just been, it's been amazing and totally wild. And I love that all these concert goers are getting this unexpected dose of, you know, cosmological physics in their music. I think it's great.

And it's quite a human take on the end of the universe as well, isn't it? Because it's not really so much about the sort of science side of it. It's sort of about coming to turns with it, isn't it? Yeah, yeah, yeah, yeah. I think that and I think that that the kind of discussion of it in that song is also very much the way I talk about in the book as well, which is, you know, thinking about what it means. for us if the universe doesn't go on forever and how that can that can actually be kind of freeing

to, you know, to think that there's, you know, there's not going to be some kind of justification at the end for everything. You have to actually live in the moment and, and experience what you can while the universe exists. So, yeah, it's a great song. I really like it. That was astrophysicist Katie Mack talking about the end of the universe. BBC Science Focus magazine this month, we dive into the depths of the ocean to see the new technology solving some of the sea's biggest mysteries. Dr Michael Mosley explains the long-term risks and benefits of veganism, and we talk to an engineer about building biological robots. As always, there are loads more science stories inside and available on sciencefocus.com,

and if you like what you've just listened to, then please leave us a rating or a review wherever you listen to your podcasts. Thank you for listening to the Science Focus podcast from the BBC Science Focus magazine team. With the UK's best-selling science and technology monthly, available in print and in several digital formats throughout the world. Find out more at sciencefocus.com or look out for us in your app store. This podcast is sponsored by Name, Audio and Focal. The texture and emotional depth of music can be lost through digital sources or poor signal.

Name Audio believes you can have digital precision with analog warmth. Alongside French acoustic specialist vocal, Name creates high-end audio systems combining innovation with craftsmanship so you can listen to music, just as the artist intended. Discover more at nameaio.com. Ambition comes in all shapes and sizes.

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