How will the Universe die?

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Speaker 1: You're basically telling me that the universe could end tomorrow, right, Um, it's very unlikely because it didn't end yesterday. Into the possibility that the laws of physics won't change is small. Yes, exactly. Hi, I'm Jorge and I'm Daniel, and this is Daniel and Jorge explain the universe, the entire god forsaken universe and everything in it. That's right, even the parts we can't see, even the parts we will never see. We're going to explain them all to you today on the program The End of the Universe. How will the universe end? Will it end? What's it going to be like? And what should you order in order to prepare? Do we have a spoiler alert at the top of the episode? Well, do you know the fate of the universe. I'm curious to hear. Do you have me at the edge of my seat now, or hey, spoil it for me. I'm desperate to know how will the universe end? Mostly I just have Internet rumors. I think you know some plot points of Leaked Well, you know, the Internet is always right, It's wisdom of the crowd thing, right, So this is an interesting question. So, Daniel, assuming that we survived the next couple of years. Why is this an important question? Why is an important question? Why do we want to know how the universe ends? Well, you had me just a minute ago in the edge of my seat because I thought you were going to tell me the answer. I think it's a it's a basic human curiosity. You know, there's this desire to understand where we came from, why we're here, how this all works, what's the point of existence, basically, what's the context? And I think people want to know how the universe is going to end because it's part of that framing. You know, it's like as interesting as knowing how the universe began, yeah, or like how are you going to die? Yeah, exactly, Or if you're gonna die, if you're gonna get uploaded to the cloud or downloaded into a robot, or I'm actually talking to you from the cloud Tenniel, Well you're talking to a robot. So I think that there's this sort of the large scale human curiosity answer, like you know, what is the answer of life, the universe and everything? And then there's also the short term like are we going to survive the next couple of years? Are our kids going to have a place to live. You know, why do we care about the environment, why do we care about human survival of human society? Because we want to be around. So when you say we, you mean like us as a species. No, I mean we as and me and my direct genetic offspring. And oh I see, I see nobody else matters. You can cut off all of the other parts of the evolutionary tree. Well, this is a deep question, And as usual, we went out and asked people how they thought the universe would end. And here's what people on the street had to say. How do you think the universe is going to end? Um? I've heard a lot of theories about this sudden reaches the end of its life cycle and like I was just combusting in this huge qual of fire the universe. Um, well, there isn't a big bang eventually predicted. It will initial collapse upon itself. I feel like it's going to end up collapsing on itself basically, sort of just like snuffing out the light in a certain way to take everything in using the forest action in order to be able to pull into a different dimension, though we don't know of all. Right, Well, first, I like how people were not very optimistic, Like, nobody said the universe is going to end. I thought it was going to go on forever in this amazing uh state of euphoria. And everyone's like, I don't think we're gonna survive the next ten years, yeah, or we're gonna get swallowed by the sun or something. Everybody had a pretty dark view of the future. But I thought it was fascinating. I had a little bit of trouble getting people to actually answer the question, or maybe to hear the question. Most of the people, have you noticed, answered the question what's going to be the fate of the Earth or humans? If I pushed them, I reminded them I said no, no, no, the whole universe. Then they would maybe think as far as the Solar system. But I think very few people have thought about the universe as a whole coming to an end. Maybe no would even imagines that's a possibility that it would end, or that it would even kind of matter to the human species, right, like, maybe we're just this tiny little blip in the history of the universe. Yeah. Absolutely. I think people are not very confident that the the humanity is gonna last a long time. But I suspect that there's this underlying confidence that the universe is going to be here forever. I mean, think about how big it is, how vast, how much stuff there is, Like, how would you even get rid of it all? You know, if your job, Jorge was to end the universe, that would take a long time, right, going around hoovering up all these stars and planets that have been created and throwing it in a in a trash compact or something otherwise known as a black hole. Yet, well, it's interesting to think about the universe even anything, like you said it, like, it's so vast, it's so huge. What would it even mean for it to end? You know, likes to get thrown out somewhere, Does it explode, does it turn into something else? Like if it turned into something else, isn't it still the universe? That's right? And it's a perfect reflection of the other really deep question, which is how did the universe begin? Right? You ask these questions what would it mean for the universe to end? What would be after that? It's the same as asking what came before the universe started? How did it begin? But we think now the universe did have a beginning, right, it has an age. Right, he started a certain moment fourteen billion years ago, the Big Bang. In the Big Bang, it's actually pretty natural to think that it might also have an end point, right, I mean at a starting point, why not an end point if it could go from nothing to something. Yeah, everything that has the beginning has an end, except for things that haven't ended. But yes, um, such as the universe and this podcast, which is you know, still going on. Do you think it's more natural to think of since the universe we think at a beginning the Big Bang, you think it's natural that it might have an end. It can't just be an open and the thing it could be. But it's also could be something that has a finite life. I mean, it had a specific beginning, so we could also have a specific end, and what happens after that we'll just be could be something else we don't really call the universe because it's so alien and different. The way before the universe began, we think of there being no space and no time. I mean maybe there was something you know, inflatons or pre inflationary matter, whatever, but not anything recognizable, not anything that followed the laws of physics as we know them, or anything that would make any sense to us. I mean, what does it even mean to not have any space or time? Right? Right? Right? And it's also amazing that we can even consider this question, right, Like, we are standing here fourteen billion years after the Big Bang, and possibly the end of the universe is not for another like trillion years, but we like here in this moment in time, can think about can look around us and be like, all right, this is where things are headed. Yeah, yeah, And I love that feeling, like we don't know if we're halfway through the lifetime of the universe, were like one one trillion of the way through the universe. Imagine if we had been if there was life, you know, a hundred thousand years after the universe began in that hot plasma, they would figure, wow, look the universe is pretty old. It's already a hundred thousand years old, right, but you know, so much was left to happen. They didn't even have stars or planets or black holes or anything exciting. Right, Maybe we're still in those first initial blip. That's just the first slice of time, and most of the history of the universe is deep ahead of us. It could go on for ten to the one thousand years, like we could be in the universe's pre pubescent years, like this is the awkward tween years, or it could be the birth Busicists in a trillion years could classify this whole part as the Big Bang. They're like, oh, that was just you know, the first part of the Big Bang, and the second part of the Big Bang, and then the last dregs the Big Bang before we really got started, like this is the Empire strikes back of the Big Bank, the relg So yeah, so we could be like, uh, this could be like just the universe getting started, or it could be like maybe the fading years, like this is this is it like we've plateaued, or it could be like, um, we are under the decline of the universe. So I think we figured it out. We need to know whether the universe will end so that we know whether it should have a midlife crisis, right, and they don't want to miss your midlife crisis, your opportunity to drive fast cars and buy some buy some new galaxies. Maybe those galaxies are way too young for you, Universe. That's disgusting. So we don't know where we are in the lifetime of the universe, like we could be at the youth, or we could be in the middle age of the universe. We don't know. Um, so what what I guess what do we know from looking around us about the lifetime or the age of the universe. Well, basically nothing, but basically nothing. We have no concrete evidence of the universe will ever end. I mean as far as we know. But we were extrapolating from, as you say, a very small amount of information only for teen billion years of history, and now we're trying to extrapolate into billions and trillions and gazillions of years. Right, So, currently we know and if you listen to our podcast episode about dark energy, you know the universe is expanding and that that expansion is accelerating. So things are moving away from each other, and every year that movement happens faster and faster. Things are spreading out right. Yeah, the universe is getting bigger and things are getting more spacious. Yeah, So we have to think carefully about what we mean for the universe to end. For a while, people thought the universe's expansion might stop and slow down, and it might even be that there was enough gravity to pull everything back in to collapse it back into a dot and the sort of the way the universe started. A nice symmetry there. Yeah, the big crunch, Yeah, the big crunch. And in theories where you have a big bang and then expansion and then a big crunch which starts another big bang, you don't think of that big crunch is a big crunch. You call it the big bounce because it's sort of like the universe has these cycles. We have bang and crunch and bang and crunch and sort of more like a bunch of bounces where the universe expands and contracts. It's kind of like when you when you're like hyperventilating and you grab a paper bag and you're like breathing into it and out of it, into it and out of it. That's kind of like the view of the universe, right, like it's expanding and then it collapses compands exactly, and then you get into some semantic distinctions, like if the universe expands and then collapses back down to a singularity or something really small and dense again, is that really the end of the universe and the start of a new universe or is it really just you know, another cycle in the lifetime of universe. In which case the universe could have been going on forever, bouncing and bouncing and bouncing along merrily as we as we live and breathe, you know. Or or it could be that between bounces it could be very different. It's like the same energy would be the same energy, but maybe not the same particles, right, because like when they get compressed at a small they just kind of turned into pure energy, and then then when it expands again, it becomes other particles. Right. Yeah, if you're like naming this electron, then an individual electron name read no longer exists in the next universe. Fred E fred e exactly. And uh, it's anti particle, anti freddy and um, just like pasta and anti pasta. But the energy is of course the same and so and even the rules of physics would probably be the same, So it's not like you get a dramatically different universe. Although you know, the quantum fluctuations in those blobs could give you all sorts of weird things and weird different structure in future universes. So that's one possibility, is that the expansion could turn around and crunch. I have so many questions for you, But before we dive in let's take a short break before. We only need about gravity and scars and matter. And we assumed that gravity, at some point it's just gonna bring everything because if you put a bunch of like, um, those particles out in space, the gravity will pull them together. Right, that's right. Gravity is really weak, but it's got a lot of time, and so eventually it will gather it all together and crunch it down into a planet or an asteroid, or a star or a black hole, depending on how much stuff there is. And that's what people thought. People thought, like all those all the stars and galaxies eventually would slow down and get pulled together into one ginormous black hole thing. Point. Yeah, that was one idea people had. And then you know, we discovered dark energy. We discovered that the universe is expanding faster and faster every year right now. So then for a long time, this idea of a big crunch was crossed off the list, but I think prematurely. Oh you mean, like, so we've we discovered dark energy, meaning that there's some kind of energy permeating the whole universe that's making it expand faster and faster. And so we said, um, it's not going to crunch back in guys like this. Dark energy is a big deal. It's pushing everything further away faster and faster. We're never going to come back together again. Yeah, that was sort of the new prevailing wisdom as about twenty years ago. But I think that's premature because we don't know, Like, we don't know what dark energy is. We don't know how it works. We don't know what it's going to do in the future. We do know that it has some time dependence, like it turned on five billion years ago. Is going to keep going? Is it going to accelerate more? Is it going to stop? I mean to extrapolate from the last few billion years into the next trillion requires a lot of confidence, and we can't do that extrapolation. Like dark energy could flame out or something right or flip flip exactly. It could turn around and make a massive crunch. It might even like bring everything back together or something. Yeah, nobody can predict what it's going to do because we don't understand it at all. We're just watching it happen. Dark energy is the observation that the universe expansion is accelerating recently, but it's not really a solid prediction, what's going to happen. So most of the prevailing wisdom these days about the future universe assumes dark energy is going to continue, but there's no guarantee there, and you know, there could be new things in waiting in the future. For us, dark energy only came around five billion years ago. There could be like a dark error energy that comes on in five more billion years and and it totally drowns out dark energy and dominates it, right our er energy, Oh my god, exactly. And then the sequel that the third part of the trilogy, Darkest Energy, fifty Shades of dark Energy exactly. That's the erotic version of the children. So what are the like, what are the scenarios that side of physicists are considering if dark energy doesn't change. Yeah, so if dark energy doesn't change, then it continues pulling the universe apart, meaning creating new space between us and other galaxies, and doing that faster and faster every year. So this scenario is sometimes called the big Rip because essentially feels like somebody's taking the universe. Something shouldn't anthropomorphize. Something is taking the universe and pushing it apart, ripping it to shreds. Things get farther and farther apart every year, and if you look up in the night sky, things start to disappear because they move outside of our observable horizon, and so things get further and further in space apart. Well, now, is that is that like the same franchise, like The Big Rip, the Big Crunch, the Big Bang? Is it all like copyrighted by physicists? That's right, Yeah, it's all owned by the same agents somewhere in Hollywood who we now have to pay royalties to, um if we want to option this. Yeah, exactly, And there's lots of fascinating scenarios there. You know, if things just continue to spread out, then things get more and more dilute, right, and things um things, because everything gets further and further apart, and then you can just sort of let the laws of physics play out and like, what's going to happen to our galaxy? For example, Well, we know that in a few billion years, our galaxy is probably gonna collide with a nearby galaxy, Andromeda. And that's going to be less dramatic than it sounds, because it's mostly just gonna mean the stars shifting around a little bit, and you know, we might get some new asteroids passing through our solar system. But galaxies are mostly really diffuse, right, They don't when when they hit each other. They don't the stars don't actually collide and smash into each other and create enormous cosmic explosions, but they sort of affect each other, right, Like we might get a giant star flying eros and disrupt their whole orbit. Maybe, yeah, absolutely, Yeah, So it's like if two whirlpools join, if you ever see that happen in a pool, they sort of join, emerge in their combined spin forms one new spinning blob. And so for the individual stars, you know, they might get a little disrupted here and there, and in some cases maybe by a lot in rare circumstances um, but mostly we just form a big combined galaxy. But you know, then fast forward another few zillion years and eventually the stars burn out, right, So at some point we keep fast forwarding, the stars are gonna snuff out, like they're just going to become embers and then eventually just kind of like hot stones and then just rocks, then just rocks. Yeah, and we've already gone through several cycles. I mean, the first stars that were in the universe are no longer around. We can't even see their light. Kidding, several cycles of stars that have already happened. The first stars were all hydrogen and they formed and they burned and they imploded and they exploded, right, and then those materials gathered together make new stars, And that's happened, I'm not sure how many times, several times where several cycles deep, which is why we have such interesting atoms like gold and heavy stuff lying around. Right. We aren't there new stars being formed right now out of hydrogen, none of but none of them are hydrogen stars. There are still new stars being formed, but there's being formed out of a mix of hydrogen and heavier stuff. So like stars one point, Oh, nobody knows what that looks like. Yeah, yeah, I think recently people's found some light they think comes from the first stars, but it's still still very preliminary stuff. Yeah. So the stars get heavier and heavier and eventually run out of stuff that burns, and then the universe goes dark. Right then, it's just like the era of stars is over. And it could be that the era of stars is just like a little blip in the history of the universe, and then it goes on for like another gazillion years before anything interesting. Complete darkness, of complete darkness or other things that bread burn right, aren't aren't like quasars and black holes in those amid radiation and light. Yeah, some of them amid some sort of radiation, but nothing as powerful as stars. So what we're facing is a pretty dark time. You know, this could be like the only bright period in the universe, Yes, exactly. Um. You know, in the way I think about the very early universe, is this hot plasma that only lasted a brief period of time, you know, three or four hundred thousand years, and then it was over. And from the point of view of that hot plasma, the universe now is very dark and quiet and cold. But we could be looking forward to another period which is even darker, even quieter, even colder. Right. It's just these rocks floating around, bumping into each other in the dark. Yeah, and then black holes take over. What it means take over, like things just keep bumping into each other in the dark and forming black holes. Yeah, because eventually gravity coalesces these things together. Um, And you know we're talking about two different forces at the same time. Dark energy is pulling galaxies apart, but again, we think probably gravity has enough power to locally hold a clump of stuff together. It's a dark energy can't rip a black hole apart, for example, or rip a star apart. It has enough energy to push away between things, but probably not to shred those things themselves. So gravitationally bound group of matter will probably survive even the dark energy is pushing it away from things, and it will gather together and form a black hole. But this is still the same fate that we would get if you didn't have dark energy, right, Like, eventually the stars would also go out and things would form into black holes. It's kind of like what happens after that that depends on dark energy. Yeah, that's right. Dark energy just tells you, essentially how closely grouped these things are. We're gonna do this all by ourselves and all the other galaxies are going to be invisibly far away, or are we're gonna be able to watch the same thing happened to Andromeda that's happening to us. That's sort of the question. But yeah, you're right. On a local scale, I think it's going to be the same. One scenario is that, you know, black holes take over and then we have a period of the universe where it's just basically only black holes, only black holes, nothing in between. Yeah, or black holes, um, And that that makes a lot of sense to me. You know, like what happens when gravity pushes stuff together, Eventually it gets dense enough to form black holes. And so give gravity enough time and it'll get that done, right. But the problem is black holes. These black holes are going to eventually evaporate, right, Yeah. Black holes do not last forever. As powerful as they are. At some point they like disappear. Yeah, they evaporate because they have energy to them. And everything that has energy gives off radiation, even black holes. And if you're wondering how can a black hole give off radiation, you know, think about a little particle that's living right at the edge of the event horizon in the black hole. These particles can split into two other particles, you know, sometimes just briefly, and this happens all the time. A photon that's flying through the air in front of you splits into an electron and a positron and then back into a photon. But if that happens right at the edge of the black hole, then um, one of them can get sucked into the black hole and one of them can escape, and that's what's called hawking radiation. So yeah, they can lose energy by radiating these particles one at a time, just at the surface of the event horizon, right, yeah, exactly at the surface of the event horizon. And then things get really uncertain, meaning so if we have these black holes, they they're evaporating at the surface, and so they get smaller and smaller or less massive and less massive. And then but that radiation that gets admitted out, where does that go? Doesn't I keep bouncing around the universe? Yeah, and it can get grabbed up by other black holes or conform new black holes, or you know, do other interesting stuff. Or you know, if black holes have shredded enough matter, then maybe you can start to get enough simple matter around that you can make hydrogen and maybe even make another star to um. This is where things get really speculative because the time we don't understand black holes very well. You know, our understanding black holes is very primitive, and so like speculating about how long they live and what happens to that radiation, how much radiation there is exactly. This is all still very theoretical. Um and so then other theoretical questions start to come in, like how stable is matter itself? You know, One question we don't know the answer to is like how long does a proton live? We don't know. We don't know. We've never seen a proton decay. As far as we know, protons are stable. Like that is, you have a proton floating out in the middle of empty space, it will stay there forever as far as we know. Meaning protons are made out of quarks, and so these like the three quarks inside of a pronon just like never ever split off on their own. We've never seen it happen. Yeah, And so we think that proton lives at least billions of years, but you know, it could be that it's lifetime is only a hundred billion years or five hundred billion years, and then it decays. And so it could be that all the protons in the universe eventually decay and into quarks or smaller particles, yeah, exactly, into quarks or other arrangements. There could be a new arrangement that they decay into something else we haven't seen before. But if everything was in a black hole, uh, and then these holes evaporate from hawking radiation that hawking radiation. Does that include like protons or is it only like, um, you know, like photons and gamma rays and things like that. That's a good question. I'm pretty far outside my air of expertise, but my understanding is that it conclude it can include any kind of particle because black holes are very democratic when it comes to particle physics. They can create any kind of particle because we're talking about the creation of virtual particles, which means it can any kind of particle that can be created would be created, but I think predominantly with the lighter particles because those are those dominated for for these ERTI processes. Well, this is a perfect point to take a break. So now that we went from hot plasma, two stars and planets to rocks floating around in the dark, two black holes. Now all these black holes of evap braded and now we're like in the sea of particles. Yeah, exactly. We're well out of our comfort range here because we're extrapolating our knowledge into the zillion year future, and you know, we don't have enough information to confidently say what happens to a black hole after it's been alive for a zillion years? Or how long does a proton survive and can't really decay into something else? And so we really don't know, um, And that's a really fascinating question, is how long can we apply the laws of physics for like are they stable? You know? Do they are they the same forever? We think they've been the same for the last few billion years, but it could be that they change on the time scale of a trillion years and we just haven't noticed. So even like the rules of the game you're saying, could change exactly. And there's one really fascinating, slightly scary scenario that I love that people thought about a lot since the discovery of the Higgs boson, and that's that all the rules of physics could change, and they could change kind of suddenly. What do you mean, like the rules that tell you how things are might suddenly change for everywhere in the universe at the same time. It wouldn't be all everywhere at the same time, but it could happen all of a sudden in one moment and then spread. So let me tell you how that might happen. Um the way the Higgs boson works, it gives mass to other particles, and it does so by feeling the whole universe with this thing called the Higgs field. And if you want to know more about that, listen to our episode on the Higgs field. But the basic idea is that the Higgs field has energy even an empty space, right there's nothing there in it, no matter or nothing happening in a in a cube of space, but there's still the Higgs field there has non zero energy, and that's what gives things mass interacting with this this field that has non zero energy even when it's empty. Okay, But what we don't know is that field itself stable? Like is it stuck in some local minimum, you know? Is it like caught on a ledge somewhere and it just got stuck and it's going to roll out and find a more comfortable, relaxed configuration where it has zero energy. Is that temporary that it has this amount of energy stuck into it, or is it permanent? And there are a lot of theories and particle physics that suggests that it might be temporary, And then it might also be kind of fragile, and then if it's the right thing happens, you could shatter that field or disturb it and perturb it and break it, and so that it could collapse, and that collapse could spread very rapidly. Oh my god. And not that I'm saying that the large hage On collider is going to destroy the whole universe. I'm not saying that, people, I'm very definitely not saying that. But but there are some physics theories in which the Higgs vacuum, this lowest energy state, is not stable and it could collapse into a true vacuum, which would mean there's no Higgs field, which means no particles have mass, which means everything changes. Right, The very laws of physics would be totally different if the Higgs field was different, and the universe as we know it would like suddenly like turning into something else. Turn into something else. Yeah, I mean all of chemistry relies on the structure of the periodic table, which lies on the masses of the particles that make up the atoms, and that would all be different. And the new universe within with the zero Higgs vacuum would also probably be fascinating and beautiful. And interesting, but it would be very different, and you know, your maserati would no longer work, and your bank account would no longer be relevant. We wouldn't work, exactly, We would not work. But you're saying I feel like you're saying, like, hey, don't worry about us. We're just doing physics here. We're not going to blow things up. But well, you know you can always say that, or hey, you're just cartooning in your garage, right, You're not intending to destroy the universe with your cartoons. But but I might draw something of such incredible beauty. Yes, it will collapsed the laws of physics. You know, these theories about how the Higgs vacuum might be unstable. These are just ideas people have and it's fun to think about, and people write papers about how they might end the universe to be dramatic. Um, But I don't think anybody's serious. I'm certainly not worried at all that any cticle physics experiment is going to destroy the Higgs vacuum and change the universe, right right, keep sending those checks exactly so everything next week to download another podcast exactly. Well. It is sort of kind of like knowing when you're going to die, Right, Like, if you knew you were going to die in a week, you would live your life totally different, as opposed to if you knew you were going to live till you're a hundred and twenty, calmly, peacefully in bed, surrounded by your loved ones, you would change the way you make decisions every day. Right, That's right, And I think that's what's reflecting in people's answers to our on the street interviews that they were thinking more immediately, what is the future of the human race, what's the future of my family? How is this all going to affect us? Right? And it is totally possible that, like my jeans, what makes me who I am now? That might live on in my kids, my ancestors, and trillions of years from now, there could be a little piece of me like looking out at the sky and and being like, why is it so dark? That's right, it's possible the humans live for a trillion years. It's absolutely possible, And so we should be concerned about the fate of the universe, not just because we're curious about how the story ends and it's fascinating from a scientific point of view, but yeah, because it could be our home for the next trillion or two trillion years. Yea, if things go well, if people listen to this podcast, that I put your minds at ease or today unsettle you a little bit, a little bit. I mean I thought that this was far way into the future and I wouldn't have to worry about it. But now like the universe could end tomorrow. Yeah, so you know, organize your finances and get your stuff in order, and it's a good idea anyway, appreciate the bright period of the universe. That's right, Yes, this early, beautiful, glamorous, star lit, starfield period of the universe. Yeah, all right, thank you very much for joining us. This has been Daniel and Jorge explained the universe and its end. If you still have a question after listening to all these explanations, please drop us a line. We'd love to hear from you. You can find us at Facebook, Twitter, and Instagram at Daniel and Jorge that's one word, or email us at Feedback at Daniel and Jorge dot com.