Astronomy Cast Ep. 801: The Beginning & End of Everything - Part 2

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2:35comes, that comes next. Right. And, and I have to give a shout out to everyone who's watching this live over in the YouTube chat. I have people making me hungry by making, uh, references to the restaurant at the end of the universe. Right. I, I have folks over in, uh, Twitch filling my head with song lyrics as they talk about it's the end of the world as we know it. Yeah. You feel, I feel fine. We have the best chat on the internet. Yeah. Uh, so just, if you want to join our Patreon, help us, you know, any amount, you know, coming

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The end of everything

3:20Today we do the sequel to our two part series. We jump to the end of the universe and all of the major moments that will occur from now until the heat death of the universe, the end of everything. All right, Pamela. Uh, so now we've like, we last episode, I've just like speed ran through, you know, star formation, galaxy formation, planets, life, uh, technology, you know, just whatever blips. Now let's cast our eyes forward into the future of the universe.

3:52What would you say is the sort of the first major, uh, you know, now we're starting to enter the, the, the end stages of this universe that we live in. So there's, there's so many different ways to look at that. There, there was a, a planetarium show I saw when I was in college that, that was the story of a sci-fi future where all the stars have shut off. And, and so that really starts to feel like the end, but other people I know will say the end

4:30is when expansion has carried everything away so that that future milk dromeda combined galaxy is the only thing in our sky. I, I don't know what you call the beginning of the end. Okay, fine. I will tell you. Fair. Fair. I was, I was, I'm being indecisive. I was hoping to set you up, but clearly you can't decide. So, uh, you know, if you wonder if there's like the actual kind of script, we do not.

Merging with Andromeda

5:00Um, so, all right. I'm going to start with the beginning of the end about the end of the Milky Way as an isolated galaxy. All right. So as the story goes about 5 billion years from now, uh, our galaxy and the Andromeda galaxy, which is hanging out, able to be seen with your unaided eye, they're going to undergo some things and become a single galaxy, probably more elliptical in nature and then hang out together. And 34 is going to join the party.

5:31All of the dwarf galaxies are going to join the party. And, and like, don't, we know that there was like one paper that suggested that in fact, Andromeda won't merge with the Milky Way in all chances. There is a chance that Andromeda will skip off, that they will, they will be separate. Fine. Don't send us the email. We know about the research, but we're just going to go with the cool one, which is that they merge into this giant elliptical galaxy. Think M87, but you're living in it. It, it, it'll be smaller than M87, but we're living in it.

6:05And, and at this point in time, we're, we're going to be heading in towards other galaxy clusters. But as that happens, it turns out the universe, the expansion rate is going to carry us away faster than we're falling in. Right. And, and that means we never get there. We never get to join the cool kids in the big galaxy cluster. And that's okay. That line is about 5 million light years. So, so there are galaxies, like sort of three to five, like Andromeda is two and a half million

6:41light years away from us. And 33 is kind of in the same family. Yeah. Yeah. Um, and that then the closest galaxies are on the sort of 5 million light year range. And it's believed those ones are sort of the momentum left over from the big bang. The acceleration caused by dark energy are going to push those galaxies over the cosmic horizon that we will never, but we were, the, the gravity is trying, but we will never merge with them as well.

7:12So we will just become more and more isolated over time. And, and the way to think about this is imagine that you're trying to run against a moving walkway. If the moving walkway, and we've all seen little kids try and do this with escalators. Yeah. Little kids, not grown adult men in their fifties do this, but yeah, go ahead. Okay. Fair, fair enough. Yeah. I do this. If, if, if a, a human being or other creature with legs attempts to go against the motion

7:48of a moving walkway of an escalator, if they are fast enough, they can reverse directions and run against the flow of motion and get to where they're trying to get. Yeah. If they can't move fast enough, and we've all seen little kids go through this, they end up either, it appears like they're running in place because they just can't get ahead of the motion because they're moving at the same rate as the motion, or they're moving for all their worth and still getting carried backwards.

8:22And as the universe continues to expand, it's going to be like a little kid getting tired and first making progress and then holding still and then falling away as everything disappears out of our sky. Every moment of time, we luckily are unaware of this because it would be existential dread. We are seeing a slightly different part of the cosmic microwave background. We are seeing a slightly different part of the universe as things get carried away from

8:55us. And so that merger with Andromeda, and the correct technical term is Milkdromeda, as you said, if anyone says Milkmedia, they're wrong. It's Milkdromeda. That's about 5 billion years from now. So when the sun is starting to consider the end of life is when we will begin our merger with Andromeda. Or not, whatever. Don't send me emails. But that isolation that you're talking about, that point where the galaxies fall over the

9:27cosmic horizon, that's more like 100 to 150 billion years from now. And this always leads to the beginning of this kind of existential crisis where you say like a future astronomer, someone who shows up at that time in the universe, will have no evidence. We'll build a big telescope and they won't see anything. There will just be the stars in the galaxy. There will be maybe the last few dwarf galaxies that have finished, haven't finished merging. And they'll look off in all directions.

9:58There will be no evidence of galaxies. So Immanuel Kant was actually a physicist. We remember him as a philosopher, but he was a physicist. And he's the person who looked at all the different nebulae that were being discovered by folks like Herschel and Messier. And looked at the Andromeda nebula at the time, was what they called it. And said the only way we could explain its shape is if it was another island universe. And so this idea that galaxies are island universes was first come up with by Immanuel Kant.

10:34And in that future that we're looking at, our Milk Dramada galaxy will be the entirety of our visible universe. So it truly will be an island universe. And other, I believe it would be a waste of space if there isn't other civilizations out there. Other civilizations will each be in their own island universes. And yeah, that's only a little bit depressing.

11:04Science doesn't care. Yeah, I know, I know, I know. Yeah, we could get used to it. Like this whole episode is going to feel sad and existential, but, you know, we'll do with a smile. And so there will still be evidence that like if you build a powerful enough detector, something that is the equivalent of looking for the cosmic microwave background radiation, you will pick up this glow in all directions. That is the sort of the last light that was sent by all of these galaxies as it fell over the cosmic horizon.

11:36The cosmic microwave background radiation will still be there. It will just be red shifted. So far, you'll need gigantic telescopes that you will be able to detect that there is something outside the galaxy, you know, maybe a trillion years into the future. And the thing to also think about here is that cosmic microwave background that we see today as microwave, it didn't start that. It started much, much hotter. It started out in the ultraviolet. Now, as the universe continues to expand and continues to expand and continues to cool, we're going to see the cosmic microwave background slipping to longer and longer wavelengths as the universe in the background slips to longer and longer temperatures, cooler and cooler temperatures.

12:25So it'll never go away. Right. But it will be effectively undetectable by technology. And you'll sort of get to this place where the universe is cooling down faster than the technology can advance, than the telescopes can be built and grow. You know, you need to build a telescope that is an interferometer that is a light year across to detect the cosmic microwave background radiation with wavelengths that are whatever, a light year long.

12:59And it's not like we're going to have a light year. And it's not like we're going to have a whole lot of energy for these future civilizations to be basking in either. That's another problem.

The last stars die

13:07Well, now we've moved to the next step, which is that the power, the stellar engines of the universe will wink out one after the other. And we already can see places where star formation has ended. You look at globular clusters, no star formation. You look at some particularly have had no recent consumption of other galaxies, elliptical systems, and there's extraordinarily limited star formation going on.

13:39Once star formation ends, you're in the cool down period after a while. So your average star, it's going to go through its life. It's going to eventually exhale its outer atmosphere. That atmosphere is going to drift away as a planetary nebula. You might get lucky and have a supernova, which is a bit more exciting. But this material that is drifting away isn't going to form these high-density star forming regions because some of their mass just isn't getting to go back out there into the mix.

14:14It's getting left behind in the neutron star and the white dwarf and the black hole. And so you have a more and more diffuse background of material out there with embedded nuggets of cooling diamonds, of cooling neutrons. And as all of that heat just slips away, we start to see more and more of what's called the heat death of the universe creeping up on us.

14:44And this is where things start to get messy because protons don't behave as predicted. Right. But hold on. I want to put a – I keep skipping ahead. Yeah, you sure do. Why? God. Well, that's okay because we don't have a script and we don't have an outline, a shared outline. We have no idea what we're going to talk about.

15:01Yeah, we keep it real. So you're talking about sort of like essentially the death of all stars. And the longest-lived red dwarf stars will live maybe 10 trillion years. And those galaxy collisions will inject fresh material into the galaxies that you'll have pockets of star-forming material that will eventually find the level of density required to form stars. But you will get to about 100 trillion years from now and that will have all been used up.

15:37Whatever galaxies were going to collide will have collided. Whatever stars that were going to form, even the smallest possible red dwarf stars will live out their lives. And about 100 trillion years from now, the last star will die and there will be no more stars. And by die, we mean we'll cease having nuclear reactions generating new energy through fusion.

16:07And so they will continue to radiate heat as they cool. And this is where with the white dwarfs, like our star, they end up as carbon white dwarfs, which are essentially diamonds. So that's kind of cool to think about. Super cool. Yeah, one little moment, just like one little more happiness in what is a sad and depressing future. And those will eventually get cool enough that you could actually like hold your hand as it gets gravitationally destroyed up to the diamond, but it wouldn't get burned.

16:37Just gravitationally destroyed, no big deal. And those little red dwarf stars, depending on how little they are, are going to end up as either helium or higher atom, white dwarf stars. Because they're fully convecting. They're lava lamp stars. And once they have completely mixed and used up everything, they're like, oh, no more, and collapse. So this is known as the degenerate era.

17:07The previous was the stelliferous, stelliferous. I leave these words for you. Yeah, right. The stelliferous era was the time when stars can form. Yes.

Entering the degenerate era

17:19And now we've reached the degenerate era. And so all stars have turned into white dwarfs. Or neutron stars. Or black holes. Or black holes. That's all you've got. You've got galaxies where you've got a supermassive black hole at the center. You've got stellar mass black holes, neutron stars, and white dwarfs that are orbiting around this central supermassive black holes. But this is not stable. And so the three-body interactions between these objects will pluck away these objects one at a time and send them on escape trajectories out of the galaxy.

17:59And so over the, you know, now the numbers are gigantic, right? Like we're in the degenerate era, you know, 10 to the power of 19. You will end up with every star, every white dwarf, every neutron star, every black hole, a stellar mass black hole that didn't get absorbed into the supermassive black hole at the center, is now going to just be, will fall over its own version of the cosmic horizon, get caught up by dark energy, expanding away from everything else.

18:30And so everything will be in its own pocket universe, effectively. There will be supermassive black hole universes. There will be stellar mass black hole universes. There will be, you know, in the not real universe, but like just practically, there will be nothing around these things. Yeah.

Proton decay theories

18:45Now you can jump to proton decay. Okay, fine. If it exists. Fine. So, so after all of these three-body interactions, after all the mergers, then if grand unified theories can ever be made to work, every single one of the grand unified theories so far has made the prediction that protons will decay into energy, just switch identities.

19:19And we have been watching them in massive vats of liquids where we're also looking for other high energy particles, where we're looking for dark matter, where we're looking for neutrinos. And you can either watch one proton for 10 to the 30 years, which I do not recommend doing. That's a lot of time. Or you can watch 10 to the 30 protons, which we're aiming to get towards.

19:50Or somewhere in the middle, you watch 10 to the large number of protons for years. I love that, though. You watch 10 to the 30 protons for a year. Yeah. You watch, you know. Right. Watch them for 10 to the 30 years. Watch every proton for 10 to the 30 years. Anyone, pick your, you pick. Yeah. And so we pick to go with vast vats and watch them for long periods of time that are not as long as 10 to the 30 years. But so far, the protons are like, no, I will not. And they are sitting there being extremely stable.

20:22Yeah. And so the question starts to become, if every single path we've gone down trying to create a grand unified theory that requires these suckers to be unstable is wrong, because the protons are like, no, won't do it, then what happens? And this is where we could have a future of just, like, cold diamonds in the universe, which is kind of awesome. It is kind of awesome, and it is another little glimmer of hope.

20:54Yeah. That you will be left with a cold, dead diamond in the universe and not a background glow of additional energy when all of the protons that made up that giant diamond evaporated into nothing. That would be great. But the evaporation is coming. Yeah. So we're going to get to that in a second. So we are now, like, what, 10 to the 40 years. If the protons do go, you said maybe 10 to the 30. Yeah. Maybe it's 10 to the 40. All the protons. We have run out of words that get used in common conversation for how far in the future this is.

21:28Yeah. This is like a super guptillion years, I believe, is the technical term for this. But, yeah, we have lost – like, all the protons have either given up the ghost and they all decayed or they've held together laws of physics. We will figure out what that will be before that actually happens. We'll keep you up to date. But if they do decay, then all of these objects – so the black holes are going to evaporate no matter what. They're sitting there losing –

21:58Whoa, whoa. Just whoa. You're already jumping ahead. So I'm going back to the protons, going back to the protons. Okay. So all of our little white dwarf stars, all of our neutron stars are going to – so at the surface of neutron stars, the densities are low enough that you have neutrons break apart into protons and electrons. If the protons are unstable, protons end up radiating away. White dwarfs made of protons and electrons, protons radiate away. And you end up with this background ghost of energy kind of permeating everything as the universe works on experiencing extreme amounts of entropy.

22:38So we're considering a future where basically the energy is so diffuse that it can't clump up anymore and the universe is so vast that the speed of light means nothing can even communicate anymore. And so if protons decay, we are looking at just this diffuse energy punctuated with supermassive black holes still getting their supermassive black hole on.

23:18And so to take that analogy that I was giving earlier about how essentially every white dwarf ends up in its own isolated observable universe. Every photon of decayed proton will end up in its own observable universe, that all of the other photons that were made up from that white dwarf that decayed will all expand away from each other at the speed of light to the point that you will have an observable universe for each one and there will be nothing in your observable universe.

23:57Yeah. And before you start adding us, we're going to go with the kinder, gentler universe end first. Yeah, I guess. It's all right. So all that we're left now is the decayed protons and the black holes.

Black hole evaporation

24:16Yeah. And black holes disappear at different rates depending on their size. Yeah. So any microscopic black holes left over from the formation of the universe have already bit the dust. Any current black hole of noticeable size is absorbing mass energy from the cosmic microwave background and everything else so that its decay isn't causing it to obviously lose mass. So that's not a concern in the modern universe. But as the universe expands, the feeding of black holes comes to an end.

24:49Right. And when you stop feeding a black hole, it starts losing energy and energy and mass of the same thing. And over time, through this radiation of Hawking radiation, they get smaller and smaller and smaller until in a flash, they cease to exist. Right. And that number depends on the mass, as you said, it depends on the mass of the black hole. Yeah. So the most massive, supermassive black holes that are in the cores of the galaxies that sit in the centers of galaxy clusters.

25:24So like that central seedy galaxy in the core of Koma, in the core of Virgo. Yeah. Like the Phoenix, the Phoenix black hole, there's the ton 618 or something like that. These supermassive black holes that will be even more supermassive in the future, they will be the last ones to decay away. Okay. So we will go from a universe that is, I don't know the correct word, poxed with black holes of stellar mass, of intermediate mass, of supermassive, to just intermediate and supermassive, to just supermassive, to just the most supermassive.

26:09Yeah. Until nothing. And then eventually it's just energy. And so this Hawking radiation, mostly in the form of photons, will end up again in each one in effectively its own observable universe. Yeah. That there will be no, and they will all be the same temperature. There will just be this giant universe filled with energy, Hawking radiation, unable to communicate with any other photon, even at the speed of light. Right. And as the universe expands, those photons get redder and redder and redder.

26:44Right, right, right. And the thing that's important to understand, because we talked about thinking maybe protons will decay, maybe they won't, but the thinking right now is that all matter falls under Hawking radiation. Yeah. So not just black holes. Black holes are sort of the extreme end of this, but even like neutron stars, white dwarfs, you, me, that whatever is this mechanism, it probably affects all matter. And so if proton decay isn't a thing, don't worry, just wait. Hawking radiation will be a thing.

27:14And so even the longest lived person in the robot body who's been around for 10 to the power of 100 years will lose their particles one by one to Hawking radiation until nothing survives. Yeah. And in fact, probably these things will go sooner because they don't have the same kind of gravity well like black holes do. So I forget, there was this paper that we reported on where they sort of gave you the dates when neutron stars will evaporate, when people will evaporate.

27:49Yeah. Yeah. That was a paper that I looked at and I'm like, we still don't know protons. I decided to just push it over there. But this is nothing with proton decay. Like this is a separate mechanism. This is Hawking radiation. Right. You know, I understand it's a separate mechanism, but I simply took the, I do not wish to, to read this theory of paper right now. Yeah. Yeah. We did. And we reported on it. It was fun. I think even Brian Koberlein did it. Anyway. Um, so now we are 10 to the power of a hundred years. The universe is nothing but energy and maximum entropy.

28:26Yeah. Yeah. Okay. All right. So you're going to offer one alternate, um,

Dark energy and the big rip

28:35Hell hole.

Dark energy and the big rip

28:36What? I guess. Right. No, please. You know, like, I hope we get the heat death of the universe, but no, maybe there's something even more horrifying. Yeah. Yeah. So, well, there, there's actually an option C, which is our universe merges with another universe and physics, as we know, it simply ceases to exist, but that's a different episode. Um, so in the, our universe doesn't, uh, have some outside force decides to make it cease to exist. Given our universe is allowed to see its natural ending. Um, we're still piecing together how the amount of dark energy in the universe changes with time.

29:15Yeah. And if the amount of dark energy is such that the universe keeps accelerating. Accelerating. And if that acceleration is accelerating, there could come a moment that is actually a strange nightmare I had as a small child. I was a very weird child, which surprises absolutely no one. And for reasons that will never make sense to me, someone attempted to explain the expansion of the universe to me when I was like in kindergarten, don't do that to kindergartners.

29:54And I was honestly afraid that by the time I was an adult expansion would have made it so that the neutrons in my brain couldn't talk to each other anymore. Don't explain expansion in the universe to five-year-old people. It's fine. It's fine. It's fine. Just don't explain it to little Pam. Anyone else, they'll love it. But in the idea of the cosmic rip, that weird nightmare I had as a five-year-old sort of becomes reality because it gets to the point that regular matter is getting torn apart as the universe is expanding faster than other things are tearing things apart.

30:37And so, like, our galaxy will still be doing galaxy things, and then expansion will start tearing stars apart, and then expansion will start tearing atoms apart. And that's just horrifying. Yeah. And this all depends on whether the rate of dark energy changes over time. And for the longest time, the answer was it does not, right? It really looks like dark energy has been consistent over time.

31:09The most modern research is that maybe dark energy does change over time, but weakens. And so what the evidence appears to be leaning towards is that dark energy might be variable, but it appears to be lessening over time. And so, you know, if you asked us this question maybe five years ago, we'd be like, I don't know. But now we're at the point where dark energy is actually being measured quite well. And we've got more coming. Nancy Grace, Roman, Vera Rubin. Yeah, Euclid. Euclid. That combination.

31:40Yeah. Desi, Desi. Yeah. So there's like five or six different instruments all working to kind of get to the bottom of this question. At different scales. It's really cool. At different scales, yeah. Yeah, it is amazing. I think we did an episode about this anyway, but we are getting to this point. The answer is it looks like, you know, dark energy is either constant or variable. And if it's variable, it seems to be decreasing. And if it's decreasing, don't worry about the big rep. But it would be like, you know, 10 billion years from now, 15 billion years from now. Like it's a fraction of that current, that future age of the universe.

32:12The way I think about it is it's the kind of thing that is unlikely the way my coffee cup simultaneously aligning all of its atoms in such a way that it falls through the desk to the floor is unlikely. Could it happen? Yes. Is that a theoretically interesting thing to contemplate? Yes. In an infinite universe, it would happen inevitably. But is it going to happen in my lifetime? No. Probably not.

32:43And so is the big rip probably going to happen? Probably not. But you have to consider these realities because we don't have enough data to completely rule them out. So you're thinking like long enough time, sort of the quantum mechanical weirdness rips the universe in half just randomly. Yeah. Yeah. Or makes a new Big Bang. Which is something else that people have been theoretically exploring. Totally. Yeah. Yeah. There was a calculation.

33:14Sean Carroll did this. And I forget the number and I apologize. But it was like two to the power of a number and then to the power of another number. Like it was a ludicrously large amount of time. But you would just get randomly the raw material for another Big Bang appearing in a spot in the sky that could begin that process. An observable universe anyway. Not more outside of that. Quantum fluctuations are funky. They're awesome. And if the universe is infinite in time, a new universe forming is an inevitable outcome of eternity.

33:54So there you go. Hopefully, yeah, you're going to end up within just a ludicrous amount of time where you have the heat death of the universe. And it's not death by heat. It's the death of heat. But hopefully, if quantum mechanics are right, then a new universe will form and destroy this one. And that, in two episodes, is the beginning and the end of everything. We did it. We did. It's excellent. We just had to skip that Missy middle part. Exactly.

Patron supporters and credits

34:22All right. That was wonderful. Thanks, Pamela. Thank you, Fraser. And thank you to all of you out there who are supporting the show. Just as a reminder, we are now ad-free. There were no ad breaks in this episode. There will be no ads running associated with this episode. This is our new future. Ride or die. If you want to help make sure that my heavily beating heart doesn't explode as I worry about paying salaries for Ali, Aviva, and Rich, please join us at patreon.astronomycast.com.

34:56All episodes are without any paywalls. They're Creative Commons licensed. We rely on you to make everything we do possible and paying patrons get early access to everything we possibly can. This month, we'd like to thank the following patrons for all of their support here at AstronomyCast. BoogieNet, Burry Gowen, Eric Lee, Jeanette Wink, Michael Purcell, Andrew Palestra, David, David Resetter, Gerhard Schweitzer, Jason Kwong, Joe McTee, Sergey Manilav, and Segei Kemmler.

35:31Now, if you notice that list is a whole lot shorter than it was last year, this is because we have updated our Patreon tiers, moving around some benefits to reflect the effort it takes our team to do things. Believe it or not, reading your names is one of the most stressful things I do because I really struggle with pronouncing things and feel bad when I screw up. We have moved Read Your Name to the $50 and up tiers, meeting with you once a year to the $20 and up tiers, adding your name to the end of videos to $10, with lower and higher tiers remaining unchanged.

36:09Thank you. You are what makes this show possible. All of you in all of the tiers. We did it. We did it. Thanks, Pamela. Thank you, Fraser. We'll see you next week. Bye-bye, everyone. You are listening. Welcome to the 365 Days of Astronomy Podcast.

36:34Cool.

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