Hopefully you’ve all recovered from part 1 of this set, where we make you sad about the future of the humanity, the Earth, the Sun and the Solar System. But hang on, we’re really going to bring you down. Today we’ll look far far forward into the distant future of the Universe, at timescales that we can barely comprehend.
Fraser Cain: I’m not so sad after last week’s show. Which actually we recorded an hour ago because you’re traveling again we’re doing both shows, one after another. Take your medicine at the same time and kinda just get through it. [Laughter]
So, some of you might have noticed that we have a new outro to the show and a new editor for the show. Well, why don’t you talk about this Pamela?
Pamela: We hired a new student, Preston Gibson, a mass communications major here at Southern Illinois University Edwardsville. He’s doing what he is trained to do best. Rebecca is going off to do the things she’s trained to do best which is to work in Science and Engineering. She’s going off to do great new things and we brought someone new in to hopefully help our show do great new things as well.
Fraser: There you go. Welcome aboard Preston. You will hear him at the end of the show. And good luck to Rebecca.
Hopefully, you’ve all recovered from part one of this set where we make you really sad about the future of humanity, the Earth, the Sun, the Solar System. But hang on we’re really going to bring you down. Today we’re going to look far forward into the distant future of the Universe at time scales that we can barely comprehend.
When last we left our heroes [Laughter] the Sun had turned into a white dwarf and was slowly cooling down. Maybe there were planets huddled around it. And it would cool down for the next trillion years or so and turn into a black dwarf. But now we kinda need to rewind because things will happen to our neighborhood after the Sun dies and turns into a white dwarf. What is the next major phase that happens?
Pamela: The Universe and its destruction is a long and violent process. So, perhaps the next thing that we look to as a major mile marker is the end of the Milky Way Galaxy.
We live in this nice happy little, fairly we think pretty looking spiral galaxy with a bar in its center. We have the Magellanic Clouds off to the side helping influence the shape of our system. But we’re not always going to be this pretty little galaxy. In fact we’re on a collision course gravitationally with Andromeda galaxy. Our Milky Way is what we call a part of a local group; which is a group of gravitationally bound together objects that we’re going to be talking about a fair amount in this particular episode.
Over time gravity is going to cause us to interact with pretty much everything in the local group. Us (The Milky Way), and Andromeda are going to collide, probably light up our central super mass of black holes and send huge amounts of energy off into the Universe.
Fraser: When Astronomers look out into the Universe everywhere they look, galaxies are moving quickly away from us.
Pamela: Except for the local group.
Fraser: Except for one; [Laughter] except for the local group. And specifically Andromeda is bearing down on us, right? Or we’re bearing down on it.
Fraser: When will we actually encounter Andromeda and what will that look like?
Pamela: It’s going to happen probably in about 3 to 5 billion years. It depends on who you’re looking at, their papers. There’s always a little bit of argument on when things are going to happen. Our Sun will still not be done being done; our planet will probably be toast as we talked about last episode. But our galaxy will start to collide with Andromeda while our Sun is still going through its normal happy little main sequence life span.
So our Solar System will be around to watch the black hole in the center of the Milky Way lighting up. To watch our sky radically change as Andromeda gets bigger and bigger and bigger and fills the sky and then collides with the sky rather violently. It’s not that far in the future. It’s just kinda cool to think about.
Fraser: It’s not going to happen over night. The two galaxies will pass through each other and then move away and then come back together and do that a bunch of times until they merge.
Pamela: We’re actually going to go through a phase where we look a lot like the Mice Galaxies, the two little colliding galaxies that everyone has seen Hubble pictures of a million times. It’s going to be a very pretty event for people sitting in other parts of the Universe.
That’s really the next big thing we have to look forward to is the destruction of the Milky Way Galaxy and all galaxy life as we know it, or at least changing.
Fraser: Whence that process is done, I think I read some of that research as well that it will take 3 to 5 billion years to begin, but it won’t be done for several billion years after that.
It’s sort of like thrashing the two galaxies [Laughter] are thrashing around each other until finally it’s just a ball of stars. We’re just going to turn into an irregularâ€¦.
Pamela: We’re just going to be another elliptical galaxy in the Universe.
Fraser: Right and these are some of the largest galaxies out there which have gone through many galaxy collisions and consumed a lot of stars. They’re mostly populated with the older stars, right?
Pamela: A lot of the dust and gas that would otherwise go into forming new stars gets knocked out of the galaxy in the process. Or it gets churned into a final magnificent burst of star formation. About the time that our Sun is ending it’s main sequence life, our galaxy and Andromeda are probably going to be starting to end their final dance andâ€¦
Fraser: What will happen to the black holes? I know there are super massive black holes at the middle of both galaxies? Will they come together?
Pamela: Very slowly. Actually, when we look out at other spiral galaxies that are in the process of merging together to form elliptical galaxies, we actually see two black holes embedded in the cores of these very dramatic systems. We believe that over time these smaller black holes will merge together to form larger and larger black holes.
Actually as we look out around the Universe one of the things we notice is the size of the super massive black holes in the center of galaxies is directly related to the dynamics of the spheroid of stars surrounding that super massive black hole. The larger that spheroid of stars the larger the super massive black hole, and in order to build that black hole you have to have in these collisions the black holes merging. That’s going to give off a huge amount of energy when that happens.
Fraser: Okay, so the Galaxies have come together and eventually the super massive black holes have merged, what’s next? I guess we’re going to run into other galaxies?
Pamela: Over time the entire local group, us, the Magellanic Clouds, Andromeda, the other smaller galaxies that hang out amongst us will all merge into a bigger and bigger system until eventually we’re basically one giant island galaxy. It’s going to actually look like an island galaxy to us as well. The next perhaps big mile-marker is when pretty much the rest of the Universe disappears.
Fraser: The, what? What? [Laughter]
Pamela: That’s what it’s always just fun to say. So our Universeâ€¦.
Fraser: The Universe is going to disappear?
Pamela: Our Universe is expanding and we can only see so far. As objects get red-shifted further away from us, their light is changed in color and the energy gets stretched out. Eventually as our Universe expands it will get to the point where the next closest object we can’t see anymore.
Fraser: Right, I think we talked about this a bit. About how big the Universe is that the objects that are really, really far away will be moving away from us so quickly that they appear to be moving faster than the speed of light, or they are traveling further away from us at faster than the speed of light.
Those galaxies, as you said, will just fade away. The photons they are emitting will never reach us and so whatever photons are left we’ll see and then the galaxy will fade away. Then I guess you can imagine a sphere around whatever we’re going to call this new galaxy closing inward of things that can no longer be seen with the Universe accelerating apart. Eventually, there is just us.
Pamela: So the nearest other galaxy clusters, the nearest other galaxy groups are going to fade to red and red and red and further red and then fade away completely. So over the course of billions of tens of billions of years, we’re going to watch the Universe fade to nothing.
Fraser: Right, I’ve done several articles on this one that Lawrence Krauss did a recent paper where they predicted that there would be a time when future cosmologists would have no way of knowing anything outside of our galaxy. So, there would be no concept of cosmology to understand that we are in an expanding Universe that began with a Big Bang because all of the evidence that we have today comes from the fact that we see the cosmic background radiation. That will disappear.
We see galaxies moving away from us and that will no longer happen. I think he said even the abundance of hydrogen and helium stars will have gone through so many generations and mixed everything up that astronomers won’t even be able to figure that out anymore. So they will think they live in an eternal and unchanging Universe.
Pamela: What’s even worse than that, they’re going to think that they live in a Universe that is gravitationally bound and at some point is going to crunch in on itself. It actually is going to return future cosmologists if they lose the history of the observations we’re making today, which over a hundred billion years, you have to kind of think we’re going to lose data.
Back in the 1900s, like year 1900, we thought that our Universe was only what we could see. Only the galaxy, the stars, the Milky Way and Andromeda was a nebula or something out there. There is this fear of what if everything is gravitationally bound in such a way that it eventually collapses back in on itself. All observational evidence is going to point in the far distant future to that also being the case of we live in the island of stars. On the distance scales that they’ll be stuck to observe, they’ll have no knowledge of dark energy.
You have to be able to see other galaxies expanding away from you in order to measure dark energy so we won’t be able to measure that anymore. Their understanding is going to be limited by being stuck in this small mundane island of what used to be a bunch of galaxies and not being able to see everything out past the event horizon; everything out past the observable horizon. It’s sad to think that we’re going to lose knowledge as we lose sight of the Universe.
Fraser: It’s quite amazing to think about the fact that we live at a really fortunate time. You think, oh, it’s great to live when I do and where I do, but to know that in all of possible time we happen to be at a point where cosmology is even possible. To get a pretty true sense of what the Universe is doing. That will be lost to way future generations.
Pamela: And that’s just kind of sad.
Fraser: Yeah, well, we think we’ve told people this would be the sad episode. It gets worse. [Laughter] So, at least you know what’s outside our galaxy? I don’t know. What’s going to be the future for the stars in the future galaxy and all of the stars in the Universe?
Pamela: Over time they will run out of the ability to burn stuff. The planet Earth actually has the same problem at a certain level. Someday, we’re going to run out of fuel. The Universe is someday also going to run out of reasonably accessible fuel.
Stars start burning by having hydrogen fuse in their core; then having helium fuse next. You can’t start off with a lump of carbon and get it burning, at least not easily. Eventually, we will have burned up all the nebulas. We will have burned up all the dust clouds. Everything that could easily be turned into a star and burned up is going to be burned up.
What’s left over is going to be in the form of white dwarfs. Is going to be in the form of if you take a red dwarf star it just sort of burns out and turns into charcoal. It’s going to be left over in the form of neutron stars and black holes. We’re going to have a bunch of stellar embers. In about a hundred trillion years there won’t be any stars that are actively burning the fusion processes things into higher elements.
Fraser: So in about what, a hundred trillion years?
Pamela: In about a hundred trillion years.
Fraser: In about a hundred trillion years there will no longer be stars. At that point I guess the Universe would be pretty dark. And I can imagine you would start out with no more super novae because you just can’t get big stars anymore. There’s not enough concentration of material and then you no longer have stars big enough to turn into neutron stars or even main sequence stars.
You just have now every now & then a pocket of gas can collapse and you get a red dwarf or a brown dwarf. Eventually there’s not even enough material for red dwarfs and then you’re just waiting for all of the main sequence stars to turn into white dwarfs. You’re waiting for the white dwarfs to turn into black dwarfs. Then you’re waiting for all the red dwarf stars to turn into black dwarfs. Then all the brown dwarfs to turn into black dwarfs. [Laughter]
Then you have a Universe filled with black holes, neutron stars and black dwarfs, right? And planets I guess whatever there was left orbiting all of this dead material.
Pamela: One of the questions left for people who work on dynamics is will eventually everything fall into a black hole?
Fraser: That was going to be my next question. You can imagine that over a hundred trillion years the chances of three body interactions or stuff just decaying, or things colliding and falling into the path of a black hole. I wonder what the chances are. Space is big.
Pamela: Space is big. I’d like to say that there will always be some rogue planet shooting out between the black holes. There will always be some rogue white dwarf that turns into a black dwarf as it cools off. There will always be some rogue star shooting off between the black holes.
Fraser: Last episode, we were hopeful for moving the Earth. [Laughter] We were hopeful for finding some way to sneak a planet around a white dwarf star and huddle up to the embers as it dies out. Now all we’re hoping for is that some black dwarf doesn’t get consumed by a black hole. That’s it. That’s the best we could hope for.
Pamela: Yeah, it is kinda sad where the expectation bar has been set in this episode. [Laughter]
Fraser: It gets worse. [Laughter] It’s funny. Let’s hope that some chunk of degenerate matter doesn’t get gobbled up by a black hole.
Pamela: Right, but there are people out there working on this who say that in 1030 years, that’s a one followed by thirty zeros years pretty much everything will have fallen into a black hole.
Fraser: So you would get these momentary flashes, right? You get darkness everywhere you looked and then every now and then, something would fall into a black hole. The black hole would flare up and you would get like a mini-quasar for a little while there and then nothing.
Pamela: Yeah, and then nothing. And then in about 1030 years, even those flashes will stop.
Fraser: Right, there will be nothing left. Everything will be gobbled up.
Pamela: Except for that little hopeful planet that I leave that is shooting off between all the black holes.
Fraser: Yeah, that one where all our hopes and dreams are resting on, shooting off to a terrible future. [Laughter] Let’s imagine we’ve looked at the Milky Way or a future version of the Milky Way. You’d have the super massive black hole, would it be orbited by other black holes? Or would they all have just fallen into the super massive black hole?
Pamela: This is one of the questions for people who work on dynamics. If we have enough collisions going on, it could all end up being one giant black hole.
Fraser: See, once again rooting for many black holes. [Laughter] But we’re probably going to end up with one. So wherever there was a galaxy, now you have one super massive black hole.
Pamela: But there’s always the probability that you’ll end up with just the right alignments of orbits and you’ll end up with a bunch of smaller black holes orbiting the big black holes.
Fraser: Right, our plucky black hole, escaping doom, [Laughter] heading off into the Universe to seek a terrible future. Alright, what’s next?
Pamela: Once you reach the stage where everything except for this one little planet they’re all rooting forâ€¦..
Fraser: I guess we also have to mention that dark energy has been accelerating the expansion of the Universe for one hundred trillion years.
Pamela: Yeah, so there’s nothing that you can see outside of our galaxy. [Laughter]
Fraser: There’s nothing. To say that things are far apart is an understatement.
Pamela: Basically, the Universe is expanding faster than something can go.
Fraser: Right. So there’s no way that anything can reach anything else.
Pamela: Yeah, it’s just not going to happen. It’s that whole the graph paper is expanding faster than you can draw.
Fraser: Okay, so then we’ve got our black holesâ€¦.
Pamela: Now the problem with black holes is they evaporate given enough time.
Fraser: And we’ll give them time.
Pamela: And we’re going to give them a lot of time. At a certain level once you have a big black hole the cosmic microwave background is filling it with energy faster than it is evaporating. In about a hundred billion years, even the cosmic microwave background is going to be red-shifted to the point that it is fairly meaningless.
It’s going to end up with a wave length of about one meter and that’s a frequency of about 300 megahertz. The amount of energy it is carrying is going to be twelve orders of magnitude less than what we currently experience. So its ability to keep those black holes going will be vastly diminished. It is just going to keep getting worse.
Fraser: So right now the only thing that will be keeping these super massive black holes their current size is this trickle of radiation coming from the cosmic microwave background radiation, I guess errant photons that somehow make it. The occasional particles of interstellar dust that fall into it keep the black hole instability. I guess eventually there will be a point where not even that material is reaching the black hole and it starts to decay.
Pamela: Yeah and so these black holes are evaporating. The small ones go first. They sort of pop off into nothingness.
Fraser: So, our plucky black hole that thought it had escaped destruction is the first to die because it is smaller, doesn’t have the mass and so it will evaporate. We did a question show on how black holes evaporate so we won’t go into that in this episode.
Pamela: Even the big ones are not going to last forever. Here’s where you take your google number. It’s a number it’s a one followed by a hundred zeros. You take your one followed by a hundred zeros, place the unit years after it and that’s when even the black holes have evaporated. Our Universe is basically nothing more than these low energy photons forming background radiation. Everything is cool, coldâ€¦â€¦
Fraser: I can imagine these particles coming off of black holes one at a time getting swept up in dark energy and being accelerated away from the black hole, right? Because they’ve been able to escape from the black hole they’re not necessarily gravitationally bound to it anymore. So they’re just going to start escaping awayâ€¦.
Pamela: It’s not so much that they’re escaping away as they’re getting stretched out. So, as this photon tries to fly across the Universe, the Universe is expanding and what might have started off as a high energy blue photon is going to become red. Then become infrared, become radio, and no useful amount of energy at all.
Fraser: Right, a state of energy, a wavelength that could be measured in light years.
Pamela: We’re looking at a Universe where someday in the future, basically everything sits as close to absolute zero as atoms can get. Imagine the entire Universe basically becoming a Bose-Einstein condensate.
What a cold, scary place to be. The thing is, all energy, all mass, is going to be conserved. The amount of mass and energy our Universe started with is still there but the volume it is spread out over is basically all this wonderful stuff that makes you, me our desk, our table, our planet, is going to be spread out so much that it’s as though were the deepest vacuum you could ever imagine.
Fraser: And what then?
Pamela: Then it’s essentially over. It’s energy death. The Universe just hangs out being cold.
Fraser: But, it’s not hanging out. It’s accelerating.
Pamela: Well, yeah, it’s accelerating itself apart but there’s nothing there. So, it’s a very sad, cold place to think about. Then there’s always the question of what if our Universe shreds itself apart and shreds itself into other dimensions?
But that’s where we start getting completely out of all observational, conceptional ideas and into the land of scary math.
Fraser: That is the same thing as people hoping that we can huddle up next to that white dwarf. That we can prevent the Earth being consumed by the Sun as it turns into a red giant.
It’s this hope against all hope that there is a way to avoid the final heat death of the Universe.
Pamela: This is why we read Sci-Fi.
Fraser: [Laughter] We should all read science fiction and you have some future astrophysicist come up with a portal to another dimension and head off to that other dimension.
This too would probably also end up in a heat death. [Laughter] I think a lot of this thinking of what if there are multiple big bangs. What if they happen regularly? A lot of this is driven by the awful conclusion that this is the future that our Universe faces.
That far, far, far down in the future beyond our lives, the Universe is a rapidly expanding place of nothing. All that came before is gone. And that’s too bad. That’s really sad.
Pamela: We don’t want to be erased.
Fraser: We don’t want to be erased and that’s how to think what it means. That’s why even putting our hopes and dreams into that black dwarf floating away is a way to say we were there. That was us. That’s all we have for this week.
This transcript is not an exact match to the audio file. It has been edited for clarity. Transcription and editing by Cindy Leonard.