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TRANSCRIPT: TAI ASKS WHY - THE END

Tai: [crunching sound] So, the other day I was just sitting on my couch eating some chips and thinking about the Big Bang. You know, casual stuff, for a weekend. But, like, the universe started as this super-hot, super-dense, super-tiny point in space and time. And then 13.8 billion years ago, it started to expand super-fast. [exploding sounds] Eventually, forming things like stars and galaxies, and eventually - us! The Big Bang. Well, a very smart person told me recently that the Big Bang actually worked more like a big balloon. It was less of an explosion and more like a big, long inflation. And that cosmic balloon has been inflating and expanding for 13.8 billion years. But this is what I was wondering as I was chomping my chips. A balloon can only hold so much. What happens when it’s filled up to its limit? Is all of it going to just go [blowing away] and blow away? Bye-bye, Milky Way. Peace out, Pluto. Because, if the universe had a beginning, then it has to have an ending, right? But how would that happen? And when? I mean, will humans be around to see it? How is the universe going to end?

[show open] [music] Tai Asks Why

Tai: I'm Tai, and this is my podcast, Tai Asks Why. There are just so many good questions out there that you just really, really want to have answered. What’s at the bottom of the ocean? Can you actually predict the future? How can I tell what's true on the Internet? What’s the deal with screen time? And how is the universe going to end? Do you guys think that the universe is going to end?

Finn: Well, it depends.

Tai: OK. Elaborate

Finn: Mmm, could decay like a black hole. No one knows.

Zoe: Well, isn't there that theory that black holes are like pathways into different universes?

Finn: I try not to think about it.

Kaden: I just sort of just acknowledge that it's gonna happen and just continue on.

Finn: What if the universe is already ended? We're living in a hologram or something like that.

Zoe: When I was a toddler, I thought the universe was inside a treasure chest that was inside a giant stomach. And the giant was walking around somewhere.

Tai: Now, why would they eat treasure chest, though?

Zoe: Because it was tasty.

Tai: I kinda dig Zoe’s tasty treasure chest theory of the universe. And maybe she’s not completely out to lunch because, apparently, in order to know how the universe is going to end we got to look at how it began first.

Katie: The main reason we think that the universe is going to end is that we have really good reason to believe that it began.

Tai: That’s Katie Mack. She’s a theoretical astrophysicist at North Carolina State University. She’s spent years studying the whole universe from beginning to end. And she says there a couple of different ways that it could go down. Here are her top five ways she says the universe can end. Number one.

Katie: The first is the Big Crunch, where the universe is currently expanding but the expansion turns around and everything crashes back together like the Big Bang in reverse.

Tai: Number two.

Katie: The second one is the heat death where the universe is expanding and expanding and expanding and everything gets so far apart and so distant. And the universe gets so cold and dark and empty that everything kind of just fades away.

Tai: Number three.

Katie: Then the third one is called the Big Rip. And that's where you start out like heat deaths. So everything's moving apart. The universe is expanding, but then it starts expanding so fast and so extremely that the galaxies themselves are kind of ripped apart. And then solar systems and the stars and everything is just ripped apart at some point in the future.

Tai: Number four.

Katie: Then the fourth scenario is called Vacuum Decay where you have this kind of bubble that forms somewhere in space, and it's a bubble of a different kind of space. And that bubble expands out at the speed of light, or close to it, and envelops everything and destroys the whole universe. Kind of like this giant bubble of death.

Tai: And finally, number five.

Katie: The last one is called a Bouncing Cosmology. There are a lot of different ideas for bouncing cosmologies. But they're ideas where either the universe kind of cycles between a Big Bang and a Big Crunch over and over again. Or sometimes you have a scenario where two universes, kind of, smack into each other and create a new big bang and then, kind of, go back and forth and back and forth and make a cycle of new universes from these collisions.

Tai: To summarize, we have Big Crunch, Heat Death, the Big Rip, Vacuum Decay, and Bouncing Cosmology. These sound like something a supervillain would dream up. And they're all really, really big and terrifying ways to go out. Which end of the universe is your personal favourite?

Katie: My personal favourite is Vacuum Decay. It's just - it's just so weird, just so weird and cool [laughter] and kind of weirdly scary.

Tai: OK. I like it too.

Katie: Yeah, it is.

Tai: And you make it sound so cute, you know.

Katie: Yeah, you get this little bubble of death, and it just grows up.

Tai: [silly voice] Hi, I'm going to consume everything.

Katie: It's great. It's funny because they're so dramatically different. Right. And none of them are things that we can say, this is definitely not going to happen because there's so much we're still trying to learn. Every day when we're learning new things about the universe, it can shift our understanding such that really different things happen. So, yeah, we can't say for sure that the expansion won't stop and turn around and cause this big collapse. We can say that it wouldn't be anytime soon. We're talking billions and billions and billions of years in the future if that's going to happen.

Tai: That’s good, at least. I can deal with billions and billions of years into the future. I mean, I’m thirteen so far. So I probably won’t live until then. I’m glad to know that it won’t affect me, personally, or anybody I know. So, maybe I should stop stressing about this - a bit. But I can’t help but wonder. Like, which of these should I be rooting for?

[music]

Katie: I mean, I guess it depends on what your preferences are. If you want to live as long as possible, if you want the universe to persist as long as possible, then you probably want to go with the Heat Death because the Heat Death takes, you know, trillions and trillions and trillions of years. But in the meantime, everything's kind of OK. It just kind of slowly fades to black. Right. But if you want something that's quick and painless and you don't notice it, then the Vacuum Decay is probably your best bet because that one where you have this bubble that expands through the universe, that bubble as it's expanding, it expands through the universe at about the speed of light, which means that you can't see it coming. So, it doesn't hurt or anything like that. It just erases the whole universe. And if this could happen, it would be, you know, one followed by a hundred zeros years. So, it's a long, long time. And so, you'd have a lot of time still, and when it does come you don't feel it. You know, you don't have to be sad about it or anything. You just blink and everything's gone.

Tai: Whoa, OK, then. But, like, when everything is gone, is there just nothing? Will there be no space and no time? And, like, with that Vacuum Decay option, it sounds like there’s one type of space that will just eat up another type of space? How does that work?

Katie: Yeah, that's a good question. So, if there is this possibility of Vacuum Decay, that means we live in what's called a 'false vacuum.' And that just means it's a kind of space that's not the only possibility. There's this other possibility for what space could be like with the laws of physics, could be like, and that’s called the 'true vacuum.' And the reason the other one is called the true vacuum is because there's some sense in which the universe would prefer to have that kind of space, you know. And that's why if you make a little bubble of that kind of space - that's why it’ll take over the whole universe, because the universe kind of would rather be in that kind of space.

Tai: Oh, man. This is getting kind of weird. So, the universe has preferences for the different kind of space it likes? It’s like kid in a candy shop being like, "Hmm, I’ll take the one with atomic particles please. But not the sour ones. I don't really like sour atomic particles." It kind of hurts the mind to think of different spaces, like, I thought space was space. But, I guess there are different spaces that have different rules.

Katie: You know, like, the laws of physics will be different inside that bubble. So you won’t have particles and atoms the way that we have now. And, also, the space inside that bubble, it will want to come together and collapse into one giant black hole. So, if our universe were taken over by this big bubble, not only would the universe be enveloped by this weird kind of space where the laws of physics are different and particles can't really exist in the same way, but also it would collapse into a giant black hole. So, that would be a very sort of complete ending.

Tai: Kind of a bummer to think that the universe would prefer to be a black hole. I mean, I thought it liked us. I don’t really think I like the vacuum option. What else do we got?

Katie: The other possibilities for the end of the universe have kind of slightly different things that can happen at the end. So, you know, if you have a Big Crunch where the expansion the universe reverses and all the galaxies come together again, then there's a possibility that you could have a Big Crunch and then a new Big Bang. You could have, like, cycles of Big Crunch and a Big Bang and so on. You know, a new universe come out of it. With the Heat Death possibility, where everything just kind of expands and expands and expands, there are sort of weird possibilities at the end of that where you could have like these random quantum fluctuations where you could have a new universe born out of that or a new part of the universe or even just one person or something. All sorts of strange things can happen at the end state of that of that situation.

Tai: There's just like a single person that just exists in the middle of nowhere, and they're like, "Hello." Just, like, look around and stuff. "Well, I seem to be a little bit screwed."

Katie: [laughter] Yeah, there are a lot of wild things that can happen, kind of, after the end if you just define the end as being when everything that we see around us is destroyed in some way or decays away.

Tai: Now, I’m imagining being the only human left to watch the universe just collapse. That would pretty much be my nightmare. But, if we are talking billions of years from now, is there a chance, even a tiny chance, that we’ll still be around?

Chris: Not unless we figure out how to move. We do have this little problem that the sun isn't going to live that long.

Tai: Oh, right. That thing. This is Chris Kochanek. He’s a professor of astronomy at Ohio State University, where he specializes in studying what he calls 'stars behaving badly.' He says that before we get too caught up worrying about the universe collapsing, we should keep in mind that our sun is a giant star that might end way before that. So let's look at problem number one first.

Chris: Most of these massive stars will eventually explode. And along the way they like to have various digestive problems, and they do burps and hiccups and blow stuff off in what are called supernovae. And so, in those cases what will happen is that the bulk of the star gets ejected in an explosion. And what's left behind is, in almost all cases, going to be these objects called a neutron star which will be somewhat more massive than our sun and about the size of a big city like Toronto's.

Tai: You say it in such a nonchalant way, like, you just study how these stars go [blowing up] like these crazy, big explosions. You're just talking about it so casually.

Chris: Well, it's not like they're uncommon. I mean, if you could seriously survey the universe for the stars exploding as a supernova, there's about one happening every second. So, they're not exactly unusual things. And you depend on them a little bit. So, almost all of the oxygen you're breathing comes from these explosions. That's where most of the oxygen we deal with comes from.

Tai: So, breathe with me now, people. [deep breathing] Taste the supernova dust. You see, when a supernova explodes, that blasts oxygen atoms into space. At some point - a long, long time ago, some of these oxygen atoms found their way into the cloud that spawned our solar system. How convenient. But Chris tells me that our sun is not one of these ones that are behaving badly. In fact, it’s totally a goody two shoes - for now.

Chris: The sun is a boring star, but it is a boring star that only lives awhile. It is going to reach its old age, and when it reaches its old age, it's going to be rather cranky. So at that point, you sort of have to figure out how to get somewhere else, or there are going to be no humans around to check out the end of the universe.

Tai: OK, but, what exactly is the sun going to do to us?

Chris: The big problem for the long-term history of the earth is that the sun slowly gets brighter. And so about every billion years the sun gets about 10% brighter. The problem is that, even before it sort of starts to really change its structure, it will slowly drive what's called a 'runaway greenhouse effect' on Earth. Not our everyday greenhouse effect that we worry about in all of our political fun, but a greenhouse effect more like what happened to Venus, which is not a very happy place to try to live.

[music]

Tai: Oh, yeah, the average temperature on Venus at this time of year. 470 degrees Celsius or 878 Fahrenheit. Oh, and when it rains? It rains sulfuric acid! The atmosphere is so thick on Venus that no heat escapes. So it is literally is like 'H' 'E' double hockey sticks. So, that’s what's in store for our little planet as soon as the sun starts heating up. And that’s not even the worst part.

Chris: The last phases are the ones that are sort of most dramatic. It's that eventually once the sun actually runs out of hydrogen at the center, it starts to expand into a red giant. And at that point, you really do have a problem because, you know, even if you can cope with the sun getting brighter by 10, 20, 30% before you reach this, when it becomes 10 times or 100 times more luminous than it is now, you really have a problem.

Tai: But that's in a while, right? That's not going to be like next Tuesday. Like, I won't have to mark it in my calendar. It's just, the world will end and the sun will eat us.

Chris: No, you know, it's next Tuesday, 4 billion years from now. So, you need a big calendar.

[music]

Tai: If you’re starting to get freaked out about, you know, our sun exploding or the universe collapsing in on itself, don’t be. I mean, these scientists who study it all the time don’t seem to be stressing it. So, I don't think we should either.

Katie:

I don't find it depressing. I find it really fun to think about these things. I think it helps that it's all so far in the future that it's not going to affect me. If I were working on something that would destroy everything tomorrow, that would make me sad. But in this case, you know, we’re talking billions and billions and billions of years. Right, like, I can sort of think about decades. I can kind of get my head around the idea of like 10 years, 20 years, 50 years. A hundred years gets to be confusing. A thousand years, I can barely conceive of that. And then, you know, you're talking hundreds of thousands, millions, billions of years. It's really just so far in the future that it's hard to get too connected to those kinds of timescales. So, I don't know. I think that it's kind of motivating. It makes me think, "I really do want to figure this out because it's a big mystery." And it also makes me think, you know, that we should kind of make the most of the universe while we have it. Even though we are this very insignificant little speck of dust, you know, floating in this giant dark space, we can learn a lot about it.

Tai: And even though the end of our solar system is going to happen even sooner than the end of the whole universe, Chris is pretty chill about that.

Chris: Well, at the moment there's not much I can do about it. So, it'd be probably a bad idea if I started losing all of my sleep because of it. You know, we're talking about, you know, it's in a billion years to have even a 10% change brightness of the sun. And so, you know, one of the real problems with anything astronomical is it involves timescales which are, sorry, you get the pun - astronomical. OK. The entire existence of homo sapiens is what? It's about a half a million years. So, this is a problem which you're barely going to have to worry about. It's something which is thousands of times longer than there have even been human beings. And if you’re going to worry about the existence of a society which might grump that the sun is getting brighter, if things evolve the way they do on earth, in a billion years, there won't be any homo sapiens just because something else would have evolved.

[music]

Tai: Oh. Maybe my distant descendants in a billion years will be like supreme robot overlords who don’t even need sunlight, but instead feast off of water and chips. Although, that's pretty much me, anyway. Man, the universe really is a magical place.

And, yeah, we shouldn’t be sad that it’ll eventually end, because everything ends. That’s just how it goes, you know, the circle of life and all that. And in a way, the fact that it's ending makes it so much more special that we're here now. So, whether it’s by crunching, ripping, vacuuming, or just a very big explosion, we just get to have fun imagining it using theoretical astrophysics. Only time will tell which one of these will actually happen. I got my money on crunching. Speaking of crunch, I'm gonna go back to eating my chips. [crunch noise]

[theme music] Tai Asks Why

Thank you, guys, so much for listening. I'm Tai Poole. This show was produced by Amanda Buckiewicz and Judy Ziyi Gu. Judy’s also our digital producer. This podcast was created by Veronica Simmonds, and she is also our editor and sound designer. The theme music is by Johnny Spence. Sound engineer is my dad, Minh Nguyen, and our location manager is my mom, Nicky Poole. Thanks, guys, for stepping in and letting me invade your closet.

Today my guests were Katie Mack, and Chris Kochanek. Check out Katie’s book, 'The End of Everything - Astrophysically Speaking,' it’s really awesome. Special thanks to Austin Pomeroy for his assistance, and my friends Zoe, Pyper, Finn, and Kaden for always being up for brain melting conversations. Our senior producer is Tina Verma and Executive Producer of CBC Podcasts is Arif Noorani. Until next time, I'm Tai, keep asking why. Hey, did you like this journey through space. Well, I still have so many more questions. Like, what is the biggest star in the universe. And how would you even figure that out? And so, I have brought this question to Daniel and Jorge who answer big, mind-blowing questions all about the universe on their podcast. And they totally schooled me. You can listen to my conversation with them on Daniel and Jorge Explain the Universe, wherever you get your podcasts.

Transcript: Tai Asks Why - Season 3: How is the Universe going to end?

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