Short Wave - SPACE WEEK: An Astrophysicist On The End Of Everything

Episode Date: September 4, 2020

*Astrophysically speaking. That's the subject of Katie Mack's new book: the possible ends to our entire universe. Specifically, she breaks down some following potential outcomes: heat death, the big crunch and vacuum decay. (Spoiler alert: the names of the other scenarios we don't get to in this episode are just as cool.)Email the show your existential questions at [e-mail]. But please, no existential dread at this time — we're full up on that.P.S. We're off Monday for Labor Day. So, catch you Tuesday!See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. Maddie Safaya here, bringing Shortwave Space Week to an end with the end of everything, the entire universe, which seems very fitting for the moment. You know, when I was first proposing this book, it was 2017, and there was definitely a kind of a kind of nihilistic vibe going on. And so I felt like at the time, you know, the timing might be pretty good. But I didn't know how bad things would get. Katie Max, an astrophysicist at North Carolina State University. And she has a new book out called The End of Everything, Astrophysically speaking. And so, you know, in a sense, I'm a little bit worried that people are going to be like,

oh, there's enough terrible stuff happening. But what I've heard from people is that the book is actually kind of a nice thing. escape from the day-to-day terribleness and stress and worries that everybody's going through. But the thing is, it's Katie's job to think about this kind of stuff. Stuff like the universe, the beginning of the universe, the end of the universe, what the universe is made of, how it works, all of the kind of questions about the nature of the cosmos, how it's changing over time, and, you know, our whole cosmic story.

you know, super casual. By studying this and lots of other fancy stuff, astrophysicists like Katie are able to theorize possible ends to our universe, and all of these different universe-ending scenarios have surprisingly kind of awesome names? Based on name alone, I think the big rip is pretty good. So today on the show, we're breaking down some of the possible ends. to this universe, we and gazillions of other bits of stardust call home. So before we get into it, we need to talk about something that will definitely play a role

in the end of the universe, dark energy. See, our universe is expanding, spread on out. And that expansion is speeding up. Scientists think that's due to something called dark energy, but they don't really know what dark energy is. And there's nothing in normal physics that'll do that. Like regular matter won't do that. You know, it has to be something weird and whatever it is, we call it dark energy. But we do not know what dark energy is made of. We don't know how it got here, you know, why it exists. It might be just a property of space, something called a cosmological constant that space just has this kind of inherent stretchiness in it. But it may be something different that changes over time and could get very extreme.

in the far future and lead to the big rip. Depending what dark energy is really kind of dictates potentially the end of the universe. So how long do you think that'll take you to figure out, Katie, like 10 or 15 years? I'm personally not working on dark energy myself. I see. Really passing the buck, Katie. Really pass. It's a very hard thing to study, okay? Because all it does is make the universe expand faster.

Okay, okay. So are you ready to start talking about the end of the universe, the different situation as you will? Okay, all right. So let's start with heat death. Our universe is expanding and that expansion is accelerating due to dark energy. And in the heat death scenario, our universe kind of continues to expand and expand and expand, right? Yeah, yeah. What happens is that everything gets farther apart from everything else. You have fewer of these galaxy interactions, so you make fewer stars. and eventually each galaxy gets more and more isolated. So we would get to a point, you know, in only about 100 billion years, we will get to this point where we can't see other galaxies in the sky anymore because they'll be so far away and their light will be stretched out so much

that we won't be able to see them. And so the universe will just get a lot darker and then, you know, the stars in our galaxy will be dying out, so our galaxy will kind of fade away and then, you know, even black holes will start to evaporate, because that's something that can happen to a black hole, is that it can lose its mass through this process called hawking evaporation. So black holes will start disappearing, and then matter decays,

and then eventually you end up with a universe that's just cold, dark, and empty, and all that's left is kind of a traced amount of waste heat from the processes of the universe, and that's called the heat death. Cold, dark, and empty, you know? Mm-hmm. That's actually just sounds right. But really, like, that is considered to be one of the more likely ends. Yeah, that's kind of what happens if you just extrapolate from what we know about the universe's evolution today

and assume that dark energy is this cosmological constant, this just property of space, that it has this expansion built in. It takes a ridiculous number of trillions and trillions of years, but you end up with basically an empty universe. Yeah. All right. So if dark energy acts a little differently, then we potentially get to a different endgame, the big rip, right? You describe it as an unraveling. And this happens considerably faster than heat death, right? Yeah, yeah. So the idea behind the big rip is if dark energy is something else, if it's a particular kind of stuff we call phantom dark energy, where instead of just being a property of space, it actually, is something that grows in its intensity over time. So it's something that there's more and more of it, you know, in each little space of space over time,

then it can be something that doesn't just move galaxies apart from each other and isolate them, but actually tears the galaxies themselves apart. So what it would do is it would pull the stars away from our galaxy. So we'd see the Milky Way kind of dissipating. And then it would pull planets away from their stars, and then it would start to actually rip apart stars and planets, and then atoms and molecules, and eventually rip apart space itself.

And that's the big rip. Wow. I can't believe that one's your favorite, Katie. No, no. You asked about my favorite in terms of the name, and it's definitely my favorite in terms of the name. My favorite one is the next one, which we'll get to, I assume. But, no, the big rip is, it's one of the most terrifying ones

because you would see it coming. You know, you would know that this was happening and you would know that there's, you can't, you can't hide. Because you would see these things being kind of unraveled out there in space. And then you would know that there's nothing you can do. You can't hide from space itself, right? The dark energy would be inside your own space, your own body, and it would be starting to kind of pull you apart. It's a terrifying prospect. I just want to quote, you can't hide from space, Katie Beck.

You just can't. Just can't. No. Yeah. Okay. So last up is the end of the universe situation called vacuum decay. And Katie, this ending is very metal. Like, it is very intense.

Yeah. So the idea behind vacuum decay is sort of that there's an instability built into how physics works in our universe. So, you know, we have laws of physics. We have the way that electrons move around in atoms and stuff like that. There are relationships between particles and forces that make our universe work the way it does, make atoms work, make chemistry and biology and planets and everything possible. And there's a possibility that there's an instability built into that where, you know, something could change in the universe, specifically in something we call the Higgs field,

which is this energy field that sort of pervades all of space, that would rewrite the laws of physics where that happens. So somewhere in the universe, there would be this weird little quantum transatlose. in the Higgs field. And that would create a bubble of a new kind of space where the laws of physics are different inside that bubble. And that bubble would expand through the universe at about the speed of light. And then anything that ends up, you know, being engulfed by this bubble would be in a kind of space where the laws of physics are different. So atoms can't hold together anymore and everything would be just totally destroyed. And it's my favorite of these scenarios because it's just so out of left feet.

so out of left field, you know? Everything else is about like, oh, the universe is expanding, whatever. This is just like, no, physics breaks somewhere and creates a bubble of death. And that bubble of death expands out of the speed of light. You don't see it coming. And it just destroys everything. That's kind of merciful. I mean, it's, yeah, it's very humane. Like, there's nobody left to miss you. There's no tragic aftermath. And then it's done. Yeah, I like it. I like it because it's like, here are all these scenarios based on things we can observe. But what if physics was just broken and everything was wiped out all at once? Come on.

But I love it. Okay. So I do think one of, and let me know if this is wrong, but like one of the things about this that I find particularly unsettling is that this could happen just like whenever. Is that fair? Yeah. Well, so it's a quantum transition. It's a quantum tunneling event.

And one thing we know about quantum mechanics is it really breaks our ability to predict things precisely. So we can give probabilities about when it might happen, but we can't say exactly when it will happen, if it even will. And people write me email saying that they're freaked out about this idea. So I always want to make sure that I put in caveats. Like, the chance is so small, you know, you're more likely to be, you know, hit by a meteor and a lightning bolt at the same time while winning the lottery. Like, it's, you know, it's really small chances. Right. So Katie, bigger question. here, which is hard to do, since it's already a pretty big question you're talking about, but why study this? You know what I mean? Like, why spend resources trying to figure out the end of our universe

that's, you know, so far in the future that humans won't have existed for billions of years? You know what I mean? Right. Yeah, I mean, I think that the main reason is just curiosity. You know, we want to know how the universe works and we want to know where we came from and we want to know where we're going. And so when we think about the far future and we extrapolate our current cosmic evolution into the future, it's a way that we can kind of examine our theories of physics and kind of push things to their theoretical breaking point. They can give us new insights into how physics works. That's kind of just built into human nature that we want to understand things. We want to figure out how we fit into everything. What does it all mean? And I wanted to write something that would

give people access to that and give people some way to step into that. Well, I'll tell you what, Mac. The book was really fun. This was so much fun. I really, I really appreciate you. I had a lot of fun. Awesome. Yeah, this is a fun chat. Thank you very much for having me on. To learn about other possible ends to our dear universe, check out Katie Mac's book, which is out now. It's called The End of Everything, Astrophysically Speaking. Oh, and before we get to the credits, just want to remind y'all that we, at Shortwave, take the holidays off. So we'll be going dark on Monday for Labor Day. Okay, music, music, universe music. Today's episode was produced by our Lil Vacuum Decay herself, Rebecca Ramirez.

Viet Le, aka Heat Death, was our brilliant editor. Burley McCoy, all-knowing Big Crunch, faithfully checked the facts. I'm Maddie Safaya, also known round these parts as Big Rip. All right, y'all, see you Tuesday, when we bring NPR's shortwave back to Earth. I want you to know one of my producers messaged me to hearing this and said, Let's quit and study astrophysics about halfway through. Awesome. So thanks a lot, Katie Mack.

Thanks a lot. I'm down a producer now. Sorry.