Dean chats with Dr. Katie Mack, astrophysicist, cosmologist, and author of the book, "The End of Everything." They discuss how all of this might end, could it be a crunch, a freeze or a rip?
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EPISODE TRANSCRIPT:
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Dean Regas: Astronomers love to link two things, space and time. It takes time for a light to leave its origin and reach your eye. So, when you stargaze, you're also time traveling. That means reality, it's all relative. From the studios of Cincinnati Public Radio, I'm your host Dean Regas, and this is Looking Up, the show that takes you deep into the cosmos or just to the telescope in your backyard to learn more about what makes this amazing universe of ours so great.
My guest today is Dr. Katie Mack, astrophysicist, cosmologist, and author of the book The End of Everything. So yes, astronomy links space and time in a real deep way. So, let's take the Sun for instance. It takes about eight minutes for the sunlight to leave the surface of the Sun and reach the Earth. That means when you're looking at a sunset, you're actually looking at the past, at where the sun was 8 minutes ago.
Other stars are so much farther away that we use the distance light year instead of miles or kilometers. A light year is the distance light travels in a year, or about 5. 8 trillion miles, or 10 trillion kilometers. So, take that bright star named Vega that shines in the summer and fall months, From the Northern Hemisphere, that is.
Vega is about 25 light years away, so that twinkling starlight you see is 25 years old. It left that star 25 years ago and is now getting to your eyes. So, you're looking at how that star was. Then, the nearest major galaxy to us is the Andromeda Galaxy. Its estimated distance is 2. 5 million light years.
That is some old, old light. So, what are these places really like? Right now, and When's now anyway? The one good part is the farther in space we look the closer to the beginning of the universe we get so maybe Just maybe we can find out how this whole thing got started. Well, Katie. Thanks so much for joining me today Thanks for having me So let's start at the beginning.
How do we think everything, like the whole universe, how did it start?
Dr. Katie Mack: So, we have some information about the very beginning of the universe. Uh, there are some things that we're still trying to figure out, but what we know is that at the early stages, the universe was very hot and very dense, and in some sense smaller than it is today.
It's been expanding over the last, uh, 13. 8 billion years. But as for what the very, very, very beginning is, we're still working on that.
Dean Regas: And how do we find out about the earliest years of the universe?
Dr. Katie Mack: Well, so we can actually see a lot of it, which is kind of amazing. When we look at really distant objects, we're looking into the past because light takes time to travel.
And so, if we look at a distant galaxy, it might be that that light is billions of years old by the time it reaches us. So we're seeing that galaxy as it was billions of years ago. And so we can actually see the time when the universe was hot and glowing with heat, because we're seeing it as it was in those first million years.
Dean Regas: And so here we stand now, and, uh, you know, isn't this a lovely universe we're at right now? And how do you characterize this period of the universe's history?
Dr. Katie Mack: So, maybe six billion years ago when stars were forming much more rapidly, when there was a lot more collision of galaxies, and black holes were swallowing up a lot of matter and putting out a lot of radiation, and there were a lot of stars being formed.
So we're past that. We're past the peak of star formation in our universe. And we're kind of Moving toward the the sort of slow wind down of the cosmos, the stars are forming less frequently, things are going to kind of slowly fade away into the very, very distant future of the cosmos.
Dean Regas: Oh man. You mean we've peaked already?
Dr. Katie Mack: We have. We have. A lot of what we look at in astronomy is how frequently stars are forming or how much stars are shining because what we see most of the time is starlight. And so we can measure that. If you look at it from that perspective, like most of the stars that ever have or ever will form in the universe have already happened.
And like to an extreme degree. Something like 90 percent of the stars that ever Will form in the universe have already formed. So, from now until the end of time, we're looking at like maybe five or 10 percent of star formation.
Dean Regas: Oh, man, I guess it's all this downhill slide to the end of the universe, which is, you know, at least I guess a fun thing to think about in the future.
Is that something that, you know, cosmologists like get really excited about the end of the universe and, and what are possible? Scenarios that would mark the end of everything.
Dr. Katie Mack: Well, some of us get more excited than others about these topics. Um, I find it a really fascinating topic to think about the far future of the cosmos and what things will look like.
Um, there are a few things that we can, we can say with reasonable certainty about the future because we can look at how the universe has expanded up to today and we can extrapolate how it will expand in the future. And we can say that, you know, in the future, the universe will get more spread out, you know, galaxies are getting farther apart, the light, the radiation of the universe is getting more diffuse.
You know, we started in this very, very hot, dense soup, and now we're in this sort of cooler, more diffuse sort of darkness, right? Um, and it's going to get darker, and it's going to get colder, and, and we can, we can calculate, The expectation for that and we and we think that in about 100 billion years, things will be so spread out that we won't be able to see other galaxies anymore.
They'll be so far away. They'll be moving away from us so quickly that we won't be able to see them. And so, if you want to learn about other galaxies, you want to learn about the history of the universe. Now is the time because in 100 billion years, we won't be able to do that. But then in terms of sort of what will be the ultimate end.
There are a lot of different possibilities and they, they hinge on things that we don't fully understand right now. Um, so one of the things that we don't fully understand right now is something called dark energy. Now, um, as I said, the universe is expanding, but it's been expanding faster and faster over time for the last several billion years, and we're not entirely sure why that expansion is speeding up.
Uh, based on what we understand about gravity, you know, as things get farther away, their attraction to each other gets weaker, but it's still there, and so it should So it sort of slowed down the expansion as, as galaxies get farther apart. And that's not happening. The expansion is actually speeding up.
And so that means there's something that we didn't account for in the universe that's making the expansion faster. Whatever that is, we call it dark energy. We don't know what it'll do in the future. And there are a few possibilities. It might just carry on as it is now. And it might be something that's just a property of the universe, that there's a little bit of expansion sort of built into all of space.
And so then we know that the universe will just kind of keep expanding and keep expanding and get colder and darker and sort of eventually fade away as everything sort of decays. And that possibility is something we call the heat death; other people call it the big freeze. It's this idea that, you know, everything kind of decays into the waste heat of everything that happened in the universe.
And then that heat kind of distributes throughout the cosmos evenly and nothing interesting happens anymore. That's, that's sort of the short version of the heat death. And that takes a really, really long time. That's, you know, trillions and trillions and trillions and trillions of years. There are other possibilities.
If dark energy does something else, it might be something that changes over time, where it might be that it gets more powerful over time and starts pulling things apart faster and faster and faster. And that could lead to what we call a big rip where it's not just the galaxies get moved away from each other, but that they sort of get torn apart from the inside and then space gets torn apart.
That one's pretty unlikely in terms of how we understand the physics of the universe, but we don't really know what dark energy will do. It's also possible that dark energy could kind of reverse, like maybe it's, it's pushing everything apart now, but maybe at some point it'll turn around and start pulling things together.
We don't exactly know how it works, and that would cause what we call a big crunch, where everything kind of comes back together, and, and you get, you know, back into that hot, dense stoop and it sort of, you know, collapses. We also don't think that's very likely based on what we see for how dark energy works, but again, we don't know for certain.
So those are kind of the three big ones that depend on dark energy.
Dean Regas: Well, you know what you just kind of made me think about is the big freeze is kind of like on weekends you just do Netflix and chill. That's what that is. And the big crunch is I want to go back out to the clubs again and, you know, mix it up again.
And so, so you're a big freeze person then.
Dr. Katie Mack: Yeah. I mean, I don't, I don't want our universe to be consumed in, you know, hard radiation and fire. I don't think that sounds like fun to me.
Dean Regas: I miss those exciting days for actually I am a big crunch. I prefer a big crunch. I wanted, I wanted to, I want to come back again. I want to do it again. That's, that's what I think.
Dr. Katie Mack: Well, well, the thing about a big crunch is when, when the big crunch was originally kind of talked about, there's a lot of supposition that maybe you could have a big crunch and then a new universe would form after, you know, to have like a bounce, right?
And it's actually, in terms of building a theory, it's hard to make a theory that has a big crunch and then a new big bang. Like, it's hard to get the equations to do that. So when we talk about a big crunch, we're generally talking about, like, a big crunch, a collapse, and that's it. Right? Like, you don't get another go at it.
I think that's one of the misconceptions that people have is the idea that, like, if we have a big crunch, then of course you bounce back and, and start again. And that's, that's, That's, that's not necessarily, um, something that would happen.
Dean Regas: Yeah. You don't bounce back from going to clubs. I mean, that's just, uh, yeah, you know.
Dr. Katie Mack: True.
Dean Regas: Yeah. 13. 8 billion years of history. A lot to, a lot to go on. Well, uh, Katie, uh, thanks so much for doing this today, for chatting. It's been a lot of fun.
Dr. Katie Mack: Yeah. Thanks for having me. I, I always enjoy talking about the universe.
Dean Regas: Me. I like thinking about the beginning of the universe because we go back 13.
8 billion years ago, or so. The universe was born from a spectacular event called the Big Bang. Everything we see came from that moment. As every good precocious student might ask, I know I do, What happened before that? Aha! That could be an unanswerable question, because we can't see beyond the beginning, because before that there was no space or time.
Both were created in that moment, so we can't look farther than 13. 8 billion light years because nothing would be there.
So, if your brain hurts, like mine, welcome to the wonderful world of astronomy. It hurts so good to think that big. Looking Up with Dean Regas is a production of Cincinnati Public Radio. Kevin Reynolds and I created the podcast in 2017. Ella Rowen and Marshall Verbsky produce and edit our show, and claim my voice is the source of all dark matter.
Hey, I'm not sure if I should be offended, or if that's ultra cool. Yeah, that's ultra cool. Yeah, thanks guys, thanks guys. Jenell Walton is our Vice President of Content, and Ronny Salerno is our Digital Platforms Manager. Our theme song is Possible Light by Ziv Moran, and our cover art is by Nicole Tiffany.
I'm Dean Regas and keep looking up!
