A Cosmologist’s Guide to the End of the Universe | Katie Mack and Debbie Millman | TED

00:04Katie. Yes. Hi. Hi. I understand that you earned your private pilot license during the pandemic. Yes. And are now doing aerobatic training. I've heard of acrobatic training, but never aerobatic training. Tell us what that is. Yeah. So, arerobatics is flying the airplane in unusual ways.

00:26So things like loops and and uh spins and rolls and really learning how to control the airplane at all areas of the envelope, you know, really beyond the normal straight and level flying. And it's super fun because it's like creating your own roller coaster in the sky.

00:47And it's not scary. It's it can be scary sometimes. So you're a daredevil. No, I I enjoy it because it's it's challenging. It's interesting. It's a different perspective and it's a way to learn enough about how the plane behaves to be safer when you're trying to just fly straight and level.

01:06Sometimes things happen and you need to learn how to recover. So, I do it because it's a challenge, because I enjoy it. I'm not an adrenaline junkie in any way. Um, but uh it's it's just something that I feel like it it can make you a better pilot and it's just a different way of seeing the world.

01:24Has flying given you a different perspective on your work as a cosmologist? I think what it has done is it's allowed me to have a space where I don't think about work. Actually, it's um when you are fully fully absorbed in something and fully focused, it's you you get into this zone where nothing else can touch you.

01:47And when you're flying, you have to be focused. you can't think about other things because things will go very badly if you if you take your focus away from what you're doing. And so I really enjoy that that opportunity to just be in the moment, be in the plane, have that different view of the world.

02:06Um and and I enjoy, you know, the extra challenge of of trying to do something else. Your grandfather worked on the Apollo 11 mission. Yes. and I believed he saved the lives of the Apollo 11 astronauts. Can you share some of that story with us?

02:25Yeah, so my grandfather was a meteorologist in the Navy and um he worked on things like um creating uh satellite views of the weather with these new rockets that they just developed. And he was asked to help with the Apollo 11 mission. and his job was to figure out if the weather conditions at the splashdown site when the capsule came back were going to be okay, right?

02:49Because you you don't want to come into a storm when you're when the capsule's coming in on the parachutes. And he was, you know, checking all the usual charts and it looked fine, but he knew there was a a secret satellite that was a weather satellite, but it was a secret because it could also be used for spying and he had been in the Navy.

03:04um and he wanted to make sure that there was nothing in the splashdown area that was going to be a problem. So he went over to his connections through the Navy and checked on that satellite and it turned out that the splashdown zone that they designated had a a storm coming something called screaming eagle thunderclouds like something really bad that was does not sound good.

03:28No. No. And apparently it was it was bad enough that it could have just ripped the parachutes right off the capsule as it was coming in. And so he managed to convince NASA to move the splashdown site just 72 hours before the splashdown. And he couldn't tell them why because NASA is a civilian agency.

03:46They couldn't know about these secret satellites. And so he had to just use the weight of his expertise and his reputation to tell them you have to move the splash down. I cannot tell you why. Here's an alternative. And so they moved it a few hundred kilometers uh in some direction and it was fine.

04:02But so basically it was a trust me I've got this. Yeah. But they did say we are also going to send some planes to the original site and if it's fine there you're in trouble. So they did send the planes. There was there was a storm. Um but the astronauts were were fine.

04:21You said you were a curious child drawn to the night sky before you even knew the word cosmology. Were you influenced by your grandfather's work? I was definitely influenced by him as a scientist. So, I knew him. I didn't know him through his uh Apollo 11 work because that was actually classified until I was sort of an adolescent, but I knew him through just his expertise about the weather.

04:45Um I knew him through he was a volunteer at the Monterey Bay Aquarium. Uh, so he knew everything about the sea animals and I I just loved to see him talk about the things he was excited about and and he had gone to Caltech as a as a student to learn about meteorology.

05:01And so I I I knew a little bit about Caltech and about the you know all the nerdy people there doing fun exciting science and so he was definitely an influence in getting me excited about science. Katie, you've written about how you were just 10 years old, 10 years old, when you read Stephven Hawkings book, A Brief History of Time.

05:23I had to read that book really, really slowly to grasp what he was writing, and I did that when I was 30. Yeah. Um, how did you first hear about the book when you were 10 years old? And what what provoked you to pick it up and start reading it?

05:38I think that I, you know, I had exposure to a lot of different kinds of science through just my my family. I think my family picked up on the fact that I was curious. I was always a tinkerer. I was taking things apart and putting them back together, you know, sometimes correctly.

05:52And I I they knew that I was trying to understand everything. And so I had subscriptions to children's magazines about science and stuff like that. And um my my mom is a big science fiction um fan. And so I was reading her science fiction stuff and every once in a while there would be like a public talk about science somewhere in our area.

06:12We lived in the LA area and so she'd take me to talks by scientists and so I think I just kind of accumulated um some of those books and and uh when I read Hawkings book I didn't understand very much of it as a 10-year-old but I knew what kept you reading it then I just wanted to know.

06:29I just really I really wanted to try to understand this stuff. And I thought, you know, if I keep studying, I'll I'll I'll get this and I'll I'll maybe be able to work in this area. I didn't know before I read that book that you could be a cosmologist.

06:42You know, I saw that Stephen Hawking is called a cosmologist. I was like, you know, what is that? What is that work? And I thought, well, that's what I want to do. I want to study the universe. I want to study the big bang and black holes and and spaceime.

06:55I thought that sounded really cool. You attended Caltech for your undergrad education and graduated with a degree in physics. And you said that theoretical physics is not just a discipline of of equations but of imagination. Yeah. Um how so?

07:12You know theoretical physics in general is the attempt to create kind of a mathematical cartoon of the world. So you know we have certain observations we get data and we try to find a way to connect that data to whatever the input was and and so we build sort of a mathematical machine as a way to figure out how that all fits together and you have to be creative you have to you know think about like what are the possibilities here what are the things you know what kinds of symmetries can I find in this system you know how do how are the these things similar to these

07:46other things so it's very creative it's very interactive you know there's The theoretical physics community is extremely collaborative. You know, everybody's gathered around chalkboards arguing about equations and, you know, going to conferences all the time, giving talks.

07:59You know, we don't we don't sit in isolation, you know, just writing down equations by ourselves. It's it's always a conversation and it's always it's it's it's very much a creative, imaginative kind of work. You went on to Princeton University for your PhD where your doctoral research focused on early universe cosmology, cosmic inflation and dark matter.

08:24And you've written about how much of cosmology is trying to tell a story from the faintest traces of light. Katie, how are you able to decipher those earliest traces? And what are some of the most important things you've learned about that light?

08:43Yeah. So, um I think in that in that I must have been talking about the cosmic microwave background, which is light that's all around us in the universe. Um if you if you tune a a microwave receiver, so microwaves are just a kind of light, a kind of electromagnetic radiation.

08:57Um and if you tune your receiver to the right frequencies, you can see this background of just a glow all around you everywhere in space. And um that's the light from the big bang. And and the way that we know that what that is is that we can look at the spectrum of that light.

09:13How much energy is at different frequencies. And we can see that the spectrum is exactly the same spectrum you get when something is glowing because it's hot. Like if you take a poker and you stick it in the fire, it glows red. And that has a certain spectrum, a certain distribution of light.

09:28And it's just anything you heat up that glows, it glows because it's hot. because of the way the particles are moving around and creating light. And this background light has exactly the same spectrum and it's everywhere in space. And so what it is is is if you look far enough away in any direction, you're looking so far away that the light has taken a really long time to get to you.

09:48Um, you know, light takes some time to travel. So, you know, even in this room, you know, you're maybe six feet away from me. It takes about six nanconds for the light to get from you to me. So, you're you're six nanconds in the past to me.

10:00And you are to me and you and I am to you. But if I look far enough out in the cosmos, I can look billions of years in the past and I'm seeing directly that the past. And if you look so far away that you're looking 13.8 billion years ago, you're looking at the time when the whole universe was glowing with heat because it was in this this hot dense phase of the very early universe.

10:23And so you see that glow very directly in the cosmic microwave background. And that's that's something that we can study. We can study that globe because we are looking directly at the very very early universe. It's incredible. Given that light travels, the light that is being picked up in this background where is that going?

10:44It's it's just it's just diffusing through space. So it's going in every direction. So it's just continually moving. Yeah. Yeah. So if you turn on a light bulb, the light moves out in every direction. And you know the light from the the the time the whole universe was glowing with heat.

10:59You know that light was just moving in every direction. Eventually the universe cooled down and the light you know kept traveling in every direction. And the places we see it at the sort of edges of our vision in the universe that light is also going away from us.

11:13But the part that's going toward us we see and we see that that background radiation. Voyager is not even one full light day away from Earth, but it's going to be another 40,000 years before it encounters another celestial body. Yeah. Cosmology often deals with scales that defy comprehension.

11:40How do you hold on to the human scale with this sort of infinite what seems like it's infinite? I mean, I can't conceptualize these scales really any more than anyone else can. You know, we we talk about, you know, billions of light years and and all this stuff and and I I just have to write down the number and trust it.

12:01I don't I don't have a sense, you know, I can't hold in my head this this notion of, you know, that much space or that much time. Um so for me you know there's there's a kind of you know sort of a a ruler in my mind of you know million billion trillion and I don't have a sense for how far apart those are.

12:21I just know that these are the scales that I'm working with and then I I think about on the human scale you know what what I can do as a as a scientist to to try to understand it. But um you know my work on my in my work even even individual galaxies are are not that important.

12:37So, so um you know professionally, yeah, I mean professionally I I you know all the human stuff is kind of lost in the weeds. Um but uh but the the work itself is is very human because we're all working together and we're all having this continual conversation and the mathematical models we're building are very much tied to our humanity because these are you know just things that come out of our our imaginations that that are tested with the data and we are constantly making choices and constantly you know trying to better understand the universe we live in.

13:12What provoked you to choose a field that is primarily about how we end? Um, so I am really interested in the whole story of the universe. So, I've done a lot of work about the beginning of the universe, and I've worked on how the universe evolves over time, how the first stars formed, how the dark matter, this invisible stuff that holds galaxies together, how that's evolved over time and brought galaxies into existence.

13:39And at some point, I started getting really curious about the end as well. And um I just, you know, we know the universe is evolving and changing and we know that it's not going to be the same forever. It's going to be different. And it's it's uh we we know that there was it was different in the beginning and it's changing and it's going to be real different in the future.

13:59And so I'm really curious what that ending looks like. And so that's why I wrote a book about the end of the universe just cuz I'm I wanted to talk about, you know, what are the possibilities? What are we thinking about how the universe will end?

14:13And like what is that whole story? You know, I when you read a story, you want to know the beginning, the middle, and the end. and and you know, I feel like uh it's it's really part of how we fit into this cosmos. Your book is titled The End of Everything.

14:28And in it, you explore five possible endings for the cosmos. The Big Crunch, Heat Death, The Big Rip, Vacuum Decay, and Bounce. Were there others that you left out, or is this the only five options? Um so I focus on sort of five categories of endings um that are things that are actually talked about in the physics literature.

14:53So all of these are possibilities that physicists have put together models. We've uh you know worked out what what the physics would be in each of these scenarios. Um there are there are ways to to tweak each of these where they're going to be a little bit different, but basically, you know, in terms of the whole cosmos, there there only a finite number of ways that it can be destroyed, right?

15:18Like it can it can collapse, it can keep going. Um you can have these weird transitions where there's basically a bubble of of a new kind of space that spreads through the universe and destroys everything. And then there's like cyclic models and that's um and there are a lot of different ways where the universe can end and start again or or the beginning of our universe could be the end of a previous universe and there are are a few of those that I talk about in the book as well.

15:41Yeah, that that to me feels the most hopeful. Um you've said that writing this book changed your relationship to time. Yeah. In what way? you know, talking about the very very distant future of the universe, you you really think about this kind of deep time idea and and how, you know, the the bit of time we live in is so small.

16:06Um, and the the bit of time humanity has existed in is so small and and there's there was time before us and there's going to be so much time after us. Um and it made me think a lot about not just time but like how our our impact on the world you know we we are really unimportant in the universe just to say like like uh humanity is is completely insignificant in the cosmos in every possible way you can imagine.

16:33Um but optimistic morning folks I mean but you know absolutely we are it's impressive that we know so much even though we are so inconsistent. Um, but uh, you know, it made me think about like, you know, everything is is going to end at some point and there's not going to be some, you know, final thing that makes it all worthwhile, right?

16:53At some point everything will be destroyed. It kind of won't have mattered that we were here. Um, so when we think about how to find meaning and purpose, it's, you know, it has to be something that's self-contained. You know, something that exists in the universe now.

17:08and what is, you know, how do we find meaning in the moment? How do we find meaning that doesn't depend on it all being wrapped up with a tidy bow, you know, at some future point? Um, and that that really made me think differently about what's important in my life.

17:22Um, what to be upset about or not upset about. Um, because you know, we are we are just temporary and we are doing the best we can while we're here. Katie, in addition to your work in theoretical, astrophysics, cosmology, writing, and aerero acrobatics, um, you're also a poet.

17:45I've I've done a little bit of poetry. Yeah, I I enjoy that. I I'm wondering if it's possible. I know I know we talked a little bit about this ahead of time, but my TED friends and I asked if you would read one of your poems today on the TED Next Stage, and you agreed.

18:00Um, how lucky are we? Um, so can you tell us a little bit about what you're going to share with us today? So, I've written a few things here and there. I've done a lot of science writing. I've written a few poems. Um, and at some point I was contacted by a sort of graphic uh design company saying that they were putting together a sort of reel of their um their work and they wanted uh they wanted a poem.

18:22They wanted to create, you know, have a poem to go along with it and could I write a poem about something sciency and then they would illustrate it. They they were called Finger Industries. Now they're called Ouch. Ouch Health. Um and uh and so I wrote this poem for for their their sort of demo reel.

18:39Cool. Wonderful. Would it be okay for you to scan? Sure. Sure. Excellent. Thank you. Okay. So the poem is called Constructs. What do you see when you look at the world at this infinite variety of objects, colors, textures, weights, flavors?

18:58What makes each person, animal, object, unique, special? There are around 90 chemical elements naturally found on this planet. But each one, hydrogen, oxygen, or carbon, is just a construct, a tiny shivering mass of the same protons, neutrons, and electrons found in any other, same ingredients, different recipe.

19:33We are not essentially our constituent parts. We are the knowledge that unites them. Katie Mack, thank you so much.