Daniel and Kelly’s Extraordinary Universe - Listener Questions 68

Episode Date: October 1, 2024

Daniel and Kelly answer a question about whether space can be infinite and finiteSee omnystudio.com/listener for privacy information.

This is an I-Heart podcast. Let's start with a quick puzzle. The answer is Ken Jennings' appearance on The Puzzler with A.J. Jacobs. The question is, what is the most entertaining listening experience in podcast land? Jeopardy-truthers believe in... I guess they would be conspiracy theorists. That's right. They gave you the answers, and you still blew it.

The Puzzler. Listen on the I-Heart. radio app, Apple Podcasts, or wherever you get your podcasts. Every case that is a cold case that has DNA. Right now in a backlog will be identified in our lifetime. On the new podcast, America's Crime Lab, every case has a story to tell. And the DNA holds the truth. He never thought he was going to get caught.

And I just looked at my computer screen. I was just like, ah, gotcha. This technology is already solving so many cases. Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Do we really need another podcast with a condescending finance brof trying to tell us how to spend our own money? No thank you. Instead, check out Brown Ambition. Each week, I, your host, Mandy Money, gives you real talk, real advice with a heavy dose of I feel uses.

Like on Fridays when I take your questions for the BAQA. Whether you're trying to invest for your future, navigate a toxic workplace, I got you. Listen to Brown Ambition on the IHeart Radio app, Apple Podcast, or wherever you get your podcast. Hi, it's Honey German, and I'm back with season two of my podcast. Grazacios, come again. We got you when it comes to the latest in music and entertainment with interviews with some of your favorite Latin artists and celebrities. You didn't have to audition? No, I didn't audition.

I haven't audition in like over 25 years. Oh, wow. That's a real G-talk right there. Oh, yeah. We'll talk about all that's viral and trending with a. a little bit of cheesement and a whole lot of laughs. And of course, the great Vibras you've come to expect. Listen to the new season of Dacius Come Again on the IHeartRadio app, Apple Podcasts, or wherever you get your podcast.

I'm Dr. Scott Barry Kaufman, host of the Psychology Podcast. Here's a clip from an upcoming conversation about how to be a better you. When you think about emotion regulation, you're not going to choose an adaptive strategy, which is more effortful to use. Unless you think there's a good outcome. Avoidance is easier. Ignoring is easier. Denials is easier.

Complex problem solving. Takes effort. Listen to the psychology podcast on the IHeartRadio app, Apple Podcasts, or wherever you get your podcasts. Hey, Daniel. So who do you think is going to figure out the secrets of the universe? Is there like somebody that you, you know, have been keeping your eye on? Oh man, I wish I knew to the answer to that question. Well, but, but like, do you think it's someone we already know about, like a smart person like Lisa Randall or Ed Witten?

It could be, but my money is on somebody smart, somebody young, maybe somebody who's listening to this podcast right now. Whoa. So, like, how would you feel if it turned out that, like, the big questions weren't answered by you, but you were upstaged by some, like, 10 year old after you failed for decades. After failing for decades, I would be relieved if somebody else came along to figure this stuff out for us. I feel like that's the right answer. The answer matters more than the person. Love it.

Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine, and I just desperately want the answers. I'm Kelly Weiner-Smith. I'm a parasitologist at race university, and I also desperately want the answers, but the questions need to be about parasites. And you're also the Hugo Award-winning author of a non-fiction book. Congratulations. Thanks. I'll try to not scream too loud. The trophy arrived, and I am still losing my mind every time I look at it. I cannot believe that that happened. But I also can believe that Zach didn't prepare an acceptance speech, even though the flight to Glasgow takes like eight hours. He just assumed we weren't going to win, so he prepared nothing. And I almost killed him.

Oh, wow. Well, I'm sure his spontaneous speech was even better than anything he could have written. It was fine. But I wanted all of you out there to appreciate that. Kelly is not just one of the hosts on this podcast, but she's actually a... an award-winning, best-selling science writer. So we're grateful to have her here. Thanks very much for joining us.

Oh, you're the best. Thanks, Daniel, Daniel, and Jorge, explain the universe, a production of iHeartRadio, in which we explore everything about the universe. It's ups and its downs, its lefts and its rights, the things that wins awards for and the things that drive physics is crazy, hopeful that somebody young out there will figure it all out for us. As soon as possible, guys, get on it. And as part of that process, we want you to be thinking about the nature of the universe.

Yes, you are relaxing as you fall asleep or you are commuting to work and hoping to be educated and entertained. But this podcast also requires you to do some work to fit all these ideas into your head and to write to us when they don't quite click together. If you have a question about the nature of the universe, we want to hear it. That's part of the progress of science. Everybody out there wondering and thinking and trying to figure this. out. So please send me your questions to questions at danielanhorpe.com. You will definitely hear back from us. And sometimes we choose those questions to answer right here on the podcast. And sometimes the questions that you get from people new to the field are way better than any question you get at a

department seminar with a bunch of pros in the field because like you're not constrained by all the assumptions that that people who have been in the field for a while have. So we get some pretty great questions from the listeners. Yes, absolutely. We do. And we get questions. And we get questions. questions that I don't anticipate. And so I hope that these questions line up with your questions, that these ones we've chosen are also questions that other folks out there have and want to hear the answer to. So please don't be shy. If you're thinking of a question, somebody else also wants to hear the answer. And I need somebody to write in and send it to me. So please don't be shy. I love hearing from all of you. Please keep Daniel company, guys. And so today on the podcast,

we'll be answering. Listener questions number 68. And we are featuring a question from a young future physicist, Clara from Germany. So without further ado, here's Clara's question. Hello, I'm Clara from Germany 12 years old and a new listener of your podcast. My question is, could it be possible that the universe is finite in one direction and infinite in all the others? Your podcast is just great and you two guys can explain. so well. Thanks, Clara. So Daniel, when I was 12 years old, I was sequestered in my bedroom

listening to Silver Chair and playing the first three chords to Smells Like Teen Spirit by Nirvana, but not bothering to learn any of the rest of the song. I was not pondering the nature of the universe. So good on you, Clara. What were you doing when you were 12, Daniel? I was reading a lot of science fiction and a lot of fantasy. And I definitely was pondering the nature of the universe. I remember trying to think about whether space was in three dimensions everywhere or maybe parts of the universe might have additional dimensions and really struggling to get my mind around what that meant and what would be like to exist in those dimensions. So yeah, Claire and I have a lot in common. Good job, Clara. Well, some of us are late blossoming nerds, I guess, but what we get there

eventually. So give us some background on what we know about this question so far, Daniel. Yeah, Claire's question touches on two really important ideas, and she's doing something I love, which is trying to bring two ideas together. You know, physics is about unification of your understanding. It's not like chemistry where you use this equation over here and that equation over there, and it's just like these patches of understanding. In physics, we hope to have a complete cloth, you know, to stitch everything together into one idea. So it's really important that When you hear related ideas, you try to understand how they fit together. And that's what she's doing here.

And here, the related ideas are about the size and the scope of the universe, like, is the universe infinite or is the universe finite? And when you just imagine space and the whole universe, you probably just fill your mind with blackness and you imagine that it goes on forever, that you could shoot a laser beam and it would just fly on forever and ever until it hits something. But if the universe was empty, it would just go on forever. You can imagine these like dotted lines of X, Y, and Z dimensions, just stretching out to infinity, limited only by your imagination. That's an infinite universe.

And we don't know if the universe is infinite, but such an infinite universe, though it's a little bit weird to holding your mind, is actually one of the most natural ideas for how the universe might be shaped. Is this a question that you think we'll have an answer to in your lifetime, or will we be wondering if the universe is finite or infinite 300 years from now? Wow. Awesome. It's hard to prove that the universe is infinite because if it goes on forever, then you need infinite data to prove that. But we might be able to prove the opposite. We might be able to prove that it's not infinite because you could discover the universe is finite because the extent of the universe is connected to another question about the shape of the universe. Like if the universe is flat, and by flat we don't mean like a 2D sheet of paper. mean the two parallel lines will not cross. It's a three-dimensional version of flatness.

But if the universe is curved to the two parallel lines either diverge or do cross over each other, and again, curved in three dimensions in a sort of general relativistic sort of way, that means that the universe could be finite, that it could loop around on itself. Again, in a weird three-dimensional way, not exactly the same way as like the surface of a sphere loops around on itself, but in analogy to that. So if we discover that, space is curved, that suggests the space might be finite. And so we can't prove that it's infinite, but we might discover that it is finite. Whoa. I feel like I'm lost in thought here. So if it's curved, then what's on the other side of the curve? No, this is a big mental pothole that we should

totally address because if you imagine the universe as finite and curved, you probably have in your mind something like a sphere, a ball, right? I'm thinking of a donut because I'm hungry. All right. It could also be a donut, right? But the problem is, as soon as you name, some object like that, you imagine it with its boundaries inside some other vast mental space. Like if I close my eyes and I think of a donut, it's hovering in some blackness. And that's a mistake. I've like sketched around it some empty space. But when we talk about the universe as finite, we don't mean like there's a bunch of stuff

and around it is empty space. We mean finite including space. We mean that's all there is. Don't sketch anything around it. Don't fill in that mental space with something. The finite universe is limited in size, but it doesn't have an edge, a boundary. Every point on it is exactly the same. It's very, very difficult to think about.

It's very counterintuitive. Yeah, I feel like the world is split into people who think that that's fun and people who just are really frustrated. I think we might be in different camps there. So we should get to Claire's question, but first we have to take a quick break. I had this overwhelming sensation that I had to call it right then, and I just hit call. I said, you know, hey, I'm Jacob Schick, I'm the CEO of One Tribe Foundation, and I just wanted to call on and let her know. There's a lot of people battling some of the very same things you're battling, and there is help out there.

The Good Stuff Podcast, Season 2, takes a deep look into One Tribe Foundation, a nonprofit fighting suicide in the veteran community. September is National Suicide Prevention Month, so join host Jacob and Ashley Schick as they bring you to the front-line of one tribe's mission. I was married to a combat army veteran and he actually took his own life to suicide. One tribe saved my life twice. There's a lot of love that flows through this place and it's sincere. Now it's a personal mission. I don't have to go to any more funerals, you know. I got blown up on a React mission. I ended up having amputation below the knee of my right leg and a traumatic brain injury because I landed on my head. Welcome to Season 2 of the Good Stuff. Listen to the Good Stuff Podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast.

Hola, it's Honey German, and my podcast, Grasas Come Again, is back. This season, we're going even deeper into the world of music and entertainment with raw and honest conversations with some of your favorite Latin artists and celebrities. You didn't have to audition? No, I didn't audition. I haven't audition in, like, over 25 years. Oh, wow. That's a real G-talk right there.

Oh, yeah. We've got some of the biggest actors, musicians, content creators, and culture shifters sharing their real stories of failure and success. You were destined to be a start. We talk all about what's viral and trending with a little bit of chisement, a lot of laughs, and those amazing vivas you've come to expect. And of course, we'll explore deeper topics dealing with identity, struggles, and all the issues affecting our Latin community.

You feel like you get a little whitewash because you have to do the code switching? I won't say whitewash because at the end of the day, you know what I'm me? but the whole pretending and cold, you know, it takes a toll on you. Listen to the new season of Grasas Has Come Again as part of My Cultura Podcast Network on the Iheart radio app, Apple Podcasts, or wherever you get your podcast. Your entire identity has been fabricated. Your beloved brother goes missing without a trace. You discover the depths of your mother's illness,

the way it has echoed and reverberated throughout your life, impacting your very legacy. Hi, I'm Danny Shapiro. And these are just a few of the profound and powerful stories I'll be mining on our 12th season of Family Secrets. With over 37 million downloads, we continue to be moved and inspired by our guests and their courageously told stories. I can't wait to share 10 powerful new episodes with you, stories of tangled up identities, concealed truths, and the way in which family secrets almost always need to be told. I hope you'll join me and my extraordinary guests for this new season of Family Secrets.

Listen to Family Secrets Season 12 on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. A foot washed up a shoe with some bones in it. They had no idea who it was. Most everything was burned up pretty good from the fire that not a whole lot was salvageable. These are the coldest of cold cases, but everything is about to change. Every case that is a cold case that has DNA right now in a backlog will be identified in our lifetime. A small lab in Texas

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It is so expensive in these streets. I 100% can see how in just a few months you can have this much credit card debt when it weighs on you. It's really easy to just like stick your head in the sand. It's nice and dark in the sand. Even if it's scary, it's not going to go away just because you're avoiding it. And in fact, it may get even worse.

For more judgment-free money advice, listen to Brown Ambition on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. What do we think? Let's follow up on Claire's idea. Yeah, so Claire's question is, because no los do. Right? She's like, why can't it be infinite and finite? And she's saying, what if you have a few dimensions in which it's infinite, but other dimensions in which it's finite? So imagine, for example, like an infinite cylinder. In one dimension, it goes on forever. But in the other dimensions, it's limited. You know, it's like a centimeter wide or a meter wide or something. So you can picture geometric shapes which are like this that are infinite in one dimension and finite in others. And she's basically asking, could our universe, be like that? Could it have two different kinds of dimensions, some that are infinite and some that are finite? Are there any current theories that encapsulate that? Like, has she identified a theory that physicists are working with right now as far as you know? Or is this a totally new way

of thinking about it? Claire has actually thought her way into a very popular area of research right now because it's totally possible to have a geometry of the universe where you have some infinite dimensions and some finite. There's no theoretical reason saying you can't do that. And first, let's talk about like how to try frustratingly to visualize that in your mind. And then let's talk about why theorists are excited about this kind of idea. So we know that there are three dimensions in our universe, X, Y, and Z. These are the normal spatial dimensions.

And let's just say those are infinite, that they go on forever. And if you shine a laser beam out into space, if you don't hit some other galaxy or some alien eyeball, it's just going to go on forever. And if you shine two, they're going to be in parallel forever, right? So that's infinite flat space. Okay, so hold that in your mind. Now we want to add a fourth dimension.

And we don't want to add a fourth infinite dimension, some new direction you could shoot your laser beam, which is already very difficult to put into your 3D mental space. Let's add a fourth finite dimension. And so there's sort of two mental ways to visualize this. One is take your 3D infinite space, And at every point, replace that point with a loop, like a little circle, you know, like a bracelet, essentially. I'm getting angry.

You're getting angry. So I'm kidding. Let's go for it. All right. Lots and lots of loops in infinite space. Yes, exactly. So instead of space being filled with points, now it's filled with loops. And where you are along that loop is essentially the fourth dimension.

So now you have like four numbers in your address, three numbers to tell you where you are in the usual. 3D space and one to tell you how far you are along this loop. So now space is like more complex. Is there a way to help me picture that? Like I move in a direction and I get stuck in a loop and it's like being in a whirlpool or is that extra dimension time and it determines how long I'm there? The extra dimension is not time. It's space, right? And you could still move through 3D space jumping from loop to loop the same way you can like move only in X without changing your Y value. you. An alternative way to think about it instead of an infinite space filled with loops is to take a single loop and at every point put infinite space in it. So imagine like a big loop of infinite spaces instead of an infinite space of loops. It doesn't really matter which order you think about it. Geometrically, it's the same. And both of them will give you a migraine because it's really hard to think about four dimensions at all. But that's my best effort. my bottle of Tyletol.

Especially in an audio format, this is challenging to describe. But the bottom line is, yes, Claire, it's possible to build a geometry where space is finite in some dimensions and infinite in others. And this is actually very exciting theoretically because it might explain one of the open puzzles in physics, which is why gravity is so much weaker than the other forces. Like if you think of gravity as a force, we know that it's much, much weaker than all the other forces out there. And like the canonical example is that you can hold up a paper clip using a kitchen magnet,

which is counteracting the entire gravitational force of the earth, right? A huge mass. Or, you know, like a toddler's legs are strong enough to overcome the gravity of the earth and learn to jump. That's electromechanical. And they're so cute and squishy. I know. And they're defeating an entire planet's gravity, right? So gravity is a crazy weak force.

And that's a puzzle for physicists because we like things to be in balance. We like to understand why things are out of balance if they are. So the explanation is maybe the reason gravity is weak is because it's special. Maybe the universe has a bunch of other dimensions, but like Clara suggests, their loops and their small little dimensions. Their loops are like a centimeter or even a millimeter or even smaller. And so what happens is that gravity actually isn't weaker than the other forces. It's just the same strength, but it feels weaker to us because at distances, bigger than a centimeter or bigger than these dimensions, it's already sort of bled out into these

other dimensions. It spreads out in these other dimensions. And so it seems weak to us. So that's like a cool explanation for another puzzle in particle physics if we could prove that the universe did have additional dimensions that were finite. So one of my favorite parts of doing science is designing experiments. Is there an experiment you could design to test, like for example, to look for those loops? Or this is just too hard because it's all too big and it goes on too long? No, there absolutely is an experiment, but you're not going to like it. You don't know me. No, you probably know me well enough. I'm probably not going to like it, but go for it. Tell me anyway. I mean, it might destroy the planet. So if you're cool with that,

then yeah. No, no. My kids are on this planet. You know how I feel about when you endanger my kids. So the idea is to do an experiment that tests whether gravity gets really strong when things get close together. And one way you can do that is try to just measure the gravity of things that are really close together, like take two balls and put them a millimeter apart and measure their gravity. This turns out to be really, really hard because gravity is so weak and anything you build is going to have really weak gravity. And there's some real experimental virtuosos at University of Washington who've been doing these kinds of experiments. And it's really amazing. They have to isolate it from like anytime somebody coughs three blocks away or like a dog wags its tail

and changes the, you know, the airflow or whatever. It's ridiculous what they have to buffer themselves against because they're looking for such a tiny effect. On the other hand, we can also do it at the large Hedron Collider because if gravity gets really powerful when things get close together, hey, that's what we do all day. We take protons, we put them really close together. And so the idea is maybe sometimes when protons get really close together,

their gravity gets really strong and they make a tiny black hole. And so these extra dimensions, could enhance the power of gravity at short distances and give us a chance to make more black holes than we otherwise could, maybe even seeing one evaporate in our detector and, of course, not destroying the earth and keeping Kelly's children alive and healthy.

Thank you. My children in particular. Wait, so if we're worried about dimensions, does creating a black hole, is that, you know, sort of analogous to the loops in the dimensions that you were talking about? The black hole, if it exists, would also exist in those other dimensions. The idea is that those dimensions also weaken the gravity

for things that are further apart than the size of those dimensions. And so you can create a black hole by getting things really, really close. That's sort of the idea. We've never seen a black hole, the Large Hadron Collider. So we have no experimental proof of any of these additional spatial dimensions. There's another way you could look for them, which is to look for weird echoes of the particles that we have seen. Like if the electron exists in our universe,

there might be an echo of the electron in which it's like vibrating in this additional dimension. And so it would look like an electron, but with more mass, like a heavier version of the electron. And because of resonance effects, you would get a bunch of these. You would get like one that's heavier and one that's twice as heavy and three times as heavy. You get this whole tower of weird heavy electrons. So we've looked for those and haven't seen them. So yes, we can look for these things. No, we have no evidence that the universe does have additional.

finite dimensions on top of the three probably infinite dimensions that we know about. And finding another dimension doesn't immediately answer the question is the universe finite in one direction and infinite in the other, right? You'd still need additional information. That's part of it. Yeah, that's right. First step is discover the other dimension. Second is to measure the curvature of that dimension. If it's highly curved, then it probably is a loop, then it probably is finite. Clara wins a Nobel Prize. If it turns out to be infinite than like that blows our minds in a whole other way like another infinite dimension in our universe that would be crazy or infuriating or headache inducing now it would be cool all right so

that's the answer for clara yes the universe could have finite and infinite dimensions at the same time as much as that's difficult to think about and while we are doing experiments to search for these additional dimensions. We do not yet have any evidence that they exist. But we're going to keep looking to hope to provide Clara with a Nobel Prize in the future. Yeah, thank you for this amazing question. And thanks to everybody out there who thinks about the universe, wonders about it, wants to understand it, and writes to us. Send us your questions to questions at Danielanhorpe.com. Everybody gets an answer and some people get highlighted on the podcast. Woo! It's like getting a Hugo. Yes, you can put it on your CP for sure.

All right, thanks very much, Kelly, for helping me answer these questions. Thanks so much for having me on the show. It was a lot of fun. All right, everyone, tune in next time. For more science and curiosity, come find us on social media where we answer questions and post videos. We're on Twitter, Discord, Insta, and now TikTok. Thanks for listening, and remember that Daniel and Jorge Explain the Universe

is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. I'm Dr. Scott Barry Kaufman, host of the psychology podcast. Here's a clip from an upcoming conversation

about how to be a better you. When you think about emotion regulation, you're not going to choose an adaptive strategy which is more effortful. to use unless you think there's a good outcome avoidance is easier ignoring is easier denials easier complex problem solving takes effort listen to the psychology podcast on the iheart radio app apple podcasts or wherever you get your podcasts do we really need another podcast with a condescending finance brof trying to tell us how to spend our own money no thank you instead check out brown ambition each week i your host

Mandy Money gives you real talk, real advice with a heavy dose of I-feel uses, like on Fridays when I take your questions for the BAQA. Whether you're trying to invest for your future, navigate a toxic workplace, I got you. Listen to Brown Ambition on the IHeart Radio app, Apple Podcast, or wherever you get your podcast. Let's start with a quick puzzle. The answer is Ken Jennings' appearance on The Puzzler with AJ Jacobs. The question is, what is The most entertaining listening experience in podcast land. Jeopardy Truthers believe in... I guess they would be conspiracy theorists.

That's right. To give you the answers and you still blew it. The Puzzler. Listen on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. It's important that we just reassure people that they're not alone and there is help out there. The Good Stuff Podcast Season 2 takes a deep look into One Tribe Foundation. a non-profit fighting suicide in the veteran community. September is National Suicide Prevention Month,

so join host Jacob and Ashley Schick as they bring you to the front lines of One Tribe's mission. One Tribe, save my life twice. Welcome to Season 2 of the Good Stuff. Listen to the Good Stuff podcast on the Iheart Radio app, Apple Podcasts, or wherever you get your podcast. Every case that is a cold case that has DNA. Right now in a backlog will be identified in our lifetime.

On the new podcast, America's Crime, crime lab, every case has a story to tell. And the DNA holds the truth. He never thought he was going to get caught. And I just looked at my computer screen. I was just like, ah, gotcha. This technology's already solving so many cases. Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. This is an IHeart podcast.