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Speaker 3: Hey, Daniel, so, who do you think is going to
Speaker 3: figure out the secrets of the universe? Is there, like
Speaker 3: somebody that you you know, have been keeping your eye on?
Speaker 1: Oh? Man, I wish I knew the answer to that question.
Speaker 3: Well, but like, do you think it's someone we already
Speaker 3: know about, like a smart person like Lisa Randall or
Speaker 3: Ed Witten.
Speaker 1: It could be, but my money is on somebody smart,
Speaker 1: somebody young, maybe somebody who's listening to this podcast right now.
Speaker 3: Whoa so like. How would you feel if it turned
Speaker 3: out that, like the big questions weren't answered by you,
Speaker 3: but you were upstaged by some like ten year old
Speaker 3: after you failed for.
Speaker 1: Decades, after failing for decades, I would be relieved if
Speaker 1: somebody else came along to figure this stuff out for us.
Speaker 3: I feel like that's the right answer. The answer matters
Speaker 3: more than the person love it.
Speaker 1: Hi. I'm Daniel. I'm a particle physicist and a professor
Speaker 1: at UC Irvine, and I just desperately want the answers.
Speaker 3: I'm Kelly Wiener Smith. I'm a parasitologist at Race University,
Speaker 3: and I also desperately want the answers, but the questions
Speaker 3: to be about parasites.
Speaker 1: And you're also the Hugo Award winning author of a
Speaker 1: nonfiction book. Congratulations.
Speaker 3: Thanks. I'll try to non scream too loud that the
Speaker 3: trophy arrived, and I am still losing my mind every
Speaker 3: time I look at it. I cannot believe that that happened.
Speaker 3: But I also can believe that Zach didn't prepare an
Speaker 3: acceptance speech, even though the flight to Glasgow takes like
Speaker 3: eight hours. He just assumed we weren't gonna win, so
Speaker 3: he prepared nothing, and I almost killed him.
Speaker 10: Oh wow.
Speaker 1: Well, I'm sure his spontaneous speech was even better than
Speaker 1: anything he could have written. It was fine, but I
Speaker 1: wanted all of you out there to appreciate it. Kelly
Speaker 1: is not just one of the hosts on this podcast,
Speaker 1: but she's actually an award winning best selling science writer,
Speaker 1: so we're grateful to have her here. Thanks very much
Speaker 1: for joining us.
Speaker 3: Oh you're the best. Thanks Daniel, I love being.
Speaker 1: Here and welcome to the podcast. Daniel and Jorge Explain
Speaker 1: the Universe, a production of Iheartrate You in which we
Speaker 1: explore everything about the universe, it's ups and it's downs,
Speaker 1: it's lefts and its rights, the things that wins the
Speaker 1: awards for, and the things that drive physicists crazy. Hopeful
Speaker 1: that somebody young out there will figure it all out.
Speaker 3: For us as soon as possible. Guys, get on.
Speaker 1: It, and as part of that process, we want you
Speaker 1: to be thinking about the nature of the universe. Yes,
Speaker 1: you are relaxing as you fall asleep, or you are
Speaker 1: commuting to work and hoping to be educated and entertained,
Speaker 1: but this podcast also requires you to do some work
Speaker 1: to fit all these ideas into your head and to
Speaker 1: write to us when they don't quite click together. If
Speaker 1: you have a question about the nature of the universe,
Speaker 1: we want to hear it. That's part of the progress
Speaker 1: of science. Everybody out there wondering and thinking and trying
Speaker 1: to figure this stuff out. So please send me your
Speaker 1: questions to questions at Daniel and Jorge dot com. You
Speaker 1: will definitely hear back from us, and sometimes we choose
Speaker 1: those questions to answer or right here on the podcast.
Speaker 3: And sometimes the questions that you get from people new
Speaker 3: to the field are way better than any question you
Speaker 3: get at a department seminar with a bunch of pros
Speaker 3: in the field, because, like you're not constrained by all
Speaker 3: the assumptions that people who have been in the field
Speaker 3: for a while have. So we get some pretty great
Speaker 3: questions from the listeners.
Speaker 1: Yes, absolutely we do, and we get questions that I
Speaker 1: don't anticipate, and so I hope that these questions line
Speaker 1: up with your questions. That these ones we've chosen are
Speaker 1: also questions that other folks out there have and want
Speaker 1: to hear the answer to. So please don't be shy
Speaker 1: if you're thinking of a question, somebody else also wants
Speaker 1: to hear the answer, and I need somebody to write
Speaker 1: in and send it to me, So please don't be shy.
Speaker 1: I love hearing from all of you.
Speaker 3: Please keep Daniel company, guys, And.
Speaker 1: So today on the podcast, we'll be answering listener questions
Speaker 1: number sixty eight who and we are featuring a question
Speaker 1: from a young future physicist, Clara from Germany. So without
Speaker 1: further ado, here's Clara's question.
Speaker 11: Hello and Clara from Germany, twelve years old and you
Speaker 11: listener of your podcast. My question is could it be
Speaker 11: possible that the universe is finite in one direction and
Speaker 11: incident and all the others? Your podcast is just right
Speaker 11: and you two guys can explain so well. Thanks Clara.
Speaker 3: So Daniel, when I was twelve years old, I was
Speaker 3: sequestered in my bedroom listening to Silverchair and playing the
Speaker 3: first three chords to smells like teen Spirit by Nirvana,
Speaker 3: but not bothering to learn any of the rest of
Speaker 3: the song. I was not pondering the nature of the universe.
Speaker 3: So good on you, Clara. What were you doing when
Speaker 3: you were twelve, Daniel.
Speaker 1: I was reading a lot of science fiction and a
Speaker 1: lot of fantasy, and I definitely was pondering the nature
Speaker 1: of the universe. I remember trying to think about whether
Speaker 1: space was in three dimensions everywhere, or maybe parts of
Speaker 1: the universe might have additional dimensions, and really struggling to
Speaker 1: get my mind around what that meant, and what would
Speaker 1: be like to exist in those dimensions? So, yeah, Clara
Speaker 1: and I have a lot in common. Good job, Clara.
Speaker 3: Well some of us are late blossoming nerds, I guess,
Speaker 3: but what we get there eventually. So give us some
Speaker 3: background on what we know about this question so far, Daniel.
Speaker 1: Yeah, Clara's question touches on two really important ideas, and
Speaker 1: she's doing something I love, which is trying to bring
Speaker 1: two ideas together. You know, physics is about unification of
Speaker 1: your understanding. It's not like chemistry where you use this
Speaker 1: equation over here and that equation over there, and it's
Speaker 1: just like these patches of understanding and physics we hope
Speaker 1: to have a complete cloth, you know, to stitch everything
Speaker 1: together into one idea. So it's really important that when
Speaker 1: you hear related ideas, you try to understand how they
Speaker 1: fit together. And that's what she's doing here and here
Speaker 1: the related ideas are about the size and the scope
Speaker 1: of the universe, like is the universe infinite or is
Speaker 1: the universe finite? And when you just imagine space and
Speaker 1: the whole universe, you probably just fill your mind with
Speaker 1: blackness and you imagine that it goes on forever, that
Speaker 1: you you could shoot a laser beam and it would
Speaker 1: just fly on forever and ever until it hits something.
Speaker 1: But if the universe was empty, it would just go
Speaker 1: on forever. You can imagine these like dotted lines of x, y,
Speaker 1: and z dimensions just stretching out to infinity, limited only
Speaker 1: by your imagination. That's an infinite universe. And we don't
Speaker 1: know if the universe is infinite. But such an infinite universe,
Speaker 1: though it's a little bit weird to hold in your mind,
Speaker 1: is actually one of the most natural ideas for how
Speaker 1: the universe might be shaped.
Speaker 3: Is this a question that you think will have an
Speaker 3: answer to in your lifetime or what will we be
Speaker 3: wondering if the universe is finite or infinite three hundred
Speaker 3: years from now.
Speaker 1: Wow? Awesome. It's hard to prove that the universe is
Speaker 1: infinite because if it goes on forever, then you need
Speaker 1: infinite data to prove that. But we might be able
Speaker 1: to prove the opposite. We might be able to prove
Speaker 1: that it's not infinite because you could discover that the
Speaker 1: universe is finite. Because the extent of the universe is
Speaker 1: connected to another question about the shape of the universe,
Speaker 1: like if the universe is flat, and by flat, we
Speaker 1: don't mean like a two D sheet of paper. We
Speaker 1: mean the two parallel lines will not cross. It's a
Speaker 1: three dimensional version of flatness. But if the universe is curved,
Speaker 1: the two parallel lines either diverge or do cross over
Speaker 1: each other, and again curved in three dimensions in a
Speaker 1: sort of general relative physics sort of way. That means
Speaker 1: that the universe could be finite, that it could loop
Speaker 1: around on itself again in a weird three dimensional way,
Speaker 1: not exactly the same way as like the surface of
Speaker 1: a sphere loops around on itself, but in analogy to that. So,
Speaker 1: if we discover that space is curved, that suggests that
Speaker 1: space might be finite, and so we can't prove that
Speaker 1: it's infinite, but we might discover that it is finite.
Speaker 3: WHOA, I feel like I'm lost in thought here. So
Speaker 3: if it's curved, then what's on the other side of
Speaker 3: the curve.
Speaker 1: No, this is a big mental pothole that we should
Speaker 1: totally address, because if you imagine the universe as finite
Speaker 1: and curved, you probably have in your mind something like
Speaker 1: sphere a ball.
Speaker 3: Right, I'm thinking of a donut because I'm hungry.
Speaker 1: All right, it could also be a donut, right, But
Speaker 1: the problem is as soon as you name some object
Speaker 1: like that, you imagine it with its boundaries inside some
Speaker 1: other vast mental space. Like if I close my eyes
Speaker 1: and I think of a donut, it's hovering in some blackness,
Speaker 1: and that's a mistake. I've like sketched around it some
Speaker 1: empty space. But when we talk about the universe as finite,
Speaker 1: we don't mean like there's a bunch of stuff and
Speaker 1: around it is empty space. We mean finite including space.
Speaker 1: I mean that's all there is. Don't sketch anything around it,
Speaker 1: don't fill in that mental space with something. The finite
Speaker 1: universe is limited in size, but it doesn't have an edge,
Speaker 1: a boundary. Every point on it is exactly the same.
Speaker 1: It's very, very difficult to think about. It's very counterintuitive.
Speaker 3: Yeah, I feel like the world is split into people
Speaker 3: who think that that's fun and people who just are
Speaker 3: really frustrated. They might be a different camps there.
Speaker 1: We should get too clear's question, But first we have
Speaker 1: to take a quick break.
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Speaker 10: Listen to the Taken a Walk podcast on the iHeartRadio app,
Speaker 10: Apple Podcasts, or wherever you get your podcasts.
Speaker 2: Hey, I'm Jackie Thomas, the host of a brand new
Speaker 2: Black Effect original series, black Lit, the podcast for diving
Speaker 2: deep into the rich world of black literature. I'm Jackie Thomas,
Speaker 2: and I'm inviting you to join me in a vibrant
Speaker 2: community of literary enthusiasts dedicated to protecting and celebrating our stories.
Speaker 2: Black Lit is for the page turners, for those who
Speaker 2: listen to audio books while commuting or reading errands, for
Speaker 2: those who find themselves seeking solace, wisdom, and refuge. Between
Speaker 2: the chapters, from thought provoking novels to powerful poetry, we'll
Speaker 2: explore the stories.
Speaker 3: That shape our culture.
Speaker 2: Together. We'll dissect classics and contemporary works while uncovering the
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Speaker 2: iHeartRadio app, Apple Podcasts, or wherever you get your podcasts.
Speaker 4: I'm doctor Laurie Santos, host of the Happiness Lab podcast.
Speaker 4: Is the US elections approach. It can feel like we're
Speaker 4: angrier and more divided than ever, but in a new
Speaker 4: hopeful season of my podcast, I'll share with the science
Speaker 4: it really shows that we're surprisingly more united than most
Speaker 4: people think.
Speaker 7: We all know something is wrong in our culture, in
Speaker 7: our politics, and that we need to do better, and
Speaker 7: that we can do better with.
Speaker 4: The help of Stanford psychologist Jamil Zaki.
Speaker 9: It's really tragic.
Speaker 6: If cynicism were appeal, it'd be a poison.
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Speaker 4: are more generous than we assume.
Speaker 3: My assumption, my feeling.
Speaker 2: My hunch is that a lot of us are actually
Speaker 2: looking for a way to disagree and still be in relationships.
Speaker 6: With each other.
Speaker 4: All that on the Happiness Lab, listen on the iHeartRadio app,
Speaker 4: Apple podcasts, or wherever you listen to podcasts.
Speaker 13: Hey, I'm Bruce Bosi on my podcast Table for two.
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Speaker 1: Thank you for that introduction. I'm going to slip you,
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Speaker 13: get your podcasts.
Speaker 3: What do we think let's follow up on Clara's idea.
Speaker 1: Yeah, so Clara's question is porque nolos dos?
Speaker 9: Right?
Speaker 1: She's like, why can't it be infinite and finite? And
Speaker 1: she's saying, what if you have a few dimensions in
Speaker 1: which it's infinite, but other dimensions in which it's finite.
Speaker 1: So imagine, for example, like an infinite cylinder. In one
Speaker 1: dimension it goes on forever, but in the other dimensions
Speaker 1: it's limited. You know, it's like a centimeter wide or
Speaker 1: a meter wide or something. So you can picture geometric
Speaker 1: shapes which are like this, that are infinite in one
Speaker 1: dimension and finite in others. And she's basically asking, could
Speaker 1: our universe be like that? Could it have two different
Speaker 1: kinds of dimensions, some that are infinite and some that
Speaker 1: are finite.
Speaker 3: Are there any current theories that encapsulate that, like has
Speaker 3: she identified a theory that physicists are working with right
Speaker 3: now as far as you know, or is this a
Speaker 3: totally new way of thinking about it.
Speaker 1: Claire's actually thought her way into a very popular area
Speaker 1: of research right now, because it's totally possible to have
Speaker 1: a geometry of the universe where you have some infinite
Speaker 1: dimensions and some finite there's no theoretical reasons saying you
Speaker 1: can't do that. And first let's talk about like how
Speaker 1: to try, frustratingly to visualize that in your mind, and
Speaker 1: then let's talk about why theorists are excited about this
Speaker 1: kind of idea. So we know that there are three
Speaker 1: dimensions in our universe X, y, and z. These are
Speaker 1: the normal spatial dimensions, and let's just say those are infinite,
Speaker 1: that they go on forever. If you shine a laser
Speaker 1: beam out into space, if you don't hit some other
Speaker 1: galaxy or some alien eyeball, it's just going to go
Speaker 1: on forever. And if you shine two, they're going to
Speaker 1: be in parallel forever. Right, So that's infinite flat space. Okay,
Speaker 1: so hold that in your mind. Now we want to
Speaker 1: add a fourth dimension, and we don't want to add
Speaker 1: a fourth infinite dimension. Some new direction you could shoot
Speaker 1: your laser beam, which is already very difficult to put
Speaker 1: into your three D mental space. Let's add a fourth
Speaker 1: finite dimension. And so the sort of two mental ways
Speaker 1: to visualize this one is take your three D infinite
Speaker 1: space and at every point, replace that point with a loop,
Speaker 1: like a little circle, you know, like a bracelet.
Speaker 3: Essentially, I'm getting angry.
Speaker 1: You're getting angry.
Speaker 3: Yeah, I'm kidding. Let's go for it, all right, And
Speaker 3: lots of loops in infinite space.
Speaker 1: Yes, exactly. So instead of space being filled with points,
Speaker 1: now it's filled with loops, and where you are along
Speaker 1: that loop is essentially the fourth dimension. So now you
Speaker 1: have like four numbers in your address, three numbers to
Speaker 1: tell you where you are in the usual three D
Speaker 1: space and one to tell you how far you are
Speaker 1: along this loop. So now space is like more complex.
Speaker 3: Is there a way to help me pick that? Like,
Speaker 3: like I move in a direction and I get stuck
Speaker 3: at a loop and it's like being in a whirlpool.
Speaker 3: Or is that extra dimension time and it determines how
Speaker 3: long I'm there?
Speaker 1: The extra dimension is not time, it's space, right, OK.
Speaker 1: And you could still move through three D space, jumping
Speaker 1: from loop to loop the same way you can like
Speaker 1: move only in x without changing your y value. An
Speaker 1: alternative way to think about it instead of an infinite
Speaker 1: space filled with loops is to take a single loop
Speaker 1: and at every point put infinite space in it. So
Speaker 1: imagine like a big loop of infinite spaces instead of
Speaker 1: an infinite space of loops. It doesn't really matter which
Speaker 1: order you think about it. Geometrically, it's the same, and
Speaker 1: both of them will give you a migraine because it's
Speaker 1: really about four dimensions at all.
Speaker 3: But that's my best of til it all.
Speaker 1: Especially in an audio format, this is challenging to describe,
Speaker 1: but the bottom line is, yes, Claia, it's possible to
Speaker 1: build a geometry where space is finite in some dimension
Speaker 1: an infinite in others. And this is actually very exciting
Speaker 1: theoretically because it might explain one of the open puzzles
Speaker 1: in physics, which is why gravity is so much weaker
Speaker 1: than the other forces. Like, if you think of gravity
Speaker 1: as a force, we know that it's much much weaker
Speaker 1: than all the other forces out there, and like the
Speaker 1: canonical example is that you can hold up a paper
Speaker 1: clip using a kitchen magnet, which is counteracting the entire
Speaker 1: gravitational force of the Earth, right a huge mass, or
Speaker 1: you know, like a toddler's legs are strong enough to
Speaker 1: overcome the gravity of the Earth and learn to jump.
Speaker 1: That's electro mechanical, and they're so cute and squishy, I know,
Speaker 1: And they're defeating an entire planet's gravity.
Speaker 9: Right.
Speaker 1: So gravity is a crazy weak force, and that's a
Speaker 1: puzzle for physicists because we like things to be in balance.
Speaker 1: We like to understand why things are out of balance
Speaker 1: if they are. So the explanation is, maybe the reason
Speaker 1: gravity is weak is because it's special. Maybe the universe
Speaker 1: has a bunch of other dimensions, but like Clara suggests,
Speaker 1: their loops and their small little dimensions, their loops are
Speaker 1: like a centimeter or even a millimeter or even smaller.
Speaker 1: And so what happens is that gravity actually isn't weaker
Speaker 1: than the other forces. It's just the same strength, but
Speaker 1: it feels weaker to us because at distances bigger than
Speaker 1: a centimeter or bigger than these dimensions, it's already sort
Speaker 1: of bled out into these other dimensions. It spreads out
Speaker 1: in these other dimensions, and so it seems weak to us.
Speaker 1: So that's like a cool explanation for another puzzle in
Speaker 1: particle physics, if we could prove that the universe did
Speaker 1: have additional dimensions that were finite.
Speaker 3: So one of my favorite parts of doing science is
Speaker 3: designing experiments. Is there an experiment you could design to test, like,
Speaker 3: for example, to look for those loops? Or this is
Speaker 3: just too hard because it's all too big and it
Speaker 3: goes on too long.
Speaker 1: No, there absolutely is an experiment, but you're not gonna
Speaker 1: like it.
Speaker 3: You don't know me, but you probably know me well enough.
Speaker 3: I'm probably not gonna like it, but go for it.
Speaker 1: I mean, it might destroy the planet. So if you're
Speaker 1: cool with that, then yeah.
Speaker 3: No, no, my kids are on this planet. You know
Speaker 3: how I feel about when you endanger my kids.
Speaker 1: So the idea is to do an experiment that tests
Speaker 1: whether gravity gets really strong when things get close together.
Speaker 1: And one way you can do that is try to
Speaker 1: just measure the gravity of things that are really close together,
Speaker 1: Like take two balls and put them a millimeter apart
Speaker 1: and measure their gravity. This turns out to be really,
Speaker 1: really hard because gravity is so weak and anything you
Speaker 1: build is going to have really weak gravity. And there's
Speaker 1: some real experimental Virtuoso's at University of Washington who've been
Speaker 1: doing these kinds of experiments, and it's really amazing. They
Speaker 1: have to isolate it from like anytime somebody coughs three
Speaker 1: blocks away, or like a dog wags its tail and
Speaker 1: changes the you know, the airflow or whatever. It's ridiculous
Speaker 1: what they have to buffer themselves against because they're looking
Speaker 1: for such a tiny effect. On the other hand, we
Speaker 1: can also do it at the large Hagon collider because
Speaker 1: if gravity gets really powerful when things get close together. Hey,
Speaker 1: that's what we do all day. We take protons, we
Speaker 1: put them really close together. And so the idea is
Speaker 1: maybe sometimes when protons get really close together, their gravity
Speaker 1: gets really strong and they make a tiny black hole.
Speaker 1: And so these extra dimensions could enhance the power of
Speaker 1: gravity at short distances and give us a chance to
Speaker 1: make more black holes than we otherwise could, maybe even
Speaker 1: seeing one evaporate in our detector, and of course not
Speaker 1: destroying the earth and keeping Kelly's children alive and healthy.
Speaker 3: Thank you, my children in particular. Wait, so if we're
Speaker 3: worried about dimensions, does creating a black hole is that,
Speaker 3: you know, sort of analogous to the loops in the
Speaker 3: dimensions that you were talking about.
Speaker 1: The black hole, if it exists, would also exist in
Speaker 1: those other dimensions. But ideas that those dimensions also weaken
Speaker 1: the gravity for things that are further apart than the
Speaker 1: size of those dimensions, and so you can create a
Speaker 1: black hole by getting things really really close. That's sort
Speaker 1: of the idea. We've never seen a black holes large
Speaker 1: a drunk light, So we have no experimental proof of
Speaker 1: any of these additional spatial dimensions. There's another way you
Speaker 1: could look for them, which is to look for weird
Speaker 1: echos of the particles that we have seen. Like if
Speaker 1: the electron exists in our universe, there might be an
Speaker 1: echo of the electron in which it's like vibrating in
Speaker 1: this additional dimension, and so it would look like an
Speaker 1: electron but with more mass, like a heavier version of
Speaker 1: the electron, and because of resonance effects, you would get
Speaker 1: a bunch of these. You would get like one that's heavier,
Speaker 1: and when that's twice is heavy and three times is heavy,
Speaker 1: you get this whole tower of weird heavy electrons. So
Speaker 1: we've looked for those and haven't seen them. So yes,
Speaker 1: we can look for these things. No, we have no
Speaker 1: evidence that the universe does have additional finite dimensions on
Speaker 1: top of the three probably infinite dimensions that we know about.
Speaker 3: And finding another dimension doesn't immediately answer the question. Is
Speaker 3: the universe finite in one direction and infinite in the other, Right,
Speaker 3: you'd still need additional that's just part of it.
Speaker 1: Yeah, that's right. First step is discover the other dimension.
Speaker 1: Second is to measure the curvature of that dimension. If
Speaker 1: it's highly curved, then it probably is a loop. Then
Speaker 1: it probably is finite. Clara wins the Nobel Prize. If
Speaker 1: it turns out to be infinite, then like that blows
Speaker 1: our minds in a whole other way. Like another infinite
Speaker 1: dimension in our universe.
Speaker 3: That would be crazy or infuriating.
Speaker 1: Or headache inducing.
Speaker 3: Now it would be cool.
Speaker 1: All right. So that's the answer for Clara. Yes, the
Speaker 1: universe could have finite and infinite dimensions at the same time,
Speaker 1: as much as that's difficult to think about. And while
Speaker 1: we are doing experiments to search for these additional dimensions,
Speaker 1: we do not yet have any evidence that they exist.
Speaker 1: But we're going to keep looking to hope to provide
Speaker 1: Clara with a Nobel Prize in the future.
Speaker 3: Yeah, thank you for this amazing question.
Speaker 1: And thanks to everybody out there who thinks about the universe,
Speaker 1: wonders about it, wants to understand it, and writes to us.
Speaker 1: Send us your questions to questions at Dangel and Jorge
Speaker 1: dot com. Everybody gets an answer and some people get
Speaker 1: highlighted on the podcast.
Speaker 3: Woo, it's like getting a hugo.
Speaker 1: Yes, you can put it on your CP for sure.
Speaker 1: All right, Thanks very much Kelly for helping me answer
Speaker 1: these questions.
Speaker 3: Thanks so much for having me on the show. It
Speaker 3: was a lot of fun.
Speaker 1: All right. Everyone, tune in next time for more science
Speaker 1: and curiosity. Come find us on social media where we
Speaker 1: answer questions and post videos. We're on Twitter, Discorg, instat,
Speaker 1: and now TikTok. Thanks for listening, and remember that Daniel
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