Cosmic Queries - Bits of Spacetime with Janna Levin

Neil deGrasse Tyson
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Chuck Nice
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Janna Levin
Coming up on Startalk, cosmic queries with our friend Jan Eleven. Yeah, it's going to be relativistic, cosmological, higher dimensions, lower dimensions, big bang, end of the universe, edge of black holes, everything that blows your freaking mind. Welcome to Startalk, your place in the universe where science and pop culture collide. Startalk begins right now. This is startalk.

Neil degrasse Tyson, your personal astrophysicist. We've got a Startalk cosmic Aquarius today with is one of our favorites. Or Chuck, is she our very favorite? She's our very favorite theoretical physicist. Oh, he got out of the.

D
That is for sure. Totally. I want to know who's on this list. So, Jan eleven, welcome back to Startalk. Always fun to be here.

Yeah, very glad. Chuck was saying we're getting closer and closer together here. I love it. Just for the, just for the video. For the video.

Janna Levin
You know why? Cause we spent three years zoomed away in. I love it. I know.

So you are a theoretical physicist. And you're a professor? A toe professor. That's the founder of your endowed chair, I guess. Yes.

E
I think we say tau. Tau? Yes. Tau. Profess not Taewoo.

I'd get in trouble if I don't say it right. Yeah. Not tow the Tau professor of astronomy and physics at Barnard and at Columbia University, which is up the street here in New York City. And you've written several books, and, forgive me, but all the titles of your three books have merged into your mind in a flow of words. You say them better than anybody else on the planet.

Janna Levin
So one of them is how the universe got its spots. How the universe got its spots. Okay. The other one was black hole survival guide. Yes.

And the third one was black hole blue. The black hole blue. Excellent. There's one more. I wrote a novel.

F
What? Yeah. I won a pen award for fiction. What? Yeah.

E
You guys know 1% about me. I'm sorry. I am going to be your favorite by the end of today. What's the novel? So, what's the novel?

A madman dreams of Turing machines. Maybe the title's too long. Wow. A madman dreams of Turing machines. It's about Alan.

Yeah. Okay, it's a little trippy. Yeah. That was a long time ago. Oh, wow.

D
So, it's a. I thought it was something that was relatively new. No, it's not. That's where you started. So that's where your heart is.

E
Yeah. Well, every once in a while, I dabble with unfinished fiction. What a sentence that is. Oh, my gosh. How many people get to say that?

Janna Levin
Very cool. Very cool. Well, all right. It's a cosmic queries where our fan base knows you, and we left it wide open. Fun just to have to be in.

Your bailiwick is theoretical, cosmological, relativistic physics. Love it. She's ready. Bring it on. Ready to throw down.

But before we do that, I just want to catch up on a few things. You are also very active in pioneer works. Just remind people briefly what that is. Pioneer Works is a cultural center. It's pretty new.

E
It's for arts and sciences. It was founded by artist Dustin Yellen, and the founding artistic director is Gabriel Florence. And then I came in as the founding director of sciences. We're kind of a triad, and we really have science and art really rubbing together. So we have exhibitions for artists rubbing.

Janna Levin
In a good way. In a good way. If it rubs together in a bad way, you want to stop. That's a WD 40. But this one is rubbing so that they can influence.

E
Yeah. And we're, you know, we're not crowbarring things together in a. I hope not a fake way. It's very genuine and spirited. It's a real labor of love.

So we have organic. We've had you, Neil. We've had you, Chuck. We performed a live startalk at your space in Brooklyn. Absolutely.

D
No, I wasn't there for that. You were not there for that. Ok. I did something totally different. Paul Mercurio, I believe was Paul.

Janna Levin
We have Paul. Very funny. Paul Mercurio was our. Yeah, we do like, we'll have an exhibition about. We had one for the Hiroshima panels, which were made in 1945.

E
And then we had conversations with scientists about nuclear energy and nuclear weaponry and the history of things like containment. And so we riff off each other. And you have a social conscience? Yes, definitely.

We don't prescribe anything politically, morally, socially. It's radical as all art spaces have to be in. Challenging, challenging even to our own ideas. But it very much is a place for community. I really believe that science is part of culture.

It's at the forefront of culture, along with art, music. It doesn't have to be hidden like a wall inside the walnut of those other things that we have a community around us. Inside the walnut. That's good. That's good.

So I believe people need a place to gather and to be together and to break bread and to talk about things and think about things. So very much central to sort of our thinking around the place. If you come to an event, you'll stay after. You'll hang out in our garden. We often have telescopes.

Scientists will mill around so you can ask them questions. And the telescopes, because you have a relationship with the amateur astronomers? Yes, the New York City amateurs. Yes, the amateur Astronomers association of New York are tried and true. They're wonderful.

Janna Levin
Are you a member of them? Amazing. Ten years old. Yeah. They bring out the telescopes, rain or shine.

E
They're always there. They're terrifics. For a while, I was getting. Not in the rain. Well, they come out in the rain because even so, they'll be like, I'll show you what a telescope looks like or how it operates.

Like they're really not observing rain or. Shine, but they're there. Not observing rain or shine. They rarely drop out around the city, too. Yeah, yeah.

D
If you join, if you just want to look through a telescope and see celestial bodies, they set up on the high line. Amazing. Just go there and look. Now, you know, we're trying to build an observatory on top of high, and. I caught wind of it.

E
This is our big aspiration. Oh, yeah. Yes. And, you know, I know you and I were talking about it, and there is a sense like, ah, I could buy a telescope for a couple of grand and it'll be great. Right.

And that is true. But we have this old telescope from 18 93 95 that is being refurbished, and it's just a stunning, museum quality piece. And it's very inspiring to have that. And of course, we'll have modern telescopes available, but that kind of central piece is gonna be part of arts and performances around it and exhibition ethos. Yes.

Janna Levin
Of what you're about. Yes. It's romance. When you refurbish it, you put in like, new glass. Better, actually, no, the glass is so excellent.

E
We know the provenance of the. Of the lenses, and they're incredible. They were made by kind of people at the peak of that kind of engineering and craftsmanship. Cool. That's very neat.

D
That's amazing stuff. That's amazing. All right, let's hope we hoist it up on the building without incident. So, Janet, your field of study is, I bet most people would say, would be the most mind blowing science that anyone does. Wow.

Janna Levin
Because it's just out. It's out there. Yeah. You know, I could talk about stars and planets, and there's a tangibility to that, even the size, even the expanding universe. It's a little weird, but it's not.

It doesn't blow your mind. You think about stuff that's like, what? Yeah. One of my favorite experiences when I'm doing research is when I have a huge shift, when I'm shocked by something and I realize I've had some kind of preconceived notion that has just been shattered. Nice.

E
And it's really amazing. I'm following the science. I'm not dragging it along. And, yeah, it literally blows your mind. Many people who don't know the moving frontier of science think, and I think want to believe that somehow we all sit around wanting to agree with one another.

Right. But in fact, the advances come when someone says, I have an idea. Was it Isaac Asimov said that true scientific discovery is never Eureka. Right. It's.

Janna Levin
That's odd. Yes. It's just a little thing. Totally. That doesn't fit that.

E
Yeah. And I love, I really appreciate what you're saying. I really feel that debate is not actually how scientists, they don't sit there trying to win an argument. That would be so unscientific. No, not at all.

You want to say, wait, what are you talking about? Basically, it's I call B's. Yeah, that's really a nutshell. I call B's. And then you got it set about to prove it.

Absolutely. So, Janet, what I think you're saying is, the way I've described it is two scientists in an argument. There's an unwritten contract between them. Okay? Okay.

Janna Levin
Either I'm right and you're wrong, you're right and I'm wrong, or we're both right. And if we can't agree at the end of that conversation, we do agree that more or better data will resolve it. Absolutely. In which case, you could both be right. Yes.

So there are the rarer case where we're both right, if, in the classical example of the, the blind people touching an elephant, they give completely disparate accounts, okay? One is the trunk, one is the leg, one is the toenails, one is the tail, one is the tusk. And we can argue what the actual nature of that animal is, but at the end of the day, we're all correct, because it's all part of the same animal. And then there's a bigger vision. It's a bigger vision.

So the bigger visions are often very hard to reach, but that can happen, and it can and does happen. I totally agree with you. One thing that drives me a little crazy is when people say, oh, science is always overturning what came before completely and rewriting. So why should I believe in it? And that's not true.

It's not only not true, it's very false. It's very false. Very false. So if we were logicians, we would care about that distinction. So if I look back at what Newton did, it is absolutely a part of the elephant, an excellent description of a part of the elephant that he was able to palpate at the time.

E
Einstein comes along and it's bigger. See, that's like. That's the novelist. So, you know, Einstein comes along and has a bigger vision, but he absolutely requires of his work that it match Newton. Right.

Not that it has nothing to do with Newton. Suddenly, when I pour my coffee, it doesn't go upward. Right. Right. So Einstein enclosed Newton as a special.

Janna Levin
View within a larger understanding of the world, right. It was not overthrown. It was extended. Extended. Right.

E
Cool. Anything that was experimentally determined to be true previously does not all of a sudden become false. It becomes embedded in a deeper truth. And that's true even when you look at continental drift, which famously was delayed, had delayed acceptance among geologists. All the while, they're still trying to understand volcanoes and they're still trying.

Janna Levin
And so they're coming up with local accounts for what would happen in a volcano when they had continental drift that just attached to the continental drift. And there's a lot of that science that was completely portable into the new idea that the surface of the earth moves within itself.

F
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D
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H
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Neil deGrasse Tyson
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D
I'm Nicholas Costello. And I'm a proud supporter of startalk on Patreon. This is startalk with Neil degrasse Tyson.

Janna Levin
I don't have any mind blowing questions that await us. Well, we have questions now. Whether or not they're mind blowing, that remains to be seen. We're not gonna blow Janna's mind. Oh, maybe that's what we'll find.

D
See if we can find a. I'm. Susceptible, you know, I'm vulnerable to that. Find a question that blows Jana's mind and we'll send you a special gift. Which.

E
A piece of my debris from the explosion. There you go. All right. This is David Garvin. And David says hello.

D
Lady Levin, Doctor Tyson, Lord Nice. I'm David, a mechanical engineer in Seattle. Now, we know that spacetime can stretch. Is there anything within known physics which requires that spacetime be infinitely elastic? Could dark matter observations be plastic?

Deformation of space time dimples, as you will in space time, which would be non interactive, but are in two things we now call galaxies. Wow. Okay, so tell me about the stretchability of spacecraft. Let's start there. Well, let's start there.

E
Really. I think it's more of a dark energy tie in than a dark matter tie in. So is there anything that requires space is infinitely elastic, that can be stretched forever? Probably not. Just like when I look at the continuum of water, as I get closer and closer and higher energy and more microscopic, I realize it's actually not a continuous medium.

It's made up of discrete pieces, molecules. Molecules, and so it's not infinitely smooth. By the way, there's a big, big debate. I don't know if it's still raging, but it was for a while in deep philosophy literature. Is h two o water really fascinating.

D
Okay. Right. Because everything we know and understand and love about water requires an ensemble of h two O's. But if you pull out one of. Them, is that right?

Janna Levin
You get to call that water. Right. Yeah. So it's interesting. Philosophical challenge.

That's where they're going there. So, you know, water is not infinitely stretchable in that sense. In that sense, right. And so if I looked at spacetime, at higher and higher energies and smaller and smaller scales, much, much smaller than what I need to look at for water, like trillions and trillions and trillions of times smaller, something we will never reach, even in the most powerful accelerators on earth, but probably with smaller than. The atoms in the big bangladesh, smaller than the particles in the nucleus.

E
Absolutely. And probing energies, we really haven't seen since the big Bang. Because it takes high energy to get to those. That's right. To those regimes.

Absolutely. Because that's not always made obvious when people talk about, why do you need a bigger accelerator? Right. Why do you need high energy to look small? But you do, because you need to get really in there.

You need to get really high energies to probe into the tiniest regions. You gotta bust in. Otherwise, you're just, like, kind of big and lumbering and low energy. You're not sufficiently powerful to do so at those scales. We do think it's completely conceivable that spacetime will start to come in individual quanta, just like particles, and that we will find there are little bits of spacetime.

Janna Levin
So could it be that bits of. Space, like, almost like little manifolds, it could be all big origami. So that would mean that there's space. In between space time. Well, then you have a hard time.

E
See, that's a very interesting question, because then you can't really talk about space and time between. If there's space and time between, then that is part of the universe that we're talking about. So now you're just talking relationally in, like, an abstract space that they relate to each other, but I can no longer think of the distance between them in any realistic way. So isn't it true that quantum physics requires that space be quantized at some point? Quantum.

Excellent question, too. Quantum gravity requires that spacetime be quantized. But there might not be a theory of quantum gravity. We might look deeper and deeper, and instead of finding quantum bits of spacetime, we will only find pure quantum mechanics with no gravity in it whatsoever. And that gravity emerges only out of the collective of tons and tons of these quantum interactions.

Janna Levin
That's crazy. So that just, like, water is like. Yeah, it's crazy. So the quantum interactions manifests as what we call gravity. Right.

That's why the ensemble of h two o manifests as water. Exactly. Right. And the same way you would pull out a single molecule. You're not necessarily looking at water at that point.

D
Right. You can't. You can't pull out a quantum and say, is this gravity? Is this space time anymore? Is this space time anymore?

E
Exactly. You're saying gravity might not exist as a fundamental thing in the universe? I'm saying gravity might not exist as a fundamental thing in the universe. Wow. Let's keep that between us, everybody else.

I don't know. You didn't hear that? You didn't hear that? Because I don't want to turn on the Internet. You know, there's no such thing as gravity.

Now, right now, we're all floating. Wait, there's no such thing as gravity? I heard it, Janet. Eleven told me there's no such thing as gravity. Okay, I'm floating right now.

D
You floatin'too, we don't even know that we're floating. So I would say, you know, there is such a thing as gravity. It's just. It only emerges out of the collective ensemble, and just like the temperature in this room, only emerges out of the collective ensemble of bunches of particles. But another analogy I like to give is if we imagine quantum interactions or even quantum entanglement, complex things like that, as, like, threads sewn between quantum interactions, out of those threads, like embroidery.

E
From a. From a macroscopic distance, it might look like there's a black hole event horizon, for instance, out in space time. But if I look very closely, I realize, oh, it's just sewn together, quantum entangled threads. And it's not, fundamentally.

Janna Levin
Is love real? Is it? Yeah. Yeah, love is real, but it's a. Thread that goes around your neck and slowly chokes you.

E
It's a black hole horizon. It's a black hole in your heart that can never be found. It's a branch of strength theory that. So, as somebody said to me recently, reality isn't overrated, but realism is. Wow.

So there's a reality out there, but our attachment philosophically to realism is misplaced. All right, I have to, like, digest this, man. I'm telling you right now, this would be the end of the show, right? Oh, no. We should all be lying.

D
Seriously, that's enough to think about for the next. I gotta, like, digest this. Wait, wait. So, Janna, so why isn't. Or might it be, why the planck length?

Janna Levin
Why isn't that the quantum of space time? Well. Cause I've read. Because I try to trail behind you guys, as you think about this, that I've heard, that there's nothing in principle asserting that that is a quantization of space and time. It's just a convenient metric for us to talk about things that small.

D
And once I found out what it actually is, I'm like, that ain't even real.

E
Well, I think what the planck length tells you is the scale at which we really have to be concerned about these things, where the universe is behaving in a way that these questions are revealed. And until then, it's really hard to say what's going on. Cause it's okay, but that itself is not the limit of your stretchability, right? No. Well, yes, I think in some sense, it will tell you the scale at which these ideas break down.

D
See, you make it sound like it's setting the perspective, but. So once you set the perspective, okay, and now we know, can we then say, all right, half a planck length? Well, what we can say is when we. If we were living, if you get there. And then you might be able to get there.

Janna Levin
Yeah, if you get there. Right. You know what I'm saying? If you're in the big bang, unhappily, and that happens at the Planck energy scale, where the energies can probe planck lengths, you will either probably, as far as we can understand, find individual bits of spacetime that are quantized via a quantum gravity description would be correct for that. Or you will only find, for instance, little loops of string from string theory.

E
And they're not yet. Spacetime hasn't yet emerged. So I'm saying it's setting the scale at which we would have to. The answer to that question is relevant. Is not even real.

D
I'm telling you, the gravity's not real. Space time's not real. I don't know what to believe anymore. To make it worse, even an Einstein. Make it worse.

E
To make it worse. No, I'll cover my ears. I'm even looking at books on your shelf that might even talk about this. So even at the scales of big astrophysics, where space time seems to be doing really well as a description, you can rewrite the entire theory of general relativity just in terms of particle interactions. You don't have to resort to the geometry of spacetime.

It's my preferred language. But as we say, there's a lot of extras that are required in that description that aren't necessary. I can simply look at it like I would any particle interaction. Two particles exchange a graviton, something happens. I don't ever need to resort to the whole beautiful geometry.

I like to. I prefer it. But I can cast it as what we would call a field theory just as easily. And that's how we describe matter, because there's no field. Well, the gravitational field would be it has a spin to particle associated with it, just like there's an electromagnetic field.

Janna Levin
With a spin, had none of that knowledge or awareness. He's saying we have curved space time. And so. And it worked. And it worked beautifully.

It worked. But you're saying even that as a manifestation, is a macroscopic manifestation of something more fundamental. Yeah. You can think of that as a quantum field theory in a sense. And if you look at Steven Weinberg and the great geniuses like Feynman from that era that we're developing a quantum description of matter.

I went to my high school just like that. Get out. Really?

E
Amazing. I sound like a brag. Yeah, I mean, you can brag about Steven. That's a nice association. So he showed that you can rewrite Einstein's theory of general relativity strictly in a field theory language.

Okay, it's very nice. And so then, like, photons are replaced by gravitons, particle charges, electric charges are replaced by mass charges, and it works. Wow. Chuck, what's next up? All right, thank you, David Darvin.

Janna Levin
I don't if I brain lift for any.

D
This is Judy Sade. I'll say. Or sade. Okay, whatever. Judy.

Hey, Judy. She says, I can't say whatever about someone's name. It's their name. I gave her a new last name. It's called whatever.

Janna Levin
All right, go on. No. S a a d d e h. So, saday, I will say. She says, hi, my name is Judy.

D
I'm a second year Ohio state student with an inquiry. What are your residual thoughts on Klauser entanglement experiment and how it disproves our local universe? Do you still believe we exist? And does this theory change how physicists can view topology of the observable universe? That question's so easy, even my driver knows the answer.

Janna Levin
You know that story with Einstein? No. So, back in, Einstein was getting famouser by the day when relativity was published, but there weren't many photos of people, because the newspapers, you couldn't put photos in a paper yet. Really? Not really.

So no one could recognize he didn't have that classic wiry Harriet. Plus, he was very young. He was 20. He was 30 years old. Oh, my gosh.

And so he went around to give his tour, and this is probably just apocryphal, but it's fun nonetheless. And the driver sits in every one of his talks, and the driver, they come to some new location. The driver says, you know, I've heard your talk. I think I can deliver your talk. Oh, my God.

And give you a day off. Okay. And so you come. You sit in the back, I'll give your talk. No one will know the difference.

He gives the talk some resounding no way. And then someone says, doctor Einstein, could you comment on the topological deformation in the field of the high density matter? He says, that's such an easy question. My driver can answer that question. Who's Einstein?

D
Who's Einstein? Right? It's fantastic. That's classic. Yeah.

E
While you're mentioning Einstein, it reminds me that what catapulted his fame in the english speaking world was the eclipse of 1919. And, you know, less than six months after World War one, Europe's devastated, Germany and England were at war. And Eddington, as a pacifist. Eddington made this the first astrophysicist, really, of the century. Yeah.

And a british scientist took an expedition off the coast of Africa, off the coast of Principia. Not Principia. That's the. That's Newton's book, Principe Principay. The coast of Newton's.

Janna Levin
Newton's greatest work is called. So they're off the coast of principe and they're observing the eclipse. And what Eddington's trying to do is look for a star cluster behind the sun, because the light will be bent by the curved spacetime of the sun, but you need to block out the blinding solar rays to do so. So you need a total eclipse to make this measurement. And, in fact, he sees that a cluster that should be behind the sun, in fact, is visible, meaning that the rays have made it around and into their telescopes, and it catapults Einstein's fame in the english speaking world.

E
And I always think of it as like, you know, a shadow of war. And I really feel like Eddington did this intentionally as a pacifist, a british person confirming a german scientist's work, because that transcends all. Wow. That's a good story. That's good story.

I don't know if it'll make it into our cosmic queries. And by the way, there was a total solar eclipse in 1918, where they could have done this a year earlier, but the war conditions prevented it. It wasn't safe to travel. Oh, wow. Yeah.

Crazy. All right, well, I feel like. Yeah, I was going to say, basically what Judy is saying is, do you have any thoughts on the clauser experiment and how it disproves the local universe? And do you believe that this theory would change how physics can view the topology of the observable universe? So I'm not going to speak directly to that particular experiment, but there was a kind of thought experiment that I know that it must be referring to, which is the Einstein Podolsky Rosen argument, that quantum mechanics is absurd.

With those three names and often called EPR. And their argument, really, Einstein was very much trying to show that quantum mechanics was absurd. And an argument he gave for the absurdity of quantum mechanics is that it wasn't local, because let's say I entangle two particles. Think of it as the quantum version of a wishbone wishing bone experiment. A wishbone.

A wishbone. If you're wishing well, it's a wishbone, and two people break it apart. One person has the big piece and wins. One person has the little piece, but the quantum version, they're permanently entangled. I put my particle, my part, in my pocket.

You put yours in your pocket. But they're still entangled. There are neither in either state yet there's still the potential for both. Right? You haven't observed it.

You haven't disturbed it. They're entangled. There's two possibilities. I've got the big piece. You got the little piece, vice versa.

But it hasn't assumed either of those two possibilities. And we don't know. Right. I travel to Andromeda, and it's still like that. Now, the absurdity they said is.

Now, let's say I look at my experiment, and I find out I have the big piece. Then you automatically have the little piece. Or the other person. Exactly. And we all know this with certainty.

And that's highly unlocal. It seems like information traveling faster than the speed of light, right? Cause that would mean that you're breaking the speed of light law. Now, Bell came along, and I assume that this experiment is in that spirit and showed that, in fact, Einstein was right and wrong. They were right.

That experiment shows that it's non local. And all the statistics of the experiment are consistent with the non locality of quantum mechanics. So it's not local. What does that say about anything that we think of as local? You know, most of the stuff we think of as local is because it's big, lumbering lots of particles.

And that experiment's impossible because it requires such delicacy. And even the temperature in this room, the particles bouncing around would collapse any attempts. But you can imagine a world where we are not these lumbering, macroscopic things. We are particles that are entangled with something else at a distance. So that in that way, the entire universe will be holding hands with itself.

Yeah. I mean, there's lots of great science fiction plots that hinge on these simultaneous things existing at once, seemingly in conflict. And, of course, this goes back to Schrodinger's famous cat, which is simultaneously alive and dead. So I think that the question about how does it affect the topology of the universe? I don't think it's going to affect the observable topology for all the same reasons.

Topology is the connectedness of the space time, not just its local curves. But like, if I pound out, would I find that the universe wraps back onto itself and it has handles and holes? Right, but if you're looking origami, you step away. But you see the local region. But if we're connected to another local region, you're not seeing the whole picture.

Yeah, you can't see the whole picture. So it's like looking at a little patch of the earth and not realizing, oh, if I walk in a straight line, I'm gonna actually come all the way back to where I started. Lots of people saw a little patch of the earth and didn't know it was round. Yeah, correct. So its topology is simply connected, but compact and finite.

The earth's surface isn't infinite. And no, it is not flat. And no, you will not sail off the edge. So that is the topology of the earth. Cause you were arguing it was flat, basically.

D
I still stand by that.

E
So what I will say is that if you looked at the topology of possibly small extra dimensions, we might see some curious quantum effects there. Okay, so it's possible that there's a whole bunch of other dimensions which is really teeny tiny, wrapped up real small.

F
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D
That takes us to our next question. You just walked right into William Walkers question and he says hello to you all. Lord, nice Doctor Tyson. Doctor Levitt. I've read that the consensus among professionals is that the math supports a universe of eleven dimensions.

Assuming this is generally accepted, even if we cannot observe these other dimensions, have they been described or labeled? I've always been confused about how a tesseract is supposedly a fourth dimensional object when we also describe time as the fourth dimension. Thanks for all you do. Yeah, I love that. So, not to repeat his question, but I want to sharpen it in a different way.

Janna Levin
When we talk about a hypercube, those are four spatial dimensions. Time is not one of those dimensions. But if time is a dimension, the fourth dimension, can you make a hypercube where time is the fourth dimension? Would you need four spatial dimensions for that? Well, that's a tricky question.

E
So. And just to clarify, in the Marvel series, the tesseract that they describe, and they look at and they bring out. A tesseract, it's a mathematical object. It's a mathematically real object. Right.

Janna Levin
Right. So usually we don't try to compactify time. I'm not saying no one's tried it. The problem with compactifying time is, so when I compactify space, we try not to conceptify time. It's frowned upon.

E
So, you know, if speech, we sometimes fail. Right. I can talk about my local left and right, but there's no global left and right. Right. Like, if I go to the right, I'll just come back on the left again.

So left is really, really far to my right, because two wrongs don't make. A right, but three right make a left.

So, in time, you don't want to be able to come back to where you started. You don't want to be able to travel forward and that it's wrapped back into your past and connected. They did that in the movie arrival. Yeah, they do that in movies. That was a weird approach.

It has been tried, and sometimes it has some very cool implications, but. So you say it's fundamentally a different kind of dimension? Yes, it is fundamentally a different kind of dimension. You can tell us. And all my relativity professors told me it's just another dimension.

Janna Levin
You calculate with it. Right. It's still a little different. I know exactly what you mean. It is another dimension.

E
But one way to say it is. Sometimes we call euclidean space to be space. It means all the dimensions are on equal footing. I can rotate between them just by doing a normal rotation that we're used to doing. I can rotate my left into your left just by physically rotating.

Right. So in other words, you're facing him and put these two hands together. It's my left hand against his right hand, but I can turn around. And now my left hand is lined up with his left hand. So we know a spatial rotation aligns things, and that's great with time.

You can't do a spatial rotation. I can't spatially rotate into time. I have to do something called sometimes a Lorentz boost. It's a kind of a rotation in space time Lorentz boost. A Lorentz boost is similar in the health store.

Janna Levin
It's next to the testosterone boost. Right. And if you're at a restaurant, it's right before the abuse. Well, if you do one of these, you can rotate space and time into space and different space times, and we can, you know, if you're traveling past me and I say your clock is running slowly relative to mine, et cetera, I can realign us by doing a boost. It's equivalent to me coming up to your speed in some sense.

D
I gotcha. Now there's different. But anyway, what all that to say is, it's much harder to compactify spaces that have this space time difference. You can do it mathematically, but the question is, will physics allow it? Can I make sense of physics on a space that also has a compact time?

E
I can certainly make the mathematical object. But of course, the problem is the famous grandfather paradox, where I could go back and murder my grandfather before my parent was born, thereby. Right. Just have them not meet each other. So.

Well, actually, that's actually part of the resolution is that, well, what would be consistent with that compact time would be if I tried to go back in time and I tried to murder my grandfather, but I just injured him severely, so that he was neurologically damaged and had terrible children. And I therefore was so deranged that I went back and tried to injure him. It's odd that it's not the grandmother, because you could still kill the grandfather and have it make no change in you having been born. Right. And that's the truth.

D
You can end up still being born and you're just like, oh, my God, my grandmother cheated on my grandmother. That's what I'm saying. Just a milkman. Oh, my God. All right, keep going.

Janna Levin
Okay. This is Morgan Fisher. He says hi. Doctor Tyson. Doctor Levin.

D
Lord. Nice, Morgan. He him here from Waterloo, Ontario, where doctor Levin gave a brief talk at the perimeter institute back in 2017, and I was honored to attend. Wow, look at that. You made an impression.

2017. He's still late. I'm still thinking about that. Still a fan, still a fan. Can you please explain, in layman's terms, the fundamentals of Hugh Everett's many worlds interpretation?

From what I understand, every quantum fluctuation could mean the spawning of an entire new universe, while the universes are under no obligation to us, as Doctor Tyson says. Makes sense. This seems so bizarre, so peculiar, so outlandish. Wow. That was very willing swettner to me.

Janna Levin
So very Captain Kirk, that it seems. To defy every bit of both common sense and physical reality. For instance, where does all this new mass come from when the new universe is created? Wow. Yeah, I.

So there. So there. I will say I am not an avid proponent of the many worlds interpretation of quantum mechanics. Well, there you go. Neither am I, but I am surprised at how many of my peers are.

E
And I did a kind of anecdotal survey amongst friends, and I was surprised how many said, oh, yeah, yeah. I really think it's many worlds interpretation. I do not think that. But let's just quickly describe the many worlds interpretation. It says it doesn't even have to be as fancy as quantum entanglement.

It just says a particle can be in more than one state. So the analogy I like to give, I don't know if I've done it here before, is chords in music versus individual notes in music. Okay, so let's say I play a chord, and it's a definite chord. That is a superposition of certain notes. So I can't simultaneously be in a single state of one note and in the state of the chords.

D
Correct. Right. So particles can be like this if they're in a particular place. An eloquent depiction. That's cause I live with musicians.

That is amazing, what you just said. Thank you. I mean, that is beautiful. It's almost painterly, the way, because when you. You don't think of a musical chord as something physical, but it is indeed physical.

It is the reverberation of the sound, and at the same time, they coexist as one. However, you can identify every note in the chord at the same time. That is fricking amazing. Yeah. Isn't that amazing?

E
Because I am surrounded by musicians. I myself can't play. But in the universe, it's just like this. If I have a particle in a particular state it's in, it's like a chord where there's superposition of momentum states. I no longer have a precise, definitive state of its motion.

And so it's like positions are chords where momenta are the notes, or vice versa. It can have an exact location on its momentum. But now I don't know where it is in space. It's like a chord. It has a superposition of positions.

D
Pretty crazy, man. That's pretty nice. That is. That's pretty nice. So the many worlds interpretation says, okay, now let's say it assumes a definite position state.

E
It's in, like, this superposition of locations, this particle. But now I get it. To assume a specific state. And it could have assumed any one. Let's pretend with equal weighting.

It doesn't really matter. The many worlds says, well, every one of those things happened. It's just there's a you in one world. Which found the particle over here to the left, let's say. And there's a U in another world which found the particle to the right.

And they branched off, and now there's just two worlds. Isn't this their attempt to try to make sense. Classical sense. Of something that is inherently non classical? I think that that's true.

I think there is a deeper thinking to it that is intriguing. Which is to say, if we really believe Schrodinger's equation. Which describes these superpositions. If we really believe quantum mechanics as it is now. With no added ingredients.

It is actually the barest interpretation. It's the most minimal interpretation of quantum mechanics. Now, these questions are great about what does that mean about all the mass of the entire universe reproduced? It doesn't. It's hard to talk about it in that way.

D
But see, if you're from the way you just explained. If this is we'll call it a super state. Where these positions are already assumed. You're not really creating a new universe. You're just realizing a universe at that particular point.

Where you. It's a nice way of saying it. Where you actually take the position. So when you assume the position.

When you do, that state now becomes solidified. We'll say, yeah, that's all right. So when you didn't create a new universe. No, you didn't do anything. You were always in a superposition yourself.

E
Of finding it here and there. Exactly. So, again, this is a kind of Schrodinger's cat argument. But it's not as though part of the mass of the particles over here. And part of the mass of the particles over there.

That's not it. The whole particle is either here or there. And, in fact, the particle isn't real. Back to realism. In the way that we used to think.

The only thing that's real and deterministic. And has all the properties we used to assign to particles. Is the probability what we call the wave function in chodrajers? Well, remind me the next time we have Janet in here to make sure I take an edible before I do the show. Cause I can't smoke in this office, but I can dog on sore, swallow a gummy before I come in.

D
That is something else, man. Well, one more small thing about this, if I could. It means that if you're doing this with a coin toss, like a particle's heads up or heads down, it means that there is factually a world, if this were true, in which somebody, every single coin toss, gets heads, right. And they have to walk away and say, oh, I'm just that. That unlucky guy in the multiverse who happens to get heads every time, right?

Janna Levin
Cause that would be harder to swallow than. Yeah, it doesn't sound great. Right? But then again, I don't think nature cares about our plans for understanding the world. So I don't use that as my argument for why.

E
I don't think it's true, but it certainly would be peculiar. Cool. Chuck, we hardly have any time left. Let's see if it's possible for us to answer two questions in half the time. Yeah.

D
All right. Do the math. Right.

E
Number two in two locations. Well, then it'll be a little bit more than that, because Logan Davis has a two parter. He says, greetings from Alabama. I have two questions that are somewhat related. One, if you were the mass of a black hole, would your gravity affect your flow of time?

D
And two, does the speed of an object's vibration affect its flow of time? Ooh, I love that. Look at that.

E
Well, this is an intriguing question. Different observers around a black hole experience a different passage of time. It's not as though the black hole sets an absolute notion of time. So, let's say I'm hovering right outside the event horizon of a black hole, and I'm firing my engines like crazy, and I'm trying to escape. I will measure very, very different time than somebody who's passing right by me.

We can look each other in the eye, and it's like I'm just going to succumb to the fall, and I'm going to go right through the event horizon. We will not agree on the passage of time. So it's not as though at a particular spacetime point, the black hole fixes the passage of time. Gotcha. So it certainly affects the passage of time of anyone trying to navigate or explore, but how they navigate and explore matters.

Okay, so that's maybe a partial answer to that one. And does the speed of an object's vibration. Vibration affect its flow of time? That's interesting, because it seems to me if you have a vibrating membrane or. Drum or something, then the middle is moving faster than the outer edges.

Janna Levin
So, yeah, so whatever is the relativistic effects will affect the middle of the drum more than the edges of the drum. I agree. So, yeah, I would say, you know, it's always relative to something, as Neil, you just cautiously laid out, because it's not as though the person with the clock in the middle is gonna say, hey, my time's funky. Everyone always thinks their time's fine. Yeah, right.

Your time is messed up. It's your time. It's messed up. So it's the relative vibration to some other part. Will yes, for sure be affected by any emotion.

D
Wow, that's great stuff. All right, last question. This is Lynn Newton. Lynn says hello. Doctor Levin, Doctor Tyson, your lordship.

I saw Doctor Levin post on Twitter recently about quantum teleporting of a molecule that was achieved, and I'm wondering if you can tell us a bit more about what that is in Layperson's terms. Oof. Hmm. Well, this is related to quantum entanglement. Okay?

E
So in quantum teleportation, what they're trying to do is entangle two particles and then it gives you a mechanism by which you can throw information from one particle to the other without clomping in between and the non locality that we were talking about in the previous question. So in those entanglement, you still have to sometimes communicate information ahead of time. So it's a little bit sneaky. Like you have to send plans, you know, through the mail, which is slower than light travel, but you don't have to send 100% of the information, you just have to have a plan and you send it across and then you kind of have to break, crush some of the information on one side to get it out, and it gets tossed or reappears in some sense as though the molecule itself was teleported. So if you were talking about this with a person, you basically have to destroy Chuck and Neil here to reproduce them on the planet.

Janna Levin
You're allowed to say it was teleported. It's not some tricky. That would be quantum teleportation. I mean, if it's exactly, you know, if you give me an electron, I can't tell you which electron it is in the universe. It's just there's no experiment I can perform.

E
It's identical to every other electron. And so it's might as well be exactly the same electron. I don't know what it means to say, no, this one's not the same electron. Wow. So if I quantum teleport it, I have no logical way of saying it's not exactly the same particle.

Janna Levin
Did you hear about the idea where the universe repeats, but there's a soul electron that is going forward and then backwards through time that flushes out? I have not heard that of every other electron. So that the reason why the electrons are identical is because it's the same electron and it's gone through the universe this many times to then populate. Right? Yeah, yeah.

D
It's just. It's doing a lot here. So everything. So, basically a lot going on. There's just one electron all around us.

Janna Levin
There's a whole chapter in my quantum physics book called identical particles. Right. Just to get you to understand what that means. Oh, and in the context of this conversation, the reason why black holes are so odd, and you were talking about this earlier, you talked about stars and planets and things. Black holes are peculiar because they are like fundamental particles.

E
They have something in common with fundamental particles, and that is that they are flawless and indistinguishable. So, once a black hole is, you can throw things on and it can be active. But once it settles down to a pure, bare black hole with nothing else going on, it is indistinguishable. There is no experiment I can perform to tell me which one it is from every other black hole with that mass, charge, or spin. And in that sense, it shares more in common with fundamental particles than it does with.

With matter. Look at that. I mean, I'm sorry. With physical things like stars and planets. Look at that.

D
Yeah, that's pretty wild, man. Yeah, that's pretty weird. So, we think black holes were created as quantum particles in the big bang. Very, very small. Planck scale black holes, they would evaporate quickly.

E
They would evaporate very quickly. Yeah. Through hawking radiation. The smaller the black hole, the hotter they are. So they actually explode.

Yeah. Wow. Yeah. In fact, I think his original paper was primordial black holes. I don't know what the original paper is.

Janna Levin
One of his papers described the search for evaporating black holes as bursts of gamma rays. That's the last gasp of a black hole as it dies. And I think the wavelength of the light that it emits is the diameter of the event horizon. That's right. As it gets smaller and smaller, the wavelength gets smaller and smaller, and the energy of the light gets higher and higher.

E
Exactly. Wow. Yeah. Yeah. Exactly.

Janna Levin
That's all the time we have. That's it. Damn. How you guys feeling? I'm exhausted.

E
I'm so tired. My God. So I should stock some gummy bears for you. Edibles. So, janips, you don't come by often enough, I think.

Oh, yeah. It's always fun to be here. I love it. All that far away. You got to make sure.

Janna Levin
And we were delighted to do that event at pioneer works. Oh, I'm so glad. Yeah, that was so we should collaborate more on that. Absolutely. Love it.

All right. All right, guys. So let me just reflect on this for a moment. When we think about life and everything that matters to us, we think about tangible objects. I'm speaking to a microphone.

I'm wearing clothing. But there's some people among us who think way deeper thoughts than that, like how does it all work and why does it work in that way? And it's. Much of it sounds completely irrelevant. It'll probably forever be irrelevant.

However, let's remind ourselves what it is to be human. We are comfortable sleeping on our backs and we sleep at night. If we wake up at night, what are you looking at? You're looking at the night sky. Looking at objects that are there one night and move the next night.

There's a curiosity that we can natively embrace that other animals have no access to because they never look up. Does a beetle ever look up? I don't know. I've never asked one, but I don't think so. We look up and we see things change and it stimulates our curiosity.

A curiosity about things that have nothing to do with life on earth. Not directly, or maybe not ever. But that curiosity is fundamental to what it is to be human. And when we study cosmology and the origin of the universe, the birth, the death, that is a fulfillment of what it is to be human in the first place. And I wouldn't trade that for anything.

That's a cosmic perspective. Neil degrasse Tyson coming to you from my office at the Hayden Planetarium right here at the American Museum of Natural History. I thank Chuck Dana for being on. A pleasure, as always, I bid you to keep looking up.

G
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F
Because I got the charcoal mask. Great. Because why would I put that on. My face when I could drop it in my sink? This is what I get for multitasking.

E
Ugh. Why is charcoal so sticky? Hello? Hey, Janice. I am so sorry.

F
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Cosmic Queries - Bits of Spacetime with Janna Levin

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1: Introduction to Spacetime

2: Quantum Mechanics and Reality

3: Theoretical Physics and Black Holes

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