StarTalk Radio - Cosmic Queries: The Multiverse

Episode Date: August 19, 2016

Itching to know more about the multiverse? You’re not alone! Join us when Neil deGrasse Tyson and Princeton theoretical physicist Paul Steinhardt answer fan-submitted questions about cosmology chosen by co-host Chuck Nice. Subscribe to SiriusXM Podcasts+ on Apple Podcasts to listen to new episodes ad-free and a whole week early.

Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now. This is StarTalk, and I'm your host, Neil deGrasse Tyson, your personal astrophysicist. And I hail from the American Museum of Natural History right here in New York City, where I also serve as the director of the Hayden Planetarium. My first planetarium as a kid, when I was nine years old. And I was never the same since then. I think the universe found me.

For this edition of StarTalk, it's the ever-favorite Cosmic Queries, fielding your questions, and today's topic is the multiverse. I know you've read about it, I know you've heard about it, and I know you're itching to know more. And I've got my co-host, Chuck Nice.

Chuck. Hey, Neil. You're going to help me get through this. That's right. my co-host, Chuck Nice. Chuck. Hey, Neil. You're going to help me get through this. That's right. I have the questions right in my very hands. Solicited from... All over the internet, wherever our fans may be found. May be found.

Their inquisitive little minds want to know all sorts of things. And I need a backup for this, because I know a little bit about the multiverse, but I claim no particular expertise in it. So we get on the horn and called one of my old friends and colleagues Paul Steinhardt Paul hi welcome to star talk well thank you professor of physics Princeton University yes and you are a proponent of one of the multiverses that people have been talking about well I'm not sure I would put it quite that way but I'm actually a proponent of alternatives to the multiverse. Oh!

Yeah. Oh, really? Yeah. So I'm not a big fan of the multiverse. Really? Oh! Okay. Why not?

What did the multiverse do to you? The multiverse destroyed one of my favorite ideas. Oh! Oh, so, oh. Awesome. So it's a problem. Oh, okay. It's a problem for you. Oh! Oh, so, whoa. Oh. Awesome. So it's a problem. Oh, okay. A problem for you.

A problem for me, yeah. Okay. So what was your idea that the multiverse destroyed? Well, it's an idea that we call cosmic inflation. So one of the longstanding problems that we've had in trying to understand the universe is why the distribution of matter and energy is so uniform on large scales. And we thought we had a really... In other words, I look to one side of the universe, there's statistically a number of

galaxies and stuff. And any direction I look, it kind of looks like that. That's right. And you're saying it shouldn't look like that. Well, according to our initial idea of the Big Bang, the universe should have emerged from some random quantum state and been very, had a very uneven distribution of matter and energy. And space itself should have been curved and warped. And all that should have happened is that you just stretched that out over time very, very slowly. So that if you looked at the universe today, you should see remnants of that unevenness

and warping. Like an area where there's tremendous amount of matter and other areas where there's hardly anything and bizarre curvatures of the space-time continuum. Yes. Like a fire. Yeah. So a fire is like unpredictable in the way it moves. It has certain burn patterns. And so you would look for that to see where the fire, how it progressed in certain areas.

But it wouldn't be like a very uniform. I hadn't thought of using fire. But, yeah, I guess a room would not burn uniformly because some things in the room are more flammable than others. Let me tell you something. You have no idea. I just bailed you out. No, that's exactly what I meant.

That's exactly what I meant, but I was just like the way you looked at me, I was like, ah, you shit the bed again, Chuck. We're trying to wrap our heads around this. Okay, continue, Paul. So we thought that the idea for solving this problem was to have a period of very rapid acceleration, accelerated expansion that occurs right after the bang. So that instead of expanding at a sort of slow, modest rate that would preserve this unevenness, at a sort of slow, modest rate that would preserve this unevenness.

Instead, you would stretch it at such a space, at such a fast rate, that the matter and radiation that existed before would all be spread out, dissipated. All you'd have left is the energy that would be driving this super expansion. And then when that energy decayed into ordinary matter and radiation that we see today, because it had made the... Matter and energy are one and the same. E equals mc squared tells us that. Yeah, but it also includes light and other forms, all forms of energy. Then you would discover that the only energy that was left was very uniform,

very uniformly distributed. So that was the initial idea. That seemed to be a sweet idea for explaining how you would get this expansion. Universe we see. Universe we see, which has this peculiar and unexpected uniformity. Okay. So then we came up with another added idea to this, which is, in this description I just gave you, I didn't include anything about quantum physics. So I said just stretching the universe

would make it uniform, but quantum physics resists uniformity. It produces fluctuations, random fluctuations that prevent perfect uniformity, and they would lead to some regions of space ending inflation slightly before or after the average. So you wouldn't end up with a perfectly uniform universe. You'd end up a universe with a specific non-uniformity in the distribution of matter. That you can predict. That we thought we could predict. Okay.

It seemed to be predictive. It seemed to be something you could work out on the back of an envelope. That you could work out on the back of an envelope. That some of us worked out on the back of an envelope. Me and my supercomputer equals you in the back of your envelope. Okay. out of the back of it. Me and my supercomputer equals you in the back of your envelope. And curiously

enough, those naive predictions agree with what we've observed when we actually look out in space with the pattern of unevenness that existed in the early universe. It's not as uneven as it might have otherwise been, but it has the right amount of unevenness that's consistent with the hypotheses.

With this naive calculation. So what's wrong? What's the problem? Well, there are a couple of things wrong with this idea, as we've discovered. The first is that it presumed that after the Big Bang, it would be easy to get this inflation, that just by introducing the right forms of energy, hypothetical energy, into the universe, you could automatically start inflation. So you could begin with a very random, uneven state and start the inflation. You would tune inflation to occur when you needed it to match the universe that we know. Yes, but you also need to start the inflation.

It needs to ignite somehow. You can count its analogy to flames, yes. But we thought it would be easy to ignite, but we discovered actually the opposite is true. So, as an analogy, imagine that I was trying to, I told you I had a theory for how to become a billionaire. Okay, I am very interested. I thought you might be.

I'm writing, I'm taking notes. Okay. So, I have a theory of how to become a billionaire. And I show you a little part of my theory, which tells you how to invest some money. And sure enough, it demonstrates that it could make some money by following that procedure. And so you buy my theory and I give you the book, which explains the theory. And you open up to page one. It says, page one, let's assume that your parents were billionaires.

So basically, this is Trump University. Okay. All right. How to become a billionaire, start with a billion dollars. Right. Well, this is essentially what happened in the story of inflation. We thought originally just simply stretching the universe would be an easy start, but we discovered actually only under very rare conditions, essentially the

conditions you needed. You needed to start with a universe which was already smooth enough and unwarped enough. Only then could inflation start. So it's just like saying, I need to have a billion dollars in order to become, in order to make a billion dollars. So that was the first big problem. And we've never gotten around that up to the present time. We've known about this for 30 years, but we haven't figured out, despite lots of clever attempts, how to get around that problem. You're all such idiots. You can't. I'm telling these early universe guys, you've been 30 years now.

I'm waiting. I'm still waiting. Is it because the problem's hard or because you all just aren't smart enough? It's because probably it's actually not a good way of smoothing the universe out, I would say. It's probably not a good book that I gave you for the billionaire solution. Recipe. Then the second problem that we found is, well, suppose I let you start as a billionaire. Okay.

I give you the conditions you need to start inflation, okay? And I let you choose your inflationary energy to have whatever properties you want. We thought that you could then calculate, as I said, on the back of an envelope, what the predictions would be. But there's a little something that we left out of the story that we didn't realize. When we thought about these quantum fluctuations that slightly change the rate at which inflation ends one place to another, inevitably, there's also going to be regions which are going to have large quantum fluctuations. They're not going to just delay the end of inflation by a little bit, but by a huge amount. And the longer you delay, because this inflation is stretching the universe so fast the bigger those regions become so a typical region is not the region

you thought it was which just had tiny fluctuations a typical region in terms of where most of the universe is is one of these huge regions which continues to inflate and then itself it will repeat the process we patches of it will end inflation but patches of it will continue. So that over- Patches within it. Within it. And so it'll keep producing patches and patches and patches with most of the universe continuing

to inflate, and only rare patches where it ends. We don't see these patches. We, according to this idea, we would live in one of these patches. But these patches are not all the same. This is where the problem begins to break down. I know, but looking around, we don't see such non-uniformity in the universe. We only think, yeah, we see uniformity. We don't see any evidence. Unless our entire universe is one of these patches.

Which is the concept of multiverse. Now we get it! So that's one kind of multiverse. But that is one patch of the multiverse. Right. But the problem is that... Just to be clear, this is not a universe in some other dimension. No, no, no.

This is all one universe. This is an area, volume, whatever, in a meta-universe, and we're thinking it's our thing. Right. We think it's everything. Right. And we're thinking it's our own, it's our thing. Right. We think it's everything.

Right. But, but, outside of that, our patch, if you went far enough out, would be more inflating universe. And finally, you'd hit another patch. That patch would have different properties. Right. Due to quantum fluctuations. Different fluctuations. Quantum fluctuations would cause different properties in that little patch. That means you can actually travel within this universe from one patch to another

and then experience different, slightly different laws of physics. Too bad. Damn. Not. Why not? And the reason is because the space between these patches is growing so fast, it's continuing to inflate that light either you and a rocket nor light

could make up the difference. Okay, so we can't overcome the expanding boundaries between us. You can't beat the expansion. You can never get ahead of that expansion. So you're never going to reach that patch. Wow! So it's completely there. That's good, though, because you don't want to wander into a place that has slightly different laws of physics.

Yeah, for example, where all the molecules in our body would decay into radiation. That wouldn't be a good news. Or perhaps I show up in the wrong outfit. That would be disastrous. Perhaps. I believe this is black tie, sir. Okay. So how would you ever test this?

Well, it's actually hard to test this idea because one of the consequences of this idea is over time you produce patches of ever, ever increasing variety so that every conceivable possibility that can occur will occur in some patch. So the patch that has a slightly different law of physics will have patches that are slightly different from it. Yes. Which will have patches slightly different from it. Right. Wow. So it's a theory which... Well, you're freaking us out here.

That is freaking crazy, man. Well, I think it is. Because our goal was to explain why the universe is the way it is, and we haven't... But our heads are exploding, but yours had exploded long ago when you first did it. Now you're just cool with it. That's right. And you know, what's also like blowing my mind is that, I mean, it's so incredible that you're able to conceptualize this as all a part of, like you said, the meta-universe. One expansion of a thing.

Whereas our common perception of a multiverse is we're making jumps and leaps to these parallel universes that are existing on different planes, you're saying, no, this is like whirlpools in a giant lake. Yes. Yeah, that's amazing. Connected, a connected fabric of space. Yes, okay, yeah. Wow. Let's get into it.

Okay, yes. And we're not done with you here. No, I know. Wow. All right, Chuck, what do you have? Here we go. Of course, we always start our queries with a Patreon patron. Are these people who paid to get their question first?

Yes, because... Is that even fair? Listen. Life is not fair. Okay, fine. That's all we know. Life is not fair. These are supporters of the show.

These people support the show, and so we support them back by giving them preferential treatment. Mutual back scratching. There you go. It's the same reason why my parents like me better than my siblings. I'm not even going to. There you go. Or at least they pretend to. Here we go.

Christopher Cohen from Patreon says, Hi, Dr. Tyson. How far do you think we are away from determining the theory of everything, i.e. a theory of quantum gravity? What will we need to perform experiments that could prove or disprove a particular hypothesis? Chris and Samantha Cohen from Hartworth, New Jersey. So, Paul, how interconnected is a theory of everything to what's going on on the frontier of multiverse thought? on the frontier of multiverse thought? Well, I think it's intimately connected in the sense that one of the problems

we talked about already was how you would start the universe off. So a presumption of this conventional picture is the universe has a beginning. The only cosmologists get to sound like God. Well, we're going to make the universe this way at this time. Right.

The power that they wield. All right, go on. Go on, yeah? So the question is, so the idea is that at some point there was nothing, no space, no time, no matter, no energy. That's the presumption. That's the presumption, which we can question. But that's the presumption.

Then suddenly it burst into something, space, time, filled with energy that was first quantum and then suddenly became later, a few inches later, large enough and became classical, described by general relativity. Now, those are words. What actually happened there? What's the theory that explains that creation event or that replaces it with a better idea. Let's go to the tape. Go to the videotape. That reminds me of the Sid Harris cartoon

where there are two physicists at the chalkboard, and it's filled with equations. And then at the end, at the bottom right-hand corner, it says, then a miracle occurred. So the other physicist says, we need some more detail here

for what happens at this stage. That's the theory of everything. So that's what we're looking for. So it would dovetail into what you're trying to describe what happened after. Yeah, a full theory would have to incorporate

a quantum theory of gravity and an explanation of either this creation from nothing or something that replaces it with a different idea. So is that where you hear people talk about the eternality of matter, like that it just, it's not about that it came from someplace, that it just always existed? I mean, I've actually heard that as people try to explain that's how everything started, and that this just goes over and over again. So the idea of this creation idea of this Big Bang, the traditional Big Bang idea, is that there would have been no matter.

There would have been no space for matter to even exist in. So matter already presumes a notion that exists in some space background. Stupid. What the hell was I thinking? Chuck! Chuck, you idiot! But let me say, but we don't know that this creation idea is right. So there are some of us,

and myself included, who have been... Rethinking the creation scenario. Yeah, and thinking that maybe what we thought was a big bang was really a big bounce. The universe went through a period of contraction and then bounced to expansion. So that space would not have had a created moment,

but would have existed before, during, and after. That's what I was trying to say. Yeah. So there's your eternality, at least of space. At least of space. And what do you call this idea? The big bounce is just describing this event. I like that. Two syllables. A version of it, the universe undergoes not just one bounce, but periodic bounces. So we call that a cyclic universe. So the universe goes through. It bounces a little better. Okay.

If you are into your Greek, one version of that is called an ekperotic universe. Another version of it is called. Worst name ever. Thank you. Thank you. Ekperotic universe. Oh, who worst name ever. Thank you. Thank you Who wants to live there? Exactly oh by the way once you get done with the ekperotic universe. Why don't you make your way over to the enema universe? So ekperotic for the Greek means what what are those words from out of the fire?

So actually an ancient Greek idea was the idea of a universe went under regular periods of creation, evolution, and then cataclysm, disappear, and then a new universe would be created, an ekperotic universe. Let's go with Phoenix universe, maybe? Phoenix is another version of this. Otherwise, you're just showing off that you know Greek and obfuscating what... Fair enough. We're going to take a quick break.

And we come back to StarTalk Cosmic Queries Edition. We've got Paul Steinhardt, physicist at Princeton University, and he's our expert in-house on the multiverse. See you in a moment. We're back on StarTalk. How could we reach? Today's topic, the multiverse.

Topic I would not dare tackle on my own, so I brought in Chuck Nice. Of course, Chuck knows everything about the multiverse. Right. Chuck is reading questions from you our fan base and I brought in Paul Steinhardt Princeton University professor

yes physics it's been a fascinating conversation thus far and he's been doing some thinking of his own yes on the multiverse

so a quick question your ecpriotic universe which is repeating bouncing you remove

the need for singularity, is that correct? Yes. So time would exist arbitrarily far back, maybe infinitely far back in time. Maybe space and time existed forever, and we're just in the most recent cycle. I'm going to ask you a philosophical question. Did you come up with this idea because the singularity was too hard, and so you needed an easier way to understand the universe, or did you have compelling reasons to go there? Actually, it was a very practical reason.

I didn't have a philosophical outlook at all. It was to get rid of the multiverse problem. Because the multiverse caused the... You took out a hit on the multiverse. The multiverse got two in the back of the head. That's right. And then Paul went, leave the gun, take the cannoli.

Take the cannoli. Damn. Wow. That's pretty wild. That was the motivation, though. That actually was the motivation. Because the multiverse, essentially, as I was saying at the outset, destroyed an idea which I thought explained how the universe could have been smooth and uniform.

Right. Just because we didn't properly understand the effect of quantum physics and that due to these rare quantum effects it totally changed the structure. Instead of getting a smooth universe we expected to get, we got this patch universe which every outcome is possible. So I just want to explain it in a sentence

that feels comfortable with me. This patchwork universe where you have causally separated regions that cannot know about one another, they are nonetheless connected in the fabric of space-time. Yes. We cannot and should not think of them as some separate parallel universe in another dimension, as is so commonly thought of in movies and the rest. Yeah. Okay. That is really just an incredibly mind-blowing concept.

What are the questions again? Let's move on. Let's get back to the questions. All right. This one from Greg Fisher on Facebook says, Hi, Dr. Tyson et al. I remember reading a while back that in a quantum state, electrons were shown to not only have spin, but were kind of able to jump or

teleport between and within their shells. While this still seems a bit far-fetched, and I'm not a physicist. Hey, thanks for that, Greg. Thanks for letting us know that you're not a physicist, because I was, for one, I was very concerned. What's new, and what can be explained about this? So, Paul, this is not specifically multiverse, but if you're worrying about quantum phenomenon, it's got to show up at some point. We know that when electrons jump energy levels or even when particles what we call tunnel from one state to another state, the time delay is basically zero. Isn't that correct? A particle can show up in one place having traveled from another place. If it tunneled there, it got there faster than the speed of light. Isn't that correct? Is that the wrong way to think about it? I think it's the wrong way to think about it. I think there's a period of time during which its location is uncertain. And if you

account for that lost time, that's the time it would take for, that would be longer time or equal to the time it would take light to travel from its first location to the other. So it's like you would see it here, and then there'd be a period, if you weren't watching, that it would suddenly appear here, and then that period of uncertainty would account for the light travel time. Okay, now the period where you're not watching, that's a necessary part of this phenomenon. Yes, because to see it would mean you'd have to be shining light on it to see it. Now you'd be cheating. You'd actually be kicking the electron, and you'd say, oh, the reason why it went from here to here is because I kicked it.

So it's important that you don't look. Because then you're not studying the tunneling phenomenon. Well, that's like the old joke, I know how to teleport. And they say, prove it. And you say, okay, I'm going to go to San Francisco right now. I'm back.

Okay. You know what I mean? It works. It works. I can't disprove it. Okay, so just, I mean, you said something fun and deep, as you have been doing in this time that you've been sharing with us, that for a particle to disappear

from one place and reappear in another spontaneously via some kind of tunneling phenomenon, it does that because you stopped looking at it. The act of looking at it sort of keeps it in that quantum state, if you will, in this scenario. Or kicks it out. Or kicks it out. You look at it, it kicks it out. You interact with it.

Now you're studying a different effect right right and this is happening all the time for everything it's just that we can be illuminated by light but our mass is so high that we don't jump to another quantum state body and soul but an electron is such low mass and it has this interaction capacity with a photon that you can't shine a photon on it and expect it to stand there and smile for you. Yes. Okay. Wow. Okay.

Yeah. That's pretty awesome. So the act of trying to measure it changes what you're trying to measure. Right. You can't measure it because once you pull out whatever it is you're measuring, that actually affects it. And the New Age movement completely misunderstood this, thinking that it's your consciousness that's somehow affecting it, and it's a human thing. No, it's the act of measurement is a thing, whether or not the human is doing it. You have to have a machine, whatever, doesn't matter.

And this spontaneous process, by the way, is the same idea that's involved with producing the multiverse. It's a similar tunneling or decay-like process. In this case, it's a decay of inflationary energy into matter and radiation that's occurring randomly due to quantum effects. And the fact that it's random and sometimes produces a huge expansion is all part and parcel of this quantum uncertainty, randomness. Gotcha. Quantum is some badass stuff. Let me tell you, it's crazy. It's a powerful thing. Yeah, and the fact is that, I'm going to be very honest,

I don't understand any of it. That's fine. Okay, I'm just letting you know. No, but you don't have to. By the way, by the way. I mean, I understand what you're saying. Paul, who was it? Was it Feynman?

One of the greats of yesteryear said, the day you say you understand quantum physics is the guarantee that you do not. Probably so, yeah. It's not something to understand. It just is. Oh, right. Okay.

Well, then I feel much better. No, you just... No, no. We were freaking out. Our historical brethren who discovered this, they were freaking out just like you are right now. Right. Oh, my God. A particle? A wave? Why? Who?

Einstein said God does not play dice. People were freaking out, even Einstein. So you're in good company, Chuck. Even today. Even today, there's still a community of people that debate the interpretation of quantum mechanics. And then there's another community of us who just say, This is it. Shut up and compute. Compute, Exactly. I'm in that camp, by the way. And by the way, if I had a time machine and I somehow found myself in the 1920s, I would be the greatest

heralder of the discovery of quantum physics, which I think did not get much public play back in the 1920s when most of the foundations of it were laid to paper. I mean, think about it. Newspapers of the day aren't saying a new branch of physics has just been discovered. It's not there. It's only when it became useful for the IT revolution and our entire creation, storage, and retrieval of information has anyone been able to fully appreciate what came out of that era. That's pretty much.

Transistor, too, you needed. And partially it's because there was a lot of confusion as to how to interpret the idea. been able to fully appreciate what came out of that error. That's pretty well. The transistor, too, you needed quantum. And partially it's because there was a lot of confusion as to how to interpret the idea and exactly at what point it was convincingly true. So the point is, as a professional physicist, you study quantum physics, which historically had only been applied to the small.

Now, as a cosmologist, when the entire universe was once small, you're invoking the rules of quantum physics to now affect the entire universe. Right. Wow. And the effects... Now, that's pretty awesome. Well, think about it, right?

Because when the large was small, quantum physics is kicking cosmic butt. And you know what? Not just particle butt. And that's in the Bible. The large shall be small and physics is kicking cosmic butt. And you know what? Not just particle butt. And that's in the Bible. The large shall be small and the small shall be large. So, yeah. All right, Chuck, what else you got?

Hey, this is Matt Eli from Facebook. That was a great question. Matt Eli from Facebook and also from San Antonio, Texas. A little more, who wants to know this? A little more existential. Why should we take the multiverse theory Seriously in the first place Might there be extraordinary evidence

For this extraordinary claim Whoa He is not the least bit skeptical Good I like this question So go ahead Yeah it's You gotta admit Paul

To assert multiple universes Is extraordinary And if you're not on the And you're a theorist Last I checked Yeah, you've got to admit, Paul, to assert multiple universes is extraordinary. And you're a theorist, last I checked. So you're not even, well, of course, good theorists think of how to test hypotheses. Have you? How's that for a setup? Good theorists do this. Do you?

Well, I think I've already sort of laid out my cards and said that I think the multiverse is a sign of breakdown of this inflationary idea. It's a failure. It's a failure mode of the theory, something we didn't expect. It wasn't designed to produce a multiverse. It's something we discovered after the fact. And the problem is that because it produces an infinite number of patches of every possible variety, if you ask what the theory predicts, the answer is nothing, or everything, anything. So it's a little bit analogous. If it explains everything, then in fact it explains nothing.

Yes. So in my view, that makes it no longer a scientifically interesting theory. So it's not testable. Even if it's true, it's just not interesting. It's not interesting, because anything you'd measure, you could say, oh, we live in that patch of the universe. And then you measure something else tomorrow and it doesn't fit that patch. You say, oh, they must be in that patch. We live in the patch where both of those are the fact.

Yeah, that's right. That makes sense. I mean, yeah. And according to the multiverse idea, if it's physically possible, and obviously our physical world is one of the possibilities, then it must exist somewhere in the multiverse. Unless we're a simulation. Oh, no. But even that would be somewhere in the multiverse. Unless we're a simulation. Oh, no. But even that would be part of the multiverse. Oh, there's the...

You can't get away from this idea. Drats. Once you have a bad idea, you can't get away from it. That's funny. Drats. All right. So there you have it. Okay.

Hey, Matt. Nice question. So you agree that it doesn't really set the standard yet for a testable theory? I think by construction it does not. And if you read what the proponents of the multiverse say, that's exactly what they'll tell you. What about the quantum foam bursting forth multiple whole other universes from the very early universe? And these would be universes that you would be able to see in a higher dimension, but they don't interact and they're perfectly... So they're separate fabrics.

Separate fabrics, yeah. I don't know what to make of that. That's another untestable idea in principle. So it's another version of a... Well, so there are two possibilities. One possibility is that those different fabric regions have completely different properties, again, like the multiverse, and it's just random chance...

Like a patchwork multiverse. Like a patchwork multiverse in which, again, everything could possibly... Everything that could happen will happen, in which case it has no scientific predictive value. Or it could be that you have a theory which says, actually, the same thing will happen will happen, in which case it has no scientific predictive value. Or it could be that you have a theory which says actually the same thing will happen each time, every time you produce one of these fabrics, so that if I suddenly transport it to the other one, imagine doing that, it would look familiar to me. That's a different story.

That's a predictive theory. That is. But the problem is you can't get there, is what you're saying. Yeah, and so it doesn't have a meaningful scientific value. Well, Paul, isn't it true, for reasons that I never learned because I never took advanced field theory in graduate school, but my wife did. Okay, she has a PhD in mathematical physics. I know, I know your wife, and she's smarter than you. That's right.

I'm just saying. No, I know your wife, and she's smarter than you. That's right. I'm just saying. But from what I've been told, gravity is not contained in the space-time in which it is formed, in which you have it. So, in other words, the effect of gravity can leak out of whatever is the membrane that it's contained and be felt by other universes outside of that? Unlike electromagnetic radiation, which is trapped within the space-time, gravity is not. I've heard that. So I think you're referring to theories like in string theory you have extra dimensions, and where we might live in a membrane-like surface, in which we think we're living in a world of three space dimensions.

There's actually extra dimensions, which we, our particles, can't move there. Our light can't move there, so electromagnetic radiation can't move there. But gravity would be felt even along that extra dimension. So that, for example, if there were another similar membrane parallel to us, now we are thinking about this idea of parallel universes.

This is the parallel. Yeah, and something were happening over there, let's say a matter lumped together to form a star or a black hole or something like that, that would be felt, it's gravitational effect. So why isn't that dark matter? It could be. Dark matter, our universe, would be ordinary, its gravitational effect. So why isn't that dark matter? It could be. Dark matter, our universe, would be ordinary matter in a parallel universe

that's leaking into ours, and we're mysteriously inventing stuff to account for it, when in fact it's just ordinary matter. I think that's a conceivable idea, that it could be matter on the other side, another brain and another membrane that's a small distance away. It couldn't be like our matter, because if it were, it would also, when it gravitationally clumped, it would produce radiation, and that radiation would affect us as well in a way that we know there aren't those sources of radiation there. And the dark matter, one of the things about dark matter compared to ordinary matter is ordinary matter collapses to form stars and stick together and stick together and sits in a halo of

very diffuse dark matter if this dark matter were like us but on the other side it would also collapse and it wouldn't form the halo which we know of dark matter that we observe that we infer from measures and there's another little fact here a gravity drops off as one over distance squared But if you're feeling gravity from another universe that's gravity permeating through another dimension Yes, and then that therefore gravity from another universe would have to drop off faster than one over R squared Okay, so little but ever so little As as of course the foremost authority on this in the room, let me just say, what the hell are you talking about? It's time for commercial break.

You lost me until one over the other gravity thing there. If you're spilling out and you've got to go through another dimension for it to be felt, then your equations have to somehow recognize that fact. I got you. The dilution of gravity as you get so in other words gravity The surface area of a sphere as it grows up You're thinning out whatever the fabric was by the the square of the distance so I got a sphere That's three times bigger so cuz the sphere is expanding as nine times the area And so you see so it's thin it whatever was there before is now One ninth is that so gravity thins out at that rate? Okay?

Okay, but now that makes sense of gravity even a single I'm thinking of this as a blowing up balloon Okay, if you want to think right out into a whole other dimension and that equation can't just be 1 over R squared Gotcha now that makes them let me just go Paul was I okay with that? Okay, all right. I get that for those of you listening at home, you're welcome. When StarTalk comes back, more on the anatomy of the multiverse. We're back on StarTalk, and I'm here with Chuck Nice. Sir. And an old friend and colleague of mine from my Princeton days, Paul Steinhardt, professor of physics.

And lord of the Phoenix universe. So, Paul, does your chair have an endowed name to it? It does. What is that? It's called the Albert Einstein Professorship in Science. Excuse the hell out of me. That's pretty rough, man. Okay, I'm thinking it was some name,

some rich guy that just gave money. No, the Albert Einstein professorship. So do you realize you could only be a disappointment? Yes, absolutely. That's the price. Oh, man, that's just so raw. I know. I just thought of that's just so raw. I know. I just thought of that in that moment.

I'm sorry. That's funny. So, Chuck, we're Cosmic Queries. What else do you have? Yes, let's move on. Multiverse Cosmic Queries. Multiverse we are talking about. This is somewhat in that range, but Michael Ranger from Twitter says this. Reality is

granular. I love how people put their own little stuff. Let them do it. How then can, say, the Earth's gravity reach infinitely far? Wouldn't it eventually wink out? Ooh.

So let me recast that question. Yeah, it's a good question. In a quantum construct of the universe You cannot get arbitrarily small things You cannot have arbitrarily short time intervals Because there's a quantum size that limits it Do we agree? Okay So if you have gravity dropping off ever so slowly One over r squared size that limits it. Do we agree? Okay.

So, if you have gravity dropping off ever so slowly, 1 over r squared, and that means r gets bigger and bigger, gravity gets smaller and smaller, but there's always something there. You can always calculate how much is there. Is there some calculation where the gravity is so low, it goes from some quantum higher level to app to zero Did I say that did I make sense in that question was that a fair interpreter that's a fair interpretation Okay, I'm sure if you were talking about time or space though you're talking about just gravity this gravity as we go Out away from the gravity go away away from Earth, so it's Earth's gravity right right right right, you know

It's you know just like It's like cleaning up broken glass. There's like a gazillion pieces that you'll never get at all, but eventually there's the last piece of glass you've cleaned, and there's no more glass left, even though it felt infinite at the time. So is there a last piece of gravity that Earth is expressing into the universe? I'll give you one interpretation of that question and see if that will help answer it. So it's important to appreciate

that the Earth hasn't always existed. It came into existence. So before it came into existence, there was no gravitational field associated with it. There was matter that was going to eventually come together to form the Earth. So if you go far enough out in space,

you would not know that the Earth was about to form. Wait, wait, wait. I've got to wrap my head around that. So Earth is about 4.5 billion years old. If you go 4.5 billion light years away, there's a point where Earth had not yet assembled from the void.

Yes, if you were looking from that vantage point. You even have a field of gravity to measure. Man, okay. I'm telling you right now, there are people listening to this and they're just like, I am never doing drugs again. This is so crazy. I'm never doing drugs again. This is so crazy.

I'm never doing drugs again. So you're out there. They're just going to do cosmology. Yeah, exactly. You don't need drugs when you got this. You really don't. I mean, that's freaking crazy. Take up cosmology.

Just take up cosmology, people. I'm telling you right now. So what you're saying is you could be there and you would watch the formation of a source of gravity in front of you. Even though it's too far away to see, you would feel, you'd measure this gravity arise. Yes. So it'd be like throwing a rock in a puddle and eventually the wave is going to meet you, is going to reach out to you. And eventually the wave is going to meet you, is going to reach out to you,

and then you'd be aware that a rock, if you weren't using your eyes, you're just feeling the water, you'd be aware that something happened. Except the rock hitting the puddle was a spontaneous thing. Yes. Because the assembly of the earth was slower and piecemeal. That's right. Okay. So that's an awesome reply, but I think it still avoids the question. Yes.

Is there a point where the gravity of something, quantum drops to, the strength of gravity of something, quantum drops to zero from some quantum level above it? When I say quantum, I don't even mean quantum physics so much as can it smoothly go to zero asymptotically or not? That's really the question um you could say i don't know yeah i was gonna say that even though you're a princeton professor you say you know i don't know well the question could mean i'm more confused because the question could mean various things so let me mention another issue which is there in the by the way let me just say uh i am glad that right now you guys are not two surgeons trying to figure out how we

should approach this open-heart situation. What is that wiggly thing? Should we take it out or leave it in? Go ahead. Let's use a paper stone and find out. Right, it's a paper stone. So go ahead. As you can see, there is a deep puzzle, which is if you buy this idea that the universe began from a quantum beginning, rather than a bounce,

one of the puzzles there is, how do you go from a quantum world to a world which is described by your 1 over r squared force and by the laws of general relativity? How do we go from quantum to classical? And at this point, what proponents do is simply wave their hands and said, something must do it. And so we'll just, you know, sometimes we work on one side of this something,

sometimes on the other. But exactly how that occurred is a mystery and is another reason to be suspicious of this setup of a Big Bang leading to a classical expansion. Okay.

Yeah, Michael, here's the deal. We didn't answer your question at all. No, no, no. Here's what I say. We turned it into a better question. Actually, that's what really happened. We turned your question into a better question.

Or a question we could answer. Right, there you go. Here we go. Maria Simon from Facebook would like to know, Dr. Tyson, would our perception of time be the same throughout the multiverse? Thanks. I can't wait to see you live

on Monday. Where are you going on Monday? I have no idea where this child is. Oh no, actually I'm in the Pacific Northwest. We're doing some public talks. So, I'm actually, I'm in the Pacific Northwest. Okay. Some public talks. All right. Okay. So I'm sorry. What was the question? So she's talking about the perception of time. Oh, yeah. Is that going to be consistent? Okay. So Paul, we know from relativity that the passage of time is relative to an observer. Yes. So other than that, which we're kind of, we live with, we live with, in fact, daily, you

realize the GPS satellites at their elevation above Earth experience a different strength of Earth's gravity than we do here. And Einstein's general theory of relativity prescribes the difference in the rate at which its clocks tick compared with ours. And so what that means is when it is telling us what time it is, we have pre-corrected the change in its time because of Einstein's general theory of relativity so that we all have the same time here on Earth's surface. Gotcha. The same time as one another. No, that makes sense. It's a general relativity at work. Right. The same time as one another. No, that makes sense.

It's a general relativity at work. Right. At work. Okay, so, Paul, so we got this. Yes. But if you go to another one of your multiverse pockets, could just time have a whole other kind of thing going on? What about it?

Well, certainly there would be no way to synchronize it compared to our time. So, for example, patches would be born at different times. So the period, the time that would have transpired since the creation of our patch to reach a point where there's Earth and people would be different maybe in this other patch.

It might have just been born. So their calendar would be BP for before patch. Yes. Okay. So go calendar would be BP for before patch. Yes. So it would be simply no way to correlate our time. So unlike the case of the satellite where we can send signals back and forth to the earth to synchronize and to make this correction

and only by having that communication. Because we can't communicate with one another, there's no meaningful way to synchronize our clocks. But in the quantum fluctuations of these patches, could time mean something different there? Could a quantum fluctuation change what time is? Conceivably. It's not part of the usual multiverse picture. It's rather conventional in that sense that the patches would more or less have normal space and time like we think about here. Although some of them could be, in some cases, the space could be, space-time could be so warped that time could never lose its quantumness. It might remain quantum and have no classical meaning in some patches. That's conceivable. That's a kind of

version of what you're asking. I like that. So time would just not be even a thing. It may not even be. Yeah, right. They could figure out some other way to meet you at the corner. They put it in a bottle. They couldn't meet you at the corner because space wouldn't have a meaning either.

So the corner would... The corner wouldn't be there either. Yeah, right. We got time just for a quick lightning round. Okay, let's do it. All right, all right. Here we go, here we go.

Sound bite answers. Jonathan Nagy, Jonathan Nagy from Twitter wants to know this. Will quantum gravity mean GR is incorrect since QFT is based on flat space time and GR is a curvature? He's just showing off.

Paul, what's the answer to that? Yes. Yes. Okay. Next question. Gabriel from Twitter wants to know this. What, if anything, is stopping gravity waves from traveling faster than the speed of light? Yeah, Paul. That's a of light. Yeah, Paul.

That's a good idea. Yeah, yeah. Well, relativity. Okay, good. Dang. You are really good at this part. I got to tell you. Okay, we got to take it as an answer because this is the lightning round.

Not a good answer, but just an answer. By the way, Gabriel, look it up. In other words, relativity does not allow anything to go faster than light, therefore gravity waves are not traveling faster than light, even though they be gravity and not light. That's right. Okay, good. You got it. Good. All right. Datons

on Twitter says this. Can a telescope be made to see so far that it sees the Big Bang? What is the limit of telescopes, including the ones that we launch into space? Because light takes time to move from one location to another, it means as you look out in space, you see things not as they are, but as they once were. And as you just take that far enough back, yes, in principle, you can see the birth of

the universe, provided that there is matter out there that is as old as the universe. Okay. So now the reason why we have any evidence of the Big Bang at all is because we have this expanding horizon that is washing over parts of the whole universe that was born 13.8 billion years ago. Here's what would scare the daylights out of me. Go ahead. If all of a sudden the cosmic microwave background began to disappear, it would mean that our cosmic horizon would be entering a region of our universe where there is no longer any

matter. We'd reach the physical edge of our universe. And then that wave is coming our way. No, then there would be no cosmology because we would have no information about what happened in the past. That's why we can see the Big Bang at all. Okay.

You've been listening and possibly watching StarTalk, the Cosmic Queries edition on the multiverse. Let me thank my friend and colleague Paul Steinhardt from Princeton University. Chuck Nice. Yes. I think we're having fun. Got my name there, huh?

I was thinking of Chuck Norris. That's a common, common confusion. All right. My name is Neil Tyson, and as always, I bid you to keep looking up.