Cosmic Queries: The Multiverse

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.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:01Neil deGrasse Tyson?

  Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now.

• 0:22Neil deGrasse Tyson?

  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.

• 1:05Chuck Nice?

  Chuck? Hey Neil.

• 1:07Neil deGrasse Tyson?

  You're gonna help me get through this.

• 1:08Chuck Nice?

  That's right, I have the questions right in my very hands.

• 1:09Neil deGrasse Tyson?

  Solicited from...

• 1:10Chuck Nice?

  All over the internet, wherever our fans may be found.

• 1:15Neil deGrasse Tyson?

  Maybe...

• 1:16Chuck Nice?

  Their inquisitive little minds want to know all sorts of things.

• 1:18Neil deGrasse Tyson?

  And I needed 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?

• 1:30Speaker 02

  Hi.

• 1:31Neil deGrasse Tyson?

  Welcome to StarTalk.

• 1:32Speaker 02

  Well, thank you, thank you for having me.

• 1:33Neil deGrasse Tyson?

  Professor of Physics, Princeton University.

• 1:34Speaker 02

  Yes.

• 1:35Neil deGrasse Tyson?

  And you are a proponent of one of the multiverses that people have been talking about.

• 1:42Speaker 02

  Well, I'm not sure I would put it quite that way, but I'm actually a proponent of alternatives to the multiverse.

• 1:49Neil deGrasse Tyson?

  Oh!

• 1:50Chuck Nice?

  Really?

• 1:51Speaker 02

  So I'm not a big fan of the multiverse.

• 1:53Neil deGrasse Tyson?

  Really? Oh, okay.

• 1:55Chuck Nice?

  Why not? What did the multiverse do to you?

• 1:59Speaker 02

  The multiverse destroyed one of my favorite ideas.

• 2:02Neil deGrasse Tyson?

  Oh, oh, so, oh.

• 2:04Speaker 02

  So it's a problem.

• 2:05Neil deGrasse Tyson?

  Oh, problem for you.

• 2:07Speaker 02

  Problem for me, yeah.

• 2:08Neil deGrasse Tyson?

  Okay, so what was your idea that the multiverse destroyed?

• 2:11Speaker 02

  Uh, well, it's an idea that we call cosmic inflation.

• 2:14Neil deGrasse Tyson?

  Mm-hmm.

• 2:15Speaker 02

  Uh, so, uh, 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-

• 2:27Neil deGrasse Tyson?

  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 kinda looks like that.

• 2:35Speaker 02

  That's right, so-

• 2:35Neil deGrasse Tyson?

  And you're saying it shouldn't look like that?

• 2:37Speaker 02

  Well, a- according to our initial idea of the big bang, the universe should have emerged from some random quantum state and been very, uh, 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.

• 2:59Neil deGrasse Tyson?

  Like an area where there's tremendous amount of matter and other areas where there's hardly anything, and, and bizarre, uh, curvatures of the spacetime continuum.

• 3:08Speaker 02

  Yes.

• 3:08Chuck Nice?

  Like a fire.

• 3:09Speaker 02

  Yeah.

• 3:10Chuck Nice?

  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 area, but it wouldn't be like a very uniform-

• 3:21Neil deGrasse Tyson?

  Okay, I hadn't thought of using fire, but yeah, I guess a room would not burn uniformly-

• 3:26Chuck Nice?

  Right.

• 3:26Neil deGrasse Tyson?

  Because some things in the room are more flammable than others.

• 3:28Chuck Nice?

  Flammable than others, so, yeah.

• 3:29Speaker 02

  Yeah.

• 3:31Chuck Nice?

  Let me tell you something, you have no idea-

• 3:33Neil deGrasse Tyson?

  I just bailed you out of that.

• 3:34Chuck Nice?

  No, no, 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."

• 3:44Neil deGrasse Tyson?

  All right, we're trying to come, wrap our heads around this, okay, continue, Paul.

• 3:47Speaker 02

  So, so we thought that the idea for solving this problem was to have a period of very rapid acceleration, uh, 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, instead you would stretch it at such a space, at such a fast rate, that the matter and radiation would all, that existed before, would all be spread out, dissipated. All you'd have left is the energy that would be driving this expansion, this super-expansion, and then when that energy decayed into ordinary matter and radiation that we see today- Because it had made the

• 4:24Neil deGrasse Tyson?

  Matter and energy are one and the same. E equals MC squared tells us that.

• 4:27Speaker 02

  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.

• 4:38Neil deGrasse Tyson?

  Mm-hmm.

• 4:38Speaker 02

  Um, so that was the initial idea. That seemed to be a sweet idea for explaining how you would get this.

• 4:44Neil deGrasse Tyson?

  Universe we see.

• 4:45Speaker 02

  Universe we see, which is, has this peculiar and unexpected uniformity.

• 4:50Neil deGrasse Tyson?

  Okay.

• 4:50Speaker 02

  So, um, then we came up with another, uh, added idea to this, which is, uh, in this description I just gave you, I didn't include anything about quantum physics.

• 5:00Neil deGrasse Tyson?

  Mm-hmm.

• 5:00Speaker 02

  Uh, so I said, it, uh, just stretching the universe would make it uniform. But quantum physics resists uniformity. It produces fluctuations, random fluctuations that, that, 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 uni- universe with a, a specific non-uniformity in the distribution of matter.

• 5:27Neil deGrasse Tyson?

  You can predict.

• 5:28Speaker 02

  That you, that we thought we could predict.

• 5:29Neil deGrasse Tyson?

  Mm-hmm.

• 5:30Speaker 02

  Okay, it seemed to be predictive. It seemed to be something you could work out on the back of an envelope. Um.

• 5:36Neil deGrasse Tyson?

  That you could work out on the back of an envelope.

• 5:39Speaker 02

  That some of us worked out on the back of it.

• 5:40Neil deGrasse Tyson?

  Me and my supercomputer equals you in the back of your envelope, okay?

• 5:44Speaker 02

  But the, um, uh, uh, and, and, and curiously enough, those naive predictions

• 5:50Neil deGrasse Tyson?

  Uh-huh.

• 5:50Speaker 02

  agree with what we've observed when we actually look out in space with a pattern of unevenness that existed in the early universe.

• 5:57Neil deGrasse Tyson?

  It's, uh, it's not as uneven as it might have otherwise been.

• 6:00Speaker 02

  Yeah.

• 6:00Neil deGrasse Tyson?

  But it has the right amount of unevenness that's consistent with the hypotheses.

• 6:04Speaker 02

  This na- with this naive calculation.

• 6:06Neil deGrasse Tyson?

  So, so what's wrong?

• 6:07Speaker 02

  Okay.

• 6:07Neil deGrasse Tyson?

  What's the problem?

• 6:08Speaker 02

  Well, there are a couple of things wrong with this idea, as we've discovered. Um, the first is that, um, it had 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. And so you could begin with a very random, uh, uneven state and start the inflation.

• 6:31Neil deGrasse Tyson?

  Would tune inflation to occur when you needed it to match the universe that we know.

• 6:34Speaker 02

  Yes, but you also need to start the inflation. It needs to ignite if you've somehow.

• 6:40Neil deGrasse Tyson?

  You can chuck analogy to flames, yes.

• 6:42Speaker 02

  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.

• 6:57Chuck Nice?

  Okay, I am very interested.

• 7:00Speaker 02

  I thought you might be.

• 7:01Chuck Nice?

  I'm taking notes.

• 7:02Speaker 02

  Okay, so I have a theory of how to become a billionaire. And I show you a little part of my theory, which it 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."

• 7:28Chuck Nice?

  So basically, this is Trump University. Okay, alright.

• 7:32Neil deGrasse Tyson?

  How to become a billionaire, start with a billion dollars.

• 7:34Speaker 02

  Right, well, this is essentially what happened in the story of inflation. We thought originally just simply stretching the universe would be easy, an easy start. But we discovered actually only under very rare conditions, essentially the conditions you needed. You needed to start with the universe which was already smooth enough and unworped 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."

• 7:59Neil deGrasse Tyson?

  Okay.

• 8:00Speaker 02

  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.

• 8:11Neil deGrasse Tyson?

  You're all such idiots, you can't.

• 8:15Neil deGrasse Tyson?

  I'm telling these early universe guys, you've been 30 years now, I'm waiting.

• 8:19Speaker 02

  Still waiting.

• 8:20Neil deGrasse Tyson?

  Yeah, is it because the problem is hard or because you all just aren't smart enough?

• 8:23Speaker 02

  Um, it's because probably it's actually not a good way of smoothing the universe out.

• 8:28Neil deGrasse Tyson?

  Okay.

• 8:29Speaker 02

  I would say. It's probably not a good, it's probably not a good book that I gave you for the billionaire.

• 8:35Neil deGrasse Tyson?

  Right, recipe.

• 8:37Speaker 02

  Um, 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, but, uh, 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.

• 9:21Speaker 02

  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. Patches of it will end inflation, but patches of it will continue.

• 9:47Neil deGrasse Tyson?

  Patches within it.

• 9:48Speaker 02

  Within it.

• 9:49Neil deGrasse Tyson?

  Yeah.

• 9:50Speaker 02

  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.

• 9:57Neil deGrasse Tyson?

  We don't see these patches.

• 9:59Speaker 02

  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.

• 10:06Neil deGrasse Tyson?

  I know, but looking around, we don't see such non-uniformity in the universe.

• 10:09Speaker 02

  The only thing, yeah, we see, we see uniformity. We don't see any evidence.

• 10:12Neil deGrasse Tyson?

  Unless our entire universe is one of these patches.

• 10:15Speaker 02

  Which is the, which is the concept of multiverse.

• 10:18Chuck Nice?

  Now we get it!

• 10:20Speaker 02

  But, but...

• 10:21Neil deGrasse Tyson?

  So that's one kind of multiverse.

• 10:23Speaker 02

  But that is one patch of the multiverse.

• 10:25Chuck Nice?

  Right.

• 10:26Speaker 02

  And that is, but the problem is that, so...

• 10:28Neil deGrasse Tyson?

  Just to be clear, this is not a universe in some other dimension.

• 10:32Chuck Nice?

  No, no, no, this is all one universe.

• 10:34Neil deGrasse Tyson?

  It's an area.

• 10:35Chuck Nice?

  An area.

• 10:36Neil deGrasse Tyson?

  Volume, whatever, in a meta-universe, and we're thinking it's our own, it's our thing.

• 10:43Speaker 02

  Right.

• 10:44Chuck Nice?

  That is fascinating!

• 10:45Speaker 02

  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.

• 10:55Chuck Nice?

  Right.

• 10:56Speaker 02

  Due to...

• 10:57Chuck Nice?

  Quantum fluctuations.

• 10:58Speaker 02

  Exactly.

• 10:59Chuck Nice?

  Quantum fluctuations would cause different properties in that little patch.

• 11:01Neil deGrasse Tyson?

  That means you can actually travel within this universe from one patch to another, and then experience different, slightly different laws of physics.

• 11:11Speaker 02

  Too bad. Not.

• 11:13Neil deGrasse Tyson?

  Okay, why not?

• 11:14Speaker 02

  And the reason is because the space between these patches is growing so fast, it's continuing to inflate, that light, either you in a rocket nor a light could make up the difference.

• 11:25Neil deGrasse Tyson?

  Okay, so we can't overcome the expanding boundaries between us?

• 11:29Speaker 02

  Yes.

• 11:29Chuck Nice?

  You can't beat the expansion.

• 11:31Speaker 02

  Right.

• 11:31Chuck Nice?

  You can never get ahead of that expansion.

• 11:33Speaker 02

  Right.

• 11:33Chuck Nice?

  So you're never gonna reach that patch.

• 11:35Speaker 02

  Right.

• 11:35Neil deGrasse Tyson?

  Okay.

• 11:36Chuck Nice?

  Wow!

• 11:36Speaker 02

  So it's completely, it's there in this idea.

• 11:39Neil deGrasse Tyson?

  That's good though, because you don't wanna wander into a place that has slightly different laws of physics.

• 11:43Speaker 02

  Yeah, for example, where all the molecules in our body would decay into radiation, that wouldn't be a good news.

• 11:49Chuck Nice?

  Yeah, that would be cool. Or perhaps I show up in the wrong outfit.

• 11:52Neil deGrasse Tyson?

  That's right.

• 11:53Chuck Nice?

  And that would be disastrous.

• 11:55Speaker 02

  Perhaps.

• 11:56Chuck Nice?

  I believe this is black tie, sir. Okay.

• 12:00Neil deGrasse Tyson?

  So Paul, how would you ever test this?

• 12:02Speaker 02

  Um, 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.

• 12:17Neil deGrasse Tyson?

  So the patch that has a slightly different law of physics will have patches that are slightly different from it.

• 12:21Speaker 02

  Yes.

• 12:21Neil deGrasse Tyson?

  Which will have patches slightly different from it.

• 12:23Speaker 02

  Right.

• 12:24Chuck Nice?

  Wow!

• 12:25Speaker 02

  So it's a theory which-

• 12:26Neil deGrasse Tyson?

  Well, you're freaking us out here.

• 12:27Chuck Nice?

  That is frickin' crazy, man!

• 12:29Speaker 02

  Well, I think it is. Because our goal was to explain why the universe is the way it is, and we haven't-

• 12:37Neil deGrasse Tyson?

  But our heads are exploding, but your head exploded long ago when you first did it. Now you're just cool with it.

• 12:41Speaker 02

  That's right.

• 12:42Chuck Nice?

  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 say, the meta-universe.

• 12:53Neil deGrasse Tyson?

  One expansion of a thing.

• 12:54Chuck Nice?

  Whereas our, 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, it's, this is like whirlpools in a giant lake.

• 13:10Speaker 02

  Yes.

• 13:10Chuck Nice?

  Yeah, that's amazing.

• 13:12Speaker 02

  Connected, a connected fabric of space.

• 13:13Neil deGrasse Tyson?

  Yes, okay, yeah, let's, let's get into it.

• 13:17Chuck Nice?

  Yeah, let's get into it, okay, yes.

• 13:19Neil deGrasse Tyson?

  And we'll still, we're not done with you here.

• 13:21Speaker 02

  No, I know.

• 13:21Chuck Nice?

  Wow!

• 13:23Neil deGrasse Tyson?

  All right, Chuck, what do you have?

• 13:24Chuck Nice?

  Here we go, of course, we always start our queries with a Patreon, patron.

• 13:29Neil deGrasse Tyson?

  Are these people who paid to get their question first?

• 13:31Chuck Nice?

  Yes, because-

• 13:32Neil deGrasse Tyson?

  Is that even fair?

• 13:33Chuck Nice?

  Listen.

• 13:36Chuck Nice?

  Life is not fair.

• 13:38Neil deGrasse Tyson?

  Okay, fine.

• 13:39Chuck Nice?

  That's all we know. Life is not fair.

• 13:40Neil deGrasse Tyson?

  These are supporters of the show.

• 13:42Chuck Nice?

  These people support the show, and so we support them back by giving them preferential treatment.

• 13:46Neil deGrasse Tyson?

  Mutual back scratching.

• 13:46Chuck Nice?

  There you go. Same reason why my parents like me better than my siblings.

• 13:52Neil deGrasse Tyson?

  I'm not even going there.

• 13:52Chuck Nice?

  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 Harworth, New Jersey."

• 14:14Neil deGrasse Tyson?

  Yeah, so Paul, how interconnected is a theory of everything to what's going on on the frontier of multiverse thought?

• 14:22Speaker 02

  Um, well, um, 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.

• 14:39Neil deGrasse Tyson?

  See, only cosmologists get to sound like God. Well, this is how, we're gonna make the universe this way, this time.

• 14:44Chuck Nice?

  Exactly. Right.

• 14:46Neil deGrasse Tyson?

  The power that they wield. Alright, go on, go on, yeah?

• 14:49Speaker 02

  So, so the question is, so the idea is that at some point there was nothing? No space, no time, no matter, no energy?

• 14:56Chuck Nice?

  That's the presumption.

• 14:57Speaker 02

  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 instances later, uh, 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?

• 15:25Chuck Nice?

  Let's go to the tape.

• 15:27Neil deGrasse Tyson?

  Go to the videotape. That reminds me, you know, the Sid Harris cartoon where the two physicists at the chalkboard, and it's filled with equations, and then at the end, in 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."

• 15:46Speaker 02

  That's the theory of everything.

• 15:49Speaker 02

  So that's what we're looking for. Okay, 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.

• 16:06Chuck Nice?

  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 that try to explain that's how everything started, and that this just goes over and over again.

• 16:25Speaker 02

  Well, so the idea of this creation idea, of this big bang, the traditional big bang idea, is that there would have been no matter.

• 16:31Chuck Nice?

  Right.

• 16:32Speaker 02

  There would have been no space for matter to even exist in, so matter already presumes a notion that exists in some space background.

• 16:39Chuck Nice?

  Stupid. No, what the hell was I thinking? Chuck! Chuck, you idiot!

• 16:46Speaker 02

  But, let me say, but we don't know that this creation idea is right.

• 16:51Chuck Nice?

  Right.

• 16:51Speaker 02

  So there are some of us, and... Yourself included. 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.

• 17:12Chuck Nice?

  That's what I was trying to say.

• 17:13Speaker 02

  Yeah, so there's your eternality, at least of space.

• 17:16Chuck Nice?

  At least of space.

• 17:17Speaker 02

  And what do you call this idea? The big bounce is one, is just describing this event. I like that, two syllables, yeah. 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...

• 17:33Chuck Nice?

  It bounces a little better, okay.

• 17:35Speaker 02

  If you, if you are into your Greek, one version of that is called an epirotic universe, another version of it's called...

• 17:42Chuck Nice?

  Worst name ever.

• 17:44Speaker 02

  Thank you, thank you.

• 17:45Chuck Nice?

  Epirotic universe, oh, who wants to live there?

• 17:48Speaker 02

  We might. Rolls off the tongue.

• 17:50Chuck Nice?

  Right, exactly. Oh, by the way, once you get done with the epirotic universe, why don't you make your way over to the enema universe?

• 17:57Speaker 02

  So epirotic 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 ecperiodic universe.

• 18:15Chuck Nice?

  Let's go with phoenix universe, maybe?

• 18:18Speaker 02

  I, we, phoenix is another version of this.

• 18:20Neil deGrasse Tyson?

  Otherwise, you're, you're just showing off that you know Greek and obfuscating what...

• 18:25Speaker 02

  Fair enough.

• 18:26Neil deGrasse Tyson?

  We're gonna take a quick break.

• 18:29Chuck Nice?

  Okay.

• 18:29Neil deGrasse Tyson?

  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 Cosmic Queries. Today's topic, the multiverse. Topic I would not dare tackle on my own, so I brought in Chuck Nice.

• 18:56Chuck Nice?

  Of course Chuck knows everything about the multiverse. Right.

• 19:01Neil deGrasse Tyson?

  Chuck is reading questions from you, our fanbase, and I brought in Paul Steinhardt, Princeton University professor of physics.

• 19:10Chuck Nice?

  Yes, and it's been a fascinating conversation thus far.

• 19:12Neil deGrasse Tyson?

  And he's been doing some thinking of his own on the multiverse. So, a quick question. Your ecperiodic universe, which is repeating, bouncing, you remove the need for singularity, is that correct?

• 19:27Speaker 02

  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 latest, most recent cycle.

• 19:37Neil deGrasse Tyson?

  I'm gonna 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?

• 19:47Speaker 02

  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...

• 19:56Chuck Nice?

  You took out a hit on the multiverse. The multiverse got two in the back of the head.

• 20:02Speaker 02

  That's right.

• 20:02Chuck Nice?

  And then Paul went, "Leave the gun, take the cannoli."

• 20:09Neil deGrasse Tyson?

  Damn.

• 20:09Chuck Nice?

  Wow, that's pretty wild.

• 20:11Speaker 02

  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. 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 that we, instead of getting a smooth universe we expected to get, we got this patchy universe which every outcome is possible.

• 20:36Neil deGrasse Tyson?

  So I just want to, I 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 spacetime.

• 20:54Speaker 02

  Yes.

• 20:54Neil deGrasse Tyson?

  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.

• 21:03Speaker 02

  Yeah.

• 21:03Neil deGrasse Tyson?

  Okay.

• 21:04Chuck Nice?

  That's, that is really just

• 21:06Neil deGrasse Tyson?

  Yes, it's mind blowing.

• 21:07Chuck Nice?

  Incredibly mind blowing concept.

• 21:09Neil deGrasse Tyson?

  What are the questions you got?

• 21:10Chuck Nice?

  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. Um, what's new? And what can be explained about this?

• 21:46Neil deGrasse Tyson?

  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,

• 22:03Speaker 02

  Yes.

• 22:04Neil deGrasse Tyson?

  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 tunnelled there, it got there faster than the speed of light. Isn't that correct?

• 22:16Speaker 02

  Um.

• 22:17Neil deGrasse Tyson?

  Is that the wrong way to think about it?

• 22:18Speaker 02

  I think it's the wrong way to think about it.

• 22:20Neil deGrasse Tyson?

  Right.

• 22:20Speaker 02

  I think there's a, a period of time during which its location is uncertain.

• 22:25Neil deGrasse Tyson?

  Mm-hmm.

• 22:25Speaker 02

  And i- if you, uh, account for that, that lost time, that's the time it would take for, uh, that would be longer time it would take for, or equal to the time it'd 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 would, that period of uncertainty would account for the light travel time.

• 22:51Neil deGrasse Tyson?

  Okay, now the period where you're not watching, that's a necessary-

• 22:54Speaker 02

  Or can't see it.

• 22:54Neil deGrasse Tyson?

  Yeah, that's a necessary part of this phenomenon.

• 22:57Speaker 02

  Yes.

• 22:57Neil deGrasse Tyson?

  Right.

• 22:58Speaker 02

  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.

• 23:05Neil deGrasse Tyson?

  Mm-hmm.

• 23:06Speaker 02

  And you'd say, "Oh, the reason why it went from here to here is because I kicked it."

• 23:09Chuck Nice?

  Was light, right.

• 23:09Speaker 02

  Yeah, yeah.

• 23:10Chuck Nice?

  Used the light.

• 23:10Speaker 02

  So it's important that you don't look. Okay?

• 23:12Chuck Nice?

  (laughing).

• 23:14Speaker 02

  Because then you're, you're not studying the tunneling phenomenon.

• 23:17Chuck Nice?

  Well, that's like the old joke, uh, "I, I, I know how to teleport." And they say, "Prove it." And you say, "Okay, I'm gonna go to San Francisco right now." "I'm back."

• 23:27Neil deGrasse Tyson?

  Okay.

• 23:27Chuck Nice?

  You know what I mean? That's, yeah.

• 23:29Speaker 02

  It works.

• 23:30Chuck Nice?

  (laughing). It works.

• 23:34Speaker 02

  I can't just prove it.

• 23:35Neil deGrasse Tyson?

  Okay, so just, I mean, you said something fun and, and deep, as you have been doing in this time that you've been sharing with us, that, uh, 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, in this scenario.

• 24:00Speaker 02

  Or kicks it out, or-

• 24:01Neil deGrasse Tyson?

  Or kicks it, you look at it, it kicks it out.

• 24:02Speaker 02

  Interact with it, now you're studying a different effect.

• 24:05Neil deGrasse Tyson?

  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-

• 24:24Neil deGrasse Tyson?

  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.

• 24:31Speaker 02

  Yes.

• 24:31Neil deGrasse Tyson?

  Okay.

• 24:32Chuck Nice?

  Wow, okay.

• 24:33Neil deGrasse Tyson?

  Yeah.

• 24:34Chuck Nice?

  That's pretty awesome.

• 24:34Neil deGrasse Tyson?

  So the act of trying to measure it changes what you're trying to measure.

• 24:37Chuck Nice?

  Right, you can't measure it because once you pull out whatever it is you're measuring, that actually affects it.

• 24:44Neil deGrasse Tyson?

  Right, 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, it's the act of measurement is a, is a thing, whether or not the human is doing it. You have to have a machine.

• 24:57Chuck Nice?

  Right.

• 24:58Neil deGrasse Tyson?

  Whatever, doesn't matter.

• 24:59Speaker 02

  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. This case, it's a decay of inflationary energy into matter and radiation that's occurring randomly due to quantum effects. And the, and the fact that it's random and sometimes produces a huge expansion is all part and parcel of this quantum uncertainty, randomness.

• 25:26Chuck Nice?

  Gotcha.

• 25:27Neil deGrasse Tyson?

  Quantum is some badass stuff.

• 25:28Chuck Nice?

  Let me tell you, it's, it's crazy. It's a powerful thing, yeah, and the fact is that, uh, I'm gonna be very honest, I don't understand any of it.

• 25:35Neil deGrasse Tyson?

  That's funny.

• 25:37Chuck Nice?

  Okay, I'm just letting you know.

• 25:38Neil deGrasse Tyson?

  No, but, but you don't have to, by the way, by the way.

• 25:40Chuck Nice?

  I mean, I understand what you're saying.

• 25:41Neil deGrasse Tyson?

  Paul, who's it said, was it Feynman? So one of the, one of the greats of yesteryear said, "The day you say you understand quantum physics is the guarantee that you do not."

• 25:51Speaker 02

  Probably so, yeah.

• 25:52Neil deGrasse Tyson?

  Because it's, it's not something to understand, it just is.

• 25:55Chuck Nice?

  Oh, right, okay. Well, then I feel much better.

• 25:58Neil deGrasse Tyson?

  No, you just, no, no, we, we were freaking out. We are, our, our historical brethren who discovered this, that they, they were freaking out just like you are right now.

• 26:07Chuck Nice?

  Right.

• 26:07Neil deGrasse Tyson?

  Oh my god, a particle, a wave, why, who, what? Einstein said, "God does not play dice." And people were freaking out, even Einstein. So you in good company, Chuck.

• 26:15Speaker 02

  Even today, even today, people still, 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...

• 26:24Neil deGrasse Tyson?

  It just, it just is.

• 26:25Chuck Nice?

  This is it.

• 26:25Speaker 02

  Shut up and compute.

• 26:26Neil deGrasse Tyson?

  Compute, exactly, I'm in that, 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. Uh, 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.

• 26:52Speaker 02

  Yeah.

• 26:52Neil deGrasse Tyson?

  It's only when it became useful for the IT revolution and

• 26:55Speaker 02

  Right.

• 26:55Neil deGrasse Tyson?

  our entire creation, storage and retrieval of information has anyone been able to fully appreciate what came out of that era.

• 27:02Speaker 02

  Yeah.

• 27:03Chuck Nice?

  That's pretty low.

• 27:03Neil deGrasse Tyson?

  The transistor too, you needed.

• 27:04Speaker 02

  And partially, 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, yeah, what it meant and what point it was convincingly true.

• 27:16Neil deGrasse Tyson?

  So the point is, as a, as a professional physicist, you, 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, the rules of quantum physics.

• 27:33Speaker 02

  You have to.

• 27:34Neil deGrasse Tyson?

  To now affect the entire universe.

• 27:36Speaker 02

  Right.

• 27:36Chuck Nice?

  Wow.

• 27:37Speaker 02

  And the effects.

• 27:37Chuck Nice?

  Now, that's pretty awesome.

• 27:38Neil deGrasse Tyson?

  The thing about, right, because when the large were small, quantum physics is kicking cosmic butt.

• 27:43Chuck Nice?

  Okay, and you know what?

• 27:44Neil deGrasse Tyson?

  Not just particle butt.

• 27:44Chuck Nice?

  And that's in the Bible, the large shall be small and the small shall be large, so.

• 27:50Neil deGrasse Tyson?

  All right, Chuck, what else you got?

• 27:51Chuck Nice?

  Hey, this is Matt Eli from Facebook, that was a great question that we had, uh, Matt Eli from Facebook, uh, and also from San Antonio, Texas, uh, little more, uh, he 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?

• 28:13Neil deGrasse Tyson?

  Whoa.

• 28:14Chuck Nice?

  He is not the least bit skeptical.

• 28:16Speaker 02

  Good, I like this question.

• 28:18Chuck Nice?

  Yeah, so go ahead.

• 28:19Neil deGrasse Tyson?

  Yeah, it's, it's, you gotta admit, Paul, to assert multiple universes

• 28:24Speaker 02

  Hmm.

• 28:24Neil deGrasse Tyson?

  is extraordinary, and if you're not on the tail, and you're a theorist, last I checked, so you're not even, well, of, of course, good theorists think of how to test

• 28:33Speaker 02

  Yeah.

• 28:33Neil deGrasse Tyson?

  hypotheses, have you? How's that for a setup? Good theorists do this.

• 28:40Chuck Nice?

  Right.

• 28:40Neil deGrasse Tyson?

  Do you, yeah?

• 28:41Speaker 02

  Well, I think I've already sort of played, 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, I, analogy-

• 29:11Neil deGrasse Tyson?

  If it explains everything, then in fact it explains nothing.

• 29:14Speaker 02

  Yes. That's what, that's so, in my view, that makes it no longer a scientifically interesting theory. So it's not testable.

• 29:21Neil deGrasse Tyson?

  Even if it's true, it's just not interesting.

• 29:23Speaker 02

  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 have been in that patch.

• 29:31Neil deGrasse Tyson?

  We live in the patch where both of those are the fact.

• 29:32Speaker 02

  Yeah, that's right.

• 29:33Neil deGrasse Tyson?

  Right, right.

• 29:34Chuck Nice?

  Okay, that makes sense. I mean, yeah.

• 29:35Speaker 02

  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.

• 29:44Neil deGrasse Tyson?

  Unless we're a simulation.

• 29:45Chuck Nice?

  Ooh.

• 29:46Speaker 02

  But even that would be part of the multiverse.

• 29:48Neil deGrasse Tyson?

  Oh, there's the, there's the-

• 29:51Speaker 02

  You can't get away from this, that idea.

• 29:53Neil deGrasse Tyson?

  Oh, man, drats.

• 29:54Speaker 02

  Once you have a bad idea, you can't get away from it.

• 29:57Chuck Nice?

  That's funny.

• 29:58Neil deGrasse Tyson?

  Drats.

• 29:58Chuck Nice?

  All right, so there you have it. Okay. Hey, Matt, nice question.

• 30:03Neil deGrasse Tyson?

  Wait, so you agree that it has, it doesn't really set the standard yet for a testable theory?

• 30:09Speaker 02

  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. So-

• 30:18Neil deGrasse Tyson?

  Well, now, what about, 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-

• 30:32Speaker 02

  Sort of separate fabrics.

• 30:34Neil deGrasse Tyson?

  Separate fabrics, yeah.

• 30:35Speaker 02

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

• 30:54Neil deGrasse Tyson?

  The patchwork multiverse.

• 30:55Speaker 02

  Like a patchwork multiverse in which you wouldn't, in which again, you, everything could possibly, everything that could happen will happen. In which case it has no scientific predictive value. Uh, 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 transported to the other one, imagine doing that, it would look familiar to me. Uh, that's a different story. That's a predictive theory.

• 31:19Chuck Nice?

  That is, right. But the problem is you can't get there, is what you're saying.

• 31:23Speaker 02

  Yeah, and, and so it doesn't have a meaningful scientific value.

• 31:29Neil deGrasse Tyson?

  Well, Paul, could, uh, isn't it true for reasons that I never learned because I never took advanced field theory in graduate school? But my wife did, and, okay, she, she has a PhD in mathematical physics.

• 31:39Chuck Nice?

  I know, I know your wife, and she's smarter than you. I'm just saying.

• 31:47Neil deGrasse Tyson?

  So, but from what I've been told, the, gravity is not contained in the spacetime in which it is formed, in which you have it. So in other words, the, 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.

• 32:08Speaker 02

  Uh, so.

• 32:09Neil deGrasse Tyson?

  Unlike electromagnetic radiation, which is trapped within the spacetime, gravity is not. I've heard that.

• 32:15Speaker 02

  So I think you're referring to theories like in string theory, you have extra dimensions. And where we might live in a, in a membrane-like surface, in which we seem, 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 we, so that, for example, if there were another similar membrane parallel to us. Now, we are thinking about this idea of parallel universes.

• 32:51Chuck Nice?

  This is the parallel.

• 32:52Speaker 02

  Yeah, and something were happening over there, let's say a matter lumped together to form a, a star.

• 32:58Chuck Nice?

  Right.

• 32:59Speaker 02

  Or a black hole or, or something like that, that would be felt, it's gravitational effect.

• 33:03Neil deGrasse Tyson?

  Why isn't that dark matter? 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.

• 33:14Speaker 02

  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.

• 33:33Neil deGrasse Tyson?

  Mm-hmm.

• 33:33Speaker 02

  And that radiation would affect us as well, in a way that we know, 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 dark, ordinary matter collapses to form stars.

• 33:47Neil deGrasse Tyson?

  Can stick together.

• 33:48Speaker 02

  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.

• 33:59Neil deGrasse Tyson?

  Mm-hmm.

• 34:00Speaker 02

  That we infer from measure.

• 34:01Neil deGrasse Tyson?

  And there's another little fact here, a gravity drops off as one over distance squared.

• 34:06Speaker 02

  Mm-hmm.

• 34:06Neil deGrasse Tyson?

  But if you're feeling gravity from another universe, that's gravity permeating through another dimension.

• 34:11Speaker 02

  Yes.

• 34:12Neil deGrasse Tyson?

  And then, therefore, gravity from another universe would have to drop off faster than one over r squared.

• 34:18Speaker 02

  Yeah. Okay, now, ever so little, but ever so little.

• 34:20Chuck Nice?

  No, no, as, as, as of course the foremost authority on this in the room, let me just say, what the hell are you talking about?

• 34:29Neil deGrasse Tyson?

  It's time for commercial break.

• 34:31Chuck Nice?

  You lost me until one over r, the gravity thing there.

• 34:36Neil deGrasse Tyson?

  If you're spilling out and you gotta go through another dimension to, for it to be felt.

• 34:40Chuck Nice?

  Right.

• 34:40Neil deGrasse Tyson?

  Then your equations have to somehow recog- recognize that fact.

• 34:44Chuck Nice?

  I got you.

• 34:45Neil deGrasse Tyson?

  The dilution of gravity as you get, so in other words, gravity, the, the surface area of a sphere, as it grows, you're thinning out whatever the fabric was by the, the square of the distance. So.

• 34:57Chuck Nice?

  I got you.

• 34:57Neil deGrasse Tyson?

  A, a sphere that's. Three times bigger.

• 35:00Chuck Nice?

  So, cause the sphere is expanding.

• 35:01Neil deGrasse Tyson?

  Has nine times the area. And so you're see, so it's thinner, whatever was there before is now one ninth as thin. So, gravity thins out at that rate.

• 35:09Chuck Nice?

  Okay, I got you. Now that makes sense.

• 35:11Neil deGrasse Tyson?

  Of gravity, you're gonna thin gravity out.

• 35:12Chuck Nice?

  I'm thinking of this as a blowing up balloon.

• 35:14Neil deGrasse Tyson?

  Okay, if you wanna thin gravity out into a whole other dimension, then that equation can't just be one over r squared.

• 35:19Chuck Nice?

  Gotcha, now that makes sense.

• 35:20Neil deGrasse Tyson?

  Let me just, Paul, was I okay with that explanation? Yeah, that's fine.

• 35:23Chuck Nice?

  Alright.

• 35:23Neil deGrasse Tyson?

  I get, I get the, I get the.

• 35:25Chuck Nice?

  And for those of you listening at home, you're welcome.

• 35:29Neil deGrasse Tyson?

  When StarTalk comes back, more on the anatomy of the multiverse.

• 35:41Neil deGrasse Tyson?

  We're back on StarTalk, and I'm here with Chuck Nice.

• 35:45Chuck Nice?

  Sir.

• 35:45Neil deGrasse Tyson?

  And an old friend and colleague of mine from my Princeton days, Paul Steinhardt, professor of physics.

• 35:50Chuck Nice?

  And lord of the Phoenix Universe.

• 35:54Neil deGrasse Tyson?

  So, so Paul, is, does your, does your chair have an endowed name to it?

• 35:57Speaker 02

  It does.

• 35:58Neil deGrasse Tyson?

  What, what is that?

• 35:59Speaker 02

  It's called the Albert Einstein, um, professorship in science.

• 36:04Neil deGrasse Tyson?

  Excuse the hell out of me.

• 36:06Chuck Nice?

  That's pretty, that's pretty rough, man.

• 36:07Neil deGrasse Tyson?

  Okay, I'm thinking it was some name, that some rich guy that just gave money.

• 36:11Chuck Nice?

  No, no, the Albert Einstein professorship.

• 36:13Neil deGrasse Tyson?

  So, do you realize you could only be a disappointment?

• 36:16Speaker 02

  Yes, absolutely.

• 36:20Speaker 02

  That's the price.

• 36:22Chuck Nice?

  Oh, man, that's just so wrong.

• 36:25Neil deGrasse Tyson?

  I know, I know. I just, I just thought of that in that moment, I'm sorry.

• 36:30Neil deGrasse Tyson?

  So Chuck, you got weird cosmic queries, what else you have?

• 36:33Chuck Nice?

  Yes, let's move on.

• 36:34Neil deGrasse Tyson?

  Multiverse cosmic queries.

• 36:36Chuck Nice?

  Multiverse, we are talking about, um, uh, uh, this is somewhat in that range, but, uh, Michael Ranger, uh, from Twitter, says this, "Reality is granular." I love how people put their own little stuff.

• 36:49Neil deGrasse Tyson?

  The thing, let them do it, let them do it.

• 36:51Chuck Nice?

  "How then can, say, the Earth's gravity reach infinitely far? Uh, wouldn't it eventually wink out?"

• 37:01Neil deGrasse Tyson?

  Ooh, so let me, 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. Uh, do we agree?

• 37:24Speaker 02

  Mm-hmm.

• 37:24Neil deGrasse Tyson?

  Okay, so if you have gravity dropping off ever so slowly, one 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 apt to zero? Did I say that? Did I make sense in that question? Was that a fair interpretation? That's a fair interpretation, yeah.

• 37:53Speaker 02

  I wasn't sure if you were talking about time or space, though. Were you talking about?

• 37:56Neil deGrasse Tyson?

  About just gravity.

• 37:57Speaker 02

  Just gravity as we go out away from the source.

• 38:00Neil deGrasse Tyson?

  You go away from Earth, so it's Earth's gravity. Right, right, right, right. You know, it's, you know what it's like? It's like cleaning up, uh, 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?

• 38:22Speaker 02

  Um, uh, the various, I'll give you one interpretation of that question. Let me see if that will, 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 to existence, there was no gravitational field associated with it.

• 38:41Neil deGrasse Tyson?

  Hmm.

• 38:41Speaker 02

  Okay, there was matter that was gonna eventually come together to form the Earth. Um, so if you go far enough out, so that if you go far enough out in space, um, uh, you would not know that the Earth was about to form.

• 38:56Neil deGrasse Tyson?

  Ooh.

• 38:56Speaker 02

  Then the Earth.

• 38:57Neil deGrasse Tyson?

  Wait, wait, wait, we gotta wrap my head around that. So, Earth is about four and a half billion years old.

• 39:01Speaker 02

  Yes.

• 39:01Neil deGrasse Tyson?

  If you go four and a half billion light years away. There's a point where Earth had not yet assembled.

• 39:07Speaker 02

  Yeah.

• 39:08Neil deGrasse Tyson?

  From the void.

• 39:08Speaker 02

  Yes, if you were looking from that.

• 39:09Neil deGrasse Tyson?

  Even have a field of gravity.

• 39:11Chuck Nice?

  Holy.

• 39:11Neil deGrasse Tyson?

  To measure.

• 39:12Chuck Nice?

  Man, okay.

• 39:14Neil deGrasse Tyson?

  Ooh.

• 39:14Chuck Nice?

  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."

• 39:27Neil deGrasse Tyson?

  So, so you're out there.

• 39:28Speaker 02

  They're just gonna do cosmology.

• 39:30Chuck Nice?

  Yeah, exactly. You don't need drugs when you got this. You really don't. I mean, that's friggin' crazy.

• 39:36Neil deGrasse Tyson?

  Take up cosmology.

• 39:36Chuck Nice?

  Just take up cosmology, people, I'm telling you right now.

• 39:40Neil deGrasse Tyson?

  So, 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.

• 39:49Speaker 02

  Right.

• 39:50Neil deGrasse Tyson?

  You would feel, you'd measure this gravity arise.

• 39:54Speaker 02

  Yes, so it'd be like, uh, uh, you know, throwing a rock in the, in a puddle and, and eventually the wave is going to meet you, is gonna reach out to you, and then you'd be aware that a rock, i- i- if you weren't using your eyes, you're just feeling the water. You'd be aware that something happened.

• 40:12Neil deGrasse Tyson?

  Except, the rock hitting the puddle was a spontaneous thing.

• 40:14Speaker 02

  Yes.

• 40:15Neil deGrasse Tyson?

  The assembly of the Earth was a.

• 40:16Speaker 02

  It'd be slow.

• 40:16Neil deGrasse Tyson?

  Was slower and, and piecemeal.

• 40:18Speaker 02

  That's right.

• 40:19Neil deGrasse Tyson?

  Okay, okay, so that's, that's an awesome reply, but I think it still avoids the question.

• 40:24Speaker 02

  Yes.

• 40:25Neil deGrasse Tyson?

  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?

• 40:37Speaker 02

  Uh.

• 40:37Neil deGrasse Tyson?

  When I say quantum, I don't even mean, I don't even mean quantum physics so much as, can it smoothly go to zero asymptotically or not? That's really the question.

• 40:47Speaker 02

  Um.

• 40:49Neil deGrasse Tyson?

  You could say, "I don't know."

• 40:50Speaker 02

  Yeah, I was gonna say that.

• 40:51Neil deGrasse Tyson?

  Even though you're a Princeton professor, you say, "You know, I don't know."

• 40:54Speaker 02

  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.

• 41:02Chuck Nice?

  By the way, let me just say, uh, I am glad that right now you guys are not two surgeons.

• 41:08Chuck Nice?

  Trying to figure out how we should approach this open-heart situation.

• 41:12Neil deGrasse Tyson?

  What is that Wiggly thing? Take it out or leave it in?

• 41:16Neil deGrasse Tyson?

  Scissor, paper, stone and find out.

• 41:18Chuck Nice?

  Right, scissor, paper, stone. So, go ahead, sorry.

• 41:21Speaker 02

  I was gonna say, there is a deep puzzle, which is, if you buy this idea that the universe began from a quantum beginning, which, rather than a bounce. Uh, one of the puzzles there is, how do you go from a quantum world to a world which is described by your one 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 you 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.

• 42:04Chuck Nice?

  Okay. Uh, yeah, Michael, here's the deal. Um, we didn't answer your question at all, so...

• 42:13Chuck Nice?

  So...

• 42:14Neil deGrasse Tyson?

  No, no, no, here's what I say, say, "We turned it into a better question that we..."

• 42:17Chuck Nice?

  Actually, that's what really happened. We turned your question into a better question.

• 42:21Neil deGrasse Tyson?

  Or a question, yeah, just a question we could answer.

• 42:23Chuck Nice?

  Right, there you go. All right. Uh, here we 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 you going on Monday?"

• 42:39Neil deGrasse Tyson?

  I have no idea where this child is.

• 42:42Neil deGrasse Tyson?

  Oh, no, actually, I'm in the Pacific Northwest.

• 42:44Chuck Nice?

  Okay.

• 42:45Neil deGrasse Tyson?

  Doing some public talks.

• 42:46Chuck Nice?

  All right, okay.

• 42:47Neil deGrasse Tyson?

  So, I'm sorry, I lost the question.

• 42:50Chuck Nice?

  So, she's talking about the perception of time.

• 42:52Neil deGrasse Tyson?

  Oh, yeah, yeah.

• 42:53Chuck Nice?

  And is that going to be, uh, is that gonna be consistent?

• 42:56Neil deGrasse Tyson?

  Okay, so, Paul, we know from relativity that the passage of time is relative to an observer.

• 43:03Speaker 02

  Yes.

• 43:03Neil deGrasse Tyson?

  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, 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.

• 43:42Chuck Nice?

  Gotcha.

• 43:43Neil deGrasse Tyson?

  The same time as one another.

• 43:44Chuck Nice?

  No, that's, that makes sense.

• 43:45Neil deGrasse Tyson?

  It's a general relativity at work.

• 43:46Chuck Nice?

  Right.

• 43:47Neil deGrasse Tyson?

  At work. Okay, so Paul, so we, we got this.

• 43:49Speaker 02

  Yeah.

• 43:50Neil deGrasse Tyson?

  If you go to another one of your multiverse pockets. Could just time have a whole other kind of thing going on? About it?

• 43:58Speaker 02

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

• 44:21Neil deGrasse Tyson?

  Uh, in this- So their calendar would be BP for before patch.

• 44:24Speaker 02

  Yes.

• 44:27Neil deGrasse Tyson?

  Alright, so go on, yeah.

• 44:29Speaker 02

  Yeah, so, uh, so it'd be simply no way to, uh, to, uh, to correlate our time. So unlike the case of the satellite where we can send signals back and forth to the Earth to, 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.

• 44:50Neil deGrasse Tyson?

  But in the quantum fluctuations, in the quantum fluctuations of these patches, could time mean something different there? Could a quantum fluctuation change what time is?

• 45:04Speaker 02

  Uh, conceivably, but it's not part of the usual multiverse picture.

• 45:09Neil deGrasse Tyson?

  Okay.

• 45:09Speaker 02

  It's rather conventional in that sense that the patches would more or less have normal space and time like we think about here.

• 45:17Neil deGrasse Tyson?

  Uh huh.

• 45:17Speaker 02

  Uh, although some of them could be, in some cases, uh, the space could be, spacetime could be so warped that time could never lose its quantum, its quantumness, it might remain quantum and have a sort of, uh, no classical meaning in some patches, that's conceivable. And that's a kind of version of what you're, what you're asking.

• 45:38Neil deGrasse Tyson?

  I like that, so time would just not be even a thi- not even a thing.

• 45:41Chuck Nice?

  Right, it may not, it may not even be.

• 45:42Neil deGrasse Tyson?

  Yeah, right, it's just they could figure out some other way to meet you at the corner.

• 45:46Chuck Nice?

  They, they put it in a bottle.

• 45:47Speaker 02

  Couldn't meet you at the corner because space wouldn't have a meaning either.

• 45:50Neil deGrasse Tyson?

  Oh.

• 45:50Speaker 02

  So the corner would.

• 45:51Chuck Nice?

  The corner wouldn't be there either.

• 45:53Speaker 02

  Yeah, right, right.

• 45:54Neil deGrasse Tyson?

  We got time just for a quick lightning round?

• 45:56Chuck Nice?

  Okay, let's do it.

• 45:56Neil deGrasse Tyson?

  All right, all right.

• 45:57Chuck Nice?

  Here we go, here we go.

• 45:58Neil deGrasse Tyson?

  Soundbite answers.

• 45:59Chuck Nice?

  Jonathan Nagy, Jonathan Nagy from Twitter wants to know this. Will quantum gravity mean GR is incorrect since QFT is based on flat spacetime and GR is a curvature? Uh, he's just showing off.

• 46:10Neil deGrasse Tyson?

  Yeah. Paul, what's the answer?

• 46:12Speaker 02

  Yes.

• 46:12Neil deGrasse Tyson?

  Yes, okay.

• 46:15Neil deGrasse Tyson?

  Next question.

• 46:16Chuck Nice?

  Uh, Gabriel from Twitter wants to know this. What, if anything, is stopping gravity waves from traveling faster than the speed of light?

• 46:24Neil deGrasse Tyson?

  Ooh, yeah, Paul.

• 46:25Chuck Nice?

  That's a good idea.

• 46:26Neil deGrasse Tyson?

  Yeah, yeah.

• 46:27Speaker 02

  Hmm, uh, well, relativity.

• 46:30Neil deGrasse Tyson?

  Okay, good.

• 46:31Chuck Nice?

  Hey, you are really good at this part, Paul. I gotta tell you.

• 46:38Neil deGrasse Tyson?

  Okay, well, we gotta take it as an answer because this is the lightning round.

• 46:41Speaker 02

  Right. Not a good answer, just an answer.

• 46:43Chuck Nice?

  By the way, Gabriel, uh, look it up.

• 46:45Neil deGrasse Tyson?

  But in other words, relativity does not allow anything to go faster than light.

• 46:48Speaker 02

  That's right.

• 46:49Neil deGrasse Tyson?

  Therefore, gravity waves are not traveling faster than light.

• 46:51Speaker 02

  Correct.

• 46:51Neil deGrasse Tyson?

  Even though they be gravity and not light.

• 46:53Speaker 02

  Yeah, that's right.

• 46:53Neil deGrasse Tyson?

  Okay, good.

• 46:54Chuck Nice?

  There you go, good. All right, Datons, uh, at 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?

• 47:08Neil deGrasse Tyson?

  Because light takes time to move from one location to another.

• 47:12Chuck Nice?

  Hmm.

• 47:13Neil deGrasse Tyson?

  It means as you look out in space, you see things not as they are but as they once were.

• 47:18Chuck Nice?

  Right.

• 47:18Neil deGrasse Tyson?

  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.

• 47:42Neil deGrasse Tyson?

  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. Oh. 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 would, is coming our way. No, then, 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. Thank you.

• 48:26Neil deGrasse Tyson?

  From Princeton University. Chuck Nice. Yes. I think we're having a sound there, huh?

• 48:33Neil deGrasse Tyson?

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