Exploring Hidden Dimensions with Brian Greene

Is our universe an inevitable outcome of the laws of physics? Neil deGrasse Tyson and comic co-host Chuck Nice sit down with theoretical physicist Brian Greene to discuss the Many-Worlds Interpretation, the structure of the multiverse, levels of infinity, and respond to cosmic queries Neil couldn’t answer.

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

• 0:00Neil deGrasse Tyson?

  In an extended version of StarTalk. That's right. I'm loving it. All things you never knew you didn't know about what's going on in the universe coming right up.

• 0:11Neil deGrasse Tyson?

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

• 0:24Neil deGrasse Tyson?

  This is StarTalk. Neil deGrasse Tyson, your personal astrophysicist, got with me check night, baby. What's up, Neil? All right. This is a special Cosmic Queries edition. Okay. Because half of it is not going to be Cosmic Queries. Oh, okay. Half of it, I'm just gonna be talking to my man. Okay, for a moment, I thought you meant you were just gonna talk.

• 0:47Neil deGrasse Tyson?

  Up the street. Yes. Professor of mathematics and physics. And physics. At Columbia University. That's right. Let it go for Brian Greene. The returning champion, Brian Greene.

• 0:57Brian Greene?

  Thank you.

• 0:57Neil deGrasse Tyson?

  Fan favorite, by the way. Yeah. Right?

• 1:00Brian Greene?

  Appreciate that.

• 1:00Neil deGrasse Tyson?

  Our fans love you.

• 1:02Brian Greene?

  That's great to hear.

• 1:03Neil deGrasse Tyson?

  We love you because you're a theoretical physicist. Yeah. And while, of course, data matter, people like just thinking in an unfettered way about what could be true. Yeah. Or not true about the universe. And there's so many things being bandied about lately, especially in the quantum realm, that we thought we'd bring you in for a special recording where there are no time limits on this. We're just gonna talk universe, everything cool, weird and wacky about the universe. Nice.

• 1:33Brian Greene?

  Let's do it.

• 1:33Neil deGrasse Tyson?

  And you're the man for it. Yes. By the way, when you're not here, I just sort of fumble over how I, what I know, but when you're here, we got him. Yep, exactly. Okay, so let's remind people, you, your specialty, I mean, historically is, is particle physics specifically?

• 1:48Brian Greene?

  Yeah, certainly came from the particle physics side, quantum mechanics, and then moving toward gravity, which of course is the other end of the spectrum.

• 1:56Neil deGrasse Tyson?

  Okay.

• 1:57Brian Greene?

  And that's what took me to string theory, which is this attempt to put them both together.

• 2:01Neil deGrasse Tyson?

  We'll get there.

• 2:02Brian Greene?

  Yeah.

• 2:03Neil deGrasse Tyson?

  We're totally gonna get there. All right, so that means there's no... Scale of physics that's out of your reach.

• 2:09Brian Greene?

  Well, I wouldn't quite go that far, but.

• 2:12Neil deGrasse Tyson?

  You are kind of covering it all.

• 2:19Brian Greene?

  Well, what's left are the complicated things. Like the brain, like the mind, like consciousness, like biology, you know, so yeah.

• 2:28Neil deGrasse Tyson?

  You do the easy stuff. The physics is the easy stuff. You've written multiple bestselling books. And the one people remember most perhaps was The Elegant Universe. Was that your first?

• 2:37Brian Greene?

  That was my first.

• 2:38Neil deGrasse Tyson?

  And it was a runaway bestseller. Yeah, for W W Norton. And your most recent book in 2020 came out just in time for COVID. Until the end of time.

• 2:51Brian Greene?

  Yeah, nice. Wow.

• 2:56Neil deGrasse Tyson?

  Religious would be the end of days.

• 3:01Neil deGrasse Tyson?

  So what I like about you is you have a breezy way with communicating your complex physics thoughts. And in no small measure is that honed in books that are written for the public, A. B, your co-founder, I think with your wife Tracy Day, former news correspondent. Interviewed me many years ago. I think for NBC.

• 3:23Brian Greene?

  Good, well, A B C.

• 3:26Neil deGrasse Tyson?

  And Tracy Day co-founded the World Science Festival.

• 3:29Brian Greene?

  Oh, wow. We did.

• 3:30Neil deGrasse Tyson?

  Yeah. Now, that's just initially it's just being badass because it was New York.

• 3:34Brian Greene?

  Which is the world.

• 3:37Brian Greene?

  I'm not sure if you realize this.

• 3:39Neil deGrasse Tyson?

  So I haven't attended as many of these as I have always wanted, but those that I attended, I thoroughly enjoyed. The juxtaposition of the science and the art and the music and just science as culture.

• 3:50Brian Greene?

  Yeah, I mean, that's the point. I mean, much of what your work is about the same thing. People need to see science as part of the fabric of culture as opposed to something off there on the side that you are forced to take in school. And then you leave it.

• 4:02Neil deGrasse Tyson?

  You leave it behind. And so I think World Science Festival does that brilliantly.

• 4:06Brian Greene?

  Thank you.

• 4:07Neil deGrasse Tyson?

  Congratulate you on that. Year in and year out, it's still going strong. So before we get to cosmic queries, because we poll our fan base, our donors, really, the Patreon members. And they all know you, so they're coming in with questions, hot and heavy, straight in. And I worry that I might be asking some questions that they'd be asking.

• 4:26Brian Greene?

  Well.

• 4:26Neil deGrasse Tyson?

  Is that allowed?

• 4:27Brian Greene?

  Yeah, so what? And for everyone that we come across that you have asked that they will ask because they've already submitted, you will just give us five dollars. Because that's how much it costs to be a Patreon member.

• 4:43Neil deGrasse Tyson?

  At the entry level.

• 4:44Brian Greene?

  At the entry level, yeah.

• 4:45Neil deGrasse Tyson?

  Okay, so Brian, let's just, right off the bat, we hear about the multiverse. Okay? On one side of a fence, and then you cross the other side of the fence, and then we hear about the many worlds hypothesis in quantum physics. Do these two have anything to do with each other?

• 5:02Brian Greene?

  Yeah, they do. The idea of a multiverse is the umbrella concept for any variation on the theme where our world is not the entirety of reality.

• 5:14Neil deGrasse Tyson?

  Oh, so that would cover all cases?

• 5:15Brian Greene?

  All cases.

• 5:16Neil deGrasse Tyson?

  Oh.

• 5:17Chuck Nice?

  Whether it's a multiverse or not.

• 5:18Brian Greene?

  Yeah.

• 5:19Chuck Nice?

  So the multiverse is under the many worlds.

• 5:21Brian Greene?

  Well, I think many worlds is under.

• 5:22Chuck Nice?

  It's under the multiverse?

• 5:23Brian Greene?

  Yeah, because the multiverse is the umbrella idea.

• 5:25Chuck Nice?

  Okay, so the multiverse encompasses every single possibility.

• 5:29Brian Greene?

  And there are, there's something like 10 versions of many worlds that have emerged from radically different ideas, and quantum mechanics is simply one of those.

• 5:38Neil deGrasse Tyson?

  Okay, so I was mistaken to think that the more, dare I say, traditional multiverse descriptions, there's one where there's multiple bubbles within our spacetime.

• 5:50Brian Greene?

  Sure, that's the inflationary multiverse.

• 5:52Neil deGrasse Tyson?

  You know, I'm thinking that's the multiverse.

• 5:54Chuck Nice?

  I'm bringing it down, by the way, inflation.

• 5:56Neil deGrasse Tyson?

  You bring it down.

• 5:59Chuck Nice?

  Affordability.

• 6:00Neil deGrasse Tyson?

  The universe is not really inflated.

• 6:04Chuck Nice?

  It's not really inflated. It's the best price it's ever been. There's never been a better price for the universe.

• 6:17Neil deGrasse Tyson?

  So, and then when I, and I'd learned many worlds when I first learned quantum physics. Where you needed some way.

• 6:26Neil deGrasse Tyson?

  To get out of the conundrum that you're observing statistical phenomena.

• 6:31Brian Greene?

  Yes, exactly.

• 6:32Neil deGrasse Tyson?

  So catch us up on the many worlds specifically, and then tell us how that plugs into the multiverse.

• 6:38Brian Greene?

  Yeah, so when people develop quantum mechanics, this is now going back to the 1920s and 1930s.

• 6:44Neil deGrasse Tyson?

  Centennial decade of quantum physics.

• 6:46Brian Greene?

  Precisely, which is why I'm writing a book on it. That will be published in this decade.

• 6:50Neil deGrasse Tyson?

  Oh, writing a book to catch people up on that.

• 6:53Brian Greene?

  Yeah, yeah, exactly.

• 6:54Neil deGrasse Tyson?

  Yeah, very good.

• 6:55Brian Greene?

  And the progression of the ideas beginning in the 1920s was to note that a particle, and we'd be specific, like an electron, it could be partly here and partly there, 50% here and 50% there. And the question was, but when you look and you measure, you always find the electron here or there. You never find it in a blended mixture being at two locations.

• 7:18Neil deGrasse Tyson?

  Okay.

• 7:19Brian Greene?

  And people scratched their head for a long time trying to figure out, what, how do we transition from a theory that describes a fuzzy haze of possibilities to the single definite reality when we make an observation or an experiment?

• 7:32Neil deGrasse Tyson?

  How much of that definite reality was a bias coming out of classical physics?

• 7:36Brian Greene?

  Well, you could say all of it, because our brains are big, and we think they probably operate according to laws that are biased toward the classical, the big stuff.

• 7:47Neil deGrasse Tyson?

  Yeah.

• 7:47Brian Greene?

  And our experience.

• 7:49Neil deGrasse Tyson?

  So classical physics, there's an object, it drops, there's a thing, you move it.

• 7:52Brian Greene?

  Right.

• 7:53Neil deGrasse Tyson?

  There's just stuff that kind of makes sense to us.

• 7:54Brian Greene?

  Yeah, exactly.

• 7:55Neil deGrasse Tyson?

  And nothing in quantum physics makes sense.

• 7:57Brian Greene?

  And nothing in experience suggests there's anything but one single definite reality. And that was the conundrum. Experience shows one reality. Quantum mechanics speaks of many possibilities.

• 8:09Neil deGrasse Tyson?

  And measurements in that realm.

• 8:11Brian Greene?

  Right. That's right. So measurements in the realm of the small somehow seemed to pick out one singular definite reality. But here's the problem. When you look at the mathematics, which comes from Erwin Schrodinger, you can't transition.

• 8:26Neil deGrasse Tyson?

  Of cat fame, yes.

• 8:27Brian Greene?

  Of cat fame.

• 8:29Neil deGrasse Tyson?

  What a shame. There should have been a Schrodinger's cat in the Broadway musical, I think.

• 8:32Brian Greene?

  Of cats?

• 8:33Neil deGrasse Tyson?

  Yeah, that would have been really cool.

• 8:34Brian Greene?

  Well, there was one in the other world.

• 8:39Brian Greene?

  And this is the point. So Schrodinger's mathematics forbids a transition from many possibilities to the single definite outcome of experience. And so people said, maybe the transition never happens. And this is Hugh Everett, 1957 at Princeton. He looks at the equations and says, we are imposing a classical bias on reality. We think there's a single definite reality, but according to the math, if you look at that cat, there's one universe in which the cat's alive and you see it alive and you're happy. There's another universe where you see the cat dead and you're chagrined. And that's the true reality. Neither of you knows about the other version of you. Each thinks they live

• 9:22Brian Greene?

  in a single definite reality, but the bigger picture embraces more than one world.

• 9:27Neil deGrasse Tyson?

  Was that other world always there? Was it created in the moment that they had the

• 9:32Chuck Nice?

  The realization of another world.

• 9:33Neil deGrasse Tyson?

  Realization of the

• 9:34Brian Greene?

  It's a really good and subtle question, and I don't think every physicist sitting in this chair would give you the same answer. As I look at the mathematics, I would say all those worlds in a sense are there. There's nothing really splitting, which is how we often describe it. The world splits into two. It's more that the description of the quantum realm allows

• 9:57Neil deGrasse Tyson?

  See his body language?

• 9:58Chuck Nice?

  Let me say some of that more.

• 10:00Neil deGrasse Tyson?

  I know. I love that. Give me some more of that.

• 10:03Brian Greene?

  The mathematical description now allows us to use the language of one world or another when that language wouldn't have been applicable before your measurement. But it's not like the world splits and splits and splits. It's all sitting there in some giant uber realm.

• 10:19Chuck Nice?

  Gotcha. So does the realization of the measurement, are you saying that there's a possibility that you're not measuring a definite thing at that moment, or instant, I'll call it, in that instant? Or are you just seeing that and everything else is just still there? But like you can't see it because you're looking at this.

• 10:43Brian Greene?

  See, it all depends on what you mean by you. And I hate to be so specific in the wording because if by you, you have the conventional notion of a single human being.

• 10:53Chuck Nice?

  Okay.

• 10:53Brian Greene?

  Each version of me does see a single world, carries out a single measurement.

• 10:59Chuck Nice?

  Snap!

• 10:59Brian Greene?

  It's just that if you had a God's eye view, which we don't have, you would see many versions of me with many outcomes.

• 11:07Chuck Nice?

  Okay, that is so freaky, man.

• 11:09Neil deGrasse Tyson?

  But it sounds like you just pulled that out of your ass.

• 11:11Brian Greene?

  I, I, I didn't.

• 11:17Chuck Nice?

  I assure you.

• 11:19Neil deGrasse Tyson?

  All right.

• 11:19Brian Greene?

  But that's an important point. Let me just emphasize that when Hugh Everett came up with this idea, it was the most conservative interpretation of the mathematics. Yes, it seems ridiculously uneconomical to have all these worlds. But the math, if you just take it at face value, this is what it seems to say.

• 11:49Speaker 03

  Hey, this is Kevin the Sommelier and I support StarTalk on Patreon. You're listening to StarTalk with Neil deGrasse Tyson.

• 12:03Neil deGrasse Tyson?

  So let's back up. You and I have chatted, we've hung out socially. And you confided in me that when you were a kid and when you were in school, if you picked a book off the shelf and there were no equations in it, you immediately put it back.

• 12:18Brian Greene?

  Yep. Wow.

• 12:19Neil deGrasse Tyson?

  Who does, who does that?

• 12:21Brian Greene?

  I gotta say, that's.

• 12:22Neil deGrasse Tyson?

  Who, who does that?

• 12:23Brian Greene?

  A math teacher's favorite kid. That's who does that.

• 12:28Brian Greene?

  Every math teacher's favorite student.

• 12:30Neil deGrasse Tyson?

  Teacher's pet in the math class. So, so you have a math brain. You have a brain wiring where the math is clear and present to you, more so than any words or descriptions that surround it. I don't have a problem with that. You are also dual professor at Columbia in physics and mathematics.

• 12:51Neil deGrasse Tyson?

  What you just told me makes math the preeminent supreme account of reality. Because you're saying the math forces it. And I'm asking you, math is our tool. Why should math that you invented, you, anybody, humans, force anything? Why can't I say there's a different idea that's gonna have different math that doesn't lead to that conundrum?

• 13:17Brian Greene?

  So if you asked me that question 20 years ago, I would have given you one answer, which would have been very combative. And I would have been defending mathematics as like the deep truth of the world. In the past 20 years, I've shifted closer to your perspective. I really do see math as a powerful tool for describing the external world. I don't see it necessarily as the truth of what's out there, which is why I don't support the many worlds interpretation of quantum mechanics the way some of my colleagues do. I allow for it. It could be true. It's interesting. It blows your mind. But I do not say it's true because it comes out of the equation.

• 13:55Neil deGrasse Tyson?

  Thank you.

• 13:56Chuck Nice?

  Wow, okay. That's a very, um, I'll say mature and advanced.

• 14:02Neil deGrasse Tyson?

  Yeah, that's right. That's a mature, mature stance. You have matured in the past.

• 14:07Brian Greene?

  I have.

• 14:08Neil deGrasse Tyson?

  Because I don't, you know, I love me some math. Don't get me wrong, not as much as you do. But when I look at Kepler, who was a mathematician fundamentally, and he knew about the platonic solids. Do you know about the platonic solids?

• 14:21Brian Greene?

  I know that they're friends.

• 14:23Neil deGrasse Tyson?

  Platonic friends? Yeah. So you could, if you have polygons, uh, which are flat shapes that have the same sides on them. So a triangle would be a polygon. A regular polygon. A triangle, a square, a hexagon, that sort of thing. So if you ask, can you make solid objects with these as its sides?

• 14:42Brian Greene?

  Right.

• 14:42Neil deGrasse Tyson?

  There's only five.

• 14:44Brian Greene?

  Five poly, five shapes that do that.

• 14:47Neil deGrasse Tyson?

  Five shapes.

• 14:48Brian Greene?

  That do exactly that.

• 14:49Neil deGrasse Tyson?

  Where each side is the same polygon.

• 14:52Brian Greene?

  Okay.

• 14:53Neil deGrasse Tyson?

  Only five.

• 14:54Brian Greene?

  Right. And one of the, some are obvious. Pyramid, definitely. One's a soccer ball.

• 14:58Neil deGrasse Tyson?

  Uh, no, soccer ball has two different kinds of shapes on it.

• 15:00Brian Greene?

  Oh, really?

• 15:01Neil deGrasse Tyson?

  Yes, it does. Oh, so they're not all the same. No, I'll check next time. All right. But it is a way to tile. Tile them so that you can do it. So, so one is a pyramid, another one is a cube. Cube, of course. Right. And then there's like three others given to me.

• 15:12Brian Greene?

  Yeah, dodecahedron, and I don't even remember the rest of the name. Yeah, so.

• 15:17Neil deGrasse Tyson?

  And there's another one. Okay, so now Kepler, a mathematician, said, there must be some divine reason. For this. There's five of them. And we have six planets. There was Mercury, Venus, Earth, Mars, Jupiter, and Saturn. So he said, wait a minute, if the universe is, is, is special and math is special, obviously, they have to be connected. Right. They must be connected. So he embedded these platonic shapes in each other, circumscribing one around the other to see if that gave him the orbital distances of those six planets. Because we have six planets, you have five separations between them. He thought that was a major connection. So he's, he spends 10 years doing that.

• 15:58Brian Greene?

  And then it was over, he was like, wasted my life! Oh, God, what have I done?

• 16:04Neil deGrasse Tyson?

  But the math is what took him there. Yeah.

• 16:07Brian Greene?

  Right.

• 16:07Neil deGrasse Tyson?

  The beauty of the math. Yeah. And so that was my lesson, that, you know, I ain't going there.

• 16:13Brian Greene?

  But it goes the other way too, right? Because you go back to, say, Georges Le Metteau.

• 16:18Neil deGrasse Tyson?

  So he's a priest, a Belgian priest.

• 16:19Brian Greene?

  Yep.

• 16:20Neil deGrasse Tyson?

  Yeah.

• 16:20Brian Greene?

  He's studying Einstein's mathematics, finds that the equations, the math, says that the universe should be expanding or contracting. He goes to Einstein, and Einstein says, "Your calculations are correct, but your physics is abominable. This math is not relevant to the world. It's like the platonic solids, you're wasting your time." And yet, in this case, Einstein was wrong.

• 16:44Neil deGrasse Tyson?

  Oh.

• 16:44Brian Greene?

  Einstein's math was relevant in the way that Georges Le Metteau was suggesting the universe is expanding.

• 16:50Neil deGrasse Tyson?

  It is.

• 16:50Brian Greene?

  So you have to go.

• 16:51Neil deGrasse Tyson?

  Einstein didn't even know his math was relevant. Yeah, so, so Lamarck.

• 16:57Neil deGrasse Tyson?

  He used calculations of Einstein's equations to force upon him a feature of the universe that not even Einstein was imagining.

• 17:08Brian Greene?

  Exactly right.

• 17:09Neil deGrasse Tyson?

  So that's math being bad. The math discovered that. The math discovered it.

• 17:13Brian Greene?

  Yeah, so it's all just to say that it has to be case by case.

• 17:16Neil deGrasse Tyson?

  You got me.

• 17:16Brian Greene?

  Yeah.

• 17:17Neil deGrasse Tyson?

  You got me there. Okay. So now if everybody's doing these quantum physics experiments all over Earth and in all alien planets, is this a countable number of worlds?

• 17:27Brian Greene?

  Yeah, that's a tough, tough question. It's infinite in any reckoning, but exactly which kind of infinity? We kind of understand it because we don't want to go into the deep mathematics, but there's a whole structure due to David Hilbert, a mathematician, who actually raced Einstein to the finish line in general relativity.

• 17:46Neil deGrasse Tyson?

  Did not know he was on the track.

• 17:49Brian Greene?

  Yes, in fact, he published general relativity a little bit before Einstein did. It's a little known fact.

• 17:56Neil deGrasse Tyson?

  That must hurt. What's his name again?

• 17:58Brian Greene?

  His name is David Hilbert.

• 17:59Neil deGrasse Tyson?

  Damn.

• 17:59Brian Greene?

  And the thing that was-

• 18:00Neil deGrasse Tyson?

  I don't know Hilbert because it's Hilbert space.

• 18:01Brian Greene?

  Hilbert space.

• 18:02Neil deGrasse Tyson?

  Tell me about that in a minute.

• 18:03Brian Greene?

  But in this particular story, Einstein had visited Hilbert in June of 1915, showed him everything that he'd worked out for 10 years. Then Hilbert took it the final step and published before him. In the end of the day, Hilbert said, no, no, it's your theory. It's your theory, Albert. I'm not trying to take it from you.

• 18:21Neil deGrasse Tyson?

  That's very cool.

• 18:21Brian Greene?

  But he did publish a little bit before him. Yes, yes.

• 18:24Neil deGrasse Tyson?

  Even though he would not have published had Einstein not visited him.

• 18:27Brian Greene?

  Yeah, he wouldn't have known anything about this. But the point for quantum mechanics is that there is this thing that you made reference to, Hilbert space, which is the mathematical structure within which all these worlds live. And we understand the math of that pretty well.

• 18:41Neil deGrasse Tyson?

  I did not know that. So why does it need a mathematical structure in which they live?

• 18:45Brian Greene?

  Well, if you're going to describe things with rigor mathematically, you've got to define things, you've got to have the operations, you have to be able to categorize the ingredients. And remarkably, this space that Hilbert introduced has just the right mathematical properties to be the space in which all these worlds live.

• 19:04Neil deGrasse Tyson?

  Does it suffer from an incompleteness? Feature.

• 19:08Brian Greene?

  You know, everything.

• 19:09Neil deGrasse Tyson?

  Who's the dude completing his theorem?

• 19:10Brian Greene?

  Yeah, Gödel.

• 19:11Neil deGrasse Tyson?

  Gödel?

• 19:12Brian Greene?

  Yeah. So, so, so, yeah, so Gödel had a very powerful result that any basically sufficiently complex mathematical structure will have true statements that can't be proven true within the axioms of that structure itself.

• 19:26Neil deGrasse Tyson?

  So it just has to be asserted?

• 19:27Brian Greene?

  It has to be asserted, or you have to somehow intuit it, or feel it, or.

• 19:31Neil deGrasse Tyson?

  In, you know.

• 19:32Brian Greene?

  In the general relativity.

• 19:33Chuck Nice?

  That sounds a little suspect.

• 19:34Brian Greene?

  But the deep question is, are there interesting physical features of the world that would be undecidable in this Gödelian sense?

• 19:44Neil deGrasse Tyson?

  That's what I'm asking you. So is there a feature?

• 19:46Brian Greene?

  I don't know the answer.

• 19:46Neil deGrasse Tyson?

  Of general relativity, where you, you part the curtains enough, and then there's just some assumption you had to make.

• 19:53Brian Greene?

  Yeah.

• 19:53Neil deGrasse Tyson?

  And everything issues forth from that, that you cannot deduce from anything that follows.

• 19:58Brian Greene?

  Yeah, I mean, there certainly are axioms within these theories, for sure, but are there then deductions that are true but can't be proven within this structure itself? I don't know, because when you look at Gödel's proof, the kinds of things that are undecidable are very contrived, you know, with things like, you know, the set of all sets that are not subsets of themselves. You're like, well, does that ever come up in the real world?

• 20:25Neil deGrasse Tyson?

  Right, right.

• 20:26Brian Greene?

  You know, or the barber of Seville, you know, nobody shaves themselves, but then, like, who shaves the barber? Who's, you know, so they're all very self-referential, and it's not obvious that they have direct relevance to things that we could measure.

• 20:38Neil deGrasse Tyson?

  But it's still an important discovery that he made.

• 20:41Brian Greene?

  Hugely important.

• 20:41Neil deGrasse Tyson?

  Yeah.

• 20:42Brian Greene?

  Hugely important.

• 20:42Neil deGrasse Tyson?

  And the thing about the bar, the closest I got to that barber question was I used to read brain teaser books when I was a kid.

• 20:48Brian Greene?

  Okay.

• 20:48Neil deGrasse Tyson?

  And so one of them is you come over town, only two barbers.

• 20:51Brian Greene?

  Yeah.

• 20:51Neil deGrasse Tyson?

  And one of them's just completely messy, and the guy's unkempt, and he's got, and his hair all.

• 20:56Brian Greene?

  But the town looks amazing.

• 20:58Neil deGrasse Tyson?

  Wait, and then there's another barber where he's clean, shaven, he's, everything's neat, so which barber do you go to?

• 21:04Brian Greene?

  I'm going to the messy one, because he clearly does the other barber.

• 21:07Neil deGrasse Tyson?

  Exactly. Exactly. Somebody cut the guy's hair.

• 21:12Brian Greene?

  That's the guy.

• 21:13Neil deGrasse Tyson?

  That's the closest I've gotten to the barber.

• 21:16Brian Greene?

  Good.

• 21:16Neil deGrasse Tyson?

  So with the many worlds, now connect that up to a multiverse.

• 21:21Brian Greene?

  Yeah.

• 21:22Neil deGrasse Tyson?

  It's just a declaration, it's a multiverse of a kind.

• 21:24Brian Greene?

  It's one flavor. Of multiverse.

• 21:27Neil deGrasse Tyson?

  Right.

• 21:27Brian Greene?

  That comes directly from the math of quantum mechanics. And the natural next question is, can you prove it? Can you demonstrate it?

• 21:34Neil deGrasse Tyson?

  It feels less real to me than the multiverses I've read about.

• 21:37Brian Greene?

  Yeah, no, I understand that feeling because our consciousness feels singular. And this theory is saying there are many individuals in this larger realm that have your memories, that have your experiences, and they only differ from you that they saw the cat dead and you saw the cat alive.

• 21:54Neil deGrasse Tyson?

  In some universe.

• 21:55Brian Greene?

  And that's just, yeah.

• 21:55Chuck Nice?

  And now let me ask you this with respect to that.

• 21:57Neil deGrasse Tyson?

  How to react to this? Give me a second to like, all right, just tear up.

• 22:00Chuck Nice?

  See, I watch a lot of Rick and Morty, so it doesn't bother me. It doesn't bother me at all. I'm just like, oh, okay. Of course it works that way.

• 22:10Neil deGrasse Tyson?

  Duh. But this other me, that's me identically, except we observed a different outcome of the experiment.

• 22:18Brian Greene?

  Yeah, and then from there you continue to diverge because we know that little changes right now over time can turn into major deviations in your lives later on.

• 22:30Neil deGrasse Tyson?

  Cause I've seen in several films, but let me pick one and specifically H. D. Wells, The Time Machine. I'm referenced, I didn't read the novel, but I saw the movie, when is it, from the 60s? And the guy, the main protagonist befriends a woman who shortly after they have this encounter, she's like hit by a truck. And he says, well, I have a time machine. I can go back and fix this. So he goes back and says, oh, don't exit the park this way. Go the other way. She goes the other way and something else hits her and she dies.

• 23:00Brian Greene?

  Yeah, and the safe drops on her head.

• 23:03Neil deGrasse Tyson?

  One anvil.

• 23:03Brian Greene?

  Right, and that was even better.

• 23:05Neil deGrasse Tyson?

  Right. And so after two or three iterations of this, or in another one, she's mugged and killed.

• 23:11Brian Greene?

  Yeah.

• 23:12Neil deGrasse Tyson?

  He concludes that it was just her time and he can't change fate.

• 23:17Brian Greene?

  Can't change the outcome.

• 23:18Neil deGrasse Tyson?

  Okay, but when I saw that, I said, the molecules of air that are around her are in a different place because she's displacing these molecules relative to these. That's a different universe.

• 23:30Brian Greene?

  Yep.

• 23:31Neil deGrasse Tyson?

  I'm not going to look at these as just this is the only thing that has to stay constant. Tell me about all the other little things that change relative to the big thing that you notice.

• 23:42Brian Greene?

  Yeah, so in that version, I think you're right. You know, if the person could really go back in time, change things, I think you would get a different universe. I don't know of any Uber law that says certain major events or minor events have to be preserved. But in the quantum mechanical version, it's completely different. If you take on board this idea, you are committing to different worlds where things are radically different. And one, she would live, and the other, she would die. If they are allowed, if these outcomes are compatible with the laws of physics, then they will happen in one or more of the worlds in the quantum mechanical multiverse.

• 24:23Chuck Nice?

  Wow.

• 24:23Brian Greene?

  All, all things compatible with the laws of physics are realized.

• 24:27Chuck Nice?

  Wow, that's pretty wild, man.

• 24:30Neil deGrasse Tyson?

  Okay, so, so, but, all right.

• 24:31Brian Greene?

  I love that.

• 24:32Neil deGrasse Tyson?

  Wait, wait, stop.

• 24:34Brian Greene?

  I love that.

• 24:36Chuck Nice?

  Here's the only thing that I can't get with that, all right? In that case, how do you reconcile infinity or an infinite number of worlds?

• 24:47Neil deGrasse Tyson?

  Let me get there. So, so watch. We went from the many worlds hypothesis where it is exactly me, but I'd look at a dead cat instead of a live cat, or vice versa. In the multiverses to which I've grown accustomed, there's possibly an infinite number of them. But maybe in one of them, I'm there mostly myself, except I have a goatee, or I'm evil Neil instead of friendly Neil. So that's not a many worlds Neil.

• 25:16Chuck Nice?

  You're Neil who believes in tarot cards.

• 25:21Neil deGrasse Tyson?

  So that's, that's, that's not a many worlds Neil. That's just another statistically configured Neil out of the random molecules in that universe.

• 25:30Brian Greene?

  Right, but the beautiful thing about the quantum mechanical multiverse is that when you study the possible worlds that can emerge, they embrace effectively anything that would have a non-zero chance of occurring.

• 25:45Chuck Nice?

  Okay.

• 25:46Brian Greene?

  And that's anything in effect that's allowed by the laws of physics. So if the laws of physics allow you to have a goatee, then there will be a world in the many worlds where you do have a goatee.

• 25:55Neil deGrasse Tyson?

  Right, but in, in that world, that's a different me looking at the cat. Because the, the dead cat, live cat version of me, they each have a goatee.

• 26:05Brian Greene?

  Uh, yes. So if it's a very minor event, like doing a single observation, usually a single observation can't yield such a radical change immediately. It'll be you without a goatee in one, you without a goatee in another. But then if you wait long enough and you accumulate the huge number of ways you could have gone left, you could have gone right, you could have gone up, you could have said yes, you could have said no. When you put all of those possible...

• 26:31Neil deGrasse Tyson?

  I could have pepperoni on that.

• 26:32Brian Greene?

  Exactly. Yeah, now, one of them results in you having a goatee because that came along for the ride in that particular world.

• 26:40Chuck Nice?

  So here's what I want to know. Back to the infinity.

• 26:42Neil deGrasse Tyson?

  Yeah.

• 26:43Chuck Nice?

  Are there a finite number of particles in this universe?

• 26:46Brian Greene?

  There are finite number of particles in the observable universe.

• 26:48Chuck Nice?

  Ah!

• 26:49Brian Greene?

  But the universe could go on infinitely far.

• 26:51Chuck Nice?

  Okay, then that, that, that answers my question.

• 26:53Neil deGrasse Tyson?

  Yeah, beyond the horizon, we don't know.

• 26:54Chuck Nice?

  Yeah, because my point is, then that means there's a finite combination of all these particles that could create these worlds. And so, how do you get to infinity? But if the universe goes on and on and on, then yeah.

• 27:07Brian Greene?

  Yeah.

• 27:08Chuck Nice?

  Yeah, there is no, there's no end.

• 27:10Neil deGrasse Tyson?

  But even with an infinite number of universes with the same number of particles, you just configure them and keep reconfiguring them.

• 27:16Chuck Nice?

  No, my point is this, can you reconfigure a finite number of particles to get to infinity?

• 27:21Brian Greene?

  You can't, because it's not reusing the same electron or the same proton in one world and another.

• 27:27Chuck Nice?

  Okay.

• 27:27Brian Greene?

  It's a realization of that particle in a different configuration.

• 27:32Neil deGrasse Tyson?

  Right.

• 27:32Brian Greene?

  And, and that's, so it's not like a conservation of particle number, yeah.

• 27:36Chuck Nice?

  Yeah, so, God, wow!

• 27:37Neil deGrasse Tyson?

  So I used to be into, I used to be into big numbers. I still am, but I haven't stayed with it. And one of my favorite big numbers was Skew's number. Do you know Skew's?

• 27:46Brian Greene?

  I don't know Skew's number.

• 27:47Neil deGrasse Tyson?

  It's 10 to the 10 to the 10 to the 34th power.

• 27:50Chuck Nice?

  Okay.

• 27:52Neil deGrasse Tyson?

  And if you, if you play that out,

• 27:54Chuck Nice?

  Yeah.

• 27:55Neil deGrasse Tyson?

  you get the total number of configurations.

• 28:00Neil deGrasse Tyson?

  Of all the particles in the observable universe. Right, so it's as though if the universe were a cosmic chessboard, it'd be the total number of possible moves.

• 28:10Brian Greene?

  Right.

• 28:10Neil deGrasse Tyson?

  Because you're not counting objects at this point. You're counting events. You're counting things.

• 28:14Brian Greene?

  Yeah, combinations.

• 28:15Neil deGrasse Tyson?

  Combinations.

• 28:16Brian Greene?

  Yeah, I would get a different number if I was to use the entropy of the observable universe, which we can calculate from the dark energy. I would get a 10 to the 10 to the 120.

• 28:27Neil deGrasse Tyson?

  Okay, is that much different from 10 to the 10?

• 28:29Brian Greene?

  Yeah, so I think it has to do with whether you're only looking at material particles that, yeah.

• 28:35Neil deGrasse Tyson?

  Yes, yes, it is.

• 28:36Brian Greene?

  Versus the energy that.

• 28:37Neil deGrasse Tyson?

  Oh, no, well, of course, yeah, the energy is all in there too.

• 28:39Brian Greene?

  Yep, yep.

• 28:40Neil deGrasse Tyson?

  Yeah, this is just counting up the the physical particles.

• 28:42Brian Greene?

  Sure, that makes sense.

• 28:43Neil deGrasse Tyson?

  Okay, cool.

• 28:45Brian Greene?

  So do we, do we actually know the amount of, of dark energy that's in the universe? Well, we measure it. We do measure it. We do measure it by the rate at which distant galaxies are accelerating away from us. And it's this ridiculously small number Okay. in the units that we typically use to measure these things. And that translates into this particular number for the entropy, the number of states that the universe can possibly be found in. Right, okay, that makes sense. But the question you asked before, if we could return it for a second, because it is issue, this issue of infinite number of worlds.

• 29:18Neil deGrasse Tyson?

  Yeah, wait, just before you get there, I just want to remind people that when you say, if there's a chance something can happen, no matter how small.

• 29:26Brian Greene?

  Yeah.

• 29:27Neil deGrasse Tyson?

  You multiply that very small number by infinity, and you get a, you get a real number.

• 29:34Brian Greene?

  And you get many worlds.

• 29:35Neil deGrasse Tyson?

  You get many worlds.

• 29:36Brian Greene?

  In which that could, that small probability thing could happen.

• 29:39Neil deGrasse Tyson?

  Exactly, so the, the infinity that you're, where you're about to go.

• 29:42Brian Greene?

  Right.

• 29:43Neil deGrasse Tyson?

  Helps bring out of the, out of the depths, the statistically unlikely possibilities.

• 29:48Brian Greene?

  And that, to me, is the Achilles' heel, or a potential Achilles' heel of this approach. And again, I have to say, different people in this chair, they will say different things. But the issue that many of us have taken with the many worlds is just that. If an outcome has very small probability, right? That should mean it's very unlikely to happen. But from the analysis that you just gave, no matter how unlikely it is to happen, it will be realized in some world. So what does it mean to say something is unlikely if you're sure it's going to happen in some world? Exactly. Yeah.

• 30:22Neil deGrasse Tyson?

  Now.

• 30:22Brian Greene?

  It's like having a drink, it's 5 o'clock somewhere.

• 30:29Neil deGrasse Tyson?

  So we encounter this in astrophysics where we talk about supernovae as being extremely rare event. Okay, not all stars will go supernova, even high mass stars, some go black hole. It's rare. However, the galaxy has 100 billion stars in it. There's 100 billion galaxies in the universe. So when people realize if you have enough of a sample size, you could deliver every single night supernova into your catalog. It's a rare event that happens often. Exactly. So that was initially kind of hard to explain to the public. How you get that?

• 31:07Brian Greene?

  Yeah, so we have a version of that in the quantum mechanical multiverse, but it is more of an issue because you're guaranteeing the existence of a world, a whole world filled with observers and experimenters who are guaranteed to see the most unlikely things on a regular basis. And that is an issue. Now, there are some people who work on this who say, we've solved that. Just read our paper, read our book, and they do some interesting mathematics. I am not convinced. And that, to me, is where the issue is.

• 31:37Neil deGrasse Tyson?

  Okay. Interesting. So, let me ask, I think we chatted about this over lunch a few moons back. Thanks for inviting me. Oh, it's in your inbox. And forgive me, I might have had this conversation with Brian Cox.

• 31:57Brian Greene?

  Sure, yeah.

• 31:58Neil deGrasse Tyson?

  Forgive me, because you're my favorite physicists out there. But, so do you feel bad that I have another physicist who I?

• 32:05Brian Greene?

  A little bit, but it's all right.

• 32:08Neil deGrasse Tyson?

  So, I happened, I learned this early because I said I was into big numbers when I was a kid, that there are levels of infinity.

• 32:15Brian Greene?

  Yeah.

• 32:16Neil deGrasse Tyson?

  I think there are at least five.

• 32:17Brian Greene?

  You can keep on going.

• 32:18Neil deGrasse Tyson?

  All right. You buried the lead, guys. Now you gotta explain that. You can't just say that. You weren't at the lunch. And move on. That there are levels of infinity? Yeah, yeah, yeah, yeah. But you weren't at the lunch. Do you know how counterintuitive that is? You weren't at the lunch, so should, do I have to drag you behind us? I know, man. Listen, I'll take a doggy bag, okay?

• 32:38Brian Greene?

  Because that's crazy what you just said.

• 32:40Neil deGrasse Tyson?

  Well, we'll get, we'll explain that in a minute.

• 32:41Brian Greene?

  All right, go ahead.

• 32:42Neil deGrasse Tyson?

  So I kept thinking to myself that you can have an infinity of universes. And that would not be a big enough infinity to exactly reproduce me. And that you would maybe needed higher levels of infinity. To get all the combinations that people like to talk about in the multiverse.

• 33:04Brian Greene?

  Right, right.

• 33:05Neil deGrasse Tyson?

  So does it, does it require the higher levels of infinity?

• 33:07Brian Greene?

  You know, the, the, the most straightforward answer would be to say, I don't fully know. Because I don't know that science understands you, and by you, I mean life, well enough to say.

• 33:19Neil deGrasse Tyson?

  You know what he just said? He said, I could be so simple.

• 33:21Brian Greene?

  Right.

• 33:22Neil deGrasse Tyson?

  It's trivial to copy.

• 33:23Chuck Nice?

  Science is under no obligation to understand you.

• 33:26Brian Greene?

  But, but, but if you take on board the idea that you are just a collection of particles that are governed by the quantum mechanical laws. If that is something you're willing to accept. Then there is enough room inside of, you know, Hilbert space and the quantum mechanical infinity to reproduce you and to reproduce every variation on you where some of your particles.

• 33:46Neil deGrasse Tyson?

  Every variation conceivable.

• 33:47Brian Greene?

  Yes, yes. Every variation allowed by the quantum laws, which simply means.

• 33:52Neil deGrasse Tyson?

  Is there a version of me that has a tooth cavity because I've never had a cavity?

• 33:54Brian Greene?

  If that's compatible with the laws of physics, and I think it is, then yes.

• 33:58Chuck Nice?

  So non-dental plan Neil. This is the Neil with no dental plan. If that's within the bounds of quantum mechanics.

• 34:07Neil deGrasse Tyson?

  Laws of physics don't prevent it.

• 34:09Chuck Nice?

  Then we got enough, we got enough ma- not matter. We have enough material to make sure that that happens.

• 34:14Neil deGrasse Tyson?

  I don't need the higher levels of infinity to get there.

• 34:16Brian Greene?

  No, no, absolutely.

• 34:17Neil deGrasse Tyson?

  Okay, so now let's, let's catch up Chuck because everyone else out there knows about multiple infinities. Uh, so.

• 34:26Brian Greene?

  Please catch me up.

• 34:26Neil deGrasse Tyson?

  So these are levels of infinity. I think there's a Hebrew letter associated.

• 34:30Brian Greene?

  Aleph, aleph.

• 34:31Neil deGrasse Tyson?

  Aleph zero is a traditional infinity. Aleph one, two, three. So we don't have to do all five. Just get me to like the second infinity.

• 34:38Brian Greene?

  Yeah, so the simplest one is the one that comes to mind immediately. You just count the numbers. One, two, three.

• 34:43Neil deGrasse Tyson?

  And they just go on.

• 34:45Brian Greene?

  And they just go on. And that's the simplest, straightforward. But then if I ask you, how many numbers are there between zero and one on the number line?

• 34:53Chuck Nice?

  Oh, wow.

• 34:54Brian Greene?

  Now you say to yourself, well, can I enumerate them? Can I put them into a correspondence with the counting numbers and just list them?

• 35:00Chuck Nice?

  However, but am I not, but I'm still going towards infinity. I was gonna say, aren't I dividing then, when I go in between numbers?

• 35:09Brian Greene?

  Yes.

• 35:09Chuck Nice?

  I'm kinda dividing now.

• 35:10Brian Greene?

  You are, and you could say, well, let me put a dot in the midpoint, call that one, and then a dot in the midpoint between it and zero and call that two. You won't cover all the numbers, and, and there was a wonderful.

• 35:23Chuck Nice?

  I'll never reach one, because there'll always be a place where I can, once again, put something in between one and where I am.

• 35:29Brian Greene?

  It's another way of saying it, but Cantor had a powerful argument that's actually pretty easy to understand. We'd need to write it out for me to show it to you, but he established that if you try to enumerate the numbers between zero and one, just list them, you will fail, you will always miss some, and therefore there are more than an infinity of numbers between zero and one, and that next level of infinity is the version that Neil was referring to.

• 35:57Chuck Nice?

  Yeah. Alice, give me my bag, I'm gonna need my weed.

• 36:02Neil deGrasse Tyson?

  Okay, so you just skipped by it, and I wanna make sure we can contemplate it briefly. The one way to know which infinity is bigger than the other is you correspond them to each other.

• 36:13Brian Greene?

  Yes, exactly.

• 36:14Neil deGrasse Tyson?

  Right, so you can say, because this is kind of a little freaky, the odd numbers is the same size infinity as all the counting numbers that include odd and even numbers.

• 36:24Brian Greene?

  Of course.

• 36:25Neil deGrasse Tyson?

  Now, how do you, how do you get that?

• 36:27Brian Greene?

  Well, you know, you could take any given number and say, multiply it by two and add one to it. And in that way, you're certainly getting an odd number. You get an odd number, and now you've lined up, you've lined up the numbers one, two, three upward, and the list that it corresponds to are all odd numbers.

• 36:44Neil deGrasse Tyson?

  They all just go up.

• 36:45Brian Greene?

  Yeah.

• 36:45Chuck Nice?

  Damn, that's wild. Wow, math is kinda cool.

• 36:51Chuck Nice?

  Who knew?

• 36:51Neil deGrasse Tyson?

  Okay, and, and just, just to, just to taste it, if I remember correctly, aleph two, does it go into another dimension, the, the number of? Lines in three dimensional space is a bigger infinity than the counting numbers on a number.

• 37:09Brian Greene?

  Yeah, that may be a way of saying it. I'm not sure. There are many ways of expressing these infinities. And there's actually a kind of an, almost an algorithm that allows you to start to build up this set of infinities. You can look at subsets of subsets and things of that sort. Look at power sets, as it's called. And so it's a astoundingly strange idea, which is why mathematicians who thought about this in the early days.

• 37:34Neil deGrasse Tyson?

  You're all in asylums right now.

• 37:50Neil deGrasse Tyson?

  So, and if you go to higher dimensions, in principle, does that take you to?

• 37:54Brian Greene?

  Not necessarily. No, I mean, if you start to look at the number of points in the plane, you know.

• 38:00Neil deGrasse Tyson?

  Points on a line versus points on a plane.

• 38:02Brian Greene?

  Yeah, so you have to be fairly sophisticated in how you build up these infinities.

• 38:06Neil deGrasse Tyson?

  Okay.

• 38:07Brian Greene?

  But for our purpose, there is this thing that we've made reference to. It's a bit abstract. This thing called Hilbert space.

• 38:15Neil deGrasse Tyson?

  Mm-hmm.

• 38:15Brian Greene?

  And we understand it reasonably well. It's an infinite dimensional space that David Hilbert developed. But we understand it well enough to say it does have enough room to embrace all the quantum mechanical space.

• 38:28Neil deGrasse Tyson?

  It has infinite dimensions. You think it has enough room?

• 38:30Brian Greene?

  Yeah. And, and within that space, in principle, there is a place that describes you.

• 38:37Neil deGrasse Tyson?

  All right. So now, I am, however improbable, in the configuration of atoms and molecules.

• 38:44Brian Greene?

  Even here, in this actual reality.

• 38:48Neil deGrasse Tyson?

  Okay. So have you thought much about whether or not something can exist and whether or not it does? The, the, the likelihood of such things?

• 38:57Brian Greene?

  Yeah, and it's a mind blowing thing. When you think about this sequence of steps by which you came to be. And I'm saying, let's go to your childhood, to your birth. Let's keep on going further back. Your grandparents, great. Let's go all the way back to the big bang. And if you look at the sequence of steps from the Big Bang.

• 39:15Neil deGrasse Tyson?

  Go back to the Big Bang.

• 39:16Brian Greene?

  You do, actually.

• 39:17Chuck Nice?

  We all do.

• 39:17Brian Greene?

  We all do, right?

• 39:18Neil deGrasse Tyson?

  That's how we get here.

• 39:20Brian Greene?

  You know, we, we, we, we have collections of particles that are configured in a certain way, and they have a history. And it's that history which resulted in them being in the configuration that's called Neil deGrasse Tyson. And if you look at the sequence of quantum steps, each of them are incredibly unlikely. And the collection of those sequences is innumerably huge and therefore incredibly unlikely. And yet here each of us are.

• 39:48Neil deGrasse Tyson?

  So what do I do with this information?

• 39:49Brian Greene?

  Well, I think it gives you a certain. Well, you know, there's, if you want me to be a little bit sappy.

• 39:55Neil deGrasse Tyson?

  Yeah.

• 39:56Brian Greene?

  You know, I think it inspires a gratitude. The unlikeness of us being here against of being at all. And therefore is a certain kind of thankfulness that the universe turned out in a way that gave us a brief moment to stand up, look around and appreciate everything.

• 40:13Chuck Nice?

  That's wild. So now I'm looking at that and immediately going back to our previous conversation about the two observers, okay?

• 40:21Neil deGrasse Tyson?

  With a dead cat, live cat.

• 40:22Chuck Nice?

  Dead cat, live cat, and the, and the many worlds. What you just said can negate that, meaning that also there are an infinite number of worlds where there's just no Neil, and then there's an infinite number of worlds where there is no cat. And then there's an infinite number, you, you.

• 40:38Brian Greene?

  You're absolutely right. And I think that's one of the lessons. If you take the many worlds approach to quantum mechanics to heart. It is saying that clearly we are compatible with the laws of physics because we're here, existence proof.

• 40:52Chuck Nice?

  Right.

• 40:52Brian Greene?

  And if you take the many worlds seriously, then we were guaranteed to live in some world in this grand collection of many worlds. Now, in some sense, this world is incredibly unlikely within the panoply of possibilities. But you're right, in that sense, we were an inevitable outcome of the quantum laws because we are allowed by those very laws of physics.

• 41:14Neil deGrasse Tyson?

  Okay, right. But Brian, I, I have a more anchored version of what you just said that I, that I credit to Richard Dawkins.

• 41:19Brian Greene?

  Yeah.

• 41:20Neil deGrasse Tyson?

  If you look at the total possible genetic combinations.

• 41:26Neil deGrasse Tyson?

  That will make a human being, a viable human being. Okay. It's a stupefyingly large number. Like four to the three billion or something, right? It's or but ten to the thirtieth power. It's it's it's high. Right. Yeah, what matters is not even how big it is. Yeah. But it's vastly larger than the total number of people who have ever been born. Right, yeah. Which if plus or minus, it's about a hundred billion. Yeah. Okay, so Dawkins' point is, we should cherish life because most people who could ever exist will never even be born. That's right.

• 42:02Brian Greene?

  Yeah.

• 42:03Neil deGrasse Tyson?

  Yeah. So we can be sad that you die, but he describes those people who die as the lucky ones. Who got to live in the first place. Because you can only die if you got to live. Right. And for me, that's a little more anchored than than.

• 42:15Brian Greene?

  Yeah, but to take the point we're saying before, if the multiverse version of quantum mechanics is the right way of thinking about it.

• 42:21Neil deGrasse Tyson?

  They did.

• 42:22Brian Greene?

  Then they did live if their genetic sequence was compatible with the law of physics.

• 42:27Neil deGrasse Tyson?

  Alright.

• 42:27Brian Greene?

  So, you know, so.

• 42:29Neil deGrasse Tyson?

  So don't feel bad for all those little swimmers that didn't quite make it to the egg.

• 42:38Neil deGrasse Tyson?

  The sperm you're talking about? Yes, exactly. So Brian, I get this question often, surely you do as well. If we live in a multiverse and we're just one of an infinitude, where are the other universes? Yeah. And you're gonna cop out and say, oh, they're in the infinite dimensional Hilbert space?

• 42:54Brian Greene?

  Well, it's easier to answer that question for other flavors of multiverse like the inflationary multiverse that you made reference to before because.

• 43:03Neil deGrasse Tyson?

  That's the simplest.

• 43:04Brian Greene?

  That's the simplest one to picture.

• 43:05Neil deGrasse Tyson?

  So those are the other places.

• 43:07Brian Greene?

  Yeah.

• 43:08Neil deGrasse Tyson?

  In our own, we're in a bubble. Right. And there's another bubble over there in the same sort of space time. Same construct. Construct.

• 43:14Brian Greene?

  Yeah, yeah, because according to inflationary cosmology, as you're making reference to, there was an energy field that gave rise to a pulse of gravity that drove our big bang, but the math shows that it would not have used up all of that energy in the process. Some would be left over. The leftover energy would yield another big bang and it would not be fully used up, yielding another big bang. And so these distinct big bangs, as you say, would give rise to these sort of bubbles in a big cosmic bubble bath.

• 43:43Neil deGrasse Tyson?

  Okay, so that's in one construct.

• 43:45Brian Greene?

  Yeah.

• 43:45Neil deGrasse Tyson?

  Okay, but now. There are other variants

• 43:49Brian Greene?

  Yeah.

• 43:49Neil deGrasse Tyson?

  Uh, multiverses where it's sort of separate.

• 43:52Brian Greene?

  Yeah, when you, when you talk about the quantum mechanical multiverse, it's much harder to think about where those other worlds are. They're not kind of adjacent to our space. It's a more abstract place that they inhabit. And I'm gonna try to avoid using the word Hilbert space, but that's the mathematical architecture within which we can see these worlds existing. I can't picture, I can't picture where these other worlds are. If you ask me, do I have a mental image of them? Not really.

• 44:23Neil deGrasse Tyson?

  Okay, so that's a mathematical architecture. Can I divine an experiment that would show that they exist? Is it, can I wormhole to them?

• 44:31Brian Greene?

  Yeah.

• 44:32Neil deGrasse Tyson?

  Do I even want to wormhole to them? Because quantum physics might give you slightly different laws of physics.

• 44:37Brian Greene?

  It's unlikely the laws of physics are different, but the properties of ingredients might be different in principle. If there are sufficient quantum mechanical processes that could yield worlds with those distinctions. But I don't know of an experiment, and I don't think anybody does, where when you can say, if we could get this and this result, we would establish that the multiverse is true.

• 45:00Neil deGrasse Tyson?

  You tell me that other universes, gravity can leak out of them?

• 45:03Brian Greene?

  Yeah, so that's another variation on the multiverse. It comes from string theory, which we can talk about.

• 45:08Neil deGrasse Tyson?

  Oh, we'll get there, yeah, okay.

• 45:09Brian Greene?

  But, but just to presage what we might talk about, in this version, our universe is sort of like one piece of bread in a big cosmic loaf. And the other slices of bread would be the other universes. So they would really be hovering next to us, just displaced in an actual additional dimension of space. And then you're right, gravity can influence, permeate that space.

• 45:32Chuck Nice?

  So, when I was having my little ayahuasca trip, I met these beings that were in-betweeners, and they were in-between dimensions. That's where they occupied. Okay, I feel so silly, but they

• 45:47Neil deGrasse Tyson?

  We're listening.

• 45:48Chuck Nice?

  Okay, they explained that

• 45:50Neil deGrasse Tyson?

  They talked to you.

• 45:51Chuck Nice?

  They did. They talked to me. And they were two dimensional beings that I could see in 3D. Sounds creepy, but that's the only way I can explain it. Okay? And they explained to think of it like an infinite number, and they call them dimensions. Going out and going up and going out, but to think of them as a deck of cards. Slapped up the way we see a deck of cards. We see it as one deck of cards, but it's not. It's however many cards are in that deck.

• 46:25Brian Greene?

  Right.

• 46:26Chuck Nice?

  And until you separate them, that's when you can see the different things. That's how it was explained to me.

• 46:31Brian Greene?

  So this is almost the reverse of that. It's as if we only see one card in the deck. That's our world.

• 46:37Chuck Nice?

  Right.

• 46:37Brian Greene?

  But a God's eye view would see the entire deck, which would have the other cards.

• 46:41Chuck Nice?

  And that's who, that's where they see. They, I see it as the one card, and they were explaining that they see it as the deck. But anyway, I'm just, I, I had, I had shared that with Janet Levin, and she was like, that's pretty interesting because. And then she gave me some speak that I didn't understand.

• 46:56Brian Greene?

  Yeah, it must be the same basic idea. Actually, we just wrote a paper on these so-called brain worlds in, in string theory. So this is something

• 47:04Neil deGrasse Tyson?

  Brain is short for membrane.

• 47:05Brian Greene?

  Membrane. Yeah, yeah, yeah. Sorry. Yeah, yeah. Should've said that. Thank you. You know, so these ideas, these are universes that are like a membrane, and there can be multiple membranes, which would be multiple worlds.

• 47:15Chuck Nice?

  Right.

• 47:15Brian Greene?

  And in principle, as Neil was mentioning, they can influence each other. Gravity from one can influence things in the other.

• 47:22Neil deGrasse Tyson?

  So, so I never took, I'm saddened by this. In graduate school, I'm taking astrophysics classes, but I wanted to take more physics. And a physics class I never took was field theory.

• 47:32Brian Greene?

  Yeah.

• 47:32Neil deGrasse Tyson?

  A whole course on field theory. And

• 47:34Brian Greene?

  You can come to my class. One of these, yeah, I've taught field theory a number of times. Yeah, I'll let you know next time.

• 47:41Neil deGrasse Tyson?

  Excellent. I sit in the back.

• 47:42Brian Greene?

  Yeah, exactly.

• 47:43Chuck Nice?

  Boy, that's not intimidating. I'm gonna fail, I swear to god, I'm gonna fail.

• 47:52Neil deGrasse Tyson?

  No, but I'm not in a position to calculate or even really know why. Gravity can escape, but not the electromagnetic forces.

• 48:01Brian Greene?

  Well, I could give you a quick mnemonic, sort of to think about that, which is, so in string theory, gravity is communicated by a string that has no ends. It's a closed loop.

• 48:12Neil deGrasse Tyson?

  Okay.

• 48:13Brian Greene?

  The electromagnetic force is communicated by photons, which in string theory are strings that have two open ends, and those ends are anchored to the membrane. They can't escape the membrane, but because the gravity particle, the graviton, has no ends, just a loop, it's not anchored. It can get off and travel between those worlds.

• 48:33Neil deGrasse Tyson?

  Is that a description that would be in the book, String Theory for Dummies?

• 48:37Brian Greene?

  It's there, no doubt.

• 48:39Neil deGrasse Tyson?

  Okay, so if that's the case, why isn't what we measure as dark matter just gravity leakage from another slice of bread?

• 48:46Brian Greene?

  People have made proposals like that. If you're, dark matter is meant to explain the gravity that we know is there, but it's dark gravity. Yeah, so if you can have some source of gravity that you don't literally see, it's a candidate. And so people have put forward, it's hard to make this idea really work, but in terms of its general possibility, sure.

• 49:07Neil deGrasse Tyson?

  Because the betting persons, you know, if you're into betting what an outcome would be, an exotic particle is sort of the betting man's solution to.

• 49:16Brian Greene?

  Yeah.

• 49:16Neil deGrasse Tyson?

  And, but that's, that's put forth by particle physicists.

• 49:20Brian Greene?

  Right.

• 49:20Neil deGrasse Tyson?

  You know, if you're a hammer, you're.

• 49:21Brian Greene?

  A little bit of bias, right?

• 49:22Neil deGrasse Tyson?

  A little bit of bias, right? So, I'm likening me the, you know, this gravity spillage.

• 49:28Brian Greene?

  No, I like the idea. It's in detail, it's only when you get down to brass tacks, it's hard to make this really work.

• 49:33Neil deGrasse Tyson?

  Alright, so let's pick up the baton here on string theory.

• 49:37Brian Greene?

  Yeah.

• 49:38Neil deGrasse Tyson?

  Where, I'm a little older than you, but we, we came of age with enough overlap, so I can speak of the 1980s as a time where string theory was birthed.

• 49:50Neil deGrasse Tyson?

  And started taking off with some vigor.

• 49:54Brian Greene?

  Yeah.

• 49:54Neil deGrasse Tyson?

  All right. Everybody I spoke to at the time, and at the time I was at the University of Texas, which had its share of string theorists.

• 50:01Brian Greene?

  Yes.

• 50:02Neil deGrasse Tyson?

  And Steve Weinberg.

• 50:03Brian Greene?

  Steve Weinberg, for sure.

• 50:04Neil deGrasse Tyson?

  A graduate of my high school.

• 50:06Brian Greene?

  That's true. That's true.

• 50:08Neil deGrasse Tyson?

  Not your high school.

• 50:09Brian Greene?

  Yeah, I agree.

• 50:09Neil deGrasse Tyson?

  Okay. So Steve Weinberg, a Nobel laureate in physics, cosmologist, you know, all the way back. Anyhow, so I asked people, so when you guys gonna figure this out? Because you're trying to unify quantum physics and the large and the small. And it's, oh, we're almost there. Five years. In five years, we think we'll do it. So, you know, 10 years later, well, when are you gonna do it? Oh, in five years, whatever. 20 years later, oh, in five years, the problem is hard. It's a hard problem, but we're on the, and so I, I've never heard convergence.

• 50:44Brian Greene?

  Yeah.

• 50:44Neil deGrasse Tyson?

  In any conversation about string theory landing where it had intended.

• 50:50Brian Greene?

  Yeah.

• 50:50Neil deGrasse Tyson?

  A, B, could it be, and I think I've said this on stage to you, and you didn't jump up and try to hurt me, could it be that all of you are just too stupid to figure out the solution? And let me say that more charitably. Are we awaiting the birth of some 21st century Einstein to see the solution here that none of the rest of you are?

• 51:12Brian Greene?

  Yeah, yeah, it's all possible. First off, I would never have said five years back then. It's a very dangerous thing to make a prognostication of that sort of.

• 51:21Neil deGrasse Tyson?

  Yeah, there was huge enthusiasm.

• 51:23Brian Greene?

  But look, string theory has done miraculous things since the 1980s, and I'm happy to sort of list the achievements, but you're right, it's not done the one thing that ultimately matters, which is make a prediction that we can test, you know, at a particle collider and determine whether these ideas are correct. And it could well be that we just don't have the brain power to get there. And it may not be that we're awaiting the birth of the next Einstein. Maybe we're just awaiting the next configuration of AI that may be able to do what we as individuals.

• 51:59Brian Greene?

  have not been able to do. I do think there's a real possibility of the nature of research changing in the next five to 10 years.

• 52:07Neil deGrasse Tyson?

  I said five in the next five years, you hear that?

• 52:10Brian Greene?

  This one, this one I'm willing to stick with though, uh, because you know, the, uh, I give you an example. I mentioned this paper that I wrote with Jana Levin that you may reference to.

• 52:21Neil deGrasse Tyson?

  Is this the loaf of bread paper?

• 52:23Brian Greene?

  No, it's a, so that we wrote a handful of papers together. This is a more recent one. And I wondered, could chat get the answer that took us a long time to get? Chat GPT, if I treat it as sort of a good graduate student. So I just gave it a few prompts, the way you would to a graduate student, did not give it the answer and it couldn't look up the answer. We hadn't yet published the paper. And within a half an hour, it was able to reproduce the results that took us months to get.

• 52:50Neil deGrasse Tyson?

  Oh my gosh.

• 52:51Brian Greene?

  And so it's as if you have the greatest graduate student known to humankind, even an army of them. At your disposal and that's now.

• 53:00Neil deGrasse Tyson?

  This is a hologram right now.

• 53:05Brian Greene?

  So what is it going to be like in five years? You know, it's, it's both exciting and scary.

• 53:11Neil deGrasse Tyson?

  Yeah, who has a similar story regarding his research where he was prompting chat. To think about a problem.

• 53:19Brian Greene?

  Yeah.

• 53:19Neil deGrasse Tyson?

  And it solved the problem that he could, he had not been able to solve.

• 53:22Brian Greene?

  And actually solved it.

• 53:23Neil deGrasse Tyson?

  Yeah, actually solved it.

• 53:24Brian Greene?

  Wow.

• 53:24Neil deGrasse Tyson?

  In, in, in the sort of, you prompt a really good graduate student in just the way you're describing.

• 53:29Brian Greene?

  Right.

• 53:29Neil deGrasse Tyson?

  But catch us up just on why the whole field is called string theory.

• 53:33Brian Greene?

  Well, the basic ingredient is a filament that looks like a tiny piece of string. The idea is that it can vibrate in different patterns. And the different particles that we know and love, electrons, quarks, neutrinos and so forth.

• 53:47Neil deGrasse Tyson?

  Fundamental particles.

• 53:48Brian Greene?

  Fundamental particles would each correspond to different vibrational patterns of this new entity called the string.

• 53:54Neil deGrasse Tyson?

  So the string becomes the fundamental particle.

• 53:56Brian Greene?

  Yes, and it's a unity because it's one thing that can manifest as many different things, depending on how it's vibrating.

• 54:02Neil deGrasse Tyson?

  Which is for people who like unity, this is a, this is a beautiful thing.

• 54:06Brian Greene?

  It's a beautiful thing and it goes even further. When you look at the math of this, you. Find that not only does it unify all the particles, but it unifies quantum mechanics and general relativity. Laws of the small and the laws of the big.

• 54:17Neil deGrasse Tyson?

  Does it do that for free?

• 54:18Brian Greene?

  It does that for free. It just comes out. I'm telling you, you look at the math.

• 54:22Neil deGrasse Tyson?

  That's a nice fact.

• 54:23Brian Greene?

  Look at, let me, you know, you look at the math, right? You stare at the equations and out pops Einstein's equations from general relativity.

• 54:31Neil deGrasse Tyson?

  To whom does it pop?

• 54:35Neil deGrasse Tyson?

  Who do you have to be for it to pop out? So I, I had not fully embraced that reality of string theory. So I'm delighted to hear that. So that, that was part of the enthusiasm that people would have then had.

• 54:48Brian Greene?

  That was really the heart of it all. Major obstacle. The major obstacle is that the theory is mathematically complex. And the pathway from the fundamental equations to physics we can see in the laboratory is fraught. It's difficult. It's tough terrain to cover. And so we've been developing mathematical tools to do that for now 30 years. We've made progress on black holes.

• 55:14Neil deGrasse Tyson?

  The eighties was 40 years ago.

• 55:16Brian Greene?

  I guess you're right. Oh my God.

• 55:19Brian Greene?

  String theory hasn't answered that question yet. Yeah.

• 55:21Neil deGrasse Tyson?

  Forty years ago.

• 55:22Brian Greene?

  Forty years ago.

• 55:22Neil deGrasse Tyson?

  Forty years before that was the 1940s.

• 55:24Brian Greene?

  Yeah. I'm with you on that.

• 55:26Neil deGrasse Tyson?

  All right.

• 55:27Brian Greene?

  You know, so we've been for 40 years.

• 55:32Brian Greene?

  And so we've understood things about space and time and, and gravity and black holes, which I didn't think we'd ever understand in my lifetime. On the flip side, though, we've not understood the things that I thought we would have understood by now, which would be make a prediction for what's going to happen at the Large Hadron Collider and let's check it. And so it's an interesting thing that we've made headway in the very things I thought would be too hard. And we've not made headway in the things that I thought we would be able to reach by now.

• 56:04Neil deGrasse Tyson?

  Right. So I don't like making arguments that other people make just for the sake of bringing the argument to you. But just let me just do that.

• 56:12Brian Greene?

  Let me do it anyway.

• 56:12Neil deGrasse Tyson?

  Let me do it anyway. So string theory has not been without some criticism.

• 56:17Brian Greene?

  Yeah.

• 56:18Neil deGrasse Tyson?

  As something that has consumed the ambitions of graduate students and faculty and promotions. And so it's a field without a prediction that can be tested, yet it had such a presence on the landscape of physics departments. That it might have. smothered some other branches of physics that might have been a little more promising. You just comment on that.

• 56:42Chuck Nice?

  That sound like jealousy to me.

• 56:45Brian Greene?

  Well, it's an interesting argument because the very graduate students and junior faculty and senior faculty who this person is making this argument fears may have wasted their time not looking at something more promising. You gotta assume they're really smart people because they're the very people you think who could have pushed the frontier of another field. Then if they're that smart, allow them to make the choice for where they think the greatest promise is.

• 57:13Neil deGrasse Tyson?

  Yeah, who are you to say that they're not gonna?

• 57:15Brian Greene?

  Yeah, so it's not as if somebody was like putting the, a bag over their head or, you know, putting a gun to you. They were looking at the ideas that were out there, found the string theoretic ideas so compelling that they were willing to take a chance. And, and that chance may not pay off in our lifetime.

• 57:33Neil deGrasse Tyson?

  And tell me about the 10 or 11 dimensions?

• 57:35Brian Greene?

  Yeah.

• 57:36Neil deGrasse Tyson?

  Because that sounded very cop outy.

• 57:39Brian Greene?

  Well.

• 57:40Neil deGrasse Tyson?

  You know, it's like, I can't explain this, let me throw in a dimension.

• 57:42Brian Greene?

  Ah, good, good, good.

• 57:43Neil deGrasse Tyson?

  I need another dimension.

• 57:43Brian Greene?

  But, but.

• 57:44Neil deGrasse Tyson?

  Let me add another dimension.

• 57:45Chuck Nice?

  Why do you need the dimensions?

• 57:46Brian Greene?

  Good, good, good. And I think if I articulate this correctly, I think you'll have the same epiphany that you did about gravity coming out of string theory a moment ago. Because again, you wondered, do you have to put general relativity into string theory? I said, no, no, it just comes out for free, which is a beautiful thing. How about the extra dimensions? They come out for free too. They're forced upon you by the equations.

• 58:09Neil deGrasse Tyson?

  You don't put, you don't put them in.

• 58:10Brian Greene?

  Not at all.

• 58:11Neil deGrasse Tyson?

  The math does it for you.

• 58:13Brian Greene?

  Literally, this is, this is, this is not a joke. There's an equation in string theory that basically looks like D, the number of dimensions, minus 10 times this complicated factor must be equal to zero for this theory to be self-consistent. The complicated thing is never zero, therefore D minus 10 must be zero, therefore D must equal 10. That is where the extra dimensions are forced upon you by the equations.

• 58:39Neil deGrasse Tyson?

  That's insane. That's pretty cool though.

• 58:41Brian Greene?

  Yeah.

• 58:42Neil deGrasse Tyson?

  I mean, that's so ten dimensions.

• 58:44Brian Greene?

  That wow.

• 58:44Neil deGrasse Tyson?

  So we don't experience them. Why?

• 58:47Brian Greene?

  Because we believe that they're probably too small for us to see with the naked eye.

• 58:52Neil deGrasse Tyson?

  I don't know what a small dimension means.

• 58:54Brian Greene?

  It means that if you head off in a given direction, you kind of return to your starting place so quickly. You can think about a straw, right? A straw has a long dimension that we can easily see, but it has a curled up circular dimension. And if that circle, of course, we can see that with the naked eye. But if you made that circle.

• 59:11Neil deGrasse Tyson?

  You're sucking liquid through it.

• 59:12Brian Greene?

  Yes, but if you made that circle smaller and smaller and smaller, at some point, you won't see it at all and you'll think it's just a line. You've hidden the extra dimension.

• 59:23Neil deGrasse Tyson?

  So all the other dimensions are hidden?

• 59:25Brian Greene?

  We think that is one explanation for why we don't see them.

• 59:30Neil deGrasse Tyson?

  Can anything exist in those hidden dimensions?

• 59:32Brian Greene?

  I was gonna call the elegant universe hidden dimensions. That was the title I was playing with back, you know, 25 years ago. But anyway, yes, exactly.

• 59:40Neil deGrasse Tyson?

  Alright, so you're hiding the dimensions from us?

• 59:42Brian Greene?

  Yes.

• 59:43Neil deGrasse Tyson?

  Okay, but it has to be there.

• 59:44Brian Greene?

  Now that is by hand. So when we look at the math, the equations don't tell us these extra dimensions are really tiny. Instead, we're doing what you accuse me of perhaps on other things. We're saying, how can we make this theory compatible with what we see? Let's envision that the extra dimensions are really small.

• 1:00:01Neil deGrasse Tyson?

  Got it. Okay, and so how, so a string is 10 dimensions?

• 1:00:04Brian Greene?

  A string is living in a 10 dimensional space.

• 1:00:07Neil deGrasse Tyson?

  Okay, now, why would a string be fundamental? And not, because a string is one dimensional.

• 1:00:12Brian Greene?

  Yeah.

• 1:00:13Neil deGrasse Tyson?

  And dimensions are just dimensions. Why can't there be another reality? Maybe in which we're embedded with the string is not fundamental, but a plane is what's fundamental.

• 1:00:22Brian Greene?

  Yes, and that's one of the developments in string theory itself. So when we talk about these membranes, the piece of bread or the card in the deck.

• 1:00:30Neil deGrasse Tyson?

  String theory upped by a dimension.

• 1:00:32Brian Greene?

  And string theory takes you there. It's not something, again, that you put in by hand.

• 1:00:36Neil deGrasse Tyson?

  He goes wherever his equations want to tell him.

• 1:00:38Brian Greene?

  I gotta say, it's pretty fascinating. I need to say, this is a purely mathematical undertaking. Totally. You know, but the beauty of it is, you don't put things in from the outside. You study the equations and it takes decades sometimes, but you extract what the equations are trying to tell you.

• 1:00:57Neil deGrasse Tyson?

  So before we go to queries. What is the current state of string theory?

• 1:01:01Brian Greene?

  Current state is...

• 1:01:02Neil deGrasse Tyson?

  It's health.

• 1:01:03Brian Greene?

  Yeah, I, you know, it's funny, I asked this question in a program to three string theorists, a World Science Festival program, I asked them, "Guys, grade string theory." How, you know, if a string theorist was a student, you know, how would you grade it? And the grades went from B+, I think that may have been Nobel laureate David Gross, I could be getting their grades wrong, to an A+, which was Andy Strominger, who's a string theorist at Harvard. And if you look at its theoretical insight into black holes, the mathematical insights that it's given started whole fields of mathematics. If you have any interest in the nature of space and time and what it might be made of,

• 1:01:47Brian Greene?

  these are the kinds of insights that string theorists giving. So I'd say it's very healthy, but it has not made a prediction allowing us to determine whether it's correct, yeah.

• 1:01:56Neil deGrasse Tyson?

  And that's almost a violation of one of the most important tenets of a viable theory.

• 1:02:02Brian Greene?

  Yes, and that's why maybe you shouldn't call it string theory.

• 1:02:06Neil deGrasse Tyson?

  Oh, should we call it?

• 1:02:07Brian Greene?

  Yeah, maybe call it the string hypothesis.

• 1:02:09Neil deGrasse Tyson?

  Okay.

• 1:02:10Brian Greene?

  This theory really should be preserved.

• 1:02:11Neil deGrasse Tyson?

  That's a more humble...

• 1:02:13Brian Greene?

  Yeah.

• 1:02:13Chuck Nice?

  But the math makes it a theory!

• 1:02:15Brian Greene?

  Well...

• 1:02:16Neil deGrasse Tyson?

  No, no, the theory, you, for a theory to be a bona fide theory, it's got to not only account for what you see...

• 1:02:24Brian Greene?

  Right.

• 1:02:24Neil deGrasse Tyson?

  Or in an organized, coherent way, it's got to make predictions that you have verified.

• 1:02:28Brian Greene?

  Right, you gotta be able to, you gotta be able to measure it.

• 1:02:30Neil deGrasse Tyson?

  If you have not predicted, then it's only one half of what's going on and...

• 1:02:34Brian Greene?

  Yeah, so we're using the word wrong, and I agree with people who are sticklers on that.

• 1:02:38Neil deGrasse Tyson?

  Got it.

• 1:02:39Chuck Nice?

  But is that because, and I don't want to sound like a, you know, a jackass, but what you just explained, I gotta say, like Einstein had it easy. I'm serious.

• 1:02:51Brian Greene?

  Yeah, right.

• 1:02:52Chuck Nice?

  Like Einstein had it easy compared to what you're just talking about.

• 1:02:54Brian Greene?

  I agree, he wrote down his equations and within a handful of years, you could test it.

• 1:02:59Chuck Nice?

  Right, because it's like, it's here!

• 1:03:00Brian Greene?

  Right.

• 1:03:01Chuck Nice?

  It's right, it's around us, it's everywhere, like you're talking about stuff that is, I mean, how do you get to it?

• 1:03:07Brian Greene?

  Right.

• 1:03:07Neil deGrasse Tyson?

  We've had problems, unsolved problems, that have lasted much longer than these 40 years in the history of science.

• 1:03:12Brian Greene?

  Okay.

• 1:03:13Neil deGrasse Tyson?

  So, it took a long time to understand heat and energy.

• 1:03:17Brian Greene?

  That's very funny what you just said. It took us a very long time to understand heat.

• 1:03:23Neil deGrasse Tyson?

  No, we didn't know what it was.

• 1:03:24Brian Greene?

  The fundamental basis of it.

• 1:03:25Neil deGrasse Tyson?

  That's hilarious. No, no, we didn't know. Is it some fluid?

• 1:03:28Brian Greene?

  A fluid, caloric? They called it caloric that could flow.

• 1:03:31Neil deGrasse Tyson?

  Yeah, and you know where we did most of it? Well, no, that's the air looking like. The air is a fluid. The air is a fluid, though. That's not the heat. But go ahead. One of the main centers of experiments for this? Yeah. Were cannons. Because you'd fire cannons, the metal gets hot. Yeah. So as it got hotter, they weigh it to see if it had more heat. If the heat was a thing. Right, if it was, if it was like possessing heat. Possessing heat. Exactly. So, yeah, so we went decades and decades with other... So maybe I shouldn't be so hard on string theory.

• 1:04:01Brian Greene?

  Yeah, this is a pretty good place to have gotten. Let's wrap it up right here, folks.

• 1:04:06Neil deGrasse Tyson?

  Thank you. Good night.

• 1:04:09Neil deGrasse Tyson?

  Okay, and one last thing. I want to hear it again, just because it was so beautiful. All right. So beautiful. Just tell me, speak to me, Brian.

• 1:04:21Neil deGrasse Tyson?

  Because it's sweetness to my ears when I heard you say, I think it was you, that the virtual particles in the vacuum of space coming in and out of existence as predicted by quantum physics, they are quantum entangled with each other, and that quantum entanglement are wormholes. And those wormholes represent the literal fabric that stitches together the universe itself.

• 1:04:54Brian Greene?

  Yeah, we were definitely talking about this at some point.

• 1:04:58Neil deGrasse Tyson?

  Where are we on that?

• 1:05:00Brian Greene?

  Well, it's a beautiful idea.

• 1:05:01Neil deGrasse Tyson?

  Beautiful.

• 1:05:01Brian Greene?

  It really comes from Lenny Susskind and Juan Maldacena and a whole army of string theorists who've developed these ideas.

• 1:05:08Neil deGrasse Tyson?

  He came here, gave a talk, one of our evening talks at the Planetarium.

• 1:05:12Brian Greene?

  Yeah, he has wonderful books.

• 1:05:13Neil deGrasse Tyson?

  Very innovative guy.

• 1:05:14Brian Greene?

  Yeah, I mean, he's driven physics for decades. So, so he and Juan Maldacena realized that these quantum entangled particles, which Einstein really, in a sense, predicted in his EPR paper, Einstein, Podolsky, and Rosen in 1935.

• 1:05:32Brian Greene?

  Maybe connected to another Einsteinian idea, which he came up with a two months distinct from that first paper, an Einstein Rosen paper on wormholes. That is, two particles that are far apart can have a subtle quantum link, and that quantum link may be nothing but a wormhole yielding a shortcut through the fabric of space that in some sense makes them very close to each other.

• 1:05:59Neil deGrasse Tyson?

  And those wormholes themselves are what spacetime is comprised of.

• 1:06:05Brian Greene?

  Yeah, so substrate of space itself would be wormholes.

• 1:06:08Neil deGrasse Tyson?

  Yes.

• 1:06:09Brian Greene?

  That's right. So Mark van Romsdijk, British Columbia, Canadian physicist, realized that these wormholes may be the fiber stitching together the fabric of space itself, because he could show mathematically, if you cut the quantum entanglement, the fabric of space pulverizes, it falls apart, because you no longer have the wormholes connecting pieces of space together. That is wild.

• 1:06:33Neil deGrasse Tyson?

  Okay, I'm gonna keep watching that space.

• 1:06:36Brian Greene?

  That's great.

• 1:06:57Neil deGrasse Tyson?

  It's time for Cosmic Queries.

• 1:06:58Brian Greene?

  Oh.

• 1:06:59Neil deGrasse Tyson?

  We should have some jingle or something that's, that, or some animation.

• 1:07:03Brian Greene?

  Some animation would be good.

• 1:07:04Neil deGrasse Tyson?

  You know, Cosmic Queries.

• 1:07:06Brian Greene?

  Right.

• 1:07:07Neil deGrasse Tyson?

  Questions asked by you, if you're a Patreon member, knowing that our guest today is Brian Greene, the one and only.

• 1:07:14Brian Greene?

  Mm-hmm.

• 1:07:15Neil deGrasse Tyson?

  So, we have a starter question.

• 1:07:17Brian Greene?

  Yes.

• 1:07:18Neil deGrasse Tyson?

  From one of our own producers.

• 1:07:20Brian Greene?

  Yeah, Tamsin, our producer.

• 1:07:22Neil deGrasse Tyson?

  Yeah.

• 1:07:23Brian Greene?

  Our taskmaster.

• 1:07:24Neil deGrasse Tyson?

  Yeah.

• 1:07:25Brian Greene?

  Uh, Tamsin wants to know this, Brian, if spacetime had consciousness and could have a favorite movie, what do you think that movie would be? I think it would be Planet of the Apes.

• 1:07:40Neil deGrasse Tyson?

  Really?

• 1:07:42Brian Greene?

  Oh. That scene at the end, you know, with the half submerged or sunken statue.

• 1:07:49Neil deGrasse Tyson?

  You fool, you liar, you damn liar, damn you!

• 1:07:58Chuck Nice?

  That's it.

• 1:08:01Neil deGrasse Tyson?

  Wow.

• 1:08:02Chuck Nice?

  Wow, yeah.

• 1:08:03Neil deGrasse Tyson?

  Because that played Lucy Goosey with space time.

• 1:08:06Chuck Nice?

  Yeah.

• 1:08:07Neil deGrasse Tyson?

  To go into the future, there's another Earth and it had a different evolutionary path.

• 1:08:12Chuck Nice?

  It was the first time that time travel really meant something to me as a kid. I was like, oh, man, this is crazy.

• 1:08:19Neil deGrasse Tyson?

  Yeah. Wow. That's a good one, man.

• 1:08:21Chuck Nice?

  Yeah.

• 1:08:21Neil deGrasse Tyson?

  Planet of the Apes, the original.

• 1:08:22Chuck Nice?

  The original. Forget about the other seventy-five thousand follow-ups, man.

• 1:08:27Neil deGrasse Tyson?

  Exactly. Return to my escape from the planet, bride of the Planet of the Apes. Finality of the Planet of the Apes. You know what? When I went back and saw that film, it's actually quite deep because the, the different species of apes had different roles.

• 1:08:43Chuck Nice?

  They have a caste system.

• 1:08:45Neil deGrasse Tyson?

  It's a caste system.

• 1:08:45Chuck Nice?

  Caste system, for sure.

• 1:08:46Neil deGrasse Tyson?

  Right, so the chimpanzees were the academic class.

• 1:08:49Chuck Nice?

  Right.

• 1:08:49Neil deGrasse Tyson?

  Because they're close, why not? Of course, they're our closest cousins. And the baboons were like the police, right? Or the gorillas were the police. The orangutans are the elders. No, no, the orangutans were the diplomats. Diplomats, that's correct, right. The politicians. It wasn't politicians, it was a caste system.

• 1:09:06Chuck Nice?

  Yeah.

• 1:09:06Neil deGrasse Tyson?

  Right.

• 1:09:06Chuck Nice?

  It's pretty wild.

• 1:09:07Neil deGrasse Tyson?

  Yeah.

• 1:09:08Chuck Nice?

  So our first few questions have been previously, previously asked by our Patreon supporters. But you said, I'm gonna have to see what Brian says about this.

• 1:09:19Neil deGrasse Tyson?

  Oh.

• 1:09:20Chuck Nice?

  Right.

• 1:09:20Neil deGrasse Tyson?

  So they were elevated.

• 1:09:21Chuck Nice?

  So they were elevated.

• 1:09:23Neil deGrasse Tyson?

  Okay, it was above my pay grade, right there.

• 1:09:25Chuck Nice?

  So they, they, they wrote in with a question and you were like, let me get my supervisor.

• 1:09:33Neil deGrasse Tyson?

  I punched it, I punched it, okay. I wish you would go.

• 1:09:36Chuck Nice?

  So this is Brian Burke, he says, hey, Dr. Tyson, Lord nice, Chuck, you should be able to nail this one. It's Brian from Portugal. Brian, shut up.

• 1:09:46Chuck Nice?

  He says, can you help explain the information paradox with black holes? My understanding is that quantum mechanics and Hawking radiation are at odds about this. One says, information is forever. The other says, information disappears when a black hole evaporates. Are we any closer to understanding how this can be? Thanks and please keep doing what you're doing. We need real science to carry on, live long and prosper.

• 1:10:11Neil deGrasse Tyson?

  Ooh, nice.

• 1:10:12Chuck Nice?

  Yeah.

• 1:10:13Neil deGrasse Tyson?

  Now, let me preface that a little more here.

• 1:10:14Chuck Nice?

  Sure, please.

• 1:10:15Neil deGrasse Tyson?

  So. I was delighted to learn that the evaporation of black holes, the Hawking radiation, is the exact inventory of fundamental particles that went in, even though it's being conjured out of the gravitational field of the black hole itself, the energy density of the field. So I said, "Oh, so that's a total reckoning of ingredients." But if I went in as a DNA molecule and I come out as the various fundamental particles, the information that I was DNA is gone. So, no, there's no preservation of information there.

• 1:10:50Brian Greene?

  And that's what Stephen Hawking said. So when Stephen Hawking did his initial calculations in the 1970s, he came up with this idea that black holes could actually radiate through quantum processes. The production of particles just outside the edge of a black hole, one falls in and the other races away. And the question was, do the particles race away have the information content about everything that fell in, or don't they? He said, "They don't. My calculations show it's a thermal bath of particles, a vanilla, featureless bath of particles, no information inside of it." We particle physicists said, "Come on. Quantum mechanics doesn't allow information to be lost or destroyed."

• 1:11:34Brian Greene?

  So if you're saying that, you're saying quantum mechanics is wrong.

• 1:11:37Neil deGrasse Tyson?

  Okay.

• 1:11:38Brian Greene?

  And we're not willing to go there.

• 1:11:39Neil deGrasse Tyson?

  Yeah, quantum is so, it's so successful.

• 1:11:41Brian Greene?

  Right.

• 1:11:42Neil deGrasse Tyson?

  That's, you gotta be ready for okay.

• 1:11:44Chuck Nice?

  You gotta be somebody more than Stephen Hawking.

• 1:11:47Brian Greene?

  And this led Lenny Suskin again, and Gerard Tofu, who won the Nobel Prize, and various other people, to spend 25 years trying to answer this question. And we believe, largely from string theory, that we do understand that the information does, in a very subtle way, come out of the black hole. Subtle quantum correlations between the particles that emerge from the black hole do carry all the information of, say, the DNA molecule that fell in. So you can recover all the information, we believe. Now, there are still mysteries that we're still figuring out, but just about every- Buddy, including Hawking before he passed away, agrees that we believe the information does come out.

• 1:12:32Chuck Nice?

  Preservation.

• 1:12:32Neil deGrasse Tyson?

  He had that with somebody, wasn't it? Was it with Presko?

• 1:12:35Brian Greene?

  John Presko?

• 1:12:36Neil deGrasse Tyson?

  Yeah, great. He was a postdoc when I was a graduate student at the University of Texas.

• 1:12:40Brian Greene?

  Okay, yeah.

• 1:12:40Neil deGrasse Tyson?

  Yeah. So Presko won the bet then.

• 1:12:42Brian Greene?

  So, so Presko won the bet, but Kip Thorne was also part of this. And Kip Thorne was unwilling to concede.

• 1:12:49Neil deGrasse Tyson?

  Thorne is on, in our archives. Check him out.

• 1:12:51Brian Greene?

  Yeah, absolutely.

• 1:12:52Neil deGrasse Tyson?

  We interviewed him in his office in Pasadena.

• 1:12:54Brian Greene?

  So, so Hawking conceded the bet that John Presko said the information does come out, and he gave him an encyclopedia of baseball, a lot of information he provided him as, as the way to...

• 1:13:07Neil deGrasse Tyson?

  Baseball already has too much information. Now you have an encyclopedia.

• 1:13:10Brian Greene?

  That's right. It made good on his bet. I don't know where Kip Thorne stands on this. I don't know that he has conceded.

• 1:13:16Neil deGrasse Tyson?

  Okay.

• 1:13:16Chuck Nice?

  Okay. And what's the business about the information being stored in the event horizon? Have you?

• 1:13:22Brian Greene?

  Yes.

• 1:13:22Neil deGrasse Tyson?

  Oh, that's the, what do you call that? That's the holographic.

• 1:13:25Brian Greene?

  Holographic idea, and that's part of the solution for why we believe the information comes out.

• 1:13:29Neil deGrasse Tyson?

  And that's Susskind again.

• 1:13:30Brian Greene?

  Susskind again. That's, this guy is incredible. Things fall into a black hole, and we believe that they leave on the surface, in some sense, a copy, a residue of their information, and that's how it can come back out. It never actually goes in.

• 1:13:43Chuck Nice?

  It never went in. The imprint was left on the event horizon.

• 1:13:46Brian Greene?

  Yes.

• 1:13:47Chuck Nice?

  Very cool, man.

• 1:13:48Brian Greene?

  Super cool, man.

• 1:13:49Neil deGrasse Tyson?

  Yeah, so we have an explainer on whether or not we are living in a black hole.

• 1:13:53Brian Greene?

  We could be.

• 1:13:54Neil deGrasse Tyson?

  Just the properties. Yeah.

• 1:13:55Chuck Nice?

  Right.

• 1:13:56Brian Greene?

  If it's big enough, yeah.

• 1:13:57Neil deGrasse Tyson?

  Yeah, yeah, okay.

• 1:13:58Chuck Nice?

  All right, here we go. This is Rachel. Rachel says...

• 1:14:00Neil deGrasse Tyson?

  And we're still in questions that I, I had to call my boss.

• 1:14:05Chuck Nice?

  Rachel says, what's up, Dr. T? Rachel here from Austin, Texas. I've been thinking about the spinning universe hypothesis, which suggests our cosmos might be rotating as a whole. This idea has been proposed as a potential way to resolve the Hubble tension, but it got me wondering, if the universe is indeed spinning, could the force we attribute to dark energy, which is causing the accelerated expansion, actually be explained by a kind of cosmic centrifugal force? So she's... Saying that we we just on a whirlig Whirling bird. Whirling. Whirling dervish. We're in the whirling dervish. We're we're in a teacup ride.

• 1:14:44Brian Greene?

  It's hard to see how you'd make that work when we see the evidence for dark energy. It seems to be so-called isotropic. It's the same in every direction in which you look. Whereas if the universe is spinning, there's an axis. There's an angular momentum that picks out some directions as different from others.

• 1:15:01Chuck Nice?

  That's right.

• 1:15:02Brian Greene?

  So it's hard to see.

• 1:15:03Neil deGrasse Tyson?

  If you look along the axis, there's no centrifugal force.

• 1:15:06Brian Greene?

  Yes, but if you look off the axis, we study the motion of distant galaxies. We look across the entire sky. And and so we have sufficient data, I think, to rule that possibility out. But who knows? May write a paper and we'll see.

• 1:15:19Chuck Nice?

  We'll check it out. Yeah, that was all right. What a great question. These. Okay. Um, we're going to move into regular questions now.

• 1:15:26Neil deGrasse Tyson?

  Wait, wait, why don't we pull out one that was there and I forgot who asked it and was about whether we'd have a quark catastrophe. So we had a Patreon member write in. The questioner knew.

• 1:15:36Brian Greene?

  Yeah.

• 1:15:36Neil deGrasse Tyson?

  That if you have two quarks.

• 1:15:38Brian Greene?

  Yeah.

• 1:15:39Neil deGrasse Tyson?

  In some kind of nucleon, then you try to pull them apart.

• 1:15:42Brian Greene?

  Hmm.

• 1:15:43Neil deGrasse Tyson?

  There's a point where that snaps, but you've invested so much energy in it. The two new quarks show up in that instant. Now you have two pairs of quarks. Right? We good with that?

• 1:15:53Brian Greene?

  Yeah.

• 1:15:53Neil deGrasse Tyson?

  Okay, so in a black hole, or maybe in the big rip, either.

• 1:16:01Brian Greene?

  Mm hmm.

• 1:16:02Neil deGrasse Tyson?

  Let's go. Let's look at the you're descending to the to the singularity. The the two quark particle falls. Title forces get greater and greater, and then it splits the two quarks. So now we come two pairs of quarks as they fall in. Then it becomes four pairs and then eight pairs. And it'll just be this unlimited increase in the number of quarks as it descends to the singularity. Why doesn't that happen?

• 1:16:30Brian Greene?

  Well, you you do feel tidal forces as you get ever closer to the center for sure.

• 1:16:36Neil deGrasse Tyson?

  But I'm not a quark.

• 1:16:37Brian Greene?

  And and it's a finite time scale between when you cross the event horizon and you hit the singularity and I could well imagine that particle pairs are created in the last moments of this, but whether all of the energy gets transformed in this way, that seems unlikely. You'd have to calculate.

• 1:16:56Neil deGrasse Tyson?

  After I rethought about it, it occurred to me, it's pulling that energy out of the black hole. So it would evaporate the whole.

• 1:17:01Brian Greene?

  Oh, if they're thinking that an infinite energy transfer, then yeah, absolutely. Everything is finite, time scales, finite energies. And so, yeah, exotic processes can certainly happen when the gravitational force is that powerful.

• 1:17:13Neil deGrasse Tyson?

  Right.

• 1:17:14Brian Greene?

  Now, of course, when you get to the singularity, we have no idea what actually happens.

• 1:17:18Neil deGrasse Tyson?

  Because you street theorists haven't figured it out yet.

• 1:17:19Brian Greene?

  We have not. But that's actually a real point. That's one of the goals that we've not yet achieved.

• 1:17:24Neil deGrasse Tyson?

  And the big rip would be the same thing. There's a point where the.

• 1:17:28Brian Greene?

  Yeah, that's true, too. If it was sufficiently high.

• 1:17:31Neil deGrasse Tyson?

  If would get on the scale of nucleons and split apart the.

• 1:17:38Brian Greene?

  Quark antiquor pairs.

• 1:17:39Neil deGrasse Tyson?

  And then make another pair and just keep doing that.

• 1:17:41Brian Greene?

  Yep. I mean, there are many other processes that can happen in the world, so I wouldn't just focus on this. There are all sorts of ways that energy can transfer from the big rip or the gravitational energy of a black hole into particle production into various kinds of processes.

• 1:17:55Neil deGrasse Tyson?

  Yeah, creates a whole universe of quarks.

• 1:17:58Brian Greene?

  You'd have to sort of calculate the rate at which those processes happen versus other things.

• 1:18:04Neil deGrasse Tyson?

  It eats the entire dark energy universe.

• 1:18:08Brian Greene?

  Inside you, but we're still inside the black hole?

• 1:18:10Neil deGrasse Tyson?

  No, no, now we're just looking at the big rip. I'm just wondering if this keeps happening, it's using up the energy of.

• 1:18:16Brian Greene?

  But then, of course, if that were the case, it would no longer undergo the accelerated expansion.

• 1:18:21Neil deGrasse Tyson?

  Exactly.

• 1:18:22Brian Greene?

  Yeah, yeah.

• 1:18:22Neil deGrasse Tyson?

  Exactly. Okay.

• 1:18:24Chuck Nice?

  All right, this is Michael de la Morena, who says, is time a dimension or a field? It seems more like a field because it can be affected by gravity.

• 1:18:36Neil deGrasse Tyson?

  That was another one that I punted to Brian.

• 1:18:39Chuck Nice?

  Mm hmm. Is time a dimension or a field?

• 1:18:42Brian Greene?

  Well. I'd say the deep lesson of Einstein was that space and time can be affected by their environment and they in turn create the very environment that then back reacts on their own shape and structure.

• 1:19:00Neil deGrasse Tyson?

  Mm-hmm.

• 1:19:01Brian Greene?

  And so, we usually think about time as a coordinate, a label, telling us when things happen, just like coordinates in space tell us where things happen. And the unexpected thing is, that label, the amount of time between two different locations, can be influenced by the force of gravity.

• 1:19:20Neil deGrasse Tyson?

  Right, but that doesn't require that it be a field.

• 1:19:23Brian Greene?

  Yes, it doesn't require it be a field.

• 1:19:25Neil deGrasse Tyson?

  Right, to be influenced by a force.

• 1:19:27Brian Greene?

  But I understand the intuition because we used to think that the labels, the locations of where and when things happen in a Newtonian perspective, they're just inert, they just sit there, they don't do anything.

• 1:19:39Neil deGrasse Tyson?

  Mm-hmm.

• 1:19:40Brian Greene?

  Einstein elevated them to be dynamical qualities of the world, and that's the deep lesson.

• 1:19:46Chuck Nice?

  Very cool.

• 1:19:47Neil deGrasse Tyson?

  All right.

• 1:19:48Chuck Nice?

  Great question, Michael. All right, this is Cody Rosenberg, who says, "Hello, doctors and Chuck. I'm Cody Rosenberg from Eugene, Oregon. Please know that y'all are goaded for us armchair astrophysicists, physicists, or physics enthusiasts."

• 1:20:04Neil deGrasse Tyson?

  Nice.

• 1:20:05Chuck Nice?

  All right, very nice. Anyway, do you guys think that life is inevitable? Do you think it would be weird for a universe to exist that can't be experienced or observed? Do you think we are the physical manifestations of the universe yearning to experience itself?

• 1:20:20Brian Greene?

  So it's a very John Wheeler-like way of looking at the world. Wheeler loved to say that we are the way that the universe becomes cognizant of itself. It's a poetic...

• 1:20:31Neil deGrasse Tyson?

  In fact, he drew a picture, he had a U.

• 1:20:33Brian Greene?

  With an eyeball.

• 1:20:34Neil deGrasse Tyson?

  Yeah, yeah, a U, a serif-ed U, and on one of the upwards of the U, there's an eyeball looking at the other line of the U.

• 1:20:41Chuck Nice?

  Oh, very nice.

• 1:20:42Neil deGrasse Tyson?

  So the universe...

• 1:20:43Brian Greene?

  Looking at itself.

• 1:20:44Chuck Nice?

  Looking at itself.

• 1:20:45Brian Greene?

  So it's, you know, narcissistic or beautiful, depending on your perspective, that we're here so the universe can think about itself.

• 1:20:51Neil deGrasse Tyson?

  Yeah.

• 1:20:52Brian Greene?

  I don't know of any law... That makes life inevitable. It seems it was a lot of happenstance between the big bang and today. But, you know, we don't understand a lot about the world and maybe one day we'll find there's this law, this inevitability of the existence of galaxies and stars and planets and people, at least on one such planet. I don't know of any such law today.

• 1:21:14Chuck Nice?

  Let me ask you both this.

• 1:21:15Neil deGrasse Tyson?

  Well, there's some thinking that, and this is wishful thinking, not because someone has researched this.

• 1:21:20Chuck Nice?

  Okay.

• 1:21:20Neil deGrasse Tyson?

  That you go to a different planet, you can take a geologist there. They'll be comfortable there because they'll know what a rock, you know, there's an.

• 1:21:28Chuck Nice?

  Cause they see their crap everywhere.

• 1:21:29Neil deGrasse Tyson?

  Yeah, that's right. So the rocks and the minerals, there might be some more exotic ones.

• 1:21:33Chuck Nice?

  Exactly.

• 1:21:33Neil deGrasse Tyson?

  But they have a sense of how, what elements do when they're heated for a certain amount of time under pressure.

• 1:21:40Chuck Nice?

  Right.

• 1:21:41Neil deGrasse Tyson?

  And that repeats depending on the planet. So we can, so there are general rules of geology that apply to all planets.

• 1:21:49Chuck Nice?

  All planets.

• 1:21:49Neil deGrasse Tyson?

  So let's go to biology.

• 1:21:50Chuck Nice?

  Okay.

• 1:21:51Neil deGrasse Tyson?

  Could the DNA molecule be a natural consequence of complex chemistry operating on planetary surfaces? Could it be as natural on a planet as rocks are to the geologists?

• 1:22:04Chuck Nice?

  And that, that's what I was about to ask, and both of you can chime in on this. How cheap is life? So forget if it's inevitable, how cheap is life?

• 1:22:12Neil deGrasse Tyson?

  I don't know what that means.

• 1:22:13Brian Greene?

  Well, in the sense that it formed relatively quickly on the planet, so it didn't take an enormous amount of time.

• 1:22:19Neil deGrasse Tyson?

  If it took billions of years, you'd say, whoa, that was some hard stuff.

• 1:22:21Brian Greene?

  Yeah.

• 1:22:22Neil deGrasse Tyson?

  Yeah. It formed in just, in fact, we used to, how long do you think it took?

• 1:22:26Brian Greene?

  Half a billion, I'd say.

• 1:22:27Neil deGrasse Tyson?

  Okay, that's what we used to say.

• 1:22:28Brian Greene?

  Ah.

• 1:22:28Neil deGrasse Tyson?

  Okay.

• 1:22:29Brian Greene?

  What would you say now?

• 1:22:30Neil deGrasse Tyson?

  Okay. We used to say that because you'd start the clock at when Earth formed, right? Four and a half billion years. Yeah, yeah. And then the early, early signs of life are like 3.8, 3.9. So you say 600 million years. We used to say. And then we said, no, no, that's unfair. That's unfair. When Earth formed, there was periods of heavy bombardment.

• 1:22:50Brian Greene?

  Yeah.

• 1:22:50Neil deGrasse Tyson?

  Where the surface of the Earth could not have sustained complex chemistry.

• 1:22:54Brian Greene?

  Of course.

• 1:22:55Neil deGrasse Tyson?

  Because the energy is too high, it breaks apart all your, let the Earth cool for goodness sake.

• 1:22:59Brian Greene?

  Yeah.

• 1:22:59Neil deGrasse Tyson?

  So the cooling, you let it cool at about four billion years. It's half a billion years. At four billion years, now you start the clock and you have life 200 million years later.

• 1:23:08Brian Greene?

  Wow.

• 1:23:10Neil deGrasse Tyson?

  That's really great.

• 1:23:11Chuck Nice?

  Yeah.

• 1:23:11Neil deGrasse Tyson?

  Right.

• 1:23:12Chuck Nice?

  In the grand scheme.

• 1:23:12Neil deGrasse Tyson?

  In the grand scheme.

• 1:23:13Chuck Nice?

  Yeah, so that's what I'm saying. So life is pretty cheap then.

• 1:23:15Neil deGrasse Tyson?

  Yeah, it's it's 5% of the total time Earth has been around, so.

• 1:23:19Brian Greene?

  Again, however, I I think that's likely the way to talk about it, but there are so many detailed physical, chemical processes that maybe they just so happen to come together in this one planet of the trillion that are out there. So when we understand it better, that cheapness, we may explain it by a coincidence of a whole lot of factors that just happened to align on our planet. I don't think that's how it's going to turn out, but it's a possibility.

• 1:23:47Chuck Nice?

  It's a possibility, yeah.

• 1:23:48Neil deGrasse Tyson?

  Well, except that, you know, there are amino acids on on meteorites.

• 1:23:51Chuck Nice?

  Yeah, we've found them already.

• 1:23:52Neil deGrasse Tyson?

  Right, yeah.

• 1:23:53Brian Greene?

  An interesting question, though, is the way that proteins are coded by amino acids is uniform across all life. It's the same code. Three base pairs on the genetic code give rise to a particular amino acid. That is the code that works for you, me, and all life. On another planet, if there is other form of life, the deep question will be, is it the same code?

• 1:24:16Neil deGrasse Tyson?

  Right.

• 1:24:17Brian Greene?

  Or is it different? So.

• 1:24:19Neil deGrasse Tyson?

  It doesn't need DNA at all.

• 1:24:20Brian Greene?

  And right.

• 1:24:21Chuck Nice?

  Right!

• 1:24:22Brian Greene?

  And so if it's different, that would be wonderful. That would suggest that life in a whole variety of different forms can exist throughout the end of it.

• 1:24:29Neil deGrasse Tyson?

  We've not fully explored all the ways of being alive.

• 1:24:30Brian Greene?

  Yeah, yeah.

• 1:24:31Neil deGrasse Tyson?

  Yeah.

• 1:24:31Chuck Nice?

  Wow. All right. Well, great question. Way to go, Cody. All right, this is Aaron Bailey, who says, hey, StarTalk, I am Aaron from Florida, and and we're sorry.

• 1:24:42Neil deGrasse Tyson?

  Stop!

• 1:24:45Chuck Nice?

  Florida's trying. They're trying. All right. Yeah, so Aaron says, longtime viewer, first time subscriber. Thank you, Aaron.

• 1:24:52Neil deGrasse Tyson?

  Thank you.

• 1:24:52Chuck Nice?

  We appreciate that. According to Einstein's equations, is time travel still possible if you are traveling to a black hole? And why can't we use gravitational detectors to measure the properties of dark matter?

• 1:25:07Brian Greene?

  So in the first question, yeah, I mean Einstein's special and general relativity both embrace a certain kind of time travel. And the black hole provides the mechanism for one kind. If you go hang out near a black hole, time for you elapses more slowly compared to someone who's far away.

• 1:25:24Neil deGrasse Tyson?

  Famously portrayed in Interstellar.

• 1:25:26Brian Greene?

  And so if you go to the edge of a black hole and you hang out and then you come back, everyone that you meet is going to be much older. Their clock was going much faster than your clock. And that is, some people say, well, that's not time travel. That is time travel. You've traveled into their future, which would have been your future if you stayed there.

• 1:25:44Neil deGrasse Tyson?

  And you know who they left up in the ship?

• 1:25:46Chuck Nice?

  The black dude. He came back like, oh, goddamn.

• 1:25:50Brian Greene?

  Twenty-three years.

• 1:25:52Chuck Nice?

  You know, I'm on social security. You go down there, you tell me you'll come right back. You're worse than my kids. I don't get it, Matthew McConaughey.

• 1:26:11Neil deGrasse Tyson?

  All right. What was the second half to that question? And so the second half, he says, why can't we use gravitational detectors to measure the properties of dark matter?

• 1:26:23Brian Greene?

  Well, we do. The way we know dark matter exists is by the gravitational influence that it has on its environment. What we're unable to do is identify what the dark matter is made of. And so we have these detectors all over the planet trying to capture little particles of dark matter. If that's the right explanation, we haven't been able to find any yet.

• 1:26:44Neil deGrasse Tyson?

  You know what I'm doing now? Okay, you know, they're pulsars. Rapidly rotating neutron stars.

• 1:26:49Brian Greene?

  In a very precise way.

• 1:26:50Neil deGrasse Tyson?

  Extremely precise. And they're across the galaxies. There are not all that many of them, but there's enough to map out the galaxy. So if you precisely know and measure the pulses of these pulsars, you can track.

• 1:27:07Neil deGrasse Tyson?

  A gravitational wave moving across the galaxy.

• 1:27:11Chuck Nice?

  Yeah, so you're kind of using them like buoys in the ocean.

• 1:27:15Neil deGrasse Tyson?

  Good analogy there. Beautiful idea, and you don't even need LIGO for that.

• 1:27:19Chuck Nice?

  Yeah.

• 1:27:19Neil deGrasse Tyson?

  You just need height sensitive, uh, uh, high precision time.

• 1:27:23Brian Greene?

  Yeah, for gravitational waves of a certain wavelength, this is a beautiful way of detecting their influence.

• 1:27:28Chuck Nice?

  Super cool, man.

• 1:27:29Neil deGrasse Tyson?

  Yeah.

• 1:27:30Chuck Nice?

  All right, let's move on to Alex Frias, who says, "Hey, Dr. Tyson, Lord and I, Alex here from Mexico." Oh, I should say Alex.

• 1:27:42Neil deGrasse Tyson?

  No, Alejandro.

• 1:27:43Chuck Nice?

  Alexandro from Mexico.

• 1:27:46Neil deGrasse Tyson?

  What? Isn't that racist that you assume?

• 1:27:49Chuck Nice?

  I can be racist. I'm black, I don't know if you realize.

• 1:27:55Chuck Nice?

  Okay?

• 1:27:55Neil deGrasse Tyson?

  Oh!

• 1:27:56Chuck Nice?

  The world invented racism for me.

• 1:28:02Chuck Nice?

  Okay, here we go.

• 1:28:05Neil deGrasse Tyson?

  Did I tell you? Did I tell you? It was, I, I was giving a public talk and I would, I thought I'd say something funny.

• 1:28:11Chuck Nice?

  Right.

• 1:28:11Neil deGrasse Tyson?

  I was talking about the dinosaurs, and they went extinct by an asteroid that hit the Yucatan Peninsula, the Yucatan Peninsula of Mexico. And I said, um, "But that's not what the dinosaurs called it." Okay?

• 1:28:25Chuck Nice?

  Okay.

• 1:28:25Neil deGrasse Tyson?

  I thought it'd be funny. I thought it'd be funny.

• 1:28:27Chuck Nice?

  Right.

• 1:28:27Neil deGrasse Tyson?

  I thought it'd be funny. And then someone in the front row said, "They called it Mexico."

• 1:28:32Chuck Nice?

  That's funny, too.

• 1:28:35Neil deGrasse Tyson?

  Spanish.

• 1:28:35Chuck Nice?

  Spanish for dinosaurs. Yeah.

• 1:28:38Neil deGrasse Tyson?

  Okay.

• 1:28:39Chuck Nice?

  All right. And then you had Trumposaurus, who was just like, "Give 'em out." Anyway, uh, I've always been intrigued and confused by the idea of supersymmetry.

• 1:28:50Neil deGrasse Tyson?

  Ooh, nice.

• 1:28:51Chuck Nice?

  If the standard model of particle physics is one of the most successful theories we have, what is telling us that it needs doubling up? What would supersymmetry fix in our understanding of the universe? And what problems might it create? Thank you both, and greetings from your neighbors, uh, in the beautiful Upper West Side.

• 1:29:11Neil deGrasse Tyson?

  Oh, nice.

• 1:29:12Chuck Nice?

  Look at that, way to go, Alex, from right up the street.

• 1:29:15Neil deGrasse Tyson?

  Of Manhattan.

• 1:29:16Chuck Nice?

  Right, he's...

• 1:29:16Neil deGrasse Tyson?

  So, let me, let me sharpen that even further.

• 1:29:19Chuck Nice?

  Sure.

• 1:29:19Neil deGrasse Tyson?

  So, the standard model is quite an organizational map of our particles and our forces and the like. In its current state, now that we've got the...

• 1:29:29Chuck Nice?

  Higgs.

• 1:29:29Neil deGrasse Tyson?

  The Higgs. Is it missing anything? Is it a closed box right now? And if we do anything to it, does it simply make it more powerful? Or do we know we need things to explain other things that we don't yet understand?

• 1:29:44Brian Greene?

  Good, good. So the main motivation for supersymmetry is to address exactly the way you framed the question. Which is, when we study this Higgs particle, this newest addition that we found on July 4th, 2012, at least that's where the announcement was. When you look at the mathematics, it says that the mass of the Higgs particle should be much, much bigger than the mass that we find.

• 1:30:10Neil deGrasse Tyson?

  What?

• 1:30:11Brian Greene?

  And when we try to keep the mass at the value measured, we have to stand on our mathematical heads to do so. We have to tune and tune and tune. If supersymmetry were true, the terms that would push the Higgs mass up, they cancel out from those pairings. That's why we need the pairings, that's why we need the doubling. And if you can cancel out the new contributions, you can rest easy, the Higgs mass will stay at a small value.

• 1:30:39Chuck Nice?

  Look at that.

• 1:30:40Neil deGrasse Tyson?

  So how many more particles come along?

• 1:30:41Brian Greene?

  It doubles it, it really does. For every known particle, there is a partner, electrons have-

• 1:30:45Neil deGrasse Tyson?

  A super symmetric particle.

• 1:30:46Brian Greene?

  Yeah, super symmetric electron. Yes, so the electron has the selectron, quarks, squarks, neutrinos, snutrinos.

• 1:30:54Neil deGrasse Tyson?

  No, no.

• 1:30:55Brian Greene?

  Yes.

• 1:30:56Neil deGrasse Tyson?

  No.

• 1:30:57Brian Greene?

  Yes, I don't name them.

• 1:30:58Neil deGrasse Tyson?

  Snutrino, no. You know why? Because somebody, when they found it, they're like, nah, neutrinos, snutrinos.

• 1:31:06Brian Greene?

  And so, the big hope, if you would have spoken to me on as a graduate student in the 1980s, the big hope and the reason we believe that string theory might be five years away, was we expected supersymmetry, which is the super in superstring theory. We thought it would be found, those particles would be found at the Large Hadron Collider. And they were not found.

• 1:31:28Chuck Nice?

  Wow.

• 1:31:29Brian Greene?

  And so this did not-

• 1:31:30Neil deGrasse Tyson?

  And they will never be found.

• 1:31:30Brian Greene?

  Well, that's probably true, because the collider has a limited energy reach. Nothing in our theories tells us how massive the partner particles would be. If they're sufficiently massive, they'll be beyond the reach of the Large Hadron Collider. So there's a natural explanation for why we didn't find the particles, but we were certain that we would.

• 1:31:51Neil deGrasse Tyson?

  He wants another collider.

• 1:31:51Chuck Nice?

  Yeah, there you go. You're gonna need one. Look at that. Wow, that is fascinating, though. Okay, and, and does the Higgs have the, do we have a name for the other particle?

• 1:32:03Brian Greene?

  Higgsino.

• 1:32:03Chuck Nice?

  Higgsino?

• 1:32:04Brian Greene?

  Yeah.

• 1:32:05Neil deGrasse Tyson?

  I prefer squigs.

• 1:32:08Chuck Nice?

  You're gonna go with squigs.

• 1:32:13Neil deGrasse Tyson?

  The photon, what's the similar?

• 1:32:15Brian Greene?

  Photino.

• 1:32:16Neil deGrasse Tyson?

  Really?

• 1:32:16Brian Greene?

  Yeah.

• 1:32:17Chuck Nice?

  Okay.

• 1:32:18Brian Greene?

  And the W and Z bosons, those are harder, zinos or winos?

• 1:32:24Neil deGrasse Tyson?

  Winos.

• 1:32:24Brian Greene?

  Winos, they get a little bit, yeah.

• 1:32:26Neil deGrasse Tyson?

  Yeah, that's getting a little. Okay, and how about the graviton?

• 1:32:29Brian Greene?

  Well, you see, the supersymmetry that we're talking about doesn't have gravity in it when you're just talking about the standard model.

• 1:32:36Neil deGrasse Tyson?

  Oh, standard model doesn't have gravity.

• 1:32:37Brian Greene?

  Yeah, yeah, but if you include gravity.

• 1:32:40Neil deGrasse Tyson?

  Right.

• 1:32:40Brian Greene?

  Then there is a version, it's called supergravity, and it comes out of string theory as well, and it's the gravitino.

• 1:32:46Chuck Nice?

  Right, from the graviton.

• 1:32:47Brian Greene?

  Yeah.

• 1:32:48Neil deGrasse Tyson?

  Right, okay.

• 1:32:48Chuck Nice?

  All right, all right, well, way to go there, Alex.

• 1:32:52Neil deGrasse Tyson?

  So we're still looking for them?

• 1:32:53Chuck Nice?

  Yeah.

• 1:32:53Brian Greene?

  You, you, you're still looking for them, there's no evidence for them, yeah.

• 1:32:56Chuck Nice?

  Is this just a matter of a lack of detectors? Could you build enough detectors where we could get all this, capture all this stuff?

• 1:33:04Brian Greene?

  Not so much detectors, it's a matter of the energy, so how big the detector, how big the collider is. And that's, you know, colliders are expensive, and the bigger they are, the more money they cost.

• 1:33:15Neil deGrasse Tyson?

  And we had a big one going in our, you know, in our side of the pond. These superconducting supercollider in Texas, funded in the 1980s, under Reagan.

• 1:33:26Chuck Nice?

  Right.

• 1:33:26Neil deGrasse Tyson?

  And dug the hole, got all ready, Waukesha, Texas. It would, it would be three times as powerful, I think.

• 1:33:34Brian Greene?

  Yeah, about 50 TeV and we have 14 TeV.

• 1:33:36Neil deGrasse Tyson?

  Yeah, yeah, so three times the power of, of the one that was built in Switzerland, and then early 90s, they zeroed the budget. And they said, oh, those cost overruns and this sort of thing, but, but.

• 1:33:50Brian Greene?

  Oh, some kind of defense thing. We no longer were fighting for our lives.

• 1:33:54Neil deGrasse Tyson?

  Peace broke out in Europe.

• 1:33:56Chuck Nice?

  That was a fall ago.

• 1:33:57Neil deGrasse Tyson?

  Yes.

• 1:33:58Brian Greene?

  Yes.

• 1:33:59Neil deGrasse Tyson?

  Peace breaks out and all of a sudden, it's like, we don't need physicists.

• 1:34:02Brian Greene?

  We don't need this.

• 1:34:02Neil deGrasse Tyson?

  What do we need physicists for? And they're little toys. You never heard of cost overruns in any other particle accelerator for the whole 20th century.

• 1:34:10Chuck Nice?

  Right. Interesting. This is Blake, who says, hey, it's Blake. Greetings from warm, sunny Columbia, South Carolina.

• 1:34:20Neil deGrasse Tyson?

  Oh.

• 1:34:21Chuck Nice?

  Way to, way to rub it in there, Blake. He says, there are quite a few theoretical particles that have been discussed on this show, the graviton, the tachyon, strings, et cetera. But we don't seem close to actually finding any of them. Are there any experiments proposed that might help us capture and learn about these elusive particles, if they exist? And slightly more an engineering question, if we did find them, how might we use them for the benefit of humanity?

• 1:34:48Brian Greene?

  Yeah.

• 1:34:48Chuck Nice?

  Uh, do they have a use if we find them? I mean?

• 1:34:51Brian Greene?

  Well, if dark matter is actually found and it is a particle, look, it'll deepen our confidence, our understanding. Can I imagine applying dark matter particles to build something? The whole point is they're incredibly elusive. They only interact gravitationally.

• 1:35:08Chuck Nice?

  How do we even capture them if they don't interact with anything?

• 1:35:11Brian Greene?

  Well, they do interact.

• 1:35:12Neil deGrasse Tyson?

  With themselves.

• 1:35:13Chuck Nice?

  They interact with themselves.

• 1:35:14Brian Greene?

  Well, yes, but anything that has energy interacts gravitationally. And, and these dark matter particles, through indirect quantum processes, do interact with ordinary matter. And that's how these detectors are set up.

• 1:35:27Neil deGrasse Tyson?

  Accelerating.

• 1:35:28Brian Greene?

  Uh.

• 1:35:28Neil deGrasse Tyson?

  Or is that the energy?

• 1:35:29Brian Greene?

  Well, yes, you could, well, that's the dark energy. Yeah, but it's the same basic idea. And so, yes, you can detect these things, but that's different from gathering them together and engineering with them. So I don't, I don't see any direct benefit that comes out.

• 1:35:44Neil deGrasse Tyson?

  There's no bricks and mortar.

• 1:35:46Brian Greene?

  You know, but again, it's the same argument we made before. The deeper your understanding, that's step one. And then someone figures out where that goes.

• 1:35:53Chuck Nice?

  That's gonna take you someplace else. Right. Okay, gotcha. All right, this is Luke Senior, who says, best regards from Joli. He says, Dr. Luca Laporta, PhD, translation scholar and sonologist. He says, could it be the entanglement phenomenon is simply a matter of absence of the time dimension at the scale of the particles? And that we see two particles interacting instantaneously at a distance in some, he now his word, magical way. In their own three dimensions only universe, they're just unaware that a change of state

• 1:36:34Chuck Nice?

  has occurred, that for them, there's no before entanglement slash after entanglement. Thank you very much. It's a very well thought out question. What, does it make sense?

• 1:36:47Brian Greene?

  It, it does. And I think we can interpret it more or less along this wormhole idea that we were describing before. The wormhole notion, again, this is still very much at the forefront. We're still working out the details, but if it is the case that two distant particles are connected by a wormhole, if they're entangled quantum mechanically, then it would be as if they're right next to each other.

• 1:37:12Neil deGrasse Tyson?

  To them, they don't know the difference.

• 1:37:13Brian Greene?

  To them, they don't know that they're far apart. And so that's a variation on the same thing. I don't think you can say they live in a world without time. Because the conundrum is to us beings that do have time, you do something here and it instantaneously, according to us, affects something over there. And that would still be a puzzle, no matter what. And one explanation would be, well, they're actually closer together than you think by looking at them because they have this secret shortcut connection, which could be the wormhole.

• 1:37:40Neil deGrasse Tyson?

  So I think for so many years, people were imagining wormholes as some kind of a ride on, in a water park.

• 1:37:47Brian Greene?

  Exactly.

• 1:37:48Neil deGrasse Tyson?

  You know, even in the movie Contact.

• 1:37:49Brian Greene?

  Right.

• 1:37:49Neil deGrasse Tyson?

  Jodie Foster is going through. And so, but no, you just stepped through.

• 1:37:53Brian Greene?

  No, you stepped through. I think it depends on the nature of the wormhole, but yeah, there can be versions where it's effectively stepping from one place to another.

• 1:38:00Chuck Nice?

  Star Trek did it right, though. They had a portal where it looked like a doorway threshold.

• 1:38:05Brian Greene?

  City on the edge of forever.

• 1:38:06Chuck Nice?

  City on the edge of forever.

• 1:38:07Brian Greene?

  Yeah.

• 1:38:07Chuck Nice?

  And that's a wormhole. You step through it and you're already there. There's no ride, there's no, you just step through it and you're already there.

• 1:38:13Brian Greene?

  And that's another one where they were going to save someone's life.

• 1:38:16Neil deGrasse Tyson?

  And they decided not to. And they realized they shouldn't.

• 1:38:18Brian Greene?

  What they're going to change the future.

• 1:38:19Neil deGrasse Tyson?

  Yes. In fact, I was, I was talking with Bill and. Uh, he said that was his favorite episode.

• 1:38:26Brian Greene?

  Oh, really? Yeah, it's my favorite watching as a viewer.

• 1:38:28Neil deGrasse Tyson?

  Yeah, just because it was, it dealt with time travel in a very

• 1:38:32Brian Greene?

  Emotional way.

• 1:38:32Neil deGrasse Tyson?

  Emotional and unorthodox way.

• 1:38:35Brian Greene?

  Yeah.

• 1:38:35Chuck Nice?

  And causality is, is actually addressed. All right, Zachary E says, hello, Dr. Tyson, Lord Nice, Dr. Green. Is it possible that through the many worlds interpretation, quantum immortality can become macroscopic? If every single possible state of every single particle in existence is equally real, I feel like the superposition of a single particle in quantum immortality theory can be expanded to incorporate the superposition of every single particle in existence.

• 1:39:06Brian Greene?

  Yeah. And look, you know, another way of saying it is, we said before that the many worlds allows a world in which anything compatible with physics is realized. Us living to a hundred, two hundred, five hundred, a thousand, I don't know that there's a law of physics that prevents that can happen.

• 1:39:26Chuck Nice?

  Now, there is a law of Jesus, I'm bored. That will allow that. The boredom, the boredom, can you imagine living a thousand years? Ugh. Who, I'm, oh, kill me, just thinking about it, I want to die.

• 1:39:40Neil deGrasse Tyson?

  So wait, here's something that we did not raise, which was, if there's another identical me, is it me?

• 1:39:46Brian Greene?

  That's the deep question.

• 1:39:47Chuck Nice?

  Wow, that's, now, that's a consciousness question.

• 1:39:49Brian Greene?

  And I think the answer to that is yes, because that-

• 1:39:51Neil deGrasse Tyson?

  No, I think the answer is no.

• 1:39:52Brian Greene?

  Why?

• 1:39:53Neil deGrasse Tyson?

  Because we've already kind of done that experiment, they're called twins.

• 1:39:56Brian Greene?

  No, I'm saying that person has literally your memories, literally yourself of sense of self, until something, measurement happens that causes you to be different.

• 1:40:08Chuck Nice?

  From that.

• 1:40:09Brian Greene?

  Yeah.

• 1:40:09Chuck Nice?

  Yeah.

• 1:40:09Brian Greene?

  So it's truly you.

• 1:40:11Chuck Nice?

  That's wild.

• 1:40:11Brian Greene?

  I mean, if, if, if I spoke to that version of you, you would adamantly can't, claim, yes, I'm the same guy.

• 1:40:18Chuck Nice?

  That's me.

• 1:40:18Brian Greene?

  It's me.

• 1:40:19Chuck Nice?

  It's me, damn it. That's funny.

• 1:40:21Brian Greene?

  Yeah.

• 1:40:23Neil deGrasse Tyson?

  I don't know what to say.

• 1:40:25Chuck Nice?

  I've never heard you say that before.

• 1:40:34Chuck Nice?

  So that means we are living forever.

• 1:40:38Brian Greene?

  There.

• 1:40:38Chuck Nice?

  The reincarnation.

• 1:40:40Brian Greene?

  Yeah, yeah.

• 1:40:40Chuck Nice?

  Are all over this.

• 1:40:41Brian Greene?

  That's right, right. Or at least extraordinarily long, you know, maybe there is some physical law about maybe the proton decays.

• 1:40:49Chuck Nice?

  Right, right.

• 1:40:50Brian Greene?

  Ten to the thirty-eight years.

• 1:40:52Chuck Nice?

  It's not ten thirty-eight?

• 1:40:53Brian Greene?

  Yeah. Or the call ten to the whatever, you know.

• 1:40:56Chuck Nice?

  More than ten to the thirty-two.

• 1:40:57Brian Greene?

  Yeah.

• 1:40:57Chuck Nice?

  Wow. All right, this is Marcus Ruzan, and Marcus Ruzan says, hello Neil and Brian, love the show. I've been wondering something about time and light. If nothing can travel faster than light, and the speed of light is a universal constant, could it be that time itself is actually an emergent property of light? Is it possible that what we perceive as time is actually just a consequence of us traveling through spacetime at a finite speed below the speed of light? Is that not confirmed by the fact that from the point of view of a photon, there is no time? Thanks, and keep looking up from Singapore.

• 1:41:40Brian Greene?

  Yeah.

• 1:41:41Chuck Nice?

  Nice.

• 1:41:41Brian Greene?

  Okay. And in some poetic sense, I agree with what the questioner asked. They're saying that if a photon had consciousness.

• 1:41:49Chuck Nice?

  Right.

• 1:41:50Brian Greene?

  From its perspective.

• 1:41:51Chuck Nice?

  It would not know.

• 1:41:52Brian Greene?

  It would not know that time is a last thing.

• 1:41:54Chuck Nice?

  And there's lots of things in time.

• 1:41:55Brian Greene?

  Now, I think it's really important to recognize that you're extrapolating Einstein's result to a particle for whom the equations don't literally apply in the way that we're using them.

• 1:42:09Chuck Nice?

  Correct.

• 1:42:09Brian Greene?

  So if you apply Einstein's ideas to any massive body, you find that they can't travel at the speed of light, and therefore they will always have this conception of time. But if you want to push it to the absolute limit, which I call poetry, not quite mathematics, then yes.

• 1:42:24Chuck Nice?

  Right. Because the key is, the photon has no mass.

• 1:42:28Brian Greene?

  Yes.

• 1:42:29Chuck Nice?

  That's the key.

• 1:42:29Brian Greene?

  Yes.

• 1:42:30Chuck Nice?

  That's it.

• 1:42:31Brian Greene?

  Yep.

• 1:42:31Chuck Nice?

  So once you have mass, you can't be a photon, and you can't, you'll never experience with that photon experience.

• 1:42:36Brian Greene?

  Precisely.

• 1:42:37Chuck Nice?

  All right. Okay, well, there you go, Marcus, but thanks for the, you know. I had nothing to add to that.

• 1:42:46Chuck Nice?

  All right. This is Patrick Dietz. And Patrick says, hello, Dr. Tyson, Dr. Green, Lord Nice, Pat Dietz from Rivana, Michigan. Could the reason we cannot see dark matter also account for the expansion of the universe due to dark matter moves faster than light? Let me read that again. Could the reason we cannot see dark matter also account for the expansion of the universe due to dark matter moving faster than light? Okay.

• 1:43:21Brian Greene?

  That's a tough one to parse for me.

• 1:43:22Chuck Nice?

  It's not really rough, but I see what he's saying. How can you see the thing that's faster than the thing that allows you to see the thing?

• 1:43:29Brian Greene?

  Right. I get this sort of collection of words, but the problem is...

• 1:43:36Chuck Nice?

  Okay, by the way, people, this is why I love scientists. Because they know how to call you a dumbass.

• 1:43:44Chuck Nice?

  Without ever saying those words.

• 1:43:49Brian Greene?

  The important point is that for a particle to be a particle of dark matter, it has to have mass. Once it has mass, it can't travel faster than the speed of light. So the ideas don't meld together in a consistent way.

• 1:44:04Chuck Nice?

  There you go. All right. I like the question, just for the fun of it. All right. Thank you, Patrick. This is Mr. Zoot. And Mr. Zoot says, dear Star Talkers, Jeffrey here. Pronounce Jeffrey Chuck.

• 1:44:19Chuck Nice?

  Screw you, Mr. Zoot.

• 1:44:22Chuck Nice?

  He says, I understand electron orbitals are really probability clouds, but still exist in discrete energy levels around the nucleus. What then happens during ionization?

• 1:44:35Neil deGrasse Tyson?

  Do they stay as a probability cloud? Just untethered from their anchor, so to speak? Do they still have discrete energy levels? Hey, what gives and thanks?

• 1:44:47Brian Greene?

  So if that is a great question.

• 1:44:49Neil deGrasse Tyson?

  Somebody's thinking.

• 1:44:50Brian Greene?

  And so it certainly does stay as a probability cloud or probability wave. Right. If an electron is ionized, say, from hydrogen. But if that electron is living in a universe that is not a box. That's infinitely big. Then we don't believe its energy levels will be quantized.

• 1:45:10Neil deGrasse Tyson?

  You think it'll be continuous?

• 1:45:11Brian Greene?

  Yes. So if you have a particle in a box. If you have a particle in a box, then the energy levels are quantized, but they are dependent upon the size of the box.

• 1:45:19Neil deGrasse Tyson?

  Because you're solving the wave equation.

• 1:45:21Brian Greene?

  You're saving the wave equation in a box.

• 1:45:23Neil deGrasse Tyson?

  You're expanding the, what's it called?

• 1:45:24Brian Greene?

  The harmonics.

• 1:45:25Neil deGrasse Tyson?

  The harmonics of the wave.

• 1:45:26Brian Greene?

  And the harmonics have to die.

• 1:45:28Neil deGrasse Tyson?

  They have to fit inside the box.

• 1:45:29Brian Greene?

  But if there's no box, then they could have any wavelength at all, any energy at all.

• 1:45:34Neil deGrasse Tyson?

  The energy of a free electron is not quantized.

• 1:45:36Brian Greene?

  Correct.

• 1:45:37Neil deGrasse Tyson?

  I did not know that.

• 1:45:38Brian Greene?

  That's, I've never heard that before either.

• 1:45:40Neil deGrasse Tyson?

  It's obvious that it could only be that way.

• 1:45:42Brian Greene?

  That makes, that's wild.

• 1:45:44Neil deGrasse Tyson?

  Wow.

• 1:45:45Brian Greene?

  That's absolutely wild. Very cool, man. Wow. Great, great question, Jeffrey.

• 1:45:50Neil deGrasse Tyson?

  Just a highlight because he said something important here.

• 1:45:52Brian Greene?

  Yeah.

• 1:45:52Neil deGrasse Tyson?

  So once, we'll call it a box, but let's, let's, let's look at a tube. Let's look at like a, a, an organ tube.

• 1:45:59Brian Greene?

  Okay.

• 1:45:59Neil deGrasse Tyson?

  Okay.

• 1:46:00Brian Greene?

  So like a pipe organ.

• 1:46:01Neil deGrasse Tyson?

  Pipe organ.

• 1:46:01Brian Greene?

  Right.

• 1:46:02Neil deGrasse Tyson?

  And you can ask, what kind of wave can you set up inside that tube? And it can only hold a wave where the complete wave is there.

• 1:46:13Brian Greene?

  Right.

• 1:46:13Neil deGrasse Tyson?

  You can't hold like a half a wave. Right, right. So it sets what the wavelength is, the, the, the frequency of the sound, that's the wavelength. Um, you get that from the wavelength in each tube. So different tubes have different frequencies that resonate inside of those tubes.

• 1:46:29Brian Greene?

  Right.

• 1:46:30Neil deGrasse Tyson?

  And so when I think of atoms, I think of, you got the nucleus with the protons sets up a box. And so you then, you do the math and you get a set of wavelengths, I'll call them that, that fit inside this box. And it's unique for every atom. And that's what gives you the spectra of each atom.

• 1:46:49Neil deGrasse Tyson?

  That's where each atom has a unique spectrum.

• 1:46:50Brian Greene?

  Right.

• 1:46:51Neil deGrasse Tyson?

  Yeah, it's really cool.

• 1:46:52Brian Greene?

  That is excellent. Wow, I learned stuff on this show. So great.

• 1:46:57Neil deGrasse Tyson?

  So did I. I just never thought about free electrons and their energies.

• 1:47:01Brian Greene?

  Yeah, okay. Um, this is Brian Nadoo, who says, hey, Dr. Tyson, Dr. Green, Lord Nice, Brian from upstate New York here. Would the discovery and verification of the graviton assist at all in reconciling general relativity and quantum mechanics?

• 1:47:18Neil deGrasse Tyson?

  I love that.

• 1:47:19Brian Greene?

  Huge.

• 1:47:20Neil deGrasse Tyson?

  Isn't it just assumed that there's a graviton?

• 1:47:23Brian Greene?

  And that assumption needs to be verified, hopefully.

• 1:47:26Neil deGrasse Tyson?

  And what's the energy of a graviton relative to the waves that we just detected?

• 1:47:30Brian Greene?

  Well, the energy, the mass of a graviton, we believe, uh, is zero because gravity also travels at the speed of light.

• 1:47:40Neil deGrasse Tyson?

  Oh, okay.

• 1:47:41Brian Greene?

  So it's much like a photon in that particular way.

• 1:47:44Neil deGrasse Tyson?

  Yeah, okay.

• 1:47:45Brian Greene?

  And yes, if we could ever really detect a graviton, do experiments with gravitons, scatter gravitons off of each other, then yes, we would learn an enormous amount about general relativity and quantum mechanics.

• 1:47:56Neil deGrasse Tyson?

  Yeah, but we'll help you merge them.

• 1:47:58Brian Greene?

  Well, our...

• 1:47:59Neil deGrasse Tyson?

  Because that's a quantum expression of gravity.

• 1:48:02Brian Greene?

  That's right. In fact, the very existence of a graviton would be the first evidence that gravity is quantized.

• 1:48:09Neil deGrasse Tyson?

  Wow.

• 1:48:10Brian Greene?

  And so we're assuming that there is a graviton, but verifying it would be a huge step.

• 1:48:15Neil deGrasse Tyson?

  Who was the first to presume that?

• 1:48:17Brian Greene?

  The idea of the graviton? I don't historically know.

• 1:48:20Neil deGrasse Tyson?

  So, so, but my understanding was the gravitational wave.

• 1:48:23Brian Greene?

  Yeah, well, he was a reluctant gravitational wave person. He was really uncertain in 1916 and 1918 about whether they were real.

• 1:48:32Neil deGrasse Tyson?

  Okay.

• 1:48:32Chuck Nice?

  Amazing.

• 1:48:33Brian Greene?

  Yeah.

• 1:48:34Neil deGrasse Tyson?

  Yeah. So, so, I'm just saying... The quantum assumption is that where you have a wave, you also have a particle.

• 1:48:44Brian Greene?

  Yeah.

• 1:48:45Neil deGrasse Tyson?

  And like the photon is a wave and a particle.

• 1:48:47Brian Greene?

  Yep.

• 1:48:49Chuck Nice?

  Wow.

• 1:48:50Neil deGrasse Tyson?

  Okay.

• 1:48:50Chuck Nice?

  That's super cool, man.

• 1:48:52Brian Greene?

  That's a good question. Who first introduced the very idea of a graviton? I don't know the answer.

• 1:48:57Neil deGrasse Tyson?

  It feels kind of natural if you're gonna.

• 1:48:59Brian Greene?

  I'm gonna look that one up.

• 1:49:00Neil deGrasse Tyson?

  Quantum. Quantum quantify.

• 1:49:03Brian Greene?

  Yep.

• 1:49:04Chuck Nice?

  All right, this is Tash Shaw and Tash says, Dear Dr. Tyson, Dr. Green, Lord Nice, I'm Tash from Orange, Australia. I'm a longtime listener, so my boyfriend bought me a subscription to Patreon for Christmas.

• 1:49:19Neil deGrasse Tyson?

  Oh, nice.

• 1:49:20Chuck Nice?

  Very nice. What a nice boyfriend.

• 1:49:22Neil deGrasse Tyson?

  Very nice gift.

• 1:49:22Chuck Nice?

  Yeah, that's a smart man. I have read that other dimensions could potentially be detected through gravitational and other anomalies. I was wondering how we would be able to distinguish these from any effects of dark matter. So would there be dimensional differentiations?

• 1:49:43Brian Greene?

  Yeah. In fact, a proposal that was made a while ago is that at a collider, like the Large Hadron Collider, when you slam protons together, you can calculate and measure how much energy you have before the collision. You can measure how much energy you have after the collision. And if you have less energy after the collision, that energy must have gone somewhere. And the possibility is the energy went into the other dimensions. And so this was a missing energy signature of extra dimensions that we were again hoping we would see.

• 1:50:21Neil deGrasse Tyson?

  Why would you presume that and not as what occurred in the first neutrino experiment?

• 1:50:25Brian Greene?

  That's right. So it could be some other particle, mysterious particle carrying away.

• 1:50:30Neil deGrasse Tyson?

  Right, because in the first neutrino, they didn't experiment and there was.

• 1:50:32Brian Greene?

  An imbalance.

• 1:50:33Neil deGrasse Tyson?

  Yeah, there was an imbalance. There was like, you start with this much energy and they have less.

• 1:50:37Brian Greene?

  Right.

• 1:50:38Neil deGrasse Tyson?

  And you accounted for all the particles.

• 1:50:39Brian Greene?

  Right.

• 1:50:41Chuck Nice?

  Well, maybe there's another particle.

• 1:50:42Neil deGrasse Tyson?

  But what's up with that? And they said, if there is a particle, it has to be neutral and it has to be very low mass. And the guy who proposed it was Italian. So little neutral one neutrino.

• 1:50:54Chuck Nice?

  Oh.

• 1:50:55Neil deGrasse Tyson?

  Like bambino, little baby.

• 1:50:56Chuck Nice?

  Like bambino neutrino.

• 1:50:59Neil deGrasse Tyson?

  What you got, Jeff?

• 1:51:00Chuck Nice?

  Let's go to Cosmic Moss. Says, hello, everyone. Love the show and every star you've had on it. You guys are great. I love the way you teach. Please keep the education up. Dr. Tyson, Dr. Green could theoretically a frequency be matched at two points in space by a micro particle uninhibited by resistance only to be met by its astrophysical counterpart.

• 1:51:25Brian Greene?

  Neil, I think you should take this.

• 1:51:28Neil deGrasse Tyson?

  I don't know that I understand the question.

• 1:51:30Chuck Nice?

  Kind of like matter antimatter, but the particle is already in existence. And then it's a counterpart that impedes, I guess, the entanglement. It's kind of like.

• 1:51:41Neil deGrasse Tyson?

  Read the first sentence again.

• 1:51:42Chuck Nice?

  All right, he goes, uh, could theoretically a frequency. All right, so that's the, I guess, his version of the string, string be matched at two points in space by a micro particle. So that's the entanglement.

• 1:51:57Neil deGrasse Tyson?

  Maybe.

• 1:51:58Chuck Nice?

  Uninhibited by a resistance only to be met by its astrophysical counterpart.

• 1:52:04Neil deGrasse Tyson?

  The only counterpart particles are antimatter.

• 1:52:06Chuck Nice?

  That's it.

• 1:52:07Neil deGrasse Tyson?

  Yeah, there's no other.

• 1:52:08Chuck Nice?

  That's what I'm saying.

• 1:52:09Neil deGrasse Tyson?

  And there's not much antimatter in the universe.

• 1:52:11Chuck Nice?

  Right.

• 1:52:12Neil deGrasse Tyson?

  In fact, well, other than the centers of stars, we probably make all the antimatter there is in the universe on Earth. Would you say?

• 1:52:18Brian Greene?

  I haven't done the calculation, but I could imagine that.

• 1:52:20Neil deGrasse Tyson?

  I mean, just think about that, right? There's plenty antimatter made in the center of something.

• 1:52:23Brian Greene?

  Most antimatter in the universe will get annihilated and find a matter.

• 1:52:26Neil deGrasse Tyson?

  Immediately in the centers of the sun, so.

• 1:52:28Brian Greene?

  Yeah.

• 1:52:30Neil deGrasse Tyson?

  The cool part was in one of the Dan Brown stories, the Catholic Church had a vial of antimatter that they carried.

• 1:52:37Brian Greene?

  That's so funny. Dominus is spirit. Oh, he's gone.

• 1:52:47Chuck Nice?

  Physics jokes, people. Alright.

• 1:52:51Neil deGrasse Tyson?

  So, yeah, I don't, it's not quite clear. If it met its, the counterpart, it would annihilate, no matter what else is going on.

• 1:52:57Chuck Nice?

  Right, no matter what else is going on.

• 1:52:57Neil deGrasse Tyson?

  Yeah, yeah.

• 1:52:58Chuck Nice?

  Alright, so here we go. Kenny Watts says this. "Hey, Dr. Tyson, Dr. Green, sup, Lord Nice, Kenny from Dothan, Alabama. Is the reason why we can't reach the absolute zero degrees in temperature because of the CMB? Is it due to the act of time using energy to move forward, creating heat? And if we were to reach absolute zero degrees, would spacetime move forward in that region?"

• 1:53:28Neil deGrasse Tyson?

  Yeah. Interesting. I was thinking pieces of this, Brian.

• 1:53:30Chuck Nice?

  Yeah.

• 1:53:31Neil deGrasse Tyson?

  So, so my understanding of absolute zero is that, you know, all particle motion stops, except it doesn't because you have quantum fluctuations, even at absolute zero.

• 1:53:41Chuck Nice?

  That's the key point right there.

• 1:53:43Neil deGrasse Tyson?

  Okay.

• 1:53:43Chuck Nice?

  That's the real barrier.

• 1:53:44Neil deGrasse Tyson?

  Okay, so, but why isn't the cosmic microwave background a barrier?

• 1:53:48Chuck Nice?

  Well, if you didn't shield yourself from 2.7 degree photons, they would influence, but presumably if you're able to shield your environment...

• 1:54:00Neil deGrasse Tyson?

  Yeah, but the shielding would have to be temporary because the heat transfers.

• 1:54:04Chuck Nice?

  Yeah, sure. But an experiment takes place over a period of time, so as long as your time scales are set, right?

• 1:54:10Neil deGrasse Tyson?

  That's what how a thermos works.

• 1:54:12Chuck Nice?

  Yeah, exactly.

• 1:54:13Neil deGrasse Tyson?

  There's a time with which the...

• 1:54:14Chuck Nice?

  So I think it's really the uncertainty principle is a true barrier against truly having particles at a definite location, not moving. That would mean position and speed were both nailed down at the same time.

• 1:54:24Neil deGrasse Tyson?

  Which is not happening, right. You're not gonna do that. Not happening.

• 1:54:27Chuck Nice?

  Wow. So the wave function would cease to exist if you were ever to get to the place where you could get the particle to stay exactly frozen, like still and definable in one point.

• 1:54:41Neil deGrasse Tyson?

  Okay, so what is the temperature of that state of matter?

• 1:54:44Brian Greene?

  Well, it depends on the details. I mean, you can calculate the quantum fluctuations of a field, and if you tell me how it interacts and its mass, you can calculate its quantum fluctuations, and indeed, that's how you make predictions about the Casimir effect. Oh. Where you have, you know, two metal plates and there's empty space between them.

• 1:55:02Neil deGrasse Tyson?

  Exacuated completely.

• 1:55:03Brian Greene?

  And yet, those plates can pull together because the fluctuations of the field inside are a little bit less than the fluctuations outside, and that imbalance, you can actually calculate it, and you can determine how the plates come together. That is so freaky, man.

• 1:55:18Neil deGrasse Tyson?

  It's all freaky.

• 1:55:19Brian Greene?

  That is so freaky. I love it.

• 1:55:20Neil deGrasse Tyson?

  It's all freaky.

• 1:55:21Brian Greene?

  Oh, my goodness.

• 1:55:22Chuck Nice?

  And then, and then they attract.

• 1:55:24Brian Greene?

  Yeah.

• 1:55:24Chuck Nice?

  Yeah.

• 1:55:25Neil deGrasse Tyson?

  Brian, you freaky dude.

• 1:55:31Neil deGrasse Tyson?

  So, we should do this every week. What do you think? No, Brian, you have a life. Thank you, Brian.

• 1:55:36Brian Greene?

  My pleasure. This is great.

• 1:55:37Neil deGrasse Tyson?

  You're working on a quantum physics book?

• 1:55:39Brian Greene?

  Yep.

• 1:55:39Neil deGrasse Tyson?

  And this is the decade, the centennial decade of the discovery of quantum physics.

• 1:55:43Brian Greene?

  Exactly.

• 1:55:44Neil deGrasse Tyson?

  So, we can't have too much quantum physics out there.

• 1:55:46Brian Greene?

  Yep.

• 1:55:46Neil deGrasse Tyson?

  And this is for the general public?

• 1:55:48Brian Greene?

  Yeah, so we're finishing it up now. In 2027, it should be out.

• 1:55:52Neil deGrasse Tyson?

  Get it up in this decade?

• 1:55:53Brian Greene?

  Yeah, that's the key thing.

• 1:55:54Neil deGrasse Tyson?

  Okay.

• 1:55:56Neil deGrasse Tyson?

  All right, and this year, we're recording this in 2026, this is the centennial of Edwin Hubble discovering that the Milky Way is not the only galaxy in the universe.

• 1:56:07Brian Greene?

  Wow.

• 1:56:07Neil deGrasse Tyson?

  He discovers that Andromeda is not just a fuzzy spiral sitting within our stars.

• 1:56:12Brian Greene?

  Right.

• 1:56:13Neil deGrasse Tyson?

  It's a whole other.

• 1:56:13Brian Greene?

  It's a whole nother.

• 1:56:14Neil deGrasse Tyson?

  Island universe out there.

• 1:56:15Brian Greene?

  That's, I love that term.

• 1:56:16Neil deGrasse Tyson?

  That was 100 years ago. So, uh, this has been a special edition because it's an extended conversation with my friend and colleague, Brian Greene, right up the street at Columbia University. A delight. Thanks for spending the afternoon in my office.

• 1:56:30Brian Greene?

  My pleasure. It was great fun.

• 1:56:31Neil deGrasse Tyson?

  All right, and Chuck? Always a pleasure. Chuck, you baby. Yes. And catching you on YouTube. Were you just smart enough? That's right, on the StarTalk YouTube channel. Were you just smart enough for this conversation? Today, I was the dumbass, and happy to be so.

• 1:56:46Neil deGrasse Tyson?

  All right. Till next time. Neil deGrasse Tyson. Keep looking up.