Cosmic Queries – Understanding Infinity with Stephon Alexander

What is infinity? Neil deGrasse Tyson and comedian Negin Farsad explore whether we are in a finite universe, the issues with infinity, string theory, and more with theoretical physicist Stephon Alexander.

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

• 0:01Neil deGrasse Tyson?

  Welcome to StarTalk. Your place in the universe where science and pop culture collide. StarTalk begins right now. This is StarTalk. Field of grass Tyson here, your personal astrophysicist. We're doing another cosmic queries. These have become fan favorites. I guess I understand why because you get to participate. Well, actually, if you're a Patreon member, you get to participate in asking those questions at the entry level of Patreon. Today's topic, infinity with my friend and fellow physicist, Stefan Alexander. We'll get to him in a moment.

• 0:45Neil deGrasse Tyson?

  Let me introduce my co-host, Nagin Fassad. Nagin, it's been so long.

• 0:49Negin Farsad?

  Hello. Yes, I'm your honorary astrophysicist comedian friend.

• 0:58Neil deGrasse Tyson?

  Everybody needs one of those, right?

• 1:00Negin Farsad?

  Mine, right? Minus any of the astrophysics, just to be clear. I have none of that.

• 1:06Neil deGrasse Tyson?

  You are a host of the show Fake the Nation?

• 1:10Negin Farsad?

  That's right.

• 1:11Neil deGrasse Tyson?

  And very cool. And in addition to Fake the Nation, you've got some side gig where you've got a succession recap?

• 1:18Negin Farsad?

  That's right.

• 1:18Neil deGrasse Tyson?

  What's up with that?

• 1:19Negin Farsad?

  I'm doing a succession recap pod on the Fake the Nation feed. And I, in addition to talking about space, I love talking about billionaires. So those are my two main interests right now. So yeah, definitely subscribe to hear all the succession chatter.

• 1:35Neil deGrasse Tyson?

  Succession from HBO, right? I saw the whole first season and it was too, it's like really weird for me to continue.

• 1:43Negin Farsad?

  Yeah.

• 1:43Neil deGrasse Tyson?

  It's like, I don't, I don't want this to be true. You know, I don't want that. Please, you know?

• 1:49Negin Farsad?

  I know, it's pretty gross, but so hilarious at the same time.

• 1:55Neil deGrasse Tyson?

  Well, help me welcome my friend and colleague, Stefan Alexander. Stefan, your returning guest. You first appeared with us with when we were on the Nat Geo channel. And you had it was a Nat Geo TV episode. You're a theoretical physicist, a cosmologist, a musician, and an author and professor of physics at Brown University up in Providence, Rhode Island. And among those books, the one I remember most is from now six years ago, seven years ago, The Jazz of Physics. Let me get the right subtitle here. The Secret Link Between Music and the Structure of the Universe. And then you followed that up with Fear of a Black Universe,

• 2:39Neil deGrasse Tyson?

  An Outsider's Guide to the Future of Physics. So you're still at it, but you're also a jazz saxophonist. So you're out of control here, it seems. You also appeared in the 2022 Netflix documentary, A Trip to Infinity. And that is the subject of today. Infinity, which boggles everybody's mind who's ever thought about it. And so could you just tell us what infinity? Wait, can I tell you my first encounter with infinity? I'll tell you, I'm old enough to remember this. Okay, so I am five when Kennedy is assassinated. Okay, that's how old I am.

• 3:22Neil deGrasse Tyson?

  And there's the burial and they put him in in Arlington Cemetery. And there's a flame there at the burial spot. And they called it the Eternal Flame. And I said, what? Does this flame never go out? How could it never go out? What? And and at age five, this. with me, okay? Sorry. This was like, how at night do they secretly put more oil in the flame? You know, but there's the camera doesn't show it. I was, and then I would later learn, yes, that was figurative that it's eternal. But there is a formal mathematical concept called infinity.

• 4:07Neil deGrasse Tyson?

  Nagin, did you have any existential angst over infinity at any time in your life?

• 4:11Negin Farsad?

  Um.

• 4:12Neil deGrasse Tyson?

  Just to put that on, put it on the table right now, because we got the man who's going to straighten us out.

• 4:16Negin Farsad?

  God, I feel, I feel, I mean, I had just an existential angst as a teenager in general and started reading all of the works of Jean Paul Sartre as like a 16 year old and not fully understanding them.

• 4:29Neil deGrasse Tyson?

  Oh, that'll mess you up. That'll mess you up.

• 4:31Negin Farsad?

  So that messed me up big time. And it led to a lot of brooding and a lot of eye rolls on my part. But it didn't, it didn't freak me out the way infinity freaked you out.

• 4:43Neil deGrasse Tyson?

  Okay, okay. All right. So Stefan, tell me about infinity. What's up with that?

• 4:47Speaker 02

  Let me admit something to you and again. I don't know what infinity is. Okay.

• 4:53Neil deGrasse Tyson?

  Okay, we're done here. Okay.

• 4:55Negin Farsad?

  Bye, everybody.

• 4:57Neil deGrasse Tyson?

  Nagin, you got any jokes to take us out? Okay.

• 5:02Negin Farsad?

  Wow, who booked this guy?

• 5:04Neil deGrasse Tyson?

  I know, right? Right?

• 5:06Speaker 02

  I think my first encounter with infinity was just as a kid, like, you know, you get taught how to count. And it's okay, one, two, three. And you realize that you could just go on counting for eternity. And, you know, at some point, I think it was a friend or a teacher, I forget, that was in third grade, who said, actually, there's this number, it's called infinity. And so basically, once you get to the largest possible number you can count in, and infinity is that number that goes on basically and is passed to what? To infinity.

• 5:37Neil deGrasse Tyson?

  And plus, the old geek contest is what's the biggest number you can name? Then you're naming it and say, is that plus one? You know, and that's how you win. You win the geek counting contest.

• 5:48Speaker 02

  Exactly. And so what I'm going to do is give a couple of like, you know, examples of like where infinity comes up in everyday common sense stories. Let's look at fractions, right? I have one over two. Well, if you tell a kid, hey, I'm going to give you half of a pie of pizza or one quarter of a pie of pizza, right? The kid will know I want half of the pie of pizza. They know that the larger you make that fraction of the of the slice, right, they get a smaller slice of pizza. If I say, you get one over one of the pizza. Well, a smart kid will say, I get the whole, I get the whole pie. One over one.

• 6:30Speaker 02

  If I make, if I go smaller than one, which is smaller than one is something that looks like zero. One over zero, then that number goes, that's what infinity is. Um, and that we call that a division by zero. And so computers crash, actually, because, you know, you want to avoid these kind of things when you wrote code, these divisions by zero, because what would happen, right?

• 6:55Neil deGrasse Tyson?

  Yeah, the program crashes.

• 6:57Speaker 02

  It crashes, exactly. Computer doesn't know what to do with it.

• 7:00Neil deGrasse Tyson?

  By the way, in Star Trek, smoke would come out of the computer if they did that.

• 7:06Speaker 02

  Are you trying to say the computer was, the computer was doing things that you didn't want to do?

• 7:10Neil deGrasse Tyson?

  Yeah, yeah, computer would, Captain Kirk would out reason the computer and then the smoke would come out. But in modern times, no, they're just, the computer, it just crashes, yeah.

• 7:19Negin Farsad?

  Wait, can I, this is actually giving me flashbacks of when I first had to graph an asymptote. Which is, this is essentially right asymptotic, this situation. And I remember just being like, oh, let them touch, let the thing touch the line.

• 7:37Neil deGrasse Tyson?

  You, you cared for them, you wanted them.

• 7:40Negin Farsad?

  I wanted them to touch, and it felt, you know, it just felt like a missed connection forever, you know? And it felt so frustrating.

• 7:50Neil deGrasse Tyson?

  At infinity.

• 7:55Neil deGrasse Tyson?

  So get your ass to infinity and you'll see them touch.

• 8:00Neil deGrasse Tyson?

  But right, so Stefan, asymptote is another one of these concepts, right? It's a great word, it's a great word, too.

• 8:06Speaker 02

  Right, you, you kind of, you almost get there but never quite until you go out to infinity. Um, and that's a very good, that's another, in fact, that's very relevant to physics. And by the way, the idea is that the asymptote and this division by zero, all of these things, you know, um, does, you know, touch, you know, have, you know, a deep relationship with, with physics and astrophysics and cosmology.

• 8:29Neil deGrasse Tyson?

  So you're saying it shows up in a lot of different ways?

• 8:32Speaker 02

  It shows up in a lot of different ways and we. Physicists, you know, there's of course philosophers pay a lot of attention to infinities. Mathematicians actually make a living from it. And we physicists try to run away from it. Try to avoid it.

• 8:48Neil deGrasse Tyson?

  I'm trying to see a mathematician busker on the street. You know, trying to make a living off of infinity. You know, I don't, I can't, I'm trying to picture that. I don't, I'm sorry. Someone makes a living off infinity. But, but Nagin, you have, you have questions from our Patreon members.

• 9:04Negin Farsad?

  I, I absolutely do. Let me dive in with a question from Captain James Riley. They write, "It always drives me crazy when I hear that a singularity has infinite density or that the universe is infinite. Is this just something we label things that we don't fully understand? I hate the concept of infinity. It seems like a cop out."

• 9:24Neil deGrasse Tyson?

  I love that.

• 9:26Negin Farsad?

  Which is how I felt about asymptotes. So I'm totally with you, Captain Riley.

• 9:32Neil deGrasse Tyson?

  Yeah, so Stefan, it's, you know, the captain's got a point here, you know. Are we, are we just invoking infinity because we can't otherwise solve the problem?

• 9:42Speaker 02

  Yes and no. Can we, can we evoke one of your favorite astrophysical objects, Neil? The black hole, the black hole.

• 9:49Neil deGrasse Tyson?

  What's that?

• 9:50Speaker 02

  Because I think this is a perfectly, very good example of where you kind of get to have your cake and eat it too. Because here is an interesting thing. When Einstein came up with his theory of general relativity, which describes, you know, how matter and energy can warp the spacetime fabric and create the effect that we call gravity. A mathematical prediction, a mathematical solution came out of that, that theory. This theory spat out a very extreme, sort of extreme warp in a spacetime from a very, you know, from a basically a collapse, a star that has collapsed into a very dense region. And this thing is called a black hole.

• 10:33Speaker 02

  And Neil, you've done some excellent reports on that in the past.

• 10:37Neil deGrasse Tyson?

  But just to be clear, Nagin, he said that Einstein's theory just spat out the equations for a black hole, but with the help of really brilliant people who understood the theory. It did just poop it out like, like.

• 10:55Negin Farsad?

  Yeah, yeah. Although I like the imagery of just a bunch of numbers coming out of someone's butt.

• 11:01Neil deGrasse Tyson?

  It just pooped it out on route to whatever it was doing. No, no, some brilliant people applied, applied Einstein's general relativity. Now that they had that framework to arrive at a black hole as a new, a new object, a new prediction. Yeah.

• 11:16Speaker 02

  Right.

• 11:16Neil deGrasse Tyson?

  Yeah.

• 11:17Speaker 02

  And it was a ma- it was literally, you know, the Einstein's theory was ten, what we call ten couple nonlinear partial differential equations. Very comp- very, very, um, difficult and still difficult to solve. So you're lucky when you get one solution. And the black hole solution or the Schwarzschild solution. But at that time, like people, some people, and one of my mentors, David Finkelstein, I have the Edington-Finkelstein, um, coordinate system, which was based on Schwarzschild's solution about the event horizon. Right? The point of no return. Once you fall into this black hole after it gobbles you up. You know, this was seen by many to just be some mathematical trickery, some mathematical solution that has not, no element of reality.

• 12:02Speaker 02

  Until of course we found one.

• 12:04Neil deGrasse Tyson?

  Right.

• 12:04Speaker 02

  Okay. And we found many, right? Um, now there are black hole laboratories out there.

• 12:09Neil deGrasse Tyson?

  Yeah, yeah, yeah, yeah.

• 12:10Speaker 02

  Um, and so the thing I find interesting about that was people already knew that the black hole, this, the reason why they thought it was a mathematical artifact or mathematical gobbledygook of this, of, of Einstein's theory. Some, some physicists thought was because it actually had a singularity. It actually had an infinity. What do I mean by that? If you actually, this is the, the example we used before. If you look at the, you know, if I fall into a black hole, if I, um, you know, describe going in as some, the radius, you know, like a ball, think of the black hole as a gigantic ball in outer space. A gigantic invisible dark ball. And as I go in.

• 12:54Speaker 02

  To the center of the black hole, this radius will eventually go to zero. But if I divide, and it turns out that the density and the force really falls off. It actually decreases as one over R, sometimes one over R squared, one of R. So what happens when R goes to zero? You get an infinity. You get an infinity in the density, the mass density.

• 13:16Neil deGrasse Tyson?

  Infinite density.

• 13:17Speaker 02

  You also get an infinite density, thank you. You get an infinity in the forces, right? And you get an infinity in the curvature, because the curvature becomes infinite as well.

• 13:27Neil deGrasse Tyson?

  So, so, so, I, okay, so I think the person who asked the question knew that that's what you would say. The question is, is that real? Is it, is it?

• 13:37Speaker 02

  Yes.

• 13:38Neil deGrasse Tyson?

  No.

• 13:39Speaker 02

  Good, good. Now, this is interesting.

• 13:41Neil deGrasse Tyson?

  I'm pretending I'm the dude who has, I'm the captain. No, you're just making this.

• 13:48Neil deGrasse Tyson?

  How can you have anything that's infinite anything? That's, that's a physical thing. How is that even possible? We, we agree you can do that mathematically. No one's arguing.

• 13:57Speaker 02

  Right.

• 13:58Neil deGrasse Tyson?

  Now you're gonna tell me an actual physical thing. It's the infinity that your math delivered. And that's what.

• 14:05Negin Farsad?

  Cause like, yeah, cause like, at the end of the day, if we're looking at like, a top, if the black hole is in a Tupperware container.

• 14:13Speaker 02

  Yes, very good.

• 14:14Neil deGrasse Tyson?

  Okay, where are you going with this? I'll stay with you, go.

• 14:18Speaker 02

  You're gonna bake the black hole?

• 14:20Negin Farsad?

  I'm just saying, like, it can't, if it's infinitely dense, the Tupperware container's gonna break, right? Or whatever. Does that make any sense?

• 14:31Speaker 02

  No, that's actually, so that's right. So what, it's interesting that you, you had a theory that put out a sick solution. So many people thought that's not real, but then you find this thing in reality. So what do you do with the fact that this infinity is there in the prediction? And so then this is where you get disagreements amongst physicists and astrophysicists. Some people say, well, there's something that replaces that theory. Um, meaning in general relativity, there's some new physics that we yet, we do not know. Some people say you have to accept the infinity. Um, and you know, there's something is censoring that infinity from actually realizing itself and coming out and doing bad things.

• 15:13Neil deGrasse Tyson?

  I like that idea that nature might be censoring our infinities. I like that.

• 15:18Speaker 02

  Yes.

• 15:18Neil deGrasse Tyson?

  And so it could, it could be that the infinity is the limit of the applicability of this theory of the universe.

• 15:25Speaker 02

  That's, that's, that's a take I take, actually.

• 15:27Neil deGrasse Tyson?

  Okay, alright.

• 15:28Speaker 02

  That's why I land on, that's why.

• 15:30Neil deGrasse Tyson?

  Okay, now, but now where, where's the Tupperware go? We got enough.

• 15:33Negin Farsad?

  Exactly. I know, I feel like.

• 15:36Neil deGrasse Tyson?

  Back to the Tupperware.

• 15:37Negin Farsad?

  You, you have some really, yeah, some really expansive Tupperware. Leftovers forever in your Tupperware.

• 15:45Neil deGrasse Tyson?

  Leftovers for, because it's infinitely dense, it could feed everyone forever. We gotta take a quick break, but when we come back, more with Stefan Alexander, who's taken us to infinity and beyond with, of course, my co-host, Nagin Fassad. We'll be right back.

• 16:12Speaker 03

  Hi, I'm Chris Cohen from Hallworth, New Jersey, and I support StarTalk on Patreon. Please enjoy this episode of StarTalk Radio with your and my favorite personal astrophysicist, Neil deGrasse Tyson.

• 16:35Neil deGrasse Tyson?

  We're back, StarTalk Cosmic Queries. We're talking about infinity. Oh, yeah. And we got one of the world's experts who thinks about this subject, Stefan Alexander, a friend and colleague, professor of physics at Brown University, Rhode Island. And I got Nagin Fassad. Nagin, you wrote, you wrote a book.

• 16:55Negin Farsad?

  I did.

• 16:56Neil deGrasse Tyson?

  A few years ago.

• 16:58Negin Farsad?

  Yeah.

• 16:59Neil deGrasse Tyson?

  Just, it was, and I'm trying to remember the title. Is it How to Make White People Laugh or something like that?

• 17:04Negin Farsad?

  Yes, How to Make White People Laugh. Neil, it wasn't for you.

• 17:07Neil deGrasse Tyson?

  Oh, it wasn't for me. That's why I never, I, I heard about the book, but I'd said, no, this is not, no, not addressed to me.

• 17:16Negin Farsad?

  That's right.

• 17:17Neil deGrasse Tyson?

  Okay.

• 17:17Negin Farsad?

  To make white people laugh.

• 17:18Neil deGrasse Tyson?

  So I remembered the title correctly?

• 17:20Negin Farsad?

  That's the title, yeah.

• 17:21Neil deGrasse Tyson?

  Okay, very cool. Okay, so Stefan, you were gonna add to the point about the black hole singularity being an infinite density point and possibly others stepping in to save the day.

• 17:33Speaker 02

  Yes, so there are other types of singularities that show up in physics that can maybe, I think that where we were able to, what we call tame or cure the singularity.

• 17:44Neil deGrasse Tyson?

  And the beast.

• 17:46Speaker 02

  The beast, yes.

• 17:47Neil deGrasse Tyson?

  Tame the beast.

• 17:48Speaker 02

  One was the electric charge and the electric force. So if you look at a charged particle.

• 17:53Neil deGrasse Tyson?

  An electron, okay.

• 17:55Speaker 02

  Or a magnet, or a magnet, right? Um, the magnetic force also between two magnets, actually, as I bring the magnets closer together and closer together, actually turns out that that force, when you go to zero distance, according to the equations, that worked really well for all of our motors and all of our, you know, electricity and all that, wind energy and all that stuff, it uses the same physics that we trust. But according to this physics, when you go here, all that good stuff goes out the window because you will get, according to the theory, an infinite force, an infinite amount of energy.

• 18:31Neil deGrasse Tyson?

  Hmm.

• 18:31Speaker 02

  And we do not measure that because the magnets touch and nothing blows up.

• 18:35Neil deGrasse Tyson?

  And you're strong enough to make the magnets touch if they're resisting each other, for example.

• 18:39Speaker 02

  That's right, you're strong enough to do that. But according to this thing, the magnets should never touch, you can never be strong enough because you require infinite force to make them touch.

• 18:46Neil deGrasse Tyson?

  All right.

• 18:47Speaker 02

  Okay, so what solved that problem? It turns out, Richard Feynman and, you know, his colleagues figured out, actually, there's quantum physics going on. So what happens is that quantum physics fuzzifies and softens in a sense, like, you know.

• 19:04Neil deGrasse Tyson?

  You just made up that word, fuzzify. I'm pretty sure you just made up. I'm pretty sure, but okay, we know what you mean.

• 19:10Negin Farsad?

  Yeah, yeah, yeah.

• 19:11Neil deGrasse Tyson?

  Let the record show, he's making up words as he goes along.

• 19:15Negin Farsad?

  Which, by the way, which is what infinity sometimes sound like, sounds like. Just throw in the word infinity and that's exactly the point of the question. It sounds like a cop out, like it fuzzifies, but continue.

• 19:27Neil deGrasse Tyson?

  Fuzzifying infinity.

• 19:28Speaker 02

  Okay, so, so this is, so weird things happen. So in the quantum world now, if you say, okay, you know, the force between the magnets, you know, is really what we call a non-quantum or classical theory doesn't require quantum things. What do you mean by quantum now? Well, it means that there are things called quanta. And in this case, the thing that becomes the quanta is light. Because light is actually the thing that's mediating, communicating the force, actually. And so what Feynman taught us is that you can't no longer think about the magnetic field as a magnetic field, but actually as a particle called a photon that gets transmitted, bouncing back and forth. And as a photon goes, is communicating this force and the magnet gets closer and closer,

• 20:13Speaker 02

  the photon can actually, you know, do weird things. It can do weird quantum.

• 20:17Neil deGrasse Tyson?

  Okay, but the point is, you are saving the magnetic field problem invoking quantum physics.

• 20:23Speaker 02

  Yes, yes.

• 20:23Neil deGrasse Tyson?

  Is quantum physics going to save you from the center of the black hole? From the singularity?

• 20:28Speaker 02

  Very good. So there are now people, not people, the great physicists that argue, like Stephen Hawking being one, and Gerard Toff and Lenny Susskind and others, that said, ah, what if, what happened with, you know, with real magnets? By analogy, there's something quantum. What, what quantum? Quantum gravity. There's something to do with gravity being a quantum, having a quantum effect. What if that would like, jump in and save the day? And as I go into the singularity of a black hole, you don't get infinity, but you get new quantum effects. What would that look like?

• 21:06Neil deGrasse Tyson?

  You'd have to marry quantum physics with Einstein relativity for that.

• 21:10Speaker 02

  You have to do that.

• 21:11Neil deGrasse Tyson?

  And it's some kind of shotgun wedding, right at that last moment.

• 21:14Speaker 02

  Some kind of shotgun wedding.

• 21:15Neil deGrasse Tyson?

  I'm just saying.

• 21:16Speaker 02

  But here's the problem.

• 21:17Negin Farsad?

  None of the in-laws are happy in that scenario.

• 21:20Neil deGrasse Tyson?

  None of the in-law.

• 21:23Speaker 02

  Here's the funny thing. If gravity and quantum mechanics were to be a couple, they're very incompatible with each other. Every reconciled differences that this allowed them from actually making a bond.

• 21:33Neil deGrasse Tyson?

  Yeah, all right.

• 21:34Negin Farsad?

  It's like when I've tried to date a Pisces, it never works out.

• 21:38Neil deGrasse Tyson?

  You know, I could have told you that. Why didn't you call me? That's right.

• 21:43Neil deGrasse Tyson?

  So, that's the, we replied to the captain whether or not we fully satisfied his question. So what are the questions you got, Nagin?

• 21:50Negin Farsad?

  All right, let's move on to David. Um, he's actually happy to submit his very first question after years of being a Patreon subscriber.

• 21:57Neil deGrasse Tyson?

  Oh, excellent. Oh, David, does he have a last name or is it just David?

• 22:00Negin Farsad?

  Um, he just, it's just David. He's like Madonna. He just goes by the one. Um, I once heard Alex Filippenko explain infinity and our universe is operationally infinite, infinite to us because we can never achieve the edges of it, not even at the speed of light, because space is expanding faster than the speed of light, almost like going up an escalator that is going faster than you can walk up it, you'll never reach the top. Is my small mind grasping this concept of an infinite universe? And if so, or if not, how do multiple universes fit into our infinite universe?

• 22:34Neil deGrasse Tyson?

  Ooh, I love those questions.

• 22:36Negin Farsad?

  But I love that escalator metaphor because if that, if that's right, that puts things into making sense for me.

• 22:46Neil deGrasse Tyson?

  Right, right, right. The way I look at it is, and I can, I can contribute a little bit to this answer. All right, so I'll contribute two parts, you take care of the rest. So, yes, if the universe is expand, and Alex Filippenko is a colleague of mine, we came up together actually in graduate school. Uh, and so if you, if you have an infinite universe that's expanding, right, you'll never reach the edge. Like, and I'd love, like you said, we all agree that escalator analogy is excellent. However, you don't need an infinite universe to never reach the edge. For example, the surface of the earth is not infinite,

• 23:30Neil deGrasse Tyson?

  yet you could just keep walking and never reach the edge. So don't equate reaching an edge with something having to be infinite, because the space can turn back on itself. And you can end up just making loops and never stop walking and always walk in the same direction. Whichever direction you choose and you'll never get to the edge. So that's my first point to that. And the second point is, if you embed, so I can have a sheet of paper that's infinite.

• 24:04Neil deGrasse Tyson?

  Infinite, okay? Now, but a sheet of paper is two dimensions. I can have another sheet of paper. That's infinite. And put them one centimeter apart from each other and they will never intersect. Even though they're both infinite. Because I pulled one into a third dimension.

• 24:25Neil deGrasse Tyson?

  And so when you embed infinities in higher dimensions. You got no problems at all. You can cram as many as you want in there, there's plenty of room. So, you take it from there, Stefan.

• 24:38Speaker 02

  You took all the good examples.

• 24:40Neil deGrasse Tyson?

  Oh, no.

• 24:43Speaker 02

  And of course, you know, there's um, infinite time.

• 24:47Neil deGrasse Tyson?

  Oh.

• 24:48Speaker 02

  You can have a finite world. But the clock can continue ticking for, you know, for an infinity. You know, meaning that the universe um, could be finite in extent. But just continue expanding for infinity.

• 25:01Negin Farsad?

  So the universe is like a vampire that never dies in that scenario.

• 25:07Neil deGrasse Tyson?

  Nagin, it's exactly like that.

• 25:11Negin Farsad?

  Great, got it. Just wanted to explain for the listeners.

• 25:14Neil deGrasse Tyson?

  Minus the blood, minus the blood.

• 25:16Negin Farsad?

  Okay.

• 25:16Neil deGrasse Tyson?

  And just to follow up on what you just said, Stefan. So if the spherical universe were expanding. You would still have a finite universe, but you could walk in it forever. Even though it's expanding. So there's a lot of variations on this geometry that make for fascinating thought.

• 25:35Speaker 02

  Absolutely, absolutely. And in fact, um, one of the great mathematicians, um, you know, somebody that you know, Neil. He went off and made a lot of money. But he literally, you know. He put a lot of money towards this satellite. So that he can, you know, know about the Big Bang, call it Simon's Observatory.

• 25:54Neil deGrasse Tyson?

  Oh, yes, yes, Jim Simons.

• 25:55Speaker 02

  Jim Simons, he's, he's a geometry, so he came up with some important mathematics all about this topic. He believes that the universe actually is finite. It's a sphere. It has a spherical geometry. And. If you, you know, if you play with the, if you play with the assumptions and the data and the statistics enough, you might be able to still accommodate that the universe actually might be finite in terms of the data. So that's an interesting side note.

• 26:25Neil deGrasse Tyson?

  And, and just for, in case people don't know, Jim Simons made his billions trading in the stock market, bringing high level mathematics to his predictive models that no one knew was even possible at the time. And, and now he's put his money back to further research. There's a Simons Foundation, the Simons Center for Research in Physics, Biology and Computing, which is right here in downtown Manhattan.

• 26:54Negin Farsad?

  Oh, I thought you were gonna say, which is on a yacht, because that's what he gets to afford now.

• 27:00Neil deGrasse Tyson?

  He does have a yacht, and I've been on his yacht, and it's called the Archimedes. And it's called the Archimedes.

• 27:06Negin Farsad?

  Of course, of course.

• 27:07Neil deGrasse Tyson?

  Yes, yes. So thank you for that, for queuing. That was your cue.

• 27:12Negin Farsad?

  Time for another question?

• 27:13Neil deGrasse Tyson?

  Yeah, please, please.

• 27:15Negin Farsad?

  So from Gavin Bamber, he says, hello from North Vancouver, please visit. Can string theory be represented by music? If so, would it be more of a monophony, classical or jazz? Would it be a complete composition, or would it continue on into infinity?

• 27:32Neil deGrasse Tyson?

  Wait, is that a word, monophony? Is that, is that like, does that mean a one-note concert? What are you saying there?

• 27:39Speaker 02

  That's what it sounds like to me, but maybe it's something else.

• 27:42Negin Farsad?

  Oh my God, we have two of the smartest people on the planet, and, and none of us know if that's like a word.

• 27:50Speaker 02

  Well, this is actually a good point to actually talk about, you know, going back to Feynman, so, and, and his colleagues, that they use quantum mechanics to smoothen out, for lack of a better words, de-infiniteize the infinity. I'm getting up a new word. Get rid of the infinity.

• 28:06Neil deGrasse Tyson?

  We've got six new words this episode, right? Keep going.

• 28:09Speaker 02

  There is now a, you know, an uber quantum theory, and that theory is called string theory.

• 28:16Speaker 02

  And it turns out that just when you thought that quantum mechanics actually would help with infinities, it turned out that quantum mechanics itself had infinities. Okay, and we call these things divergences or, you know, instabilities. These are all words that just basically mean that things in your theory go to infinity. Okay.

• 28:36Neil deGrasse Tyson?

  Okay.

• 28:37Speaker 02

  And so anyway, so in a long, it turns out that there is.

• 28:40Neil deGrasse Tyson?

  You're saying quantum physics was brought on to possibly help with the classical infinities, but then it introduces infinities of its own.

• 28:49Speaker 02

  That's correct.

• 28:49Neil deGrasse Tyson?

  Okay, that ain't right. That ain't right.

• 28:51Speaker 02

  That ain't right, right.

• 28:52Neil deGrasse Tyson?

  Right.

• 28:52Speaker 02

  And these things are called like ultraviolet or infrared divergences for the audience member who want to get fancy.

• 28:57Neil deGrasse Tyson?

  Mm hmm.

• 28:59Speaker 02

  Now, so it turns out that string theory actually, one of the reasons why many people got behind string theory, including a younger version of myself, when I was a younger researcher, was that it actually was an infinity-free theory, quantum theory, actually, that contained gravity in it as well, contained, you know, aspects of all the forces, but you had to live in ten dimensions, okay. Um, there's some gift.

• 29:27Neil deGrasse Tyson?

  There's a catch.

• 29:29Speaker 02

  There's a catch. And going back to what Neil exactly said is that now that you have all these other dimensions, you can go and stuff infinities in those other dimensions now, right? Um, but anyway, string theory is such a theory that does that. Um, it's a theory that does not have in its mathematical structures, and the solution it spits out, it does not have infinities. So we all love that. It's elegant and beautiful. And it's also a musical theory. That's correct.

• 29:59Neil deGrasse Tyson?

  I do want to hear what you have to say about string theory and music because that is a part of the questioner's content. But we got to take a quick break. When we come back, the third and final segment of infinity. Does infinity have three segments? Can it have three segments? I don't know. Come back and find out on StarTalk Cosmic Query.

• 30:39Neil deGrasse Tyson?

  We're back, the infinity edition, with Stephane Alexander, a physicist who's thought a lot about cosmology and infinities. And of course, Nagin Persad. Nagin.

• 30:52Negin Farsad?

  Hello.

• 30:52Neil deGrasse Tyson?

  Love having you here. It's been too long. Come back more often, okay?

• 30:55Negin Farsad?

  Absolutely.

• 30:56Neil deGrasse Tyson?

  Yeah, yeah, alright.

• 30:57Negin Farsad?

  But I'm on nearly every show in other dimensions.

• 31:01Neil deGrasse Tyson?

  Oh!

• 31:02Negin Farsad?

  So...

• 31:05Negin Farsad?

  You have to go to the other dimensions, I think is what's going on.

• 31:08Neil deGrasse Tyson?

  And if you don't tell me that dimension, I will never find you. Right. You'll be found only when you allow yourself to be found.

• 31:16Negin Farsad?

  I've also got hot dog fingers in those other dimensions, but don't worry about it.

• 31:20Neil deGrasse Tyson?

  Oh, yes, oh, okay. Everything, everywhere, all at once, I think that was. So Stephane, why would string theory have to do with music at all? Just because it has the word "string" in it? And just because their music has string instruments? I don't, you know...

• 31:35Negin Farsad?

  It's a weak connection.

• 31:36Neil deGrasse Tyson?

  Yes, yes. Yeah, that feels really weak.

• 31:39Speaker 02

  They should have just called it maybe something like guitar string theory.

• 31:45Speaker 02

  But, yeah, you know, so, string theory, the one good reason Weyz was able to solve these infinities had to do with an assumption that we made about even our physics pre-string theory, which is that things fundamentally are made up of point particles. And the minute you talk about a particle, then you're forced to go to zero, and that's when things blew up on you. The infinity revealed itself. But the idea of string theory is that replace... Nothing is ever made up of a point particle anymore. When you, even when you take a magnifying glass and you try to resolve that point, instead, what looks like a point from really, really far away, you zoom in and you realize it's a string. But it's not just any old string.

• 32:28Speaker 02

  The string, because it's quantum, has to be vibrating. We know very well the physics of any kind of vibrating string. The vibrating string generates a spectrum or, you know, generates characteristics types of waves. And these waves are called standing waves. What is a standing wave? It's basically what you'd know as a note, a tone.

• 32:52Neil deGrasse Tyson?

  Okay.

• 32:52Speaker 02

  A particular type of vibration that can be represented as a sound.

• 32:58Speaker 02

  Um, or, you know, a note on the piano. So like when I play a note on a piano, what's really going on is that there's a piano string hitting and that piano string is vibrating. And because it vibrates, it undulates at a very, at a given rate, that rate of vibration called a frequency denotes what we call a tone or a sound. And so, so string theory, the physics of strings really does match on very nicely.

• 33:24Neil deGrasse Tyson?

  Oh, okay.

• 33:24Speaker 02

  The physics of how notes are generated in instruments.

• 33:29Neil deGrasse Tyson?

  So sorry to badmouth you at the front of that. Sorry. Nagin needs to apologize too.

• 33:33Negin Farsad?

  I'm so sorry.

• 33:38Negin Farsad?

  Um, but.

• 33:40Speaker 02

  It's an analogy. It's an analogy, but it's a really good analogy.

• 33:42Neil deGrasse Tyson?

  I get it. I get it. It feels right. It feels right. All right. Nagin, keep going. We have, it's the last segment.

• 33:48Negin Farsad?

  Okay. So rapid fire section. Here we go. From anthropoc cosmic Dylan in San Diego writes, question for Dr. Alexander. Neil says, quote, "The universe is under no obligation to make sense to us. So how do the concepts of infinity and quantum mechanics get distorted due to our human condition? And how do you reconcile this gap with your research and your artistic expression through jazz music?"

• 34:12Neil deGrasse Tyson?

  Whoa, whoa, whoa, whoa. So let me tighten up the beginning of that. So, so he's asking, if, if I say the universe is under no obligation to make sense to you, uh, are you, do these infinities make sense to you? And does it bother you? Do you keep going? Do you just accept it? Or because it doesn't make sense, you have to do something about it and then violate the Neil principle?

• 34:36Speaker 02

  Very good. I, I like the Neil principle. I, I adhere to it actually because it doesn't make sense to me a lot of times, but you know, but I have to pay my bills.

• 34:48Speaker 02

  Yeah. Making the fun. No, no, I write and publish papers and respect to journals. Um, but having said that, um, so yes, I think there is a sense in which we have to, my take on it is that I actually embrace the infinities. I embrace it. I said, let's live with the infinities and wherever we can try to sidestep it and make progress. And, um.

• 35:11Neil deGrasse Tyson?

  I see. Okay. So you kind of, even if they're difficult. It doesn't, shouldn't prevent you from making other kinds of discoveries in the terrain that surrounds them. I get it. Okay. And how about the, again, the second part was about jazz. What was the, read that again?

• 35:28Negin Farsad?

  Yeah, uh, they wrote, um, how do you reconcile this gap with your research and your artistic expression through jazz music?

• 35:37Speaker 02

  Hmm. Yeah, I mean, you know, one of the things that's great about jazz music is that, you know, you, you know, it's a dual thing. You're always striving to master your craft and, you know, and build on the foundations of others. But you also must try to break the rules and stumble and fall to make something new based on that foundation. So really embracing the mistakes that you made and not being afraid of that. That's kind of what jazz improvisation is also about. While at the same time, building on the foundation and getting your traps together and practicing and all that good stuff.

• 36:13Neil deGrasse Tyson?

  And there's surely some people who would say, would invoke the nihilism on jazz. Jazz is under no obligation to make sense to you.

• 36:25Neil deGrasse Tyson?

  I'm pretty sure some people out there feel that way.

• 36:27Speaker 02

  Well, there's a funny story about that. I mean, I want to hear your thoughts about very quickly. Um, when I first heard On It Coleman, I was like, what kind of, I, I made no sense. It didn't make any musical sense. And then much later on in life, as I thought I became more, um, advanced musically, it started making sense to me.

• 36:44Neil deGrasse Tyson?

  Oh, okay. All right. So it doesn't have to make sense upfront. That's right.

• 36:49Negin Farsad?

  Also, and I would just, uh, for, for when jazz doesn't make sense, I usually go to the bar, get another drink, and then jazz starts to make a lot of sense.

• 36:59Neil deGrasse Tyson?

  Right. That's why jazz is in bars. That's why.

• 37:03Negin Farsad?

  And also why all physicists and astrophysicists should be drinking when they talk about infinity.

• 37:11Speaker 02

  Well, I learned something very cool about it. I'm very proud of this. I always feel like I was the outsider physicist that played music. It turned out that the hero, the guy that won a Nobel Prize for figuring out how to actually deal with infinities and our quantum field theory that led to the discovery of the Higgs boson, his name is Ken Wilson. I just found out that he played the oboe.

• 37:30Neil deGrasse Tyson?

  Okay.

• 37:31Speaker 02

  Played when he was a postdoc, yeah.

• 37:33Neil deGrasse Tyson?

  Except I don't know that the oboe shows up much in jazz concerts. I'm pretty sure.

• 37:37Speaker 02

  Well, now it should.

• 37:37Neil deGrasse Tyson?

  I'm pretty sure that that was not a first choice.

• 37:42Negin Farsad?

  I know, the oboe feels like something you just get saddled with in middle school.

• 37:45Neil deGrasse Tyson?

  Exactly.

• 37:46Negin Farsad?

  You don't choose it.

• 37:48Neil deGrasse Tyson?

  In elementary school, you would have lasted in line.

• 37:52Negin Farsad?

  Exactly, exactly.

• 37:53Neil deGrasse Tyson?

  You get the oboe.

• 37:54Negin Farsad?

  Now he's saddled with a Nobel, ugh.

• 37:59Negin Farsad?

  Well, let's take a question from Bruce Ryan. Bruce writes, um, I saw that Stefan's specialty includes quantum loop gravity, and I've always wanted to ask, what the heck is quantum loop gravity?

• 38:11Neil deGrasse Tyson?

  Yeah, me too, me too. Count me in that question as well.

• 38:14Speaker 02

  It's a beautiful, it is, it's a very tantalizing idea, and it actually does deal with gravitational infinities in some respects. And the idea is really interesting. You know, like how, let's go back to our picture of the magnet. You know, if you actually can see a magnetic field line with these iron filaments, you see that it's like, some of it is concentrated in like a tube, like a magnetic tube. Well, what loop quantum gravity is saying is that imagine that you can make tubes of gravitational fields and sort of loop them around like, um, like chains, like, you know, like a chain.

• 38:48Neil deGrasse Tyson?

  A chain, a link in a chain, like a link in a chain.

• 38:50Speaker 02

  A link in a chain, and I can link, I can link a fabric of space-time with those loops. But what's linked in is a gravitational field, and they're kind of, you can think of them as atoms of space.

• 39:00Neil deGrasse Tyson?

  Oh, I see, not atoms, pixels of space.

• 39:02Speaker 02

  Pixels, even better.

• 39:03Neil deGrasse Tyson?

  Yeah, pixels of space.

• 39:04Speaker 02

  Pixels of space, yes.

• 39:05Neil deGrasse Tyson?

  The smallest unit of space, yeah, okay. All right, again, we might have time for one, maybe one and a half more questions.

• 39:10Negin Farsad?

  Okay, so let's see, Abinav Yadav from Philly asks, I struggle to think about spacetime as a concept that exists in our daily lives. As a medium, though, which light wave travels, as a fabric that gets shaped by mass, and as a vacuum out of which virtual particles pop in and out of, what's an easier way to think about spacetime?

• 39:31Speaker 02

  Well.

• 39:33Neil deGrasse Tyson?

  Silence. Wait, wait, what, what, what was that, what was that question?

• 39:39Neil deGrasse Tyson?

  Wait, spacetime is all those things, so what is the question?

• 39:42Negin Farsad?

  I guess, uh, yeah, there's like, there's a, there's a grammatical something missing that's making it hard to-

• 39:49Neil deGrasse Tyson?

  Yeah, we need some semicolons, but, we need some semicolons, but, all those things are true, right Stefan? They're all going on in spacetime, right?

• 39:56Negin Farsad?

  And what's the easiest way of thinking about the concept of, of spacetime?

• 40:02Neil deGrasse Tyson?

  Okay, so if all that's going on in spacetime-

• 40:05Negin Farsad?

  Yeah.

• 40:05Neil deGrasse Tyson?

  What's the first way you teach it? You don't dump the, the bucket onto people before they know what's going on, right? What's your first step to say what spacetime is?

• 40:15Negin Farsad?

  To like a kid?

• 40:18Speaker 02

  Um, yeah, so I would say that, yeah, I, I, I think it's, I think it's a good analogy to think of spacetime as some sort of very, very faint and invisible, um, fabric, um, that, but it's a special kind of fabric because that fabric can also support spacetime itself to move along, like gravitational waves, right? So spacetime itself can actually support motion of, of ripples up itself, and, and that is different than any other types of medium that we know, right? Normally, something like, like an electric field or particles need spacetime to move through,

• 41:03Speaker 02

  but they can't move through their own, their own medium. Spacetime has a, it's a very special type of medium in that sense. But, um, it's a very weird medium, for lack of a better word.

• 41:14Neil deGrasse Tyson?

  Okay.

• 41:14Speaker 02

  It's what we call, it's a, it's a relational medium, okay?

• 41:19Neil deGrasse Tyson?

  And nor is it under any obligation to make sense to us, yes, okay.

• 41:22Negin Farsad?

  But it just sounds like what, what you described is kind of like-

• 41:25Speaker 02

  It still makes no sense to me.

• 41:26Negin Farsad?

  Yeah.

• 41:28Negin Farsad?

  So the, the answer to this person's question is basically, there's no way of really thinking about it in your daily life.

• 41:34Speaker 02

  No, I mean, again, this is what Neil just said makes no sense. But I know I could write down this object called a spacetime metric and we describe it as a field of, you know, spacetime as some kind of a field. But again, these are just words that we attach to the equations that we write down. Yeah.

• 41:53Neil deGrasse Tyson?

  But they make predictions and they work. So.

• 41:55Speaker 02

  They make very good predictions and they work very well.

• 41:57Neil deGrasse Tyson?

  So that's why, however fantastical they sound, they still are connected to reality in that important way. So it's very.

• 42:05Speaker 02

  I mean, the detection of gravitational waves with Lygo and Virgo.

• 42:09Neil deGrasse Tyson?

  Yep. Yeah, yeah, yeah.

• 42:10Speaker 02

  And that's some.

• 42:11Neil deGrasse Tyson?

  Again, I think we got one more question.

• 42:13Negin Farsad?

  So I mean, this is sort of like related. Everyone seems to be having a crisis in understanding, but Malcolm Marfan from Trinidad and Tobago says infinity is often described as a mathematical abstraction. How can we know that the concept of infinity exists in the physical world and not just in our minds? They are really testing you today.

• 42:35Neil deGrasse Tyson?

  Yeah, they are, Stefan.

• 42:37Negin Farsad?

  They want hard answers.

• 42:38Neil deGrasse Tyson?

  And I tell you, I remembered learning infinity mathematically and they said one divided by zero is undefined. Okay. I remember being taught that in my math class. Well, I have a math friend who we actually had as a guest, John Allen Paulus, professor of math at Temple University outside of Philly. And I tweeted, I called him out in Twitter and I said, John, if one, one divided by zero is undefined, why don't you guys define it? What are you waiting for? Okay. I've been waiting my whole life and all you have to do is define it and we're cool. What's up with that?

• 43:18Neil deGrasse Tyson?

  So, so apparently to him, infinity is undefined because one divided by zero is infinity.

• 43:24Speaker 02

  Mm hmm, mm hmm.

• 43:25Negin Farsad?

  So wait, so this thing is just totally up for grabs. Like I could just do a journal, like a journal article right now and just be like one divided by infinity is a bowl of jello and like that's, if this is up for grabs, I'd like to take a stab.

• 43:40Neil deGrasse Tyson?

  We have to put closure on your theory and one divided by zero is an acetate captured in Tupperware.

• 43:54Negin Farsad?

  That's bea- I mean, that's beautiful.

• 43:56Neil deGrasse Tyson?

  And that, that, that's a, that's a beautiful theorem, right there, right there. We gotta call it quits there. Stefan, great to have you back on the show.

• 44:03Speaker 02

  Thanks for having me again, Neil.

• 44:04Neil deGrasse Tyson?

  All right, Nagin, it's been a delight. And, and by the way, Nagin, just quickly, weren't you on TV with Hillary Clinton? Did I? I'm channel surfing. They say, "That's Nagin!" Wait, that's Hillary Clinton? Phil, what's he, what are you doing? What was that? Briefly, tell me real quick.

• 44:22Negin Farsad?

  She was, I'm on the show Gutsy on Apple TV. Hillary Clinton is just basically doing a series about gutsy women. And I, and crazily, I, I'm one of them. So check it out. It's a really great series.

• 44:35Neil deGrasse Tyson?

  You're one of the gutsy women? Okay, it's cool. Just call gutsy.

• 44:37Negin Farsad?

  Yeah, it's called Gutsy on Apple TV.

• 44:39Neil deGrasse Tyson?

  Gutsy? Very cool. I don't mean to, I don't mean to brag, but Hillary Clinton said, "I'm her favorite astrophysicist."

• 44:45Negin Farsad?

  Oh, uh...

• 44:47Neil deGrasse Tyson?

  Yeah, I'm sure, I'm pretty sure she knows only one astrophysicist.

• 44:51Speaker 02

  Oh, the best is when I meet my favorite musician and, and he goes, "Hey, by the way, can you, can you, can you get me introduced to Neil deGrasse Tyson, please?"

• 45:06Neil deGrasse Tyson?

  All right, guys, we're done here. Land this plane. This has been StarTalk Cosmic Queries, the Infinity Edition. It's a delight to have an old friend and colleague, Stefan Alexander. And Nagin Persad, always good to have you back. Neil deGrasse Tyson here, as always, bidding you to keep looking.