Cosmic Queries–Multiverse Madness with Max Tegmark

Do we live in one of many universes? On this episode of StarTalk, Neil deGrasse Tyson and comic co-host Chuck Nice investigate the theory of the multiverse with physicist and author, Prof. Max Tegmark.

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

• 0:01Neil deGrasse Tyson?

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

• 0:14Neil deGrasse Tyson?

  This is StarTalk. I'm your host, Neil deGrasse Tyson, your personal astrophysicist. And this is going to be a Cosmic Queries edition, the ever-popular format that we started many years ago, and it just keeps going strong. And today's topic is going to be the multiverse. I got with me my co-host Chuck.

• 0:36Chuck Nice?

  Hey Neil, how are you?

• 0:38Neil deGrasse Tyson?

  Chuck, nice. You know, you're getting such a schooling here with all this cosmic knowledge.

• 0:44Chuck Nice?

  Yes, I am.

• 0:44Neil deGrasse Tyson?

  We're going to have to give you a degree of your own.

• 0:47Chuck Nice?

  No, no, no, because then that, you know, normally, once you get the degree, that means that your time at the institution is over unless you start paying more money.

• 0:55Neil deGrasse Tyson?

  Okay, so they kick you out the front door.

• 0:58Chuck Nice?

  Right. So I'm just going to continue to, I'm just staying in school forever, that's all.

• 1:04Neil deGrasse Tyson?

  Lifelong learner, alright.

• 1:05Chuck Nice?

  That's it, just stay in school.

• 1:08Neil deGrasse Tyson?

  Well, this topic is in part celebration for the release of the second StarTalk book. And guess what that book is called, Chuck?

• 1:17Chuck Nice?

  Let me take a stab at it. Could it possibly be Cosmic Queries?

• 1:22Neil deGrasse Tyson?

  Cosmic Queries, inspired by this very format.

• 1:25Chuck Nice?

  Yes.

• 1:25Neil deGrasse Tyson?

  There are questions that people just ask that are so deep and so interesting, and not all of them can we get to on a podcast. And so we had to like, take it to the book. And so there's a whole section in that book on the multiverse.

• 1:39Chuck Nice?

  Nice.

• 1:40Neil deGrasse Tyson?

  Yeah, yeah. And I learned almost everything I know about the multiverse from our guest today. And that is the one and the only Max Tegmark. Max, welcome back. I mean, I've had you, I've had you in other events at the museum for Hayden Planetarium panels and things. It's just always good to know you're in arm's reach of us.

• 2:01Speaker 02

  Thank you. But you know, you just said something dubious. You said the one and only Max Tegmark. And if you take the multiverse seriously, I'm not the one and only.

• 2:09Neil deGrasse Tyson?

  Damn, I just got schooled on my first sentence.

• 2:17Neil deGrasse Tyson?

  But Max, we go way back. I mean, when you were at the Institute for Advanced Study, and I was post-docing at Princeton, I think that's when I first met you and I followed your career. It's been a brilliant melange of topics that are just so interesting. And the multiverse is the least among them that I have found interesting in your career. So we'll have to have you back for other topics, for sure. Plus Chuck.

• 2:42Chuck Nice?

  Wow, that is a serious compliment.

• 2:45Neil deGrasse Tyson?

  If...

• 2:46Chuck Nice?

  You know what I mean?

• 2:47Neil deGrasse Tyson?

  The universe is a side gig.

• 2:50Chuck Nice?

  Multiple universes are the least interesting thing.

• 2:56Neil deGrasse Tyson?

  I'm sorry, I'm just leveling with you here.

• 3:00Speaker 02

  To be honest, guys, it has been officially my side gig all along, just so I wouldn't tank my career with it. Because like when I was a grad student, I was already fascinated by this, but nobody else seemed to be. And it was generally considered a bit too fringe. So I played the multiverse very close to my chest. And I didn't even, I even wrote some papers when I was a grad student. I didn't show my advisor until after he had signed my PhD thesis.

• 3:27Neil deGrasse Tyson?

  Under a pseudonym, John Doe. Yes, okay.

• 3:30Chuck Nice?

  Oh, that's so funny.

• 3:32Speaker 02

  And it's so weird how now gradually, some of these topics have actually come in a bit from the cold, and gone from being just considered a career-ending to being things that are considered legitimate scientific controversies that we actually could talk about openly at physics conferences.

• 3:48Neil deGrasse Tyson?

  So you're a professor of physics at MIT, of course, the Massachusetts Institute of Technology, basically up the street in Cambridge, Massachusetts. And Chuck, I've always been jealous of this man's name. It's like movie star Max Tegmark starring.

• 4:06Chuck Nice?

  It does. It's, you know, it could be either the star of the show, or the producer. This is a Max Tegmark production. Yeah, it works. It works either way.

• 4:18Neil deGrasse Tyson?

  All of the above. And Max, you've got a couple of books under your belt, at least. One of my favorites is Our Mathematical Universe, where you argue that everything is math, and if everything is math, someone could have programmed it that way. And so, a brilliant exercise there. And of course, Life 3.0. Where you're exploring the future of what we even think of as life. And I've enjoyed both of those books. So thanks for, I think of them as a gift to civilization to share in how you think about this world.

• 4:49Chuck Nice?

  And I enjoyed the conversation that I heard on NPR about your book about about Mathematical Universe.

• 4:58Neil deGrasse Tyson?

  Okay, but now we have the guy, we got him ourselves.

• 5:02Chuck Nice?

  Exactly.

• 5:03Speaker 02

  You know, actually, I changed the name of that book in the last second for reasons we're going to talk about now. The first title was The Mathematical Universe. And then I thought, that's so arrogant. If we really believe that there are other universes, we shouldn't just say the universe, ours. We should talk about, be more humble and acknowledge that it might just, that our universe might not be the only one.

• 5:27Neil deGrasse Tyson?

  Okay, all right. So, so we went through a brief last minute title change so that you wouldn't sound like an a-hole.

• 5:37Speaker 02

  We used to talk about the solar system and then we realized, oops, there are others, right?

• 5:42Neil deGrasse Tyson?

  Yeah, or, or the universe. And we're not saying that anymore. It's our universe. I like that. It's a good, it's a good shift for that.

• 5:50Chuck Nice?

  You changed the universe into the humble verse. That's cool.

• 5:53Neil deGrasse Tyson?

  Oh, humble verse. Very good, Chuck. Making up words on the spot. So Max, tell me, what motivated people to you and your, you know, either you early on when you were doing this sort of under the cover of night to what is now mainstream research on the multiverse? What motivated it?

• 6:15Speaker 02

  Well, I think, first of all, throughout human history, you know, we've had this epiphany again and again that, hey, stuff is bigger than we thought. And we, you know, we used to go into it with this hubristic assumption that all we knew about was all there was, kind of like an ostrich with the head of the sound. And then people realized.

• 6:33Neil deGrasse Tyson?

  Oh, by the way, the corollary to it's bigger than we thought is we're littler than we thought. The flip side of that coin.

• 6:42Speaker 02

  We realized, well, actually, we're part of this huge, we're standing on this huge round ball in space, which in turn is just part of this gigantic solar system, part of a galaxy, part of a cluster of galaxies, part of the supercluster, part of this that we then would call our universe. And, you know, why stop there? So people started wondering, could there be still more? And the earliest people got into much more trouble, you know, than I ever did in grad school, like Giordano Bruno, 400 years ago, started talking about how maybe space went on forever. And you know what happened to him, right?

• 7:16Neil deGrasse Tyson?

  Yeah, he was burned at the stake upside down with a, with a, something plugged into his mouth.

• 7:23Speaker 02

  Wow.

• 7:24Neil deGrasse Tyson?

  So that even in death, he could not repeat these heresies. They drove a stake into his mouth so that even when he died, you know.

• 7:34Chuck Nice?

  You know, that's what I liked about that time. Overkill. Overkill. Everything was overkill.

• 7:41Speaker 02

  So, you know, now, I went to Campo dei Fiori, actually, in Rome, where this happened. And I started to think, you know, compared to that, that just getting burned on the job market, there's a lot less of a threat. So we're making some progress and.

• 7:55Neil deGrasse Tyson?

  A little bit of progress.

• 7:57Speaker 02

  But.

• 7:58Neil deGrasse Tyson?

  But just to be clear, that square that in Italy, there is, in all fairness, there is a statue to him where he's looking very solemn, but it's a very honorific statue in his memory.

• 8:10Speaker 02

  It is.

• 8:10Chuck Nice?

  Yeah. Small consolation for being burned at the stake.

• 8:17Neil deGrasse Tyson?

  I'll take life, you keep your statue. Is that what you're telling me?

• 8:20Chuck Nice?

  Thank you. Exactly.

• 8:21Speaker 02

  But you asked this very good question. What drove us to these things? And it's basically just natural, logical steps. It's just, you know, Euclid himself.

• 8:31Speaker 02

  Postulated that space is infinite, right? And when we were kids and we started wondering, does this space go on forever? It seemed pretty natural that there wouldn't just be an end to it. Right, so if you just take that idea logically, then that means that the part we can see, right? This is finite because light has only reached us from this spherical region that it could get here from during the 13.8 billion years since our big bang. So if that's what we call our universe, then by definition, there are others, other regions of space just as big, just as cool. And it's sort of hard to dismiss. Right now, I don't have a single astrophysicist colleague anymore who thinks space magically ends right at that edge.

• 9:14Speaker 02

  And in fact, you can just wait one day and you see some more light arriving from farther away. Right? And then, and then, so that's what I call the level one multiverse. Just other regions of space that we haven't had any access to. But then it gets, it gets kind of weirder, so.

• 9:33Neil deGrasse Tyson?

  So initially, it wasn't that people were motivated to try to answer some other question. They just more fully explored what we were already thinking and already knew to be true about the universe. So in that sense, it's not some epiphany. It's just an extension of what we're already thinking. Is that a fair way to think about your level one multiverse?

• 9:52Speaker 02

  I think so. And I think a lot of the pushback honestly wasn't really based on science so much, but based on arrogant hubris. You know, we, the reason Pope Urban the eighth or whatever was so pissed at Galileo, you know, wasn't because he had a good scientific argument, but we were so stuck to the idea that we, everything orbits around us, you know, we humans are so important. And we didn't like to be demoted to just being an average planet and an average solar system orbiting a galaxy, et cetera, et cetera. And I think we see still a little bit of that today. Some people argue that they don't like this idea of reality being even bigger just because it makes their egos feel even smaller.

• 10:32Chuck Nice?

  After, after the last four years, I, I can't imagine that people would actually have hold to those sentiments.

• 10:40Neil deGrasse Tyson?

  All right, so what I don't know, because I haven't quizzed people, is what are they thinking of when they hear multiverse? And my sense is their thinking is maybe a parallel universe that you might be able to to sort of move between at some distant future time. So is there any truth to the concept of a parallel universe in the way it's commonly thought of in the public?

• 11:05Chuck Nice?

  Is there an evil Chuck somewhere?

• 11:07Neil deGrasse Tyson?

  With a goatee? Oh, you already have a goatee.

• 11:11Chuck Nice?

  Is there a clean-shaven evil Chuck?

• 11:16Neil deGrasse Tyson?

  You are the evil Chuck, Chuck.

• 11:18Chuck Nice?

  Oh, my God. Oh, my God, that's right.

• 11:22Neil deGrasse Tyson?

  Just think that through.

• 11:24Speaker 02

  What's incredibly confusing here is that different people mean different things when they say universe, and they mean to talk about different kinds of... And in fact, I remember once, very vividly, Martin Rees had organized a conference in his house about these forbidden topics. And I heard you-

• 11:41Neil deGrasse Tyson?

  Chuck, these are the kind of friends we have, that you get that, you know, you get invited for tea, and you solve the issues of the universe. Okay, go on.

• 11:48Speaker 02

  You know, this was considered pretty taboo back then, but because Martin was organizing it, people still came and behaved. But I noticed the two people were arguing about the multiverse, and I realized they're talking past each other. One guy was talking about what we call the inflationary multiverse, which is just really big space, and we can get back to that. Another guy was talking about the quantum multiverse, and they thought they were talking about the same thing. So I felt I have... I stood up and said, "Hey, wait a minute. Aren't there actually three different... No, four different kinds of multiverse that we should give different names to, to not confuse ourselves so much?" And then I wrote that up in the book you mentioned.

• 12:25Neil deGrasse Tyson?

  But just to be clear, the book that you're talking about is... You posted something, it's online, which is a very clean and clear exposition of the multiple levels of the multiverse. And that's what we referenced when we included, when we fleshed out our section on the multiverse in Cosmic Queries. So I just want to be clear that, you know, you're not just pulling this out of your ass. This is... You've thought about this for a long time.

• 12:51Speaker 02

  So- I think it's very important to be clear on what we're talking about. Yeah, thank you. So by our universe, we mean what astronomers call our observable universe. It's just this spherical region of space from which light has reached us so far. I know this. Then what I call the level one multiverse is just other parts of space that are so far away that light hasn't reached us yet. Level two multiverse is what you get if you take seriously Alan Guth and Andre Linde and others and the theory of inflation that made our space so big, which says that far, far away in the same space now, you have something much more diverse than you might have thought, where even the number of different kinds of quarks could be different or the

• 13:34Speaker 02

  sort of forces that are there are different and we can talk about why. And then there's this third kind, and that's what gets more into the parallel evil feeling thing, which has to do with studying not the big, but the very small, studying quantum mechanics, where you can argue, and people love arguing about that at physics conferences, that in some sense, our reality feels like it's splitting out into parallel branches. And that's the whole, if that is true, you can tap into that weirdness by building quantum computers. And then finally, there's the fourth one, which is so weird that almost nobody except myself believe in it, which is the biggest. And I think of all of this as basically Russian dolls. They're nested, they're all inside of each other, right?

• 14:17Speaker 02

  You start with our universe, many of those, that's level one, many of those that makes level two, many of those makes level three, and many of those makes the ultimate one, the fourth level.

• 14:30Neil deGrasse Tyson?

  So these are, these are, these are multiverses of multiverses?

• 14:35Speaker 02

  That's right, that's right.

• 14:37Chuck Nice?

  But the only one that ever gets any real attention is that kind of, you know, tree limb version that you put, that you depicted, this splintering, you know, where there's so many different infinite paths that are separate, yet existing simultaneously. That seems to be the one that captures the Imagination of every sci fi writer and and even Rick and Morty, which is like a hugely popular show. I mean, it's like it's it's, you know, it because I think you could do so much with it. You know, there's an infinite number of Ricks and they're all geniuses.

• 15:21Chuck Nice?

  So they, you know, so I mean, you have an unlimited of um, reservoir of stories to tell.

• 15:27Neil deGrasse Tyson?

  Chuck Chuck Max is Rick.

• 15:31Neil deGrasse Tyson?

  We're gonna take a quick break. When we come back, we'll go straight into our questions from our Patreon members when StarTalk Cosmic Queries returns.

• 15:50Speaker 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.

• 16:09Neil deGrasse Tyson?

  We're back, Cosmic Queries, the multiverse edition. And and Max, we've got Max Tegmark, professor of physics from MIT. I've known him for 25 years and no longer 30 years, I think.

• 16:23Chuck Nice?

  I'm fine.

• 16:24Neil deGrasse Tyson?

  Yeah, yeah, yeah. Are we that old?

• 16:25Chuck Nice?

  In every universe.

• 16:26Neil deGrasse Tyson?

  In every universe. Thank you, Chuck, for clarifying that. Uh, Max, you're into so many things, uh, into AI, into um, most recently, you've been thinking about news and the biases in news. But I just love the work you're doing. It's fun to follow you uh, from afar. And so we've got you on this program to talk about the multiverse because that's one of your many expertise. And Chuck, you've got questions for us. Let's do it.

• 16:53Chuck Nice?

  Okay, let's just jump right into uh, all the questions that we have taken from our Patreon patrons, the people who support us uh, out of their substance to keep our show going. So thank you, guys, for your support. And if you uh, are listening to this and you want to be a Patreon member, go to patreon.com/starTalk and uh, and give us some support and maybe I'll reach her.

• 17:17Neil deGrasse Tyson?

  I didn't know that's how you're gonna end that.

• 17:19Chuck Nice?

  Yeah, yeah.

• 17:20Neil deGrasse Tyson?

  Maybe I'll think about it.

• 17:21Chuck Nice?

  Maybe I'll think about reading your li- no. Of course, I'm joking. Of course, I'll read your letter and I'll butcher your name, no doubt.

• 17:28Neil deGrasse Tyson?

  Okay, alright.

• 17:28Chuck Nice?

  No doubt. Here we go. Alright, this is Eric Gross. He says, "Hello, fellow Earthicans. Can you explain the mind-boggling idea of infinite infinities?"

• 17:44Speaker 02

  Ooh, wow.

• 17:45Chuck Nice?

  Ooh. Wow.

• 17:46Speaker 02

  That's a good one.

• 17:47Chuck Nice?

  Wow, that's a great question.

• 17:49Neil deGrasse Tyson?

  So Max, let's, let's, let's start simple and let me ask you, what does it mean for one infinity to be bigger than another? And then, let's take it from that into that, directly into the que- let's drive the truck right into that question.

• 18:05Chuck Nice?

  One infinity big- wait a minute, guys, give me one second here.

• 18:09Neil deGrasse Tyson?

  Wait, wait, wait, what, Chuck?

• 18:10Chuck Nice?

  Alright, sorry. I gotta get this little pipe here.

• 18:17Chuck Nice?

  You know, if we gonna, if we gonna talk about one infinity being bigger than another, I'm just saying, I need to be, I need to be prepared.

• 18:27Neil deGrasse Tyson?

  The pipe has to be right there. Okay.

• 18:29Speaker 02

  If you have a pile of oranges and you have a pile of apples and you wanna know, is it the same number of apples as oranges? The way you do it is, if you compare up each apple with exactly one orange, you say the two numbers are the same. So now play that game with infinities and weird stuff happens. Let me, for example, you might think that there are more numbers, 1, 2, 3, 4, 5, than there are even numbers, 2, 4, 6, but they're actually the same because you can pair them up. I can pair up 1 with 2, I can pair up 8 with 16, I pair up every number with one that's twice as big, which is always even. So it's very counterintuitive. So for a while, mathematicians started to-

• 19:10Neil deGrasse Tyson?

  But just to be clear, you just said something, but not everyone knows this.

• 19:13Speaker 02

  Yeah.

• 19:13Neil deGrasse Tyson?

  Max, that twice any number-

• 19:18Neil deGrasse Tyson?

  Any whole number is always an even number.

• 19:21Speaker 02

  Thanks for clarifying, yeah.

• 19:22Neil deGrasse Tyson?

  Yeah, yeah, that is always the case. So you can't take twice anything and end up twice a whole number and get an odd number. So when you say twice the number, that's always even. That's a fundamental fact about mathematics. Okay.

• 19:35Speaker 02

  That's right.

• 19:35Neil deGrasse Tyson?

  Pick me up.

• 19:37Speaker 02

  The quite weird conclusion is that some infinities, which intuitively would seem like they're much bigger, are actually all the same size. And some mathematicians start to think maybe all infinities are the same size. But then George Cantor came along and said, no, there are some infinities that are even bigger. And he proved famously that the number of real numbers, like 3.1415 with infinitely many decimals, that there are actually more of those than the numbers you can count. And after that, people have realized that there's this whole tower of infinities. So what's that got to do with parallel universes and this question? Well, it's got a lot to do actually with the level one and the level two multiverse. Because.

• 20:18Neil deGrasse Tyson?

  Wait, wait, Chuck has to take a toke. Okay, go ahead.

• 20:24Neil deGrasse Tyson?

  Toke break.

• 20:25Speaker 02

  Yes, exactly.

• 20:28Speaker 02

  So far, this is good. This is great. Take a deep breath because I'm going to tell you one of the things that I find the weirdest. This is one of the weirdest things I believe to be true.

• 20:38Neil deGrasse Tyson?

  And if Max finds it weird, brace yourself. Go. Right, exactly.

• 20:42Speaker 02

  It is actually impossible. It is according to Einstein's theory of general relativity, possible to take a little piece of space, just finite, and inside of there, make an infinite space that doesn't stick out anywhere. And actually infinitely many, and make many different infinite spaces inside of this finite thing. So Alan Guth, Andre Linde and others came up with this most popular theory we have so far for what put the bang into our big bang, right? And made this expanding universe of ours, starting with something tinier than an atom. It's very, very big. And the ultimate party trick is inside of this tiny region, it can not only make one space,

• 21:24Speaker 02

  which when you live in it feels infinite, that's a level one multiverse for you in there. So it has room for infinitely many of our universes. But you can have infinitely many of those within there.

• 21:39Neil deGrasse Tyson?

  So you can have an infinite number of infinitely large universes in a finite universe?

• 21:44Speaker 02

  Basically, that's why it feels so utterly weird. And the way that general relativity kind of pulls this trick is because even though it was a finite volume of space, it has an infinite amount of future time to play with, and it keeps stretching the space. And then general relativity has this funny thing where it can kind of mix up space and time, so that for someone who lives inside this, what they consider to be space was something that you might have considered a little bit of time. And I don't want to get too nerdy about this, but you know, Einstein told us that what really we should...

• 22:20Neil deGrasse Tyson?

  Only now are you saying you don't want to get too nerdy? It's only just occurred to you now?

• 22:25Speaker 02

  I think I already blew it. But you know, Einstein told us, right, that we shouldn't think of reality as a three-dimensional place where stuff happens, but rather as time being just the fourth dimension in this never-changing place called spacetime. So if like, if life is a movie, then spacetime is the whole DVD. And basically because you have this infinite future time to mess with, if you can sort of bend your definition of what space is in there, this is how Alan Guth and Andre Linde and Alex Velikin and others have demonstrated this apparently crazy thing, that maybe everything we see here, an infinity of infinities, could actually be emerging inside of this little bubble.

• 23:10Neil deGrasse Tyson?

  So just to clarify your DVD analogy, what you're saying is we live as prisoners of the present, transitioning from our past to our future. So we experience a moment in time and many places in space. But if you have the whole DVD of the movie, then your entire timeline is manifest in that place, in that all at once. All at once. All the time. Of your life is in that DVD, and you can have random access to it. If you can move throughout the time coordinate.

• 23:43Speaker 02

  Yeah.

• 23:43Neil deGrasse Tyson?

  Is that a fair?

• 23:44Speaker 02

  Right.

• 23:45Neil deGrasse Tyson?

  Reference to how you use the concept of DVD?

• 23:48Speaker 02

  It is, it is.

• 23:49Neil deGrasse Tyson?

  Okay.

• 23:51Speaker 02

  That's right. Einstein even told some of his friends that they shouldn't worry so much about his death because he argued that it's just from a spacetime perspective, an illusion. It's not like.

• 24:02Chuck Nice?

  Right. Cause I'm already dead, man. And so are you. We're all dead, man. And we're not. I haven't even been born yet, man. And I'm dead. What?

• 24:15Speaker 02

  It is pretty weird, Chuck. I mean, I'm sure sometimes people come up to you when they're lost and ask, hey, excuse me, but where am I? Right? But they never come and ask, when am I?

• 24:27Chuck Nice?

  Right.

• 24:28Speaker 02

  Local English, we treat time as a very different sort of thing as space. Whereas when we say, what's the time? That's actually very arrogant, just like talking about the universe or the solar system. The, what is the time? I mean, that's saying that somehow the instant when we're having this experience is the only time? I mean, all the other times, past and present and spacetime have just as much claim to be real. They certainly felt real to people who had experiences then, right? So if we want to be a little bit more rigorous, we should always go ask people, excuse me, when am I?

• 25:06Speaker 02

  What you are right now at this particular time, having this experience.

• 25:10Neil deGrasse Tyson?

  Wow. Okay. So that doesn't have the arrogance that it otherwise would by asking, what is the time?

• 25:14Speaker 02

  I mean, it's like going up and saying, what is the place?

• 25:19Chuck Nice?

  Right.

• 25:19Speaker 02

  Of course, where I am is the only place.

• 25:25Neil deGrasse Tyson?

  All right, Chuck, give me some more questions.

• 25:26Chuck Nice?

  All right. Wow, that was way to, way to kick things off. That is something else. All right, let's move on to, you know, this, that, that other level you talk about. This is Chris Hampton. Could the parallel universe theory and the multiverse theory be combined? For example, we are living in a universe with billions of other organisms. But what if each organism in the universe is itself a universe on a relative scale? Each one thus containing billions of organisms, so on and so on.

• 26:05Chuck Nice?

  So he's taking your nesting doll and breaking it all the way down to every single organism.

• 26:13Neil deGrasse Tyson?

  Right, but yeah, he's thinking, I mean, so Max, if we have as a lead into that, the early concept of the atom, where people said, oh, my gosh, atoms have structure and there's a nucleus and there's electrons orbiting. So that's just like the solar system. So maybe it's like turtles all the way down. So how do we go from any understanding of scales of everything's just on a different scale, rather than something is a completely different universe unto itself?

• 26:45Speaker 02

  Yeah, very good question. We see, of course, in nature, this fairly beautiful hierarchy, right? You have some quarks stuck together into neutrons and protons that are stuck together into this thing we call a nucleus, stuck together in an atom. And then you can make molecules and cells, and you can make Neil deGrasse Tyson and society and a planet and galaxy, et cetera. What's different about the hierarchy of universes is it's not just that the hierarchy exists, but by definition, I like to define the universe, our universe, as everything that we could possibly have any access to with unlimited funding and never mind other stuff that's in the way, right?

• 27:27Speaker 02

  So if you're one person in a society, there are a lot of people you haven't met, but you could in principle meet them. So they're not part of another universe. You could in principle go to Uruguay, even if you've never been there, right? But you can never go. A hundred billion light years in that direction. Even if you wanted to, it's it's just off limits to you. That's basically the definition, I think, is helpful about universe.

• 27:52Neil deGrasse Tyson?

  Okay, but otherwise, we'd use the term sort of poetically or metaphorically. Like, the cell is a universe unto itself.

• 27:59Speaker 02

  Yeah.

• 27:59Neil deGrasse Tyson?

  You know, so I think that's fair poetically, but you're saying from the world of physics, no, that's not how we use the term.

• 28:06Speaker 02

  Yeah, exactly. And I mean, it's whatever we need to have, we should have a word for everything we can access. It's very important for us, especially in the future, both if we're curious, that's the limits of what we can observe, and if we're ambitious, that's also setting roughly the limits of where we could ever go in the future. So if you don't want to call it universe, call it schmuniverse and make up another word for it, but it deserves to be called something, right? And we, where space, I think, is a word that's better used to actually describe all of space, and it's not the same thing. Space is probably bigger than our universe.

• 28:43Neil deGrasse Tyson?

  We have confirmed that Chuck lives in the schmuniverse, just to be clear.

• 28:45Chuck Nice?

  Yes, the schmuniverse is it's where all dismissive people live. Universe schmuniverse. Yeah, whatever.

• 28:54Speaker 02

  The tuniverse, so it's.

• 28:56Chuck Nice?

  Or the, I don't mind a tuniverse. Now you're making me hungry. Well, Chris Hampton, actually, it looks like he, from what you just said, is, speaking of smoking, is that whole, hey, man, there's a universe in my thumbnail, like, that whole vibe. That seems to be where he's coming from.

• 29:15Speaker 02

  But it is, I like what you said, Neil. The reason people use it poetically in that sense is because we think we refer to things poetically as a universe unto its own, basically, if it really is doing its own thing and not interacting with the rest, right, which is what we're trying to capture scientifically here.

• 29:34Chuck Nice?

  Okay, so now, I gotta, I want to ask my own question, but I don't want to, I don't want to take up these people's time.

• 29:40Neil deGrasse Tyson?

  Chuck, are you a Patreon member? If not, shut the hell up and read the next question. Okay?

• 29:46Chuck Nice?

  Well Neil, I gotta tell you, you have bested me, sir. Cause that was a damn good point.

• 29:54Chuck Nice?

  Oh my God, hold on, now I gotta go online right now.

• 29:59Chuck Nice?

  I gotta get on Patreon right now. So I can ask my question. All right, here we go. This is Curtis. Oh man, you really got me with that one, okay. This is Curtis, Curtis Lee Zadohak, I think. Zadohak, yeah. He says, first and foremost, my name is pronounced Zadohak. Okay, so I, okay, I was wrong, but I got it close.

• 30:24Neil deGrasse Tyson?

  Okay.

• 30:26Chuck Nice?

  Conceptually, I do not really understand how a multiverse affects our universe. What is the most important effect on our universe?

• 30:40Neil deGrasse Tyson?

  And I'm gonna paraphrase that and say, is there any observational evidence that such a thing exists? And we're gonna get to that in the next segment. We gotta take a quick break.

• 30:50Chuck Nice?

  Cliffhanger.

• 30:52Neil deGrasse Tyson?

  When we come back, more StarTalk Cosmic Queries with my longtime friend and colleague, multiversist, Max Tegmark on StarTalk.

• 31:12Chuck Nice?

  Time for a Patreon shout out to the following Patreon patrons. Eric Columbell, David Johnston, and Tracy Fox. Guys, you're the best and we are so appreciative of your support. And for anybody out there who would like their very own Patreon shout out, do what these guys did. Go to patreon.com/startalkradio and support us.

• 31:37Neil deGrasse Tyson?

  We're back, StarTalk Cosmic Queries, multiverse edition.

• 31:42Neil deGrasse Tyson?

  Or is it the schmultiverse? We're trying to figure out. A creative naming of these things. I got Max Tegmark. Max, what's your Twitter handle?

• 31:52Speaker 02

  It's simply Tegmark.

• 31:54Neil deGrasse Tyson?

  Tegmark.

• 31:55Chuck Nice?

  Look at that.

• 31:56Neil deGrasse Tyson?

  Damn.

• 31:57Chuck Nice?

  Wow.

• 31:58Neil deGrasse Tyson?

  The only Tegmark in the world.

• 31:59Chuck Nice?

  Doesn't even need a first letter, just Tegmark.

• 32:02Speaker 02

  Well, if you believe in the multiverse, then there's undoubtedly some other planet out there with someone who looks exactly like me and talks like me. But the first one you come to will probably be named Schmegmark or something else. Because if you take seriously this idea that space is just infinite and started out a little bit differently in different places, it's much more likely to get someone who is kind of, sort of, like me, but not exactly.

• 32:27Chuck Nice?

  Right.

• 32:28Neil deGrasse Tyson?

  Okay.

• 32:29Chuck Nice?

  There you go. Well, I mean, in the meantime, that's not a problem for Twitter.

• 32:38Neil deGrasse Tyson?

  Plus, there's that scene where they have the whole room of a million monkeys typing away on a typewriter, and they're trying to get the works of Shakespeare. And so they finally get one. It was like, "To be or not to shring them wreck."

• 32:53Speaker 02

  Yeah, you know, there is about a googol particles you have to put together right in our observable universe, so one with 100 zeros. So you actually have to try about a googolplex times, which is one with a googol zeros after it, until you get it right, which is why your nearest clone might be ridiculously far away. So I love the question you just asked before we got cut off there about what's the evidence for this? Is this just silly?

• 33:21Neil deGrasse Tyson?

  Yeah, Chuck, who asked that again?

• 33:22Chuck Nice?

  That would be Curtis Zidlhoff.

• 33:24Neil deGrasse Tyson?

  Yeah, he's wondering, do we feel, see this other universe? And so another, the official way to say that is, do we have experimental evidence that they exist? Right? Or is this just what you talk about at the beer halls?

• 33:36Speaker 02

  So it's a really great question, because by definition of what you mean by universe, you are not affected by things outside of it. So isn't that by definition untestable? And the interesting thing is, no, that's not true. First of all, if you just take the theory that space is actually much bigger than we thought and with more stuff in it, right?

• 34:01Speaker 02

  If that's false, that would mean that actually things kind of end at exactly the edge that we can see now. That's very testable. You just wait a little bit. And then light from farther reaches you and keeps coming into view. And so we've already falsified that many times over. Now, there's a more profound way in which you can test this also, though. We have to remember in science, right? We test theories. And for a theory to be testable, you don't have to be able to test everything that it predicts. Just at least one thing. Take Einstein's theory of general relativity, right? It predicts all sorts of stuff that we can observe. Like how Mercury orbits around the sun in a different way than people thought it was supposed to because of Newton.

• 34:46Speaker 02

  We can test that, we can test how light is bent by gravity, etc. But it also predicts what happens inside of black holes, which you know very well. We cannot go and observe it and then come back and tell our friends about it. Why do we still take it seriously? What happens inside black holes? Because this theory of general relativity has passed so many other tests that we could test. That we also start taking seriously its untestable predictions. And you can't just do, say, "Well, you know, I kind of like what Einstein's theory predicts for the motion of Mercury and gravitational lensing and yada, yada, yada. But I don't like the interior of black holes. I'm just going to opt out of that." Like if I go to Starbucks and say, "I want my coffee," but I'm going to opt out of the caffeine

• 35:31Speaker 02

  and have decaf. That's not the way science works. If you want to opt out of the black holes, then go come up with your own gravitational theory, which doesn't have black holes in it, but still succeeds in everything Einstein's theory did. That turns out to be such a tall order that despite a lot of smart people trying, you know, for 100 years, they've all failed. Wow. So what's that got to do with the multiverse? Well, replace general relativity now with the theory of inflation.

• 36:01Speaker 02

  That we talked about, it makes a bunch of testable predictions. It predicts that our universe should be expanding, that it should be very uniform.

• 36:07Neil deGrasse Tyson?

  But just to be clear, you're not, you're not actually replacing general relativity. You're enclosing it.

• 36:13Speaker 02

  Yeah.

• 36:14Neil deGrasse Tyson?

  In inflation, isn't that correct?

• 36:17Speaker 02

  Correct. Thank you for correcting me. We take generativity and then we add and it's some additional assumptions to it. That there is a certain kind of substance there which behaves in a certain way. And then we do the math and it predicts all sorts of things that we've tested now successfully with great prediction, like these ripples in the microwave background, their statistical patterns. For example, I've worked, as you know, a lot on, on trying to rule out this theory of inflation and I've failed. And because of that, we take it seriously and we also have to then take seriously the things inflation predicts that we cannot test, such as that space is actually way bigger than our universe.

• 36:55Neil deGrasse Tyson?

  Wow. Okay, that's, I think that's an excellent, excellent way to think about it. So, so if the one theory has these multiple consequences, it's okay if some of them you'll never, you can't or you never will, if the ones that you can test turn out to be correct.

• 37:11Speaker 02

  Right.

• 37:11Neil deGrasse Tyson?

  And you say, if this is correct, I'm gonna take a stronger look over, I'm gonna start thinking about this. By the way, is it fair to say, Max, that if you explore the things you cannot measure, you might come up with a discovery that you can measure?

• 37:27Speaker 02

  Very true too, because very often when people have been going off and thinking about these things, which they knew they could never test, they came, it led them to ask questions would lead them back.

• 37:38Neil deGrasse Tyson?

  Back to a whole fresh way.

• 37:39Speaker 02

  Could test.

• 37:40Neil deGrasse Tyson?

  Excellent.

• 37:41Speaker 02

  For example, another very good reason, not just that we shouldn't think of these cool things just because they're fun, but they often turn out to be very useful. People started thinking about what the ultimate building blocks of matter were and atoms and so on, and people for a long time thought that was completely useless, but then by thinking about that, they invented quantum mechanics, which gave us the whole computer technology, which lets us have this podcast now and so on.

• 38:06Neil deGrasse Tyson?

  Wow.

• 38:07Speaker 02

  And that's a, so, and that's another example, actually, of exactly this, this same question. The quantum parallel universes, of course, we can't visit them either, but quantum mechanics predicts so much else that we can test. And it turned out to be very, very difficult to come up with a theory of physics that predicts only that we sort of creation mechanism for a universe that creates only the part we can see and then stops and doesn't make anything more.

• 38:36Chuck Nice?

  So let me ask you this with with respect to what you're saying.

• 38:40Neil deGrasse Tyson?

  Chuck, you're not a Patreon member yet.

• 38:41Chuck Nice?

  I I that's right. You never know what I did during the.

• 38:47Neil deGrasse Tyson?

  I don't know what you did during the break.

• 38:49Chuck Nice?

  Yeah, that's right.

• 38:50Neil deGrasse Tyson?

  All right, I'll let you slip one in and go.

• 38:51Chuck Nice?

  All right. So Max, with respect to what you just said, are there things that we are able to observe or at least able to observe the forces thereof that remain a mystery that may in some way be attached to the multiverse theory?

• 39:13Neil deGrasse Tyson?

  Isn't that what we just answered? Is that? Are you saying, Chuck, if the multiverse is what it is, is there some piece of a dangling and visible in our own universe?

• 39:23Chuck Nice?

  Yes, that we're observing that that but what we're actually observing, but it's still a mystery. Like, you know, are there mysteries that are that are observable that?

• 39:33Neil deGrasse Tyson?

  Oh, I got it, Chuck. I'm going to read. I'm going to read. I'm going to recast your question. You ready, Chuck?

• 39:37Chuck Nice?

  Okay, go ahead.

• 39:39Neil deGrasse Tyson?

  Are there deep mysteries in our own universe that could themselves be evidence of a multiverse and we have yet to put the two together? How's that, Chuck?

• 39:48Chuck Nice?

  That's what I'm saying.

• 39:49Neil deGrasse Tyson?

  That's not what you said. You mangled it.

• 39:54Chuck Nice?

  But I didn't mangle it up that you didn't know what I was saying.

• 39:58Speaker 02

  And I will answer it with a resounding yes.

• 40:01Chuck Nice?

  Okay.

• 40:01Speaker 02

  Take dark energy, for example. We all know by now that we have no clue what 95% of our universe is made of, and most of it is made of this weird stuff called dark energy. And what's really odd about it is when you work out exactly how much there is in the sort of most natural units of measurement that we would do in physics, we get this number, which is 0.00000 with 123 zeros and then a one. And we wonder like, why is that?

• 40:32Speaker 02

  It turns out, if you look closer, that if you have a little bit more, we would all be dead. Wouldn't be any galaxies actually ever formed. And if you had less, so this was a bit negative, we would be inside of a black hole by now, and also not having this conversation. So why is it that our universe was so fine tuned? That the amount of dark energy was dialed in to this very special value that let us have this conversation? That is one of those mysteries, Chuck, I think that you're fishing for here. We, some people said, "Well, tough luck. We sometimes, we're just lucky. Let's just be grateful for it and shut up." Other people said, "Maybe this is evidence that we were designed, either by a divine being or by some simulator who tuned our universe specially to be able to have life."

• 41:16Neil deGrasse Tyson?

  In the parents' basement, they did this, yes.

• 41:19Speaker 02

  And then, but then, if you actually have parallel, this thing with space being very big, with parallel universes, with all sorts of different values of that knob setting in different places, suddenly you have an actual, simple explanation for this. The picture you get then is that the bigger space is like the Sahara Desert. It's mostly just a barren wasteland with no galaxies. But in a few places, you know, that knob is set just right. And you have an oasis where there is life, and there are galaxies, and there is star talk, you know? And surprise, surprise, of course, that's where we're going to be having these conversations.

• 41:55Neil deGrasse Tyson?

  But just to be clear, it's not that it was set that way. It's that if you have an infinite or a huge number of these universes, where the knobs are set at random, one of those random knob settings will be the right combination for us.

• 42:08Chuck Nice?

  It's like tuning, tuning your dial up and down. What used to be radio, kids. There used to be a thing, used to be this thing called "Radio Guys", where you would actually tune your dial. And like, most of it was just

• 42:21Neil deGrasse Tyson?

  Noise.

• 42:21Chuck Nice?

  white noise and empty. But every once in a while, you would come across somebody talking or some music or something like that.

• 42:27Neil deGrasse Tyson?

  Exactly.

• 42:27Chuck Nice?

  Oh, that is frickin' brilliant. God, I love science!

• 42:32Neil deGrasse Tyson?

  Okay, keep going.

• 42:33Chuck Nice?

  All right, here we go, here we go.

• 42:34Neil deGrasse Tyson?

  We've got just a few minutes left. See if we can squeeze them all in.

• 42:36Chuck Nice?

  All right, here we go. This is Woody. And Woody says, "What are your thoughts on how a multiverse could actually begin? Would each one require a Big Bang? And how many of those would end up with a Chuck being possible?"

• 42:51Neil deGrasse Tyson?

  Okay.

• 42:53Neil deGrasse Tyson?

  The Chuck-iverse.

• 42:54Chuck Nice?

  Yeah. Yeah, that ain't whatever.

• 42:57Neil deGrasse Tyson?

  Yeah, so Max, does everyone have a Big Bang just like us? That's a great question.

• 43:01Speaker 02

  Yeah, so I've actually had a total rethink about the Big Bang concept because first I was taught that that's the beginning. And now it's pretty clear if you take inflation theory seriously, you should think of the Big Bang just as the end of this crazy creative inflation process in our little part of space. When things calm down enough that you can make galaxies and a Neill and a Chuck and other in other places, it kind of keeps going. So even if you have only one bang, but that it keeps going at infinitum, you will end up having many, many different regions where it stops and and you get what we would call a level one multiverse, you know, with the universe. So all it takes is ultimately one bang to get it all.

• 43:44Speaker 02

  And and if you have each one of those places where it stops being actually infinite, then no matter how unlikely it is that you Chuck arise because the particles started out in exactly right configurations for your mom to meet your dad and all of that, it probably wasn't zero because it happened here and you're rolling the dice infinitely many times now, right? So it's guaranteed.

• 44:06Chuck Nice?

  Well, there you go. And by the way, both my parents lost on that bet. So on the roll of that dice.

• 44:12Neil deGrasse Tyson?

  I mean, by making you, is that what you're saying?

• 44:14Chuck Nice?

  Exactly.

• 44:15Neil deGrasse Tyson?

  All right.

• 44:16Chuck Nice?

  Believe me, I was not a good kid. All right.

• 44:19Neil deGrasse Tyson?

  Keep it going.

• 44:20Chuck Nice?

  Here we go. This is Cameron Bishop. Hello, Max. Hello, Neil. I've always been curious, is it flawed to ask what's between these universes? Is that measurable space? That's a great question.

• 44:36Speaker 02

  So between the different level one multiverses and the level two multiverse, there is still space, but that space in between is still doing this inflation thing and doubling its size over and over and over go and and regular intervals. That's why it's impenetrable because.

• 44:54Speaker 02

  If you start flying through, go for a while and now you're still farther away from where you're supposed to go.

• 44:59Neil deGrasse Tyson?

  It's expanding faster than you can gain distance through it.

• 45:02Speaker 02

  Exactly.

• 45:02Neil deGrasse Tyson?

  Exponentially, okay.

• 45:04Chuck Nice?

  That's great. That's super cool. All right.

• 45:06Neil deGrasse Tyson?

  But in the quantum multiverse, there are actually whole other spacetimes. There's not one spacetime system, right?

• 45:14Speaker 02

  Yeah, the quantum multiverse, the level three, lives in a bigger space we call Hilbert space, which may even have infinitely many dimensions, so.

• 45:23Chuck Nice?

  I hear the rents there are out of control.

• 45:27Chuck Nice?

  Yeah, the property values are just off the charts in Hilbert. Something has to be done about Hilbert, damn it.

• 45:36Neil deGrasse Tyson?

  So, but, so what would you call what was between those quantum universes?

• 45:42Speaker 02

  In the quantum case, it's much more tricky. When quantum mechanics was first invented, people didn't know about this phenomenon called decoherence. It was only discovered by Hans Dieter Tse in 1970, and he should be more famous than he is, which is a kind of censorship mechanism that explains why we don't experience all those other weird quantum realities if they're actually there. Basically, what comes out of the math is that these quantum superpositions, as they're called, they only survive as long as they're kept secret. And whenever something gets really big, you know, air molecules bounce off, photons bounce off, and the secret is out. It's like you tell a friend, they tell a friend, and so on.

• 46:25Speaker 02

  That's why big things like us always seem to only be in one place at once. And we can only experience and measure quantum weirdness with tiny things that can keep their properties secret.

• 46:38Neil deGrasse Tyson?

  So Chuck, time for that last toke on that pipe.

• 46:40Chuck Nice?

  Yeah, man. I'm telling you right there. That's, wow. That was, that was cool. What's it called? What's it called? D what now?

• 46:50Speaker 02

  Decoherence.

• 46:52Chuck Nice?

  Decoherence.

• 46:53Neil deGrasse Tyson?

  No, here's Chuck. When your kids are babbling on and you don't know what they're saying, say, "Stop being decoherent."

• 46:57Chuck Nice?

  Yeah, don't be decoherent, okay?

• 47:02Chuck Nice?

  You quantum dummy.

• 47:04Neil deGrasse Tyson?

  That's worse than incoherent. You are decoherent.

• 47:06Chuck Nice?

  You are decoherent.

• 47:08Speaker 02

  Yeah, they're just decohering the whole conversation.

• 47:12Neil deGrasse Tyson?

  Chuck, give me one last question and see if Max has a soundbite in him to answer because that's all the time we have left for it. Go.

• 47:18Chuck Nice?

  Okay. This is Jay Hunt. Greetings Neil and Max. This is Jeff from Titan. My question is...

• 47:28Neil deGrasse Tyson?

  Titan, the moon of Saturn, I guess. Okay.

• 47:31Chuck Nice?

  Yeah, gotta love that, right? My question is...

• 47:33Neil deGrasse Tyson?

  That means it's full of methane gas, just so you know.

• 47:41Speaker 02

  I'll cut down on those beans, man.

• 47:44Neil deGrasse Tyson?

  Yeah, watch out for the beans. Right, go on.

• 47:48Chuck Nice?

  My question is, is a new multiverse created every time we make a this or that decision? So the idea that the infinite number of possibilities are not actually possibilities until we make one of those possibilities?

• 48:05Speaker 02

  Fantastic question about the level three multiverse. Basically, if you make a snap decision that you're really torn about, right, what ends up happening might come down to the position of a single little calcium ion somewhere in some synaptic junction and where, depending on where it is...

• 48:20Neil deGrasse Tyson?

  Of your brain, yeah.

• 48:21Speaker 02

  Off the things go and you end up with a completely different pattern and either you decide to say yes to that date and live happily ever after, or say no and do something different, right? So that can, a micro superposition can get amplified into something that's so different macroscopically that this decoherence thing comes along and makes these two things really, really separate. So in that sense, yes, when you make a decision that you really could have made both ways, you are, in a sense, if the level three multiverse is real, creating two parallel realities that are equally real. And each one of you is only, of course, aware of one outcome and is going to think that's all that happened.

• 49:00Chuck Nice?

  Oh my god. That is crazy, man.

• 49:03Neil deGrasse Tyson?

  I love that.

• 49:04Chuck Nice?

  That is awesome. Oh my god. Oh, right now it's somewhere...

• 49:08Neil deGrasse Tyson?

  So it means you created another Chuck, but you're only this Chuck. And so that's all you know.

• 49:12Chuck Nice?

  Right. That other, that other guy's actually half...

• 49:14Neil deGrasse Tyson?

  And he's having fun.

• 49:18Speaker 02

  I try to think about that every time I get a parking ticket, you know, that there's some other parallel universe where I didn't. But then I think a bit more and realize there's another parallel universe where I got towed.

• 49:31Speaker 02

  Win some, you lose some.

• 49:32Neil deGrasse Tyson?

  All right. Max, we got to call it quits there. It's been a delight to have you on. It's always great to talk to you and probe your brain for all the fun stuff that you're thinking about. So, thanks for being on StarTalk. Chuck, always good to have you. Always a pleasure. All right. This has been StarTalk, Cosmic Queries, the multiverse edition. Neil deGrasse Tyson bidding you to keep looking up.