Cosmic Queries – Fixing Physics with Sabine Hossenfelder

Can a whole universe fit inside a black hole? Neil deGrasse Tyson and Paul Mecurio explore grand unification, dark matter, wave function collapse, and other problems in physics with theoretical physicist and author of “Existential Physics,” Sabine Hossenfelder.

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 Cosmic Queries Edition. As always, I've got a co-host who's a stand-up comedian, Paul Mecurio. Paul, welcome back to StarTalk.

• 0:25Paul Mecurio?

  Nice to see you again, Neil. Great to be back.

• 0:28Neil deGrasse Tyson?

  And I'd like, I can count you as my friend. We had a couple of lunches together and so you're more than just my co-host. I count you as a friend.

• 0:36Paul Mecurio?

  Yeah, you treat us to a great lunch and the three of us need to do that again soon. We were talking about that. That was really fun.

• 0:41Neil deGrasse Tyson?

  Yeah, excellent, excellent. And so also, just some people, if they don't otherwise know you, or they know you only a little bit, I first knew of your work as the warm-up guy for the audience for Colbert's The Late Show. Then I see clips of you doing stand-up on the show. Excuse me.

• 0:58Paul Mecurio?

  Yeah, I'm a big shot. I don't think you realize that. And one would call me an international superstar, at least that one person would be me.

• 1:08Neil deGrasse Tyson?

  Yeah, or your mother.

• 1:09Paul Mecurio?

  Or my mother. No, I was, well, I left Wall Street to be a comedian, so I'm just, I think the word she uses is disappointment, but yeah, no, I mean, Stephen and I go back to The Daily Show together. I was a writer-performer on that show.

• 1:21Neil deGrasse Tyson?

  Excellent.

• 1:22Paul Mecurio?

  And so, yeah, so I've been part of that DNA of those shows for a while, but yeah, that's where we got to know each other.

• 1:27Neil deGrasse Tyson?

  Excellent.

• 1:28Paul Mecurio?

  You're always, you're always great on the show. You're always great.

• 1:31Neil deGrasse Tyson?

  Oh, thank you, thank you, just as a guest. So today, we're tackling the big questions. The big questions. And that could mean different things to different people, but on this show, it means the big questions in the universe. And we combed the world, no, we combed the universe. And we found someone who just published a book titled "Existential Physics: A Scientist's Guide to the Biggest Questions." And that person is in the, is in the house right now, except...

• 2:07Neil deGrasse Tyson?

  Dialing in from Germany. We have Sabina Hossenfelder. Did I pronounce that right, Sabina?

• 2:13Speaker 02

  That was wonderful. Good to see you guys.

• 2:15Neil deGrasse Tyson?

  Excellent, excellent. You're a theoretical physicist. And Paul, it's not that she's theoretically a physicist. I just want to clarify that. She's a theoretical physicist, a research fellow at the Frankfurt Institute of Advanced Studies, of course, in Germany. And you've got a popular YouTube channel called Science Without the Gobbledygook. How could you not tune into that with a name such as that? And one of my favorite works of hers is an earlier book that was indicting the expectation that elegance and beauty and math should guide science.

• 2:55Neil deGrasse Tyson?

  And I agree, Sabina, with you 100% that it has often derailed what could be an actual discovery because we place our own expectations on what the universe should be. Could you just comment on that briefly?

• 3:13Speaker 02

  Yeah, it's an ongoing disaster. It's still happening. It's not like it's over. Yeah, so my first book dealt with the question why there's been pretty much no progress in the foundations of physics in the past 50 years or so, since the standard model was completed. So we've gotten stuck with all those big questions. What is dark matter? What is dark energy? How did the universe begin?

• 3:38Neil deGrasse Tyson?

  And just to be clear, the standard model is it's the array of particles that we know exist in the universe and how they all fit together, how they interact and what forces they enact upon each other. And that was quite an achievement coming out, you know, in the mid to late 20th century. And you're saying there hasn't been much fundamental progress since then?

• 4:00Speaker 02

  For what the theory development is concerned, no. So since the time that the standard model was completed in the mid 1970s or something, loosely speaking, there have been a lot of experimental discoveries. A lot of the particles in the standard model had not been observed at the time, like, for example, the heavier quarks and stuff like this. Of course, the Higgs, which wasn't...

• 4:24Neil deGrasse Tyson?

  Higgs boson, can't leave that out, right.

• 4:26Speaker 02

  Exactly, right. Which was only experimentally confirmed 10 years ago, right? It just had the 10-year anniversary. But for what the mathematical structure is concerned, it hasn't changed.

• 4:40Neil deGrasse Tyson?

  And Sabina, don't feel alone about this. We haven't been back to the moon in 50 years, okay? So you're not the only one.

• 4:47Paul Mecurio?

  Is that because that so much information came out of that first tranche of discovery that it just sort of processing all of those different elements of knowledge just takes so much time that it's hard to sort of advance to another tranche? Is that one particular reason, maybe?

• 5:07Speaker 02

  Well, the message that I'm trying to get across in the book is that the problem is the physicists got too enchanted by certain ideals of beauty.

• 5:17Neil deGrasse Tyson?

  So Paul, her answer is no to that question.

• 5:21Paul Mecurio?

  By the way, for the record...

• 5:22Neil deGrasse Tyson?

  I'll translate.

• 5:23Paul Mecurio?

  For the record, Sabina, I was this close to writing that book. You beat me to the punch by like an hour. I had it almost all done and yours came out. And I'm like, you know what? Forget it. I'm not gonna bother.

• 5:35Neil deGrasse Tyson?

  What's an example of one of the most distracting beauty elements that people want to be true in the universe?

• 5:43Speaker 02

  Unification, I guess. So after the standard model was completed, there were a lot of physicists who thought it should be more unified. They were looking for this grand unified theory, which was pretty... You know, at the time, I think at the 70s, 80s, they thought it was pretty much around the corner. And it's out of this spirit that string theory was born. And what happened was that all the predictions that were made from those theories were falsified, to the extent that they could be falsified. So now we're left with the non-falsifiable ideas. Yeah, so it was grand unification, also symmetry, supersymmetry.

• 6:21Neil deGrasse Tyson?

  But wait, this is a good tradition, though. Einstein... Was headed there, right? So you don't want to be in the wake of Einstein's work?

• 6:31Speaker 02

  Well, for one thing, I think Einstein wasn't driven by symmetry. Though it's certainly true that the way that we understand general relativity today, it's based on symmetries. But I think it wasn't Einstein's intention. But so what happened was that, I think in the 70s, 80s, relying on symmetries was the next natural thing to do. It had worked before, so of course you do it again. But the problem was, it didn't work. And physicists just didn't learn the lesson. So instead of saying, "Okay, we tried it, it didn't work. Let's move on and try something different." They tried the same thing over and over and over again. And basically, they're still trying it. So how is it surprising that there's no progress?

• 7:15Neil deGrasse Tyson?

  So I bet you're popular at their parties.

• 7:19Speaker 02

  Yeah, I'm great fun.

• 7:23Paul Mecurio?

  You get a lot of the "my invitation must have been lost in the mail" kind of thing, right?

• 7:26Neil deGrasse Tyson?

  Exactly. So you're...

• 7:29Paul Mecurio?

  Is it because they lack the security of their own analysis that they keep testing it over and over again? I mean, is it... I mean, you know, they're not insane, right? There must be some rationale in their mind that they keep retesting the same. So maybe there's doubt in their own mind about their processes or their analysis?

• 7:49Speaker 02

  Yeah, I think there's not one factor to it, but a couple of them, which is why my book has 300 pages.

• 7:59Speaker 02

  If it was that short an answer, it wouldn't have been worth writing a book. So I think it's partly a lack of understanding of the philosophy of science. So I think that they're not really thinking about what's going on. So they don't recognize it's not working. And they try the same thing over and over again. Even though good scientists, you know, you should use the scientific method and not do this kind of thing. But it's also, I think it's a community problem. It's kind of baked into the way that... Academic communities work in the way that they are funded. It's just really, really hard to get out of some kind of research direction

• 8:41Speaker 02

  after you've spent a significant time of your career on it and do something else. There are very few physicists, and I know some of them, so they exist, who said, "Okay, so we've tried supersymmetry, it doesn't work. I'll stop it and do something else." Because it makes your life very, very difficult if you do this, because all your funding goes out of the window and your whole track record has evaporated.

• 9:04Paul Mecurio?

  So it's like being a one-trick pony, like Def Leppard, right? Like, it's like sort of just the same song over and over and you kind of get locked into it. Yeah, I see.

• 9:13Speaker 02

  Yeah, so I wrote something for Physics World and I wrote advice for Postdocs. "Don't be a one-trick pony." And my British friend was like, "This is such an American idiom."

• 9:27Neil deGrasse Tyson?

  So what's Def Leppard's one-trick pony?

• 9:29Paul Mecurio?

  Uh, no, it's their songs. Everything sounds the same.

• 9:32Neil deGrasse Tyson?

  Oh, everything sounds the same?

• 9:33Paul Mecurio?

  It's over and over and over again. It's the same thing, yeah.

• 9:36Neil deGrasse Tyson?

  So Sabina, so that early work, that early book really puts you in a good way and it positions you to take on a broader topic here, sort of existential questions. And so what prompted you to write this book?

• 9:55Speaker 02

  Oh, my first book is like really depressing. I mean, I was basically going on for those 300 pages about why there's no progress in the foundations of physics and trying to explain what everybody else is doing wrong, which, you know, doesn't exactly make me look like a particularly nice person. And it kind of, I felt that it was necessary to write the book because I thought, "Someone's got to say it," you know? There's no reason why the LHC should be seeing new particles, all those stories that they've told about dark matter.

• 10:26Neil deGrasse Tyson?

  LHC, the Large Hadron Collider.

• 10:27Speaker 02

  Yeah, exactly that thing. You know, there have been all those stories. It would see supersymmetric particles or dark matter. It would make black holes and all that kind of stuff. And all those supposed predictions were based on arguments from beauty. And in my book, I explain this. But, you know, it kind of makes me this person who's always complaining about what other people do and I'm kind of unhappy with the picture that I've painted of myself. So I was thinking, you know, I would try to remind myself why I studied physics in the first place, which is that I was really intrigued by how much you can learn about nature from pure mathematics, basically, you know, all those symmetries that we were

• 11:12Speaker 02

  just talking about, they're like really, really powerful tools that have taught us so much about how the universe works. And a lot of those stories haven't really been told to the public, like when it comes to those big existential questions. And so I've collected them in my book.

• 11:29Neil deGrasse Tyson?

  Good. So you saw a gap that you're filling. Excellent. Excellent. So we got questions. We solicited questions from our Patreon fanbase, and these are supporters of the show, and they get their questions on. So apparently you have to actually become a Patreon member in order to even get your question looked at, much less selected. So that's kind of cold, I think, but that's how that works. I didn't set up that rule, just that you know, our producers and other folks who pay the bills set up that rule. Okay. So Paul, why don't you start off? You've got the questions. I haven't seen them or heard them, and I don't think Sabina has seen them, correct?

• 12:07Paul Mecurio?

  No. So there's some really great questions this time around. So we're going to jump in with Quentin on microwaves. Hi.

• 12:14Neil deGrasse Tyson?

  Was Quentin from, did we know where these people are from?

• 12:16Paul Mecurio?

  From Switzerland. This is.

• 12:18Neil deGrasse Tyson?

  Well, tell us where they're from. Why you leave that out?

• 12:20Paul Mecurio?

  I was about to say, hi, greetings from Switzerland before you started yelling at me, Dad.

• 12:25Neil deGrasse Tyson?

  Switzerland is where the LHC is. So this person is like on top of the situation?

• 12:29Paul Mecurio?

  Yeah. I was reading his thing, and it said, hi, guys, greeting from Switzerland. You see the tension, Sabina? This is how this goes. All right. What's more knowledge is there to gain by making more and more detailed measurements of the cosmic microwave background? Love the show.

• 12:46Speaker 02

  I think the thing that everyone is looking after at the moment are the B modes, right? They want to measure the polarization of the CMB to try and figure out if there were gravitational waves in the early universe.

• 13:01Neil deGrasse Tyson?

  Are you saying that there's nothing in there that can help you and your dark matter search?

• 13:08Speaker 02

  In the CMB, well, me and my dark matter search. Exactly, exactly what are you talking about?

• 13:17Neil deGrasse Tyson?

  Are we all looking for dark matter?

• 13:19Speaker 02

  My personal satellite has just launched. No, so, yeah, I mean, so the CMB does put constraints on dark matter. It's been doing this for some time. And every time the data gets better, then the parameters of Lambda CDM shift around for a little bit and people adjust their models. I don't think the CMB is the best tool to learn something about dark matter because it just, you know, the overall dark matter fraction of the universe is one of those parameters. But what you really want to know, like where the properties of the dark matter stuff, if it's stuff, become important is more on the smaller scales, galaxies, galaxy clusters, when you have to take into account how the stuff actually clumps.

• 14:04Speaker 02

  And there are some things that you can do in the CMB, loosely speaking, because those structures give rise to gravitational lenses, so it distorts the CMB, and there's a fancy name for it, which escapes me at the moment, but this is how it goes with my brain. And you can look for this. So this is interesting, but it has fairly large error bars. So I think that the stuff with the B modes is more exciting if you want to understand how the universe evolves.

• 14:34Neil deGrasse Tyson?

  So I have a slightly different outlook on that, Sabina? But we're going to get to that right when we come back from our break. We'll take our first break from Cosmic Queries and our special guest dialing in from, what town are you in right now, Sabina?

• 14:46Speaker 02

  Heidelberg.

• 14:48Neil deGrasse Tyson?

  Heidelberg, Heidelberg, dialing in from Heidelberg. I have great memories of Heidelberg. Hossenfelder.

• 14:56Neil deGrasse Tyson?

  We'll be right back and we'll learn maybe what Paul did in Heidelberg when we come back to StarTalk. You don't want to know.

• 15:15Speaker 03

  Hey, I'm Roy Hill Percival and I support StarTalk on Patreon. Bringing the universe down to earth, this is StarTalk with Neil deGrasse Tyson.

• 15:34Neil deGrasse Tyson?

  We're back, segment two, Cosmic Queries. We're talking about the big questions and the release of Sabina Hossenfelder's book. Sabina, give me the full title, it's like existential...

• 15:47Speaker 02

  Existential Physics: A Scientist's Guide to Life's Biggest Questions.

• 15:51Neil deGrasse Tyson?

  There you go, there you go. And it's just always good to have someone in arms' reach with that kind of expertise, because you just never know.

• 16:01Paul Mecurio?

  By the way, I have a book coming out, Peanut Butter. Do you need jelly, or don't you?

• 16:05Neil deGrasse Tyson?

  Yeah, no, I'm with you on that. I'm with, peanut butter doesn't need jelly. I'm all good with the peanut butter.

• 16:10Paul Mecurio?

  It's 400 pages, it's a very deep analysis. Sorry, Sabina, it's gonna be competing with your book. I hope yours works out, that's all I'm saying.

• 16:20Neil deGrasse Tyson?

  So before the break, Paul, we got this question from this person in Switzerland, wanting to know whatever more detailed measurements of the cosmic microwave background can do for us. Here's what I would say, Sabina, that if I'm at a distance and I see a home, and I see a region around the home that's all green, and I say, oh, that's like a green carpet or something, okay? But then I get closer, or I look with higher resolution, and I say, no, wait a minute, there are blades of grass there. And then I'd say, okay, so it's a green thing made of blades of grass. And I look even closer, wait, the blades of grass have cells in them, right? And so every next layer, I would not have even known to ask if that was there,

• 17:05Neil deGrasse Tyson?

  until I had that extra resolution that empowered me to inquire in ways I had not previously imagined.

• 17:14Neil deGrasse Tyson?

  So are you prepared to say that a higher, even higher resolution of the cosmic microwave background, there's nothing there for us? Like, looking at a lawn of grass?

• 17:24Speaker 02

  No, of course, I would never say that. You never know what you're going to find. It's just my guess that we will have a bigger turnout from the B modes than from a higher-resolution cosmic microwave background.

• 17:39Neil deGrasse Tyson?

  Okay, all right.

• 17:40Paul Mecurio?

  Can I ask, like, why is it that CMB gives us information about the nature of the universe just after the Big Bang, but not the last scattering? And is there any been, is there been movement on that?

• 17:54Speaker 02

  Well, you know, the phrase "just after the Big Bang" is kind of ambiguous, because...

• 18:01Paul Mecurio?

  That's the best I can do. I'm a comedian.

• 18:03Speaker 02

  All the interesting things that happened in the early universe are right after the Big Bang, like, in the first, like, ten to the minus ten seconds or something like this.

• 18:12Paul Mecurio?

  Right.

• 18:12Speaker 02

  So I'm afraid you have to be a little bit more specific.

• 18:18Neil deGrasse Tyson?

  Well, no, no, so I guess the point is, the cosmic microwave background is several hundred thousand years after the Big Bang, and it has an imprint...

• 18:27Paul Mecurio?

  Right, 380,000, right?

• 18:29Neil deGrasse Tyson?

  Of what had unfolded before then. And so it gives us some insight into an earlier time, but maybe not as far back as you're otherwise indicating.

• 18:39Speaker 02

  As you're otherwise indicating. I mean, so what you say is, of course, entirely correct. It's kind of difficult to see through all this plasma, which is opaque. There are several things that people have proposed. I mean, looking for those gravitational waves in the B modes kind of allows you to look back to earlier times, at least if you trust the interpretation. People have also suggested to look for the neutrino cosmic microwave background, which should be there. So they have traveled undisturbed for a longer time. But the problem with the neutrinos is, well, they interact very weakly. So, you know, good knows how long it would take to measure the thing. Like, maybe we'd be measuring, I don't know, 100,000 years or something.

• 19:24Speaker 02

  So don't expect results anytime soon.

• 19:27Paul Mecurio?

  Yeah, neutrinos have always been very difficult. They don't play well with others.

• 19:32Neil deGrasse Tyson?

  No, they don't, at all. So Paul, give me some more questions.

• 19:36Paul Mecurio?

  Yeah, this is on wave function from Stephen Murphy. I'm not sure where this person is from, but if I understand quantum physics correctly, there is something about measurements that collapses the wave function. Some people, especially sci-fi authors, seem to believe our conscious observation of the measurement is what does the collapsing. How do we know that our observation is not the key factor? I think we know. I think there's an esteemed scientist, Dr. Emmett Brown, from Back to the Future, who said, "If you travel in the past and you play with the past, you're going to alter the future." So I think we could just move on.

• 20:10Neil deGrasse Tyson?

  We could just move on, yes, exactly. We don't need Sabina to answer that.

• 20:15Neil deGrasse Tyson?

  Look, so Sabina, what do you have there? This collapse of the wave function?

• 20:20Speaker 02

  Yeah, so I think this is something that people were really confused about in the early days of quantum mechanics. Like, when the thing came up, it became clear that there's something going on in the measurement. They didn't know what, and they made what's now known as the Heisenberg cut, which basically says wave function does one thing when you're not looking at it, and when you do look at it, booms, it collapses into something that corresponds to our classical reality. I don't think that today anybody believes this, or I mean, maybe I shouldn't put it that strongly, but there are probably one or two weird people who still believe that consciousness has something to do with the collapse of the wave function.

• 21:04Speaker 02

  But certainly, the vast majority of physicists have abandoned this idea, simply because we know that we can make quantum measurements without the involvement of any conscious observer. We can do it with some kind of apparatus that was programmed by a computer, and in the soon future, maybe we can do it with robots, or maybe this is already happening, and I haven't gotten the memo.

• 21:29Speaker 02

  So what do you need consciousness for, basically, in the measure?

• 21:32Neil deGrasse Tyson?

  Wait, wait, Sabina, you just missed a deep discovery. It's that the machines making the measurement are conscious. It's obvious.

• 21:40Speaker 02

  Oh, right, yes, it's evidence for panpsychism now.

• 21:44Neil deGrasse Tyson?

  Exactly.

• 21:45Speaker 02

  All right.

• 21:46Paul Mecurio?

  It's an AI.

• 21:46Neil deGrasse Tyson?

  How could you have missed that revelation there? Come on.

• 21:51Speaker 02

  Yeah, right. But so maybe more interesting, Neil, it's like the the opposite combination that quantum mechanics plays some kind of role for consciousness. It has not completely gone out of the window. Maybe most prominently, it's represented by Roger Penrose, who thinks that something about those quantum processes and the measurement, the collapse of the wave function in particular, is necessary to give rise to consciousness in the human brain. And I'm not at all convinced by this, but then he has won a Nobel Prize and I haven't.

• 22:27Neil deGrasse Tyson?

  Yeah, he won it for black holes, not for not for, you know, consciousness, just to be clear.

• 22:33Paul Mecurio?

  Yeah. So what does he so what does he know?

• 22:35Neil deGrasse Tyson?

  Yeah, what an idiot. What does he know?

• 22:37Paul Mecurio?

  Everybody can have a Nobel. I have one. I got it.

• 22:40Neil deGrasse Tyson?

  Yeah, he's one of the most eminent among us in the in the physics and astrophysics universe, Roger Penrose, still alive, still at it. And I think he's old enough so he can have some borderline flaky ideas and you still end up giving it some respect. And so I think, Sabina, that's where that's where you were landing there, I think. Is that right?

• 23:01Speaker 02

  Yeah. I mean, you know, by all chances, I just don't understand it.

• 23:08Neil deGrasse Tyson?

  So Paul?

• 23:09Paul Mecurio?

  Yeah, we're going to time exists in black holes. This is from Queensland, Queensland, Peter Jacobs, Australia. Where is where it is a different time and a different day and 293 degrees this winter morning. This is what Peter says. All right, here's his question. Does time exist in a black hole? And if you travel through a wormhole, could you end up in a different place in time and not be able to get back? Well, I don't know. If you're going to do air travel, by the way, Peter, right now, you're not getting it. You're not going anywhere because your flight's going to be canceled. So.

• 23:46Paul Mecurio?

  You're not traveling through any wormhole, anywhere, anytime. Try taking a train.

• 23:50Neil deGrasse Tyson?

  Anytime soon, yes.

• 23:51Paul Mecurio?

  Anytime soon, exactly.

• 23:52Neil deGrasse Tyson?

  So Sabina, what happens, what's the fate of someone broadly? We're thinking about the fate of someone in a wormhole and in a black hole, other than that they'll rip apart and die?

• 24:00Speaker 02

  Right.

• 24:01Neil deGrasse Tyson?

  Hole aside that complication.

• 24:03Speaker 02

  I'm still trying to digest the phrase "a different place in time", but I think, I think I know what it means. Yeah, so the weird thing about Einstein's theory is that he made time into a coordinate like space. And it has the consequence that the labels on those coordinates are kind of ambiguous. You know, you can change them the same way that you can change the labels on your ruler from, I don't know, inches to centimeters or something like this. They don't really mean anything. So this coordinate time has to be enjoyed with a lot of care. If you want to interpret it, usually what we deal with in Einstein's theory is what's called the proper time.

• 24:48Speaker 02

  So this is the time that an observer would experience, who would be traveling in this spacetime. And for we know, if you fall into a black hole or if you go through a wormhole, then your proper time just moves forward, so you get older. Where you come out in this coordinate time is a completely different question. And indeed, if you go through a wormhole, you could in principle come out in the past according to this coordinate time. And this is also why a lot of physicists believe that wormholes are hugely problematic because they could lead to all kinds of paradoxes. You could go back in time, kill your grandfather, that kind of story.

• 25:29Neil deGrasse Tyson?

  And why is everyone always talking about killing their ancestors? Why not just prevent them from meeting? And then they don't marry and have babies? Why do I always gotta kill them? I mean, what, what's, you know?

• 25:40Paul Mecurio?

  Or you go back and you ask that girl or that guy out that you wanted to ask out on a date and you didn't? And you were, and then you ended up in, with the person you're with? And that's not working out? I'm getting too personal right now.

• 25:52Neil deGrasse Tyson?

  Yeah, yeah, I don't hear your, your issues.

• 25:55Paul Mecurio?

  Because Sabina, my wife and I are not talking. And I was wondering if you might be able to help.

• 26:01Neil deGrasse Tyson?

  Is there a quantum relativity therapy session that is in need?

• 26:05Speaker 02

  Exactly. Wait, wait for my next book.

• 26:09Paul Mecurio?

  Exactly. So in traveling through the wormhole, there really the answer is you could end up anywhere at any time. Is that sort of for the layperson? Is that sort of one of the answers there in a very crude way?

• 26:24Speaker 02

  Mathematically, yes. But no one's ever built a wormhole, and we have no idea how to build one. Or if actually, most physicists think it's not possible because it requires negative energy. So who knows? You know, mathematically, you can write it down, but...

• 26:40Paul Mecurio?

  I can get you negative energy. Meet my mother.

• 26:44Neil deGrasse Tyson?

  Suck the energy right out of a room.

• 26:46Paul Mecurio?

  Exactly. Why? Why are you killing me?

• 26:51Speaker 02

  I see you. Meeting your mother makes you travel to the past.

• 26:56Paul Mecurio?

  Exactly.

• 26:57Neil deGrasse Tyson?

  Well, so an important point that you just glossed over there, Sabina, that you go through into a black hole and you have what we call proper time. But that's as applies to you. So it doesn't really make sense to ask, what is the time in a black hole? Because it has to reference someone who's making the measurement of a time. And then you can get different measurements depending on whose coordinate is behaving in which way. Is that a fair way to sort of add nuance to what you just said?

• 27:27Speaker 02

  Yes, that's of course entirely correct. And it's also why people get confused about this issue that it takes seemingly forever to cross the horizon of a black hole if you fall in. That's what you see from the outside. So an observer who sits outside and sees you falling into a black hole would just see you freeze as you get close to the horizon. But in your own proper time, if you fall in, it's a finite amount of time. And it's a finite amount of time that it takes to hit the singularity, if there is a singularity in a black hole, which we don't really know. But assuming that there is one, it takes a finite amount of time.

• 28:03Neil deGrasse Tyson?

  So Paul, we can solve that question by you just visiting a black hole. And see if there's a singularity there.

• 28:09Paul Mecurio?

  I am gonna go. I'm taking Amtrak.

• 28:12Paul Mecurio?

  I was gonna take Delta, but you know how they are. They never get anywhere on time. But so I'm sorry, Neil, real quick and follow up to what you just asked and Sabina confirmed. You're saying, again, from a layman's perspective, the person, the individual, and the time and place at which that measurement is taking place specifically has an effect on the issue and the concept of time. It's not a general answer in terms of what we mean by time. It's specific to who and when.

• 28:42Neil deGrasse Tyson?

  I think classically, you can think of this one time system everywhere, and we learned in relativity, that's just not the case. If time is just another coordinate, then you can experience that coordinate in different ways. And so that's how I think about it, Sabina. Is that fair?

• 28:57Speaker 02

  Yeah, I think that's a pretty good summary.

• 29:00Neil deGrasse Tyson?

  Yeah, so you experience straight time falling into a black hole. Someone watching you, it would take forever for them to see that happen. And you're both perfectly legitimate wristwatches making these measurements.

• 29:11Paul Mecurio?

  And so what is the scientific measurement of a friend telling me a long-winded story that doesn't do anything for me in my life? The time?

• 29:18Neil deGrasse Tyson?

  They're actually slowly falling into a black hole in that moment.

• 29:20Paul Mecurio?

  Thank you. That's exactly how I felt. I couldn't describe the feeling until now. I'm falling into a black hole, which is why when I talk to people now, I want to wear a welding helmet up. So if I find that the conversation's just going in a place that's just doing nothing for me, I just put the helmet down, and that pretty much tells you that we're done.

• 29:39Neil deGrasse Tyson?

  That's the evidence. Okay.

• 29:41Paul Mecurio?

  That's how I work.

• 29:43Neil deGrasse Tyson?

  Time for one more question in this segment.

• 29:44Paul Mecurio?

  Yeah, absolutely. Other universes inside the black hole. This is Ryan Gurintes, and it says, "Hey, everyone, I want to know how possible it is that inside black holes are actually other universes."

• 29:59Neil deGrasse Tyson?

  Yeah, we've all heard this, Sabina, and it's kind of, on the face of it, it's completely outlandish. How can this giant sucking machine called a black hole be the repository of an entire universe? And Sabina, you're gonna answer that question when we come back from this break.

• 30:22Neil deGrasse Tyson?

  Because I want to know the answer too. Very nice. Damn it, what the hell is going on inside of a black hole? When StarTalk Cosmic Queries continues.

• 30:48Neil deGrasse Tyson?

  We're back, StarTalk Cosmic Queries. Sabina Hossenfelder. So she's got a new book out on the big questions. Existential questions in physics. And we're trying to get through some of these bigger questions about spacetime, black holes and the like. Sabina, how do we find you on social media?

• 31:06Speaker 02

  Well, you can find me on Facebook under my name, Sabina Hossenfelder, or on Twitter under the handle SKDH. Those are my initials, just in case you wonder. And of course, on YouTube.

• 31:22Neil deGrasse Tyson?

  And of course, your big YouTube channel. And Paul, we find you on social media where?

• 31:26Paul Mecurio?

  Yes, @SKKB. No, that's yours. I was wondering why I was getting all of these really intense questions about quantum theory and you were probably getting ridiculous comments about comedy. No, it's @PaulMecurio. M-E-C-U-R-I-O.

• 31:43Neil deGrasse Tyson?

  M-E-C-Mecurio.

• 31:45Paul Mecurio?

  Mecurio. I had to drop the first R because of the Australian actor.

• 31:49Neil deGrasse Tyson?

  No, it's because you have a planet with that and you didn't want to be confused for Mercury. I think that's really what it is.

• 31:56Paul Mecurio?

  I get confused with planets a lot, very often.

• 32:00Neil deGrasse Tyson?

  Because Mercury's got its own Twitter stream, just to let you know.

• 32:02Paul Mecurio?

  Exactly, exactly.

• 32:03Neil deGrasse Tyson?

  So Sabina, I remember the question from the second segment. Are there... Who's the person who asked it, Paul?

• 32:09Paul Mecurio?

  This is Ryan Gertes.

• 32:12Neil deGrasse Tyson?

  So are there... We've heard, we've all read, that you enter a black hole, there's a whole universe opens up in front of you. Could you like, have that make sense for any of us, please?

• 32:22Speaker 02

  Yeah, so we don't know what's inside a black hole. But it's not just...

• 32:26Neil deGrasse Tyson?

  Okay, that's the answer. Paul, next.

• 32:28Speaker 02

  Yeah, basically. But that it could be...

• 32:32Paul Mecurio?

  Can I just say something?

• 32:34Speaker 02

  Let's move on to the next question.

• 32:36Paul Mecurio?

  I...

• 32:39Neil deGrasse Tyson?

  Okay, but the theoretical hypotheses is what gives us this, right?

• 32:43Speaker 02

  Yeah, so that it's a black... That it's a portal to another universe is one of the possibilities that people have put forward. You can do it. Basically, the reason it works is that... If you know one thing about Einstein's theory of general relativity is that space and time becomes curved. And you can curve it so much that you create pockets, and those pockets can become infinitely large. So, a black hole might be much larger in the inside than it looks from the outside. And indeed, it could be infinitely large. So mathematically, you can stuff another universe inside a black hole. It's indeed possible.

• 33:23Speaker 02

  And given that we don't have any evidence that could tell us whether it's true or not, I would say, yeah, it's possible.

• 33:31Paul Mecurio?

  Here's your Nobel Prize. You just... I'm... I'm gonna give it to you. That's the Russian Doll theory. Take it, run with it. And you write up a paper. And then... But in a sense, isn't that it? Aren't you saying that in a way?

• 33:44Neil deGrasse Tyson?

  That would mean black holes in that black hole universe would have universes.

• 33:48Paul Mecurio?

  Yes.

• 33:49Neil deGrasse Tyson?

  That it would mean that in principle, Sabina, right?

• 33:52Speaker 02

  Yeah, so that's basically what Lees-Moore's idea of cosmological natural selection is based on. So you have universes in black holes, and those universes make their own black holes, and so on and so forth. So you get an entire tree of offspring of universes, and then you have some natural selection stuff going on on them. And I've forgotten the details, but this is basically what it is.

• 34:16Neil deGrasse Tyson?

  In fact, he wrote a whole book on this.

• 34:17Speaker 02

  He did write a whole book on it, yeah. It's called "The Life of the Cosmos," I think.

• 34:22Neil deGrasse Tyson?

  So it would imply that the most successful universes are the ones that have the most black holes, because they would be making even more copies of themselves. So you step back and say, "What is the most common kind of universe?" It would be the kind of universe where the laws of physics promote the maximum number of black holes you can get. And that would just be the naturals... That's borrowed right off the pages of evolutionary biology, right?

• 34:48Speaker 02

  That's the idea, yeah.

• 34:50Neil deGrasse Tyson?

  Yeah, yeah.

• 34:50Paul Mecurio?

  Does this, is this sort of related to this loop quantum gravity theory?

• 34:56Neil deGrasse Tyson?

  He's big on that, but I don't know if they're related. What do you think, Sabina?

• 35:00Speaker 02

  I don't think so. I think they're pretty much independent. I mean, I'm pretty sure you can probably connect them somehow, but...

• 35:06Neil deGrasse Tyson?

  But I think he was also big on that idea as well, if memory serves.

• 35:10Paul Mecurio?

  I mean, since we're talking about the universe, can you guys explain to me?

• 35:13Neil deGrasse Tyson?

  I love the beginning sentences like that, since we're talking about the universe.

• 35:17Paul Mecurio?

  Well, how is it that Dwayne Johnson and Kevin Hart keep making buddy movies and the universe doesn't implode? How is that possible? Either of you could address that for me, I would appreciate it. Do you want me to move on to the next one?

• 35:29Neil deGrasse Tyson?

  We'll get our top people working on that.

• 35:31Paul Mecurio?

  Okay, next question.

• 35:33Neil deGrasse Tyson?

  Just to be clear, Arnold Schwarzenegger made movies with Danny DeVito, okay?

• 35:37Paul Mecurio?

  He did. That is, that is true. Tall and, tall and small, tall and small. That's the whole relationship. And a pretty good movie, actually. All right, opinion or theory, or opinion or theory from your past? That's the title of this question. This is from Adam Crowder. Not sure where this person is from. Can each of you give an example of a cherished opinion or theory from your past? Maybe that you defended publicly at the time, but now turns out to be completely wrong, as proven by new evidence? I would like to hear some good examples of the scientific method as intended. We don't hold on to our beliefs in the same contradicting, contradicting evidence.

• 36:18Neil deGrasse Tyson?

  Okay. So Sabina, what do you have going there?

• 36:23Speaker 02

  Well, I wrote a whole book saying that there hasn't been any progress in the foundations of physics. You know, I would have been happy if there had been something ruled out that I believed in, but I'm afraid I can't really come up with anything. What springs to my mind, though, is that I've changed my mind on dark matter. So I have a background in particle physics, and for a long time I was pretty convinced it's probably some kind of particle, because if you can use particle physics to explain the why, look any further. Now I'm, I've pretty much drifted over to the modified gravity side.

• 36:59Neil deGrasse Tyson?

  Ooh, ooh, blood drawn.

• 37:06Neil deGrasse Tyson?

  Modified Newtonian gravity, this is like, so we don't need dark matter, we just have to fix Newton's laws of gravity because they're incomplete. So, ooh, ooh, she's crossed over. I'm just letting you know, Paul, she crossed over, she just admitted that.

• 37:22Speaker 02

  Well, you know, I said modified gravity, you brought in Newton, so, you know, I think we do need a relativistic theory, Newtonian, non-relativistic one isn't going to do.

• 37:36Neil deGrasse Tyson?

  Got it, got it.

• 37:37Paul Mecurio?

  I've been saying that for years.

• 37:39Neil deGrasse Tyson?

  So I have a more holistic view of that question. I think it's a great question, but I have a more holistic view. It's, I don't run around espousing strongly things I believe in for which there is insufficient evidence to justify that confidence. So I apportion the confidence I have in my statements according to how much evidence is available to it. And I will follow the evidence wherever it takes me. So it's not like I have some cherished belief that then has to be thrown out the window and I'm kicking and screaming while it happens. I'm there at every step of what the evidence is telling us. And when you have conflicting evidence, then people choose sides,

• 38:24Neil deGrasse Tyson?

  as is true here with dark matter, and that's a fun part. It's the bleeding edge of physics. And, but the real problem comes about, and I think this is an important component of Sabina's book, is that if you start holding tightly to a belief system that either has no evidence or only partial evidence, then you're gonna fall harder when that's, if the day comes where you've gotta discard the, what might be decades of your invested hard work, so.

• 38:56Paul Mecurio?

  But where is that, where is that fine line? Like, so, okay, if you apportion your confidence based on the evidence available. I mean, and I don't mean you, I mean in the third person just generally. This kind of gets back to what Sabina was saying in her book about sort of the lack of advances in fifty years, et cetera, et cetera. So don't you have to kind of walk the edge a little bit and say, okay, the evidence shows me this. I have this level of confidence, thirty percent. I'm going to make some assumptions and put myself out there and make this statement or make.

• 39:25Neil deGrasse Tyson?

  Not a problem. The question is, how, how, how, how much emotional energy have you put into it? And Sabina, this is what you've been, you've found. People were totally into what they thought the universe should have been. And are, and will not give it up, like, no matter what. And that's, that's a problem. Isn't that right, Sabina?

• 39:48Speaker 02

  Uh, yeah, I mean, it's just, it's psychologically really difficult. I think if you, you spend a big portion of your life researching a particular idea that you're fond of. Uh, and then the evidence doesn't come forward as readily as you thought it would. And indeed, there's conflicting evidence. What are you going to do? Uh, are you going to admit that you wasted a lot of time of your life?

• 40:13Paul Mecurio?

  Right. But, I mean, wow, you just described my life. You really did. But wait, isn't that a tautological argument on some level? It's sort of like, if you're a great scientist or even an average one, and you've spent an X number of years, and it didn't sort of play out the way you hoped or anticipated. Isn't that knowledge in and of itself? That it's not playing out the way you hoped and you did make advances? Because you disproved something that you thought was otherwise, but still you've proved something. You see what I'm saying?

• 40:44Speaker 02

  Yeah, I see what you're saying. Uh, and yeah, that's how it should be, but you know, scientists are only human.

• 40:50Neil deGrasse Tyson?

  Right, right.

• 40:51Speaker 02

  I, I, I guess the, the only thing that I, I have to add is that it gets easier if you do it more often. Like, I, I've worked on a lot of different things at this point, like in the past twenty years. Like the phenomenology of particle physics and quantum gravity and modified gravity. And a little bit statistical mechanics and some foundations of quantum mechanics and so on and so forth. And you, you get used to giving up cherished ideas and just moving on and doing something else.

• 41:21Neil deGrasse Tyson?

  Yeah, so you like an idea, but maybe you shouldn't cherish it. Maybe that's the problem.

• 41:27Paul Mecurio?

  So you gotta temper your passion, I guess, right?

• 41:30Neil deGrasse Tyson?

  So Paul, we only have like three minutes left, so.

• 41:33Paul Mecurio?

  Yes, okay. This is on vacuum decay from Sandra Pagliani. Don't know where she's from. What is most terrifying to you? Vacuum decay sneaking up on us and suddenly destroying us? Or the big rip? Which one is the most probable to occur? Also, given that we are matter, what are the chances that we bump into antimatter and vanish in a puff of gamma rays? I don't know why I had to go so dark. Sorry about that, so. Clearly Sandra is having trouble keeping a relationship.

• 42:02Neil deGrasse Tyson?

  Sandra needs to get help on that one.

• 42:04Paul Mecurio?

  She's a little, she's a little on the dark side. She's the Debbie Downer of this particular StarTalk session. Yes, so big rip, vacuum decay.

• 42:13Neil deGrasse Tyson?

  And in sound bites, what do you have?

• 42:15Speaker 02

  So I think the best way to die would be vacuum decay because we would all die without any advance warning and we would all die together instantly.

• 42:25Paul Mecurio?

  I feel good. All right, that makes me feel.

• 42:30Neil deGrasse Tyson?

  And the thing about bumping into your antimatter self, there's hardly any antimatter in the universe. So if that's one of your worries, put it lower on the list.

• 42:40Paul Mecurio?

  And you know Sabina, what you just did with your answer? You just gave Tom Cruise the idea for his next movie where he saves the universe from vacuum decay by riding a rocket in an improbable amount of speed. So I'm just putting that out there, that you just created a next movie coming up. Should we move on to another question?

• 42:57Neil deGrasse Tyson?

  Yeah, sure, sure.

• 42:58Paul Mecurio?

  Okay. Angus McNeil. If there are an infinite amount of planets in the universe, then does that mean that every possible planet from a video game or a made up world could exist with real life physics? Now Angus is 12, so it sounds to me like he is just trying to justify playing video games.

• 43:16Neil deGrasse Tyson?

  That's what it sounds like. And his parents are watching for the answer to see.

• 43:22Paul Mecurio?

  Ma, I gotta play. Neil Tyson and Sabina said that this is where it's.

• 43:28Neil deGrasse Tyson?

  So Sabina, do you think he's really thinking of the multiverse there instead of just the infinite number of planets in our own universe?

• 43:33Speaker 02

  Yeah, it sounds a little bit like a multiverse idea. So on some level, the answer might be, yes, there could be planets with other laws of nature. On the other hand, I'm not sure that the kind of physics that you get shown in video games is actually consistent with the existence of planets in the first place. So you have to be a little bit careful that if you actually work out the maths, the universe still exists.

• 44:04Paul Mecurio?

  Well, it still exists, but in any, you know, I guess in any universe you're in, though, grand theft auto is still illegal, like no matter what happens where you are.

• 44:13Neil deGrasse Tyson?

  But I've seen Mario American jump off a ledge and then just scurry back onto the ledge. There's some really weird laws of physics and stuff.

• 44:22Paul Mecurio?

  Yes, he never twists an ankle, he never blows out, he never blows out his knee. It's just, how is that, how do you steal a car in three seconds?

• 44:30Neil deGrasse Tyson?

  But an important point, Sabina, I think if you imply this, if you didn't say this explicitly, other universes might have slightly different laws of physics in them. And so you'd have to create a system of laws that would be compatible with having planets. We know our laws are compatible with planets because we're on one, all right, and other evidence as well. Yeah. Paul, one last question, see if we can squeeze it in.

• 44:55Paul Mecurio?

  Yes, this is Sam. G'day, I'm a tractor operator from Australia, so I listen to StarTalk a lot, and I got to thinking about black holes and the Big Bang. And if no one actually knows how the Big Bang started, is it a possibility that the Big Bang was the result of a universe that had been consumed by a black hole and popped out of the backside of the black hole?

• 45:16Neil deGrasse Tyson?

  Whoa.

• 45:17Paul Mecurio?

  I say no because there's flex tape. And when you have flex tape, ain't nothing popping out of the back.

• 45:23Neil deGrasse Tyson?

  You keep it together. I saw that TV commercial.

• 45:25Paul Mecurio?

  You ain't nothing popping out of a black.

• 45:27Paul Mecurio?

  I really want to try the part where you go into a pool and you put a... Anyway, go ahead.

• 45:31Neil deGrasse Tyson?

  So let me reshape that question. If the black hole can contain a universe, is that the same thing as popping a universe out the other side and birthing one? Is that a fair way to think about that or not?

• 45:43Speaker 02

  Yeah, and the answer is pretty much the same. It's possible, at least mathematically, you can do it. You can have the universe come out of a black hole and glue this in the place where you normally have the Big Bang. It's one of the theories for the beginning of the universe that physicists have looked at.

• 46:03Neil deGrasse Tyson?

  Whoa. So my boy on a tractor in Australia is deducing the nature of the universe and he's on a roll.

• 46:10Speaker 02

  It tells you a lot about the current state of physics.

• 46:13Neil deGrasse Tyson?

  Or tell you a lot about how deep a thinker we got there on the tractor.

• 46:18Paul Mecurio?

  Well, I just want to say, Sam, you just won the Nobel Prize, so congratulations. Get off that tractor and come on down.

• 46:24Neil deGrasse Tyson?

  Come on down.

• 46:26Paul Mecurio?

  Maybe wear your tuxedo overalls for the ceremony, how about that?

• 46:32Neil deGrasse Tyson?

  All right, we got to end it there. Paul, always good to have you, man.

• 46:35Paul Mecurio?

  It's great to be on.

• 46:36Neil deGrasse Tyson?

  All right, and Sabina Hossenfelder, it was a delight to have you. Good luck with the book, sometimes it needs a little luck as well. But the topics are, as you can see, deeply of deep interest to so many people, especially in our fanbase. So thanks for agreeing to come on to StarTalk.

• 46:53Speaker 02

  Wonderful to talk to you, Gus.

• 46:55Neil deGrasse Tyson?

  All right. I'm Neil deGrasse Tyson, your personal astrophysicist. As always, I bid you to keep looking up.