Into the Impossible With Brian Keating - Clifford Will and Nicolas Yunes: Is Einstein Still Right? (#092)

Episode Date: November 13, 2020

Albert Einstein is often viewed as the icon of #genius, and his theories are admired for their beauty and correctness. Yet the final judge of any theory is the rigorous test of experiment, not the fame of its inventor or the allure of its mathematics. For decades, general relativity has passed test after test with flying colors, including some remarkable new tests using the recently detected gravitational waves. Still, there are reasons for doubt. Einstein’s theory of gravity, as beautiful as it is, seems to be in direct contradiction with another theory he helped create: quantum mechanics. Until recently, this was considered to be a purely academic affair. But as more and more data pour in from the most distant corners of the universe, hinting at bizarre stuff called “dark energy” and “dark matter,” some scientists have begun to explore the possibility that Einstein’s theory may not provide a complete picture of the cosmos. This book chronicles the latest adventures of scientists as they put Einstein’s theory to the test in ever more precise and astonishing ways, and in ever more extreme situations, when gravity is unfathomably intense and rapidly churning. From the explosions of neutron stars and the collisions of black holes to the modern scientific process as a means to seek truth and understanding in the cosmos, this book takes the reader on a journey of learning and discovery that has been 100 years in the making. Brian Keating’s most popular Youtube Videos: Eric Weinstein: https://youtu.be/YjsPb3kBGnk?sub_confirmation=1 Jim Simons: https://youtu.be/6fr8XOtbPqM?sub_confirmation=1 Noam Chomsky: https://youtu.be/Iaz6JIxDh6Y?sub_confirmation=1 Sabine Hossenfelder: https://youtu.be/V6dMM2-X6nk?sub_confirmation=1 Sarah Scoles: https://youtu.be/apVKobWigMw Stephen Wolfram: https://youtu.be/nSAemRxzmXM Host Brian Keating: ‍♂️ Twitter at https://twitter.com/DrBrianKeating Instagram at https://instagram.com/DrBrianKeating Buy my book LOSING THE NOBEL PRIZE: http://amzn.to/2sa5UpA Subscribe for more great content https://www.youtube.com/DrBrianKeating?sub_confirmation=1 ✍️Detailed Blog posts here: https://briankeating.com/blog.php Join my mailing list: http://briankeating.com/mailing_list.php Learn more about your ad choices. Visit megaphone.fm/adchoices

Brianar Gensel, you'll learn about that. And it's not watered down, but it's not intimidatingly technical. There are no equations in the entire book. And the most delightful part of the book is really seeing the perspective of a young person, in this case, Nico Eunice, in conversation with an older gentleman who happens to be Cliff Will, and getting their perspectives, very disparate, but united in the kind of magic that is Einstein. And in some sense, his unfinished quest still continues, and we're still, revealing some of the truths of what you would say is maybe his finished quest, maybe his finest

quest, which was general relativity. Sit back, enjoy the ride into the impossible today. Please do me a favor. Just go down in your podcast catcher, where are you listening to this, rate the Into the Impossible podcast, give it any kind of rating you desire, and leave a review, and please check out their book. Is Einstein still right? Welcome to Into the Impossible. Any sufficiently advanced technology is indistinguish from magic. Welcome everybody to this edition of pandemic podcasting as part of the Arthur C. Clark Center for Human Imagination. I am your fearful host, Professor Brian Keating, co-director of the Arthur C. Clark Center

for Human Imagination. And today, it's a treat to have not only two fellow physicists, but two incredibly engaging, interesting, and fascinating authors of a wonderful new book called Is Einstein still right. And so we'll be talking about that book most of today, but I'm also going to take this opportunity, because how often do I get a chance to talk to luminaries such as Nico Eunice and Clifford Will, who are my guest today. And I want to talk to them about some topics that I've had been discussing on The Into the Impossible Podcasts a lot lately, including Einstein. So I've had on, this is now the third podcast just dedicated to Einstein. I have a

fourth one coming up soon, hopefully with Lee Smolin, who's a friend of both of yours, I know. And that will be about his book, Einstein's Unfinished Revolution, I think is the name of it. So it's funny, because Einstein has a book about his war with Professor Matt Stanley. He's got a book about, is he still right? And then I have a book called Proving Einstein Right by Professor Jim Gates, who is on the podcast earlier this year. And so there's a lot of Einstein in the air. But first, let's get to our two guests who are no slouches themselves.

First up, Professor Clifford Will, a legend. a Titan in the field. He is the distinguished professor of physics at the University of Florida in Gainesville, Florida. He's also involved in the Institute for Fundamental Theory, the Institute for High Energy Physics and Astrophysics. And he's written numerous books, given tons of papers. And what I most really respect about Cliff is that he's one of the few people that has done it all. He's done everything from worked on aspects of experiments to test various phenomena, mostly in gravitational physics, to pure theory, to phenomenology, to data analysis. This is a man who can do it all.

Cliff, how are you doing today in the southern wilds of our countries? Very well. Of course, it turns out I live on the beach near St. Petersburg, so it's a very pleasant surrounding. So, yeah, Florida's very nice these days. I'm wearing shorts all day long. Not the people in Michigan and New York thought to feel bad,

but there you're right. Or Illinois, as the case may be, in the case of Professor Anika Yunus, who received his bachelor's degree from Washington University in St. Louis in 2003 and his Ph.D. from Penn State University in 2008. He was at Princeton. He had an Einstein Fellowship.

I want to see if that influenced him when he was at MIT and Harvard. and then he was a professor at Montana State University for eight years. And recently last year, he became a professor at the University of Illinois, and he's the director of the Illinois Center for Advanced Studies of the Universe. That is very intriguing. Nico, how are you? We've known each other for a long time.

It's a first time really doing a podcast together. How are you, sir? I'm very good. Thank you so much for having us. You know, I am not, I don't have an apartment by the beach. there's a lake nearby i've heard it's pretty great yes that's correct but you know many times we're pretty much all uh you know

staying home and you know dealing with kids and all of that stuff yeah we'll get to that when we talk about the differences between the two of you you guys are kind of like the uh the original odd couple when it comes to this uh young and old uh different backgrounds and different interests but I want to get to the book first and foremost. I found it very delightful. I consumed it very quickly. It's an easy read.

It's dense. The book is actually surprisingly dense. You know, you pick it up and you think it's like a paperback, like, you know, let's say this piece of news junk over here that I wrote. But it's about eight times more dense than that. So I want to commend you, first of all, on the printing and the binding of the book. But what I always like to do is ask the authors, unlike the advice, to never judge a book by its cover.

I always judge books by their covers. I think most people do. Where did you guys come up with the title? And how'd you come up with the cover design? It sort of depicts a colorized version of America's are the world's most famous physicist. Title and cover design. How did it go?

Either one of you. Well, the title was pretty easy because 30 years ago, more than 30, it's pushing 34 years ago. I wrote a book called Was Einstein, Right. That was the last century. That was in the last century, right, long before Nico was born.

And it did pretty well, but it described the tests of GR up to general relativity up to that point. And so, and this in some ways gets to how we decided to write this book. But first of all, if you want to sell a book about science, you should have Einstein in the title. So that was a given. And then anything with a question mark is good because people wonder, you know, is Einstein right? But now today, because there are these things on the horizon that may make us think about going beyond Einstein, like the acceleration of the universe, the problem of quantum gravity and so on, it's a nice question to ask, is he still right? We believe the answer is yes, but still implies that in the future there's still room possibly to go beyond Einstein. time. So that part of the title came, you know, we agreed within a little second that that was

a basic title. And Nico, what about the cover design, the art? Yeah, there was a lot of, a lot of back and forth between Oxford and us about the cover design. The design was made by artists at the publishing house. And we considered multiple different alternatives, and we looked at other books that have been published in the past 10 years and looked at their covers and went to make sure that ours was not too similar to other people's, but still, like, attractive and engaging, and you would just catch your eye and be like, oh, yeah, you know, that's a book I want to, like, open. And, you know, a lot of what we talk, not all of it, but a good chunk of the book deals

with gravitational waves, because not only because they got the Nobel Prize a few years ago, but also because it was a huge demonstration of Einstein's, of the theory's success, at predicting something and then spending 50 years to build the machines and, you know, create the theory or, sorry, develop the theory and develop the data analysis tools to be able to really verify this prediction of Einstein's. So we thought, you know, well, we should depict gravitational waves somehow on the cover. That's why it's like all sort of on you lady. And of course, you know, you had to have the man.

in the back cover sort of is evocative of a black hole, sort of maybe a merging black hole, merging with the Oxford University Press logo, which, you know, surprisingly for a publisher, they made their black hole much smaller than yours. But I want to talk about, you know, the timeliness of the book. So you mentioned essentially everybody who's won a Nobel Prize, which is not surprising, as readers of my book,

losing the Nobel Prize will recognize the Nobel Prize, a sort of a catechism or sort of a way of a bestowing idolatry or bestowing upon laureates, this kind of everlasting praise that some say, you know, in some cases, the winner of the Nobel Prize gives prestige to the prize. In other words, some people win the prize and it gives them great prestige. In the case of Einstein, I think, Drach and Feynman, others sort of conceived that by winning the prize, they almost did a favor for the, for the Nobel Prize itself. And of course, Einstein looms large. Niko had a fellowship named after him after Einstein Cliff. Just next year, you're going to win the Einstein Prize of the American Physical Society.

He's already won the Einstein Prize. We have to give it to you. That's right. Well, exactly a hundred years ago to the year since Einstein had the same thing happen. And he won the 2021 Nobel Prize, but he didn't receive it until 2022. So, Cliff, you're in good company. So the biggest changes, obviously, is that, as you guys discuss in the end section where we're going to get to maybe at the end of this discussion, you guys have a dialogue, young and old, pretty and handsome. I don't know.

You guys are both handsome. But the point is you guys talk. Don't forget wise. Wise. Yes, brilliant and wise. Yes, Nico is quite wise. But the changes that you've seen, Cliff, let's talk about that. Starting as a young graduate student, meeting folks like you talk about Kip Thorne, you know,

who is to become a noblist himself. What do you attribute this massive increase in testing something, which Einstein himself, correct me if I'm wrong? He never thought any of the gravitational lensing was an oddity. Gravitational waves had never been detected. So he got a lot of things wrong, right? Well, I mean, wrong, but it was right for his time. The technology in his day didn't exist at all to see some of the things he calculated.

I mean, we now know that gravitational lenses exist. Light can be bent by distant galaxies, but in Einstein's day, it was not known that there were galaxies outside the Milky Way. So, you know, based on what he knew, he did the best he could. Right. But I was lucky enough to enter Caltech. I was a graduate student of Kiporn at a time when astronomical discoveries like of quasars, pulsars, the cosmic background radiation for the Big Bang, these all took place in the 60s, combined with new technology of the space program, atomic clocks, high precision laser tracking of things, all came together right around the this time, the 60s and early 70s, to on the one hand, make general relativity relevant for astronomy. That just caused a huge amount of interest to grow in the theory, but at the same time provided the kinds of tools that you could use to test it to make sure it was right. This episode is brought to you by Netflix.

Most valuable promotions in Netflix are hosting a blockbuster triple headliner Saturday, May 16th. Ronda Rousey returns to face fellow woman's MMA pioneer. Gina Carrano in the main event. Plus Co-Mains, Nate Diaz versus Mike Perry. And the best heavyweight in the world, Francis Ngano versus Felipe Lins. Watch Rhonda Rousey versus Gina Carano,

live only on Netflix. Saturday, May 16th at 9 p.m. Eastern Center time, 6 p.m. Pacific time. And Nico, when you got into this game, obviously a lot had happened that kept talked about. We knew about gravitational lensing. We hadn't detected gravitational waves. But no, we detected planets around other or stars in the galaxy using gravitational,

well, using physical effects, Doppler, ships, et cetera. What drew you into this field as a young person in the early part of this millennium, as you keep pointing out, the cliff are much older than you go? Yeah, so for me, I grew up in Argentina. I went to school there. I started a university there. And so I came to the U.S. with what we call football scholarship, but it's not your football.

it's, you know, the other football. That's just what 99.7% of the world calls it. And even though I had this scholarship, I knew ahead of time that I wanted to do physics. So you see in Argentina, you sort of have to decide what area you want to specialize in when you're like registered for university. So I knew it was physics. I knew it was theoretical physics. I wasn't quite sure exactly what kind of theoretical physics I wanted to do. But I was always fascinated by sci-fi and in particular about a start-trane.

and they thought like black holes were really cool, androids were really, really cool, and being able to like, you know, understand what happens close to a black hole or close to a neutron star, those were like fascinating topic. That's why I wanted to study. But it was not until I got to Washu where Cliff was a professor,

I think he was head of the department at the time, that I realized that, you know, the field that studies all those things within physics was like general relativity, gravitation. And there was this awesome gravitation group at Washoe at the time with Professor Wemussewin and Matt Visser and Cliff, and, you know, it was purpose. Like, okay, this is what I want to do.

And, you know, of course, you know, as I was beginning to learn about GR and so on, pretty much everyone, especially in grad school, everyone I talked to, you know, pretty much questioned, why would you, why would you go into gravitational waves? Nobody's going to detect gravitational waves. We don't even know those exist. GR, what's GR? I mean, we all know GR is right. Why are you wasting your time doing this? You know, can do condensed matter or, you know, look at this fascinating materials and this quantum mechanics that we can actually measure in the lab, which I thought was super cool. But, you know, I stuck to my guns. I was like, you know, I knew as a kid that I wanted to understand black holes.

And, you know, I'm just very stubborn. So she's going to continue trying to study that. And it paid up by some sort of miracle. You know, when I was a grad student, Pretorius, succeeded in completing the first numerical simulation of two merging black holes. So you could see how two black holes, if you evolve the Einstein equations on clusters of supercomputers for many, many weeks, sometimes months, you could see visualizations of these black holes spiraling into each other and colliding and forming a very distorted monster that would just wring down and then settle to a stationary black hole. And you could see all this gravitational waves. And that was a huge break. That was the biggest breakthrough I had seen at that time. So, you know, that gave me hope.

And sure enough, you know, about 10 years later, Ligo would detect the first gravitational waves. Yeah. So, Nico, you're the second Argentinian, at least to my knowledge, that's been on the Into the Impossible podcast. The first, to my knowledge, was Juan Maldesana, who is no slouch when it comes to theoretical physics. And he and I had a wonderful conversation a couple of weeks ago about wormholes. and other exotic features of quantum mechanics married with general relativity. And you guys mentioned this a lot in your book, and I can't resist because I have an interest in things such as the theories of everything.

I want to ask you, why is it important that there be a theory of everything? And either one of you guys can answer this question, not just Argentinians. Well, so since you talk to Juan, Juan is amazing. In fact, I have an anecdote. He probably doesn't remember, but I contacted him when I was in Argentina as a high school student. He said, him and he was like, hey, I'm this young kid. And I think he replied. And he was super nice.

And then I got to meet him at the Institute of Advanced Studies when I was a postdoc at Princeton. And he was always super nice to me, an incredibly smart guy, of course. You know, so why do we want a theory of everything? In part, it's because we know that every time in the history of physics, every time we've unified what seemed like this joint theories, the new phenomena emerged, new predictions could be made, and sometimes true revolutions in the field would appear, right?

So Einstein is the classic example when he unified electromagnetism with the concept of classical mechanics and Newtonian gravitation and made this theory compatible with each other. Then a slew of other phenomena and consequences emerged. And so in some sense, the hope is that something like that will also occur, that by unifying quantum mechanics with relativity, we'll get a deeper understanding. understanding of the cosmos and new phenomena will be predicted that we will be able to observe. Maybe new technology will have to be built in order to make those measurements and push engineering forward as well. So part of it, I think, is that. From a physicist's point of view, I think pretty much everyone I know would agree after enough alcohol consumption, that we are very deeply dissatisfied with the current status of things, right?

We have two theories that are incredibly successful in the regimes of validity, but that seemed to be incompatible. And that's just not, it's not fulfilling. It just makes you think that there's something else that we're missing. There's a piece of the puzzle. It's like we're trying to put this puzzle together, There is jigs or puzzle, but somebody has removed some of the pieces. But you know there should be a piece right here, but you just can't find it on the table.

It's like your little six-year-old just took six or seven pieces away from the table, and now you're going crazy trying to figure out what should go there. Right. Yeah, but the hardest puzzles are the ones that have no pictures on the front, right? So, Cliff, is there any guarantee that there needs to be a theory of everything? I mean, we'd all like it. It would be pretty. It would be beautiful.

but we know that many of our desires in life are unfulfilled. You know, I wanted to be in a corn maze this weekend with Nico, but I can't do it. So in what sense are we, you know, maybe pursuing a fool's errand, that there may not be a theory of everything? Well, I mean, I think that is certainly a possibility. I mean, this desire, this desire for unification is a human desire, and it's not clear that nature actually follows what humans want. I mean, so while I respect the desire, and in some ways I'm fascinated by it,

I'm totally open to the idea that it's possible that there is no quantum theory of gravity. There doesn't need to be, and that these two fundamental theories, quantum mechanics and GR just are always going to be incompatible with each other. friendly and they'll, you know, they'll socially distance and communicate with each other at some level, but they're never going to just totally get it together. So I'm open to that idea, although I'm certainly respective people who want to work on it. To me, the big problem is, and since I'm, as you mentioned, so heavily embedded in the idea of experiments, although I don't do experiments, nobody ever allows me in their lab because it's usually a disaster. But

the idea of experiment I view is so important and even the practitioners of these unified theories in quantum gravity admit that it's very difficult to conceive of experiments that could actually tell you whether any of these ideas are correct or

which ideas are correct which ones are incorrect. The experiments are for the most part out of the realm of what we could conceivably perform and so that to me gets to another issue of what is a scientific decision then if you can't really verify something experimentally. So there's that part of it swirling around too when you discuss theories of everything. But as the great sage physicist Yogi Berra once said, it's very tough to make predictions,

especially about the future. And, you know, Einstein thought that this calculation, I think there was a Mr. Mandel or somebody who came to him asking about a little calculation, having to do with bending of light, you know, by gravitational lensing, what we call weak lensing nowadays. And he didn't think much of it. I love the way that his little note to the editor of nature, you know, is basically published, accepted on site. But he also died without, you know, achieving this unification that we desired. And I want to keep going on the theory of everything just for one more minute because it's not so often I get to speak to a genius such as yourself, Nico.

No, for both of you guys. Not enough. Cliff or Nico, usually the standard, and I've read about a half a dozen of these books in the last year that say, well, because there are singularities at the center of black holes and that the universe began with a singularity, there must be a unification of gravity with quantum mechanics because we can't understand things at the microscopic scale, let alone the infinitesimal, scale. First of all, is there, is there any evidence for singularities at any point in the universe today, in the deep past? I mean, is there any physical evidence that one could ever get?

The issue that I have is that a singularity is like an infinity. It's something that doesn't exist in the physical world. There's no example of something that's infinite in the physical world. I mean, correct me if I'm wrong, except for as Einstein once said, human stupidity, perhaps. But tell us, you know, why is it that that's always pointed to as evidence for the need for quantum theory of gravity, the existence of singularities? I claim we don't have any evidence for singularities as yet, physical evidence. All right. I mean, from one point of view, the one class of singularities that appear inside black holes, we actually can never get evidence of such singularities because there are whatever garbage might be.

come out of that singularity is always hidden inside the event horizon and will never affect the outside world. So to someone who's skeptical of these ideas, that's one answer. They're there, sure, but nobody ever has to worry about them because they're always behind an event horizon. Alan, you could have evidence, right? I mean, we could just throw Brian into the black hole and let him Well, that's true. Let him. Let him... You can't destroy infinite amounts of intelligence. It's impossible. But the other bycola, the other singularity in some ways is more significant. I mean, obviously the universe started from an incredibly state of very high density,

very, you know, tight compaction of everything. Classical general relativity says that that actually has to be a space-time singularity. Everything really has to be infinite. This, in fact, it was one of the many things that love. Roger Benrose proved, along with Stephen Hawking, about the cosmic singularity, if you believe standard general relativity. It literally must be infinite, no way around it. So there, I think, the argument that if you want to really understand the origin of the

universe, you have to bring in quantum mechanics. That argument, to me, makes a little more, is a little more cogent than the one about the singularities inside black holes. Interesting. And, Nico, you've worked a lot with CMB probes. and talk about that. Actually, that's the one bone I wanted to pick with you guys. There's very little mention of my precious B-modes and primordial gravitational waves in this book. But Nico, I was on purpose.

It was on purpose? Okay, you're excluding me. I knew it. You have an antiqueting bias, a bicep bias. But I want to know, when we think about, I've often heard it said, even by my colleagues and friends, who shall remain nameless, that if we detect B-modes, that will be from primordial gravitational waves. That would be evidence of quantum gravity. Can you talk a little bit about that? Does that have the ring of truth, so to speak, in your opinion, that detection of primordial B modes is tantamount to detection of the quantum gravity epoch?

Well, right. So there are these ideas that have been put forth about ways to try to construct something close to a quantum theory of gravity, right? So pretty much everyone has heard of string theory, although if you ask the general public, probably nobody understands what that means. And other efforts have been made as well to unify general relativity with quantum mechanics,

such as, for example, Luke Quantum Gravity, who Lees-Malling, for example, has worked a lot on, and you mentioned would be on your show later. So what is the... lot of these quantum theories have in common is that they predict that certain effects should be present at sufficiently high energies and at sufficiently large curvatures. And one of these effects is one that's called, or it's labeled party violation or party

breaking. And so some people, we can go into like a long mathematical discussion that I don't want to get into about exactly how those terms are represented at the level of the theory. But the bottom line is that some of these quantum gravitational effects should sort of percolate into observations through these B modes and through a breaking of parity that could be present in the B modes. So if you could see these B modes, then you could say something about parity violation in gravity, and then that would have to be built on top of Einstein's theory, because Einstein's theory doesn't describe that amount of parity violation. And that's important, like, looking for ways to experimentally probe whether what we think

of fundamental symmetries are really true symmetries of nature. That's super key, right? you know, things like Lawrence invariance, right, that sort of led Einstein to impart to the development of special relativity and general relativity, looking for violations of that would be revolutionary, right? If you did an experiment and you saw that gravitationally

there's a violation of variance symmetry, that would indicate that there's, in some sense, perhaps a preferred direction or in space time, that our theory would have to deal with. And general relativity is not equipped for doing that because it's built on the axioms that Einstein postulated. And those axioms do not allow for the breakage of that symmetry at the classical level. Even if that breaking is weak, for example,

I had a conversation with Sean Carroll on Friday on my channel that was revolving around a claimed piece of evidence for cosmic birefringens. So chiral behavior of the electromagnetic vacuum, consistent with adding a Lorentz and parity-breaking four-vector to the electromagnetic Lagrangian. In this case, we know it would have to be incredibly small because we could only detect it via the traversal of photons since the last scattering surface to today or to the plank satellite. This is a paper by Miami and I, and Itiro Komatsu, that Sean and I were talking about. that claimed evidence for this effect or, you know, weak evidence at this level. But is it true that if you break Lorentz invariance, we'd have to get rid of GR altogether? What if it's just a tiny bit of, you know, of violation like we observe in the weak sector?

We don't throw out, you know, on Maxwell's equations. Right. And that's a great point. And I think that's a point that we're making the book quite a bit. It's about the self-correcting nature of science. You know, when you when you are confronted with an experiment that suggests that your previous theory is not quite right, or the predictions of your theory are not quite right. You don't just grab that theory and you throw it in the trash. What rather you do is you try to figure out what that theory is missing, so you can add to that theory, this new interaction that would predict the new observation,

or at least explain the new observation you've made, and hopefully also predict new phenomena that you can observe. So at no point, and this is essential, right, because you want to make sure that your new theory with these amendments that you've made, is still able to explain and predict all of the other phenomena that you've observed over the past millennia, right? So it's not like when we say Einstein's theory of general relativity proved Newton wrong. It's not that Newton's theory is completely invalid. It's not that if we are trying to calculate how, you know, projectile motion or, you know,

to launch a satellite out of Earth so that it's in orbit, it's not that we have to solve the theories of the equation of Einstein. I mean, we still, for the most part, use Newtonian mechanics because in the regime where we're doing this experiments, Newtonian mechanics is perfectly valid. And deviations through Newtonian predictions are truly minuscule in the solar system, really hard to measure. So I don't know, Cliff, I've been talking for a long time. In fact, we're careful to say in various parts of the book that when we talk about possibly modifying general relativity, for example, as a possible explanation for the acceleration of the universe, the accelerated expansion of the universe, we talk about it in terms of beyond Einstein rather than overthrowing.

So whatever theory you need to construct has to agree with general relativity in all the realms, and the realms are now vast, over which it's been verified to high precision. But then this theory then can do something slightly different in these other regimes like the large-scale cosmological regime. Yeah, and I think let me just play up over that idea, Cliff, because I think this is also something that we mentioned in the book, and it's very important, is the idea of a scientific fact. There are certain things in science that are scientific truths. And we don't, so people agree on. on this concepts. And different communities are not entitled to their own set of truths. We all sort of come together and decide through experiment whether a particular prediction

is correct or not. And if there's a prediction or if there's an observation that, you know, seems to disagree with a prediction of a well-known theory that has been tested to that day, what we do is we repeat the experiment. And we ask the people that did the first experiment to check that, you know, all the cables have been properly plugged in and that, you know, before you jump and do a press release, bring bottles of champagne to the creators of the theory, you need to make absolutely sure that what you've observed is really what you thought you observed and other people can reproduce that observation. That really hurts. Thank you. Thank you for sticking it to me.

Yeah, it actually reminds me of a quote by none other than Isaac Asimov in a piece that he wrote called The Relativity of Wrong. And you guys mentioned this briefly in passing in the book, but he says, Isaac Asimov was writing to somebody who really believed the world was flat. And he wrote, when people thought the Earth was flat, they were wrong. When people thought the Earth was spherical, they were wrong. But if you think that thinking the Earth is spherical is just as wrong as thinking the Earth is flat, then your view is wronger than both of them. put together. And I think that that's, you know, kind of beautifully apropos of some of the things you point out in this book. What you guys are doing, what you're talking about, what we physicists are doing, is incredibly hard. We're trying to test something to see if it breaks when we know it's

passed test to the, you know, 10th decimal place and beyond in the case of the, you know, binary pulsar that you guys talk about. But I know Cliff provided me some slides. I want to see Cliff. Are you able to share your screen right now? And we'll go through your slide. show. And then we'll wrap up with some questions about the dialogue that you guys conducted at the end of the book, which I found so delightful. As the Krispy Chicken Sandwich from 7-Eleven, people always call me loud. And I'm like, yeah, I know. I'm crispy. Did you expect me to whisper? If you want quiet, go eat some soup and reflect. Like, I know I'm a handful. I'm bold. I'm juicy. Throw some pickles and barbecue sauce on me, and baby, I'm a whole meal. And with seven rewards,

I'm just $4. Quiet? No. Krispy, saucy, and $4. Very. Only at 711. Valley through 62326, participating stores only well supplies, Lassie app for full terms. So please take away the screen.

Right. So is it sharing? Yes. That's just a brief promo for the book. I'm an unabashed promoter. So I will say that part of the book covers, you know, we really talk about the kinds of experiments

that have been done to verify general relative. So we talk about famous experiments like the bending of starlight tested in 1919 by Arthur Stanley Eddington. Those were measurements that made Einstein an international celebrity. This bending has been tested many, many times recently, including by an amateur astronomer and during the eclipse, American eclipse of 2017, who used off-the-shelf equipment and did a better job than the astronomers in 1919 in terms of accuracy. And we talk about how time, the rate of time, depends on where you are in a gravitational field and so on. But really, the bulk of the book talks about more recent stuff, like detecting the motions of stars near the black hole at the Arctawactic Center, which was rewarded with the Nobel Prize, part of the Nobel Prize just a few weeks ago. We talk about the black hole shadows produced by the event horizon telescope.

Then we turn to gravitational waves and we really give the full story of how gravitational waves were detected, the ins and outs, the backstory. We explain gravitational waves. We even show how to convince yourself that the gravitational waves were really detected. And then we conclude with this, there's a dialogue between the wise person and the young person. The one thing that the book has, thanks to my artistic collaborator, P. Point, his first name is Power. We have very simple line drawings. We didn't want to get fancy or exotic, but simple line drawings to try to illustrate, you know, what's going on. We tried to explain the event horizon of a black hole by talking about a swimmer, swimming upstream before going over in Niagara Falls. And we describe how the interferometers work in LIGO. We describe what the gravitational wave actually was doing as it approached the solar system from the south side of the solar system.

Things like that. We talk about LIGO, its construction, its development. We describe the first detection, the first waves. This is almost raw data that they collected, just filtered in a minimal way. and just looking at the peaks and troughs and how they're the same in the two detectors, anybody can convince him or herself that this was from outside the solar system. This is a wave detector from somewhere else. You just look at these peaks.

They're the same, you know, exactly the same. They're actually about seven milliseconds apart, but that's because of the distance between the two detectors. So we try our best to use simple language to explain these things. And for example, we also describe how as one of these stars orbited very close to the black hole at the center of our galaxy, the light from the star was reddened because of this redshift effect of Einstein. This star was only a hundred times the Earth's sun distance from the black hole. And so it was very deep in the heart of that gravity field. until the light from that star was red and has reached us, and that was measured. This, of course, is an artist's rendition, not real photographs.

So, and this, of course, we spent a fair amount of time discussing the stars at the center of our galaxy, and this is an animation based on the actual data showing the star is the center of the galaxy. see, these moving dots are the actual stars orbiting. This star with the yellow orbit is a star called S2. It is now completed about one and a half orbits around the black hole. And two years ago, in May of 2018, it passed very close to the black hole and that produced that measurement of the gravitational redshift that you saw. So we describe all these.

And of course, the book came out just in time for Andrea Ghez and Reinhardt Gensel, the lead of the two teams to win the Nobel Prize. Of course, they point out in the citation that the word black hole does not get mentioned. It just says there's a compact object. Yeah, I mean, because, I mean, the trouble is to really prove it's a black hole, you have to go into it, but then you can't write a paper to win your next Nobel Prize. Well, that's when your graduate, that's what graduate students are for, right, Niko? That's right.

But I think the idea is to prove, you know, that it's such a compact thing that it can't be anything else. But by the way, with things like this orbiting close to the black hole, we can start to prove aspects of the nature of the curve space time, close enough to the black hole, that you can really get to a higher level of proving that it has to be a black hole without ever going through the event horizon. So we talk about this future. We're only at the beginning of testing general relativity, testing the nature of black holes with these kinds of incredible observations. And if it smells like a duck, it looks like a duck, you don't have to, like, cook it and taste. But if it's an invisible duck made of, what are black holes made of, actually? I mean, this is a question I get a lot. How do you guys answer that?

You go inside a black hole. What's it made of? Protons, neutrons, croutons. Doesn't Kiphton say that it's full of love? That's how you get to. You would say that. And movie royalties. Good one, Will.

Close. That's great. Black holes are formed by the collapse of matter, right? And this matter can be of all different forms. It could be gas, it could be charged particles. And so when all of these material collapses, eventually it's dense enough that an event horizon, like we call it, forms and dynamically grows to the size is going to be and stop growing.

And so inside the black hole, you know, if the black hole is isolated, there's nothing else around it. Let's just imagine that there's no interstellar gas or anything else in the universe, just like the black hole after it's formed. Then there's really nothing inside of the black hole except for at the very point of this, like at the center, if it's not rotating, at the singularity where all of the matter that formed it from a collapse would be located. And that's where all of the energy, the pressure, and so on are infinite, where our classical description of space time breaks down. What's the most fascinating aspect of GR of Einstein to you guys? You guys have the first coherent description of the lens-thearing effect. Maybe you talk about that for a second.

How do you think about that? That's sort of one of the most interesting, and it takes up a good chunk of Chapter 2. or three, I can't remember. And it took a large chunk of the U.S. gravitational research budget from 1959 or so to just a few years ago in GP Gravity Prob. Talk about the lens theorying effect. Why is it so important? What are we interested in? And couldn't we have saved a lot of money and just given that money to Andrea Gez? And she could have shown it using the images that you just showed. I mean, this experiment is in many ways close to my heart. because I was not directly involved in it, but I chaired an external committee on behalf of NASA to oversee aspects of the project.

But first, this effect is very important for two reasons. One, it's a prediction of general relativity that literally does not exist in Newtonian theory. I mean, it really is a purely relativistic result that a rotating body can effectively drag space and time around with it. and cause forces that can affect body simply due to the rotation. This phenomenon simply doesn't exist in Newtonian theory. But in many ways, the most more important reason, the interest that's attached to it is because it undoubtedly plays a role in things like quasars and black holes of the centers of the galaxies. You know, people see these images of a bright emission from the center of a galaxy

enormous jet coming away from the black hole, often in both directions. And then people often ask me, lay people out, well, how can this stuff be coming out of the black hole, you know, once it's in, can't you ever escape? But the point is that stuff going around just outside the black hole, the swirling of ionized gas coupled with these effects that caused space time to be dragged around the hole the way batter is dragged by a rotating beater, that combination. can produce forces on charged particles that actually repel them from the black hole. And many, many models and theories have been developed to account for these jets,

and this effect plays an intrinsic role. And so this experiment, to try to measure this effect precisely, using the rotating Earth as the basis, was, as you say, conceived in the late 1950s, began development in the roughly late 60s, and ultimately became a space program that ran in the early 2000s. So it took a very long time, almost 50 years, cost about $750 million. So it was very expensive to measure one number.

And so needless to say, this experiment fell under a lot of criticism. And one of the things we do in our book is try to discuss this issue. You know, as a case study and how you make decisions about experiments. and projects. How do you weigh cost versus scientific knowledge gained? How do you deal with different communities? The astronomers wanted to cancel GPV. Physicists were more positive toward it because it was a fundamental physics experiment. So how do you balance different communities when you try to consider priorities? So we try to, for the lay reader, give a bit of a sense of how scientists struggle with you know, justifying experiments based on cost and importance.

And Nico, in terms of general relativity's next century, what are you looking forward to? What sorts of tests, what sorts of observations, what sorts of new theories might come about that might challenge you and have to do a, you know, second edition with two question marks? Or in chess, we use these exclamation points. That means brilliancy. and exclamation point and a question mark is a blunder, I guess. What are you looking forward to in the future in the aspects of relativity itself? Yeah, I think the future is super bright when it comes to this field.

We're really at the dawn of a lot. That's lucky for a young guy like, Nico. Everything is great. We're going to do awesome. You just wait, Cliff. I mean, yeah, so I am honestly optimistic about it, especially now that they're having so many advances in the field, both in data analysis, in technology, in theory. So I guess there's two main things that I'm really looking forward to and I think are going to be discovered or Danbury. One of them is a little bird told me that at some point B-MOT would be discovered.

Really? That was an exclusive. That was my source said you cannot mention that on this podcast. At some point, I think we'll get a better sense of the polarization of the CMB. And I think cosmologies is quite ripe for new discoveries. There are things that we don't fully understand when it comes to cosmological observations. And we attribute the adjective dark to them because we don't understand them. But that's, so I think progress can be made there.

And through more observations, that I think is what really going to feed this progress. It can't just be theoretical ideas. We really need guidance from observations. So cosmological observations on the CMB, I think, are going to be very interesting. And then the second thing I think it's going to be super interesting is gravitational waves. And I don't just say that because that's one of the fields that I identify with. but also because Lago just essentially turned on, you know, metaphorically speaking yesterday, right? It's a very new experiment.

And it hasn't even reached its design sensitivity, the sensitivity, the accuracy that it was built to achieve. I always tell the story that if you, you know, build an amplifier, you don't, when the first time you put it together, you don't crank the volume to 15. and just let it go, right? Like you sort of... One of my kids does. But you don't get... Instruments are super expensive.

They're super complicated. You turn it on slowly and you fill with it and you increase sensitivity little by little. And that's what they've been doing and they've been doing great. And the amount of engineering, there's a lot of unsung heroes. And that's also something we tried to do in the book, to describe all the work that has gone into doing, creating these experiments.

And so the bottom line is these instruments should achieve design sensitivity by 2025 or so. So that's like five years from now. And there's already plans to build the next generation of detectors, either in space through something called Lisa or through what we call third generation detectors on Earth, which may be very, very large or may be buried underground to increase their sensitivity. And estimates right now say that once we reach those third generation detectors with Lisa, and so with Lisa in space and with the ground-based ones, we would be able to see gravitational waves emitted by all sources, all compact binaries in the universe ever, period. That's awesome to say we can see all of neutron stars that have ever merged

or will ever merge in the universe. And the amount of astrophysical information that's going to provide, it's really outstanding. From the point of view of test of GR, there's things that we currently can't really test for because the data is just not sensitive enough, it's just not loud enough, or the systems that we've observed are not just right to test this particular effect. But, you know, as we detect millions and tens of millions of sources, and I'm talking now not in 2025, or like 2035, 2040, then this test will really be very, very powerful. Yeah.

If there's a deviation in GR in binary mergers, and we don't see them by them, then I would say that there aren't any. Well, so Barry Barish and Kip Thorne have agreed to come on the End to the Impossible podcast after hearing that I got you two guys on the podcast. So I will ask them whatever questions you suggest. So please send them to me. They'll be coming in the next few weeks. Hopefully we'll get those out commemorating this amazing epoch that we're in.

I've heard it likened to somebody saying, oh, what good are gravitational waves? We detected black holes as being akin to asking Galileo in 1610. Is this telescope useful for anything besides looking at the moons of Jupiter? As if that wasn't enough. I want to conclude with Galileo, who's my hero, And he has a lot of, you know, kind of influence on my career and the way I perceive scientists and the way that we do our craft.

And your book concludes with not necessarily an homage to the great maestro, as he preferred to be called. I actually asked my grad students to call me maestro. But it concludes with a dialogue of sorts. There's only two of you, not three of you, is in the famous Dialago and the Discorsi, his two final books that Galileo wrote, which was written in platonic style. But I was thinking as I was reading it, Cliff, if you could go back in time and advise a young Mr. Will back in the 60s when he was first attending graduate school, would you have told him to take the career path that you ended up taking or other other things, honestly,

that young Mr. Will should have been studying besides this field? I mean, from a practical point of view, he, you know, like most physics, he should have been studying, you know, solid state or condensed matter physics. That's where the jobs are, right? Plastics, yeah. If you were really interested in getting a job, it's the biggest branch of physics that has the most applications and so on and so forth. You know, it's hard to answer the question with hindsight. But in many ways, how I started out was I think how a lot of students. start out in their careers. It was just

pure luck. I mean, I arrived at Teltec not knowing that Tip Thorne existed because he was so new to the faculty who was not listed in their brochure that they sent me. I didn't know about general relativity. I didn't learn any of my undergraduate

college. It was such a new field. No one thought it. And I just happened to be, you know, advised by some fellow Canadian students who I knew I was Canadian at the time, to go talk to this new professor. He's kind of weird looking

and there's a strange name, Kip, what is that, right? Just go talk to him and find out what he's doing. And so I did. And sort of the rest is history, as they said. So to me, it was a very contingent thing. I mean, I just really had no idea what I was doing. And I think a lot of students are that way

and they kind of fall into a good situation. And then, you know, then they go on from there. But to me, certainly today I would advise anyone to think about this as a career because it really has an exciting future. It's a substantial field. It was a really tiny field when I started. It was not well respected by other branches, other physicists and astronomers. So now gravitational physics is established and you know, you should if it excites you, you should do it.

Very good. And Nico, what are you most excited about and being perplexed by and challenging your students to think about these days. Well, so I always tell my students, especially the first years that approach me or even the undergrad, they should really think deep and hard about what it is that excites them the most. What wakes them up at night? Or, you know, when they wake up in the morning, they look forward to investigating. Where is their passion? And they should always be asking that to themselves.

And they should just pursue whatever area of physics, if they like physics, of course, that really truly fascinates them, because that's what's going to make them the most happy. Whether there's jobs or not, you know, I think, and this is my, of course, personal opinion, but it's, and of course I am in a position of privilege because, you know, I have a faculty position. and I managed to do what I wanted and get hired for researching what I want. But with that said, I think you're better off at, you know, having a job that maybe doesn't pay you as much, but that makes you happy and it allows you to go to work and enjoy what you're doing, that having a job that perhaps is very well paid, but that you hate, because that's just going to make you unhappy

and affect your person alive, and that's no way to live. And if that happens to be in relativity, then great. That happens to be condensed matter, then go for it. If you want to do, if you want to work for a defense contractor, more power to you. You need to decide. You are the one that has all the answers.

Most of my former graduate students remember receiving from me. I wasn't Nico because he was an undergraduate with me at Washington News. But I first an undergraduate student comes and wants to work with me. I give them what I call my stern lecture. I wouldn't even wag my finger at them saying this is a small field. There are very, very few jobs doing general relativity in the world. I mean, you could be a professor, but hardly any of them. It might be work for NASA, et cetera.

So very few jobs. Grant support is very minimal. But if you're willing to accept all that, that after you graduate, you might have to go into something else, computers, whatever it is, teaching. If you're willing to accept all that, then doing a PhD in general relativity

will be the most fantastic five or six years of your life. That's good. That's my story. Has your lecture changed, though, in recent years? It's pretty much the same because still, I mean, gravitational physics is in some ways a big field, but a lot of those jobs are for experimentalists.

There are 1,000 people at LIGO, and 2 thirds of them are engineers and data analysts, not what we would call general relatives. So I think we're still a small sub-branch of physics with very few practical applications. So I want to conclude with a statement from NICO's Institute for, what is it again, the Institute, Illinois Center for Advanced Studies of the Universe where we talk about the book, Nico, and you say, we keep asking if Einstein was right,

not because we think he was wrong, but because that's what physicists do. Even though GR has passed every test we devised, we have yet to, we have to continue searching for deviations from Einstein's predictions. We know Einstein's theory cannot be the final word since it remains incompatible with quantum mechanics. So he must be missing something. Newton appeared to be right for hundreds of years before observations of Mercury suggested something was a mess, and then Einstein came along. And I want to thank you guys for writing this wonderful book, which will hopefully inspire many, many graduate students to subvert their free will, as we might say, and work for physicists and work with physicists like Cliff Will, the renowned Cliff Will, and the superstar Nico Yunus.

Thank you guys so much for spending your time with The Into the Impossible podcast. And let our audience know where can they find you, where can they get this book, et cetera. It's on Amazon.com. Just ask the question. Is Einstein still right? And you'll find it. Yeah. Whatever books are sold.

That's right. We don't want to give a monopoly to the giant river in Niko's home continent. Thank you. Nico Eunice, Professor Eunice, Professor Will. Thank you guys so much. Cliff, you've been a big influence on me and my style and sort of my interest for many, many decades.

It's been great to meet you finally and have this wonderful occasion. Nico, thank you so much, my friend. It's a wonderful book. I urge everybody to get a copy of it. Is Einstein still right? And it's available, as they say, wherever books are sold.

Thank you both so much. Have a great rest of your day and your week. Thank you, Brian. great to meet you. Any sufficiently advanced technology is in distinguishing from magic.