Into the Impossible With Brian Keating - What Happened Before the Big Bang? | An Infinity of Worlds - Will Kinney (#224)

Episode Date: April 17, 2022

Will Kinney is a professor in the Department of Physics at the University at Buffalo, SUNY, where he has been on faculty since 2003. Dr. Kinney's research focuses on the physics of the very early universe, including inflationary cosmology, the Cosmic Microwave Background, Dark Matter, and Dark Energy. He has authored more than seventy published research articles and received the SUNY Chancellor's award for excellence in teaching in 2014. In his new book, An Infinity of Worlds, physicist Will Kinney explains the theory that may hold the answers to these questions such as Why is the universe so big? Why is it so old? What is the origin of structure in the cosmos? It may even explain the ultimate origins of the universe. The theory of cosmic inflation, before the primordial fire of the Big Bang. Kinney argues that cosmic inflation is a transformational idea in cosmology, changing our picture of the basic structure of the cosmos and raising unavoidable questions about what we mean by a scientific theory. He explains that inflation is a remarkable unification of inner space and outer space, in which the physics of the very large (the cosmos) meets the physics of the very small (elementary particles and fields), closing in a full circle at the first moment of time. With quantum uncertainty its fundamental feature, this new picture of cosmic origins introduces the possibility that the origin of the universe was of a quantum nature.  Kinney considers the consequences of eternal cosmic inflation. Can we come to terms with the possibility that our entire observable universe is one of infinitely many, forever hidden from our view? Get the book: https://amzn.to/3JLi7ng twitter.com/WKCosmo Topics discussed include: What does inflationary theory say about cosmogenesis? Does inflation require a singularity? Alternative theories to cosmic inflation Is inflationary theory "dangerous"!? Why Paul Steinhardt is wrong! There is no single theory of inflation so how do you classify and think of it as a concept? What evidence would cause you to doubt inflationary theory? For example the topology of the Universe? What other tools can prove or refute the multiverse? Consistency Relations and primordial gravitation waves. Please Visit our Sponsors: LinkedIn: LinkedIn.com/impossible to post a job for FREE Athletic Greens, makers of AG1 which I take every day. Get an exclusive offer when you visit https://athleticgreens.com/impossible AG1 is made from the highest quality ingredients, in accordance with the strictest standards and obsessively improved based on the latest science. All 33 Chairs. My All33 Chair is the ideal chair for all of us ‘knowledge workers’ suffering through unending Zoom calls. Sitting still is bad for you. All33 chairs are my choice because they allow your pelvis to move the way it does while you walk — so all 33 vertebrae align into perfect posture. The result? Better breathing, better blood flow, and relief from pain. It’s crazy what you can do when you set your body to it. To get $100 off your order, visit https://all33.com/impossible Search for The Jordan Harbinger Show on Apple Podcasts, Spotify, wherever you listen to podcasts, or go to jordanharbinger.com/subscribe Be my friend: 🏄‍♂️ Twitter: https://twitter.com/DrBrianKeating 🔔 Subscribe https://www.youtube.com/DrBrianKeating?sub_confirmation=1 📝 Join my mailing list; just click here http://briankeating.com/mailing_list.php ✍️ Detailed Blog posts here: https://briankeating.com/blog.php 🎙️ Listen on audio-only platforms: https://briankeating.com/podcast.php A production of http://imagination.ucsd.edu/ Support the podcast: https://www.patreon.com/drbriankeating Produced by Stuart Volkow (P.G.A) and Brian Keating Edited by Stuart Volkow Music:  Yeti Tears Miguel Tully - www.facebook.com/yetitears/ Theo Ryan - http://the-omusic.com/ Learn more about your ad choices. Visit megaphone.fm/adchoices

What happened before the Big Bang? Does it even make sense to speculate about the universe before the origin of matter, time, and space of our own universe? These are the questions tackled in an infinity of worlds by my friend Will Kinney, who's a professor at the State University of New York at Buffalo. It's been widely praised both by advanced readers and blurbers such as myself and another Brian, Brian Green. You'll find our comments alongside of those of Sabina Hasenfelder and others like Stefan Alexander,

all guests on the show in the past. This book takes us on a journey into the essence of time and the most controversial theory of them all. The multiverse. Is it possible that there are an infinity of other universes, not just worlds, not just planets, not just stars, galaxies, but of other universes? Can we ever hope to find experimental evidence or a refutation of such a claim? Why is it so controversial? What does he make of so-called multiverse deniers?

We talked about all that, and we also got in to the patented, thrilling three questions of existential reality that you'll subscribe to my newsletter at prionkeating.com to get. For now, come join me as we go into the impossible, asking the question of the nature of time and space itself. before our universe even existed. Come along. Let's go. Into the impossible. Any sufficiently advanced technology is indistinguishable from magic. Open the pod bay doors, please help. Well, it's a pleasure to welcome today, another friend and author of a brand new book,

Popular Science, called An Infinity of Worlds. And it's a magical book that really takes us on a tour as this book was blur. by two Bryans, two eminent Bryans. One, my kids' favorite Brian in all of cosmology, and that's Brian Green. He blurbed it. But then another Brian, Brian Keating, blurbed it, saying it thoroughly documents the latest observations and challenges to the theory of cosmological inflation. Will Kinney's shimmering prose demystifies the most inscrutable cosmic epoch,

illuminating the way forward for future generations to explore its manifold mysteries. So that is what I thought about it. And the author is here today, Professor Will Kinney of the State University of Nueva, York, where I used to hang out, getting some wick, some roast beef on wick, no doubt. It's Will Kinney. How are you, Will? Good, Brian. Thanks.

Appreciate the blur, by the way. The other Brian, of course, you may know is my old boss, actually. I was a postdoc for him at Columbia for three years. So he's an old friend. And there are other Encomia on the back of the book, including by our friend Sabina Hassanfelder. who had much kinder things to say about your book than my book. It should be noted. It's only antagonistic blur by, no, no, she didn't write a blur.

And then by our friend Professor Stefan Alexander as well, who is Professor Brown University, where I was a graduate student, Lowe, these many years ago. And I want to start Will as longtime listeners to the show, viewers of the show, now we start with a special segment when someone is a guest who has written a book. And then we end with a special segment that we call the thrilling three existential questions. But now we're going to start with our patented segment that we call judging books by their covers.

So, Will, we're going to do what you're advised never to do, which is to judge a book by its cover. And I'm going to ask you, how did you come up with the title, the cover design, the subtitle? Tell me how you did so for this wonderful new work of science popularization. So this is the cover and the title. So the title is the main title is an infinity of worlds and the subtitle is cosmic inflation in the beginning of the universe. The subtitle should be fairly self-explanatory. That's the scientific subject of the book. The main title is actually a quote from the sort of the guy who is in many ways the philosophical heart of the book,

which is the Renaissance astronomer Giordano Bruno, who was a Copernican philosopher in the late 1500s, who in a way, really, he took Copernicus's idea of this concept that Copernicus came up with, that the Earth is special, right? If you're going to have a heliocentric cosmology, you're going to have the Earth move just be one of the planets. You kind of have to demote it from its special place. in the universe. And Bruno took Copernicus's ideas and extended them further than Copernicus ever

dared to. And he borrowed a lot of ideas from earlier philosophers, the Epicureans, who believed in an infinity of worlds. And so the title is a quote from Giordano Bruno. And Bruno wrote in 1584 in a book called On the Infinite Eiffon, universe and worlds, quote, God is infinite. So his universe must be two. He is glorified not in one, but in countless sons, not in a single earth, a single world, but in a thousand thousand. I say in an infinity of worlds. And so the title is a reference to Giordano Bruno's 1584 work on the infinity of worlds. It's worth noting that Bruno's belief in an infinity of rules was one of eight charges of heresy that were leveled against him, which ultimately resulted in him

being burned at the stake at Campo di Fiore in 1600. Another one being his advocacy for a heliocentric cosmology as well. So the title is a direct reference to my man Giodonno Bruno, who was, in my opinion, really hundreds of years ahead at this time. Yeah. So you're actually the second guest on the into the impossible podcast to compare himself to Giodonor Bruno, the first being Avi Lobb. We'll get into that. I'm not comparing myself to Bruno. I'm just teasing. I always say when you get a referee report back, the thing that you should never do is compare yourself to the plight of Gerdonar Bruno. Oh, I kind of heard was kind of a little bit of a schmuck in some ways in that he had actually, you know, known very full well what he was doing and kind of extended, similar to what

Galileo did, right? Galileo was forbidden to teach Copernicism, but he could research it. That's why he wasn't convicted of heresy or killed or, you know, really tortured beyond, you know, bending down and kissing the Pope's ring or whatever he had to do to recant. But nevertheless, can you, I mean, this book is not mainly about that, but that the topic of worlds in his conception was really that the stars were sort of like other sons, but was it really that each one had a planet and on each planet there were people. And then the problem was Jesus couldn't visit all these, and this is a Jew talking to, I don't know what you are, but I forget my theology.

I used to be, I used to be a Catholic altar boy, but well, those days are long behind me. So what was the heresy? Yeah, so one of the things was, yeah, Bruno was an extraordinarily abrasive personality by all reports and managed to piss off just about everybody. So he was actually turned into the Inquisition by a friend who was visiting. He was visiting, right? So he was hanging out at a friend's house, and the friend tipped off the Inquisition, who apparently he was a pretty poor house guest is the only thing I can think of there.

And he was in prison for seven years before he was executed. And unlike Galileo, didn't even make any pretense of recanting. I mean, he was very stubborn and eventually it resulted in his death. But Bruno's, yeah, Bruno thought of the other stars as correctly as being other sons, which would have planets around them, which would have other civilizations like ours. He was, as far as I know, I spent a lot of time reading him when I was writing this book. I didn't read any other like pop science or anything, but I read a lot of Bruno while I was writing the book. And his concern primarily was the problem of in the,

Talmaic cosmology, right? So there was a whole theology built around the Talmaic cosmology in which heaven was a place, right? It was outside the crystal sphere, about the outer sphere of the universe, right? So in the Palaamac universe, the Earth is at the center and there are various spheres going outward, the crystal sphere of the stars, and then the prima mobile, which was a sphere outside the sphere of the stars, and finally the imperial realm, which was outside the premium mobile. And if you get rid of that structure, you have nowhere left for God to live. And so now, so Bruno says, okay, we have a Copernican universe, it's infinite and extent.

There are an infinity of worlds just like our own. Where then does God reside? And his solution to this problem was, once again, borrowing from the Epicureans, he believed that God actually lived inside atoms. And so it was this sort of God was eminent from the smallest structures in the universe. So it was kind of a form of pantheism almost where God was resonant in the smallest particles of the universe

rather than living in some place that was outside the universe was his solution to this problem. So his cosmology was very, very prescient. It was very far ahead of its time. His theology was like completely nuts. And, you know, so he had God living inside the atoms that corresponded. And it was that he came up with all of these crazy theories that, of course, have not really survived the test of time. Although, you know, past guests on the show, Mitch Okaku won't call, you know, the equations of string theory, the God equation.

So if not in literal form, you know, we have vestiges of Bruno and those pantheistic ideas. And I wonder, you know, when we think about communicating, to the public and you've done a spectacular job in this brand new book, the infinity of worlds. When you take on writing a book, to be blunt, what made you want to undertake this? You're a professor. You're doing hardcore research, advising students. What made it, you know, incumbent upon you to take on this mission to describe the multiverse from this perspective? Why was that such a priority for you at this stage in your career? It's peak pollination season, and my business is scaling fast.

To keep the nectar flowing, I need a phone plan with top priority data speeds. That's why I chose GoogleFi Wireless. My connections stay strong even when the hive is buzzing. Plus, unlimited plans started $35 a month. Now, that's a deal that doesn't stay. Explore GoogleFi Wireless plans today. Plus taxes and government fees, Google Fiore Wiarless is not subject to data traffic deprioritization during times of high network usage?

Well, the story of how this happened is that MIT Press actually came to me and said, hey, we're looking for somebody to write a book on inflation. And we think you'd be a good person to do it. And so I said, sure. And so I probably wouldn't have written it if they hadn't recruited me to do it. I didn't have any particular ambition in mind to write a pop science book. it's a difficult task. But once it got going, it was a, and to be honest, I didn't really have, like, you know,

when I started working on it, it's like, okay, so you're doing an explainer on inflation. It's sort of what they asked me for was a 40,000 word explainer on inflation, and what they got was a 47,000 word manifesto on Copernicanism. And my editor, Jeremy Matthews, was very kind about that in terms of, he sort of got what he asked for, but he got a lot more than he asked. for in a lot of ways. And so, but, but he recognized that, you know, he saw the potential in it. And so we decided to put it out as a hardback trade book.

So, but it became increasingly evident as you start writing this is that you can't write about inflation without writing about eternal inflation in the multiverse. And that gets you into sticky philosophical territory extremely quickly. And so I found that structuring it around Bruno's ideas gave me a place to situate it. And in particular, sort of a reaction against the popularity of anthropic principle in cosmology, which I spend rather, I criticize at length in the book. And one of the themes of the book is proposing a Copernican viewpoint on the multiverse that is an alternative to this anthropic viewpoint. And really when the anthropic principle, this is the idea that, to explain this to your listeners who might not be familiar with it, is the idea that the universe appears to be fine-tuned for life.

The strength of electromagnetism is just so. The structure of atoms is just so the universe seems to be built to form galaxies and planets and things like that. It's almost like it's built for us to live in it. And this has been remarked upon by a number of authors. And so my viewpoint is a bit of a reaction to that. So the idea of the anthropic principle is that the laws of physics are what they are in order to enable our existence in some sense. In the weakest form, it's just saying that we wouldn't be here if the laws of physics were different so that we can say that, you know, the laws of physics have to be consistent with our existence. That's a basic consistency condition.

But I think in stronger form where it's as you that you can use that as a predictive tool to actually decide to predict what the value, for example, the the density of dark energy or the value of the strength of electromagnetism. That's where it gets more controversial. And that this picture is that in this great multiverse, if you have many, many, many universes, almost all of them, the vast, overwhelming majority, I mean, mathematically, hugely, will be these empty, barren places that have no life in them at all. And we live in this very special oasis that is built just for us.

The alternative viewpoint is that our universe is in some sense typical. extending this Copernican idea that the Earth is typical or the solar system is typical in the universe out to the idea that a universe is very likely typical in this larger multiverse. And so it's a lot of the philosophical treatment of the book is the contrast and the clash between these two viewpoints on how one would structure a larger universe of which ours is only apart. So looking, you know, from the present backwards, is how I typically will think about teaching cosmology as I'm doing right now with my students,

some of whom are undoubtedly watching right now because their entire grade depends on their subscription to my YouTube. I'm just kidding. That's not true. But many of them do follow the channel and are taking a class based on past guest, Barbara Riden's wonderful introduction to cosmology text. That is a great book. It is.

It's one of my favorite books. And I pointed out to the students, I think it's the most widely read of all books because it's the primary book for cosmology in general. And to my knowledge, I confirm this with Barbara. I think it's the most widely read textbook for undergrads written by a female professor, which is pretty amazing when you think about how 99% of the books are not. And so it's markable in that she's such a delightful intellect and playful person and just genius at writing. But in that book, we end with inflation, but really I always felt that was kind of like putting the cart before the horse. I mean, shouldn't we start by talking about the beginning of the universe and teach the controversy,

so to speak, and that, you know, learning about the evolution of the universe has some bearing. We have to say something about cosmogenesis, but by the time I get to inflation at the end of the quarter, there's usually, you know, no time left to really dwell into it. But really, it's kind of the reason a lot of them are taking the clause, right? So what does inflation have to say about cosmogenesis, cosmogity, the origin of the universe itself, if anything, or is it just assuming that the universe began to exist? And if so, what quandaries does that pose for physicists such as yourself? A lot of complicated questions.

Certainly, I mean, the selling point of inflation, it's reason to be there is that inflation is a dynamical way to set the boundary conditions for the hot Big Bang. This gets a little funny because the word Big Bang is a loaded word that's used in many ways. So Big Bang refers to, in one sense, it refers to this hot, dense, early stage of the universe, which we know was there because of things like the cosmic microwave background and primordial abundances of the elements. We know that the universe was hot. It was in thermal equilibrium. It was dominated by relativistic species, da, da, da. But there's also, the Big Bang sometimes also refers to the initial singularity, right?

If you take the standard cosmological model, you run it backward in time, you find that the universe has a finite age. And at that time zero, there was a point at which the universe became so dense that all the known laws of physics break down in some sense. And this is the initial singularity. Inflation replaces that initial singularity with an earlier epoch. And the end of inflation is the end of that earlier epoch and the onset of this hot thermal equilibrium universe. So that thermal equilibrium, the hot, dense early universe with the Big Bang, is a consequence. of inflation. So inflation explains why the universe is so big, why it is so close to geometrically flat, which is an observed fact that is not explained by the standard cosmological model.

And so why is geometrically flat? Why it's so old? Why it's so big? The other question is, does inflation get rid of that initial singularity? Right. So the end of inflation is now where the initial singularity was in the standard Big Bang model. But you can now ask the question, does inflation get rid of the initial singularity or does it just displace it to some earlier time? And there are theorems on this that show that in fact that initial singularity doesn't disappear, but it just gets pushed far, far back into a murky past of what happened before inflation itself. And inflation doesn't provide any real answers to that question. So unfortunately, it doesn't allow us to get rid of the initial singularity that led to the

Big Bang. All it does is separate that from that initial hot, hot, dense equilibrium state that was the early universe as we can observe it. I mean, one of the consistent themes on this channel, and I'll put links to videos, I've had to conversations with people like Paul Steinhart, Giant Narla Kar, and even Sir Roger Penrose, all of whom have alternative cosmologies to inflation. And one of the selling points of this book, that I found refreshing is that it doesn't, you know, assume that inflation had to be occurring and that it's the only choice. It's the only thing that you could possibly consider. But if I got the gist of it right, and it's going back about six months since I read it. But the fact that if inflation

did occur, then it's sort of unavoidable that there was something like a singularity, right? That that you basically can avoid this according to the so-called Bordeaux-Guth-Velan theorem. And yet one issue I have with that, and I've raised with Roger Penrose as well, is that we have no examples of singularities in physics, as far as I understand it. Mathematics, there's abundant. They're resplendent. But what evidence do we have for anything being infinite in temperature, pressure, density, however whatever physical unit you want to use, that's infinite?

and then furthermore transitioning from something infinite to something finite and some finite amount of time. So the concept of singularities often gets brought up in the context of quantum gravity, that we need a theory of quantum gravity because we need to understand, A, the origin of the universe, because that seemed to require a singularity, or to understand the properties of singularities in black holes. But will, neither one of these is in principle even observable. So to what extent do we need to have a singularity at all as mandated by the fact we can never observe it? And therefore, does the BGV theorem fall apart because there's no evidence that there could be

a singularity, in other words? This is kind of the House of Cards argument. Yeah. I mean, the BGV theorem, which says there must be a singularity in inflationary space times, an initial one, is as a classical theorem. It doesn't include quantum mechanics, right? So the supposition here is that when you have a theory of quantum gravity, that it will resolve those singularities in some way,

that it will take these points of infinity and turn them into something and chop them off in some way, resolve them so that they're not actually infinite. Some application of the Heisenberg uncertainty principle, the space time that would mean that that singularity really never goes to infinity. So things don't fall into an infinite point at the center of a black hole and the universe doesn't evolve out of a singular, out of a spacetime singular. Sorry to interrupt, but if there was this Heisenberg kind of classical, you know, quasi-classical WKB transition, I mean, doesn't that then obviate the BGV theorem and that like now you're saying

you've smoothed out the singularity, so then you can't extrapolate that there was an eternal inflation going forward because there wasn't an initial singularity to begin with. It was just a classical high-density, you know, caustic or something. You don't know. I mean, there's no theory for it, right? So nobody's constructed a quantum theory of singularities. Because we don't have a theory of quantum gravity, we don't have a self-consistent theory of how you resolve singularities. People assume that it will be true once we have a theory of quantum gravity, but we don't know that. Right. It could well be that when we come up with a theory of quantum gravity,

it will still contain singularities. We don't know. So that's the alternate possibility. But the thing that's fortunate is those are all hidden behind horizons. And so because of the presence of space-time horizons, which are boundaries beyond which you can't see, for example, the event horizon of a black hole or correspondingly in cosmology, the edge of our observable universe, because those singularities are hidden behind those horizons, we never have observational access to them. To a certain extent, you start to ask the question, is this really science at all, right? It's sort of this blurry boundary between a proper scientific proposition and a purely philosophical one. would be my viewpoint on that.

And then, you know, considering these, you know, the delightful description that you have of some of the competitor theories, if I asked you to put on your Montana, by the way, you're my at least third guest from Montana, if I have that right. Sarah Ruhkeheimer, Professor Ruechheimer, and then Brian Schmidt, another one of my kids' favorite Bryans. So at least third, and there may be more Montana. What is it about Montana that creates? Is it the big sky that you then want to pursue the biggest questions under the sky?

I got no answer for you there. Well, Montanans are a peculiar bunch. Yes, that's right. Mavericks, all of you. It is probably a very high ratio of astronomers per capita, professors of physics or astronomy per capita. When we think about the alternatives that you very, you know, delightfully do this.

discuss in this book, which, you know, well, I get, I get a little bit frustrated. I've reviewed a book. I forget who the author was now, but for physics today, about three or four years ago, it was also about the multiverse. And in it, the guy, the author, and again, I'm not going to use his name, but he calls like people that that don't support the multiverse, multiverse deniers. That's his literal term. And I railed against that in my review for physics today. But nevertheless, I mean, how do you look at people? And is it, is it like global warming or, God forbid, Holocaust denial. I hate these kind of comparisons, but he brought it up. So I want to ask you, if you question inflation, does that make you a crank? I mean, how do you address these people

that are deniers or supporters of alternative cosmogenic, you know, instantiations before the hot big ban? Well, they're legitimate theories. And, you know, one of the things is that inflation, inflation has definite shortcomings. And I discuss these, you know, in detail in the book. So one of is this problem of that the BGV theorem, it doesn't get rid of the initial singularity. So you really haven't solved the problem of the universe coming into being out of nothing, which physicists don't like, right? Because we like to have a continuous chain of cause and effect. And if the universe had a beginning, it had to have a first cause,

an idea going all the way back to Aristotle. So people have tried to come up with alternatives that solve this problem, that really push the, you know, give you a universe that can extend infinitely into the past and infinitely into the future, which I think is a bias that most physicists have about the world. But we really don't like the idea of the universe having had a beginning. It makes physicists uncomfortable. One of the other usefulnesses of an alternative theory that I want to bring up is that it allows you to say, okay, I have a theory that has certain shortcomings.

what are the alternatives in the sense of what price do I have to pay in order to compensate for those shortcomings of this other theory? I mean, is my alternative, does it have even more shortcomings or is it better? And I think I argue in the book that these alternatives, although they're self-consistent and certainly possible, right? You can't really, there's no observational way necessarily to rule them out. Although, for example, in the case of Steinhart's cyclic models, you would rule them out by detecting primordial gravitational waves since they're not produced in that. So there's a real definite prediction there. You can say if we find primordial gravitational waves from the Big Bang, then these cyclic models that Steinhard has proposed would be falsified. So you look at these alternatives, even if you feel like inflation is the preferred.

model, and I certainly do. The alternatives give you, considering alternatives gives you a sense of what the boundaries of your existing theories are and how you might work around the existing shortcomings of the theory. And what I argue in the book is that these alternatives introduce more problems than they solve really. They have different problems, but they're in many ways worse. And then yet, you know, just to push back with respect, as I always do, you know, and speaking not on behalf of Paul Steinhard or Anna EGIS upcoming guest on the podcast. You know, they will say that their model in particular with a, you know, doesn't require a singularity. So it has a classical bounce. And also accounts for entropic considerations, which inflation also has to explain as pointed

out by none other than Sir Roger Penrose. What I like about the alternatives, and I'll have to, you know, not dwell too long on this, but they're the three major alternatives, you know, the Narlacar Aussie steady state cosmology with the sea field that kind of eventually kind of look like dark energy according to them, ruled out by CMB polarization in particular, as I discussed in my book. And then Paul's book, Paul's work rather with Anaegis, and even Sir Roger Penrose, not only do they kind of criticize inflation, they can attack, but they also promote new alternative ideas. That's kind of rare in science.

In other words, it's easy to attack. There are a lot of people that say dark energy doesn't exist. you know, dark matter doesn't exist, but they don't come up with some other alternatives to explain existing data. They just saw current data is inconsistent with the precepts of the theory. And yet, Anna, Paul, Roger, even Giant, they propose alternative models, which are testable, as you just said, they can be falsified. And I think, you know, is that not right to require as a virtue? As Paul has said, as you undoubtedly know, from the scientific American, you know, back and forth, which is reminiscent of index of...

I've heard Paul give many talks on this as well. Yeah. So, you know, thinking about the notion of testability and the scientific method, he's claimed not only is inflation wrong, it's dangerous. It's dangerous not only to science, but to society, because it upends our kind of cherished notions about predictability and testability and kind of the Paparian sense. So how do you react to that, that inflation is...

I think that's complete bunk, and I think he is totally wrong about it. Okay. How so? Well, inflation makes a whole bunch of really definite predictions, especially if you look at, you know, consider the simplest type of inflation model, which just has a single order parameter, right, a single dynamical degree of freedom. That makes a whole laundry list of very, very definite predictions. It predicts that the perturbations should be purely adiabatic. That is, that they should, they should couple directly to the curvature. It predicts that the perturbation should be nearly scale invariant, but not quite. It says that the perturbation should be a Gaussian random field, and it predicts the existence of primordial gravitational ways.

Three of those four things have been tested in detail by observations, and all of them turned out to be right. So this idea that inflation can predict anything, well, in a sense, that's true. In the same sense that quantum field theory can predict anything. You know, any observation you can come up with a field theory that will fit it. But the standard model is extremely predictive as a quantum field theory. And I think the situation is the same as inflation. So that the larger picture of using quantum field theory to describe an accelerating expansion in the early universe is very broad.

But model builders and inflationary models, particular models of inflation, make extremely precise predictions. and those predictions have been borne out by data. So it seems to me that saying that inflation doesn't predict anything is keeps raising the bars. Other than all of these other things that it predicted and came true, well, what has it done for us lately? And I think it's a little bit of a disingenuous argument, and I just don't buy it.

Make every get-together chill. This Memorial Day, get up to an extra $1,000 off select top brand appliances like LG. Plus get free delivery at the Home Depot. tackle pool towels and camp laundry with a large capacity washer and host in style with the fridge serving craft ice, mini craft ice, cube dice, and crushed ice. Shop appliance savings now through June 3rd at the Home Depot. Offer valid May 14th through June 3rd, U.S. only free delivery on appliance purchases of $998 or more. C store online for details. Well, yeah, I mean, just to dwell on it, and I'm not asking you to, you know, I'm not speaking on behalf of Paul or Anna necessarily, but of course they'll bring up as did Saran.

Roger Penrose, issues of consistency, extraordinarily low entropy required in the inflationary paradigm at very early times. Obviously, the singularity, unresolved singularity issue. And oftentimes when I hear this, people say, well, first of all, the multiverse isn't a theory. It's a consequence of inflation. And then they'll say inflation is not a theory. They'll say inflation is sort of a paradigm. And I've argued with Paul even respectfully saying, look, it'll be great if you didn't need a quantum field, you know, but, you know, and Sir Roger has a quantum field. In other words, if you're going to, you know, subvert inflation, you'll be great if you did it without some magical scalar field that somehow is present, you know, perhaps all time internally

going forward. But, but nevertheless, he has a quantum field and a scalar field at that, of which we only know there's one example, right? The Higgs is the only known scalar field, right? So the fact that all these alternatives need scalar fields, the sea field and Narlac, Carr and Hoyle, the scalar field of Anna Aegis and Paul Steinhart, and then Sir Roger Penrose has these error bombs and so forth, none of which can we observe. The inflation involves a scalar field, as you know.

What's that? Yeah, I'm saying all these do. So I'm saying to get rid of it, to have an alternative to inflation, be nice not to have the core element of inflation, which is a scalar fit, which, as you know, Paul was very instrumental and understanding in early times in 1980s, rather. That counts early times. To the model of Anna and Paul, that, that inflation. involves a scalar field and also involves inflation. It involves accelerating expansion. That's how they

get rid of the entropy that builds up. Right. But it doesn't involve that what they call the quantum runaway and the multiverse, right? There is no multiverse. There are no B modes. You know, I'd be out of a job. So, you know, obviously I'm pulling for it. But I mean, just thinking back, you know, historically, going back to say the early discoveries of the CMB before the CMB was discovered in 65, there were many predictions by people like Gamov and others working together, and they kept fluctuating. Some days the CNB temperature would be 5 Kelvin. Other days it would be 20 Kelvin.

And there were some early measurements on cyanogen and other things by McKellar. But yet, the fact that the numbers kept fluctuating, and as Hoyle said, when the CNB was discovered, you know, if they had measured, you know, 2.9 Kelvin or 6.9 Kelvin, they would have said that's consistent with the, with the big bang. Of course, depending on what your starting temperature is, that's true. I mean, it's just a consequence of radiation domination, right?

So to what extent I remember, and I may be wrong, but I wanna give you credit, I remember as a grad student, you know, making these plots of, you know, tenser to scalar ratio versus n-sab-s. I believe you were the first person to make those types of plots. We invented that, right?

So that was me and Scott Doodleson and Rocky Cold were the people who invented the zoo plot. That's zoo plot, yeah. So now the zoo plot, of course, there's not only, you know, an infinite number of points that can tile a plane. There's an seeming infinite number. My former postdoc, I met Yadav once wrote a paper already,

listed every single name of every model of inflation. So there is no one theory of inflation, right? And even the classification of inflation, single field just seems natural, but there's no letter from God or, you know, Gaia or whoever that says it has to be single field. So do you think of inflation as a theory like BBN or how do you think about it, like when you wake up and work on it?

This thing, back to the predictivity issue, right? So if you take that plot of n-sab-s- versus tensor fraction, you can pick any region of that and you can find an inflation model that will land there. Different choices of inflationary potential densely tile that claim. Yeah. Which, you know, back a long time ago, that was not really well-established. One of the questions I remember it was Rocky who first asked, you know, is like, do inflation models fill this densely or do they live in particular?

regions and it took a while to answer that question. And it turns out they fill it densely, that there's no particular prediction. But that's not any different than saying, you know, Newton's law of gravity tells, or Kepler's laws tells you, tell you how planets orbit, but it doesn't tell you the radius of the planetary orbits. Kepler had another theory involving platonic solids that he claimed predicted the orbits of the planetary radia. But he didn't have one over R cubed, one of the fourth. He had one. He did not, right. Or multiple gravitational fields, like multiple scalar. So, you know, yeah, there is that degree of freedom and we really don't know.

And so you have this free function that you can use to fit this data. But in the case of a single field model, it will still always be gousy and it will still always be adiabatic. All of these other things will be true. It's just that it doesn't make any particular prediction, for example, for the amplitude of the tensor modes. It predicts they'll be there, but there's no prediction of how strong they will be. So it might be that you will never see the B mode, right?

because the tensor fraction is just too small. So I don't consider that necessarily a crushing lack of predictivity for the inflationary paradigm. We know, for example, that alternative theories involving what are called non-canonical Lagrangians, things that are very common in string theory predict that you would have a speed of sound during inflation that's much, much less than the speed of light. And those can be ruled out. we have a lower bound on what the speed of sound was in inflation of about 8% of the speed of light.

It has to be bigger than that, but from measurements of non-Gausianity. So there are lots of, there's lots of theories that have already been falsified. And it turns out that the very simplest theories, these single field models are still perfectly consistent with the data. So whatever you might want to criticize them on the basis of, it's like, no, there is no, there's no writ from God that tells us it has to be this way. But what we know about things like phase transitions and other kinds of symmetry breaking in nature is that these single order parameter phase transitions are very common. And there's no reason to particularly reason to expect that it wouldn't have been that way. And it certainly fits the data. So we have a model that works extremely well.

And I consider that a real triumph. With respect to the singular, I wanted to bring up that in, for example, in the Paul and Anna's latest cyclic universe, universe, right? Which definitely avoids a singularity at the bounce, right? So they have a contracting universe that then goes through a bounce and then expands again, and they have a modified gravity theory that explains the bounce. You have to modify general relativity to get rid of that singularity so that they add that in. But one of the questions that we had was, does that really avoid the initial singularity? Right. So inflation, you have the BGV theorem that tells you that the singularity still has to be there in the past. And at first glance, the cyclical

models where the universe just is cyclic in time seem to avoid that problem that there's no initial singularity. And this came out after I finished the book, but I actually still, I had this derivation in mind when I was writing the book, is that we, my grad student Nina Stein and I recently came out with a paper where we show that the BGV theorem that tells you that there's an initial singularity in inflation also applies to the Steinhart IS model, right? Their model also has an initial singularity of exactly the same time that inflation does. So in fact, their model does not avoid that problem. Right, which, to be fair, they, so as I understand it, and about 10 years ago, with

bars and Turok, you know, Paul discovered that that also applied, or they did apply it to cyclic cosmology. So, you know, that was, that was sort of, you know, dependent, contingent, perhaps on some new Higgs field type behavior. But yeah, so I think just to recap for the listeners is getting a little bit into the weeds. And of course, my listeners is getting a lot with technical. Yeah, but it's fun because my audience is extremely technically savvy. And I reserve the right to always to go as deep as my guest will be willing to go.

But I think it's important to hear, you know, for even a lay person, that these are topics worthy of debate, that we should debate with comity and some comment. to that there are alternatives and that they're worth exploring and not necessarily as previous people saying didn't call it deniers or so forth that I find kind of a little bit distaste. That's extremely unhelpful. Yeah. I mean, yeah. Now talk about some of the consequences.

I mentioned the Higgs inflation that Steinhart, Turak, and Barr's had discussed a little while back. But talk about the Higgs. Could it be the Higgs, the only scalar field we know exists? and the inflaton and maybe dark energy, could they all be related in some way? Possible. People have come up with models for that.

As far as I know, in order to make the Higgs work as the inflaton, which for your listeners is that whatever field is responsible for inflation, we just give it a generic name called the inflaton, like the Higgs boson. It's the particle responsible for inflation. Yeah. It could indeed be the Higgs boson, but you pay a price to do that, which is that you have to have it coupled directly to gravity in a very non-standard way.

So that if you have what's called a minimal model where you have the Higgs boson and gravity being separate sectors of the theory, the Higgs boson doesn't work because the potential is too steep. It rolls off the top of the hill too quickly to be the infloton. But if you couple it directly to gravity in a non-standard way, then you can make it work for inflation. and there is a number of really interesting papers that have been written on this subject about using the Higgs itself. So possibly, yeah.

If some intelligent, you know, alien wakes you up at three in the morning and forces you to disclose your greatest reason for credulity in inflation, what would it be? I, for me, it, I really started to view inflation as being a well-established theory rather than just a, you know, one of a number of competing hypotheses with the release of the W-map satellite data, right? So the first really high resolution, high, high sensitivity, all-sky map of the cosmic microwave

background that really fell exactly into where you expected inflation to be. And that's certainly been strengthened by subsequent measurements like the Planck measurement and the things that you're involved with, like the Bicep KEC measurement at the South Pole, all of that evidence put together really points to confirming a set of predictions that were made by inflationary cosmology long, long before the data came in. And I think that's a very powerful thing. If you were really making these, and these aren't trivial predictions.

They're complicated calculations. You're not just pulling this out of a hat. These are really strong consequences of the theory. and the fact that the data matches so well, give me a lot more confidence that inflation is right. I've been a lot more dubious about the multiverse for a long time. I was harder to convince about that. But I've also finally come around on that score as well.

So what was the most convincing? I mean, obviously, you know, most convincing of all, perhaps, at least that's what we put in our grant proposals, would be a detection of B mode polarization, right? But there's an additional smoking gun that we have seen, which is the presence of super horizon perturbations. So for the listeners, the observable universe is a big, is a little patch of a much larger space.

And a prediction of inflation that you don't get from, really from any other theory is that you should have waves, density waves in the universe, waves in the over density and underdensity of the universe, whose wavelength is actually larger than the size of the observable universe, where one end of the wave is causally disconnected from the other end of the wave. That is a really peculiar prediction of inflationary cosmology that you don't get in most of the theories.

And it turns out that there's very few theories that will accommodate that. And there is very definite evidence in the cosmic microwave background for the presence of these superhorizon perturbations. They're just there. And this is really the big. thing that I think gives one confidence in inflation is the correct theory, is the presence of these modes with wavelengths longer than the size of the observable universe. That's extremely weird and doesn't come about with much physics that is alternative to inflation.

Bouncing universe is being an exception. Yeah, so yeah, bounce, I was going to mention it. And also just to be, you know, to push back on myself or maybe on Paul and is to say, well, you know, inflation could have been, it's not true to say that it can't be falsified. Because we could have measured that the universe isn't flat. Like imagine we do much more precise, you know, angular correlations or we, you know, get barren acoustic costs. You know, we do whatever we need to do. And within the context of, well, that's a model dependency, the universe isn't flat. Then would you rule out? I mean, would that cause you, which is still an open possibility, no pun intended. But would that then cause you to doubt both the inflation

paradigm and then perforce the multiverse, you know, kind of consequence within inflation? For example, yeah. If the universe had, if the universe it turned out to have like a measurable positive curvature, if we lived in a closed universe, I think that that would be a very, very difficult to accommodate within inflation. You could probably come up with some highly contrived model to do it, but it would be lots and lots of gears and bells and whistles in order to accomplish it, right? So it would be unattractive. Another thing that I think would have really made one question inflation is if there hadn't been, if there weren't any acoustic peaks in the CMB, right? We see the evidence of these coherent sound waves in the early universe propagating in the plasma when the cosmic microwave background formed that, for example, would not be there if structure were ceded by cosmic strings instead of by adiabatic perturbations, right?

Cosmic strings would have given you just a big featureless bump in the CMB. Right. Although I do recall a paper by Turok, maybe with others, not with Paul, though, where he contrived. And, you know, you can, of course, with enough free parameters, as von Neumann said, you can make an elephant, you know, and as add one more to make his trunk wiggle, I think. But yeah, you're right. That was kind of ruled out. You talk about that in the book, and it's a wonderful passage in there. What other, like, new or alternative data could one hope for to validate the infinity of other worlds? What else? In addition, I'm a CMB maximalist. You've heard of Bitcoin maximalist. I'm a CMB maximalist. So tell me, what other tools do we have to dial in and get more confidence or refecation of the multiverse? Well, there are a couple of predictions of inflation that we haven't tested yet that are very specific. And these are called consistency relations. And these come about by connections between different observable quantities that are there, because the perturbations are generated by inflation. The first one is a relationship between the gravitational wave,

the shape of the spectrum of gravitational waves. So if you could not just measure primordial gravity waves, but measure them at different wavelengths. The slope of that spectrum as a function of wavelength is actually related to the amplitude of the tensors, the gravity waves in a particular way. And that is in principle test, It's difficult to do in practice, but in principle, you could do it.

And there's another one which is a prediction for single field inflation models, which tells you that the deviation from Gaussian random statistics should have a particular form. And this was first derived by Juan Naldesana in 2002. And if we could get accurate enough measurements of the primordial perturbations on many, many scales, that would also be a testable thing. We probably won't do it with the CMB. the CMB alone is not powerful enough. The best bounds we're going to get on this parameter

for this non-gaussianity is of order one, right? Even with something like the Simons array or CMBS4, you're going to talk FNL is an upper bound of around one, where from Planck, the upper bound is around four. So you're going to do it by, you know, a factor of four better with upcoming experiments. But to really test the Maldesana relationship, which tells you that that should be about 10 and minus two,

it's about two orders of magnitude smaller than what way the best we can do with CMB. Then you're going to have to talk about measuring, for example, neutral gas clouds during the dark ages with 21 centimeter radiation, for example. And if you could do that, you could actually test that. So there's a possibility in the quite far future, extremely difficult measurements, but in principle possible, where you could test other predictions of this model that would really tend to lend even more observational support than we already have.

And then one thing that comes up quite frequently, you know, throughout the book is this issue of non-Gausianity. And I wonder if you could describe for listeners that are technically savvy maybe or maybe not. What does non-Gausianity refer to? Why is that such a cornerstone of the inflationary paradigm? Well, the analogy I use in the book is imagine you were in Las Vegas and you were shooting craps. right and when you roll dice you roll two dice uh the most common possible roll you have is a seven right and anything so and then a six or an eight is less common and a five or a nine is less common and all the way out to like two and twelve are really rare right so there's a particular

distribution of probability according to what what die you would roll and this actually a proxy it's a binomial distribution it approximates what's what inflation would predict is a Gaussian distribution. So inflation predicts that certain fluctuations in density will be more probable than other fluctuations in density, and it forms what's called a bell curve. That's very, very common in nature. The distribution of shoe size and humans forms a bell curve. All kinds of probability distributions form this what's called a Gaussian or a bell curve. And inflation predicts that the perturbation should have this Gaussian or bell curve shape. So how do you test this, right? Well, Well, testing this is very much like going to Vegas and trying to figure out whether or not the dice you're rolling or loaded, right?

If the dice are loaded, the probability that you're going to get a certain number is going to be shifted a little bit. And if they're a very clever cheater, they're going to make that shift very small. So it would be hard to notice. But so if you're trying to, if you're playing craps in Vegas and you're trying to decide whether the dice are fair or the dice are loaded, one way you might look for that is to say, well, if I see a whole bunch more snake, eyes than I would expect from a normal, from a binomial distribution, I might, I might start to guess that those dice are loaded, that the game is fixed against me. If I'm rolling lots of way more twos and 12s than I expect from a standard probability distribution. So you could tell the dice are loaded by playing for a long time, plotting how many numbers you get as a function of the roll. And you could

see that if you had extras, if you had extra rolls way out on those fringes, you might decide that the the dice are loaded. Same thing with non-gaussianity. So what's an example of an outlier in the density perturbations? It would be really large density perturbations, huge shifts in the density. And what those would do, for example, is those very large fluctuations are responsible for, for example, for seeding clusters of galaxies, the largest structures in the universe. So one way you might look for loaded dice for a non-gaussian distribution of primordial perturbations is if the there are way more galaxy clusters in the universe, way more of these large outliers

than you would expect from a standard probability distribution. And people have actually put bounds on non-gaussianity from the abundance of galaxy clusters using exactly that method. So that's kind of, that's the process you would look. It's like looking for loaded dice in Vegas. And then why is that a consequence of inflation uniquely? Because inflation generates these fluctuations in the universe

by quantum mechanical process. and in particular it's what's called a free field is the technical term for it. And when you work through the math, free fields give you Gaussian distributions. So it's a consequence of the fact that inflation uses quantum mechanics to generate the seed perturbations for structure in the universe. So it's really kind of neat that you're actually seeing this outcome of a quantum mechanical process. And you can really test whether or not it's consistent with that quantum mechanical process

by looking at the statistics of the fluctuations. It's a brilliant thing. And that's unique to inflation. In other words, a bouncing models, a scalar field doesn't feature that? Or can it accommodate? Some bouncing models have very strong non-gaussianity, right? And a number of earlier proposals for these bouncing models have been ruled out by the fact that they would have produced

non-gaussianity much larger than where we see bounds, so that there have actually been the number of those bouncing models that have been falsified on these grounds. You said this place was steps from the water. We just haven't found the steps yet. How much did we save? Enough. Enough to get lost.

Or you could book a stay with Hilton. Welcome to your oceanfront room. Just steps from the water. The Hilton sale is on now. Book on Hilton.com or the Hilton app and save up to 20% to get the stay you expected. When you want savings, not surprises. It matters where you stay.

Hilton, for the stay. So one of the powers of the theory, I'm an experimentalist, so what do I know? But one of the powers of a theory is the ability to predict the, you know, constituent parameters with some, level of precision, not just be accurate. And, you know, the question of, you know, why N-sub-S, the tilt of the scalar spectral index, why it has the particular value it has, it's certainly consistent with inflation, but is it a consequence of the inflation? Obviously, there's an

infinite number of points that could be consistent with it. But, you know, until we detect tensor modes, or if they are detected conclusively this time, not artificial, So, you know, to what extent is that, you know, the ability to, I mean, should we have been able to predict n-s-s-sab-s if inflation's right, or is it we need to know more about the underlying theory before we could be expected to make a prediction? And in other words, we calculated a lamb shift, you know, 50, 60, I didn't do it, but somebody did it back in the 50s and 60s, 40s and 50s, rather. And, you know, that was a consequence of our understanding of QED.

And I'm wondering, you know, is it fair to require that that be a prediction of an, of an order to call inflation rightly a proper quantum field theory, resultant of a quantum field theory. Explation does not make a definite prediction for this, which is the slope of the, so if I plot the strength of the density perturbations in the universe is a function of wavelength that forms a power law, and the slope of that power law is called the spectral index. And this is something actually that is a bone I have to pick with the inflationary community at this point, because you see a lot people saying, well, inflation predicts a slightly red spectrum, which means that you should have stronger perturbations on long wavelength scales and slightly less strong perturbations on short wavelength

scales. And that's in fact what we see, right? So it's slightly red tilted that the perturbations at very long wavelength are a little bigger than the corresponding ones are very short wavelength. That certainly is a consequence of some inflationary models, but it is not generic. And in fact, before the red spectrum was observed, right, which was with the WMAP satellite, primarily came up with the first real good bound on that. So the proof that the spectrum was in fact, non-scale invariant and a little bit red, came about mostly by the WMAP satellite, and it was quite well established by Klont. In fact, before that, there was a fairly widespread consensus in the inflationary community, was that the most attractive models of inflation

from supersymmetry and string theory actually predicted the opposite, predicted the blue spectrum, one that would have greater, bigger fluctuations on short wavelengths. And these were called hybrid inflation models, and I went to many, many, many talks where people said, these are the favored models because this is what we get out of supersymmetry

and string theory. And there has been very little institutional memory of that now that we have seen a red spectrum, and it's become common knowledge that inflation generically predicts a red spectrum, and this blue spectrum was never really a good prediction of inflation, which is a historical. People said exactly the opposite before the observation. So inflation doesn't make a good prediction.

You can accommodate either a red or a blue spectrum. You can accommodate strongly tilted spectra, very weakly tilted spectra. It's a parameter of the theory. It's not you can come up with a reasonable inflationary model that will accommodate all of these outcomes. Is that a shortcoming of the theory? Well, it is what it is. I mean, it would be really nice if inflation predicted something specific for that, but it does not. Right. Very good. Well, let's see. Will, I want to close with, you know, some of the speculation that you talk about going forward. Your professor at top research university in my home state of New York,

upstate, as we used to call it, not so far away where the Buffalo, was genetically modified to make wings. I don't know how that happened, but we certainly love those treats down over here. We're about as far away from each other as we could get, and that's not by design. It's just worked out that way, well. But I want to ask you,

if you're advising a new student comes to your office, Professor Kenny got accepted to this wonderful school, what is the challenge that you posed to him or her? What is the most exciting thing if you were to start your career again and go into this field with you as your advisor, What would you advise such a student? What's the most exciting thing about your field for inspiring a new student to get involved in in the project of what we call cosmology? I think, I mean, for me, this particular project of understanding the early universe, right?

If that's, you know, so let's just focus on that because there are many other things that I think are very exciting going on right now, exoplanets, for example. I'm super bullish on exoplanets as a field. Be careful. Pace, Bruno, there. You've got to be careful. Well, yeah. But in terms of early universe physics, I think that one of the really exciting things is that we are in a process right now where we're actually refining and able to refine and test these models. And this is a really profound thing.

The idea that we can actually test models of particle physics at energy scales that are 100 billion times as large as the energies that we're testing at the LHC, we're actually direct. directly accessing these with observational data and coming up with real predictions that we can test. We can rule out models. We can do real physics. This is not philosophy. This is hard-nosed, experimentally based empirical physics. That to me is a tremendously exciting thing. And I think that there's still a big future in it in terms of refining these models, figuring out

predictions, coming up with ways of testing them. And it's a difficult process. It's going to take a long time and a lot of money and a lot of effort. but I think that the nature of the questions is so profound that it's really worth it. And I remain excited by it. And you talk about just so stories at the end, and I think it's a delight to consider these things. Nowhere else in science do you get to talk about the origin of the entire universe aside from cosmology. So that's why, and I always tell my students, you know, aside from biophysics, if you study cosmology,

you have access to every branch of physics from quantum mechanics, thermodynamics, observational technology, solid state physics, everything on the experimental side and analogous depth on the theoretical side. So I think that's really fascinating. So Will, now I want to speculate outside the realm of hardcore science that you were a master of. I want to speak about philosophy, maybe even theology, if you're willing to go there. And what about these stories? We started off talking about Bruno, obviously interrelated with theology, with the Catholic Church in that case. In my case, I'm practicing Jew, the Torah, the five books of Moses, the Old Testament,

starts with the creation of the universe in some time. To what extent do is our questions of our existence, of ultimate meaning, of the philosophy or theology that underpins reality? Is that of interest to you? Not is it important to your daily job? It's obviously not. But to what level does it motivate you or maybe not? And you may be an atheist.

I don't know. But are there aspects outside of physics, metaphysics even, that you find worthy of devoting some of your attention to? Well, I mean, I'm a pretty hardcore atheist. So I am not a religious person per se. But I think that when you start to talk about these edge cases, like for example, the inflationary multiverse, which is in principle untestable, right? These other universes are things that you will, because of just inescapable rules of

causality, you'll never be able to see. So at that point, you're starting to blur the boundaries between what I call a hard-nosed scientific idea, something that is empirically verifiable. You can test these inflation models and so on. But then when you say, you take these well-tested models and you just say, what's the consequence of this? You end up with a universe that looks absolutely nothing like what you started. The basic, the fundamental structure of the universe is completely different. Not only that is something that you have no way of testing. And at that point, you sort of slipped beyond the boundary of what you can really even call science and you're really addressing more philosophical questions. And I don't have any answers. And one of the things I try to do in the

book is really be honest and clear about the point at which not only do we not understand things, but it may be that it won't be possible for us in any reasonable sense to understand the, you know, to answer some of these questions. And that puts us in a very difficult place of scientists. And I don't know how to resolve that cognitive dissonance. I have no advice for anybody except that it seems to be true. We walk, we take these theories that we can test, we calculate their consequences, and it gives us this completely crazy, picture of the world that we have ultimately no way of being able to go out and verify. And where that leaves us philosophically or religiously, I honestly don't know.

And I have no particular answer, which is okay, I guess. You know, it's maybe, maybe there are some questions that the science is sort of fundamentally forbidden from answering. And one of the interesting things is that you can use this process of scientific deduction to demarcate those boundaries in a well-defined mathematical way, which I find fascinating, actually, that we can actually measure where that boundary between, where science starts to break down and where we can no longer say anything with confidence. We can find that boundary very, very accurately, you know, using science. as Stephen J. Gould used to call it the non-overlapping magisteria. And we have, I think, a lot to learn from folks that can be comfortable in each camp without being, you know, attacking or being too strident in their views.

And I think it is, it's delightful to think about these things. And I always say, you know, to my students, you know, if you don't think about these things sometimes, like, you may not be in the right field for it. there's so many, because in very few other fields of physics, you know, you study solid state, you know, nemectic superconduct, you're not going to think about necessarily this is the work of God or that that the multiverse spawned an infinite number of, you know, that would allow without much fine-tuning, according to like Fred Adams and other people, that you could have, you know, such a behavior. No, you won't, typically, most people won't think about that as part of their job, but we effectively

get paid to think about such questions. And I think it's delightful and we should take advantage of it. even if we don't agree. Yeah. I think this, maybe to finish up I can talk about, so basically inflation brings two things, two philosophical problems to the four. One is that if you accept inflation

as the picture of the universe, or even some of these cyclic models, as we are now discovering, you have to come to terms with the idea that the universe had a beginning, that there was some sort of initial state. Even if it wasn't a singularity, it was something where other physics

must have been taking place. And the second one is, in inflation, you have this infinite multiverse, you're constantly producing new universes infinitely into the future. And one thing that Bruno did in the 1500s was realized that these two problems were linked. And he grappled with both of these problems in a way that was very aggression and very really anticipated modern sensibilities in that he realized that the infinity of worlds in some sense could give one a framework which would allow you to understand the idea that the universe had a beginning as well.

That it sort of softens the philosophical impact in a way because that beginning is diluted infinitely by the infinity of worlds. And it becomes less of a philosophical conundrum. You don't have to care so much about Aristotle's prime mover anymore because the prime mover is infinitely removed from anything that you would actually have any practical concern. So I think Bruno, in his Copernican view of the universe, paints a philosophical picture that allows us to understand an inflationary multiverse in a very simple way. And I find that very satisfying. Yes. Of course, you know, we don't have to, we don't have access to what referee number two said about Bruno.

It probably wasn't that good. Referee number two set him on fire. That's right. They were a lot harsher back then. Damn. Yeah. We complain about referee number two today, but we don't know how good we got it. Well, it's been a delight to talk to you, and I wonder if now you'd be willing to go into the impossible and answer my thrilling three existential questions about your life and thoughts, philosophy and your testimony for the future.

If you'd be willing to play the game, I call the thrilling three, three, three. Pay off your home, travel for life, drive a Ferrari. In celebration of the world premiere of the Monopoly, Big Board Buckslot Machine by Aristocrat Gaming, Yamava Resort and Casino at San Manuel is giving one person a $1.6 million dream package. The biggest prize in Yamava's history. Club Serrano members can earn daily instant prizes and secure a spot in the finale May 29. Don't pass go and own it all. Only at Yamava, celebrating its 40th anniversary.

You win? Details at yamava.com must be 21-20. Please gamble responsibly. Monopoly is a trademark of Hasbro. Hasbro is not a sponsor of this promotion. First question relates to your relatively, you know, hopefully not too near term, but your ultimate future. when you go into the springing forth of the mortal coil, as the bard called it,

going into the future and your so-called ethical will, which has to do not with Will, Kinney, but with your bequeathment to future generations, biological, ideological. I don't ask you, if you were to put something, some piece of wisdom or some teaching of an ethical or wisdom-based process,

not material into your material will, what would you put into your ethical will? I think, I mean, one of the things that I think is an underlying theme that I try to keep in mind as a teacher, right? I teach science to students. And I, so I have lots of, everywhere from beginning students in a gen ed class. So I teach a general education astronomy class with theater majors and business majors in it all the way up to graduate classes. I think the thing that is a theme that connects all of those and that I, as a teacher, I try to pass down to a, younger generation is the value of a scientific worldview of really valuing evidence and

rational thinking as a as a way to organize your viewpoint on the world. I think it's extraordinarily powerful and I think it's something that that every human being can benefit from. And as a science teacher, I am the point of contact for a lot of students in developing that scientific worldview as a citizen and as a human being. And for me, it's been a very powerful philosophical organizing principle, and it's something I try to pass on to others as well. Wonderful. And now we're going to go a little bit further

into the future and ask you to look into your crystal ball, and that crystal ball will reveal to my audience what you think is the most highest accomplishment of humanity. And I phrase this in terms of the movie 2001, a space odyssey. There are these monoliths that proliferate throughout the galaxy and the earth. And you see in the very beginning, these primitive primates hitting it with a bone and trying to

break it open. We don't really know what it is. It could be an omen. It could be a USB drive. Who knows what it is. But it could be a time capsule. So I like to think of it as a time capsule. So if I ask you, Will, if you had a time capsule that you knew for sure would last a billion

years looking into the crystal ball in the future, what would you put on it or in it? To summarize, to kind of brag and show a little swagger for what humanity has accomplished in your field or in anything, really. So if I had something that I could send to the alien civilization that discovers the remnants of ours. Correct. I think what I would put in preferentially over anything else is our art and literature. I think that that's by far the thing that defines us most as human beings. I mean, presumably whatever alien creatures would come and discover this would have,

science similar to ours and they would in fact probably have a far profounder understanding of the world than we do now. But what makes us human and what makes us unique creatures in the world is our really our humanity as expressed in our arts and in our culture. And these are the things that I think of the species that I would be most anxious to preserve. It's very reminiscent of past guest on the show and fellow upstate New York denizen and Druryan, widow of Carl Sagan, Finger Lakes Denizzen, who said that she would put her brainwaves on a golden disc and attach it to the pioneer spacecraft. And then she kind of bragged said, well, I actually did that.

She is the one person who has actually done this. She claims it the last four billion years. So I'm shortchanging one billion. She said NASA told her it's going last four years. Okay. Last question, Will, now we're going backwards in time for some advice to your former self. This is actually the raison d'etre of this podcast in a certain sense. And it harkens to another one of Arthur C. Clark's famous laws.

He had many laws. Of course, you're probably familiar with the one that goes like this. Any sufficiently advanced technology is indistinguishable from magic. That's how we open the show. And the second law is for every expert, there's an equal and opposite expert, which I like to lay on my department chair from time to time. And then the third law states the following. The only way of discovering the limits of the possible is to venture beyond them into the impossible.

And that's how I got the name of the podcast. I want to ask you and kind of turning that around advice to your former self, 20-year-old will, what would you tell him to give him the courage to do as you have done to go into the impossible? Well, there's another quote from Clark that I think applies here too, which is that if an elderly scientist if an elderly and distinguished scientist says that something is possible he is almost certainly correct and if he says it is impossible he is almost certainly incorrect and i i think that so my advice going back to my 20 year old self or to whatever whatever human being is is a current version of that is to keep a radically open mind and to

not limit yourself in terms of saying that, you know, this is this sort of narrow version of reality that we, that we're stuck in. And because that will only, if you, if you keep your viewpoint too narrow and you and you don't, and you don't ever venture outside that, then you'll only ever do things that are derivative. I think that the people who have come up with the great ideas have been the ones who have dared to believe in things that were, you know, or consider things that were believed in conventionalism to be impossible. And so I think that that Clark vote encapsulated that pretty well to work within the theme. Yes, the theme of impossibility and two old scientists.

Well, hold up the book. And I'm an old scientist now. And, you know, I think maybe I'm a little too set in my ways. And I hope that there is some young person out there who just like blows it all away and comes up with something even better. Yeah, that's the hope. Will, hold up the book, please. Hold up the book.

real kinney author of infinite not that side the side with my name on it i don't care about here's yeah there we go that's the money shop brian keating there we go will i want to thank you uh it's been delight to chat with you uh i love following you on twitter and you could be found there on and we'll have links to the book obviously and to your twitter account and anything else you'd like to mention right now will before we uh the book is uh will be available it's available for pre-order uh uh Prior to publication, it appears in bookstores on April 5th, Tuesday. We were recording this a little bit before that. It'll be out by the time.

Yeah, the book will be out by the time. We'll have links to it to buy it directly, contribute to Will's retirement fund. Well, it's a delightful book. It was a fast, easy, delightful, delicious comment on. And really an update, Goose's classic book from 1995 or six or seven or whatever that was, told by one of the real heavy lifters in the field. You do a lot, Will, for communication, for outreach, for education. You do it selflessly.

And it's a delight to speak to you finally after so long. I don't think, we must have met at one point, but I hope to see you in person. Maybe I can come there in January and you can come here in January and we'll get a taste of how each other lives. We can swap. We'll do a house swap. All right. Thank you, Brian. Thanks, you.

Have a great day. Bye, bye. All right, my. Any sufficiently advanced technology is indistinguishable from magic. Ambition comes in all shapes and sizes. At First Citizens Bank, we roll with your goals because we're built for what you're building. Fit for your ambition for Citizens Bank.