Into the Impossible With Brian Keating - Exploring the Scientific Validity of the Multiverse Theory w/ Paul Halpern [Ep. 408]

Episode Date: April 28, 2024

Join my mailing list https://briankeating.com/list to win a real 4 billion year old meteorite! All .edu emails in the USA 🇺🇸 will WIN! The multiverse has captured the imagination of scientists and thinkers for centuries, sparking debates in physics, philosophy, and beyond. But is it a valid scientific theory or just science fiction?  I’ve had the pleasure of exploring this issue with the leading expert in this field, physicist and author Paul Halpern. Halpern is a professor of physics at Saint Joseph’s University and the author of eighteen popular science books, including Flashes of Creation, The Quantum Labyrinth, Einstein's Dice, Schrodinger's Cat, and Synchronicity. He is the recipient of a Guggenheim Fellowship and is a Fellow of the American Physical Society.  Halpern recently published The Allure of the Multiverse: Extra Dimensions, Other Worlds, and Parallel Universes, which tells the epic story of how science became besotted with the multiverse and the controversies that ensued. Today, we’re going to dive headfirst into this fascinating investigation! Tune in. Key Takeaways: 00:00:00 Intro 00:01:17 Judging a book by its cover 00:06:39 Bruno’s speculations about exoplanets 00:11:20 Why is the multiverse such a controversial theory?  00:16:54 Richard Feynman And John Wheeler 00:23:31 Can we falsify the multiverse? 00:30:30 Has anyone ever written a biography of Bob Dickey?  00:39:11 Inflationary models, multiverse and cyclic cosmology 00:45:36 Evidence of bubble collisions in the CMB?  00:57:45 String theory and the multiverse 01:01:41 Outro — Additional resources: 📝 Get one month of Snipd Premium for free with this link: https://get.snipd.com/Cx7S/brianSnipd Snipd lets you take Smart Notes 🧠 with AI 💡 — it’s my favorite podcast player 😀 ! ➡️ Follow me on your fav platforms: ✖️ Twitter: https://twitter.com/DrBrianKeating  🔔 YouTube: https://www.youtube.com/DrBrianKeating?sub_confirmation=1  📝 Join my mailing list: https://briankeating.com/list  ✍️ Check out my blog: https://briankeating.com/cosmic-musings/  🎙️ Follow my podcast: https://briankeating.com/podcast Into the Impossible with Brian Keating is a podcast dedicated to all those who want to explore the universe within and beyond the known. Make sure to subscribe so you never miss an episode! Learn more about your ad choices. Visit megaphone.fm/adchoices

What if there's more than one universe? After all, there's more than one planet, more than one star, more than one galaxy, more than one cluster of galaxy. So why not study this fascinating question? One that's captured the imagination of scientists and thinkers for century, sparking debate, in physics, philosophy, theology, and more. Today, in the end of the Impossible Podcast, we have the incredible opportunity to dive, head first into this investigation with one of the leading experts in the field. physicist, author, and three-time guest on the Enter the Impossible podcast, Professor Paul Halpern. He's a professor of physics at St. Joseph's University and the author of 18 popular science books, including flashes of creation, the quantum labyrinth, Einstein's Dye, Strangeners Cat, and Synchronicity.

Join us as we explore the multiverse theory and its implications for our understanding of all reality. Let's dive deep. Into the multiverse, we go. Any sufficiently advanced technology is indistinguishable from magic. Open the pod bay doors, Hal. Paul, how are you doing today in the city of Brotherly Love? I'm doing great, and thank you for having me on again, Brian. I think this is my third time.

It's really amazing to be on your show again. I love it. You keep writing books. I think you're writing a book right now as we speak with your left hand. I can't see your left hand, but it would not surprise me, Paul, because you're such a prolific author. Such a delight. You're a physicist, physicist-slash-physist author.

You know kind of books that could be devoured, but appreciated and savored. And this book is no different. And I want to start by doing what you're never supposed to do, which is to judge a book by its cover, a feature we've added since your previous book that made your appearance, I think two years ago, maybe three years ago. Jeez. This book is called the allure of the multiverse. So, Paul, do what you're not supposed to do. Explain the title, the subtitle, and this mysterious effort. effervescent cover illustration. That's so beautiful.

So first of all, the title is meant to convey a little bit of ambiguity because my feeling going into the book is that there are good reasons to want to investigate ideas of a multiverse, but there are good reasons for people to say, hey, wait a minute, that's not really science. So I appreciate both sides of the argument. I know people who are kind of aghast that I would even write a book about the multiverse. They use Powell Lee's famous quote, it's not even wrong to condemn it. Then there are people who kind of surprised me because there are hard-headed astrophysicists like Virginia Trimball, who I'm sure you know, at UC Irvine.

And she's done all this observatory work over the years. She was one of the first women to get observatory time. And she's written a lot about the history of physics. And I interviewed her, and she said, wait a minute. You know, in the past, people weren't sure if there were other solar systems. They weren't sure if there were planets around other stars. You know, even about 100 years ago, they weren't sure if there were other galaxies outside the Milky Way. And every time people talk about other things, it turns out to be right.

So she said, well, maybe I would bet on this idea of other universes being right, too. And that kind of surprised me, but I kind of see the logic there too. And, you know, she's a very hard-headed astrophysicist. So, and of course, Martin Rees, the astronomer Royale, who she is friends with and respects, is a big supporter of multiverse ideas. So it's, you know, there are people show up on both sides of the issue of, you know, whether or not we should even take this seriously. And I'm not saying in the book that anything in the book is factual, it's hypothetical, but that we should take it seriously. And there are very serious

reasons, including reasons suggested by Stephen Weinberg about explaining the small size of the cosmological constant, which I'll talk about later, to take multiverse ideas very seriously. So that's why I say allure. It's something that is kind of a little bit of a seduction, a little bit of an enticement to go to other universes to try to explain the observable universe. But it's not necessarily the best way to do things. It's a possibility. If we could explain the observable universe with completely detectable methods, I think everybody would be on board with that. Like, okay, we can explain everything with things that are completely detectable.

that's great. But what if we can't explain everything through directly detectable means? Do we consider the idea of things that might be outside direct detection? And that's what I talk about in the book. Now, the cover was done by a very talented artist. I don't know who. I guess I could look in the inside cover and find out who the artist was. But somebody did a great job with expressing the idea of multiple worlds, different versions of Earth with different color schemes to convey the idea of many worlds. And the subtitle are some of the topics I look at the book, Higher Dimensions, which in a way is a kind of multiverse, if you consider the idea, there might be other membranes out there that collide with ours. It's a little bit of a multiverse idea. Although, interestingly,

people who support that idea are saying it's not a multiverse, but I would call that a variation of a multiverse and parallel universes, other worlds, going back to the idea of Giordano Bruno that there are many worlds, in fact, an infinity of worlds out there that we don't detect, which was very prescient of him. That wraps up the cover, the subtitle, the title. Hey there, it's me, your fearless host, Professor Brian Keating. I hope you're enjoying this interview with my friend, Paul Halpert. If you're as captivated by these cosmic mysteries as I am, I'm really hoping you'll subscribe to my YouTube channel and follow the show. your favorite podcasting platform. You'd be able to find this episode in many, many more conversations.

Again, this is Paul's third time on the podcast. You don't want to miss the previous two, as well as the interviews I've done with other incredible intellectuals, astronauts, thinkers, Nobel Prize winners, and more. So hit that subscribe button wherever you're listening to this or watching this and join us on The Voyage into the Impossible. So yeah, that's a very expedient and efficient way to look at it. I did want to start with Bruno because it's one of my pet peeves And I've told this to our mutual friend, Will Kinney, who's endorsed the book as what he calls an informative and entertaining read, whichever corner of the multiverse you inhabit. Multiverse makes appearances in popular culture and media.

Talk to a character in this book who's very significant, Kip Thorne recently in my podcast for his new book, he features in this book. And Will Kinney's book, which is called Infinity of Worlds after the Bruno world. I picked the bone with him. I want to pick it with you too, even though I love and respect you. Bruno, in my mind, wasn't talking about multiverses as universes, anything of the sort that we now, and now meaning in the last couple hundred years, have conceived of this term. I mean, when you and I were kids, the universe was everything there is. Now the multiverse could be everything there is.

But I believe that Bruno was looking at stars and hypothesizing that they could have actual planets on them. And for his troubles, they burned him at the stake. But he was also kind of a jerk in some ways. I mean, he was a very arrogant thought that the church would kind of forgive his brilliance, as was Galileo, who didn't learn from Bruno's execution. And he proceeded 30 years to the day, 32 years later, to make the same kinds of mistakes. But let's talk about that. What kind of multiverse, if any, was Bruno really talking about?

Or was he talking about alien world? To clarify, I don't claim that Bruno, came up with the idea of the multiverse. I actually mentioned the real ideas in the multiverse really started with Hugh Everett in the 1950s, and that was popularized by Bryce DeWitt in the 1970s, and really took off at the turn of this century when people start wondering, why is a cosmological constant so small, why are there so many string vacua, and all these things and said, hey, wait a minute, maybe we can talk about an array of universes. But I just mentioned Bruno, just from the point of view, and very briefly in the book, from the idea that people speculate about things that you cannot observe.

And it's possible that it's lucky that we've been able to find exoplanets and detect exoplanets. But, of course, when I was, what was little, you know, the furthest planet out there was Pluto, of course, which is not a planet anymore. So things have really changed. And, you know, it was unclear even when I was little if we'd be able to detect exoplanets. And there were some failed attempts at detecting exoplanets, which are in one case, Peter Vandekamp at the Sprawl Observatory, as I talk about in one of my earlier books, claimed to have found an exoplanet around Barnard Star. And then his assistant, another person in his department, Wolf Heinz, said, hey, wait a minute, you just, took apart the telescope and reassembled it. It's a glitch in new detection methods. And he was furious, but it turned out to be a false sighting of that exoplanet. So we could still be in a

situation where exoplanets are unobservable. And in that case, we would say, hey, wait a minute, we really think there must be planets from our models. There must be planets around other stars, but we haven't observed them yet. And of course, gravitational waves were not observed until relatively recently. And there are things that we believe that are essentially not observable. Like we believe that an interior of a black hole

has certain properties, but we can never observe an interior of a black hole and make it out safely. There are things in the universe, and I argue beyond the observable radius of the universe, there's a lot out there that we can observe. And that was my point with Bruno, is that at that time, no one could possibly have observed exoplanets, and yet he speculated about it. And you can say, well, was that science, or was that science fiction? So someone could have said, like, that's not even

wrong. There's no way to prove or disprove that. So why are you even saying that, Bruno? And, you know, so that was kind of my point is that our range of what we can observe, continue. to increase. So sometimes things that are speculation to one generation and even idle speculation, even laughed at, turn out to be real in the next generation. Yeah. And I think, you know, it's, of course, not an easy concept for people to grapple with, but it's a popular concept. So it's strange. It's almost like we have this great concept that's in the words of, Carl Sagan used to say, you know, never have we lived in an age so ignorant about science, but so dependent on technology.

Carl Sagan makes an appearance in this book because of the L.E. R.O.A. Time transport. Fun fact, I had the co-author for that book, which is And Druryan, who wrote contact with Carl Sagan. She was a guest on the show, along with her daughter, Sasha Sagan, many years ago. But when we think about the multiverse, there are these different levels of it, as past guest and friend Max Tagmark talks about. Nobody disputes that there's regions of the cosmos we can't access that are beyond what is called the observable horizon or the Hubble radius in some case. Very many people start to disagree when you get above, you know, level two in the multiverse. So I guess I want to start with with Everett because it's actually one of the more interesting

aspects of, you know, both the microphysical manifestation of a multiverse, a lot of M's there, but also we'll connect later with the quantum mechanical kind of successor to it, which is the string theory landscape. So all of these are super controversial. And I think nothing in my particle, I had lunch with a condensed matter physicist yesterday. Yeah, they have their superconductivity claims, but nobody has the brawls that we have, that you're not doing physics, that you're, you know, what you're doing is bad for science and society like Paul Steinhardt has said about.

So tell me, why does this gender such hostility as compared to? you know, nemectics, you know, superconductors or, you know, type two phase transitions. Why is this so, you know, so fraught with peril for a card carrying scientist to wait into? Well, I think there's a lot of public interest in what is called the multiverse. I call it the cultural multiverse. And that's so different from the scientific multiverse. So there's a lot of misunderstanding. And I think that might carry over to some physicists might say.

hey, wait a minute, you know, let's say they're in condensed matter physics and they're not, they haven't read any papers about internal inflation or something. So they don't know about eternal inflation and its claims. And all they hear about is, okay, some researchers doing multiverse stuff and there's this idea that every time you make a decision in life, you, you branch out and then there's all these versions of you out there somewhere. And, you know, in the movies, there's all these versions of Spider-Man and, you know, different versions of Flash and so forth. And they say, oh, wait a minute, you know, these are just physicists who are trying to get grant money or trying to get credit for doing stuff that's just like science fiction

and it's just completely ridiculous stuff. And, you know, but they might not even look into, you know, some of these models. And I would argue that. that if you look into the idea of eternal inflation, and you look at evidence for inflation, and you look at the idea that inflation is very simple to generate using, you know, as Andre Linday showed, then you say, wait a minute, you know, why not other inflating regions?

That seems to make sense. And then if you have other inflating reasons, you've essentially other places. You can call them other enclaves. You can call them other universes. It's a question of terminology. You could say that the universe is this super inflating, you know, structure that emerge from the Big Bang and that all the bubbles are just subsets of that.

Or you could say that there's a multiverse and that we have our universe, which is what we see or detect, but there are other bubble universes out there, which is the usual way of saying that. And it just, it's something that's very. you know, scientific and stems from real theory. It stems from general relativity, if you have what is called a scalar field or an energy field. And it's completely, it completely makes sense on a theoretical level and has absolutely nothing to do with the idea that you can walk through a portal and encounter a doppelganger who says to you like, I'm the evil version of you. Get out of my

universe. There's something like that. So, you know, the two are so far apart. but I would imagine that the idea of the cultural multiverse might excite, especially among private donors, some interest in these ideas. So it's a benefit to some physicists like, hey, there's a private donor out there who's a fan of Marvel Universe and is like really excited that somebody is studying what's called the multiverse in eternal inflation, trying to test eternal inflation. And then there are other people out there, scientists who might be on, let's say, a committee for an NSF grant and say, hey, wait a minute, this is not real science and not even

really look at, you know, the technical details because maybe they don't know GR or don't know string theory or something like that and just immediately dismissed the idea as being not pseudoscience. So it's a mixed bag. 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.

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Hilton, for the stay. This book kind of is the, in some level, if you had to only read one book, it might just be this one, because it weaves together so many of the different topics that you explored in, you know, the quantum labyrinth, where you talked about quantum physics and flashes of a creation. You talked about the Big Bang Theory, which couples into, you know, the origin of the universe, inflation, et cetera, you know, time travel, et cetera, even, you know, dark matter and possible alien

worlds, as he talked about much longer ago. Let's talk about two characters that appear in almost all of your books, John Wheeler and Richard Feynman. In this book, as opposed to Quantum Labyrinth, where you explore the intersecting lives of Feynman and his advisor, mentor, John Wheeler, it's quite surprising in some sense that they were also figures that played a role

in the Everettian are many worlds interpretation-type multivers. And I've had on Sean Carroll for his book. And so he talks about the many worlds at that point. But what is, in your mind, the greatest strength of the many worlds interpretation, MWI, and perhaps some of its lacunae failures deficiencies. And I'll share some of mine as an experimental physicist when you're done. I've been really interested in the life of John Wheeler,

and it's correct that he appears in a few of my books and Feynman as well as his student. And it's very interesting that some of her histories, which I mentioned in the quantum labyrinth, in some ways anticipates Everettian ideas, but it's different because you're not detecting, you're not detecting these branches. These branches are things that are happening internally, whereas the Everettian view is that somehow Hilbert space becomes real, that this abstract quantum space is something that not just quantum systems have, you know, live in, but also people live in, you know, which is kind of an interesting idea.

Wheeler was trying in the 1950s to come up with a quantum theory of gravity, and that was based on Feynman's idea of some of her histories. So he wanted to be able to come up with a universal wave function or universal quantum state of the universe, and then show how that kind of devolves, we would say, these days decoherers into the classical universe we see. So that was Wheeler's ambition. And he said, as I mentioned in my book, Charles Mizner, the job as a graduate student, Mizner was assigned the task of, okay, well, why don't you come up with a quantum theory of general relativity, just like Feynman did for electrodynamics, I'm sure it will only take a few months. Just, you know, write down the same types of Feynman diagrams and stuff for GR,

and then you can have a quantum gravity. You know, that will be, you know, a quick project for your PhD. And, you know, Mizner, of course, discovered that he could only really start doing that. He really didn't make much headway, but that was Mizner's thesis. But then Mizner enticed Everett to get involved in kind of a similar project. And Everett attended a talk by Einstein about, you know, that related to some of the problems with quantum physics. And one of the issues had to do with the fact that at that time, at least, we imagine that you need a human observer to collapse the quantum wave function or quantum state down to, you know, what we see is, classical system. And Wheeler's problem with that was that you couldn't really have a human observer

look, stand outside of the universe and collapse it that way. Later, Wheeler became interested in this idea of the participatory universe in which astronomer in the present day observes the past of the universe and by observing the past retro causally, using retrocausory, causality collapses the universe. And that was, Wheeler thought that was a satisfactory solution to that problem, that someone from the future can cause quantum collapse in the past, which is kind of an interesting idea. I don't quite buy that, but interesting solution. But Everett's solution, inspired by Einstein's talk, where Einstein asked, could a mouse collapse the wave function, like our tongue in cheek, Everett said, well, wait a minute, humans are part of the

universe too. Humans are quantum systems. So really humans should live in Hilbert space, just like quantum systems live in Helbert space. And there should be a universal wave function that just evolves deterministically using the Schroninger equation, you know, Dirac equation and so forth, just keeps going and never collapses. And just we would branch in our conscious existence. every time as a quantum measurement, we would observe all of the outcomes. So it would be seamless. There would not be a special function

to collapse the wave function, but everything would operate on the basis of the Schroenger equation and other similar deterministic equations. So there's a certain elegance to that, and I see that. I see that the idea of Hilbert space is pretty weird.

So the question is, is adding the fact that people bifurcate in Hilbert space, along with other things being stretched out or blended in Hilbert space, much weirder. I can see a case for the fact that we don't experience that as, you know, an argument against that. But at the same time, I think that Hilbert space, the idea that electron can live, you know, multiple dimensions in Hilbert space, and evolved that way is pretty weird. And it doesn't seem beyond plausibility that human consciousness can be spread out

over different dimensions in Hilbert space as well. When I look at, and I had this conversation with Sean Carroll, who's one of the most popular, you know, expositors or most noteworthy expositors of the many worlds, he almost assumes to me that it's a done deal, that it's the correct interpretation, that everything else Copenhagen is to be dispensed with.

And you go into great, you know, kind of excellent detail about how Wheeler was very much influenced by Boer and very much reluctant to give up. You know, it almost reminded me of when LaMaitre allegedly told Einstein about the Big Bang solution of, you know, GR. He said, you know, math is okay, but your physics is atrocious. And it seemed like Wheeler reacted that way. Sean and others are reacting almost the opposite. And so I wonder, you know, and I asked him this, what would it take to actually falsify, you know, the many world's interpretation? Is it possible that you can do an experiment that would reveal this branching ratio? And I should also say that it's not at all clear to me that, you know, it's always presented as Schrodinger's cat has, you know, a binary outcome living and dead because that's the way we perceive cats.

normally, but in fact, in any quantum system, there's an infinite superposition, as well as for the cat, you know. So to say that it's living or dead is to kind of impose upon an artificiality in this artifice that there's only two outcomes of every quantum measurement, which is nonsense. So I believe that when I asked him about this, he said something like, well, the rate of branching into different worlds, you know, is extremely short. You know, it's a billionth of an attosecond or something. It's not out of the question. It could be measured. Who knows? But the point is, is there any observable signature that could distinguish between the many-world scenario and, you know, the Copenhagen interpretation? In other words, are we just debating, you know,

the taste of things? And, you know, as the French say, you know, the Latin say, the Romans say, de gusto is non-disputandum. So taste is not debatable. So let me ask you, can we falsify many worlds, branching ratios, etc. Is there any crisp experiment in the words of Popper that could be done to distinguish these two different interpretations? So I think you've kind of hit the nail in the head that the biggest problem with many worlds is this idea of the branching ratio, also known as the Bourne Rule. And we always use the example of Schrodinger's cat.

It's kind of binary like live or dead. And then you have, you know, spin states could be up, you spin up or spin down. But then you say, hey, wait a minute, like an electron could be, you know, if you have some kind of marker, it could be like 0.01, 6, 7, you know, nanometers from the marker or something else. And then you have this continuous system. And then you say, okay, the probability of it ending up like that is a certain amount. And then you say, wait a minute. Like how could many worlds get that branching ratio if it's like point, you. you know, some tiny fraction of, you know, of the thousands or something like 0.003, you know, 3003, like do you have all these, you know, multiple possibilities out there? Do you have thousands of branches? Do you have millions of branches? Trillions of branches out there? And somehow, you know, the many worlds gets them exactly right, right on the nail that the probabilities end up that way.

So that I find a little far-fetched, but philosophers of physics have been trying to tackle that using the idea of betting theory that somebody would make a wager that, you know, of something ending up a certain way, and based upon their knowledge of quantum physics and the Bourne Rule, the wager would end up being similar to the outcome, and therefore they would get a certain reward, and that would weigh the chances that they would pick that outcome because they would want the reward that would exactly match up with the outcome of the born rule. So it would be kind of a gambler's method of guaranteeing the born raw. And I don't know if I quite buy into that. But to answer your question about falsifiability, and I think the problem is that decoherence, which is the idea, which is the

idea that the environment influences a quantum system can only get you so far and can't quite explain why in certain cases you almost immediately or instantly get, you know, a single outcome instead of a blur of outcomes. And the big argument to me in favor of many worlds is that every other method for spontaneous localization or localization, you know, any kind of experiment idea of, you know, that the environment will localize things precisely has come out short. So I almost see, you know, many worlds as kind of a default solution if you can't really explain things dynamically. But I'm kind of thinking that someday maybe there'll be a successful way to explain quantum collapse dynamically. We haven't been able to do that yet.

but in that case, many worlds will be ruled out. So it's more like it's the default way of explaining something if you can't find a dynamical way to explain it. And I would extend that to cosmology. If somebody could find a way to exactly explain why there is only one universe and that there's only one inflation event and rule out everything else, or if someone could come up with a dynamical way to say, hey, there's only one viable string theory vacuum and that we can rule out all the others, then, you know, these multiverse ideas would eventually disappear because people wouldn't have to consider other possibilities. But the reason they're out there is because we say, okay, without a dynamical method, maybe, you know, as maybe a last resort or, you know,

an alternative, we can say that there's a range of options out there and that we explain, you know, one of them because it's the one where we're here, but the other possibilities are out there and isn't this an elegant way in the absence of dynamical methods to come up with a solution? So it's kind of a default way of explaining something if you don't have a dynamical solution. 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 Google Fi Wireless plans today. Plus taxes and government fees. Google Fi Wireless is not subject to data traffic deprioritization during times of high network usage. You know, we touched upon a few things and then answer, including, uh, inflation, which we're going to spend some time on, is near and dear to my paycheck. That's how bread is buttered around the Keating household. But you also mentioned, you know, in the context

of, you know, quantum collapse, et cetera, we touched a little bit upon these major questions. And I think one of them is explored in this book. It's a really unsung hero of physics. I don't know. You're the expert. Has anyone ever written a biography of Bob Dickie? Yeah, I do think he's an unsung hero. I played a role a few years ago in honoring him at Princeton. We set up a historic plaque, and Kip Thorne was there. Kip Thorne was very much, wasn't a student of Dickey, but he was very much influenced by Dickey. Because Dickey was the experimentalist with some theoretical ideas, who was kind of a counterpart to Wheeler's theory.

And the two of them, I found out relatively recently. I kind of made a bet on observations of, you know, gravitational lensing. And Dickie thought that eventually solar eclipse experiments and so forth would reveal that general relativity has some, you know, is not completely correct. And that instead of the gravitational constant G, you have a scalar field instead, a changing scalar field, which was what we called Brands-Dickey. Jordan models and Dickie really believed in that. So he didn't really believe in conventional GR, which was kind of ironic because he helped interpret the CMB. But his interpretation was that

there was a previous version of the universe that collapsed and that that produced a big bang and that the CMB was leftover noise from the previous universe. And I credit Peebles for all. also interpreting it as a single Big Bang singularity as an opportunity. Yeah, the Dickie paper is published as a companion to the Penzias and Wilson discovery paper. And Penzias just passed away at age 90. We should recognize his influence. And that paper never mentions the Big Bang once. There's no mention of it.

They talk about a cyclic, you know, previous cycle and stuff like that. So people may have had influence in later years. But for that, you know, companion paper, which they were trying to stake their claims for, you know, discovering you and it's really kind of tragic in some ways because Dickie did measure the CMB. He just forgot about it or he forgot, you know, the level that he had measured in the 40s or 30, 50, you know, 40s and 50s and forgotten about the fact that, you know, this could be a very, you know, easily, and they were trying to measure it on top of Jadwin Hall or back in the early 60s when he made the famous call into his boys that they've been scooped.

But the reason I bring him up is because he, you know, he kind of pointed out a lot of these planted these, you know, he's kind of like planting talisman along the path that would eventually influence Gooth, you know, to have his spectacular realization in double-boxed letters in his lab notebook, why a theorist needs a lab notebook is beyond me, but he did as a struggling postdoc at Slack. And he was influenced by this, you know, kind of fine-tuning issue. And I wonder if you can talk about that, that Dickie had alerted him to, which is really about the flatness of the universe, if I remember correctly. Dickie was trying to make the claim that, you know, the universe is special and we can't really explain it dynamically, the flatness of the universe.

And, you know, and, you know, the fact that Omega is so close to zero, which is, you know, the constant telling us what the curvature of the universe is. And if Omega deviated, even though. slightly from zero in the beginning, it would be huge today and the universe would be so curved that it wouldn't have evolved in the same way. So these are really interesting questions that Bob Dickey pointed out. And it's related to the isotropy problem in the universe, why is the universe so isotropic? And then finally, Mizner was the one who brought up the horizon problem. Why is the universe, the cosmic background radiation so correlated across different sky directions. And these first led Mizner to develop what's called the Mix Master model of the

universe. And I talk about that in my book, that people were thinking inspired by Wheeler about all these weird alternative versions of GR, and including ones in which instead of a uniform Big Bang, you have the universe expanding in two directions and contracting in a third direction, and then kind of changing directions, almost in a chaotic way of contraction and expansion in something that almost resembles tossing dice or flipping a coin because you go through maybe three cycles one way, and then suddenly you go through like 18 cycles. And this Mixmaster model was changing directions, and it's named after a blender, you know, like blending the universe together to try to get this uniformity, to try to get all the radiation at the same temperature. And it was a valid solution to

GR, but not the standard solution. It wasn't the Friedman Robertson Walker solution to the universe. These kind of stirred up interest in alternatives. And, you know, Dickie was involved in looking at alternatives to, you know, the standard Big Bang. And that, and Dickie, at some point, asked the question of what is the role of humanity in ruling out other alternatives? And that kind of led to, led Brandon Carter and others to kind of talk about what Carter called the Anthropic principle. So often the Anthropic principle is attributed not just to Brandon Carter, who coined the term in 1970, but also to Bob Dickie, who speculated earlier, like, what is the human role in ruling out other things? And the fact that life develops

at a certain phase of the history of the universe kind of places certain bounds on how the universe develops. You need a universe that's, you know, a universe that's, you know, a certain number of billions of years old, you know, to develop, you know, develop stable planets and to develop life and, and Dick you thought that was kind of an interesting coincidence that we live in a certain time of the universe and in a certain region of the universe and that that kind of can help explain some of the constants of the universe that they have to be a certain way. and helps resolve the fine-tuning problem because of the constants were different,

and the universe didn't last billions of years and only lasted hundreds of millions of years, that you would never have stable structures, such as stars developing, you know, sun-like stars developing, and you wouldn't have planets like Earth and you wouldn't have life, and then one would be able to talk about the universe.

So that was the beginning of what we call the Anthropic principle. Hey there, it's your captain again, exploring the multiverse with the brilliant physicist Paul Halpern. And I know that you've been interested in these incredible discoveries that we're hoping to make in experimental cosmology, which sometimes get hampered by these little objects here, micrometeorites. Small versions of this chunk of space dust that you can get yourself by joining my Monday Magic mailing list, which comes out once a week where I talk about the hottest, coolest science news, exclusive content, and giveaways. and you'll be entered to win if you go to Brian Keating.com slash list to win one of these space suckers,

and I hope that you'll enjoy it. And if you have a .edu email address, as Paul does, you can be guaranteed to win one of these guaranteed four billion-year-old piece of space rock called a meteorite. Go to Briankeeting.com slash edu if you have a dot edu email address. Enjoy it. For me, the kind of curious thing when we think about this is all the diverging sort of opinions, including the diverging opinions of the founding fathers of the inflationary universe and the bubble kind of cosmological implications that come from what's called new inflation

or was was called new. It's 45 years old now. Or 40 years old, you really can't call it new. It's not a spring chicken anymore. But let's talk about these two ideas. And I have two kind of things in mind from me that I've come upon in my research, but also in conversation with Andre Lindy. I haven't talked to Alan Gooth.

I keep meaning to do it. We've collaborated and had many wonderful discussions. But he told me he'd come on the podcast as soon as he's done cleaning up his office. So Alan said, as you quote in the book, essentially all inflationary models are eternal. In my opinion, this makes inflation very robust. If it starts anywhere at any time in eternity, it produces an infinite number of pocket universes. And Linday has said similarly, and essentially it's very difficult to find inflationary solutions that don't produce multiverses. But Paul Steinhart, I call him kind of the deadbeat dad of inflation.

He's denying paternity, and he kind of thinks this wretched Frankenstein. He regrets that he ever sired it or was responsible for it. And he says the following. He says in an oral history that you quote, any combination of properties that's physically allowed by the fundamental laws will occur an infinite number of times. Everything is possible. Nothing is preferred, such as the nature of the multidverse, which is a very nice name for saying what I call a theoretical disaster. And Paul's told me, and he's written it elsewhere, you know, the multiverse is not only dangerous for cosmology.

And not only is it dangerous for science in general, but he's called it a danger to society as well. How do we reconcile these things? They're all eminent scientists. Paul even has an alternative cosmology called the bouncing or cyclic cosmology, which we can talk about along with my friend and past guest, Anegis, Neil Turrock. It seems inarguable that the multiverse is concomitantly with inflation. Would you agree? I've interviewed Paul Steinhard. I interviewed him at a key period in his career for an earlier book.

I went to his office at Princeton, and I interviewed him about the cyclic universe shortly after he developed it. And I asked him, why did you develop the cyclic universe? At that time, it was called the Ac Pyrotic Universe. Apparently, there's some differences between that in the cyclic universe. As Justin Corey points out, the act pyrotic was the original name, and Corey was on the first paper, but not on the second paper. There are some subtle differences, but there are essentially the same. same thing. And I interviewed Paul Steiner and I said, why, as one of the founders of inflation, why are you developing this? And at that time, he said, well, we need to be open-minded. We can't assume that inflation is necessarily correct. So we need to have alternatives. So I think at that

point, he was a little bit agnostic about whether or not inflation is okay or not. But, you know, since then, he's really turned against inflation, and now this idea of multiverse being dangerous to science and anti-scientific. I don't quite see that, especially because if I were to explain to, let's say, somebody who's not in theoretical physics, the idea of the cyclic cosmology, and say one millimeter or whoever the amount is, away from us, there is another universe, which we call a a brain world in another dimension, and at any moment, it can collide with us, and it has collided in the past and will collide in the future. And it's just out there, just, you know, closer in the higher dimension, you know, than, you know, the length of our finger. They would say,

wait a minute, that's not science. That's just speculation. That's, you know. So it's hard for me to see why internal inflation is not science if we accept something like brain world models. To me, they're both delightful ways to take things that we do know about like GR, general relativity, and extend them and take things we know about like quantum field theory and extend them and kind of speculate about, you know, other possibilities. And I really like the idea that brain worlds have of explaining the weakness of gravity, the hierarchy problem, why gravity is so much weaker than the other forces,

by kind of imagining gravity kind of, as I see it, kind of exuding or spreading out along a higher dimension or being captured by a higher dimension. I think it's a really brilliant way to explain it. So I'm not opposed to brain world ideas. I think they're, you know, they should be examined. And I'm not opposed to internal inflation ideas, even though aspects of them are, you know, not completely testable. And of the two, I think eternal inflation comes more within the bounds of scientific rigor because there's so much evidence out there based upon, you know, analysis. of the CMB for slow roll inflation. And even Justin Corey, who was, you know, on the

Epirotic Universe paper, said at this point he thinks that almost everyone in the astrophysics community is a supporter of inflation, which means that they support eternal inflation because that's the most logical version of inflation. So he, not to say that he's broken with Steinhardt, but he's very much interested in, you know, standard inflation at this point. In the book, let's turn this now to my favorite subject, which is me, and the Bicep 2 instrument. So I created Bicep 1 with Jamie Bach and the late great Andrew Lang, my postdoc mentor back in 2000, hard to believe, 24 years and gone by. And it was later upgraded to Bicep 2.

And exactly 10 years ago when this episode comes out, most likely or a little bit before this episode comes out, March 17, 2014, so 10 years ago, incredible, people woke up to hear and read headlines in the New York Times, space ripples reveal Big Bangs smoking gun. And of course, this wasn't to be, as my book is called Losing the Nobel Prize, first book, my three, four books. And so it wasn't to be. Obviously, it went away, but there were immediately not only claims of detection of inflation, but also detections of the multiverse. So Max Tagmark in the Huffington Post wrote on that very morning, good morning inflation, hello multiverse.

And what the discovery would be the implications of it and how it would give rise perhaps to a new vistas in our understanding of reality. And then past guest Lawrence Krauss opine that this was not only the death knell of alternatives like the ecparodic or the, you know, colliding brains or cyclic models or Sir Roger Penrose's conformal cyclic model. But it was the end of the need for supernatural shenanigans. It was the end of God, basically. We didn't need God.

And it was interesting because also in a post by the disclosures. Discovery Institute, I think it was. There were, which is a Christian Apology website and, and, and with many eminent scientists and thinkers involved with it, some of whom have been on the show. But they said this is quite the contrary. This is, you know, evidence for the existence of God. And it kind of made me sympathetic to Paul Steinhart's viewpoint that, you know, anything that can happen will happen. How is this part of the scientific endeavor? So what do you say to people who make those claims, Paul? Well, I kind of remember

with those announcements and it was a very exciting time and I kind of remember even Paul Steinhart was kind of saying well, maybe inflation is right after all. So he kind of was kind of

becoming convinced too at that time. Later, of course, you know, of course he went back to saying, you know, that eternal inflation is not scientific, the implications of it, the multiverse implications. But there has been a serious quest for proving eternal inflation through the idea of bubble collisions. And I mentioned in my book about Herania Pira's and her team of Matthew Johnson and so forth, trying to look in the

CMB for scars of collisions of bubbles of other universes. And they had to have, you know, there are mathematical models out there that they're trying to perfect, trying to do simulations of collisions with other bubble universes, and trying, you know, very hard to look for a signature of the idea of eternal inflation and bubble collisions. And so far, it has, you know, there have been some hints of it, but nothing that's with statistical significance. And I think teams have also been looking for what are called polarization profiles, which is near and dear to your heart, of evidence of bubble collisions too. And so far nothing's been found with statistical significance. But it's possible in the future with even higher resolution

maps of the CMB and its polarization profile. And just for you viewers, light can be polarizing, in different directions, and that can provide evidence of, you know, early interactions and, you know, the effect of gravitational waves and so forth on the early universe. So that it's an interesting avenue of inquiry looking at the CMB, not just for temperature fluctuations, but also polarization differences, getting a little bit technical. No, that's fine. My audience is the brightest in the multiverse. Anyway, if people say, well, can you prove the multiverse or disprove it, I think the best, you know, it would be only one type of multiverse, but the best opportunity would be if they could find scars of evidence of bubble collisions in the CMBR. So I'm still holding out hope for that. Absolutely. And you quote from Hirania, and I want to make one point. She is on the.

external advisory committee for the Simon's Observatory, for which I serve as PI, principal investigator. And she's been a wealth of insight and knowledge. And part of that was born out of the Bicep 2 affair that we needed a check and balance to the exuberance that all scientists have when their work is, you know, is operating at the high stakes that we had with Bicep 2. And, you know, different types of pursuits are worthy of having an, internal kitchen cabinet, if you will, that we sorely lacked with Bicep 2. And in fact, we never even, you know, shared it with the results, we meaning me, including for collective punishment and blame, but, you know, John Covec, the PI of Bicep 2, especially, you know,

they shared it with Andre Linday, as you talk about it in the book, with my friend Chalin Quo going up there with champagne. And the video is still up on Stanford's, you know, YouTube channel. It's got three million views. I'd kill for some of those some days on my videos. But it's still there. And I've talked, you know, Chalind's a great friend. And there was almost no, you know, comeuppance that that happened. I mean, Bicep continues creatively. It went from Bicep 1, Bicep 2, Bicep 3.

Now it's Bicep array. And the lessons that we learned were we can't only seek to confirm that inflation is true. We need to also have guardrails against the possible imprimatur of inflation being mimicked mocked by dust grains, microscopic grains of dust. that are actors in you know inflationary interlopers and by the way I give away the villain of my book losing them about probably give away little tiny meteorites not micrometeights but I give away meteorites to anyone who's got a dot edu email address gets a meteorite if they live in the USA so you get one paul because you have one dot edu email address but go to brian kating

dot com slash edu and you'll get one and if you don't have an edu email address You're not fortunate enough to be in the academe as Paul and I are. You can take your chances. I give away one to randomly to have signer-upper at briankeating.com slash list. So anyway, that's my plug, but also for Hierania, serving in such a valuable role, as someone who's really trying to make sure that we are most suspicious, as Feynman said, that we are the biggest fool.

And even though she has a horse in this race, as does Paul Steiner, who is a past member of the External Advisory Committee. We've got experimentalists, theorists, data analysts, and not just people like Alan Gooth reading over the preprint. So she says in this paper when you talk about Lightbird, which is a successor space experiment, NASA, Jaxa collaboration, very, very tangentially involved with it. So my students are involved with it. She talks about the data from the Simon's Observatory, which were scheduled to get first light in April, Paul. It's very exciting. Jim Simon's 86 birthday is coming up.

I promised him that present back in 2015 when we pitched him, the idea. She talks about the bubble collisions, and I want to talk about that eternal inflation. She says, I think the chances are slim, she said to you, because nature has been so kind to us to see a signal. But these tests should be done because the implications of the theory are so monumental momentous. There may be another avenue to test the physical understanding of the bubble nucleation process itself through a completely different method on part of consortium, this quantum simulator for fundamental physics. As one of our wrap-up questions today, I think about these bubble universes, they're really kind of, of not that different from, you know, kind of the island universes that people once thought galaxies were, right? Emmanuel Kant and others hypothesized that the Andromeda, you know, nebula or something eventually,

we call the adramina nebula, the great spiral nebula, is actually a galaxy. And these galaxies, as you've pointed out many times, you know, Einstein thought the Milky Way was the universe. And effectively it is, we're kind of bound, captured, you know, and beholden to the cruelty of the speed of light being so slow. But tell me, Paul, if there were bubble universes, if there was, you know, as Philip K. Dick said, there's a universe right next door, I hear it's pretty cool. If there was a universe, a couple of, you know, light years away from our universe, I've been wondering about what would be the implication for things like Mock's principle in that we believe that these, you know, kind of inertial, an inertial reference frame is one at which all the fixed stars and you can replace fixed stars with fixed galaxies.

But would that not be invalidated in a scenario where there's bubble universes literally one light day away so that tomorrow Hirania may celebrate its discovery? Is it not possible that Mock's law could be invalidated if there's even one such thing? Wouldn't that inviolate Mach's principle, Lorenz invariance, all sorts of things? Mach's principle is interesting from a historic point of view. It's basically Mach's speculated that inertia is the result of the distant stars or the combined influence of, you know, massive objects in the universe. And Einstein was motivated by Mach's principle to develop general relativity. But Einstein soon found out through a paper by the sitter's first paper, the decider's first paper,

the decider cosmology that you can have an empty space and you still have, the sitter showed you could still have inertia without having matter and kind of proved that he took a point mass in this paper and said that the point mass would be at rest and it didn't, it didn't matter, no pen intended, that there was no matter in the universe, you can have a vacuum universe and still have inertia. So that kind of, he kind of disproved Mock's principle. And Dickie, speaking of Dickey, was trying to revive Mock's principle. And I think Dennis Shama and other cosmologists tried to come up with alternatives to GR.

But if you believe in GR, GR does not address Mock's principle. So the idea of bubble universes would not, I don't think, have any bearing on that. But it would call into question the idea of the special. specialness, and this is, I think, Paul Steinhard's big contention, the specialness of our young universe, because you wouldn't really be able to use inflation to do fine-tuning anymore. You'd have to use something like the Anthropic principle and say, well, all the bubble universes are just not suitable. The cosmological constants are too high. They expand too quickly. Or, you know, strength of gravity is not right. Strength of electromagnetism is not right. We're in the

Goldilocks universe, we're in the one that's just perfect for development of structure and the development of life. And that becomes more of a philosophical argument, which some people don't really like. Yes, they definitely don't. Maybe the last question, and I was reading the book, you know, kind of Princeton always plays a big role in everything in cosmology and quantum mechanics. It's impossible for the, you know, the viewers, et cetera. to not notice that. But I was reminded of past guest Juan Maldesana's heroic work in the realm of, you know, kind of ADS-CFT and sort of the response that was leading to a unification of concepts as disparate as, you know,

the quantum fields at the early universe and the, you know, extremely universe by invoking this, you know, anti-desitter space, but also ranging to things like holography, et cetera. I wonder, could you see, could there be a similar rosetta stone that would map between the microphysical landscape, which governs string theory, and the macrophysical multivers? Is there some lookup table? Is there some rosetta stone, as I say? Is that a possibility to have a Maldesamian unification between these two? two inarguably different skills.

Well, there's so many different string vacua, but if you believe in string theory, and some people do because it's, you know, a finite theory, quantum finite field theory. So that's, you know, immediately a strong argument for the idea that things aren't point particles, because then you get a finite theory. So once you say, okay, things are finite strands of energy

rather than point particles, let's explore the possibilities. You immediately are led to the idea of a 10 or 11-dimensional universe. That immediately leads you to compactification. And then as we know, there's 10 to the 500th power ways that you can compactify, and each of them implies a different version, a different quantum field theory of the 3 plus 1 dimensional universe. So the compactification tells you what physical.

goes on in our universe that we observe. And one of them is, or at least one of them is the standard model, we hope. But there's an argument that maybe, and I don't know if some advanced computer can somehow someday go through all those possibilities. But there's an argument that a large chunk of them would not produce anything that's viable and that only a very small subset would even lead to, for example, eternal inflation or inflation, and most of those models would just fizzle out. So if you could somehow go through all of those possibilities and say, okay, there's a small subset that are viable, and those produce, let's say, different variations, different versions of the universe and kind of an eternal inflation theory, and that most of those have, you know,

cosmological constant, which is not viable, then you can narrow it down further. So the idea is to keep narrowing it down and narrowing down until you get a universe which has the standard model, a particle physics, has a very small cosmological constant. And you say, okay, that's our universe. We got it.

And we live here, so that's why we're here. And now we can say string theory is right. So that's the idea in the far future for unifying everything through string theory, internal inflation, enthrobic principle, and then you get our universe. Maybe wishful thinking, but some people believe. Paul Halperin is a professor of physics at St. Joseph's University and the author of 18 popular science books, including maybe his 19th being written right now. His books include flashes of creation, the quantum labyrinth.

Dys, Strudinger's and Strangeners cat, and Synchronicity. He's a recipient of a Guggenheim Fellowship and is a fellow of the American Physical Society, lives near Philadelphia, Pennsylvania, and recently published this delightful, delicious alluring book, the allure of the multiverse, extra dimensions, other worlds, and parallel universes, which tells the epic story of how science and society culture became besotted with the multiverse and the controversy surrounding it. Paul, I can't thank you enough for your appearance today. It's always such a great time to be with you and spend so much of your valuable time. Thank you so much, Paul. Thank you, Brian. It was a pleasure being on your show. Thank you. Own it all. Pay off your home, travel for life, drive a Ferrari. In celebration of the

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