What came before the Big Bang?

Daniel and Kelly talk to Phil Halper about the many mysteries of the origins of the Universe. See omnystudio.com/listener https://omnystudio.com/listener for privacy information.

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

• 0:00Daniel Whiteson?

  This is an iHeart Podcast. Guaranteed Human.

• 0:08Speaker 01

  Every small business owner has that one moment that could have broken them, but remarkably, it didn't. Hi, I'm Kathleen Griffith, co-host of The Unshakeables, along with Stevie Barron, CEO of Chase for Business. We have more incredible stories of overcoming the impossible still to come in season three. Listen to The Unshakeables wherever you get your podcasts and learn more at chase.com/podcast. JPMorgan Chase Bank, N.A., member FDIC. Copyright 2026 JPMorgan Chase and Company.

• 0:45Speaker 02

  Hey, I'm Niall Rogers. This fall, I'll be driving across the country, meeting some of today's coolest and most fascinating artists. We'll explore the stories before the moments that changed everything. Because every musician remembers the moment where it all began. Experience Before the Moment, a Lincoln original series on the iHeart Radio app, YouTube, or wherever you get your podcasts.

• 1:24Daniel Whiteson?

  Everybody wants to know where we came from, how we got to be here. That means understanding the events that set in motion your life, all of its ups and downs. Historians can tell you about the journey of your ancestors, how it shapes your culture and way of life. Anthropologists can tell us the story of humanity itself, why we walk on two feet, and how we got to be so darn smart. But physicists can take us deepest into the past, even beyond the chaotic formation story of our solar system or of the galaxy itself. Incredibly, we can look billions of years deeper into history, to a time before there were galaxies or stars, when the universe was filled with a hot, dense plasma.

• 2:10Daniel Whiteson?

  But then we hit a wall. Beyond 13.8 billion years ago, the universe was opaque and all photons emitted before then have been lost, reabsorbed. And beyond another 380,000 years, the universe was so hot and dense that our theories of physics no longer apply, like trying to explain steam using fluid dynamics. Our curiosity, of course, is limitless, and so we desperately want to know what came before. What is the original fundamental context of the universe? And what does it say about those of us scratching out a living on a tiny dot of rock? Today, we'll take a tour of the current ideas about

• 2:52Daniel Whiteson?

  the earliest moments in the universe, if there even were any, and think about what we might learn in the future. Welcome to Daniel and Kelly's Extraordinary Ancient Universe.

• 3:16Kelly Weinersmith?

  Hello, I'm Kelly Wiener-Smith. I study parasites and space. And today, we're talking about where it all began.

• 3:22Daniel Whiteson?

  Hi, I'm Daniel. I'm a particle physicist, and I love physics because it subsumes every other question in science.

• 3:29Kelly Weinersmith?

  So today, we're talking about like, what happened before the Big Bang? Do you think, will we ever get solid answers where we're like, bam, we don't have to debate this anymore? We've got it figured out? Or is this the kind of thing that we will always be tinkering with? I think either answer is okay and exciting, I should say.

• 3:45Daniel Whiteson?

  Yeah, I don't think there's going to be a moment where we're like, yeah, we figured it out. And here's the rest of the grant money back, by the way. Nothing else we're curious about, and we don't want to think about it anymore. No, I think we're always going to wonder, what about this? What about that? Where did that come from? Why not this? Why the other thing? I think it raises a lot of philosophical questions, just thinking about the origins of the universe, but also wondering which answers are acceptable, which ones we go, hmm, yeah, that makes sense. Let's move on. And which ones we're like, wait a second, why that? I think that reveals a lot about our humanity and our curiosity, which is one of the reasons why I love this topic so much.

• 4:21Kelly Weinersmith?

  Yeah, and we've talked on past shows about why there are some explanations we get where we're like, oh, that makes sense. We don't have to dig any deeper. And how that can like, sort of send us down the wrong path, actually, by just, you know, oh, that makes sense. No more questions needed.

• 4:34Daniel Whiteson?

  Exactly. And whether aliens would find this answer satisfactory or not.

• 4:40Kelly Weinersmith?

  I know, Dan, the constant question that is ringing in Daniel's mind. What would the aliens say?

• 4:47Daniel Whiteson?

  Exactly. Well, you know, they're not here to speak for themselves. So I feel like some pressure to speak up for the aliens.

• 4:52Kelly Weinersmith?

  I'm so glad that they have an advocate in Daniel Whitehead.

• 4:55Daniel Whiteson?

  Well, look, if there are aliens all over the galaxy, then they are literally the silent majority, right? Because nobody's speaking for them. So yes, I stand here to speak for the aliens. But today, we didn't have an alien on the podcast. We instead had a human being who thought a lot about cosmology and how to communicate it to the public. Because we wanted to dig deep into this question of what is the Big Bang and what came before it? And so before we get to that interview, let's hear what folks on the street, by which I mean podcast listeners who volunteered, think came before the Big Bang. Here's what folks had to say.

• 5:32Speaker 04

  Our understanding of physics breaks down with the Big Bang, but one idea is eternal inflation.

• 5:38Speaker 05

  It could be that there was something that was just so different from our current experience or understanding that we don't even have the language to describe it.

• 5:46Daniel Whiteson?

  According to Postafari in scripture, the great flying spaghetti monster made us. All hail the cosmic cannelloni.

• 5:57Speaker 06

  It's just all theories, I guess. At the singularity, there was no spacetime, thus no time, no causation, no before. But how can there be an after without a before? That's like asking what, no what up the no what the pole? I don't think there's an answer, but prove me wrong, please.

• 6:21Speaker 07

  Nothing came before the Big Bang because, as I understand it, it's when time started.

• 6:29Daniel Whiteson?

  All right. What a wonderful spectrum of answers as usual. Aren't our listeners wonderful, Kelly?

• 6:33Kelly Weinersmith?

  Yeah, obviously, obviously.

• 6:37Kelly Weinersmith?

  Clearly, they have a good sense of taste for podcasts. Exactly. But we've got a real professional on today to tell us about the many theories, actually, for what came before the Big Bang. I think we don't even manage to get to all of the ones we had thought about because there's a lot of them out there. So instead, we dug deep into about two of them. And let's go ahead and jump in.

• 6:58Daniel Whiteson?

  It's my pleasure to welcome to the podcast Phil Helper. He's a Fellow of the Royal Astronomical Society and a science popularizer. He's the creator of the popular YouTube series Before the Big Bang. His astronomy images have been featured in The Washington Post, BBC and The Guardian. He's one of the rare breed of pop physics authors that also has deep credentials in physics. And together with cosmologist Nayesh Ashfordi, he's the co-author of Battle for the Big Bang: The New Tales of Our Cosmic Creation. Phil, welcome to the podcast.

• 7:29Speaker 08

  Thank you. Great to be on.

• 7:30Kelly Weinersmith?

  We're excited to have you. And if I can get the ball rolling, so like my, for my PhD, I studied fish. And I really like things that you can have in the lab and you can see and manipulate. And studying something like the Big Bang, which happened so long ago, sounds really difficult. What, what got you interested in this question in particular?

• 7:49Speaker 08

  Well, who cannot be absolutely fascinated by the origin of the universe? I mean, I think that's deeply ingrained in

• 7:57Daniel Whiteson?

  Right.

• 7:58Speaker 08

  in human nature. I mean, it's no surprise that every culture, well, maybe not every culture, but many, many cultures have an origin story, something where they can point to and say, this is how the universe came to be. So I think we all have that deep curiosity in us. And the beauty is that science has actually found a way to probe the very origin of the universe. And that's cosmology. So why not follow, follow us down that rabbit hole and see how far it goes?

• 8:29Kelly Weinersmith?

  Amazing.

• 8:31Daniel Whiteson?

  Well, I like how you appeal to our innate curiosity. But I think in the end, there is something subjective, right? About what you find exciting, what you find interesting, what questions you think are worth exploring. And so, you know, some of us are excited about fish guts and some of us are excited about the whole universe. It's all valid for sure.

• 8:52Kelly Weinersmith?

  I can see the fish guts in front of me. I like that.

• 8:55Speaker 08

  I have actually published a paper on fish.

• 8:58Kelly Weinersmith?

  Oh, yeah?

• 8:59Speaker 08

  Scientific journal. Yeah. Yeah. So I'm interested in fish as well.

• 9:03Kelly Weinersmith?

  OK, good.

• 9:04Speaker 08

  Literally, it's about fish pain.

• 9:07Kelly Weinersmith?

  Oh, that's an important topic.

• 9:08Speaker 08

  I think so, yeah. We tried to show that the case of fish pain is stronger than than some people think.

• 9:14Kelly Weinersmith?

  Yeah.

• 9:15Daniel Whiteson?

  Well, the thing I love about the Big Bang is that it explains everything. Like, literally, we're going back to the beginning and trying to find the cause of, you know, planets and life and fish guts and Kelly and everything. So it's all inclusive. But something we have to clear out before we dig deeper into theories about what happened before the Big Bang is what we mean when we say the Big Bang. And in your book, I really appreciated that you attacked this head on. You were like, look, there's a lot of confusion about what this means and cosmologists aren't even always consistent about what they mean by the words. So can you give us a clear and crisp definition of what we mean when we say the Big Bang?

• 9:54Speaker 08

  Well, the answer is no, I can't because there's more than one definition of the Big Bang. And that's kind of the whole problem. People mean different things when they say Big Bang. But what we can do, which I hope will be really helpful, is to explain the different meanings. And then people might try and infer which meaning is being used in which context. So we sort of highlight two definitions of the Big Bang. So one is that the Big Bang is a theory that says the universe evolved from a very hot dense state. So it was different in the past, very different in the past than it is today. So it was very hot, very dense, highly curved. And that's very, very different to the sort of cold sparse universe we see today. So that's one definition.

• 10:38Speaker 08

  We call that the hot Big Bang.

• 10:40Daniel Whiteson?

  And that's what scientists mean when they refer to the Big Bang. Because we know the universe is expanding and getting less dense as time goes forwards. But we can also run the clock backwards and figure out that it was more dense in the past. And if we run it back 13.8 billion years, we get to a very hot and very dense state. And that's it. The hot big bang doesn't go any further than that because it can't. That state is so hot and so dense, you'd need quantum gravity to predict what happens before that. So it doesn't go all the way to a singularity. It can't without quantum gravity. So it doesn't tell us what happened before or how time began. It assumes that initial state and explains what happens afterwards as time goes forward.

• 11:24Daniel Whiteson?

  And it does it very well. And there's a lot of experimental evidence for it.

• 11:29Speaker 08

  Another definition, we call the big bang singularity. So that's an idea that says the universe started in a state that's infinitely dense, infinitely hot, infinitely curved, and that marks the beginning of time. So there is nothing before the big bang.

• 11:46Daniel Whiteson?

  And this idea, the big bang singularity, is what most people think of when they hear the phrase big bang. This takes that hot dense state from 13.8 billion years ago and extrapolates it even further backwards in time, but ignoring quantum mechanics. It says, if we just account for gravity, what would happen? So you get a singularity. It's a collapse. That's like how general relativity predicts a singularity inside a black hole, which also ignores quantum mechanics. So we don't really believe it. So the big bang singularity is an extrapolation past what we know, using an approximation of quantum gravity that we know is wrong, which ignores all of the quantum effects. And there's no experimental data for this extrapolation. It's all very speculative.

• 12:29Speaker 08

  Now here's the interesting thing. We did a survey of physicists. We went to a conference in Copenhagen, very large conference. It was interdisciplinary. We had theorists, we had observers. We had like numerical relativists. We had people working in quantum gravity, all kind and some of the leading figures in the field. And we asked various questions about controversies within physics, such as what's the right interpretation of quantum mechanics? What's the best candidate for quantum gravity? What do you think dark matter is? And we got consensus on almost nothing.

• 13:06Speaker 08

  I can't think of any topic where we got 50% for any one thing.

• 13:10Daniel Whiteson?

  Wow.

• 13:10Speaker 08

  Except one, one exception. And that was, how should we define the term Big Bang? And the consensus was that it should only be defined as this evolution from a hot dense state. So the idea that the universe began at the Big Bang, or there was a singularity, is not perceived as the way we should understand the Big Bang. That is a theoretical extrapolation that most people don't trust, I would say.

• 13:37Daniel Whiteson?

  And let's dig into that a little bit more. Like, we have this theoretical extrapolation, the Big Bang singularity, as you say, which might predate the hot, early universe that you described as the hot Big Bang. And that's very speculative, but we have a lot of evidence for the hot Big Bang, right? When we say the universe was dense and hot 13.8 billion years ago, that's not speculation, that's something we have on fairly solid grounds, right?

• 14:03Speaker 08

  That's right. There's, I don't think there's any serious doubt about the hot Big Bang. So that's very well established. We've got lots of independent lines of evidence for that. People will probably be familiar with, you know, the expansion given by the redshifted galaxies. They've got the cosmic microwave background, the abundance of light elements. And there's various properties of the cosmic microwave background that we should see if the Big Bang had happened, and we see them. So I don't think there's any doubt that there was a hot Big Bang. But the observational evidence stops there. We can't have observational evidence of a singularity. They are sort of hidden from us if they were to exist. But I think most physicists would say they don't really exist. They're just a part of our physics that breaks down and we need better physics.

• 14:47Speaker 08

  And that will sort of get rid of the singularities. But how to do that is an open question. And what would replace a singularity is where all the debate is. That's why we call our book The Battle of the Big Bang. Because once you concede, okay, we don't really know the universe began with a Big Bang singularity. It might have had a prior state. Okay, so what was that prior state? And that's the battle, because there's all kinds of ideas out there and no one knows which one is right.

• 15:13Kelly Weinersmith?

  So for the biologist, if I were to be floating in space. And I was observing the big bangs of the two different varieties happening. What would I be seeing in a hot big bang? And what would I be seeing in a big bang singularity?

• 15:26Speaker 08

  So in a hot big bang, uh, well, I think the name kind of gives you a clue. It's very, very hot and dense, basically. But you also, you know, as you go back in time, it's a bit like looking at the sun. You know, if you look at the surface of the sun, you can see that it's about 5,700 Kelvin. But you can't, it's opaque, right? If you were to go through it, all the photons would be bouncing off the materials. You couldn't really see very far. It'd be like a fog. So that's the sort of hot dense state.

• 15:57Daniel Whiteson?

  And to clarify, you're saying that the whole universe was hot and dense? Like the entire universe was 13.8 billion years ago, something like the inside of the sun is now. And photons made inside the sun get reabsorbed almost immediately, which is why the sun is opaque. You can't see through it. So it's not a great view.

• 16:17Speaker 08

  Now, the singularity, again, most people would say it's just a part where the math breaks down. But, but the description involves, you know, there was what's called a curvature singularity. So here, the temperature would literally be infinite.

• 16:30Kelly Weinersmith?

  So it's hot, too?

• 16:31Speaker 08

  It's also hot. Yes. Yes.

• 16:33Kelly Weinersmith?

  Okay.

• 16:34Speaker 08

  Yeah, it would be hotter.

• 16:36Daniel Whiteson?

  Hotter big bang, yeah.

• 16:37Speaker 08

  The hotter big bang.

• 16:38Kelly Weinersmith?

  Wait, so the hot big bang is not the hottest of the big bangs?

• 16:40Speaker 08

  No, it's not the hottest.

• 16:41Kelly Weinersmith?

  Oh, good naming job, guys.

• 16:43Speaker 08

  It's, but it is hot.

• 16:44Kelly Weinersmith?

  All right, so okay.

• 16:45Speaker 08

  But no, but we'll come, we'll come to what might have come before the big bang. And that could have been something very cold.

• 16:51Kelly Weinersmith?

  Okay.

• 16:52Speaker 08

  So, yeah, that's to do with something called inflationary cosmology. So if we believe that story of the big bang, then actually the universe is very cold before the big bang.

• 17:02Daniel Whiteson?

  All right, so we have this scientific conception that the universe is cold and sparse now. And we run the clock backwards. We get to a hot dense state 13.8 billion years ago. And the big question is, what came before that? Where did that hot dense state come from? We know a lot about that state and its evolution from that point to now, but not a lot from before that. That's the scientific conception of the big bang. But I think if you talk to people in the The general public and you ask them about the Big Bang, they mostly think about the Big Bang singularity. They think the universe started from a tiny dot that exploded into empty space. Why do you think there's such a persistent gap between the scientific view and the popular view? I mean, you work on both sides of the aisle.

• 17:44Speaker 08

  Yeah.

• 17:45Daniel Whiteson?

  Why do you think there's been a disconnect there?

• 17:47Speaker 08

  Well, um, I think there's a couple of reasons. One, when you do an animation and you know, I've got YouTube videos where you're trying to animate the Big Bang. You kind of, it's hard not to draw a bit of light exploding outwards, right? Because that's how you're going to animate it. So it's hard for people to not have that visualization, which is, you know, sort of a rough approximation, but it's not precise in their head.

• 18:13Daniel Whiteson?

  And I want to be clear here that it's not precise because it implies that the universe was empty, that a dot of matter exploded into empty space. This is misleading because the universe was never empty. Matter was always everywhere. If the universe was infinite, then matter was infinite and then expanded everywhere simultaneously. If the universe was finite, then it was small, but still always filled with matter. There was never a tiny dot exploding out into empty space.

• 18:42Speaker 08

  But the other thing is, I think two things happened at the same time, roughly. In the mid 1960s, we got the evidence now clear that there was a cosmic microwave background. That's the afterglow of the Big Bang. It was a very hot surface and then it cooled down into microwaves as the universe expanded and stretched. So it stretched that light into the microwaves. And that was very clear evidence of the hot Big Bang. At the same time, Roger Penrose and Stephen Hawking, roughly at the same time, were establishing these singularity theorems that say the Big Bang must have been a singularity.

• 19:23Speaker 08

  So that looked like you've got the theory and the evidence all dancing in harmony. So it would appear then that the universe had this definite beginning of the singularity. And of course, one of the authors of these, Penrose Hawking Theorem is Stephen Hawking. And he was an incredible figure, popularizing science. And whilst Roger Penrose was a bit reluctant to even use the phrase singularity, wasn't sure that we should trust this extrapolation. I think Stephen Hawking was much more brash. You know, so he was sort of proclaim, you know, this is the beginning of the universe. But what has happened is that some of the assumptions of those singularity theorems

• 20:07Speaker 08

  have started to unravel. And this happened, you know, in the decades after the singularity theorems were proven. So any physical theorem is only good as the assumptions that it has. And those assumptions in the Penrose Hawking theorem, we can go over them one by one if you wish, but bottom line is people started to question those assumptions. So then it was like, well, maybe there isn't really a singularity. Or maybe it's just an artifact of pushing the equations beyond their domain of validity. And we need new physics to explore what really happened 14 billion years ago.

• 20:44Kelly Weinersmith?

  So the problem is that the popular science conception of the Big Bang hasn't caught up with where we are now in our understanding of the Big Bang. Would that be fair to say?

• 20:52Daniel Whiteson?

  Yeah, but I think there's more than that. Two ideas were developed at the same time, the hot Big Bang and the Big Bang singularity. And they were both just called the Bing Bang, and so they get confused for each other. The hot Big Bang is still a very solid idea scientifically. And the Big Bang singularity kind of never was, and we've moved on from it. But most people still think of the Big Bang singularity when you say the Big Bang.

• 21:15Speaker 08

  I think that's right, yes. Although there were people even at the time, in the 60s, saying these singularity theorems don't prove the universe had a beginning. But I don't think they were as loud a voice as those who said it did.

• 21:27Daniel Whiteson?

  Sounds like we should blame Stephen Hawking. Yeah, exactly. But it sounds also like a familiar story. You have one story that somebody tells in a compelling way, and it sticks in people's mind. It's like, even if it's hard for people to wrap their mind around this idea of the universe beginning in a point, it is a compelling story. It's easy to tell, and it's stuck in the popular imagination long after people are like, well, we actually only know a certain part of the story. The rest of it's speculative. That's the nuance. That's the subtlety. That's hard to convey. I feel like that's sort of what's happening with popular science everywhere, that the details are being lost and the compelling clickbait headlines are getting propagated and embedded in people's minds.

• 22:12Daniel Whiteson?

  As a science popularizer yourself, how do you feel about the sort of state of science journalism right now?

• 22:17Speaker 08

  Yeah, it's depressing. Well, one thing I do want to say just before I come on to that, another correction that we want to make to the popularizing is that the Big Bang wasn't a point. Rather, it could have happened everywhere. Well, in fact, it would have happened everywhere. And in fact, the universe could be infinite today, and it could have been infinitely big even at the Big Bang. So it wasn't a point. But anyway, no, science journalism, very, very depressing at the moment. I think you see people just trying to get headlines, clickbait. They're not, I think, being rigorous and of course, probably underfunded. So you just get people, you know, copying press releases, or they're going for like

• 23:00Speaker 08

  the big angry headline, you know, oh, everyone's got everything wrong. And that's usually also dubious too. So yeah, I'm not optimistic about the state of science journalism.

• 23:12Daniel Whiteson?

  All right, well, let's do our best to push back. And so to reiterate, we know a lot about the last 13.8 billion years of the universe. We have evidence. It all comes together. We have multiple lines of evidence. It all tells a very compelling story. And it tells us that there was a hot, dense state a long time ago. But then the question, of course, is where does that come from? And so let's explore some of those theories. One of the most popular ones is the theory of inflation. Can you give us a quick primer on what inflation is and why it's compelling explanation for how we got that hot density?

• 23:46Speaker 08

  Right, so before we say what inflation is, it's probably worth saying why people take it so seriously, what the problems that it's supposed to solve, and then maybe we can then explain what it is. So the problems that inflation is supposed to solve, well, there are kind of a few. One is called the monopole problem. So this is that if you think of a magnet, it has a north and a south pole. If you cut it in two, you don't get one with a north pole, one with a south pole. You just get another two magnets with a north and a south pole. However, theorists in the 1970s thought that in the hot early conditions of the universe, you would get something called monopoles, which would literally have only one pole.

• 24:28Speaker 08

  And these monopoles would be very, very abundant and so should dominate the universe. But yet we don't see any, there are no monopoles ever observed. And also, they'd probably be too heavy to allow the universe to expand anyway. So this was called the monopole problem. And actually, this was the motivation to come up with inflation.

• 24:47Daniel Whiteson?

  That's super fascinating and not something I think is widely enough appreciated. Inflation wasn't conceived of to explain the origins of the universe, but to solve a little technical problem. The theory at the time predicted that when the universe was hot and dense and cooling, as it cooled, it shouldn't just make protons and electrons, but it should also make magnetic monopoles, weird particles that have just a magnetic north or south, the way electrons just have a negative and protons just have a positive. The universe does this when it has a phase transition as it cools, like when water goes from steam to liquid, it forms droplets. Here, the phase transition was predicted to make all these magnetic monopoles, and they should stick around, they don't go anywhere.

• 25:29Daniel Whiteson?

  So if they were supposed to have been made in the early universe, they should still be here for us to see, but of course, we don't see them anywhere. We've looked, we can't find any. So that's a problem, and you need to find some way to tweak the theory so it doesn't predict a bunch of monopoles that we know don't exist in the universe. I love how thinking about weird magnets helps us in the end accidentally understand the origins of the universe. All right, so then tell us what happens next.

• 25:56Speaker 08

  So what happened was, um, two scientists, Henry Ty and Alan Guth, were trying to solve this monopole problem. And they imagined there could be like phase transitions in the early universe. Uh, phase transitions you might be familiar with if you have, I'm, I'm sitting out in my garden right now, it's very hot. So if I had, uh, some ice in my drink, uh, it's going to melt. It's going to go from solid to liquid. That's a phase transition. So these are the sorts of phase transitions we're, we're familiar with. Uh, however, there can be phase transitions that are a bit weird that we're not so familiar with. One of them is called supercooling. So supercooling is if you put some, uh, water, very, very pure, you can do this experiment at home. Who would think you could do an experiment about the very early universe and the origin of the big bang

• 26:42Speaker 08

  in your freezer, uh, at home. So what you have to do is get some very, very pure water and keep it nice and still and put it in the freezer. Leave it in there and after a while, you take it out, it should have frozen. But actually, if it's pure enough and you were careful enough, it will not freeze. It's what's in what's called a supercooled state. It will stay liquid. Then if you shake it, it will very quickly freeze. So this sort of delayed transition is called supercooling. Why? It's just a way that the, the, the molecules can be in a certain state that sort of resist being frozen.

• 27:14Daniel Whiteson?

  Chemistry.

• 27:15Speaker 08

  Yeah, chemistry is awesome.

• 27:18Daniel Whiteson?

  It is chemistry, but it's also super interesting. I know that's unusual for me to say, but this one I love. For freezing to start, the liquid needs a tiny seed of a solid, like an ice crystal or a dust speck or a surface bump to organize molecules into the solid lattice. If no seed is present and the liquid is very pure and undisturbed, the molecules stay disordered even though they are cold enough to be a solid. It's like a crowd waiting for someone to start clapping. Nobody does anything until the first person starts to clap. And this chemistry trivia is actually important because it helps us understand the universe cooling. It lets the universe cool without making those monopoles.

• 27:58Daniel Whiteson?

  The universe passes that point, but it stays super cooled and doesn't make monopoles, the way supercooled liquid doesn't make ice crystals.

• 28:07Speaker 08

  Basically, the, the, Ty and Guth imagined that the universe would be in a supercooled state. And they calculated this would actually stop monopole production, like, great, we've solved the monopole problem. And then they said, well, let's just see if this would affect the expansion rate of the early universe. And what they found was that it would expand exponentially. It would, if it's in a supercooled state, it would expand at incredibly rapid rate. The sorts of rates we're talking about is doubling in size every 10 to the minus 37 seconds. And so that in words, that is, let me think, 10 trillionth of a trillionth of a trillionth of a second. So that is a very, very fast rate of expansion.

• 28:51Daniel Whiteson?

  So they did this trick to avoid predicting monopoles would be made and then discovered that it also predicted that the universe expanded super fast. That's awesome.

• 29:01Speaker 08

  But then what happened was Guth had heard a lecture about another problem in cosmology called the flatness problem. And the flatness problem basically is that the universe can have a sort of different geometries at large scale. It could be curved, positively curved like a ball or negatively curved like a saddle, or it could be flat like a piece of paper. And observations showed it was reasonably close to flat in the 1970s. But what had been pointed out by another scientist called Bob Dickey was that those flat solutions unstable. So if it doesn't start out really, really flat, it'll be driven away from flatness.

• 29:35Daniel Whiteson?

  So if the universe has positive curvature, that means it has enough mass density to curve in on itself and gravity wins and it curves more and eventually collapses and becomes super duper dense. Even if it's very slightly curved in the early universe, it will get more curved and then more curved and it's a runaway effect. And the same thing happens in the opposite direction if it has negative curvature. It will get slightly more negatively curved and then more and then More, it's a runaway effect towards negative curvature. But the universe as we see it today is still very close to flat, if not perfectly flat. That's weird because in order to be flat now, the universe had to have been born exactly on the knife's edge of flat.

• 30:14Daniel Whiteson?

  Any tiny deviation from flatness would, after almost 14 billion years, make the universe either collapse or explode. That's the flatness problem.

• 30:23Speaker 08

  So it's very surprising then how the universe could be so flat because it's this unstable solution. When Guth thought about inflation, he realized if you're going to go inflation, then actually it'll be driven towards flatness. And the way you could think about this is imagine, have you ever seen like a circus show where people walk on like Pilates balls? And you ever seen that? Okay, quite difficult, I imagine. Yeah, you need some skills for that, I imagine. So imagine you were standing on that ball or you tried and you fell off, let's say. But then you expanded the ball rapidly to the size of the earth. Be pretty easy to stand on that ball. You wouldn't even notice any curvature.

• 31:05Daniel Whiteson?

  I rarely fall off the earth, that's true, yeah.

• 31:07Speaker 08

  Yeah, I don't fall off the earth very often either. So then anything will appear, will automatically appear flat if it goes, undergoes this exponential expansion. So he realized it would fix this flatness problem. So now it solves two problems at once. And then it turns out it solves many other problems at once. I won't go all of them, but I'll do one more.

• 31:25Daniel Whiteson?

  Wait, hold on, I understood how the rapid expansion solves the flatness problem. Like it seems curved, you expand it, all of a sudden it doesn't seem very curved. How does it solve the monopole problem exactly? Like why, because you're not putting the universe in a freezer. It's not, no, no 10 year olds doing the experiment on us.

• 31:43Speaker 08

  The monopoles would be thrown out of the horizon because there would only be like a handful of monopoles in any patch. So as the universe expands, they'd be thrown out of the horizon and you wouldn't see any.

• 31:55Kelly Weinersmith?

  I like that as a solution, anything that you don't like gets exploded out of the picture.

• 31:58Speaker 08

  Just throw it away, throw it out.

• 32:02Speaker 08

  Yeah, exactly.

• 32:03Daniel Whiteson?

  I think that's a fascinating sort of bit of science where you're like, let me calculate what I think should have happened in the early universe. And then I'm going to compare that to what I'm seeing. Like, yeah, I don't see a lot of monopoles. So obviously something must be wrong. I'm missing a piece.

• 32:16Speaker 08

  Yeah.

• 32:16Daniel Whiteson?

  And what can I add to the universe? So like now it's more likely to describe the universe I see today. I think that's super fascinating. Let's digest that and take a break. And when we come back, Phil is going to tell us more about how inflation solved these problems and whether or not we should believe in it.

• 32:41Speaker 02

  Hey, it's Niall Rogers, host of Before the Moment, a Lincoln original series. I'm driving across the country, meeting some of today's most fascinating artists. We're exploring the stories before the moment that changed everything. This week, I'm joined by breakout singer-songwriter Alex Warren.

• 33:02Speaker 09

  I'm like a kid when I play music and I make music and I'm constantly asking questions. You know, whether it's an instrument I haven't played or it's a melody that seems foreign. You know, there's every night you play a show and it's the same set, but it's not the same show. At a certain point, your brain kind of goes on autopilot. When I'm in the studio or if I'm making music, that's where that curiosity kind of comes back, you know? I haven't lost it yet, but I'm also on my sophomore album. So, and you, you obviously are an expert here.

• 33:27Speaker 02

  Experience Before the Moment, a Lincoln original series on the iHeartRadio app, YouTube, or wherever you get your podcasts.

• 33:37Speaker 10

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• 33:53Speaker 11

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• 34:37Speaker 11

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• 35:00Speaker 10

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• 35:18Daniel Whiteson?

  Okay, we're back and we're talking to Phil about the state of the early universe. What we know about the universe before it was hot and dense. And we've been talking about inflation, this theory that the universe expanded super rapidly in a very short amount of time. So tell us, Phil, inflation sounds a lot like the expansion that we have now. We talk about dark energy and the universe is accelerating in its expansion. Is inflation a different mechanism for expansion? Is it the same thing, just at a different moment in the universe? How do those two things connect?

• 35:48Speaker 08

  They are similar because the universe is currently accelerating in its expansion. So you could say the dark energy we see today is a very dilute form of inflation. And so that does raise the question, are they really the same physics? But I think that's... Still to be determined, like there's a lot unknown about inflation if it even happened. So whether inflation and a dark energy are the different manifestations of the same phenomenon, or whether they're different things that just result in something broadly similar, I think is still an open question. But one thing I do want to just highlight is that one of the things that inflation solves,

• 36:30Speaker 08

  and there are a number of problems, but there's one in particular that I think is the most relevant. And that is how you get galaxy structures. Because if you had a very uniform start to the universe, you've got to ask the question, well, how on earth do all these networks of clusters of galaxies form? What laid the seeds? And in inflation, the idea is there are, there'll be quantum fluctuations. And these would be stretched by inflation to create the seeds of galaxies. So amazingly, these enormous, enormous structures, you know, hundreds of thousands of light years across, if for a particular galaxy, and for clusters of galaxies, even millions of light years across.

• 37:09Speaker 08

  You know, these, these were seeded by tiny subatomic quantum fluctuations that were stretched by inflation. And I think out of all the problems that inflation is supposed to address, I think that's the one that's the most impressive. And where cosmologists are really thinking this is the leading candidate to explain the properties of our universe.

• 37:29Kelly Weinersmith?

  So I, I think I get bogged down by this idea that the big bang started at a tiny point. And so what I'm imagining is we're looking at before the tiny point, where it's inflating and there's areas where you're going to get galaxies eventually. But then it all kind of sucks down to a little point and then blows back out again. But that is not the right way to be thinking about it, right? Because I, I don't see how stuff that happened before the big bang is going to result in galaxies after the big bang. Uh, what am I missing?

• 37:56Speaker 08

  I mean, there are ideas. That the universe could undergo cycles like that, it could expand and contract and expand and contract. But that's independent of inflation. So that depends on, I guess, on the properties of the dark energy we see today. If it's a cosmological constant, i.e. if the energy of empty space is of a constant, I should say better, that what's driving the accelerated expansion is that empty space has a constant energy, then the universe will not recollaps. However, there have been observations recently suggesting that the dark energy is not a cosmological constant, that it could be some dynamical field that changes over time. And in that case, it could recollaps. So that hopefully would address this issue of,

• 38:40Speaker 08

  you know, getting sucked back down. But to answer your question, how could it be that this tiny fluctuating sea of space could have anything to do with what we see today? Well, you need basically density fluctuations. So if you imagine the universe being perfectly smooth, then you wouldn't get the universe we see today because some regions are more dense than others. So those regions that have galaxies in them are more dense and there are voids in space that are under dense. Also, when you look at the cosmic microwave background, this oldest light that we can see is very, very, very, very uniform. Like there's, there's almost no differences across the sky until you get to a point of about one part in a hundred thousand, then you start to see these tiny fluctuations. So

• 39:25Speaker 08

  that's telling you there were definitely density fluctuations in the early universe. So they have to come from somewhere. And inflation is a very nice, but not the only possible mechanism to, to give you those density fluctuations. Now, I said before that the universe could have been infinitely big at the big bang, but what wouldn't have been infinitely big is our patch of the universe. That would have been very, very small. So if you're struggling to think, oh, I want to think of this very, very small universe, you can think of the observable universe that we see around us. Think of that being very, very small. So now in this quantum state, there would be fluctuations. That's just part of quantum theory. And then they get stretched as the universe expands very, very rapidly. And they, that gives you some regions that are more dense than

• 40:09Speaker 08

  others. And then gravity sculpts them, putting more matter into the denser regions, less matter in the under dense regions. And that gives you the seeds for galaxies to form.

• 40:19Kelly Weinersmith?

  Thanks, Phil.

• 40:20Daniel Whiteson?

  And I think there's a possibility there of getting confused about the two ideas, the Big Bang, right? What Phil is talking about is the hot Big Bang. So not that the universe started from a point, just that the universe started from a hot, dense soup. And he's saying that soup is pretty uniform. So how does that soup then grow up to give you galaxies? And the answer is that soup plus quantum fluctuations. And we're not zooming all the way back to the singularity. We're leaving the singularity aside for now.

• 40:44Speaker 08

  Right. But what's interesting is that during inflation, the universe is as cold as it can possibly be. And it's only when inflation ends that it heats up. So then inflation, we can say, is a pre-Big Bang model. Because a lot of textbooks tell you that inflation happened after the Big Bang. But actually, if we use the definition of the Big Bang that everyone, well, not everyone, but most scientists adopt, then we're going to say it's the hot dense state. So inflation happened before that hot dense state. It was it was cold during inflation, as cold as it can possibly be. And then when inflation ends, it heats up the universe, lots of the energy in the inflating space gets converted into matter and radiation. And then you have our Big Bang.

• 41:26Speaker 08

  So our Big Bang is like a bubble that appeared from this soup of inflating space.

• 41:34Kelly Weinersmith?

  Where does the heat come from? How do you go from cold to hot?

• 41:36Daniel Whiteson?

  And let me clarify, because cold means something very specific here. It doesn't mean low energy like you might imagine. Because remember that energy can take many forms. It can be in the form of motion, or mass, or heat, but there can also be potential energy, like when you put a book high on a shelf, or a spring that's squeezed down. And that doesn't make the universe hot. And sometimes fields like the Higgs field can get stuck in a state with a lot of potential energy. And so that energy can fill the universe and the universe still be cold. Inflation theory says that the inflation field had a lot of this potential energy, which is exactly also what you need to make the universe expand. In general relativity, matter and energy density make the universe contract,

• 42:21Daniel Whiteson?

  that's gravity, but potential energy like dark energy or the Higgs field or the inflaton field makes the universe expand. So there's a lot of energy in the universe, but it's not heat. It's in the potential energy, the inflation field. So the universe is nearly empty. Nothing is moving very fast, but it is expanding. Now, when inflation ends, that potential energy is converted into normal matter fields and into mass and motion. So then the universe is hot. That's reheating. It went from cold and full of potential energy to hot and full of mass in motion.

• 42:54Speaker 08

  But there's another way you can think of it. And that is when particles pop in and out of existence from the vacuum, they have to go back into existence very, very quickly. This is a function of the uncertainty principle. And there's an equation which will tell you how long they can exist for and so on and so forth. Now, they pop into existence in pairs, but in inflation, they can't get back together again because the universe has sort of ripped them apart. So you kind of get, you can actually, expanding space can create, literally create matter and radiation because it rips these virtual particles, which would otherwise just appear and disappear out of the vacuum. And they, they form into real particles. And this is similar to what you see in black holes.

• 43:36Speaker 08

  Because in black holes, Hawking famously showed that virtual particles can get, also get ripped apart. Some would go into the black hole, some would come out. And this would emit radiation. It's called Hawking radiation. So it's something similar to that, basically.

• 43:49Daniel Whiteson?

  So we have the hot dense universe a long time ago, which we're pretty confident about. There's questions and problems and theoretical issues. People come up with this idea of inflation. The universe before that hot dense state expanded super duper rapidly and that solves a lot of those problems. But doesn't it also just kick the questions down the road? Like you say, if you have this incredible inflation, then it solves those problems. But where does that inflation come from? What causes that?

• 44:16Speaker 08

  So that's an excellent question. And the short answer is you don't know. I mean, we're not sure that inflation happened. I mean, some people are pretty confident it happened. And we did a survey physicist about that. And we didn't get more than 50% saying inflation happened. But they, I had to be fair, it was a black hole conference that we were at. If we did a cosmology conference. I guess it would be higher, but I think, I can't remember exactly what we got, about forty percent. But it was the most popular candidate. It didn't get past the fifty percent mark. So now, one idea is that inflation is eternal into the past and the future. So let me try and unpack what that means. So you might have heard of the idea of a multiverse. Surely, anyone that switches on the TV these days

• 45:00Speaker 08

  must see some sci fi with a multiverse, whether it's

• 45:03Speaker 05

  Yeah.

• 45:04Speaker 08

  Doctor Strange, or The Man in the High Castle, or whatever, you know. It's very pervasive now in popular culture. But its origins in the cosmological setting is with inflationary cosmology. So remember I said you can think of our universe as like this bubble that appears out of an inflating sea. But the idea is that it wouldn't produce one bubble, it would produce an infinite number of bubbles. And the way this works is pretty straightforward. Just think of the inflating space as something that decays, like a radioactive particle decays. So it decays with a half-life. So when it decays, that's that moment what we talked about, you know, where all the energy gets converted into imagine radiation.

• 45:48Speaker 08

  Boom, a big bang, the universe is born. But what has happened to the bit that hasn't decayed yet? Well, it's undergoing exponential expansion. So as long as that exponential expansion is faster than the exponential decay, then the amount of inflating space can never go down, it can only go up. So the analogy I always give is my mum makes this fantastic chocolate cake, it's really yummy. And I go around there for Sunday afternoon tea. She puts the chocolate cake down on the table and we eat half the cake. Then at some point we go back for seconds and now the cake is gone. You can't have your cake and eat it, right? However, what would happen if when we went back for that second piece, the cake had expanded exponentially?

• 46:33Speaker 08

  Now we could have more cake. We have the same volume of cake that we had in the first bite, you know, but the cake's expanded. Then we go back for thirds, well, the same thing's happened, the cake has grown faster than we could have eaten it. In which case the amount of cake can never, ever go down. So you get infinite number of pieces of cake and you can have your cake and eat it.

• 46:52Daniel Whiteson?

  I think you also get infinite fill in that scenario, don't you?

• 46:55Speaker 08

  Yeah.

• 46:57Speaker 08

  Yeah, you'd have to have a very big belly.

• 46:59Daniel Whiteson?

  All right, so I'm imagining space filled with this inflationary material we don't understand or don't know its origin of.

• 47:06Speaker 08

  Yeah, yeah, yeah.

• 47:06Daniel Whiteson?

  And random little bits of it are decaying into our normal universe kind of stuff. So we get these bubbles of normal universes that appear at random places, but they're separated by this rapidly inflating space?

• 47:18Speaker 08

  Yes, that's exactly right. Yep, yep. So then you get this multiverse and it's eternal. Now, when I say it's eternal, there's a bit of a subtlety there. It's eternal into the future, but is it eternal into the past?

• 47:34Daniel Whiteson?

  Right.

• 47:34Speaker 08

  Now, there is a theorem called the Bourdieu-Guth-Vilenko theorem that says it can only be eternal into the future, but it is not eternal into the past. So we still have to ask what came before inflation or what might have caused inflation. However, there have been people that have disputed this theorem and said, no, it could be eternal into the past. So if you want to know what came before inflation in that scenario, it's just more inflation and it just goes back forever and ever for eternity. However, if we take the Bourdieu-Guth-Vilenko theorem, then we have to ask, okay, what came before inflation? And there are a number of suggestions. And I should also add that there are people that don't like inflation. So one idea is, well, inflation didn't happen at all and there's some other thing that happened.

• 48:18Speaker 08

  But let's, let's stick with the inflation since you asked. So I would say there's a few ideas out there. The first one that probably came on the scene was 1982. And this was proposed by Alex Vilenko. It's called the tunneling from nothing idea. So the idea is that what if we treat space quantum mechanically? So normally when they do this cosmological modeling, you're using Einstein's theory of gravity. So you're assuming spacetime is classical. But if you're assuming spacetime is quantum mechanical, as Vilenko did, then the suggestion is that space itself could fluctuate into existence from a state where there was no space.

• 49:03Speaker 08

  So that's really hard to get your head around, but this is why it's called the tunneling. From nothing idea, the idea is what controls the expansion of the universe, so partly its radius. So if you have a small universe, it would actually just collapse back in on itself. So how would you go from a small universe to a universe big enough to inflate at least? And classically, it seems to be impossible. However, quantum mechanically, it can, what's called tunnel. It can tunnel from one state to another. So the small one could tunnel to the larger one. And then what he asked was, well, what's the smallest size that the universe could tunnel from? And he concluded it was zero. So that's pretty hard to get your head around. So that's the tunneling idea, tunneling from nothing idea. Then you have this thing called the Hartle-Hawking no boundary state.

• 49:48Daniel Whiteson?

  Hold on, let's dig into the Valenkin idea a little bit more.

• 49:51Speaker 08

  Yeah.

• 49:51Daniel Whiteson?

  Because this is still pre-inflation. This is not an alternative to inflation. This is saying, where does the inflationary universe come from?

• 49:57Speaker 08

  Yeah, yeah, yeah.

• 49:57Daniel Whiteson?

  And you're saying that we're adding quantum mechanics to it. So it's not full quantum gravity, it's some sort of like semi-classical.

• 50:04Speaker 08

  No, no, this is, yeah, yeah, we would call it semi-classical. It's not full quantum gravity and we should come to full quantum gravity in a moment.

• 50:11Daniel Whiteson?

  But, and so this is speculating that the inflationary conditions before the hot big bang fluctuated into existence from, and I'm just going to kick the can down the road further here, from, and you said something that has no spacetime, so it's a universe.

• 50:24Speaker 08

  Yeah.

• 50:25Daniel Whiteson?

  But without spacetime, or it's nothing, meaning not a universe?

• 50:29Speaker 08

  What's the difference?

• 50:30Daniel Whiteson?

  Yeah, well, that was going to be my next question, that was a trap. You avoided it.

• 50:35Speaker 08

  There's no space there at all. I mean, there's nothing sort of physical there. That's at least one conception of it.

• 50:42Daniel Whiteson?

  But how can you have the laws of the universe and follow those laws if there is no universe? So there is a universe, but without spacetime?

• 50:49Speaker 08

  Well, that depends on your view of laws. What are laws of physics?

• 50:54Daniel Whiteson?

  Yeah.

• 50:54Speaker 08

  Now, some people would say they're just descriptions, so they can't cause the universe. Another view might be, we don't need a cause because there's no time and time. You need time for causality. If there's no time, don't worry about what the cause was. You're asking the question, what caused?

• 51:10Daniel Whiteson?

  But if there's no time.

• 51:12Speaker 08

  It is a question that is asked in a condition. The condition is time exists. But if the time doesn't exist, then don't worry about causality.

• 51:21Daniel Whiteson?

  Yeah, but if you have. But how can you speculate about a transition to an evolution of the universe from this to that if there's no time in the universe, right? How does that? How do I wrap my mind around this?

• 51:33Speaker 08

  Well, it is hard to wrap your head around. You know, we're answering in analogies, but you know, it's all a mathematical description. So the question is, you know, could you compute what would happen if the universe had zero size? And then what is there a tunneling amplitude for? And people have challenged this. I mean, I don't want to claim this always worked out and everyone understands it and it's all agreed upon. This is one of like 20 something ideas that we talk about in the book. And this is a problem with it. So I don't, you know, some people have said, well, you're always tunneling from one quantum state to another. So maybe we shouldn't consider this, this model. However, one idea that Philenkin suggests is that actually laws are more than just descriptions,

• 52:16Speaker 08

  that they actually are, they exist in a sort of platonic sense in a sense. And this has some advantages to it because, you know, you can ask, why is it that objects obey the laws of physics? You know, if you have an electron, let's say it gets excited, it shoots out a photon. How does it know to shoot out a photon? You know, is it all that information written inside the electron? It seems hard to believe. So the idea is that laws are actually sort of platonic objects in some sense. They're pretty weird.

• 52:46Daniel Whiteson?

  And when you say platonic objects, for those of us who are not reading philosophy papers all the time, you mean that they exist outside of our ability to observe them?

• 52:54Speaker 08

  Yeah, I think, I think that's a fair, fair description. Yeah, they don't sit on something else. You know, if you think of a table, all right, it's made of particles. And you might even say it's they're made out of quantum fields or, you know, so the laws themselves have a, have their own sort of physical existence. Well, I don't know if physical is the right word, independent existence. So that may be required by a Philenkin's model. And if you don't like that idea, then maybe you don't want to entertain Philenkin's model. But I do think that it's uncertain what the status of laws is. So those that say that cannot be right because laws are just descriptions.

• 53:36Speaker 08

  Uh, I challenge that and say, are you sure that they're just descriptions? You know, how do you solve problem of induction? You know, we ask, how do we know that there are these regularities? You know, why, why, why don't we think the sun might stop rising tomorrow? You know, uh, if you just think they're descriptions, it's hard to uh, solve this problem of induction. But one possible solution is no, the laws are more than that. They're sort of ironclad objects that the other particles have to sort of obey. And then you can see why induction makes sense. So there's a lot of debate in the philosophical literature about the nature of laws. And I think as long as that is not settled, and I think it's right to say it isn't settled, then you can entertain this view.

• 54:18Speaker 08

  But, you know, let's be honest, it's pretty wacky and out there. So people have come up with other views and maybe, you know, we can get onto those if you want.

• 54:26Daniel Whiteson?

  I do want to get onto those and I meant to ask you about the philosophical implications later, but I can't not follow up on, on that fascinating conversation. You know, because it makes me wonder about the future of this line of inquiry. Like if we discover the hot big bang and then we find proof of inflation, then we find proof of what became before that. Is this an infinite line of study where we're always going to be asking what came before that? Or do you think there's some point at which we find something where like, ah, this caused itself? Or this is obviously something which is fundamental? And isn't that just some philosophical sleight of hand where we're like, this requires a cause. Now we found something which we define to not require a cause and therefore we don't have to ask questions anymore. I mean, why isn't this going to be an infinite line of inquiry? Or do you think it will be?

• 55:10Speaker 08

  Well, it could be, but there are sort of ideas out there that might stop that infinite regress, shall we say. I mean, Valenkin thinks that he stops the infinite regress because, you know, we've got this solution, if you like. The universe doesn't need a cause because it's quantum mechanical and causes are emergent properties. They exist for the macroscopic world, but not for the quantum world. So we don't need to ask what the cause for the universe is. It's a meaningless question, maybe. Or maybe not meaningless, but it's just, you know, you don't need to demand, you can't demand there must be a cause when you get into the quantum realm. So that's one approach. Another approach is that maybe the universe just existed eternally into the past. So you can always just go back one step further and further and there's no end.

• 55:55Speaker 08

  It just goes on forever into the past. That's certainly an idea.

• 55:59Daniel Whiteson?

  Infinite grants for cosmologists.

• 56:01Speaker 08

  Yeah, maybe. Yeah, so it may just go on forever, but that's certainly a logical possibility. And it's certainly something that I think many physicists entertain. Certainly, that's one of the battles, actually. The battle for the Big Bang is, was there a beginning? Even if it wasn't the Big Bang, maybe there was some other beginning. And some physicists think there was, and some physicists think there wasn't. Another idea is that there could be what's called a closed time like curve. So if you've seen the movie Groundhog Day, think of that. So you wake up, you know, and you're just experiencing yesterday all over again. So now there are solutions in Einstein's theory of relativity,

• 56:44Speaker 08

  which describes, you know, gravity as a curvature of spacetime. And there are solutions to say it gets so curved, it curves back on itself and it forms a loop. So there are a couple of models that sort of take advantage of this and say the universe would cause itself because it curves back in a loop. And so there is no origin point of a circle, even though the circle is not infinitely long, it doesn't have a starting point. So you can't ask what happened at the start. There is no start. It just goes around in a loop. So in the book Battle of the Big Bang, we talk about two different models that exploit this. So there are some of the different ideas.

• 57:24Speaker 08

  One, maybe there was a beginning and you described the universe maybe without the language of causality. Or maybe there was no beginning and it's infinitely far into the past. Or maybe there's a sort of loop in time. So there's no starting point, even though maybe it's not sort of eternal in some sense.

• 57:44Daniel Whiteson?

  All right, so let's take another break. And when we come back, we're going to explore some of these other ideas. Some propose that the universe has no first moment.

• 58:02Speaker 02

  Hey, it's Nile Rodgers, host of Before the Moment, a Lincoln original series. I'm driving across the country, meeting some of today's most fascinating artists. We're exploring the stories before the moment that changed everything. This week, I'm joined by breakout singer-songwriter Alex Warren.

• 58:22Speaker 09

  I'm like a kid when I play music and I make music and I'm constantly asking questions. You know, whether it's an instrument I haven't played, or it's a melody that seems foreign. You know, this every night you play a show and it's the same set, but it's not the same show. At a certain point, your brain kind of goes on autopilot. When I'm in the studio, or if I'm making music, that's where that curiosity kind of comes back, you know? I haven't lost it yet, but I'm also on my sophomore album, so, and you, you obviously are an expert here.

• 58:48Speaker 02

  Experience Before the Moment, a Lincoln original series on the iHeartRadio app, YouTube, or wherever you get your podcasts.

• 58:58Speaker 10

  Snoring, gasping for air during sleep, daytime sleepiness? I'm Shaquille O'Neal, and this shouldn't be anybody's experience. Ask your doctor about Zepbound Trisepotide, the first and only FDA-approved prescription medicine for moderate to severe obstructive sleep apnea in adults with obesity.

• 59:13Speaker 11

  Zepbound is a prescription medicine used with a reduced calorie diet and increased physical activity to help adults with moderate to severe obstructive sleep apnea, OSA, and obesity to improve their OSA. Zepbound is approved as a 2.5, 5, 7.5, 10, 12.5, or 15-milligram injection. Zepbound contains trisepotide and should not be used with other trisepotide-containing products or any GLP-1 receptor agonist medicines. It is not known if Zepbound is safe and effective for use in children. Don't share needles or pens, or reuse needles. Don't take if allergic to it, or if you or someone in your family had medullary thyroid cancer, or if you've had multiple endocrine neoplasia syndrome type 2. Tell your doctor if you get a lump or swelling in your neck. Stop Zepbound and call your doctor if you have severe stomach pain or a serious allergic

• 59:58Speaker 11

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• 1:00:21Speaker 10

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• 1:00:39Daniel Whiteson?

  Okay, we're talking to Phil about the origins of the universe, what we know, what we might know, and what we can only speculate while smoking banana peels. You referenced earlier this fascinating idea, this no boundary proposal, this alternative to like a singularity or a first moment. Tell us about this idea. How does it come about? And how does it help us avoid a first moment in time?

• 1:01:01Speaker 08

  Well, it's not clear that whether it does avoid the first moment. If I was going to suggest models that avoid a first moment in time, I'd probably go to another model, like a bouncing model, which was, or some other, maybe some cyclic models that I think are more unambiguously, don't have a beginning. The no boundary proposal, I worked with Stephen Hawking and Jim Hartle and Thomas Hough to make a film to explain it to the public. And I did get the impression they didn't quite agree on how to interpret it. I think Hawking saw it as like something closer to what Valenkin proposed, like a universe from nothing.

• 1:01:42Speaker 08

  Whereas Jim Hartle, I asked him, could this realize the idea of a universe from nothing? And he's like, what do you mean by nothing? Quantum mechanics is always something.

• 1:01:52Daniel Whiteson?

  I know that Hawking's special sauce is getting gravity and quantum mechanics to play together, even without a full theory of quantum gravity. He did for black holes, and that's how he came up with his prediction for Hawking radiation.

• 1:02:02Speaker 08

  So he started to think, well, what if we do the same for the Big Bang? Because the singularity theorem that he proved with Penrose was just classical. It didn't include quantum mechanics. So he said, right, let's try and include quantum mechanics. And when he did that, he found that, to cut a long story short, the description that we have with space having three dimensions and time having one dimension changes such that

• 1:02:30Speaker 08

  The time dimension turns into a space dimension. So now you have four space dimensions and no time dimension.

• 1:02:36Daniel Whiteson?

  Okay, that's really weird. Let's unpack it. So Hawking is saying that the universe used to have four spatial dimensions and one of them became a time dimension. So we had four spatial dimensions and then we had three spatial dimensions and one time dimension, which we're familiar with now. That's really confusing. So let's try to think of an analogy. And Hawking's famous analogy is like, if you're standing at the North Pole, it's not only that there's no more northiness, there's also no sense of east or west. East and west have no meaning of the North Pole. But as you move away from the North Pole, you don't change the number of dimensions on the surface of a sphere, but now the concept of east and west makes sense.

• 1:03:17Daniel Whiteson?

  It's a direction that emerges smoothly as you move away from the North Pole. One of the directions on the sphere becomes east-west like. The idea here is that the universe has one end where all the directions are space-like. And as you move away from that end, one dimension changes to have new time-like properties. It's pretty hard to wrap your mind around, honestly.

• 1:03:39Speaker 08

  And what this does, it actually smooths out the singularity. You don't get this infinite dense state. You get a smooth state. And think of it, unlike the point of a cone, think of it more like a shuttlecock, like a smooth surface. Now, this is bounded, it's not infinite, but it doesn't have a starting, there's no point on this surface. This is many better than any other point. So you could say it doesn't have a beginning, but you might say, well, it's not infinite to the past either. And then there's some more complications to it, which we go into in the book. But bottom line is, whether it has a beginning or not is sort of slightly ambiguous and it depends on how you interpret the model.

• 1:04:22Speaker 08

  But there are other models that I think are less, have less ambiguity and clearly don't have a beginning in them. So the most obvious one, I would say, is one where you replace the singularity with a bounce. So here, the idea is that there's a, so remember we said with the singularity, the universe goes to infinite density. Now, the idea in some theories of quantum gravity. The suggestion has been that you will actually get a maximum density. So think of a sponge. You pour water on a sponge and it absorbs the water. But there comes a point where it won't absorb the water anymore. It will switch its properties from being water absorbent to water repellent.

• 1:05:06Speaker 08

  So space might be like that. And in certain theories of quantum gravity, that's what happens. Spaces are like a limit. So when you try and squeeze more and more energy into space, it gets to a point where it gets full up. And then if you try and squeeze more in, it will bounce back out. It becomes repellent. Uh, so gravity switches from becoming an attractive force to a repulsive force. And that triggers a bounce. So then if we could go back in time, what we would see is the, uh, well, if we started today, 14 billion years since the big bang roughly, we go back in time, it's getting denser and denser and denser and denser. Then when we get to its maximum density, it just bounces back out again. So you'd get another expanding universe. Or if you wanted to think of it as going from the past to today, it would be a contracting universe and then an expanding universe.

• 1:05:51Speaker 08

  And that contracting universe could have been contracting for infinitely long ago. Um, you might just have it mirror like, it doesn't have to be cyclic, although it could be. It could just be one contracting universe mirrored by one expanding universe, something like, like an hour class. So that's, that's the idea of a bounce. And I think that that is less ambiguous that it does not have a beginning in this model. So that's one idea. And of course, there are cyclic universes as well and all kinds of other ideas we explore.

• 1:06:23Kelly Weinersmith?

  So this idea that at some point, gravity stops pulling things in and starts to repel energy. Do we have evidence for that in other domains? Or like, where did this idea come from?

• 1:06:33Speaker 08

  We, yeah, arguably we do. The fact that the universe is accelerating in its expansion is an effect of the vacuum having a pressure. But, but think of it this way. I mean, this, this is different to what we're talking about in the quantum gravity case. But I just want to answer your question. Is there some evidence of a repulsive gravity? So in our, in Newton's theory, the only thing that contributes to gravity is mass. So you can't have negative mass, as for sign o. So you can't have negative gravity, therefore gravity is always attractive. However, in Einstein's theory, there's also a pressure term. So it's not just mass and the pressure can be negative, it's like a suction. And in fact, vacuum has negative pressure.

• 1:07:16Speaker 08

  So it is a repulsive gravity force. And the fact that we see the universe accelerating in expansion is direct empirical evidence of repulsive gravity. So that is clear that there is repulsive gravity. Now, that's not necessarily what's going on here at the big bounce, because there you're assuming it's coming from quantum gravity. So there you have to use a different type of geometry. So the geometry that's used in relativity is classical geometry. Whereas in these quantum gravity theories, it's a quantum geometry. So it's all fluctuating. And the idea is that then, because it's discrete, it can't have infinite compression.

• 1:07:57Speaker 08

  It will bounce back at some point and that then gravity switches signs and you get repulsive gravity. So that's the theoretical extrapolation from the quantum gravity theory. So in particular, loop quantum gravity is a candidate for quantum gravity. They've done a lot of work on this bouncing cosmology, but there have been ideas even in string theory that you might get a bouncing cosmology from this fact that if you discretize space, then it will have a maximum limit of what you can put into it. And then if you try go beyond it, it pushes back.

• 1:08:28Daniel Whiteson?

  I like these bouncing ideas because they sort of avoid the question of a first moment. They're like, let's just bounce forever. And that's cool, but I wonder if there's any evidence for that. Like, you know, if the universe compresses to a singularity or a near singularity, some quantum version of it, does it do so intensely that all evidence of the previous, you know, pre-bounce universe is lost? Or can we find some hints, some clues in the universe today that show that it had to have a bounce?

• 1:08:57Speaker 08

  Yeah, so this is an active research programme. So as I said, I think it's in the loop quantum gravity case where there's the most consensus that you get a bounce. As I said, there have been ideas in string theory for a bounce as well, and even in some other proposals for quantum gravity. But in the loop case, loop quantum gravity, which is one of the candidates for a theory to mix ISAS theory of general relativity and quantum mechanics, as we get this quantum theory of gravity. Because we should point out to the listener, if they're not familiar, these two theories are the cornerstones in modern physics, but yet they contradict each other. So we know we need a deeper theory. So we need to modify one of the existing

• 1:09:38Speaker 08

  theories, or maybe both of them. But we know we need new physics in some way. So one of the contenders is this theory called loop quantum gravity. And what they've got this program called loop quantum cosmology, where what they want to do is calculate what we should see in the cosmic microwave background if there was a bounce. And they claim that they've already done this, and it matches their observations. Now, obviously, not everyone agrees that this is correct. So they have to make certain assumptions, and then the question is, are they valid assumptions? And then, in particular, I'll give you one that I think is important, or especially important, I should say. And that is, you have to assume whether there was inflation or not. And as we said, not everyone agrees

• 1:10:21Speaker 08

  there was inflation. So they have to put in inflation, and then there's different models of inflation. So what they do is they try and say, well, which one is favored by the data? Put that in, then we calculate corrections to what we see in the cosmic microwave background. And then they claim that there's actually matches better than the standard model. But the differences are not big enough to be decisive. And of course, as I said, you could challenge the assumptions. So it's still an ongoing program, and people are still working on the theory to see if they can make the predictions more robust. So maybe it depends on some of these assumptions. The other thing you could try and do is

• 1:11:02Speaker 08

  look at black holes, and how black holes might behave. Because there also, we think we need quantum gravity. So people have made Black holes using quantum gravity. And then maybe you could look for signatures of what they might do. Uh, maybe there are signs of quantum gravity in in black holes. So those are the two areas. Um, that I think are the most exciting about looking for signs of quantum gravity. And if we could find those, then we might know what the right theory of quantum gravity is. And then we might know whether this bounce took place or if it didn't.

• 1:11:38Kelly Weinersmith?

  That would be exciting.

• 1:11:39Speaker 08

  Yes, oh yeah.

• 1:11:40Daniel Whiteson?

  Well, now we've been looking into the past, tell us about the future of looking into the past. What do you think we're going to learn in the next 10 years or 50 years that could help us understand? What came before the hot big bang?

• 1:11:50Speaker 08

  Well, there's a number of avenues we can explore. So one is to look more at this cosmic microwave background. So this is the oldest light that we can see. You can't see beyond that with light. It's emitted 380,000 years after the big bang. And the reason that you can't see anything earlier is that if you went earlier, as I said, the universe would look more like the sun. And if you if you look at the sun, you can't look into the interior because it's opaque. So same with the with the universe before the emission of a cosmic microwave background, it was opaque. So you cannot look earlier. But there are these patterns of hot and cold spots, and they give you information that you could try and guess as to what came before. And some theories make different predictions for those patterns of hot and cold spots.

• 1:12:35Speaker 08

  Also, there's patterns of polarization. So this is the way that light sort of twirls around. That's a new frontier. So looking for polarization of the cosmic microwave background. And some different models make different predictions for what we might see there. Uh, another avenue you could look at is um, the distribution of galaxies, because that that was set in the very earliest moments of the big bang. So different models might make different predictions um, for the distribution of galaxies. But I think the most exciting idea for how we can probe much earlier in into the into the big bang is something called primordial gravitational waves.

• 1:13:16Speaker 08

  So this you might people probably might have heard in 20, let me think, was it 2016? Um, LIGO, which was these giant lasers that they have in Louisiana and Washington State. And they detected sort of um, a ripple in the fabric of space and time. They're called gravitational waves. And they came not from the big bang, they came from colliding black holes. But they send out this ripple in the fabric of space and time. And we can detect them amazingly because they're very, very feeble when they get to the earth. They change the distance of like these lasers. They basically have these lasers, they're about four kilometres apart and they bounce between mirrors. And if there are no gravitational waves, they should stay in phase with each other.

• 1:14:01Speaker 08

  When a gravitational wave passes through, they go out phase. And so you can detect their existence. And they have two of them, one in Louisiana and one in Washington state. Initially, I mean, they've been more built since then. There's one now in Italy and India and Japanese that are, they're building one of, I don't know what the state is that one is. But so, so the idea is to have stations of them around the world. So these ripples can go through that plasma that you can't see through. So even though you can't see light from the Big Bang, you could in some sense see these gravitational waves. You don't see them. Maybe you hear them, you know, they're kind of sound waves actually in the early universe. Well, they're core sound waves in the early universe, I should say.

• 1:14:44Speaker 08

  So these ripples in the fabric of space time are potentially detectable. Either they might change the polarization of the light of the cosmic microwave background. Or we could detect them directly via building something like these giant laser observatories. But the ones that we have today are optimized to see them from black hole collisions. They can't even see them from supermassive black holes, which are the really big black holes that sit in the centre of galaxies. However, we are building a space-based observatory called LISA, the Laser Interpretable Space Antenna. And that will be able to detect supermassive black hole mergers. So maybe it could see signatures of quantum gravity in these extreme conditions. So that might help us understand the Big Bang.

• 1:15:29Speaker 08

  But beyond LISA, I mean, LISA is not going to get launched in the 2030s. But then beyond that, there are projects, one called DSAIGO, another one called Big Bang Observer. These are kind of pie in the sky ideas, right? So we don't think that they're, you know, going to be built anytime soon. But often what you do is just dream big, just say, what would you do if you had like? Endless money and resources and the idea is just get something on the table and then, you know, maybe decades into the future, maybe people find cheaper ways to do it and then you can actually launch these things. So the Big Bang Observer, for example, is like Lisa, it's a similar idea, but it has 12 spacecraft, Lisa has three. And Lisa's funded, that is happening, it's being built as we speak. But Big Bang Observer is much, much

• 1:16:14Speaker 08

  more ambitious. But that could potentially see these ripples from the Big Bang. And now, why that is that important? Because some models predict that there should be these ripples and some don't. So a lot of cyclic models say there are no ripples. And some of these cyclic models are alternatives to the inflationary screen, which says there are these ripples. Not only that, but they actually have different properties. So they have different strengths, different wavelengths. And so we call that the spectrum of the gravitational waves. So by probing the gravitational wave universe, and this is an area of astronomy that is brand new. I mean, we only detected the first gravitational wave in 2015. It's

• 1:16:56Speaker 08

  like Galileo first looking up in his telescope in 1610. Think of what a small telescope he had and how radically it changed our view of the universe. Because before Galileo looked through that telescope, most people were sure that we lived in a geocentric universe with everything going around the Earth. And I think when Galileo looked through that telescope, and he saw that there were moons going around Jupiter, it was clear, as clear as day, that not everything goes around the Earth. And then he saw the phases of Venus, which was a direct prediction of the heliocentric model, or particular properties of the phases of Venus. So it was incredibly revolutionary. And now we're at the birth of this new revolution,

• 1:17:38Speaker 08

  gravitational wave astronomy. And this could probe which models of the Big Bang or even pre-Big Bang universe are right. And that is the incredibly exciting frontier for early universe cosmology in the decades or maybe centuries to come, depending on whether we decide to fund this area of science.

• 1:17:59Daniel Whiteson?

  That's right. It'll finally tell us whether we're in the Marvel multiverse or the DC multiverse or another version.

• 1:18:05Speaker 08

  Right, yes, exactly right, yeah.

• 1:18:10Daniel Whiteson?

  All right. Well, thank you, Phil, very much for coming on the podcast and talking to us about all these crazy ideas. It's amazing to me we can know anything about the universe so long ago and we can even have debates about various ideas. I really enjoyed the book. The book is called Battle for the Big Bang: The New Tales of Our Cosmic Origins.

• 1:18:34Kelly Weinersmith?

  Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio. We would love to hear from you.

• 1:18:39Daniel Whiteson?

  We really would. We want to know what questions you have about this extraordinary universe.

• 1:18:45Kelly Weinersmith?

  We want to know your thoughts on recent shows, suggestions for future shows. If you contact us, we will get back to you.

• 1:18:52Daniel Whiteson?

  We really mean it. We answer every message. Email us at [email protected].

• 1:18:59Kelly Weinersmith?

  Or you can find us on social media. We have accounts on X, Instagram, Blue Sky, and on all of those platforms, you can find us at D and K Universe.

• 1:19:08Daniel Whiteson?

  Don't be shy. Write to us.

• 1:19:12Speaker 10

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