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What came before the Big Bang? · Daniel and Kelly’s Extraordinary Universe

• 0:07
  Speaker 1: Everybody wants to know where we came from, how we
• 0:11
  Speaker 1: got to be here. That means understanding the events that
• 0:14
  Speaker 1: set in motion your life, all of its ups and downs.
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  Speaker 1: Historians can tell you about the journey of your ancestors,
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  Speaker 1: how it shapes your culture and way of life. Anthropologist
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  Speaker 1: can tell us the story of humanity itself, why we
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  Speaker 1: walk on two feet, and how we got to be
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  Speaker 1: so darn smart. But physicists can take us deepest into
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  Speaker 1: the past, even beyond the chaotic formation story of our
• 0:39
  Speaker 1: solar system or of the galaxy itself. Incredibly, we can
• 0:43
  Speaker 1: look billions of years deeper into history, to a time
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  Speaker 1: before there were galaxies or stars, when the universe was
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  Speaker 1: filled with hot, dense plasma. But then we hit a wall.
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  Speaker 1: Beyond thirteen point eight billion years ago, the universe was opay,
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  Speaker 1: and all photons emitted before then have been lost, reabsorbed,
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  Speaker 1: and beyond another three hundred and eighty thousand years, the
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  Speaker 1: universe was so hot and dense that our theories of
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  Speaker 1: physics no longer apply, like trying to explain steam using
• 1:15
  Speaker 1: fluid dynamics. Our curiosity, of course, is limitless, and so
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  Speaker 1: we desperately want to know what came before, What is
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  Speaker 1: the original fundamental context of the universe, and what does
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  Speaker 1: it say about those of us scratching out a living
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  Speaker 1: on a tiny dot of rock. Today we'll take a
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  Speaker 1: tour of the current ideas about the earliest moments in
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  Speaker 1: the universe, if there even were any, and think about
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  Speaker 1: what we might learn in the future. Welcome to Daniel
• 1:43
  Speaker 1: and Kelly's Extraordinary Ancient Universe.
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  Speaker 2: Hello, I'm Kelly Wiener Smith. I study parasites and space,
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  Speaker 2: and today we're talking about where it all began.
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  Speaker 1: Hi, I'm Daniel. I'm a particle physicist, and I love
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  Speaker 1: physics because it subsumes every other question in science.
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  Speaker 2: So today we're talking about, like, what happened before the
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  Speaker 2: Big Bang? Do you think will we ever get solid
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  Speaker 2: answers where we're like, Bam, we don't have to debate
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  Speaker 2: this anymore. We've got to figure it out. Or is
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  Speaker 2: this the kind of thing that we will always be
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  Speaker 2: tinkering with. I think either answer is okay and exciting.
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  Speaker 1: I should say yeah. I don't think there's going to
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  Speaker 1: be a moment where we're like, yeah, we figured it out,
• 2:31
  Speaker 1: and here's the rest of the grant money back. By
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  Speaker 1: the way, we have nothing else we're curious about, and
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  Speaker 1: we don't want to think about it anymore.
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  Speaker 3: Yeah.
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  Speaker 1: No, I think we're always going to wonder what about this?
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  Speaker 1: What about that? Where did that come from? Why not this?
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  Speaker 1: Why the other thing? I think it is a lot
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  Speaker 1: of philosophical questions, just thinking about the origins of the universe,
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  Speaker 1: but also wondering which answers are acceptable, which ones we go, yeah,
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  Speaker 1: that makes sense, let's move on, and which ones were like,
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  Speaker 1: wait a second, why that? I think that reveals a
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  Speaker 1: lot of about our humanity and our curiosity, which is
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  Speaker 1: one of the reasons why I love this topic so much.
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  Speaker 2: Yeah, and we've talked on past shows about why there
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  Speaker 2: are some explanations we get where we're like, oh, that
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  Speaker 2: makes sense, we don't have to dig any deeper, and
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  Speaker 2: how that can like sort of send us down the
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  Speaker 2: wrong path actually by just you know, oh, that makes sense,
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  Speaker 2: no more questions needed?
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  Speaker 1: Yeah, exactly, And whether aliens would find those answer satisfactory
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  Speaker 1: or not?
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  Speaker 2: I know, Dan, the constant question that is ringing in
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  Speaker 2: Daniel's mind, what would the alien say.
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  Speaker 1: Exactly? Well, you know, they're not here to speak for themselves,
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  Speaker 1: so I feel like some pressure to speak up for
• 3:35
  Speaker 1: the aliens.
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  Speaker 2: I'm so glad that they have an advocate in Daniel Whitson.
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  Speaker 1: Well, look, if they're aliens all over the galaxy, then
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  Speaker 1: they are literally the silent majority, right because everybody's speaking
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  Speaker 1: for them. So yes, I stand here to speak for
• 3:47
  Speaker 1: the aliens. But today we didn't have an alien on
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  Speaker 1: the podcast. We instead had a human being. We thought
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  Speaker 1: a lot about cosmology and how to communicate it to
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  Speaker 1: the public because we wanted to dig deep into this
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  Speaker 1: question of what is the Big Bang and what came
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  Speaker 1: before it? And so before we get to that interview,
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  Speaker 1: let's hear what folks on the street, by which I
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  Speaker 1: mean podcast listeners who volunteered think came before the Big Bang.
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  Speaker 1: Here's what folks had to say.
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  Speaker 3: Our understanding of physics breaks down with a big bang,
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  Speaker 3: but one idea so a turn of inflation. It could
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  Speaker 3: be that there was something that was just so different
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  Speaker 3: from our current experience or understanding that we don't even
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  Speaker 3: have the language to describe it.
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  Speaker 1: According to Pastafarian scripture, the great flying spaghetti Monster made
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  Speaker 1: us all hail the cosmic Cannloni. It's just all theories.
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  Speaker 1: I guess at the singularity, there was no space time,
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  Speaker 1: thus no time, no causation, no before. But how can
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  Speaker 1: there be an after without a before?
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  Speaker 3: That's like asking what the NOI at the Pope. I
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  Speaker 3: don't think that's an answer, but prove me wrong, please.
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  Speaker 1: Nothing came before the Big Ban, because as I understand it,
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  Speaker 1: it's when time started. All right. What a wonderful spectrum
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  Speaker 1: of answers as usual? Aren't our listeners wonderful? Kelly?
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  Speaker 2: Yeah, obviously, obviously, clearly they have a good sense of
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  Speaker 2: taste for podcasts. But exactly, but we've got a real
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  Speaker 2: professional on today to tell us about the mini theories
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  Speaker 2: actually for what came before the Big Bang. I think
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  Speaker 2: we don't even manage to get to all of the
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  Speaker 2: ones we had thought about, because there's a lot of
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  Speaker 2: them out there. So instead we dug deep into about
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  Speaker 2: two of them. And let's go ahead and jump in.
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  Speaker 1: It's my pleasure to welcome to the podcast Phil Helper.
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  Speaker 1: He's a Fellow of the Royal Astronomical Society and a
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  Speaker 1: science popularizer. He's a creator of the popular YouTube series
• 5:51
  Speaker 1: Before the Big Bang. His astronomy images have been featured
• 5:54
  Speaker 1: in The Washington Post, BBC, and The Guardian. He's one
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  Speaker 1: of the rare breed of pop physics authors that also
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  Speaker 1: who has deep credentials in physics, and together with cosmologist
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  Speaker 1: naish Ash forty, he's the co author of Battle for
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  Speaker 1: the Big Bang The New Tales of Our Cosmic Creation. Phil,
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  Speaker 1: welcome to the podcast.
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  Speaker 3: Thank you great to be on.
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  Speaker 2: We're excited to have you. And if I can get
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  Speaker 2: the ball rolling. So, like my for my PhD, I
• 6:18
  Speaker 2: studied fish, and I really like things that you can
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  Speaker 2: have in the lab and you can see and manipulate,
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  Speaker 2: and studying something like the Big Bang, which happened so
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  Speaker 2: long ago, sounds really difficult. What got you interested in
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  Speaker 2: this question in particular?
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  Speaker 4: Well, who cannot be absolutely fascinated by the origin of
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  Speaker 4: the universe. I mean, I think that's deeply ingrained in
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  Speaker 4: right in human nature. I mean, it's no surprise that
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  Speaker 4: every culture, well maybe not every culture, where many many
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  Speaker 4: cultures have an origin story, something where they can point
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  Speaker 4: to and say, this is how the universe came to be.
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  Speaker 4: So I think we all have that deep curiosity in us.
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  Speaker 4: And the beauty is that science has actually found a
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  Speaker 4: way to probe the very origin of the universe and
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  Speaker 4: that's cosmology. So why not follow follow us down that
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  Speaker 4: rabbit hole and see how far it goes?
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  Speaker 2: Amazing?
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  Speaker 1: Well, I like how you appeal to our innate curiosity,
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  Speaker 1: but I think in the end there is something subjective,
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  Speaker 1: right about what you find exciting? Would you find interesting?
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  Speaker 1: What questions you think are worth exploring? And so you know,
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  Speaker 1: some of us are excited about fish guts and some
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  Speaker 1: of us are excited about the whole universe. So it's
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  Speaker 1: all about it, for sure.
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  Speaker 2: I can see the fish guts in front of me.
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  Speaker 2: I like that.
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  Speaker 3: Oh I have actually published a paper on fish.
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  Speaker 4: Oh yeah, scientific und yeah, yeah, so I'll have.
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  Speaker 3: Been interested in fish as well. Okay, good, Literally it's
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  Speaker 3: about fish pains.
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  Speaker 2: Oh that's an important topic, I think.
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  Speaker 1: So.
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  Speaker 4: Yeah, we tried to show that the case of fish
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  Speaker 4: pain is stronger than some people think.
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  Speaker 3: Yeah.
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  Speaker 1: Well. The thing I love about the BANG is that
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  Speaker 1: it explains everything. Like literally, we're going back to the
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  Speaker 1: beginning and trying to find the cause of you know,
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  Speaker 1: planets and life and fish guts and Kelly and everything.
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  Speaker 1: So it's all inclusive, but something we have to clear
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  Speaker 1: out before we dig deeper into theories about what happened
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  Speaker 1: before the Big Bang is what we mean when we
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  Speaker 1: say the big bang. And in your book, I really
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  Speaker 1: appreciated that you attack this head on. You're like, look,
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  Speaker 1: there's a lot of confusion about what this means, and
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  Speaker 1: cosmologists aren't even always consistent about what they mean by
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  Speaker 1: the words. So can you give us a clear and
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  Speaker 1: crisp definition of what we mean when we save the
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  Speaker 1: big Bang?
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  Speaker 4: Well, the answer is now, I can't, because there's all
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  Speaker 4: than one definition of the big Bang, and that's kind
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  Speaker 4: of the whole problem. People mean different things when they
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  Speaker 4: say a big bang. But what we can do, which
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  Speaker 4: I hope will be really helpful, is to explain the
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  Speaker 4: different meanings and then people might try and infer which
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  Speaker 4: meaning is being used in which context. So we sol
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  Speaker 4: highlight two definitions of the big Bang. So one is
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  Speaker 4: that the big Bang is a theory that says the
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  Speaker 4: universe evolved from a very hot, dense state. So it
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  Speaker 4: was different in the past, very different in the past
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  Speaker 4: than it is today. So it was very hot, very dense,
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  Speaker 4: highly curved, and that's very very different to the sort
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  Speaker 4: of cold, sparse universe we see today. So that's one
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  Speaker 4: definition we call without the hot Big.
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  Speaker 1: Bang, and that's what scientists mean when they refer to
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  Speaker 1: the Big Bang, because we know the universe is expanding
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  Speaker 1: and getting less dense as time goes forwards. But we
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  Speaker 1: can also run the clock backwards and figure out that
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  Speaker 1: it was more dense in the past. And if we
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  Speaker 1: run it back thirteen point eight billion years, we get
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  Speaker 1: to a very hot and very dense state, and that's it.
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  Speaker 1: The hot Big Bang doesn't go any further than that
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  Speaker 1: because it can't. That state is so hot and so
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  Speaker 1: dense you'd need quantum gravity to predict what happens before that,
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  Speaker 1: So it doesn't go all the way to a singularity.
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  Speaker 1: It can't without quantum gravity, so it doesn't tell us
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  Speaker 1: what happened before or how time began. It assumes that
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  Speaker 1: initial state and explains what happens afterwards as time goes forward,
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  Speaker 1: and it does it very well, and there's a lot
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  Speaker 1: of experimental evidence for it.
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  Speaker 4: Another definition we call the Big Bang singularity. So that's
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  Speaker 4: an idea that says the universe start a denist state
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  Speaker 4: that's infinitely dense, infinitely hot, infinitely curved, and that marks
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  Speaker 4: the beginning of time.
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  Speaker 3: So there is nothing before the Big Bang, and this idea.
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  Speaker 1: The Big Bang singularity is what most people think of
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  Speaker 1: when they hear the phrase big Bang. This takes that hot,
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  Speaker 1: dense state from thirteen point eight billion years ago and
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  Speaker 1: extrapolates it even further backwards in time, but ignoring quantum mechanics.
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  Speaker 1: It says, if we just account for gravity, what would happen?
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  Speaker 1: So you get a singularity. It's a collapse. That's like
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  Speaker 1: how general relativity predicts the singularity inside a black hole,
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  Speaker 1: which also ignores quantum mechanics. So we don't really believe it.
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  Speaker 1: So the Big Bang singularity is an extrapolation past what
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  Speaker 1: we know using an approximation of quantum gravity that we
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  Speaker 1: know is wrong, which ignores all of the quantum effects.
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  Speaker 1: And there's no experimental data for this extrapolation. It's all
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  Speaker 1: very speculative.
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  Speaker 4: Now here's the interesting thing. And we did a survey
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  Speaker 4: of physicists. We went to a conference in Copenhagen, very
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  Speaker 4: large conference. It was interdisciplinary. We had theorists, we had observers,
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  Speaker 4: we had like numerical relativists, we had people working in
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  Speaker 4: quantum gravity or kind and lead some of the leading
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  Speaker 4: figures in the field. And we asked various questions about
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  Speaker 4: controversies within physics, such as what's the right interpretation of
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  Speaker 4: quantum mechanics, what's the best candidate for quantum gravity, what
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  Speaker 4: do you think dark matter is? And we got consensus
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  Speaker 4: on almost nothing. I can't think of any topic where
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  Speaker 4: we got fifty percent for any one thing except one
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  Speaker 4: one exception, and that was how should we define the
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  Speaker 4: term big And the consensus was that it should only
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  Speaker 4: be defined as this evolution from a hot, dense stay.
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  Speaker 4: So the idea that the universe began at the Big
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  Speaker 4: Bang or there was a singularity is not perceived as
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  Speaker 4: the way we should understand the Big Bank. That is
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  Speaker 4: a theoretical extrapolation that most people don't trust, I would say.
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  Speaker 1: And let's dig into that a little bit more. Like,
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  Speaker 1: we have this theoretical extrapolation, the Big Bang singularity, as
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  Speaker 1: you say, which might predate the hot early universe that
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  Speaker 1: you described as the hot Big Bang. And that's very speculative.
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  Speaker 1: But we have a lot of evidence for the hot
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  Speaker 1: Big Bang. Right when we say the universe was dense
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  Speaker 1: and hot thirteen point eight billion years ago, that's not speculation.
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  Speaker 1: That's something we have unfairly solid grounds, right.
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  Speaker 3: That's right.
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  Speaker 4: I don't think there's any serious doubt about the hot
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  Speaker 4: big bank. So that's very well established. We've got lots
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  Speaker 4: of independent lines of evidence for that. People will probably
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  Speaker 4: be familiar with, you know, the expansion given by the
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  Speaker 4: red shifted galaxies. We've got the cosmic microwave background, the
• 13:02
  Speaker 4: abundance of elements, and there's various properties of the cosmic
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  Speaker 4: microve background that we should see if the Big Bank
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  Speaker 4: had happened, and we see them. So I don't think
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  Speaker 4: there's any doubt that there was a hot Big Bang.
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  Speaker 4: But the observational evidence stops there. We can't have observational
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  Speaker 4: evidence of a singularity. They are sort of hidden from
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  Speaker 4: us if they were to exist, but I think most
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  Speaker 4: physics would say they don't really exist. They're just part
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  Speaker 4: of our physics that breaks down, and we need better
• 13:30
  Speaker 4: physics and that will sort of get rid of the singularities.
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  Speaker 4: But how to do that is an open question, and
• 13:35
  Speaker 4: what would replace a singularity is where all the debate is.
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  Speaker 4: That's why we call our book the Battle of the
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  Speaker 4: Big Bang, because once you concede, Okay, we don't really
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  Speaker 4: know the universe began with a big bank singularity. It
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  Speaker 4: might have had a prior stay, Okay, so what was
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  Speaker 4: that prior's day? And that's the battle because there's all
• 13:54
  Speaker 4: kinds of ideas out there and no one knows which
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  Speaker 4: one is right.
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  Speaker 2: So for the biologist, if I were to be floating
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  Speaker 2: in and I was observing the big bangs of the
• 14:04
  Speaker 2: two different varieties happening, what would I be seeing in
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  Speaker 2: a hot big bang and what would I be seeing
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  Speaker 2: in a big bank's singularity?
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  Speaker 4: So in a hot big bang, well, I think the
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  Speaker 4: name kind of gives you a clue. It's very, very
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  Speaker 4: hot and dense basically, but soon you know, as you
• 14:18
  Speaker 4: go back in time. It's a bit like looking at
• 14:21
  Speaker 4: the sun. You know, if you look at the surface
• 14:24
  Speaker 4: of the sun, you can see that it's about five thousand,
• 14:26
  Speaker 4: seven hundred colvin, but you can't it's.
• 14:28
  Speaker 3: Opaque, right.
• 14:29
  Speaker 4: If you to go through it, all the photons would
• 14:31
  Speaker 4: be bouncing off the materials, you couldn't really see very far.
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  Speaker 3: It'd be like a fog. So that's this sort of hot,
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  Speaker 3: dense state.
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  Speaker 1: And to clarify, you're saying that the whole universe was
• 14:43
  Speaker 1: hot and dense, like the entire universe was thirteen point
• 14:47
  Speaker 1: eight billion years ago, something like the inside of the
• 14:50
  Speaker 1: sun is now and photons made inside the sun get
• 14:53
  Speaker 1: reabsorbed almost immediately, which is why the sun is opaque.
• 14:57
  Speaker 1: You can't see through it, so it's not a great view.
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  Speaker 4: Now the singularity again, most people would say it's just
• 15:05
  Speaker 4: a part with a mass breaks down. But but the
• 15:07
  Speaker 4: description involves you know, there was what was called a curve.
• 15:09
  Speaker 4: It's your singularity. So here the temperature would literally be infinite.
• 15:13
  Speaker 2: So it's hot too.
• 15:14
  Speaker 4: It's also hot, yes, yes, okay, yeah, it would.
• 15:18
  Speaker 3: Be hotter, hotter a big bang, yeah, the holter big bang.
• 15:21
  Speaker 2: Oh wait, so the hot Big Bang is not the
• 15:23
  Speaker 2: hardest of the Big Bass.
• 15:24
  Speaker 4: Not the hot good naming, h guys, it is all
• 15:27
  Speaker 4: right yeah, but no, but we'll come. We'll come to
• 15:31
  Speaker 4: what might have come before the Big Bang, and that
• 15:33
  Speaker 4: could have been something very cold.
• 15:35
  Speaker 3: Okay.
• 15:35
  Speaker 4: So yeah, that's to do with something called inflationary cosmology.
• 15:40
  Speaker 4: So if we believe that story of the Big Bang
• 15:42
  Speaker 4: or then actually the universe is very cold before the
• 15:44
  Speaker 4: Big Bang.
• 15:45
  Speaker 1: All right, So we have this scientific conception that the
• 15:49
  Speaker 1: universe is cold and sparse now and we run the
• 15:52
  Speaker 1: clock backwards, we get to a hot, dense state thirteen
• 15:55
  Speaker 1: billion years ago, and the big question is what came
• 15:58
  Speaker 1: before that? Where did that hot dance state come from?
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  Speaker 1: We know a lot about that state and its evolution
• 16:03
  Speaker 1: from that point to now, but not a lot from
• 16:06
  Speaker 1: before that. That's the scientific conception of the Big Bang.
• 16:09
  Speaker 1: But I think if you talk to people in the
• 16:11
  Speaker 1: general public and you ask them about the Big Bang,
• 16:13
  Speaker 1: they mostly think about the Big Bang singularity. They think
• 16:16
  Speaker 1: the universe started from a tiny dot that exploded into
• 16:19
  Speaker 1: empty space. Why do you think there's such a persistent
• 16:22
  Speaker 1: gap between the scientific view and the popular view. I mean,
• 16:26
  Speaker 1: you work on both sides of the aisle. Why do
• 16:28
  Speaker 1: you think there's been a disconnect there.
• 16:30
  Speaker 3: Well, I think there's a couple of reasons.
• 16:33
  Speaker 4: One, when you're doing animation, and you know, I've got
• 16:37
  Speaker 4: YouTube videos that we try and animate the big fact,
• 16:39
  Speaker 4: you kind of it's hard not to draw bit a
• 16:42
  Speaker 4: light exploding outwards, right, because that's how you're going to
• 16:45
  Speaker 4: animate it. So it's hard for people to not have
• 16:49
  Speaker 4: that visualization, which is, you know, a rough approximation, but
• 16:53
  Speaker 4: it's not precise in their head.
• 16:56
  Speaker 1: And I want to be clear here that it's not
• 16:58
  Speaker 1: precise because applies that the universe was empty, that a
• 17:02
  Speaker 1: dot of matter exploded into empty space. This is misleading
• 17:06
  Speaker 1: because the universe was never empty. Matter was always everywhere.
• 17:11
  Speaker 1: If the universe was infinite, then matter was infinite and
• 17:13
  Speaker 1: then expanded everywhere simultaneously. If the universe was finite, then
• 17:18
  Speaker 1: it was small but still always filled with matter. There
• 17:21
  Speaker 1: was never a tiny dot exploding out into empty space.
• 17:25
  Speaker 4: But the other thing is, I think two things happened
• 17:28
  Speaker 4: at the same time. Roughly in the mid nineteen sixties,
• 17:32
  Speaker 4: we got the evidence now clear that there was a
• 17:35
  Speaker 4: cosmic microwave background, that's the afterglow of the Big Bang.
• 17:40
  Speaker 4: It was a very hot surface and then it cooled
• 17:44
  Speaker 4: down into microwaves as the universe expanded and stretched, so
• 17:47
  Speaker 4: it stretched that light into into the microwaves, and that
• 17:50
  Speaker 4: was very clear evidence of the hot Big Bank. At
• 17:53
  Speaker 4: the same time, Roger Penrose and Stephen Hawking, roughly at
• 17:57
  Speaker 4: the same time, we're establishing these singularity theorems that say
• 18:03
  Speaker 4: the Big Bang must have been a singularity. So that
• 18:07
  Speaker 4: looked like you've got the theory and the evidence all
• 18:10
  Speaker 4: dancing in harmony. So it would appear then that the
• 18:14
  Speaker 4: universe had this definite beginning of the singularity, and of
• 18:16
  Speaker 4: course one of the authors of these Penrose Hawking. Theorems
• 18:20
  Speaker 4: of Stephen Hawking, and he was an incredible figure popularizing science.
• 18:27
  Speaker 4: And whilst Roger Penrose was a bit reluctant to even
• 18:32
  Speaker 4: user RaSE singularity, wasn't sure that we should trust it
• 18:36
  Speaker 4: this distrapolation, I think Stephen Hawking was much more brash,
• 18:39
  Speaker 4: you know, so he was sort of proclaimed, you know,
• 18:42
  Speaker 4: this is the beginning of the universe. But what hers
• 18:45
  Speaker 4: happened is that some of the assumptions of those singularity
• 18:49
  Speaker 4: theorems have started to unravel. And this happened, you know,
• 18:56
  Speaker 4: in the decades after the singularity theorems were proven. So
• 19:00
  Speaker 4: physical theory is only good as the assumptions that it has,
• 19:03
  Speaker 4: and those assumptions in the peneris hooking theory. We can
• 19:07
  Speaker 4: go over them one by one if you wish, But
• 19:09
  Speaker 4: bottom line is people started to question those assumptions. So
• 19:13
  Speaker 4: then it was like, well, maybe there isn't really a
• 19:15
  Speaker 4: singularity or it maybe it's just an artifact of pushing
• 19:19
  Speaker 4: the equations beyond their domain of validity, and we need
• 19:23
  Speaker 4: new physics to explore what really happened to fourteen billion
• 19:26
  Speaker 4: years ago.
• 19:27
  Speaker 2: So The problem is that the popular science conception of
• 19:30
  Speaker 2: the Big Bang hasn't caught up with where we are
• 19:33
  Speaker 2: now in our understanding of the Big Bang. Would that
• 19:34
  Speaker 2: be fair to say.
• 19:35
  Speaker 1: Yeah, But I think there's more than that. Two ideas
• 19:38
  Speaker 1: were developed at the same time, the hot big Bang
• 19:40
  Speaker 1: and the big Bang singularity, and they were both just
• 19:43
  Speaker 1: called the bing bang, and so they get confused for
• 19:45
  Speaker 1: each other. The hot big Bang is still a very
• 19:48
  Speaker 1: solid idea scientifically, and the big Bang singularity kind of
• 19:51
  Speaker 1: never was and we've moved on from it. But most
• 19:54
  Speaker 1: people still think of the big Bang singularity when you
• 19:57
  Speaker 1: say the big Bang.
• 19:58
  Speaker 3: I think that's right.
• 20:00
  Speaker 4: Yes, although there were people even at the time in
• 20:02
  Speaker 4: the sixties saying these singularity theorems don't prove the universe
• 20:06
  Speaker 4: at a beginning, but I don't think they were as
• 20:08
  Speaker 4: loud a voice as those He said it did.
• 20:11
  Speaker 1: Sounds like we should blame Stephen Hawking. Yeah, exactly, But
• 20:14
  Speaker 1: it sounds also like a familiar story. You have one
• 20:18
  Speaker 1: story that somebody tells in a compelling way and it
• 20:21
  Speaker 1: sticks in people's mind. It's like, even if it's hard
• 20:23
  Speaker 1: for people to wrap their mind around this idea of
• 20:26
  Speaker 1: the universe, beginning in a point. It is a compelling story,
• 20:29
  Speaker 1: it's easy to tell, and it's stuck in the popular
• 20:32
  Speaker 1: imagination long after people are like, well, we actually only
• 20:35
  Speaker 1: know a certain part of the story. The rest of
• 20:37
  Speaker 1: it's speculative. That's the nuance, that's the subtlety that's hard
• 20:41
  Speaker 1: to convey. I feel like that's sort of what's happening
• 20:45
  Speaker 1: with popular science everywhere, that the details are being lost
• 20:49
  Speaker 1: and the compelling clickbait headlines are getting propagated and embedded
• 20:53
  Speaker 1: in people's minds. As a science popularizer yourself, how do
• 20:57
  Speaker 1: you feel about the sort of state of science journalism
• 21:00
  Speaker 1: right now?
• 21:00
  Speaker 3: Yeah, it's depressing.
• 21:02
  Speaker 4: I Well, one thing I do want to say, just
• 21:05
  Speaker 4: before I come on to that, another correction that we
• 21:08
  Speaker 4: want to make to the popular I'm saying is that
• 21:10
  Speaker 4: the Big Bang wasn't a point. Rather, it could have
• 21:13
  Speaker 4: happened everywhere. Well if it would have happened everywhere, and
• 21:17
  Speaker 4: in fact, the universe could be infinite today, and it
• 21:19
  Speaker 4: could have been infinitely big even at the Big Bang,
• 21:21
  Speaker 4: So it wasn't a point. But anyway, no, siche journal
• 21:24
  Speaker 4: isn't very very depressing at the moment. I think you
• 21:28
  Speaker 4: see people just trying to get headlines clickbaits. They're not,
• 21:33
  Speaker 4: i think, being rigorous and of course probably underfunded. So
• 21:38
  Speaker 4: you just get people, you know, copying press releases or
• 21:42
  Speaker 4: they're going for like the big angry headline. You know,
• 21:46
  Speaker 4: Oh everyone's got everything wrong, and that's usually also dubious too.
• 21:51
  Speaker 4: So yeah, I'm not optimistic about the state of journalism.
• 21:56
  Speaker 1: All right, Well, let's do our best to push back,
• 21:58
  Speaker 1: and so to reiterate, we know a lot about the
• 22:01
  Speaker 1: last thirteen point eight billion years of the universe. We
• 22:04
  Speaker 1: have evidence, it all comes together, we have multiple lines
• 22:07
  Speaker 1: of evidence. It all tells a very compelling story, and
• 22:10
  Speaker 1: it tells us that there was a hot density a
• 22:12
  Speaker 1: long time ago. But then the question, of course is
• 22:15
  Speaker 1: where does that come from? And so let's explore some
• 22:18
  Speaker 1: of those theories. One of the most popular ones is
• 22:21
  Speaker 1: the theory of inflation. Can you give us a quick
• 22:24
  Speaker 1: primer on what inflation is and why it's a compelling
• 22:26
  Speaker 1: explanation for how we got that hot density?
• 22:29
  Speaker 4: Right, So before we say what inflation is, it's probably
• 22:32
  Speaker 4: worth saying why people take it so seriously? What the
• 22:35
  Speaker 4: problems that are supposed to solve, And then maybe we
• 22:37
  Speaker 4: can some one will explain what it is. So the
• 22:40
  Speaker 4: problems that inflation are supposed to solve, I, well, there
• 22:44
  Speaker 4: are kind of a few. One is called the monopole problem.
• 22:47
  Speaker 4: So this is that if you think of a magnet,
• 22:50
  Speaker 4: it has a north and a south pole. If you
• 22:52
  Speaker 4: cut it in two, you don't get one with a
• 22:55
  Speaker 4: north pole, one with a south pole. You just get
• 22:57
  Speaker 4: another two magnets with the northern sealf pole. However, theorists
• 23:02
  Speaker 4: in the nineteen seventies thought that in the whole early
• 23:05
  Speaker 4: conditions of the universe you would get something called monopoles,
• 23:09
  Speaker 4: which would literally have only one pole, and these monopoles
• 23:13
  Speaker 4: would be very, very abundant and so should dominate the universe.
• 23:16
  Speaker 4: But yet we don't see any There are no monopoles
• 23:19
  Speaker 4: ever observed, and also they probably be too heavy to
• 23:22
  Speaker 4: allow the universe to spand anyway, So this was called
• 23:24
  Speaker 4: the monopole problem. And actually this was a motivation to
• 23:29
  Speaker 4: come up with inflation.
• 23:30
  Speaker 1: That's super fascinating and not something I think is widely
• 23:33
  Speaker 1: enough appreciated. Inflation wasn't conceived of to explain the origins
• 23:38
  Speaker 1: of the universe, but to solve a little technical problem.
• 23:41
  Speaker 1: The theory at the time predicted that when the universe
• 23:44
  Speaker 1: was hot and dense and cooling as it cooled, it
• 23:46
  Speaker 1: shouldn't just make protons and electrons, but it should also
• 23:49
  Speaker 1: make magnetic monopoles, weird particles that have just a magnetic
• 23:53
  Speaker 1: north or south, the way electrons just have a negative
• 23:57
  Speaker 1: and protons just have a positive. The use does this
• 24:00
  Speaker 1: when it has a phase transition as it cools, like
• 24:03
  Speaker 1: when water goes from steam to liquid, it forms droplets. Here,
• 24:07
  Speaker 1: the phase transition was predicted to make all these magnetic monopoles,
• 24:10
  Speaker 1: and they should stick around. They don't go anywhere, So
• 24:13
  Speaker 1: if they were supposed to have been made in the
• 24:15
  Speaker 1: early universe, they should still be here for us to see.
• 24:17
  Speaker 1: But of course we don't see them anywhere we've looked.
• 24:20
  Speaker 1: We can't find any. So that's a problem, and you
• 24:24
  Speaker 1: need to find some way to tweak the theory so
• 24:26
  Speaker 1: it doesn't predict a bunch of monopoles that we know
• 24:29
  Speaker 1: don't exist in the universe. I love how thinking about
• 24:32
  Speaker 1: weird magnets helps us, in the end accidentally understand the
• 24:36
  Speaker 1: origins of the universe. All right, so then tell us
• 24:38
  Speaker 1: what happens next.
• 24:40
  Speaker 4: So what happened was to scientists Henry Tyane, and we're
• 24:45
  Speaker 4: trying to solve this monopole problem. And I imagine there
• 24:48
  Speaker 4: could be like phase transitions in the early universe.
• 24:51
  Speaker 3: Phase resistion might be familiar with.
• 24:52
  Speaker 4: If you have I'm setting out my going and right
• 24:54
  Speaker 4: now is very hot, So if I had some ice
• 24:57
  Speaker 4: similar drink, it's going to melt, It's going to go
• 25:01
  Speaker 4: from solid to liquid. That's a phase transition. So these
• 25:04
  Speaker 4: are the sorts of phag transitions we're familiar with. However,
• 25:07
  Speaker 4: there can be phase transitions that are a bit weird
• 25:10
  Speaker 4: that we're not so familiar with. One of them is
• 25:12
  Speaker 4: called supercooling. So supercooling is if you put some water
• 25:18
  Speaker 4: very very pure. You can do this experiment at home.
• 25:21
  Speaker 4: Who would think you could do an experiment about the
• 25:23
  Speaker 4: very early universe and the origin of the Big Bang
• 25:25
  Speaker 4: in you your breezer at home. So what you have
• 25:27
  Speaker 4: to do is get some very very pure water, keep
• 25:30
  Speaker 4: it nice and still, and put it in the freezer.
• 25:33
  Speaker 4: Leave it in there, and after a while you take
• 25:36
  Speaker 4: it out. It should have frozen. But actually, if it's
• 25:39
  Speaker 4: pure enough and you are careful enough, it will not freeze.
• 25:42
  Speaker 4: It's what's in it. What's called a super cooled state,
• 25:44
  Speaker 4: it will stay liquid. Then if you shake it, it
• 25:46
  Speaker 4: will very quickly freeze. So this sort of delayed transition
• 25:50
  Speaker 4: is called supercooling.
• 25:51
  Speaker 2: Why.
• 25:52
  Speaker 4: It's just a way that the molecules can be in
• 25:55
  Speaker 4: a certain state that sort of resists being frozen.
• 25:57
  Speaker 1: Chemistry. Yeah, chemistry, this chemistry, but it's also super interesting.
• 26:04
  Speaker 1: I know that's unusual for me to say, but this
• 26:07
  Speaker 1: one I love. For freezing. The start, the liquid needs
• 26:10
  Speaker 1: a tiny seed of a solid like an ice crystal
• 26:12
  Speaker 1: or a dust spec or a surface bump to organize
• 26:15
  Speaker 1: molecules into the solid lattice. If no seed is present
• 26:19
  Speaker 1: and the liquid is very pure and undisturbed, the molecules
• 26:22
  Speaker 1: stay disordered, even though they are cold enough to be
• 26:25
  Speaker 1: a solid. It's like a crowd waiting for someone to
• 26:28
  Speaker 1: start clapping. Nobody does anything until the first person starts
• 26:32
  Speaker 1: to clap. And this chemistry trivia is actually important because
• 26:35
  Speaker 1: it helps us understand the universe cooling. It lets the
• 26:39
  Speaker 1: universe cool without making those monopoles. The universe passes that point,
• 26:44
  Speaker 1: but it stays super cooled and doesn't make monopoles the
• 26:48
  Speaker 1: way super cooled liquid doesn't make ice crystals.
• 26:51
  Speaker 4: Basically, they had time, because imagine that the universe would
• 26:55
  Speaker 4: be in a super cooled state, and they calculate this
• 26:57
  Speaker 4: would actually stop monopole production.
• 27:00
  Speaker 3: We've solved the monopare problem.
• 27:02
  Speaker 4: And then they said, well, let's just see if this
• 27:04
  Speaker 4: would affect the expansion rate of the early universe. And
• 27:06
  Speaker 4: what they found was that it would expand exponentially if
• 27:10
  Speaker 4: it's in this super called state. It would expand an
• 27:14
  Speaker 4: incredibly rapid rate. The source of race we're talking about
• 27:18
  Speaker 4: is doubling in size every ten to the minus thirty
• 27:22
  Speaker 4: seven seconds, and so that in words, that is and
• 27:26
  Speaker 4: I think ten trillionth of a trillionth of a trillionth
• 27:29
  Speaker 4: of a second. So that is a very very fast
• 27:33
  Speaker 4: rate of expansion.
• 27:34
  Speaker 1: So they did this trick to avoid predicting monopoles would
• 27:37
  Speaker 1: be made, and then discovered that it also predicted that
• 27:40
  Speaker 1: the universe expanded super fast.
• 27:43
  Speaker 4: That's awesome, But then what happened was Gooth had heard
• 27:46
  Speaker 4: a lecture about another problem in cosmology called the flatness problem.
• 27:51
  Speaker 4: And the flatness problem basically is that the universe can
• 27:54
  Speaker 4: have a sort of different geometries at large scale. It
• 27:56
  Speaker 4: could be curved, positively curved like a bore or negatively
• 28:00
  Speaker 4: like a saddle, or it could be flat like a
• 28:02
  Speaker 4: piece of paper, and observation showed it was reasonably close
• 28:06
  Speaker 4: to flat in the nineteen seventies. But what had been
• 28:09
  Speaker 4: pointed out by another scientist called Pop Dickie was that
• 28:12
  Speaker 4: those flat solution is unstable. So if it doesn't start
• 28:15
  Speaker 4: out really, really flat, it will be driven away from flatness.
• 28:18
  Speaker 1: So if the universe has positive curvature, that means it
• 28:21
  Speaker 1: has enough mass density to curve in on itself and
• 28:25
  Speaker 1: gravity winds and it curves more and eventually collapses and
• 28:28
  Speaker 1: becomes super duper dense. Even if it's very slightly curved
• 28:32
  Speaker 1: in the early universe, it will get more curved and
• 28:34
  Speaker 1: then more curved, and it's a runaway effect. And the
• 28:36
  Speaker 1: same thing happens in the opposite direction. If it has
• 28:38
  Speaker 1: negative curvature, it will get slightly more negatively curved, and
• 28:42
  Speaker 1: then more and then more. It's a runaway effect towards
• 28:44
  Speaker 1: negative curvature. But the universe as we see it today
• 28:47
  Speaker 1: is still very close to flat, if not perfectly flat.
• 28:51
  Speaker 1: That's weird because in order to be flat now, the
• 28:53
  Speaker 1: universe had to have been borne exactly on the knife's
• 28:57
  Speaker 1: edge of flat any tiny deviation from flatness would after
• 29:00
  Speaker 1: almost fourteen billion years, make the universe either collapse or explode.
• 29:05
  Speaker 1: That's the flatness problem.
• 29:07
  Speaker 4: So it's very surprising then how the universe could be
• 29:09
  Speaker 4: so flat because it's this unstable solution. When Gooth thought
• 29:13
  Speaker 4: about inflation, he realized that if you're undergo inflation, then
• 29:18
  Speaker 4: actually it'll be driven towards flatness, and the rays you
• 29:22
  Speaker 4: can think about this is it. Imagine have you ever
• 29:24
  Speaker 4: seen like a circle show where people walk on like
• 29:28
  Speaker 4: pilates balls and you're saying that, m okay, quite difficult.
• 29:32
  Speaker 4: I imagine you need some skills for that.
• 29:35
  Speaker 3: I imagine. So imagine you were standing aren't that ball?
• 29:40
  Speaker 3: Or you tried and he fell off.
• 29:41
  Speaker 4: Let's say, but then you expanded the ball rapidly to
• 29:44
  Speaker 4: the size of the Earth. Be pretty easy to stand
• 29:46
  Speaker 4: on that ball. You wouldn't even notice any curvature.
• 29:49
  Speaker 1: I rarely fall off the Earth, that's true.
• 29:50
  Speaker 3: Yeah, yeah, I don't fall off the Earth often either.
• 29:53
  Speaker 4: So then anything will appear will automatically appear flat if
• 29:57
  Speaker 4: it goes undergoes this exponential experience so real, it would
• 30:00
  Speaker 4: fix this flatness problem. So now it solves two problems
• 30:04
  Speaker 4: at once, and then it turns out it solves many
• 30:06
  Speaker 4: other problems it once.
• 30:06
  Speaker 3: I won't go all of them, but I'll do one more.
• 30:08
  Speaker 1: Wit. Hold on, I understood how the rapid expansion solves
• 30:12
  Speaker 1: the flatness problem, Like it seems curved, you expand it,
• 30:15
  Speaker 1: all of a sudden, it doesn't seem very curved. How
• 30:18
  Speaker 1: does it solve the monopole problem? Exactly? Like why because
• 30:22
  Speaker 1: you're not putting the universe in a freezer. It's not.
• 30:24
  Speaker 1: No ten year old is doing the experiment on us.
• 30:26
  Speaker 4: The monopoles would be thrown out of the horizon because
• 30:29
  Speaker 4: there would only be like a handful of monopoles in
• 30:32
  Speaker 4: any patch. So as the universe expands, they'd be thrown
• 30:35
  Speaker 4: out of the horizon and you wouldn't see any.
• 30:38
  Speaker 2: I like that as a solution. Anything that you don't
• 30:40
  Speaker 2: like gets exploded out of the picture.
• 30:43
  Speaker 3: Throw it out. Yeah, yeah, exactly.
• 30:46
  Speaker 1: I think that's a fascinating sort of bit of science
• 30:48
  Speaker 1: where you're like, let me calculate what I think should
• 30:51
  Speaker 1: have happened in the early universe, and then I'm going
• 30:53
  Speaker 1: to compare that to what I'm seeing, Like, yeah, I
• 30:55
  Speaker 1: don't see a lot of monopoles, so Obviously something must
• 30:57
  Speaker 1: be wrong. I'm missing a piece. What can I add
• 31:00
  Speaker 1: to the universe is like now it's more likely to
• 31:03
  Speaker 1: describe the universe I see today. I think that's super fascinating.
• 31:06
  Speaker 1: Let's digest that and take a break, and when we
• 31:08
  Speaker 1: come back, Phil is going to tell us more about
• 31:10
  Speaker 1: how inflation solved these problems and whether or not we
• 31:13
  Speaker 1: should believe in it. Okay, we're back and we're talking
• 31:36
  Speaker 1: to Phil about the state of the early universe. What
• 31:38
  Speaker 1: we know about the universe before it was hot and dense,
• 31:41
  Speaker 1: and we've been talking about inflation, this theory that the
• 31:44
  Speaker 1: universe expanded super rapidly in a very short amount of time.
• 31:48
  Speaker 1: So tell us, Phil, inflation sounds a lot like the
• 31:51
  Speaker 1: expansion that we have now we talk about dark energy
• 31:54
  Speaker 1: in the universe is accelerating in its expansion. Is inflation
• 31:58
  Speaker 1: a different mechanism for expansion? Is it the same thing,
• 32:01
  Speaker 1: just at a different moment in the universe? How do
• 32:03
  Speaker 1: those two things connect?
• 32:05
  Speaker 4: They are similar because the universe is currently accelerating in
• 32:08
  Speaker 4: its expansion. So you could say the dark energy we
• 32:11
  Speaker 4: see today is a very dilute form of inflation, and
• 32:16
  Speaker 4: so that does raise the question are they really the
• 32:19
  Speaker 4: same physics? But I think that's still to be determined,
• 32:24
  Speaker 4: Like there's a lot unknown about inflation, if it even happened.
• 32:28
  Speaker 4: So whether inflation and the dark energy are are the
• 32:31
  Speaker 4: different manifestations the same phenomenon, or whether they're different things
• 32:35
  Speaker 4: that just result in something broadly similar.
• 32:39
  Speaker 3: I think it's still an open question.
• 32:41
  Speaker 4: But one thing I do want to just highlight is
• 32:44
  Speaker 4: that one of the things that inflation solves, and there
• 32:47
  Speaker 4: are a number of problems, but there's one in particular
• 32:49
  Speaker 4: that I think is the most relevant, and that is
• 32:52
  Speaker 4: how you get galaxy structures. Because if you had a
• 32:56
  Speaker 4: very uniform start at the universe, you've got to ask
• 32:59
  Speaker 4: the question, how on Earth to all these networks of
• 33:01
  Speaker 4: clusters of galaxies form what laid the seeds? And in inflation,
• 33:06
  Speaker 4: the idea is there will be quantum fluctuations and these
• 33:10
  Speaker 4: would be stretched by inflation to create the seeds of galaxies.
• 33:15
  Speaker 4: So amazingly, these enormous, enormous structures, you know, hundreds of
• 33:19
  Speaker 4: thousands of light years across for a particular galaxy, and
• 33:23
  Speaker 4: for clusters of galaxies even millions of light years across.
• 33:26
  Speaker 3: You know, these are succeeded.
• 33:28
  Speaker 4: By tiny subatomic quantum fluctuations that were stretched by inflation.
• 33:32
  Speaker 4: And I think, out of all the problems that inflation
• 33:35
  Speaker 4: is supposed to address, I think that's the one that's
• 33:37
  Speaker 4: the most impressive, and where cosmologists so really thinking, this
• 33:42
  Speaker 4: is the leading candidate to explain the properties of our universe.
• 33:46
  Speaker 2: So I think I get bogged down by this idea
• 33:48
  Speaker 2: that the Big Bang started at a tiny point. And
• 33:50
  Speaker 2: so what I'm imagining is we're looking at before the
• 33:53
  Speaker 2: tiny point where it's inflating, and there's areas where you're
• 33:56
  Speaker 2: going to get galaxies eventually, but then it all kind
• 33:59
  Speaker 2: of such down to a little point and then blows
• 34:01
  Speaker 2: back out again. But that is not the right way
• 34:03
  Speaker 2: to be thinking about it, right because I don't see
• 34:05
  Speaker 2: how stuff that happened before the Big Bang is going
• 34:08
  Speaker 2: to result in galaxies after the Big Bang?
• 34:12
  Speaker 3: What am I missing?
• 34:13
  Speaker 4: I mean, there are ideas that the universe could undergo
• 34:16
  Speaker 4: cycles like that, I could expand and contract and expand
• 34:19
  Speaker 4: and contract, But that's independent of inflation. So that depends
• 34:24
  Speaker 4: on I guess, on the properties of the dark energy
• 34:26
  Speaker 4: we see today, if it's a cosmological constant, I if
• 34:30
  Speaker 4: the energy of empty space is sort of a constant
• 34:33
  Speaker 4: I should say better, what's driving the accelerated expansion is
• 34:36
  Speaker 4: that empty space has a constant energy, then the universe
• 34:40
  Speaker 4: will not recollapse. However, there have been observations recently suggesting
• 34:45
  Speaker 4: that the dark energy is not a cosmological constant, that
• 34:48
  Speaker 4: it could be some dynamical field that changes over time,
• 34:51
  Speaker 4: and in that case it could recollapse. So that I
• 34:55
  Speaker 4: hopefully address as this issue of you know, getting sack
• 34:57
  Speaker 4: back down. But to answer your question, how could it
• 35:00
  Speaker 4: be that this tiny fluctuating sea of space could have
• 35:05
  Speaker 4: anything to do with what we see today where you
• 35:08
  Speaker 4: need basically density fluctuations. So if you imagine the universe
• 35:11
  Speaker 4: being perfectly smooth, then you wouldn't get the universe we
• 35:16
  Speaker 4: see today because some regions are more dense than others.
• 35:19
  Speaker 4: So those regions that have galaxies in them are more dense,
• 35:22
  Speaker 4: and there are voids in space that are under dense. Also,
• 35:26
  Speaker 4: when you look at the cosmic microwave background, this oldest
• 35:29
  Speaker 4: light that we can see is very very very very uniform,
• 35:32
  Speaker 4: like there's almost no differences across the sky until you
• 35:36
  Speaker 4: get to a point of about one part in one
• 35:38
  Speaker 4: hundred thousand then you start to see these tiny fluctuations.
• 35:41
  Speaker 4: So that's telling you there were definitely density fluctuations in
• 35:44
  Speaker 4: the early universe.
• 35:46
  Speaker 3: So they have to.
• 35:47
  Speaker 4: Come from somewhere, and inflation is a very nice but
• 35:51
  Speaker 4: not the only possible mechanism to give you those density fluctuations. Now,
• 35:55
  Speaker 4: I said before that the universe could have been infinitely
• 35:58
  Speaker 4: big at the Big Bang. What wouldn't have been infinitely
• 36:01
  Speaker 4: big is our patch of the universe that would have
• 36:02
  Speaker 4: been very very small. So if you're struggling to think, oh,
• 36:05
  Speaker 4: I want to think of this very very small universe,
• 36:07
  Speaker 4: you can think of the observable universe that we see
• 36:09
  Speaker 4: around us. Think of that being very very small. So
• 36:13
  Speaker 4: now in this quantum state, there would be fluctuations. That's
• 36:17
  Speaker 4: just part of quantum theory. And then they get stretched
• 36:20
  Speaker 4: as the universe expands very very rapidly, and they gives
• 36:24
  Speaker 4: you some regions that are more dense than others, and
• 36:27
  Speaker 4: then gravity sculpts them, putting more matter into the denser
• 36:30
  Speaker 4: regions less matter in the under dense regions, and that
• 36:33
  Speaker 4: gives you the seeds for galaxies to form.
• 36:36
  Speaker 1: Thanks well, and I think there's a possibility there of
• 36:39
  Speaker 1: getting confused about the two ideas of the Big Bang. Right,
• 36:42
  Speaker 1: what Phils talking about is the hot Big Bang, So
• 36:44
  Speaker 1: not that the universe started from a point, just that
• 36:47
  Speaker 1: the universe started from a hot dense soup. And he's
• 36:49
  Speaker 1: saying that soup is pretty uniform. So how does that
• 36:52
  Speaker 1: soup then grow up to give you galaxies? And the
• 36:55
  Speaker 1: answer is that soup plus quantum fluctuations. We're not zooming
• 36:58
  Speaker 1: all the way back to the singularity with that's singularly
• 37:00
  Speaker 1: aside from.
• 37:01
  Speaker 4: That, right, But what's interesting is that during inflation, the
• 37:05
  Speaker 4: universe is as cold as it can possibly be, and
• 37:07
  Speaker 4: it's only when inflation ends that it heats up. So
• 37:10
  Speaker 4: then inflation, we can say is a pre Big Bang model,
• 37:13
  Speaker 4: because a lot of textbooks tell you that inflation happened
• 37:15
  Speaker 4: after the Big Bang. But actually, if we use the
• 37:18
  Speaker 4: definition of the Big Bang that everyone, well not everyone,
• 37:21
  Speaker 4: but most scientists adopt, then we're going to say it's
• 37:25
  Speaker 4: the hot dense state. So inflation happened before that hot
• 37:28
  Speaker 4: dense state. It was cold during inflation, as cold as
• 37:31
  Speaker 4: it can possibly be, and then when inflation ends, it
• 37:34
  Speaker 4: heats up. The universe lots all the energy and the
• 37:36
  Speaker 4: inflating space gets converted into matter and radiation, and then
• 37:41
  Speaker 4: you have our Big Bang. So our Big Bang is
• 37:44
  Speaker 4: like a bubble that appeared from this soup of inflating space.
• 37:50
  Speaker 2: Where does the heat come from? How do you go
• 37:52
  Speaker 2: from cold to hot?
• 37:53
  Speaker 1: And let me clarify because cold means something very specific here.
• 37:56
  Speaker 1: It doesn't mean low energy like you might imagine. Is
• 38:00
  Speaker 1: Remember that energy can take many forms. It can be
• 38:03
  Speaker 1: in the form of motion or mass or heat, but
• 38:06
  Speaker 1: there can also be potential energy, like when you put
• 38:08
  Speaker 1: a book high on a shelf or a spring that
• 38:10
  Speaker 1: squeezed down, and that doesn't make the universe hot. And
• 38:15
  Speaker 1: sometimes fields like the Higgs field can get stuck in
• 38:18
  Speaker 1: a state with a lot of potential energy, and so
• 38:20
  Speaker 1: that energy can fill the universe and the universe still
• 38:23
  Speaker 1: be cold. Inflation theory says that the inflation field had
• 38:27
  Speaker 1: a lot of this potential energy, which is exactly also
• 38:30
  Speaker 1: what you need to make the universe expand. In general, relativity,
• 38:35
  Speaker 1: matter and energy density make the universe contract. That's gravity,
• 38:38
  Speaker 1: but potential energy like dark energy or the Higgs field
• 38:41
  Speaker 1: or the inflant On field makes the universe expand. So
• 38:46
  Speaker 1: there's a lot of energy in the universe. But it's
• 38:48
  Speaker 1: not heat. It's in the potential energy the inflation field.
• 38:51
  Speaker 1: So the universe is nearly empty, nothing is moving very fast,
• 38:55
  Speaker 1: but it is expanding. Now when inflation ends, that potential
• 38:58
  Speaker 1: energy is converted into normal matter fields and into mass
• 39:03
  Speaker 1: and motion. So then the universe is hot. That's reheating.
• 39:06
  Speaker 1: It went from cold and full of potential energy to
• 39:09
  Speaker 1: hot and full of mass in motion.
• 39:11
  Speaker 4: But there's another way you can think of it in
• 39:13
  Speaker 4: that is, when particles pop in and out of existence
• 39:16
  Speaker 4: from the vacuum, they have to go back into existence
• 39:19
  Speaker 4: very very quickly. This is the function of the uncertainty principle.
• 39:23
  Speaker 4: And there's an equation which will tell you how long
• 39:25
  Speaker 4: they can exist for and someone and so forth. Now
• 39:27
  Speaker 4: they pop into resistance in pairs, but in inflation they
• 39:31
  Speaker 4: can't get back together again.
• 39:33
  Speaker 3: Because the universe is all ripped them apart.
• 39:35
  Speaker 4: So you kind of get you can actually expanding space
• 39:38
  Speaker 4: can create literally create massuin radiation because it rips these
• 39:43
  Speaker 4: virtual particles which would otherwise just appear and disappear out
• 39:46
  Speaker 4: of the vacuum and they form into real particles. And
• 39:50
  Speaker 4: this is similar to what you see in black holes,
• 39:53
  Speaker 4: because in black holes Hawking famously showed that virtual particles
• 39:57
  Speaker 4: can get also get ripped apart. Someone go into the
• 39:59
  Speaker 4: black hole, some would come out and this would emit
• 40:01
  Speaker 4: Radiation's called Hawking radiation. So something similar to that basically, So.
• 40:06
  Speaker 1: We have the hot Danse universe a long time ago,
• 40:09
  Speaker 1: which were pretty confident about. There's questions and problems and
• 40:13
  Speaker 1: theoretical issues. People come up with this idea of inflation.
• 40:15
  Speaker 1: The universe before that hot Dnse state expanded super duper rapidly,
• 40:20
  Speaker 1: and that solves a lot of those problems. But doesn't
• 40:22
  Speaker 1: it also just kick the questions down the road. Like
• 40:25
  Speaker 1: you say, if you have this incredible inflation, then it
• 40:29
  Speaker 1: solves those problems. But where does that inflation come from?
• 40:31
  Speaker 1: What causes that?
• 40:33
  Speaker 4: So that's an excellent question and the short answer as
• 40:36
  Speaker 4: you don't know. I mean, we're not sure that inflation happened.
• 40:39
  Speaker 4: I mean, some people are pretty confident it happened. And
• 40:42
  Speaker 4: we did a survey physicist about that and we didn't
• 40:45
  Speaker 4: get more than fifty percent saying inflation happened, but they
• 40:48
  Speaker 4: I had to be fair. It was a black hole
• 40:49
  Speaker 4: conference that we were at. If we did a cosmology conference,
• 40:53
  Speaker 4: I guess it would be high. But I think I
• 40:55
  Speaker 4: can't remember exactly what we've got about forty percent, but
• 40:57
  Speaker 4: it wasn't most popular candidate.
• 40:58
  Speaker 3: It didn't get past fifty.
• 41:01
  Speaker 4: So now, one idea is that inflation is eternal into
• 41:06
  Speaker 4: the past and the future. So let me try and
• 41:08
  Speaker 4: unpack what that means. So you might have heard of
• 41:10
  Speaker 4: the idea of a multiverse. Surely anyone that's witches on
• 41:15
  Speaker 4: the TV these days, we must see some sci fi
• 41:18
  Speaker 4: with a multiverse, whether it's Doctor Strange or the Man
• 41:22
  Speaker 4: in the High Castle or whatever. You know, it's very
• 41:27
  Speaker 4: pervasive now in popular culture, but its origins in the
• 41:30
  Speaker 4: cosmological setting is with inflationary cosmology. So remember I said,
• 41:35
  Speaker 4: you can think of our universe as like this bubble
• 41:37
  Speaker 4: that appears out of inflating sea. But the idea is
• 41:41
  Speaker 4: that it wouldn't produce one bubble, it would produce an
• 41:43
  Speaker 4: infinite number of bubbles. And the way this works is
• 41:47
  Speaker 4: pretty straightforward. Just think of the inflating space as something
• 41:52
  Speaker 4: that decays, like a radioactive particle decays, So it decays
• 41:56
  Speaker 4: with a half life. So when it decays, that's that.
• 41:59
  Speaker 3: Moment what we talked about.
• 42:00
  Speaker 4: You know where all the energy gets converted into Madgine radiation. Boom,
• 42:04
  Speaker 4: a big bang, the universe is born. But what has
• 42:08
  Speaker 4: happened to the bit that hasn't decayed yet? Well, it's
• 42:11
  Speaker 4: undergoing exponential expansion. So as long as that exponential expansion
• 42:15
  Speaker 4: is faster than the exponential deka, then the amount of
• 42:18
  Speaker 4: inflating space can never go down.
• 42:20
  Speaker 3: It can only go up.
• 42:21
  Speaker 4: So the analogy I always give is my mum makes
• 42:24
  Speaker 4: this fantastic chocolate cake is really yummy, and I go
• 42:29
  Speaker 4: around there for Sunday afternoon tea. She prints the chocolate
• 42:32
  Speaker 4: cake down on the table and we eat half the cake.
• 42:36
  Speaker 4: Then at some point we go back for seconds, and
• 42:38
  Speaker 4: now the cake is gone. You can't have your cake
• 42:41
  Speaker 4: and eat it right. However, what would happen if when
• 42:44
  Speaker 4: we went back for that second piece the cake had
• 42:47
  Speaker 4: expanded exponentially? Now we could have more cake. We have
• 42:52
  Speaker 4: the same volume of cake that we had in the
• 42:54
  Speaker 4: first bite, you know, but the cakes expanded. Then we
• 42:57
  Speaker 4: go back for thirds. Well, the same thing's happened. The
• 42:59
  Speaker 4: carown faster than we could have eaten it, in which
• 43:02
  Speaker 4: case you rut, the cake can never ever go down,
• 43:04
  Speaker 4: so you get infinite number of pieces of cake and
• 43:07
  Speaker 4: you can have your cake and eat it.
• 43:09
  Speaker 1: I think you also get infinite fill in that scenario,
• 43:11
  Speaker 1: don't you.
• 43:12
  Speaker 4: Yeah, yeah, you have to have a very big belly.
• 43:16
  Speaker 1: All right. So I'm imagining space filled with this inflationary
• 43:20
  Speaker 1: material we don't understand or don't know it's original, and
• 43:23
  Speaker 1: random little bits of it are decaying into our normal
• 43:27
  Speaker 1: universe kind of stuff. So we get these bubbles of
• 43:29
  Speaker 1: normal universes that appear to train in places, but they're
• 43:33
  Speaker 1: separated by this rapidly inflating space.
• 43:35
  Speaker 4: Yes, that's exactly right, yep, yep. So then you get
• 43:38
  Speaker 4: this multiverse and it's eternal. Now, when I say it's eternal,
• 43:43
  Speaker 4: there's a bit of a subtlety there. It's eternal into
• 43:46
  Speaker 4: the future, but is it eternal into the past? Now
• 43:51
  Speaker 4: there is a theorem called the Bordais Gooth and Velenkad
• 43:54
  Speaker 4: theorem of that is, it can only be eternal into
• 43:56
  Speaker 4: the future, but it is not eternal into the past.
• 44:00
  Speaker 4: Still have to ask what came before inflation or what
• 44:01
  Speaker 4: might cause inflation. However, there have been people that have
• 44:05
  Speaker 4: disputed this theorem and said, no, it could be eternal
• 44:07
  Speaker 4: into the past. So if you want to know what
• 44:09
  Speaker 4: came before inflation. In that scenario, it's just more inflation,
• 44:13
  Speaker 4: and it just goes back forever and ever for eternity. However,
• 44:16
  Speaker 4: if we take the body Goose for Lincoln theorem, then
• 44:20
  Speaker 4: we have to ask, okay, what came before inflation? And
• 44:23
  Speaker 4: there are a number of suggestions. And I should also
• 44:27
  Speaker 4: add that there are people that don't like inflation. So
• 44:30
  Speaker 4: one idea as well, inflation didn't happen at all, and
• 44:33
  Speaker 4: there's some other thing that happened, but let's stick with
• 44:36
  Speaker 4: the inflation. Since you asked, so, I would say there's
• 44:40
  Speaker 4: a few ideas out there. The first one that probably
• 44:44
  Speaker 4: came on the scene was nineteen eighty two, and this
• 44:47
  Speaker 4: was proposed by Alex for Lincoln. It's called the tunneling
• 44:50
  Speaker 4: from Nothing idea. So the idea is that what if
• 44:54
  Speaker 4: we treat space quantum mechanically. So normally, when they do
• 45:00
  Speaker 4: this cosmological modeling, you're using Einstein's theory of gravity, so
• 45:05
  Speaker 4: you're assuming space time is classical. But if you'd seen
• 45:09
  Speaker 4: in space time as quantum mechanical as the linking did,
• 45:11
  Speaker 4: then the suggestion is that space itself could fluctuate into
• 45:16
  Speaker 4: existence from a state where there was no space, so
• 45:19
  Speaker 4: that's really hard to get your head round that. This
• 45:22
  Speaker 4: is why the tunneling from nothing idea. The idea is
• 45:25
  Speaker 4: what controls the expansion of the universe, so it's partly
• 45:27
  Speaker 4: it's radius. So if you have a small universe, so
• 45:29
  Speaker 4: we'd actually just clapse back in on itself. So how
• 45:32
  Speaker 4: would you go from a small universe to a universe
• 45:34
  Speaker 4: big enough to inflate? At least and classically it seems
• 45:38
  Speaker 4: to be impossible. However, quantum mechanically it can what's called tunnel.
• 45:43
  Speaker 4: It can tunnel from one set to another, so the
• 45:46
  Speaker 4: small one could tunnel to the larger one. And then
• 45:48
  Speaker 4: what he asked was, well, what's the smallest size that
• 45:51
  Speaker 4: the universe could tunnel from? And he concluded it was zero.
• 45:55
  Speaker 4: So that's pretty hard to get your head round. So
• 45:58
  Speaker 4: that's the tunneling idea. It tunneling from nothing idea. Then
• 46:01
  Speaker 4: you have to sink with a hard tour hawking no
• 46:04
  Speaker 4: boundary state.
• 46:05
  Speaker 1: Hold on, let's dig into the linking idea a little
• 46:07
  Speaker 1: bit more. Yeah, because this is still pre inflation. This
• 46:09
  Speaker 1: is not an alternative inflation. This thing where does the
• 46:12
  Speaker 1: inflation areyas come from? And you're saying that we're adding
• 46:15
  Speaker 1: quantum mechanics to it, so it's not full quantum gravity.
• 46:18
  Speaker 1: It's certain sort of like semi classical.
• 46:20
  Speaker 4: No, no, this is yeah, we'd call it some classic.
• 46:23
  Speaker 4: It's not full quantum gravity. And we should come to
• 46:25
  Speaker 4: full quantum gravity and in a moment.
• 46:27
  Speaker 1: And so this is speculating that the inflationary conditions before
• 46:31
  Speaker 1: the hot Big Bang fluctuated into existence. From and I'm
• 46:36
  Speaker 1: just going to kick the can down the road further
• 46:37
  Speaker 1: here from and you said something that has no space time.
• 46:40
  Speaker 1: So it's a universe but without space time, or it's
• 46:43
  Speaker 1: nothing meaning not a universe.
• 46:45
  Speaker 3: What's the difference?
• 46:46
  Speaker 1: Yeah, well that was gonna be my next question. That
• 46:48
  Speaker 1: was a trap you avoided it.
• 46:52
  Speaker 4: There's no space there at all. I mean, there's nothing
• 46:55
  Speaker 4: so physical there. That's at least one conception of it.
• 46:58
  Speaker 1: But how can you have the laws of the universe
• 47:01
  Speaker 1: and follow those laws if there is no universe? So
• 47:04
  Speaker 1: there is a universe but without space time, Well.
• 47:06
  Speaker 3: That depends on your view of laws. What are laws
• 47:10
  Speaker 3: of physics?
• 47:11
  Speaker 4: Now some people would say they're just descriptions, so they
• 47:14
  Speaker 4: can't cause the universe. Another view might view, we don't
• 47:17
  Speaker 4: need a cause because there's no time and time you
• 47:20
  Speaker 4: need time for causality.
• 47:22
  Speaker 3: If there's no time, don't worry about what the cause was.
• 47:25
  Speaker 3: You're asking the question what caused?
• 47:27
  Speaker 1: But if there's no time, it is.
• 47:29
  Speaker 4: A question that is asked in a condition. The condition
• 47:33
  Speaker 4: is time exists. But if the time doesn't exist, then
• 47:36
  Speaker 4: don't worry about causality.
• 47:38
  Speaker 1: Yeah, but if you have that, but how can you
• 47:41
  Speaker 1: speculate about a transition and evolution of the universe from
• 47:44
  Speaker 1: this to that? If there's no time in the universe? Right,
• 47:47
  Speaker 1: how does that? How do I wrap my mind around this?
• 47:49
  Speaker 4: Well, it is hard to head round. You know, we're
• 47:53
  Speaker 4: answering in analogies. But you know, I saw a mathematical description.
• 47:57
  Speaker 4: So the question is, you know, you compute what would
• 48:01
  Speaker 4: happen if the universe of zero size? And then what
• 48:04
  Speaker 4: is there a tunneling aptitude for one? Yeah, people have
• 48:06
  Speaker 4: challenged this. I mean, I don't want to claim it's
• 48:08
  Speaker 4: always worked out and everyone understands it and it's all agreedable.
• 48:11
  Speaker 4: This is one of like twenty something ideas that we
• 48:15
  Speaker 4: talk about in the book, and this is a problem
• 48:17
  Speaker 4: with it. So I don't you know, some people have said, well,
• 48:20
  Speaker 4: you're always tunneling from one quantum state to another, so
• 48:23
  Speaker 4: maybe we shouldn't consider this this model. However, one idea
• 48:28
  Speaker 4: that Valncan suggests is that actually laws are more than
• 48:32
  Speaker 4: just descriptions that they actually are. They exist in a
• 48:35
  Speaker 4: sort of platonic sense in a sense. And this has
• 48:38
  Speaker 4: some advantages to it because you know, you can ask
• 48:42
  Speaker 4: why is it that objects obey the laws of physics?
• 48:44
  Speaker 4: You know, if you have an electron, let's say it
• 48:46
  Speaker 4: gets excited, it shoots out a photon. How does it
• 48:50
  Speaker 4: know to shoot out a photon? You know, it's all
• 48:53
  Speaker 4: that information written inside the electronic That seems hard to believe.
• 48:56
  Speaker 4: So the idea is that laws are actually sort of
• 49:00
  Speaker 4: photonic objects in some sos it's pretty weird.
• 49:03
  Speaker 1: And when you say platonic objects, for those of us
• 49:05
  Speaker 1: who are not reading philosophy papers all the time, you
• 49:08
  Speaker 1: mean that they exist outside of our ability to observe them.
• 49:11
  Speaker 4: Yeah, I think that's a fair fair description. Yeah, they
• 49:14
  Speaker 4: don't sit on something else. You know, if you think
• 49:17
  Speaker 4: of a table, all right, it's made of particles, and
• 49:21
  Speaker 4: you might even say they're made out of quantum fields
• 49:23
  Speaker 4: or you know, so the laws themselves have their own
• 49:27
  Speaker 4: sort of physical existence.
• 49:29
  Speaker 3: Well, I don't know.
• 49:30
  Speaker 4: Physical isn't the right word independent existence, So that may
• 49:35
  Speaker 4: be required by a the Lincoln's model, And if you
• 49:39
  Speaker 4: don't like that idea, then maybe you don't want to
• 49:42
  Speaker 4: entertain the Lincoln's model. But I do think that it's
• 49:46
  Speaker 4: uncertain what the status of laws is. So those that
• 49:49
  Speaker 4: say that cannot be right because laws are just descriptions.
• 49:53
  Speaker 4: I challenged that and say, are you sure that they're
• 49:55
  Speaker 4: just descriptions? You know, how do you solve problem of induction?
• 50:00
  Speaker 4: You know, we ask how do we know that there
• 50:02
  Speaker 4: are these regularities? Why do why don't we think the
• 50:05
  Speaker 4: sun might stop rising tomorrow? You know, if you just
• 50:08
  Speaker 4: think their descriptions, it's hard to solve this problem of induction.
• 50:13
  Speaker 4: But one possible solution is, no, the laws are more
• 50:16
  Speaker 4: than that. They're sort of ironclad objects that the other
• 50:19
  Speaker 4: particles have to sort of obey, And then you can
• 50:23
  Speaker 4: see why induction makes sense. So there's a lot of
• 50:26
  Speaker 4: debate in the philosophical literature about the nature of laws,
• 50:29
  Speaker 4: and I think as long as that is not settled,
• 50:31
  Speaker 4: and I think it's right to say it isn't settled,
• 50:33
  Speaker 4: then you can entertain this view, but you know, let's
• 50:36
  Speaker 4: be honest, it's pretty wacky and out there. So people
• 50:40
  Speaker 4: have come up with other views and maybe, you know,
• 50:41
  Speaker 4: we can get onto those if you want.
• 50:43
  Speaker 1: I do want to get onto those, and I'm meant
• 50:44
  Speaker 1: to ask you where the philosophical implications later, But I
• 50:46
  Speaker 1: can't not follow up on that fascinating conversation, you know,
• 50:50
  Speaker 1: because it makes me wonder about the future of this
• 50:53
  Speaker 1: line of inquiry, Like if we discover the heart big being,
• 50:56
  Speaker 1: and then we find proof of inflation, then we find
• 50:58
  Speaker 1: proof of what became before that? Is this an infinite
• 51:01
  Speaker 1: line of study where we're always going to be asking
• 51:03
  Speaker 1: what came before that? Or do you think there's some
• 51:06
  Speaker 1: point at which we find something where like, ah, this
• 51:08
  Speaker 1: caused itself, or this is obviously something which is fundamental.
• 51:13
  Speaker 1: And isn't that just some philosophical sleight of hand where
• 51:15
  Speaker 1: we're like, this requires a cause and now we found
• 51:18
  Speaker 1: something which we define to not require a cause and
• 51:20
  Speaker 1: therefore we don't have to ask questions anymore. I mean,
• 51:23
  Speaker 1: why isn't this going to be an infinite line of
• 51:25
  Speaker 1: inquiry or do you think it will be what.
• 51:27
  Speaker 3: It could be?
• 51:28
  Speaker 4: But there are sort of ideas out there that might
• 51:31
  Speaker 4: stop that infinite regress, shall we say, I mean the
• 51:34
  Speaker 4: Lincoln thinks that he stops the infinite regress because you know,
• 51:38
  Speaker 4: we've got this solution, if you like. The universe doesn't
• 51:41
  Speaker 4: need a cause because it's quantum mechanical and causes our
• 51:45
  Speaker 4: emergent properties. They exist for the microscopic world, but not
• 51:48
  Speaker 4: for the quantum world. So we don't need to ask
• 51:51
  Speaker 4: what the cause for the universe is. It's a meaningless
• 51:53
  Speaker 4: question maybe, or maybe not meaningless, but it's just you know,
• 51:56
  Speaker 4: you don't need to demand. You can't demand there must
• 51:59
  Speaker 4: be a cause when you get into the quantum realm.
• 52:01
  Speaker 4: So that's one approach. Another approaches that maybe the universalist
• 52:05
  Speaker 4: existed eternally into the past, so you can always just
• 52:08
  Speaker 4: go back one step further and further and there's no end.
• 52:12
  Speaker 4: It just goes on forever into the past. That's certainly
• 52:15
  Speaker 4: an idea.
• 52:15
  Speaker 1: Infinite grants for cosmology.
• 52:17
  Speaker 4: Yeah maybe, yeah, so it may just go on forever.
• 52:22
  Speaker 4: But that's certainly a logical possibility, and it's certainly something
• 52:26
  Speaker 4: that I think many physicists entertain. Certainly that's one of
• 52:30
  Speaker 4: the battles. Actually the Battle of the Big Bang is
• 52:34
  Speaker 4: was there a beginning even if it wasn't the Big Bang,
• 52:35
  Speaker 4: maybe there was some other beginning, and some physicists think
• 52:38
  Speaker 4: there was, and some physicis think there wasn't. Another idea
• 52:42
  Speaker 4: is that there could be what's called a closed time
• 52:44
  Speaker 4: like curve. So if you've seen the movie Groundhog Day,
• 52:48
  Speaker 4: think of that. So you wake up, you know, and
• 52:54
  Speaker 4: you're just experiencing yesterday all over again. So now there
• 52:57
  Speaker 4: are solutions in ice Sei's Theoria relativity, which describes you know,
• 53:03
  Speaker 4: gravity as a curvature of space time, and there are
• 53:06
  Speaker 4: solutions to say it gets so curve, it curves back
• 53:09
  Speaker 4: on itself and it forms a loop. So there are
• 53:12
  Speaker 4: a couple of models that sort of take advantage of
• 53:15
  Speaker 4: this and say the universe would cause itself because it
• 53:19
  Speaker 4: curves back in a loop. And so there is no
• 53:22
  Speaker 4: origin point of a circle. Even though the circle is
• 53:25
  Speaker 4: not infinitely long, it doesn't have a starting point, so
• 53:28
  Speaker 4: you can't ask what happened at the start.
• 53:31
  Speaker 3: There is no start. It just goes around in a loop.
• 53:34
  Speaker 4: So in the book Battle the Big Bang, we talk
• 53:37
  Speaker 4: about two different models that exploit this. So there are
• 53:40
  Speaker 4: some of the different ideas. One, maybe there was a
• 53:42
  Speaker 4: beginning and you describe the universe maybe without the language
• 53:46
  Speaker 4: of causality. Or maybe there was no beginning and it's
• 53:49
  Speaker 4: infinitely far into the past. Or maybe there's a sort
• 53:53
  Speaker 4: of loop in time, so there's no starting point, even
• 53:57
  Speaker 4: though maybe it's not sort of eternal in some sense.
• 54:01
  Speaker 1: All right, so let's take another break, and when we
• 54:03
  Speaker 1: come back, we're explore some of these other ideas, some
• 54:06
  Speaker 1: proposing the universe has no first moment. Okay, we're talking
• 54:29
  Speaker 1: to Phil about the origins of the universe, what we know,
• 54:32
  Speaker 1: what we might know, and what we can only speculate
• 54:34
  Speaker 1: while smoking banana peels. You referenced earlier, this fascinating idea,
• 54:39
  Speaker 1: the no boundary proposal, this alternative to like a singularity
• 54:44
  Speaker 1: or a first moment. Tell us about this idea. How
• 54:46
  Speaker 1: does it come about and how does it help us
• 54:48
  Speaker 1: avoid a first moment in time?
• 54:51
  Speaker 4: Well, it's not clear whether it does avoid the first
• 54:55
  Speaker 4: If I was going to suggest models that avoid the
• 54:58
  Speaker 4: first moment and so on, I might probably go to
• 54:59
  Speaker 4: a another model, like a bouncing model, which was or
• 55:03
  Speaker 4: you know, some other maybe some cyclic models. Now I
• 55:06
  Speaker 4: think I'm more unambiguously don't have a beginning that the
• 55:10
  Speaker 4: no boundary proposal.
• 55:11
  Speaker 3: I work with.
• 55:13
  Speaker 4: Stephen Hawking and Jim Hartl and Thomas hog to make
• 55:15
  Speaker 4: a film to explain it to the public, and I
• 55:19
  Speaker 4: did get the impression they didn't quite agree on how
• 55:21
  Speaker 4: to interpret it. I think, I think Corking sawy it
• 55:26
  Speaker 4: is like something closer to what for Lincoln proposed, like
• 55:31
  Speaker 4: a universe for nothing. Whereas Jim hart Or I asked
• 55:34
  Speaker 4: him he could just realize the idea of the universe
• 55:36
  Speaker 4: fy nothing, and he's like, what do you mean by nothing?
• 55:39
  Speaker 4: Quantum mechanics is always something.
• 55:41
  Speaker 1: I know that hacking special sauce is getting gravity and
• 55:44
  Speaker 1: quantum mechanics to play together, even without a full theory
• 55:47
  Speaker 1: of quantum gravity. He did for black holes, and that's
• 55:50
  Speaker 1: how we came up with his prediction for Hockeing radiation.
• 55:52
  Speaker 4: So he started to think, well, what if we do
• 55:54
  Speaker 4: the same for the Big Bang? Because the singularity theorem
• 55:57
  Speaker 4: that he approved with Penrose was just classical. It didn't
• 56:01
  Speaker 4: include quantum mechanics. So he said, loris, let's try and
• 56:03
  Speaker 4: include quantum mechanics. And when it did that, he found
• 56:09
  Speaker 4: that it's cut a long story short, the description that
• 56:12
  Speaker 4: we have with space having three dimensions and time having
• 56:16
  Speaker 4: one dimension changes such that the time dimension turns into
• 56:21
  Speaker 4: a space dimension.
• 56:22
  Speaker 3: So now you have four space dimensions and no time dimension.
• 56:26
  Speaker 1: Okay, that's really weird. Let's unpack it. So Hawking is
• 56:29
  Speaker 1: saying that the universe used to have four spatial dimensions
• 56:33
  Speaker 1: and one of them became a time dimension. So we
• 56:37
  Speaker 1: had four spatial dimensions, and then we had three spatial
• 56:40
  Speaker 1: dimensions and one time dimension, which we're familiar with. Now
• 56:43
  Speaker 1: that's really confusing, So let's try to think of an analogy.
• 56:46
  Speaker 1: And hawking student's analogy is like, if you're standing at
• 56:49
  Speaker 1: the north pole. It's not only that there's no more northiness,
• 56:53
  Speaker 1: there's also no sense of east or west. East and
• 56:56
  Speaker 1: west have no meaning of the north pole. But as
• 56:59
  Speaker 1: you move away from the north pole, you don't change
• 57:02
  Speaker 1: the number of dimensions on the surface of a sphere.
• 57:04
  Speaker 1: But now the concept of east and west makes sense.
• 57:07
  Speaker 1: It's a direction that emerges smoothly. As you move away
• 57:10
  Speaker 1: from the north pole. One of the directions on the
• 57:13
  Speaker 1: sphere becomes east west. Like the idea here is that
• 57:17
  Speaker 1: the universe has one end where all the directions are spacelike,
• 57:21
  Speaker 1: and as you move away from that end, one dimension
• 57:24
  Speaker 1: changes to have new time like properties. It's pretty hard
• 57:28
  Speaker 1: to wrap your mind around, honestly.
• 57:29
  Speaker 3: What this does.
• 57:30
  Speaker 4: It actually smooths out the singularity. You don't get this infinite,
• 57:34
  Speaker 4: dense state. You get a smooth state. And think of
• 57:38
  Speaker 4: it unlike the point of a cone. Think of it
• 57:41
  Speaker 4: more like a shuttlecock, like a smooth surface. Now this
• 57:45
  Speaker 4: is bound it. It's just not infinite, but it doesn't
• 57:48
  Speaker 4: have a starting. There's no point on the surface. This
• 57:52
  Speaker 4: is many better than any other point. So you could
• 57:55
  Speaker 4: say it doesn't have a beginning, but you might say, what,
• 57:58
  Speaker 4: it's not infinite to the past either, And then there's
• 58:01
  Speaker 4: some more complications to it, which we go into in
• 58:03
  Speaker 4: the book. But bottom line is whether it has a
• 58:05
  Speaker 4: beginning or not is sort of slightly ambiguous, and it
• 58:09
  Speaker 4: depends on how you interpret the model. But there are
• 58:12
  Speaker 4: other models that I think are They have less ambiguity
• 58:16
  Speaker 4: and clearly don't have a beginning in them. So the
• 58:18
  Speaker 4: most obvious one, I would say, is one with where
• 58:21
  Speaker 4: you replace the singularity with a bounce. So here the
• 58:25
  Speaker 4: idea is that there's so remember we said with the singularity,
• 58:29
  Speaker 4: the universe goes to infinite density. Now, the idea in
• 58:33
  Speaker 4: some theories of quantum gravity, the suggestions being that you
• 58:37
  Speaker 4: will actually get a maximum density. So think of a sponge.
• 58:42
  Speaker 4: You pour water on a sponge and it absorbs the water,
• 58:46
  Speaker 4: but there comes a point where it won't absorb the
• 58:49
  Speaker 4: water anymore. It will switch its properties from being water
• 58:53
  Speaker 4: absorbent to water repellent. So space might be like that,
• 58:57
  Speaker 4: and in certain theories of quantum gravity that's what happen.
• 59:00
  Speaker 4: Spaces are like a limit. So when you try and
• 59:03
  Speaker 4: squeeze more and more energy into space, it gets to
• 59:06
  Speaker 4: a point where it gets fill up, and then if
• 59:08
  Speaker 4: you try and squeeze more in, it will bounce back out.
• 59:10
  Speaker 3: It becomes repellent.
• 59:11
  Speaker 4: So gravity switches from becoming attractive force to a repulsive force,
• 59:15
  Speaker 4: and that triggers a bounce. So then if we could
• 59:18
  Speaker 4: go back in time, what we would see is, well,
• 59:21
  Speaker 4: if we started today fourteen billionaires, it is a big bang.
• 59:24
  Speaker 4: Roughly you go back in time is getting denser and
• 59:26
  Speaker 4: dancer and dancer and denser. When we get to its
• 59:28
  Speaker 4: maximum density, it just bounces back out again. So you'd
• 59:32
  Speaker 4: get another expanding universe, or if you wanted to think
• 59:35
  Speaker 4: of it as going from the past today, it would
• 59:38
  Speaker 4: be a contracting universe and then an expanding universe, and
• 59:41
  Speaker 4: that core attracting universe could have been contracting for infinitely
• 59:46
  Speaker 4: long ago. You might just have it mirror like. It
• 59:50
  Speaker 4: doesn't have to be cyclic, or though it could be.
• 59:52
  Speaker 4: It could just be one contracting universe mirrored by it
• 59:55
  Speaker 4: one expanding it.
• 59:56
  Speaker 3: Something like that, like an hour class.
• 59:58
  Speaker 4: So that's that's the idea of a. And I think
• 1:00:00
  Speaker 4: that is less ambiguous, that it does not have a
• 1:00:04
  Speaker 4: beginning in this model.
• 1:00:06
  Speaker 3: So that's one idea.
• 1:00:07
  Speaker 4: And of course there are cyclic universes as well, and oh, guys,
• 1:00:11
  Speaker 4: of other ideas we explaw.
• 1:00:13
  Speaker 2: So this idea that at some point gravity stops pulling
• 1:00:15
  Speaker 2: things in and starts to repel energy, do we have
• 1:00:19
  Speaker 2: evidence for that in other domains or like, where did
• 1:00:22
  Speaker 2: this idea come from?
• 1:00:24
  Speaker 3: Arguably we do.
• 1:00:25
  Speaker 4: The fact that the universe is accelerating in its expansion
• 1:00:29
  Speaker 4: is an effect of the vacuum having a pressure.
• 1:00:33
  Speaker 3: But think of it this way.
• 1:00:34
  Speaker 4: I mean, this is different to what we're talking about
• 1:00:37
  Speaker 4: in the quantum gravity case. But I just want to
• 1:00:39
  Speaker 4: ask your questions, is there some evidence of a repulsive gravity.
• 1:00:42
  Speaker 4: So in Newton's theory, the only thing that contributes to
• 1:00:46
  Speaker 4: gravity is mass, so you can't have a negative mass
• 1:00:49
  Speaker 4: as far as I know, so you can't have negative gravity.
• 1:00:52
  Speaker 4: Therefore gravity is always attractive. However, in Einstein's theory there's
• 1:00:57
  Speaker 4: also a pressure term, so it's not just mass, and
• 1:01:00
  Speaker 4: the pressure can be negative. It's like a suction, and
• 1:01:02
  Speaker 4: in fact, vacuum has negative pressure, so it is a
• 1:01:07
  Speaker 4: repulsive gravity force. And the fact that we see the
• 1:01:10
  Speaker 4: universe accelerating an expansion is direct emperical evidence of repulsive gravity.
• 1:01:15
  Speaker 3: So that is clear that there is repulsive gravity.
• 1:01:18
  Speaker 4: Now that's not necessarily what's going on here at the
• 1:01:21
  Speaker 4: big bounce, because there you're assuming it's coming from quantum gravity.
• 1:01:26
  Speaker 4: So there you have to use a different type of geometry.
• 1:01:30
  Speaker 4: So the geometry that's used in relativity is classical geometry,
• 1:01:35
  Speaker 4: whereas in these quantum gravity theories it's a quantum geometry,
• 1:01:39
  Speaker 4: so it's sort of fluctuating. And the idea is that
• 1:01:41
  Speaker 4: then because it's discrete, it can't have infinite compression. It
• 1:01:47
  Speaker 4: will bounce back at some point and that and then
• 1:01:49
  Speaker 4: the gravity switch assigned and you get repulsive gravity. So
• 1:01:52
  Speaker 4: that's the theoretical trapulation from the quantum gravity theory. So
• 1:01:56
  Speaker 4: in particular, Luke quantum gravity is that it's a candidate
• 1:01:59
  Speaker 4: for for quantum gravity. They've done a lot of work
• 1:02:02
  Speaker 4: on this bouncing cosmology, but there have been ideas even
• 1:02:04
  Speaker 4: in string theory that you might get a bounce in
• 1:02:06
  Speaker 4: cosmology from this fact that if you discretize space then
• 1:02:11
  Speaker 4: it will have a maximum limit of what you can
• 1:02:13
  Speaker 4: put into it, and then if you try to go
• 1:02:16
  Speaker 4: beyond it, it pushes back.
• 1:02:17
  Speaker 1: I like these bouncing ideas because they sort of avoid
• 1:02:20
  Speaker 1: the question of our first moment. They're like, lit's just
• 1:02:22
  Speaker 1: bounce forever, and that's cool. But I wonder if there's
• 1:02:26
  Speaker 1: any evidence for that, Like, you know, if the universe
• 1:02:28
  Speaker 1: compresses to a singularity or a near singularity, some quantum
• 1:02:32
  Speaker 1: version of it, does it do so in so intensely
• 1:02:35
  Speaker 1: that all evidence of the previous you know, pre bounce
• 1:02:39
  Speaker 1: universe is lost? Or can we find some hints, some
• 1:02:43
  Speaker 1: clues in the universe today that showed that it had
• 1:02:45
  Speaker 1: to have a bounce.
• 1:02:46
  Speaker 3: Yes, So this is an active research program.
• 1:02:50
  Speaker 4: So, as I said, I think it's in the lib
• 1:02:52
  Speaker 4: quantum gravity case where there's the most consensus that you
• 1:02:55
  Speaker 4: get a bounce. As I said, they have been ideas
• 1:02:58
  Speaker 4: in string theory for a bounce as well, and even
• 1:03:00
  Speaker 4: in some other proposals of quantum gravity. But in the
• 1:03:02
  Speaker 4: loop case, loop quantum gravity, which is one of the
• 1:03:05
  Speaker 4: candidates for a theory to mix ie thereogenerativity and quantum mechanics,
• 1:03:11
  Speaker 4: as we've got this quantum theory gravity. Because we should
• 1:03:15
  Speaker 4: point out to the listener if they're not familiar, these
• 1:03:17
  Speaker 4: two theories are the cornerstones and modern physics. But yet
• 1:03:21
  Speaker 4: they contradict each other. So we know we need a
• 1:03:23
  Speaker 4: deeper theory. So we know or we need to modify
• 1:03:27
  Speaker 4: one of the existing theories, or maybe both of them,
• 1:03:29
  Speaker 4: but we know we need new physics in some way.
• 1:03:32
  Speaker 4: So one of the contenders this is theory called loop
• 1:03:34
  Speaker 4: quantum gravity. And what they've got this program called loop
• 1:03:37
  Speaker 4: quantum cosmology, where what they want to do is calculate
• 1:03:42
  Speaker 4: what we should see in the cosmic microwave background if
• 1:03:44
  Speaker 4: there was a bounce, and they claim that they've already
• 1:03:48
  Speaker 4: done this and they it matches their observations. Now obviously
• 1:03:53
  Speaker 4: not everyone agrees, so this is correct so they have
• 1:03:55
  Speaker 4: to make certain assumptions, and then the question is are
• 1:03:57
  Speaker 4: they valid assumptions? And then you know, in particular, I'll
• 1:04:02
  Speaker 4: give you one I think is important or especially important,
• 1:04:05
  Speaker 4: and I should say, and that is you have to
• 1:04:06
  Speaker 4: assume whether there was inflation or not. And as we said,
• 1:04:10
  Speaker 4: not everyone agrees there was inflation, so they have to
• 1:04:13
  Speaker 4: put in inflation. And then there's different models of inflation.
• 1:04:17
  Speaker 4: So what they do is they try and say, well,
• 1:04:18
  Speaker 4: which one is favored by the data.
• 1:04:21
  Speaker 3: Put that in.
• 1:04:21
  Speaker 4: Then we calculate corrections to what we see in the
• 1:04:25
  Speaker 4: couse of micro background, and then they claim that there's
• 1:04:29
  Speaker 4: actually much is better than the standard model, but the
• 1:04:32
  Speaker 4: differences are not big enough to be decisive. And of course,
• 1:04:36
  Speaker 4: as I said, you could challenge the assumptions. So it's
• 1:04:39
  Speaker 4: still an ongoing program and people are still working on
• 1:04:43
  Speaker 4: the theory to see if they can make the predictions
• 1:04:45
  Speaker 4: more robust. So maybe it doesn't depend on some of
• 1:04:49
  Speaker 4: these assumptions. The other thing you could try and do
• 1:04:52
  Speaker 4: is look at black holes and how black holes might
• 1:04:55
  Speaker 4: behave because there also we think we need quantum gravity,
• 1:04:58
  Speaker 4: so people have made models of black holes using quantum gravity.
• 1:05:02
  Speaker 4: And then maybe you could look for signatures of what
• 1:05:05
  Speaker 4: they might do. Maybe there are signs of quantum gravity
• 1:05:09
  Speaker 4: in black holes. So those are the two areas that
• 1:05:14
  Speaker 4: I think are the most exciting about looking for signs
• 1:05:18
  Speaker 4: of quantum gravity. And if we can find those, then
• 1:05:22
  Speaker 4: we might know what the right theory of quantum gravity is.
• 1:05:24
  Speaker 4: And then we might know whether this bounce took place
• 1:05:27
  Speaker 4: or if it didn't.
• 1:05:28
  Speaker 2: That would be exciting.
• 1:05:29
  Speaker 1: Yes, oh yeah, Well, now we've been looking into the past.
• 1:05:31
  Speaker 1: Tell us about the future of looking into the past.
• 1:05:34
  Speaker 1: What do you think we're going to learn in the
• 1:05:35
  Speaker 1: next ten years or fifty years that could help us
• 1:05:37
  Speaker 1: understand what came before the hot Big Bang.
• 1:05:40
  Speaker 4: Well, there's a number of avenues we can explore. So
• 1:05:43
  Speaker 4: one is to look more at this cosmic microwave background.
• 1:05:46
  Speaker 4: So this is the oldest light that we can see.
• 1:05:49
  Speaker 4: You can't see beyond that with light. It's admitted three
• 1:05:52
  Speaker 4: hundred and eighty thousand years after the Big Bang. And
• 1:05:55
  Speaker 4: the reason that you can't see anything earlier is that
• 1:05:57
  Speaker 4: if you went earlier, as I said, the university more
• 1:06:00
  Speaker 4: like the sun, and if you look at the Sun,
• 1:06:03
  Speaker 4: you can't look into the interior because it's opaque.
• 1:06:05
  Speaker 3: So same with the universe.
• 1:06:07
  Speaker 4: Before the emission of a cosmic microwave background, it was opaque,
• 1:06:11
  Speaker 4: so you cannot look earlier. But there are these patterns
• 1:06:15
  Speaker 4: of hot and cold spots, and they give you information
• 1:06:17
  Speaker 4: that you could try and guess as to what came before.
• 1:06:20
  Speaker 4: And some theories make different predictions for those patterns of
• 1:06:23
  Speaker 4: hot and cold spots. Also, there's patterns of polarization, so
• 1:06:28
  Speaker 4: this is a way that light sort of twirls around.
• 1:06:30
  Speaker 4: That's a new frontier, So looking for polarization of the
• 1:06:32
  Speaker 4: cosmic microwave background, and some different models make different predictions
• 1:06:36
  Speaker 4: for what we might see there.
• 1:06:39
  Speaker 3: Another avenue you.
• 1:06:40
  Speaker 4: Could look at is the distribution of galaxies because that
• 1:06:45
  Speaker 4: was set in the very earliest moments of the Big Bang,
• 1:06:48
  Speaker 4: So different models might make different predictions for the distribution
• 1:06:52
  Speaker 4: of galaxies. But I think the most exciting idea for
• 1:06:57
  Speaker 4: how we can probe much earlier into the into the
• 1:07:01
  Speaker 4: Big Bang is something called primordial gravitational waves. So this
• 1:07:07
  Speaker 4: you might people might have heard in twenty let me
• 1:07:10
  Speaker 4: think was it twenty sixteen Ligo, which was these giant
• 1:07:14
  Speaker 4: lasers that they have in Louisiana and Washington State, and
• 1:07:18
  Speaker 4: they detected sort of a ripple in the fabric of
• 1:07:22
  Speaker 4: space and time. They're called gravitational waves, and they came
• 1:07:25
  Speaker 4: not from the Big Bank. They came from colliding black holes.
• 1:07:28
  Speaker 4: But they send out this ripple in the fabric of
• 1:07:31
  Speaker 4: space and time, and we can detect them amazingly because
• 1:07:35
  Speaker 4: they're very, very feeble. When they get to the Earth,
• 1:07:37
  Speaker 4: they change the distance of like these lasers that they
• 1:07:42
  Speaker 4: basically have. These lasers, they're aout four kilometers apart and
• 1:07:45
  Speaker 4: they bounce between mirrors and if there are no gravitational waves,
• 1:07:49
  Speaker 4: they should stay in phase with each other. When a
• 1:07:51
  Speaker 4: gravitational wave passes through, they go out phase, and so
• 1:07:54
  Speaker 4: you can detect their existence. And they have two of them,
• 1:07:56
  Speaker 4: one in Louisiana and one in Washington State. Initially, I
• 1:08:01
  Speaker 4: mean they've been more built since then. There's one now
• 1:08:03
  Speaker 4: in Italy and India and Japanese that they're building one
• 1:08:08
  Speaker 4: or I don't know what the status of that one is.
• 1:08:09
  Speaker 4: But so so the idea is have a station stations
• 1:08:13
  Speaker 4: of them around the world, so these ripples can go
• 1:08:16
  Speaker 4: through that plasma that you can't see through. So even
• 1:08:20
  Speaker 4: though you can't see light from the Big Bang, you
• 1:08:22
  Speaker 4: could in some sense see these gravitational ways.
• 1:08:25
  Speaker 3: You don't see.
• 1:08:25
  Speaker 4: Them, maybe you hear them, you know, they're kind of
• 1:08:29
  Speaker 4: sound ways actually in the early universe. That were they
• 1:08:31
  Speaker 4: cause dounways in the early universe.
• 1:08:32
  Speaker 3: They should say.
• 1:08:33
  Speaker 4: So, these ripples in the fabric of space are potentially detectable.
• 1:08:37
  Speaker 4: Either they might change a polarization of the light of
• 1:08:41
  Speaker 4: the cosmic microwave background, or we could detect them directly
• 1:08:44
  Speaker 4: via building something like these giant laser observatories. But the
• 1:08:47
  Speaker 4: ones that we have today are optimized to see them
• 1:08:51
  Speaker 4: from black hole collisions. They can't even see them from
• 1:08:55
  Speaker 4: super massive black holes, which are the really big black
• 1:08:57
  Speaker 4: holes that.
• 1:08:58
  Speaker 3: Sit in the center of galaxies.
• 1:09:00
  Speaker 4: However, we are building a space based observatory called LISA,
• 1:09:04
  Speaker 4: the Laser Interformance of Space Antenna, and that will be
• 1:09:08
  Speaker 4: able to detect super massive black hole mergers. So maybe
• 1:09:12
  Speaker 4: it could see signatures of quantum gravity in these extreme conditions,
• 1:09:16
  Speaker 4: So that might help us understand the Big Bang. But
• 1:09:20
  Speaker 4: beyond LISA, I mean lisa's not going to get launched
• 1:09:22
  Speaker 4: on the twenty thirties. But then beyond that there are projects,
• 1:09:26
  Speaker 4: one called the Psycho, another one called Big Bang Observer.
• 1:09:29
  Speaker 4: These are kind of pie in the sky ideas, right,
• 1:09:30
  Speaker 4: so we don't think that they're going to be built
• 1:09:34
  Speaker 4: anytime soon. But often what you do is just dream big,
• 1:09:37
  Speaker 4: because just say, what would you do if you had
• 1:09:38
  Speaker 4: like endless money and resources, and the idea is just
• 1:09:43
  Speaker 4: get something on the table and then you know, maybe
• 1:09:46
  Speaker 4: decades into the future, maybe people find cheaper ways to
• 1:09:48
  Speaker 4: do it, and then you can actually launch these things.
• 1:09:51
  Speaker 4: So the Big Bang Observer, for example, is like Lisa,
• 1:09:54
  Speaker 4: it's a similar idea, but it has twelve spacecraft. Lisa
• 1:09:58
  Speaker 4: has three that is happening as being built as we speak.
• 1:10:02
  Speaker 4: But Big Bang Obsurvey is much much more ambitious. But
• 1:10:06
  Speaker 4: that could potentially see these ripples from the Big Bang.
• 1:10:10
  Speaker 4: And now why that is that important because some models
• 1:10:14
  Speaker 4: predict that there should be these ripples and some don't.
• 1:10:18
  Speaker 4: So a lot of cyclic models say there are no ripples.
• 1:10:21
  Speaker 4: And some of these cyclic models are alternatives to the
• 1:10:23
  Speaker 4: inflationary screen, which says.
• 1:10:25
  Speaker 3: There are these ripples.
• 1:10:27
  Speaker 4: Not only that, but they actually have different properties, so
• 1:10:30
  Speaker 4: they have different strengths at different wavelengths, and so we
• 1:10:33
  Speaker 4: call that the spectrum of the gravitational waves. So by
• 1:10:37
  Speaker 4: probing the gravitational wave universe. And this is an area
• 1:10:40
  Speaker 4: of astronomy that is brand new. I mean, we only
• 1:10:43
  Speaker 4: detected the first gravitational wave in twenty fifteen. It's like
• 1:10:46
  Speaker 4: Galileo first looking at in this telescope in sixteen ten.
• 1:10:50
  Speaker 4: Think of what a small telescope we had and how
• 1:10:54
  Speaker 4: radically it changed our view of the universe. Because before
• 1:10:57
  Speaker 4: Galileo looked through our telescope, most people will sure that
• 1:11:01
  Speaker 4: we lived in a geocentric universe with everything going around
• 1:11:04
  Speaker 4: the Earth. And I think mccalilet took through that telescope
• 1:11:08
  Speaker 4: and he saw that there were moons going around Jupiter.
• 1:11:10
  Speaker 4: It was clear as clear as day that not everything
• 1:11:14
  Speaker 4: goes around the Earth. And then he saw the phases
• 1:11:16
  Speaker 4: of Venus, which was a direct prediction of the helocentric
• 1:11:19
  Speaker 4: model or particular properties of the phases of Venus. So
• 1:11:23
  Speaker 4: it was incredibly revolutionary. And now we're at the birth
• 1:11:26
  Speaker 4: of this new revolution gravitational wave of astronomy. And this
• 1:11:30
  Speaker 4: could probe which models of the Big Bang or even
• 1:11:34
  Speaker 4: pre Big Bang universe are right. And that is the
• 1:11:38
  Speaker 4: incredibly exciting frontier for the universe cosmology in the decades
• 1:11:44
  Speaker 4: or maybe centrics to come. Depending on whether we decide
• 1:11:47
  Speaker 4: to find this area of science.
• 1:11:49
  Speaker 1: That's right, it'll finally tell us whether we're in the
• 1:11:51
  Speaker 1: Marvel Multiverse or the DC Multiverse or another version. Right, yes,
• 1:11:57
  Speaker 1: exactly right, all right, well, thank you Phil very much
• 1:12:02
  Speaker 1: for coming on the podcast and talk to us about
• 1:12:04
  Speaker 1: all these crazy ideas. It's amazing to me we can
• 1:12:06
  Speaker 1: know anything about the universe so long ago, and we
• 1:12:09
  Speaker 1: can even have debates about various ideas. I really enjoyed
• 1:12:12
  Speaker 1: the book. The book is called Battle for the Big Bang,
• 1:12:15
  Speaker 1: The New Tales of our Cosmic Origins.
• 1:12:24
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• 1:12:28
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