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Speaker 1: One of the deepest goals of physics is to help

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Speaker 1: us understand our context. Are we humans at the center

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Speaker 1: of everything or are we in an irrelevant little corner

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Speaker 1: of the universe? Was the universe created with us in it?

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Speaker 1: Or did it exist for an unimaginable eons before we arrived.

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Speaker 1: The answers to each of these questions helps us know

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Speaker 1: our place or lack of it, in the universe. It

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Speaker 1: helps us know how to live our lives. But nothing

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Speaker 1: touches these issues more deeply than understanding the very birth

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Speaker 1: of the universe. What, if anything, can we ever hope

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Speaker 1: to reveal about those first few moments of creation? Hi,

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Speaker 1: I'm Daniel Whitson. I'm a particle physicist and a professor

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Speaker 1: you see Irvine, and I am the co host of

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Speaker 1: today's podcast, Daniel and Jorge Explain the Universe, brought to

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Speaker 1: you by I Heart Radio listeners. The podcast now that

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Speaker 1: we love to examine big questions, deep questions, questions about

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Speaker 1: things really far away, questions about things under our feet,

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Speaker 1: questions about how things around us work. But we're also

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Speaker 1: interested in the really deep questions, not just questions of space,

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Speaker 1: but also questions of time and so while Jorge is

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Speaker 1: still away and not available today. I'm very pleased to

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Speaker 1: have on the podcast today a friend of mine, a collaborator,

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Speaker 1: a colleague, and a upcoming author of a book I

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Speaker 1: think all of you would be excited about. His name

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Speaker 1: is Dan Hooper. He is a theoretical astrophysicist at FIRMY

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Speaker 1: National Accelerator Laboratory and ACT. He is the head of

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Speaker 1: the theoretical astrophysics group there, and he has a new

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Speaker 1: book coming out about the beginning of the universe. It's

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Speaker 1: called At the Edge of Time and it's going to

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Speaker 1: be available in November five from Princeton University Press. Now,

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Speaker 1: I've had the opportunity to take a look and at

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Speaker 1: advanced copy of this book, and I think it's awesome.

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Speaker 1: It talks about a lot of the really amazing questions

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Speaker 1: we like to dig into on the podcast. So without

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Speaker 1: further Ado, let me introduce to you my friend and colleague,

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Speaker 1: Dan Hooper. Thanks. I'm really excited to be here. Yeah. Well,

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Speaker 1: thanks for coming on the podcast and talking to us

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Speaker 1: about all the amazing and incredible things that we like

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Speaker 1: to think about. And apparently you like to write about

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Speaker 1: one thing we like to do in this podcast is

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Speaker 1: talk about things that are on the cutting edge of science,

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Speaker 1: things that scientists themselves are thinking about, but then trying

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Speaker 1: to break it down in a way that makes sense

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Speaker 1: to people. People can actually come away feeling like they

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Speaker 1: understand what we're talking about, not just repeating various jargon. Thanks.

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Speaker 1: I really enjoy trying to think of ways to a

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Speaker 1: some of the scientific ideas that I explore my research

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Speaker 1: for people who aren't scientists, whether that be my non

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Speaker 1: scientist friends or uh my family members. Uh. I really

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Speaker 1: like stretching that part of my brain that uh one

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Speaker 1: uses and communicating these exciting and very different ideas. And

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Speaker 1: I think your book does a great job of this.

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Speaker 1: I really conveying not just what we know, but also

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Speaker 1: what we don't know, where the edge of knowledge is

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Speaker 1: and and it is something else. It shows us that

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Speaker 1: science is personal. I think one of the great things

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Speaker 1: about your book is that it reflects who you are.

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Speaker 1: Doesn't just show science for being some monolith of knowledge

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Speaker 1: or something some sort of objective intellectual pursuit, but it

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Speaker 1: shows us that science really is of the people, by

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Speaker 1: the people, and for the people, because in the end,

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Speaker 1: science is just humans answering human questions. For other humans.

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Speaker 1: Science is always just a work in progress. Um, the

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Speaker 1: questions we're asking today, we'll probably not be the questions

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Speaker 1: that we find answers to ultimately. And when it comes

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Speaker 1: to the sort of stuff that I work on, I

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Speaker 1: would be shocked and maybe a little disappointed if it

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Speaker 1: turns out that the ideas we have about how things

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Speaker 1: are going to play out turn out to be right.

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Speaker 1: I really like the mystery that that's involved. And uh,

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Speaker 1: the surprise when we find out something we weren't expecting,

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Speaker 1: I only hope. So I love scientific surprises. But tell me,

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Speaker 1: what was your motivation for writing a popular science book

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Speaker 1: about this rather than just sort of continuing in the

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Speaker 1: conversation at the level of academia. Why bring this question

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Speaker 1: to the people. Long before I ever became a scientist,

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Speaker 1: I loved popular physics books. I used to read any

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Speaker 1: number of books by folks like Paul Davies, MITCHA. Kaku,

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Speaker 1: Kip Thorne, and this st just blew my mind learning

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Speaker 1: about quantum mechanics and learning about UH relativity, cosmology and

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Speaker 1: kind of the philosophical implications of all of it. Um. So,

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Speaker 1: when I became a science entist, I decided it would

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Speaker 1: be fun to kind of stretch my brain and uh

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Speaker 1: and try to try my hand at popular science writing myself.

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Speaker 1: This isn't the first time I've ever been in a

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Speaker 1: popular science book, but I haven't written popular science in

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Speaker 1: a long time. And uh, it's exciting, new challenge. I

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Speaker 1: love new challenges, and uh, this was no exception wonderful.

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Speaker 1: So as a theoretical astrophysicist and a cosmologist, you're dealing

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Speaker 1: with questions about like the origin of the universe and

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Speaker 1: the beginning of space and time, the very creation of

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Speaker 1: our cosmos. When you travel around, say you're on an

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Speaker 1: airplane and some random person asks you what do you do?

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Speaker 1: Do you have an easy time explaining to them what

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Speaker 1: you do and why it's interesting, or do you get

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Speaker 1: a sort of a lot of glazed looks. The reactions

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Speaker 1: I get are kind of all over the map. Occasionally

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Speaker 1: person is excited, and uh, you know, maybe they think

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Speaker 1: that's the perfect person to sit next to for the

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Speaker 1: course of the flight. Um, they always wanted to know

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Speaker 1: about cosmology and finally have an opportunity to to ask

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Speaker 1: somebody all the questions they build up over time. And

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Speaker 1: sometimes you sit next to somebody who, just for whatever reason,

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Speaker 1: they just don't have the you know, the kind of

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Speaker 1: intellectual curiosity for this sort of subject that you or

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Speaker 1: I might have and uh and in sometimes you get

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Speaker 1: the people who confuse cosmologists with cosmetologists, and that's pretty awkward. Um,

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Speaker 1: so yeah, you can. You can have just about any

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Speaker 1: kind of experience on a plane. When you tell them,

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Speaker 1: UM about my line of work. Are you willing to

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Speaker 1: give advice on lipstick colors or not? I mean, I'd

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Speaker 1: be willing to give you my advice and just about anything,

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Speaker 1: but I don't think you should take it. For one thing,

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Speaker 1: I'm I'm color blind, so i'd probably be pretty bad

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Speaker 1: at that job. All right, Well, I think that these

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Speaker 1: kind of topics are totally accessible because I think everybody

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Speaker 1: wants to know the origins where we came from, because

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Speaker 1: it tells us something about why we're here and what

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Speaker 1: it means. Um And I posted a question on Twitter

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Speaker 1: this week, and I say, hey, I get to ask

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Speaker 1: a leading cosmologist questions about the beginning of the universe.

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Speaker 1: What should I ask? And boy, our listeners really showed up.

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Speaker 1: We've got a long list of questions, and we're going

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Speaker 1: to listen to some of those questions and answer some

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Speaker 1: of those questions. But I was just impressed at how

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Speaker 1: much of a vein it touched in people. It doesn't

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Speaker 1: surprise me. I'm excited about this stuff. I guess our listeners,

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Speaker 1: of course, are also excited about this stuff. But I

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Speaker 1: think it goes to something else about cosmology and early

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Speaker 1: universe physics, is that it really borders with philosophy. You know,

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Speaker 1: some of the questions we ask are hard physics questions,

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Speaker 1: like when was dark matter made? Do we have a

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Speaker 1: model for the production of these nuclei? But the answers

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Speaker 1: to those questions have broad reaching implications for philosophy, for

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Speaker 1: the nature of our existence, the meaning of the context

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Speaker 1: of it. Throughout history, human beings of all times and

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Speaker 1: all cultures have looked up at their night sky and

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Speaker 1: wondered about the universe and how it came to be

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Speaker 1: the way that it is. In that respect, we're just

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Speaker 1: like all of those people, but in one important way

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Speaker 1: we're really different. For the first time in human history,

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Speaker 1: when we look up at the night sky, we more

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Speaker 1: or less know what it is we're looking at. We

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Speaker 1: understand these things, and that's a truly new development. Um.

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Speaker 1: I think it's just amazing that we can take pictures

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Speaker 1: of things in the sky and when we see a star,

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Speaker 1: we know how nuclear fusion works in its core. And

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Speaker 1: when we see planets, we understand how they formed and

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Speaker 1: why they behave the way they do and what they're

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Speaker 1: made of. When we look at the expansion of the

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Speaker 1: universe and we look at the Big Bang, we understand

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Speaker 1: how our universe evolved from its first second up to

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Speaker 1: the current era, like over thirteen billion years. I I

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Speaker 1: think that's absolutely, you know, flabbergasing, just amazing that that

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Speaker 1: we've been able to make this incredible human accomplishment. It's

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Speaker 1: the kind of thing that if you went back a

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Speaker 1: few hundred years and drop that knowledge on leading minds

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Speaker 1: of the day, their minds would be blown right, It'd

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Speaker 1: be hard for them to really even understand what you're

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Speaker 1: talking about. And now we know those things, and that

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Speaker 1: gives me enthusiasm that today's questions will one day be answered.

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Speaker 1: The humans will know the answer to the questions we

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Speaker 1: are struggling with today. Makes me want to jump in

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Speaker 1: a time machine and fast forward. In the long run,

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Speaker 1: I'm definitely a scientific optimist. I think only a fool

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Speaker 1: bets against the progress of science and the very long run.

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Speaker 1: We might not solve every question tomorrow, but as long

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Speaker 1: as human beings managed to exist and not destroy themselves,

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Speaker 1: I don't think there are any answerable questions that we

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Speaker 1: won't eventually answer. Wonderful Well, I noticed in your book

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Speaker 1: that while your topics touch on these important matters that

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Speaker 1: connect to philosophy, unlike some other noted cosmologists, you sort

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Speaker 1: of stayed in your lane and talked mostly about the

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Speaker 1: physics um and so I want to take the opportunity

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Speaker 1: to push you a little bit on this podcast. When

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Speaker 1: we have an expert come in, we like to play

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Speaker 1: a game we call ask the wrong Expert. So I'm

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Speaker 1: gonna ask you some questions about philosophy, and this gives

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Speaker 1: you an opportunity to, you know, pun tificate ignorantly, and

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Speaker 1: we don't expect you to be an expert. First question

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Speaker 1: is about whether the universe actually exists. So do you

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Speaker 1: think the universe, the physical universe a exists sort of

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Speaker 1: outside of our human experience, like it would be there

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Speaker 1: even if we weren't here to experience it. B only

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Speaker 1: exists as a mathematical model in our minds. C is

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Speaker 1: an unanswerable question. We can never know or D you're

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Speaker 1: already regretting coming onto our podcast, I definitely come down

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Speaker 1: on C for this one. Um. All we can really

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Speaker 1: do is organize our consciousness experiences, including our observations of

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Speaker 1: the world. UM, try to make sense of them. Try

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Speaker 1: to come up with order organizing principles or theories, if

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Speaker 1: you will, that explain as much about our observations as

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Speaker 1: we can, and then use those theories to make predictions

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Speaker 1: about what will happen in our conscious experience going forward.

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Speaker 1: It could be that those theories we construct in that

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Speaker 1: way map very precisely or or closely onto something real,

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Speaker 1: a real world that those theories describe, or maybe not.

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Speaker 1: We don't really have any way of finding out. But

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Speaker 1: it doesn't really matter, because science works even if the

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Speaker 1: world it describes is not a real thing. UM. I

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Speaker 1: have a supercomputer in my pocket in the form of

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Speaker 1: a cell phone, and that thing works because of the

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Speaker 1: scientific method. And um, you know, modern medicine and transistors

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Speaker 1: and any number of other amazing modern technologies work because

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Speaker 1: of the scientific method, even if the world that it

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Speaker 1: underpins uh is very different from that described in our theories. Well,

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Speaker 1: that's amazing, Um. I agree with you. We might not

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Speaker 1: be able to answer it, but to me it matters

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Speaker 1: deeply whether what we're doing is just sort of playing

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Speaker 1: in our minds or answering real questions about the univers

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Speaker 1: And that's one of the reasons why I'm very much

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Speaker 1: looking forward to the day when we meet alien physicists

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Speaker 1: and perhaps get a chance to understand how a different

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Speaker 1: kind of consciousness might probe the universe, and and maybe

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Speaker 1: draw some sort of triangulation there about what's really happening.

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Speaker 1: But in the end, I agree with you, we probably

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Speaker 1: can't ever know. But that leads me to my second

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Speaker 1: question about the working of the human brain. Do you

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Speaker 1: a big complicated mechanical watch in which we have no

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Speaker 1: free will, be deterministic, but yet there's somehow still room

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Speaker 1: in there for free will see nondeterministic because of quantum

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Speaker 1: mechanics like Penrose things, or d nondeterministic because of sort

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Speaker 1: of sort of magic, supernatural extra extra physical force. I

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Speaker 1: think this is a really good question, but I don't

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Speaker 1: think any of my my answer really falls into any

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Speaker 1: of these four categories or A, B, C, or D.

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Speaker 1: So I'm going to kind of give you my my

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Speaker 1: own e if you will answer. So. I think the

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Speaker 1: laws of nature are not deterministic. Quantum mechanics doesn't appear

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Speaker 1: to be deterministic. It might be in some sort of

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Speaker 1: everready in many world sense, But as far as any

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Speaker 1: experiment I would conduct, I can only probabilistically work out

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Speaker 1: what's going to happen in that experiment. So, for all

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Speaker 1: intents and purposes, UH, the laws of physics are not deterministic,

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Speaker 1: And since the human brain is a machine that follows

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Speaker 1: the laws of physics in our world, it also is

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Speaker 1: not deterministic. But as far as free will is concerned,

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Speaker 1: I don't think that matters. What I mean by that

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Speaker 1: is just because something in my brain is random and

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Speaker 1: not predictable doesn't mean I'm free to make any choices.

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Speaker 1: If I walked around flipping a coin to decide whether

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Speaker 1: I'm gonna do thing A or thing B next, that

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Speaker 1: doesn't give me any freedom. It just means I'm not predictable. So,

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Speaker 1: at least in any morally culpable sense, I don't believe

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Speaker 1: there's any reason to think there's free will and unit

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Speaker 1: that's a very sophisticated answer. I think I agree with

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Speaker 1: you on all points, and we're actually gonna dig into

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Speaker 1: that in depth in a future episode of this podcast.

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Speaker 1: So thanks for playing along with our silly game. But

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Speaker 1: the reason we brought you onto the podcast is to

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Speaker 1: talk about what you are an expert in, and that's

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Speaker 1: the early universe and the very beginning of time. And

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Speaker 1: so I want to dig into the details and pick

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Speaker 1: your brain about how our universe began. But first let's

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Speaker 1: take a quick break. Okay, we're back and we're talking

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Speaker 1: with Dan Hooper. He's a theoretical physicist at Firmy National

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Speaker 1: Accelerated Laboratory and the author of the upcoming book At

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Speaker 1: the Edge of Time, which explores the very beginning of

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Speaker 1: the universe. And Dan, first question for you to have

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Speaker 1: about what you actually know about is about how the

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Speaker 1: universe began. I would I would love if you would

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Speaker 1: sort of walk us through the very beginning of the universe.

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Speaker 1: And I'll give you two options here. Either walk us

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Speaker 1: through forwards from the moments of creation or backwards from

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Speaker 1: what we actually know into what we don't know. But

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Speaker 1: I'd love a sort of tour of the very first

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Speaker 1: moments of the universe. So even if you hadn't given

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Speaker 1: me the option, I definitely would have suggested going from

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Speaker 1: the present backwards because that's just a lot easier way

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Speaker 1: to describe it. So let me do it that way.

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Speaker 1: When we look at it out at our universe today,

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Speaker 1: we see that space is expanding. And what I mean

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Speaker 1: by that is all the objects in space, at least

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Speaker 1: the objects that are far away, like galaxies, for example,

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Speaker 1: they're all moving away from us, and the farther away

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Speaker 1: something is from us, the faster it's moving away from us.

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Speaker 1: This is because any two points in space, the amount

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Speaker 1: of space between them is growing as time goes on.

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Speaker 1: This is something we call Hubble's law. So because space

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Speaker 1: is expanding, that means that in the past our universe

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Speaker 1: uh was more compact, more dense, and as a consequence,

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Speaker 1: it was hotter, and in the future it will be

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Speaker 1: less dense and even cooler than it is today. So

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Speaker 1: if you run those equations backwards, you'll eventually point a

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Speaker 1: time reach a point in time where the universe was

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Speaker 1: very hot. Um So thirteen point eight billion years ago,

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Speaker 1: only a few hundred thousand years after the Big Bang,

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Speaker 1: you reach a point where the entire universe was filled

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Speaker 1: with uh some light and electrons and protons and things

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Speaker 1: that were all at a temperature of about three thousand degrees.

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Speaker 1: So three thousand degrees is an important point in in

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Speaker 1: the history of the universe because at three thousand degrees

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Speaker 1: you find that atoms begin to melt. This is what

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Speaker 1: I mean by that. So if I take some ordinary

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Speaker 1: atoms and I dump it in some thorough baths somewhere

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Speaker 1: that has a temperature more than three thousand degrees, well,

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Speaker 1: if I do that, those atoms, all the electrons that

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Speaker 1: are bound up on those atoms are gonna break off.

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Speaker 1: They're gonna basically those atoms are going to fall apart

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Speaker 1: into their protons and nuclei and electrons. So that means

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Speaker 1: that before this this key point three eighty thousand years

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Speaker 1: after the Big Bang, the universe was full of electrons

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Speaker 1: and protons and nuclei, but no neutral atoms. And then

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Speaker 1: after this point, basically all those things glued together into

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Speaker 1: into electrically neutral atoms. Before that transition, the universe was opaque,

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Speaker 1: meaning light couldn't couldn't move through space. Because of all

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Speaker 1: these charged particles in it. But after this point, the

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Speaker 1: universe became transparent to light. And that means that at

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Speaker 1: this transition, um awful lot of light was dumped into

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Speaker 1: the universe, and that light exists everywhere today. It's moving

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Speaker 1: in all directions and in all places, and in fact,

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Speaker 1: in this very room, or any any room, every cubic

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Speaker 1: centimeter of space has over four hundred photons that were

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Speaker 1: produced in this transition. We call that the causing mic

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Speaker 1: wave background. And over the last fifty years or so,

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Speaker 1: becausemologists have been studying this been greater and greater detail.

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Speaker 1: A lot of what we know about our universe's history

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Speaker 1: comes directly from observing that light that was released when

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Speaker 1: the first atoms are formed only a few hundred thousand

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Speaker 1: years after the Big Bang. All right, but let me

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Speaker 1: ask you a question there to clarify. So you're saying,

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Speaker 1: we look out of the universe, we see things are expanding,

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Speaker 1: and if we want to run the clock backwards, we say, well,

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Speaker 1: therefore things must have been denser before, because things are

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Speaker 1: getting less dense now. And so the universe now is transparent.

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Speaker 1: Light can fly through it. It seems, you know, we

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Speaker 1: can look out in the night sky and see billions

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Speaker 1: of light years away because you run the clock backwards

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Speaker 1: until everything sort of scrunches back together, and you talk

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Speaker 1: about this plasma that fills all of space, and I

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Speaker 1: think a lot of our listeners probably imagine that the

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Speaker 1: Big Bang is sort of the creation from one point,

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Speaker 1: that everything in the universe came from one spot. And

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Speaker 1: so if you talk about running the clock backwards from

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Speaker 1: the current universe getting to something that fills all of space,

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Speaker 1: and I think I wonder if our listeners have a

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Speaker 1: clear mental picture of what that means, Like, are you

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Speaker 1: saying that the cosmic microwave background was created by a

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Speaker 1: plasma that literally filled the entire universe or was the

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Speaker 1: stuff in the universe sort of smaller and more localized

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Speaker 1: back then. Probably the single biggest misconception about the Big

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Speaker 1: Bang it was is that it was some event that

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Speaker 1: took place at some place, some explosion that all the

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Speaker 1: stuff came out of. But that's kind of misses the point.

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Speaker 1: So when I say the cosmic microwave background fills all

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Speaker 1: of space today, I mean all of space everywhere, and

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Speaker 1: when it was formed, it was formed at a point

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Speaker 1: in time where the entire universe, all of space was

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Speaker 1: filled with this three thousand degree plasma that slowly or

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Speaker 1: solely transformed into a three thousand degree gas of electrically

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Speaker 1: neutral particles. And if you go back farther, it's not

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Speaker 1: that the Big Bang happened somewhere, is that the entire

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Speaker 1: universe was in this hot and dense state. The Big

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Speaker 1: Bang wasn't something it happened in one place. It was

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Speaker 1: a state that the universe started out in. So I

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Speaker 1: wonder if people would find it more natural to talk

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Speaker 1: about space being more dense or the stuff in space

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Speaker 1: being more dense, rather than actually being smaller, because it

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Speaker 1: sounds like you're talking about sort of stretching out the

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Speaker 1: space between the stuff, not actually shrinking it down into

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Speaker 1: a dot. But it's pretty hard to get your mind

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Speaker 1: around an infinite universe filled with an infinite amount of

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Speaker 1: stuff and having it still squished down into an infinite universe. Well,

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Speaker 1: there are a couple of different ways you can think

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Speaker 1: about it. Um One way you can think about it

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Speaker 1: is to imagine that the universe might not go on

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Speaker 1: in all directions forever. It might not be infinite, and

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Speaker 1: we don't know it. It's possible that that's true. Maybe

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Speaker 1: the universe, if you go far enough in one direction,

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Speaker 1: wraps around on itself. Uh. And and this would be

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Speaker 1: a much farther away than we can see at the

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Speaker 1: present time. But maybe if you went far enough, you'd

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Speaker 1: find you'd come out back where you started. Um. I

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Speaker 1: like using the analogy of the old arcade game from

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Speaker 1: My My Youth of Asteroids. If you fly the UH

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Speaker 1: spaceship off the side of the screen Asteroids, you come

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Speaker 1: out on the opposite side of the screen. Maybe our

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Speaker 1: universe works this way too. And if that's the case,

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Speaker 1: then essentially the screen that you're playing on in the

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Speaker 1: to take my analogy further, has been expanding. And that

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Speaker 1: means that the total volume of the screen or area

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Speaker 1: of the screen and the two dimensional example was smaller

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Speaker 1: in the past, but still the screen occupied all of

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Speaker 1: the space that existed at the time. So if you

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Speaker 1: if that helps you to think about it better, that's

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Speaker 1: one way you can imagine expanding space, uh, without imagining,

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Speaker 1: for example, space growing into something or or the Big

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Speaker 1: Bang happening somewhere as opposed to everywhere at the same time. Yeah,

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Speaker 1: and I think that it's just hard for us to

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Speaker 1: grasp the concept of infinity. Like, if you take a ruler,

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Speaker 1: there's an infinite number of places on that ruler between

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Speaker 1: you know, one inch and two inch, because you know,

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Speaker 1: there's an infinite number of real numbers. If you shrunk

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Speaker 1: that ruler, there would still be an a number of places, right.

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Speaker 1: The infinity doesn't get less infinite just because you shrunk it,

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Speaker 1: which is sort of counterintuitive. Okay, So let's go back

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Speaker 1: even farther in time now. So instead of talking about

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Speaker 1: the universe as it was a few hundred thousand years

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Speaker 1: after the Big Bang, let's go back to the first

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Speaker 1: seconds or minutes after the Big Bang. In this state,

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Speaker 1: the universe was at a billion degrees everywhere throughout all

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Speaker 1: of space, and at a billion degrees um, things start

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Speaker 1: to resemble what you would find today inside the core

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Speaker 1: of very massive stars, and that means that nuclear reactions

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Speaker 1: can efficiently go on so throughout the entire universe. During

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Speaker 1: these first seconds and minutes, the entire universe functioned like

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Speaker 1: a giant nuclear fusion reactor. Protons and neutrons, which up

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Speaker 1: until this point have been free, we're being combined to

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Speaker 1: form things like deuterium and helium and lithium and brillium

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Speaker 1: and releasing energy in the pro sys and uh, we

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Speaker 1: can use our theories to calculate how much of all

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Speaker 1: this should have been formed, how much helium, hydrogen, deuterium, lithium,

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Speaker 1: and brillium. And when we go out and measure how

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Speaker 1: much of these things there are in the universe, it

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Speaker 1: turns out that it gives the right answer. So that

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Speaker 1: gives us a lot of confidence that we understand how

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Speaker 1: our universe has expanded and evolved from about the first

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Speaker 1: second after the Big Bang up to the present. All right,

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Speaker 1: but that's sort of in more indirect evidence than the

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Speaker 1: stuff we know about later, Like when we talk about

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Speaker 1: this cosmic microwave background radiation, that's sort of a smoking

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Speaker 1: gun that that plasma existed because we're seeing it, whereas

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Speaker 1: the indirect evidence is just sort of like the expansion

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Speaker 1: of the universe. Now we're talking about things that happened

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Speaker 1: before that that we can't directly see because the universe

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Speaker 1: was was opaque. You're talking about developing models that predict

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Speaker 1: what we would see today if that were true, and

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Speaker 1: then we find that stuff that's confirmation, But is do

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Speaker 1: we find more direct evidence would be possible to see

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Speaker 1: more crisply into into that sort of initial plasma, those

433
00:24:07,560 --> 00:24:10,920
Speaker 1: those hot fusion seconds, and and and prove more directly

434
00:24:10,920 --> 00:24:13,040
Speaker 1: that that really happened. Well, first of all, I think

435
00:24:13,119 --> 00:24:16,880
Speaker 1: the evidence that the universe played out in the way

436
00:24:16,880 --> 00:24:19,720
Speaker 1: that the big Bang theory predicts from the first few

437
00:24:19,760 --> 00:24:23,080
Speaker 1: seconds onward is pretty strong. It would be quite a

438
00:24:23,119 --> 00:24:26,440
Speaker 1: coincidence if the ratios of all those light nuclear elements

439
00:24:27,119 --> 00:24:30,679
Speaker 1: matched what we observed just by you know, just your coincidence.

440
00:24:30,680 --> 00:24:33,480
Speaker 1: So I think probably a pretty good reason to think

441
00:24:33,480 --> 00:24:36,080
Speaker 1: that that's how things played out. That being said, there

442
00:24:36,119 --> 00:24:39,080
Speaker 1: are ways that we one day could hope to more

443
00:24:39,200 --> 00:24:42,840
Speaker 1: directly measure this era of cosmic history. Um, it's a

444
00:24:42,920 --> 00:24:45,400
Speaker 1: little bit science fiction any because it's it's very hard

445
00:24:45,440 --> 00:24:48,520
Speaker 1: to do, But someday I think we will directly measure

446
00:24:48,880 --> 00:24:52,119
Speaker 1: the neutrinos that were released from our universe about a

447
00:24:52,200 --> 00:24:54,720
Speaker 1: second after the Big Bang, so kind of like the

448
00:24:54,840 --> 00:24:57,560
Speaker 1: light was released into the universe a few hundred thousand

449
00:24:57,600 --> 00:25:00,560
Speaker 1: years after the Big Bang, those neutrinos started to be

450
00:25:00,600 --> 00:25:04,080
Speaker 1: able to travel uh safely through the universe without interacting

451
00:25:04,080 --> 00:25:06,480
Speaker 1: too much at about a second after the Big Bang.

452
00:25:06,480 --> 00:25:10,040
Speaker 1: In other words, the universe became transparent to neutrinos very

453
00:25:10,040 --> 00:25:12,639
Speaker 1: shortly after the Big Bang. Now, these neutrinos are very

454
00:25:12,680 --> 00:25:15,520
Speaker 1: hard to detect, and uh, there are some ideas about

455
00:25:15,520 --> 00:25:17,480
Speaker 1: how one might go about doing it, but I think,

456
00:25:17,560 --> 00:25:21,199
Speaker 1: you know, some decades from now, it's very possible that

457
00:25:21,400 --> 00:25:24,320
Speaker 1: will be measuring these neutrinos and studying them, studying those

458
00:25:24,320 --> 00:25:27,439
Speaker 1: neutrinos in the same sort of way we currently study

459
00:25:27,520 --> 00:25:30,439
Speaker 1: the photons that were released much later. Wonderful. That's a

460
00:25:30,520 --> 00:25:34,200
Speaker 1: great point, um. I think the cosmic microwave background radiation

461
00:25:34,359 --> 00:25:37,399
Speaker 1: is fascinating because it's light we directly see from the

462
00:25:37,440 --> 00:25:40,840
Speaker 1: early universe, and of course it's limited because before that

463
00:25:40,880 --> 00:25:43,840
Speaker 1: time the universe was opaque. The light that was created

464
00:25:43,840 --> 00:25:46,840
Speaker 1: before that was reabsorbed. But as you point out, neutrinos

465
00:25:46,960 --> 00:25:51,119
Speaker 1: operate differently, and the universe is transparent to neutrinos today,

466
00:25:51,160 --> 00:25:54,760
Speaker 1: and it was transparent earlier. Right that cosmic microwave background

467
00:25:54,840 --> 00:25:58,040
Speaker 1: or sorry, that initial plasma in the first hundred thousand

468
00:25:58,160 --> 00:26:00,040
Speaker 1: years or fifty thousand years or first few minut it

469
00:26:00,119 --> 00:26:03,359
Speaker 1: to the universe. The universe was still transparent to neutrinos. Then,

470
00:26:03,400 --> 00:26:05,040
Speaker 1: that's what you're saying, And so we can see those

471
00:26:05,080 --> 00:26:08,119
Speaker 1: initial neutrinos. That's right. I mean it will won't be easy.

472
00:26:08,320 --> 00:26:11,879
Speaker 1: The same reason that the universe was transparent to neutrinos

473
00:26:11,920 --> 00:26:15,800
Speaker 1: so early makes those neutrinos really hard to detect. But

474
00:26:15,960 --> 00:26:18,960
Speaker 1: we do imagine one day we'll be able to conduct

475
00:26:19,040 --> 00:26:21,119
Speaker 1: a sort of measurements that would actually be able to

476
00:26:21,119 --> 00:26:24,280
Speaker 1: detect these neutrinos and learn what that our universe was

477
00:26:24,320 --> 00:26:27,439
Speaker 1: like only a second after the Big Bang, much more

478
00:26:27,440 --> 00:26:30,639
Speaker 1: directly than we currently can. And it's just another reason

479
00:26:30,680 --> 00:26:33,280
Speaker 1: why we should keep sort of opening new eyes to

480
00:26:33,320 --> 00:26:37,240
Speaker 1: the universe, looking at the universe through electromagnetic radiation, through neutrinos,

481
00:26:37,240 --> 00:26:40,160
Speaker 1: through gravitational waves, because they give us power to look

482
00:26:40,200 --> 00:26:42,359
Speaker 1: further and further back on the universe and see different

483
00:26:42,480 --> 00:26:45,200
Speaker 1: kinds of stuff. But we haven't seen that yet, right,

484
00:26:45,840 --> 00:26:49,119
Speaker 1: that's right. We can't do the sort of direct observations

485
00:26:49,160 --> 00:26:51,240
Speaker 1: of the first second or fraction of a second yet.

486
00:26:51,600 --> 00:26:55,080
Speaker 1: There's no reason to think that in the distant future, uh,

487
00:26:55,680 --> 00:26:59,480
Speaker 1: cosmologists won't be able to do precisely that. Well, this

488
00:26:59,560 --> 00:27:01,280
Speaker 1: is a per fixed spot to take a break. We'll

489
00:27:01,320 --> 00:27:16,720
Speaker 1: be right back, all right, So take us further back.

490
00:27:16,760 --> 00:27:18,720
Speaker 1: We were with a few minutes after the Big Bang,

491
00:27:18,880 --> 00:27:22,240
Speaker 1: So going back even further into the first seconds or

492
00:27:22,600 --> 00:27:25,800
Speaker 1: first fractions of a second after the Big Bang, we

493
00:27:25,920 --> 00:27:29,600
Speaker 1: don't really have any direct way to create images or

494
00:27:29,640 --> 00:27:32,240
Speaker 1: even to see the stuff that emerged from this period

495
00:27:32,280 --> 00:27:36,959
Speaker 1: of universe's history. So instead what we have to do

496
00:27:37,040 --> 00:27:39,040
Speaker 1: is we have to rely on experiments that we can

497
00:27:39,040 --> 00:27:42,040
Speaker 1: do in the laboratory where we try to recreate the

498
00:27:42,040 --> 00:27:45,640
Speaker 1: conditions of the very early universe and just to understand

499
00:27:45,680 --> 00:27:48,560
Speaker 1: where the laws of physics were at that very very

500
00:27:48,600 --> 00:27:52,320
Speaker 1: early time. So the main experiments I'm talking about are

501
00:27:52,359 --> 00:27:54,920
Speaker 1: what we call particle accelerators, which you you know very

502
00:27:54,960 --> 00:27:58,560
Speaker 1: well of course, Daniel um So right now, the world's

503
00:27:58,600 --> 00:28:01,920
Speaker 1: most powerful particle accelerator is the Large Hadron Collider. The

504
00:28:02,000 --> 00:28:06,439
Speaker 1: Large Hatron Collider is a seventeen mile underground circular tunnel,

505
00:28:06,800 --> 00:28:10,480
Speaker 1: and around that tunnel, powerful magnets accelerate protons to nearly

506
00:28:10,520 --> 00:28:12,800
Speaker 1: a speed of light um. I think the number is

507
00:28:12,880 --> 00:28:17,720
Speaker 1: ninety nine nine nine of the speed of light, awfully

508
00:28:17,720 --> 00:28:20,520
Speaker 1: close to the maximum and speed limit of the universe.

509
00:28:21,240 --> 00:28:23,879
Speaker 1: We then take those protons and collide them head on

510
00:28:23,960 --> 00:28:27,000
Speaker 1: inside of big detectors, and the goal here is to

511
00:28:27,000 --> 00:28:30,240
Speaker 1: put as much energy at one place at one time um,

512
00:28:30,320 --> 00:28:33,800
Speaker 1: and through Einstein's equals mc squared, we convert that energy

513
00:28:34,160 --> 00:28:38,000
Speaker 1: into mass, so we can create exotic forms of matter

514
00:28:38,720 --> 00:28:43,080
Speaker 1: that don't exist very accessively or readily in our universe today.

515
00:28:44,040 --> 00:28:45,920
Speaker 1: We discovered the Higgs boson this way, but there are

516
00:28:45,920 --> 00:28:48,360
Speaker 1: a bunch of different kinds of quarks and leptons and

517
00:28:48,480 --> 00:28:50,960
Speaker 1: things called gauge bosons, and all of these things we

518
00:28:51,000 --> 00:28:54,000
Speaker 1: can study in these particle accelerators, and all of these

519
00:28:54,000 --> 00:28:57,720
Speaker 1: things we think we're plentiful and abundant throughout the universe

520
00:28:57,840 --> 00:29:00,600
Speaker 1: is early fraction of a second. I see. So we

521
00:29:00,720 --> 00:29:03,520
Speaker 1: developed models that we think describe what happened, and then

522
00:29:03,560 --> 00:29:07,040
Speaker 1: we can go test those models by creating similar situations

523
00:29:07,040 --> 00:29:09,880
Speaker 1: in the laboratory. Yeah, that's exactly right. So if we

524
00:29:09,920 --> 00:29:13,960
Speaker 1: don't know what the laws of physics were under these conditions,

525
00:29:13,960 --> 00:29:17,120
Speaker 1: what how the universe works under these really really high

526
00:29:17,400 --> 00:29:22,240
Speaker 1: temperatures or energies, we can't really put forth a educated

527
00:29:22,280 --> 00:29:25,080
Speaker 1: guess about how the early universe might have played out.

528
00:29:25,880 --> 00:29:28,440
Speaker 1: If we can study those laws of physics in these

529
00:29:28,480 --> 00:29:33,640
Speaker 1: particles accelerators, we can at least intelligently speculate about what

530
00:29:33,760 --> 00:29:36,440
Speaker 1: the first say, trillionth of a second after the Big

531
00:29:36,440 --> 00:29:40,280
Speaker 1: Bang was likely. Uh like, right, So let's us test

532
00:29:40,280 --> 00:29:43,360
Speaker 1: our models, so lets us understand whether what we think

533
00:29:43,440 --> 00:29:47,320
Speaker 1: happened might have actually happened. But again, it's not as

534
00:29:47,400 --> 00:29:50,320
Speaker 1: direct as we'd like. It's another piece of the evidence

535
00:29:50,360 --> 00:29:53,960
Speaker 1: that constrains what could have happened. But of course, as humans,

536
00:29:54,000 --> 00:29:57,880
Speaker 1: we like visual proof, we like very direct evidence. Sometimes

537
00:29:57,880 --> 00:30:01,560
Speaker 1: I think about solving science questions is as the way

538
00:30:01,600 --> 00:30:04,280
Speaker 1: a a detective might be solving a murder mystery. In

539
00:30:04,320 --> 00:30:06,560
Speaker 1: the end, you'd love to have the body and a

540
00:30:06,560 --> 00:30:09,280
Speaker 1: lot of physical evidence, but sometimes all you have is

541
00:30:09,320 --> 00:30:12,840
Speaker 1: indirect constraints. You know when the person was by videos

542
00:30:12,840 --> 00:30:15,400
Speaker 1: somewhere else, and you have an alibi here and alibi there.

543
00:30:15,440 --> 00:30:18,160
Speaker 1: You can sort of piece the story together without the

544
00:30:18,200 --> 00:30:21,160
Speaker 1: direct evidence of the body of the smoking gun. You're

545
00:30:21,160 --> 00:30:24,080
Speaker 1: never sure, but you can do your best with what

546
00:30:24,200 --> 00:30:26,440
Speaker 1: you have. Sure, I of course agreed, but I think

547
00:30:26,480 --> 00:30:30,680
Speaker 1: it's important to not uh say that just because your

548
00:30:30,720 --> 00:30:34,480
Speaker 1: evidence is indirect, that it's necessarily weak. There are a

549
00:30:34,480 --> 00:30:38,240
Speaker 1: lot of things that science has done by accumulating indirect

550
00:30:38,280 --> 00:30:42,960
Speaker 1: evidence that has led to really strong conclusions. Conclusions we

551
00:30:43,000 --> 00:30:48,320
Speaker 1: have enormous confidence in um. Sometimes the right array of

552
00:30:48,440 --> 00:30:52,880
Speaker 1: indirect evidence can lead you very confident you understand the

553
00:30:52,880 --> 00:30:55,480
Speaker 1: problem you're looking at. Now. I'm very sensitive to that

554
00:30:55,520 --> 00:30:58,280
Speaker 1: as well, because everything we discovered in particle colliders we

555
00:30:58,320 --> 00:31:01,880
Speaker 1: have seen indirectly. We never observed these particles in our

556
00:31:01,920 --> 00:31:04,280
Speaker 1: hands or can play with them or touch them, where

557
00:31:04,280 --> 00:31:07,600
Speaker 1: we're looking at their indirect decays and then the observations

558
00:31:07,640 --> 00:31:10,520
Speaker 1: in the detectors. That's right. But just because we haven't

559
00:31:10,560 --> 00:31:14,040
Speaker 1: ever seen a Higgs boson doesn't mean we're in any

560
00:31:14,040 --> 00:31:17,320
Speaker 1: way not confident that it exists. We've measured it in

561
00:31:17,760 --> 00:31:21,000
Speaker 1: numerous number of indirect ways. We measured all these things

562
00:31:21,040 --> 00:31:23,920
Speaker 1: about it, and as a consequence, we're really sure that

563
00:31:23,960 --> 00:31:26,640
Speaker 1: the Higgs boson is a real thing that we're we're

564
00:31:26,680 --> 00:31:29,160
Speaker 1: observing and at the large Hattern collider, all right, And

565
00:31:29,240 --> 00:31:33,040
Speaker 1: so our knowledge of physics, let's is extrapolated back and

566
00:31:33,120 --> 00:31:35,720
Speaker 1: we can check our understanding of how that works. Using

567
00:31:35,920 --> 00:31:39,960
Speaker 1: particle colliders to create really hot, dense, energy rich environments.

568
00:31:40,000 --> 00:31:42,040
Speaker 1: How far back does that take us? How far back

569
00:31:42,080 --> 00:31:45,120
Speaker 1: do we think we might understand the universe? Well? The

570
00:31:45,160 --> 00:31:48,840
Speaker 1: protons that we're colliding together at the Large Hattern Collider. Um,

571
00:31:48,880 --> 00:31:51,880
Speaker 1: they're colliding with the kinds of energies that the particles

572
00:31:51,920 --> 00:31:55,360
Speaker 1: had about a trillionth of a second after the Big Bang.

573
00:31:56,040 --> 00:31:58,600
Speaker 1: So by studying these collisions at the Large Hattern collider,

574
00:31:59,200 --> 00:32:02,520
Speaker 1: we get a atty good picture for what the unit

575
00:32:02,640 --> 00:32:05,800
Speaker 1: early universe was very likely to be have been like

576
00:32:05,960 --> 00:32:08,560
Speaker 1: about a trillionth of a second after the Big Bang.

577
00:32:09,160 --> 00:32:12,040
Speaker 1: Before that, we don't really have a clue as to

578
00:32:12,080 --> 00:32:14,960
Speaker 1: what the laws of physics were, how the sequence of

579
00:32:15,000 --> 00:32:17,160
Speaker 1: events might have played out. And is that because we

580
00:32:17,280 --> 00:32:19,360
Speaker 1: don't have accelerators that are big enough, Like we built

581
00:32:19,360 --> 00:32:21,760
Speaker 1: an accelerator the size of the Solar system that could

582
00:32:21,840 --> 00:32:24,200
Speaker 1: collide particles that even higher energy. Would that let us

583
00:32:24,200 --> 00:32:26,959
Speaker 1: see further back in time? Yeah, that's right. If we

584
00:32:27,040 --> 00:32:31,840
Speaker 1: had a particle accelerator that accelerated particles to even higher

585
00:32:31,880 --> 00:32:34,280
Speaker 1: speeds and collided them with more energy than a large

586
00:32:34,280 --> 00:32:39,240
Speaker 1: hatter and clider does, we could push back even farther

587
00:32:39,280 --> 00:32:41,520
Speaker 1: and closer to the Big Bang if we'd understand the

588
00:32:41,600 --> 00:32:44,440
Speaker 1: laws of physics at earlier times and be able to

589
00:32:44,600 --> 00:32:49,080
Speaker 1: reasonably construct that early history of our our universe. So

590
00:32:49,120 --> 00:32:51,120
Speaker 1: what do we imagine? What do we think might have

591
00:32:51,200 --> 00:32:53,680
Speaker 1: happened before a trillionth of a second. We don't know

592
00:32:53,760 --> 00:32:56,960
Speaker 1: for sure, but we have at least some good reasons

593
00:32:57,000 --> 00:33:01,000
Speaker 1: to think that at some early point in our univers history,

594
00:33:01,160 --> 00:33:05,400
Speaker 1: space then just expand quickly and and steadily, but in

595
00:33:05,480 --> 00:33:07,680
Speaker 1: kind of a giant burst. This is what we call

596
00:33:07,800 --> 00:33:13,800
Speaker 1: cosmic inflation. So when we look at, for example, the

597
00:33:13,880 --> 00:33:17,080
Speaker 1: uniformity of our universe, it's basically got the same amount

598
00:33:17,120 --> 00:33:20,160
Speaker 1: of stuff everywhere. Or when we look at the geometrical

599
00:33:20,240 --> 00:33:22,800
Speaker 1: flatness of the universe, by which I mean that space

600
00:33:22,880 --> 00:33:25,440
Speaker 1: on large scales doesn't seem to be curved or warped.

601
00:33:25,760 --> 00:33:28,440
Speaker 1: But as the you know, follows the sorts of laws

602
00:33:28,480 --> 00:33:31,800
Speaker 1: of geometry that you learned in high school. Uh, these

603
00:33:31,840 --> 00:33:34,960
Speaker 1: things lead us to think that the universe probably underwent

604
00:33:35,080 --> 00:33:38,520
Speaker 1: this burst of inflationary growth at a very early time.

605
00:33:38,920 --> 00:33:41,440
Speaker 1: That being said, we can't really be sure that happened.

606
00:33:41,480 --> 00:33:46,120
Speaker 1: We have some, you know, provisional evidence that it probably did,

607
00:33:46,800 --> 00:33:49,360
Speaker 1: but we don't know much about this period or why

608
00:33:49,440 --> 00:33:51,280
Speaker 1: or how it took place. All right, And here is

609
00:33:51,320 --> 00:33:54,480
Speaker 1: a perfect opportunity to ask you a question from Twitter.

610
00:33:54,880 --> 00:33:59,200
Speaker 1: Here's a question from Twitter user myself, Bara, who says

611
00:33:59,240 --> 00:34:02,960
Speaker 1: how does physics actually test or prove inflation theory. What

612
00:34:03,120 --> 00:34:06,480
Speaker 1: kind of test would you propose to verify whether inflation

613
00:34:06,600 --> 00:34:09,400
Speaker 1: was reality or just a model we use that explains

614
00:34:09,440 --> 00:34:13,120
Speaker 1: the data we have. That's a great question. So let

615
00:34:13,120 --> 00:34:14,960
Speaker 1: me start, though by going back a little bit, so

616
00:34:15,600 --> 00:34:18,239
Speaker 1: in the nineties seventies, when the Big Bang theory was

617
00:34:18,360 --> 00:34:22,960
Speaker 1: kind of becoming, uh the established consensus view of our

618
00:34:23,000 --> 00:34:27,080
Speaker 1: universe's history at that point in time, there were a

619
00:34:27,080 --> 00:34:29,560
Speaker 1: couple of problems that emerged. One is is that the

620
00:34:29,640 --> 00:34:32,719
Speaker 1: universe really seems to be quite uniform, and it's very

621
00:34:32,719 --> 00:34:36,840
Speaker 1: hard to understand why, um, some piece of the universe

622
00:34:36,880 --> 00:34:38,920
Speaker 1: way over there, and some other piece of universe and

623
00:34:38,960 --> 00:34:41,680
Speaker 1: some opposite direction billions and billions and billions of light

624
00:34:41,719 --> 00:34:44,799
Speaker 1: years away, why they would be so much alike. It

625
00:34:44,880 --> 00:34:47,600
Speaker 1: really seemed like these parts of the universe had had

626
00:34:47,640 --> 00:34:50,839
Speaker 1: a chance to synchronize with each other, and we didn't

627
00:34:50,840 --> 00:34:53,360
Speaker 1: have any way of explaining that. Also, we didn't have

628
00:34:53,400 --> 00:34:56,680
Speaker 1: any way of understanding why the universe was so flat.

629
00:34:56,719 --> 00:34:58,879
Speaker 1: And I mentioned this before, but what I really mean

630
00:34:58,920 --> 00:35:02,000
Speaker 1: by that is if I take three points in space

631
00:35:02,040 --> 00:35:03,960
Speaker 1: and I draw a triangle between them, this is a

632
00:35:04,040 --> 00:35:07,080
Speaker 1: huge triangle billions of light years across. If I add

633
00:35:07,160 --> 00:35:09,360
Speaker 1: up the angles of that triangle, I always get about

634
00:35:09,800 --> 00:35:13,680
Speaker 1: eighty degrees. In other words, like the Euclidean geometry you

635
00:35:13,760 --> 00:35:16,400
Speaker 1: learned about in ninth or tenth grade, that seems to

636
00:35:16,440 --> 00:35:19,239
Speaker 1: apply to our universe and a larger scales, and that

637
00:35:19,320 --> 00:35:22,200
Speaker 1: doesn't have to be the case. Einstein showed us that

638
00:35:22,320 --> 00:35:25,760
Speaker 1: space can be curved positively or negatively, and we should

639
00:35:25,800 --> 00:35:28,120
Speaker 1: have kind of expected our universe to have been curved,

640
00:35:28,160 --> 00:35:32,160
Speaker 1: or at least people argued that. So to solve these puzzles,

641
00:35:32,480 --> 00:35:36,440
Speaker 1: people around ninety Alan Bouth and others proposed that the

642
00:35:36,480 --> 00:35:39,200
Speaker 1: early universe may have had this inflationary phase where it

643
00:35:39,200 --> 00:35:43,200
Speaker 1: grew really fast. When it grows, it flattens out space.

644
00:35:43,760 --> 00:35:47,319
Speaker 1: That's kind of a natural dynamical consequence of inflation, and

645
00:35:47,400 --> 00:35:50,040
Speaker 1: also it gives all of the points that we see

646
00:35:50,080 --> 00:35:53,640
Speaker 1: in space a chance to synchronize early on, explaining why

647
00:35:53,680 --> 00:35:56,920
Speaker 1: there's so much alike. Now, Okay, So if that were

648
00:35:56,960 --> 00:35:59,480
Speaker 1: the end of the story, I think it would be

649
00:35:59,560 --> 00:36:03,640
Speaker 1: unclear yer weather inflation would be a popular theory. It

650
00:36:03,680 --> 00:36:06,839
Speaker 1: would have been really hard to say that, uh, we're

651
00:36:06,880 --> 00:36:09,120
Speaker 1: really convinced that happened, it would would just not be

652
00:36:09,280 --> 00:36:12,560
Speaker 1: enough evidence. But inflation back in the eighties was shown

653
00:36:12,600 --> 00:36:15,279
Speaker 1: to make a couple of predictions. For one thing, it

654
00:36:15,360 --> 00:36:18,200
Speaker 1: said that when you get around one day to measuring

655
00:36:18,280 --> 00:36:21,800
Speaker 1: the details of the temperature patterns and the causic microwave background,

656
00:36:22,239 --> 00:36:24,640
Speaker 1: you're going to find that those temperature patterns are what

657
00:36:24,680 --> 00:36:28,680
Speaker 1: we call nearly scale invariant and adiabatic. Now those are

658
00:36:28,719 --> 00:36:32,720
Speaker 1: some complicated sounding words, but they predicted fairly specific kinds

659
00:36:32,719 --> 00:36:35,720
Speaker 1: of patterns in this light. And when we got around

660
00:36:35,719 --> 00:36:38,520
Speaker 1: to measuring that and the nineties, two thousands, and as

661
00:36:38,600 --> 00:36:40,680
Speaker 1: recently as as as the last few years of the

662
00:36:40,680 --> 00:36:44,880
Speaker 1: Pluck satellite, it turns out that those predictions panned out.

663
00:36:45,360 --> 00:36:49,319
Speaker 1: The way that the these temperature patterns actually appear in

664
00:36:49,320 --> 00:36:53,799
Speaker 1: the universe are consistent with what inflationary theory predicted. And

665
00:36:53,840 --> 00:36:57,840
Speaker 1: as a result, most cosmologists today think it's probably pretty

666
00:36:57,920 --> 00:37:01,080
Speaker 1: likely that inflation or something like it took place. We're

667
00:37:01,120 --> 00:37:04,000
Speaker 1: not sure, but we think it's pretty likely for the

668
00:37:04,040 --> 00:37:06,719
Speaker 1: most part. And so that's very important because sometimes you

669
00:37:06,719 --> 00:37:09,520
Speaker 1: cook up a scientific theory to sort of describe what

670
00:37:09,680 --> 00:37:11,680
Speaker 1: you've seen, you have a lot of freedom there to

671
00:37:11,719 --> 00:37:14,400
Speaker 1: sort of tweak the parameters and make sure it describes

672
00:37:14,440 --> 00:37:16,080
Speaker 1: what you've seen. But the real test, of course of

673
00:37:16,080 --> 00:37:19,080
Speaker 1: whether it's real is can it predict something it hasn't

674
00:37:19,120 --> 00:37:21,359
Speaker 1: seen yet, And so you're saying that inflation has sort

675
00:37:21,360 --> 00:37:24,000
Speaker 1: of passed that test. It says, if this was true,

676
00:37:24,000 --> 00:37:27,880
Speaker 1: you should expect to see these weird, particular fluctuations in

677
00:37:27,880 --> 00:37:30,560
Speaker 1: the energy from the early universe. And we have seen that.

678
00:37:30,560 --> 00:37:32,719
Speaker 1: That's right. If it weren't for these predictions and the

679
00:37:32,719 --> 00:37:35,239
Speaker 1: fact that they turned out to be correct, um, there

680
00:37:35,320 --> 00:37:38,200
Speaker 1: wouldn't be nearly as much confidence that our universe really

681
00:37:38,239 --> 00:37:41,880
Speaker 1: had an inflationary era and shortly after the Big Bang?

682
00:37:42,080 --> 00:37:44,520
Speaker 1: Do you think that's a widely held view in cosmology?

683
00:37:44,520 --> 00:37:47,160
Speaker 1: Would a random cosmologist I asked on the street agree

684
00:37:47,160 --> 00:37:49,040
Speaker 1: with you about that? Yeah, more or less. I mean,

685
00:37:49,040 --> 00:37:52,520
Speaker 1: there are a few cosmologists out there who are, you know,

686
00:37:52,719 --> 00:37:56,080
Speaker 1: argue against inflation as the best answer, and uh, and

687
00:37:56,160 --> 00:37:59,200
Speaker 1: they're they're they're constructing competing theories and things. But I

688
00:37:59,200 --> 00:38:01,040
Speaker 1: think if you did a of it, you'd find the

689
00:38:01,120 --> 00:38:03,719
Speaker 1: vast majority of cosmologists would agree with the statement that

690
00:38:03,760 --> 00:38:07,239
Speaker 1: our universe probably had an inflation area. All right, So

691
00:38:07,360 --> 00:38:10,400
Speaker 1: you've taken us back to the very very early moments

692
00:38:10,400 --> 00:38:13,000
Speaker 1: of the universe, where we have inflation, when the universe

693
00:38:13,040 --> 00:38:17,080
Speaker 1: expands by a ridiculous quantity in a in a ridiculously

694
00:38:17,080 --> 00:38:20,560
Speaker 1: short time. What about before that? What caused inflation? What

695
00:38:20,640 --> 00:38:23,759
Speaker 1: happened before inflation? Well, the real answer is, we just

696
00:38:23,800 --> 00:38:27,359
Speaker 1: don't know. We don't have any way to observe how

697
00:38:27,360 --> 00:38:32,000
Speaker 1: our universe was in this extremely early era of cosmic history,

698
00:38:32,040 --> 00:38:34,440
Speaker 1: and we don't have any experiments that we know how

699
00:38:34,480 --> 00:38:36,920
Speaker 1: to do, at least yet to tell us what the

700
00:38:37,000 --> 00:38:39,279
Speaker 1: laws of physics that dictated that era might have been.

701
00:38:39,920 --> 00:38:41,839
Speaker 1: We do know that if you go back far enough

702
00:38:41,840 --> 00:38:45,080
Speaker 1: in time, the theories we have that describe the laws

703
00:38:45,120 --> 00:38:47,920
Speaker 1: of physics and our universe must break down. We know

704
00:38:48,040 --> 00:38:51,480
Speaker 1: this because the general theory of relativity describes gravity and

705
00:38:51,520 --> 00:38:56,279
Speaker 1: space and time isn't compatible at extremely high energies with

706
00:38:56,360 --> 00:39:00,080
Speaker 1: the laws of quantum mechanics as we know them, So

707
00:39:00,200 --> 00:39:04,120
Speaker 1: one or both of those theories must break down um.

708
00:39:04,160 --> 00:39:06,400
Speaker 1: As it turns out, sometime in the first ten of

709
00:39:06,440 --> 00:39:09,040
Speaker 1: the minus forty three seconds after the Big Bang, we

710
00:39:09,120 --> 00:39:13,719
Speaker 1: simply have no clue uh what uh the universe might

711
00:39:13,760 --> 00:39:15,920
Speaker 1: have been like or even if we're asking the right

712
00:39:16,000 --> 00:39:18,680
Speaker 1: questions about it during that era that we call the

713
00:39:18,760 --> 00:39:21,040
Speaker 1: quantum gravity era. Well, that sounds like the way we

714
00:39:21,080 --> 00:39:23,920
Speaker 1: talk about the interior of black holes. We know that

715
00:39:24,000 --> 00:39:26,600
Speaker 1: general relativity is a strong theory, it's been tested in

716
00:39:26,640 --> 00:39:29,240
Speaker 1: lots of ways, but we suspect that inside a black

717
00:39:29,280 --> 00:39:32,279
Speaker 1: hole it might be wrong because it gives predictions that

718
00:39:32,400 --> 00:39:35,279
Speaker 1: disagree with quantum mechanics. Is it a similar way to

719
00:39:35,280 --> 00:39:37,480
Speaker 1: think about it. Yeah, it's a lot like that. In fact,

720
00:39:37,520 --> 00:39:39,680
Speaker 1: I would go as far as to say that it's

721
00:39:39,719 --> 00:39:42,840
Speaker 1: possible that when we do have a you know, real

722
00:39:42,960 --> 00:39:46,239
Speaker 1: theory of quantum gravity, questions like what's inside of a

723
00:39:46,280 --> 00:39:49,040
Speaker 1: black hole, those questions won't even make sense anymore. That

724
00:39:49,120 --> 00:39:51,840
Speaker 1: they will have a complete description of nature um, but

725
00:39:51,960 --> 00:39:54,520
Speaker 1: there won't be an interior of black holes. And and

726
00:39:54,600 --> 00:39:59,080
Speaker 1: maybe something equally surprising pertains to the quantum gravity era

727
00:39:59,160 --> 00:40:01,320
Speaker 1: of our universe. Who knows? Wonderful, Well, this is the

728
00:40:01,320 --> 00:40:03,680
Speaker 1: perfect time to ask you a question from a listener.

729
00:40:03,960 --> 00:40:08,040
Speaker 1: Here's an audio question from Anders from Norway. Hi. This

730
00:40:08,120 --> 00:40:11,680
Speaker 1: is Ander's moan from Oslo, Norway. I was wondering about time.

731
00:40:11,760 --> 00:40:15,440
Speaker 1: Did it behave differently when the universe was younger and denser.

732
00:40:15,760 --> 00:40:18,520
Speaker 1: That's a great question. So the first thing to appreciate

733
00:40:18,640 --> 00:40:23,640
Speaker 1: is that time is awfully weird even in the universe today. Um,

734
00:40:23,680 --> 00:40:26,840
Speaker 1: the sort of linear, you know, series of events that

735
00:40:26,840 --> 00:40:29,840
Speaker 1: that UH physics used to be based on, like in

736
00:40:29,840 --> 00:40:35,200
Speaker 1: the Newtonian worldview, was overturned by UH by Einstein more

737
00:40:35,239 --> 00:40:39,440
Speaker 1: than a century ago. And in general relativity time really

738
00:40:40,440 --> 00:40:43,720
Speaker 1: behaves pretty weird. So the length of time that passes

739
00:40:43,760 --> 00:40:47,399
Speaker 1: between two events will depend on, for example, what frame

740
00:40:47,440 --> 00:40:50,719
Speaker 1: of reference you're doing the measuring, and and things like this,

741
00:40:50,840 --> 00:40:53,759
Speaker 1: and the being in the presence of a strong gravitational

742
00:40:53,800 --> 00:40:56,279
Speaker 1: field can make time pass differently in things like this.

743
00:40:56,360 --> 00:41:00,000
Speaker 1: So time is very weird. But what I would say

744
00:41:00,360 --> 00:41:02,760
Speaker 1: with that being said is that the way that time

745
00:41:02,800 --> 00:41:06,839
Speaker 1: works in the universe today is not meaningfully different from

746
00:41:06,840 --> 00:41:09,560
Speaker 1: how it worked a thousand years or a year, or

747
00:41:09,560 --> 00:41:11,600
Speaker 1: a second after the Big Bang, or even a trillion

748
00:41:11,640 --> 00:41:14,480
Speaker 1: of a second. But if you go back even farther,

749
00:41:14,880 --> 00:41:17,719
Speaker 1: if you reach the point of the quantum gravity area era,

750
00:41:17,840 --> 00:41:21,040
Speaker 1: we know that time must have been very different than

751
00:41:21,080 --> 00:41:24,200
Speaker 1: anything we're currently imagining. We don't know what it was like,

752
00:41:24,600 --> 00:41:27,359
Speaker 1: but um, I think it's a safe bet that it

753
00:41:27,440 --> 00:41:31,920
Speaker 1: was very different from anything one might experience today. So

754
00:41:31,960 --> 00:41:34,600
Speaker 1: you're painting a pretty big question mark earlier than ten

755
00:41:34,640 --> 00:41:37,759
Speaker 1: of the mind seconds is and we don't know what's there.

756
00:41:37,840 --> 00:41:40,600
Speaker 1: We can't even really imagine it. But if you're a cosmologists,

757
00:41:40,600 --> 00:41:42,799
Speaker 1: you spend your life thinking about this stuff. You must

758
00:41:42,840 --> 00:41:45,200
Speaker 1: have a sort of a mental picture when you think

759
00:41:45,200 --> 00:41:47,520
Speaker 1: about what happened before inflation, when you think about the

760
00:41:47,560 --> 00:41:49,960
Speaker 1: moment of creation WATI equal zero, what do you have

761
00:41:50,000 --> 00:41:52,280
Speaker 1: in your mind? Well'm usually the kind of person who's

762
00:41:52,360 --> 00:41:55,240
Speaker 1: perfectly happy to speculate about things we don't know anything about.

763
00:41:55,680 --> 00:41:58,120
Speaker 1: But when it comes to that quantum gravity era era,

764
00:41:58,239 --> 00:42:00,680
Speaker 1: I'm not even you know, super comple doing it, and

765
00:42:00,800 --> 00:42:04,560
Speaker 1: just there's we have no foundation to really build upon um.

766
00:42:04,560 --> 00:42:06,839
Speaker 1: But that being said, you know, some people in the

767
00:42:06,880 --> 00:42:10,200
Speaker 1: worlds of string theory or loop quantum gravity do try

768
00:42:10,239 --> 00:42:14,480
Speaker 1: to construct ideas of what sort of things may have

769
00:42:14,560 --> 00:42:19,000
Speaker 1: existed at this time. Maybe the universe wasn't four dimensional

770
00:42:19,120 --> 00:42:21,360
Speaker 1: or with three dimensions was based on one time, but

771
00:42:21,440 --> 00:42:25,640
Speaker 1: it had more dimensions of space, and maybe space consisted

772
00:42:25,719 --> 00:42:28,960
Speaker 1: of you know, concluded things like you know, strings and

773
00:42:29,520 --> 00:42:33,480
Speaker 1: membranes and other sorts of exotic objects. Um, you know,

774
00:42:33,560 --> 00:42:37,320
Speaker 1: maybe the space itself was in a superposition of different

775
00:42:37,400 --> 00:42:39,480
Speaker 1: states of curvature and all this sort of stuff, and

776
00:42:39,920 --> 00:42:41,399
Speaker 1: you can put all these sorts of words of things.

777
00:42:41,440 --> 00:42:44,239
Speaker 1: I'm not sure that, uh, your listeners are going to

778
00:42:44,520 --> 00:42:46,799
Speaker 1: really be able to wrap their head around the stuff

779
00:42:46,840 --> 00:42:48,560
Speaker 1: I'm saying right now, But frankly, I'm not sure that

780
00:42:48,640 --> 00:42:50,680
Speaker 1: I'm able to either. So we're all in the same boat,

781
00:42:53,480 --> 00:42:56,000
Speaker 1: all right. But it was fascinated here anyway. Um, I

782
00:42:56,040 --> 00:42:59,040
Speaker 1: was wondering, what would you sort of hope for in

783
00:42:59,120 --> 00:43:01,400
Speaker 1: so in terms of future experiments that we're going to

784
00:43:01,440 --> 00:43:04,200
Speaker 1: get a grasp on what happened before ten of the

785
00:43:04,239 --> 00:43:07,640
Speaker 1: minus forty three? What future experiments would you like to

786
00:43:07,680 --> 00:43:11,360
Speaker 1: fund if you had infinite resources, what would you build

787
00:43:11,400 --> 00:43:12,799
Speaker 1: in order to give us a clue as to what

788
00:43:12,840 --> 00:43:15,440
Speaker 1: happened in the very first instance of the universe. Well,

789
00:43:15,440 --> 00:43:17,799
Speaker 1: in the more near term, we're going to measure the

790
00:43:17,840 --> 00:43:21,200
Speaker 1: cause of microave background in greater and greater detail. We're

791
00:43:21,200 --> 00:43:25,520
Speaker 1: gonna look for things like B mode polarization and non gaussianity.

792
00:43:25,600 --> 00:43:29,160
Speaker 1: These are the sorts of signatures that, if we were

793
00:43:29,200 --> 00:43:31,680
Speaker 1: to see them, would tell us something about the inflation

794
00:43:31,719 --> 00:43:34,680
Speaker 1: are epoch. So, for example, if we measure these what

795
00:43:34,760 --> 00:43:37,480
Speaker 1: we call demode polarization signals, you'd be able to know

796
00:43:37,840 --> 00:43:41,520
Speaker 1: roughly what the energy density of the universe was during inflation.

797
00:43:41,680 --> 00:43:44,160
Speaker 1: That allows us to like take the list of all

798
00:43:44,200 --> 00:43:46,919
Speaker 1: of our different inflationary theories and shrink it down into

799
00:43:46,920 --> 00:43:50,040
Speaker 1: a much more manageable number of possibilities. Um, it won't

800
00:43:50,080 --> 00:43:52,120
Speaker 1: tell us everything we want to know about inflation, but

801
00:43:52,160 --> 00:43:54,200
Speaker 1: it will give us a lot closer and it will

802
00:43:54,320 --> 00:43:56,680
Speaker 1: make us a lot more confident that you know, something

803
00:43:56,760 --> 00:44:00,120
Speaker 1: like inflation in fact took place in the more are

804
00:44:00,680 --> 00:44:03,120
Speaker 1: distant future a little bit more science fiction. E. I

805
00:44:03,120 --> 00:44:05,640
Speaker 1: imagine one day we're going to study the cause of

806
00:44:05,719 --> 00:44:08,000
Speaker 1: neutrino background, and we're not only going to detect it,

807
00:44:08,040 --> 00:44:10,600
Speaker 1: but we're gonna measure it with the kind of precision

808
00:44:10,680 --> 00:44:14,920
Speaker 1: that we've already measured the cosmic microwave background. So we

809
00:44:14,960 --> 00:44:17,440
Speaker 1: will learn as much about the universe as it was

810
00:44:17,719 --> 00:44:20,000
Speaker 1: a second after the Big Bang as we currently know

811
00:44:20,040 --> 00:44:22,880
Speaker 1: about the universe hundreds of thousands of years after the

812
00:44:22,880 --> 00:44:26,120
Speaker 1: Big Bang. This is something that will happen a long

813
00:44:26,239 --> 00:44:28,120
Speaker 1: long time from now. It's not something that I'm going

814
00:44:28,120 --> 00:44:31,640
Speaker 1: to see happen in my career, probably, But you know,

815
00:44:31,680 --> 00:44:34,399
Speaker 1: there's lots of reasons to think that the long term

816
00:44:34,440 --> 00:44:37,600
Speaker 1: future of cosmology is going to be a very exciting endeavor.

817
00:44:37,760 --> 00:44:40,800
Speaker 1: All these experiments that you envisioned, they all sound wonderful,

818
00:44:40,880 --> 00:44:42,520
Speaker 1: and I'd like to know the answers to them also,

819
00:44:42,840 --> 00:44:44,800
Speaker 1: But would any of them give us an insign to

820
00:44:44,880 --> 00:44:47,879
Speaker 1: what happened in those very first few moments before ten

821
00:44:47,920 --> 00:44:49,839
Speaker 1: to the minors forty three? Some of them will give

822
00:44:49,880 --> 00:44:52,360
Speaker 1: us a clue as to what happened in the later epics,

823
00:44:52,560 --> 00:44:54,680
Speaker 1: But will any of them pierce that veil and tell

824
00:44:54,760 --> 00:44:56,880
Speaker 1: us what happened in the quantum gravity era? Well, the

825
00:44:56,960 --> 00:44:59,840
Speaker 1: veil that separates us from the quantum gravity era is

826
00:44:59,880 --> 00:45:03,480
Speaker 1: a very thick veil. Indeed, Um, it's hard to imagine

827
00:45:03,600 --> 00:45:06,400
Speaker 1: how we're really going to figure out what that period

828
00:45:06,400 --> 00:45:09,000
Speaker 1: of our universe's history might have been like. I don't know.

829
00:45:09,080 --> 00:45:13,160
Speaker 1: Maybe one day strength theorists will UH make progress in

830
00:45:13,200 --> 00:45:16,120
Speaker 1: such a way that allows us to make testable predictions

831
00:45:16,160 --> 00:45:19,480
Speaker 1: that will give it this period of time. Um. But

832
00:45:19,800 --> 00:45:23,239
Speaker 1: I suspect that when or if we ever do UH

833
00:45:23,560 --> 00:45:25,480
Speaker 1: get some insights in this period of time, it will

834
00:45:25,520 --> 00:45:28,080
Speaker 1: be in the context of theories that we haven't even

835
00:45:28,120 --> 00:45:30,680
Speaker 1: thought about yet, or experiments that I can't even wrap

836
00:45:30,680 --> 00:45:32,920
Speaker 1: my heads around, like and it head around it. It

837
00:45:32,920 --> 00:45:35,759
Speaker 1: would be like asking a philosopher from a thousand years

838
00:45:35,760 --> 00:45:39,799
Speaker 1: ago to speculate about how twentieth century physics is going

839
00:45:39,840 --> 00:45:43,040
Speaker 1: to play out. Um, you know, there's no one could

840
00:45:43,040 --> 00:45:47,520
Speaker 1: have imagined relativity and quantum mechanics. Uh, you know, some

841
00:45:47,520 --> 00:45:51,680
Speaker 1: some distance in time ago like that. And Uh. Similarly,

842
00:45:51,719 --> 00:45:54,600
Speaker 1: I imagine that if you, you know, if we try

843
00:45:54,640 --> 00:45:57,640
Speaker 1: to imagine what physics three years from now will look like,

844
00:45:58,160 --> 00:46:00,920
Speaker 1: we would come up very very short and trying to

845
00:46:01,120 --> 00:46:03,400
Speaker 1: put our heads around anything like that or even imagining

846
00:46:03,400 --> 00:46:06,080
Speaker 1: what that might look like. I agree. I think if

847
00:46:06,120 --> 00:46:08,800
Speaker 1: you showed a philosopher from a thousand years ago a

848
00:46:08,960 --> 00:46:13,239
Speaker 1: children's book about astrophysics, they would not understand it. And

849
00:46:13,320 --> 00:46:16,120
Speaker 1: in a similar way, if you could somehow steal a

850
00:46:16,239 --> 00:46:19,200
Speaker 1: children's book about astrophysics from the year three thousand, you

851
00:46:19,280 --> 00:46:20,960
Speaker 1: and I would be baffled. We wouldn't be able to

852
00:46:21,000 --> 00:46:23,959
Speaker 1: get past the first page. I expect um, But those

853
00:46:24,000 --> 00:46:27,120
Speaker 1: concepts would be very natural to people, people thinking and

854
00:46:27,480 --> 00:46:30,439
Speaker 1: breathing and living and asking questions. Then something I really

855
00:46:30,440 --> 00:46:32,680
Speaker 1: liked about your book is that you said we are

856
00:46:32,680 --> 00:46:35,080
Speaker 1: in a time of reckoning, and it gives me the

857
00:46:35,160 --> 00:46:38,960
Speaker 1: sense that we expect physics to be revolutionized. We expect

858
00:46:39,000 --> 00:46:41,040
Speaker 1: that we might learn things about the universe that would

859
00:46:41,120 --> 00:46:44,760
Speaker 1: fundamentally change our ideas about them. I think this connects

860
00:46:44,760 --> 00:46:48,200
Speaker 1: back to the sort of philosophical implications of this kind

861
00:46:48,200 --> 00:46:50,400
Speaker 1: of research. And so to close out, I want to

862
00:46:50,400 --> 00:46:53,040
Speaker 1: ask you, what do you imagine the sort of deep

863
00:46:53,160 --> 00:46:56,560
Speaker 1: problems with physics might be reconciled in the next hundred

864
00:46:56,640 --> 00:46:58,600
Speaker 1: or two hundred years. I can't expect you to know

865
00:46:58,640 --> 00:47:00,080
Speaker 1: the answers, but at least what do you think there

866
00:47:00,080 --> 00:47:02,560
Speaker 1: are the questions we might get answers too? Well? Of

867
00:47:02,560 --> 00:47:05,680
Speaker 1: course I don't know for sure, no one does. But

868
00:47:05,800 --> 00:47:09,440
Speaker 1: when I look at the various puzzles and problems faced

869
00:47:09,680 --> 00:47:14,360
Speaker 1: by cosmologists today, it gives me reason to at least

870
00:47:14,400 --> 00:47:19,120
Speaker 1: suspect that the early universe played out very differently than

871
00:47:19,520 --> 00:47:24,440
Speaker 1: the textbooks currently describe. So here's what I have in mind. So, um,

872
00:47:24,480 --> 00:47:26,520
Speaker 1: when I if we if we just take the laws

873
00:47:26,520 --> 00:47:28,920
Speaker 1: of physics as we currently understand them and run them

874
00:47:28,920 --> 00:47:31,960
Speaker 1: through the early universe, those laws of physics say that

875
00:47:32,040 --> 00:47:34,760
Speaker 1: all of the matter and all of the antimatter should

876
00:47:34,760 --> 00:47:36,680
Speaker 1: have been destroyed. They should have destroyed each other in

877
00:47:36,680 --> 00:47:39,560
Speaker 1: the first fraction of a second um and that would

878
00:47:39,560 --> 00:47:41,920
Speaker 1: have left our universe without any atoms in it. And

879
00:47:42,000 --> 00:47:44,560
Speaker 1: yet our universe is full of atoms. I'm made of atoms,

880
00:47:44,560 --> 00:47:47,440
Speaker 1: You're made of atoms. Everything we know and directly experience

881
00:47:47,520 --> 00:47:50,640
Speaker 1: is made of atoms. So somehow things must have played

882
00:47:50,640 --> 00:47:54,280
Speaker 1: out differently than anything we currently understand in that first

883
00:47:54,280 --> 00:47:58,040
Speaker 1: fraction of a second after the Big Bang. Similarly, a

884
00:47:58,080 --> 00:47:59,680
Speaker 1: problem that I work on a lot is that of

885
00:47:59,760 --> 00:48:03,320
Speaker 1: dark matter. If you asked a bunch of people specialized

886
00:48:03,360 --> 00:48:05,719
Speaker 1: in the dark matter ten years ago, they would have

887
00:48:05,800 --> 00:48:08,600
Speaker 1: probably told you that it's likely that dark matter consists

888
00:48:08,600 --> 00:48:11,960
Speaker 1: of these things called whimps, weekly interacting massive particles. But

889
00:48:12,040 --> 00:48:14,000
Speaker 1: we've looked for whimps, and we we we know what

890
00:48:14,080 --> 00:48:16,240
Speaker 1: kind of experiments we needed to do to find whimps,

891
00:48:16,760 --> 00:48:20,399
Speaker 1: and we've done those experiments and we just haven't found anything. Um. Now,

892
00:48:20,440 --> 00:48:23,600
Speaker 1: it's possible that whimps will be discovered any day now,

893
00:48:23,680 --> 00:48:25,920
Speaker 1: and they're right around the corner. But I think at

894
00:48:25,960 --> 00:48:28,759
Speaker 1: a minimum, it's fair to say that it's surprising that

895
00:48:28,800 --> 00:48:32,239
Speaker 1: those whimps haven't shown up. So that could be that

896
00:48:32,280 --> 00:48:34,839
Speaker 1: the dark matter is just made of something different than

897
00:48:34,960 --> 00:48:38,799
Speaker 1: we had currently imagined, or it might mean that the

898
00:48:38,800 --> 00:48:42,880
Speaker 1: early universe played out differently. Our arguments for what whimps

899
00:48:42,880 --> 00:48:45,080
Speaker 1: should look like in what experiments we would have to

900
00:48:45,120 --> 00:48:48,440
Speaker 1: do to discover them, we're based on our understanding of

901
00:48:48,440 --> 00:48:50,640
Speaker 1: how things played out in the early universe when the

902
00:48:50,640 --> 00:48:53,879
Speaker 1: whimps were being created. If the early universe played out

903
00:48:53,920 --> 00:48:57,879
Speaker 1: differently than we had imagined, then the way that dark

904
00:48:57,920 --> 00:49:00,239
Speaker 1: matter would have been created and the kind of experiens

905
00:49:00,280 --> 00:49:02,279
Speaker 1: we'd have to do to find dark batter could be

906
00:49:02,400 --> 00:49:06,239
Speaker 1: very different. And then of course there's a problem of inflation. Uh,

907
00:49:06,280 --> 00:49:09,080
Speaker 1: somehow the universe got very flat and somehow the universe

908
00:49:09,120 --> 00:49:13,000
Speaker 1: got very uniform, and inflation is a good description of that.

909
00:49:13,080 --> 00:49:16,200
Speaker 1: But we don't know how how that played out. We

910
00:49:16,239 --> 00:49:18,960
Speaker 1: don't know how or why inflation happened the way it did.

911
00:49:19,560 --> 00:49:21,759
Speaker 1: Um I think it's fair to say that we have

912
00:49:22,360 --> 00:49:25,719
Speaker 1: more more questions than answers when it comes to the

913
00:49:25,760 --> 00:49:30,160
Speaker 1: inflationary era, and possibly related to inflation is the issue

914
00:49:30,160 --> 00:49:33,239
Speaker 1: of dark energy. We've learned in the last twenty years

915
00:49:33,239 --> 00:49:36,160
Speaker 1: at our universe isn't just expanding, it's expanding at an

916
00:49:36,200 --> 00:49:39,800
Speaker 1: accelerating rate, and that seems to suggest that empty space

917
00:49:40,120 --> 00:49:42,400
Speaker 1: has a certain amount of energy built into it, a

918
00:49:42,440 --> 00:49:45,680
Speaker 1: kind of vacuum energy. Um. Maybe this is similar to

919
00:49:45,719 --> 00:49:49,680
Speaker 1: the kind of energy that drove inflation shortly after the

920
00:49:49,680 --> 00:49:52,200
Speaker 1: Big Bang, and is happening now in a more gentle way.

921
00:49:52,600 --> 00:49:55,560
Speaker 1: We don't know, But all of these things, to my mind,

922
00:49:55,880 --> 00:49:59,880
Speaker 1: collectively point to some very weird and counterintuitive stuff that

923
00:50:00,000 --> 00:50:03,880
Speaker 1: I'd have played out in that first second or millions

924
00:50:03,960 --> 00:50:07,000
Speaker 1: or billions or trillion of a second after the Big Bang. Um,

925
00:50:07,040 --> 00:50:10,680
Speaker 1: that's where my money is on a new big revolutions

926
00:50:10,680 --> 00:50:14,399
Speaker 1: in physics. Well, I appreciate your scientific honesty that you're

927
00:50:14,400 --> 00:50:17,080
Speaker 1: willing to admit what we don't know, and also you're

928
00:50:17,080 --> 00:50:21,000
Speaker 1: a scientific optimism that one day scientists will unravel these

929
00:50:21,120 --> 00:50:23,560
Speaker 1: ideas and maybe on a podcast in a hundred years

930
00:50:23,640 --> 00:50:26,959
Speaker 1: they'll be chatting casually about answers to these questions. Thanks

931
00:50:27,040 --> 00:50:29,360
Speaker 1: very much for coming on our podcast today and talking

932
00:50:29,400 --> 00:50:32,160
Speaker 1: to us about these amazing questions about the nature of

933
00:50:32,160 --> 00:50:35,479
Speaker 1: the universe and its origins. And remember, everybody, Dan's book

934
00:50:35,520 --> 00:50:37,759
Speaker 1: is called At the Edge of Time. It comes out

935
00:50:37,760 --> 00:50:41,360
Speaker 1: on November five from Princeton University Press. I totally encourage

936
00:50:41,360 --> 00:50:44,080
Speaker 1: you to check it out if you're into origins of

937
00:50:44,120 --> 00:50:47,759
Speaker 1: the universe and cosmic questions. Thanks again, Dan for joining us,

938
00:50:47,840 --> 00:50:58,120
Speaker 1: and thank you listeners for tuning in. If you still

939
00:50:58,160 --> 00:51:01,120
Speaker 1: have a question after listening to all these explanations, please

940
00:51:01,400 --> 00:51:03,720
Speaker 1: drop us a line. We'd love to hear from you.

941
00:51:03,719 --> 00:51:06,560
Speaker 1: You can find us at Facebook, Twitter, and Instagram at

942
00:51:06,880 --> 00:51:09,960
Speaker 1: Daniel and Jorge That's one Word, or email us at

943
00:51:10,280 --> 00:51:14,000
Speaker 1: Feedback at Daniel and Jorge dot com. Thanks for listening,

944
00:51:14,000 --> 00:51:16,719
Speaker 1: and remember that Daniel and Jorge Explain the Universe is

945
00:51:16,760 --> 00:51:20,239
Speaker 1: a production of I Heart Radio. For more podcast from

946
00:51:20,280 --> 00:51:24,040
Speaker 1: my Heart Radio, visit the I Heart Radio app, Apple Podcasts,

947
00:51:24,160 --> 00:51:31,919
Speaker 1: or wherever you listen to your favorite shows. Yeah