Latest / Daniel and Kelly’s Extraordinary Universe / Journey to the Beginning of Time (featuring Dan Hooper)

Transcript

Journey to the Beginning of Time (featuring Dan Hooper) · Daniel and Kelly’s Extraordinary Universe

0:08
Speaker 1: One of the deepest goals of physics is to help
0:11
Speaker 1: us understand our context. Are we humans at the center
0:16
Speaker 1: of everything or are we in an irrelevant little corner
0:20
Speaker 1: of the universe? Was the universe created with us in it?
0:24
Speaker 1: Or did it exist for an unimaginable eons before we arrived.
0:28
Speaker 1: The answers to each of these questions helps us know
0:32
Speaker 1: our place or lack of it, in the universe. It
0:35
Speaker 1: helps us know how to live our lives. But nothing
0:38
Speaker 1: touches these issues more deeply than understanding the very birth
0:42
Speaker 1: of the universe. What, if anything, can we ever hope
0:46
Speaker 1: to reveal about those first few moments of creation? Hi,
1:08
Speaker 1: I'm Daniel Whitson. I'm a particle physicist and a professor
1:12
Speaker 1: you see Irvine, and I am the co host of
1:14
Speaker 1: today's podcast, Daniel and Jorge Explain the Universe, brought to
1:19
Speaker 1: you by I Heart Radio listeners. The podcast now that
1:22
Speaker 1: we love to examine big questions, deep questions, questions about
1:26
Speaker 1: things really far away, questions about things under our feet,
1:30
Speaker 1: questions about how things around us work. But we're also
1:33
Speaker 1: interested in the really deep questions, not just questions of space,
1:37
Speaker 1: but also questions of time and so while Jorge is
1:41
Speaker 1: still away and not available today. I'm very pleased to
1:44
Speaker 1: have on the podcast today a friend of mine, a collaborator,
1:47
Speaker 1: a colleague, and a upcoming author of a book I
1:50
Speaker 1: think all of you would be excited about. His name
1:54
Speaker 1: is Dan Hooper. He is a theoretical astrophysicist at FIRMY
1:58
Speaker 1: National Accelerator Laboratory and ACT. He is the head of
2:01
Speaker 1: the theoretical astrophysics group there, and he has a new
2:04
Speaker 1: book coming out about the beginning of the universe. It's
2:07
Speaker 1: called At the Edge of Time and it's going to
2:10
Speaker 1: be available in November five from Princeton University Press. Now,
2:13
Speaker 1: I've had the opportunity to take a look and at
2:15
Speaker 1: advanced copy of this book, and I think it's awesome.
2:18
Speaker 1: It talks about a lot of the really amazing questions
2:20
Speaker 1: we like to dig into on the podcast. So without
2:23
Speaker 1: further Ado, let me introduce to you my friend and colleague,
2:26
Speaker 1: Dan Hooper. Thanks. I'm really excited to be here. Yeah. Well,
2:29
Speaker 1: thanks for coming on the podcast and talking to us
2:32
Speaker 1: about all the amazing and incredible things that we like
2:35
Speaker 1: to think about. And apparently you like to write about
2:38
Speaker 1: one thing we like to do in this podcast is
2:40
Speaker 1: talk about things that are on the cutting edge of science,
2:43
Speaker 1: things that scientists themselves are thinking about, but then trying
2:46
Speaker 1: to break it down in a way that makes sense
2:48
Speaker 1: to people. People can actually come away feeling like they
2:51
Speaker 1: understand what we're talking about, not just repeating various jargon. Thanks.
2:56
Speaker 1: I really enjoy trying to think of ways to a
3:00
Speaker 1: some of the scientific ideas that I explore my research
3:03
Speaker 1: for people who aren't scientists, whether that be my non
3:07
Speaker 1: scientist friends or uh my family members. Uh. I really
3:11
Speaker 1: like stretching that part of my brain that uh one
3:15
Speaker 1: uses and communicating these exciting and very different ideas. And
3:20
Speaker 1: I think your book does a great job of this.
3:22
Speaker 1: I really conveying not just what we know, but also
3:25
Speaker 1: what we don't know, where the edge of knowledge is
3:28
Speaker 1: and and it is something else. It shows us that
3:30
Speaker 1: science is personal. I think one of the great things
3:33
Speaker 1: about your book is that it reflects who you are.
3:36
Speaker 1: Doesn't just show science for being some monolith of knowledge
3:39
Speaker 1: or something some sort of objective intellectual pursuit, but it
3:44
Speaker 1: shows us that science really is of the people, by
3:47
Speaker 1: the people, and for the people, because in the end,
3:49
Speaker 1: science is just humans answering human questions. For other humans.
3:53
Speaker 1: Science is always just a work in progress. Um, the
3:56
Speaker 1: questions we're asking today, we'll probably not be the questions
4:01
Speaker 1: that we find answers to ultimately. And when it comes
4:04
Speaker 1: to the sort of stuff that I work on, I
4:07
Speaker 1: would be shocked and maybe a little disappointed if it
4:10
Speaker 1: turns out that the ideas we have about how things
4:13
Speaker 1: are going to play out turn out to be right.
4:15
Speaker 1: I really like the mystery that that's involved. And uh,
4:18
Speaker 1: the surprise when we find out something we weren't expecting,
4:21
Speaker 1: I only hope. So I love scientific surprises. But tell me,
4:25
Speaker 1: what was your motivation for writing a popular science book
4:28
Speaker 1: about this rather than just sort of continuing in the
4:30
Speaker 1: conversation at the level of academia. Why bring this question
4:34
Speaker 1: to the people. Long before I ever became a scientist,
4:37
Speaker 1: I loved popular physics books. I used to read any
4:40
Speaker 1: number of books by folks like Paul Davies, MITCHA. Kaku,
4:45
Speaker 1: Kip Thorne, and this st just blew my mind learning
4:48
Speaker 1: about quantum mechanics and learning about UH relativity, cosmology and
4:54
Speaker 1: kind of the philosophical implications of all of it. Um. So,
4:58
Speaker 1: when I became a science entist, I decided it would
5:01
Speaker 1: be fun to kind of stretch my brain and uh
5:05
Speaker 1: and try to try my hand at popular science writing myself.
5:09
Speaker 1: This isn't the first time I've ever been in a
5:10
Speaker 1: popular science book, but I haven't written popular science in
5:13
Speaker 1: a long time. And uh, it's exciting, new challenge. I
5:16
Speaker 1: love new challenges, and uh, this was no exception wonderful.
5:20
Speaker 1: So as a theoretical astrophysicist and a cosmologist, you're dealing
5:25
Speaker 1: with questions about like the origin of the universe and
5:27
Speaker 1: the beginning of space and time, the very creation of
5:30
Speaker 1: our cosmos. When you travel around, say you're on an
5:33
Speaker 1: airplane and some random person asks you what do you do?
5:36
Speaker 1: Do you have an easy time explaining to them what
5:38
Speaker 1: you do and why it's interesting, or do you get
5:40
Speaker 1: a sort of a lot of glazed looks. The reactions
5:43
Speaker 1: I get are kind of all over the map. Occasionally
5:47
Speaker 1: you get lucky and you start that conversation and the
5:50
Speaker 1: person is excited, and uh, you know, maybe they think
5:54
Speaker 1: that's the perfect person to sit next to for the
5:56
Speaker 1: course of the flight. Um, they always wanted to know
6:00
Speaker 1: about cosmology and finally have an opportunity to to ask
6:03
Speaker 1: somebody all the questions they build up over time. And
6:06
Speaker 1: sometimes you sit next to somebody who, just for whatever reason,
6:10
Speaker 1: they just don't have the you know, the kind of
6:12
Speaker 1: intellectual curiosity for this sort of subject that you or
6:16
Speaker 1: I might have and uh and in sometimes you get
6:20
Speaker 1: the people who confuse cosmologists with cosmetologists, and that's pretty awkward. Um,
6:25
Speaker 1: so yeah, you can. You can have just about any
6:28
Speaker 1: kind of experience on a plane. When you tell them,
6:31
Speaker 1: UM about my line of work. Are you willing to
6:33
Speaker 1: give advice on lipstick colors or not? I mean, I'd
6:36
Speaker 1: be willing to give you my advice and just about anything,
6:38
Speaker 1: but I don't think you should take it. For one thing,
6:40
Speaker 1: I'm I'm color blind, so i'd probably be pretty bad
6:43
Speaker 1: at that job. All right, Well, I think that these
6:47
Speaker 1: kind of topics are totally accessible because I think everybody
6:51
Speaker 1: wants to know the origins where we came from, because
6:53
Speaker 1: it tells us something about why we're here and what
6:55
Speaker 1: it means. Um And I posted a question on Twitter
6:59
Speaker 1: this week, and I say, hey, I get to ask
7:01
Speaker 1: a leading cosmologist questions about the beginning of the universe.
7:04
Speaker 1: What should I ask? And boy, our listeners really showed up.
7:07
Speaker 1: We've got a long list of questions, and we're going
7:10
Speaker 1: to listen to some of those questions and answer some
7:12
Speaker 1: of those questions. But I was just impressed at how
7:15
Speaker 1: much of a vein it touched in people. It doesn't
7:17
Speaker 1: surprise me. I'm excited about this stuff. I guess our listeners,
7:19
Speaker 1: of course, are also excited about this stuff. But I
7:22
Speaker 1: think it goes to something else about cosmology and early
7:25
Speaker 1: universe physics, is that it really borders with philosophy. You know,
7:29
Speaker 1: some of the questions we ask are hard physics questions,
7:32
Speaker 1: like when was dark matter made? Do we have a
7:34
Speaker 1: model for the production of these nuclei? But the answers
7:37
Speaker 1: to those questions have broad reaching implications for philosophy, for
7:41
Speaker 1: the nature of our existence, the meaning of the context
7:44
Speaker 1: of it. Throughout history, human beings of all times and
7:48
Speaker 1: all cultures have looked up at their night sky and
7:51
Speaker 1: wondered about the universe and how it came to be
7:53
Speaker 1: the way that it is. In that respect, we're just
7:56
Speaker 1: like all of those people, but in one important way
7:59
Speaker 1: we're really different. For the first time in human history,
8:03
Speaker 1: when we look up at the night sky, we more
8:06
Speaker 1: or less know what it is we're looking at. We
8:08
Speaker 1: understand these things, and that's a truly new development. Um.
8:12
Speaker 1: I think it's just amazing that we can take pictures
8:17
Speaker 1: of things in the sky and when we see a star,
8:19
Speaker 1: we know how nuclear fusion works in its core. And
8:22
Speaker 1: when we see planets, we understand how they formed and
8:25
Speaker 1: why they behave the way they do and what they're
8:27
Speaker 1: made of. When we look at the expansion of the
8:29
Speaker 1: universe and we look at the Big Bang, we understand
8:32
Speaker 1: how our universe evolved from its first second up to
8:35
Speaker 1: the current era, like over thirteen billion years. I I
8:39
Speaker 1: think that's absolutely, you know, flabbergasing, just amazing that that
8:45
Speaker 1: we've been able to make this incredible human accomplishment. It's
8:48
Speaker 1: the kind of thing that if you went back a
8:50
Speaker 1: few hundred years and drop that knowledge on leading minds
8:53
Speaker 1: of the day, their minds would be blown right, It'd
8:55
Speaker 1: be hard for them to really even understand what you're
8:57
Speaker 1: talking about. And now we know those things, and that
9:00
Speaker 1: gives me enthusiasm that today's questions will one day be answered.
9:04
Speaker 1: The humans will know the answer to the questions we
9:06
Speaker 1: are struggling with today. Makes me want to jump in
9:08
Speaker 1: a time machine and fast forward. In the long run,
9:11
Speaker 1: I'm definitely a scientific optimist. I think only a fool
9:15
Speaker 1: bets against the progress of science and the very long run.
9:18
Speaker 1: We might not solve every question tomorrow, but as long
9:21
Speaker 1: as human beings managed to exist and not destroy themselves,
9:26
Speaker 1: I don't think there are any answerable questions that we
9:29
Speaker 1: won't eventually answer. Wonderful Well, I noticed in your book
9:32
Speaker 1: that while your topics touch on these important matters that
9:36
Speaker 1: connect to philosophy, unlike some other noted cosmologists, you sort
9:40
Speaker 1: of stayed in your lane and talked mostly about the
9:44
Speaker 1: physics um and so I want to take the opportunity
9:47
Speaker 1: to push you a little bit on this podcast. When
9:49
Speaker 1: we have an expert come in, we like to play
9:51
Speaker 1: a game we call ask the wrong Expert. So I'm
9:54
Speaker 1: gonna ask you some questions about philosophy, and this gives
9:58
Speaker 1: you an opportunity to, you know, pun tificate ignorantly, and
10:01
Speaker 1: we don't expect you to be an expert. First question
10:03
Speaker 1: is about whether the universe actually exists. So do you
10:08
Speaker 1: think the universe, the physical universe a exists sort of
10:12
Speaker 1: outside of our human experience, like it would be there
10:14
Speaker 1: even if we weren't here to experience it. B only
10:18
Speaker 1: exists as a mathematical model in our minds. C is
10:23
Speaker 1: an unanswerable question. We can never know or D you're
10:26
Speaker 1: already regretting coming onto our podcast, I definitely come down
10:30
Speaker 1: on C for this one. Um. All we can really
10:34
Speaker 1: do is organize our consciousness experiences, including our observations of
10:39
Speaker 1: the world. UM, try to make sense of them. Try
10:42
Speaker 1: to come up with order organizing principles or theories, if
10:46
Speaker 1: you will, that explain as much about our observations as
10:49
Speaker 1: we can, and then use those theories to make predictions
10:54
Speaker 1: about what will happen in our conscious experience going forward.
10:58
Speaker 1: It could be that those theories we construct in that
11:01
Speaker 1: way map very precisely or or closely onto something real,
11:06
Speaker 1: a real world that those theories describe, or maybe not.
11:10
Speaker 1: We don't really have any way of finding out. But
11:13
Speaker 1: it doesn't really matter, because science works even if the
11:18
Speaker 1: world it describes is not a real thing. UM. I
11:22
Speaker 1: have a supercomputer in my pocket in the form of
11:25
Speaker 1: a cell phone, and that thing works because of the
11:28
Speaker 1: scientific method. And um, you know, modern medicine and transistors
11:34
Speaker 1: and any number of other amazing modern technologies work because
11:41
Speaker 1: of the scientific method, even if the world that it
11:44
Speaker 1: underpins uh is very different from that described in our theories. Well,
11:49
Speaker 1: that's amazing, Um. I agree with you. We might not
11:52
Speaker 1: be able to answer it, but to me it matters
11:53
Speaker 1: deeply whether what we're doing is just sort of playing
11:57
Speaker 1: in our minds or answering real questions about the univers
12:00
Speaker 1: And that's one of the reasons why I'm very much
12:02
Speaker 1: looking forward to the day when we meet alien physicists
12:06
Speaker 1: and perhaps get a chance to understand how a different
12:09
Speaker 1: kind of consciousness might probe the universe, and and maybe
12:12
Speaker 1: draw some sort of triangulation there about what's really happening.
12:15
Speaker 1: But in the end, I agree with you, we probably
12:17
Speaker 1: can't ever know. But that leads me to my second
12:20
Speaker 1: question about the working of the human brain. Do you
12:24
Speaker 1: think that the human brain is either a deterministic like
12:28
Speaker 1: a big complicated mechanical watch in which we have no
12:30
Speaker 1: free will, be deterministic, but yet there's somehow still room
12:35
Speaker 1: in there for free will see nondeterministic because of quantum
12:40
Speaker 1: mechanics like Penrose things, or d nondeterministic because of sort
12:44
Speaker 1: of sort of magic, supernatural extra extra physical force. I
12:48
Speaker 1: think this is a really good question, but I don't
12:51
Speaker 1: think any of my my answer really falls into any
12:53
Speaker 1: of these four categories or A, B, C, or D.
12:56
Speaker 1: So I'm going to kind of give you my my
12:57
Speaker 1: own e if you will answer. So. I think the
13:01
Speaker 1: laws of nature are not deterministic. Quantum mechanics doesn't appear
13:05
Speaker 1: to be deterministic. It might be in some sort of
13:08
Speaker 1: everready in many world sense, But as far as any
13:12
Speaker 1: experiment I would conduct, I can only probabilistically work out
13:16
Speaker 1: what's going to happen in that experiment. So, for all
13:19
Speaker 1: intents and purposes, UH, the laws of physics are not deterministic,
13:24
Speaker 1: And since the human brain is a machine that follows
13:28
Speaker 1: the laws of physics in our world, it also is
13:31
Speaker 1: not deterministic. But as far as free will is concerned,
13:34
Speaker 1: I don't think that matters. What I mean by that
13:37
Speaker 1: is just because something in my brain is random and
13:41
Speaker 1: not predictable doesn't mean I'm free to make any choices.
13:45
Speaker 1: If I walked around flipping a coin to decide whether
13:49
Speaker 1: I'm gonna do thing A or thing B next, that
13:52
Speaker 1: doesn't give me any freedom. It just means I'm not predictable. So,
13:56
Speaker 1: at least in any morally culpable sense, I don't believe
14:00
Speaker 1: there's any reason to think there's free will and unit
14:03
Speaker 1: that's a very sophisticated answer. I think I agree with
14:05
Speaker 1: you on all points, and we're actually gonna dig into
14:08
Speaker 1: that in depth in a future episode of this podcast.
14:12
Speaker 1: So thanks for playing along with our silly game. But
14:14
Speaker 1: the reason we brought you onto the podcast is to
14:16
Speaker 1: talk about what you are an expert in, and that's
14:18
Speaker 1: the early universe and the very beginning of time. And
14:21
Speaker 1: so I want to dig into the details and pick
14:23
Speaker 1: your brain about how our universe began. But first let's
14:26
Speaker 1: take a quick break. Okay, we're back and we're talking
14:41
Speaker 1: with Dan Hooper. He's a theoretical physicist at Firmy National
14:45
Speaker 1: Accelerated Laboratory and the author of the upcoming book At
14:49
Speaker 1: the Edge of Time, which explores the very beginning of
14:52
Speaker 1: the universe. And Dan, first question for you to have
14:55
Speaker 1: about what you actually know about is about how the
14:58
Speaker 1: universe began. I would I would love if you would
15:00
Speaker 1: sort of walk us through the very beginning of the universe.
15:03
Speaker 1: And I'll give you two options here. Either walk us
15:05
Speaker 1: through forwards from the moments of creation or backwards from
15:10
Speaker 1: what we actually know into what we don't know. But
15:12
Speaker 1: I'd love a sort of tour of the very first
15:15
Speaker 1: moments of the universe. So even if you hadn't given
15:17
Speaker 1: me the option, I definitely would have suggested going from
15:21
Speaker 1: the present backwards because that's just a lot easier way
15:24
Speaker 1: to describe it. So let me do it that way.
15:27
Speaker 1: When we look at it out at our universe today,
15:30
Speaker 1: we see that space is expanding. And what I mean
15:33
Speaker 1: by that is all the objects in space, at least
15:35
Speaker 1: the objects that are far away, like galaxies, for example,
15:38
Speaker 1: they're all moving away from us, and the farther away
15:41
Speaker 1: something is from us, the faster it's moving away from us.
15:44
Speaker 1: This is because any two points in space, the amount
15:48
Speaker 1: of space between them is growing as time goes on.
15:50
Speaker 1: This is something we call Hubble's law. So because space
15:55
Speaker 1: is expanding, that means that in the past our universe
15:59
Speaker 1: uh was more compact, more dense, and as a consequence,
16:04
Speaker 1: it was hotter, and in the future it will be
16:06
Speaker 1: less dense and even cooler than it is today. So
16:10
Speaker 1: if you run those equations backwards, you'll eventually point a
16:14
Speaker 1: time reach a point in time where the universe was
16:17
Speaker 1: very hot. Um So thirteen point eight billion years ago,
16:20
Speaker 1: only a few hundred thousand years after the Big Bang,
16:22
Speaker 1: you reach a point where the entire universe was filled
16:26
Speaker 1: with uh some light and electrons and protons and things
16:30
Speaker 1: that were all at a temperature of about three thousand degrees.
16:34
Speaker 1: So three thousand degrees is an important point in in
16:37
Speaker 1: the history of the universe because at three thousand degrees
16:40
Speaker 1: you find that atoms begin to melt. This is what
16:44
Speaker 1: I mean by that. So if I take some ordinary
16:47
Speaker 1: atoms and I dump it in some thorough baths somewhere
16:51
Speaker 1: that has a temperature more than three thousand degrees, well,
16:54
Speaker 1: if I do that, those atoms, all the electrons that
16:56
Speaker 1: are bound up on those atoms are gonna break off.
16:59
Speaker 1: They're gonna basically those atoms are going to fall apart
17:01
Speaker 1: into their protons and nuclei and electrons. So that means
17:06
Speaker 1: that before this this key point three eighty thousand years
17:10
Speaker 1: after the Big Bang, the universe was full of electrons
17:15
Speaker 1: and protons and nuclei, but no neutral atoms. And then
17:18
Speaker 1: after this point, basically all those things glued together into
17:22
Speaker 1: into electrically neutral atoms. Before that transition, the universe was opaque,
17:28
Speaker 1: meaning light couldn't couldn't move through space. Because of all
17:31
Speaker 1: these charged particles in it. But after this point, the
17:35
Speaker 1: universe became transparent to light. And that means that at
17:38
Speaker 1: this transition, um awful lot of light was dumped into
17:42
Speaker 1: the universe, and that light exists everywhere today. It's moving
17:46
Speaker 1: in all directions and in all places, and in fact,
17:50
Speaker 1: in this very room, or any any room, every cubic
17:53
Speaker 1: centimeter of space has over four hundred photons that were
17:56
Speaker 1: produced in this transition. We call that the causing mic
17:59
Speaker 1: wave background. And over the last fifty years or so,
18:02
Speaker 1: becausemologists have been studying this been greater and greater detail.
18:06
Speaker 1: A lot of what we know about our universe's history
18:09
Speaker 1: comes directly from observing that light that was released when
18:13
Speaker 1: the first atoms are formed only a few hundred thousand
18:16
Speaker 1: years after the Big Bang. All right, but let me
18:18
Speaker 1: ask you a question there to clarify. So you're saying,
18:20
Speaker 1: we look out of the universe, we see things are expanding,
18:24
Speaker 1: and if we want to run the clock backwards, we say, well,
18:26
Speaker 1: therefore things must have been denser before, because things are
18:29
Speaker 1: getting less dense now. And so the universe now is transparent.
18:33
Speaker 1: Light can fly through it. It seems, you know, we
18:35
Speaker 1: can look out in the night sky and see billions
18:38
Speaker 1: of light years away because you run the clock backwards
18:40
Speaker 1: until everything sort of scrunches back together, and you talk
18:43
Speaker 1: about this plasma that fills all of space, and I
18:46
Speaker 1: think a lot of our listeners probably imagine that the
18:49
Speaker 1: Big Bang is sort of the creation from one point,
18:53
Speaker 1: that everything in the universe came from one spot. And
18:55
Speaker 1: so if you talk about running the clock backwards from
18:59
Speaker 1: the current universe getting to something that fills all of space,
19:02
Speaker 1: and I think I wonder if our listeners have a
19:04
Speaker 1: clear mental picture of what that means, Like, are you
19:06
Speaker 1: saying that the cosmic microwave background was created by a
19:09
Speaker 1: plasma that literally filled the entire universe or was the
19:12
Speaker 1: stuff in the universe sort of smaller and more localized
19:15
Speaker 1: back then. Probably the single biggest misconception about the Big
19:18
Speaker 1: Bang it was is that it was some event that
19:20
Speaker 1: took place at some place, some explosion that all the
19:24
Speaker 1: stuff came out of. But that's kind of misses the point.
19:28
Speaker 1: So when I say the cosmic microwave background fills all
19:33
Speaker 1: of space today, I mean all of space everywhere, and
19:36
Speaker 1: when it was formed, it was formed at a point
19:38
Speaker 1: in time where the entire universe, all of space was
19:41
Speaker 1: filled with this three thousand degree plasma that slowly or
19:46
Speaker 1: solely transformed into a three thousand degree gas of electrically
19:50
Speaker 1: neutral particles. And if you go back farther, it's not
19:53
Speaker 1: that the Big Bang happened somewhere, is that the entire
19:56
Speaker 1: universe was in this hot and dense state. The Big
19:59
Speaker 1: Bang wasn't something it happened in one place. It was
20:02
Speaker 1: a state that the universe started out in. So I
20:05
Speaker 1: wonder if people would find it more natural to talk
20:07
Speaker 1: about space being more dense or the stuff in space
20:10
Speaker 1: being more dense, rather than actually being smaller, because it
20:13
Speaker 1: sounds like you're talking about sort of stretching out the
20:15
Speaker 1: space between the stuff, not actually shrinking it down into
20:19
Speaker 1: a dot. But it's pretty hard to get your mind
20:21
Speaker 1: around an infinite universe filled with an infinite amount of
20:24
Speaker 1: stuff and having it still squished down into an infinite universe. Well,
20:29
Speaker 1: there are a couple of different ways you can think
20:30
Speaker 1: about it. Um One way you can think about it
20:33
Speaker 1: is to imagine that the universe might not go on
20:37
Speaker 1: in all directions forever. It might not be infinite, and
20:39
Speaker 1: we don't know it. It's possible that that's true. Maybe
20:43
Speaker 1: the universe, if you go far enough in one direction,
20:45
Speaker 1: wraps around on itself. Uh. And and this would be
20:48
Speaker 1: a much farther away than we can see at the
20:51
Speaker 1: present time. But maybe if you went far enough, you'd
20:53
Speaker 1: find you'd come out back where you started. Um. I
20:56
Speaker 1: like using the analogy of the old arcade game from
20:59
Speaker 1: My My Youth of Asteroids. If you fly the UH
21:02
Speaker 1: spaceship off the side of the screen Asteroids, you come
21:05
Speaker 1: out on the opposite side of the screen. Maybe our
21:07
Speaker 1: universe works this way too. And if that's the case,
21:10
Speaker 1: then essentially the screen that you're playing on in the
21:14
Speaker 1: to take my analogy further, has been expanding. And that
21:18
Speaker 1: means that the total volume of the screen or area
21:21
Speaker 1: of the screen and the two dimensional example was smaller
21:23
Speaker 1: in the past, but still the screen occupied all of
21:26
Speaker 1: the space that existed at the time. So if you
21:31
Speaker 1: if that helps you to think about it better, that's
21:33
Speaker 1: one way you can imagine expanding space, uh, without imagining,
21:39
Speaker 1: for example, space growing into something or or the Big
21:42
Speaker 1: Bang happening somewhere as opposed to everywhere at the same time. Yeah,
21:46
Speaker 1: and I think that it's just hard for us to
21:48
Speaker 1: grasp the concept of infinity. Like, if you take a ruler,
21:51
Speaker 1: there's an infinite number of places on that ruler between
21:54
Speaker 1: you know, one inch and two inch, because you know,
21:56
Speaker 1: there's an infinite number of real numbers. If you shrunk
21:58
Speaker 1: that ruler, there would still be an a number of places, right.
22:01
Speaker 1: The infinity doesn't get less infinite just because you shrunk it,
22:04
Speaker 1: which is sort of counterintuitive. Okay, So let's go back
22:08
Speaker 1: even farther in time now. So instead of talking about
22:10
Speaker 1: the universe as it was a few hundred thousand years
22:14
Speaker 1: after the Big Bang, let's go back to the first
22:16
Speaker 1: seconds or minutes after the Big Bang. In this state,
22:19
Speaker 1: the universe was at a billion degrees everywhere throughout all
22:23
Speaker 1: of space, and at a billion degrees um, things start
22:27
Speaker 1: to resemble what you would find today inside the core
22:31
Speaker 1: of very massive stars, and that means that nuclear reactions
22:35
Speaker 1: can efficiently go on so throughout the entire universe. During
22:40
Speaker 1: these first seconds and minutes, the entire universe functioned like
22:44
Speaker 1: a giant nuclear fusion reactor. Protons and neutrons, which up
22:49
Speaker 1: until this point have been free, we're being combined to
22:52
Speaker 1: form things like deuterium and helium and lithium and brillium
22:57
Speaker 1: and releasing energy in the pro sys and uh, we
23:02
Speaker 1: can use our theories to calculate how much of all
23:04
Speaker 1: this should have been formed, how much helium, hydrogen, deuterium, lithium,
23:10
Speaker 1: and brillium. And when we go out and measure how
23:13
Speaker 1: much of these things there are in the universe, it
23:15
Speaker 1: turns out that it gives the right answer. So that
23:18
Speaker 1: gives us a lot of confidence that we understand how
23:22
Speaker 1: our universe has expanded and evolved from about the first
23:25
Speaker 1: second after the Big Bang up to the present. All right,
23:29
Speaker 1: but that's sort of in more indirect evidence than the
23:32
Speaker 1: stuff we know about later, Like when we talk about
23:34
Speaker 1: this cosmic microwave background radiation, that's sort of a smoking
23:38
Speaker 1: gun that that plasma existed because we're seeing it, whereas
23:41
Speaker 1: the indirect evidence is just sort of like the expansion
23:44
Speaker 1: of the universe. Now we're talking about things that happened
23:46
Speaker 1: before that that we can't directly see because the universe
23:49
Speaker 1: was was opaque. You're talking about developing models that predict
23:53
Speaker 1: what we would see today if that were true, and
23:56
Speaker 1: then we find that stuff that's confirmation, But is do
24:00
Speaker 1: we find more direct evidence would be possible to see
24:03
Speaker 1: more crisply into into that sort of initial plasma, those
24:07
Speaker 1: those hot fusion seconds, and and and prove more directly
24:10
Speaker 1: that that really happened. Well, first of all, I think
24:13
Speaker 1: the evidence that the universe played out in the way
24:16
Speaker 1: that the big Bang theory predicts from the first few
24:19
Speaker 1: seconds onward is pretty strong. It would be quite a
24:23
Speaker 1: coincidence if the ratios of all those light nuclear elements
24:27
Speaker 1: matched what we observed just by you know, just your coincidence.
24:30
Speaker 1: So I think probably a pretty good reason to think
24:33
Speaker 1: that that's how things played out. That being said, there
24:36
Speaker 1: are ways that we one day could hope to more
24:39
Speaker 1: directly measure this era of cosmic history. Um, it's a
24:42
Speaker 1: little bit science fiction any because it's it's very hard
24:45
Speaker 1: to do, But someday I think we will directly measure
24:48
Speaker 1: the neutrinos that were released from our universe about a
24:52
Speaker 1: second after the Big Bang, so kind of like the
24:54
Speaker 1: light was released into the universe a few hundred thousand
24:57
Speaker 1: years after the Big Bang, those neutrinos started to be
25:00
Speaker 1: able to travel uh safely through the universe without interacting
25:04
Speaker 1: too much at about a second after the Big Bang.
25:06
Speaker 1: In other words, the universe became transparent to neutrinos very
25:10
Speaker 1: shortly after the Big Bang. Now, these neutrinos are very
25:12
Speaker 1: hard to detect, and uh, there are some ideas about
25:15
Speaker 1: how one might go about doing it, but I think,
25:17
Speaker 1: you know, some decades from now, it's very possible that
25:21
Speaker 1: will be measuring these neutrinos and studying them, studying those
25:24
Speaker 1: neutrinos in the same sort of way we currently study
25:27
Speaker 1: the photons that were released much later. Wonderful. That's a
25:30
Speaker 1: great point, um. I think the cosmic microwave background radiation
25:34
Speaker 1: is fascinating because it's light we directly see from the
25:37
Speaker 1: early universe, and of course it's limited because before that
25:40
Speaker 1: time the universe was opaque. The light that was created
25:43
Speaker 1: before that was reabsorbed. But as you point out, neutrinos
25:46
Speaker 1: operate differently, and the universe is transparent to neutrinos today,
25:51
Speaker 1: and it was transparent earlier. Right that cosmic microwave background
25:54
Speaker 1: or sorry, that initial plasma in the first hundred thousand
25:58
Speaker 1: years or fifty thousand years or first few minut it
26:00
Speaker 1: to the universe. The universe was still transparent to neutrinos. Then,
26:03
Speaker 1: that's what you're saying, And so we can see those
26:05
Speaker 1: initial neutrinos. That's right. I mean it will won't be easy.
26:08
Speaker 1: The same reason that the universe was transparent to neutrinos
26:11
Speaker 1: so early makes those neutrinos really hard to detect. But
26:15
Speaker 1: we do imagine one day we'll be able to conduct
26:19
Speaker 1: a sort of measurements that would actually be able to
26:21
Speaker 1: detect these neutrinos and learn what that our universe was
26:24
Speaker 1: like only a second after the Big Bang, much more
26:27
Speaker 1: directly than we currently can. And it's just another reason
26:30
Speaker 1: why we should keep sort of opening new eyes to
26:33
Speaker 1: the universe, looking at the universe through electromagnetic radiation, through neutrinos,
26:37
Speaker 1: through gravitational waves, because they give us power to look
26:40
Speaker 1: further and further back on the universe and see different
26:42
Speaker 1: kinds of stuff. But we haven't seen that yet, right,
26:45
Speaker 1: that's right. We can't do the sort of direct observations
26:49
Speaker 1: of the first second or fraction of a second yet.
26:51
Speaker 1: There's no reason to think that in the distant future, uh,
26:55
Speaker 1: cosmologists won't be able to do precisely that. Well, this
26:59
Speaker 1: is a per fixed spot to take a break. We'll
27:01
Speaker 1: be right back, all right, So take us further back.
27:16
Speaker 1: We were with a few minutes after the Big Bang,
27:18
Speaker 1: So going back even further into the first seconds or
27:22
Speaker 1: first fractions of a second after the Big Bang, we
27:25
Speaker 1: don't really have any direct way to create images or
27:29
Speaker 1: even to see the stuff that emerged from this period
27:32
Speaker 1: of universe's history. So instead what we have to do
27:37
Speaker 1: is we have to rely on experiments that we can
27:39
Speaker 1: do in the laboratory where we try to recreate the
27:42
Speaker 1: conditions of the very early universe and just to understand
27:45
Speaker 1: where the laws of physics were at that very very
27:48
Speaker 1: early time. So the main experiments I'm talking about are
27:52
Speaker 1: what we call particle accelerators, which you you know very
27:54
Speaker 1: well of course, Daniel um So right now, the world's
27:58
Speaker 1: most powerful particle accelerator is the Large Hadron Collider. The
28:02
Speaker 1: Large Hatron Collider is a seventeen mile underground circular tunnel,
28:06
Speaker 1: and around that tunnel, powerful magnets accelerate protons to nearly
28:10
Speaker 1: a speed of light um. I think the number is
28:12
Speaker 1: ninety nine nine nine of the speed of light, awfully
28:17
Speaker 1: close to the maximum and speed limit of the universe.
28:21
Speaker 1: We then take those protons and collide them head on
28:23
Speaker 1: inside of big detectors, and the goal here is to
28:27
Speaker 1: put as much energy at one place at one time um,
28:30
Speaker 1: and through Einstein's equals mc squared, we convert that energy
28:34
Speaker 1: into mass, so we can create exotic forms of matter
28:38
Speaker 1: that don't exist very accessively or readily in our universe today.
28:44
Speaker 1: We discovered the Higgs boson this way, but there are
28:45
Speaker 1: a bunch of different kinds of quarks and leptons and
28:48
Speaker 1: things called gauge bosons, and all of these things we
28:51
Speaker 1: can study in these particle accelerators, and all of these
28:54
Speaker 1: things we think we're plentiful and abundant throughout the universe
28:57
Speaker 1: is early fraction of a second. I see. So we
29:00
Speaker 1: developed models that we think describe what happened, and then
29:03
Speaker 1: we can go test those models by creating similar situations
29:07
Speaker 1: in the laboratory. Yeah, that's exactly right. So if we
29:09
Speaker 1: don't know what the laws of physics were under these conditions,
29:13
Speaker 1: what how the universe works under these really really high
29:17
Speaker 1: temperatures or energies, we can't really put forth a educated
29:22
Speaker 1: guess about how the early universe might have played out.
29:25
Speaker 1: If we can study those laws of physics in these
29:28
Speaker 1: particles accelerators, we can at least intelligently speculate about what
29:33
Speaker 1: the first say, trillionth of a second after the Big
29:36
Speaker 1: Bang was likely. Uh like, right, So let's us test
29:40
Speaker 1: our models, so lets us understand whether what we think
29:43
Speaker 1: happened might have actually happened. But again, it's not as
29:47
Speaker 1: direct as we'd like. It's another piece of the evidence
29:50
Speaker 1: that constrains what could have happened. But of course, as humans,
29:54
Speaker 1: we like visual proof, we like very direct evidence. Sometimes
29:57
Speaker 1: I think about solving science questions is as the way
30:01
Speaker 1: a a detective might be solving a murder mystery. In
30:04
Speaker 1: the end, you'd love to have the body and a
30:06
Speaker 1: lot of physical evidence, but sometimes all you have is
30:09
Speaker 1: indirect constraints. You know when the person was by videos
30:12
Speaker 1: somewhere else, and you have an alibi here and alibi there.
30:15
Speaker 1: You can sort of piece the story together without the
30:18
Speaker 1: direct evidence of the body of the smoking gun. You're
30:21
Speaker 1: never sure, but you can do your best with what
30:24
Speaker 1: you have. Sure, I of course agreed, but I think
30:26
Speaker 1: it's important to not uh say that just because your
30:30
Speaker 1: evidence is indirect, that it's necessarily weak. There are a
30:34
Speaker 1: lot of things that science has done by accumulating indirect
30:38
Speaker 1: evidence that has led to really strong conclusions. Conclusions we
30:43
Speaker 1: have enormous confidence in um. Sometimes the right array of
30:48
Speaker 1: indirect evidence can lead you very confident you understand the
30:52
Speaker 1: problem you're looking at. Now. I'm very sensitive to that
30:55
Speaker 1: as well, because everything we discovered in particle colliders we
30:58
Speaker 1: have seen indirectly. We never observed these particles in our
31:01
Speaker 1: hands or can play with them or touch them, where
31:04
Speaker 1: we're looking at their indirect decays and then the observations
31:07
Speaker 1: in the detectors. That's right. But just because we haven't
31:10
Speaker 1: ever seen a Higgs boson doesn't mean we're in any
31:14
Speaker 1: way not confident that it exists. We've measured it in
31:17
Speaker 1: numerous number of indirect ways. We measured all these things
31:21
Speaker 1: about it, and as a consequence, we're really sure that
31:23
Speaker 1: the Higgs boson is a real thing that we're we're
31:26
Speaker 1: observing and at the large Hattern collider, all right, And
31:29
Speaker 1: so our knowledge of physics, let's is extrapolated back and
31:33
Speaker 1: we can check our understanding of how that works. Using
31:35
Speaker 1: particle colliders to create really hot, dense, energy rich environments.
31:40
Speaker 1: How far back does that take us? How far back
31:42
Speaker 1: do we think we might understand the universe? Well? The
31:45
Speaker 1: protons that we're colliding together at the Large Hattern Collider. Um,
31:48
Speaker 1: they're colliding with the kinds of energies that the particles
31:51
Speaker 1: had about a trillionth of a second after the Big Bang.
31:56
Speaker 1: So by studying these collisions at the Large Hattern collider,
31:59
Speaker 1: we get a atty good picture for what the unit
32:02
Speaker 1: early universe was very likely to be have been like
32:05
Speaker 1: about a trillionth of a second after the Big Bang.
32:09
Speaker 1: Before that, we don't really have a clue as to
32:12
Speaker 1: what the laws of physics were, how the sequence of
32:15
Speaker 1: events might have played out. And is that because we
32:17
Speaker 1: don't have accelerators that are big enough, Like we built
32:19
Speaker 1: an accelerator the size of the Solar system that could
32:21
Speaker 1: collide particles that even higher energy. Would that let us
32:24
Speaker 1: see further back in time? Yeah, that's right. If we
32:27
Speaker 1: had a particle accelerator that accelerated particles to even higher
32:31
Speaker 1: speeds and collided them with more energy than a large
32:34
Speaker 1: hatter and clider does, we could push back even farther
32:39
Speaker 1: and closer to the Big Bang if we'd understand the
32:41
Speaker 1: laws of physics at earlier times and be able to
32:44
Speaker 1: reasonably construct that early history of our our universe. So
32:49
Speaker 1: what do we imagine? What do we think might have
32:51
Speaker 1: happened before a trillionth of a second. We don't know
32:53
Speaker 1: for sure, but we have at least some good reasons
32:57
Speaker 1: to think that at some early point in our univers history,
33:01
Speaker 1: space then just expand quickly and and steadily, but in
33:05
Speaker 1: kind of a giant burst. This is what we call
33:07
Speaker 1: cosmic inflation. So when we look at, for example, the
33:13
Speaker 1: uniformity of our universe, it's basically got the same amount
33:17
Speaker 1: of stuff everywhere. Or when we look at the geometrical
33:20
Speaker 1: flatness of the universe, by which I mean that space
33:22
Speaker 1: on large scales doesn't seem to be curved or warped.
33:25
Speaker 1: But as the you know, follows the sorts of laws
33:28
Speaker 1: of geometry that you learned in high school. Uh, these
33:31
Speaker 1: things lead us to think that the universe probably underwent
33:35
Speaker 1: this burst of inflationary growth at a very early time.
33:38
Speaker 1: That being said, we can't really be sure that happened.
33:41
Speaker 1: We have some, you know, provisional evidence that it probably did,
33:46
Speaker 1: but we don't know much about this period or why
33:49
Speaker 1: or how it took place. All right, And here is
33:51
Speaker 1: a perfect opportunity to ask you a question from Twitter.
33:54
Speaker 1: Here's a question from Twitter user myself, Bara, who says
33:59
Speaker 1: how does physics actually test or prove inflation theory. What
34:03
Speaker 1: kind of test would you propose to verify whether inflation
34:06
Speaker 1: was reality or just a model we use that explains
34:09
Speaker 1: the data we have. That's a great question. So let
34:13
Speaker 1: me start, though by going back a little bit, so
34:15
Speaker 1: in the nineties seventies, when the Big Bang theory was
34:18
Speaker 1: kind of becoming, uh the established consensus view of our
34:23
Speaker 1: universe's history at that point in time, there were a
34:27
Speaker 1: couple of problems that emerged. One is is that the
34:29
Speaker 1: universe really seems to be quite uniform, and it's very
34:32
Speaker 1: hard to understand why, um, some piece of the universe
34:36
Speaker 1: way over there, and some other piece of universe and
34:38
Speaker 1: some opposite direction billions and billions and billions of light
34:41
Speaker 1: years away, why they would be so much alike. It
34:44
Speaker 1: really seemed like these parts of the universe had had
34:47
Speaker 1: a chance to synchronize with each other, and we didn't
34:50
Speaker 1: have any way of explaining that. Also, we didn't have
34:53
Speaker 1: any way of understanding why the universe was so flat.
34:56
Speaker 1: And I mentioned this before, but what I really mean
34:58
Speaker 1: by that is if I take three points in space
35:02
Speaker 1: and I draw a triangle between them, this is a
35:04
Speaker 1: huge triangle billions of light years across. If I add
35:07
Speaker 1: up the angles of that triangle, I always get about
35:09
Speaker 1: eighty degrees. In other words, like the Euclidean geometry you
35:13
Speaker 1: learned about in ninth or tenth grade, that seems to
35:16
Speaker 1: apply to our universe and a larger scales, and that
35:19
Speaker 1: doesn't have to be the case. Einstein showed us that
35:22
Speaker 1: space can be curved positively or negatively, and we should
35:25
Speaker 1: have kind of expected our universe to have been curved,
35:28
Speaker 1: or at least people argued that. So to solve these puzzles,
35:32
Speaker 1: people around ninety Alan Bouth and others proposed that the
35:36
Speaker 1: early universe may have had this inflationary phase where it
35:39
Speaker 1: grew really fast. When it grows, it flattens out space.
35:43
Speaker 1: That's kind of a natural dynamical consequence of inflation, and
35:47
Speaker 1: also it gives all of the points that we see
35:50
Speaker 1: in space a chance to synchronize early on, explaining why
35:53
Speaker 1: there's so much alike. Now, Okay, So if that were
35:56
Speaker 1: the end of the story, I think it would be
35:59
Speaker 1: unclear yer weather inflation would be a popular theory. It
36:03
Speaker 1: would have been really hard to say that, uh, we're
36:06
Speaker 1: really convinced that happened, it would would just not be
36:09
Speaker 1: enough evidence. But inflation back in the eighties was shown
36:12
Speaker 1: to make a couple of predictions. For one thing, it
36:15
Speaker 1: said that when you get around one day to measuring
36:18
Speaker 1: the details of the temperature patterns and the causic microwave background,
36:22
Speaker 1: you're going to find that those temperature patterns are what
36:24
Speaker 1: we call nearly scale invariant and adiabatic. Now those are
36:28
Speaker 1: some complicated sounding words, but they predicted fairly specific kinds
36:32
Speaker 1: of patterns in this light. And when we got around
36:35
Speaker 1: to measuring that and the nineties, two thousands, and as
36:38
Speaker 1: recently as as as the last few years of the
36:40
Speaker 1: Pluck satellite, it turns out that those predictions panned out.
36:45
Speaker 1: The way that the these temperature patterns actually appear in
36:49
Speaker 1: the universe are consistent with what inflationary theory predicted. And
36:53
Speaker 1: as a result, most cosmologists today think it's probably pretty
36:57
Speaker 1: likely that inflation or something like it took place. We're
37:01
Speaker 1: not sure, but we think it's pretty likely for the
37:04
Speaker 1: most part. And so that's very important because sometimes you
37:06
Speaker 1: cook up a scientific theory to sort of describe what
37:09
Speaker 1: you've seen, you have a lot of freedom there to
37:11
Speaker 1: sort of tweak the parameters and make sure it describes
37:14
Speaker 1: what you've seen. But the real test, of course of
37:16
Speaker 1: whether it's real is can it predict something it hasn't
37:19
Speaker 1: seen yet, And so you're saying that inflation has sort
37:21
Speaker 1: of passed that test. It says, if this was true,
37:24
Speaker 1: you should expect to see these weird, particular fluctuations in
37:27
Speaker 1: the energy from the early universe. And we have seen that.
37:30
Speaker 1: That's right. If it weren't for these predictions and the
37:32
Speaker 1: fact that they turned out to be correct, um, there
37:35
Speaker 1: wouldn't be nearly as much confidence that our universe really
37:38
Speaker 1: had an inflationary era and shortly after the Big Bang?
37:42
Speaker 1: Do you think that's a widely held view in cosmology?
37:44
Speaker 1: Would a random cosmologist I asked on the street agree
37:47
Speaker 1: with you about that? Yeah, more or less. I mean,
37:49
Speaker 1: there are a few cosmologists out there who are, you know,
37:52
Speaker 1: argue against inflation as the best answer, and uh, and
37:56
Speaker 1: they're they're they're constructing competing theories and things. But I
37:59
Speaker 1: think if you did a of it, you'd find the
38:01
Speaker 1: vast majority of cosmologists would agree with the statement that
38:03
Speaker 1: our universe probably had an inflation area. All right, So
38:07
Speaker 1: you've taken us back to the very very early moments
38:10
Speaker 1: of the universe, where we have inflation, when the universe
38:13
Speaker 1: expands by a ridiculous quantity in a in a ridiculously
38:17
Speaker 1: short time. What about before that? What caused inflation? What
38:20
Speaker 1: happened before inflation? Well, the real answer is, we just
38:23
Speaker 1: don't know. We don't have any way to observe how
38:27
Speaker 1: our universe was in this extremely early era of cosmic history,
38:32
Speaker 1: and we don't have any experiments that we know how
38:34
Speaker 1: to do, at least yet to tell us what the
38:37
Speaker 1: laws of physics that dictated that era might have been.
38:39
Speaker 1: We do know that if you go back far enough
38:41
Speaker 1: in time, the theories we have that describe the laws
38:45
Speaker 1: of physics and our universe must break down. We know
38:48
Speaker 1: this because the general theory of relativity describes gravity and
38:51
Speaker 1: space and time isn't compatible at extremely high energies with
38:56
Speaker 1: the laws of quantum mechanics as we know them, So
39:00
Speaker 1: one or both of those theories must break down um.
39:04
Speaker 1: As it turns out, sometime in the first ten of
39:06
Speaker 1: the minus forty three seconds after the Big Bang, we
39:09
Speaker 1: simply have no clue uh what uh the universe might
39:13
Speaker 1: have been like or even if we're asking the right
39:16
Speaker 1: questions about it during that era that we call the
39:18
Speaker 1: quantum gravity era. Well, that sounds like the way we
39:21
Speaker 1: talk about the interior of black holes. We know that
39:24
Speaker 1: general relativity is a strong theory, it's been tested in
39:26
Speaker 1: lots of ways, but we suspect that inside a black
39:29
Speaker 1: hole it might be wrong because it gives predictions that
39:32
Speaker 1: disagree with quantum mechanics. Is it a similar way to
39:35
Speaker 1: think about it. Yeah, it's a lot like that. In fact,
39:37
Speaker 1: I would go as far as to say that it's
39:39
Speaker 1: possible that when we do have a you know, real
39:42
Speaker 1: theory of quantum gravity, questions like what's inside of a
39:46
Speaker 1: black hole, those questions won't even make sense anymore. That
39:49
Speaker 1: they will have a complete description of nature um, but
39:51
Speaker 1: there won't be an interior of black holes. And and
39:54
Speaker 1: maybe something equally surprising pertains to the quantum gravity era
39:59
Speaker 1: of our universe. Who knows? Wonderful, Well, this is the
40:01
Speaker 1: perfect time to ask you a question from a listener.
40:03
Speaker 1: Here's an audio question from Anders from Norway. Hi. This
40:08
Speaker 1: is Ander's moan from Oslo, Norway. I was wondering about time.
40:11
Speaker 1: Did it behave differently when the universe was younger and denser.
40:15
Speaker 1: That's a great question. So the first thing to appreciate
40:18
Speaker 1: is that time is awfully weird even in the universe today. Um,
40:23
Speaker 1: the sort of linear, you know, series of events that
40:26
Speaker 1: that UH physics used to be based on, like in
40:29
Speaker 1: the Newtonian worldview, was overturned by UH by Einstein more
40:35
Speaker 1: than a century ago. And in general relativity time really
40:40
Speaker 1: behaves pretty weird. So the length of time that passes
40:43
Speaker 1: between two events will depend on, for example, what frame
40:47
Speaker 1: of reference you're doing the measuring, and and things like this,
40:50
Speaker 1: and the being in the presence of a strong gravitational
40:53
Speaker 1: field can make time pass differently in things like this.
40:56
Speaker 1: So time is very weird. But what I would say
41:00
Speaker 1: with that being said is that the way that time
41:02
Speaker 1: works in the universe today is not meaningfully different from
41:06
Speaker 1: how it worked a thousand years or a year, or
41:09
Speaker 1: a second after the Big Bang, or even a trillion
41:11
Speaker 1: of a second. But if you go back even farther,
41:14
Speaker 1: if you reach the point of the quantum gravity area era,
41:17
Speaker 1: we know that time must have been very different than
41:21
Speaker 1: anything we're currently imagining. We don't know what it was like,
41:24
Speaker 1: but um, I think it's a safe bet that it
41:27
Speaker 1: was very different from anything one might experience today. So
41:31
Speaker 1: you're painting a pretty big question mark earlier than ten
41:34
Speaker 1: of the mind seconds is and we don't know what's there.
41:37
Speaker 1: We can't even really imagine it. But if you're a cosmologists,
41:40
Speaker 1: you spend your life thinking about this stuff. You must
41:42
Speaker 1: have a sort of a mental picture when you think
41:45
Speaker 1: about what happened before inflation, when you think about the
41:47
Speaker 1: moment of creation WATI equal zero, what do you have
41:50
Speaker 1: in your mind? Well'm usually the kind of person who's
41:52
Speaker 1: perfectly happy to speculate about things we don't know anything about.
41:55
Speaker 1: But when it comes to that quantum gravity era era,
41:58
Speaker 1: I'm not even you know, super comple doing it, and
42:00
Speaker 1: just there's we have no foundation to really build upon um.
42:04
Speaker 1: But that being said, you know, some people in the
42:06
Speaker 1: worlds of string theory or loop quantum gravity do try
42:10
Speaker 1: to construct ideas of what sort of things may have
42:14
Speaker 1: existed at this time. Maybe the universe wasn't four dimensional
42:19
Speaker 1: or with three dimensions was based on one time, but
42:21
Speaker 1: it had more dimensions of space, and maybe space consisted
42:25
Speaker 1: of you know, concluded things like you know, strings and
42:29
Speaker 1: membranes and other sorts of exotic objects. Um, you know,
42:33
Speaker 1: maybe the space itself was in a superposition of different
42:37
Speaker 1: states of curvature and all this sort of stuff, and
42:39
Speaker 1: you can put all these sorts of words of things.
42:41
Speaker 1: I'm not sure that, uh, your listeners are going to
42:44
Speaker 1: really be able to wrap their head around the stuff
42:46
Speaker 1: I'm saying right now, But frankly, I'm not sure that
42:48
Speaker 1: I'm able to either. So we're all in the same boat,
42:53
Speaker 1: all right. But it was fascinated here anyway. Um, I
42:56
Speaker 1: was wondering, what would you sort of hope for in
42:59
Speaker 1: so in terms of future experiments that we're going to
43:01
Speaker 1: get a grasp on what happened before ten of the
43:04
Speaker 1: minus forty three? What future experiments would you like to
43:07
Speaker 1: fund if you had infinite resources, what would you build
43:11
Speaker 1: in order to give us a clue as to what
43:12
Speaker 1: happened in the very first instance of the universe. Well,
43:15
Speaker 1: in the more near term, we're going to measure the
43:17
Speaker 1: cause of microave background in greater and greater detail. We're
43:21
Speaker 1: gonna look for things like B mode polarization and non gaussianity.
43:25
Speaker 1: These are the sorts of signatures that, if we were
43:29
Speaker 1: to see them, would tell us something about the inflation
43:31
Speaker 1: are epoch. So, for example, if we measure these what
43:34
Speaker 1: we call demode polarization signals, you'd be able to know
43:37
Speaker 1: roughly what the energy density of the universe was during inflation.
43:41
Speaker 1: That allows us to like take the list of all
43:44
Speaker 1: of our different inflationary theories and shrink it down into
43:46
Speaker 1: a much more manageable number of possibilities. Um, it won't
43:50
Speaker 1: tell us everything we want to know about inflation, but
43:52
Speaker 1: it will give us a lot closer and it will
43:54
Speaker 1: make us a lot more confident that you know, something
43:56
Speaker 1: like inflation in fact took place in the more are
44:00
Speaker 1: distant future a little bit more science fiction. E. I
44:03
Speaker 1: imagine one day we're going to study the cause of
44:05
Speaker 1: neutrino background, and we're not only going to detect it,
44:08
Speaker 1: but we're gonna measure it with the kind of precision
44:10
Speaker 1: that we've already measured the cosmic microwave background. So we
44:14
Speaker 1: will learn as much about the universe as it was
44:17
Speaker 1: a second after the Big Bang as we currently know
44:20
Speaker 1: about the universe hundreds of thousands of years after the
44:22
Speaker 1: Big Bang. This is something that will happen a long
44:26
Speaker 1: long time from now. It's not something that I'm going
44:28
Speaker 1: to see happen in my career, probably, But you know,
44:31
Speaker 1: there's lots of reasons to think that the long term
44:34
Speaker 1: future of cosmology is going to be a very exciting endeavor.
44:37
Speaker 1: All these experiments that you envisioned, they all sound wonderful,
44:40
Speaker 1: and I'd like to know the answers to them also,
44:42
Speaker 1: But would any of them give us an insign to
44:44
Speaker 1: what happened in those very first few moments before ten
44:47
Speaker 1: to the minors forty three? Some of them will give
44:49
Speaker 1: us a clue as to what happened in the later epics,
44:52
Speaker 1: But will any of them pierce that veil and tell
44:54
Speaker 1: us what happened in the quantum gravity era? Well, the
44:56
Speaker 1: veil that separates us from the quantum gravity era is
44:59
Speaker 1: a very thick veil. Indeed, Um, it's hard to imagine
45:03
Speaker 1: how we're really going to figure out what that period
45:06
Speaker 1: of our universe's history might have been like. I don't know.
45:09
Speaker 1: Maybe one day strength theorists will UH make progress in
45:13
Speaker 1: such a way that allows us to make testable predictions
45:16
Speaker 1: that will give it this period of time. Um. But
45:19
Speaker 1: I suspect that when or if we ever do UH
45:23
Speaker 1: get some insights in this period of time, it will
45:25
Speaker 1: be in the context of theories that we haven't even
45:28
Speaker 1: thought about yet, or experiments that I can't even wrap
45:30
Speaker 1: my heads around, like and it head around it. It
45:32
Speaker 1: would be like asking a philosopher from a thousand years
45:35
Speaker 1: ago to speculate about how twentieth century physics is going
45:39
Speaker 1: to play out. Um, you know, there's no one could
45:43
Speaker 1: have imagined relativity and quantum mechanics. Uh, you know, some
45:47
Speaker 1: some distance in time ago like that. And Uh. Similarly,
45:51
Speaker 1: I imagine that if you, you know, if we try
45:54
Speaker 1: to imagine what physics three years from now will look like,
45:58
Speaker 1: we would come up very very short and trying to
46:01
Speaker 1: put our heads around anything like that or even imagining
46:03
Speaker 1: what that might look like. I agree. I think if
46:06
Speaker 1: you showed a philosopher from a thousand years ago a
46:08
Speaker 1: children's book about astrophysics, they would not understand it. And
46:13
Speaker 1: in a similar way, if you could somehow steal a
46:16
Speaker 1: children's book about astrophysics from the year three thousand, you
46:19
Speaker 1: and I would be baffled. We wouldn't be able to
46:21
Speaker 1: get past the first page. I expect um, But those
46:24
Speaker 1: concepts would be very natural to people, people thinking and
46:27
Speaker 1: breathing and living and asking questions. Then something I really
46:30
Speaker 1: liked about your book is that you said we are
46:32
Speaker 1: in a time of reckoning, and it gives me the
46:35
Speaker 1: sense that we expect physics to be revolutionized. We expect
46:39
Speaker 1: that we might learn things about the universe that would
46:41
Speaker 1: fundamentally change our ideas about them. I think this connects
46:44
Speaker 1: back to the sort of philosophical implications of this kind
46:48
Speaker 1: of research. And so to close out, I want to
46:50
Speaker 1: ask you, what do you imagine the sort of deep
46:53
Speaker 1: problems with physics might be reconciled in the next hundred
46:56
Speaker 1: or two hundred years. I can't expect you to know
46:58
Speaker 1: the answers, but at least what do you think there
47:00
Speaker 1: are the questions we might get answers too? Well? Of
47:02
Speaker 1: course I don't know for sure, no one does. But
47:05
Speaker 1: when I look at the various puzzles and problems faced
47:09
Speaker 1: by cosmologists today, it gives me reason to at least
47:14
Speaker 1: suspect that the early universe played out very differently than
47:19
Speaker 1: the textbooks currently describe. So here's what I have in mind. So, um,
47:24
Speaker 1: when I if we if we just take the laws
47:26
Speaker 1: of physics as we currently understand them and run them
47:28
Speaker 1: through the early universe, those laws of physics say that
47:32
Speaker 1: all of the matter and all of the antimatter should
47:34
Speaker 1: have been destroyed. They should have destroyed each other in
47:36
Speaker 1: the first fraction of a second um and that would
47:39
Speaker 1: have left our universe without any atoms in it. And
47:42
Speaker 1: yet our universe is full of atoms. I'm made of atoms,
47:44
Speaker 1: You're made of atoms. Everything we know and directly experience
47:47
Speaker 1: is made of atoms. So somehow things must have played
47:50
Speaker 1: out differently than anything we currently understand in that first
47:54
Speaker 1: fraction of a second after the Big Bang. Similarly, a
47:58
Speaker 1: problem that I work on a lot is that of
47:59
Speaker 1: dark matter. If you asked a bunch of people specialized
48:03
Speaker 1: in the dark matter ten years ago, they would have
48:05
Speaker 1: probably told you that it's likely that dark matter consists
48:08
Speaker 1: of these things called whimps, weekly interacting massive particles. But
48:12
Speaker 1: we've looked for whimps, and we we we know what
48:14
Speaker 1: kind of experiments we needed to do to find whimps,
48:16
Speaker 1: and we've done those experiments and we just haven't found anything. Um. Now,
48:20
Speaker 1: it's possible that whimps will be discovered any day now,
48:23
Speaker 1: and they're right around the corner. But I think at
48:25
Speaker 1: a minimum, it's fair to say that it's surprising that
48:28
Speaker 1: those whimps haven't shown up. So that could be that
48:32
Speaker 1: the dark matter is just made of something different than
48:34
Speaker 1: we had currently imagined, or it might mean that the
48:38
Speaker 1: early universe played out differently. Our arguments for what whimps
48:42
Speaker 1: should look like in what experiments we would have to
48:45
Speaker 1: do to discover them, we're based on our understanding of
48:48
Speaker 1: how things played out in the early universe when the
48:50
Speaker 1: whimps were being created. If the early universe played out
48:53
Speaker 1: differently than we had imagined, then the way that dark
48:57
Speaker 1: matter would have been created and the kind of experiens
49:00
Speaker 1: we'd have to do to find dark batter could be
49:02
Speaker 1: very different. And then of course there's a problem of inflation. Uh,
49:06
Speaker 1: somehow the universe got very flat and somehow the universe
49:09
Speaker 1: got very uniform, and inflation is a good description of that.
49:13
Speaker 1: But we don't know how how that played out. We
49:16
Speaker 1: don't know how or why inflation happened the way it did.
49:19
Speaker 1: Um I think it's fair to say that we have
49:22
Speaker 1: more more questions than answers when it comes to the
49:25
Speaker 1: inflationary era, and possibly related to inflation is the issue
49:30
Speaker 1: of dark energy. We've learned in the last twenty years
49:33
Speaker 1: at our universe isn't just expanding, it's expanding at an
49:36
Speaker 1: accelerating rate, and that seems to suggest that empty space
49:40
Speaker 1: has a certain amount of energy built into it, a
49:42
Speaker 1: kind of vacuum energy. Um. Maybe this is similar to
49:45
Speaker 1: the kind of energy that drove inflation shortly after the
49:49
Speaker 1: Big Bang, and is happening now in a more gentle way.
49:52
Speaker 1: We don't know, But all of these things, to my mind,
49:55
Speaker 1: collectively point to some very weird and counterintuitive stuff that
50:00
Speaker 1: I'd have played out in that first second or millions
50:03
Speaker 1: or billions or trillion of a second after the Big Bang. Um,
50:07
Speaker 1: that's where my money is on a new big revolutions
50:10
Speaker 1: in physics. Well, I appreciate your scientific honesty that you're
50:14
Speaker 1: willing to admit what we don't know, and also you're
50:17
Speaker 1: a scientific optimism that one day scientists will unravel these
50:21
Speaker 1: ideas and maybe on a podcast in a hundred years
50:23
Speaker 1: they'll be chatting casually about answers to these questions. Thanks
50:27
Speaker 1: very much for coming on our podcast today and talking
50:29
Speaker 1: to us about these amazing questions about the nature of
50:32
Speaker 1: the universe and its origins. And remember, everybody, Dan's book
50:35
Speaker 1: is called At the Edge of Time. It comes out
50:37
Speaker 1: on November five from Princeton University Press. I totally encourage
50:41
Speaker 1: you to check it out if you're into origins of
50:44
Speaker 1: the universe and cosmic questions. Thanks again, Dan for joining us,
50:47
Speaker 1: and thank you listeners for tuning in. If you still
50:58
Speaker 1: have a question after listening to all these explanations, please
51:01
Speaker 1: drop us a line. We'd love to hear from you.
51:03
Speaker 1: You can find us at Facebook, Twitter, and Instagram at
51:06
Speaker 1: Daniel and Jorge That's one Word, or email us at
51:10
Speaker 1: Feedback at Daniel and Jorge dot com. Thanks for listening,
51:14
Speaker 1: and remember that Daniel and Jorge Explain the Universe is
51:16
Speaker 1: a production of I Heart Radio. For more podcast from
51:20
Speaker 1: my Heart Radio, visit the I Heart Radio app, Apple Podcasts,
51:24
Speaker 1: or wherever you listen to your favorite shows. Yeah