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Can the Universe exist without space? · Daniel and Kelly’s Extraordinary Universe

0:08
Speaker 1: Hey, Jorge, are you a hoarder or do you like
0:11
Speaker 1: to throw things away? We keep everything, we have, every drawing,
0:15
Speaker 1: my kids ever made. Man, not me. I value space
0:20
Speaker 1: more than stuff. I love to throw things away. Wow,
0:24
Speaker 1: what does your family give you for your birthday? Then?
0:26
Speaker 1: Empty space? Actually, my wife rent a dumpster and says
0:30
Speaker 1: I can throw out anything I want. It's like a
0:33
Speaker 1: negative present. Hey, space is precious. You know you can't
0:36
Speaker 1: have too much of it. You can't have too much
0:38
Speaker 1: nothing said nobody never, Nothing is better than nothing. This
0:42
Speaker 1: is the best nothing I ever got. Hi more handmade
1:00
Speaker 1: cartoonists and the creator of PhD comics. Hi. I'm Daniel,
1:04
Speaker 1: I'm a particle physicist and I really do love space.
1:07
Speaker 1: And Welcome to our podcast. Daniel and Jorge explain the
1:10
Speaker 1: university production of I Heart Radio, in which we explore
1:13
Speaker 1: all the stuff in space, empty space, not so empty space,
1:17
Speaker 1: space builled with really crazy bonk, or stuff that's hard
1:20
Speaker 1: to understand, and sometimes even the very nature of space.
1:25
Speaker 1: We talk about all of these things in this podcast,
1:27
Speaker 1: and we break them down, and our goal is to
1:29
Speaker 1: deliver them to you in a way that actually makes sense,
1:31
Speaker 1: so you go away thinking, huh, I get it, or
1:34
Speaker 1: at least I get it as much as scientists get it,
1:37
Speaker 1: which sometimes isn't that much. And sometimes it feels like
1:40
Speaker 1: we're talking about a whole lot of nothing, and sometimes
1:43
Speaker 1: we are literally talking about nothing, and sometimes we're trying
1:46
Speaker 1: to figure out what is nothing exactly right. Yeah, deep questions, now, Daniel,
1:51
Speaker 1: when you say you love space, do you mean like
1:53
Speaker 1: you love, you know, just space travel, like where the
1:56
Speaker 1: planets are, or did you just like, you know, having
1:59
Speaker 1: the idea of space in your life. I love all
2:02
Speaker 1: of it. I love outer space, I love deep space.
2:04
Speaker 1: I live near space. I also love having space in
2:07
Speaker 1: my living room, Like it's not unusual for me to
2:09
Speaker 1: toss out a piece of furniture and go, you know what,
2:11
Speaker 1: the room is just better with nothing there. You like
2:14
Speaker 1: everything about space. There's nothing negative about space for you.
2:17
Speaker 1: I'm pretty pro space. Yeah. Absolutely, you would live in
2:20
Speaker 1: an empty box if you could, exactly. I'm like a
2:23
Speaker 1: cat that way. Are you looking forward and to your
2:26
Speaker 1: children leaving the house then, because that's just more space,
2:30
Speaker 1: is more space. I'm not looking for to them leaving,
2:32
Speaker 1: but if they do, I'm looking forward to throwing all
2:34
Speaker 1: their stuff away. Oh man, that's going to come back
2:37
Speaker 1: to want you. They're like, why did you throw away
2:40
Speaker 1: my comic book collection that's worth three million dollars? Now, yeah, exactly,
2:45
Speaker 1: but this space is priceless, right, Well, we like to
2:48
Speaker 1: talk about space in this podcast and also about what
2:51
Speaker 1: it represents, what it means, because it's kind of a
2:54
Speaker 1: topic that businesses don't have a super clear idea about.
2:57
Speaker 1: That's right. It's one of these really fun quite in
3:00
Speaker 1: physics because only recently did we figure out that it's
3:03
Speaker 1: a question that sort of has an answer. It's a
3:05
Speaker 1: question that's worth asking. It's one of these questions that's
3:08
Speaker 1: so basic that we just sort of assumed we knew
3:11
Speaker 1: the answer. You know, space is space. It's the nothing,
3:13
Speaker 1: it's the emptiness. And only recently have we realized, Wow,
3:16
Speaker 1: space could be much more than that, and it really
3:19
Speaker 1: deserves our attention. Right. Even more important is this sort
3:23
Speaker 1: of idea that maybe we don't need space, Like maybe
3:27
Speaker 1: it's just sort of like an add on to the universe. Yeah,
3:30
Speaker 1: is it at the foundation of reality or is it
3:32
Speaker 1: just something that fills up something else? You know, imagine
3:35
Speaker 1: what it would have been like to be a person
3:37
Speaker 1: ten thousand years ago. You never would have experienced reality
3:40
Speaker 1: without air, for example, So the concept of like a vacuum,
3:43
Speaker 1: a place where there was no air would have been
3:46
Speaker 1: totally alien to you. So now, of course we know
3:48
Speaker 1: that that's possible. It seems obvious that air is not
3:51
Speaker 1: a fundamental property of the universe. But we're at the
3:53
Speaker 1: next level and wondering, like, well, is space fundamental? Could
3:56
Speaker 1: you take it apart? Do you really need it? Yeah?
3:59
Speaker 1: In fact, so the universe, it doesn't have any air
4:02
Speaker 1: in it, right, most of the universe is pretty empty. Yeah,
4:06
Speaker 1: from that point of view, exactly, we were dealing with
4:08
Speaker 1: a very unrepresentative example. And we do this all the
4:11
Speaker 1: time in science. We assume that the things we experience
4:15
Speaker 1: our universal and we can generalize from these examples to
4:18
Speaker 1: the whole universe. We're doing this all the time, left
4:21
Speaker 1: and right without even realizing it. So now we're asking
4:23
Speaker 1: a similar question about space. You know, our our assumptions
4:27
Speaker 1: about space valid. Can we break it apart? Do we
4:30
Speaker 1: even need it? Is it possible for it to have
4:32
Speaker 1: bubbled up from something else? Yeah, it's a space topic.
4:35
Speaker 1: But space is pretty empty. I think we have a
4:37
Speaker 1: whole podcast episode about that, right, Like, what's the average
4:40
Speaker 1: density of the universe or like how much stuff is
4:43
Speaker 1: there really on a like cubic foot Yeah, we do
4:46
Speaker 1: have a whole podcast about how empty spaces and we
4:49
Speaker 1: take you on a journey from the top of the
4:50
Speaker 1: atmosphere into the Solar System and then out into interstellar
4:54
Speaker 1: space and then finally into intergalactic space. And mostly space
4:58
Speaker 1: is intergalactic space, right, Like there are these huge streams
5:02
Speaker 1: of galactic clusters of galaxies swinging around each other, but
5:06
Speaker 1: between them there are these vast bubbles and voids that
5:09
Speaker 1: don't have galaxies in them. So most of the universe
5:12
Speaker 1: sort of by volume, is this intergalactic space, which is
5:17
Speaker 1: not totally empty. There's still stuff in there. That's a
5:19
Speaker 1: little bit of dark matter, there's definitely dark energy. But
5:22
Speaker 1: it's most of the universe and it's pretty empty, but
5:25
Speaker 1: not down to zero. Yeah, and there's a lot of
5:28
Speaker 1: it space, I mean, in the universe, there's a whole
5:31
Speaker 1: bunch of it. Like if you are going at the
5:32
Speaker 1: speed of light, it would still take you as far
5:35
Speaker 1: as we know right now, you know, tens of billions
5:37
Speaker 1: of years just to go from one side to the other.
5:40
Speaker 1: That's a lot of time. Absolutely, And remember the speed
5:42
Speaker 1: of light is like mind boggling lee fast, right, It's
5:45
Speaker 1: incredibly fast. And yet these distances, even inside our Solar
5:49
Speaker 1: System are incredible, Like it takes minutes for light to
5:53
Speaker 1: get from here just to Mars, which is our neighbor,
5:56
Speaker 1: and hours to get out to the outer Solar system.
5:59
Speaker 1: You know, when we communicate with probes and rovers and
6:02
Speaker 1: stuff on other planets, the reason you can't drive them
6:04
Speaker 1: is because they are so far away. You can't do
6:07
Speaker 1: real time driving because the lag is too long. And
6:09
Speaker 1: that's just inside our Solar system. So the distances to
6:13
Speaker 1: other galaxies millions of light years and deeper into space
6:16
Speaker 1: billions of light years, they're hard for us to get
6:19
Speaker 1: our mind around. So, yeah, space is pretty spacious. I
6:22
Speaker 1: guess I hadn't thought about it before. Like if even
6:24
Speaker 1: if you're Superman or Superwoman and you're traveling, you can
6:26
Speaker 1: you're able to fly at the speed of light, it
6:28
Speaker 1: would still take you like a billion years just to
6:31
Speaker 1: you know, go to the other galaxies out there in
6:33
Speaker 1: the universe. Yeah, well that's an interesting question. Does Superman
6:36
Speaker 1: have to travel at the speed of light? Can he
6:38
Speaker 1: be superluminal? I mean, how far away is his home
6:41
Speaker 1: planet anyway, I don't know you're the physicist. I just
6:44
Speaker 1: read the comic books. I don't dissect them scientifically. I'll
6:47
Speaker 1: go find out exactly where his home planet is and
6:49
Speaker 1: figure out if he broke the law on the way here,
6:52
Speaker 1: and if so, I'll issue him a physics ticket. Well,
6:54
Speaker 1: he can just bring it up with his heat visioned Daniel.
6:57
Speaker 1: And also, how are you going to arrest him? Good
6:58
Speaker 1: luck with that, citizens arrest Mr Superman. But yeah, there's
7:04
Speaker 1: a lot of space out there. It's definitely not a
7:06
Speaker 1: small part of the universe. But I guess the question
7:09
Speaker 1: is it a necessary part of the universe. So today
7:13
Speaker 1: on the podcast, we'll be asking the question can the
7:21
Speaker 1: universe exist without space? Space? Space? Space space? That question
7:27
Speaker 1: is so profound it needs an echo. It echoes through
7:29
Speaker 1: the vacuum of infinity, through the vacuum of our understanding
7:33
Speaker 1: of the universe. Absolutely, through the empty space in my head.
7:37
Speaker 1: But it's a fun question, and it sort of mirrors
7:39
Speaker 1: the way I treat furniture. You know, I look around
7:42
Speaker 1: my house and I asked myself, do we need that chair?
7:44
Speaker 1: Nobody ever sits there and we get rid of it.
7:46
Speaker 1: We're like, ah, it's better off. And now we're cycling
7:49
Speaker 1: through modern physics and we're like, m, do we really
7:52
Speaker 1: need the whole concept of space? Like is it really
7:55
Speaker 1: have to be included in the sort of fundamental list
7:58
Speaker 1: of things you need to build a universe or is
8:00
Speaker 1: it like you know, ice cubes or atoms or hurricanes,
8:04
Speaker 1: something that you know comes from your more basic ingredients.
8:07
Speaker 1: I would hate to be a furniture in your house.
8:09
Speaker 1: I feel like I would live in constant fear. Yes, absolutely,
8:12
Speaker 1: you must constantly justify your existence in my house, or
8:16
Speaker 1: you're on the trashy. It's like huff Post reporters. You know,
8:19
Speaker 1: hopefully that's just for your furniture, not your family as well.
8:23
Speaker 1: Or pets. Absolutely, living creatures definitely belong to the family.
8:27
Speaker 1: Chairs not so much so if you could have a
8:29
Speaker 1: bigger house, would you have a bigger house? No? No,
8:32
Speaker 1: I don't need a bigger house. In fact, I had
8:34
Speaker 1: some friends who once moved to a bigger house and
8:36
Speaker 1: I almost ruin their marriage because they ended up shouting
8:38
Speaker 1: each other from different rooms across the house. And they
8:41
Speaker 1: did better when they had to, you know, share a
8:43
Speaker 1: small apartment. Yeah, we talked about this and I offered
8:45
Speaker 1: the better solution of just getting an intercom system. You
8:49
Speaker 1: are going to engineer everybody's marriage. Huh. I'm gonna go
8:52
Speaker 1: to your your couple's counseling. There's a solution for everything
8:54
Speaker 1: in engineering, marital engineering. Wow, that's a better name for therapist.
8:58
Speaker 1: But anyways, Yeah, it's a big question whether or not
9:00
Speaker 1: we need space in the universe. It seems pretty fundamental,
9:04
Speaker 1: you know, like, how can you have a universe without space? Like,
9:07
Speaker 1: isn't space the universe? Yeah, but just because it's hard
9:10
Speaker 1: to imagine doesn't mean it's not reality. Right. A lot
9:13
Speaker 1: of what reality is was difficult for us to wrap
9:16
Speaker 1: our minds around. So when you do this kind of exploration,
9:19
Speaker 1: you got to sort of be willing to give up
9:21
Speaker 1: something you thought was fundamental, something you assumed was inherent,
9:25
Speaker 1: and ask your question whether it can come from something else.
9:28
Speaker 1: All right, Well, as usual, we were wondering how many
9:31
Speaker 1: people out there have thought about this spacious question, whether
9:34
Speaker 1: or not we need space. So Daniel went out there
9:37
Speaker 1: into the well to the internet to ask people is
9:40
Speaker 1: it possible to have a universe without space. Here's what
9:43
Speaker 1: they had to say. Oh, that's a good question. I
9:47
Speaker 1: don't think, so okay, why, Well, I don't know. I
9:52
Speaker 1: don't know. I don't know. I don't know why. I
9:54
Speaker 1: just know I think space is only one of the dimensions, right,
10:00
Speaker 1: you can probably have a universe. It's just time and
10:01
Speaker 1: maybe not space. I'm gonna say yes. Well, my understanding
10:06
Speaker 1: is that, yeah, I guess you can. Um. I mean,
10:11
Speaker 1: was this space when the Big Bang occurred in the
10:14
Speaker 1: moments after that, or was it all dense metal with
10:17
Speaker 1: zero space? But my understanding is that if you have
10:22
Speaker 1: a different universe that could operate off a completely different
10:24
Speaker 1: set of physical laws. So I guess never say never
10:27
Speaker 1: in that regard. You can have a universe without space.
10:34
Speaker 1: Our situation with matter having out competed antimatter, I think
10:41
Speaker 1: is actually pretty unique. Um there, and I would I
10:49
Speaker 1: think they're a little universe blips all over where universe
10:52
Speaker 1: pops into existence and annihilates and no spaces created. I
10:58
Speaker 1: guess you can have universe with out just this dimension space,
11:04
Speaker 1: and you can have all the other dimensions possible, but
11:09
Speaker 1: it will be crowded. I guess it would mean what
11:12
Speaker 1: you mean by universe, because before the Big Bang all
11:17
Speaker 1: the universe was there. It was just compressed and to
11:20
Speaker 1: my knowledge, there was no space. So if you can't
11:23
Speaker 1: that just the universe then yeah, all right, some mixed
11:27
Speaker 1: reactions here. Some people could live without it, some people
11:29
Speaker 1: could really want it. Yeah. It basically wraps up the
11:32
Speaker 1: whole question of what spaces and where it comes from
11:35
Speaker 1: and all these answers I see echoes of general relativity
11:38
Speaker 1: and quantum mechanical perspectives on this question. So good job listeners,
11:42
Speaker 1: And to those of you who would like to participate
11:44
Speaker 1: in future rounds of answer random questions for the podcast,
11:48
Speaker 1: please write to us two questions at Daniel and Jorge
11:51
Speaker 1: dot com. There's a lot of reference here and the
11:53
Speaker 1: answers to the Big Bang to write that's something I
11:55
Speaker 1: hadn't thought about before. Was their space before the Big Bang?
11:58
Speaker 1: At the Big Bang? Or was space created at some
12:01
Speaker 1: point in the history of the universe? Yeah, space and time? Right,
12:06
Speaker 1: all right, Well, let's dig into it, Daniel. Let's start
12:08
Speaker 1: with maybe the basic stuff, like what is space? How
12:11
Speaker 1: do physicists think about what space is? Yeah, this is
12:15
Speaker 1: a great question, and we have sort of two answers
12:18
Speaker 1: for what space is based on whether you're thinking about
12:22
Speaker 1: it from the point of view of like quantum mechanics
12:24
Speaker 1: or whether you're thinking about it from the point of
12:26
Speaker 1: view of general relativity. And remember that these are the
12:29
Speaker 1: two pillars of thinking in modern physics, too great ways
12:33
Speaker 1: to describe parts of the experiments we've done. Quantum Mechanics
12:37
Speaker 1: describes basically everything that has to do with little particles
12:40
Speaker 1: at small scales and all the forces that were familiar
12:43
Speaker 1: with except for gravity, and general relativity talks about how
12:46
Speaker 1: space is curved and it's bent, and that's really what
12:49
Speaker 1: gravity is. And so the answer to the question what
12:52
Speaker 1: is space sort of depends on whose perspective you want
12:55
Speaker 1: to take first? What do you mean, how can something
12:57
Speaker 1: depend on your perspective? Aren't you looking for like one answer?
13:00
Speaker 1: We are absolutely looking for one answer, but we don't
13:03
Speaker 1: have one answer. We have two theories, quantum mechanics and
13:06
Speaker 1: general relativity. They treat space very differently and we haven't
13:10
Speaker 1: been able to unify them. So the short answer is
13:13
Speaker 1: we don't know what space is because we don't have
13:15
Speaker 1: a single coherent theory for the whole universe, and the
13:18
Speaker 1: two theories we do have disagree about what space is,
13:21
Speaker 1: all right, So what are the two theories about space?
13:24
Speaker 1: And is there enough space between them to tell the difference. Well,
13:27
Speaker 1: you know, let's start with quantum mechanics. Quantum mechanics is
13:30
Speaker 1: the theory that tells us how electromagnetism works, how the
13:34
Speaker 1: weak force works, you know, how photons move, and it
13:37
Speaker 1: tells us that space is fundamental. It assumes that space
13:41
Speaker 1: exists and it adds stuff to it. So if you're
13:44
Speaker 1: gonna build a universe using at least our current theory
13:47
Speaker 1: of quantum mechanics, then you start from space. You say,
13:50
Speaker 1: let's assume there's a space, and then at every point
13:52
Speaker 1: in that space, I'm gonna say whether or not there's
13:54
Speaker 1: a quantum field and how much energy it has. But
13:56
Speaker 1: it's sort of like at the bedrock of the whole theory,
13:59
Speaker 1: just like assuming that space and time are things that
14:03
Speaker 1: you can put fields in them, right, because that's kind
14:05
Speaker 1: of baked into the definition of a field, right, Like
14:08
Speaker 1: you can't have a field without space, like a field
14:11
Speaker 1: is by definition like how things vary in a space.
14:15
Speaker 1: That's right exactly. And we'll talk later about whether you
14:17
Speaker 1: can generalize that to like abstract spaces rather than physical
14:21
Speaker 1: spaces and what that means. But you're right for the
14:24
Speaker 1: physical fields that we're talking about, you know, like the
14:26
Speaker 1: photon field. It's just a value all through space. But
14:30
Speaker 1: as you say, space is fundamental to that. You need
14:32
Speaker 1: to know like there's a certain value of field here
14:35
Speaker 1: and over there at a different location in space, it
14:39
Speaker 1: has a different value. And for example, the shrouding your
14:41
Speaker 1: equation tells us how a wave function exists across space,
14:46
Speaker 1: and how that wave function evolves through time it spreads
14:49
Speaker 1: out through space, for example. So it's pretty deeply baked in.
14:53
Speaker 1: So quantum field theory sort of the modern version of it,
14:55
Speaker 1: as we think about it, doesn't really have an answer
14:58
Speaker 1: to the question of what is space. It just sort
15:00
Speaker 1: of like assumes it exists and starts from there. It's
15:03
Speaker 1: like the basical list of ingredients. Would you say then
15:06
Speaker 1: that maybe quantum fields defined space or do you think
15:10
Speaker 1: space could exist without quantum fields. Well, that's a great question.
15:14
Speaker 1: In our current theory, you can't have space without quantum fields,
15:17
Speaker 1: Like quantum fields filled the entire universe. There's no sense
15:21
Speaker 1: in which you could have space without them. That's just
15:23
Speaker 1: sort of according to the theory. But do they define space?
15:27
Speaker 1: I think they're deeply coupled to it. Yeah, absolutely, so
15:30
Speaker 1: I think it's definitely part of the inherent nature of
15:32
Speaker 1: space in quantum field theory that you have these fields
15:36
Speaker 1: that live on top of it. But remember that quantum
15:38
Speaker 1: field theory can also have stuff in it that doesn't
15:41
Speaker 1: sort of come into the very beginning, right, Like we
15:43
Speaker 1: can talk about the very basic ingredients of the universe,
15:47
Speaker 1: space and quantum fields, but we don't add to that
15:50
Speaker 1: things like you know the atom, right, The atom is
15:53
Speaker 1: not a required element of the definition of the universe.
15:56
Speaker 1: It comes from that other stuff. So the ad and
16:00
Speaker 1: we think it exists, but it's not like fundamental. And
16:03
Speaker 1: remember the goal of physics, as you say, is to
16:05
Speaker 1: come to one theory, one explanation, one most basic list
16:09
Speaker 1: of ingredients and the rules for combining them that then
16:11
Speaker 1: explains everything else. So we're constantly trying to throw stuff
16:16
Speaker 1: out on purpose so we can get like the minimal
16:18
Speaker 1: list of fundamental things that can then explain everything else.
16:22
Speaker 1: As emergent. We want to explain ice cream and atoms
16:25
Speaker 1: and hurricanes in terms of the simpler, more basic elements.
16:28
Speaker 1: Do you guys want the dumpster then too, so you
16:30
Speaker 1: can throw out theories. I definitely want to throw space
16:34
Speaker 1: out on the physics dumpster. I would love to explain
16:37
Speaker 1: space in terms of something more basic and fundamental and say, man,
16:40
Speaker 1: remember when we had space criming in here and we
16:43
Speaker 1: had no space because we had so much space. But
16:46
Speaker 1: then if there's no space, then there's no space in
16:49
Speaker 1: the dumpster either, Daniel, where would you throw it out? Oh? Man,
16:53
Speaker 1: I'll get a bigger dumpster, all right, So then that's
16:56
Speaker 1: quantum mechanics. But then general relativity has a different view
17:00
Speaker 1: of space. Yeah, General relativity tells us that space is
17:03
Speaker 1: not something which is just like inherent and that you
17:06
Speaker 1: can assume. General relativity tells us that space is really different.
17:11
Speaker 1: It's dynamical. It's not like the backdrop for everything. Instead,
17:14
Speaker 1: it's in this dance with matter. Right. When you have
17:17
Speaker 1: matter and energy around, space bends and it curves, and
17:21
Speaker 1: it can do weird things like it can ripple, right,
17:24
Speaker 1: and it can expand. And this is the things that
17:26
Speaker 1: we see, like we see ripples in space. We know
17:29
Speaker 1: that this general relativity picture is at least approximately correct.
17:32
Speaker 1: It might not be the fundamental theory of the universe,
17:35
Speaker 1: but it's really accurate. It predicts these gravitational waves and
17:39
Speaker 1: we see them. It can accommodate at least the accelerated
17:42
Speaker 1: expansion of the universe in terms of a cosmological constant.
17:46
Speaker 1: We don't understand why that's there, what's happening, etcetera, but
17:49
Speaker 1: it can be accommodated in general relativity. So it's very
17:52
Speaker 1: successful description of how matter and space interact. And it
17:56
Speaker 1: suggests that space is not fundamental, that it sort of
17:58
Speaker 1: states at the same level as matter our energy, because
18:00
Speaker 1: the too sort of have this feedback loop between each other.
18:04
Speaker 1: Basically says that space is a thing, right like, it's
18:06
Speaker 1: not static, it doesn't exist, it doesn't ignore matter, you know,
18:11
Speaker 1: like it responds to matter, and you know, it's not
18:13
Speaker 1: independent of matter exactly. And you can do these weird
18:16
Speaker 1: things that we never imagined that it could do, which
18:19
Speaker 1: means it might be able to do other weird things
18:21
Speaker 1: we also hadn't yet had the imagination to do. Anytime,
18:25
Speaker 1: we're limited by our imagination. I'm always skeptical that we've
18:28
Speaker 1: thought of everything. I know, the theorists are very smart,
18:31
Speaker 1: and even our science fiction authors are always pushing the
18:33
Speaker 1: boundaries of creativity when it comes to like, you know,
18:36
Speaker 1: intellectual concepts. But there's always the possibility that there's always
18:40
Speaker 1: something else out there we just haven't thought of that
18:42
Speaker 1: could be happening in our universe. So space could have
18:45
Speaker 1: really weird properties that we never imagined. Imagine, for example,
18:49
Speaker 1: being a scientist that's a fish swimming through water all
18:52
Speaker 1: the time and not realizing, you know, that space could end,
18:55
Speaker 1: or that your water wasn't actually fundamental, and they could
18:58
Speaker 1: do other weird things like boil and turn into a gas.
19:01
Speaker 1: You know, space like that could have other phases, other
19:03
Speaker 1: weird properties we just haven't observed yet, and so we
19:06
Speaker 1: assume are impossible because I guess, once you can get
19:09
Speaker 1: space to bend or ripple or expand then who knows
19:12
Speaker 1: what you can make it do? Who knows what you
19:14
Speaker 1: can make it do exactly? And the solutions to general
19:17
Speaker 1: relativity are so complicated and difficult, and that it's not
19:20
Speaker 1: possible to conceive of all the possible configurations that are
19:23
Speaker 1: consistent with it. Those are the two views of space.
19:26
Speaker 1: One says that it's something that you know, can't touch
19:29
Speaker 1: or that you live on top of, and the other
19:31
Speaker 1: one says that it's something that it's more of a thing,
19:33
Speaker 1: like it's dynamic and you can manipulate it and it
19:36
Speaker 1: can change, So that those are the two basic views
19:39
Speaker 1: about space, right, But it doesn't sort of explain what
19:41
Speaker 1: space is. It's just sort of like how you regard space. Yeah,
19:45
Speaker 1: but that's sort of what space is. You know, space
19:47
Speaker 1: is how we treat it. Some people might say space
19:50
Speaker 1: is just like a mathematical construct in our minds. You know,
19:54
Speaker 1: that's not actually something that's physical. For example, in quantum mechanics,
19:57
Speaker 1: we never deal with space itself directly, right, All we
20:01
Speaker 1: ever do is deal with the fields in space. We
20:04
Speaker 1: never like interact with space itself, and so it's sort
20:07
Speaker 1: of like just an abstraction. It's just like a way
20:10
Speaker 1: of thinking about organizing these fields. Whereas in general relativity,
20:13
Speaker 1: like spaces the thing. It's the thing that's keeping us
20:16
Speaker 1: on the Earth. It explains gravity, which is pretty important.
20:19
Speaker 1: So you know, how we represent them in our theories
20:22
Speaker 1: goes a long way to telling you what we think
20:24
Speaker 1: they are. All right, Well, I think that sets the
20:26
Speaker 1: space for a deeper discussion about space and whether or
20:30
Speaker 1: not Daniel can through it in the dumpster or not.
20:32
Speaker 1: Please please please, please, please please please. I would be
20:36
Speaker 1: so offended if I was space right now, I would
20:40
Speaker 1: limit your space Daniel. But let's get into that question
20:43
Speaker 1: and also whether or not we will ever be able
20:46
Speaker 1: to know what the answer is. But first, let's take
20:49
Speaker 1: a quick break. All right, we're talking about space and
21:05
Speaker 1: whether or not we can just toss it out, Daniel,
21:07
Speaker 1: I feel like that's so unappreciative. How can you just
21:11
Speaker 1: throw the thing out that you know you grew up in. Well,
21:14
Speaker 1: you know, let's make a distinction here. We are, of
21:16
Speaker 1: course searching to explain space, to figure out whether it's
21:19
Speaker 1: the basic ingredient of the universe or whether it emerges
21:23
Speaker 1: from something else. But that's not to say the things
21:25
Speaker 1: that emerge are uninteresting or unimportant. Right, Like, the entire
21:29
Speaker 1: field of biology is emergent in the sense that you could,
21:34
Speaker 1: in principle, calculated all from fundamental particles. But that's not
21:38
Speaker 1: like a smart way to do biology. Nobody would anybody
21:41
Speaker 1: does do biology from the particle perspective. I just want
21:44
Speaker 1: to make sure people don't think that we're being negative
21:46
Speaker 1: about emergent phenomena. They're fascinating, they're amazing, they're incredible. We
21:50
Speaker 1: are emergent phenomena. It's just, you know, part of this
21:52
Speaker 1: question of getting down, drilling down to the deepest nature
21:55
Speaker 1: of reality is to ask what's fundamental and what's emergent,
21:58
Speaker 1: not necessarily to judge them. You just want to add
22:00
Speaker 1: your bets and not offend your spouse's biologist. I have
22:04
Speaker 1: the deepest of respects for my spouse and also for biology,
22:07
Speaker 1: which is not your furniture. Just not my furniture, absolutely
22:11
Speaker 1: all right. So there are two perspectives about space. It
22:14
Speaker 1: seems like quantum mechanics doesn't say anything about space other
22:17
Speaker 1: than it's there and you can't mess with it, and
22:20
Speaker 1: general relativity says that it's something that you can sort
22:22
Speaker 1: of mess with and change and bend. And I guess
22:25
Speaker 1: the question is are those two things incompatible or is
22:29
Speaker 1: there a sort of a fundamental conflict about them? Like
22:31
Speaker 1: couldn't you have quantum mechanics sit on top of general relativity? Yeah, exactly,
22:35
Speaker 1: And people are working on exactly that, trying to unify
22:39
Speaker 1: general relativity and quantum mechanics in several different ways, and
22:43
Speaker 1: in doing so, they're giving us hints about answers to
22:46
Speaker 1: this question about whether space is fundamental or not. Like
22:50
Speaker 1: when they put these two things together, they basically have
22:52
Speaker 1: to make a decision like, well, do we have spaces
22:54
Speaker 1: the list of fundamental ingredients in our new theory of
22:57
Speaker 1: quantum gravity or not. And there's a couple of different approaches.
23:01
Speaker 1: One is sort of like make gravity a quantum theory,
23:04
Speaker 1: thinking about it as like just another quantum force that
23:07
Speaker 1: exchanges particles the gravitons in order to make gravity happen,
23:12
Speaker 1: and sort of making quantum mechanics primary. And the other
23:15
Speaker 1: is to try to quantize gravity itself, you know, either
23:18
Speaker 1: make the universe into little pixels or take the gravitational
23:21
Speaker 1: field and make a discreet and so that would make
23:24
Speaker 1: a general relativity sort of at the primary foundational level
23:27
Speaker 1: of these new theories of quantum gravity, and which direction
23:30
Speaker 1: you go sort of dictates the fate of the idea
23:33
Speaker 1: of space and whether it's fundamental or emergent. I guess
23:37
Speaker 1: maybe one difference is that like in general relativity, if
23:40
Speaker 1: you have a speck of dust, it's technically bending the
23:43
Speaker 1: space around it. But in quantum mechanics, if you have
23:45
Speaker 1: like a proton or an electron, it's not really bending
23:48
Speaker 1: space around it. Right, In quantum mechanics, we have no
23:51
Speaker 1: description of the curvature of space that works, right, So yeah, absolutely,
23:55
Speaker 1: we don't have a quantum mechanical description of gravity or
23:59
Speaker 1: the bending of space, so we can't describe how space
24:02
Speaker 1: has bent around of dust particle. We know that it
24:04
Speaker 1: is though, right we think that that's true. One of
24:06
Speaker 1: the difficulties is that we can't test these things very
24:09
Speaker 1: well because particles have very very small amounts of gravity.
24:13
Speaker 1: Member gravity so much weaker than all the other forces,
24:17
Speaker 1: like ten to the thirty times weaker. So we can't
24:20
Speaker 1: really test these things because all the other forces dominate.
24:23
Speaker 1: Two protons, for example, coming together, the large Hage and
24:25
Speaker 1: collider feel almost no gravity in comparison to the strong
24:29
Speaker 1: and the weak and the electromagnetic forces, So it's very
24:32
Speaker 1: hard to do an experiment at the particle level that
24:34
Speaker 1: tests gravity. I guess maybe then to get back to
24:37
Speaker 1: our question, then what do these two theories say about
24:40
Speaker 1: the idea of having no space? Like could you have
24:44
Speaker 1: no space in plantum mechanics or general relativity or is
24:47
Speaker 1: that impossible according to the theories. So there are now
24:50
Speaker 1: really fun ideas about how space might not be fundamental,
24:54
Speaker 1: how you could have a universe without space in quantum mechanics.
24:59
Speaker 1: And I think these ideas are really cool because they
25:01
Speaker 1: make us think about quantum mechanics sort of at a
25:04
Speaker 1: more basic level. You know, we think about the wave function.
25:07
Speaker 1: For example. Wave function is like this basic element of
25:10
Speaker 1: quantum mechanics. It tells you what's going to happen to
25:13
Speaker 1: a particle, or for example, where a particle might be.
25:16
Speaker 1: If you have a question about the outcome of your experiment,
25:19
Speaker 1: the wave function tells you this outcome has a certain probability,
25:22
Speaker 1: and that outcome has another probability. And typically we think
25:25
Speaker 1: about the wave function as distributed across space, like is
25:29
Speaker 1: the electron here or is the electron there, But in
25:32
Speaker 1: principle it can be distributed across abstract states also, you know,
25:36
Speaker 1: like the electron spin or the outcome of your experiment,
25:40
Speaker 1: or all sorts of other kinds of things. And so
25:43
Speaker 1: it's not hard for us to sort of augment the
25:45
Speaker 1: current concept of space with these like abstract spaces. We
25:49
Speaker 1: call them Hilbert spaces in which the wave function lives.
25:52
Speaker 1: And it might be that those Hilbert spaces are the
25:55
Speaker 1: actual primary thing that we can sort of let go
25:58
Speaker 1: of these concepts of position and based the whole existence
26:02
Speaker 1: of the universe just on those sort of abstract spaces
26:04
Speaker 1: than the ones that are not physical, that don't represent
26:07
Speaker 1: actual locations, that are not anywhere. I think what you're
26:10
Speaker 1: saying is that, like maybe space, according to the theory,
26:14
Speaker 1: is not like a physical thing or physical space, but
26:17
Speaker 1: it's rather just sort of like a mathematical concept or
26:21
Speaker 1: set of relationships. Is that what you mean. Yeah, we
26:23
Speaker 1: know that it's a set of relationships. As we said earlier,
26:26
Speaker 1: in quantum mechanics, we never actually interact with space. All
26:30
Speaker 1: we do is we see sort of the propagation of
26:33
Speaker 1: information through fields as that information moves through space. But
26:37
Speaker 1: really that information is moving through the field, and so
26:40
Speaker 1: you can think about it in terms of like pieces
26:42
Speaker 1: of space that are sort of woven together. So it's
26:45
Speaker 1: like the relationships between different elements of the field, and
26:49
Speaker 1: the space itself is really just like the relationship between
26:52
Speaker 1: those elements. So this one is far away from that one,
26:55
Speaker 1: or this one is close to that one. So you
26:57
Speaker 1: don't have to have those bits of the field like
27:00
Speaker 1: hanging in an absolute, actually existing space. It might just
27:04
Speaker 1: be that they have those relationships in another way and
27:07
Speaker 1: woven together that gives the same effect as if they
27:10
Speaker 1: were actually in a space. I wonder if it's sort
27:12
Speaker 1: of like the concept of money. You know, like something
27:16
Speaker 1: is worth more or has a bigger price on it
27:18
Speaker 1: just because it doesn't mean that it has more energy
27:21
Speaker 1: to it or more matter to it, or you know,
27:23
Speaker 1: sits closer to you, or you can do more things
27:26
Speaker 1: with it. It's just so happens that this thing has
27:29
Speaker 1: a labeled with a big price on it, and that
27:31
Speaker 1: that one has a labeled with a lower price on it.
27:33
Speaker 1: Is that kind of what you mean, Like, maybe space
27:35
Speaker 1: is really just like the economy of the yeah, exactly.
27:39
Speaker 1: And you can also think about it in terms of
27:41
Speaker 1: like your networks. Think about your relationships with your family.
27:44
Speaker 1: Who are you close to We even use that word close, right,
27:47
Speaker 1: Even if you're physically far away from somebody else, you
27:50
Speaker 1: have a network of people that you interact with who
27:53
Speaker 1: know you very well, and then people who are distant,
27:56
Speaker 1: and then people who are basically super impossibly far away. Well,
27:59
Speaker 1: it might be that that sort of like the fundamental
28:01
Speaker 1: definition of who you are and what your spaces rather
28:04
Speaker 1: than like where you actually are sitting in your bedroom
28:07
Speaker 1: or in Los Angeles or in Germany or wherever. Maybe
28:10
Speaker 1: space is just an emotional space, you know what I mean?
28:13
Speaker 1: Like space is really just the emotional currency of your relationships. Yeah,
28:19
Speaker 1: and these are just analogies we're using to try to
28:21
Speaker 1: get your mind away from this primacy of space that
28:24
Speaker 1: we've been assuming and thinking about the universe as built
28:27
Speaker 1: out of things that don't hang in space but still
28:30
Speaker 1: have relationships with each other, and then those relationships are
28:33
Speaker 1: what space emerges from. And we can actually do this
28:36
Speaker 1: not just by doing analogies to social media, but actually mathematically,
28:40
Speaker 1: and people have taken the way function of the universe.
28:42
Speaker 1: For example, think about, like what is a quantum mechanical
28:45
Speaker 1: description of the whole universe? Can you describe everything in
28:48
Speaker 1: the universe and you don't have to necessarily put them
28:51
Speaker 1: in a location, you know, just say there's a probability
28:54
Speaker 1: for this particle and probably for that particle, and then
28:56
Speaker 1: link them together and say, well, this one is entangled
29:00
Speaker 1: that one. This concept of quantum entanglement of particles having
29:03
Speaker 1: like their fates connected to each other because they have
29:06
Speaker 1: a common past. This entanglement might provide that weave, It
29:10
Speaker 1: might provide the connection between like the bits of the
29:13
Speaker 1: universe that when you weave them together, some things are
29:16
Speaker 1: more entangled than others, and so they seem closer together,
29:19
Speaker 1: and other things are less entangled, and so they seem
29:22
Speaker 1: more distant. It might be that this quantum entanglement are
29:25
Speaker 1: those same relationships that connect these bits of the wave
29:28
Speaker 1: function that make it seem as if it is hanging
29:31
Speaker 1: in some space. And this sort of set of relationships
29:33
Speaker 1: or currency or valuations, that's what you call these Hilbert
29:37
Speaker 1: spaces or is that different? The Hilbert space is the
29:40
Speaker 1: set of possible wave functions that you can have, and
29:43
Speaker 1: then the relationships between the different wave functions that are disconnected,
29:46
Speaker 1: those are the entanglements. Those come together to make this
29:49
Speaker 1: sort of like grand weave that we call space. And
29:52
Speaker 1: if this is true, it doesn't mean that space is
29:54
Speaker 1: not like real. It just means that it comes from
29:57
Speaker 1: something else, you know, that it bubbles up from something
30:00
Speaker 1: more primary, just like air is real, even if it's
30:03
Speaker 1: not fundamental to the universe. You can still breathe it.
30:06
Speaker 1: It's still very nice on a nice, fresh windy day
30:09
Speaker 1: in Los Angeles. Come on, never happens. But I guess
30:12
Speaker 1: maybe a question is what's the difference? You know, like
30:15
Speaker 1: the word Hilbert space still has the word space in it,
30:19
Speaker 1: So like what would be the difference between a Hilbert
30:21
Speaker 1: space or these abstract connection space and maybe a more
30:26
Speaker 1: regular definition of space. Well, our four dimensional space has
30:31
Speaker 1: certain properties. You know, information transforms through it in a
30:34
Speaker 1: certain way. It follows the speed of light. There are
30:36
Speaker 1: four dimensions, including time. An abstract Hilbert space is much
30:40
Speaker 1: broader and more general, like it can be infinite dimensional.
30:43
Speaker 1: You can have complex values, you know, imaginary numbers, all
30:47
Speaker 1: sorts of things. So this is sort of like a
30:49
Speaker 1: subset of all the possible Hilbert spaces. It's like it
30:52
Speaker 1: turns out that the relationship between all these quantum wave
30:55
Speaker 1: functions can be described in this sort of simpler subspace,
31:00
Speaker 1: this four dimensional subspace, in which all that information can
31:03
Speaker 1: be mapped onto the whole hill of beans. It's the
31:06
Speaker 1: whole hill of beans. But it also means other interesting things.
31:09
Speaker 1: If this is true. It means that, for example, you
31:11
Speaker 1: could have different spaces inside this, like larger Hilbert space.
31:15
Speaker 1: You can have like our chunk of space which is
31:18
Speaker 1: all woven together, and you could have another one somewhere
31:20
Speaker 1: else was also emerged and is totally disconnected from ours,
31:24
Speaker 1: and you could have maybe parts of it without these relationships, right,
31:27
Speaker 1: Like you could have a whole bunch of people with
31:30
Speaker 1: no friends on Facebook exactly, or even parts of the
31:34
Speaker 1: world where there is no Facebook. Hard to imagine, right,
31:38
Speaker 1: but it might be true. And so if this picture
31:41
Speaker 1: is accurate, then the answer is absolutely you can have
31:43
Speaker 1: the universe without space. It's not necessarily clear that you
31:46
Speaker 1: need space to have the universe. And you can have
31:49
Speaker 1: parts of the universe with space, parts of the universe
31:51
Speaker 1: without space, and other parts of the universe you know
31:54
Speaker 1: that have different kinds of spaces. And you might be thinking,
31:57
Speaker 1: hold on, he's saying the word parts. What does he
31:59
Speaker 1: mean if there's no space, what parts is he talking about?
32:02
Speaker 1: And again, you know, these parts don't necessarily have like
32:05
Speaker 1: a spatial relationship. You can't say this one is here
32:08
Speaker 1: and that one is there in the sense of like
32:11
Speaker 1: where is your family? You know, you guys might be
32:14
Speaker 1: physically somewhere, but the actual relationships between you, those connections
32:17
Speaker 1: that tie you together, like where is that It isn't
32:20
Speaker 1: really anywhere, It just sort of in your emotional space. Yes,
32:23
Speaker 1: if you can't find your family, that's a whole different
32:25
Speaker 1: problem there, and a whole different type of podcast. There's
32:28
Speaker 1: the whole genre for that. But that's sort of the
32:30
Speaker 1: quantum mechanical view. If you say quantum mechanics is primary
32:34
Speaker 1: and the way function for the universe is the most
32:36
Speaker 1: basic thing, then can you build up a universe without spaces?
32:39
Speaker 1: Space necessary? That's the quantum mechanical path, right, And it
32:42
Speaker 1: sounds like the answer is sort of yes, Like if
32:45
Speaker 1: quantum mechanics is all there is, then it might be
32:48
Speaker 1: possible to see how you could not have space absolutely.
32:51
Speaker 1: And there's some really fun recent ideas things called like
32:54
Speaker 1: condensate cosmology, where space condenses in these like steam like
32:59
Speaker 1: droplets from these weird fun spin networks that are more fundamental,
33:03
Speaker 1: but we're gonna do a whole podcast about that sometime
33:05
Speaker 1: in the future. Well all right, well then, and now,
33:07
Speaker 1: what does general relativity say about not having any space?
33:11
Speaker 1: Is that possible? According to that view, general relativity really
33:14
Speaker 1: has no problem with space not existing because in our
33:18
Speaker 1: general relativistic understanding of the universe, think about what happens
33:23
Speaker 1: in the history, Right, we have the current universe. We
33:25
Speaker 1: look back in time and we see the universe getting
33:28
Speaker 1: more and more compact, and we propagate back and further
33:31
Speaker 1: and further and further and approaches this special moment, this singularity,
33:36
Speaker 1: this time before which space does not exist. And you know,
33:40
Speaker 1: there are various ideas for how to tackle that and
33:42
Speaker 1: what that means and if it's a breakdown of the
33:44
Speaker 1: theory and if it needs to be replaced by something else.
33:47
Speaker 1: But in our current albeit imperfect, non quantum mechanical general relativity,
33:52
Speaker 1: there is this concept that there is no space before
33:55
Speaker 1: the Big Bang, there's no space or it was just
33:59
Speaker 1: super compressed. It's super compressed in the very first moments
34:03
Speaker 1: of the universe, but before that, before the singularity itself, right,
34:07
Speaker 1: this moment of infinite density, that space did not exist.
34:10
Speaker 1: That it doesn't make sense to ask where is something
34:13
Speaker 1: or when is something because the whole notion of space
34:16
Speaker 1: and time came into existence then, like there is no
34:20
Speaker 1: space and time before then. And this is not something
34:23
Speaker 1: that's very easy to think about because we don't think
34:25
Speaker 1: about space and definitely not time beginning right, But a
34:28
Speaker 1: whole other podcast episode about whether you need time and
34:31
Speaker 1: if time is an emergent phenomena. It's a whole even
34:34
Speaker 1: more difficult question to grapple with because you have to
34:37
Speaker 1: think about, like, could there be a time before which
34:39
Speaker 1: there was no time. But putting that aside for the
34:42
Speaker 1: time being, at least, it's hard still to think about
34:45
Speaker 1: a universe existing without space. But if you can still
34:48
Speaker 1: have time, right, if you say time exists, but maybe
34:50
Speaker 1: space is not fundamental, it might make sense to you
34:53
Speaker 1: to think about like space itself is this weird thing
34:56
Speaker 1: we talked about, this weird do that does stuff, and
34:59
Speaker 1: it can bubble and it can expand. It's being created
35:02
Speaker 1: right now. If it's being created, then you know, maybe
35:04
Speaker 1: there was a moment before it was created, or you know,
35:07
Speaker 1: you can think about what is there when it's not
35:10
Speaker 1: being created right and there's there's no space, if there's
35:13
Speaker 1: no space being created exactly, and it might be that
35:16
Speaker 1: you can have a universe before space is created. Might
35:19
Speaker 1: be the time existed before the Big Bang, but just
35:22
Speaker 1: not space. And there's some like conditions required for space
35:26
Speaker 1: to be created for it to expand. Like you might
35:29
Speaker 1: think it's a weird concept for space to be created,
35:32
Speaker 1: but remember that it's happening right now. You know, the
35:35
Speaker 1: expansion of the universe is not the motion of stuff
35:38
Speaker 1: through the universe. It's the creation of new space between
35:42
Speaker 1: us and other galaxies, between you and your couch between
35:45
Speaker 1: everything and everything else. So it's happening right now. And
35:49
Speaker 1: it's just that we have only recently realized that space
35:51
Speaker 1: is this bizarre fabric that can do these things like
35:54
Speaker 1: be created spontaneously everywhere simultaneously, that we've come to ask
35:59
Speaker 1: these quests, and so we just really don't have a
36:01
Speaker 1: notion and understanding of what space is even in general relativity.
36:05
Speaker 1: But it's certainly is possible that it can be created.
36:07
Speaker 1: And so yeah, you can imagine there being a pre
36:10
Speaker 1: Big Bang moment when there was a universe but just
36:13
Speaker 1: no space. All right, Well, it sounds like both theories
36:16
Speaker 1: are pretty cool with the idea of not having space.
36:19
Speaker 1: They can both take it or leave it. Yeah, absolutely,
36:22
Speaker 1: variations of quantum mechanics can accommodate space not being fundamental
36:27
Speaker 1: even though our current quantum field theory sort of assumes
36:29
Speaker 1: that it's there. You can build these extensions that sort
36:32
Speaker 1: of make it possible for space to be emergent, for
36:34
Speaker 1: it to bubble up, rather than just being an assumed
36:37
Speaker 1: property of the universe. Alright, so space, take it or
36:41
Speaker 1: leave it? Leave it? All right, Let's get into how
36:44
Speaker 1: we would ever know if space is or not disposable
36:49
Speaker 1: or dispensable. But speaking of time, it's time to take
36:51
Speaker 1: another quick break, all right, Daniel. It sounds like physicists
37:08
Speaker 1: could take space or leave it. It sounds like both
37:10
Speaker 1: theories about the universe would be okay. They wouldn't break
37:14
Speaker 1: down if you suddenly got rid of space. Yeah. And
37:17
Speaker 1: I think if you took a survey of physicists right
37:20
Speaker 1: now and you ask them if space was fundamental or emergent,
37:23
Speaker 1: if it came from something else more fundamental, I bet
37:26
Speaker 1: you get like saying that it's an emergent, that it's
37:29
Speaker 1: not fundamental, that it's comes up from something else, which
37:32
Speaker 1: means that you could have a universe without it, or
37:34
Speaker 1: portions of the universe without it. I think that's the
37:37
Speaker 1: current mainstream thinking. And as we all know, the universe
37:40
Speaker 1: works democratically, so whatever the majority says must be true. No,
37:44
Speaker 1: we're definitely capable of being misled and having the wrong idea.
37:48
Speaker 1: But I think it's sort of exciting that it's widespread.
37:50
Speaker 1: It means that lots of people are working on it,
37:51
Speaker 1: People are developing new ways of thinking about these really
37:54
Speaker 1: really basic questions, and people out there also should be
37:58
Speaker 1: excited it means that, like we're just the beginning of
38:00
Speaker 1: asking questions about the universe and tackling them. If you
38:04
Speaker 1: are excited about questions like you know, what is the
38:07
Speaker 1: universe and where did they come from? And what's it
38:09
Speaker 1: really made out of? Remember that there are huge tracts
38:12
Speaker 1: of questions that are just really being explored by This
38:15
Speaker 1: is just now, and so there's plenty of room to
38:17
Speaker 1: make like really fundamental Einstein level discoveries about the nature
38:22
Speaker 1: of the universe. Right. I think what you're saying is
38:24
Speaker 1: that there's an electoral college in the universe, and who knows,
38:27
Speaker 1: who knows what the rules are for that? That's right. Fortunately,
38:31
Speaker 1: physics is easier to calculate than the electoral college. All right,
38:35
Speaker 1: I guess maybe now the big question is how would
38:38
Speaker 1: we know or not whether space is fundamental or whether
38:41
Speaker 1: or not it's like an add on or like an
38:44
Speaker 1: optional preference in the universe you could live in. Is
38:48
Speaker 1: there a way for us to test it because we
38:50
Speaker 1: live in this space that we're trying to test. Is
38:53
Speaker 1: it possible to I don't know, create an experiment where
38:56
Speaker 1: you have no space? Yeah, there's really two steps to that. First,
38:59
Speaker 1: is we gotta make more theoretical progress and then we
39:02
Speaker 1: got to do some experiments. So on the theoretical side,
39:06
Speaker 1: what we really need is a unification of quantum mechanics
39:09
Speaker 1: and general relativity. We need a theory of quantum gravity
39:13
Speaker 1: that tells us how the universe works, so that we
39:16
Speaker 1: can think about, like what is space, and this theory
39:19
Speaker 1: if it all hangs together and like does everything it
39:21
Speaker 1: has to do, meaning it can describe everything that gravity
39:25
Speaker 1: can do, and they can describe all the tiny fundamental
39:27
Speaker 1: particles and it brings those together in a way that
39:31
Speaker 1: makes sense that you know, they don't disagree with each
39:33
Speaker 1: other like the current quantum mechanics and general relativity do.
39:36
Speaker 1: Then we can ask questions of that theory. So first
39:39
Speaker 1: we've got to make progress. Theoretically, we need like an
39:41
Speaker 1: actual theory that totally works. Before the break, we talked
39:44
Speaker 1: about a few possibilities like directions people are going. These
39:47
Speaker 1: are like half formed ideas. People are like building scaffolding.
39:51
Speaker 1: You can see the outlines of a structure of people
39:53
Speaker 1: are trying to make work, but nobody has an actual
39:55
Speaker 1: functioning theory of quantum gravity where we can ask these
39:59
Speaker 1: kind of questions and get answers. I guess you need
40:01
Speaker 1: some sort of theory first, right, Like, you can't just
40:03
Speaker 1: take out space and measure it and not measure it.
40:06
Speaker 1: How do you measure not space? Well, we have done
40:08
Speaker 1: a lot of really cool experiments about space, right, Like
40:11
Speaker 1: seeing gravitational waves is incredible. It tells us that space
40:15
Speaker 1: really is sort of fungible and dynamic. And measuring the
40:19
Speaker 1: expansion of the universe that's also kind of an experiment
40:22
Speaker 1: that tells us what's going on with space. And a
40:24
Speaker 1: lot of times experiment informs us. Remember that we didn't
40:27
Speaker 1: expect the universe to be expanding in an accelerating manner
40:31
Speaker 1: until we saw it, and it totally shocked us and
40:33
Speaker 1: surprised us. So sometimes experiments can inform us. I think
40:36
Speaker 1: in this case, we really need theory to tell us,
40:40
Speaker 1: like how we can do experiments to answer this question,
40:43
Speaker 1: because currently the only experiments I can think of are
40:46
Speaker 1: ones that are like at the center of a black
40:48
Speaker 1: hole or requires super colliders the size of a solar system,
40:52
Speaker 1: not things we can get done tomorrow. No, exactly, because
40:56
Speaker 1: for example, general relativity and quantum mechanics they disagree about
41:00
Speaker 1: what's at the center of a black hole. You know,
41:01
Speaker 1: general relativity says, oh, there's a singularity there, but quantum
41:05
Speaker 1: mechanics says, you can't have a singularity because that's too
41:08
Speaker 1: much information isolated in one little spot and it violates
41:11
Speaker 1: the Heisenberg uncertainty principle. And so if you could see
41:14
Speaker 1: what was going on inside the black hole, you can
41:16
Speaker 1: get great clues as to how to build your theory
41:18
Speaker 1: of quantum gravity. Or if you could somehow do tests
41:22
Speaker 1: of particles feeling gravitational forces by building a super huge
41:26
Speaker 1: collider and smashing those particles together at crazy high energies
41:30
Speaker 1: enough energy where like gravity is as powerful as the
41:33
Speaker 1: other forces, that maybe you could get a clue as
41:35
Speaker 1: to how to build your theory of quantum gravity. But
41:37
Speaker 1: we can't do either of those experiments today, And so
41:40
Speaker 1: I think what we need is some inside from the
41:43
Speaker 1: theory to tell us, well, look, here's how the universe
41:45
Speaker 1: is put together. Here's our theory of what spaces, and
41:48
Speaker 1: this theory gives us a clue about how to look
41:51
Speaker 1: for evidence that the theory is correct. You know, there's
41:53
Speaker 1: some like wrinkles, some experiment we can predict the outcome
41:57
Speaker 1: of that can tell you whether or not this is right.
41:59
Speaker 1: It's like if only you can break the loss of
42:01
Speaker 1: physics so that you could figure out the laws of exactly.
42:06
Speaker 1: And there's maybe one more hint of something that we
42:08
Speaker 1: can do, which is that we can look for more
42:11
Speaker 1: evidence of this creation of space. We can look for
42:14
Speaker 1: evidence of those first moments just after the Big Bang
42:18
Speaker 1: and trying to find some gravitational radiation from the Big
42:22
Speaker 1: Bang itself. But what do you mean, like a shock wave,
42:24
Speaker 1: or like actual radiation, or like gravitons. Yes, exactly all
42:28
Speaker 1: of those things. You know that we have microwave background
42:31
Speaker 1: radiation from about four hundred thousand years after the Big Bang,
42:35
Speaker 1: when this hot plasma cooled and became transparent. We see
42:38
Speaker 1: those photons, and people often say that that radiation is
42:42
Speaker 1: like from the Big Bang itself. It's not quite as
42:44
Speaker 1: from you know, four hundred thousand years after the Big Bang,
42:48
Speaker 1: when the universe became transparent and that light is now
42:51
Speaker 1: still propagating around. We'd love to see earlier. We'd have
42:54
Speaker 1: to look further back to the actual creation of the universe,
42:57
Speaker 1: whatever happened there, And so it might be Passe will
43:00
Speaker 1: do that by looking for gravitational waves that were created
43:03
Speaker 1: in those very first moments when the universe was expanding
43:07
Speaker 1: so rapidly, we think that gravitational waves were made. So
43:10
Speaker 1: there's another kind of radiation called the cosmic gravitational background
43:15
Speaker 1: that might have clues as to what the nature of
43:17
Speaker 1: spaces and whether it was created in those first moments,
43:20
Speaker 1: if we could see it like the echoes of the
43:23
Speaker 1: creation of space, yes, exactly, and so we have theories
43:26
Speaker 1: about what that might look like under various configurations. And
43:29
Speaker 1: you might remember several years ago people didn't experiment where
43:33
Speaker 1: they thought they measured those waves. It was called BICEP two.
43:36
Speaker 1: But then it turns out that they were mistaken and
43:38
Speaker 1: they were actually just measuring dust between galaxies. So that
43:40
Speaker 1: was disappointing, But it might still be possible with a
43:43
Speaker 1: better round of experiments, more precision and control of that dust,
43:46
Speaker 1: to see the actual radiation from the early universe and
43:49
Speaker 1: get a glimmour as to whether space was created or
43:52
Speaker 1: whether it had always been there. And there's another possibility
43:56
Speaker 1: right us to whether or not we can confirm this
43:58
Speaker 1: existence or the tendency of space, and that is that
44:02
Speaker 1: maybe in the future there might not be any space.
44:04
Speaker 1: Right exactly, are we going to run out of space
44:08
Speaker 1: or are we just gonna, you know, get a victim
44:12
Speaker 1: from our house. No, you're absolutely right. And some of
44:14
Speaker 1: these theories of loop quantum gravity, for example, they predict
44:18
Speaker 1: that the universe's expansion will stop and it will turn
44:21
Speaker 1: around and it will compactify, so that space is like
44:25
Speaker 1: being destroyed instead of being created, and we'll have like
44:28
Speaker 1: a reverse big bang, this big crunch, And it's not
44:31
Speaker 1: clear what would happen after that. Would we get another
44:33
Speaker 1: big bang? Would we just have no space for a while?
44:36
Speaker 1: But does time even exist anymore? We don't know. So yeah,
44:39
Speaker 1: stick around another few trillion years and the question might
44:41
Speaker 1: just answer itself. Yeah, things might get a little bit
44:44
Speaker 1: more crowded or were space and cluttered? All right? Well,
44:48
Speaker 1: it sounds like it is possible for the universe to
44:50
Speaker 1: not have any space, But we may not find out
44:53
Speaker 1: any time, you know, unless we observe something incredible or
44:56
Speaker 1: we make a breakthrough in one of these theories that
44:59
Speaker 1: let us look or you know, kinks that we can
45:02
Speaker 1: use this evidence that space cannot exist. Yes, and I
45:05
Speaker 1: think that there will be theoretical progress. People are working
45:07
Speaker 1: really hard on this stuff. Black hole information paradox is
45:10
Speaker 1: giving us some clues. So there's a lot of really
45:12
Speaker 1: smart people working really hard on these questions, and I
45:15
Speaker 1: think in the next five or ten years we'll see
45:17
Speaker 1: some really clever, fascinating, mind blowing theories coming out to
45:21
Speaker 1: explain our bunkers universe. They just need a little space,
45:25
Speaker 1: you know, no pressure. All right, Well, we hope you
45:28
Speaker 1: enjoyed that discussion. Thanks for joining us, see you next time.
45:40
Speaker 1: Thanks for listening, and remember that Daniel and Jorge Explain
45:43
Speaker 1: the Universe is a production of I Heart Radio or
45:46
Speaker 1: more podcast from my heart Radio visit the I heart
45:49
Speaker 1: Radio app, Apple Podcasts, or wherever you listen to your
45:53
Speaker 1: favorite shows.