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Can quantum gravity save physics? · Daniel and Kelly’s Extraordinary Universe

0:08
Speaker 1: Hey, Daniel, do you think physics is in a rut?
0:11
Speaker 1: A rut like we've been solving deep problems and delivering
0:14
Speaker 1: amazing technology for too long. You're getting tired of it? Yeah,
0:19
Speaker 1: I mean it's getting a little repetitive, all these discoveries. No, No,
0:23
Speaker 1: I mean, like, is it on the right track? You know?
0:25
Speaker 1: Do you think it will it get to the final
0:27
Speaker 1: deep questions about the universe? I don't know. Sometimes I
0:30
Speaker 1: wonder if we need like a revolution in physics. Does
0:33
Speaker 1: physics need to be disrupted? Somebody out there should start
0:36
Speaker 1: uber for physics. I'm more of a lift person, to
0:40
Speaker 1: be honest, I think they have a better outlook in
0:43
Speaker 1: the world. But yes, that's what I mean. You know,
0:45
Speaker 1: I want to be able to call a physicist anytime
0:48
Speaker 1: in my with my phone. Um, well you already have that.
0:51
Speaker 1: That's this podcast. Nice, I'll give you four stars. Daniel here.
1:12
Speaker 1: Hi am Rhema cartoonist and the creator of PhD comics. Hi.
1:16
Speaker 1: I'm Daniel Whitson. I'm a particle physicist, and I'm here
1:19
Speaker 1: to answer any question of physics on your app anytime.
1:22
Speaker 1: Welcome to our podcast. Daniel and Jorge invent new physics apps.
1:26
Speaker 1: For people who need physics on demand. Daniel and Jorge
1:30
Speaker 1: make up terrible business ideas and pretending they're awesome. Now
1:35
Speaker 1: it's Daniel and Jorge Explained the Universe, a production of
1:38
Speaker 1: Our Heart Radio, in which we talk about all the
1:40
Speaker 1: things amazing and beautiful but crazy and bonkers about our
1:44
Speaker 1: universe because the more we learn, the more it makes sense,
1:47
Speaker 1: the more it seems surprising and amazing. You know, within
1:50
Speaker 1: we joke about it. But I think it would be
1:52
Speaker 1: kind of a useful app. Don't you think, like anytime
1:54
Speaker 1: anyone has a question about anything, you could just request
1:58
Speaker 1: a physicist on your phone own and the nearest or
2:02
Speaker 1: the most available physicists would answer and then answer your question.
2:05
Speaker 1: Do you think that would be used a lot? Like
2:07
Speaker 1: what kind of questions would people ask? How do we
2:09
Speaker 1: reconcile the different theories about quantum physics? Sure? I think
2:15
Speaker 1: it's more prosaic. It's like can I build a force
2:17
Speaker 1: field to keep my teenager in his bedroom all night long? Also?
2:22
Speaker 1: How does my toaster work? Why doesn't my toaster work?
2:26
Speaker 1: That's probably be the number one question again? Can you
2:28
Speaker 1: come fix my toaster? No, we're not engineers. You need
2:31
Speaker 1: a different Uber for that. Yeah, but think about all
2:33
Speaker 1: those grad students and post talcs and physics who are
2:35
Speaker 1: looking for a little extra money. You know, they would,
2:38
Speaker 1: I'm sure they would sign up to answer people's questions. Yeah,
2:41
Speaker 1: you know, there actually is a physics consulting service where
2:44
Speaker 1: if you think you have the great next theory of
2:48
Speaker 1: physics but you're not being taken seriously by the mainstream establishment,
2:52
Speaker 1: there is a service where expert physicists will read your
2:55
Speaker 1: theory and give you like top level criticism of it.
2:58
Speaker 1: Why it's probably not the winner of the next year's
3:01
Speaker 1: Nobel Prize. Yeah, it's called Daniel at Daniel and Jorge
3:07
Speaker 1: dot com. It's true. There are people who send me
3:11
Speaker 1: their theories two questions at Daniel and Jorge dot com,
3:14
Speaker 1: and I try to take a look at them. But
3:16
Speaker 1: there is a service which will spend you know, half
3:18
Speaker 1: an hour or an hour actually digging into your theory. Yeah,
3:22
Speaker 1: but they charge a lot, don't they don't They charge
3:24
Speaker 1: you like fifty or something. You think that's a lot.
3:27
Speaker 1: You think, like, you know, deep deep expertise of the
3:30
Speaker 1: universe should coming like seven. Sure, I mean, you know,
3:34
Speaker 1: I want to know how my toaster works. But not
3:37
Speaker 1: for fifty dollars, buy any toaster Roman for fifty dollars. Well,
3:40
Speaker 1: then I guess you don't really want to know how
3:42
Speaker 1: it works. You just want to buy a new one.
3:46
Speaker 1: I want to buy a transparent toaster so I can
3:47
Speaker 1: see how it works. Well, that's the difference between the
3:50
Speaker 1: scientists and the engineer. The engineer just wants to make
3:52
Speaker 1: it work, and the scientist wants to know why it
3:55
Speaker 1: doesn't work. Yeah, we we just want to eat toast.
3:57
Speaker 1: That's the basic difference. But sometimes scientists also want a
4:01
Speaker 1: theory that just works. And in physics we were making
4:05
Speaker 1: progress towards sort of like answering those deep questions of
4:08
Speaker 1: the universe, but we're not quite there yet. Yeah, you
4:11
Speaker 1: guys have been pretty successful. You have a standard model
4:14
Speaker 1: of the universe and some pretty good theories. You know,
4:17
Speaker 1: you have the standard model, not the not the non
4:19
Speaker 1: standard model. We should have called it something else, right,
4:21
Speaker 1: Standard models just so boring. It's like the Beije model
4:24
Speaker 1: of the universe. We should have called it the amazing model. Yeah,
4:28
Speaker 1: but you have pretty much everything answered right, kind of,
4:31
Speaker 1: except for some basic things about the universe. Yeah, we've
4:35
Speaker 1: made a lot of progress, which is incredible. We've explained electromagnetism,
4:40
Speaker 1: we've explained the weak foce, we've made a lot of
4:42
Speaker 1: progress and understanding the strong nuclear force. And then, in
4:46
Speaker 1: a totally different camp, with totally different people, using completely
4:50
Speaker 1: different mathematics and ways of thinking, we've made some in
4:53
Speaker 1: rows into understanding gravity. Yeah, but there are some You
4:57
Speaker 1: have all these great theories, but there's something not wide
5:00
Speaker 1: right right, Like it works, it's pretty successful for a
5:04
Speaker 1: lot of things, but there's something kind of fundamentally almost
5:07
Speaker 1: wrong with all of your theories. What did you say, Yeah,
5:10
Speaker 1: the problem is we have no theory that describes sort
5:12
Speaker 1: of all of it. We have people who started from
5:14
Speaker 1: the quantum mechanical side of things understanding that building an
5:17
Speaker 1: incredible mind bending theory of the universe that seems to
5:21
Speaker 1: be like an accurate description of the way things actually are.
5:25
Speaker 1: And then we have people working from the other side,
5:27
Speaker 1: starting from gravity and saying like, let's understand gravity is
5:30
Speaker 1: a bending of space man, and they're actually making progress. Also,
5:33
Speaker 1: the problem is these two theories don't agree with each other.
5:37
Speaker 1: They don't play well, they don't have completely different views
5:41
Speaker 1: of how the universe actually is. They're sort of incompatible.
5:44
Speaker 1: It's kind of like if you're building a bridge across
5:46
Speaker 1: the Atlantic, and you know, you build one side starts
5:50
Speaker 1: building a bridge, and the other side starts building a
5:52
Speaker 1: bridge from their side, and you find out that you're
5:54
Speaker 1: nowhere near each other in the middle. Yeah, exactly. Or
5:57
Speaker 1: you're using technologies which just cannot fit to other and
6:00
Speaker 1: that's the problem. Right. You're hoping that there is one
6:03
Speaker 1: truth that you can start in different places in your
6:06
Speaker 1: investigation and sort of work together to find the central truth.
6:10
Speaker 1: But sometimes we wonder if these models just depend on
6:12
Speaker 1: your perspective. There's different ways to look at the universe,
6:15
Speaker 1: and some are successful and some are limited, and so
6:18
Speaker 1: we don't know like which is the right way to
6:19
Speaker 1: look at the universe, if if either of them are
6:22
Speaker 1: even right, or we need something totally new, right, if
6:25
Speaker 1: either of them right, because it almost sounds like maybe
6:28
Speaker 1: both of them are not looking at the world, at
6:31
Speaker 1: the universe and quite the right way, you know, if
6:34
Speaker 1: you can't make them work together. Yeah, And there's a
6:36
Speaker 1: lot of examples in history where physics has been like
6:39
Speaker 1: very confidently almost wrapped everything up except for a couple
6:42
Speaker 1: of little details which turn out when you pull on them,
6:45
Speaker 1: unravel everything and reveal like a completely different view of
6:50
Speaker 1: the universe that was quantum mechanics. You know, in the
6:52
Speaker 1: late eighteen hundreds, people felt like we've almost got this
6:55
Speaker 1: thing wrapped up except for like, you know, the photoelectric
6:58
Speaker 1: effect and the black body radiation, which revealed, of course
7:01
Speaker 1: that the universe is quantized on a fundamental scale, which
7:03
Speaker 1: blew everybody's minds. Kind of makes you wonder if maybe
7:07
Speaker 1: physics needs to be shaken up a little bit, you know,
7:10
Speaker 1: kind of reset or you know, disrupted, or you know,
7:14
Speaker 1: start from a totally needed perspective. Yeah, I think it's
7:18
Speaker 1: possible physics today has all those elements of needing a
7:22
Speaker 1: new idea, of needing a new perspective, of discovering, of
7:25
Speaker 1: stumbling over something which shows us that we've just been
7:28
Speaker 1: asking the wrong questions or starting our solutions from the
7:31
Speaker 1: wrong point of view. And that's not embarrassing, you know.
7:34
Speaker 1: That's the way we explore the world. We start from
7:36
Speaker 1: our current understanding. We see how long it works, and
7:39
Speaker 1: when it breaks, we think, can we just add another
7:41
Speaker 1: little widget to it, or do we have to toss
7:43
Speaker 1: everything out and build it from a different kind of
7:46
Speaker 1: bit In today's episode, we'll be talking about one such
7:49
Speaker 1: idea that might help bridge this connector gap between quantum
7:54
Speaker 1: mechanics and gravity. And it's a pretty new theory when
7:58
Speaker 1: you say, it's sort of it's come out in the
8:00
Speaker 1: last maybe what ten years, twenty years. I think it
8:03
Speaker 1: has its history in the eighties, but it's been picking
8:06
Speaker 1: up steam in the last ten or fifteen years, and
8:09
Speaker 1: it's sort of emerging as a dark horse. It was
8:11
Speaker 1: like first was sort of laughed off as a fringe
8:14
Speaker 1: theory and you know, not nearly this popular other theories
8:17
Speaker 1: of everything in quantum gravity, and so I think it's
8:21
Speaker 1: recently gaining some sort of respectability. It's like millennials, you know,
8:24
Speaker 1: born in the eighties but kind of easily discounted, but
8:27
Speaker 1: now they're taking over the world. Are millennials getting respectable?
8:30
Speaker 1: When did that happen? When we died? There? I'm working
8:35
Speaker 1: on my theory of quantum respectability and currently I have
8:38
Speaker 1: zero there you go. So today we'll be talking about
8:40
Speaker 1: what about that theory. And the theory is loop quantum gravity.
8:51
Speaker 1: What is it? Why is it in a loop? And
8:53
Speaker 1: will it solve all the problems in physics? And here
8:56
Speaker 1: I have to make a shout out to one of
8:57
Speaker 1: our listeners, Jim Milco. Jim has been sending me questions
9:01
Speaker 1: for about as long as we've been doing this podcast,
9:03
Speaker 1: and he has been consistently asking for a podcast episode
9:07
Speaker 1: about loop quantum gravity. So thanks for your patients, Jim,
9:10
Speaker 1: here's your episode. Awesome as he sent you, any idea
9:13
Speaker 1: is worthy of a Nobel price yet, Jim has sent
9:15
Speaker 1: a lot of ideas and they're always fun to read.
9:18
Speaker 1: So if you have ideas about the universe, or just questions,
9:21
Speaker 1: or there's something you really want to understand more deeply
9:23
Speaker 1: and you think we might be able to break it down,
9:25
Speaker 1: please send your questions, your suggestions, your fundamental new theories
9:30
Speaker 1: of the universe to questions at Daniel and Jore dot com. Yeah,
9:34
Speaker 1: thanks to Jim for listening and to everyone out there listening.
9:37
Speaker 1: And so as usual, we were wondering how many people
9:39
Speaker 1: out there know or have heard of loop quantum gravity.
9:44
Speaker 1: It's sort of a it's sort of a it has
9:46
Speaker 1: two sort of technical familiar words, but then a pretty
9:49
Speaker 1: common word, which is loop. I was very curious in
9:52
Speaker 1: these interviews to see if anybody had heard of this
9:54
Speaker 1: thing and had any ideas. So I went in with
9:57
Speaker 1: a completely open mind. So before you hear these answers,
10:01
Speaker 1: think to yourself, do you know what Luke quantum gravity is?
10:04
Speaker 1: Could you describe it? What would you answer? Here's what
10:07
Speaker 1: people had to say. I mean, I would assume it
10:10
Speaker 1: has something to do with gravity, nothing at all, nothing
10:14
Speaker 1: at all. So I heard of quantum mechanics and read
10:17
Speaker 1: like brief history of time. Okay, but I don't don't
10:21
Speaker 1: know what loup quantum gravity could be. What came to
10:25
Speaker 1: mind first was entanglement. But I don't think that necessarily
10:28
Speaker 1: has anything to do with that. So it's just as
10:31
Speaker 1: opposed to just making up something that I think it
10:33
Speaker 1: might be. I don't know. I have not no no
10:36
Speaker 1: idea that I'm not No, I have it nothing. I
10:41
Speaker 1: don't know, all right, not a lot of penetration in
10:44
Speaker 1: the public market. No, these folks have to work on
10:48
Speaker 1: their pr for sure. String theory has them beat, for sure.
10:53
Speaker 1: Maybe they need to get it mentioned in the next
10:55
Speaker 1: Big Bang Theory episode. Oh maybe we should create a
10:58
Speaker 1: setim called loop quantum gravity. I want to see you
11:02
Speaker 1: pitching that, like, Hey, it worked for the Big Bang theory.
11:08
Speaker 1: We just need another physics theory named titled sitcom that
11:12
Speaker 1: makes fun of nerds. Yeah, well I'm in as long
11:15
Speaker 1: as we have characters that both are smart and can
11:19
Speaker 1: talk to human beings. Oh really yeah? Any Oh that hurts, man,
11:29
Speaker 1: That hurts. So not. Not only a lot of people
11:32
Speaker 1: seem to have heard of it. I mean I imagine
11:34
Speaker 1: they most of them have heard of quantum mechanics or
11:37
Speaker 1: have heard the word quantum if anything, from the Marvel movies,
11:41
Speaker 1: and they surely have heard of gravity, but loop quantum
11:44
Speaker 1: gravity is pretty pretty unknown. Yeah, it's a little bit esoteric,
11:48
Speaker 1: but it's fascinating and it has really interesting ideas, and
11:52
Speaker 1: those ideas could have really deep implications. It's the kind
11:55
Speaker 1: of theory which, if it's correct, really changes the way
11:59
Speaker 1: we think about the entire universe and the fundamental nature
12:02
Speaker 1: of our relationship with it. So it's super fun to
12:05
Speaker 1: think about. And it's also really complicated and very technical,
12:10
Speaker 1: and there's a humongous amount of complicated math involved, none
12:14
Speaker 1: of which none of which you will have to understand
12:17
Speaker 1: to get the basic ideas today, which is why Daniel,
12:20
Speaker 1: you went out there and found an expert to talk
12:21
Speaker 1: to about this topic. Right, that's right, because I'm a
12:24
Speaker 1: particle physicist and my expertise doesn't extend to theories of
12:28
Speaker 1: quantum gravity. So I went and I talked to Bianca Dittrich.
12:32
Speaker 1: She's a professor at the Perimeter Institute in Canada, and
12:36
Speaker 1: she's an active researcher on the forefront of quantum gravity.
12:39
Speaker 1: So here is Bianca. So my name is Bianca Ditwich,
12:43
Speaker 1: originately from Germany. Also studied in Germany and then oscillated
12:49
Speaker 1: between the Canada and Europe a number of times and
12:54
Speaker 1: ended up at in Canada. It's a parameter institute, a faculty.
13:00
Speaker 1: All right, cool, So Bianca explained to you what loop
13:03
Speaker 1: quantum gravity is. Yeah. I had a long conversation with
13:06
Speaker 1: Bianca about why we need loop quantum gravity, how it
13:09
Speaker 1: solves the problems in physics, where the current criticisms of
13:12
Speaker 1: it are, how we could test it, and of course
13:15
Speaker 1: then I had to ask her at the end about
13:17
Speaker 1: black holes. Of course, because every good conversation ends in
13:22
Speaker 1: a black hole literally, right, maybe at the end of
13:25
Speaker 1: the universe, all that every conversation, everyone will ever have,
13:29
Speaker 1: all that information will end up maybe in a black hole. Well,
13:32
Speaker 1: what happens if you take a black hole and you
13:34
Speaker 1: put it in a toaster oven. There's a question nobody's
13:37
Speaker 1: ever asked, if I need to ask that a crunchy
13:41
Speaker 1: outside of the inside will still be cold black hole temperature. Yes,
13:46
Speaker 1: So what if I put a black hole in a microwave?
13:48
Speaker 1: Then do I heat up the inside of the black hole.
13:51
Speaker 1: That's a question I've never thought of. That's really a
13:53
Speaker 1: fun question. All right, Well, that step us through what
13:56
Speaker 1: Bianca explained to you, Daniel was so first of all,
13:58
Speaker 1: I guess what is the big problem in physics? Did
14:01
Speaker 1: that needs to be fixing? The big problem is that,
14:04
Speaker 1: as we said earlier, we have two different basic ideas
14:07
Speaker 1: about sort of how the universe works at the smallest scale,
14:10
Speaker 1: and they start from very different places, and as you
14:13
Speaker 1: said that they when they come together across the Atlantic,
14:16
Speaker 1: they just don't meet. And those two ideas are quantum
14:19
Speaker 1: mechanics and general relativity of theory Einstein's theory of gravity.
14:23
Speaker 1: It's weird to me that there would be too so
14:26
Speaker 1: many so different theories about the universe. You know, wouldn't
14:29
Speaker 1: they all sort of meet at the at the you know,
14:31
Speaker 1: plus and minus mathematical level. Well, you'd hope so. And
14:34
Speaker 1: this is sort of the way physics starts. You know,
14:36
Speaker 1: if your caveman cave woman physicist, you begin building your
14:39
Speaker 1: model of the universe by sort of looking at all
14:41
Speaker 1: this stuff around you, cataloging what it can do, and
14:45
Speaker 1: then saying, can I understand all of this stuff in
14:48
Speaker 1: as simple as possible terms? And so you're like, all right,
14:51
Speaker 1: there's the thing where things fall down, there's the thing
14:53
Speaker 1: where lightning comes from the sky. You know, there's a
14:56
Speaker 1: thing where there's wind. And then you have a very
14:58
Speaker 1: long list of stuff and try to boil it down
15:00
Speaker 1: and say, oh, you know, this lightning thing is the
15:02
Speaker 1: same as this other thing where I get zapped, and
15:05
Speaker 1: things falling down is actually the same thing as stars
15:07
Speaker 1: moving through the sky. There's all these moments when we
15:10
Speaker 1: sort of shrunk the list of ideas we need to
15:12
Speaker 1: explain the universe. And so you hope that as this
15:15
Speaker 1: list gets shorter and shorter, they fit together nicely. And
15:18
Speaker 1: that's happened a lot of time so far. Electricity is
15:20
Speaker 1: the same thing as magnetism, and it's all part of
15:22
Speaker 1: this other thing called the electroweak force that has happened.
15:26
Speaker 1: But sometimes you get, you know, you get two puzzle
15:28
Speaker 1: pieces and they just don't fit together, all right. So
15:31
Speaker 1: maybe step remind us Daniel, what each of these theories are, Like,
15:35
Speaker 1: what's the what's the easy way to describe what general
15:38
Speaker 1: relativity is, And what's the easy way to describe what
15:42
Speaker 1: quantum mechanics is. So general relativity is a way to
15:44
Speaker 1: try to understand what is gravity. And remember that Newton
15:48
Speaker 1: said gravity is things pulling on each other, things that
15:51
Speaker 1: have mass pull on each other. So take a force, yeah, Newton,
15:54
Speaker 1: that was the old thinking. That was the old thinking.
15:56
Speaker 1: Newton thought gravity is a force, and it seems kind
15:59
Speaker 1: of like a force. It acts like a force, like
16:01
Speaker 1: electricity and magnetism, and he was able to write down
16:04
Speaker 1: an equation that described how the Earth moved around the
16:07
Speaker 1: Sun and how to move the Moon moved around the Earth,
16:10
Speaker 1: and it works pretty well. Now, Einstein came along and
16:13
Speaker 1: he gave us general relativity, which is a complete reconception
16:16
Speaker 1: of how gravity works. He said, no, no, gravity is
16:19
Speaker 1: not a force. Gravity is a change in the shape
16:23
Speaker 1: of space and time itself. Like you have a blob
16:27
Speaker 1: of mass or blob of any kind of energy density,
16:29
Speaker 1: it changes the shape of space and that's what makes
16:32
Speaker 1: things move in curves. Rather than moving and what feels
16:36
Speaker 1: like a straight line to us, things moved through bent space.
16:39
Speaker 1: It's not like a mysterious invisible force that pulls things together.
16:43
Speaker 1: It's more like when things exist, they distort, they bend
16:46
Speaker 1: the space around them, and that's why they come together. Yeah.
16:49
Speaker 1: And it's a beautiful idea and it's been tested exilient
16:52
Speaker 1: ways and it works. It describes very tiny deviations in
16:58
Speaker 1: Mercury's orbit. It describes how light bends around the Moon
17:02
Speaker 1: during an eclipse. Big stuff, big stuff, Yeah, really thoroughly
17:06
Speaker 1: extensively tested. It predicted gravitational waves, which we've actually seen
17:10
Speaker 1: black holes to right and black holes. Yeah. And and
17:14
Speaker 1: the thing to understand the things that that's going to
17:16
Speaker 1: be make it in conflict with quantum mechanics is that
17:19
Speaker 1: it's a classical theory meeting that it assumes that, like
17:22
Speaker 1: you can describe everything perfectly, that everything has a position
17:26
Speaker 1: and a direction and a location, right, and that the
17:29
Speaker 1: space is operating in is smooth, Like you can subdivide
17:33
Speaker 1: space as many times as you want between me and you.
17:37
Speaker 1: There's an infinite possible locations for like a ball that
17:41
Speaker 1: we're throwing back and forth. That's Einstein's vision of space. Right,
17:45
Speaker 1: it assumes that everything is kind of smooth and continuous,
17:49
Speaker 1: and there there are no bumps in the universe at
17:51
Speaker 1: the microscopic level. That's right. You can zoom in forever
17:55
Speaker 1: according to Einstein and general relativity, and things still stay
17:58
Speaker 1: smooth and and everything has a fixed location. Right, the
18:01
Speaker 1: ball is somewhere and space and time makes some sense.
18:05
Speaker 1: There's no uncertainty or or weird or weirdness. That's right.
18:09
Speaker 1: The world can be known, everything can be determined according
18:12
Speaker 1: to general relativity. But then you have quantum mechanics, that's right.
18:15
Speaker 1: And then on the other hand, building from the other
18:18
Speaker 1: side of the ocean, you know, the toaster side of
18:20
Speaker 1: the ocean instead of the microwave side of the ocean.
18:22
Speaker 1: Um completely mixing metaphors, there is quantum mechanics. And quantum mechanics,
18:26
Speaker 1: of course developed in the early part of this century
18:29
Speaker 1: to explain some things that didn't make sense, some experiments
18:32
Speaker 1: we saw which just could not be described using a
18:36
Speaker 1: classical understanding of electromagnetism. It was really what was light
18:40
Speaker 1: that gave us the first clues. We did a whole
18:42
Speaker 1: podcast episode about the photoelectric effect and how we know,
18:46
Speaker 1: the photon is a thing, and they did these experiments
18:49
Speaker 1: that just didn't make sense unless you thought of light
18:52
Speaker 1: as being made of tiny little packets of energy rather
18:55
Speaker 1: than a smooth, continuous beam. You had to think about
18:58
Speaker 1: it as these tiny packets. When you zoom in, things
19:01
Speaker 1: don't behave nice and smooth and continuous there are sort
19:04
Speaker 1: of lumpy and clumpy. Yeah, And there were also just
19:08
Speaker 1: some problems with the theory, like there's a kind of
19:11
Speaker 1: radiation in the universe called black body radiation, which is
19:13
Speaker 1: just how things glow, Like everything in the universe has
19:16
Speaker 1: a temperature and it glows with that temperature, and quantum
19:20
Speaker 1: mechanics predicted that well. Classical theory electromagnetism predicted a certain spectrum,
19:25
Speaker 1: like if you're this temperature, you should glow with this color.
19:28
Speaker 1: If you're that temperature, you should glow with that other color.
19:30
Speaker 1: The problem was that it predicted that for certain temperatures
19:34
Speaker 1: you should glow at a crazy nonsensical color, like if
19:37
Speaker 1: you get an infinite amount of radiation. The original theory,
19:40
Speaker 1: the one before quantum mechanics, said that things that certain
19:44
Speaker 1: temperatures should have an infinite amount of light at very
19:48
Speaker 1: very low wavelengths, right, it really really sort of it's
19:52
Speaker 1: called ultra violet light, and that they should have like
19:54
Speaker 1: a ridiculous amount of infinite amount of ultra violet light,
19:57
Speaker 1: which is nonsensical. So you can do an ex perament
20:00
Speaker 1: basically that proves that general relativity doesn't work for all cases. Well,
20:05
Speaker 1: you can do an experiment that proves that the old
20:08
Speaker 1: theory of electricity and magnetism doesn't work. And we knew
20:11
Speaker 1: that didn't work. We're like, okay, this theory is making
20:13
Speaker 1: a prediction that just doesn't make sense. But if you
20:15
Speaker 1: add quantum mechanics to it, quantum mechanics says, oh, that's
20:18
Speaker 1: just because light is not continuous. If you make light
20:22
Speaker 1: into chunks, then if you predict that, you don't see
20:25
Speaker 1: this crazy behavior. And that's in fact what we saw
20:27
Speaker 1: in nature. And so we needed to sort of change
20:29
Speaker 1: the theory. The theory gave nonsensical results. I mean, I
20:32
Speaker 1: have to add this bit to it to say bit
20:34
Speaker 1: that says, okay, well there's a minimum size to a photon,
20:38
Speaker 1: and that solved that problem. It said, okay, now you
20:40
Speaker 1: can make realistic predictions. And so but the thing to
20:44
Speaker 1: understand is that like quantum mechanics changes also the way
20:47
Speaker 1: we think about the universe, right, it says things are uncertain,
20:51
Speaker 1: things are fluctuating. This is like crazy randomness the heart
20:54
Speaker 1: of the universe. All right. So those are the two
20:57
Speaker 1: two big titans in physics theories, right, general activity and
21:00
Speaker 1: quantum mechanics to try to explain the universe. And the
21:03
Speaker 1: problem is that they don't play well together. So let's
21:06
Speaker 1: get into a little bit of why they don't play
21:08
Speaker 1: well together and whether this idea of loop quantum gravity
21:12
Speaker 1: can help solve that. But first let's take a quick break,
21:28
Speaker 1: all right, Daniel, So general relativity and quantum mechanics don't
21:31
Speaker 1: play well together. Is it fair to say? Is it?
21:33
Speaker 1: Is it kind of like I'm trying to think of
21:34
Speaker 1: an analogy. Is it kind of like microeconomics and macro economics, Like,
21:38
Speaker 1: you know, macro economics is good for you know, big
21:42
Speaker 1: economies and countries and and micro economics is good for
21:46
Speaker 1: like how people make decisions, but like somehow they don't always.
21:50
Speaker 1: It's weird to think about where they meet in the middle. Perhaps,
21:53
Speaker 1: but in those two cases, one should be an extreme
21:57
Speaker 1: case of the other. Here it's really you have a
21:59
Speaker 1: fundamental different view of how the universe works. You know,
22:02
Speaker 1: it's it's more like totally different kinds of art, you know,
22:05
Speaker 1: like figurative art versus symbolic art. Like what's a better
22:09
Speaker 1: way to describe the human experience? You know? Is that
22:12
Speaker 1: through abstract splashes of color or is it by you know,
22:17
Speaker 1: depicting the things we see in interesting juxtapositions or something.
22:20
Speaker 1: I don't know, it's right, right, it's like a totally
22:24
Speaker 1: lens or you know, totally set of glasses. Yes, it's
22:27
Speaker 1: a completely different way of thinking about the world. And
22:30
Speaker 1: people have been trying for a long time to bring
22:32
Speaker 1: them together to say, all right, are these things in
22:35
Speaker 1: conflict or can we make a consistent sort of quantum
22:38
Speaker 1: theory of gravity that brings it all together? Right? And
22:41
Speaker 1: so here is Bianca talking about that question. It's one
22:44
Speaker 1: of the really big outstanding questions and physics and and
22:49
Speaker 1: my view it really means quantum gravity should include a
22:53
Speaker 1: new notion of space time. We have to replace it, however,
22:56
Speaker 1: with something completely new we expected that which change quite
23:01
Speaker 1: dramatically as a foundation, so physics um and get very
23:05
Speaker 1: interesting insights into you know, the nature of space and time.
23:09
Speaker 1: All right, So it seems like we need something totally
23:12
Speaker 1: new here um, And so Daniel, can you explain to
23:14
Speaker 1: me kind of what the problem is, like why can't
23:17
Speaker 1: they play well together? The ones that we have. Well,
23:19
Speaker 1: people have been trying to bring these two things together
23:21
Speaker 1: since basically they've existed. You know, people have been working
23:24
Speaker 1: on making gravity into a quantum theory for a very
23:28
Speaker 1: very long time. But you know, quantum theories traditionally thinking
23:31
Speaker 1: about forces very differently than gravity does. They think about
23:34
Speaker 1: forces is like ripples in a quantum field. You know,
23:38
Speaker 1: you have like the electromagnetic field, and you think about
23:41
Speaker 1: how do photons communicate the electromagnetic field. There are ripples
23:45
Speaker 1: in this electromagnetic field, and you quantize those ripples. That's
23:49
Speaker 1: how quantum mechanics thinks about forces. But in general, relativity
23:52
Speaker 1: of force is really more like a bending out space.
23:54
Speaker 1: That's right, And mostly you can do this. You can say, like,
23:58
Speaker 1: all right, well, can I make a quantum theory of gravity?
24:00
Speaker 1: Can I build a theory where I exchange where gravity
24:04
Speaker 1: is a field and it has ripples and those ripples
24:06
Speaker 1: are quantized, just like I can for electromagnetism, And mostly
24:10
Speaker 1: you can, actually you can. It's mostly it works, but
24:14
Speaker 1: it fails in some moments. Couldn't you just have quantum
24:17
Speaker 1: fields in a general relativity you know world? You know, like,
24:21
Speaker 1: couldn't you have quantum particles that bend space as well?
24:26
Speaker 1: Like why can't I a quantum particle also bend space
24:29
Speaker 1: like a planet? Well, but then gravity is coming from
24:31
Speaker 1: something that's classical, that's smooth and continuous, and general relativity
24:36
Speaker 1: is just not a quantum theory, right, Like it assumes
24:40
Speaker 1: that you know everything about the location and the time
24:43
Speaker 1: and the position. What couldn't you just make the bending
24:46
Speaker 1: also kind of uncertain? I'm just trying to figure out
24:48
Speaker 1: why why you can't marry the two, you know, why
24:51
Speaker 1: can't these particles and these fields exist in a world
24:54
Speaker 1: that is as Einstein envisioned with the bending and the
24:58
Speaker 1: gravity that's exactly what Looke gravity is? Or hey, you
25:01
Speaker 1: just basically invented the idea prize right now, Thank you
25:07
Speaker 1: very much. That's right, And you know this other idea
25:11
Speaker 1: that like, let's take the gravitational field and think about
25:13
Speaker 1: as a quantum field that mostly works. The important thing
25:17
Speaker 1: to understand is that it only fails when gravity gets
25:20
Speaker 1: really really strong, right, things like inside a black hole,
25:24
Speaker 1: and what happens is that it makes nonsense predictions like
25:28
Speaker 1: it just like we saw for the black body radiation.
25:31
Speaker 1: It predicts like infinite amount of energy will be released,
25:34
Speaker 1: but we know that's not true. We know it doesn't happen.
25:37
Speaker 1: And so the theories work except in extreme circumstances. And
25:41
Speaker 1: that's what makes it really hard, is like it's easy
25:44
Speaker 1: to fix the theory when you can see it breaking.
25:47
Speaker 1: But these theories general relativity and quantum mechanics, they only
25:49
Speaker 1: disagree about like what happens in the inside of a
25:52
Speaker 1: black hole, and we can't see that. Why don't we
25:55
Speaker 1: just like nor black hole? If we just like nor
25:57
Speaker 1: black holes in the universe, wouldn't that make our there's
26:00
Speaker 1: a lot wouldn't that make physics a little bit easier,
26:04
Speaker 1: you know, because it's all it seems like it seems
26:06
Speaker 1: like everything breaks in a black hole, and so why
26:08
Speaker 1: don't It's like, you know, the mess in my closet.
26:10
Speaker 1: Let's just ignore it's the engineering, you man, that's the engineering.
26:13
Speaker 1: The scientist in me is desperate to know. You have
26:16
Speaker 1: to know inside a black hole. Yes, if you have,
26:20
Speaker 1: you created a black hole in your closet, because if
26:22
Speaker 1: so I'm coming over and I want to check it out.
26:24
Speaker 1: I think we're close to the singularity. To be honest,
26:27
Speaker 1: in there, you don't want to go in there that
26:28
Speaker 1: you may never come out like you have all these
26:30
Speaker 1: rejected toaster microwave prototypes in there, that's right, all these
26:36
Speaker 1: rejected app ideas as well. And so these two things
26:40
Speaker 1: aren't working together. Well. People have tried, but they just
26:42
Speaker 1: give nonsense predictions like the calculations you get suggested, you know,
26:46
Speaker 1: infinite amount of energy in a radiated inside a black
26:49
Speaker 1: hole when gravity gets really strong, And we can't easily
26:52
Speaker 1: test that because we don't have a black hole and
26:54
Speaker 1: and I don't have a galaxy sized particle collider. I
26:57
Speaker 1: would need to create the sort of energy density in
27:00
Speaker 1: order to break quantum gravity. And so what we need
27:03
Speaker 1: is we need to see inside a black hole, or
27:05
Speaker 1: we need a new idea, and so we need Jorge's
27:08
Speaker 1: vision of quantum gravity. I have an idea. How about
27:11
Speaker 1: something called loop quantum gravity. That's such a great name too.
27:17
Speaker 1: All right, So we have these two fourth theories, and
27:19
Speaker 1: you know, one of them has an h thunderbolt cable
27:23
Speaker 1: connector and the other side is a mini USB cable connector,
27:28
Speaker 1: and so they don't fit. And so that's what this
27:30
Speaker 1: idea of loop quantum gravity is. It's like, maybe it's
27:32
Speaker 1: like an adapter. That is it like an adapter that
27:34
Speaker 1: makes it to work or is it a totally new
27:36
Speaker 1: cabling system. Yeah, it says instead of trying to think
27:40
Speaker 1: of gravity is like a Newtonian gravity as a force
27:44
Speaker 1: um and and and quantizing that gravitational field directly. Instead
27:49
Speaker 1: take Jorges idea, which is just takes space itself and
27:52
Speaker 1: quantize that and say, well, maybe general relativity is basically right,
27:57
Speaker 1: except that instead of working on a smooth continue in
28:00
Speaker 1: US space, we work on a space that is quantized,
28:03
Speaker 1: like there are pixels of space instead of space being
28:07
Speaker 1: infinite and smooth, they are like little chunks of space.
28:10
Speaker 1: It would explain how quantum particles move, or it would
28:14
Speaker 1: explain how gravity can be quantized. It would allow us
28:18
Speaker 1: to build a theory of quantum gravity that doesn't make
28:21
Speaker 1: nonsense predictions, because it basically makes the places where those
28:25
Speaker 1: predictions get nonsense impossible, like the predictions of quantum gravity
28:30
Speaker 1: breakdown really high energies and really small distances. So the
28:34
Speaker 1: idea is basically, well, what if really small distances aren't allowed,
28:37
Speaker 1: like there's just nothing smaller than ten of the minus
28:40
Speaker 1: thirty five where things break down, then there isn't the problem.
28:44
Speaker 1: Let's just ignore the closet and assume that the closet
28:48
Speaker 1: is QUANTIEDA it's just one thing, I see. Yeah, it's
28:53
Speaker 1: it's not ignoring the closet. It's saying the closet doesn't exist.
28:56
Speaker 1: You were so worried about the closet. It turns out
28:58
Speaker 1: it's impossible. There is no clause it. But it sounds
29:01
Speaker 1: like you're trying to make gravity quantized. You're not trying
29:04
Speaker 1: to make quantum things the bendy like space. Well, if
29:09
Speaker 1: space is bendy and quantized, then you quantum things move
29:12
Speaker 1: through quantizes bend bendy space. So this would allow you
29:16
Speaker 1: to bend space in a quantized way. Yeah, it would
29:20
Speaker 1: allow you to bend space in a quantized way. And
29:22
Speaker 1: it's it's kind of a beautiful idea because it's very
29:25
Speaker 1: similar to the origin of quantum mechanics itself. Right, we
29:28
Speaker 1: solve the problem of black body radiation, of this thermal
29:31
Speaker 1: emission giving crazy numbers by saying, oh, maybe we can
29:34
Speaker 1: just um quantize photons and that mathematically solves that problem. Here,
29:39
Speaker 1: we're solving the problem of infinite emissions inside black holes
29:42
Speaker 1: and really high energies and small distances by saying, oh,
29:46
Speaker 1: maybe we quantize space, and so those small distances are impossible.
29:50
Speaker 1: So there's there's a beautiful sort of analogy there to
29:52
Speaker 1: previous structures of solutions that suggests like tensively like, oh,
29:56
Speaker 1: maybe this is the right track because it feels like
30:00
Speaker 1: nineteen fifteen a little bit. That's right. We're gonna party
30:04
Speaker 1: like it's people are growing mustaches and wearing top hats,
30:08
Speaker 1: and you're like, I like it. I like it, except
30:11
Speaker 1: for the fact that like, no women are allowed to
30:12
Speaker 1: do physics. That's the bad part, all right. So the
30:16
Speaker 1: idea is that maybe space and time itself like space
30:20
Speaker 1: and time like there are no there's no there's no
30:23
Speaker 1: infinite as at least small second. That's right, And that's
30:26
Speaker 1: a question people have been sending me over email many times.
30:29
Speaker 1: If you quantize space, you also quantize time. And you know,
30:33
Speaker 1: space time is a fabric in this theory and they're
30:37
Speaker 1: deeply connected, and so if you're quantizing space, then yes,
30:39
Speaker 1: you're also probably quantizing time. Well, it's like you're there's
30:43
Speaker 1: actually a ticking clock to the universe. Maybe, yeah, there's
30:46
Speaker 1: a minimum time that makes sense. You know, you can't
30:49
Speaker 1: infinitely divide a second into arbitrarily tiny slices. There's a
30:53
Speaker 1: minimum of time below which makes no sense. Okay, And
30:56
Speaker 1: so what does that mean? I guess space is not
30:58
Speaker 1: really like space. Space is more like a clump of
31:03
Speaker 1: little spaces. Well, the reason it's called loop quantum gravity
31:06
Speaker 1: is that the way to think about it is that
31:08
Speaker 1: space is a bunch of these loops and they're sort
31:11
Speaker 1: of woven together. And so think about spaces like chain mail.
31:15
Speaker 1: If you're into D and D. You know, it's like
31:18
Speaker 1: a bunch of links that are all connected to each other.
31:21
Speaker 1: And space comes out of that, right spaces, There are
31:24
Speaker 1: these The fundamental thing in the universe are these little loops,
31:28
Speaker 1: and the loops are woven together. And the way that
31:31
Speaker 1: things move through space, and the way that gravity happens
31:34
Speaker 1: is how these little loops interact with each other and
31:36
Speaker 1: pull on each other and are built together. To what
31:40
Speaker 1: are these little loops? They're like little bits of the universe.
31:43
Speaker 1: That's the next Nobel prize, man, you want to win
31:46
Speaker 1: two Nobel prizes in a single podcast, in a single
31:48
Speaker 1: let's do you have enough for this to be a physicist?
31:51
Speaker 1: For the what do you call the hat the hat trick?
31:55
Speaker 1: A hat trick? You're gonna go for three Nobel prizes.
31:58
Speaker 1: That's when you get fifteen minutes off, Daniel, Let's do
32:00
Speaker 1: it when you invent the perfect toaster microwave combination, that
32:04
Speaker 1: definitely is worth a novel prize. Well, nobody knows what
32:06
Speaker 1: these loops are, and you know that's sort of the
32:09
Speaker 1: next question, Like if you can start from these loops
32:12
Speaker 1: and build a theory that describes everything and predicts the
32:15
Speaker 1: universe and it is consistent with everything we know, then
32:18
Speaker 1: the next question is you're like, well, why these little loops?
32:21
Speaker 1: What do they mean? How do we get those little
32:23
Speaker 1: loops right? Where do they come from? Do they emerge
32:25
Speaker 1: from something deeper? You know, physicists are great at making
32:29
Speaker 1: answers that create more questions. But I guess why call
32:32
Speaker 1: them loops? Are they actually like little rings that are
32:35
Speaker 1: tied together? What does that? Why not call them I
32:38
Speaker 1: don't know, bubbles or uh pixels or you know what
32:42
Speaker 1: I mean? Like, what is it about the idea of
32:44
Speaker 1: a loop that gives it the name loop quantum gravity. Well,
32:47
Speaker 1: I guess bubbles would work also, But I think it's
32:49
Speaker 1: just a visualization idea. You know that these things are
32:51
Speaker 1: linked together um and it's sort of a mesh, and
32:55
Speaker 1: you know there are also loops, like we're doing calculations
32:58
Speaker 1: around in a circle. You have to avoid a sort
33:01
Speaker 1: of trap, Like you can't think about these as loops
33:03
Speaker 1: in space. They're not like um circles on some axis, right,
33:08
Speaker 1: because when you have what is that access, we're talking
33:10
Speaker 1: about the very nature of space itself. It's not like
33:14
Speaker 1: these loops are somewhere and like this loop is at
33:17
Speaker 1: this point in that loop is at that point. The
33:19
Speaker 1: loops are the points like space is these this thing
33:23
Speaker 1: we're talking about like the nature of space itself, which
33:26
Speaker 1: is really hard to sort of wrap your mind around. Oh,
33:28
Speaker 1: I see you. You were just looking at you guys
33:30
Speaker 1: were just looking for like a word that implies that
33:34
Speaker 1: space is made up of little things that are kind
33:36
Speaker 1: of interconnected or overlapping, right, or like hooked together. M
33:41
Speaker 1: m okay. And so you went with them loops. I
33:44
Speaker 1: was like loops. They went with loops. I think it's
33:48
Speaker 1: not a terrible idea, you know, they could have called
33:50
Speaker 1: it the bubble quantum gravity, but hear it. But you know,
33:56
Speaker 1: we talked about this another time in the podcast. You
33:58
Speaker 1: can think of these things as little bubbles, and then
34:00
Speaker 1: you get to talk about things like space foam and
34:02
Speaker 1: quantum foam because these loops aren't fixed, right, they can
34:05
Speaker 1: like fluctuate in and out of existence. I see. So
34:08
Speaker 1: these are all related ideas loop quantum gravity, space foam,
34:12
Speaker 1: quantum foam. They're all sort of coming at this idea
34:16
Speaker 1: of a bubbly space and thinking about space not as
34:20
Speaker 1: continuous and smooth but made up of little quantized bits,
34:23
Speaker 1: like let's quantize space itself because general relativity is an
34:27
Speaker 1: attempt to understand gravity in terms of the nature of space.
34:31
Speaker 1: And so if we're gonna get a quantum theory of gravity,
34:33
Speaker 1: the idea is, let's let's just quantize space itself, all right.
34:36
Speaker 1: So that's quantum loop or loop quantum gravity, and so
34:40
Speaker 1: we'll get into what are some of the open questions
34:43
Speaker 1: and why people think it may or may not be
34:45
Speaker 1: the ultimate answer to how the universe works. But first
34:49
Speaker 1: let's take a quick break. Okay, Daniel, what does it
35:04
Speaker 1: all mean? What does loop quantum gravity mean? If it's
35:08
Speaker 1: true or if it's not true, and why do we
35:11
Speaker 1: think it might not be true? All right, well here's
35:13
Speaker 1: the big letdown. Right, So, so far it seems like
35:16
Speaker 1: you're gonna break the loop. I'm gonna break the loop. Yeah.
35:18
Speaker 1: It seems like a beautiful idea. It seems really promising.
35:21
Speaker 1: It seems like dot dot dot the next obvious step
35:24
Speaker 1: in physics. Right. The problem is there's a lot of
35:27
Speaker 1: problems with it, and there's a lot of open questions.
35:29
Speaker 1: And that doesn't mean it's not gonna work. It just
35:31
Speaker 1: means it's far from clear that it is going to work. Well,
35:35
Speaker 1: I see, there's a room for us skepticism. Yeah, and
35:38
Speaker 1: even among physicists there's a lot of skepticism about loop
35:41
Speaker 1: quantum gravity. It's a bit of a fringe theory. There
35:44
Speaker 1: are a lot more people working, for example, on string theory,
35:47
Speaker 1: which is a completely different attempt to unify gravity and
35:51
Speaker 1: quantum mechanics and all of the other forces all at once.
35:54
Speaker 1: String theories like a theory of everything, where loop quantum
35:57
Speaker 1: gravity is like, let's just focus on make in gravity
36:00
Speaker 1: of quantum theory. If you can do that, then that's
36:03
Speaker 1: another way to unify these two big theories. Yeah, the
36:06
Speaker 1: string theory is sort of a The other idea is
36:09
Speaker 1: that the opponent of Looke quantum gravity, let's build a
36:13
Speaker 1: tunnel under the Atlantic instead of trying to make these
36:15
Speaker 1: two bridges work. And the string theory is a much
36:18
Speaker 1: bigger community, has a lot more people working on it,
36:21
Speaker 1: people are sort of more excited about it, whereas Looke
36:23
Speaker 1: quantum gravity is like, you know, the younger sibling in
36:26
Speaker 1: terms of theories of quantum the underdog exactly making me
36:30
Speaker 1: like it more now, And one reason is that it
36:34
Speaker 1: sort of hasn't yet delivered on its promise. Like, what
36:37
Speaker 1: you want to do is start from this concept of
36:39
Speaker 1: loops and from it should emerge Einstein's theory of relativity.
36:44
Speaker 1: You should be like, I'm gonna have a completely different
36:46
Speaker 1: picture of the world, but it's going to give the
36:48
Speaker 1: same predictions sort of at my scale. I should still
36:51
Speaker 1: describe how a ball flies over my neighbor's wall, and
36:56
Speaker 1: how and gravitational waves and all of that stuff. You
36:58
Speaker 1: should be able to sort of are from there and
37:00
Speaker 1: build up to general relativity. You start off imagining the
37:03
Speaker 1: world the universe is a mesh of of loops, but
37:07
Speaker 1: it doesn't give you baseballs and fences. Yeah, not yet.
37:11
Speaker 1: And it's not like they can't do it. It's just like,
37:13
Speaker 1: well they haven't quite figured it out yet, and it's hard,
37:17
Speaker 1: right this is are difficult things, and people are hacking
37:20
Speaker 1: with their machetes through the jungle of mathematics that's involved,
37:24
Speaker 1: and it's not always clear that we have the right tools,
37:26
Speaker 1: and sometimes progress is paused for like a decade or
37:29
Speaker 1: thirty years until somebody's like, hey, we've heard this new
37:32
Speaker 1: idea from mathematics. Turns out that's exactly what we need
37:35
Speaker 1: over here. That kind of thing has happened in physics
37:37
Speaker 1: at a lot of times. And there are other sort
37:39
Speaker 1: of really interesting problems with loop quantum gravity, which actually
37:43
Speaker 1: conflict with relativity. Okay, so there's maybe something fundamentally wrong here,
37:47
Speaker 1: you know, or not necessarily wrong, but it would again
37:50
Speaker 1: change the way we think about the universe. Like, here's
37:52
Speaker 1: the problem with quantizing space. Says there are space pixels, right,
37:57
Speaker 1: that means that in some sense there's a minimum distance
38:00
Speaker 1: to the universe. But what is that distance? Because we
38:04
Speaker 1: know that distances depend on velocities, right, Like as you
38:08
Speaker 1: move faster, things get shrunk, so do things that are
38:12
Speaker 1: moving see smaller space pixels than things that are stationary,
38:16
Speaker 1: And if so, it would mean that there is some
38:19
Speaker 1: sort of absolute velocity to the universe. Right, if you
38:22
Speaker 1: can measure your space pixel the size of your space pixels,
38:26
Speaker 1: that tells you sort of what your absolute speed is.
38:28
Speaker 1: But special relativity has always told us velocity is relative.
38:32
Speaker 1: There is no absolute frame, and so this is sort
38:35
Speaker 1: of conflict with a really really core concept and special relativity.
38:40
Speaker 1: Couldn't it be like the speed of light, which like
38:42
Speaker 1: it always looks the same no matter how fast you're going.
38:45
Speaker 1: Couldn't these loops always look the same no matter how
38:47
Speaker 1: fast you're going. Yeah, So there's a lot of ways
38:50
Speaker 1: to try to solve this problem. One is to say,
38:52
Speaker 1: you know, we have these weird space pixels which to
38:55
Speaker 1: form under certain circumstances, and there's some very complicated mathematics
38:59
Speaker 1: involved to do essentially what you just described. You're really
39:02
Speaker 1: hidden out of the park today with like going for
39:05
Speaker 1: the hat track here, wait wait till you see why
39:08
Speaker 1: what I pull out at the last five minutes. And
39:11
Speaker 1: the other is to accept it and to say, you
39:13
Speaker 1: know what, maybe there is maybe there is an absolute
39:16
Speaker 1: reference frame. Maybe special relativity is slightly wrong, But wouldn't
39:20
Speaker 1: that throw the whole light speed thing off. Well, not
39:25
Speaker 1: all of special relativity has to be wrong. The consequence
39:27
Speaker 1: would be that light would travel at a slightly different
39:31
Speaker 1: speed as a function of its frequency. So like high
39:35
Speaker 1: frequency light would travel that is slightly different speed from
39:38
Speaker 1: lower frequency light like X rays and UV light would
39:41
Speaker 1: move faster than radio waves. But it'd be a really
39:46
Speaker 1: small difference to be really hard to tell, all right,
39:49
Speaker 1: So there's some skepticism or I guess some open questions
39:52
Speaker 1: about it, because it's not quite hitting it out of
39:54
Speaker 1: the ballpark, over your fence or not into your neighbors
39:59
Speaker 1: house or not um And so I guess the question
40:02
Speaker 1: is what does it all mean? I mean, what if
40:04
Speaker 1: it happens to be true? And how are we even
40:07
Speaker 1: going to know of something like this is true? Yeah,
40:09
Speaker 1: so of course the deep question I have is what
40:13
Speaker 1: does this mean for the nature of the universe? And
40:15
Speaker 1: how could we see it? Right? Where would it manifest itself?
40:18
Speaker 1: And as we talked about at the beginning of the episode,
40:21
Speaker 1: the place this would really be important, the place you
40:23
Speaker 1: would notice at difference, the place where it matters is
40:26
Speaker 1: inside a black hole of course, of course, right, so
40:29
Speaker 1: let's go there, Let's go into the closet there. That's right,
40:33
Speaker 1: we're opening the closet and all who knows what's in
40:37
Speaker 1: there and who knows what's been growing? And so I
40:40
Speaker 1: asked Bianca the professor, because she thinks about this stuff, right,
40:44
Speaker 1: she thinks about what happens inside black holes when gravity
40:46
Speaker 1: gets really strong and space gets twisty. And I asked her, like,
40:50
Speaker 1: what is your mental image of inside a black hole?
40:53
Speaker 1: Because I want to know, right, I mean, there's a
40:55
Speaker 1: black hole in her mind at least, and I want
40:56
Speaker 1: to know what does it look like inside her mind?
41:00
Speaker 1: Effects will be only important very near the singularity. There,
41:05
Speaker 1: the space and coviatures really getting very large. And maybe
41:09
Speaker 1: I'd like to think that there's a new universe which
41:13
Speaker 1: opens up with each singularity, which gives us much more
41:17
Speaker 1: universes than we know of. Yeah, she went there, she
41:20
Speaker 1: went for there are new universes inside black holes. I
41:24
Speaker 1: love it. There's a new universe in my closet. I
41:27
Speaker 1: would believe that. And inside that closet there are other
41:31
Speaker 1: closets with other closets inside them, I meaning meaning that's
41:35
Speaker 1: kind of a consequence of quantum blue gravity is that
41:38
Speaker 1: when you get to these extreme singularities, these loops kind
41:41
Speaker 1: of what like open up or you know, become their
41:44
Speaker 1: own little universes. Is that the idea, I will not
41:47
Speaker 1: pretend to even understand what that means, because there's some
41:52
Speaker 1: crazy consequences that like, if there's a universe inside every
41:55
Speaker 1: black hole, is our universe inside a black hole? You know,
42:00
Speaker 1: maybe who knows? It's crazy stuff? Yes, is your answer.
42:04
Speaker 1: I go with the s and that's my third Nobel
42:06
Speaker 1: Prize claim. Or is that the conclusion to your pitch
42:11
Speaker 1: or your loop quantum gravity sitcom episode there Echo at
42:16
Speaker 1: the end of season twenty, it turns out they're all
42:19
Speaker 1: in a black hole. That's right, And you know, we
42:22
Speaker 1: might be able to figure this out in ways other
42:24
Speaker 1: than going to a black hole. We actually do have
42:27
Speaker 1: ideas for how you could test this, and they revolve
42:29
Speaker 1: around seeing whether we can tell the difference in the
42:32
Speaker 1: speed of light from high frequency and low frequency light.
42:35
Speaker 1: The speed of light changes, which we didn't think it did,
42:39
Speaker 1: but if it changes with frequency, then that's an indication
42:42
Speaker 1: maybe there's something loopy going on. Yeah, maybe there's something
42:45
Speaker 1: loopy going on, And this would be a really small effect.
42:48
Speaker 1: So what you need to do is like have a
42:50
Speaker 1: race between photons of different frequencies high frequency versus low frequency,
42:54
Speaker 1: and the race would have to be super long because
42:57
Speaker 1: light goes super past of course, and it's different is
43:00
Speaker 1: really small. And so what they do is they look
43:02
Speaker 1: for light sources that are really really far away and
43:06
Speaker 1: then try to measure see if there's a difference in
43:08
Speaker 1: like the arrival time of photons. Would you would I
43:11
Speaker 1: need to know where they're coming from, right, Yeah, So
43:14
Speaker 1: we have these sources which are variable, like quasars and
43:16
Speaker 1: pulsars that are really far away. You know, they pulse,
43:19
Speaker 1: and so you can sort of line the two up
43:21
Speaker 1: and say, well, we know these two were emitted at
43:23
Speaker 1: the same moment because they are the top of the
43:25
Speaker 1: pulse at the same time or something. And then you
43:27
Speaker 1: can say, well, did they arrive in sync or are
43:29
Speaker 1: they sort of out of sync? And so there's a
43:31
Speaker 1: satellite which looked out and measured this and looked for this.
43:35
Speaker 1: What did they find, Well, this is the integral satellite.
43:38
Speaker 1: And that's some tortured acronym for I don't even know
43:40
Speaker 1: what is it. Really, It's called integral up and what
43:44
Speaker 1: they found they didn't see anything, right, They didn't see
43:46
Speaker 1: any difference in the arrival times. I didn't see any loops.
43:50
Speaker 1: And they were able to say that if there are loops,
43:52
Speaker 1: they're smaller than ten to the minus forty eight meters.
43:57
Speaker 1: What they can do that, that's by looking at two photons. Yeah,
44:03
Speaker 1: by looking at these photons, because the photons come from
44:05
Speaker 1: really really far away, and so the differences would be
44:08
Speaker 1: added up across the universe. And they claim they should
44:11
Speaker 1: have seen them. They saw that they were in sync.
44:14
Speaker 1: They were in sync. Yeah, and this is thirteen orders
44:17
Speaker 1: of magnitudes smaller than what we think the size of
44:20
Speaker 1: the loops are. So like that seems pretty definitive. Yeah,
44:24
Speaker 1: but what did the loop quantum gravity folks say, Well,
44:26
Speaker 1: you know, there's only one branch of loop quantum gravity.
44:29
Speaker 1: The people who say that maybe that's that special relativity
44:32
Speaker 1: needs to be tweaked. Other people have solutions, as you say,
44:36
Speaker 1: to make light travel the same speed no matter what,
44:39
Speaker 1: by having you know, crazy deformations these things, and all
44:41
Speaker 1: sorts of complicated interactions between light and space, and so
44:45
Speaker 1: it just sort of rules out one branch of loop
44:48
Speaker 1: quantum gravity. You can never kill these theories. Man, They're
44:50
Speaker 1: like weeds. They always there's another version that crops up there,
44:54
Speaker 1: like exide one head of But they're fascinating, you know.
45:00
Speaker 1: Each one is a wonderful exploration and sort of the
45:02
Speaker 1: intellectual space of like how could the universe work? What
45:06
Speaker 1: possible universes might we live in? And the amazing thing
45:10
Speaker 1: is that there is an answer, right, there is one
45:12
Speaker 1: way that the universe actually works. And what's kind of
45:16
Speaker 1: interesting I think is that it wouldn't affect your everyday life,
45:20
Speaker 1: like things would still work the same way. But who
45:22
Speaker 1: knows what's going on down at the fundamental level? Right,
45:24
Speaker 1: it could be one of these crazy theoretical ideas. Yeah,
45:29
Speaker 1: and it's important now to scientists, but it might eventually
45:31
Speaker 1: be important to engineers. You know, knowledge that seems impractical
45:35
Speaker 1: and useless but reveals the fundamental nature of reality could
45:39
Speaker 1: eventually be useful and hate to me, that's fun anyway.
45:42
Speaker 1: I don't really care if it's useful. I just gotta know, right, Yeah,
45:46
Speaker 1: I mean I think that's how micro rays were invented,
45:48
Speaker 1: actually by accident, by looking at something else. And where
45:52
Speaker 1: would we be? Where would burritas be these days? That's right.
45:55
Speaker 1: And you know, there have been actually fascinating advances in
45:58
Speaker 1: microwave and the technology the engineer ring of microwaves. And
46:01
Speaker 1: I guess, you know, if you can unlock kind of
46:03
Speaker 1: the magic and the power that's happening at that microscopic level,
46:07
Speaker 1: who knows what you could do, right, what kind of
46:09
Speaker 1: energies you can get, or what kinds of warp drives
46:13
Speaker 1: or microwave ovens. Yeah, microwave toaster opens powered by artificial intelligence. Yeah,
46:20
Speaker 1: And so I have to give a shout out to Nico.
46:22
Speaker 1: He's one of our listeners and he heard our episode
46:25
Speaker 1: about microwave ovens actually, and he wrote to me and
46:28
Speaker 1: told me that they have a new fancier AI powered
46:31
Speaker 1: microwave oven um which can heat stuff up at different
46:35
Speaker 1: temperatures and monitor to make sure the heating is all
46:38
Speaker 1: smooth and fancy, and actually dropped by my house and
46:40
Speaker 1: delivered one of these prototypes, which has been a lot
46:43
Speaker 1: of fun. That's amazing that you let one of your
46:46
Speaker 1: listeners into your house. Hey, he was offering a brand
46:49
Speaker 1: new appliance, so I thought. And while he was there,
46:51
Speaker 1: I asked him about Luke quantum gravity, but he didn't
46:53
Speaker 1: have any ideas. Oh man, there's no setting on that
46:56
Speaker 1: in the microwave, not yet. Um. The next in the
47:00
Speaker 1: prototype will be quantum gravity powered, I'm sure. All right, Well,
47:03
Speaker 1: it sounds like the answer is stay tuned. You know,
47:06
Speaker 1: that's what we explain, what Luke. Quantum gravity is and
47:09
Speaker 1: who knows, and maybe it is the way that the
47:11
Speaker 1: universe works at that level, and we may find out
47:14
Speaker 1: in the near future. That's right, And these are the
47:17
Speaker 1: kinds of mysteries that are going to help us figure
47:20
Speaker 1: out the deep nature of the universe. You know. It's
47:22
Speaker 1: when things break that we have an opportunity to figure
47:24
Speaker 1: out how things should work. And so it's exciting to
47:27
Speaker 1: have these kind of problems. It's exciting to know sort
47:30
Speaker 1: of where to work, even if we don't know what
47:32
Speaker 1: the answer should look like. All right, well, we hope
47:34
Speaker 1: you enjoyed that. Daniel. How much this podcast costs me
47:37
Speaker 1: in terms of your physics time? One loop one? Let's
47:42
Speaker 1: tend to the minus thirty five dollars, My tend to
47:45
Speaker 1: the minus thirty one plank dollar? Yeah, pick up plank dollar.
47:49
Speaker 1: Oh good, I gotta I got a couple here in
47:51
Speaker 1: my pocket. Okay. Quantum of the mover to me all right.
47:54
Speaker 1: We hope you enjoyed that. Thanks for joining us, and
47:57
Speaker 1: as usual, thank you to everybody who wrote in with
47:59
Speaker 1: your questions. See you next time. Before you still have
48:09
Speaker 1: a question after listening to all these explanations, please drop
48:13
Speaker 1: us the line. We'd love to hear from you. You
48:15
Speaker 1: can find us on Facebook, Twitter, and Instagram at Daniel
48:18
Speaker 1: and Jorge That's one Word, or email us at Feedback
48:22
Speaker 1: at Daniel and Jorge dot com. Thanks for listening and
48:25
Speaker 1: remember that Daniel and Jorge Explain the Universe is a
48:28
Speaker 1: production of I Heart Radio. For more podcast from my
48:31
Speaker 1: Heart Radio, visit the i Heart Radio, a Apple Podcasts,
48:35
Speaker 1: or wherever you listen to your favorite shows.