Latest / Daniel and Kelly’s Extraordinary Universe / What is membrane theory?

Transcript

What is membrane theory? · Daniel and Kelly’s Extraordinary Universe

• 0:07
  Speaker 1: Hey, Daniel, have you guys figured out what's inside a
• 0:10
  Speaker 1: black hole? Yet?
• 0:12
  Speaker 2: Unfortunately not? Still pretty confused.
• 0:14
  Speaker 1: Okay, it sounds like you guys need to go back
• 0:17
  Speaker 1: to the drawing board get some new ideas.
• 0:20
  Speaker 2: I know, but like from where the smartest people on
• 0:23
  Speaker 2: the planet have been stuck in this question for literally decades.
• 0:26
  Speaker 1: See that is where you are going wrong. You are
• 0:29
  Speaker 1: looking to the smart people. If you need wacky, crazy ideas,
• 0:34
  Speaker 1: you need to ask the wacky crazy people like me.
• 0:39
  Speaker 2: You're saying we should go to the insane asylum and
• 0:41
  Speaker 2: ask people what they think is inside a black hole.
• 0:43
  Speaker 1: I think that they could come up with some good ideas.
• 0:46
  Speaker 1: They might be insane enough in the membrane to figure
• 0:48
  Speaker 1: it out.
• 0:51
  Speaker 2: Insane in the brain. Hi, I'm Daniel. I'm a particle
• 1:09
  Speaker 2: physicist and a professor at UC Irvine. And if you
• 1:12
  Speaker 2: didn't get my Cypress Hill reference, you're officially young.
• 1:16
  Speaker 1: I am Katie. I am not a physicist. I like animals, though,
• 1:22
  Speaker 1: and I like the universe. And I got that reference.
• 1:26
  Speaker 2: Because you're insane in the membrane.
• 1:28
  Speaker 1: Exactly, just the membrane, though the rest of me is perfectly.
• 1:32
  Speaker 2: Sane and welcome to the podcast Daniel and Jorge Explain
• 1:37
  Speaker 2: the Universe, in which we do our best to bring
• 1:40
  Speaker 2: this insane universe into your brain. We try to make
• 1:44
  Speaker 2: it all make sense, from the tiniest little quantum particles
• 1:47
  Speaker 2: to the hugest swirling accretion disks surrounding super massive black holes.
• 1:52
  Speaker 2: We have this hunch that maybe the universe is understandable,
• 1:57
  Speaker 2: that it's a big mathematical puzzle that we can of
• 2:00
  Speaker 2: eventually figure it out if we put all of our
• 2:02
  Speaker 2: brains and membranes together. And our goal on this podcast
• 2:06
  Speaker 2: is to explain all of it to you.
• 2:08
  Speaker 1: Now, that's another song, super Massive black Hole. I think
• 2:12
  Speaker 1: muse soundtrack to that really sort of indie movie called Twilight.
• 2:19
  Speaker 2: Are you sure that wasn't part of the hip hop
• 2:21
  Speaker 2: wars in the nineties, super Massive black Hole?
• 2:24
  Speaker 1: I couldn't say. In the nineties, I was not cool
• 2:28
  Speaker 1: enough to know.
• 2:29
  Speaker 2: Well, you know, maybe there are some secrets in music
• 2:32
  Speaker 2: that can help us crack the mysteries of the universe,
• 2:35
  Speaker 2: because you know, some people say the universe is musical
• 2:38
  Speaker 2: and there's a connection between music and mathematics, right, So
• 2:41
  Speaker 2: maybe we have been looking in the wrong places.
• 2:44
  Speaker 1: Yeah, Like I've heard this in terms of string theory,
• 2:47
  Speaker 1: where strings aren't you know, they're not like violin strings,
• 2:50
  Speaker 1: But it's something about some like either vibration or pattern. Honestly,
• 2:56
  Speaker 1: I do not understand it, but you know, well, I
• 3:00
  Speaker 1: think that is interesting that there is the idea that
• 3:04
  Speaker 1: a lot of the mysteries of the universe could be
• 3:07
  Speaker 1: about certain frequencies or patterns, which is also what is
• 3:12
  Speaker 1: the major components of music.
• 3:16
  Speaker 2: Exactly, Although if you listen to Terrence Howard on Joe Rogan,
• 3:19
  Speaker 2: it's all frequencies.
• 3:20
  Speaker 1: Man, is all frequencies?
• 3:22
  Speaker 2: Man?
• 3:22
  Speaker 1: Why am I not on Joe Rogan? See, I just
• 3:25
  Speaker 1: can say that too.
• 3:27
  Speaker 2: I can because you believe that one times one equals one,
• 3:30
  Speaker 2: and Terrence Howard proves that it equals to And that's
• 3:34
  Speaker 2: why you're just not mathematically qualified to be.
• 3:38
  Speaker 1: I just can't think outside of the box enough to
• 3:40
  Speaker 1: not do mauth good exactly.
• 3:43
  Speaker 2: But we are fascinated by the mysteries of the universe.
• 3:46
  Speaker 2: We do think that there are mathematical solutions to them.
• 3:49
  Speaker 2: Maybe they are encoded in the sonatas of Mozart. Maybe
• 3:52
  Speaker 2: the engineers are right that it's all vibrations all the
• 3:55
  Speaker 2: way down. But we hope that there is an explanation.
• 3:59
  Speaker 2: And one of the biggest things and we need an
• 4:00
  Speaker 2: explanation for is how to think about the universe on
• 4:03
  Speaker 2: the smallest scales. What happens when things get really, really
• 4:07
  Speaker 2: dense and really really tiny. One of the biggest puzzles
• 4:10
  Speaker 2: in modern physics is how to put together the two
• 4:13
  Speaker 2: pillars of our understanding of the universe, relativity and quantum mechanics.
• 4:18
  Speaker 2: We've been banging our heads against this for almost one
• 4:20
  Speaker 2: hundred years, basically since we've had relativity and quantum mechanics
• 4:25
  Speaker 2: and realize that they are fundamentally incompatible at the smallest scale.
• 4:30
  Speaker 2: And we've been trying to figure this out. And today
• 4:31
  Speaker 2: on the podcast, we'll be exploring yet another attempt to
• 4:35
  Speaker 2: unify relativity and quantum mechanics. So on the podcast today
• 4:40
  Speaker 2: we'll be answering the question what is membrane theory?
• 4:49
  Speaker 1: Okay, as a biology nerd, I'm pretty sure I can
• 4:53
  Speaker 1: answer this. A membrane is a semi permeable barrier, So
• 5:00
  Speaker 1: I solved it. Congratulations to me.
• 5:04
  Speaker 2: What about the audio barrier between us and the listeners
• 5:07
  Speaker 2: the ideas from our brains and that their brains have
• 5:10
  Speaker 2: we permeated a membrane.
• 5:12
  Speaker 1: I yes, why not. I don't know enough about audio
• 5:17
  Speaker 1: engineering to say no or philosophy, so I'm gonna say yes.
• 5:21
  Speaker 1: We're like salt ions through the airwaves, permeating the membrane,
• 5:27
  Speaker 1: so hopefully you can reach homeostasis.
• 5:32
  Speaker 2: So I'm not surprised that when you heard this phrase
• 5:34
  Speaker 2: you thought of cellular membranes divisions between solutions. You want
• 5:39
  Speaker 2: to keep osmosis from, like moving all these bits of
• 5:41
  Speaker 2: salt over here, or using fats to keep that over there.
• 5:45
  Speaker 2: But it's not just in biology that we have membranes.
• 5:48
  Speaker 2: It turns out that they are fundamental concept in theories
• 5:52
  Speaker 2: of quantum gravity. But before we dig into that, I
• 5:55
  Speaker 2: was curious what everybody else out there thought when they
• 5:58
  Speaker 2: heard membrane theory. As usual, I asked our cadre of
• 6:02
  Speaker 2: volunteers to speculate on the question without the opportunity to
• 6:06
  Speaker 2: use Google. So, if you would like to join this
• 6:09
  Speaker 2: group of volunteers in the future, please don't be shy.
• 6:11
  Speaker 2: Write me to questions at Danielandjorge dot com. We all
• 6:15
  Speaker 2: want to hear what you have to say. In the meantime,
• 6:19
  Speaker 2: check out these answers from listeners. What do you think
• 6:22
  Speaker 2: membrane theory is here's what people had to say. That's
• 6:26
  Speaker 2: the first time I'm hearing golfit.
• 6:27
  Speaker 3: But if I had to guess membranes, the function of
• 6:30
  Speaker 3: the membranes are to pass on stuff in one direction
• 6:34
  Speaker 3: and other stuff not in the other direction. So maybe
• 6:37
  Speaker 3: we're talking about it's a mechanism about particle coexistence through
• 6:43
  Speaker 3: a wall of things something like that.
• 6:45
  Speaker 4: Just to guess, what comes to mind for me on
• 6:47
  Speaker 4: that one is that it's something that you use to
• 6:50
  Speaker 4: separate things, like in a fuel cell car, you know,
• 6:52
  Speaker 4: you separate components and you make energy. Maybe it's like
• 6:55
  Speaker 4: a desalination thing where you take salt.
• 6:57
  Speaker 2: Out of water.
• 6:58
  Speaker 4: So maybe there's some membrane here in the universe that's doing.
• 7:01
  Speaker 2: That in space.
• 7:03
  Speaker 5: I'm guessing membrane theory has to do with the outside
• 7:07
  Speaker 5: of a cell. Maybe how the membrane, you know, protects
• 7:12
  Speaker 5: the core of the cell and how it stays intact.
• 7:16
  Speaker 2: I think it has to do with string theory. There
• 7:18
  Speaker 2: are strings that vibrate in there one dimension, and I
• 7:20
  Speaker 2: think a membrane is a something similar that can have
• 7:25
  Speaker 2: more than one dimension.
• 7:26
  Speaker 1: See, I'm I'm definitely with the theory that everything is
• 7:32
  Speaker 1: a cell. If you look at the universe, it's just
• 7:35
  Speaker 1: a giant body for some kind of huge animal. You know,
• 7:40
  Speaker 1: it makes sense, right, you're saying the universe is alive. Yeah,
• 7:44
  Speaker 1: it's a big maybe a giant cat. I don't know.
• 7:47
  Speaker 1: Have you ever looked at like a black cat? Right,
• 7:51
  Speaker 1: It's it kind of has that sort of quantum mechanics
• 7:55
  Speaker 1: and general relativity paradox. Right, it's like a fluid, it's
• 7:59
  Speaker 1: a solid. It's sweet and loving, and then it bites you.
• 8:03
  Speaker 1: So yeah, I think the universe could be a giant cat.
• 8:06
  Speaker 1: And when you get down to the tiniest components there cells,
• 8:09
  Speaker 1: and yeah, it's been solved.
• 8:11
  Speaker 2: You're welcome and we're done, Thank you very much. Physics
• 8:15
  Speaker 2: is over. Katie wins all of the Nobel prices. Heay, Well,
• 8:19
  Speaker 2: we're definitely hearing from listeners the connection to biology, which
• 8:22
  Speaker 2: makes a lot of sense, and the idea of having
• 8:25
  Speaker 2: two dimensional surfaces or even connections to string theory. So
• 8:30
  Speaker 2: there's a lot of good stuff in here that we're
• 8:31
  Speaker 2: going to dig into and explain in this episode. But
• 8:35
  Speaker 2: a plus to all the listeners.
• 8:37
  Speaker 1: I mean, I would assume that, yes, it's probably not
• 8:40
  Speaker 1: like a cellular membrane. But if we're talking about a membrane,
• 8:44
  Speaker 1: I would guess it is some kind of barrier through
• 8:49
  Speaker 1: which certain physics transactions can occur. But that would be
• 8:54
  Speaker 1: my guess.
• 8:56
  Speaker 2: Is this whole podcast a physics transaction? We are taking
• 8:59
  Speaker 2: your time and exchanging it for knowledge, is like a
• 9:02
  Speaker 2: physics transaction.
• 9:03
  Speaker 1: You know what? That's pretty good. I think I'm wondering
• 9:06
  Speaker 1: about the exchange rate, though, because that's that's the real issue.
• 9:10
  Speaker 2: Yeah, I think we're too high on the jokes permit
• 9:12
  Speaker 2: it and too low and the physics permitted so far.
• 9:14
  Speaker 2: Let's try to flip that right now.
• 9:16
  Speaker 1: All right, well, okay, let me have it. Like, what's
• 9:19
  Speaker 1: going on with this membrane theory?
• 9:21
  Speaker 2: So membrane theory is an attempt to crack the puzzle
• 9:23
  Speaker 2: of quantum gravity. So let's start with that. What is
• 9:26
  Speaker 2: the puzzle of quantum gravity? Why do we want to
• 9:29
  Speaker 2: crack it? What is the issue? Why are all the
• 9:31
  Speaker 2: smart people on the planet thinking they need to go
• 9:33
  Speaker 2: into the insane this islum if they can't figure this out?
• 9:36
  Speaker 2: The basic issue is we have two ways to describe
• 9:38
  Speaker 2: the universe. There's general relativity, which tells us about space
• 9:42
  Speaker 2: and time and energy, and the expansion of the universe
• 9:46
  Speaker 2: describes a lot of the big stuff. It tells us
• 9:48
  Speaker 2: how gravity works and how the universe is expanding, and
• 9:52
  Speaker 2: how far away galaxies are getting red shifted and all
• 9:54
  Speaker 2: that good stuff. And then we have quantum mechanics, which
• 9:57
  Speaker 2: describes the really small stuff, the little part of goals
• 10:00
  Speaker 2: light and all this kind of quantum fields and sort
• 10:03
  Speaker 2: of our understanding of microscopic matter. And the issue is
• 10:07
  Speaker 2: that we don't know how to make these two things
• 10:09
  Speaker 2: play well together.
• 10:11
  Speaker 1: They don't play nice because I've actually, i think I've
• 10:15
  Speaker 1: been on the show a couple times when we talked
• 10:17
  Speaker 1: about this conundrum, and so it seems like, you know,
• 10:21
  Speaker 1: when you have these mathematical theories that describe each of them,
• 10:24
  Speaker 1: it works within it. So the general relativity math works
• 10:28
  Speaker 1: within general relativity. It seems really nice and neat and good.
• 10:32
  Speaker 1: Same thing for quantum mechanics. But then when you try
• 10:35
  Speaker 1: to cross the beams the math beams, suddenly it doesn't work.
• 10:40
  Speaker 1: Like if you're trying to use general relativity math to
• 10:43
  Speaker 1: describe what you know is observed in experiments happening on
• 10:48
  Speaker 1: sort of the quantum level, or vice versa. It no
• 10:50
  Speaker 1: longer works. Is that more or less?
• 10:53
  Speaker 2: Yeah? I love crossing the math beams. That's awesome. I
• 10:55
  Speaker 2: want a t shirt that says I'm crossing the math beams.
• 10:58
  Speaker 2: But yeah, that's basic the idea. And remember that what
• 11:01
  Speaker 2: we're doing in physics is trying to build a mental
• 11:04
  Speaker 2: model that describes the universe easy. Those mental models are
• 11:09
  Speaker 2: always imperfect. They're always incomplete, they're always simplifications. Even if
• 11:14
  Speaker 2: you're talking about like the flight of a baseball, right,
• 11:17
  Speaker 2: how does a baseball fly across the field? Well, I'm
• 11:19
  Speaker 2: going to use a parabola in Newton's equations, but I
• 11:22
  Speaker 2: can't do the calculation very easily. I have had to
• 11:24
  Speaker 2: include air resistance, so I decide I'm not including that
• 11:27
  Speaker 2: because it's probably not important, and really, to answer my
• 11:30
  Speaker 2: question of whether the guy's going to catch it, air
• 11:32
  Speaker 2: resistance doesn't matter. I'm not going to include effects of
• 11:34
  Speaker 2: humidity and the siazillion things I could include in my
• 11:37
  Speaker 2: model to make it a very accurate description of the
• 11:40
  Speaker 2: universe that I don't need to to answer my question.
• 11:43
  Speaker 2: And so the models that we build to answer questions
• 11:45
  Speaker 2: about the universe are always incomplete, they are always approximations,
• 11:49
  Speaker 2: but they're still very very useful. And that's the issue
• 11:52
  Speaker 2: with quantum mechanics and general relativity is that they are
• 11:54
  Speaker 2: two different approximate descriptions of the universe that make different approximations,
• 11:59
  Speaker 2: different foundations assumptions that go into building those models that
• 12:03
  Speaker 2: are incompatible, and they let us describe different parts of
• 12:06
  Speaker 2: the universe, as you say, very very well. So if
• 12:08
  Speaker 2: I want to talk about how two electrons scatter off
• 12:11
  Speaker 2: of each other, I can use quantum mechanics and talk
• 12:13
  Speaker 2: about how they interact and the virtual particles they exchange
• 12:16
  Speaker 2: or the fields that ripple between them, and it all
• 12:18
  Speaker 2: works out amazingly well. And that can ignore what general
• 12:21
  Speaker 2: relativity would do in that situation because it's irrelevant. It's
• 12:24
  Speaker 2: like the wind resistance or the humidity on the baseball.
• 12:27
  Speaker 2: It doesn't affect the calculations, so I can ignore it.
• 12:30
  Speaker 2: Or if I want to say, hey, how do galaxies
• 12:32
  Speaker 2: form and how do they swirl around each other? I
• 12:35
  Speaker 2: can use general relativity to answer those questions, and that
• 12:38
  Speaker 2: can ignore the quantum effects because who cares what one
• 12:42
  Speaker 2: electron does in Andromeda doesn't affect whether our galaxy is
• 12:46
  Speaker 2: going to crash into that galaxy, general relativity dominates. The
• 12:50
  Speaker 2: amazing thing is that in every situation in our universe
• 12:53
  Speaker 2: you can use either quantum mechanics to explain it or
• 12:57
  Speaker 2: general relativity and ignore the other one. A perfect divorced
• 13:00
  Speaker 2: couple that have separated their lives and never have to interact.
• 13:03
  Speaker 2: You know, there are no argument at McDonald's about who's
• 13:06
  Speaker 2: taking the kid. Yeah, they're co parenting the universe. And
• 13:11
  Speaker 2: so you might think, all right, great, what's the problem,
• 13:14
  Speaker 2: right co parents can live in harmony without ever talking
• 13:16
  Speaker 2: to each other. Well, there's two problems. One is that's
• 13:20
  Speaker 2: really unsatisfying, right, Like, we want one explanation for the universe.
• 13:24
  Speaker 2: We don't want two different explanations. We don't want a
• 13:27
  Speaker 2: Russiaman universe where both parents tell very very different stories
• 13:31
  Speaker 2: about what's going on. Right.
• 13:34
  Speaker 1: I get that.
• 13:36
  Speaker 2: We think that there is one story about the universe.
• 13:39
  Speaker 2: There's something that's happening, and that there are rules that
• 13:41
  Speaker 2: are being followed, and we want to know what they are.
• 13:44
  Speaker 2: We want our best approximation of them. So it's deeply
• 13:47
  Speaker 2: unsatisfying to have two different, incompatible theories of the universe.
• 13:52
  Speaker 2: And also, there are moments in the universe a very
• 13:55
  Speaker 2: few places. In times when you can't ignore one ar
• 13:58
  Speaker 2: or the other, you need things like the heart of
• 14:01
  Speaker 2: a black hole a singularity. In general, relativity is incompatible
• 14:06
  Speaker 2: with quantum mechanics, which says you've got to have some
• 14:08
  Speaker 2: fuzziness or the Big Bang or the very early universe
• 14:12
  Speaker 2: when things were really, really hot and dense. You need
• 14:14
  Speaker 2: the rules of quantum mechanics to describe those particles. But
• 14:17
  Speaker 2: you can't ignore gravity because things are so hot and
• 14:20
  Speaker 2: so dense. So we desperately want to find a way
• 14:22
  Speaker 2: to bring these two together. But as you say, the
• 14:24
  Speaker 2: math beings don't cross, right.
• 14:27
  Speaker 1: I mean, it's like, as physicists you now kind of
• 14:30
  Speaker 1: have to play as a couple's therapist, where you have
• 14:34
  Speaker 1: these two theories that are essentially speaking different languages and
• 14:38
  Speaker 1: they cannot come to an agreement, and they can be
• 14:42
  Speaker 1: perfectly functional on their own, but then when they come together,
• 14:45
  Speaker 1: they are unable to communicate. And the Yeah, I mean,
• 14:50
  Speaker 1: it seems like resolving that difference between the two theories,
• 14:55
  Speaker 1: like resolving why they don't work with each other, would
• 14:58
  Speaker 1: actually reveal some big things that we just fundamentally have
• 15:04
  Speaker 1: not understood yet about the universe.
• 15:06
  Speaker 5: M M.
• 15:06
  Speaker 2: You know, I've heard anecdotally about couples that don't actually
• 15:09
  Speaker 2: speak the same language, you know, where they have like
• 15:11
  Speaker 2: literally now yet they've fallen in love. That's actually true,
• 15:17
  Speaker 2: they have some other love language.
• 15:18
  Speaker 1: Hi language interpretive there.
• 15:21
  Speaker 2: Love at first sight, right, doesn't love it first word?
• 15:24
  Speaker 1: Yeah.
• 15:24
  Speaker 2: Anyway, you're right that quantum mechanics in general relativity don't
• 15:27
  Speaker 2: get along, and one of the reasons is that they
• 15:29
  Speaker 2: are built on very different assumptions. Like general relativity says
• 15:32
  Speaker 2: the universe is smooth, it's continuous, it's precise, there's an
• 15:37
  Speaker 2: infinite number of locations. It says that you can divide
• 15:40
  Speaker 2: space an infinite number of times, like relativity agrees with
• 15:44
  Speaker 2: Zeno's paradox, right that between you and a candy store,
• 15:47
  Speaker 2: there's always a distance that you can cut in half.
• 15:50
  Speaker 2: Space from the point of view of general relativity is
• 15:52
  Speaker 2: something that's smooth and continuous and you always have a
• 15:55
  Speaker 2: very specific location, whereas quantum mechanics says not. Nothing is
• 15:59
  Speaker 2: actually smooth and continuous. There are not infinite number of
• 16:02
  Speaker 2: locations between any two points. Things are discrete and chunky.
• 16:06
  Speaker 2: A beam of light is actually made up of little
• 16:08
  Speaker 2: pieces of light, little packets of light. Everything in the
• 16:11
  Speaker 2: universe is discrete, and it's also imprecise. None of these
• 16:16
  Speaker 2: little packets have a precise location that have probabilities. So
• 16:20
  Speaker 2: you see the foundations of these two theories are very
• 16:22
  Speaker 2: very different. They start from two very different places, and
• 16:25
  Speaker 2: so weaving them together has a lot of challenges. People
• 16:29
  Speaker 2: have been trying to make theories of quantum gravity to say, hey,
• 16:33
  Speaker 2: let's take gravity and try to describe it in the
• 16:35
  Speaker 2: language of quantum mechanics. For example, think of it like
• 16:38
  Speaker 2: a quantum field that are exchanging virtual particles. They even
• 16:42
  Speaker 2: have a name for these particles, it would be the graviton.
• 16:44
  Speaker 2: But when you sit down and try to do those calculations,
• 16:47
  Speaker 2: gravity is different from the other quantum forces because it
• 16:50
  Speaker 2: couples to itself. Everything that has energy has gravity, and
• 16:53
  Speaker 2: so if you emit a graviton, it also feels gravity,
• 16:56
  Speaker 2: and it emits gravitons, which emit more gravitons. You can
• 17:00
  Speaker 2: infinite number of gravitons, and then you start to get
• 17:02
  Speaker 2: nonsense answers. So as you say, the math beams don't cross.
• 17:06
  Speaker 1: So in terms of gravitons, is that something that has
• 17:10
  Speaker 1: ever been able to be studying the same way that
• 17:13
  Speaker 1: you can study protons or is it just sort of
• 17:16
  Speaker 1: a byproduct of this seems like this could be a
• 17:19
  Speaker 1: thing based on the math that we have theorized about.
• 17:23
  Speaker 2: Yeah, gravitons are purely theoretical, and they're not even coherently theoretical.
• 17:28
  Speaker 2: Theories that have gravitons in them just don't work their
• 17:31
  Speaker 2: problems with them, and so it's not just that we
• 17:33
  Speaker 2: haven't seen them. We don't even understand how they would
• 17:36
  Speaker 2: work if they did exist. And there also would be
• 17:39
  Speaker 2: really really hard to spot, Like if you're thinking about
• 17:42
  Speaker 2: gravitational waves from rotating black holes, for example, those are
• 17:46
  Speaker 2: not gravitons. Those are ripples in space and time. They
• 17:50
  Speaker 2: are like a beam of light. Gravitons would be like
• 17:52
  Speaker 2: taking that beam of light and breaking it up into photons.
• 17:55
  Speaker 2: So you take that gravitational wave and now break it
• 17:57
  Speaker 2: up into tiny little gravitons. But even gravitational waves are
• 18:02
  Speaker 2: really hard to see. Gravitons would be much much tinier,
• 18:05
  Speaker 2: well beyond our capability. But also mathematically they just don't work.
• 18:09
  Speaker 2: If you try to do calculations with gravitons, you get
• 18:12
  Speaker 2: weird answers like what's the probability that this electron is
• 18:16
  Speaker 2: going to go left? Oh, one hundred and forty percent?
• 18:18
  Speaker 2: What that doesn't make any sense, right, And so that's
• 18:21
  Speaker 2: telling you that fundamentally there is a problem with the
• 18:23
  Speaker 2: mathematics that you need to go deeper and start from
• 18:26
  Speaker 2: something else, change one of your assumptions in order to
• 18:29
  Speaker 2: make a working theory of quantum gravity.
• 18:31
  Speaker 1: I mean this kind of reminds me in biology of
• 18:34
  Speaker 1: how like the history of biology and medicine, where we
• 18:37
  Speaker 1: would start to understand things like we would start to
• 18:40
  Speaker 1: understand how certain medications work, or you know, understand things like,
• 18:45
  Speaker 1: you know, a man and a woman make a baby
• 18:47
  Speaker 1: and the like, there seems to be these germinal cells responsible.
• 18:52
  Speaker 1: But then we didn't have the ability to get tiny
• 18:57
  Speaker 1: enough inside the human body where we couldn't see like proteins,
• 19:00
  Speaker 1: we couldn't see, you know, maybe we at some point
• 19:03
  Speaker 1: could see cells, but we couldn't see DNA. So there
• 19:07
  Speaker 1: were so many strange and interesting theories that kept circling
• 19:11
  Speaker 1: around trying to get closer and closer to the truth.
• 19:14
  Speaker 1: Like there were really funny ones like imagining that there's
• 19:17
  Speaker 1: just like a tiny person inside of a sperm cell
• 19:20
  Speaker 1: and then that grew into a baby. But essentially it's
• 19:24
  Speaker 1: like we were able to make scientific observations, but without
• 19:28
  Speaker 1: the ability to get small enough in terms of like
• 19:31
  Speaker 1: we didn't have electron microscopes, we didn't have the technology
• 19:34
  Speaker 1: or understanding to study DNA, these theories could not kind
• 19:38
  Speaker 1: of you know, interweave until we got to that point.
• 19:42
  Speaker 1: And that kind of seems like where, you know, sort
• 19:45
  Speaker 1: of like what's happening with the universe. Like we're able to,
• 19:49
  Speaker 1: you know, make all of these really interesting scientific observations
• 19:52
  Speaker 1: and they're not necessarily wrong, but there is some fundamental
• 19:56
  Speaker 1: aspect that it's not necessarily that it's too small to see,
• 20:00
  Speaker 1: but it's something that we can't see yet or something
• 20:03
  Speaker 1: that is really hard to observe that might help tie
• 20:06
  Speaker 1: these things together exactly.
• 20:09
  Speaker 2: And because it's a question mark, it's deeply unsatisfying to
• 20:13
  Speaker 2: not have figured it out. We suspect that when we
• 20:16
  Speaker 2: do figure it out, it'll be something new, something fascinating,
• 20:19
  Speaker 2: something that tells us about the basic nature of the universe.
• 20:23
  Speaker 2: Because it's telling us that Gr's description of the universe
• 20:26
  Speaker 2: is wrong. Space is not just some bendable manifold and
• 20:29
  Speaker 2: the quantum mechanics description of the universe is wrong in
• 20:32
  Speaker 2: some important way. That's what I love about physics, because
• 20:36
  Speaker 2: it's not just I have a model in my head
• 20:38
  Speaker 2: that is predicting the universe. You can then look at
• 20:40
  Speaker 2: that model and ask questions about it that are philosophical
• 20:43
  Speaker 2: and like, huh, why does the universe work this way?
• 20:45
  Speaker 2: Or you can look at it and say, oh, that's
• 20:47
  Speaker 2: why time flows forwards and there's only one dimension of
• 20:50
  Speaker 2: it in three dimensions of space. If you have that
• 20:53
  Speaker 2: fundamental theory of the universe, we hope that those kind
• 20:56
  Speaker 2: of answers can come from it deep insights about the
• 20:59
  Speaker 2: very nature of reality. And for people who think like, oh,
• 21:02
  Speaker 2: that's so weird and abstract, I mean, that's like the
• 21:05
  Speaker 2: context of our whole lives, you know, our entire existence.
• 21:09
  Speaker 2: Understanding the basic nature of reality of space and time
• 21:12
  Speaker 2: and matter and energy like that is the stage of
• 21:15
  Speaker 2: our life, the context of our existence. The stakes could
• 21:18
  Speaker 2: literally not be higher.
• 21:19
  Speaker 1: I mean it's interesting because I'm really curious about things
• 21:23
  Speaker 1: like animal and human behavior, understanding them and understanding things
• 21:27
  Speaker 1: like perception and you know, but those kinds of questions
• 21:31
  Speaker 1: I don't see as too fundamentally different from the questions
• 21:34
  Speaker 1: that physicists are answering, because in a way, you know,
• 21:38
  Speaker 1: our perception of things are sort of like behaviors and stuff.
• 21:41
  Speaker 1: That is how we're able to perceive the universe. And
• 21:45
  Speaker 1: so these kinds of questions of understanding. Of course, the
• 21:48
  Speaker 1: methodologies are very different, and what we find are going
• 21:51
  Speaker 1: to be very different with these two questions, but it's
• 21:53
  Speaker 1: that's still that kind of desire to understand what are
• 21:57
  Speaker 1: we and where are we? How do we function, and
• 22:00
  Speaker 1: how do we function in relation to our environment? And
• 22:04
  Speaker 1: you know, of course the universe being the largest environment
• 22:09
  Speaker 1: that we can think of in which we are. But
• 22:13
  Speaker 1: you know what, we should probably take a quick break
• 22:16
  Speaker 1: while I really ponder an egg and the membrane of
• 22:20
  Speaker 1: an egg and try to think about whether this is
• 22:23
  Speaker 1: something that could describe the universe. All right, so we
• 22:39
  Speaker 1: are back. I've been staring at this egg for five minutes.
• 22:43
  Speaker 1: Daniels can attest to that, and you know, I think
• 22:47
  Speaker 1: maybe the universe could be an egg with yellow stuff
• 22:50
  Speaker 1: on the inside. What do you think?
• 22:53
  Speaker 2: I love your egg theory of the universe. I want
• 22:56
  Speaker 2: to see the math behind it before I really commit to.
• 22:58
  Speaker 1: It one plus one equals too or wait, one time
• 23:02
  Speaker 1: is one equals too? I accidentally did I'm so bad
• 23:06
  Speaker 1: at math. I was trying to make a joke where
• 23:08
  Speaker 1: I did it bath and I did it correctly.
• 23:11
  Speaker 2: Oops. Oops, oops.
• 23:13
  Speaker 1: So, Daniel, I really want to get deeper into these
• 23:17
  Speaker 1: ideas because we've talked about how these things don't seem
• 23:20
  Speaker 1: to add up, and these attempts to make things to
• 23:22
  Speaker 1: add up have in some sense, I don't want to
• 23:25
  Speaker 1: say failed, but they haven't reached the finish line yet.
• 23:28
  Speaker 1: So like gravitons don't make sense yet, are there is
• 23:33
  Speaker 1: there anything promising where we are seeing some revelations that
• 23:37
  Speaker 1: may help us get closer to why there is this
• 23:40
  Speaker 1: fundamental miscommunication between general relativity and quantum mechanics.
• 23:46
  Speaker 2: So there definitely has been some progress. Nobody's totally figured
• 23:50
  Speaker 2: it out, but some of the smartest folks on the
• 23:52
  Speaker 2: planet have some ideas. And before we get into membrane theory,
• 23:56
  Speaker 2: you need to take a step back and understand where
• 23:58
  Speaker 2: it came from, which is from string theory.
• 24:01
  Speaker 1: Okay, I'm excited because I remember I remember watching I
• 24:05
  Speaker 1: Think like a PBS nova thing and they tried to
• 24:08
  Speaker 1: explain string theory, and it just confused me more than
• 24:12
  Speaker 1: I think, you know, like if you just said, like,
• 24:15
  Speaker 1: imagine what string theory is, I'd probably be less confused
• 24:19
  Speaker 1: at that point until after watching this documentary. I'm not
• 24:22
  Speaker 1: I don't want to be mean to PBS, but I
• 24:24
  Speaker 1: don't think they really explained it very well because it
• 24:26
  Speaker 1: was like they're like these vibrating strings like on a violin,
• 24:30
  Speaker 1: and it's like, I don't know that that makes a
• 24:33
  Speaker 1: lot of sense, and I'm confused. You mean, there's tiny
• 24:35
  Speaker 1: violins everywhere. What's going on? Are the world's smallest violins
• 24:39
  Speaker 1: making up the universe? So I do want to understand better.
• 24:44
  Speaker 2: All right, let's see if we can do better than
• 24:46
  Speaker 2: Brian Green on PBS. The idea is to avoid some
• 24:50
  Speaker 2: of the mathematical problems that come when you try to
• 24:52
  Speaker 2: cross the beam. Those infinities. A lot of those infinities
• 24:55
  Speaker 2: come from the basic assumption that things are points, that
• 24:59
  Speaker 2: particles are time need dots because those have infinities in them.
• 25:02
  Speaker 2: There's infinite densities and the zero volume, et cetera. So
• 25:06
  Speaker 2: instead of having points, string theory says, what if everything
• 25:10
  Speaker 2: is a line, so a point is like zero dimensions, right,
• 25:13
  Speaker 2: it doesn't go in any way. But a string is
• 25:15
  Speaker 2: one dimension. It's like, well, let's have it have some extent,
• 25:19
  Speaker 2: and having it have a length means it's not infinitely
• 25:22
  Speaker 2: dense anymore. There's like a fundamental length to it, and
• 25:25
  Speaker 2: that avoids some of the infinities in the calculations. Is
• 25:27
  Speaker 2: like a minimum size to stuff, and that's the length
• 25:30
  Speaker 2: of a string. And so these strings would be the
• 25:33
  Speaker 2: fundamental bits of the universe. Essentially the universe is strings.
• 25:37
  Speaker 2: But these strings can do things. They can wiggle, right,
• 25:40
  Speaker 2: just like strings in our world, like a violin string.
• 25:42
  Speaker 1: Can or or a guitar string if you prefer that.
• 25:48
  Speaker 2: But we can't see those wiggles directly. And so what
• 25:51
  Speaker 2: we see is something really zoomed out, like the string wiggles.
• 25:54
  Speaker 2: This way, it looks like an electron. When you zoom
• 25:56
  Speaker 2: way out with string wiggles that way, it looks like
• 25:59
  Speaker 2: a muon the string. Another way it looks like a quark.
• 26:02
  Speaker 2: So the idea is not that the electrons and the
• 26:04
  Speaker 2: quarks are made of tinier particles the way that like
• 26:08
  Speaker 2: the atom is made of smaller particles, but that you
• 26:10
  Speaker 2: get something fundamentally different. Right, we need something fundamentally different
• 26:14
  Speaker 2: to solve this puzzle of quantum gravity. We need a
• 26:17
  Speaker 2: new idea, and so we say that these particles are
• 26:20
  Speaker 2: instead made of vibrating strings, and they just look like
• 26:23
  Speaker 2: different particles because we're too zoomed out to see the details.
• 26:26
  Speaker 1: I guess for me, the question is like, I understand
• 26:29
  Speaker 1: the difference between a point and a line in terms
• 26:32
  Speaker 1: of dimensionality, but in terms of like a line of what?
• 26:37
  Speaker 1: Like That's where I get caught up, because I, you know,
• 26:40
  Speaker 1: usually it's so hard to think about the fundamental like
• 26:46
  Speaker 1: unit of something because maybe this is just biology brain,
• 26:51
  Speaker 1: but everything has a smaller thing in it, right, Like
• 26:54
  Speaker 1: You've got a mouse and the mouse has tissues, and
• 26:58
  Speaker 1: the tissues have cells. Cells have proteins, and the proteins
• 27:02
  Speaker 1: have molecules, and the molecules have atoms, and the atoms
• 27:05
  Speaker 1: have quarks, et cetera, et cetera. I might have skipped
• 27:07
  Speaker 1: a few steps, but you get the idea, which is
• 27:09
  Speaker 1: that I'm always thinking, like, what, what do you mean
• 27:11
  Speaker 1: like a string of what? A line of what?
• 27:14
  Speaker 5: So?
• 27:14
  Speaker 1: How has that resolved? Like what is? Because I'm assuming
• 27:17
  Speaker 1: it is not like a literal strand of you know,
• 27:20
  Speaker 1: like in biology, like a strand of protein. Like if
• 27:23
  Speaker 1: you're like, there's a string of something, I'm thinking like, oh,
• 27:25
  Speaker 1: is it proteins? Like you know, is it lipids? What's
• 27:28
  Speaker 1: it made out of? So in in physics, like what
• 27:31
  Speaker 1: is this line?
• 27:32
  Speaker 2: Yeah, it's a great question, and I understand what you're saying.
• 27:35
  Speaker 2: You're imagining string in your mind. And you know, if
• 27:38
  Speaker 2: you're thinking about like a line of frosting on a cake,
• 27:40
  Speaker 2: you're thinking that squeezed out of some tube and the
• 27:43
  Speaker 2: line of frosting is made out of that frosting, and
• 27:45
  Speaker 2: therefore the frosting is the basic universe stuff, not the
• 27:48
  Speaker 2: line of it. And so you're wondering, like, well, what's
• 27:50
  Speaker 2: that string made out of? What is string stuff? And
• 27:53
  Speaker 2: the answer is we don't know. And you're right that
• 27:56
  Speaker 2: the pattern is that stuff has made a smaller stuff,
• 27:58
  Speaker 2: which has made a smaller stuff, which is made of
• 28:00
  Speaker 2: smaller stuff. And so far we've never seen anything that
• 28:03
  Speaker 2: is just itself that is not made of something.
• 28:06
  Speaker 1: That's the truth, You're absolutely right.
• 28:09
  Speaker 2: But we have this hunch, We have this hunch that
• 28:12
  Speaker 2: maybe it is that maybe there's a bottom to the
• 28:15
  Speaker 2: explanations of the universe. We don't know, And there are
• 28:17
  Speaker 2: philosophers out there who argue that it could be infinitely regressive, right,
• 28:21
  Speaker 2: that you just could keep going forever and ever and ever,
• 28:23
  Speaker 2: and there is no foundational firmament to the universe. Everything
• 28:27
  Speaker 2: is made of something smaller.
• 28:29
  Speaker 1: I hate it either way, Daniel, like either explanation. It
• 28:32
  Speaker 1: feels uncomfortable somehow, right, Like if the explanation is like
• 28:36
  Speaker 1: there is the smallest unit and it's a line that wiggles,
• 28:40
  Speaker 1: I'm like really. And then if you're like no, but
• 28:42
  Speaker 1: then the line that wiggles, can you can infinitely get
• 28:45
  Speaker 1: smaller and smaller and smaller, And then still that It's like, really,
• 28:49
  Speaker 1: it's so hard, And I feel like maybe the reason
• 28:52
  Speaker 1: it's so difficult is that our human brains are geared
• 28:57
  Speaker 1: towards a certain type of understanding of things based on
• 29:00
  Speaker 1: what our evolutionary needs are in terms of something has
• 29:04
  Speaker 1: a start point and endpoint, or something is made out
• 29:06
  Speaker 1: of something else and time goes from point A to
• 29:10
  Speaker 1: point B. When someone who is not a physicist is
• 29:13
  Speaker 1: trying to think about these things, I think about stuff
• 29:17
  Speaker 1: that is probably not very relevant to it, Like when
• 29:20
  Speaker 1: I think of I don't know, you keep talking about
• 29:22
  Speaker 1: wiggly lines, and I just think about al dente spaghetti
• 29:25
  Speaker 1: and that's not what it is and it can't be.
• 29:28
  Speaker 1: But it's so hard to think of. Okay, there's a
• 29:33
  Speaker 1: basic unit that can't get any smaller, but it's not
• 29:37
  Speaker 1: made out of anything, and that, you know, it just
• 29:40
  Speaker 1: kind of breaks my brain. I cannot conceive of that.
• 29:44
  Speaker 2: Well, let me put it in another way, which is
• 29:45
  Speaker 2: maybe easier to sit with in your brain, which is,
• 29:49
  Speaker 2: we don't know whether strings, if they exist, are the
• 29:52
  Speaker 2: fundamental basis of the universe, or if they're made of
• 29:54
  Speaker 2: something smaller. You can put it that way, right, And
• 29:56
  Speaker 2: we can put it that way because we actually don't
• 29:58
  Speaker 2: have to know. This is one of the beautiful things
• 30:01
  Speaker 2: about physics is that we can do calculations at various scales,
• 30:05
  Speaker 2: ignoring the internal details, not having to know them. Like
• 30:08
  Speaker 2: when we did that calculation of the baseball flying across
• 30:10
  Speaker 2: the field, we didn't have to keep track of all
• 30:12
  Speaker 2: the electrons and even the air resistance on all those
• 30:15
  Speaker 2: details to mostly get the right answer. You can do
• 30:18
  Speaker 2: physics at lots of different scales. So even if the
• 30:21
  Speaker 2: universe infinitely is made of smaller stuff, or if there
• 30:24
  Speaker 2: is some fundamental chunk to it, we can still do
• 30:27
  Speaker 2: physics about it without even knowing the answer. So thanks
• 30:30
  Speaker 2: to the universe for being understandable at lots of levels
• 30:33
  Speaker 2: even before we figured out quantum gravity. You can imagine
• 30:36
  Speaker 2: another scenario where in order to do any calculation you
• 30:40
  Speaker 2: had to understand all the little bits inside of it.
• 30:42
  Speaker 2: You had to figure out the fundamentals of quantum gravity
• 30:45
  Speaker 2: before you could make chicken soup. Right, But fortunately in
• 30:48
  Speaker 2: our universe you can throw baseballs and make chicken soup
• 30:50
  Speaker 2: and play violins without understanding all the details, so we
• 30:53
  Speaker 2: can make progress. We can say, well, maybe electrons are
• 30:57
  Speaker 2: made of strings without knowing whether those strings are also
• 31:00
  Speaker 2: made of something else, and still have some insight into
• 31:03
  Speaker 2: this layer of the universe, without knowing if there are
• 31:05
  Speaker 2: more layers beyond it.
• 31:07
  Speaker 1: So we've got possible strings that we don't know exactly
• 31:11
  Speaker 1: if they exist. But it's a line that can wiggle
• 31:14
  Speaker 1: in the way in which it wiggles forms some kind
• 31:17
  Speaker 1: of different thing, which I can kind of accept at
• 31:22
  Speaker 1: this point. Is that sort of it? In terms of
• 31:25
  Speaker 1: string theories, it seems like there would probably be a
• 31:27
  Speaker 1: lot more complexity involved.
• 31:30
  Speaker 2: Yeah, there is more complexity. The mathematics of those strings
• 31:33
  Speaker 2: is very cool. At first, when people were working it out,
• 31:36
  Speaker 2: they were only able to use strings to describe some
• 31:39
  Speaker 2: kinds of particles, particles that we call bosons, which are
• 31:42
  Speaker 2: photons and the W and the Z and the higgs
• 31:46
  Speaker 2: and the gluons. These are all the bosons, the force
• 31:48
  Speaker 2: carrying particles. So the original string theory could only describe bosons.
• 31:53
  Speaker 2: And then people worked on it and found new ways
• 31:55
  Speaker 2: for those strings to wiggle, so they could also describe fermions,
• 31:58
  Speaker 2: and that's called super string theory. Super as a reference
• 32:02
  Speaker 2: to this other idea, supersymmetry, which connects fermions and bosons.
• 32:06
  Speaker 2: Check out our whole episode about that. But so then
• 32:09
  Speaker 2: people developed super string theory, and then there was this
• 32:11
  Speaker 2: sort of revolution in the nineteen eighties when people got
• 32:14
  Speaker 2: really excited about it. They call it the first super
• 32:16
  Speaker 2: string revolution. And that's when people realize, Wow, this string
• 32:19
  Speaker 2: theory is not just a cool mathematical model. It can
• 32:22
  Speaker 2: describe all the kinds of particles in our universe. And
• 32:24
  Speaker 2: also it seems like a very promising theory of quantum gravity.
• 32:28
  Speaker 2: They were able to avoid some of the infinities of
• 32:30
  Speaker 2: earlier attempts the problems with gravitons by describing things in
• 32:34
  Speaker 2: terms of strings. So it was a very exciting time.
• 32:37
  Speaker 2: A lot of people worked on it, and the problem
• 32:39
  Speaker 2: was that they had lots of different ideas. So there's
• 32:42
  Speaker 2: not like one string theory or one way to do
• 32:44
  Speaker 2: string theory. People figured out a bunch of different kinds
• 32:47
  Speaker 2: of string theories, like you can have strings that are
• 32:50
  Speaker 2: always open, like they're just lines, or strings that are
• 32:53
  Speaker 2: closed which means they're loops, or you can have a
• 32:55
  Speaker 2: theory with strings sometimes are open and sometimes are closed,
• 32:58
  Speaker 2: or different kinds of ways to solve super gravity. And
• 33:02
  Speaker 2: so at the end of the eighties there was sort
• 33:04
  Speaker 2: of a confusion because there were like five different types
• 33:07
  Speaker 2: of string theory that were all seemed very very different
• 33:10
  Speaker 2: and all kind of worked, and people weren't sure sort
• 33:12
  Speaker 2: of where to go from there.
• 33:13
  Speaker 1: Right. I mean, that seems kind of tricky because it's
• 33:15
  Speaker 1: almost like you're sort of filling in the gaps, right
• 33:20
  Speaker 1: with these different theories, and you can it seems like
• 33:22
  Speaker 1: they were able to come up with different sort of
• 33:25
  Speaker 1: math or different theories that did fill that gap in
• 33:28
  Speaker 1: different ways, and so I don't know how you would
• 33:33
  Speaker 1: pick which one works if they all sort of can
• 33:36
  Speaker 1: on average kind of like fix that gap.
• 33:39
  Speaker 2: And that's very unsatisfying, right, because we think the universe
• 33:42
  Speaker 2: is following a set of laws. We think there is
• 33:44
  Speaker 2: one set of laws, and so then if you find
• 33:47
  Speaker 2: like two explanations for the universe that both work, you're like, well,
• 33:50
  Speaker 2: which one is really happening?
• 33:52
  Speaker 1: Right?
• 33:53
  Speaker 2: You know, is a deep philosophical question.
• 33:55
  Speaker 1: Could there actually be something where on this level there
• 33:58
  Speaker 1: could be multiple sets of rules that all work at
• 34:02
  Speaker 1: the same time.
• 34:03
  Speaker 2: Yeah, philosophers think it's possible that there are multiple explanations
• 34:07
  Speaker 2: for the universe, multiple theories that predict the universe and
• 34:11
  Speaker 2: describe it and explain what's happening, but have fundamentally different
• 34:15
  Speaker 2: stories about sort of what's going on behind the curtain.
• 34:18
  Speaker 2: We don't know if that's possible, but there's a group
• 34:20
  Speaker 2: of philosophers who think it might be. And boy, I
• 34:23
  Speaker 2: hope they're wrong because that would be very frustrating. In
• 34:26
  Speaker 2: the stupid strink community also was hoping they were wrong.
• 34:29
  Speaker 2: And we're trying to figure out this puzzle, and one
• 34:31
  Speaker 2: way to try to figure it out is to see
• 34:33
  Speaker 2: are there connections between these different theories. Can we show
• 34:37
  Speaker 2: that actually these theories are really the same thing dressed
• 34:41
  Speaker 2: up in different clothing, Like are we really just telling
• 34:43
  Speaker 2: the same story using different words or using different symbols.
• 34:47
  Speaker 2: It harkens back to like the nineteen twenties when people
• 34:50
  Speaker 2: were developing quantum mechanics, for example, and you had Schroeninger
• 34:54
  Speaker 2: he had his wave equation of quantum mechanics, and you
• 34:56
  Speaker 2: had Heisenberg, he had his matrix formulation of quantum mechanics,
• 35:00
  Speaker 2: and those two guys did not like each other. In fact,
• 35:03
  Speaker 2: they hated each other, and they also disliked each other's ideas,
• 35:07
  Speaker 2: like Heisenberg really didn't like Schrodinger's wave equation. You thought
• 35:10
  Speaker 2: it made quantum mechanics like too visual, it gave you
• 35:12
  Speaker 2: a mental image when in stage you just focus on
• 35:15
  Speaker 2: the math of the matrices. And everybody else hated Heisenberg's
• 35:19
  Speaker 2: matrices because nobody could understand what they meant. And then
• 35:23
  Speaker 2: a few decades later John von Neumann showed actually they're
• 35:26
  Speaker 2: the same. They make the same calculations. You can convert
• 35:29
  Speaker 2: one into the other, and so they're just like two
• 35:32
  Speaker 2: different ways to write the same thing, the way that
• 35:34
  Speaker 2: like algebra and geometry are fundamentally the same. You want
• 35:38
  Speaker 2: to solve a system of equations like two lines, you
• 35:40
  Speaker 2: can either draw them on a piece of paper and
• 35:42
  Speaker 2: see when they cross, or you can do a bunch
• 35:44
  Speaker 2: of algebra and solve for it. In the end, those
• 35:46
  Speaker 2: feel like two different kinds of math, but they really
• 35:48
  Speaker 2: are revealing the same thing or the same relationship between concepts.
• 35:53
  Speaker 2: So people were wondering, can we do that first dring theory?
• 35:56
  Speaker 2: Can we show that these different string theories They're called
• 35:59
  Speaker 2: type one, type two A, type two B, so.
• 36:03
  Speaker 1: Thirty two sounds like a disease.
• 36:05
  Speaker 2: And E eight x E eight. These are crazy names,
• 36:09
  Speaker 2: I know, terrible, terrible names. Will be deeply offended.
• 36:12
  Speaker 1: I have type one string theory.
• 36:17
  Speaker 2: I'm so sorry, kame. There's a group for that. So
• 36:21
  Speaker 2: people were wondering, is it possible these actually are different
• 36:25
  Speaker 2: mathematical expressions for the same phenomena. And it was a
• 36:28
  Speaker 2: hard problem. But there are smart people out there, and
• 36:32
  Speaker 2: this guy, Ed Witten, maybe one of the smartest dudes ever.
• 36:35
  Speaker 2: He's at the Institute for Advanced Studies near Princeton, and
• 36:39
  Speaker 2: he was playing with these strings. Remember, the strings don't
• 36:42
  Speaker 2: just exist in our three dimensions of space, the math
• 36:45
  Speaker 2: works best if space has nine dimensions. So these strings
• 36:48
  Speaker 2: are one dimensional lines through nine dimensional space, our three dimensions,
• 36:53
  Speaker 2: and then six more dimensions that we can't sense or
• 36:56
  Speaker 2: perceive or really experience in any way, but the strings
• 37:00
  Speaker 2: need them in order to make their math wiggle correctly.
• 37:03
  Speaker 1: Hmm, yeah, no, I mean I think this is it's
• 37:06
  Speaker 1: always a wild time trying to think about other dimensions,
• 37:11
  Speaker 1: because we could probably explain other dimensions with math, but
• 37:15
  Speaker 1: to try to conceptualize them, I don't know if that's
• 37:18
  Speaker 1: even possible with our brains, given that our brains are
• 37:21
  Speaker 1: three dimensional brains and function in a sort of three
• 37:25
  Speaker 1: dimensional way. So without your neurons being able to span
• 37:31
  Speaker 1: into the other six dimensions, that seems difficult.
• 37:34
  Speaker 2: It is very difficult. You're right, We intuitively think in
• 37:37
  Speaker 2: three dimensions. It's very hard to think in additional dimensions.
• 37:41
  Speaker 2: It's even hard to think in fewer dimensions. Like if
• 37:44
  Speaker 2: you try to imagine a two D sheet or one
• 37:47
  Speaker 2: D line, you're imagining it in three D space. You
• 37:50
  Speaker 2: put that sheet into three D space, or that line
• 37:53
  Speaker 2: in three D space. Or if I tell you imagine
• 37:55
  Speaker 2: a zero dimensional dot, you think of a point and
• 37:57
  Speaker 2: you sketch it out into some three D space, because
• 38:00
  Speaker 2: that's the natural playground of our mind. So if you
• 38:03
  Speaker 2: can't go down the dimension, there's no hope angling up
• 38:05
  Speaker 2: a dimension. It's really very difficult.
• 38:08
  Speaker 1: I almost passed out once trying to think about like nothing,
• 38:11
  Speaker 1: like going you know, sort of the zero dimension thing,
• 38:13
  Speaker 1: trying to think about nothing. And I felt very weird
• 38:17
  Speaker 1: to try to think about that for too long. It
• 38:19
  Speaker 1: felt like my brain was kind of leaving my body.
• 38:22
  Speaker 1: Maybe I was just sleepy. I don't know. But yeah.
• 38:25
  Speaker 1: There's also that book Flat Landers, where it tries to,
• 38:29
  Speaker 1: in an artistic way, represent how difficult it is to
• 38:32
  Speaker 1: bridge the gap between a two D existence and a
• 38:36
  Speaker 1: three D existence. But you know, fundamentally, even that book
• 38:39
  Speaker 1: is describing it as a visual experience where having vision
• 38:43
  Speaker 1: requires three dimensions. It seems so yeah, and.
• 38:48
  Speaker 2: So making progress on this requires super smart dudes to
• 38:51
  Speaker 2: do superstring theory. And so Edwinten was thinking about these
• 38:55
  Speaker 2: nine dimensional strings, and so those theories are ten dimensional
• 38:59
  Speaker 2: because it's nine facial dimensions and one time dimension. He
• 39:02
  Speaker 2: was thinking about these nine dimensional strings, and he was
• 39:04
  Speaker 2: inspired by this leap from zero dimensional points to one
• 39:08
  Speaker 2: dimensional lines. Strings and he was wondering, should we take
• 39:11
  Speaker 2: it a step further. Instead of thinking about these things
• 39:15
  Speaker 2: as one D strings in nine dimensional spaces, maybe they're
• 39:18
  Speaker 2: actually two dimensional objects membranes, right, sheets in higher dimensional space.
• 39:25
  Speaker 2: And so these would be like two D sheets in
• 39:29
  Speaker 2: ten dimensional space, which looks like one dimensional objects strings
• 39:34
  Speaker 2: if you only look at them in nine dimensions. So
• 39:37
  Speaker 2: the idea is he invents this extra dimension, this eleventh
• 39:40
  Speaker 2: dimension or a tenth dimension of space, and extends the
• 39:44
  Speaker 2: strings into that space to make them into membranes.
• 39:48
  Speaker 1: So more like a sheets theory.
• 39:50
  Speaker 2: Yeah, exactly, from strings to.
• 39:52
  Speaker 1: Sheets sponsored by sheets the convenience store and gas station.
• 39:58
  Speaker 2: So the exciting thing is that Witten thought that if
• 40:02
  Speaker 2: you worked with membranes instead of strings, you could explain
• 40:07
  Speaker 2: all these different string theories. That these five string theories
• 40:11
  Speaker 2: were actually just five different ways to look at the
• 40:14
  Speaker 2: same sheet. So you roll it up this way, it
• 40:16
  Speaker 2: looks like one. You roll it up another way it
• 40:18
  Speaker 2: looks like another. You look at it from this perspective,
• 40:20
  Speaker 2: it looks like a different string theory. But these five
• 40:23
  Speaker 2: string theories that people were playing with and confused about
• 40:26
  Speaker 2: were actually just like extreme examples of one membrane theory,
• 40:31
  Speaker 2: and this this famous talkie gives at University of Southern
• 40:33
  Speaker 2: California in ninety five where he points this out and
• 40:36
  Speaker 2: he makes this connection, and he has this diagram on
• 40:39
  Speaker 2: the slide which is just like all five theories and
• 40:42
  Speaker 2: it just like draws lines between them.
• 40:44
  Speaker 1: Is it like a corkboard was the eldest shoveled?
• 40:48
  Speaker 2: It's exactly like that. Yeah, it's not very compelling as
• 40:51
  Speaker 2: a diagram, and even his explanation is somewhat lacking. You know,
• 40:55
  Speaker 2: he doesn't have all the math. He has sort of
• 40:57
  Speaker 2: like this leap of intuition. He has some hints that
• 41:00
  Speaker 2: these things do connect to each other. It's like a
• 41:02
  Speaker 2: new direction forward. And it's sort of like the way
• 41:05
  Speaker 2: Fineman worked. You know, Fineman developed QED and he didn't
• 41:08
  Speaker 2: work out all the math came later when like Schwinger
• 41:11
  Speaker 2: worked through all the details to prove that Fineman's leaps
• 41:13
  Speaker 2: of intuition were correct. Witness sort of similar. He's like
• 41:16
  Speaker 2: sees these connections in his brain. He knows that it
• 41:18
  Speaker 2: can work, even if he hasn't like actually sat down
• 41:21
  Speaker 2: and worked through it all. And so this one talk
• 41:24
  Speaker 2: in ninety five inspired what they called the Second super
• 41:27
  Speaker 2: string Revolution and led to like hundreds and hundreds of
• 41:30
  Speaker 2: papers of people working on membranes. The interesting thing is
• 41:35
  Speaker 2: that Witten himself wasn't actually sure that membranes who were
• 41:38
  Speaker 2: going to work. He was like, hmm, it might be membranes,
• 41:41
  Speaker 2: it might not be memoranes. I'm not sure. He knew
• 41:43
  Speaker 2: that these things were connected, but he didn't want to
• 41:45
  Speaker 2: actually call his theory membrane theory, so he just called
• 41:49
  Speaker 2: it M theory, and he wrote in his paper quote,
• 41:52
  Speaker 2: we will non committally call it the M theory, leaving
• 41:56
  Speaker 2: to the future the revelation of M to membranes, Like
• 42:00
  Speaker 2: people really worked through the math and showed that these
• 42:02
  Speaker 2: things were two D objects or actually ten D objects,
• 42:06
  Speaker 2: then we could call it membrane theory. But until then,
• 42:09
  Speaker 2: let's just keep it M theory in case it turns
• 42:11
  Speaker 2: out to be like mouse theory or mama theory or
• 42:14
  Speaker 2: something else.
• 42:15
  Speaker 1: Yeah. No, I mean I like that your hedge in
• 42:17
  Speaker 1: your bets. I also like this guy kind of sounds
• 42:20
  Speaker 1: like there's this I forgot his name, but I think
• 42:23
  Speaker 1: he is like a quote unquote neurosurgeon who kept claiming
• 42:29
  Speaker 1: that he could do like head transplants, and his demonstration
• 42:34
  Speaker 1: was a bunch of dried spaghetti and a banana to
• 42:37
  Speaker 1: show how you could basically like connect all of the
• 42:41
  Speaker 1: arteries and spinal cord and everything. I think maybe the
• 42:45
  Speaker 1: banana was supposed to be the spinal cord. Anyways, it
• 42:48
  Speaker 1: was like a spaghetti banana demonstration, which did not inspire confidence. So,
• 42:55
  Speaker 1: of course, I think with the physics, when you go
• 42:58
  Speaker 1: out on a branch in terms of physics, it's maybe
• 43:01
  Speaker 1: less risky than trusting someone who says they can do
• 43:04
  Speaker 1: a head transplant.
• 43:06
  Speaker 2: Yeah, so I think Edwinten. I wouldn't trust him to
• 43:09
  Speaker 2: do a head transplant. But I'm glad that he's around
• 43:12
  Speaker 2: and he's helping us figure out the mysteries of quantum gravity.
• 43:15
  Speaker 2: And it's really cool that he was able to show
• 43:17
  Speaker 2: that these theories are related to each other. You know,
• 43:21
  Speaker 2: there are these funny dualities they find where they show
• 43:24
  Speaker 2: that this theory is mathematically equivalent to that theory. You know,
• 43:27
  Speaker 2: like this theory if you make it really strong, looks
• 43:30
  Speaker 2: like that theory if you make it really weak. It's
• 43:32
  Speaker 2: fascinating to show that the theories, even though they have
• 43:35
  Speaker 2: again very different of mathematical foundations. They really are exploring
• 43:39
  Speaker 2: the same concepts because the symbolism, the notation we use
• 43:43
  Speaker 2: is really just a way to describe the abstract ideas.
• 43:46
  Speaker 2: And so even if you use different notations and different symbols,
• 43:49
  Speaker 2: if you can show that the ideas are equivalent, then
• 43:52
  Speaker 2: you really have made a connection between them. And it's
• 43:54
  Speaker 2: a relief also to think, like, well, maybe there is
• 43:57
  Speaker 2: a connection, because then we don't have to pick one
• 43:59
  Speaker 2: of the theory. We don't have to have a reason
• 44:01
  Speaker 2: to choose one. We can just say, oh, they're all
• 44:03
  Speaker 2: just special cases of one unifying idea. And in the end,
• 44:07
  Speaker 2: that's what physics is trying to do, is come up
• 44:09
  Speaker 2: with some unifying, simplifying explanation for everything we see out
• 44:13
  Speaker 2: there in the universe.
• 44:14
  Speaker 1: I mean, I find it really appealing not having to
• 44:17
  Speaker 1: make a decision between like really hard choices. That sounds great.
• 44:22
  Speaker 1: Sign me up for physics. Let's take a really quick break,
• 44:25
  Speaker 1: and then when we get back, let's talk more about
• 44:29
  Speaker 1: membrane theory and how it could tie everything up in
• 44:32
  Speaker 1: a nice little bow. All right, So I was a
• 44:47
  Speaker 1: little bit glib about tying everything up in a nice
• 44:50
  Speaker 1: little bow. I know that is the desire of physics,
• 44:54
  Speaker 1: and yet it seems pretty tricky to do that.
• 44:58
  Speaker 2: It is pretty tricky, but along the way, we can
• 45:02
  Speaker 2: entertain ourselves by amusing notation and making up really weird
• 45:07
  Speaker 2: phrases and names for things. So physics, as everybody knows,
• 45:10
  Speaker 2: is very good at using inappropriate and confusing words to
• 45:13
  Speaker 2: describe things. And so physicists have taken this phrase membrane
• 45:17
  Speaker 2: and tried to generalize it to any dimensional surface. So, like,
• 45:21
  Speaker 2: you know, a membrane is like a two D surface.
• 45:23
  Speaker 2: You can imagine like a sheet or like a cell wall.
• 45:26
  Speaker 2: It's two dimensions, right, And so physicists don't call that
• 45:30
  Speaker 2: a membrane. They call that a two brain, okay, so
• 45:33
  Speaker 2: that they can call a string a one brain, or
• 45:36
  Speaker 2: like the point a zero brain. You're a zero brain, yeah, exactly. Well,
• 45:45
  Speaker 2: even worse is the general phrase for it. If you
• 45:48
  Speaker 2: have a surface in P dimensions, you call it a
• 45:51
  Speaker 2: P brain.
• 45:52
  Speaker 1: That's what I call my dog all the time. I'm like,
• 45:54
  Speaker 1: look at you, old pepe brain.
• 45:56
  Speaker 2: Yeah, well you didn't realize you're actually giving it a
• 45:59
  Speaker 2: vast You're connecting it to the fundamental theory of the universe.
• 46:03
  Speaker 2: Maybe cookie can reveal something true about reality.
• 46:06
  Speaker 1: I look into her eyes, I see these deep pools
• 46:09
  Speaker 1: of knowledge. But then it turns out she just had
• 46:11
  Speaker 1: to burn.
• 46:14
  Speaker 2: Cookie, had too many cookies.
• 46:15
  Speaker 1: It sounds like, yeah, exactly. So now I'm confused because
• 46:21
  Speaker 1: I kind of got the idea of the membrane being like,
• 46:26
  Speaker 1: it's not a point, it's not a line. It's like
• 46:28
  Speaker 1: a plane, but not necessarily a flat plane, one that
• 46:32
  Speaker 1: could be sort of wrapped around different dimensions. So I
• 46:37
  Speaker 1: kind of get that. Now we're sort of this terminology
• 46:40
  Speaker 1: of zero brain being a point, one brain being a string,
• 46:45
  Speaker 1: two brain being a two D surface. What is the
• 46:48
  Speaker 1: point of having brain in there? Like as a term?
• 46:52
  Speaker 1: Like what and I don't mean this like in a
• 46:55
  Speaker 1: mean way, just like what purpose is that serving in
• 46:58
  Speaker 1: terms of helping with the research or the explanation.
• 47:02
  Speaker 2: Yeah, it's a good question. Maybe physicists just like saying
• 47:05
  Speaker 2: brain because it doesn't sound smart, sounds like they're talking
• 47:08
  Speaker 2: about their brains. But physicists like to think about different
• 47:12
  Speaker 2: versions of ideas, not to be limited by our experience
• 47:16
  Speaker 2: of the universe, you know, where we have one dimensional
• 47:18
  Speaker 2: objects and two dimensional objects and three dimensional objects. They'd
• 47:21
  Speaker 2: like to generalize it and to be opened to other
• 47:23
  Speaker 2: dimensions and other scales, and so for example, Edwinton's first
• 47:27
  Speaker 2: idea was maybe the way to do this is to
• 47:30
  Speaker 2: use two dimensional sheets, which is fascinating to think, like, Okay,
• 47:34
  Speaker 2: the universe isn't made of points of stuff or even
• 47:38
  Speaker 2: lines of stuff, but maybe like sheets of stuff. It
• 47:41
  Speaker 2: would be pretty weird if the universe was made of
• 47:44
  Speaker 2: two dimensional things the fundamental nature of it, the basic
• 47:47
  Speaker 2: building block where sheets, that would be weird. But recently
• 47:51
  Speaker 2: people have been making some progress in an alternative version
• 47:54
  Speaker 2: of m theory in which the brains are five dimensionals,
• 47:58
  Speaker 2: so they use five brains, meaning that like you still
• 48:01
  Speaker 2: work in a theory where there are ten spatial dimensions
• 48:04
  Speaker 2: in one time dimension, but the fundamental building blocks of
• 48:07
  Speaker 2: the universe are not sheets. There five dimensional objects, which
• 48:11
  Speaker 2: is pretty hard to think about and impossible to visualize
• 48:15
  Speaker 2: with our three brains.
• 48:16
  Speaker 1: Yeah, that's an interesting thing because usually the intuitive direction
• 48:21
  Speaker 1: of units right of stuff or like building blocks of
• 48:26
  Speaker 1: stuff is like you go from simple to more complex, right,
• 48:30
  Speaker 1: so like you'd start out with you know, zero dimensions
• 48:34
  Speaker 1: than one dimensions than two dimensions and three dimensions than
• 48:37
  Speaker 1: four dimensions, et cetera. Right, and then like as you
• 48:40
  Speaker 1: get to the smaller building blocks, the kind of intuitive
• 48:43
  Speaker 1: way is like the smaller the building block, the fewer
• 48:46
  Speaker 1: the dimensions. Right. But I think it is really interesting
• 48:49
  Speaker 1: the idea that the smallest building block could be something
• 48:53
  Speaker 1: that is actually operates among you know, more dimensions than say,
• 48:59
  Speaker 1: we did as human consciousness. Is because that seems, I
• 49:06
  Speaker 1: don't know, for some reason, that makes more sense to
• 49:09
  Speaker 1: me than like the smallest unit being like a point,
• 49:14
  Speaker 1: even though I cannot there is no way I can
• 49:16
  Speaker 1: even begin to conceive of five dimensions without sounding like
• 49:20
  Speaker 1: I'm high on Joe Rogan, I.
• 49:25
  Speaker 2: Think you're right though, and I think the lesson there
• 49:28
  Speaker 2: is the universe is filled with surprises. You know. We
• 49:31
  Speaker 2: set up this question with we have a puzzle about
• 49:34
  Speaker 2: the fundamental nature of reality. Is a quantum mechanical? Is
• 49:36
  Speaker 2: it general relativistic? Is this something new and weird and different?
• 49:40
  Speaker 2: And we don't have an answer yet, But this line
• 49:43
  Speaker 2: of investigation building strings into membranes into p brains is
• 49:48
  Speaker 2: suggesting that we've been thinking about it wrong in terms
• 49:51
  Speaker 2: of tiny little objects that actually at the foundation of
• 49:54
  Speaker 2: the universe, the basic level of reality, the intellectual firmament
• 49:58
  Speaker 2: that we can finally reach built out of complex objects,
• 50:02
  Speaker 2: objects with five dimensions to them, or even two dimensions.
• 50:06
  Speaker 2: And that's the kind of revelation we're looking for, you know,
• 50:08
  Speaker 2: that's exactly the hope that the math points us to
• 50:12
  Speaker 2: structures that tell us something about what's actually happening out
• 50:14
  Speaker 2: there in reality. And in a way, that's a surprise,
• 50:17
  Speaker 2: because I don't expect our intuition to correctly guess how
• 50:21
  Speaker 2: the universe works. I expect it to be a surprise.
• 50:23
  Speaker 2: It would be quite disappointing if the universe was a
• 50:26
  Speaker 2: certain way and we were like, oh, yeah, that makes sense. Instead,
• 50:29
  Speaker 2: I want that moment where we're like, oh, wow, the
• 50:31
  Speaker 2: universe actually works in this weird way, how could that
• 50:34
  Speaker 2: possibly be? And then it requires like a reworking off
• 50:37
  Speaker 2: your mental model to incorporate that, But that brings you
• 50:40
  Speaker 2: more in aligned with the way the universe actually works.
• 50:43
  Speaker 2: And that's kind of the whole goal of science, right,
• 50:46
  Speaker 2: is to align our brains with the workings of the universe,
• 50:49
  Speaker 2: not just our silly, clueless, primitive guesses about how the
• 50:53
  Speaker 2: universe might work.
• 50:55
  Speaker 1: So if it was up to me, I would just
• 50:57
  Speaker 1: hazard a guess that the universe is man, little worms, man,
• 51:01
  Speaker 1: just tile worms.
• 51:04
  Speaker 2: I see. So that's your worm brain theory of the universe.
• 51:06
  Speaker 1: My brain theory.
• 51:09
  Speaker 2: You and RFKU.
• 51:10
  Speaker 1: Yeah, I should run for president and me and my
• 51:13
  Speaker 1: worms know how.
• 51:15
  Speaker 2: To run this chuntry Vice President Terrence Howard, all right, well,
• 51:21
  Speaker 2: thanks for coming along on this crazy mental journey down
• 51:24
  Speaker 2: into the fundamental nature of the universe to think about
• 51:27
  Speaker 2: weird quantum objects, also obeying the rules of gravity and
• 51:31
  Speaker 2: revealing that the universe is made out of building blocks
• 51:34
  Speaker 2: that we do not yet understand, but they might require
• 51:38
  Speaker 2: one brain's two brains or p dimensional pea brains.
• 51:42
  Speaker 1: Thank you for helping me understand that the universe is
• 51:45
  Speaker 1: not made out of tiny violence. That really helps.
• 51:49
  Speaker 2: It's only possible because your brain is not a banana.
• 51:54
  Speaker 2: All right, Thanks very much everybody, and tune in next
• 51:56
  Speaker 2: time for more science and curiosity. Come find us on
• 52:04
  Speaker 2: social media where we answer questions and post videos. We're
• 52:08
  Speaker 2: on Twitter, Discorg, Instant, and now TikTok. Thanks for listening,
• 52:12
  Speaker 2: and remember that Daniel and Jorge Explain the Universe is
• 52:15
  Speaker 2: a production of iHeartRadio. For more podcasts from iHeartRadio, visit
• 52:20
  Speaker 2: the iHeartRadio, app, Apple podcasts, or wherever you listen to
• 52:24
  Speaker 2: your favorite shows.