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Speaker 1: Hey, Daniel, I have a question about the physics of space.

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Speaker 2: Oh cool, I love those Space is so amazing and

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Speaker 2: fun to talk about.

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Speaker 1: Well, not the physics of space space, I mean like

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Speaker 1: the office space of physics.

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Speaker 2: What's the physics of office space?

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Speaker 3: You know?

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Speaker 1: I remember when I visited at CERN and I walked

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Speaker 1: by the office of a physicists called John Ellis, and

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Speaker 1: it was so messy, with paper stacks so high it

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Speaker 1: looked almost impossible to walk in.

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Speaker 2: Yeah, he is famously disorganized.

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Speaker 1: Now how does that work? Do particle physicists have some

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Speaker 1: kind of special trick that makes their office bigger on

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Speaker 1: the inside than on the outside, you know, kind of

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Speaker 1: like those Harry Potter tents.

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Speaker 2: Actually, I think it might be the opposite. I think

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Speaker 2: their offices are on the verge of collapsing into personal

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Speaker 2: black holes.

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Speaker 1: No, but that's kind of what I mean, Like black

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Speaker 1: holes might have whole universes inside of him. Do physicist

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Speaker 1: offices have a whole universe inside of him? And what

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Speaker 1: are they doing inside of there?

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Speaker 2: I don't know, but I suspect in John Ellis's office

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Speaker 2: there's lots of ideas lost behind his personal event.

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Speaker 1: Horizon, event horizon or mess Horizon.

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Speaker 2: The disorganization Horizon.

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Speaker 1: I am Jorge May, cartoonist and the creator of PhD comments.

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Speaker 2: Hi, I'm Daniel. I'm a particle physicist and a professor

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Speaker 2: at UC Irvine. And contrary to popular perception, I do

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Speaker 2: try to keep my office kind of organized.

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Speaker 1: Kinda that that sounds like a little bit of a

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Speaker 1: loophole there. Yeah, my office is totally kind of organized

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Speaker 1: if you set the bar really for the definition of

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Speaker 1: the word organization.

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Speaker 2: I didn't want to brag too much, but yes, I

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Speaker 2: do like to keep my office neat and tidy.

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Speaker 1: M I'm not sure that's something to brag about it.

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Speaker 1: Don't they say genius is related to how messy your

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Speaker 1: desk is?

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Speaker 2: Yeah? Well, Obama said physical discipline leads to mental discipline, So.

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Speaker 1: Yeah, well, I think Yoda said something similar. Also, organization

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Speaker 1: leads to hate. Hate leads to suffering, and suffering leads

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Speaker 1: to the dark side.

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Speaker 2: But who do you think would win in basketball? Obama

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Speaker 2: or Yoda?

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Speaker 1: Yoda? I mean, I love Obama, but come on, Yoda,

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Speaker 1: I can do like Super summersaults with a lightsaber.

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Speaker 2: Yeah, that dude could probably dunk, that's true.

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Speaker 1: Anyways, Welcome to our podcast Daniel and Jorge in the Universe,

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Speaker 1: a production of iHeartRadio in which we.

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Speaker 2: Do mental summersaults to try to explain the entire universe

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Speaker 2: to you. We go out there into the vast stretches

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Speaker 2: of empty space, wondering about what is actually out there,

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Speaker 2: what it's made out of, zoom down to the very

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Speaker 2: granular nature of reality itself, and ask questions about what

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Speaker 2: it is, what it means, and how we can figure

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Speaker 2: it all out. We zoom in, we zoom out, we

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Speaker 2: zoom everywhere in the universe to try to explain everything

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Speaker 2: to you.

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Speaker 1: That's right, because it is a pretty amazing universe, and

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Speaker 1: we like to explore the force in it, the dark

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Speaker 1: side of it, and also the physics of basketball sometimes

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Speaker 1: as well.

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Speaker 2: You know, I wonder in the Star Wars universe you

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Speaker 2: have like young Jedi. Are they playing sports with each other?

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Speaker 2: Do they have some version of like Jedi quidditch where

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Speaker 2: they're you know, pushing balls around with their minds?

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Speaker 1: Oh, interesting question. You should write like a fan fiction

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Speaker 1: bbble based on just that Harry Potter Star Wars like

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Speaker 1: qui gon quidditch fan fiction for Star Wars, and throw

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Speaker 1: in some brooms as well.

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Speaker 2: But I'm asking a serious question. I think give a

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Speaker 2: deeper knowledge of these universes than I do. Do young

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Speaker 2: Jedi play some sort of ball sports with their minds.

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Speaker 1: I don't see why they wouldn't. I guess I don't

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Speaker 1: think it's canon. I mean, I do play with a

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Speaker 1: little like a floating ball where they try to hit

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Speaker 1: it with the lightsaber. Maybe may that's a sport. I

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Speaker 1: don't know. We'll have to ask George Lucas. Can we

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Speaker 1: get them on the podcast Lucas?

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Speaker 2: Oh yeah, I totally email with George Lucas all the time.

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Speaker 2: I send him all of my Star Wars ideas.

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Speaker 1: Oh good, that would explain a lot.

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Speaker 2: I don't get any answers, but I do email him.

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Speaker 1: But it is a pretty wonderful universe. We do explore

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Speaker 1: all sides of it because it's kind of a big universe.

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Speaker 1: There's a lot of space in it.

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Speaker 2: In fact, the universe is mostly space. The kind of

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Speaker 2: thing that you're standing on and the sun that's in

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Speaker 2: the sky is pretty unusual. If you're going to pick

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Speaker 2: like a random spot in the universe, you're mostly going

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Speaker 2: to end up in a spot without a whole lot

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Speaker 2: of stuff in it.

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Speaker 1: Yeah, because, as we talked about on the podcast, space

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Speaker 1: it's not just emptiness, it's not nothing. It is actually

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Speaker 1: a thing, the thing that can stretch, that can bend,

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Speaker 1: that can slow down time. It's reactive to things, So

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Speaker 1: it's not nothing exactly.

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Speaker 2: We know that space is something interesting and it's a

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Speaker 2: really fascinating step in our sort of multi stage exploration

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Speaker 2: of the universe. You know, we start just by looking

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Speaker 2: at the stuff that's around us. We ask what's that

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Speaker 2: made out of? What's that made out of? What's that

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Speaker 2: made out of? But we sort of never stop I'm

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Speaker 2: asking those questions, and now we're at the point where

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Speaker 2: we're trying to understand, like what is the thing that

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Speaker 2: all the stuff is in. You know, if matter in

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Speaker 2: the end is made of particles, and those particles are

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Speaker 2: oscillations and quantum fields, and those quantum fields sit in space,

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Speaker 2: then the next frontier of understanding really is to understand

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Speaker 2: what that space itself is, and is space sitting in

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Speaker 2: some sort of like meta super or subspace.

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Speaker 1: Yeah, it's a very spacey question. There are many possibilities

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Speaker 1: out there for what space can be. If you can't

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Speaker 1: imagine that.

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Speaker 2: And it's a fundamental question at the heart of modern physics.

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Speaker 2: We're trying to understand quantum theory, were trying to understand

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Speaker 2: relativity and gravitation, and if the nexus of those two

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Speaker 2: is the fundamental mystery of what space actually is? Can

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Speaker 2: it actually been to make black holes? Are black holes

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Speaker 2: really black holes? Or are they something else? Why is

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Speaker 2: the universe expanding? What will be its ultimate fate? At

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Speaker 2: their hearts, all of these questions really are asking what

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Speaker 2: is space? And what are the rules of it? What

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Speaker 2: earns it? What is it fundamentally? Is it in fact

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Speaker 2: fundamental or is it just a frothing, emergent phenomena of

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Speaker 2: something even deeper? Yeah?

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Speaker 1: And do the rules of space apply to office space?

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Speaker 1: And I mean where people work, not just a.

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Speaker 2: Movie Office space turns out to be mostly politics. You know,

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Speaker 2: every time somebody retires here, there's like a scramble to

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Speaker 2: see who gets their big office.

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Speaker 1: Oh really, does it go by seniority? Like the more

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Speaker 1: senior you are, the closer you are to the snack

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Speaker 1: room or the restrooms, or the closer you need to

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Speaker 1: be to the restroom.

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Speaker 2: Perhaps, you know academics. Academics always have ladder systems and

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Speaker 2: ranking systems and it's no different here. We have like

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Speaker 2: many levels of being a professor. It's not just like assistant,

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Speaker 2: associate and full professor. Within each of those, it's like

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Speaker 2: many gradations, like full professor four or associate professor seven

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Speaker 2: or whatever. So when a new office opens up, they

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Speaker 2: go down the ladder and ask people at the top

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Speaker 2: of the ladder if they want it or not. And ridiculously,

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Speaker 2: all the offices in my building at least are different sizes.

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Speaker 2: And it would have been so much simpler if just

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Speaker 2: every office was the same size. I know, they made

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Speaker 2: some really big ones and some really little ones.

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Speaker 3: Hmm.

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Speaker 1: It's almost like they wanted some drama, political drama. Maybe

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Speaker 1: that was the architects revenge.

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Speaker 2: Maybe it was I don't know.

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Speaker 1: Isn't there some kind of like office space inertia, Like ooh,

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Speaker 1: that that is a slightly bigger office, But I would

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Speaker 1: have to clean my office and pack everything up to move,

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Speaker 1: so maybe I'll just skip.

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Speaker 2: Yeah. I do think that a lot of people don't

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Speaker 2: take a bigger office just because they're happy where they are,

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Speaker 2: or they don't really care, or their office is such

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Speaker 2: a disaster that it's impossible to imagine moving. And I

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Speaker 2: think That's also why it's sometimes hard to get people

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Speaker 2: out of their offices, because if you've been in there

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Speaker 2: for thirty years, you got a lot of stuff you

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Speaker 2: got to move out.

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Speaker 1: Are you saying there is such a thing as space inertia?

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Speaker 1: Like space can have inertia.

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Speaker 2: Turns out space can have politics. That's even weirder.

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Speaker 1: Or can a black hole have inertia?

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Speaker 2: Back to actual physics? Black holes definitely do have inertia, right,

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Speaker 2: They have mass, which means that they have inertia. If

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Speaker 2: you pushed on a black hole, then it's acceleration be

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Speaker 2: inversely proportional to its mass.

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Speaker 1: But you wouldn't actually recommend that, right, pushing a black hole?

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Speaker 1: That would be not good.

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Speaker 2: It depends if the black hole is headed towards our

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Speaker 2: solar system, then I would say, yes, let's launch something

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Speaker 2: heavy to push on the black hole so that it

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Speaker 2: doesn't come through our solar system.

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Speaker 1: Well, I guess what I meant is you wouldn't want

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Speaker 1: to push it yourself, like send Daniel up into space

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Speaker 1: having pushed on the black hole. I don't think that

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Speaker 1: would end well.

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Speaker 2: Am I going to get a big office out of it? Maybe?

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Speaker 1: Probably? Yeah, you might have the whole black hole to yourself.

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Speaker 2: That sounds great, except there are no windows, and I

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Speaker 2: really like an office with a view.

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Speaker 1: Well, it would be all windows except except yeah, I

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Speaker 1: guess you couldn't stick your head out of the window. Mm.

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Speaker 2: Yeah.

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Speaker 1: But it is interesting to think about what space could

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Speaker 1: be like, what is it made out of, and what

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Speaker 1: actually makes space happen.

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Speaker 2: Sometimes I think about scientists the way we think about

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Speaker 2: fish swimming around in water, probably not even really aware

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Speaker 2: that they are inside some sort of fluid because that's

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Speaker 2: their entire world. It might take fish like hundreds of

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Speaker 2: years or thousands of years to discover that the thing

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Speaker 2: they're inside is not the fundamental nature of the universe.

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Speaker 2: It doesn't exist everywhere, and it can do other kinds

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Speaker 2: of things like boil and freeze and all sorts of stuff.

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Speaker 2: So I wonder if we are sort of like fish,

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Speaker 2: exploring the nature of space and only now discovering that

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Speaker 2: it can do weird things that might have strange properties

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Speaker 2: and might not even be the fundamental layer of reality

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Speaker 2: so to be.

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Speaker 1: On the podcast, we'll be asking the question is space

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Speaker 1: time a fluid? What do you mean it's a fluid?

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Speaker 1: It's certainly a gas isn't it.

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Speaker 2: Well, time definitely seems to flow, so why not space time?

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Speaker 1: Right, Well, it's basfinitely a solid thing. It's always there,

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Speaker 1: you can rely on it.

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Speaker 2: Well, back to the analogy with fish scientists, which I

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Speaker 2: think probably originates with Max Tegmark. If you discover that

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Speaker 2: space is more complicated than just the backdrop of the universe,

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Speaker 2: and you discover that it might have other properties, it

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Speaker 2: might be able to do things like flow or bubble

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Speaker 2: or have different phases. And so that's a fascinating question

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Speaker 2: about the nature of space itself and sort of what

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Speaker 2: it can do. Can we described using the mathematics of

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Speaker 2: fluids or do we need a completely different kind of

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Speaker 2: mathematics to explain what space is up to?

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Speaker 1: Well, it is kind of a mind blowing question to

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Speaker 1: think that space time could be a fluid. It makes

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Speaker 1: it seem like it's a physical thing, like it actually

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Speaker 1: has like mass to it or something, or that it

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Speaker 1: responds to forces and things like that.

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Speaker 2: Yeah, as we'll see, space time being a fluid would

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Speaker 2: give very specific predictions for how things propagate through it,

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Speaker 2: how energy is spread or dissipates. So it's a really

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Speaker 2: fascinating hypothesis and I know we've talked about it in

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Speaker 2: the podcast before, how space time could be like a bubble,

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Speaker 2: right or like a foam?

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Speaker 1: Is not a fluid is it?

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Speaker 4: Now?

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Speaker 2: There are many theories of what space might be down

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Speaker 2: at the granular level. Is it made of little pixels

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Speaker 2: which are woven together with quantum entanglement into a kind

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Speaker 2: of foam or do those pixels operate in a different

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Speaker 2: sort of way. So this is more about, like at

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Speaker 2: the fundamental level, what are the rules of how those

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Speaker 2: pixels interact with each other and what phenomena emerges from that.

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Speaker 2: Can you describe them using the physics of foam, or

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Speaker 2: of liquids, or of ice cream, or office space bright

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Speaker 2: or interpersonal politics.

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Speaker 1: Or any kind of politics. Well, as usual, we were

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Speaker 1: wondering how many people out there had thought about this question,

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Speaker 1: had thought that maybe space time could be a fluid.

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Speaker 1: So Daniel went out there as usual and ask the

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Speaker 1: internet what they thought.

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Speaker 2: Thanks very much to everybody who answers these questions. We

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Speaker 2: love to hear your voice on the podcast, and anybody

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Speaker 2: out there who wants to volunteer, please don't be shy,

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Speaker 2: just write to me. Two questions at Danielandjorge dot com.

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Speaker 1: So think about it for a second. Do you think

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Speaker 1: space time could be a fluid? Here's what people had

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Speaker 1: to say.

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Speaker 4: I remember this was the argument for a theory in

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Speaker 4: the Bigavon theory. So yeah, maybe spacetime could be a fluid,

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Speaker 4: and that's the reason it only goes in one direction.

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Speaker 3: Maybe in previous episodes, I've noticed that you say that

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Speaker 3: space time can be stretched and squashed and almost like

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Speaker 3: molded in that kind of way. So I always imagine

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Speaker 3: space time being in some sort of matter state. So yes,

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Speaker 3: I would say space time could be similar.

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Speaker 1: To a fluid. I guess that space time is fluid

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Speaker 1: ish because you can't put it in a jar or something,

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Speaker 1: but it may behave like a fluid for some physics calculation.

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Speaker 5: I don't know, man, it seems like, you know, there's

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Speaker 5: waves in it, and we talk about it as some

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Speaker 5: sort of foam, But like what space is the fluid occupying?

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Speaker 5: That's that's a That's what gets me. I don't know.

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Speaker 6: So if I think about it, what is a fluid?

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Speaker 6: A fluid is a fluid will flow and it could

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Speaker 6: flow very slow like a glacier is ice? You think

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Speaker 6: ice is a solid but over long time scares a

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Speaker 6: glacier would flow like a river, and I think space

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Speaker 6: time around really massive objects like a black hole spinning

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Speaker 6: black hole in particular will also get dragged around. I

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Speaker 6: think it's called frame dragging, so space time itself will

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Speaker 6: spin around the black hole. And I think as you

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Speaker 6: go past the event horizon, doesn't space time itself kind

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Speaker 6: of flow towards the singularity.

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Speaker 1: I'm guessing that you could consider the curvature that some

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Speaker 1: kind of and start to exert on space time could

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Speaker 1: be considered blue. All right. I feel like we blew

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Speaker 1: people's minds with this question. Somebody's like one of the

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Speaker 1: people is like, WHOA, I don't know, man.

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Speaker 2: Well, that's my favorite part of this podcast is making

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Speaker 2: people explore crazy ideas, is dig deep into whether the

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Speaker 2: universe could really be different from the way that we

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Speaker 2: imagine it, you know, so contrary to our intuition. Those

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Speaker 2: are the best kinds of discoveries. And I think these

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Speaker 2: responses really reflect that kind of moment of exhilaration to

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Speaker 2: imagine that the universe could be so different.

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Speaker 1: I like the person to say they think it's fluid ish. Hey,

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Speaker 1: that's a good answer for anything. Do you think the unerus.

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Speaker 1: Is this there that way? I think it's this way ish.

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Speaker 2: Hmmm, my office is organized ish.

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Speaker 1: That's right. Yeah. But somebody else wrote in here that

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Speaker 1: space can have ways. We know that. You know you

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Speaker 1: can feel gravitational ways. We detected those. So if something

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Speaker 1: can have ways in it, does that mean it's like

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Speaker 1: a fluid?

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Speaker 2: Yeah, it's a really good deep question.

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Speaker 1: Like if you can make ripples in it, it's sort

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Speaker 1: of does that mean it is a fluid? I guess

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Speaker 1: you can make ripples in a gas too, or a solid.

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Speaker 2: Yeah. Liquids have special kinds of mathematics that describe them,

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Speaker 2: and that's what we're going to dig into. And there

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Speaker 2: are even people who have tried to build liquid analogies

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Speaker 2: of space time and liquid and analogies of black holes.

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Speaker 2: Is a guy in Israel who builds sonic black holes.

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Speaker 2: Sonic black holes. That sounds like a good definition for

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Speaker 2: our podcast. We're soundways good to die. I hope we're

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Speaker 2: not just speaking into the void. I hope there's somebody

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Speaker 2: out there listening. Maybe we're hawking radiationing our ideas into

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Speaker 2: the universe.

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Speaker 1: M you mean like we're fish in a fish tank. Maybe,

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Speaker 1: hopefully our soundways, are you going out there beyond the

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Speaker 1: fish tank?

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Speaker 2: I have some evidence that there are people out there

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Speaker 2: listening and we're not trapped into a sonic black hole

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Speaker 2: because we get responses from listeners. So if y'all are

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Speaker 2: actually out there and we're not trapped in a sonic

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Speaker 2: black hole, right back to us and confirm.

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Speaker 1: What if we're all in your mind, Daniel, what if

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Speaker 1: we're all like multiple personality aspects of you plot twist?

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Speaker 1: It's like the plot of an m. Jamelon movie.

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Speaker 2: I always wanted to be in one of his movies,

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Speaker 2: so I'd be pretty happy with that outcome.

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Speaker 1: But one of our responders here also asked an interesting

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Speaker 1: question like if space is a fluid, what is the

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Speaker 1: fluid in, Like what is it occupying? Is something holding

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Speaker 1: it like a jar or a fissible.

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Speaker 2: Or some sort of super space Like revealing the fundamental

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Speaker 2: nature of space time really just opens us up to

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Speaker 2: the next level of questions, like if space is a fluid,

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Speaker 2: or if space emerges from something else, and that other

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Speaker 2: thing and emerges from is more fundamental, and now we

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Speaker 2: can focus all of our energy on that thing. It

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Speaker 2: might be a never ending cycle where were always just

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Speaker 2: digging deeper and finding deeper and deeper layers of reality.

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Speaker 2: We don't know if we'll ever find some sort of

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Speaker 2: bedrock fundamental nature to the universe or not, or we

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Speaker 2: can always just ask, well, what's that made out of

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Speaker 2: or what's that sitting in?

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Speaker 1: Yeap goes on forever, and so let's start to dig

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Speaker 1: our way through it. Daniel, let's explain what is space time?

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Speaker 2: So the short version is we just really have no

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Speaker 2: idea what space is.

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Speaker 1: Boom and done, all right, thanks for joining us. It

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Speaker 1: is kind of a black hole. See question Yeah, good

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Speaker 1: diet on our podcast.

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Speaker 2: One of the most confusing things about it is that

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Speaker 2: we have very crisp and clear pictures of what space

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Speaker 2: might be in the theories that we have built up

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Speaker 2: about the universe, and as we've talked about in the

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Speaker 2: podcast many times, we have like two pillars of modern physics,

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Speaker 2: two different sets of ideas that have helped us answer

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Speaker 2: questions about what's going on in the universe. We have

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Speaker 2: quantum mechanics and we have general relativity. They're fundamentally inconsistent,

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Speaker 2: and they each give us a very different picture of

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Speaker 2: what space might be and how it works. So one

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Speaker 2: of the biggest puzzles is like trying to bring these

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Speaker 2: two things together to give us at least a unified

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Speaker 2: picture of what space is. But as of now, nobody's

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Speaker 2: been able to do that.

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Speaker 1: Yeah, there are two different views, so let's do one

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Speaker 1: of them at a time. What is space time according

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Speaker 1: to quantum mechanics or does quantum mechanics even call it

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Speaker 1: space time or does it treat space and time differently?

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Speaker 2: Yeah, quantum mechanics treat space and time very differently. It

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Speaker 2: treats space as the backdrop for quantum fields. It says

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Speaker 2: that space is filled with these fields that can oscillate,

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Speaker 2: and we have great equations that describe exactly how they

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Speaker 2: oscillate and buzz, and you can use those equations to

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Speaker 2: explain how electrons fly through space and how they radiate

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Speaker 2: photons which are absorbed by other particles. And so far

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Speaker 2: it seems like a super duper accurate description of what's

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Speaker 2: going on in the universe. We've done amazing experiments to

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Speaker 2: validate this description of the universe and compare it to

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Speaker 2: quantum mechanics predictions, which agreed to like eight or nine

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Speaker 2: decimal places. It's really super impressive. But the picture of

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Speaker 2: space and quantum mechanics is just sort of like the backdrop.

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Speaker 2: It's where the fields are. You know, we do the

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Speaker 2: mathematics of quantum field theory. We write these fields as

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Speaker 2: a function of space. We say every location in space

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Speaker 2: has a value of these fields, or if it's a

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Speaker 2: vector field, multiple values. There are like these numbers embedded

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Speaker 2: in space. The time is different. Time just tells us

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Speaker 2: how those fields change. And one really important thing about

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Speaker 2: time in quantum mechanics is that it should be infinite.

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Speaker 2: Like quantum mechanics says that the universe should have always

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Speaker 2: existed and should always exist because information in the universe

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Speaker 2: can't be lost, it can't just go away. And so

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Speaker 2: if you take the shorten your equation, for example, and

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Speaker 2: use it to describe the universe, you can run it

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Speaker 2: backwards and forwards in time to infinity. And that actually

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Speaker 2: tells you something about space itself, because it says that

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Speaker 2: space should have always existed throughout the whole universe. That's

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Speaker 2: sort of the quantum mechanical view of space time.

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Speaker 1: I feel like quantum mechanics. I feel like you're saying

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Speaker 1: that quantum mechanics is still basically stuck in the same

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Speaker 1: view of space as Newton was kind of right, like

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Speaker 1: before general relativity and Einstein, we just thought space was

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Speaker 1: this big emptiness. It couldn't change. It was like a

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Speaker 1: giant warehouse, you know, couldn't change or move or ripple

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Speaker 1: or anything like that. It was just fixed. Space was fixed.

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Speaker 1: And then you had time making things move forward in time.

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Speaker 1: And so quantum mechanics sort of started from that, and

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Speaker 1: it didn't really kind of think about what space could be.

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Speaker 1: It's sort of still stuck in that Newtonian or classical

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Speaker 1: physics view of space.

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Speaker 2: I think the broad strokes of that are definitely true.

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Speaker 2: There's a couple of sort of interesting and important caveats.

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Speaker 2: One is that we have succeeded in making quantum mechanics

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Speaker 2: act relativistically in some cases, like behaving with the rules

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Speaker 2: of relativity. Like we can describe the motion of super

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Speaker 2: duper fast quantum particles. Take an electron accelerate to almost

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Speaker 2: the speed of light, or protons at almost the speed

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Speaker 2: of light, and then you need like relativistic quantum mechanics.

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Speaker 2: But that's special relativity. That's just dealing mostly again with

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Speaker 2: flat space. So we can bring sort of special relativity's

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Speaker 2: view of space time into quantum mechanics. But you're right, fundamentally,

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Speaker 2: we're still just talking about things happening in the backdrop

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Speaker 2: of space. The other important thing to understand there is

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Speaker 2: that we have to add these things to quantum mechanics.

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Speaker 2: Quantum mechanics doesn't naturally have the sort of symmetries and

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Speaker 2: laws that we find in the universe. For example, you

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Speaker 2: can build quantum mechanics without a constant speed of light

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Speaker 2: or an invariant speed of light. We know that out

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Speaker 2: there in the universe the speed of light is the

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Speaker 2: speed of light is the speed of light, no matter

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Speaker 2: who's measuring it or what the setup is. But quantu

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Speaker 2: mechanics doesn't require that. It's not like built in. It

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Speaker 2: doesn't fall out of quantum mechanics naturally. So something you

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Speaker 2: have to add on to quantum mechanics, and that we've

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Speaker 2: been able to do we haven't been able to do

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Speaker 2: is make quantum mechanics consistent with curving spaces, to make

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Speaker 2: a quantum version of general relativity. That's the part we

442
00:21:16,119 --> 00:21:18,080
Speaker 2: haven't been able to do yet. But you're right, it

443
00:21:18,119 --> 00:21:21,080
Speaker 2: still sits in the sort of Newtonian backdrop where space

444
00:21:21,440 --> 00:21:23,280
Speaker 2: is the stage on which things happen.

445
00:21:23,520 --> 00:21:27,320
Speaker 1: So quantum mechanics maybe their view of space, it's viewo

446
00:21:27,400 --> 00:21:30,040
Speaker 1: space kind of matches maybe what most people think of

447
00:21:30,119 --> 00:21:32,719
Speaker 1: as space, or at least what you know, anyone who's

448
00:21:32,880 --> 00:21:36,000
Speaker 1: had a high school education in physics would think of

449
00:21:36,040 --> 00:21:36,480
Speaker 1: a space.

450
00:21:36,680 --> 00:21:39,520
Speaker 2: Weird stuff happens in that space, according to quantum mechanics,

451
00:21:39,560 --> 00:21:42,199
Speaker 2: but the space itself is just sort of like the

452
00:21:42,240 --> 00:21:44,680
Speaker 2: playground on which that weird stuff happens.

453
00:21:44,800 --> 00:21:47,160
Speaker 1: Yeah, Like nothing weird happens to space itself.

454
00:21:48,480 --> 00:21:51,119
Speaker 2: Yeah. And also that space really is Newtonian in the

455
00:21:51,160 --> 00:21:53,240
Speaker 2: sense that it doesn't have a lot of the symmetries

456
00:21:53,280 --> 00:21:56,400
Speaker 2: and principles that Einstein showed us that it does have,

457
00:21:56,520 --> 00:22:00,160
Speaker 2: like respecting the speed of light and all sorts of relativistic.

458
00:21:59,600 --> 00:22:02,960
Speaker 1: And varying interesting. All right, well, let's get into what

459
00:22:03,160 --> 00:22:06,879
Speaker 1: general relativity says that space is and whether or not

460
00:22:07,200 --> 00:22:10,119
Speaker 1: we could ever match it up with quantum mechanics, and

461
00:22:10,160 --> 00:22:12,879
Speaker 1: whether that could mean that space is a fluid. So

462
00:22:12,960 --> 00:22:15,399
Speaker 1: let's get into that, but first let's take a quick break.

463
00:22:27,960 --> 00:22:30,800
Speaker 1: All right, we're talking about the question of whether space

464
00:22:30,840 --> 00:22:33,560
Speaker 1: time is a fluid and whether that would mean that

465
00:22:33,600 --> 00:22:35,399
Speaker 1: you can drink it. And what kind of straw what

466
00:22:35,560 --> 00:22:38,280
Speaker 1: you need? Do you need a space time straw?

467
00:22:39,080 --> 00:22:41,920
Speaker 2: What's a good mixer for space? I wonder something dark?

468
00:22:42,280 --> 00:22:46,720
Speaker 1: Yeah, dark dark vodka, dark tequila. I don't know, maybe

469
00:22:46,800 --> 00:22:48,199
Speaker 1: some kalua pick your poison.

470
00:22:48,320 --> 00:22:50,360
Speaker 2: I think maybe some cream because space is pretty dark,

471
00:22:50,359 --> 00:22:51,720
Speaker 2: so you got to lighten it up a little bit,

472
00:22:51,760 --> 00:22:53,600
Speaker 2: you know. I'll take my space with some cream and

473
00:22:53,640 --> 00:22:54,280
Speaker 2: sugar please.

474
00:22:54,560 --> 00:22:56,520
Speaker 1: Or if it's a fluid, I guess that means you

475
00:22:56,520 --> 00:22:58,680
Speaker 1: can flush it? Can you flush space space time? You

476
00:22:59,000 --> 00:23:00,720
Speaker 1: sort of can, right, a black hole?

477
00:23:00,760 --> 00:23:04,280
Speaker 2: Maybe black holes are a sort of the toilets of

478
00:23:04,320 --> 00:23:05,320
Speaker 2: the universe. That's true.

479
00:23:05,440 --> 00:23:07,240
Speaker 1: Yeah, they suck in a lot of dark matter.

480
00:23:09,400 --> 00:23:11,840
Speaker 2: They actually don't, but it's a good joke.

481
00:23:12,760 --> 00:23:16,040
Speaker 1: Well, do you know, I guess that's the topic of

482
00:23:16,160 --> 00:23:17,000
Speaker 1: a different podcast.

483
00:23:17,040 --> 00:23:19,560
Speaker 2: Yeah, exactly. It's a really fun question.

484
00:23:19,800 --> 00:23:21,800
Speaker 1: You were talking about whether space time is the fluid,

485
00:23:21,800 --> 00:23:24,119
Speaker 1: and we talked about what space time is according to

486
00:23:24,200 --> 00:23:27,119
Speaker 1: quantum mechanics, which is pretty much the same view that

487
00:23:27,200 --> 00:23:30,040
Speaker 1: Newton had the classical physics have about space. But then

488
00:23:30,080 --> 00:23:33,200
Speaker 1: at some point at the beginning of the twentieth century,

489
00:23:33,400 --> 00:23:36,080
Speaker 1: Einstein came along and said, wait, dam minute. Space time

490
00:23:36,520 --> 00:23:39,720
Speaker 1: is not like fixed and immovable. It it does things,

491
00:23:39,760 --> 00:23:41,240
Speaker 1: It has properties of its own.

492
00:23:41,400 --> 00:23:45,280
Speaker 2: Yeah, Einstein showed us that space is dynamic. It's not

493
00:23:45,320 --> 00:23:48,600
Speaker 2: just a flat backdrop to the universe. It participates in

494
00:23:48,680 --> 00:23:52,159
Speaker 2: the motion of the universe in everything that happens. You know,

495
00:23:52,200 --> 00:23:54,840
Speaker 2: as I think John Wheeler said, mass tells space how

496
00:23:54,880 --> 00:23:58,480
Speaker 2: to mend, and space tells mass how to move. That

497
00:23:58,560 --> 00:24:00,440
Speaker 2: means that if you have a mass and certain part

498
00:24:00,480 --> 00:24:02,680
Speaker 2: of space, or a bunch of energy, then it curves

499
00:24:02,800 --> 00:24:07,040
Speaker 2: space itself. And Einstein's big realization was that what we

500
00:24:07,240 --> 00:24:10,040
Speaker 2: think of as the force of gravity isn't actually a force.

501
00:24:10,119 --> 00:24:13,840
Speaker 2: It's just due to our inability to directly see the

502
00:24:13,920 --> 00:24:17,480
Speaker 2: curvature of space, which is affecting how things are moving.

503
00:24:17,600 --> 00:24:19,399
Speaker 2: So the actions that we attribute to the force of

504
00:24:19,400 --> 00:24:24,080
Speaker 2: gravity are really just inertial motions of objects through curved space.

505
00:24:24,240 --> 00:24:28,280
Speaker 2: And his conception of space is this incredibly fascinating sort

506
00:24:28,320 --> 00:24:31,800
Speaker 2: of curved manifold, this sort of like shape that has

507
00:24:31,840 --> 00:24:34,639
Speaker 2: features to it. It's curved here, it's not curved there.

508
00:24:34,680 --> 00:24:37,760
Speaker 2: But it's really totally different from the conception of space

509
00:24:38,119 --> 00:24:41,480
Speaker 2: in quantum mechanics. It's not just a backdrop right, it's

510
00:24:41,480 --> 00:24:43,679
Speaker 2: not just like here's something that's happening at this location

511
00:24:43,800 --> 00:24:48,000
Speaker 2: and that location. The locations themselves now have interesting relationships,

512
00:24:48,080 --> 00:24:50,160
Speaker 2: like instead of just having a grid and every point

513
00:24:50,240 --> 00:24:53,760
Speaker 2: is equally spaced, those points can have weird relative distances,

514
00:24:53,880 --> 00:24:56,199
Speaker 2: like this point is actually closer than that point on

515
00:24:56,240 --> 00:24:58,640
Speaker 2: the grid, and these two points, which are super far

516
00:24:58,680 --> 00:25:01,399
Speaker 2: apart in the universe normally, can actually be adjacent to

517
00:25:01,480 --> 00:25:04,119
Speaker 2: each other. That's what a wormhole is. So really general

518
00:25:04,119 --> 00:25:06,639
Speaker 2: relativity is telling us that space can do this weird

519
00:25:06,640 --> 00:25:10,600
Speaker 2: thing about changing the relative distances internally between the points

520
00:25:10,840 --> 00:25:13,199
Speaker 2: that affects the motion of objects through it. And they

521
00:25:13,200 --> 00:25:17,159
Speaker 2: also discovered all these fascinating symmetries, like there's a maximum

522
00:25:17,200 --> 00:25:19,879
Speaker 2: speed of information through the universe. That was one of

523
00:25:19,880 --> 00:25:25,320
Speaker 2: the other big revelations in Einsteinian gravity, which contradicts Newtonian gravity.

524
00:25:25,520 --> 00:25:29,480
Speaker 2: That said that information propagates instantly according to Newton's gravity.

525
00:25:29,520 --> 00:25:33,240
Speaker 2: So Einstein's view of space is this smooth, continuous, but

526
00:25:33,480 --> 00:25:36,720
Speaker 2: dynamic thing that really plays a role in the universe.

527
00:25:36,760 --> 00:25:38,879
Speaker 2: It doesn't just sort of sit in the background and

528
00:25:38,880 --> 00:25:39,639
Speaker 2: provide a frame.

529
00:25:39,960 --> 00:25:42,560
Speaker 1: Yeah, it's pretty amazing. Eislin was able to kind of

530
00:25:42,640 --> 00:25:47,199
Speaker 1: revolutionize that video space. And I wonder if you or

531
00:25:47,240 --> 00:25:49,399
Speaker 1: we know how that came about, Like what was the

532
00:25:49,440 --> 00:25:51,679
Speaker 1: thing that set them off in that direction? Was it

533
00:25:51,720 --> 00:25:54,199
Speaker 1: basically observing what happens out there in nature that the

534
00:25:54,200 --> 00:25:57,040
Speaker 1: speed of light doesn't change. And if you start from there,

535
00:25:57,119 --> 00:25:59,360
Speaker 1: then you can sort of put together this idea that's

536
00:25:59,440 --> 00:26:00,960
Speaker 1: based on and bend and ripple.

537
00:26:01,040 --> 00:26:04,000
Speaker 2: Well, there are many stages in Einstein's thinking. The first is,

538
00:26:04,040 --> 00:26:07,280
Speaker 2: as you describe special theory of relativity, trying to understand

539
00:26:07,280 --> 00:26:09,560
Speaker 2: the Michaelson Morley experiment that showed that the speed of

540
00:26:09,600 --> 00:26:11,920
Speaker 2: light was the same in every direction, and also trying

541
00:26:11,960 --> 00:26:15,280
Speaker 2: to understand some puzzles in electromagnetic theory at the time,

542
00:26:15,560 --> 00:26:18,560
Speaker 2: like why a static electron gives an electric field, but

543
00:26:18,600 --> 00:26:22,200
Speaker 2: an electron in motion gives an electric and magnetic field.

544
00:26:22,280 --> 00:26:24,879
Speaker 2: Like it seemed like what was happening there dependent on

545
00:26:25,040 --> 00:26:27,840
Speaker 2: your perspective. So Einstein was trying to resolve all of

546
00:26:27,880 --> 00:26:30,560
Speaker 2: these puzzles. We have a whole podcast episode about that,

547
00:26:30,760 --> 00:26:33,200
Speaker 2: and that's what led to the special theory of relativity,

548
00:26:33,400 --> 00:26:36,280
Speaker 2: the idea of the speed of light being maximum and

549
00:26:36,400 --> 00:26:39,960
Speaker 2: information propagating at a certain speed and time not being

550
00:26:40,000 --> 00:26:42,320
Speaker 2: the same everywhere in the universe. That was already a

551
00:26:42,320 --> 00:26:44,440
Speaker 2: big step forward, But then it took like another ten

552
00:26:44,520 --> 00:26:46,480
Speaker 2: years for him to come up with the general theory

553
00:26:46,480 --> 00:26:49,560
Speaker 2: of relativity that's the one we're describing here, which is

554
00:26:49,560 --> 00:26:52,520
Speaker 2: about how space is curved and that curvature can explain

555
00:26:52,640 --> 00:26:55,760
Speaker 2: gravity for him, that came from puzzling over this question

556
00:26:55,800 --> 00:26:59,199
Speaker 2: about like, why is gravitational mass the massive controls how

557
00:26:59,240 --> 00:27:01,600
Speaker 2: much we get pulled on one seem to be exactly

558
00:27:01,600 --> 00:27:04,720
Speaker 2: the same as our inertial mass, the one that determines

559
00:27:04,920 --> 00:27:07,679
Speaker 2: how much we accelerate when we get pushed, Like the

560
00:27:07,720 --> 00:27:11,160
Speaker 2: mass in f equals M versus the mass in Newton's

561
00:27:11,240 --> 00:27:13,480
Speaker 2: law of gravity. Why do those two things seem to

562
00:27:13,480 --> 00:27:16,160
Speaker 2: be the same. So Einstein's sort of made that connection

563
00:27:16,240 --> 00:27:18,520
Speaker 2: and realized that they're really all bound up in the

564
00:27:18,560 --> 00:27:21,880
Speaker 2: same idea. Able to explain all of it by changing

565
00:27:21,920 --> 00:27:27,280
Speaker 2: space into a curved object or space time or space time. Yeah,

566
00:27:27,520 --> 00:27:31,080
Speaker 2: and there's a really important consequence there, right, If Einstein's

567
00:27:31,119 --> 00:27:34,240
Speaker 2: theory of space is correct, then you can also track

568
00:27:34,320 --> 00:27:37,119
Speaker 2: it backwards in time and say, look, the universe is expanding,

569
00:27:37,200 --> 00:27:39,200
Speaker 2: and that means that we can go backwards instead. The

570
00:27:39,280 --> 00:27:42,280
Speaker 2: universe used to be hotter and denser, and in Einstein's

571
00:27:42,280 --> 00:27:44,880
Speaker 2: theory at least that means that space and time can

572
00:27:44,920 --> 00:27:48,760
Speaker 2: have a beginning, right Unlike in quantum mechanics infinite in time,

573
00:27:48,960 --> 00:27:51,520
Speaker 2: Einstein's theory says that space could have had a beginning,

574
00:27:51,880 --> 00:27:53,439
Speaker 2: that there could have been a moment when there was

575
00:27:53,640 --> 00:27:57,760
Speaker 2: no space. So these are really very contradictory views of space.

576
00:27:57,920 --> 00:28:00,359
Speaker 2: Quantum mechanics view says time is infinite and space has

577
00:28:00,359 --> 00:28:05,040
Speaker 2: always existed. General relativity allows for a universe where space begins.

578
00:28:04,800 --> 00:28:07,159
Speaker 1: And so that brings us to maybe the biggest I

579
00:28:07,200 --> 00:28:10,840
Speaker 1: guess conflict in physics, the conflict between quantum mechanics and

580
00:28:10,880 --> 00:28:14,560
Speaker 1: general relativity and how they treat space. And this conflict

581
00:28:14,640 --> 00:28:17,800
Speaker 1: is kind of theoretical but also very conceptual. Like you said,

582
00:28:17,800 --> 00:28:20,720
Speaker 1: it's about, you know, whether time can begin or how

583
00:28:20,760 --> 00:28:24,560
Speaker 1: a beginning, whether time can bend? Is the conflict here

584
00:28:24,880 --> 00:28:28,400
Speaker 1: mostly theoretical, like we can make the theories work or

585
00:28:29,240 --> 00:28:31,760
Speaker 1: do you think it's something maybe more fundamental, that maybe

586
00:28:31,760 --> 00:28:34,240
Speaker 1: the properties of space change once you get to a

587
00:28:34,240 --> 00:28:35,440
Speaker 1: certain size level.

588
00:28:35,760 --> 00:28:39,040
Speaker 2: Yeah, we definitely cannot make the theories work currently, Like

589
00:28:39,160 --> 00:28:41,800
Speaker 2: people are trying from all sorts of directions to unify

590
00:28:41,840 --> 00:28:44,120
Speaker 2: these things. One set of theories is saying, well, let's

591
00:28:44,120 --> 00:28:47,200
Speaker 2: take quantum mechanics and try to do it in curved space,

592
00:28:47,640 --> 00:28:50,120
Speaker 2: and that actually kind of works, like if you have

593
00:28:50,200 --> 00:28:53,080
Speaker 2: space that already curves. For other reasons, we do know

594
00:28:53,120 --> 00:28:56,080
Speaker 2: how to do some quantum mechanics of particles moving in

595
00:28:56,200 --> 00:28:58,840
Speaker 2: curved space. We don't know how to do is show

596
00:28:58,880 --> 00:29:02,360
Speaker 2: how quantum mechanics can make space curved, like to get

597
00:29:02,400 --> 00:29:05,720
Speaker 2: that curvature just from the particles, to show how like

598
00:29:05,760 --> 00:29:08,000
Speaker 2: having a bunch of electrons in one place will make

599
00:29:08,120 --> 00:29:10,720
Speaker 2: space curved. When people try to do that, it gets

600
00:29:10,800 --> 00:29:13,560
Speaker 2: really complicated and hairy, and you get all sorts of infinities.

601
00:29:13,680 --> 00:29:15,520
Speaker 2: And one of the reasons is that gravity is are

602
00:29:15,520 --> 00:29:18,400
Speaker 2: real nest to do calculations with. If you emit gravitons,

603
00:29:18,400 --> 00:29:21,280
Speaker 2: gravitons feel gravity, and they emit more gravitons, which emit

604
00:29:21,320 --> 00:29:24,240
Speaker 2: more gravitons, so it very quickly gets out of control,

605
00:29:24,640 --> 00:29:26,920
Speaker 2: sort of like the strong nuclear force. We were talking about

606
00:29:26,960 --> 00:29:30,200
Speaker 2: how gluons emit gluons, which emit gluons, which makes it

607
00:29:30,240 --> 00:29:33,720
Speaker 2: almost impossible to do those calculations. But gravity is even trickier.

608
00:29:33,760 --> 00:29:36,640
Speaker 2: And so people have really failed in trying to do that.

609
00:29:37,200 --> 00:29:39,160
Speaker 2: And from the other direction, people are saying, well, let's

610
00:29:39,160 --> 00:29:42,600
Speaker 2: take space and quantize it and say maybe instead of

611
00:29:42,640 --> 00:29:46,160
Speaker 2: the force being quantum mechanical, maybe space itself is quantum mechanical.

612
00:29:46,160 --> 00:29:49,640
Speaker 2: It's chopped up into little discrete bits. And this idea

613
00:29:49,680 --> 00:29:52,640
Speaker 2: also hasn't quite worked yet. Nobody's really been able to

614
00:29:52,680 --> 00:29:55,880
Speaker 2: bring these two things together mathematically. What you asked is like,

615
00:29:55,960 --> 00:29:58,560
Speaker 2: is this a mathematical problem or a theoretical problem? And

616
00:29:58,560 --> 00:30:01,040
Speaker 2: I think the answers are connected. If we are able

617
00:30:01,080 --> 00:30:04,200
Speaker 2: to come up with a mathematical description that explains everything

618
00:30:04,200 --> 00:30:06,719
Speaker 2: we see in the universe and sort of hangs together,

619
00:30:06,800 --> 00:30:09,720
Speaker 2: doesn't give us nonsense, then we'll have a theoretical or

620
00:30:09,720 --> 00:30:12,960
Speaker 2: philosophical question like what does that mean? You know, how

621
00:30:12,960 --> 00:30:14,600
Speaker 2: far do we have to go in order to make

622
00:30:14,600 --> 00:30:16,719
Speaker 2: that theory? Can we just try to bring these two

623
00:30:16,760 --> 00:30:18,800
Speaker 2: theories together, or do we need to dig a level

624
00:30:18,880 --> 00:30:22,600
Speaker 2: deeper and start from something else which can then explain

625
00:30:22,760 --> 00:30:24,520
Speaker 2: what we're seeing on the larger level?

626
00:30:24,760 --> 00:30:28,040
Speaker 1: Interesting, I guess you'll just have a big fight about it.

627
00:30:28,080 --> 00:30:30,120
Speaker 1: And then wherever win in spins.

628
00:30:29,840 --> 00:30:32,040
Speaker 2: And I think one of the deepest questions really is

629
00:30:32,120 --> 00:30:36,400
Speaker 2: like is space itself the fundamental fabric of the universe?

630
00:30:36,480 --> 00:30:38,320
Speaker 2: Do we need to be building on top of space

631
00:30:38,800 --> 00:30:40,720
Speaker 2: or do we need to be tearing it apart and

632
00:30:40,720 --> 00:30:44,120
Speaker 2: trying to understand what it's made out of? Like is

633
00:30:44,200 --> 00:30:48,080
Speaker 2: space itself fundamental? Meaning it just is, it's like the

634
00:30:48,120 --> 00:30:52,280
Speaker 2: base layer of reality. Or is space emergent it's just

635
00:30:52,360 --> 00:30:56,840
Speaker 2: something that arises from something deeper and it's complicated interactions.

636
00:30:56,880 --> 00:30:58,360
Speaker 1: That's kind of I feel like that maybe that's a

637
00:30:58,480 --> 00:31:02,000
Speaker 1: separate question. Then this idea whether quantum mechanics or general

638
00:31:02,000 --> 00:31:04,960
Speaker 1: relativity is right, right, it's sort of a separate question,

639
00:31:05,080 --> 00:31:07,560
Speaker 1: like whether either one is right. We can also ask

640
00:31:07,600 --> 00:31:10,600
Speaker 1: the question like where does space come from?

641
00:31:10,640 --> 00:31:13,160
Speaker 2: Well, it might be a path forward to giving us

642
00:31:13,200 --> 00:31:15,840
Speaker 2: these two different explanations of space. Space seems to be

643
00:31:15,920 --> 00:31:19,280
Speaker 2: kind of different in quantum mechanics and in relativity, And

644
00:31:19,360 --> 00:31:22,120
Speaker 2: instead of harmonizing them and of trying to mash them together,

645
00:31:22,440 --> 00:31:24,760
Speaker 2: you might be able to explain them just by saying, well,

646
00:31:24,800 --> 00:31:27,280
Speaker 2: they're sort of both wrong. Neither of them are actually

647
00:31:27,320 --> 00:31:30,520
Speaker 2: true descriptions of what space is. Space is something deeper

648
00:31:30,560 --> 00:31:33,200
Speaker 2: and weirder that can do these two kinds of things

649
00:31:33,320 --> 00:31:36,480
Speaker 2: the way for example, fish scientists might argue and say, look, look,

650
00:31:36,640 --> 00:31:39,840
Speaker 2: ice is different from liquid water, which is different from gas.

651
00:31:39,920 --> 00:31:42,280
Speaker 2: They're just different, right, And we know of course they're

652
00:31:42,280 --> 00:31:44,240
Speaker 2: all made out of the same thing deep down. This

653
00:31:44,360 --> 00:31:47,520
Speaker 2: is just different stuff that water can do. Ice is

654
00:31:47,560 --> 00:31:50,240
Speaker 2: not fundamental to the universe. Water is not fundamental to

655
00:31:50,280 --> 00:31:52,840
Speaker 2: the universe. Steam is not fundamental to the universe. It's

656
00:31:52,880 --> 00:31:55,560
Speaker 2: just an emergent property of water. If we can come

657
00:31:55,640 --> 00:31:59,000
Speaker 2: up with like a deeper understanding of what space is,

658
00:31:59,400 --> 00:32:03,320
Speaker 2: something beyond our understanding currently, maybe we can explain are

659
00:32:03,400 --> 00:32:06,240
Speaker 2: the quantum mechanical view of space and the general relativistic

660
00:32:06,320 --> 00:32:10,000
Speaker 2: view of space is like different phases of space the

661
00:32:10,040 --> 00:32:13,160
Speaker 2: way we think about different phases of water having you know,

662
00:32:13,240 --> 00:32:16,200
Speaker 2: fundamentally inconsistent kinds of behavior.

663
00:32:16,320 --> 00:32:18,200
Speaker 1: Well, that's kind of what I meant before, is that,

664
00:32:18,360 --> 00:32:20,680
Speaker 1: like you know, it's the conflict between quantum mechanics and

665
00:32:20,720 --> 00:32:24,080
Speaker 1: general relativity. Could it be explained by just like having

666
00:32:24,480 --> 00:32:27,720
Speaker 1: space behave differently at different scales, like in the scale

667
00:32:27,720 --> 00:32:30,640
Speaker 1: of planets and black holes, it behaves like one way

668
00:32:30,680 --> 00:32:33,240
Speaker 1: where you have grampetition waves and it bends. But maybe

669
00:32:33,280 --> 00:32:35,840
Speaker 1: at the level of small particles, it behaves differently.

670
00:32:36,120 --> 00:32:38,880
Speaker 2: Yeah, that's exactly the right direction, and a lot of

671
00:32:38,920 --> 00:32:41,760
Speaker 2: people are pushing that way, like can we start at

672
00:32:41,760 --> 00:32:44,400
Speaker 2: a lower level and come up with a more fundamental

673
00:32:44,400 --> 00:32:47,040
Speaker 2: description of space and then as you say, it turns

674
00:32:47,040 --> 00:32:49,600
Speaker 2: into quantum mechanics at this scale, or turns into general

675
00:32:49,600 --> 00:32:52,680
Speaker 2: relativity at that scale, and fundamentally, what that means is

676
00:32:52,720 --> 00:32:55,320
Speaker 2: that both are wrong. Instead of trying to start from

677
00:32:55,320 --> 00:32:58,120
Speaker 2: general relativity and at quantum mechanics, or start from quantum

678
00:32:58,080 --> 00:33:01,000
Speaker 2: mechanics and ad general relativity, of throw both out the

679
00:33:01,040 --> 00:33:03,840
Speaker 2: window and say let's start from something deeper and try

680
00:33:03,880 --> 00:33:06,760
Speaker 2: to reproduce both of them, but neither of them fundamentally

681
00:33:06,800 --> 00:33:08,080
Speaker 2: would be correct in that picture.

682
00:33:08,120 --> 00:33:09,920
Speaker 1: Well you want to throw them out? That sounds very

683
00:33:10,400 --> 00:33:13,560
Speaker 1: negative and I feel like a lot of work has

684
00:33:13,560 --> 00:33:16,360
Speaker 1: gone into those It could just be that they're both right.

685
00:33:16,400 --> 00:33:19,800
Speaker 1: They're just right at different scales perhaps or in different situations,

686
00:33:19,840 --> 00:33:22,560
Speaker 1: like we still use Newtonian physics to calculate the path

687
00:33:22,680 --> 00:33:24,800
Speaker 1: of baseball when you throw it or something like that.

688
00:33:24,880 --> 00:33:28,280
Speaker 2: Yeah, they both work right. They're effective theories in that

689
00:33:28,560 --> 00:33:31,880
Speaker 2: they give good predictions in certain situations. But if what

690
00:33:31,920 --> 00:33:34,840
Speaker 2: we're trying to do is understand the deep nature of

691
00:33:34,880 --> 00:33:38,520
Speaker 2: the universe. Then they're not like philosophically true. I think

692
00:33:38,560 --> 00:33:41,040
Speaker 2: our final goal is to get a description of the

693
00:33:41,080 --> 00:33:44,640
Speaker 2: universe that we think mirrors what's actually happening out there.

694
00:33:45,040 --> 00:33:48,560
Speaker 2: Like conceptually describes the laws the universe itself is like

695
00:33:48,680 --> 00:33:51,960
Speaker 2: actually following. So in that sense, general relativity and quantum

696
00:33:51,960 --> 00:33:55,040
Speaker 2: mechanics wouldn't reflect what's actually happening out there in the universe.

697
00:33:55,160 --> 00:33:57,640
Speaker 2: Though you're totally right, they're very useful and they're very

698
00:33:57,640 --> 00:34:00,840
Speaker 2: effective the same way we use like fluid mechanics to

699
00:34:00,920 --> 00:34:03,200
Speaker 2: explain what happens when you flush your toilet, and it

700
00:34:03,240 --> 00:34:06,280
Speaker 2: works right, it's very good. It helps us avoid lots

701
00:34:06,320 --> 00:34:09,160
Speaker 2: of ugly disasters. Doesn't mean we should stop doing it,

702
00:34:09,239 --> 00:34:11,880
Speaker 2: but it doesn't mean that the assumptions behind fluid mechanics

703
00:34:11,920 --> 00:34:14,080
Speaker 2: are the right way to think about the reality of

704
00:34:14,160 --> 00:34:14,880
Speaker 2: the universe.

705
00:34:15,080 --> 00:34:17,440
Speaker 1: Well, my toilet seems to flush, whether or not I

706
00:34:17,520 --> 00:34:23,440
Speaker 1: understand the fluid dynamics. Fortunately, otherwise, you enough and you put.

707
00:34:23,320 --> 00:34:28,080
Speaker 2: Enough dark matter in there, and I promise you won't flush.

708
00:34:28,480 --> 00:34:30,239
Speaker 1: Then you need dark energy to push it through.

709
00:34:32,320 --> 00:34:34,560
Speaker 2: Suggest that to your plumber and see how that goes.

710
00:34:35,239 --> 00:34:36,839
Speaker 1: Oh, there you go, that could be a good name

711
00:34:36,880 --> 00:34:40,000
Speaker 1: for plumbing business dark plumbers.

712
00:34:40,280 --> 00:34:43,680
Speaker 2: Dark plumbers. That sounds like a CIA operation.

713
00:34:43,880 --> 00:34:45,080
Speaker 1: Yeah, or SITH operation.

714
00:34:45,320 --> 00:34:48,160
Speaker 2: Were like, Yeah, if that van is parked outside your house,

715
00:34:48,200 --> 00:34:49,200
Speaker 2: I would suggest moving.

716
00:34:49,960 --> 00:34:52,839
Speaker 1: If your plumber brings out a lightsaber. First of all,

717
00:34:53,000 --> 00:34:55,480
Speaker 1: super cool, you totally take a selfie with your plumber,

718
00:34:56,080 --> 00:34:58,440
Speaker 1: but they might damage the plumbing.

719
00:34:58,600 --> 00:35:00,600
Speaker 2: Yeah, but also see if you can dune. I hear

720
00:35:00,680 --> 00:35:02,040
Speaker 2: those Jedi are really good at.

721
00:35:01,920 --> 00:35:06,360
Speaker 1: Basketball, Well, would they be dunking with a toilet? I

722
00:35:06,360 --> 00:35:06,680
Speaker 1: don't know.

723
00:35:06,840 --> 00:35:08,240
Speaker 2: This analogy has gone off the rails.

724
00:35:08,280 --> 00:35:10,360
Speaker 1: All right, Well, let's tackle maybe the question that we

725
00:35:10,400 --> 00:35:13,760
Speaker 1: started off with, which is is space time a fluid

726
00:35:14,120 --> 00:35:17,480
Speaker 1: like space time flow? I guess and swirl or get

727
00:35:17,520 --> 00:35:21,120
Speaker 1: flushed down a toilet? Daniel, Where does this idea come from?

728
00:35:21,200 --> 00:35:23,440
Speaker 2: This comes from an attempt to try to explain the

729
00:35:23,560 --> 00:35:26,879
Speaker 2: nature of space, as we talked about, as not fundamental

730
00:35:26,920 --> 00:35:30,520
Speaker 2: but something that emerges from a lower level of reality.

731
00:35:30,719 --> 00:35:34,920
Speaker 2: And it says essentially that maybe space is like water.

732
00:35:35,280 --> 00:35:38,080
Speaker 2: It's made out of some smaller pieces that follow very

733
00:35:38,160 --> 00:35:41,719
Speaker 2: very different rules, and that our experience of it is

734
00:35:41,760 --> 00:35:44,000
Speaker 2: sort of like the experience of water. We really are

735
00:35:44,160 --> 00:35:47,000
Speaker 2: like the fish. Scientists that space itself is made out

736
00:35:47,000 --> 00:35:49,239
Speaker 2: of some smaller bits we have yet to discover, and

737
00:35:49,320 --> 00:35:51,719
Speaker 2: those bits interact with each other in a way that

738
00:35:51,880 --> 00:35:56,040
Speaker 2: follows the laws of fluid mechanics, that our understanding of

739
00:35:56,120 --> 00:35:58,800
Speaker 2: fluids and water actually might be able to be applied

740
00:35:59,160 --> 00:36:03,720
Speaker 2: to space self. Space emerges from some weird quantum bits

741
00:36:03,920 --> 00:36:06,279
Speaker 2: and those bits come together in a way that can

742
00:36:06,320 --> 00:36:08,600
Speaker 2: be described by fluid mechanics.

743
00:36:08,920 --> 00:36:11,279
Speaker 1: Yeah, it's kind of like the idea. Then maybe there's

744
00:36:11,360 --> 00:36:15,279
Speaker 1: like a superspace and inside of that superspace is what

745
00:36:15,360 --> 00:36:18,040
Speaker 1: we call space, and that it's actually made up of

746
00:36:18,080 --> 00:36:20,880
Speaker 1: like little bits of space, meaning like when I think

747
00:36:20,960 --> 00:36:23,319
Speaker 1: I'm moving through space, or when a particle thinks it's

748
00:36:23,320 --> 00:36:27,120
Speaker 1: moving through space, it's actually like maybe hopping between bits

749
00:36:27,160 --> 00:36:29,360
Speaker 1: of space. Is that's kind of the idea, right.

750
00:36:29,239 --> 00:36:31,680
Speaker 2: That's kind of the idea, And it's also attractive from

751
00:36:31,719 --> 00:36:34,359
Speaker 2: the point of view of explaining some of the symmetries

752
00:36:34,440 --> 00:36:38,200
Speaker 2: and the invariances that we see, Like we don't understand where,

753
00:36:38,320 --> 00:36:40,960
Speaker 2: for example, this law of the speed of light comes from.

754
00:36:41,280 --> 00:36:44,640
Speaker 2: Why is there a maximum speed of information in our universe?

755
00:36:45,040 --> 00:36:47,560
Speaker 2: In quantum mechanics, we just don't see that right, it

756
00:36:47,600 --> 00:36:50,160
Speaker 2: doesn't exist in the theory of quant mechanics. Something we

757
00:36:50,200 --> 00:36:53,040
Speaker 2: had to add two quantum mechanics sort of by hand.

758
00:36:53,239 --> 00:36:55,640
Speaker 2: But if space is an emergent phenomena, if it comes

759
00:36:55,680 --> 00:36:58,400
Speaker 2: from the weaving together of these weird quantum bits, they

760
00:36:58,520 --> 00:37:01,400
Speaker 2: might be able to have the maximum speed of information

761
00:37:01,719 --> 00:37:04,520
Speaker 2: sort of emerge from those laws. The way that like

762
00:37:05,000 --> 00:37:07,600
Speaker 2: water as a liquid can do things that water as

763
00:37:07,600 --> 00:37:10,640
Speaker 2: an individual particle doesn't do, or that water as a

764
00:37:10,680 --> 00:37:13,640
Speaker 2: crystal can do things has properties that water as an

765
00:37:13,640 --> 00:37:17,400
Speaker 2: individual particle doesn't do. Maybe these invariances in these symmetries

766
00:37:17,719 --> 00:37:20,919
Speaker 2: sort of emerge with space. They're the properties that come

767
00:37:21,200 --> 00:37:25,560
Speaker 2: when space comes together to form these liquids. And fundamentally,

768
00:37:25,600 --> 00:37:27,839
Speaker 2: you're right, it's like these little bits of space sort

769
00:37:27,840 --> 00:37:31,200
Speaker 2: of woven together, and it's fascinating to think about, like

770
00:37:31,320 --> 00:37:34,240
Speaker 2: how you weave space together to make it a liquid.

771
00:37:34,360 --> 00:37:36,799
Speaker 2: It says that you start from a universe where all

772
00:37:36,840 --> 00:37:39,520
Speaker 2: you have are like weird little quantum bits. You have

773
00:37:39,600 --> 00:37:42,920
Speaker 2: these locations, but they don't sort of exist in space yet.

774
00:37:43,000 --> 00:37:45,600
Speaker 2: They just sort of like are there, and then they

775
00:37:45,640 --> 00:37:48,879
Speaker 2: get quantum entangled with each other, which sort of connects them.

776
00:37:49,000 --> 00:37:52,640
Speaker 2: Then things that are really tightly quantum entangled with each other.

777
00:37:52,880 --> 00:37:55,319
Speaker 2: We call those things close to each other. Things that

778
00:37:55,320 --> 00:37:58,560
Speaker 2: are loosely quantum entangled. We call those things further from

779
00:37:58,600 --> 00:38:00,759
Speaker 2: each other, things that are not intense at all, or

780
00:38:00,760 --> 00:38:03,839
Speaker 2: like out of your light cone completely. So you sort

781
00:38:03,840 --> 00:38:07,239
Speaker 2: of like build space up by quantum entangling all these

782
00:38:07,280 --> 00:38:10,800
Speaker 2: weird little sort of non space bits, and space itself

783
00:38:10,840 --> 00:38:13,400
Speaker 2: comes out of all those things working together.

784
00:38:13,920 --> 00:38:16,080
Speaker 1: Yeah, And I think maybe the idea is, like, maybe

785
00:38:16,160 --> 00:38:19,120
Speaker 1: as you're moving around these space bits, there are rules

786
00:38:19,160 --> 00:38:22,280
Speaker 1: about moving through these space bits that maybe explain things

787
00:38:22,320 --> 00:38:24,880
Speaker 1: like the speed of light limit in our universe. Right, Like,

788
00:38:24,960 --> 00:38:27,600
Speaker 1: maybe if I'm switching between space bits, there's a certain

789
00:38:27,640 --> 00:38:30,239
Speaker 1: cost to that, and then that would explain the limit

790
00:38:30,320 --> 00:38:32,080
Speaker 1: of the speed of light. And that's kind of what

791
00:38:32,080 --> 00:38:34,200
Speaker 1: you're saying, is that maybe these things that we think

792
00:38:34,239 --> 00:38:37,839
Speaker 1: of as fundamental phenomenas or properties of the unverse could

793
00:38:37,920 --> 00:38:41,520
Speaker 1: just be like the little tiny rules between space bits

794
00:38:41,560 --> 00:38:43,040
Speaker 1: that make up space exactly.

795
00:38:43,080 --> 00:38:44,920
Speaker 2: So that picture, which is more like a sort of

796
00:38:45,080 --> 00:38:48,000
Speaker 2: quantum space foam, says you build space out of these

797
00:38:48,000 --> 00:38:50,560
Speaker 2: little bits, and the rules that we observe sort of

798
00:38:50,560 --> 00:38:52,759
Speaker 2: come out of the arrangement of those things. They're not

799
00:38:52,800 --> 00:38:54,960
Speaker 2: fundamental to the bits themselves or sort of how you

800
00:38:54,960 --> 00:38:57,760
Speaker 2: put them together. This new theory says, well, maybe space

801
00:38:57,880 --> 00:39:00,319
Speaker 2: isn't like a foam. It's kind of like a but

802
00:39:00,360 --> 00:39:03,080
Speaker 2: it's a little bit different. You don't use the mathematics

803
00:39:03,080 --> 00:39:06,600
Speaker 2: of foam. Instead use the mathematics of liquids. Say, space

804
00:39:06,640 --> 00:39:10,040
Speaker 2: isn't like a grid that's woven together with quantum entanglements.

805
00:39:10,120 --> 00:39:12,239
Speaker 2: Maybe there's a little bit of a different physics there.

806
00:39:12,400 --> 00:39:14,320
Speaker 2: And what's happening is that these little bits of space

807
00:39:14,320 --> 00:39:16,960
Speaker 2: can sort of like slide past each other, they can

808
00:39:17,000 --> 00:39:19,799
Speaker 2: like flow around each other. They can do things that

809
00:39:20,040 --> 00:39:23,360
Speaker 2: foam or crystal can't do. This actually leads to slightly

810
00:39:23,440 --> 00:39:26,680
Speaker 2: different predictions for the behavior of space, and one of

811
00:39:26,719 --> 00:39:28,920
Speaker 2: them is that the limit on the speed of light

812
00:39:29,040 --> 00:39:33,000
Speaker 2: is not actually absolute. It's like approximate. That light doesn't

813
00:39:33,000 --> 00:39:35,160
Speaker 2: always travel at the speed of light. There might be

814
00:39:35,160 --> 00:39:37,400
Speaker 2: like very small variations there.

815
00:39:37,600 --> 00:39:39,759
Speaker 1: I see. The idea is and maybe these bits of

816
00:39:39,800 --> 00:39:42,759
Speaker 1: space that space is made out of aren't connected to

817
00:39:42,760 --> 00:39:45,759
Speaker 1: each other, Like they're not linked together like you might

818
00:39:45,840 --> 00:39:49,480
Speaker 1: link like a chain mail or a chain link fence.

819
00:39:49,960 --> 00:39:52,440
Speaker 1: Maybe they're just kind of like floating out there in

820
00:39:52,520 --> 00:39:55,000
Speaker 1: some super meta space, and they can actually kind of

821
00:39:55,160 --> 00:39:57,360
Speaker 1: slosh around and move relative to each other. Is that

822
00:39:57,440 --> 00:39:57,840
Speaker 1: the idea?

823
00:39:57,880 --> 00:40:00,000
Speaker 2: That's sort of the idea, though what you described sounds

824
00:40:00,080 --> 00:40:02,480
Speaker 2: more like a space gas. Think about like a crystal

825
00:40:02,680 --> 00:40:05,600
Speaker 2: where the bonds between the atoms are really really strong. Right,

826
00:40:05,600 --> 00:40:08,040
Speaker 2: that's sort of like our idea of a space foam. Now,

827
00:40:08,120 --> 00:40:09,960
Speaker 2: relax those bonds a little bit, and you have like

828
00:40:10,000 --> 00:40:13,200
Speaker 2: a space liquid you're write, things can slide past each other,

829
00:40:13,239 --> 00:40:16,240
Speaker 2: but they're not totally ignoring each other. There's still interactions

830
00:40:16,239 --> 00:40:20,160
Speaker 2: between those space bits, which is how fluid effects emerge.

831
00:40:20,480 --> 00:40:23,360
Speaker 2: If they were totally disconnected, you have like a collisionless,

832
00:40:23,440 --> 00:40:26,800
Speaker 2: non interacting gas of space bits, then you would expect

833
00:40:26,880 --> 00:40:29,600
Speaker 2: very very different kinds of behavior. This theory says, instead

834
00:40:29,600 --> 00:40:33,400
Speaker 2: of having space like a rigid crystal of locations that

835
00:40:33,440 --> 00:40:36,200
Speaker 2: are fixed to each other, loosen it up a little

836
00:40:36,200 --> 00:40:39,000
Speaker 2: bit and let those flow, not completely where they're ignoring

837
00:40:39,000 --> 00:40:41,640
Speaker 2: each other. There's still sort of some bonds between them,

838
00:40:41,719 --> 00:40:44,000
Speaker 2: but let them flow a little bit, and it leads

839
00:40:44,040 --> 00:40:47,040
Speaker 2: to different predictions for how light moves through this sort

840
00:40:47,040 --> 00:40:48,360
Speaker 2: of liquidity space.

841
00:40:48,560 --> 00:40:50,319
Speaker 1: Well, I guess what does that mean? Does that mean

842
00:40:50,360 --> 00:40:53,280
Speaker 1: that as I'm moving through space, if the space liquid

843
00:40:53,320 --> 00:40:56,920
Speaker 1: happens to be moving, then I'm going to move differently

844
00:40:57,000 --> 00:41:00,360
Speaker 1: through it? Or would I even notice if the liquid

845
00:41:00,400 --> 00:41:01,600
Speaker 1: around me is flowing.

846
00:41:01,719 --> 00:41:03,760
Speaker 2: When things move through liquid, they move in a different

847
00:41:03,800 --> 00:41:06,560
Speaker 2: way than when they move through a solid, right, And

848
00:41:06,600 --> 00:41:08,440
Speaker 2: a solid is more rigid, and so it's sort of

849
00:41:08,480 --> 00:41:12,000
Speaker 2: better at propagating waves, right, which is why, like sound

850
00:41:12,080 --> 00:41:14,839
Speaker 2: moves faster through your table than it does through the air.

851
00:41:15,080 --> 00:41:18,720
Speaker 2: In denser materials, things are more tightly bound, sound moves faster,

852
00:41:18,920 --> 00:41:22,120
Speaker 2: and so things in space time liquid would move differently

853
00:41:22,160 --> 00:41:24,320
Speaker 2: than things in sort of a space time foam or

854
00:41:24,400 --> 00:41:27,680
Speaker 2: space time crystal. And specifically, it would mean that it

855
00:41:27,800 --> 00:41:30,839
Speaker 2: slashes a little bit, so there'd be like a dissipation

856
00:41:31,360 --> 00:41:34,040
Speaker 2: that if you shoot a super high energy photon across

857
00:41:34,080 --> 00:41:36,160
Speaker 2: the universe, instead of it getting to the other side

858
00:41:36,160 --> 00:41:37,920
Speaker 2: of the universe with the same amount of energy, it

859
00:41:37,960 --> 00:41:40,759
Speaker 2: would lose some of that energy to like this slashing

860
00:41:40,920 --> 00:41:42,279
Speaker 2: of space itself.

861
00:41:42,560 --> 00:41:48,120
Speaker 1: Mmm, sounds like we're all in a hut tub. I

862
00:41:48,120 --> 00:41:50,760
Speaker 1: feel like you're saying the universe just a nice bubbly

863
00:41:51,560 --> 00:41:54,280
Speaker 1: huttub that we're all relaxing it all right, Well, let's

864
00:41:54,320 --> 00:41:57,880
Speaker 1: talk about what makes us think that the universe or

865
00:41:57,920 --> 00:41:59,920
Speaker 1: that space time can be a fluid, and whether we

866
00:42:00,200 --> 00:42:02,279
Speaker 1: have any evidence of it, and if we do, what

867
00:42:02,360 --> 00:42:05,680
Speaker 1: would that mean about our understanding of how everything works.

868
00:42:06,200 --> 00:42:08,520
Speaker 1: So let's get into that, but first let's take another

869
00:42:08,680 --> 00:42:23,799
Speaker 1: quick break. Right we're asking the question can space time

870
00:42:23,920 --> 00:42:26,880
Speaker 1: be a fluid? And it sounds like this is the

871
00:42:26,920 --> 00:42:29,440
Speaker 1: idea that we're all just sitting in a hot tub somewhere.

872
00:42:30,040 --> 00:42:33,040
Speaker 1: This is a hot tub time machine Universion of dealers.

873
00:42:33,320 --> 00:42:36,400
Speaker 1: We started out with an office space as a comedy

874
00:42:36,520 --> 00:42:40,360
Speaker 1: and now we're in space. Time Machine could be the sequel.

875
00:42:40,080 --> 00:42:42,920
Speaker 2: Me you, Barack, Obama, and Yoda all sitting in a

876
00:42:43,000 --> 00:42:45,239
Speaker 2: hot tub understanding in the nature of space time.

877
00:42:47,280 --> 00:42:49,720
Speaker 1: That's an awesome picture. And I can't wait for our

878
00:42:49,760 --> 00:42:53,080
Speaker 1: listeners to draw and draw on this fan art.

879
00:42:53,280 --> 00:42:55,320
Speaker 2: Or maybe if Obama is a listener to the podcast

880
00:42:55,360 --> 00:42:57,680
Speaker 2: Chill Ride In and you know, come and join us

881
00:42:57,719 --> 00:43:00,799
Speaker 2: on our acoustic hot tub that is this podcast.

882
00:43:00,960 --> 00:43:03,400
Speaker 1: And also we can finally answer the question what happens

883
00:43:03,440 --> 00:43:06,120
Speaker 1: if you turn a lightsaber on inside of a hot tub?

884
00:43:07,960 --> 00:43:09,919
Speaker 2: Or maybe he's got an opinion about whether he could

885
00:43:09,920 --> 00:43:11,719
Speaker 2: beat Yoda in one on one basketball.

886
00:43:11,880 --> 00:43:14,480
Speaker 1: Mm, well, Obama seems like a humble guy. I don't

887
00:43:14,520 --> 00:43:17,520
Speaker 1: think he would try to take on Yoda.

888
00:43:17,760 --> 00:43:19,840
Speaker 2: He is respectful, that's true.

889
00:43:19,640 --> 00:43:22,280
Speaker 1: All right. Well, I guess this is an interesting idea

890
00:43:22,280 --> 00:43:25,359
Speaker 1: that space time can be fluid, that maybe it's not

891
00:43:25,560 --> 00:43:27,480
Speaker 1: fixed out there in the universe. Maybe it's a thing

892
00:43:27,600 --> 00:43:29,919
Speaker 1: that can slash around, that it's made up of little

893
00:43:29,960 --> 00:43:33,359
Speaker 1: bits that kind of move relative to each other. And now,

894
00:43:33,680 --> 00:43:37,480
Speaker 1: Daniel Dewey have any inclination that this theory is true.

895
00:43:38,000 --> 00:43:40,400
Speaker 1: Does it match up well with some observations that we

896
00:43:40,480 --> 00:43:42,759
Speaker 1: have in experiments or is it just an idea out

897
00:43:42,760 --> 00:43:46,280
Speaker 1: there that we think that maybe one day could possibly

898
00:43:46,320 --> 00:43:47,080
Speaker 1: explain things.

899
00:43:47,200 --> 00:43:49,359
Speaker 2: At this stage, it's really just an idea, but there

900
00:43:49,400 --> 00:43:52,600
Speaker 2: are some fun experiments we can do to try to

901
00:43:52,680 --> 00:43:55,080
Speaker 2: test it, so it's not just an idea people are

902
00:43:55,080 --> 00:43:57,359
Speaker 2: having a hot tubs. It's something people are out there

903
00:43:57,400 --> 00:44:00,319
Speaker 2: really working on trying to verify because it does makes

904
00:44:00,360 --> 00:44:03,279
Speaker 2: some very cool predictions. And the's sort of two categories

905
00:44:03,280 --> 00:44:05,800
Speaker 2: of experiments. There's experiments we're doing up in the sky,

906
00:44:06,000 --> 00:44:08,439
Speaker 2: like looking at things out in the universe, and also

907
00:44:08,520 --> 00:44:10,680
Speaker 2: things people are doing in the lab to try to

908
00:44:10,680 --> 00:44:13,919
Speaker 2: make like sonic black holes to study them. The first

909
00:44:13,960 --> 00:44:16,520
Speaker 2: one has to do with like how light propagates through

910
00:44:16,560 --> 00:44:19,920
Speaker 2: the universe. As we said earlier, there are rules about

911
00:44:19,960 --> 00:44:23,520
Speaker 2: how fluid behaves, and if you shoot something through fluid,

912
00:44:23,560 --> 00:44:26,960
Speaker 2: it will lose energy, will dissipate its energy. Fluids have

913
00:44:27,000 --> 00:44:30,080
Speaker 2: these two properties. That's called dissipation where you lose energy

914
00:44:30,120 --> 00:44:34,160
Speaker 2: over time, and dispersion where things that different energies travel

915
00:44:34,200 --> 00:44:37,240
Speaker 2: at different speeds. And so that's not something we've seen

916
00:44:37,360 --> 00:44:40,800
Speaker 2: in space. Like if you shoot photons across the universe currently,

917
00:44:40,840 --> 00:44:43,279
Speaker 2: we think they arrive with the same energy as when

918
00:44:43,320 --> 00:44:45,840
Speaker 2: they left, like they never get tired. We've also seen

919
00:44:45,920 --> 00:44:49,560
Speaker 2: that photons at all different energies, red photons, blue photons,

920
00:44:49,600 --> 00:44:53,600
Speaker 2: green photons, infrared photons all travel at the same speed.

921
00:44:53,719 --> 00:44:56,120
Speaker 2: So people are trying to understand if this is really true,

922
00:44:56,480 --> 00:44:59,319
Speaker 2: because if space time was a liquid, then those would

923
00:44:59,320 --> 00:45:02,120
Speaker 2: be broken little bit. Photons would lose a little bit

924
00:45:02,160 --> 00:45:04,719
Speaker 2: of energy as they move through the universe, and red, green,

925
00:45:04,760 --> 00:45:08,080
Speaker 2: and blue photons would travel at slightly different speeds. So

926
00:45:08,120 --> 00:45:10,600
Speaker 2: they're trying to do this experiment, though it's tricky because

927
00:45:10,600 --> 00:45:13,239
Speaker 2: we don't have like a huge laser pointed at the

928
00:45:13,239 --> 00:45:14,960
Speaker 2: Earth to let us do this experiment.

929
00:45:15,160 --> 00:45:19,440
Speaker 1: Sounds like a dastardly plot for a supervillain slash experiment.

930
00:45:19,040 --> 00:45:21,239
Speaker 2: Though we almost do have a huge laser. There's this

931
00:45:21,280 --> 00:45:23,759
Speaker 2: thing up in the sky called the crab Nebula, which

932
00:45:23,800 --> 00:45:27,719
Speaker 2: is an excellent source of really really high energy photons.

933
00:45:28,080 --> 00:45:31,439
Speaker 2: It's shooting photons at us up to like eighty terra

934
00:45:31,640 --> 00:45:35,320
Speaker 2: electron bolts. Remember the Large Hadron Collider, the most powerful

935
00:45:35,400 --> 00:45:38,480
Speaker 2: human accelerator on Earth, only gets things up to like

936
00:45:38,640 --> 00:45:42,040
Speaker 2: six and a half or seven terra electronvolts. So this

937
00:45:42,040 --> 00:45:45,080
Speaker 2: thing is shooting photons at us more than ten times

938
00:45:45,120 --> 00:45:47,920
Speaker 2: the energy of the LAC, which makes it a great

939
00:45:47,960 --> 00:45:51,320
Speaker 2: way to study how photons propagate through the universe.

940
00:45:52,360 --> 00:45:54,120
Speaker 1: It sounds like you have a lot of ideas for

941
00:45:54,280 --> 00:45:57,440
Speaker 1: disproving this crazy theory, but I guess my question was

942
00:45:57,480 --> 00:46:00,400
Speaker 1: more like what makes us think that this crazy theory

943
00:46:00,440 --> 00:46:03,200
Speaker 1: could be true? Like? Is there something that it predicts

944
00:46:03,320 --> 00:46:07,440
Speaker 1: that maybe matches up with some unexplained phenomenon in space.

945
00:46:07,520 --> 00:46:10,280
Speaker 2: We don't need this theory to explain anything that we see.

946
00:46:10,840 --> 00:46:14,239
Speaker 2: It's just an attempt theoretically to try to harmonize our

947
00:46:14,280 --> 00:46:16,360
Speaker 2: idea of the universe to come up with a new

948
00:46:16,440 --> 00:46:19,280
Speaker 2: explanation for what's out there, sort of from the bottom

949
00:46:19,400 --> 00:46:22,760
Speaker 2: level up to explain how we end up with general

950
00:46:22,760 --> 00:46:25,400
Speaker 2: relativity and how we end up with quantum mechanics. But

951
00:46:25,480 --> 00:46:28,040
Speaker 2: you know, you can't just describe something theoretically and say

952
00:46:28,239 --> 00:46:30,480
Speaker 2: here's my description of the universe. You also have to

953
00:46:30,480 --> 00:46:32,879
Speaker 2: make predictions that can be verified and tested to see

954
00:46:32,880 --> 00:46:36,080
Speaker 2: if this is what's really happening out there. So we

955
00:46:36,120 --> 00:46:38,759
Speaker 2: don't need this to explain any results of experiments, and

956
00:46:39,000 --> 00:46:41,680
Speaker 2: we don't have any experiments where quantum mechanics and general

957
00:46:41,719 --> 00:46:45,319
Speaker 2: relativity disagree because those experiments are essentially impossible to do.

958
00:46:45,480 --> 00:46:47,960
Speaker 2: But it does make predictions that we can test so

959
00:46:48,000 --> 00:46:50,600
Speaker 2: that we can prove or disprove this theory.

960
00:46:51,320 --> 00:46:53,560
Speaker 1: I guess what I mean is like, does this crazy

961
00:46:53,640 --> 00:46:57,719
Speaker 1: theory actually make quantum mechanics in general relativity play well

962
00:46:57,719 --> 00:47:01,160
Speaker 1: together or we just think it might, or does it

963
00:47:01,200 --> 00:47:02,640
Speaker 1: actually harmonize everything.

964
00:47:02,719 --> 00:47:05,279
Speaker 2: If it's true, then it does allow for us to

965
00:47:05,320 --> 00:47:09,720
Speaker 2: derive sort of general relativity and quantum mechanics from one source.

966
00:47:09,920 --> 00:47:12,359
Speaker 2: All the math is not completely worked out, like there

967
00:47:12,440 --> 00:47:15,960
Speaker 2: is no completely well worked out theory of quantum gravity

968
00:47:16,080 --> 00:47:18,400
Speaker 2: from which you can get the effects of general relativity

969
00:47:18,680 --> 00:47:21,800
Speaker 2: and quantum mechanics. This is sort of like one direction

970
00:47:21,920 --> 00:47:24,160
Speaker 2: people are working in, and there's a series of recent

971
00:47:24,200 --> 00:47:26,840
Speaker 2: papers sort of thinking about the consequences of it, Like,

972
00:47:26,880 --> 00:47:28,759
Speaker 2: we don't have all the details worked out yet, but

973
00:47:29,200 --> 00:47:32,120
Speaker 2: if this theory is true, it would have these consequences.

974
00:47:32,360 --> 00:47:34,799
Speaker 2: Let's go check and see if we can see those

975
00:47:34,800 --> 00:47:37,279
Speaker 2: things happening in the universe, because if we can, that

976
00:47:37,360 --> 00:47:38,520
Speaker 2: means we're on the right track.

977
00:47:39,239 --> 00:47:40,719
Speaker 1: I mean not I mean to tell you how to

978
00:47:40,760 --> 00:47:43,319
Speaker 1: do your business, but like before you point a giant

979
00:47:43,360 --> 00:47:45,680
Speaker 1: laser of the Earth, wouldn't we want to make sure

980
00:47:45,800 --> 00:47:48,799
Speaker 1: that this is a theory that is going to be

981
00:47:48,920 --> 00:47:50,719
Speaker 1: worth doing that, do you know what I mean? Like,

982
00:47:50,840 --> 00:47:54,840
Speaker 1: I would see how it would be important to verify

983
00:47:54,920 --> 00:47:56,960
Speaker 1: this theory, but only if it made things work. But

984
00:47:57,080 --> 00:47:58,480
Speaker 1: it sounds like we don't even know if it's going

985
00:47:58,520 --> 00:47:59,200
Speaker 1: to make things work.

986
00:47:59,320 --> 00:48:01,200
Speaker 2: We don't know if the theory of a space time

987
00:48:01,239 --> 00:48:03,960
Speaker 2: fluid actually works theoretically right, and the same way that

988
00:48:04,000 --> 00:48:07,200
Speaker 2: we don't know as string theory works fundamentally. People are

989
00:48:07,200 --> 00:48:09,839
Speaker 2: still working on it, but we'd also love to have

990
00:48:09,920 --> 00:48:13,160
Speaker 2: ways to test string theory to verify its predictions to

991
00:48:13,239 --> 00:48:16,160
Speaker 2: understand if we're on the right track or not. And

992
00:48:16,200 --> 00:48:20,600
Speaker 2: also sometimes getting experimental verification provides clues it like says, oh,

993
00:48:20,640 --> 00:48:23,640
Speaker 2: you have a whole different set of ideas about this theory, Well,

994
00:48:23,680 --> 00:48:25,880
Speaker 2: the experiment prefers this one or that one, so it

995
00:48:25,880 --> 00:48:28,839
Speaker 2: can give you some guidance sometimes. So it's nice when

996
00:48:28,920 --> 00:48:31,240
Speaker 2: theory and experiment can sort of work hand in hand.

997
00:48:31,400 --> 00:48:33,360
Speaker 2: I mean, we don't develop a complete theory of the

998
00:48:33,360 --> 00:48:36,640
Speaker 2: standard model before we build our first particle detector, right,

999
00:48:36,680 --> 00:48:38,600
Speaker 2: We sort of do it in increments, and we get

1000
00:48:38,600 --> 00:48:41,000
Speaker 2: clues from experiment and then ideas from theory, and it's

1001
00:48:41,000 --> 00:48:42,040
Speaker 2: sort of like a tag team.

1002
00:48:42,280 --> 00:48:44,200
Speaker 1: Well, at least with the Higgs boson, I feel like

1003
00:48:44,320 --> 00:48:46,040
Speaker 1: that theory was sent and kind of worked out, and

1004
00:48:46,040 --> 00:48:48,160
Speaker 1: there were predictions of it, and then you went off

1005
00:48:48,400 --> 00:48:49,279
Speaker 1: and built the giant thing.

1006
00:48:49,440 --> 00:48:52,239
Speaker 2: Yeah, that is one example of success from having a

1007
00:48:52,239 --> 00:48:55,239
Speaker 2: theoretical idea. But of course that theoretical idea came from

1008
00:48:55,239 --> 00:48:58,439
Speaker 2: experimental observations that we didn't understand at that time, right,

1009
00:48:58,760 --> 00:49:00,840
Speaker 2: seeing the W and the Z were massive and the

1010
00:49:00,840 --> 00:49:03,560
Speaker 2: photon wasn't, and not understanding that, and so we got

1011
00:49:03,600 --> 00:49:04,919
Speaker 2: to do is go out there and do a bunch

1012
00:49:04,920 --> 00:49:07,359
Speaker 2: of experiments and look for weird stuff. Sometimes you get

1013
00:49:07,400 --> 00:49:09,680
Speaker 2: a confirmation of the idea you had, and sometimes you don't.

1014
00:49:10,000 --> 00:49:11,520
Speaker 1: Are you trying to say that when it comes to

1015
00:49:11,560 --> 00:49:13,560
Speaker 1: space time being a fluid, you just got to go

1016
00:49:13,600 --> 00:49:15,640
Speaker 1: with the float. You don't want to flush it all down.

1017
00:49:15,880 --> 00:49:17,719
Speaker 2: Well, I do think that these results from the crab

1018
00:49:17,760 --> 00:49:20,319
Speaker 2: nebula are super awesome. I mean, they look at these

1019
00:49:20,320 --> 00:49:22,840
Speaker 2: photons and they try to measure whether there's any like

1020
00:49:23,040 --> 00:49:25,640
Speaker 2: change in the energy spectrum, the kind that you would

1021
00:49:25,680 --> 00:49:28,839
Speaker 2: expect if space time was a fluid, and they didn't

1022
00:49:28,880 --> 00:49:31,279
Speaker 2: see any, which means that you know, space time might

1023
00:49:31,360 --> 00:49:33,480
Speaker 2: still be a fluid. But if it is, it's a fluid,

1024
00:49:33,480 --> 00:49:37,000
Speaker 2: it's like super duper slippery. Like the fluid effects, these

1025
00:49:37,000 --> 00:49:39,359
Speaker 2: like friction, the effects where you're losing energy as you're

1026
00:49:39,360 --> 00:49:42,319
Speaker 2: moving through space time are very very small. So like,

1027
00:49:42,440 --> 00:49:45,680
Speaker 2: maybe space time isn't a fluid, maybe it's say superfluid.

1028
00:49:46,000 --> 00:49:50,560
Speaker 1: Ooh, it has superpowers kind of meani like it doesn't.

1029
00:49:51,080 --> 00:49:54,239
Speaker 1: It's not like a thick, gooey fluid. It's almost like

1030
00:49:54,400 --> 00:49:55,480
Speaker 1: supernatural fluid.

1031
00:49:55,600 --> 00:49:58,760
Speaker 2: Yeah, superfluids are like superconductors. They have almost no friction.

1032
00:49:59,120 --> 00:50:01,960
Speaker 2: They flow very very smoothly. So if space time is

1033
00:50:02,000 --> 00:50:04,760
Speaker 2: a fluid, then it has to have like very very

1034
00:50:04,800 --> 00:50:06,200
Speaker 2: slight fluid effects.

1035
00:50:06,320 --> 00:50:08,880
Speaker 1: So we do have an experiment or an observation at

1036
00:50:08,920 --> 00:50:11,440
Speaker 1: least it says that space time is not a fluid.

1037
00:50:11,440 --> 00:50:15,000
Speaker 1: Then it might still be a superfluid, but it's definitely

1038
00:50:15,080 --> 00:50:17,440
Speaker 1: not a fluid. Is that what the observation says.

1039
00:50:17,560 --> 00:50:20,320
Speaker 2: Yeah, it's not like thick, chunky soup. That's for sure

1040
00:50:20,600 --> 00:50:22,960
Speaker 2: that we can rule that out. If it is a fluid.

1041
00:50:23,040 --> 00:50:26,040
Speaker 2: If space time does follow these properties and bubbles up

1042
00:50:26,040 --> 00:50:28,839
Speaker 2: from something deeper and has fluid like effects, they would

1043
00:50:28,840 --> 00:50:31,799
Speaker 2: be very very very subtle. But it doesn't mean they're

1044
00:50:31,800 --> 00:50:33,920
Speaker 2: not right. You can always rule it out to some level.

1045
00:50:33,960 --> 00:50:35,920
Speaker 2: But there's sort of another direction we can approach this,

1046
00:50:35,960 --> 00:50:38,799
Speaker 2: which is to try to do experiments on Earth to

1047
00:50:39,000 --> 00:50:41,719
Speaker 2: understand whether this theory even holds together. And there's a

1048
00:50:41,760 --> 00:50:45,360
Speaker 2: guy in Israel, the Technion who builds these sonic black

1049
00:50:45,400 --> 00:50:49,239
Speaker 2: holes try to understand like how gravity might emerge from

1050
00:50:49,239 --> 00:50:52,000
Speaker 2: a fluid theory of space time. He's notices a lot

1051
00:50:52,040 --> 00:50:56,440
Speaker 2: of similarity mathematically between how waves propagate in fluids and

1052
00:50:56,480 --> 00:51:00,000
Speaker 2: how waves propagate in curved space time. So what he's done,

1053
00:51:00,080 --> 00:51:03,560
Speaker 2: he's experimentally built a weird kind of fluid that has

1054
00:51:03,600 --> 00:51:07,719
Speaker 2: strange behaviors that are very similar to the behavior of gravity,

1055
00:51:07,760 --> 00:51:10,239
Speaker 2: to the point where he's even built a fluid with

1056
00:51:10,320 --> 00:51:13,880
Speaker 2: what he calls an acoustic horizon. I mean, he generates

1057
00:51:13,920 --> 00:51:17,680
Speaker 2: sound waves that cannot escape this weird little blob inside

1058
00:51:17,680 --> 00:51:18,280
Speaker 2: his fluid.

1059
00:51:18,480 --> 00:51:22,680
Speaker 1: WHOA, So wait, he's like building fluids out of real atoms,

1060
00:51:23,160 --> 00:51:26,560
Speaker 1: like real materials, and using that like a lego model

1061
00:51:26,640 --> 00:51:28,239
Speaker 1: of what space might actually be.

1062
00:51:28,400 --> 00:51:30,879
Speaker 2: Is that what you're saying, Yeah, exactly, He's doing what

1063
00:51:30,920 --> 00:51:34,759
Speaker 2: they call analog gravity. He's like, if the mathematics of

1064
00:51:34,800 --> 00:51:38,040
Speaker 2: this works for space time, it should also work when

1065
00:51:38,080 --> 00:51:40,759
Speaker 2: you put other things together. So instead of doing experiments

1066
00:51:40,800 --> 00:51:43,120
Speaker 2: using space time bits, which we don't know how to manipulate,

1067
00:51:43,280 --> 00:51:45,600
Speaker 2: it's like, let me do it with other kind of bits.

1068
00:51:45,840 --> 00:51:48,520
Speaker 2: So he does it with rubidium atoms, and he builds

1069
00:51:48,560 --> 00:51:51,279
Speaker 2: these Bose Einstein condensates, and he gives them all sorts

1070
00:51:51,320 --> 00:51:54,800
Speaker 2: of weird properties so that the sound waves moving through

1071
00:51:54,880 --> 00:51:59,560
Speaker 2: those rubidium atom fluids should operate the same way photons

1072
00:51:59,640 --> 00:52:03,520
Speaker 2: move through the space time liquid. So he's actually successfully

1073
00:52:03,520 --> 00:52:06,480
Speaker 2: built what they call an analog black hole. It's not

1074
00:52:06,560 --> 00:52:10,200
Speaker 2: a literal black hole, but it has similar properties in

1075
00:52:10,280 --> 00:52:13,880
Speaker 2: that fluid to photons moving through space time.

1076
00:52:14,239 --> 00:52:15,799
Speaker 1: That feels like a little bit of a stretch, but

1077
00:52:15,840 --> 00:52:18,919
Speaker 1: I guess I trust see that. It's an interesting way

1078
00:52:18,960 --> 00:52:20,840
Speaker 1: to study the I feel like you're building a model,

1079
00:52:20,920 --> 00:52:23,120
Speaker 1: but in trying to say that, like, if it works

1080
00:52:23,160 --> 00:52:25,040
Speaker 1: for my legos, it works for quarks.

1081
00:52:25,160 --> 00:52:27,719
Speaker 2: Yeah. He's definitely made some very bold claims and there's

1082
00:52:27,719 --> 00:52:29,960
Speaker 2: a lot of controversy about what it means, but it's

1083
00:52:29,960 --> 00:52:32,600
Speaker 2: definitely fascinating. So the fascinating thing about this is that

1084
00:52:32,600 --> 00:52:35,040
Speaker 2: they're not black holes. Black holes don't emit light. These

1085
00:52:35,080 --> 00:52:38,600
Speaker 2: are like silent holes because they don't emit sound right,

1086
00:52:38,800 --> 00:52:40,240
Speaker 2: there's like quiet holes.

1087
00:52:40,400 --> 00:52:44,840
Speaker 1: They're like the uncomfortable silence in social situations. It's like,

1088
00:52:44,880 --> 00:52:46,759
Speaker 1: what would you even say, you're the hot up with

1089
00:52:46,840 --> 00:52:49,879
Speaker 1: Yoda and Obama. It would be a sonic black hole

1090
00:52:49,920 --> 00:52:50,360
Speaker 1: as well.

1091
00:52:50,600 --> 00:52:51,640
Speaker 2: It might be a little awkward.

1092
00:52:51,719 --> 00:52:54,080
Speaker 1: Yeah, all right, Well, it sounds like this is a

1093
00:52:54,160 --> 00:52:58,759
Speaker 1: super fascinating theory and kind of challenges our views of

1094
00:52:58,840 --> 00:53:02,799
Speaker 1: space time itself, like maybe the fundamental platform of the

1095
00:53:02,920 --> 00:53:05,360
Speaker 1: universe isn't what we think it is. Maybe it's something

1096
00:53:05,360 --> 00:53:08,600
Speaker 1: that sits inside of an even bigger meta or super

1097
00:53:08,600 --> 00:53:12,600
Speaker 1: space platform or environment. And these are interesting ideas that

1098
00:53:12,680 --> 00:53:16,399
Speaker 1: might bring together quantum mechanics and general relativity. But stay tuned.

1099
00:53:16,480 --> 00:53:20,400
Speaker 1: Experiments so far say that maybe space isn't a fluid,

1100
00:53:20,480 --> 00:53:22,640
Speaker 1: but that maybe the hut tub of the universe is

1101
00:53:22,680 --> 00:53:24,880
Speaker 1: actually a super hot tub of the universe.

1102
00:53:25,120 --> 00:53:28,000
Speaker 2: Yeah, and these ideas take a while to bubble up

1103
00:53:28,040 --> 00:53:30,640
Speaker 2: and too perkoly through the brains of humans. And it

1104
00:53:30,719 --> 00:53:32,359
Speaker 2: might be that one day we look back at our

1105
00:53:32,480 --> 00:53:35,680
Speaker 2: understanding of space time and think, Wow, we were so foolish.

1106
00:53:35,680 --> 00:53:38,640
Speaker 2: We didn't even understand the liquid we were swimming in.

1107
00:53:38,840 --> 00:53:40,480
Speaker 1: Yeah, it sounds like we need to soak on it

1108
00:53:40,560 --> 00:53:41,440
Speaker 1: for a little bit longer.

1109
00:53:43,040 --> 00:53:44,960
Speaker 2: I always prefer to soak rather than scrub.

1110
00:53:45,120 --> 00:53:47,560
Speaker 1: Just don't do it with a lightsaber. I guess all right. Well,

1111
00:53:47,560 --> 00:53:49,960
Speaker 1: we hope you enjoyed that. Thanks for joining us, See

1112
00:53:49,960 --> 00:53:50,560
Speaker 1: you next time.

1113
00:53:58,360 --> 00:54:01,160
Speaker 2: Thanks for listening, and remember that Annel and Jorge Explain

1114
00:54:01,200 --> 00:54:05,160
Speaker 2: the Universe is a production of iHeartRadio. For more podcasts

1115
00:54:05,239 --> 00:54:09,880
Speaker 2: from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever

1116
00:54:09,960 --> 00:54:11,680
Speaker 2: you listen to your favorite shows.