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Speaker 1: I got into physics because I want to know how

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Speaker 1: things work, what's going on?

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Speaker 2: What are the rules of the universe?

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Speaker 1: Because I figured there must be rules, and there must

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Speaker 1: be reasons why this happens, and on that there should

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Speaker 1: be an explanation out there for us to find. Right

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Speaker 1: and over millennia and centuries, a pattern has emerged where

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Speaker 1: humans encounter lots of different kinds of phenomena like lightning

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Speaker 1: and magnets, and then later realize these are actually deeply connected.

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Speaker 1: There are two sides of the same coin. And this

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Speaker 1: all makes sense if there is in fact a single

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Speaker 1: reason why things happen, a unified theory to explain it all.

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Speaker 1: We might be discovering pieces of it and then snicking

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Speaker 1: them together. We're making zigzagging progress towards this idea, but

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Speaker 1: what guarantees do we have that it actually exists? I mean,

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Speaker 1: we have been trying to unify quantum mechanics and gravity

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Speaker 1: for a century without much success. What if they don't

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Speaker 1: just play along? Could the universe be governed by more

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Speaker 1: than one theory, or like a patchwork of theories for

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Speaker 1: different regimes, or even weirder, could there be more than

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Speaker 1: one valid theory of the universe. Maybe the human project

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Speaker 1: of physics has just gone down the wrong path, and

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Speaker 1: when the aliens come, they can provide us a reset.

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Speaker 1: Or maybe they'll tell us the whole project is hopeless.

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Speaker 1: Either way, Welcome to Daniel and Kelly's Extraordinary Unexplained Universe.

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Speaker 3: Hello. I'm Kelly Widersmith. I study parasites and space.

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Speaker 4: Hi.

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Speaker 2: I'm Daniel.

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Speaker 1: You know I'm a particle physicist, and I really do

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Speaker 1: believe there is a reason why things happen.

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Speaker 3: Oh that's very philosophical of you, Daniel. So my question

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Speaker 3: for you today is if you could go back in

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Speaker 3: time to be present at any physics discovery, what physics

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Speaker 3: discovery would you want to be present for.

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Speaker 1: Oh, well, back in time to be present for a

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Speaker 1: physics discovery.

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Speaker 2: No, no, I'm going to flip the question. I want

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Speaker 2: to go forwards in time.

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Speaker 3: No, no, Daniel, No, we're talking about going forwards. I'm

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Speaker 3: specifically asking you a backwards looking question.

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Speaker 1: Okay, backwards looking question. Moments of discovery. You know, I

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Speaker 1: wouldn't have minded being on that rooftop with Galileo as

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Speaker 1: he looks through the telescope for the first time and

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Speaker 1: sees Jupiter and its moons. What an incredible moment to

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Speaker 1: understand our place and the cosmos and how it all

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Speaker 1: works must have been mind blowing.

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Speaker 4: Yeah.

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Speaker 1: Also, I would have liked to bring him like a

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Speaker 1: mug of hot because I think you got chili up there.

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Speaker 5: That's really nice.

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Speaker 3: And maybe he would have named something after you for that.

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Speaker 2: You know exactly.

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Speaker 1: Also, I wish I could have been there to point

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Speaker 1: out to him that he discovered Neptune without realizing it. Oh,

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Speaker 1: if you go back and look at Galileo's original logbooks,

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Speaker 1: because the dude kept great notes. You see Neptune in

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Speaker 1: his notes. He didn't appreciate what he was seeing. And

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Speaker 1: it wasn't until like a couple hundred years later that

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Speaker 1: we discovered Neptune. So Galles actually missed out on a

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Speaker 1: great discovery.

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Speaker 3: So you actually want to go back and tinker with

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Speaker 3: the past. That's interesting. I just meant observing.

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Speaker 1: Anytime you go back, you're going to tinker with it.

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Speaker 1: There is it's all quantum mechanical. You can't observe it

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Speaker 1: without interacting, right, So yeah, if I go back and

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Speaker 1: chat with Galleo, then I'm going to change the course

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Speaker 1: of history.

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Speaker 3: Okay, all right, Well, In today's episode, we're looking forward

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Speaker 3: and we are asking if there's a single unified theory

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Speaker 3: of physics that we might discover in the future, it

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Speaker 3: will all of the pieces fit together like some giant

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Speaker 3: at some point, and I, you know, I would like

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Speaker 3: to go forward to that moment if I could.

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Speaker 1: Yeah, Well, I also want to explain my earlier comment

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Speaker 1: when I say I think that there's a reason for everything.

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Speaker 1: I'm not being like mystical, like you know, there's a

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Speaker 1: reason why children die of cancer or something horrible like that.

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Speaker 1: I'm just suggesting that, you know, the universe is self consistent,

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Speaker 1: that the universe follows some rules that when a particle

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Speaker 1: goes this way instead of that way, that there's a

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Speaker 1: reason for it, even if that reason is like, hey,

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Speaker 1: it's sarcastic, it's random, but it comes from this probability

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Speaker 1: distribution at least, you know, as we talked about on

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Speaker 1: that episode with Sean Carroll recently. And you're right that

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Speaker 1: this is a philosophical position. It's not a scientific position, right,

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Speaker 1: It's just sort of like, we hope the universe works

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Speaker 1: this way.

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Speaker 2: We assume the universe works this way, and we use.

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Speaker 1: It as a foundation of basically the whole scientific method,

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Speaker 1: and we're just going to keep going until it breaks down.

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Speaker 3: Hmmm, I feel like I'm still not totally convinced. You

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Speaker 3: haven't just said, like a hand wavy guruy, everything happens

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Speaker 3: for a reason.

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Speaker 1: Well, you know, if you buy my crystal and hanging

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Speaker 1: around your neck, then you can control those reasons.

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Speaker 3: But you know what people should buy? Do aliens speak physics?

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Speaker 2: That's right.

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Speaker 1: In today's episode, we're digging deep into questions of physics

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Speaker 1: and philosophy and wondering about is there a theory out

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Speaker 1: there for us to discover? This is one of the

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Speaker 1: questions I dig into in my new book Do Aliens

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Speaker 1: Speak Physics? Which attacks some of these philosophical questions in

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Speaker 1: a very concrete way. It imagines, Hey, aliens have just

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Speaker 1: shown up here on Earth, and we're excited to talk

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Speaker 1: to them about what they know about physics. What if

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Speaker 1: they don't have a unified theory of everything because one

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Speaker 1: doesn't exist?

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Speaker 2: Is that possible?

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Speaker 1: Or what if they have a different unified theory than

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Speaker 1: the one we've been working on? Could you have two theories?

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Speaker 1: Those are some of the questions we're going to touch

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Speaker 1: on in today's episode, But there's a deep dive on

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Speaker 1: all of that in my book, Do Aliens Speak Physics?

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Speaker 3: Out November fourth, eleven out of ten or six out

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Speaker 3: of five stars, best book.

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Speaker 1: Ever, amazingly good reviews from the parasitologists who've read it.

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Speaker 3: Yeah. Well, this parasitologist was very impressed with the deep

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Speaker 3: dive and the entertaining and clear way it was presented.

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Speaker 1: Thanks very much, And I do think that listeners to

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Speaker 1: this podcast who are excited about physics and philosophy and

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Speaker 1: the big questions of the universe will enjoy it. So

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Speaker 1: please do me a favor and check it out.

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Speaker 2: Thanks very much.

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Speaker 1: But today we're not just here to say in live book.

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Speaker 1: We're here to talk about the big theories of the universe.

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Speaker 1: And so first I asked our audience if they thought

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Speaker 1: there needed to be a single, unified theory of physics

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Speaker 1: out there for us to discover. Here's what folks had

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Speaker 1: to say.

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Speaker 2: I don't think so, because maybe somethings are separate.

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Speaker 4: Just the feeling that I have that the universe is

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Speaker 4: like Russian Matrioska dolls nested dolls, except that there's no

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Speaker 4: final kernels. And let's just keep going and going.

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Speaker 6: Maybe, if the universe is composed of two or more

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Speaker 6: types of nature, a unified theory of physics might be impossible,

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Speaker 6: But otherwise one seems fine.

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Speaker 7: It would be ideal to have a single quiet theory,

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Speaker 7: but I don't think it's necessary to have some progress

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Speaker 7: or functional results out of that. So I don't think

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Speaker 7: it's a bad idea to have competing theories.

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Speaker 8: The expectation has been yeah, wandering to rule them all

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Speaker 8: and in the darkness behind them. But maybe we should

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Speaker 8: also consider that we're so far down the ladder of

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Speaker 8: magnitude that we can't forge a united theory without comprehending

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Speaker 8: the entirety of the universe and what may exist beyond

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Speaker 8: it further up the ladder, beyond what we can conceive.

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Speaker 9: No, I don't think so. I think physics is just

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Speaker 9: the way that humans are trying to understand the universe,

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Speaker 9: but it doesn't need to be unified or fully understandable.

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Speaker 5: For it's a human lust to have like simplified down

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Speaker 5: to one.

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Speaker 10: As seeing the unified theory of physics sounds like the

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Speaker 10: search for a very simple solution to a very complex problem,

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Speaker 10: and those seldomly work out.

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Speaker 2: So I vote, though.

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Speaker 11: Given what we've already learned about how the universe works,

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Speaker 11: I'm inclined to believe that there is a single unifying

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Speaker 11: theory of kind of everything, and it isn't actually separated

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Speaker 11: into quantum and classical. But we have to keep funding

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Speaker 11: and celebrating science to find that out.

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Speaker 3: As ever amazing answers from the audience.

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Speaker 1: Absolutely thanks everyone for contributing your hilarious ideas, and so

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Speaker 1: let's jump into the episode today.

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Speaker 2: We're actually joined by a friend of mine.

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Speaker 1: A fellow physicist and podcaster and science communicator extraordinaire, Ethan Siegel.

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Speaker 1: He's a theoretical physicist and science writer. He's previously been

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Speaker 1: a professor at Lewis and Clark and is now a

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Speaker 1: prolific writer and podcaster. You can find him online at

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Speaker 1: Starts with a Bang. His books include Infinite Cosmos, Visions

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Speaker 1: from the James Webspace Telescope by National Geographic and upcoming

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Speaker 1: is a new book in November, The Grand Cosmic Story,

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Speaker 1: which tells the whole history of the universe, where each

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Speaker 1: page is one hundred million years. Ethan, thanks very much

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Speaker 1: for joining us today.

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Speaker 5: Oh it's my pleasure to be here. Thanks for inviting

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Speaker 5: me to an extraordinary conversation about the universe.

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Speaker 3: I can tell you're going to fit right in already.

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Speaker 1: So today we're talking about the concept of a unified theory.

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Speaker 1: Is it possible to have a unified theory of physics?

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Speaker 1: One are the arguments for it and against it? But

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Speaker 1: as usual, because of the philosophical discussion, we have to

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Speaker 1: start with some definitions. So what do you understand to

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Speaker 1: be a unified theory When somebody talks about a unified

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Speaker 1: theory of physics, what does that mean to you?

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Speaker 5: Well, let's start. Let's start at the basics, right which is,

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Speaker 5: where are we now and why don't we have a

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Speaker 5: unified theory of physics right now? And that's because what

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Speaker 5: we have is we have two very fundamentally different ways

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Speaker 5: of making sense of the universe from a physics perspective.

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Speaker 5: On the one hand, we say, oh, everything is made

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Speaker 5: up of these tiny, tiny, tiny, little quantized packets of

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Speaker 5: matter of stuff, whether it's matter or energy or antimatter

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Speaker 5: or radiation. We have everything is discretized, everything is quantized

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Speaker 5: into these little packets, and these packets obey the quantum

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Speaker 5: rules of the universe, and we have the quantum field

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Speaker 5: theories that describe the electromagnetic force and the weak nuclear

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Speaker 5: force and the strong nuclear force, and these all play

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Speaker 5: on the same footings. Even though there are different theories

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Speaker 5: that describe these different aspects, they are all quantum field

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Speaker 5: theories that do kind of fit together into our framework

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Speaker 5: of the standard model. And then on the other hand,

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Speaker 5: we have general relativity, which is our theory of gravity.

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Speaker 5: This is our best theory of gravity. Now this is

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Speaker 5: not a quantum theory of the universe. This is not

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Speaker 5: you know, if you say I'm gonna take an electron

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Speaker 5: and I'm gonna pass it through a double slit, you say, great,

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Speaker 5: I can do all my quantum stuff for where is

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Speaker 5: the electron, what's its momentum, where's it going to appear?

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Speaker 5: And I can do my probabilistic calculations and give you

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Speaker 5: all of that, and then you can ask a question like, yeah, well,

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Speaker 5: what happens to the gravitational field of the electron as

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Speaker 5: it goes through that double slit? And general relativity says,

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Speaker 5: I do not know how to deal with that. I

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Speaker 5: can't deal with that. I don't have an answer to

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Speaker 5: that question. If we wanted to answer that question, we

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Speaker 5: would need a quantum theory of gravity. So to me,

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Speaker 5: a theory of everything would be not just taking well,

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Speaker 5: I can take all the forces of the standard model

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Speaker 5: and all the particles of the standard model and unify

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Speaker 5: them together into the same framework, and it even goes beyond.

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Speaker 5: I'm gonna take general relativity, which I don't know how

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Speaker 5: to do, and I'm gonna make it quantum too and

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Speaker 5: make it play nice with these quant forces. Or maybe

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Speaker 5: I'll take the quantum forces and make them play nice

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Speaker 5: on general relativity's footing. We don't know how to do

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Speaker 5: that either. If we wanted a theory of everything, it

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Speaker 5: would have to not just unify those known parts of

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Speaker 5: the universe, it would also have to solve the currently

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Speaker 5: unsolved problems of our universe, like what is dark matter?

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Speaker 5: What is dark energy? How did we get to have

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Speaker 5: more matter than antimatter in the universe? Why is there

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Speaker 5: a matter antimatter asymmetry? So a theory of everything would

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Speaker 5: be some framework where all of these different questions were

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Speaker 5: described within the same framework in a unique and unambiguous way,

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Speaker 5: where we had the same level of predictive power that

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Speaker 5: we demand from general relativity and quantum field theory today,

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Speaker 5: but where we had a unified structure that could solve

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Speaker 5: all of these problems together. The idea of a theory

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Speaker 5: of everything, or of a unified theory would take all

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Speaker 5: of these things and solve them together and put them

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Speaker 5: in a single framework where you can explain and derive

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Speaker 5: everything about our universe.

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Speaker 3: Well, that sounds pretty straightforward. Why haven't y'all like figured

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Speaker 3: that out yet, says the biologist.

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Speaker 5: I know, right, it's sort of like it's sort of

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Speaker 5: like the question of like, if I'm down at the

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Speaker 5: base of a pyramid, even if it's a foggy day,

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Speaker 5: I can assume there's a summit to that pyramid, and

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Speaker 5: why is it so hard to get to the top.

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Speaker 5: And the answer is, well, first off, it's a foggy

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Speaker 5: day down here. I'm not even sure this pyramid has

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Speaker 5: a top, or ever had a top. I'm not sure

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Speaker 5: that's what it looks like. It's sort of like, you know,

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Speaker 5: that classic mountain shape, that classic stratovolcano shape. That's what

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Speaker 5: Mount Fuji looks like. And if you came to the

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Speaker 5: United States in the Pacific Northwest prior to nineteen eighty,

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Speaker 5: you would have discovered, oh, Mount Saint Helens, is known

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Speaker 5: as the Mount Fuji of the West or because because

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Speaker 5: you that's us, like we're the Mount Fuji on the

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Speaker 5: other side of the world. And then in nineteen eighty,

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Speaker 5: Mount Saint Helen's, you know, famously exploded and now there's

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Speaker 5: no top to it anymore. It does not look anything

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Speaker 5: like Mount Fuji anymore. So what happened in our universe

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Speaker 5: was there a unified theory at some point in the

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Speaker 5: very very distant past, and and we just can't recognize

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Speaker 5: it because it blew up in some spectacular fashion? Was

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Speaker 5: there never a theory of everything? And we just have

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Speaker 5: these disconnected parts of the universe. And so what we've

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Speaker 5: attempted to do mostly is, yes, there are some people

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Speaker 5: saying like, I'm just gonna go for the big prize.

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Speaker 5: I'm going to assume there's a unified thee I'm going

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Speaker 5: to work on that. And then you want to as

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Speaker 5: a physicist, as someone who's connected to reality, you want

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Speaker 5: to say, like, okay, well, well, what signatures would we

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Speaker 5: see if that was true? And how could we observe

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Speaker 5: or measure the universe in some way to reveal that

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Speaker 5: this is what it's actually like. And it turns out

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Speaker 5: that the very very unified theories, they they make predictions

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Speaker 5: that are way outside of what we can observer or measure.

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Speaker 5: Their predictions are. You know, it's it's really an exercise

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Speaker 5: in like, oh, no, company's coming over, and I'm going

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Speaker 5: to do like a cartoon, and I'm gonna lift up

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Speaker 5: the rug and I'm going to sweep all the things

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Speaker 5: I don't want under the rug and put the rug down,

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Speaker 5: and hopefully they don't notice this giant bulge of dog

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Speaker 5: fur underneath the rug. Right Because because when we actually

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Speaker 5: go to do that, you can say, well, what are

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Speaker 5: the things I can add in to unify my theory?

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Speaker 5: You can add in, for example, if you if you

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Speaker 5: want to work to unify by the three forces of

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Speaker 5: the standard model together, you can make something called a

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Speaker 5: grand unified theory. Grand unified theories all have extra predictions

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Speaker 5: of things we should expect to see that we don't see.

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Speaker 2: In our universe.

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Speaker 5: For example, for example, we have our neutrinos in the universe.

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Speaker 5: All the neutrinos seem to be left handed particles. Where

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Speaker 5: if you watch a neutrino moving and you say what

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Speaker 5: direction is its spinning, it spins like your left hand

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Speaker 5: fingers curl around it. Meanwhile, all the anti neutrinos are

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Speaker 5: right handed. They all curl in the opposite direction. These

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Speaker 5: are not the same particles. They're not spinning in the

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Speaker 5: same direction. If you have a unified theory. Unified theories

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Speaker 5: are left right symmetric. So where are all the right

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Speaker 5: handed neutrinos and where are all the left handed anti neutrinos?

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Speaker 5: Why don't we have them? The universe would also be

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Speaker 5: symmetric between electric and magnetic forces. We have electric positive

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Speaker 5: and negative charges. We do not have magnetic north and

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Speaker 5: south monopoles. We only generate magnetism through the motion of

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Speaker 5: electric charges. So where are they. It also predicts a

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Speaker 5: super heavy set of what we call bosons. It's a

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Speaker 5: class of particles that would allow quarks and leptons to

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Speaker 5: separate parts of the standard model to couple together through

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Speaker 5: both of them. This has the advantage that maybe it

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Speaker 5: could explain the matter antimatter asymmetry, but it has the

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Speaker 5: disadvantage that it makes particles like the proton inherently unstable.

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Speaker 5: So we build these big tanks of water and we

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Speaker 5: say there's a bunch of hydrogen atoms in there with

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Speaker 5: a bunch of protons for nuclei. Let's wait and see

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Speaker 5: if any of them decay, and we don't see any

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Speaker 5: proton decay. We don't see any proton decay for tens

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Speaker 5: of thousands of times longer than we would expect the

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Speaker 5: proton to decay if the simplest model of grand unified

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Speaker 5: theory was true. So this is sort of why we

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Speaker 5: haven't gotten there is we look at well, before we

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Speaker 5: even go all the way up to the top of

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Speaker 5: the mountain, let's try and take that next step up,

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Speaker 5: and any direction that we try and take that next step,

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Speaker 5: you try and add supersymmetry, And where are my extra

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Speaker 5: higgs bosons that the LHC should have found. Where's the

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Speaker 5: lightest supersymmetric particle that should be at about the same

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Speaker 5: energy as the top quark? Not there? Where are my

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Speaker 5: extra dimensions not there? Where's proton decay? Not there? So

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Speaker 5: it's really hard to say, like, well, you know, maybe

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Speaker 5: we're just not adding enough things and we should add

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Speaker 5: more and more and more and more and more, and

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Speaker 5: just say oh. It's sort of like if I imagine

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Speaker 5: I have a giant mystery box and I stick the

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Speaker 5: right key into it and the whole box explodes and

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Speaker 5: crumbles away, and I'm left with like four little crumbs. Oh,

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Speaker 5: and maybe this crumbs are what our universe is and

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Speaker 5: all the other shrapnel it just disappeared somewhere that isn't here,

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Speaker 5: and that's why we can't see it. It's it's kind

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Speaker 5: of hard to say, like that is that how we

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Speaker 5: really do science? Is that's something we would accept as like, oh,

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Speaker 5: that's a good story for how our universe is. Really

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Speaker 5: we really demand something more than that.

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Speaker 1: So you're painting this picture of unified theories as requiring

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Speaker 1: extra bits which we don't see in the universe, which

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Speaker 1: we have to somehow explain why we don't see them.

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Speaker 1: But why is that necessary? Why is it required? And

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Speaker 1: you have a unified theory to have these extra mathematical machinery,

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Speaker 1: which then you have to then do all this work

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Speaker 1: to hide.

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Speaker 5: Well, if you talk about a unified theory, the first

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Speaker 5: job of any new theory you want to propose is

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Speaker 5: it has to explain the things you already know to

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Speaker 5: be true, right, And there's no simpler way you can

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Speaker 5: actually prove this. There's no simpler way to explain what

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Speaker 5: we we already know with fewer parts. You can't say like, oh,

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Speaker 5: I'm gonna have a smaller group than the standard model

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Speaker 5: that explains everything in the standard model. Like no, you

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Speaker 5: can prove the standard model is the smallest representation of

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Speaker 5: what contains the Standard model anything else any other way,

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Speaker 5: I could also represent the standard model inherently has that

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Speaker 5: much at least stuff or more if I wanted to

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Speaker 5: do the same thing with general relativity. Now I'm saying like,

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Speaker 5: it's basically asking how can I fit these puzzle pieces

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Speaker 5: and these puzzle pieces together into a puzzle. Your puzzle,

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Speaker 5: your whole puzzle, has to at least contain the pieces

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Speaker 5: you know are present. That's sort of the basic explanation

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Speaker 5: of how you do it. You can't say I'm going

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Speaker 5: to make something simpler or that contains less and then

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Speaker 5: the more stuff comes out of it like that. That's

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Speaker 5: not how math works. You can't make a bigger thing

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Speaker 5: out of a smaller thing. You have to at least

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Speaker 5: include the pieces you already know are there. So if

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Speaker 5: you're talking about unifying this, you're inherently going to say,

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Speaker 5: I need to at least include what I already have,

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Speaker 5: and then if I want to unify them because they're

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Speaker 5: not unified. Now, I need some grander framework somehow that

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Speaker 5: these pieces either are both embedded in or we'll both

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Speaker 5: emerge out of. That's sort of the general picture of it.

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Speaker 5: But Daniel, you're an expert on this just as much

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Speaker 5: as I am, at least, like surely surely you have

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Speaker 5: an opinion on this too.

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Speaker 2: I do.

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Speaker 1: I want to hear Kelly's question, but I also want

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Speaker 1: to first provide maybe a helpful historical analogy. People might

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Speaker 1: be thinking, well, what about like electricity and magnetism, Maxwell

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Speaker 1: click those together without reading some big, complicated framework with

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Speaker 1: all these extra moving bits he had to then handle.

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Speaker 1: And the actual story is the opposite, right, He clicked

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Speaker 1: together electricity and magnetism, but to do so he had

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Speaker 1: to create a larger framework, and that framework contained pieces

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Speaker 1: he wasn't familiar with, like the displacement current, which is

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Speaker 1: necessary to put these two together and make everything symmetric.

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Speaker 1: And then he went out and discovered, oh, it actually

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Speaker 1: is out there in the universe. And so you know,

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Speaker 1: that's actually an example of putting things together into a

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Speaker 1: larger framework and then discovering that some of those pieces

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Speaker 1: of the framework really are out there in the universe.

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Speaker 1: We have to take a break, but when we come back,

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Speaker 1: we're going to hear Kelly's question about unified theories in physics. Okay,

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Speaker 1: we're back when we're talking to doctor Ethan Siegel about

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Speaker 1: unified theories in physics, and I'm dying to hear what

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Speaker 1: Kelly wants to know.

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Speaker 3: I guess I was just going to ask our physicists

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Speaker 3: really sure that all of the smaller pieces are separate, Like,

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Speaker 3: could could you discover at some point that like, oh,

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Speaker 3: some of these things we thought they were different, but

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Speaker 3: actually it's the same thing, just under different conditions. Or

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Speaker 3: are we like one hundred percent confident and all of

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Speaker 3: the smaller pieces of the puzzle already?

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Speaker 5: Oh, Kelly, that's actually a genius question. So it turns

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Speaker 5: out like now I get to be the excited one

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Speaker 5: to tell you, guess what you know? How I told

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Speaker 5: you that over on this side we have general relativity,

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Speaker 5: and over on this other side we have quantum field

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Speaker 5: theory with the strong nuclear force, the weak nuclear force,

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Speaker 5: and the electromagnetic force. One of the huge advances that

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Speaker 5: was made in the nineteen sixties, and I'm going to

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Speaker 5: credit Shelley Glashau for it, although there were others. Is

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Speaker 5: this idea that the weak interactions and the electromagnetic interactions

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Speaker 5: can be unified into a single framework, and this is

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Speaker 5: electroweak theory, and so this is actually a part of

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Speaker 5: the standard model. It says that here at are low energies,

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Speaker 5: we see one, two, three, four separate forces gravity, strong, nuclear, weak, nuclear,

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Speaker 5: and electromagnetic. But if you go up to high energies,

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Speaker 5: like the types of energies they've reached at the large

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Speaker 5: electron positron collider at Fermilabs tevitron and now at the

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Speaker 5: Large Hadron Collider at CERN, you can actually say, oh, no,

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Speaker 5: it looks like electroweak unification does happen, and that the

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Speaker 5: theory of electroweak symmetry breaking is where the Higgs sector

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Speaker 5: and the Higgs boson comes from. It's why we have

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Speaker 5: the Wnz bosons be very massive instead of massless, because

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Speaker 5: when the symmetry breaks, there are degrees of freedom that

437
00:24:54,800 --> 00:24:58,560
Speaker 5: get eaten by well, they're not displacement currents like Daniel

438
00:24:58,600 --> 00:25:02,280
Speaker 5: talked about. They're different types of currents that arise in physics,

439
00:25:02,320 --> 00:25:05,640
Speaker 5: but they get eaten by those directional degrees of freedom,

440
00:25:05,880 --> 00:25:09,840
Speaker 5: and that produces three very massive bosons, the wn z

441
00:25:10,000 --> 00:25:16,240
Speaker 5: bosons that mediate radioactive decay, along with that one massless boson,

442
00:25:16,520 --> 00:25:19,560
Speaker 5: which is the photon, which is why the electromagnetic force

443
00:25:19,640 --> 00:25:22,439
Speaker 5: is a long range force and travels at the speed

444
00:25:22,440 --> 00:25:25,919
Speaker 5: of light, whereas all the weak interactions are very short

445
00:25:26,000 --> 00:25:29,920
Speaker 5: range because of the high mass of the bosons, and well,

446
00:25:30,080 --> 00:25:32,160
Speaker 5: they're not going to reach very far. You know, it's

447
00:25:32,200 --> 00:25:33,879
Speaker 5: not like what's happening in me is going to make

448
00:25:33,920 --> 00:25:36,720
Speaker 5: a neutron inside you decay. The weak force isn't going

449
00:25:36,760 --> 00:25:39,720
Speaker 5: to reach from me to you, but the electromagnetic force does,

450
00:25:39,880 --> 00:25:42,080
Speaker 5: and that's why you can get the radio waves from

451
00:25:42,119 --> 00:25:42,760
Speaker 5: me right now.

452
00:25:43,160 --> 00:25:46,800
Speaker 1: And that's another example of bringing two ideas together which

453
00:25:46,880 --> 00:25:50,320
Speaker 1: creates more theoretical machinery which turned out to actually be

454
00:25:50,359 --> 00:25:51,359
Speaker 1: out there in the universe.

455
00:25:51,359 --> 00:25:53,840
Speaker 5: We see it, and there are a lot of examples

456
00:25:53,880 --> 00:25:56,240
Speaker 5: of this. You know, you go back to electromagnetism and

457
00:25:56,280 --> 00:26:00,440
Speaker 5: you have the magnetic vector potential and the associated like said,

458
00:26:00,440 --> 00:26:03,800
Speaker 5: displacement currents in the quantum world. This leads to things

459
00:26:03,840 --> 00:26:07,640
Speaker 5: like the ahronav Bom effect in the electroweak sector. When

460
00:26:07,680 --> 00:26:10,320
Speaker 5: you unify that, that's where the prediction of the Higgs

461
00:26:10,400 --> 00:26:13,919
Speaker 5: boson came from and why we have the Higgs mechanism

462
00:26:14,119 --> 00:26:17,400
Speaker 5: and the Higgs particle, and turns out we were able

463
00:26:17,440 --> 00:26:20,720
Speaker 5: to find it at the Large Hadron Collider. So these

464
00:26:20,720 --> 00:26:25,359
Speaker 5: were additional predictions that without that unification, and of course,

465
00:26:25,400 --> 00:26:28,080
Speaker 5: because we don't live in a unified universe today, we

466
00:26:28,160 --> 00:26:31,439
Speaker 5: see things are playing on these different footings today. It

467
00:26:31,600 --> 00:26:35,960
Speaker 5: means those symmetries have to be broken. And there's actually

468
00:26:36,359 --> 00:26:42,280
Speaker 5: a theorem, a provable theorem called Goldstone's theorem that tells

469
00:26:42,320 --> 00:26:47,680
Speaker 5: you in particle physics, every time you have a symmetry

470
00:26:47,760 --> 00:26:51,720
Speaker 5: that gets restored at some point and that symmetry then

471
00:26:51,800 --> 00:26:57,119
Speaker 5: gets broken, there are essentially new particles that have to emerge,

472
00:26:57,440 --> 00:27:01,679
Speaker 5: these Namboo Goldstone bosons that have to show up. So

473
00:27:01,840 --> 00:27:04,399
Speaker 5: this is sort of one of these things we're looking for,

474
00:27:04,880 --> 00:27:09,720
Speaker 5: is if there was some extra form of unification, and

475
00:27:09,840 --> 00:27:14,480
Speaker 5: that things are not unified, now, where are those extra

476
00:27:14,960 --> 00:27:17,200
Speaker 5: components that needed to come out of it?

477
00:27:17,440 --> 00:27:17,560
Speaker 2: Now?

478
00:27:17,720 --> 00:27:20,159
Speaker 5: Are they around somewhere? Do we need to figure out

479
00:27:20,200 --> 00:27:23,119
Speaker 5: how to detect them? Are they hiding because they get

480
00:27:23,400 --> 00:27:27,399
Speaker 5: eaten or subsumed into particles that exist like the W

481
00:27:27,640 --> 00:27:30,680
Speaker 5: and Z bosons. These are the sorts of things that

482
00:27:30,800 --> 00:27:34,240
Speaker 5: we need to ask ourselves. But I sort of look

483
00:27:34,320 --> 00:27:37,560
Speaker 5: at it as the you know, it's great to be

484
00:27:37,680 --> 00:27:39,479
Speaker 5: like I want to look and see what's on the

485
00:27:39,480 --> 00:27:43,240
Speaker 5: top of the mountain. I think that's maybe a little

486
00:27:43,280 --> 00:27:46,480
Speaker 5: too ambitious to be connected to reality. I just want

487
00:27:46,480 --> 00:27:49,040
Speaker 5: to know what direction should I go take my next

488
00:27:49,080 --> 00:27:52,480
Speaker 5: step in if I want to get towards this goal

489
00:27:53,000 --> 00:27:56,720
Speaker 5: or is any step at all futile? And have we

490
00:27:56,760 --> 00:28:00,720
Speaker 5: already discovered the most unified version of the universe that

491
00:28:00,800 --> 00:28:04,080
Speaker 5: there is? And this is it? And any new physics

492
00:28:04,080 --> 00:28:08,280
Speaker 5: we have dark matter, dark energy, barriogenesis, it isn't built

493
00:28:08,359 --> 00:28:11,800
Speaker 5: on unifying the framework we already have. It's some new

494
00:28:12,160 --> 00:28:16,800
Speaker 5: framework or phenomena that's outside of our current standard picture

495
00:28:16,880 --> 00:28:19,080
Speaker 5: with general relativity and quantum field theory.

496
00:28:19,240 --> 00:28:22,240
Speaker 1: So let me just summarize for the listeners where we are.

497
00:28:22,600 --> 00:28:25,280
Speaker 1: You're saying that anytime you bring things together into a

498
00:28:25,320 --> 00:28:28,720
Speaker 1: unified picture, it generates new theoretical predictions. There are new

499
00:28:28,880 --> 00:28:31,639
Speaker 1: elements of that theory that we can go out and

500
00:28:31,680 --> 00:28:34,719
Speaker 1: search for. And in the past that's worked, like electricity

501
00:28:34,720 --> 00:28:37,800
Speaker 1: and magnetism unify. We see these other pieces we unify

502
00:28:37,960 --> 00:28:41,240
Speaker 1: electromagnetism with a weak force, we see the Higgs boson

503
00:28:41,280 --> 00:28:44,160
Speaker 1: and the WZ sector. We see these things, but that

504
00:28:44,400 --> 00:28:48,000
Speaker 1: recent efforts to try to unify everything else together has

505
00:28:48,040 --> 00:28:50,440
Speaker 1: made predictions that we haven't been able to verify. And

506
00:28:50,480 --> 00:28:53,360
Speaker 1: so the question is like, well, how do you construct

507
00:28:53,400 --> 00:28:56,720
Speaker 1: this new complex theory of everything with all these extra

508
00:28:56,800 --> 00:28:59,400
Speaker 1: moving pieces and then somehow make it so we don't

509
00:28:59,440 --> 00:29:02,040
Speaker 1: see them in the universe to be consistent. But I

510
00:29:02,040 --> 00:29:04,880
Speaker 1: also wanted to clarify one thing, which is the definition

511
00:29:04,920 --> 00:29:06,960
Speaker 1: of what we're talking about for a unified theory, because

512
00:29:07,080 --> 00:29:09,240
Speaker 1: you said a couple of times, we don't live in

513
00:29:09,280 --> 00:29:11,640
Speaker 1: a universe with a unified theory, and I think what

514
00:29:11,680 --> 00:29:14,760
Speaker 1: you're referring to is sort of phase changes in the universe.

515
00:29:15,280 --> 00:29:17,560
Speaker 1: That it might be that when the universe was hotter

516
00:29:17,720 --> 00:29:20,920
Speaker 1: and denser, all these things which look like different phenomena

517
00:29:21,040 --> 00:29:25,000
Speaker 1: now looked more similar. That electricity and magnetism were more similar,

518
00:29:25,000 --> 00:29:27,840
Speaker 1: they were more closely connected with the weak force, that

519
00:29:27,880 --> 00:29:30,960
Speaker 1: the weak force had the same strength as electromagnetism, for example.

520
00:29:31,360 --> 00:29:33,800
Speaker 1: But I was thinking about it more philosophically, like, even

521
00:29:33,800 --> 00:29:35,760
Speaker 1: if various parts of the universe broke off at different

522
00:29:35,800 --> 00:29:39,400
Speaker 1: times and changed into very different kinds of phenomena. Now,

523
00:29:39,920 --> 00:29:42,520
Speaker 1: if we can connect them theoretically, I would still say

524
00:29:42,520 --> 00:29:45,880
Speaker 1: that's a unified theory of everything, even if you know

525
00:29:45,960 --> 00:29:48,520
Speaker 1: those pieces are still playing out in different ways today.

526
00:29:48,560 --> 00:29:50,080
Speaker 2: Would you disagree?

527
00:29:50,240 --> 00:29:52,720
Speaker 5: I can accept that as a as a valid perspective.

528
00:29:52,720 --> 00:29:55,400
Speaker 5: That maybe isn't the one I share, but it's it's

529
00:29:55,560 --> 00:29:57,680
Speaker 5: it's just not how I choose to look at it,

530
00:29:57,760 --> 00:30:00,360
Speaker 5: because I sort of say, like, well, today, in our

531
00:30:00,400 --> 00:30:04,360
Speaker 5: low energy universe, the electromagnetic force and the weak force,

532
00:30:04,400 --> 00:30:07,240
Speaker 5: they aren't unified. I would not say that they are

533
00:30:07,360 --> 00:30:10,600
Speaker 5: unified today. I would say that they are broken today

534
00:30:10,600 --> 00:30:13,440
Speaker 5: because we live in a low energy universe. We don't

535
00:30:13,480 --> 00:30:16,560
Speaker 5: live up at one hundred GeV of energy or higher.

536
00:30:16,600 --> 00:30:20,080
Speaker 5: We live down in a milliev universe. If you look

537
00:30:20,080 --> 00:30:23,680
Speaker 5: at the background energies of the universe, we live in

538
00:30:23,720 --> 00:30:26,720
Speaker 5: a very low energy state. So I would say that

539
00:30:27,240 --> 00:30:29,800
Speaker 5: if there's a theory of everything out there, if there's

540
00:30:29,840 --> 00:30:33,760
Speaker 5: a unified theory out there, it has to be hiding

541
00:30:33,960 --> 00:30:37,560
Speaker 5: up at not just high energies, but higher energies than

542
00:30:37,600 --> 00:30:40,720
Speaker 5: we've ever observed. It has to be hiding at higher

543
00:30:40,840 --> 00:30:44,160
Speaker 5: energies than the highest energy cosmic rays we've ever detected,

544
00:30:44,200 --> 00:30:47,680
Speaker 5: which themselves are millions of times higher than the highest

545
00:30:47,760 --> 00:30:51,320
Speaker 5: energies we have ever created in the laboratory. So our

546
00:30:51,440 --> 00:30:56,080
Speaker 5: universe today is a low energy, non unified universe. But

547
00:30:56,720 --> 00:31:01,080
Speaker 5: it is possible that we do come from a unified

548
00:31:01,200 --> 00:31:04,720
Speaker 5: theory or a theory of everything that is just I

549
00:31:04,720 --> 00:31:08,680
Speaker 5: would say, very badly broken today. And I also want

550
00:31:08,680 --> 00:31:12,400
Speaker 5: to say, just to give people a little more historical context,

551
00:31:12,480 --> 00:31:14,720
Speaker 5: is when you talked about that this has worked in

552
00:31:14,760 --> 00:31:18,000
Speaker 5: the past. Right worked for electricity and magnetism, which is

553
00:31:18,000 --> 00:31:23,000
Speaker 5: now electromagnetism. Worked for electroweek, which is you know, electromagnetism

554
00:31:23,000 --> 00:31:27,520
Speaker 5: in week unified except broken by electroweak symmetry, breaking right

555
00:31:27,560 --> 00:31:31,080
Speaker 5: the Higgs symmetry we have we have examples of like

556
00:31:31,160 --> 00:31:34,280
Speaker 5: this is where it's worked, but we also have plenty

557
00:31:34,320 --> 00:31:38,120
Speaker 5: of historical examples where we tried to unify things in

558
00:31:38,200 --> 00:31:39,960
Speaker 5: ways that did not work.

559
00:31:40,360 --> 00:31:40,520
Speaker 2: Right.

560
00:31:40,640 --> 00:31:44,320
Speaker 5: We have collusion Kline theory, which tried to unify Maxwell's

561
00:31:44,320 --> 00:31:49,479
Speaker 5: electromagnetism with Einstein's general relativity, which produces an extra field

562
00:31:49,520 --> 00:31:52,120
Speaker 5: known as a dileton, which doesn't appear to exist in

563
00:31:52,160 --> 00:31:56,320
Speaker 5: the universe, which also predicts cross terms where electromagnetism and

564
00:31:56,360 --> 00:31:59,680
Speaker 5: gravity impact each other, which they do not do. So

565
00:32:00,240 --> 00:32:03,080
Speaker 5: I would say we have a lot of false starts, right.

566
00:32:03,160 --> 00:32:06,920
Speaker 5: We have technicolor theory, we have the Sakata model for

567
00:32:07,560 --> 00:32:12,240
Speaker 5: baryons and masons, and those are brilliant ideas that turn

568
00:32:12,240 --> 00:32:15,200
Speaker 5: out to not be reflected in reality. So I think

569
00:32:15,280 --> 00:32:18,239
Speaker 5: it's very important to say, you know, yeah, we have

570
00:32:18,440 --> 00:32:21,640
Speaker 5: we have a lot of different ways of or ideas

571
00:32:21,640 --> 00:32:28,280
Speaker 5: of going about unification or grander theories or more comprehensive explanations.

572
00:32:28,920 --> 00:32:31,840
Speaker 5: But the ones that disagree with reality we were smart

573
00:32:31,920 --> 00:32:35,240
Speaker 5: enough to throw away, and the ones that agreed with

574
00:32:35,360 --> 00:32:38,840
Speaker 5: reality we kept. And we say, look at those successes,

575
00:32:38,840 --> 00:32:41,959
Speaker 5: but don't forget that the history of science was not

576
00:32:42,040 --> 00:32:44,960
Speaker 5: just success success, success, success, And now we're like, oh,

577
00:32:45,000 --> 00:32:47,080
Speaker 5: I don't know where to go next. At no point

578
00:32:47,080 --> 00:32:49,040
Speaker 5: did we know where to go next. We had lots

579
00:32:49,040 --> 00:32:52,880
Speaker 5: of ideas, and the ones that agreed with reality were

580
00:32:52,920 --> 00:32:55,280
Speaker 5: the ones we kept, and the ones that disagreed with

581
00:32:55,360 --> 00:32:59,160
Speaker 5: reality we let fall by the wayside. Because no matter

582
00:32:59,520 --> 00:33:02,360
Speaker 5: you know, I I'm a theorist by trade, and so

583
00:33:02,480 --> 00:33:05,280
Speaker 5: are a lot of people who talk about unified theories.

584
00:33:06,000 --> 00:33:10,160
Speaker 5: But in the end, physics is an experimental, observational, measurement

585
00:33:10,240 --> 00:33:14,920
Speaker 5: based science, and if your theory does not agree with

586
00:33:15,000 --> 00:33:17,479
Speaker 5: the measurements and experiments and observations you make in the

587
00:33:17,480 --> 00:33:20,480
Speaker 5: real world, it's not going to be accepted as a

588
00:33:20,480 --> 00:33:21,320
Speaker 5: physical theory.

589
00:33:21,440 --> 00:33:23,680
Speaker 3: So if I can try to, as a biologist, summarize

590
00:33:23,680 --> 00:33:26,600
Speaker 3: a couple different camps here, So there's a is there

591
00:33:26,640 --> 00:33:29,959
Speaker 3: a unified theory is one question, and some people might

592
00:33:30,040 --> 00:33:32,360
Speaker 3: say yes, probably we just haven't found yet. Others might

593
00:33:32,400 --> 00:33:35,600
Speaker 3: say no, there's no peak at all. But then there's

594
00:33:35,640 --> 00:33:39,080
Speaker 3: another axis along which there's a debate, which is is

595
00:33:39,120 --> 00:33:42,960
Speaker 3: the universe unified now or was it only unified in

596
00:33:43,040 --> 00:33:45,960
Speaker 3: the past? Is that right? Or does everybody agree there's

597
00:33:45,960 --> 00:33:48,400
Speaker 3: nothing unified now, we're just trying to look into the past.

598
00:33:48,840 --> 00:33:50,800
Speaker 5: I think that I want to let Daniel answer this,

599
00:33:50,960 --> 00:33:55,040
Speaker 5: because you already know what I would say. I want

600
00:33:55,080 --> 00:33:57,760
Speaker 5: to hear what Daniel has to say about that, because

601
00:33:58,560 --> 00:34:00,000
Speaker 5: I don't know what his answer is going to be.

602
00:34:01,040 --> 00:34:03,320
Speaker 1: Yeah, well, I think we're not unified on the question

603
00:34:03,360 --> 00:34:06,640
Speaker 1: of what we mean by unified. To me, it would

604
00:34:06,640 --> 00:34:09,400
Speaker 1: be sufficient to have a theory which explains all of

605
00:34:09,400 --> 00:34:12,200
Speaker 1: our phenomena and to have that theory be self consistent,

606
00:34:12,600 --> 00:34:14,480
Speaker 1: even if there are various parts of it, even if

607
00:34:14,520 --> 00:34:17,640
Speaker 1: it has broken symmetries within it. You know, even if

608
00:34:17,640 --> 00:34:21,480
Speaker 1: electricity and magnetism are different in that theory in the

609
00:34:21,520 --> 00:34:23,000
Speaker 1: sense that you know, there are two sides of the

610
00:34:23,040 --> 00:34:27,000
Speaker 1: same coin, but they're not the same exactly in the

611
00:34:27,040 --> 00:34:29,880
Speaker 1: same way that like the weak force, I consider electricity

612
00:34:29,880 --> 00:34:32,439
Speaker 1: and magnantism to have been unified with a weak force

613
00:34:32,440 --> 00:34:34,920
Speaker 1: in the sense that we have a consistent, coherent theory.

614
00:34:35,200 --> 00:34:37,759
Speaker 1: We have one prediction. It makes a single prediction for

615
00:34:37,800 --> 00:34:40,960
Speaker 1: what happens. You know, when you collide particles, for example,

616
00:34:41,160 --> 00:34:43,319
Speaker 1: you don't have to use the weak force and electromagnetic

617
00:34:43,320 --> 00:34:46,000
Speaker 1: force separately in some way. So that's the question for

618
00:34:46,040 --> 00:34:48,760
Speaker 1: me about unity. I think you have a higher standard,

619
00:34:49,040 --> 00:34:52,000
Speaker 1: which is like earlier in the universe, at higher energy,

620
00:34:52,040 --> 00:34:54,960
Speaker 1: does this theory become even simpler? Do these things all

621
00:34:55,000 --> 00:34:57,880
Speaker 1: become one so we have like a single force in

622
00:34:57,920 --> 00:35:01,600
Speaker 1: the universe to rule them all. And I think that's

623
00:35:01,640 --> 00:35:05,359
Speaker 1: a beautiful, ambitious goal. But I think it's beyond even

624
00:35:05,400 --> 00:35:07,479
Speaker 1: what I would ask for. So let's take a break

625
00:35:07,480 --> 00:35:09,399
Speaker 1: and come back and talk about the arguments for whether

626
00:35:09,520 --> 00:35:12,239
Speaker 1: or not. It's possible to have a unified theory, either

627
00:35:12,239 --> 00:35:33,600
Speaker 1: one that meets Daniel's requirements or Ethan's higher level demands.

628
00:35:35,680 --> 00:35:38,600
Speaker 1: So let's talk about the arguments for and against the

629
00:35:38,680 --> 00:35:42,080
Speaker 1: existence of a unified theory. For a lot of people

630
00:35:42,120 --> 00:35:44,520
Speaker 1: and for me, one of the strongest arguments is that

631
00:35:44,760 --> 00:35:48,319
Speaker 1: it's been working so far. If you just assume that

632
00:35:48,400 --> 00:35:51,840
Speaker 1: the universe makes sense, that there is a single reason

633
00:35:51,880 --> 00:35:54,560
Speaker 1: why things happen out there. You know why a particle

634
00:35:54,640 --> 00:35:56,880
Speaker 1: goes this way or not that way, or you know

635
00:35:56,920 --> 00:35:59,440
Speaker 1: why things interact to this level not at that level,

636
00:36:00,360 --> 00:36:03,680
Speaker 1: that it works. We have made great progress in discovering

637
00:36:03,760 --> 00:36:06,960
Speaker 1: laws of physics through experiment and deduction and inference on

638
00:36:07,000 --> 00:36:10,160
Speaker 1: all of this stuff, and that the answer keeps getting simpler,

639
00:36:10,320 --> 00:36:13,880
Speaker 1: right that over time we've harmonized various kinds of phenomena

640
00:36:14,080 --> 00:36:17,760
Speaker 1: into smaller numbers of things, and now we're left essentially,

641
00:36:17,760 --> 00:36:20,839
Speaker 1: as you said, with quantum mechanics and general relativity, and

642
00:36:20,920 --> 00:36:23,839
Speaker 1: we're stuck at this level so far. But you know,

643
00:36:24,040 --> 00:36:27,600
Speaker 1: the trend of history seems to be with us. What

644
00:36:27,680 --> 00:36:29,440
Speaker 1: do you guys think of that argument? Is that compelling?

645
00:36:29,760 --> 00:36:33,320
Speaker 5: I mean, this is sort of like the argument of like,

646
00:36:33,360 --> 00:36:35,200
Speaker 5: should we all be taking our shoes off at the

647
00:36:35,239 --> 00:36:39,120
Speaker 5: airport because we know that sometimes there's a shoe bomber

648
00:36:39,200 --> 00:36:41,759
Speaker 5: at the airport, and so this way, if everyone takes

649
00:36:41,760 --> 00:36:45,200
Speaker 5: their shoes off, we won't repeat the previous mistake that

650
00:36:45,239 --> 00:36:47,480
Speaker 5: we made by letting the shoe bomber on the plane.

651
00:36:47,800 --> 00:36:52,600
Speaker 5: Is like, this is great for addressing yesterday's problems, this

652
00:36:52,680 --> 00:36:56,600
Speaker 5: is not necessarily great for addressing today's problems, right, because

653
00:36:56,920 --> 00:37:00,960
Speaker 5: everything works until it doesn't. And I would argue that

654
00:37:01,239 --> 00:37:05,360
Speaker 5: the evidence we have today strongly suggests that all of

655
00:37:05,400 --> 00:37:09,560
Speaker 5: the avenues we've been pursuing towards unification have been showing

656
00:37:10,160 --> 00:37:14,360
Speaker 5: consistent with null evidence that there's no evidence for proton decay,

657
00:37:14,560 --> 00:37:17,759
Speaker 5: no evidence for extra dimensions, no exvidence for grand unification,

658
00:37:18,160 --> 00:37:21,400
Speaker 5: no evidence for quantum gravity, no evidence that gravity and

659
00:37:21,440 --> 00:37:24,240
Speaker 5: the other forces unify, no evidence that the strong force

660
00:37:24,280 --> 00:37:28,279
Speaker 5: and the electroweak force unify. And so you really just

661
00:37:28,360 --> 00:37:32,479
Speaker 5: start saying, like, but but it's pretty but I would

662
00:37:32,719 --> 00:37:36,200
Speaker 5: like it if it did. But it works in the past,

663
00:37:36,440 --> 00:37:39,600
Speaker 5: and I would These are great arguments for someone who's

664
00:37:39,640 --> 00:37:43,719
Speaker 5: completely ignorant about the existence of experimental data driven physics,

665
00:37:43,840 --> 00:37:46,959
Speaker 5: which is not us. We know about that, and that's

666
00:37:46,960 --> 00:37:50,480
Speaker 5: what we confront our universe with. So it's it's great

667
00:37:50,640 --> 00:37:54,040
Speaker 5: for I have a motivation in the absence of any data,

668
00:37:54,520 --> 00:37:58,200
Speaker 5: and then I say, okay, now, now come down off

669
00:37:58,239 --> 00:38:01,319
Speaker 5: your theory cloud and come meet reality. And so what

670
00:38:01,360 --> 00:38:04,720
Speaker 5: does reality say? And the same people who say those

671
00:38:04,760 --> 00:38:08,200
Speaker 5: things that you brought up just now, Daniel, they don't

672
00:38:08,239 --> 00:38:11,520
Speaker 5: want to talk about reality. And that's that's that's a

673
00:38:11,520 --> 00:38:12,440
Speaker 5: bit off putting to me.

674
00:38:12,719 --> 00:38:15,279
Speaker 3: So like again the biologists jumping in to see if

675
00:38:15,280 --> 00:38:17,279
Speaker 3: she can summarize it in one sentence. So, are you

676
00:38:17,400 --> 00:38:19,959
Speaker 3: saying that you don't believe in a unified theory because

677
00:38:20,000 --> 00:38:23,600
Speaker 3: reality just suggests it doesn't exist, or we just haven't

678
00:38:23,600 --> 00:38:25,080
Speaker 3: found the right unified theory yet.

679
00:38:25,440 --> 00:38:31,360
Speaker 5: I would say that no one should believe in something

680
00:38:32,000 --> 00:38:37,080
Speaker 5: that the data you know, you shouldn't. You shouldn't have

681
00:38:37,239 --> 00:38:41,879
Speaker 5: beliefs in things that the data's butt can't cash as

682
00:38:41,880 --> 00:38:44,640
Speaker 5: far as like a check goes. So like if you

683
00:38:44,719 --> 00:38:47,799
Speaker 5: wanted to say, like, but I think in my heart

684
00:38:47,920 --> 00:38:49,759
Speaker 5: or in my gut that there's got to be a

685
00:38:49,880 --> 00:38:53,279
Speaker 5: unified theory out there because I just know it, Like

686
00:38:53,320 --> 00:38:56,360
Speaker 5: that's great, but this is this is the same argument

687
00:38:56,560 --> 00:39:00,959
Speaker 5: that has led us astray for for countless malays since

688
00:39:01,040 --> 00:39:04,560
Speaker 5: before we were writing down human history. I know in

689
00:39:04,640 --> 00:39:07,560
Speaker 5: my gut, I know in my heart, I feel the instinct.

690
00:39:07,920 --> 00:39:11,640
Speaker 5: This is not how we do science. This is fine

691
00:39:11,840 --> 00:39:13,719
Speaker 5: if you want to say, oh, I can write down

692
00:39:13,760 --> 00:39:17,520
Speaker 5: a mathematic theory, and is this mathematics interesting? Sure, the

693
00:39:17,560 --> 00:39:23,799
Speaker 5: mathematics is interesting, but mathematics is outstanding at taking physicists

694
00:39:24,120 --> 00:39:29,480
Speaker 5: to worlds that never were Only one form of mathematics

695
00:39:29,680 --> 00:39:32,960
Speaker 5: actually winds up reflecting the reality we live in. It's

696
00:39:33,000 --> 00:39:36,759
Speaker 5: sort of like if I asked you, hey, what's the

697
00:39:36,800 --> 00:39:39,480
Speaker 5: square root of four and you said, I know this one,

698
00:39:39,520 --> 00:39:42,279
Speaker 5: it's two. Two is the square root of four? I

699
00:39:42,280 --> 00:39:44,120
Speaker 5: would say are you sure? And you'd go, oh, no,

700
00:39:44,239 --> 00:39:46,200
Speaker 5: he's trying to trick me. Why is he trying to

701
00:39:46,200 --> 00:39:48,600
Speaker 5: trick me? And I would say, well, it could be two,

702
00:39:48,800 --> 00:39:51,880
Speaker 5: or it could be negative too, and you would go, oh, yeah,

703
00:39:51,960 --> 00:39:55,120
Speaker 5: that's right. Square roots can have plus or minus solutions.

704
00:39:55,680 --> 00:39:59,080
Speaker 5: Then I say, but that's only true mathematically. If I

705
00:39:59,160 --> 00:40:01,279
Speaker 5: say I'm going to throw this ball and the ball

706
00:40:01,360 --> 00:40:03,239
Speaker 5: is going to land at the square root of four,

707
00:40:03,960 --> 00:40:07,560
Speaker 5: you can go measure that ball and find if it's

708
00:40:07,600 --> 00:40:12,040
Speaker 5: at plus two or minus two. Our universe gives one

709
00:40:12,280 --> 00:40:16,080
Speaker 5: answer to physical questions, and we can only find that

710
00:40:16,200 --> 00:40:19,960
Speaker 5: out by measuring it. So, as a theorist, your goal

711
00:40:20,320 --> 00:40:26,520
Speaker 5: is to provide not just the possible spectrum of explanations.

712
00:40:26,920 --> 00:40:30,040
Speaker 5: You want to be able to have someone who uses

713
00:40:30,080 --> 00:40:35,560
Speaker 5: your theory predict the answer. And until we get concrete,

714
00:40:35,840 --> 00:40:40,440
Speaker 5: unique predictions that we can test against reality, we only

715
00:40:40,520 --> 00:40:44,680
Speaker 5: have ideas. We don't have something that's worth believing, got it?

716
00:40:44,719 --> 00:40:48,360
Speaker 5: Believing requires evidence in a physical science.

717
00:40:48,640 --> 00:40:50,520
Speaker 1: Wow, that's some hardcore skepticism.

718
00:40:50,560 --> 00:40:51,840
Speaker 2: I love it.

719
00:40:51,880 --> 00:40:53,759
Speaker 3: Is it skepticism? I feel like you just said you

720
00:40:53,840 --> 00:40:54,400
Speaker 3: need data?

721
00:40:54,640 --> 00:40:56,960
Speaker 5: Do you want to provide a counter argument? Though? Like,

722
00:40:57,640 --> 00:41:00,959
Speaker 5: what would someone say who thinks that? No, Ethan, You're

723
00:41:01,160 --> 00:41:04,919
Speaker 5: you're too cold in your skepticism here, Like, what would

724
00:41:04,960 --> 00:41:07,080
Speaker 5: you say to argue against that?

725
00:41:07,239 --> 00:41:07,839
Speaker 2: All right? Fair?

726
00:41:07,960 --> 00:41:10,560
Speaker 1: I will play that role, you know. I think the

727
00:41:10,760 --> 00:41:14,160
Speaker 1: argument is not we don't need data. We just have

728
00:41:14,239 --> 00:41:16,879
Speaker 1: to think about things. I mean, we're not the ancient Greeks, right,

729
00:41:17,320 --> 00:41:19,920
Speaker 1: But I think the argument is instead, we can be

730
00:41:20,080 --> 00:41:26,879
Speaker 1: inspired by things like simplicity or beauty, or just random

731
00:41:27,280 --> 00:41:30,560
Speaker 1: moments of inspiration. Science tells us we have to go

732
00:41:30,640 --> 00:41:33,600
Speaker 1: out and test our theories. It doesn't tell us necessarily

733
00:41:33,600 --> 00:41:35,680
Speaker 1: how we have to come up with those theories, right,

734
00:41:36,120 --> 00:41:38,640
Speaker 1: So you could be like, you know, smoking banana peels

735
00:41:38,840 --> 00:41:41,799
Speaker 1: and have an idea and then just go and test

736
00:41:41,840 --> 00:41:44,080
Speaker 1: it and if it works, great, And so I think

737
00:41:44,120 --> 00:41:48,279
Speaker 1: it's okay to be motivated by, you know, esthetic preferences

738
00:41:48,320 --> 00:41:50,239
Speaker 1: for various kinds of theories, as long as it's not

739
00:41:50,280 --> 00:41:54,480
Speaker 1: the only way you're looking around for ideas, and to

740
00:41:54,520 --> 00:41:57,279
Speaker 1: be motivated by what has worked in the past. You know,

741
00:41:57,520 --> 00:42:00,760
Speaker 1: I agree with you. Of course, you shouldn't believe things

742
00:42:00,880 --> 00:42:03,400
Speaker 1: that don't have data to support them. But you know,

743
00:42:03,400 --> 00:42:05,080
Speaker 1: I think what we're talking about here is more like

744
00:42:05,480 --> 00:42:08,440
Speaker 1: what questions do you ask? What ideas do you try?

745
00:42:08,920 --> 00:42:11,600
Speaker 1: And so I think it's valid to continue to try

746
00:42:11,640 --> 00:42:13,560
Speaker 1: things which have worked in the past.

747
00:42:13,600 --> 00:42:16,920
Speaker 5: You but you also agree that it's really essential to

748
00:42:16,960 --> 00:42:20,600
Speaker 5: the scientific process that you do come back to data,

749
00:42:20,640 --> 00:42:23,080
Speaker 5: that whatever theory you come up with, you do connect

750
00:42:23,120 --> 00:42:26,600
Speaker 5: it with reality, with an observable, with a measurable thing,

751
00:42:27,200 --> 00:42:30,760
Speaker 5: and that if your theory does not give you something

752
00:42:30,840 --> 00:42:34,640
Speaker 5: that's born out as a measurement, that's born out by experiment,

753
00:42:34,760 --> 00:42:39,360
Speaker 5: by observation, then you can't just accept it or believe

754
00:42:39,400 --> 00:42:42,800
Speaker 5: in it because of you know, esthetic reasons or natural

755
00:42:42,840 --> 00:42:46,800
Speaker 5: reasons or beauty reasons, that you really have to say, no,

756
00:42:46,960 --> 00:42:51,160
Speaker 5: there's physical evidence that supports that this picture of reality

757
00:42:51,239 --> 00:42:51,680
Speaker 5: is true.

758
00:42:51,840 --> 00:42:55,160
Speaker 1: Absolutely I agree with that. But then let me make

759
00:42:55,239 --> 00:42:58,160
Speaker 1: a different argument than in favor of a unified theory,

760
00:42:58,280 --> 00:43:01,760
Speaker 1: which is a little bit more flowery. And and that's

761
00:43:01,880 --> 00:43:05,040
Speaker 1: this argument about mathematics. That you know, so far the

762
00:43:05,200 --> 00:43:09,799
Speaker 1: universe seems to be well described by mathematical theories, right that,

763
00:43:09,880 --> 00:43:11,480
Speaker 1: as you say, you have to go and write down

764
00:43:11,520 --> 00:43:13,840
Speaker 1: your theory and makes predictions, you can test them, et cetera.

765
00:43:14,080 --> 00:43:15,319
Speaker 2: And all those theories.

766
00:43:14,960 --> 00:43:19,600
Speaker 1: Are mathematical, and the mathematics is so powerful, so famously

767
00:43:19,800 --> 00:43:24,600
Speaker 1: unreasonably effective, that it's not unreasonable to argue that, like, hmm,

768
00:43:24,640 --> 00:43:28,080
Speaker 1: maybe mathematics is part of the universe. We're discovering it.

769
00:43:28,480 --> 00:43:32,120
Speaker 1: It's out there. The universe itself is mathematical. There's math

770
00:43:32,160 --> 00:43:34,880
Speaker 1: that runs as sort of the source code of the universe.

771
00:43:35,160 --> 00:43:37,480
Speaker 1: And if that's true, then there has to be some

772
00:43:37,800 --> 00:43:41,760
Speaker 1: math that describes the universe, even if we haven't found

773
00:43:41,800 --> 00:43:43,759
Speaker 1: it yet. What would you say to that argument? Do

774
00:43:43,760 --> 00:43:46,359
Speaker 1: you believe that math is discovered.

775
00:43:45,840 --> 00:43:47,880
Speaker 2: Or do you think that it's invented by humans?

776
00:43:48,120 --> 00:43:51,120
Speaker 5: I mean, for me, I look at math as math

777
00:43:51,239 --> 00:43:57,960
Speaker 5: is the best language we have for quantitatively describing anything.

778
00:43:58,320 --> 00:44:01,680
Speaker 5: As soon as you start asking the question how much

779
00:44:02,040 --> 00:44:07,279
Speaker 5: in what amount? As soon as you go from asking, well, qualitatively,

780
00:44:07,760 --> 00:44:10,279
Speaker 5: what's going to happen? Like will it exist or not?

781
00:44:10,440 --> 00:44:15,080
Speaker 5: And you start asking how much? You need mathematics to

782
00:44:15,239 --> 00:44:18,799
Speaker 5: describe it. And that's kind of the basics of what

783
00:44:18,920 --> 00:44:24,080
Speaker 5: physics and physical sciences are is it is a quantitative science.

784
00:44:24,120 --> 00:44:26,800
Speaker 5: We do care about how much, we do care about

785
00:44:26,840 --> 00:44:30,160
Speaker 5: what amount, And so the idea that you would be

786
00:44:30,239 --> 00:44:34,640
Speaker 5: able to describe that without mathematics is alien to our

787
00:44:34,840 --> 00:44:38,600
Speaker 5: understanding of how nature works. The very fact that we

788
00:44:39,080 --> 00:44:44,359
Speaker 5: dare to ask the question how much means it's like

789
00:44:44,680 --> 00:44:48,959
Speaker 5: it's like tautologically means that we have to describe it mathematically,

790
00:44:49,040 --> 00:44:51,000
Speaker 5: because if we want to know the answer to the

791
00:44:51,080 --> 00:44:55,319
Speaker 5: question how much, a non mathematical description will not give

792
00:44:55,360 --> 00:44:59,719
Speaker 5: you that answer. So it's because we chose to investigate

793
00:44:59,719 --> 00:45:02,160
Speaker 5: the un verse in this way that of course it's

794
00:45:02,280 --> 00:45:06,719
Speaker 5: describable in terms of mathematics. But again, I want to

795
00:45:06,840 --> 00:45:12,680
Speaker 5: strongly reinforce. Just because mathematics exist doesn't mean that it

796
00:45:12,719 --> 00:45:17,120
Speaker 5: corresponds to anything in physical reality. We can invent all

797
00:45:17,200 --> 00:45:21,920
Speaker 5: sorts of mathematics that cannot correspond to reality we know of.

798
00:45:22,000 --> 00:45:24,719
Speaker 5: Like oh, like I went to a mathematics conference when

799
00:45:24,719 --> 00:45:28,120
Speaker 5: I was a grad student that on mathematical physics, and

800
00:45:28,560 --> 00:45:31,520
Speaker 5: I was like, well, hang on, someone is giving a

801
00:45:31,600 --> 00:45:35,759
Speaker 5: talk on the E ten exceptional group. And I said,

802
00:45:35,760 --> 00:45:38,319
Speaker 5: but but you can't have more than E eight. You're

803
00:45:38,360 --> 00:45:40,960
Speaker 5: not a group anymore. And they're like, oh, yeah, well

804
00:45:41,000 --> 00:45:43,200
Speaker 5: we just ignore that and we just continue and write

805
00:45:43,239 --> 00:45:46,239
Speaker 5: it down anyway, and we just apply the rules that

806
00:45:46,360 --> 00:45:48,440
Speaker 5: used to work for the things that were groups and

807
00:45:48,480 --> 00:45:50,880
Speaker 5: we apply them to this too, and we see what

808
00:45:50,960 --> 00:45:53,960
Speaker 5: comes out of it. I was like, but can you

809
00:45:54,160 --> 00:45:57,040
Speaker 5: do that? Can you rigorously do that? Can you do

810
00:45:57,120 --> 00:46:00,959
Speaker 5: that in a logical, self consistent manner? And some people

811
00:46:01,040 --> 00:46:03,799
Speaker 5: don't care, and they just do it anyway, regardless of

812
00:46:03,840 --> 00:46:06,759
Speaker 5: what the answer to that question is. And you know,

813
00:46:07,280 --> 00:46:09,880
Speaker 5: I would say, as you put it, Ethan has a

814
00:46:09,920 --> 00:46:14,040
Speaker 5: more stringent requirement than some other physicists do. He's like, hey,

815
00:46:14,080 --> 00:46:16,600
Speaker 5: you have to connect it to reality too, Like this

816
00:46:16,719 --> 00:46:19,400
Speaker 5: is this is nuts. Like I don't want to be

817
00:46:19,480 --> 00:46:22,879
Speaker 5: hampered by reality. But I say you do, because if

818
00:46:22,880 --> 00:46:26,520
Speaker 5: you have, for example, a theory or a framework that

819
00:46:26,680 --> 00:46:31,360
Speaker 5: predicts the presence of a large number of flavor changing

820
00:46:31,440 --> 00:46:35,399
Speaker 5: neutral currents in particle physics, like that predicts I can

821
00:46:35,440 --> 00:46:40,840
Speaker 5: go from a heavy unstable quark directly to a lighter

822
00:46:40,960 --> 00:46:45,400
Speaker 5: quark with the same quantum numbers, except that's a lighter

823
00:46:45,440 --> 00:46:48,680
Speaker 5: flavor that has the same electric charge, but a lighter flavor.

824
00:46:48,960 --> 00:46:54,280
Speaker 5: We have enormous constraints from reality, from experiments, from observations,

825
00:46:54,280 --> 00:46:58,160
Speaker 5: from colighter data that we know that doesn't happen. To

826
00:46:58,360 --> 00:47:04,319
Speaker 5: a shocking degree, Almost any attempt towards unification that you

827
00:47:04,360 --> 00:47:07,520
Speaker 5: can write down is going to have enormous numbers of

828
00:47:07,560 --> 00:47:10,839
Speaker 5: these flavor changing neutral currents. So I would say if

829
00:47:10,880 --> 00:47:14,720
Speaker 5: you want to take that approach, you immediately are faced

830
00:47:14,719 --> 00:47:17,960
Speaker 5: with the problem of how do I suppress the extra

831
00:47:18,239 --> 00:47:24,080
Speaker 5: ingredients I'm adding in that are inconsistent with already established reality.

832
00:47:24,320 --> 00:47:27,239
Speaker 5: I'm not saying you can't do it. I'm saying that's

833
00:47:27,280 --> 00:47:30,279
Speaker 5: a challenge, that's a hurdle you have to clear or

834
00:47:30,320 --> 00:47:32,480
Speaker 5: your theory is dead in the water. From the start.

835
00:47:32,600 --> 00:47:34,560
Speaker 3: I'm enjoying this gloves off de base.

836
00:47:35,640 --> 00:47:38,400
Speaker 1: Well, let me throw another philosophical argument at you, Ethan,

837
00:47:38,719 --> 00:47:40,560
Speaker 1: And I'm happy to take either side of this. So

838
00:47:40,560 --> 00:47:43,120
Speaker 1: I'm curious what your thoughts are. What are your thoughts

839
00:47:43,160 --> 00:47:47,000
Speaker 1: on the possibility that there could be multiple theories of everything?

840
00:47:47,200 --> 00:47:50,240
Speaker 1: I mean, what if we eventually figure out quantum gravity

841
00:47:50,520 --> 00:47:52,640
Speaker 1: and we have, you know, some theory of strings and

842
00:47:52,680 --> 00:47:55,200
Speaker 1: it works, and you know, somebody comes up with a

843
00:47:55,239 --> 00:47:57,520
Speaker 1: way to test it, and we do experiments and boom

844
00:47:57,680 --> 00:48:00,360
Speaker 1: if they are confirmed, and we have this fantastic theory

845
00:48:00,400 --> 00:48:02,759
Speaker 1: and incorporate dark energy and dark matter and all of

846
00:48:02,800 --> 00:48:06,120
Speaker 1: our questions are answered. And then aliens arrive one day

847
00:48:06,320 --> 00:48:08,960
Speaker 1: and they have another theory and it's not strings, it's

848
00:48:09,080 --> 00:48:14,400
Speaker 1: shmings or something, and it also exactly and it also

849
00:48:14,520 --> 00:48:18,480
Speaker 1: explains everything. Do you think that's possible or do you

850
00:48:18,520 --> 00:48:21,800
Speaker 1: think there's a demand that the universe has a single

851
00:48:21,840 --> 00:48:22,800
Speaker 1: reason for everything?

852
00:48:22,960 --> 00:48:26,920
Speaker 5: Oh my goodness, I mean, so I'm gonna answer your

853
00:48:27,000 --> 00:48:31,839
Speaker 5: question by talking about something entirely different, which is, how

854
00:48:31,880 --> 00:48:36,920
Speaker 5: do you interpret quantum mechanics. What is your philosophy on

855
00:48:37,040 --> 00:48:40,719
Speaker 5: quantum mechanics? Do you say, oh, you know, well, these

856
00:48:40,760 --> 00:48:43,719
Speaker 5: things that we call particles, they aren't really particles. They're

857
00:48:43,840 --> 00:48:47,760
Speaker 5: wavelike entities while they propagate, and only when you observe

858
00:48:47,840 --> 00:48:51,600
Speaker 5: them do they actually interact like particles. Or you know,

859
00:48:52,080 --> 00:48:55,040
Speaker 5: the particle is actually a wave function, and the wave

860
00:48:55,080 --> 00:48:58,279
Speaker 5: function is what's fundamental and universal. And when I make

861
00:48:58,320 --> 00:49:01,960
Speaker 5: a measurement, I'm not even collapsing the wave function. I'm

862
00:49:02,040 --> 00:49:06,000
Speaker 5: just selecting out which aspect of the wave function is

863
00:49:06,120 --> 00:49:09,759
Speaker 5: most accurately represented by our universe. Or you know, do

864
00:49:09,800 --> 00:49:13,640
Speaker 5: I take the uncertainty away from the particle entirely and

865
00:49:13,760 --> 00:49:19,480
Speaker 5: move all of that uncertainty and probabilitiness into the quantum operator. Right,

866
00:49:19,920 --> 00:49:23,080
Speaker 5: this is if it's sort of like you're asking me

867
00:49:24,360 --> 00:49:28,040
Speaker 5: which interpretation of quantum mechanics is right, and I'm going

868
00:49:28,080 --> 00:49:32,040
Speaker 5: to tell you they're all equally right, because they all

869
00:49:32,120 --> 00:49:35,879
Speaker 5: give you the same answers. I don't think there's any

870
00:49:35,960 --> 00:49:39,719
Speaker 5: way to tell them apart. So if you're telling me like, oh, yeah, well,

871
00:49:39,760 --> 00:49:42,920
Speaker 5: we use strings, but we the other aliens out there

872
00:49:42,960 --> 00:49:45,719
Speaker 5: they use springs and it works just great. They just

873
00:49:45,760 --> 00:49:49,000
Speaker 5: said like buoying and here we go, right that that's great.

874
00:49:49,040 --> 00:49:51,600
Speaker 5: I put a dart. I put a harmonic oscillator into

875
00:49:51,600 --> 00:49:54,640
Speaker 5: my Newtonian gravity term and boom, I get dark energy out.

876
00:49:54,640 --> 00:49:58,520
Speaker 5: It's perfect spring theory. There we go, and I believe

877
00:49:58,560 --> 00:50:00,480
Speaker 5: that or not that actually works, but but you know

878
00:50:00,520 --> 00:50:04,000
Speaker 5: it's not doesn't lead anywhere, which is also a problem.

879
00:50:04,400 --> 00:50:08,320
Speaker 5: I would say, yeah, of course, you can have many

880
00:50:08,360 --> 00:50:15,920
Speaker 5: different equivalent mathematical formulations of the same theory, and they

881
00:50:15,960 --> 00:50:19,959
Speaker 5: can all be equally correct. The only way you can

882
00:50:20,040 --> 00:50:23,760
Speaker 5: say I demand a unique thing is when you start

883
00:50:23,840 --> 00:50:29,319
Speaker 5: devising ways to test different predictions that arise from these

884
00:50:29,320 --> 00:50:32,080
Speaker 5: different ways of looking at it against each other. Many

885
00:50:32,160 --> 00:50:37,760
Speaker 5: mathematical theories are dual or holomorphic or isomorphic to one another.

886
00:50:38,239 --> 00:50:41,560
Speaker 5: And so if someone says, well, I've formulated so thirty

887
00:50:41,600 --> 00:50:44,400
Speaker 5: two string theory, and someone goes, well, I've formulated eight

888
00:50:44,480 --> 00:50:47,600
Speaker 5: cross eight super string theory. And someone says, well, my

889
00:50:47,680 --> 00:50:50,040
Speaker 5: theory only has twenty six dimensions, they go, well, mine

890
00:50:50,040 --> 00:50:52,319
Speaker 5: only has ten. Is like, actually, I can show you

891
00:50:52,360 --> 00:50:55,000
Speaker 5: that these are mathematically equivalent. Like they'll both yell how

892
00:50:55,080 --> 00:50:57,239
Speaker 5: dare you? And then they'll be like, oh crap, there's

893
00:50:57,280 --> 00:51:00,279
Speaker 5: also three others that are also equivalent to this, and

894
00:51:00,320 --> 00:51:01,640
Speaker 5: so yeah.

895
00:51:01,400 --> 00:51:03,680
Speaker 1: All right, So I thought you were arguing on one side.

896
00:51:03,719 --> 00:51:05,759
Speaker 1: I thought you were going to say, look, it doesn't matter,

897
00:51:05,800 --> 00:51:08,360
Speaker 1: you can have two different stories that explain the universe.

898
00:51:08,360 --> 00:51:11,200
Speaker 1: But I think you're actually arguing that the contrary point

899
00:51:11,200 --> 00:51:13,319
Speaker 1: of view. You're saying, if there are two theories that

900
00:51:13,360 --> 00:51:16,400
Speaker 1: explain the universe, they're going to be mathematically equivalent. You

901
00:51:16,400 --> 00:51:19,040
Speaker 1: can have a mapping from one to the other that

902
00:51:19,120 --> 00:51:21,440
Speaker 1: you couldn't have two incoherent stories.

903
00:51:21,760 --> 00:51:24,719
Speaker 5: My argument is if they're not mathematically equivalent, if there

904
00:51:24,760 --> 00:51:29,680
Speaker 5: are actually major differences between different theories that equally describe

905
00:51:29,719 --> 00:51:35,680
Speaker 5: the universe, then theoretically there's some difference between them that

906
00:51:35,719 --> 00:51:39,600
Speaker 5: will manifest physically that you could go out test, measure

907
00:51:39,920 --> 00:51:43,200
Speaker 5: and determine which one's right and which one's less right.

908
00:51:43,440 --> 00:51:45,680
Speaker 1: All right, So that leads me to the last topic

909
00:51:45,800 --> 00:51:49,520
Speaker 1: on this question, which is reductionism. Right, if we think

910
00:51:49,719 --> 00:51:52,960
Speaker 1: that the universe is controlled by the microscopic reality, that

911
00:51:53,000 --> 00:51:55,840
Speaker 1: everything bubbles up from what's happening at the smallest scale,

912
00:51:55,840 --> 00:51:59,640
Speaker 1: which so far has seemed to work, then shouldn't there

913
00:51:59,719 --> 00:52:02,839
Speaker 1: be a way to test the ultimate theory? Shouldn't there

914
00:52:02,880 --> 00:52:06,120
Speaker 1: be one answer to what's happening down there? As you

915
00:52:06,200 --> 00:52:09,600
Speaker 1: just said, there should be some physical consequence to this theory.

916
00:52:10,239 --> 00:52:11,640
Speaker 1: What do you think about that? Do you think that

917
00:52:11,680 --> 00:52:15,279
Speaker 1: we're guaranteed to have some fundamental layer of reality if

918
00:52:15,280 --> 00:52:18,279
Speaker 1: we keep building bigger and bigger accelerators, eventually we will

919
00:52:18,320 --> 00:52:21,440
Speaker 1: expose and probe the base layer of reality. Or do

920
00:52:21,480 --> 00:52:23,400
Speaker 1: you think there's a risk that it's like you know,

921
00:52:23,480 --> 00:52:26,360
Speaker 1: turtles all the way down, just effective theories forever.

922
00:52:26,640 --> 00:52:29,239
Speaker 5: The fact that you use the word guarantee makes me

923
00:52:29,320 --> 00:52:31,640
Speaker 5: say there's no way. There's no way I can guarantee

924
00:52:31,719 --> 00:52:36,320
Speaker 5: this because we don't get to tell nature how it works.

925
00:52:36,640 --> 00:52:38,600
Speaker 5: We don't get to say nature, this is how you

926
00:52:38,800 --> 00:52:42,200
Speaker 5: have to work. You can say, Look, all I can

927
00:52:42,280 --> 00:52:46,040
Speaker 5: do is say I've made a good approximation of reality.

928
00:52:46,080 --> 00:52:48,799
Speaker 5: It works for now, and if I go down to

929
00:52:48,880 --> 00:52:51,239
Speaker 5: the next level, the next level, the next level, each

930
00:52:51,360 --> 00:52:54,680
Speaker 5: level I go to, I'm testing it. I'm testing is

931
00:52:54,719 --> 00:52:58,359
Speaker 5: this approximation still good? At some point it might break down.

932
00:52:58,680 --> 00:53:00,680
Speaker 5: If you had come to me one hundred and fifty

933
00:53:00,719 --> 00:53:04,040
Speaker 5: years ago and said, Ethan, cause and effect, that's the

934
00:53:04,080 --> 00:53:06,359
Speaker 5: way everything has to work, I would have said, yeah,

935
00:53:06,360 --> 00:53:09,440
Speaker 5: I believe that. Because we hadn't discovered quantum mechanics, we

936
00:53:09,480 --> 00:53:15,080
Speaker 5: hadn't discovered radioactive decay, We hadn't discovered probabilistic wave function

937
00:53:15,200 --> 00:53:18,000
Speaker 5: behavior yet, but that exists. That's a part of nature.

938
00:53:18,200 --> 00:53:21,279
Speaker 5: So I don't know what assumptions we're making today that

939
00:53:21,320 --> 00:53:23,960
Speaker 5: are going to be proven that that's not congruent with

940
00:53:24,040 --> 00:53:26,680
Speaker 5: reality in the future. I just know enough to keep

941
00:53:26,719 --> 00:53:30,080
Speaker 5: an open mind that maybe some of these assumptions are

942
00:53:30,120 --> 00:53:32,960
Speaker 5: not necessarily good. All the way down to the level

943
00:53:32,960 --> 00:53:33,960
Speaker 5: of the bottom turtle.

944
00:53:34,360 --> 00:53:37,160
Speaker 1: All right, well, thanks very much for answering all of

945
00:53:37,200 --> 00:53:39,600
Speaker 1: our questions today and taking us down to the bottom turtle.

946
00:53:39,600 --> 00:53:40,880
Speaker 2: We really appreciate you coming on.

947
00:53:41,200 --> 00:53:43,160
Speaker 5: Thank you. It's been my pleasure to be here. And

948
00:53:43,239 --> 00:53:45,839
Speaker 5: thank you Daniel. Thank you Kelly for hosting me and

949
00:53:46,239 --> 00:53:49,880
Speaker 5: having an extraordinary conversation about yet another aspect of the

950
00:53:50,000 --> 00:53:51,960
Speaker 5: universe we still aren't sure about.

951
00:53:58,920 --> 00:54:02,480
Speaker 3: Daniel and Kelly's extra Ordinary Universe is produced by iHeartRadio.

952
00:54:02,680 --> 00:54:04,200
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953
00:54:04,320 --> 00:54:05,360
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954
00:54:05,520 --> 00:54:08,239
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955
00:54:08,480 --> 00:54:10,120
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956
00:54:10,200 --> 00:54:13,160
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957
00:54:13,160 --> 00:54:16,160
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958
00:54:16,200 --> 00:54:16,600
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959
00:54:16,880 --> 00:54:19,680
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960
00:54:19,800 --> 00:54:23,640
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961
00:54:22,719 --> 00:54:24,800
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962
00:54:24,880 --> 00:54:28,680
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963
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964
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965
00:54:32,920 --> 00:54:34,440
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