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Speaker 1: Hey, Jorhan Daniel here, and we want to tell you

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Speaker 1: about our new book. It's called Frequently Asked Questions about

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Speaker 1: the Universe because you have questions about the universe, and

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Speaker 1: so we decided to write a book all about them.

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Speaker 1: We talk about your questions, we give some answers, we

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Speaker 1: make a bunch of silly jokes as usual, and we

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Speaker 1: tackle all kinds of questions, including what happens if I

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Speaker 1: fall into a black hole? Or is there another version

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Speaker 1: of you out there that's right? Like usual, we tackle

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Speaker 1: the deepest, darkest, biggest, craziest questions about this incredible cosmos.

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Speaker 1: If you want to support the podcast, please get the

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Speaker 1: book and get a copy, not just for yourself, but

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Speaker 1: you know, for your nieces and nephews, cousins, friends, parents, dogs, hamsters,

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Speaker 1: and for the aliens. So get your copy of Frequently

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Speaker 1: Asked Questions about the Universe is available for pre order now,

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Speaker 1: coming out November two. You can find more details at

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Speaker 1: the book's website, Universe f a Q dot com. Thanks

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Speaker 1: for your support, and if you have a hamster that

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Speaker 1: can read, please let us know. We'd love to have

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Speaker 1: them on the podcast. Hey Daniel, I have a question

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Speaker 1: for you about time? All right? I got time for that,

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Speaker 1: all right. So you do a lot of things, right,

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Speaker 1: you're a professor, you have a podcast, and you're always

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Speaker 1: switching between them. That's true. It's a lot of different

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Speaker 1: things to manage, all right. So then what do you

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Speaker 1: think is the shortest useful unit of time? Like, can

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Speaker 1: you get something done in five minutes? Or do you

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Speaker 1: need like an hour just to dig into something? Well,

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Speaker 1: you know, sort of depends on what it is. Is

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Speaker 1: it serious research or just like writing bad jokes for

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Speaker 1: the podcast? What do you mean? All right? Well, which

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Speaker 1: one takes more time? Oh? Bad jokes for sure? I

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Speaker 1: mean at some point you just can't scrape that barrel

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Speaker 1: any deeper. What if you just give you more time?

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Speaker 1: As long as you're writing jokes about time, they basically

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Speaker 1: just right themselves. Hi, I'm Jorge. I'm a cartoonist and

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Speaker 1: the creator of PhD comics. I'm Daniel. I'm a particle

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Speaker 1: physicist and a professor, and I never seem to have

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Speaker 1: enough time. Really, can't you just make time in your

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Speaker 1: particle collider? I mean, right, it's called space time. Can

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Speaker 1: you just transform some space into time? You know? What

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Speaker 1: I need to do is to speed up the rest

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Speaker 1: of the world near the speed of light, so it

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Speaker 1: runs slowly, and then I can just get all my

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Speaker 1: work done while everybody else is frozen. Oh that's a

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Speaker 1: good idea. But then you'd be left behind. Everyone would

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Speaker 1: be really far away, you'd be light years away, but

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Speaker 1: you would catch up and work. I would made all

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Speaker 1: my deadlines even though I'd be in the neighboring star system. Yeah,

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Speaker 1: there you go. And then how do you turn your

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Speaker 1: work in? You can't. I knew there was a flaw

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Speaker 1: on this plan. Yeah, you paradox yourself into unemployment. The

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Speaker 1: twin professor paradox. But welcome to our podcast. Daniel and

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Speaker 1: Jorge explained the Universe say production of I Heart Radio,

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Speaker 1: in which we take that mental journey around the universe,

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Speaker 1: speeding your brain up to near the speed of light,

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Speaker 1: so that we can try to understand the very nature

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Speaker 1: of the universe that we find ourselves in, this incredible,

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Speaker 1: glittering cosmos with all of its wonderful questions that it inspires,

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Speaker 1: the things that make us go, huh, why is it

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Speaker 1: like that? Why couldn't it be like this other thing?

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Speaker 1: We dig into all of that on this podcast. We

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Speaker 1: stare right into the abyss of our ignorance, and we

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Speaker 1: ask why, and we do our best to explain what

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Speaker 1: we do and don't know to you. Yeah, because it

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Speaker 1: is a pretty wonderful universe, but it's also kind of

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Speaker 1: a weird universe. We grow up thinking that space is

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Speaker 1: fixed and firm and never changes, but actually it sort

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Speaker 1: of does. It's it's squishy and also kind of ripley.

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Speaker 1: I'm glad it's a weird universe, though, What would it

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Speaker 1: be like if we were doing physics and discovering Yeah,

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Speaker 1: the universe is basically exactly as you thought it was

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Speaker 1: and kind of boring. After all, you would have to

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Speaker 1: switch careers to just writing joke. I don't think I

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Speaker 1: could have that as a career. But I wonder sometimes

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Speaker 1: about how, you know, we find the universe beautiful, We

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Speaker 1: find nature beautiful, and we also find it mysterious and interesting,

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Speaker 1: And I wonder if that's an accident or a product

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Speaker 1: of the way the human mind works, that we just

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Speaker 1: find beauty and mystery everywhere around us. Yeah, or even

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Speaker 1: like the word weird, like why is it weird to us? Right? Like?

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Speaker 1: What makes us the overall judges of what is weird,

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Speaker 1: and what is not? Like, maybe the universe is offended

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Speaker 1: by us calling it weird. Yeah, and then the word

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Speaker 1: weird itself is weird? Mean you say it enough times,

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Speaker 1: it sounds pretty weird. It's got an E and I

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Speaker 1: in it, like weird, weird, weird, it's a pretty weird word. Yeah. Yeah,

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Speaker 1: but that's the English people's fault. Blame it on the Brits.

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Speaker 1: So yeah, it is a pretty, let's say, interesting universe.

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Speaker 1: You think the universe would be offended if we called

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Speaker 1: it interesting, sort of like living in interesting times. No,

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Speaker 1: I think it's good. I think we are lucky. It's

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Speaker 1: one of the things that makes life worth living. You know.

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Speaker 1: People sometimes ask me this question, like why should we

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Speaker 1: fund particle physics? What good is it? And I hear

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Speaker 1: my colleagues making arguments like, well, you know, we might

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Speaker 1: have spinoff technologies or we invented the Worldwide Web. But

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Speaker 1: for me, the true answer is that it explores the universe.

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Speaker 1: It explores the nature of the human existence, sort of

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Speaker 1: the same way like art does you ask an artist like,

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Speaker 1: and why should we pay for art? Why should people

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Speaker 1: write books? Well, it's you know, just part of the

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Speaker 1: joy of life. Is unraveling the mystery of the universe

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Speaker 1: we find ourselves in. That's it, and that's enough. Well,

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Speaker 1: I'm not sure you want to be in the same

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Speaker 1: position that the arts are in trying to get funding

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Speaker 1: using that argument, So I would stick with the Worldwide

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Speaker 1: Web and useful technology for now. To be honest, I

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Speaker 1: think you just haven't asked big enough, Like why don't

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Speaker 1: you pitch your ten billion dollar cartoon to the government.

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Speaker 1: You know, the more you ask for, the more you get.

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Speaker 1: I'm not sure the time is right for that crazy idea,

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Speaker 1: the large hay drawing cartoon. Yeah, there you go. It

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Speaker 1: will break open the universe probably and create imaginary black

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Speaker 1: holes of ink that will swallow up the Earth. That's right,

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Speaker 1: that sounds good. I'd read that my pitching my tax

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Speaker 1: dollars for that. Anyway, we love for the universe is mysterious,

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Speaker 1: and it presents us with really fun, interesting, basic questions,

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Speaker 1: things that we don't understand about, you know, the very

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Speaker 1: like ABC's of reality. Yeah, because I guess you know,

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Speaker 1: we grow up experiencing the universe in one way and

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Speaker 1: we think it works in a certain way in our brains.

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Speaker 1: But really, when you sort of drill down into it,

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Speaker 1: or you scale up to bigger things. There are big

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Speaker 1: surprises and it doesn't work the way we think it does. Yeah,

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Speaker 1: I think of the universe is sort of like a ladder.

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Speaker 1: You know, if you look at it at one distance

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Speaker 1: scale and one time scale, it works a certain way.

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Speaker 1: If you look at another distance scale, like if you're

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Speaker 1: looking at particles or if you're looking at water droplets

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Speaker 1: or galaxies, there seem to be different rules that apply

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Speaker 1: at these different distance scales, and that's fascinating. It makes

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Speaker 1: you wonder, like, are any of these fundamental Are we

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Speaker 1: learning anything really deep and true about the universe? Or

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Speaker 1: does it all just depends on the questions you're asking?

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Speaker 1: And so it's not just scientists who have questions about

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Speaker 1: the universe and about the nature of the universe. It's

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Speaker 1: also our listeners and everyday people just like you. That's right,

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Speaker 1: because remember that science is just people asking questions, and

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Speaker 1: the investigations we do are motivated by the individual questions

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Speaker 1: of individual scientists wondering things about the universe, and that

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Speaker 1: includes you, because we are all out there wondering about

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Speaker 1: the universe and trying to figure it out. So today

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Speaker 1: we are tackling a question that we got from a

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Speaker 1: listener who comes from Sweden. It's Henrik, and Henrik is

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Speaker 1: a pretty interesting question about time. So here is Henrick's question. Hi,

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Speaker 1: I'm Henrik from Sweden and I have been wondering if

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Speaker 1: time could be pixelated? Is there any minimum unit of time?

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Speaker 1: Or could it be infinitely short? And when I listened

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Speaker 1: to your episode about space being pixelated or not, I

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Speaker 1: started wondering if time could be pixelated while space isn't,

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Speaker 1: or vice versa. Thank you guys. All right, it's a

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Speaker 1: pretty interesting question from Henry. So today on the podcast

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Speaker 1: will be tackling is time pixelated? That's a pretty strange question,

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Speaker 1: Is time pixelated? I don't usually associate pixels with time. Yeah,

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Speaker 1: it's a wonderful question, and I love hearing Henrik do physics.

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Speaker 1: You know, he is absorbing what we're talking about and

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Speaker 1: he's taking it to the next natural consequence. And that's

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Speaker 1: what you got to do with the theory. You say,

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Speaker 1: all right, well, this describes what I'm thinking about or

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Speaker 1: describes what I've seen. Can I extrapolate from it to

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Speaker 1: the rest of the universe or what are the consequences

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Speaker 1: of it? How can I test and explore this? So

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Speaker 1: that's exactly doing physics. So kudos to you, Henrick, for

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Speaker 1: doing some physics in your mind. Yeah, Daniel will be

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Speaker 1: sending you a check in the mill right now, right

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Speaker 1: after this podcast. I'm gonna email you some Swedish fish,

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Speaker 1: my favorite Swedish candy. All right. So then it's a

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Speaker 1: pretty interesting question. And Henrick was saying that he listened

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Speaker 1: to an episode that we had about whether or not

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Speaker 1: space is pixelated. So there's this idea that space could

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Speaker 1: be pixelated, meaning like it's not smooth and continuous, maybe

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Speaker 1: it's like a grid or something, or it's disc rate

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Speaker 1: at the very smallest level. And his question is whether

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Speaker 1: or not it applies to time as well. That's right,

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Speaker 1: because we often talk on the podcast about how space

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Speaker 1: and time are related, and then in relativity at least

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Speaker 1: we see them as parts of space time a four

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Speaker 1: dimensional object. So it's a very natural question. Yeah, and

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Speaker 1: so what did we conclude in that podcast episode about

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Speaker 1: space being pixelated? We concluded that we don't know, and

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Speaker 1: we might never know, but there are good reasons to

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Speaker 1: think that space might be pixelated, right, due to like

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Speaker 1: quantum physics and they're being like a theoretical plank scale

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Speaker 1: to the universe as well. Right, exactly, we don't know

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Speaker 1: how small the pixels of space are if they exist,

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Speaker 1: and we have a very simple, kind of bad estimate

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Speaker 1: for how small they might be, just by multiplying constants

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Speaker 1: of the universe together. And it's very very small number,

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Speaker 1: like ten to the minus thirty five meters. That's not

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Speaker 1: a measurement of how small the space pixels are or

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Speaker 1: proof that space pixels exist. But if you have no

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Speaker 1: other information about how to estimate it, this is all

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Speaker 1: you can do. It gives you a sense for like

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Speaker 1: what the neighborhood of the size might be, all right,

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Speaker 1: So then if you're curious, you can look up that

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Speaker 1: episode in our archive. But today we're talking about time

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Speaker 1: and whether it's pixelated, and so, as usually, we were

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Speaker 1: wondering how many people out there have thought about this

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Speaker 1: question or had had time to think about this question

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Speaker 1: at least a pixel of time and maybe had an

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Speaker 1: answer for it. So Daniel went out there into the

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Speaker 1: internet to ask listeners is time pixelated? And so if

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Speaker 1: you have time to donate your thoughts on random physics

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Speaker 1: questions for future podcast episodes. Please don't be shy, right

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Speaker 1: to me. Two questions at Daniel and Jorge dot com.

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

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Speaker 1: there is a minimum amount of time in the universe?

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Speaker 1: Here's what people had to say. I guess if you

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Speaker 1: zoomed in far enough, time might be pixelated, like if

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Speaker 1: you imagined it as a film strip, if you zoomed

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Speaker 1: in just millions and millions and millions of times, that

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Speaker 1: it would beam moving sort of in frames, as if

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Speaker 1: like a movie kind of thing. Tom, pixelation, haven't heard

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Speaker 1: of it? Um, tell me about it. Sounds crazy, Yes,

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Speaker 1: it's a usual thing. So do you think it's pixelated

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Speaker 1: or continuous? Okay, it's continuous? Okay? Wow? Man, I don't

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Speaker 1: even know how to wrap my head around this question.

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Speaker 1: Is time pixelated? What does that even mean? Is it

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Speaker 1: just like if a second is a pixel or even

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Speaker 1: nano second is a pixel. I have no idea how

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Speaker 1: to answer this question. I really don't know what that

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Speaker 1: question means. Maybe like, is is time quantized in some form? Honest?

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Speaker 1: I have no idea time. It's very strange. A lot

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Speaker 1: we don't know. I'm not sure. I think that there

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Speaker 1: are some theories that suggest it might be, but I

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Speaker 1: don't know that we've measured that definitively. My understanding of

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Speaker 1: the measuring of time is that it's not infinitely divisible,

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Speaker 1: that it is hypothesized that ultimately you'll get two units

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Speaker 1: of time that are so short you can't get any short.

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Speaker 1: And I think it's referred to as plunk time pixilated

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Speaker 1: like all the video games. I'm not sure about. The

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Speaker 1: term doesn't seem right. I'm probably not. I have no

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Speaker 1: idea from a physics standpoint, but from a perception standpoint,

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Speaker 1: I feel like it is um and I think deja

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Speaker 1: vu has something to do with that. It's like it

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Speaker 1: arrives into my brain in little packets and then my

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Speaker 1: brain goes and smooths it all out after the fact,

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Speaker 1: so that it in my memories it seems like it's

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Speaker 1: all smooth, and I can't actually sense what's going on

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Speaker 1: in real time. I have no idea what that means.

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Speaker 1: I guess not because I think it's continuous with the

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Speaker 1: way that Madam moves in space. All right. Not a

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Speaker 1: lot of ideas here. Maybe people didn't spend enough time

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Speaker 1: thinking about it. They only thought one or two units

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Speaker 1: of time on this and they should have at least

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Speaker 1: been ten or two. Yeah, it's a tough question. It

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Speaker 1: seems to have puzzled people. Most people just throw their

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Speaker 1: hands up in the air and said, I don't know. Yeah,

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Speaker 1: it seems a little bit more foreign to people than

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Speaker 1: the idea that space is pixelated, like you're familiar with

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Speaker 1: looking at a screen, the idea of locations being a

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Speaker 1: grid that makes some sense. But the idea of time

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Speaker 1: being pixelated, that you know that there are discrete units

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Speaker 1: of time as we move forward, that we're stepping forward

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Speaker 1: instead of sliding forward, that seems to be a little

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Speaker 1: bit more alien. Yeah, so let's maybe tackle this one

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Speaker 1: kind of idea at a time. So, first of all,

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Speaker 1: what would it mean for time to be pixelated? Would

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Speaker 1: it mean like you can cut up time or you

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Speaker 1: can step through time in small increments, but at some

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Speaker 1: point there comes a point where you can take smaller

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Speaker 1: steps in time. There's sort of two very different but

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Speaker 1: closely related ways for time to be discreet, for there

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Speaker 1: to be like a minimal, sensible unit of time. The

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Speaker 1: first is what you were just talking about. This idea

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Speaker 1: of pixelization, and pixelization is something we think about for space, right,

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Speaker 1: like pixels on the screen. You can either be at

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Speaker 1: x equals seven or x equals eight, but you can't

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Speaker 1: be at x equals seven and a half. So that's

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Speaker 1: very natural sense for space and for time. The idea

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Speaker 1: would be that things step forwards in time, that you

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Speaker 1: could be like time equals one point seven or time

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Speaker 1: equals one point eight, but there is no time equals

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Speaker 1: one point seven and a half. That the universe just

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Speaker 1: goes from one point seven boom to one point eight.

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Speaker 1: It's like ticks on a clock, but there's no moment

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Speaker 1: in between the ticks, Like you can't have a half

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Speaker 1: of a second or something like that. Yeah, and you know,

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Speaker 1: obviously seconds aren't the minimum immunity of time. You can't

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Speaker 1: have half of a second. If time units exist, but

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Speaker 1: there's a minimum discrete chunk of time, it would be

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Speaker 1: super duper small. So that to us it seems continuous, right,

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Speaker 1: and you think it doesn't exist or like what happens

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Speaker 1: in between those two times? Yeah, well what does it

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Speaker 1: mean for the universe to be in between those times?

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Speaker 1: It's like it doesn't have a meaning, Like time is

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Speaker 1: here and time is there, but in between there isn't anything.

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Speaker 1: It just doesn't exist. This is something that's sort of

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Speaker 1: familiar to us from learning quantum mechanics, that not everything

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Speaker 1: has like a smooth classical path, you know, like an electron.

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Speaker 1: You measure it here and then you later you measure

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Speaker 1: it over there. Does that mean that it went from

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Speaker 1: here to there? No, it just means it was here

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Speaker 1: and then it was there. It doesn't have to have

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Speaker 1: a location in between. We think of everything as smooth

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Speaker 1: and continuous because that's the way it seems to us,

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Speaker 1: because we're kind of big and slow. But the universe,

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Speaker 1: as you were saying earlier, could be drastically different from

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Speaker 1: the way we experience it, all right, So that's one

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Speaker 1: possibility that time just doesn't exist in between time pixels,

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Speaker 1: like there's a grade of the time in the universe.

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Speaker 1: And that's actually something that makes sense to us sort

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Speaker 1: of numerically, like when we simulate things in the computer.

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Speaker 1: You want to describe, for example, how a hurricane moves

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Speaker 1: or how galaxies form, and we want to simulate them.

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Speaker 1: That's exactly how we do it. We make a grid

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Speaker 1: in time, and we step our simulated universe forward. We say,

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Speaker 1: something's happening right now, what's going to happen at the

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Speaker 1: next time step, and you can decide is it going

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Speaker 1: to be a nanosecond in the future or ten minutes

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Speaker 1: in the future. Depends on how much computing time you have.

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Speaker 1: But it's very natural to step things forward in time

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Speaker 1: in simulations, right, You do simulations with time steps. But

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Speaker 1: simulations are not perfect, right, and that that's one of

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Speaker 1: the main reasons is that they do have sort of

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Speaker 1: a resolution. It doesn't do it continuously like the universe

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Speaker 1: sort of seems to be. Yeah, exactly, they're not continuous,

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Speaker 1: they're discreet. And you're right that you want really small

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Speaker 1: time steps so that you're extrapolating in a reasonable way.

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Speaker 1: But it might be that the universe actually does have

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Speaker 1: the same sort of time steps, and if you did

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Speaker 1: your simulation with a time step equal to that of

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Speaker 1: the universe, then it would be perfect. But wow, that

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Speaker 1: would be weird, right, Like the universe would be operating

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Speaker 1: at the minimum possible time step because but the computer

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Speaker 1: is in the universe, so that would blows my mind

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Speaker 1: a little bit. But all right, So that's the first

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Speaker 1: kind of time pixelization. What's the second. The second is

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Speaker 1: that time isn't actually pixelized in the sense that you

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Speaker 1: could have any value of time. It's not like values

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Speaker 1: in between one point seven and one point eight are disallowed.

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Speaker 1: If you try to measure like when did something happen?

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Speaker 1: You could get any number between one point seven and

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Speaker 1: one point eight. All those values are real and possible.

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Speaker 1: In this idea, though, there's a minimum resolution, like you

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Speaker 1: can't measure differences in time that are smaller than a

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Speaker 1: certain number, Like if you measure something twice, you can't

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Speaker 1: get two measurements that are closer than a certain minimum distance,

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Speaker 1: but you can get any value. So it's sort of

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Speaker 1: like you have this minimum resolution, but it can slide

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Speaker 1: up and down the time scale where and land wherever. Okay,

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Speaker 1: I think I know what you're saying. You're saying that

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Speaker 1: maybe like every possible time step exists or is possible,

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Speaker 1: like you can have one point oh three seconds and

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Speaker 1: up one point two four seven seconds, but maybe at

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Speaker 1: some point, at some scale of smallness and time, it

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Speaker 1: just kind of becomes random or fuzzy or sort of unknowable. Yeah, exactly,

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Speaker 1: And we can think about that because we think about

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Speaker 1: quantum particles in exactly that way. Like an electron is quantized, right,

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Speaker 1: it's a single object quantized of the electron field. So

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Speaker 1: it's got a certain like natural width to it, below

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Speaker 1: which you can't really probe where its location is, but

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Speaker 1: it could be anywhere. It can live in continuous space.

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Speaker 1: If space is continuous, you can still have discrete objects

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Speaker 1: in side of it. And in that same way, time

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Speaker 1: might be like fundamentally continuous, but there might be a

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Speaker 1: minimum basic resolution of time below which the time difference

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Speaker 1: between two events has no meaning, no meaning, but it exists,

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Speaker 1: but it's sort of random. And because it's random, you're

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Speaker 1: saying it doesn't have any meaning. But is that really

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Speaker 1: pixelated though? Like it's so it doesn't fit our idea

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Speaker 1: of a pixel, right, It's more like there's no pixel,

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Speaker 1: but it's sort of fuzzy at a certain scale. Yeah, exactly.

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Speaker 1: It sets a scale which I think that the physicist

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Speaker 1: is interesting because it means that you can't infinitely divide time.

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Speaker 1: That was the other part of Hendrick's question, like can

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Speaker 1: you have infinitely small slices in time? Does it make

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Speaker 1: sense to think about things happening at one moment and

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Speaker 1: then tend to the minus one thousand seconds later, Like

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Speaker 1: does their universe really evolve things step by step at

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Speaker 1: that granularity. And what this would tell you is not

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Speaker 1: that things are locked into specific numbers, but that it

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Speaker 1: makes no sense to think about steps in time that

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Speaker 1: are that small. You can just make stuff u It's

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Speaker 1: unknown and it's undetermined, right in the same way that like,

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Speaker 1: not all the information about an electron is knowable, not

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Speaker 1: just because we can't measure it, but because it's not

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Speaker 1: specified as undetermined. In that same way, pieces of time

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Speaker 1: smaller than like whatever is the minimum resolution and time

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Speaker 1: are not known or knowable. All right, Well, those are

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Speaker 1: the two ways in which time could be pixelated, and

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Speaker 1: so let's get into why we think it might be

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Speaker 1: pixelated and whether or not we'll ever know if it

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Speaker 1: is or not. But first let's take a quick break.

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Speaker 1: All right, we're asking the question is time pixelated? And

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Speaker 1: so we had a whole episode about whether space was pixelated,

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Speaker 1: and we had all those reasons there. But now we're

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Speaker 1: asking if time is pixelated, And so the question is

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Speaker 1: why do we think time might be pixelated? It seems

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Speaker 1: pretty continuous and smooth to me. It does seem continuous

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Speaker 1: and smooth, but you know, our intuition breaks down when

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Speaker 1: we try to apply it to things that are much

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Speaker 1: much faster or much much smaller, and they reveal that

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Speaker 1: the rules of the universe are really pretty different. Of course,

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Speaker 1: when you zoom out to things like our skill, those

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Speaker 1: rules do sort of coalesce to recover our experience. So

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Speaker 1: it's amazing that you can have like one set of

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Speaker 1: rules for the very tiny particles and it can all

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Speaker 1: sort of work together to conspire to give a very

401
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Speaker 1: different kind of universe at the human scale. Right, So

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Speaker 1: then maybe step us through. What are some of the

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Speaker 1: arguments for saying that time is pixelated and what are

404
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Speaker 1: maybe some of the arguments against it being pixelated? Well,

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Speaker 1: I think there's a few elements here. One is, you know,

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Speaker 1: what is more natural? Like what do we expect to

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Speaker 1: be the truth? Like, is continuity of time really the

408
00:21:49,320 --> 00:21:52,920
Speaker 1: most natural thing? Or in the end, is discreete this

409
00:21:53,080 --> 00:21:55,960
Speaker 1: more natural? What would make more sense to us was

410
00:21:56,000 --> 00:21:58,520
Speaker 1: the sort of default position. And I think a lot

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Speaker 1: of people out there would assume, well, continuousness, right, like

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Speaker 1: time should flow smoothly. It seems to flow smoothly to me,

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Speaker 1: But you know that doesn't mean that that's the case.

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Speaker 1: You know, you watch TV and it seems to flow continuously,

415
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Speaker 1: but you know deep down that it is actually discreete.

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Speaker 1: Your television is not updating infinitely many times per second.

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Speaker 1: And that's the key, is that continuity, having continuous time,

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Speaker 1: implies a sort of infinity, and we just don't see

419
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Speaker 1: infinities in nature very often, right, Yeah, I guess like

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Speaker 1: if you showed it a four K, you know, high

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Speaker 1: resolution television to somebody from the you know, a tenth century,

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Speaker 1: they would probably be fooled into thinking like there's actually

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Speaker 1: something magical, real going on inside of it to be

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Speaker 1: but really it's you know, flashing, you know, twenty nine

425
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Speaker 1: times a second, and it's really only like two thousand

426
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Speaker 1: by two thousand pixels exactly. And continuity is really strange,

427
00:22:50,119 --> 00:22:53,760
Speaker 1: Like to imagine an infinite amount of information as the

428
00:22:53,840 --> 00:22:56,840
Speaker 1: universe evolves forwards, it's sort of like Zeno's paradox, Like

429
00:22:57,080 --> 00:22:59,440
Speaker 1: how do you even get from one second to two

430
00:22:59,480 --> 00:23:02,360
Speaker 1: seconds if you have to go through an infinite number

431
00:23:02,800 --> 00:23:05,679
Speaker 1: of sub seconds to get there? You know, it feels

432
00:23:05,680 --> 00:23:07,639
Speaker 1: like at some point you've got to take an actual

433
00:23:07,640 --> 00:23:10,840
Speaker 1: step forward, and to do that, you can imagine a

434
00:23:10,960 --> 00:23:13,840
Speaker 1: minimum unit of time where the universe is finally like

435
00:23:14,000 --> 00:23:17,000
Speaker 1: ticking over Otherwise, how does it even leave the one

436
00:23:17,119 --> 00:23:19,879
Speaker 1: second mark if it's always taking a smaller and smaller

437
00:23:19,960 --> 00:23:22,680
Speaker 1: and smaller and infinitely smaller step forwards. So you're saying

438
00:23:22,680 --> 00:23:25,479
Speaker 1: that a continuous universe sort of makes sense to us

439
00:23:25,480 --> 00:23:27,920
Speaker 1: from our experience, but it starts to break down when

440
00:23:27,920 --> 00:23:30,480
Speaker 1: you really drill into it, because you come up with infinities.

441
00:23:30,560 --> 00:23:33,080
Speaker 1: You do, you come up into infinities. And what we've

442
00:23:33,080 --> 00:23:35,719
Speaker 1: discovered is we look around us in the universe, is

443
00:23:35,720 --> 00:23:39,480
Speaker 1: that discreetness is actually much more natural. Like the things

444
00:23:39,480 --> 00:23:42,880
Speaker 1: that we see around us that seem continuous are actually discreet.

445
00:23:43,320 --> 00:23:45,800
Speaker 1: Like that chair you're sitting on right now. It seems

446
00:23:45,800 --> 00:23:48,280
Speaker 1: like it has a smooth surface, right, but it doesn't.

447
00:23:48,600 --> 00:23:51,719
Speaker 1: It's actually a lattice. A lattice is a network of

448
00:23:51,840 --> 00:23:56,159
Speaker 1: points that are tied together to approximate a smooth surface.

449
00:23:56,160 --> 00:23:58,000
Speaker 1: And if you zoom out, of course it looks smooth,

450
00:23:58,200 --> 00:24:00,439
Speaker 1: but if you zoom in far enough, it looks like

451
00:24:00,480 --> 00:24:02,919
Speaker 1: a chain link fence, you know, and a beam of

452
00:24:03,000 --> 00:24:06,800
Speaker 1: light that is shining on your plants, it's actually a

453
00:24:06,840 --> 00:24:09,879
Speaker 1: bunch of packets of photons. So the world around you,

454
00:24:09,920 --> 00:24:13,760
Speaker 1: though it seemed continuous, almost everything about it is actually discreet.

455
00:24:14,520 --> 00:24:17,680
Speaker 1: I see you're saying, because maybe the space and physical

456
00:24:17,720 --> 00:24:20,439
Speaker 1: things around this are sort of pixelated in a way

457
00:24:20,440 --> 00:24:23,199
Speaker 1: through discrete, then it would sort of make sense for

458
00:24:23,359 --> 00:24:25,639
Speaker 1: time to also be pixelated, exactly. And that's sort of

459
00:24:25,640 --> 00:24:28,520
Speaker 1: a natural intuitive argument, right, And it doesn't really hold

460
00:24:28,560 --> 00:24:30,760
Speaker 1: that much water. It's just sort of to get you

461
00:24:30,880 --> 00:24:33,560
Speaker 1: in the mindset of thinking, maybe discreete is the more

462
00:24:33,680 --> 00:24:36,639
Speaker 1: natural outcome instead of continuous. Right, then you need to

463
00:24:36,640 --> 00:24:40,200
Speaker 1: be persuaded against being discrete instead of being persuaded against

464
00:24:40,200 --> 00:24:42,480
Speaker 1: it being continuous. Right. But I guess the universe doesn't

465
00:24:42,480 --> 00:24:45,399
Speaker 1: care about what we think are our opinion of it.

466
00:24:45,880 --> 00:24:48,560
Speaker 1: So what are sibility I guess more of physically robust

467
00:24:48,680 --> 00:24:51,720
Speaker 1: arguments for or against time pixelation. Right. And so it

468
00:24:51,800 --> 00:24:54,760
Speaker 1: turns out that when you drill down into the very

469
00:24:54,800 --> 00:24:57,879
Speaker 1: small time and the very small space, what you do

470
00:24:57,960 --> 00:25:01,720
Speaker 1: is you run into questions about how gravity works. You know,

471
00:25:01,760 --> 00:25:04,280
Speaker 1: in very very small spaces. Now you have things like

472
00:25:04,320 --> 00:25:06,679
Speaker 1: particles moving around, and you get into questions of like

473
00:25:07,040 --> 00:25:10,199
Speaker 1: what are the forces between those particles? And if you

474
00:25:10,200 --> 00:25:12,480
Speaker 1: have very very short time, then you're talking about very

475
00:25:12,560 --> 00:25:15,879
Speaker 1: very high energy gravity kicks in and in the end

476
00:25:15,920 --> 00:25:19,240
Speaker 1: you need to know something about how quantum gravity works,

477
00:25:19,280 --> 00:25:22,960
Speaker 1: like what are the gravitational effects for very high energies

478
00:25:23,000 --> 00:25:26,560
Speaker 1: and very short distances, And people who are working on

479
00:25:26,720 --> 00:25:29,679
Speaker 1: quantum gravity these theories of like, you know, what is

480
00:25:29,720 --> 00:25:32,760
Speaker 1: the fundamental nature of space? Is it sliced up into

481
00:25:32,760 --> 00:25:35,720
Speaker 1: pieces or not? Are there gravitons? All these fun questions.

482
00:25:35,880 --> 00:25:38,600
Speaker 1: They make a lot of arguments about space being discreete

483
00:25:38,880 --> 00:25:40,679
Speaker 1: and we can dig into those in a minute. And

484
00:25:40,760 --> 00:25:44,840
Speaker 1: almost all of those arguments also apply to time because

485
00:25:44,880 --> 00:25:48,520
Speaker 1: space and time are very closely related. So the physical

486
00:25:48,600 --> 00:25:51,199
Speaker 1: arguments that there might be a minimum unity to space,

487
00:25:51,280 --> 00:25:54,320
Speaker 1: a lot of those same arguments you can use to

488
00:25:54,400 --> 00:25:58,639
Speaker 1: make minimum unit of time. Yeah, because I guess in

489
00:25:58,680 --> 00:26:01,919
Speaker 1: physics there is this idea that time is just another

490
00:26:02,040 --> 00:26:05,359
Speaker 1: dimension maybe or it's like you know the fourth leg

491
00:26:05,440 --> 00:26:08,040
Speaker 1: and the table that is space time, and that it's

492
00:26:08,160 --> 00:26:10,960
Speaker 1: somehow like the same thing, right, you sort of think

493
00:26:10,960 --> 00:26:13,680
Speaker 1: about it that way in physics. Yeah, and it's even

494
00:26:13,720 --> 00:26:15,840
Speaker 1: more closely connected. Let me give you an example. You

495
00:26:15,880 --> 00:26:18,639
Speaker 1: can make a pretty simple argument that there should be

496
00:26:18,680 --> 00:26:21,040
Speaker 1: a minimum unit of space, and then you can take

497
00:26:21,080 --> 00:26:23,359
Speaker 1: the same argument and use it for time. So it

498
00:26:23,359 --> 00:26:26,520
Speaker 1: goes like this. You say, let's, for example, try to

499
00:26:26,560 --> 00:26:28,879
Speaker 1: measure a particle. What happens if you try to measure

500
00:26:28,880 --> 00:26:32,480
Speaker 1: a particle really really precisely, so you know it's position,

501
00:26:32,560 --> 00:26:36,000
Speaker 1: like basically exactly well. Quantum mechanics says, if you know

502
00:26:36,119 --> 00:26:39,240
Speaker 1: something's position really really well, then you don't know it's

503
00:26:39,320 --> 00:26:42,760
Speaker 1: momentum very very well. Right that the more precisely you

504
00:26:42,800 --> 00:26:45,600
Speaker 1: measure the position, the less you know about the momentum.

505
00:26:45,720 --> 00:26:48,880
Speaker 1: That means that this particle now has a huge uncertainty

506
00:26:48,960 --> 00:26:52,400
Speaker 1: on its momentum, so much so that it might have

507
00:26:52,560 --> 00:26:56,240
Speaker 1: enough momentum basically enough energy to create a black hole.

508
00:26:57,040 --> 00:26:59,240
Speaker 1: And once you create a black hole, well, then you

509
00:26:59,280 --> 00:27:01,960
Speaker 1: can no longer measure something about this particle because it's

510
00:27:01,960 --> 00:27:05,480
Speaker 1: inside a black hole. So, like, these very simple arguments

511
00:27:05,480 --> 00:27:09,240
Speaker 1: suggest that there's a minimum distance below which you can't

512
00:27:09,320 --> 00:27:11,640
Speaker 1: measure something because if you did, it would turn into

513
00:27:11,640 --> 00:27:14,520
Speaker 1: a black hole and prevent you from measuring it. So

514
00:27:14,600 --> 00:27:16,879
Speaker 1: that's the argument about space, And you can make a

515
00:27:16,960 --> 00:27:20,040
Speaker 1: very similar argument about time. WHOA, you just kind of

516
00:27:22,320 --> 00:27:24,760
Speaker 1: skipped through a few time steps there. You're saying the argument,

517
00:27:24,880 --> 00:27:28,439
Speaker 1: like one argument for space being pixelated is that you know,

518
00:27:28,640 --> 00:27:30,760
Speaker 1: if you don't have a pixel to the universe. Then

519
00:27:30,880 --> 00:27:34,239
Speaker 1: basically kind of like um, things can be anything at

520
00:27:34,240 --> 00:27:36,159
Speaker 1: a certain level, and one of those things could be

521
00:27:36,200 --> 00:27:38,600
Speaker 1: a black hole, and that's that's impossible or is that's

522
00:27:38,640 --> 00:27:40,560
Speaker 1: weird or are you saying that we don't see that.

523
00:27:40,800 --> 00:27:43,640
Speaker 1: I'm saying that the universe has a mechanism to prevent

524
00:27:43,720 --> 00:27:47,040
Speaker 1: you from knowing something very precisely, because if you knew

525
00:27:47,040 --> 00:27:49,600
Speaker 1: it that precisely, it would turn into a black hole,

526
00:27:49,800 --> 00:27:52,240
Speaker 1: and then censored that information. So it's sort of like

527
00:27:52,240 --> 00:27:55,880
Speaker 1: a fundamental limit there, because if you ask questions deeply enough,

528
00:27:56,040 --> 00:27:59,280
Speaker 1: basically the universe responds by covering things up with black holes.

529
00:27:59,520 --> 00:28:02,399
Speaker 1: And we don't see that, thankfully, which means that the

530
00:28:02,480 --> 00:28:06,199
Speaker 1: universe does have sort of like a fundamental maybe a

531
00:28:06,359 --> 00:28:09,520
Speaker 1: pixelation of space. Yeah, although we can't really do this experiment,

532
00:28:09,600 --> 00:28:12,000
Speaker 1: like how could you measure a particle with such precision

533
00:28:12,520 --> 00:28:14,840
Speaker 1: that it's momentum would be so uncertain that it might

534
00:28:14,840 --> 00:28:17,480
Speaker 1: turn into like a microscopic black hole. So that's not

535
00:28:17,520 --> 00:28:19,159
Speaker 1: an experiment we could do. We'd love to do that

536
00:28:19,240 --> 00:28:22,800
Speaker 1: experiment and observe microscopic quantum black holes. Wow, we would

537
00:28:22,880 --> 00:28:24,800
Speaker 1: learn so much. It's just really sort of a thought

538
00:28:24,880 --> 00:28:28,840
Speaker 1: experiment that demonstrates how if you ask precise enough a question,

539
00:28:28,960 --> 00:28:31,200
Speaker 1: the universe sort of counters with a black hole to

540
00:28:31,240 --> 00:28:32,960
Speaker 1: prevent you from learning about it. But how do you

541
00:28:33,000 --> 00:28:34,840
Speaker 1: know those black holes aren't there? Maybe they are there,

542
00:28:34,840 --> 00:28:36,960
Speaker 1: but they're so small you can't see them. Yeah, maybe

543
00:28:37,000 --> 00:28:39,720
Speaker 1: they are there, but it still means that you can't

544
00:28:39,840 --> 00:28:43,160
Speaker 1: know the position of this particle to a certain resolution

545
00:28:43,520 --> 00:28:45,880
Speaker 1: because it turns into a black hole, and you can't

546
00:28:45,880 --> 00:28:48,280
Speaker 1: measure what's inside a black hole. Okay, so that's an

547
00:28:48,320 --> 00:28:50,720
Speaker 1: argument for space being pixelated. So then how do you

548
00:28:50,760 --> 00:28:54,040
Speaker 1: translate that into time? Well, the relationship and quantum mechanics

549
00:28:54,080 --> 00:28:58,600
Speaker 1: between position and momentum, there's exactly the same relationship between

550
00:28:58,720 --> 00:29:00,760
Speaker 1: energy and time. And if you want to make a

551
00:29:00,800 --> 00:29:03,560
Speaker 1: bunch of measurements of a particle at very very small

552
00:29:03,600 --> 00:29:06,240
Speaker 1: time steps like now, and then tend to the mind

553
00:29:06,360 --> 00:29:10,200
Speaker 1: is one hundred seconds later, that introduces uncertainty in the

554
00:29:10,240 --> 00:29:14,240
Speaker 1: particle's energy. So time and energy have the same relationship

555
00:29:14,280 --> 00:29:17,480
Speaker 1: and quantum mechanics as position and momentum. It's another of

556
00:29:17,520 --> 00:29:20,600
Speaker 1: the Heisenberg and certainty principles. And so if you measure

557
00:29:20,600 --> 00:29:23,920
Speaker 1: a particle trajectory in time very very precisely. Then you

558
00:29:24,040 --> 00:29:27,200
Speaker 1: create the same uncertainty in its energy, which allows it

559
00:29:27,240 --> 00:29:29,640
Speaker 1: to potentially have enough energy to create a black hole,

560
00:29:29,720 --> 00:29:34,480
Speaker 1: and boom, cosmic censorship rises again. I see, But isn't

561
00:29:34,520 --> 00:29:37,840
Speaker 1: it maybe even the same argument, right, because I feel

562
00:29:37,880 --> 00:29:40,600
Speaker 1: like momentum is sort of related to velocity and velocities

563
00:29:40,640 --> 00:29:43,400
Speaker 1: like distance divided by time, So it really aren't you

564
00:29:43,440 --> 00:29:46,840
Speaker 1: just making the same argument twice, except that you know

565
00:29:46,880 --> 00:29:50,040
Speaker 1: you're using the fact that time and space and velocity

566
00:29:50,040 --> 00:29:53,960
Speaker 1: are related to each other to carry over the argument, right, Like,

567
00:29:54,040 --> 00:29:58,280
Speaker 1: couldn't maybe space be pixelated but time not pixelated. But

568
00:29:58,360 --> 00:30:02,479
Speaker 1: because they're related when you're trying to measure velocities, then

569
00:30:02,840 --> 00:30:06,280
Speaker 1: it implies that time is pixelated. That's exactly the argument. Yeah,

570
00:30:06,560 --> 00:30:09,120
Speaker 1: it says that space and time are very closely connected,

571
00:30:09,360 --> 00:30:12,280
Speaker 1: and therefore an argument you can use to pixelate space

572
00:30:12,360 --> 00:30:15,400
Speaker 1: is going to also give you pixelization of time. Right,

573
00:30:15,400 --> 00:30:18,680
Speaker 1: But maybe time is fundamentally not pixelated. It just appears

574
00:30:18,920 --> 00:30:23,640
Speaker 1: pixelated because spaces or maybe space is not fundamentally pixelated,

575
00:30:23,680 --> 00:30:26,760
Speaker 1: but time is. Right, Yeah, that's what I mean. I

576
00:30:26,800 --> 00:30:28,520
Speaker 1: feel like, Yeah, I feel like that's not really an

577
00:30:28,600 --> 00:30:31,680
Speaker 1: argument four time being pixelated, right, I see that's interesting.

578
00:30:31,720 --> 00:30:34,680
Speaker 1: That's a philosophical question. I think that it shows you

579
00:30:34,760 --> 00:30:37,760
Speaker 1: that the two things have the same relationship, so it

580
00:30:37,760 --> 00:30:39,800
Speaker 1: makes the most ends for them to both be pixelated

581
00:30:40,160 --> 00:30:42,960
Speaker 1: or not. In this case, quantum mechanics suggests that they

582
00:30:43,040 --> 00:30:45,920
Speaker 1: both are. But I see that other interpretation. Yeah, all right,

583
00:30:45,960 --> 00:30:49,000
Speaker 1: So there is an argument for time being pixelated, and

584
00:30:49,080 --> 00:30:52,360
Speaker 1: it has to do with quantum mechanics, and so that

585
00:30:52,560 --> 00:30:54,880
Speaker 1: sort of the uncertainty principle. So then, but do you

586
00:30:54,880 --> 00:30:56,920
Speaker 1: have then have a reason of why space and time

587
00:30:56,960 --> 00:30:59,240
Speaker 1: are pixelated like that? And it all comes down to

588
00:31:00,040 --> 00:31:02,640
Speaker 1: what happens at these very very small distance scales when

589
00:31:02,640 --> 00:31:04,920
Speaker 1: you have a lot of energy, and this is the

590
00:31:04,960 --> 00:31:08,320
Speaker 1: province of quantum gravity. And unfortunately, we don't have a

591
00:31:08,360 --> 00:31:10,920
Speaker 1: strong theory of quantum gravity, Like we don't have a

592
00:31:11,000 --> 00:31:15,680
Speaker 1: theory that works that describes what happens when gravity comes

593
00:31:15,680 --> 00:31:19,120
Speaker 1: into play with quantum objects and that gravity is strong.

594
00:31:19,400 --> 00:31:21,320
Speaker 1: If we did, then it would lay out for us

595
00:31:21,520 --> 00:31:23,400
Speaker 1: what is the minimum unit of time, what is the

596
00:31:23,400 --> 00:31:26,280
Speaker 1: minimum unity of space if there is one at all,

597
00:31:26,840 --> 00:31:30,160
Speaker 1: And the different flavors of quantum gravity that we're considering,

598
00:31:30,200 --> 00:31:32,800
Speaker 1: the different ideas people are working on for what's going

599
00:31:32,800 --> 00:31:35,360
Speaker 1: on at the very smallest scale and how this all works.

600
00:31:35,640 --> 00:31:39,160
Speaker 1: Have sort of different approaches to dealing with minimum distance

601
00:31:39,240 --> 00:31:42,960
Speaker 1: and minimum time. But I guess, couldn't you take the

602
00:31:43,000 --> 00:31:47,400
Speaker 1: sort of theoretical size of the space pixel and then

603
00:31:47,400 --> 00:31:50,320
Speaker 1: convert that to a time pixel because you're saying they're

604
00:31:50,360 --> 00:31:53,680
Speaker 1: sort of related or tied together. Yes, exactly, and that's

605
00:31:53,720 --> 00:31:57,040
Speaker 1: what's done, for example, in loop quantum gravity. Loop quantum

606
00:31:57,080 --> 00:32:01,360
Speaker 1: gravity says maybe the universe is not continuous in space.

607
00:32:01,440 --> 00:32:04,760
Speaker 1: It quantizes space itself, right, instead of trying to quantize

608
00:32:04,800 --> 00:32:08,320
Speaker 1: gravity is a maybe gravity is a quantum theory and

609
00:32:08,360 --> 00:32:12,720
Speaker 1: you're exchanging gravitons. It says, takes space itself and imagine

610
00:32:12,720 --> 00:32:15,440
Speaker 1: it not to be smooth and continuous, but like a

611
00:32:15,480 --> 00:32:17,840
Speaker 1: big foam, like a bunch of tiny little bubbles that

612
00:32:17,880 --> 00:32:21,040
Speaker 1: are all linked together as these loops. And so it's

613
00:32:21,120 --> 00:32:23,760
Speaker 1: very natural to think about space as having a minimum

614
00:32:23,760 --> 00:32:27,360
Speaker 1: distance in loop quantum gravity. It's actually essential because in

615
00:32:27,400 --> 00:32:31,160
Speaker 1: loop quantum gravity, if space has no minimum distance, then

616
00:32:31,200 --> 00:32:34,160
Speaker 1: a bunch of the calculations they do give nonsense results.

617
00:32:34,160 --> 00:32:36,840
Speaker 1: You get like infinities and craziness. So it sort of

618
00:32:36,880 --> 00:32:40,320
Speaker 1: saves the whole theory to have these minimum values, so

619
00:32:40,360 --> 00:32:43,360
Speaker 1: they rely on that, and the same arguments can be

620
00:32:43,440 --> 00:32:46,960
Speaker 1: used in loop quantum gravity to argue for minimum steps

621
00:32:46,960 --> 00:32:50,680
Speaker 1: in time, so like maybe space is pixelated or foamy,

622
00:32:50,800 --> 00:32:53,200
Speaker 1: but gravity is maybe continuous. But this would sort of

623
00:32:53,480 --> 00:32:57,360
Speaker 1: merge quantum mechanics and relativity together exactly. And I actually

624
00:32:57,360 --> 00:33:00,360
Speaker 1: asked Carlo Ravelli about this yesterday. He's an expert in

625
00:33:00,440 --> 00:33:03,160
Speaker 1: loop quantum gravity, and I asked him if in looke

626
00:33:03,200 --> 00:33:07,400
Speaker 1: quantum gravity you could have a theory that is patilated

627
00:33:07,440 --> 00:33:11,520
Speaker 1: in space but continuous in time, or if you absolutely

628
00:33:11,600 --> 00:33:15,400
Speaker 1: had to have discrete time as well, And he said

629
00:33:15,840 --> 00:33:18,200
Speaker 1: that he thinks that the theory is on solid footing

630
00:33:18,640 --> 00:33:21,720
Speaker 1: from the point of view of space pixels that you

631
00:33:21,720 --> 00:33:25,280
Speaker 1: can represent areas having discrete units. So that's very solid

632
00:33:25,280 --> 00:33:27,040
Speaker 1: and very confident about that. And he says that you

633
00:33:27,080 --> 00:33:29,880
Speaker 1: can do something similar with time, but there are some

634
00:33:29,960 --> 00:33:32,480
Speaker 1: complicated jumps you have to make in the argument, and

635
00:33:32,520 --> 00:33:36,880
Speaker 1: he wasn't a confident in it. But he also said

636
00:33:36,920 --> 00:33:40,560
Speaker 1: that he would be very surprised if anything that included

637
00:33:40,640 --> 00:33:42,840
Speaker 1: time and it's a measurement could really have a continuous

638
00:33:42,840 --> 00:33:45,800
Speaker 1: spectrum because from his point of view, the world is quantum,

639
00:33:46,360 --> 00:33:49,240
Speaker 1: everything about the universe is discrete, and then he would

640
00:33:49,240 --> 00:33:51,520
Speaker 1: be very surprised if time was any different. It seems

641
00:33:51,560 --> 00:33:56,440
Speaker 1: like the theorists don't think time is continues, that it's

642
00:33:56,640 --> 00:33:59,400
Speaker 1: maybe more likely or would make more sense, that it's

643
00:33:59,440 --> 00:34:02,480
Speaker 1: pixelated exactly in loop quantum gravity, it makes most sense

644
00:34:02,560 --> 00:34:05,560
Speaker 1: for time to be pixelated in the same way that

645
00:34:05,680 --> 00:34:09,120
Speaker 1: space is. Now there are other theories of quantum gravity,

646
00:34:09,239 --> 00:34:12,799
Speaker 1: theories like string theory, that have a different approach on

647
00:34:12,960 --> 00:34:16,200
Speaker 1: minimum units of time. Well, I guess maybe the question

648
00:34:16,440 --> 00:34:18,400
Speaker 1: that a lot of people might be thinking at this

649
00:34:18,440 --> 00:34:20,319
Speaker 1: point is that would it makes sense for time to

650
00:34:20,320 --> 00:34:23,719
Speaker 1: be pixelated or could it still be continuous? And one hand,

651
00:34:23,719 --> 00:34:26,960
Speaker 1: it makes perfect sense for time to be chopped up

652
00:34:26,960 --> 00:34:30,000
Speaker 1: in the minimum units, because, as we say, quantum mechanics

653
00:34:30,000 --> 00:34:33,000
Speaker 1: tells us that the universe is discrete, right, But there's

654
00:34:33,040 --> 00:34:36,000
Speaker 1: a problem when you do that. Introducing like a minimum

655
00:34:36,040 --> 00:34:40,040
Speaker 1: time scale or a minimum length scale is tricky because

656
00:34:40,080 --> 00:34:43,800
Speaker 1: we know from the other great theory of the universe relativity,

657
00:34:44,080 --> 00:34:48,200
Speaker 1: that things like distances and times are not universal. So like,

658
00:34:48,280 --> 00:34:51,120
Speaker 1: for example, if we're in the laboratory and we're measuring

659
00:34:51,360 --> 00:34:54,640
Speaker 1: the universe down to its minimum distance. We have some

660
00:34:54,719 --> 00:34:57,160
Speaker 1: pair of tweezers that can work at the plank length.

661
00:34:57,239 --> 00:35:00,120
Speaker 1: For example, what happens if somebody is zooming by the

662
00:35:00,160 --> 00:35:03,440
Speaker 1: spaceship and they're watching our experiment, They see us like

663
00:35:03,640 --> 00:35:07,600
Speaker 1: length contracted. They see everything shortened because they're moving at

664
00:35:07,600 --> 00:35:10,160
Speaker 1: a fast speed relative to us. So then they would

665
00:35:10,200 --> 00:35:13,719
Speaker 1: be seeing things at smaller than the minimum distance. So like,

666
00:35:13,840 --> 00:35:17,759
Speaker 1: having a minimum distance breaks special relativity in a really

667
00:35:17,840 --> 00:35:20,960
Speaker 1: important way. Right, what do you mean It doesn't break

668
00:35:21,000 --> 00:35:24,040
Speaker 1: relativity in a way. It just means that it's it's

669
00:35:24,080 --> 00:35:26,719
Speaker 1: all sort of relative. Right, Like to someone moving at

670
00:35:26,760 --> 00:35:29,399
Speaker 1: a certain speed, the minimum distance in the universe would

671
00:35:29,400 --> 00:35:32,200
Speaker 1: be this much, and to someone not moving at that speed,

672
00:35:32,200 --> 00:35:33,719
Speaker 1: it would be this much, but it would still have

673
00:35:33,800 --> 00:35:36,799
Speaker 1: a minimum distance. Yeah, if you assert the primacy of relativity,

674
00:35:37,160 --> 00:35:39,759
Speaker 1: then you're giving up an absolute minimum distance. You're saying

675
00:35:39,800 --> 00:35:42,560
Speaker 1: minimum distance is not really minimum, it's relative. But if

676
00:35:42,560 --> 00:35:44,439
Speaker 1: you start from the other direction, you say, no, there's

677
00:35:44,440 --> 00:35:48,080
Speaker 1: an absolute minimum distance anybody can measure, no matter how

678
00:35:48,120 --> 00:35:50,959
Speaker 1: their speed. Then that would break relativity. If you can't

679
00:35:51,000 --> 00:35:53,239
Speaker 1: have the two things at the same time, you can

680
00:35:53,280 --> 00:35:55,960
Speaker 1: have one, but then it breaks the other one. So

681
00:35:55,960 --> 00:36:00,000
Speaker 1: you're saying that a pixelated universe, even a space pixelated universe,

682
00:36:00,080 --> 00:36:04,040
Speaker 1: would break relativity or it's not consistent with relativity exactly.

683
00:36:04,040 --> 00:36:07,680
Speaker 1: It's inconsistent with special relativity, which we thought until now

684
00:36:07,960 --> 00:36:10,719
Speaker 1: was like pretty well established, Like we have measured it

685
00:36:10,719 --> 00:36:13,359
Speaker 1: out the wazoo and it works pretty well. But you know,

686
00:36:13,640 --> 00:36:16,719
Speaker 1: these directions in quantum gravity really do suggest that there

687
00:36:16,800 --> 00:36:21,400
Speaker 1: might be space pixels. But that's fundamentally inconsistent with special relativity.

688
00:36:21,680 --> 00:36:23,959
Speaker 1: So that's a big puzzle to work out. I see,

689
00:36:23,960 --> 00:36:27,960
Speaker 1: safe relativity is true, as Einstein said, then the universe

690
00:36:28,080 --> 00:36:30,200
Speaker 1: is not pixelated, or it can't be pixelated, or it

691
00:36:30,200 --> 00:36:32,319
Speaker 1: doesn't make sense for it to be pixelated. Yeah, and

692
00:36:32,360 --> 00:36:35,600
Speaker 1: you know we're focusing today on pixels in time. There's

693
00:36:35,600 --> 00:36:38,879
Speaker 1: another consequence of having pixels in time. You know, if

694
00:36:38,920 --> 00:36:42,600
Speaker 1: the universe is not continuous, if it's discreet, right, if

695
00:36:42,640 --> 00:36:44,880
Speaker 1: you can have like time equals one point five seconds

696
00:36:45,080 --> 00:36:47,480
Speaker 1: and one point six seconds but not time equals one

697
00:36:47,480 --> 00:36:50,120
Speaker 1: point five five seconds, that means the time is not

698
00:36:50,239 --> 00:36:53,239
Speaker 1: smooth and the universe sort of cares what time you're

699
00:36:53,280 --> 00:36:56,240
Speaker 1: at that you can't like do the same experiment halfway

700
00:36:56,280 --> 00:36:59,759
Speaker 1: between time pixels, and that actually has a really important consequence.

701
00:37:00,000 --> 00:37:02,480
Speaker 1: As we've talked about once on the podcast before. This

702
00:37:02,640 --> 00:37:06,319
Speaker 1: basic concept that energy in the universe is conserved that

703
00:37:06,440 --> 00:37:09,920
Speaker 1: relies on an assumption, and that assumption is that space

704
00:37:09,960 --> 00:37:13,239
Speaker 1: has a symmetry in time, that space always looks the same,

705
00:37:13,280 --> 00:37:16,440
Speaker 1: that the universe doesn't care when you do an experiment.

706
00:37:16,840 --> 00:37:20,480
Speaker 1: It's just could happen now or later or yesterday. You know,

707
00:37:20,560 --> 00:37:23,640
Speaker 1: it doesn't care about your deadlines. And discrete time breaks

708
00:37:23,680 --> 00:37:26,719
Speaker 1: that it says there are special values of time that

709
00:37:26,760 --> 00:37:29,840
Speaker 1: makes sense, and so that would throw conservation of energy

710
00:37:29,920 --> 00:37:33,400
Speaker 1: out the window. So if you have discrete units of time,

711
00:37:33,480 --> 00:37:37,200
Speaker 1: then basically you break conservation of energy. That seems like

712
00:37:37,200 --> 00:37:39,840
Speaker 1: an important rule in the universe. Yeah, so we're breaking

713
00:37:39,840 --> 00:37:42,160
Speaker 1: all the rules today. All right, Well, I guess what

714
00:37:42,200 --> 00:37:45,200
Speaker 1: I'm getting is that it makes sense for time to

715
00:37:45,239 --> 00:37:48,960
Speaker 1: be pixelated by some arguments like loop quantum theory and

716
00:37:49,080 --> 00:37:51,759
Speaker 1: thinking about space being pixelated, but it doesn't make any

717
00:37:51,760 --> 00:37:54,000
Speaker 1: sense for it to be pixelated from other points of

718
00:37:54,040 --> 00:37:57,400
Speaker 1: view like relativity or conservation of energy. All right, well,

719
00:37:57,480 --> 00:37:59,800
Speaker 1: let's get into our last question, which is how would

720
00:37:59,800 --> 00:38:03,120
Speaker 1: we even know if time is pixelated. Could we device

721
00:38:03,160 --> 00:38:05,520
Speaker 1: an experiment to tell us whether or not it's true

722
00:38:05,760 --> 00:38:08,399
Speaker 1: or whether it will be a mystery until the end

723
00:38:08,520 --> 00:38:23,799
Speaker 1: of time? But first, let's take another quick break. All right,

724
00:38:24,080 --> 00:38:27,080
Speaker 1: is time pixelated? I guess Daniel, The biggest question is

725
00:38:27,880 --> 00:38:30,239
Speaker 1: how would we know? Like, are we trapped in the

726
00:38:30,280 --> 00:38:33,719
Speaker 1: matrix and we think times smooth and continuous, and are

727
00:38:33,719 --> 00:38:36,120
Speaker 1: we always gonna be trapped in this matrix thinking that

728
00:38:36,160 --> 00:38:38,360
Speaker 1: it's continuous or will we ever be able to step

729
00:38:38,400 --> 00:38:42,840
Speaker 1: outside of time and see that it's actually you know, discrete. Unfortunately,

730
00:38:42,840 --> 00:38:45,879
Speaker 1: we might never know. You know, it might be that

731
00:38:46,000 --> 00:38:49,319
Speaker 1: time is continuous and we are hunting forever for the

732
00:38:49,360 --> 00:38:52,640
Speaker 1: minimum unit and not finding it, but not finding it

733
00:38:52,680 --> 00:38:55,200
Speaker 1: doesn't mean it doesn't exist. So there's a possibility that

734
00:38:55,239 --> 00:38:58,319
Speaker 1: we could always be frustrated, sort of like you know,

735
00:38:58,440 --> 00:39:01,399
Speaker 1: finding the smallest particle. You never really know if it's

736
00:39:01,400 --> 00:39:04,840
Speaker 1: the smallest particle or if there's a smaller particle inside

737
00:39:04,840 --> 00:39:07,160
Speaker 1: that that's so small you can't see it. But that

738
00:39:07,160 --> 00:39:10,520
Speaker 1: would be sort of a limitation of our technology, right

739
00:39:10,800 --> 00:39:13,360
Speaker 1: or is that always gonna be true because you know,

740
00:39:13,440 --> 00:39:16,239
Speaker 1: you're sort of like you can't prove a negative kind

741
00:39:16,239 --> 00:39:19,520
Speaker 1: of or you know, since infinity is forever, there's no

742
00:39:19,560 --> 00:39:22,000
Speaker 1: way we can never get down to the small enough

743
00:39:22,080 --> 00:39:24,279
Speaker 1: level to be sure that it's not pixelated. You know,

744
00:39:24,320 --> 00:39:26,600
Speaker 1: I think there are ways that we could like convince

745
00:39:26,680 --> 00:39:30,160
Speaker 1: ourselves that it probably is pixelated, but it'd be pretty

746
00:39:30,160 --> 00:39:33,239
Speaker 1: hard to prove that it's not, you know, pretty hard

747
00:39:33,239 --> 00:39:36,319
Speaker 1: to prove that it's infinitely continuous. I think you need

748
00:39:36,360 --> 00:39:39,520
Speaker 1: some pretty elaborate theory of physics that requires that that

749
00:39:39,560 --> 00:39:42,320
Speaker 1: has some other consequences somehow that I can't even imagine

750
00:39:42,520 --> 00:39:44,760
Speaker 1: that you could then confirm. So I think it's easier

751
00:39:44,800 --> 00:39:47,560
Speaker 1: to prove that it is discrete than to prove that

752
00:39:47,600 --> 00:39:50,120
Speaker 1: it's continuous. But you just gave me some arguments for

753
00:39:50,160 --> 00:39:53,480
Speaker 1: why space might be pixelated, right with the whole infinitely

754
00:39:53,560 --> 00:39:55,560
Speaker 1: small black holes. Couldn't we come up with a theory

755
00:39:55,680 --> 00:39:58,640
Speaker 1: or some sort of way or some sort of consequence

756
00:39:58,640 --> 00:40:00,960
Speaker 1: over the theory of the equation to say that, look it,

757
00:40:01,160 --> 00:40:03,640
Speaker 1: time has to be pixelated. Yeah, exactly. I think that's

758
00:40:03,680 --> 00:40:06,399
Speaker 1: the best way forward. If we come up with a

759
00:40:06,480 --> 00:40:10,279
Speaker 1: rigorous theory of quantum gravity and it requires, because of

760
00:40:10,280 --> 00:40:13,239
Speaker 1: its very nature, you know, for time to be pixelated,

761
00:40:13,640 --> 00:40:15,719
Speaker 1: and then that theory holds together and makes a bunch

762
00:40:15,760 --> 00:40:18,680
Speaker 1: of predictions. You know, maybe not directly showing us the

763
00:40:18,760 --> 00:40:23,239
Speaker 1: clock ticks of the universe, but having other consequences of

764
00:40:23,320 --> 00:40:26,400
Speaker 1: that it's inherent nature. Then we can be pretty confident

765
00:40:26,760 --> 00:40:29,320
Speaker 1: that the universe is pixelated when it comes to time.

766
00:40:29,480 --> 00:40:32,200
Speaker 1: All right, Well, then how could we hope to prove

767
00:40:32,239 --> 00:40:34,520
Speaker 1: that it is pixelated? Then? What kinds of experiments can

768
00:40:34,560 --> 00:40:37,560
Speaker 1: we make or what experiments have been made so so far?

769
00:40:37,800 --> 00:40:42,040
Speaker 1: The edge of our knowledge is basically particle colliders. Particle

770
00:40:42,080 --> 00:40:46,239
Speaker 1: colliders smash particles together at very very high energy, which

771
00:40:46,280 --> 00:40:48,279
Speaker 1: is the same thing as saying that they're studying things

772
00:40:48,280 --> 00:40:52,080
Speaker 1: at very very small distance scales. Remember that the energy

773
00:40:52,239 --> 00:40:56,120
Speaker 1: of an object controls its effective wave function right at

774
00:40:56,120 --> 00:40:58,640
Speaker 1: the width of its wave function, and really really high

775
00:40:58,840 --> 00:41:02,399
Speaker 1: energy object is one with very high frequency, which means

776
00:41:02,400 --> 00:41:05,239
Speaker 1: that you can localize it to very specific place. And

777
00:41:05,280 --> 00:41:08,200
Speaker 1: so with very high energy particles you can probe things

778
00:41:08,480 --> 00:41:11,680
Speaker 1: really small distances. Or think about it another way, the

779
00:41:11,719 --> 00:41:14,080
Speaker 1: more you crank of the energy of your particle colliders,

780
00:41:14,239 --> 00:41:17,319
Speaker 1: the smaller the particles you can discover, because you can

781
00:41:17,560 --> 00:41:20,480
Speaker 1: break them open and see small things inside them. So

782
00:41:20,520 --> 00:41:22,839
Speaker 1: we've made a lot of progress there, and we are

783
00:41:22,840 --> 00:41:26,800
Speaker 1: studying things that are like tend the minus twenty meters wide,

784
00:41:27,160 --> 00:41:29,759
Speaker 1: you know, quarks that are inside the proton. So that

785
00:41:29,880 --> 00:41:32,600
Speaker 1: sounds pretty small, right, It's like ten to the minus

786
00:41:32,640 --> 00:41:35,760
Speaker 1: twenty meters is a very small slice of the universe.

787
00:41:36,239 --> 00:41:39,560
Speaker 1: But you know it's ten to the fifteen times bigger

788
00:41:39,640 --> 00:41:41,719
Speaker 1: than what we think is the Plank scale, which is

789
00:41:41,760 --> 00:41:44,840
Speaker 1: tend of the minus thirty five meters. And that's a

790
00:41:44,960 --> 00:41:47,680
Speaker 1: big ratio, right, Yeah, you just need more money, tenie,

791
00:41:48,480 --> 00:41:51,439
Speaker 1: just as the taxpayers for more money. Yeah, we should

792
00:41:51,520 --> 00:41:54,280
Speaker 1: siphon funds out of your ten billion dollar comics project.

793
00:41:55,440 --> 00:41:57,720
Speaker 1: You can't touch that. Some some things are more important

794
00:41:57,760 --> 00:42:00,799
Speaker 1: than understanding the nature of the universe, that's right. But

795
00:42:00,840 --> 00:42:03,800
Speaker 1: that's a limited distance, right, that's not quite the limited

796
00:42:03,960 --> 00:42:06,239
Speaker 1: time or is it the equivalent you're saying. I'm saying

797
00:42:06,280 --> 00:42:09,840
Speaker 1: their equivalent because these experiments also happened really really fast,

798
00:42:09,960 --> 00:42:12,000
Speaker 1: and to be really really fast you have to have

799
00:42:12,080 --> 00:42:15,279
Speaker 1: really really high energy also, and so fundamentally, these high

800
00:42:15,320 --> 00:42:20,520
Speaker 1: energy experiments are probing short times and small distances at

801
00:42:20,520 --> 00:42:24,440
Speaker 1: the same time. But unfortunately they're like way too weak

802
00:42:24,800 --> 00:42:27,600
Speaker 1: to probe really the fundamental nature of the universe and

803
00:42:27,640 --> 00:42:30,400
Speaker 1: to make them big enough and powerful enough to probe

804
00:42:30,400 --> 00:42:33,320
Speaker 1: that distance scale you need like a collider the size

805
00:42:33,320 --> 00:42:36,239
Speaker 1: of the Solar System or maybe even the galaxy. So

806
00:42:36,280 --> 00:42:39,319
Speaker 1: it's not even something we even imagine asking for a

807
00:42:39,320 --> 00:42:41,600
Speaker 1: little too expensive to make a collider of the size

808
00:42:41,640 --> 00:42:44,000
Speaker 1: of the Solar system. So then what can we do? What?

809
00:42:44,280 --> 00:42:46,799
Speaker 1: What are alternatives to break in the bank here to

810
00:42:46,960 --> 00:42:48,839
Speaker 1: find the answer? So people are trying to come up

811
00:42:48,920 --> 00:42:51,600
Speaker 1: with tabletop experiments, things you can do in a single

812
00:42:51,719 --> 00:42:55,960
Speaker 1: laboratory to probe either directly, like the discrete nature of

813
00:42:56,000 --> 00:42:58,799
Speaker 1: space and time, or to try to like do really

814
00:42:58,840 --> 00:43:02,760
Speaker 1: subtle experiments to understand quantum gravity. There's some really cool

815
00:43:02,880 --> 00:43:06,400
Speaker 1: ideas developing experiments that might really work and could actually

816
00:43:06,440 --> 00:43:08,960
Speaker 1: help us understand how things work at the smallest scale.

817
00:43:09,040 --> 00:43:12,560
Speaker 1: The first idea was proposed about ten years ago by Bekenstein.

818
00:43:12,880 --> 00:43:15,160
Speaker 1: He's a guy who worked closely with Stephen Hawking to

819
00:43:15,239 --> 00:43:18,040
Speaker 1: develop the understanding of black holes that we have today,

820
00:43:18,080 --> 00:43:21,120
Speaker 1: so definitely a smart person. And he had this crazy

821
00:43:21,200 --> 00:43:25,279
Speaker 1: idea of shooting a single photon at a crystal. And

822
00:43:25,320 --> 00:43:27,440
Speaker 1: the idea is that what happens when you shoot a

823
00:43:27,440 --> 00:43:30,400
Speaker 1: photon at a crystal. It's a quantum object. Either it

824
00:43:30,440 --> 00:43:33,640
Speaker 1: gets absorbed or it doesn't. And if it gets absorbed,

825
00:43:33,920 --> 00:43:36,680
Speaker 1: then you know where does its momentum go like pushes

826
00:43:36,880 --> 00:43:39,879
Speaker 1: the crystal a little bit, the same way we talk about,

827
00:43:39,960 --> 00:43:43,200
Speaker 1: you know, like solar sales, shooting photons from the sun

828
00:43:43,480 --> 00:43:45,960
Speaker 1: and hitting a sale of pushing a spacecraft forward. This

829
00:43:46,000 --> 00:43:48,160
Speaker 1: is like a mini version of that, where you shoot

830
00:43:48,160 --> 00:43:51,040
Speaker 1: a single photon at a crystal and if it gets absorbed,

831
00:43:51,239 --> 00:43:54,000
Speaker 1: it needs to like move forward a little bit. And

832
00:43:54,040 --> 00:43:56,880
Speaker 1: so the idea is to like tune the energy of

833
00:43:56,920 --> 00:44:01,280
Speaker 1: the photon so it matches like the basic minimum distance

834
00:44:01,440 --> 00:44:05,120
Speaker 1: of the universe, so you can measure somehow if this

835
00:44:05,200 --> 00:44:09,480
Speaker 1: crystal like slides forward a tiny bit. All right, So

836
00:44:09,719 --> 00:44:11,799
Speaker 1: you're shooting a photon, and I guess you make the

837
00:44:11,840 --> 00:44:14,920
Speaker 1: photon small enough that maybe you'll see that jump between

838
00:44:14,960 --> 00:44:17,439
Speaker 1: like oh it hit the crystal and oh it didn't

839
00:44:17,520 --> 00:44:19,359
Speaker 1: hit the crystal, which would sort of tell you that

840
00:44:19,760 --> 00:44:22,080
Speaker 1: the universe is not continuous. Is that kind of what

841
00:44:22,120 --> 00:44:24,960
Speaker 1: the experiment would be doing. Yeah, that's the idea that

842
00:44:25,080 --> 00:44:27,839
Speaker 1: you have like lots of these little photons and they're

843
00:44:27,880 --> 00:44:30,360
Speaker 1: interacting with elements of the crystal. If you tune in

844
00:44:30,520 --> 00:44:33,479
Speaker 1: just right, they have like just enough energy to move

845
00:44:33,520 --> 00:44:37,680
Speaker 1: it one like quantum universe step forwards. And so this

846
00:44:37,760 --> 00:44:40,959
Speaker 1: is an idea that beckn Seem proposed about ten years ago,

847
00:44:41,160 --> 00:44:43,240
Speaker 1: and some people thought it was very exciting, like, oh wow,

848
00:44:43,280 --> 00:44:46,040
Speaker 1: maybe we could measure quantum gravity on a tabletop. Other

849
00:44:46,080 --> 00:44:48,840
Speaker 1: folks I've asked have frankly said it's probably bullcrap and

850
00:44:48,880 --> 00:44:51,480
Speaker 1: would never work. I see, all right, so that's a

851
00:44:51,600 --> 00:44:53,640
Speaker 1: no no. What are other ways in which we could

852
00:44:53,680 --> 00:44:56,080
Speaker 1: maybe figure out if time is pixelated? Well, the really,

853
00:44:56,120 --> 00:44:58,480
Speaker 1: I think the most promising way to figure out if

854
00:44:58,480 --> 00:45:00,960
Speaker 1: time is pixelated is to try to get it these

855
00:45:01,000 --> 00:45:04,560
Speaker 1: theories of quantum gravity, to understand, you know, basically the

856
00:45:04,640 --> 00:45:07,080
Speaker 1: nature of space and time itself, and to do it

857
00:45:07,080 --> 00:45:09,719
Speaker 1: all at once. So these aren't experiments where you can

858
00:45:09,760 --> 00:45:12,239
Speaker 1: like see the universe take forward in time, but they

859
00:45:12,239 --> 00:45:15,319
Speaker 1: are experiments that might help reveal the very nature of

860
00:45:15,360 --> 00:45:18,360
Speaker 1: space and time, which we give us clues about whether

861
00:45:18,440 --> 00:45:21,440
Speaker 1: space and time are pixelated. And the way to make

862
00:45:21,480 --> 00:45:24,880
Speaker 1: progress there is to try to see gravity having influence

863
00:45:24,960 --> 00:45:28,760
Speaker 1: on individual particles, because we don't know how gravity works

864
00:45:28,760 --> 00:45:30,480
Speaker 1: when it comes to little particles like we know how

865
00:45:30,520 --> 00:45:33,359
Speaker 1: gravity works when it comes to the Earth and the Moon,

866
00:45:33,760 --> 00:45:36,120
Speaker 1: or the Earth and the Sun for example, or even

867
00:45:36,160 --> 00:45:39,480
Speaker 1: black holes. But we don't know what happens between two particles.

868
00:45:39,719 --> 00:45:42,640
Speaker 1: Are they like passing little gravitons back and forth? Are

869
00:45:42,680 --> 00:45:46,000
Speaker 1: they bending space? Is space discrete? There? Like? What we

870
00:45:46,040 --> 00:45:49,920
Speaker 1: need to do is see really strong gravitational effects on particles.

871
00:45:50,160 --> 00:45:52,880
Speaker 1: The problem, of course, is that particles have almost no

872
00:45:53,000 --> 00:45:56,319
Speaker 1: mass and so they have almost no gravity. But we've

873
00:45:56,320 --> 00:46:00,360
Speaker 1: gotten pretty good recently at building larger quantum of objects,

874
00:46:00,400 --> 00:46:03,239
Speaker 1: like getting a whole bunch of particles and getting them

875
00:46:03,239 --> 00:46:07,000
Speaker 1: like in sync together into one quantum state like a

876
00:46:07,080 --> 00:46:10,359
Speaker 1: Bose Einstein condensate or something similar, where you can make

877
00:46:10,440 --> 00:46:14,759
Speaker 1: like larger and larger objects that have quantum properties, and

878
00:46:14,840 --> 00:46:17,040
Speaker 1: maybe we can make them large enough that we can

879
00:46:17,040 --> 00:46:20,560
Speaker 1: start to see the gravitational effects between like clumps of

880
00:46:20,640 --> 00:46:23,520
Speaker 1: quantum objects. I see, like if you make a big

881
00:46:23,600 --> 00:46:26,880
Speaker 1: enough quantum object, you would see how anything quantum interacts

882
00:46:26,880 --> 00:46:29,319
Speaker 1: with gravity. Because right now we don't really know, right

883
00:46:29,680 --> 00:46:33,400
Speaker 1: like our theories breakdown when you try to make quantum

884
00:46:33,480 --> 00:46:36,880
Speaker 1: particles interact with gravity. We just don't know what happens

885
00:46:36,880 --> 00:46:40,879
Speaker 1: when quantum particles are feeling gravity. And so what we've

886
00:46:40,920 --> 00:46:44,440
Speaker 1: done so far is made things like Bose Einstein condensates

887
00:46:44,600 --> 00:46:47,240
Speaker 1: that have like, you know, maybe up to a thousand

888
00:46:47,320 --> 00:46:50,680
Speaker 1: atoms in them, these tiny little blobs of stuff. And

889
00:46:50,719 --> 00:46:53,760
Speaker 1: that's really not big enough to observe any gravity, because remember,

890
00:46:53,760 --> 00:46:57,400
Speaker 1: gravity is the weakest force out there. But we're making progress,

891
00:46:57,400 --> 00:46:58,680
Speaker 1: and it's the kind of thing where like in ten

892
00:46:58,760 --> 00:47:01,839
Speaker 1: years undergrads will be doing that in their freshman physics lab.

893
00:47:02,160 --> 00:47:04,440
Speaker 1: It'll be very easy or be like on a computer

894
00:47:04,560 --> 00:47:07,400
Speaker 1: chip kind of thing, And in the basements of research

895
00:47:07,560 --> 00:47:11,600
Speaker 1: facilities they will be like having quantum diamonds and superpositions

896
00:47:11,600 --> 00:47:14,360
Speaker 1: and doing crazy experiments. But I guess maybe the question is,

897
00:47:14,480 --> 00:47:17,279
Speaker 1: you know, that might help us figure out if gravities quantized,

898
00:47:17,640 --> 00:47:19,320
Speaker 1: but how does that help us know if time is

899
00:47:19,400 --> 00:47:22,840
Speaker 1: quantized or pixelated. Yeah, it will tell us if gravity

900
00:47:22,880 --> 00:47:25,359
Speaker 1: is a quantum theory or not, you know, or if

901
00:47:25,440 --> 00:47:27,680
Speaker 1: space is quantized or not. So it will sort of

902
00:47:27,680 --> 00:47:32,200
Speaker 1: help us get direction theoretically for how to tackle this

903
00:47:32,280 --> 00:47:34,440
Speaker 1: very question about the nature of space and time. So

904
00:47:34,480 --> 00:47:37,480
Speaker 1: it won't directly tell us if time is pixelated, it

905
00:47:37,520 --> 00:47:39,480
Speaker 1: will give us a lot of clues about how to

906
00:47:39,480 --> 00:47:42,360
Speaker 1: build a theory of quantum gravity, and gravity of course

907
00:47:42,760 --> 00:47:45,960
Speaker 1: very closely connected to space and time, so it'll sort

908
00:47:45,960 --> 00:47:48,880
Speaker 1: of like help us lay the foundations to maybe eventually

909
00:47:48,880 --> 00:47:51,400
Speaker 1: get there. But it's you know, it's nice to know

910
00:47:51,560 --> 00:47:53,840
Speaker 1: that we might be able to do some experiments that

911
00:47:53,880 --> 00:47:57,080
Speaker 1: can help us figure out if gravity is quantum or not,

912
00:47:57,400 --> 00:47:59,080
Speaker 1: so that we can try to get our heads around

913
00:47:59,120 --> 00:48:02,040
Speaker 1: these basic questions. Is about the nature of space and time, right,

914
00:48:02,080 --> 00:48:04,160
Speaker 1: But even if you find out the gravity is quantized

915
00:48:04,160 --> 00:48:07,800
Speaker 1: and spaces quantized, you still wouldn't technically right. Maybe possibly

916
00:48:07,920 --> 00:48:11,200
Speaker 1: now if time itself is also quantized, like we said earlier,

917
00:48:11,239 --> 00:48:12,560
Speaker 1: it could be the one of the is quantized on

918
00:48:12,600 --> 00:48:14,560
Speaker 1: the other one is not. But it depends on the

919
00:48:14,560 --> 00:48:17,200
Speaker 1: details of your quantum theory. Right, So if you discover,

920
00:48:17,280 --> 00:48:20,799
Speaker 1: for example, string theory is right, then string theory says, well,

921
00:48:20,840 --> 00:48:22,840
Speaker 1: time is sort of continuous, but there are is a

922
00:48:22,840 --> 00:48:26,080
Speaker 1: minimum resolution below which it doesn't make sense to ask questions.

923
00:48:26,400 --> 00:48:28,120
Speaker 1: Or if you discover oh no, it looks like loop.

924
00:48:28,200 --> 00:48:31,520
Speaker 1: Quantum gravity is correct and Carlo Revelli was right and

925
00:48:31,560 --> 00:48:34,759
Speaker 1: time is also quantized, So it might help you because

926
00:48:34,800 --> 00:48:38,839
Speaker 1: it would reveal the quantum theory that describes space and time,

927
00:48:38,840 --> 00:48:42,400
Speaker 1: which might require time to be continuous or smooth, or

928
00:48:42,480 --> 00:48:44,279
Speaker 1: it might show us that none of our ideas are

929
00:48:44,280 --> 00:48:47,239
Speaker 1: correct in something else totally weird and new is required,

930
00:48:47,360 --> 00:48:49,479
Speaker 1: and time might not be quantized. It might be something

931
00:48:49,480 --> 00:48:52,480
Speaker 1: else totally different than we haven't even imagined. It might

932
00:48:52,520 --> 00:48:55,120
Speaker 1: be a different time. It would be time for a

933
00:48:55,160 --> 00:48:58,200
Speaker 1: new idea. It will be a timely discovery. Yeah, so

934
00:48:58,239 --> 00:49:00,200
Speaker 1: I would say that in summary. You know, it's not

935
00:49:00,440 --> 00:49:03,080
Speaker 1: something that we're gonna be able to directly probe very easily,

936
00:49:03,080 --> 00:49:04,600
Speaker 1: but we can get around to it's sort of at

937
00:49:04,600 --> 00:49:07,160
Speaker 1: the back by trying to build a consistent theory of

938
00:49:07,200 --> 00:49:11,239
Speaker 1: space and time, which requires understanding quantum gravity. Because you

939
00:49:11,280 --> 00:49:13,680
Speaker 1: don't think there is there could ever be an experiment

940
00:49:13,680 --> 00:49:17,160
Speaker 1: that could test it directly. I think those experiments require

941
00:49:17,360 --> 00:49:21,960
Speaker 1: such enormous energy they're effectively like creating black holes, and

942
00:49:22,000 --> 00:49:24,920
Speaker 1: so it's hard to imagine you ever doing experiments at

943
00:49:24,960 --> 00:49:27,359
Speaker 1: that scale, right, Who would ever make a black hole

944
00:49:27,400 --> 00:49:31,279
Speaker 1: on purpose? I would. I totally would sign me up.

945
00:49:32,760 --> 00:49:34,520
Speaker 1: I'm not saying I wouldn't want to. I'm just saying

946
00:49:34,560 --> 00:49:36,800
Speaker 1: I don't think it's possible. I think maybe it's time

947
00:49:36,840 --> 00:49:40,200
Speaker 1: to cut short this episode now before we introduce too

948
00:49:40,239 --> 00:49:43,000
Speaker 1: many bad ideas into a physicist brain. All right, well,

949
00:49:43,040 --> 00:49:45,560
Speaker 1: I guess the question is yet to be determines. There

950
00:49:45,560 --> 00:49:48,520
Speaker 1: are their arguments for time being pixelated and arguments against

951
00:49:48,560 --> 00:49:51,000
Speaker 1: time being pixelated. It sounds like we might never know.

952
00:49:51,440 --> 00:49:54,440
Speaker 1: But if we make enough progress just in basic, you know,

953
00:49:54,640 --> 00:49:57,880
Speaker 1: fundamental theories of the universe, maybe it'll come up. Hopefully

954
00:49:57,880 --> 00:50:00,560
Speaker 1: it will come up. Is that kind of the planned there,

955
00:50:00,680 --> 00:50:04,560
Speaker 1: Let's focus on something else and let's procrastinate, and maybe

956
00:50:04,560 --> 00:50:06,520
Speaker 1: we'll come up on its own. Let's figure out the

957
00:50:06,560 --> 00:50:09,800
Speaker 1: foundations of everything, and maybe along the way we'll solve

958
00:50:09,840 --> 00:50:12,520
Speaker 1: this other problem. All right, and maybe we'll find more

959
00:50:12,560 --> 00:50:14,040
Speaker 1: time for you, Daniel, to do all the things we

960
00:50:14,160 --> 00:50:16,640
Speaker 1: wanted to all right, Well again, I think it's an

961
00:50:16,640 --> 00:50:19,120
Speaker 1: interesting reminder of how much we don't know about the universe,

962
00:50:19,160 --> 00:50:22,319
Speaker 1: about basic things like space and time, and it's time

963
00:50:22,360 --> 00:50:24,200
Speaker 1: that we figure them out. It's always a good time

964
00:50:24,239 --> 00:50:27,080
Speaker 1: for for physics, right, It's always a good time, and

965
00:50:27,120 --> 00:50:30,000
Speaker 1: there's always a good time for physics, and physicists are

966
00:50:30,000 --> 00:50:32,600
Speaker 1: always a good time and that's the But that's a

967
00:50:32,680 --> 00:50:36,080
Speaker 1: theoretical conjecture there, Daniel that's never been proven in the lab.

968
00:50:36,600 --> 00:50:40,040
Speaker 1: No experiments have proven that. I think unfortunately that's true.

969
00:50:40,280 --> 00:50:42,400
Speaker 1: Maybe we should collige physicist together and just see what

970
00:50:42,520 --> 00:50:44,840
Speaker 1: happens that. Now, that sounds like fun. That sounds like

971
00:50:44,840 --> 00:50:46,640
Speaker 1: a good time to you. All right, Well, we hope

972
00:50:46,640 --> 00:50:49,439
Speaker 1: you enjoyed that. Thanks for giving us your time, See

973
00:50:49,440 --> 00:50:59,720
Speaker 1: you next time. Thanks for listening, and remember that Daniel

974
00:50:59,760 --> 00:51:02,120
Speaker 1: and or Hey Explain the Universe is a production of

975
00:51:02,239 --> 00:51:05,600
Speaker 1: I Heart Radio or more podcast from my heart Radio.

976
00:51:05,719 --> 00:51:09,320
Speaker 1: Visit the I heart Radio app, Apple Podcasts, or wherever

977
00:51:09,440 --> 00:51:13,040
Speaker 1: you listen to your favorite shows. H