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Speaker 4: Hey, Daniel, who do you think would win in a

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Speaker 4: fight theoretical or an experimental physicist?

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Speaker 1: That depends are we're talking arm wrestling or like integration

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Speaker 1: competitions into what mathematical race?

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Speaker 4: Then I think I would put my money into theoretical physicist,

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Speaker 4: I mean, no offense.

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Speaker 1: Maybe we have to do the experiment, or maybe.

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Speaker 4: You should keep this theoretical. I don't know if you

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Speaker 4: want to pick a fight.

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Speaker 1: Well, maybe the two sides of the field just compliment

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Speaker 1: each other beautifully.

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Speaker 4: Is that all. It takes us some compliments and you

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Speaker 4: guys are back at friends.

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Speaker 1: Theories are cheap, right, They don't need money for experiments,

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Speaker 1: they just need compliments in theory.

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Speaker 4: In my experience, Hi, I am more Headmaye, cartoonist and

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Speaker 4: the creator of PhD comics.

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Speaker 1: Hi, I'm Daniel. I'm a particle physicist and a professor

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Speaker 1: at UC Irvine, And back in the day, I did

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Speaker 1: want to be a theorist.

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Speaker 4: Back in the day. How old were you.

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Speaker 1: When I started grad school? I wasn't sure if I

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Speaker 1: wanted to do experimental or theoretical physics, so I guess

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Speaker 1: I was in my early twenties, which by now is

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Speaker 1: pretty far back in the day.

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Speaker 4: Did you actually get a choice, like they offer you

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Speaker 4: an option of which way to go, or do you

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Speaker 4: have to, like, I don't know, test into it.

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Speaker 1: You definitely have to kind of try out and work

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Speaker 1: with the theorists if you want to be a theorist.

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Speaker 1: But you have all the options when you start grad school.

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Speaker 1: You could end up being an experimental particle physicist or

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Speaker 1: a theoretical cosmologist or whatever. All those paths are available.

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Speaker 1: You just got to like it enough and be good

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Speaker 1: at it.

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Speaker 4: So what happened? Why didn't you pick the theory?

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Speaker 1: I discovered I just didn't like writing down equations as

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Speaker 1: much as the theorists. They would sit there and like

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Speaker 1: develop several different mathematical fonts to write their equations in,

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Speaker 1: and I was like, Wow, I'm just not loving this

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Speaker 1: as much as they're loving this.

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Speaker 4: It sounds like you were against the idea of it

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Speaker 4: in theory.

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Speaker 1: My experience was the experiments were more fun.

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Speaker 4: But anyways, welcome to our podcast Daniel and Jorge Explain

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Speaker 4: the Universe, a production of iHeartRadio.

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Speaker 1: In which we try to blur the line between theory

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Speaker 1: and the experiment. We wanted to talk about all the

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Speaker 1: concepts in theoretical physics that try to explain what's going

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Speaker 1: on in our world, but we also try to touch

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Speaker 1: back on the ground and understand what experiments are telling

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Speaker 1: us about the nature of reality. What is nature actually

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Speaker 1: saying to us as she spins the story of the universe,

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Speaker 1: And then we try to explain all of it to you.

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Speaker 4: That's right, because it is a pretty storied universe, full

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Speaker 4: of amazing little details and facts and things to discover

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Speaker 4: out there that we are still puzzling over. And which

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Speaker 4: require all kinds of scientists to figure out, theorists and experimentalists.

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Speaker 1: And in the history of physics we have made progress

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Speaker 1: in lots of different ways. Sometimes the theorists have come

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Speaker 1: up with a clever idea, a suspicion about how the

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Speaker 1: universe might work, with lots of cool directions for experimentalists.

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Speaker 1: Go out and check this thing. Measure how light bends

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Speaker 1: around the sun. See if you can find the Higgs boson.

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Speaker 1: Those can be wonderful directions to help unravel the mysteries

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Speaker 1: of the universe. But sometimes the experimentalists lead the way,

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Speaker 1: turning on particle smashers and discovering gobs and gobs of

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Speaker 1: new particles that nobody Expectedestion.

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Speaker 4: And danially is why can't you be both? Why can't

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Speaker 4: you be a theoretical and an experimental physicist.

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Speaker 1: I'm doing my best. Actually, i'm doing my best. But

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Speaker 1: the reality of academia these days is to get one

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Speaker 1: of these jobs, you have to be the world's expert

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Speaker 1: in some subfield, and that makes it really hard to

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Speaker 1: sort of live between two fields, because you have to

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Speaker 1: be like the top person in that field that year.

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Speaker 1: And so if the theorists aren't sure if you're a

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Speaker 1: theorist and the experimentalist aren't sure. If you're an experimentalist,

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Speaker 1: nobody's going to give you that job. So you've got

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Speaker 1: to sort of get the job in one category and

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Speaker 1: then inch your way over to the other one if

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Speaker 1: you're interested.

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Speaker 4: That's kind of clickish, it's.

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Speaker 1: Definitely very cliquish. Absolutely, these fields form and then they

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Speaker 1: protect themselves and it can be hard for new kinds

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Speaker 1: of sub fields to emerge. Like right now we have

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Speaker 1: the emergence of physicists who are experts in machine learning,

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Speaker 1: and people aren't sure is that theoretical is it experimental?

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Speaker 1: Because you're running a bunch of calculations. Nobody's really sure.

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Speaker 1: Everybody knows that it's valuable, but we aren't quite sure

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Speaker 1: where to put with them.

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Speaker 4: That's because they're robots? Are they?

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Speaker 1: In disguise? We're all just biological robots?

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Speaker 5: Man?

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Speaker 1: Oh, there you go, aren't you the expert in squishy robots?

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Speaker 4: I am, yeah, Well I used to be at least

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Speaker 4: a lifetime ago, or a couple of lifetimes ago.

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Speaker 1: Now back in the day. Is there such a thing

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Speaker 1: as a theoretical roboticist?

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Speaker 4: Uh? Yeah, there's a lot of theory in robotics as well.

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Speaker 4: But no, as we I guess we're not as cliqu

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Speaker 4: as you're just a roboticist. If you're into robots, you're

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Speaker 4: just a roboticist.

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Speaker 1: New York because you just build your own friends. You're like, hey,

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Speaker 1: look I don't need people's friends. I can build my own.

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Speaker 4: Yeah. But as you said, I guess you need both

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Speaker 4: kinds of endeavors or research. You need experimental research and

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Speaker 4: you need theoretical research in order to figure out how

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Speaker 4: things work in the universe, because I guess you need

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Speaker 4: to come up with a theory so that you can

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Speaker 4: prove it with an experiment, and you need an experiment

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Speaker 4: to prove the theories. Otherwise there's no science.

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Speaker 1: That's sort of a theoretical way of thinking about it,

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Speaker 1: that we come up with the theories and improve them

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Speaker 1: with experiment. Remember that sometimes experiments don't just prove theories,

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Speaker 1: they blow up theories and tell us that the universe

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Speaker 1: is different from the way we understand it and operates

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Speaker 1: in some other way we don't yet understand. Like the

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Speaker 1: photo electric effect was a demonstration that boy, we really

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Speaker 1: don't understand light and how it works, and it took

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Speaker 1: a few years before the theorist came up with any sort

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Speaker 1: of explanation for it.

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Speaker 4: Yeah, but I guess experimenters blunches kind of experiment blindly, right.

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Speaker 4: You usually have some sort of theory at hand when

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Speaker 4: you design your experiments, when you go out there and

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Speaker 4: turn stuff on.

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Speaker 1: It's a bit of a raging debate right now in

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Speaker 1: experimental physics whether we should be focused on searching for

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Speaker 1: the ideas that theoretical physicists are suggesting, or whether we

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Speaker 1: should be developing strategies that are more just exploratory that

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Speaker 1: leave us open to surprises. Like when you turn on

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Speaker 1: the Hubble Space telescope and look out into space. Sure,

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Speaker 1: you want to see the things that you had in

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Speaker 1: mind to look at, but you're also open to like

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Speaker 1: seeing aliens waving at you, or seeing new kinds of

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Speaker 1: stuff you didn't even expect to see.

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Speaker 4: But I guess also at the same time, we're getting

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Speaker 4: to a spot where you know, things are so complex

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Speaker 4: and so subtle and so hidden that you kind of

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Speaker 4: need to know what you're looking for in a way, Right,

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Speaker 4: it's kind of hard to just like look for everything.

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Speaker 1: It is really hard to look for everything. You really

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Speaker 1: put your finger on it, especially when your data is

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Speaker 1: very statistical. If you do like a single experiment and

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Speaker 1: you get some weird result, you might be able to say, hey, look,

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Speaker 1: there's definitely something new here. But if the data are subtle,

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Speaker 1: if the new things appear as like trends in your data,

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Speaker 1: then you're right. It can be hard to know how

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Speaker 1: to find them. So then you have to play some

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Speaker 1: clever statistical arguments and say, well, you're the kinds of

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Speaker 1: things that we could see, and here are the ways

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Speaker 1: that we could search for them. So you have to

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Speaker 1: do a little bit more work to define the kinds

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Speaker 1: of things you might be able to see, even if

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Speaker 1: you aren't sure which specifically might pop up in your data.

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Speaker 4: Well, sometimes there are cases where both the theories and

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Speaker 4: the experimental lists are stumped. And that is the case

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Speaker 4: where non physics. There's kind of a big hole in

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Speaker 4: physics in terms of our knowledge of how things work

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Speaker 4: in the universe.

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Speaker 1: That's right, at the most fundamental level, we still don't

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Speaker 1: really understand the basic rules of physics. We have two

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Speaker 1: pillars of modern physics relativity that tells us about space

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Speaker 1: time and gravity, and quantum mechanics that tells us about

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Speaker 1: particles and forces, and we just don't know how to

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Speaker 1: bring them together. And it's important because it has to

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Speaker 1: do with one of the most basic questions in physics,

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Speaker 1: which is what is the universe made out of? What

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Speaker 1: is the fundamental fabric of reality? After all?

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Speaker 6: Yeah?

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Speaker 4: And is it soft and comfortable? Is what I want

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Speaker 4: to know.

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Speaker 1: It seems to have a little bit of spandex in it.

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Speaker 4: Here, you guys, long is a stretchy that can accommodate

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Speaker 4: all sizes.

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Speaker 1: Because my waste is not the size it was back

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Speaker 1: in the day.

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Speaker 4: Yeah, you want the universe to kind of expand with you,

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Speaker 4: your mind and your waste. But yeah, there's kind of

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Speaker 4: a big hole in our understanding of the universe. And

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Speaker 4: it has to do with gravity. We're not quite sure

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Speaker 4: where gravity falls, whether it falls where it fits with

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Speaker 4: quantum mechanic skill theory, or whether it works the way

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Speaker 4: that Einstein envisioned it in special relativity.

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Speaker 1: Right, that's right. Einstein and special relativity tells us about

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Speaker 1: light and how it propagates. His theory of general relativity

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Speaker 1: tells us about space time and how it bends. And

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Speaker 1: these two theories are in conflict and tell us very

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Speaker 1: different stories about the nature of the universe, but so

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Speaker 1: far we haven't been able to figure out a way

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Speaker 1: to test them without building a solar system sized particle

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Speaker 1: collider or peering inside a black hole. So experimental physicists

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Speaker 1: have not really been able to contribute to this conversation

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Speaker 1: until now.

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Speaker 4: So the deal in the podcast, we'll be asking the question,

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Speaker 4: can we test quantum gravity in a tabletop experiment? And

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Speaker 4: right here the word tabletop I think of board games.

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Speaker 4: Is this what we're talking about? Like a little cardboard

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Speaker 4: unfolding thing with pieces, and then you test quantum gravity exactly.

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Speaker 1: You can download the schematics from the internet and print

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Speaker 1: out your own Nobel Prize winning experiment.

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Speaker 4: There you go. Is it called Settlers of Park or

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Speaker 4: quantum ton.

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Speaker 1: I'll leave you to do the branding of it. But

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Speaker 1: when we say tabletop experiment in physics, we basically mean

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Speaker 1: something not like the large hadron collider or something that

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Speaker 1: doesn't require a ten billion dollar facility staffed by thousands

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Speaker 1: of people. We mean the kind of thing a single

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Speaker 1: physicist could do in their laboratory in the basement of

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Speaker 1: your nearby university.

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Speaker 4: I see, you're talking about a million dollar table talk,

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Speaker 4: not a billion dollar table.

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Speaker 1: Talk exactly, just like everybody has a million dollar table

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Speaker 1: in their kitchen. No, it's really like a single physicist experiment,

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Speaker 1: something you can do in a reasonable physics lab, not

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Speaker 1: something people are going to be doing on their kitchen table.

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Speaker 4: Well, as usual, we were wondering how many people out

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Speaker 4: there had thought about this question or perhaps have any

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Speaker 4: ideas about how to do it.

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Speaker 1: So thanks very much to everybody who participates in this

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Speaker 1: segment of the podcast. If you've been listening for years

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Speaker 1: and would like to hear your voice speculating about the

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Speaker 1: topic of the day, please write to us two questions

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Speaker 1: at Danielandjorge dot com. Everybody's welcome them.

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Speaker 4: So think about it for a second. Do you think

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Speaker 4: we can test quantum gravity on somebody's table? Here's what

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Speaker 4: people have to say.

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Speaker 7: Well, since quantum gravity is, you know, with the gravity

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Speaker 7: of the really small, I don't see why the experiments

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Speaker 7: with it couldn't be done on a tabletop. I just

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Speaker 7: have no idea what those experiments would even begin to

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Speaker 7: look like.

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Speaker 3: Though.

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Speaker 1: If yes, then it will come to our table soon.

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Speaker 4: But till then, I don't think it is possible at all.

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Speaker 5: Uh.

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Speaker 1: Yeah, you probably could, but probably not today.

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Speaker 5: I do not feel like we could test quantum gravity

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Speaker 5: in a tabletop experiment because you need a lot of

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Speaker 5: gravity for it to work, and I don't think the

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Speaker 5: Earth has that kind of gravity.

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Speaker 4: All right, not a lot of optimism. I like the

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Speaker 4: person who said the tabletop, I don't think so. But

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Speaker 4: maybe a desktop or on the floor or on a shelf,

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Speaker 4: maybe mountaintop maybe, yeah, tabletop on a mountain. There you go,

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Speaker 4: lower gravity.

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Speaker 1: Well, we talked recently about how to measure big g

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Speaker 1: and that experiment was definitely done on a mountain side

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Speaker 1: swinging pendulums next to a big mountain in Scotland. So yeah,

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Speaker 1: you can do funny gravity experiments on tops of mountains.

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Speaker 4: And I like the person said, probably but not today?

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Speaker 4: Like is today a bad day for that? Were they

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Speaker 4: busy that day? How about next week? Next week? Work?

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Speaker 1: Please fill out this doodle pole for when we will

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Speaker 1: win a Nobel prize. There you go.

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Speaker 4: Yeah, I guess people didn't feel like it could work,

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Speaker 4: but let's find out. Daniel step us through this. What

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Speaker 4: is quantum gravity?

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Speaker 1: So when we say quantum gravity, what we mean is

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Speaker 1: a theory that explains both the quantum mechanical behavior of

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Speaker 1: super tiny particles, the way like electrons and photons do

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Speaker 1: things that baseballs and basketballs and mountaintops don't do. You know,

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Speaker 1: they don't move in smooth paths. They have weird quantized

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Speaker 1: energy levels. They can be in a superposition of different states,

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Speaker 1: like maybe they're here, maybe they're there. They can interact

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Speaker 1: with each other and interfere in all sorts of complicated

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Speaker 1: ways described by their wave function. And we want a

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Speaker 1: theory that explains gravity as we know it. That things

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Speaker 1: seem to move in these inertial paths through curved space time,

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Speaker 1: and that mass in space tends to bend the path,

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Speaker 1: which affects the motion of other mass. So we have

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Speaker 1: these two very different theories of the universe, and so

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Speaker 1: far we can't bring them together. So quantum gravity would

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Speaker 1: be a theory that explains both these things somehow harmoniously.

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Speaker 1: But it's not a theory that we have today.

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Speaker 4: Well, I guess maybe step us through a little bit

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Speaker 4: of what we haven't been able to bring these two

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Speaker 4: things together. As far as I understand it, it's kind

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Speaker 4: of due to two things, right, Like one is that

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Speaker 4: we haven't measured the gravitational force at the level of

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Speaker 4: the quantum particles, right, that's one thing. And also we

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Speaker 4: don't know what happens to general relativity when you get

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Speaker 4: down to that small level.

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Speaker 1: Too exactly, I think you put your finger on it. Really,

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Speaker 1: we don't know what the gravity is for little particles.

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Speaker 1: The gravity for a baseball or for a moon, we

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Speaker 1: think we understand and we've been able to test that.

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Speaker 8: Right.

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Speaker 1: We see moon's orbiting planets, we see planets orbiting suns.

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Speaker 1: We see how gravity works. But that's all really really

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Speaker 1: big stuff. What we don't know is what happens when

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Speaker 1: you have gravity for particles, because particles are super duper tiny,

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Speaker 1: which makes it really complicated for two reasons. One is

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Speaker 1: that they have almost no gravity. Remember that gravity is

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Speaker 1: like the weakest force in the universe, and so the

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Speaker 1: other forces overwhelm it. You try to do experiments with electrons,

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Speaker 1: then their charge is much more powerful than their mass. Right.

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Speaker 1: The electromagnetic force is much more powerful than the gravitational

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Speaker 1: force on an electron. So it's basically impossible to measure

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Speaker 1: the gravitational force on an electron.

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Speaker 4: Can I ask why that is?

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Speaker 1: Though?

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Speaker 4: Like, couldn't I shoot an electron from here? To London

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Speaker 4: and see if it curves with the curvature of the Earth.

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Speaker 1: You could try that, absolutely, I think you probably shouldn't

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Speaker 1: shoot beams across the surface of the Earth without getting

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Speaker 1: signatures from everybody who might live in between. But say

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Speaker 1: you did that, the electors would be affected by all

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Speaker 1: sorts of charge particles between here and London. Right, There'd

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Speaker 1: be lots of other effects on the electron which would

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Speaker 1: swamp out any gravitational effects.

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Speaker 4: But I guess maybe, like from a satellite, I'm thinking,

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Speaker 4: you know, I just shoot a whole bunch of them,

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Speaker 4: and wouldn't the effects from other things kind of even

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Speaker 4: out if you shoot a bunch of them out, Like

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Speaker 4: don't we have like quantum drives or like electron cannons.

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Speaker 4: What happens if I just shoot them out there in space?

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Speaker 4: Do they keep going straight or do they bend?

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Speaker 1: Yeah, you could build an electron gun and put it

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Speaker 1: in space and shoot them out, but still it would

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Speaker 1: be dominated by the effects of other particles. Remember space

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Speaker 1: is not totally empty. There's cosmic microwave background photons there,

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Speaker 1: there's other charge particles from the Sun, and all of

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Speaker 1: these would dominate the fate of that electron. Really the

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Speaker 1: problem is that the charge is more powerful than the mass.

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Speaker 1: We talked about this once, and this is either because

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Speaker 1: gravity itself is just weaker than the other forces for

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Speaker 1: reasons we don't understand, or because electrons are just packed

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Speaker 1: with a lot of charge compared to how much mass

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Speaker 1: they have. You can think about it sort of either way.

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Speaker 1: But that just means that the effect of gravity is

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Speaker 1: tiny compared to the effect of electromagnetism. So to do

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Speaker 1: that experiment, you'd need to isolate those particles from any

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Speaker 1: sort of effect. And today we'll talk about an experiment

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Speaker 1: that's going to try to do that, all.

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Speaker 4: Right, So then that's where quantum gravity comes in. It's

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Speaker 4: kind of a is it a theory or an idea

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Speaker 4: that tries to bring these two big ideas together.

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Speaker 1: It's not a theory. It's like a category of theories.

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Speaker 1: It's like a dreamt of theory. What we want is

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Speaker 1: a theory that bring these two things together. We don't

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Speaker 1: have one. We don't know what the theory of quantum gravity is.

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Speaker 1: You know, sometimes you have like ten different theories that

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Speaker 1: describe the universe, and the experiment has to go off

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Speaker 1: and tell you which one is correct. Right now, we

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Speaker 1: have zero We have zero theories that explain quantum mechanics

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Speaker 1: and gravity at the same time. So we sort of

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Speaker 1: need an experimental result to be like, hey, this is

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Speaker 1: the right direction, no where, Hey here's something to grab

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Speaker 1: on to, here's a clue. But there's the second reason

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Speaker 1: why these experiments are difficult that we didn't get to yet.

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Speaker 1: One is just that gravity is so weak, and the

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Speaker 1: other is that these particles do things that we don't

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Speaker 1: know how to explain with gravity. Like particles don't have

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Speaker 1: smooth paths. It's not like the electron is always somewhere,

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Speaker 1: has some velocity. You know, you want to calculate the

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Speaker 1: gravity of an electron, you have to know where it is,

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Speaker 1: so you know how far away it is you can

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Speaker 1: calculate it's gravity. But electrons don't have specific locations that

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Speaker 1: have probabilities, So we don't know. For example, if an

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Speaker 1: electron when it has probabilities to be in multiple places,

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Speaker 1: does it mean it has like multiple different possible gravityes.

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Speaker 1: We just don't know how to do gravity for things

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Speaker 1: that have uncertainties in their locations.

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Speaker 4: You mean, we don't know how to do that. If

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Speaker 4: gravity was not a quantum force, right, Like you're sort

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Speaker 4: of assuming that you I guess you want gravity to

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Speaker 4: be like a quantum force like the other forces that

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Speaker 4: we know about, right.

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Speaker 1: Yeah, that's sort of one of the basic questions when

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Speaker 1: you want to build the theory of quantum gravity, like

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Speaker 1: is it a quantum force. If so, then two electrons

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Speaker 1: interact I think gravitationally wouldn't like collapse each other's wave functions.

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Speaker 1: Some bits of one wave function would interact with some

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Speaker 1: bits of another wave function, and they could do all

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Speaker 1: sorts of weird quantum interactions. But if gravity's actually a

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Speaker 1: classical force and not a quantum force, then it would

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Speaker 1: collapse the wave function, sort of like when you use

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Speaker 1: a detector in a double slit experiment, it forces the

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Speaker 1: particle to pick one of the options instead of the

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Speaker 1: other one. So we just don't know, like is gravity

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Speaker 1: classical is it quantum mechanical? We just don't even know

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Speaker 1: where to begin.

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Speaker 4: And when you say classical, you mean like basically not

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Speaker 4: quantum mechanical, like not fuzzy, not uncertain.

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Speaker 1: Yeah, exactly, we mean not quantum. Classical is sort of

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Speaker 1: an overused word. Some people say classical to mean not

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Speaker 1: relativistic like Newtonian, but today we mean not quantum mechanical,

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Speaker 1: So we don't know if gravity like really is just

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Speaker 1: classical the way Einstein described it, thinking about space as

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Speaker 1: smooth and continuous and everything having passed, or if it

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Speaker 1: is a quantum effect, in which case it could either

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Speaker 1: be a force like you suggested medi by weird gravitons,

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Speaker 1: or maybe like space itself is quantum mechanical and uncertain.

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Speaker 1: If gravity is the curvature of space, maybe space itself

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Speaker 1: can be like maybe bent here and maybe bent there

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Speaker 1: in some weird quantum mechanical way. There's so many possible

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Speaker 1: directions for quantum gravity, nobody really knows which one is

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Speaker 1: going to build a viable theory that even can do calculations.

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Speaker 4: All right, well, let's get a little bit deeper into

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Speaker 4: quantum gravity and whether or not we can test it,

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Speaker 4: and test it for under a billion dollars, because I

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Speaker 4: guess the cheaper the better. We'll dig into that be first,

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Speaker 4: let's take a quick break.

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Speaker 4: All right, we're talking about quantum gravity and whether or

505
00:24:21,440 --> 00:24:24,119
Speaker 4: not that is a thing at all, whether it will

506
00:24:24,400 --> 00:24:27,440
Speaker 4: bring together quantum mechanics in general relativity to give us

507
00:24:27,760 --> 00:24:30,119
Speaker 4: one theory of the universe, and whether or not we

508
00:24:30,160 --> 00:24:32,919
Speaker 4: can even design experiments to test such a theory.

509
00:24:33,040 --> 00:24:34,920
Speaker 1: I like your threshold of a billion dollars.

510
00:24:35,560 --> 00:24:38,880
Speaker 4: Yeah, well, though these days with inflation, maybe that's more

511
00:24:38,960 --> 00:24:39,600
Speaker 4: like ten billion.

512
00:24:39,640 --> 00:24:39,800
Speaker 8: Though.

513
00:24:41,359 --> 00:24:43,560
Speaker 1: You know, if we could spend a billion dollars and

514
00:24:43,600 --> 00:24:46,520
Speaker 1: get the answer to quantum gravity, I'm pretty sure we

515
00:24:46,560 --> 00:24:48,600
Speaker 1: would do it. The truth is, the experiments might cost

516
00:24:48,800 --> 00:24:50,719
Speaker 1: a lot more than one billion dollars.

517
00:24:50,720 --> 00:24:54,200
Speaker 4: All right, well, let's dig into the cost of these experiments.

518
00:24:54,240 --> 00:24:56,400
Speaker 4: How can we test quantum gravity and figure out whether

519
00:24:56,480 --> 00:24:57,560
Speaker 4: or not it's a real thing or not?

520
00:24:57,680 --> 00:24:59,520
Speaker 1: Well, you had sort of the right idea, which is like,

521
00:25:00,040 --> 00:25:02,280
Speaker 1: let's just zoom in on a quantum particle and look

522
00:25:02,320 --> 00:25:05,120
Speaker 1: at its gravity somehow. But remember the scale of things

523
00:25:05,160 --> 00:25:08,199
Speaker 1: we're talking about here, like these particles are super duper tiny,

524
00:25:08,520 --> 00:25:11,080
Speaker 1: and the effects we're talking about what happened on really

525
00:25:11,160 --> 00:25:15,240
Speaker 1: really short distance scales, Like gravity gets more powerful when

526
00:25:15,240 --> 00:25:18,159
Speaker 1: things get closer together. In order for gravity to be

527
00:25:18,240 --> 00:25:20,960
Speaker 1: powerful enough for us to really test it, you need

528
00:25:21,000 --> 00:25:23,919
Speaker 1: to get things together to like the Plank scale distances

529
00:25:24,160 --> 00:25:27,720
Speaker 1: we're talking about, like ten to the minus thirty five meters.

530
00:25:27,880 --> 00:25:30,280
Speaker 1: So until recently, it seemed like, well, the only way

531
00:25:30,320 --> 00:25:33,160
Speaker 1: to test quantum gravity is to have like a microscope

532
00:25:33,240 --> 00:25:35,280
Speaker 1: that can see effects at the scale of ten to

533
00:25:35,320 --> 00:25:38,600
Speaker 1: the minus thirty five meters, which felt almost impossible.

534
00:25:38,800 --> 00:25:41,000
Speaker 4: Now, I guess, pain me a picture here of what

535
00:25:41,080 --> 00:25:43,879
Speaker 4: it is that you would be trying to do. Like,

536
00:25:43,920 --> 00:25:45,560
Speaker 4: for example, what if I just take a bunch of

537
00:25:45,680 --> 00:25:49,000
Speaker 4: hydrogen atoms. Like a hydrogen atom is just an electron

538
00:25:49,040 --> 00:25:53,040
Speaker 4: and a proton, so it's perfectly balanced in terms of charge.

539
00:25:53,080 --> 00:25:54,480
Speaker 4: And I know that if I stick a bunch of

540
00:25:54,440 --> 00:25:58,119
Speaker 4: them in a container, they'll sort of tend to fall

541
00:25:58,160 --> 00:26:00,240
Speaker 4: down because of gravity. Right, those sort of acumulate the

542
00:26:00,240 --> 00:26:02,879
Speaker 4: pressure of the hydrogen tank will be higher at the

543
00:26:02,880 --> 00:26:05,879
Speaker 4: bottom than at the top. That means gravity is working

544
00:26:05,960 --> 00:26:07,960
Speaker 4: on them and it is pulling them down. Why can't

545
00:26:07,960 --> 00:26:10,080
Speaker 4: I build some sort of model or theory that kind

546
00:26:10,080 --> 00:26:12,760
Speaker 4: of models or tells me how it's working at the

547
00:26:12,800 --> 00:26:13,440
Speaker 4: quantum level.

548
00:26:13,560 --> 00:26:17,120
Speaker 1: Well, there's the theoretical difficulty, and then there's the experimental difficulty.

549
00:26:17,480 --> 00:26:20,720
Speaker 1: On the theoretical side. Like we've tried to build those theories,

550
00:26:20,760 --> 00:26:23,879
Speaker 1: they just don't work. Gravity is complicated because everything is

551
00:26:23,880 --> 00:26:27,160
Speaker 1: affected by it. It's not like electromagnetism where you can

552
00:26:27,200 --> 00:26:32,400
Speaker 1: like shoot out photons and those photons themselves don't feel electromagnetism, right,

553
00:26:32,400 --> 00:26:36,640
Speaker 1: Photons don't interact with other photons. Gravity interacts with everything

554
00:26:36,640 --> 00:26:39,160
Speaker 1: with energy. So when you try to build a quantum

555
00:26:39,200 --> 00:26:43,160
Speaker 1: theory of gravity, like including the exchange of gravitons, those

556
00:26:43,200 --> 00:26:46,879
Speaker 1: gravitons amid other gravitons which feel those gravitons, and it

557
00:26:46,920 --> 00:26:49,639
Speaker 1: gets very hairy, very quickly. We talked once about the

558
00:26:49,920 --> 00:26:52,960
Speaker 1: strong nuclear force, which has a similar property that it's

559
00:26:53,040 --> 00:26:56,880
Speaker 1: gluons amid other gluons which affect other gluons and it's

560
00:26:57,000 --> 00:27:01,080
Speaker 1: a nightmare to do any calculations. Gravity's even more complex

561
00:27:01,200 --> 00:27:03,600
Speaker 1: than that, and that's sort of one of the reasons

562
00:27:03,640 --> 00:27:06,080
Speaker 1: why it's been so difficult to build a theory. So

563
00:27:06,119 --> 00:27:08,359
Speaker 1: anytime people build a theory of quantum gravity, it just

564
00:27:08,400 --> 00:27:12,440
Speaker 1: sort of predicts nonsense. We just can't mathematically make it work.

565
00:27:12,560 --> 00:27:15,280
Speaker 1: And then there's the experimental challenge. And what you're talking

566
00:27:15,280 --> 00:27:17,119
Speaker 1: about is like trying to build a setup where you

567
00:27:17,160 --> 00:27:21,160
Speaker 1: can see the gravitational effects on particles. But the experiment

568
00:27:21,200 --> 00:27:23,320
Speaker 1: that you describe like a bunch of hydrogen, you know,

569
00:27:23,359 --> 00:27:26,040
Speaker 1: those are classical effects. The fact that those hydrogen atoms

570
00:27:26,040 --> 00:27:28,600
Speaker 1: are quantum particles is irrelevant to the fact that they

571
00:27:28,680 --> 00:27:30,439
Speaker 1: have more pressure on the bottom of the tank than

572
00:27:30,480 --> 00:27:31,240
Speaker 1: the top of the tank.

573
00:27:31,359 --> 00:27:34,160
Speaker 4: Oh, I see, you're trying to kind of like see

574
00:27:34,160 --> 00:27:39,120
Speaker 4: what happens to gravity at the quantum distance level. Right,

575
00:27:39,160 --> 00:27:41,720
Speaker 4: that's kind of the problem, right, Like you might be

576
00:27:41,720 --> 00:27:44,800
Speaker 4: able to design a hydrogen gun something that shoots hydrogen

577
00:27:44,800 --> 00:27:48,200
Speaker 4: atoms and you can track how the gravity affects its path, maybe,

578
00:27:48,240 --> 00:27:51,160
Speaker 4: but that doesn't necessarily tell you whether or not there's

579
00:27:51,200 --> 00:27:56,280
Speaker 4: like uncertainty or whether the there's fuzziness at the you know,

580
00:27:56,640 --> 00:27:57,920
Speaker 4: really small distance.

581
00:27:57,880 --> 00:27:59,520
Speaker 1: Exactly in the same way that like every time you

582
00:27:59,560 --> 00:28:03,119
Speaker 1: toss a baseball, and principle, you're tossing quantum objects, right,

583
00:28:03,119 --> 00:28:05,480
Speaker 1: a baseball just a bunch of quantum objects, and definitely

584
00:28:05,520 --> 00:28:08,920
Speaker 1: they're feeling gravity. We're not asking like, do electrons and

585
00:28:08,960 --> 00:28:11,800
Speaker 1: protons feel gravity? We're pretty sure they do. We're asking is,

586
00:28:11,840 --> 00:28:16,280
Speaker 1: how does their quantum mechanicalness interact with their gravitational attraction?

587
00:28:16,760 --> 00:28:19,520
Speaker 1: You know, when they're doing their weird quantum stuff, how

588
00:28:19,520 --> 00:28:22,320
Speaker 1: does gravity play a role with that? You know, if

589
00:28:22,359 --> 00:28:24,359
Speaker 1: you have a particle that like has a possibility to

590
00:28:24,359 --> 00:28:28,040
Speaker 1: be here and they're simultaneously, what is its gravity? So

591
00:28:28,080 --> 00:28:30,320
Speaker 1: you've got to get something to be showing as quantum effects,

592
00:28:30,359 --> 00:28:34,720
Speaker 1: which means really small distances and revealing its gravitational interactions,

593
00:28:34,880 --> 00:28:38,440
Speaker 1: which requires really really large masses, Which is why some

594
00:28:38,480 --> 00:28:41,800
Speaker 1: people are excited to see inside black holes, because that's

595
00:28:41,800 --> 00:28:45,080
Speaker 1: where you have like really really really big masses squeeze

596
00:28:45,160 --> 00:28:48,800
Speaker 1: down to quantum distances, and so what's going on inside

597
00:28:48,800 --> 00:28:51,360
Speaker 1: a black hole would really tell us about the nature

598
00:28:51,400 --> 00:28:54,720
Speaker 1: of quantum gravity and therefore the deepest nature of space

599
00:28:54,800 --> 00:28:58,480
Speaker 1: time itself. Of course, we can't see inside black holes,

600
00:28:58,720 --> 00:29:00,440
Speaker 1: so those secrets are hidden from us.

601
00:29:01,400 --> 00:29:04,440
Speaker 4: Yeah, you might want to let that one go. It

602
00:29:04,520 --> 00:29:07,120
Speaker 4: seems like we're never going to find out what's inside

603
00:29:07,120 --> 00:29:07,840
Speaker 4: of a black hole.

604
00:29:08,080 --> 00:29:11,720
Speaker 1: There's even a theory called cosmic censorship that suggests will

605
00:29:11,760 --> 00:29:13,800
Speaker 1: never be able to answer this because the answers are

606
00:29:13,880 --> 00:29:16,840
Speaker 1: always going to be hidden behind some weird horizon. It's

607
00:29:16,840 --> 00:29:18,240
Speaker 1: sort of a pessimistic approach.

608
00:29:18,600 --> 00:29:21,440
Speaker 4: WHOA, I didn't know there was a ratings board for

609
00:29:21,480 --> 00:29:22,000
Speaker 4: the universe.

610
00:29:22,960 --> 00:29:25,200
Speaker 1: And there are even some theorists that suggests this whole

611
00:29:25,320 --> 00:29:28,040
Speaker 1: enterprise is a waste of time. Like Freeman Dyson, the

612
00:29:28,080 --> 00:29:30,320
Speaker 1: guy who thought of Dyson's fears. He likes to think

613
00:29:30,360 --> 00:29:33,920
Speaker 1: that we live in a dualistic universe, that quantum mechanics

614
00:29:33,920 --> 00:29:36,720
Speaker 1: and gravity just sort of like rule in different regimes

615
00:29:36,760 --> 00:29:39,320
Speaker 1: and they never actually overlap at any place where they

616
00:29:39,320 --> 00:29:43,120
Speaker 1: come into contact is hidden from us by these event horizons.

617
00:29:43,560 --> 00:29:47,560
Speaker 4: Like maybe gravity is classical and it's not quantum. But

618
00:29:47,880 --> 00:29:50,680
Speaker 4: you're saying, or he's saying that at the quantum level,

619
00:29:51,240 --> 00:29:53,880
Speaker 4: there's things that are happening that you will never find out.

620
00:29:54,000 --> 00:29:56,720
Speaker 1: Yeah, exactly that maybe you don't have a single theory

621
00:29:56,720 --> 00:29:59,320
Speaker 1: at the universe. You like two theories and each have

622
00:29:59,400 --> 00:30:02,360
Speaker 1: their own REGI and they never overlap anywhere we could

623
00:30:02,440 --> 00:30:04,880
Speaker 1: test them. But a lot of people don't really like

624
00:30:04,880 --> 00:30:07,720
Speaker 1: that theory. I really don't like that theory because I

625
00:30:07,760 --> 00:30:10,200
Speaker 1: want there to be one theory of the universe, one

626
00:30:10,240 --> 00:30:13,600
Speaker 1: thing that explains everything. And I'd love to see these

627
00:30:13,640 --> 00:30:16,320
Speaker 1: two different concepts battle it out. I want to force

628
00:30:16,360 --> 00:30:18,160
Speaker 1: the universe to show us what the answer is.

629
00:30:18,400 --> 00:30:21,040
Speaker 4: But I wonder couldn't they Couldn't he be right though, Like,

630
00:30:21,080 --> 00:30:24,080
Speaker 4: couldn't it just be the gravity, you know, bend space

631
00:30:24,600 --> 00:30:29,040
Speaker 4: and quantum fields and quantum particles exist in that band space.

632
00:30:29,240 --> 00:30:31,880
Speaker 1: Yeah, he could be right. But if we can come

633
00:30:31,960 --> 00:30:36,000
Speaker 1: up with some experiments that force quantum mechanics and gravity

634
00:30:36,040 --> 00:30:39,080
Speaker 1: to speak at the same moment, to say, like, all right,

635
00:30:39,440 --> 00:30:42,400
Speaker 1: here's what happens when you have a particle that has

636
00:30:42,440 --> 00:30:45,600
Speaker 1: two possibilities and it has some gravity, then we'll know.

637
00:30:45,680 --> 00:30:49,040
Speaker 1: And maybe he's right. Maybe gravity really is classical And

638
00:30:49,080 --> 00:30:52,120
Speaker 1: what happens when particles interact gravitationally is that their wave

639
00:30:52,200 --> 00:30:56,080
Speaker 1: functions collapse, because that's what happens when classical objects interact

640
00:30:56,120 --> 00:30:58,480
Speaker 1: with quantum objects. But it sure would be nice to know.

641
00:30:58,880 --> 00:31:02,200
Speaker 4: Yeah, gravity is pretty cool. So talk to us a

642
00:31:02,240 --> 00:31:05,160
Speaker 4: little bit about how we've been trying to study this

643
00:31:05,320 --> 00:31:06,680
Speaker 4: or get answers to this question.

644
00:31:06,960 --> 00:31:09,080
Speaker 1: So other than like wishing we could see inside a

645
00:31:09,080 --> 00:31:12,560
Speaker 1: black hole, the other typical tool in our toolkit is

646
00:31:12,600 --> 00:31:16,040
Speaker 1: a particle collider. You build a big particle smasher, you

647
00:31:16,080 --> 00:31:19,440
Speaker 1: pour a lot of energy into one tiny little spot.

648
00:31:19,600 --> 00:31:22,120
Speaker 1: Then you can like break open bonds, you can see

649
00:31:22,120 --> 00:31:26,120
Speaker 1: how the pieces interact. But in order to see gravitational effects,

650
00:31:26,160 --> 00:31:29,640
Speaker 1: you would need so much energy. You'd basically need like

651
00:31:29,640 --> 00:31:32,640
Speaker 1: the Plank energy. It would require building a collider that's

652
00:31:32,720 --> 00:31:35,200
Speaker 1: like the size of the galaxy in order to get

653
00:31:35,280 --> 00:31:38,160
Speaker 1: enough energy into it. Or some calculations suggest if you

654
00:31:38,160 --> 00:31:40,680
Speaker 1: build a particle collider that big, it would collapse into

655
00:31:40,720 --> 00:31:41,400
Speaker 1: a black hole.

656
00:31:41,560 --> 00:31:43,320
Speaker 4: Wait, why do you need so much energy?

657
00:31:43,400 --> 00:31:46,640
Speaker 1: Because gravity is really really weak, which means it operates

658
00:31:46,640 --> 00:31:49,640
Speaker 1: on really small distance scales. In order to get to

659
00:31:49,720 --> 00:31:52,920
Speaker 1: small distant scales, you need a lot of energy. It's

660
00:31:52,920 --> 00:31:55,280
Speaker 1: sort of like the de Burglely wavelength, right, Like the

661
00:31:55,320 --> 00:31:58,960
Speaker 1: wavelength of a particle is inversely proportional to its momentum,

662
00:31:59,120 --> 00:32:02,320
Speaker 1: and so the more momentum an object has, the smaller

663
00:32:02,400 --> 00:32:04,400
Speaker 1: its wavelength. And you want to see like really really

664
00:32:04,440 --> 00:32:08,400
Speaker 1: short distance effects, you need really really high energy probes.

665
00:32:08,840 --> 00:32:12,240
Speaker 1: So you need like super duper high energy particle collisions

666
00:32:12,360 --> 00:32:15,480
Speaker 1: in order to see things happening at really short distance scales.

667
00:32:15,680 --> 00:32:18,480
Speaker 4: Why because I guess the more energy two particles have

668
00:32:18,520 --> 00:32:20,840
Speaker 4: when they smash into each other somehow, that gives you

669
00:32:20,880 --> 00:32:22,920
Speaker 4: more resolution in space.

670
00:32:23,280 --> 00:32:26,840
Speaker 1: Yeah, exactly, The more momentum the particle has, the smaller

671
00:32:26,840 --> 00:32:29,240
Speaker 1: the wavelength of their wave function. You can think of

672
00:32:29,280 --> 00:32:31,920
Speaker 1: the motion of every particle is described by a little

673
00:32:31,960 --> 00:32:34,520
Speaker 1: wave function that determines what happens to it, the same

674
00:32:34,560 --> 00:32:36,480
Speaker 1: way you can think of like light as a wave. Right,

675
00:32:36,520 --> 00:32:40,160
Speaker 1: it's wiggling around. And if you're using light to see things,

676
00:32:40,280 --> 00:32:42,440
Speaker 1: you only really see things that are the wavelength of

677
00:32:42,440 --> 00:32:46,120
Speaker 1: that light or larger. Anything smaller than that wavelength the

678
00:32:46,120 --> 00:32:48,800
Speaker 1: photon sort of can't interact with it. And so you

679
00:32:48,800 --> 00:32:51,000
Speaker 1: want to see really really small effects, you need really

680
00:32:51,040 --> 00:32:54,640
Speaker 1: really high energy photons or in our case, we need

681
00:32:54,680 --> 00:32:57,400
Speaker 1: really really high energy particle beams to see very very

682
00:32:57,440 --> 00:32:59,040
Speaker 1: short distance interactions.

683
00:32:59,360 --> 00:33:01,600
Speaker 4: Right, Because I guess you need things with mass right

684
00:33:01,640 --> 00:33:04,960
Speaker 4: to test the quantum gravity or gravity at the quantum level.

685
00:33:05,000 --> 00:33:07,240
Speaker 4: And so that's also true for things with mass, Like

686
00:33:07,240 --> 00:33:11,000
Speaker 4: the faster they're going, the smaller they are.

687
00:33:11,480 --> 00:33:14,239
Speaker 1: Is that what you're saying, effectively, the smaller their wavelength is.

688
00:33:14,320 --> 00:33:16,440
Speaker 1: Another way to think about it is that you need

689
00:33:16,560 --> 00:33:20,400
Speaker 1: enough energy in those collisions to make gravity stronger, Like

690
00:33:20,480 --> 00:33:23,440
Speaker 1: you want to overcome the electromagnetic force and the strong

691
00:33:23,520 --> 00:33:26,920
Speaker 1: force and make gravity as powerful as those other forces

692
00:33:27,200 --> 00:33:28,960
Speaker 1: so that you can see its effects. You need to

693
00:33:29,000 --> 00:33:31,280
Speaker 1: pour a lot of energy into those collisions because the

694
00:33:31,280 --> 00:33:33,360
Speaker 1: power of gravity is linked to the mass and to

695
00:33:33,440 --> 00:33:36,200
Speaker 1: the energy of these things. So you pour enough energy

696
00:33:36,200 --> 00:33:40,040
Speaker 1: into one little location, you'll get a very strong gravitational interaction.

697
00:33:40,440 --> 00:33:42,480
Speaker 1: So if we want to see the gravitational effects on

698
00:33:42,560 --> 00:33:44,880
Speaker 1: quantum particles, you need to pour a lot of energy

699
00:33:44,920 --> 00:33:46,000
Speaker 1: into one little spot.

700
00:33:46,800 --> 00:33:48,400
Speaker 4: And is that the only way to do it through

701
00:33:48,440 --> 00:33:51,720
Speaker 4: particle colliders? Isn't there some like I don't know, like

702
00:33:51,800 --> 00:33:56,320
Speaker 4: aim your beams better approach or make smaller wavelength particles.

703
00:33:56,360 --> 00:33:58,120
Speaker 4: I don't know, Like can we do this without making

704
00:33:58,120 --> 00:33:59,560
Speaker 4: a black hole in our solar system?

705
00:34:00,040 --> 00:34:02,320
Speaker 1: Short answer is no. I mean, we do our best

706
00:34:02,360 --> 00:34:05,440
Speaker 1: with particle beam aiming already, but really the limitation is

707
00:34:05,480 --> 00:34:07,760
Speaker 1: the energy of the particles, and we have them going

708
00:34:07,800 --> 00:34:10,600
Speaker 1: as fast as we can, and the wavelength of the

709
00:34:10,600 --> 00:34:13,960
Speaker 1: particle is determined by its energy, so really sort of

710
00:34:14,000 --> 00:34:16,880
Speaker 1: at the limit there. We talked recently about other strategies

711
00:34:16,920 --> 00:34:20,240
Speaker 1: for accelerating particles that might make it smaller, faster, cheaper.

712
00:34:20,520 --> 00:34:23,919
Speaker 1: So there might be a breakthrough in accelerator technology which

713
00:34:23,960 --> 00:34:26,160
Speaker 1: could leap us up like a factor of ten or

714
00:34:26,239 --> 00:34:28,799
Speaker 1: one hundred. But we are like a factor of a

715
00:34:28,920 --> 00:34:32,320
Speaker 1: trillion away from being able to test quantum gravity in

716
00:34:32,400 --> 00:34:35,200
Speaker 1: particle colliders. So really, nowhere in the near future will

717
00:34:35,200 --> 00:34:37,160
Speaker 1: particle colliders be able to answer this question.

718
00:34:37,440 --> 00:34:39,719
Speaker 4: All right, Well, I think part of what we're going

719
00:34:39,760 --> 00:34:42,440
Speaker 4: to be talking about here today are experiments that have

720
00:34:42,960 --> 00:34:45,600
Speaker 4: kind of ideas about how to test this without destroying

721
00:34:45,640 --> 00:34:50,520
Speaker 4: the Solar system. And they involve diamonds and lasers and

722
00:34:50,640 --> 00:34:51,480
Speaker 4: space lasers.

723
00:34:52,080 --> 00:34:57,440
Speaker 1: No tabletop lasers in space. No, no tabletop lasers in Pasadena.

724
00:34:57,600 --> 00:35:01,520
Speaker 4: Oh that take up space in Pasadena a table near you?

725
00:35:01,880 --> 00:35:04,080
Speaker 4: All right, well, if it's stay into it, Daniel, What

726
00:35:04,160 --> 00:35:05,560
Speaker 4: is the first of these experiments?

727
00:35:05,680 --> 00:35:08,880
Speaker 1: So the first of the experiments involves falling diamonds, and

728
00:35:08,920 --> 00:35:12,440
Speaker 1: the goal here essentially is to create a situation where

729
00:35:12,480 --> 00:35:16,120
Speaker 1: a particle has the probability of being in two places

730
00:35:16,160 --> 00:35:19,160
Speaker 1: at once, and then you test its gravity. You see

731
00:35:19,160 --> 00:35:21,800
Speaker 1: if it's gravity really is sort of like split between

732
00:35:21,800 --> 00:35:25,160
Speaker 1: its two possible locations, or if when you probe it

733
00:35:25,200 --> 00:35:29,240
Speaker 1: with gravity, it somehow collapses into just having one possible location.

734
00:35:29,320 --> 00:35:32,000
Speaker 1: Because remember this, quantum particles can do this weird thing.

735
00:35:32,040 --> 00:35:34,319
Speaker 1: They can be in a superposition, like if there's two

736
00:35:34,360 --> 00:35:37,600
Speaker 1: possibilities for an electron, it doesn't have to choose A

737
00:35:37,880 --> 00:35:42,040
Speaker 1: or B. It can maintain both possibilities until something interacts

738
00:35:42,080 --> 00:35:45,000
Speaker 1: with it classically, which forces it to choose. That's the

739
00:35:45,040 --> 00:35:48,200
Speaker 1: weird thing about quantum mechanics and something we don't understand.

740
00:35:48,360 --> 00:35:50,759
Speaker 1: So this is very hard, of course, because particles are

741
00:35:50,800 --> 00:35:53,160
Speaker 1: very small and they're very delicate. But they've come up

742
00:35:53,160 --> 00:35:55,719
Speaker 1: with a clever way that they think might be possible,

743
00:35:55,800 --> 00:35:59,719
Speaker 1: and it involves electrons embedded in falling diamonds.

744
00:36:00,120 --> 00:36:02,360
Speaker 4: Sounds like a rap video where there's like money and

745
00:36:02,440 --> 00:36:05,719
Speaker 4: diamonds falling from the sky. Break it down for a

746
00:36:05,760 --> 00:36:07,200
Speaker 4: How does his experiment work?

747
00:36:07,280 --> 00:36:09,160
Speaker 1: So what you do is you take a very tiny

748
00:36:09,239 --> 00:36:12,239
Speaker 1: diamond and has a nitrogen ated inside of it, like

749
00:36:12,360 --> 00:36:16,000
Speaker 1: embedded inside the diamond, and this has a cool property,

750
00:36:16,120 --> 00:36:18,320
Speaker 1: which is that if you zap it with a laser,

751
00:36:18,400 --> 00:36:21,279
Speaker 1: the electrons have a probability to absorb that photon, which

752
00:36:21,280 --> 00:36:23,319
Speaker 1: case they flip their spin to be up, or to

753
00:36:23,440 --> 00:36:26,240
Speaker 1: ignore that photon and flip their spin to be down.

754
00:36:26,840 --> 00:36:29,279
Speaker 1: So you shoot a laser at this diamond, and now

755
00:36:29,280 --> 00:36:32,960
Speaker 1: it's in a quantum superposition of two possibilities. Maybe the

756
00:36:33,000 --> 00:36:35,840
Speaker 1: electron inside there on the nitrogen is spin up, and

757
00:36:35,920 --> 00:36:38,759
Speaker 1: maybe it's spin down. So you have your particle now

758
00:36:38,800 --> 00:36:41,400
Speaker 1: in a quantum superposition. But what you need is for

759
00:36:41,440 --> 00:36:44,080
Speaker 1: it to be in a quantum superposition of two locations

760
00:36:44,160 --> 00:36:46,440
Speaker 1: rather than two spins. So then you pass it to

761
00:36:46,560 --> 00:36:49,960
Speaker 1: a little magnetic field. The magnetic field will push it

762
00:36:50,080 --> 00:36:52,440
Speaker 1: left or right based on the spin. So you have

763
00:36:52,480 --> 00:36:55,560
Speaker 1: this falling diamond which passes through a magnetic field and

764
00:36:55,560 --> 00:36:58,000
Speaker 1: it either moves left or it moves right. Now, if

765
00:36:58,040 --> 00:37:01,360
Speaker 1: it's in a quantum superposition, then has both possibilities to

766
00:37:01,400 --> 00:37:04,800
Speaker 1: move left and to move right. So now it's location

767
00:37:05,320 --> 00:37:08,359
Speaker 1: depends on this quantumness. Now you do the same thing

768
00:37:08,400 --> 00:37:11,600
Speaker 1: for another diamond nearby. Now you have this pair of

769
00:37:11,680 --> 00:37:14,680
Speaker 1: falling diamonds, each of which has the possibility to be

770
00:37:15,000 --> 00:37:18,640
Speaker 1: in two slightly different locations, and you see how they interact.

771
00:37:18,760 --> 00:37:21,839
Speaker 1: Do the possibilities for one diamond interact with the possibilities

772
00:37:21,840 --> 00:37:24,120
Speaker 1: for the other diamond, or do the two diamonds like

773
00:37:24,160 --> 00:37:26,000
Speaker 1: collapse each other's wave functions?

774
00:37:26,560 --> 00:37:28,919
Speaker 4: I see. So you embed a little nitrogen atom into

775
00:37:28,960 --> 00:37:32,800
Speaker 4: the diamond ezacly with a laser, and now the nirogen

776
00:37:32,880 --> 00:37:36,400
Speaker 4: atom has quantumn certainty, which kind of extends to the

777
00:37:36,440 --> 00:37:39,080
Speaker 4: whole diamond. Is basically what you're saying, right like if

778
00:37:39,080 --> 00:37:42,880
Speaker 4: I don't know, there's quantum certainty about the electron into nitrogen,

779
00:37:42,920 --> 00:37:45,440
Speaker 4: and that means there's quantum certainty about the whole diamond,

780
00:37:45,719 --> 00:37:48,360
Speaker 4: because it could be swinging right or left. And now

781
00:37:48,520 --> 00:37:51,040
Speaker 4: if you put two of them together really close, they

782
00:37:51,040 --> 00:37:53,719
Speaker 4: should interact with gravity. And so now you have the

783
00:37:53,760 --> 00:37:57,800
Speaker 4: system where you have two quantum objects interacting with gravity exactly.

784
00:37:57,840 --> 00:38:00,160
Speaker 1: And they have some really clever mathematical way to tell

785
00:38:00,200 --> 00:38:03,399
Speaker 1: if the two diamonds interacted in a quantum way or

786
00:38:03,440 --> 00:38:06,360
Speaker 1: if the two diamonds interacted in a classical way, like

787
00:38:06,400 --> 00:38:09,280
Speaker 1: if they interacted in a quantum way, when you measure

788
00:38:09,360 --> 00:38:12,359
Speaker 1: the spins of those electrons after they fall far enough

789
00:38:12,360 --> 00:38:15,520
Speaker 1: in your experiment, they'll have some cool correlation to them,

790
00:38:15,680 --> 00:38:18,279
Speaker 1: and if they interacted in a classical way, then they'll

791
00:38:18,320 --> 00:38:20,879
Speaker 1: be uncorrelated, like whether they're spin up or down will

792
00:38:20,920 --> 00:38:23,360
Speaker 1: just be random. And so because of the weird rules

793
00:38:23,360 --> 00:38:26,680
Speaker 1: of quantum mechanics, you can tell whether quantum mechanics has

794
00:38:26,760 --> 00:38:29,800
Speaker 1: been at play in the gravitational interaction, Like did gravity

795
00:38:30,080 --> 00:38:32,319
Speaker 1: cancel out the quantum mechanic effects because it's really just

796
00:38:32,360 --> 00:38:36,359
Speaker 1: a classical force, or did it allow the quantum uncertainty

797
00:38:36,640 --> 00:38:39,800
Speaker 1: to be maintained, meaning that gravity would be a quantum

798
00:38:40,000 --> 00:38:42,440
Speaker 1: mechanical effect not a classical effect.

799
00:38:42,640 --> 00:38:46,320
Speaker 4: Well, I guess quantum mechanics aside. Can you measure gravity

800
00:38:46,360 --> 00:38:48,880
Speaker 4: the force of gravity by just dropping two diamonds together

801
00:38:49,000 --> 00:38:51,440
Speaker 4: and seeing if they attract each other? Is that like

802
00:38:51,480 --> 00:38:52,400
Speaker 4: a real thing you can do.

803
00:38:52,560 --> 00:38:54,600
Speaker 1: It's a real thing you can try to do. That's

804
00:38:54,719 --> 00:38:59,360
Speaker 1: very very difficult because little diamonds have very very gentle gravity,

805
00:38:59,400 --> 00:39:01,040
Speaker 1: and so this is it's not something we think we

806
00:39:01,120 --> 00:39:03,880
Speaker 1: can do today. There's a group in the UK that

807
00:39:04,040 --> 00:39:05,680
Speaker 1: thinks that they can figure out how to do this,

808
00:39:05,760 --> 00:39:09,440
Speaker 1: and there's lots of complicated steps involved, and they're hoping

809
00:39:09,480 --> 00:39:12,360
Speaker 1: to maybe pull this off sometime in the next ten years.

810
00:39:13,000 --> 00:39:16,000
Speaker 1: But there's a lot of really complicated moving parts involvement

811
00:39:16,040 --> 00:39:19,200
Speaker 1: getting the nitrogen inside the diamond, flipping its spin with

812
00:39:19,239 --> 00:39:22,319
Speaker 1: a laser beam, getting two pairs of diamonds to fall

813
00:39:22,360 --> 00:39:25,120
Speaker 1: simultaneously close enough each other that maybe they have a

814
00:39:25,120 --> 00:39:28,120
Speaker 1: gravitational interaction. Now you don't actually have to see any

815
00:39:28,200 --> 00:39:31,359
Speaker 1: sort of like gravitational pull. You're not measuring like how

816
00:39:31,400 --> 00:39:34,239
Speaker 1: far did the diamond move because of gravity. You're just

817
00:39:34,280 --> 00:39:37,480
Speaker 1: bringing them close enough together that you think gravity is

818
00:39:37,520 --> 00:39:40,000
Speaker 1: at play. That gravity like wakes up and says, ooh,

819
00:39:40,160 --> 00:39:42,160
Speaker 1: there's something going on here. You don't have to measure

820
00:39:42,280 --> 00:39:44,960
Speaker 1: the gravity. You just have to see if gravity messes

821
00:39:45,040 --> 00:39:46,719
Speaker 1: up the quantum state. I see.

822
00:39:46,760 --> 00:39:48,800
Speaker 4: But to measure the quantum state at the end, wouldn't

823
00:39:48,840 --> 00:39:51,799
Speaker 4: you be doing something like measuring that whether or not

824
00:39:51,880 --> 00:39:55,200
Speaker 4: the two diamonds were attracted to each other gravitationally or not.

825
00:39:55,560 --> 00:39:57,680
Speaker 1: No, all you need to do is measure the spins

826
00:39:57,719 --> 00:40:01,680
Speaker 1: of those electrons embedded inside the nitrogen atoms in the diamonds.

827
00:40:01,800 --> 00:40:04,360
Speaker 1: You don't see the gravitational effects directly. It's sort of

828
00:40:04,360 --> 00:40:06,080
Speaker 1: like in the double slit experiment when you add a

829
00:40:06,120 --> 00:40:09,799
Speaker 1: detector and that ruins the interference. We're adding gravity to

830
00:40:09,880 --> 00:40:12,839
Speaker 1: a quantum interaction and seeing if it ruins the interference

831
00:40:12,960 --> 00:40:13,200
Speaker 1: or not.

832
00:40:14,280 --> 00:40:18,640
Speaker 4: But would that necessarily tell you anything about quantum gravity

833
00:40:18,719 --> 00:40:19,759
Speaker 4: or gravitons.

834
00:40:19,800 --> 00:40:21,520
Speaker 1: It wouldn't tell you that much, but it would be

835
00:40:21,520 --> 00:40:24,239
Speaker 1: a powerful clue. It would tell you if gravity is

836
00:40:24,320 --> 00:40:28,640
Speaker 1: classical or quantum mechanical. Like, if gravity is classical, it'll

837
00:40:28,640 --> 00:40:31,320
Speaker 1: act like a detector and it'll collapse those wave functions

838
00:40:31,320 --> 00:40:35,000
Speaker 1: and destroy this interference. If gravity is quantum mechanical, it won't,

839
00:40:35,040 --> 00:40:37,800
Speaker 1: and everything quantum mechanical will stay quantum mechanical, and you

840
00:40:37,840 --> 00:40:40,520
Speaker 1: get all sorts of weird interference. So that just tells

841
00:40:40,520 --> 00:40:43,400
Speaker 1: you if gravity is classical or quantum mechanical. It doesn't

842
00:40:43,440 --> 00:40:45,920
Speaker 1: tell you like, oh, space is quantized, or oh there

843
00:40:45,960 --> 00:40:49,040
Speaker 1: are gravitons. It doesn't tell you which theory of quantum gravity.

844
00:40:49,320 --> 00:40:51,520
Speaker 1: But it is a powerful clue. It would mean, for example,

845
00:40:51,560 --> 00:40:54,400
Speaker 1: if we know gravity is quantum mechanical, the Freeman Dyson

846
00:40:54,520 --> 00:40:58,200
Speaker 1: is wrong about classical gravity and quantum mechanics being able

847
00:40:58,200 --> 00:40:58,880
Speaker 1: to play together.

848
00:41:00,360 --> 00:41:02,120
Speaker 4: Yeah, he could be wrong, in which case he might

849
00:41:02,160 --> 00:41:06,560
Speaker 4: need to stick to making vacuum cleans. All right, Well,

850
00:41:07,239 --> 00:41:09,960
Speaker 4: that's one experiment, and I guess it's in progress. I

851
00:41:10,000 --> 00:41:12,319
Speaker 4: guess they're designing it or making it. Where are they

852
00:41:12,360 --> 00:41:12,640
Speaker 4: with that?

853
00:41:12,880 --> 00:41:15,959
Speaker 1: This physicist at University College London who's leading a team

854
00:41:16,000 --> 00:41:18,680
Speaker 1: of researchers who are trying to make this work, and

855
00:41:18,800 --> 00:41:21,520
Speaker 1: there's folks in Santa Barbara as well, and they're trying

856
00:41:21,520 --> 00:41:22,839
Speaker 1: to work on this. But you know, there's a lot

857
00:41:22,880 --> 00:41:25,840
Speaker 1: of complicated steps and making this thing do its stance

858
00:41:25,880 --> 00:41:28,080
Speaker 1: and being sure you know, what they're doing is a

859
00:41:28,120 --> 00:41:31,879
Speaker 1: lot of pieces involved, lots of complicated experimental cleverness really

860
00:41:31,920 --> 00:41:34,600
Speaker 1: required just to be able to do this test. So

861
00:41:34,640 --> 00:41:36,680
Speaker 1: they're hoping sometime in the next ten years to be

862
00:41:36,719 --> 00:41:37,600
Speaker 1: able to pull this off.

863
00:41:37,719 --> 00:41:39,600
Speaker 4: All right, Well, let's get to the second of these

864
00:41:39,640 --> 00:41:43,120
Speaker 4: potential experiments to measure quantum gravity. We'll dig into that,

865
00:41:43,200 --> 00:41:45,160
Speaker 4: but first let's take another quick break.

866
00:41:49,320 --> 00:41:51,080
Speaker 1: When you pop a piece of cheese into your mouth,

867
00:41:51,200 --> 00:41:54,360
Speaker 1: or enjoy a rich spoonful of Greek yogurt, you're probably

868
00:41:54,400 --> 00:41:58,440
Speaker 1: not thinking about the environmental impact of each and every bite.

869
00:41:58,480 --> 00:42:01,279
Speaker 1: But the people in the dairy industry. US Dairy has

870
00:42:01,280 --> 00:42:05,720
Speaker 1: set themselves some ambitious sustainability goals, including being greenhouse gas

871
00:42:05,760 --> 00:42:08,279
Speaker 1: neutral by twenty to fifty. That's why they're working hard

872
00:42:08,360 --> 00:42:10,840
Speaker 1: every day to find new ways to reduce waste, conserve

873
00:42:10,920 --> 00:42:14,680
Speaker 1: natural resources, and drive down greenhouse gas emissions. Take water,

874
00:42:14,719 --> 00:42:18,320
Speaker 1: for example, most dairy farms reuse water up to four times.

875
00:42:18,360 --> 00:42:21,760
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916
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Speaker 4: All right, we're talking about quantum gravity and whether or

917
00:44:48,560 --> 00:44:52,600
Speaker 4: not it's a thing, whether gravity is quantum mechanical or

918
00:44:52,960 --> 00:44:56,520
Speaker 4: is it pretty class and classical and doesn't care about

919
00:44:56,600 --> 00:45:00,920
Speaker 4: quantum mechanics and this weirdness of things be uncertain, And

920
00:45:01,000 --> 00:45:03,560
Speaker 4: so we talked about one possible experiment that it might

921
00:45:03,640 --> 00:45:07,200
Speaker 4: look at that using falling diamonds. And there's another interesting

922
00:45:07,480 --> 00:45:10,400
Speaker 4: potential experiments happening also, right.

923
00:45:10,320 --> 00:45:12,840
Speaker 1: That's right, And this one is being developed and built

924
00:45:12,920 --> 00:45:13,480
Speaker 1: in your.

925
00:45:13,360 --> 00:45:15,600
Speaker 4: Backyard, like literally my backyard.

926
00:45:16,239 --> 00:45:17,080
Speaker 1: Look at your window.

927
00:45:17,120 --> 00:45:17,279
Speaker 5: Man.

928
00:45:17,440 --> 00:45:20,600
Speaker 1: You ever wonder what those people want? Told you what? No,

929
00:45:20,840 --> 00:45:23,440
Speaker 1: it's at cal Tech. Both the theorists and the experimental

930
00:45:23,440 --> 00:45:26,800
Speaker 1: list are at Caltech and it's a really cool idea

931
00:45:26,960 --> 00:45:29,399
Speaker 1: and what they're trying to do in this experiment, it's

932
00:45:29,440 --> 00:45:32,120
Speaker 1: completely different from the other one, is try to see

933
00:45:32,160 --> 00:45:36,120
Speaker 1: if space itself is quantum mechanical. Like, if gravity is

934
00:45:36,160 --> 00:45:39,840
Speaker 1: quant mechanical and there are gravitons, then that would mean

935
00:45:39,920 --> 00:45:42,840
Speaker 1: that graviton should be like popping out of the vacuum

936
00:45:42,920 --> 00:45:45,919
Speaker 1: all the time, the same way that other quantum particles are.

937
00:45:46,160 --> 00:45:48,240
Speaker 1: Like if you go out into the middle of empty space,

938
00:45:48,280 --> 00:45:51,160
Speaker 1: there's nothing there, there's still always a little bit of

939
00:45:51,320 --> 00:45:54,239
Speaker 1: energy in the quantum fields, which means that like those

940
00:45:54,239 --> 00:45:57,120
Speaker 1: fields can turn into particles briefly and then back into

941
00:45:57,160 --> 00:46:01,160
Speaker 1: potential energy. So if space itself is quantum mechanical, if

942
00:46:01,200 --> 00:46:05,320
Speaker 1: gravity is quantum mechanical, then gravitons should also be popping

943
00:46:05,360 --> 00:46:08,200
Speaker 1: out of the vacuum. There should be like effectively tiny

944
00:46:08,360 --> 00:46:13,560
Speaker 1: little ripples in space making quantum size gravitational waves.

945
00:46:14,280 --> 00:46:16,759
Speaker 4: WHOA wait, I think you just confused me a little bit.

946
00:46:16,800 --> 00:46:19,040
Speaker 4: So I thought there were two possibilities. Either gravity is

947
00:46:19,080 --> 00:46:23,080
Speaker 4: quantum mechanical or space is quantized. Which one are you

948
00:46:23,120 --> 00:46:23,799
Speaker 4: talking about here?

949
00:46:23,880 --> 00:46:26,719
Speaker 1: Here we're talking about gravity being quantum mechanical, that there

950
00:46:26,760 --> 00:46:30,560
Speaker 1: exists gravitons which mediate the force of gravity, which in

951
00:46:30,560 --> 00:46:33,399
Speaker 1: this theory would be a quantum force like the other

952
00:46:33,480 --> 00:46:34,680
Speaker 1: forces in the universe.

953
00:46:34,960 --> 00:46:37,720
Speaker 4: Okay, so we're not talking about quantizing space itself.

954
00:46:37,920 --> 00:46:40,400
Speaker 1: That's right. We're not talking about quantizing space and like

955
00:46:40,400 --> 00:46:43,400
Speaker 1: a space foam, but we're talking about space being filled

956
00:46:43,400 --> 00:46:46,480
Speaker 1: with a quantum force of gravity, which would have fluctuations

957
00:46:46,520 --> 00:46:49,920
Speaker 1: in it, right, And those fluctuations would be like quantum

958
00:46:50,000 --> 00:46:54,320
Speaker 1: gravitons popping in and out of the quantum gravitational field.

959
00:46:55,400 --> 00:46:57,600
Speaker 4: I see. So anything that is quantum or has a

960
00:46:57,640 --> 00:47:00,920
Speaker 4: quantum field by its nature, by its kind of statistical

961
00:47:01,000 --> 00:47:04,880
Speaker 4: random nature, has these particles popping out of nothingness. But

962
00:47:04,920 --> 00:47:06,960
Speaker 4: doesn't it need some sort of like energy to it.

963
00:47:06,960 --> 00:47:09,719
Speaker 1: It does, but quantum fields always have energy to them.

964
00:47:09,719 --> 00:47:13,360
Speaker 1: They can never relax down to zero because the uncertainty principle,

965
00:47:13,560 --> 00:47:16,120
Speaker 1: the minimum energy level of a quantum field is always

966
00:47:16,200 --> 00:47:19,120
Speaker 1: above zero energy, which is why there's always energy in

967
00:47:19,200 --> 00:47:21,600
Speaker 1: quantum fields, which is why there's energy in all of

968
00:47:21,719 --> 00:47:23,560
Speaker 1: space because of this quantum nature.

969
00:47:23,680 --> 00:47:25,880
Speaker 4: Well, that's kind of an odd idea, Like what happens

970
00:47:25,920 --> 00:47:28,440
Speaker 4: if a graviton appears out of nothingness, well.

971
00:47:28,320 --> 00:47:31,360
Speaker 1: Mostly almost nothing, because gravitons would be super duper tiny.

972
00:47:31,520 --> 00:47:34,359
Speaker 1: Gravity is super duper weak, and so it would be

973
00:47:34,520 --> 00:47:37,279
Speaker 1: basically impossible to see these things. What have effects on

974
00:47:37,360 --> 00:47:40,640
Speaker 1: super tiny distance scales we typically can't probe. But a

975
00:47:40,719 --> 00:47:44,280
Speaker 1: theorist at Caltech, Catherine Zurich, came up with this idea

976
00:47:44,320 --> 00:47:47,840
Speaker 1: that maybe gravitons can all work together. Instead of just

977
00:47:47,880 --> 00:47:50,680
Speaker 1: looking for one graviton, maybe she can look for like

978
00:47:50,840 --> 00:47:53,680
Speaker 1: larger effects of graviton, sort of working together to make

979
00:47:53,719 --> 00:47:58,080
Speaker 1: something else emerge from this quantum craziness. And she designed

980
00:47:58,120 --> 00:48:00,480
Speaker 1: an experiment to maybe see that. Hmm.

981
00:48:00,920 --> 00:48:05,120
Speaker 4: Interesting. Well, we actually have an interview of Daniel talking

982
00:48:05,160 --> 00:48:08,560
Speaker 4: with professor Catherine Zurich from cal Tech about her idea

983
00:48:08,680 --> 00:48:09,600
Speaker 4: for this experiment.

984
00:48:09,680 --> 00:48:11,359
Speaker 1: That's right. Kathy and I have known each other since

985
00:48:11,360 --> 00:48:13,120
Speaker 1: we were postos, and so I called her up and

986
00:48:13,160 --> 00:48:16,000
Speaker 1: asked her about her crazy idea to not build a

987
00:48:16,000 --> 00:48:17,120
Speaker 1: black hole in Pasadena.

988
00:48:17,200 --> 00:48:18,759
Speaker 4: I feel like it's a little says. You had to

989
00:48:18,800 --> 00:48:22,360
Speaker 4: throw that disclaimer in there. It's like, what are you

990
00:48:22,360 --> 00:48:26,279
Speaker 4: guys doing? I am not destroying your town if that's

991
00:48:26,280 --> 00:48:29,759
Speaker 4: what you're asking. First of all, let's get that clear.

992
00:48:30,040 --> 00:48:31,600
Speaker 1: That didn't make you feel any better.

993
00:48:32,320 --> 00:48:36,399
Speaker 4: Nobody asked I wasn't something I was concerned about before, all.

994
00:48:36,360 --> 00:48:38,680
Speaker 1: Right, in that case, I'm also not testing any nuclear

995
00:48:38,719 --> 00:48:39,680
Speaker 1: weapons in Pasadena.

996
00:48:39,880 --> 00:48:42,520
Speaker 4: Oh good, thank you? What else are you not doing

997
00:48:42,520 --> 00:48:47,040
Speaker 4: in Pasadena? Let's go down the list. All right, Well,

998
00:48:47,040 --> 00:48:50,480
Speaker 4: here is Daniel's interview with Professor Catherine Zurich from cal Tech.

999
00:48:50,760 --> 00:48:54,400
Speaker 1: All right, so it's my pleasure to welcome Professor Katherin

1000
00:48:54,520 --> 00:48:57,320
Speaker 1: Zurich the podcast. Thank you very much for chatting with us.

1001
00:48:57,560 --> 00:48:59,040
Speaker 8: It's my pleasure to join you.

1002
00:48:59,400 --> 00:49:02,400
Speaker 1: So help me stand first of all, how it's possible

1003
00:49:02,560 --> 00:49:06,240
Speaker 1: at all to see effects of quantum gravity. We understood

1004
00:49:06,239 --> 00:49:07,880
Speaker 1: for a long time that these things were just on

1005
00:49:07,920 --> 00:49:10,720
Speaker 1: the plank scale. How do they sort of work together

1006
00:49:10,800 --> 00:49:14,280
Speaker 1: to emerge to some signal we can see experimentally.

1007
00:49:14,560 --> 00:49:17,280
Speaker 8: So it's just like smoke. So if you ask yourself

1008
00:49:17,280 --> 00:49:22,279
Speaker 8: the question how to smoke spread? So there are interactions

1009
00:49:22,320 --> 00:49:25,880
Speaker 8: of molecules on very short distance scales, much shorter than

1010
00:49:25,920 --> 00:49:28,279
Speaker 8: what we can observe, and yet you can see the

1011
00:49:28,320 --> 00:49:33,319
Speaker 8: effects of those short distance interactions simply by waiting a

1012
00:49:33,360 --> 00:49:39,640
Speaker 8: while for the effects of those short range interactions to

1013
00:49:39,680 --> 00:49:45,839
Speaker 8: accumulate over time. So that's a physical analogy for what

1014
00:49:45,840 --> 00:49:50,360
Speaker 8: we're interested in doing. So we have these quantum fluctuations

1015
00:49:50,400 --> 00:49:53,480
Speaker 8: on very short distance scales. So in this case, it's

1016
00:49:53,520 --> 00:49:55,520
Speaker 8: the plank length, which is about ten to the minus

1017
00:49:55,560 --> 00:50:01,320
Speaker 8: thirty five meters. And the idea is that if those

1018
00:50:01,719 --> 00:50:08,719
Speaker 8: quantum fluctuations accumulate over long times, then we can observe them.

1019
00:50:09,040 --> 00:50:12,200
Speaker 8: They're still very small, but we can observe them then

1020
00:50:12,320 --> 00:50:16,360
Speaker 8: with sufficiently precise instruments.

1021
00:50:16,719 --> 00:50:20,080
Speaker 1: So what makes quantum fluctuations add up to make a

1022
00:50:20,160 --> 00:50:24,520
Speaker 1: microscopic effect and what makes them not because sometimes they don't. Right,

1023
00:50:24,600 --> 00:50:26,360
Speaker 1: you have like a bunch of electrons in a baseball,

1024
00:50:26,440 --> 00:50:29,120
Speaker 1: they have all such fluctuations, those average out to nothing.

1025
00:50:29,160 --> 00:50:32,520
Speaker 1: You can see what makes these guys add up over

1026
00:50:32,920 --> 00:50:34,120
Speaker 1: longer distance scales.

1027
00:50:34,320 --> 00:50:38,360
Speaker 8: So it's really the fact that you're losing information. Any

1028
00:50:38,600 --> 00:50:43,480
Speaker 8: measurement that you make is over a finite time. So

1029
00:50:43,840 --> 00:50:45,960
Speaker 8: you know, I turn on my instrument. Let's say it's

1030
00:50:46,000 --> 00:50:49,879
Speaker 8: in an intraferometer, and the light goes out, it comes back,

1031
00:50:49,920 --> 00:50:52,279
Speaker 8: and I make a measurement of it. And so what

1032
00:50:52,320 --> 00:50:55,160
Speaker 8: it does. What an instrument does is it defines what

1033
00:50:55,200 --> 00:50:58,000
Speaker 8: we call a horizon. So there's a region of the

1034
00:50:58,040 --> 00:50:59,880
Speaker 8: space time that I measure and there's a region of

1035
00:50:59,880 --> 00:51:02,600
Speaker 8: the space time that I don't, And so that leads

1036
00:51:02,680 --> 00:51:08,080
Speaker 8: to a quantum mismeasurement effect that accumulates over time. So

1037
00:51:08,120 --> 00:51:12,040
Speaker 8: You're absolutely right that, you know, normal systems, where we

1038
00:51:12,120 --> 00:51:16,680
Speaker 8: can confine all of our information to a particular region,

1039
00:51:17,040 --> 00:51:20,000
Speaker 8: there's no information that's going to accumulate over time. But

1040
00:51:20,080 --> 00:51:24,560
Speaker 8: in this case, we can't actually confine quantum fluctuations. There's

1041
00:51:24,560 --> 00:51:26,800
Speaker 8: just part of the space time that we can't measure.

1042
00:51:27,080 --> 00:51:31,680
Speaker 8: And so what we're doing now is quantifying how much

1043
00:51:31,840 --> 00:51:36,120
Speaker 8: of that information is lost over the period of time

1044
00:51:36,160 --> 00:51:37,760
Speaker 8: that I make that measurement.

1045
00:51:37,680 --> 00:51:41,200
Speaker 1: Very cool, and so what kind of models of quantum

1046
00:51:41,239 --> 00:51:44,239
Speaker 1: space time is as sensitive to generally any kind of

1047
00:51:44,360 --> 00:51:48,400
Speaker 1: model where space time has quantum fluctuations or only specific

1048
00:51:48,440 --> 00:51:50,000
Speaker 1: sort of kinds of ideas.

1049
00:51:50,320 --> 00:51:54,920
Speaker 8: So what we're trying to show is that this effect

1050
00:51:55,280 --> 00:52:05,239
Speaker 8: occurs very generally the space of theoretical ideas that people explore,

1051
00:52:05,920 --> 00:52:10,239
Speaker 8: you know, commonly. So what do I mean by that exactly?

1052
00:52:10,560 --> 00:52:14,319
Speaker 8: So we're still trying to understand a precisely what are

1053
00:52:14,320 --> 00:52:18,239
Speaker 8: the minimal sets of requirements that you need. At minimum,

1054
00:52:18,440 --> 00:52:22,200
Speaker 8: we need quantum fluctuations at the plank scale, so that

1055
00:52:22,280 --> 00:52:28,439
Speaker 8: has to be there, and those quantum fluctuations have to

1056
00:52:28,480 --> 00:52:32,960
Speaker 8: accumulate into the infrared. And there are various ways that

1057
00:52:33,000 --> 00:52:35,480
Speaker 8: we can see that we can see it actually coming

1058
00:52:35,520 --> 00:52:38,680
Speaker 8: out in a quite broad range of theories where we

1059
00:52:38,719 --> 00:52:42,160
Speaker 8: can just write down some general properties of the theory

1060
00:52:42,760 --> 00:52:44,840
Speaker 8: and then crank through it and we see this effect

1061
00:52:44,920 --> 00:52:48,600
Speaker 8: come out. So we think it's pretty generic.

1062
00:52:48,800 --> 00:52:52,520
Speaker 1: Wonderful, And so why can't existing in a pometers like LEGO,

1063
00:52:52,560 --> 00:52:55,280
Speaker 1: which is already very very precise, why can't it see

1064
00:52:55,440 --> 00:52:57,120
Speaker 1: signatures of this quantum fluctuation.

1065
00:52:57,600 --> 00:52:59,959
Speaker 8: So we actually think that LEGO is not very far

1066
00:53:00,080 --> 00:53:02,440
Speaker 8: from being able to see it. But one of the

1067
00:53:02,480 --> 00:53:06,400
Speaker 8: reasons why LIGO is not optimally sensitive to this signal

1068
00:53:06,760 --> 00:53:12,399
Speaker 8: is because they recycle their light by which I mean

1069
00:53:12,960 --> 00:53:16,120
Speaker 8: the light beam goes out and it comes back, and

1070
00:53:16,160 --> 00:53:19,080
Speaker 8: they don't make a measurement of it after one round trick.

1071
00:53:19,440 --> 00:53:22,240
Speaker 8: It actually goes out and comes back many times before

1072
00:53:22,280 --> 00:53:25,200
Speaker 8: they make a measurement of it. And so for the

1073
00:53:25,280 --> 00:53:29,160
Speaker 8: signals that they're interested in, which come from you know,

1074
00:53:29,239 --> 00:53:33,080
Speaker 8: let's say black holes merging, that's fine because there's a

1075
00:53:33,080 --> 00:53:36,920
Speaker 8: classical source that generates a wave at some frequency. And

1076
00:53:37,080 --> 00:53:40,719
Speaker 8: this case, we're also interested in gravitational waves, but they're

1077
00:53:40,760 --> 00:53:45,840
Speaker 8: gravitational waves that come from the vacuum fluctuating, and they're uncorrelated.

1078
00:53:46,200 --> 00:53:50,080
Speaker 8: If I measured the system over time scales that are

1079
00:53:50,120 --> 00:53:52,799
Speaker 8: long in comparison to the light crossing time. So the

1080
00:53:52,840 --> 00:53:56,400
Speaker 8: fact that ligo weights and their beam goes out and

1081
00:53:56,480 --> 00:53:59,279
Speaker 8: comes back many times before they measure it means that

1082
00:53:59,280 --> 00:54:01,880
Speaker 8: they're actually average down their signal, and so they have

1083
00:54:01,960 --> 00:54:05,440
Speaker 8: a reduced sensitivity to it in comparison to if they

1084
00:54:05,480 --> 00:54:08,200
Speaker 8: had this same that they could measure the same space

1085
00:54:08,239 --> 00:54:10,840
Speaker 8: time fluctuation. But they did it after the light just

1086
00:54:10,880 --> 00:54:13,960
Speaker 8: went out and came back. Then we claim that you

1087
00:54:13,960 --> 00:54:15,200
Speaker 8: can actually see this signal.

1088
00:54:15,360 --> 00:54:18,719
Speaker 1: Do these space time fluctuations look different from a gravitational

1089
00:54:18,760 --> 00:54:21,000
Speaker 1: way you would get from black hole collisions for example?

1090
00:54:21,360 --> 00:54:24,200
Speaker 8: Yeah, they do. So one thing that's different about this

1091
00:54:24,280 --> 00:54:27,040
Speaker 8: signal in comparison to what you would get from let's say,

1092
00:54:27,040 --> 00:54:29,920
Speaker 8: black hole mergers is in that case, the signal is

1093
00:54:29,920 --> 00:54:33,040
Speaker 8: the signal. It doesn't depend on my measuring apparatus. If

1094
00:54:33,120 --> 00:54:35,839
Speaker 8: I have a gravitational wave coming in at some frequency,

1095
00:54:35,880 --> 00:54:39,160
Speaker 8: it's like your radio station is broadcasting something and it

1096
00:54:39,200 --> 00:54:41,960
Speaker 8: has a frequency, and that's just you know, you tune

1097
00:54:41,960 --> 00:54:45,319
Speaker 8: it to some station and that's what it is. In

1098
00:54:45,360 --> 00:54:49,880
Speaker 8: this case, what you measure actually depends on your apparatus,

1099
00:54:49,920 --> 00:54:53,840
Speaker 8: Like your interferometer. So if I have a smaller apparatus,

1100
00:54:54,880 --> 00:54:57,440
Speaker 8: my signal is going to be coming in at a

1101
00:54:57,560 --> 00:55:02,880
Speaker 8: higher number radio state. Then if I have a bigger apparatus,

1102
00:55:02,920 --> 00:55:05,239
Speaker 8: then it comes in at a lower frequency station. The

1103
00:55:05,280 --> 00:55:09,000
Speaker 8: reason for that is because it's the quantum mismeasurement. And

1104
00:55:09,040 --> 00:55:11,440
Speaker 8: of course how much you're mismeasuring the space time depends

1105
00:55:11,480 --> 00:55:14,040
Speaker 8: on how big you know, the volume of space time.

1106
00:55:13,880 --> 00:55:16,200
Speaker 1: You're measuring affects your horizon.

1107
00:55:16,520 --> 00:55:18,719
Speaker 8: Yeah, it depends on the size of your horizon. That's

1108
00:55:18,760 --> 00:55:20,680
Speaker 8: another way of saying it. It depends on the size

1109
00:55:20,719 --> 00:55:23,239
Speaker 8: of your horizon, depends on how many quantum degrees of

1110
00:55:23,280 --> 00:55:28,160
Speaker 8: freedom or fluctuating inside your volume, which depends on how

1111
00:55:28,200 --> 00:55:30,799
Speaker 8: big your horizon is. And so as a result, you know,

1112
00:55:30,960 --> 00:55:33,279
Speaker 8: you would really know about this signal. First of all,

1113
00:55:33,320 --> 00:55:36,399
Speaker 8: it would have a very particular shape, but it would

1114
00:55:36,400 --> 00:55:39,080
Speaker 8: depend on your measuring apparatus, so you could compare between

1115
00:55:39,120 --> 00:55:41,920
Speaker 8: different instruments and then start to tell what the source

1116
00:55:41,960 --> 00:55:42,560
Speaker 8: of it would be.

1117
00:55:42,760 --> 00:55:45,839
Speaker 1: And can you also see things unexpected, like if there's

1118
00:55:45,840 --> 00:55:48,759
Speaker 1: a general enough detector that you might see things that

1119
00:55:48,960 --> 00:55:52,680
Speaker 1: aren't these quantum fluctuations, then aren't gravitational wave Some black holes,

1120
00:55:52,680 --> 00:55:55,280
Speaker 1: but something else, you know, surprising.

1121
00:55:55,600 --> 00:55:58,840
Speaker 8: Yeah. Sure, So these instruments that were interested in building,

1122
00:55:58,880 --> 00:56:02,640
Speaker 8: they can be sensitive to anything that's generating gravitational waves

1123
00:56:02,680 --> 00:56:06,920
Speaker 8: in that same frequency range. So the signal definitely has

1124
00:56:07,000 --> 00:56:09,640
Speaker 8: to be predictive enough to be able to tell apart

1125
00:56:09,800 --> 00:56:13,560
Speaker 8: different sources. And our claim is that the signal has

1126
00:56:13,719 --> 00:56:17,520
Speaker 8: very particular you know, frequencies that it's peaked at. It

1127
00:56:17,640 --> 00:56:21,080
Speaker 8: has angular correlations, like it depends on the angle between

1128
00:56:21,080 --> 00:56:24,920
Speaker 8: the arms and your interferometer. So therefore you'll be able

1129
00:56:24,960 --> 00:56:28,360
Speaker 8: to tell what the source of these gravitational waves.

1130
00:56:28,120 --> 00:56:30,560
Speaker 1: Are and what's the sort of timeline like best case

1131
00:56:30,600 --> 00:56:33,240
Speaker 1: scenario when you guys can build this thing and discover

1132
00:56:33,320 --> 00:56:34,000
Speaker 1: quantum gravity.

1133
00:56:34,239 --> 00:56:34,479
Speaker 2: Yeah.

1134
00:56:34,680 --> 00:56:40,960
Speaker 8: Yeah, So we've got the first bit of funding to

1135
00:56:41,040 --> 00:56:46,120
Speaker 8: come in, and my colleague Lemacullor, who's spearheading this effort

1136
00:56:46,320 --> 00:56:50,319
Speaker 8: here at Caltech, you know, his lab is ramping up

1137
00:56:50,360 --> 00:56:55,160
Speaker 8: on this. There are some technological objectives that they have

1138
00:56:55,239 --> 00:56:57,760
Speaker 8: to demonstrate. They have to do R and D because

1139
00:56:57,800 --> 00:57:04,279
Speaker 8: they're proposing a novel readout scheme for these interferometer. What

1140
00:57:04,360 --> 00:57:09,919
Speaker 8: we have proposed is to have a demonstrator apparatus that

1141
00:57:10,120 --> 00:57:15,240
Speaker 8: would kind of scrape the signal. Okay, we're talking about

1142
00:57:15,280 --> 00:57:20,080
Speaker 8: two sigma kind of sensitivity in five years, so I

1143
00:57:20,080 --> 00:57:23,720
Speaker 8: think to really start to see this, you know, like

1144
00:57:23,960 --> 00:57:27,360
Speaker 8: five sigma, you're just really confident you can start to

1145
00:57:27,600 --> 00:57:31,200
Speaker 8: test various aspects of it. I think we're probably talking

1146
00:57:31,520 --> 00:57:32,800
Speaker 8: the ten year timescale.

1147
00:57:32,920 --> 00:57:35,400
Speaker 1: So I've read your paper. There's a lot of nice

1148
00:57:35,440 --> 00:57:38,560
Speaker 1: theoretical maneuvers in there. My question to you is, do

1149
00:57:38,600 --> 00:57:40,360
Speaker 1: you believe this is going to be real? Like we

1150
00:57:40,480 --> 00:57:43,200
Speaker 1: turn this thing on in ten years? Nature tales? You answer,

1151
00:57:43,720 --> 00:57:46,320
Speaker 1: what's your confidence that this is out there that you're

1152
00:57:46,320 --> 00:57:46,840
Speaker 1: going to see it?

1153
00:57:47,240 --> 00:57:50,800
Speaker 8: Yeah, so it doesn't seem to be going away. Let's

1154
00:57:50,840 --> 00:57:54,080
Speaker 8: put it that way. When you see something in a calculation,

1155
00:57:55,120 --> 00:57:58,440
Speaker 8: you know, you try to test it by doing a

1156
00:57:58,480 --> 00:58:02,880
Speaker 8: different calculation that behaves differently. You know, it has different

1157
00:58:02,920 --> 00:58:06,320
Speaker 8: theoretical systematics, and the kinds of things that you could

1158
00:58:06,320 --> 00:58:09,640
Speaker 8: mess up in the calculation are different, so on and

1159
00:58:09,680 --> 00:58:12,560
Speaker 8: so forth, and then you also check for whether it's

1160
00:58:12,600 --> 00:58:16,840
Speaker 8: in conflict with anything that you know. And through the

1161
00:58:16,920 --> 00:58:20,120
Speaker 8: process of doing this, you know, based on my experience,

1162
00:58:20,160 --> 00:58:22,920
Speaker 8: when you try to build a theory, oftentimes it'll fail,

1163
00:58:23,520 --> 00:58:25,320
Speaker 8: and then you try to fix it up. By adding

1164
00:58:25,360 --> 00:58:28,400
Speaker 8: other things to it. This has not been like that.

1165
00:58:30,280 --> 00:58:32,440
Speaker 8: If it seems like it's going to fail for some reason,

1166
00:58:33,200 --> 00:58:35,480
Speaker 8: it means that you should just stop and wait and

1167
00:58:35,520 --> 00:58:39,560
Speaker 8: try to understand what's there better, because it fixes itself.

1168
00:58:40,000 --> 00:58:44,200
Speaker 8: So to me, that's an indication that there's something there.

1169
00:58:44,920 --> 00:58:49,080
Speaker 8: It hangs together in a very self consistent way, and

1170
00:58:49,120 --> 00:58:52,280
Speaker 8: so from that point of view, I find it theoretically

1171
00:58:52,400 --> 00:58:56,560
Speaker 8: very attractive, very interesting. It smells right now. I don't

1172
00:58:56,600 --> 00:58:59,680
Speaker 8: want to tell nature what to do. Right. Nature gets

1173
00:58:59,680 --> 00:59:02,080
Speaker 8: to decid. You know, there are some things that go

1174
00:59:02,160 --> 00:59:06,080
Speaker 8: in right, there's this fundamental fluctuations, and then spacetime needs

1175
00:59:06,080 --> 00:59:08,160
Speaker 8: to remember right, So there needs to be the sense

1176
00:59:08,200 --> 00:59:11,040
Speaker 8: in which you're losing information. And if those two things

1177
00:59:11,080 --> 00:59:14,400
Speaker 8: are there in nature, and we certainly know lots of

1178
00:59:14,440 --> 00:59:19,080
Speaker 8: analogous physical systems where that happens, then we'll see it.

1179
00:59:19,520 --> 00:59:23,320
Speaker 8: But at the end of the day, nature decides. And

1180
00:59:23,360 --> 00:59:25,480
Speaker 8: that's one of the things I really like about this

1181
00:59:25,560 --> 00:59:27,680
Speaker 8: problem is I can write these things down on paper

1182
00:59:27,720 --> 00:59:31,040
Speaker 8: and they're beautiful, and I'm understanding more things about it

1183
00:59:31,080 --> 00:59:33,520
Speaker 8: from a mathematical perspective. But at the end of the day,

1184
00:59:33,880 --> 00:59:35,200
Speaker 8: nature gets to the side.

1185
00:59:35,200 --> 00:59:37,880
Speaker 1: All right, well, we look forward to hearing nature's side

1186
00:59:37,880 --> 00:59:40,200
Speaker 1: of the story. Thanks very much for joining us today.

1187
00:59:40,760 --> 00:59:43,280
Speaker 4: All right, pretty interesting. I'm super impressed you can talk

1188
00:59:43,320 --> 00:59:45,960
Speaker 4: to a theorist. I thought you guys spoke different languages

1189
00:59:46,040 --> 00:59:47,560
Speaker 4: and didn't like each other.

1190
00:59:47,760 --> 00:59:50,760
Speaker 1: They mostly speak in Greek symbols exactly, but sometimes I

1191
00:59:50,800 --> 00:59:53,160
Speaker 1: can translate. These days, I'm trying to move a little

1192
00:59:53,200 --> 00:59:55,640
Speaker 1: bit in the direction of theoretical physics, so it's really

1193
00:59:55,640 --> 00:59:57,600
Speaker 1: fun for me to talk to these folks. But yeah,

1194
00:59:57,600 --> 01:00:00,200
Speaker 1: they think on a whole different plane of existence. But

1195
01:00:00,240 --> 01:00:03,800
Speaker 1: what's really cool are theorists who propose experiments, who develop

1196
01:00:03,960 --> 01:00:07,720
Speaker 1: new techniques and new ideas that allow experimentalists to maybe

1197
01:00:07,760 --> 01:00:11,200
Speaker 1: force the universe to reveal something about its nature. And

1198
01:00:11,240 --> 01:00:13,240
Speaker 1: the story of this one is similar to the story

1199
01:00:13,280 --> 01:00:17,000
Speaker 1: of a very similar experiment, which is LIGO, the interferometer

1200
01:00:17,080 --> 01:00:21,000
Speaker 1: that looked for classical gravitational waves. That was originally just

1201
01:00:21,040 --> 01:00:24,120
Speaker 1: a theoretical idea, and experimentalists were like, all right, let's

1202
01:00:24,160 --> 01:00:25,720
Speaker 1: try to build it, see if we can find it,

1203
01:00:25,800 --> 01:00:28,800
Speaker 1: and they did. This is like the quantum version of it,

1204
01:00:29,160 --> 01:00:32,640
Speaker 1: which would look for little quantum ripples in space time,

1205
01:00:32,760 --> 01:00:37,440
Speaker 1: basically little quantum gravitational waves, and the experiment itself is similar.

1206
01:00:37,440 --> 01:00:40,880
Speaker 1: It's a little interferometer, like shoot laser beams back and forth,

1207
01:00:41,200 --> 01:00:43,200
Speaker 1: see how they overlap, and see if you can catch

1208
01:00:43,200 --> 01:00:46,520
Speaker 1: a graviton interfering with those laser beams.

1209
01:00:46,880 --> 01:00:50,280
Speaker 4: Hmmm, because the gravit times would be sort of like

1210
01:00:50,440 --> 01:00:54,000
Speaker 4: bending space. Is that the idea? Because gravity can't interact

1211
01:00:54,040 --> 01:00:56,600
Speaker 4: with photons unless or candy.

1212
01:00:56,720 --> 01:00:59,440
Speaker 1: Gravity doesn't interact with photons in a sort of Newtonian

1213
01:00:59,440 --> 01:01:02,560
Speaker 1: way because toons have no mass, but gravity does bend space,

1214
01:01:02,600 --> 01:01:05,760
Speaker 1: and photons move through that bend space. And so yeah,

1215
01:01:05,800 --> 01:01:09,720
Speaker 1: you're exactly right. Like a little gravitational quantum fluctuation the

1216
01:01:09,800 --> 01:01:13,320
Speaker 1: kind she's looking for, would affect the shape of space

1217
01:01:13,440 --> 01:01:15,560
Speaker 1: for one of these beams and would sort of knock

1218
01:01:15,640 --> 01:01:18,200
Speaker 1: a photon out of the path. And that's what they're

1219
01:01:18,240 --> 01:01:18,680
Speaker 1: looking for.

1220
01:01:19,440 --> 01:01:21,480
Speaker 4: The idea is that like a graviton would pop out

1221
01:01:21,520 --> 01:01:24,560
Speaker 4: of nowhere, it pops out, it bends space around it

1222
01:01:24,640 --> 01:01:27,160
Speaker 4: and maybe able to deflect the photon. Is that the idea.

1223
01:01:27,200 --> 01:01:29,760
Speaker 1: That's the idea. But it's not one single graviton that

1224
01:01:29,760 --> 01:01:32,560
Speaker 1: would be totally invisible. It's this effect where a lot

1225
01:01:32,560 --> 01:01:36,200
Speaker 1: of gravitons are working together and the super duper weird

1226
01:01:36,240 --> 01:01:39,040
Speaker 1: thing is that this effect only happens when you're making

1227
01:01:39,040 --> 01:01:42,240
Speaker 1: a measurement. It's a quantum effect. It comes from not

1228
01:01:42,280 --> 01:01:45,640
Speaker 1: being able to see the whole universe. So she's imagining

1229
01:01:45,680 --> 01:01:48,400
Speaker 1: space filled with all these gravitons, and when you make

1230
01:01:48,440 --> 01:01:50,360
Speaker 1: this measurement, it can only be affected by like a

1231
01:01:50,400 --> 01:01:53,560
Speaker 1: certain bubble of the universe, a bubble of the universe

1232
01:01:53,560 --> 01:01:56,000
Speaker 1: that's like close enough to you that light can travel

1233
01:01:56,040 --> 01:01:59,480
Speaker 1: to you. Because you create this information horizon, you limit

1234
01:01:59,640 --> 01:02:02,560
Speaker 1: like the links of these gravitons, and so only some

1235
01:02:02,600 --> 01:02:04,800
Speaker 1: of them can talk to your experiment, and that's what

1236
01:02:04,920 --> 01:02:07,640
Speaker 1: creates this weird effect. And I'll be totally honest, there's

1237
01:02:07,680 --> 01:02:09,960
Speaker 1: a lot of math there that I just don't even understand.

1238
01:02:10,160 --> 01:02:12,600
Speaker 1: But she's been trying to prove to herself that this

1239
01:02:12,680 --> 01:02:15,040
Speaker 1: works or that this doesn't work, and the math just

1240
01:02:15,160 --> 01:02:17,760
Speaker 1: keeps holding together no matter how she probes it. So,

1241
01:02:17,880 --> 01:02:20,320
Speaker 1: as you heard maybe in the interview, she really believes

1242
01:02:20,320 --> 01:02:20,919
Speaker 1: this is real.

1243
01:02:21,320 --> 01:02:23,160
Speaker 4: And so the idea is that you could maybe build

1244
01:02:23,160 --> 01:02:26,440
Speaker 4: this experiment on a tabletop like it could be, you know,

1245
01:02:26,560 --> 01:02:29,800
Speaker 4: a small experiment to prove a huge thing like quantum gravity.

1246
01:02:29,960 --> 01:02:34,960
Speaker 1: Exactly, Ligo. The classical gravitational wave experiment is like kilometers

1247
01:02:35,000 --> 01:02:37,280
Speaker 1: long and cost billions of dollars. This would be like

1248
01:02:37,320 --> 01:02:39,840
Speaker 1: meters long. You literally could build it in a lab

1249
01:02:40,120 --> 01:02:43,320
Speaker 1: in the basement at Caltech, and if it works, they

1250
01:02:43,320 --> 01:02:47,440
Speaker 1: could see quantum gravitational effects on these beams of light,

1251
01:02:47,480 --> 01:02:50,320
Speaker 1: and they could prove that gravitons are out there and

1252
01:02:50,360 --> 01:02:53,040
Speaker 1: that they're dancing together to make these little tiny ripples

1253
01:02:53,040 --> 01:02:53,840
Speaker 1: in space time.

1254
01:02:54,200 --> 01:02:57,240
Speaker 4: Cool. Well, she's welcome to hang out in my backyard

1255
01:02:57,360 --> 01:03:00,960
Speaker 4: and do the experiment here. That could be exciting.

1256
01:03:02,840 --> 01:03:04,760
Speaker 1: I don't think she wants her experiment it's sprayed by

1257
01:03:04,760 --> 01:03:06,320
Speaker 1: the hose or like doused with water.

1258
01:03:06,160 --> 01:03:10,960
Speaker 4: Balloons, yeah, or have screaming kids running all around it

1259
01:03:11,000 --> 01:03:13,840
Speaker 4: that you usually it tends to make gravitons shy.

1260
01:03:14,120 --> 01:03:16,560
Speaker 1: I tend to dampen the effects of your experiment.

1261
01:03:16,960 --> 01:03:19,800
Speaker 4: All right, Well, pretty exciting. Thank you to doctor Catherine

1262
01:03:19,880 --> 01:03:23,920
Speaker 4: Zurich for talking about her research. What does this all mean, Daniel?

1263
01:03:24,200 --> 01:03:27,640
Speaker 4: Are we far or near proving the idea of quantum gravity?

1264
01:03:28,120 --> 01:03:30,640
Speaker 1: I think we're still pretty far from figuring anything out.

1265
01:03:30,680 --> 01:03:32,920
Speaker 1: The theorists are working hard and making progress all the

1266
01:03:32,920 --> 01:03:36,200
Speaker 1: time about building their theories. But now it's exciting that

1267
01:03:36,280 --> 01:03:39,800
Speaker 1: we have experimental efforts which maybe in the next five, ten,

1268
01:03:39,920 --> 01:03:42,800
Speaker 1: fifteen years, could provide us with really valuable clues to

1269
01:03:42,840 --> 01:03:45,720
Speaker 1: tell us, Oh, gravity is classical or nope, gravity is

1270
01:03:45,760 --> 01:03:48,360
Speaker 1: quantum mechanical. You better figure it out. That would be

1271
01:03:48,440 --> 01:03:52,400
Speaker 1: really powerful indication for sort of which direction to go theoretically.

1272
01:03:52,800 --> 01:03:55,760
Speaker 1: And I love this dance between experimental and theoretical physics.

1273
01:03:55,800 --> 01:03:58,200
Speaker 1: You know, the ideas flourish and then experiments kill them,

1274
01:03:58,480 --> 01:04:02,040
Speaker 1: or sometimes experiments discover something weird which inspires lots of

1275
01:04:02,040 --> 01:04:05,280
Speaker 1: new theoretical ideas. It's really beautiful to see the interplay

1276
01:04:05,320 --> 01:04:07,440
Speaker 1: of these two different avenues of exploration.

1277
01:04:08,960 --> 01:04:11,280
Speaker 4: It's like a theoretical tango exactly.

1278
01:04:11,360 --> 01:04:13,160
Speaker 1: Even the physicists don't really know how to flirt, and

1279
01:04:13,160 --> 01:04:14,880
Speaker 1: I think the tango is pretty flirtatious.

1280
01:04:15,040 --> 01:04:18,280
Speaker 4: All right, well, it sounds like the answer is stay tuned.

1281
01:04:18,560 --> 01:04:20,800
Speaker 4: In theory, it might be ten to fifteen years, but

1282
01:04:20,880 --> 01:04:23,920
Speaker 4: in reality, who knows. It could be that we may

1283
01:04:23,960 --> 01:04:26,439
Speaker 4: never answer this question, or it could be that we'll

1284
01:04:26,480 --> 01:04:28,200
Speaker 4: answer it within our lifetimes.

1285
01:04:28,440 --> 01:04:31,560
Speaker 1: That's right. We could be flirting with understanding or confusion.

1286
01:04:31,880 --> 01:04:34,640
Speaker 4: We hope you enjoyed that thanks for joining us, see

1287
01:04:34,640 --> 01:04:35,200
Speaker 4: you next time.

1288
01:04:43,080 --> 01:04:45,880
Speaker 1: Thanks for listening, and remember that Daniel and Jorge Explain

1289
01:04:45,960 --> 01:04:49,960
Speaker 1: the Universe is a production of iHeartRadio. For more podcasts

1290
01:04:49,960 --> 01:04:54,600
Speaker 1: from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever

1291
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Speaker 1: to learn more.

1301
01:05:38,880 --> 01:05:42,400
Speaker 3: There are children, friends, and families walking, riding on passing

1302
01:05:42,400 --> 01:05:44,800
Speaker 3: the roads every day. Remember they're real people with loved

1303
01:05:44,840 --> 01:05:47,040
Speaker 3: ones who need them to get home safely. Protect our

1304
01:05:47,080 --> 01:05:49,160
Speaker 3: cyclists and pedestrians because they're people too.

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01:05:49,440 --> 01:05:49,960
Speaker 1: Go safely.

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01:05:50,040 --> 01:05:52,960
Speaker 3: California from the California Office of Traffic Safety and Caltrans.

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01:05:53,120 --> 01:05:55,840
Speaker 1: This is Malcolm Gladwell from revisionist history.

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01:05:56,280 --> 01:05:58,480
Speaker 4: eBay Motors is here for the ride.

1309
01:05:58,800 --> 01:06:02,280
Speaker 6: With samelbow grease, fresh installs, and a whole lot of love,

1310
01:06:02,600 --> 01:06:05,200
Speaker 6: you transformed a hundred thousand miles and a body full

1311
01:06:05,240 --> 01:06:09,040
Speaker 6: of rust into a drive that's all your own. Break kits,

1312
01:06:09,400 --> 01:06:10,240
Speaker 6: led headlights.

1313
01:06:10,280 --> 01:06:14,320
Speaker 4: Whatever you need, eBay Motors has it, and with eBay

1314
01:06:14,400 --> 01:06:18,600
Speaker 4: Guaranteed Fit, it's guaranteed to fit your ride the first time,

1315
01:06:19,120 --> 01:06:23,120
Speaker 4: every time, or your money back plus. At these prices,

1316
01:06:23,480 --> 01:06:26,800
Speaker 4: you're burning rubber, not cash. Keep your rider die Alive

1317
01:06:27,080 --> 01:06:30,360
Speaker 4: at ebaymotors dot com. Eligible items only.

1318
01:06:30,760 --> 01:06:31,640
Speaker 1: Exclusions apply.