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Speaker 1: Picture the Solar system. Likely you have put the Sun

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Speaker 1: at the center, motionless in your mind, with the planets

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Speaker 1: whizzing all around it. Or maybe you've seen that viral

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Speaker 1: video that breaks the common view and shows the Sun

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Speaker 1: in motion through the galaxy. But isn't the galaxy moving

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Speaker 1: to what's the right way to think about all this

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Speaker 1: to assemble a mental universe? How fast are we going?

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Speaker 1: And does that question even make sense? A new study

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Speaker 1: raises some interesting puzzles. Today we're going to dig into

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Speaker 1: all of that and help you make sense of it.

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Speaker 1: Welcome to Daniel and Kelly's Extraordinary Universe in Motion.

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Speaker 2: Hello, I'm Kelley Winer Smith.

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Speaker 3: I study parasites and space, and it doesn't matter what

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Speaker 3: I am moving relative to, I am always moving pretty slow.

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

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Speaker 1: interested in our cosmic context.

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Speaker 2: So, Daniel, cosmic context?

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Speaker 3: Yes, what in your mind would be the coolest spot

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Speaker 3: for us to be in the universe? If we could know, like,

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Speaker 3: should we be in the center, should we be at

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Speaker 3: the edge, if we could be anywhere you wanted us

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Speaker 3: to be? Where would we be?

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Speaker 1: Wow, that's a crazy question, And I can't believe nobody's

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Speaker 1: ever asked me that before, and I have never thought

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Speaker 1: about that before. You know, if the universe is infinite,

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Speaker 1: then there are no places. Really, They're all the same.

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Speaker 1: So then the question is only interesting if the universe

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Speaker 1: is not infinite. And even if the universe is finite

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Speaker 1: and closed, there's still no special places. So the most

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Speaker 1: interesting thing would be if the universe is finite and

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Speaker 1: has an edge, in which case being near the edge

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Speaker 1: would be amazing because the edge would have to be

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Speaker 1: different in some way from other kinds of space, and

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Speaker 1: it'll be like a different kind of lego brick that

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Speaker 1: makes up the universe, and different is always fascinating because

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Speaker 1: like at the edge, for example, momentum wouldn't be conserved.

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Speaker 1: You know, for example, like when you throw a ball

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Speaker 1: against a wall, the ball bounces back, but also the

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Speaker 1: wall gets pushed back a little bit, even if the

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Speaker 1: wall is attached to the Earth, right, But if you

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Speaker 1: throw a ball against the edge of the universe, it

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Speaker 1: bounces back and the universe doesn't get pushed it can't,

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Speaker 1: and so momentum is not conserved. So that would be

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Speaker 1: pretty interesting to see momentum not conservation. Hey, was that

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Speaker 1: the nerdiest possible answer I could have given.

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Speaker 2: You pretty close.

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Speaker 1: I'm trying to max out all the metrics here today.

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Speaker 2: Awesome.

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Speaker 3: All right, Well, let's see what other metrics Daniel can

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Speaker 3: max out today as we discuss how fast we're moving

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Speaker 3: through space.

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Speaker 1: Yeah, this is a really fun topic because we get

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Speaker 1: to talk about not just like our cosmic context, where

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Speaker 1: are we in the universe? How is everything slashing around?

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Speaker 1: Give you like a sense for our neighborhood and the

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Speaker 1: bigger picture of view of the universe. But also it

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Speaker 1: touches on some really deep and basic but hard to

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Speaker 1: grapple with concepts in relativity, like what does velocity even mean?

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Speaker 3: Man?

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Speaker 1: So get at your banana peels. We are going to

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Speaker 1: smoke them today.

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Speaker 2: Oh, we're getting philosophical.

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Speaker 1: I guess we always get philosophical when it's physics. Episode

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Speaker 1: amazing can't be avoided. So I was wondering what people

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Speaker 1: thought about this question before we dive into the physics

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Speaker 1: of it. So I reached out to our amazing group

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Speaker 1: of volunteers who stand at the ready to offer their

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Speaker 1: ungoogled opinions on questions of the day Today. I asked

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Speaker 1: them how fast are we moving through space? Think about

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Speaker 1: it for a moment. What would be your answer. Here's

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Speaker 1: what our group of experts had to say. Should be

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Speaker 1: dependent upon the relative location and velocity of the observer.

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Speaker 2: We're all going back to the same location, so effectively,

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Speaker 2: we haven't gone anywhere.

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Speaker 1: Ninety six thousand kilometers per second. They don't know how

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Speaker 1: fast the Milky Way galaxy is moving.

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Speaker 2: We're moving at thousands and thousands and thousands of kilometers

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Speaker 2: per second.

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Speaker 4: How fast we're going depends on our frame of reference.

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Speaker 4: I'm sitting down zero miles per hour.

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Speaker 2: It must be thousands of miles an hour.

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Speaker 1: If the universe is infinity in size, then we're going

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Speaker 1: infinity speed around something.

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Speaker 4: Relative to the galaxy in the universe.

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Speaker 1: I don't know, man, tough question. Speed is always relative,

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Speaker 1: So the question is how fast are we moving relative

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Speaker 1: to what? Velocity is relative?

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Speaker 2: When it comes to space time, we're moving all at

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Speaker 2: the speed of light.

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Speaker 4: Relative to what's not fast enough, guys, hit the nitrous

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Speaker 4: are side.

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Speaker 3: But on these are great answers. And having listened to

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Speaker 3: you explain physics for over a year now, my guess was,

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Speaker 3: it's got to be relative to something.

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Speaker 2: And then I was like, and that's all I know.

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Speaker 3: But I will hear a whole hour on this topic,

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Speaker 3: so soon I'll be an experts And so, yeah, what

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Speaker 3: did you think of these answers?

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Speaker 1: I thought they were great. They were very well informed

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Speaker 1: and really funny. Also, but I have a question about

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Speaker 1: your response, Kelly. Do you have a different relationship now

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Speaker 1: to like the random physics question that might come up

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Speaker 1: in conversation, Like if your kids ask you a random

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Speaker 1: question about the universe, do you feel like more qualified

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Speaker 1: to maybe answer it or dig into it with them

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Speaker 1: than you did a year ago.

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Speaker 3: I do, and I'm much more likely to like interject

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Speaker 3: physics information. Like Hata said something about an electron the

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Speaker 3: other day, and I was like, did you know that

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Speaker 3: we don't know if the electron is made up of

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Speaker 3: other bits.

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Speaker 2: We've tried to figure it out, but we did. It

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Speaker 2: doesn't look like it's made up of other stuff, but

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Speaker 2: we just don't know.

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Speaker 3: Because we haven't been able to, like, you know, if

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Speaker 3: we had more money, we could dig in more.

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Speaker 2: And she didn't. You know, I can't say she looked interested, but.

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Speaker 3: I was excited and so so yes, I do feel

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Speaker 3: like now that I know more about physics. I'm more

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Speaker 3: excited about physics. It feels less opaque and I'm excited. Yeah,

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Speaker 3: life is good.

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Speaker 1: Okay, yeah, physician accomplished one person at a time.

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Speaker 2: Woo. Yes, you want a biologist over.

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Speaker 1: Well, then I'm one for two because I'm not sure

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Speaker 1: Katrina feels the same way. Oh.

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Speaker 3: Ouch, And how many years have you been working there?

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Speaker 3: Is that like twenty years now? Yeah?

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Speaker 1: Twenty six, twenty seven? Yeah? I know, right, Well, she

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Speaker 1: definitely knows more particle physics than she did when she started,

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Speaker 1: So I don't know if her enthusiasm has gone up,

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Speaker 1: but her knowledge definitely has.

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Speaker 3: Well, how do you feel about poop in the fridge?

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Speaker 3: I guess maybe your knowledge of what's happening with the

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Speaker 3: poop in the fridge has gone up, but your excitement

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Speaker 3: about it has probably not.

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Speaker 1: Yeah, so that's probably fair. Yeah, okay, comparison. All right,

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Speaker 1: The day I'm excited to see poop in the fridge

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Speaker 1: is the day I expect Katrina to be excited to talk.

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Speaker 2: About particles, all right, urriage in a nutshell.

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Speaker 1: Everybody likes to talk about the interdisciplinary work, but we're

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Speaker 1: living it, baby.

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Speaker 2: That's right, that's right, it's messy.

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Speaker 1: All right, let's get back on track and talk about

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Speaker 1: our emotion through the universe, not bowel motions that ended

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Speaker 1: up in Daniel's freezer.

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Speaker 3: Amazing, all right, all right, so all motion, because I've

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Speaker 3: been listening, motion has to be defined relative to something else. Yeah,

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Speaker 3: And is there like an obvious thing to compare your

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Speaker 3: motion too for this question, or do you can just

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Speaker 3: pick anything?

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Speaker 1: No, the obvious thing to compare your emotion to is space.

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Speaker 1: And people like to think about our motion through space.

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Speaker 1: They like to think about the question how fast are

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Speaker 1: we moving? How fast is the Earth moving? And they

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Speaker 1: imagine that we are moving through some medium. But space

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Speaker 1: is really weird. Space is not something that has a

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Speaker 1: frame of reference. You cannot measure your motion relative to space.

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Speaker 1: You can only measure your motion relative to other stuff

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Speaker 1: in space, which you know already opens the door to

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Speaker 1: deep philosophical questions like well then what is space anyway?

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Speaker 1: And I think that it's really hard to hold in

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Speaker 1: your mind an idea of what space is because you know,

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Speaker 1: on one hand, we talk about it is like having

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Speaker 1: things in it like fields and matter, which is excitation

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Speaker 1: of those fields, which are a property of space. Right,

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Speaker 1: So it feels like there's stuff in space. I'm talking

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Speaker 1: about these fields, and they're oscillating, they're doing things. But

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Speaker 1: on the other hand, I'm also telling you you can't

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Speaker 1: measure your velocity relative to those fields. They somehow exist,

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Speaker 1: they're out there, they're part of this medium. It's a

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Speaker 1: kind of an ether theory because it's not an ether

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Speaker 1: that provides a frame of reference. That's really the crucial thing.

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Speaker 1: And so velocity is measured between two objects, and space

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Speaker 1: is not an object. It's kind of a thing, but

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Speaker 1: it doesn't have this property that you can measure your

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Speaker 1: velocity relative to that thing.

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Speaker 3: And if you really have smoked a lot of banana pills,

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Speaker 3: you should listen to one of our early episodes What

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Speaker 3: is Space, where you dig into that for a whole hour,

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Speaker 3: and that is some trippy stuff.

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Speaker 1: And it's amazing that we don't really have a solid

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Speaker 1: answer to this question. Like we have these theories and

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Speaker 1: they work, and we can pull apart the philosophical implications

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Speaker 1: of them. What does it mean that you can't measure

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Speaker 1: your velocity relative to the thing in which light travels,

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Speaker 1: for example, But we don't still really understand what it

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Speaker 1: is and how it all works, and we can't pull

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Speaker 1: it all together. And like quantum mechanics, view of space

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Speaker 1: and general relative to view of space are very different.

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Speaker 1: And so somebody please give us a theory of quantum

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Speaker 1: gravity which answers all of these questions. But you know,

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Speaker 1: it means something to say that velocity is relative. It

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Speaker 1: means that velocity is not a property of an object.

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Speaker 1: It's a property of a pair of objects. So any

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Speaker 1: physics question you ask start out saying, say I'm in

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Speaker 1: a ship and I'm going ninety percent of the speed

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Speaker 1: of light, I'm going to ask you with respect to

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Speaker 1: what it doesn't mean anything to say I'm going ninety

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Speaker 1: percent of the speed of light, because you can be

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Speaker 1: going ninety percent of the speed of light relative to

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Speaker 1: one observer, and ten percent of the speed of light

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Speaker 1: relative to another, and zero relative to another who's standing

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Speaker 1: next to you on the ship, right, Your velocity only

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Speaker 1: means something if you say who's measuring it? Because again,

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Speaker 1: there is no absolute frame, no preferred velocity in the universe.

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Speaker 3: And for those of us who have to admit that

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Speaker 3: they had a little trouble remembering the difference between velocity

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Speaker 3: and acceleration and motion and all of those terms when

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Speaker 3: they started physics. Let's do a real quick recap motion, velocity, acceleration.

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Speaker 3: What do these terms mean? Yeah, great for the purpose

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Speaker 3: of this discussion.

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Speaker 1: Yeah, so let's start with location, right, because that's the

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Speaker 1: basic thing. You know. Location also is relative, Like I

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Speaker 1: can say, like if I live in a one dimensional universe,

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Speaker 1: I can say, over here location x equal zero. Then

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Speaker 1: I can measure how far I am from that location

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Speaker 1: from zero. So I'm at x equals five. You're at

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Speaker 1: x equal zero. I can say we're five units apart. Right,

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Speaker 1: But somebody else could have put x equal zero somewhere else,

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Speaker 1: So my location would be different if they're measuring it

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Speaker 1: or if I'm measuring it. So even location itself is

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Speaker 1: relative because there's no like glowing tick marks in space.

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Speaker 1: There's no like origin where the universe says this is

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Speaker 1: zero or that is zero. It's just relative. So that's

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Speaker 1: the basic measurement that's your location. Velocity is how your

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Speaker 1: location changes with time. I was at x equals five

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Speaker 1: one second later, I'm at xequal six. Then I'm at

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Speaker 1: xequal seven. That's my velocity. But that's why velocity is relative,

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Speaker 1: because it's a measurement of how location is changing, and

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Speaker 1: location is just relative.

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Speaker 2: Got it all?

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Speaker 1: That's great? And what that means, for example, is that

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Speaker 1: any experiment you can do can't measure your velocity relative

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Speaker 1: to space. So if I build some contraption and it

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Speaker 1: does something the wiz bang experiment, and I run my

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Speaker 1: experiment and does a wiz in a bang, cool, and

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Speaker 1: then I put it in a box. Then I speed

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Speaker 1: it up and I get it going really fast relative

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Speaker 1: to Earth, and I do the same experiment, it should

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Speaker 1: still whiz in bang in exactly the same way. The

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Speaker 1: fact that it has some velocity now relative to Earth

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Speaker 1: doesn't change the physics inside the box. And it can't

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Speaker 1: because if it did, then somehow I'd be measuring the

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Speaker 1: velocity like within the box without measuring my distance relative

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Speaker 1: to Earth. You can only measure your velocity relative to

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Speaker 1: Earth by measuring your distance relative to Earth. So if

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Speaker 1: the experiment just does the wiz bang experiment, if it

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Speaker 1: does not like a ruler to measure the distance to Earth,

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Speaker 1: then it should get the same result regardless of its

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Speaker 1: location or its velocity relative to Earth. And in fact,

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Speaker 1: you can promote this to a general principle. You can

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Speaker 1: say you can't measure your location or your velocity. If

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Speaker 1: you're like trapped in inside a box with no access

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Speaker 1: to the outside universe, there's nothing you can do to

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Speaker 1: measure your velocity relative to stuff in the outside universe

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Speaker 1: because your velocity only has meaning relative to that stuff,

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Speaker 1: and if you don't have access to that stuff, you

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Speaker 1: can't measure your velocity. Does that all make sense?

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Speaker 2: So you could still measure your velocity with respect to

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Speaker 2: stuff in the box, right, but not? Okay, got it.

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Speaker 1: But the amazing thing is that that's not true for acceleration. Right.

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Speaker 1: So we talked about location, and we talked about how

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Speaker 1: change in location is velocity. You can also talk about

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Speaker 1: the change in velocity. So for those mathematically inclined, these

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Speaker 1: are derivatives. Right. Velocity is the first derivative of location.

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Speaker 1: Acceleration is the second derivative of location. It's how velocity

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Speaker 1: is changing with time. Now, acceleration is something that's absolute.

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Speaker 1: If you are in a box, you can measure whether

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Speaker 1: that box is accelerating or not. It's very easy. You

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Speaker 1: just like draw a ball. If the box is not accelerating,

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Speaker 1: the ball will float in front of you. If the

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Speaker 1: box is accelerating, the ball will move to the back

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Speaker 1: of the box. If the box has a negative acceleration,

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Speaker 1: like somebody's putting on the brakes, the ball will move

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Speaker 1: to the front of the box. It's just like having

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Speaker 1: a bowling ball in the back of a truck. You

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Speaker 1: can use that bowling ball to tell if you're accelerating

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Speaker 1: or decelerating. You can't use it to measure the velocity

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Speaker 1: of the truck, but you can use it to measure

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Speaker 1: the acceleration. So acceleration is absolute, but velocity is not.

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Speaker 2: Okay, I get that.

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Speaker 3: It still feels kind of counterintuitive because if it's the

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Speaker 3: second derivative of location, it still feels like location should matter.

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Speaker 3: But your box example, I understand how that works.

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Speaker 1: And you know, for those philosophically inclined, you might wonder, like, well,

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Speaker 1: why is that Why it's taking one more derivative make

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Speaker 1: it absolute instead of relative. And that's a whole digression.

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Speaker 1: But very briefly, acceleration is philosophically very similar to curvature. Right.

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Speaker 1: The effect acceleration is almost exactly the same as the

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Speaker 1: effect of space time curvature. In fact, acceleration can create

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Speaker 1: event horizons. There are scenarios for example, where if you

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Speaker 1: are constantly accelerating, you can outrun photons, effectively making like

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Speaker 1: an event horizon relative to photons. That's a whole other

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Speaker 1: episode we should dig into.

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Speaker 2: Wait wait, wait, whoa, whoa. Did you say something can

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Speaker 2: go faster than light?

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Speaker 1: No, you can never go faster than light, but you

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Speaker 1: can outrun a photon. So, for example, if you take

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Speaker 1: off in your spaceship and you're moving slowly but you're

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Speaker 1: accelerating constantly, if I then try to shoot a laser

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Speaker 1: beam to catch you, it will never catch you. If

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Speaker 1: you're accelerating constantly, you can outrun that photon. So it's

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Speaker 1: not like if we have a race Kelly versus the photon,

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Speaker 1: that you'll go faster than the photon. You'll never go

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Speaker 1: faster than light, but I can't catch you with a

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Speaker 1: photon if you have left earlier and are constantly exciting.

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Speaker 2: Okay, all right, Yeah.

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Speaker 1: So acceleration is weird. It's kind of like curvature. It's

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Speaker 1: a whole thing in general relativity. But the point is

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Speaker 1: that velocity is relative, and this leads to some sort

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Speaker 1: of weird things like, for example, what if it's just

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Speaker 1: you in the universe and nothing else, imagine an empty

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Speaker 1: universe with just you. What's your velocity? There is no velocity,

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Speaker 1: not that your velocity is zero. Velocity has no meaning

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Speaker 1: because it's a property of pairs of objects. In an

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Speaker 1: empty universe, there are no pairs of objects.

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Speaker 2: It sounds very lonely.

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Speaker 1: It's like being married to yourself.

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Speaker 3: Oh, I can't imagine to be around for very long either,

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Speaker 3: in the vastness of space. If it was just you,

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Speaker 3: it would be a short, lonely existence.

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Speaker 1: Always thinking about the practical aspects of weird philosophical hypotheticals,

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Speaker 1: love it.

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Speaker 2: Always thinking of death is pretty much where it goes to.

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Speaker 1: And conversely, you can never imagine a scenario where you

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Speaker 1: are at rest relative to a photon because photons always

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Speaker 1: have velocity of the speed of light relative to everything.

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Speaker 1: So you can never pull up alongside of photon and say, oh, look,

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Speaker 1: this is what a photon looks like when it's at rest,

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Speaker 1: because the photon is pure motion.

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Speaker 2: If you pulled up alongside a photon, what kind of

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Speaker 2: music do you think it would be?

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Speaker 4: Listening to?

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Speaker 1: Classic rocks?

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Speaker 3: Ah?

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Speaker 2: Nice, Yeah, all right, let's go with that.

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Speaker 1: Yeah, or quantum punk. I'm not sure actually, so What

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Speaker 1: this means is, you know, space has no texture, there's

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Speaker 1: no reference frame. It feels like space is a thing,

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Speaker 1: but it's not, and it's the same thing everywhere. We

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Speaker 1: mentioned earlier the idea of space having a boundary and

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Speaker 1: its connection to conservation and momentum, and this tells you

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Speaker 1: that the idea that space has no reference frame has

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Speaker 1: really important consequences. Like Nother's theorem is what tells us

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Speaker 1: that space being the same everywhere leads to conservation of momentum,

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Speaker 1: which is why space have an edge to it would

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Speaker 1: lead to a violation of the conservation of momentum. So

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Speaker 1: the fact that we never see violations of the conservation

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Speaker 1: of momentum tells us space really is the same everywhere,

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Speaker 1: and we've never noticed that. Like if you do an

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Speaker 1: experiment here and you do an experiment there, you get

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Speaker 1: different answers. Your whiz bang experiment always whizzes and bangs

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Speaker 1: the same way no matter where you are. So velocity

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Speaker 1: and location are purely relative, right, And this means that,

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Speaker 1: for example, it doesn't mean anything to ask are you motionless?

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Speaker 1: Can we be motionless with respect to space? Right? Because

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Speaker 1: you can't measure your velocity relative to space.

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Speaker 2: At all, because there's no space, man.

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Speaker 1: Yeah, exactly. No space is a thing. It just doesn't

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Speaker 1: have a velocity. So in one sense, it's like trivial

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Speaker 1: to be motionless. You just say, well, I'm gonna choose

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Speaker 1: my frame of reference to be me, and I'm gonna

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Speaker 1: measure my velocity relative to myself. Okay, look, I'm going zero.

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Speaker 3: Yay.

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Speaker 1: It's also kind of trivial to have a velocity near

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Speaker 1: the speed of light. Choose any of the zillions of

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Speaker 1: cosmic rays that are approaching the Earth at nearly the

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Speaker 1: speed of light and say that's my reference frame.

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Speaker 2: I do go fast.

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Speaker 1: Yes, And from the point of view of those cosmic rays, Kelly,

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Speaker 1: you are moving towards them at nearly the speed of light,

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Speaker 1: So buckle.

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Speaker 2: Up, way to go me. I was also fast that

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Speaker 2: time I jumped out of a plane that.

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Speaker 1: Was fast too ooh fast, and then slow I hope.

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Speaker 3: Yeah, yeah, yeah yeah yeah, and then not split not

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Speaker 3: very slow, not fast and slow than very slow.

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Speaker 2: But anyway, all right.

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Speaker 3: So we have learned that space is confusing and you

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Speaker 3: need to be careful what you're talking about your speed

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Speaker 3: relative to And when we get back from the break,

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Speaker 3: we're going to talk about our speed relative to lots

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Speaker 3: of stuff in the universe.

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Speaker 2: All right, we're back.

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Speaker 3: Let's start by talking about our speed relative to let's say,

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Speaker 3: my favorite planet in the Solar System.

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Speaker 2: Earth.

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00:20:18,320 --> 00:20:21,520
Speaker 1: Yeah. Earth is already kind of complicated. You might think, well,

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Speaker 1: I'm standing on Earth. My velocity is zero, right, but

390
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Speaker 1: the Earth itself is spinning, right, So which part of

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Speaker 1: the Earth are we talking about? Yes, if you say

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Speaker 1: the part of the Earth that's under your feet, your

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Speaker 1: velocity is zero, that's kind of boring. But if you

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Speaker 1: say the center of the Earth, then at the surface

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Speaker 1: of the Earth you're already moving quite fast. Now, at

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Speaker 1: the north pole you're not moving at all due to

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Speaker 1: the spin, But at the equator, the Earth is spinning

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Speaker 1: at sixteen hundred kilometers per hour. Woa, Like, that's not

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Speaker 1: a small amount of motion.

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Speaker 3: No, you know, I realize that we don't feel that,

401
00:20:56,720 --> 00:20:58,760
Speaker 3: but it is kind of amazing that we don't feel that.

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Speaker 2: That is pretty quick.

403
00:20:59,760 --> 00:21:04,120
Speaker 1: Yeah, And it's a little counterintuitive because this is acceleration. Right.

404
00:21:04,160 --> 00:21:08,760
Speaker 1: To move in a circle at constant velocity requires acceleration

405
00:21:08,920 --> 00:21:12,440
Speaker 1: because velocity is a vector, and if it's changing direction,

406
00:21:12,640 --> 00:21:16,560
Speaker 1: even if its magnitude is constant. Then moving in a circle,

407
00:21:16,600 --> 00:21:20,320
Speaker 1: your velocity doesn't change, but the direction of your velocity changes,

408
00:21:20,359 --> 00:21:22,960
Speaker 1: and that requires acceleration. Like if you have a rock

409
00:21:23,040 --> 00:21:25,800
Speaker 1: moving through space at ten meters per second and you

410
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Speaker 1: want it to be going a different direction at ten

411
00:21:27,600 --> 00:21:29,480
Speaker 1: meters per second, you've got to give it a push.

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00:21:29,760 --> 00:21:33,480
Speaker 1: That's a force, that's acceleration. You might think I should

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00:21:33,480 --> 00:21:36,679
Speaker 1: be able to measure that, and you can. Actually you

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00:21:36,720 --> 00:21:39,720
Speaker 1: can measure the rotation of the Earth because it affects

415
00:21:40,000 --> 00:21:43,000
Speaker 1: how much you weigh, Like at the equator, you weigh

416
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Speaker 1: a little bit less than you do at the north

417
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Speaker 1: pole because you're being flung out a little bit. Like

418
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Speaker 1: if you are on a merry go round and somebody

419
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Speaker 1: spinning it faster and faster and faster, there's this apparent

420
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Speaker 1: force that's pushing you away from the center. Right, that's

421
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Speaker 1: due to the acceleration, which, as we were saying earlier,

422
00:22:00,200 --> 00:22:02,600
Speaker 1: is something that you can measure. And so you can

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Speaker 1: actually measure this acceleration.

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Speaker 3: How long did it take for us to like figure

425
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Speaker 3: out and accept that, because it's like that's all pretty counterintuitive.

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Speaker 1: Yeah, it is counterintuitive, and it took a long time

427
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Speaker 1: before people accepted this. When it was first proposed, people

428
00:22:16,960 --> 00:22:20,520
Speaker 1: were like, what, that's crazy, And it took like having

429
00:22:20,560 --> 00:22:23,320
Speaker 1: fairly precise experiments in order to be able to measure it.

430
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Speaker 1: There are a few different effects from this kind of rotation.

431
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Speaker 1: There is the fact that you weigh less at the equator,

432
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Speaker 1: and there's also this Coriolis force, which is effectively like

433
00:22:33,400 --> 00:22:37,240
Speaker 1: a sideways force. If, for example, you drop something from

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Speaker 1: like one hundred and fifty meters, then it doesn't go

435
00:22:40,000 --> 00:22:42,439
Speaker 1: straight down. It departs from straight down by like a

436
00:22:42,520 --> 00:22:46,959
Speaker 1: millimeter or so, so it takes kind of a precise measurement. Actually,

437
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Speaker 1: that was a question I was asked during my oral

438
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Speaker 1: exam in grad school to like calculate that on the

439
00:22:52,119 --> 00:22:54,840
Speaker 1: spot on a chalkboard in front of the professor's I

440
00:22:54,880 --> 00:22:57,000
Speaker 1: remember that. Oh my god, that was terrible, But I

441
00:22:57,000 --> 00:22:57,840
Speaker 1: think I got it right.

442
00:22:57,920 --> 00:22:59,320
Speaker 2: They let you through one way or another.

443
00:22:59,520 --> 00:23:03,280
Speaker 1: They did. Yes. In eighteen fifty one, the foll called pendulum,

444
00:23:03,320 --> 00:23:07,080
Speaker 1: which is basically like a lead filled brass sphere suspended

445
00:23:07,119 --> 00:23:10,840
Speaker 1: on a really long string, in this case sixty seven meters.

446
00:23:11,320 --> 00:23:13,960
Speaker 1: You can see it rotate at a rate depending on

447
00:23:14,040 --> 00:23:16,959
Speaker 1: its latitude, so it's like a pendulum that swings back

448
00:23:17,040 --> 00:23:19,640
Speaker 1: and forth, but it also processes. If you ever see

449
00:23:19,640 --> 00:23:22,120
Speaker 1: these pendulums in like a science museum, like a really

450
00:23:22,160 --> 00:23:24,159
Speaker 1: long string, and it doesn't just go back and forth

451
00:23:24,359 --> 00:23:26,520
Speaker 1: like it goes back and forth, but also the back

452
00:23:26,560 --> 00:23:28,960
Speaker 1: and forth itself sort of rotates around and like leaves

453
00:23:29,040 --> 00:23:32,040
Speaker 1: marks in the sand. That's because of the rotation of

454
00:23:32,080 --> 00:23:35,479
Speaker 1: the Earth, and that depends on the latitude. So if

455
00:23:35,520 --> 00:23:38,000
Speaker 1: you do that experiment at the equator or you do

456
00:23:38,119 --> 00:23:40,240
Speaker 1: that at the North Pole, you get a different answer

457
00:23:40,320 --> 00:23:42,240
Speaker 1: because of the difference in tripetal acceleration.

458
00:23:42,680 --> 00:23:45,000
Speaker 3: This kind of stuff is amazing and like, so I

459
00:23:45,040 --> 00:23:46,399
Speaker 3: have you know, I got to be honest, like I

460
00:23:46,400 --> 00:23:51,959
Speaker 3: wouldn't want to spend my life creating precision weights or precision.

461
00:23:51,640 --> 00:23:53,840
Speaker 2: Instruments and stuff. But like, so you know when you've said.

462
00:23:53,640 --> 00:23:56,320
Speaker 3: If you took your weight at the equator and at

463
00:23:56,320 --> 00:23:58,639
Speaker 3: the North Pole, they'd be different. But of course you

464
00:23:58,800 --> 00:24:01,560
Speaker 3: don't actually mean like you weight, because the journey from

465
00:24:01,760 --> 00:24:05,320
Speaker 3: the North Pole to the equator, you know, you'd probably

466
00:24:05,359 --> 00:24:07,040
Speaker 3: like change your weight. You know, you'd eat a big

467
00:24:07,080 --> 00:24:08,000
Speaker 3: meal in between balla.

468
00:24:08,119 --> 00:24:09,560
Speaker 2: So so you're like, I'm sure what you mean.

469
00:24:09,680 --> 00:24:12,200
Speaker 3: You're like you'd have like a you know, twenty kilogram

470
00:24:12,240 --> 00:24:15,400
Speaker 3: weight or that you'd you know, compare at both locations

471
00:24:15,400 --> 00:24:15,720
Speaker 3: and like.

472
00:24:15,760 --> 00:24:17,960
Speaker 1: And you wouldn't feed any snacks to your twenty kilogram

473
00:24:17,960 --> 00:24:18,720
Speaker 1: weight along the way.

474
00:24:18,840 --> 00:24:20,239
Speaker 2: Yeah, exactly right.

475
00:24:20,320 --> 00:24:24,000
Speaker 3: No Cheetos, No, none of those stroop waffles that they're

476
00:24:24,000 --> 00:24:26,160
Speaker 3: giving on the flights now, which I am so excited

477
00:24:26,200 --> 00:24:27,720
Speaker 3: that that's a new thing you can get on flights.

478
00:24:27,920 --> 00:24:29,520
Speaker 1: Are you saying I couldn't go from the Equator to

479
00:24:29,560 --> 00:24:31,320
Speaker 1: the North Pole without resisting a stroop waffle?

480
00:24:32,000 --> 00:24:34,880
Speaker 2: I could not, But but what I'm saying is.

481
00:24:35,200 --> 00:24:35,960
Speaker 1: I couldn't either.

482
00:24:36,160 --> 00:24:39,080
Speaker 2: Yeah, So eighteen fifty one is one of the experiments

483
00:24:39,080 --> 00:24:42,040
Speaker 2: you were talking about, And so back then it wouldn't

484
00:24:42,080 --> 00:24:42,360
Speaker 2: just be.

485
00:24:42,359 --> 00:24:44,320
Speaker 3: A couple hours to get from the equator to the

486
00:24:44,320 --> 00:24:46,720
Speaker 3: North Pole. It would be you know, like half a

487
00:24:46,800 --> 00:24:48,760
Speaker 3: year or more or something. You make that journey, so

488
00:24:48,800 --> 00:24:51,560
Speaker 3: you change your weight during that time, but your twenty

489
00:24:51,680 --> 00:24:54,320
Speaker 3: kilogram mass might not. But like, there's so many things

490
00:24:54,320 --> 00:24:57,360
Speaker 3: we learned about the world by getting really good at

491
00:24:57,359 --> 00:25:01,240
Speaker 3: making precision measurements, and like, yeah, we're such a boring

492
00:25:01,359 --> 00:25:05,560
Speaker 3: and amazing species, Like, way to go us for managing

493
00:25:05,600 --> 00:25:07,639
Speaker 3: to do that kind of stuff, and anyway, props to

494
00:25:07,800 --> 00:25:08,640
Speaker 3: props to humans.

495
00:25:08,800 --> 00:25:10,919
Speaker 1: Yeah, props to nerds, you know, people who are like,

496
00:25:11,040 --> 00:25:13,400
Speaker 1: I'm super interested in this. I'm going to get really

497
00:25:13,440 --> 00:25:16,000
Speaker 1: good at that, and I'm going to somehow manage to

498
00:25:16,040 --> 00:25:18,080
Speaker 1: take my twenty kilogram weight from the equator to the

499
00:25:18,119 --> 00:25:22,320
Speaker 1: north pole without getting caramel smeared on it or something. Yeah, right, right,

500
00:25:22,400 --> 00:25:23,240
Speaker 1: thank you nerds.

501
00:25:23,640 --> 00:25:24,120
Speaker 2: That's right.

502
00:25:24,200 --> 00:25:27,040
Speaker 1: Yeah. And it's because of the diversity of people's interest

503
00:25:27,080 --> 00:25:29,080
Speaker 1: in weird stuff that we know all these amazing things

504
00:25:29,080 --> 00:25:32,600
Speaker 1: about the universe. So yay. Yeah, So that's how we

505
00:25:32,640 --> 00:25:34,199
Speaker 1: know that the Earth is spinning. Of course, we can

506
00:25:34,200 --> 00:25:36,480
Speaker 1: also see it from space, et cetera. So the Earth

507
00:25:36,520 --> 00:25:39,720
Speaker 1: is spinning at sixteen hundred kilometers per hour at the equator.

508
00:25:40,080 --> 00:25:42,840
Speaker 1: The Earth itself, of course, is moving relative to the Sun.

509
00:25:43,200 --> 00:25:48,040
Speaker 1: That's thirty kilometers per second, right, So any fast again

510
00:25:48,359 --> 00:25:51,720
Speaker 1: relative to the Sun. And this again is motion in

511
00:25:51,800 --> 00:25:55,400
Speaker 1: a circle, and motion in a circle requires constant acceleration

512
00:25:55,640 --> 00:25:59,600
Speaker 1: to maintain the same magnitude of velocity. So this is

513
00:25:59,640 --> 00:26:02,160
Speaker 1: also something you could measure, like even if you were

514
00:26:02,160 --> 00:26:04,159
Speaker 1: in a box, if you were orbiting a star, you

515
00:26:04,200 --> 00:26:06,720
Speaker 1: could tell you were orbiting a star because that is

516
00:26:06,720 --> 00:26:07,520
Speaker 1: an acceleration.

517
00:26:07,800 --> 00:26:09,560
Speaker 3: Well, now I want to know when and how we

518
00:26:09,640 --> 00:26:12,440
Speaker 3: figured that out, but it's not on your outline, so

519
00:26:12,440 --> 00:26:13,439
Speaker 3: I'm putting you on the spot.

520
00:26:13,840 --> 00:26:17,400
Speaker 1: Well, this all goes back to geocentrism and heliocentrism, right.

521
00:26:17,400 --> 00:26:19,840
Speaker 1: We had these two theories of the organization of the

522
00:26:19,840 --> 00:26:22,439
Speaker 1: solar system, one in which the Earth was at the

523
00:26:22,440 --> 00:26:24,760
Speaker 1: center and everything moved around it, another one where the

524
00:26:24,800 --> 00:26:27,440
Speaker 1: Sun was at the center and everything moved around it.

525
00:26:28,000 --> 00:26:30,719
Speaker 1: And I think it's fascinating that the Greeks actually had

526
00:26:30,720 --> 00:26:34,520
Speaker 1: the idea for heliocentrism. People often say, oh, the Greeks

527
00:26:34,600 --> 00:26:36,680
Speaker 1: just assumed that the Earth is at the center. They

528
00:26:36,760 --> 00:26:40,679
Speaker 1: considered heliocentrism. They considered the idea that the Sun was

529
00:26:40,720 --> 00:26:42,679
Speaker 1: at the center, and they even had an idea for

530
00:26:42,720 --> 00:26:45,080
Speaker 1: how to check. They thought that they could look at

531
00:26:45,119 --> 00:26:47,680
Speaker 1: the stars and if the Earth was moving around the Sun,

532
00:26:47,920 --> 00:26:50,280
Speaker 1: they would see the stars wiggle in the sky. And

533
00:26:50,320 --> 00:26:53,000
Speaker 1: they were right, they should be seeing that. That's called parallax.

534
00:26:53,680 --> 00:26:56,040
Speaker 1: But they were wrong about the distance to the stars.

535
00:26:56,280 --> 00:26:58,800
Speaker 1: They thought the stars were pretty close so that they

536
00:26:58,800 --> 00:27:00,520
Speaker 1: should be able to see the parallax. And when they

537
00:27:00,600 --> 00:27:04,080
Speaker 1: didn't see the parallax, they concluded incorrectly that the Earth

538
00:27:04,200 --> 00:27:06,520
Speaker 1: wasn't moving. If they had known the stars were so

539
00:27:06,600 --> 00:27:08,440
Speaker 1: far away, they would have realized that you can't use

540
00:27:08,480 --> 00:27:11,280
Speaker 1: parallax to discover the motion of the Earth unless you

541
00:27:11,320 --> 00:27:14,199
Speaker 1: have really fine telescopes. And we weren't able to do

542
00:27:14,200 --> 00:27:15,600
Speaker 1: that until like the eighteen hundreds.

543
00:27:15,800 --> 00:27:17,760
Speaker 2: Oh man, how frustrating. They were so close.

544
00:27:18,119 --> 00:27:19,800
Speaker 1: I know, they really on the edge of this. They

545
00:27:19,840 --> 00:27:22,560
Speaker 1: made the wrong assumption, led them down the wrong path. Anyway,

546
00:27:22,600 --> 00:27:24,840
Speaker 1: a couple thousand years later people figured out that the

547
00:27:24,880 --> 00:27:27,560
Speaker 1: Earth is moving around the Sun, but not by measuring

548
00:27:27,680 --> 00:27:30,840
Speaker 1: the acceleration the local acceleration of the Earth, but by

549
00:27:30,840 --> 00:27:33,959
Speaker 1: seeing the phases of Venus and then also getting more

550
00:27:34,000 --> 00:27:36,440
Speaker 1: precise measurements of the motion of the planets, so we

551
00:27:36,480 --> 00:27:39,600
Speaker 1: could see the geocentrism didn't really work, though it worked

552
00:27:39,640 --> 00:27:42,720
Speaker 1: surprisingly well even with cycles and epicycles.

553
00:27:42,760 --> 00:27:45,480
Speaker 3: But then how did we figure out the thirty kilometers

554
00:27:45,520 --> 00:27:46,800
Speaker 3: per second figure?

555
00:27:47,000 --> 00:27:49,120
Speaker 1: Oh? There, you could just use Kepler's laws, like if

556
00:27:49,160 --> 00:27:52,440
Speaker 1: you know the period of the planet and the distance

557
00:27:52,480 --> 00:27:55,720
Speaker 1: to the Sun, then you can figure out our local velocity.

558
00:27:55,880 --> 00:27:58,480
Speaker 1: It's just basic kinematics. So we've known that for hundreds

559
00:27:58,520 --> 00:27:58,920
Speaker 1: of years.

560
00:27:59,119 --> 00:28:01,159
Speaker 3: Folks, you should all know that Daniel didn't write that

561
00:28:01,200 --> 00:28:02,760
Speaker 3: down in his notes. He just has the soul in

562
00:28:02,800 --> 00:28:06,200
Speaker 3: his head. He's a smart guy, all right, keep going.

563
00:28:07,280 --> 00:28:10,359
Speaker 2: This is basic stuff, Kelly. You didn't have to be

564
00:28:10,359 --> 00:28:11,040
Speaker 2: a jerk face.

565
00:28:11,080 --> 00:28:13,560
Speaker 4: I was just something nice.

566
00:28:14,600 --> 00:28:16,880
Speaker 1: I'm just trying to deflect your compliment. Thank you very much,

567
00:28:17,200 --> 00:28:17,560
Speaker 1: all right.

568
00:28:17,600 --> 00:28:19,159
Speaker 2: Yeah, that's what you're supposed to say, Daniel.

569
00:28:19,720 --> 00:28:22,840
Speaker 1: And so there are these videos out there that try

570
00:28:22,880 --> 00:28:24,879
Speaker 1: to break people out of the mental image of the

571
00:28:24,920 --> 00:28:27,800
Speaker 1: Earth moving around the Sun and the Sun being stationary.

572
00:28:28,200 --> 00:28:30,199
Speaker 1: And I think that's cool, because it's true that the

573
00:28:30,240 --> 00:28:33,679
Speaker 1: Sun is not stationary with respect to the galaxy. But

574
00:28:33,720 --> 00:28:35,639
Speaker 1: it doesn't really mean anything to say the Sun is

575
00:28:35,720 --> 00:28:39,880
Speaker 1: moving through space, right, It's always relative to something. So

576
00:28:39,920 --> 00:28:42,000
Speaker 1: even if you have like a stationary image of the

577
00:28:42,000 --> 00:28:45,640
Speaker 1: Solar System, if you're approaching the Solar System with the velocity,

578
00:28:45,680 --> 00:28:47,920
Speaker 1: then the Sun is in motion relative to you. Like

579
00:28:47,960 --> 00:28:50,959
Speaker 1: if you are on three I at lists the Interstellar Visitor,

580
00:28:51,240 --> 00:28:53,320
Speaker 1: then the Sun is in motion. Or if you put

581
00:28:53,320 --> 00:28:55,200
Speaker 1: yourself at the center of the galaxy, then the Sun

582
00:28:55,360 --> 00:28:57,800
Speaker 1: is in motion. So it's true that you can move

583
00:28:57,840 --> 00:28:59,920
Speaker 1: to a frame where the Sun is in motion instead

584
00:28:59,920 --> 00:29:02,520
Speaker 1: of a frame where the Sun is at rest. But

585
00:29:02,520 --> 00:29:05,480
Speaker 1: it's a little misleading to suggest that, like, oh, really,

586
00:29:05,520 --> 00:29:08,800
Speaker 1: the Sun is moving through space. It's moving relative to something,

587
00:29:09,240 --> 00:29:11,720
Speaker 1: and the most interesting thing it's moving with respect to

588
00:29:12,240 --> 00:29:13,800
Speaker 1: is the center of the galaxy.

589
00:29:14,120 --> 00:29:16,480
Speaker 2: And how fast is it moving with respect to the

590
00:29:16,480 --> 00:29:17,400
Speaker 2: center of the galaxy.

591
00:29:17,480 --> 00:29:21,240
Speaker 1: It's moving eight hundred thousand kilometers per hour around the

592
00:29:21,280 --> 00:29:23,840
Speaker 1: center of the galaxy, which is like a big number,

593
00:29:24,240 --> 00:29:26,600
Speaker 1: but you know, it doesn't really affect your life because

594
00:29:26,840 --> 00:29:29,040
Speaker 1: think about it the other way. It means that the

595
00:29:29,080 --> 00:29:32,080
Speaker 1: center of the galaxy is moving eight hundred thousand kilometers

596
00:29:32,160 --> 00:29:34,800
Speaker 1: per hour relative to us, but it's really far away,

597
00:29:34,960 --> 00:29:37,880
Speaker 1: so like, who cares how fast it's moving relative does

598
00:29:38,160 --> 00:29:41,200
Speaker 1: doesn't mean anything for us here on Earth, though it

599
00:29:41,280 --> 00:29:43,880
Speaker 1: is fun to think about, like how long it takes

600
00:29:43,920 --> 00:29:46,640
Speaker 1: the Sun to go around the center of the galaxy.

601
00:29:47,120 --> 00:29:50,120
Speaker 1: It takes like a couple hundred million years for the

602
00:29:50,200 --> 00:29:52,840
Speaker 1: Sun to do one orbit. So if you think about

603
00:29:52,840 --> 00:29:55,360
Speaker 1: that as like a galaxy year, the way that like

604
00:29:55,680 --> 00:29:58,400
Speaker 1: the Earth takes one Earth year to go around the Sun,

605
00:29:58,680 --> 00:30:01,520
Speaker 1: the Sun takes one like galaxy year to go around

606
00:30:01,520 --> 00:30:04,480
Speaker 1: the center of the galaxy, then our solar system is

607
00:30:04,480 --> 00:30:06,440
Speaker 1: about twenty galaxy years old.

608
00:30:06,560 --> 00:30:10,640
Speaker 2: She's almost old enough to drink. I wonder what her

609
00:30:10,680 --> 00:30:13,160
Speaker 2: preferred drink's going to be. It might be tea, maybe

610
00:30:13,160 --> 00:30:14,280
Speaker 2: she's not into alcohol.

611
00:30:14,520 --> 00:30:20,320
Speaker 1: Cosmopolitan maybe, oh, cute love it, that's probably what it's

612
00:30:20,320 --> 00:30:20,680
Speaker 1: going to be.

613
00:30:20,960 --> 00:30:21,280
Speaker 4: Yeah.

614
00:30:21,520 --> 00:30:23,720
Speaker 1: I think that's pretty cool because it means the galaxy

615
00:30:24,120 --> 00:30:27,360
Speaker 1: has not had that many rotations. It's already formed all

616
00:30:27,360 --> 00:30:29,840
Speaker 1: of the structure and the spiral arms and all that

617
00:30:29,880 --> 00:30:33,920
Speaker 1: stuff without spinning more than fifty times. Right, that's kind

618
00:30:33,920 --> 00:30:34,560
Speaker 1: of mind blowing.

619
00:30:34,640 --> 00:30:37,080
Speaker 2: That is kind of mind blowing. How many turns around

620
00:30:37,080 --> 00:30:39,280
Speaker 2: the galaxy is it going to have? Do you know?

621
00:30:39,680 --> 00:30:42,440
Speaker 1: Well, that's a great question. Well, we're scheduled for a

622
00:30:42,480 --> 00:30:47,560
Speaker 1: collision with Andromeda in a few billion years, and that's

623
00:30:47,600 --> 00:30:50,720
Speaker 1: only another like ten ish or fifteen ish rotations.

624
00:30:50,840 --> 00:30:53,960
Speaker 3: Change the subject all messed up again? No, no, I

625
00:30:53,960 --> 00:30:57,360
Speaker 3: don't want to hear this all right, moving on, And.

626
00:30:57,280 --> 00:30:59,600
Speaker 1: Of course you can ask, well is the galaxy in motion?

627
00:31:00,040 --> 00:31:02,680
Speaker 1: And you have to ask is it motion relative to what?

628
00:31:03,760 --> 00:31:06,080
Speaker 1: And so there's a bunch of different choices you can

629
00:31:06,120 --> 00:31:08,960
Speaker 1: make here. You could choose the local galaxy cluster and

630
00:31:09,000 --> 00:31:12,000
Speaker 1: say we're orbiting around the center of mass and the

631
00:31:12,040 --> 00:31:15,280
Speaker 1: galaxy cluster. But I think here we should like skip

632
00:31:15,320 --> 00:31:18,120
Speaker 1: forward to the biggest picture question and say, like, is

633
00:31:18,160 --> 00:31:21,120
Speaker 1: there any kind of frame out there you could use

634
00:31:21,280 --> 00:31:25,120
Speaker 1: that's like the center of stuff? Because on one hand,

635
00:31:25,360 --> 00:31:28,040
Speaker 1: there is no preferred frame in the universe for space.

636
00:31:28,440 --> 00:31:31,160
Speaker 1: You can't say I'm moving through space with respect to anything,

637
00:31:31,480 --> 00:31:33,760
Speaker 1: But there is a bunch of stuff in the universe,

638
00:31:34,120 --> 00:31:37,040
Speaker 1: and you can ask like how fast am I moving

639
00:31:37,120 --> 00:31:40,840
Speaker 1: relative to all the stuff in the universe. So this

640
00:31:40,880 --> 00:31:43,239
Speaker 1: feels like a weird kind of card trick. You have

641
00:31:43,240 --> 00:31:46,680
Speaker 1: no velocity relative to space, but I can then fill

642
00:31:46,760 --> 00:31:49,280
Speaker 1: space with a bunch of stuff like space was filled

643
00:31:49,280 --> 00:31:52,080
Speaker 1: with the hot dense plasma a few billion years ago,

644
00:31:52,520 --> 00:31:55,680
Speaker 1: and that stuff has no velocity relative to space either, right,

645
00:31:55,720 --> 00:31:58,440
Speaker 1: Because you can't have velocity relative to space, but it

646
00:31:58,480 --> 00:32:00,360
Speaker 1: doesn't mean that Now I can ask like, how fast

647
00:32:00,400 --> 00:32:03,880
Speaker 1: on going relative to that stuff? Right? So it's sort

648
00:32:03,880 --> 00:32:06,440
Speaker 1: of like I put wallpaper on the wall and I said,

649
00:32:06,720 --> 00:32:09,320
Speaker 1: you can't ask your velocity relative to the wall, but

650
00:32:09,360 --> 00:32:12,440
Speaker 1: you can ask your velocity relative to the wall paper. Right.

651
00:32:12,520 --> 00:32:13,600
Speaker 2: Yeah, it feels like cheating.

652
00:32:13,760 --> 00:32:15,880
Speaker 1: It does feel like cheating, but in this case.

653
00:32:15,680 --> 00:32:20,480
Speaker 3: The wallpaper isn't there, right, or because the plasma's not

654
00:32:20,600 --> 00:32:22,560
Speaker 3: there right, or it was a long time ago, but

655
00:32:22,600 --> 00:32:23,520
Speaker 3: it's not there now.

656
00:32:23,760 --> 00:32:27,720
Speaker 1: Yeah, so the plasma's not there anymore. And really, you know,

657
00:32:27,880 --> 00:32:30,720
Speaker 1: the wallpaper has no velocity relative to the wall. It's

658
00:32:30,760 --> 00:32:33,360
Speaker 1: just like there's something else in the room with us. Now,

659
00:32:33,640 --> 00:32:36,520
Speaker 1: so we can finally ask do we have a velocity

660
00:32:36,520 --> 00:32:39,880
Speaker 1: relative to something? It's like, go back to that empty universe.

661
00:32:40,200 --> 00:32:42,600
Speaker 1: You have no velocity. It means nothing to have a velocity.

662
00:32:42,800 --> 00:32:45,600
Speaker 1: Then I fill that universe with stuff. Now you have

663
00:32:45,640 --> 00:32:49,000
Speaker 1: a velocity relative to all of that stuff. And that

664
00:32:49,120 --> 00:32:51,960
Speaker 1: stuff has no velocity relative to anything else in the

665
00:32:52,040 --> 00:32:55,720
Speaker 1: universe except for you or itself. It has no velocity

666
00:32:55,760 --> 00:32:59,720
Speaker 1: relative to space. Right, But there is a preferred frame

667
00:32:59,760 --> 00:33:02,480
Speaker 1: in the universe. That frame is the frame of all

668
00:33:02,520 --> 00:33:05,880
Speaker 1: the stuff in the universe. And so you can't ask

669
00:33:05,920 --> 00:33:09,080
Speaker 1: about your velocity relative to space, but you can ask

670
00:33:09,120 --> 00:33:12,760
Speaker 1: about your velocity relative to the stuff in the universe.

671
00:33:13,400 --> 00:33:17,360
Speaker 3: And why is that the preferred Why is the frame

672
00:33:17,400 --> 00:33:21,240
Speaker 3: that doesn't actually exist and is a mind trick the

673
00:33:21,360 --> 00:33:22,720
Speaker 3: preferred frame.

674
00:33:22,840 --> 00:33:24,760
Speaker 1: Because it's the only one we can think of.

675
00:33:25,040 --> 00:33:28,600
Speaker 3: Okay, all right, there's no other option, right, digging the honesty,

676
00:33:28,640 --> 00:33:29,320
Speaker 3: you can either.

677
00:33:29,200 --> 00:33:31,480
Speaker 1: Give up or you can choose this one, and neither

678
00:33:31,520 --> 00:33:32,440
Speaker 1: a satisfactory.

679
00:33:33,280 --> 00:33:35,960
Speaker 3: And how fast are we going relative to the space wallpaper?

680
00:33:38,440 --> 00:33:40,960
Speaker 1: The answer is, we don't know. We actually have two

681
00:33:41,000 --> 00:33:43,840
Speaker 1: different measurements, and they disagree by a lot.

682
00:33:44,160 --> 00:33:46,640
Speaker 2: What All right, let's take a break, and when we

683
00:33:46,680 --> 00:33:49,720
Speaker 2: come back, boy, things even more confusing.

684
00:33:53,560 --> 00:33:55,400
Speaker 1: You thought this was going to be a simple episode,

685
00:33:55,440 --> 00:33:55,760
Speaker 1: didn't you.

686
00:33:56,320 --> 00:34:16,440
Speaker 4: I hope so.

687
00:34:18,480 --> 00:34:21,640
Speaker 3: And we're back, and we should have saved this episode

688
00:34:21,640 --> 00:34:23,880
Speaker 3: for Halloween because we're going to talk about this spooky

689
00:34:24,080 --> 00:34:25,640
Speaker 3: radio dipole anomaly.

690
00:34:26,880 --> 00:34:29,000
Speaker 1: So we're interested in the question of how fast are

691
00:34:29,040 --> 00:34:32,080
Speaker 1: we moving relative to all the stuff in the universe.

692
00:34:32,560 --> 00:34:34,480
Speaker 1: Because you take an empty universe and you PLoP a

693
00:34:34,520 --> 00:34:37,080
Speaker 1: bunch of stuff into it. Now there's a frame, right,

694
00:34:37,120 --> 00:34:40,160
Speaker 1: the frame in which that stuff is at rest, and

695
00:34:40,239 --> 00:34:42,319
Speaker 1: how do you measure that? Well, we're going to talk

696
00:34:42,320 --> 00:34:45,440
Speaker 1: about two different ways of measuring it. One tries to

697
00:34:45,440 --> 00:34:48,719
Speaker 1: measure our velocity relative to the stuff in the early universe.

698
00:34:49,239 --> 00:34:51,920
Speaker 1: So brief history of the universe, A bunch of stuff

699
00:34:51,920 --> 00:34:54,359
Speaker 1: happened that we don't understand at all, but somehow led

700
00:34:54,400 --> 00:34:58,600
Speaker 1: to a universe filled with a very hot dense plasma.

701
00:34:59,200 --> 00:35:01,840
Speaker 1: That plasma is a and then it's cooling as the

702
00:35:01,960 --> 00:35:05,560
Speaker 1: universe expands. Suddenly it cools enough for the protons and

703
00:35:05,600 --> 00:35:08,480
Speaker 1: electrons to get together and make neutral hydrogen, and the

704
00:35:08,560 --> 00:35:12,719
Speaker 1: universe suddenly becomes transparent, which means all the light that

705
00:35:12,760 --> 00:35:16,120
Speaker 1: previously was being absorbed just after it was emitted now

706
00:35:16,160 --> 00:35:20,400
Speaker 1: flies free, free lights, and the universe has been transparent

707
00:35:20,440 --> 00:35:23,200
Speaker 1: ever since then, which means we can still see that light.

708
00:35:23,400 --> 00:35:26,799
Speaker 1: We can see evidence of that hot dense plasma, and

709
00:35:26,840 --> 00:35:31,200
Speaker 1: that's what's called the cosmic microwave background radiation. It's microwave

710
00:35:31,200 --> 00:35:33,960
Speaker 1: because that's the frequency we see it at. It was

711
00:35:34,080 --> 00:35:37,759
Speaker 1: a very very high frequency because very hot plasma's emit

712
00:35:37,880 --> 00:35:41,359
Speaker 1: a very high frequency light, but it's been stretched out

713
00:35:41,360 --> 00:35:44,480
Speaker 1: by the expansion of the universe to very long wavelengths

714
00:35:44,480 --> 00:35:47,399
Speaker 1: and low frequency. So we can still see that light

715
00:35:47,880 --> 00:35:51,200
Speaker 1: and we can see Doppler shifts in that light. Okay,

716
00:35:51,400 --> 00:35:53,360
Speaker 1: so we can still see that light, which means basically

717
00:35:53,400 --> 00:35:57,080
Speaker 1: we can look around and see that plasma right And

718
00:35:57,320 --> 00:35:59,600
Speaker 1: you know, it's a little bit confusing to think about

719
00:35:59,680 --> 00:36:01,799
Speaker 1: what part of the plasma we're seeing. If you look

720
00:36:01,800 --> 00:36:05,000
Speaker 1: in one direction from Earth, you're seeing light that's been

721
00:36:05,040 --> 00:36:09,560
Speaker 1: traveling basically fourteen billion years since it was emitted and

722
00:36:09,880 --> 00:36:11,719
Speaker 1: just got to Earth. If you look in the other

723
00:36:11,800 --> 00:36:14,520
Speaker 1: direction from Earth, you're seeing light that traveled to fourteen

724
00:36:14,560 --> 00:36:17,440
Speaker 1: billion years since it was admitted and just got to Earth.

725
00:36:17,920 --> 00:36:20,360
Speaker 1: So you're looking at bits of plasma that were like

726
00:36:20,400 --> 00:36:23,279
Speaker 1: across the universe from each other. If you look all

727
00:36:23,320 --> 00:36:26,000
Speaker 1: around the Earth, you're seeing light from a shell of

728
00:36:26,080 --> 00:36:29,279
Speaker 1: plasma that emitted light in the direction where Earth was

729
00:36:29,320 --> 00:36:32,439
Speaker 1: going to be and just arrived here now. And as

730
00:36:32,520 --> 00:36:35,600
Speaker 1: time goes on, we see light from a different shell

731
00:36:35,640 --> 00:36:38,840
Speaker 1: of plasma, a larger and larger shell, further and further

732
00:36:38,960 --> 00:36:41,640
Speaker 1: away from us. But we're always going to see CMB

733
00:36:41,760 --> 00:36:45,239
Speaker 1: light because the universe was filled with this plasma. So

734
00:36:45,280 --> 00:36:48,080
Speaker 1: it's a great way to measure our velocity relative to

735
00:36:48,120 --> 00:36:50,520
Speaker 1: the stuff in the universe back when the universe was

736
00:36:50,560 --> 00:36:54,320
Speaker 1: filled with this plasma that conveniently all gave off this light.

737
00:36:54,120 --> 00:36:58,839
Speaker 2: But so everything you just said made sense, but we're

738
00:36:58,880 --> 00:37:01,920
Speaker 2: talking about in an anoma, So I feel like I

739
00:37:01,960 --> 00:37:04,120
Speaker 2: wasn't supposed to understand all of it.

740
00:37:04,719 --> 00:37:07,799
Speaker 1: No, you're still supposed to understand it, And the way

741
00:37:07,840 --> 00:37:10,480
Speaker 1: we measure our velocity relative to that light is pretty simple.

742
00:37:10,719 --> 00:37:12,439
Speaker 1: We just look to see if the light is blue

743
00:37:12,480 --> 00:37:15,560
Speaker 1: shifted or red shifted. Because if you're moving towards something,

744
00:37:15,880 --> 00:37:18,800
Speaker 1: frequency goes up. If you're moving away from something, frequency

745
00:37:18,880 --> 00:37:21,960
Speaker 1: goes down. Wavelengths to get longer. And most of the time,

746
00:37:22,000 --> 00:37:24,480
Speaker 1: when you look at a picture of the CMB, like

747
00:37:24,719 --> 00:37:27,680
Speaker 1: on the internet, it looks like all these little red

748
00:37:27,719 --> 00:37:29,880
Speaker 1: and blue dots, and what you're looking at there is

749
00:37:29,920 --> 00:37:32,799
Speaker 1: not the raw CMB light. What you're looking at is

750
00:37:32,800 --> 00:37:36,200
Speaker 1: that when they remove our velocity effect, if you look

751
00:37:36,200 --> 00:37:38,439
Speaker 1: at the raw CMB, it's like blue on one side

752
00:37:38,440 --> 00:37:41,360
Speaker 1: and red on the other. Because we are moving relative

753
00:37:41,400 --> 00:37:43,640
Speaker 1: to the CMB, we're not at rest relative to it,

754
00:37:43,920 --> 00:37:46,680
Speaker 1: so they usually subtract this part out. Because we're moving

755
00:37:46,760 --> 00:37:50,880
Speaker 1: at three hundred and seventy kilometers per second through the CMB,

756
00:37:51,200 --> 00:37:52,240
Speaker 1: so pretty fast.

757
00:37:52,560 --> 00:37:53,560
Speaker 2: Yeah, look at us go.

758
00:37:54,080 --> 00:37:55,920
Speaker 1: So that's sort of the closest we can come to

759
00:37:55,960 --> 00:37:58,560
Speaker 1: saying how fast are we moving through this stuff in

760
00:37:58,600 --> 00:38:01,640
Speaker 1: the universe. That's a big number, and people would like

761
00:38:01,680 --> 00:38:04,440
Speaker 1: to know is that really correct? Are we making a mistake?

762
00:38:04,960 --> 00:38:07,560
Speaker 1: And you know, what we're measuring there is our velocity

763
00:38:07,640 --> 00:38:10,200
Speaker 1: relative to the stuff that used to be in the

764
00:38:10,280 --> 00:38:13,000
Speaker 1: universe fourteen billion years ago. We can do a cross

765
00:38:13,080 --> 00:38:15,280
Speaker 1: check by looking at the stuff in the universe now

766
00:38:15,320 --> 00:38:17,840
Speaker 1: and asking, well, how fast are we moving relative to

767
00:38:17,920 --> 00:38:21,360
Speaker 1: like distant galaxies for example, and all that stuff, And

768
00:38:21,400 --> 00:38:23,359
Speaker 1: so we can make the same measurement. We can look

769
00:38:23,440 --> 00:38:26,680
Speaker 1: for galaxies and we can ask, like, is there like

770
00:38:26,719 --> 00:38:29,160
Speaker 1: blue shifted or red shifted and that should make a

771
00:38:29,160 --> 00:38:31,719
Speaker 1: map across the sky of like blue shifted versus red

772
00:38:31,760 --> 00:38:35,160
Speaker 1: shifted galaxies and tell us which direction are we going

773
00:38:35,239 --> 00:38:39,120
Speaker 1: and how fast relative to all the galaxies out there

774
00:38:39,120 --> 00:38:41,880
Speaker 1: in the universe. Not relative to space again, but relative

775
00:38:42,120 --> 00:38:44,799
Speaker 1: to the stuff in the universe. And we should get

776
00:38:44,840 --> 00:38:47,840
Speaker 1: the same answer because the galaxies out there in the universe,

777
00:38:48,160 --> 00:38:51,760
Speaker 1: they came from this CMB stuff, right, that's stuff clumped

778
00:38:51,800 --> 00:38:54,800
Speaker 1: together and made structure and eventually formed galaxies which spun

779
00:38:54,880 --> 00:38:57,600
Speaker 1: for a few times before they collided with other galaxies,

780
00:38:57,600 --> 00:39:00,560
Speaker 1: et cetera. So we should get the same answer, right.

781
00:39:00,680 --> 00:39:02,160
Speaker 3: Well, so then why did we need to do all

782
00:39:02,239 --> 00:39:04,400
Speaker 3: this CMB stuff if we could have just done it

783
00:39:04,440 --> 00:39:07,040
Speaker 3: with the galaxies or it's just nice to double check.

784
00:39:07,200 --> 00:39:08,200
Speaker 2: Replication is good.

785
00:39:08,600 --> 00:39:10,439
Speaker 1: It's nice to double check, and you think you should

786
00:39:10,440 --> 00:39:11,960
Speaker 1: get the same answer in two different ways, so you

787
00:39:12,040 --> 00:39:14,160
Speaker 1: always got to do it both ways, right, got it?

788
00:39:14,160 --> 00:39:16,160
Speaker 1: That's the worrier in you, like, h what have we

789
00:39:16,239 --> 00:39:17,759
Speaker 1: got it wrong? Let's double check?

790
00:39:17,840 --> 00:39:18,520
Speaker 2: Yeah, anxiety.

791
00:39:18,640 --> 00:39:21,719
Speaker 1: And so they recently made this measurement. It's tough to do.

792
00:39:21,760 --> 00:39:23,719
Speaker 1: You got to look at galaxies in the radio you

793
00:39:23,719 --> 00:39:26,920
Speaker 1: have to subtract all sorts of other effects. Galaxies are

794
00:39:26,960 --> 00:39:30,279
Speaker 1: not as spread out evenly as the CMB is, and

795
00:39:30,360 --> 00:39:33,439
Speaker 1: so fascinatingly what they find is they measure the same

796
00:39:33,480 --> 00:39:36,920
Speaker 1: direction of motion. So they agree. The CMB measurement and

797
00:39:36,960 --> 00:39:40,960
Speaker 1: this radio galaxy measurement agree in the direction. But the

798
00:39:41,080 --> 00:39:44,200
Speaker 1: radio galaxy suggests that we're moving two to five times

799
00:39:44,440 --> 00:39:46,520
Speaker 1: faster than the CMB measurement.

800
00:39:46,560 --> 00:39:49,480
Speaker 2: Says, oh, that's the anomaly.

801
00:39:50,000 --> 00:39:52,520
Speaker 1: That's the anomally. It's called the radio dipole anomaly. A

802
00:39:52,520 --> 00:39:56,600
Speaker 1: pretty recent measurement, and it's not understood like either. It

803
00:39:56,640 --> 00:40:00,040
Speaker 1: means there's something very wrong with our understanding of the

804
00:40:00,120 --> 00:40:03,080
Speaker 1: universe and how it's evolved over time. But that would

805
00:40:03,120 --> 00:40:05,960
Speaker 1: be pretty surprising, because you know, we really think the

806
00:40:05,960 --> 00:40:08,319
Speaker 1: CMB was there and it filled the universe and it

807
00:40:08,360 --> 00:40:12,360
Speaker 1: was mostly smooth, and the universe has expanded isotropically, so

808
00:40:12,400 --> 00:40:16,200
Speaker 1: it'd be pretty hard to explain how this happened. Most

809
00:40:16,480 --> 00:40:19,840
Speaker 1: likely this is due to something boring like these radio

810
00:40:19,880 --> 00:40:22,560
Speaker 1: galaxies have to be seen through a telescope. They're all

811
00:40:22,560 --> 00:40:25,560
Speaker 1: in different locations, and the telescope isn't as good at

812
00:40:25,600 --> 00:40:29,080
Speaker 1: spotting them in different locations, or the measurements of their

813
00:40:29,160 --> 00:40:33,040
Speaker 1: velocity are not quite as accurate, or the calibration changes

814
00:40:33,080 --> 00:40:36,600
Speaker 1: over the sky and maybe drifts as you move the telescope.

815
00:40:36,760 --> 00:40:39,440
Speaker 1: So people are hunting for an explanation, and you know,

816
00:40:39,600 --> 00:40:42,400
Speaker 1: usually what you do is like look for a boring explanation,

817
00:40:42,920 --> 00:40:45,280
Speaker 1: like oh, every time somebody made ramen in the microwave

818
00:40:45,320 --> 00:40:48,200
Speaker 1: in the breakroom, or data shifted by two points, right,

819
00:40:48,440 --> 00:40:53,120
Speaker 1: that was an actual explanation for an astrophysical anology in Australia. Yeah,

820
00:40:53,160 --> 00:40:56,040
Speaker 1: it was burritos in the microwave. So you always look

821
00:40:56,080 --> 00:40:58,520
Speaker 1: for those kind of things before you conclude everything we

822
00:40:58,600 --> 00:41:01,680
Speaker 1: know about the universe is, which is how the clickbait

823
00:41:01,719 --> 00:41:03,560
Speaker 1: of many of these articles started out.

824
00:41:04,320 --> 00:41:04,720
Speaker 2: Yeah.

825
00:41:04,960 --> 00:41:07,240
Speaker 3: Well, also, you know, I think what we should conclude

826
00:41:07,280 --> 00:41:09,880
Speaker 3: is that we need more money for better telescope. So

827
00:41:09,920 --> 00:41:12,839
Speaker 3: that we can make all of these measurements more accurately.

828
00:41:12,400 --> 00:41:14,960
Speaker 1: Exactly, And you should look at not just radio galaxies,

829
00:41:14,960 --> 00:41:17,360
Speaker 1: but other kinds of galaxies and other stuff in the universe,

830
00:41:17,400 --> 00:41:19,480
Speaker 1: and we should measure this kind of stuff in lots

831
00:41:19,520 --> 00:41:22,600
Speaker 1: of different ways, because this is how you make discoveries. Folks.

832
00:41:22,880 --> 00:41:25,200
Speaker 1: You think you understand something, you double check it, you

833
00:41:25,239 --> 00:41:28,120
Speaker 1: get an answer that's not what you expected, and that

834
00:41:28,239 --> 00:41:32,239
Speaker 1: forces you to reconsider your ideas about the universe. And

835
00:41:32,320 --> 00:41:34,239
Speaker 1: you sometimes hear out there on the internet that, like,

836
00:41:34,640 --> 00:41:37,799
Speaker 1: scientists will protect the narrative because they don't want to

837
00:41:37,840 --> 00:41:40,799
Speaker 1: upend the apple cart in order to get grants, and like, no,

838
00:41:41,160 --> 00:41:45,200
Speaker 1: absolutely not. Scientists love to upend the narrative. I know.

839
00:41:45,280 --> 00:41:47,480
Speaker 1: That's why you see these crazy clickbait articles. It's a

840
00:41:47,480 --> 00:41:50,760
Speaker 1: scientist trying to upend the narrative with their latest study

841
00:41:50,760 --> 00:41:53,320
Speaker 1: which blows up our understanding of the universe.

842
00:41:53,480 --> 00:41:54,719
Speaker 2: That's how you get the awards.

843
00:41:54,920 --> 00:41:58,480
Speaker 1: Exactly. Scientists are not working together to protect some narrative.

844
00:41:58,680 --> 00:42:02,239
Speaker 1: They're all working against each other, desperately using every trick

845
00:42:02,280 --> 00:42:05,120
Speaker 1: they can to prove their friends and rivals wrong.

846
00:42:05,480 --> 00:42:09,040
Speaker 2: Yeah, they're varying degrees of cutthroat.

847
00:42:09,080 --> 00:42:11,640
Speaker 3: I don't want to make everybody sound like a jerk,

848
00:42:11,680 --> 00:42:14,000
Speaker 3: but yes, I agree. If you can prove the dominant

849
00:42:14,080 --> 00:42:18,640
Speaker 3: narrative wrong, that's when you get all the awards. All right, Well, Daniel,

850
00:42:18,719 --> 00:42:21,480
Speaker 3: I am exhausted from all of this moving. Can we

851
00:42:21,520 --> 00:42:24,640
Speaker 3: talk about Are there ways to not move? Ways to

852
00:42:24,680 --> 00:42:26,400
Speaker 3: stay motionless in space?

853
00:42:26,840 --> 00:42:29,000
Speaker 1: Yeah? So it doesn't mean anything to be motionless with

854
00:42:29,080 --> 00:42:32,640
Speaker 1: respect to space, right, And people sometimes write to me

855
00:42:32,680 --> 00:42:35,520
Speaker 1: about this question when they read time travel fiction and

856
00:42:35,560 --> 00:42:38,160
Speaker 1: they're like, if I went back in time to fourteen

857
00:42:38,239 --> 00:42:40,640
Speaker 1: ninety two, wouldn't the Earth be in a different place?

858
00:42:41,120 --> 00:42:43,400
Speaker 1: And how come this science fiction novel I read didn't

859
00:42:43,400 --> 00:42:46,640
Speaker 1: account for that? And you're giving me a funny look.

860
00:42:46,800 --> 00:42:50,320
Speaker 1: This is a very common question. People think that they gotcha,

861
00:42:50,480 --> 00:42:52,480
Speaker 1: and like, well, number one, time travel breaks a lot

862
00:42:52,520 --> 00:42:55,719
Speaker 1: of physics anyway, and so maybe you should give the

863
00:42:55,719 --> 00:42:58,720
Speaker 1: author a little bit of leeway on this detail. Also,

864
00:42:59,200 --> 00:43:02,360
Speaker 1: it's question doesn't have any meaning, Like the Earth's location

865
00:43:03,000 --> 00:43:06,960
Speaker 1: over time only means something relative to some axis, to

866
00:43:07,040 --> 00:43:10,280
Speaker 1: some frame. So if you choose the frame of the Earth,

867
00:43:10,760 --> 00:43:12,640
Speaker 1: then like you go back in time and you're still

868
00:43:12,680 --> 00:43:15,200
Speaker 1: on the Earth. So yes, if you choose the frame

869
00:43:15,200 --> 00:43:16,760
Speaker 1: of the Sun, the Earth would be in a different

870
00:43:16,800 --> 00:43:19,520
Speaker 1: location in fourteen ninety two than it is now. But

871
00:43:19,719 --> 00:43:21,600
Speaker 1: the question doesn't really have meaning.

872
00:43:21,880 --> 00:43:23,799
Speaker 2: Oh, I see what they were getting at. Now, you

873
00:43:23,960 --> 00:43:27,800
Speaker 2: would your time machine would dump you in the vastness

874
00:43:27,800 --> 00:43:29,520
Speaker 2: of space instead of on Earth, then that.

875
00:43:29,440 --> 00:43:29,960
Speaker 1: Would be bad.

876
00:43:30,080 --> 00:43:34,520
Speaker 2: Okay, okay, all right, okay, But we've decided let it go.

877
00:43:35,400 --> 00:43:36,120
Speaker 2: Enjoy your fiction.

878
00:43:36,520 --> 00:43:39,399
Speaker 1: Number one, let it go, which is my approach when

879
00:43:39,400 --> 00:43:41,960
Speaker 1: I read time travel fiction, as I rarely do for

880
00:43:42,000 --> 00:43:46,320
Speaker 1: that reason. And number two, the question assumes some absolute

881
00:43:46,400 --> 00:43:50,359
Speaker 1: reference frame, right, which just doesn't exist. And you might think, well,

882
00:43:50,360 --> 00:43:52,640
Speaker 1: what is the right reference frame? And there is none, right,

883
00:43:52,920 --> 00:43:54,960
Speaker 1: And the problem here is that time travel doesn't make

884
00:43:55,000 --> 00:43:58,280
Speaker 1: any sense anyway, and so there's no like hard physics

885
00:43:58,320 --> 00:44:01,200
Speaker 1: way to ask that question. But you can be motionless

886
00:44:01,239 --> 00:44:04,160
Speaker 1: with respect to other stuff, which can be cool, like,

887
00:44:04,239 --> 00:44:07,759
Speaker 1: for example, you can be motionless with respect to a

888
00:44:07,800 --> 00:44:09,399
Speaker 1: point on the Earth's surface, right, like.

889
00:44:09,400 --> 00:44:10,760
Speaker 2: A point on the Earth's surface.

890
00:44:10,920 --> 00:44:13,480
Speaker 1: If, for example, you want to build a space elevator,

891
00:44:13,920 --> 00:44:16,360
Speaker 1: you want that space elevator to be connected to the

892
00:44:16,400 --> 00:44:18,279
Speaker 1: Earth by a cable, and so you'd like it to

893
00:44:18,320 --> 00:44:22,680
Speaker 1: be effectively in geosynchronous orbit above someplace, hopefully on the

894
00:44:22,719 --> 00:44:26,560
Speaker 1: equator that you built this thing, and so that's geosynchronous orbit.

895
00:44:26,600 --> 00:44:29,960
Speaker 1: We have no motion relative to the Earth's surface. You're

896
00:44:30,000 --> 00:44:33,240
Speaker 1: still in orbit, and it's still acceleration your velocity relative

897
00:44:33,280 --> 00:44:35,839
Speaker 1: to the center of the Earth. But you can have

898
00:44:36,160 --> 00:44:38,600
Speaker 1: no motion relative to the Earth's surface.

899
00:44:38,760 --> 00:44:41,080
Speaker 3: Can I tell you a fun story about Yes, you

900
00:44:41,120 --> 00:44:42,320
Speaker 3: can space elevators.

901
00:44:42,440 --> 00:44:44,200
Speaker 2: I'll try I'll keep it. I'll try to keep it short.

902
00:44:44,200 --> 00:44:44,880
Speaker 2: No do so.

903
00:44:45,040 --> 00:44:47,080
Speaker 3: The bit the hard thing about making a space elevator

904
00:44:47,160 --> 00:44:49,799
Speaker 3: is trying to come up with a material for the

905
00:44:49,840 --> 00:44:52,279
Speaker 3: cable that is strong enough to hold the elevator, but

906
00:44:52,320 --> 00:44:55,160
Speaker 3: also isn't so heavy that you're just like lifting the

907
00:44:55,200 --> 00:44:58,520
Speaker 3: cable a whole time, right, And so carbon nanotubes might

908
00:44:58,719 --> 00:45:00,320
Speaker 3: one day maybe work. What we have it made a

909
00:45:00,360 --> 00:45:02,960
Speaker 3: continuous one that's long enough. But even if you did,

910
00:45:03,239 --> 00:45:05,040
Speaker 3: what you'd really have to worry about is if it

911
00:45:05,080 --> 00:45:08,239
Speaker 3: ever got struck by lightning, that could, like you the

912
00:45:08,320 --> 00:45:10,560
Speaker 3: game over, Like it could destroy the cable. And so

913
00:45:10,600 --> 00:45:12,640
Speaker 3: I was talking to somebody about what to do about that,

914
00:45:13,160 --> 00:45:16,640
Speaker 3: and their answer was, well, you know, there's this part

915
00:45:16,680 --> 00:45:18,120
Speaker 3: of the ocean that's never recorded.

916
00:45:18,160 --> 00:45:22,680
Speaker 2: A lightning strike got to be kidding me.

917
00:45:23,200 --> 00:45:25,640
Speaker 1: You know that meme where they have the airplane and

918
00:45:25,760 --> 00:45:29,120
Speaker 1: like airplanes that return only have hits in these locations,

919
00:45:29,120 --> 00:45:30,439
Speaker 1: like the survivor effect meme.

920
00:45:30,680 --> 00:45:32,000
Speaker 4: Yeah, it's basically that one.

921
00:45:32,080 --> 00:45:32,360
Speaker 1: Wow.

922
00:45:32,680 --> 00:45:34,319
Speaker 3: I think that wasn't just a meme. I think that

923
00:45:34,400 --> 00:45:40,600
Speaker 3: was actually like a study during World War one or two. Yeah, yeah, yeah, yeah, okay, anyway, yeah, yes.

924
00:45:40,440 --> 00:45:41,319
Speaker 2: Yes, that cracked me up.

925
00:45:41,360 --> 00:45:43,800
Speaker 3: I'm like, all right, fingers crossed, there's never any lightning

926
00:45:43,800 --> 00:45:45,279
Speaker 3: here again. And then I think you also wanted the

927
00:45:45,280 --> 00:45:46,759
Speaker 3: ability to be able to move it a little bit

928
00:45:47,080 --> 00:45:48,480
Speaker 3: in case a storm came through.

929
00:45:48,600 --> 00:45:50,680
Speaker 1: Well, I think the terrifying thing is you guys pointed

930
00:45:50,680 --> 00:45:52,440
Speaker 1: out in your book soon is is what happens when

931
00:45:52,480 --> 00:45:56,000
Speaker 1: the cable snaps, because basically, now you have this like

932
00:45:56,400 --> 00:46:00,200
Speaker 1: kill wire moving at high velocity like somehow or us

933
00:46:00,200 --> 00:46:02,200
Speaker 1: the Earth's surface, and like yikes.

934
00:46:02,000 --> 00:46:04,320
Speaker 3: Yeah right, or if somebody decides to snip your wire,

935
00:46:04,600 --> 00:46:08,000
Speaker 3: forget if there's lightning, just like a terrorist cutting your wire. Okay, anyway,

936
00:46:08,640 --> 00:46:12,960
Speaker 3: no more doomsday scenarios relative to space elevators. Let's talk

937
00:46:12,960 --> 00:46:15,680
Speaker 3: about lagrange points because I always found these slightly confusing,

938
00:46:15,719 --> 00:46:17,040
Speaker 3: but you can clear it up for me.

939
00:46:17,920 --> 00:46:20,280
Speaker 1: Well, what I'm confused because I call them lagrange points.

940
00:46:20,719 --> 00:46:24,200
Speaker 3: Look at you, nobody. Nobody expects me to say it right.

941
00:46:24,520 --> 00:46:27,280
Speaker 3: They expect you to say it right. That's your responsibility,

942
00:46:27,320 --> 00:46:27,840
Speaker 3: not mine.

943
00:46:28,080 --> 00:46:30,960
Speaker 1: Well, it depends. Are they named after, you know, Jean

944
00:46:31,040 --> 00:46:33,160
Speaker 1: Louis Lagrange or are they named after the city in

945
00:46:33,200 --> 00:46:36,239
Speaker 1: Texas or the Zzy Top song or you know, I.

946
00:46:36,160 --> 00:46:38,160
Speaker 2: Think the zz Top song probably.

947
00:46:40,760 --> 00:46:41,040
Speaker 1: Nice.

948
00:46:41,320 --> 00:46:43,000
Speaker 3: Now that we've both done that together, I think we've

949
00:46:43,000 --> 00:46:45,920
Speaker 3: made this joke before and we'll probably make it.

950
00:46:45,880 --> 00:46:48,239
Speaker 1: Again, probably because that's how our memories work.

951
00:46:48,280 --> 00:46:48,600
Speaker 2: I look for.

952
00:46:48,800 --> 00:46:50,960
Speaker 1: Yeah, there are these fun points where you can be

953
00:46:51,400 --> 00:46:55,840
Speaker 1: at rest relative to the Earth Sun system. Like, for example,

954
00:46:56,080 --> 00:46:58,800
Speaker 1: if you are the James Webb Space Telescope and you

955
00:46:58,840 --> 00:47:00,600
Speaker 1: don't want to be in orbit or on the Earth

956
00:47:00,640 --> 00:47:03,560
Speaker 1: because you need to be super duper cold, you can

957
00:47:03,640 --> 00:47:06,719
Speaker 1: choose to be at lagrange point two, which is on

958
00:47:06,840 --> 00:47:10,040
Speaker 1: the other side of the Earth from the Sun, where

959
00:47:10,080 --> 00:47:12,040
Speaker 1: all the gravitational effects of the Earth and the Sun

960
00:47:12,360 --> 00:47:14,279
Speaker 1: cancel out, and so you could just sort of like

961
00:47:14,360 --> 00:47:15,320
Speaker 1: hang out there.

962
00:47:15,640 --> 00:47:17,880
Speaker 3: Yeah, so I guess so when I look, all right,

963
00:47:17,880 --> 00:47:20,360
Speaker 3: so I'm looking at the diagram that you provided, and

964
00:47:20,400 --> 00:47:22,600
Speaker 3: so you've got this spot that's on the far side

965
00:47:22,640 --> 00:47:24,200
Speaker 3: of the Earth and on the far side of the Sun.

966
00:47:24,719 --> 00:47:27,920
Speaker 2: And I guess I always kind of feel like, why doesn't.

967
00:47:27,680 --> 00:47:30,160
Speaker 3: It just drift away? But I guess you still have

968
00:47:30,200 --> 00:47:32,080
Speaker 3: the gravity pulling it in. I'm not sure I have

969
00:47:32,120 --> 00:47:34,480
Speaker 3: a really great question to ask here, just kind.

970
00:47:34,280 --> 00:47:36,480
Speaker 1: Of Well, so imagine that you wanted to be in

971
00:47:36,600 --> 00:47:39,480
Speaker 1: the Earth's orbit. Right, So you have Earth and it's

972
00:47:39,560 --> 00:47:41,560
Speaker 1: orbiting the Sun, and you're like, hey, I want to

973
00:47:41,640 --> 00:47:45,000
Speaker 1: join the Earth's orbit. Where could you be in Earth's orbit? Well,

974
00:47:45,040 --> 00:47:47,480
Speaker 1: if you're right next to the Earth, then you and

975
00:47:47,560 --> 00:47:49,279
Speaker 1: the Earth would pull on each other and you would

976
00:47:49,320 --> 00:47:51,759
Speaker 1: smash into the Earth. So try to get a little

977
00:47:51,760 --> 00:47:53,680
Speaker 1: bit further from the Earth. Well, how far away from

978
00:47:53,680 --> 00:47:56,200
Speaker 1: the Earth you have to be? Well, one solution is

979
00:47:56,200 --> 00:47:58,160
Speaker 1: to be on the other side of the Sun from

980
00:47:58,200 --> 00:48:00,480
Speaker 1: the Earth. So that's the lagrange point three. If you

981
00:48:00,560 --> 00:48:02,480
Speaker 1: and the Earth are on opposite sides of the Sun,

982
00:48:02,719 --> 00:48:04,799
Speaker 1: then you won't pull on each other and you can

983
00:48:04,840 --> 00:48:07,920
Speaker 1: share an orbit with the Earth, right, Okay, So you

984
00:48:07,960 --> 00:48:10,080
Speaker 1: can both hang out in the same orbit without crashing

985
00:48:10,160 --> 00:48:12,880
Speaker 1: into each other. So that's what you want. It turns

986
00:48:12,880 --> 00:48:15,439
Speaker 1: out there are two more points there's a leagarnge point

987
00:48:15,440 --> 00:48:18,560
Speaker 1: four and five, which are like thirty degrees ahead or

988
00:48:18,640 --> 00:48:21,360
Speaker 1: behind the Earth. It can also be in those points

989
00:48:21,520 --> 00:48:23,799
Speaker 1: where everything balances out and you can both be in

990
00:48:23,880 --> 00:48:27,440
Speaker 1: orbit together. And this is why Jupiter, for example, has

991
00:48:27,480 --> 00:48:30,480
Speaker 1: a big cluster of asteroids ahead of it and behind

992
00:48:30,520 --> 00:48:33,200
Speaker 1: it in its orbit. Right. I think they're called the

993
00:48:33,280 --> 00:48:35,080
Speaker 1: Trojans and the Greeks.

994
00:48:34,960 --> 00:48:37,719
Speaker 2: Cool love it. I hope they get along.

995
00:48:39,280 --> 00:48:43,440
Speaker 1: Ironic foreshadowy. And another one is to be between the

996
00:48:43,480 --> 00:48:46,600
Speaker 1: Earth and the Sun, so closer to the Earth because

997
00:48:46,640 --> 00:48:48,800
Speaker 1: the Earth has less gravity, but between the Earth and

998
00:48:48,840 --> 00:48:51,239
Speaker 1: the Sun, that's the lagrange point one. Lagarage point two

999
00:48:51,320 --> 00:48:55,160
Speaker 1: is on the outside past the Earth's orbit, and it's

1000
00:48:55,200 --> 00:48:57,480
Speaker 1: basically in a line from the Sun to the Earth

1001
00:48:57,520 --> 00:48:59,799
Speaker 1: and then past it. And so you can be out

1002
00:48:59,840 --> 00:49:02,879
Speaker 1: there where your orbit is not disturbed by the Earth.

1003
00:49:02,920 --> 00:49:05,279
Speaker 1: You could also just be in lagrange point two in

1004
00:49:05,400 --> 00:49:08,120
Speaker 1: orbit around the Sun and be fine. But then if

1005
00:49:08,160 --> 00:49:10,080
Speaker 1: you're not synced up with the Earth, the Earth is

1006
00:49:10,080 --> 00:49:12,400
Speaker 1: going to disturb your orbit every time it passes you.

1007
00:49:12,920 --> 00:49:14,560
Speaker 1: But if you're synced up with the Earth, so you're

1008
00:49:14,600 --> 00:49:18,680
Speaker 1: always keeping the Earth, Sun and your telescope in a line,

1009
00:49:18,800 --> 00:49:21,239
Speaker 1: then everything is stable, and that's where the James web

1010
00:49:21,320 --> 00:49:24,040
Speaker 1: Space Telescope hangs out because the Earth provides a shade

1011
00:49:24,080 --> 00:49:26,720
Speaker 1: from the Sun and the telescope needs to be super

1012
00:49:26,840 --> 00:49:30,000
Speaker 1: duper cold so that it doesn't emit radiation in the

1013
00:49:30,000 --> 00:49:31,760
Speaker 1: same wavelengths that it's observing.

1014
00:49:32,000 --> 00:49:35,880
Speaker 3: Okay, so it's constantly in motion relative to the Sun,

1015
00:49:37,239 --> 00:49:40,279
Speaker 3: but not the Earth. But not the Earth, and have

1016
00:49:40,560 --> 00:49:43,800
Speaker 3: humans put things in all of these lagrange points.

1017
00:49:44,160 --> 00:49:47,360
Speaker 1: So we've used lagrange points one and two. One is

1018
00:49:47,360 --> 00:49:49,239
Speaker 1: the one that's closer to the Sun, and two is

1019
00:49:49,239 --> 00:49:52,080
Speaker 1: the one that's further from the Sun. And two, for example,

1020
00:49:52,120 --> 00:49:53,960
Speaker 1: we have the James Webs Space Telescope, and it's not

1021
00:49:54,000 --> 00:49:56,839
Speaker 1: actually at too, it's orbiting too, so you can put

1022
00:49:56,920 --> 00:49:59,399
Speaker 1: other stuff there. And there are things that one which

1023
00:49:59,440 --> 00:50:01,880
Speaker 1: is pretty clear to Earth. For example, there's like the

1024
00:50:02,080 --> 00:50:05,960
Speaker 1: Solar and Heliospheric Observatory is there, and other stuff likes

1025
00:50:05,960 --> 00:50:09,000
Speaker 1: to be there, and we haven't put anything at four

1026
00:50:09,080 --> 00:50:11,680
Speaker 1: and five. They're kind of a little bit far away.

1027
00:50:12,200 --> 00:50:14,480
Speaker 1: That James Wes Space Telescope is already like kind of

1028
00:50:14,520 --> 00:50:18,400
Speaker 1: far away for an observatory, and four and five are even.

1029
00:50:18,200 --> 00:50:21,160
Speaker 2: Further and three is super far, so we have we

1030
00:50:21,280 --> 00:50:22,000
Speaker 2: put anything at three.

1031
00:50:22,120 --> 00:50:22,680
Speaker 4: Yet No.

1032
00:50:22,760 --> 00:50:24,520
Speaker 1: Three is super duper far away. It's on the other

1033
00:50:24,640 --> 00:50:27,120
Speaker 1: side of the Earth. And that wouldn't be terribly convenient

1034
00:50:27,160 --> 00:50:30,080
Speaker 1: because we couldn't communicate with it very easily because the

1035
00:50:30,120 --> 00:50:32,799
Speaker 1: Sun would be in the way. Yeah, and so that's

1036
00:50:32,840 --> 00:50:35,640
Speaker 1: basically all you can do to be like motionless in

1037
00:50:35,680 --> 00:50:38,440
Speaker 1: the universe. You could try to be like motionless with

1038
00:50:38,480 --> 00:50:41,680
Speaker 1: respect to the CMB frame if you'd like that wouldn't

1039
00:50:41,719 --> 00:50:44,719
Speaker 1: like feel very special. You could try to be motionless

1040
00:50:44,760 --> 00:50:46,600
Speaker 1: with respect to the Earth and hang out in space

1041
00:50:46,640 --> 00:50:49,160
Speaker 1: at one of the lagrange points, and that's kind of

1042
00:50:49,200 --> 00:50:51,760
Speaker 1: special and you can see things about the universe. That's cool.

1043
00:50:52,120 --> 00:50:54,800
Speaker 1: But in general, motion is something kind of slippery because

1044
00:50:54,800 --> 00:50:57,920
Speaker 1: it requires you to measure your velocity with respect to

1045
00:50:57,960 --> 00:51:01,680
Speaker 1: something else in the universe. A lonely concepts requires you

1046
00:51:02,000 --> 00:51:04,640
Speaker 1: to be paired up with something out there in the universe.

1047
00:51:05,120 --> 00:51:08,480
Speaker 1: So there is no solo motion or solo location in

1048
00:51:08,520 --> 00:51:10,600
Speaker 1: the universe. If you want to be in motion, you

1049
00:51:10,680 --> 00:51:11,600
Speaker 1: gotta find a friend.

1050
00:51:11,880 --> 00:51:12,880
Speaker 2: Ah.

1051
00:51:12,920 --> 00:51:17,520
Speaker 3: That's a nice note to end on, all right, extraordinaries,

1052
00:51:17,640 --> 00:51:20,240
Speaker 3: thank you for moving through the universe with us.

1053
00:51:20,400 --> 00:51:22,120
Speaker 2: We appreciate you. Spending time with us.

1054
00:51:29,160 --> 00:51:32,720
Speaker 3: Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio.

1055
00:51:32,920 --> 00:51:34,439
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1056
00:51:34,560 --> 00:51:37,520
Speaker 1: We really would. We want to know what questions you

1057
00:51:37,719 --> 00:51:40,360
Speaker 1: have about this Extraordinary Universe.

1058
00:51:40,440 --> 00:51:43,400
Speaker 3: We want to know your thoughts on recent shows, suggestions

1059
00:51:43,400 --> 00:51:44,400
Speaker 3: for future shows.

1060
00:51:44,480 --> 00:51:46,840
Speaker 2: If you contact us, we will get back to you.

1061
00:51:47,120 --> 00:51:50,640
Speaker 1: We really mean it. We answer every message. Email us

1062
00:51:50,680 --> 00:51:53,720
Speaker 1: at Questions at Danielankelly dot org.

1063
00:51:53,719 --> 00:51:55,319
Speaker 3: Or you can find us on social media. We have

1064
00:51:55,400 --> 00:51:59,239
Speaker 3: accounts on x, Instagram, Blue Sky and on all of

1065
00:51:59,280 --> 00:51:59,920
Speaker 3: those platforms.

1066
00:51:59,880 --> 00:52:02,920
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1067
00:52:03,120 --> 00:52:04,680
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