Daniel and Kelly’s Extraordinary Universe - Can you be motionless in space?

Episode Date: September 9, 2021

Everything is moving and spinning -- is it possible to be totally still in the Universe? Learn more about your ad-choices at https://www.iheartpodcastnetwork.comSee omnystudio.com/listener for privac...y information.

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Starting point is 00:00:00 This is an I-Heart podcast. December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, everything changed. There's been a bombing at the TWA terminal. Just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, terrorism. Listen to the new season of Law and Order Criminal Justice System
Starting point is 00:00:33 On the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, luckily, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend's been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now he's insisting we get to know each other, but I just want or gone.
Starting point is 00:01:01 Hold up. Isn't that against school policy? That seems inappropriate. Maybe find out how it ends by listening to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Why are TSA rules so confusing? You got a hood of you. I take it all. I'm Mani. I'm Noah. This is Devin. And we're best friends and journalists with a new podcast called No Such Thing, where we get to the bottom of questions like that. Why are you screaming it?
Starting point is 00:01:28 I can't expect what to do. Now, if the rule was the same, go off on me, I deserve it. You know, lock him up. Listen to No Such Thing on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. No such thing. It's important that we just reassure people that they're not alone, and there is help out there. The Good Stuff Podcast Season 2 takes a deep look into One Tribe Foundation, a non-profit fighting suicide in the veteran community. September is National Suicide Prevention Month, so join host Jacob and Ashley Schick as they bring you to the front lines of One Tribe's mission.
Starting point is 00:02:02 One Tribe, save my life twice. Welcome to Season 2 of the Good Stuff. Listen to the Good Stuff podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. Hey, Jorge, when did you get up today? How do you know I got up? I could be recording this from my bed right now. Thanks for that mental image now. I kind of regret asking.
Starting point is 00:02:31 And even if I'm in bed, I'm technically still moving. Really? Is your bed on wheels or something, or you have like a flying bed? That would be exciting. But no, I'm on Earth, and Earth is spinning, right? In space, and it's also flying around the sun. So I'm still moving, right? Does that count?
Starting point is 00:02:46 I mean, does your Fitbit give you steps for it? Well, I don't really believe in Fitbits. I believe in that bits. I have one. They make one for cartoonists. Hi, I'm Jorge. And the creator of PhD comics. Hi, I'm Daniel.
Starting point is 00:03:15 I'm a particle physicist and a professor at UC Irvine. And it feels like I'm always in motion. Oh, yeah? Like your mental gears are always turning. Or are you one of those people that work on a treadmill all the time? No, I definitely do not work on a treadmill. I work on a chair and I lean way back with a crazy, ridiculous posture that would make like any ergonomic specialist cringe. And that's what you mean by motion?
Starting point is 00:03:37 That's your workout, leaning back for a nap? No, I mean, I'm sort of always scrambling from one thing to the other. Working on this. Oops, that's late. Running over here. It feels like being an adult in today's modern world is always scrambling from one thing to another. I know what you mean. But you do know.
Starting point is 00:03:53 you have a choice there, Daniel. I could retire early. Yeah, you can not do so many things. Then who would I even be, man? Who would I even be? Welcome to existential questions with Daniel and Jorge. Now, but seriously, welcome to our podcast, Daniel and Jorge Explain the Universe, a production of IHeart Radio.
Starting point is 00:04:10 In which we do delve into the deepest of existential questions. Why does the universe exist? How does it all work? What is our place in it? How long will it last? How will it end? And whose fault will it be? when it finally goes poof in which we dig deep into the very smallest, tiniest little bits of that universe,
Starting point is 00:04:29 ask the basic questions about how everything works and explain all of the answers as far as we know them to you. Yeah, because it is a confusing and vast universe and it's a pretty restless universe. It seems to be always in motion. There's always something going on in the universe because, you know, it's so big and there's always, I don't know, an exploding star somewhere. There's planet spinning everywhere, asteroids flying through the sky. It does seem to be sort of in slow motion violence. You know, you look out into the night sky, and you just sort of glance at it, and it seems static.
Starting point is 00:05:00 It's not like the stars are whizzing around in front of your eyes. But, you know, you pay attention. You see the night sky slide by. And the longer you watch, the more you notice that, like, crazy stuff is happening out there. Vast explosions that take millions of years, but are still very dramatic. So everything up there is actually in motion. We just sort of live in a tiny little burst of time. where things seem to be stationary.
Starting point is 00:05:25 Yeah, and there's not just a lot of action going on out there. There's a lot of action inside of us and in the smallest of particles. Everything is always, you know, vibrating or spinning or quantum spitting or disappearing and appearing at the same time. Yeah, you're right. Quantum mechanics says that everything is in motion and has to be in motion, that nothing can actually come to rest, that nothing in the end can really have no energy. So the very nature of our existence seems to be in motion.
Starting point is 00:05:51 Yeah, and it does seem like now it's. days, life involves a lot of moving around. You know, it seems like things are spinning and moving and changing faster than we can, you know, get a hold of it. And so, you know, the idea of resting or being motionless or, you know, just stopping and not doing anything is kind of weird, right? Maybe to a lot of people? Yeah. Maybe that I think a lot of people did more of that in this last year than they're used to. Went to fewer places, canceled traveling, didn't go to the office as much. So a lot of people were sort of stuck in a smaller orbit than they usually are by the pandemic, but still everybody is still moving. Yeah, it's been kind of a tough year for everybody, but it's still fun to kind of think
Starting point is 00:06:31 about the universe and all the things that are going on inside of it. And we especially like to ask interesting questions in this podcast about, you know, what's theoretically possible and what is theoretically impossible or what is theoretically nonsensical. That's right. And we're not the only ones wondering about those kinds of questions. all of our listeners are out there thinking about the nature of the universe and what's possible and what their experience is like in it. And a lot of people write in with a particular question when they notice that everything in the universe seems to be moving. Everything is sliding or spinning or orbiting or zooming through space. And I think this inspires people to ask this particular
Starting point is 00:07:09 question about whether motionlessness is possible. Yeah. So today on the podcast, we'll be tackling the question. Can you be motionless in space? Now, Daniel, do you think people are, you know, being aspirational with this question? Like, how can I be motionless in space? Or are they asking you think the theoretical question, is it possible to be not moving at all in this universe? I don't think anybody's asking a practical question. I don't think they're trying to develop one of those like extreme isolation pods where you can float out in space and have nothing touch you or anything like that.
Starting point is 00:07:47 I think people are pushing the envelopes because they want to know what's possible. So in that sense, I guess it's a theoretical question. Just like in our extreme universe podcast episodes, sometimes you learn something about the nature of space by looking at the extreme situation, asking what's the fastest you can go or what's the slowest you can go? What's the hottest something can be? So since everything seems to be moving, I think people are wondering, is it even possible theoretically for something to be totally at rest? What would that mean? What would it require? What does it reveal about the nature of the universe?
Starting point is 00:08:21 Right. Yeah. Still, let me to think that if physicists might ask a practical question. Sorry about that. But it is a pretty interesting theoretical question. Like, can you be not moving, I guess? And do you think that's more about staying still or a feeling that you're not moving? Do you know what I mean?
Starting point is 00:08:37 Like, do you think people are asking about, is there a point in the universe that's technically not moving relative to everything else? Or do you think it means just like, how can I? not have any motion relative to anything else. Yeah, I think there's a lot of interesting stuff to unpack there about the very nature of what it means to be in motion that we're going to have to dig into because I think something about this question reveals
Starting point is 00:08:59 that people are thinking about speed in a way that comes naturally to them on the surface of the earth where it makes sense to talk about what my speed is. But when you go out into space, things change. Things are different. The same way that like up and down have a meaning on the surface of the earth but don't really make sense anymore out in space. I think we're going to learn that the whole concept of velocity is a little bit different
Starting point is 00:09:20 than what a lot of people had in mind. So this is a great question, not because the answer is simple and reveals the truth about the universe, but because the nature of the question makes you rethink the whole nature of motion. Yeah. And then you have to ask the follow-up question, which is can you be emotionless in space after learning the answer to the first question? I think we know the answer to that. It's called the movie Gravity. Oh, movie criticism and physics, all in one podcast.
Starting point is 00:09:47 Seriously, nobody seems to have any emotions in that movie. They're all just like, stoic. I'm just trying to not die, I think, in space. Can you be alive in space? That's the question they were asking. Not just standing still because you're dead. But yeah, this is a pretty interesting question. And so as usual, we were wondering how many people out there had thought about this question
Starting point is 00:10:06 and whether or not they have an answer that they might have thought of. So Daniel went out there into the internet to ask the question, can you be motionless in space? That's right. I go out into the web and beat the bushes for people who are interested in answering these questions for us. If you are out there on the internet and have not participated, please we want to hear your voice, especially if you're from a location we haven't heard anybody from before. We would love to hear your voice on the podcast. So please write to us to Questions at Danielanhorpe.com. So think about it for a second. Do you think it's possible to be motionless in space? Here's what people had to say. Well, I can be motionless if I don't move a muscle, so nothing on me would move, that would
Starting point is 00:10:50 qualify as motionless, I guess. But relative to something else, I would probably never be motionless because everything else is moving. The sun is moving around the center of the galaxy, the planets around the sun, everything else is moving. Even space itself is expanding. So even if I'm in a point in space and the space around me is expanding, then the things around me would be moving along with it as well. So can you be motionless in space? Yes, if I don't move a muscle, no, relative to anything else. I don't think you can be motionless in space.
Starting point is 00:11:25 If two bodies are passing by each other and neither is accelerating, both bodies, from their perspective, would feel that they were standing still and the other one was moving. It doesn't seem like it, since your motion would be relative to whatever was around you. So even if you're standing still on Earth, the Earth is spinning and moving around the sun. And if you're standing still next to the sun,
Starting point is 00:11:52 it's spinning around the galaxy, and the galaxy is moving. But maybe it's possible to just stick still with respect to the fabric of space. Well, if I'm not moving at all, yes. But motionless, like, I'm not moving. from the way regarding to something like the moon, earth, sun, galaxy, the galaxy cluster,
Starting point is 00:12:27 Lanquier and so on, probably I'll be moving. Motion is relative, measured relatively to other things. So I guess you could technically, you would always be motionless and always be moving in all different directions at the same time. With space expanding, I don't know if that becomes a factor too, but probably does. I don't think that you can be motionless in space. I think that there's a reason why Einstein thought up the theory of relativity, because there is no super position that we can use to compare positions in space against.
Starting point is 00:13:01 You've only really got what you have, which is your own frame of reference, and then you compare that to something else. And because everybody else has a different reference, there is no set central position where something is not moving. If I somehow ended up in space and I wasn't moving for some reason, according to which one, Newton's first law, an object that is not moving will stay stationary. So I suppose if somehow, I don't know, if the Earth vanished,
Starting point is 00:13:39 and I was left suspended in space and I wasn't moving then I would be motionless in space. All right. A lot of people doesn't seem to think it's possible to be motionless. Yeah, yeah, exactly. It's fascinating. You think a lot of people are just naturally restless
Starting point is 00:14:01 or they have one of those restless leg syndromes? Yeah, there are all those people who are always tapping on something or got like a fidget spinner or something. Yeah. Yeah, I know what my kids would say. They would say, no, it's impossible. I know what I would say about my children, even if they were in space.
Starting point is 00:14:18 And the kids would say like, and why would you want to? That seems really boring, right? Just lying there doing nothing. Yeah. So it's an interesting question. I guess the question sort of boils down to like, it's not about standing still, but it's more about moving, right? Like your whole body moving somewhere, right?
Starting point is 00:14:32 Because technically we are always vibrating, right? Like if we have a temperature, our molecules are moving. This is more about, you know, whether we're as a whole thing still or translating or moving or going from one place to another, right? Yeah, I think we should sort of like approximate you as a little dot or a point particle and ignore all the motion inside you and then ask the question, can point particle you, can spherical you be motionless with respect to everything? Is that even possible? Right, like cartoon Jorge. So this should be easy because I'm good at ignoring all the emotions inside of me. Oh, right. That was a little dark.
Starting point is 00:15:10 No, I'm just kidding. But yeah, it's about whether or not we're moving in relative or moving in space as a whole. Yeah, exactly. And one of the most important things to understand is that there is no absolute motion. All motion is relative. It's always defined relative to something else. You know, people write in often and ask questions about like special relativity. And usually their questions start with something like, if I was in a spaceship and I was going really, really fast.
Starting point is 00:15:35 And they don't say what they're going really, really. fast relative to you know they have this sense that like there's something that happens when you get up to high speeds but the thing that's missing there is like who are you speeding by where are you going fast relative to there is no sense in which you have speed other than that it's measured relative to other things or people right because i guess motion is a quantity that is that can't exist on its own right yeah exactly if you are for example in an empty unit universe, right? It's just you floating in space and there's nothing else in the universe. Then your speed doesn't make any sense. You have no velocity. You can't have velocity because velocity is
Starting point is 00:16:19 just motion relative to something else. You know, I guess this might be confusing to people because I wonder like, you know, I think a lot of us maybe imagine that, you know, the universe maybe has an extent, like a limit, like a wall at some point. Maybe it's a big sphere. Maybe it's a big blob. maybe it's a donut, but it has sort of like a shape of it. So couldn't I measure my speed or my motion relative to that shape? No, because the universe is actually symmetric. Like if you do some experiment over here and then you do the same experiment over there, you always get the same answer.
Starting point is 00:16:51 There's no point in space that's different than another point in space. Like space has no texture. There's no like way to tell where you are in space. I mean, it might be that the universe is finite and has some, like, like weird edge to it, but we haven't observed that. And the current cosmological models usually assume that the universe is infinite and that every point in it behaves the same way. Like the laws of physics are the same no matter where you are. And so you can't do an experiment to determine where you are. So it's not like you can feel space moving by or measure yourself your location
Starting point is 00:17:26 relative to some like absolute point in space. There is no absolute point. And so there is also no absolute velocity. Well, there's no absolute point that we know of, right? But could there be one if like the universe does have a shape or like a wall or limit? In some scenarios, yes. In most scenarios, no. Like even if the universe is not infinite, right? It might not have an edge.
Starting point is 00:17:49 Like imagine the universe is closed and finite the way it like wraps around itself. That doesn't mean that there's any special point. It can be finite and still have like no special location to it. Imagine you're like on the surface of a sphere, right? Then every point on that sphere is really the same, even though the service is not infinite. Right. Yeah, I guess like if the universe was like at the Pac-Man screen, then there's technically no real place in the Pac-Man screen because it just loops around forever. But I guess I'm just trying to get to the possibility that maybe it does have an edge, in which case there would be something like an absolute position, right?
Starting point is 00:18:24 If the universe did have some sort of like strange wall as an edge to it or some like deformity in its geometry. then yes, that would break this cosmological principle that every location is the same. And then you could measure your velocity relative to that. There would be a special location in space. But still your velocity would only have meaning relative to something. And you can define your velocity to be relative to like that weird edge of space or the sun or the moon or this dust particle. But the definition of your velocity still only has meaning relative to something. Right.
Starting point is 00:18:59 Yeah, because I guess, you know, motion or velocity, it's like the change in a quantity, which is distance. So you can't have distance if you don't measure it relative to something else, right? Yeah, exactly. And this is actually really closely connected to like all sorts of interesting deep physics of the universe. You know, the fact that space seems to be the same everywhere, that if you do your experiment here and then you transport it 10 light years over there and do it again, that you get the same answer, that's connected to an important law of physics, which is conservation of moment. momentum. And we're going to do a whole fun podcast episode about this deep theory of physics called Neuthr's theorem that tells you that any time you have a symmetry like that, something where the universe doesn't care where you are, you get some conserved quantity, something which doesn't
Starting point is 00:19:43 change as you do your experiments. So in this case, the connection is the fact that you can move from one place in space to another and not have your experiment change is why we have conservation of momentum, which is sort of mind blowing to me. But yeah, exactly. Velocity defined relative to other things in space, not relative to space itself. Right. And I think it extends not just to like your precision in the universe, right? Like you can do an experiment here or there and it should be worked at the same. But it also comes up in doing the experiment at different velocities, right?
Starting point is 00:20:14 I can do my experiments going at 100 miles per hour relative to the earth or I can do it at 100,000 miles per hour. I should get the same results if I'm going at a constant speed, right? Yeah, exactly. If you're in a box, you can't measure your velocity relative to stuff out. outside the box. You can't see that stuff at all. So if you do an experiment, it shouldn't be sensitive to your velocity relative to that stuff. So the classic scenario is like you set up some experiment. I don't know what it is. It's got, you know, like ball swinging and hitting
Starting point is 00:20:40 each other or whatever. And then you gently accelerate up to some higher speed, right? And the key there is gently accelerate so you don't like destroy everything. Now your speed is high relative to like the surface of the earth or the planet you were on or whatever. You do the same experiment, you should get exactly the same result. And that's not just some like weird esoteric thing that means that you can't measure your velocity. There's no experiment you could do that would give a different answer if your velocity relative to that planet is zero or a thousand meters per second. And that means you can't build a device to measure that velocity. Right. And again, this applies to just to double check, this applies to like constant velocity, right? If I'm
Starting point is 00:21:20 accelerating, then that's a whole different ballgame. Exactly. Acceleration is totally different, which is also really interesting. Acceleration is something you can measure. There is absolute acceleration. If you're in a box, you can measure your acceleration, right? You can do a simple experiment. Toss a ball up in the air and it will move differently if you're under acceleration than if you're not.
Starting point is 00:21:39 And also, you'll feel it. If you're in a box and it's accelerating, it will feel just like gravity, right? Acceleration feels just like gravity, which was the whole insight which led to general relativity and that whole revolution and understanding space and time. But position and velocity only makes sense relative to other things. Right. And I think what you're saying basically, just to kind of drive this home, is that like if you're inside of a box out in space,
Starting point is 00:22:06 it's sort of impossible to know how fast that box you're in is moving relative to other things, right? Like if it's moving at a constant speed or not, it's impossible to tell if that, you know, box is floating out in space or it's like moving super fast across the galaxy. Yeah, exactly, as long as you can't look outside the box. Like if you have a window, you can look outside and you can see things moving by and measure it. But if all you can do is measure things inside the box, then yeah, you can't measure your velocity relative to anything outside the box.
Starting point is 00:22:35 There's no way to tell. Right. And so I think what you're getting at is that basically just the word motionless doesn't really have any meaning, right? Because you might think you're motionless now inside your box, but really you could be moving really fast or not at all or moving in any kind of crazy direction outside of that box. So really, the word motionless doesn't mean anything from a physics, math point of view. Yeah, it's either totally meaningless or it's just totally arbitrary. Like, you can pick a definition of a reference frame and say, I'm going to say that the earth is at the center of my reference frame. Now my velocity has meaning.
Starting point is 00:23:08 I'm talking about velocity relative to the earth. But you could also pick anything else. You could pick the sun. You could pick that grain of dust. You could pick a distant comet. Your answer depends on your choice and your choice is totally arbitrary and no choice is better than any other. So you can either say velocity is meaningless, right? Or you can say it only has meaning when you make an arbitrary choice of what you're measuring it relative to.
Starting point is 00:23:31 Right. So basically when you try to answer the question, can you be motionless in space? You're saying that's kind of a nonsensical question or like an impossible question to ask in terms of the math and the physics? Because there's no way to tell if you are motionless because it depends on what you measure your motion relative to. And it could be anything. It could be anything. And even if you pick something, it would be totally different. according to somebody else.
Starting point is 00:23:54 Yeah, exactly. Like, in some sense, the answer is trivial. Like, yes, you can be motionless in space if you measure your motion relative to yourself. So by definition, your velocity is zero relative to yourself. Boom, you're motionless in space. So that's what I meant when I said, like, this question is interesting because this whole question of velocity,
Starting point is 00:24:11 I think people have an intuitive sense that, like, motion is something that you can measure, but you can't actually measure it in a pure sense. You can only measure relative to other things. And so it becomes kind of arbitrary. and unfortunately meaningless. All right. Well, I think that's a little counterintuitive
Starting point is 00:24:26 because our daily experience is that we are moving on Earth and the Earth is moving around the sun and then the sun is moving around the galaxy. So let's dig a little bit deeper into these types of motions and then let's try to answer whether or not it is actually possible to get around that loophole. But first, let's take a quick break. December 20th, December 20th,
Starting point is 00:24:51 9th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed. There's been a bombing at the TWA terminal. Apparently, the explosion actually impelled metal, glass. The injured were being loaded into ambulances, just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, and it was here to stay. Terrorism.
Starting point is 00:25:28 Law and Order Criminal Justice System is back. In Season 2, we're turning our focus to a threat that hides in plain sight. That's harder to predict and even harder to stop. Listen to the new season of Law and Order Criminal Justice System on the IHeartRadio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Oh, wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, it's back to school week on the OK Storytime podcast, so we'll find out soon.
Starting point is 00:26:04 This person writes, my boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now, he's insisting we get to know each other, but I just want her gone. Now, hold up. Isn't that against school policy? That sounds totally inappropriate. Well, according to this person, this is her boyfriend's former professor, And they're the same age.
Starting point is 00:26:23 And it's even more likely that they're cheating. He insists there's nothing between them. I mean, do you believe him? Well, he's certainly trying to get this person to believe him because he now wants them both to meet. So, do we find out if this person's boyfriend really cheated with his professor or not? To hear the explosive finale, listen to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. Culture eats strategy for breakfast.
Starting point is 00:26:45 I would love for you to share your breakdown on pivoting. We feel sometimes like we're leaving a part of us behind when we enter a new space, but we're just building. On a recent episode of Culture Raises Us, I was joined by Volusia Butterfield, media founder, political strategist, and tech powerhouse for a powerful conversation on storytelling, impact, and the intersections of culture and leadership. I am a free black woman who worked really hard to be able to say that. I'd love for you to break down.
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Starting point is 00:28:13 And on our new show, no such thing. We get to the bottom of questions like these. Join us as we talk to the leading expert on overconfidence. Those who lack expertise lack the expertise they need to recognize that they lack expertise. And then as we try the whole thing out for real. Wait, what? Oh, that's the run right. I'm looking at this thing. Listen to no such thing on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts.
Starting point is 00:28:49 All right, we're trying to answer the question. Can you be motionless in space? And the answer is yes and no or ask a better question is the answer? It's yes, according to our legal department, as long as you define a reference brain. Right, because the idea is that, you know, I can always say emotionless relative to whatever box I'm in. But, you know, who knows what this box is moving relative to. Yeah. And that's sort of like the abstract theoretical answer, and it's unsatisfying because there are some reasonable choices you can make, right?
Starting point is 00:29:25 In theory, what reference frame you pick to measure your motion is totally arbitrary and there's no one preferred over others. But there are things around us that it makes sense to define your motion relative to, right? You know, we have the Earth, we have the Sun, we have the galaxy, and it's fascinating how we are moving relative to those things. Yeah, and it's not a little bit of motion. we're going pretty fast, right, here on Earth? So, like, let's maybe take it one step at a time. What if I define our motion as relative to the Earth or the center of the Earth? How fast are we moving?
Starting point is 00:29:58 Yeah, right. Relative to the Earth or the center of the Earth, those are two different things. If you say, what's my motion relative to this patch of Earth underneath my feet? Well, if you're just standing on it, then it's obviously zero. But if you say, what's my motion relative to the very center of the Earth, then you have to measure the spinning of the Earth, right? because the Earth is not just a ball of rock moving through space. It's also spinning, spinning pretty quickly.
Starting point is 00:30:21 Like, it's a big rock, and it spins once every 24 hours. So that's pretty high speed. You know, at the equator, for example, the surface of the Earth is moving at 1,600 kilometers per hour relative to the center of the Earth. Of course, that depends on your latitude, because at the North Pole, it's not moving at all, and then the South Pole is not moving at all, and at the equator, it has that maximum speed. Right. Although I wonder if you're committing the same error that we were pointing out earlier, because you just said the Earth is spinning really fast, but don't you have to say what it's spinning fast relative to? Yeah, exactly. Like couldn't the whole universe, like strange coincidence, be spinning kind of at the same rate the Earth is, in which case we're not really spinning?
Starting point is 00:31:04 Yes. And here we're talking about spinning relative to the center of the Earth, right? When you talk about spin, you have to pick an axis around which you're spinning. And so you're right that there's no like preferred access there. And that's actually a really interesting question I want to get into it in a future episode about whether or not the whole universe is spinning or whether the earth is spinning. It's a deep question called Mach's principle that we should dig into. But you're right, you need to pick a reference frame there. So here we've picked the center of the earth or more specifically if we're talking about spinning an axis that goes from the north to the south pole.
Starting point is 00:31:38 Right. So we're spinning really fast relative to that axis and maybe a common. question might be like, why don't we feel that motion? Like, you know, if I sit in a merry-go-round or one of those state fair rides that spin your ride, I definitely feel that, but we don't feel this crazy spinning of the earth right now. Yeah, it's really interesting. And if you dig back into history, as science was sort of like figuring out that the earth was spinning, that it was moving in this way, people realize this. And they're like, well, that's ridiculous. Like, if the earth was spinning that fast, we would definitely feel it, wouldn't we? And so it was counter to people's
Starting point is 00:32:13 impressions. Like, wouldn't we fly off into space, right? And the answer is, yes, we would fly off into space if the Earth was spinning faster. You know, like if you speed up a merry-go-round and you can't hold on anymore, then you fly off the merry-go-round. Well, what's happening here on Earth is that we are spinning, but gravity is holding us down to the surface of the Earth, and gravity is more powerful than that centripetal force. Also, the Earth spin is very, very smooth and doesn't change. Like, if the Earth was spinning up and slowing down all the time, then you would definitely notice that. But because it's very nearly constant, it just sort of gets like subtracted out from the gravity that you feel. Like you feel gravity, right? It's holding you to the earth.
Starting point is 00:32:53 You notice it. If the earth wasn't spinning, it would be more effective gravity. Like gravity would feel stronger if the earth wasn't spinning. So you are feeling the spinning of the earth as a sort of like slight lessening of the gravity you feel. But it doesn't change very much so you don't notice. Right. Which you just made me think that like if the earth wasn't spinning, we would all weigh a little bit more. Yeah. Like we would feel gravity. Yeah. We would be heavier.
Starting point is 00:33:16 Yes. And you do weigh more at the North Pole than you do at the equator, but only by a very small amount. And that's why you don't typically notice these things. And that's why the whole sense that the Earth is spinning underneath us feels weird because it's not something you could like intuitively grasp. Right. But I think, you know, I think you sort of hit on it when you said that the Earth is spinning really smoothly. Like, like, I think that's one reason why we don't feel this crazy spinning. But I think maybe the other part of it is that.
Starting point is 00:33:43 that it's not kind of like a perfect motion system, right? Like, we still do technically feel things like Coriolis Acceleration, right? And things that would happen if you were kind of in a merry-go-round trying to get to the center or trying to move around a merry-go-round, we technically still feel those weird forces that they're just kind of small relative to the size of the Earth. Absolutely. You can do experiments to prove that the Earth is spinning because a rotating reference frame is not an inertial reference frame for you special relativity wonks out there.
Starting point is 00:34:12 And so you can definitely detect that. What happens when you have a reference frame that's accelerating, and when you're spinning, that's acceleration because you need a force towards the center of the spinning. What happens when your reference frame is spinning is that you get some apparent force. It feels like there's some force doing something, even though it's just due to your spinning. And here on Earth, that's the Coriolis Force. And so, for example, if you drop a rock from the top of a very tall tower, you can measure how far it moves sort of sideways in a way that it wouldn't if the Earth was.
Starting point is 00:34:42 wasn't spinning. You know, it moves like a couple of centimeters when it falls like 150 meters. So it's a small and subtle effect, but you definitely can measure it. And it would be more dramatic if the earth sped up. Interesting. So like if you went up to the top of a tall tower and you dropped a rock, it wouldn't fall straight down. It would sort of curve in this weird way because the earth is spinning.
Starting point is 00:35:01 Yeah, exactly. Like imagine you're back on that merry-go round and you want to throw a ball to your friend who's in a different spot on the merry-go-round. You can't actually just throw it in a straight line towards your friend because by the time the ball gets there, your friend will have, like, rotated away. So if you want to throw the ball so that it gets to your friend, you throw it, like, a little bit to the left.
Starting point is 00:35:20 Because if you throw a ball straight while you're spinning on a merry-go-round, in your view, the ball doesn't move straight. It'll, like, curve to the right. So you've got to account for all these things when you're throwing the ball. And so because the earth is spinning, the same effect happens when you, like, drop a rock from the top of a tower. Or if you've ever been to one of those cool science museums where they have one of those really tall pendulum,
Starting point is 00:35:40 It's called a focal pendulum. But you have to say it with a French accent. It's called a pendulum focal. It's an experiment done in the 1850s originally that proved that the earth was spinning because you can feel this effect on this pendulum. The pendulum is like a heavy weight on a very long string. And so it's sensitive to small pushes in various directions. You set the pendulum going back and forth and then it eventually just starts spinning on its own.
Starting point is 00:36:05 And that spinning, of course, is coming from the Coriola's force. It's coming from the spin of the earth. Right. I think all these things kind of add up to that conclusion that we might feel like we're motionless here on Earth and that even though motionless doesn't mean anything, we still sort of feel motionless. But really, there are these strange forces going on, right? Because the Earth is spinning and the reference frames are accelerating, right? Exactly. And if the earth was not spinning, if there was no like acceleration, because remember spin is acceleration, then there'd be no way to measure the earth's velocity relative to other stuff. So we can measure the earth's spin only because it is acceleration. It's not just constant velocity. That's a bit counterintuitive because it feels like it's constant because it's a constant rate of spin. But constant spin requires acceleration because it requires a force to move you towards the center of the spin. Hmm. All right. Well, what about relative to the sun? That's a pretty stable and almost stationary big thing. Can we be motionless relative to the sun? Yeah, that's actually a really interesting question. And, you know, the Earth, of course, is moving pretty fast relative to the sun. And we should be glad that we are because it's the reason that we don't just like plunge head first into the sun, right? People think about like, if you're near a black hole, would you just get automatically sucked up? Well, the answer is no, if you can get into it. orbit around the black hole. And the same thing is true for orbiting around any gravitational object. Like the reason the Earth doesn't fall into the sun is because we have high speed relative
Starting point is 00:37:35 to the sun. You know, this is the kind of stuff people are talking about with these like New Shepherd and Virgin Galactic launches into space. You know, people are saying that's really super cool and awesome. But you know, all they did was sort of like go up into space. The much more difficult thing is to get up into space and then get it into orbit because that requires a super fast velocity relative to the Earth. So the Earth is moving relative to the Sun at like 30 kilometers per second. And we should be glad that it is because otherwise we would fall headfirst into that huge burning ball of plasma. Oh, you mean those commercial flights? They just kind of dip into space. They don't like staying in space is a lot harder. Yeah. Staying in space is a lot harder than
Starting point is 00:38:14 dipping your toes and then coming back to Earth. Like they were just up in space for a few minutes and they just came right back. But you know what NASA has done and even SpaceX has done is much more difficult because you need a much higher velocity to stay in space, right? Staying in space basically means falling towards the earth and missing it, sort of like in the hitchhiker's guide to the galaxy. And to do that, you need to be moving fast enough that when you fall towards the earth, it's sort of like not there anymore, just like the motion on the merry-go-round. Yeah, you like overshoot it. Yeah, exactly, overshoot it. And so that's what the earth is doing around the sun. We're moving at 30 kilometers per second, which is pretty fast. But that's the
Starting point is 00:38:50 velocity we need because the sun's gravity is so strong, that's the velocity we need to overshoot it every time we fall in towards it. Wow. Well, what about relative to the galaxy? Can we, how fast is the sun moving relative to the galaxy? The sun is really zipping around, right? Here we're talking about gravitational systems and at the core of the galaxy is an enormous mass of stuff, right? We are sort of like out in the suburbs where there's like one star every few cubic light years. But in the center of the galaxy, things are much denser, much crazier, right? In the hot throbbing urban center, there's an enormous black hole with millions and millions of stars worth of mass, and then just lots of stars. And so there's an extraordinarily strong
Starting point is 00:39:34 gravitational force on the sun from the center of the galaxy. And so the sun is orbiting the center of the galaxy, but to avoid falling into that black hole, it has to move really fast. It moves at 800,000 kilometers per hour relative to the center of the galaxy. Wow, that's crazy. Like if you plant the flag in the middle of the galaxy, that's how fast we're moving relative to that. Yeah, relative to that black hole, we are moving at 800,000 kilometers per hour. It's pretty impressive. But you know, the galaxy is so big that it still takes like 200 million years for the sun to go around the center of the galaxy. Like a galactic year is 200 million earth years. Wow. That's a long time to wait for your birthday every time.
Starting point is 00:40:20 But I think the point is that, you know, you might think that you're motionless here, but actually you're moving relative to the center of the Earth. And actually, you might think that the Earth is not moving, but then it's moving relative to the sun and the sun is moving relative to the galaxy by a lot. But then I guess the question is, is the galaxy moving relative to anything else? Right. I think this sort of goes back to the heart of the original question, which is like, can you be motionless in space?
Starting point is 00:40:44 Can you, like, get away from all of this stuff? or like the other question is like the galaxy itself can it just be hanging out in space so this is a really interesting question but again you have to measure the motion of the galaxy relative to other stuff and so now what's the other stuff well you can look at other nearby galaxies and measure like our velocity relative to andromeda or relative to other galaxies that are nearby but that just sort of seems arbitrary is just like you know a random galaxy nearby what you can do though which i think is pretty cool is you can find the motion of how galaxy relative to like all of the stuff in the universe, like the average of all of the things in the universe. Interesting. I mean in terms of mass or energy or just like to think that it has some sort of like aggregate that's not moving. Exactly. We talked earlier about how you can't measure your velocity relative to space itself, right? But you can measure your velocity relative to stuff. And even though there's no preferred location in space, there is stuff in space, right? you can ask like, is there a velocity where you're not moving relative to like all of the average
Starting point is 00:41:49 stuff? And so the way cosmologists do this is they look at the cosmic microwave background radiation. This is the radiation that's left over from the very, very early universe. That plasma that was hot and glowing around 380,000 years after the beginning of the universe, the universe became transparent and that light has been bouncing around ever since then. So that light sort of tells us about where the stuff was in the very early universe. And we can measure our velocity relative to this radiation, which is sort of like measuring your velocity relative to the stuff in the early universe. So while you can't measure your velocity relative to like empty space,
Starting point is 00:42:26 space is not empty. It's filled with stuff. And you can actually find a preferred reference frame in which the cosmic microwave background radiation or the plasma that generated it is at rest. Whoa, whoa. I feel like you just kind of pulled a fast one on me. Like at first, you convince me at first that there's no way to have an absolute velocity, but now you're sort of telling me that there is kind of a way to do it,
Starting point is 00:42:48 depending on how you define what the universe is, right? Exactly. Imagine an empty universe. You can't have any velocity in that empty universe. Now put 10 galaxies in that universe. You could say, well, I could have a velocity relative to one galaxy or another one, or I could just say, what's my velocity relative to all the stuff? Like find the average motion of all the stuff.
Starting point is 00:43:11 in the universe and you could say that's my velocity and it's a reasonable definition it's sort of arbitrary but it also sort of not arbitrary because like there's only one way to choose the average velocity of all the stuff in the universe right because that is the universe right like who cares is that space is slippery and undefinedable and you can't you know measure relative to it what matters is the stuff in it maybe I guess it you know depends philosophically if you think space is fundamental or mass is fundamental or whatever I mean you could also define a frame in which those 10 galaxies, your whole universe in this example, is moving, right, at a billion miles per hour to the left.
Starting point is 00:43:48 You know, you could define that reference frame also. The universe, theoretical physics says they're equivalent. But yeah, I think it makes sense to define a reference frame relative to all the stuff in the universe. And the crazy thing is we can kind of do that. And we can do that by looking at the cosmic microwave background radiation and asking, are we moving through that radiation at some speed in some direction? All right.
Starting point is 00:44:08 Well, let's get into how we can actually tell that velocity. relative to the background radiation, and maybe there are other ways to be motionless in the universe. But first, let's take another quick break. December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed. There's been a bombing at the TWA terminal. Apparently the explosion actually impelled metal glass.
Starting point is 00:44:51 The injured were being loaded into ambulances, just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, and it was here to stay. Terrorism. Law and order, criminal justice system is back. In season two, we're turning our focus to a threat that hides. in plain sight. That's harder to predict and even harder to stop. Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly and now I'm seriously
Starting point is 00:45:31 suspicious. Well, wait a minute, Sam, maybe her boyfriend's just looking for extra credit. Well, Dakota, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, My boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now, he's insisting we get to know each other, but I just want her gone. Now, hold up. Isn't that against school policy? That sounds totally inappropriate.
Starting point is 00:45:53 Well, according to this person, this is her boyfriend's former professor, and they're the same age. And it's even more likely that they're cheating. He insists there's nothing between them. I mean, do you believe him? Well, he's certainly trying to get this person to believe him because he now wants them both to meet. So, do we find out if this person's boyfriend really cheated with his boyfriend? professor or not. To hear the explosive finale, listen to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast.
Starting point is 00:46:18 Culture eats strategy for breakfast. I would love for you to share your breakdown on pivoting. We feel sometimes like we're leaving a part of us behind when we enter a new space, but we're just building. On a recent episode of Culture Raises Us, I was joined by Valicia Butterfield, media founder, political strategist, and tech powerhouse for a powerful conversation on storytelling, impact, and the intersections of culture and leadership. I am a free black woman who worked really hard to be able to say that. I'd love for you to break down. Why was so important for you to do C? You can't win as something you didn't create.
Starting point is 00:46:55 From the Obama White House to Google to the Grammys, Malicia's journey is a masterclass in shifting culture and using your voice to spark change. A very fake, capital-driven environment and society will have a lot of people tell half-truths. I'm telling you, I'm on the energy committee. Like, if the energy is not right, we're not doing it, whatever that it is. Listen to Culture raises us on the IHeart Radio app, Apple Podcasts, or wherever you
Starting point is 00:47:19 get your podcasts. Imagine that you're on an airplane, and all of a sudden you hear this. Attention, passengers. The pilot is having an emergency, and we need someone, anyone, to land this plane. Think you could do it? It turns out that nearly 50% of men think that
Starting point is 00:47:37 they could land the plane with the help of air traffic control. And they're saying like, okay, pull this, pull that, turn this. It's just, I can do it my eyes close. I'm Mani. I'm Noah. This is Devon.
Starting point is 00:47:48 And on our new show, no such thing. We get to the bottom of questions like these. Join us as we talk to the leading expert on overconfidence. Those who lack expertise lack the expertise they need to recognize that they lack expertise. And then, as we try the whole thing out for real. Wait, what? Oh, that's the run right.
Starting point is 00:48:10 I'm looking at this thing. Listen to no such thing on the I Heart Radio app, Apple Podcasts, or wherever you get your podcasts. All right, so it is sort of possible to define motion relative to all the stuff in the universe, not to space, but to all the stuff in the universe. You're saying you can do that through the cosmic. microwave background radiation. Now, that's the like the leftover light from the Big Bang.
Starting point is 00:48:44 Are you saying that we can tell which way we're moving relative to that kind of glow? We can, absolutely. Because like everything else, we can measure our velocity relative to the stuff that emitted it by using red shifts and blue shifts. Like if a star is moving away from us, then the light that it sends us is redshifted. Its wavelength is lengthened. It's stretched out because that star is moving away from us. And if a star is moving towards us, then its wavelength is shrunk.
Starting point is 00:49:10 It's like squeezed down. It's blue shifted. And when we measure the cosmic microwave background radiation, we notice a very, very strong effect that one side of the sky is redshifted and the other side of the sky is blue shifted. So that very clearly gives you a measurement for like our motion through the cosmic microwave background radiation. Interesting. It's sort of like if you stick your head out the side of a moving car, you know, one side of your head would feel the air hitting. one side of your face harder than it would on the other side. And then that's how you know that you're moving in a particular direction relative to the
Starting point is 00:49:43 area you're moving in. Yeah, exactly. It's like if you said, well, let's fill the whole universe with air. Then all of a sudden, there is a reference frame that makes sense, like your air speed through this universe, right? And it kind of is sort of filled with air. I mean, it's not actually air molecules, of course, but it's radiation from the early universe and we can measure our speed relative to it, like the speed of the cosmic microwave
Starting point is 00:50:05 background radiation, wind. So like if we look in one direction, this microwave background radiation looks a little bluer, and then we looked on the other side, it looks a little redder, and that doesn't change, I guess, right? It's sort of relative to what frame of motion. I guess you can measure it relative to our galaxy, right?
Starting point is 00:50:24 Yeah, our galaxy is moving through this. Now, Earth, of course, is moving around the sun, which is moving around the center of the galaxy, so you have to subtract that out. But we measure this as the motion of our galaxy, through the CMB. And it's pretty cool. And it's also not that small. Like, we're kind of clipping along through the CMB at a pretty healthy rate. Yeah, it's like millions of kilometers per hour. Yeah, exactly. 2.1 million kilometers per hour through the CMB. And for those of you who
Starting point is 00:50:52 are enthusiasts about the CNB, you might know that we talk a lot about the details of the CNB, like the wiggles in it, how it's a little hotter here and a little colder there. And that corresponds to fascinating information about the nature of the early universe. That's after we subtract out this big redshift and blue shift effect. We sort of like neutralize that so we can just look at the relative variations. Here we're talking about a velocity relative to the CMB. We subtract that out and then we look for these wiggles to extract all sorts of cool physics juice about the universe.
Starting point is 00:51:22 And it has a lot of vitamin C, I imagine, or cosmos. It's probably toxic. You know, everything out there in space will kill you. We'll give you a good sunburn. You just made me think that, you know, the CMB comes from the, the Big Bang, which is the beginning of the universe, right? Mm-hmm. So if there was a relative velocity between the CMB,
Starting point is 00:51:43 which represents the stuff in the universe and actual space, then it would have to come from the Big Bang, right? Like, it would mean that the Big Bang was sort of moving relative to space when it happened. But that's arbitrary, right? The motion of the C&B relative to space depends on defining a reference frame for space, which doesn't exist. So you can imagine the CMB as stationary in space or you can imagine the CNB and the Big Bang is like moving through space at a zillion miles per hour. They're totally equivalent and you can't tell the difference because you can't define a reference frame for space.
Starting point is 00:52:16 Right. But it's kind of weird to think that the Big Bang happened at a zillion miles per hour. Yeah. It is weird and it is more natural to define a reference frame for like the stuff. And it's also kind of cool because it feels like a choice was made, right? It feels like, well, the stuff is here and it's not over there and it's not more. moving at this speed, but really it's all relative, right? It feels unnatural to imagine the stuff moving in a million miles per hour. It feels more natural to say, let's choose a reference
Starting point is 00:52:42 frame with the stuff is zero. But that's sort of our intuition. It's not like physically meaningful. So I guess then, you know, if we are moving relative to the C&B, do you know which way we're going? Like, are we moving up? Like relative to California, are we moving up, down, left, right, relative to the universe? Like, can you compute that? We can compute that and there is a vector. It doesn't make sense to talk about it relative to California because California's direction through the CMV changes all the time because the earth is spinning and the earth is moving around the sun. Yeah, it's always moving, but at any given time you could compete like,
Starting point is 00:53:14 oh, right now we are technically moving through the stuff in the universe in this direction. Yeah, yeah, you can do that calculation. In fact, maybe we should make a website for that. That would be pretty fun for people to see where we're moving through the universe and how fast we're going at any particular time. Yeah. Now, is it possible then to be sort of motionless relative to the CMB?
Starting point is 00:53:33 Are there spots in the universe or could we, you know, as we're moving and spinning and moving through the galaxy and the solar system, could we at some, for an instant, be not moving relative to the CMB? Yeah, that is totally possible. And astronomers and astrophysicists call this peculiar velocity because, you know, like on average, all the stuff is stationary relative to the CMB. But, you know, nothing is stationary. Everything is like swishing around and moving relative to each other. Like our galaxy and the next galaxy over andromeda are moving towards each other for. example. But it is possible. We just don't happen to be stationary relative to the CMB, but you could like get in a spaceship, fly out between galaxies, measure your velocity relative
Starting point is 00:54:13 to the CMB and like perfectly adjust it so that you're not moving. So it is sort of technically possible to be motionless relative to the stuff in the universe. Yes. But not to space. Yes. But to the stuff in the universe, you could, you know, fly out there, go 2.1 million kilometers per hour in the right direction and you might achieve a velocity that make you still relative to the entire universe. Yeah, exactly. You would have no average velocity relative to all the stuff in the universe. That wouldn't change like special relativity effects because those things are still relative to other observers and stuff like that. But yeah, you could be motionless relative to the stuff in the universe. Oh, that's pretty cool to think that there is, it is possible to
Starting point is 00:54:59 achieve that. And I wonder if we sometimes sort of achieve it, right? Like as we're spinning around the Earth and as the Earth is spinning around the Sun or do you think that because the galaxy is moving so fast that there's no way we can sort of cancel out that motion? Yeah, our motion relative to the CMB
Starting point is 00:55:15 as the galaxy is much greater than even the Sun's motion through the galaxy. The galaxy is moving at 2.1 million kilometers per hour through the CMB. The sun is moving in 800,000 kilometers per hour. So, even if the sun was moving in just the right direction, like opposing the galaxy's motion to the CMB,
Starting point is 00:55:34 it would still only reduce it down to like, you know, 1.3 million kilometers per hour. Or it can make it even faster up to like, you know, almost 3 million kilometers per hour. But we don't ever actually achieve zero velocity relative to the CMB. Interesting. But it is possible, which I think is pretty cool. But there is one last sort of confounding factor,
Starting point is 00:55:55 which is the fact that space is expanding. Now, how does that affect this possibility? of being motionless relative to the universe. Yeah, it confuses everything, you know, because we're not just talking about objects being static in space, right? Space is expanding, which means new space is being made between things, right? So you have a bunch of different things happening at once. You have like the universe expanding so that even if nothing was moving relative to any of the other stuff,
Starting point is 00:56:21 still distances between things would be growing because space is being created between us and other galaxies, which is like a whole mind-bending concept of its own, right? But then we're also interested in that motion, like, are we moving relative to intromeda? Where's our galaxy going? So cosmologists separate this out into two pieces. They say, all right, there's the expansion of the whole universe, which is like happens in the same level,
Starting point is 00:56:45 the same way everywhere between us and other galaxies, between me and you, between the earth and the sun, all of this stuff. And then there's this sort of local motion, like we call this peculiar velocity, relative to that expansion. And so astronomers define these things called co-moving coordinates where you basically subtract out
Starting point is 00:57:04 the expansion of the universe and say, let's just isolate the peculiar velocity, the stuff that's like only due to like local gravity. I guess I'm not sure quite what that means. Does that mean that it is not possible to find that spot where you're not moving relative to the universe
Starting point is 00:57:19 because the universe is also expanding so things will be sort of moving relative to you even if you find that spot? No, I think it still makes sense. I mean, find that spot where you're not moving relative to the CMB. Now everything is expanding away from you, but that's true wherever you are. So it doesn't change your average velocity relative to the CMB because things are moving away from you always in every direction. So the average velocity still would be zero.
Starting point is 00:57:44 It does mean that everything is moving away from you always and so nothing is really ever at rest. But you can still have average velocity of zero relative to all the stuff in the universe, even though that stuff is expanding. Like, imagine you're standing on the surface of a sphere and you find a spot where you're not moving relative to like all the average stuff in the universe. Now that sphere is expanding. So everything's getting bigger, but you're sort of still at the center of all those velocities. Right. I see. Like, the universe could be getting bigger, but you'd still be still relative to all of it, even though it's growing.
Starting point is 00:58:18 Yes, as long as you're defining your reference frame to be like the average motion of all the stuff in the universe. Right. And as long as the universe is not finite, because if it is finite, then you kind of have to find the center of mass or you have to kind of find the sweet spot center in order for really to be motionless. All right. Well, there is another interesting scenario, which is this idea that you can move through time or not move through time. I'm not sure. So Daniel, how does time fit into this idea of being motionless in space? Yeah, I think a lot of people think about our motion through space when they read time travel novels because sometimes you have.
Starting point is 00:58:53 have like your protagonist creates a time travel device and they go back in time. And then the astute reader thinks, hold on a second. If you're going back in time, aren't you going to miss the earth? Like the earth is moving around the sun. If you go back in time a month, you should be in deep space, right? Don't you need to move through time and space in order to catch up with the earth? So a lot of readers write into me with this quibble about the science fiction novels they read. Right, because like a million years ago, the earth was not in the same spot at all, right?
Starting point is 00:59:22 because the galaxy is technically moving a couple million miles per hour. Yeah, sort of. And it's a fair point because things are in motion. And so you need to move sort of through time and through space. But again, it sort of depends on your reference frame. If your reference frame is like the center of the earth, then, you know, none of that motion is really relevant. And it doesn't affect like how time works or how space works. If your reference frame is the center of the galaxy, then it does kind of matter.
Starting point is 00:59:47 And so it sort of depends on like when you're programming your time machine, what coordinates does it take? Is it taking its coordinates relative to the center of the galaxy, in which case you better be careful about how you type them in, or is it taking its coordinates relative to the Earth, for example? Right, but the problem is that the Earth is accelerating and the
Starting point is 01:00:05 galaxies and the solar system is accelerating, so it would probably be really, really complicated, right, to sort of keep that same reference frame. Exactly. And so if you're going to move through time, you need to also be moving through space to make sure you land in the right spot. some good advice for when we build that time machine
Starting point is 01:00:24 or at least good advice for science fiction authors when you write time travel into your novel at least make sure to include this so that our listeners don't get annoyed right right you know you have to add the caveat that it's a space time machine not just a time machine exactly exactly every working time travel machine is actually a space time travel machine
Starting point is 01:00:42 there you go HG Wells got it totally wrong we should have meant its titles too bad we can't have him on the podcast If we had a time machine, we could have him on the podcast. Yeah, but he would be in a totally different place in the universe. Dang it, you're right. We'd be interviewing him from 2 million miles away. All right, well, I think that answer is a question pretty well. Can you be motionless in space?
Starting point is 01:01:02 The answer is no, but you could be motionless relative to the stuff in the universe, which is pretty much the universe, right? Like, you could technically be motionless relative to the stuff in the universe, just not relative to space. Whoa, you just demoted space to not. not be like an important part of the nature of the universe. That's kind of a big deal. I think I demoted it relative to the question in the podcast episode,
Starting point is 01:01:26 but no disrespect to space. I like space. I like my space. But yeah, we hope you enjoyed that. Thanks for joining us. See you next time. Thanks for listening. And remember that Daniel and Jorge Explain the Universe is a production of Eye Heart
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