WEBVTT - Can you be motionless in space? 0:00:08.520 --> 0:00:11.039 Hey, we're hey. When did you get up today? How 0:00:11.039 --> 0:00:12.760 do you know I got up? I could be recording 0:00:12.760 --> 0:00:16.320 this from my bed right now. Thanks for that mental image. 0:00:16.360 --> 0:00:19.000 Now I kind of regret asking. And even if I'm 0:00:19.000 --> 0:00:22.239 in bed, I'm technically still moving. Really is your bed 0:00:22.280 --> 0:00:24.799 on wheels or something, or you have like a flying bed? 0:00:24.960 --> 0:00:27.320 That would be exciting, But no, I'm on Earth and 0:00:27.360 --> 0:00:29.880 the Earth is spinning right in space and it's also 0:00:29.960 --> 0:00:32.800 flying around the Sun. So I'm still moving right? Did 0:00:32.800 --> 0:00:36.839 that count? I mean, does your fitbit give you steps forth? Well? 0:00:37.080 --> 0:00:40.000 I don't really believe in fitbits. I believe in that bits. 0:00:40.320 --> 0:00:58.360 I have one to make one for cartoonists. Hi am 0:00:58.440 --> 0:01:02.040 rhand Ma cartoonists and the creator PhD Comics. I'm Daniel. 0:01:02.120 --> 0:01:05.319 I'm a particle physicist and a professor. You see Irvine 0:01:05.440 --> 0:01:08.199 and it feels like I'm always in motion. Oh yeah, 0:01:08.240 --> 0:01:11.040 like your mental gears are always turning or one of 0:01:11.040 --> 0:01:13.840 those people that have worked on a treadmill all the time. No, 0:01:14.000 --> 0:01:16.240 I definitely do not work on a treadmill. I work 0:01:16.280 --> 0:01:18.959 on a chair and I lean way back with a crazy, 0:01:19.040 --> 0:01:22.679 ridiculous posture that would make like any ergonomic specialist cringe. 0:01:23.200 --> 0:01:25.120 And that's what you mean by motion, that's your workout, 0:01:25.560 --> 0:01:27.560 leaning back for a nap. No, I mean that's sort 0:01:27.560 --> 0:01:30.559 of always scrambling from one thing to the other, working 0:01:30.640 --> 0:01:33.400 on this. Oops, that's late running over here. It feels 0:01:33.400 --> 0:01:35.960 like being an adult in today's modern world is always 0:01:36.000 --> 0:01:39.040 scrambling from one thing to another. You know what you mean. 0:01:39.080 --> 0:01:41.000 But you do know you have a choice there, Daniel, 0:01:41.160 --> 0:01:44.200 I could retire early, Yeah, you can. You cannot do 0:01:44.319 --> 0:01:47.440 so many things that who would I even be? Man? 0:01:47.680 --> 0:01:51.040 Who would I even be? Welcome to existential questions with 0:01:51.160 --> 0:01:53.680 Daniel and Jorge, No, but seriously, welcome to a podcast 0:01:53.760 --> 0:01:56.280 Daniel and Hojorge Explain the Universe, a production of I 0:01:56.400 --> 0:01:59.240 Heart Radio in which we do delve into the deepest 0:01:59.280 --> 0:02:02.840 of exist to questions why does the universe exist? How 0:02:02.920 --> 0:02:05.400 does it all work? What is our place in it? 0:02:05.600 --> 0:02:08.079 How long will it last? How will it end? And 0:02:08.120 --> 0:02:11.000 whose fault will it be when it finally goes poof? 0:02:11.200 --> 0:02:14.519 In which we dig deep into the very smallest, tiniest 0:02:14.560 --> 0:02:17.680 little bits of that universe, asked the basic questions about 0:02:17.720 --> 0:02:20.720 how everything works, and explain all of the answers as 0:02:20.760 --> 0:02:23.280 far as we know them to you. Yeah, because It 0:02:23.400 --> 0:02:27.239 is a confusing and vast universe, and it's a pretty 0:02:27.280 --> 0:02:30.040 restless universe. It seems to be always in motion. There's 0:02:30.080 --> 0:02:32.440 always something going on in the university because you know, 0:02:32.480 --> 0:02:34.639 it's so big, and there's always I don't know, and 0:02:34.720 --> 0:02:39.040 exploding stars somewhere. There's planet spinning everywhere, asteroids flying through 0:02:39.040 --> 0:02:40.960 the sky. It does seem to be sort of in 0:02:41.120 --> 0:02:43.880 slow motion violence. You know, you look out into the 0:02:44.000 --> 0:02:46.080 night sky and you just sort of glance at it, 0:02:46.120 --> 0:02:48.760 and it seems static. It's not like the stars are 0:02:48.760 --> 0:02:51.320 whizzing around in front of your eyes. But you know, 0:02:51.400 --> 0:02:54.519 you pay attention, you see the night sky slide by, 0:02:54.560 --> 0:02:56.680 and the longer you watch, the more you notice that, 0:02:56.760 --> 0:03:00.960 like crazy stuff is happening out there, that the explosions 0:03:00.960 --> 0:03:04.120 that take millions of years but are still very dramatic. 0:03:04.240 --> 0:03:06.520 So everything up there is actually in motion. We just 0:03:06.560 --> 0:03:09.280 sort of live in a tiny little burst of time 0:03:09.320 --> 0:03:12.440 where things seem to be stationary. Yeah, and there's not 0:03:12.600 --> 0:03:14.320 just a lot of action going on out there. There's 0:03:14.320 --> 0:03:16.480 a lot of action inside of us. And in the 0:03:16.520 --> 0:03:20.160 smallest of particles, everything is always you know, vibrating or 0:03:20.160 --> 0:03:23.400 spinning or quantum spitting or disappearing and appearing at the 0:03:23.400 --> 0:03:26.320 same time. Yeah, you're right. Quantum mechanics says that everything 0:03:26.440 --> 0:03:28.280 is in motion and has to be in motion, that 0:03:28.480 --> 0:03:32.040 nothing can actually come to rest, that nothing in the 0:03:32.160 --> 0:03:35.200 end can really have no energy. So the very nature 0:03:35.240 --> 0:03:38.160 of our existence seems to be in motion. Yeah, and 0:03:38.200 --> 0:03:41.000 it does seem like nowadays live involves a lot of 0:03:41.040 --> 0:03:43.600 moving around. You know, it seems like things are spinning 0:03:43.640 --> 0:03:46.480 and moving and changing faster than we can you know, 0:03:46.520 --> 0:03:49.160 get ahold of it. And so you know, the idea 0:03:49.440 --> 0:03:53.160 of resting or being motionless, or you know, just stopping 0:03:53.240 --> 0:03:55.720 and not doing anything is it's kind of weird, right, 0:03:55.800 --> 0:03:57.920 maybe to a lot of people. Yeah, maybe that. I 0:03:57.960 --> 0:03:59.600 think a lot of people did more of that in 0:03:59.600 --> 0:04:01.600 this life last year than they're used to. Went to 0:04:01.680 --> 0:04:05.480 fewer places, canceled traveling, didn't go to the office as much. 0:04:05.480 --> 0:04:07.280 So a lot of people were sort of stuck in 0:04:07.280 --> 0:04:10.480 a smaller orbit than they usually are by the pandemic. 0:04:10.680 --> 0:04:14.040 But still everybody is still moving. Yeah, it's been kind 0:04:14.040 --> 0:04:17.480 of a tough year for everybody, but it's still fun 0:04:17.520 --> 0:04:19.520 to kind of think about the universe and all the 0:04:19.560 --> 0:04:21.480 things that are going on inside of it, and we 0:04:21.600 --> 0:04:25.280 especially like to ask interesting questions in this podcast about 0:04:26.200 --> 0:04:30.280 you know, what's theoretically possible and what is theoretically impossible 0:04:30.480 --> 0:04:33.400 or what is theoretically nonsensical. That's right, and we're not 0:04:33.480 --> 0:04:36.560 the only ones wondering about those kinds of questions. All 0:04:36.560 --> 0:04:39.000 of our listeners are out there thinking about the nature 0:04:39.040 --> 0:04:42.240 of the universe and what's possible and what their experience 0:04:42.400 --> 0:04:44.640 is like in it. And a lot of people right 0:04:44.720 --> 0:04:47.480 in with a particular question when they notice that everything 0:04:47.520 --> 0:04:50.200 in the universe seems to be moving. Everything is sliding 0:04:50.360 --> 0:04:53.560 or spinning or orbiting or zooming through space. And I 0:04:53.600 --> 0:04:57.400 think this inspires people to ask this particular question about 0:04:57.440 --> 0:05:01.239 whether motionlessness is possible. Yeah, so to be on the podcast, 0:05:01.279 --> 0:05:11.400 we'll be tackling the question can you be motionless in space? Now? Daniel, 0:05:11.440 --> 0:05:14.000 do you think people are you know, being aspirational with 0:05:14.040 --> 0:05:16.480 this question, like how can I be motionless in space? 0:05:16.800 --> 0:05:19.760 Or are they asking you think the theoretical question is 0:05:19.760 --> 0:05:23.520 is it possible to be not moving at all in 0:05:23.560 --> 0:05:26.640 this universe? I don't think anybody is asking a practical question. 0:05:26.680 --> 0:05:28.400 I don't think they're trying to develop one of those 0:05:28.440 --> 0:05:31.560 like extreme isolation pods where you can float out in 0:05:31.600 --> 0:05:34.240 space and have nothing touch you or anything like that. 0:05:34.279 --> 0:05:37.240 I think people are pushing the envelopes because they want 0:05:37.279 --> 0:05:39.440 to know what's possible. So in that sense, I guess 0:05:39.480 --> 0:05:42.600 it's a theoretical question. Just like in our Extreme Universe 0:05:42.680 --> 0:05:45.880 podcast episodes, sometimes you learn something about the nature of 0:05:45.920 --> 0:05:50.080 space by looking at the extreme situation, asking what's the 0:05:50.120 --> 0:05:52.520 fastest you can go or what's the slowest you can go, 0:05:52.600 --> 0:05:55.080 what's the hottest something can be, what's the coldest something 0:05:55.120 --> 0:05:57.599 can be. So since everything seems to be moving, I 0:05:57.600 --> 0:06:00.280 think people are wondering is it even post the all 0:06:00.360 --> 0:06:03.960 theoretically for something to be totally at rest? What would 0:06:04.000 --> 0:06:06.280 that mean, what would it require? What does it reveal 0:06:06.360 --> 0:06:09.120 about the nature of the universe? Right? Yeah, Still I 0:06:09.200 --> 0:06:11.839 mean to think that a physicist might ask a practical question. 0:06:12.080 --> 0:06:15.880 Sorry about that, but it is a pretty interesting theoretical question, 0:06:16.040 --> 0:06:19.320 like can you be not moving? I guess, And do 0:06:19.360 --> 0:06:22.640 you think that's more about staying still or a feeling 0:06:22.839 --> 0:06:24.520 that you're not moving? Do you know what I mean? Like, 0:06:24.560 --> 0:06:26.479 do you think people are asking about is there a 0:06:26.520 --> 0:06:29.880 point in the universe that's technically not moving relative to 0:06:29.920 --> 0:06:32.839 everything else? Or do you think it means just like, 0:06:32.960 --> 0:06:36.160 how can I not have an emotion relative to anything else? Yeah, 0:06:36.200 --> 0:06:38.360 I think there's a lot of interesting stuff to unpack 0:06:38.440 --> 0:06:40.599 there about like the very nature of what it means 0:06:40.680 --> 0:06:42.960 to be in motion, that we're going to have to 0:06:43.000 --> 0:06:46.000 dig into, because I think something about this question reveals 0:06:46.000 --> 0:06:48.440 that people are thinking about speed in a way that 0:06:48.640 --> 0:06:50.839 comes naturally to them on the surface of the Earth, 0:06:50.880 --> 0:06:53.160 where it makes sense to talk about what my speed is. 0:06:53.400 --> 0:06:56.040 But when you go out into space, things change. Things 0:06:56.040 --> 0:06:58.680 are different the same way that like up and down 0:06:58.760 --> 0:07:00.560 have a meaning on the surface of the Earth but 0:07:00.760 --> 0:07:03.880 don't really make sense anymore out in space. I think 0:07:03.920 --> 0:07:06.279 we're going to learn that the whole concept of velocity 0:07:06.360 --> 0:07:08.520 is a little bit different than what a lot of 0:07:08.560 --> 0:07:11.400 people had in mind. And so this is a great question, 0:07:11.680 --> 0:07:13.720 not because the answer is simple and reveals the truth 0:07:13.800 --> 0:07:16.000 about the universe, but because the nature of the question 0:07:16.320 --> 0:07:19.160 makes you rethink the whole nature of motion. Yeah, and 0:07:19.160 --> 0:07:20.960 then you have to ask the follow up question, which 0:07:21.000 --> 0:07:24.880 is can you be emotionless in space? After learning the 0:07:24.960 --> 0:07:26.720 answer to the first question, I think we know the 0:07:26.760 --> 0:07:31.720 answer that it's called the movie gravity. Oh, movie criticism 0:07:31.760 --> 0:07:35.000 and physics all in one podcast. Seriously, nobody seems to 0:07:35.040 --> 0:07:37.480 have any emotions in the movie. They're all just like stoic, 0:07:38.560 --> 0:07:42.200 just trying to not die. I think in space? Can 0:07:42.240 --> 0:07:44.640 you be alive in space? That's the question they were asking, 0:07:44.960 --> 0:07:47.920 not just standing still because you're dead. But yeah, this 0:07:48.000 --> 0:07:50.200 is a pretty interesting question, and so, as usually, we 0:07:50.200 --> 0:07:52.240 were wondering how many people out there have thought about 0:07:52.280 --> 0:07:55.040 this question and whether or not they have an answer 0:07:55.320 --> 0:07:57.880 that they might have thought of. Daniel went out there 0:07:57.920 --> 0:08:00.880 into the internet to ask the question, Shan, can you 0:08:00.960 --> 0:08:04.240 be motionless in space? That's right, I go out into 0:08:04.240 --> 0:08:06.560 the web and beat the bushes for people who are 0:08:06.640 --> 0:08:09.600 interested in answering these questions for us. If you are 0:08:09.680 --> 0:08:12.880 out there on the internet and have not participated, please 0:08:13.120 --> 0:08:15.600 we want to hear your voice, especially if you're from 0:08:15.600 --> 0:08:17.800 a location we haven't heard anybody from before. We would 0:08:17.840 --> 0:08:20.400 love to hear your voice on the podcast, So please 0:08:20.480 --> 0:08:23.920 write to us two questions at Daniel and Jorge dot com. 0:08:24.080 --> 0:08:25.840 So think about it for a second. Do you think 0:08:25.880 --> 0:08:29.800 it's possible to be motionless in space? Here's what people 0:08:29.840 --> 0:08:33.040 had to say. Well, I can be motionless if I 0:08:33.040 --> 0:08:35.800 don't move a muscle, So nothing on me would move, 0:08:36.400 --> 0:08:40.800 that would qualify as motionless, I guess, But relative to 0:08:41.200 --> 0:08:44.320 something else, I would probably never be motionless because everything 0:08:44.320 --> 0:08:46.920 else is moving. The Sun is moving around the center 0:08:46.920 --> 0:08:49.640 of the galaxy, and the planets around the Sun, everything 0:08:49.640 --> 0:08:53.920 else is moving. Even space itself is expanding. So even 0:08:53.960 --> 0:08:56.880 if I'm in a point in space and the space 0:08:56.920 --> 0:09:00.440 around me is expanding, then the things around me would 0:09:00.520 --> 0:09:03.480 be moving along with it as well. So can you 0:09:03.559 --> 0:09:07.520 be motionless in space? Yes, if I don't move a muscle. No, 0:09:08.040 --> 0:09:10.720 relative to anything else, I don't think you can be 0:09:10.840 --> 0:09:14.880 motionless in space. If two bodies are passing by each 0:09:14.920 --> 0:09:21.479 other and neither is accelerating, both bodies, from their perspective 0:09:21.960 --> 0:09:24.080 would feel that they were standing still and the other 0:09:24.120 --> 0:09:27.760 one was moving. It doesn't seem like it, since your 0:09:27.840 --> 0:09:31.160 motion would be relative to whatever it was around you. 0:09:31.320 --> 0:09:34.600 So even if you're standing still on Earth, the Earth 0:09:34.640 --> 0:09:37.520 is spinning and moving around the Sun, And if you're 0:09:37.640 --> 0:09:40.640 standing still next to the Sun, it's spinning around the 0:09:40.679 --> 0:09:46.680 galaxy and the galaxy is moving. Um, but maybe it's 0:09:46.679 --> 0:09:50.600 possible to just stick still with respect to the the 0:09:50.720 --> 0:09:55.120 fabric of space. Well, if I'm not moving at all, yes, 0:09:56.280 --> 0:10:02.360 But motionless like not moving from the we really regard 0:10:02.440 --> 0:10:12.120 into something like the moon, Earth's sun, galaxy, the galaxy 0:10:12.160 --> 0:10:17.360 cluster Lannique, and so on. Probably I would be moving. 0:10:17.800 --> 0:10:22.280 Motion is relative, measured relatively to other things. So I 0:10:22.280 --> 0:10:25.640 guess you could technically you would always be motionless and 0:10:25.720 --> 0:10:29.560 always be moving in all different directions at the same time. 0:10:29.880 --> 0:10:31.680 With space expanding, I don't know if that becomes a 0:10:31.720 --> 0:10:34.280 factor too, but probably does. I don't think that you 0:10:34.320 --> 0:10:37.680 can be motionless in space. I think that there's a 0:10:37.720 --> 0:10:41.040 reason why Einstein thought up the theory of relativity, because 0:10:41.440 --> 0:10:45.200 there is no super position that we can use to 0:10:45.280 --> 0:10:49.800 compare positions in space against. You've only really got what 0:10:50.160 --> 0:10:52.720 you have, which is your own frame of reference, and 0:10:52.760 --> 0:10:56.120 then you compare that to something else. And because everybody 0:10:56.120 --> 0:11:01.200 else has a different reference, there is no set central 0:11:01.240 --> 0:11:06.440 position where something is not moving. If I somehow ended 0:11:06.520 --> 0:11:12.120 up in space and I wasn't moving for some reason, um, 0:11:12.160 --> 0:11:17.840 according to which one Newton's first law, UM, an object 0:11:18.160 --> 0:11:22.600 that is not moving, we'll stay stationary. UM. So I 0:11:22.640 --> 0:11:25.760 suppose if somehow, I don't know, if the Earth vanished 0:11:26.640 --> 0:11:33.000 and I was left suspended in space, UM, and I 0:11:33.040 --> 0:11:37.959 wasn't moving, then I would be motionless in space, all right. 0:11:38.600 --> 0:11:40.920 A lot of people there doesn't think to think it's 0:11:40.960 --> 0:11:45.800 possible to be motionless. Yeah, yeah, exactly, It's it's fascinating. 0:11:45.800 --> 0:11:50.800 I think people are just naturally reathless or they have 0:11:50.880 --> 0:11:53.360 one of those restless leg syndromes. Yeah, there are those 0:11:53.360 --> 0:11:55.679 people who are always tapping on something or got like 0:11:55.760 --> 0:11:59.000 a fidget spinner or something. Yeah, I know what my 0:11:59.200 --> 0:12:02.280 kids would say. I would say, no, it's impossible right now, 0:12:02.320 --> 0:12:04.520 what I would say about my children even if they 0:12:04.520 --> 0:12:06.080 were in space, and the kids would say, like, and 0:12:06.120 --> 0:12:08.559 why would you want to? That seems really boring, right, 0:12:09.040 --> 0:12:12.160 just lying there doing nothing. Yeah, So it's an interesting question. 0:12:12.240 --> 0:12:14.240 I guess the question sort of boils down to, like 0:12:14.400 --> 0:12:17.200 it's not about standing still, but it's more about moving, right, 0:12:17.240 --> 0:12:20.600 like your whole body moving somewhere, right, because technically we 0:12:20.640 --> 0:12:23.320 are always vibrating, right, like if we have a temperature, 0:12:23.320 --> 0:12:26.640 your our molecules are moving. This is more about, you know, 0:12:26.679 --> 0:12:30.640 whether we're as a whole dane still or translating or 0:12:30.679 --> 0:12:33.040 moving or going from one place to another, right. Yeah, 0:12:33.080 --> 0:12:35.439 I think we should sort of like approximate you as 0:12:35.480 --> 0:12:38.200 a little dot or a point particle and ignore all 0:12:38.240 --> 0:12:40.840 the motion inside you, and then ask the question, can 0:12:41.040 --> 0:12:45.520 point particle, you can spherical? You be motionless with respect 0:12:45.520 --> 0:12:49.000 to everything? Is that even possible? Right? Like cartoon Jorge, 0:12:50.080 --> 0:12:52.559 So this should be easy because I'm good at ignoring 0:12:52.559 --> 0:12:56.520 all the emotions inside of me. Right, that was a 0:12:56.559 --> 0:12:59.120 little dark. No, I'm just kidding, but yeah, it's about 0:12:59.240 --> 0:13:02.160 whether or not we're moving in relative or moving in 0:13:02.240 --> 0:13:04.680 space as a whole. Yeah, exactly. And one of the 0:13:04.679 --> 0:13:07.800 most important things to understand is that there is no 0:13:08.000 --> 0:13:13.120 absolute motion. All motion is relative. It's always defined relative 0:13:13.200 --> 0:13:15.520 to something else. You Know. People writing often and ask 0:13:15.600 --> 0:13:18.760 questions about like special relativity, and usually their questions start 0:13:18.760 --> 0:13:20.720 with something like if I was in a spaceship and 0:13:20.760 --> 0:13:23.560 I was going really really fast, and they don't say 0:13:23.600 --> 0:13:26.800 what they're going really really fast relative to? You know, 0:13:26.840 --> 0:13:29.160 they have this sense that like there's something that happens 0:13:29.200 --> 0:13:31.839 when you get up to high speeds. But the thing 0:13:31.920 --> 0:13:35.599 that's missing there is like who are you speeding by? 0:13:35.679 --> 0:13:38.920 Where are you going fast relative to? There is no 0:13:39.000 --> 0:13:42.080 sense in which you have speed other than that it's 0:13:42.120 --> 0:13:46.040 measured relative to other things or people, right, Because I 0:13:46.080 --> 0:13:50.800 guess motion is a quantity that is that can't exists 0:13:50.840 --> 0:13:53.640 on its own, right, Yeah, exactly. If you are, for example, 0:13:53.720 --> 0:13:57.000 in an empty universe, right it's just you floating in 0:13:57.120 --> 0:13:59.880 space and there's nothing else in the universe, then you 0:14:00.160 --> 0:14:03.439 or speed doesn't make any sense. You have no velocity. 0:14:03.720 --> 0:14:07.120 You can't have velocity because velocity is just motion relative 0:14:07.240 --> 0:14:09.600 to something else. You know. I guess this might be 0:14:09.600 --> 0:14:11.679 confusing to people because I wonder, like, you know, I 0:14:11.720 --> 0:14:13.880 think a lot of us maybe imagine that, you know, 0:14:14.040 --> 0:14:17.920 the universe maybe has an extent, like a limit, like 0:14:17.960 --> 0:14:20.320 a wall at some point. Maybe it's a big sphere, 0:14:20.360 --> 0:14:22.440 maybe it's a big blob, maybe it's a donut. But 0:14:22.520 --> 0:14:24.960 it has sort of like a shape of it. So 0:14:25.320 --> 0:14:28.360 couldn't I measure my speed or my motion relative to 0:14:28.400 --> 0:14:31.240 that shape? No, because the universe is actually symmetric. Like 0:14:31.360 --> 0:14:34.440 if you do some experiment over here and then you 0:14:34.480 --> 0:14:36.840 do the same experiment over there, you always get the 0:14:36.880 --> 0:14:40.600 same answer. There's no point in space that's different than 0:14:40.640 --> 0:14:43.840 another point in space, Like space has no texture. There's 0:14:43.880 --> 0:14:47.160 no like way to tell where you are in space. 0:14:47.680 --> 0:14:50.520 I mean, it might be that the universe is finite 0:14:50.520 --> 0:14:53.520 and has some like weird edge to it, but we 0:14:53.600 --> 0:14:57.120 haven't observed that, and the current cosmological models usually assume 0:14:57.200 --> 0:15:00.080 that the universe is infinite and that every point in 0:15:00.160 --> 0:15:02.920 it behaves the same way, Like the laws of physics 0:15:02.960 --> 0:15:05.480 are the same no matter where you are, and so 0:15:05.560 --> 0:15:08.720 you can't do an experiment determine where you are. So 0:15:08.760 --> 0:15:11.240 it's not like you can feel space moving by or 0:15:11.280 --> 0:15:15.520 measure yourself your location relative to some like absolute point 0:15:15.600 --> 0:15:18.240 in space. There is no absolute point, and so there 0:15:18.280 --> 0:15:21.440 is also no absolute velocity. Well, there's no absolute point 0:15:21.480 --> 0:15:23.920 that we know of, right, But could there be one 0:15:23.960 --> 0:15:27.120 if like the universe does have a shape or like 0:15:27.320 --> 0:15:31.480 a wall or limit in some scenarios, yes, in most scenarios, no, Like, 0:15:31.560 --> 0:15:34.760 even if the universe is not infinite, right, it might 0:15:34.760 --> 0:15:38.440 not have an edge. Like imagine the universe is closed 0:15:38.480 --> 0:15:41.520 and finite the way it like wraps around itself. That 0:15:41.560 --> 0:15:44.400 doesn't mean that there's any special point. It can be 0:15:44.520 --> 0:15:47.720 finite and still have like no special location to it. 0:15:47.840 --> 0:15:50.240 Imagine you're like on the surface of a sphere, right, 0:15:50.320 --> 0:15:52.720 then every point on that sphere is really the same, 0:15:52.840 --> 0:15:55.960 even though the service is not infinite, right, Yeah, I guess, 0:15:56.040 --> 0:15:58.680 like if the universe was like at the pag max screen. 0:15:58.760 --> 0:16:02.400 Then there's technically no real place in the pac Man's 0:16:02.440 --> 0:16:05.400 screen because it just loops around forever. But I guess 0:16:05.440 --> 0:16:07.400 I'm just trying to get to the possibly that maybe 0:16:07.560 --> 0:16:09.360 it does have an edge, in which case there would 0:16:09.360 --> 0:16:12.040 be something like an absolute position. Right. If the universe 0:16:12.120 --> 0:16:14.960 did have some sort of like strange wall as an 0:16:15.040 --> 0:16:18.320 edge to it, or some like deformity in its geometry, 0:16:18.480 --> 0:16:21.600 then yes, that would break this cosmological principle that every 0:16:21.640 --> 0:16:24.000 location is the same, and then you could measure your 0:16:24.040 --> 0:16:27.760 velocity relative to that there would be a special location 0:16:27.840 --> 0:16:31.080 in space. But still your velocity would only have meaning 0:16:31.120 --> 0:16:34.280 a relative to something. And you can define your velocity 0:16:34.280 --> 0:16:37.040 to be relative to like that weird edge of space 0:16:37.480 --> 0:16:40.840 or the Sun or the moon, or there's dust particle, 0:16:40.960 --> 0:16:43.920 but the definition of your velocity still only has meaning 0:16:44.080 --> 0:16:47.320 relative to something, right, Yeah, because I guess you know 0:16:47.560 --> 0:16:50.720 motion or velocity, it's like the change in a quantity, 0:16:50.800 --> 0:16:53.080 which is distance. So you can have distance if you 0:16:53.120 --> 0:16:56.640 don't measure relative to something else, right, yeah, exactly, And 0:16:56.640 --> 0:16:59.240 this is actually really closely connected to like all sorts 0:16:59.280 --> 0:17:02.200 of interesting deep physics of the universe. You know the 0:17:02.200 --> 0:17:05.359 fact that space seems to be the same everywhere. That 0:17:05.400 --> 0:17:07.919 if you do your experiment here and then you transport 0:17:07.920 --> 0:17:10.000 it ten light years over there and do it again, 0:17:10.119 --> 0:17:13.199 that you get the same answer. That's connected to an 0:17:13.280 --> 0:17:16.480 important law of physics, which is conservation of momentum. And 0:17:16.480 --> 0:17:19.000 we're gonna do a whole fun podcast episode about this 0:17:19.119 --> 0:17:21.800 deep theory of physics called Nuther's theorem that tells you 0:17:21.840 --> 0:17:24.359 that anytime you have a symmetry like that, something where 0:17:24.520 --> 0:17:27.720 the universe doesn't care where you are, you get some 0:17:27.840 --> 0:17:31.600 conserved quantity, something which doesn't change as you do your experiments. 0:17:31.640 --> 0:17:33.480 So in this case, the connection is the fact that 0:17:33.520 --> 0:17:36.000 you can move from one place in space to another 0:17:36.160 --> 0:17:38.560 and not have your experiment change. Is why we have 0:17:38.760 --> 0:17:42.440 conservation of momentum, which is sort of mind blowing to me. 0:17:42.680 --> 0:17:46.639 But yeah, exactly, velocity is defined relative to other things 0:17:46.720 --> 0:17:50.399 in space, not relative to space itself, right, And I 0:17:50.440 --> 0:17:53.240 think it extends not just to like your precision in 0:17:53.280 --> 0:17:55.320 the universe, right, Like you can do an experiment here 0:17:55.359 --> 0:17:57.040 or there and it should be worked out the same, 0:17:57.080 --> 0:17:59.520 but it also it comes up in doing the experiment 0:17:59.560 --> 0:18:02.320 at different velocities. Right. I can do my experiments going 0:18:02.320 --> 0:18:04.840 at a hundred moss per hour relative to the Earth, 0:18:04.920 --> 0:18:06.480 or I can do it at a hundred thousand miles 0:18:06.520 --> 0:18:08.480 per hour. I should get the same results if I'm 0:18:08.520 --> 0:18:11.120 going at a constant speed, right, Yeah, exactly. If you're 0:18:11.160 --> 0:18:13.879 in a box, you can't measure your velocity relative to 0:18:13.920 --> 0:18:16.760 stuff outside the box if you can't see that stuff 0:18:16.800 --> 0:18:19.240 at all. So if you do an experiment, it shouldn't 0:18:19.240 --> 0:18:22.000 be sensitive to your velocity relative to that stuff. So 0:18:22.040 --> 0:18:24.560 the classic scenario is like you set up some experiment. 0:18:24.600 --> 0:18:25.919 I don't know what it is. It's got you know, 0:18:26.000 --> 0:18:28.760 like balls swinging and hitting each other or whatever, and 0:18:28.800 --> 0:18:32.680 then you gently accelerate up to some higher speed, right, 0:18:32.720 --> 0:18:35.160 And the key there is gently accelerates so you don't 0:18:35.160 --> 0:18:38.280 like destroy everything. Now your speed is high relative to 0:18:38.320 --> 0:18:40.400 like the surface of the Earth or the planet you're 0:18:40.440 --> 0:18:42.800 on or whatever. You do the same experiment, you should 0:18:42.840 --> 0:18:45.159 get exactly the same result. And that's not just some 0:18:45.280 --> 0:18:49.320 like weird esoteric thing that means that you can't measure 0:18:49.359 --> 0:18:51.600 your velocity. Is no experiment you could do that would 0:18:51.600 --> 0:18:54.720 give a different answer if your velocity relative to that 0:18:54.760 --> 0:18:58.119 planet is zero or a thousand meters per second, And 0:18:58.160 --> 0:19:02.000 that means you can't build a device to measure that velocity. Right, 0:19:02.320 --> 0:19:04.919 And again this applies to just to double check, this 0:19:04.960 --> 0:19:08.080 applies to like constant velocity. Right. If I'm accelerating, then 0:19:08.119 --> 0:19:11.600 that's a whole different ball game, exactly. Acceleration is totally different, 0:19:11.600 --> 0:19:15.159 which is also really interesting. Acceleration is something you can measure. 0:19:15.200 --> 0:19:18.199 There is absolute acceleration. If you're in a box, you 0:19:18.240 --> 0:19:20.879 can measure your acceleration. Right. You can do a simple 0:19:20.920 --> 0:19:22.680 experiment toss a ball up in the air and it 0:19:22.720 --> 0:19:26.239 will move differently if you're under acceleration then if you're not. 0:19:26.359 --> 0:19:28.520 And also you'll feel it. If you're in a box 0:19:28.560 --> 0:19:31.880 and it's accelerating, it will feel just like gravity. Right. 0:19:32.080 --> 0:19:35.200 Acceleration feels just like gravity, which was the whole inside 0:19:35.240 --> 0:19:38.399 which led to general relativity and that whole revolution and 0:19:38.480 --> 0:19:42.200 understanding space and time. But position and velocity only makes 0:19:42.200 --> 0:19:45.840 sense relative to other things, right. And I think what 0:19:45.960 --> 0:19:49.440 you're saying, basically just to kind of drive this home, 0:19:49.560 --> 0:19:51.920 is that like, if you're inside of a box out 0:19:51.960 --> 0:19:56.280 in space, it's sort of impossible to know how fast 0:19:56.440 --> 0:19:59.840 that box you're in is moving relative to other things. Right. 0:20:00.080 --> 0:20:02.800 If it's moving at a constant speed, or not. It's 0:20:02.800 --> 0:20:06.200 impossible to tell that, you know, boxes floating out in 0:20:06.280 --> 0:20:10.080 space or it's like moving super fast across the galaxy. Yeah, exactly, 0:20:10.160 --> 0:20:12.000 as long as you can't look outside the box. Like 0:20:12.040 --> 0:20:13.960 if you have a window, you can look outside and 0:20:14.000 --> 0:20:16.040 you can see things moving by and measure it. But 0:20:16.080 --> 0:20:18.480 if all you can do is measure things inside the box, 0:20:18.520 --> 0:20:21.359 then yeah, you can't measure your velocity relative to anything 0:20:21.359 --> 0:20:24.119 outside the box. There's no way to tell, right, And 0:20:24.119 --> 0:20:26.280 so I think what you're getting at is that basically 0:20:26.400 --> 0:20:30.560 just the word motionless doesn't really have any meaning, right 0:20:30.680 --> 0:20:33.800 because you might think you're motionless now inside your box, 0:20:33.840 --> 0:20:35.879 but really you could be moving really fast or not 0:20:35.960 --> 0:20:38.400 at all, or moving in any kind of crazy direction 0:20:38.520 --> 0:20:41.440 outside of that box. So really the word motionless doesn't 0:20:41.440 --> 0:20:44.080 mean anything from a physics math point of view. Yeah, 0:20:44.119 --> 0:20:47.640 it's either totally meaningless or it's just totally arbitrary. Like 0:20:47.720 --> 0:20:50.960 you can pick a definition of a reference frame and say, 0:20:51.160 --> 0:20:52.840 I'm going to say that the Earth is at the 0:20:52.880 --> 0:20:55.400 center of my reference frame. Now my velocity has meaning. 0:20:55.400 --> 0:20:58.159 I'm talking about velocity relative to the Earth. But you 0:20:58.200 --> 0:21:00.680 could also pick anything else. You could pick the sun, 0:21:00.720 --> 0:21:02.800 you could pick that grain of dust. You could pick 0:21:02.840 --> 0:21:05.960