WEBVTT - What is Frame Dragging? 0:00:08.480 --> 0:00:11.440 Hey, Daniel, do people ever send you their personal theories 0:00:11.600 --> 0:00:14.720 of the universe? Oh? Yeah, I get plenty of those. 0:00:15.560 --> 0:00:17.159 What do you think they're hoping for? A lot of 0:00:17.200 --> 0:00:22.040 them want to prove Einstein was wrong? Really, aim high? 0:00:22.040 --> 0:00:25.680 I guess after all these years, aren't we convinced Einstein 0:00:25.800 --> 0:00:29.200 was right? Actually, I'm pretty convinced Einstein was wrong. What 0:00:30.640 --> 0:00:32.960 you think you know better than Einstein? I don't have 0:00:33.000 --> 0:00:35.640 a better theory of the universe, but I'm pretty sure 0:00:35.720 --> 0:00:39.960 his theory general relativity is not a correct description of nature. Well, 0:00:40.040 --> 0:00:41.840 you should come up with your own theory then, Yeah, 0:00:41.880 --> 0:00:44.159 and then I could send it to myself and then 0:00:44.200 --> 0:00:46.640 you can answer it on the podcast. Done Nobel Prize 0:00:46.680 --> 0:01:05.280 for the two of us. Hi am more Hammad, cartoonists 0:01:05.319 --> 0:01:08.200 and the creator of PhD comics. Hi. I'm Daniel. I'm 0:01:08.240 --> 0:01:11.520 a particle physicist, and I would love if somebody out 0:01:11.520 --> 0:01:15.520 there proved Einstein wrong. Yeah, maybe even the ghost of Einstein, 0:01:15.760 --> 0:01:20.240 Einstein's grandchildren, son of Einstein or daughter of Einstein. Einstein 0:01:20.280 --> 0:01:23.120 had a pretty scandalous family situation, so I wouldn't be 0:01:23.120 --> 0:01:25.440 surprised if some of his kids or grandkids are great 0:01:25.480 --> 0:01:28.120 grandkids were a little grumpy at him. Well, they definitely 0:01:28.160 --> 0:01:31.040 heard it a nice brand name. So I mean, can 0:01:31.040 --> 0:01:33.120 you imagine going for a job and put an ice 0:01:33.240 --> 0:01:35.520 and on your resume and people are like, yeah, he's 0:01:35.520 --> 0:01:37.959 probably not or she's not, probably not smart enough, not 0:01:38.120 --> 0:01:40.120 likely to happen, right, It's a lot of pressure. What 0:01:40.160 --> 0:01:42.080 if you, like, want to be a basketball player in 0:01:42.120 --> 0:01:44.840 your name is Einstein and they're like, get off the core, Einstein, 0:01:45.880 --> 0:01:49.080 go back to your chalk board there. Yeah, exactly what 0:01:49.160 --> 0:01:50.680 do they call it when an actor can only get 0:01:50.680 --> 0:01:53.040 one kind of real type cast? Right? Like Einstein and 0:01:53.120 --> 0:01:55.320 all of his generations are all going to be forced 0:01:55.320 --> 0:01:58.000 to be doing fundamental physics. Right. I haven't seen a 0:01:58.000 --> 0:02:01.200 lot of stand up comedians, right, Or are is name Einstein? 0:02:01.280 --> 0:02:03.800 Well they probably changed their names, right, they have stage names, 0:02:03.840 --> 0:02:07.160 you know, the comedian formerly known as Einstein. I guess 0:02:07.160 --> 0:02:09.960 that would help them. But anyways, welcome to our podcast. 0:02:10.040 --> 0:02:12.920 Daniel and Jorge explain the universe in production of I 0:02:13.040 --> 0:02:15.959 Heart Radio, in which we make everybody out there and 0:02:16.120 --> 0:02:19.400 Einstein by explaining to you everything that we do know 0:02:19.480 --> 0:02:23.320 about our crazy, beautiful, hot and wet and weird universe 0:02:23.560 --> 0:02:26.920 and everything that we don't yet understand from the tiniest 0:02:26.960 --> 0:02:29.120 little bits of space and how they fit together to 0:02:29.160 --> 0:02:33.120 make this incredible, emergent, bonkers beautiful world, to the vast 0:02:33.360 --> 0:02:35.720 nature of the cosmos. How far does it go on? 0:02:35.880 --> 0:02:38.120 What's out past there? Will we ever see it? We 0:02:38.200 --> 0:02:41.520 wrap up all those questions and explain them to you. Yeah, 0:02:41.560 --> 0:02:45.400 because it is a vast universe full of intricate secrets 0:02:45.440 --> 0:02:48.799 and lots of wonders for us discover hiding and plain 0:02:48.880 --> 0:02:52.560 site sometimes right even around our own neighborhood. It is exactly. 0:02:52.680 --> 0:02:55.400 I look at the universe like the biggest murder mystery 0:02:55.440 --> 0:02:58.200 or the grandest detective novel ever written. It's like a 0:02:58.240 --> 0:03:01.040 big puzzle figuring out how does it work. We're gathering 0:03:01.120 --> 0:03:03.480 clues and trying to narrow down and figure out, like 0:03:03.760 --> 0:03:06.280 what really makes the universe tick? What does it have 0:03:06.360 --> 0:03:08.480 to be a murder mystery? Daniel, I feel like you 0:03:08.600 --> 0:03:11.360 just went kind of dark there, like like somebody had 0:03:11.400 --> 0:03:13.600 to die to make the universe. Well, you know, the 0:03:13.639 --> 0:03:17.399 universe is going to kill you, Jorge. I'm sure it's 0:03:17.400 --> 0:03:21.760 not the universe itself, but maybe my eating habits. Well, 0:03:21.800 --> 0:03:23.600 I just think it adds some drama, you know, it's 0:03:23.600 --> 0:03:25.679 always more fun to work on a mystery if there's 0:03:25.720 --> 0:03:27.959 a body involved, I suppose, I don't know. That's why 0:03:27.960 --> 0:03:30.840 there's that whole genre of murder mysteries, right, It's not like, 0:03:31.120 --> 0:03:34.240 you know, who got gently tapped on the head in 0:03:34.280 --> 0:03:36.800 the library with the candlestick. You know, it's like who 0:03:36.840 --> 0:03:39.440 got killed? So, yeah, this is a big mystery. We 0:03:39.480 --> 0:03:42.560 want to understand what is the fundamental nature of the universe, 0:03:42.600 --> 0:03:44.800 what are the rules by which it runs? How can 0:03:44.840 --> 0:03:47.360 we figure that out? And frankly, I'm amazed that we 0:03:47.480 --> 0:03:49.840 really made any progress at all. Yeah. I guess if 0:03:49.880 --> 0:03:51.960 the mystery was just word that I put my reading glasses, 0:03:52.520 --> 0:03:55.480 that wouldn't attract a lot of viewers there, or physicists, 0:03:55.640 --> 0:03:59.400 to be honest, Yeah, exactly, or true crime novelists named Einstein. 0:03:59.560 --> 0:04:01.840 All right, we like to talk about all the great 0:04:01.880 --> 0:04:03.560 mysteries out there on the universe, and also we like 0:04:03.600 --> 0:04:06.800 to talk about what scientists are doing to uncover those 0:04:06.800 --> 0:04:09.480 secrets and figure out what's really going on, because there 0:04:09.520 --> 0:04:13.280 are a lot of interesting projects and interesting science experiments 0:04:13.280 --> 0:04:16.760 going on right now as we speak, trying to peer 0:04:17.160 --> 0:04:20.760 further into the universe and closer to the very nature 0:04:20.800 --> 0:04:23.960 of matter. That's right, because even though folks like Einstein 0:04:24.040 --> 0:04:27.559 gave us a beautiful glimpse into how the universe might work, 0:04:27.880 --> 0:04:31.279 we are still figuring out whether his vision is correct 0:04:31.720 --> 0:04:35.080 or not, whether it describes the way the universe actually works, 0:04:35.400 --> 0:04:38.599 or if it's just like a very effective approximation which 0:04:38.680 --> 0:04:41.359 from some point of view seems to be successful in 0:04:41.440 --> 0:04:44.800 predicting what happens in weird situations. Yeah, and so you're 0:04:44.800 --> 0:04:48.600 convinced that Eisen is wrong, you said earlier, like you're 0:04:48.640 --> 0:04:50.719 pretty sure he's wrong, or you think he's wrong. I 0:04:50.720 --> 0:04:52.840 think he's got to be wrong. I mean, there's no 0:04:52.920 --> 0:04:56.799 way general relativity is correct. Why not, Well, it flies 0:04:56.839 --> 0:04:59.279 in the face of the nature of the universe as 0:04:59.320 --> 0:05:02.960 we know it. We know that the universe is quantum mechanical. 0:05:03.360 --> 0:05:07.000 We know that nothing is smooth and continuous. But general 0:05:07.040 --> 0:05:10.560 relativity assumes that the universe is smooth, it's continuous, that 0:05:10.600 --> 0:05:13.760 you can like slice up space and time into infinitely 0:05:13.839 --> 0:05:17.440 small pieces, that you can know everything about the configuration 0:05:17.640 --> 0:05:21.200 of particles, for example. It just ignores the fundamental nature 0:05:21.200 --> 0:05:23.200 of the universe that's been revealed to us over the 0:05:23.279 --> 0:05:26.599 last hundred years. And that's why it breaks down. For example, 0:05:26.640 --> 0:05:28.719 we have singularities at the hearts of black holes and 0:05:28.720 --> 0:05:31.599 at the beginning of the universe. Those singularities reflect a 0:05:31.640 --> 0:05:34.920 failure of the theory. So it just can't be right, 0:05:35.000 --> 0:05:37.720 and yet it works, so darn well, well you don't 0:05:37.720 --> 0:05:39.920 think it works. But maybe there is a singularity. I 0:05:39.960 --> 0:05:42.080 don't know, isn't that possible? Well, we talked about this 0:05:42.120 --> 0:05:45.200 in our fun episode about singularities. But singularity is like 0:05:45.200 --> 0:05:48.640 a mathematical oddity. It's like an infinity. It's a failure. 0:05:48.640 --> 0:05:50.360 It's like when the theory is going I don't know, 0:05:50.920 --> 0:05:53.360 you know, it's not a real prediction, Like you can't 0:05:53.440 --> 0:05:58.520 actually have infinite density. It's nonsensical. It's like an infinite universe, 0:05:58.760 --> 0:06:01.240 which I here used to for it as a theory. 0:06:01.520 --> 0:06:04.720 That's true, and it certainly could be that weird mathematical 0:06:04.800 --> 0:06:08.400 features of the universe that we dismiss as artifacts could 0:06:08.440 --> 0:06:10.640 actually be real. Right, It wouldn't be the first time 0:06:10.680 --> 0:06:12.880 that had happened. But it seems to me like a failure. 0:06:12.960 --> 0:06:15.880 And also it seems to me impossible to reconcile general 0:06:15.920 --> 0:06:19.520 relativities view of the universe as smooth and continuous with 0:06:19.600 --> 0:06:22.279 this quantum mechanical nature of the universe. We see that 0:06:22.360 --> 0:06:25.560 it's discreet, we see that there are smallest bits. We 0:06:25.640 --> 0:06:28.400 see that there is limited information. So we're desperate to 0:06:28.440 --> 0:06:31.240 know the true story of the universe, how it actually works. 0:06:31.360 --> 0:06:34.159 But to do that we need to see Einstein's theory fail. 0:06:34.279 --> 0:06:36.560 We need to find a place where it's wrong. Yeah, 0:06:36.600 --> 0:06:38.920 and that's really hard because so far as you said, 0:06:39.000 --> 0:06:42.320 Einstein's theory, it's pretty good. It's past every test with 0:06:42.480 --> 0:06:45.239 flying colors. It's got an A plus plus plus plus 0:06:45.279 --> 0:06:49.520 plus plus. Like nobody's ever seen general relativity get anything wrong. 0:06:49.839 --> 0:06:53.560 No matter what configuration of matter or weird effects you study, 0:06:53.960 --> 0:06:57.600 or crazy intense things going on in the distance universe 0:06:57.640 --> 0:07:02.200 like black holes colliding, general activity gets its spot on. Yeah, 0:07:02.320 --> 0:07:04.280 and so there's a big question of whether or not 0:07:04.360 --> 0:07:08.760 Einstein's theories are ultimately correct or not. And there is 0:07:08.800 --> 0:07:12.120 one experiment right now, right above you will most likely 0:07:12.360 --> 0:07:15.600 trying to figure that out. That's right. We physicist her 0:07:15.680 --> 0:07:19.200 inventing more and more crazy scenarios to try to test 0:07:19.240 --> 0:07:22.720 the details of these predictions of general relativity, hoping to 0:07:22.760 --> 0:07:26.000 get it wrong, hoping to find a scenario where Einstein's 0:07:26.040 --> 0:07:28.880 theory fails and forces us to come up with another theory, 0:07:28.960 --> 0:07:31.000 or like gives us a clue as to how to 0:07:31.160 --> 0:07:33.960 formulate that next theory. So today on the podcast we'll 0:07:34.000 --> 0:07:44.800 be talking about what is frame dragging? I have to say, Daniel, 0:07:44.880 --> 0:07:47.200 it feels like the disappointing title after all that build up. 0:07:47.240 --> 0:07:49.360 I felt like we should have, you know, probing the 0:07:49.400 --> 0:07:52.680 mysteries of the nature of space and time, But no, 0:07:53.040 --> 0:07:55.520 we're going with but what is frame dragging? Well, that's 0:07:55.560 --> 0:07:58.680 because frame dragging is one of the mysteries of space 0:07:58.720 --> 0:08:01.640 and time. It's one of these bizarre effects predicted by 0:08:01.760 --> 0:08:04.280 general relativity that people go out to see, like is 0:08:04.360 --> 0:08:07.560 this actually real or is it just a mathematical artifact 0:08:07.840 --> 0:08:10.320 or was Einstein wrong? Or it could just be that 0:08:10.360 --> 0:08:12.920 you're taking a picture frame and dragging it across the floor. 0:08:13.320 --> 0:08:15.880 It could go either way. Yeah, it doesn't really conjure 0:08:15.960 --> 0:08:18.800 up the gravity of the situation if you ask me. 0:08:18.960 --> 0:08:21.800 But coincidentally does have to do with gravity, right, and 0:08:22.040 --> 0:08:24.600 I signed theory about how it all works. Yeah, and 0:08:24.720 --> 0:08:28.600 reference frames like this idea of where you put your axes, 0:08:28.680 --> 0:08:30.880 your X, Y and z, and how you measure your 0:08:30.920 --> 0:08:35.360 position and your velocity is absolutely fundamentally central to the 0:08:35.400 --> 0:08:38.920 whole concept of relativity, and so you know that gives 0:08:38.920 --> 0:08:40.839 you clues to what it might be about. And I 0:08:40.880 --> 0:08:43.240 think this is a super fun topic and I especially 0:08:43.240 --> 0:08:45.920 hope that it's being enjoyed by one particular listener out 0:08:45.960 --> 0:08:49.240 there from the Netherlands. He wrote to us last week 0:08:49.280 --> 0:08:51.800 and he said that he really liked our podcast, but 0:08:52.320 --> 0:08:54.840 that it had led to more than one occasion in 0:08:54.840 --> 0:08:58.120 which he burned dinner. Oh no, well, out of frustration 0:08:58.240 --> 0:09:01.600 or out of just not paying attention. Apparently he listened 0:09:01.600 --> 0:09:03.680 to our podcast while he's cooking, and when things get 0:09:03.760 --> 0:09:07.040 really complicated or interesting, he ignores what's on the stove 0:09:07.320 --> 0:09:10.600 and things good things go up in flames. Wow, I 0:09:10.600 --> 0:09:13.480 feel like we're destroying this person's family life here, if 0:09:13.520 --> 0:09:16.360 not his actuate home. Yeah. He also said that his 0:09:16.440 --> 0:09:19.520 kids know not to ask him anything or for anything 0:09:19.559 --> 0:09:22.400 when he's listening to the podcast, because he'll just ignore them. 0:09:22.559 --> 0:09:24.839 He or she should invite their kids to listen with 0:09:25.200 --> 0:09:30.400 him her which kid doesn't want to know about frame dragging. Yeah, 0:09:30.480 --> 0:09:32.800 so pay attention to the podcast, learn the secrets of 0:09:32.800 --> 0:09:35.880 the universe, but also don't burn your dinner. Sorry, flipped 0:09:35.880 --> 0:09:39.559 the chicken right now before it gets Yeah, let's pause 0:09:39.720 --> 0:09:41.719 so that he's can finish the dinner. All right, Well, 0:09:41.760 --> 0:09:44.720 this is an interesting question, and so as usual we 0:09:44.720 --> 0:09:47.080 were wondering how many people out there had even heard 0:09:47.080 --> 0:09:50.120 of this question and what it might mean or even 0:09:50.160 --> 0:09:52.679 have an answer. So as usual, Daniel went out there 0:09:52.760 --> 0:09:56.240 and ask people on the internet what is frame dragging? 0:09:56.440 --> 0:09:59.040 So thanks to everybody who was willing to play along. 0:09:59.280 --> 0:10:01.960 And if you have listened to the podcast and chuckle 0:10:02.000 --> 0:10:05.040 along with these answers but never contributed your own, please 0:10:05.320 --> 0:10:08.160 write to me two questions at Daniel and Jorge dot 0:10:08.240 --> 0:10:11.840 com and volunteer. I promise it's fun. Here's what people 0:10:11.880 --> 0:10:14.760 had to say. I'm going to guess that it has 0:10:14.800 --> 0:10:20.600 something to do with photography, maybe photographing of planets in 0:10:20.600 --> 0:10:23.920 a three dimensional space where we can only view them 0:10:23.920 --> 0:10:28.800 in a two dimensional aspect. We take enough pictures of 0:10:28.840 --> 0:10:32.440 the two dimensional aspects to drag them together to create 0:10:32.440 --> 0:10:36.520 a three dimensional picture. Frame dragging is when it's moving 0:10:36.600 --> 0:10:41.280 day and none of your friends show up to help. Um. 0:10:41.800 --> 0:10:47.760 Frame dragging from physics point of view, UM, I don't know. 0:10:48.520 --> 0:10:54.440 I have no idea frame dragging. UM, nothing all right. 0:10:54.920 --> 0:10:57.280 Not a lot of people seem to have a good 0:10:57.320 --> 0:10:59.719 idea here, like the one who said it's moving day 0:10:59.720 --> 0:11:02.720 and none of your friends want to heppy move drag 0:11:02.760 --> 0:11:05.839 your art frames around. Yeah, that's a great one. Should 0:11:05.960 --> 0:11:10.000 ordered more pizza man, sorry, or you know, hired verse 0:11:10.160 --> 0:11:14.000 perhaps so. Yeah, it's a pretty interesting question because it 0:11:14.040 --> 0:11:16.640 doesn't sound physics ee, but I'm guessing it has something 0:11:16.720 --> 0:11:20.240 to do with maybe like frames of reference or coordinate 0:11:20.280 --> 0:11:23.520 systems or something like that. Exactly. It has to do 0:11:23.640 --> 0:11:27.640 with a really bizarre prediction of general relativity. Remember that 0:11:27.720 --> 0:11:33.079 general relativity is Einstein's theory of gravity, replaced Newton's theory. 0:11:33.400 --> 0:11:36.920 Newton says two objects with mass will pull on each other, 0:11:36.960 --> 0:11:39.800 that gravity is a force, but Einstein tells us that 0:11:39.840 --> 0:11:42.600 gravity shouldn't be seen as a force. It's actually just 0:11:42.679 --> 0:11:45.720 due to the fact that space and time curve around 0:11:45.800 --> 0:11:48.800 massive objects. And if you can't see those curves, like 0:11:48.840 --> 0:11:51.800 we can't detect them directly, then things will move in 0:11:51.800 --> 0:11:54.640 a surprising way, and they move as if they were 0:11:54.760 --> 0:11:57.880 under some force. And that's what gravity is. It's the 0:11:57.920 --> 0:12:01.560 effect of the curvature of space time itself. Most of 0:12:01.559 --> 0:12:04.320 the time those two things totally agree, Like you could 0:12:04.320 --> 0:12:06.880 treat gravity as a force like Newton did, or you 0:12:06.880 --> 0:12:09.200 could treat gravity is the mending of space time like 0:12:09.240 --> 0:12:11.880 Einstein does. It doesn't really change the way the Earth 0:12:11.880 --> 0:12:14.600 moves around the Sun, for example. But there are some 0:12:14.679 --> 0:12:18.000 cases where they disagree, and that lets us probe Einstein's 0:12:18.000 --> 0:12:21.040 theory as different from Newton's theory. Really, I thought it 0:12:21.080 --> 0:12:23.800 was sort of like mathematically burned in that it was 0:12:23.840 --> 0:12:26.560 the same thing. But no, there are exceptions. No, they're 0:12:26.600 --> 0:12:30.000 fundamentally different ways of seeing the universe, and they give 0:12:30.040 --> 0:12:33.640 different predictions in some cases, and almost every case they don't, 0:12:33.679 --> 0:12:36.720 which is why Newton's theory worked so well. Right, Newton 0:12:36.840 --> 0:12:39.080 got a lot of stuff right because for the most 0:12:39.120 --> 0:12:41.680 part his theory is correct, and like that's a lesson 0:12:42.160 --> 0:12:45.240 getting a bunch of experiments right. And like nailing predictions 0:12:45.480 --> 0:12:48.199 for hundreds of years in a row doesn't mean that 0:12:48.240 --> 0:12:51.120 your theory is fundamentally true. It doesn't mean that it's 0:12:51.120 --> 0:12:54.880 an actual description of nature. It just means the experimentalists 0:12:54.880 --> 0:12:57.440 having come up with a way to break your idea. Yet. Yeah, 0:12:57.520 --> 0:12:59.560 and I imagine for Einstein it was a little bit 0:12:59.640 --> 0:13:02.480 like it is now for us. With him, and that 0:13:02.600 --> 0:13:05.040 you know, at the time, Newton was like the eyesight 0:13:05.440 --> 0:13:07.560 of his day. And for him to be like I 0:13:07.559 --> 0:13:09.880 think Newton's wrong, people were like, what do you think 0:13:09.920 --> 0:13:12.240 you're smarter than Newton or for sure? And remember that 0:13:12.280 --> 0:13:15.160 Einstein is further in time from Newton than we are 0:13:15.240 --> 0:13:17.880 from Einstein. So I think Newton was probably like an 0:13:17.880 --> 0:13:21.840 even grander, you know, person in the history of science 0:13:21.920 --> 0:13:24.000 due to the passage of time, like his ideas had 0:13:24.000 --> 0:13:27.040 stood longer, and whereas Einstein, like, you know, you can 0:13:27.040 --> 0:13:28.600 see movies of the guy, you know, he's like a 0:13:28.679 --> 0:13:31.679 real person. Well, there are the effects of internet relativity, 0:13:31.760 --> 0:13:35.600 which you know makes time seem go faster, alright, So 0:13:35.640 --> 0:13:39.920 there are instances where Einstein's theory of special relativity is 0:13:39.960 --> 0:13:42.839 different than Newton's, and so we can test whether or 0:13:42.880 --> 0:13:45.480 not the theories are correct exactly. And it really comes 0:13:45.520 --> 0:13:49.440 down to things spinning. Like for Newton, it doesn't really 0:13:49.480 --> 0:13:52.680 matter if the Earth is spinning. It's gravitational pull on 0:13:52.679 --> 0:13:55.400 the Moon is the same. Like for Newton, the only 0:13:55.520 --> 0:13:58.400 thing that gravity depends on are the masses of the 0:13:58.400 --> 0:14:01.280 two objects and their relative stance. If you know Newton's 0:14:01.280 --> 0:14:04.920 equation g mm over our squared. There's no factor in 0:14:04.960 --> 0:14:07.200 there that can be influenced by the fact that the 0:14:07.200 --> 0:14:10.480 Earth is spinning. It's irrelevant because like the configuration of 0:14:10.520 --> 0:14:13.120 the mass doesn't actually change. Right, you have a perfect 0:14:13.120 --> 0:14:16.880 sphere and you spin, it doesn't change the distance between 0:14:16.960 --> 0:14:20.600 any of the objects. But for Einstein's theory it does matter. Right, 0:14:20.640 --> 0:14:22.640 But as long as the I guess the center of 0:14:22.680 --> 0:14:26.080 mass of the Earth is kind of onund the spin access, right. Yeah, 0:14:26.120 --> 0:14:28.720 if you have a perfect sphere and it's spinning around 0:14:28.760 --> 0:14:32.600 its center, then it's gravity is totally unaffected by its spin, 0:14:32.800 --> 0:14:35.920 according to Newton, because the only thing that Newton cares 0:14:35.960 --> 0:14:39.320 about is the relative distance between two little bits of mass, 0:14:39.320 --> 0:14:42.000 and so if that's not changing, then the gravity shouldn't 0:14:42.080 --> 0:14:44.800 change at all, right, and specifically like between the center 0:14:44.840 --> 0:14:47.000 of masses of the two things, Right, that's the only 0:14:47.000 --> 0:14:49.360 thing that counts for Newton. Yeah, for Newton, that's all 0:14:49.360 --> 0:14:52.280 that counts. You can treat the Earth, for example, as 0:14:52.320 --> 0:14:54.960 if it was a point particle with the same mass, 0:14:55.160 --> 0:14:57.600 and you put that point particle at the center of mass, 0:14:57.760 --> 0:14:59.760 and all the other effects of some things being closer 0:14:59.760 --> 0:15:02.320 in some things being further away cancel out which is 0:15:02.320 --> 0:15:04.960 a pretty cool, nice simplification. It makes a lot of 0:15:04.960 --> 0:15:08.560 physics much easier to do. But Einstein's special relativity is 0:15:08.600 --> 0:15:11.520 not the same. Einstein's theory of general relativity says that 0:15:11.640 --> 0:15:16.119 spin does matter, that the way an object spins affects 0:15:16.160 --> 0:15:19.240 the way that it bends space and time, and that 0:15:19.280 --> 0:15:23.200 will change the gravitational effect on objects moving around a 0:15:23.280 --> 0:15:26.320 spinning Earth versus a non spinning Earth, and we can 0:15:26.320 --> 0:15:29.200 do experiments to see if that's correct. Wait, what you 0:15:29.240 --> 0:15:33.520 mean the spinning somehow it changes the way it's bending 0:15:33.520 --> 0:15:36.080 space around it. Yes, even even for a perfect sphere. 0:15:36.200 --> 0:15:39.120 Even for a perfect sphere, what it does is it 0:15:39.400 --> 0:15:42.880 drags the space around it a little bit. It pulls 0:15:42.960 --> 0:15:46.240 the space itself, and that's why they call it frame dragging. 0:15:46.640 --> 0:15:49.440 It's sort of like if you had a ball and 0:15:49.520 --> 0:15:51.400 you dipped it in honey, and then you spun the 0:15:51.400 --> 0:15:53.800 ball a little bit, you would get the honey dragged 0:15:53.800 --> 0:15:56.280 along with the ball, right, be a little bit of friction, 0:15:56.280 --> 0:15:58.640 they would pull it along with it. Einstein says that 0:15:58.680 --> 0:16:00.520 if you have a really big mass of object and 0:16:00.640 --> 0:16:04.520 you spin it, then you drag space itself along with 0:16:04.640 --> 0:16:07.080 the object. So they should have called it like space 0:16:07.160 --> 0:16:09.560 dragging or something, but they call it frame dragging. You 0:16:09.600 --> 0:16:12.040 said it not I it should have called it a 0:16:12.040 --> 0:16:14.240 better name for sure, But what do you mean like 0:16:14.240 --> 0:16:16.960 it drag space? How can you drag space? Long? Like? 0:16:17.000 --> 0:16:18.920 How can you pull on space? Yeah? How can you 0:16:18.960 --> 0:16:21.200 pull on space? Right? Like? Well, what is you in space? 0:16:21.280 --> 0:16:23.160 We don't know? But space can do a bunch of 0:16:23.200 --> 0:16:26.120 weird things, right. It can bend, and it can ripple, 0:16:26.320 --> 0:16:28.680 and it can twist. So what we talk about when 0:16:28.680 --> 0:16:31.720 we say space is curved, really what we mean there. 0:16:31.960 --> 0:16:34.360 It's not that it's like curved like a big sheet 0:16:34.440 --> 0:16:37.200 relatives to some other direction, but that we're changing the 0:16:37.320 --> 0:16:41.200 relative distances between points in space, so that, for example, 0:16:41.360 --> 0:16:43.920 the shortest path from A to B is no longer 0:16:44.200 --> 0:16:46.360 what you would imagine to be a straight line, but 0:16:46.480 --> 0:16:49.040 a different path because the distances between the points along 0:16:49.040 --> 0:16:51.360 the way have been shrunk. So in the same way, 0:16:51.480 --> 0:16:54.680 you can talk about dragging space with you as this 0:16:54.840 --> 0:16:58.720 weird effect and additional sort of curvature of space, Like 0:16:58.760 --> 0:17:02.640 when an object is spinning, it curves space differently around 0:17:02.680 --> 0:17:04.840 it than if it isn't spinning. Does that due to 0:17:04.920 --> 0:17:07.359 the fact that you know, maybe the particles or the 0:17:07.440 --> 0:17:09.920 masses at the surface of the sphere are have some 0:17:10.000 --> 0:17:12.719 kind of velocity, and so there's some sort of you know, 0:17:12.760 --> 0:17:15.520 sort of lagging its effect to the things around it. 0:17:15.680 --> 0:17:19.200 Or how would you explain what what's causing that dragging 0:17:19.240 --> 0:17:24.040 of space. You're right that Newton assumes that gravity is instantaneous. 0:17:24.080 --> 0:17:27.520 Like in Newton's world, if an object disappears, then it's 0:17:27.560 --> 0:17:31.679 gravity disappears instantaneously, even for objects really far away. But 0:17:31.800 --> 0:17:35.400 in Einstein's world, gravity takes time for information to propagate. 0:17:35.480 --> 0:17:38.280 So if the sun disappears, we don't notice that for 0:17:38.359 --> 0:17:40.720 eight minutes in this situation, I don't think that's the 0:17:40.800 --> 0:17:45.040 explanation for frame dragging, because frame jagging exists even in 0:17:45.200 --> 0:17:47.640 a object that's been spinning for like a long long 0:17:47.720 --> 0:17:50.959 time and there's no change, no update, no like information 0:17:51.000 --> 0:17:53.440 needs to propagate, So it can be like a steady 0:17:53.440 --> 0:17:56.600 state situation. It's not like a transient effect. A better 0:17:56.680 --> 0:17:59.840 way to think about it is as the gravitational version 0:18:00.000 --> 0:18:03.960 of electromagnetic induction. If you're familiar with that concept. All right, well, 0:18:04.040 --> 0:18:06.439 let's get a little bit deeper into this frame dragging, 0:18:06.560 --> 0:18:09.399 and most importantly, how could we measure it and potentially 0:18:09.520 --> 0:18:26.080 prove Einstein wrong. But first, let's take a quick break. Alright, 0:18:26.119 --> 0:18:30.000 we're talking about proving Einstein wrong, and there's a bunch 0:18:30.000 --> 0:18:32.040 of people out there trying to do this. Right, there's 0:18:32.080 --> 0:18:36.840 an official government funded experiment trying to prove his theories wrong. Yeah, 0:18:36.840 --> 0:18:40.000 there's lots of ways that we've been testing Einstein's theories. One, 0:18:40.040 --> 0:18:42.240 of course, we're just like looking for black holes. That 0:18:42.280 --> 0:18:44.480 was a prediction of Einstein's theory, which turned out, of 0:18:44.480 --> 0:18:48.440 course to be correct. Another is gravitational waves. People were 0:18:48.480 --> 0:18:51.840 looking to see if space itself would ripple when two 0:18:51.880 --> 0:18:54.800 black holes orbit around each other and then finally gobble 0:18:54.840 --> 0:18:57.040 each other up. And you know, we saw those that's 0:18:57.080 --> 0:18:59.880 pretty awesome. And so all of these things are tests 0:19:00.000 --> 0:19:03.320 of Einstein's relativity. But there's a series of folks developing 0:19:03.359 --> 0:19:06.240 like hyper sensitive tests to look for like these like 0:19:06.359 --> 0:19:10.240 small little deviations because we can't like organize our own 0:19:10.280 --> 0:19:12.880 black hole experiment where were like shoot one black hole 0:19:12.920 --> 0:19:15.560 at another, so we have to do the experiments here 0:19:15.600 --> 0:19:18.440 on Earth. And because gravity is so weak, the effects 0:19:18.480 --> 0:19:21.600 are really really small effects that are like really dramatic 0:19:21.600 --> 0:19:24.440 when black holes are involved, are really not very dramatic 0:19:24.440 --> 0:19:27.600 when ping pong balls are involved. What about black pink bubballs? 0:19:28.240 --> 0:19:30.600 Oh my god, we didn't try that. Hold on a second, 0:19:31.560 --> 0:19:35.359 noble price please. Alright, So one of these effects that 0:19:35.400 --> 0:19:38.119 you're trying to test is called frame dragging, which is 0:19:38.280 --> 0:19:42.080 how a spinning object kind of drag space around at 0:19:42.080 --> 0:19:44.320 the edges. But there's another effect that that has to 0:19:44.320 --> 0:19:46.960 do with gyroscopes, right, Yeah, all these effects can be 0:19:47.000 --> 0:19:49.680 well measured by gyroscopes because what they do, in effect 0:19:49.800 --> 0:19:53.600 is make something spin. Like the Earth has its gravity, 0:19:53.600 --> 0:19:56.760 it's pulling on you, but if it's spinning, it's gravity 0:19:56.800 --> 0:19:59.320 will also give you a little bit of a twist. 0:19:59.720 --> 0:20:02.479 And so we measure these things by using gyroscopes. And 0:20:02.480 --> 0:20:05.200 you're right, there are two different effects that can happen 0:20:05.240 --> 0:20:08.119 to a gyroscope here. One is this frame dragging effect, 0:20:08.200 --> 0:20:12.119 and the other is this really awesome effect, this geodetic effect. 0:20:12.160 --> 0:20:16.080 It's called that lets you measure the curvature of space directly. 0:20:16.320 --> 0:20:19.040 You can like exactly measure whether or not space is 0:20:19.119 --> 0:20:23.600 curved by putting a gyroscope in orbit around a planet. Now, gyroscope, again, 0:20:23.640 --> 0:20:26.240 it's just like a spinning mass, right exactly. You take 0:20:26.280 --> 0:20:28.239 something and you spin it and you try to make 0:20:28.240 --> 0:20:31.080 you really precise so it doesn't wobble, and because of 0:20:31.200 --> 0:20:34.160 conservation of angular momentum, if nothing touches it, it should 0:20:34.240 --> 0:20:37.520 keep spinning. Right, So there are no external forces on 0:20:37.560 --> 0:20:39.800 a spinning object. It should keep spinning the way like 0:20:39.840 --> 0:20:42.200 if you push something in outer space, it should keep 0:20:42.240 --> 0:20:45.800 going forever unless something stops it. Because of angular momentum, 0:20:45.840 --> 0:20:47.920 if you spin something like the Earth, and the Earth 0:20:48.000 --> 0:20:50.720 is a gyroscope, it should keep spinning. And so you 0:20:50.720 --> 0:20:54.000 can measure if there's any force on a gyroscope by 0:20:54.080 --> 0:20:56.959 seeing if the angle of its spin changes or if 0:20:56.960 --> 0:20:59.919 it's spin rate changes, and also like if it starts 0:21:00.000 --> 0:21:03.240 tilting to right m exactly, they called that precession. So 0:21:03.280 --> 0:21:05.200 if you put some force on a gyroscope, you could 0:21:05.200 --> 0:21:07.600 slow it down, or you could change the angle of 0:21:07.640 --> 0:21:09.679 its spin if it tilts a little bit. And so 0:21:09.760 --> 0:21:12.520 that's what these experiments are. The one in particularly called 0:21:12.520 --> 0:21:16.520