WEBVTT - How stable is the Earth's orbit? 0:00:08.480 --> 0:00:10.800 Hey, Daniel, did you see the reason launch at tempt 0:00:10.800 --> 0:00:11.719 by SpaceX. 0:00:12.000 --> 0:00:12.160 Oh? 0:00:12.240 --> 0:00:16.560 Yeah, I did. That massive rocket with so many engines attached. 0:00:16.760 --> 0:00:17.920 Really awesome to watch. 0:00:18.160 --> 0:00:18.560 Yeah, I hear. 0:00:18.640 --> 0:00:21.800 The fireworks were great. It really popped. But the whole 0:00:21.800 --> 0:00:23.320 thing kind of has me worried a little bit. 0:00:23.520 --> 0:00:25.600 You worried the rocket's going to crash into your house? 0:00:26.680 --> 0:00:30.120 A little bit? I mean I live in my house. 0:00:30.120 --> 0:00:32.080 That would be a problem. No, But I guess I'm 0:00:32.080 --> 0:00:34.120 more worried about the effect it has on the Earth 0:00:34.240 --> 0:00:36.599 than all those engines in the rocket also push on 0:00:36.640 --> 0:00:37.000 the Earth. 0:00:37.200 --> 0:00:39.520 Yeah. I guess it's kind of like putting a rocket 0:00:39.520 --> 0:00:41.600 engine on the Earth itself. 0:00:41.320 --> 0:00:44.680 A little bit, right, So we're letting elon Musk steer 0:00:44.720 --> 0:00:45.280 our planet. 0:00:45.479 --> 0:00:47.000 I mean, you can't even steer Twitter. 0:00:48.760 --> 0:00:50.400 It would be pretty cool if a planet had a 0:00:50.440 --> 0:00:52.080 steering wheel. I guess that'd be fun. 0:00:52.400 --> 0:00:55.480 I would probably fall asleep, so maybe I shouldn't be 0:00:55.720 --> 0:00:56.440 driving the Earth. 0:00:57.440 --> 0:00:58.840 It probably flies into the sun. 0:01:14.200 --> 0:01:14.320 Hi. 0:01:14.360 --> 0:01:17.080 I'm Orham, a cartoonists and the creator of PhD comics. 0:01:17.280 --> 0:01:20.319 Hi I'm Daniel. I'm a particle physicist and a professor 0:01:20.360 --> 0:01:23.479 at UC Irvine, and I don't want to fly into 0:01:23.520 --> 0:01:23.880 the Sun. 0:01:24.240 --> 0:01:29.160 What do you want to do into the sun? Drive? Walk, fall, dive? 0:01:29.520 --> 0:01:32.120 I guess I want to look into the Sun. Of 0:01:32.160 --> 0:01:34.360 all the verbs, I think that's the least destructive one. 0:01:35.200 --> 0:01:37.559 I like hearing about the Sun and feeling the Sun. 0:01:37.720 --> 0:01:37.960 I don't know. 0:01:38.000 --> 0:01:39.240 I don't know if I want to look at it. 0:01:39.240 --> 0:01:40.120 It isn't that dangerous. 0:01:40.160 --> 0:01:42.560 I want us to build new scientific eyeballs that let 0:01:42.680 --> 0:01:46.160 us peer into the Sun and understand the chaotic churning 0:01:46.200 --> 0:01:46.760 inside of it. 0:01:47.319 --> 0:01:48.520 You want to peer into the Sun? 0:01:48.640 --> 0:01:51.680 Yeah, exactly, yes, I consider the Sun to be our 0:01:51.720 --> 0:01:52.919 peer in the Solar system. 0:01:53.200 --> 0:01:56.080 I see. Are you saying you're like a sun god? 0:01:57.360 --> 0:01:59.600 No, I'm saying we're ever accused of breaking a law 0:01:59.600 --> 0:02:01.720 of physic that I want a jury of our peers, 0:02:01.760 --> 0:02:03.320 which I guess would include the Sun. 0:02:03.280 --> 0:02:06.200 M and who else? Who else do you consider your 0:02:06.240 --> 0:02:07.320 peers in the cosmos? 0:02:08.280 --> 0:02:11.079 Jupiter is pretty good. Yeah, it carries a lot of weight. 0:02:12.720 --> 0:02:15.799 Yeah, he would be a massive help on the jury. 0:02:15.960 --> 0:02:18.400 But anyways, Welcome to our podcast, Daniel and Jorge Explain 0:02:18.480 --> 0:02:20.840 the Universe, a production of iHeart Radio. 0:02:20.680 --> 0:02:23.200 In which we try to thread the needle of understanding 0:02:23.280 --> 0:02:26.000 the entire universe without pissing it off too much. We 0:02:26.040 --> 0:02:28.200 try to pay attention to what's going on out there 0:02:28.200 --> 0:02:30.480 in the universe, from the tiny little particles to the 0:02:30.600 --> 0:02:33.880 very massive objects swirling around each other, to try to 0:02:33.919 --> 0:02:37.079 deduce the laws that this universe follows as it moves 0:02:37.120 --> 0:02:40.520 forward through time towards its eventual end, whatever that may be. 0:02:40.919 --> 0:02:43.000 And we hope that before that end comes, we can 0:02:43.040 --> 0:02:44.480 figure out how it all works. 0:02:44.680 --> 0:02:47.160 That's right, because it is a massively cool universe, fools, 0:02:47.200 --> 0:02:51.200 amazing and incredible laws and mechanism that seem to make 0:02:51.240 --> 0:02:54.320 the whole thing work like a giant clock, it seems, 0:02:54.800 --> 0:02:58.200 going around and around, taking away till the end of time. 0:02:58.360 --> 0:03:01.240 A clock makes it seem like very organized and stable. 0:03:01.320 --> 0:03:04.440 I see it more like a really complicated Rube Goldberg machine, 0:03:04.480 --> 0:03:06.880 you know, like ball rolls down a wheel and hits 0:03:06.880 --> 0:03:09.440 this lever which makes the cat jump, and then that 0:03:09.520 --> 0:03:12.919 knocks something else over. Sometimes it feels like the mechanisms 0:03:12.960 --> 0:03:16.959 on which our entire existence are based are very precarious. 0:03:17.120 --> 0:03:19.040 Like it knocks a ball, the ball rolls sound a 0:03:19.120 --> 0:03:23.080 ramp and then outcomes humans, and out of those humans, 0:03:23.080 --> 0:03:26.200 one of them bumps into another, and you and I 0:03:26.320 --> 0:03:29.960 are born, and this podcast is born exactly. 0:03:30.000 --> 0:03:31.720 It seems like it could have gone a lot of 0:03:31.760 --> 0:03:34.880 different ways, and in many of those ways we wouldn't 0:03:34.880 --> 0:03:38.880 be here. So in some respects our existence here seems very, 0:03:39.000 --> 0:03:42.240 very fortunate, and I wonder sometimes about the future of 0:03:42.280 --> 0:03:46.920 our existence here. How long these special cozy conditions will continue. 0:03:47.280 --> 0:03:49.480 I know, I feel pretty inevitable. I feel like r 0:03:49.760 --> 0:03:51.000 cham was meant to be. 0:03:51.200 --> 0:03:52.920 You feel like the whole project of the universe was 0:03:52.920 --> 0:03:54.000 to bring you into existence? 0:03:56.560 --> 0:03:59.000 Why not at least my universe now. I don't know 0:03:59.040 --> 0:04:01.720 if my kids feel the same way. Over my spouse. 0:04:03.120 --> 0:04:05.880 I'm an unfortunate byproduct. Sometimes it seems. 0:04:05.640 --> 0:04:08.040 Well one of the joys of understanding the universe is 0:04:08.080 --> 0:04:10.880 being able to predict its future, taking those laws of 0:04:10.920 --> 0:04:13.440 physics that describe what we have seen and also applying 0:04:13.440 --> 0:04:16.280 them to the future, and thinking what's going to happen, 0:04:16.320 --> 0:04:18.800 what's likely to happen in the next one hundred years, 0:04:18.960 --> 0:04:20.760 million years, or billion. 0:04:20.480 --> 0:04:23.080 Years, m or the next hour. I mean, I don't 0:04:23.120 --> 0:04:24.880 know where this conversation is going. 0:04:24.560 --> 0:04:28.240 To be honest, the podcast does seem kind of unpredictable. 0:04:28.440 --> 0:04:30.800 Doesn't seem to matter too much what I write any outline. 0:04:31.160 --> 0:04:32.680 Well, I think that's what happens when you put two 0:04:32.760 --> 0:04:38.080 unstable people and try to create a stable system here. 0:04:38.440 --> 0:04:40.960 But it is kind of an interesting question how precarious 0:04:40.960 --> 0:04:44.080 our existence is and how likely it was that we 0:04:44.200 --> 0:04:47.279 are here in this place talking about the universe. It 0:04:47.320 --> 0:04:49.400 seems like the universe kind of could go either way 0:04:49.440 --> 0:04:50.039 at any moment. 0:04:50.200 --> 0:04:52.760 Mm hmmm. And there's lots of ways that things could 0:04:52.800 --> 0:04:54.800 go south for us. But on the podcast a few 0:04:54.800 --> 0:04:57.320 times we've talked about one in particular, which is the 0:04:57.400 --> 0:05:00.480 requirement that the Earth stay in orbit around the Sun 0:05:00.680 --> 0:05:03.840 at just the right distance to keep water nice and 0:05:03.920 --> 0:05:06.840 toasty on our surface but without bubbling it into steam 0:05:07.040 --> 0:05:08.839 or dropping it into a deep freeze. 0:05:09.080 --> 0:05:12.040 Yeah, the Earth is and what's called the Goldilock zone 0:05:12.480 --> 0:05:14.680 of our solar system, where it's not too hot and 0:05:14.760 --> 0:05:17.200 not too cold, which makes it just right for life 0:05:17.240 --> 0:05:21.919 to flourish on it and for vicious birds, animals, and 0:05:22.560 --> 0:05:26.039 humans which I guess are also animals for them to 0:05:26.240 --> 0:05:26.679 come about. 0:05:26.839 --> 0:05:29.720 So you might wonder how long this Goldilock situation can 0:05:29.760 --> 0:05:32.160 continue before the bears come home and ask for their 0:05:32.200 --> 0:05:33.280 porridge back, so to. 0:05:33.240 --> 0:05:40.440 Be On the podcast, we'll be asking the question, how 0:05:40.480 --> 0:05:44.320 stable is the Earth's orbit? Never thought about the stability 0:05:44.320 --> 0:05:47.120 of our planet's orbit. I guess it seems so predictable 0:05:47.160 --> 0:05:50.719 and regular, right, I mean, nobody questions whether the sun 0:05:50.760 --> 0:05:53.159 will rise in the morning every day. 0:05:53.640 --> 0:05:54.600 We just assume it is. 0:05:55.520 --> 0:05:57.799 It's one of these really fun questions where the answer 0:05:57.880 --> 0:06:01.000 depends a lot on the time frame your imagining. Nobody 0:06:01.000 --> 0:06:03.120 suspects that the Earth will fall out of its orbit 0:06:03.160 --> 0:06:05.880 tomorrow or next year, or in one hundred years, and 0:06:05.960 --> 0:06:07.960 on the kind of time scales the humans are used 0:06:08.000 --> 0:06:10.960 to thinking about. The Solar System is kind of static. 0:06:11.120 --> 0:06:13.360 We imagine it's looked the same way for one hundred years, 0:06:13.400 --> 0:06:16.000 a thousand years, probably a million years. But when you 0:06:16.000 --> 0:06:18.520 look on longer time scales, hundreds of millions of years 0:06:18.640 --> 0:06:21.200 or billions of years, you see the Solar System is 0:06:21.240 --> 0:06:25.159 actually quite chaotic. Planets have been lost, they've changed their orbit, 0:06:25.200 --> 0:06:27.080 they've moved from the outer Solar System to the Inner 0:06:27.080 --> 0:06:30.760 Solar System and back. All sorts of crazy stuff has happened. 0:06:30.839 --> 0:06:33.000 So then you can ask, like, well, how long will 0:06:33.040 --> 0:06:35.080 this phase of our Solar system last? 0:06:35.440 --> 0:06:38.080 Yeah, I guess the Solar system was just a giant 0:06:38.120 --> 0:06:40.840 cloud of dust and gas at someone, right, and then 0:06:40.880 --> 0:06:43.080 the Sun form, and then the planet's form. But even 0:06:43.080 --> 0:06:45.520 after the planet's form, the Solar System kind of had 0:06:45.560 --> 0:06:48.640 to find its groove kind of right, it's rhythm, it's orbits. 0:06:48.880 --> 0:06:51.800 Things will crash into each other a lot before settling 0:06:51.839 --> 0:06:52.520 into planets. 0:06:52.600 --> 0:06:54.400 Right, Yeah, that's exactly right. And you look at the 0:06:54.400 --> 0:06:56.760 surface of anything in the Solar System, like the Moon, 0:06:57.080 --> 0:07:00.520 and you'll see lots of evidence for collisions. Basically, anything 0:07:00.560 --> 0:07:02.799 that's out there is getting smacked into all the time. 0:07:03.080 --> 0:07:05.440 The Earth doesn't have a surface filled with craters because 0:07:05.440 --> 0:07:07.920 we have an atmosphere that mostly burns those things up 0:07:08.160 --> 0:07:10.560 before they hit the ground, but of course sometimes they don't. 0:07:10.640 --> 0:07:14.200 Sixty five million years ago or so, something really big 0:07:14.520 --> 0:07:16.640 hit the Earth, and billions of years before that, the 0:07:16.680 --> 0:07:19.240 Moon was formed in an even more giant collision. 0:07:19.320 --> 0:07:21.800 We've been hit around a lot, and yet we're still here. 0:07:21.840 --> 0:07:23.640 And if we look at Jupiter, for example, there's a 0:07:23.640 --> 0:07:26.600 lot of evidence that Jupiter and Saturn migrated to the 0:07:26.600 --> 0:07:29.560 inner Solar System and then turned around and went back out, 0:07:29.720 --> 0:07:32.600 returning to the depths of the outer Solar System. So 0:07:32.800 --> 0:07:37.040 planetary orbits are not as fixed as you might imagine. 0:07:37.040 --> 0:07:39.720 At least some large time scales. As you were saying, well, 0:07:39.720 --> 0:07:41.600 as usually, we were wondering how many people out there 0:07:41.600 --> 0:07:45.200 had thought about this question, about the stability of our orbit, 0:07:45.280 --> 0:07:48.840 about how steady the Solar system is. So, as usual, 0:07:48.960 --> 0:07:51.000 Daniel went out there into the Internet to ask people 0:07:51.120 --> 0:07:53.040 how stable is the Earth's orbit. 0:07:53.280 --> 0:07:56.160 I'm eternally grateful to everybody who answers these questions. If 0:07:56.200 --> 0:07:58.280 you want to be part of this segment, please don't 0:07:58.280 --> 0:08:01.480 be shy. Just write to me to question at Danielandjorge 0:08:01.640 --> 0:08:02.280 dot com. 0:08:02.320 --> 0:08:04.320 So think about it for a second. How stable do 0:08:04.360 --> 0:08:08.040 you think our orbit is? Here's what people had to say. 0:08:08.600 --> 0:08:11.400 So I would say that the Earth orbit is very 0:08:11.440 --> 0:08:15.960 stable millions or maybe even billions of years. But perhaps 0:08:16.000 --> 0:08:19.240 when the Sun turns into a ridge giant and expands, 0:08:19.360 --> 0:08:21.840 maybe that will change things and throw that we're further 0:08:22.000 --> 0:08:23.000 or closer. 0:08:22.680 --> 0:08:26.200 In Well, I think earth orbit is quite stable, but 0:08:26.280 --> 0:08:29.280 we are slowly drifting away from the Sun because of 0:08:29.320 --> 0:08:32.000 the Moon, and we might get hit by asteroids in 0:08:32.000 --> 0:08:34.600 the future. But otherwise I think the Earth's orbit is stable. 0:08:34.880 --> 0:08:38.400 I don't think the Earth's orbit is stable forever. 0:08:38.800 --> 0:08:41.560 I think it looks pretty stable to us, because the 0:08:41.559 --> 0:08:42.360 time scale of. 0:08:42.600 --> 0:08:44.760 The universe, of the Solar System is pretty long. 0:08:45.040 --> 0:08:47.320 I would say it's like a metastable state, and maybe 0:08:47.440 --> 0:08:50.319 even an asteroid could kick the Earth out of orbit. 0:08:50.760 --> 0:08:53.920 It's more like a castle of cards. Remove one and 0:08:54.080 --> 0:08:55.000 everything falls apart. 0:08:55.480 --> 0:08:57.520 It seems pretty stable to me. 0:08:57.880 --> 0:09:03.040 If Hummans had long enough to you will, so hopefully 0:09:03.080 --> 0:09:04.960 it'll hang in there a bit longer. 0:09:05.280 --> 0:09:08.800 I know from your podcast about when stars collide that 0:09:08.920 --> 0:09:16.400 any object that's accelerating gives off gravitational waves because of 0:09:16.440 --> 0:09:23.400 its acceleration. So fundamentally the orbit is not stable, and 0:09:23.720 --> 0:09:27.679 although it will take a really really long time, eventually 0:09:28.640 --> 0:09:31.680 the Earth's orbit will fall into the Sun. 0:09:32.320 --> 0:09:34.720 I think the Earth's orbit is very stable. I have 0:09:34.840 --> 0:09:37.920 heard about studies that talk about Jupiter moving around in 0:09:37.960 --> 0:09:42.800 the ancient Solar System, and studies of sensitivity of mercury 0:09:42.840 --> 0:09:45.840 and Venus to subtle perturbations. But I just think that 0:09:45.880 --> 0:09:47.240 the Earth's orbit is very stable. 0:09:47.320 --> 0:09:50.319 I think it's stickaying just like you know might expect 0:09:50.360 --> 0:09:53.000 it to, but you know, not going into the Sun 0:09:53.040 --> 0:09:53.760 anytime soon. 0:09:54.040 --> 0:09:58.200 I think the Earth's orbit about the Sun is very stable, 0:09:58.240 --> 0:10:02.320 at least over the timeframes that we're concerned with long 0:10:02.480 --> 0:10:06.360 term millions or billions of years. There might be some 0:10:06.480 --> 0:10:09.760 drift in its position relative to the Sun, just like 0:10:10.360 --> 0:10:14.000 there's some drift of the Moon relative to the Earth 0:10:14.200 --> 0:10:14.840 over time. 0:10:15.320 --> 0:10:18.239 I think it's bruey stable in a human time scale, 0:10:18.720 --> 0:10:23.000 but on the long term I think that either gravity 0:10:23.240 --> 0:10:26.439 or angular momentum will be more revalent. 0:10:27.040 --> 0:10:29.560 All right, it seems like most people think it's kind 0:10:29.559 --> 0:10:31.400 of stable. Only a few dissenters. 0:10:31.559 --> 0:10:33.400 Not a lot of people worried about this out there, 0:10:33.480 --> 0:10:36.439 although maybe they got more worried after they read this question. 0:10:37.160 --> 0:10:38.760 Maybe they should be more worried. 0:10:39.320 --> 0:10:43.560 That's what we're here for, to make people think about 0:10:43.600 --> 0:10:45.400 all the different ways that the universe can kill them. 0:10:45.480 --> 0:10:48.480 Mmm. Maybe we should be selling Earth orbit insurance somehow. 0:10:48.600 --> 0:10:49.120 There you go. 0:10:49.320 --> 0:10:51.319 If the Earth plunges into the Sun, we will pay 0:10:51.400 --> 0:10:54.120 you any arbitrary amount of money. 0:10:54.160 --> 0:10:58.480 A bazillion dollars exactly. Just give us a million dollars 0:10:58.720 --> 0:10:59.080 a year. 0:10:59.120 --> 0:11:01.240 That's right, submit request of this po box. 0:11:01.440 --> 0:11:03.640 But yeah, it's kind of an interesting question. How stable 0:11:03.760 --> 0:11:06.400 is the Earth's orbit? Because I guess we're going around 0:11:06.400 --> 0:11:09.559 the Sun pretty steadily, right, is our orbit? 0:11:09.920 --> 0:11:10.000 Like? 0:11:10.440 --> 0:11:12.680 Do we always go through the same spot in the 0:11:13.040 --> 0:11:16.000 Solar system or is our orbit kind of wobbling? 0:11:16.120 --> 0:11:18.839 Well, our orbit around the Sun is not perfectly circular, right, 0:11:18.880 --> 0:11:22.000 It's an ellipse, and that ellipse can process a little bit, 0:11:22.120 --> 0:11:23.840 which means if you imagine an ellipse or like a 0:11:23.840 --> 0:11:28.319 football or anything oblong, then that orbit itself can rotate. Right, 0:11:28.360 --> 0:11:30.880 the path of the ellipse itself can rotate. 0:11:31.880 --> 0:11:34.000 And is that the same for the whole Solar system? 0:11:34.080 --> 0:11:36.720 Like there, everyone's orbits also kind of rotating. 0:11:36.760 --> 0:11:39.800 There are some changes in the eccentricity of the Earth's 0:11:39.880 --> 0:11:43.520 orbit that's deviation from it being circular over like one 0:11:43.600 --> 0:11:47.120 hundred thousand year timescale, and these things actually can affect 0:11:47.120 --> 0:11:49.960 like the climate. These are called Milankovich cycles. We talked 0:11:49.960 --> 0:11:52.560 about it once in the podcast about ice ages. But 0:11:52.679 --> 0:11:55.640 that doesn't make the Earth's orbit stable or unstable. An 0:11:55.640 --> 0:11:59.240 elliptical orbit can be stable over very very long time periods. 0:12:00.000 --> 0:12:02.679 Whether or not your circular or elliptical doesn't change whether 0:12:02.800 --> 0:12:03.480 or not your stable. 0:12:03.679 --> 0:12:06.480 M I see the orbit is changing a little bit. 0:12:06.520 --> 0:12:08.440 But I think maybe what you mean by stable or 0:12:08.559 --> 0:12:11.520 unstable is whether, like if you move the Earth a 0:12:11.600 --> 0:12:14.240 little bit, is it gonna go back to its same orbit, 0:12:14.360 --> 0:12:16.160 or is it gonna spin out of control and like 0:12:16.520 --> 0:12:19.439 shoot out of the Solar System. That's kind of more 0:12:19.440 --> 0:12:20.120 what you mean, right. 0:12:20.120 --> 0:12:22.960 Yeah, my stability. We mean will it return to its 0:12:22.960 --> 0:12:26.600 current configuration if it's pushed a little bit, Say, for example, 0:12:26.800 --> 0:12:29.920 you jump. Every time you jump, you are pushing on 0:12:30.080 --> 0:12:32.679 the Earth. Right, You're using your leg muscles to push 0:12:32.760 --> 0:12:35.200 yourself away from the Earth, but you're also pushing the 0:12:35.240 --> 0:12:38.320 Earth away from you. And Newton's laws tell us, you know, 0:12:38.360 --> 0:12:41.360 every force is an equal and opposite reaction, and so 0:12:41.480 --> 0:12:43.120 you're moving away from the Earth and the Earth is 0:12:43.160 --> 0:12:45.840 also moving away from you. Now, of course, because the 0:12:45.880 --> 0:12:49.000 Earth has so much mass, your push doesn't really affect 0:12:49.000 --> 0:12:51.640 it as much as it affects yourself. It's sort of 0:12:51.720 --> 0:12:54.040 like when you fire a rifle. The bullet gets going 0:12:54.080 --> 0:12:56.840 really really fast, but the rifle itself also has a 0:12:56.840 --> 0:12:59.120 little bit of recoil, and so when you jump, the 0:12:59.160 --> 0:13:02.839 Earth recoil a little bit against you. And so if 0:13:02.880 --> 0:13:06.120 the Earth's orbit is stable, then a little push like 0:13:06.160 --> 0:13:08.840 that won't like send it spiraling into the Sun, it 0:13:09.040 --> 0:13:11.800 like drift back to its original orbit. If the Earth 0:13:11.880 --> 0:13:15.280 is unstable, then it's more like a pencil balancing on 0:13:15.360 --> 0:13:17.920 its tip. Any tiny little touch will knock it out 0:13:17.920 --> 0:13:21.400 of its configuration and it won't come back. So stability 0:13:21.400 --> 0:13:23.600 tells you about whether you come back to your current 0:13:23.679 --> 0:13:25.559 orbit when you're given a little push. 0:13:25.720 --> 0:13:26.120 Hmmm. 0:13:26.800 --> 0:13:28.959 First of all, it's cool that every time I take 0:13:29.000 --> 0:13:31.520 a step, basically I'm sort of moving to Earth a 0:13:31.559 --> 0:13:34.480 little bit. Right, every step I take is earth shattering, 0:13:34.679 --> 0:13:35.240 Earth moving. 0:13:35.360 --> 0:13:37.520 It sort of is, though. You return to the Earth 0:13:37.640 --> 0:13:40.040 right and the Earth returns to you, So in the end, 0:13:40.080 --> 0:13:43.160 the Earth's orbit isn't actually changed by that. To really 0:13:43.240 --> 0:13:44.880 change the Earth's orbit, you need to like take a 0:13:45.000 --> 0:13:47.240 rock and throw it into outer space and have it 0:13:47.440 --> 0:13:50.280 escape from the Earth. So the rock and the Earth 0:13:50.320 --> 0:13:53.280 are now like parting ways and going in opposite directions. 0:13:53.480 --> 0:13:55.720 M yeah, I guess that's what I meant. It's like, 0:13:55.760 --> 0:13:58.839 if I jump, I'm going to fall back down onto 0:13:58.840 --> 0:14:01.800 the Earth unless I jump super duper high. But I'm 0:14:01.800 --> 0:14:04.240 not that fit, I guess. But if I jump, but 0:14:04.240 --> 0:14:06.120 the Earth pulls me back and then it sort of 0:14:06.160 --> 0:14:09.280 recovers right, Like, as it's pulling me back down into Earth, 0:14:09.640 --> 0:14:12.240 it's also moving a little bit towards me exactly. 0:14:12.320 --> 0:14:14.520 You come back together, and so there's no effective change. 0:14:14.679 --> 0:14:16.640 That's why I was talking about Elon Musk instead of 0:14:16.800 --> 0:14:19.640 you and your ripped thighs jumping off the surface. You know, 0:14:19.640 --> 0:14:22.520 if Elon Musk launches a rocket away from the Earth, 0:14:22.760 --> 0:14:25.560 then it really is giving the Earth a push. Now, 0:14:25.600 --> 0:14:27.720 if that rocket ends up in orbit, then it isn't 0:14:27.760 --> 0:14:30.280 because it's still in the Earth's gravitational system. But if 0:14:30.320 --> 0:14:32.320 he launches a rocket to Mars or a to deep 0:14:32.360 --> 0:14:34.560 space or something like that, so it really leaves the 0:14:34.600 --> 0:14:37.720 earth gravitational system, then it's given the Earth a push. 0:14:37.800 --> 0:14:40.680 And if the Earth was in an unstable situation, like 0:14:40.680 --> 0:14:43.280 a pencil balanced on its tip, then even a tiny 0:14:43.360 --> 0:14:45.000 push would knock it out of orbit. 0:14:45.080 --> 0:14:47.720 Yeah, I guess maybe an analogy is that sort of 0:14:47.760 --> 0:14:51.640 like tossing a coin or like rolling a coin. That's 0:14:51.640 --> 0:14:53.680 a system that's kind of unstable, right, Like if you 0:14:53.720 --> 0:14:55.280 tip the coin just a little bit to the right, 0:14:55.360 --> 0:14:57.600 it's the whole coin is going to veer off to 0:14:57.640 --> 0:14:59.520 the ride a lot. Or if you tip it a 0:14:59.520 --> 0:15:01.240 little bit to the left's going to veer off to 0:15:01.280 --> 0:15:03.600 the left a lot. That's what you mean by sort 0:15:03.600 --> 0:15:06.360 of unstable kind of sitting on the edge of something. 0:15:06.160 --> 0:15:09.440 Mm hmm exactly. Or imagine you have a ball in 0:15:09.520 --> 0:15:12.000 a glass, right, you shake the glass a little bit, 0:15:12.040 --> 0:15:13.720 the ball moves from the bottom of the glass, but 0:15:13.800 --> 0:15:16.400 it comes back to where it was. When it deviates 0:15:16.400 --> 0:15:19.000 from its preferred location, there are forces to push it 0:15:19.080 --> 0:15:20.840 back to where it was. Or if you have the 0:15:20.880 --> 0:15:23.960 situation upside down, like ball balance on the top of 0:15:24.000 --> 0:15:26.720 a hill, for example, if it's precariously balanced there and 0:15:26.800 --> 0:15:28.640 you give it a push, then the forces are going 0:15:28.680 --> 0:15:31.800 to pull it away from that configuration place. So another 0:15:31.800 --> 0:15:34.160 way to think about stability is are there forces that 0:15:34.200 --> 0:15:37.040 are restoring you back to your original location or are 0:15:37.120 --> 0:15:39.600 there forces that are pushing you away. So in the 0:15:39.600 --> 0:15:42.320 stable case, their forces restoring you to where you were, 0:15:42.400 --> 0:15:45.480 and in the unstable case, their forces pushing you away. 0:15:45.880 --> 0:15:47.640 Right, I guess it's kind of what you mean by 0:15:47.680 --> 0:15:50.120 basing a pencil, or like if you take a long 0:15:50.480 --> 0:15:52.680 rod or stick and you try to bous it on 0:15:52.720 --> 0:15:54.680 the palm of your hand, like there is a way 0:15:54.680 --> 0:15:57.160 for you to like move your hand around a lot 0:15:57.360 --> 0:16:00.440 and not have this stick fall over. But that's sort 0:16:00.440 --> 0:16:03.040 of an unstable situation, Like if you deviate a little 0:16:03.040 --> 0:16:05.840 bit from that path, then the stick will fall exactly. 0:16:05.880 --> 0:16:08.400 And in physics we call that equilibrium. Right, there is 0:16:08.440 --> 0:16:10.720 a configuration for the stick to be balanced, for all 0:16:10.760 --> 0:16:12.920 the forces to be equal, and for it to just 0:16:13.000 --> 0:16:15.720 stay there, but it would be unstable. Like a tiny 0:16:15.720 --> 0:16:18.160 fly lands on it pushes it in one direction. Now 0:16:18.200 --> 0:16:20.120 the forces are going to keep it going in that 0:16:20.200 --> 0:16:23.160 direction rather than pushing it back. Whereas if you have 0:16:23.200 --> 0:16:25.160 a ball and a glass and a fly lands on 0:16:25.200 --> 0:16:28.120 it and pushes it a tiny little bit up the glass, 0:16:28.200 --> 0:16:29.880 the glass is going to return it back to the 0:16:29.880 --> 0:16:34.080 equilibrium location. So you can have stable and unstable equilibrium. 0:16:34.160 --> 0:16:36.160 And the difference really is whether you have forces pushing 0:16:36.200 --> 0:16:38.800 you back towards the equilibrium or away. 0:16:38.520 --> 0:16:40.600 From it, right, And so that's what we're talking about 0:16:40.600 --> 0:16:42.520 here for the Earth, I mean, we're going around the 0:16:42.560 --> 0:16:45.560 Sun in a circle or a semicircle sort of a circle, 0:16:46.040 --> 0:16:49.040 and it seems stable, but it could be an unstable orbit, 0:16:49.240 --> 0:16:51.560 meaning like we're going around this path and we just 0:16:51.600 --> 0:16:53.360 got lucky to get into this groove. 0:16:53.440 --> 0:16:55.520 But if we actually sort of step. 0:16:55.280 --> 0:16:58.000 Away from the groove or fall a little bit to 0:16:58.040 --> 0:17:00.280 the one side, then maybe it'll take us into a 0:17:00.280 --> 0:17:02.880 completely different orbit or even away from the Solar System 0:17:03.160 --> 0:17:03.840 or into the Sun. 0:17:03.880 --> 0:17:06.359 I guess yeah, And you might be worried like that 0:17:06.440 --> 0:17:08.480 if you jump too high you're going to push the 0:17:08.520 --> 0:17:10.520 Earth out of orbit, because if you imagine that the 0:17:10.520 --> 0:17:13.000 Earth like DV it's a little bit towards the Sun, 0:17:13.440 --> 0:17:16.040 gravity gets stronger and it pulls on it harder. So 0:17:16.119 --> 0:17:18.159 you might worry that, like if you jump on the 0:17:18.160 --> 0:17:20.320 wrong side of the Earth, you could actually push the 0:17:20.400 --> 0:17:23.240 Earth into the Sun like a fly toppling that balanced 0:17:23.320 --> 0:17:24.119 pole on your hand. 0:17:24.400 --> 0:17:26.800 Although I guess it would depend on which way you jump, 0:17:26.880 --> 0:17:29.600 like you just said, like if I jump in the direct, 0:17:29.680 --> 0:17:31.720 like if I jump off of the North pole, maybe 0:17:31.760 --> 0:17:34.000 I'll just move the orbit up and down a little bit. 0:17:33.920 --> 0:17:36.280 Right, Yeah, exactly. 0:17:36.400 --> 0:17:39.000 Or if I jump sort of like trailing the Earth 0:17:39.359 --> 0:17:42.639 in the direction where a bit behind the Earth, I 0:17:42.640 --> 0:17:44.879 guess then I will give it a little boost. Or 0:17:44.880 --> 0:17:46.879 if I jump in the front, I'll slow down to 0:17:46.920 --> 0:17:47.919 Earth a little bit mm hm. 0:17:48.080 --> 0:17:49.360 Or if you have a friend on the other side 0:17:49.359 --> 0:17:51.400 of the Earth and you time your jumps together, then 0:17:51.440 --> 0:17:54.080 it doesn't matter, right, So really this question is about 0:17:54.359 --> 0:17:56.639 can you do exercise whenever you like, or do you 0:17:56.680 --> 0:17:59.159 need to coordinate it with the rest of humanity. 0:17:58.800 --> 0:17:59.240 That's right? 0:17:59.800 --> 0:18:02.960 Or do we have any friends? All right, So that's 0:18:03.000 --> 0:18:05.840 what stability means for an orbit and for our planet. 0:18:06.040 --> 0:18:09.199 And now let's get into whether or not it is 0:18:09.240 --> 0:18:12.560