WEBVTT - Spring equinox listener questions 0:00:07.960 --> 0:00:11.720 Daniel, it's been like forever. How are things good? 0:00:11.760 --> 0:00:11.959 Good? 0:00:12.000 --> 0:00:14.280 You know, same stuff in my world? Do big updates. 0:00:14.680 --> 0:00:18.040 So you guys didn't like move across the planet again? 0:00:18.640 --> 0:00:21.960 Oh no, we are done with those trans continental moves. 0:00:22.000 --> 0:00:22.960 I hate moving. 0:00:23.320 --> 0:00:25.239 Oh my gosh, I hate moving too, But you know, 0:00:25.280 --> 0:00:27.639 I think what I hate the most about moving is 0:00:27.680 --> 0:00:30.840 needing to like pack everything up and then not only unpacked, 0:00:30.840 --> 0:00:33.000 but then you discover like, oh I need new curtains, 0:00:33.000 --> 0:00:35.000 and like, oh we forgot the plunger, we need to 0:00:35.000 --> 0:00:37.560 get a new one, and like all of that stuff. 0:00:37.600 --> 0:00:40.159 So what if you could move and stay in the 0:00:40.200 --> 0:00:42.520 same house, like lift it up and move it. Would 0:00:42.520 --> 0:00:43.640 you move across the country? 0:00:43.680 --> 0:00:47.360 Then I think that's a billion dollar idea. You shouldn't 0:00:47.360 --> 0:00:49.320 be sharing it on the podcast. You should be starting 0:00:49.320 --> 0:00:49.879 that company. 0:00:50.400 --> 0:00:55.800 Delete delete now. I have no business acumen, so somebody 0:00:55.800 --> 0:00:57.640 else can go ahead and make a billion dollars on that. 0:00:57.680 --> 0:00:58.280 You're welcome. 0:01:14.040 --> 0:01:14.240 Hi. 0:01:14.400 --> 0:01:17.520 I'm Daniel, I'm a particle physicist, a professor at UC Irvine, 0:01:17.560 --> 0:01:19.840 and I've never started a billion dollar company. 0:01:21.480 --> 0:01:25.640 I'm Kelly Wiener Smith. I'm a parasitologist at Race University. 0:01:25.720 --> 0:01:28.440 I also have never started a billion dollar company. But 0:01:28.480 --> 0:01:31.080 I did move my husband across the country something like 0:01:31.360 --> 0:01:34.080 three or four times. But he made me promise we'd 0:01:34.080 --> 0:01:36.280 never move again, which is good because we can't move 0:01:36.319 --> 0:01:36.760 our farm. 0:01:39.400 --> 0:01:41.520 There's something about moving. It's sort of like having kids. 0:01:41.640 --> 0:01:44.760 It's horrible, it's painful. You swear you'll never do it again, 0:01:45.000 --> 0:01:47.400 and then a few years later you sort of forget 0:01:47.400 --> 0:01:49.840 how bad it was, and you're like, actually, that sounds 0:01:49.920 --> 0:01:50.520 kind of fun. 0:01:50.680 --> 0:01:53.160 I don't think my husband ever forgot how bad it was. 0:01:53.440 --> 0:01:55.520 He was always I'd be like, let's move again, and 0:01:55.560 --> 0:01:58.360 he'd always be like, no, don't you remember, And I'd 0:01:58.400 --> 0:02:02.240 be like, no, no, it's fine, fine, fine, But anyway, 0:02:02.240 --> 0:02:04.600 we're done moving and we're done having kids. So there 0:02:04.640 --> 0:02:06.880 you go. Everything about our life is standing still. 0:02:07.600 --> 0:02:09.920 Well, there was a period in our lives when we 0:02:09.960 --> 0:02:13.120 went back and forth from California to Geneva, I think 0:02:13.280 --> 0:02:17.160 ten times over a five or six year period, with 0:02:17.400 --> 0:02:20.320 tiny kids. Oh my gosh, I don't know how our 0:02:20.360 --> 0:02:22.160 sanity or our marriage survived. 0:02:22.400 --> 0:02:24.760 Oh okay, that is way more intense than what I did. 0:02:25.520 --> 0:02:29.040 That's incredible. Yes, I am also amazed that your sanity 0:02:29.080 --> 0:02:31.680 and marriage survived you too. It must be a very 0:02:31.720 --> 0:02:32.440 strong family. 0:02:34.440 --> 0:02:36.400 I think you should be less impressed and more doubting 0:02:36.480 --> 0:02:40.639 our judgment. But anyway, Welcome to the podcast Daniel and 0:02:40.720 --> 0:02:44.799 Jorge Explain the Universe, a production of iHeartRadio in which 0:02:44.840 --> 0:02:47.480 we try to move you to a place of deep 0:02:47.600 --> 0:02:51.200 understanding about the universe. We want to transport your brain 0:02:51.320 --> 0:02:55.040 to that mysterious location where everything makes sense. We're it 0:02:55.080 --> 0:02:57.600 all clicked together in your mind to give you a 0:02:57.600 --> 0:03:01.360 harmonious understanding of the deep knee of the universe, at 0:03:01.440 --> 0:03:03.760 least as far as we understand it. 0:03:04.040 --> 0:03:07.480 Right, or to give you a headache wondering wondering how 0:03:07.560 --> 0:03:08.280 this all works. 0:03:10.040 --> 0:03:12.520 Sometimes no pain, no gain, right, Kelly. That doesn't just 0:03:12.560 --> 0:03:16.000 apply to lifting weights. It also applies to understanding the universe. 0:03:16.400 --> 0:03:19.040 Yeah no. And there's a lot of pain in physics. 0:03:20.600 --> 0:03:22.560 And we want to help you with that pain. So 0:03:22.639 --> 0:03:24.880 if you are thinking about things and they don't quite 0:03:24.919 --> 0:03:27.280 click together in your mind, or if you have a 0:03:27.280 --> 0:03:30.200 physics question and you've tried googling it but haven't found 0:03:30.280 --> 0:03:32.800 any answers, we want to help you out. This is 0:03:32.840 --> 0:03:35.360 not just a one direction a lecture from us to you. 0:03:35.640 --> 0:03:38.480 We want this to be a conversation and we miss 0:03:38.480 --> 0:03:41.240 hearing from you, so please write to us two questions 0:03:41.240 --> 0:03:45.280 at Daniel iinhorge dot com. You'll always get an answer back. 0:03:45.880 --> 0:03:48.120 And on today's podcast, we're going to be doing just that, 0:03:48.360 --> 0:03:52.320 answering questions from a listener. So today on the podcast, 0:03:52.360 --> 0:04:02.960 we'll be answering listener questions. Bring Equinox edition. We thought 0:04:02.960 --> 0:04:05.240 it was time to come back and fill your ears 0:04:05.240 --> 0:04:07.600 with answers to physics questions. 0:04:07.160 --> 0:04:09.520 About the universe because missing you. 0:04:10.280 --> 0:04:13.360 And we hope you've been missing us. And today we 0:04:13.400 --> 0:04:17.359 have a really fun question about transportation or about moving, 0:04:17.600 --> 0:04:20.240 not just moving yourself, not just moving your house and family, 0:04:20.560 --> 0:04:24.080 but moving the entire solar system. So here's a great 0:04:24.160 --> 0:04:27.200 question from John in Kansas. 0:04:27.240 --> 0:04:30.680 Hello, Daniel, this is John and I listened to your 0:04:30.680 --> 0:04:35.440 show from south central Kansas near the Oklahoma border, and 0:04:35.520 --> 0:04:40.599 I love it. Anyway, my question is I've heard you 0:04:40.640 --> 0:04:45.200 discussed many times that occasionally stars get ejected from their systems, 0:04:46.000 --> 0:04:49.480 perhaps due to the pull of a passing star, and 0:04:49.560 --> 0:04:53.360 I remember you once even speculated that we ourselves may 0:04:53.400 --> 0:04:56.800 have started out as a binary system and our son's 0:04:57.440 --> 0:05:01.680 own twin brother got ejected ago. But my question is 0:05:01.720 --> 0:05:05.920 this Suppose this did happen and our Sun did get 0:05:05.960 --> 0:05:10.240 flung out of our galaxy. Would it be violently ripped 0:05:10.240 --> 0:05:14.120 away from its own planets? Or would the event be 0:05:14.200 --> 0:05:20.120 so gradual that we wouldn't even notice it? And if 0:05:20.120 --> 0:05:25.600 that happened, would be be towed with it along with 0:05:25.640 --> 0:05:31.039 the other planets, asteroids, the asteroid belt, the Kuiper Belt, 0:05:31.080 --> 0:05:36.719 the Oort Cloud, and all of the celestial bodies, all 0:05:36.760 --> 0:05:41.919 remaining nicely tucked away in their own orbits as we 0:05:42.080 --> 0:05:45.799 follow the Sun into oblivion. Thank you for answering. 0:05:47.240 --> 0:05:53.599 Oh fantastic. Another question that inspires existential dread what would 0:05:53.640 --> 0:05:56.720 happen if the Sun would would it rip apart our 0:05:56.720 --> 0:05:59.800 solar system? Or would our planets go with it? And anyway, 0:05:59.839 --> 0:06:02.960 it's okay, I don't need to sleep, so let's go 0:06:03.000 --> 0:06:06.280 ahead and dig right in, Daniel, how stable is our 0:06:06.320 --> 0:06:07.120 solar system? 0:06:07.920 --> 0:06:10.640 Yeah, this is a really fun question thinking about what 0:06:10.760 --> 0:06:13.480 might happen if our Sun got ejected from the galaxy. 0:06:13.880 --> 0:06:16.240 And you're right. The first part of the question is understanding, 0:06:16.320 --> 0:06:19.440 like how well are we latched onto the Sun? If 0:06:19.440 --> 0:06:22.080 the Sun gets thrown out somewhere, how likely are we 0:06:22.320 --> 0:06:24.440 to go along? For the ride, and this depends on 0:06:24.520 --> 0:06:28.400 the stability of the whole Sun Earth system, right, So 0:06:28.920 --> 0:06:32.320 good news is that mostly things are stable, Like the 0:06:32.360 --> 0:06:35.240 Earth is orbiting the Sun, and even if the Earth 0:06:35.279 --> 0:06:37.520 got like a little bit of a push, it would 0:06:37.560 --> 0:06:40.200 slide right back into its orbit. That's what we usually 0:06:40.240 --> 0:06:42.960 mean by stable. You know, if you have, for example, 0:06:43.080 --> 0:06:45.840 like a ball inside a cup and you push it 0:06:45.880 --> 0:06:47.880 a little bit, it's gonna roll right back down to 0:06:47.920 --> 0:06:50.719 the bottom. Whereas if you have like the ball sitting 0:06:50.720 --> 0:06:52.839 on top of another ball, or on top of a rock, 0:06:52.960 --> 0:06:54.520 or on top of a hill or something, and you 0:06:54.560 --> 0:06:56.600 give it a push, it's gonna roll away and not 0:06:56.720 --> 0:07:00.160 come back. That's an unstable configuration. So we call the 0:07:00.200 --> 0:07:03.280 Earth's orbit stable because it's pretty resistant to these kinds 0:07:03.279 --> 0:07:03.839 of pushes. 0:07:04.520 --> 0:07:07.839 So even though it's resistant to a kind of push, 0:07:08.240 --> 0:07:11.640 anything that could push Earth away from the Sun would 0:07:11.680 --> 0:07:12.720 have to be catastrophic. 0:07:12.800 --> 0:07:13.000 Right. 0:07:13.800 --> 0:07:16.160 Well, there's lots of little pushes that the Earth could survive, 0:07:16.200 --> 0:07:18.600 and the Earth is getting tugged on and pushed in 0:07:18.640 --> 0:07:21.120 lots of different ways. So the Earth's orbit would be 0:07:21.160 --> 0:07:23.840 perfectly stable if it was just the Earth and the 0:07:23.880 --> 0:07:27.680 Sun in totally empty space with nothing happening in classical mechanics, 0:07:27.760 --> 0:07:29.840 that could go forever. But you know, the situation is 0:07:29.840 --> 0:07:32.760 a little bit more complex. For example, like the Sun 0:07:32.960 --> 0:07:35.200 is pushing on the Earth. It's not just pulling on it. 0:07:35.480 --> 0:07:38.520 The radiation from the Sun, the wind, and the photons 0:07:38.560 --> 0:07:41.600 are actually applying a momentum pushing the Earth away from 0:07:41.600 --> 0:07:44.480 the Sun. But the Earth's orbit is stable enough that 0:07:44.560 --> 0:07:46.960 it can overcome that. It's like accommodates that. 0:07:47.360 --> 0:07:52.120 So I've read proposals. I don't know how serious any 0:07:52.160 --> 0:07:54.560 of them were, but like to deal with climate change 0:07:54.600 --> 0:07:57.640 by like putting like a big screen out that would 0:07:57.640 --> 0:08:00.400 block some of the photons from hitting the Earth. If 0:08:00.480 --> 0:08:05.160 you blocked enough photons, could the Earth move closer to 0:08:05.160 --> 0:08:07.680 the Sun because we're not getting pushed back and like 0:08:07.720 --> 0:08:09.280 not much. I know you said it's a small effect, 0:08:09.280 --> 0:08:11.560 but when we move like a couple feet closer if 0:08:11.560 --> 0:08:15.040 you blocked enough photons, well. 0:08:14.840 --> 0:08:17.280 That depends a little bit on where you put that shield. 0:08:17.400 --> 0:08:19.920 Like if it's connected to the Earth, then it's basically 0:08:19.960 --> 0:08:22.080 just part of the Earth and it doesn't change how 0:08:22.080 --> 0:08:25.880 we're getting pushed. If it's somehow floating separated from the 0:08:25.880 --> 0:08:29.880 Earth and absorbing that momentum itself by like firing rockets 0:08:29.960 --> 0:08:32.960 or something. Then yeah, that would relieve a little bit 0:08:32.960 --> 0:08:34.600 of the pressure on the Earth. But this is really 0:08:34.640 --> 0:08:38.000 a tiny, tiny effect on the Earth's orbit. Much more 0:08:38.040 --> 0:08:41.680 substantial are tugs by like Jupiter and Saturn, because the 0:08:41.720 --> 0:08:43.760 Solar System is not just the Earth and the Sun. 0:08:43.840 --> 0:08:46.440 There are other big players out there, and Jupiter is 0:08:46.600 --> 0:08:49.200 much more massive than the Earth. So if you want 0:08:49.240 --> 0:08:51.840 to model the Earth's orbit and its stability really accurately, 0:08:52.040 --> 0:08:53.920 you got to think about what the big boys do 0:08:54.160 --> 0:08:56.320 as they move around the Solar System, and they're constantly 0:08:56.320 --> 0:08:59.280 tugging on the Earth giving it little nudges here and there, 0:08:59.520 --> 0:09:02.600 and that the Earth is pretty stable towards like the 0:09:02.640 --> 0:09:05.720 Earth can tolerate a push from Jupiter, push from Saturn 0:09:05.840 --> 0:09:07.800 and then slide right back into its orbit. 0:09:08.240 --> 0:09:11.560 Okay, And so does the answer to this question then 0:09:11.600 --> 0:09:14.400 depend on how close does Jupiter need to be to 0:09:14.480 --> 0:09:15.679 Earth when this happens. 0:09:16.320 --> 0:09:19.000 Yeah, so Jupiter and Saturn are basically irrelevant to this question, 0:09:19.120 --> 0:09:22.000 is the good news. The bad news is that there 0:09:22.040 --> 0:09:24.720 are other things that can also perturb the Earth's orbit, 0:09:25.120 --> 0:09:27.679 And the biggest, number one thing to worry about are 0:09:27.760 --> 0:09:31.559 other stars because where the Sun is in the galaxy 0:09:31.880 --> 0:09:34.560 is not fixed relative to the other stars. Like all 0:09:34.640 --> 0:09:37.280 the stars in the galaxy are rotating around the center 0:09:37.320 --> 0:09:40.719 of the galaxy, but they're not all rotating together, so 0:09:40.760 --> 0:09:44.360 our distance to other stars changes as time goes on. 0:09:44.840 --> 0:09:47.239 So even if we don't get ejected from the galaxy, 0:09:47.480 --> 0:09:50.800 there is a danger that sometime in the future, another 0:09:50.960 --> 0:09:53.640 star will come close to us and that could perturb 0:09:53.720 --> 0:09:56.840 the Earth's orbit. It could provide enough of a gravitational 0:09:56.920 --> 0:09:59.719 nudge to knock us out of our orbit, or even 0:09:59.760 --> 0:10:02.600 a doesn't, it could disturb all the frozen objects out 0:10:02.640 --> 0:10:04.800 in the deep Solar System and rain down a bunch 0:10:04.840 --> 0:10:07.000 of comments on us, both of which would be bad. 0:10:07.760 --> 0:10:09.360 I know that doesn't sound like a lot of fun, 0:10:09.400 --> 0:10:12.200 but it might actually be spectacular. Well, dig into what 0:10:12.240 --> 0:10:28.240 it means just after this short break. Okay, we're back, 0:10:28.280 --> 0:10:30.880 and we're talking about what might happen if our star 0:10:31.160 --> 0:10:35.320 is ejected from the galaxy and whether it's likely. 0:10:35.800 --> 0:10:38.600 Do we think this could happen? Probably not in our lifetimes. 0:10:38.200 --> 0:10:42.720 Right, probably not in our lifetimes. But we do understand 0:10:43.160 --> 0:10:46.840 the Sun's path through the galaxy pretty well. It's actually 0:10:46.880 --> 0:10:49.920 pretty awesome to think about it, because you imagine space, 0:10:49.960 --> 0:10:53.080 you probably think about the Sun primarily as the center 0:10:53.360 --> 0:10:56.719 of our galactic coordinates, right, everything else is relative to that. 0:10:57.040 --> 0:10:59.760 But you know, the Sun is in motion relative to 0:10:59.800 --> 0:11:02.679 this center of the galaxy. And this is sort of 0:11:02.679 --> 0:11:06.720 a big conceptual step because remember that all motion is relative. 0:11:07.080 --> 0:11:08.960 So some people say, oh, you know, the Sun is 0:11:09.000 --> 0:11:12.079 moving through space, but everything is moving through space, it's 0:11:12.120 --> 0:11:14.720 just relative to what. So when you talk about like 0:11:14.760 --> 0:11:17.040 the earth velocity is relative to the Sun, you talk 0:11:17.040 --> 0:11:20.360 about the Sun's velocity is relative to the center of 0:11:20.400 --> 0:11:23.640 the galaxy. And the Sun, like everything else, is swirling 0:11:23.640 --> 0:11:25.800 around the center, and it takes about two hundred and 0:11:25.800 --> 0:11:30.440 fifty million years to orbit. It's like a really huge 0:11:30.480 --> 0:11:31.160 amount of time. 0:11:31.240 --> 0:11:34.800 But that's happened a number of times since the planet started, 0:11:34.960 --> 0:11:37.920 like many times since the planet started, So it's moving. 0:11:38.600 --> 0:11:39.880 I don't know, that's kind of impressive. 0:11:39.880 --> 0:11:42.040 I think, yeah, Well, the Earth is like four and 0:11:42.080 --> 0:11:45.040 a half billion years old, which means in terms of 0:11:45.200 --> 0:11:48.240 galactic spins, right, how long it takes the Milky Way 0:11:48.280 --> 0:11:50.640 to cycle, which in many ways is like a very 0:11:50.840 --> 0:11:53.200 natural unit. You could call it like a galactic year. 0:11:53.600 --> 0:11:56.040 Instead of measuring time in terms of how many times 0:11:56.040 --> 0:11:57.839 the Earth goes around the Sun, measure in terms of 0:11:57.880 --> 0:12:00.600 how many times the Sun goes around the galaxy. And 0:12:00.679 --> 0:12:03.720 so that makes Earth like twenty galactic years old. Earth 0:12:03.800 --> 0:12:06.880 is just grown up. It's like entering its adult phase. 0:12:07.360 --> 0:12:08.920 It can't even drink yet. 0:12:11.000 --> 0:12:13.640 That's right. So, yeah, the Earth is kind of young 0:12:13.679 --> 0:12:16.400 and sprightly. Right, it's still probably the fittest it's ever 0:12:16.440 --> 0:12:16.800 gonna be. 0:12:17.280 --> 0:12:19.720 Oh oh man, wait till you hit your thirties. 0:12:19.760 --> 0:12:20.040 Earth. 0:12:20.240 --> 0:12:21.760 It's all downhill after that. 0:12:23.400 --> 0:12:25.400 But the other thing is that the Sun doesn't just 0:12:25.600 --> 0:12:28.400 orbit around the center of the galaxy. It also wiggles. 0:12:28.880 --> 0:12:31.680 It's above the galactic plane sometimes, and then it zooms 0:12:31.720 --> 0:12:34.400 down through the galactic plane and then past it, and 0:12:34.440 --> 0:12:36.839 then the gravity of the galactic plane pulls it back. 0:12:37.160 --> 0:12:40.840 So it's like oscillating up and down above the galactic plane. 0:12:41.000 --> 0:12:43.240 So it's not just going in a circle around the 0:12:43.240 --> 0:12:46.480 center of the galaxy. It's more like a zigzag up 0:12:46.520 --> 0:12:48.400 and down as it circles around. 0:12:48.679 --> 0:12:50.960 All right, So now I'm picturing my son when we 0:12:51.040 --> 0:12:53.320 walk around the track together. He's like jumping up and 0:12:53.360 --> 0:12:55.640 down the whole time that we're doing. Yes, So this 0:12:55.760 --> 0:12:58.440 young Earth is going up and down while it's making 0:12:58.480 --> 0:12:59.400 its laps. 0:13:00.040 --> 0:13:03.920 Exactly, and that cycle takes about thirty million years. So 0:13:04.120 --> 0:13:06.640 as we go around the galaxy, we go up and 0:13:06.679 --> 0:13:10.720 down like eightish times every galactic year, and that's different 0:13:10.760 --> 0:13:13.720 for different stars. And so now imagine this whole galaxy. 0:13:13.760 --> 0:13:17.080 It's a chaotic swarm of all these stars moving closer 0:13:17.120 --> 0:13:19.880 and farther away from each other. There's a real possibility, 0:13:20.120 --> 0:13:22.640 of course, over millions and billions of years, that we 0:13:22.720 --> 0:13:26.000 come pretty close to another star. We've actually predicted that 0:13:26.080 --> 0:13:28.160 there is going to be a close approach by the 0:13:28.200 --> 0:13:31.959 star Glease seven to ten in a few million years. 0:13:32.360 --> 0:13:35.760 Oh that's how close, Daniel, How close? 0:13:37.280 --> 0:13:38.800 It's not going to be that close. I mean it 0:13:38.840 --> 0:13:42.120 depends on the units. In one point three million years, 0:13:42.240 --> 0:13:46.720 it's going to pass within zero point one seven light years, 0:13:46.800 --> 0:13:49.360 so like a seventh of a light year. That doesn't 0:13:49.400 --> 0:13:52.240 sound very far, but it's like a twenty fifth of 0:13:52.280 --> 0:13:55.280 the distance to the nearest star. So it's going to 0:13:55.320 --> 0:13:57.640 mean that the closest star to Earth is a lot 0:13:57.800 --> 0:14:01.000 closer than it is currently, but it's still pretty far away. 0:14:01.400 --> 0:14:05.320 It's like ten thousand astronomical units ten thousand times the 0:14:05.360 --> 0:14:07.880 distance from the Sun to the Earth. So it's not 0:14:07.920 --> 0:14:10.199 like gonna appear in our sky as bright as the 0:14:10.240 --> 0:14:12.760 Sun or anything. It's just going to be something moving 0:14:12.840 --> 0:14:13.679 in the night sky. 0:14:13.880 --> 0:14:15.920 Will it still be brighter than the other stars. 0:14:16.240 --> 0:14:18.520 It'll be brighter than the other stars. Yeah, it'll be 0:14:18.640 --> 0:14:21.720 very visible. But you know, in one point three million years, 0:14:21.840 --> 0:14:24.680 so your super great grandkids have this to look forward to. 0:14:25.160 --> 0:14:28.120 Yeah, yeah, I guess I'm gonna miss it. Oh well, 0:14:28.600 --> 0:14:29.560 this is important. 0:14:29.240 --> 0:14:31.920 To answer John's question because this is how stars get 0:14:32.000 --> 0:14:35.160 thrown out of the galaxy. Like just left alone. The 0:14:35.240 --> 0:14:37.520 Sun's orbit is pretty stable, it's just going to keep 0:14:37.520 --> 0:14:40.280 going around the center of the galaxy. But the same 0:14:40.280 --> 0:14:43.200 way that, like Earth is nudged by Jupiter and Saturn, 0:14:43.400 --> 0:14:45.800 the Sun can be nudged by other stars, and so 0:14:45.840 --> 0:14:48.880 a close approach with another star could end up doing 0:14:48.880 --> 0:14:52.600 a gravitational slingshot on our star, so it gets sent 0:14:52.720 --> 0:14:53.720 out of the galaxy. 0:14:54.000 --> 0:14:56.320 Obviously, if you live on Earth, whether Earth stays put 0:14:56.440 --> 0:15:00.000 or not, you're dead without the Sun and the light 0:15:00.040 --> 0:15:03.240 that it provides. But what kind of factors would determine 0:15:03.240 --> 0:15:06.320 if Earth stays put or not? Would it depend on 0:15:06.360 --> 0:15:09.600 how fast the Sun moves, or if the Sun came 0:15:09.720 --> 0:15:12.720 close to us on its way out, Yeah, what would 0:15:12.720 --> 0:15:13.520 we have to worry about. 0:15:14.160 --> 0:15:18.240 It's basically all proximity. Like if that star comes by 0:15:18.280 --> 0:15:20.640 and it's not super close, and it just like gives 0:15:20.680 --> 0:15:24.119 our Sun a new direction. Even if that direction eventually 0:15:24.120 --> 0:15:26.520 takes us out of the Milky Way, we'll be fine 0:15:26.600 --> 0:15:29.800 because if it's gradual, then the Earth's orbit can respond 0:15:29.840 --> 0:15:32.200 to these things, respond to little nudges. It's just like 0:15:32.440 --> 0:15:35.840 another Jupiter effect or another Saturn effect, and it'll follow 0:15:35.880 --> 0:15:38.600 the Sun as it takes its new trajectory. But if 0:15:38.600 --> 0:15:41.560 it's dramatic enough so that like the Sun gets accelerated 0:15:41.600 --> 0:15:45.720 significantly and new direction comes on quickly, then the Earth's 0:15:45.800 --> 0:15:48.920 orbit can't adapt. Because the Earth's orbit is pretty stable, 0:15:48.960 --> 0:15:51.040 but it's not infinitely stable. If you gave it a 0:15:51.080 --> 0:15:54.400 really big kick relative to the Sun, or equivalently, you 0:15:54.480 --> 0:15:56.440 give the Sun a really big kick, the two are 0:15:56.480 --> 0:15:59.000 the same, then the Earth will not be able to 0:15:59.000 --> 0:16:02.400 follow the Sun. And so if for example, another star 0:16:02.560 --> 0:16:05.440 comes very close to our Solar system, so the Sun 0:16:05.480 --> 0:16:08.360 feels a very strong gravitational pull, the kind of thing 0:16:08.400 --> 0:16:11.760 that can and does kick stars out of our galaxy, 0:16:12.080 --> 0:16:14.720 then the Earth has almost no chance of following. Oh Man. 0:16:15.240 --> 0:16:18.200 So, in the scenario where something is big enough to 0:16:18.200 --> 0:16:21.480 move the Sun, but the Sun is moving slowly, when 0:16:21.520 --> 0:16:24.640 the Earth reached the part of its path around the 0:16:24.640 --> 0:16:26.720 Sun where it was between the Sun and this other 0:16:26.800 --> 0:16:29.160 sun that was big enough and close enough to move 0:16:29.240 --> 0:16:34.960 the Sun, would that push Earth towards the other gigantic 0:16:35.600 --> 0:16:38.400 sun object then we would go back. And so would 0:16:38.400 --> 0:16:40.840 that be like a wobble in our orbit or would 0:16:40.880 --> 0:16:42.880 we get pulled out to that other Sun. 0:16:43.200 --> 0:16:46.080 Yeah, well, you're talking about a three body problem, and 0:16:46.120 --> 0:16:47.960 this is known to be very chaotic. 0:16:48.480 --> 0:16:48.640 Right. 0:16:48.640 --> 0:16:50.960 If you have two stars and a planet, then it's 0:16:51.040 --> 0:16:53.320 very difficult for that planet to find a stable orbit. 0:16:53.440 --> 0:16:55.760 And if that system is changing because one star is 0:16:55.800 --> 0:16:59.160 like flying by the other one, then it's essentially impossible. 0:16:59.760 --> 0:17:03.120 So the details depend on exactly the angle and exactly 0:17:03.200 --> 0:17:06.360 the velocity. That's what we mean by chaos and physics. 0:17:06.400 --> 0:17:09.400 We mean that a very small change in the situation 0:17:09.520 --> 0:17:12.120 can result in a very big change in the outcome. 0:17:12.760 --> 0:17:14.400 Like if you're playing pool and you hit one ball 0:17:14.440 --> 0:17:16.760 against the other, a very small change in how you're 0:17:16.800 --> 0:17:18.600 hitting the cue ball can mean you win the game 0:17:18.680 --> 0:17:21.480 or lose the game. Right, So in this scenario, a 0:17:21.640 --> 0:17:24.080 very small change in the direction of that star, or 0:17:24.119 --> 0:17:26.199 the mass of that star, or the velocity of that 0:17:26.280 --> 0:17:29.399 star could result in a completely different outcome. Some like 0:17:29.520 --> 0:17:31.680 you and vision like, oh, we wobble towards the star 0:17:31.720 --> 0:17:34.280 and then we wabble away from it, and others where 0:17:34.280 --> 0:17:36.760 we just got we just get ejected into deep space 0:17:37.080 --> 0:17:40.159 on our own. So I think if the star comes 0:17:40.320 --> 0:17:43.680 close enough to eject our Sun from the Milky Way, 0:17:43.800 --> 0:17:46.360 it's going to also come close enough to perturb our 0:17:46.520 --> 0:17:49.240 orbit around that Sun. It's going to be very unlikely 0:17:49.320 --> 0:17:51.080 we are along for the ride. But you know, there's 0:17:51.080 --> 0:17:52.520 a possible bright outcome there. 0:17:52.760 --> 0:17:53.080 What's that. 0:17:54.119 --> 0:17:56.240 It might be that this new star comes along, messes 0:17:56.359 --> 0:17:59.280 up our happy orbit around the Sun, ejects the Sun 0:17:59.280 --> 0:18:02.159 from the Milky Way, and then steals the Earth. It 0:18:02.240 --> 0:18:03.720 might be that we get a new Sun. 0:18:03.960 --> 0:18:07.600 But like, that's got to be an extinction level event. 0:18:07.840 --> 0:18:10.639 Even if it works out like a you know, on 0:18:10.720 --> 0:18:14.600 par with taking out the dinosaurs, that couldn't work smooth. 0:18:14.640 --> 0:18:16.480 That wouldn't be good for us. I don't want my 0:18:16.560 --> 0:18:17.600 kids to experience that. 0:18:18.520 --> 0:18:21.560 You know I'm reaching for a sliver of positivity here Elly, 0:18:21.920 --> 0:18:23.760 in very dark times. I need you to work with me, 0:18:23.920 --> 0:18:24.399 work with me. 0:18:25.119 --> 0:18:25.280 You know. 0:18:25.359 --> 0:18:27.240 A friend asked me the other day why I'm so 0:18:27.440 --> 0:18:31.919 relentlessly depressing. So I think you just you picked the 0:18:31.960 --> 0:18:35.360 wrong person to have on your show. I'm sorry. 0:18:35.720 --> 0:18:37.520 Well, you know, if we knew about it far enough 0:18:37.560 --> 0:18:40.480 in advance, and we could build bunkers to survive the 0:18:40.560 --> 0:18:43.359 intervening period where things very bright or very cold, the 0:18:43.400 --> 0:18:46.960 seasons are totally wacko. Then there's a situation where in 0:18:46.960 --> 0:18:49.280 the far future the Earth is in the habitable zone 0:18:49.440 --> 0:18:52.600 of another star, which I think would be an amazing 0:18:52.640 --> 0:18:54.800 premise for a science fiction novel. And I haven't read 0:18:54.840 --> 0:18:57.040 it yet, and I want somebody out there to put 0:18:57.080 --> 0:18:59.800 pen to paper and write me that story and make 0:18:59.800 --> 0:19:01.080 it happy ending for Kelly. 0:19:01.720 --> 0:19:07.439 And that's your billion dollar idea. There we go. We 0:19:07.600 --> 0:19:08.880 just keep throwing them out there. 0:19:09.960 --> 0:19:14.480 That's basically the next Harry Potter, I'm sure. Yeah, Harry 0:19:14.480 --> 0:19:16.480 Potter and the Adventure of the Alternate Earth. 0:19:17.280 --> 0:19:17.920 There you go. 0:19:19.119 --> 0:19:21.320 All right, Well, thank you very much, John for thinking 0:19:21.400 --> 0:19:23.399 about the nature of the universe and how it affects 0:19:23.480 --> 0:19:26.560 life here on Earth and how our future might be 0:19:26.600 --> 0:19:30.520 impacted by visitations from other stars. I hope we answered 0:19:30.520 --> 0:19:32.760 your question, and I hope we inspired everybody out there 0:19:32.800 --> 0:19:36.000 to think about their own questions about the universe. What 0:19:36.080 --> 0:19:38.960 doesn't make sense to you? What physics scenario are you 0:19:39.080 --> 0:19:41.680 wondering about that you can't find the answer to. Please 0:19:41.680 --> 0:19:43.600 write to us. We want to hear from you. Send 0:19:43.680 --> 0:19:47.320 us a message to questions at Danielandjorge dot com. And 0:19:47.359 --> 0:19:50.240 thanks very much Kelly for bringing your relentless optimism to 0:19:50.280 --> 0:19:50.919 the podcast. 0:19:52.760 --> 0:19:55.080 Oh you're welcome. Yeah. I hope we get more questions 0:19:55.080 --> 0:19:58.280 so that our list of reasons to feel existential dread 0:19:58.320 --> 0:20:01.120 can grow and grow and grow and grow. But yeah, 0:20:01.119 --> 0:20:02.760 thanks for having me on the show. It's always a 0:20:02.760 --> 0:20:03.160 good time. 0:20:03.600 --> 0:20:06.480