1 00:00:07,960 --> 00:00:11,720 Speaker 1: Daniel, it's been like forever. How are things good? 2 00:00:11,760 --> 00:00:11,959 Speaker 2: Good? 3 00:00:12,000 --> 00:00:14,280 Speaker 3: You know, same stuff in my world? Do big updates. 4 00:00:14,680 --> 00:00:18,040 Speaker 1: So you guys didn't like move across the planet again? 5 00:00:18,640 --> 00:00:21,960 Speaker 3: Oh no, we are done with those trans continental moves. 6 00:00:22,000 --> 00:00:22,960 Speaker 3: I hate moving. 7 00:00:23,320 --> 00:00:25,239 Speaker 1: Oh my gosh, I hate moving too, But you know, 8 00:00:25,280 --> 00:00:27,639 Speaker 1: I think what I hate the most about moving is 9 00:00:27,680 --> 00:00:30,840 Speaker 1: needing to like pack everything up and then not only unpacked, 10 00:00:30,840 --> 00:00:33,000 Speaker 1: but then you discover like, oh I need new curtains, 11 00:00:33,000 --> 00:00:35,000 Speaker 1: and like, oh we forgot the plunger, we need to 12 00:00:35,000 --> 00:00:37,560 Speaker 1: get a new one, and like all of that stuff. 13 00:00:37,600 --> 00:00:40,159 Speaker 1: So what if you could move and stay in the 14 00:00:40,200 --> 00:00:42,520 Speaker 1: same house, like lift it up and move it. Would 15 00:00:42,520 --> 00:00:43,640 Speaker 1: you move across the country? 16 00:00:43,680 --> 00:00:47,360 Speaker 3: Then I think that's a billion dollar idea. You shouldn't 17 00:00:47,360 --> 00:00:49,320 Speaker 3: be sharing it on the podcast. You should be starting 18 00:00:49,320 --> 00:00:49,879 Speaker 3: that company. 19 00:00:50,400 --> 00:00:55,800 Speaker 1: Delete delete now. I have no business acumen, so somebody 20 00:00:55,800 --> 00:00:57,640 Speaker 1: else can go ahead and make a billion dollars on that. 21 00:00:57,680 --> 00:00:58,280 Speaker 1: You're welcome. 22 00:01:14,040 --> 00:01:14,240 Speaker 2: Hi. 23 00:01:14,400 --> 00:01:17,520 Speaker 3: I'm Daniel, I'm a particle physicist, a professor at UC Irvine, 24 00:01:17,560 --> 00:01:19,840 Speaker 3: and I've never started a billion dollar company. 25 00:01:21,480 --> 00:01:25,640 Speaker 1: I'm Kelly Wiener Smith. I'm a parasitologist at Race University. 26 00:01:25,720 --> 00:01:28,440 Speaker 1: I also have never started a billion dollar company. But 27 00:01:28,480 --> 00:01:31,080 Speaker 1: I did move my husband across the country something like 28 00:01:31,360 --> 00:01:34,080 Speaker 1: three or four times. But he made me promise we'd 29 00:01:34,080 --> 00:01:36,280 Speaker 1: never move again, which is good because we can't move 30 00:01:36,319 --> 00:01:36,760 Speaker 1: our farm. 31 00:01:39,400 --> 00:01:41,520 Speaker 3: There's something about moving. It's sort of like having kids. 32 00:01:41,640 --> 00:01:44,760 Speaker 3: It's horrible, it's painful. You swear you'll never do it again, 33 00:01:45,000 --> 00:01:47,400 Speaker 3: and then a few years later you sort of forget 34 00:01:47,400 --> 00:01:49,840 Speaker 3: how bad it was, and you're like, actually, that sounds 35 00:01:49,920 --> 00:01:50,520 Speaker 3: kind of fun. 36 00:01:50,680 --> 00:01:53,160 Speaker 1: I don't think my husband ever forgot how bad it was. 37 00:01:53,440 --> 00:01:55,520 Speaker 1: He was always I'd be like, let's move again, and 38 00:01:55,560 --> 00:01:58,360 Speaker 1: he'd always be like, no, don't you remember, And I'd 39 00:01:58,400 --> 00:02:02,240 Speaker 1: be like, no, no, it's fine, fine, fine, But anyway, 40 00:02:02,240 --> 00:02:04,600 Speaker 1: we're done moving and we're done having kids. So there 41 00:02:04,640 --> 00:02:06,880 Speaker 1: you go. Everything about our life is standing still. 42 00:02:07,600 --> 00:02:09,920 Speaker 3: Well, there was a period in our lives when we 43 00:02:09,960 --> 00:02:13,120 Speaker 3: went back and forth from California to Geneva, I think 44 00:02:13,280 --> 00:02:17,160 Speaker 3: ten times over a five or six year period, with 45 00:02:17,400 --> 00:02:20,320 Speaker 3: tiny kids. Oh my gosh, I don't know how our 46 00:02:20,360 --> 00:02:22,160 Speaker 3: sanity or our marriage survived. 47 00:02:22,400 --> 00:02:24,760 Speaker 1: Oh okay, that is way more intense than what I did. 48 00:02:25,520 --> 00:02:29,040 Speaker 1: That's incredible. Yes, I am also amazed that your sanity 49 00:02:29,080 --> 00:02:31,680 Speaker 1: and marriage survived you too. It must be a very 50 00:02:31,720 --> 00:02:32,440 Speaker 1: strong family. 51 00:02:34,440 --> 00:02:36,400 Speaker 3: I think you should be less impressed and more doubting 52 00:02:36,480 --> 00:02:40,639 Speaker 3: our judgment. But anyway, Welcome to the podcast Daniel and 53 00:02:40,720 --> 00:02:44,799 Speaker 3: Jorge Explain the Universe, a production of iHeartRadio in which 54 00:02:44,840 --> 00:02:47,480 Speaker 3: we try to move you to a place of deep 55 00:02:47,600 --> 00:02:51,200 Speaker 3: understanding about the universe. We want to transport your brain 56 00:02:51,320 --> 00:02:55,040 Speaker 3: to that mysterious location where everything makes sense. We're it 57 00:02:55,080 --> 00:02:57,600 Speaker 3: all clicked together in your mind to give you a 58 00:02:57,600 --> 00:03:01,360 Speaker 3: harmonious understanding of the deep knee of the universe, at 59 00:03:01,440 --> 00:03:03,760 Speaker 3: least as far as we understand it. 60 00:03:04,040 --> 00:03:07,480 Speaker 1: Right, or to give you a headache wondering wondering how 61 00:03:07,560 --> 00:03:08,280 Speaker 1: this all works. 62 00:03:10,040 --> 00:03:12,520 Speaker 3: Sometimes no pain, no gain, right, Kelly. That doesn't just 63 00:03:12,560 --> 00:03:16,000 Speaker 3: apply to lifting weights. It also applies to understanding the universe. 64 00:03:16,400 --> 00:03:19,040 Speaker 1: Yeah no. And there's a lot of pain in physics. 65 00:03:20,600 --> 00:03:22,560 Speaker 3: And we want to help you with that pain. So 66 00:03:22,639 --> 00:03:24,880 Speaker 3: if you are thinking about things and they don't quite 67 00:03:24,919 --> 00:03:27,280 Speaker 3: click together in your mind, or if you have a 68 00:03:27,280 --> 00:03:30,200 Speaker 3: physics question and you've tried googling it but haven't found 69 00:03:30,280 --> 00:03:32,800 Speaker 3: any answers, we want to help you out. This is 70 00:03:32,840 --> 00:03:35,360 Speaker 3: not just a one direction a lecture from us to you. 71 00:03:35,640 --> 00:03:38,480 Speaker 3: We want this to be a conversation and we miss 72 00:03:38,480 --> 00:03:41,240 Speaker 3: hearing from you, so please write to us two questions 73 00:03:41,240 --> 00:03:45,280 Speaker 3: at Daniel iinhorge dot com. You'll always get an answer back. 74 00:03:45,880 --> 00:03:48,120 Speaker 3: And on today's podcast, we're going to be doing just that, 75 00:03:48,360 --> 00:03:52,320 Speaker 3: answering questions from a listener. So today on the podcast, 76 00:03:52,360 --> 00:04:02,960 Speaker 3: we'll be answering listener questions. Bring Equinox edition. We thought 77 00:04:02,960 --> 00:04:05,240 Speaker 3: it was time to come back and fill your ears 78 00:04:05,240 --> 00:04:07,600 Speaker 3: with answers to physics questions. 79 00:04:07,160 --> 00:04:09,520 Speaker 1: About the universe because missing you. 80 00:04:10,280 --> 00:04:13,360 Speaker 3: And we hope you've been missing us. And today we 81 00:04:13,400 --> 00:04:17,359 Speaker 3: have a really fun question about transportation or about moving, 82 00:04:17,600 --> 00:04:20,240 Speaker 3: not just moving yourself, not just moving your house and family, 83 00:04:20,560 --> 00:04:24,080 Speaker 3: but moving the entire solar system. So here's a great 84 00:04:24,160 --> 00:04:27,200 Speaker 3: question from John in Kansas. 85 00:04:27,240 --> 00:04:30,680 Speaker 2: Hello, Daniel, this is John and I listened to your 86 00:04:30,680 --> 00:04:35,440 Speaker 2: show from south central Kansas near the Oklahoma border, and 87 00:04:35,520 --> 00:04:40,599 Speaker 2: I love it. Anyway, my question is I've heard you 88 00:04:40,640 --> 00:04:45,200 Speaker 2: discussed many times that occasionally stars get ejected from their systems, 89 00:04:46,000 --> 00:04:49,480 Speaker 2: perhaps due to the pull of a passing star, and 90 00:04:49,560 --> 00:04:53,360 Speaker 2: I remember you once even speculated that we ourselves may 91 00:04:53,400 --> 00:04:56,800 Speaker 2: have started out as a binary system and our son's 92 00:04:57,440 --> 00:05:01,680 Speaker 2: own twin brother got ejected ago. But my question is 93 00:05:01,720 --> 00:05:05,920 Speaker 2: this Suppose this did happen and our Sun did get 94 00:05:05,960 --> 00:05:10,240 Speaker 2: flung out of our galaxy. Would it be violently ripped 95 00:05:10,240 --> 00:05:14,120 Speaker 2: away from its own planets? Or would the event be 96 00:05:14,200 --> 00:05:20,120 Speaker 2: so gradual that we wouldn't even notice it? And if 97 00:05:20,120 --> 00:05:25,600 Speaker 2: that happened, would be be towed with it along with 98 00:05:25,640 --> 00:05:31,039 Speaker 2: the other planets, asteroids, the asteroid belt, the Kuiper Belt, 99 00:05:31,080 --> 00:05:36,719 Speaker 2: the Oort Cloud, and all of the celestial bodies, all 100 00:05:36,760 --> 00:05:41,919 Speaker 2: remaining nicely tucked away in their own orbits as we 101 00:05:42,080 --> 00:05:45,799 Speaker 2: follow the Sun into oblivion. Thank you for answering. 102 00:05:47,240 --> 00:05:53,599 Speaker 1: Oh fantastic. Another question that inspires existential dread what would 103 00:05:53,640 --> 00:05:56,720 Speaker 1: happen if the Sun would would it rip apart our 104 00:05:56,720 --> 00:05:59,800 Speaker 1: solar system? Or would our planets go with it? And anyway, 105 00:05:59,839 --> 00:06:02,960 Speaker 1: it's okay, I don't need to sleep, so let's go 106 00:06:03,000 --> 00:06:06,280 Speaker 1: ahead and dig right in, Daniel, how stable is our 107 00:06:06,320 --> 00:06:07,120 Speaker 1: solar system? 108 00:06:07,920 --> 00:06:10,640 Speaker 3: Yeah, this is a really fun question thinking about what 109 00:06:10,760 --> 00:06:13,480 Speaker 3: might happen if our Sun got ejected from the galaxy. 110 00:06:13,880 --> 00:06:16,240 Speaker 3: And you're right. The first part of the question is understanding, 111 00:06:16,320 --> 00:06:19,440 Speaker 3: like how well are we latched onto the Sun? If 112 00:06:19,440 --> 00:06:22,080 Speaker 3: the Sun gets thrown out somewhere, how likely are we 113 00:06:22,320 --> 00:06:24,440 Speaker 3: to go along? For the ride, and this depends on 114 00:06:24,520 --> 00:06:28,400 Speaker 3: the stability of the whole Sun Earth system, right, So 115 00:06:28,920 --> 00:06:32,320 Speaker 3: good news is that mostly things are stable, Like the 116 00:06:32,360 --> 00:06:35,240 Speaker 3: Earth is orbiting the Sun, and even if the Earth 117 00:06:35,279 --> 00:06:37,520 Speaker 3: got like a little bit of a push, it would 118 00:06:37,560 --> 00:06:40,200 Speaker 3: slide right back into its orbit. That's what we usually 119 00:06:40,240 --> 00:06:42,960 Speaker 3: mean by stable. You know, if you have, for example, 120 00:06:43,080 --> 00:06:45,840 Speaker 3: like a ball inside a cup and you push it 121 00:06:45,880 --> 00:06:47,880 Speaker 3: a little bit, it's gonna roll right back down to 122 00:06:47,920 --> 00:06:50,719 Speaker 3: the bottom. Whereas if you have like the ball sitting 123 00:06:50,720 --> 00:06:52,839 Speaker 3: on top of another ball, or on top of a rock, 124 00:06:52,960 --> 00:06:54,520 Speaker 3: or on top of a hill or something, and you 125 00:06:54,560 --> 00:06:56,600 Speaker 3: give it a push, it's gonna roll away and not 126 00:06:56,720 --> 00:07:00,160 Speaker 3: come back. That's an unstable configuration. So we call the 127 00:07:00,200 --> 00:07:03,280 Speaker 3: Earth's orbit stable because it's pretty resistant to these kinds 128 00:07:03,279 --> 00:07:03,839 Speaker 3: of pushes. 129 00:07:04,520 --> 00:07:07,839 Speaker 1: So even though it's resistant to a kind of push, 130 00:07:08,240 --> 00:07:11,640 Speaker 1: anything that could push Earth away from the Sun would 131 00:07:11,680 --> 00:07:12,720 Speaker 1: have to be catastrophic. 132 00:07:12,800 --> 00:07:13,000 Speaker 2: Right. 133 00:07:13,800 --> 00:07:16,160 Speaker 3: Well, there's lots of little pushes that the Earth could survive, 134 00:07:16,200 --> 00:07:18,600 Speaker 3: and the Earth is getting tugged on and pushed in 135 00:07:18,640 --> 00:07:21,120 Speaker 3: lots of different ways. So the Earth's orbit would be 136 00:07:21,160 --> 00:07:23,840 Speaker 3: perfectly stable if it was just the Earth and the 137 00:07:23,880 --> 00:07:27,680 Speaker 3: Sun in totally empty space with nothing happening in classical mechanics, 138 00:07:27,760 --> 00:07:29,840 Speaker 3: that could go forever. But you know, the situation is 139 00:07:29,840 --> 00:07:32,760 Speaker 3: a little bit more complex. For example, like the Sun 140 00:07:32,960 --> 00:07:35,200 Speaker 3: is pushing on the Earth. It's not just pulling on it. 141 00:07:35,480 --> 00:07:38,520 Speaker 3: The radiation from the Sun, the wind, and the photons 142 00:07:38,560 --> 00:07:41,600 Speaker 3: are actually applying a momentum pushing the Earth away from 143 00:07:41,600 --> 00:07:44,480 Speaker 3: the Sun. But the Earth's orbit is stable enough that 144 00:07:44,560 --> 00:07:46,960 Speaker 3: it can overcome that. It's like accommodates that. 145 00:07:47,360 --> 00:07:52,120 Speaker 1: So I've read proposals. I don't know how serious any 146 00:07:52,160 --> 00:07:54,560 Speaker 1: of them were, but like to deal with climate change 147 00:07:54,600 --> 00:07:57,640 Speaker 1: by like putting like a big screen out that would 148 00:07:57,640 --> 00:08:00,400 Speaker 1: block some of the photons from hitting the Earth. If 149 00:08:00,480 --> 00:08:05,160 Speaker 1: you blocked enough photons, could the Earth move closer to 150 00:08:05,160 --> 00:08:07,680 Speaker 1: the Sun because we're not getting pushed back and like 151 00:08:07,720 --> 00:08:09,280 Speaker 1: not much. I know you said it's a small effect, 152 00:08:09,280 --> 00:08:11,560 Speaker 1: but when we move like a couple feet closer if 153 00:08:11,560 --> 00:08:15,040 Speaker 1: you blocked enough photons, well. 154 00:08:14,840 --> 00:08:17,280 Speaker 3: That depends a little bit on where you put that shield. 155 00:08:17,400 --> 00:08:19,920 Speaker 3: Like if it's connected to the Earth, then it's basically 156 00:08:19,960 --> 00:08:22,080 Speaker 3: just part of the Earth and it doesn't change how 157 00:08:22,080 --> 00:08:25,880 Speaker 3: we're getting pushed. If it's somehow floating separated from the 158 00:08:25,880 --> 00:08:29,880 Speaker 3: Earth and absorbing that momentum itself by like firing rockets 159 00:08:29,960 --> 00:08:32,960 Speaker 3: or something. Then yeah, that would relieve a little bit 160 00:08:32,960 --> 00:08:34,600 Speaker 3: of the pressure on the Earth. But this is really 161 00:08:34,640 --> 00:08:38,000 Speaker 3: a tiny, tiny effect on the Earth's orbit. Much more 162 00:08:38,040 --> 00:08:41,680 Speaker 3: substantial are tugs by like Jupiter and Saturn, because the 163 00:08:41,720 --> 00:08:43,760 Speaker 3: Solar System is not just the Earth and the Sun. 164 00:08:43,840 --> 00:08:46,440 Speaker 3: There are other big players out there, and Jupiter is 165 00:08:46,600 --> 00:08:49,200 Speaker 3: much more massive than the Earth. So if you want 166 00:08:49,240 --> 00:08:51,840 Speaker 3: to model the Earth's orbit and its stability really accurately, 167 00:08:52,040 --> 00:08:53,920 Speaker 3: you got to think about what the big boys do 168 00:08:54,160 --> 00:08:56,320 Speaker 3: as they move around the Solar System, and they're constantly 169 00:08:56,320 --> 00:08:59,280 Speaker 3: tugging on the Earth giving it little nudges here and there, 170 00:08:59,520 --> 00:09:02,600 Speaker 3: and that the Earth is pretty stable towards like the 171 00:09:02,640 --> 00:09:05,720 Speaker 3: Earth can tolerate a push from Jupiter, push from Saturn 172 00:09:05,840 --> 00:09:07,800 Speaker 3: and then slide right back into its orbit. 173 00:09:08,240 --> 00:09:11,560 Speaker 1: Okay, And so does the answer to this question then 174 00:09:11,600 --> 00:09:14,400 Speaker 1: depend on how close does Jupiter need to be to 175 00:09:14,480 --> 00:09:15,679 Speaker 1: Earth when this happens. 176 00:09:16,320 --> 00:09:19,000 Speaker 3: Yeah, so Jupiter and Saturn are basically irrelevant to this question, 177 00:09:19,120 --> 00:09:22,000 Speaker 3: is the good news. The bad news is that there 178 00:09:22,040 --> 00:09:24,720 Speaker 3: are other things that can also perturb the Earth's orbit, 179 00:09:25,120 --> 00:09:27,679 Speaker 3: And the biggest, number one thing to worry about are 180 00:09:27,760 --> 00:09:31,559 Speaker 3: other stars because where the Sun is in the galaxy 181 00:09:31,880 --> 00:09:34,560 Speaker 3: is not fixed relative to the other stars. Like all 182 00:09:34,640 --> 00:09:37,280 Speaker 3: the stars in the galaxy are rotating around the center 183 00:09:37,320 --> 00:09:40,719 Speaker 3: of the galaxy, but they're not all rotating together, so 184 00:09:40,760 --> 00:09:44,360 Speaker 3: our distance to other stars changes as time goes on. 185 00:09:44,840 --> 00:09:47,239 Speaker 3: So even if we don't get ejected from the galaxy, 186 00:09:47,480 --> 00:09:50,800 Speaker 3: there is a danger that sometime in the future, another 187 00:09:50,960 --> 00:09:53,640 Speaker 3: star will come close to us and that could perturb 188 00:09:53,720 --> 00:09:56,840 Speaker 3: the Earth's orbit. It could provide enough of a gravitational 189 00:09:56,920 --> 00:09:59,719 Speaker 3: nudge to knock us out of our orbit, or even 190 00:09:59,760 --> 00:10:02,600 Speaker 3: a doesn't, it could disturb all the frozen objects out 191 00:10:02,640 --> 00:10:04,800 Speaker 3: in the deep Solar System and rain down a bunch 192 00:10:04,840 --> 00:10:07,000 Speaker 3: of comments on us, both of which would be bad. 193 00:10:07,760 --> 00:10:09,360 Speaker 3: I know that doesn't sound like a lot of fun, 194 00:10:09,400 --> 00:10:12,200 Speaker 3: but it might actually be spectacular. Well, dig into what 195 00:10:12,240 --> 00:10:28,240 Speaker 3: it means just after this short break. Okay, we're back, 196 00:10:28,280 --> 00:10:30,880 Speaker 3: and we're talking about what might happen if our star 197 00:10:31,160 --> 00:10:35,320 Speaker 3: is ejected from the galaxy and whether it's likely. 198 00:10:35,800 --> 00:10:38,600 Speaker 1: Do we think this could happen? Probably not in our lifetimes. 199 00:10:38,200 --> 00:10:42,720 Speaker 3: Right, probably not in our lifetimes. But we do understand 200 00:10:43,160 --> 00:10:46,840 Speaker 3: the Sun's path through the galaxy pretty well. It's actually 201 00:10:46,880 --> 00:10:49,920 Speaker 3: pretty awesome to think about it, because you imagine space, 202 00:10:49,960 --> 00:10:53,080 Speaker 3: you probably think about the Sun primarily as the center 203 00:10:53,360 --> 00:10:56,719 Speaker 3: of our galactic coordinates, right, everything else is relative to that. 204 00:10:57,040 --> 00:10:59,760 Speaker 3: But you know, the Sun is in motion relative to 205 00:10:59,800 --> 00:11:02,679 Speaker 3: this center of the galaxy. And this is sort of 206 00:11:02,679 --> 00:11:06,720 Speaker 3: a big conceptual step because remember that all motion is relative. 207 00:11:07,080 --> 00:11:08,960 Speaker 3: So some people say, oh, you know, the Sun is 208 00:11:09,000 --> 00:11:12,079 Speaker 3: moving through space, but everything is moving through space, it's 209 00:11:12,120 --> 00:11:14,720 Speaker 3: just relative to what. So when you talk about like 210 00:11:14,760 --> 00:11:17,040 Speaker 3: the earth velocity is relative to the Sun, you talk 211 00:11:17,040 --> 00:11:20,360 Speaker 3: about the Sun's velocity is relative to the center of 212 00:11:20,400 --> 00:11:23,640 Speaker 3: the galaxy. And the Sun, like everything else, is swirling 213 00:11:23,640 --> 00:11:25,800 Speaker 3: around the center, and it takes about two hundred and 214 00:11:25,800 --> 00:11:30,440 Speaker 3: fifty million years to orbit. It's like a really huge 215 00:11:30,480 --> 00:11:31,160 Speaker 3: amount of time. 216 00:11:31,240 --> 00:11:34,800 Speaker 1: But that's happened a number of times since the planet started, 217 00:11:34,960 --> 00:11:37,920 Speaker 1: like many times since the planet started, So it's moving. 218 00:11:38,600 --> 00:11:39,880 Speaker 1: I don't know, that's kind of impressive. 219 00:11:39,880 --> 00:11:42,040 Speaker 3: I think, yeah, Well, the Earth is like four and 220 00:11:42,080 --> 00:11:45,040 Speaker 3: a half billion years old, which means in terms of 221 00:11:45,200 --> 00:11:48,240 Speaker 3: galactic spins, right, how long it takes the Milky Way 222 00:11:48,280 --> 00:11:50,640 Speaker 3: to cycle, which in many ways is like a very 223 00:11:50,840 --> 00:11:53,200 Speaker 3: natural unit. You could call it like a galactic year. 224 00:11:53,600 --> 00:11:56,040 Speaker 3: Instead of measuring time in terms of how many times 225 00:11:56,040 --> 00:11:57,839 Speaker 3: the Earth goes around the Sun, measure in terms of 226 00:11:57,880 --> 00:12:00,600 Speaker 3: how many times the Sun goes around the galaxy. And 227 00:12:00,679 --> 00:12:03,720 Speaker 3: so that makes Earth like twenty galactic years old. Earth 228 00:12:03,800 --> 00:12:06,880 Speaker 3: is just grown up. It's like entering its adult phase. 229 00:12:07,360 --> 00:12:08,920 Speaker 1: It can't even drink yet. 230 00:12:11,000 --> 00:12:13,640 Speaker 3: That's right. So, yeah, the Earth is kind of young 231 00:12:13,679 --> 00:12:16,400 Speaker 3: and sprightly. Right, it's still probably the fittest it's ever 232 00:12:16,440 --> 00:12:16,800 Speaker 3: gonna be. 233 00:12:17,280 --> 00:12:19,720 Speaker 1: Oh oh man, wait till you hit your thirties. 234 00:12:19,760 --> 00:12:20,040 Speaker 2: Earth. 235 00:12:20,240 --> 00:12:21,760 Speaker 1: It's all downhill after that. 236 00:12:23,400 --> 00:12:25,400 Speaker 3: But the other thing is that the Sun doesn't just 237 00:12:25,600 --> 00:12:28,400 Speaker 3: orbit around the center of the galaxy. It also wiggles. 238 00:12:28,880 --> 00:12:31,680 Speaker 3: It's above the galactic plane sometimes, and then it zooms 239 00:12:31,720 --> 00:12:34,400 Speaker 3: down through the galactic plane and then past it, and 240 00:12:34,440 --> 00:12:36,839 Speaker 3: then the gravity of the galactic plane pulls it back. 241 00:12:37,160 --> 00:12:40,840 Speaker 3: So it's like oscillating up and down above the galactic plane. 242 00:12:41,000 --> 00:12:43,240 Speaker 3: So it's not just going in a circle around the 243 00:12:43,240 --> 00:12:46,480 Speaker 3: center of the galaxy. It's more like a zigzag up 244 00:12:46,520 --> 00:12:48,400 Speaker 3: and down as it circles around. 245 00:12:48,679 --> 00:12:50,960 Speaker 1: All right, So now I'm picturing my son when we 246 00:12:51,040 --> 00:12:53,320 Speaker 1: walk around the track together. He's like jumping up and 247 00:12:53,360 --> 00:12:55,640 Speaker 1: down the whole time that we're doing. Yes, So this 248 00:12:55,760 --> 00:12:58,440 Speaker 1: young Earth is going up and down while it's making 249 00:12:58,480 --> 00:12:59,400 Speaker 1: its laps. 250 00:13:00,040 --> 00:13:03,920 Speaker 3: Exactly, and that cycle takes about thirty million years. So 251 00:13:04,120 --> 00:13:06,640 Speaker 3: as we go around the galaxy, we go up and 252 00:13:06,679 --> 00:13:10,720 Speaker 3: down like eightish times every galactic year, and that's different 253 00:13:10,760 --> 00:13:13,720 Speaker 3: for different stars. And so now imagine this whole galaxy. 254 00:13:13,760 --> 00:13:17,080 Speaker 3: It's a chaotic swarm of all these stars moving closer 255 00:13:17,120 --> 00:13:19,880 Speaker 3: and farther away from each other. There's a real possibility, 256 00:13:20,120 --> 00:13:22,640 Speaker 3: of course, over millions and billions of years, that we 257 00:13:22,720 --> 00:13:26,000 Speaker 3: come pretty close to another star. We've actually predicted that 258 00:13:26,080 --> 00:13:28,160 Speaker 3: there is going to be a close approach by the 259 00:13:28,200 --> 00:13:31,959 Speaker 3: star Glease seven to ten in a few million years. 260 00:13:32,360 --> 00:13:35,760 Speaker 1: Oh that's how close, Daniel, How close? 261 00:13:37,280 --> 00:13:38,800 Speaker 3: It's not going to be that close. I mean it 262 00:13:38,840 --> 00:13:42,120 Speaker 3: depends on the units. In one point three million years, 263 00:13:42,240 --> 00:13:46,720 Speaker 3: it's going to pass within zero point one seven light years, 264 00:13:46,800 --> 00:13:49,360 Speaker 3: so like a seventh of a light year. That doesn't 265 00:13:49,400 --> 00:13:52,240 Speaker 3: sound very far, but it's like a twenty fifth of 266 00:13:52,280 --> 00:13:55,280 Speaker 3: the distance to the nearest star. So it's going to 267 00:13:55,320 --> 00:13:57,640 Speaker 3: mean that the closest star to Earth is a lot 268 00:13:57,800 --> 00:14:01,000 Speaker 3: closer than it is currently, but it's still pretty far away. 269 00:14:01,400 --> 00:14:05,320 Speaker 3: It's like ten thousand astronomical units ten thousand times the 270 00:14:05,360 --> 00:14:07,880 Speaker 3: distance from the Sun to the Earth. So it's not 271 00:14:07,920 --> 00:14:10,199 Speaker 3: like gonna appear in our sky as bright as the 272 00:14:10,240 --> 00:14:12,760 Speaker 3: Sun or anything. It's just going to be something moving 273 00:14:12,840 --> 00:14:13,679 Speaker 3: in the night sky. 274 00:14:13,880 --> 00:14:15,920 Speaker 1: Will it still be brighter than the other stars. 275 00:14:16,240 --> 00:14:18,520 Speaker 3: It'll be brighter than the other stars. Yeah, it'll be 276 00:14:18,640 --> 00:14:21,720 Speaker 3: very visible. But you know, in one point three million years, 277 00:14:21,840 --> 00:14:24,680 Speaker 3: so your super great grandkids have this to look forward to. 278 00:14:25,160 --> 00:14:28,120 Speaker 1: Yeah, yeah, I guess I'm gonna miss it. Oh well, 279 00:14:28,600 --> 00:14:29,560 Speaker 1: this is important. 280 00:14:29,240 --> 00:14:31,920 Speaker 3: To answer John's question because this is how stars get 281 00:14:32,000 --> 00:14:35,160 Speaker 3: thrown out of the galaxy. Like just left alone. The 282 00:14:35,240 --> 00:14:37,520 Speaker 3: Sun's orbit is pretty stable, it's just going to keep 283 00:14:37,520 --> 00:14:40,280 Speaker 3: going around the center of the galaxy. But the same 284 00:14:40,280 --> 00:14:43,200 Speaker 3: way that, like Earth is nudged by Jupiter and Saturn, 285 00:14:43,400 --> 00:14:45,800 Speaker 3: the Sun can be nudged by other stars, and so 286 00:14:45,840 --> 00:14:48,880 Speaker 3: a close approach with another star could end up doing 287 00:14:48,880 --> 00:14:52,600 Speaker 3: a gravitational slingshot on our star, so it gets sent 288 00:14:52,720 --> 00:14:53,720 Speaker 3: out of the galaxy. 289 00:14:54,000 --> 00:14:56,320 Speaker 1: Obviously, if you live on Earth, whether Earth stays put 290 00:14:56,440 --> 00:15:00,000 Speaker 1: or not, you're dead without the Sun and the light 291 00:15:00,040 --> 00:15:03,240 Speaker 1: that it provides. But what kind of factors would determine 292 00:15:03,240 --> 00:15:06,320 Speaker 1: if Earth stays put or not? Would it depend on 293 00:15:06,360 --> 00:15:09,600 Speaker 1: how fast the Sun moves, or if the Sun came 294 00:15:09,720 --> 00:15:12,720 Speaker 1: close to us on its way out, Yeah, what would 295 00:15:12,720 --> 00:15:13,520 Speaker 1: we have to worry about. 296 00:15:14,160 --> 00:15:18,240 Speaker 3: It's basically all proximity. Like if that star comes by 297 00:15:18,280 --> 00:15:20,640 Speaker 3: and it's not super close, and it just like gives 298 00:15:20,680 --> 00:15:24,119 Speaker 3: our Sun a new direction. Even if that direction eventually 299 00:15:24,120 --> 00:15:26,520 Speaker 3: takes us out of the Milky Way, we'll be fine 300 00:15:26,600 --> 00:15:29,800 Speaker 3: because if it's gradual, then the Earth's orbit can respond 301 00:15:29,840 --> 00:15:32,200 Speaker 3: to these things, respond to little nudges. It's just like 302 00:15:32,440 --> 00:15:35,840 Speaker 3: another Jupiter effect or another Saturn effect, and it'll follow 303 00:15:35,880 --> 00:15:38,600 Speaker 3: the Sun as it takes its new trajectory. But if 304 00:15:38,600 --> 00:15:41,560 Speaker 3: it's dramatic enough so that like the Sun gets accelerated 305 00:15:41,600 --> 00:15:45,720 Speaker 3: significantly and new direction comes on quickly, then the Earth's 306 00:15:45,800 --> 00:15:48,920 Speaker 3: orbit can't adapt. Because the Earth's orbit is pretty stable, 307 00:15:48,960 --> 00:15:51,040 Speaker 3: but it's not infinitely stable. If you gave it a 308 00:15:51,080 --> 00:15:54,400 Speaker 3: really big kick relative to the Sun, or equivalently, you 309 00:15:54,480 --> 00:15:56,440 Speaker 3: give the Sun a really big kick, the two are 310 00:15:56,480 --> 00:15:59,000 Speaker 3: the same, then the Earth will not be able to 311 00:15:59,000 --> 00:16:02,400 Speaker 3: follow the Sun. And so if for example, another star 312 00:16:02,560 --> 00:16:05,440 Speaker 3: comes very close to our Solar system, so the Sun 313 00:16:05,480 --> 00:16:08,360 Speaker 3: feels a very strong gravitational pull, the kind of thing 314 00:16:08,400 --> 00:16:11,760 Speaker 3: that can and does kick stars out of our galaxy, 315 00:16:12,080 --> 00:16:14,720 Speaker 3: then the Earth has almost no chance of following. Oh Man. 316 00:16:15,240 --> 00:16:18,200 Speaker 1: So, in the scenario where something is big enough to 317 00:16:18,200 --> 00:16:21,480 Speaker 1: move the Sun, but the Sun is moving slowly, when 318 00:16:21,520 --> 00:16:24,640 Speaker 1: the Earth reached the part of its path around the 319 00:16:24,640 --> 00:16:26,720 Speaker 1: Sun where it was between the Sun and this other 320 00:16:26,800 --> 00:16:29,160 Speaker 1: sun that was big enough and close enough to move 321 00:16:29,240 --> 00:16:34,960 Speaker 1: the Sun, would that push Earth towards the other gigantic 322 00:16:35,600 --> 00:16:38,400 Speaker 1: sun object then we would go back. And so would 323 00:16:38,400 --> 00:16:40,840 Speaker 1: that be like a wobble in our orbit or would 324 00:16:40,880 --> 00:16:42,880 Speaker 1: we get pulled out to that other Sun. 325 00:16:43,200 --> 00:16:46,080 Speaker 3: Yeah, well, you're talking about a three body problem, and 326 00:16:46,120 --> 00:16:47,960 Speaker 3: this is known to be very chaotic. 327 00:16:48,480 --> 00:16:48,640 Speaker 2: Right. 328 00:16:48,640 --> 00:16:50,960 Speaker 3: If you have two stars and a planet, then it's 329 00:16:51,040 --> 00:16:53,320 Speaker 3: very difficult for that planet to find a stable orbit. 330 00:16:53,440 --> 00:16:55,760 Speaker 3: And if that system is changing because one star is 331 00:16:55,800 --> 00:16:59,160 Speaker 3: like flying by the other one, then it's essentially impossible. 332 00:16:59,760 --> 00:17:03,120 Speaker 3: So the details depend on exactly the angle and exactly 333 00:17:03,200 --> 00:17:06,360 Speaker 3: the velocity. That's what we mean by chaos and physics. 334 00:17:06,400 --> 00:17:09,400 Speaker 3: We mean that a very small change in the situation 335 00:17:09,520 --> 00:17:12,120 Speaker 3: can result in a very big change in the outcome. 336 00:17:12,760 --> 00:17:14,400 Speaker 3: Like if you're playing pool and you hit one ball 337 00:17:14,440 --> 00:17:16,760 Speaker 3: against the other, a very small change in how you're 338 00:17:16,800 --> 00:17:18,600 Speaker 3: hitting the cue ball can mean you win the game 339 00:17:18,680 --> 00:17:21,480 Speaker 3: or lose the game. Right, So in this scenario, a 340 00:17:21,640 --> 00:17:24,080 Speaker 3: very small change in the direction of that star, or 341 00:17:24,119 --> 00:17:26,199 Speaker 3: the mass of that star, or the velocity of that 342 00:17:26,280 --> 00:17:29,399 Speaker 3: star could result in a completely different outcome. Some like 343 00:17:29,520 --> 00:17:31,680 Speaker 3: you and vision like, oh, we wobble towards the star 344 00:17:31,720 --> 00:17:34,280 Speaker 3: and then we wabble away from it, and others where 345 00:17:34,280 --> 00:17:36,760 Speaker 3: we just got we just get ejected into deep space 346 00:17:37,080 --> 00:17:40,159 Speaker 3: on our own. So I think if the star comes 347 00:17:40,320 --> 00:17:43,680 Speaker 3: close enough to eject our Sun from the Milky Way, 348 00:17:43,800 --> 00:17:46,360 Speaker 3: it's going to also come close enough to perturb our 349 00:17:46,520 --> 00:17:49,240 Speaker 3: orbit around that Sun. It's going to be very unlikely 350 00:17:49,320 --> 00:17:51,080 Speaker 3: we are along for the ride. But you know, there's 351 00:17:51,080 --> 00:17:52,520 Speaker 3: a possible bright outcome there. 352 00:17:52,760 --> 00:17:53,080 Speaker 1: What's that. 353 00:17:54,119 --> 00:17:56,240 Speaker 3: It might be that this new star comes along, messes 354 00:17:56,359 --> 00:17:59,280 Speaker 3: up our happy orbit around the Sun, ejects the Sun 355 00:17:59,280 --> 00:18:02,159 Speaker 3: from the Milky Way, and then steals the Earth. It 356 00:18:02,240 --> 00:18:03,720 Speaker 3: might be that we get a new Sun. 357 00:18:03,960 --> 00:18:07,600 Speaker 1: But like, that's got to be an extinction level event. 358 00:18:07,840 --> 00:18:10,639 Speaker 1: Even if it works out like a you know, on 359 00:18:10,720 --> 00:18:14,600 Speaker 1: par with taking out the dinosaurs, that couldn't work smooth. 360 00:18:14,640 --> 00:18:16,480 Speaker 1: That wouldn't be good for us. I don't want my 361 00:18:16,560 --> 00:18:17,600 Speaker 1: kids to experience that. 362 00:18:18,520 --> 00:18:21,560 Speaker 3: You know I'm reaching for a sliver of positivity here Elly, 363 00:18:21,920 --> 00:18:23,760 Speaker 3: in very dark times. I need you to work with me, 364 00:18:23,920 --> 00:18:24,399 Speaker 3: work with me. 365 00:18:25,119 --> 00:18:25,280 Speaker 2: You know. 366 00:18:25,359 --> 00:18:27,240 Speaker 1: A friend asked me the other day why I'm so 367 00:18:27,440 --> 00:18:31,919 Speaker 1: relentlessly depressing. So I think you just you picked the 368 00:18:31,960 --> 00:18:35,360 Speaker 1: wrong person to have on your show. I'm sorry. 369 00:18:35,720 --> 00:18:37,520 Speaker 3: Well, you know, if we knew about it far enough 370 00:18:37,560 --> 00:18:40,480 Speaker 3: in advance, and we could build bunkers to survive the 371 00:18:40,560 --> 00:18:43,359 Speaker 3: intervening period where things very bright or very cold, the 372 00:18:43,400 --> 00:18:46,960 Speaker 3: seasons are totally wacko. Then there's a situation where in 373 00:18:46,960 --> 00:18:49,280 Speaker 3: the far future the Earth is in the habitable zone 374 00:18:49,440 --> 00:18:52,600 Speaker 3: of another star, which I think would be an amazing 375 00:18:52,640 --> 00:18:54,800 Speaker 3: premise for a science fiction novel. And I haven't read 376 00:18:54,840 --> 00:18:57,040 Speaker 3: it yet, and I want somebody out there to put 377 00:18:57,080 --> 00:18:59,800 Speaker 3: pen to paper and write me that story and make 378 00:18:59,800 --> 00:19:01,080 Speaker 3: it happy ending for Kelly. 379 00:19:01,720 --> 00:19:07,439 Speaker 1: And that's your billion dollar idea. There we go. We 380 00:19:07,600 --> 00:19:08,880 Speaker 1: just keep throwing them out there. 381 00:19:09,960 --> 00:19:14,480 Speaker 3: That's basically the next Harry Potter, I'm sure. Yeah, Harry 382 00:19:14,480 --> 00:19:16,480 Speaker 3: Potter and the Adventure of the Alternate Earth. 383 00:19:17,280 --> 00:19:17,920 Speaker 1: There you go. 384 00:19:19,119 --> 00:19:21,320 Speaker 3: All right, Well, thank you very much, John for thinking 385 00:19:21,400 --> 00:19:23,399 Speaker 3: about the nature of the universe and how it affects 386 00:19:23,480 --> 00:19:26,560 Speaker 3: life here on Earth and how our future might be 387 00:19:26,600 --> 00:19:30,520 Speaker 3: impacted by visitations from other stars. I hope we answered 388 00:19:30,520 --> 00:19:32,760 Speaker 3: your question, and I hope we inspired everybody out there 389 00:19:32,800 --> 00:19:36,000 Speaker 3: to think about their own questions about the universe. What 390 00:19:36,080 --> 00:19:38,960 Speaker 3: doesn't make sense to you? What physics scenario are you 391 00:19:39,080 --> 00:19:41,680 Speaker 3: wondering about that you can't find the answer to. Please 392 00:19:41,680 --> 00:19:43,600 Speaker 3: write to us. We want to hear from you. Send 393 00:19:43,680 --> 00:19:47,320 Speaker 3: us a message to questions at Danielandjorge dot com. And 394 00:19:47,359 --> 00:19:50,240 Speaker 3: thanks very much Kelly for bringing your relentless optimism to 395 00:19:50,280 --> 00:19:50,919 Speaker 3: the podcast. 396 00:19:52,760 --> 00:19:55,080 Speaker 1: Oh you're welcome. Yeah. I hope we get more questions 397 00:19:55,080 --> 00:19:58,280 Speaker 1: so that our list of reasons to feel existential dread 398 00:19:58,320 --> 00:20:01,120 Speaker 1: can grow and grow and grow and grow. But yeah, 399 00:20:01,119 --> 00:20:02,760 Speaker 1: thanks for having me on the show. It's always a 400 00:20:02,760 --> 00:20:03,160 Speaker 1: good time. 401 00:20:03,600 --> 00:20:06,480 Speaker 3: Wonderful to be in your ear again everyone, and hope 402 00:20:06,520 --> 00:20:14,040 Speaker 3: you hear from us soon. Thanks for tuning in for 403 00:20:14,119 --> 00:20:17,160 Speaker 3: more science and curiosity. Come find us on social media 404 00:20:17,240 --> 00:20:21,760 Speaker 3: where we answer questions and post videos. We're on Twitter, Discord, Insta, 405 00:20:21,880 --> 00:20:25,600 Speaker 3: and now TikTok. Thanks for listening and remember that Daniel 406 00:20:25,640 --> 00:20:29,080 Speaker 3: and Jorge Explain the Universe is a production of iHeartRadio. 407 00:20:29,359 --> 00:20:34,520 Speaker 3: For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple podcasts, 408 00:20:34,640 --> 00:20:37,000 Speaker 3: or wherever you listen to your favorite shows.