WEBVTT - Listener Questions 66 0:00:07.640 --> 0:00:10.800 Hey, Orge, are you preparing your kids for when the 0:00:10.920 --> 0:00:11.960 end times come? 0:00:12.560 --> 0:00:12.760 Oh? 0:00:12.960 --> 0:00:16.760 You mean when bananas go extinct? Or do you mean 0:00:16.800 --> 0:00:17.480 when I retire? 0:00:17.880 --> 0:00:20.439 Yeah, I mean the fall of civilization, when we're all 0:00:20.560 --> 0:00:22.880 listening to podcast in our caves. 0:00:23.800 --> 0:00:25.560 I feel like I've been preparing my whole life. If 0:00:25.560 --> 0:00:29.000 there's a post apocalyptic movie out there, I probably see it. 0:00:29.880 --> 0:00:32.080 Well, then I hope you're teaching your kids some useful skills, 0:00:32.120 --> 0:00:34.920 you know, blacksmithing, martial arts, cartooning. 0:00:35.200 --> 0:00:38.440 Oh yeah, cartooning for sure, that's going to come in handy. 0:00:39.320 --> 0:00:41.440 But you don't think they should learn a particle physics. 0:00:42.360 --> 0:00:44.800 I don't know that anybody's going to be building colliders 0:00:44.840 --> 0:00:46.360 out of sticks and rocks. 0:00:46.720 --> 0:00:49.360 Isn't it fire? Doesn't it fire evolve particles colliding? 0:00:49.600 --> 0:00:52.120 A fire is kind of a chemical accelerator. I suppose 0:00:52.159 --> 0:00:54.200 there must be some collisions, or. 0:00:54.160 --> 0:00:56.600 Are you going to be like, you know, freezing out there, 0:00:56.640 --> 0:00:58.680 and you're gonna be like, oh no, no, sorry, the 0:00:58.760 --> 0:01:00.560 fire is just not fundamental. 0:01:00.080 --> 0:01:04.640 Enough for me. I think I would be hiding in 0:01:04.680 --> 0:01:07.399 my cave eating the last of the world's chocolate reserves. 0:01:08.080 --> 0:01:10.520 Who would that be a useful skill? You could be 0:01:10.560 --> 0:01:14.160 it the world's only chocolate tear. Hopefully the zombies like chocolate. 0:01:15.800 --> 0:01:29.919 Dark chocolate is the world's final currency. 0:01:33.680 --> 0:01:36.200 I am Poorge, my corctoonist and the author of Oliver's 0:01:36.200 --> 0:01:37.040 Great Big Universe. 0:01:37.160 --> 0:01:39.920 Hi, I'm Daniel. I'm a particle physicist and a professor 0:01:39.959 --> 0:01:43.480 at UC Irvine, and I purposely got into particle physics 0:01:43.520 --> 0:01:45.120 because it was useless. 0:01:45.319 --> 0:01:47.319 You're like, how can I make my time here on 0:01:47.360 --> 0:01:48.760 Earth less useful? 0:01:50.640 --> 0:01:53.720 I wasn't so much worried about the positive practical benefits 0:01:53.760 --> 0:01:56.240 as the negative. You know, my parents worked in the 0:01:56.280 --> 0:01:58.880 weapons programs, and I really really didn't want to do 0:01:58.960 --> 0:02:01.320 anything that could be used as the basis of a 0:02:01.360 --> 0:02:01.880 death ray. 0:02:02.200 --> 0:02:05.040 I see, But you could have picked something positively useful, 0:02:07.760 --> 0:02:10.720 like making a chocolate Yeah, there you go, making people happy. 0:02:11.680 --> 0:02:13.600 Well, you know, my dad did retire from the lab 0:02:13.639 --> 0:02:16.680 and then became a blacksmith, so he's definitely got useful 0:02:16.680 --> 0:02:17.880 skills for the end times. 0:02:18.000 --> 0:02:21.920 He became a blacksmith. Wow, was he forging like swords 0:02:22.080 --> 0:02:25.000 or internal combustion engines in your garage? 0:02:25.280 --> 0:02:28.680 Or what swords? Spears? All kinds of stuff? 0:02:28.760 --> 0:02:32.600 Yes, He's like, I want to wait more weapons. 0:02:35.240 --> 0:02:37.320 I wish I were joking more and. 0:02:37.200 --> 0:02:41.880 More direct, but anyways, Welcome to our podcast. Daniel and 0:02:41.960 --> 0:02:45.680 Jorge Explain the Universe, a production of iHeartRadio. 0:02:45.080 --> 0:02:47.960 In which our only weapon is our minds. As we 0:02:48.040 --> 0:02:51.799 tackle the quest of understanding the universe, we go forging 0:02:51.840 --> 0:02:54.360 through all of the craziness that's out there and try 0:02:54.400 --> 0:02:57.040 to weave it all together into an explanation that makes sense. 0:02:57.440 --> 0:02:59.680 We hope that whatever the universe is made out of 0:02:59.680 --> 0:03:02.400 its time, any little basic bits that somehow they're danced 0:03:02.440 --> 0:03:05.919 together can explain everything that we experience in the universe, 0:03:06.080 --> 0:03:08.600 that we can somehow find fundamental laws, and then we 0:03:08.600 --> 0:03:11.400 can also make sense of it all that's right. 0:03:11.440 --> 0:03:14.080 We try to hone our knowledge of signs here and 0:03:14.200 --> 0:03:17.680 try to prepare you for the end times when we'll 0:03:17.680 --> 0:03:19.679 all be looking up at the stars wondering how do 0:03:19.760 --> 0:03:21.880 we all get here? And how do we avoid those 0:03:21.919 --> 0:03:22.840 pesky zombies. 0:03:24.720 --> 0:03:26.720 I guess we should all try to sharpen our minds 0:03:26.760 --> 0:03:28.679 so we can slice our way through these problems. 0:03:28.840 --> 0:03:32.160 Yeah, I'm sure having physics knowledge will be helpful in 0:03:32.200 --> 0:03:37.400 the apocalypse, right, you can, I guess, try to build 0:03:37.400 --> 0:03:39.320 a laser gun to fight the zombies. 0:03:40.280 --> 0:03:42.440 If the zombies assigned a lot of homework problems, then 0:03:42.480 --> 0:03:43.640 I'm definitely there to help. 0:03:45.200 --> 0:03:47.000 Oh, that could be another way to defeat them. You know, 0:03:47.040 --> 0:03:50.120 you give them physics problems that are so tricky that 0:03:50.200 --> 0:03:53.040 their brains explode, and that everyone knows that's how you 0:03:53.080 --> 0:03:53.720 kill zombies. 0:03:54.000 --> 0:04:00.720 Wow. Yes, exactly. Too many into girls. 0:04:01.280 --> 0:04:01.960 Calculus. 0:04:02.040 --> 0:04:09.200 No, you know, Newton definitely believed in zombies. Really, Newton 0:04:09.200 --> 0:04:12.040 definitely believed in some weird stuff. I don't know about zombies, 0:04:12.440 --> 0:04:15.320 but you know, he was an alchemist and he definitely 0:04:15.360 --> 0:04:16.600 was a fan of the arcane. 0:04:17.480 --> 0:04:19.640 Wasn't he really into currencies too? 0:04:20.040 --> 0:04:21.800 Mm hmmm, yeah, exactly. 0:04:21.839 --> 0:04:23.960 At some point became like a coin master or something. 0:04:24.000 --> 0:04:25.599 He was definitely a weird dude. 0:04:25.760 --> 0:04:30.120 Yes, by word, do you mean a genius who basically 0:04:30.120 --> 0:04:31.040 invented science. 0:04:32.440 --> 0:04:34.240 I think that's actually giving him a little bit too 0:04:34.360 --> 0:04:37.280 much credit. But yeah, he invented lots of physics and 0:04:37.640 --> 0:04:40.080 big chunks of math, and I think he would be 0:04:40.120 --> 0:04:43.359 pretty tickled if we could use calculus against the zombies. 0:04:43.720 --> 0:04:45.440 Oh well, I'm sure a lot of people will be 0:04:45.640 --> 0:04:48.680 relieved to learn it's useful for something after all that 0:04:48.720 --> 0:04:49.560 work in high school. 0:04:49.920 --> 0:04:51.719 Yeah, they can integrate it into their lives. 0:04:52.320 --> 0:04:56.359 Oh boy, that was very terrifical joke. But anyways, we 0:04:56.400 --> 0:04:58.040 do like to think about the universe and we try 0:04:58.040 --> 0:05:00.520 to explain it here on the podcast, and sometimes that 0:05:00.600 --> 0:05:02.280 involves answering questions. 0:05:02.839 --> 0:05:05.080 That's right. It's not just Isaac Newton who's thinking about 0:05:05.080 --> 0:05:08.000 the nature of the universe. It's everybody. The goal of 0:05:08.040 --> 0:05:10.440 science is to understand the universe, and that means for 0:05:10.520 --> 0:05:13.599 everybody to figure it out. And that, of course means 0:05:13.600 --> 0:05:15.920 everybody's got to be out there thinking about the universe, 0:05:16.000 --> 0:05:19.240 asking questions, wondering how it all works, and we want 0:05:19.400 --> 0:05:21.680 you to be doing that. We hope that this podcast 0:05:21.880 --> 0:05:25.280 stimulates your curiosity. You hear on the podcast about the 0:05:25.320 --> 0:05:27.240 questions we are asking, but we want to hear about 0:05:27.240 --> 0:05:30.120 the questions you are asking, and then we want to 0:05:30.160 --> 0:05:32.760 answer them. So if you have questions about the nature 0:05:32.800 --> 0:05:35.000 of the universe or something you heard about on the podcast, 0:05:35.080 --> 0:05:38.440 or something you heard about on Gass another podcast, please 0:05:38.520 --> 0:05:42.280 write to me to questions at Danielanjorge dot com. We'll 0:05:42.279 --> 0:05:43.039 clear it up for you. 0:05:43.200 --> 0:05:46.040 Yeah, because it's part of human nature to be asking questions, 0:05:46.120 --> 0:05:49.000 and it's totally fun to ask questions as well, and 0:05:49.080 --> 0:05:51.080 so here in the podcast we sometimes like to answer 0:05:51.200 --> 0:05:53.479 questions that listeners send us, and so to be on 0:05:53.480 --> 0:06:02.560 the podcast, we'll be tackling listener questions number sixty six. 0:06:02.880 --> 0:06:05.279 You have a sixty six related snide comment. 0:06:06.000 --> 0:06:08.479 Only a warning, Daniel. If we keep going, we're going 0:06:08.560 --> 0:06:10.480 to hit listener questions six sixty six. 0:06:11.760 --> 0:06:12.880 Oh, I thought you were going to warn me. But 0:06:13.000 --> 0:06:16.040 listener question sixty nine, where we turn everything upside down. 0:06:17.800 --> 0:06:23.120 I have warned you repeatedly about that milestone, and you 0:06:23.200 --> 0:06:24.240 don't seem very concerned. 0:06:24.360 --> 0:06:26.360 I'm mindlessly barreling towards it. 0:06:27.400 --> 0:06:30.240 Well, just maybe we'll record it, but then we'll censor it. 0:06:32.200 --> 0:06:34.320 Maybe we'll just skip it. We'll go straight to seventy. 0:06:34.600 --> 0:06:36.560 Yeah, seventy isn't new sixty nine. 0:06:37.000 --> 0:06:40.640 Nobody says that. Don't make that a thing. 0:06:41.560 --> 0:06:43.560 I don't care if other people say, oh I see, 0:06:43.839 --> 0:06:45.640 but yeah. We do like to answer questions here on 0:06:45.680 --> 0:06:48.039 the podcast that listeners said this, and so today we 0:06:48.120 --> 0:06:52.480 have three awesome questions. They are about galaxies colliding but 0:06:52.640 --> 0:06:57.000 extreme forces, and about the air we breathe. So let's 0:06:57.040 --> 0:07:01.200 jump right in. Our first question comes from Pedra from Boston. 0:07:01.880 --> 0:07:05.080 Hi, Daniel and jre I routinely hear not to worry 0:07:05.080 --> 0:07:08.920 about the impending collision between our galaxy and the Andromeda galaxy, 0:07:09.560 --> 0:07:12.440 since the space between the stars within each galaxy is 0:07:12.520 --> 0:07:16.520 so great there won't be any direct collisions. However, on 0:07:16.560 --> 0:07:19.200 some of the podcast episodes, it seems as though the 0:07:19.320 --> 0:07:22.880 orbital stability of the planets in our Solar system isn't 0:07:22.960 --> 0:07:27.280 all that great. For example, some planets may have traded places, 0:07:27.640 --> 0:07:31.880 while other planets could have been captured or ejected. So, really, 0:07:32.120 --> 0:07:35.160 which argument wins? Do I need to tell my descendants 0:07:35.200 --> 0:07:38.160 to start worrying about it in four point five billion years, 0:07:38.840 --> 0:07:40.800 I really want them to see the Sun become a 0:07:40.840 --> 0:07:41.480 red giant. 0:07:41.760 --> 0:07:42.960 Thanks for the great podcast. 0:07:43.440 --> 0:07:48.440 All right, interesting question. Basically, should we be worried four 0:07:48.480 --> 0:07:49.680 and a half billion years from now? 0:07:50.120 --> 0:07:54.520 Yeah, exactly if we're all alive, or should the zombies 0:07:54.600 --> 0:07:57.640 that have succeeded us, should they be worried about. 0:07:57.400 --> 0:08:00.800 What's going to happen? I think that's the best part 0:08:00.800 --> 0:08:02.480 of being a zombies is you don't have to worry 0:08:02.480 --> 0:08:03.080 about anything. 0:08:03.640 --> 0:08:05.320 As long as you've killed off all the people who 0:08:05.400 --> 0:08:07.040 might assign you homework problems, you're. 0:08:06.920 --> 0:08:08.920 Fine, man, I wou think the best part of being 0:08:08.920 --> 0:08:10.520 a zombies you can just turn your brain off. 0:08:10.640 --> 0:08:12.880 Don't you need to protect it from exploding? Right? Isn't 0:08:12.880 --> 0:08:14.320 that the kryptonite of zombies? 0:08:14.640 --> 0:08:16.600 Well, I think fire also kills zombies. 0:08:16.640 --> 0:08:19.480 Oh boy, wow, Yeah, I'm so glad you've been doing 0:08:19.480 --> 0:08:20.000 this research. 0:08:20.120 --> 0:08:21.680 I'm glad the people I'll be hanging out with know 0:08:21.680 --> 0:08:22.880 how to make a fire. 0:08:26.160 --> 0:08:28.800 But I think Petra's question is really touching on two 0:08:28.840 --> 0:08:31.800 things we hear about a lot in science. One that 0:08:31.880 --> 0:08:35.360 our galaxy is colliding with another galaxy and the other 0:08:35.480 --> 0:08:37.800 that our solar system is kind of fragile, that the 0:08:37.920 --> 0:08:41.400 orbits are not really that stable, and so he's worried 0:08:41.720 --> 0:08:44.080 that even if stars are pretty dilute in the galaxy, 0:08:44.760 --> 0:08:46.440 would our solar system get upset? 0:08:47.720 --> 0:08:51.280 Basically, what's going to happen when our galaxy collides with Andromeda? 0:08:51.400 --> 0:08:51.520 Like? 0:08:51.640 --> 0:08:52.440 Will be safe? 0:08:52.480 --> 0:08:52.560 Like? 0:08:52.679 --> 0:08:54.800 Is nothing going to happen to us? Or should we 0:08:55.080 --> 0:08:58.600 be concerned that maybe our plant might get disrupted and 0:08:58.679 --> 0:08:59.720 thrown out into space? 0:09:00.080 --> 0:09:02.840 Yeah, it's definitely a valid concern, and it touches on 0:09:02.880 --> 0:09:05.040 a lot of really interesting physics. And the first thing 0:09:05.080 --> 0:09:08.280 I want to talk about is why Andrama is going 0:09:08.360 --> 0:09:09.880 to collide with the Milky Way, because I get a 0:09:09.920 --> 0:09:13.040 lot of questions about exactly this. People hear us talking 0:09:13.080 --> 0:09:15.640 about how the universe is expanding and space is being 0:09:15.720 --> 0:09:19.200 created between galaxies, and then they hear us talking about 0:09:19.240 --> 0:09:21.600 how Andromeda is coming towards us and say, how does 0:09:21.640 --> 0:09:24.640 that make any sense? Why isn't space expanding between us 0:09:24.679 --> 0:09:28.160 and Andromeda and pushing it further and further away? And 0:09:28.240 --> 0:09:30.959 so first we should try to reconcile that apparent contradiction. 0:09:31.320 --> 0:09:31.480 Mm. 0:09:33.120 --> 0:09:36.760 Yeah, because we talked about like how because dark energy 0:09:36.800 --> 0:09:39.800 is expanding the universe, the galaxies out there getting further 0:09:39.840 --> 0:09:42.120 and further away from us, But we've also talked about 0:09:42.120 --> 0:09:44.800 how Drama is in a collision course with our galaxy. 0:09:45.080 --> 0:09:48.120 Yeah, And the answer comes down to distances, and dark 0:09:48.200 --> 0:09:51.400 energy is something that gets more powerful for distant objects. 0:09:51.559 --> 0:09:54.839 It's basically like a chunk of space grows a little bit, 0:09:54.880 --> 0:09:57.720 and so more chunks of space are growing more. So 0:09:57.800 --> 0:10:00.240 a little tiny chunk of space is hardly growing, but 0:10:00.320 --> 0:10:04.480 a vast distance between our galaxy cluster and a really 0:10:04.520 --> 0:10:08.000 distant other galaxy cluster that's kind of growing a lot. 0:10:08.360 --> 0:10:11.280 And gravity is the opposite. Gravity gets weaker with distance. 0:10:11.280 --> 0:10:14.720 As things get further apart, gravity fades away. So for 0:10:14.760 --> 0:10:17.160 stuff that's really close together, like the Earth and the Sun, 0:10:17.600 --> 0:10:21.560 or even our galaxy in the neighboring galaxy, gravity wins 0:10:21.600 --> 0:10:24.720 over dark energy. Things that are really really far apart, 0:10:24.760 --> 0:10:29.400 like clusters of galaxies, not individual galaxies. Dark energy is winning, 0:10:29.800 --> 0:10:31.680 And most of the universe is far apart from most 0:10:31.720 --> 0:10:35.079 of the universe, so mostly things are expanding away from 0:10:35.080 --> 0:10:38.280 each other, but in little neighborhoods like our cluster of galaxy, 0:10:38.440 --> 0:10:41.640 stuff is still getting pulled together by gravity. So gravity 0:10:41.679 --> 0:10:44.080 is the reason the Milky Way and Andromeda will collide 0:10:44.400 --> 0:10:45.439 in a few billion years. 0:10:45.960 --> 0:10:47.800 Is it gravity or is it just that we just 0:10:47.840 --> 0:10:50.960 happen to be in a course that intercepts the course 0:10:51.000 --> 0:10:55.160 of Andromeda, Like is Indrameda really being attracted to our galaxy? 0:10:55.600 --> 0:10:57.960 I mean, obviously it is, But is it really significant 0:10:58.440 --> 0:11:00.720 to call it the main reason we're going to collide 0:11:00.760 --> 0:11:01.120 with it? 0:11:01.120 --> 0:11:03.200 It definitely is. I mean, the Milky Way Andromeda are 0:11:03.240 --> 0:11:06.520 part of a cluster of galaxies, and that cluster exists 0:11:06.559 --> 0:11:09.400 because of gravity, so it's holding it together and the 0:11:09.440 --> 0:11:12.040 galaxies are sort of sloshing around. It's not guaranteed at 0:11:12.080 --> 0:11:14.640 any moment that they're going to hit each other, but 0:11:14.760 --> 0:11:17.400 it's gravity that holds them together, that's pulling them together. 0:11:17.760 --> 0:11:20.679 It's sort of like asking if a comet falls towards 0:11:20.679 --> 0:11:23.040 the Sun and it collides to the Sun, why is 0:11:23.040 --> 0:11:25.400 that Well, it's definitely because of the gravity. That doesn't 0:11:25.400 --> 0:11:27.840 mean that every comet does collide with the Sun. Gravity 0:11:27.920 --> 0:11:30.040 is not omnipotent. Sometimes comets go around the back of 0:11:30.120 --> 0:11:32.280 the Sun in the same way in the local cluster. 0:11:32.559 --> 0:11:35.160 Not every galaxy is gonna collide with every other galaxy 0:11:35.200 --> 0:11:38.400 as soon as possible. Sometimes they pass around each other. 0:11:38.760 --> 0:11:40.840 But it is gravity that's pulling these two together. 0:11:41.400 --> 0:11:42.840 Well, I guess what I mean is like if you 0:11:42.920 --> 0:11:45.839 have to asteroids, for example, in the Solar System, and 0:11:45.880 --> 0:11:48.240 they're gonna collide with each other. I mean, sure, they're 0:11:48.280 --> 0:11:50.800 in the Solar System together because of the gravity well 0:11:50.840 --> 0:11:52.800 of the Sun, but the fact that they're colliding with 0:11:52.840 --> 0:11:55.520 each other as opposed to not colliding, it's mostly just 0:11:55.600 --> 0:11:57.800 kind of look right, Yeah. 0:11:57.600 --> 0:12:01.520 It's gravity plus chance. It's possible a cluster where galaxies 0:12:01.640 --> 0:12:05.800 like ours and Andromeda don't collide until later on. Eventually 0:12:05.840 --> 0:12:07.880 everything is going to collide and it's all going to 0:12:07.920 --> 0:12:11.080 collapse into one supermassive black hole. So it's really just 0:12:11.120 --> 0:12:11.880 a waiting game. 0:12:12.120 --> 0:12:13.800 But the collision that's going to happen in four and 0:12:13.840 --> 0:12:18.040 a half billion years, that's basically luck. Right. It's not 0:12:18.080 --> 0:12:20.440 like it's inevitable. Like if our galaxy was moving a 0:12:20.440 --> 0:12:22.920 few degrees in another direction, or to the right or 0:12:22.960 --> 0:12:25.360 to the left, we wouldn't be colliding with Andromeda, would we. 0:12:25.679 --> 0:12:27.800 Yeah, that's right. If you change the initial conditions, that 0:12:27.800 --> 0:12:30.640 collision might happen later. It also might happen earlier, Right, 0:12:30.960 --> 0:12:32.720 it could be that we're lucky we got this far 0:12:32.760 --> 0:12:35.240 without colliding with Andromeda. So yeah, the whole system is 0:12:35.320 --> 0:12:37.880 very chaotic, but it is gravity. But gravity is really 0:12:37.960 --> 0:12:39.200 the only force at play here. 0:12:40.600 --> 0:12:42.679 And so the reason we're worried about Andromeda and not 0:12:42.800 --> 0:12:45.920 other galaxies is because the other galaxies are further away, 0:12:46.200 --> 0:12:49.000 and those are definitely moving away from us because of 0:12:49.080 --> 0:12:52.360 dark energy, or are some of them potentially getting closer 0:12:52.400 --> 0:12:52.679 to us. 0:12:52.960 --> 0:12:56.560 Everything in our galaxy cluster is gravitationally bound, which means 0:12:56.559 --> 0:12:59.200 it has enough gravity to hold itself together and resist 0:12:59.280 --> 0:13:02.760 the pull of dark energy, and galaxy clusters are like 0:13:02.800 --> 0:13:06.160 the biggest thing that have that property. Anything that's larger 0:13:06.200 --> 0:13:09.440 than that, what we call a supercluster, is probably too 0:13:09.480 --> 0:13:12.240 big and too spread out for gravity to hold itself together, 0:13:12.280 --> 0:13:14.240 and dark energy is going to win. So that's sort 0:13:14.240 --> 0:13:17.120 of the tipping point. So anything that's in our galaxy 0:13:17.120 --> 0:13:20.400 cluster is eventually going to collapse into one big, super 0:13:20.440 --> 0:13:23.120 massive black hole. And we're talking very very far in. 0:13:23.120 --> 0:13:26.760 The future unless dark energy changes, right, Yes, like if 0:13:26.800 --> 0:13:30.080 it accelerates, then it's going to get a little more crowded, 0:13:30.120 --> 0:13:33.079 but or if it like weekends, things might get a 0:13:33.080 --> 0:13:33.679 little room hear. 0:13:33.760 --> 0:13:36.199 Yeah, I think it's the opposite. If dark energy accelerates, 0:13:36.520 --> 0:13:38.640 then even our galaxy cluster is going to get torn 0:13:38.679 --> 0:13:41.719 apart because it becomes more powerful than gravity. We talked 0:13:41.760 --> 0:13:43.959 about that once on the podcast. There's even a theory 0:13:44.000 --> 0:13:46.680 of like phantom dark energy, where dark energy gets so 0:13:46.760 --> 0:13:50.200 powerful that it tears apart atoms and even protons. And 0:13:50.280 --> 0:13:53.960 if dark energy weakens, then gravity wins over larger distances 0:13:54.000 --> 0:13:56.240 and it might gather together even superclusters. 0:13:56.520 --> 0:13:58.280 Right, that's what I meant. I meant the opposite of what. 0:13:58.240 --> 0:14:00.960 I said, But you're definitely right, and the conceptual part, 0:14:00.960 --> 0:14:03.280 which is that we don't know what dark energy is 0:14:03.440 --> 0:14:05.240 or what it's going to do, and we can't really 0:14:05.240 --> 0:14:08.360 predict it. So this is assuming a naive extrapolation of 0:14:08.440 --> 0:14:10.600 dark energy, which is basically all we can do at 0:14:10.600 --> 0:14:10.960 this point. 0:14:11.120 --> 0:14:13.319 All Right, so we're in a collision course with Andromeda. 0:14:13.960 --> 0:14:15.640 What's going to happen when we collide? 0:14:15.960 --> 0:14:18.199 So when we collide with Andromeda, there's a bunch of 0:14:18.240 --> 0:14:20.800 different components of the galaxy, and you really need to 0:14:20.840 --> 0:14:23.520 think about each of them individually because they all have 0:14:23.600 --> 0:14:26.680 different behavior. So, for example, the gas and the dust 0:14:27.000 --> 0:14:28.760 that are in the two galaxies, those are going to 0:14:28.800 --> 0:14:30.800 collide and you're going to get all sorts of dramatic stuff. 0:14:30.920 --> 0:14:33.360 It's going to see the creation of lots of new stars, 0:14:33.640 --> 0:14:36.320 which would be really exciting. But the stars themselves are 0:14:36.400 --> 0:14:38.240 very different from the gas and the dust. Right the 0:14:38.240 --> 0:14:40.520 gas in the dust is very spread out, it's definitely 0:14:40.560 --> 0:14:42.840 going to smash into the other stuff. But stars are 0:14:42.920 --> 0:14:45.360 very different from gas and dust. They're not as spread out. 0:14:45.400 --> 0:14:48.080 They're tiny, and they're clumpy, and they're really really dilute. 0:14:48.680 --> 0:14:51.920 So when stars approach other stars, it's very hard for 0:14:51.960 --> 0:14:55.320 them to actually collide because space is really really big, 0:14:55.360 --> 0:14:57.320 and the stars are really really far apart. 0:14:58.480 --> 0:15:00.520 I guess how far apart are they? Like how far 0:15:00.600 --> 0:15:01.720 is there our year's neighbor? 0:15:01.960 --> 0:15:05.240 So our nearest neighbor is light years away, right, the 0:15:05.280 --> 0:15:08.000 closest star to us is almost four light years away, 0:15:08.480 --> 0:15:10.880 and the Sun is the tiny fraction of a light 0:15:10.960 --> 0:15:13.480 year wide. I mean, if you shrink, for example, the 0:15:13.520 --> 0:15:15.160 Sun down to the size of a tennis ball that 0:15:15.160 --> 0:15:17.720 you could hold in your hand, then the nearest neighbor 0:15:17.800 --> 0:15:20.640 star would be four or five thousand miles away. 0:15:21.160 --> 0:15:24.680 WHOA, that's like on the other side of the Atlantic kind. 0:15:24.520 --> 0:15:28.040 Of yeah, exactly. So imagine you're throwing a tennis ball 0:15:28.120 --> 0:15:30.320 and somebody on the other side of the ocean is 0:15:30.360 --> 0:15:32.800 throwing a tennis ball. What are the chances that they're 0:15:32.800 --> 0:15:36.560 going to hit each other over the ocean? Like basically zero? 0:15:37.520 --> 0:15:41.800 But I guess how wide is the sphere of influence 0:15:41.800 --> 0:15:44.240 of something like the sun? Like how close do you 0:15:44.240 --> 0:15:46.320 need to get to it before you feel it's gravity? 0:15:46.560 --> 0:15:49.640 Yeah? Exactly, good point, because we're not actually just interested 0:15:49.680 --> 0:15:52.880 in like a collision where like the two stars really 0:15:52.920 --> 0:15:55.800 touch each other and merge and become one. Stars can 0:15:55.840 --> 0:15:58.360 pull in each other if they're even near each other. Right, 0:15:58.600 --> 0:16:01.360 And that's really what Petro's quest is about, is how 0:16:01.360 --> 0:16:03.760 close does the star need to get to distort our 0:16:03.760 --> 0:16:07.360 star or distort the orbit of stuff around the star? Right? 0:16:07.440 --> 0:16:10.600 Because near misses can destabilize things, and we know that 0:16:10.640 --> 0:16:13.920 already in our galaxy, because other stars are moving relative 0:16:13.920 --> 0:16:16.240 to the Sun. Sometimes they come closer, sometimes they come 0:16:16.320 --> 0:16:19.360 further away, and that can distort the orbits of stuff 0:16:19.400 --> 0:16:22.600 in our Solar system. So it's not a clear, crisp answer. 0:16:22.600 --> 0:16:25.880 It's not like there's a certain distance within which something 0:16:25.920 --> 0:16:28.960 happens and out of which nothing happens. It's gradual, Right. 0:16:29.000 --> 0:16:31.480 The closer it comes, the greater the gravitational distortion. 0:16:32.640 --> 0:16:36.080 But I guess maybe it depends on how unstable our 0:16:36.200 --> 0:16:40.680 orbit is or how fragile our orbit is. Do you 0:16:40.680 --> 0:16:44.520 have a sense of how precarious are a path around 0:16:44.560 --> 0:16:47.280 the Sun is? Like if I bring in another Sun, 0:16:48.080 --> 0:16:51.520 I don't know, a few million miles away, is it 0:16:51.560 --> 0:16:53.240 going to affect us and kick us out of the 0:16:53.280 --> 0:16:55.880 Solar system or maybe cause us to fall into the Sun, 0:16:56.000 --> 0:16:57.000 or are we going to be Okay? 0:16:57.320 --> 0:17:00.560 Yeah, it's a good question. The Earth is pretty stable, 0:17:01.040 --> 0:17:03.120 like just the Earth in the Solar System is a 0:17:03.120 --> 0:17:05.639 pretty stable orbit. There's a lot of stuff going on 0:17:05.720 --> 0:17:08.679 that's going to influence the Earth's orbit that makes its 0:17:08.880 --> 0:17:11.720 orbit change. For example, like the Sun is losing mass, 0:17:11.760 --> 0:17:15.080 so it's gravity shrinks. The Sun is also pushing on 0:17:15.119 --> 0:17:17.159 the Earth, not just pulling on it with gravity, but 0:17:17.200 --> 0:17:20.440 its wind pushes on the Earth. There's effects of Jupiter, 0:17:21.080 --> 0:17:24.919 there's gravitational radiation. But you're right, the biggest wild card 0:17:25.040 --> 0:17:27.960 are like things from outside the Solar System. And this 0:17:28.040 --> 0:17:30.280 is something we've thought about, not just in the case 0:17:30.320 --> 0:17:33.679 of another galaxy, but again just stuff in our Solar system. So, 0:17:33.720 --> 0:17:36.840 for example, there is a star it's called Glease seven 0:17:36.800 --> 0:17:39.800 to ten that we've been tracking, and we predict that 0:17:39.840 --> 0:17:43.320 it's gonna come kind of close to our star. It's 0:17:43.320 --> 0:17:46.480 gonna come within one twenty fifth of the distance to 0:17:46.600 --> 0:17:51.760 Proxima Centauri. So Proximus Centauri is four light years away, 0:17:52.280 --> 0:17:54.119 and so this is gonna come like an eighth of 0:17:54.160 --> 0:17:56.120 a light year away from our star. 0:17:56.560 --> 0:17:58.480 Oh wait, wait, wait, so this is a star that's 0:17:58.520 --> 0:18:01.080 gonna come within one twenty fifth of the nearest star. Yeah, 0:18:01.240 --> 0:18:03.480 would it become the nearest star if it's coming close 0:18:03.520 --> 0:18:04.040 to us. 0:18:04.200 --> 0:18:06.840 Yeah, that's just for scale, our current nearest stars for 0:18:07.080 --> 0:18:09.640 light years away. This one's going to come within one 0:18:09.720 --> 0:18:13.480 twenty fifth of that distance again in the far far future. 0:18:13.920 --> 0:18:16.200 How far in the future, in about one and a 0:18:16.240 --> 0:18:17.560 half million years. 0:18:18.000 --> 0:18:20.679 Oh, that's pretty soon cosmically speaking. 0:18:21.119 --> 0:18:24.560 Yeah, it's a lot of generations to survive between now 0:18:24.560 --> 0:18:26.760 and then. But yeah, that's not far away, and it's 0:18:26.800 --> 0:18:29.360 definitely a lot sooner than when the Milky Way collides 0:18:29.400 --> 0:18:30.399 with Andromeda. 0:18:30.440 --> 0:18:32.920 And this is a star that's like traveling through space 0:18:33.080 --> 0:18:37.000 relative to us, or are we traveling close to it? 0:18:37.440 --> 0:18:39.240 You know what I mean? Like, is this an anomaly 0:18:39.440 --> 0:18:42.280 or in our quiet neighborhood or is it all part 0:18:42.280 --> 0:18:43.879 of the movement of the stars. 0:18:44.160 --> 0:18:46.359 It's part of all the movement of the stars around 0:18:46.400 --> 0:18:48.359 the center of the galaxy. You know, all the stars 0:18:48.400 --> 0:18:51.520 are orbiting the center and they orbit at different velocities. Also, 0:18:51.560 --> 0:18:53.560 the stars are moving up and down. They're sort of 0:18:53.560 --> 0:18:57.159 like wiggling through the plane of the galaxy. And so 0:18:57.200 --> 0:19:00.520 the stars that are in our immediate neighborhood change over 0:19:00.600 --> 0:19:03.000 millions of years as these stars sort of swim through 0:19:03.040 --> 0:19:06.320 the lazy river differently. So this is a totally normal 0:19:06.400 --> 0:19:07.240 thing to happen. 0:19:07.760 --> 0:19:09.760