WEBVTT - Has our solar system lost any planets? 0:00:08.480 --> 0:00:10.680 Hey, Daniel, what pets do you have these days? 0:00:10.800 --> 0:00:13.119 Oh, we just have our rescue dog, Peppito. 0:00:14.080 --> 0:00:16.680 Haven't you had other pets in the past, like rodents. 0:00:17.680 --> 0:00:19.680 We did have rats for a time, and we actually 0:00:19.680 --> 0:00:20.800 had cats before that. 0:00:21.320 --> 0:00:23.680 Oh what happened Pepito? 0:00:23.880 --> 0:00:29.040 Ate them? No, we've never had a pet eat another pet. 0:00:29.080 --> 0:00:30.520 We've only lost them to old age. 0:00:30.840 --> 0:00:33.240 Old age. All that dark chocolate and big goods in 0:00:33.280 --> 0:00:35.520 your house just did them in with the heart attack. 0:00:37.440 --> 0:00:40.320 We don't feed dark chocolate at the dog, but everybody 0:00:40.360 --> 0:00:42.200 does eat pretty well at our house. 0:00:42.800 --> 0:00:44.680 Unless you like white chocolate, then your starved. 0:00:44.840 --> 0:00:46.560 You know. If that's the reason you run away from home, 0:00:46.640 --> 0:00:48.479 then maybe you never were really a white sun. 0:00:48.640 --> 0:00:50.440 Wait, if you don't like white chocolate, you're not a 0:00:50.479 --> 0:00:53.520 white son. It sounds like a white lie. 0:00:53.720 --> 0:01:10.280 I have a dark secret. Hi. 0:01:10.280 --> 0:01:12.560 I am Poor hammy cartoonists and the author of Oliver's 0:01:12.600 --> 0:01:13.600 Great Big Universe. 0:01:13.880 --> 0:01:17.119 Hi. I'm Daniel. I'm a particle physicist and a professor 0:01:17.200 --> 0:01:20.280 at UC Irvine, and I will not waiver in my 0:01:20.400 --> 0:01:21.440 campaign for dark. 0:01:21.319 --> 0:01:25.520 Chocolate, Dark chocolate, dark matter. You're just a very dark physicist. 0:01:27.720 --> 0:01:29.440 I'm trying to bring light to the world at the 0:01:29.480 --> 0:01:32.319 same time as exposed all the dark secrets of the universe. 0:01:32.680 --> 0:01:35.679 Oh, you're trying to expose dark matter. I thought you 0:01:35.720 --> 0:01:37.600 were all about letting the universe. 0:01:37.240 --> 0:01:40.560 Be Absolutely not. I do not believe in universe privacy. 0:01:40.680 --> 0:01:42.080 You're like the universe paparazzi. 0:01:42.959 --> 0:01:45.080 That's exactly right, except I'm not selling it to the 0:01:45.160 --> 0:01:47.520 national inquirer. I'm just publishing papers. 0:01:47.720 --> 0:01:52.520 Well, your buyer is the cosmological inquirer, the human inquirer. 0:01:55.120 --> 0:01:56.680 Inquiring brains want to know. 0:01:57.160 --> 0:01:59.360 Yeah, do you stand outside their home, like, Hey, dark 0:01:59.400 --> 0:02:02.640 matter over here, over here snapping pictures? 0:02:03.040 --> 0:02:05.240 If I knew where dark matter lived, I would definitely 0:02:05.280 --> 0:02:06.800 go there with my dark matter camera. 0:02:06.840 --> 0:02:09.040 I thought dark matter was all around us. It lives 0:02:09.080 --> 0:02:13.079 in us and within us. It surrounds us and binds 0:02:13.080 --> 0:02:13.919 the galaxy together. 0:02:14.160 --> 0:02:16.720 You're absolutely right, it's everywhere. We just don't know how 0:02:16.800 --> 0:02:17.680 to take a picture of it. 0:02:17.919 --> 0:02:20.400 But anyways, welcome to our podcast, Daniel and Jorge Explain 0:02:20.480 --> 0:02:23.240 the Universe, a production of iHeartRadio. 0:02:22.639 --> 0:02:25.800 In which we join our inquiring minds with yours to 0:02:25.960 --> 0:02:29.280 wonder together about the nature of the universe, to think 0:02:29.320 --> 0:02:33.040 deeply about how everything comes together to make the cosmos 0:02:33.040 --> 0:02:35.639 and the night sky that we appreciate to think about 0:02:35.639 --> 0:02:38.880 how the tiniest little particles and the most massive black 0:02:38.880 --> 0:02:41.919 holes shape the very world we live in, and whether 0:02:42.040 --> 0:02:43.600 it has always looked this way. 0:02:43.680 --> 0:02:46.280 That's right. We satisfy our curiosity for stars and what 0:02:46.320 --> 0:02:48.600 they're doing with their lives, and we take pictures and 0:02:48.680 --> 0:02:51.760 also sound recordings of what's out there in the universe 0:02:51.800 --> 0:02:54.239 and what's going on to maybe get a clue about 0:02:54.280 --> 0:02:55.280 how it all works. 0:02:55.360 --> 0:02:57.639 We'd like to figure out the fundamental nature of the 0:02:57.720 --> 0:03:00.680 universal laws that everything follows. But I also like to 0:03:00.720 --> 0:03:04.200 know the story of the universe. What happened, How did 0:03:04.280 --> 0:03:07.200 we end up where we are? How long have things 0:03:07.280 --> 0:03:09.640 looked this way for? How long can we rely on 0:03:09.720 --> 0:03:11.960 things to look this way? Do we live in a 0:03:12.000 --> 0:03:14.560 momentary blip of the universe or is this a long 0:03:14.680 --> 0:03:15.360 term trend? 0:03:15.639 --> 0:03:17.760 Yeah, looking at our past is a way to look 0:03:17.800 --> 0:03:19.960 into our future. We can try to deduce. But the 0:03:20.040 --> 0:03:22.280 rules of the universe are and what they might mean 0:03:22.320 --> 0:03:24.320 for us in the deep future? What is going to 0:03:24.360 --> 0:03:26.720 be the future of humanity here in our solar system? 0:03:26.840 --> 0:03:29.040 Can we call this our home for the next few 0:03:29.040 --> 0:03:29.680 billion years? 0:03:31.480 --> 0:03:32.919 Are you not planning to move out of that house 0:03:32.919 --> 0:03:34.800 for a few billion years, so your kids can always 0:03:34.800 --> 0:03:36.840 come home and their kids and their kids and their kids. 0:03:36.880 --> 0:03:38.880 Well, we're kind of just squatting in this solar system, 0:03:38.960 --> 0:03:41.280 right like we just popped in here, started living here. 0:03:41.640 --> 0:03:44.920 We didn't ask if anyone owned these planets. What if 0:03:44.960 --> 0:03:46.760 the real owners come back when they they're like, what 0:03:46.960 --> 0:03:49.400 is going on here? Call pest control. 0:03:50.440 --> 0:03:52.200 Don't we have some sort of like solar B and 0:03:52.200 --> 0:03:57.520 B contract squatter rights. Maybe exactly after one hundred million years, 0:03:57.560 --> 0:04:00.200 we're officially allowed to call ourselves the owners. It's a 0:04:00.200 --> 0:04:02.800 good question how long things have looked this way. When 0:04:02.840 --> 0:04:04.640 you look by the night guy, you expect to see 0:04:04.680 --> 0:04:07.120 basically the same stars as you did a year ago, 0:04:07.240 --> 0:04:09.440 and you know that you're looking at roughly the same 0:04:09.520 --> 0:04:12.600 stars that Newton looked at, and the Egyptians looked at 0:04:12.640 --> 0:04:15.880 and the Sumerians looked at thousands of years ago. But 0:04:15.960 --> 0:04:18.320 the Solar system operates on a very different kind of 0:04:18.360 --> 0:04:21.919 timescale than your life or even human civilization. And in 0:04:22.000 --> 0:04:24.720 fast forward things don't seem so stable. They seem quite 0:04:24.839 --> 0:04:26.240 chaotic and dynamic. 0:04:26.600 --> 0:04:28.359 Yeah, when we were all kids, we learned in school 0:04:28.360 --> 0:04:30.400 about the different planets in our solar system and how 0:04:30.440 --> 0:04:33.279 many of there are. And that's basically the same story 0:04:33.279 --> 0:04:35.520 that our kids are learning in school as well, right, Like, 0:04:35.560 --> 0:04:38.000 it hasn't really changed so much, except maybe for Pluto. 0:04:39.320 --> 0:04:41.800 We of course change what we mean by a planet 0:04:42.080 --> 0:04:45.120 and make up new categories all the time. But you're right, 0:04:45.160 --> 0:04:48.120 the stuff that's out there that we're seeing, whatever name 0:04:48.160 --> 0:04:51.120 we give it, hasn't changed in our lifetime or in 0:04:51.160 --> 0:04:52.560 our grandparents' lifetime. 0:04:52.760 --> 0:04:54.000 Yeah, And so I guess you kind of get the 0:04:54.080 --> 0:04:56.839 sense that maybe it will never change, you know, you 0:04:56.920 --> 0:04:59.599 sort of memorize these facts and these things and think 0:04:59.600 --> 0:05:02.040 that maybe it's going to be like that forever. But actually, 0:05:02.160 --> 0:05:04.040 if you look at the grand scale of the Solar 0:05:04.040 --> 0:05:07.279 System and the universe in or galaxy, things are rapidly changing. 0:05:07.320 --> 0:05:08.800 If you look at it from that point of view. 0:05:08.839 --> 0:05:10.600 If the Solar system changes, do you think we all 0:05:10.600 --> 0:05:12.440 have to go back to elementary school to learn a 0:05:12.440 --> 0:05:13.040 new mnemonic? 0:05:13.200 --> 0:05:15.240 Oh, there's a mnemonic. I didn't grow up yours. I 0:05:15.279 --> 0:05:21.040 don't know what do you use? Obviously the mnemonic did 0:05:21.080 --> 0:05:22.200 it work because you don't remember it. 0:05:24.000 --> 0:05:26.000 There's a lot of mnemonics to help you memorize the 0:05:26.080 --> 0:05:29.320 order of the planets. One of them is my very 0:05:29.440 --> 0:05:36.720 easy method just speeds up nothing. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Urinus, Neptune. 0:05:36.880 --> 0:05:40.159 Whoa, that is so not kit friendly. How many kids 0:05:40.320 --> 0:05:42.120 use methods and have methods? 0:05:42.200 --> 0:05:44.080 The history of them is actually really funny. There's ones 0:05:44.080 --> 0:05:47.719 from the fifties that go like men very easily make jugs, 0:05:47.800 --> 0:05:48.719 serve useful needs. 0:05:48.720 --> 0:05:52.440 Perhaps, Oh man, I wonder why we'd stopped using that one. 0:05:52.920 --> 0:05:55.760 And then a more recent one says, my very energetic 0:05:55.760 --> 0:05:58.159 mother jumps skateboards under nana's patio. 0:05:58.320 --> 0:06:00.159 Oh, there you go. That's a pretty good one, and 0:06:00.279 --> 0:06:01.919 true as well for some people. 0:06:01.920 --> 0:06:05.719 I'm sure my very educated mother just served us notches. 0:06:06.040 --> 0:06:07.560 Oh that's an even tastier. 0:06:07.160 --> 0:06:11.320 One, exactly. But the point is that though these things 0:06:11.360 --> 0:06:14.599 have seemed stable for a long time, it's not necessarily 0:06:14.640 --> 0:06:16.200 true that they always will be. 0:06:16.360 --> 0:06:18.400 Yeah, things are always changing, And in fact, you can 0:06:18.440 --> 0:06:21.640 ask the question of whether our solar SYSM had more 0:06:21.720 --> 0:06:22.920 planets in the past. 0:06:23.160 --> 0:06:25.640 It might be that the planets we know today are 0:06:25.720 --> 0:06:29.120 not all the planets that have ever orbited our star. 0:06:29.240 --> 0:06:31.760 And if we had more, what happened to them? So 0:06:31.839 --> 0:06:39.159 today on the podcast will be tackling the question has 0:06:39.240 --> 0:06:43.480 our Solar System lost any planets? That just seems kind 0:06:43.480 --> 0:06:45.880 of irresponsible there. How can you lose a whole planet? 0:06:47.320 --> 0:06:49.000 I mean I had it in my hands and then 0:06:49.040 --> 0:06:51.480 I put my keys down and the last place. 0:06:51.440 --> 0:06:54.240 Remember having that planet was on top of the dog. 0:06:56.000 --> 0:06:57.840 Blamed the dog. Huh, that's the first thing. 0:06:58.640 --> 0:07:01.360 The dog ate my planet. Classic excuse. 0:07:02.040 --> 0:07:04.600 Or maybe it just went rogue because it needed to 0:07:04.640 --> 0:07:07.440 find a white chocolate friendly Solar system. You know, maybe 0:07:07.480 --> 0:07:08.520 it just didn't fit in here. 0:07:09.000 --> 0:07:12.640 It just rebelled against your tyranny of trying to dictate 0:07:12.680 --> 0:07:14.680 what kind of chocolate people should eat or feel good 0:07:14.720 --> 0:07:16.360 about eating. Doctor, Why. 0:07:17.960 --> 0:07:20.760 You call it tyranny, I call it wisdom. Let's call 0:07:20.760 --> 0:07:21.480 the whole thing off. 0:07:22.080 --> 0:07:25.440 Yeah, that's what I'll tyrn say at two. Yeah, So 0:07:25.480 --> 0:07:28.040 it's been an interesting story of the Solar System. You 0:07:28.120 --> 0:07:30.080 got to wonder if maybef we had more than nine 0:07:30.160 --> 0:07:32.320 or eight planets in the past. Well, we definitely had 0:07:32.320 --> 0:07:34.840 more planets to pay in the past before Pluto got downgraded. 0:07:34.880 --> 0:07:37.160 But that's a separate story and a separate reason. 0:07:37.240 --> 0:07:37.400 Right. 0:07:37.520 --> 0:07:39.960 Yeah, Pluto is still there, it's just not called the 0:07:40.000 --> 0:07:42.400 planet anymore. It's called a dwarf planet. 0:07:42.200 --> 0:07:44.720 Right, But we can ask the question of whether our 0:07:44.720 --> 0:07:48.360 solar system did really have other giant planets like Jupiter 0:07:48.480 --> 0:07:51.280 or Mars or Venus, but maybe they decided they didn't 0:07:51.320 --> 0:07:51.720 like it here. 0:07:51.760 --> 0:07:53.560 It's really fun to dig into the history of the 0:07:53.600 --> 0:07:56.280 Solar system and understand how we got here, how it 0:07:56.360 --> 0:07:58.360 might have been different, and give us a sense for 0:07:58.440 --> 0:08:01.560 what other solar systems out there are likely to look like. 0:08:01.720 --> 0:08:03.640 So, as usual, we were wondering how many people had 0:08:03.680 --> 0:08:07.040 thought about the question of whether our solar system lost 0:08:07.120 --> 0:08:10.800 any planets, or at least misplaced them temporarily. Maybe, So, 0:08:10.840 --> 0:08:12.720 as usual, Daniel went out there into the internet to 0:08:12.720 --> 0:08:16.560 ask people has our Solar system lost any planets? 0:08:16.720 --> 0:08:19.280 Thanks very much to our group of volunteers. We greatly 0:08:19.280 --> 0:08:21.640 appreciate them, but we also would like to add you 0:08:21.760 --> 0:08:24.400 to their ranks. Please don't be shy write to me 0:08:24.480 --> 0:08:27.400 two questions at Danielanjorge dot com. 0:08:27.440 --> 0:08:29.160 What do people get I know if they sign up. 0:08:29.160 --> 0:08:32.240 The satisfaction of hearing their voice on the podcast and 0:08:32.480 --> 0:08:35.960 a weekly injection of hard physics questions. 0:08:35.640 --> 0:08:38.240 And also a monthly supply of white chocolate that gets 0:08:38.320 --> 0:08:39.120 kicked out of your house. 0:08:39.280 --> 0:08:41.959 I will send you exactly zero grams of white chocolate. 0:08:44.480 --> 0:08:46.480 Well, think about it for a second. Do you think 0:08:46.520 --> 0:08:50.160 our Solar System has lost any planets? Here's what people 0:08:50.160 --> 0:08:50.600 had to say. 0:08:50.880 --> 0:08:52.760 I don't know if we can know for sure, maybe 0:08:52.760 --> 0:08:55.079 by the orbits of current planets, but I'd have to 0:08:55.120 --> 0:08:57.520 assume given the five billion years or so that or 0:08:57.520 --> 0:08:59.360 some spent around, that at least one planet has come 0:08:59.400 --> 0:09:02.160 in and been kicked out. But maybe it depends on 0:09:02.200 --> 0:09:04.240 if we consider those objects planets. 0:09:04.360 --> 0:09:07.480 So I think that there have been planets knocked out 0:09:07.480 --> 0:09:10.560 of the Solar System, especially since when the Solar System 0:09:10.640 --> 0:09:13.160 was first created there would have been loads of rocks 0:09:13.160 --> 0:09:16.360 flying around to form planets. So then there would have 0:09:16.360 --> 0:09:19.360 been planets formed and then hit by maybe another planet 0:09:19.360 --> 0:09:20.720 which knocked them out of the system. 0:09:20.880 --> 0:09:23.240 Nothing that I know of, they're all accounted for. Some 0:09:23.280 --> 0:09:26.480 of them have lost the designation planet, like Pluto. I 0:09:26.480 --> 0:09:31.160 think regularly objects get flung out of Solar systems due 0:09:31.200 --> 0:09:32.559 to gravitational interactions with. 0:09:32.559 --> 0:09:33.400 Other own jobjects. 0:09:33.400 --> 0:09:36.959 So I can imagine Jupiter getting tired of somesome little 0:09:37.000 --> 0:09:39.760 planet and flinging it out. Maybe when we were forming 0:09:39.840 --> 0:09:41.920 all the planets performing them. Some of them were close 0:09:41.920 --> 0:09:43.760 to the Sun and got gabbled up. I'm curious to 0:09:43.800 --> 0:09:46.640 know if there's any record of planets that we're here 0:09:46.679 --> 0:09:47.480 in now or not. 0:09:47.720 --> 0:09:51.160 Apart from the reclassification of Pluto as a dwarf planet, 0:09:51.240 --> 0:09:54.559 meaning that we've effectively lost one planet, I have heard 0:09:54.640 --> 0:09:57.319 rumors about a tenth planet, which would now be a 0:09:57.400 --> 0:10:01.400 ninth planet, that potentially all within our inn a soda 0:10:01.400 --> 0:10:04.040 system and then could have collided with Earth and created 0:10:04.080 --> 0:10:07.439 the Moon and then spun off out into an orbit 0:10:07.679 --> 0:10:10.640 way out in our outer Soder system. Other than that, 0:10:10.760 --> 0:10:12.280 I'm unaware of any lost planets. 0:10:12.360 --> 0:10:15.440 Interesting answers. It seems to be all over the place. 0:10:15.480 --> 0:10:17.920 Some people say yes, some people say no, not really, 0:10:17.960 --> 0:10:19.400 some people say poor Pluto. 0:10:21.280 --> 0:10:23.920 There does generally seem to be an appreciation of the 0:10:23.960 --> 0:10:26.920 fact that the Solar System might not have always been 0:10:27.040 --> 0:10:31.520 an orderly, stately placed that there might have been primordial chaos. 0:10:31.720 --> 0:10:33.200 That's right. It was a big party here in the 0:10:33.280 --> 0:10:35.480 Solar System, where we're kind of in the after party 0:10:35.520 --> 0:10:36.760 of the Solar System, right. 0:10:37.360 --> 0:10:40.280 We're waking up the next morning going, man, what happened? 0:10:40.280 --> 0:10:42.120 And has anybody seen a dog? 0:10:43.360 --> 0:10:46.400 Yeah? Well, why am I waking up next to Venus here? 0:10:46.760 --> 0:10:47.520 How did that happen? 0:10:47.640 --> 0:10:49.720 And why is the hot tub filled with white chocolate? 0:10:50.280 --> 0:10:54.520 Yeah, so let's start with the basics, Daniel, is it 0:10:54.559 --> 0:10:58.320 even possible for Solar system to lose the planet? I 0:10:58.360 --> 0:11:01.520 thought that, you know, once you form, things are kind 0:11:01.520 --> 0:11:05.000 of stuck to you gravitationally in orbits, or that at 0:11:05.080 --> 0:11:07.920 least that it's hard to escape the gravitational field of 0:11:08.040 --> 0:11:11.640 like Sun or all these planets. Wouldn't they either fall 0:11:11.640 --> 0:11:13.280 in or go into a stable orbit. 0:11:13.360 --> 0:11:16.000 I think the key idea is the word you used, form, Like, 0:11:16.160 --> 0:11:19.640 when do you consider the Solar System to have formed? 0:11:20.040 --> 0:11:24.080 The Solar system? Formation is a slow and gradual, constant process. 0:11:24.120 --> 0:11:27.440 It's basically always changing. And so you can go all 0:11:27.480 --> 0:11:29.680 the way back to the very beginning of the Solar 0:11:29.679 --> 0:11:33.840 system to understand the chaos of that formation and understand 0:11:33.840 --> 0:11:36.880 that that formation is a constant process, that things are 0:11:37.040 --> 0:11:39.880 always potentially bumping into each other and disturbing each other. 0:11:40.040 --> 0:11:42.320 Wait, are you saying that if we leave the window 0:11:42.440 --> 0:11:44.640 open for the fact that maybe the Solar System is 0:11:44.640 --> 0:11:48.000 still forming, does that mean we technically haven't lost any planets? Like? 0:11:48.080 --> 0:11:50.480 Can I use it in my real life. 0:11:51.320 --> 0:11:54.040 No, it just means that during the formation, planets could 0:11:54.120 --> 0:11:57.280 form and be lost. There is no final form to 0:11:57.320 --> 0:12:00.360 the Solar System. It's a constantly evolving thing. It's not 0:12:00.400 --> 0:12:02.760 like at some point somebody says, Okay, the Solar System 0:12:02.840 --> 0:12:05.240 is finished, let's package it and ship it and move 0:12:05.280 --> 0:12:06.880 on to the next project. I see. 0:12:06.920 --> 0:12:09.960 It's like a Pokemon, is what you're saying. It's always evolving, 0:12:10.240 --> 0:12:11.640 it's looking for its final form. 0:12:12.000 --> 0:12:13.920 I don't know enough about Pokemon to know whether that 0:12:13.960 --> 0:12:15.600 analogy holds, So I'm just gonna. 0:12:15.400 --> 0:12:18.160 Trust you on that. I don't know either. To be honest, 0:12:19.320 --> 0:12:21.000 I just heard final form and it made me think 0:12:21.040 --> 0:12:21.600 of Pokemon. 0:12:21.720 --> 0:12:23.560 Well, it's sort of in the same way that animals 0:12:23.559 --> 0:12:26.480 never have a final form. Evolution is a constant process. 0:12:26.720 --> 0:12:29.760 Things are always changing in response to the environment. 0:12:30.400 --> 0:12:33.240 Except for crocodiles and sharks, they're pretty settled there. 0:12:33.080 --> 0:12:34.800 In the plateau. Yeah that's true. 0:12:35.000 --> 0:12:37.480 Yeah, but let me take us through to some of 0:12:37.480 --> 0:12:39.360 the early history of the Solar System. How do we 0:12:39.400 --> 0:12:40.679 get planets in the first place. 0:12:40.800 --> 0:12:43.920 So planetary formation is a super fascinating topic, and it 0:12:43.960 --> 0:12:46.560 helps us understand like the formation of the Solar System 0:12:46.600 --> 0:12:49.360 as a whole. Remember that the Solar system forms from 0:12:49.360 --> 0:12:52.680 the collapse of a huge cloud of like gas and dust. 0:12:53.000 --> 0:12:55.240 It's mostly hydrogen, which is made in the Big Bang, 0:12:55.559 --> 0:12:57.960 and it's also interspersed with a bunch of other heavier 0:12:58.000 --> 0:13:01.000 stuff that's made from other solarss where the stars have 0:13:01.040 --> 0:13:04.200 already fused heavier elements out of that hydrogen. So you 0:13:04.200 --> 0:13:06.320 have this big cloud of mostly hydrogen with a few 0:13:06.320 --> 0:13:09.400 heavier bits in it, and it collapses into stars. You 0:13:09.400 --> 0:13:11.720 don't just get one solar system. You typically get several 0:13:11.720 --> 0:13:14.280 made at the same time. In one of these stellar nurseries, 0:13:14.600 --> 0:13:16.040 we have a big blob of this stuff and it 0:13:16.080 --> 0:13:18.520 collapses and most of the stuff goes into the center 0:13:18.840 --> 0:13:20.920 to make a star, like ninety nine percent of the 0:13:20.960 --> 0:13:23.800 stuff goes in to make the star. But you typically 0:13:23.840 --> 0:13:27.000 have a disc of gas and dust that's orbiting that star. 0:13:27.440 --> 0:13:29.640 It's spinning too fast to collapse in the way the 0:13:29.679 --> 0:13:32.880 Moon is orbiting the Earth without falling into the Earth, 0:13:33.320 --> 0:13:37.520 and so you get this protoplanetary disc around this new star, 0:13:38.240 --> 0:13:42.120 and that disc then coalesces into larger stuff. Gravity is 0:13:42.200 --> 0:13:44.440 doing the work there to pull the gas and dust 0:13:44.559 --> 0:13:47.360 in the disk into heavier things. And where you have 0:13:47.520 --> 0:13:50.960 like little spots of iron or little spots of heavier metals, 0:13:51.000 --> 0:13:54.120 those things will use their gravity to form larger objects. 0:13:54.840 --> 0:13:57.840 But I think the Solar System formed into a disc first, 0:13:57.920 --> 0:13:59.520 and then the star kind of ignited. 0:13:59.600 --> 0:14:02.040 Right. Moment of ignition depends a little bit on the 0:14:02.040 --> 0:14:03.760 mass of the star. I mean, in some cases you 0:14:03.760 --> 0:14:06.280 don't even get ignition if there isn't enough mass there. 0:14:06.320 --> 0:14:09.120 You have like a subcritical brown dwarf, but it's definitely 0:14:09.160 --> 0:14:11.680 collapsing into a disc as it forms. Right, a big 0:14:11.679 --> 0:14:13.920 amorphous blob is going to collapse, and it's going to 0:14:13.960 --> 0:14:16.560 collapse into a disc shape because of its angular rotation. 0:14:17.120 --> 0:14:19.400 So the two things can sort of happen simultaneously, And 0:14:19.440 --> 0:14:22.160 when ignition happens depends on the mass of the star. 0:14:22.440 --> 0:14:24.880 Right, And there's also kind of an intermediate step there 0:14:24.880 --> 0:14:28.680 where the disc kind of turns into rings for a while. 0:14:28.720 --> 0:14:30.840 Right before you get the planets. 0:14:30.520 --> 0:14:33.000 Exactly, you get the seeding of structure and they pull 0:14:33.120 --> 0:14:36.960 together into larger and larger objects, and rings are basically 0:14:37.000 --> 0:14:40.800 just clusters of larger objects. So you get these gaps emerging, 0:14:41.200 --> 0:14:44.040 and then you get those things formed together into planets 0:14:44.160 --> 0:14:47.720 or not, depending on the tidal forces. A large object 0:14:47.760 --> 0:14:49.440 can form and sort of gather up a lot of 0:14:49.440 --> 0:14:51.280 the gas and dust near it, and then it can 0:14:51.320 --> 0:14:54.640 also distort the other stuff nearby, preventing it from forming. 0:14:54.760 --> 0:14:57.080 So it's a bit of a chaotic process in the beginning, 0:14:57.520 --> 0:14:59.480 and it also depends a little bit on your distance 0:14:59.520 --> 0:15:02.040 from the st There's a point it's called the snow line, 0:15:02.120 --> 0:15:04.800 after which water tends to be ice, tends to be 0:15:04.840 --> 0:15:07.360 a solid, and before which it tends to be vapor. 0:15:07.480 --> 0:15:09.760 Like if you're close enough to the star, it's warm 0:15:09.840 --> 0:15:11.960 enough that the water is vapor and if you're further 0:15:11.960 --> 0:15:14.960 from that point, the water is frozen. That helps form 0:15:15.040 --> 0:15:18.080 giant planets. So you tend to have these large planets 0:15:18.120 --> 0:15:21.080 with ice and rock seeding structure on the outer part 0:15:21.120 --> 0:15:23.000 of the Solar System past the snow line, and then 0:15:23.120 --> 0:15:26.040 less ice so smaller planets before the snow line in 0:15:26.080 --> 0:15:27.080 the inner Solar system. 0:15:27.200 --> 0:15:28.840 Right in the inner Solar system, you get all the 0:15:28.960 --> 0:15:30.040 rocky planets. 0:15:29.720 --> 0:15:32.640 Right exactly because the gas there is blown away by 0:15:32.640 --> 0:15:35.000 the radiation from the ignition of the Sun. In the 0:15:35.080 --> 0:15:37.200 very beginning of the Solar system, the Sun is pumping 0:15:37.200 --> 0:15:40.600 out a huge amount of ultraviolet, very high energy photons, 0:15:40.920 --> 0:15:44.120 which tends to blast the inner planets clean, which is why, 0:15:44.160 --> 0:15:47.440 like our initial atmosphere on Earth was blown off by 0:15:47.480 --> 0:15:50.160 this stellar wind in the very early years of the 0:15:50.160 --> 0:15:52.440 Solar System. So you get the rocky planets in the core, 0:15:52.720 --> 0:15:55.040 and then you get the gas and ice giants out 0:15:55.120 --> 0:15:56.680 past the snow line. 0:15:56.520 --> 0:15:58.480 Right, And I think the process is like, yep, these 0:15:58.600 --> 0:16:01.920 rings kind of like Saturn has rings right now, and 0:16:01.960 --> 0:16:05.680 the rings eventually little by little collapse into planets or 0:16:05.720 --> 0:16:07.320 first planet tesimals first, right. 0:16:07.320 --> 0:16:09.920 Yeah, planet testimals a super fun word. They sound like 0:16:10.080 --> 0:16:13.160 many cute little planets where they're basically like building blocks 0:16:13.200 --> 0:16:15.760 of planets, and they don't always form, right, which is 0:16:15.760 --> 0:16:18.320 why you have like the asteroid belt and the Kuiper Belt. 0:16:18.640 --> 0:16:21.560 It depends on the tidal forces of the nearby stuff, 0:16:21.840 --> 0:16:25.200 so it's not happening in isolation. This is complicated interplay 0:16:25.240 --> 0:16:27.040 between all of the objects. 0:16:26.680 --> 0:16:28.760 Right, But it's kind of a bit of a runaway process. 0:16:28.800 --> 0:16:31.920 Like once you seed a planet or once more you know, 0:16:31.960 --> 0:16:34.880 some planet tesimals moush together, then that becomes kind of 0:16:34.920 --> 0:16:37.120 a center of gravity and more and more stuff falls 0:16:37.120 --> 0:16:39.359 into it, and that's kind of how you get a planet. 0:16:39.160 --> 0:16:41.440 Right, Yeah, that's kind of how you get a planet exactly. 0:16:41.840 --> 0:16:45.360 And in this initial picture, everything forms very orderly, like 0:16:45.440 --> 0:16:47.440 they tend to be mostly in the same plane, and 0:16:47.480 --> 0:16:50.440 it be mostly circular because you have this big disc 0:16:50.560 --> 0:16:52.520 as we say, that collapses in the rings and then 0:16:52.560 --> 0:16:55.600 planet ismals and then planets. But once you have these 0:16:55.760 --> 0:16:59.400 large objects formed with their own significant gravity, then they 0:16:59.400 --> 0:17:01.400 can start to hug on each other pretty hard, and 0:17:01.440 --> 0:17:04.360 you can get instabilities, you can get chaos, you can 0:17:04.400 --> 0:17:07.960 get resonances, and that's how planets can migrate, and they 0:17:07.960 --> 0:17:10.440 can tug on each other and you might even lose. 0:17:10.240 --> 0:17:13.080 One, right, because I guess there's no guarantee that your 0:17:13.160 --> 0:17:14.840 orbit is going to be stable. I mean, it's such 0:17:14.840 --> 0:17:18.680 a complex and you know, there's so many things moving 0:17:18.720 --> 0:17:21.080 around that there's no guarantee that even if you're orbiting 0:17:21.119 --> 0:17:23.160 around the Sun, you're going to be there forever, because 0:17:23.160 --> 0:17:26.040 something else might come around and knock you off your 0:17:26.119 --> 0:17:28.280 orbit or pull you away from your orbit, right. 0:17:28.119 --> 0:17:30.439 And that can be things from outside the Solar System, 0:17:30.560 --> 0:17:34.359 like a passing star can nudge something and perturb the 0:17:34.440 --> 0:17:37.840 otherwise stable orbits of the Solar System like even just 0:17:37.880 --> 0:17:40.600 a little nudge from a star that's coming nearby, it's 0:17:40.640 --> 0:17:42.320 not like it has to pass right through the Solar 0:17:42.359 --> 0:17:45.720 system can cause a cascade effect of instabilities. But also, 0:17:46.000 --> 0:17:48.159 just like the planetismals and the Kuyper Belt or the 0:17:48.160 --> 0:17:50.879 asteroid belt can tug on stuff, and enough of that 0:17:51.000 --> 0:17:52.840 happening can cause things to go. 0:17:52.880 --> 0:17:56.240 Wonky and wonky. They might have gone in our Solar system, 0:17:56.400 --> 0:17:58.919 perhaps wonky enough to lose a couple of planets here 0:17:58.920 --> 0:18:02.240 and there. Let's get into that idea and whether or 0:18:02.280 --> 0:18:05.639 not we did misplace a couple of planets in our history. 0:18:05.720 --> 0:18:20.240 But first let's take a quick break. All right, we're 0:18:20.240 --> 0:18:23.640 talking about whether our Solar system has lost any planets. 0:18:23.720 --> 0:18:27.480 I feel like that sounds very irresponsible of the Solar system. 0:18:27.800 --> 0:18:30.199 Can would you say, like, have any planets escaped our 0:18:30.240 --> 0:18:30.840 Solar system? 0:18:30.960 --> 0:18:33.920