WEBVTT - Can planets share an orbit? 0:00:08.560 --> 0:00:11.800 Hey, org, did you share a room with siblings when 0:00:11.800 --> 0:00:12.319 you were a kid? 0:00:12.440 --> 0:00:14.040 I did. I shared a room with my brother. 0:00:14.160 --> 0:00:16.320 Ooh, And was that like cozy and fun for the 0:00:16.360 --> 0:00:18.439 two of you? Or did you get on each other's nerves? 0:00:18.800 --> 0:00:20.880 It was pretty fun. We get along pretty good. How 0:00:20.880 --> 0:00:21.320 about you? 0:00:21.440 --> 0:00:24.200 I shared a room with two brothers and there was 0:00:24.280 --> 0:00:26.639 not a whole lot of coziness there. We got on 0:00:26.680 --> 0:00:27.800 each other's nerves a lot. 0:00:28.240 --> 0:00:29.640 Yikes. Sounds intense. 0:00:29.960 --> 0:00:32.599 Yeah, I remember after one argument my mom telling us 0:00:32.680 --> 0:00:35.840 if we couldn't get along, we'd have to live outside. Intense. 0:00:36.120 --> 0:00:39.960 WHOA, sounds intense? But is that why you like camping 0:00:40.000 --> 0:00:42.600 so much? Because you did end up outside in the tent? 0:00:42.800 --> 0:00:44.839 That's that where your love of the stars came from. 0:00:45.080 --> 0:00:47.760 This is your origin story. It's all because of your brother, 0:00:47.920 --> 0:00:49.800 your nemesis or nemesi. 0:00:50.240 --> 0:00:52.880 Is how I extracted something beautiful from a difficult story. 0:00:53.040 --> 0:00:55.760 Sounds like a hallmark. We we know how you overcame, 0:00:56.000 --> 0:00:56.920 sibling Riberry. 0:00:57.280 --> 0:00:59.080 Depends on whether it ends well or not. 0:00:59.480 --> 0:01:01.400 I guess only ends and one of you dies. 0:01:16.880 --> 0:01:19.600 Hi am Jorhemick, cartoonist and the author of Oliver's Great 0:01:19.640 --> 0:01:20.440 Big Universe. 0:01:20.600 --> 0:01:23.160 Hi, I'm Daniel, I'm a particle physicist and a professor 0:01:23.160 --> 0:01:25.960 at u C Irvine, and I've been totally eclipsed by 0:01:26.000 --> 0:01:26.759 my younger brother. 0:01:27.000 --> 0:01:30.240 Oh boy, is he a more shiny star or something. 0:01:32.000 --> 0:01:34.840 He's taller than me, he's a professor at a fancier 0:01:34.920 --> 0:01:38.119 university than I am. What else is there? 0:01:39.760 --> 0:01:41.160 But does he have a podcast? 0:01:42.360 --> 0:01:45.040 There you go. I don't know if he wants a podcast, 0:01:45.080 --> 0:01:46.679 but yeah, that's a good point. I'm going to bring 0:01:46.720 --> 0:01:47.600 that up at Thanksgiving. 0:01:47.640 --> 0:01:50.200 Thanks You know, it's super hard to do a podcast, 0:01:51.000 --> 0:01:55.040 or at least the start one. There's a high bar 0:01:55.080 --> 0:01:56.800 for putting things on the internet. They don't just let 0:01:56.840 --> 0:01:58.280 anyone post things on the internet, you know. 0:01:58.400 --> 0:01:59.920 I guess we'll find out if he listens to the 0:02:00.480 --> 0:02:01.520 if he responds to this. 0:02:01.680 --> 0:02:03.480 Oh boy one. 0:02:03.480 --> 0:02:06.080 In case you're listening, Hello, Daniel's brother. It sounds like 0:02:06.120 --> 0:02:08.520 we should have you on a podcast and break it 0:02:08.560 --> 0:02:10.040 down Oprah style. 0:02:10.200 --> 0:02:12.119 He's been on the podcast once before when we talked 0:02:12.120 --> 0:02:15.119 about artificial intelligence because he's a machine learning professor. 0:02:15.440 --> 0:02:17.240 Oh I thought you were going to say he's a 0:02:17.280 --> 0:02:23.120 machine that too. But anyways, welcome to our podcast. Daniel 0:02:23.160 --> 0:02:25.880 and Jorge explain the Universe a production of our Heart 0:02:25.960 --> 0:02:26.560 Radio in. 0:02:26.520 --> 0:02:29.679 Which we try not to eclipse your knowledge of the universe. 0:02:29.760 --> 0:02:31.760 We try to shine a light on it. We think 0:02:31.800 --> 0:02:34.480 everybody should be cozy with the physics of the universe, 0:02:34.760 --> 0:02:37.680 snuggling up to a deep understanding of what's going on 0:02:37.840 --> 0:02:40.280 out there, how it all works, how it started, and 0:02:40.320 --> 0:02:43.040 what story it tells us about where we live and 0:02:43.080 --> 0:02:44.920 where we will live in the future. 0:02:45.000 --> 0:02:45.360 That's right. 0:02:45.400 --> 0:02:47.440 We tried to be your big brother in terms of 0:02:48.280 --> 0:02:50.639 telling you how the universe works and what we've learned 0:02:50.639 --> 0:02:53.280 from our mistakes and our discoveries so that you can 0:02:53.360 --> 0:02:56.360 navigate this fantastic universe with a little bit more ease 0:02:56.480 --> 0:02:57.720 and a little bit more confidence. 0:02:58.200 --> 0:03:01.399 I'm not sure Big Brother has the meditations we're looking for. 0:03:01.840 --> 0:03:03.960 You know, it's a little bit overwhelminging, isn't it. 0:03:04.160 --> 0:03:07.080 M not necessarily Isn't there like a Big Brother program 0:03:07.120 --> 0:03:08.760 where you mentor kids. 0:03:09.040 --> 0:03:10.079 That's a positive thing too. 0:03:10.280 --> 0:03:12.840 Yeah, there you go. We're not telling you what to 0:03:12.880 --> 0:03:14.800 think of what not to think. We're just teaching you 0:03:14.840 --> 0:03:15.680 about the universe. 0:03:16.000 --> 0:03:16.480 That's right. 0:03:17.200 --> 0:03:19.040 And there is a lot to know about the universe 0:03:19.080 --> 0:03:21.120 and to discover and to find out because it is 0:03:21.240 --> 0:03:25.640 pretty interesting, pretty complex, pretty vast, and also microscopic in 0:03:25.680 --> 0:03:27.520 the way that it reveals its secrets. 0:03:27.639 --> 0:03:30.280 And one surefire way to figure out how the universe 0:03:30.320 --> 0:03:33.320 works is to ask basic questions about it. To look 0:03:33.400 --> 0:03:35.320 up at the night sky and ask why does this 0:03:35.400 --> 0:03:37.440 do this? And why does this not do that? How 0:03:37.440 --> 0:03:40.040 can we see this happening and not some other thing happening. 0:03:40.280 --> 0:03:43.040 What are the rules of the universe that allow us 0:03:43.040 --> 0:03:46.080 to have huge planets like Jupiter but not other situations 0:03:46.120 --> 0:03:47.760 like planets shaped like a pretzel. 0:03:47.840 --> 0:03:50.280 Yeah, because I guess you can look around and wonder like, 0:03:50.480 --> 0:03:53.320 are we a result of the rules of the universe 0:03:53.440 --> 0:03:55.360 or are we like an exception to the rules of 0:03:55.400 --> 0:03:55.920 the universe. 0:03:56.080 --> 0:03:58.240 Well, we definitely a results of the rules of the universe, 0:03:58.480 --> 0:04:01.240 if you believe the universe has rules and it follows them. 0:04:01.560 --> 0:04:03.760 But there might be weird outcomes and there might be 0:04:03.800 --> 0:04:05.960 standard outcomes like it. It could be that our solar system 0:04:06.000 --> 0:04:09.240 is very unusual as an example of things in the galaxy, 0:04:09.320 --> 0:04:11.040 or it could be that were totally vanilla. 0:04:11.240 --> 0:04:13.520 Yeah, because as humans here on planet Earth, we only 0:04:13.560 --> 0:04:16.080 really have one view of one planet that we can 0:04:16.120 --> 0:04:19.760 study up close so far, and so it makes you 0:04:19.839 --> 0:04:23.839 wonder if other planets are the same, or if humans 0:04:23.839 --> 0:04:26.000 could have lived in other planets, could things have been 0:04:26.040 --> 0:04:27.320 different in our history? 0:04:27.480 --> 0:04:30.000 That's true, and there are other planets nearby that we 0:04:30.040 --> 0:04:32.599 can study, though not quite as up close, to try 0:04:32.600 --> 0:04:35.200 to get more insight into what a planet can be, like, 0:04:35.440 --> 0:04:38.400 what are the various possibilities how planets can turn out? 0:04:38.520 --> 0:04:41.440 And do they get along as siblings? Or have any 0:04:41.440 --> 0:04:44.000 siblings been kicked out of the Solar System and are 0:04:44.040 --> 0:04:46.960 living in intents by the asteroid build That's right. 0:04:47.000 --> 0:04:49.240 We talked recently about those really fun theories that there 0:04:49.320 --> 0:04:51.760 was once an ice giant in the outer Solar System 0:04:51.960 --> 0:04:54.400 that was ejected during a period of chaos. 0:04:54.839 --> 0:04:57.960 WHOA, so you think it just couldn't get along with 0:04:57.960 --> 0:04:58.680 the other planets. 0:04:58.760 --> 0:05:00.960 I'm wondering who the parent is this analogy? Like, is 0:05:00.960 --> 0:05:02.960 it really the Sun's fault that it didn't work out? 0:05:03.360 --> 0:05:03.520 Yeah? 0:05:03.560 --> 0:05:06.440 And how responsible is it to kick your children outside 0:05:07.720 --> 0:05:08.640 and live outside? 0:05:08.720 --> 0:05:12.440 Yeah? Yeah, somebody should call it you universal child services. 0:05:12.920 --> 0:05:15.360 But one thing we do notice about our Solar System 0:05:15.680 --> 0:05:18.880 is that the planets all seem to have their own orbits. 0:05:19.160 --> 0:05:21.479 Jupiter's got an orbit, or Earth has an orbit, Mars 0:05:21.480 --> 0:05:23.880 has an orbit. It's sort of like everybody's got their 0:05:23.920 --> 0:05:24.920 own room. 0:05:24.920 --> 0:05:25.960 They all have their own lane. 0:05:26.000 --> 0:05:28.120 You mean, yeah, exactly. 0:05:27.960 --> 0:05:30.159 Like there's no other Earth on the other side of 0:05:30.160 --> 0:05:32.560 our orbit, right, or didn't scientists think for a while, 0:05:32.680 --> 0:05:33.359 or maybe there was? 0:05:34.440 --> 0:05:36.640 It sounds like a pretty cool science fiction story, right, 0:05:36.680 --> 0:05:38.440 a second Earth on the other side of the Sun. 0:05:38.560 --> 0:05:40.479 Planet X. Wasn't it called Planet X? 0:05:40.760 --> 0:05:43.400 I think planet X is an idea for a tenth 0:05:43.560 --> 0:05:46.080 or now ninth planet that might be out there tugging 0:05:46.120 --> 0:05:49.880 on distant planets, but wouldn't necessarily share an orbit with ours. 0:05:50.680 --> 0:05:53.599 But it's technically is it possible that there's like another 0:05:53.680 --> 0:05:55.120 Earth on the other side of the Sun? Weich just 0:05:55.400 --> 0:05:57.320 have never seen it because it's on the other side 0:05:57.320 --> 0:05:57.760 of the Sun. 0:05:58.600 --> 0:06:00.960 We wouldn't be able to see it directly from Earth. 0:06:01.000 --> 0:06:03.240 But of course we've had probes go all over the 0:06:03.279 --> 0:06:05.400 Solar System. We would have seen it, and we would 0:06:05.440 --> 0:06:08.440 have noticed its gravitational effects on Mars and Venus and 0:06:08.720 --> 0:06:10.120 other stuff in the Solar System. 0:06:10.200 --> 0:06:12.640 So I guess each planet does have its own orbit, 0:06:12.760 --> 0:06:13.440 its own lane. 0:06:13.520 --> 0:06:16.280 In our Solar System, each planet mostly does have its 0:06:16.279 --> 0:06:19.000 own lane. But of course the question is why is 0:06:19.080 --> 0:06:21.600 that and is that typical? So today on the podcast, 0:06:21.600 --> 0:06:30.240 we'll be tackling the question why don't planet share an orbit? 0:06:30.680 --> 0:06:33.040 Is it because they couldn't get along? Yeah? 0:06:33.200 --> 0:06:35.520 And are we the little the younger sibling or are 0:06:35.520 --> 0:06:38.360 we the more accomplished sibling. 0:06:38.480 --> 0:06:41.560 I think the younger sibling is often motivated to eclipse 0:06:41.600 --> 0:06:42.560 the older siblings. 0:06:42.640 --> 0:06:44.880 Boy, it sounds like a lot to impact there in 0:06:44.920 --> 0:06:45.760 your family. 0:06:48.120 --> 0:06:49.839 I'm nothing but proud of my younger brother. 0:06:50.160 --> 0:06:53.560 Let's stick to physics maybe, but yeah, it's an interesting question. 0:06:53.640 --> 0:06:56.680 I guess the implied fact is that no planets in 0:06:56.720 --> 0:07:00.600 our Solar system share an orbit, meaning they're not going 0:07:00.600 --> 0:07:02.400 around the Sun at the same distance. 0:07:02.720 --> 0:07:05.040 Yeah, although you could quibble about that in the case 0:07:05.080 --> 0:07:08.080 of Jupiter. There is some stuff in Jupiter's orbit, not 0:07:08.120 --> 0:07:10.920 another planet, but it does share its orbit with some 0:07:10.960 --> 0:07:11.679 other chunks. 0:07:12.200 --> 0:07:14.400 And I guess the other implied fact is that all 0:07:14.440 --> 0:07:17.320 the orbits don't overlap. I guess right, because most of 0:07:17.360 --> 0:07:20.400 the orbits are pretty much circular, right, They're not like 0:07:21.160 --> 0:07:23.280 ellipses that kind of overlap with each other. 0:07:23.480 --> 0:07:25.200 You mean, like if they intersect, Yeah. 0:07:25.080 --> 0:07:27.000 Like they intersect, or if you look at them from 0:07:27.040 --> 0:07:30.200 the top they're maybe like the two ellipsoids are overlapped. 0:07:30.320 --> 0:07:32.880 Yeah, I think two ellipsoids that overlap and have different 0:07:32.880 --> 0:07:35.960 periods would eventually collide. So I don't think you could 0:07:36.000 --> 0:07:37.440 have that situation for very long. 0:07:37.560 --> 0:07:39.520 But it's true that most of the orbits are pretty 0:07:39.600 --> 0:07:40.560 much circular, right. 0:07:40.800 --> 0:07:43.120 They're all a little bit eccentric. None of them are 0:07:43.160 --> 0:07:44.560 exactly circular, kind of. 0:07:44.560 --> 0:07:46.880 Like you and your brothers. They're all a little eccentric 0:07:46.920 --> 0:07:49.680 as well. I think a little is kind of generous there. 0:07:50.040 --> 0:07:53.280 We're all quite eccentric. Actually called professors or something. 0:07:55.200 --> 0:07:57.320 Exactly how does that happen? But in the case of 0:07:57.360 --> 0:08:00.000 the Solar system, none of the orbits are perfectly circular. 0:08:00.120 --> 0:08:02.640 They're all at least a little bit eccentric. But yeah, 0:08:02.680 --> 0:08:05.120 none of them are overlapping. They basically all have their 0:08:05.160 --> 0:08:05.840 own lanes. 0:08:06.160 --> 0:08:08.440 So the question is why don't two planets have the 0:08:08.520 --> 0:08:10.720 same orbit? So, as usually'll be ever wondering how many 0:08:10.720 --> 0:08:12.360 people out there had thought about this question. 0:08:12.480 --> 0:08:14.920 Thanks very much to our group of volunteers. We'd love 0:08:15.040 --> 0:08:17.760 if you joined them. Right to me two questions at 0:08:17.840 --> 0:08:20.440 Daniel and Jorge dot com, and I'll send the questions 0:08:20.480 --> 0:08:21.160 on over. 0:08:21.080 --> 0:08:24.000 So think about it for a second. Why do you 0:08:24.040 --> 0:08:28.160 think no two planets share an orbit. Here's what people 0:08:28.160 --> 0:08:28.640 had to say. 0:08:28.800 --> 0:08:32.560 I think planets don't share orbits because the center of 0:08:32.559 --> 0:08:37.000 gravity would have to be absolutely stationary, or it'd oscillate 0:08:37.120 --> 0:08:39.240 and shake itself out of sync. 0:08:39.480 --> 0:08:43.040 But I think they actually do. It's just very unlikely 0:08:43.520 --> 0:08:45.120 because it'd be a major coincidence. 0:08:45.360 --> 0:08:48.640 So I'm under the impression that planet's by definition or 0:08:48.640 --> 0:08:52.600 celestial objects orbiting stars that have cleared their orbital path 0:08:52.840 --> 0:08:56.920 of competing debris like asteroids, and that as a planet forms, 0:08:56.960 --> 0:09:01.120 it's gravity gets stronger and it sucks up other objects 0:09:01.160 --> 0:09:03.760 in that orbital path. And that's one of the reasons 0:09:03.800 --> 0:09:07.640 that objects like series are not considered true planets because 0:09:07.679 --> 0:09:10.720 they share their orbit with a number of other large 0:09:10.760 --> 0:09:13.520 asteroids and other computing debris. 0:09:13.559 --> 0:09:17.559 Planets don't share orbits because of the way closters get together. 0:09:18.280 --> 0:09:20.680 If there is a clumpup matter very close to another 0:09:20.679 --> 0:09:22.960 glombal matter, they will make a planet, and the things 0:09:23.040 --> 0:09:25.600 that are fought up are they will make another planet. 0:09:25.880 --> 0:09:28.559 All right, some interesting answers. Some people think it's maybe 0:09:28.640 --> 0:09:31.360 unlikely because there would be a big coincidence. 0:09:31.120 --> 0:09:33.040 Or that gravity just doesn't work that way, that it 0:09:33.120 --> 0:09:35.080 can't pull things together into two planets. 0:09:35.120 --> 0:09:38.800 Oh interesting, but I guess you know, thinking about it, 0:09:38.840 --> 0:09:41.959 like the asteroid built has a whole bunch of mini 0:09:41.960 --> 0:09:44.120 planets and they're all kind of in the same orbit. 0:09:44.280 --> 0:09:46.400 Mm hmm, yeah, absolutely, I. 0:09:46.400 --> 0:09:48.720 Guess we'll dig into that. So first of all, Daniel, 0:09:48.800 --> 0:09:51.680 let's maybe start with the basics. What is a planet 0:09:51.960 --> 0:09:53.400 or what do you define as a planet? 0:09:53.600 --> 0:09:57.960 So a planet famously has a fairly legalistic definition of 0:09:58.000 --> 0:10:00.480 what it is. And remember this is just a rooms 0:10:00.520 --> 0:10:02.920 giving names to things, Like there's stuff out there in 0:10:02.920 --> 0:10:05.480 the universe. The rocks don't care whether you call them 0:10:05.520 --> 0:10:08.000 a rock or an asteroid or a planet or a planetismal, 0:10:08.000 --> 0:10:10.280 They're still out there and doing the physics. This is 0:10:10.320 --> 0:10:14.600 just humans applying like our framework of categorization to the stuff, 0:10:14.960 --> 0:10:17.560 and different humans on a different planet, or aliens whatever 0:10:17.559 --> 0:10:20.320 it might come up with a totally different categorization. It's 0:10:20.320 --> 0:10:24.040 mostly historical. It doesn't really reflect deep underlying physics. But 0:10:24.360 --> 0:10:27.040 it's language and we should all agree what the meanings 0:10:27.040 --> 0:10:29.680 of words are. And so in the case of a planet, 0:10:29.760 --> 0:10:34.200 there are three requirements. One that it's mostly spherical, This 0:10:34.320 --> 0:10:37.800 is basically isn't big enough, because anything that's big enough 0:10:38.000 --> 0:10:40.080 is going to be mostly as fear due to gravity. 0:10:40.320 --> 0:10:43.880 Requirement Number two is that it orbits the Sun and 0:10:43.960 --> 0:10:46.920 not some other object like a planet, otherwise the Moon 0:10:47.000 --> 0:10:49.079 would be a candidate for a planet. And then the 0:10:49.160 --> 0:10:53.319 last one is that it's cleared its path of planetismals 0:10:53.320 --> 0:10:56.959 and other big objects, basically that of all the stuff 0:10:57.000 --> 0:10:59.320 in its lane, it's gathered up all the bits into 0:10:59.400 --> 0:11:00.240 one object. 0:11:00.520 --> 0:11:04.280 Well, it sounds like by definition then a planet cannot 0:11:04.280 --> 0:11:08.160 share an orbit, because a planet in your definition, is 0:11:08.200 --> 0:11:10.679 something that is by itself in an orbit exactly. 0:11:10.760 --> 0:11:15.000 So technically speaking, like the legal answer is no, because 0:11:15.040 --> 0:11:17.120 then it wouldn't be a planet. But really we're asking, like, 0:11:17.320 --> 0:11:19.640 could you have two Jupiters on opposite sides of the 0:11:19.640 --> 0:11:22.880 Sun orbiting in the same orbit. That would be really fascinating. 0:11:23.000 --> 0:11:26.160 Now astronomers from this committee would say, well, technically those 0:11:26.200 --> 0:11:28.319 aren't planets, and we say like, well, we don't really care. 0:11:28.360 --> 0:11:31.200 It's fascinating that they're doing this thing, whether or not 0:11:31.280 --> 0:11:32.320 you call them planets. 0:11:32.440 --> 0:11:34.640 I mean, if there was another Earth orbiting in our orbit, 0:11:34.720 --> 0:11:36.440 just on the other side of the Sun, we wouldn't 0:11:36.480 --> 0:11:38.240 be like, that's not a planet. We would still call 0:11:38.280 --> 0:11:40.600 it a planet, and you'd just be forced to change 0:11:40.600 --> 0:11:41.760 the definition of a planet. 0:11:42.000 --> 0:11:45.040 Yeah. Maybe, Or we'd have t shirts saying like Earth 0:11:45.080 --> 0:11:47.040 isn't a planet, or Earth is a planet, or I'm 0:11:47.040 --> 0:11:49.720 on Team Earth or whatever. It'd be a whole ridiculous 0:11:49.760 --> 0:11:52.240 battle really just over names. You know, where do you 0:11:52.320 --> 0:11:53.400 draw the dotted line? 0:11:53.480 --> 0:11:55.440 But I guess maybe the question is like, why is 0:11:55.440 --> 0:11:58.120 that part of the definition? Why is it important for 0:11:58.720 --> 0:12:02.720 astronomers it a planet? It quote unquote has its own orbit. 0:12:02.840 --> 0:12:04.760 It's a good question, and I don't think the answer 0:12:04.880 --> 0:12:08.800 is just scientific. I think it's historical. You know, we 0:12:08.880 --> 0:12:12.480 try to sometimes reverse engineer these definitions to reflect the 0:12:12.480 --> 0:12:16.240 decisions we've been making historically. We've been calling these things planets, 0:12:16.280 --> 0:12:18.680 and we sort of want to have a definition that 0:12:18.760 --> 0:12:22.280 aligns with the decisions we've already made, even if they 0:12:22.360 --> 0:12:25.400 aren't the decisions we would have made if we knew 0:12:25.400 --> 0:12:28.040 better at the time. You know, early on, when we 0:12:28.080 --> 0:12:30.760 started talking about planets, we didn't understand everything that was 0:12:30.800 --> 0:12:33.400 out there in the Solar System, all the smaller rocks 0:12:33.400 --> 0:12:35.800 that were invisible to us. We didn't realize that there 0:12:35.840 --> 0:12:38.720 was like a full spectrum from tiny rocks to planetisimals, 0:12:38.760 --> 0:12:40.599 to dwarf planets to real planets. 0:12:40.720 --> 0:12:42.800 But I guess maybe the idea that this is part 0:12:42.840 --> 0:12:46.520 of the definition maybe tells me that there are things 0:12:46.520 --> 0:12:49.920 out there that are spherical that orbit the Sun but 0:12:49.960 --> 0:12:53.319 that don't have cleared its path of planetesimals, that are 0:12:53.320 --> 0:12:55.040 maybe as big as some of the things we do 0:12:55.120 --> 0:12:55.679 call planets. 0:12:55.760 --> 0:12:56.320 Is that true? 0:12:56.440 --> 0:12:59.839 Well, basically that's Pluto, right. Pluto got rejected as a 0:12:59.840 --> 0:13:03.800 planet because it was judged to have not sufficiently cleared 0:13:03.840 --> 0:13:07.839 the neighborhood around its orbit of other stuff. Basically, if 0:13:07.840 --> 0:13:10.720 you look in Pluto's orbit, you find other pretty big 0:13:10.800 --> 0:13:13.760 rocks that are roughly the size of Pluto. Pluto is 0:13:13.800 --> 0:13:16.160 just one of an example of lots of we call 0:13:16.200 --> 0:13:19.480 them dwarf planets that far out in the Solar System. 0:13:19.720 --> 0:13:22.880 They have not gathered together sufficiently to say there's one 0:13:23.080 --> 0:13:25.600 really dominant object and nothing else out there. 0:13:25.720 --> 0:13:27.920 Wait wait, wait, wait wait, this was the rule that. 0:13:27.920 --> 0:13:31.240 They kicked Pluto out because of you mean it's not 0:13:31.480 --> 0:13:33.400 because of its size. I always thought it was because 0:13:33.440 --> 0:13:34.200 of its size. 0:13:34.440 --> 0:13:36.720 It's sort of indirectly because of its size. I mean, 0:13:36.760 --> 0:13:39.560 if everything else out there in Pluto's orbit was just 0:13:39.679 --> 0:13:42.240 dust and tiny grains, then they would have said, okay, 0:13:42.240 --> 0:13:44.520 it's a planet. But because there are chunks of rock 0:13:44.600 --> 0:13:47.240 out there that are sort of too big to ignore, 0:13:47.960 --> 0:13:51.160 then you say Pluto hasn't really cleared its orbit. I mean, really, 0:13:51.200 --> 0:13:54.480 technically speaking, nothing has cleared its orbit, because you know 0:13:54.520 --> 0:13:56.920 there's dust and all sorts of other rocks in Earth's 0:13:56.960 --> 0:14:00.559 orbit certainly, right, It's not like it's perfectly empty space 0:14:00.679 --> 0:14:02.520 in Earth's orbit, So you can ask like, well, what 0:14:02.520 --> 0:14:04.840 does it mean to clear its orbit? Even that definition 0:14:04.880 --> 0:14:07.120 gets a little bit fuzzy, but that's the reason why 0:14:07.160 --> 0:14:08.280 Pluto was demoted. 0:14:08.679 --> 0:14:10.680 WHOA, I'm a little bit outraged. 0:14:11.360 --> 0:14:14.000 I feel like this is such a weird technicality to 0:14:14.120 --> 0:14:15.280 have kick Pluto for. 0:14:15.800 --> 0:14:18.439 Well, this is the problem with creating categories, right, You're 0:14:18.440 --> 0:14:20.880 always going to find something on the edge of the category, 0:14:20.880 --> 0:14:22.400 and then you're going to have to try to crisply 0:14:22.440 --> 0:14:25.040 define the category, and then you discover the category is 0:14:25.080 --> 0:14:28.240 just artificial. You're just really drawing dotted lines between a 0:14:28.280 --> 0:14:31.000 smooth spectrum of stuff. Like I remember when we talked 0:14:31.040 --> 0:14:34.000 about space centaurs, the things that are so kind of 0:14:34.000 --> 0:14:36.480 comets and kind of asteroids, And what you discover is 0:14:36.840 --> 0:14:39.800 really the two things are part of a larger community. 0:14:39.840 --> 0:14:42.840 And you've drawn a dotted line between comets and asteroids, 0:14:42.880 --> 0:14:45.840 and it doesn't really make sense to distinguish between them. 0:14:45.880 --> 0:14:47.960 This is just a problem of humans creating categories that 0:14:48.080 --> 0:14:49.120 don't really work. 0:14:49.400 --> 0:14:51.240 But there was sort of like a voter, there was 0:14:51.240 --> 0:14:53.880 a lot of discussion about Pluto. So what is it 0:14:53.920 --> 0:14:57.240 about not having anything in its path that is so 0:14:57.320 --> 0:15:01.880 important to scientists to kick go, you know, change science 0:15:01.880 --> 0:15:04.440 books basically for everybody. You know, why is that important 0:15:04.520 --> 0:15:06.840 whether or not it has little chunks of rocks in 0:15:06.880 --> 0:15:07.560 its path or not. 0:15:07.760 --> 0:15:10.160 I think it's just sociological, Like we look at Earth 0:15:10.240 --> 0:15:12.960 and Jupiter and Mars and Venus and we say this 0:15:13.040 --> 0:15:15.760 is one kind of thing, and Pluto is sort of 0:15:15.800 --> 0:15:18.800 a different kind of thing because it's different in this way. 0:15:19.280 --> 0:15:22.320 Is just one example of many big chunks of rock 0:15:22.400 --> 0:15:24.480 out there in the Pluto orbit. So I think there 0:15:24.520 --> 0:15:27.720 is a distinction to be made between these two different 0:15:27.720 --> 0:15:30.800 categories of objects. Then again, it's sort of fuzzy. 0:15:30.600 --> 0:15:32.800 Meaning like the fact that it has chunks in its 0:15:32.800 --> 0:15:36.080 path is maybe the only thing that sits it apart 0:15:36.360 --> 0:15:37.920 from the others, like none of the other things that 0:15:37.960 --> 0:15:40.840 we call planets have things in its path, and so 0:15:41.200 --> 0:15:44.640 they're using this as an excuse to kick Pluto out exactly. 0:15:44.640 --> 0:15:46.880 And when we talk about the history of the formation 0:15:46.960 --> 0:15:48.760 of the Solar System, you see that it's sort of 0:15:48.840 --> 0:15:51.200 like one step, you know, the Solar System. You have 0:15:51.240 --> 0:15:53.840 the planetary disk, and it gathers into rocks and those 0:15:53.880 --> 0:15:56.880 become planetesimals, and then in some cases they form big 0:15:56.920 --> 0:15:59.040 planets and other cases they just stay a big spread 0:15:59.040 --> 0:16:01.880 of planet isimals, they don't really form planets. So in 0:16:01.880 --> 0:16:04.000 that sense, planets really are sort of like the next 0:16:04.040 --> 0:16:06.720 step in the formation of an object in the Solar System, 0:16:07.120 --> 0:16:09.160 and you've got to respect that or reflect it, or 0:16:09.200 --> 0:16:10.600 at least, you know, describe it. 0:16:11.200 --> 0:16:11.320 You know. 0:16:11.360 --> 0:16:12.800 I guess it would make sense if there were a 0:16:12.840 --> 0:16:15.400 lot of Pluto like planets that look like Pluto or 0:16:15.440 --> 0:16:17.640 the size of Pluto, but didn't clear its path, and 0:16:17.680 --> 0:16:19.400 then maybe I could see like, Okay, if you let 0:16:19.400 --> 0:16:21.760 Pluto in, you have to let all these other things in. 0:16:22.200 --> 0:16:24.760 But is that the case, or is Pluto just like 0:16:24.840 --> 0:16:26.240 a loan border case. 0:16:26.400 --> 0:16:28.800 Well, Pluto is maybe the thing closest to the edge. 0:16:28.800 --> 0:16:30.960 But there are a lot of things out there, you know, 0:16:30.960 --> 0:16:33.040 there aren't a lot of these dwarf planets that you 0:16:33.160 --> 0:16:36.200 might call planets. You know, Series, for example, is a 0:16:36.320 --> 0:16:38.600 dwarf planet, but it's part of the asteroid belt, and 0:16:38.640 --> 0:16:40.600 there's lots of other stuff in the asteroid belt. So 0:16:40.640 --> 0:16:43.120 you can't say that Series really is a planet because 0:16:43.120 --> 0:16:45.920 it didn't gather together all the other bits. So I 0:16:45.920 --> 0:16:48.000 think that is true that once you open the door 0:16:48.040 --> 0:16:50.480 to Pluto, you have to let in lots of other folks. 0:16:50.600 --> 0:16:52.360 I don't know why that's the problem. Like, let's have 0:16:52.400 --> 0:16:54.840 a solar system with hundreds of planets. That sounds awesome 0:16:54.840 --> 0:16:55.960 to be big party. 0:16:56.320 --> 0:16:58.160 Yeah, more savings to fight with. 0:16:59.360 --> 0:17:01.760 But there is something of a distinction here between objects 0:17:01.840 --> 0:17:04.840 that are basically alone in their orbit and objects that 0:17:04.920 --> 0:17:07.480 are not. And I do think it's really interesting to wonder, like, 0:17:07.640 --> 0:17:11.200 could you have two planet like objects orbiting the Sun 0:17:11.359 --> 0:17:13.159 in the same orbit. Why don't we see that in 0:17:13.200 --> 0:17:15.320 our solar system? Is that something you might see in 0:17:15.359 --> 0:17:16.680 other solar systems, et cetera. 0:17:16.920 --> 0:17:18.320 I see, you want to sort of pivot to the 0:17:18.359 --> 0:17:20.600 question of like what would happen if two planets did 0:17:20.640 --> 0:17:23.840 share an orbit, or two large objects like the Earth 0:17:24.320 --> 0:17:25.360 share it an orbit. 0:17:25.200 --> 0:17:27.560 Could that situation be stable? Why don't we see it? 0:17:27.600 --> 0:17:29.800 Could that form at all? I think those are really 0:17:29.840 --> 0:17:34.200