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Can planets share an orbit? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Hey, org, did you share a room with siblings when
• 0:11
  Speaker 1: you were a kid?
• 0:12
  Speaker 2: I did. I shared a room with my brother.
• 0:14
  Speaker 1: Ooh, And was that like cozy and fun for the
• 0:16
  Speaker 1: two of you? Or did you get on each other's nerves?
• 0:18
  Speaker 3: It was pretty fun. We get along pretty good. How
• 0:20
  Speaker 3: about you?
• 0:21
  Speaker 1: I shared a room with two brothers and there was
• 0:24
  Speaker 1: not a whole lot of coziness there. We got on
• 0:26
  Speaker 1: each other's nerves a lot.
• 0:28
  Speaker 2: Yikes. Sounds intense.
• 0:29
  Speaker 1: Yeah, I remember after one argument my mom telling us
• 0:32
  Speaker 1: if we couldn't get along, we'd have to live outside. Intense.
• 0:36
  Speaker 3: WHOA, sounds intense? But is that why you like camping
• 0:40
  Speaker 3: so much? Because you did end up outside in the tent?
• 0:42
  Speaker 3: That's that where your love of the stars came from.
• 0:45
  Speaker 3: This is your origin story. It's all because of your brother,
• 0:47
  Speaker 3: your nemesis or nemesi.
• 0:50
  Speaker 1: Is how I extracted something beautiful from a difficult story.
• 0:53
  Speaker 3: Sounds like a hallmark. We we know how you overcame,
• 0:56
  Speaker 3: sibling Riberry.
• 0:57
  Speaker 1: Depends on whether it ends well or not.
• 0:59
  Speaker 2: I guess only ends and one of you dies.
• 1:16
  Speaker 3: Hi am Jorhemick, cartoonist and the author of Oliver's Great
• 1:19
  Speaker 3: Big Universe.
• 1:20
  Speaker 1: Hi, I'm Daniel, I'm a particle physicist and a professor
• 1:23
  Speaker 1: at u C Irvine, and I've been totally eclipsed by
• 1:26
  Speaker 1: my younger brother.
• 1:27
  Speaker 3: Oh boy, is he a more shiny star or something.
• 1:32
  Speaker 1: He's taller than me, he's a professor at a fancier
• 1:34
  Speaker 1: university than I am. What else is there?
• 1:39
  Speaker 2: But does he have a podcast?
• 1:42
  Speaker 1: There you go. I don't know if he wants a podcast,
• 1:45
  Speaker 1: but yeah, that's a good point. I'm going to bring
• 1:46
  Speaker 1: that up at Thanksgiving.
• 1:47
  Speaker 3: Thanks You know, it's super hard to do a podcast,
• 1:51
  Speaker 3: or at least the start one. There's a high bar
• 1:55
  Speaker 3: for putting things on the internet. They don't just let
• 1:56
  Speaker 3: anyone post things on the internet, you know.
• 1:58
  Speaker 1: I guess we'll find out if he listens to the
• 2:00
  Speaker 1: if he responds to this.
• 2:01
  Speaker 2: Oh boy one.
• 2:03
  Speaker 3: In case you're listening, Hello, Daniel's brother. It sounds like
• 2:06
  Speaker 3: we should have you on a podcast and break it
• 2:08
  Speaker 3: down Oprah style.
• 2:10
  Speaker 1: He's been on the podcast once before when we talked
• 2:12
  Speaker 1: about artificial intelligence because he's a machine learning professor.
• 2:15
  Speaker 3: Oh I thought you were going to say he's a
• 2:17
  Speaker 3: machine that too. But anyways, welcome to our podcast. Daniel
• 2:23
  Speaker 3: and Jorge explain the Universe a production of our Heart
• 2:25
  Speaker 3: Radio in.
• 2:26
  Speaker 1: Which we try not to eclipse your knowledge of the universe.
• 2:29
  Speaker 1: We try to shine a light on it. We think
• 2:31
  Speaker 1: everybody should be cozy with the physics of the universe,
• 2:34
  Speaker 1: snuggling up to a deep understanding of what's going on
• 2:37
  Speaker 1: out there, how it all works, how it started, and
• 2:40
  Speaker 1: what story it tells us about where we live and
• 2:43
  Speaker 1: where we will live in the future.
• 2:45
  Speaker 2: That's right.
• 2:45
  Speaker 3: We tried to be your big brother in terms of
• 2:48
  Speaker 3: telling you how the universe works and what we've learned
• 2:50
  Speaker 3: from our mistakes and our discoveries so that you can
• 2:53
  Speaker 3: navigate this fantastic universe with a little bit more ease
• 2:56
  Speaker 3: and a little bit more confidence.
• 2:58
  Speaker 1: I'm not sure Big Brother has the meditations we're looking for.
• 3:01
  Speaker 1: You know, it's a little bit overwhelminging, isn't it.
• 3:04
  Speaker 3: M not necessarily Isn't there like a Big Brother program
• 3:07
  Speaker 3: where you mentor kids.
• 3:09
  Speaker 2: That's a positive thing too.
• 3:10
  Speaker 1: Yeah, there you go. We're not telling you what to
• 3:12
  Speaker 1: think of what not to think. We're just teaching you
• 3:14
  Speaker 1: about the universe.
• 3:16
  Speaker 2: That's right.
• 3:17
  Speaker 3: And there is a lot to know about the universe
• 3:19
  Speaker 3: and to discover and to find out because it is
• 3:21
  Speaker 3: pretty interesting, pretty complex, pretty vast, and also microscopic in
• 3:25
  Speaker 3: the way that it reveals its secrets.
• 3:27
  Speaker 1: And one surefire way to figure out how the universe
• 3:30
  Speaker 1: works is to ask basic questions about it. To look
• 3:33
  Speaker 1: up at the night sky and ask why does this
• 3:35
  Speaker 1: do this? And why does this not do that? How
• 3:37
  Speaker 1: can we see this happening and not some other thing happening.
• 3:40
  Speaker 1: What are the rules of the universe that allow us
• 3:43
  Speaker 1: to have huge planets like Jupiter but not other situations
• 3:46
  Speaker 1: like planets shaped like a pretzel.
• 3:47
  Speaker 3: Yeah, because I guess you can look around and wonder like,
• 3:50
  Speaker 3: are we a result of the rules of the universe
• 3:53
  Speaker 3: or are we like an exception to the rules of
• 3:55
  Speaker 3: the universe.
• 3:56
  Speaker 1: Well, we definitely a results of the rules of the universe,
• 3:58
  Speaker 1: if you believe the universe has rules and it follows them.
• 4:01
  Speaker 1: But there might be weird outcomes and there might be
• 4:03
  Speaker 1: standard outcomes like it. It could be that our solar system
• 4:06
  Speaker 1: is very unusual as an example of things in the galaxy,
• 4:09
  Speaker 1: or it could be that were totally vanilla.
• 4:11
  Speaker 3: Yeah, because as humans here on planet Earth, we only
• 4:13
  Speaker 3: really have one view of one planet that we can
• 4:16
  Speaker 3: study up close so far, and so it makes you
• 4:19
  Speaker 3: wonder if other planets are the same, or if humans
• 4:23
  Speaker 3: could have lived in other planets, could things have been
• 4:26
  Speaker 3: different in our history?
• 4:27
  Speaker 1: That's true, and there are other planets nearby that we
• 4:30
  Speaker 1: can study, though not quite as up close, to try
• 4:32
  Speaker 1: to get more insight into what a planet can be, like,
• 4:35
  Speaker 1: what are the various possibilities how planets can turn out?
• 4:38
  Speaker 3: And do they get along as siblings? Or have any
• 4:41
  Speaker 3: siblings been kicked out of the Solar System and are
• 4:44
  Speaker 3: living in intents by the asteroid build That's right.
• 4:47
  Speaker 1: We talked recently about those really fun theories that there
• 4:49
  Speaker 1: was once an ice giant in the outer Solar System
• 4:51
  Speaker 1: that was ejected during a period of chaos.
• 4:54
  Speaker 3: WHOA, so you think it just couldn't get along with
• 4:57
  Speaker 3: the other planets.
• 4:58
  Speaker 1: I'm wondering who the parent is this analogy? Like, is
• 5:00
  Speaker 1: it really the Sun's fault that it didn't work out?
• 5:03
  Speaker 4: Yeah?
• 5:03
  Speaker 3: And how responsible is it to kick your children outside
• 5:07
  Speaker 3: and live outside?
• 5:08
  Speaker 2: Yeah? Yeah, somebody should call it you universal child services.
• 5:12
  Speaker 1: But one thing we do notice about our Solar System
• 5:15
  Speaker 1: is that the planets all seem to have their own orbits.
• 5:19
  Speaker 1: Jupiter's got an orbit, or Earth has an orbit, Mars
• 5:21
  Speaker 1: has an orbit. It's sort of like everybody's got their
• 5:23
  Speaker 1: own room.
• 5:24
  Speaker 2: They all have their own lane.
• 5:26
  Speaker 1: You mean, yeah, exactly.
• 5:27
  Speaker 3: Like there's no other Earth on the other side of
• 5:30
  Speaker 3: our orbit, right, or didn't scientists think for a while,
• 5:32
  Speaker 3: or maybe there was?
• 5:34
  Speaker 1: It sounds like a pretty cool science fiction story, right,
• 5:36
  Speaker 1: a second Earth on the other side of the Sun.
• 5:38
  Speaker 2: Planet X. Wasn't it called Planet X?
• 5:40
  Speaker 1: I think planet X is an idea for a tenth
• 5:43
  Speaker 1: or now ninth planet that might be out there tugging
• 5:46
  Speaker 1: on distant planets, but wouldn't necessarily share an orbit with ours.
• 5:50
  Speaker 3: But it's technically is it possible that there's like another
• 5:53
  Speaker 3: Earth on the other side of the Sun? Weich just
• 5:55
  Speaker 3: have never seen it because it's on the other side
• 5:57
  Speaker 3: of the Sun.
• 5:58
  Speaker 1: We wouldn't be able to see it directly from Earth.
• 6:01
  Speaker 1: But of course we've had probes go all over the
• 6:03
  Speaker 1: Solar System. We would have seen it, and we would
• 6:05
  Speaker 1: have noticed its gravitational effects on Mars and Venus and
• 6:08
  Speaker 1: other stuff in the Solar System.
• 6:10
  Speaker 3: So I guess each planet does have its own orbit,
• 6:12
  Speaker 3: its own lane.
• 6:13
  Speaker 1: In our Solar System, each planet mostly does have its
• 6:16
  Speaker 1: own lane. But of course the question is why is
• 6:19
  Speaker 1: that and is that typical? So today on the podcast,
• 6:21
  Speaker 1: we'll be tackling the question why don't planet share an orbit?
• 6:30
  Speaker 1: Is it because they couldn't get along? Yeah?
• 6:33
  Speaker 2: And are we the little the younger sibling or are
• 6:35
  Speaker 2: we the more accomplished sibling.
• 6:38
  Speaker 1: I think the younger sibling is often motivated to eclipse
• 6:41
  Speaker 1: the older siblings.
• 6:42
  Speaker 2: Boy, it sounds like a lot to impact there in
• 6:44
  Speaker 2: your family.
• 6:48
  Speaker 1: I'm nothing but proud of my younger brother.
• 6:50
  Speaker 3: Let's stick to physics maybe, but yeah, it's an interesting question.
• 6:53
  Speaker 3: I guess the implied fact is that no planets in
• 6:56
  Speaker 3: our Solar system share an orbit, meaning they're not going
• 7:00
  Speaker 3: around the Sun at the same distance.
• 7:02
  Speaker 1: Yeah, although you could quibble about that in the case
• 7:05
  Speaker 1: of Jupiter. There is some stuff in Jupiter's orbit, not
• 7:08
  Speaker 1: another planet, but it does share its orbit with some
• 7:10
  Speaker 1: other chunks.
• 7:12
  Speaker 3: And I guess the other implied fact is that all
• 7:14
  Speaker 3: the orbits don't overlap. I guess right, because most of
• 7:17
  Speaker 3: the orbits are pretty much circular, right, They're not like
• 7:21
  Speaker 3: ellipses that kind of overlap with each other.
• 7:23
  Speaker 1: You mean, like if they intersect, Yeah.
• 7:25
  Speaker 3: Like they intersect, or if you look at them from
• 7:27
  Speaker 3: the top they're maybe like the two ellipsoids are overlapped.
• 7:30
  Speaker 1: Yeah, I think two ellipsoids that overlap and have different
• 7:32
  Speaker 1: periods would eventually collide. So I don't think you could
• 7:36
  Speaker 1: have that situation for very long.
• 7:37
  Speaker 3: But it's true that most of the orbits are pretty
• 7:39
  Speaker 3: much circular, right.
• 7:40
  Speaker 1: They're all a little bit eccentric. None of them are
• 7:43
  Speaker 1: exactly circular, kind of.
• 7:44
  Speaker 3: Like you and your brothers. They're all a little eccentric
• 7:46
  Speaker 3: as well. I think a little is kind of generous there.
• 7:50
  Speaker 3: We're all quite eccentric. Actually called professors or something.
• 7:55
  Speaker 1: Exactly how does that happen? But in the case of
• 7:57
  Speaker 1: the Solar system, none of the orbits are perfectly circular.
• 8:00
  Speaker 1: They're all at least a little bit eccentric. But yeah,
• 8:02
  Speaker 1: none of them are overlapping. They basically all have their
• 8:05
  Speaker 1: own lanes.
• 8:06
  Speaker 3: So the question is why don't two planets have the
• 8:08
  Speaker 3: same orbit? So, as usually'll be ever wondering how many
• 8:10
  Speaker 3: people out there had thought about this question.
• 8:12
  Speaker 1: Thanks very much to our group of volunteers. We'd love
• 8:15
  Speaker 1: if you joined them. Right to me two questions at
• 8:17
  Speaker 1: Daniel and Jorge dot com, and I'll send the questions
• 8:20
  Speaker 1: on over.
• 8:21
  Speaker 3: So think about it for a second. Why do you
• 8:24
  Speaker 3: think no two planets share an orbit. Here's what people
• 8:28
  Speaker 3: had to say.
• 8:28
  Speaker 5: I think planets don't share orbits because the center of
• 8:32
  Speaker 5: gravity would have to be absolutely stationary, or it'd oscillate
• 8:37
  Speaker 5: and shake itself out of sync.
• 8:39
  Speaker 2: But I think they actually do. It's just very unlikely
• 8:43
  Speaker 2: because it'd be a major coincidence.
• 8:45
  Speaker 4: So I'm under the impression that planet's by definition or
• 8:48
  Speaker 4: celestial objects orbiting stars that have cleared their orbital path
• 8:52
  Speaker 4: of competing debris like asteroids, and that as a planet forms,
• 8:56
  Speaker 4: it's gravity gets stronger and it sucks up other objects
• 9:01
  Speaker 4: in that orbital path. And that's one of the reasons
• 9:03
  Speaker 4: that objects like series are not considered true planets because
• 9:07
  Speaker 4: they share their orbit with a number of other large
• 9:10
  Speaker 4: asteroids and other computing debris.
• 9:13
  Speaker 6: Planets don't share orbits because of the way closters get together.
• 9:18
  Speaker 6: If there is a clumpup matter very close to another
• 9:20
  Speaker 6: glombal matter, they will make a planet, and the things
• 9:23
  Speaker 6: that are fought up are they will make another planet.
• 9:25
  Speaker 3: All right, some interesting answers. Some people think it's maybe
• 9:28
  Speaker 3: unlikely because there would be a big coincidence.
• 9:31
  Speaker 1: Or that gravity just doesn't work that way, that it
• 9:33
  Speaker 1: can't pull things together into two planets.
• 9:35
  Speaker 3: Oh interesting, but I guess you know, thinking about it,
• 9:38
  Speaker 3: like the asteroid built has a whole bunch of mini
• 9:41
  Speaker 3: planets and they're all kind of in the same orbit.
• 9:44
  Speaker 1: Mm hmm, yeah, absolutely, I.
• 9:46
  Speaker 3: Guess we'll dig into that. So first of all, Daniel,
• 9:48
  Speaker 3: let's maybe start with the basics. What is a planet
• 9:51
  Speaker 3: or what do you define as a planet?
• 9:53
  Speaker 1: So a planet famously has a fairly legalistic definition of
• 9:58
  Speaker 1: what it is. And remember this is just a rooms
• 10:00
  Speaker 1: giving names to things, Like there's stuff out there in
• 10:02
  Speaker 1: the universe. The rocks don't care whether you call them
• 10:05
  Speaker 1: a rock or an asteroid or a planet or a planetismal,
• 10:08
  Speaker 1: They're still out there and doing the physics. This is
• 10:10
  Speaker 1: just humans applying like our framework of categorization to the stuff,
• 10:14
  Speaker 1: and different humans on a different planet, or aliens whatever
• 10:17
  Speaker 1: it might come up with a totally different categorization. It's
• 10:20
  Speaker 1: mostly historical. It doesn't really reflect deep underlying physics. But
• 10:24
  Speaker 1: it's language and we should all agree what the meanings
• 10:27
  Speaker 1: of words are. And so in the case of a planet,
• 10:29
  Speaker 1: there are three requirements. One that it's mostly spherical, This
• 10:34
  Speaker 1: is basically isn't big enough, because anything that's big enough
• 10:38
  Speaker 1: is going to be mostly as fear due to gravity.
• 10:40
  Speaker 1: Requirement Number two is that it orbits the Sun and
• 10:43
  Speaker 1: not some other object like a planet, otherwise the Moon
• 10:47
  Speaker 1: would be a candidate for a planet. And then the
• 10:49
  Speaker 1: last one is that it's cleared its path of planetismals
• 10:53
  Speaker 1: and other big objects, basically that of all the stuff
• 10:57
  Speaker 1: in its lane, it's gathered up all the bits into
• 10:59
  Speaker 1: one object.
• 11:00
  Speaker 3: Well, it sounds like by definition then a planet cannot
• 11:04
  Speaker 3: share an orbit, because a planet in your definition, is
• 11:08
  Speaker 3: something that is by itself in an orbit exactly.
• 11:10
  Speaker 1: So technically speaking, like the legal answer is no, because
• 11:15
  Speaker 1: then it wouldn't be a planet. But really we're asking, like,
• 11:17
  Speaker 1: could you have two Jupiters on opposite sides of the
• 11:19
  Speaker 1: Sun orbiting in the same orbit. That would be really fascinating.
• 11:23
  Speaker 1: Now astronomers from this committee would say, well, technically those
• 11:26
  Speaker 1: aren't planets, and we say like, well, we don't really care.
• 11:28
  Speaker 1: It's fascinating that they're doing this thing, whether or not
• 11:31
  Speaker 1: you call them planets.
• 11:32
  Speaker 3: I mean, if there was another Earth orbiting in our orbit,
• 11:34
  Speaker 3: just on the other side of the Sun, we wouldn't
• 11:36
  Speaker 3: be like, that's not a planet. We would still call
• 11:38
  Speaker 3: it a planet, and you'd just be forced to change
• 11:40
  Speaker 3: the definition of a planet.
• 11:42
  Speaker 1: Yeah. Maybe, Or we'd have t shirts saying like Earth
• 11:45
  Speaker 1: isn't a planet, or Earth is a planet, or I'm
• 11:47
  Speaker 1: on Team Earth or whatever. It'd be a whole ridiculous
• 11:49
  Speaker 1: battle really just over names. You know, where do you
• 11:52
  Speaker 1: draw the dotted line?
• 11:53
  Speaker 3: But I guess maybe the question is like, why is
• 11:55
  Speaker 3: that part of the definition? Why is it important for
• 11:58
  Speaker 3: astronomers it a planet? It quote unquote has its own orbit.
• 12:02
  Speaker 1: It's a good question, and I don't think the answer
• 12:04
  Speaker 1: is just scientific. I think it's historical. You know, we
• 12:08
  Speaker 1: try to sometimes reverse engineer these definitions to reflect the
• 12:12
  Speaker 1: decisions we've been making historically. We've been calling these things planets,
• 12:16
  Speaker 1: and we sort of want to have a definition that
• 12:18
  Speaker 1: aligns with the decisions we've already made, even if they
• 12:22
  Speaker 1: aren't the decisions we would have made if we knew
• 12:25
  Speaker 1: better at the time. You know, early on, when we
• 12:28
  Speaker 1: started talking about planets, we didn't understand everything that was
• 12:30
  Speaker 1: out there in the Solar System, all the smaller rocks
• 12:33
  Speaker 1: that were invisible to us. We didn't realize that there
• 12:35
  Speaker 1: was like a full spectrum from tiny rocks to planetisimals,
• 12:38
  Speaker 1: to dwarf planets to real planets.
• 12:40
  Speaker 3: But I guess maybe the idea that this is part
• 12:42
  Speaker 3: of the definition maybe tells me that there are things
• 12:46
  Speaker 3: out there that are spherical that orbit the Sun but
• 12:49
  Speaker 3: that don't have cleared its path of planetesimals, that are
• 12:53
  Speaker 3: maybe as big as some of the things we do
• 12:55
  Speaker 3: call planets.
• 12:55
  Speaker 2: Is that true?
• 12:56
  Speaker 1: Well, basically that's Pluto, right. Pluto got rejected as a
• 12:59
  Speaker 1: planet because it was judged to have not sufficiently cleared
• 13:03
  Speaker 1: the neighborhood around its orbit of other stuff. Basically, if
• 13:07
  Speaker 1: you look in Pluto's orbit, you find other pretty big
• 13:10
  Speaker 1: rocks that are roughly the size of Pluto. Pluto is
• 13:13
  Speaker 1: just one of an example of lots of we call
• 13:16
  Speaker 1: them dwarf planets that far out in the Solar System.
• 13:19
  Speaker 1: They have not gathered together sufficiently to say there's one
• 13:23
  Speaker 1: really dominant object and nothing else out there.
• 13:25
  Speaker 2: Wait wait, wait, wait wait, this was the rule that.
• 13:27
  Speaker 3: They kicked Pluto out because of you mean it's not
• 13:31
  Speaker 3: because of its size. I always thought it was because
• 13:33
  Speaker 3: of its size.
• 13:34
  Speaker 1: It's sort of indirectly because of its size. I mean,
• 13:36
  Speaker 1: if everything else out there in Pluto's orbit was just
• 13:39
  Speaker 1: dust and tiny grains, then they would have said, okay,
• 13:42
  Speaker 1: it's a planet. But because there are chunks of rock
• 13:44
  Speaker 1: out there that are sort of too big to ignore,
• 13:47
  Speaker 1: then you say Pluto hasn't really cleared its orbit. I mean, really,
• 13:51
  Speaker 1: technically speaking, nothing has cleared its orbit, because you know
• 13:54
  Speaker 1: there's dust and all sorts of other rocks in Earth's
• 13:56
  Speaker 1: orbit certainly, right, It's not like it's perfectly empty space
• 14:00
  Speaker 1: in Earth's orbit, So you can ask like, well, what
• 14:02
  Speaker 1: does it mean to clear its orbit? Even that definition
• 14:04
  Speaker 1: gets a little bit fuzzy, but that's the reason why
• 14:07
  Speaker 1: Pluto was demoted.
• 14:08
  Speaker 2: WHOA, I'm a little bit outraged.
• 14:11
  Speaker 3: I feel like this is such a weird technicality to
• 14:14
  Speaker 3: have kick Pluto for.
• 14:15
  Speaker 1: Well, this is the problem with creating categories, right, You're
• 14:18
  Speaker 1: always going to find something on the edge of the category,
• 14:20
  Speaker 1: and then you're going to have to try to crisply
• 14:22
  Speaker 1: define the category, and then you discover the category is
• 14:25
  Speaker 1: just artificial. You're just really drawing dotted lines between a
• 14:28
  Speaker 1: smooth spectrum of stuff. Like I remember when we talked
• 14:31
  Speaker 1: about space centaurs, the things that are so kind of
• 14:34
  Speaker 1: comets and kind of asteroids, And what you discover is
• 14:36
  Speaker 1: really the two things are part of a larger community.
• 14:39
  Speaker 1: And you've drawn a dotted line between comets and asteroids,
• 14:42
  Speaker 1: and it doesn't really make sense to distinguish between them.
• 14:45
  Speaker 1: This is just a problem of humans creating categories that
• 14:48
  Speaker 1: don't really work.
• 14:49
  Speaker 3: But there was sort of like a voter, there was
• 14:51
  Speaker 3: a lot of discussion about Pluto. So what is it
• 14:53
  Speaker 3: about not having anything in its path that is so
• 14:57
  Speaker 3: important to scientists to kick go, you know, change science
• 15:01
  Speaker 3: books basically for everybody. You know, why is that important
• 15:04
  Speaker 3: whether or not it has little chunks of rocks in
• 15:06
  Speaker 3: its path or not.
• 15:07
  Speaker 1: I think it's just sociological, Like we look at Earth
• 15:10
  Speaker 1: and Jupiter and Mars and Venus and we say this
• 15:13
  Speaker 1: is one kind of thing, and Pluto is sort of
• 15:15
  Speaker 1: a different kind of thing because it's different in this way.
• 15:19
  Speaker 1: Is just one example of many big chunks of rock
• 15:22
  Speaker 1: out there in the Pluto orbit. So I think there
• 15:24
  Speaker 1: is a distinction to be made between these two different
• 15:27
  Speaker 1: categories of objects. Then again, it's sort of fuzzy.
• 15:30
  Speaker 3: Meaning like the fact that it has chunks in its
• 15:32
  Speaker 3: path is maybe the only thing that sits it apart
• 15:36
  Speaker 3: from the others, like none of the other things that
• 15:37
  Speaker 3: we call planets have things in its path, and so
• 15:41
  Speaker 3: they're using this as an excuse to kick Pluto out exactly.
• 15:44
  Speaker 1: And when we talk about the history of the formation
• 15:46
  Speaker 1: of the Solar System, you see that it's sort of
• 15:48
  Speaker 1: like one step, you know, the Solar System. You have
• 15:51
  Speaker 1: the planetary disk, and it gathers into rocks and those
• 15:53
  Speaker 1: become planetesimals, and then in some cases they form big
• 15:56
  Speaker 1: planets and other cases they just stay a big spread
• 15:59
  Speaker 1: of planet isimals, they don't really form planets. So in
• 16:01
  Speaker 1: that sense, planets really are sort of like the next
• 16:04
  Speaker 1: step in the formation of an object in the Solar System,
• 16:07
  Speaker 1: and you've got to respect that or reflect it, or
• 16:09
  Speaker 1: at least, you know, describe it.
• 16:11
  Speaker 6: You know.
• 16:11
  Speaker 3: I guess it would make sense if there were a
• 16:12
  Speaker 3: lot of Pluto like planets that look like Pluto or
• 16:15
  Speaker 3: the size of Pluto, but didn't clear its path, and
• 16:17
  Speaker 3: then maybe I could see like, Okay, if you let
• 16:19
  Speaker 3: Pluto in, you have to let all these other things in.
• 16:22
  Speaker 3: But is that the case, or is Pluto just like
• 16:24
  Speaker 3: a loan border case.
• 16:26
  Speaker 1: Well, Pluto is maybe the thing closest to the edge.
• 16:28
  Speaker 1: But there are a lot of things out there, you know,
• 16:30
  Speaker 1: there aren't a lot of these dwarf planets that you
• 16:33
  Speaker 1: might call planets. You know, Series, for example, is a
• 16:36
  Speaker 1: dwarf planet, but it's part of the asteroid belt, and
• 16:38
  Speaker 1: there's lots of other stuff in the asteroid belt. So
• 16:40
  Speaker 1: you can't say that Series really is a planet because
• 16:43
  Speaker 1: it didn't gather together all the other bits. So I
• 16:45
  Speaker 1: think that is true that once you open the door
• 16:48
  Speaker 1: to Pluto, you have to let in lots of other folks.
• 16:50
  Speaker 1: I don't know why that's the problem. Like, let's have
• 16:52
  Speaker 1: a solar system with hundreds of planets. That sounds awesome
• 16:54
  Speaker 1: to be big party.
• 16:56
  Speaker 2: Yeah, more savings to fight with.
• 16:59
  Speaker 1: But there is something of a distinction here between objects
• 17:01
  Speaker 1: that are basically alone in their orbit and objects that
• 17:04
  Speaker 1: are not. And I do think it's really interesting to wonder, like,
• 17:07
  Speaker 1: could you have two planet like objects orbiting the Sun
• 17:11
  Speaker 1: in the same orbit. Why don't we see that in
• 17:13
  Speaker 1: our solar system? Is that something you might see in
• 17:15
  Speaker 1: other solar systems, et cetera.
• 17:16
  Speaker 3: I see, you want to sort of pivot to the
• 17:18
  Speaker 3: question of like what would happen if two planets did
• 17:20
  Speaker 3: share an orbit, or two large objects like the Earth
• 17:24
  Speaker 3: share it an orbit.
• 17:25
  Speaker 1: Could that situation be stable? Why don't we see it?
• 17:27
  Speaker 1: Could that form at all? I think those are really
• 17:29
  Speaker 1: interesting sort of physics questions instead of like category legalistic questions.
• 17:33
  Speaker 3: That sounds like something siblings would argue about for no
• 17:37
  Speaker 3: good reason. All right, well let's dig into these interesting questions.
• 17:40
  Speaker 3: But first let's take a quick break. All right, we're
• 17:55
  Speaker 3: asking the question here today why don't planets share an orbit?
• 17:59
  Speaker 3: And we just went through a defined print to find
• 18:03
  Speaker 3: out that astronomers call a planet something that doesn't share
• 18:07
  Speaker 3: an orbit, So technically planets cannot share an orbit. But
• 18:10
  Speaker 3: now we're going to pivot a little bit and ask
• 18:12
  Speaker 3: the question, well, what would happen if something like the
• 18:14
  Speaker 3: Earth share it an orbit with another big thing like
• 18:18
  Speaker 3: the Earth. Well, first of all, you would get kicked
• 18:20
  Speaker 3: out of the planet category, right.
• 18:24
  Speaker 1: Yeah, that's right. If you built an earth sized death
• 18:26
  Speaker 1: star and put it in orbit on the other side
• 18:28
  Speaker 1: of the Sun, then Earth would no longer be a planet.
• 18:32
  Speaker 3: Would you say, maybe the Moon is still something that
• 18:34
  Speaker 3: we haven't cleared.
• 18:35
  Speaker 1: Well, but the Moon is orbiting the Earth, right, so
• 18:38
  Speaker 1: mm hmmm, Oh, I see what you mean. Does the
• 18:40
  Speaker 1: Moon disqualify the Earth because we haven't absorbed it into
• 18:43
  Speaker 1: the Earth? Oh yeah, these are complicated legal questions.
• 18:47
  Speaker 3: That sounds like we need a lawyer. Is the brother
• 18:49
  Speaker 3: a lawyer, also an accomplished lawyer.
• 18:53
  Speaker 1: Probably he's arguing in front of the Astronomy Supreme Court
• 18:56
  Speaker 1: right now.
• 18:57
  Speaker 2: Yeah. No, he just broken a machine to do it
• 18:59
  Speaker 2: for it.
• 19:00
  Speaker 3: But yeah, so I guess we're asking more of a
• 19:02
  Speaker 3: physics question, not a technical definition question like could you
• 19:06
  Speaker 3: have two giant Earth or to jupiters kind of circling
• 19:10
  Speaker 3: each other maybe opposite sides of the Sun or maybe not.
• 19:14
  Speaker 2: I don't know. That's kind of the question now, right, Yeah, I.
• 19:16
  Speaker 1: Think that's the interesting physics question. You know, is that possible?
• 19:19
  Speaker 1: Is there some law physics that prevents that from happening,
• 19:22
  Speaker 1: either to stop it from forming or to break it
• 19:25
  Speaker 1: up if it did somehow randomly land that way?
• 19:28
  Speaker 3: Because I guess the question is have we seen that
• 19:30
  Speaker 3: We haven't seen that in our Solar system or have
• 19:32
  Speaker 3: we maybe like Pluto has it and anti Pluto out there.
• 19:36
  Speaker 1: So we don't have examples of Earth sized objects with
• 19:40
  Speaker 1: other Earth sized objects in their orbits. But we do
• 19:42
  Speaker 1: have in our Solar system some sort of edge cases,
• 19:46
  Speaker 1: Like Jupiter has a whole collection of asteroids that are
• 19:50
  Speaker 1: not in the asteroid belt per se, the one you
• 19:52
  Speaker 1: think about between Mars and Jupiter, but are actually in
• 19:55
  Speaker 1: its orbit. There's two different groups of asteroids that are
• 19:58
  Speaker 1: orbiting with jupil Wait.
• 20:00
  Speaker 3: Wait, wait, Like on the opposite side of Jupiter from
• 20:03
  Speaker 3: the Sun, there's a whole bunch of debris.
• 20:05
  Speaker 1: So not on the opposite side of Jupiter. It's sort
• 20:07
  Speaker 1: of thirty degrees trailing and thirty degrees ahead of it.
• 20:10
  Speaker 1: Because there are several stable points around Jupiter where you
• 20:13
  Speaker 1: can balance the gravity of Jupiter and the gravity of
• 20:16
  Speaker 1: the Sun, so they cancel out. These are called the
• 20:18
  Speaker 1: lagrange points, And in the fourth and fifth Lagrange points
• 20:22
  Speaker 1: in front of Jupiter and behind Jupiter in its orbit,
• 20:25
  Speaker 1: there's a whole collection of asteroids that are sort of
• 20:27
  Speaker 1: hanging out there.
• 20:28
  Speaker 2: Whoa Well, does that mean Jupiter is not a planet?
• 20:31
  Speaker 1: I know exactly right, Like, has Jupiter really cleared its orbit? Well,
• 20:35
  Speaker 1: it's so much bigger than these rocks that I guess
• 20:38
  Speaker 1: you can say so. But like if I were Pluto's lawyers,
• 20:41
  Speaker 1: I would have raised that example, right right.
• 20:43
  Speaker 3: Why didn't anybody raise that example? Was nobody advocating for
• 20:47
  Speaker 3: Pluto or four science books in general and not confusing
• 20:52
  Speaker 3: the entire human population.
• 20:55
  Speaker 1: I'm not going to make the mistake of trying to
• 20:57
  Speaker 1: defend any of these definitions, because to me, they're all
• 21:00
  Speaker 1: just arbitrary, and they all break down under some scenario.
• 21:03
  Speaker 1: And this is an example, you know, and Earth even
• 21:06
  Speaker 1: has one of these. Earth has an object like this
• 21:09
  Speaker 1: that's in its orbit. That orbit's in one of its
• 21:11
  Speaker 1: lagrange points. It's a pretty big rock.
• 21:13
  Speaker 3: Wait, what really? How big is it? It's not that big.
• 21:17
  Speaker 3: It's like five kilometers in diameter. We've only known about
• 21:20
  Speaker 3: it since like nineteen eighty six when it was first spotted.
• 21:23
  Speaker 3: It's got this terrible name I won't even try to pronounce,
• 21:26
  Speaker 3: but it's spelled c r ui, thh and E. Maybe
• 21:30
  Speaker 3: you can pronounce it, maybe, yeah, but not on air apparently.
• 21:35
  Speaker 1: Anyway, It's the sort of feature of gravity. You know,
• 21:38
  Speaker 1: there are places you can be where you can be
• 21:40
  Speaker 1: in a stable orbit, like the James Web Space Telescope
• 21:42
  Speaker 1: is in one of these lagrange points relative to the
• 21:45
  Speaker 1: Earth and the Sun.
• 21:47
  Speaker 3: Well, I think what you mean by stable orbit points
• 21:50
  Speaker 3: meaning that it has the same location relative to the
• 21:54
  Speaker 3: Earth and it goes around the Sun at the same rate,
• 21:57
  Speaker 3: like it takes the same amount of time to go
• 21:58
  Speaker 3: around the Sun. That's what you mean by like being
• 22:00
  Speaker 3: in a stable position.
• 22:01
  Speaker 1: Well, there's two different things there. One is being in
• 22:03
  Speaker 1: the same orbit, and that means following the same path,
• 22:06
  Speaker 1: taking the same amount of time to go around the Sun.
• 22:08
  Speaker 1: The second thing is whether you're stable, and stability beings
• 22:12
  Speaker 1: like if you get a little push, do you return
• 22:14
  Speaker 1: back to the path you are on or does that
• 22:17
  Speaker 1: cause like a cascade where it creates a bigger push
• 22:19
  Speaker 1: and then a bigger push, and then a bigger push
• 22:21
  Speaker 1: and then you fall away, sort of the way like
• 22:23
  Speaker 1: a pencil balanced on its tip is unstable. The tin
• 22:27
  Speaker 1: is little push and it will fall over. But like
• 22:29
  Speaker 1: a ball in the bottom of a glass is stable.
• 22:31
  Speaker 1: You give it a little push, gravity restores it back to
• 22:34
  Speaker 1: where it was. So some configurations are stable, meaning that
• 22:37
  Speaker 1: gravity will push them back to that configuration if they
• 22:40
  Speaker 1: get pushed by a little rock or hit by the
• 22:42
  Speaker 1: solar wind or whatever. And if you have two objects
• 22:44
  Speaker 1: like the Sun and the Earth, there are five points
• 22:47
  Speaker 1: are called the garage points that are stable. Three of
• 22:50
  Speaker 1: them are in your orbit, and two of them are.
• 22:52
  Speaker 3: Not right, meaning three of them are in the same
• 22:54
  Speaker 3: circle that the Earth traces around the Sun, and two
• 22:57
  Speaker 3: of them are like one of them a little bit
• 22:59
  Speaker 3: further the circle and the other one closer to the Sun.
• 23:02
  Speaker 3: And if you're at those positions going at the right speed,
• 23:04
  Speaker 3: then you're going to trace a circle kind of along with.
• 23:07
  Speaker 1: The Earth exactly. The simplest one to understand is that
• 23:09
  Speaker 1: there's a point between the Earth and the Sun where
• 23:12
  Speaker 1: the gravity cancels up because the Sun is pulling in
• 23:14
  Speaker 1: one way and the Earth is pulling another way. And
• 23:17
  Speaker 1: if you're just the right point, it's not halfway between
• 23:19
  Speaker 1: the Earth and the Sun, because the Sun is obviously
• 23:21
  Speaker 1: more massive and has more gravity, But there is a
• 23:23
  Speaker 1: point there where the Earth and the Sun gravity balances out,
• 23:26
  Speaker 1: and if you're right there, there's effectively no gravity and
• 23:29
  Speaker 1: you could just move with the same period though not
• 23:32
  Speaker 1: the same velocity as the Earth and stay there.
• 23:34
  Speaker 3: Meaning like you'll go around the Sun in exactly a year,
• 23:37
  Speaker 3: just like the Earth.
• 23:38
  Speaker 1: Mm hmm, exactly.
• 23:39
  Speaker 3: That's what it means to kind of share an orbit
• 23:41
  Speaker 3: in that case, you would have a different radius, so
• 23:43
  Speaker 3: you'd have the same period, but it wouldn't really be
• 23:45
  Speaker 3: the same orbit. But there are three of these points
• 23:47
  Speaker 3: that are actually in the same orbit, meaning you're following
• 23:49
  Speaker 3: the same path. One of them is on the other
• 23:52
  Speaker 3: side of the Sun from the Earth, as you said,
• 23:53
  Speaker 3: And that's very intuitive, right, and because you're like exactly
• 23:56
  Speaker 3: balancing the Earth, and so you could just be like
• 23:59
  Speaker 3: constantly a hundred eighty degrees out of phase with the Earth.
• 24:02
  Speaker 3: And then there are two points thirty degrees behind and
• 24:05
  Speaker 3: thirty degrees ahead of the Earth that also have this
• 24:08
  Speaker 3: special gravitational balance where the Sun and the Earth effectively
• 24:12
  Speaker 3: neutralize each other's gravity.
• 24:14
  Speaker 2: And does it depend on how big you are or
• 24:16
  Speaker 2: how heavy you are.
• 24:17
  Speaker 1: So the location of some of these points do depend
• 24:19
  Speaker 1: on the mass ratios, but the other ones are just geometric.
• 24:22
  Speaker 1: So Jupiter has them, Earth has them. All the planets
• 24:26
  Speaker 1: have these lagrange points, and that's why, for example, Jupiter
• 24:29
  Speaker 1: has this collection of asteroids behind it and ahead of it,
• 24:33
  Speaker 1: because they're hanging out at one of these lagrange points.
• 24:36
  Speaker 3: Okay, so I think what we're trying to say here
• 24:38
  Speaker 3: is that each planet has an orbit and each orbit
• 24:41
  Speaker 3: sort of has these spots where you could maybe put
• 24:43
  Speaker 3: in another planet and it would still be stable, and
• 24:46
  Speaker 3: both of them keep going around the Sun, like it's possible.
• 24:48
  Speaker 1: It's possible. One tiny little wrinkle there is that some
• 24:51
  Speaker 1: of these logrange points are stable, some of them are unstable.
• 24:55
  Speaker 1: There are all locations where the gravity balance is out
• 24:57
  Speaker 1: and if you're exactly at the right spot, you can
• 24:59
  Speaker 1: stay there for ever. But some of them are unstable,
• 25:01
  Speaker 1: meaning if you deviate a tiny little bit, it's like
• 25:04
  Speaker 1: a pencil leaning over on the table. It's going to
• 25:06
  Speaker 1: fall over and you're not going to return. Where some
• 25:08
  Speaker 1: of them are stable, meaning that if you deviate a
• 25:10
  Speaker 1: little bit, you'll come back. So the fourth and fifth
• 25:13
  Speaker 1: le Graunge points, so one ahead and behind you in
• 25:15
  Speaker 1: the orbit, are actually stable locations. So yeah, and principle,
• 25:19
  Speaker 1: you could have another Earth that's not on the other
• 25:21
  Speaker 1: side of the Sun, but just like thirty degrees behind
• 25:24
  Speaker 1: us in our orbit, and it could be there and
• 25:26
  Speaker 1: be stable gravitationally.
• 25:28
  Speaker 3: But didn't you say it sort of depends on the mass,
• 25:30
  Speaker 3: like and you can imagine if I put a James
• 25:32
  Speaker 3: Web telescope, it'll be stable there, or maybe a small
• 25:35
  Speaker 3: asteroid or five kilometer rock. But if I put a
• 25:38
  Speaker 3: whole Earth, wouldn't it just destabilize the whole thing? Or
• 25:42
  Speaker 3: wouldn't it be totally a different point?
• 25:45
  Speaker 1: If you put another Earth there, it would be stable,
• 25:47
  Speaker 1: Like the situation is symmetric and they could both survive there.
• 25:51
  Speaker 1: There are mass limitations, like if you put a star
• 25:54
  Speaker 1: there that's much more massive than the Earth I think
• 25:57
  Speaker 1: is like a limit of like twenty five times the
• 25:58
  Speaker 1: mass of the Earth, then make some assumptions it doesn't
• 26:01
  Speaker 1: work anymore. But you could put a pretty massive planet
• 26:03
  Speaker 1: there and it would be stable.
• 26:05
  Speaker 3: Interesting. But then now the question is why isn't there
• 26:08
  Speaker 3: something there? Because I'm sure at the beginning of the
• 26:09
  Speaker 3: Solar system they're asteroids everywhere, there are rocks everywhere. Why
• 26:12
  Speaker 3: didn't those two points start to gather things? And why
• 26:15
  Speaker 3: don't we have a little twin Earth.
• 26:17
  Speaker 1: The answer to that is that we don't really know.
• 26:19
  Speaker 1: I mean, we think that in the formation of a
• 26:21
  Speaker 1: Solar system, it's possible for it to happen. Remember the
• 26:24
  Speaker 1: story we told earlier. We start from a big cloud
• 26:27
  Speaker 1: of gas and dust and leftover bits from other solar
• 26:30
  Speaker 1: systems that have died and that collapses most of it
• 26:33
  Speaker 1: into the star, but like one percent of it stays
• 26:35
  Speaker 1: in this proto planetary disc, a bunch of heavy metals
• 26:39
  Speaker 1: and gas and dust and ice that is moving too
• 26:42
  Speaker 1: fast to fall into the stars. The star gobbles up
• 26:44
  Speaker 1: mostly gas and leaves behind this protoplanetary disc. And then
• 26:48
  Speaker 1: gravity does this thing. It starts from little seeding locations there,
• 26:51
  Speaker 1: little dots of heavy metal or little gravitational spots that
• 26:55
  Speaker 1: have over densities. Starts to cluster together other stuff, and
• 26:57
  Speaker 1: you get the string of rocks. So now instead of
• 27:00
  Speaker 1: having like a disc, you have a bunch of rings,
• 27:02
  Speaker 1: rings of these rocks of various sizes, which then gather
• 27:05
  Speaker 1: together and form stuff. And so one option is that
• 27:09
  Speaker 1: you know it forms into a planet. There's like one
• 27:11
  Speaker 1: dominant thing that pulls out all together into a planet.
• 27:14
  Speaker 1: Another option is that it just sort of stays a
• 27:18
  Speaker 1: ring of rocks because of tidal forces from neighboring planets
• 27:21
  Speaker 1: that prevent it from gathering together. But there's nothing that
• 27:23
  Speaker 1: says in physics that you couldn't have two objects coalescing.
• 27:27
  Speaker 1: You know that two things couldn't have pulled together sort
• 27:30
  Speaker 1: of an each other's lagrange points and ended up being
• 27:33
  Speaker 1: what looks like two planets, although you know the astronomers
• 27:36
  Speaker 1: would have said neither of them are planets.
• 27:38
  Speaker 3: Well, I feel like maybe we skipped the step there.
• 27:40
  Speaker 3: So you're saying, like the early Solar system was a
• 27:43
  Speaker 3: flat disc and then the stuff that was orbiting the
• 27:46
  Speaker 3: Sun or the new Sun kind of arrange itself into rings,
• 27:51
  Speaker 3: sort of like maybe Saturn's rings. So you can imagine
• 27:54
  Speaker 3: the Sun in the middle a bunch of rings, just
• 27:57
  Speaker 3: like Saturn has rings of rocks, and then those rings
• 28:00
  Speaker 3: eventually collapse into planets. Now, what's the process for that, Like,
• 28:06
  Speaker 3: what causes a ring of rocks to suddenly collapse into
• 28:09
  Speaker 3: a giant ball on one specific spot.
• 28:11
  Speaker 1: Well, that's gravity. Also, you know you have one spot
• 28:14
  Speaker 1: along the ring that's denser than another, and so it's
• 28:17
  Speaker 1: going to pull on stuff nearby, stuff that's ahead of it,
• 28:20
  Speaker 1: it's going to pull closer. The stuff that's behind it,
• 28:22
  Speaker 1: it's going to pull closer. And then as it gathers
• 28:24
  Speaker 1: more stuff, it's going to have more gravity. It's gonna
• 28:26
  Speaker 1: be able to reach further along that ring and essentially
• 28:29
  Speaker 1: grab that stuff together.
• 28:30
  Speaker 3: But I can see that for gathering the things around
• 28:32
  Speaker 3: it but what about the things that we're on, like
• 28:34
  Speaker 3: on the opposite side.
• 28:35
  Speaker 1: Of the ring. I think the answer is that we
• 28:36
  Speaker 1: aren't one hundred percent sure how that happens. We don't
• 28:39
  Speaker 1: know for example, if you can really form stuff on
• 28:42
  Speaker 1: the other side of the Solar System that stays there,
• 28:46
  Speaker 1: like for example, Jupiter's asteroids. Did those form? There is
• 28:49
  Speaker 1: an example of exactly what you're talking about, stuff forming
• 28:52
  Speaker 1: along that same ring and not getting absorbed into the
• 28:55
  Speaker 1: planet basically resisting because it's in a lagrange point and
• 28:59
  Speaker 1: it's gravity is to totally balanced. Or is that stuff
• 29:02
  Speaker 1: that came later? Did Jupiter actually clear its own path,
• 29:05
  Speaker 1: use up all the stuff in the ring, and then
• 29:07
  Speaker 1: later on stuff fell into Jupiter's legrange points. We just
• 29:11
  Speaker 1: don't know the answer to that. If stuff really can
• 29:13
  Speaker 1: form stably at the same time as a planet, that's
• 29:17
  Speaker 1: what you're asking, right.
• 29:18
  Speaker 3: Well, I think i'm asking like it once we had
• 29:20
  Speaker 3: a ring of rocks sort of like Saturn has rings.
• 29:23
  Speaker 3: Is it the case that each ring could only clasp
• 29:25
  Speaker 3: into one planet because of the bath Basically like the
• 29:28
  Speaker 3: math doesn't let you make more than one big planet
• 29:32
  Speaker 3: because anything else would be unstable.
• 29:34
  Speaker 1: No, the math would let you imagine a perfectly symmetric ring,
• 29:37
  Speaker 1: and then imagine like ten or twelve or fifty tiny
• 29:41
  Speaker 1: points perfectly spaced around that ring that are a little
• 29:43
  Speaker 1: bit heavier. Those would gather up all the stuff around them.
• 29:46
  Speaker 1: You'd end up with like ten or twelve or fifty
• 29:49
  Speaker 1: or whatever identically sized objects in an orbit around the Sun.
• 29:52
  Speaker 1: Physically and mathematically, it is nothing preventing that from happening.
• 29:55
  Speaker 1: I think the reason why it's not likely to happen
• 29:58
  Speaker 1: is that it requires a lot of symmetry balance for
• 30:00
  Speaker 1: that arrangement to get set up. It's much more likely
• 30:03
  Speaker 1: that one of them is bigger and one of them
• 30:04
  Speaker 1: is smaller, and then the bigger when it eats the
• 30:06
  Speaker 1: smaller one.
• 30:06
  Speaker 3: But I feel like you told me that before that
• 30:09
  Speaker 3: there's only like two stable spots around and stable orbit
• 30:13
  Speaker 3: where other things can be. You know, if I form
• 30:15
  Speaker 3: four miniplanets along the Earth's orbit, that wouldn't like some
• 30:18
  Speaker 3: of them be unstable.
• 30:19
  Speaker 1: It gets much more complicated as soon as you add
• 30:22
  Speaker 1: more than two objects. But no, you could have that
• 30:24
  Speaker 1: stable arrangement. You could have like a thousand planets in
• 30:26
  Speaker 1: a stable orbit around the Sun, as long as they're
• 30:29
  Speaker 1: perfectly equally spaced in equal mass. That's also allowed. Earlier,
• 30:34
  Speaker 1: we were just talking about the two planets around the Sun.
• 30:36
  Speaker 1: But if you allow them for more than two planets,
• 30:38
  Speaker 1: there's a lot more configurations you could have, but they're
• 30:41
  Speaker 1: also much more unstable, like they need to be perfectly
• 30:44
  Speaker 1: balanced in mass. In fact, I found some guy on
• 30:47
  Speaker 1: the web who's done a bunch of simulations of like
• 30:49
  Speaker 1: crazy solar systems.
• 30:51
  Speaker 2: You know, we have to say, some guy on the web, Yeah,
• 30:57
  Speaker 2: what this is? Okay?
• 31:00
  Speaker 6: Mm hmm.
• 31:00
  Speaker 1: I found some guy in the web who posted a
• 31:02
  Speaker 1: blog about simulations he had done about crazy solar systems
• 31:06
  Speaker 1: where you have like sixty jubiters in orbit around the
• 31:10
  Speaker 1: Sun and it's stable, Like if you arrange them perfectly,
• 31:13
  Speaker 1: sixty jupiters can stay in orbit around the Sun if
• 31:17
  Speaker 1: you set them up perfectly.
• 31:18
  Speaker 3: I see, I see. But how do you know he's right?
• 31:21
  Speaker 3: I mean, no offence. But if I told you that
• 31:24
  Speaker 3: some guy in the internet it's only something, would you
• 31:28
  Speaker 3: assume it's true?
• 31:29
  Speaker 1: No, But this one makes sense. I mean, just from
• 31:31
  Speaker 1: symmetry arguments, a ring could collapse and do a bunch
• 31:34
  Speaker 1: of objects as long as it does it symmetrically, then
• 31:37
  Speaker 1: it's still stable. Every one of those objects is the
• 31:39
  Speaker 1: same as any other objects, so it feels the same
• 31:42
  Speaker 1: gravity from all the other ones. They all cancel out essentially.
• 31:45
  Speaker 2: But I wonder how true that is. I don't know.
• 31:48
  Speaker 3: I mean not that I don't trust your guy on
• 31:49
  Speaker 3: the internet, but you know, at some point, maybe, like
• 31:52
  Speaker 3: if you have four things going around the Sun, maybe
• 31:54
  Speaker 3: the angles and the way they interact with each other,
• 31:57
  Speaker 3: and depending on how big they are, maybe it would
• 31:59
  Speaker 3: make it un.
• 32:00
  Speaker 1: I think it's a pretty simple extension of the argument
• 32:03
  Speaker 1: for why you don't feel gravity from anything that orbits
• 32:06
  Speaker 1: the Sun at like the same radius as you or
• 32:09
  Speaker 1: larger or for example, as you dig into the Earth,
• 32:11
  Speaker 1: you're not feeling gravity from layers of the Earth that
• 32:14
  Speaker 1: are larger than you because they all add up to
• 32:16
  Speaker 1: cancel out. There are fewer that are closer to you
• 32:19
  Speaker 1: and more that are further and they all balance out.
• 32:21
  Speaker 1: It's basically the same argument. It's like gravitational shell argument.
• 32:25
  Speaker 1: If you have a whole string of earths in orbit
• 32:27
  Speaker 1: with you, all of their gravity will cancel out.
• 32:30
  Speaker 2: All right.
• 32:30
  Speaker 3: Well, it sounds like we have a big mystery, which
• 32:32
  Speaker 3: is that it sounds like it's possible for two planets
• 32:35
  Speaker 3: to share an orbit definitions notwithstanding, But we don't really
• 32:39
  Speaker 3: see that in our solar system or maybe in other
• 32:42
  Speaker 3: solar systems out there in space. So let's dig a
• 32:45
  Speaker 3: little bit more into that mystery. But first, let's take
• 32:48
  Speaker 3: a quick break. All right, we're asking the question why
• 33:03
  Speaker 3: can't planets share? What's going on? Why are they so selfish?
• 33:08
  Speaker 1: It's the parent's fault.
• 33:09
  Speaker 3: It's always the parent's fault. But yeah, the planets like
• 33:15
  Speaker 3: to be loners. They don't like to share an orbit.
• 33:17
  Speaker 3: And we sort of know that mostly from what we
• 33:20
  Speaker 3: can see, right, because it sounds like theoretically it is
• 33:22
  Speaker 3: possible to have like two Earth orbiting or maybe for
• 33:26
  Speaker 3: Earth orbiting the same circle around the Sun. But we
• 33:30
  Speaker 3: just don't see that, and so the question is like
• 33:32
  Speaker 3: why not?
• 33:32
  Speaker 1: Yeah, I think that mathematically it's possible. If you set
• 33:36
  Speaker 1: up a solar system that way, you're like a solar
• 33:38
  Speaker 1: system builder, and you bring into Jupiter's and you align
• 33:41
  Speaker 1: them perfectly, you could build a solar system like that
• 33:44
  Speaker 1: which would be stable and last a long time.
• 33:46
  Speaker 6: You know.
• 33:46
  Speaker 1: The other question is would a solar system like that
• 33:49
  Speaker 1: form naturally? I think they're. The answer is that it's
• 33:52
  Speaker 1: most likely for things to collapse into one big planet,
• 33:55
  Speaker 1: or for things to not really collapse at all, like
• 33:57
  Speaker 1: Pluto or the asteroid belt because of tidal forces, or
• 34:00
  Speaker 1: they're just two distant gravity. And for things to collapse
• 34:02
  Speaker 1: into two really big or three big objects would require
• 34:06
  Speaker 1: a sort of a perfect symmetry where they like divide
• 34:09
  Speaker 1: up the mass budget into two or three portions and
• 34:12
  Speaker 1: each of them gather it up themselves. I think that
• 34:15
  Speaker 1: just requires a lot of balance for it to happen.
• 34:17
  Speaker 3: Like it basically a big coincidence you're saying. But I
• 34:20
  Speaker 3: guess maybe paint the scenario for us. So we have
• 34:22
  Speaker 3: initially around the young Sun sort of a ring of rocks.
• 34:26
  Speaker 3: Let's say, like there's a ring of rocks around where
• 34:28
  Speaker 3: Earth goes around the Sun in the Earth's orbit, and
• 34:32
  Speaker 3: maybe there's a little bit more more rocks in one spot,
• 34:35
  Speaker 3: and so that one starts to gather more things. But
• 34:37
  Speaker 3: there's a whole bunch of things all around the circle.
• 34:40
  Speaker 3: Does that mean like the things on the other side
• 34:42
  Speaker 3: of the orbit somehow speed up in order to catch
• 34:45
  Speaker 3: up to the Earth or slow down. What causes those
• 34:48
  Speaker 3: things to slow down or speed up, and if they did,
• 34:50
  Speaker 3: wouldn't they change orbits?
• 34:52
  Speaker 1: No, you're right, something on the other side of the Earth,
• 34:55
  Speaker 1: like perfectly opposed to the Earth feels no gravitational tug. Right,
• 34:59
  Speaker 1: the Earth cannot pull that thing into itself because it's
• 35:02
  Speaker 1: at a labraange point, right, So something that's there will
• 35:05
  Speaker 1: stay there. But that's a really tiny spot, the actual
• 35:08
  Speaker 1: exact lagrange point. Anything slightly ahead of it or slightly
• 35:12
  Speaker 1: behind it will feel a gravitational tug from the Earth,
• 35:15
  Speaker 1: and eventually the Earth will pull it into itself.
• 35:19
  Speaker 3: But it has to go all the way around the circle,
• 35:21
  Speaker 3: meaning like it speeds up in the orbit.
• 35:24
  Speaker 2: But if it speeds up, wouldn't it change orbits?
• 35:27
  Speaker 1: Yeah, that's possible. Also, the Earth could tug it, not
• 35:29
  Speaker 1: so that it ends up in the Earth, but that
• 35:31
  Speaker 1: it falls into another orbit or falls into the Sun. Right.
• 35:35
  Speaker 1: And remember that this is a very simplified way of
• 35:37
  Speaker 1: thinking about the Solar System, just one planet and the
• 35:39
  Speaker 1: Sun and one rock. In reality, there's lots of other
• 35:42
  Speaker 1: things going on there, so lots of chaotic tugs from
• 35:45
  Speaker 1: Jupiter and Mars as it passes by, so all sorts
• 35:48
  Speaker 1: of stuff disrupting this pile of rocks, some of them
• 35:50
  Speaker 1: falling out of this orbit and landing on Venus or
• 35:52
  Speaker 1: landing on Mars, or some of them ending up on Earth.
• 35:55
  Speaker 1: That's why Earth has rocks from all over the Solar
• 35:58
  Speaker 1: System that are landing on it, not just things from
• 36:00
  Speaker 1: our orbit.
• 36:01
  Speaker 3: Oh I see you're saying, like maybe the picture I
• 36:03
  Speaker 3: had of how planet's form is not quite correct, Like
• 36:06
  Speaker 3: you know, maybe to go from the equivalent of Saturn's
• 36:08
  Speaker 3: rings around the Sun to a planet, it doesn't mean
• 36:10
  Speaker 3: like a ring of rocks is kind of collapsed into
• 36:13
  Speaker 3: a planet, like Earth might be made out of the.
• 36:16
  Speaker 2: Rocks from different rings.
• 36:17
  Speaker 1: Absolutely it is.
• 36:19
  Speaker 2: Other planets might be made from rocks from other rings.
• 36:22
  Speaker 1: Absolutely, Yeah, there is is not just made from rocks
• 36:25
  Speaker 1: from one specific range of radii. Definitely, stuff has contributed
• 36:29
  Speaker 1: from the inner Solar System and from further out. Absolutely
• 36:32
  Speaker 1: there's a big mix.
• 36:34
  Speaker 2: Oh I see.
• 36:34
  Speaker 3: So like the history of the Solar System is that
• 36:36
  Speaker 3: it pour into a disc then rings. Then it was
• 36:39
  Speaker 3: a free for all or all the siblings for fighting
• 36:42
  Speaker 3: over who gets which toys and which rocks, and then
• 36:45
  Speaker 3: and then whoever was left victorious, whoever it was bigger
• 36:51
  Speaker 3: one exactly yeah, and whoever, I couldn't get along sleeping
• 36:54
  Speaker 3: outside in the tent.
• 36:55
  Speaker 1: And that's mostly the story. And to understand whether that's
• 36:58
  Speaker 1: the story the Solar system, we look around if there's
• 37:00
  Speaker 1: like weird stuff happening, you know, we'd love to have
• 37:02
  Speaker 1: seen two planets in the same orbit so we could
• 37:04
  Speaker 1: try to understand how that happened. There are some really
• 37:07
  Speaker 1: fascinating and interesting counter examples to this that we see
• 37:10
  Speaker 1: even in our own Solar system, like the moons of Saturn.
• 37:14
  Speaker 2: What do you mean, what's going on with the moons
• 37:16
  Speaker 2: of Saturn.
• 37:17
  Speaker 1: So Saturn's got lots of moons, and there's two in
• 37:20
  Speaker 1: particular that swap orbits. So there's the moon Janus and
• 37:25
  Speaker 1: then there's the moon Epimetheus, and these two swap orbits
• 37:29
  Speaker 1: every four years. Like Janus is on the outside and
• 37:32
  Speaker 1: Epimetheus is on the inside, which has a short orbit
• 37:36
  Speaker 1: and it comes really close to Janus and tugs on it,
• 37:39
  Speaker 1: and the gravitational interaction means that they end up swapping.
• 37:42
  Speaker 1: So now Genus is on the inside and Epimetheus is
• 37:45
  Speaker 1: on the outside.
• 37:46
  Speaker 3: Well, well do they swap orbits or it's just that
• 37:49
  Speaker 3: they both have really complicated orbits that overlap each other.
• 37:52
  Speaker 1: Well, there's two different radii and for four years, one
• 37:55
  Speaker 1: of them has the inner one and the other one
• 37:56
  Speaker 1: has the outer one, and then they swap. So you
• 37:58
  Speaker 1: can think about it two ways, like one is they
• 38:00
  Speaker 1: have different lanes and they're changing lanes, or you could
• 38:03
  Speaker 1: think about it in the more general sense, like each
• 38:05
  Speaker 1: moon does four laps on the outer one and then
• 38:08
  Speaker 1: four laps on the inner one, and they're perfectly synced
• 38:10
  Speaker 1: to never be on top of each other.
• 38:13
  Speaker 3: And the reason they change lanes is from the where
• 38:15
  Speaker 3: they interact with each other, or just the way they
• 38:18
  Speaker 3: interact with Saturn, the.
• 38:19
  Speaker 1: Way they interact with each other, like the one on
• 38:21
  Speaker 1: the inner lane catches up to the one on the
• 38:23
  Speaker 1: outer lane and tugs on it, pulling it in, and
• 38:26
  Speaker 1: the gravitational interaction pushes the one from the inner lane out.
• 38:30
  Speaker 3: Well, meaning sort of like a younger sibling who's motivated
• 38:33
  Speaker 3: to catch up to its older sibling and then or
• 38:36
  Speaker 3: takes it for four years.
• 38:38
  Speaker 1: What else motivates younger siblings If not that, I mean
• 38:40
  Speaker 1: that's basically it, right.
• 38:43
  Speaker 3: Wait, are you trying to take credit for your brother's accomplishments?
• 38:45
  Speaker 3: Is this what this is all about.
• 38:48
  Speaker 1: That's right?
• 38:48
  Speaker 3: Is this why this whole episode is just the far
• 38:51
  Speaker 3: you to take some of your brother's glory.
• 38:54
  Speaker 1: My entire life is just nothing but setting the stage
• 38:56
  Speaker 1: to take credit from a younger brother.
• 38:59
  Speaker 3: That's all right, Yeah, okay, you're trying to overtake him
• 39:02
  Speaker 3: and steal his orbit.
• 39:04
  Speaker 1: Yeah. The whole thing is a fifty year long con man.
• 39:08
  Speaker 2: The whole thing is a therapy session.
• 39:11
  Speaker 1: I feel like, Oh, in the end, you know, you're
• 39:14
  Speaker 1: defined by the circumstances in which you're born, just like
• 39:17
  Speaker 1: Saturn and Janus and Epimetheus doomed to do this dance forever.
• 39:21
  Speaker 1: But it's really fascinating to see this like every four years.
• 39:24
  Speaker 1: And it's a funny story because when these moons were discovered,
• 39:26
  Speaker 1: they didn't realize there were actually two moons there basically
• 39:29
  Speaker 1: in the same orbit. They saw one, and then somebody
• 39:31
  Speaker 1: else was looking at that moon and realizing, huh, this
• 39:34
  Speaker 1: doesn't look like the same moon that was previously reported,
• 39:36
  Speaker 1: but it's in the right orbit. What's going on? And
• 39:39
  Speaker 1: took people a while to figure out, actually the two
• 39:41
  Speaker 1: moons here that are swapping orbits?
• 39:43
  Speaker 3: Whoa and does the swapping happen like really fast or
• 39:46
  Speaker 3: over years as well.
• 39:47
  Speaker 1: The swapping happens pretty fast. I mean it's every four
• 39:50
  Speaker 1: years that happens, but the swap itself doesn't take years.
• 39:54
  Speaker 3: And could something like that happen elsewhere or is this
• 39:56
  Speaker 3: like a super duper bizarre circumstance.
• 39:58
  Speaker 1: It's a pretty bizarre sir cumstance. You need exactly the
• 40:01
  Speaker 1: right radii and exactly the right masses. We also don't
• 40:04
  Speaker 1: know how long it can go on for. You know,
• 40:07
  Speaker 1: it's pretty chaotic, and so it seems like something else
• 40:10
  Speaker 1: passing nearby gives just the right tug and one of
• 40:12
  Speaker 1: these things just plummets into Jupiter. But it's an example
• 40:15
  Speaker 1: of how really weird, rare stuff can happen in the
• 40:19
  Speaker 1: Solar system. And it might mean that even if two
• 40:21
  Speaker 1: big planets forming in the same orbit seems unlikely because
• 40:24
  Speaker 1: you need just the right balance, it might happen. It
• 40:27
  Speaker 1: might happen in other solar systems. It might happen more
• 40:30
  Speaker 1: than we even expect.
• 40:31
  Speaker 3: Well, it sounds like it might happen just from how
• 40:33
  Speaker 3: random and chaotic the you know, young Solar system is, right, Like,
• 40:38
  Speaker 3: you know, maybe you wouldn't get two plants from the
• 40:39
  Speaker 3: same ring of rocks. But maybe, you know, you could
• 40:42
  Speaker 3: get the Earth and then something like Mars drifts into
• 40:45
  Speaker 3: our orbit or something, or we swap orbits with Mars,
• 40:48
  Speaker 3: just like these two moons. That's totally possible, right.
• 40:50
  Speaker 1: It's totally possible, And some people think that something like
• 40:53
  Speaker 1: that might have been a cause for the collision actually
• 40:57
  Speaker 1: between the proto Moon and the proto Earth. The theory
• 41:00
  Speaker 1: of the Moon's formation is that there were two proto
• 41:02
  Speaker 1: planets that slammed into each other that formed the Earth
• 41:04
  Speaker 1: in the Moon, and it could have been like two
• 41:06
  Speaker 1: planets that formed separately and then got too close to
• 41:09
  Speaker 1: each other, or maybe they were in each one of
• 41:11
  Speaker 1: each other's lagrange points for a while, but it wasn't
• 41:14
  Speaker 1: stable and then it ended up colliding.
• 41:15
  Speaker 3: And it sounds like it could still happen maybe in
• 41:17
  Speaker 3: our Solar system, Like you know, those meteors that are
• 41:20
  Speaker 3: orbiting with Jupiter ahead and behind it, those could kind
• 41:23
  Speaker 3: of maybe cluster together into something that might look like
• 41:26
  Speaker 3: a planet, couldn't they.
• 41:27
  Speaker 1: Yeah, eventually they might unionize and work together and form
• 41:30
  Speaker 1: their own planet, and then they could protest Jupiter and
• 41:32
  Speaker 1: they could get Jupiter demoted from being a planet or
• 41:36
  Speaker 1: Pluto upgraded. You never know once you start an astronomical
• 41:40
  Speaker 1: lawsuit what happens.
• 41:41
  Speaker 3: Right, it might be like a planetary conspiracy and they
• 41:44
  Speaker 3: all get you know, sued together.
• 41:48
  Speaker 1: Maybe we just get rid of this whole name for
• 41:50
  Speaker 1: a planet. We just stuff out there, man.
• 41:52
  Speaker 3: Unless you just call them, yeah, rocks, big floating rocks,
• 41:56
  Speaker 3: unless they're made out of gas.
• 41:57
  Speaker 1: Oh no, there's big planets the size of the.
• 42:01
  Speaker 3: Balls, just calling balls if it's circular, and as southern space,
• 42:06
  Speaker 3: just call space balls.
• 42:07
  Speaker 1: I know. And they even require these things to be spherical,
• 42:09
  Speaker 1: and none of them actually are sphericle, right, even the
• 42:11
  Speaker 1: Earth is not technically spherical.
• 42:13
  Speaker 3: Oh boy, so it's a lawsuit waiting to happen. Well,
• 42:16
  Speaker 3: how about out there beyond our Solar system? You know
• 42:19
  Speaker 3: now we can see with our telescopes really far away
• 42:23
  Speaker 3: distant stars and distant planets. Have we seen two planets
• 42:27
  Speaker 3: share in orbit out there in the wider universe?
• 42:30
  Speaker 1: We have not yet seen it, and we've looked. You know,
• 42:32
  Speaker 1: we are pretty good at seeing planets around stars in
• 42:36
  Speaker 1: other solar systems in some scenarios. And we can tell
• 42:40
  Speaker 1: because those planets like orbit the star and eclipse it,
• 42:43
  Speaker 1: or they tug on the star, and we can tell
• 42:44
  Speaker 1: about the change and the light from the star. And
• 42:47
  Speaker 1: so it's looking for the wobble in the star and
• 42:50
  Speaker 1: dips in its brightness that give us clues. And from
• 42:53
  Speaker 1: those dips or from those wobbles, we can get a
• 42:55
  Speaker 1: sensul like the period of the planet. And so far
• 42:58
  Speaker 1: we've never seen like two waters or dips with the
• 43:01
  Speaker 1: same period that would indicate like co orbiting planets. So
• 43:06
  Speaker 1: so far we haven't seen anything like that.
• 43:08
  Speaker 3: I feel like maybe there's something else going on here,
• 43:10
  Speaker 3: maybe something that physicists haven't thought about, because it seems possible,
• 43:13
  Speaker 3: it seems sort of not impossible. And given so many
• 43:18
  Speaker 3: planets and asteroids and things out there floating in space
• 43:22
  Speaker 3: in our Solar system, and also all of the trillions
• 43:25
  Speaker 3: of Solar systems we can see out there that we
• 43:27
  Speaker 3: haven't seen one, it seems like there's something going on.
• 43:30
  Speaker 1: There's a conspiracy. Remember that we've looked at only several
• 43:33
  Speaker 1: thousand stars to see if there are planets around them,
• 43:36
  Speaker 1: and there's billions and billions of stars in the galaxy.
• 43:39
  Speaker 1: That might mean that it's unlikely and not that common,
• 43:41
  Speaker 1: but it doesn't mean it doesn't happen. In fact, there
• 43:43
  Speaker 1: are astronomers that used a radio array in Chile to
• 43:46
  Speaker 1: look at a planetary system that's still forming. There's a
• 43:49
  Speaker 1: young star like three hundred and seventy light years from Earth,
• 43:52
  Speaker 1: and it's not done making its planets, like they see
• 43:55
  Speaker 1: exoplanets forming around it, but it's still got a really
• 43:57
  Speaker 1: big disc of protoplanetary stuff. And when they studied this system,
• 44:02
  Speaker 1: they found a big blob of dust in one of
• 44:04
  Speaker 1: the lagrange points near that exoplanet. So that might be
• 44:08
  Speaker 1: like a coplanet that's forming, or it could be that
• 44:12
  Speaker 1: whatever this conspiracy is, you know, breaks that up before.
• 44:15
  Speaker 3: It can happen, Like maybe it's not as stable as
• 44:17
  Speaker 3: you think it is or something. That's what you're saying.
• 44:19
  Speaker 1: Right, Maybe it's technically possible, but this requires such ridiculous
• 44:24
  Speaker 1: balance between all the factors that's never practically achieved in
• 44:27
  Speaker 1: the universe.
• 44:28
  Speaker 3: All right, well, it sounds like maybe the answer to
• 44:29
  Speaker 3: the question of why don't you have two planets sharing
• 44:32
  Speaker 3: in orbit. The answers that are like, we don't know.
• 44:34
  Speaker 3: It seems possible, but we just haven't seen it yet.
• 44:37
  Speaker 1: Yeah, it seems possible. It might just require a very
• 44:40
  Speaker 1: very special set of circumstances that we just haven't had
• 44:43
  Speaker 1: a chance to see yet. But as you look deeper
• 44:45
  Speaker 1: into the universe, everything that's possible, everything that's weird, I
• 44:48
  Speaker 1: think eventually.
• 44:49
  Speaker 3: You will see, like two brothers that get along statistically,
• 44:53
  Speaker 3: it might happen two.
• 44:55
  Speaker 1: Brothers that are professors at exactly the same level of
• 44:58
  Speaker 1: prestigious university.
• 44:59
  Speaker 2: There you go.
• 45:00
  Speaker 3: Make it all depends on their intent. All right, Well,
• 45:04
  Speaker 3: we hope you enjoyed that. Thanks for joining us. See
• 45:07
  Speaker 3: you next time.
• 45:12
  Speaker 1: For more science and curiosity, come find us on social
• 45:15
  Speaker 1: media where we answer questions and post videos. We're on Twitter, Discord, Insta,
• 45:20
  Speaker 1: and now TikTok. Thanks for listening, and remember that Daniel
• 45:24
  Speaker 1: and Jorge Explain the Universe is a production iHeartRadio. For
• 45:27
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• 45:33
  Speaker 1: or wherever you listen to your favorite shows.