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Has our solar system lost any planets? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Hey, Daniel, what pets do you have these days?
• 0:10
  Speaker 2: Oh, we just have our rescue dog, Peppito.
• 0:14
  Speaker 1: Haven't you had other pets in the past, like rodents.
• 0:17
  Speaker 2: We did have rats for a time, and we actually
• 0:19
  Speaker 2: had cats before that.
• 0:21
  Speaker 1: Oh what happened Pepito?
• 0:23
  Speaker 2: Ate them? No, we've never had a pet eat another pet.
• 0:29
  Speaker 2: We've only lost them to old age.
• 0:30
  Speaker 1: Old age. All that dark chocolate and big goods in
• 0:33
  Speaker 1: your house just did them in with the heart attack.
• 0:37
  Speaker 2: We don't feed dark chocolate at the dog, but everybody
• 0:40
  Speaker 2: does eat pretty well at our house.
• 0:42
  Speaker 1: Unless you like white chocolate, then your starved.
• 0:44
  Speaker 2: You know. If that's the reason you run away from home,
• 0:46
  Speaker 2: then maybe you never were really a white sun.
• 0:48
  Speaker 1: Wait, if you don't like white chocolate, you're not a
• 0:50
  Speaker 1: white son. It sounds like a white lie.
• 0:53
  Speaker 2: I have a dark secret. Hi.
• 1:10
  Speaker 1: I am Poor hammy cartoonists and the author of Oliver's
• 1:12
  Speaker 1: Great Big Universe.
• 1:13
  Speaker 2: Hi. I'm Daniel. I'm a particle physicist and a professor
• 1:17
  Speaker 2: at UC Irvine, and I will not waiver in my
• 1:20
  Speaker 2: campaign for dark.
• 1:21
  Speaker 1: Chocolate, Dark chocolate, dark matter. You're just a very dark physicist.
• 1:27
  Speaker 2: I'm trying to bring light to the world at the
• 1:29
  Speaker 2: same time as exposed all the dark secrets of the universe.
• 1:32
  Speaker 1: Oh, you're trying to expose dark matter. I thought you
• 1:35
  Speaker 1: were all about letting the universe.
• 1:37
  Speaker 2: Be Absolutely not. I do not believe in universe privacy.
• 1:40
  Speaker 1: You're like the universe paparazzi.
• 1:42
  Speaker 2: That's exactly right, except I'm not selling it to the
• 1:45
  Speaker 2: national inquirer. I'm just publishing papers.
• 1:47
  Speaker 1: Well, your buyer is the cosmological inquirer, the human inquirer.
• 1:55
  Speaker 2: Inquiring brains want to know.
• 1:57
  Speaker 1: Yeah, do you stand outside their home, like, Hey, dark
• 1:59
  Speaker 1: matter over here, over here snapping pictures?
• 2:03
  Speaker 2: If I knew where dark matter lived, I would definitely
• 2:05
  Speaker 2: go there with my dark matter camera.
• 2:06
  Speaker 1: I thought dark matter was all around us. It lives
• 2:09
  Speaker 1: in us and within us. It surrounds us and binds
• 2:13
  Speaker 1: the galaxy together.
• 2:14
  Speaker 2: You're absolutely right, it's everywhere. We just don't know how
• 2:16
  Speaker 2: to take a picture of it.
• 2:17
  Speaker 1: But anyways, welcome to our podcast, Daniel and Jorge Explain
• 2:20
  Speaker 1: the Universe, a production of iHeartRadio.
• 2:22
  Speaker 2: In which we join our inquiring minds with yours to
• 2:25
  Speaker 2: wonder together about the nature of the universe, to think
• 2:29
  Speaker 2: deeply about how everything comes together to make the cosmos
• 2:33
  Speaker 2: and the night sky that we appreciate to think about
• 2:35
  Speaker 2: how the tiniest little particles and the most massive black
• 2:38
  Speaker 2: holes shape the very world we live in, and whether
• 2:42
  Speaker 2: it has always looked this way.
• 2:43
  Speaker 1: That's right. We satisfy our curiosity for stars and what
• 2:46
  Speaker 1: they're doing with their lives, and we take pictures and
• 2:48
  Speaker 1: also sound recordings of what's out there in the universe
• 2:51
  Speaker 1: and what's going on to maybe get a clue about
• 2:54
  Speaker 1: how it all works.
• 2:55
  Speaker 2: We'd like to figure out the fundamental nature of the
• 2:57
  Speaker 2: universal laws that everything follows. But I also like to
• 3:00
  Speaker 2: know the story of the universe. What happened, How did
• 3:04
  Speaker 2: we end up where we are? How long have things
• 3:07
  Speaker 2: looked this way for? How long can we rely on
• 3:09
  Speaker 2: things to look this way? Do we live in a
• 3:12
  Speaker 2: momentary blip of the universe or is this a long
• 3:14
  Speaker 2: term trend?
• 3:15
  Speaker 1: Yeah, looking at our past is a way to look
• 3:17
  Speaker 1: into our future. We can try to deduce. But the
• 3:20
  Speaker 1: rules of the universe are and what they might mean
• 3:22
  Speaker 1: for us in the deep future? What is going to
• 3:24
  Speaker 1: be the future of humanity here in our solar system?
• 3:26
  Speaker 1: Can we call this our home for the next few
• 3:29
  Speaker 1: billion years?
• 3:31
  Speaker 2: Are you not planning to move out of that house
• 3:32
  Speaker 2: for a few billion years, so your kids can always
• 3:34
  Speaker 2: come home and their kids and their kids and their kids.
• 3:36
  Speaker 1: Well, we're kind of just squatting in this solar system,
• 3:38
  Speaker 1: right like we just popped in here, started living here.
• 3:41
  Speaker 1: We didn't ask if anyone owned these planets. What if
• 3:44
  Speaker 1: the real owners come back when they they're like, what
• 3:46
  Speaker 1: is going on here? Call pest control.
• 3:50
  Speaker 2: Don't we have some sort of like solar B and
• 3:52
  Speaker 2: B contract squatter rights. Maybe exactly after one hundred million years,
• 3:57
  Speaker 2: we're officially allowed to call ourselves the owners. It's a
• 4:00
  Speaker 2: good question how long things have looked this way. When
• 4:02
  Speaker 2: you look by the night guy, you expect to see
• 4:04
  Speaker 2: basically the same stars as you did a year ago,
• 4:07
  Speaker 2: and you know that you're looking at roughly the same
• 4:09
  Speaker 2: stars that Newton looked at, and the Egyptians looked at
• 4:12
  Speaker 2: and the Sumerians looked at thousands of years ago. But
• 4:15
  Speaker 2: the Solar system operates on a very different kind of
• 4:18
  Speaker 2: timescale than your life or even human civilization. And in
• 4:22
  Speaker 2: fast forward things don't seem so stable. They seem quite
• 4:24
  Speaker 2: chaotic and dynamic.
• 4:26
  Speaker 1: Yeah, when we were all kids, we learned in school
• 4:28
  Speaker 1: about the different planets in our solar system and how
• 4:30
  Speaker 1: many of there are. And that's basically the same story
• 4:33
  Speaker 1: that our kids are learning in school as well, right, Like,
• 4:35
  Speaker 1: it hasn't really changed so much, except maybe for Pluto.
• 4:39
  Speaker 2: We of course change what we mean by a planet
• 4:42
  Speaker 2: and make up new categories all the time. But you're right,
• 4:45
  Speaker 2: the stuff that's out there that we're seeing, whatever name
• 4:48
  Speaker 2: we give it, hasn't changed in our lifetime or in
• 4:51
  Speaker 2: our grandparents' lifetime.
• 4:52
  Speaker 1: Yeah, And so I guess you kind of get the
• 4:54
  Speaker 1: sense that maybe it will never change, you know, you
• 4:56
  Speaker 1: sort of memorize these facts and these things and think
• 4:59
  Speaker 1: that maybe it's going to be like that forever. But actually,
• 5:02
  Speaker 1: if you look at the grand scale of the Solar
• 5:04
  Speaker 1: System and the universe in or galaxy, things are rapidly changing.
• 5:07
  Speaker 1: If you look at it from that point of view.
• 5:08
  Speaker 2: If the Solar system changes, do you think we all
• 5:10
  Speaker 2: have to go back to elementary school to learn a
• 5:12
  Speaker 2: new mnemonic?
• 5:13
  Speaker 1: Oh, there's a mnemonic. I didn't grow up yours. I
• 5:15
  Speaker 1: don't know what do you use? Obviously the mnemonic did
• 5:21
  Speaker 1: it work because you don't remember it.
• 5:24
  Speaker 2: There's a lot of mnemonics to help you memorize the
• 5:26
  Speaker 2: order of the planets. One of them is my very
• 5:29
  Speaker 2: easy method just speeds up nothing. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Urinus, Neptune.
• 5:36
  Speaker 1: Whoa, that is so not kit friendly. How many kids
• 5:40
  Speaker 1: use methods and have methods?
• 5:42
  Speaker 2: The history of them is actually really funny. There's ones
• 5:44
  Speaker 2: from the fifties that go like men very easily make jugs,
• 5:47
  Speaker 2: serve useful needs.
• 5:48
  Speaker 1: Perhaps, Oh man, I wonder why we'd stopped using that one.
• 5:52
  Speaker 2: And then a more recent one says, my very energetic
• 5:55
  Speaker 2: mother jumps skateboards under nana's patio.
• 5:58
  Speaker 1: Oh, there you go. That's a pretty good one, and
• 6:00
  Speaker 1: true as well for some people.
• 6:01
  Speaker 2: I'm sure my very educated mother just served us notches.
• 6:06
  Speaker 1: Oh that's an even tastier.
• 6:07
  Speaker 2: One, exactly. But the point is that though these things
• 6:11
  Speaker 2: have seemed stable for a long time, it's not necessarily
• 6:14
  Speaker 2: true that they always will be.
• 6:16
  Speaker 1: Yeah, things are always changing, And in fact, you can
• 6:18
  Speaker 1: ask the question of whether our solar SYSM had more
• 6:21
  Speaker 1: planets in the past.
• 6:23
  Speaker 2: It might be that the planets we know today are
• 6:25
  Speaker 2: not all the planets that have ever orbited our star.
• 6:29
  Speaker 1: And if we had more, what happened to them? So
• 6:31
  Speaker 1: today on the podcast will be tackling the question has
• 6:39
  Speaker 1: our Solar System lost any planets? That just seems kind
• 6:43
  Speaker 1: of irresponsible there. How can you lose a whole planet?
• 6:47
  Speaker 2: I mean I had it in my hands and then
• 6:49
  Speaker 2: I put my keys down and the last place.
• 6:51
  Speaker 1: Remember having that planet was on top of the dog.
• 6:56
  Speaker 2: Blamed the dog. Huh, that's the first thing.
• 6:58
  Speaker 1: The dog ate my planet. Classic excuse.
• 7:02
  Speaker 2: Or maybe it just went rogue because it needed to
• 7:04
  Speaker 2: find a white chocolate friendly Solar system. You know, maybe
• 7:07
  Speaker 2: it just didn't fit in here.
• 7:09
  Speaker 1: It just rebelled against your tyranny of trying to dictate
• 7:12
  Speaker 1: what kind of chocolate people should eat or feel good
• 7:14
  Speaker 1: about eating. Doctor, Why.
• 7:17
  Speaker 2: You call it tyranny, I call it wisdom. Let's call
• 7:20
  Speaker 2: the whole thing off.
• 7:22
  Speaker 1: Yeah, that's what I'll tyrn say at two. Yeah, So
• 7:25
  Speaker 1: it's been an interesting story of the Solar System. You
• 7:28
  Speaker 1: got to wonder if maybef we had more than nine
• 7:30
  Speaker 1: or eight planets in the past. Well, we definitely had
• 7:32
  Speaker 1: more planets to pay in the past before Pluto got downgraded.
• 7:34
  Speaker 1: But that's a separate story and a separate reason.
• 7:37
  Speaker 3: Right.
• 7:37
  Speaker 2: Yeah, Pluto is still there, it's just not called the
• 7:40
  Speaker 2: planet anymore. It's called a dwarf planet.
• 7:42
  Speaker 1: Right, But we can ask the question of whether our
• 7:44
  Speaker 1: solar system did really have other giant planets like Jupiter
• 7:48
  Speaker 1: or Mars or Venus, but maybe they decided they didn't
• 7:51
  Speaker 1: like it here.
• 7:51
  Speaker 2: It's really fun to dig into the history of the
• 7:53
  Speaker 2: Solar system and understand how we got here, how it
• 7:56
  Speaker 2: might have been different, and give us a sense for
• 7:58
  Speaker 2: what other solar systems out there are likely to look like.
• 8:01
  Speaker 1: So, as usual, we were wondering how many people had
• 8:03
  Speaker 1: thought about the question of whether our solar system lost
• 8:07
  Speaker 1: any planets, or at least misplaced them temporarily. Maybe, So,
• 8:10
  Speaker 1: as usual, Daniel went out there into the internet to
• 8:12
  Speaker 1: ask people has our Solar system lost any planets?
• 8:16
  Speaker 2: Thanks very much to our group of volunteers. We greatly
• 8:19
  Speaker 2: appreciate them, but we also would like to add you
• 8:21
  Speaker 2: to their ranks. Please don't be shy write to me
• 8:24
  Speaker 2: two questions at Danielanjorge dot com.
• 8:27
  Speaker 1: What do people get I know if they sign up.
• 8:29
  Speaker 2: The satisfaction of hearing their voice on the podcast and
• 8:32
  Speaker 2: a weekly injection of hard physics questions.
• 8:35
  Speaker 1: And also a monthly supply of white chocolate that gets
• 8:38
  Speaker 1: kicked out of your house.
• 8:39
  Speaker 2: I will send you exactly zero grams of white chocolate.
• 8:44
  Speaker 1: Well, think about it for a second. Do you think
• 8:46
  Speaker 1: our Solar System has lost any planets? Here's what people
• 8:50
  Speaker 1: had to say.
• 8:50
  Speaker 3: I don't know if we can know for sure, maybe
• 8:52
  Speaker 3: by the orbits of current planets, but I'd have to
• 8:55
  Speaker 3: assume given the five billion years or so that or
• 8:57
  Speaker 3: some spent around, that at least one planet has come
• 8:59
  Speaker 3: in and been kicked out. But maybe it depends on
• 9:02
  Speaker 3: if we consider those objects planets.
• 9:04
  Speaker 4: So I think that there have been planets knocked out
• 9:07
  Speaker 4: of the Solar System, especially since when the Solar System
• 9:10
  Speaker 4: was first created there would have been loads of rocks
• 9:13
  Speaker 4: flying around to form planets. So then there would have
• 9:16
  Speaker 4: been planets formed and then hit by maybe another planet
• 9:19
  Speaker 4: which knocked them out of the system.
• 9:20
  Speaker 5: Nothing that I know of, they're all accounted for. Some
• 9:23
  Speaker 5: of them have lost the designation planet, like Pluto. I
• 9:26
  Speaker 5: think regularly objects get flung out of Solar systems due
• 9:31
  Speaker 5: to gravitational interactions with.
• 9:32
  Speaker 2: Other own jobjects.
• 9:33
  Speaker 5: So I can imagine Jupiter getting tired of somesome little
• 9:37
  Speaker 5: planet and flinging it out. Maybe when we were forming
• 9:39
  Speaker 5: all the planets performing them. Some of them were close
• 9:41
  Speaker 5: to the Sun and got gabbled up. I'm curious to
• 9:43
  Speaker 5: know if there's any record of planets that we're here
• 9:46
  Speaker 5: in now or not.
• 9:47
  Speaker 6: Apart from the reclassification of Pluto as a dwarf planet,
• 9:51
  Speaker 6: meaning that we've effectively lost one planet, I have heard
• 9:54
  Speaker 6: rumors about a tenth planet, which would now be a
• 9:57
  Speaker 6: ninth planet, that potentially all within our inn a soda
• 10:01
  Speaker 6: system and then could have collided with Earth and created
• 10:04
  Speaker 6: the Moon and then spun off out into an orbit
• 10:07
  Speaker 6: way out in our outer Soder system. Other than that,
• 10:10
  Speaker 6: I'm unaware of any lost planets.
• 10:12
  Speaker 1: Interesting answers. It seems to be all over the place.
• 10:15
  Speaker 1: Some people say yes, some people say no, not really,
• 10:17
  Speaker 1: some people say poor Pluto.
• 10:21
  Speaker 2: There does generally seem to be an appreciation of the
• 10:23
  Speaker 2: fact that the Solar System might not have always been
• 10:27
  Speaker 2: an orderly, stately placed that there might have been primordial chaos.
• 10:31
  Speaker 1: That's right. It was a big party here in the
• 10:33
  Speaker 1: Solar System, where we're kind of in the after party
• 10:35
  Speaker 1: of the Solar System, right.
• 10:37
  Speaker 2: We're waking up the next morning going, man, what happened?
• 10:40
  Speaker 2: And has anybody seen a dog?
• 10:43
  Speaker 1: Yeah? Well, why am I waking up next to Venus here?
• 10:46
  Speaker 1: How did that happen?
• 10:47
  Speaker 2: And why is the hot tub filled with white chocolate?
• 10:50
  Speaker 1: Yeah, so let's start with the basics, Daniel, is it
• 10:54
  Speaker 1: even possible for Solar system to lose the planet? I
• 10:58
  Speaker 1: thought that, you know, once you form, things are kind
• 11:01
  Speaker 1: of stuck to you gravitationally in orbits, or that at
• 11:05
  Speaker 1: least that it's hard to escape the gravitational field of
• 11:08
  Speaker 1: like Sun or all these planets. Wouldn't they either fall
• 11:11
  Speaker 1: in or go into a stable orbit.
• 11:13
  Speaker 2: I think the key idea is the word you used, form, Like,
• 11:16
  Speaker 2: when do you consider the Solar System to have formed?
• 11:20
  Speaker 2: The Solar system? Formation is a slow and gradual, constant process.
• 11:24
  Speaker 2: It's basically always changing. And so you can go all
• 11:27
  Speaker 2: the way back to the very beginning of the Solar
• 11:29
  Speaker 2: system to understand the chaos of that formation and understand
• 11:33
  Speaker 2: that that formation is a constant process, that things are
• 11:37
  Speaker 2: always potentially bumping into each other and disturbing each other.
• 11:40
  Speaker 1: Wait, are you saying that if we leave the window
• 11:42
  Speaker 1: open for the fact that maybe the Solar System is
• 11:44
  Speaker 1: still forming, does that mean we technically haven't lost any planets? Like?
• 11:48
  Speaker 1: Can I use it in my real life.
• 11:51
  Speaker 2: No, it just means that during the formation, planets could
• 11:54
  Speaker 2: form and be lost. There is no final form to
• 11:57
  Speaker 2: the Solar System. It's a constantly evolving thing. It's not
• 12:00
  Speaker 2: like at some point somebody says, Okay, the Solar System
• 12:02
  Speaker 2: is finished, let's package it and ship it and move
• 12:05
  Speaker 2: on to the next project. I see.
• 12:06
  Speaker 1: It's like a Pokemon, is what you're saying. It's always evolving,
• 12:10
  Speaker 1: it's looking for its final form.
• 12:12
  Speaker 2: I don't know enough about Pokemon to know whether that
• 12:13
  Speaker 2: analogy holds, So I'm just gonna.
• 12:15
  Speaker 1: Trust you on that. I don't know either. To be honest,
• 12:19
  Speaker 1: I just heard final form and it made me think
• 12:21
  Speaker 1: of Pokemon.
• 12:21
  Speaker 2: Well, it's sort of in the same way that animals
• 12:23
  Speaker 2: never have a final form. Evolution is a constant process.
• 12:26
  Speaker 2: Things are always changing in response to the environment.
• 12:30
  Speaker 1: Except for crocodiles and sharks, they're pretty settled there.
• 12:33
  Speaker 2: In the plateau. Yeah that's true.
• 12:35
  Speaker 1: Yeah, but let me take us through to some of
• 12:37
  Speaker 1: the early history of the Solar System. How do we
• 12:39
  Speaker 1: get planets in the first place.
• 12:40
  Speaker 2: So planetary formation is a super fascinating topic, and it
• 12:43
  Speaker 2: helps us understand like the formation of the Solar System
• 12:46
  Speaker 2: as a whole. Remember that the Solar system forms from
• 12:49
  Speaker 2: the collapse of a huge cloud of like gas and dust.
• 12:53
  Speaker 2: It's mostly hydrogen, which is made in the Big Bang,
• 12:55
  Speaker 2: and it's also interspersed with a bunch of other heavier
• 12:58
  Speaker 2: stuff that's made from other solarss where the stars have
• 13:01
  Speaker 2: already fused heavier elements out of that hydrogen. So you
• 13:04
  Speaker 2: have this big cloud of mostly hydrogen with a few
• 13:06
  Speaker 2: heavier bits in it, and it collapses into stars. You
• 13:09
  Speaker 2: don't just get one solar system. You typically get several
• 13:11
  Speaker 2: made at the same time. In one of these stellar nurseries,
• 13:14
  Speaker 2: we have a big blob of this stuff and it
• 13:16
  Speaker 2: collapses and most of the stuff goes into the center
• 13:18
  Speaker 2: to make a star, like ninety nine percent of the
• 13:20
  Speaker 2: stuff goes in to make the star. But you typically
• 13:23
  Speaker 2: have a disc of gas and dust that's orbiting that star.
• 13:27
  Speaker 2: It's spinning too fast to collapse in the way the
• 13:29
  Speaker 2: Moon is orbiting the Earth without falling into the Earth,
• 13:33
  Speaker 2: and so you get this protoplanetary disc around this new star,
• 13:38
  Speaker 2: and that disc then coalesces into larger stuff. Gravity is
• 13:42
  Speaker 2: doing the work there to pull the gas and dust
• 13:44
  Speaker 2: in the disk into heavier things. And where you have
• 13:47
  Speaker 2: like little spots of iron or little spots of heavier metals,
• 13:51
  Speaker 2: those things will use their gravity to form larger objects.
• 13:54
  Speaker 1: But I think the Solar System formed into a disc first,
• 13:57
  Speaker 1: and then the star kind of ignited.
• 13:59
  Speaker 2: Right. Moment of ignition depends a little bit on the
• 14:02
  Speaker 2: mass of the star. I mean, in some cases you
• 14:03
  Speaker 2: don't even get ignition if there isn't enough mass there.
• 14:06
  Speaker 2: You have like a subcritical brown dwarf, but it's definitely
• 14:09
  Speaker 2: collapsing into a disc as it forms. Right, a big
• 14:11
  Speaker 2: amorphous blob is going to collapse, and it's going to
• 14:13
  Speaker 2: collapse into a disc shape because of its angular rotation.
• 14:17
  Speaker 2: So the two things can sort of happen simultaneously, And
• 14:19
  Speaker 2: when ignition happens depends on the mass of the star.
• 14:22
  Speaker 1: Right, And there's also kind of an intermediate step there
• 14:24
  Speaker 1: where the disc kind of turns into rings for a while.
• 14:28
  Speaker 1: Right before you get the planets.
• 14:30
  Speaker 2: Exactly, you get the seeding of structure and they pull
• 14:33
  Speaker 2: together into larger and larger objects, and rings are basically
• 14:37
  Speaker 2: just clusters of larger objects. So you get these gaps emerging,
• 14:41
  Speaker 2: and then you get those things formed together into planets
• 14:44
  Speaker 2: or not, depending on the tidal forces. A large object
• 14:47
  Speaker 2: can form and sort of gather up a lot of
• 14:49
  Speaker 2: the gas and dust near it, and then it can
• 14:51
  Speaker 2: also distort the other stuff nearby, preventing it from forming.
• 14:54
  Speaker 2: So it's a bit of a chaotic process in the beginning,
• 14:57
  Speaker 2: and it also depends a little bit on your distance
• 14:59
  Speaker 2: from the st There's a point it's called the snow line,
• 15:02
  Speaker 2: after which water tends to be ice, tends to be
• 15:04
  Speaker 2: a solid, and before which it tends to be vapor.
• 15:07
  Speaker 2: Like if you're close enough to the star, it's warm
• 15:09
  Speaker 2: enough that the water is vapor and if you're further
• 15:11
  Speaker 2: from that point, the water is frozen. That helps form
• 15:15
  Speaker 2: giant planets. So you tend to have these large planets
• 15:18
  Speaker 2: with ice and rock seeding structure on the outer part
• 15:21
  Speaker 2: of the Solar System past the snow line, and then
• 15:23
  Speaker 2: less ice so smaller planets before the snow line in
• 15:26
  Speaker 2: the inner Solar system.
• 15:27
  Speaker 1: Right in the inner Solar system, you get all the
• 15:28
  Speaker 1: rocky planets.
• 15:29
  Speaker 2: Right exactly because the gas there is blown away by
• 15:32
  Speaker 2: the radiation from the ignition of the Sun. In the
• 15:35
  Speaker 2: very beginning of the Solar system, the Sun is pumping
• 15:37
  Speaker 2: out a huge amount of ultraviolet, very high energy photons,
• 15:40
  Speaker 2: which tends to blast the inner planets clean, which is why,
• 15:44
  Speaker 2: like our initial atmosphere on Earth was blown off by
• 15:47
  Speaker 2: this stellar wind in the very early years of the
• 15:50
  Speaker 2: Solar System. So you get the rocky planets in the core,
• 15:52
  Speaker 2: and then you get the gas and ice giants out
• 15:55
  Speaker 2: past the snow line.
• 15:56
  Speaker 1: Right, And I think the process is like, yep, these
• 15:58
  Speaker 1: rings kind of like Saturn has rings right now, and
• 16:01
  Speaker 1: the rings eventually little by little collapse into planets or
• 16:05
  Speaker 1: first planet tesimals first, right.
• 16:07
  Speaker 2: Yeah, planet testimals a super fun word. They sound like
• 16:10
  Speaker 2: many cute little planets where they're basically like building blocks
• 16:13
  Speaker 2: of planets, and they don't always form, right, which is
• 16:15
  Speaker 2: why you have like the asteroid belt and the Kuiper Belt.
• 16:18
  Speaker 2: It depends on the tidal forces of the nearby stuff,
• 16:21
  Speaker 2: so it's not happening in isolation. This is complicated interplay
• 16:25
  Speaker 2: between all of the objects.
• 16:26
  Speaker 1: Right, But it's kind of a bit of a runaway process.
• 16:28
  Speaker 1: Like once you seed a planet or once more you know,
• 16:31
  Speaker 1: some planet tesimals moush together, then that becomes kind of
• 16:34
  Speaker 1: a center of gravity and more and more stuff falls
• 16:37
  Speaker 1: into it, and that's kind of how you get a planet.
• 16:39
  Speaker 2: Right, Yeah, that's kind of how you get a planet exactly.
• 16:41
  Speaker 2: And in this initial picture, everything forms very orderly, like
• 16:45
  Speaker 2: they tend to be mostly in the same plane, and
• 16:47
  Speaker 2: it be mostly circular because you have this big disc
• 16:50
  Speaker 2: as we say, that collapses in the rings and then
• 16:52
  Speaker 2: planet ismals and then planets. But once you have these
• 16:55
  Speaker 2: large objects formed with their own significant gravity, then they
• 16:59
  Speaker 2: can start to hug on each other pretty hard, and
• 17:01
  Speaker 2: you can get instabilities, you can get chaos, you can
• 17:04
  Speaker 2: get resonances, and that's how planets can migrate, and they
• 17:07
  Speaker 2: can tug on each other and you might even lose.
• 17:10
  Speaker 1: One, right, because I guess there's no guarantee that your
• 17:13
  Speaker 1: orbit is going to be stable. I mean, it's such
• 17:14
  Speaker 1: a complex and you know, there's so many things moving
• 17:18
  Speaker 1: around that there's no guarantee that even if you're orbiting
• 17:21
  Speaker 1: around the Sun, you're going to be there forever, because
• 17:23
  Speaker 1: something else might come around and knock you off your
• 17:26
  Speaker 1: orbit or pull you away from your orbit, right.
• 17:28
  Speaker 2: And that can be things from outside the Solar System,
• 17:30
  Speaker 2: like a passing star can nudge something and perturb the
• 17:34
  Speaker 2: otherwise stable orbits of the Solar System like even just
• 17:37
  Speaker 2: a little nudge from a star that's coming nearby, it's
• 17:40
  Speaker 2: not like it has to pass right through the Solar
• 17:42
  Speaker 2: system can cause a cascade effect of instabilities. But also,
• 17:46
  Speaker 2: just like the planetismals and the Kuyper Belt or the
• 17:48
  Speaker 2: asteroid belt can tug on stuff, and enough of that
• 17:51
  Speaker 2: happening can cause things to go.
• 17:52
  Speaker 1: Wonky and wonky. They might have gone in our Solar system,
• 17:56
  Speaker 1: perhaps wonky enough to lose a couple of planets here
• 17:58
  Speaker 1: and there. Let's get into that idea and whether or
• 18:02
  Speaker 1: not we did misplace a couple of planets in our history.
• 18:05
  Speaker 1: But first let's take a quick break. All right, we're
• 18:20
  Speaker 1: talking about whether our Solar system has lost any planets.
• 18:23
  Speaker 1: I feel like that sounds very irresponsible of the Solar system.
• 18:27
  Speaker 1: Can would you say, like, have any planets escaped our
• 18:30
  Speaker 1: Solar system?
• 18:30
  Speaker 2: Maybe we've grown up and graduated planets. They're like off
• 18:34
  Speaker 2: into the universe living their best lives.
• 18:36
  Speaker 1: Yeah, there you go. You don't want it to live
• 18:38
  Speaker 1: at home forever.
• 18:39
  Speaker 2: Exactly when your kid graduates and goes to college, you
• 18:42
  Speaker 2: don't consider that you've lost them.
• 18:43
  Speaker 1: Yeah, there you go. So have we shepherded planets out
• 18:47
  Speaker 1: into the larger cosmos is the question of the day.
• 18:50
  Speaker 2: Yeah, in this scenario, they would like come back and
• 18:52
  Speaker 2: visit with their own little moons or something that we
• 18:54
  Speaker 2: could coop over. Oh look, how cute.
• 18:56
  Speaker 1: Oh yeah, yeah, except we already turned their bedroom into
• 18:58
  Speaker 1: like a workout room or a craft and so now
• 19:01
  Speaker 1: there's no room for them.
• 19:02
  Speaker 2: Sorry about that, your orbits being used?
• 19:05
  Speaker 1: Yes, sorry, you'll have to airbnb a nearby apartment or something.
• 19:09
  Speaker 1: But yeah, So it's possible in the early chaos of
• 19:13
  Speaker 1: a solar system to lose a planet, right because things
• 19:16
  Speaker 1: aren't quite settled. Even though we're all bound gravitationally to
• 19:20
  Speaker 1: the central star, things can get kind of wonky and
• 19:23
  Speaker 1: maybe wank enough to actually fling a planet out into space.
• 19:27
  Speaker 2: Exactly and when this happens is sort of the most
• 19:30
  Speaker 2: recent question people have been struggling with. There's a classic
• 19:34
  Speaker 2: model of the formation of the Solar system and how
• 19:36
  Speaker 2: the planets move around that we'll talk about. It's called
• 19:38
  Speaker 2: the Nice model because it was developed by researchers in Nice, France,
• 19:43
  Speaker 2: that has a bit of an issue with when exactly
• 19:45
  Speaker 2: all this chaos happened that might be solved by a
• 19:48
  Speaker 2: more recent model with a different picture for how these
• 19:51
  Speaker 2: instabilities might have been triggered.
• 19:53
  Speaker 1: Well, now, I wonder if some listeners out there might
• 19:55
  Speaker 1: be confused about how you can lose a planet, Like,
• 19:58
  Speaker 1: there isn't that much around us, right in terms of
• 20:00
  Speaker 1: other Solar systems or any large stars or galaxy or
• 20:04
  Speaker 1: you know, very heavy objects. So even if something gets
• 20:07
  Speaker 1: flung into space, wouldn't it eventually come back?
• 20:09
  Speaker 2: You're right that space near the Solar System is pretty empty.
• 20:12
  Speaker 2: I mean, the closest star is light years away, and
• 20:15
  Speaker 2: so its gravitational pull is pretty weak. But you can
• 20:17
  Speaker 2: still have an escape velocity. If you throw something hard
• 20:20
  Speaker 2: enough off the Earth, it will leave the Earth and
• 20:23
  Speaker 2: never return. If you throw something out of the Solar
• 20:26
  Speaker 2: System with enough velocity enough to escape the gravitational well
• 20:30
  Speaker 2: of the Solar System, then it will not return.
• 20:33
  Speaker 1: Mmmmm yeah, I think we talked about that in an
• 20:36
  Speaker 1: other episode. It's kind of a weird kind of math, right,
• 20:38
  Speaker 1: Like you need to have enough velocity so that as
• 20:40
  Speaker 1: you get further and further, the pool of gravity pulling
• 20:43
  Speaker 1: your back gets weaker and weaker, and so actually you
• 20:46
  Speaker 1: kind of outrun the pool of gravity exactly.
• 20:49
  Speaker 2: It seemed confusing because you know that gravity has an
• 20:51
  Speaker 2: infinite extent, like no matter how far away you are,
• 20:54
  Speaker 2: and the Sun is always pulling on you. But just
• 20:56
  Speaker 2: because there are infinite number of contributions doesn't mean it
• 20:59
  Speaker 2: adds up to an infinite force. It's just like any
• 21:01
  Speaker 2: integral or converging series. It can add to a finite
• 21:04
  Speaker 2: amount of energy. So as long as you have more
• 21:06
  Speaker 2: energy than the sum of all the tugs the Sun
• 21:09
  Speaker 2: will ever pull on you, you can escape the Solar System.
• 21:12
  Speaker 2: So if, for example, you have a planet that gets
• 21:15
  Speaker 2: a push from another planet and gets flung out into
• 21:18
  Speaker 2: the deep dark space, it might never return.
• 21:20
  Speaker 1: Yeah, I guess sort of like we've done with spacecraft
• 21:22
  Speaker 1: that we sent out into space right like it left
• 21:25
  Speaker 1: Earth eventually, it was going so fast it left the
• 21:27
  Speaker 1: gravity of Earth and through the gravity of maybe other planets.
• 21:30
  Speaker 1: And now we have some that are going out of
• 21:32
  Speaker 1: the Solar System exactly.
• 21:33
  Speaker 2: That can be a little bit more complicated because they
• 21:35
  Speaker 2: can have rockets and they can use gravitational assists from
• 21:38
  Speaker 2: other planets, but the principle is the same. Like Voyager
• 21:41
  Speaker 2: and Pioneer, they have enough velocity that they're leaving the
• 21:44
  Speaker 2: Solar System without any more rocket burns or gravitational assists.
• 21:48
  Speaker 2: It's definitely possible to leave home.
• 21:50
  Speaker 1: All right. Well, now the question here today is have
• 21:53
  Speaker 1: we actually lost any planets? Did the Solar System have
• 21:56
  Speaker 1: more planets than the eight that we have now, and
• 21:58
  Speaker 1: have we missed or have any left home?
• 22:01
  Speaker 2: But if you look at the pattern of the planets
• 22:03
  Speaker 2: that we have now and you try to tell a
• 22:04
  Speaker 2: story about how we got there, it's a hard thing
• 22:07
  Speaker 2: to do without another planet. The patterns that we see
• 22:10
  Speaker 2: in the eccentricities of the planets and the structure of
• 22:13
  Speaker 2: the Kuiper Belt and the asteroids is much easier to
• 22:16
  Speaker 2: explain if there was at one point another ice giant
• 22:20
  Speaker 2: like Neptune that was flung out of the Solar System.
• 22:24
  Speaker 1: I mean, you sort of look at how the planets
• 22:25
  Speaker 1: are moving now and their orbits, and you basically hit
• 22:29
  Speaker 1: the rewind button, kind of like you use math and
• 22:31
  Speaker 1: a computer to backtrack what the Solar System was doing
• 22:36
  Speaker 1: millions and millions of years ago, and you're saying that
• 22:38
  Speaker 1: it doesn't make sense or what.
• 22:40
  Speaker 2: It actually usually works. In the forward direction, like you
• 22:42
  Speaker 2: start from the Protosolar System and try to evolve forward
• 22:46
  Speaker 2: and see if it matches what we see today. Conceptually
• 22:48
  Speaker 2: it's the same as backtracking, but the way the simulations
• 22:51
  Speaker 2: actually work is forwards. You know, we model physics equations
• 22:54
  Speaker 2: forwards in time, and we try to see if we
• 22:57
  Speaker 2: can get to the current Solar system and explain everything
• 22:59
  Speaker 2: we see. And what we find is that doesn't really
• 23:02
  Speaker 2: work without another planet.
• 23:03
  Speaker 1: But are there like a million things that could have
• 23:05
  Speaker 1: happened in between? Absolutely, how do you make it match
• 23:09
  Speaker 1: what we have now? Like, what do you start with?
• 23:12
  Speaker 1: And if you can make it match, how do you
• 23:14
  Speaker 1: know it's not just you're making it error?
• 23:16
  Speaker 2: Absolutely, it's not definitive, right, it's statistical. It's totally possible
• 23:20
  Speaker 2: that our solar system could have arisen without another planet.
• 23:24
  Speaker 2: But it's just a question of what's more likely. Like
• 23:26
  Speaker 2: when you run the simulations of our solar system, how
• 23:29
  Speaker 2: many times do you get to something like what we
• 23:31
  Speaker 2: have now with a lost planet and without a lost planet?
• 23:35
  Speaker 2: And so is it just easier to make this arrangement
• 23:38
  Speaker 2: with a lost planet or without? It's totally possible to
• 23:41
  Speaker 2: do it without, but it's just less likely. It happens
• 23:43
  Speaker 2: in fewer of those simulations.
• 23:45
  Speaker 1: And by like what we have now, you don't mean
• 23:47
  Speaker 1: like exactly what we have now just kind of like
• 23:49
  Speaker 1: sort of like what we have now.
• 23:51
  Speaker 2: If you run enough simulations, you can get essentially a
• 23:53
  Speaker 2: sense for what's more likely and what's less likely under
• 23:56
  Speaker 2: various hypotheses. And if you have another planet in your system,
• 24:00
  Speaker 2: then you get more simulations that are similar to ours. Yeah,
• 24:03
  Speaker 2: so more like probability gets clustered in the kind of
• 24:06
  Speaker 2: arrangement that we have now. And the cool thing about
• 24:08
  Speaker 2: that is that it tells the story. You can look
• 24:10
  Speaker 2: at those simulations and you can see, oh, what happened
• 24:12
  Speaker 2: in the inner what happened in the early days of
• 24:14
  Speaker 2: the Solar System? How did this happen?
• 24:17
  Speaker 1: Okay, So then scientists have been running these simulations and
• 24:19
  Speaker 1: it's kind of hard to get what we have now
• 24:22
  Speaker 1: without some mystery planet that moved away from the Solar System.
• 24:26
  Speaker 1: How did scientists think that happen?
• 24:28
  Speaker 2: So the original models, called the NIE model, basically blames
• 24:31
  Speaker 2: it on the Kuiper Belt. So in the original Solar system,
• 24:34
  Speaker 2: you have Jupiter, Saturn, Urinus, Neptune, all formed in very nice,
• 24:39
  Speaker 2: neat circular orbits like we talked about, in fairly closely
• 24:41
  Speaker 2: spaced to each other. But then you have these planetismals
• 24:44
  Speaker 2: out in the Kuiper Belt that haven't formed into planets,
• 24:47
  Speaker 2: but they're tugging on Neptune, they're tugging on Urinus, they're
• 24:50
  Speaker 2: tugging on Saturn, and they get pulled into the inner
• 24:52
  Speaker 2: Solar System. And when that happens, these big planets get
• 24:55
  Speaker 2: pushed out a little bit, and then the planetismal falls
• 24:57
  Speaker 2: further into the Solar System until it reaches Jupiter, and
• 25:00
  Speaker 2: then Jupiter actually pushes it back out and Jupiter gets
• 25:03
  Speaker 2: pushed in. The effect of these little planetismals, these little
• 25:06
  Speaker 2: tugs is to pull out Neptune, Saturn, Uriness and to
• 25:09
  Speaker 2: push Jupiter in a little bit. So they're disturbing the
• 25:12
  Speaker 2: Solar System. And you might think, well, what can one
• 25:14
  Speaker 2: little rock do? And the key is that there's lots
• 25:17
  Speaker 2: of these rocks, and so over time this can really
• 25:20
  Speaker 2: have an effect on the orbit of the.
• 25:21
  Speaker 1: Planets because we know that at around that space, that
• 25:25
  Speaker 1: ring of the Solar System, you had a lot of
• 25:27
  Speaker 1: big rocks, and maybe you have a lot of big
• 25:28
  Speaker 1: rocks right now exactly.
• 25:30
  Speaker 2: The Kuiper Belt is huge. There could be like trillions
• 25:32
  Speaker 2: of objects out there. We think today it's the source
• 25:35
  Speaker 2: of comets that fall into the Solar System, the short
• 25:38
  Speaker 2: period comets. There's an even bigger blob of stuff out
• 25:41
  Speaker 2: in the Oort Cloud. It might be the source of
• 25:43
  Speaker 2: long term comments, but it's an enormous, massive stuff out there,
• 25:46
  Speaker 2: and each of those little bits as they interact with
• 25:48
  Speaker 2: the Solar System can give a little tug. You have
• 25:51
  Speaker 2: these nice circular orbits that were formed initially, but now
• 25:54
  Speaker 2: they're getting perturbed by these tugs from all these rocks
• 25:57
  Speaker 2: in the Kuiper Belt. Mmm.
• 25:59
  Speaker 1: Okay, scientist think that maybe these rocks from the Kuyper
• 26:01
  Speaker 1: berl maybe cause some planet that we had before to
• 26:05
  Speaker 1: exit the Solar System.
• 26:06
  Speaker 2: Well, essentially leads to some instability because you're pushing Jupiter in,
• 26:10
  Speaker 2: you're pushing Neptune, Saturn, Urinus out, and then those planets
• 26:13
  Speaker 2: start to interact like they used to be in a nice,
• 26:15
  Speaker 2: happy orbit. But now you get instabilities and resonances from
• 26:19
  Speaker 2: those planets themselves. Jupiter starts to drift inwards, and then
• 26:23
  Speaker 2: Saturn pulls on Jupiter, and Jupiter pulls on Saturn. You
• 26:26
  Speaker 2: start to get a regular orbits, and Saturn actually pulling
• 26:28
  Speaker 2: on Jupiter is what saves it. Saturn pulls on Jupiter
• 26:31
  Speaker 2: and changes its direction so it migrates back out away
• 26:34
  Speaker 2: from the Sun. Without Saturn there, it might have been
• 26:37
  Speaker 2: that Jupiter would have just like plummeted into the Sun
• 26:39
  Speaker 2: thanks to the influence of the Kuiper Belt.
• 26:41
  Speaker 1: You know, it all sounds kind of complicated, So I
• 26:43
  Speaker 1: wonder why do scientist think that making it more complicated
• 26:46
  Speaker 1: by adding another planet makes it easier to understand? Like
• 26:49
  Speaker 1: it's all really complex dynamics, right, Like, so then how
• 26:52
  Speaker 1: does adding another planet make it easier to predict, like
• 26:56
  Speaker 1: what's the missing thing that we currently have? That missing
• 27:00
  Speaker 1: planet would help with.
• 27:01
  Speaker 2: Some of the features of our Solar system that we
• 27:03
  Speaker 2: see today are difficult to explain without adding another planet,
• 27:07
  Speaker 2: you know, like the irregular orbits of Jupiter and Saturn.
• 27:10
  Speaker 2: They're not perfect circles. There are sort of ellipses that
• 27:13
  Speaker 2: have like a five percent eccentricity, And there's this structure
• 27:16
  Speaker 2: in the material of the Kuiper Belt. A lot of
• 27:18
  Speaker 2: it seems to have been lost, and a lot of
• 27:20
  Speaker 2: the rest of it is in resonance with Neptune. And
• 27:23
  Speaker 2: these things aren't like smoking guns that say like, oh, look,
• 27:26
  Speaker 2: there has to be another planet here. But when you
• 27:28
  Speaker 2: run the simulations, you get these kind of features more
• 27:30
  Speaker 2: often when you add another planet. If you put another
• 27:33
  Speaker 2: ice giant in around the size of Neptune between Saturn
• 27:37
  Speaker 2: and Urinus, then the story you get when you run
• 27:40
  Speaker 2: these simulations more closely resembles the Solar System we have today.
• 27:44
  Speaker 1: And I guess scientists just throw this mystery planet in
• 27:47
  Speaker 1: and all kinds of velocities in all kinds of sizes,
• 27:50
  Speaker 1: and you sort of see overall, like, hey, it does
• 27:52
  Speaker 1: kind of shape the Solar System more into what we
• 27:55
  Speaker 1: have now.
• 27:56
  Speaker 2: Yeah. Another way to say it is like they were
• 27:58
  Speaker 2: running the simulations with just the planets and they were
• 28:01
  Speaker 2: noticing that they pretty rarely ended up describing the situation
• 28:05
  Speaker 2: that we see today, Like it was very unlikely to
• 28:07
  Speaker 2: get Jupiter and Saturn to have these eccentricities, and to
• 28:10
  Speaker 2: have these asteroid belts along Jupiter's orbit, the Trojans and
• 28:14
  Speaker 2: the Greek camp of asteroid belts, those things were pretty
• 28:16
  Speaker 2: rare to get in a Solar system without this additional planet.
• 28:19
  Speaker 2: But when you put that new planet in, it started
• 28:21
  Speaker 2: to be less unlikely. It started to be like, oh,
• 28:23
  Speaker 2: this kind of thing happens pretty frequently, and so it's
• 28:25
  Speaker 2: just a question of like, how do you explain it.
• 28:27
  Speaker 2: It's not the only possible story, right, Maybe there are
• 28:30
  Speaker 2: two other planets. Maybe something else happened that could explain this,
• 28:33
  Speaker 2: but it does make the story more likely.
• 28:36
  Speaker 1: Maybe the planet had a big fight with Jupiter, stormed
• 28:39
  Speaker 1: out of the house with all their bags, left to
• 28:41
  Speaker 1: go live with their aunt or their niece. This is
• 28:43
  Speaker 1: the Nice model, right, This.
• 28:45
  Speaker 2: Is the Nie model exactly. They went to live with
• 28:48
  Speaker 2: their aunt in France.
• 28:49
  Speaker 1: So then that's one model you're seeing. One model says
• 28:51
  Speaker 1: and maybe it was all these big rocks from the
• 28:53
  Speaker 1: Kuiper Belt that maybe caused a lot of instability out
• 28:56
  Speaker 1: there in the icy planets, and then maybe it caused
• 28:58
  Speaker 1: a planet that we used to have to flyway exactly.
• 29:01
  Speaker 2: And one of the nice things about this model until
• 29:03
  Speaker 2: recently was that it lined up with other pieces of
• 29:06
  Speaker 2: evidence for when this instability happened. And in the Nice model,
• 29:10
  Speaker 2: this happens like about a billion years after the Solar
• 29:12
  Speaker 2: system is formed, so you get like the ignition of
• 29:15
  Speaker 2: the Sun, you get the formation and the gas planets
• 29:17
  Speaker 2: and the rocky planets. Things cycle around for a little while,
• 29:21
  Speaker 2: and it takes time for the Kuyper Belt to sort
• 29:23
  Speaker 2: of drive this because these are tiny little rocks. This
• 29:26
  Speaker 2: sort of lines up with another piece of evidence from
• 29:28
  Speaker 2: looking at our Moon. Our moon is a great record
• 29:30
  Speaker 2: for impacts in the Solar System, like when rocks have
• 29:33
  Speaker 2: been raining down in the inner Solar System. And when
• 29:35
  Speaker 2: the astronauts in the Apollo mission went to the Moon,
• 29:38
  Speaker 2: they gathered a bunch of samples to study, like the
• 29:40
  Speaker 2: craters and the impacts, to try to get a sense
• 29:42
  Speaker 2: for like what is the history of the Solar system.
• 29:45
  Speaker 2: One of them been sort of more or less impacts
• 29:48
  Speaker 2: when it's been like bad weather and good weather, and
• 29:50
  Speaker 2: for a long time, there was this evidence for what
• 29:52
  Speaker 2: we call a late heavy bombardment, that there's this period
• 29:55
  Speaker 2: of billion years after the Solar system formed when a
• 29:58
  Speaker 2: lot of rocks were raining down in the the Solar system,
• 30:01
  Speaker 2: And that kind of lines up with the story of
• 30:02
  Speaker 2: the nice model that like all these rocks from the
• 30:04
  Speaker 2: Kuiper Belt were coming in and making trouble and maybe
• 30:07
  Speaker 2: also some of them were landing on the Moon. So
• 30:09
  Speaker 2: that was sort of a nice story.
• 30:11
  Speaker 1: For a while, meaning like there's a lot of activity
• 30:14
  Speaker 1: from the Kuiper Bell which may have contributed to us
• 30:17
  Speaker 1: kicking out an icy planet.
• 30:19
  Speaker 2: Exactly, and until a few years ago that all seemed
• 30:21
  Speaker 2: to kind of hang together. But then there was a
• 30:23
  Speaker 2: reanalysis of this data from the Moon and it turns
• 30:27
  Speaker 2: out that it may have been a mistake.
• 30:28
  Speaker 1: Well, we lost the theory the dog at theory.
• 30:31
  Speaker 2: It turns out of the way the astronauts gathered the
• 30:33
  Speaker 2: data that may have basically only collected data from one
• 30:37
  Speaker 2: big impact. So what we thought was a bunch of
• 30:40
  Speaker 2: impacts that all happened at the same time, like three
• 30:43
  Speaker 2: and a half billion years ago, might have actually just
• 30:45
  Speaker 2: been one big impact that the astronauts gathered from. So
• 30:48
  Speaker 2: it could have been like essentially just a statistical anomaly
• 30:51
  Speaker 2: in the data that made it look like there was
• 30:52
  Speaker 2: really bad weather for like a few hundred million years
• 30:55
  Speaker 2: three and a half billion years ago, But it was
• 30:57
  Speaker 2: really just one bad day that the astronauts happened to
• 31:00
  Speaker 2: elect data from.
• 31:00
  Speaker 1: Wait what, so we didn't we just had one sample.
• 31:04
  Speaker 1: We didn't take some samples from all over the Moon
• 31:06
  Speaker 1: or analyze the craters visually through telescopes, so.
• 31:10
  Speaker 2: We don't have samples from all over the Moon. And
• 31:11
  Speaker 2: they definitely collected a bunch of samples from different locations,
• 31:15
  Speaker 2: and that's why they thought maybe this was like a
• 31:17
  Speaker 2: fair sample from everywhere on the Moon. But a reanalysis
• 31:20
  Speaker 2: of it suggests that a single impact site Imbrium might
• 31:24
  Speaker 2: be responsible for basically all of the evidence that the
• 31:27
  Speaker 2: astronauts gathered. I don't know if the astronauts are being
• 31:29
  Speaker 2: lazy and not following instructions or if it was not
• 31:32
  Speaker 2: a well organized study, but more recent analysis suggests there
• 31:35
  Speaker 2: may have been no late heavy bombardment. There may just
• 31:38
  Speaker 2: be like a gradual decline in the number of impacts
• 31:40
  Speaker 2: over time.
• 31:42
  Speaker 1: And so maybe this idea that kyper Berl maybe caused
• 31:44
  Speaker 1: us to lose an icy planet maybe didn't really happen,
• 31:47
  Speaker 1: or could it still have happened without this late heavy bombardment.
• 31:50
  Speaker 2: This really causes us to doubt that model. And there's
• 31:53
  Speaker 2: been another lingering problem with this Nie model that has
• 31:56
  Speaker 2: never really been answered, which is why the terrestrial planets
• 32:00
  Speaker 2: kind of survived it. If you have these gas giants
• 32:02
  Speaker 2: doing this dance a billion years after the Solar System
• 32:05
  Speaker 2: is formed, when Earth and Mars are also already formed,
• 32:09
  Speaker 2: then how did the Earth and Mars and Venus survive
• 32:12
  Speaker 2: all these gravitational tugs. If Jupiter comes into the inner
• 32:15
  Speaker 2: Solar System basically turns around at the asteroid belt, how
• 32:18
  Speaker 2: does Mars stay in orbit? How does Earth stay where
• 32:21
  Speaker 2: it is? So one concerned about the Nie model has
• 32:24
  Speaker 2: always been how did the terrestrial planets not get disrupted
• 32:27
  Speaker 2: by the giants. So now there's a news story about
• 32:30
  Speaker 2: when this instability happened and what the cause was that
• 32:33
  Speaker 2: doesn't rely on this late heavy bombardment and places the
• 32:36
  Speaker 2: blame on the instability somewhere else.
• 32:39
  Speaker 1: But I guess why do we assume that there was
• 32:41
  Speaker 1: an instability because we think that maybe we did lose
• 32:44
  Speaker 1: a planet.
• 32:44
  Speaker 2: Because we can't explain the orbits and the eccentricities and
• 32:47
  Speaker 2: the structure of the Kyper Belt without some kind of
• 32:50
  Speaker 2: motion of these planets. We know the planets moved around,
• 32:52
  Speaker 2: we know there was interaction. We know that they did
• 32:55
  Speaker 2: not form in the order that we see them today.
• 32:57
  Speaker 1: All right, So then what's this new model? Not so nice,
• 33:02
  Speaker 1: the less nice model exactly, not the Nie model, the
• 33:06
  Speaker 1: Nephew model.
• 33:07
  Speaker 2: The nibbling model. So this model is called the rebound model,
• 33:11
  Speaker 2: and it suggests that this instability happened much much earlier. Actually,
• 33:15
  Speaker 2: while the rocky planets were forming, or maybe even before
• 33:18
  Speaker 2: they formed, that was basically an early instability.
• 33:21
  Speaker 1: Well, that's a big difference in timescale, But don't your
• 33:24
  Speaker 1: simulations as a solar system sort of help you pinpoint
• 33:27
  Speaker 1: when it happened.
• 33:28
  Speaker 2: It turns out that the simulations can come in to
• 33:30
  Speaker 2: either an early instability or a later instability, like the
• 33:34
  Speaker 2: instability for in the nice model, like a billion years
• 33:36
  Speaker 2: after the formation of the Solar system, can explain the
• 33:39
  Speaker 2: orbits that we got if there, in fact was a
• 33:42
  Speaker 2: bunch of interactions from the Kuiper Belt. But you could
• 33:45
  Speaker 2: also have an instability much earlier on that could reproduce
• 33:48
  Speaker 2: the orbits and the eccentricities that we see today.
• 33:51
  Speaker 1: All right, so then what does this model say? What
• 33:53
  Speaker 1: happened according to this model? So this is called the
• 33:56
  Speaker 1: rebound model, and essentially the instability trigger here, the thing
• 33:59
  Speaker 1: that can kicked off all this bouncing around was the
• 34:03
  Speaker 1: interaction of the planets with this gas. Imagine the formation
• 34:07
  Speaker 1: of the Solar system, as we talked about earlier. You
• 34:09
  Speaker 1: have these planets forming and they're pulling their stuff together,
• 34:11
  Speaker 1: but you still have something of a protoplanetary disk. You
• 34:14
  Speaker 1: still have a bunch of gas sort of in between
• 34:16
  Speaker 1: the planets. Now we don't have that today, and the
• 34:18
  Speaker 1: reason is that the Sun has effectively blown all that out.
• 34:21
  Speaker 1: As the Sun triggered and the ignited and its radiation
• 34:24
  Speaker 1: grew and grew, it blew out all that gas from
• 34:26
  Speaker 1: the Solar system. So in the first ten million years
• 34:29
  Speaker 1: or so, that gas disc is sort of moving out
• 34:33
  Speaker 1: through the Solar System and it affects the orbits of
• 34:35
  Speaker 1: those planets. If the planets are passing through the gas,
• 34:38
  Speaker 1: it slows them down, and if that gas is getting
• 34:40
  Speaker 1: pushed out by the star, it actually carries those planets
• 34:44
  Speaker 1: with them a little bit. So as this gas disc
• 34:46
  Speaker 1: is getting pushed out of the Solar System, it passes
• 34:49
  Speaker 1: through all of these orbits and it gives them all
• 34:51
  Speaker 1: a little tweak. So this rebound model suggests that the
• 34:55
  Speaker 1: interaction of the planets with this gas disc as it's
• 34:57
  Speaker 1: getting blown out of the Solar System and trigger these
• 35:00
  Speaker 1: same instabilities and can explain all the features we see
• 35:03
  Speaker 1: in the Solar system today. But couldn't you kind of
• 35:06
  Speaker 1: make the same argument as before with the other model,
• 35:09
  Speaker 1: like Wooden Huck How is it then that we'd the
• 35:11
  Speaker 1: Earth and Mars and Venus have such a nice even
• 35:13
  Speaker 1: orbits if we were disturbed and blown out.
• 35:16
  Speaker 2: Yeah, great question. It's because this happened much earlier, and
• 35:19
  Speaker 2: so essentially this happened before those terrestrial planets even form.
• 35:23
  Speaker 2: The terrestrial planets we think formed after the gas giants.
• 35:26
  Speaker 2: M how come the gas giants have a lot of
• 35:28
  Speaker 2: advantages over the rocky planets in the inner solar systems.
• 35:31
  Speaker 2: Number one, there's ice out there, which is like a
• 35:33
  Speaker 2: solid that can help seed the formation of planets. To
• 35:36
  Speaker 2: there's a lot more gas out there because the Sun
• 35:38
  Speaker 2: hasn't gobbled it up, and you don't have this proto
• 35:41
  Speaker 2: star messing everything up and heating things. So it's much colder,
• 35:44
  Speaker 2: which makes it easier for gravity to pull things together.
• 35:46
  Speaker 2: So the outer Solar system is a much easier place
• 35:49
  Speaker 2: to form planets. So we think that gas planets formed
• 35:51
  Speaker 2: before the gas disc actually evaporated, sometimes in like the
• 35:54
  Speaker 2: two to ten million year range. But rocky planets take
• 35:57
  Speaker 2: longer because the inner Solar system is much hotter and messier,
• 36:01
  Speaker 2: is less gas available to form planets and no ice whatsoever,
• 36:04
  Speaker 2: So those take like thirty to one hundred million years
• 36:06
  Speaker 2: to form.
• 36:07
  Speaker 1: Okay, so I think what you're saying is that this
• 36:09
  Speaker 1: new model, this rebound model, is saying that we kicked
• 36:12
  Speaker 1: off a gassy icy planet a long time ago, before
• 36:16
  Speaker 1: we even had Earth and Venus and Mars and the
• 36:18
  Speaker 1: rocky planets inside, and that it was due to a
• 36:21
  Speaker 1: lot of this gas being blown out of the center.
• 36:23
  Speaker 2: Exactly, and as the sort of inner radius of that
• 36:25
  Speaker 2: gas passes through these early ice giants and gas planets,
• 36:30
  Speaker 2: it triggered that instability. They did their crazy dance with
• 36:33
  Speaker 2: Jupiter moving in and the other planets moving out and
• 36:35
  Speaker 2: ejected an ice giant planet that left the Solar System,
• 36:38
  Speaker 2: And all that happened even before the Earth and Mars
• 36:41
  Speaker 2: were formed, so they didn't mess up the formation of
• 36:44
  Speaker 2: the Earth and Mars because it was already done by then.
• 36:47
  Speaker 1: All right, well, those are both great stories. Now the
• 36:49
  Speaker 1: question is can we see the planet that we kicked out?
• 36:52
  Speaker 1: Are there lonely dejected planets floating out there in space
• 36:56
  Speaker 1: that we can see and maybe identify and track to
• 36:59
  Speaker 1: perhaps our Solar System? So let's stick into that, But
• 37:02
  Speaker 1: first let's take another quick break. All right, we're asking
• 37:17
  Speaker 1: the question, did our Solar system lose a planet or
• 37:22
  Speaker 1: I guess shepherd it out peacefully into the cosmos.
• 37:26
  Speaker 2: That's the niser model. If anything happened, it sounds like
• 37:28
  Speaker 2: we can blame it on the gas giants, Like we
• 37:30
  Speaker 2: weren't even around when all of this went down. It's
• 37:33
  Speaker 2: just the drama we heard about when we showed up.
• 37:35
  Speaker 2: Oh I see.
• 37:36
  Speaker 1: It's like, yeah, it's like you're the younger sibling and
• 37:38
  Speaker 1: there's all this drama before you were even born.
• 37:41
  Speaker 2: Exactly, Like why is everybody so mad? And who is
• 37:44
  Speaker 2: this missing sibling everybody's talking about you never met?
• 37:47
  Speaker 1: Oh wow, this is just god, this is just turned
• 37:50
  Speaker 1: into a Korean drama. I feel like super complicated.
• 37:53
  Speaker 2: But it is sort of the story. I mean, what
• 37:55
  Speaker 2: we learned from this is that these unstable giant planets,
• 37:58
  Speaker 2: the ice giants and the gas basically sculpted the inner
• 38:02
  Speaker 2: Solar system. I mean, it didn't disrupt the already formed
• 38:05
  Speaker 2: Earth in Mars and Venus, but it created the gravitational
• 38:08
  Speaker 2: context for them to form and probably changed how they
• 38:11
  Speaker 2: did form, the way younger siblings arrive, and family dramas
• 38:15
  Speaker 2: that have existed for years.
• 38:17
  Speaker 1: But again, I guess this is just kind of a model, right,
• 38:20
  Speaker 1: or sort of a guess to maybe explain some of
• 38:22
  Speaker 1: what we see. We don't quite know for sure, right.
• 38:24
  Speaker 2: We definitely don't know for sure. We've quibbled before about
• 38:27
  Speaker 2: what a guess means. Scientifically, I think we have a model,
• 38:31
  Speaker 2: we have some evidence for it, we're never exactly sure.
• 38:34
  Speaker 2: I mean, we have not identified a planet and said
• 38:36
  Speaker 2: that's our lost planet. It's just easier to explain what
• 38:40
  Speaker 2: we see in the universe when you add this to
• 38:42
  Speaker 2: the story. But that happens for lots of things, like
• 38:44
  Speaker 2: we don't witness the early years of the Earth's formation,
• 38:47
  Speaker 2: but we have a pretty detailed story about the formation
• 38:50
  Speaker 2: of the Earth based on the patterns of evidence that
• 38:52
  Speaker 2: we see in the rocks beneath our feet. And so
• 38:55
  Speaker 2: that's a big part of science, is developing a story
• 38:57
  Speaker 2: to explain the data, even if you don't directly witness
• 38:59
  Speaker 2: all of those events, right, right.
• 39:01
  Speaker 1: But I guess what I'm trying to say is that
• 39:03
  Speaker 1: we had a pretty good story that seemed to check
• 39:05
  Speaker 1: out and make sense before, but then it turned out
• 39:07
  Speaker 1: to be not quite correct.
• 39:09
  Speaker 2: Yeah, that's true. These stories are always evolving in they're
• 39:11
  Speaker 2: getting better, Like we like the nice model, but there
• 39:13
  Speaker 2: were some dangling questions about how the Earth and Mars
• 39:16
  Speaker 2: survived it. And now we like this new model, the
• 39:18
  Speaker 2: rebound model, But there's always going to be dangling questions,
• 39:20
  Speaker 2: and somebody's going to come along with a better model
• 39:23
  Speaker 2: and maybe tell a different story in five years. It's
• 39:25
  Speaker 2: a constantly evolving story.
• 39:27
  Speaker 1: I guess. But I wonder if maybe like a smoking
• 39:31
  Speaker 1: gun or something to definitely be able to say, like, hey,
• 39:34
  Speaker 1: there used to be a planet here in the Solar
• 39:36
  Speaker 1: System that we don't have anymore, is to actually maybe
• 39:38
  Speaker 1: see this planet that we kicked out or that left
• 39:41
  Speaker 1: Liane its own out there in space. Isn't it possible
• 39:44
  Speaker 1: that we could see a planet like and track it
• 39:46
  Speaker 1: to our Solar system out there beyond our Solar System?
• 39:49
  Speaker 2: I suppose it's possible, But we're talking about events that
• 39:52
  Speaker 2: happened four billion or more years ago, so that planet
• 39:56
  Speaker 2: is pretty far gone by now. If it did leave,
• 39:59
  Speaker 2: we can do so of more indirect discoveries, though. We
• 40:01
  Speaker 2: can look out and say, are there any rogue planets?
• 40:04
  Speaker 2: If this is happening in our Solar System, it should
• 40:06
  Speaker 2: be happening in other Solar systems. Shouldn't space be filled
• 40:10
  Speaker 2: with these ejected ice giants when it happened in other families,
• 40:14
  Speaker 2: not just ours, and we can go and look for those.
• 40:17
  Speaker 1: Yeah, we had a whole episode on rogue planets. There
• 40:20
  Speaker 1: might be a billions of them out there right exactly.
• 40:22
  Speaker 2: We can actually spot some of these using what we
• 40:25
  Speaker 2: call micro lensing. If one of these planets out there
• 40:28
  Speaker 2: floating between stars, passes in front of a star, like
• 40:30
  Speaker 2: a little eclipse, then it'll blink out and actually change
• 40:33
  Speaker 2: the way that light bends around the planet. So we
• 40:36
  Speaker 2: can use these micro lensing techniques to try to spot them.
• 40:39
  Speaker 2: We also have infrared telescopes like the Wise telescope that
• 40:42
  Speaker 2: can try to directly image them. These planets don't glow
• 40:45
  Speaker 2: in the visible light, but they do have some temperature,
• 40:48
  Speaker 2: and everything with the temperature glows in some frequency. These
• 40:51
  Speaker 2: would low in infrared, and so it's possible to see them.
• 40:54
  Speaker 2: So we have seen a bunch of these rogue planets,
• 40:57
  Speaker 2: and so we can estimate that there's like one of
• 41:00
  Speaker 2: these things for every star in the galaxy.
• 41:03
  Speaker 1: Well, I mean there's ae hundred billion of them right
• 41:05
  Speaker 1: in our galaxy.
• 41:06
  Speaker 2: Exactly, and we've only spotted a few of them. And
• 41:08
  Speaker 2: so the calculation of like how many there are is
• 41:11
  Speaker 2: very uncertain. There's a huge extrapolation there, which means a
• 41:14
  Speaker 2: huge uncertainty, but we know it's a pretty big number.
• 41:17
  Speaker 2: We know it's not just like ten in the galaxy.
• 41:20
  Speaker 2: There's lots of these things out there, and that lends
• 41:22
  Speaker 2: credence to this story that, like when solar systems form,
• 41:26
  Speaker 2: there's a period of instability when big planets can get
• 41:29
  Speaker 2: thrown out.
• 41:30
  Speaker 1: So we've actually seen these like if you look at
• 41:32
  Speaker 1: a picture of the nice guy in the infrared, you
• 41:33
  Speaker 1: can see these thoughts moving across the sky.
• 41:36
  Speaker 2: We can actually see these planets, and we have seen
• 41:38
  Speaker 2: with direct imaging some of these rogue planets. Again, not
• 41:41
  Speaker 2: very many, and so we're extrapolating from a handful up
• 41:44
  Speaker 2: to a big number. We've definitely seen non zero and
• 41:47
  Speaker 2: very recently James Webb saw some really crazy stuff out there.
• 41:51
  Speaker 2: They found these Jupiter mass binary objects. They call them jumbos.
• 41:55
  Speaker 2: These are pairs of planets floating out there in the
• 41:58
  Speaker 2: galaxy with no star near by.
• 42:00
  Speaker 1: Wait what, well, first of all, James Webb, you mean
• 42:02
  Speaker 1: the telescope right, Yes, not James web from Erie, Pennsylvania.
• 42:07
  Speaker 2: We did not exhume the previous NASA administrator and ask
• 42:10
  Speaker 2: him to look at the night sky and then write
• 42:12
  Speaker 2: down with what he said. Though that would make a
• 42:14
  Speaker 2: pretty cool graphic novel. Yeah.
• 42:16
  Speaker 1: Yeah, Well, I just don't want to assume everyone knows
• 42:17
  Speaker 1: what James Webb is.
• 42:19
  Speaker 2: No, you're exactly right. The James web Space Telescope a
• 42:22
  Speaker 2: very powerful device that we launched a couple of years
• 42:24
  Speaker 2: ago and is an infrared telescope capable of seeing things
• 42:27
  Speaker 2: that are pretty cold. Spotted forty two pairs of jumbos.
• 42:32
  Speaker 1: WHOA and so is there? Is it weird that they're
• 42:35
  Speaker 1: in pairs? Or does it feel normal that they're in pairs? Meaning?
• 42:38
  Speaker 1: Does that mean that they were ejective from their Solar
• 42:40
  Speaker 1: system in pairs like they left together.
• 42:43
  Speaker 2: It's a great question. We don't know the answer to that.
• 42:46
  Speaker 2: Simulations suggest that it's unlikely for big planets to leave
• 42:50
  Speaker 2: the Solar system together, right. They would have to be
• 42:52
  Speaker 2: like bound together and then leave together, which means that
• 42:55
  Speaker 2: their fragile orbits around each other would have survived very
• 42:58
  Speaker 2: chaotic period. Seems very unlikely. So these are rogue planets
• 43:03
  Speaker 2: that are out there without their star, but they don't
• 43:05
  Speaker 2: seem to have been ejected from solar systems. So it
• 43:08
  Speaker 2: just sort of like adds to the murkiness of what's
• 43:10
  Speaker 2: going on with rogue planets.
• 43:12
  Speaker 1: Whoa wait, wait, so maybe they were ejected and then
• 43:14
  Speaker 1: they met up with another jumbo out there in space.
• 43:18
  Speaker 2: We actually don't have a great story to explain how
• 43:20
  Speaker 2: these even exist. Like that seems very unlikely for all
• 43:24
  Speaker 2: these jupiters to like start dancing around each other just
• 43:26
  Speaker 2: in space.
• 43:27
  Speaker 1: Well, maybe they have like a planet dating app or something.
• 43:31
  Speaker 2: Maybe they're speed dating there, or they're square dancing or something.
• 43:34
  Speaker 2: They're all changing partners.
• 43:35
  Speaker 1: That's right, they have jumpler under phones.
• 43:39
  Speaker 2: Some people suggested maybe they just formed independently, like you
• 43:42
  Speaker 2: had a solar system and it didn't have enough stuff
• 43:45
  Speaker 2: to actually have a star. You just got a couple
• 43:46
  Speaker 2: of jupiters. But we think that there's like a minimum
• 43:49
  Speaker 2: amount of mass you need to get like your own
• 43:51
  Speaker 2: solar system, otherwise you just get slurped up in like
• 43:54
  Speaker 2: a neighboring solar system when that huge stellar nurseries breaking
• 43:57
  Speaker 2: up into chunks that form solar systems. So we think
• 44:00
  Speaker 2: that these things are probably too small to have seeded
• 44:03
  Speaker 2: their own structure and be their own solar system. We
• 44:06
  Speaker 2: don't think they could have been ejected from other solar systems.
• 44:08
  Speaker 2: So it's something of a question of where these came from,
• 44:11
  Speaker 2: you know, just to paint the picture that like, there's
• 44:13
  Speaker 2: a lot we still don't know. There's a lot of
• 44:14
  Speaker 2: guessing going on.
• 44:16
  Speaker 1: But I guess if they didn't come from a solar system,
• 44:19
  Speaker 1: then that doesn't really tell us anything about this idea
• 44:21
  Speaker 1: of how often solar systems kick out planets exactly.
• 44:25
  Speaker 2: But it adds doubt to the argument that because we
• 44:28
  Speaker 2: see a bunch of rogue planets out there that suggest
• 44:31
  Speaker 2: that planets are lost from solar systems, because there are
• 44:33
  Speaker 2: planets out there whose formations we just don't understand and
• 44:36
  Speaker 2: we think don't come from having been lost by a
• 44:38
  Speaker 2: solar system.
• 44:39
  Speaker 1: All right, well, I guess to answer the question of
• 44:41
  Speaker 1: the episode, has our solar system lost any planets? The
• 44:43
  Speaker 1: answer is maybe, we guess. So we guess. Maybe we
• 44:50
  Speaker 1: used to have a brother, an older brother, but now
• 44:53
  Speaker 1: nobody likes to talk about him or her, and it's
• 44:56
  Speaker 1: very awkward. It makes all the models break, all the
• 45:00
  Speaker 1: pets are uncomfortable.
• 45:01
  Speaker 2: Almost all of the models we use to explain the
• 45:03
  Speaker 2: solar system do have an additional planet. It's not absolutely required.
• 45:08
  Speaker 2: It's possible to explain the Solar System without an additional
• 45:11
  Speaker 2: planet that got ejected during one of these early instabilities.
• 45:14
  Speaker 2: But it just makes the story come together more crisply.
• 45:17
  Speaker 2: It makes our Solar system seem less unlikely.
• 45:19
  Speaker 1: Now, how does this match up with I know there
• 45:21
  Speaker 1: are scientists that think that we have maybe a ninth
• 45:24
  Speaker 1: planet in our Solar system. We just can see it
• 45:27
  Speaker 1: planet X, right.
• 45:28
  Speaker 2: Yeah, there are some people who look at like gravitational
• 45:30
  Speaker 2: aberrations in the orbits of our planet to see if
• 45:33
  Speaker 2: there's something else out there tugging on it. But there's
• 45:35
  Speaker 2: no conclusive evidence for that. It's like very very gentle,
• 45:38
  Speaker 2: and there's a lot of disagreement about whether it's just
• 45:40
  Speaker 2: noise or has other explanations.
• 45:42
  Speaker 1: It's almost sort of the same, right, They use simulations
• 45:45
  Speaker 1: and try to figure out what would best explain what
• 45:47
  Speaker 1: we have now.
• 45:48
  Speaker 2: Yeah, exactly, but the data there are not conclusive.
• 45:50
  Speaker 1: All right. Well, another interesting lesson to keep track of
• 45:54
  Speaker 1: your planets. Don't lose them because once they're gone, they're
• 45:56
  Speaker 1: gone forever.
• 45:57
  Speaker 2: And try to understand where you came from and what's
• 45:59
  Speaker 2: your contact is, what happened before you showed up on
• 46:02
  Speaker 2: the scene.
• 46:03
  Speaker 1: Yeah, well, not that we have much influence over what happens,
• 46:05
  Speaker 1: but it's interesting to think about what might happen in
• 46:07
  Speaker 1: the future, Like, is it possible that the Earth might
• 46:10
  Speaker 1: get kicked out of the Solar System right in the
• 46:13
  Speaker 1: future exactly?
• 46:13
  Speaker 2: The difference between these models tells a very different story.
• 46:16
  Speaker 2: If it really is lots of gentle tugs from planet Esimals, well,
• 46:20
  Speaker 2: that could still happen in the future. We have the
• 46:21
  Speaker 2: Orc Cloud, we have the Kuyper Belt. There's still tugging
• 46:24
  Speaker 2: going on. But if it was something that only happened
• 46:27
  Speaker 2: in the very early formation of the Solar System itself,
• 46:30
  Speaker 2: as this gas was pushed out, that's not something that's
• 46:32
  Speaker 2: likely to be reproduced, and so that level of instability
• 46:35
  Speaker 2: is probably not going to happen again.
• 46:37
  Speaker 1: Now, Daniel, if we did have an icy gas planet before,
• 46:40
  Speaker 1: but it was filled with white chocolate, are you happy
• 46:42
  Speaker 1: that it's gone or are you sad that we don't
• 46:45
  Speaker 1: have anymore?
• 46:45
  Speaker 2: No, it's bittersweet. I wish it's the best.
• 46:48
  Speaker 1: No, it's not bitter, it's sweet. It's white chocolate. That's
• 46:51
  Speaker 1: the whole point of white chocolate.
• 46:53
  Speaker 2: It's oversweetened. That's the problem.
• 46:55
  Speaker 1: But maybe it'd be good for you because it would
• 46:56
  Speaker 1: make all the white chocolate lovers go to this planet
• 46:59
  Speaker 1: and leave ours exactly.
• 47:00
  Speaker 2: Let's arrange transit to the frozen planet of white chocolate.
• 47:04
  Speaker 1: Well call it white.
• 47:07
  Speaker 2: No son of mine?
• 47:10
  Speaker 1: All right, Well, we hope you enjoyed that. Thanks for
• 47:12
  Speaker 1: joining us, See you next time.
• 47:19
  Speaker 2: For more science and curiosity, come find us on social media,
• 47:22
  Speaker 2: where we answer questions and post videos. We're on Twitter, Discord, Instant,
• 47:27
  Speaker 2: and now TikTok. Thanks for listening, and remember that Daniel
• 47:30
  Speaker 2: and Jorge Explain the Universe is a production of iHeartRadio.
• 47:34
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• 47:39
  Speaker 2: or wherever you listen to your favorite shows.