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How Did The Moon Form? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: You know, I look up at the sky at night,
• 0:09
  Speaker 1: and one of the most amazing things to stare at
• 0:11
  Speaker 1: as the moon, because it just seems so calm and peaceful,
• 0:15
  Speaker 1: hanging up there in the sky and looking down at us. Yeah,
• 0:18
  Speaker 1: moonlight is so calming, right and reassuring. Yes, especially if
• 0:22
  Speaker 1: you're a vampire or a werewolf. I heard that the
• 0:27
  Speaker 1: moon actually has this crazy, violent, cataclysmic past. Yeah, that's right,
• 0:33
  Speaker 1: hanging up there in the sky acting all common nights.
• 0:35
  Speaker 1: It turns out it may have been party to one
• 0:37
  Speaker 1: of the greatest murder mysteries in the history of the
• 0:40
  Speaker 1: Solar system, a very impactful event, that's right. And I
• 0:45
  Speaker 1: love when there are things hanging out right there on
• 0:48
  Speaker 1: our faces that give us clues as to great drama
• 0:52
  Speaker 1: that took place in deep dark history. Hi. I'm Jorge.
• 1:12
  Speaker 1: I'm a cartoonist, and I'm Daniel. I'm a particle physicist,
• 1:16
  Speaker 1: And welcome to our podcast. Daniel and Jorge explained the
• 1:19
  Speaker 1: universe in which we look around at anything in the
• 1:21
  Speaker 1: universe and try to explain it to you. On today's program,
• 1:25
  Speaker 1: that big white, shiny thing in the night sky, the
• 1:31
  Speaker 1: thing you referred to as the moon, not any moon,
• 1:34
  Speaker 1: Not a moon, The moon, the moon earth little sidekick.
• 1:39
  Speaker 1: That's right. And if you're a person who wonders and
• 1:42
  Speaker 1: thinks about the history of things, you like all of
• 1:45
  Speaker 1: humanity must have looked up in the night sky wondered
• 1:47
  Speaker 1: what are the stars? Where do they come from? But
• 1:49
  Speaker 1: the biggest thing, the fattest thing out there in the
• 1:52
  Speaker 1: night sky is the moon. And what a mystery that
• 1:54
  Speaker 1: must have presented to ancient man and woman. Right, what
• 1:57
  Speaker 1: is that giant disk and where did it come from?
• 2:01
  Speaker 1: That's right, And that's a question that science is still
• 2:04
  Speaker 1: trying to answer. We've gone to the moon, We've looked
• 2:07
  Speaker 1: at the moon with crazy telescopes, people have walked across
• 2:10
  Speaker 1: it and brought samples back. But we still don't know
• 2:12
  Speaker 1: the answer to the question how did the Earth get
• 2:15
  Speaker 1: its moon. That's a crazy idea to me that we
• 2:18
  Speaker 1: don't know where the moon came from, you know, like
• 2:20
  Speaker 1: we it could have just appeared out of door one day,
• 2:24
  Speaker 1: or aliens could have dropped it off. Oh that's an
• 2:26
  Speaker 1: option I haven't heard yet that like somebody opened a
• 2:29
  Speaker 1: wormhole in the moon just look popped, there's a moon
• 2:32
  Speaker 1: all of a sudden. That's an awesome idea. Yeah, how
• 2:35
  Speaker 1: does something that big just come about right, so perfectly
• 2:38
  Speaker 1: round and pretty smooth and bright. Yeah, but it turns
• 2:42
  Speaker 1: out the Earth's moon is not like the other moon's.
• 2:45
  Speaker 1: You know, one of these things is not like the
• 2:47
  Speaker 1: other things, and the moon is kind of weird, which
• 2:49
  Speaker 1: makes it hard to explain. Yeah, it's a weird moon.
• 2:53
  Speaker 1: It's the only one we have, and so for a
• 2:55
  Speaker 1: long time it's sort of defined the whole concept of moon. Right,
• 2:58
  Speaker 1: But now that we've seen other planet and we've seen
• 3:00
  Speaker 1: how many little moons they have, were like, jeez, our
• 3:03
  Speaker 1: moon is kind of weird. Does my moon make me
• 3:05
  Speaker 1: look fat? You know, because we've got a big, fat moon. Yeah.
• 3:08
  Speaker 1: So this is an interesting question, and we wondered how
• 3:11
  Speaker 1: many of you out there no or think they know
• 3:13
  Speaker 1: the answer to the question where did the moon come from?
• 3:16
  Speaker 1: So I walked around the campus of UC Irvine and
• 3:19
  Speaker 1: accosted random strangers who are willing to talk to me
• 3:22
  Speaker 1: and asked them this question, where do you think the
• 3:24
  Speaker 1: moon came from? Yeah, so before you listen to these answers,
• 3:27
  Speaker 1: think for yourself what would be your best guess. Here's
• 3:31
  Speaker 1: what people have to say. I'm not entirely certain. I
• 3:33
  Speaker 1: just know gravity plays a part in it. There was
• 3:36
  Speaker 1: like a meteorite that hit the Earth which broke off
• 3:38
  Speaker 1: some rocks or something like that. From what I remember,
• 3:41
  Speaker 1: it might be that, well this is like the big Thing,
• 3:43
  Speaker 1: but I don't really know, no, No, My best guess
• 3:49
  Speaker 1: is that it either came from some sort of material
• 3:53
  Speaker 1: that was already in the atmosphere and by some sort
• 3:59
  Speaker 1: of a potational pull was brought in. Alright, So not
• 4:03
  Speaker 1: a lot of strong ideas here. I think it's a
• 4:06
  Speaker 1: pretty there's a good breath of ideas. Yeah. I like
• 4:09
  Speaker 1: the people who answer where did the moon come from?
• 4:11
  Speaker 1: And they would just say gravity, Like that's the answer too,
• 4:16
  Speaker 1: pretty much everything there, or the or someone said the
• 4:20
  Speaker 1: Big Bang. I'm like, yeah, of course everything came from
• 4:23
  Speaker 1: the Big Bang. That is that is a good default
• 4:26
  Speaker 1: physics answer that somebody asked you a physics question. The
• 4:28
  Speaker 1: answer is always the Big Bang. How does the hig
• 4:31
  Speaker 1: boson give mass to other particles? It's the Big Bang? Really,
• 4:35
  Speaker 1: you can't go wrong. So could have see that person
• 4:37
  Speaker 1: on the street figured out how to always be right? Well,
• 4:44
  Speaker 1: let's talk about the moon. How big is the moon? Daniel?
• 4:47
  Speaker 1: Or let's maybe take a step back. What is the moon? Right,
• 4:50
  Speaker 1: So it's just a definitional thing, right. You have solar
• 4:52
  Speaker 1: systems that have these hierarchies. You almost always have the
• 4:55
  Speaker 1: main masses in the center. You have star where most
• 4:58
  Speaker 1: of this has gathered, and then you have the planets
• 5:01
  Speaker 1: orbiting around it. And then you know, you have need
• 5:03
  Speaker 1: a name for the stuff orbiting around the planets. The
• 5:05
  Speaker 1: theory this could go on forever. Right, you have the
• 5:07
  Speaker 1: star with planets around it, and then moons around the planets,
• 5:10
  Speaker 1: and then you can have things orbiting around the moon,
• 5:13
  Speaker 1: and then things orbiting around those things, like moons can
• 5:16
  Speaker 1: have moonies. Yeah, I think they're called moonlits moon or
• 5:19
  Speaker 1: moon ETOs or something. Yeah. So so it's just it's
• 5:24
  Speaker 1: just the name given to something floating around a planet. Yeah, exactly.
• 5:29
  Speaker 1: If you're a blob of stuff floating around the planet,
• 5:31
  Speaker 1: then we call you a moon. But it's interesting because
• 5:33
  Speaker 1: you've got to be big enough, right, Like, if you're
• 5:34
  Speaker 1: just specks of stuff, then we call you a ring. Right,
• 5:37
  Speaker 1: if you're like distributed all the way around the planet,
• 5:39
  Speaker 1: then we got then you've got rings, Like Saturn has rings.
• 5:42
  Speaker 1: Saturn's got rings Jupiter's got rings, you know. Um, and
• 5:46
  Speaker 1: it's in some ways a question of definition, Like there
• 5:48
  Speaker 1: is stuff floating around the Earth into sort of a vague,
• 5:51
  Speaker 1: hazy rings. So could you say the Earth has rings?
• 5:53
  Speaker 1: You know, people argue about that kind of stuff, but
• 5:55
  Speaker 1: that's just like that's arguing about the definition. It's not
• 5:57
  Speaker 1: really arguing about the science generally. But it has it
• 6:00
  Speaker 1: has to have a certain size to be called a moon,
• 6:03
  Speaker 1: I think, so, yeah, otherwise it's just a rock rock
• 6:08
  Speaker 1: rock or rock let or rocky rocky dough. Yeah, there
• 6:12
  Speaker 1: must be some organization out there that's tasked with classifying
• 6:15
  Speaker 1: what the moon and what's the moonlit, and what's just
• 6:17
  Speaker 1: a piece of ring and with just random garbage in space.
• 6:20
  Speaker 1: You know. Um, that doesn't sound a very glamorous job.
• 6:24
  Speaker 1: So how big is our moon? Our Our moon is
• 6:26
  Speaker 1: really big. Our moon is two thousand miles across, which
• 6:30
  Speaker 1: is pretty big compared to the Earth, which you know,
• 6:32
  Speaker 1: is only eight thousand miles across, and most of the
• 6:35
  Speaker 1: other planets their moons are tiny in comparison to the
• 6:38
  Speaker 1: size of the planet. So it's pretty big. So it's
• 6:40
  Speaker 1: like from California to about like Arkansas or something, you're
• 6:44
  Speaker 1: giving me the worries here, Like if you took the
• 6:46
  Speaker 1: Moon and sort of gently put it down, how far
• 6:48
  Speaker 1: would it would it look? Like? Why do you even
• 6:52
  Speaker 1: imagine that? Like placing the Moon on the Earth just
• 6:54
  Speaker 1: for scale, you know, like you were to walk across
• 6:57
  Speaker 1: the Moon, how long would it take you? You know? Right? Yeah, um,
• 7:00
  Speaker 1: well not that long because you could bounce because of
• 7:01
  Speaker 1: the gravity is pretty low. But yeah, it's like two
• 7:04
  Speaker 1: thousand miles, so it's not as far as l A
• 7:06
  Speaker 1: to New York, for example. But it's pretty big, right,
• 7:08
  Speaker 1: It's pretty big. And the interesting thing is that it's
• 7:10
  Speaker 1: at the same scale as other planets in the Solar System. Okay,
• 7:15
  Speaker 1: so I looked it up, uh, and I did some
• 7:17
  Speaker 1: quick calculations because I'm a train engineer and I can
• 7:20
  Speaker 1: do some math here, and so like if the Earth
• 7:24
  Speaker 1: was the size of a basketball, the Moon would be
• 7:26
  Speaker 1: a little bit under the size of a tennis ball.
• 7:29
  Speaker 1: I prefer I preferred fruit based analogy. So I'm gonna
• 7:32
  Speaker 1: go with a watermelon and an apple. Watermelon, and then
• 7:35
  Speaker 1: are you hungry, Daniel? Do we need to take a
• 7:37
  Speaker 1: break here and break for a while? A right, as
• 7:40
  Speaker 1: a watermelon and an apple. Except what this interesting? The
• 7:43
  Speaker 1: distance is maybe a lot larger than most people think. So,
• 7:47
  Speaker 1: like you would have to put a watermelon down and
• 7:51
  Speaker 1: then walked about twenty five ft and then set down
• 7:54
  Speaker 1: that apple. And that's about the distance between the Earth
• 7:57
  Speaker 1: and the Moon. Yeah, it's crazy. These things seem big,
• 8:01
  Speaker 1: but they're tiny compared to the distances between them, right,
• 8:04
  Speaker 1: which is sort of a larger lesson for everything in space, right,
• 8:07
  Speaker 1: Like the Sun and the Earth seem huge, but they're
• 8:09
  Speaker 1: really far apart compared to their diameters. And our solar
• 8:13
  Speaker 1: system is far from the next star and and it's
• 8:15
  Speaker 1: incredible the distances between stuff and space. Yeah, okay, so
• 8:19
  Speaker 1: that's the moon. Um. The crazy thing is that we
• 8:22
  Speaker 1: don't know where the moon came from. That's right. People
• 8:24
  Speaker 1: have been trying to figure out how do you get
• 8:27
  Speaker 1: the Moon this big and this weird around the planet
• 8:30
  Speaker 1: this close to the Sun, and they can't figure it out.
• 8:33
  Speaker 1: You know, they have simulations and theories, and you know,
• 8:35
  Speaker 1: this is what scientists do. They say, can we explain
• 8:37
  Speaker 1: what we see? And they start with an idea and
• 8:39
  Speaker 1: they see does that work? Right? Can I take that
• 8:42
  Speaker 1: idea and end up with the situation I see in
• 8:44
  Speaker 1: front of me, and they have some ideas, and we'll
• 8:47
  Speaker 1: talk about them, we'll dig into them. But the bottom
• 8:49
  Speaker 1: line is that none of the ideas we currently have
• 8:51
  Speaker 1: completely work. They all have problems, which suggests that the
• 8:55
  Speaker 1: answer is something we haven't yet thought of, or some
• 8:57
  Speaker 1: weird twist on one of the current ideas. All right,
• 9:01
  Speaker 1: bring it down for us. How what are the different
• 9:03
  Speaker 1: ways that a planet can get a moon? Like? If
• 9:06
  Speaker 1: I wanted a moon, what would I need to do?
• 9:08
  Speaker 1: You just go on Amazon, man, you can order anything. Well,
• 9:10
  Speaker 1: you can probably get a moon. Tomort. You want a moon,
• 9:13
  Speaker 1: I get you a moon by tomorrow afternoon. That's what
• 9:15
  Speaker 1: Walter from the Big Labowski would saying. Can I just
• 9:16
  Speaker 1: get a slightly a shorter person to just follow me
• 9:19
  Speaker 1: around and turn around me? That's not a moon, that
• 9:23
  Speaker 1: that's an assistant. You want somebody in your orbit, right
• 9:27
  Speaker 1: who protects you from stuff? Right, cleans out all the
• 9:30
  Speaker 1: space junk that's coming at you. Um. Yeah, So how
• 9:32
  Speaker 1: does the planet get a moon? Well? One option is
• 9:35
  Speaker 1: that it's formed when the planet is formed. Right, Let's
• 9:37
  Speaker 1: remember how our planets formed, and it's um not from
• 9:40
  Speaker 1: the Big Bang, right, Like our professional physicist from earlier. Directly,
• 9:43
  Speaker 1: it is from gravity though, So you're saying that the
• 9:47
  Speaker 1: planet can get a moon at the same time that
• 9:49
  Speaker 1: it's forming, kind of like a little twin brother. Yeah, exactly.
• 9:52
  Speaker 1: So imagine how is the planet formed. Well, it starts
• 9:54
  Speaker 1: from a big poof of gas and dust and rocks, right,
• 9:57
  Speaker 1: and then gravity coalesces it together gradually, slowly, slowly into
• 10:00
  Speaker 1: a big clump. And you might wonder, why doesn't it
• 10:03
  Speaker 1: all form into one big clump, right? Why do you
• 10:05
  Speaker 1: get little bits left over as moons or other stuff? Um?
• 10:09
  Speaker 1: And this sort of two answers to that, like most
• 10:10
  Speaker 1: of it goes into the big clump. Right. First of all,
• 10:13
  Speaker 1: like most of the stuff goes into the planet. Um.
• 10:15
  Speaker 1: The reason it doesn't all is that some of it's
• 10:17
  Speaker 1: traveling really fast, and so rather than getting pulled down
• 10:21
  Speaker 1: into the central clump, essentially ends up in orbit. Right.
• 10:24
  Speaker 1: So what we call in physics, we call it angular momentum.
• 10:26
  Speaker 1: Supported you know, it's the reason that the Earth doesn't
• 10:28
  Speaker 1: just fall into the Sun. Right, It's because it's moving fast. Oh.
• 10:32
  Speaker 1: I see, So there's a bunch of stuff that came together,
• 10:34
  Speaker 1: But some of that stuff was a little bit out
• 10:37
  Speaker 1: on the periphery and didn't quite make it into the
• 10:40
  Speaker 1: main planet clump exactly. And it's all spinning, right, the
• 10:43
  Speaker 1: whole thing is spinning and it's going and so it
• 10:46
  Speaker 1: starts out spinning around and it's moving too fast to
• 10:48
  Speaker 1: get sucked in. Um. And the other part of the
• 10:51
  Speaker 1: story is that none of this happens in isolation, right.
• 10:53
  Speaker 1: The Earth is not in the middle of totally empty
• 10:56
  Speaker 1: space forming quietly. This stuff going on all the time,
• 10:59
  Speaker 1: And in the early soul or system, we think things
• 11:01
  Speaker 1: were pretty crazy and so um. It might have been
• 11:04
  Speaker 1: that the early blob that formed the Earth could have
• 11:06
  Speaker 1: formed a single planet with no moon and no other
• 11:08
  Speaker 1: objects or whatever. But it probably got perturbed a lot,
• 11:10
  Speaker 1: you know, things crash into it, things bump into it.
• 11:13
  Speaker 1: Even just the tugging of the Sun and other planets
• 11:15
  Speaker 1: coming nearby keep that stuff from really settling, and so
• 11:18
  Speaker 1: some of it ends up still out in space opening
• 11:20
  Speaker 1: around the planet. Okay, it formed at the same time
• 11:23
  Speaker 1: as the planet. Yeah, that happens in some cases, we think, um,
• 11:26
  Speaker 1: so sorry it's too late for you there. Or if
• 11:28
  Speaker 1: you wanted a moon from the from zero, you've missed
• 11:31
  Speaker 1: your window. I need to go back to the to
• 11:34
  Speaker 1: the womb. That's right, the womb moon the moon. That's
• 11:39
  Speaker 1: a that's a tongue twist right there. Um yeah. But
• 11:43
  Speaker 1: the better way, I think, the more popular way the
• 11:45
  Speaker 1: planets gives moves. All the cool planet at least get
• 11:48
  Speaker 1: moons by basically interacting with other objects. You know, like, um,
• 11:52
  Speaker 1: something smashes into them, or something flies by and they
• 11:55
  Speaker 1: capture it. Um, that kind of stuff. Wait wait wait wait, um,
• 11:58
  Speaker 1: so those are two other things. You can either capture
• 12:01
  Speaker 1: a moon, Like if the Earth was flying around and
• 12:04
  Speaker 1: suddenly there was a little bit of rock out there,
• 12:06
  Speaker 1: it would it could like bring it into its orbit.
• 12:09
  Speaker 1: It could bring it into its orbit. That's not very
• 12:11
  Speaker 1: easy to do because much more likely is that something
• 12:15
  Speaker 1: comes and smashes into the Earth and then the resulting
• 12:18
  Speaker 1: debris floats up into space and then turns into a
• 12:23
  Speaker 1: system of rings and then coalesces into a moon. That's
• 12:26
  Speaker 1: much more likely. It's because it's hard to capture something entirely.
• 12:30
  Speaker 1: Either it deflects right, it bounces off into space, or
• 12:33
  Speaker 1: it hits the Earth getting captured. It means you have
• 12:36
  Speaker 1: to be exactly the right speed at exactly the right
• 12:38
  Speaker 1: angle at exactly the right orbit. It's a difficult thing
• 12:41
  Speaker 1: to do. It's like getting a perfect pool shot, you know,
• 12:44
  Speaker 1: jumping the eight ball or something. You're saying, that's harder
• 12:46
  Speaker 1: than getting hit by something out in space. Yeah, because
• 12:49
  Speaker 1: the Earth has gravity, right, So if something comes close by,
• 12:51
  Speaker 1: it's most likely just going to spiral in and smash
• 12:53
  Speaker 1: into the Earth, or it's going to bounce off into flect.
• 12:56
  Speaker 1: So coming in from somewhere else and then ending up
• 12:58
  Speaker 1: in orbit is pretty trick. Okay, So I think the
• 13:01
  Speaker 1: most likely way to get a moon is for something
• 13:04
  Speaker 1: to smash into the planet and the debris to float
• 13:06
  Speaker 1: up and then coalesce into a moon. Alright, let's get
• 13:10
  Speaker 1: into this smashing idea, but first let's take a quick break.
• 13:27
  Speaker 1: All right. So you're saying that one way to get
• 13:28
  Speaker 1: a moon, and maybe our moon came this way, is
• 13:31
  Speaker 1: that something smashed into the Earth and kind of like
• 13:35
  Speaker 1: broke off a piece that then became the moon. That's right, Yeah,
• 13:38
  Speaker 1: And that's a that's the way we think some of
• 13:40
  Speaker 1: the moon's have occurred in the Solar System. But it's
• 13:43
  Speaker 1: tricky to explain our moon, right, Um, and because our
• 13:48
  Speaker 1: moon is so big, right, Our moon is huge compared
• 13:52
  Speaker 1: to the planet, and so in order to make that
• 13:55
  Speaker 1: size the Moon work, you need a huge impact, right,
• 13:58
  Speaker 1: You need a ridiculously big effact. You can't just be
• 14:00
  Speaker 1: hit by laroc that knocks off a bunch of stuff.
• 14:03
  Speaker 1: You need a giant impact, like a planet killing impact. Yeah.
• 14:07
  Speaker 1: And the current models say that the kind of thing
• 14:10
  Speaker 1: that hit the Earth a long long time ago to
• 14:12
  Speaker 1: make the Moon might have been something the size of
• 14:15
  Speaker 1: a planet. It might have been a proto planet, might
• 14:16
  Speaker 1: have been something the size of Mars. Right, So we're
• 14:19
  Speaker 1: talking about like two planets colliding, right, This must have
• 14:22
  Speaker 1: been amazing to watch, right, right or not if you're
• 14:26
  Speaker 1: living in these planets, that's right. Well, we don't think
• 14:30
  Speaker 1: there was anything alive on Earth when it happened. The
• 14:31
  Speaker 1: best estimates say that this happened about um zero point
• 14:35
  Speaker 1: one billion years or a hundred million years after the
• 14:38
  Speaker 1: Earth was formed, So the Earth was still pretty hot
• 14:41
  Speaker 1: and a nasty when this kind of stuff happened. We
• 14:44
  Speaker 1: don't think there was any atmosphere of life yet collided
• 14:47
  Speaker 1: with another planet about its size. That's incredible, right, two
• 14:52
  Speaker 1: giant balls of rock just yeah, exactly, and um and
• 14:57
  Speaker 1: that must have been pretty kindaclasmic, right, A lot of
• 15:00
  Speaker 1: stuff must have gotten thrown off into space, and some
• 15:03
  Speaker 1: of that stuff coalesced into rings. So the Earth probably
• 15:06
  Speaker 1: had rings for a while, no way like Saturn. Yeah,
• 15:09
  Speaker 1: I know that has been pretty awesome, right, I kind
• 15:11
  Speaker 1: of wish the Earth had rings, Like what would that
• 15:12
  Speaker 1: look like at night or during the day, you know,
• 15:15
  Speaker 1: to see rings up in the sky. That would be
• 15:17
  Speaker 1: pretty incredible. So then the two planets collected is the
• 15:20
  Speaker 1: idea to planets collided, they form a new Earth with
• 15:23
  Speaker 1: some stuff out there in rings that eventually became the Moon.
• 15:28
  Speaker 1: That's right. And this collision was huge, right, It was
• 15:30
  Speaker 1: like a hundred million times the energy of the asteroid
• 15:33
  Speaker 1: that hit the Earth and probably killed the dinosaurs. So
• 15:36
  Speaker 1: it's a ginormous explosion. It's nothing that anybody could ever survive. Yeah,
• 15:40
  Speaker 1: I've seen I've seen the videos of the stimulations. Like
• 15:43
  Speaker 1: it's basically the Earth just gets pulverized and then just
• 15:46
  Speaker 1: kind of coagulates into this new thing. But it's like
• 15:49
  Speaker 1: it's basically obliterated. Yeah, and here you'll see the strength
• 15:52
  Speaker 1: of my fruit based analogy, which is imagined you take
• 15:55
  Speaker 1: two watermelons and you throw them together. What happens, right,
• 15:58
  Speaker 1: that's pretty much what's happened. You know, it's complete destruction.
• 16:01
  Speaker 1: The watermelons do not survive that kind of impact. So
• 16:08
  Speaker 1: then how do rings become moons? And why? Like, why
• 16:12
  Speaker 1: does Saturn still have rings and nut moons? Yeah, that's
• 16:14
  Speaker 1: a really awesome question because gravity, right, you would think
• 16:17
  Speaker 1: if stuff is floating out there in space, then eventually
• 16:20
  Speaker 1: gravity would coalesce, it would pull it all together into
• 16:22
  Speaker 1: a moon. And that does happen if you're far enough
• 16:25
  Speaker 1: away from the planet. If you're too close to the planet,
• 16:29
  Speaker 1: then the strength of gravity tugging on you from one
• 16:31
  Speaker 1: side and the strength of gravity tugging you from the
• 16:33
  Speaker 1: other side are too different. Because remember the force of
• 16:36
  Speaker 1: gravity depends on your distance from an object, and so
• 16:39
  Speaker 1: one side of the Moon is closer to the Earth
• 16:41
  Speaker 1: than the other side of the Moon, So the Earth
• 16:44
  Speaker 1: pulls on one side of the Moon more than the
• 16:46
  Speaker 1: other side, So it's literally pulling the Moon apart. But
• 16:49
  Speaker 1: the Moon is far enough away from the Earth that
• 16:51
  Speaker 1: the Earth is not strong enough to shred the Moon.
• 16:54
  Speaker 1: But if the Moon was a lot closer right then
• 16:58
  Speaker 1: it then it would be pulled apart. By these gravitational
• 17:01
  Speaker 1: they're called tidal forces. By the tidal forces, so there's
• 17:04
  Speaker 1: a region around every planet where you just cannot be
• 17:06
  Speaker 1: a moon because if you are, you're gonna get shredded, right,
• 17:10
  Speaker 1: So you just kind of get ripped apart. Yeah, it's
• 17:12
  Speaker 1: like a blender. There is like a blender. Yeah, and
• 17:16
  Speaker 1: we've seen this happen if you remember the comment that
• 17:19
  Speaker 1: hit Jupiter um in the nineties. It passed really close
• 17:22
  Speaker 1: by Jupiter before it hit and Jupiter pulled it apart
• 17:24
  Speaker 1: into twenty six pieces because of his tidal forces. And
• 17:28
  Speaker 1: so the larger the planet, the stronger the force of gravity,
• 17:30
  Speaker 1: and the more likely this is to happen. Oh I see.
• 17:33
  Speaker 1: So if Saturn had bigger rings or rings that were
• 17:36
  Speaker 1: further apart, then the tidal forces would be less and
• 17:40
  Speaker 1: then the little bits of it would have time when
• 17:43
  Speaker 1: and kind of space to clump together. Yeah, but that's
• 17:47
  Speaker 1: a whole other fascinating mystery, like how long has Saturn
• 17:50
  Speaker 1: hand rings? How long will it continue to have rings? Right?
• 17:53
  Speaker 1: We think that those rings are pretty stable because they
• 17:56
  Speaker 1: have been there for like a hundred million years and um,
• 18:00
  Speaker 1: and because Saturn has really strong title forces. So anything
• 18:02
  Speaker 1: that coalesces, Saturn will tear up again, but we don't
• 18:05
  Speaker 1: really know for sure. And Saturn does have some moons,
• 18:07
  Speaker 1: and we don't know like are those moons in the
• 18:09
  Speaker 1: process of being trashed, Like if you fast forwarded a
• 18:11
  Speaker 1: billion years with Saturn look totally different or is it
• 18:13
  Speaker 1: looked this way for a long time. It's amazing to
• 18:16
  Speaker 1: me how dynamic the Solar system is. You know, like
• 18:18
  Speaker 1: if you look at a picture of the Solar System
• 18:20
  Speaker 1: from two billion years ago, you might not recognize it.
• 18:23
  Speaker 1: You could have a different number of planets, and all
• 18:25
  Speaker 1: the planets could have different number of moons, or the
• 18:27
  Speaker 1: planets could even be in a different order. It's crazy
• 18:29
  Speaker 1: stuff that's happened in our Solar system. Or even two
• 18:32
  Speaker 1: billion years from now, it might look totally different. Yeah, well,
• 18:34
  Speaker 1: in two billion years from now, I hope we've built
• 18:36
  Speaker 1: massive interstellar structures so we're recognizable from space. Um. But
• 18:41
  Speaker 1: even without that, Yeah, the planets could reorganize or realign,
• 18:44
  Speaker 1: or things could drift this way or the other way,
• 18:46
  Speaker 1: or something could come from another Solar system and knock
• 18:48
  Speaker 1: knock into something and change everything. Yeah, you know, people
• 18:51
  Speaker 1: might imagine the Solar system is really static because it's old,
• 18:55
  Speaker 1: but we've only seen the recent history of it. And
• 18:57
  Speaker 1: one of the best ways to figure out what is
• 18:59
  Speaker 1: the history, what is the whole story here, what is
• 19:01
  Speaker 1: the drama that's taking place out there in space, is
• 19:04
  Speaker 1: to ask these questions, you know, like how did the
• 19:06
  Speaker 1: moon form? Yeah, so that's one possibility, is that something
• 19:10
  Speaker 1: smashed into the Earth through all this stuff out there
• 19:12
  Speaker 1: that became a moon because it was far enough away
• 19:15
  Speaker 1: from the Earth. But there's some that's not quite right, right,
• 19:19
  Speaker 1: Like that doesn't quite fit what we see or know
• 19:22
  Speaker 1: about the moon. Yeah, it's interesting because we can't quite
• 19:25
  Speaker 1: make that story explain everything we see. And so one
• 19:29
  Speaker 1: of the things we see, for example, is that we've
• 19:31
  Speaker 1: been to the moon and we've looked at rocks from
• 19:33
  Speaker 1: the moon. You've been to the moon. I mean we
• 19:36
  Speaker 1: collectively as humanity. I like to take credit for humanities
• 19:41
  Speaker 1: of humanities collective. The Royal week there. Okay, we have
• 19:46
  Speaker 1: won a bunch of NBA championships, by which I mean
• 19:48
  Speaker 1: me and Lebron James. Yeah, we are an acclaimed internet cartoonist.
• 19:53
  Speaker 1: But which I mean me and you. We are Tom Cruise.
• 19:57
  Speaker 1: You know, we are sexy in our fifties exactly. Humanity,
• 20:02
  Speaker 1: not me personally, has been to the Moon and brought
• 20:04
  Speaker 1: back rocks, and we've looked at those rocks, and those
• 20:06
  Speaker 1: rocks look really similar to rocks on Earth. And you
• 20:09
  Speaker 1: should know that rocks on every planet look different because
• 20:12
  Speaker 1: they're formed under different circumstances from different bits and different
• 20:14
  Speaker 1: temperatures and different ages. So you can sort of tell
• 20:18
  Speaker 1: where a rock came from, Like really that different because
• 20:21
  Speaker 1: they it all came from the debris of this Solar system, right,
• 20:24
  Speaker 1: wouldn't it all be sort of the same. But like
• 20:26
  Speaker 1: Mars is different from Earth, and we can we we
• 20:28
  Speaker 1: found rocks on Earth that we can tell came from
• 20:31
  Speaker 1: Mars because we know they're different. They have different structures,
• 20:34
  Speaker 1: formed in different temperatures at different times and this you know,
• 20:37
  Speaker 1: different totally different kind of tectonic activity on different planets,
• 20:40
  Speaker 1: like Mars doesn't have any at all, you know, and
• 20:44
  Speaker 1: letters of the bottoms that made in Mars Mars first, Yeah, exactly,
• 20:50
  Speaker 1: make Mars great again. They don't like, they don't want
• 20:54
  Speaker 1: to import our rocks anymore. The high tariffs on Earth
• 20:57
  Speaker 1: rocks anyway, So they can look at these rocks from
• 20:59
  Speaker 1: the Moon and they say, they looked just like rocks
• 21:01
  Speaker 1: from Earth. Right. So that's really interesting because suggests that
• 21:05
  Speaker 1: the stuff that the Moon is made out of is
• 21:07
  Speaker 1: really similar to the stuff that the Earth is made
• 21:09
  Speaker 1: out of. But if a really really big planet came
• 21:12
  Speaker 1: and smashed into the Earth, that's not what you would
• 21:13
  Speaker 1: really expect. You would expect that planet to have mostly
• 21:17
  Speaker 1: survived or that or to bounce off, or for this
• 21:20
  Speaker 1: stuff in the Moon to be made from that planet
• 21:22
  Speaker 1: that came. Right, You started out with two objects, you
• 21:24
  Speaker 1: have a collision, you end up with two objects. You
• 21:27
  Speaker 1: expect sort of a you know, a connection between the
• 21:29
  Speaker 1: incoming and the outgoing too, but instead both objects that
• 21:32
  Speaker 1: survives seem to be like the Earth stuff, which is
• 21:35
  Speaker 1: a bit weird. But we couldn't, um, couldn't this new
• 21:39
  Speaker 1: planet have also mixed in with our old Earth. And
• 21:42
  Speaker 1: so that's why it's the same, you know what I mean?
• 21:44
  Speaker 1: Like maybe the Moon and Earth is a mix of
• 21:46
  Speaker 1: these two pre crash planets. They have these simulations that
• 21:49
  Speaker 1: are totally crazy where essentially the other planet gets like
• 21:53
  Speaker 1: subsumed into the Earth like including it's it's like core, right,
• 21:57
  Speaker 1: So there's some other planets internal bits, right, the iron
• 22:02
  Speaker 1: and the nickel that makes up the inside of a
• 22:04
  Speaker 1: planet is inside the Earth. Now, like if you cut
• 22:06
  Speaker 1: the Earth open, you would find evidence for like, you know,
• 22:09
  Speaker 1: a second planet in there. And then what made the
• 22:12
  Speaker 1: Moon was like the Earth's crust just got ejected. It's
• 22:15
  Speaker 1: like ice cream, like a swirly ice cream doesn't completely
• 22:18
  Speaker 1: just mixed together, and that you would expect chunks. Yeah,
• 22:23
  Speaker 1: I'm glad you're with me on the food out analogies. Now,
• 22:25
  Speaker 1: trying to move us here towards dessert. We had our
• 22:27
  Speaker 1: fruit as the meal is wrapping up. In some places
• 22:32
  Speaker 1: fruit is considered dessert. I think we should do something
• 22:34
  Speaker 1: a little bit more meaty. Um. Yeah. So that's one
• 22:36
  Speaker 1: mystery is like why does the stuff on the Moon
• 22:38
  Speaker 1: look just like the stuff in the Earth. And they
• 22:40
  Speaker 1: can kind of make it work, right, Like they can
• 22:43
  Speaker 1: make it work that most of the stuff from the
• 22:45
  Speaker 1: Earth's crust turned into the Moon and the other planet
• 22:47
  Speaker 1: just sort of got swallowed by the Earth. But it's tricky.
• 22:51
  Speaker 1: It's not an easy thing to make work. And if
• 22:54
  Speaker 1: that happened, then you'd expect crazy stuff to have happened
• 22:57
  Speaker 1: on Earth, like you know, huge oceans of molten talk
• 23:00
  Speaker 1: of magma like magma oceans which is just a phrase
• 23:03
  Speaker 1: I love saying and hearing, magma oceans um. But we
• 23:06
  Speaker 1: don't see any evidence of that on Earth. Like people
• 23:08
  Speaker 1: who look at the history of rocks on Earth don't
• 23:10
  Speaker 1: see evidence of these of these magma ocetions that you
• 23:13
  Speaker 1: would expected from a huge such a huge collision. It
• 23:15
  Speaker 1: doesn't look like we were hit by a big rock. Yeah,
• 23:18
  Speaker 1: we don't see evidence for that on Earth. And you know,
• 23:20
  Speaker 1: when you put together this kind of story, you want
• 23:22
  Speaker 1: to check it multiple ways and does this make sense?
• 23:24
  Speaker 1: And let's see it in this other way? And we
• 23:26
  Speaker 1: can't find any confirmation for that currently, and the simulations
• 23:29
  Speaker 1: are are pretty hard to get right. Before we keep going,
• 23:32
  Speaker 1: let's take a short break. Man, that's wild. So we
• 23:47
  Speaker 1: really don't know where the moon came from. Kind of Yeah.
• 23:50
  Speaker 1: There are some other ideas, you know, crazy ideas about
• 23:53
  Speaker 1: how two other planets may have collided and basically totally
• 23:56
  Speaker 1: annihilated each other into some other sort of cosmic doughnut,
• 24:00
  Speaker 1: which then spun around and formed the Earth in the moon.
• 24:04
  Speaker 1: I said, that's right, we're doing double dessert here. One
• 24:08
  Speaker 1: of the crazy ideas is that the Earth essentially was
• 24:11
  Speaker 1: obliterated in this collision, and everything just became a big cloud,
• 24:15
  Speaker 1: really fast spinning cloud, which ended up shaping shaped into
• 24:18
  Speaker 1: this crazy donut shape. It's spun out a blob which
• 24:21
  Speaker 1: became the Moon. Um. That theory has some trouble because
• 24:24
  Speaker 1: it turns out the Moon doesn't really have like a
• 24:27
  Speaker 1: solid iron core like you would expect, like, you know,
• 24:30
  Speaker 1: the Earth has a as a release heavy metallic core
• 24:33
  Speaker 1: like most rocky planets, but the Moon is pretty light.
• 24:36
  Speaker 1: It's mostly fluffy, right. It has a little bit of
• 24:38
  Speaker 1: a core, but not very much. And so that's better
• 24:42
  Speaker 1: explained by saying that the Moon mostly came from Earth
• 24:44
  Speaker 1: crust stuff rather than from like an entire blob of
• 24:48
  Speaker 1: planetary stuff, where you would get like the same same
• 24:51
  Speaker 1: amount of serving of the core as you would have
• 24:53
  Speaker 1: the crust. Um. So all these theories have some problems. Well,
• 24:57
  Speaker 1: what are some other crazy ideas? Yeah, Well, a theory
• 25:00
  Speaker 1: that exists for a long time was just that the
• 25:02
  Speaker 1: Moon was captured, you know, like maybe the Moon came
• 25:04
  Speaker 1: from somewhere else or used to be its own planet,
• 25:06
  Speaker 1: or was wandering around just sort of got sucked into
• 25:09
  Speaker 1: the Earth's orbit. And this theory has a couple of problems.
• 25:13
  Speaker 1: One is that that's really hard to do. Like you
• 25:15
  Speaker 1: do simulations and you have another planet approach Earth, as
• 25:18
  Speaker 1: we were saying before, usually they you know, spin off
• 25:20
  Speaker 1: each other and then one gets flung out into space
• 25:23
  Speaker 1: or they end up colliding right to get it to
• 25:26
  Speaker 1: come into stable or with that last for billions of years.
• 25:29
  Speaker 1: That's really really hard to do. That's a one in
• 25:31
  Speaker 1: a billion chance. So that might be possible, but it's
• 25:34
  Speaker 1: hard to do. And the other problem is it doesn't
• 25:36
  Speaker 1: explain why the Earth and the Moon looks so similar, right,
• 25:39
  Speaker 1: they have like these really similar rocks on them. The
• 25:41
  Speaker 1: Moon came from somewhere else. I was captured. It shouldn't
• 25:44
  Speaker 1: have the same basically rock d n a that we have. Okay,
• 25:48
  Speaker 1: but I heard another idea is that maybe the Moon
• 25:51
  Speaker 1: fell off to Earth like it was part of us,
• 25:53
  Speaker 1: but then it was like I'll see you later. Yeah.
• 25:56
  Speaker 1: I think this is a really popular, super ancient idea,
• 25:59
  Speaker 1: Like if you look in the historical documents, people speculate
• 26:01
  Speaker 1: about this, you know, a thousand years ago before really
• 26:04
  Speaker 1: anybody knew physics, and somebody even wrote that the Pacific
• 26:07
  Speaker 1: Ocean was like the scar of the moon leaving the Earth.
• 26:10
  Speaker 1: You know that a huge chunk of land to just
• 26:12
  Speaker 1: like floated off into into space because the Earth of spinning, um,
• 26:16
  Speaker 1: and it got turned into the moon. The moon is Atlantis?
• 26:21
  Speaker 1: Is Atlantis? Oh my gosh. I love when you can
• 26:23
  Speaker 1: connect to mysteries at once. Um. But there's basically no
• 26:27
  Speaker 1: data to support that at all. I mean, it's just
• 26:29
  Speaker 1: I mean, we know the Pacific Ocean is not formed
• 26:31
  Speaker 1: by somebody taking a scoop out of the Earth, um.
• 26:35
  Speaker 1: And so it was just like random speculation. But it
• 26:37
  Speaker 1: was a popular idea for you know, a long time
• 26:40
  Speaker 1: among the medieval and ancient folks. So what's kind of
• 26:47
  Speaker 1: the best current thinking about where the moon came from?
• 26:49
  Speaker 1: I think, um, if you ask most scientists, and I
• 26:52
  Speaker 1: haven't asked most scientists, but I've asked a few. He
• 26:54
  Speaker 1: was asked science scientists. I've asked a scientist who's an
• 27:00
  Speaker 1: expert in planetary science, and I've asked myself. I'm a scientist. Um,
• 27:04
  Speaker 1: So yes, I've asked scientists about this. That's the deep
• 27:10
  Speaker 1: research we do for this show, folks. UM. And the
• 27:13
  Speaker 1: prevailing theory is the giant impact, right, it has some problems.
• 27:16
  Speaker 1: There are things we don't understand about it. But that's
• 27:18
  Speaker 1: sort of the progress of science. Right, we say, here's
• 27:21
  Speaker 1: a bunch of ideas. This one doesn't quite work, but
• 27:23
  Speaker 1: it mostly works. The elements of it that explain things
• 27:26
  Speaker 1: we see. There's just stuff to figure out. And so
• 27:29
  Speaker 1: that's that's the prevailing ideas, the giant impact. It's the
• 27:32
  Speaker 1: best idea we have. That's right, that it's that or
• 27:34
  Speaker 1: the Big bang? Man. Yeah, and I like this process
• 27:40
  Speaker 1: of science. You know, we have one idea, we refine it,
• 27:42
  Speaker 1: We refined it, and then we see doesn't fit the
• 27:44
  Speaker 1: data better than it used to. Is it sort of
• 27:46
  Speaker 1: coming together? It's like solving a murder mystery, right, You
• 27:49
  Speaker 1: look for clues, you come up with the theory. Something
• 27:51
  Speaker 1: doesn't quite work, makes you change your theory. Eventually you
• 27:54
  Speaker 1: have a story that explains everything you see and that
• 27:57
  Speaker 1: fits in with what other people say and that makes sense.
• 28:00
  Speaker 1: You get more data, and that's what we're looking for,
• 28:02
  Speaker 1: and we have a story. They definitely wasn't murder. A
• 28:04
  Speaker 1: huge planet died um in the making of our moon,
• 28:08
  Speaker 1: but we don't quite know how it happened. And it
• 28:10
  Speaker 1: might be that, you know, it's just sort of weird,
• 28:12
  Speaker 1: and it's it seems unlikely that this sort of configuration
• 28:15
  Speaker 1: would happen, and maybe it was unlikely, or maybe there's
• 28:18
  Speaker 1: some part of the story we haven't understood, like there
• 28:20
  Speaker 1: was two cataclysms, or you know, two planets hit the
• 28:23
  Speaker 1: Earth or something like that makes you wonder, what if
• 28:25
  Speaker 1: that other planet or asteroid hadn't hit us, you know,
• 28:28
  Speaker 1: if it just missed by a few degrees, we wouldn't
• 28:32
  Speaker 1: have a moon and we would have a super different
• 28:34
  Speaker 1: planet Earth, right, Yeah, and things could be very different.
• 28:37
  Speaker 1: You know. The reason we have tides is because we
• 28:39
  Speaker 1: have the Moon, and the moon stabilizes the Earth's orbit,
• 28:43
  Speaker 1: and we think that the collision that caused the moon
• 28:45
  Speaker 1: might have also caused the tilt of the Earth, which
• 28:48
  Speaker 1: means if we didn't have a moon, we might not
• 28:50
  Speaker 1: have tides, we might not have seasons, and that's a
• 28:53
  Speaker 1: pretty big change in what life on Earth is like, right,
• 28:55
  Speaker 1: And a lot of people think the tides were critical
• 28:57
  Speaker 1: to life because as the sea comes in and out,
• 29:00
  Speaker 1: it's sort of like a lot of slashing around, which
• 29:02
  Speaker 1: is what you need to mix up those basic organic
• 29:05
  Speaker 1: chemicals into something that might turn into life and so yeah,
• 29:08
  Speaker 1: we might have the Moon to thank for the fact
• 29:09
  Speaker 1: that we're even here to ask about it. It just
• 29:12
  Speaker 1: that a planet had to die. That's right to get
• 29:15
  Speaker 1: to But in the interest of all things good, so
• 29:17
  Speaker 1: that we could be here eating watermelons, somebody had to
• 29:20
  Speaker 1: sacrifice a big planet. So yeah, that's another one of
• 29:25
  Speaker 1: these crazy mysteries that are just staring at us in
• 29:28
  Speaker 1: the face every single night. And when you think about
• 29:30
  Speaker 1: the Solar System next time, remember it's not static, it's dynamic.
• 29:33
  Speaker 1: There is stuff happening, and there is a story. It's
• 29:35
  Speaker 1: playing out really slowly right geological cosmic time scales. But
• 29:40
  Speaker 1: if you took a time lapse video of the Solar system,
• 29:42
  Speaker 1: it would seem like a crazy dance party. Yeah, so
• 29:46
  Speaker 1: next time you are mooning the moon, pull up your
• 29:48
  Speaker 1: pants and show some respect, because that we owe the
• 29:50
  Speaker 1: Moon a big thank you. All right, thanks for listening
• 29:52
  Speaker 1: to everyone, See you next time. If you still have
• 30:02
  Speaker 1: a question after listening to all these explanations, please drop
• 30:06
  Speaker 1: us a line. We'd love to hear from you. You
• 30:08
  Speaker 1: can find us at Facebook, Twitter, and Instagram at Daniel
• 30:11
  Speaker 1: and Jorge that's one word, or email us at Feedback
• 30:15
  Speaker 1: at Daniel and Jorge dot com