Latest / Daniel and Kelly’s Extraordinary Universe / What is the densest planet?

Transcript

What is the densest planet? · Daniel and Kelly’s Extraordinary Universe

0:08
Speaker 1: Hey, or hey, are you ready to dig into another
0:11
Speaker 1: controversial topic? Who did you take some classified physics documents
0:15
Speaker 1: to your house or something? Oh? They don't let me
0:19
Speaker 1: see any of that stuff. But this is much more
0:21
Speaker 1: important than that. I'm wondering where you land on the
0:25
Speaker 1: debate about bread? Do you prefer it light and fluffy
0:29
Speaker 1: or dark and heavy? Oh? I didn't even know there
0:32
Speaker 1: was a debate about bread. Mostly I just eat it.
0:35
Speaker 1: I mean, if people argue about like chocolate versus vanilla
0:38
Speaker 1: ice cream, you know they're going to argue about French
0:41
Speaker 1: baguettes versus German RYE. Well, it kind of depends on
0:45
Speaker 1: how hungry you are. If you're hungry, you'll eat any bread.
0:47
Speaker 1: But isn't that more of a cultural topic than a
0:49
Speaker 1: physics topic. It's a cultural topic, but it's also a
0:52
Speaker 1: physics topic because it's all about density. Do you like
0:55
Speaker 1: bread that floats or sinks when you drop it in
0:57
Speaker 1: the pool? It sounds like you've done this experiment. It's
0:59
Speaker 1: an the mental question about every object in your life?
1:02
Speaker 1: Will it float? Returned this on your children as well? Yes,
1:06
Speaker 1: and I can confirm that my children do float, and
1:09
Speaker 1: are they den only in the best way? Possible. Well,
1:11
Speaker 1: in terms of bread, I'd rather you don't throw it
1:13
Speaker 1: into a pool. I'm not sure I like my bread soggy.
1:16
Speaker 1: I'm sure there's someone out there who disagrees with you.
1:19
Speaker 1: That will be a very dense debate. I'm sure I'll
1:22
Speaker 1: rise to the occasion. Hi am or Hid, my cartoonists
1:40
Speaker 1: and the co author of Frequently Asked Questions about the Universe. Hi,
1:43
Speaker 1: I'm Daniel. I'm a particle physicist and a professor at
1:46
Speaker 1: U c Irvine, and I really miss Dave Letterman's bit
1:50
Speaker 1: called will It Float? Oh? Is that the one where
1:53
Speaker 1: he makes things float? Or is that the one where
1:55
Speaker 1: he throws things out of the roof? I love that
1:56
Speaker 1: he did so many physics experiments, but one of my
1:59
Speaker 1: favorites was will Float, where he just brings out a
2:01
Speaker 1: tub of water and random stuff and he asks the
2:03
Speaker 1: audience do you think it's going to float? And then
2:05
Speaker 1: of course he throws it in the pool and they
2:07
Speaker 1: find out it's pure physics, right right? Yeah? What kinds
2:11
Speaker 1: of things would he test? Well, you know, we had
2:13
Speaker 1: bowling balls and chainsaws, but also you know, loaves of bread, pumpkins,
2:19
Speaker 1: all sorts of things sort of right, on the edge
2:21
Speaker 1: that divided people and tested their intuition. I feel like
2:25
Speaker 1: it's also kind of an engineering question, like how watertight
2:28
Speaker 1: something is, because if something could be light and float,
2:31
Speaker 1: but eventually you'll think, yeah, that's true, like a paper
2:34
Speaker 1: boat will float initially until it gets water logged. Yeah,
2:38
Speaker 1: it's all about engineering at the end, truly the most
2:40
Speaker 1: important discipline. But anyways, welcome to a podcast Daniel and
2:43
Speaker 1: Jorge Explain the Universe, a production of I Heart Radio,
2:46
Speaker 1: in which we float various ideas about how the universe works,
2:50
Speaker 1: how it all comes together, what is made out of
2:53
Speaker 1: at its smallest bits, and how those bits to and
2:56
Speaker 1: fro and zip back and forth and buzz together to
2:59
Speaker 1: make the universe that we are familiar with, the one
3:01
Speaker 1: that we experience, the one we are so curious to understand.
3:06
Speaker 1: We dig deep into all the questions about the basic
3:08
Speaker 1: nature of reality and how everything behaves and try to
3:12
Speaker 1: explain all of it to you. That's right, because it
3:14
Speaker 1: is a pretty dense universe, pack full of interesting and
3:17
Speaker 1: amazing facts and phenomena to discover and to explore, and
3:20
Speaker 1: we like to make it all light and fluffy for
3:22
Speaker 1: you here on the podcast. And I guess you know.
3:25
Speaker 1: I was just googling will It Float and discovered that
3:27
Speaker 1: Letterman once released an Xbox version of Will It Float?
3:31
Speaker 1: What like, will it Xbox float or sink? Or can
3:35
Speaker 1: you play inside the Xbox? That is a good question,
3:38
Speaker 1: whether an Xbox will float or sink? Probably it'll sink,
3:42
Speaker 1: but no, he had a version of it, which was
3:43
Speaker 1: a game you can play on the Xbox, like you
3:46
Speaker 1: predict whether various things are going to float or sink,
3:49
Speaker 1: and then they dump them in a virtual tub. I
3:51
Speaker 1: feel like that's a little bit of an overkill for
3:54
Speaker 1: the Xbox's abilities here. I think maybe he was just
3:57
Speaker 1: playing a joke about merchandizing and commercialization of stuff. How
4:00
Speaker 1: would your son feel if you throw his Xbox into
4:02
Speaker 1: a tub of water? He would probably jump in afterwards,
4:05
Speaker 1: and then I would learn whether it floated and whether
4:07
Speaker 1: he floated at the same time, What did you throw
4:09
Speaker 1: both in? You only need to throw one in and
4:12
Speaker 1: then he jumps in after it, So as long as
4:14
Speaker 1: it's not still connected to the plug in the wall,
4:17
Speaker 1: it's not a bad exercise. But as much as we
4:20
Speaker 1: like to joke about whether things float, it's part of
4:22
Speaker 1: just wondering how things work and what's inside of them.
4:25
Speaker 1: There's a long history of dunking things in water to
4:29
Speaker 1: understand them, all the way back to measuring the volume
4:31
Speaker 1: of things by immersing them in a bathtub. Yeah. And
4:34
Speaker 1: as you know, whether something floats or doesn't float, it
4:38
Speaker 1: has everything to do with its density. If something is
4:41
Speaker 1: denser than water, then it's going to think. If it's
4:43
Speaker 1: less dense than water, it's going to float in the
4:46
Speaker 1: universe has all kinds of densities in its existence, that's right.
4:49
Speaker 1: And people have all kinds of densities in their bodies
4:52
Speaker 1: and stuff around us has all sorts of densities, which
4:55
Speaker 1: is why people have been building boats out of wood
4:57
Speaker 1: and not out of stone for thousands of years. You
5:00
Speaker 1: can make a stone boat, right, You could make a
5:02
Speaker 1: stone boat if it had a big air pocket in it, right,
5:05
Speaker 1: That's how those ships are made of steel. Steel obviously
5:08
Speaker 1: much denser than water, but a modern steel ship has
5:11
Speaker 1: a huge pocket of air inside it, like a big
5:14
Speaker 1: steel balloon essentially. Yeah. And actually, if you studies civil engineering,
5:18
Speaker 1: a big rite of passage and a lot of schools
5:19
Speaker 1: is to make a concrete boat, is that right? So
5:22
Speaker 1: that's something people really do Yeah, that's awesome. Well, I
5:26
Speaker 1: wonder what the densest material you can make a boat
5:28
Speaker 1: out of is. Can you make a neutron star boat
5:34
Speaker 1: nuclear pasta boat? You can use sheets of nuclear lasagna?
5:37
Speaker 1: I suppose, Yeah, I guess it would collapse the entire planet.
5:40
Speaker 1: But you know, at least he would test that theory.
5:42
Speaker 1: You'd win that engineering competition along the way. And for
5:45
Speaker 1: those of you out there confused about why things that
5:47
Speaker 1: are denser than water can float, the key is not
5:50
Speaker 1: the density of the container necessarily, but the overall average
5:53
Speaker 1: density of the object. So if you make a big
5:56
Speaker 1: balloon out of neutron star material, as long as it's
5:59
Speaker 1: enough air are inside of it, the average density is
6:02
Speaker 1: less than the density of water, and then it can float. Yeah,
6:05
Speaker 1: And so the universe has all kinds of dense things.
6:07
Speaker 1: We've talked on this podcast about neutron stars, which are
6:10
Speaker 1: some of the densest things in the universe, and we've
6:12
Speaker 1: also talked about the opposite, which is the emptiest spots
6:15
Speaker 1: in the universe as well. The extremes are really fun
6:17
Speaker 1: places to think about because they show us what the
6:19
Speaker 1: edge cases are, what the rules are, what it's possible
6:23
Speaker 1: to achieve, and they also illuminate how various forces in
6:26
Speaker 1: various factors come together to achieve such densities or such emptiness.
6:31
Speaker 1: Is so understanding how things can get really, really dense
6:35
Speaker 1: can give us some understanding about how things work. Yeah,
6:37
Speaker 1: they are all kinds of forces and universe. A lot
6:39
Speaker 1: of them are pushing things together, like gravity or the
6:42
Speaker 1: strong nuclear force, and a lot of things are also
6:45
Speaker 1: pushing things apart, like the electromagnetic force. Density plays an
6:49
Speaker 1: important role in the heart of our Sun, allowing us
6:52
Speaker 1: to warm our toes on that incredible cosmic fire even
6:55
Speaker 1: though it's millions and millions of miles away. It's density
6:59
Speaker 1: that creates the conditions necessary for fusion at the heart
7:02
Speaker 1: of our star, and it plays a big role in
7:05
Speaker 1: our solar system. I guess, especially here on Earth right
7:08
Speaker 1: if Earth was less dense than it was, it would
7:10
Speaker 1: probably what collapse or float away? Well, I think what's
7:14
Speaker 1: interesting is to ask how dense is Earth and why
7:17
Speaker 1: is it that dense? And then to look around to
7:19
Speaker 1: the other planets and when they're like are they more dense?
7:21
Speaker 1: Are they less dense? What's going on? It's part of
7:25
Speaker 1: understanding how our solar system came to be the way
7:27
Speaker 1: that it is, and understanding whether it's unusual because our
7:32
Speaker 1: solar system weird compared to other solar systems. Are other
7:34
Speaker 1: planets out there more massive, more dense? Are they fluffier
7:38
Speaker 1: than a French baguette? Are they denser than German rye?
7:41
Speaker 1: So today on the podcast, we'll be asking the question
7:48
Speaker 1: what is the densest planet? Now? My first question to you,
7:52
Speaker 1: Jorge is do you think this is something to be
7:54
Speaker 1: proud of or something to be embarrassed about? Which one?
7:57
Speaker 1: What do you mean like asking questions or eating bread?
8:01
Speaker 1: If we're gonna label one planet as densest, do you
8:03
Speaker 1: think that's something the denizens of that planet should be
8:06
Speaker 1: proud of or embarrassed by. Yes, I was going to
8:10
Speaker 1: ask you that you thought this was an appropriate question
8:12
Speaker 1: to ask. I guess it depends. First of all, if
8:14
Speaker 1: there are people another planets, that's amazing, But also I
8:18
Speaker 1: guess if you're talking about their planet, then they wouldn't
8:21
Speaker 1: necessarily be offended. Yeah, dense has some interesting connotations. Right,
8:24
Speaker 1: No person would want to be called dance because it
8:27
Speaker 1: applies that you're not very smart unless you're dense with
8:30
Speaker 1: awesomeness jam packed with jam packed with wonderfulness, dense with talent.
8:39
Speaker 1: On the other hand, if you're talking about a planet,
8:41
Speaker 1: maybe it means that you're filled with diamonds and gold
8:44
Speaker 1: and all sorts of valuable heavy metals. Right, A huge
8:47
Speaker 1: blob of platinum is pretty dense, and I'd rather take
8:50
Speaker 1: that than a blob of water to drink, you mean
8:53
Speaker 1: to drink or to flirt it. No, when they're like
8:56
Speaker 1: assigning mineral rights in the Solar System, you know, I'll
8:58
Speaker 1: take the denser asteroid, please, thank you very much, because
9:02
Speaker 1: then you can do what with it. You can't live
9:05
Speaker 1: in it if there's no water in it, No, you
9:07
Speaker 1: can't live in it. There's no water in it. But
9:08
Speaker 1: there's plenty of water out there in the Solar System.
9:10
Speaker 1: But you know, some of those asteroids are just like
9:13
Speaker 1: huge blobs of platinum or other rare earth metals that
9:16
Speaker 1: we need here on Earth to make batteries for all
9:19
Speaker 1: of our fancy gizmos. Yeah. So there's a huge range
9:22
Speaker 1: of density in our Solar System that I guess you
9:25
Speaker 1: can go from planets that are made out entirely out
9:27
Speaker 1: of gas, which is gas, and then there are planets
9:30
Speaker 1: that are made out of rock and metals, which are
9:33
Speaker 1: some of the densest things around, and the range of
9:35
Speaker 1: densities tells us something about how the Solar System was
9:38
Speaker 1: formed and what's under our feet and the incredible balance
9:41
Speaker 1: between gravity and the other forces. Well, as usually, we
9:44
Speaker 1: were wondering how many people have thought about the question,
9:46
Speaker 1: which is then this planet, and so Daniel went out
9:50
Speaker 1: there into the internet to find out. So thanks very
9:53
Speaker 1: much to everyone who participates. If you've been listening to
9:56
Speaker 1: the podcast and you would enjoy speculating about the next
9:59
Speaker 1: topics for future episodes, please don't be shy. Right to
10:03
Speaker 1: me two questions at Daniel and Jorge dot com and
10:06
Speaker 1: we'll set you right up and think about it for
10:07
Speaker 1: a second. Which do you think is the dancest planet?
10:12
Speaker 1: Here's what people have to say. I think it would
10:14
Speaker 1: either the Earth or Mars, but I'm pretty sure there's
10:19
Speaker 1: more warts on Earthen on Mars. So just based on that,
10:21
Speaker 1: I think Moss as the dancest planet in the Solar System.
10:25
Speaker 1: I'm going to say, just to throw it out there,
10:30
Speaker 1: the core of Jupiter or Mercury. Right now, I'm thinking
10:35
Speaker 1: about all these crazy extra planets discovered recently but I
10:43
Speaker 1: can already refer to our solar system, and from our
10:48
Speaker 1: solar system the dancers planet it's art. Yes, it's Earth.
10:56
Speaker 1: I'm going to go out on a limb and say
10:58
Speaker 1: that the dancest planet in it is actually Jupiter, because
11:02
Speaker 1: even though it is the most massive planet in our
11:04
Speaker 1: solar system, I'm guessing that there's probably a part of
11:08
Speaker 1: it that's super dense to keep it all together in
11:11
Speaker 1: a solar system. Uh, I'm going to guess one of
11:15
Speaker 1: the gas strands, the one with the most Let's go
11:19
Speaker 1: with that, all right, some dance answers here. Not a
11:24
Speaker 1: lot of love here, Yeah, a lot of variety in
11:26
Speaker 1: the thinking and in the answers. I love it. I
11:29
Speaker 1: like the people who argue that maybe we didn't specify
11:31
Speaker 1: enough that we meant planet in our solar system, because like,
11:35
Speaker 1: are we asking what's the dns is planet in the
11:37
Speaker 1: universe or just in our little local neighborhood. Yeah, well,
11:41
Speaker 1: the physicist and me wants to know what's the highest
11:43
Speaker 1: density possible in a planet anywhere in the universe, and
11:47
Speaker 1: also what is the most dense planet in our solar
11:50
Speaker 1: syst I wanted real answers to all those questions. You're
11:52
Speaker 1: dense with curiosity. But I guess maybe depends on what
11:55
Speaker 1: you mean by a planet, Like what's the definition of
11:57
Speaker 1: a planet? Like can a neutron star be a planet?
12:00
Speaker 1: If you lived on the surface of a nutron star,
12:02
Speaker 1: it would technically be your planet. I'm not sure. Maybe
12:04
Speaker 1: it would be your star, you would be the planet.
12:06
Speaker 1: But let's not get drawn into a forty minute rabbit
12:09
Speaker 1: hole about the definition of a planet. That's a whole
12:12
Speaker 1: briar patch. We don't want to get thrown into. Well,
12:14
Speaker 1: what's the one sentence answer from a physicist, Well, the
12:17
Speaker 1: official definition of a planet is a body that mostly
12:20
Speaker 1: orbits the Sun and has cleared its own path in
12:23
Speaker 1: the Solar system, a son, right, not just our son,
12:26
Speaker 1: that's right, a son or maybe multiple suns, right, because
12:29
Speaker 1: there are systems out there with binary stars at their hearts. Well,
12:32
Speaker 1: we have how many plants in our Solar system? Eight planets?
12:35
Speaker 1: We have officially eight planets in our Solar system and
12:38
Speaker 1: a bunch of dwarf planets. Also, one of them is
12:40
Speaker 1: the dances and I guess one of them is the
12:42
Speaker 1: lightest planet. Or what's the opposite of DNS fluffy? Is
12:46
Speaker 1: that the official physics word. I don't know what the
12:48
Speaker 1: SI unit is for fluff, but it's the opposite of dance.
12:52
Speaker 1: It's maybe measured in podcast episodes. It's measured in puns
12:56
Speaker 1: per podcast episode or chuckles if we if we have
12:59
Speaker 1: two many chuckles, it's not a very dense episode. All right, Well,
13:03
Speaker 1: let's dig into this, Daniel, And let's maybe start with,
13:06
Speaker 1: just like an average planet, what are planets made out of?
13:08
Speaker 1: In our Solar System? So planets come in quite a
13:11
Speaker 1: variety of stuff, right. The things that are planets are
13:15
Speaker 1: made out of depend on where they were when the
13:18
Speaker 1: planetary system was formed, because it all starts from one
13:22
Speaker 1: big blob of ingredients. But the process of planetary formation
13:26
Speaker 1: and stellar formation pulls different ingredients in different places. So
13:30
Speaker 1: where you are in the Solar System as things are
13:33
Speaker 1: forming determines what you sort of get made out of.
13:36
Speaker 1: So it all comes down to understanding that process of
13:39
Speaker 1: how you go from a huge cloud of gas and
13:41
Speaker 1: dust and bits of rock left over from other Solar
13:44
Speaker 1: systems that have now died and turned that into a
13:46
Speaker 1: new Solar system. Right, and maybe just to take us back,
13:49
Speaker 1: we start out in space, right, and there's usually a
13:51
Speaker 1: huge cloud of stuff that came from the Big Bang
13:54
Speaker 1: or maybe the remains of other suns that blew up
13:57
Speaker 1: and slowly gravity brings all of that stuff together, which
14:00
Speaker 1: is which is what forms the Sun and the planets. Right,
14:03
Speaker 1: that's exactly right, And mostly it's hydrogen. You know, we've
14:06
Speaker 1: been burning stuff in the hearts of stars for billions
14:09
Speaker 1: of years, turning the hydrogen from the Big Bang into
14:12
Speaker 1: helium and neon and carbon and iron and heavier stuff.
14:15
Speaker 1: But we haven't made that much progress. The universe is
14:18
Speaker 1: still like nineties something percent hydrogen. It's really just mostly
14:22
Speaker 1: hydrogen deferst approximation. And so even though I'm not made
14:25
Speaker 1: of hydrogen and you're not made of hydrogen, hygen is
14:28
Speaker 1: the most common thing out there in the universe. So
14:30
Speaker 1: if you're imagining this cloud that formed the Solar System,
14:33
Speaker 1: it's mostly hydrogen with like a sprinkle of other stuff
14:36
Speaker 1: like the iron and the magnesium. All that stuff is
14:38
Speaker 1: like the spice on top of the meal. Right. Although
14:41
Speaker 1: something interesting to think about is how much hydrogen we
14:43
Speaker 1: actually are, right, I mean, we're mostly made out of water,
14:46
Speaker 1: which is h two oh, right, and even our molecules
14:50
Speaker 1: are you know, hydrocarbons are called hydrocarbon because they have hydrogen,
14:53
Speaker 1: and yeah, that's true, and there's different ways of thinking
14:55
Speaker 1: about it. Also hydrogen by number or hydrogen by mass,
15:00
Speaker 1: because even if you have a lot of hydrogen, it's
15:02
Speaker 1: not very heavy. And so the universe, for example, is
15:04
Speaker 1: like hydrogen by number of molecules, but it's only seventies
15:09
Speaker 1: something percent hydrogen by mass because the other stuff is
15:12
Speaker 1: so much now or massive, even though there's less of it,
15:15
Speaker 1: it counts for a bigger proportion of the mass of
15:17
Speaker 1: the universe. So like in our bodies where maybe hydrogen
15:21
Speaker 1: is the most popular atom, but maybe not the most
15:23
Speaker 1: in terms of weight exactly, and so and if you
15:26
Speaker 1: eat a lot of bread, then yeah, you're mostly carves.
15:30
Speaker 1: And for example, the Sun today is like hydrogen, but
15:34
Speaker 1: the Earth is much less. The Earth has a huge
15:36
Speaker 1: fraction of oxygen and magnesium and iron, and so the
15:40
Speaker 1: Earth and the Sun and Jupiter, they're not all like
15:43
Speaker 1: representative samples of the stuff that started the Solar system.
15:47
Speaker 1: It differentiated itself. It's separated. The process of that gravitational
15:51
Speaker 1: collapse lead things to accumulate in different ways, which lead
15:55
Speaker 1: to different sort of scoops. Of each material in different places, right,
15:58
Speaker 1: Because you were saying it's sort of the pens and
16:00
Speaker 1: where you are in the initial kind of cloud that
16:04
Speaker 1: eventually became the Solar system, because I think what happened
16:08
Speaker 1: was that most of the hydrogen that cloud kind of
16:10
Speaker 1: rushed to the center, and that's where we're the Sun form, right, Yeah, exactly.
16:14
Speaker 1: There's sort of three zones to think about. There's the center,
16:17
Speaker 1: which forms the star, and you're right, that gathers most
16:19
Speaker 1: of the gas, at least in the inner Solar system.
16:22
Speaker 1: Then there's the inner part of it, which is you say,
16:24
Speaker 1: doesn't have much gas for two reasons. One is that
16:27
Speaker 1: the Sun steals a lot of it, and the other
16:30
Speaker 1: is that the Sun blows away some of the gas.
16:32
Speaker 1: Once the Sun gets going and starts emitting photons and
16:36
Speaker 1: solar wind, it will strip the inner planets of any
16:38
Speaker 1: gas they had. Remember that the Earth when it was
16:41
Speaker 1: first formed, it had a primordial atmosphere of hydrogen and helium,
16:45
Speaker 1: but most of that was lost because of the incredible
16:47
Speaker 1: radiation from the Sun. So the inner planets don't really
16:50
Speaker 1: keep much gas. That's why they're mostly rock. Their iron
16:54
Speaker 1: and silica and that kind of stuff. Because the gas
16:56
Speaker 1: either falls into the Sun or gets blown out into
16:59
Speaker 1: the outer system by the radiation from the Sun. Right,
17:02
Speaker 1: and I guess where did the rocks and the rocky
17:04
Speaker 1: planets come from. They came from the hearts of other stars. Right.
17:08
Speaker 1: Those rocks are made of heavier elements. And remember, astronomers
17:11
Speaker 1: think of everything that's not hydrogen or helium as a metal.
17:15
Speaker 1: And so these metals came from fusion inside the hearts
17:19
Speaker 1: of other now dead stars. They started as hydrogen from
17:22
Speaker 1: the Big Bang, or maybe a tiny little bit of helium.
17:24
Speaker 1: They were fused into heavier stuff and lived for millions
17:28
Speaker 1: or billions of years inside another star which then died.
17:31
Speaker 1: And when it died, it blew out a lot of
17:33
Speaker 1: that stuff out into the galaxy. And that's where these
17:35
Speaker 1: raw materials come from. They float out there in these
17:38
Speaker 1: big clouds until eventually they collapsed back again, triggered maybe
17:42
Speaker 1: by a shock wave from a nearby supernova, or just
17:44
Speaker 1: by a gravitational over density that gradually pulls this stuff
17:48
Speaker 1: back together. Right, So initially we had this cloud of
17:51
Speaker 1: hydrogen and some helium and a little bit, tiny little
17:54
Speaker 1: bit of some rockies and metal and solid stuff. And
17:58
Speaker 1: then I think what happened was that gas because it's lighter,
18:01
Speaker 1: kind of rushed to the middle, right, leaving some of
18:03
Speaker 1: the heavier stuff just around the Sun. That's where the
18:06
Speaker 1: rocky planets came from. Yeah, So the processes, you have
18:09
Speaker 1: the stars forming and at the same time you get
18:11
Speaker 1: what's called a protoplanetary disk. At this disc of material,
18:15
Speaker 1: it's sort of like the star has a ring system, right.
18:17
Speaker 1: All the material which will eventually form the planets is
18:20
Speaker 1: now flattened into a disc. Gravity is doing its job
18:22
Speaker 1: of pulling it together, but it's hard to pull it
18:24
Speaker 1: all into the Sun because if it's spinning around, it
18:27
Speaker 1: has a lot of angular momentum, and so it sort
18:29
Speaker 1: of stays in orbit rather than collapsing. So gravity collapses
18:33
Speaker 1: it into that disc and places where you have enough
18:36
Speaker 1: density where you have like heavy stuff like iron and
18:38
Speaker 1: magnesium and rock that's able to compete with the gravity
18:42
Speaker 1: of the Sun and pull some more stuff together. So
18:44
Speaker 1: it's sort of like a race, you know, who can
18:46
Speaker 1: get enough stuff to survive. If you don't pull enough
18:49
Speaker 1: stuff in to get massive enough, then you just get
18:51
Speaker 1: drawn into somebody else's gravity well. And so in our
18:54
Speaker 1: solar system, we had a huge planet Jupiter start to form,
18:57
Speaker 1: and it must have started from a gravitational density, and
19:00
Speaker 1: then it got bigger and bigger and bigger, because the
19:03
Speaker 1: more massive it is, the more gravity it has, the
19:05
Speaker 1: more it pulls stuff in. And so each of the
19:07
Speaker 1: planets sort of start from a spot in that protoplanetary
19:10
Speaker 1: disk where you already had a little bit of extra
19:12
Speaker 1: blob of stuff, and the mass of the planets tells
19:15
Speaker 1: you something about the initial size of that over density.
19:18
Speaker 1: The bigger it is, the faster it's able to gather mass,
19:21
Speaker 1: and the bigger the planet ends up being kind of
19:23
Speaker 1: like a maybe like a game of musical chairs, kind
19:26
Speaker 1: of like everyone's trying to grab as much stuff as
19:29
Speaker 1: possible before somebody else grabs it, right, yeah, sort of
19:31
Speaker 1: like gravitational hungry hungry hippos, right, every just grabbing more
19:35
Speaker 1: and more, and the bigger you are, the more hippos
19:37
Speaker 1: you get, and the easier it is to grab stuff.
19:39
Speaker 1: And in the inner Solar System you end up with
19:41
Speaker 1: planets of rock and silica and iron because those are
19:44
Speaker 1: the dense materials that can hold themselves together and resist
19:47
Speaker 1: being pulled into the Sun. And then the gas of
19:50
Speaker 1: course is blown out. Further out in the Solar System,
19:52
Speaker 1: the Sun's radiation is weaker and the Sun's gravity is weaker,
19:56
Speaker 1: and so gas giants can form. Jupiter and Saturn have
19:59
Speaker 1: huge contributions from helium and from hydrogen because they were
20:03
Speaker 1: far enough away from the Sun and grew fast enough
20:06
Speaker 1: that they were able to compete with the Sun's gravity,
20:08
Speaker 1: and their own gravity could protect their gas from the
20:11
Speaker 1: Sun's radiation, which is also weaker that far out in
20:14
Speaker 1: the Solar System. And while that's how we got the planets,
20:17
Speaker 1: and some of them are denser than others, and some
20:20
Speaker 1: of them is going to win the title of densest planet,
20:23
Speaker 1: and I guess another one is going to win the
20:25
Speaker 1: fluffiest planet, which is the one where I want to go.
20:28
Speaker 1: And so let's get into those details. But first let's
20:30
Speaker 1: take a quick break. All right, we're talking about the
20:45
Speaker 1: densest planet in the Solar System. Daniel, where would you
20:48
Speaker 1: put your money? I guess you know the end. Yes,
20:51
Speaker 1: I know the answer, but I do like thinking about
20:53
Speaker 1: it in terms of floating, like imagine some giant cosmic
20:57
Speaker 1: tub of water on some you know, cosmic version of
21:00
Speaker 1: the David Letterman Show and you're putting the planets in it,
21:04
Speaker 1: Like will Saturn float? Or if you drop mercury into
21:07
Speaker 1: a huge type of water, will it sink. That's just
21:10
Speaker 1: sort of a fun experiment to do. Yeah, let's do it.
21:12
Speaker 1: How much would it cost? I don't know. That's an
21:14
Speaker 1: engineering problem. It's called David Letterman. He did pretty well
21:19
Speaker 1: right with the show. He's sitting on some money. Yeah,
21:21
Speaker 1: this would be like a great way out of retirement
21:23
Speaker 1: for him. He's got some of that Netflix money now.
21:26
Speaker 1: But it is an interesting question which is the densest planet?
21:29
Speaker 1: And maybe you know, I feel like as we learn
21:31
Speaker 1: about the planets, we learn about their size. Like you
21:34
Speaker 1: sort of learned the Jupiter is the biggest one and
21:37
Speaker 1: that Mercury is the smallest one, right, but you maybe
21:40
Speaker 1: never think about the density of them. Yeah, we do
21:42
Speaker 1: focus on the size because that's what we can see.
21:44
Speaker 1: You look through your telescope, you can see Jupiter is big.
21:47
Speaker 1: You can see Saturn is huge with these big rings.
21:49
Speaker 1: So we know something about the size. And it's fun
21:52
Speaker 1: to think about, right, It's fun to try to wrap
21:54
Speaker 1: your mind around the incredible variety of sizes, right, Like
21:58
Speaker 1: Jupiter is enormous, compared to the Earth. So it's really
22:01
Speaker 1: fun to just like try to imagine filling Jupiter with
22:04
Speaker 1: Earth's and then doing the same thing for the Sun,
22:07
Speaker 1: like filling the Sun with jupiters, and imagining how many
22:10
Speaker 1: Earths would fit inside the Sun, which is like a million.
22:13
Speaker 1: And would Earth float in Jupiter if you like liquefied
22:17
Speaker 1: Jupiter and put it in a tub, I don't know,
22:20
Speaker 1: or if you like through Earth at Jupiter, would float?
22:23
Speaker 1: Would float in Jupiter? Actually would not write. Earth is
22:28
Speaker 1: much denser than Jupiter. It turns out, so Earth would
22:30
Speaker 1: sink like a stone in the ocean of Jupiter. But
22:34
Speaker 1: I guess how far right. Also, the definition of floating
22:37
Speaker 1: kind of like, are we technically floating around the Sun?
22:41
Speaker 1: I don't think there's any buoyancy, right, it's only gravity.
22:44
Speaker 1: I think in order to be floating, you need to
22:46
Speaker 1: have some sort of forces of buoyancy, you know, the displacement.
22:49
Speaker 1: I don't think that's happening in our solar system. You
22:51
Speaker 1: need the stuff from the thing that you're floating on
22:54
Speaker 1: to be pushing you up, that's what you're saying, Yeah, exactly,
22:56
Speaker 1: to be balancing gravity. Alright, Well, we're trying to get
22:58
Speaker 1: to the answer of this question what is the densest planet.
23:01
Speaker 1: And we've talked about how planets are FORGN because what
23:04
Speaker 1: you're made out of sort of depends on where you
23:06
Speaker 1: are in the Solar System when things started to form. Yeah,
23:09
Speaker 1: and there's sort of four different categories of stuff that
23:12
Speaker 1: planets can be made out of. There's like very heavy
23:14
Speaker 1: metals like iron. You're gonna find that the inner planets
23:17
Speaker 1: are mostly made out of stuff like that. And then
23:18
Speaker 1: there's rock and that's also will be found mostly in
23:21
Speaker 1: the inner planets. And then there's gas, which of course
23:23
Speaker 1: the Sun and Jupiter and Saturn have huge servings of.
23:26
Speaker 1: And then there's water. There is a lot of water
23:28
Speaker 1: in the Solar System. And there's this very interesting point
23:31
Speaker 1: where you're far enough away from the Sun. It's called
23:34
Speaker 1: the frost line or the snow line, past which water
23:37
Speaker 1: is ice instead of vapor, and beyond that line, water
23:41
Speaker 1: is a solid. And so if you have a bunch
23:43
Speaker 1: of water, it's frozen and it sort of contributes to
23:47
Speaker 1: the mass the planet and it helps planets grow faster.
23:50
Speaker 1: So planets like Urinous and Neptune, these are ice giants
23:53
Speaker 1: because they have huge amounts of ice in them. Even
23:56
Speaker 1: without accumulating a lot of hydrogen helium, they still were
23:59
Speaker 1: able to grow really large. So the proportion of what
24:02
Speaker 1: you get in the Solar System as you form really
24:04
Speaker 1: does depend on where you are, right, although if you
24:07
Speaker 1: put water out in space, even near Earth, it's going
24:09
Speaker 1: to freeze to right, it's a really good question, and
24:12
Speaker 1: it's sort of tricky. If it's close enough to the Sun,
24:14
Speaker 1: then it will vaporize, right because it's very low pressure
24:18
Speaker 1: out there in space, and the phase of a material
24:21
Speaker 1: depends not just on the temperature but also on the pressure,
24:25
Speaker 1: and so water will vaporize in space unless you're really
24:28
Speaker 1: far out, so you mean like it's the really the
24:30
Speaker 1: difference between vapor and solid like will jump straight from
24:33
Speaker 1: a vapor to at some point if you put some
24:36
Speaker 1: water out there, it will turn into an ice cube exactly,
24:39
Speaker 1: Which is why I think if you go out into space,
24:41
Speaker 1: parts of you will boil instantly right where boiling doesn't
24:45
Speaker 1: mean you're getting really hot, It just means it's sublimating.
24:47
Speaker 1: It's going directly to gas. And so you can boil
24:50
Speaker 1: at a very low temperature if the pressure is very
24:52
Speaker 1: very low, like you know, how if you're at high altitude,
24:55
Speaker 1: you can boil your water at lower temperatures. It's like
24:58
Speaker 1: harder to cook pasta at the top of Mount Everest
25:01
Speaker 1: than it is in Death Valley because the water boils
25:04
Speaker 1: at a lower temperature because of the lower pressure. Out
25:06
Speaker 1: in deep space, water boils at very very low temperature,
25:10
Speaker 1: and so it turns into vapor even if it's very cold.
25:12
Speaker 1: So I think. So you were saying that the inner
25:14
Speaker 1: planets are mostly met out of rocks because of where
25:17
Speaker 1: they are, and the outer planets are mostly med at
25:19
Speaker 1: a gas because of where they were. But that doesn't
25:21
Speaker 1: mean that there aren't rocks and metals out there in
25:24
Speaker 1: the outer Solar System. There still are, right, There's still
25:26
Speaker 1: a lot of metal and earth, maybe the same amount
25:29
Speaker 1: as there is in the inner Solar System. It's just
25:31
Speaker 1: that the inner planets don't have gas because it was
25:34
Speaker 1: all blown away, exactly. And there is definitely metal and
25:38
Speaker 1: rock out there in the outer Solar System. You know, Pluto,
25:40
Speaker 1: for example, is a lump of rock, and we suspect
25:43
Speaker 1: that at the core of Jupiter and Saturn there is metal.
25:47
Speaker 1: There is rock, absolutely, It's just that they also have
25:50
Speaker 1: a lot of gas that accumulated all this hydrogen and
25:53
Speaker 1: this helium as well, because right, because the Sun didn't
25:56
Speaker 1: get to suck up that gas before Jupiter could take
26:00
Speaker 1: it all bites for itself exactly. And Jupiter probably did
26:03
Speaker 1: begin as it just metallic or rocky blob, and then
26:06
Speaker 1: it gathered all that gas up with it. And the
26:08
Speaker 1: same thing for the ice giants. They also definitely have
26:10
Speaker 1: some rock and some metals inside of them. They just
26:13
Speaker 1: also gathered a bunch of water as well. So that
26:15
Speaker 1: helps you understand the mass the density is this combination
26:19
Speaker 1: of size and mass, right, And so you might imagine
26:23
Speaker 1: that the densest things would then be in the in
26:24
Speaker 1: your Solar system, because that's like where you have almost
26:27
Speaker 1: only the denser materials, right. But that's kind of interesting
26:31
Speaker 1: to think about. Like if you took Jupiter and any
26:33
Speaker 1: of those giant planets out there and you stripped them
26:35
Speaker 1: a while their gas, or you've got rid of all
26:37
Speaker 1: the gas in the Solar system, like all the planets
26:40
Speaker 1: would maybe be kind of the same kind of right,
26:42
Speaker 1: small dense rocky tiny balls. That's right. If you like
26:45
Speaker 1: gas blasted Jupiter so you blew away all of its
26:48
Speaker 1: helium and its hydrogen. Then you would be left with
26:51
Speaker 1: the core, which we think we don't know. We're not
26:53
Speaker 1: sure because of course we've never probed it the way
26:55
Speaker 1: we probed the Earth. We think that probably there is
26:58
Speaker 1: a rocky core there. Well, I read that Jupiter's core
27:01
Speaker 1: is actually more fluffy, that it's not like a rocky core.
27:04
Speaker 1: It's more like a kind of like a fuzzy rocky core. Yeah, well,
27:07
Speaker 1: we're not exactly sure. There's definitely some rock and some ice.
27:10
Speaker 1: It's also really interesting other chemical effects like surrounding the
27:15
Speaker 1: rock on the ice. There is hydrogen, but it's not
27:17
Speaker 1: hydrogen in the form that you're familiar with it. It's
27:20
Speaker 1: called metallic hydrogen. Hydrogen that's under such intense pressure and
27:25
Speaker 1: temperature that has formed this really strange phase. It's like
27:29
Speaker 1: liquid hydrogen. But I think the point is that, you know,
27:31
Speaker 1: if it wasn't for gas, the gas and that the
27:33
Speaker 1: outer planets have and maybe some of the water, then
27:37
Speaker 1: all the planets would be sort of the same, would
27:38
Speaker 1: be small and rocky, and Peo wouldn't be talking about
27:41
Speaker 1: the dens is one. But because those outer planets have
27:44
Speaker 1: a lot of gas, then their density changes and there's
27:46
Speaker 1: really interesting connection between the mass of a planet and
27:49
Speaker 1: its density, because remember this more than just one thing
27:52
Speaker 1: going on. It's not just like how much stuff do
27:54
Speaker 1: you have and what element is it? Right, you might
27:57
Speaker 1: think it's not just how much iron do you have
28:00
Speaker 1: or versus how much gas do you have? But how
28:02
Speaker 1: massive are you Because the larger the planet gets, the
28:05
Speaker 1: stronger it's gravity and the stronger its ability to compress
28:08
Speaker 1: itself to make it more dense. So it's not like
28:11
Speaker 1: as you add mass to a planet, it just gets
28:13
Speaker 1: bigger and stays the same density. As you add mass
28:16
Speaker 1: to a planet actually also gets more dense, so its
28:19
Speaker 1: size doesn't grow as quickly as its mass, right. But
28:22
Speaker 1: it maybe it also depends on what you put into it,
28:24
Speaker 1: what you're feeding it, right, Like if you're feeding it
28:26
Speaker 1: a gas, then that's going to be maybe a little
28:28
Speaker 1: harder to compress than the metal. Actually, the gas is
28:32
Speaker 1: easier to compress the metal. Right. It has to do
28:35
Speaker 1: with how compressible these materials are, and things like iron
28:38
Speaker 1: and rock are harder to compress than things like hydrogen
28:42
Speaker 1: and helium. And so if you look, for example, that
28:44
Speaker 1: planets made out of ice or silicon or iron, then
28:48
Speaker 1: there tends to be a bit more of a spread
28:50
Speaker 1: between their mass and their density. It's not as closely connected.
28:53
Speaker 1: But if you look at giant planets, and not just
28:55
Speaker 1: in our Solar system, but in other solar systems, you
28:58
Speaker 1: see a much tighter connection between the mass and the density.
29:01
Speaker 1: As you add more mass, the density increases pretty quickly
29:05
Speaker 1: for gas giants. It's not as tight relationship for the
29:08
Speaker 1: lower mass planets made of metals and rocks. But in general,
29:12
Speaker 1: the planets closer to the Sun are made mostly out
29:15
Speaker 1: of rocky stuff. For example, let's talk about Mercury. Yeah,
29:18
Speaker 1: so Mercury, you might imagine we should be the densest thing, right,
29:21
Speaker 1: it's closest to the Sun. It's had all the low
29:24
Speaker 1: density stuff blown off of it, and in fact it
29:27
Speaker 1: is a really crazy planet. It's got like a metallic
29:30
Speaker 1: core that's eighty five percent of its interior. So this
29:35
Speaker 1: thing is mostly metal. It's really just like a huge
29:38
Speaker 1: scoop of heavy metals surrounded by a thin layer of silica,
29:43
Speaker 1: thin layer of rock. So to compare, Earth's core is
29:46
Speaker 1: like of its interior is this metal, whereas Mercury it's
29:50
Speaker 1: eighty five So Mercury is really a very dense blob
29:54
Speaker 1: of stuff out there in the universe. Yeah, it's really
29:56
Speaker 1: into heavy metal, but I think we hear you mean
29:58
Speaker 1: actually actually like metal metal, right like. And for Earth
30:01
Speaker 1: it's mostly iron, right like our course, mostly made out
30:04
Speaker 1: of molten iron and as opposed to rock. Yeah, that's
30:07
Speaker 1: exactly right. We're talking about iron, and there's also some
30:10
Speaker 1: nickel in there. And you know, there's a lot of
30:12
Speaker 1: uncertainty here. We know a lot about the Earth's core
30:15
Speaker 1: because we can do things like study earthquakes, and as
30:17
Speaker 1: those earthquakes reverberate around the surface, they bounce across those
30:22
Speaker 1: layers in the Earth's core and they tell us something
30:24
Speaker 1: about the density. It's like ringing the Earth like a
30:26
Speaker 1: bell and studying those sound waves. We can't do that
30:30
Speaker 1: as well on mercury because we don't have mercury quake sensors.
30:33
Speaker 1: We do have those kind of sensors on Mars now
30:36
Speaker 1: and on the Moon, so we can take direct measurements.
30:38
Speaker 1: But the other ones were guessing a little bit more.
30:40
Speaker 1: They come from planetary models and from our understanding of
30:43
Speaker 1: the mass and the radius of these things. All right,
30:45
Speaker 1: So mercury is basically like a solid ball of metal, right,
30:51
Speaker 1: like a baby almost like a little ball of metal.
30:53
Speaker 1: And so you would think maybe it's the densest planet
30:56
Speaker 1: in the Solar System. You would think so, And it's
30:58
Speaker 1: pretty dense. It comes out about five point for grams
31:01
Speaker 1: per cubic centimeter, and so you know to orient yourself.
31:04
Speaker 1: Water is one gram per cubic centimeter. So Mercury would
31:08
Speaker 1: definitely not float. It's more than five times denser than water.
31:12
Speaker 1: All right, So it's not Mercury the densest planet. I
31:15
Speaker 1: guess maybe a question is what exactly makes something dense
31:19
Speaker 1: or not? Well, density here is really connected to size.
31:22
Speaker 1: As you add more stuff to the planet, it doesn't
31:25
Speaker 1: just get bigger, right if you put a whole another
31:28
Speaker 1: load of mass on Mercury, if you like, double Mercury's mass,
31:32
Speaker 1: it wouldn't double its volume and then have the same
31:35
Speaker 1: density because the gravity would get stronger, and so because
31:38
Speaker 1: the gravity gets stronger, it would squeeze those atoms more tightly.
31:42
Speaker 1: So the way to increase Mercury's density would be to
31:45
Speaker 1: increase its mass. But Mercury is a pretty small planet.
31:49
Speaker 1: It's not nearly the mass of the Earth or a
31:51
Speaker 1: venus for example. Oh I see what you're saying, Like,
31:54
Speaker 1: if maybe I added more stuff to mercury, even if
31:57
Speaker 1: it was light stuff like gas, then it would increase
32:00
Speaker 1: gravity and maybe squeeze that metal core even more and
32:03
Speaker 1: make it more dense. Exactly, because the metal core of
32:06
Speaker 1: mercury right now is denser than like if you just
32:09
Speaker 1: took that metal and had it floating out into space,
32:12
Speaker 1: if it was very cold and there was no pressure
32:14
Speaker 1: on it, it would be much less dense. You take
32:16
Speaker 1: that same amount of metal and you put it inside
32:18
Speaker 1: mercury's core, it's gonna get squeezed down. It's gonna be
32:21
Speaker 1: more dense than it otherwise would. So you add a
32:23
Speaker 1: bunch more stuff to mercury, it's going to increase its density,
32:27
Speaker 1: but maybe only up to a point, right Like this,
32:29
Speaker 1: is there a maximum size for a rocky planet? Actually,
32:32
Speaker 1: it's really interesting. We think that there's no maximum density
32:35
Speaker 1: to a planet, but there is a maximum size to
32:38
Speaker 1: a rocky planet. As a rocky planet gets larger and larger,
32:41
Speaker 1: it also gets denser and denser because you're adding more
32:43
Speaker 1: stuff and then increases the gravity and that makes it denser.
32:47
Speaker 1: And this sort of this as emptotic size, you can't
32:50
Speaker 1: really make a rocky planet bigger than about ten thousand
32:53
Speaker 1: kilometers in radius. When you get to that radius, it's
32:57
Speaker 1: so dense inside that if you add more stuff, it
33:00
Speaker 1: doesn't actually increase the size at all. It just increases
33:04
Speaker 1: the density. Like the gravity on that planet pulls that
33:06
Speaker 1: new blob of stuff in and it just makes it
33:08
Speaker 1: more dense. So for rocky planets, there's no maximum density
33:12
Speaker 1: unless you think about black hole levels, but there is
33:15
Speaker 1: probably a maximum size. Well, I think what you mean
33:18
Speaker 1: is that when you're adding more rock to it, right, Like,
33:21
Speaker 1: if you make a you have a rocky planet, then
33:23
Speaker 1: you add more rocks to it, it's not going to
33:25
Speaker 1: increase in size. It's just gonna get denser. But if
33:27
Speaker 1: you add other kinds of stuff to it, it is
33:29
Speaker 1: going to increase in size. Right, We're talking about rocky
33:32
Speaker 1: planet is having a maximum size. So if you can
33:34
Speaker 1: only make it out of rocks and metal, then there
33:36
Speaker 1: is a maximum size. But you see sort of the
33:38
Speaker 1: same kind of effect happening in our Solar System with
33:42
Speaker 1: Jupiter and Saturn. For example, Jupiter is only a little
33:45
Speaker 1: bit bigger than Saturn in terms of size, Like it's
33:48
Speaker 1: radius is seventy thousand kilometers, whereas Saturn's is about sixty.
33:53
Speaker 1: But Jupiter is more than three times more massive than Saturn, right,
33:57
Speaker 1: And that's because as you add gas to sat Learned,
34:00
Speaker 1: for example, to try to turn it into Jupiter, it
34:02
Speaker 1: doesn't just grow in volume. That gas gets compressed and
34:05
Speaker 1: gas is easier to compress than iron and metals. And
34:08
Speaker 1: so that's why adding a lot more mass to Jupiter
34:11
Speaker 1: also wouldn't make it much bigger. It would make it
34:14
Speaker 1: denser faster than it would make it bigger. Right, But
34:16
Speaker 1: it does get bigger though, right, It does get bigger. Absolutely,
34:19
Speaker 1: So you can have really really huge gas planets. They
34:22
Speaker 1: can get much bigger than rocky planets, absolutely, right. But
34:26
Speaker 1: I guess so you're saying, like Jupiter is maybe like
34:28
Speaker 1: maybe started off like a mercury, but then you added
34:31
Speaker 1: a bunch of gas, and if you had added rocks,
34:34
Speaker 1: it wouldn't have grown in size. But because you're adding gas,
34:37
Speaker 1: it doesn't increase in size, although it also increases in
34:39
Speaker 1: density because that gas gets compressed exactly, And there's also
34:43
Speaker 1: a maximum size to a gas planet because if you
34:46
Speaker 1: add enough gas to Jupiter, or what happens, it turns
34:49
Speaker 1: into a star and the pressure in the interior ignites fusion,
34:53
Speaker 1: and in fusion creates a lot of outwards pressure. So
34:56
Speaker 1: then as you add more mass, the density goes down.
34:59
Speaker 1: Like bigg your stars are less dense than smaller stars.
35:03
Speaker 1: Once you cross that threshold from gas giant into star.
35:07
Speaker 1: Then as you add mass, the density actually goes down
35:10
Speaker 1: because the fusion increases and it fluffs up the star. Interesting,
35:15
Speaker 1: and so I guess maybe in the case of Jupiter,
35:17
Speaker 1: I would think that maybe that's a good candidate for
35:19
Speaker 1: being the densest object. Then even though it's made out
35:22
Speaker 1: of a lot of gas, there's a lot of gas
35:24
Speaker 1: that's there and a lot of solid stuff in the middle.
35:27
Speaker 1: Maybe it's compressing all that gas enough to make it
35:29
Speaker 1: super dense. It's a good idea, And one of our
35:31
Speaker 1: listeners might be right that the core of Jupiter is
35:34
Speaker 1: probably very very dense, but Jupiter has so much hydrogen,
35:38
Speaker 1: and hydrogen is just not very dense. That is actually
35:40
Speaker 1: not very dense at all. Jupiter is like one point
35:43
Speaker 1: three three grams per centimeter cute. Jupiter would not float,
35:47
Speaker 1: but it almost would, right. I think That's what I
35:49
Speaker 1: meant earlier, is that you know, gas is sort of
35:51
Speaker 1: easy to compress, but ultimately is something like Jupiter. The
35:55
Speaker 1: gas doesn't compress to something denser than rock. Yeah, exactly.
35:59
Speaker 1: The gas is very low mass, right, and so it
36:01
Speaker 1: doesn't contribute as much gravity as well. And Saturn is
36:04
Speaker 1: even less dense than Jupiter. Saturn is actually points seven
36:08
Speaker 1: grams per cubic meter, which means Saturn would float. If
36:12
Speaker 1: Letterman could build a huge tupe of water, Saturn would
36:15
Speaker 1: actually float in it. Well, I guess maybe a question
36:17
Speaker 1: is why doesn't gas compressed as much as rocks? It
36:21
Speaker 1: just doesn't have as much mass, right, It's not inherently
36:23
Speaker 1: as dense. You don't have as many protons inside there,
36:26
Speaker 1: So the compression is just due to gravity. Why can
36:28
Speaker 1: I squeeze them closer together than I can with the metal?
36:32
Speaker 1: It's not about squeezing the atoms closer together. It's about
36:35
Speaker 1: the nucleus of the atom having more mass already, right,
36:38
Speaker 1: There's all those extra protons in the nucleus of iron
36:42
Speaker 1: and in silicon and in carbon and in oxygen that
36:45
Speaker 1: makes it more massive and therefore having more gravity. But
36:48
Speaker 1: couldn't I then squeeze the hydrogen atoms closer together? The
36:51
Speaker 1: reason it's hard to compress hydrogen, of course, is because
36:54
Speaker 1: the electrons repel each other, and if you squeeze even
36:57
Speaker 1: further than the protons in the nuclei will reject each
37:00
Speaker 1: other as well will repel each other. So the atoms
37:02
Speaker 1: don't like to be compressed beyond a certain point. But
37:05
Speaker 1: if you have the same sort of number density of
37:07
Speaker 1: hydrogen and number density of iron, like you have a
37:10
Speaker 1: million iron atoms in a cubic meter versus a million
37:13
Speaker 1: hydrogen atoms, you're gonna get a lot more gravity from
37:16
Speaker 1: the iron atoms. You're gonna get a lot more density.
37:19
Speaker 1: All right, Well, Mercury, apparently it's not the densest planet,
37:22
Speaker 1: even though it's the smallest and the rockiest, and Jupiter
37:26
Speaker 1: is the largest planet. But it's also not the dances
37:29
Speaker 1: and so let's get into which planet is the dance
37:31
Speaker 1: is planet in our Solar system. But first let's take
37:35
Speaker 1: another quick break. Al Right, we are giving out an
37:50
Speaker 1: award for the dances planet in the Solar system, Daniel,
37:53
Speaker 1: what is our planet gonna win for being the dances planet.
37:56
Speaker 1: It's gonna win a huge blue ribbon and we're gonna
37:58
Speaker 1: give it a nice pat of butter after we toasted
38:00
Speaker 1: for lunch. I thought you were going to get a
38:03
Speaker 1: bouquet of bread or a nice day at the spot
38:06
Speaker 1: where they can float in a tub all day or
38:09
Speaker 1: not float, I guess, or sink into a tub and
38:10
Speaker 1: they're gonna have to float in like a tub of
38:12
Speaker 1: molten lead or something like that. Well, yeah, I mean
38:16
Speaker 1: that could be relaxing, I guess, if not totally poisonous. Yeah,
38:20
Speaker 1: you do, you man, treat yourself all right. Well, the
38:22
Speaker 1: densist planet, apparently is not Mercury, which is the smallest
38:25
Speaker 1: and rockiest one that is mostly made out of metal.
38:28
Speaker 1: And it's not Jupiter, which is the biggest planet and
38:31
Speaker 1: most massive planet in our solar system, Daniel, which one
38:34
Speaker 1: is the densest planet. It's not Pluto, is it. It's
38:37
Speaker 1: not Pluto. No, it's actually the Earth. Earth is the
38:40
Speaker 1: densest planet in the Solar system. We win this one,
38:44
Speaker 1: What surprise plot twist? It was us all along, It
38:48
Speaker 1: was all along. The answer was the planet we loved
38:51
Speaker 1: along the way, but not by much, right, Like, the
38:53
Speaker 1: Earth is like five and a half grass per cubic
38:56
Speaker 1: centimeter and Mercury is like five point four three, which
38:59
Speaker 1: is pretty close. Yeah, And the reason the Earth winds
39:02
Speaker 1: is just because it's more massive, like whatever happened in
39:05
Speaker 1: the very early Solar system. Earth started forming before Mercury,
39:09
Speaker 1: or it formed from a larger initial blob, either one,
39:12
Speaker 1: and so he was able to like hungry, hungry hippo
39:15
Speaker 1: its way to just more stuff. And so because we
39:17
Speaker 1: have more stuff, we don't just get bigger again, we
39:20
Speaker 1: get more compressed. Right, more stuff means more gravity, which
39:23
Speaker 1: means more gravitational pressure, which means that the stuff we're
39:27
Speaker 1: made out of is squeezed more than the stuff mercury
39:30
Speaker 1: is made out of, just because there's more of it.
39:32
Speaker 1: And so that's why Earth is able to eke out
39:35
Speaker 1: above Mercury like you would naively expect. And if all
39:38
Speaker 1: the planets had the same mass, you would expect that
39:40
Speaker 1: the ones closer to the Sun would be denser for
39:43
Speaker 1: the reasons we've discussed several times as you went out,
39:45
Speaker 1: that would be less and less dense. But there's another
39:48
Speaker 1: factor there, which is a total mass. More mass means
39:51
Speaker 1: more density for these planets. But we're also bigger than mercury, right, Like,
39:56
Speaker 1: we're both larger in size and also denser. Exactly, we're
40:00
Speaker 1: larger we're more massive, and we're only a little bit
40:03
Speaker 1: denser than mercury. Were like just barely eat out. It's
40:06
Speaker 1: like five point five one versus five point four three
40:09
Speaker 1: grams per cubic centimeters, so neither of us would float
40:13
Speaker 1: in water. Right, But it's again it's not just because
40:15
Speaker 1: we have more mass, because Jupiter definitely has thousands of
40:18
Speaker 1: times more mass than Earth, but it's not as dense
40:20
Speaker 1: as Earth because gas doesn't get compressed as much. Yea
40:24
Speaker 1: jupiters around three hundred times in the mass of the Earth,
40:27
Speaker 1: but you're right, it's much less dense. So the reason
40:29
Speaker 1: that we're denser is because we are made out of
40:32
Speaker 1: rocks and metals instead of gas, and we'll also have
40:34
Speaker 1: a bigger scuba stuff than mercury. So we're denser than
40:38
Speaker 1: Jupiter because we're made of denser stuff, and we're denser
40:40
Speaker 1: than mercury because we're made of more dense stuff. All right,
40:43
Speaker 1: So the Earth is about five point five grams per
40:46
Speaker 1: cubic centimeters and mercury is five point four grasper cubic centimeters.
40:51
Speaker 1: What were some of the other close runner ups. Venus,
40:54
Speaker 1: which is right between us, is five point two grams
40:57
Speaker 1: per cubic centimeters, So it's like right around there. You know,
41:00
Speaker 1: these three inner planets are all very similar in mass,
41:03
Speaker 1: super closed, right, like if you were to round to
41:05
Speaker 1: the you know, nearest single digit. Uh, they're about the same. Yeah,
41:09
Speaker 1: And except for the Earth, it sort of follows the
41:12
Speaker 1: trend you expect. You know, Earth is the most massive,
41:14
Speaker 1: but then it's mercury than Venus than Mars, which is
41:17
Speaker 1: almost four grams per cubic centimeter, So the Earth is
41:21
Speaker 1: sort of an outlier there, right, it's sort of like
41:23
Speaker 1: the weird one. Other than that, it follows the rule
41:25
Speaker 1: of the inner planets being the densest and then it
41:27
Speaker 1: falling as you get further from the Sun. So the
41:30
Speaker 1: Earth just sort of like happened to be a big
41:32
Speaker 1: boy or big girl or a big thing. It's just
41:34
Speaker 1: having to get more stuff, right, because Mars is further out,
41:37
Speaker 1: but it's smaller. Yeah, Mars is further out and it's
41:40
Speaker 1: also smaller, and so it can't really compete, right. And
41:42
Speaker 1: then at some point in the Solar System, the planets
41:45
Speaker 1: become gas planets, right, which is where Jupiter and Saturn
41:48
Speaker 1: commit and those guys are about roughly the density of
41:51
Speaker 1: water you know, Jupiter is just a little bit more
41:53
Speaker 1: dense than water at one point three grams per centimeter cube,
41:56
Speaker 1: and Saturn is a little bit less dense than water
41:59
Speaker 1: at points set than Graham's per centimeters cubed. So it's
42:02
Speaker 1: interesting because then if you had a cup of water,
42:05
Speaker 1: it would sink in Jupiter technically, but it would float.
42:09
Speaker 1: Now it would sink in Saturn, but it would float
42:11
Speaker 1: in Jupiter. Yeah, exactly. If you spill your beverage and Jupiter,
42:15
Speaker 1: don't worry. You can just you know, bend down with
42:17
Speaker 1: your straw and surp it up. It's gonna be floating
42:19
Speaker 1: over the surface of Jupiter, right well, technically also maybe
42:22
Speaker 1: in Saturn, right because we're talking about average densities. Yeah, exactly.
42:25
Speaker 1: And it's a little bit fuzzy there, right, Like, because
42:28
Speaker 1: the edge of Jupiter is fuzzy. It's easy to say
42:30
Speaker 1: where we think the Earth ends right at the surface,
42:33
Speaker 1: but it's harder to say, like where to draw the
42:35
Speaker 1: line for Jupiter because it doesn't have a hard surface
42:38
Speaker 1: the way Earth does. So they sort of arbitrarily defined
42:41
Speaker 1: some drop off in the density as the edge of Jupiter.
42:44
Speaker 1: But that changes the number. You know, if you push
42:46
Speaker 1: further out to include Jupiter's full atmosphere and exosphere, then
42:49
Speaker 1: the density would drop even further. The density at the
42:51
Speaker 1: core of these planets is much higher than the density
42:54
Speaker 1: near the edges. Right, Like you said, Jupiter has metallic
42:57
Speaker 1: hydrogen at its core, and Saturn I think it rains
43:00
Speaker 1: diamonds too, right, Like, things are pretty intense inside of
43:04
Speaker 1: these fluffy planets. Yeah, and that's one reason that it's
43:07
Speaker 1: hard to study. We have dropped probes into some of
43:09
Speaker 1: these things, but they don't last very long because the
43:11
Speaker 1: pressure gets very intense pretty quickly. Right. So then after
43:15
Speaker 1: these gassy, gassy planets, then you have the icy planets, right,
43:19
Speaker 1: Urinus and Neptune, and those are actually denser than the
43:22
Speaker 1: gassy planets. Yeah, Urinus is about the same as Jupiter,
43:25
Speaker 1: but Neptune is even denser. It's one point six grams
43:28
Speaker 1: per centimeter cubed. And that's just because it has more water,
43:31
Speaker 1: more ice. It's out past the frost line, and so
43:35
Speaker 1: it can get a little bit more solid. It's a
43:36
Speaker 1: little bit more like the rocky planets than like the
43:39
Speaker 1: gas planets. I mean, it's still more like a gas planet,
43:42
Speaker 1: but sort of in the rocky direction because it has
43:44
Speaker 1: more ice in it. Right. It kind of seems to
43:46
Speaker 1: depend on what you're most of your mass comes from, right, Like,
43:50
Speaker 1: if your most of your mass comes from rocks, then
43:51
Speaker 1: you're going to be more dense. If it most mostly
43:54
Speaker 1: comes from gas, you're gonna be the least dense. And
43:56
Speaker 1: if it mostly comes from water, then you're sort of
43:59
Speaker 1: in the mid Yeah, And it's a really cool way
44:01
Speaker 1: to sort of indicate what you're made out of, which
44:03
Speaker 1: tells you where you were formed in the Solar System
44:06
Speaker 1: and something about the whole history of the Solar System's formation.
44:09
Speaker 1: There's so much wrapped information wrapped up in these few numbers,
44:12
Speaker 1: you know, the mass, the radius, the density. That tells
44:14
Speaker 1: you a lot about the history of each planet. Alright,
44:16
Speaker 1: So eartha, we are the densest planet in our Solar system.
44:20
Speaker 1: That's um. I guess that's a good distinction, right Like
44:24
Speaker 1: dense is good. It means more more is happening. We're
44:27
Speaker 1: not to be taken lightly, that's for sure. It's a
44:30
Speaker 1: pretty heavy topic, but you know, on cosmic scales, these
44:33
Speaker 1: are not very impressive densities. You were talking earlier about
44:36
Speaker 1: neutron stars. Remember that if water is one gram per
44:40
Speaker 1: cubic centimeter. A neutron star is tend to the eleven
44:45
Speaker 1: kilograms per cubic centimeter. Right, it's just like way off
44:49
Speaker 1: the scale, you know, orders and orders of aptitude. Remember
44:52
Speaker 1: that a teaspoon of neutron star material is like seven
44:56
Speaker 1: hundred thousand Eiffel towers all squeezed into a tie any spot.
45:00
Speaker 1: So the universe is capable of creating stuff at much
45:04
Speaker 1: much higher densities than we see in our solar system. Right.
45:07
Speaker 1: I guess it depends on how much mass you get
45:09
Speaker 1: to accumulate into a small spot. So basically anything would
45:13
Speaker 1: float in a neutron star, even six stunded thousand Eiffel towers.
45:16
Speaker 1: I don't know if you'd call it floating. Neutron stars
45:18
Speaker 1: actually have a crust, right, So you could build Eiffel
45:21
Speaker 1: towers on the surface of a nutron star if you
45:23
Speaker 1: made them strong enough, because nothing can be higher than
45:26
Speaker 1: about a millimeter above the surface of a neutron star
45:28
Speaker 1: because the gravity is so intense that it just gets flattened.
45:32
Speaker 1: So yeah, if you spill your drink on a neutron star,
45:33
Speaker 1: it's going to be a very thin puddle on the surface, right, Yeah, well, well,
45:37
Speaker 1: well it would be a potal but you'd still be floating. Well,
45:41
Speaker 1: those are the planets in our Solar system. What about
45:43
Speaker 1: out there into the cosmos um One of our listeners
45:46
Speaker 1: here I was asking whether we meant the Solar System
45:49
Speaker 1: or the exoplanets out there in other parts of the
45:52
Speaker 1: galaxy and other galaxies. Yeah. One of the really fun
45:55
Speaker 1: things about modern astronomy is that we are now able
45:58
Speaker 1: to use our telescopes to study planets around other stars,
46:02
Speaker 1: which gives us this amazing window into the question of
46:04
Speaker 1: whether our Solar system is weird or typical. You know,
46:07
Speaker 1: in the end, it's sort of a statistics question. We're
46:09
Speaker 1: like one example out of many, many stars, and we
46:12
Speaker 1: want to know are we usual? Are we weird? You know?
46:15
Speaker 1: How could we be different? Is the fact that there's
46:18
Speaker 1: life on this Solar system mean that our Solar system
46:20
Speaker 1: has to be different? Or if our Solar system is
46:23
Speaker 1: normal and usual, does that mean there's life everywhere in
46:26
Speaker 1: the Solar System. It's really big and fun question, and
46:29
Speaker 1: it's actually not that hard to think about the densities
46:32
Speaker 1: of these planets, because to measure the density you only
46:35
Speaker 1: need to know their mass. And their size, right, Because
46:38
Speaker 1: it's an interesting question because it could be then maybe
46:41
Speaker 1: other solar systems out there in the universe are totally
46:44
Speaker 1: different than ours. Right, it could be that ours is like,
46:47
Speaker 1: you know, a weird one where we form planets. But
46:49
Speaker 1: it could be that maybe that in other solar systems,
46:52
Speaker 1: maybe you don't even form planets, or you form like
46:54
Speaker 1: one giant planet, or you only form two planets or
46:57
Speaker 1: something like that, right, yeah, Or they're all gas giants.
47:00
Speaker 1: Maybe rocky planets are super rare in the universe, or
47:02
Speaker 1: maybe they're all rocky planets. Right until we started looking
47:06
Speaker 1: at other solar systems and we didn't know the answer
47:08
Speaker 1: to this. Now we actually know that there are a
47:10
Speaker 1: lot of gas giants out there. We call them hot jupiters.
47:13
Speaker 1: A lot of them are really big gas giants close
47:15
Speaker 1: to their sun. We also have identified a lot of
47:18
Speaker 1: rocky planets, so we know that there's rocky planets out there,
47:22
Speaker 1: and there are gassy planets out there, and there's a
47:24
Speaker 1: huge variety also in the density of these planets. Right.
47:28
Speaker 1: It's interesting because, like you say, these things are really
47:30
Speaker 1: hard to see, like we barely even seen like have
47:33
Speaker 1: or have photos of one planet out there beyond the
47:35
Speaker 1: Solar System. We kind of have to backtrack what these
47:38
Speaker 1: planets look like or how dense they are from what
47:41
Speaker 1: we can see of how their stars wiggle, or how
47:44
Speaker 1: how much light they block from the star when they
47:46
Speaker 1: pass in front of it. Right, it's kind of a
47:48
Speaker 1: tricky problem. It's a very tricky problem, and it's amazing
47:51
Speaker 1: what we can figure out. You know, you want to
47:53
Speaker 1: know what is this planet made out of? When you
47:55
Speaker 1: can't go visit it, you can't land a probe on it,
47:58
Speaker 1: you can't even really measure the light that comes from
48:01
Speaker 1: it very well. So how do you figure out what
48:03
Speaker 1: it's made out of? Well, its density is a huge clue. Right,
48:06
Speaker 1: If you were an astronomer in a far awayte Solar
48:08
Speaker 1: system studying hours and you can measure the density of
48:11
Speaker 1: Earth and the density of Jubiter, that would tell you, oh,
48:14
Speaker 1: one of those is probably a gas planet, in one
48:16
Speaker 1: of those is a rocky planet, because one of them
48:18
Speaker 1: is much denser than the others. So just getting a
48:20
Speaker 1: measure of the density of planets and other Solar systems
48:23
Speaker 1: tells you immediately what kind of things they might be
48:26
Speaker 1: made out of. And you're right, it's very tricky, but
48:28
Speaker 1: we can measure the mass of those planets and the
48:30
Speaker 1: radius of those planets. The mass comes from understanding the
48:33
Speaker 1: orbital dynamics, like how long does it take to go
48:36
Speaker 1: around the star? How far away from the star is it.
48:39
Speaker 1: We can just solve the Newton's equations, you know, use
48:42
Speaker 1: Kepler's loss to understand what are the forces of gravity,
48:45
Speaker 1: how fast this is going, and therefore how massive is it.
48:48
Speaker 1: Just by understanding its orbit, we can tell what the
48:51
Speaker 1: mass of the planet is. Like Jupiter, if Jupiter was
48:54
Speaker 1: danser or less dense, it would still have the same
48:57
Speaker 1: trajectory around the Sun. Exactly, it's mass and it's radius,
49:01
Speaker 1: determine the orbital velocity. Or like the Earth, if the
49:03
Speaker 1: Earth was fluffier or more hardcore, a year would still
49:08
Speaker 1: be a year on Earth. Yeah, exactly because gravity. Exactly,
49:11
Speaker 1: Because when you're dealing with Newtonian gravity, you can always
49:14
Speaker 1: replace an object with a point particle of the same
49:17
Speaker 1: mass and you get an effect the same gravity as
49:19
Speaker 1: long as you're on the outside of the object. So
49:21
Speaker 1: replace the Earth with a particle the mass of the Earth,
49:24
Speaker 1: and it would move the same way the Earth does, right,
49:27
Speaker 1: And so by observing the motion of those exoplanets, we
49:30
Speaker 1: can tell what their mass is regardless of what their
49:32
Speaker 1: size is, right, it's an independent thing. But then to
49:35
Speaker 1: figure out what their density is, we do need to
49:37
Speaker 1: know what is the size of that planet, and that
49:40
Speaker 1: we can do by watching them eclipse their son. Because
49:43
Speaker 1: you're saying, one way that we can detect those planets
49:45
Speaker 1: are there is that they pass in front of their star,
49:48
Speaker 1: and so they block the light from that star a
49:50
Speaker 1: tiny a little bit. But our telescopes are sensitive enough
49:53
Speaker 1: to see that. It's called the transit method. So as
49:56
Speaker 1: that distant planet passes in front of the star, it
49:58
Speaker 1: decreases the light and decrea the light more if it's
50:01
Speaker 1: a bigger planet, unless if it's a smaller planet. So
50:03
Speaker 1: by seeing how much it decreases the light, we can
50:06
Speaker 1: measure the radius of that planet the size of it,
50:09
Speaker 1: separately from its mass. Right. And once we know their
50:11
Speaker 1: mass and their size, then you can tell their density
50:15
Speaker 1: and that maybe tells you like, hey, this is a
50:17
Speaker 1: rocky planet or an icy planet or a gas planet,
50:19
Speaker 1: right exactly, or it's like, what this is a really
50:22
Speaker 1: weird planet. What's going on? This planet seems to be
50:25
Speaker 1: super fuffy or super dense. This was made out of bread.
50:28
Speaker 1: That's so weird. It's a bad death planet. Maybe the
50:32
Speaker 1: French have been colonizing before we even knew it, but
50:34
Speaker 1: you know, it's definitely going to be testing our assumptions.
50:37
Speaker 1: We have these ideas, these models for how big a
50:40
Speaker 1: rocky planet can be. I'm sure we're gonna find one
50:42
Speaker 1: that breaks that rule if we look far enough, and
50:44
Speaker 1: that's going to tell us something we didn't understand about
50:47
Speaker 1: how planets form. So it's very exciting to look for
50:49
Speaker 1: the extremes of these planets. All right. Well, that means
50:53
Speaker 1: density is an important thing to know about a planet
50:55
Speaker 1: because it tells you a lot about what it's made
50:57
Speaker 1: out of and where in the Solar System, wherever that
51:00
Speaker 1: Solar System might be it came from. Yeah, and so
51:03
Speaker 1: we have been looking and there are a few really
51:05
Speaker 1: fun candidates. One of them is called Kepler one C,
51:09
Speaker 1: which just means that the Kepler telescope discovered it. It's
51:12
Speaker 1: a dred thirty one that it's spotted and this is
51:14
Speaker 1: very uncertain, but this is the planet out there with
51:17
Speaker 1: the highest estimated density. It's more than eight times the
51:20
Speaker 1: mass of the Earth. But it's actually smaller than the
51:23
Speaker 1: Earth in radius, and so the current estimate of this
51:26
Speaker 1: thing density is seventies seven grams per cubic centimeter. Remember
51:31
Speaker 1: the Earth is like five grams per cubic centimeter, So
51:34
Speaker 1: this thing is like fifteen times the density of the
51:37
Speaker 1: Earth if these numbers are correct. Right, But is that
51:41
Speaker 1: weird or is that pretty much what you expect if
51:43
Speaker 1: the Earth was you know, if you gave it eight
51:46
Speaker 1: times the mass and rocks with the Earth also be
51:49
Speaker 1: that size. Yeah, if you took a bunch of Earths
51:51
Speaker 1: and you squeeze them together, you would get something very dense. Right,
51:56
Speaker 1: But we think that it's possible to get larger than
51:58
Speaker 1: the Earth. Remember the upper limits for the radius of
52:00
Speaker 1: a rocky planet it's like ten thousand kilometers and the
52:03
Speaker 1: Earth is six thousand kilometers. So it's possible to get
52:06
Speaker 1: bigger than the Earth. If you plopped a bunch of
52:09
Speaker 1: Earth together, you would expect them to be larger than
52:11
Speaker 1: the Earth by a little bit. So for this to
52:13
Speaker 1: be that dense, it has to also be made of
52:15
Speaker 1: denser stuff than the Earth. So maybe it's just like
52:18
Speaker 1: a huge blob of lead or like has a lot
52:21
Speaker 1: of magnesium or osmium in it. It's not a crazy number,
52:24
Speaker 1: but it's definitely out there on the extreme edge. Whoa
52:28
Speaker 1: like the whole planet just of a single metal or something. Yeah,
52:31
Speaker 1: I know there's fluffy rock that makes it less dense.
52:35
Speaker 1: Maybe it's like an alien engineering project, you know, some
52:38
Speaker 1: alien university, like make a planet out of concrete or
52:41
Speaker 1: make a planet out of osmium or something. Yeah, and
52:44
Speaker 1: see if it floats. And maybe there's a David Letterman
52:47
Speaker 1: in that planet with a very uh big budget for
52:51
Speaker 1: the his or her show exactly. So I hope somebody
52:54
Speaker 1: got an a for that project. And then there's another
52:56
Speaker 1: interesting planet that we found out there, right, So number
52:59
Speaker 1: two on the exo planet density top ten is fifty
53:03
Speaker 1: five can create e This one is six larger than
53:07
Speaker 1: the Earth, so it's a bigger radius, but also about
53:09
Speaker 1: eight times the mass of the Earth, so about twice
53:12
Speaker 1: the density of the Earth, which gives it the density
53:15
Speaker 1: of about lead. You know, that's the average density, which
53:18
Speaker 1: means that probably near the surface it's less dense and
53:21
Speaker 1: in the core it's much much more dense. Um. And
53:23
Speaker 1: it's really fun to think about, like how these planets
53:25
Speaker 1: came to be was there a huge blob of metal
53:28
Speaker 1: that formed a planet, or there are other processes that
53:30
Speaker 1: we don't understand that contribute to planetary formation. You know,
53:34
Speaker 1: we're also able to image protoplanetary disks, like we look
53:38
Speaker 1: far enough back in time, which means looking at things
53:41
Speaker 1: far away, you can see planets form, and we can
53:43
Speaker 1: see stars with disks around them, not just planets. Those
53:47
Speaker 1: are actually easier to spot than planets because the disks
53:49
Speaker 1: discs are much bigger. Well, this one's interesting because it's
53:52
Speaker 1: also eight times the mass of the Earth, but it's
53:54
Speaker 1: only twice the density as opposed to like ten times
53:58
Speaker 1: the density. Yeah, and so it might be made out
54:00
Speaker 1: of less dense stuff. You know, it might have a
54:02
Speaker 1: lot of water in it. We just don't know. Interesting,
54:05
Speaker 1: and we can use some of these facts sometimes to
54:07
Speaker 1: figure out which are maybe habitable planets, right, Like, we
54:11
Speaker 1: don't want to land in a Jupiter or a Saturn
54:14
Speaker 1: because that would be um probably not livable for us.
54:19
Speaker 1: And we don't want to live in a maybe like
54:21
Speaker 1: a Mercury, right, we want to live in a planet
54:24
Speaker 1: maybe that's similar to Earth in density exactly. If you're
54:26
Speaker 1: planning an interstellar road trip, then you probably want to
54:29
Speaker 1: target a rocky planet. It's more likely to have water
54:31
Speaker 1: on the surface of it, for example, to be in
54:33
Speaker 1: what we call the habitable zone. If you're just wondering
54:36
Speaker 1: about what's possible for planets you want. If you're a
54:38
Speaker 1: scientist and you want to visit the craziest planets out there,
54:41
Speaker 1: then yeah, you want to find stuff with really low
54:43
Speaker 1: density or really high density to help inform your models
54:47
Speaker 1: of the universe. But it's amazing how much you can
54:49
Speaker 1: learn about a planet just by understanding its density, right,
54:53
Speaker 1: but then using information that we know from our Solar
54:57
Speaker 1: system to kind of extrapolate and say, hey, that one's
54:59
Speaker 1: probably see or rocky or gassing. Yeah, you're ready. And
55:03
Speaker 1: our knowledge of how these elements work and our models
55:05
Speaker 1: for planetary formation, which come of course from what we've
55:08
Speaker 1: learned in our Solar system. So science good, but you know,
55:12
Speaker 1: I'm sure we're wrong about a lot of how this works.
55:14
Speaker 1: And if we ever do get to visit these solar
55:16
Speaker 1: systems in detail, we will find planets to make us go, what,
55:19
Speaker 1: how is that even possible? We were totally wrong? All right,
55:22
Speaker 1: Well that's kind of a pretty good lesson, I think,
55:25
Speaker 1: as you say of why it's important even to study
55:28
Speaker 1: our backyard, or why it's important to have curiosity about
55:30
Speaker 1: these things, because you know, the more you learn about
55:33
Speaker 1: how solar systems form, and how planets form, and what
55:36
Speaker 1: the terms density, the more you can learn about the
55:39
Speaker 1: rest of the universe with limited information, right, And it
55:43
Speaker 1: tells you something about our own history, which is fascinating
55:46
Speaker 1: in its own right. Something happened early in our solar
55:49
Speaker 1: system to make Earth bigger and more massive than Venus
55:53
Speaker 1: and mercury, and that's why it wins the crown today.
55:56
Speaker 1: All right, Well, that was a pretty dense episode. I
55:59
Speaker 1: guess you can make dancer by playing it twice as
56:01
Speaker 1: fast or increasing the playback speed. You have control over
56:05
Speaker 1: the density of your podcast experience. You know, we often
56:08
Speaker 1: talk about people playing the podcast at higher speeds. I
56:10
Speaker 1: wonder if there are people out there who play us
56:12
Speaker 1: at like half speed to make us more fluffy, you know,
56:17
Speaker 1: like spread it out like butter on toast, you know, right, right,
56:20
Speaker 1: But that would also spread out your chuckles, so it
56:24
Speaker 1: would be more sinister, be more like who I try
56:29
Speaker 1: to make my chuckles pure and innocent. Well, we hope
56:32
Speaker 1: you enjoyed that Thanks for joining us, see you next time.
56:44
Speaker 1: Thanks for listening, and remember that Daniel and Jorge Explain
56:47
Speaker 1: the Universe is a production of I heart Radio. For
56:50
Speaker 1: more podcast for my heart Radio, visit the i heart
56:53
Speaker 1: Radio app, Apple Podcasts, or wherever you listen to your
56:56
Speaker 1: favorite shows. No