Speaker 1: Ay, Daniel, When you were growing up, when did you
Speaker 1: first realize that the rest of the world was not
Speaker 1: like the neighborhood you lived in. Mmm, well, I grew
Speaker 1: up in Los Alngos, where I was surrounded by people
Speaker 1: with pH d s, and now I live on campus
Speaker 1: at you see Irvine, also surrounded by people with PhDs.
Speaker 1: Are you saying that's not typical? First of all, I
Speaker 1: feel a little sad for you. The second, I think
Speaker 1: maybe you need to travel more. Hey, I mean I
Speaker 1: have lots of friends who don't have PhDs like me,
Speaker 1: And you mean you do know I have a PhD. Right, Oh,
Speaker 1: that's true. Actually, well, I'm sure one of my friends
Speaker 1: out there doesn't have a PhD in something. Probably sometimes
Speaker 1: you have to leave your comfort zone to discover what
Speaker 1: the rest of the world or the universe is. Like.
Speaker 1: Hi am or hand Ma cartoonists and the creator of
Speaker 1: PhD comics. Hi, I'm Daniel. I'm a particle physicist by
Speaker 1: day and a podcaster by night. It makes it sound
Speaker 1: like you're a superhero. Like you you put on a
Speaker 1: costume and you go and fight crime and discover things. Wait,
Speaker 1: which is the alter ego and which is a superhero.
Speaker 1: Ag are you saying particle physicists are superheroes or podcasters? Well,
Speaker 1: since I'm not a physicist, I would say the podcasters
Speaker 1: are the superhero. That's right. By day, a boring, run
Speaker 1: of the mill particle physicists like the kind you meet
Speaker 1: at your grocery store every day. No more like during
Speaker 1: the day. You're a physicist scientists supervillain during night, then
Speaker 1: you try to fix fixed by being a podcaster. That's right,
Speaker 1: And I take off my glasses to reveal my secret
Speaker 1: podcast identity. You shave your beard every night never. That
Speaker 1: is the source of my knowledge and inspiration, source of
Speaker 1: your source of professor male professor's powers. That's right. I
Speaker 1: am the Samson of physics. Before I grew this beard,
Speaker 1: I never achieved anything in science. Oh man, what if
Speaker 1: you could a got Does that cut your productivity? You
Speaker 1: can have? It's nonlinear. Well, welcome to our podcast, Daniel
Speaker 1: and Jorge Explain the Universe, a production of I Heart
Speaker 1: Radio in which we tackle all things about the universe
Speaker 1: that are mysterious, that are amazing, that are bonkers, from
Speaker 1: how the universe was formed, to how big is it?
Speaker 1: To how old the Earth is, to whether or not
Speaker 1: your facial hair determines your evil or innocence yep. Or
Speaker 1: whether being a podcaster makes you a superhero or not.
Speaker 1: I think we all know the answer to that one.
Speaker 1: But basically, we talk about all the things that are
Speaker 1: interesting and different and fascinating about our universe right especially
Speaker 1: the things around us, and we try to focus on
Speaker 1: the things that science is asking right now, the questions
Speaker 1: in the minds of scientists. We try to take you
Speaker 1: to the cutting edge of current science and then do
Speaker 1: obscurify it. We don't use complicated words like de obscurify.
Speaker 1: We try to make things clear and understandable. You just
Speaker 1: contradicted yourself there. I feel like we try to explain
Speaker 1: things in the simplest way possible. When we explain it
Speaker 1: are explaining, we use the most complicated words possible. Hey,
Speaker 1: this is Daniel Jorge explained the universe, not Daniel Jorge
Speaker 1: explained the explaining and then welcome through new podcast Daniel
Speaker 1: and Jorge explain. Daniel and Jorge explain the universe. That's right,
Speaker 1: the spinoff podcast exactly. I'm looking forward to that one.
Speaker 1: A lot of TV shows now having like an aftershow,
Speaker 1: So that's the better off solid podcasts. Yeah, let's talk
Speaker 1: Daniel and Jorge podcast. Doesn't that need to have somebody
Speaker 1: else on it though, where they can ridicule all of
Speaker 1: our jokes. Yeah, let's pretend to be some other person. Oh,
Speaker 1: there you go. I'll be David and you'll be Gearmo.
Speaker 1: David and Jose. David Jose ridiculed Daniel and Jorge. Al right, well, yeah,
Speaker 1: we talked about all the things scientists want to know
Speaker 1: and um and how they look at the universe as well, right, Like,
Speaker 1: you know, one way to look at the universe is
Speaker 1: to compare it to the things around us. That's right,
Speaker 1: and something we're always trying to do in sciences. Understand
Speaker 1: our context is understand where we live, because hey, this
Speaker 1: is our planet in our solar system. We'd like to
Speaker 1: know is the rest of the of the universe similar
Speaker 1: to what we're finding around us or is it totally different? Yeah,
Speaker 1: because we like the Earth presumably, and it's pretty comfortable.
Speaker 1: And I'm pro Earth. Your pro it's pretty I'm taking
Speaker 1: a controversial opinion here at night, you're pro probably during
Speaker 1: the day your entire Earth. Well, it's not like particle
Speaker 1: physicists threatened to destroy the universe at any moment, so
Speaker 1: on purpose, right, Hey, intentions matter. Okay, I'm sure they
Speaker 1: matter once we're all made out of dissolved particles now.
Speaker 1: But we want to understand the world around us, and
Speaker 1: we want to understand if there are other worlds out there,
Speaker 1: and we'd also just like to know is the thing
Speaker 1: that we've been studying for the entire history of science
Speaker 1: is it normal? Is it typical? Or are we studying
Speaker 1: something which turns out to be really unusual and that
Speaker 1: we can't generalize from to get sort of deeper truths
Speaker 1: about the nature of the universe. Yeah, we like the Earth,
Speaker 1: we like our solar system, but um is the rest
Speaker 1: of the universe like us. And we're an amazing moment
Speaker 1: in human history when we're for the first time really
Speaker 1: getting glimpses for what the rest of the universe looked like.
Speaker 1: You know, for thousands of years, all we could see
Speaker 1: where other stars, but didn't even know if there were
Speaker 1: other planets out there. And then fairly recently in human history,
Speaker 1: thousands of years ago we discovered that there are other
Speaker 1: planets out there. And now super recently, just like twenty
Speaker 1: years ago, we've begun seeing planets around other stars. So
Speaker 1: we can now ask and answer this question people have
Speaker 1: been wondering about four thousands and thousands of years. So
Speaker 1: today on the podcast, we'll be asking the question, is
Speaker 1: our solar system weird or typical? And either way we
Speaker 1: love it. Right, it's our solar system, whatever label you
Speaker 1: put on it, we like it. But we're still curious.
Speaker 1: Is it sort of the oddball solar system it's the
Speaker 1: only one we've been studying for a long time, or
Speaker 1: is it pretty typical? Yeah, this is a really cool question.
Speaker 1: And because you know, I think we grew we grew
Speaker 1: up in this solar system, right, and we don't have
Speaker 1: we have no idea whether it's every other solar system
Speaker 1: looks like this one, or whether we're like, it's really weird,
Speaker 1: odd special gem or disaster, depending on how things work
Speaker 1: out of a solar system. Yeah, and it's all we
Speaker 1: could have studied for the long this time because our
Speaker 1: telescopes couldn't see any further, so we were limited to
Speaker 1: only looking at our cosmic neighborhood, to studying our planet
Speaker 1: and the ones nearby, and so of course we were
Speaker 1: curious what else was out there in the rest of
Speaker 1: the universe. But imagine if you had only lived in
Speaker 1: your hometown your whole life, and you never received any
Speaker 1: news in the outside world, and so you didn't know
Speaker 1: that people eight differently in other countries, and people went
Speaker 1: to the bathroom differently in other countries, and dressed differently
Speaker 1: and spoke differently. You imagined that everything else in the
Speaker 1: world was sort of like your hometown. That's where we
Speaker 1: are right now in science we're wondering if those other
Speaker 1: solar systems are totally different or just the same as ours. Yeah,
Speaker 1: you're saying humanity sort of like a like those mirror
Speaker 1: cats you've seen documentaries. We were just finally sticking our
Speaker 1: head out of the hole in the ground that we've
Speaker 1: been living in and looking around this. Yeah, but we've
Speaker 1: been desperate to do it for for a long time,
Speaker 1: and we've only recently built a technology that's let us
Speaker 1: see other solar systems and start to get an answer
Speaker 1: to this question, because you know, I feel like most
Speaker 1: people just assume that the rest of the universe looks
Speaker 1: like our solar system and our planet, right Like, if
Speaker 1: you look at most science fiction TV shows and movies,
Speaker 1: you know, everywhere they go, it sort of looks suspiciously
Speaker 1: like Earth. Yeah, And I think that's a failure of imagination,
Speaker 1: especially on the part of science fiction. When you fly
Speaker 1: to another planet and you know, hey, it has oxygen
Speaker 1: on it and trees and hills and water that looks
Speaker 1: just like ours, and oh, people on it that look
Speaker 1: just like ours, but their foreheads are slightly wrinkly. I
Speaker 1: think that's a failure of imagination. But it's also sort
Speaker 1: of understandable because it's hard to imagine things totally different
Speaker 1: from anything you've ever seen before. That's why good science
Speaker 1: fiction is rare. Did you just insult All Star Trek
Speaker 1: and Star Wars that was supposed to be sort of
Speaker 1: like a subtweet? Didn't mention it by name, but yeah, yeah.
Speaker 1: And so the question is are those science fiction movies right?
Speaker 1: Are Are there really other earths out there? Are other
Speaker 1: solar systems like ours? Or are we unique in this universe?
Speaker 1: And so, as usual, we were wondering how what people
Speaker 1: thought about this question, whether people thought that we are
Speaker 1: unique or whether things are very different out there in
Speaker 1: the verse. So I walk around campus and I asked
Speaker 1: random students about other random solar systems. I think, for
Speaker 1: a moment, do you think other solar systems look like ours?
Speaker 1: Is our solar system typical or is our solar system
Speaker 1: going to turn out to be really weird? The galactic oddball.
Speaker 1: Here's what people had to say. From what I know,
Speaker 1: it's typical. Um, I mean it depends what you say.
Speaker 1: Typical is considering there billions of stars, but it's not unusual. No,
Speaker 1: I have no idea. It's probably random. If there were
Speaker 1: gases on a planet that were closer to the Sun
Speaker 1: or like star, maybe they would like dissipate faster. I
Speaker 1: think that it's ranks. I think you say I do
Speaker 1: not know. I think it's random, and I think it's
Speaker 1: going to be different Because our solar system it revolves
Speaker 1: around the Sun. I think other systems are gonna be different.
Speaker 1: So what do you think of those answers? Or pretty good?
Speaker 1: I thought I felt like people had a strong opinion
Speaker 1: about this topic. You know, everyone said I think it's X.
Speaker 1: Nobody said I don't know or only one. Only a
Speaker 1: few people said I had no idea, But a lot
Speaker 1: of people that were like, I think I have an
Speaker 1: opinion about this. Yeah, given that nobody really knows the
Speaker 1: answer to this question, I was a little surprised at
Speaker 1: the strength of people's opinions. I mean, I often ask
Speaker 1: people questions and they go, I have no idea quantum what.
Speaker 1: But this time people had an opinion. And maybe that's
Speaker 1: just because people have thought about this. They've wondered what
Speaker 1: other solar systems look like. They've thought about traveling to
Speaker 1: the stars and walking on those planets and wondered if
Speaker 1: they would be like ours. I wonder if you would
Speaker 1: get different answers if you caveat each time you ask
Speaker 1: these questions, If you caveat them with oh, and by
Speaker 1: the way, some of the smartest people in the world
Speaker 1: don't know the answer to this, I would be so
Speaker 1: much less fun. Who would want to answer that? Nobody?
Speaker 1: I love when people speculated. I of seeing them in
Speaker 1: their minds sort of take this question on and sometimes
Speaker 1: for the first time and formulate an answer. And my
Speaker 1: favorite moments are when you can see somebody giving an
Speaker 1: answer that sort of surprises themselves. They think about it,
Speaker 1: they give an answer that, oh, I didn't realize I
Speaker 1: do think that. That's fascinating. Makes me wonder how much
Speaker 1: we actually think about the things we say. Sometimes I'm
Speaker 1: just listening to my own self talking, I'm like, what
Speaker 1: did he just say? So that's the question of the day.
Speaker 1: Is is our solar system unique? Or is it pretty typical?
Speaker 1: And if it's not typical, how different could it be
Speaker 1: out there? And you should count yourself lucky to live
Speaker 1: in a time when we will know the answer to
Speaker 1: this question. Some of the greatest minds in history, Galileo Einstein, Newton,
Speaker 1: even recent people like Richard Feynman, they looked up at
Speaker 1: the stars and they wondered if other solar systems look
Speaker 1: like ours. They all died not knowing the answer. All
Speaker 1: you have to do is listen to this podcast. Yeah,
Speaker 1: so you're welcome. Are you taking it for all the
Speaker 1: scientific discoveries? Thank you? Or hey who personally built the
Speaker 1: Hubble space telescope with his own hands? I signed the
Speaker 1: back of it. I don't know if anyone will ever
Speaker 1: you drew a doodle on it? Are you the official
Speaker 1: cartoonist of the space telescope? Technically you can't prove that
Speaker 1: I didn't sign the back of the Hubble telescope. Oh
Speaker 1: I need another telescope trained on the space telescope to
Speaker 1: see the back of it. I wonder if anybody ever
Speaker 1: does that, But yeah, do you think so? Yeah, it's
Speaker 1: an interesting question. I'm sure a lot of people have
Speaker 1: asked before. So let's break it down for people, Daniel.
Speaker 1: Let's talk about our solar system, and then let's talk
Speaker 1: about what other solar system. Well, we know about other
Speaker 1: solar systems out there, right, and our solar system is
Speaker 1: actually quite fascinating because it has some sort of trends
Speaker 1: in it. And you have to remember that all of
Speaker 1: our knowledge of solar systems and how they're formed, all
Speaker 1: of our theories how solar systems were built, have been
Speaker 1: developed over decades or hundreds of years based on just
Speaker 1: this one example, our solar system. So you know, we
Speaker 1: sort of tuned these theories to describe what we've seen here,
Speaker 1: and now comes the big test to see whether these
Speaker 1: theories can be applied and explain other solar systems, right,
Speaker 1: Because I think maybe people a lot of people don't
Speaker 1: realize that we can't. Just up until very very recently,
Speaker 1: and only just now barely, we haven't really been able
Speaker 1: to like take a telescope pointing at another star and
Speaker 1: see another solar system, right like it's up until very
Speaker 1: very recently, it's been a complete mystery. What other solar
Speaker 1: systems look like? Yeah, the first planet around another star
Speaker 1: was seen just over twenty years ago, so it's a
Speaker 1: blip in human history and even in scientific history. But
Speaker 1: even before we talk about the other solar systems, our
Speaker 1: solar system is interesting, like there are some weird trends
Speaker 1: in it. You know, the first four planets in the
Speaker 1: Solar System are all rocky planets. Planets basically come in
Speaker 1: two flavors, rocky or gassy. It sounds like sounds like
Speaker 1: a bad ice cream shop. Yeah, like like like what
Speaker 1: happens when I like those into olm prison goes to
Speaker 1: an ice cream shop? Yeah, well, the first four planets
Speaker 1: have surfaces on them, right, You've got Mercury, Venus, Earth,
Speaker 1: and Mars. These are basically balls of rock, rock and metal.
Speaker 1: And so we call those rocky planets. And there's no
Speaker 1: gas planets in the inner flour And said, you know
Speaker 1: the four rocky planets, then you have the asteroid belt
Speaker 1: that we dug into in a recent episode. And then
Speaker 1: after the asteroid belt, you've got the gas giants and
Speaker 1: the ice giants. You got Saturned, You've got Jupiter, you've
Speaker 1: got Urinus and Neptune, and those are pretty different from
Speaker 1: the inner planets. Is there a reason we don't have
Speaker 1: liquid planets or like wet planets or like giant balls
Speaker 1: of of a liquid floating around. Well, we can't have
Speaker 1: liquid planets. In the far Solar System. We have basically
Speaker 1: ice giants Uranus and Neptune. A huge fraction of them
Speaker 1: is made of water, but it's frozen. Of course, it's
Speaker 1: too cold out there. There is of course water here
Speaker 1: on Earth. But could you have just like an entire
Speaker 1: drop of water be a planet, that would be pretty amazing.
Speaker 1: I think the pressure from it would probably crystallize the inside.
Speaker 1: So basically become an ice planet with a ocean around it,
Speaker 1: kind of like a Europa or what's what's the wound
Speaker 1: that's like a giant ocean. Yeah, Europa has a huge,
Speaker 1: actually thick crust of ice on top and then a
Speaker 1: layer of water underneath, like an ocean underneath, and then
Speaker 1: we don't know what's inside of that. So that's like
Speaker 1: an eminem sort of. But as the reason we don't
Speaker 1: have liquid planets, just just depending on the elements that
Speaker 1: we have in our Solar system, I don't think you
Speaker 1: can make a blob of of liquid water large enough
Speaker 1: stay liquid because the core of it would just be
Speaker 1: too dense. It would form a solid, like by the
Speaker 1: time it got big enough to be called the planet,
Speaker 1: would it would totally not be liquid. Yeah, the gravitational
Speaker 1: pressure would make the inside of it become a solid
Speaker 1: or or something more dense, so it wouldn't be liquid anymore.
Speaker 1: Do you have this fantasy of swimming through like a
Speaker 1: planet sized pool of water? The universe is biggest swimming pool.
Speaker 1: That would be pretty cool, nothing but a huge drop
Speaker 1: of water the size of the Earth and then a
Speaker 1: single diving boards. You're like, you think you have an
Speaker 1: infinity pool. I have a planet universe universe infinity pool.
Speaker 1: But no, we don't have any liquid planets in our
Speaker 1: solar system. But hey, maybe you know, we'll find planets
Speaker 1: in other solar systems that are liquids and that will
Speaker 1: prove us wrong, and maybe liquid planets are possible, but
Speaker 1: we don't happen to have any in our solar systems.
Speaker 1: That we have four rocky planets the asteroid belt and
Speaker 1: then the gas giants and the ice giants. And you're saying,
Speaker 1: that's kind of funny in that it's sort of like
Speaker 1: a pattern, like it's four rocky asteroid belt gas giants.
Speaker 1: It's not like rocky gas, rocky gas gas gas rocky. Yeah,
Speaker 1: it doesn't seem random. Here's a question from a listener,
Speaker 1: Camille who thought just the same thing. Hello, Danielle and Jey.
Speaker 1: One of the recent episodes I have listened to your show,
Speaker 1: which was all about the asteroid belt, you, daniel mentioned
Speaker 1: that there must be a reason why we have solid
Speaker 1: rocky planets before the asteroid belt and then only gas
Speaker 1: giants afterwards. But you never got to answering this question,
Speaker 1: is there a reason we know? Why? Is it like
Speaker 1: this that we see these kind of pattern other stuff?
Speaker 1: I'm dying to know. That's such a good point. Thank
Speaker 1: you Camille for sending in that question. And every time
Speaker 1: you see a pattern, you think maybe there's a reason
Speaker 1: and you want to untangle that reason. Now, it's very
Speaker 1: dangerous when you're drawing conclusions from one example. If you
Speaker 1: visit somebody's house and they're like, oh, look, their family
Speaker 1: is boy boy, boy, boy boy, girl, girl, girl, girl girl,
Speaker 1: you're going to conclude there's a reason, right that they
Speaker 1: all have younger girls and older boys. But if you're
Speaker 1: only looking at one house, you're gonna be totally wrong.
Speaker 1: That would be kind of impolite to ask Daniel. You're like,
Speaker 1: did you guys try are you're doing something different? You
Speaker 1: know when you um um, you know you'd be desperate
Speaker 1: to know though, you'd be super curious. And also, there's
Speaker 1: lots of families where it's like five boys and then
Speaker 1: a girl, and you know that they were trying for
Speaker 1: a girl and they finally got one and that's when
Speaker 1: they stopped having kids. That's when they're like, we're a
Speaker 1: closing shop. Yeah, so maybe our source systems close shops
Speaker 1: after after Neptune or uranus. We're done trying to make
Speaker 1: a liquid planet. It's not happening. We're sorry, we're trying
Speaker 1: to make a giant swimming pool, but you know, it
Speaker 1: just hasn't happened. That's right. The kid's gotta go swim
Speaker 1: somewhere else. But so we do have some explanations we've
Speaker 1: cooked up, but of course the proviso is, we don't
Speaker 1: know if this works until we try to apply to
Speaker 1: other solar systems. And the basic idea is that you
Speaker 1: don't get gas giants close into the sun because the
Speaker 1: Sun has all this radiation it spewing up the solar wind,
Speaker 1: and that basically blows out all the light elements, the hydrogen,
Speaker 1: the helium, all the stuff you need to make a
Speaker 1: gas giant, all the gas. It blows it away from
Speaker 1: the Sun. So that's why you don't have gas giants
Speaker 1: close up to their star. It's kind of like a cloud.
Speaker 1: It gets too close to the Sun, which is kind
Speaker 1: of wish evaprate. Yeah, and so that's sort of the
Speaker 1: explanation for why you have rocky planets close in. And
Speaker 1: then in the outer planets it's colder, and so instead
Speaker 1: of having liquid water, you have ice, and then that
Speaker 1: ice helps the core of the planet's form. You're like,
Speaker 1: you know, how does the planet form? Anyway, You the
Speaker 1: initial sort of disc of stuff from the that formed
Speaker 1: the whole Solar System, and some of it is spinning
Speaker 1: so it doesn't fall into the star. And then in
Speaker 1: the outer reaches, it's cold enough that you have ice
Speaker 1: and that helps accumulate the gravity very slowly gather the
Speaker 1: stuff together. Because you have ice out there, it can
Speaker 1: sort of add ice to your basic planet core and
Speaker 1: they can get big enough to suck up all the
Speaker 1: gas and the hydrogen in the helium. Because remember hydrogen
Speaker 1: helium is very light, which means it's hard to hold onto.
Speaker 1: You need a huge gravitational mass to attract that. So
Speaker 1: to make a gas giant, you have to form a
Speaker 1: really big core of some metals and some ice in
Speaker 1: order to pull in the rest of the gas. And
Speaker 1: that can only happen in the outer reaches of the
Speaker 1: solar system, where you have ice. And so the reason
Speaker 1: you get gas giants and the outer Solar system is
Speaker 1: because that's where the gas is and because that's where
Speaker 1: the ice is to help pull those light gases together
Speaker 1: into a gas giant. At least that's our theory, and
Speaker 1: that's based on just what we've observed, all right. So
Speaker 1: that explains why our solar system looks to wait us,
Speaker 1: why it's like rocky in the middle and then gassie
Speaker 1: out there in the edges of it. And so that's
Speaker 1: kind of the picture of our solar system. We have
Speaker 1: a yellow sun, some rocky planets, some asteroids, and then
Speaker 1: giant gas balls um swirling around the edges of them, precisely.
Speaker 1: And remember we've been aware of this for decades and
Speaker 1: decades and decades and so we had a long time
Speaker 1: to cook up this model based on just this one
Speaker 1: solar system. It's become very fine tuned and and very
Speaker 1: sort of baroque to explain exactly what we're seeing. And
Speaker 1: so now comes the test. Now we get to apply
Speaker 1: it to other solar systems and see if it also
Speaker 1: explains what we see out there. Yeah, all right, so
Speaker 1: let's get into what other solar systems look like. But
Speaker 1: first let's take a quick break. All right, we're talking
Speaker 1: about how our solar system may or may not be
Speaker 1: different than other solar systems out there, and we know
Speaker 1: that we have a pretty good picture you're saying, of
Speaker 1: our solar system, and it's taken as a while, but
Speaker 1: we can have a good idea of how our solar
Speaker 1: system formed sort of and or white looks like rocky
Speaker 1: planets and then gas giants. And so now the question
Speaker 1: is is this what other solar systems look like like?
Speaker 1: If I went to a nearby star, would I also
Speaker 1: see you know, a similar sun, similar rocky planets in
Speaker 1: the middle, and similar gas giants on the edges? Yea,
Speaker 1: So maybe we should start from the center, right from
Speaker 1: the star. That is, of course the easiest thing to see.
Speaker 1: Our star is something we call a yellow dwarf, and
Speaker 1: it turns out that even our kind of star is unusual.
Speaker 1: Only like ten of the stars in our galaxy are
Speaker 1: yellow dwarfs. The rest are something else we call a
Speaker 1: red dwarf. And these names have to do with not
Speaker 1: just like the size of the Sun, but also how
Speaker 1: old the Sun is. Right, Yeah, they tell you something
Speaker 1: where the Sun is in its life cycle. And there's
Speaker 1: lots of different sort of paths that a sun can
Speaker 1: take depending on how much mass it's started with. And
Speaker 1: we had a whole episode about stellar evolution, and based
Speaker 1: on the size that the Sun started with, they will
Speaker 1: follow a certain path, And so the name of the
Speaker 1: star tells you sort of which path it's on and
Speaker 1: sort of how far along that path is. But most
Speaker 1: of the stars in our galaxy are red dwarfs, which
Speaker 1: mean that they're older than our Sun, and they're colder
Speaker 1: and they're smaller. So if you want as much heat
Speaker 1: that we as we feel on Earth, you'd have to
Speaker 1: be closer to the star than you would be to ours.
Speaker 1: So our sun is kind of is big for compared
Speaker 1: to other stars in the universe, and it's also kind
Speaker 1: of young, right, Like I think we're sort of like
Speaker 1: in the teenage years of our shunt. It's big compared
Speaker 1: to most of the stars in the galaxy. Of course,
Speaker 1: there are other stars out there that totally dwarf it.
Speaker 1: There these huge giants out there that are fantastically bigger
Speaker 1: than our star, but they're unusual. Most of the stars
Speaker 1: in the galaxy are smaller and colder and older than ours.
Speaker 1: And ours is also different in another really fascinating way,
Speaker 1: in that it's by itself. Our star doesn't have a
Speaker 1: companion star. It's not like there's another star orbiting. It
Speaker 1: turns out most stars actually formed together to like a
Speaker 1: pair of stars. Right, So our son is all alone,
Speaker 1: or or as uh Emma Watson would sage, where our
Speaker 1: son is self partnered. Yea, our star is like the
Speaker 1: runaway teenage star. It's all by itself in this lonely universe.
Speaker 1: Of other stars in the universe are totally different than
Speaker 1: our sun. Yeah. Yeah, so right there. If you want
Speaker 1: to extrapolate from our solar system to others, you have
Speaker 1: to be careful because most solar systems have a very
Speaker 1: different kind of star. And that doesn't mean it's going
Speaker 1: to be a completely different solar system where that it's
Speaker 1: impossible to live there. But it means you want the
Speaker 1: same amount of heat. For example, you have to be
Speaker 1: closer up, so the Goldilocks zone for these stars is
Speaker 1: smaller than it is for our star. The sun is colder,
Speaker 1: and then you need to be closer to it to
Speaker 1: be to have any life as we know it here
Speaker 1: on Earth. Yeah, to have liquid water on the surface,
Speaker 1: for example, which is basically what you need to have life,
Speaker 1: we think life as we defined it. Right, Then they
Speaker 1: need to be close enough to the star to get
Speaker 1: enough radiation, and that would be closer to those smaller,
Speaker 1: colder stars than ours. And so ninety percent of stars
Speaker 1: are different out there, which means that if you are
Speaker 1: in another planet, in another solar system, you know, ninety
Speaker 1: percent of the time, it's not going to look like
Speaker 1: it looks like you're it's not going to look like
Speaker 1: a bright yellow you know son. Yeah, it would be
Speaker 1: a little redder and a little colder. It sounds like
Speaker 1: maybe in a lot of or most solar systems out there,
Speaker 1: it would look like in Star Wars where they see
Speaker 1: two sons in the horizon. Yeah, most of them have companions,
Speaker 1: and those aren't necessarily super close together. Sometimes the companions
Speaker 1: can be kind of far apart. But yeah, most stars
Speaker 1: have another star pretty close by and they're orbiting each other.
Speaker 1: But ours is by itself, and that's that's more unused
Speaker 1: dual than typical. So already our star is unusual in
Speaker 1: two ways, and that it's by itself, and that it's
Speaker 1: a yellow dwarf. So already our solar system is is
Speaker 1: pretty odd compared to the universe. Well, now, let's let's
Speaker 1: talk about the Earth. Is a planet like Planet Earth,
Speaker 1: the weird to have in a solar system out there?
Speaker 1: Or is it pretty common? It turns out that the
Speaker 1: most common planet to have in one of these solar
Speaker 1: systems is not the Earth. It's something called a super Earth.
Speaker 1: It's a rocky planet that's like ten or fifteen times
Speaker 1: bigger than the Earth. And they categorize these planets in
Speaker 1: other solar systems by giving them names relative to our planets,
Speaker 1: like define the various categories. So like you have an
Speaker 1: Earth planet or a super Earth up to you know,
Speaker 1: ten or fifteen times the Earth. Anything bigger than that,
Speaker 1: they call it like a mini Neptune. So that's the
Speaker 1: names of these categories. And most solar systems have a
Speaker 1: super Earth. It's the most common planet out there. Now,
Speaker 1: you'll notice we don't have a super Earth. There's no
Speaker 1: planet in our solar system that's a rocky planet that
Speaker 1: it's like ten times the size of Earth. Is the
Speaker 1: Earth the biggest rocky planet in our solar system? Yeah,
Speaker 1: the Earth and Venus Venus is almost as big as
Speaker 1: the Earth. Mars and Mercury are much smaller. And so
Speaker 1: the Earth is the biggest rocky planet in our solar system.
Speaker 1: But most solar systems you would find one that's like
Speaker 1: ten or fifteen times bigger, bigger in terms of like
Speaker 1: the radius or like the you know, there's the weight
Speaker 1: of it. Yeah, ten times the mass, which doesn't quite
Speaker 1: correspond to ten times the radius because you know, there's
Speaker 1: some nonlinear effects there. But it's a lot more stuff, right,
Speaker 1: So ten times as many rocks came together to form
Speaker 1: a planet, and so we don't really know what that means.
Speaker 1: This is something we've only recently figured out. We don't
Speaker 1: know if that means that the distribution of rocks in
Speaker 1: our solar system was different when it formed, or maybe
Speaker 1: there was a super big planet, but it got broken up.
Speaker 1: We don't really know. Is this just random that we
Speaker 1: not unlucky, or is there some important reason for why
Speaker 1: our solar system looks different in this important way. We
Speaker 1: just don't know. So that if there are scientists on
Speaker 1: those other earths, they would probably say that we live
Speaker 1: in many Earth. Yeah, they would say, hey, look at
Speaker 1: this weird solar system we found. It has only many
Speaker 1: rocky planets. How cute. Look at those tiny little planets,
Speaker 1: Baby Earth's look at those tiny little people with tiny heads.
Speaker 1: Not only is our solar system weird in that that
Speaker 1: our Sun is weird, but also our Earth is really weird.
Speaker 1: So most earths out there are much much bigger. Yeah,
Speaker 1: and some solar systems we found out there just have
Speaker 1: more planets sort of tucked in close to the Sun.
Speaker 1: Like we found this one solar system it's called the
Speaker 1: Trappist System. It has seven planets within six million miles
Speaker 1: of their sun. Remember, the Earth is like ninety million
Speaker 1: miles from our Sun, So they have seven planets tucked
Speaker 1: in like around the distance that Mercury is. Wow, just
Speaker 1: spinning around like like crazy. Yeah, I'm just spinning around
Speaker 1: like crazy. So most of the solar systems we've seen
Speaker 1: have more planets close to the Sun than ours. Now,
Speaker 1: this is hard to know. It might be that there's
Speaker 1: a bias here because it's harder to see planets that
Speaker 1: are far from the Sun because the way we observe them. Remember,
Speaker 1: as we see planets like passing in front of the Sun,
Speaker 1: and if a planet is going around the Sun every
Speaker 1: hundred years, it just doesn't pass in front of the
Speaker 1: Sun is often, so it's easier for us to see
Speaker 1: planets that are close to their Sun. So it might
Speaker 1: be that there's a bias that we're finding the weird
Speaker 1: ones first. But they don't think so. They think they've
Speaker 1: accounted for that effect and they think it's still real
Speaker 1: that the average solar system out there has more planets
Speaker 1: close to the Sun than ours. Interesting, so the average
Speaker 1: solar system out there is busier, yeah, especially close in
Speaker 1: like more I guess, more concentrated. It's like a traffic
Speaker 1: jam every day, all day for the for for eternity literally. Yeah.
Speaker 1: But on the other hand, it means it's not as
Speaker 1: hard to get from planet to planet, like your neighboring
Speaker 1: planet is more like a neighbor, you know, you could
Speaker 1: jump from planet to planet. Wouldn't take hundreds of days
Speaker 1: like it would take for us to get from Earth
Speaker 1: to Mars. You could get to the next planet it
Speaker 1: in you know, just a few days. Right, and maybe
Speaker 1: even more dangerous to write, because all those planets that
Speaker 1: close together, they some of them could crash into each other, right, yeah,
Speaker 1: and they can also affect each other's orbits. Right, planets
Speaker 1: are big, and remember these planets are not tiny things,
Speaker 1: and so they can tweak each other's orbits. Theres lots
Speaker 1: more weird gravitational interactions, and we've also seen that we've
Speaker 1: seen that a lot of these solar systems have weird orbits.
Speaker 1: Like in our Solar system, things are very neatly laid out,
Speaker 1: like the planets are sort of equally spaced, and everything
Speaker 1: is separated, and everything is mostly flat in a single
Speaker 1: plane and pretty circular, though not completely. But other Solar
Speaker 1: systems the orbits were seeing are really eccentric. They are
Speaker 1: much less circular, some of them, Like there's one for example,
Speaker 1: I looked up and it goes from being just a
Speaker 1: few million miles of its from its star on one
Speaker 1: side to two hundred million miles on the other, so
Speaker 1: like it's super close and then whizzes out really far away, right,
Speaker 1: Because orbits can be not just circular or oval shaped,
Speaker 1: they can also be kind of off center from the Sun,
Speaker 1: kind of like comets have these weird elliptical orbits that
Speaker 1: are like go really far out and then come back
Speaker 1: in really close, right. Yeah, And commets don't have to
Speaker 1: be sort of on the plane of the planets. And
Speaker 1: what we're seeing is that other solar systems don't always
Speaker 1: have the same orderly plane, that the planets are all
Speaker 1: all on different planes, and we don't know what that means.
Speaker 1: We don't know, like is that typical and our solar
Speaker 1: system is just kind of weirdly randomly well ordered, or
Speaker 1: maybe something happened in those solar systems there were some
Speaker 1: collisions because everything was so crowded in and they got
Speaker 1: tugged and thrown off into weird orbits. We just don't know.
Speaker 1: I feel like we're getting more and more into the
Speaker 1: idea that maybe our solar system is really weird. It's
Speaker 1: like we have a weird Sun and a weird Earth,
Speaker 1: and a weird, weird arrangement of planets and a weird orbit.
Speaker 1: It's like it's just right. Yeah, And we're like that
Speaker 1: kid that went to school for the first time and
Speaker 1: discovered that his family is really, really weird. Nobody else
Speaker 1: eats peanut butter pickle sandwiches for lunch and dresses in
Speaker 1: that weird way or whatever. And the other thing that
Speaker 1: I found really fascinating is that, you know, in our
Speaker 1: Solar system we have all the gas giants on the outside.
Speaker 1: We thought we had an explanation for that, that the
Speaker 1: gas was blown out by the solar wind. But in
Speaker 1: other solar systems we find these planets we call hot jupiters,
Speaker 1: big gas giants that are close to their stars, close
Speaker 1: enough to be hot. Right, they're trending, that's right, exactly,
Speaker 1: they're viral jupiters. No. But for example, there's a system
Speaker 1: um I won't pronounce the name because it's just letters
Speaker 1: and numbers, but there's a Jupiter sized planet that's so
Speaker 1: close to its star at orbits every two days. What
Speaker 1: it's whipping around the Sun every two days. Yeah, but
Speaker 1: it's the size of Jupiter, and so people wonder, like,
Speaker 1: how did this planet form? There's not enough gas in
Speaker 1: our understanding in the center of the Solar system, to
Speaker 1: form a gas giant. Right, the gas either fell into
Speaker 1: the Sun to form the star or got blown out
Speaker 1: by that star into the outer reaches of those solar systems. So,
Speaker 1: how do you make a hot jupiter if it's just
Speaker 1: a cloud of as when in it just kind of
Speaker 1: you know, whipping around that fast wheed it just kind
Speaker 1: of break apart or dissolver smear. But no, it's somehow
Speaker 1: it's spinning around every two days. Yeah, and maybe it
Speaker 1: has a really strong magnetic field which helps protected from
Speaker 1: the solar radiation and the solar wind from blowing it apart.
Speaker 1: We don't know. And one idea is that maybe it
Speaker 1: did form on the outer reaches of that solar system,
Speaker 1: but then sort of moved up, like bumped the other
Speaker 1: planets out of the way to get closer to the Sun.
Speaker 1: This could happen, right, Planets can change orders. Wow, So
Speaker 1: you're basically saying that like our nice orderly solar system
Speaker 1: with the rocky planets first and our gas giants out there,
Speaker 1: is maybe not even typical either, Like that sort of arrangement.
Speaker 1: You can have gas giants close to the Sun and
Speaker 1: you could probably have rocky planets out there. Yeah, we've
Speaker 1: seen hot jupiters. We've seen solar systems with gas giants
Speaker 1: close to the Sun, and in some of these it
Speaker 1: does look like maybe they did migrate in from the outside,
Speaker 1: because we don't see like a lot of other inner
Speaker 1: planets nearby. What would happen if Jupiter, for example, moved
Speaker 1: in and tried to take over Venus orbit, well, Earth
Speaker 1: and Mars and Venus and Mercury, we probably get tossed
Speaker 1: out of the Solar system by Jupiter's gravity, And that's
Speaker 1: what we see in these solar systems with a hot Jupiter.
Speaker 1: We don't see a lot of other inner planets, so
Speaker 1: we think maybe, you know, the big gas giant bully
Speaker 1: came in and cleared out the playground, all right. So yeah,
Speaker 1: there's a lot of ways in which our Solar system
Speaker 1: is weird, right in terms of the Sun, the Earth,
Speaker 1: and the gas giants. And so now let's talk about
Speaker 1: UM some of the ideas that scientists have about whether
Speaker 1: solar systems all formed the same way, or whether are
Speaker 1: somehow made it into this special configuration for a special reason. First,
Speaker 1: let's take a quick break a right, So let's talk
Speaker 1: about um. What idea scientists have to explain all these
Speaker 1: weird types of solar systems, like why is ours different?
Speaker 1: How do other system solar systems form? What's the sort
Speaker 1: of prevailing theory about how solar systems are made. Yeah,
Speaker 1: So the theory we had for a long time before
Speaker 1: we saw all these other solar systems, we call that
Speaker 1: the core accretion theory, and it basically says, you start
Speaker 1: from a big rotating blob of gas and dust and
Speaker 1: some ice, and the star forms and the rest of
Speaker 1: it you get you accrete the cores of these planets.
Speaker 1: That just means that like the biggest rock that happens
Speaker 1: to be out there gathers up other rocks around it,
Speaker 1: and they form and they gather more stuff until you
Speaker 1: get stuff big enough stuff to make a planet. And
Speaker 1: that's how we explain how you get Jupiter. For example.
Speaker 1: You're gathering together a bunch of rocks and ice and
Speaker 1: that sucks up all the gas. Also, stuff was just
Speaker 1: floating around and then they just because of gravity, just
Speaker 1: formed into planets like condensation almost. And one the thing
Speaker 1: that people have always wondered about that theory that they
Speaker 1: didn't really like is that it takes a long time.
Speaker 1: I mean gravity is really weak, and we're talking about
Speaker 1: when you start, you're tugging on really small bits, you know,
Speaker 1: bits of gas and bits of dust and tiny little pebbles.
Speaker 1: So it's gonna take a long time to make Jupiter
Speaker 1: out of bits of sand, right, And they worry that
Speaker 1: it takes so long to form the core on this,
Speaker 1: you know, the dust and the ice, that by then
Speaker 1: all the gas will just have floated away or been
Speaker 1: blown away by the solar wind. So there's always been
Speaker 1: this bit of tension like how do you get these
Speaker 1: planets to form soon enough that they can gather any
Speaker 1: of that less leftover gas. So that's the old idea
Speaker 1: and the sort of the concerns people have with it.
Speaker 1: And now that we've seen these other solar systems, they're wondering, well,
Speaker 1: maybe we need new ideas. And so there is a
Speaker 1: new idea on the block. Oh I see, because this
Speaker 1: idea that solar systems kind of form slowly might explain
Speaker 1: may not even explain ours. But looking at other solar systems,
Speaker 1: we're like, oh, whoa, whoa, we don't really have a
Speaker 1: good idea about how solar systems form, because whatever we
Speaker 1: come up with has to work for all of these
Speaker 1: other solar systems. Yeah, and you know you need inspiration
Speaker 1: in science, and this old idea was inspired by this
Speaker 1: one example. Now that we've seen these other examples and
Speaker 1: sort of stretches us in the right way to come
Speaker 1: up with new ideas for how you could explain these examples.
Speaker 1: And so one of these new ideas is called the
Speaker 1: disc instability model. That idea is basically that when the
Speaker 1: Solar system formed, you have this disc, but it wasn't
Speaker 1: like a nice, calm, smooth disc that was slowly formed
Speaker 1: from the rotating blob, but that there was still a
Speaker 1: lot of sort of stuff going on. There's a lot
Speaker 1: of action there, and that these instabilities is action inside
Speaker 1: the disc might be a way to get these planets
Speaker 1: to form sooner and also for them to form closer
Speaker 1: to their stars. But what do you mean disc instability?
Speaker 1: Like there's something extra special going on that makes Jupiters
Speaker 1: and weird planets like that. Yeah. If the model you
Speaker 1: have in your head is sort of like a giant,
Speaker 1: stately cloud which is slowly rotating and then gradually gathering
Speaker 1: together into a flat disc, that's the core creation model.
Speaker 1: It assumes that everything is sort of very smoothly flowing.
Speaker 1: But if instead it's a bit more turbulent, if this
Speaker 1: is a little bit more chaos in there, you know,
Speaker 1: it's more like a storm and it's being squeezed by
Speaker 1: gravity a little bit, but there's still sort of stuff
Speaker 1: going on inside of it. That's stuff that energy can
Speaker 1: be used to sort of collide stuff together and make
Speaker 1: and from those instabilities form gravitational course that can that
Speaker 1: can gather stuff more rapidly. Oh, and that would explain
Speaker 1: our solar systems or sort of all solar systems. Well,
Speaker 1: it's not a very popular model yet and it's very fresh,
Speaker 1: but it might explain how our solar system got gas
Speaker 1: giants because it unless you form planets more rapidly. And
Speaker 1: it also might explain how you were able to form
Speaker 1: gas giants close to the star, because you could form
Speaker 1: them quickly enough that you could form them before all
Speaker 1: the gas was blown away by the Sun. But it's
Speaker 1: still it's a very fresh model and it hasn't gained
Speaker 1: wide acceptance yet, so it could be like maybe it's
Speaker 1: just like the way solar systems form, is it just
Speaker 1: this very chaotic process and sometimes you get solar systems
Speaker 1: like ours and sometimes you get totally different solar systems. Yeah, precisely.
Speaker 1: And the other idea is about planetary migration. People think
Speaker 1: that maybe it's not unusual for planets to sort of
Speaker 1: tug each other out of orbit and switch spots, you know,
Speaker 1: to take each other's seats. And there's even the idea
Speaker 1: that it could have happened in our Solar system. People
Speaker 1: think that maybe. Yeah, people think that maybe Saturday and
Speaker 1: Jupiter used to have an opposite order, and there was
Speaker 1: another planet out there, a big ice giant, and the
Speaker 1: three of them are sort of in this chaotic bumping
Speaker 1: of each other, and they switched Saturn and Jupiter switched
Speaker 1: and tossed the other planet sort of out to the
Speaker 1: far reaches of the Solar System. And we just did
Speaker 1: a whole episode about planet nine that could explain like
Speaker 1: why planet nine is so far out there. So, yeah,
Speaker 1: you're saying that even if you you form a solar system,
Speaker 1: it can still change. You can still you can still
Speaker 1: switch it around and change the structure of it, even
Speaker 1: when it's sort of stable and floating along. Yeah, and
Speaker 1: that means something interesting for our Solar system. It could
Speaker 1: be in the future if you went away on a
Speaker 1: spaceship for a billion years and came back, that you
Speaker 1: could come back and find the Solar system looking quite different. Right,
Speaker 1: Jupiter might have moved in on Mercury's territory and become
Speaker 1: hot and tossed out all the other planets. We just
Speaker 1: don't know. We don't know if this configuration is stable
Speaker 1: on billions year time scales. That would be pretty cool
Speaker 1: if you left for a few million years and then
Speaker 1: came back and you're like, what happened to my house? Remodeled?
Speaker 1: Just like everybody who goes away to college and comes
Speaker 1: back after Thanksgiving and like, hey, everything looks different. You
Speaker 1: turned my plan into a workout room. All right, Well,
Speaker 1: it sounds like our solar system is not. It is weird,
Speaker 1: that's the answer to the Today's question. It is kind
Speaker 1: of weird in that you know, our son is single
Speaker 1: and hot and young, and we apparently live in a
Speaker 1: mini Earth, are not super Earth. And it's also weird
Speaker 1: that we have all all of our gas giants out
Speaker 1: there floating out there far away from the Sun. And
Speaker 1: so it is because it sounds like it is sort
Speaker 1: of a special case or solar system, like if we
Speaker 1: go to other solar systems. We should be prepared to
Speaker 1: see things that are very different. Yeah, and I'm so
Speaker 1: glad that that's the answer. It would be so boring
Speaker 1: if we discovered every solar system looked like ours, and
Speaker 1: that the idea we have for how the solar system
Speaker 1: formed was pretty much being on. It's exactly what you
Speaker 1: hope for in science, that once you open up new
Speaker 1: eyeballs or build bigger eyeballs, that you see surprises, that
Speaker 1: you learn things, the things that shake up your ideas
Speaker 1: for how our home and our solar system have been made.
Speaker 1: And maybe it gives us a bit of a special
Speaker 1: appreciation for this particular little cute many Earth we find
Speaker 1: ourselves on. Yeah, maybe you'll go to another solar system
Speaker 1: and everybody will have two pH d s. Should be
Speaker 1: like what the Bruce Banner solar system? All right, Well,
Speaker 1: we hope you the next time you think about your
Speaker 1: planet or the solar system we're in, you sort of
Speaker 1: think about how special it is and how weird it is,
Speaker 1: and how unique it is out there in the universe.
Speaker 1: And in five years or twenty years or fifty years,
Speaker 1: we could find even more weird, surprising solar systems out
Speaker 1: there that challenge our very concept of what the universe
Speaker 1: looks like. Yeah, so stay tuned and keep funding science.
Speaker 1: Thanks for tuning in, See you next time. Before you
Speaker 1: still have a question after listening to all these explanations,
Speaker 1: please drop us the line. We'd love to hear from you.
Speaker 1: You can find us on Facebook, Twitter, and Instagram at
Speaker 1: Daniel and Jorge That's one word, or email us at
Speaker 1: Feedback at Daniel and Jorge dot com. Thanks for listening
Speaker 1: and remember that Daniel and Jorge Explain the Universe is
Speaker 1: a production of I Heart Radio. For more podcast from
Speaker 1: my Heart Radio, visit the i Heart Radio app, Apple Podcasts,
Speaker 1: or wherever you listen to your favorite shows.