Speaker 1: Hey, Jorgey, what's your favorite Solar System object? I'm gonna
Speaker 1: have to go with the Earth because you know, it's
Speaker 1: the only one I've been to, so you're not a
Speaker 1: gas giant kind of person. Depends how many tacas I
Speaker 1: had for munch. But what if I do? You do
Speaker 1: you have a favorite? I'm a big fan of the
Speaker 1: Sun and everything it does for us here on Earth,
Speaker 1: But my favorite thing in the Solar System is actually comets.
Speaker 1: Comments what have commets done for us? Well, they're like
Speaker 1: cosmic snowballs, and actually most of Earth's water turns out
Speaker 1: to be melted comets. I guess water is pretty useful
Speaker 1: to have. But wait, are you saying the Solar System
Speaker 1: is having a snowball fight. Yeah, it's more like deadly
Speaker 1: planetary dodgeball. Hi am more Hammon, cartoonists and the creator
Speaker 1: of PhD Comics. Hi. I'm Daniel. I'm a particle physicist,
Speaker 1: but I have strong opinions about various Solar System objects.
Speaker 1: And Welcome to our podcast, Daniel and Jorge Explain the Universe,
Speaker 1: a production of I Heart Radio in which we talk
Speaker 1: about everything that we know about the universe and everything
Speaker 1: that we don't know about the universe, everything that makes
Speaker 1: us wonder and everything that makes us go huh. And
Speaker 1: we explain all of it to you because we think
Speaker 1: that your curiosity is as valuable as the curiosity of
Speaker 1: scientists working on the front line. Yeah, and there's a
Speaker 1: lot to be curious about. The universe is full of
Speaker 1: amazing and incredible things and a lot of mysteries, a
Speaker 1: lot of things that we don't know where they come from,
Speaker 1: or what makes them what they are, or why they're there. Yeah,
Speaker 1: And a lot of great scientific discoveries begin with pretty
Speaker 1: simple questions, you know, like why is that thing there?
Speaker 1: Or why are those common? It's flying through space and
Speaker 1: where do they come from? Is one of them going
Speaker 1: to hit us and wipe us out? Great scientific discoveries
Speaker 1: come from really simple questions that everybody wants to know
Speaker 1: the answers to. Yeah, because we have questions even about
Speaker 1: our own backyard. Our solar system is still full of
Speaker 1: things that we don't quite fully understand. People like to
Speaker 1: talk about things in the distant universe that are still
Speaker 1: a mystery. We don't know how big it is or
Speaker 1: what's going on out there in the depths of the universe.
Speaker 1: But you're absolutely right, there's still a lot to be
Speaker 1: discovered right in our own neighborhood, big questions about what's
Speaker 1: going on in our own household that we still don't
Speaker 1: know the answers to. So they know you have a
Speaker 1: strong opinions about things in our Solar System? Are they
Speaker 1: all positive or are some of them negative? Is there
Speaker 1: someone you don't like here in system? Now? They're all positive.
Speaker 1: I love everything in the Solar System, from ice giants
Speaker 1: to planetism als, to space centaurs, to deadly comments to
Speaker 1: enormous burning balls of gas. I just think it's all
Speaker 1: pretty awesome. I can't imagine having a negative opinion about anything.
Speaker 1: Do you include in that all the people on Earth too? Yes?
Speaker 1: I love everybody. No, it's incredible when you look out
Speaker 1: there in space that you see so many beautiful, amazing things.
Speaker 1: Like when was the last time you looked at something
Speaker 1: out in space and you thought that's just kind of
Speaker 1: you know, it's all just sort of like incredible and beautiful.
Speaker 1: You know, whoever the universe's visual artist is, they're doing
Speaker 1: a good job. Although you know, we live in California,
Speaker 1: so right now, when I look up at the sky,
Speaker 1: it's mostly smoke. Well, then take a journey through the
Speaker 1: Solar System with your mind's eye. Yeah, there are a
Speaker 1: lot of big questions about the Solar System and how
Speaker 1: we got to where we are. And one of those
Speaker 1: big questions about our Solar system is where do comets
Speaker 1: come from? We don't know a comet factory here in
Speaker 1: our Solar system, do we We don't know of a
Speaker 1: comet factory. It could be that there are aliens out
Speaker 1: there in the outskirts of the Solar System packing up
Speaker 1: ice balls and shooting them at Earth. Or it could
Speaker 1: be that they come from something else, something deep out
Speaker 1: there in the Solar System. That's basically a huge reservoir
Speaker 1: of comets ready to fall in, screaming towards the Sun
Speaker 1: and boiling. And this is a big question because some
Speaker 1: people think that most of the water on Earth came
Speaker 1: from comets. That's right, Commets are mostly ice. You know,
Speaker 1: something a lot of people don't understand about the universe
Speaker 1: is that water is not rare. We talk about liquid
Speaker 1: water being something we're looking for in the surface of
Speaker 1: planets to see if there's alien life, but water as
Speaker 1: a chemical, there's tons of it out there. There's like
Speaker 1: planet size blobs of it. So most comets are icy
Speaker 1: planetism alls. They're just big balls of ice, and some
Speaker 1: of them fell towards the Earth in the early days
Speaker 1: and landed and melted and formed our oceans. Thank goodness,
Speaker 1: because that's where life came from. Right, we had them
Speaker 1: in for those snowballs, and we wouldn't be here, that's right.
Speaker 1: So next time you put your lips to a glass
Speaker 1: of melted comet, remember you're drinking. The outer Solar System
Speaker 1: are melted common Right, next time you go somewhere in
Speaker 1: order a drink, order sparkling melted comment and see what
Speaker 1: they do. Yeah, So a big question is where they
Speaker 1: come from, and so scientists have a potential answer to
Speaker 1: that question, right, Daniel, that's right. They don't know for sure.
Speaker 1: Nobody's ever actually seen it, but we've given it a name.
Speaker 1: So today on the podcast, we will be asking the question,
Speaker 1: what is now Daniel? Is that pronounced or or or
Speaker 1: because it's spelled O r T. It's a great question,
Speaker 1: and it's a Dutch name. It comes from a Dutch
Speaker 1: astronomer who first thought it up. And so I reached
Speaker 1: out to my Dutch speaking brother to ask him for
Speaker 1: his preferred pronunciation because I didn't know is it ort
Speaker 1: ort ort or something like weird Dutch vowel that we
Speaker 1: don't even have in English that can never be replicated?
Speaker 1: Keep going, keep going? Well, you know there are vowels
Speaker 1: in Danish that you know you can only replicate. You
Speaker 1: get like punched in the gut in exactly the right way,
Speaker 1: like you Dango speakers out there know what I'm talking about.
Speaker 1: But it turns out that or its spelled o o
Speaker 1: rt is pronounced like port. All right, So it's a
Speaker 1: cloud apparently of some sort, and it's I'm guessing it's
Speaker 1: out in space, and so the big question is how
Speaker 1: many people out there know what it is and what
Speaker 1: its significance is. That's right? So I pulled our listeners
Speaker 1: who have volunteered to answer random questions over the Internet
Speaker 1: from a businessist they've never met. If you'd like to
Speaker 1: participate in such absurd commentary on our physical universe, please
Speaker 1: write to me two questions at Daniel and Jorge dot com.
Speaker 1: And thanks to everybody who shared your speculations. Think about
Speaker 1: it for a second. If someone asked you what the
Speaker 1: orc cloud is, what would you answer. Here's what people
Speaker 1: had to say, The or Cloud is one of the
Speaker 1: outermost regions of the Solar System, comprised of we think
Speaker 1: a bunch of remnants of the early Solar system. The
Speaker 1: Orc Cloud is a group of like dust and rocks
Speaker 1: and asteroids and just material that's way outside are encircles
Speaker 1: our whole Solar system. I think in a giant sphere,
Speaker 1: or maybe just a circle. The art Cloud is a
Speaker 1: vast array of comets and other such I see debris
Speaker 1: forwarding around the Sun, very far away from the rest
Speaker 1: of the planetary systems. I know that the Sun, it's
Speaker 1: the middle of it, and it passes our solar systems,
Speaker 1: so passes Pluto. Is it the big cloud of dust
Speaker 1: that I'm spewing out the top and the bottom of
Speaker 1: the Milky Way? I have anything to do with equippable?
Speaker 1: Probably close to the Solar system. I think the art
Speaker 1: Cloud is like an area outside the Solar system where
Speaker 1: there are some icy objects. I'm not sure what, probably
Speaker 1: comets and things like that. All right, some pretty good answers.
Speaker 1: Most people seem to know it's something related to our
Speaker 1: Solar system, and that it's a cloud, and that maybe
Speaker 1: there's ice involved. Yeah, exactly, it's something big and fuzzy
Speaker 1: and out there and cool. Cool. And my favorite thing
Speaker 1: about the Orc cloud is at the acronym the O
Speaker 1: C is the same as the place I live, Orange County,
Speaker 1: except it's a little warmer, I think, a little warmer,
Speaker 1: but it's also still very very cool. That's the first
Speaker 1: time I've heard you give a compliment to the Orange
Speaker 1: County there. I love Orange County. Best place in the
Speaker 1: world to live. Seriously, what could you complain about? But
Speaker 1: that's not the topic of today's podcast. We're talking about
Speaker 1: the cosmic o C, the solar systems O C, not
Speaker 1: calibornias o C and to uh, it's apparently something out
Speaker 1: in space and so Daniel, let's step people through it.
Speaker 1: So what is the orc Cloud? The orc cloud is
Speaker 1: super awesome. It is a theoretical cloud of icy planetisml's
Speaker 1: or many planets planetismal. Did you just make that up
Speaker 1: or is that the actual science terms? Oh? Man, I
Speaker 1: wish I could have made that word of there's something
Speaker 1: wonderful about just saying that word planetismal. Right, but no,
Speaker 1: planetismal is a mini planet and it's smaller than a
Speaker 1: dwarf planet. Right, You've got planet dwarf planet, and then
Speaker 1: planet Tismal. They couldn't just say mini planet. Well it's
Speaker 1: sort of like Planetino, you know, that's what you do
Speaker 1: with English planet Tito. And so it's a bunch of
Speaker 1: these and they're really really far out there. Like if
Speaker 1: you have the Solar system, you know, the Earth is
Speaker 1: at one AU call an astronomical unit, and you go
Speaker 1: really far out you get out to like Neptune and Pluto.
Speaker 1: You have to go much, much, much further before you
Speaker 1: get to the arch cloud. Is it even considered our
Speaker 1: Solar system or is it technically outside of our Solar system? Yeah,
Speaker 1: it's a great question. Most people consider the end of
Speaker 1: our Solar system to be just under about a hundred
Speaker 1: a U, where the sun radiation becomes dominated by the
Speaker 1: galactic radiation. How you think of space is sort of
Speaker 1: like empty, right, but actually it's filled with streaming particles.
Speaker 1: The Sun is pumping out particles, not just photons, but
Speaker 1: protons and electrons and all sorts of crazy stuff, and
Speaker 1: it dominates the region around it with all of its
Speaker 1: pulsating radiation. But the rest of the galaxy also has
Speaker 1: a wind that's coming from all the other stars in
Speaker 1: the central black hole. And all that crazy stuff. So
Speaker 1: we define the edge of the Solar system it's called
Speaker 1: the helio pause, as the place where the Sun's radiation
Speaker 1: stops dominating the local environment and you're taken over by
Speaker 1: the galactic wind. And that's like a hundred or so A.
Speaker 1: It's like when our Sun becomes just another star kind
Speaker 1: of yeah, exactly, and the wind from the rest of
Speaker 1: the galaxy takes over the Sun's wind. And here again
Speaker 1: wind we don't mean air, We just mean the particles
Speaker 1: that it's shooting out. But the rac cloud starts like
Speaker 1: ten times further out than that, like at a thousand
Speaker 1: a U. Now it's just still sort of like bound
Speaker 1: by the gravity of the Sun, or is it pretty
Speaker 1: much like an independent thing from our solar system. It's
Speaker 1: definitely bound by the gravity of the Sun. So if
Speaker 1: you define the edge of the Solar system by the radiation,
Speaker 1: it's like a hundred a U. But stuff that's further
Speaker 1: out is still gravitationally bound to the Sun, but it's
Speaker 1: a little bit loose. It's like a little fuzzy. It's
Speaker 1: so far out from the Sun that it's not that
Speaker 1: hard to knock something off and have an escape into
Speaker 1: interstellar space, so it's not orbiting around us. It's sort
Speaker 1: of like we're tugging them and it's tugging us. It's
Speaker 1: definitely orbiting around us. Think of it like a huge
Speaker 1: shell surrounding the Solar System. The other fascinating thing about
Speaker 1: it is that it's not a disk, right, Most of
Speaker 1: the stuff in the Solar System is a big disc,
Speaker 1: it's flat. But the Orc Cloud, we think, is a sphere.
Speaker 1: It's like totally surrounding the Solar System, and it goes
Speaker 1: out really really far out to like a light year
Speaker 1: maybe two light years of just this like cloud of
Speaker 1: little frozen objects, and there could be like trillions of
Speaker 1: the planetismal, trillions of planetism many planets I'm sorry, yeah,
Speaker 1: planet titos. And it's sort of like calculus. You know,
Speaker 1: in calculus, you sum over infinitismals and you get like
Speaker 1: an actual quantity. In the same way, if you sum
Speaker 1: over all the planetism als in the ord cloud, you
Speaker 1: get a combined mass of stuff that's like five times
Speaker 1: the mass of the Earth, but then again spread out
Speaker 1: into like trillions of objects. It spread out not just
Speaker 1: like wide but tall to like it's it's pretty diffuse
Speaker 1: it's very diffuse, Like it's not like flying the millennium
Speaker 1: falcon through an asteroid field. You gonna like dodge and
Speaker 1: weave right, it's like, could we see something, like is
Speaker 1: there one there? It's so far out there, it's mostly empty.
Speaker 1: But again, they are gravitationally bound to the Sun and
Speaker 1: they are orbiting the Sun. That's why they are in
Speaker 1: a cloud around the Sun. It's not like just the
Speaker 1: whole interstellar medium is filled with these objects. It's a
Speaker 1: cloud of them. We think. Again, we think we don't
Speaker 1: know for sure. We haven't seen them because they're so
Speaker 1: small and far away, but we think that they're there
Speaker 1: in this big blob around the size see, and it's
Speaker 1: made up of like giant literally like giant balls of ice,
Speaker 1: basically snowballs. How big, Well, each one could be like
Speaker 1: bigger than a kilometer in size, So we think that
Speaker 1: they're like trillions of them that are more than a
Speaker 1: kilometer and maybe only billions that are twenty kilometers are larger.
Speaker 1: But if you wanted to have a cosmic snowball fight,
Speaker 1: that's like where your arsenal is, that's the best place
Speaker 1: to go for the stockpile. Wow, So that's like, let
Speaker 1: me see, that's like a snowball about the size of
Speaker 1: Los Angeles right kilometers. Yeah, there are billions of frozen
Speaker 1: Los Angeles is out there in the o C because
Speaker 1: they are pretty cool, icy cool. They are pretty cool,
Speaker 1: and if they weren't gravitationally bound to the Sun, they
Speaker 1: would just sort of float away into space. But they
Speaker 1: are bound there. They're floating around, but you know, it's
Speaker 1: sort of loose, and so sometimes the thought is sometimes
Speaker 1: something perturbs them and then they can get knocked out
Speaker 1: of their very loose orbit and plummet towards the inner
Speaker 1: Solar System because they're in a stable orbit. Is that
Speaker 1: the idea is that they're like happily going around our
Speaker 1: Sun in this huge, wide orbit, but sometimes they can
Speaker 1: fall in. Yeah, we think it's probably stable and if
Speaker 1: nothing perturbed them, they would just happily hang out there
Speaker 1: really far away, staying frozen. But you know, we are
Speaker 1: in a little neighborhood, and since it's sort of loosely
Speaker 1: held by the Sun, it's not that hard to perturb them.
Speaker 1: And you can have things like galactic tides that squeeze
Speaker 1: the orac cloud and knock some of them out of orbit.
Speaker 1: You mean from the center of the galaxy. Yeah, just
Speaker 1: the way the Moon has a gravitational effect on the
Speaker 1: water of the Earth. So as the Moon goes around
Speaker 1: the Earth, it tugs on the oceans and causes tides.
Speaker 1: We have a gravitational pull towards the center of the galaxy,
Speaker 1: and that tends to tug on one part of the
Speaker 1: Orc Cloud that's closer to it more than the rest
Speaker 1: of the Orc clouds, so sort of extends it. And
Speaker 1: then as we move around the center of the galaxy
Speaker 1: very slowly, you know, hundreds of millions of years, the
Speaker 1: direction of that tug changes, so it's a dynamic. So
Speaker 1: as we move around the center of the galaxy, the
Speaker 1: tides change, the galactic tides change. So are we right
Speaker 1: now and high tide or lord tide. Well, we're at
Speaker 1: the center of it right so we wouldn't feel it
Speaker 1: at all. But there's a blob of the Orc cloud
Speaker 1: that's always pointed towards the center of the galaxy that
Speaker 1: would be at high tide. There's more objects in that
Speaker 1: part of it, so we're sort of at the very
Speaker 1: center of it, so we can't tell, but it can
Speaker 1: be galactic tides. It can also be like nearby stars.
Speaker 1: If a nearby star happens to come somewhere close to
Speaker 1: us as we all swish around the Milky Way, it
Speaker 1: can perturb the orc cloud and send comets falling in
Speaker 1: towards the center of the Solar system, right or steal them,
Speaker 1: possibly steal them, or steal them absolutely, and we'll talk
Speaker 1: about where these came from. It's not clear that all
Speaker 1: of them actually came from our Solar system. And I
Speaker 1: guess the thing is that we've never actually seen the cloud, right, Like,
Speaker 1: we don't have pictures of it or even like radar
Speaker 1: of it or evidence of it. That's right. It's so
Speaker 1: far out there that it's still theoretical. There have been
Speaker 1: some glimpses of one or two objects that people debate
Speaker 1: might be like part of the Inner Inner Inner or cloud.
Speaker 1: But these things are really small and really really far away,
Speaker 1: Like it's hard to see Pluto, right, and Pluto is
Speaker 1: really close compared to these things, and nothing that we
Speaker 1: have out there in the Solar System has gotten anywhere
Speaker 1: close to them, Like the thing that we have sent
Speaker 1: out into space, that's the furthest object the humans have
Speaker 1: ever built, that's Voyager one. The fastest human spaceship ever. Right,
Speaker 1: that thing won't get to the beginning of the Orc
Speaker 1: Cloud for another three hundred years. Well, Daniel, I don't
Speaker 1: know if I believe in this thing or not, but
Speaker 1: let's get into how we know it's actually there and
Speaker 1: why we think it's important for our origin as a
Speaker 1: planet and as a human species. But first, let's take
Speaker 1: a quick break. All right, we're talking about the or Cloud,
Speaker 1: which is uh. I guess Daniel, you would describe it
Speaker 1: as like a giant shell of city size snowballs floating
Speaker 1: out hundreds of light years away from the Sun. That's right,
Speaker 1: And snowballs makes it sound quaint and fun and like
Speaker 1: if you get hit by one, you can just go
Speaker 1: inside and warm up with a cup of hot cocoa. Right,
Speaker 1: But these things are massive ice balls, and if one
Speaker 1: of them hit the Earth, we might be toasted. So
Speaker 1: we'll talk about the danger these things later on, but
Speaker 1: I want to make sure people are aware that these
Speaker 1: are basically massive space bullets waiting to hit the Earth.
Speaker 1: It's like a real snowball. If they pack enough ice
Speaker 1: into that slush ball, it can really hurt. Yeah, alright,
Speaker 1: so how do we know that it's actually there. Then
Speaker 1: what makes us think that there is this giant cloud
Speaker 1: of snowballs in space? Well, it comes um sort of
Speaker 1: a paradox. In the last hundred years, we've established that
Speaker 1: there are lots of comets, but the Solar system is
Speaker 1: not very young, and so people have been wondering, like,
Speaker 1: where do all these comets come from? Because comets are
Speaker 1: not stable. Like, once a comet starts falling in towards
Speaker 1: the Sun, it loses a lot of its mass as
Speaker 1: the Sun boils it away. So a comet can't like
Speaker 1: zip around the Sun for billions of years. It only
Speaker 1: gets like, you know, fifty or a hundred, maybe two
Speaker 1: hundred times around before it gets boiled away. Right, So
Speaker 1: if that's the case, if comets don't last very long,
Speaker 1: why are we still seeing commets? Like you lived in Arizona,
Speaker 1: and every once in a while somebody throws a snowball
Speaker 1: at your house, You're like, this is recent, Like somebody
Speaker 1: just made this. Yeah, Or you know, if you're walking
Speaker 1: around your neighborhood and everybody's eating ice cream, you're like,
Speaker 1: where's the ice cream? Chuck? It must have just come by.
Speaker 1: And so exactly, they thought there must be some sort
Speaker 1: of source of these things. The other clue was that
Speaker 1: there's sort of two types of comets. There are short
Speaker 1: period comets. Com is to have an orbit around the
Speaker 1: Sun that's like less than ten a U, and these
Speaker 1: are mostly aligned with the Solar System. It seems like
Speaker 1: they're like basically Solar System objects, just blobs of ice
Speaker 1: somewhere in the outer reaches of the Solar System. But
Speaker 1: then there's a second group of commets. They're called long
Speaker 1: period comets. These are ones that have an orbit that's
Speaker 1: like a thousand a U or more, and they take
Speaker 1: a long time to go around the Sun, and they
Speaker 1: don't follow the plane of the Solar system. So these
Speaker 1: were really the mystery. They're like, where are these long
Speaker 1: period comets coming from? They couldn't explain it. They shouldn't
Speaker 1: stick around. And so to explain where the new ones
Speaker 1: were coming from, they said, maybe there's a huge blob
Speaker 1: of them somewhere out there beyond where we can see. Oh,
Speaker 1: I see, you're saying these long period comments. They're sort
Speaker 1: of coming out of left field. Doesn't look like they're
Speaker 1: hanging out with us, or have been hanging out with
Speaker 1: us for a long time. It's like they're coming from
Speaker 1: somewhere else. Yeah, because they can't last for very long. Like,
Speaker 1: once you see a comet, you're seeing it in the
Speaker 1: end of its life cycle. It could have been out
Speaker 1: happily for billions of years deep out there in the
Speaker 1: Solar System. But once you see it, that means it's
Speaker 1: falling towards the Sun and it's going to get boiled
Speaker 1: away as it goes around the Sun, and it can't
Speaker 1: survive for very long. And even if it does make
Speaker 1: it a hundred or two hundred orbits, it's got a
Speaker 1: high chance of getting kicked out of the Solar System
Speaker 1: being perturbed by the gravity of one of the outer planets.
Speaker 1: So once you see a comet, it means it's in
Speaker 1: its last chapter of its life in the Solar System.
Speaker 1: So we're still seeing comets four and a half billion
Speaker 1: years into the story of the Solar System. There has
Speaker 1: to be some fresh resupply every once in a while.
Speaker 1: I guess if you're seeing a comment, that means it's
Speaker 1: getting hit by the rays of the Sun, which is
Speaker 1: probably melting it. It's definitely melting it, and that's where
Speaker 1: the comets tail is. Right. People like to imagine the
Speaker 1: commets tails like little action lines in a cartoon that
Speaker 1: show you where it's moving. But the commets tail is
Speaker 1: not actually pointed away from the direction of the comets motion.
Speaker 1: It's pointed away from the sun because the tail comes
Speaker 1: from the sun boiling away all the stuff on the comet. Yeah,
Speaker 1: that's the signature tale of of comets. That's what it is.
Speaker 1: It's not really a tail. It's more like a haircut.
Speaker 1: Is that what you're saying, Yeah, precisely. And comets can
Speaker 1: actually have multiple tales. They can have tales going in
Speaker 1: different directions based on like the stuff that's in there
Speaker 1: that's good and getting boiled away different compositions. So it's
Speaker 1: pretty fascinating look at the tales of comets. It's pretty awesome. Okay.
Speaker 1: So then someone named Yon Ord in the fifties said, hey,
Speaker 1: maybe all of these weird long period comets are coming
Speaker 1: from a very specific place. And so he came up
Speaker 1: with this idea of the Ord cloud. Yeah, and he
Speaker 1: looked at the orbits of these comets and he said,
Speaker 1: how far out does it have to be to generate
Speaker 1: comets with this length or but these long period comets,
Speaker 1: And so that's how he estimated. He made a very
Speaker 1: rough estimate for you know, how far away should be.
Speaker 1: And since then we have much better data, better telescopes.
Speaker 1: We can see the orbit of these comets much more clearly.
Speaker 1: We have more telescopes, we have hubble and so be
Speaker 1: can track all this stuff, and we have better estimates
Speaker 1: for what's out there and how big it is. But
Speaker 1: the basic idea came from this guy, yawned Ort in
Speaker 1: nineteen fifty. And you know, it's pretty awesome to get
Speaker 1: to put your name on the biggest thing in the
Speaker 1: Solar system, Like this thing just dwarfs the rest of
Speaker 1: the Solar system. Did he call it that the the
Speaker 1: ord cloud or was it named after him? That's a
Speaker 1: great question. I should read his original paper to see
Speaker 1: if he put his own name on it or if
Speaker 1: he was humble. Yeah, when he called the cloud of
Speaker 1: Testimal and let somebody said that's a ridiculous name. We'll
Speaker 1: go with orc. Yeah. And it's fascinating and it's cool
Speaker 1: because it answers a question, right, It tells you, oh,
Speaker 1: that must be where these comets are coming from. But
Speaker 1: like everything in science, when you answer a question, it
Speaker 1: opens up more questions, like all right, Well, where did
Speaker 1: this ort cloud come from? Why is it there? Why
Speaker 1: aren't they just closer into the rest of the Solar System.
Speaker 1: And that's an active area of research right now. So
Speaker 1: we actually haven't seen this cloud. We're just sort of
Speaker 1: tracking where comets come from, and we think they come
Speaker 1: from the cloud. Yeah, we have not seen this. We
Speaker 1: don't have telescopes that are powerful enough to spot it,
Speaker 1: none of our probes are anywhere near it. But it's
Speaker 1: sort of the best explanation and we have for the
Speaker 1: source of comets. So it's pretty well accepted in the
Speaker 1: astronomical community that it exists. Like we always like to
Speaker 1: see direct evidence of something before we conclude that it exists,
Speaker 1: like there was evidence for Pluto before we spotted it
Speaker 1: in a telescope. But you don't really claim discovery of
Speaker 1: it until you actually see it, right, It's like finding
Speaker 1: the body in a murder mystery. But sometimes it's the
Speaker 1: best you can do for a while, so we can
Speaker 1: talk later about like plans people have for how to
Speaker 1: spot the Orc cloud and to study it, but for
Speaker 1: now we have no direct evidence of it. I guess
Speaker 1: it's not a thick enough cloud that it like makes
Speaker 1: your view hazy, or you can see some of the
Speaker 1: like the light getting filtered through it. It's not that thick, No,
Speaker 1: it's not that thick. These things are very small and
Speaker 1: very far away, so thick is definitely not how you
Speaker 1: describe it. There's enormous that empty spaces between every object
Speaker 1: in the orc cloud. Even though there are trillions and
Speaker 1: trillions of objects. The space we're talking about is incredibly vast, Right,
Speaker 1: We're talking about a sphere that's basically a light year
Speaker 1: in radius, and so there's a lot of space in
Speaker 1: there to distribute the trillion objects and still have lots
Speaker 1: of room in between them. All Right, Well, I guess,
Speaker 1: like you said, a big question is where did this
Speaker 1: orc cloud come from? Like why is there all this
Speaker 1: water deposited in one spot out there in the Solar system?
Speaker 1: Beyond the Solar system. Well, as usual, we have a
Speaker 1: few theories. We have sort of like the most boring
Speaker 1: theory and then the most exciting theory, and the most
Speaker 1: boring theory is sort of a story of the formation
Speaker 1: of our Solar system. Like we start from a big
Speaker 1: cloud of molecular gas and dust and stuff that collapses
Speaker 1: and you get the Sun and you have a disc
Speaker 1: of stuff that has too much angular momentum to collapse
Speaker 1: into the Sun, so it spins around the Sun without
Speaker 1: forming part of the star. And that's the protoplanetary disc, right.
Speaker 1: And there you have of ice and gas and dust
Speaker 1: and all kinds of stuff that starts to form planets
Speaker 1: and clump together and form all sorts of stuff. The
Speaker 1: idea is that not everything clumps together to form a planet,
Speaker 1: like you have asteroids for example, of smaller things. Gravity
Speaker 1: doesn't succeed in clumping everything together. But you do get
Speaker 1: big gas giants out there, like Neptune and Urineus and
Speaker 1: Saturn and Jupiter. They start to be sort of like
Speaker 1: heavyweights of their own gravitationally, and they can perturb the
Speaker 1: other stuff. And so there was a bit of a
Speaker 1: dance in the early Solar System as these big planets
Speaker 1: we're finding their place, and as they move around, they
Speaker 1: affected everything else. So the short version of the story
Speaker 1: is that we think that they were essentially tossed out
Speaker 1: of the Solar System by some of these gas giants
Speaker 1: as they were being born. These planets sort of like
Speaker 1: muscled their way around the craziness of the Solar System. Yeah,
Speaker 1: and one of the definitions of planets, if you believe
Speaker 1: in you know, silly astronomical categories, is that it's cleared
Speaker 1: its own path around the Sun. And so that's just
Speaker 1: sort of like the job of growing up and being
Speaker 1: a modern planet is that you have to like toss
Speaker 1: the little bits out of the way, or you know,
Speaker 1: slave them and make them into your moons. But in
Speaker 1: this case, most of the stuff we think was tossed
Speaker 1: out sort of in the early days of the Solar
Speaker 1: System formation. And it also it had a reverse effect.
Speaker 1: Remember gravity is always two directions. So we think that
Speaker 1: one of the reasons that Neptune is as far out
Speaker 1: as it is is that it got tugged out by
Speaker 1: these objects as they were leaving the Solar System. I guess.
Speaker 1: One question is if a planet is kind of plowing
Speaker 1: through and sending things out into space, wouldn't it send
Speaker 1: all kinds of things like asteroids and rocks and gas.
Speaker 1: How did all this ice come together so purely, I guess,
Speaker 1: And like, you know, why isn't it a mix of
Speaker 1: all other things? Yeah, that's a great question. It is
Speaker 1: mostly a mix, right, These things are not pure water.
Speaker 1: It's like you go out there and you find these
Speaker 1: pristine cubes of ice that you're ready to chisel out
Speaker 1: and put onto your space cocktails. These things are dirty.
Speaker 1: It's definitely still rocks in there. But remember that a
Speaker 1: large fraction of the stuff in the outer Solar system
Speaker 1: is ice, like you call uranus and neptune. They are
Speaker 1: called ice giants, and so it's something of a matter
Speaker 1: of how these chemicals are distributed through the solar system,
Speaker 1: like where water ends up and ends up freezing and
Speaker 1: gathering together. But a lot of the stuff in the
Speaker 1: outer Solar system, and non significant fraction of all the
Speaker 1: mass in the outer Solar system is water. I guess
Speaker 1: out there most of it is ice and liquid, because
Speaker 1: if it was closer, it would evaporate and maybe blow
Speaker 1: out exactly. Some complicated arguments about where stuff in the
Speaker 1: solar system collapses and what falls in and what doesn't.
Speaker 1: But you end up with a lot of ice in
Speaker 1: the outer Solar system. But these things are not pure water. Again,
Speaker 1: they're definitely bits of rock. I would not recommend drinking
Speaker 1: an or object if you found one, unless you like rocks,
Speaker 1: unless they like your cocktails dirty. I guess they're dirty
Speaker 1: snowballs all right, So that's one theory about how it forms,
Speaker 1: just like you know, byproduct of the dynamics of the
Speaker 1: solar system. What are the more interesting theories? The more
Speaker 1: interesting theories are the interstellar theories. One idea is that
Speaker 1: our son, when it formed, wasn't on its own. But
Speaker 1: you know, we've discovered barely recently that a lot of
Speaker 1: stars it was a twin. Yes, we're born as twins.
Speaker 1: That binary star systems are much more common than we imagined.
Speaker 1: So it could have been that our son had a
Speaker 1: twin and that this collapsing cloud of stuff formed two
Speaker 1: stars instead of one. But then these two sort of
Speaker 1: drifted apart, as you know siblings sometimes do, and there's
Speaker 1: a lot of material exchanged, and that gives you an
Speaker 1: opportunity to sort of pull material further away from the
Speaker 1: Sun because you have this big, heavy object, the other star,
Speaker 1: tugging on your solar system. What so, what happened to
Speaker 1: this other star, sister star. It's the subject of a
Speaker 1: Netflix documentary, you know, where they're going to reunite the
Speaker 1: stars for a dramatic conclusion at the end of the universe,
Speaker 1: or a hit podcast mini series. That's right, not true crime,
Speaker 1: but true physics. No, we don't know. It's just hypothetical.
Speaker 1: We don't know that the Sun had a twin star
Speaker 1: at its birth. It's just an idea. But if it did,
Speaker 1: it could have been pulled off and gone in any direction.
Speaker 1: It's been a long time, it's been billions of years,
Speaker 1: and so it's hard to trace. It's not like the
Speaker 1: nearest star is necessarily a category for our lost twin.
Speaker 1: This thing would have been moving for a long time.
Speaker 1: It could be anywhere at this point. And so the
Speaker 1: idea is that the sister star pulled some things from
Speaker 1: the Sun and then left it out there and where
Speaker 1: the orc tod would be. Yeah, just like we were
Speaker 1: talking about the gas giants tossing stuff out of the
Speaker 1: Solar system, Now you have a much bigger object, a
Speaker 1: heavier object, another star even further out. It's going to
Speaker 1: tug out some of these stuff in our solar system
Speaker 1: to have a very large radius. And then as the
Speaker 1: to sort of separate. I'm imagining, like you know, sell
Speaker 1: mitoses here two stars are pulling apart from each other
Speaker 1: and it's sort of like threads in between them, and
Speaker 1: then as they get far enough away, they stop affecting
Speaker 1: each other gravitationally and things settle into place. But you
Speaker 1: have stuff out at a pretty far radius because the
Speaker 1: gravitational pull of the other star interesting. So it was
Speaker 1: like the leftover from the divorce or something I just
Speaker 1: got dropped there in the middle of space. That's right,
Speaker 1: the poor abandoned objects in the stellar o c so
Speaker 1: many seems appropriate. All right, let's get into our last
Speaker 1: theory about where this orc cloud came from and what
Speaker 1: it all means. The first let's take another quick break.
Speaker 1: All right, Daniel, there's a giant cloud of snowballs out
Speaker 1: in space about three light years away from the Sun,
Speaker 1: and we think that's where comments come from. But the
Speaker 1: question is where did this cloud come from? And so
Speaker 1: you have one more theory for us about that, and
Speaker 1: I'm going to guess it involves eight It involves alien stars,
Speaker 1: though we don't know if there are aliens enough living
Speaker 1: around those stars. The problem is that if you do
Speaker 1: the calculations, and you have your theory of the Solar
Speaker 1: system and you predict how many things there should be
Speaker 1: in the or cloud, you get a number that's way
Speaker 1: too small. You get a number like six billion objects.
Speaker 1: But we know the number is much much bigger than that.
Speaker 1: So the idea is like, well, where do these things
Speaker 1: come from? So wait, how do we know how big
Speaker 1: it should be? If we don't, we've never seen it
Speaker 1: and it's all theoretical. Is it just from like the
Speaker 1: frequency of comments that we get exactly to explain the
Speaker 1: number of comments that we see, and they're radius and stuff,
Speaker 1: there should be a certain number of objects in the
Speaker 1: Orc cloud, otherwise we would see fewer and fewer comments.
Speaker 1: But if we try to predict how many things are
Speaker 1: in the Orc cloud from sort of first principles formation,
Speaker 1: like how many things should have been tossed out there
Speaker 1: by Neptune and Saturn Uranus, then we get a much
Speaker 1: smaller number. So there's a discrepancy there. We know there
Speaker 1: are objects out there, we can't explain how they got there.
Speaker 1: So one idea is as well, when our star was forming,
Speaker 1: what was going on nearby? We talked about how maybe
Speaker 1: there was a sister star formed with us. But another
Speaker 1: idea is that maybe our stellar cloud that collapsed was
Speaker 1: near some other objects and it stole some material from
Speaker 1: those objects. That basically the Orc cloud is like a
Speaker 1: lot of stuff from other solar systems that was stolen
Speaker 1: by our sun when it formed. What it could be stolen? Good? Yeah,
Speaker 1: the water we're drinking could have been stolen from another
Speaker 1: solar system. Is that what you're saying? You should feel
Speaker 1: guilty every time you have a drink. It's elicit. But
Speaker 1: it could basically be all a muamua, right, Remember Mumua
Speaker 1: was this interstellar comment, this frozen object that passed through
Speaker 1: our solar system coming from some other solar system. And
Speaker 1: it could be that the Orc Cloud is basically just
Speaker 1: a bunch of these. Oh I see, is that a
Speaker 1: theory that Oma came from the Orc Cloud? No, mum
Speaker 1: It definitely did not come from the Orc Cloud. Its
Speaker 1: trajectory is totally inconsistent with that. We know that it
Speaker 1: came from another solar system. But it could be think
Speaker 1: the Orc Cloud is the product of stealing a bunch
Speaker 1: of Omumua like objects much much earlier, a long time ago,
Speaker 1: as our solar systems forming. So you know, possession is
Speaker 1: nine tenths of the law. Then you know we've had
Speaker 1: these for billions of years. They're basically ours now, but
Speaker 1: there's a bit of original sin there and having stolen
Speaker 1: them from another solar system a long time ago. Well, yeah,
Speaker 1: I guess, because you know, I think the closest stars
Speaker 1: to us our solar system are about what is it
Speaker 1: like five light years away, right, yeah, three and a
Speaker 1: half light years away to proximates Centauri. Yeah, so this
Speaker 1: orc cloud is about where those other stars are. Yeah,
Speaker 1: it's the right order of magnitude, right, it's that big.
Speaker 1: It's so big that it gets you part way to
Speaker 1: other stars. And those other stars probably have their own clouds,
Speaker 1: and these stars tugging each other, and one of the
Speaker 1: ways to perturb our or cloud is to have other
Speaker 1: stars come nearby and give it like a little gravitational tug,
Speaker 1: which results in comets falling towards the Earth. Also, an
Speaker 1: orac cloud is not necessarily like a good thing. We
Speaker 1: talked about stealing this, but like it's a bunch of
Speaker 1: bullets hanging over our head where at the bottom of
Speaker 1: this gravity, well, any of them roll down, they could
Speaker 1: totally wipe us out, like deadly hail or something. You
Speaker 1: don't You don't necessarily want that, it won't create a
Speaker 1: winter wonder lamp. You want it early on, so we
Speaker 1: can give you oceans, but then you basically want to
Speaker 1: give them away. To your neighbor, so you don't have
Speaker 1: them anymore. Wow. Alright, so it is kind of like
Speaker 1: a giant interplanetary snowball fight almost or tug of war. Yeah,
Speaker 1: and that's where we think most commets come from. And
Speaker 1: you know, every time you see a comet that's come
Speaker 1: from the outer Solar System, it's been out there for
Speaker 1: billions of years, happily orbiting, not being close to anybody,
Speaker 1: being an introvert. And now it's screaming towards the center
Speaker 1: of the Solar System, maybe hitting a planet, maybe hitting
Speaker 1: the Sun, maybe just whipping around and going back out right.
Speaker 1: It's kind of dangerous. It's actually quite dangerous. You know.
Speaker 1: People talk about asteroids hitting the Earth and worrying about
Speaker 1: big rocks and planet killers and all kinds of stuff,
Speaker 1: But the truth is NASA has most of those figured out.
Speaker 1: Like most of the asteroids, the things in our Solar System,
Speaker 1: we could see them because they're pretty close, certainly anything
Speaker 1: that's big enough to cause us any danger. And NASA
Speaker 1: has a great team of planetary protectors tracking these things
Speaker 1: and predicting where they're gonna be and letting us know
Speaker 1: if they're gonna be anywhere nearby, and often one of
Speaker 1: them slips through and we don't see it until it
Speaker 1: hits us. But that's because it's small. So a really
Speaker 1: big object that would actually cause any damage. NASA is
Speaker 1: pretty sure we're safe from those for a couple hundred
Speaker 1: years because they're hanging out in the Solar System, so
Speaker 1: we can kind of see them, but we can see them.
Speaker 1: But if it's coming from outside the Solar System, then
Speaker 1: it can surprise us. Yeah, if it comes from left field,
Speaker 1: it could be a real surprise. These things could have
Speaker 1: orbits that are hundreds or thousands of years, and so
Speaker 1: the first time we see one might be the last
Speaker 1: time we see one because it could be headed for Earth.
Speaker 1: And so these things could fall into the Solar System
Speaker 1: and smack right into a planet and you know, cause
Speaker 1: a lot of destruction. Because they also they move really
Speaker 1: really fast. They've been accelerating for a long time falling
Speaker 1: in towards the Sun, and so they have a huge
Speaker 1: amount of kinetic energy. This is not a gently tossed snowball.
Speaker 1: This is like a rocket. It's like a rocket propelled
Speaker 1: missile launched snowball. Yeah, you give like a really hard
Speaker 1: block of ice to a major League pitcher and stand
Speaker 1: right in front of the mess. He throws it at
Speaker 1: your face. That's about how terrifying this is. Just like
Speaker 1: when they threw those frozen turkeys at airplane to see
Speaker 1: if the airplanes would break. Is that a real experiment
Speaker 1: used to make that up? That's a real thing. They
Speaker 1: shot frozen turkeys at an airplanes to see what would happen.
Speaker 1: And it's happened before, right, Like our Solar system has
Speaker 1: gone pelted by giant snowballs, and some of them even
Speaker 1: hit some planets. Yeah, exactly. If you think, oh, that's
Speaker 1: not likely to happen, or it might only happen every
Speaker 1: thousand or million years, we don't know how often it happens,
Speaker 1: but we do know that it happened recently. It was
Speaker 1: in the nineties that a big comet hit Jupiter commt
Speaker 1: Maker Levy. It broke up into a bunch of pieces
Speaker 1: and each one pelted Jupiter, and even after it broke
Speaker 1: up and made fireballs that were larger than Earth when
Speaker 1: each one hit. So these are very dramatic planetary events,
Speaker 1: not the kind of thing we want to have happened
Speaker 1: to Earth. Yeah, that would be bad, It would be bad.
Speaker 1: And now, Daniel, I have a note here in the
Speaker 1: document you send me here, and I'm trying to figure
Speaker 1: out it says also space centaurs, And that's it. What
Speaker 1: does that even mean? Space centers are so much fun.
Speaker 1: I decided to make it a whole other episode for
Speaker 1: a few weeks from now. But there is this thing
Speaker 1: in the Solar System called a space center. Seriously, it's
Speaker 1: a thing. Scientists found the thing and called them space centers.
Speaker 1: But they're not like you might imagine, maybe like you know,
Speaker 1: asteroids that happened to look like the fusion between man
Speaker 1: and horse. No, they're just the name that you give
Speaker 1: small objects between Jupiter and Neptune that sort of cross
Speaker 1: back and forth between the orbits of these gas giants,
Speaker 1: sort of like transitional objects. So they're like we could
Speaker 1: call them space unicorns or space griffins. That would be
Speaker 1: too crazy, but we'll go with space centers. I don't
Speaker 1: know what kind of bananas they were smoking the day
Speaker 1: they came up with that name, but it did tickle
Speaker 1: my sense of humor. But they think that maybe space
Speaker 1: centers also have come from the orc cloud. They've essentially
Speaker 1: fallen in and then into these more stable orbits somewhere
Speaker 1: in the outer solar systems thing. Well, then I vote
Speaker 1: we rename comments to space unicorns. I second your motion,
Speaker 1: but I don't think we have any jurisdiction here. All right, Well,
Speaker 1: it sounds like comments are pretty cool. They might be
Speaker 1: coming from the Orc cloud, this theoretical cloud out there
Speaker 1: in space which gave us water, which is a good thing,
Speaker 1: but which may kill us in the future. And so
Speaker 1: we're we're studying this cloud. Now we're studying comments more.
Speaker 1: What are we doing about it? Well, we're doing everything
Speaker 1: we can. It's pretty hard to spot these things right there,
Speaker 1: so small, they're so far away. People have one really
Speaker 1: fun idea for how to visualize these things, and essentially
Speaker 1: it's to look for star eclipses. Like if we are
Speaker 1: surrounded by this huge cloud of these little objects there
Speaker 1: essentially black, they're so far away they don't reflect enough sunlight,
Speaker 1: but occasionally they should pass in front of stars, causing
Speaker 1: these little transitions where the star basically blinks out momentarily.
Speaker 1: So you can look at all the stars and watch
Speaker 1: them and wait to see if you see one of
Speaker 1: these eclipses, and if you do, then you can use
Speaker 1: that to measure like how many things there are out there,
Speaker 1: but based on the rate at which you see these things,
Speaker 1: And if you don't, then you can set a limit
Speaker 1: and say, well, there can't be that many, otherwise I
Speaker 1: would have seen them. You're looking at Like how the
Speaker 1: stars are twinkling, Yeah, because they might be twinkling because
Speaker 1: of a giant comment heading towards us, Yeah, or just
Speaker 1: a giant, silent, frozen comment passing between us and that star.
Speaker 1: And you know it has to line up just right.
Speaker 1: You have to draw a line between the Earth and
Speaker 1: that star super far away, and then the orc cloud
Speaker 1: object has to basically break that line in order for
Speaker 1: there to be this eclipse. So it's not that likely,
Speaker 1: but there are a lot of stars out there and
Speaker 1: maybe a lot of orc cloud objects, so if you
Speaker 1: get enough telescope time, you might be able to spot it.
Speaker 1: And unicorns are pretty magical, so you never know what
Speaker 1: they're gonna do. What if they're all turned out to
Speaker 1: be rainbow colored, that would be amazing. And it could
Speaker 1: also be that if we pass nearby another star, that
Speaker 1: that star could like pass through our or cloud, causing
Speaker 1: like a new bombardment of comets, and that would be
Speaker 1: sort of a confirmation because we'd see a lot of
Speaker 1: these things rushing towards the inner Solar system. Well, clearly
Speaker 1: we need to build like an ice Ford Daniel around
Speaker 1: the Earth. That um, yeah, I think it's called Neptune.
Speaker 1: That's an ice giant, and hopefully it captures these things
Speaker 1: as they come into the inner Solar system. You know,
Speaker 1: we actually do have the gas giants to thank for
Speaker 1: protecting us from a lot of these things. They tend
Speaker 1: to pull them in and they also tend to clean
Speaker 1: them up. So without those big planets out there protecting
Speaker 1: us from the o C bullies throwing snowballs, we would
Speaker 1: have had a rougher time of it. And then, to
Speaker 1: be ironic, if there was a like a giant comment
Speaker 1: heading towards us, but then at the last minute Pluto
Speaker 1: gets in the way and blocks it. That sounds like
Speaker 1: the plot of our movie. That sounds like a good
Speaker 1: slow motion scene at the end and flat and everyone's like, oh, Pluto,
Speaker 1: we took you for granted, but now you see it
Speaker 1: is all it's too late, but now we value your contribution,
Speaker 1: all right. Well, the next time you look out into
Speaker 1: the night, Skuy, we hope you think about what's out
Speaker 1: there and what could possibly be out there, and also
Speaker 1: think of ice unicorns floating out there in space. And
Speaker 1: remember that there's a lot of things out there that
Speaker 1: we still don't understand, sources of mystery, sources of wonder,
Speaker 1: and sources of danger. So we better get on it
Speaker 1: and figure this stuff out before it wipes us out,
Speaker 1: or it might be too late. We're ready or not.
Speaker 1: All right, Well, we hope you enjoyed that. Thanks for
Speaker 1: joining us, See you next time. Thanks for listening, and
Speaker 1: remember that Daniel and Jorge Explain the Universe is a
Speaker 1: production of I Heart Radio or more podcast For my
Speaker 1: heart Radio, visit the I heart Radio app, Apple Podcasts,
Speaker 1: or wherever you listen to your favorite shows.