Is there Uranium on Uranus?

Published Feb 17, 2022, 6:00 AM

Daniel and Kelly probe a heavy question about heavy metals on Uranus.

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Hey, Kelly, are you a fan of astronomy humor?

It depends as long as we're not making jokes about uranus.

Well, we'll have to try to avoid falling into that particular hole. But personally, I love a good astronomy pun.

I have more of a plutonic relationship with them.

Oh no, did you just make that joke up or did you have to plan it?

Okay, I've got one for you.

All right.

Shoot, why don't stars go to university?

All right? Why?

Because they've already got millions of degrees. I'm sorry.

Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine, and I will always laugh at astronomy puns.

Hi, I'm Kelly Wiener Smith. I'm a parasitologist at Rice University, and I think my last name is hilarious. So I will always laugh at both parasitology puns and scatological humor.

There's got to be a lot of good puns when you're talking about worms and bugs and things that crawl inside other things.

So and they never get over.

But we try to keep this podcast family friendly, and so we will spare you most of those, and so welcome to the podcast Daniel and Jorge Explain the Universe, in which we talk about all the incredible and amazing things out there in the universe. We crack jokes about the silly names they get, but we have a deep, deep love for the mysteries of the universe and we want to explore all of them with you. We think it's incredible, it's amazing that this universe is understandable at all to our tiny human brains. We want to push forward this effort and bring this understanding of the universe into all of our minds because everybody out there has questions about how the universe works and wants to know where it came from and where it's going to go and how it all fits together. So thanks very much for joining us on our journey of curiosity. My typical co host Orge isn't with us today, and so we have our wonderful and hilarious and very punny co host, Kelly Weener Smith. Thanks for joining us.

Kelly, thanks for having me. I'm super excited about today's question.

Awesome, And you know, on this podcast we often talk about things that are very far away. We're very distant in space and time. But we also have questions about things that happen in our backyard. We're very curious about the nature of our environment, how the Earth formed, how the Solar System formed, how it all came together.

You have a very broad definition of in our backyard.

That's true. I guess parasitologists, when you talk about backyard, you mean literally like what's inside my fence, right, That's exactly what I mean. Cosmologically speaking, though, our backyard to me is like the stuff that formed with us, that has like a common history that we could like go and visit it and dig up something on an asteroid and from that learned something about the Earth. We have like answers in common and actually, later on in the episode, we're gonna hear a really cool story about how asteroids told us something about the history of our planet and how uranium was involved. But you might look at our planet and think, like, hmm, it looks kind of different from the other planets. I mean, like, we have, for example, a nice surface, and we have water, and we have an atmosphere, and you know the Moon doesn't have that, and Jupiter and Saturn and Neptune and Urinus, these planets all look very different from ours, and so you might wonder like, did they form differently? Are they made of the same stuff? What do we really know about what's going on in the rest of the Solar System and how is it all connected? And so we thought a fun question to dig into would be to ask questions about what's going on inside these other big planets.

That's a great question. I've been reading a bit about what is on the various different planets that I'm always prized by, well by how much overlap there tends to be, but also the important things that seem to be missing, like carbon on the Moon. It's going to be really hard to grow plants on the Moon with no carbon.

Do you have plans to go plants on the Moon?

I do not, but plenty of people do. Fun fact, the most concentrated carbon on the Moon is probably the bags of feces that the Apollo astronaut left behind. And this is why I don't get invited to parties.

Are those frozen remains from the astronauts also useful because they contain like the microbiome of those astronauts from what they were eating like forty years ago.

I don't think that microbiome is going to be useful for much anymore. But I also think that according to the Outer Space Treaty, those bags of feces technically still belong to NASA, So I guess it depends on what NASA wants to do with them.

Well, if they become an important resource, we could end up with an international or interstellar war sparked by astronaut remains.

So why hasn't someone written about that yet? Massive lost opportunity. Contact us if you need book ideas.

Guys, I'm sure somebody out there has written that science fiction story already. But we're not so interested in where astronauts have left their remains. We're interested in whether there are really big, heavy materials on other planets, some of the most exotics, some of the most amazing, some of the weirdest things we find on Earth. We were wondering if they also exist on other planets.

And so today we will be asking is there uranium on Urinus?

Now?

I notice you very carefully pronouncing the title of the planet Uranus.

Yes, very carefully. I have a seven year old at home, and so I have to be careful to not edge anywhere near that word. Otherwise I can't talk to her for about three hours because she's laughing too.

Hard and me as well. But is there an option to pronounce uranium with the same rhythm, like, could you say uranium? How do you even say that uranium?

Uranium? As question, I've never thought about it. I don't know.

Is there uranium on Uraniness? Sorry, no, I got it backwards. Is there is there uranium? Is there uranium on Urinus? There we go, and the rest of the podcast will just be us giggling.

I control yourself, Daniel.

But it is a serious scientific question whether uranium only exists on Earth, because you can imagine the future as we're exploring the Solar System, we might want to mine other planets for useful minerals as we're powering our spaceships out of the Solar System or even around the Solar System. And also to me, it's just a fun question to think about, first of all, how it was made in the universe and how it is distributed and where it ended up. You know, is the Earth unique in its collection of heavy metals or is maybe uranium like very common on Urinus and other planets. So I think the more and just a giggle factor this is a serious scientific.

Question, very serious, very serious.

Yes, So putting on our serious faces, I went out there and I asked folks on the internet listeners to this show whether they thought there was uranium on urinus. So, if you would like to participate for future rounds of the podcast and like to play along at home, please write to me two questions at Danielandhorge dot com. I'd love to hear your answers. I know you're out there. You've been listening to the podcast for years and have never written in. Today is the day you write in, So think about it for a minute before you listen to these answers. Do you think there's uranium on urinus? Here's what people had to say.

Since Earth has it, and all the other planets like Mercury, Mars, asteroids and all that have uranium, Uranus being in our Solar system should have it too, I.

Would say that yesterday definitely has to be at least one atom of uranium on uranus, seeing that uranium is distributed throughout the universe and maybe concentrated more on rocky planets. But I guess as if we looked really, really hard, we'd find that one atom.

Yeah, why not. I guess it's a pretty big planet and it's mostly gas. But I don't think why there shouldn't be any other stuff than what it's made out of, because meteors and other things are constantly falling into it, and I guess they are bound to be some that consist of or have some uranium in them. So yeah, I'm pretty confident about that.

I would guess yes, because you're asking it, But I'm not very confident in that answer.

I'm going to guess no. Urinus was by people who did not know what uranium was, but they named it after a Greek god in Greek mythology. But what do I know?

Yeah, I would think so because if I'm not mistaken, it's a high pressure environment, and I would guess that, you know, heavier elements and radioactivelements like uranium would develop in a higher pressure environment like Uranus, possibly closer toward the core.

If there is any uranium on urs I don't think that there would be very much of it. There is probably a small amount scattered to me amongst the or particles from meteorites or just stardust, or maybe it has a rocky core. Know, I think it's mostly ice of light liquids, small molecules frozen, so probably has a lot. But I, you know, I think the two might be related in namesake only.

I would say, yes, definitely, at least one particle.

I don't know.

I don't think that's what the planet is named for, but I don't see a reason why it wouldn't have some uranium.

Thanks so much for those answers. There were some really insightful answers in there. And actually when Daniel proposed this question to me initially, it made me realize that I didn't know how Urinus got its name, and I didn't know the answer to this question. And I agreed with some of the listeners. I thought, probably there's there's at least some uranium in Urinus, because it seems like they would sort of have to be like maybe if it was in a comet or an asteroid that slammed into Uranus, even if it wasn't made in there, it might show up there. But I actually didn't know the answer for sure, so I think I was in the same boat as a bunch of these listeners. But it turns out that I don't know too much about Uranus and where it got its name, So can you tell us a bit about that, Daniel, Yeah.

I love this question because it has two really the fun science stories, the story of Uranus and the story of uranium, and then it ties them together. So Urinus is a really funny planet because its history is hilarious honestly, first of all, because it was seen many many times before anybody even understood that it was a planet. There's like so many missed opportunities to make like a cosmic scale discovery, leave your mark on humanity. Even back in like one twenty eight BC, Hipparchos saw it, and there's like recordings of people seeing this thing in the sky going back to like sixteen ninety or seventeen fifty. People like saw it and noted it in their journals, but they didn't realize it was a planet for a long time.

It still blows my mind that people in like the BC era were looking up at space and had enough of a knowledge about like what belonged to where that they could notice that something new had moved in that like needed to be identified or something. Because you know, I still look up the night sky and I'm like, oh, that's a bunch of stuff up there. Even back then they were doing a much better job than I do at cataloging these things, and I find that very impressive. So what did they think that it was.

Well, a lot of people just thought that it was a star. It's sort of dim and slowly moving because it's really far out there in the Solar System, and you know, the further out you are in the Solar System, the slower you orbit, like the actual linear speed is slower because the gravitational pull on the planet is less, so you move less rapidly. So in our sky, Urinus doesn't move very fast. So some people just thought it was a star that like wandered a little bit because you know, it's sort of hard to keep track back in the day about what was moving in the sky and what was induced by the Earth's rotation, et cetera, et cetera, And so for a long time people just thought it was a star. And then the guy who actually discovered it, a guy named Herschel, he saw it in the sky and he thought it was a comet at first, so he didn't even realize it was a planet. So the guy we give credit to for discovering it actually thought it was a comet when he saw it and recorded it.

Don't comets tend to move faster than planets. I guess it was like more than two hundred years ago, So calculating this stuff was tough. But why did he think it was a combat?

Well, because he did did the calculation very carefully. Because other people looked at his results and his data and they calculated the orbit from his data and they're like, no, that's not the orbit of a comet. That must be a planet. You know what's the difference. The difference is that the comet is like very eccentric orbit. A lot of these things come from like the Ort cloud, like really far out there in the Solar System, and then they zoom in very close to the Sun before zooming out, whereas the planet is like a much larger object that's obviously cleared its field and orbits with a much more circular orbit. Not perfectly circular, but much more circular. And so it was other people who looked at Herschel's data and they decided it was a planet, and it was only Herschel later being like, oh, okay, yeah, I agree with you. What I saw was a planet. So like, I don't even know why he gets credit.

For this there, so so did he get to name it.

And so then there was like a seventy year argument about how to name it. So Herschel wanted to name it George's Star, which is like a terrible name because it's not a star, so he thought he was a comment and he wanted to name it after a star, which makes no sense. Other people wanted to name it Neptune because we didn't have Neptune yet, or Neptune Great Britain, like even more awkward name if you can imagine. And finally somebody else suggested naming it Uranus, after the god of the sky, you know, to follow this pattern that were naming the planets after these Greek and Roman gods. And so there was a long, like seventy year battle about what to call this thing. One group of people calling it Uranus, another group of people calling it George's Star. And it wasn't until eighteen fifty when the British Navy the bureaucracy finally accepted the name Uranus that it like formally became Uranus. So it was like seventy years when people were arguing about it, like just what to call this thing?

So, like did they know what they were doing at the time, because anatomy was pretty far along at that point. Did they realize school children would be laughing for generations to come, or had all the body parts not been quite named yet at that point.

That is a great question, and it might also have to do with like the evolution of the British accent. Right, I don't know what that word sounded like one hundred and fifty years ago, or what those two words that you have in mind sounded like, and if they sounded more or less similar, that's a great question. Linguists out there were historians of the British accent, please write to us and let us know how similar those two words sounded over the years.

We asked the big question.

We do, that's right, We go all the way up there and ask all the big questions. But you know, it turns out to be scientifically a really fascinating planet for lots of reasons. One reason is that it's a great example of a giant planet that's not a gas giant, right like Jupiter and Saturn. We call these planets gas giants because they're mostly hydrogen, but Neptune and Urinus we call them ice giants. Because they really are a different composition and.

Is that water ice or is that some other kind of ice.

So there's a mixture of water ice and ammonia and also methane, and the difference is really that there's sort of like a race to get the gas. Like in the formation of the Solar system, you start out with a huge blob of stuff which is mostly hydrogen, and then you know there's some rock and some water and some other stuff, but really by mass, it's almost all hydrogen, and almost all of it got grabbed by the Sun. Right the whole Solar system is formed, because the Sun begins this gravitation will collapse and because it becomes very quickly the densest thing, the heaviest thing, then it grabs all the gas. Like hydrogen, gas is very light and so gravity pulls on it very effectively. So then to have any gas, to accumulate any gas, you have to build up enough mass to steal some from the forming Sun, and so if you don't get big enough fast enough, then you don't really get very much gas. So Jupiter and Saturn like past this point where they can sort of have a runaway effect and grab some of the gas before the Sun got almost all of it, but Neptune and Urinus didn't get big enough fast enough, so they just ended up like a blob of ice and rock.

So like the Moon and Mars didn't get most those gas either, and then Earth got theirs from getting collided with stuff.

Yeah, and we have a whole fun episode about how the Earth got its atmosphere. It had a little bit of gas in the beginning, but then it was mostly stolen away by the Sun and blown off, and then it later recreated its atmosphere from volcanoes and commentary collisions. It's an incredible story. And that's one of the things I love about these questions is that it tells you the rich, rich history of the Solar System. It's not just like, oh, the planet's formed and then they were zooming around for four and a half billion years. Like there are twists and turns and new characters and like lost characters and probably planets that existed in the Solar System for millions or billions of years, which are now lost because they've been thrown out when Jupiter went like in and then out again. It's a crazy story. It's like a soap opera.

And it's amazing we've figured any of it out. Yes, so Urinus didn't manage to grab this stuff, and then it didn't have the like help that Earth had to get it with all of that other stuff, and so that's how it ended up with not a lot of guess.

Right, And so we don't actually know that much about what's in Urinus. We have a model roughly for what it looks like, but it's important to realize that we haven't really studied it very much. We've looked at it with telescopes. We sent one probe by it, Voyager two, but that's really the only close flyby of Uranus we've ever had. And so we have a model for what's going on inside it, which comes mostly from these models of solar system formation, like what do we think had time to get in there? And that model looks like a rocky core, so like basically a huge rock about like half of the mass of the Earth and that's at the very center of it, and then it's surrounded most of the mass of Urinus is this icy mantle and you know, we say ice, but it's mostly like a big water ammonia ocean. It's like liquid or it's fluid at least it's under a lot of pressure, so it can still move and flow sort of the way the Earth's mantle can, but you wouldn't say necessarily that it's liquid.

So I think I'm getting confused yet. So we you know, when we were talking about it not up a bunch of stuff. Where did all this water and ammonia come from? Was that just stuff it got lucky to grab initially, or did it come somewhere else from Earth? I feel like I already asked this question, but now I'm confused about where all this water came from.

Right, So there's a huge amount of water and ice and ammonia in the Solar system. So the initial formation of the Solar system, you have this cloud of hydrogen. Most of the hydrogen went to the gas giants, but the other stuff is heavier, it's slower, and so it's sort of more likely to accumulate where it was initially. And this stuff is far enough out from the Sun that it stays frozen, so like the water is in ice form and the ammonia is frozen. And so all of this stuff that formed Urinus and Neptune, that was the stuff that was sort of in the outskirts of the Solar System originally and then just sort of like coalesced. Like even further out in the Solar System is the Ort Cloud, which is a bunch more frozen objects that become comets, and those are also just balls of ice. So everything that's really really far out in the Solar System is basically just rock and ice at this point, and it pulls together to form these ice giant planets.

I'm with you now.

So the core of it is this big rock, and then outside of that, like thirteen masses of the Earth, is this hot, dense fluid. It's not frozen, right, It's called ice, but it's not frozen. It's very confusing, so it's sort of like an ocean. It's more like liquid, but it's not technically in that phase. So chemists out there will be particular about how this is referred to, but they do definitely call it an ice, and that's what most of Urinus is. And then outside of that, there's like an envelope. There's an atmosphere that's like another half the mass of the Earth, and that has some hydrogen and some other gases in it. That's sort of like the triple layers of Urinus.

So I watch a bunch of kids shows with my kids, and I feel like the one fact about Urinus that we always hear is that it rotates on its side. Do we know why it's rotated? Why all those layers are rotating the wrong way? Did it get hit by something and sort of knocked off kilter.

It's super cool that it's doing that, because, as you say, it's evidence that something happened, And the reason it has to be evidence that something happened is that we're pretty sure a planet can't just naturally form that way. You notice that, like all the planets are sort of in the same plane. That's the plane we call the ecliptic, and it's also very well aligned with how the Sun rotates. So the Sun is spinning as well. Right, it's not just sitting there in the center of the Solar System. It spins and the planets spin around it, and each of the planets then spin around their axes, and almost all of this spin is in the same direction. Like if you drew a line between the north and the south pole of the Sun, that would give you an axis. And most of the Solar System is on a plane perpendicular to that, and most of the planets rotate around their own axis that's parallel to the Sun's axis. So for most of the Solar System it's very well organized. And that's not like a coincidence. It's not like it just happened to end up that way, like we could have had planets in any random direction. It comes from angular momentum conservation. Like when something is spinning, it has to keep spinning. There's no way to like for it to stop spinning unless you come in with something from the outside, Like if you start a top spinning in space, it's just going to keep going forever. And that's what happened with the Solar System, is that it collapses gravitationally but has to keep spinning, and so it has to keep spinning around that original axis. It can collapse sort of parallel to that axis, which is why you get a flat disc, but the disc itself can't collapse much further because it has to keep spinning. So everything spinning sort of along the same axis. So to get Urinus knocked over on its side requires, as you said, like some huge rock like a lost moon or another planet somehow that banged into it and knocked it over, So it's really is evidence of like an incredible cosmic collision.

I feel like I'm just going to go ahead and blame Jupiter because it seems like the answer for so many things is, well, Jupiter did something weird and that might not be consistent, but I'm going to go ahead and blame Jupiter anyway.

We don't really is that your parenting strategy, You're like, you pick one kid who's always to blame. You're like, look, I didn't see it, but it's usually you.

But I pretty much know the No, Actually it's the dog that I usually There you go. The dog is the source of chaos, Yes.

You know.

I think that's an underappreciated role of dogs in human history. You know, it's just taken the blame for other people's misdeeds or farts around the campfire or all sorts of stuff.

She is the scapegoat, but she's a good sport about it. All right. Well, so now we're all on board about what Urinus is like. So I think it's time that we take a little break and then we'll get to uranium.

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Okay, so now we've talked about what we know about uranus, and uranus and uranium sound really similar, So let's learn about uranium and see if there's any connection there.

So there actually is some connection in the name. I mentioned earlier that when they discovered the planet there was a bit of an argument about what to name it, and so uranium was discovered about eight years after Uranus, and the guy who named uranium uranium did so sort of to vote for Uranus as the name of the planet. He was like naming uranium after this newly discovered planet. He wanted to influence the astronomy community towards the name Uranus.

Whoa so did he have any influence like he did it? But did it matter? Do we know?

I don't know. We have to run the counter experiment or we see what would have happened if you hadn't done that. I'm not sure, but I think it was always going to be Urinus. It's just, you know, going to be a matter of time before the British bureaucracy gave it up.

What a kind of crummy reason for naming an element, though, like unless there's some astronomy connection there to just be like no, no, I really want you to do this naming thing. But anyway, I guess you know we're off. Our logic is sometimes contoluted.

Yeah, And you know, you discover something, you get to name it. You don't always have a good reason. As we talk about a lot on this podcast, some of these names are pretty whimsical and pretty ridiculous. I mean, there's like Berkeleham and CALIFORNICAM and America and the data names of the elements are pretty silly.

Fair enough, some of them are fun to say, like Cereal.

But as we talked about earlier, the planets each have a really cool story. Each of the elements also has a really really cool story that goes back much much further than the story of our particular solar system.

So tell us about how this one was found.

So the important thing to understand about uranium is that it's not made primordially like the very beginning of the universe, when things are super hot and dance and this particles whizzing around everywhere, and then things are cooling down. Just after the Big Bang, we get atoms formed, but mostly we just made hydrogen and a very small amount of helium. So the very early universe is basically just like a huge hydrogen cloud. Definitely no uranium, so uranium does not date back to the beginning of the Big Bang, Like the electrons in your body and the protons in your body are probably older than every uranium nucleus out there, so uranium came later, right, It took a while to make uranium in our universe. It's really cool, and we're gonna do a whole podcast episode focused just on like what is out there in the universe and how it is made in the relative population of all these materials because they all tell such cool stories, and it took a while for people to figure out, like, well, where did all the rest of this stuff come from. Like once they realized that you couldn't make anything heavier than helium or a little bit of lithium in the Big Bang, they had to look around to find a place in the universe to make these heavier elements, and it took people a while, but they figured out that some of the elements could be made, of course, inside stars.

And it's the intense heat and pressure that allows you to make these things.

Yes, stars operate by fusion, right, so they are glowing and super hot, and they're this exciting balance between gravity, which is compressing all of this stuff. It's like a runaway effect where you get this huge compression of all this hydrogen gas and then fusion. If you get all these protons close enough together, you squeeze them together, you overcome the fact that they like to repel each other because they're both two positive charges, and eventually they form heavier stuff. So two hydrogen atoms confuse together to form helium, and helium confuse together to form heavier stuff. And if you have a big enough star, then the products of one fusion cycle, like the helium from fusing hydrogen, can become the fuel for the next one, and then the fuel for the next one, and really big stars. They develop these incredible layers. We have like hydrogen on the outside, and then a layer of helium, and then a layer of something heavier and a layer of something heavier. You go calcium and oxygen all the way up and the biggest st They can fuse stuff all the way up to iron. So iron is element fifty six, and it means that at the core something is fusing two elements together and producing iron, and that's where a lot of these elements that are too heavy to have been made in the Big Bang are made. But stars can only fuse up to iron. Like before, iron anything lighter than iron. If you fuse it, you get a byproduct and you get energy out. That's how the star glows. But iron, if you try to fuse iron together, it actually costs you energy. So if you fuse iron together, you'll cool down the star. You'll kill the star if you try to fuse iron together.

But we have stuff higher than iron, and so is stuff higher than iron made in dying stars.

So for a long time people really didn't understand this. They're like, well, stars can't make higher than iron. But as you say, obviously we have like gold and platinum and plutonium and uranium. Where do all these things come from? And so people thought for a while, as you said, that maybe they come from supernova, that maybe the special can additions when a star explodes might be enough to trigger, you know, this kind of heavier element fusion. But the story didn't really hang together, like it's potentially possible for this to happen, but they didn't really see evidence for it around supernova. And the problem is that this process is very delicate. Like above iron, in order to make something heavier, you need to absorb like multiple neutrons at the same time. Like if you absorb one neutron, you become very unstable and just break up. If you absorb two neutrons, then boom, you can transmute into this heavier thing. So you have to like absorb two neutrons almost simultaneously. It's called this our process for rapid process. And to do that, you need like a lot of neutrons around you so that you have like enough that sometimes you'll get two of them coming in at the same time. And that's very difficult to do in the environment of a supernova because supernova is expanding, it's exploding. And the other problem with supernova's is that while they might make some of this stuff, they don't really like eject it out there into the Solar system. We don't just want to make uranium. We need to make your and then have it be the seeds for a future solar system. If it's just made inside a star and then like kept inside the remnant of that star, it's not going to end up here on Earth or it's part of our Solar system. So recently people found another way to make these super duper heavy elements that wasn't just supernovas.

The suspense is killing me, what is it?

So the answer to how to get a bunch of neutrons together, like a really high density of neutrons so you can do this kind of thing is neutron stars. Neutron stars are these remnants of old dead stars, right, they've already blown up and collapsed, and they have this leftover core that's super incredibly dense. Now, when two of these things collide, like two neutron stars in a binary system, for example, spiral into each other and collide, then you get this incredible cataclysmic event of really unparalleled density not enough to become a black hole, but to form maybe a larger neutron star or to blow some of this stuff out. And so recently, because of gravitational wave observatories, we've been able to see these neutron star collisions. And the really cool thing is that you can see the gravitational waves that they make, like actual shaking of space because they're so dense. You can also look at them with telescopes and you can see the light that comes from them. So like you can see it in two totally different ways, the gravitational waves and in the optical. And when they look in the optical they see light coming from these and they can see light from like excited gold or excited uranium. These like gases of gold and uranium get thrown out into the universe and because they're hot, they emit light and it has a particular fingerprint and we can see it here on Earth. So we have seen the birth of these super heavy elements in neutron star collisions.

So that's totally wild. So that seems like two super rare conditions that need to come together, and that has produced everything above iron. So many of those things are things that we depend on and so like, did any of that happen in our solar system? How did it get here?

Absolutely none of that could happen in our solar system. There's nowhere in our solar system that is capable of making these things. Like even at the heart of our star, all they can do is burn helium or hydrogen. Right, our star is not going to be big enough to even make iron. And so that means that every heavy metal that you see, if you're wearing a gold wedding ring right now, that gold was made probably in a neutron star collision before our solar system was even formed. Right, So all of the uranium, all the gold, all the heavy elements in our solar system predate our solar system completely. And our solar system comes from gathering together the remnants of a previous solar system. Some stars died and became neutron stars and then collide it together and made these heavy elements and spewed them out into some gas cloud which then coalesced into our solar system, still mostly hydrogen, but with a few nuggets of these heavier interesting things to like spice it up a little bit.

Science is so beautiful, you know, you walk around and now you know this stuff and you see the whole world differently, Like anyway, the next time I'm walking through a jewelry store, maybe all appreciate it.

It is really incredible, especially these heavy with things like gold and platinum and plutonium and uranium. They're so difficult to make, and so that tells you that something crazy must have happened really far away, a really long time ago. And so yeah, these elements on your fingers are much older than the Earth itself, right, Like that gold's been hanging out before the Earth was even formed, and it's super amazing.

So this stuff got made in not in our solar system, but it ended up in our solar system. And so because it was made before our solar system, is it sort of evenly distributed between the stuff that we have in our solar system or did it sort of get clumpy and sucked into certain bodies and not others.

That is a great question, and that is really the heart of the question. We haven't been able to study that in great detail because the only example we really can study is the Earth and then the few things that fall to the Earth from space. You know, like you could ask the question, do asteroids have the same composition of stuff as the Earth, and do things further out have the same composition of stuff? So the short answer is we don't know exactly. We know that there are variations because of where you are in the Solar System, like the further out you are there tend to be different things than closer in. But one clue is that uranium is very very abundant. It's very very widespread. It's like actually the fifty first most common element on the Earth, which you know, doesn't sound it's not in the top ten or anything. But if for us such a big heavy element and there's more than one hundred elements, it's pretty far up there.

And is it about that common in asteroids and comets and stuff as well, or we really only know that ranking for Earth.

We know that ranking well for Earth, and a lot of the asteroids are different. But when we study asteroids, we also do see these things in asteroids. And you know, something else that's I think not widely understood is that uranium is everywhere. It's basically in all the sand, it's in every rock. The biggest supply of uranium we have on Earth actually in the Earth's oceans, there's an incredible amount of uranium just dissolved into the oceans, and these days people are thinking about trying to get uranium out of the water because it might be cheaper than digging it out of the ground. So uranium is everywhere all over the planet, but it.

Must be in very low levels because none of us are worried about getting cancer from swimming in the ocean. Is that right?

That's right. Uranium is sort of just part of this radioactive background that exists from living on Earth. You know, the Earth is slightly radioactive. Also, we get radiation from the sky, you know, from cosmic rays, and so yeah, there is some effect on our DNA from naturally present uranium in the soil, just like there's effects on our DNA from muons coming from the sky that occasionally like change something or you know, create an error. And that's I think an important part of evolution. I think evolution would have happened differently if we had no radioactive elements on Earth. It would have lowered the number of mutations that occur. Right, It's not something necessarily to be worried about, though you shouldn't, you know, isolate uranium and eat a lot of it or anything, but it is definitely present all around us.

Interesting, and how long have we known about uranium?

So uranium was also discovered or just after uranus, right, and so only like more than one hundred years. And it was discovered sort of accidentally by a chemist who was just playing around with something called pitch blend and dissolving it with stuff, and he came up with something that felt to him like a new undiscovered element. And it was like one hundred years later the people realized that it was radioactive.

Oh, so they had been like studying it without knowing they should be careful. I guess we didn't understand radioactivity until much later.

Exactly this was the discovery of radioactivity. So uranium is a really important role in science itself. It's the late eighteen hundreds when Becquerel sort of left a bunch of uranium on a photography plate in a drawer, and he came back to found that it had like imprinted itself on the plate. It was like in a darkened drawer, no light in there, but somehow these blobs of uranium left an imprint of fog on this plate. And so he realized, hold on a second there's something going on here. And that was the discovery of radiation that some materials like shoot out these particles that can fog a plate, and you know, that stimulated the curies and they discovered radium, and that you know, really triggered much of nuclear physics and modern physics. So it was a real turning point sort of in science, this discovery of uranium as a radioactive element.

I love these examples of dumb luck, you know, like, whoops, I put my uranium down on a photography plate, and now the whole direction of science is shifting rapidly to understand what radioactivity means, and it's pretty cool.

Would you rather make a like historic discovery through dumb luck so you have a nice anecdote, or through like the sheer force of your brilliance?

I mean, I think I'd probably feel my ego would feel better if I did it through the sheer force of my brilliance. But I'll take it anyway it comes. So randomness is good too.

Yeah.

I love these stories of people like looking for one thing and then accidentally discovering something else because it reminds me to keep my mind open and keep my eyes wide, because you never know in what experiment is going to be the hints of some like crazy discovery. And usually once you've made a discovery, people can go back through history and find evidence for it beforehand, just like now we know Uranus is a planet. We can see in data collected hundreds of years earlier in people's log notebooks, like, oh, you could have discovered this, you had the data right here. People have missed opportunities to make incredible discoveries because they weren't looking for them or they didn't think about that, And so it's a message there. It's like keep your mind open because you never know. You know what the universe is telling you right now.

You never know when you're fumbling towards a discovery.

And the uranium we have here on Earth is a really interesting story because it comes in two different flavors. It's two isotopes of uranium. Most of the uranium we have here on Earth is two thirty eight, which is pretty stable as a half life of like four and a half billion years, but it's not as useful for things like fission if you want to make weapons or reactors. The other kind is called uranium two thirty five, and it's much better for making things like reactors, but it's pretty rare, so like most of the stuff when you mine it is uranium two thirty eight. And then if you want to do reactors or build weapons, you have to isolate and enhance the fraction of uranium two thirty five. So that's why you hear about like centrifuges, because they separate the different isotopes by weight, so you can get more of the two thirty five that you need.

Yeah, this is such a weird element for humanity. Like the one hand, I'm a huge fan of nuclear power plants because they put out less carbon. And on the other hand, I just don't know if humanity can handle it, because you can also turn it into weapons and it doesn't take too many idiots to make trouble and anyway, these things are complicated, thanks humanity, it is complicated.

And it's also interesting that the uranium two thirty five, the stuff that's useful for this, it's sort of going away because it's life is much shorter. It's only seven hundred million years, which sounds like a long time, but what it means is that like the useful fraction of uranium over the history of the Earth is dropping sort of steadily, like we have a lot less of two thirty five than we did a long time ago, and if you wait like another few hundred million years, it's going to be even less. We did a whole podcast episode once about a naturally occurring fission reactor because like a billion or two years ago, there was a uranium deposit in Africa that was rich enough in U two thirty five that it was basically a nuclear reactor naturally created that burned for hundreds of thousands of years and like heated up this rock underground. But that can't happen anymore because uranium two thirty five doesn't occur in enough density anymore for that kind of stuff to happen. So we have to like dig it out of the ground and use centrifugees to enhance the fraction of our uranium that has two thirty five.

So note, humanity, the clock is ticking on figuring out fusion. That's right on that note, Let's take a break and we'll we'll come back and hear a little bit more about uranium.

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Okay, so we've talked a little bit about the way humanity is helped or hurt by uranium two thirty five. Let's hear a little bit more about some of the other properties about uranium. So you told us that it has a high atomic weight because it's higher than iron. So you need these very particular situations so that you can get it. If you had like a chunk of uranium sitting on your table, you'd probably be scared. But what would it look like?

Yeah, that's a cool question. Well, it's actually immalleable. It's like not that hard. It's it's denser than lead, but it's soft and it's silvery white. So it's actually kind of pretty, you know. I mean, I wouldn't recommend doing any art with it, but it's kind of a cool looking thing. And it's cool that every element has its own like sort of feel to it, right, it's on like texture and color and look, and that all of these properties, the difference between uranium and the other things, just come out of the structure of the atom, right, We're talking about how the electrons fill their orbitals and all of this stuff. It's incredibly rich and interesting that all of these elements have such different properties. I love that about the universe that like a few very simple things coming together in lots of different ways can make so many interesting, different kinds of materials.

That is totally epic. And I think it's interesting that you mentioned art because when we moved to our permanent house, what we hope is our permanent house, I wanted to go out and get Fiestaware dishware because I think they look really nice. And I was warned by someone that I shouldn't get the red ones because the red ones are radioactive because of uranium. Can you tell us more about that?

Yeah, uranium mix as well with lots of other things and forms all sorts of interesting uranium oxides, and some of these have a really spectacular color. You know, some of them are yellow, some of them are very head and you know, if you're trying to create colors like these days, it's easy to do digitally, right, you just dial in whatever pixel you want, But if you're out there working with your hands and you want to create dyes, you need to find natural sources of color. And so uranium made this really sort of bright, vivid red that was hard to duplicate in other ways. And so before we understood like really the dangers of radiation and radioactivity, uranium was used all sorts of places to make these kind of things and in your dinnerware, so you're like sitting at the dinner table and your plate is like shooting particles into your body.

I guess that's okay, because there hasn't been a strong correlation between fiesta wear and cancer, I guess, or or was that bad?

I don't think it's okay. I don't think they're making it anymore, you know, for the same reasons that like they're no longer using glowing wristwatch faces. You know that like glow with radiation. I think it's sort of like lead in the sense that more radiation is definitely more bad for you, and you want to limit your exposure. You know, we used to like take X rays all the time, and the X rays would like be super powerful, much stronger than we needed in order to see clearly, because we didn't understand the danger of X rays. So now I think we work really hard to limit our exposure to radiation.

Yeah, that sounds like a good plan. And I didn't end up getting this yes toware because I didn't feel like I could get a good handle on how dangerous it was.

But uranium also tells us a lot about the history of the Earth, as Well, this is really fun story about a geologist trying to understand the age of the Earth and trying to solve the puzzle by actually looking for an asteroid that crashed onto the Earth. He wanted to know if rocks on that he found in the Earth were actually the oldest things that one could find. He was looking to see if things in the Solar System might be even older than the rocks we find on the Earth, because you know, if you're trying to date the Earth and you're just like looking around for rocks, you wonder like, well, it's his rock as old as the Earth itself. So he actually went out to Meteor Crater, this huge crater in Arizona. You should totally visit if you're ever an Arizona. It's incredible. It's just like a flat expanse. And then this incredible scoop just like dug out of the Earth by this meteor that hit a long long time ago. He been down into the center of it and they have like a chunk of the original meteor and they let him sample it. And he looked at that rock and he used uranium actually to date the age of that asteroid.

WHOA So did he get lucky because that asteroid has uranium.

Well, uranium is almost everywhere, right, It's in almost every single rock in the Solar system, it turns out. But a really interesting thing about uranium is that when rocks form, they formed these little crystals called zircons, and these crystals, for complicated reasons, they like to slurp in uranium, but they reject lead. So like, no lead ever forms in the center of these zircon crystals, but uranium turns into lead at a very regular rate because it decays radioactively. So you have there basically is like a clock. You have these crystals that start out with uranium and then they gradually get lead in them, and you know that they had no lead when they were formed because the crystals like reject the lead. So if you look at one of these crystals, you can tell how long it's been around just by counting the uranium and counting the lead, and you can figure out like, oh, this crystal has been ticking for seven hundred million years or for four point two billion years. It's an incredible way to date the age of a rock.

That is incredible and super useful. Thank you physics.

Yeah, so this guy dug out that crater and he discovered he's the first person that really nailed down the age of the Solar system to be about four and a half billion years old. So really important discovery, again connected to uranium. And an interesting side note is that when he was doing that study, he was trying to measure the amount of lead in these crystals and he discovered that his entire lab was basically covered in lead. There was lead everywhere. There's lead on the walls, it was lead in the air, that was lead everywhere because of lead in gasoline. And he actually led the charge to help remove lead from gasoline because he's the one who discovered that we were poisoning our environment with lead.

Whoa sweet, So what's this guy's name who dated the universe and led the charge against lead.

His name is Claire Patterson, and he's the one who discovered that we're basically poisoning all of our children with lead. And he came to this discovery because he wanted to know the age of the universe and he was trying to use uranium decaying into lead in order to do it.

That is incredible. So we've talked about how uranium is helpful in a lot of different ways, and we're all absolutely in awe of Urinus. So now to finally put it all together. So people have sat with us for over fifty minutes and they are waiting for the answer. Is there uranium on Urinus? What is the answer? Drum roll.

As usual. The answer is we don't really know at all because we haven't been out there to Urinus, so we don't know, but we can fairly confidently say that yes, there is, because uranium seems to be present in almost every piece of rock we find, like afterwards that fall to Earth and things that we study, they have these heavy elements in them, and not just uranium, the other heavy elements in varying mixtures, and you can tell something about where these things came from based on like how much iron or how much nickel and the various isotopes they have. But uranium is almost everywhere, and so I'm very confident that there is uranium somewhere on Urinus in its rocky core. But we're not one hundred percent sure. And you know, Urinus remains one of the planets that is not very well studied. We only passed it by with a probe once. We never like dropped anything into it or tried to dive a probe down into it, which I think would be super fun, and you know, maybe there's a big surprise down there.

I think that funder should take note, and they should also consider all of the amazing puns and jokes that could be made if we invested in studying this question more. And surely the money is going to come rolling in.

Now, Yeah, exactly. And we have found uranium in other places in the galaxy as well. For example, there's a star nearby called Krel's Star and it glows, And you can tell what's in a star based on how it glows because every element gets excited by different energy levels and gives off light at unique frequencies has their own fingerprint. So based on the spectrum of a star, you can tell what it's burning. And they have found uranium glowing in this star. Like we haven't gone out to actually visit it and sample it, but we can tell from the light that's coming from this star what's idot. And not just that, but based on the ratio of these various elements uranium and thorium and our knowledge about how they decay, we can use that to age these stars. So uranium is all over the universe and it's telling us lots of fascinating stories about all of the objects that it's hiding inside.

And we still have so much left to learn.

So thanks very much for coming on this journey with us to learn about uranium and urinus. And thanks to Kelly for coming along and refraining from making that most obvious of jokes the entire hour.

Well, you're welcome. I've become very mature in my late thirties. Thank you for inviting me. I had a lot of fun, even though I didn't make all the jokes I.

Wanted Today, and everybody out there, don't forget to embrace your curiosity and don't lose that childlike wonder and sense of puns about out absurd jokes. They go hand in hand. Thanks everyone, tune in next time. Thanks for listening, and remember that Daniel and Jorge Explain the Universe is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. When you pop a piece of cheese into your mouth, you're probably not thinking about the environmental impact, but the people in the dairy industry are. That's why they're working hard every day to find new ways to reduce waste, conserve natural resources, and drive down greenhouse gas emissions. House US Dairy tackling greenhouse gases. Many farms use anaerobic digestors to turn the methane from manure into renewable energy that can power farm towns and electric cars. Visit us dairy dot COM's Last Sustainability to learn more.

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Daniel and Jorge Explain the Universe

A fun-filled discussion of the big, mind-blowing, unanswered questions about the Universe. In each e 
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