Daniel and Kelly’s Extraordinary Universe - How do we know what elements the Universe is made of?

Episode Date: July 1, 2025

Daniel and Kelly trace the history of how we figured out what elements the stars are made of, featuring naked Greeks, hiking Scots, and villainous Harvard profs.See omnystudio.com/listener for privacy information.

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Without visiting any other planets or stars, we want to be able to. to use our ingenuity to figure out how things work in the rest of the solar system, in the heart of the sun, or in distant stars. Until recently, we didn't know the answers to basic questions about the rest of the universe, questions like, what elements is it made out of? Is the sun made out of the same mixture of atoms as the Earth? What about the rest of the universe? Today we'll tell you the story of how we figured this all out. It features naked Greeks running down the street, Scottish people climbing mountains and a clever young woman pushing back against the established but mistaken orthodoxy and not getting credit for it until recently.

So we're going to do our bit to set the record straight and to show you how clever little apes can actually learn about the recipe for making a universe stuck in the confines of our little planet. Welcome to Daniel and Kelly's extraordinary elemental universe. Hello, I'm Kelly Weider-Smith. I study parasites and space, and I'm super excited to learn about another woman that we haven't heard anywhere near enough about today. Hi, I'm Daniel. I'm a particle physicist, and I study what the universe is made out of, but I'm also curious what I'm made out of. Oh, you know, biologists have been working on that for a while. What is your question in particular?

Well, you know, people tell me that I am what I eat, which means I'm mostly dinner, I guess. Oh, that's right, because you only eat dinner. Yeah, exactly. What did you have for dinner last night? What are you? What should I expect? Last night we had a dinner party, actually. So we went a little fancy.

We made miso honey chicken. We made asparagus and scallions with barata. We made a very fancy salad. I made a lemon butter almond tart. Wow. Yeah, it was good. That's amazing. Okay, but so the main part of the dish was chicken, so I'm going to expect you to squawk about physics today. Oh, and a couple of loaves of sourdough bread, of course.

Oh, fantastic. You've got to have your carb. So, yes, I'm chicken and bread today, I guess. All right, well, don't be sour about the information that we're going to be sharing. So my question for you today, so there was this recent result that maybe there's indirect evidence of life in the solar system. And I was just wondering if you had to put a bet on it, let's say, a hundred bucks, and you were betting, yes, there are microbes somewhere in our solar system or no? In our solar system or in our galaxy?

In our solar system. Oh. In our solar system, you know, in lava tubes on Mars, in the oceans of Enceladus. What do you think? What would you put the odds on for whether or not there are microbes in our universe? Oh, wow. Put a number on something we can't possibly know and then risk money on it. Well, I mean, you know, it's not a ton of money, but...

No, I like that. I like framing these as gambling. questions because it really makes you decide on, like, how much money you'd be willing to lose. I think I'd put the odds of there being alien microbes that is not derived from Earth and, like, you know, somehow kicked off via an asteroid, somewhere in our solar system independently evolved, unique apiogenesis, somewhere like, you know, one in a million maybe. I think it's probably pretty unlikely. Somewhere in the galaxy, though, I put it, like 98%.

Whoa. Yeah. Well, how many solar systems are in our galaxy? There's hundreds of billions of stars in the galaxy and so many planets around the stars. So I just feel like that number is so big. Yeah, those odds sound pretty good. Yeah.

Are you going to take my bet? Oh. The rubber hits the road, people. That's right. That's right. Can you tell I came up with this question right before I hit record? Um, I don't know. You know, it wouldn't absolutely shock me if they found microbes on Mars, given its wet past, or, like, evidence of past microbes or something.

And so I, uh, yeah, I'll take your bet. I'll take the opposite. I, I wouldn't. Wait, does that mean I owe you $100 million if you find microbes on Mars? Oh, oh, no, let's just do, let's forget odds. Let's just do a hundred bucks if you're right, a hundred bucks if I'm right. Oh, but then I'm betting against aliens. I don't want to ever bet against aliens.

I'm rooting for aliens. I don't want to have a conflict of interest where I hope there aren't aliens, so then I get 100 bucks from Kelly. I know this is difficult for you, but we're just talking about microbes. Yeah, that's true. So the microbes that will teach you physics, you're not, or sorry, the aliens that will teach you physics, you're not betting against them. So, all right.

Don't get sour on me here, Daniel. We're moving on. Okay. Today we're not talking about what's alive on Mars or in the ocean. of Europa, or what Daniel ate for dinner, we're talking about what the whole universe is made out of, what building blocks, what elemental Lego bricks are used to put our cosmos together. And how the heck did we figure that out, especially when the stuff is not on Earth? Yeah, exactly. And we've never left Earth. Asterisk, we really did go to the moon, but that kind of

counts as part of Earth. Okay, but that definitely wasn't faking it, just to be clear. No, just to be clear. I did talk to a friend the other day who was like, And I know the moon landing wasn't real, and I was like, oh, that was, every once in a while you have one of those moments where you're like, that's, I didn't, I didn't expect that. What do I say now? All right, anyway, so let's talk to our audience, who almost certainly believes that we actually landed on the moon, and ask them, how do we know what the universe is made of? If you would like to contribute your voice for future segments on the podcast, please don't be shy. Write to us to Questions at Daniel and Kelly. We really, really love hearing from you. I think we know what the universe is made of due to spectroscopy. I don't think we definitively know what it's made of, but we're probably speculated. I think scientists can extrapolate from what's in the earth.

Lanzine-like spectrums and extrapolation from what's immediately around us? I don't think we do. We may live in a simulation, or that we may actually exist in a two-dimensional universe projected onto a 3D hologram. So when you get right down to it, the truth is nobody probably knows, right? Different observational scientific techniques to try and understand the different components of it to the best we are able and make everything else up from there. Spectroscopy. Wait, do we know that? We are the universe.

Yes, the universe is far away and out there, but if we can know the molecules that make up you and me and apples and mountains and porcupines and all the things we know of here on Earth, that tells us what the universe is made of too. spectrosity and gravity. We know by spectroscopy. A lot of guessing, followed by a lot of testing. The spectral analysis, we're not sure what dark matter is, and I seem to remember something about quantum foam, so maybe we don't really know. Data collected from ground and space-based telescopes.

I guess the bits that aren't dark matter, either emit light so we can look at the spectrum, or they have enough gravity to bend light. Easy. We take one piece of the universe, smash it into another piece of the universe, and see what comes out. A lot.

I love the person who said, do we know? Because actually, if it's an episode you and I are doing, there's a pretty good chance the answer is we don't know. So throwing it back at us is a pretty good guess. Yeah, that is a great answer. I also like the answer to frame the question much more broadly. When I wrote this,

I was thinking about what elements the universe is mad out of, like the atomic matter. that, you know, makes up the sun and the stars and the gas and the dust and the wolverines and the ferrets and all that kind of stuff. And the parasites. And the parasites. Yes, exactly. I wasn't thinking more broadly like dark matter, dark energy.

So, yeah, these are good answers. Your question was underspecified. It was, yes. I should have said, how do we know what elements the universe is made out of it? That's right. We still got some fantastic answers. So let's start with how we figured out. what elements the Earth is made out of?

What tools do we use for that here? Yeah, the story of figuring out what the universe is made out of goes like, first, let's figure out what the stuff under our feet and what we are made out of. And then let's think about whether we can extrapolate that to the rest of the universe, because unfortunately, we still can't go visit most of the universe. So in terms of, like, lab science and, like, getting our fingers literally dirty, the Earth is the only place we have to explore. And it's a really cool story how we figured out what the Earth is made out of,

because even though it's under our feet, we can't go, like, explore very deep. We haven't drilled very far into the Earth. So a lot of it is still indirect evidence that we put together by clever humans figuring out ways to basically see what's inaccessible. Well, and not only getting to the center of the Earth, but just being able to, like, pick up a handful of dirt and being like, what kind of elements are in this handful of dirt. That's amazing to me as well. Exactly. And this requires a lot of, you know, chemistry understanding what elements were there and their properties and their mixture. And so early on in the last few hundred years where people were trying to figure out like, hey, what is the earth made out of?

There are basically three big questions they were asking. One is like, what is the density of the earth? Can we figure that out? Because if we know the density of the earth, we know a lot about what it could be made out of and what it couldn't. Like if you measure the density of the earth and you discover, oh, it has the density of whipped cream, then you know it's not mostly iron, right? Whereas if you measure the density of the earth and it's like bang on nickel, and you're like, wow, it's probably mostly nickel, right? And so measuring the density of the Earth is an important question. But this isn't easy, right?

Like, how do you measure the density of something? Well, here on Earth, you're like, put it in water and see if it floats. Or you measure its mass and you measure its volume, right? The famous eureka moment of figuring out whether the crown is made of gold by measuring its volume, by dipping it in water, et cetera, et cetera. This is apparently not a particularly famous eureka moment because I've never heard that story. Oh, this is a really fun math story. Archimedes was asked to determine whether the king's crown. was made of pure gold or not.

So he said, well, I'll measure its density because if it's density, it lines it with gold, then we know it's gold. And if it's got something else in it, it'll come out a different number. Measure the density requires knowing the mass and the volume. Mass, not so hard. Volume, not so hard if you have a simple object,

like a sphere or a cube. How do you measure very precisely the volume of a really complex shape like a crown? Turns out to be really challenging. So Archimedes is puzzling over this as he's slipping into the bath at the end of his day, and as he gets into the bath, he sees the water level rise.

And he's like, oh, now I understand how to measure the volume. You just dip it in water and you measure how much it rises. And the story goes probably apocryphally that he leapt out of the bathtub ran naked down the streets of Syracuse or Syracuse, shouting Eureka, Yurika. And anyway, that's your famous ancient Greek nude story for the day. Amazing. We should have more of those. But, okay, I hadn't heard that story. Thanks for sharing.

But in the case of the earth, you can't just dip the earth in water, right? You know, we don't have like a bath of water that we could dip it in. So what we need to do is measure the gravitational pull of the Earth, right? If you knew the total mass and the volume, then you would have the density. And the volume is pretty straightforward because the Earth is a sphere. So if you could figure out the mass, then you'd know the answer. But figuring out the mass is a little bit complicated, because to do that, you have to measure the pull of gravity.

And to do that, you have to know the constant in the gravitational formula. Newton's gravitational formula says that the pull of gravity depends on two masses and on this number in between them. And for a long time, we didn't know very precisely that number. And so to get that number, you need like two large known masses that you can measure their gravitational pull between them. So you can get that number. And then you can measure gravity in the earth and finally figure out what is the mass of the earth. That sounds complicated. And so how did they find two massive objects to do this with? Yeah, they have to be massive objects, because gravity is super duper weak, right?

You can't measure the gravitational pull between like two pennies in your hand. There is a gravitational pull there, but it's unmeasurable, especially like 100, 200 years ago. So what they did is they found a mountain. There's this mountain in Scotland called Sheeholland. And in the 1770s, they decided this was a good candidate for measuring the gravitational constant because it's isolated from lots of other stuff.

So it's like a single mountain on a plane far away from other stuff. and it's kind of symmetrical. It's like not hard to measure its volume pretty accurately. It's not like the crown of the king of Syracuse, right? It's like kind of a simple shape. Okay. So there's one massive object. Yeah.

So then they took a pendulum and they held it near the mountain and they measured weather deviated from straight down. And the deviation of the pendulum from straight down is you get closer and further from the mountain is a measure of the gravitational pull of the mountain on the pendulum. Right. So here you're like actually measured. measuring gravity between two things, neither of which are the Earth.

That works! It actually does work. This was the first measurement of the gravitational constant. It required actually a lot of work by surveyors, like converting the shape of the mountain into prisms so they could calculate the volume very accurately. It was a huge project, and that allowed them to measure the gravitational constant, and then calculate the density of the Earth. And they discovered that the density of Earth is like almost twice the density of that

mountain. So this technique sounds incredibly complicated. How close did they get to the value that we believe it is today? They're within 20%. Nice. Yeah. And that's pretty good, you know, for like dudes in silly hats with pendulums, you know, walking around mountains. Like, these clever apes are figuring stuff out. Yeah, no, that's amazing. I, you know, I feel like if you took five biologists in our field closed or whatever and you were like, figure out the density of the earth, I'd feel pretty good if we got within 20%. That's pretty solid. And that is really revealing at the time because people had no idea what was inside the earth. Is it like a hollow core the way like King Kong and Godzilla are fighting down there? Is it mostly made of water? People really just didn't know. And this in a single

measurement tells you a lot about what the earth could and couldn't be made out of. And then there's a really amazing history of the measurements of the gravitational constant, which got more and more precise. Eventually people use torsion experiments like balls hanging on strings that are very sensitive and measured their deflection as it get closer together, cavendish, et cetera. There's a whole fun history there. People made these measurements very precisely to within less than 1%. So now we have a very accurate estimate of the Earth's density. That is incredible. Okay, so we have an estimate of the density. What did it lead us to believe that most of the Earth is made of? Yeah, so the density of the Earth is more dense than the mountain, which is a hint that there's like heavy stuff in there, right?

It can't just be rock. It's not water, right? Water is much less dense than the earth. And so that suggests that there's a dense core, that there's something heavy in there. And we now know, of course, there's a lot of nickel and iron in the core of the earth. And this was our first hint about what was down there. Not a giant open sphere with like dinosaurs hiding in it because that would have been cooler. Not a vast chasm filled with swarming parasites, for example.

For most people, that's a nightmare for you, that's heaven. Now I'm so bummed out to know that this is the earth I exist on, but it could have been so much better. And people attack this question of what is the earth made out of from other angles. We have density. But the next angle was age. People were trying to estimate, like, how old is the earth? Because understanding how old the earth is gives you clues about how it's formed and therefore what it's made out of. And we already knew at this point a couple hundred years ago that the earth was probably.

probably pretty old. And the biggest clue there was like, Darwin. Darwin showed us that life took a while to come together. You know, this process of evolution was slow. So we had a sense that the Earth was like cosmically old, not thousands of years. But people didn't really know. Is it like millions, hundreds of millions, billions even? It was still an open question a couple hundred years ago. Now, I love when Darwin gets credit for stuff. But I don't actually know that he should get credit for showing us that life was ancient. I mean, he was, he came up. with the theory of natural selection to explain how, like, one form sort of morphs into another. But I think there were geologists already working on this question and finding fossils and

postulating that Earth has been around for a long time and stuff has been gone. But anyway, Darwin, awesome. Maybe he just got some credit for something he didn't deserve. But biologists getting credit for stuff is always awesome. So let's move on. Yeah, that's fair. And I'm about to give some credit to some chemists. So hold on to your hats.

Oh, boy. I'm going to get sour. People were wondering, like, how long would it take the Earth? to cool. If you have a like a ball of molten stuff sitting in space, how quickly does it form a crust that you can like walk around on? And Lord Kelvin of, you know, Kelvin temperature trying to use this to calculate an approximate age for the earth. He was thinking like you have a big ball of lava basically or magma in space. How quickly can you form a crust? And he ignored a bunch of stuff. Like he didn't understand that there was convection inside the earth, that hot stuff rises until you

keep getting this like refresher of hot stuff from the core up to the surface. He also didn't know about radioactive decay, which helps heat the earth because he didn't know about radiation and quantum mechanics and all that stuff. Nobody had discovered that yet. So in Kelvin's calculation, he missed a lot of the pieces there. And he came up with a range of like 20 to 400 million years. Okay. Which is like low by more than a factor of 10 because of these pieces he missed. But you know, he's sort of getting up there into the right ballpark. Yeah. And so at the time was the predominant view, the Christian view, that the Earth was like, what, two or five thousand years old or something? I think postulating millions of years could have really like put you in

the crosshairs, but how common was the idea that it was just a couple thousand years old at that point? I think that most educated and scientific people didn't accept the young Earth hypothesis even back then. There was a sense, as you said, from geology, that things were taking a long time. But then people were trying to make a specific. They're like, can we get an actual number? And so I love when people in history are like, well, let's try to sit down and get a calculation of this. And, you know, they're wildly off. But getting that first estimate is a big step forward. And then you can refine it and think about what you're missing. And like, this is the process of science. Right. First, do the dumbest thing and then improve it. It's interdive, right?

I feel like that's kind of where we are with the Drake equation. Like, we're starting to hone in on the things that matter. And exercises like this help you think through stuff. Yeah, exactly. And now, of course, we know a lot more precisely how old the Earth is. And when we get back from the break, we're going to hear all. about that. Hey, sis, what if I could promise you you never had to listen to a condescending finance bro? Tell you how to manage your money again. Welcome to Brown ambition. This is the hard part when you pay down those credit cards. If you haven't gotten to the bottom of why you

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All right. was just telling us that Kelvin was thinking about how long it would take a molten Earth to cool to get our initial estimates for the age of the Earth. And we ended up with somewhere between 20 and 400 million years. What was the next step that we took to get more accurate? The more accurate understanding of the age of the Earth, which, again, helps you understand what it's made out of, came in this century when we understood that rocks have little clocks in them. And you can use that to figure out when the rock cooled.

So you can figure out like when something was formed. And these clocks actually depend on quantum mechanics. There are these little crystals called zircon crystals that help you understand how old a rock is. And what is it about the zircon crystals? And why isn't there a watch company called zircon? Zircon are really weird little crystals that hate lead. Like they will not allow lead to form within the crystal, but they will take uranium. So when you get a zircon crystal freshly formed, it has no lead in it, but it does have uranium in it.

And then uranium, while it's inside the crystal, decays naturally into lead at a rate we know. So if you pick up a random zircon crystal and it has no lead in it, you know, this thing is zero years old. It's a baby crystal. If you pick up a zircon crystal and it's got no uranium and it's pure lead, you're like, wow, this thing is old because uranium is slow at decaying. So every zircon crystal is like a little clock that tells you how long it's been since it's formed. That's amazing. And there's a whole incredible story about a chemist named Patterson who figured this out and then started measuring the lead in stuff. And he's actually the guy who discovered, oh, my gosh, this lead everywhere in our environment because of lead in gasoline.

And he led the crusade to get lead out of gasoline because he was realizing, wow, we have poisoned our environment. He was trying to make a clean room to measure these things really precisely. And he just, like, could not get a lead-free environment. Wow. And so anyway, another chemist who saved us all. When it's so hard to know, like, what study you're doing is going to be the thing that gives you important information for humans. Like, what sort of off-ramps you're going to end up on. And so...

Another argument for funding basic science people, right? You never know what you're going to discover. It's so important. And so because of his work, we discovered that the Earth is like four and a half billion years old, meaning that the oldest rocks we have cooled around four and a half billion years ago. Oh, my gosh. And that's pretty close to our current estimate, isn't it? Yeah, exactly.

That's amazing. And so now understanding that the Earth is really old gives you more information to figure out the puzzle of like, well, what's it made out of? Because you want to understand like how old is the Earth, how quickly did it cool. Well, to know that, you have to know, like, where's the heat coming from? Where are the layers inside the Earth? You need a complete model for where stuff is within the Earth. And that's why you need this last piece. So we have the age.

We have the density. Next thing we need is the structure of the Earth to know, like, how is stuff organized within the Earth. And that's where seismology. comes in to give us that last piece. Oh, so we're getting away from chemistry. Back to the rock, people. Seismology, of course, is a study of earthquakes, and earthquakes are cool. I mean, they're devastating and tragic, but they also do something really useful,

which is that they ring the earth like a bell. And so when there's an earthquake, these seismic waves pass through the earth, and they give you a glimpse as to what's going on inside the earth, because these waves bounce off of, like, interfaces. If the whole earth was just like one solid rock, then the waves would travel smoothly through it. But if there's an interface where you go from like one kind of rock to another or you go from nickel to iron or liquid to not liquid, then the waves bounce back at that surface and you create complicated patterns.

And so by reading the waves that reflect on the surface, you can reconstruct what was going on inside the earth. It's sort of like a sonogram, right, or an ultrasound. That is absolutely amazing. And just like parents like to brag about their kids, I don't. like to brag about the human species sometimes and just note that we've measured Mars quakes. And it is just amazing to me that we've been able to get equipment there that could then measure this happening on another planet in our solar system. So anyway, okay, amazing. All right, so now

you can do this. And so did we know at the time enough to figure out, so like, you know, if you hit water and you had been going through nickel, you're like, oh, something is different. How much work did we have to do to understand what we were seeing? Like, there's a It seems like there's a big difference between saying something changed or something changed, and I understand what that means. Yeah, the crucial thing there is having enough instrumented points. Like, you need to reconstruct these waves all across the earth because, like, a wave from an earthquake in California will propagate down into the earth and reflect back, but doesn't come straight back to California and that goes to Japan or Hawaii or somewhere else. And it also continues through the earth, and the different parts of the wave is like S waves and P waves and different frequencies reflect at different rates. And so what you really need to do is measure all the different frequencies as many places as you can around the Earth to get this complete picture.

So that's what's crucial is having this global network of seismic graphs. And yeah, on Mars, they have a few of these, but wow, if they had more, they could really get pictures of these Marsquakes and understand what's going on inside the Martian Corps, which is a whole other fascinating question about like whether there is still motion inside the core of Mars or whether it's totally frozen. And of course, that tells us a lot about like the history of Mars and maybe did it have a magnetic field and could it protect life from cosmic radiation. But anyway, that's off track. Coming back to Earth, we now have an idea of like what the structure of the Earth is, what the density of the Earth is, and how long it's been cooling. And altogether, that gives us a model for what's going on inside the Earth. Without drilling down and going to visit, this is enough information to constrain our model and tell us what it has to be made out of each of the layers and their composition. And so this is how we figured out that the core is mostly nickel and lead, not lead, iron.

Nickel and iron. Got it. And so it turns out that the earth is like 32% iron, 30% oxygen, which blows my mind. Most of it's like absorbed into rock. 15% silicon, 14% magnesium, 3% sulfur, 2% nickel, and the rest of a lot of exciting trace elements. But that's the majority of what the earth is made out of. Well, okay, so that's not a lot of nickel. So it's mostly iron and oxygen.

Mostly iron and oxygen. Yeah, exactly. There's a lot of oxygen in the earth because rocks gobble up oxygen. Like in the early days of the earth, when you produced oxygen in the atmosphere, most of it was just absorbed by rocks. You have to like satisfy all the rocks before you could leave oxygen in the atmosphere for life. I'm glad there was some leftover for us. Yeah, because oxygen is so reactive. So that gives us a sense for what our scoop of the universe is made at.

of, right? Iron, oxygen, silicon, magnesium. But then, of course, we're wondering, like, what's the rest of the universe made out of? Is it the same? Is it different? What's the sun made out of? And this is a question people have for a long time, like, what is the sun made out of? How does it work? What's going on inside of it? And what fuels it? Yeah, because I think all of the techniques that we've talked about require you to be on the surface of that planet to collect the data. So you probably need a whole different set of tools to figure out what's happening on the sun, right? Yeah, exactly. And of course, we can. can't go visit the sun. We had the Parker Solar probe, which, you know, came close to the sun,

but of course didn't go into the sun. And for a long time, we were trying to figure this out, of course, just from Earth and trying to understand what it could be made out of. And we can know some things without going to visit the sun, right? We can get a sense of the mass of the sun, if we know the gravitational constant, and we know Earth's mass, and then we can calculate from the Earth's orbit how strong the Sun's gravity has to be to keep us in orbit. So already we know the Sun's mass, right? Which gives us a lot of clues. But we don't know much about the density and what's going on inside there. Or the age, right?

We decided we needed to know age, too. Yeah. And another crucial hint is, wow, the sun is very bright. So there's something going on inside the sun producing that energy. And it's like an incredible amount of energy. I don't think people really appreciate how much energy is being put out by the sun. Like, we capture the tiniest, tiniest little fraction of it. But the sun's total power outage is four times 10 to the 26 watts.

Wow. Which is like 10 quadruly. Drillion times the amount of power released by the most energetic power plants ever constructed on Earth. Wow. It's just, we are sipping from an ocean of energy here that's just like being blasted out into space. And it powers our whole planet. It really does. And people wondered for a long time, like, what's producing all that energy?

How long has the sun been burning? They're wondering, like, is there something up there that's on fire? And that, of course, is a clue to what the sun might be made out of? People were wondering, like, is it made of the same stuff as the Earth somehow? Is it made out of something different? So, re-enter Lord Kelvin, king of approximate initial terrible estimates of what the universe is made of. Would I, I guess I'd be happy if I was known for anything, but I do feel like I wouldn't really want to be known for that in particular. No, I love that situation.

Like, getting the first bite at some apple, some fascinating question nobody's tackled. Those are the funnest ones. I'm jealous of, like, the Greeks and the Sumerians and the ancient Chinese and the Mayans who got to think. about these questions that nobody had worked on before, right? Like, the answer could have been anything. Anyway, I think that's super exciting. One of my favorite stories along this line is there was a guy who studied vaccines. His name was Sir Wright, W-R-I-G-H-T, and he, every time, got something important, incorrect,

and he ended up becoming known as, Sir, not quite right. All right, anyway, tangent complete. Where were we? So Lord Kelvin is trying to understand what's the sun made out of? And first he thought, well, what if it's just like fuel? You know, we have fire here on Earth. If the sun is a huge ball of fuel that's chemically burning, could that explain what we're seeing? And that would tell you like, oh, maybe the sun is a huge ball of gasoline, basically, or kerosene.

Don't run out. So if you do the calculation, giving your knowledge of the mass of the sun, chemical burning can only produce that much power for like tens of thousands of years, not for billions of years. Why? Because chemical burning is very inefficient. Like most of the energy in mass is not released when you just change the chemical state from one to another. Whereas fusion is what's happening inside the sun. And that's much more efficient, much more effective release of energy. You get a lot more energy out.

And so if you want to produce all the energy that the sun is producing and do it for billions of years, you can't rely on burning kerosene or some similar chemical process because there just isn't enough mass in the sun to keep that going. for billions of years. All right. It's not logs on a fire. So how did we figure out what it was? Well, people went down other rabbit holes also, which is really fun. They were thinking maybe the sun isn't limited to its current mass.

Maybe there's some source of mass. Is it like gobbling up stuff from the solar system? I mean, early days, you can think of all sorts of crazy ideas, right? Yeah. But that was ruled out pretty quickly because it would require an enormous amount of mass. Like, you'd need a sun to refuel the sun every 10,000 years. So it's like the sun is not eating other stars. every 10,000 years, that would leave a huge imprint on the orbits of planets and stuff like

that. So that was ruled out. Another thought people had is maybe the sun is like contracting gravitationally and converting that gravitational potential energy somehow into heat. And this is sort of on the right track, but if you don't understand fusion, you don't have the final piece there. And this would only fuel a star for like tens of millions of years. And this is actually what's happening to neutron stars and white dwarves that are not undergoing fusion. They're just like being compressed and kept hot by gravity. Was this Kelvin's idea? All these.

Because it matches up with his other, all of these were Kelvin's idea? These are Calvin's ideas. Yeah, this is Calvin like, you know, smoking whatever he was smoking and thinking about the universe and coming up with Dumbers. Okay. I love it.

I'm a fan of Kelvin. Yeah, he sounds like a fun guy. And I think it would have been fun to read your theories about this kind of stuff. And then I could have called you not quite rightson. Oh, nice. Daniel Ronson. That's right. Daniel, first, a terrible approximation of the Anserson.

That doesn't roll off the tongue quite as nicely. But, okay, what else did Kelvin think? So that's where the mystery stood until around the early 1900s. And at that point, people sort of naturally assumed that the sun must be made of the same stuff as the Earth. They were like, hey, the solar system comes together, stuff is formed. Why wouldn't the Sun be made of the same stuff as the Earth? And, you know, I think this goes a long way to pointing out how often we accept ideas in science because they make sense to us without really interrogating them. You know, what seems natural

doesn't always get as many questions as what seems weird. And so later on, a hundred years later, when something else seems natural, we might wonder like, huh, how could they accept that? But at the time, it was the most natural explanation. And now is the time to enter the major villain of this story, Henry Russell. In 1914, he wrote, if the earth's crust should be raised to the temperature of the sun's atmosphere, it would give a very similar absorption spectrum. The specter of the sun and other stars are similar, so it appears that the relative abundance of elements in the universe was like that in the Earth's crust. So he's saying the sun is made out of the same stuff as the Earth, and if you heat it up the Earth, it would glow just like the

sun. So that sounds wrong, but not villainous. Are we going to get to more, or do you just really thought this idea was dumb? That's not his villainy. That was just foreshadowing. Oh, okay. Let's break, and when we come back, we'll find out what made Russell villainous. A foot washed up a shoe with some bones in it. They had no idea who it was. Most everything was burned up pretty good from the fire that not a whole lot was salvageable. These are the coldest of cold cases, but everything is about to change. Every case that is a cold case that has DNA right now in a backlog will be identified in our lifetime. A small lab in Texas is cracking the code on DNA.

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Hi, I'm Danny Shapiro, and these are just a few of the profound and powerful stories I'll be mining on our 12th season of Family Secrets. With over 37 million downloads, we continue to be moved and inspired by our guests and their courageously told stories. I can't wait to share 10 powerful new episodes with you, stories of tangled up identities, concealed truths, and the way in which Family Secrets almost always need to be told. I hope you'll join me and my extraordinary guests

for this new season of Family Secrets. Listen to Family Secrets Season 12 on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. I had this overwhelming sensation that I had to call it right then. And I just hit call, said, you know, hey, I'm Jacob Schick. I'm the CEO of One Tribe Foundation, and I just wanted to call on and let her know there's a lot of people battling some of the very same things you're battling.

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All right, Daniel, I'm on pins and needles. Let's get to the story of why Russell was such a villain. So Russell was on the right track in trying to understand what the sun is made out of. And many of our listeners gave this answer. The answer is spectroscopy. Like, if you can't go there, what can you do to understand what something is made out of? And it's similar to what you might do on Earth, as you mentioned. Like, if you needed to know what is a scoop of dirt made out of, you might try to separate

into components, and then you might heat them up and look at the light that they emit, because different atoms emit at different wavelengths, right? Every atom has different energy levels. The electrons can be on those energy levels, but not between them. If you heat it up, the electrons go up energy levels. If you let it cool down, the electrons go down energy levels and emit photons. The energy of those photons matches the energy difference between those energy levels and tells you what is the difference between those energy levels.

And every atom has a different set of energies, so every atom has a different spectrum. So you take a gas of random stuff, you don't know what it is, you heat it up, you look at the energy levels, you can figure out what it's made out of and what the relative contributions are. You're like, oh, there's a little, I see hydrogen in here, I see helium in here, I see lithium or magnesium, right? It's an amazing way to tell what Earth is made out of. So in terms of the general approach, the listeners and the villain of today's episode, Henry Russell are on the right track, the spectroscopy is the way to go.

He didn't develop spectroscopy, right? He just applied it incorrectly. That's right. He didn't develop spectroscopy. And you notice in his quote, he says, if the earth's crust should be raised, it would give a very similar absorption spectrum. And so he's sort of speculating here, right? And the problem is that this wasn't as easy as we described.

There was an important complexifying factor here, which is ionization. And so, for example, you might think, well, why don't they just look at the light from the sun and you use that to figure out what the sun is made of. Boom, boom, boom, boom, done, right? Well, the problem is the atmosphere of the sun is complicated and there's one more factor we didn't describe, which is that the atmosphere is ionized. Like, sometimes these gases in the sun's atmosphere gets so much energy, they lose electrons. It's not just like, oh, you've got oxygen and has all of its electrons, and they're going up and down and emitting photons so we can tell it's oxygen. Sometimes those electrons are lost, right? And when an atom gets ionized,

its energy levels shift a little bit because it's a big complicated thing. And so the spectrum you expect from a star depends on how many electrons are around those nuclei, which depends a little bit on the temperature of the gas. So it turns out to be kind of a complex problem. So does that mean that the spectroscopy results from the sun were wrong? And he didn't realize that. And that was the main problem? The spectroscopy results from the sun, nobody could understand yet. They were like, hmm, this is weird. We don't understand these lines. They look. different from what we expect, but Russell was convinced anyway that it was made of the same stuff of the earth.

He believed it. It was natural to him. He was like, I'm sure this is just some detail. We'll figure this out. And so now enter the heroine of this episode. Yay! Cecilia Payne. Cecilia Payne is the one who solved this problem.

She read a paper by a brilliant guy named Megnad Saha, who understood all these ionization effects. He calculated exactly what you should expect for various ionizations at various temperatures of all of the elements. He was just like, he wasn't thinking about the sun. He was just like, hey, chemistry is cool, and I want to understand energy levels. And let's dig deep into this. And he totally nerded out about this. And Cecilia Payne is like, oh, this is a solution to this huge problem that we have over in astrophysics of understanding what we should expect from the sun. So she put these two things together, and she was able to interpret correctly the spectrum

of light we're getting from the sun and understand why it looked a little shifted and a little weird from what folks like Henry Russell expected. Amazing. And, like, note students the importance of reading widely. I think there are so many connections that you make that you might not be expecting. Yeah, exactly. And so this is a huge breakthrough. And, like, finally, we could understand what the sun is made out of.

And the result was a huge surprise, especially to folks like pain. Number one, the sun is made out of the same stuff as the earth. Like, there's hydrogen, there's helium, there's oxygen, this iron, this nickel, this all the same stuff. but it comes in very different numbers. Like the relative abundances are very, very different in the sun. Basically, the sun is mostly hydrogen and helium, and everything else is there, but it's tiny. Like it's 74% hydrogen, 25% helium, and everything else is 1%.

Wow. Yeah. All right, and so I'm just going to guess, based on some other conversations we've had about women in science, that Russell isn't just the villain because he was wrong, but he He probably did something to turf pain's results, am I right? Oh, absolutely. Okay. So she was at Harvard, and the director of the observatory was Russell.

Oh. And Russell had the power at the time to veto any publication he wanted for whatever reason, including her thesis. So he blocked her getting her Ph.D. thesis, unless she added the following caveat to her thesis, quote, the outstanding discrepancy between the astrophysical and terrestrial abundances are displayed for hydrogen and helium. The enormous abundance derived for these elements in the atmosphere is almost certainly not real. What? He had her add a caveat that was like, but also probably I'm wrong?

Exactly. He is. And all this amazing science, this huge breakthrough. And then he's like, I disagree with it. So probably this is BS. Don't believe these numbers, by the way. Oh, my gosh. And what a coward that he did.

It sounds like he didn't point. point out exactly where she had an error, right? Like, because, yeah. He just couldn't accept it. He was like, no. The science says so, I don't see a mistake, but no, this flies in the face of what I believe. And so I'm going to insist that you add this caveat to her thesis. Her advisor was a guy named Harlow Shapley, and Shapley ordered 600 copies of her thesis

and sent it to all the important astronomers in the world. Oh, wow. Okay, so he believed in her. He believed in her. Did he go through all 600 copies and, like, cross-examines? out that line that she had to add? I don't know, but he knew this guy because Russell was also his PhD

advisor, so I think they had a common experience there. But it gets even worse, because even though Russell said, no, this isn't true, this can't be true, a few years later, when the scientific tides turned and everybody accepted this, he took credit for this discovery.

No! Yes, exactly. And so in most historical records, until recently, people gave Henry Russell credit for a discovery of what the sun is made out of, which is like such a tragedy. Villanous. I agree. Exactly. He's a total villain. So only four years after calling it impossible, you find him in the literature taking credit

for this discovery. So it's a real shame. It isn't real shame. Okay, so then how did we rediscover Cecilia Payne then? Yeah, that's an important point. Cecilia Payne ended up getting her PhD in astronomy, only the second PhD astronomy ever by a woman at Harvard. Wow. And initially, she was borrowed from becoming a professor at Harvard because she was woman. So she did a lot of less prestigious, lower paid research job. But she ended up becoming the first

female-tenured professor at Harvard and the first female chair of a department at Harvard. So, you know, things changed. And she ended up having a good career in astrophysics. And then later, people digging into the record corrected it. And so, for example, there is an essay by Otto Struve, who called it, undoubtedly the most brilliant PhD thesis ever written in astronomy. Wow. Wow. That's pretty good, right? That's a big turnaround. That's 40 years later. She went 40 years before really getting the recognition. Was she still alive?

Yeah, she was still alive. She died in 79. I'm glad she got to see her work vindicated in her lifetime. That's amazing. Yeah, and she ended up winning some prizes and was elected to the Royal Astronomical Society. The arc of justice is long, but it does point in the right direction, even in astronomy. I mean, often, but not always. Eventually, I hope.

Yes. But Cecilia Payne taught us a lot about the native. of the universe, right? People thought for a long time that everything in the universe must be made into the same stuff as the Earth. That was a natural assumption to them. And now we know, of course, that the sun is mostly hydrogen and helium. And from our models of the formation of the solar system, it makes sense, right? Like the sun is the center of gravity and most flocks there and it pulls in all the gases in the inner solar system. And the Earth did have more hydrogen and helium early on, but because these are such light elements, they were blasted away by the

sun's radiation in the early part of the formation of the solar system. So now we have a full and complex and nuanced understanding of the formation of the solar system in the planets, and we can apply this knowledge to understanding other stars, like our star isn't the only star in the universe, and every star has its own unique pattern. We talked recently about why stars are different colors, because they are made of different stuff, and their atmospheres has different stuff, and they're different temperatures. And now with this model, with Cecilia Payne's understanding, we can use this to understand what the rest of the universe is made out of. Wow. Okay. And so with these corrections, we can now

look out into the universe and without even visiting it, we can know what different celestial bodies are made out of. Yeah, exactly. Thanks to Cecilia Payne and to Magnat Saha. He is an Indian astrophysicist who figured out the ionization equations. His Saha ionization equation is super important for us to figure out the nature of the universe. And it's incredible that we can't figure this out. I mean, think about all the little puzzles that people had to solve all. way down to figuring out how massive the earth is by measuring a mountain in Scotland. All of these pieces were necessary, and they all came together. And when you're solving a puzzle, often there's like a huge unanswered question that you don't

even know how to begin. And if you're lucky, people have been working on that question for other reasons, for hundreds of years, making progress, hiking around mountains, trying to figure it out, or just nerding out about the chemistry. But sometimes you're not so lucky. And that's why it's so important that we push in so many directions simultaneously, Even though we don't know yet how they're going to be useful or what mysteries they might unlock, we need all of these tools so that in the future, clever people can come up with answers to huge questions like, what is the universe made out of? Amen. By geeking out and by geeking out together, we can change the world.

All right. Thanks very much for coming on this tour of how we figured out what elements of the universe is made out of, diving deep into the earth and casting our minds all the way across the universe. Daniel and Kelly's Extraordinary Universe is produced by IHeart Radio. We would love to hear from you. We really would. We want to know what questions you have about this extraordinary universe. We want to know your thoughts on recent shows, suggestions for future shows. If you contact us, we will get back to you. We really mean it.

We answer every message. Email us at Questions at Daniel and Kelly. Or you can find us on social media. We have accounts on X, Instagram, Blue Sky, and on all of those platforms, you can find us at D&K Universe. Don't be shy. Write to us. Every case that is a cold case that has DNA. Right now in a backlog will be identified in our lifetime.

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Here's a clip from an upcoming conversation about how to be a better you. When you think about emotion regulation, you're not going to choose an adaptive strategy, which is more effortful to use. unless you think there's a good outcome. Avoidance is easier. Ignoring is easier. Denials is easier. Complex problem solving.

Takes effort. Listen to the psychology podcast on the Iheart radio app, Apple Podcasts, or wherever you get your podcasts. Hi, it's Honey German, and I'm back with season two of my podcast. Grazias, come again. We got you when it comes to the latest in music and entertainment with interviews with some of your favorite Latin artists and celebrities. You didn't have to audition?

No, I didn't audition. I haven't auditioned in like over 25 years. Oh, wow. That's a real G-talk right there. Oh, yeah. We'll talk about all that's viral and trending with a little bit of cheesement and a whole lot of laughs. And of course, the great Vibras you've come to expect. Listen to the new season of Dacus Come Again on the I-Heart Radio app, Apple Podcast, or wherever you get your podcast.

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