How do we know what elements the Universe is made of?

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 https://omnystudio.com/listener for privacy information.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Speaker 00

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• 1:22Daniel Whiteson?

  Trapped on this little rock, we are desperate to extend our understanding beyond our cosmic jail cell. Without visiting any other planets or stars, we want 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

• 2:06Daniel Whiteson?

  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.

• 2:36Kelly Weinersmith?

  Hello, I'm Kelly Weinersmith. 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.

• 2:46Daniel Whiteson?

  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.

• 2:54Kelly Weinersmith?

  Oh, you know, biologists have been working on that for a while. What is your question in particular?

• 3:00Daniel Whiteson?

  Well, you know, people tell me that I am what I eat, which means I'm mostly dinner, I guess.

• 3:05Kelly Weinersmith?

  Oh, that's right, because you only eat dinner.

• 3:06Daniel Whiteson?

  Yeah, exactly.

• 3:07Kelly Weinersmith?

  What did you have for dinner last night? What are you?

• 3:12Kelly Weinersmith?

  What should I expect?

• 3:14Daniel Whiteson?

  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 burrata. We made a very fancy salad. I made a lemon butter almond tart.

• 3:28Kelly Weinersmith?

  Wow.

• 3:29Daniel Whiteson?

  Yeah, it was good.

• 3:30Kelly Weinersmith?

  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.

• 3:36Daniel Whiteson?

  Oh, and a couple of loaves of sourdough bread, of course.

• 3:39Kelly Weinersmith?

  Oh, fantastic.

• 3:40Daniel Whiteson?

  Got to have your carb. So yes, I'm chicken and bread today, I guess.

• 3:44Kelly Weinersmith?

  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 100 bucks, and you were betting, yes, there are microbes somewhere in our solar system, or no?

• 4:05Daniel Whiteson?

  In our solar system or in our galaxy?

• 4:07Kelly Weinersmith?

  In our solar system, 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?

• 4:19Daniel Whiteson?

  Oh, wow. Put a number on something we can't possibly know and then risk money on it.

• 4:25Kelly Weinersmith?

  I mean, you know, it's not a ton of money, but...

• 4:28Daniel Whiteson?

  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. It is not derived from Earth and like, you know, somehow kicked off via asteroid. Somewhere in our solar system, independently evolved, unique abiogenesis. Somewhere like, you know, one in a million, maybe. I think it's probably pretty unlikely. Somewhere in the galaxy, though, I'd put it like 98%.

• 4:59Kelly Weinersmith?

  Wow.

• 4:59Daniel Whiteson?

  Yeah.

• 5:00Kelly Weinersmith?

  Well, how many solar systems are in our galaxy?

• 5:03Daniel Whiteson?

  There's hundreds of billions of stars in the galaxy and so many planets around the star. So I just feel like that number is so big.

• 5:11Kelly Weinersmith?

  Yeah, those odds sound pretty good.

• 5:13Daniel Whiteson?

  Yeah. Are you gonna take my bet?

• 5:15Kelly Weinersmith?

  Oh.

• 5:21Daniel Whiteson?

  The rubber hits the road, people.

• 5:23Kelly Weinersmith?

  That's right. That's right. Can you tell I came up with this question right before I hit record?

• 5:29Kelly Weinersmith?

  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.

• 5:46Daniel Whiteson?

  Wait, does that mean I owe you $100 million if you find microbes on Mars?

• 5:51Kelly Weinersmith?

  Oh, oh, uh, no, let's just do, let's forget odds. Let's just do 100 bucks if you're right, 100 bucks if I'm right.

• 5:57Daniel Whiteson?

  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.

• 6:07Kelly Weinersmith?

  I know this is difficult for you, but, but we're just talking about microbes.

• 6:12Daniel Whiteson?

  Yeah, that's true.

• 6:14Kelly Weinersmith?

  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.

• 6:23Daniel Whiteson?

  Today, we're not talking about what's alive on Mars or in the oceans 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.

• 6:38Kelly Weinersmith?

  And how the heck did we figure that out, especially when the stuff is not on Earth?

• 6:44Daniel Whiteson?

  Yeah, exactly. And we've never left Earth, asterisk. We really did go to the moon, but it kind of counts as part of Earth.

• 6:50Kelly Weinersmith?

  Okay, but that definitely wasn't faking it, just to be clear.

• 6:52Daniel Whiteson?

  Just to be clear.

• 6:55Kelly Weinersmith?

  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 did, I, 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?

• 7:20Daniel Whiteson?

  If you would like to contribute your voice for future segments on the podcast, please don't be shy, write to us to [email protected]. We really, really love hearing from you.

• 7:30Speaker 05

  I think we know what the universe is made of due to spectroscopy.

• 7:34Speaker 06

  I don't think we definitively know what it's made of, but we probably speculated.

• 7:38Speaker 07

  I think scientists can extrapolate from what's in the earth.

• 7:42Speaker 05

  Lensing, light 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

• 7:53Speaker 06

  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. Like, yes, the universe is far away and out there, but if

• 8:18Daniel Whiteson?

  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. Spectrocity and gravity. We know by spectroscopy.

• 8:34Speaker 01

  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.

• 8:54Speaker 02

  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 up.

• 9:04Daniel Whiteson?

  Lot.

• 9:05Kelly Weinersmith?

  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.

• 9:16Daniel Whiteson?

  Yeah, that is a great answer. I also like the answers to frame the question much more broadly. When I wrote this, I was thinking about what elements the universe is made out of, like the atomic matter that 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. I wasn't

• 9:34Kelly Weinersmith?

  And the parasites.

• 9:35Daniel Whiteson?

  And the parasites, yes, exactly. I wasn't thinking more broadly, like dark matter, dark energy. So yeah, these are good answers.

• 9:43Kelly Weinersmith?

  Your question was underspecified.

• 9:45Daniel Whiteson?

  It was, yes. I should have said, how do we know what elements the universe is made out of?

• 9:51Kelly Weinersmith?

  That's right. We still got some fantastic answers. So what, let's start with how we figured out what elements the Earth is made out of. What tools do we use for that here?

• 10:00Daniel Whiteson?

  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.

• 10:39Kelly Weinersmith?

  Well, 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.

• 10:48Daniel Whiteson?

  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, when people were trying to figure out like, hey, what is the Earth made out of? There are basically three big questions that were asked. 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?

• 11:32Daniel Whiteson?

  Well, here on Earth, you 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.

• 11:45Kelly Weinersmith?

  This is apparently not a particularly famous eureka moment because I've never heard that story.

• 11:49Daniel Whiteson?

  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 its density lines up 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.

• 12:34Daniel Whiteson?

  And the story goes, probably apocryphally, that he leapt out of the bathtub, ran naked down the streets of Syracuse or Syracuse, shouting, eureka, eureka! And anyway, that's your famous ancient Greek nude story for the day.

• 12:46Kelly Weinersmith?

  Amazing. I, we should have more of those. But, okay, I hadn't heard that story. Thanks for sharing.

• 12:50Daniel Whiteson?

  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

• 13:30Daniel Whiteson?

  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.

• 13:45Kelly Weinersmith?

  That sounds complicated. And so how did they find two massive objects to do this with?

• 13:51Daniel Whiteson?

  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.

• 14:33Kelly Weinersmith?

  Okay, so there's one massive object.

• 14:36Daniel Whiteson?

  Yeah. So then they took a pendulum and they held it near the mountain and they measured whether it 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 measuring gravity between two things, neither of which are the earth.

• 14:56Kelly Weinersmith?

  That works.

• 14:57Daniel Whiteson?

  Yeah, 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 the earth is like almost twice the density of that mountain.

• 15:21Kelly Weinersmith?

  So this technique sounds incredibly complicated. How close did they get to the value that we believe it is today?

• 15:28Daniel Whiteson?

  They're within 20%.

• 15:29Kelly Weinersmith?

  Nice.

• 15:30Daniel Whiteson?

  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.

• 15:39Kelly Weinersmith?

  Yeah, no, that's amazing. I, you know, I feel like if you took five biologists in our field clothes 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.

• 15:49Daniel Whiteson?

  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 used torsion experiments, like balls hanging on strings that are very sensitive and measured their deflection as it got closer together, Cavendish, et cetera. There's a whole fun history there. People made these measurements very precisely to within, you know, less than 1%. So now we have a very accurate estimate of the earth's density.

• 16:30Kelly Weinersmith?

  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?

• 16:37Daniel Whiteson?

  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.

• 17:00Kelly Weinersmith?

  Not a giant open sphere with like dinosaurs hiding in it? Because that would have been cooler.

• 17:04Daniel Whiteson?

  Not a vast chasm filled with swarming parasites, for example.

• 17:07Kelly Weinersmith?

  Oh, my gosh.

• 17:09Daniel Whiteson?

  For most people, that's a nightmare. For you, that's heaven.

• 17:12Kelly Weinersmith?

  Now I'm so bummed out to know that this is the earth I exist on, but it could have been so much better.

• 17:19Daniel Whiteson?

  And people attacked 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. We already knew at this point, a couple hundred years ago, that the earth was 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.

• 17:59Kelly Weinersmith?

  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.

• 18:27Daniel Whiteson?

  Yeah, that's fair. And I'm about to give some credit to some chemists. So hold on to your hats.

• 18:31Kelly Weinersmith?

  Oh, oh, boy. I'm gonna get sour.

• 18:35Daniel Whiteson?

  People were wondering like, how long would it take the earth to cool? If you have 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, if 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.

• 19:19Daniel Whiteson?

  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.

• 19:27Kelly Weinersmith?

  Okay.

• 19:28Daniel Whiteson?

  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.

• 19:35Kelly Weinersmith?

  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?

• 19:50Daniel Whiteson?

  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 it 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 iterative, right?

• 20:21Kelly Weinersmith?

  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.

• 20:28Daniel Whiteson?

  Yeah, exactly. And now, of course, we know a lot more precisely how old the Earth is.

• 20:33Kelly Weinersmith?

  And when we get back from the break, we're going to hear all about that.

• 20:46Speaker 01

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• 23:58Kelly Weinersmith?

  All right, so Daniel 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?

• 24:14Daniel Whiteson?

  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.

• 24:39Kelly Weinersmith?

  And what is it about the zircon crystals? And why isn't there a watch company called zircon?

• 24:44Daniel Whiteson?

  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.

• 25:27Kelly Weinersmith?

  That's amazing!

• 25:28Daniel Whiteson?

  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, there's 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.

• 25:51Kelly Weinersmith?

  Wow.

• 25:52Daniel Whiteson?

  And so anyway, another chemist who saved us all.

• 25:55Kelly Weinersmith?

  What 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.

• 26:04Daniel Whiteson?

  Another argument for funding basic science, people.

• 26:06Kelly Weinersmith?

  Amen.

• 26:07Daniel Whiteson?

  You never know what you're going to discover.

• 26:09Kelly Weinersmith?

  It's so important.

• 26:10Daniel Whiteson?

  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.

• 26:20Kelly Weinersmith?

  Oh, my gosh, and that's pretty close to our current estimate, isn't it?

• 26:24Daniel Whiteson?

  Yeah, exactly.

• 26:25Kelly Weinersmith?

  That's amazing.

• 26:25Daniel Whiteson?

  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? What 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.

• 26:56Kelly Weinersmith?

  Awesome. We're getting away from chemistry. Phew.

• 27:00Kelly Weinersmith?

  Back to the rock, people.

• 27:02Daniel Whiteson?

  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 like 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.

• 27:46Daniel Whiteson?

  It's sort of like a sonogram, right? Or an ultrasound.

• 27:49Kelly Weinersmith?

  That, that is absolutely amazing. And just like parents like to brag about their kids, I 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 like 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, 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 seems like there's a big difference between saying something changed or something changed and I understand what that means.

• 28:31Daniel Whiteson?

  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 like 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. Wow. So that's what's crucial is having this like 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 Mars quakes and understand what's going on inside the Martian

• 29:13Daniel Whiteson?

  core, 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.

• 29:51Kelly Weinersmith?

  And so this is how we figured out that the core is mostly nickel and lead, not lead, iron.

• 29:56Daniel Whiteson?

  Nickel and iron.

• 29:56Kelly Weinersmith?

  Nickel and iron. Got it.

• 29:58Daniel Whiteson?

  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.

• 30:18Kelly Weinersmith?

  Well, okay, so that's not a lot of nickel. So it's mostly iron and oxygen.

• 30:23Daniel Whiteson?

  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 we 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.

• 30:42Kelly Weinersmith?

  I'm glad there was some leftover for us.

• 30:44Daniel Whiteson?

  Yeah, because oxygen is so reactive. So that gives us a sense for what our scoop of the universe is made out 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?

• 31:06Kelly Weinersmith?

  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?

• 31:18Daniel Whiteson?

  Yeah, exactly. And of course, we 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.

• 31:52Kelly Weinersmith?

  Or the age, right? We decided we needed to know age, too.

• 31:55Daniel Whiteson?

  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.

• 32:18Kelly Weinersmith?

  Wow.

• 32:18Daniel Whiteson?

  Which is like 10 quadrillion times the amount of power released by the most energetic power plants ever constructed on earth.

• 32:26Kelly Weinersmith?

  Wow.

• 32:26Daniel Whiteson?

  It's just, we are sipping from an ocean of energy here. That's just like being blasted out into space.

• 32:33Kelly Weinersmith?

  And it powers our whole planet.

• 32:34Daniel Whiteson?

  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.

• 33:02Kelly Weinersmith?

  Would I, I guess I'd, 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.

• 33:08Daniel Whiteson?

  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.

• 33:26Kelly Weinersmith?

  One of my favorite stories along this line is there was a guy who studied vaccines. His name was Sir Right, 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. And, uh, all right, anyway, tangent complete. Where were we?

• 33:48Daniel Whiteson?

  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? You know, and that would, and that would tell you like, oh, maybe the sun is a huge ball of gasoline, basically. Or a kerosene.

• 34:07Kelly Weinersmith?

  Don't run out.

• 34:08Daniel Whiteson?

  So if you do the calculation, given 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.

• 34:17Kelly Weinersmith?

  Why?

• 34:18Daniel Whiteson?

  Because chemical burning is very inefficient. Like, most of the energy in mass is not released when you just like change the chemical state from one to another. Whereas, you know, 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 like 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.

• 34:48Kelly Weinersmith?

  All right. It's not logs on a fire, so how did we figure out what it was?

• 34:52Daniel Whiteson?

  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?

• 35:06Kelly Weinersmith?

  Yeah.

• 35:07Daniel Whiteson?

  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 dwarfs that are not undergoing fusion. They're just like being compressed and kept hot by gravity.

• 35:49Kelly Weinersmith?

  Was this Kelvin's idea?

• 35:51Daniel Whiteson?

  All these.

• 35:51Kelly Weinersmith?

  Because it matches up with his other, or all of these were Kelvin's?

• 35:54Daniel Whiteson?

  These are Kelvin's ideas. Yeah, this is Kelvin, like, you know, smoking whatever he was smoking and thinking about the universe and coming up with numbers.

• 36:01Kelly Weinersmith?

  Okay.

• 36:01Daniel Whiteson?

  I love it. I'm a fan of Kelvin.

• 36:02Kelly Weinersmith?

  Yeah, he sounds like a fun guy. And I think it would have been fun to read your theories about, about this kind of stuff. And then I could have called you not quite right, Sin.

• 36:11Daniel Whiteson?

  Oh, nice.

• 36:14Daniel Whiteson?

  Daniel Rongson. Daniel first, but terrible approximation of the answer. And.

• 36:20Kelly Weinersmith?

  That doesn't roll off the tongue quite as nicely. But, okay, what else did Kelvin think?

• 36:24Daniel Whiteson?

  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, 100 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's the time to enter the major villain of this story. Henry Russell.

• 37:10Daniel Whiteson?

  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 spectra 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 heated up the earth, it would glow just like the sun.

• 37:34Kelly Weinersmith?

  So that sounds wrong, but not villainous. Are we going to get to more? Or do you just really thought this idea was dumb?

• 37:41Daniel Whiteson?

  That's not his villainy. That was just foreshadowing.

• 37:43Kelly Weinersmith?

  Oh, okay. Let's take a break and when we come back, we'll find out what made Russell villainous.

• 37:59Speaker 01

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• 38:18Speaker 06

  My first ever in the world show was when I was 10 and I sang at a pub called The Georgian Devonshire. I was so nervous. I was tense. So they let me in only to sing my song and then they kicked me out right after. And then I remember I wrote, I've been writing since I was 10. So I, I wrote this song called Lady in the Mirror. Made this little track with it. But I just like pressed it. And I remember I sang this song and there was like five people in there. And I remember how myself I felt. And I felt like I understood myself and understood what I needed to do.

• 38:44Speaker 01

  So does that take us back to, I sing just to know I'm alive?

• 38:48Speaker 06

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• 38:51Speaker 01

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• 40:54Kelly Weinersmith?

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• 41:10Kelly Weinersmith?

  All right, Daniel, I'm on pins and needles. Let's get to the story of why Russell was such a villain.

• 41:15Daniel Whiteson?

  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

• 41:59Daniel Whiteson?

  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.

• 42:32Kelly Weinersmith?

  But he didn't develop spectroscopy, right? He just applied it incorrectly?

• 42:37Daniel Whiteson?

  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..." 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 it. 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 use that to figure out what the sun is made of? 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 get so much energy, they lose electrons. It's not just like, oh, you've got oxygen, it has all of its electrons, and they're going up and down and emitting photons, so we can tell it's oxygen.

• 43:21Daniel Whiteson?

  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.

• 43:42Kelly Weinersmith?

  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?

• 43:49Daniel Whiteson?

  The spectroscopy results from the sun, nobody could understand yet.

• 43:52Kelly Weinersmith?

  Okay.

• 43:52Daniel Whiteson?

  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 that 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.

• 44:09Kelly Weinersmith?

  Yay!

• 44:10Daniel Whiteson?

  Cecilia Payne. Cecilia Payne is the one who solved this problem. She read a paper by a brilliant guy named Meghna D. Saha, who understood all these ionization effects. He like 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.

• 44:55Kelly Weinersmith?

  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.

• 45:03Daniel Whiteson?

  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 Payne. Number one, the sun is made out of the same stuff as the earth. Like, there's hydrogen, there's helium, there's oxygen, there's iron, there's nickel, there's 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%.

• 45:40Kelly Weinersmith?

  Wow.

• 45:41Daniel Whiteson?

  Yeah.

• 45:41Kelly Weinersmith?

  All right. And so I'm just gonna 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 probably did something to turf Payne's results. Am I right?

• 45:54Daniel Whiteson?

  Oh, absolutely.

• 45:55Kelly Weinersmith?

  Okay.

• 45:56Daniel Whiteson?

  So she was at Harvard, and the director of the observatory was Russell. 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 PhD 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 from these elements in the atmosphere is almost certainly not real."

• 46:28Kelly Weinersmith?

  What? He had her add a caveat that was like, but also probably I'm wrong?

• 46:32Daniel Whiteson?

  Yes. 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.

• 46:40Kelly Weinersmith?

  Oh, my gosh. And what a coward that he did. It sounds like he didn't point out exactly where she had an error, right? Like, cuz...

• 46:48Daniel Whiteson?

  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 gonna insist that you add this caveat to her thesis. Now, her advisor was a guy named Harlow Shapley, and Shapley ordered- Six hundred copies of her thesis and sent it to all the important astronomers in the world.

• 47:09Kelly Weinersmith?

  Oh, wow. Okay, so he believed in her.

• 47:11Daniel Whiteson?

  He believed in her. Yeah.

• 47:12Kelly Weinersmith?

  Did he go through all 600 copies and like cross out that line that she had to add?

• 47:18Daniel Whiteson?

  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.

• 47:37Kelly Weinersmith?

  No.

• 47:38Daniel Whiteson?

  Yes, exactly. And so in most historical records, until recently, people gave Henry Russell credit for the discovery of what the sun is made out of, which is like such a tragedy.

• 47:49Kelly Weinersmith?

  Villainous. I agree.

• 47:50Daniel Whiteson?

  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.

• 48:00Kelly Weinersmith?

  It is a real shame. Okay, so then how did we rediscover Cecilia Payne then?

• 48:04Daniel Whiteson?

  Yeah, that's an important point. Cecilia Payne ended up getting her PhD in astronomy, only the second PhD in astronomy ever by a woman at Harvard.

• 48:11Kelly Weinersmith?

  Wow.

• 48:12Daniel Whiteson?

  And initially she was barred from becoming a professor at Harvard because she was a 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.

• 48:23Kelly Weinersmith?

  Whoa.

• 48:23Daniel Whiteson?

  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, quote, "Undoubtedly the most brilliant PhD thesis ever written in astronomy."

• 48:44Kelly Weinersmith?

  Wow.

• 48:45Daniel Whiteson?

  Wow.

• 48:45Kelly Weinersmith?

  That's nice. That's a big turnaround.

• 48:47Daniel Whiteson?

  That's 40 years later. She went 40 years before really getting the recognition.

• 48:52Kelly Weinersmith?

  Was she still alive?

• 48:53Daniel Whiteson?

  Yeah, she was still alive. She died in 79.

• 48:56Kelly Weinersmith?

  I'm glad she got to see her work vindicated in her lifetime. That's amazing.

• 48:59Daniel Whiteson?

  Yeah, 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.

• 49:08Kelly Weinersmith?

  I mean, often, but not always.

• 49:11Daniel Whiteson?

  Eventually, I hope.

• 49:12Kelly Weinersmith?

  Yes.

• 49:13Daniel Whiteson?

  But Cecilia Payne taught us a lot of. About the nature of the universe, right? People thought for a long time that everything in the universe must be made of the same stuff as the earth. Like, 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 stuff 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 and the planets, and we can apply this knowledge to understanding other stars.

• 49:57Daniel Whiteson?

  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.

• 50:16Kelly Weinersmith?

  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.

• 50:25Daniel Whiteson?

  Yeah, exactly. Thanks to Cecilia Payne and to Meghna 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 figure this out. I mean, think about all the little puzzles that people had to solve, all the way down to like 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.

• 51:10Daniel Whiteson?

  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?

• 51:26Kelly Weinersmith?

  Amen. By geeking out, and by geeking out together, we can change the world.

• 51:33Daniel Whiteson?

  All right. Thanks very much for coming on this tour of how we figured out what elements the universe is made of, diving deep into the earth and casting our minds all the way across the universe.

• 51:49Kelly Weinersmith?

  Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio. We would love to hear from you.

• 51:54Daniel Whiteson?

  We really would. We want to know what questions you have about this extraordinary universe.

• 52:01Kelly Weinersmith?

  We want to know your thoughts on recent shows, suggestions for future shows. If you contact us, we will get back to you.

• 52:07Daniel Whiteson?

  We really mean it. We answer every message. Email us at [email protected].

• 52:14Kelly Weinersmith?

  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 and K Universe.

• 52:23Daniel Whiteson?

  Don't be shy. Write to us.

• 52:27Speaker 02

  With ChatGPT, you can do more than get answers. You can get things done. Whether you're leading a big project, planning an elaborate trip, or trying to balance work and life, ChatGPT can help. Give it a goal, plus things like files, notes, or project plans, develop a trip itinerary with daily updates, or create a prioritized schedule, so you can spend less energy sorting out the details and more on bringing your biggest ideas to life. Get started at chatgpt.com. Are you looking for support in your weight management journey? Zepbound terzepatide may be able to help. Zepbound is a prescription medicine used with a reduced calorie diet and increased physical activity to help adults with obesity, or some adults with overweight

• 53:10Speaker 02

  who also have weight-related medical problems, to lose excess body weight and keep the weight off. Zepbound is approved as a 2.5, 5, 7.5, 10, 12.5, or 15-milligram injection. Zepbound contains terzepatide and should not be used with other terzepatide-containing products or any GLP-1 receptor agonist medicines. It is not known if Zepbound is safe and effective for use in children. Don't share needles or pens or reuse needles. Don't take if allergic to it, or if you or someone in your family had medullary thyroid cancer. Or if you've had multiple endocrine neoplasia syndrome type 2. Tell your doctor if you get a lump or swelling in your neck. Stop ZepBound and call your doctor if you have severe stomach pain or a serious allergic reaction.

• 53:53Speaker 02

  Severe side effects may include inflamed pancreas or gallbladder problems. Tell your doctor if you experience vision changes before scheduled procedures with anesthesia. If you're nursing, pregnant, plan to be, or taking birth control pills. Taking ZepBound with a sulfonalurea or insulin may cause low blood sugar. Side effects include nausea, diarrhea, and vomiting, which can cause dehydration and worsen kidney problems. Talk to your doctor. Call 1-800-545-5979, or visit zepboundslily.com.

• 54:25Speaker 02

  This is an iHeart Podcast. Guaranteed Human.