This Glass Was Made By Lightning

Could a bolt of lightning become a permanent geological relic? How small would you have to squash a hamster to turn it into a black hole? Professor Hannah Fry and Michael Stevens dismantle our perceptions of scale and texture, moving from the glassy "fulgurites" forged in sandy soil to the mathematical threshold of the Schwarzschild radius. They explore the counter-intuitive geometry of the Earth, calculate the extreme density required to collapse domestic life into a gravitational singularity and examining the crystalline remains of atmospheric discharge. This is an investigation into the smooth, the sharp, and the impossibly dense, proving that the world we touch is rarely as it seems. ------------------- For more information about Cancer Research UK, their research, breakthroughs and how you can support them, visit ⁠⁠https://cancerresearchuk.org/restisscience⁠⁠ Cancer Research UK is a registered charity in England and Wales (1089464), Scotland (SC041666), the Isle of Man (1103) and Jersey (247). A company limited by guarantee. Registered company in England and Wales (4325234) and the Isle of Man (5713F). Registered address: 2 Redman Place, London, E20 1JQ. ------------------- Find The Rest Is Science all over the internet by ⁠⁠clicking here.⁠⁠ ------------------- Video Producer: Adam Thornton + Oli OakleyVideo & Social: Bex TyrrellAssistant Producer: Imee MarriottProducer: Becki HillsSenior Producer: Lauren Armstrong-CarterHead Of Digital: Samuel OakleyExec Producer: Neil Fearn Learn more about your ad choices. Visit podcastchoices.com/adchoices

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

• 0:00Hannah Fry?

  This episode is brought to you by Cancer Research UK.

• 0:02Michael Stevens?

  So when most people think of naked mole rats, their unusual relationship to cancer probably isn't the first thing that comes to mind.

• 0:10Hannah Fry?

  But maybe it should be because it is incredibly rare for them to develop cancer, which could be partly down to their unique immune system, or it might be the way that their cells respond to damage.

• 0:22Michael Stevens?

  So scientists are studying their biology for its cancer-fighting secrets. It's a reminder that discoveries can sometimes come from places you don't expect.

• 0:31Hannah Fry?

  Cancer Research UK is the world's largest charitable funder of cancer research. Thousands of scientists, of doctors and nurses, work across more than 20 countries to help turn discoveries in the lab into new tests, new treatments and new innovations.

• 0:46Michael Stevens?

  And the impact is clear. Over the past 50 years, the charity's pioneering work has helped double cancer survival in the UK, meaning more people living longer, better lives, free from the fear of cancer.

• 0:59Hannah Fry?

  For more information about Cancer Research UK, their research, their breakthroughs and how you can support them, visit cancerresearchuk.org/restiscience.

• 1:10Speaker 02

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• 2:40Speaker 03

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• 3:16Hannah Fry?

  Welcome to The Rest of Science. This is Field Notes. This is a kind of podcast expedition diary where Michael and I are going to trade the curious objects or thoughts or sometimes feelings that are occupying our minds.

• 3:29Michael Stevens?

  And we'll answer the strange questions that are troubling yours.

• 3:33Hannah Fry?

  Mm hmm. Because every week, one of us is going to bring sort of strange, spectacular object or story onto the show. And together, we're going to see what kind of uncharted territory it takes us to.

• 3:43Michael Stevens?

  But we want to hear your questions, your theories and your thought experiments, too. So send them in and stay tuned to see where we end up.

• 3:50Hannah Fry?

  Yes. Now, later today, I'm going to be showing off a very rare physical monument of something we only ever experience as a split second flash. That's my hook and tease for you, Michael.

• 4:04Michael Stevens?

  Ooh, that's a good hook.

• 4:07Hannah Fry?

  I know. Any guesses so far?

• 4:09Michael Stevens?

  Uh, is it like how photons travel?

• 4:12Hannah Fry?

  I mean, there's photons involved, but you've got to, you've got to stay tuned for the second half. If you, uh, if you, if you want to find out more. Um, but for this first half, what we thought we'd do is we would dive into our mailbag. Um, as ever, you can send us your questions. You can send us your own objects, your own thoughts and sometimes feelings. Um, but our first question to say, uh, Madav has got a question. This I think is one for you, Michael. Why do mirrors flip us horizontally but not vertically?

• 4:40Michael Stevens?

  Yeah, that's a great question. I've done a whole bunch of videos and TikToks about mirrors. And it is weird. How come when I approach a mirror, my right hand is on the left side and vice versa. But my head isn't where my feet should be. Why is it just doing this horizontally? And of course, the answer is it's not flipping you horizontally. It's flipping you inside out. Everything that you present to a mirror gets reflected right back. When you, when you, when you look at like a letter R, you're like, yeah, that looks normal. But then you turn it to the mirror. You were the one who flipped it horizontally. You turned it and it's just getting sent right back to you.

• 5:20Hannah Fry?

  But also, if you lie down, it still knows that your left hand and your right hand and where your feet are. Like if you make yourself horizontal, right? Then it start, then it suddenly flip flips vertical, suddenly makes your left hand, your right hand. But your head is not switched with your feet.

• 5:35Michael Stevens?

  Yeah.

• 5:36Hannah Fry?

  So it's like, how does it know? How does it know that to only ever flip what's horizontal to you?

• 5:42Michael Stevens?

  That's right. Yeah. If I turn the mirror, it continues this horizontal reversing. If I put myself upside down, it continues the horizontal reversing. Words are reversed right to left. They're not reversed vertically. They're not flipped over. And the answer is that the mirror isn't flipping anything. You are. You see, all mirrors do is give back exactly what hits them. And when I Say have some text on my notepad and it looks normal. And then I turn it to a mirror. I'm the one who just turned it. Now it's as though I'm looking through the paper because that letter is hitting the mirror. And it's coming back to me without being changed.

• 6:26Hannah Fry?

  Because if you'd written on a piece of tracing paper and were holding it up and looking through the tracing paper, you would see exactly what is reflected back at you in the mirror. That would be it would be unchanged. The sort of the backside of the of the tracing paper and what you're seeing in the mirror.

• 6:40Michael Stevens?

  That's right. And so another way this has been explained is that mirrors actually flip things inside out. All right, you can think of it this way. When you look in a mirror, the closest thing to the mirror becomes the closest thing to you in the mirror image. So if my nose is closest to the mirror because I'm facing it, then that means that in my mirror reflection, the nose will be closer to me. And the back of my head is behind my nose. So I've been pushed, literally my back and my front have been pushed through each other, seemingly, apparently. And now I'm looking at myself squished inside out.

• 7:15Hannah Fry?

  You know, like those little suckers that you get that's sort of a stable and then you can pop them inside out. It's a bit like that, right? It's like the mirror is doing that to you as a human. It's sort of like grabbing you by the nose and like popping you inside out.

• 7:28Michael Stevens?

  That's right. So top and bottom stay on the same axis. Right and left stay on the same axis. It's just that now the front and the back are in different orientations relative to left and right. And so we think, well, if I froze my mirror image and walked around to join it, to face in the same direction, it would be reversed. But no, no, no. You have reversed yourself by turning around to join it and face the other way.

• 7:55Hannah Fry?

  I love that question. I mean, in general, I just really love like thinking very hard and long about things that feel like they should be obvious and then getting really confused.

• 8:06Hannah Fry?

  Great question. Absolutely great question.

• 8:08Michael Stevens?

  Let's move on to a question from Brandon, who asks, how dense would a hamster have to be to become a black hole?

• 8:15Hannah Fry?

  Okay, I cannot tell you how much fun I had this afternoon doing the calculations for this, because the answer is actually quite surprising, I think. Okay, so I looked up the average weight of a hamster. I've gone for, if you're interested, a chubby Syrian hamster, 150 grams, that's their general weight. If you wanted to turn one of those into a black hole, the problem is that you have to shrink it down to be so small that it's not just about squishing it, it's about obliterating the concept of space within it. Okay, so

• 8:47Michael Stevens?

  Excellent.

• 8:48Hannah Fry?

  Here is the sort of breakdown, right? The sparse child radius, this is a calculation, it's an equation that tells you how wide something needs to be before essentially it becomes a black hole, before it's, the density becomes so great that it becomes a black hole. So when you run the calculation for a hamster at 0.15 kilograms, you work out that the sparse child radius is 2.2 times 10 to the minus 28 meters, okay, which is, I'm gonna say it, small. To put that into perspective, a proton is 10 to the minus 15 meters.

• 9:25Michael Stevens?

  Oh no, so you've got to squish all the hamster's mass into a volume smaller than a proton?

• 9:32Hannah Fry?

  Oh yeah, I mean, like, size of atoms, forget it, that's like gigantically vast in comparison to the size this hamster's got to get down. It's got to be, it's got to be 10 trillion times smaller than a single proton, which, if you want to put that in perspective, it's the hamster is to a proton, at the moment, what a grain of sand is to the entire Earth, basically, right? It's going to be so small. So, okay, then the consequence of what happens when you do that is phenomenal.

• 10:02Michael Stevens?

  Does it hurt the hamster?

• 10:04Hannah Fry?

  I don't think, I think we've got a sort of Honey I Shrunk the Kids type smallizer machine.

• 10:10Michael Stevens?

  Okay, I love it, I love it, yeah, good.

• 10:12Hannah Fry?

  Hamster miniizer machine, I think the hamster's fine.

• 10:14Michael Stevens?

  Imagine that, and the hamster is fine the whole time, it just like starts to realise, hey, my gravitational force is getting stronger. I've become a black hole, dang it!

• 10:24Hannah Fry?

  Damn it. Okay, I'm gonna tell you, the hamster is fine. Spoiler alert, not everyone else is. Bear with me for a second, because here's the thing, right? The density, we know what the hamster weighs, it's 150 grams of like fur and cheeks, but it's now squished into this subatomic spec, which means the density that's required is 3.3 times 10 to the 81 kilograms per meter cube, okay? People can check my calculations on this if you like. But just to visualize that, that sort of crunch. Water, 1,000 kilograms per meter cube. Steel, 8,000. The core of the sun, 150,000.

• 11:04Hannah Fry?

  A neutron star, which is the most densest object in the entire universe, is 10 to the 17 kilograms per meter cube. Our hamster, remember, 10 to the 81, okay? So basically, it needs to be, I mean, many, many, many, many, many gazillions denser than a neutron star for this to work.

• 11:27Michael Stevens?

  Well, sure, I mean, we're trying to make a black hole, like, it's gotta be denser than any regular matter.

• 11:32Hannah Fry?

  Sure, but this is like even denser than that, even denser than that. And, and the problem is, is that, okay, according to Hawking radiation, little black holes will evaporate over time. But this tiny little hamster black hole is gonna be so unstable that it will probably only last for about, about 10 to the minus 26 seconds, right? So really, I mean, it barely exists. But what, what that means is that, once it's down to this tiny size, it instantly converts its entire mass of, you know, 150 grams, back into pure energy, right? And E equals mc squared.

• 12:10Michael Stevens?

  Ouch.

• 12:11Hannah Fry?

  So what this means is, the moment that you finish miniaturizing your hamster... It would detonate and the energy released would be about 3.2 megatons of TNT, which is about 200 times more powerful than the atomic bomb dropped in Hiroshima.

• 12:27Michael Stevens?

  Yeah.

• 12:27Hannah Fry?

  So, I mean, you can, if you want to, Brandon, but I would say don't.

• 12:33Michael Stevens?

  Wow. If you turned your hamster into a black hole, you would create a nuclear bomb.

• 12:39Hannah Fry?

  Probably be at least the end of the country you're in, if not wider. There'd be a nuclear winter that would wipe out much of the planet, I imagine.

• 12:48Michael Stevens?

  Now, this hamster, during its tiny fraction of a second that it's a black hole, it will at least be free. It'll be able to leave its cage.

• 12:56Hannah Fry?

  Yeah. Look, I think when people try and say that that one small creature cannot make a difference, I think this is evidence to the contrary.

• 13:05Michael Stevens?

  It depends how you define can.

• 13:09Michael Stevens?

  Look, I can imagine some oppressed hamster saying, "One of these days I will compress my mass into a size smaller than a proton, and then you'll all be sorry."

• 13:18Hannah Fry?

  You'll all be sorry. Hey, you know what? I think we've just found a new plot for a new Pixar film.

• 13:24Michael Stevens?

  Yeah, The Hamster Who Became a Black Hole.

• 13:27Hannah Fry?

  Yeah.

• 13:28Michael Stevens?

  Copyright The Rest Is Science 2026.

• 13:31Hannah Fry?

  Do right. Okay, speaking of shrinking objects down, I've got another question for you, Michael. This one's from Edward. He asks, "I've heard that if the Earth was shrunk down to the size of a pool ball, it would be smoother than any other man-made object. Is this true?" I mean, first of all, wouldn't be enough, wouldn't be small enough to be a black hole.

• 13:50Michael Stevens?

  No, it wouldn't. The Earth's Schwarzschild radius is, funny enough, I actually literally have it right here.

• 13:56Hannah Fry?

  Yeah, we'd have this in gravity, right?

• 13:58Michael Stevens?

  It'd be about, like, I think 0.8 centimeters. Yeah, so if all of Earth's mass existed in this volume... You could be so close to all that mass that even light couldn't escape. But if we're just shrinking it down to the size of a pool ball, I mean, we're still talking about something dangerous. Denser than a neutron star, but not quite able to capture light. I think light could be, you know, very bent by it. But um, here's to answer your question, Edward, it would not be particularly smooth. In fact, the earth squeezed down to the size of a pool ball would be about as rough as 320 grit sandpaper.

• 14:38Michael Stevens?

  So the next time you're at a hardware store, find the 320 grit and feel that that's what a giant would feel if they grasped earth. Now, the myth that the earth is smoother than a pool ball comes from a misreading of the International Pool Association's rules. I don't know if that's the actual governing body, but they say a pool ball must be built with a diameter of 2.25 inches plus or minus 0.005 inches. All right, so that's, that's 5 thousandths of an inch. And people have taken that to mean that a pool ball can have craters and bumps that are 5 thousandths of an inch.

• 15:22Michael Stevens?

  And at the scale of earth, that would mean 28 kilometer high mountains and trenches. So obviously, the earth is smoother than a pool ball.

• 15:34Hannah Fry?

  My.

• 15:35Michael Stevens?

  But that's not what the regulation means. The regulation isn't telling us about the texture. It's telling us about the spherical nature of the ball, how off, how oblate it can be. And so the, um, if you actually look at real pool balls, they have like sub micron scratches on them for real. Like a really well-used, quite scuffed up pool ball is going to have these little tiny scratches that you can see under a microscope. And they correspond to bumps and crannies that are actually much smaller than the Marianas Trench on earth or Mount Everest would be at that scale.

• 16:18Michael Stevens?

  So, sorry to say, the earth is not smoother than a pool ball. It is as smooth as 320 grit sandpaper, which I'm trying to think of things in real life that would feel that way. I think maybe like-

• 16:31Hannah Fry?

  Well, where is, where is 320 on the spectrum? From like, if you start off with, uh, with, you know, the coarsest of all, where you're like, just trying to get the surface down, what number's that?

• 16:42Michael Stevens?

  If you're trying to like, remove material, you're using an extra coarse sandpaper that could be like a 24, a 30, a 36. These things are like hilarious. It's almost like a saw, a piece of paper that's a saw. These are all macro grit sandpaper. You look at it and it looks like someone glued a bunch of rocks to some paper. But when you get into the, the, they call them micro grit sandpapers, very fine ones are about 240 grit. Um, but for earth's texture, we need extra fine.

• 17:12Hannah Fry?

  Okay.

• 17:13Michael Stevens?

  Between 320 and 360. So those are going to be, um, you know, used for wood polishing, uh, to, to initiate polishing. The idea that a pool ball can have these 5,000th sized pits and craters, that's describing 120 grit, which is one of those, like, it's very, that's, that'd be fine. That can't even remove varnish or paint on wood, it's so fine. But that's not earth.

• 17:38Hannah Fry?

  All right. Okay. So this is sort of somewhere in the middle. So, I mean, if you sort of run your finger along it, along this sandpaper, you're, you're, you know, it's not like your finger is sort of getting stuck as you're going. It's like you can run your finger across it. It's just, you can also feel that it's not perfectly smooth.

• 17:53Michael Stevens?

  Yes. You would say, wow, this is not smooth, for sure.

• 17:57Hannah Fry?

  Right. Cause the other one I've heard is that, um, is about the fingerprint. Have you heard this one?

• 18:04Michael Stevens?

  What's this one?

• 18:05Hannah Fry?

  That if you shrunk the earth down to the size of a pool ball and a giant held it in their hand, um, then the craters and peaks of their fingerprint would be greater. I, I mean, I was just making some quite strong assumptions about the, uh, the biological, um, surface of, of this giant and the fingertips of this giant, but that the craters in your fingerprint are greater than you see on earth.

• 18:31Michael Stevens?

  Yes. This is the thing. These are the numbers that I think you might've wanted. That, that hu- human fingers can feel objects as small as 13 nanometers.

• 18:42Hannah Fry?

  Really?

• 18:43Michael Stevens?

  We are incredibly sensitive to the like the vibrations caused by touching an object like that, which means that if your finger was the size of the earth, you could touch the earth and feel the difference between a house and a car.

• 19:01Hannah Fry?

  No.

• 19:02Michael Stevens?

  Our sense of touch is a miracle. It blows your mind.

• 19:07Hannah Fry?

  Wow.

• 19:08Michael Stevens?

  Yeah.

• 19:08Hannah Fry?

  That's incredible. I'm just sorry. I'm just feeling these scratches on my table just to see like the the you're right, you know, they're like really tiny little scratches. You can actually feel them.

• 19:19Michael Stevens?

  Yeah, and we might not be able to count the scratches, but we can tell between two different surfaces how they feel and that one's different than the other because of sub-microscopic texture differences. So a house and a car on the earth to a giant whose finger was as big as the planet, it would feel different. They'd be like, oh, that's a parking lot. Oh, there's no buildings here. They would be able to tell.

• 19:45Hannah Fry?

  Oh, Buckingham Palace.

• 19:47Michael Stevens?

  This whole this whole earth is smoother than a pool ball nonsense? Come on, let's grow up. Earth is is bumpy. It's it's it's bumpiness deserves some credit.

• 19:57Hannah Fry?

  Stop doing that, internet. Okay, well, we've got some bumpiness for you in the in the second half of this because boy, have I got a an object for you. We'll be back right after this break.

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• 22:23Hannah Fry?

  And we're back. Uh, now, Michael, can you describe what I am holding in my hand?

• 22:31Michael Stevens?

  Um, it looks like a short twig.

• 22:35Hannah Fry?

  Yes, it does.

• 22:36Michael Stevens?

  A very bumpy, stick-colored stick.

• 22:41Hannah Fry?

  I've got another one here.

• 22:43Michael Stevens?

  Oh, and now you've just pulled up a shorter one. It looks like petrified wood, like a petrified twig, because it's sort of grayish-brown and rough. It looks very organic. Again, it's, it's only about as long as a pinky finger, slightly bumpy and gray and brown. It might be hollow.

• 23:03Hannah Fry?

  You are right. It is. It's, uh, so I deliberately showed you this side because, oh my God, my nails are so bad, we could not put them on.

• 23:10Michael Stevens?

  I was going to say, Hannah, I cannot believe those nails.

• 23:15Hannah Fry?

  Uh, you know, I know you're being sarcastic, but you, you would not believe the amount of criticism that will come my way.

• 23:24Michael Stevens?

  I'm saying it so that they don't. I'm stealing their thunder. Nails, more like snails. I don't know, but does that make sense?

• 23:33Hannah Fry?

  So right, you are absolutely right that it's like, it's about the, the length of a pinky finger. It's very knobbly, it's brown, it doesn't look very interesting at all. You would walk past this lying on the ground and not notice it at all. But if I turn it around, this might give you a slightly better clue because on the other side, you can see that it's hollow and inside it has this glassy texture.

• 23:53Michael Stevens?

  Oh, like a geode almost.

• 23:55Hannah Fry?

  Almost, almost. And it feels, it feels like glass.

• 24:01Michael Stevens?

  Oh, yeah. I can hear you banging it on your table and it sounds like a piece of fine porcelain.

• 24:07Hannah Fry?

  It does indeed. Okay, here is, uh, here is my big reveal. What I am holding in my hand is fossilized lightning.

• 24:15Michael Stevens?

  Oh, wow.

• 24:16Hannah Fry?

  Isn't that cool? So what happens is that lightning, often, you know, millions of years ago, but you can, I mean, all basically throughout the entire history of, of the earth. Lightning hits sand. Okay, can you see that one? This one's a bit clearer, I think.

• 24:32Michael Stevens?

  And it turns it to glass.

• 24:34Hannah Fry?

  And it turns it to glass, yes. Because what happens is, I mean, if you imagine having a bucket of sand and like shining a mega powerful laser in there, then, then any sand that's touching the laser will just like instantly melt into goo. The goo then sort of like cools down into this, this hollow tube of glass, but the very middle of it doesn't just melt, it actually vaporizes. Where the, where the lightning hits the center of this, it will actually vaporize. So you have this, this hollow tube, this hollow glass tube. And, and then what happens is that the sort of gas from the vaporized sand expands outwards, creating this, this, this, basically this glass straw, right? Isn't that cool?

• 25:13Michael Stevens?

  Yeah, okay, right. So it's so hot in the middle, it turns not into a liquid, into a goo, but into a gas.

• 25:21Hannah Fry?

  Yeah.

• 25:21Michael Stevens?

  Glass gas.

• 25:23Hannah Fry?

  Glass gas, exactly. And what is amazing about these things, okay, so, so Darwin in particular, he was obsessed by these, they're called folgrites, by the way. They're really cheap. I got these on eBay, they're like nine, 10 quid. I mean, there's like, there's loads of them. They're not like, you know, you're not going to find this on a walk in Epping Forest, you know, like, you've got to go to the right part of the world to see a lot of these. But like, across the world, there's a lot of them because there is a lot of lightning that's happening at any moment in time.

• 25:54Michael Stevens?

  Yeah.

• 25:54Hannah Fry?

  Um, in fact, actually, there is a really brilliant website, which is called Blitzortung.org, where you can see it's a live map of where lightning is striking across the world. It comes with sounds as well.

• 26:09Michael Stevens?

  So it plays a sound for every lightning strike that occurs on Earth in in real time?

• 26:14Hannah Fry?

  In real time, exactly. And there's way more lightning going on than you would imagine. I mean, right now, there's a little pocket going on in southern, uh, southern Europe, loads across Australia, a big band, essentially by the equator is where you get lots and lots of it, almost very rarely get lightning at the poles.

• 26:32Michael Stevens?

  Yeah.

• 26:33Hannah Fry?

  And one of the theories about that, by the way, is that it's cosmic rays that give the sort of potential to, uh, in order to to sort of trigger off a lightning strike where you get some some potential difference in clouds.

• 26:45Michael Stevens?

  Oh, no kidding. Cosmic rays, once again.

• 26:47Hannah Fry?

  Once again, those guys.

• 26:50Michael Stevens?

  Particles of mini hats.

• 26:52Hannah Fry?

  Yeah.

• 26:52Michael Stevens?

  So they like seed the process required for lightning to happen.

• 27:00Hannah Fry?

  So I think it's the other way around. So there there's this, the the sort of main theory is about how in within clouds, you have ice and you have sort of like sloppy hail, right? Like soft hail. They interact with each other, that crash into each other because of the turbulence in clouds. And then they, uh, they end up separating. They have different charges, but they end up separating because one's lighter than the other. So that's how you get the sort of the potential difference between different layers of the cloud. But there is this idea, this theory that that cosmic rays then then act as like the seed for that lightning to to start, which I really like.

• 27:33Michael Stevens?

  Wow. All right. So why did you pick these up? Just as decoration? Did you use them to teach?

• 27:40Hannah Fry?

  Hey, it's a glass straw, Michael. What's uh, what's, what's not to like? Um, no, I, I read about how, how much Darwin liked them. And I just wanted to see how easy it was to get hold of. Because they are really amazing that you would have something, because it's essentially, they're so rough and nobblier on the outside, because it's, that's where the sand is, right? The sand sucked to it.

• 28:00Michael Stevens?

  Yeah, yeah.

• 28:00Hannah Fry?

  Um, but on the inside, I mean, it's a shame that I can't give this to you in person, but they are so smooth and glassy on the inside. It's like, it's really, it sort of feels otherworldly. It sort of feels like this is a freak moment that has, that has created this.

• 28:16Michael Stevens?

  Yeah, well, it was a freak moment. It's natural glass. It's accidental glass. Have you ever used one as a straw?

• 28:24Hannah Fry?

  No, I was joking. I should do that. I mean, it's not gonna hurt you.

• 28:28Michael Stevens?

  But you should, right? If they're only nine quid each.

• 28:30Hannah Fry?

  Yeah, exactly.

• 28:31Michael Stevens?

  I mean, how, how brittle are they? Could you carry it around as a reusable straw?

• 28:35Hannah Fry?

  Shall I try and snap it?

• 28:38Michael Stevens?

  Well, uh, yes.

• 28:39Hannah Fry?

  I reckon you're good, shall I? For the purposes.

• 28:42Michael Stevens?

  For the purposes of this video, it's worth it.

• 28:44Hannah Fry?

  Really? Okay, I'm gonna try and snap it.

• 28:46Michael Stevens?

  Whoa, that was easy.

• 28:48Hannah Fry?

  Yeah.

• 28:48Michael Stevens?

  That was brittle.

• 28:49Hannah Fry?

  That was, that was. Now, now I've just either halved the price or doubled it.

• 28:55Michael Stevens?

  Yeah, you may have doubled it.

• 28:57Hannah Fry?

  Um, the thing that's nice about these is that, um, because they've been being created across the whole history of the earth. Um, what they do is that, uh, as that glass, uh, sort of melts and then hardens, it traps these little air bubbles inside it. So there's all the way down here, there'll be all these little air bubbles. And that's a sort of, like a taste, as it, as it were, of the air at that moment in time, whenever the, the full gripe happened. So, um, what scientists do is they take these, they work out how odd they are, and, uh, they, you know, allow them to sort of see what the atmosphere was like in the Sahara Desert, for example, you know, fifteen thousand years ago.

• 29:38Hannah Fry?

  See what kind of plants were there, see what kind of carbon isotopes were in the air. Um, you really sort of get this, this way to look backwards in time, um, using these little things. It's cool, isn't it?

• 29:50Michael Stevens?

  So by breaking that one, you just probably, you may have released a few molecules of prehistoric air.

• 29:58Hannah Fry?

  I think this one's quite a new one, to be honest. Smells, smells modern.

• 30:02Michael Stevens?

  Smells Victorian, maybe.

• 30:04Hannah Fry?

  Victorian, exactly. You know, there is this, Folgerite has this, this quite terrifying cousin, which is called trinitite.

• 30:13Michael Stevens?

  Yes, I was gonna say, that is not naturally formed glass. It's glass that humans made by blowing up and testing nuclear weapons.

• 30:23Hannah Fry?

  Exactly. So when, when the first atomic bomb was, was detonated in New Mexico, the Trinity Test, the heat from that melted the desert sand and it turned it green as well. It's this radioactive glass. That one I did not buy on eBay. I, uh.

• 30:40Michael Stevens?

  That's harder to get because it doesn't just happen every time there's a lightning storm or not every time, but it, it, you have to test a nuclear weapon around sand. And then you've got some trinitite, which of course is named after the Trinity site, where the first atomic full-scale testing occurred. But I think it's probably called trinitite, no matter where it forms now.

• 31:01Hannah Fry?

  I think it probably is, yeah. I think it probably is. You've got a history of buying and buying radioactive objects just for your own interest. I seem to remember you telling us about some radioactive lead at one point.

• 31:13Michael Stevens?

  Yeah, yeah. Well, you can get radioactive lead isotopes just mail order. You could probably get them off of Amazon today. My mom got me some radioactive lead for my bubble chamber when I was a kid. And it was at the tip of a needle inside a little test tube and she made me keep it in the garage. But we, we also just bought some aughtonite, which is a uranium bearing mineral. My colleague, who lives in a different city, acquired a large amount of this mineral. And it came in a lead-lined box with a big warning on it that says, stay five meters away. So we found a suitable location and there's like warning labels and stuff, but it's still not really concentrated enough.

• 31:57Michael Stevens?

  We wanna remove as much of the elements that aren't uranium as possible. Now, we don't quite know how to enrich the uranium.

• 32:07Hannah Fry?

  Yeah.

• 32:08Michael Stevens?

  But I might make some calls.

• 32:10Hannah Fry?

  I would say that's closely guarded state secrets, isn't it? Uranium enrichment.

• 32:14Michael Stevens?

  Yeah, I mean, we've looked into how to enrich uranium and the old centrifuge process, um, just.

• 32:22Michael Stevens?

  I don't know how to make a good enough centrifuge. And you've got a, they don't really tell you exactly how to do it. Today, I think they use a lot of lasers. And in the future, I think they'll do nothing. I think that we're developing ways to power nuclear power stations just with uranium ore that doesn't need to be processed and enriched. Which is great, which is really great.

• 32:47Hannah Fry?

  Well, I think that that's, that's bringing us towards the end of this episode. But you can tune in next week to hear more about Michael's adventures into deeply troubling uranium enrichment. Or find out whether he's been smuggled away by the FBI.

• 33:01Michael Stevens?

  I know, I feel like maybe I shouldn't have said that because I've ruined the surprise, but not for everybody.

• 33:07Hannah Fry?

  All right, well, we'll be back on Tuesday with, with hopefully another episodes as long as, as long as Michael remains a free man. So yeah, catch us then.

• 33:17Michael Stevens?

  I will be in a week. I'll see you guys then.

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