This Glass Was Made By Lightening

0:00Hannah Fry:This episode is brought to you by Cancer Research UK. So when most people think of naked mole rats, their unusual relationship to cancer probably isn't the first thing that comes to mind. 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. 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. Cancer Research UK is the world's largest charitable funder of cancer research.

0:35Hannah Fry: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. 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. For more information about Cancer Research UK, their research, their breakthroughs, and how you can support them, visit cancerresearchuk.org forward slash rest is science. This episode is brought to you by Focus Features. On March 27th, Focus Features invites you to be a part of the most explosive movie of this year's Sundance and South by Southwest film festivals.

1:22The AI Doc, or How I Became an Apocaloptimist, is being called supremely entertaining and the most urgent movie of our time. The AI Doc, or How I Became an Apocaloptimist, rated PG-13, only in theaters March 27th. This episode is brought to you by Indeed. Stop waiting around for the perfect candidate. Instead, use Indeed-sponsored jobs to find the right people with the right skills fast. It's a simple way to make sure your listing is the first candidate C. According to Indeed data, sponsored jobs have four times more applicants than non-sponsored jobs. So go build your dream team today with Indeed.

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2:13Hannah 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. And we'll answer the strange questions that are troubling yours. Because every week one of us is going to bring a strange, spectacular object or story onto the show. And together we're going to see what kind of uncharted territory it takes us to. 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.

2:47Hannah 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. Ooh, that's a good hook. I know. Any guesses so far? Is it like how photons travel? I mean, there's photons involved, but you've got to stay tuned for the second half if you want to find out more. But for this first half, what we thought we'd do is we would dive into our mailbag. As ever, you can send us your questions, you can send us your own objects, your own thoughts and sometimes feelings. But our first question, say, Madhav has got a question.

3:31Hannah Fry:This, I think, is one for you, Michael. Why do mirrors flip us horizontally, but not vertically? 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 look at like a letter R, you're like, yeah, that looks normal.

4:08But 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.

4:18Hannah 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 suddenly flips vertical. It suddenly makes your left hand your right hand, but your head is not switched with your feet. Yeah. So it's like, how does it know? How does it know that to only ever flip what's horizontal to you? 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.

4:53They'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.

5:23Hannah 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. It would be unchanged, the sort of the backside of the tracing paper and what you're seeing in the mirror. 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.

5:58And 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.

6:12Hannah Fry:You know, like those little suckers that you get that 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. 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.

6:46You have reversed yourself by turning around to join it and face the other way.

6:52Hannah 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. Great question. Absolutely great question. Let's move on to a question from Brandon, who asks, how dense would a hamster have to be to become a black hole? OK, 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 i i uh i looked up the um the average weight of a hamster i've gone for um if you're interested a a chubby syrian hamster um 150 grams that's uh that's their general weight if you wanted to turn one of those into a black hole um 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 excellent here is the uh here's the sort of breakdown right the the 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 it's it the the density becomes so great that it that it becomes a black hole so when you run the calculation for a hamster at 0.15 kilograms, you work out that the Schwarzschild radius is 2.2 times 10 to the minus 28 meters, okay, which is, I'm going to say it, small.

8:18Hannah Fry:To put that into perspective, a proton is 10 to the minus 15 meters. Oh no, so you've got to squish all the hamster's mass into a volume smaller than a proton. 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 um which if you want to put that in perspective it's uh the hamster is to a proton at the moment what a what a grain of sand is to the entire earth basically right so it's gonna be so small so okay then the consequence of what happens when you do that is uh is phenomenal does it hurt the hamster i don't think i think we've got a sort of honey, I shrunk the kids type smallizer machine.

9:08Hannah Fry:Okay, I love it. I love it. Hamster miniaturizer machine. I think the hamster's fine. Imagine that the hamster is fine the whole time. It just like starts to realize, hey, my gravitational force is getting stronger. I've become a black hole. Dang it. Damn it. Okay, I'm going to tell you the hamster is fine. Spoiler alert, not everyone else is. Just bear with me for a second. Because here's the thing, right? to 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 atomic speck um 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 um but just to visualize that that sort of crunch um water a thousand kilograms a meter cube Steel, 8 ,000.

9:59Hannah Fry:The core of the sun, 150 ,000. 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. Well, sure. I mean, we're trying to make a black hole. Like it's got to be denser than any regular matter. Sure. But this is like even denser than that. Even denser than that. 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 going to be so unstable that it will probably only last for about 10 to the minus 26 seconds.

10:51Hannah Fry:Right. So really, I mean, it barely exists. but 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 so what this means is the moment that you finish miniaturizing your hamster it would detonate and the energy release would be about 3.2 megatons of tnt which is about 200 times more powerful than the atomic bomb dropped him in Hiroshima. So, I mean, you can if you want to, Brandon, but I would say don't. Wow. If you turned your hamster into a black hole, you would create a nuclear bomb.

11:36Hannah 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. 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. Yeah. Look, I think when people try and say that one small creature cannot make a difference, I think this is evidence to the contrary. It depends how you define can. 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.

12:15Hannah Fry:You'll all be sorry. Hey, you know what? I think we've just found a new plot for a new Pixar film. Yeah. The hamster who became a black hole. Yeah. Copyright. The rest is science. 2026. Too right. OK, 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? No, it wouldn't. The Earth's Schwarzschild radius is funny enough.

12:51I actually literally have it right here. Yeah, we'd have this in gravity, right? 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, uh, denser than a neutron star, but not quite able to capture light. I think light could be very bent by it. But 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.

13:34So 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 five thousandths of an inch. and people have taken that to mean that a pool ball can have craters and bumps that are five thousandths of an inch. And at the scale of earth, that would mean 28 kilometer high mountains and trenches.

14:27So obviously the earth is smoother than a pool ball.

14:31Hannah Fry:My. 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. So sorry to say the Earth is not smoother than a pool ball.

15:20It is as smooth as 320 grit sandpaper, which I'm trying to think of things in real life that would feel that way.

15:28Hannah Fry:I think maybe like, 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 is that if you're trying to like remove material you're using an extra coarse sandpaper that could be like a 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, they call them micro grit sandpapers, very fine ones are about 240 grit.

16:05But for earth's texture, we need extra fine.

16:09Hannah Fry:Okay. Between 320 and 360. So those are going to be, you know, used for wood polishing, 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 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 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 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.

16:50Yes. You would say, wow, this is not smooth for sure.

16:55Hannah Fry:Right. Because the other one I've heard is that is about the fingerprint. Have you heard this one? What's this one? That if you shrunk the earth down to the size of a pool ball and a giant held it in their hand, then the craters and peaks of their fingerprint would be greater. I mean, I was making some quite strong assumptions about the

17:19Hannah Fry:biological surface of this giant and the fingertips of this giant, but the craters in your fingerprint are greater than you see on Earth. Yes, this is the thing. These are the numbers that I think you might have wanted, that human fingers can feel objects as small as 13 nanometers. Really? 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. No. Our sense of touch is a miracle. it blows your mind wow yeah 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 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 uh 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.

18:36They'd be like, oh, that's a parking lot. Oh, there's no buildings here. They would be able to tell. Oh, Buckingham Palace. This whole Earth is smoother than a pool ball nonsense. Come on, let's grow up. Earth is bumpy. It's bumpiness deserves some credit.

18:54Hannah Fry:Stop doing that, internet. Okay, well, we've got some bumpiness for you in the second half of this because boy, have I got an object for you. We'll be back right after this break.

19:18This episode is brought to you by Cancer Research UK. Cancer drugs aren't developed overnight. They start as ideas in the lab, then move into testing to check they're safe and work effectively.

19:29Hannah Fry:In the late 1990s, Cancer Research UK scientists began exploring a bold idea. Could the antibodies that normally trigger allergic reactions be used to treat cancer? The lab results were promising, but allergic reactions carry real risks. After years of work, an early stage trial showed these antibodies could be used safely. And for one person on the trial, their tumour shrank. Frank. Research is ongoing, but this careful process is how treatments move from the lab into hospitals. Cancer Research UK backs innovative ideas. And thanks to decades of support, over eight in 10 people in the UK receiving cancer drugs are using one developed by or with Cancer Research UK scientists.

20:13For more information about Cancer Research UK, their research, breakthroughs, and how you can support them, visit cancerresearchuk.org forward slash the rest is science. Eczema is unpredictable,

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