A (2:31)

Mm. 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.

B (2:41)

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.

A (2:48)

Yes. Now later today I'm gonna 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.

B (3:02)

Ooh, that's a good hook.

A (3:05)

I know. Any guesses so far?

B (3:08)

Is it like how photons travel?

A (3:11)

I mean, there's photons involved, but you've got to, you've got to stay tuned for the second half if you, if you, 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 to say Madhav has got a question. This, I think, is one for you, Michael. Why do mirrors flip us horizontally but not vertically?

B (3:39)

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.

A (4:18)

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 flick, flips vertical, suddenly makes your left hand your right hand, but your head is not swept through your feet.

B (4:34)

Yeah.

A (4:34)

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

B (4:40)

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 yet 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.

A (5:24)

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, of the tracing paper and what you're seeing in the mirror.

B (5:38)

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.

A (6:13)

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.

B (6:26)

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, you have reversed yourself by turning around to join it and face the other way.

A (6:53)

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

B (7:06)

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

A (7:13)

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, I, I, I looked up the, the average weight of a hamster I've gone for. If you're interested in 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, excellent. Here's the sort of breakdown, right? The Schwarzschild 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.

B (7:59)

The.

A (8:00)

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 kg, 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. To put that into perspective, a proton is 10 to the minus 15 meters. No.

B (8:25)

So you've got to squish all the hamster's mass into a volume smaller than a proton.

A (8:30)

Oh, yeah. I mean, like size of atoms. Forget it. That's like gigantically vast in comparison to the size the SAMS has got to get done. 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. What a grain of sand is to the entire Earth, basically, right? It's going to be so small. So, okay, so then the consequence of what happens when you do that is phenomenal.

B (9:00)

Does it hurt the hamster?

A (9:02)

I don't think. I think we've got a sort of honey, I shrunk the kids type smallizer machine, okay?

B (9:09)

I love it. I love it.

A (9:10)

When it comes to miniaturizer machine, I think the hamster's fine.

B (9:12)

Imagine that hamster is fine the whole time. It just like starts to realize, hey, my. My gravitational force is getting stronger. I've become a black hole. Dang it.

A (9:22)

Damn. 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 fur and cheeks. But it's now squished into this subatomic atomic spec, which means the density that's required is 3.3 times 10 to the 81 kg per meter cubed. Okay, people can check my calculations on this if you like, but just to visualize that sort of crunch. Water, 1000 kg a meter cube. Steel, 8000. 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 cubed. 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.

B (10:25)

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

A (10:30)

Sure. But this is like even denser than that. Even denser than that. And, and the problem is, is that, okay, according to 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, about 10 to the minus 26 seconds. 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 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 released would be about 3.2 megatons of TNT, which is about 200 times more powerful than the atomic bomb dropped in Hiroshima. Yeah. So I mean, you can if you want to, Brandon, but I would say don't.

B (11:31)

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

A (11:37)

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

B (11:46)

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.

A (11:55)

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.

B (12:03)

It depends how you define can. Look, I can imagine some like 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.

A (12:16)

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

B (12:22)

Yeah, the hamster who became a black hole.

A (12:26)

Yeah.

B (12:26)

Copyright the rest is Science 2026 too.

A (12:29)

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.

B (12:48)

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

A (12:54)

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

B (12:56)

It'd be about like, I think,.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 wall, 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 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. 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 5,000ths of an inch. And people have taken that to mean that a pool ball can have craters and bumps that are 5,000ths of an inch. 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. 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. 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. 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, well, where is.

A (15:30)

Where is 320 on the spectrum from like if you start off with, with, you know, the coarsest of all, where you' just trying to get the surface down. What numbers that.

B (15:40)

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, the, they call them micro grit sandpapers. Very fine ones are about 240 grit. But for Earth's texture we need extra fine.

A (16:10)

Okay.

B (16:11)

Between 320 and 360. So those are going to be, you know, used for wood polishing to, to initiate polishing. The idea that a pool ball can have these 5,000 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.

A (16:36)

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 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.

B (16:51)

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

A (16:56)

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

B (17:02)

What's this one?

A (17:03)

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 biological surfaces of this giant and the fingertips of this giant, but that the craters in your fingerprint are greater than you see on Earth.

B (17:29)

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 13nm.

A (17:40)

Really?

B (17:41)

We are incredibly sensitive to 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.

A (17:59)

No.

B (18:00)

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

A (18:05)

Wow. Yeah, that's incredible. I'm just. Sorry. I'm just feeling these scratches on my table just to see, like, the. You're right. You know, they're like really tiny little scratches. You can actually film them if you want it.

B (18:17)

Yeah. And we might not be able to count the scratches, but we can tell the. 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.

A (18:43)

Oh, Buckingham Palace.

B (18:45)

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

A (18:55)

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.

B (19:14)

This episode is brought to you by Cancer Research UK, who over the past 50 years have helped double the cancer survival in the UK.

A (19:21)

You might have heard of BRCA genes. These are the ones that made headlines when Angelina Jolie revealed that she carried a faulty version. Yeah.

B (19:28)

BRCA genes are part of our DNA. They help to repair cells and keep them healthy. The risk comes when BRCA genes are faulty and about one in 400 people inherit a faulty version, increasing the risk of some cancers.

A (19:41)

Yeah. Now, this discovery came From Cancer Research UK scientists who came across the BRCA1 and BRCA2 genes. A breakthrough that changed how doctors prevent d, diagnose and treat cancer. And now we've got genetic testing that means that people who have faulty BRCA genes can take steps to prevent cancer or to receive tailored treatment.

B (20:01)

Yeah. The discovery also revealed a weakness in cancer. By turning that flaw against the disease, researchers developed PARP inhibitors, targeted drugs that are now helping thousands of people.

A (20:12)

And all of this really points to a future where medicine is no longer just one size fits all. It's something that's informed by your own DNA. So for more information about Cancer Research uk, their research breakthroughs, and how you can support them, visit cancerresearchuk.org restedscience. Your planet is now marked for death.

B (20:33)

Marvel Studios the Fantastic Four first steps is now streaming on Disney. We will protect you as a family. Light them up. Johnny Marvel's first family is certified fresh on rotten tomatoes. That has been tasted. And critics say it's one of the best superhero movies of all Time. Marvel Studios the Fantastic Four first steps now streaming on Disney Plus. Rated PG13 what time is it, Ben? It's clobber time.

A (21:07)

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

B (21:15)

It looks like a short twig.

A (21:19)

Yes, it does.

B (21:20)

A very bumpy stick. Colored stick.

A (21:25)

I've got another one here.

B (21:27)

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 only about as long as a pinky finger. Slightly bumpy and gray and brown. It might be hollow.

A (21:46)

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

B (21:54)

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

A (21:58)

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

B (22:07)

I'm saying it so that they don't. I'm stealing their thunder nails. More like snails. I don't know. Does that make sense?

A (22:16)

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 all. But if I turn it round, 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.

B (22:37)

Oh, like a geode. Almost, Almost.

A (22:40)

Almost. And it feels. It feels like glass.

B (22:45)

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

A (22:51)

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

B (22:59)

Oh, wow.

A (23:00)

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 the Earth, lightning hits sand. Okay, can you see that one? This one's a bit clearer, I think.

B (23:16)

And it turns it to glass.

A (23:17)

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 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 Lightning hits the center of this, it will actually vaporize. So you have this. This hollow tube, this hollow glass tube. And then what happens is that the sort of gas from the vaporized sand expands outwards, creating this basically this glass straw. Right. Isn't that cool? Yeah.

B (23:57)

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

A (24:07)

Glass gas, exactly. And what is amazing about these things. Okay, so. So Darwin in particular, he was obsessed by these. They're called fulgurites, by the way. They're really cheap. I got these on ebay. They're like nine, ten quid each. 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 gotta 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. Yeah. 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.

B (24:53)

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

A (24:58)

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

B (25:28)

Oh, no kidding. Cosmic rays. Once again, Once again, those guys. Particles of mini hats.

A (25:35)

Yeah.

B (25:36)

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

A (25:43)

So I think it's the other way around. So there's this. The sort of main theory is about how within clouds you have ice and you have sort of like sloppy hail. Right. Like soft hail that interact with each other, that crash into each other because of the turbulence in clouds. And then 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 cosmic rays then act as like the seed for that lightning to start, which I really like.

B (26:17)

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

A (26:24)

Hey, it's a glass drawer, Michael. What's not to like? No, 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 knobbly on the outside because it's. That's where the sand is, right? The sand sucked.

B (26:43)

Yeah, yeah.

A (26:44)

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.

B (26:59)

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

A (27:08)

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

B (27:12)

Right, if they're only nine quid each.

A (27:14)

Yeah, exactly.

B (27:15)

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

A (27:19)

Should I try and snap it? Yes, I reckon you're good. Shall I. For the purposes.

B (27:25)

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

A (27:27)

Ready? Okay, I'm going to try. Stuff it.

B (27:30)

Whoa. That was easy. Yeah, that was brittle.

A (27:33)

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

B (27:38)

Yeah, you may have doubled it.

A (27:41)

The thing that's nice about these is that because they've been being created across the whole history of the Earth, what they do is that as that glass sort of melts and then hardens, it traps these little 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 were, of the air at that moment in time, whenever the fulgurite happened. So what scientists do is they take these, they work out how old they are, and they, you know, allow them to sort of see what the atmosphere was like in the Sahara Desert, for example, you know, 15,000 years ago. See what kind of plants were there, see what kind of carbon isotopes were in the air. You really sort of get this. This way to look backwards in time using these little things. It's cool, isn't it?

B (28:34)

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

A (28:41)

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

B (28:46)

Smells Victorian maybe.

A (28:47)

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

B (28:57)

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

A (29:06)

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.

B (29:24)

That's harder to get because it doesn't just happen every time there's a lightning storm or not every time. But 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.

A (29:44)

It probably is, yeah. I think it probably is. You've got 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.

B (29:57)

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 also just bought some otonite, 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. We want to remove as much of the elements that aren't uranium as possible. Now we don't quite know how to enrich the uranium.

A (30:51)

Yeah.

B (30:51)

But I might make some calls.

A (30:53)

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

B (30:57)

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

A (31:30)

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.

B (31:44)

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

A (31:50)

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

B (32:00)

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