The Rest Is Science - Science Is (Literally) Cool

Episode Date: April 13, 2026

Is the kitchen home to some of the most extraordinary technology humans have ever invented? Professor Hannah Fry and Michael Stevens explore the science of everyday appliances, from the strange physics of coldness to the wartime origins of the microwave. They explore how humanity learned to trap 'coolth', beam heat into leftovers, and turn the most ordinary room in the house into a high performance laboratory! From ice merchants and exploding eggs to magnetrons and magnetic fridges, this is the surprising story of the science hiding in plain sight. ------------------- 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 Oakley + Jack Meek Animator: Sam Benson Video & Social: Bex Tyrrell Producer: Simona Rata Senior Producer: Lauren Armstrong-Carter Head Of Digital: Samuel Oakley Exec Producer: Neil Fearn Learn more about your ad choices. Visit podcastchoices.com/adchoices

Hello and welcome to The Rest is Science. I'm Michael Stevens. And I'm Anna Frye. Michael, what is your favorite room in the house and why is the answer to the kitchen? Oh my gosh, we're jumping right in. My answer has to be The Kitchen. Is this a setup for your episode? It's the correct answer. Okay, I want to tell the audience, this is an episode where Hannah has come to talk to me about something that is, dare I almost say, annoyingly close to her heart. Before we record episodes, she's always talking about refrigerators. And I'm like, Hannah, one of these days. One of these days, my time will come.

You can get it out of your system. My time will come. No, I'm really excited to hear this. And of course, my favorite room in the house is the kitchen. If that's going to help move things forward. I'm not, see, this is the thing. I've managed to, I've managed to expand from not just my love of fridges. But I'm going to do other household items in the kitchen too, Michael.

This is going to be a little justification as to why the kitchen is the room that contains all of the most interesting, high performance. scientific equipment in your house. This episode is brought to you by Cancer Research UK. If you wanted to type out the entire human genome, you would have to type at 60 words a minute for eight hours a day for about 50 years. Okay, that's the scale of the DNA rulebook inside each one of your cells, telling it when to grow, when to divide, and when to stop.

And different tissues read that same rule book in different ways. So a skin cell doesn't behave like a cell. a lung cell. And cancer can begin when those instructions change. Not one dramatic moment, but through small, gradual edits over time. Now, cancer isn't one disease. It is more than 200 types shaped by where those changes to the rulebook happen and how cells respond. Cancer Research UK is the world's largest charitable funder of cancer research, backing studies across all types of cancer. Work that takes years of very careful, steady, progress to deliver each breakthrough.

For more information about Cancer Research UK, their research, breakthroughs, and how you can support them, visit cancerresearchuk.org forward slash the rest is science. There's something else here now, something new. From exclusively on Paramount Plus, it's the series Stephen King calls Scary as Hell. Everything here is impossible, but it's also real. Sci-fi vision calls it the best show streaming right to. now. We're running out of time and we still don't know the rules.

Don't miss what the movie blog calls something you need to watch. Saving those children is how we all go home. From binge all episodes exclusively on Paramount Plus. I suppose I should probably start by saying why I like fridges so much. Well, yeah, I mean, look, I love fridges too. But your love is unique and I want you to describe it for me. It's sort of a philosophical love, you know? It's like, okay, the thermodynamics is delicious.

the history of it sumptuous, right? Are you going to love all of that stuff? But I think there's something that is just really strange to imagine that before the invention of fridges, before the ability of humors to artificially cool things down, there were areas with the world where, I don't know, people had literally never tasted a cold drink before, right? Like, you don't get this.

If you look across the universe, temperature gradients are these smoothly changing things, right? You don't get these little bubbles of anomalies of like frozen temperatures in amongst things that are many, many, many degrees high. It just doesn't happen. Right. We definitely have pockets of high heat because of gravity. We've got stars. Yeah.

But there's no natural phenomenon that creates big balls of coldness. Koof. Koff, I like to call it. You know, you got warmth. Why not have coolth? I mean, black holes, they get really hot around them because matter gets squeezed together and it's a violent. But in the middle of a black hole, I'm not even sure temperature makes sense. So really, we don't have any coolth balls. No, there are no coolth balls apart from in your kitchen, which I think is kind of interesting.

I mean, the other thing is the thing that's also kind of important to say here is that cool, cool, not only is it not a word, it also isn't really a thing, right? Like cold, cold doesn't really exist. Cold is just the absence of heat. You can't actually cool something down. You can only take away the heat from it. So would you say it's like darkness? Darkness isn't a thing. It's the absence of light. Exactly. Cold. Cold. Coldness is just the absence of heat energy. Exactly. And we are so blazze about the cult that we have created. Because, I mean, okay, the very first time that people really started to notice that actually this desire that humans have for coldness, for ice in particular, and how it could be monetized was this guy called

Frederick Tudor. So he lived up in Massachusetts. Now Massachusetts is somewhere where it's got this gigantic temperature gradient between summer and winter, right? Really frozen in the winter, really hot in the summer. So what people had done, and this is like for thousands of years, and in China people have been doing it for thousands of years. When it would snow in the winter, they would dig out these ice houses and then they would cut up ice from lakes and shove it in these ice houses. I mean, it's literally the opening sequence to Frozen. Right. Disney's Frozen. Okay. Oh, that's true. Yeah, yeah, yeah. I've also seen really great reels on TikTok where people are like, we're going to make ice cream this summer, the old-fashioned way. Oh, wow. They make an ice house.

They like dig a trench, build a structure over it. And in the winter, they cut big cubes of ice, And they fill this pit inside the ice house with straw, put the ice cubes in the straw, cover it in more straw. And literally, four months later, middle of the hot days of summer, they're like, hey, there's still some ice left. And they use it to make ice cream. Oh, that sounds amazing. Yeah. That sounds amazing. So it was possible, but you had to have access to ice in the first place.

Exactly. It was geographically anchored. I mean, you had to be in a place which had that temer. temperature gradient. So there are places, you know, like cross Africa, cross the Caribbean, you know, loads of South America where it's just, I mean, forget it, right? There's no, you'll have never seen ice. You will have never touched just anything that is, that is zero, like zero degrees. It just will never have happened, which is just mind boggling to me. Anyway, this guy, Frederick Tudor, he was like, okay, all of these people, these fancy people

are doing with their ice houses, can I not just follow that same logic? Can I not just get loads of ice, chuck it in a ship, sail down south, and then I can be on the beach selling ice cream to one of these people. When did he have this idea? Put me in historical context here. We're talking very, very early 1800s here. Okay. Okay.

So really before the Industrial Revolution has got underway in full swing. Right. But Massachusetts is a state of the USA, no longer a colony of the British. Correct. But Industrial Revolution is about to take off. Meanwhile, New York has this up-and-coming city. which has less access to ice. So he starts off doing a little run down there, and it works pretty well, right?

You can sell ice to people down in New York, and that's nice and great. So he decides to ship ice to Martinique, okay, where, you know, no one had ever seen ice before in their lives. And everyone thought that this was an absolute joke. Like, who would try and make a business out of something that melts? And it did melt, by the way. His first boat turned up, there was as much water inside the ship as there was outside. It was this total design. That's the punchline to the joke of the guy who tries to sell ice to.

Well, no, the joke is selling ice to the Inuit. But Martinique, by the way, is in the Caribbean. It is an island down southwest of Florida. Super warm, essentially. All year round. And there's no giant mountains that raise up high enough an elevation that you've got snow at the peak. So, yeah, we're talking about an ice-free zone. We're talking about an ice-free zone, and we're talking about Frederick Street and sat outside in a sad, wet, empty boat.

That's what we're talking about. But he doesn't give up. So he goes back up to Massachusetts. And this time he uses the straw trick. He's like, right, and you just need to intulate it better. And he realizes that if he goes around to local timber mills, take all of their sawdust off their hands, he can pack it around the ice.

He's just at this moment where it's like he thinks it might actually work. But what he does is very clever. He goes down to places like the Caribbean, you know, Cuba, Jamaica, even actually across to India. he gets people to sign these contracts and he essentially makes it so that he has the sole rights to sell ice in that country, region, wherever it might be. So he knows that he's going to make it work.

It's not quite there yet, but he's like, because no one believes in, they're like, yeah, yeah, yeah, sure, fine. You can do this, go right ahead. He does this other thing where he would go into bars and he would give free samples. He would let patrons experience how refreshing a chill. beverage would be. I mean, the first time ever that these people have drunk a cold drink, which is just incredible to imagine. Anyway, he makes it work that the sawdust is the thing. And he

ends up making so much money, so much money. He becomes known as the Ice King of the World. Okay. So we know even 1800s, we know that there is this like incredible demand, not just for preserving food, but for the enjoyment of having an ice cube in your glass. Wow. I want to say this guy really seems like a forerunner of this modern mentality where he's not just an inventor or an engineer. He's also a salesman. Yeah. And he's also a legal wizard. He's out there signing contracts to exclusively sell ice to your country before he really knows that he can do it. He wants to sell something not because people need it, but because it's joyful and fun. Yes. You're so right. How much more modern of a combination, constellation of elements kind of single person has. Gosh, you are so right. How perfectly, perfectly put. The thing that ends up putting him out of business, by the way, is the fridge, right? The fridge and freezer is essentially the same technology. It's just at a different level. I could see that coming, yeah. That's the kind of great punch. But he's the person. He's the person that makes us want it. But going back to your people who are making ice cream in the summer, the old-fashioned way, one thing that you can also do, you can make ice yourself. Wherever you are in the world, there is a way that you can do this actually quite easily now. I should probably put. an actual disclaimer on this. Don't actually, don't actually try this. Okay? I mean do, but don't actually. Don't actually. This is something I've done. You have to be quite careful and I would definitely do it outside because it is a little bit explodey. Oh, okay. What do I need to use? Okay, you need a can of

butane. Okay, yeah, I've got one at home. Which you can, you can get is lighter fluid or camping camping gas. Okay, the thing about butane is that it exists as a gas at room temperature. It has this boiling point of about 0.5, sorry, minus 0.5 degrees C. Okay, so below the freezing temperature of water. And it's put in these really pressurized containers. It's stored in liquid form in these pressurized containers. And so when it gets released into the air, it desperately wants to become a gas. It's squirted out as a liquid and it desperately wants to get out as a And to do that, to make that transition from liquid to gas, it needs a little kick of energy, specifically this thing called latent heat of vaporization.

It will draw that energy from its surroundings. It will kind of steal the thermal energy from anything that it's in contact with. So if you get like a little glass of water and you place it in a bowl and then pour liquid butane into that bowl surrounding the glass of water, what will happen is that liquid butane is going to really quickly boil. And it looks like that too. It looks like a pan of boiling water, right? There's bubbles on the surface. And to fuel all of that boiling, it's sucking the thermal energy right out of the water, dropping the temperature of that water so that the water will then flash freeze into ice in a matter of seconds. Wow. So you've got the yin and the yang. You've got the

boiling butane in the freezing water. Exactly. I think you could probably also do this with a can of compressed air if you didn't want an explosive gas sprayed everywhere. I know that when you spray compressed air, like from a keyboard cleaner, you can get streaks of ice. And I don't know if that's moisture from the air, or from the air in the can or from the air around you.

This idea of evaporative cooling, of anything that's from a liquid transitioning into a gas, you do get this effect of like stealing the thermal energy. I mean, it's the same thing is if you come out of a swimming pool in the summer and you've got droplets of water on your arm, those drops of water are going to evaporate and then you feel really cool. It's not like it's not like the wind affects you differently when you're wet. It's that those molecules of water are stealing your energy, stealing your thermal energy as they're escaping. Yeah. Exactly. So it is the same effect.

I just don't know whether you actually be able to make a chunk of water freeze using something which had a higher. Oh, yeah, I don't know, actually. Well, do the experiment at home. Any adults out there listening at your own risk, and let us know. Just totally old gaseous butane on our halves, okay? I'd rather suck on an ice cube made with compressed air

than compressed butane. Just for the flavor of it all. Just for the flavor of it all. But, you know, this is something where I think is quite fun to do when you go camping, right? It's like, let's make our own ice cubes. And the thing is, the way that fridges work, okay, they sort of seem like they're magical,

but they're using the exact same trick. That's it. That's the only thing that they're doing, except instead of letting the liquid butane like float off into the atmosphere, they just keep it all in a pipe. Also, technically they use isobutane, which has a boiling point that's lower.

It's minus 11.7 degrees. But it's the same, the main trick is exactly the same. Is that you spray in a pipe, you spray it in there in liquid form. The fridge is like five degrees, which for the isobutin is mega, mega hot. So it instantly boils, steals all the thermal energy from the inside of the fridge,

and then it exits down the bottom of the fridge still in the same pipe. And then that's sort of the cold bit of the fridge, as it were. And then round the back, all you ought to do is get this gas now, this hot gas into a colder liquid. So you compress it and you put it through a condenser at the back. All of the heat escapes out into the room. And then it's back into a liquid again. I mean, that's all you do. It's just a loop, the loop, the loop, the loop, the loop, the loop.

This isobutane going round and round and round for the entire life cycle of this fridge. I don't know, man. I think there's something so amazing about that, this idea that you are just recycling this liquid, round and round and round and round, round, round, around, around, giving energy, stealing energy, you know, moving the energy, you're pumping the energy out of this little box. I think that is, and as a result, we can all have cold drinks all over the world. I think that was really cool. Yeah, socially, refrigeration really is a big deal.

And today we take it so for granted that I'm remembering, I think back decades ago, there was a Fox News segment about people living in poverty in the United States and how it can't be that bad because 85% of them have refrigerators. Wow. And you watch that today and you go, wow. Yeah, I mean, first of all, they don't own them, like probably the landlord does. But a refrigerator is just such a ubiquitous part of our lives today that even if you're living paycheck to paycheck, like you've got a fridge. And that wasn't always the case.

There wasn't a time when having a fridge meant you were hoity tooty fancy pants McGee. Because I hear that number and I hear 15% of people didn't have a fridge, which makes me wonder about food preservation. It also makes me wonder about medication. I mean, vaccines is the perfect example of this. The only reason why we are able to vaccinate vast populations across the entire world, it's because of the invention of fridges. Without it, these very complex solutions that are made just can't, they're too fragile to remain active, you know, before they reach your arm.

I mean, it's really incredible what the fridge has enabled us to do, and we just don't even consider it. There is a jump, I guess, between butane and the modern fridge. So the first ever ice maker was made in. Australia. This is like 1855. Okay, so, you know, we're only 50 years after the Ice King has been giving people the delights of a cold drink. So that's all he had. He had 50 years and then an invention was made that could just do it on site. Yeah. I mean, his monopoly lasted a bit longer than that. It took some time for this engine to make its way across the world. Also, the first one, by the way, was absolutely massive. It's like the size of, I mean,

the size of a room. It's absolutely gigantic. I think the other really big difference that the fridge has made is giant societal change. You know, before fridges, back to those, what was it, 85% of people having fridges and 15% not. It was only with the invention of the fridge, particularly the fact that fridges became commonplace in people's kitchens, that leftovers were a thing, right? Or that like ready meals were possible. All of this stuff is just like a direct consequence, the time-saving nature of this. I think you can't really underestimate. Oh, yeah.

And I just looked at up today in America, 99.8% of people have a fridge, have access to a fridge. It is just like air almost. Now, 99.8 isn't 100%. But when you think about the standard of living and how that's changed and what it just means to live a routine life in America and a lot of the world, It's incredibly different than it was back when the only ice you could get had to come on a ship from Massachusetts. Yeah, yeah. I mean, this is it, right? Life expectancy is life from anything else is gigantically different from then.

And, you know, these two things are not unconnected. The fridge has made a big difference to quality of life as well as the length of it. I mean, you know those videos where people show their water of the day and they fill a cup with water and then they mix in all these flavors in different waters. A person from, you know, 1799 would watch that and go, that's like $18 million worth of ice. Are you a witch? And today we're like, oops, one of them fell off.

Better throw it in the sink so it can go away, annoyingly. It's like a bother to us. I have to say, actually, during the gold rushes. So the Australian gold rush and the California gold rush, You know, this is the point when ice is the absolute ultimate luxury, either whether it's come down from Massachusetts or whether it's been built in this absolutely giant honking machine, people would say that if you had a good day, if you'd gone out in the gold rush and you'd found a lot of gold, if you had a good day, you would come back to the bar and you would buy everybody a whiskey. But if you had a really good day, you would buy people whiskey with ice. Yeah. Big money times.

And now they're chucking it on the floor for TikToks. expanding butane cooling down and then compressing it it warms up that whole procedure is pretty well known like we all kind of have this intuitive idea

of oh yes I learned in high school when a gas expands it cools an almost opposite seemingly paradoxical thing happens with rubber bands I'm sure you've played with a rubber band before and notice that if you stretch it real fast and strong it gets warmer like it warms up

you can you can take a rubber band if you have one with you right now or later, stretch it fast and stick it on your lips, which are very sensitive to temperature. Do you have one? No, I don't have one. No, yeah, I have some downstairs, but go on, let's imagine. Okay, so you'll just have to trust me. The experience of stretching rubber band and then putting it on your lips to feel that warmth is pretty common. But if you stretch your rubber band and leave it stretched, like you just keep pulling it, you keep it stretched, it'll eventually cool down to room temperature. Won't take that long. You can even blow on it if you're impatient. Then let it collapse back down, put it on your lips. It will feel cold.

Right. It gets colder than room temperature. It's like a extremely simple refrigerator. And yet, it doesn't seem to make a lot of sense because when the rubber band shrinks, isn't it compressing? Shouldn't it heat up and shouldn't it cool down when you expand it like a gas? Obviously something very different is going on. The rubber band is. not a gas. It's made of solid molecules. The whole reason rubber bands even snap back is that essentially they've got, and this is, I'm borrowing from Richard Feynman's explanation, by the way, as we so often do. As we so often do. There are really long rubber molecules in a rubber band. And when the rubber band is relaxed, they're all crinkled up like this and they're kind of floppy. But when you stretch the rubber band,

they get pulled really taut and straight. But there are other molecules in there that have a temperature. That means they're moving. They have kinetic energy. And they're bouncing into these long polymers. And they're like hitting it, trying to like crinkle it up. That's where that force of compression comes back in. It's literally the just the motion of molecules in the rubber band trying to kink up these long polymers that you've stretched out. So what happens is that when you stretch the rubber band, those rubber molecules get really taught. And they're like, like, extremely powerful trampolines. And so the whole thing heats up.

But when you release it, now suddenly these molecules that are bouncing around, they're hitting like mud, like quicksand, like sloppy slop. And they're just like losing energy when they hit it. Rather than going, whing, and bouncing right off, they go and they get caught and they slow down. And a lot of their kinetic energy goes into just moving around these floppy rubber polymers. So the temperature drops. And Ben Krasno over at Applied Science on YouTube took that idea to the practical extreme by building a rubber band powered refrigerator. No isobutane for him.

But he had to do the same thing where you're going to have to compress or you're going to reset the rubber bands, just like the refrigerator has to reset the gas outside of the box. So he built basically like a disc that would stretch rubber bands outside and then rotate them into a little box and compress them and then take it out of the box and stretch it. And it did this with a whole chain of rubber bands. And he was able to drop the temperature like a degree or two. That is amazing. That is amazing. I like that so much. There is this amazing company that I got to go and visit once as part of my obsession of fridge.

It's called Camphridge. And they have this idea. It's like it's kind of similar to your elastic band thing, but they're using magnets. So there are some materials. I think gadolinium is one of them, these rare earth materials that really, they exhibit this really strong effect when you bring them in magnets that they do the, I mean, look, I'm going to simplify slightly, but it's essentially the same effect that it heats up and cools down. You put them in, they heat up, you leave it in there, let it get.

down to room temperature and then take it out and then it cools down to below room temperature. So they have a similar thing where you have this spinning magnet. And that feels like really cheating the universe, you know? Yeah. All you're doing is, and this works, by the way. They have this as commercial fridges. It's like unbelievably green technology because all you're paying for in energy terms is just to rotate this magnet. And that is like what a trick that is to just put.

magnet in, take a magnet out, ice. You know? Yeah, magnets already seem magic as we've discussed before, but then to use them to make a refrigerator or a freezer seems like you're treading pretty close to too much magic. Too much. And yet you're not. It's real. It's definitely an approximation of wizardry. I think that's very expensive. Are they like super expensive or something at the moment? Because current refrigerators are really affordable for what they, what they But they are, yeah, they're using like a gas that's not so great. Yeah, because this is the thing at the end of the life of a fridge, that isobutane is pretty nasty stuff. You know, you don't really, you don't want it like floating around.

You don't want that kind of in the environment. I think that at the moment, their main focuses on like, I don't know, drinks companies, for example, who have a ton, a ton, a ton, a ton, a ton, a ton of fridges all over the world. And for them, you know, decommissioning fridges is like a really serious financial burden. Right. But I mean, yeah, this is like a fridge that never runs out of juice, essentially. It doesn't even use juice. It doesn't even use.

A juiceless fridge. A juiceless fridge. Dry fridge. Absolutely wizardry. Okay. So we've done the fridge. I've got other parts of the kitchen to take you to, Michael. So my tour will continue after the break.

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Okay. From cooling things down, Michael, I'm going to go straight into hitting things up. Do you know how microwave works? Well, I mean, I've never investigated one because I'm scared of them. But I feel like I could say some things about a microwave. Like if my daughter asked how it worked, I would just say, well, okay, so microwaves are a kind of light that we can't see. But it has energy and you can shoot this kind of light at food. And I think the microwaves that microwave ovens use are like sized just right to especially wobble around water molecules. What happens when a molecule wobbles more, it means it's hotter.

So they just do that. And so unlike an oven that it's going to only just like touch the outside with heat, the microwave can make everything, all the water inside hotter all the way through. We don't need to do anything else. I've got nothing else to add. I do feel a connection to the microwave because there's this cool thing that I do every so often on X, formerly known as Twitter, if you search the word not microwave, but search the word Michael Wave, you will find a lot of people

who use Michael Wave when they mean microwave. Oh, that's adorable. I just searched it right now, and this is from last year in December, someone wrote about, like, is this Michael Wave Safe? And because I'm, my name is Michael, it's like they're

saying hi to me. So one of my dreams is to collect a whole bunch of screenshots of people calling microwaves, Michaelwaves, and just show it all in a short, and then at the end, have myself waving, and I'm like, I'm here, guys, everyone's Michael Wave safe. That is adorable. That is adorable. Isn't it adorable? Really adorable. I like that so much. I'm looking at a picture right now, which says, someone has put their microwave outside their house, and they've just written and sign on it saying, free Michael wave. Yes. As there is like, free him, he's trapped inside.

Free Michael Wave. Michael Wave did nothing wrong I don't deserve this Don't deserve this Yeah that is that is absolutely adorable I like that so much I like that so much So I love microwaves too

But for a very personal reason For that I mean that's a really great reason to love them I really like them Okay I mean all of the stuff about Sorry you're wobbling water molecules Using light In order to make your bake beans warm

Like, what? I think there's something really extraordinary about that. The other thing I like about them is that this is such one of the best examples about how often the precursor to a really revolutionary technology was not designed with that technology in mind. Okay. Oh. Because microwaves came to be the path that they took to get to us is just so wild. You would, if you were plotting it out and we're like, right, I want something that exists in everybody's kitchen to make their ready meals cook quicker. This is just, you would never plot this. Okay. Huh.

I mean, the first thing is just really technical. People were like mucking around with electrons and they realize if you have a cathode and anode, right, so one's positively charged, one's negatively charged. And you sort of slot the anode around the cathode and you kind of a solid block of copper and you just chuck a load of holes in it. Some people realize that if you introduce magnets into that situation, you can tweak it so that the electrons want to run from the cathode to the anode, but the magnets affect their path,

so they end up like swirling in and around between the two in this cloud. And as they go over the holes, it's a bit like when you blow over a bottle of, you know, a glass bottle, and it sort of makes that sound, that resonance. Yeah. That's how you make the microwaves, right? That's how you do it, is these electrons blowing past these holes. So people had like been mucking around with this being like,

look, we can make microwaves. We can make this like this type of electromagnetic wave and we can send it down a wire and like, you know, chuck it at stuff. Isn't this great? But it had absolutely no application whatsoever. People were like, there's nothing. This doesn't really do anything good or interesting. And it was just something that existed in labs in the middle of nowhere.

This is like 1900, right? Right. And then what happened in World War II, Britain had radar, okay, which is like another type of electromagnetic wave where you bounce out. Look at it bouncing back and you can sense big objects that are obstructing it. Don't need to explain radar, I don't think. So early radar or a radar today, I don't really know what they use. Radio?

Yes, radio. Yeah, early radar use radio, which is the wavelength of radio, radio waves, is like meters long. Yeah. So they're really good if you're trying to spot a massive formation of bombers on the skyline. But if you want to see anything small, I mean, forget it. It's not going to capture anything. It's just going to wrap around it, basically. It's not going to say anything.

And what was happening in World War II, there was the huge stretch of the Atlantic Ocean where the Allied ships, they had no air cover. It was too far from land. Their planes couldn't get that far. And what the Germans would do, their U-boats, which were diesel-powered, but had these batteries that they used when they were underwater. Obviously, you can't run diesel engines underwater. these U-boats would wait there knowing that they couldn't be seen from the sky

and that they couldn't be detected by radar because radar was too big to pick up on, you know, if they surfaced, it was just, it wouldn't see them at all. So they would sit there on the surface at nighttime, recharging their batteries, like quite comfortable that they were never going to get attacked. And what the British realized was that you could use microwaves as a much smaller, much more precise version of radar. So they fixed it into the nose of their aircraft and would fly out over the Atlantic.

And microwave the ocean. And microwave the ocean, right? And it was sensitive enough that it could even pick up on like a periscope. Wow. Just a U-boat periscope poking out of the water. It could spot it. It's absolutely amazing. You know, 10 miles away, you can see where the U-boat is.

Anyway, all of a sudden, these U-Boats are like just getting sunk, left, right and center, even when there's really heavy cloud cover and they've got no idea what's going on. I mean, they think that it's like that maybe the Allies must be, I don't know, like using magic essentially. Well, this seems related to a story that I should fact-check, but it's the origin of the whole carrots are good for your eyes story. I factored this before it's true. I heard that the Brits came up with that as a trick. to explain a way. No, no, no, no, don't think it's technology. It's just that our pilots are eating a lot of carrots and they're becoming very good at seeing in the dark or just seeing in general. No need to do your own experiments and invent it simultaneously. But the quite funny thing about it is that actually turns out that carrots has a vitamin in it that ends up being quite crucial for eyesight and seeing in the dark. So it's sort of true.

Yeah, I love that when the lie turns out to be a little bit true. comes back around and the liar didn't mean for that to happen and now they're a truth teller and the universe is whole again. Okay, so this up until, you know, like 40s, this is what my cravings are for. They're for finding U-boats in the ocean. And then Raytheon, this company that manufactured military items, they had all of these magnetrons sitting around, you know, they'd made loads of them, they're all just like sitting there. They're like, okay, well, we need to sort of, I don't know, get rid of them to whatever. Anyway, this guy, Percy Spencer, his job was. to muck around with these magnetrons, as they're called, right?

The magnetron is the thing that creates the microwave. Right. They're submarine detectors, essentially. And as he was working with them, he's, you know, sort of like mucking around with them. And as he stood in front of one while it was on, he knows something really weird. He had a chocolate bar in his pocket, and it had melted. He'd microwaved his own groin. Percy.

And like, thank goodness, something more serious didn't happen, but just this chocolate bar melted. And he was like, that's a bit weird. And I think a lot of people would see that and be like, you know, maybe my pocket was too hot or whatever. But instead he was like, I wonder what's going on here. So he went out, got a bag of popcorn kernels, came in, held them, like dangled them in front of the machine. And then they just exploded all over the laugh. And he was like, oh, I think I'm on something. Wait a kidding.

So microwave popcorn was one of the first deliberate foods created with a microwave. In terms of deliberate, it was the first. Wow. The absolute first. Next day, he goes off and he gets an egg. He's trying to microwave this egg with this magnetron, this military device. And the egg explodes in his colleague's face. Yeah.

And yeah, but he's the person who realized, oh, wait, this is a way that it could cook food. So at that point, Raytheon, the company who had this military items, they start building these commercial units, right? They're like six feet tall. They're, you know, cost the equivalent of 70 grand today. You only see them in really, really high-end kitchens. But meanwhile, over in Britain in the 1950s, there is this amazing, one of my favorite YouTube videos of all time

by our friend Tom Scott is about exactly this story. I think it's just so wonderful. Because what happens in Britain, there's a scientist called James Lovelock and he's doing these experiments on cryo preservation right essentially whether you can whether you can freeze something you know some tissue some creature and bring it back to life

okay right and he's doing some experiments on hamsters okay which sounds pretty good the hamsters are okay by the way it's important for me to say that but what they were doing they were freezing hamsters and then bringing them back to life, and it works. And it worked. It works. But the way that they were doing it was that, you know, you have all these hamsters in the freezer.

You get a hamster out. And then they had to heat up a spoon and then put the spoon on the chest of the hamster to bring them back around to sort of warm up their heart. It worked, right? It was okay. But it wasn't very nice for the hamster. Yeah. So don't try this at home.

No, it's a definite, definite do not freeze a hamster. I think they were doing it quite carefully as well. But he had read about this idea of a magnetron. He knew about it. He knew they were using them in America as, as, you know, the Raytheon were using this radar range, this really amazing cooking device. And he was like, well, why don't we, why don't we try and get one that will sit on top of a desk, like a small one, and use it as a humane way to de-frost hamsters? Why not? Why not? And so he builds one. And you can check out the Tom Scott video on this, because as I say, it's an absolute delight.

But he builds one and it turns out that it works. And all of a sudden there are these hamsters. You know, he tuned it perfectly so that it would exactly as you described, like vibrate the water molecules. And all of a sudden, these frozen hamsters are just like happily running around his lap. Coming back to life. Coming back to life. Okay. So the timeline of microwave cooking is chocolate bar, popcorn, hamsters.

Baked beans. Bake beans. Finally. made it to be. Finally, finally, made it to the top. Yeah, right? And like, this is it. It's just, I think this is why I'm describing that at no point in that history, when you're fixing them on the noses of an aircraft, it's someone going to say, oh, okay, well, obviously there's going to be a point where this belongs in almost every kitchen to grab the entire world. But that's what happened. But that's what happens. And it's the, is this, there's this notion in kind of the philosophy of innovation that I just really love about the adjacent possible that it's almost like humans are navigating this great network of connected rooms. And every time you walk into a new room, there is a new invention, there's a new thing to discover. But you have to have opened the room immediately before it in order to discover it.

You can't leap straight ahead. And it's like it's only because they had this U-boat device that any of this was possible. They opened the door that allowed the adjacent possible to be. be opened. Wow. Yeah. So I'm still not a big fan of World War II, but it does mean that I get my hot dogs hot fast faster. Yeah, I got to go to a microwave factory once, right? Because this is the kind of thing I do, Michael, instead of going to parties. And it was really amazing to be on the assembly line. And all of these people who are, you know, doing, like, doing their jobs, it's just the, the total difference between how mundane this object feels, how little attention we pay it,

and how it's actually using incredibly high-end particle physics to do something quite so boring. There's something so delightful about that disconnect to me. Yeah. Yeah. And it's cool to think that we all have a magnetron in our kitchens. Almost all of us do. And that we're using such a, like, space. age sounding technology to do such simple things like, oh, I need to warm up my coffee. These leftovers are cold. Fix that really quick. And you zap it with invisible light.

Yeah. And there you go. Your toaster, by the way, meanwhile, the guy looking for that, he was trying to do the opposite problem. He was trying to turn heat into electricity. And then he realized he stumbled upon nicromium, which is basically the filament that you get in toasters, but also in ovens, in kettles, in, you know, in air fryers, all of that. Right.

It's the metal that turns orange hot. Yes, exactly. When electricity passes through. Because it does exactly the opposite thing, right? He was looking for something that turned heat into electricity and he discovered something that turned electricity into heat. Ends up being phenomenally useful, like phenomenally useful. Like, incredibly, incredibly useful.

The first Bradshaw cook was invented in like the 1600s. Unfortunately, they were quite prone to exploding. It's the only thing. But it's like, you know, you change the pressure. It's a bit like trying to boil a kettle at the top of a mountain. You change the pressure. You can cook at, you know, incredible. If you can create this perfect seal and increase the pressure,

it sort of changes the situation under which you can cook, right? You can allow liquid water to reach temperatures of 120 degrees or so without boiling away. Yeah. Again, it's like it's something that is just playing with the laws of physics in order to just make your weak night. a little bit more easy. Yeah, so who knows? What new kitchen appliances are we going to get because of our upcoming missions to the moon? When am I going to have, you know, nuclear fission powered kitchen implements that will allow me to, you know, peel an orange faster? Or today, my problem is opening

packages. Okay, everything is packaged way too strong. And yes, I know this is also a problem because I'm becoming like an old person, but I'm like, guys, how come the bacon package is so hard to open? Like, Give me a break. Come on, scientists. Repurpose some crazy war machine to help me open my food. We just want enough war that everyone gets on with it and does some good science, but not enough that anyone is harmed. Okay. Right.

Let's prepare the technology. Get ready and then suddenly become, like, make a deal. No one got hurt. But what are we going to do with all this technology? Kitchen time. Yes. in time. Exactly. So there you go. I realize now that we've come to the end of Hannah's kitchen episodes that all the people who has spent the last decade or so telling me that I belong in the

kitchen, well, actually, you were right all along, frankly. Well, yeah, because look at all the joy and insight you've brought us by taking us into the kitchen. Well, there you go. Thus ends my tour. Thus ends my scientific tour of the high-end science lab that each one of us has in our own houses. Well, I appreciate that, Hannah. Thank you very much. I mean, obviously, I like fridges, but now, because of you, I understand that they are both literally and metaphorically cool. Well, you can join us for our field notes episode later on this week. And next week on Monday or Tuesday, depending on which country you live in, we'll be back for our usual episode. As ever, you can email us, the rest is science at goalhanger.com. And I think we should finish with a

microwave.