The Rest Is Science - What Happens Inside Earth's Forbidden Zones?

Episode Date: July 29, 2026

What grows in the spaces humans are forced to abandon?Hannah brings Michael an actual piece of barbed wire from the Korean Demilitarised Zone, one of the most heavily fortified and forbidden borders on Earth, and it sends them somewhere unexpected. From deserted no man's land and radioactive exclusion zones to remote islands that most of humankind has quietly agreed to leave well alone, they explore the surprising ways life adapts to the damage we leave behind.Plus your questions: the scientific fact that scared Michael most, where tectonic plates actually go when they collide, and a very good would you rather. Send questions of your own to [e-mail] or find us at r/TheRestIsScience. ------------------- 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 MeekAnimator: Sam BensonVideo & Social: Bex TyrrellAssistant Producer: Lucy LipscombeProducer: Simona RataSenior Producer: Lauren Armstrong-CarterChief Digital Officer: Samuel OakleyExec Producer: Neil Fearn Learn more about your ad choices. Visit podcastchoices.com/adchoices

Welcome to the rest of science. I'm Hannah Frye. And I'm Michael Stevens. And I've got a little treat for you today because we've got a field notes episode, as usual, this part of the week. A little bit later on, we're going to come to your questions, your big ideas, your interjections. You wanted to send us at Restor Science at Gohunger.com. But right now I've got a little object for you, Michael. I love the field notes where you bring the object because I get to just be an audience member for a while, you know? You genuinely don't know what's coming up.

I thrive when I don't know what's going on. Okay, should I give you an audio clue first? Yes, please do. I'll be honest with you, if you get this from the audio clue, I think there's a zero percent chance. I think there's a zero percent chance that you're going to get this from the audio clip. Okay, now you've got me really, really interested. I'm going to see if I can crack this with just the audio.

Okay, you ready? It sounds like a baby's rattle-type toy, like keys on a plastic keychain. I want to say a plasticy sound. It wasn't like metal, unless it was hollow metal. I think it's more like metal on glass. Well, you know what it is, though. What the heck?

Sorry. It's like something rolling around in something hollow, like a ball in a ball. You're, okay, look, obviously, that's the absolute closest you're going to get. Because what it actually is, is a bit of barbed wire in a glass jar. Oh. Why do you have a bit of barbed wire in a glass jar? I don't know. It looks strange.

Doesn't it? Looks very strange indeed. This is a bit of barbed wire from the demilitarized zone between northern South Korea. If you're only listening, Hannah is holding a glass jar that's kind of a little taller than a film canister, but about as wide, if you're old enough to remember what those are. And it's got like a cork at the top, but inside there's a little snipping, a little piece of barbed wire and like some rocks. There is a gift shop at the DMZ. I didn't know that. Is that not the craziest thing you've ever heard? And I'm not talking about like, oh, you're away from the demilitarized zone. No, no, no, no.

I mean, literally in the demilitarized zone, there is a fun fair. That makes so much sense, though, because so many tourists to South Korea would be like, I want to go up there and see North Korea with my eyes, and I've got money to spend. Uh-huh. I bet they're just putting up new barbed wire every day and then clipping it up. Just to take that old stuff down. This episode is brought to you by Cancer Research UK. Our bodies are incredible machines,

whirring away making more and more DNA to build the proteins that keep us alive. In fact, in the last minute, your body has made over 200 million new cells and enough DNA to stretch to the moon and back. To the moon and back. That's so much DNA that if you compared it to the size of the cell it fits into, that would be like squeezing the London underground into a suitcase. By the age of 50, you have copied almost 6 trillion miles of DNA. But every time that your body copies DNA, it risks making mistakes.

And over time, those mistakes can accumulate. And that collection of errors can lead to cancer. But incredibly, cancer research UK scientists can spot these errors. And by finding them, they've helped double UK cancer survival over the last 50 years and are driving even more discoveries that could tackle over 200 types of cancer. For more information about Cancer Research UK, their research and breakthroughs and how you can support them, visit cancerresearchuk.org slash rest is science. Now streaming on Disney Plus, the Hulu original series Furious follows FBI agent Alice Black,

played by Emmy Rossum, on the hunt for a mysterious and calculating serial killer. Both walk their own paths toward justice, and as their lives start to intertwine, the line between right and wrong begins to blur. New episodes week over week. Watch the Hulu original series Furious, now streaming only on Hulu on Disney Plus. The other things that you could buy, by the way, are the DMZ.

I sort of feel a bit funny thing Z, but it also doesn't sound right to say DMZ. The other things that you could buy at the DMZ gift shop are wallets that are shaped like hand grenades. And then all kinds of... of like little figurines of North Korean leaders that I think possibly the North Korean leaders would not enjoy.

But you know, the people who own those gift shops, they're lobbying both countries very hard to keep this demilitarized zone going because their business depends upon the political situation. You are absolutely right. And they're not the only ones who are desperate to keep this walk going. because actually what I want to talk to you about today is not the gift shop at the DMD.

It is the animals that have flourished. Oh yeah. In the no-go zone that has been created by human intervention. And there's a few of these places around the world, right? The DMZ is one of them, which has basically been completely unoccupied by humans since the 1950s. And in the decades that have passed since, there is this complete flourishing of nature within that zone in this crazy way. So nobody can step foot in this zone. Yeah.

Certainly not. You certainly wouldn't be authorized to do so. Right. I mean, you can, but you may not. You may not. You may not. And also, it would be extremely ill-advised because the entire place is totally covered in landmines. Yeah.

So also you would not and should not. Okay, good. You may not, you should not, and you could not. What pieces of you might make it over? So even conservationists are not able to go into this zone in order to do proper surveys of the animals that are there. So then what flourishes? So there's all kinds of bird species.

There are rumors that there are leopards and tigers that have found a home within this region. There's no sort of really good evidence of any tiger haven't been spotted. So I think that one might be a myth. But there are boars, there are deer, there are vampire deer, in fact, which don't grow horns. They grow sort of like funny teeth. Oh, wow. But the other thing is all of these paddy fields that were abandoned.

Wait, paddy fields, like, I know about how long the demilitarized zone is, but how thick is it? How wide across? Only about four kilometers. Okay, so you've got a four kilometer band separating North and South Korea where people may should and could not enter. Nature is healing there in its own way. And it's healing really well, by the way. There's some estimates that say 38% of the critically endangered species in Korea live in that tiny little area. Whoa.

So it's not just the gift shop owners. who are desperate for this place, not for the war to never end. You know, if suddenly there was a peace treaty and everybody, there was a reunited career or however it ended up being sold, it would just be devastating for their ecosystem that has been created in this abandoned land, right? It would be completely devastating. The paddy fields, by the way, that were abandoned in the 1950s,

they turned over very quickly into grassland. And then they very quickly, from then, started growing willow. And now all of these paddy fields have turned into these alder-dominated forests. So you get these little pockets. And it's just this amazing study that you can make in what happens when humans completely vacate an area. It's really extraordinary just how much nature thrives. And it's different than what's going on in Chernobyl because there you have the added variable of radiation. Exactly. We've talked about the black frogs that you see in Chernobyl, how the radiation

has ended up impacting the evolutionary path of different creatures that are there, that frogs with darker skin were able to survive the radiation better than those that didn't, those that didn't would die out. And so the closer you get to the original site in Chernobyl, the darker the frogs get. There are places that are sort of in the middle. So I was incredibly lucky to get to go to the DMZ when I was filming a documentary, I've also been inside the exclusion zone of Fukushima, which is somewhere between the two. So it has the radiation element that Chernobyl has, but nowhere near the same sort of scale, right? And it's, Chernobyl is like there's certain parts of Chernobyl that will never be inhabitable by humans, right? There's no, there's no going there ever.

But in Fukushima, the idea is that slowly, slowly they are trying to decrease the radius of how far people are not allowed in. So it's sort of like a, it's not never, how did we say it for the DMC? You can't, you shouldn't, you won't or something. Yeah, you may not, you should not and you cannot. Right. So from Fukushima, it's more like you may not, you probably. should not. And you can maybe in future, essentially. All right, it's a little more hopeful. A little more hopeful. Tell me about Fukushima. All right. So here's the thing, okay. Going inside Fukushima

is, it's wild. It's really wild. So describe it for me because I've never been there. It is an area of land. So you are just inside of the coast in Japan where the tsunami basically overwhelmed the sea wall of a power plant. A nuclear power plant. A nuclear power plant, important distinction. Flooded the reactor and cause radiation to spill out essentially in the surrounding area. So it remains very radioactive, nowhere near as bad as Chernobyl, but really dangerous still. And when you go in there, so we didn't get to go right up to the reactor, but we got to go in

the sort of the controlled zone. And when you go in, there are human settlements within that. region that were abandoned on the day and have never been returned to. Not only has the forest and, you know, nature essentially reclaimed these buildings, are sort of swallowed them up from the ground and around. The roof is caving in, there's rubble everywhere, just the elements have had their way, essentially, with these buildings. But you also, where they are closed off and locked away, you look inside the windows and you get this sense of the panic people felt when they left on that day. And for context, this was 15 years ago. It was 15 years ago, right, exactly.

So that's how long humans have left it abandoned to nature. Or the other way around is to say that's how quickly it gets swallowed by nature, how quickly nature returns to dominance. You look in the window and you see the slippers of people sort of rushed as they were leaving and they were putting their shoes back on to get out of the building. There's like teddy bears kind of strewn on the side. There was like there was one place where I looked in the window and there was like a crate of half empty beers that they must have been aiming to take to the recycling, but then never had the opportunity to do so. And when we got to go inside this exclusion zone, we were going for the story about rewilding. And we spoke to some researchers and they told.

us that there were some radioactive bears within the exclusion zone. We were going to go and film these radioactive bears. And then when we got there, we realized there'd be a slight mistranslation because it wasn't radioactive bears. It was boars. Oh, okay. Still fun. Still fun. But also, it wasn't boars so much as boar singular. And actually, it only ever been caught on capital once. So instead, we filmed some radioactive dragonflies, which was, you know, No, a close second. So they're radioactive in that they are themselves radioactive. If they land on you, you're exposed to ionizing radiation from the body of the dragonfly.

I don't think within Fukushima it's quite that extreme. Okay, so it's more like dragonflies that live in an exclusion zone. Exactly right. But why I sort of started thinking was how many of these different exclusion zones there are around the world, How many different places are now completely untouchable because of human decisions, human moments? So you've got Chernobyl, of course, Fukushima. There's also a place called Lake Karachi in Russia. And this is a place that the lake shore, sort of this, you know, around this little lake,

it read around 600 Ronken in 1990, which is basically you stay there for an hour. and you're dead. Okay, that's kind of the level that we're talking. That's a lot. This is where the Russians were testing their nuclear weapons, essentially. There's also the Bikini Atoll, Marshall Islands, where 23 different bombs between 1946 and 1958 were detonated. It's still totally uninhabitable. And the problem there, it's not so much the ground. It's more about the food chain because all in the coconut palms and the breadfruit,

that's grown there will also carry a dose. So when you were saying about radioactive dragonflies, it's radioactive coconuts. Yes. And the people who used to live there still don't. Still don't, right? I mean, astonishing. I mean, at the time the US government really did think it was going to be temporary. They were like, oh yeah, you guys got to leave for a bit. We'll do our tests and you can come back. And now I think a lot of them and their descendants are in like Arkansas. Right. And the thing is, I mean, there's, some of these places may eventually be re-inhabitable. So, you know, Bikini Atoll, for instance, that researchers can go there. It's not that you, the sort of like passing dose isn't, you, if you're very careful and very, you know, take the correct precautions, that it is possible to visit. But there are other places in Marshall Islands, the tomb, for example, where there is a concrete dome of 120,000 tons. of plutonian contaminated debris

and also it's sort of cracking which is oh no bad but that place is indefinitely there's no

going there ever you know it's just too much and where is that that's also Marshall Islands as well Runeit Island is called

and it's called the tomb oh the what's the island called Runeit Island Runeit Island There are other places

that are not just because of nuclear testing so there is in Zone Rouge, it's called in France, which is, it's still legally sealed after World War I. This is a place near Verdun, and 99% of the plants that grow there will die due to arsenic in the soil. I mean, we're talking great, it's about 17% by weight in the soil, right? This is like,

it's horrendous. So human wandering around is excluded for good reason. Have they tried to do anything to fix this, or are they just kind of leaving it? Just leaving it, I think. Someone in the comments may correct me, but in my understanding is they're leaving it. In 2019, they were like, look, it's impossible to clean. Human life's impossible there.

Don't even go there. That was used in World War I, and now it's just polluted this area of land so much that even the plants aren't, they're not flourishing there. No, exactly. Maybe for their short lifetimes they are, because there's no human development happening,

And that's one of the things that makes the DMZ so interesting because, I mean, they did spray with Agent Orange when the line was drawn in the map, essentially when this separation of North and South happened, which was when Japan evacuated Korea during the Second World War. And there were a couple of American generals who'd never been to Korea and needed to work out which bit the Soviets should take and which bits the Americans should take. and they just chose a line of latitude on the map. Didn't take into account that there were railway lines going through there. There were rivers cutting across it. It's just like just whch, kind of very bluntly and brutally. There was a bit of fighting for a few years, instantly until 1953, when they signed this peace treaty.

Sorry, forgive me, it's not a peace treaty. Crucially, it's a ceasefire. So actually, they are still technically at war. But that was what really set the boundaries of these two. But that's sort of what makes it interesting is that it is a byproduct of war, but there aren't these things like anthrax, radiation, you know, all of these incredibly horrible arsenic or anything like that. There's none of these sort of incredible weapons of war that make it mean that their wildlife can't flourish. It's not polluted with a substance. There are landmines there.

Those wouldn't affect a dragonfly or a plant. But a tiger? A tiger, maybe. Maybe, but we're not sure if there are tigers there or not. We're not sure. So anyway, I guess the point about all of this stuff, the thing that makes me, it kind of gives me a little bit of hope in a weird way,

is that in a sort of depressing way, maybe. But I think that we spend a lot of time talking about how, oh, the world might be over. But we talk in sort of apocalyptic terms about climate change, about about nuclear war, about all of the potential things that we could destroy ourselves with. But I think the thing is, is that actually we are talking about ourselves, right? Nature is going to be fine. The world is going to be fine.

Like, it's really only us. And I think that we have this real habit of imagining that it's like human made and nature, as though there's a separation and a distinction between us. but actually we are of this earth, right? And it's like, we're just one little element of it. And if we leave, they're going to be fine. They're going to be absolutely fine. Yeah, humans are just one of the many kinds of animals on Earth.

There are ways in which we have a responsibility that I don't hear discussed too often. Like we, for example, if an asteroid was hurtling towards Earth, it's not going to be the cows that save. the planet. No. That's on us. Yeah. Yeah. And that could be

genuinely the apocalyptic. Yeah. For everything. That could genuinely end all life. It will come down to us and not the tree frogs. There is one place when I was looking for

areas that are closed off to humans that you cannot go to. I did find one place that I think sounds really interesting. Okay. What is it? This is one of the few examples that has not been created

as a result of war or fighting between humans. This is a place called Ilha de quiamada Grande otherwise known as snake island

in Brazil this is a place that has got so many snakes on it that it was closed off to civilians

in the 1920s and has never been reopened it's a 43 hectare island

holding around 4,000 vipers wow each one of which has venom that is strong

enough to kill you within an hour Yeah, and so they get to live their own lives free from human intervention because we've just decided that that's how it's going to be. No, thanks. I think they're also in danger. I think that's another point. This is like a particular place where they thrive and everyone's like, okay, let's just, should we just leave them? We'll just leave them alone. We'll just let them do. Let's just not go there. Yeah, all right. The snakes can have that. So maybe that's what life will be like after we wipe ourselves out. You know, the houses will be reclaim. by the forest within 15 years, swallowed by vines, and then eventually it would just be a snake planet.

Yeah. Do you know what? I think I'm still a bit depressed about the mirrors from last episode. I think maybe I'm being a bit pessimistic. No, that's fair enough. How excluded does a place have to be? Like, there are mountains that have still not been climbed because they are sacred to the native people. Mm-hmm. And in some cases there are laws against anyone climbing those mountains.

So their places where nature can be untouched. Absolutely. Yeah. I mean, there's plenty of places like, you know, the middle of the Sahara is, it may as well be untouched. It may as well be, but it's also, I mean, there's life there. But in that life is, you know, it's flourishing. I mean, is it flourishing or is it kind of struggling? It's there.

but it made me think of places like the Trinity site where the United States did its first atomic testing that's open to the public once a year otherwise nature there gets to have its own way but you know the amount of nature things that can be done in the desert where the sand's been turned to glass trinotite is limited there are places too where humans are excluded like Sentinel Island, off the coast of India.

Absolutely. Well, not all humans. Not all humans, just the Centalese. They are a culture, a tribe of people who live on this island and have made very limited contact with the outside world. I think that they were given some coconuts maybe in the 80s or 90s by some visitors, but we don't know their language. And to what extent they are aware of that.

the outside world is unknown. What do they think about the airplanes they see way up in the sky? How big do they think the world is? These are things that we don't try to answer because it's been decided that they should be allowed to live their way without interference. They also, a couple of times, they have killed intruders, right? So people have gone there. There was a fisherman. There was a missionary who ended up, the tribe were like, no, thank you very much done. So yeah, the Indian government trolls it is really careful about making sure that nobody goes there they are yeah that missionary that was a pretty recent story he thought you know bringing the word of god to these people is my mission and he didn't come back his body was buried and they did try to maybe recover it but they

want to leave the sentinelese to them to themselves to be themselves and there was a YouTuber who tried to go there have you seen this story no this uh this uh was very recent, a YouTuber tried to sneak onto Sentinel Island to make contact with these essentially uncontacted people. And it was very, very controversial. He got arrested and finally posted his videos just a few weeks ago. And to be honest, it's not entirely clear to me that he actually went to Sentinel Island. The videos are, it's very, they're very unprofessional and un, um, serious. It's kind of like, oh, guys, I'm doing this for you. Whoa, do it for the vine. And then it's not obvious to me that he's actually there. He just kind of appears at an island.

His boats on the coast and he's like a few feet away from it. And he's like, I'm here. Okay, I don't see anything. I'm going to go back. And then on his way back, he throws a can of Diet Coke into the water and says it'll get washed up there. I wonder what they'll think. This is. I wasn't convinced he actually did it. I'm wondering how much of this was a hoax. Anyway, I'm heartened to see how controversial that whole stunt was. Me too. You don't get to make decisions for humanity on your own, okay? No, don't do that. That's right. But there you go. Anyway, that's, I've been to two of them, two exclusion zones. I'd really love to go to Trinity to the Trinity site.

Yeah, my uncle has been at least once. I think he tries to go like every year. Is that safe? Well, yeah, I think for the brief time that you're there, it's, I guess, safe enough. Imagine if he had a necklace made of Trinity glass. Did you show that in a field notes in the past?

No, I've told you privately about how. You told me privately about it. You showed, you showed the glass that was made with lightning. I'm saving it until it's ready. But one day, one day I will have something like that for you, yeah. You've shown us two kinds of natural glass. You've shown us the glass made by lightning strikes, and you've also shown us obsidian.

Look, these are my private obsessions, Michael. Did you know that I gave my wife a giant chunk of obsidian for her birthday this year? Because of you in that episode. Yeah. I always skipped by the obsidian. My wife loves rocks as well. You guys should talk soon. But I always skipped past obsidian because I didn't know what it was.

Actually, I didn't even look into it. I'm afraid to admit that I was a bit incurious, which I hate. But then you taught me so much about it that I'm like, whoa, so I got her this beautiful piece. And then we had to travel with it back from New Zealand. And she was like, don't get me heavy rocks for my birthday when we've got bags to pack for an airplane. Look, that's fair. That's absolutely fair. Did you get the one with the little dying florets in it? No, I didn't.

I went with no florets for me. yet. They had a piece like that, and I was like, oh, I don't know. I went with just the pure jet black piece of nice, fresh, geologically fresh piece. And I told her, hey, it's going to become a new gift, just give it 100 million years or more. And it's the gift that keeps on giving. Absolutely. Yeah, too right. Too right. Look, I just think the stones that everyone gets excited about are really boring. I think things like volcanic glass is much more exciting. All right, Thus ends my little foray into no-go zones. We're going to go to a go-go zone after the break,

which is going to be your questions. How was that for a link? It's a lovely link. We'll see you guys soon. This episode is brought to you by Cancer Research UK. What if your immune system could learn to recognize cancer cells? That's immunotherapy. One type is car T-cell therapy.

T-cells are your body's watchman, And doctors can now extract these and reprogram them to spot cancer. They've started showing this real promise in treating cancers of the blood like leukemia. Because unlike most cancers, blood cancer cells, they float around separately. And that makes it easier for CAR-T cells to seek them out and destroy them. And now Cancer Research UK-funded scientists are designing CAR-T cells that can tackle solid tumors too, making them tougher so they can survive a more crowded and hostile cancer environment. Now, these approaches are experimental, but they do start to show where treatment might go next.

And over the past 50 years, Cancer Research UK's pioneering work has helped to double cancer survival in the UK. I mean, this shows you how far research can take us. For more information about Cancer Research UK, their research, breakthroughs and how you can support them, visit cancerresearchuk.org forward slash rest is science. Summer heats up in FX's The Shards. Set in 80s, Los Angeles, the Shards follows a group of beautiful, privileged prep school students who are preyed on by The Trawler, a serial killer targeting teenagers across the city. This fever dream of youth, beauty, sex, and mystery is a must see.

FX's The Shards, streaming August 5th on Hulu on Disney Plus. Sign up now at Disneyplus.com. Okay, we're back, Michael. First one for you. what is the most cosmic horror science facts that you know cosmic horror i love this question this one came from our subreddit r slash the rest is science it was asked by petros and estacia dis i believe that's how you pronounce it they ask yeah what is the most cosmic horror science fact i know i guess the the most scared i've been by a scientific thing was probably, I was reading

Greg Egan's diaspora and in that story there's a robot like an android thing that lives on the moon by itself and its job is to like check readings from different astronomical objects and one of them

are these black holes that are going to be colliding and the readings aren't matching the theory. They realize that actually this is going to cause a very different effect than they predicted. And it's going to create a gamma ray burst

that will destroy Earth. And I was like, what don't we know about the universe that could just happen? You know, like, we all feel kind of safe, like, oh, there's nothing, you know, too dangerous, very close by. Gamma ray bursts don't happen that often. But we don't know every possible gamma ray burst

source near us and when it will go. And if it goes, that could just be the end. It game over, and it would just happen and we would be fried. Some of us might be able to live for a few agonizing days afterwards. But this is a phenomenon where an enormous amount of gamma rays, which is the most energetic form of electromagnetic radiation, just gets shot into space and it was going to cause immense damage. I mean, talking of nuclear bombs, that's essentially like a A giant, giant, giant, giant, giant, giant, giant, giant, giant, it is the brightest thing in the universe, right?

It's, it's getting hit, like, directly with a pulsar's pulse. It's bad. And I started to think, man, that could happen in my lifetime. I mean, is that horror enough? That's kind of just more like... I mean, so it doesn't get much worse than that. It doesn't get much worse. The thing is, is that, okay, I mean, you wouldn't see it coming, because it's true.

travels at the speed light. So it's with you before you know. It would almost certainly kill everybody instantly, wouldn't it? Yeah, I mean, it all depends on the strength of the burst. But yeah, I think that's where the horror comes in, that it's not just violent. It sneaks up on you. You don't know it's coming. And once it's there, you don't know what happened because you're already gone. There's something about everything you've ever known and loved disappearing immediately, that I mean I wouldn't say it doesn't bother me but I think that

I could handle that I could handle that actually because you just wouldn't know you wouldn't know what hit you whereas I think if it was beta radiation in some way then everyone's going to die

it's just it's going to be much more agonising and you're going to see people you love decay in front of you and know that that is coming for you and there's nothing you can do about it. Right. At least a gamma ray burst would be sudden. Well, the point is this whole book, Diaspora, it's a very hard sci-fi by Greg Egan and it scared me. I read it mainly on an airplane. I'm already

kind of a scared flyer. We've talked about this before and I couldn't really handle it. It really amped up. One of the other terrifying things it discusses is what it's like to travel near the speed of light. such that when you get to your destination, you know, it's been a few nights, but yet a thousand years has passed on earth. And everyone that you knew there is now gone, long gone. And you live in a different universe, basically. And it deals with that in ways that just boggle the mind. We start talking, because the characters are immortal artificial intelligences, and so they

can live through a trillion years easily. And they just don't even recognize this. They eventually escape into a four-dimensional universe, and he describes exactly how planets would orbit in such a universe, how life forms could eat in four dimensions, and it just makes you feel so alien that it scared me. I would call that cosmic horror. I highly recommend it.

Okay. You know, you've mentioned the Egan book a couple of times. Maybe not that one, but a few of them, I need to get on it. I need to up my sci-fi game, I think. Okay, next question that came in from Liam Brain. Liam, is that your real name? Liam Brain. That's who listens to this podcast, everyone.

Mr. Brain himself. You know what, that's a bit like, I met someone in Greece once who was called Adonis, and I thought that was a lot of pressure from his parents, you know? That's a lot of pressure. Anyway, Liam, you have a great name, and you asked, I'm quite interested in the tectonic, plate movement of the earth.

If plates move and therefore land shifts, wouldn't the earth decrease an increase in size? Where do the plates go when crashing? Great question, Mr. Brain. And really, honestly, this is like a really good instinct. This is, there was this whole theory that was built on exactly this idea, by the way, which was called expanding earth theory.

And some people who sort of championed it, they believe that, okay, well, the continents are drifting apart. And the reason they're drifting apart is because the planet must be quietly inflating beneath them. It turns out that just doesn't hold. You should really think of the earth as more like, I mean, it's as fish, sure, but it's more like you've got corks that are floating on the top of water underneath. They're sort of bobbing around, which is what the plates are like. If they crash into each other, especially if it's two land masses that crash into each other,

then they don't really have anywhere to go, but they're too kind of light. they sort of end up floating upward and that's how you end up getting mountain ranges. The Himalayas is a perfect example of that where these two tectonic plates met and the Himalayas pushed upwards and we know this for sure because you can see fossils

at the top of the Himalayas right? And there's sort of in the mountains of the Himalayas that are definitely things that used to live by the side of the sea right? They were definitely on the edge of the coast in the past. For example

Pachisetus, one of my favorite historical creatures, which is basically a dog that is the ancestor of the whale, right? There was like a dog that was living on land and would dip into the sea to go and eat some fish. That is found in the Himalayas, and we know that it used to live near the ocean.

On the other hand, if you have sort of two Teutonic plates crashing into each other and they're under the sea, sort of everything's much heavier and one of them will sink downwards. and end up getting kind of destroyed and melted into the mantle below. On the other hand, if you have things that are ripping apart, which is what's happening actively in Iceland at the moment,

Iceland has the two plates, the Eurasian plate and the America's plate, and they are ever so slowly being ripped apart. And what happens is you get effectively the magma coming up from underneath. And this is why it's an active volcano region. This is the reason why you're still getting all of these kind of bursting up as these cracks appear between the two plates. There's a football field which I went to go and see in Iceland where people were literally playing football, right? And then an earthquake started. And then a massive gigantic crater appeared in the ground over the course of like 24 hours.

It's phenomenal. But then where did the rest of the plates go? When they separate, their other ends aren't just filling in empty space. The earth is a, finite sphere. So are they crunching on the other side? So they're either going up or going down. Right. Yeah. So the Earth is not getting larger or smaller. It's just moving around. And actually, satellite images that have looked into exactly this, the expanding Earth theory, they measure that the Earth's radius overall stays incredibly steady. We're talking about a fraction of a millimeter a year. And this really is a question of scale. You know, when you're standing on the surface of the earth, sort of this crater that appears that's, you know, a few meters wide feels absolutely

enormous. But compared to the radius of the earth, I mean, we are, they call it a crust for a reason, you know, we are right, right, right on the surface of this thing. Yeah, it is thin. And, I mean, the earth is getting like more massive as space dust falls down to it. That's offset by mass the earth loses, like really light gases, hydrogen. and helium, they get up to the top and they get picked away by solar wind. And the Earth also is like radiating heat out into space, which means it does lose a little bit of mass. But overall, the falling space dust is making Earth more massive. But as Hannah said, it's like not actually growing in any noticeable way. Yeah, it's just microscopic compared to the size

of the whole planet. Okay, last question from Oscar. Oscar says, if you had to live as either one of the first humans or one of the last humans to ever exist, which would you choose and why? I love this question. I want to hear your answer first, Hannah. Oh, I think I'd choose one of the first, basically for the same reason as your cosmic horror story earlier. I think the idea of knowing that it was coming to an end and knowing that the end was inevitable, I think it's about seeing those that you loved and die around you and struggle. I think I'd rather, no thanks.

really depends on when and why you're the last human. If it's because you get to sit there and watch a black hole approach and take over our solar system, that would be terrifying. But if you, if the last human is going to be alive in the year 12 trillion as a digital consciousness or in Google years or more, and it's just the heat death of the universe you have to contend with, then I don't know, you might not even have to feel things because we've evolved to some cognitive state so far and beyond. If you mean being a first person, you mean being like a very early homo sapiens,

well, then I don't get to enjoy my favorite movies and snacks. That's true. You also don't have to get up when your alarm clock goes. Yeah. You don't have the hell of being like, God, have I really been doomscrolling for three hours? hours. Yeah, you're saved from doom scrolling. Never hung over. Yeah, you're never hung over. You're never late. You're never, ever late. So your answer is that you would like to be one of the

first humans. Yeah, I think so. Okay, well, I'm going to choose one of the last, because I'd like to be there on the complete mountain of history so that I can kind of be like, okay, I want to see how the story ends, you know? I don't want to feel like I'm missing out. I just feel like those early prehistoric homo sapiens they must have FOMO they must be like guys can you imagine there's going to be a World Cup one of these days and we won't be around for it you know what they can never say they can never say in my day they can never say back in the good old days because this is the only days oh yeah well back in my day oh we did things the same because my parents were uh homo erectus no I love that.

Obviously, to be scientifically correct, clearly we're joking. Because human evolution was not this like suddenly a bunch of babies were born one year. And they were all like, oh, yes, I'm a cognitive social species. There was no first human. There's just this smear of ever-changing organisms. But I do love jokes like that. I love thinking of, you know, five, six thousand years ago, you know, the grandkids. My parents are like, well, back in my day, we didn't have these fences. We had to go and find our food. You kids today with your agriculture, it's making you all soft.

What is this newfangled pottery? Yeah, we just carried things in our hands. What do you mean? We invented a bucket. Back in my day, we didn't have all these words. We just grunted and looked. Exactly. I want that. That's what I want. That's what I want. I think we've talked about this before. Like, I'm obsessed with this. I just, I spend so much time reading through people's concept of deep human history in antiquity. Like, when in the most ancient literature we have did people say anything about the way things used to be? And of course, there are no written records of like, you know, my great, great, great grandma, like, lived in a tree.

You know, it happened too slowly. But the ancient Greeks did have this idea that they used to be like the nomadic tribes they were aware of, that they used to not have their infrastructure and their society. They were only guessing. They didn't remember this. This wasn't in living memory or oral history, but it was an idea that they believed in. Or at least one author believed in. So, okay, yeah, basically, I'd like to be the last human and Hannah would like to be the first.

There you go. Between us, we sandwich. Everyone else. It's everyone else. All of you out there. Yes, our favorite way to be. The Hannah Michael sandwich of history. Well, we're the bread though, aren't we? Oh, yeah, we're the bread.

I guess sandwiches are named after what's inside, not what's on the outside. The human sandwich. Yeah. We're the brioch buns of humanity. Okay, well, thank you for that. What great image to finish on. as am you can send us your questions The Rest is Science at Gohungin.com

And you can check us out on our subreddit R slash the rest is science good questions there including that one about cosmic horror I've got more cosmic horrors I'll be sharing in the future so stay tuned absolutely we'll see you next week

thank you very much bye-bye