How To Drink Lava

Is lava water, and could we have a delicious hot cup of it? Is ice really a rock, and not water? And, the age old question, is water wet? From the minerals that shape the taste of our favourite drinks, to the tiny isotopes that reveal where a person, or whale, has travelled, Professor Hannah Fry and Michael Stevens reveal the hidden life of H₂O. Along the way, they uncover why pure water can be deadly, how yesterday’s sewage might be fuelling the future, and discover that the water in your glass might be older than the Sun. Prepare to rethink the world’s most familiar liquid - it’s far stranger, rarer, and more extraordinary than you ever imagined. ------------------- For more information about Cancer Research UK, their research, breakthroughs and how you can support them, visit 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 ThorntonVideo & Social: Bex TyrrellAssistant Producer: Imee MarriottProducer: Becki HillsSenior Producer: Lauren Armstrong-Carter Head of Digital: Samuel OakleyExec Producer: Neil Fearn Learn more about your ad choices. Visit podcastchoices.com/adchoices

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

• 0:00Hannah Fry?

  This episode is brought to you by Cancer Research UK.

• 0:02Michael Stevens?

  Imagine this, inside all of us, billions of cells follow millions of instructions written in microscopic code. And when a new cell grows, it copies those instructions, but the smallest error can lead cancer to develop.

• 0:17Hannah Fry?

  Right. And this is the reason why there isn't a single cure for cancer, because, you know, there are more than 200 different types, each of them have got different distinct characteristics, you know, different challenges, different mysteries. And that means that trying to cure cancer isn't like following a single path. It's like trying to map out an entire forest.

• 0:34Michael Stevens?

  That's right. And Cancer Research UK is the world's largest charitable funder of cancer research. I mean, their work spans more than 20 countries with over 4,000 scientists, doctors and nurses pushing knowledge forward to save and improve lives worldwide.

• 0:50Hannah Fry?

  You know, over the last 50 years, the work that this charity has done has helped to double cancer survival in the UK. And you have to think about, that is, that is more parents at the dinner table, right? That is more friends at their birthday parties. That is more people who are living longer, better lives.

• 1:08Michael Stevens?

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

• 1:19Speaker 02

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• 1:49Speaker 03

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• 2:20Speaker 04

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• 2:53Michael Stevens?

  Hello and welcome to The Rest Is Science. I am Michael Stevens.

• 2:57Hannah Fry?

  And I'm Hannah Fry.

• 2:58Michael Stevens?

  And today, we're going to get a little bit splashy, a little bit wet. No, but we are going to talk about something that's wet: water.

• 3:05Hannah Fry?

  Hang on, are you sure water's wet?

• 3:07Michael Stevens?

  Actually, I'm not so sure.

• 3:10Hannah Fry?

  This is quite a big question.

• 3:11Michael Stevens?

  It's a very memed question: is water wet? I have an opinion on it, do you?

• 3:15Hannah Fry?

  I... Michael, you tell me yours.

• 3:18Michael Stevens?

  Okay, what I think is that one molecule of water, dry. Once there's more, it's soaking wet.

• 3:24Hannah Fry?

  Soaking wet. Well, hold on, we should say first about why this is a memed question, right? Because it's like, water itself, the things that it touches are wet, but is the water itself wet?

• 3:37Michael Stevens?

  Yes, that's right, water makes things wet. But water on its own, would you call it wet? I would, because I think water can wet itself. Wetness is about intermolecular forces on water attracting themselves on to some other material.

• 3:51Hannah Fry?

  Okay.

• 3:52Michael Stevens?

  That other material, in my opinion, could be another water molecule. So just the surface tension between two water molecules means that they've wet each other.

• 3:59Hannah Fry?

  So, one water molecule not wet, two or more?

• 4:03Michael Stevens?

  Soaking.

• 4:04Hannah Fry?

  Soaking wet. I'm just having a little sip of my drink here, for those who are listening only. What are you drinking?

• 4:12Michael Stevens?

  Oh, I'm drinking water.

• 4:16Hannah Fry?

  I'm also drinking water, except that mine looks a lot like coffee.

• 4:20Michael Stevens?

  Mine looks like coffee too, but it's still about ninety eight percent water.

• 4:25Hannah Fry?

  Yeah.

• 4:26Michael Stevens?

  In fact, everything we drink is basically just flavored water.

• 4:29Hannah Fry?

  It is just basically flavored water, just different, different amounts of flavorings.

• 4:34Michael Stevens?

  Yeah, we give them totally different names. We say, oh, that's coffee. If someone wanted water and I gave them this, I'd be ninety eight percent correct. Because it's basically a bullseye and yet I'm wrong.

• 4:45Hannah Fry?

  Are some drinks more watery than others, though? I mean, like Coca-Cola, for example, compared to, say, a seltzer.

• 4:51Michael Stevens?

  Yeah, yeah. Seltzer is predominantly water, but it's got some carbon dioxide, maybe some minerals in there. Seltzer technically is only going to have the minerals that came from the taps, whatever that was in the source. Club soda is a lot more minerals, but something like Coca-Cola, it's about ninety percent water.

• 5:11Hannah Fry?

  Oh.

• 5:11Michael Stevens?

  So that ten percent makes a big difference because it's the difference between Coca-Cola, Pepsi, Dr. Pepper. But listen to this, Diet Coke is not ninety percent water.

• 5:23Hannah Fry?

  Higher or lower?

• 5:24Michael Stevens?

  Ninety nine percent water.

• 5:26Hannah Fry?

  Is it?

• 5:27Michael Stevens?

  It's basically just taking a bath.

• 5:29Hannah Fry?

  Wow.

• 5:30Michael Stevens?

  But it isn't though, is it? That one percent makes a huge difference. Now, the main reason is that you put sugar in Coca-Cola, there's a lot of sugar, grams and grams of it. But aspartame, it's so sweet, you just need this little sprinkling of it.

• 5:45Hannah Fry?

  By volume, it's almost nothing.

• 5:46Michael Stevens?

  By volume, it's almost nothing.

• 5:48Hannah Fry?

  Wow.

• 5:49Michael Stevens?

  So fruit juices, coffee and tea, alcoholic drinks like beer, that's also, it's like Coca-Cola, it's ninety percent water. But whiskeys, alcohol, spirits, they are, they can, they can be majority not water. So that's the thing I want to discuss today is like, what do we do with these edge cases? Because you can get one ninety two proof alcohol, that's ninety six percent alcohol, which is a liquid at room temperature that's not water.

• 6:18Hannah Fry?

  Yes, you're right. I think also there the other edge cases, right at the other end, I think it's probably important for us to say that tap water is just, is basically like a rock smoothie, you know, like, don't think of water as though it's just water. This has got all kinds of stuff in there.

• 6:31Michael Stevens?

  It's, yeah.

• 6:31Hannah Fry?

  I mean, there's calcium, there's magnesium, there's sodium, there's potassium, there's alliums.

• 6:35Michael Stevens?

  LA's water is very hard.

• 6:37Hannah Fry?

  Is it?

• 6:37Michael Stevens?

  It's got a lot of minerals in it, uh, compared to, say, the water in the Catskills, which provides water to New York City. In fact, there's a theory that it's that water that New York City gets from the Catskills that creates for them their unique, special, one of a kind pizza doughs and bagels.

• 6:57Hannah Fry?

  Makes it taste different.

• 6:58Michael Stevens?

  It makes it taste different. And this isn't just some kind of guess. It's, it really is true that those minerals affect how the gluten forms, it affects how the flour sticks together. And so there are companies that will either truck New York City tap water to your business, whether it be in Florida or Philadelphia. There are also companies that replicate New York City's tap water off-site by adding in minerals, having some kind of ionizing plant to make water that's like New York's so that you can recreate what they get for free.

• 7:30Hannah Fry?

  Because this is the thing, right? Is that, you know, if, if, if water is just absorbing all of the minerals from, from the rock that it passes through, then actually you end up with a different water being effectively like a really nice geological postcode of, of where it comes from.

• 7:47Michael Stevens?

  Oh, sure. Of course.

• 7:48Hannah Fry?

  Right? Different pieces of water from around the world end up having these different compositions of the minerals. But what that means is that you can then reverse engineer it. So let's say that you're kind of drinking water your whole life. Um, those minerals, those isotopes as well, will end up embedding themselves within your body. So you can, if you find a body, for instance, right, somebody who's died, you can take a hair sample from them, go through and work out what water they were drinking when they were alive.

• 8:17Michael Stevens?

  Right.

• 8:18Hannah Fry?

  In order to backtrace where they spent the majority of, of that time from. Um, there's also, you can do this with whales as well. So, um, whales, they have the ear bones of Whales also will absorb the isotopes in the water as they're swimming. And different parts of the world, right? It's not just kind of fresh drinking water that has this, this, this postcode element. Also, the oceans have different concentrations of minerals, different isotopes. So you can basically reverse engineer the migration patterns of a whale, work out where in the world it's been, based on an analysis of the water that it was, that it was drinking and consuming and surrounded by. Actually, do whales drink water?

• 8:59Michael Stevens?

  Well, they definitely take it in.

• 9:00Hannah Fry?

  They take it in.

• 9:00Michael Stevens?

  Yeah.

• 9:01Hannah Fry?

  Drinking's probably a bit strong.

• 9:02Michael Stevens?

  Oh, hey, guys, I haven't had a drink in a while.

• 9:06Michael Stevens?

  All right, I'm good. But yeah, no, they, yeah, so they've got traces of the, the postcode of the water.

• 9:12Hannah Fry?

  Exactly.

• 9:12Michael Stevens?

  The characteristics of the water around them.

• 9:14Hannah Fry?

  Exactly. You can do this with fossils as well, right? So whale fossils. You know, you can go through and work out the point in history at which whales started their migration patterns.

• 9:24Michael Stevens?

  How interesting.

• 9:25Hannah Fry?

  Isn't that cool?

• 9:26Michael Stevens?

  Yeah, so I could find a dead body and figure out if they were a tap water drinker or some kind of little Dasani sipper.

• 9:32Hannah Fry?

  Well, I think if they are, if they're drinking Coca-Cola exclusively, it does make it slightly harder.

• 9:36Michael Stevens?

  Tap water is a kind of mineral water. It's got minerals in it. That's the stuff that forms on your faucet. You know, over time, you get this scale that builds up and that's just minerals that had been in the water. Hot water can dissolve a lot more minerals. So hot water will tend to form much more of a scale. And it also tastes a lot different. That's why when you make tea, you warm up cold water. You don't start with the hot water because it's, it has a very different taste.

• 10:01Hannah Fry?

  Well, okay, now you're talking with tea, because this isn't just making flour and dough, right? This is like, you are directly tasting the minerals in the water. And if you speak to British people, they will tell you that if you're in Yorkshire, a cup of tea, so much more delicious than if you're in London. So you completely taste the difference in the water. But you get this in beer as well, right? Like the flavor in the water. Changes the taste of the beer. In fact, there's this British company, they're a beer subscription service. They're great guys. I like them a lot. The sponsorship team may or may not have been talking to them. Anyway. What they've done is they've gone to these really small breweries around the country and been like, hey, we want hundreds of thousands of cans of beer for our customers.

• 10:45Hannah Fry?

  And these small breweries have been like, whoa, I don't know, just not really able to fulfill that. So they've kind of stepped in to help them manufacture these numbers. But knowing that it's going to be really difficult to turn these small breweries to like up their manufacturing. What they've done is they're using this reionization plant in Buxton. Where they go in to a small brewery, they work out the chemical composition of the water, the local water that they've been using to make their beer. They go to this reionization plant in Buxton and then tweak the water ever so.

• 11:20Michael Stevens?

  In Buxton to replicate the local water of the brewery. Right.

• 11:24Hannah Fry?

  At which point they can then make these huge runs of beer.

• 11:27Michael Stevens?

  And it makes a difference?

• 11:29Hannah Fry?

  It makes a difference. I mean, look, you find a Yorkshire tea drinker and they'll tell you it'll definitely make a difference.

• 11:35Michael Stevens?

  Yeah, I mean, what's dissolved in your water makes a big difference. You mentioned earlier that a cup of water is like a rock smoothie, right? Because you've got rocks dissolved in it, magnesium and calcium. I would go a step further, though, and say that a glass of water is actually just a glass of lava.

• 11:54Hannah Fry?

  Right, right.

• 11:56Michael Stevens?

  Because I've talked about this before and I bring it up whenever I can. Ice is a rock.

• 12:02Hannah Fry?

  Sure.

• 12:03Michael Stevens?

  Because, well, hold on. Ice is a mineral. Because a mineral is just a inorganic material that is solid and has a definite crystal structure, which ice does. Water is important for life, but it's inorganic, actually. It would exist here whether there was life or not. And. What that then means is that a cube of ice is made of a mineral. So it's a monomolecular rock. So melted ice is molten rock, lava. So water is lava.

• 12:39Hannah Fry?

  I'm here for this.

• 12:40Michael Stevens?

  And this is not a joke. Ice won the mineral cup back in 2015, I believe. Like some geologists all voted on their favorite mineral and ice finally got the recognition it deserves.

• 12:49Hannah Fry?

  Got the prize.

• 12:50Michael Stevens?

  Yeah.

• 12:52Hannah Fry?

  I mean, sure, I'm happy with that classification. If the, if the rock people say it so, then, then, then I'm happy with it. They also move the same way. I mean, when lava gets spurted out of volcano, it uses the, the, the way that it, that it moves and behaves is exactly the same.

• 13:05Michael Stevens?

  What, like the fluid dynamics of lava?

• 13:07Hannah Fry?

  Fluid dynamics of lava is the same as water at that stage. Yeah. Bit later on, when it cools down, then it's a, then it changes.

• 13:14Michael Stevens?

  Is it more like ice?

• 13:15Hannah Fry?

  More like ice. There's a transition phase where it's more like toothpaste, where it needs a certain amount of sheer forces in order for it to flow.

• 13:21Michael Stevens?

  But that would be analogous to like slush, maybe.

• 13:24Hannah Fry?

  Maybe, yeah. So now that we've established that ice is a mineral and that water is lava, I think we'll take a little break.

• 13:40Speaker 03

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• 14:11Speaker 05

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• 15:18Hannah Fry?

  Okay, welcome back from the break. What we've established is that water is lava, but also, everything that you drink and eat is also water. Therefore, everything you consume is lava.

• 15:30Michael Stevens?

  Pretty much. Pretty much. But let's talk more about the water on Earth and like, how much there is and what form it's in. Because I think we, in our day-to-day lives, are very biased to think of water as this splashy puddle stuff. It's in lakes and rivers. But that is basically not what water is on Earth at all.

• 15:48Hannah Fry?

  Go on.

• 15:49Michael Stevens?

  Well, Earth has a lot of water, and it's famous for having a lot of water on the surface. But it's not water that we can just come up and drink, because it's too salty. Most of Earth's water is way too salty. It would kill you to drink it.

• 16:02Hannah Fry?

  Wait, when you say most, what are we talking here? What percentage of the water is?

• 16:05Michael Stevens?

  I'll tell you. I'm gonna have to pull up a chart, because I want to get these numbers just right. So here's the deal. Earth has a lot of water, but of all that water on the entire planet, both on it and in it, only 2.5% is fresh.

• 16:20Hannah Fry?

  The rest is salty.

• 16:22Michael Stevens?

  And the rest is salty. But that 2.5% sounds small, but what we're looking for is even smaller, because out of that 2.5% Almost 70% is frozen in glaciers and ice caps. So not accessible to just come up and sip. And then another 30% of that is groundwater, not up on the surface. So only 1.2% of the 2.5% that's fresh is on the surface, basically.

• 16:50Hannah Fry?

  So wait, wait, it's 1% of the 2.5%.

• 16:53Michael Stevens?

  1% of the 2.5% is surface freshwater, but we're still not done. Because surface is being used really broadly here. That includes 3% of that 1% of the 2% is water in the atmosphere.

• 17:07Hannah Fry?

  Right.

• 17:08Michael Stevens?

  This is very small, but it's worth mentioning. 0.26% of that little sliver is locked inside living organisms.

• 17:15Hannah Fry?

  Right.

• 17:16Michael Stevens?

  Almost 4% of that little sliver is dampness in the soil. So I can't just go up and like slurp it up. I could stick some mud in my mouth and like

• 17:28Hannah Fry?

  Try and suck on it.

• 17:29Michael Stevens?

  Suck on it. But what we think of as fresh water, water from creeks and springs and rivers and lakes, that is, I did the math here, 0.0072% of all the water on earth.

• 17:44Hannah Fry?

  Wow.

• 17:45Michael Stevens?

  It is a tiny minuscule fraction of the 1% of the 2.5% that's not saltwater.

• 17:53Hannah Fry?

  And if you think about it, all of the water that we effectively come into contact with, all the water we're drinking, all the water we're showering with, all the water you're putting in swimming pools, all of that is contained within that number.

• 18:06Michael Stevens?

  That 0.0072%, yeah. But it's the water that is the star of the human show. It's what we swim in, it's what we get out of the tap and that we drink and that we have right here. There is no saltwater around us right now.

• 18:19Hannah Fry?

  No, I'm not interested in the saltwater, thank you very much.

• 18:22Michael Stevens?

  We're interested in such a narrow kind of water.

• 18:25Hannah Fry?

  Of that tiny, tiny sliver, how much of that is in Coca-Cola? How much of that is tied up in?

• 18:30Michael Stevens?

  Yeah, how much is tied up in warehouses, in cans of soda and beer and brewed tea? Yeah, I don't know. I do know, here's a fun fact. The entire volume of refrigerated space in the United States.

• 18:48Michael Stevens?

  Is equal to two thirds the volume of Mount Everest.

• 18:52Hannah Fry?

  Really?

• 18:53Michael Stevens?

  I can't tell if that sounds small or big.

• 18:56Hannah Fry?

  I think that sounds big. And the reason why I think it sounds big, I'm slightly obsessed with fridges.

• 19:01Michael Stevens?

  Yeah.

• 19:03Hannah Fry?

  Which I appreciate isn't a normal sentence, but they're wild, like they are tricking the laws of thermodynamics.

• 19:10Michael Stevens?

  I know.

• 19:10Hannah Fry?

  It's like you have managed to create this sort of tiny bubble in the universe where you have like sucked energy away. That's not what energy likes to do. Like it is miraculous that fridges have managed to work.

• 19:24Michael Stevens?

  I know, and they do it so simply.

• 19:26Hannah Fry?

  So simply.

• 19:27Michael Stevens?

  They're just squirting around a fluid and the fluid's properties are like, let's do it. Let's dump this heat out, keep your yogurt nice and creamy.

• 19:34Hannah Fry?

  Also, just think about before fridges existed, right? You could have lived, I don't know, for like, most of the planet would never have experienced a cold drink, right?

• 19:46Michael Stevens?

  I know.

• 19:46Hannah Fry?

  Like, it's just, it's wild to me that we've had this thing for like a hundred years or so, maybe a little bit more, 150 or so. I find fridges really, can we do a whole episode on fridges, please?

• 19:55Michael Stevens?

  Yeah, we should. But where did all this water come from on Earth? How old is it? How long has it been around?

• 20:01Hannah Fry?

  Well, it didn't get made on Earth, right? That's, that's one thing that we know.

• 20:04Michael Stevens?

  Water isn't produced naturally on Earth, right?

• 20:06Hannah Fry?

  Correct. Which means it came here from space.

• 20:08Michael Stevens?

  Alien water.

• 20:09Hannah Fry?

  Alien water.

• 20:12Michael Stevens?

  Yeah, I've heard that it probably came from like comets that crashed into a dry earth. And they left all this ice. It's hard to imagine though, how many comets that would be. I guess that's why they call that the heavy bombardment period, when Earth was just getting smacked by these comets from way out beyond the solar system, made of ice, covered in ice, and they just delivered the oceans to us over time.

• 20:37Hannah Fry?

  Do we know how old the water is then?

• 20:39Michael Stevens?

  More than half of the water on Earth is older than the sun.

• 20:44Hannah Fry?

  How do they know that?

• 20:45Michael Stevens?

  Water can form naturally. It's an inorganic material. It's, it's a molecule that can form all throughout the universe. And we know this because of a couple of things. One, when the sun formed, any water near the sun would have been obliterated into oxygen and hydrogen, just elemental or molecular forms, wouldn't be water anymore. And so any of the water that remained would have had to have been. Further out, where it couldn't get destroyed by the sun forming. And then later, as the formation was complete, that water could fall down to earth. And I think they've been able to test this by looking at the amount of heavy water

• 21:24Hannah Fry?

  Right.

• 21:25Michael Stevens?

  in water on earth and compare it to how water could have been formed more recently in the solar system.

• 21:31Hannah Fry?

  And by heavy water?

• 21:33Michael Stevens?

  Right, I mean, water where the hydrogen atoms in it are deuterium, which is, what? Hydrogen with one neutron?

• 21:42Hannah Fry?

  Yeah.

• 21:43Michael Stevens?

  Yeah.

• 21:43Hannah Fry?

  Chubby hydrogen.

• 21:44Michael Stevens?

  Chubby hydrogen. So it's still hydrogen, because all you need to be a hydrogen atom is one proton with a little electron around. You get a little neutron in there, you're heavier, but you don't have any more protons. So your chemical properties are pretty similar. So it's still hydrogen, but it's called heavy. Now, I do want to give a shout out to tritium. If a second neutron comes along and joins that hydrogen nucleus, now it's got one proton and two neutrons, and it's, it's super heavy. We call it tritium, and it's unstable. It's so chubby, it's about to like just barf stuff out. So it's radioactive. So tritium is extremely light radioactive gas. And it can be used, you might find it on watches.

• 22:26Michael Stevens?

  They fill, they fill parts of the dial with tritium gas, inside little ampules covered in like some kind of phosphorus material. So when the radioactivity of the tritium hits the phosphorus, it glows. And they can make it glow for decades.

• 22:38Hannah Fry?

  Because it's decaying.

• 22:39Michael Stevens?

  Because it's radioactive.

• 22:40Hannah Fry?

  Consistent way.

• 22:41Michael Stevens?

  And I think the particles that it decays out are mainly alpha particles.

• 22:45Hannah Fry?

  Which means they can't penetrate your skin.

• 22:46Michael Stevens?

  They don't penetrate, they don't even penetrate the glass ampul.

• 22:48Hannah Fry?

  Yeah.

• 22:49Michael Stevens?

  That they only hit the phosphorus on the inside. But yeah, they won't go through even a sheet of paper. They won't go through your skin. It's much better than like what uranium does.

• 22:56Hannah Fry?

  Shout out to tritium.

• 22:59Michael Stevens?

  Shout out to tritium, yeah. But heavy water is water formed from deuterium and oxygen.

• 23:05Hannah Fry?

  I should say there, actually, if you were drinking heavy water, different story.

• 23:08Michael Stevens?

  Yeah, what happens?

• 23:09Hannah Fry?

  Well, because then you've got this radioactivity going on inside you, and the particles cannot escape your body.

• 23:15Michael Stevens?

  But deuterium isn't radioactive.

• 23:17Hannah Fry?

  No, but you don't want to be drinking tritium.

• 23:20Michael Stevens?

  What do they call water made with tritium?

• 23:22Hannah Fry?

  Super heavy water.

• 23:24Michael Stevens?

  I don't think there's much.

• 23:25Hannah Fry?

  No.

• 23:25Michael Stevens?

  I think deuterium happens much more frequently in a context where water can be made, but I don't know. I know that if you drink a lot of heavy water... Deuterium oxygen water, it can be bad over time. We're always drinking a little bit.

• 23:43Hannah Fry?

  Yeah.

• 23:43Michael Stevens?

  There's some deuterium, there's some heavy water in there.

• 23:47Hannah Fry?

  You know what you also shouldn't be drinking is pure water.

• 23:50Michael Stevens?

  Why not?

• 23:50Hannah Fry?

  I mean, it is not good, not good. Because if you think about tap water as how it's got all of this, these minerals, these rock basically dissolved inside of it. If you took away all of that.

• 24:03Michael Stevens?

  So you only had water molecules?

• 24:05Hannah Fry?

  H2O.

• 24:05Michael Stevens?

  H2O.

• 24:06Hannah Fry?

  Right. Now, you have to remember that water is extremely good at dissolving things within it. So if that goes through your body, what that will do effectively is strip your body of all of the minerals that it naturally uses. And it can just be a very bad thing. You can give yourself water poisoning, not by drinking pure water, I mean, although that too, but by drinking huge amounts of just tap water.

• 24:30Michael Stevens?

  Yeah. Oh, man, I, I know about water poisoning. One of our producers would say that in college, they would even try to get drunk on water, which is, by the way, a terrible idea. If you drink too much water, even, even like water that does have minerals in it, you get confused.

• 24:48Hannah Fry?

  Hallucinate?

• 24:48Michael Stevens?

  You hallucinate. I looked up the LD50 of water.

• 24:52Hannah Fry?

  Go on.

• 24:52Michael Stevens?

  The LD50 is the dosage of, of anything all at once that causes 50% of a test population to die. And in, in rats, it's poor waterlogged rats, it's 90,000 milligrams per kilogram of body mass.

• 25:08Hannah Fry?

  Sorry, 90,000 milligrams of water?

• 25:11Michael Stevens?

  Per kilogram.

• 25:12Hannah Fry?

  Per kilogram of mass.

• 25:12Michael Stevens?

  Body mass.

• 25:13Hannah Fry?

  Wait, 90,000 milligrams? Oh, God, can I just give it in kilos?

• 25:16Michael Stevens?

  Okay, look, okay, 90 grams of water per kilogram of body mass in rats, which like a lab rat doesn't even weigh a kilo.

• 25:24Hannah Fry?

  Like half a kilo maybe?

• 25:25Michael Stevens?

  Like, what, yeah.

• 25:26Hannah Fry?

  So 40 grams of water could kill a rat or give a 50% chance of killing a rat?

• 25:32Michael Stevens?

  A 50% chance of killing a rat if you gave them 40 grams of water right away.

• 25:36Hannah Fry?

  That's nothing.

• 25:36Michael Stevens?

  Isn't that incredible?

• 25:37Hannah Fry?

  That's like a double shot.

• 25:39Michael Stevens?

  Sorry, rats.

• 25:42Hannah Fry?

  I mean, I guess when you think about it, if you have a rat, like a pet rat, and when they drink water, they drink like literally a drop at a time.

• 25:48Michael Stevens?

  That's right. Yeah, they're drinking like a gram at a time and then they're done for a while.

• 25:53Hannah Fry?

  That's not very much though, still.

• 25:55Michael Stevens?

  It's not very much. No, I mean, our bodies have this very fragile balance of homeostasis where we're healthy.

• 26:01Hannah Fry?

  Hold on.

• 26:01Michael Stevens?

  Just like a rat does.

• 26:02Hannah Fry?

  Let me work it out for humans. So what was that, 90 grams per kilogram?

• 26:05Michael Stevens?

  Yeah.

• 26:06Hannah Fry?

  Seven kilos of water, basically.

• 26:08Michael Stevens?

  Seven kilos of water. That's because what, how much water weighs a kilo?

• 26:13Hannah Fry?

  A thousand, it's the same, right?

• 26:14Michael Stevens?

  It's a liter.

• 26:15Hannah Fry?

  So seven liters of water, oh, seven liters of water is a lot, though, actually.

• 26:18Michael Stevens?

  Because as I was looking into actual cases of water poisoning, there was someone who drank six liters of water in three hours and died.

• 26:25Hannah Fry?

  Yeah.

• 26:26Michael Stevens?

  So that kind of makes sense. Three hours is a long period of time, though, compared to, LD50 usually means immediately. Like, you'd give it all at once. You couldn't probably put six or seven liters of water into someone right away.

• 26:39Hannah Fry?

  And the way that this kills you is that, I mean, it's the same as if you drink pure water, right? That you have these minerals in your body that are actually extremely important to the function of your cells. And because you are putting through effectively a solvent through your system, it's stripping away those minerals and ejecting them from your body and robbing your body of the things that it needs to function.

• 26:56Michael Stevens?

  That's right. Yeah, your blood and your tissues, they've all got a much higher concentration of dissolved solids than water does. So you water your body down, you lose those electrolytes and you can die. Six or seven liters in three hours will do it.

• 27:10Hannah Fry?

  My mum once gave us our water poisoning. She was in hospital and she had a kidney infection. She'd been in for pneumonia. And the doctor said to her, just make sure you drink lots of water. And she's Irish and really has an unhealthy respect for authority. So she took it very, very, very literally. And I don't know how much she drank, but my goodness me, it was awful.

• 27:32Michael Stevens?

  What happened?

• 27:33Hannah Fry?

  She just, she just, for a few days, she just, well, I think she basically induced the same effect that our producer intended.

• 27:42Michael Stevens?

  Right.

• 27:42Hannah Fry?

  As a student. Don't do it to yourselves, though, because you also, I mean, people, as you say, right? You genuinely can die from this.

• 27:49Michael Stevens?

  You genuinely can, and it's. I think underappreciated how dangerous it is. There are a lot of like hazing rituals that involve making people chug a bunch of water. And then they'll wind up having to go to the hospital because they're intoxicated with water. Their bodies, their brains, their cognition, it's all hampered by this electrolyte imbalance induced by drinking too much water.

• 28:10Hannah Fry?

  You know, I um, I went to Singapore to go and talk to them about their water system. And in Singapore, they have like, you wouldn't think it because it's, you know, where it is in the world, it rains all the time. But it's extremely water scarce, right? They have real critical issues about the amount of water they have because they've got very small land area and a really high population of people. So what they do in Singapore is they take raw sewage and they process it through a plant. And then immediately with the output of that that system, put that purified distilled water back into the taps, right?

• 28:43Michael Stevens?

  Ah, yeah, just like the International Space Station.

• 28:45Hannah Fry?

  Just like the International Space Station, exactly.

• 28:47Michael Stevens?

  Yesterday's coffee is today's coffee.

• 28:49Hannah Fry?

  I, you know, luckily didn't have to be there for the sewage part, but it was effectively drinking water that that morning had been sewage.

• 28:56Michael Stevens?

  Wow.

• 28:58Hannah Fry?

  Just tasted like water, to be honest with you.

• 29:00Michael Stevens?

  Of course, yeah.

• 29:00Hannah Fry?

  But the thing is, the water they create ends up being so pure, right? So like stripped of minerals, they don't actually even use it for drinking water. Instead, they use it, they sell it to to places that are making semiconductors and electrical equipment. Who need that pure water.

• 29:16Michael Stevens?

  So every time you blush, you're helping technology.

• 29:19Hannah Fry?

  Helping technology. That's what they say in the ISS, huh?

• 29:23Michael Stevens?

  That's really good to know. When you look at Earth from the outside, it is covered in water.

• 29:28Hannah Fry?

  Seventy percent or so.

• 29:29Michael Stevens?

  Seventy percent of its surface is just covered in water. But Earth's surface is nothing compared to its inside, especially because it's a sphere. Smallest surface area to volume ratio. Uh, and I once did this calculation that if you scaled the Earth down to be just thirty centimeters across, like a foot across, like a typical classroom globe. The total amount of water on there would be just, just under a tablespoon. Fourteen milliliters. So imagine like a little less than a tablespoon of water, throw that on a globe in a classroom. That's all the water that fills all the oceans. Cause they're just not that deep compared to Earth's radius.

• 30:07Hannah Fry?

  Well, I guess if you think about it, it's like the distance between the top of Mount Everest to the bottom of the Mariana Trench is like, what, thirteen kilometers, something like that?

• 30:14Michael Stevens?

  Yeah.

• 30:15Hannah Fry?

  Roughly. And yet the Earth is forty thousand kilometers in circumference. So we're talking about, I mean, it's unimaginably smooth. And it's just, I guess with surface tension on the globe in the classroom, you can't.

• 30:26Michael Stevens?

  Yeah, how would you do this at that scale? You'd somehow need to get like about a tablespoon of water on the globe. So it would just kind of be like a damp globe. A giant that could hold our Earth wouldn't be like, oh, it's soaking wet. It'd be like.

• 30:42Hannah Fry?

  A tiny bit sleepy.

• 30:43Michael Stevens?

  Brush it off. Yeah. Oh, it's got a little dew on it.

• 30:46Hannah Fry?

  You could imagine doing it with something that had a different viscosity, right? Like some, some different fluid properties. You could like, it's almost like you put a polish.

• 30:54Michael Stevens?

  That's right. You could take like a, like fourteen milliliters, a little less than a tablespoon of honey, and smear that onto a globe and say, that's it. That's all the water, period. Am I including like groundwater and stuff here? I think in those figures, I was including all types, even the water in the atmosphere.

• 31:10Hannah Fry?

  But then of that, the fourteen milliliters, it's, what was it? Nought point, nought?

• 31:15Michael Stevens?

  Yeah, yeah. As an American would say, zero point zero zero seven six percent of all of Earth's water is surface liquid.

• 31:24Hannah Fry?

  Drinkable.

• 31:24Michael Stevens?

  Fresh water.

• 31:25Hannah Fry?

  Which means the water we're drinking slash coffee, um, I mean, has been through many, many animals, creatures in the past. Almost certainly, we're drinking dinosaur pee.

• 31:37Michael Stevens?

  Oh, almost certainly. Yeah. Yeah, that whole thing about like, oh yeah, you know, every breath you take contains some atoms that Julius Caesar breathed in.

• 31:46Hannah Fry?

  Here's the thing that I like to think, right? In our evolutionary past, I mean, we started off in the water and then there was one point where, you know, started laying eggs on land and kind of eventually evolved into creatures that could live predominantly on land. You know, we didn't. Leave the water behind us. All we did was we just turned ourselves into water balloons and carried it with us as we go.

• 32:04Michael Stevens?

  That's right, isn't it?

• 32:05Hannah Fry?

  And like as you're, you know, drinking your drink during the day, what you're doing is you're just, you're just topping up the evaporation that you're, that you're experiencing.

• 32:13Michael Stevens?

  We like to call ourselves land animals, but really we're water balloons. In fact, the first, the first living things to move on to land would do it, but then they'd go back into the water to lay their eggs. But there was a major evolutionary step where animals evolved that laid their eggs on land and they needed to have a hard shell for that so that the water wouldn't all evaporate away.

• 32:35Hannah Fry?

  Exactly.

• 32:36Michael Stevens?

  They needed to evolve water balloon production, reproduction organ, organs, and they did. And that's still what we do today. We're moisturizing, we are drinking water, we're eating water in our foods, and we just don't really belong up here still.

• 32:53Hannah Fry?

  This is the reason why you weigh less in the morning. Do you know this?

• 32:55Michael Stevens?

  Yes.

• 32:56Hannah Fry?

  Is that you are basically, you are literally evaporating overnight.

• 32:59Michael Stevens?

  Yeah. Yeah, you weigh less in the morning because you're losing water and you know how you're losing it, right?

• 33:07Hannah Fry?

  As you're breathing, as you're coming out.

• 33:08Michael Stevens?

  As you're breathing it out. Your hot, moist breath is just like a weight loss secret.

• 33:14Hannah Fry?

  If you just carried on like that, you would eventually end up as a raisin.

• 33:17Michael Stevens?

  Yeah, you would. The land is just a raisin factory and we are temporary tourists up here.

• 33:26Hannah Fry?

  Are there any liquids that aren't predominantly water, though?

• 33:29Michael Stevens?

  Yeah, that's what I was just thinking about.

• 33:31Hannah Fry?

  Well, honey. Okay, sure.

• 33:33Michael Stevens?

  Honey is liquid-like, but yeah.

• 33:35Hannah Fry?

  I want more, though. I want more than 18%. I want something that is not water at all.

• 33:38Michael Stevens?

  Yeah, so let's look at things that are liquid at room temperature and pressure on earth. So, okay, mercury.

• 33:46Hannah Fry?

  Can't drink it. Not interested.

• 33:47Michael Stevens?

  Can't drink it. Bromine. Can't drink it. Alcohols and oils.

• 33:53Hannah Fry?

  But alcohols, if you're talking 100% pure alcohols, ethanol, methanol, whatever.

• 33:59Michael Stevens?

  Which is pretty hard to make.

• 34:00Hannah Fry?

  Pretty hard to make, but also don't drink it.

• 34:02Michael Stevens?

  Don't drink it. And you, okay, you could drink like olive oil.

• 34:06Hannah Fry?

  Surely there's still some water in olive oil?

• 34:08Michael Stevens?

  Olive oil contains about 0.03% water.

• 34:12Hannah Fry?

  Wow. Which is very small.

• 34:14Michael Stevens?

  It's very small. It almost seems like you could find that much water in anything, even like in, you know, pure gasoline. There's going to be a little bit of like moisture just from the humidity of the environment.

• 34:24Hannah Fry?

  What about glycerin, actually?

• 34:25Michael Stevens?

  Glycerin. You could drink that, right?

• 34:29Hannah Fry?

  I reckon.

• 34:29Michael Stevens?

  What would happen if you did?

• 34:31Hannah Fry?

  Probably pass through. I mean, once you start categorizing things, then we're basically down to everything is either olive oil or dinosaur pee.

• 34:39Michael Stevens?

  Yeah, as it should be.

• 34:40Hannah Fry?

  As it should be.

• 34:42Michael Stevens?

  And I'm glad for it. You know, I was once looking up the etymology of the word loser. Don't ask me why. But as it turns out, to be a loser is the same as to be dissolved.

• 34:55Hannah Fry?

  Is it?

• 34:55Michael Stevens?

  Dissolving, solution, loser. These words all come from the same observed phenomenon, which is dissolving, to be lost in water.

• 35:05Hannah Fry?

  And so lose is the same, lose from the same.

• 35:08Michael Stevens?

  When you put water or minerals into water, they get lost. They dissolve.

• 35:12Hannah Fry?

  Because you can't see them anymore.

• 35:13Michael Stevens?

  You can't see them anymore. And when you work on a math problem or just a problem in your own life, what you're looking for is a solution, a circumstance in which the problem, just like minerals in water, dissolves and it goes away and it's no longer visible.

• 35:28Hannah Fry?

  I love that.

• 35:29Michael Stevens?

  Isn't that beautiful? So.

• 35:30Hannah Fry?

  But then, wait, what are you losing? What's the like?

• 35:34Michael Stevens?

  What is dissolving away and disappearing? I guess your like, opportunity to be a winner is now gone?

• 35:41Hannah Fry?

  Hmm, yeah.

• 35:42Michael Stevens?

  Maybe you've lost the respect of the spectators or something, but.

• 35:48Hannah Fry?

  Yourself.

• 35:49Michael Stevens?

  Yourself, yeah.

• 35:50Hannah Fry?

  Family.

• 35:52Michael Stevens?

  But if it wasn't for losers, we wouldn't be here. We need dissolved solids in water.

• 35:58Hannah Fry?

  I mean, there is, as I have very much come to the conclusion over the last half an hour, nothing more important than this particular loser here, this jug of largely H2O and a lot of other stuff.

• 36:11Michael Stevens?

  Exactly, yeah. Life depends on that loser. We're all losers in a way. You and I are losers and you are a loser that we love very much. If you've had fun, follow us on wherever you listen to podcasts. If you're watching on YouTube, leave a comment, subscribe, give us a favorite. What else does YouTube offer? Can you do favorites anymore? Oh, I'm really dating myself here.

• 36:35Michael Stevens?

  As always, you can email us at [email protected]. Thank you.

• 36:40Hannah Fry?

  Thank you so much for listening. We'll see you next time.

• 36:54Speaker 06

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