Why Sharks Attack The Internet

Every week, around three undersea internet cables get damaged badly enough to need urgent repair... and the culprit usually isn’t sabotage. Submarine cables carry more than 99% of the world’s international data, from your video calls to global financial transactions. Yet they lie on the ocean floor, where fishing gear and dragging ship anchors cause huge amounts of the damage. In this episode of The Rest Is Science, Professor Hannah Fry and Michael Stevens (Vsauce) investigate the hidden network of underwater cables holding the internet together, and the problems that come with running it across the bottom of the ocean. How do you lay a cable across an entire ocean? What happens when one breaks miles below the surface? And in the age of satellites, why are we still relying on cables on the seabed? ------------------- 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 + Lucy Lipscombe Senior Producer: Lauren Armstrong-Carter Chief Digital Officer: Samuel Oakley Exec 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.

• 0:01Hannah Fry?

  Welcome to The Rest Is Science. I am Hannah Fry.

• 0:03Michael Stevens?

  And I'm Michael Stevens. I think, I think it's the tone she doesn't like. Let's do, it should be, I'm Michael Stevens. It's no big deal.

• 0:12Hannah Fry?

  Shall we let the audience in on why we're laughing before we've even started?

• 0:16Michael Stevens?

  Yeah, okay. So basically, my wife came up to me and she's, she's listens to the podcast, which I love, right? She's like, please stop introducing yourself as, and I am Michael Stevens. Just make a contraction out of it. I'm Michael Stevens. It sounds like you're, you think you're really important or something, and I am Michael Stevens.

• 0:36Hannah Fry?

  You are really important.

• 0:38Michael Stevens?

  Oh, Hannah Fry, please. I am Michael Stevens. I'm Hannah Fry, and I am. So I'm trying to do the opposite. So, so say, say your name, Hannah.

• 0:49Hannah Fry?

  I'm Hannah Fry.

• 0:50Michael Stevens?

  And I'm Michael Stevens. So today, we're gonna, that's what she wants.

• 0:53Hannah Fry?

  I like the plant a flag, right? It's like claiming the land.

• 0:59Hannah Fry?

  I personally like it. Okay, well, Michael Stevens, now that we know that you're here, flag planted.

• 1:05Michael Stevens?

  I am here.

• 1:07Hannah Fry?

  I've got Field Notes episode for you. I'm really excited about this.

• 1:10Michael Stevens?

  I know you are. I can't wait to see what it is because I have no idea.

• 1:13Hannah Fry?

  Okay, so yesterday I was filming a little experiment in a pub. I'll tell you about that another time. But once we finished filming, the doors of the pub opened and people came in and were buying drinks at the bar. And because this big show in the UK has just been on, there were a few people who were asking for photographs and whatever, asking me about the show. And then, as part of that, this guy came over to me and he was like, I need to talk to you. And I was like, okay, sure, you know, if you'd like to have whatever. He was like, no, no, I need to talk to you about deep sea internet cables. And I was like, okay, you immediately have my attention.

• 1:49Michael Stevens?

  You're like, I need to talk about this too. Thank you.

• 1:52Hannah Fry?

  Yes, please. Because the thing is, I actually have had a secret obsession for deep sea internet cables for quite some time. Anyway, it turns out, by the way, while all of this is going on, this guy's wife was there. She, I think, was quite mortified that he'd come over to try and have a conversation with me about deep sea internet cables. But I could not have been more excited because not only did he tell me loads of really cool stuff about deep sea internet cables, he then let me borrow the one that he had in his house.

• 2:23Michael Stevens?

  Look at that.

• 2:25Hannah Fry?

  How fun is this? I just feel so grateful that we've now got to the point in our lives where people approach us with really interesting things and really interesting stuff that not only do I get really excited about, but also I can bring on here to show you.

• 2:46Hannah Fry?

  This episode is brought to you by Cancer Research UK.

• 2:49Michael Stevens?

  We know that DNA holds a lot of information, but here's a way to visualize it. If we encoded all the movies ever made in all of history into DNA, that clump of DNA would be smaller than a sugar cube.

• 3:05Hannah Fry?

  It is packed with data. And so Cancer Research UK scientists are analyzing cancer DNA to understand what makes every cancer different. They're even searching through what was once considered genetic junk.

• 3:18Michael Stevens?

  That's because uncovering these differences could lead to more personalized and precise ways to prevent, detect, and treat the disease.

• 3:26Hannah Fry?

  Over the last 50 years, Cancer Research UK's work has helped to double cancer survival in the UK. And today is continuing to save and improve lives around the world.

• 3:36Michael Stevens?

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

• 3:47Speaker 02

  Observe the North American dad. 50s, great polo collection. He enters his vehicle information on Carvana. An offer appears in minutes. Remarkable. He squints, reads it again, smiles and says, dang, that's a good offer. The highest form of approval. No haggling, no hassle. No one called him boss. He's still on the couch. Astonishing. Sell your car today on carvana.com. Pickup fees may apply.

• 4:19Speaker 03

  This episode is brought to you by Google Chrome. You think you know a browser, but Gemini and Chrome, that's new. It can help you with practically anything on the web, like restoring a vintage motorcycle from a 50-page restoration blog, or finally break down that long article you've had open for weeks. Gemini and Chrome is here for it. Ready to make anything online make sense? There's no place like Chrome. Check responses set up required. Compatibility and availability varies. 18 plus.

• 4:50Michael Stevens?

  Yeah, not only is that so cool to look at, it's beautifully presented with this kind of steered pattern. This is like one thick wire, and the layers have been cut in a staggered way so we can see. Because what you're holding up looks like the Tower of Babel.

• 5:06Hannah Fry?

  It does. That's a really good description.

• 5:09Michael Stevens?

  It looks like a cake where the layers get a little thinner as you go up, and they're all cylindrical. Some of them are black, some of them are silver in color, one is white, some are copper in color. And at the very tip, it becomes just like thin copper electrical wire.

• 5:23Hannah Fry?

  Yes, and then poking out of the top are almost like these hairs.

• 5:27Michael Stevens?

  Oh, they're like hairs. They're so thin.

• 5:29Hannah Fry?

  They're super doop, doop, doop, doop thin. Can you see that?

• 5:31Michael Stevens?

  But the whole thing is about the size of like a can of soda.

• 5:36Hannah Fry?

  It's sort of nearly the size of my hand, right? From, from bottom to top. Okay, so here's the thing, right? Is that I think everybody knows that subsea cables exist. But I, before I knew about this, I was imagining these like gigantic sort of sewage pipe sized things that kind of run between continents, allowing there to be internet connectivity in the same way that you see great big pipes that run under our streets, you know, like a massive giant network of them. I think that's sort of what I was imagining. But this thing that I'm holding in my hand, which, you know, I can, I can really easily pinch it between my, my thumb and my finger. This is like the whole width of the entire whole thing, but it lies on the bottom of the sea.

• 6:21Hannah Fry?

  This is like, it's basically the diameter of a garden hose, okay? So the different layers here, I should also add, most of these layers do not exist in the main. So what you have here, right, the bottom, the very bottom one is, is just a stand. So this first layer here, this is like the outer coating. Then you have this like, this armor reinforcement essentially. You've got two layers of that and then two layers of this waterproof coating. So waterproof coating, bit of reinforcement, waterproof coating, bit of reinforcement. Now, all of those, the two layers of reinforcement, they only appear in the cable that is near to a shoreline.

• 7:01Michael Stevens?

  Oh.

• 7:02Hannah Fry?

  Because near to a shoreline, people are dropping anchors, you've got trawlers, you've got that kind of thing going on. And you want to protect the delicate interior from potential damage. But for most of the ocean, the only thing that is lying on the bottom of the sea floor, the ocean floor, is just the thickness of that white bit. That's literally it.

• 7:27Michael Stevens?

  No kidding? And what do these do? Because surely the internet goes through satellites as well. What did the deep sea ocean ones do?

• 7:37Hannah Fry?

  Oh, they are way more important than the satellites. They, they're the main arteries of the internet. I should tell you, in fact, actually, the entire Starlink fleet, everyone's been going on about Starlink, aren't they amazing? They're great. The entire Starlink fleet only carries as much internet as one of these cables. And I'm talking, when I say one of these cables, the actual bit that matters are these little hairs that are poking out inside, okay?

• 8:05Michael Stevens?

  Is that it?

• 8:06Hannah Fry?

  That is it. That's it.

• 8:08Michael Stevens?

  So the cable is only about as thick as a soda can, but how many of them are needed?

• 8:14Hannah Fry?

  Nowhere near as thick as a soda can. I always say, hang on, let me see if I can get this up.

• 8:17Michael Stevens?

  Hold it, hold it so I can see the base. How thick is that bottom?

• 8:20Hannah Fry?

  Okay, so the base is quite thick. So it's basically, see the silver bit? It's that bit, right? That's with the armory, but, but the actual diameter, we're talking the actual cable, the bit that's in the bottom of the main ocean, the white bit, is 21 millimeters thick.

• 8:36Michael Stevens?

  Wow.

• 8:37Hannah Fry?

  It's tiny, teeny, teeny, tiny. And then even inside that, you've got this copper, this copper layer, which is conducting the electricity so that you can boost the signal across this cable. But the bit that really matters, the fiber optic bit, are these hairs inside, which is where light is sort of sent down it in a really efficient way so it can travel really long distances. And it gets boosted at various stages by this kind of electrical current. But you have to think, some of these cables are, you know, 10,000 kilometers long.

• 9:13Michael Stevens?

  Yeah.

• 9:13Hannah Fry?

  And so it would be so expensive to try and armor plate all of it, which is why you only just have this laughably little skinny thing that is sitting there at the bottom of the ocean.

• 9:24Michael Stevens?

  Okay, so right now, you and I are traveling through one or, or some of these right now.

• 9:31Hannah Fry?

  Oh, we absolutely are. You're, I mean, you're in the States, right? I'm in London. Absolutely guaranteed, just me talking to you is passing through, passing through some of these.

• 9:42Michael Stevens?

  And if you're watching or listening to this show, it's probably coming to you through one of these cables from a server across an ocean. I don't even know where this stuff is stored. Where are the servers? They can be anywhere, but they get to you because of this network.

• 9:54Hannah Fry?

  Right, that this thing has, has created. Now, the thing is about, about these, these cables, okay? They are so skinny that in the early days, when they first started laying them, they didn't insulate them properly from the electromagnetic field that's created as you have this electricity and light kind of traveling down these, these wires. And so when they laid down the first ones, sharks, which are really sensitive to electromagnetic fields, were really confused by them and would go along and bite them. And so when they were repairing them, when there were sort of, you know, problems with it and brought them up, they would see all of these shark bites and like teeth that had been caught in them. So now there's like, there's a bit more insulation to try and leave the, the poor sharks alone.

• 10:35Michael Stevens?

  Talk about sharks breaking the internet.

• 10:38Hannah Fry?

  Sharks. Um, the, the laboratory tests, uh, they identified the culprit as the crocodile shy shark instantly, which lives about two kilometers down, really near the bottom of the, of the ocean. Um, but there have also been stories about, uh, whales that have died getting tangled in these things. And the thought is that what whales are doing is they're at the bottom of the ocean and they're sort of like using their mouths to sort of scoop up any potential food, getting tangled in this cable and getting like in a real knot and then, and then basically dying.

• 11:18Michael Stevens?

  So there must be redundancies in the system. Like if, if one gets damaged, they, it's going to take a while to get out there and repair it.

• 11:27Hannah Fry?

  Surely there's loads of them. Surely there's billions of these things. Is that what you're thinking? Surely it's like, surely it's like a fishing net laid along the bottom of the ocean.

• 11:35Michael Stevens?

  Well, there's probably at least like a dozen.

• 11:37Hannah Fry?

  I think a dozen is a very small number.

• 11:40Michael Stevens?

  Yeah, but these seem like such powerful things. I'm like, I'm trying to guess an appropriate number.

• 11:45Hannah Fry?

  So I don't know. My guess, right? And, and may, maybe this is because you're, because you're smarter than me, but my guess is that given that this is like the, the width of the actual fibers that are going in. I mean, these are like hairs that I'm handing up, right? My guess was that given how skinny each one of these is, there must be hundreds and hundreds and hundreds, if not thousands of these things along the bottom of the ocean. But in actual fact, connecting America and the UK, there is about a dozen.

• 12:12Michael Stevens?

  Oh yeah, I'm looking this up and I'm seeing the number 14. How's that for a guess?

• 12:17Hannah Fry?

  That was pretty good.

• 12:18Michael Stevens?

  I am Michael Stevens.

• 12:20Hannah Fry?

  Yeah.

• 12:20Michael Stevens?

  But overall, uh, telegeography's interactive submarine cable map hit a new milestone. Seven hundred and nine cable systems.

• 12:29Hannah Fry?

  That's across the entire world.

• 12:31Michael Stevens?

  Across the entire world and I'm, and that's a system, not like just a big, long length that stretches the ocean. So, you know, but this is giving us some ballpark figures of what's down there.

• 12:41Hannah Fry?

  Yeah, but there's not many.

• 12:42Michael Stevens?

  What surprises me is that we don't hear more about them and their vulnerabilities. Why are these not attacked more often?

• 12:50Hannah Fry?

  Oh, they're attacked. Oh, they are attacked. And when they go down, it can really cause really serious problems. So sometimes, uh, in fact, one of the things that has been happening, uh, as a sort of act of war is that sometimes you will see people divers going down with saws. There's a little bit in viewed in Cornwall, which is where the main, uh, sort of artery comes in from America. You know, and when I say the main artery, I'm talking like half a dozen glorified garden hoses. Okay. It's nothing. And that comes in through, through Cornwall and it's extremely carefully protected, this,

• 13:30Hannah Fry?

  this area, because if that were to be damaged, we would, I mean, how would you survive really? Right? Like a lot of stuff would shut down if you suddenly lost all access, um, to the internet, which is one of the reasons why you have both satellites and these, these deep sea cables so that you're protected from solar storms, um, and this sort of vulnerability of someone physically cutting the, the cable. My favorite story though is in Georgia, so Georgia in Asia rather than Georgia in America, um, where they had this cable that kept on getting severed. And, uh, as it got severed, I mean, essentially would knock out the internet for Armenia. And it turned out there was this woman who had a spade, who was, um, trying to scavenge copper.

• 14:14Michael Stevens?

  Oh, really? It was just kind of an innocent, I mean, maybe not innocent, but it wasn't some big military action.

• 14:21Hannah Fry?

  It wasn't some big military action, no.

• 14:23Michael Stevens?

  I know that on the other side of the States, there's a place in Whittier, Alaska, where cables come up and it is very protected. I mean, first of all, Whittier, Alaska is literally only accessible periodically by going through a tunnel in a mountain. But I looked at that, I remember, and I was like, what is that? And they were like, that's the internet. And I was like, what?

• 14:45Hannah Fry?

  Right. I just think that's the coolest thing. I mean, there was a big, big, um, uh, sort of explosion in, uh, attention in this stuff when high frequency trading really started to take off. Because with high frequency trading, let's say, I say to you, hey, Michael, can I buy that watch, please? And you say, yes, you can, right? And then someone else, uh, Bob comes in and they, they've got really extremely fast internet access. Bob comes in, hears me saying it to you, and then very quickly gets into you first and says, I will buy 10 of them, please. Buys 10, 10 of your watches.

• 15:27Hannah Fry?

  And then by the time my order actually arrives, I have increased the value of the watches by virtue of the fact that there is now this demand for them. So end up paying you more. And then they can go off and sell their watches elsewhere. Now their price is higher. So it's like these tiny, tiny, tiny little changes in price that you can exploit if your internet is faster than other people.

• 15:51Michael Stevens?

  That's right. Just, it just comes down to a matter of milliseconds.

• 15:53Hannah Fry?

  Oh yeah. And we're talking out where the, the, the speed of light is your limiting factor. So people started buying offices closer and closer and closer to where these deep sea cables came out from the ocean floor. Right? Like if you were a hundred meters down that way in Manhattan, forget it, you know? Even like the floor of your building, as to how close you were to the floor of your building would allow you to be exploited by these extremely fast paced algorithms. People were tunneling through mountains to lay your cable straight rather than go around just to, in order to get the fastest possible access, uh, to the internet for these trades.

• 16:35Michael Stevens?

  That makes me think about how financial markets will deal with an interplanetary human species. Like once light speed really matters. And I mean, already, whether you go through a mountain or around it, or whether you're a hundred feet this way or that way, does make a difference of nanoseconds. And if your machine can work really quickly, then you've got an advantage. What do you do when you've got traders on Mars and traders on earth? And they're like, wait a second, how do we protect this action? Because it's going to take it minutes for my order to get there. And if it's intercepted along the way, um, the time it takes for the, the, the, I don't know enough about light, but you see where I'm going with this.

• 17:17Hannah Fry?

  I see where you're going with this. I see where you're going with this. Like, I tell you what, can I tell you something about light though? Because, because I think the way that these things work is so interesting. Because what you, what you've got is you've got this like, it, this little tube of glass and you're essentially bouncing a laser down the tube of glass. And the glass is designed to be, uh, to have as little resistance as possible so that this beam of light can travel unimpeded. The thing is, is that if you vibrate the tube of glass, there is a disturbance in the light beam as it arrives. And if you do some very clever calculations, you can reverse engineer what kind of vibration and where that vibration happened.

• 18:00Hannah Fry?

  So this technology, this, the sort of this, the clever bit of math basically, was originally developed for when these cables were laid in roads and there would be a pneumatic drill getting close to the cable. And then this sort of internet company could come and say, you know, please step away from, please don't break up or, or, or, you know, um, proactively go and send somebody out to repair the cable. But what they realized as the technology got more and more sensitive was that you could use this, this network of cables on the ocean floor to detect seismic changes. So now some of the best sensors that we have about earthquakes, about tsunamis, about

• 18:42Hannah Fry?

  all these kind of geological events are through the way that the light vibrates, uh, according to what's going on to the cables, uh, on, on the bed of the, of the ocean floor.

• 18:55Michael Stevens?

  Wow.

• 18:56Hannah Fry?

  Isn't that cool?

• 18:57Michael Stevens?

  It won't be that long until we're able to do that with electrical lines running through cities, you know? And, and, and, and also like, you know, fiber cables for internet in cities, suddenly we can like track where everyone is just by looking at the tiny little nano fluctuations in that light signal.

• 19:17Hannah Fry?

  I mean, it turns out you can go even further than this because I told you already about the whales who are scooping up things on the bottom of the floor. Actually, the sensitivity of these things is so extraordinary that you can detect whales passing overhead now, right? You can, you can detect in the surface of the signal, can detect whales passing overhead, but you can also detect submarines passing overhead.

• 19:42Michael Stevens?

  See, exactly.

• 19:43Hannah Fry?

  And so now this has like this obvious military, um, military application where if you want to monitor where all the submarines are around the world, you can use your deep sea internet cables in order to do so.

• 19:58Michael Stevens?

  That's amazing. Totally unsurprising, but it also makes me convinced that in 10 years, the government is going to know how many times I go to the bathroom each day.

• 20:08Hannah Fry?

  I think they probably already do, Michael.

• 20:10Michael Stevens?

  They might already know that, of course. I take my phone with me most of the time.

• 20:15Hannah Fry?

  Right. I think what they definitely know is how long it takes you to urinate, because as we all know, it's 21 seconds.

• 20:22Michael Stevens?

  They already know mathematically on average how long I take, just because I'm an animal.

• 20:26Hannah Fry?

  You know what? If someone heard me say that and hadn't seen any of our previous episodes, that would sound so weird.

• 20:32Michael Stevens?

  It would sound really weird, especially me being like, because I'm an animal, you know how long it takes me to pee. But this is a throwback to a real.

• 20:40Hannah Fry?

  No, I don't think we should say. I don't think we should say. I think we should just leave it like that.

• 20:44Michael Stevens?

  Okay, let's not explain it. Forget what I said.

• 20:46Hannah Fry?

  You're an animal who takes 21 seconds to pee. Okay, let's move on. Okay, I have one more thing to tell you about these cables. How the hell does all of the internet go through something that's that skinny? How?

• 20:59Michael Stevens?

  Yeah, that's what I was gonna wonder. What is the bandwidth?

• 21:03Hannah Fry?

  What is the internet? What is going on? What is actually going on?

• 21:06Michael Stevens?

  Yeah.

• 21:07Hannah Fry?

  Okay, so it turns out the internet is basically fancy Morse code. Right? It's like genuinely what it is. So you could imagine if I got a torch and I switched it off to be zero and on to be one, right? I could kind of blink out a message and I could spell out different letters. I could use binary essentially to blink out a message to you. And especially if we agreed, okay, I'm gonna do one bit, one bit per second. So every second is gonna be either on or off, and that's how we're gonna communicate with each other. So that's essentially what you're doing down these cables, is you're just going on, off, on, off. So that would be one bit per second, which is great, right?

• 21:52Hannah Fry?

  And they just happen to be really skinny because the lasers are really good and so on and so on. But that only allows you to do one bit per second, okay? And that is gonna be way too slow, right? It would take you, it would take you 40 seconds just to spell out hello, right? Which is not, you're not gonna, you're not gonna be streaming the rest to science very easily if that's how the internet actually works. But then, somebody was like, okay, this is horrifically slow, but these lights, they don't just need to be on or off. What if we use the, how bright they are to encode information? So off could be 00, and then low light could be 01, and medium light could be 10, and really bright light could be 11, okay?

• 22:36Hannah Fry?

  And then someone was like, well, hang on a second. You could use different colors here. Instead of just sending white light as like on or off, or a bit on, very on, medium on, you could send through blue light as on or off, and red light as on or off.

• 22:52Michael Stevens?

  Ah, simultaneously.

• 22:53Hannah Fry?

  Simultaneously, exactly. And then at the other end, you split it back off into red and blue, and you can then, I mean essentially you're sending two messages at exactly the same time, across those two channels.

• 23:05Michael Stevens?

  So the number of messages you can send is only limited by the frequency sensitivity of the sender and receiver.

• 23:11Hannah Fry?

  In terms of how quickly they can go on and off?

• 23:14Michael Stevens?

  In terms of how, how big of a difference between colors they can detect? Because each difference is a whole new message.

• 23:23Hannah Fry?

  Yes, because you can have red, you can have blue, you can have green, you can have turquoise, you can have maroon, you can have whatever, whatever, whatever.

• 23:29Michael Stevens?

  Well, even within green, you could have 500 nanometers, 501 nanometers, at the speed of wavelength now.

• 23:35Hannah Fry?

  Exactly, exactly. And we're talking the narrowest, narrowest, narrowest bands that get, end up getting shared. But they also, what they can do is rather than it being every second, on, off, medium on, high intensity, blue light, red light, whatever, you can also fluctuate it incredibly quickly. You can switch it on and off essentially incredibly quickly. So when you put all of this together, so as fast as computers can flashlights on and off, and as fast as you can read it on and off, the record here, me with a torch going on and off once a second is one bit per second.

• 24:14Hannah Fry?

  The record is 450, 000, 000, 000, 000, bits per second along one single fiber.

• 24:29Michael Stevens?

  In the quadrillions?

• 24:30Hannah Fry?

  So it's almost.

• 24:32Michael Stevens?

  Half a quadrillion bits per second.

• 24:34Hannah Fry?

  It's half a quadrillion bits a second.

• 24:38Michael Stevens?

  Delicious.

• 24:39Hannah Fry?

  Isn't that incredible? I mean, that is basically enough for, I think, the whole population of Ireland, Wales, Scotland, Belgium, England, and France to watch this video.

• 24:52Michael Stevens?

  Through one hair-thin fiber optic cable.

• 24:57Hannah Fry?

  One of these in one second?

• 25:00Michael Stevens?

  How many of those are in an undersea cable? Because they're all kind of wrapped up in the core.

• 25:07Hannah Fry?

  Yeah, well, this one, thanks Andre from the pub in Dulwich, has got on to about 10, max. So the reason why I love this, right, is not only is this just the most absurd story of human optimization, my god. What, it's ridiculous to me that this engineering and marvel where we have harnessed the speed of light in this unimaginably powerful way. And actually, we just use it to watch cat videos.

• 25:43Michael Stevens?

  As we should.

• 25:45Hannah Fry?

  The complete spectrum of human excellence to human stupidity, all contained within one single fiber.

• 25:52Michael Stevens?

  Well, yeah, it's the entirety of human society now flattened to the thickness of the speed of light, which, from its perspective, is nothing. So it's incredible.

• 26:03Hannah Fry?

  Yeah. But my other favorite thing about this, you know, apart from what it tells us about humans, is that, okay, all of this is sort of infrared spectrum, by the way. So when I, when I talk about light colors, it's sort of, it's all shifted. But if you, if you did shift it back so that it would be visible, and then you slowed it down so that our eyes could see the flashing, what it means is that if you were watching the internet, it would look, with all of these colors flashing on and off, it would look like a glittering rainbow.

• 26:31Michael Stevens?

  Yeah, it would.

• 26:32Hannah Fry?

  It's like a little disco.

• 26:33Michael Stevens?

  If you watched it not slowed down, would it just look like a bunch of white light? With slight, there wouldn't even be slight changes. I bet it would just look white.

• 26:43Hannah Fry?

  Yeah, I don't think your eye could perceive it.

• 26:44Michael Stevens?

  It would not perceive the split second changes.

• 26:48Hannah Fry?

  Because if you think about how many channels are being used, it's, it's sort of like a, you know, sort of statistical average of all of these different channels, you just wouldn't get enough, you wouldn't get fluctuations at the sort of the grand level, the kind of meta level.

• 27:06Michael Stevens?

  That would be cool. Plug the entire internet into your brain. Just look at it. Your retina is just not sensitive enough to make sense of it, but what if it was? Someday it could be.

• 27:17Hannah Fry?

  Someday it could be. So there we go. That's my, that's my delightful, delightful object for this week. Thank you very much, Andre. I really appreciate it. I will get this back to you. Post haste, but I cannot tell you how excited I was to bump into somebody nerdy in a pub. Thank you. Should we go for a break?

• 27:36Michael Stevens?

  Let's go for a quick break, and when we come back, we've got a question from you all.

• 27:47Michael Stevens?

  This segment is brought to you by British Airways.

• 27:50Hannah Fry?

  We've all heard that phrase, in your own little world. And when you are settled in British Airways business class, that can feel particularly true. But is there actually any science behind it?

• 28:01Michael Stevens?

  First of all, neuroscientists have shown over and over again that the brain does more than just record the world around us. Our brains combine what our senses tell us and also what we expect to find, which means that right now, you aren't seeing the world as it is in and of itself. You are seeing your brain's interpretation.

• 28:21Hannah Fry?

  Exactly. I mean, two people can experience the exact same moment but come away with two very different versions of it. So today, we are asking, if we each live in our own version of reality, how do we make ours count? Should we go back to some of the neuroscience for this, Michael? Because we've said this a thousand times, but your brain is, you have to remember, is sitting inside your skull. It's dark in there, it's quiet in there. There's sort of no sensory signals at all, just electrical signals that are being fed in from other parts of your body, your eyes, your nose, your skin, et cetera. On the flip side, outside of your body, the physical world, there are all of these different signals that you could absorb, you know? So you have to imagine that your version of reality, it's like looking at the universe through a keyhole.

• 29:07Hannah Fry?

  You are sensing a tiny sliver of what is potentially out there. There are other animals, for example. Bees or mantis shrimp that have a completely different colour perception to what we do. Humans, we only see this very narrow band of visible light waves. Bees can see ultraviolet light waves. And when you look at flowers under ultraviolet light, there's like runways, there's like arrows, there's all kinds of crazy disco stuff going on that is just completely invisible to us. The mantis shrimp, we think they have 27 primary colours, right? We have three. You cannot even conceive of what the world looks like to a mantis shrimp.

• 29:47Hannah Fry?

  Our perception is just a sliver, a sliver of what is potentially available out there.

• 29:54Michael Stevens?

  I will even go one step further and say that we aren't looking through a keyhole. Because that presumes that there's a looker and something to look at through the keyhole, a subject and an object. But look at a, look at a cup of coffee, okay? It's got colour, it's got an aroma, it's got a taste. But where the heck are those qualities? Are they in the coffee? Not really, because people disagree on what it tastes like. Is it within you? Not really, because you can't create that exact sensation all by yourself. It only happens when you are together with the coffee, combined. The subject and object become one. And how can that happen? By exploring the world, by travelling, by having new experiences.

• 30:37Michael Stevens?

  And if you're gonna have new ones, they better be nice.

• 30:40Hannah Fry?

  You better believe they better be nice. Because I tell you what else is going on inside of your brain is that you are this amazing prediction engine. You are change detector extraordinaire. And when everything is the same again and again and again and again, your brain's like, I've seen this before, I can relax it, I can chill out. It's when you have new experiences that your brain knows to sit up and pay attention.

• 31:06Michael Stevens?

  That's right. It's when you have those new unpredictable experiences that you exist. When everything's monotonous, you're not even there. You're on autopilot, literally. We've all been there before. You're at the airport, you get your tickets and you're told, hey, have a great flight. And you respond, you too, to a person who is not going to be flying today, okay? That's your autopilot on, you aren't there. But we can take this even further. When you are present, when your awareness is present, more memories are formed, your experiences are richer. And what winds up happening is that time flies and you have a bunch of fun. And when you reflect on that activity, it fills up your life. It defines you, it's full of great things and great stories to tell.

• 31:50Hannah Fry?

  Right. So if you're gonna form some memories, you may as well make them good ones. You may as well make them ones that allow for a collaboration between your brain and the environment around you. Every new experience that you do gives your brain something to draw on. And over time, that can change what you expect to see from the world itself.

• 32:10Michael Stevens?

  And with British Airways Business Class, new experiences start from the moment you get to the airport.

• 32:16Hannah Fry?

  A glass of something you'd ever tried before in the lounge, maybe. A dinner on board that is worth remembering.

• 32:21Michael Stevens?

  Ooh, and then Hannah, there's Club Suite. A six foot six, fully flat bed with a door for privacy.

• 32:29Hannah Fry?

  Six foot six? What?

• 32:31Michael Stevens?

  Six foot six, thank you very much.

• 32:33Hannah Fry?

  Wow.

• 32:33Michael Stevens?

  You're going to arrive rested, ready to take in all the sights and sounds of somewhere new, joining object to subject, boom, qualia, qualities, existence.

• 32:45Hannah Fry?

  Look, your brain's gonna build its own version of reality either way. May as well make your version count. So to plan your next trip in Business Class, visit britishairways.com.

• 32:56Speaker 03

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• 33:58Hannah Fry?

  And we're back. We've got questions from you, our lovely listeners. The first one is from Enzo, who asks, who named Earth?

• 34:07Michael Stevens?

  I mean, we know who named Pluto. We know who named Uranus.

• 34:12Hannah Fry?

  I don't think I know.

• 34:14Michael Stevens?

  Well, I don't know off the top of my head, but there is a person who named it. Same with Uranus, right? It was like, should we call it Herschel's? Should we call it George? Let's call it Uranus. Funny story, do you know Uranus? I am gonna answer your question, by the way, but I just, I have to get this out of my system. So Uranus, the seventh planet, it sounds like part of the digestive tract. That's one of the, like, almost at this point, like, tiresome jokes about it. I've said before that we should just change its, its name to be its Latin form, which is Kylus, okay? Every other planet, except for Earth, uses a Latin name. But then for some reason Uranus is here using a Greek name. Let's just call it by the Greek version of Uranus, which was Kylus.

• 34:56Michael Stevens?

  It's cool, you know, Kylus, Neptune, it's, it sounds spacey. But also, listen to this, not only does Uranus sound like part of the digestive tract, its actual etymological root is where we get the urinary tract. Uranus and urine are related. They come from the same root, proto Indo-European language words that meant, like, it's like the ur sound, which meant to moisten.

• 35:24Hannah Fry?

  But why is Uranus called that?

• 35:26Michael Stevens?

  Because naturally, where does moisture come from? The sky, rain and fog and all these things that are in the air. So Yoranos came to mean the sky, after it originally meant moisture. And, and then from there, it doesn't take you very long to get to Uranus, which is the mythological personification of the sky. And his great granddaughter Urania, who's the muse of astronomy and astrology. Okay, so you've got this. And then there's another kind of moisture, which is much less heavenly, and that becomes urine.

• 36:03Hannah Fry?

  Much less heavenly, yes.

• 36:05Michael Stevens?

  Yeah.

• 36:06Hannah Fry?

  I'm really resisting the urge to make some wee jokes right now, by the way, to be absolutely clear, just so you know what's going on in my mind, all right?

• 36:12Michael Stevens?

  Don't resist the urge to make wee jokes.

• 36:14Hannah Fry?

  No, mine, mine were really filthy. Carry on.

• 36:16Michael Stevens?

  Okay, all right. Well, the filthy ones we'll save for our members only. The rest is science after dark, which maybe we'll do someday. Point is, who named Earth? Wouldn't it be cool if we knew the exact person? Like how we know America is named after Amerigo Vespucci? But we don't know who named Earth individually. We know that Earth came from, we can trace it etymologically back to, again, proto Indo-European languages where er meant soil, okay? That's where, even where we get words like aardvark, earth, that er sound. We, we also know that human comes from another word for dirt, humus, like the rich soil. That's where we get the word human.

• 37:00Michael Stevens?

  We don't know where the word body comes from. The furthest back it's been traced is like old high German. But we just don't know what the heck body meant. I, I personally feel like almost every word is an onomatopoeia originally. I think that noises replicated the things, like indicated them much more directly. And then slowly they took on abstract meanings. So why dirt would be er, er? I don't know. Dirt doesn't really make a sound. But er is also a very basic noise that you can make.

• 37:43Hannah Fry?

  I guess it's also, yeah, no, I mean, I love it though. I really love it. It's also, I like the idea of the various meanings of it. So Earth is in literally the soil, the thing that you're touching, the, the kind of the ground beneath your feet. And then that definition sort of expanding to the entire planet itself. There's something quite nice about that, that it's like, as our understanding of what we were standing on expanded, so too did the meaning of the word.

• 38:10Michael Stevens?

  Well, yeah, and so many of the. Place names we have for just regions on Earth are what its indigenous people used to mean everything, the planet, the ground. Okay, so moving on to another question. Apurva asks via email, why are mathematicians so obsessed with knots?

• 38:31Hannah Fry?

  I'll tell you why they're so obsessed with knots, because knots are absolutely amazing and I love them. Unfortunately, I'm not a knot theory mathematician. In another life, I would be because they are so delicious and incredible. So it all started in about like the 1860s or 70s or so, when there was a theory that maybe different atoms, although they hadn't worked out they were atoms yet, but different elements maybe, were just some kind of smoke that was like knotted in a different way. That was kind of how the idea started to like, is it just this one's like a little loop like this? And this one's sort of like this.

• 39:11Michael Stevens?

  That sounds like string theory today.

• 39:13Hannah Fry?

  It sort of does, doesn't it? Anyway, it turns out not the case. But that set some mathematicians off because they were like, well, okay, how do you categorize a knot? If you get something that's like wrapped up in a particular way, sometimes you can, you cannot actually fundamentally change the knot, but you can rotate it so it looks like something else. You know, an example of this is I could hand you a piece of string that looks extremely knotted, but all you have to do is pull the two ends and it just, it completely unfolds into, into a straight line. And so that's sort of when is a knot not a knot? When can you unfurl a knot? And is there a sort of fundamental nature of, of knots that is like,

• 39:55Hannah Fry?

  that you can simplify things down to and then categorize them? Anyway, it started as sort of like a mathematical playground essentially. And for, you know, maybe nearly a hundred years, that's all it was, was, was, was people sort of toying around with them. The reason why I really love it, you, you see videos of this on sort of TikTok and YouTube of people doing things that look like they should be impossible. Managing to get a plug through the, the leg of a desk in a way that it shouldn't look like it should happen. Or people having a necklace where they managed to thread the loop through the hole of the necklace, despite it not actually fitting, right? Essentially what they're doing is like using tricks from knot theory.

• 40:38Hannah Fry?

  My favorite example is when you get two people and you tie them by their wrists. So it's sort of where one has their hands perpendicular to the other. So it's almost like, I, I, maybe we should do this as a live version when we're next in person, Michael, and I can, I can try this on you.

• 40:54Michael Stevens?

  Ooh, yes.

• 40:55Hannah Fry?

  Where you have one person with their wrists tied together and the other person's hands are also tied together, but they're sort of in between. So you're locked together, you cannot escape.

• 41:05Michael Stevens?

  Right, yes, I've seen that.

• 41:06Hannah Fry?

  And then the question is, not using any, not cutting anything, not tying anything. Is there a way that you can both free yourselves from that, from that setting? And it's just another great example of knot theory of like finding a way that two, two setups are identical. I'm not going to tell you the answer.

• 41:26Michael Stevens?

  If you know the answer, then you and I shouldn't get tied together. You should tie me to like a producer and see if we can topologically picture the solution. Cause I'm assuming there is one.

• 41:37Hannah Fry?

  Oh yeah, there's a solution and it's great. And it's really great and it's really counterintuitive and it's really surprising and it feels like a magic trick, but actually it's just not theory.

• 41:46Michael Stevens?

  Okay, I'm game, I want to do this.

• 41:47Hannah Fry?

  Anyway, the thing is, is that this was all just like mathematical amusement, sort of mathematical recreation almost for a really long time. But as with most things in mathematics, it turns out that just like following our own curiosity ends up, because math is so completely fundamental to the nature of the universe, ends up being extremely applicable in numerous different ways. So one is in the way that DNA is tightly, tightly, tightly bound inside of a cell. And there are all kinds of elements of knot theory that really come into play when you're trying to untangle that, understand what's happening in the kind of code of the DNA

• 42:30Hannah Fry?

  and how that then presents itself in the human more generally or the organism more generally. The other place where it ends up being incredibly useful is in quantum computing, where you are tracing the path of quantum states passing between two different plates. And you can kind of think of this as though it's like, it's a knot of like, this one has gone from here down to here, this one has gone from here down to here, and they passed over, passed over each other. It's sort of like an imaginary knot that has been created between the two. There's this real idea that actually knot theory is going to be really, really fundamental to getting quantum computing to end up working.

• 43:09Michael Stevens?

  Wow, I did not know that, that's cool. I mean, I just think they're very amusing. There's something really, really powerful about understanding the topology of a knot. Like, oh, I get why it works and how to undo it and how it's different. It just, it's a kind of mastery that tickles that like niche, I think we're all evolved to, to in some, in our own way, explore.

• 43:32Hannah Fry?

  It's very like recreational mathematics. You know what, let's, we're going to do a field notes on this. At the very least, we'll do a field notes, maybe something more, but we'll wait until we're in person. We've got better cameras then. Okay, last question is from Charlotte Walton, who says, you're both obviously very rational, science-led people, but I was wondering if there are any irrational, perhaps superstitious or spiritual beliefs or practices that you like to indulge in?

• 43:55Michael Stevens?

  Let me think, so when it comes to watching American football games, it's really hard to avoid the impulse to be superstitious. Like I'll go to the bathroom and something good happens and I'm like, okay, I should stay in the bathroom or I should go there next time we need some points. I wear the same jersey every time I watch a game, until it stops working. And then I'll be like, oh, okay, I need to find something new. And I don't think, I clearly, I don't believe that it's having some effect on the players, but I think it does allow me to feel like I'm participating in some way.

• 44:35Hannah Fry?

  Right, of course.

• 44:36Michael Stevens?

  And even though I know, I have absolutely no belief that what I'm doing is actually changing the psychic fabric of the world and helping the result happen that I want. I still do it for me. It's for me alone to be like, yes, I have made a choice and I'm committing to this and I'm, my life is different because I wouldn't normally wear this shirt. You know, it feels like, like how I like, I like having an office and not working at home because it makes me feel great to just be in a different location. There's something psychological about it. I want to have to put on shoes, I need to travel and then my, my brain can change wavelengths. Putting on the right jersey or having the right snack before a game puts me into the mood that I want to be in.

• 45:21Michael Stevens?

  So I guess I'm kind of describing it like it's not supernatural or superstitious. Instead, it's just about set and setting and my own psychology. But it certainly looks superstitious from the outside.

• 45:33Hannah Fry?

  Yeah, I like that though. I mean, I do think that it's like, actually, we might be rational, we might be science level, we're still just human, right? And it's like, actually, we still like all the same things that other people like.

• 45:46Michael Stevens?

  Yeah, and it just, it feels good.

• 45:47Hannah Fry?

  It feels good. My one is, I like manifesting, you guys, right? Like, I know that it's all a bit woo woo and I know that people like take the piss out of people for manifesting stuff. But I actually think that sitting down and like really carefully thinking about what it is that I'm trying to achieve and really carefully thinking about what my goals are and what I'm looking for and like in the word of sort of the woo woo, like asking the universe. I actually think there's something really good about that, about like, it's not that I then think that the universe responds, but, but I do think that you are priming yourself to be more open to seeing opportunities as they arise.

• 46:30Hannah Fry?

  I, I think it's like, it's somewhere between, similar to you, right? Somewhere between just superstitious nonsense and actually I think there's a credible theory behind it.

• 46:39Michael Stevens?

  Oh yeah, for sure. I mean, it helps so much to be clear about what you want and to express it through, through language or through writing, get other muscles involved. And like now, you're even non-consciously just more aware of those opportunities and whatnot. I mean, I don't think that there's anything that ultimately couldn't be rationally explained about why manifesting would work. I don't think there's a patron ghost of manifesting who goes, aha, because you put that on Instagram, I will now make it happen. But I think that that mystical, you know, manifest ghost is made out of your perspective and also other people in the world knowing and now being able to help you because you have expressed what you want.

• 47:24Hannah Fry?

  Yes, exactly. I'm manifesting right now, okay?

• 47:29Michael Stevens?

  Manifesting privately in your own mind? How, how manifested does it have to be?

• 47:33Hannah Fry?

  I think it's all about an internal thing. I think it's all about what you want in your own mind. All right, well, I guess that brings us to the end.

• 47:39Michael Stevens?

  It sure does. Thank you for watching, everybody out there. If you have other questions you would like us to answer, email them to us at [email protected], our subreddit. I love that place, there's amazing stuff going on there.

• 47:52Hannah Fry?

  Isn't there?

• 47:53Michael Stevens?

  Isn't there? And I just, I can't engage unless I make a new account. I, I'm trying to get someone to please give me access to my old account.

• 48:02Hannah Fry?

  Manifest it, manifest it, Michael, manifest it.

• 48:04Michael Stevens?

  Well, I have, I've talked about this before. I've done even more than manifesting, I've talked to our producers and they've, I don't know if they've done anything about it, I think it's hard to do. I might just have to make a new account because I want to engage with people there and all over Reddit.

• 48:21Hannah Fry?

  They say they're working on it. They say they've just sent us a message saying, we're working on it, I promise.

• 48:25Michael Stevens?

  They're working on it.

• 48:26Hannah Fry?

  Oh, Lucy had a meeting about it today, apparently.

• 48:28Michael Stevens?

  No kidding? That is wonderful news, guys. See, now is the best time to start engaging with us on The Rest Is Science on Reddit because we're all going to soon be there. Be sure to also follow us, like us on whatever platform you're using. And until next time, we'll see you soon.

• 48:46Hannah Fry?

  Bye bye, everyone.

• 49:02Michael Stevens?

  This holiday, all plans, even unlimited, are just $15 a month. A holiday deal this good obviously deserves an enormously expensive holiday song, like All I Want. Right, okay, we can afford that. You know what, forget the music budget, we're going to stick with whatever's in the public domain. Give it a try at mintmobile.com/switch.

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