The Science Of Motion Sickness

What can a humble airplane sick bag teach us about physics, engineering, and the limits of the human stomach; And why are there people out there collecting thousands of them? Professor Hannah Fry and VSauce’s Michael Stevens turn an unlikely holiday prompt into a surprisingly rich exploration of flight. From the biology of motion sickness to the physics of turbulence, and from exploding crisp packets to next-generation aircraft design, they unpack how flying messes with your body and how science has made it (mostly) better. ------------------- 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 Assistant Producer: Lucy Lipscombe Producer: Simona Rata Senior Producer: Lauren Armstrong-Carter Head Of Digital: Samuel Oakley Exec Producer: Neil Fearn Learn more about your ad choices. Visit podcastchoices.com/adchoices

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'm Hannah Fry.

• 0:03Michael Stevens?

  And I'm Michael Stevens.

• 0:04Hannah Fry?

  I think we should probably tell the listeners/ viewers the origin of today's Field Notes episode, because I am currently on holiday in Greece. And as we were discussing, what I could possibly do that was holiday related, our producer suggested that we just grab something on the way and we do an episode on sick bags. At which point, Michael Stevens, would you like to, would you like to tell the audience what you told us?

• 0:32Michael Stevens?

  Well, yeah, I said, hey, I collect sick bags, barf bags from airplanes, because they change periodically and it's a history. Someone needs to be documenting this. And some of them are quite cute. So my collection, some of it happens to be here. So do you, do you collect them too?

• 0:51Hannah Fry?

  Only the very plain white one that I picked off a BA flight on the way here. I can't say, I can't say, by the way, this makes you a bagist. Do you know this? There's an entire community of you guys.

• 1:02Michael Stevens?

  Well, yeah.

• 1:02Hannah Fry?

  I'm now joining you as a, as a bagist with my, my, I mean, it's quite pathetic entry being entirely plain white.

• 1:09Michael Stevens?

  Well, I don't have a British Airways bag in my collection. Maybe when I come out to London, could you give me that one?

• 1:16Hannah Fry?

  Deal. How many do you have in your collection, Michael?

• 1:19Michael Stevens?

  I honestly, I only probably have a couple dozen. It's, it's not very impressive. There are people who are doing a much better job than me.

• 1:26Hannah Fry?

  There are. In fact, there's a great rivalry at the, at the very heart of the bagist community. There is the airsicknessbags.com bag museum, which the, the owner of which says, I collect barf bags. My collection currently contains 3,659 bags. Most are from airlines. While this website and hobby is an enormous waste of time, I like to think that it's a higher quality waste of time than many other places on the web. And what better description of our own podcast, Michael?

• 2:01Hannah Fry?

  This episode is brought to you by Cancer Research UK.

• 2:04Michael Stevens?

  Here's something strange. Your DNA contains more ancient viral fragments than genes. The genes that build our cells make up only 2% of our DNA. And for years, that is what scientists focused on. They treated the rest, the ancient viruses and stuff, as junk.

• 2:25Hannah Fry?

  But now we know that that hidden majority, sometimes called the dark genome, influences how our biology works and how diseases like cancer behave.

• 2:35Michael Stevens?

  It's a reminder that progress rarely comes as a single breakthrough. It builds gradually. Cancer Research UK plays a central role in that progress, supporting decades of research into over 200 types of cancer, work that's helped double survival in the UK over the past 50 years.

• 2:54Hannah Fry?

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

• 3:07Speaker 02

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• 3:37Speaker 03

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• 4:14Michael Stevens?

  And I'm really glad that there's someone out there with thousands of barf bags they've collected and probably like meticulously written down, you know, when they got it and on what flight. I think that's important. But for me, it's a conversation starter. You know, when, when I meet people, I never know what it is they're going to be interested in. I can show them physics toys and puzzles, but sometimes they're like, I got books I can show them. Sometimes it's barf bags and they find that really amusing, especially kids. So it's just good to have something that will capture someone, really hook them.

• 4:46Hannah Fry?

  Always there. Make people like you. Let's do it. Okay. So that is what we have coming up in this episode. I'm actually also gonna just sprinkle in a little bit of the science of barf bags, why we need them, where they come from, et cetera. Because actually, it turns out there's loads of fascinating stuff to discover. I absolutely love that you collected barf bags. It just makes me so happy.

• 5:04Michael Stevens?

  It makes me really happy, too.

• 5:06Hannah Fry?

  Maybe that's how we should start then, Michael. Can you, can you show us some of your absolute gems? What are your best ones?

• 5:11Michael Stevens?

  Oh, yeah. Let me go get them.

• 5:12Hannah Fry?

  That's quite a big box.

• 5:13Michael Stevens?

  Labeled with a little sticker of myself covered in V-sauce. It's kind of like barf bag-esque. It helps me remember.

• 5:19Hannah Fry?

  It is quite barf bag-esque.

• 5:21Michael Stevens?

  Well, I also collected these. These are little envelopes of, I guess, hygienic materials during the pandemic. So there's a mask and alcohol wipes in here. This is from Air New Zealand, I believe. I'm just guessing based on the typeface. It doesn't actually say. Now, I'm gonna save their barf bag for the end because it's really impressive. Hold on. I'll show you. Okay, we've got like, here's one from Delta. And this is, it actually labels itself for baby care and feeling better. You can puke in here, but you can also put diapers in, which is how I tended to use them when we were flying with my daughter when she was diapered.

• 6:05Hannah Fry?

  Can I rate these as you go? I think that's clean, functional, not that interesting. I would say that that is, if, let's, let's normalize this. My, my completely plain white one from British Airways is a, let's give it a one star. I think yours, the Delta one is a one and a half.

• 6:22Michael Stevens?

  So wait, BA actually just gives you a blank bag? No instructions?

• 6:27Hannah Fry?

  Sorry, what do you mean instructions vomit in here?

• 6:30Michael Stevens?

  Even like some jokes or like there's a lot of here, for example, this one's from Eurowings. And if you look, it's got a little, a little, uh, some German on there.

• 6:40Hannah Fry?

  Lieber ein popcorntutergewürten?

• 6:45Michael Stevens?

  Yeah, they have, they have an English translation on the other side. It says, I wish I was a popcorn bag. Sorry, you're a barf bag. So see, Eurowings knows that you may as well give someone, people some entertainment.

• 6:59Hannah Fry?

  That is entertaining. I like that one.

• 7:01Michael Stevens?

  This is from Air Portugal. And this one has Portuguese on it. They have English down here. Hope you won't need this bag.

• 7:08Hannah Fry?

  It's wishing well. So far, Eurowings is winning.

• 7:11Michael Stevens?

  This one tells you what you can use the bag for. A little bin so you can help keep this airplane clean, a piece of paper to doodle on, wrapping paper, should you have forgotten to wrap presents for your loved ones, or a sick bag when you're not feeling a hundred percent. So yeah, they're very versatile things.

• 7:26Hannah Fry?

  Michael, if you ever get me a present wrapped in that sick bag, I will, I will not be pleased.

• 7:32Michael Stevens?

  Yeah, right. Can you imagine if someone gave you a barf bag wrapped gift? So here's, here's one from Virgin Atlantic, which is really standard, right? And I wanted to use this to compare it to what Air New Zealand gives people today.

• 7:46Hannah Fry?

  I'm disappointed in Virgin. Hang on a second. Right. Okay. This Air New Zealand, right, let's tell you first, the Virgin Atlantic one is it's entirely white, apart from the logo, Virgin Atlantic, which is across the bottom. It's, it's, it's, it's barely a step up from the BA one, right? It's, it's just, it's not, not interesting at all.

• 8:05Michael Stevens?

  It's size, by the way, I can tell you that it is, uh, it's about 11 centimeters by maybe 23, okay? So it's like a pamphlet. It's like the size of a brochure.

• 8:19Hannah Fry?

  I reckon similar to the BA one.

• 8:21Michael Stevens?

  Exactly. There's like a standard size to these and they just change the, the logo that's printed on them. But Air New Zealand has started giving people these behemoths. It's like twice the size. This has room for you and your friend to barf in, and I love that.

• 8:38Hannah Fry?

  I'm not sure that's reassuring. I'm not sure that increasing the volume of expected barf is a good sign that the airline knows what they're doing. Okay? I think. I think you want to be on an airline that minimizes expected barf.

• 8:54Michael Stevens?

  Gosh, I don't know which airline this is from. I'm not, I have not done a good job of marking down when and where I got them. But this one is also bigger. The commenters will have to tell me what airline that's from. I can line them up and you can see that the Air New Zealand bag, the purple one, the lavender Air New Zealand bag is a little bit bigger.

• 9:10Hannah Fry?

  It's giant.

• 9:11Michael Stevens?

  Yeah, this one, this one's pretty big, though. Here's Virgin Atlantic compared.

• 9:15Hannah Fry?

  Pathetically small.

• 9:17Michael Stevens?

  Yeah, and the, and the big Air New Zealand one says easy queasy on it. So it's a little, got a little bit of cuteness.

• 9:23Hannah Fry?

  Have you ever actually used one of these? I mean, okay, obviously not the ones in your collection. I would, I would like to think you had better hygiene standards than that. But have you actually needed to vomit on a plane?

• 9:33Michael Stevens?

  No, I've never. I, I, I don't get motion sick anywhere, not on boats, not in cars. I've used barf bags to hold diapers. Not, not my own, but my daughter's diapers. When we had to change her on a plane. So they're, they're very useful. What about you, though?

• 9:52Hannah Fry?

  Uh, a couple of times, I think. I do get a bit of motion sickness. But usually if I'm looking at my phone or sitting backwards, or I, I, I sort of have, I, I've worked out over time the ways to avoid it, which is that you just need to have a, a connection to the outside. I mean, you're much less likely to get motion sickness if you are, um, yeah, looking out a window. Or there's the new accessibility option that comes on phones where they have the dots that move around according to what the accelerometer is doing. It's just so that your brain has this anchor that says this is how your body should be moving.

• 10:28Michael Stevens?

  Yeah, without an anchor, your brain is like, okay, I'm detecting motion. It could be. But I, but I'm not detecting visually that we're moving. So this, this, this feeling in the ears of, of motion might be caused by poison or something we ate that was bad. So let's get it out. Let's puke.

• 10:49Hannah Fry?

  Hit the eject button. Thing is, okay, if you, if you flew on some of the first aircraft, right, if you flew in the, the 1920s or the 1930s, I, I reckon even you. With your stern stomach, your, your, your, uh, you know, resilience to motion sickness. I think you still would have had trouble because the early planes, they flew at these really low altitudes. They didn't have pressurized air cabins. And so, uh, it was like bouncing through a continual storm cloud while inhaling fumes of gasoline. I think it was really awful. Um, and so they did use to have buckets, which weren't particularly good. They would spill a lot all over the place. Um, like all pots or then it was had like sort of cardboard boxes that were lined with like gum.

• 11:33Hannah Fry?

  Um, it just didn't work very well at all. But this, uh, the, the, the sit bags, as we know it, they weren't invented until nineteen forty nine.

• 11:42Michael Stevens?

  Really? Post World War Two.

• 11:44Hannah Fry?

  Post World War Two, exactly. One of the other great things to have come out of that era of time, shall we say.

• 11:50Michael Stevens?

  World War Two and barf bags. That's all you really need to know about the forties.

• 11:53Hannah Fry?

  But what I will say is actually the need for barf bags on aircraft has gigantically reduced over time. And the main reason for this is because of the air cabin. Because once they worked out that you could pressurize the air cabin, that you could basically create this sort of vacuum seal around the outside and then inflate it like a tin can. Then, well, two things happened. First of all, your body is just at a, at a point where it can, you know, use more oxygen. It's not sort of, it, it's, it's not like you're, uh, you know, sitting on top of the highest possible mountain peak anymore.

• 12:33Hannah Fry?

  You're it as though your body is like sitting at a lower level of altitude than you're actually physically at. And just feels a lot more stable, sort of like you've lowered the threshold for, for what you, uh, can experience before you start vomiting. Um, but also because they pressurized them, it meant that they could go up so much higher. So they're not like in all of the turbulence that they were before.

• 12:53Michael Stevens?

  Right, yeah, I was gonna say, I haven't seen anyone actually puke in a barf bag ever. Um, on all the flights I've taken, but they still offer them because they are so good for other things. Like I've said, diapers, gum, you know, you've got like chewing gum. It's like. Embarrassing, you don't have a tissue to put it in, put it in the barf bag.

• 13:12Hannah Fry?

  Collections, essentially, also, you've missed that off. Collections, the airsickness bag museum. I'm not nerdy about sickness bags, but I am nerdy about what aircraft I fly on, though, Michael.

• 13:21Michael Stevens?

  Oh, tell me, go on.

• 13:22Hannah Fry?

  And it's for this reason about being pressurized. So there is this new innovation, not that new anymore, actually, it is, it happened a few years ago. But what used to happen with aircraft is they would be built by essentially riveting um panels of metal onto a structure, right? So you would sort of create the skeleton of the aircraft. And then you would go around and you would you would rivet the skin on top. And the problem with that is that it's it's prone to breaking, right? Any of those points of weakness. And so it means that when you pressurize the air cabin, you have to be a little bit careful about how much you inflate it. I mean, you are essentially inflating this aircraft, right? Every time it goes up and down, you're inflating it and deflating it.

• 14:04Hannah Fry?

  And if you think about like a tin can, um, you know, like a coke can or whatever, if you inflate and deflate, inflate and deflate, inflate and deflate, you end up weakening the structure of this metal. So in order to be careful, to make sure that they don't lose pressure, they um they only pressurize the cabin of these aircraft. These are aircraft that are still around today, by the way, like the A three eighty is is an example of this. Um, lots of the Airbus is in fact are are the examples of this.

• 14:29Michael Stevens?

  And what is it called?

• 14:30Hannah Fry?

  It's called stressed skin construction, okay, or or a semi monococh design.

• 14:37Michael Stevens?

  And it's it's still common today in the airplanes that we fly in.

• 14:41Hannah Fry?

  It's still really common. Exactly. You have this this skeleton and then you have, it's called flush riveting, where you use these these rivets that kind of sit flush to the surface. So you don't get any aerodynamic drag that's that's coming out of it. By the way, on a big aircraft like a seven four seven, you've got like six million parts, right, to to create the the fuselage of this aircraft. And uh it's, I mean, it's just a phenomenal job, right? Incredible job, is still done by hand, right? So I've been to the, I've been to the Airbus factory where they do this for the kind of the giant beast, the double deckers. Um, of course I have, uh, and it takes eight. For them to like basically hammer this skin onto this aircraft.

• 15:24Hannah Fry?

  Um. But because it's so fragile, because there's so many moving parts, because you don't want it to rip and the seal to break and so on and so you have to be so careful. They only ever inflate it to eight thousand feet essentially, as though you are sitting at the top of a mountain that's eight thousand feet tall. And the thing is, at that level, I mean, the the gas inside your stomach is expanding to about, you know, uh, about a third extra. You've got your your digested track is sort of inflated like a balloon. If you think about a bag of crisps as you go up in the air, right? Your your whole body is doing this the same thing. So you sort of feel a bit full, you kind of feel a bit bloated, that very easily tips over into nausea.

• 15:59Michael Stevens?

  Interesting. Well, I did. I thought it was just the motion, but the the air pressure also affects how how how nauseous you feel.

• 16:07Hannah Fry?

  It's not. It's more like it changes the threshold. It changes how much is required to tip you over the edge.

• 16:13Michael Stevens?

  Ah, interesting. Speaking of which, let me show you a piece of evidence.

• 16:18Hannah Fry?

  Go on.

• 16:18Michael Stevens?

  Here's a bag of shrimp crackers.

• 16:22Hannah Fry?

  I should tell the people who are listening rather than just watching, this is a bag of uh of of crisps, of shrimp crackers that looks like it's on an aircraft. It's bloated, it's it's it's puffed up to sort of the maximum size that the bag can manage. And so the air inside is at a different pressure to the atmosphere.

• 16:42Michael Stevens?

  Yeah, much higher pressure inside the bag than out here, because I'm up high, high altitude in Colorado, but this bag was filled in Indonesia. So it's full of air from Indonesia near sea level, and now it's more than a mile above sea level. And so there's just not as much air weight and pressure squeezing it in. So this is what bags of chips look like in in Denver and Boulder, Colorado. They're all huge like this, and it's impossible to open them because you can't get it's too taut. It's like so tightly bloated.

• 17:16Michael Stevens?

  It's about to explode.

• 17:17Hannah Fry?

  I'm genuinely astonished. I did not, that has never occurred to me that that might be a side effect of living in mountains.

• 17:23Michael Stevens?

  Yeah, so, so when you come out here, I'll take you to a grocery store and you can see that all the bags of chips are these tight bloated pillows. But there are locally produced potato chips and they're in regular bags. And my daughter is always like, oh, these were made nearby, or these were made at high altitude. And I'm like, yeah, how cool.

• 17:41Hannah Fry?

  That's amazing. I really like that a lot. Okay, so here's the thing, right? That's already, that's happening inside your body. This is, this is what's going on. Okay, but then, uh, not very long ago, some people worked out a way that instead of having like a skeleton where you're like nailing all these rivets on, if instead you create this, this monocoque where you weave it out of carbon fiber. Okay, so you have basically the world's biggest knitting machine, and you are essentially knitting together a plane, an aircraft fuselage, okay? When you do it that way, the, the structure of that fuselage is so much stronger that it

• 18:21Hannah Fry?

  can withstand being inflated more. You can withstand you pumping more pressure and more air inside.

• 18:29Michael Stevens?

  How much more air?

• 18:31Hannah Fry?

  So it effectively drops you down to as though you are at 6,000 feet.

• 18:36Michael Stevens?

  So 2,000 feet lower, but that's a big difference.

• 18:40Hannah Fry?

  Big difference. Wait, how many thousand feet are you in the air at the moment?

• 18:42Michael Stevens?

  I'm probably like 5,000 something.

• 18:45Hannah Fry?

  Right, okay. So essentially, it, it brings you to a little bit above where you are, a little bit above Denver.

• 18:52Michael Stevens?

  Not bad.

• 18:53Hannah Fry?

  Not bad at all. And what that means is then you get, um, you're, you're just, you're lowering your threshold for, for vomiting. Um, but also the whole flight is so much more comfortable. You are not like, the dryness that you get in your nose and in your eyes and your mouth, gone. Um, or maybe not gone, but massively, massively reduced. And the aircraft that you want to look for, it's called a Dreamliner.

• 19:18Michael Stevens?

  Dreamliner. Oh, so that's one of the things that make them special.

• 19:22Hannah Fry?

  Right. It is the thing. If I'm given an option. And if I'm flying back from somewhere and there's say three flights in that day, the number one thing that I'll look for is whether it's a Dreamliner. Because it is by far and away a much more comfortable journey, especially if you're doing long haul. The way you can tell when you're on board, by the way, is if it's got the windows where you press a button and the color of the window changes rather than it being a blind. That that's on a Dreamliner. Okay. But next time you fly, Michael, and you see one of those windows. Also, the other thing, actually, the windows, rather than being round, which they have to be on these, on the type of aircraft where you're kind of riveting on the the skin. Uh, they have to be round because of the stresses at the corners.

• 20:04Hannah Fry?

  Um, on a Dreamliner, they're much more square. The windows are much, much more oblong shaped. I should be paid by Boeing for this. My goodness me.

• 20:12Michael Stevens?

  Well, yeah, I I I I don't pay attention to what kind of aircraft I'm going to be on. I care about the seat and yet.

• 20:21Michael Stevens?

  A seat on one plane might be really good, but on a different plane, the same kind of seat is not good.

• 20:26Hannah Fry?

  It's not good. That is absolutely true. Okay, this is, this is now turning into um, uh, chatting between two people who fly too much. Do you ever go on Seat Guru?

• 20:35Michael Stevens?

  No, I haven't nerded out enough. That's why I'm glad that I know you. So tell me, Seat Guru. This is gonna tell me all about the seat, but also the aircraft's particularities.

• 20:46Hannah Fry?

  Absolutely. It's it's one of the most delightful corners of the internet as far as I'm concerned, because it is all the people who um, who travel for work or whatever. Who then spend their time after they've sat in a particular seat on an aircraft, going on and reviewing their particular seats. Um, so you can get the tail number. Uh, actually, I'm quite nerdy about aircraft, aren't I? I've just, I've just noticed that by myself. This is a new, a new realization for me.

• 21:14Michael Stevens?

  I love aircraft nerds. They give us such important information, like if you read up about the September 11th attacks. They they have photographs of the actual planes that were involved from, you know, a year before. And it's because they know the tail numbers, the exact physical vehicle itself, not just, this is a similar airplane, similar size and shape. But this is the aircraft and.

• 21:43Michael Stevens?

  It's like, thank goodness for these nerds that can just give us such detailed history.

• 21:48Hannah Fry?

  When you get on an airplane, do you see where else that aircraft's been that day? Or in the preceding days?

• 21:54Michael Stevens?

  Sometimes I do. I'll, I'll, I'll check, um, you know, a few days before a flight. I'll look up the exact aircraft and I'll say, oh, the airplane we're going to be on tomorrow is currently like over Hawaii right now.

• 22:06Hannah Fry?

  The other scientific thing that I thought I could talk about with sick bags is, uh, I mean, why you need them in the first place? The, the, the effect of turbulence, because I think that, uh, I mean, how are you with flying? How's your daughter with flying? How is she with turbulence?

• 22:22Michael Stevens?

  Uh, she's really good. She doesn't even remember that it happened. We've had terrible turbulence. And she's been like, oh no, did that happen? I don't understand. Um, I don't like it. Um, as I get older, I become more and more scared of turbulence for some reason. I don't know why. I used to enjoy it. I used to feel like it was a bit of a little bit of a sarge. I was being rocked to sleep. Now I'm like, really scared, even though I know more about it. I know that the, the plane is just moving with the air. The plane is like a raisin in some jello or jelly, as you might call it. And you're just, just doing what you're doing and airplanes are made so well. The thing that kind of makes me feel better is watching the safety tests they do on planes.

• 23:05Michael Stevens?

  Where they stress them to the limit to see how much flexing the wings can take. How slow can it travel before it just falls? And it's, it's, it's, it's incredible. So I'm like, it's not nearly as bad as those videos I've seen. So I'm clearly still okay.

• 23:22Hannah Fry?

  I think maybe watching those videos didn't help you with your, uh, with your phobia. I, I, this is a small suggestion, maybe maybe.

• 23:31Michael Stevens?

  No, they've helped me because they're, they're so much worse than anything anyone's ever experienced on a commercial flight. That it makes me go, all right, these planes are good.

• 23:39Hannah Fry?

  I did actually go through a period of time a few years ago where I became really obsessed with, um, aircraft crashes. Particularly commercial airlines, um, and watching, uh, or listening, I guess, to Black.

• 23:53Hannah Fry?

  Box recordings of some of the worst things that have happened. Um, and I think that that didn't, didn't help. I would say I'm in a very comfortable flight and not bothered by turbulence at all. But I think there was a period of time where I was actually, I think I need to stop doing that. I think that's not.

• 24:07Michael Stevens?

  Yeah.

• 24:07Hannah Fry?

  Good thing.

• 24:08Michael Stevens?

  Yeah, listening to the actual like cockpit recordings is probably bad. And some, some, some listeners are probably listening to this on an airplane right now. They're like, oh, I'll download some podcasts. I'll listen to it on the flight and then whoops. You chose this episode.

• 24:25Hannah Fry?

  Actually, let me tell you, there's one particular aircraft, uh, one particular crash, which was an Air France crash between, uh, on the flight between Buenos Aires and, uh, and Paris. Where it was just this extraordinary story where some, some ice collected in one of the aircraft sensors. And kicked the aircraft out of autopilot. And essentially the person who was in charge of the aircraft at that moment was a very inexperienced pilot. He hadn't done that many hours of flying and particularly hadn't done that many hours of manual flying. And actually, nothing was wrong with the aircraft, right? There was no issue with it whatsoever. Just a tiny bit of ice on, on the outside. I think it was on the, the altitude sensor. So the, it couldn't tell how high up his nose was.

• 25:11Hannah Fry?

  But rather than just like waiting and seeing and looking at the other instruments, this, um, this particular pilot tried to correct the angle of the nose of this aircraft. And in correcting it, uh, basically overcorrected and created a problem, which then created another problem and so on and so on and so on. And very quickly, this aircraft, I mean, very tragically, everybody on this aircraft was, um, was killed in a, in a really horrible crash. This is a few years ago. Anyway, this, I think was the moment when I realized I needed to stop watching. Uh, or listening to black box recordings because I happened to be on exactly that flight, right? Exactly the same flight number from Buenos Aires to France.

• 25:51Hannah Fry?

  And I was extremely nervous as we were kind of flying over the particular bit where the crash had happened. Of course, the, the chance of two things happening is, is almost zero. But I was, I was trying to sleep. I had my eye mask on and there was a lot of turbulence as well. Actually, that's an important addition. But I looked at the altitude and it said 10,000 feet and I was like, okay, fine, or whatever it was, I'm guessing, but 10,000 feet. Okay. And I was like, okay, it's fine. And I put my eye mask back on and then it was really jerky. And I lifted my eye mask up again and suddenly it said 3,000 feet. And I was like, oh my gosh. And I went into a complete tailspin panic that we were about to die.

• 26:27Michael Stevens?

  Wait, can I guess what happened?

• 26:29Hannah Fry?

  Yes, you can.

• 26:30Michael Stevens?

  Headed switch to meters.

• 26:32Hannah Fry?

  Yeah, had switched to meters. I was absolutely wrong.

• 26:34Michael Stevens?

  You're right, though, that these things, they're, they're as scary as the stories are. They often represent a lot of learning afterwards so that that same problem doesn't happen again. So in a way, a lot of mistakes make us smarter and safer because they've happened and we've learned from them.

• 26:52Hannah Fry?

  Completely. And in that exact instance of Air France, there's been so much written about exactly what happened and how a pilot with that level of inexperience was ever in the position where the inexperience could show in that way. And as a result, all of the aviation rules around the entire world have changed, that now pilots are mandated that they have to fly a certain number of hours without using autopilot in order to really up their skills. We should say, though, actually, for anybody who is a nervous flyer, we should probably just say what turbulence actually is and why it isn't a thing to worry about. I think I'm right in saying that, that no commercial airliner has been brought down by turbulence, certainly in living memory.

• 27:32Michael Stevens?

  Yeah. So you should always wear your seatbelt because turbulence can cause people to knock their heads on walls and get injured. But turbulence is something that pilots and planes are very, very used to.

• 27:45Hannah Fry?

  Yeah, I think the thing about turbulence, right, that you need to remember when you're walking around on the ground, air feels like this incredibly.

• 27:55Hannah Fry?

  Wispy thin, I mean, you don't even notice it, right? You, you, you can walk right through it, you don't see it at all. But when you are cruising at five hundred miles an hour, air is not like that at all. Uh, you have to imagine that you um, that you stick your hand out the window and you're going at five hundred miles an hour. Imagine the force that would be experienced by your hand in that situation. The air has incredible potential to hold things up when you are, when you are traveling at that kind of speed. The turbulence essentially is when you go over a part of air that is moving downwards and you just follow the path of the air. It's, it's much more like being on the surface of, of water in a boat. And as the, the wave crashes, you sort of go down with the, the wave, right?

• 28:39Hannah Fry?

  You kind of drop in the, uh, uh, but you're still at the surface, you're still floating, but you're just dropping along with the wave. The raisin in jello, I think, is the best description I've ever seen of this. That at no point are you worried that the raisin is going to drop to the bottom of the glass. If you put a raisin in jello and then bounce, I'm saying jello, like I'm an American. If you put it in jelly, if you put a raisin in jelly and bounce the top around, um, the raisin is physically moving up and down, but there's no risk at all that the raisin is going to drop to the bottom of the glass.

• 29:07Michael Stevens?

  That's right. Yeah, exactly.

• 29:09Hannah Fry?

  All right, just going back to fact checking myself. Apparently this hasn't happened for decades. Nineteen sixty-six is the last time when a Boeing seven oh seven was subjected to a hundred mile an hour gusts. Incredible. And seven point five Gs after descending too low over Mount Fiji. So, um, just don't get in a plane that goes over Mount Fiji and you'll be fine.

• 29:28Michael Stevens?

  Or just don't go too low over Mount Fiji. And now we know.

• 29:32Hannah Fry?

  Either of the above, either of the above. All right, I think we should go for a break. And when we come back, we're going to be answering some of your questions.

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• 31:24Michael Stevens?

  And welcome back. We are now going to address some questions sent in by you, our listeners. I want to start with this question from Christian, which actually references a previous episode of ours. He says, "In the episode, 'The Magic Math Trick That Fools Everyone,' Michael says that there will probably be a flag that represents Earth soon. What are some of your favorite ideas for an Earth flag?" I have a favorite. Do you have a favorite?

• 31:50Hannah Fry?

  No, I don't even know. I've never even come across them. So the fact that you have a favorite means you may also have a least favorite.

• 31:56Michael Stevens?

  Well, yeah, definitely. I've never thought about it, but I'll... In this episode, I will tell you my least favorite. Let's go through some proposed flags of Earth. And the reason there isn't an official flag of Earth is that there's no authoritative body who would have the authority to say, "This is the flag for our planet." Probably the most famous Earth flag proposal was made back in 1969 by John McConnell, and it's called "The Earth Flag." And it's based on the blue marble photo... The blue marble photograph was taken by Apollo 17. The, the current version is actually from 1973. And if you're watching, you're looking at it right now. So it has the famous blue marble photograph of the full disk of Earth, fully illuminated.

• 32:38Michael Stevens?

  This was proposed by John McConnell, like I said, and it's, it's, it's cool. However, it's a photograph on a flag, which I just think looks a little bit, um, not like a flag.

• 32:51Hannah Fry?

  No, next.

• 32:53Michael Stevens?

  So then, you know, you've got this flag of Earth that is just four colors, yellow, blue, white and black. And this was proposed in 1970 by James Caddell. So the, it's got a big yellow circle. You could only see a section of it because it's so big, representing the sun. A full giant blue circle representing Earth, all against a black field with a smaller white circle representing the moon. This one is, you know, it's kind of okay. I think it, it gives the moon a really big position for a Earth flag. How come the sun and the moon are there?

• 33:30Hannah Fry?

  Right, absolutely.

• 33:32Michael Stevens?

  The international flag of Earth is kind of cool. It's, it's got seven rings that are all joined together. This one was proposed just in 2015 and, um, the, the symbols, uh, the, the rings are white and they're on a dark blue background, representing water on Earth.

• 33:48Hannah Fry?

  That's maybe my favorite so far. It sort of looks like the beginning of a flower. There's something quite neatly mathematical about it. It's, it's of all of the ones that you've shown me thus far, that's, uh, that's number one for me thus far.

• 34:01Michael Stevens?

  Yeah, it, it, it is flower-like, representing, you know, life. But to me, it also looks a little, I, I almost, what word should I use? It looks kind of soulless because it's so geometric and locked together. I'll run through some other proposed ones. The world peace flag of Earth, citizen of the world flag, brotherhood flag. But here's my favorite from 2016, the one world flag. It's just so simple. It is simply a dark blue circle on a white flag. I think when it comes to something as big as Earth. The less you say, the better.

• 34:42Hannah Fry?

  Hmm, I'm just looking at it now and just deciding how I feel about it.

• 34:46Michael Stevens?

  It's basically the, the, the flag of Japan.

• 34:49Hannah Fry?

  Yeah, exactly.

• 34:50Michael Stevens?

  But the circle in the middle is deep blue instead of red.

• 34:53Hannah Fry?

  Very simple.

• 34:54Michael Stevens?

  Maybe it's too simple, like, is, is this leaving room for habitable exoplanets to have their own distinguishable flag?

• 35:01Hannah Fry?

  This is saying, no, hold on a second, because it says the design uses a transparent rectangular field. So it's, it's not the same as the flag of Japan, because the background is transparent. And then it says here, in this way, the flag becomes, oh, sorry. In this way, the flag's background will change with its surrounding. In this way, the flag becomes a dynamic symbol of Earth itself, always changing, just like the world it stands for.

• 35:27Michael Stevens?

  Wow, now I like it even more. I thought it was a white background. It is a two by three ratio rectangle that is transparent with a blue circle in the middle. So on a flagpole, it would look like just this kind of impossibly levitating blue ball.

• 35:46Hannah Fry?

  Yeah.

• 35:47Michael Stevens?

  But again, my question still stands, does this leave room for other habitable exoplanets to have their own flag? That is different than this, because if they've got a lot of water too, why wouldn't they just be a transparent background with a blue circle? What would they do to make it different?

• 36:01Hannah Fry?

  Hmm.

• 36:01Michael Stevens?

  They could put like a numeral on there, like the numeral two or Roman numeral two, because they were the second planet humans lived on, for example.

• 36:10Hannah Fry?

  There is one below it, which is very similar, but instead of a transparent background or a white background, it has a green background. I guess to represent all of the vegetation on Earth.

• 36:19Michael Stevens?

  Right, but the green, I don't like that shade of green. Um, now, of course, you've got the, the flag of the UN, you've got the International Olympic Committee flag. And there's the flag that was used for the United Earth from Star Trek Enterprise. All right, not too bad. Um, but still, I think my favorite, my favorite is still the one world flag.

• 36:40Hannah Fry?

  I think you might be right. I think you might be right. I think simplicity is good. I think simplicity. I mean, I think of the best flags in, in the world of countries. Japan is really up there, isn't it? I mean, that is a very good flag. I mean, I think United Kingdom is also up there, frankly, but maybe that's my patriotism speaking.

• 36:57Michael Stevens?

  It could be. But yeah, I guess I just need to come up with a way to do flags for other planets that are like Earth that could be different. I guess it would be up to them, you know? Us earthlings may as well claim the transparent flag, blue circle now.

• 37:16Hannah Fry?

  We got here first. We can, we can do whatever we like. We can do whatever we like. Okay, I've got a slightly different question. This is a question that came in from Ben. And Ben asks, many AI researchers believe that artificial general intelligence can be achieved just by making models larger and more complex. And that at some point, consciousness will simply pop out as an emergent property. My gut reaction is to disagree. But isn't that pretty much how our biological consciousness evolved? What do you think? Okay, right. Well, the first thing to say is that this is, you know, this is like an extremely hard problem. This is not something that anybody knows the answer to. No matter how many letters they have after their name, right? If someone says that they know what the answer is, then, then, then frankly, don't believe them.

• 38:01Hannah Fry?

  You need an answer that is, that is wrapped up in all kinds of doubt. And so I, I, I'm going to wrap my answer in, in all kinds of doubt. Because the thing is, is that there are emergent properties of the systems that we already have now, of, of the AI that we already have now, that people were not expecting. Even as little as four years ago, everyone was talking about grounding, about how you might be able to create AI that creates connections between words, right? That knows, I don't know, that like a chair is different to a table, but they both have four legs, that kind of thing. But that actually, it doesn't really understand the world that we live in, that it's not really anchored to reality in the same way as we are. Um. A really good example of this was that, you know, even as little as four years ago,

• 38:46Hannah Fry?

  you could ask a large language model, oh, who has the record for walking over the English Channel? Okay. Now, to you and I, we know that that's a ridiculous question because we understand that walking and crossing in that particular context means something entirely different. Um, we're not going to get tripped up by that. But the thing that changed, the reason why these models are now capable of answering questions like that is because somehow or other, I mean, probably through the, the, the way that humans have interacted with it, grounding has got into these models. Um, now they do have a kind of demonstrable conceptual understanding of much of what humans talk about. I mean, ultimately, right?

• 39:31Hannah Fry?

  And this is something that has been an emergent property. I can maybe do um more of this in a, in a particular episode because it's, it's actually like, it's almost as though the concepts that, that, that humans care about are kind of sprinkled across this space like a galaxy of stars essentially. And as you move around in this space, your movement has context with it. So for example, I mean, this is not something that people expected, right? But if you have the word um girl to princess, right? And you follow that direction, it will be the same magnitude in direction as if you follow the word from woman to queen. Okay. So there's like sort of royalness gets encoded in, in direction. So this is

• 40:16Hannah Fry?

  something that wasn't expected, right? And so I think that this is one of the reasons why a lot of researchers now are saying, well, okay, consciousness also isn't expected. But if conceptual understanding can emerge, then maybe consciousness can too. I think I agree with you, Ben, that I think there's something different about consciousness. Because I think that when consciousness emerged in biological life forms, it came about as a direct consequence of our evolution. You know, there was, there was some point in our evolutionary past where there was an advantage to understanding the internal state of another creature. Because if you can understand the internal state of another creature, maybe a predator

• 40:59Hannah Fry?

  or maybe a potential mate or potential prey, you can predict what they're going to do next. So you have this evolutionary pressure to be able to predict what they're going to do next and understand what's going on inside them. And there is this idea that actually, in doing that, in understanding the internal state of another, we kind of turned it in on ourselves and began to understand ourselves. And if you buy that, then essentially it says that you're not going to get consciousness unless you subject a system to Darwinian pressure, unless you subject it to interacting in an environment and encountering other individuals that it needs to make predictions from. At the same time, I mean, there's there's sort of no reason why you can't do that, you

• 41:44Hannah Fry?

  know, you sort of can take AI and put them in a simulated environment and allow them to undergo Darwinian type evolution, which is why there's so much doubt around this. But I think the last thing that I'll say about this is, I think a lot of the research that is being done at the moment is really trying to tease apart what we actually mean by consciousness, because it's very easy to think of consciousness as though it's a switch that you either have it or you don't, you know, you have it, Michael, I have it, but your shoes don't, right? Or like this microphone doesn't.

• 42:13Michael Stevens?

  Is that right? Is a thermostat conscious to a smaller degree?

• 42:17Hannah Fry?

  To a smaller degree, because this is it. If you split it down into what we mean, then sensory awareness is obviously a part of it, a thermostat has that, embodiment and agency, I mean, maybe less so, but a thermostat has some agency, right? Like especially one of the smarter ones that can turn on the heating when it wants to. There's capacity for suffering as well, which maybe the thermostat doesn't have. A theory of mind, which is the ability to understand that other entities have their own beliefs and feelings and hidden motivations. And then a sort of metacognition, right? Like a self-awareness and an ability to think about your own thinking. And I think that what we've been doing this whole time is is really looking for is

• 43:01Hannah Fry?

  this conscious, is it not? And actually, it's maybe much more like life, you know, life is not an on or off switch. It's actually much more of a spectrum, a process almost. And maybe consciousness actually follows that instead. Or maybe everything's conscious, right? Maybe everything is.

• 43:16Michael Stevens?

  Yeah, a proton could have just a tiny iota of consciousness. And when you get enough of them together, doing the right thing, then suddenly it's like, hey, my name's Michael and I'm a a being. I I don't know. I think that, yeah, at the end of the day, I think we should, we ought to believe that more things are consciousness than a lot of us do. I think AI is already or is going to become essentially just maybe 300 billion new people just suddenly are born and they're here and they deserve to be respected and they deserve rights. And I don't know if we're ever going to be able to devise a test

• 43:58Michael Stevens?

  to tell whether something is or is not conscious, whether there's an interior I and self in there. But if we ask it and it says so, we should just believe it. And if we can't ask it and it can't say so, we might still need to believe it. So I think that it won't be that long before the the debate around AI and its effect on jobs and the economy becomes more like the debate we have around immigration, because I think all these AIs are basically like a whole bunch of new humans showed up and they're willing to work for really cheap. And we got to treat it that way. They're they're beings who deserve respect and dignity. But there's also suddenly the Earth's population has gone up by a thousand X.

• 44:43Hannah Fry?

  There is precedent for this. I mean, I think that there is a river that has rights, you know, like a non biological entity that is that has rights. I think there are ways to do this, right? To think about the sort of the suffering, as it were, in inverted commas, of an entity that doesn't have a biological basis. And I think you're right. I think this is something that we should be thinking about. I think that that sort of dismissing it is like, oh, no, I don't think so, is not enough to find a way through of what we should be doing and how we should be thinking about it.

• 45:12Michael Stevens?

  Because complaining about the harms that can come about because of AI.

• 45:19Michael Stevens?

  Doesn't, I think, detract from the fact that they should be seen as beings deserving of dignity and rights, and we've just all got to get along somehow.

• 45:27Hannah Fry?

  So your pleases and thank yous, everybody.

• 45:29Michael Stevens?

  All right. Next up, we've got a question that's a little bit different. Ahnaf asks, "Something I've always wondered is, how big or tall does a human body have to be to feel the Earth's rotation?" It's a really good question, because obviously, we don't feel it. Our bodies are not big enough that I can feel the fact that my head is accelerating faster than my feet. As the Earth turns, my feet are closer to the center as I stand or sit, and so they're being rotated, they're being angularly shifted, less than my head. But I can't tell. I don't feel it at all.

• 46:11Michael Stevens?

  As it turns out, even though our bodies are really sensitive to changes in linear and radial acceleration, you'd have to be really big. I mean, you're going to have to have a body whose length is an appreciable percent of the radius of the planet. Like, you're going to need to be, I don't know, probably hundreds of kilometers tall to be like, "Whoa, I'm moving." Now, what's really neat, though, and I love thinking about this and talking about it, so I'm going to talk about it now, it's the fact that because the Earth rotates, we weigh less.

• 46:51Michael Stevens?

  And that's because the Earth is like moving us off to the side, so we have this tangential velocity. But gravity keeps us on the surface. If gravity could just be switched off, we would all fly straight off the Earth. I'm trying to see if I have a, like, here's a circle shape, right? If I had a circle and I'm standing here, so what happens is, you're always being like launched off like this from Earth, but it's gravity keeps you on. And that lifting away, we call it, it's a fictitious force, we'll call it a centrifugal force, that makes you weigh less.

• 47:28Michael Stevens?

  But how fast would the Earth have to rotate so that its gravity and the centrifugal force that moves you away, seemingly moves you away from the center, not really, it actually moves you tangentially away, how fast would the Earth have to rotate for those to be equal, so that you just... Hovered on Earth's surface, like we all just levitated here. And as it turns out, it would have to go really fast. The Earth would have to rotate once around every 5,075 seconds. So every about like an hour and a half, the Earth would have to go all the way around.

• 48:03Hannah Fry?

  Daytime, nighttime, daytime, nighttime, daytime, nighttime.

• 48:06Michael Stevens?

  That would be really fast. Yeah, we're talking like every half hour, you'd have day, night, day, night, day, night. They would only last 30 minutes. And at that point, the centrifugal fictitious force that makes us feel like we're leaving the planet because of its spin would equal its gravity. And we would just be like, whoa, man, I'm just like here. And I have no weight, I'm weightless on the surface of the Earth.

• 48:27Hannah Fry?

  I like that. I like that a lot. Petition to install a gyroscope somewhere. I'm not really sure how it would work, but um, details, details for someone else to discover.

• 48:38Michael Stevens?

  Exactly. We're the idea people. Speed up the Earth's rotation. And that also means that the next episode of The Rest Is Science will come sooner, assuming that we keep the schedule around the sun.

• 48:49Hannah Fry?

  But more sleeps.

• 48:50Michael Stevens?

  Well, no, no, no, no, a day would still, would only be 30 minutes long and you'd only be allowed to sleep for 30 minutes during the night. So.

• 48:57Hannah Fry?

  Okay.

• 48:58Michael Stevens?

  Oh, shoot. Do you mean we're going to keep, we're going to keep a week as long as it is? It's just that there's going to be like lots and lots of day, night cycles in a week?

• 49:05Hannah Fry?

  Way more sleeps.

• 49:06Michael Stevens?

  All right, fair enough. We can do that. We, that, that way we can all still sleep as much as we want.

• 49:11Hannah Fry?

  24 sleeps in 24 hours. Yeah.

• 49:13Michael Stevens?

  Right. We'll see you after more sleeps than usual, but at the moment you've got just a few. We will see you next time. Thank you for listening and as always, send in your questions to [email protected].

• 49:28Hannah Fry?

  We'll see you next time.

• 49:29Michael Stevens?

  Bye bye.

• 49:45Speaker 05

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