How To Prove You're A Time Traveller

10:50Michael Stevens:The dream is to eventually make an entire like pocketbook that has much more than just a few items on it and that will allow you to travel through all of human history, you know, and that's going to have to teach you how to speak the languages you might encounter. If you, you know, you need to be able to speak Middle English perhaps or who knows what, right? We'll try to put that together. We also made a slap bracelet that's a ruler. It's got inches and centimeters on it. But since a slap bracelet

11:26Michael Stevens:wraps around.

11:27Hannah Fry:You've never looked more cool, Michael.

11:29Michael Stevens:I've never looked more cool. Imagine it looks more like a medical bracelet. Like, oh, this guy's got some kind of.

11:35Hannah Fry:It does a bit. It just escaped from the hospital.

11:38Michael Stevens:I just came from the hospital. But we also made one that takes advantage of this wrapping effect. And it is not a ruler. It's a pie tape. So instead of having a mark every centimeter and every inch, we put a mark every pie centimeters and every pie inches. So from here to here, that gap between my two thumbs is four pie centimeters. Why would you want to know that? Well, if I wrap that around something, what I'm finding when I look at 4 pi centimeters, that's the circumference, which means the diameter is 4 centimeters.

12:18Hannah Fry:So you can instantly measure the diameter of something.

12:21Michael Stevens:You can instantly measure the diameter of something. Like imagine you find a pipe and the ends of the pipe are inaccessible. So you can't like actually just go across the diameter of the pipe to tell. You have to go around it and divide by pi. Not with the pi tape. You just go around. The number it reads is the diameter.

12:38Hannah Fry:This is extremely useful. I do feel like making these tools and then not wearing them is your real downfall here though. I think you need to commit. I think you need to start tattooing some of these onto your body.

12:48Michael Stevens:I could tattoo them on my body. Yeah. The one fear though is that the existence of the tattoo itself might make me look like a witch. I mean the knowledge of where these things are might make me look like a witch. If I went back to like the 1100s and I'm like, hey guys, I know where this Archimedes thing is and blah, blah, blah. they might say, okay, either you're from the future or you're in a pact with the devil. I haven't actually solved that problem, have I?

13:19Hannah Fry:I do like the idea of you going to the center in Paris where they have the definition of the meter and you've been like, hang on a second, and just whopping out your leg and being like, look, this is, I've got the measurement on me. You know, my sister who makes a lot of her own clothes, she's been discussing for a while now having an inch tattooed onto her thumb. Ah, yes. Just so that you can do an inch hem. I like that idea.

13:43Michael Stevens:Yeah, it's a really good idea. So Adam Savage is someone I know in real life who has a ruler tattooed on his body. Does he? Is it accurate? Well, no. It's symbolic. You know, the problem is that your body changes, your skin changes. And so the inch changes. But again, as a sign of like I'm a maker and I'm a measurer and I love quantities and quantification, it's a great tattoo to have. But we struggled with this at the Curiosity Box trying to come up with a shirt that had rulers on it because inevitably the shirt will stretch. The shirt is a material that moves. It's just not useful as a measuring tape.

14:27Michael Stevens:It can be useful for, you know, formulas and conversion tables. That's great. We've done two shirts that have that property. But this is so far the best I've been able to come up with. And I'm just now realizing that this is the prototype. The real ones we made were adult sized. Look at that.

14:45Hannah Fry:Ah, more space for more coordinates.

14:49Michael Stevens:This is for your time traveling children. This is an adult slap bracelet. It is like really long, by the way. You could wear it as a neckerchief. You could, yeah. Let's see if I can. Oh, no, I can't. Look at that.

15:05Hannah Fry:Any of you who are listening rather than watching, you just missed the absolute delight of watching Michael Stephenson, Feastful Spame, slap himself in the neck with a slap bracelet.

15:17Michael Stevens:I'm kind of a Gaston-y guy. My neck is too thick. Even my pie tape won't tell me the diameter of my neck. It's just not long enough. Well, that'll be for a future item. Look at that. See? Doesn't make it.

15:30Hannah Fry:So close.

15:31Michael Stevens:So close.

15:32Hannah Fry:Careful now. You have to lift up your head quite far to get your beard out of the way. I don't want you to get your top shelf there to go. I know.

15:38Michael Stevens:Isn't that funny? Like my beard is so long now. It's changed. It's been long for so long. It's changed even my own perception of what my head looks like. I think of my head as being this huge thing. But actually, my head is like a little bean. Look at this guy. Yeah. My daughter looked at our wedding photos the other day and she was like, Dad used to be so small. And it's because my head used to be half the length.

16:07Hannah Fry:I'm slightly disappointed, I've got to be honest with you, that when you pulled your beard back there, your head was small underneath. I really wanted you to have a jaw all the way down. I don't.

16:17Michael Stevens:I don't have anything else to share about my object. I'm open to all kinds of questions and comments. I did just finish a time travel book, Bid Time Return by Richard Matheson. I love it because the method of time travel is literally just believing strong enough that you've traveled.

16:35Hannah Fry:I mean, look, some forms of time travel are not necessarily completely impossible, right? It's just the going backwards that's going to be difficult.

16:43Michael Stevens:Exactly. I can travel through time forward at regular speed effortlessly. That's just called living. Sleep is pretty good too. With sleep, you can travel through time with your consciousness. Like the travel seemed to not happen.

17:01Hannah Fry:If you did jump forwards in time, though, rather than backwards, how could you prove you were from the past? Whoa. That's really tough, isn't it? I don't know.

17:12Michael Stevens:Where's the slap bracelet for that? I know, because what would you do? Because your only evidence would be your own ignorance of things.

17:18Hannah Fry:And anyone can have that. Unless there's something the other way around, unless there's something that we have now that is lost to the future.

17:25Michael Stevens:Okay. In that case, you need to carry around with you a very, very priceless relic that's well known. So that when you jump forward, people will say, oh, hey, that medieval chalice has been missing since you jumped. And you're like, I know I've got it because it came with you.

17:44Hannah Fry:Here it is. Or what about a skill? You know, you could say, ask me a phone number. I know six different phone numbers, you know, and people in the future just won't know any phone numbers. Or like I can write with a fountain pen. I still, because actually, I think if you got somebody from, you know, whatever, the 1700s, they would probably have skills that modern people. I'm sure they could weave a basket, you know, make ice cream in the traditional way. Yes.

18:17Michael Stevens:So skills, obviously, although they're funny, the skills anyone could learn, you could learn to read cursive, even though it's the year 2700. I don't know why I'm anticipating the demise of cursive. I've just always felt that it was confusing.

18:35Hannah Fry:And difficult to read. You're right. It's going to be difficult to prove.

18:38Michael Stevens:I have a friend who I was talking to about this time travel idea, and I wanted to do it as a Vsauce episode. It became a product, but she said it should just be a book. It should be a science fiction novel about time travelers and how they have to have slap bracelets like this or almanac books they carry. We didn't think about going to the future, in which case, yes, there needs to be like a big collection of important relics that are always kept track of. And you get to carry one with you when you travel through time to prove that you are the time traveler and that you're from the past.

19:15Hannah Fry:Maybe we're overthinking this. Maybe it's just that all you need is to prove that you know how a slap bracelet works, you know? Maybe that's the skill that's going to be lost in the future. And maybe you get a two in one.

19:26Michael Stevens:Yeah, you could say, hey, guys, I remember the joy of a plastic straw. What's that tweet? It's like, look, I just want a straw that somewhere in between dissolves immediately and kills turtles and destroys the rainforest. Just somewhere in between would be nice.

19:44Hannah Fry:Is there nothing in between? Bamboo, you know, maybe, maybe bamboo. Should we have a quick break first? Let's do that.

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21:03Michael Stevens:All right, and welcome back. We are having the time of our lives answering and reading your questions about time. Here's one for Hannah. It comes from Alex. Watching a documentary about the dinosaurs got me thinking, if somehow a human ended up on Earth 150 million years ago, would they be able to find food they can digest? What is the earliest time when we would be able to find food?

21:30Hannah Fry:This is such a good question. This has never occurred to me. I like how your mind works, Alex, because until you mentioned this, I just honestly hadn't even thought about it. But you are totally right because 150 million years ago, this is the late Jurassic period, there's no flowering plants. I mean, you can go back and listen to our episode on what's the most vegetable vegetable to discover that you're just... Wait, wait, wait, wait. I didn't know this. So there was no fruit? No fruit, no grasses. There's no legumes. There's no root vegetables. Surely I could eat a dinosaur. I mean, sure. Meat.

22:05Meat.

22:06Hannah Fry:Well, you can, except that, well, okay, two things. First off, it would be like chewing on an old goat, right? Like the meat would be so tough. It would be really horrible.

22:17Michael Stevens:One of my favourite foods, go on.

22:20Hannah Fry:But also loads of the stuff, loads of the, I mean, you're basically in fern territory. There's like conifers, there's loads, it's like big green stuff, you know, like you've got conifers, you've got ginkgos and you've got cycads, I think they're called. And the problem is, is that all of the dinosaurs are eating those fine, but they are totally loaded with carcinogens. So it's almost certain that the dinosaurs themselves would be carcinogenic. No kidding. So, I mean, your options are basically eat nothing or cancer. So enjoy. Basically, none of the aisles of the supermarket exist. I mean, you've sort of got fiddleheads, which are like the coiled fronds of young ferns.

23:11Hannah Fry:And you've got something that's like kind of old school pine nuts, like prehistoric pine nuts, like conifer seeds. But the thing is, is that, you know, even if you're trying to eat the vegetation and it's not carcinogenic, even if you manage to find some stuff like that, modern humans, we've basically lost the ability to ferment really high fibre kind of woody plant material efficiently.

23:37Michael Stevens:Yeah.

23:37Hannah Fry:And Jurassic plants, they are way tougher, way more fibrous than the soft vegetables that we get today. So it would be a lot less like eating salad and more like eating furniture, essentially. It's going to be, it's not going to be very fun. And then also loads of the foods that we eat now, we've like bred the toxins out of them. You know, things like almonds, potatoes, we've like bred them over the years so they don't kill your kidneys or your liver. So, I mean, you could survive, but you've basically got roasted dinosaur and pine nuts and that's it. That's all you got. You can't even flavor them.

24:11Hannah Fry:You know, chilies don't even exist for another 100 million years. It's going to be boring.

24:15Michael Stevens:Wow, I had never thought of that before. But yeah, I mean, 150 million years ago, you can go further than that before there are even early mammals. And then you're really in trouble because the mammalian diet needed to be there for mammals, which we are, to exist. Now, I feel like I could maybe eat some fish, but you're saying that the food chain is probably pretty contaminated with stuff that we're not ready for.

24:42Hannah Fry:Absolutely. Absolutely. I mean, you probably would be able to. You probably would be able to, but it's not – I mean, you're really going to struggle. Also, by the way, it's not just the food, because if you're going back 150 million years ago, the CO2 levels are 5 to 10 times higher than you've got today. So you are going to be perpetually out of breath, basically. You might be trying to hunt down a dinosaur to eat them, but you're going to be suffering from CO2 toxicity just trying to get dino steak.

25:11Michael Stevens:That's wild. How have I never thought of that before? Yeah, of course. It'd be easier to go to Mars than to go live in the early Jurassic. But you're on Earth, and yet it's just not for you yet. The air isn't right. If you're a vegan, sorry. if you're willing to to hunt living creatures you don't have any chicken um you've basically got fish sharks reptiles other than that you've got a bunch of like tree bark yeah bit of tree bark

25:47Hannah Fry:that's it not even any grass can't even chew on any grass so no wheat no wheat no grains nothing yeah it's gonna be it's gonna be you're gonna have a terrible time and no one around to tell about the bracelet. Okay, here's a question from Adam. I really like this question because, of course, everything that's going on with Artemis at the moment, that amazing expedition around the dark side of the moon. Adam asks, what would the lag on a FaceTime call be like from space or from the moon? Oh, yeah. What would it be like?

26:23Michael Stevens:So, you know, the lag that we get in FaceTime calls is caused by all kinds of factors. But ultimately, at the very end, even if your technology is perfect, you're always bound by the speed of light, the speed at which an electromagnetic signal travels. It's finite and it's really fast. But when you talk about really long distances, it becomes a big problem. So for the astronauts on Artemis 2, at their furthest point, well, I mean, at their furthest point, they couldn't contact Earth at all, right? For 40 minutes, they were out of contact with Earth because the moon was in the way. They couldn't radio.

27:04Michael Stevens:And just as a side note, on the Apollo missions, when people actually left and walked around on the moon's surface and someone stayed up in the command module, that one person in the module was alone on the far side of the moon by themselves with no radio contact with anybody. And the first guy to do that was Michael Collins, who also I think went the furthest away, but he did it alone. Artemis 2 crew, they have each other. Michael Collins was alone and he was the furthest any human has ever been from any other human. Even Buzz and Neil on the moon's surface were further away from him than you can be from another human here on earth on the surface yeah because he was orbiting around the dark side well the far side let's call it because the dark side is always changing but yeah he was he was on the far side of the moon by himself in the command module and the closest people were the two other guys on the surface of the moon on the other side you know no humans have ever been on on on the moon at night, by the way.

28:10Hannah Fry:Is that true?

28:11Michael Stevens:Yeah. Wow. Yeah. So, I mean, it would kind of make sense. Every crude mission to the moon has happened during the lunar day. And it makes sense because at night, it would be harder to see things, right? You wouldn't be able to see where you're going. But what that means is that no human has ever experienced earth shine alone. at night on the moon, it's actually quite bright because the earth is, you know, when there's a full earth on the moon, it's like a full moon, but times like 20 because the earth is bigger and it's brighter. The moon is actually pretty dusty gray, but, but earth is very white because of the clouds and the ice caps.

28:53Michael Stevens:Um, so night on the moon is just not nearly as dark as what we get here on Earth.

28:59Hannah Fry:Oh, that's so beautiful.

29:00Michael Stevens:Yeah, right? I mean, night on the moon with a full Earth is going to give you like pretty distinct shadows at night on the moon because of Earth. But look, I'm actually going to answer your question. The light speed delay from Earth to Artemis 2 is at its maximum was 1.357 seconds. That's how long it took a light speed message to get from mission control on Earth to the Artemis spacecraft. And that's just one way.

29:31Hannah Fry:Just because of how far away it is. Incredible.

29:34Michael Stevens:That's how far away it is. And so, like, just to give you guys a sense of the radio delay because of how far Artemis 2 is, Hannah and I are going to have a conversation with that 1.357 second delay, thanks to our editors. Okay. Hannah, how are you? I'm good, Michael.

29:55Hannah Fry:How are you?

29:56Michael Stevens:How's the Earthshine? The Earthshine is fantastic, but I'm not loving this 1.357 second delay.

30:05Hannah Fry:It does slightly get in the way of really having a good conversation.

30:13Michael Stevens:And so there you go. That is the delay between the Earth and the moon.

30:19Hannah Fry:Hey, Mom, I'm on the other side of the moon.

30:21Michael Stevens:Yeah, did we fool you? Thanks, editors, for recreating, for demonstrating that fact. But when you get further than the moon, things get really messy. I mean, Mars, okay, we're going to – yeah, let's go to Mars, all right? Mars is so much further away. And it's also much more variable. The moon is sometimes a little bit closer, sometimes a little bit further away. But I think the difference in its distance literally creates a light speed delay difference of only about a tenth of a second between when it's at its closest and furthest from Earth. But for Mars, that radio message delay is going to be anywhere from three minutes at its closest to 21 minutes.

31:10Michael Stevens:Three minutes.

31:11Hannah Fry:We're not talking about seconds anymore. That's not a conversation anymore, is it? That's voice notes. You're in voice note territory. That's right. It's voice note territory.

31:19Michael Stevens:It's like, okay, even when they're, I mean, three minutes is actually pretty long to wait to be like, hey, hello, are you okay? And then you wait three minutes just for them to get the message. Then they have to reply. And then once they send, you have to wait three more minutes. So it's at least six minutes minimum. Or up to 40. Up to 40. And once you get to Jupiter, that's 33 to 53 minutes one way. Wow. Pluto, five hours.

31:53Hannah Fry:Is it? Goodness me. Five hours. Do you know what, though? That also really demonstrates how much closer we are to the sun. I mean, the sun is nine minutes light speed, right, from us. So, and then if we are five hours to Pluto, I mean, that's a really good way to think of the scale of the solar system and just how close we are to the sun in comparison to the other planets. How long was Jupiter? An hour, basically.

32:20Michael Stevens:Jupiter, yeah, between half an hour to an hour, depending on where each planet is in its orbit, right? And then the nearest star that isn't our sun, that gets you out of the hours into the years, right? four years to Proxima Centauri, the nearest star to Earth. And what's so interesting to me about Proxima Centauri is that it's the nearest star. It's about 4.25 light years away. And yet it's so dim, we can't see it with the naked eye. It's like, guys, I'm right here. I'm the closest to you. And yet we cannot see it unless we have a tool.

32:59Hannah Fry:Four years really doesn't feel like a very long time. I mean, if you were sort of, if you were giving it an update on what was going on on earth and be like, Hey, we've got a new president. Oh no, wait, strike that. We've got a new president. It would be a...

33:11Michael Stevens:That's a good point. Yeah. You would tell them the results of the election. And by the time they got the message, there would have been another election. And then by the time they responded and you got their response, more than eight and a half years would have passed. And so you would have had, you would have been having the third election already. By that point, it's just not really worth keeping them in the loop, is it? No, you wouldn't. And this isn't something that technology is going to fix. Well, I mean, it could, I guess. But this is the limit of the speed of light. We would have to discover something very brand new about space-time.

33:48Michael Stevens:For example, create wormholes for instantaneous communication across these light-year distances. Otherwise, the separation is essentially total.

33:57Hannah Fry:I'll tell you what, actually talking about wormholes, we had in another question about wormholes, the downsides of wormholes, let's say. This was Anders TX on YouTube. This is one of the comments on YouTube. Great question. If we had wormholes connecting to each other's homes, would there also be a rush of air through the wormhole due to pressure differentials? Like if you connected from somewhere at sea level to another location at high elevation, like Denver or Mexico City? And the answer, absolutely, yes, they would. It would be a complete nightmare. You guys are really good at thinking about the real caveats of instituting this, you know, time travel wormhole, what are the downsides?

34:38Hannah Fry:Okay, so of course, air moves from high pressure to low pressure. At sea level, air pressure is 14.7 psi right in denver which is at 5 000 odd feet um not far from you michael right uh it's 12.1 psi uh mexico city by the way it's about 11.1 psi so if you open a wormhole in london right where i am to to where you are near denver you've got a difference about you know 2.6 psi which doesn't sound that small, but in Blois-Lumming's terms, it's going to be an absolute monster because you've got this Benui principle, you've got this pressure drop of like 17 ,000 pascals. Essentially, the air would rush through the wormhole at roughly 150 metres per second.

35:28Hannah Fry:I mean, you're talking, it's way worse than a Category 5 hurricane, essentially. It's not just like a little rush of air. It would be this absolute deafening structural failure-inducing blast. It would just strip the wallpaper off your walls. It would sort of suck you through the wall before anything. So yeah, I mean, I would say careful, careful with what you wish for. It would rip the snap bracelet right off your arm, put it that way.

35:52Michael Stevens:You know, it's another way to think of it too, is that you're pretty near sea level right now, Hannah, more or less. Yeah, pretty much. I'm in Colorado, high enough up that the air pressure where I am is about the same as the air pressure in a Hoover that you would use today. And by Hoover, I mean vacuum for those of you who are Americans. And that's kind of like blew my mind when I learned that to be like, wow, so this is what it's like to be inside a vacuum cleaner at sea level. That's literally true. And yeah, that pressure difference is what it takes to Hoover up all the debris.

36:34Hannah Fry:See, the other thing is, though, you'd also have this temperature issue, because if you have the air rushing around, right, it will go under this expansion. Because when you get an air that sort of expands rapidly, right, into a much lower pressure environment without losing heat, then its temperature just drops really significantly. So the air, as it blew out into Denver, because it would go from London to Denver, right? That would be the direction of the airflow, or to Colorado more generally. You know, it would probably drop by tens of degrees instantly. So you would have this Category 5, worse than Category 5, blast of freezing air shooting into your room.

37:20Michael Stevens:Yeah. And you would have condensation so clouds could form or disappear. depending on, yeah, the humidity in the areas, they would have their own weather. Yeah, I hadn't thought of that.

37:32Hannah Fry:I mean, you would also have me, Michael. I would be there. I probably wouldn't be in one piece. I would probably be frozen and much mutilated by the journey, but nonetheless, I would be there. So there's upsides and downsides. That's what I'm saying. There's one more question that came in from Jacob Fletcher. And I think this is quite a nice one. This rounds it all off very neatly, actually. Going back to your snap bracelet containing the information. At what point did it become impossible for a single person to learn everything that humans had collectively learned, Michael?

38:02Michael Stevens:I love this question. And of course, it's difficult to actually answer. But the first thing I thought about was a smaller question, which is one that XKCD tackled in What If? And many other people have taken their own approaches to. And it's the question of at what point could a person have actually truthfully said that they had read every single book in English ever written? Because today that's impossible. And that in and of itself is almost one of the saddest facts that you and I will never read every book ever written. Even if we read really quickly and that's all we ever did as a full-time job.

38:45Michael Stevens:If we never slept, we still couldn't catch up. But if you look at the past, there was a time when there were fewer books that had been written. Now, there's a distinction we need to make between written and printed. Printed becomes much easier to answer because we know a lot more about what was printed on a printing press. And the first book in English that was printed on a printing press was printed in 1473. And it was called the Requie of the Histories of Troy. That book, printed in 1473, great. Go ahead and read it. And you've read every book ever printed in English. So yeah, you're right. At that point, you read that, you're done.

39:28Michael Stevens:You read that and you're done. But books get published. And there's this great book content creator named Tom Ayling, who I follow on all the different platforms. And he went through this like year by year. Because we know about how many books were published every year in English. So he's like, you could actually keep up with this process. I'm not going to get into the hairy details of it all. But Tom Ayling actually did something really interesting. He said, don't even start reading with the first English book printed. Just don't even start reading until the year 1500, at which point there were 294 books in English that had ever been printed, different titles.

40:14Michael Stevens:I could do that. I could do that. You could do that. And every year there's like, you know, it looks like maybe 20 new ones printed. And he's like, you could actually catch up and have read every English book that had ever been printed until 1530. In that year, there weren't 15 or 18 books printed, new books. There were 96.

40:39Hannah Fry:Oh, that's going to be tough.

40:41Michael Stevens:That's one every three days. That's tough. You can't catch up. So 1529 was his estimated year at which was the last year a person could have ever claimed that they had read every single book ever printed in English. 1529. So unfortunately, we're not there. But that's an answer to a question that's much more specific. We're talking about reading a book in English that has been printed. Reading in any language or reading anything in English that's been written, that's where it starts to become basically impossible for this to have ever even existed. To have read everything ever written, you would have to talk about some time period just after the invention of writing because once people were writing, they were writing.

41:28Michael Stevens:OK, just the accumulation of tax records alone would have meant that you would have had to have lived in the Stone Age to have actually read everything. You wouldn't have been able to get access to everything because there were people writing in China, in Mesoamerica, in Europe. You'd have to somehow get all this stuff. And it depends on how we define writing. Does this also require that you have read all the notches put on bones to represent numbers of oil jugs shared? But the question that is being asked here by Jacob Fletcher is when did it become impossible for a single person to learn everything that humans had collectively learned?

42:09Michael Stevens:And that I think my answer is never. To have learned everything that humans collectively knew? I mean we don't even know everything we collectively know. And what I mean by that is that we've got knowledge, but then there's also the meta memory of it all. Do we know what we know? And we don't always. We've got to refer back to written records. We've kind of externalized our memories. And so I think to know everything that humanity has known collectively becomes basically how do you define collective knowledge? but I'm going to say it's never been possible because of the definitions of these words, which is an unhappy answer.

42:57Michael Stevens:But that's why I also gave you the like, when could you have read every book kind of an answer.

43:01Hannah Fry:Let me think about this though, because I wonder whether there was a point, I'm just wondering about, I don't know, cats, right? Where cats have different lived experiences. Of course they do. Each one is like their own individual entity. But if you think about the sort of spectrum of what cats know, right? It's a pretty tightly, tightly packed distribution, right? There's not like, if you take an average cat, right? Sort of imagine the full distribution of everything that all cats know, take an average cat, there's pretty much going to be overlapping, isn't it really? There's like, there's maybe a couple of little things that some clever cats have learned here and there, but they're just quite a simple species.

43:47Hannah Fry:So I do wonder whether there was a point where actually the only things that we knew as humans were foraging for food, finding mates, taking care of our young, looking for shelter, you know, where actually there was such simplicity to our knowledge that there just wasn't very much to learn at all.

44:06Michael Stevens:Yeah, you're right. I'm not really happy with the answer that I gave. I think you're right that if we include sort of instinctive knowledge, then it could be possible to know, oh, it gets cold at night or those kind of things. Once you get tool use, I think you're right. As soon as you start getting tool use. Yeah. Once you get into technology, tools, things that we aren't born already knowing, things that we have discovered and invented, then I guess it's tough because you could say, well, yeah. Do you know how to nap a stone to create like a stone blade? Do you know how to make paper? Do you know how to interact with a dog?

44:52Michael Stevens:Like these things that people invented, oh man, I think there really is an answer to his question, at least a hand wavy one where you're like, well, you know, the fermentation of liquids into alcohol happened around this point and that could be a skill that you learned and you could also learn. But it's, hold on, it's gotta be things that we collectively know. And that's what I'm getting stuck on because to know how to use a musical instrument that was invented in China and Egypt and in the Americas, that's not collective knowledge. Only certain groups have that knowledge. So what does it mean, the collective knowledge of humanity?

45:34Michael Stevens:I guess if someone were to write a book of everything that humans like invented and discovered, could you know everything in that book? and and at what point was there just too much in it for someone to even be familiar with everything in it you know i also think that actually human knowledge and technology i mean one of my guilty

45:53Hannah Fry:it's actually not a guilty pleasure at all it's a what's the opposite of guilty proud pleasure yeah is watching videos about primitive technology uh-huh uh do you remember the guy who was in australia who would be there just in his shorts and and like every single tool he would he had a knife and that was it that was all he was allowed to have yeah he would build the most unimaginably sophisticated I mean practically entire villages right pottery um you know roof tiles fires I mean weapons all sorts of stuff um I think that the sort of collective knowledge of things that humans invented and created it's it's very very quick I think that that that it becomes this vast wealth of stuff that you would have to potentially learn.

46:37Michael Stevens:Yeah. Again, I think that you're going to need to look at some like stone age time period to even be able to wrap your head around all of the skills, techniques and observations that humans collected and weren't just simply born with, like knowing to drink when you're thirsty. You know, if that kind of stuff counts, then you can go back pretty far and we all had that knowledge. But, you know, I met the primitive technology guy.

47:05Hannah Fry:Did you?

47:06Michael Stevens:Yeah. When Adam and I were doing Brain Candy Live in Australia, he came to the show and that was awesome.

47:14Hannah Fry:Did he have to announce himself or did you know immediately who he was? Because you don't really see his face that much on camera, do you?

47:19Michael Stevens:No, no, no, no. But he had been in contact with Adam Savage. And so that's how it like happened. And Adam met him and I just kind of tagged along and was like, hello, me too. Hello.

47:31Hannah Fry:Imagine Vsauce tagging along and being like me too Rather than the central character I was like sorry to butt in but I just wanted to shake your hand

47:41Michael Stevens:Yeah that's what it was It was really cool

47:44Hannah Fry:The other thing I've become quite obsessed with is like ancient chemistry Yeah My Saturday mornings that's the treat that I give myself A little bit of a lie in and watching videos about ancient chemistry techniques ancient technology. I'll tell you what, we'll link some of my favorite channels in the description below. Now, could there come a point where the past is so big and new discovery is so

48:10Michael Stevens:slow that our species is actually forgetting things faster than we're learning new things? That'd be a good science fiction future premise for a book.

48:21Hannah Fry:Yeah.

48:22Michael Stevens:Because there's certainly a lot of things people used to know that we literally no longer know.

48:26Hannah Fry:That we've outsourced basically to technology instead, really.

48:30Michael Stevens:Yeah, that we've outsourced or we literally have lost. Like we don't know what they did. We don't know what they put in this concrete to make it so strong.

48:43Hannah Fry:Well, that was an absolutely delightful field notes. We went backwards in time. We went forwards in time. We went through wormholes and around the other side of the moon. I hope you enjoyed it too. Told you it wasn't going to be boring. Told you it was going to be. and this is not going to be the one where we've got zero views on YouTube, Michael. We'll have to save that one for another time. That one is coming. We're going to crack that nut.

49:02Michael Stevens:We're going to figure it out. Everyone's trying to beat the algorithm and we are going to try to be beaten by the algorithm.

49:09Hannah Fry:Do you know that is quite a nice game theory idea, isn't it? Like whether we could actually do it, whether we could get everybody to collectively agree to not watch one video.

49:18Michael Stevens:Yeah, how would you? But see, there's going to be the reverse psychology of it, the psychological reactance of it, where if you tell people not to watch it, it's going to make them want to watch it more. So honestly, it would have to be like an advertisement that we desperately want everyone to watch. Like this is an ad for a really boring product and we were paid to do this and please watch it. And people are like, no, literally no.

49:41Hannah Fry:We'll think on that. We'll ponder on that. If you have any suggestions in the comments of how we can get zero views, then let us know. I would be well up for that. It'd be great. But anyway, anything else that you have, let us know in the comments. or send them to us at therestisscience at goalhanger.com. We love hearing from you.

49:58Michael Stevens:And we'll see you next time.

50:00Hannah Fry:Bye-bye.

50:13Michael Stevens:Two kinds of fishing out here.

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