The Rest Is Science - Hacking The Kendama With Physics

Episode Date: September 30, 2026

Michael hands Hannah a kendama, the Japanese cup-and-ball toy, and asks her to land a single catch. Then he brings out one built for him by Adam Savage of MythBusters and explains why a heavier kendama is a completely different physics problem. A kendama looks like a children's toy. It is really a pendulum, a lesson in angular momentum and a catching problem borrowed from spacecraft docking. Michael and Hannah get into why the swing timing barely changes when the ball gets heavier, why the trick is to match the ball's velocity rather than grab at it, why bending your knees on the catch is doing real work, and why the paint finish on a kendama changes how it plays. Then Hannah and Michael take on your questions: what would actually happen if you flew into Jupiter and kept going, whether there is a mathematical way to swim faster, and which books they'd hand an adult who wants to get back into maths after school ruined it. ------------------- 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 Chief Digital Officer: Samuel Oakley Exec Producer: Neil Fearn Learn more about your ad choices. Visit podcastchoices.com/adchoices

Hello and welcome to the rest is science. I'm Michael Stevens. And I'm Hannah Fry. And today on field notes, I have brought you a gift, Hannah. My favorite kind of field notes. There you go. Your very own, Kendama. Okay.

Is it like a cup and ball? It's a cup and ball. It's a style of the cup and ball game. You've basically got this wooden stick with two cups on either side and one on the bottom. And a string attaches. I got scissors for you. You've also got a, a string that attaches a wooden ball to the stick and you just get to swoop the ball up and catch it in the cups on the stick or because there's a hole in the ball, you can catch it on a spike.

Right now in the package, it's sitting on that spike. So hold on a second. This is, it's like a more complicated version of cup and ball. Exactly. Where you have more options. You've got more options. You can do a lot more tricks. And you can also do a lot of physics with it.

Are you really good at this? I don't think so. Okay. Those of you in this room that saw me practicing while Hannah was out of the room, you know how bad I am. I did try to get really good. When I was on tour with Adam Savage, a fan gave me one and I just played with it all day on tour and I got, I thought I got pretty good.

This is saying it's a classic Japanese skill toy. Exactly. And that's why it's called a kin dama. So the kin is what you call the stick, the spike-cuped stick. And the dama is the Japanese word for the ball. Right. So it is a ken dama. Those are its two parts.

I mean, thus far, it's been quite a struggle to even get it out of its packaging. So I'm not sure this is going to go that well. This episode is brought to you by Cancer Research UK. As if they weren't cool enough already, some astronauts have now added cancer scientists to their CV. They are making use of microgravity conditions in space to carry out experiments. That's because the same thing that lets astronauts experience weightlessness also affects how cancer cells grow, behave, and respond to drugs.

And back down on Earth, Cancer Research UK is working with astronomers to explore tumors with technologies that are typically used to map the Milky Way, which I think gives you an idea of just how complex this disease is. That's right. There are over 200 different types of cancer. But by pushing boundaries and embracing the latest technologies, Cancer Research UK has helped double cancer survival in the UK over the past 50 years. years. And today it is continuing to save and improve lives around the world. For more information about Cancer Research UK, their research and breakthroughs, and how you can support them,

visit cancer research, UK.org slash rest of science. Mr. President, my company formed for me of the explosion on our rig on October 2nd. Causing massive water displacement and triggering a tsunami. They all heap the blame on me. Tom Cruise is. Digger got us into this mess. And digger's going to dig us out. From the director of Birdman and the Revenant. What would happen if I stop grilling? You starve, you freeze to death, that's what? With great power, comes great deniability.

I'm not the first, Danny. Digger, see the trailer online. Only in here's October 2nd. From the studio that brought you Wanda Vision. I was an Avenger, but I'm not a hero anymore. On October 14th, the Vision returns for the final chapter of the groundbreaking trilogy. That family wasn't real. You sure about that?

I had a father called. Vision. How is this possible? Don't miss the two-episode premiere of Marvel Television's Vision Quest. Nothing bonds a family together quite like Mortal Jeopardy. Streaming October 14th. Only on Disney Plus. I want you to try to spike the ball.

Okay. Flip it up and I'll give you one tip. It helps to start by just letting the ball hang all the way down to the ground. And then unwrap it a little bit more. There we go. And then pull it straight up because the hole is on the bottom of the ball. So if you pull it straight up and you get it to fall onto the spike, it might. Okay, yeah, so you've got the technique down.

But that hole was not in the right place. I mean, no, definitely not. Imagine if I'm amazing at this. That would ruin the entire episode because of what I'm going to show you next. Every time I try something new There's a little bit of my brain Which is like, this might be This might be what I was born to do

It's never the thing It's never been true But still, every time, every time Okay, actually that's not true Once I went clay pigeon shooting And I really was And you really were a natural Amazing, I don't

And you continued to be amazing as you Oh yeah I mean I've only done it once But I was amazing All right, let's try this one more time At least Okay, so you're hitting the ball With the spike

All right You want to get into the little hole All right, what is this? We're back to... I'm not getting it quite... It's not quite the right angle. Hang on. How many...

Is the entire episode just watching me do this until I... Yeah, we cannot stop recording until you... Okay, let me do. What I want you to do is I'd like to do this as many times as it takes to get it in. And then I want you to cut the episode so that it looks like I got it in first time. Yeah. You're right. It might help if you were standing, to be honest.

Because it's hard to get the angle just right. Oh, that was close. You've made contact every time. This is fun to learn and difficult to master. Yeah. Okay, okay, okay. I'm just going to do three more and then I'm going to give up. Okay.

Damn it. Can you do it? Maybe. Go on, go on, go on, go on, go on. God, you're so close. Oh. Okay. So, was that fun?

to master? I haven't mastered it yet, but I'm having fun trying. It was definitely easy to learn. Yeah. Is that what they call it easy to learn? Fun to master. Fun to master. But let's try to master this faster.

That was the challenge I gave to Adam Savage, one half of the MythBusters. I said, can you make me one that makes it easier? And so he built me this. This is a machined Delron Condon. you'll notice it's a lot heavier. Okay, here's the thing. You just throw that into conversation. Oh, yeah, Adam Savage made me a version.

For people who are watching Slash Nett into this, who haven't come across Adam Savage, he's like a massive, massive hero of mine. Gigantic hero of mine. Okay, let's give it this a go. All right, it's much heavier. The ball is heavier and the handle is heavier. Before you use it, let me tell you what makes it special.

Do you think it's easier with this one? Is it going to be easier? It should be easier for a couple of reasons. Okay. So first of all, it's made of Delrin, which is a plastic that you can machine on a lathe. And we made this to hopefully use physics to make it easier. So for example, the string is attached to the very center of the dama of the ball. So when you lift it, you don't put a torque on the ball.

So it comes straight up with that hole facing the ground and it doesn't get twisted as much. Because in here, it might be at the sort of apex of the ball, but inside it's not sitting in the center. Exactly. It's just like a kind of random knot. Exactly. So you kind of have to like learn the personality of the kandama. Whereas with this one, the physics should help us. Secondly, the dama is really heavy.

And it's built to spin. So you can use gyroscopic stability to keep that whole facing down. let me try this one get it spinning and then we'll lift it would have been really cool let's pretend this is the first time

let's pretend this is the first one beautiful right I'm so jealous it's beautiful okay now you give it a try I'll take out some of the spin on that string okay okay so let me just think about this then

so because you've got the gyroscopic effect of it because it's spinning around it means that the ball is less likely to rotate in any axis other than the one that you can spike. Yeah, you just pull it straight up. Hang on, let me get it spinning. It doesn't need to spin too fast to be more stable. That actually was pretty close. I saw where the hole was.

It's a bit unfair because what you'll notice, if you look at the original dama, it's got this. The hole's gigantic. The hole's gigantic and it's even easier to catch, whereas that hole is, designed just to fit the spike dead on. Oh man. We have to get me doing it because otherwise it doesn't make sense. Yeah, pull it up a little less high.

Okay. It helps also to imagine that you're stabbing the ball. You're not hoping that it lands on the spike. You're hoping to shove the spike into where the hole is. I'm sorry, guys. I've got to do it. No, no, no. This is fun.

If you were standing, I think it would be a lot easier. because the trick is to pull it straight up. That I didn't think that was amazing. That dama went up like so high above the spike and yet it still fell right on the spike. Because again, it's so heavy. And when it's spinning, it's just so much less likely for the hole that you need to go out of the way. It's like here, this is how I was and this is how I still am and it goes right on the spike. So I treasure this for the physics behind it and for the whole the whole journey that we took.

And how Adam Savage made it amazing. That whole thing, exactly. You can watch an entire hour long video on his tested channel where I tell him, I just would really like the DOMA to be heavier. And he's like, okay, I've got a special machine that can build spheres on a lathe, whatever radius you want. And the same tool could be inverted to make the cups. It can do it a reverse sphere as well.

And then the nerling on the handle is actually done with a lathe attachment for making the threads on a screw. So wait, what material is it? It's like a plastic. Yeah, it's a plastic called Delrin. Okay. And it's a dense plastic that you can machine. Like if you put a softer plastic on a lathe, the blade would just grip it and the whole thing would break. It would be very dangerous.

But this you can just put a little blade on it while it spins and you just cut pieces away. You cut strings of it away. It's amazing. But then you end up with something that's more robust than if you 3D printed it, for example. More robust. Yeah, exactly. Exactly. It's very robust.

And it will, it has some give. It won't wear away. It'll even last longer than wood. I mean, no surprise. It's plastic. If I come back in 10,000 years, that'll still be there. It'll still be here. That's right.

Still be relatively dark. There will be, you know, whatever humans evolve into. What, 10,000 years you said? Yeah, and it won't be that different. But they'll still be struggling with it. And I... What about these bits? Can you do, like, cool tricks with this stuff?

Yeah, try to catch the ball in a cup. Okay. Like, trick with the cup is to just put the cup right underneath the ball. Oh, it turned. It turned. There's not enough friction. Do you know what this really reminds me of the cup and ball thing? Hmm. So when it comes to robots, you'll have seen loads of really impressive videos of robots doing like backflips and then running through forests and all of this amazing stuff.

The thing about those robots is that they are, they're pre-programmed. They're sort of, is it like a script that they're following? So they can adjust it slightly for wind and, you know, terrain and things. But they're essentially like someone has sat down and worked out exactly how they should move. if you get a robot to feel its way through a problem instead, they struggle way more. Oh, like a human? Like a human.

And a few years ago, I got to go in, I mean, I've been several times, but in particular, a few years ago, I went to go into the robotic labs at Deep Mind, where they were at the phase where they were teaching robots how to play cup and ball. Oh. That was what they were using as a way for the robot to understand its own limbs, to understand an environment,

understand physics, gravity, and so on, and so on, like the solidity of different things. And so it's sort of in a little, in a way, it was a little bit sad, but this robot was just there. I mean, it was just an arm, not a whole body, but this robot was just there, like over and over again, like this, fail, okay? And then reset, and then over and over again, and then fail, and then reset. And it would be there overnight day after day, after day, after day, after day, after day, after day, just like, and go. You want to help it. And fail. Even though giving people advice on this thing probably just annoys them.

Let's see if I can catch it in the cup below. Oh, so close. So close. I feel like some parts of the savage designed Kandama are harder. For example, we already talked about how the hole is so much more narrow. I think the cups are also less deep. This is great, though. This is, this is, my kids don't need an iPad anymore.

They've got one of these. Yeah, exactly. You know what toy my daughter recently fell in love with? Tell me. Paper yo-yo's. Just the stick that's got a lot of paper, a long ribbon of paper wound up all around it. And so you can throw it like this. Right.

And it shoots out. And she just played with that all day. And then at her birthday, she wanted to give one to every kid that came. And I'm like, I love that this paper on a. stick is still so exciting to kids who have literally the entire world and history of media at their fingertips, they're still like the properties of wrapped paper is so cool. Right, but that's who we are, you know. We love experimenting with our environment and like finding things that surprise and delight us.

Exactly. It's all about, I mean, basically back to the robotics thing, you know, the way that our brains work is that we make predictions about what's going to happen and then are delighted when the world meets our predictions, exactly what the robots are doing. Yeah, and children and robots alike, doing the same thing. And adults. So you can take that home and you can practice. Oh, I'm going to.

I'm going to. And you'll be amazed. We actually made a custom Kandama with Kandama USA for the Curiosity Box years ago. I could not find one in the time that I was packing. But we put holes in all the cups so that you could take these additional spikes and make it a spike everywhere. Also, doubles as a way to beat people off. Exactly. It became a weapon.

They were trying to bully you in the playground. Yeah, it became a weapon. Are they like Kandama world champions? Oh, yeah. You should look up what some of the pros do. They are, you know, spinning the string around their finger, and it's called juggling. I don't have anything else to say about it, except that I really treasure this as a memory of a build with Adam Savage, a deep dive into the physics of how it works. but also the lesson that even when you try to hack the physics and make the easiest condama to catch on a spike,

you're still not that good at it. It still takes that human flesh neural network, a lot of tries to get the knack of it. To get the physical memory of it. Hey, look, my main memory for this is that I managed to do it while standing up with listening. You did. I did manage. On your very first try,

because of the way the editors put the clips together. Thank you guys. Here's a problem. This one, it's changed. I feel like the white plastic has expanded or the black has contracted because, look, if I try to catch it on the cup, it rotates off. Like, it doesn't have enough friction anymore. At the end of the day, things that are spinning are more stable because they accelerate differently in response to forces. imagine you are you're a piece of mass that's going around in a circle that's

parallel to the plane of the floor okay let's say when you come around here to the front I put a force on you right from above like I'm going to push you down to the ground what happens are you going to go like this whoa and just suddenly start spinning now perpendicular to the floor no your velocities combine and now you go you keep going counterclockwise around a little to the floor, but you're also going to be going down a little bit. You're going to go a combination. You're going to go diagonally. But look at this diagonal motion. Now you go down and then you come back up and back down. So if you were, if you imagine that you were an entire disk,

what's happened is someone has put a force in the front and you've moved that way. So the effects of the force are translated 90 degrees ahead in the rotation. So someone pushing right here. So someone pushing right here feels an enormous amount of resistance because normally when we push things, they move in the direction of our force, but not a spinning object. It goes like that. Right. So any little torque, any rotating force applied to a spinning object is going to cause it to behave differently. It's going to cause a lot of resistance. So it stays stable where it is unless you put a lot of force on it. But if it's just, if it's just in a gimbal or something, then as the ship moves, the gyroscope goes, nah, now, move around me. I've got way more inertia or it feels like I have way

more than you do. So that's why they're so stable. Which is why you have them on on ships, on ships to make a little gyro compass. And it just keeps pointing north. Because as the ship moves, the little like axles that hold this gyroscope in place, they're like, come with us. And it's like, you got to try harder than that. And they're like, okay, we'll just go around you. and it just keeps pointing north. Right. But also, I guess on a ship, in particular, you've got these, so it's not just that you've got the one force pushing there at one point

because you're a moment in the future, you'll have another force in that direction. And if you are feeling that force, but averaging it with the existing velocity of it turning round in the circle, then you've just got a little bit more time, I guess, right? Yeah, and you have to make sure that the object is spinning fast enough that it barely gets moved by those forces so that it's spinning so fast and it's so much, or it's so heavy, that a little touch here causes the smallest change 90 degrees ahead.

Gravity tries to make it fall over this way, and it goes like that, and gravity goes, okay, fine, I'll tip you over that way and this way. And then it's processing. And that's why we see gyroscopes process like this, where they point their tops around in a circle until eventually they run out of it. energy. Did you go to a break? Yeah, let's go to a break.

See if you can guess what I'm going to be doing in the break. And we'll answer your questions when we come back. Certainly will. I brought you Wonder Vision. I was an Avenger, but I'm not a hero anymore. On October 14th, the Vision returns for the final chapter of the groundbreaking trilogy. That family wasn't real. You sure about that?

I had a father called Vision. How is this possible? Why am I losing my? Don't miss the Tons. Two-episode premiere of Marvel Television's Vision Quest. Nothing bonds a family together quite like Mortal Jeopardy. Streaming October 14th, only on Disney Plus. Welcome back. It's time for your questions.

Certainly is. Bring them. First one, I got one from Ben from email. Ben asks, are there any mathematical advantages that can be used when swimming? Is it possible to swim faster with the power of? Math. Okay, look, Ben, you're on my own turf here. We're in Fluid Dynamics, right? In math. I'm happy, happy. I'm happy, happy. Okay, here's the thing, right? When you are taught, did you do swimming lessons? Oh, yeah. Oh, yeah. Okay. Show me how you're taught to hold your hand in swimming lessons.

Like a little cup? Math says no. Math says what should I be doing? Okay, so here's the thing, right? If you had like paddles for hands, right? You would, you would, you would do way better at swimming. This is one of the reasons why you look at sort of professional athletes, professional swimmers. And they do this. They should look at these shovels, like giant shovel hands. Oh, right. There's still gaps between the fingers, but they keep them spread?

They keep them spread because you can make it bigger. And the reason why you can make it bigger is because, I mean, if you go too far, then, yeah, the, the wash. It's like a comb. But closer. But closer, you can get little eddies that appear between your fingers, so you can increase the size of your hand. Without more flesh. Without more flesh. Oh, wow.

Right? So what you should do is basically like a natural hand position. Uh-huh. And there are real legitimate scientists that have looked into this, by the way, that have done all of the calculations about what your hand should be. So it's like essentially your natural resting hand position, that is how you should be shoveling water. That, I bet this isn't true, but I've always wondered why our resting hand position is the way it is.

why when I flex no muscles is my hand not like this or like this? Yeah. Why is it kind of this weird intermediate thing? And I haven't heard a definitive answer. There's just a lot of speculation that like, well, that gives you the best leverage on both sides. The muscles only have half as much to do from rest versus like if my hand was always at rest like this, then closing it would require a lot. a really long muscle that had a lot of work to do against the natural phase and vice versa. So it's like you're on your average position, essentially.

But the fact that our resting position is ideal for swimming and pushing fluids makes me revisit the aquatic ape theory, huh? We evolved to be water people. I love the aquatic ape theory. Yeah. It's one of my favorite examples of how you can tie together evidence that basically makes it look like you can prove any argument by induction essentially you could say look we've got blubber like attached to our skin do you know who else has got that whales and dolphins

we breathe there you know who else does that whales and dolphins we don't have any hair on our bodies you know who else doesn't whales and dolphins and so on and so on exactly and then as long as you give it a really clever name aquatic ape stoned ape like people go oh wow now I now it's got like a banner, it's got a team name. I'd get behind that. Yeah, unfortunately, don't get behind it because there's way more evidence that says that we weren't aquatic apes than that we were. Okay, other things you can do with swimming, basically a lot of it is about streamlining your body. So you want to be long and thin.

The more streamlined you can be, the better. So there were swimsuits a few years ago that would compress your body as much as possible. You have to literally squeeze yourself into them because the small surface area, the less drag that you'll be creating. There was also swimsuits where they had, okay, so sort of a flotation effectively in the back that would keep your legs up higher, again, to reduce drag. And that would have certain little inlets on the surface of the costume that would allow the water to slip off it much easier. at that point all of the records for swimming

just went down, down, down, down, down. Yeah. And then I think they banned them. Yep. I think they banned them and now we're sort of back to like, no,

what's your, what's your flabby little flash body going to do with this track? Can it do on its own? Yeah. Yeah. But that's the main one.

The main one is, yeah. The hand position. Swimming a straight line. That's a shortest distance. Mathematically. Yeah. Yep.

Yep. That's a good one. And swim with your hand like an aquatic cape. Okay. Question for you. This is from Neil Fresh. who sent in an email, despite his name sounding very Reddit like, since Jupiter is a gas giant, what would happen if you flew right through the middle of it?

You would not make it through. We've actually learned a lot about the inside of Jupiter recently. Before Juno went around Jupiter, it launched in 2011. I don't know when we got the results back, but before 2011, for sure. People did not know what was in the middle of Jupiter. We still don't really. but there were kind of two competing theories. One was that there's nothing.

It really is a gas giant. It's just gas all the way down. The other theory was that, no, it might have a big, hard, rocky core. Like, if Earth was 20 times more massive, it would have enough gravity to hold on to hydrogen. Maybe that's what Jupiter did. Maybe it has a surface. It's a rocky planet that's surrounded by, you know, hundreds and hundreds of miles of gas. So the Juno satellite orbited around Jupiter measuring its gravitational anomalies across the surface to kind of figure out what's underneath and what its sort of composition is and how symmetric it is.

And as it turns out, it is not only, it's not just gaseous all the way through. It doesn't have a core though either. The answer is somewhere in between. It's got what they call a fuzzy core. And it maybe isn't solid in the middle. but it's incredibly dense. We don't even really know what hydrogen

in this sort of super critical phase is going to behave like. We call it a liquid metal, but it's not like mercury. It's probably not metal colored, but it's very electrically conductive. That's what makes it a metal. And so that might explain

Jupiter's extremely strong magnetic field, that it's this very fast spinning, electrically conductive ball. So if you tried to just fall, into Jupiter and shoot out the other end, you would hit this dense ocean, this slowly more and more dense gradient of hydrogen that became more and more dense. It doesn't have a surface with an atmosphere above it. It just becomes more and more thick and dense as you get to the middle. Hold on there. You said you wouldn't be able to pass through it. So, okay, I accept that it's like

dense and thick, but has it ever become solid or is it still liquidy? It's still liquidy. we're not entirely sure though. There could be the heaviest metals in the middle, but what state they will be in under the kind of pressure they would be in? It's not like, oh, yeah, eventually you drop a coin, whoops, down onto Jupiter, it's going to land on this hard surface in the middle. It's going to get lost in the fuzzy, gurgling mess that is the gradient of its density. So if you tried to go through it, there's no known material that would not get crushed up and phase changed in the middle.

Right. Well, there you go. That's my ambition off the cards. It'd be a way to go. I was about to make a reference about swearing inside it, but that was a different thing. That was a different thing. It was a different thing. The first to say a bad word in Jupiter's gooey middle.

Wait, did you know probe? Where did it actually go? Well, I know Jupiter for sure, but it didn't go to other places. Did it go in? Did it go in any of just? No. It had this big elliptical orbit and it would come really close to Jupiter and then fly way back out. And it did that like scan thing where it scanned like slices over time so that we could learn from how it's speed changed very slightly.

Like even by a tenth of a millimeter per second, we could tell based on the radio waves it sent back, how it was being changed. by what happened to be underneath it on Jupiter. So we could get this really detailed look at what the density of the mass is where. That's amazing. Yeah. And then presumably it flew off into space. It didn't come back. No, it didn't come back.

But I don't know if it, it's not the one that went off to other planets later, was it? It just feels like a bit of a missed opportunity to not nose dive into it at the end. I guess we've crashed them into Saturn. We don't want to bother any potential life forms that might live in places, so I know that we won't crash probes onto the jovial or saturnine moons. Just in case. Just in case. But I don't know, Juno may have crashed into Jupiter.

I don't actually know its final fate. Let me look it up. Did it get slingshot off eventually? Is it still orbiting? Where is it now? It's still alive. It's still orbiting Jupiter. It's still there.

Oh, good for Juno. Good for Juno. So it's approved to continue operating until its hardware finally gives out and contact is lost. Eventually it will go into Jupiter. Okay, all right. But it will be a slow natural death rather than a controlled dive. I wonder how long it could give us reports of what it was detecting as it fell into Jupiter. I'm sure there's not like a big 4K camera on it so we could really see the insides.

I wonder how quickly it gets dark. Inside Jupiter. Inside Jupiter. On the sun facing side as you fall in, when does it become dark as night, but you're still falling. Because the cloud clouds, I mean, it would be discolored pretty quickly, wouldn't it? Yeah, but I mean, how quickly? Because it's, it's like mainly hydrogen gas and other gases, but you could probably fall for 200 miles and still like see out into space.

I'm really scary about that. I'm still not even close to breaking the kind of outside. Amazing. Okay. Last question. This is a question from Matt, who asks this question on Spotify. Matt says, which books would you recommend for an adult interested in getting back into math, stats,

and statistics some years after high school? I would love to hear your answer to this. Okay. Right. Here's the thing. I think textbooks are literally designed for this, you know? That's the whole point, is to start you at the beginning and walk your hand through and pick up incrementally on the ideas one after the other.

There are a few textbooks that I think are terrible. There's quite a lot of them I think are terrible. The famous American one, the calculus one, hang on, the Stuart book for calculus. Right. This literally brings me out in hives. Maybe it's just the way my brain works, but it just, oh God, it's been so long defining limits before you actually get. to any of the juicy, delicious stuff.

Okay. In a really, really laborious way. It's like, you know what? If I learn how to play the piano as an adult, I don't want to spend four years on scales before I get to just try something. Maybe I'm not going to be very good at it. Maybe I'll only be able to do like a little section of it,

but I want to like play with it. I want to like enjoy the process. I don't just want to like hammer myself overhead. So Stuart Calculus, not good. Now, I really like the spivic. Spivik one. Okay. Did you, you mentioned this on here before? I may have mentioned it before. Oh, yes. This one is nice. Yes, because it has lots of examples, right? It's like projectiles. It does a lot of, okay, let's define a limit. And it goes, well, it's obviously just this. Okay, well, if that's what it is, here's a problem. And you keep going, oh my God, it's almost like a drama. You're like, oh, you're right. It can't be that. And eventually it gets down to like, look, like what a function is, it just blew my mind. And it just blew my mind. And, and it's, it just blew my mind. And, and it's, And at the end, it's like, look, all you can say is a function is a bunch of ordered pairs. Specifically where what, like there's the second number only is ever assigned to one first number.

And you're like, that's it. That's a function. That's a function. And I get why. And I get why it can't be anything else. It really was just like a page turner. See, that's it. That's what you want in a really good textbook.

Yeah. You're starting with stuff that feels. That is extremely fundamental, extremely basic in a lot of ways, but it feels really revelatory, you know? I think this is actually, if I'm honest with you, this is what I think you do really well. You take things that feel really obvious on the surface and then make them feel like a great discovery, this giant discovery. I think really good textbooks do that. The other types of textbooks that I really like are the ones where it's really anchored in tangible ideas. So the one for statistics that I really like, and I go back to it all the time, because I just think,

the explanations are so good and it's called beginning statistics and introduction for social scientists. Who's it by? It's by Ian Diamond and Julie Jeffries. It's not big. It's not chunky. It's just really plain language. And because it's for social scientists, all of the examples are anchored in people and what people are doing and how people change, which is how statistics was created in the first place, right? Like statistics was the science of studying individuals and.

how they vary between one and other. Yeah, I find that really helpful with statistics especially. I cannot learn the difference between a geometric and a harmonic mean. If you just show me an equation and then you say, oh, it's this ratio. Like, I need you to say, look, if you're talking about how population grows, geometric mean is better than the arithmetic mean. And here's why. And I go, I get it. Okay. Or if you're like, okay, we've got this exam that's been marked.

marked over here and this exam that's been marked over here. How can we possibly compare the two? What can you possibly do to say this student is better than this student, even though they study different exams? It's like, well, yeah, of course you need a set score. You get it, right? So those are the ones that I really like. The other one that I really like is there's a Stroud textbook,

which is called Engineering Mathematics. And I like that one as well because it's just, it's very practical. It's very sort of like, okay, you want to build a bridge. You know, what the hell do you need to do to build a bridge? So these aren't like pure mathematical ones. You know, if you like the pure stuff, there's other places to go. But these are the ones that I particularly like. Yeah.

But I mean, it's textbooks. That's literally what they're for. That's literally what they're for. Just really miss those days where you would get a massive textbook and your whole job was to go through it. Oh, the luxury. The luxury that somebody else has thought about your path from where you are to where you need to get to. and like incrementally advanced each piece of knowledge for you.

It can feel embarrassing to be like, I'm going to read a textbook, but they actually are, yeah, they are one of the best ways to learn and to, yeah, go on a journey as opposed to just like, oh, here's some kind of cool facts. Right. That the reviewers can write up in their review about like, oh, did you know this about Saturn? Do you know this about the center of Jupiter? What's your favorite book that you've written? My favorite book that I've written. Do you know what? I dislike everything I've ever written.

Okay. I thought you might say that. But if you, if someone was like, where should I start? With stuff that I'm written. I'm going to judge you based on this one book of yours that I read. Which one would you recommend? Then it's Hello World. Hello World.

Okay. Yeah. Which I wrote in 2017, 2018. It's about, it's called How to Be Human in the Age of the Machine. And it's about, um, essentially how how people everywhere are increasingly applying mathematical algorithms to making decisions. I mean, sort of turns out I was right. Whoops. And it's all about the really big problems that can arise unless you think about how to do that

really carefully. And the reason why I'm putting this one forward is that it was written a long time ago, right? This is like 6,000 years ago in the... Yeah. In technological terms, yeah. In technological terms, yeah. Really, really long time ago.

And honestly, every now and then I go back to it, and it's like, yeah, yeah, yeah, still applies. Hello, world. Hello, world. Goodbye viewers. Thanks for watching. Gosh, you're slick. Sit in your questions to The Rest is Science at Gollhanger.com. Or join us on our Reddit, our subreddit, the rest is science, I think.

Or leave comments down below. That gives us engagement, right? In fact, do both. Comment it, but then also email it. And say you commented and liked and subscribed and hit that bell. Yeah. And then we'll be more likely to answer it. No, just kidding.

I would never do that. You're all equal in my eyes. We love you no matter what you do. We'll see you next time. Hi, everybody. It's Dominic Sambrook here from The Rest Is History. And we are here to tell you about a thrilling new series on the blood-soaked climax of the French Revolution. the reign of terror.

So the French Revolution is one of the most significant episodes in the whole of world history. It essentially lays the foundations for contemporary politics as we know it, but it is also unbelievably dramatic. We'll be discussing the murder of the firebrand Jean-Paul Marais in his bathtub. We will be going to the guillotine with Marie Antoinette. And in our final episode, we will be. will be telling the story of the extraordinary and grotesque downfall of one of the chief architects of the terror, one of the most evil men in history, some would say, Maximilin Crobespierre.

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