The Infinite Monkey Cage - Fantastic Elastic

Episode Date: December 11, 2024

Brian Cox and Robin Ince expand their knowledge of elasticity with Olympian Bryony Page, comedian Jessica Fostekew & experts Dr Anna Ploszajski and Prof James Busfield. What makes stretchy things stretch? Together our panel journey through different applications of elastic materials and examine, at the molecular level, what happens when we stretch a material and crucially what causes it to return to its original shape. This is especially pertinent to our guest Olympic and British champion trampolinist Bryony Page who has capitalised on elasticity in her 24 year long career. We discover that the bounce of a trampoline mainly comes from the elasticity of steel and how dependent this is on temperature. Cold temperatures are not only treacherous for trampolines; we explore how the cold proved fatal to the elastic components of both the Titanic and the Challenger space shuttle.Plus we hear how scientists sometimes just can’t beat nature; natural rubber and spiders silk are two such cases. Anna Ploszajski takes us through some of the more inventive techniques scientists have engineered to produced more of these natural materials, including genetically engineering goats to be milked for silk.Producer: Melanie Brown Exec Producer: Alexandra Feachem Researcher: Olivia JaniBBC Studios Audio production

This BBC podcast is supported by ads outside the UK. BBC Sounds Music Radio podcasts. Hello, I'm Brian Cox. Hello, and I am Robin Ince. And this is the Infinite Monkey Cage. Now, perhaps the question we're most often asked is, what is the Infinite Monkey Cage made of? Now, because of the scale of the construction project we've only ever made one of course. And it did take ages and if I'm honest we haven't really finished it. Don't tell the BBC because

initially we said it would cost about 50 quid not really in quite how many materials we would need for an infinite monkey cage. It is I don't even really think we've started to be honest. Still though I think we could change builders. It's taken a while. Yeah we're using a company called Hilbert's Builders. One, you can never get hold of them. You're just kept on cool waiting the whole time. And by the way, Brian, I'd just like to say that the one person in the room who suggested that this introduction was two in, I think was correct. Anyway, let's continue reading it anyway.

I want to say it's a number theory joke. How many of those are there? So anyway that is why we're here. We're here for number theory jokes. We're also here to explain why we created an infinite monkey cage or at least started creating an infinite monkey cage out of elastic and rubber bands. And it's a beautiful cage. Not all the monkeys like it. They don't like it if you flick them too much. Some of them like it a lot if you flick them too much. So I don't quite know what's wrong with those monkeys. Have I left the script too far for you now? Have I now?

I've jettisoned too early on. Brian, you just say that the, okay, I'll say it. Anyway, it gets bigger and bigger and bigger forever. And then you say, just say your comedy line. Which was a bit of a stretch there we go so today yes we're allowed to be meta every now and again we get accused of dumbing down here at the BBC there it is that's dumbing up to an extremely high level you've got to know you've got to have a degree in number theory to get

the joke I'll tell you what you were right to drop that joke You were gonna do what was the punchline to that one? Oh About a pole in the complex plane. Yep. Good. Glad we didn't do that one So what are we about contour integration where you get one over one minus X, right? So if X is one so I said yes, which will actually mean stop you've got now You've got to integrate around that because it's undefined. Anyway, so this week, as you can see from that introduction, we're talking about elasticity. What is the stretchiest known material? Why are some things able to stretch and some not? What happens at the molecular level when a material stretches or shrinks?

To help us expand our knowledge of elasticity, we are joined by two material scientists, a comedian and the world's greatest trampolinist. And it seems ridiculous that it's taken us nearly 200 episodes to finally get a gold medal winning trampolinist on. In fact, we probably won't make a show after this. This is the end of it all. And they are... I'm Anna Podjasky.

I'm a material scientist and writer. And my favorite application of elasticity is waistbands. Hi, I'm Briony Page, Olympic champion in trampoline, and my favourite application of elasticity is of course trampolining. Hi, I'm Jess Foster-Kew, I'm a comedian, and I'm a feminist, but my favourite application of elasticity is Spanx.

LAUGHTER Hi, everybody, I'm James Busfield, I'm a professor of materials who specialises in rubber elasticity. And my favourite application is anything that Wiley E. Coyote has tried to do to catch the road runner. LAUGHTER This is our panel. Woo! Woo! Woo!

Woo! Woo! Woo! Woo! Woo! Woo! Woo! Woo!

Woo! Woo! Woo! Woo! Now, we're going to begin with the definition. So James, given that you're a professor of elasticity, essentially, that's not your title, I know. No, it's good enough.

But given that's your specialist area, is there a definition? What does it what does elasticity mean to a scientist? So if you turn the clock back to the time of Robert Hooke who invented the sort of concept of elasticity When you take a solid and you deform it like a spring and it you let go of it It goes back to its original shape That is essentially the concept of elasticity and that's been applied then as a way of That is essentially the concept of elasticity. And that's been applied then as a way of characterizing materials. And if you go on a bit later on in history, you end up with Thomas Young, and he comes up with an idea that he can measure the modulus of a material.

And that modulus of the material is a way of characterizing its essential stiffness of that material. So get back to your earlier question as to how you think about elasticity. Any material that you stretch and then let go and it goes back to its original shape, that's an elastic solid. And we have ways of measuring how different materials compare against each other. So this is when we see a number being put on, so Young's modulus. That everyone who's done science at school will know Young's modulus. Before that, what are we seeing in terms of historically within the world of elasticity? I guess the main thing I think of is the Mesoamericans and their love of natural rubber.

Natural rubber trees, they're from Brazil originally. And the Aztecs and the Mayan people had loads of rubber. They loved this stuff. They would make shoes out of it. They invented games out of it. They made bouncy balls and they created these big Temples in which they would play these yeah these games with rubber balls And what's happening? So if we go down to the molecular level

So so when when something like a rubber band for example, what's happening when you stretch a rubber band? An easier way to describe is actually going back to metals because they're sort of simpler materials So when you when you stretch a rubber band? An easier way to describe it is actually going back to metals, because they're simpler materials. So when you stretch a metal, the atoms are very strongly bonded together and you stretch it a little bit and they move very slightly further apart. But the forces of physics force them to come back together again, and that's elasticity. I just wanted to quickly go back to the Mayan temples with the elastic made out of natural fibre, the balls, is that the origin story of squash?

So, the Mesoamericans, when they played these games, the victor, the person who won the ball game, was often killed in a ceremony to demonstrate his devotion to the sport. Wow. I think there are still some businessmen who play squash like that. But why did anybody ever win? Was it a very low scoring game? It's like 0-0 again. It was an honor to be the victor and therefore sacrifice yourself. Now Bryony, in terms of trampolining,

is there a difference? Because we've all sort of bounced around on a trampoline at some point in our lives. But when you go to an Olympic trampoline, this tremendously sort of presumably elastic thing, are they more or less bouncy than the little ones? Of course, Olympic trampolines are extra bouncy, as you might imagine, but that means it's more force going through the body as well and they're a bit more chaotic so if you aren't holding your body line in the trampoline in your strength you'll just get kind of jumped off the trampoline essentially. So by chaotic what do you mean it can throw you off in any direction?

Well whichever way your body is weak if you lose the power through your knees or your core isn't strong enough and you kind of slip your hips, you'll go to the side and be sprung off the trampoline. So you've got to be really strong. So essentially, if you're going to throw something like a block of wood on the trampoline directly straight, it's going to go straight back up. But if you drop something that's wobbly, like an elastic band, it might just ping off another way because it's not got any force to it. How is it so powerful but also chaotic?

It's interesting that that's a payoff. There is clearly some issues. So Olympic trampolines, they're very elastic so that you get all the energy that you created and make it so you can jump yourself four and a half meters in it. Not creating the energy, I just, it's a physicist. Brian refuses to be a creationist. I would avoid any more biblical illusions at this juncture. As the trampoline pops, and there they travel through the middle. So ultimately, a lot of the elasticity of your trampoline comes from the metal springs all around the edges.

So if you've got a rubber device, you're dissipating energy, So ultimately, a lot of the elasticity of your trampoline comes from the metal springs all around the edges. So if you've got a rubber device, you're dissipating energy. It's a viscoelastic material. If you've got a metal spring, you get the energy release immediately given back to you with very little energy lost. So you're making use of the metal springs

that are around the perimeter. And the mat itself is made out of polypropylene or a nylon material that doesn't stretch a great deal. So actually what you're doing is you're transferring your kinetic energy into stretching the springs and you get all that energy back and then you stretch your legs and you get a little bit higher every time or you do whatever maneuver you're trying to do. So in practice you're exploiting metal elasticity from the springs. And the oldest trampolines they were actually

bungee rigs. So instead of springs around the side, it was rubber bands or thick string rubber bands. And then the different types of trampoline you can get, instead of just webbing, which is elastics, it can be string beds as well. And then you've got supertramps, which aren't a competitive trampoline,

but they can be used as a tool to learn new skills because it's essentially like a bigger trampoline. Did you just call it a super tramp? A super tramp. Isn't that the greatest tribute band where you've basically just got four musicians bouncing up and down singing Breakfast in America. I think that would be beautiful. Jess, I know you spend obviously a lot of time in the gym you did an incredible show called Hench about you know kind of the training that you've done. Do you ever look towards the trampoline end and think, oh, do you know what, I'm sick of lifting things, I'm going to...

Has that ever been part of your...? I... No. LAUGHTER It's the honest answer. But I do trampoline for fun sometimes. I've got an eight-year-old and you know there are places where you can just go for a laugh and every now and again the lights go, the lights go disco and the music will really ramp up but I tell you what the first time I went with him I got cocky

couple of times, first time I'd trampoline since my own childhood and I was all out there were some flips there were some tuck jumps and I don't know I know it's Radio 4 but I'm just gonna be honest I'd overestimated the state of my pelvic floor lesson learned. How high do you get in Olympic competition? So we're like about 8 to 10 meters so if you put trampoline underneath the diving board we'll touch Tom Daly's feet essentially and if you're a man you might go a little bit higher but so 10 meters yeah jumping on top of a double decker bus so it's not without risk if you land wrong and go flying off yeah definitely not and that's

like a huge part of trampolining is that that mental game and just being able to be brave enough to do it but I actually prefer jumping higher than I do if I have to if I'm losing my height in the trampoline and in the routine. That's more scary to me, because I have less time to figure things out and if something goes wrong. So the higher we jump, although if we fall off the trampoline,

it's not gonna be super, super good. I just wondered thinking about, we're at the moment thinking of jumping up and down, but in terms of, I was thinking about bungee ropes. I would never do anything like that because I find life creates enough anxiety without jumping off a cliff. In terms of working out, I mean, there is a very, very kind of high risk checking of elasticity, isn't there?

So how, for instance, is something like that, is the process of checking a bungee rope before you jump? With all materials, you can stretch them to a certain amount and then they break, generally. Very brittle materials don't stretch very much before they break. Very elastic materials stretch a lot. And with a bungee rope, I would imagine there would be an element of stretching it and making sure that it is not getting to its critical limit at which it's going to snap. But also checking the material to see has it degraded over time because elastic materials there can be changes in the atomic structure as you stretch them and then they go back and stretch them and

they go back and over time it can what we call fatigue and eventually that can cause them to break. And James if we go down to the molecular, it's why I'm happy, it's the atomic and molecular level. So we go back to my... So if something breaks, what is the molecular level description of that? Because it seems strange that something would break all at the same time, which is what happens when a material fails. So bungees are unusual because they're made of quartz, so there's lots of individual filaments within a bungee. So if one breaks, the other 900 will support you. So bungees are designed to avoid that problem. But in practice, you're absolutely right. What drives the fracture mechanics of a material when it gets beyond its strength limit,

is you get a new fracture surface created. And for most materials, that relates to something like the surface energy and that's required to create the new material. So you can calculate how much energy is required to break a rubber band, for example. But by fracture surface, so how am I to visualize that? What's happening? So on the atomic scale in a rubber band,

you've got lots of individual long chain molecules. As they get stretched, they all line up. and so those molecules are starting to form a line and when you start to fracture them one will ping and then it puts more stress on its neighbour and then that will ping. It's like a chain reaction. It's a chain reaction, a cascading chain reaction, yes. But if you can dissipate that energy by cleverly spreading it to lots of neighbours when one breaks then you make the material tougher and that's essentially what happens with rubber

bands so Anna's about to break a rubber band it would appear like and she's struggling she's got a cis polyisoprene natural rubber why would she do that? Anna is trying to break a rubber band. It looks like it's going to be horrendously painful. Do you want me to try it? Yes. Right, Brian, cover your eyes. This is. Oh, no. I actually can't do it.

I can't do it. It's really strong. But it's surprisingly tough. I'm trying to break it. I know, but Jess, we've. Oh. Oh. Oh.

Oh. Oh. Oh. Oh. Oh. Oh. Oh. Oh.

Oh. Oh. Oh. Oh. Oh. Oh. Oh. Oh. Oh. Oh. Oh. Oh. Oh. Oh. Oh. It feels like the right time to... we're talking about things that have broken and Jess you recently were broken weren't you? Yes in the mind, no yeah I was.

But you had, what was it your arm or your? I broke my arm and wrist in one injury, yes in gymnastics injury, where my body went one way and my hand stayed in one place as it was stuck there. And so, yeah, my arm bone snapped in half. You now have titanium in there as well? Titanium plate, seven pins, and for a while, for seven weeks, I had a key wire in my wrist as well to make sure that where that was reset that was going to reset in a stable way which it has. But that's I'm just I'm fascinated to think about you know everything as far as I know

in terms of solids it's considered that everything has some sense of elasticity. And natural materials like bone are a really nice example of the materials properties being honed over millennia not through creationism through evolution To do a really really good job most of the time unless we do something that they're not designed to do and so bone we can think of as a composite material sort of two primary elements of it are the mineral side of it and And if it was just minerals, it would be incredibly brittle. It also needs the more fibrous type substance, more polymer like substance and those two things together give it strength and stiffness but also an element of

pliability and energy absorption which means that most of the time if we're throwing ourselves around we don't break our bones. And James, so I was just wondering with Jess now, but now with the titanium, how's that working together with the bones in terms of with exercise and movement? So there's a really good point here that when we're looking to support a body with a prosthetic implant or something like a plate

that you've had implanted, you want to make it appear and behave just like the bone used to behave. And so you've had implanted, you want to make it appear and behave just like the bone used to behave. And so you've got this problem that metals, going back to this thing about the Young's modulus, they've got modulus of 200 plus gigapascals, which is just a random number I'm going to throw out.

But your bone is around 20 gigapascals. So it's an order of magnitude less. So the consequence is, if you put in a piece of metal made out of stainless steel, it's going to be 10 times stiffer than the material that it's replacing. That's why they've put a titanium plate inside you. That's only about 70 gigapascal. It's only about three times stiffer than the bone. What happens if you put something really stiff inside your body,

it takes all the stresses. So it's really important from a biomechanics point of view that we keep loading the bone, the bone around it. So I must keep weightlifting. You've got to keep weightlifting. Yes. And swimming and other less dangerous sports. Yes.

You mentioned steel there. Because steel's sort of a counter-intuitive thing to me. Because you mentioned it's, we think of it as completely undeformable and and that the strongest thing you can imagine But it's also one of the most elastic materials It's different steels behave in different ways So some steels are very ductile which means that low forces they start to plastically deform and that's the sort of steels that you make Your car door panel out of if somebody runs into it

It doesn't suddenly spring back to its original shape a door panel out of if somebody runs into it, it doesn't suddenly spring back to its original shape. Some steels, like the ones inside your watches that you wind up, are made out of spring steel and they have a very high elastic limit which means they're very strong. So you can actually absorb a lot of energy in springs that allow you to sort of store it and reuse it to power your watch or to do whatever. Barney, I just wonder in terms of the risks that you're taking in terms of you know what have you had to learn a lot about you know again the the amount of stress you can place on your bones you that ability when when you're jumping up down a trampoline to go oh hang on a minute I think I need to stop at this point do you get those kind of senses of your own possible fragility at

times? Yeah I wish I'd known this a few years ago. So the loading of the bones, I've actually experienced bony stress, essentially a stress fracture from jumping too much without listening to my body to the point where you're jumping and it feels like you know someone's putting shards of glass into your leg and you're like what's going on. So if I listened to my body earlier to know that I've been overloading it then that would have helped me not get to that point in bony stress and actually just loading it in a better way

to be able to deal with the volume of trampolining and the stress that we put our bodies through. So when you bring it back to that maximum depression of the trampoline when it's fully as close to the floor as you're going to get through the trampoline, that can be more than 15 times our body weight. That is a huge amount of force going through our bodies that we have to be able to withstand. And we're not just doing that once, we're doing that hundreds of times in the training session. James, when we're talking about materials, so you mentioned earlier, you both mentioned

the historic use of materials, rubber and so on, natural materials. But if we come to the present day, your research developing new materials, how do you go about that if you have a specification for something that has a particular elasticity, particular properties, what kind of work are you doing in the lab? So the rubber that's been around for, since the Mesoamericans, that's cis-polyisoprene, the natural rubber material that you find, is still widely used. In fact, it's the most commonly used rubber on the planet. So if you've got a car tire, it contains some element of that. So nature got it right, essentially.

Essentially, yes. And it's quite miraculous in the way it behaves. So it's very tough, as we demonstrated with elastic band earlier and it's it's got fantastic properties One of the strangest things is if you take a rubber band It's amorphous the polymer chains will amorphous you stretch it you line them up You've changed its entropy second or a thermodynamics. I'm sorry. It's a bit geeky for a radio for audience. No, it's brilliant now I understand. And the universe is moving forwards in time, always increasing entropy, so it wants to go back to a chaotic state. So what's driving a rubber is its desire to go back to its completely random conformation.

So that's what we're familiar with. And we have elastic band, we stretch it, second law of thermodynamics, Q equals TDS, and you let go and it goes back to its original shape I thought I'd be like just to say so what you're doing is you're ordering the structure as you stretch the thing exactly So you're decreasing the entropy you are which is not the way we were supposed to work. We want to have an universe It's got ADHD And then so so it's an entropy spring a rubber bands and it be spring looking at what we're trying to do That the future is about trying to make these entry springs do better things. So we take the car tires an example We're all familiar with car tires. We go and buy a new car tire

We've got this label on it from from the EU which we still keep and that EU label Tells us about the rolling resistance of the tire touch how much fuel it's going to consume I suspect most in the audience don't realize this but every time you drive your car about a quarter resistance of the tire. It tells you how much fuel it's going to consume. I suspect most of the audience don't realize this, but every time you drive your car, about a quarter of all the fuel you put in the tank or the juice you put in your battery is consumed on heating up your tires.

It's actually generating that rolling resistance. That, from an environmental point of view, is a disaster. We want to reduce the energy that's dissipated. So I spend a lot of my life trying to think about how to reduce the rolling resistance of car tires. The other thing that's on the label that's sitting there is about how safe is it to grip the tire onto the road. So if you slam on the brakes, a child runs out in front of you, you slam on the brakes, you're going to stop in time. So you've got these two measures that you're using to judge how effective the tire is.

And they are diametrically opposed to each other. You need, for good friction, you need lots of viscoelastic energy dissipation. For low roading resistance, you want no energy dissipation. So you've got this balance. How can a tyre do both things well? So that's what I spend most of my life trying to worry about. How to do two things that are completely different at the same time. It's so interesting. I did a show called World's Most Dangerous Roads, where we had to do some really terrifying off-road driving.

And it was the first time I'd learned anything about this. But why is it World's Most Dangerous Roads? Why did you go off-road? Well, this is it. Because it's, it seems. I wouldn't have done the show if I I did the show thinking how dangerous can a road be they had us driving through a river I had to drive through something called a gulch at one point I drove up a ski

slope it was terrifying it's just misleading then it's not the world's most dangerous road he's not a ski slope is it? I don't know. The first time I'd learned about 4x4 driving and how effectively you know my point is I found it really interesting that and it wasn't shown on camera but our tires were deflated down to about 10% before doing anything really technical so that our grip was exceptional but obviously that was probably horrific environmentally. We were talking about the heat of rubber and the damage in terms of elasticity. And I was thinking, you know, one of the most famous tragic stories of elasticity being lost is probably the Challenger story where you had these, for those who don't know, there were O-rings which basically were meant to,

they would expand and contract when Challenger was leaving the atmosphere. They were the seals in the solid rocket boosters. But they would basically, they would make sure the tiles stayed in place. That actually what happened was on the launch day it was so cold that they lost that ability and that's kind of how it was proved in the committee they did where Richard Feynman popped in an O-ring into a glass of ice water and then pulled it out and went, look, you see it cracks now. So, firstly, I don't know how much you can tell us about what went on there, but also

what happens, again, in these different temperature situations where these risks arrive and the loss of elasticity. Yeah. It's related to the colder it gets, the less energy the molecules have and the less able they are to move basically and there's a lot of materials have a property called the brittle to ductile transition temperature. Why is that funny? It was the way that you... it was so perfect.

So let's just have that one more time so we can all use this at home. The brittle to ductile transition temperature. Deductile. Deductile. Brittle deductile. Brittle to ductile. Brittle to ductile. Brittle... I'll say it a third time. Brittle to ductile.

Brittle to ductile transition temperature. And essentially what it is, is that when you cool the material down, it becomes brittle. It's more likely to break, it's more likely to snap. And again, it's not just rubbers that have this. Metals have a brittle to ductile transition temperature as well. And it's thought that actually for steel, for the sort of steel that the Titanic was made out of, one of the reasons that the Titanic disaster was so bad was that, as we know, they were going through very cold water. So cold, some of it was frozen. And the steel on the hull of the Titanic

was below its brittle deductile transition temperature. And so it was a brittle material It wasn't like a car when you hit it and it forms and instead it just smashed like glass There's one reason why it was so catastrophic is because the steel was so cold and I would think that the Challenger disaster Is a similar kind of mechanism. So on the same sort of level as that. That's a term Titanic And with trampolines the so when it's cold, the springs break a lot more often. So when we're jumping, we'll have a spring or two that,

I've got a whole trophy cabinet full of broken springs throughout my career. But yeah, so that explains why on a cold day, the trampoline one feels harder and the scientific term harder or softer, trampolines. Though if it feels really hard, basically you're not depressing the trampoline very well. It feels really dead and you can't really get any bounce from it, but also the trampoline springs just break. Wow, and is that quite a subtle temperature difference?

Because a cold day can't be that much colder than a warm day. Yeah, I guess it's a subtle temperature difference, but I can feel the difference than most people jump in. But also it's our bodies as well. If we're not as warm as we used to and you're getting cooled down quickly, then that also you're feeling more pain. You don't feel like you're as springy and jumping as high as you would like to, but the trampoline is not giving you anything either. Is that part of this? I think you could put that though in it, because I think in a trampoline movie, like a kind of disaster movie, I would love to have that scene where you go, God damn it, we've got to close down the trampoline. It's brittle to ductile, you know, or something like that.

Is that part of the... because it would seem that you would just say, okay, well, the response to that would be, can't we just use a kind of steel or whatever that make the springs out of something that aren't sensitive in that way around freezing point. But is that part of the compromise or the payoff with the material? Exactly, that's exactly the point. I do a lot of work with motorsports tyres. You want to imagine a Formula One team, they want to make sure they get the quickest lap time. They don't really care about generating abrasion debris and stuff like that. They don't care about the fuel efficiency. They care about grip. So if you're trying to design a Formula One tyre, you make

it so they've got this transition at a very high temperature. So the tyres actually have a glass transition or brittle to ductile transition of around zero degrees. It's kind of a conversation now isn't it? You can say brittle to ductile faster. You can just say B-T-D-T-T. I'm going to call it the glass transition from now on, okay? This is somewhere between My Fair Lady and Sesame Street today now, isn't it? Just as an aside, why is it called a glass transition? So it's called a glassy transition because above TG, if you've got a rubber band, and

I've got one here that you can stretch, it stretches. And TG is the glass transition temperature. Or the brittle to ductile transition. here that you can stretch, it stretches. If you drop the glass transition temperature, or the brittle to ductile transition, yes, it's the same temperature. If you take this rubber band below its glass transition temperature, which for this is minus 70 degrees C, so I'd have to have a bucket of liquid nitrogen

or something like that, and I stretched it, it would break. Similarly, when I'm working with Formula 1 tyres, I had them delivered to me once on a cold morning. And the man who delivered it was the typical delivery man and he says, I've got this delivery of new tyres for you, you're going to do some work on. And he threw them from the top of his, the roof of his truck and it was about minus five outside and they all broke because the TG of Formula One tyres is above the temperature. So they were already brittle. So when you're choosing a particular material, developing a particular material,

you have to consider very carefully the environment in which it's used. Exactly right, so you've got to pick a material that's got a low glass transition temperature, so if you're doing something like the O-ring seals for the Challenger and you know there's a potential for it to come into contact with liquid, oxygen or liquid, the fuel, the rocket propellant or whatever that it came into contact with you need to make sure that that o-ring will be able to survive and still be Elastic at the temperature. It's operating at and in the case of the challenger It wasn't it was very famous wasn't because it was it was a cold day

Day and that also Exacerbated there was a leak as well as a consequence of it being a cold day. I think yeah I've got to ask you James you've got because we're getting near the end of the show, you have a huge rubber band in front of you. I do, but it's a visual gag. That's absolutely fine, our audience have fantastic imaginations. Jess will describe what you're doing. I can do commentary on this.

Last time you had to describe a paper, scissors, stone, didn't you? I wasn't great at that. No, I think you were excellent. We're going to work a commentary on this. Last time you had to describe a paper, scissors, stones, didn't you? Yeah. I wasn't great at that, so. No, I think you were excellent. We're going to work on it for this. It's a big, red rubber band. And don't let go. Am I allowed to walk off? And I'll go off mic.

Yes, OK. So it's the sort of band that I would use to do physio on my arm. It's that kind of. Use your good arm, not the one that's broken already. Mind you, I really need the one that's... Oh my crumb, he's gone so far. I'm going to go into the audience. I'm nervous to let this go into the audience.

Do you want me to hold it? Yeah. Okay, I'm going to let Brian hold it. I don't want to be responsible for twanging it into the audience. Not the face, Brian, not the face! The audience is so big. Okay, it's now as long as the room. So right to the back of the theatre. Oh my crumbs.

James is now right in the back of the theatre. James is at the back of the theatre. On the count of three, two, one. Oh! Ay, ay, ay. James, are you still there? James, are you still there? James, and thatuffield who died.

So that was quite frightening actually. And I think we have a... I'm not sure we did the risk assessment. But so what happened there other than something very frightening that scared half the audience and leaves us open to legal issues? So as has been described, this is a rehabilitation band. You've stretched it. You've stretched it a long way because it's a long band. And you've aligned all the molecules.

And you've got it to a point where it's reaching quite a high stiffness. And as a consequence, when you let go, it goes back at the wave speed. So that's determined by the elasticity of the material. So it goes back really fast and makes that noise. And you were very confident that it would go back in a straight line straight back to you, I think.

Because just as a proper one at home, that went straight down the aisle. Yes. I was too scared to do it. Hell was very close to people's heads. Because it looks like, I'm going to use real scientific language now, it looks like quite a flappy material. That didn't. That looked quite chaotic, and like it could have thwacked an audience.

It didn't though, did it? Not today. No, I've done this experiment before. And what was... Not in the edit anyway. Take two. But what was interesting to me is it was quite slow. It was a lot slower than I imagined, which, as you said,

is the wave speed. It's the retraction wave speed of the material, which is determined by the modus. And because it's soft, the wave speed is relatively slow. So is that the speed of sound? It's the speed of sound of the rubber band, yes. I think probably the reason I and many other people were nervous about it is they go quick.

So not if you stretch them 20 metres. I mean, you're right. If you stretch it far enough, rubber is a mysterious material, cis-polyisobene is a mysterious thing. It's to reinforce trees. That's what it's for. So in the tropical jungle, the tree has got this tree sap in its bark.

And that's what we tap to make natural rubber. It actually, when you stretch it a long way, crystallizes. So the material then becomes tougher. So if it's in a really big storm, the rubber is self-reinforcing and makes itself tougher, which is why evolution has done such a great job at making rubber as tough as it is. In terms of what we do hear about the you know that there ultimately won't be enough rubber for the demands of the world so James...

Where do you hear that? I've never heard that, is that true? So there are a number of risks here first of all natural rubber is indeed a natural resource. And so you could think that's really good, it's sustainable. But of course, it's grown in places like Malaysia or Indonesia or Thailand. And they deforest. Vast ways of tropical rainforest to plant

a monocultured source crop of Heva Brazilianis trees, which are all genetically identical to each other. So from a biodiversity point of view, natural rubber isn't that sustainable. So they're clones. They're all clones, they're all essentially cloned from the same tree which makes them very vulnerable to things like viruses. So if you have a virus that hits it and wipes out the whole of Malaysia or Thailand we have a real problem. So we clearly have a number

of issues there. About 18 million tonnes of natural rubber are harvested every year. If you think about what we do at the end of life with all that natural rubber, things like training shoes that are made out of it, we landfill them or we burn them or we don't recycle them. We don't really properly recycle tires either globally. So the aim here will be to make sure that we can create a renewable use of that material. So recycling of natural rubber is hugely important. There is an awful lot of other rubbers that are synthetically produced. So you've got synthetic cis-polyisoprene that you can have, which is available on the market,

made from gas sources. And actually, your car tires are mostly made out of styrene butadiene rubber. And so that is also a huge amount of material that's been taken out of the earth, converted from oil or gas stream into producing rubber. So yeah, that's not sustainable either. So there's a lot of effort putting in to think of more sustainable sources for these materials and recycling these materials at the end of the life. One of the things that we haven't really talked about is, in terms of elasticity, is why men

wear those really horrible, really, really tight jeans that don't go as far down as the ankle and then no socks and tassely shoes. Is there any way we can get rid of that? Does anyone know? I don't like it at all. It's not, they're not sustainable, are they? No, they're not sustainable. No.

We're almost talking about a world without rubber, but then we're also talking about that which is not rubber. So explain what biomimicry, what we see there. Biomimicry is my favorite concept in materials engineering. And it's basically, as we've already said, there are some amazing natural materials, natural rubber, bone, good ones, that do fantastically for the job that they've been evolved to do and because they're so great things like

underwater glues and spider silk that can stretch super super long and still be strong and flexible we are now looking to nature to see oh okay can we make a synthetic spider silk in the same way that we said, oh, can we make synthetic natural rubber? And this is this concept of biomimicry. And I just think it's genius because why do all the work that evolution has done? And can we just copy these structures ourselves? I was walking down down the street the other day and I saw it almost looked like a spider was flying

because it was just hung, it was so far across the street and trying to work out where is that attached, right? I can see the other side, I can see it's attached to that bush there, but that to me, you know, again as you say, to look at nature and go, well that is more remarkable than the human imagination is capable of at this particular time. Yeah and the depressing thing is that these materials are often so complicated and so well-made that it's actually really, really hard to engineer stuff ourselves that does even half the job of spider silk.

I found some ways that we are trying to make spider silk ourselves. And it's basically to do with just genetically modifying other bits in nature that can do it for us. We can't really do it in a vat in a lab yet. And the things that we've genetically modified are silkworms, okay that's a boring one, E. coli, and goats. Goats? Yeah.

Oh the spider goat thing. Yeah the spider goat thing. So hang on, so we're implanting the genome of spiders into goats. Yep. And I really hope they've called that goat Peter Parker. Yeah. Robin sees one strung up across the road, folks. Goat.

Imagine that. It's like a Ray Harryhausen movie. A goat right in the middle of a web. I just want to bring up, is there anything that you think you've heard today about the science So you last just seems to think that may well lead to a change in technique for the next goal that I'm gonna get I think stuff we've already known about the the temperature of the trampoline And trying to warm up the body in the right way so that we can get the full amount of power

I'm sure I can't get over how is the goat spinning aware? It's in the milk Milk spider silk from a goat and with that, you know, we find When you find a fly in your goats cheese, you know where that goat has been. Jess, do you feel it's helped you in terms of now that you've found out from your own experience the elasticity of your bones? Do you feel that if we'd done this show beforehand, this whole malarkey would never have happened? It would never have happened. And I would have unbreakable bones because I'd have already been drinking goat's milk. Why goats? Why? Why did you say?

Well, we'll be covering that in the next week's episode, which is called, Why goats? So join us for the infinite mind cage, why goats? Why do you say I've got to get this spider gene and put it into something? I'll put it into a goat. Why? Because there's somewhere for the silk to come out, but. I'll tell you what, let's write Charlotte's web too and see where we get to with that. Billy's web.

So thank you very much to our wonderful panel, James Busfield, Anna Posheisky, Brian E. Page, and Jess Foster-Key. Now, that audience you can hear just there, well, we asked them a question and our question is what is the best use of a rubber band? What have you got Brian? DIY dental floss for both the innovative and dangerously optimistic. This one for Katrina, I can think of something at a stretch. What have you got, Jess? To improve your underwear because thongs can only get better.

And with that, what is the best view for a rubber band? Ping it as often as you can because pings can only get better. often as you can because pings can only get better. To upgrade a guitar because strings can only get better. Next week we will be joined by a giant sloth, a dodo, a woolly mammoth, and British Rail. Yeah, that is correct. Because we're going to be discussing bringing the extinct back to life. I used to love it actually, Class 77 on the woodhead line.

Right, now I know that this being Radio 4, some listeners will understand that reference, and so we leave you with this question. What is the link between the Class 77 locomotive and the planet Jupiter? Answers on a postcard, please to Brian Cox multicolored swap shop BBC TV Center London W12 8Qt. Goodbye. Goodbye I'm back with another play Which might just explain why I'm losing my hair In the Infinite Monkey Cage The Naughty Monkey Cage In the Infinite Monkey Cage Without your trousers

In the Infinite Monkey Cage Turned out nice again. Nature. Nature. Bang. Bang. Bang. Hello. Hello. And welcome to Nature Bang. I'm Becky Ripley. I'm Emily Knight. And in this series from BBC Radio 4, we look to the natural world to answer some of life's big questions.

Like how can a brainless slime mould help us solve complex mapping problems? And what can an octopus teach us about the relationship between mind and body? It really stretches your understanding of consciousness. With the help of evolutionary biologists. I'm actually always very comfortable comparing us to other species. Philosophers. You never really know what it could be like to be another creature. And spongologists.

Is that your job title? Are you a spongologist? Well, I am in certain spheres. It's science meets storytelling with a philosophical twist. It really gets at the heart of free will and what it means to be you. So if you want to find out more about yourself via cockatiers that dance, frogs that freeze and single-cell amoebas that design border policies, subscribe to Nature Bang from BBC Radio 4, available on BBC Sounds. Yoga is more than just exercise.

It's the spiritual practice that millions swear by. And in 2017, Miranda, a university tutor from London, joins a yoga school that promises profound transformation. It felt a really safe and welcoming space. After the yoga classes I felt amazing. But soon, that calm, welcoming atmosphere leads to something far darker, a journey that leads to allegations of grooming, trafficking and exploitation across international borders. I don't have my passport, I don't have my phone, I don't have my bank cards, I have nothing.

The passport being taken, the being in a house and not feeling like they can leave. World of Secrets is where untold stories are unveiled and hidden realities are exposed. In this new series, we're confronting the dark side of the wellness industry, where the hope of a spiritual breakthrough gives way to disturbing accusations. You just get sucked in so gradually and it's done so skillfully that you don't realize. And it's like this secret that's there. I wanted to believe that, you know, that whatever they were doing, even if it seemed gross to me,

was for some spiritual reason that I couldn't even understand. Revealing the hidden secrets of a global yoga network. I feel that I have no other choice. The only thing I can do is to speak about this and to put my reputation and everything else on the line. I want truth and justice and for other people to not be hurt, for things to be different in the future. To bring it into the light and almost alchemize some of that evil stuff that went on. And take back the power.

World of Secrets Season 6 The Bad Guru. Listen wherever you get your podcasts.