Quiz: eye science & football physics!

It's time for a science quiz - and Chris Smith had a range of head-scratchers for the panel, pairing astrophysicist Katie Mack with microbiome geneticist Rob Finn, and chemist Kate Biberdorf with neuroscientist Giles Yeo...

Chris - The first round is called The Eyes Have It. And Question 1, for Katie and Rob: the cornea is the only part of the body with no blood supply - it gets its oxygen directly from the air. Science fact, or science fiction? What do you think?

Rob - Katie, I think that it doesn't have a blood supply, but I don't think it gets its oxygen entirely from the air, because I believe that you have a very thin membrane over the surface of the eye. I'm not sure you think.

Katie - Yeah, I mean it's not fully exposed to the open air I don't think. Are there not other parts of the body that don't have a blood supply? Do teeth... I guess the outer parts of teeth don't, but the inner parts do, I guess? But I'm surprised if it's really the only piece.

罗伯-所以我猜是:唯一的部分添加is the oxygen coming from if it's not coming directly from the air? And I guess the fluid of the eye would be the obvious place where the diffusion of the oxygen comes. But...

Katie - Yeah, that sounds... I mean, there's that vitreous humour, the stuff inside the eye. Maybe that's oxygen dissolved into it, I don't know.

Chris - You're going to have to reach a consensus now. Science fact or science fiction - the cornea is the only part of the body with no blood supply?

Katie - The blood supply part is not the... there were two parts of this, right? No blood supply, and getting oxygen from the air.

Chris - Yeah, in other words, it gets its oxygen directly from the air. True or false?

Katie - I would go with false here, but I don't know.

Rob - Yeah, I think I would go there. False.

Chris - No, I'm really sorry. This is actually true. The cornea is avascular - it has no blood vessels normally, in health, in humans. Some animals do have vascularised corneas, and in humans who wear contact lenses, especially not very gas-permeable, thick, non rigid contact lenses, you can get a phenomenon called neovascularisation when blood vessels will grow into the cornea to deliver oxygen, because the cornea is dependent on close contact between itself and the air that hits the front of the eye to extract oxygen, to nourish that very thin layer of avascular tissue. Let's try Question 2 for Team 2! Kate and Giles: the fear of eyes - and this is eyes, as in things we've just been talking about, not letter I's as opposed like P's and Q's and so on - this is known as Callum phobia. The fear of eyes is known as kalampokiphobia. Is that true or false?

Kate - I'm going with false, but I'm basing that on nothing. That just sounds like a false word.

贾尔斯- ...and I have nothing intelligent to say about this. Kalam... the only bit of this is the suffix of phobia, which I understand. Kalam... say it again? Kalam-hooby-hooby-whatsit?

Chris - Kalampokiphobia.

贾尔斯- There is nothing to confer. I'll go with Kate's gut feeling.

Kate - They made up a fun word to try to trick us into it. That's what I'm going with.

贾尔斯- Yeah, okay. I'll go with Kate. False.

Chris - It is indeed false. It's actually ommetaphobia which is the fear of eyes. But you pair, who accused us of fabrication - very unfairly - kalampokiphobia is actually fear of corn. Although why you'd be frightened of that I don't know. Perhaps if you have some kind of pathological allergy or something. But one point so far to Team 2. Right, Round 2: Bigger is Better. So Katie and Rob, Team 1. Which is the longest: the Nile - that's the river - the Great Wall of China, or the Andes range of mountains. Which is the longest.

Katie - I have no idea.

Rob - They're all very long. I'll give you that.

Chris - Rob's frantically googling...

Rob - I'll put my hands up...

Chris - I'll just list them again. Nile River, Great Wall of China, or the Andes mountain range. The longest please.

Rob - Great Wall of China because you can see it from space.

Katie - You can see anything from space if you have a good enough telescope! I would flip a three-sided coin and get Andes, I guess, but I don't know.

Rob - Let's go Andes then.

Chris - Going for the Andes, and... hooray! Yes, it is the Andes. The Andes range of mountains, 7,600 kilometres in length; the Nile, a close 6,700; the Great Wall of China, only 3,400 kilometres. So still pretty big all the same. Right, level pegging. Let's see if you can retain your lead, Kate and Giles, with your Question 2 of Round 2. What is bigger: lion, tiger, or jaguar?

贾尔斯- Okay. I'm going to put the jaguar out of this, only because I watch too many David Attenborough films. And I'm going to go with tiger. I know 'the king of the beasts', 'Lion King', yada yada, yada... I just get the feeling it's going to be a Bengal tiger.

Kate - I think so, right? Have you seen the video of the tigers where they run through the field and then jump up over the big trucks? I mean, those tigers are huge. I've never seen a lion do that. I'm going with the tiger.

贾尔斯- Yeah, we're going to go with a tiger.

Chris - So Kate's basing this firmly on Discovery Channel, and Giles is ruling out David Attenborough. So on that basis, you're going with tiger, and you get... yep, you're absolutely right, a point for that one. The tiger is the correct answer - the Siberian and Amur tiger. The males have a total length of 2.7-3.3 metres from nose to tail tip. They also weigh up to 306 kilos, almost a third of a tonne, one single cat. So 2 points to Team 2, 1 point to Team 1, and we're into Round 3. This could be the decider. And it is the football at the moment, so we've got to have a round on the Euros, haven't we? I hope you're all sports fans. No, I'm only kidding - it is a round on the Euros, but we're not going to be basing it just on football. Katie and Rob: the impact force of heading a football - and for you Katie, just to translate, that means soccer - that is enough to break a femur. True or false?

罗伯- mis-headed几个balls in my time, I would say it probably is true, because it doesn't half hurt.

Katie - I mean, it takes a lot to break a femur. But also the forehead part of your skull, if you get the angle right, is quite strong. So I guess the question is: if you headed a femur, which would break first...

Chris - You can tell she's a physicist, can't you! So what do you reckon then? We're going to have to press you for an answer. Heading the football: break a femur or not?

Katie - Rob, I'll go with your instinct here.

Rob - True.

Chris - I'm afraid... this is false. If you consider a professional regulation size 5 soccer ball with an inflation pressure of 16 pounds per square inch...

Rob - Ahh, you didn't give me those details!

Chris - ...this yields an average impact force of 3,606 Newtons, but it takes about 4,000 Newtons to break a human femur. So you probably can head with some impunity, but you might get Alzheimer's disease. Unfortunately, nil points there. Let's see if you can retain your crown, Kate and Giles. A strong enough kick with enough spin on a football could, theoretically, make it complete a full circle and return to you. Science fact, or science fiction?

Kate - Oh yeah. Have a ball flip around and come back to you? I'm going with yeah.

贾尔斯- So this is if you're strong enough - this is the if, right? So if you're Ronaldo or someone, you kick the ball and it curves - whether or not you're strong enough to actually maintain the spin. Or are you assuming 'strong'. Lack of gravity, anything... just on earth?

Chris - What do you think?

贾尔斯- I have no idea. When I kick a ball, I try and will it to bend; it normally heads in the opposite direction I'm trying to hit it. So I'm the wrong person to say anything intelligent about this. I'm going to go with Kate again and say, yes, it is possible. Boomerang balls.

Kate - I think so. I'm convinced.

Chris - No, it's false I'm afraid! As the ball moves through the air, frictional losses, the air rubbing on the outside of the ball, does slow it down. And that means the radius of the turn does become smaller and smaller, because the ball will become susceptible to various other forces once it drops down and becomes slow enough for the air to stick to the surface of the ball. So that means the ball theoretically can go in smaller and smaller circles, but in order to do that, it would have to be spinning incredibly fast. And that in fact is much faster than a human could possibly kick it. So it's a no. Anyway, congratulations Team 2, you are the Naked Scientists Big Brain of the Week award winners. Don't tell all your friends.