It depends what colour the flame is. What's happening with a flame is you're reacting something with oxygen. You have a gas coming up which is reacting with oxygen and giving off lots of heat. If that's reacting very cleanly you tend to just get a plain blue flame, or possibly white. If you get little soot particles in there, they glow very brightly yellow. So if you see a very yellow, sooty flame, that is the carbon you're talking about glowing. You can put other things into flames which is how they make colours. So if you have copper salts you get blues and greens, and strontium makes nice red colours.

A flame goes upwards because of convection. The hot gas created by the flame rises. As you say, there's no up or down in space so the gas just forms a sphere around where it's burning and you just get a sort of circular flame. But actually stuff doesn't really burn very well in space. This is because the process of the gas going upwards (as happens on Earth) gets rid of the carbon dioxide formed in the burning process and sucks in more oxygen to keep the flame stoked. This keeps everything burning quickly. As there's no upward movement of gas in space, you don't have much oxygen getting into the flame and it's quite a poor flame that is formed. So essentially it chokes itself in its own waste products and just goes out.

If I'm quite honest no one really knows the answer. However, there are a lot of interesting ways to look at it. My favourite way is to imagine that the world was two dimensional, so you and the Earth are stuck on a flat bit of paper. Now imagine that that piece of paper is part of a giant globe (you can also think of it as a flat spot of ink on a balloon). As the balloon expands, it's expanding in three dimensions, but the surface area you can see as a two dimensional human being will be getting bigger and bigger and bigger. Now if you can imagine that we see the world in 3D, if you can imagine that was maybe just the surface, as it were, of a four dimensional shape, (I really struggle to imagine it) then that would be one way that you could imagine it. There are more dimensions that we can actually see and we are expanding in these other dimensions. A lot of people ask what is it expanding into, because there must be something. But of course if the universe is everything, then as soon as it expands it just makes the thing that exists bigger. There are also ideas that there are millions of different universes all competing for space and going at different speeds. Like little bubbles, all crowding each other out. And actually, maybe the black holes in our universe go through to other universes that are being created. It's really one of those questions that's more philosophy almost, than science. Everyone's really only making guesses. Everyone's trying to get the evidence to prove that it's one way or another and that evidence just isn't here yet.

Spiders are really actually quite clever. Ancestrally they go back a couple of hundred million years, we think. They have glands at the back end of the spider and now it turns out also on their feet that make silk. And what scientists think, is that the glands on the back of their abdomen that make silk are just adapted limbs, where they used to have some legs. Silk is the reaction of proteins. So you have a chemical reaction going on at the back end of the spider that literally spins silk on demand. The spider eats something that has got protein in it. So when it goes and catches something in its web, it injects a venom into that insect that kills it by paralysing it. The insect is paralysed and doesn't die instantly so it remains fresh, the spider injects digestive juices which liquify an insect. And because an insect is like a husk, with a hard skeleton on the outside with the soft bits in the middle, the spider can literally suck the good bits out of the inside leaving behind a dry, wizened up shrivelled skeleton. That's why you see these sort of husks of insects left under spider webs. All the protein and goodness from inside the insect ends up inside the spider, the spider digests that, absorbs it, and then the proteins go to the back end of the spider. And they get turned into new web, amongst other things a spider needs to make. And some spiders have taken this a step further. What they've done is to make the process even more efficient, by eating their own web. This doesn't do them any harm because web is just protein. By eating their own web they're getting the proteins back into their body and they can then reuse them. Spiders' web is incredible stuff and it can absorb immense amounts of energy. It's got the tensile strength of steel. Scientists are now looking at ways of using it for bullet-proof vests, for example. If you can make this artificially in enough quantities you've got something with the tensile strength of a piece of steel, and the ability to stop bullets much better than a bullet-proof vest. Which means rather than police having to go around in these very thick outfits which restrict movement, if you could make it out of spider silk it would be a) lighter, b) a breatheable fabric, so it wouldn't make you so hot and uncomfortable, and c) it wouldn't restrict your movement so much.

The body has an incredibly high metabolic rate, so you're burning off oxygen really, really fast. The brain has the highest metabolic rate and in fact the retina is the part of the brain with the highest metabolic rate. So that's why when you stand up out of a hot bath very quickly you get a very brief dip in blood pressure, because all the blood is in your legs. The result of that is the retina gets slightly less blood for a fraction of a second and that's why you see those funny lights and you feel a bit woozy. But then as your blood pressure comes back up again the brain gets a good supply back. That's evidence of how oxygen dependent your brain is. If you cut off the supply for a fraction of a second, the reduced blood flow just makes you lose consciousness. Tissues like the brain are incredibly sensitive to just a minor interruption in their oxygen supply. And that's why you faint. When I was at medical school we did an interesting experiment where they simulated going to the top of a mountain. So I said "oh I'll be the subject". I was laying on a table and breathing out of a bag which was 10% of oxygen instead of 20% you normally find in a room. They were trying to see if my blood would get slightly less oxygen dissolved in the blood stream. But it didn't actually work very well. I breathed this bag for about 20 minutes and it didn't actually reduce my oxygen capacity terribly much. If you do go mountaineering what you do to compensate is you just breathe more. So you pack more breaths in and your haemoglobin's very good at grabbing oxygen out of the lung and putting it in the blood stream. A red blood cell takes about 0.8 seconds to go through the tiny blood vessel through each of the air sacks in the lungs. But it only takes about 0.3 seconds for the oxygen to get into it. So there's a safety factor of at least threefold. It's got three times longer to pick up oxygen that it needs, so if you breath a bit harder and shove more oxygen into the lung, you can pick it up. This is also why you've got to be careful breathing helium balloons, because there's no oxygen in that helium. I did it a while ago and it made my head go incredibly dizzy.

The way most of these work is by having a tiny little electric circuit in it. They've got an aerial around the outside of that, and when you walk past one of those detectors, that puts radio frequency energy through you. This powers up the circuit. The little circuit sends a code back to the detector and says "Help, help I'm being stolen" and then the alarm goes off. There are also the solid ones you find in clothes, which are attached, and the reason you might think they're magnetic is the way you deactivate them by using a magnet which allows them to detach without spreading dye all over your nice new clothes. However, the tag will still activate the alarm. The ones which are actually stuck to the things you're buying are deactivated in a slightly different way. What they do is they have a little an electronic thing which puts in such a huge amount of power that it basically melts something in the circuit and causes it to break.

That's a really good question that no one quite knows the answer to. You're right in saying that there have been theories that space has got a curvature, but the most recent results show that it hasn't got a curvature at all. It might be completely flat, or it's so close to flat that we can't tell the difference between curved and flat. How do they work this out? It's pretty tough but it's all to do with the speed at which that things are flying away from us. If you can imagine measuring the angles of a triangle on a flat piece of paper, they add up to 180 degrees. On a curved space that's not the case. So we use these geometries to work out what exactly this curvature is. As I said, at the moment it looks like everything's completely flat, or at least very very close to it.

There are a number of things that can determine how long we live. The first thing is the rate of your metabolism. If you compare a mouse with a human, then we're very very genetically similar. But if you look at the heart rate of a mouse it's running along at several hundred beats a minute, whereas our heart's beating at 50 times a minute. So a mouse, in order to survive because it's so small, has to run it's body very very fast. It's almost like you being whipped along by a slave driver. In a mouse, the cells are growing faster, they're dividing more, they're doing everything more quickly, and so the mouse burns itself out more quickly than a bigger animal, like a human. If you compare animals like tortoises, which are cold-blooded, they're big, they're cold blooded, and their metabolism is running much more slowly. Giant tortoises can live for 100, maybe 200 years. So it's down to the speed of your metabolism. Scientists have found whales in the ocean which might even be several hundred years old. There are harpoon tips which have been recovered from the blubber of whales that date back historically to the types of harpoons that haven't been used for several hundred years. Leading scientists to conclude that they really are quite old. The second thing is something called a telomere.These are structures on the ends of each of your chromosomes that are almost like the pieces of cellophane you find around the end of your bootlaces to keep the lace from fraying. Every time a cell divides, it erodes a little piece off of the telomere so it gets shorter and shorter and shorter. If you look at cancer cells that seem to live forever, they have switched on an enzyme that makes telomeres get longer and longer and longer. That seems to be what gives the cells the ability to divide forever. But in a normal cell, the problem is that eventually the telomeres get so short that they run out, and that seems to determine how many times a cell can actually divide. It's called the Hayflick number so there's a limited number of times a cell can divide. But that's not why someone dies. They usually die because something has damaged their DNA and that causes the cells to work less well, and so you get things like cancer.

Flies are quite cunning. They have little grappling hooks on the end of their feet, and when they're going towards a surface, they literally have to throw themselves straight upwards towards the ceiling so their head points towards the thing they want to hit. They reach out with their front legs and they grab hold of something spiky or rough that they can latch these miniature grappling hooks onto. They then switch off and fold their wings away, and swing their body under them in order to lock onto the ceiling. Now they're hanging on upside down. When they want to drop away again, gravity does the work for them. They can just let themselves go, but they hang on with some feet first so that one part of their body drops away and then the rest of their body drops after it so they're in the right position to begin flying again. People know this because they wondered that very question and someone clever invented a camera that could take pictures fast enough, called time lapse photography. You can get pictures now at 4000 times a second so you can see individual wing beats of insects and things. Now they were able to work out exactly how they're doing this.

This is moving relatively slowly so this isn't complicated by the problems of relativity. All you have to do is add up the speeds. The one going forwards will be going at 1000mph plus 1000mph so 2000mph. The one going backwards will be going at 1000 minus 1000, so not at all it will fall straight down.