Sand is tiny fragments of rock. When rock wears down you get smaller bits of rock, or pebbles, and when they wear down you get even smaller bits and eventually you get down to sand, or silica. The reason it ends up washing up on the beach is that the sea or wind can move sand around very easily while rocks are more likely to stay put. This separates things by size, and the sand ends up on the beach and the rocks end up on the seabed. There were lots of sand stones in the Sahara which have weathered and broken down over time from rain, and sun and wind. This has produced accumulations of sand which have built up over time to produce this massive desert. Rocks are made up of lots of different things other than silica, or quartz. But the silica is the toughest material which is why it gets left over after a lots of weathering, when everything else has dissolved or turned to dust.

If you drink milk that isn't skimmed, it's got lots and lots of fat in it. Having lots of fat isn't good for you because of the calories, but also because it furs up your blood vessels. Milk is also very rich in calcium which, in people who are prone to stones, can deposit in the kidney and cause kidney stones. And the other side effect of milk that not many people know, is if you have irritation to the stomach lining and you're at risk of getting stomach ulcers, calcium is used as a co-signal by the wall of the stomach to produce acid. If you have calcium levels in the blood going up, you make more acid. Some people think when they have a dodgy stomach that drinking milk will settle it. When you first do that your stomach feels happier because you've given the acid something to eat other than the wall of your stomach. But then the calcium is absorbed and goes into the blood stream and increases the amount of acid your stomach makes, causing a vicious cycle.

It depends what you make the mirror out of. If you're looking at radio waves then the mirror will have to be made of thicker metal, because as you increase the wavelength you also have to increase the thickness of the metal to get the same reflectivity. That's actually how satellite dishes work. They're basically a big curved mirror that concentrates all of the microwaves coming down from the satellite. They're often full of holes to keep the weight down, and this doesn't matter because the wavelength of the waves is larger than the holes. This is the same principle as seeing a light on in your microwave. You can see the light escaping through the door but the microwaves aren't escaping because they're too long. Once you get beyond visible light into the shorter wavelengths; ultraviolet light is easy to make mirrors for, but x-rays are very difficult. And so making x-ray telescopes is very difficult. Sometimes they do it by using a bag of gas to act like a lens rather than mirrors or by using a metal mirror but at a very grazing angle which makes the mirror very large. Mobile phone waves are at the microwave end of radio waves, and a sheet of aluminium would work nicely as a mirror for those.

Your lungs are not just like balloons. They are filled with millions of tiny balloons called alvioli, which are the air sacs you mentioned. The reason the lungs don't just have one big balloon, but instead have millions of tiny balloons is that each balloon has to have a wall. In the wall of each balloon is tiny capillaries which are very thin walled blood vessels. The blood from your heart gets pumped through your lungs, around the walls of those tiny air sacs first, and then back to the heart before it gets jetted off around the rest of the body. As the blood flows through these tiny blood vessels around the air sacs or alvioli, it exchanges carbon dioxide which is dissolved in the blood, that gets chucked out of the blood because there's more in the blood than there is in the air sac. And oxygen, which there's lots of in the air sac, comes out of the alviolus and into the blood. It forms a compound with the haemoglobin which is the stuff that makes your blood red, and gets carried away. And the average red blood cell takes about 0.3 seconds to pick up all the oxygen it can from the wall of the alviolus but it spends 0.8 seconds actually making that journey. So the red blood cell has nearly three times the time it needs to pick up all the gas it needs. So that's how the gas exchange occurs and why you don't just have one balloon in your chest but millions of tiny balloons. It gives your lungs the surface area of about a tennis court if you were to spread them all out.

Unfortunately it takes the same energy or more to split the water into hydrogen and oxygen than you could possibly get by burning the two back together again. So it will just cost you energy and not get you anywhere. There's no such thing as a free lunch in the world of physics! However, there are some fuel cells that use the energy from light to split the hydrogen and oxygen in water, and you can then use that to get power.

It's far less dangerous than using the phone yourself. No one's actually found a dangerous relationship with using a phone. When you use a phone, that transmitter is a couple of centimetres away from your head, and the strength of the signal goes down with the distance squared. So it's going to be thousands and thousands of times weaker than your mobile phone right next to your head.

To explore the science of this - if you look at the energy of a microwave, and the reason we have these things in our kitchen and cook with them and we are happy to put a microwave source or a mobile phone to the side of our heads, is because the energy in the wave of a microwave is not sufficient to break chemical bonds in the same way that an x-ray or a gamma ray, or more intense forms can. And therefore they're viewed as non-ionising forms of radioation, and are viewed to be safe. That said, there's no evidence that if you do expose your nervous system to these things that they won't have a temperature effect; because we think that they might warm your head up a little bit if you're exposed to a phone. But of course the mast is much further away than a phone is. But also, exposing tissue to microwaves for long periods of time may or may not have some sort of growth related effect.

Certainly in terms of cancer there isn't enough energy in phone radiation to damage DNA which is the ultimate cause of cancer. Virtually all the studies that have been done have not found a significant link between mobile phone use and cancer. The one thing we don't have is really long term data and that's hopefully coming in in the next couple of years. But the studies certainly haven't found an effect in terms of cancer.

The sandstone was probably produced in the permian period when the country was basically a big desert. And then the rocks probably all dropped a few metres and was under water, which is when the chalk was deposited by little things under the sea. And then it's all been lifted up again to make the cliffs you know at the moment.

When people begin to diet and lose weight they lose enormous amounts of weight in the first few weeks, and then their progress slows. The reason for that is that the body initially burns off things called glycogens. That's a polymer of sugar, and it binds enormous amounts of water. Which means that when you burn that off and use it for energy, you lose the water from the body as urine. So you lose double the amount of weight - sugar weight plus water weight. Then you start to burn fat and of course fat doesn't mix with water. So the weight loss slows down. Every so often if you have a bit of a binge, or it's Christmas or whatever, and you pack in some carbohydrates, they tend to turn into a bit of glycogen and your weight creeps up a tiny bit. Then you go back on your severe diet and carry on burning fat and the first thing your body does is to say I'm getting hungry, I'm going to burn that bit of glycogen. So it does that, you lose the water again and you're back to how you were when you were just burning fat.

Morphine gets into the brain and gives pain relief very effectively because it's very very soluble in fat. When you stick one of these patches on the body, the morphine is in a special reservior in the patch and it slowly comes through a membrane, and dissolves in the fat that's in your skin and your body and gets into the blood stream. And that's how you absorb it.