There are a couple of reasons but it's unlikely that it's anything to do with the x-ray machine itself, but more to do with the phone being turned off. One explanation might involve it being cold when you went into the airport. Batteries work by a chemical reaction going on inside. When they get cold, the chemical reaction slows down, which means that they can't produce as much current. This makes the battery appear to be a lot emptier than it is. This is why you sometimes get a flat battery on a cold day. If you have a battery and you've been using it a lot, it will drain quickly and the voltage will go down. If you turn it off, that voltage will slowly build up as long as you're not drawing a current. This means that when Adamski turned his mobile phone back on, it was full.

That's a very good question and it's the question that's been frustrating stem cell biologists and people who want to fix the human body. It's for exactly the same reason as when you have a stroke, part of your brain gets damaged forever and doesn't really recover very well. It's also the reason that when you have a heart attack, part of the muscle dies and doesn't recover. When an egg is fertilised it turns from being one cell and divides into many more cells. What these cells do is to specialise. As they divide and turn into tissues, they specialise and sub-specialise for the job that they're going to do. It's a bit like when you go into medical school: at the start you can become any kind of doctor. After you go through lots of training, you might end up as a surgeon but you don't really do much medicine anymore. The next thing you do is become, say, a specialist in vascular surgery and only work on that. Then you become so good that you only do surgery on people's aneurisms. That's the kind of specialisation that happens in our bodies as we develop. This means that the tissues in our bodies are specialised to do one kind of job and that means that they've turned off the genes that make them a general cell and they lock onto being one kind of cell. That's a process called differentiation, and it seems in some tissues to be an irreversible step. But now we're beginning to see that it might be possible to persuade cells to go back the other way with the right environment. The other way is to go back and get a stem cell that can turn into anything.

When you do an emergency stop, the car is accelerating everything in it backwards. This means that everything relative to the car rushes forwards. The balloon is obviously floating in the air. But if it's a helium balloon, the air is heavier than the balloon itself. This means that the air wants to rush forwards more than the helium balloon is going to want to rush forward. The air will then push the helium balloon out of the way, making it move backwards.

This is not exactly a myth but is something that's becoming less of an issue nowadays. The reason that that happens is that there is sulphur in fuel and when sulphur burns in oxygen it forms sulphur dioxide. This only really happens in a petrol engine, which can operate under fuel-rich or fuel-lean conditions. In fuel-lean conditions there's quite a lot of oxygen so the sulphur in the fuel gets oxidised to sulphates. This is a real pain because this clogs up the catalyst and builds up on the surface of the monolith. But when you start a car, this is the point when you have fuel-rich conditions. This is going to convert the sulphate that has built up on the catalyst into H2S, which is hydrogen sulphide. That's the kind of eggy smell that you get out. But this is also why we're getting a lot more low-sulphur fuels nowadays and to be honest it's a lot less of a problem than it used to be.

There are two sides to this and that's the amount of carbon monoxide, which is what we call CO, and also the amount of soot which is much closer to pure carbon. The amount that's formed depends on the carbon to oxygen ratio in the mixture. Coal, for example, and many long-chain hydrocarbons have a much higher carbon content and it's necessary to have a much higher oxygen content in the mixture in order to avoid the formation of what we call lower oxides or soot. So if there's lots of carbon there it's much easier to get something wrong and not have enough oxygen to take it all the way to CO2.

The chemical that you usually dye or bleach your hair with is hydrogen peroxide. Now interestingly, that's a typical reaction that you do in school. Hydrogen peroxide decomposes into oxygen very very slowly, but if you add something like potassium iodide you can make this happen a lot more quickly. There's a fantastic experiment you can do where you put some hydrogen peroxide (also found in contact lens fluid) and add a little bit of potassium iodide and bubbles. The whole thing comes sweeping out of the top in this big fountain of bubbles. As for trying to dye your hair without a catalyst, I'd go for the catalyst way myself!

I understand the point you're making and it's a good one. You're half right and half not right and the reason is as follows: the north pole is ice that's already floating. If that melts, you're quite right, it's never going to overflow because when it melts it will displace an equal volume of water as itself. As it's made of water it will just turn into water and never overflow. But here's the spanner in the works: Greenland for example and Antarctica are continents and there's land under there. The ice is not under water but sitting on land, so if that melts it's going to raise sea levels drastically. In fact there's enough ice locked up in Antarctica and Greenland to give us about 7 - 70 metres of sea level rise. There's a paper that was published in this week's edition of the journal Nature in which scientists have used two satellites in space. It's called GRACE but should be called BRACE because they work in concert with each other, and they work out how much mass there is on Earth underneath them by working out how fast one is accelerating because of gravity compared with the other one. What they've done is to watch Greenland for the last two years and they've found that Greenland has lost 248 cubic kilometres, plus or minus about 60, of water every single year in the past two to four years. It's gone up 250%, so it's a scary amount. That is enough to raise sea levels every single year by about 0.5 millimetres. That's Greenland on its own in one year. So if things really do take off with global warming, we're in trouble.

Water itself cannot be a chemical fuel because it is the end product of a very favourable chemical reaction. However the vast amount of water on this planet, which is of course comprised of hydrogen and oxygen, can be split into hydrogen and oxygen if we apply large amounts of primary energy such as solar energy or even nuclear. From this type of reaction may come our salvation in the future when we no longer have any fossil fuels to use. Hydrogen is not a primary fuel but an energy carrier or storable fuel that can be obtained by energising water with a primary fuel, which causes it to form hydrogen and oxygen.

The calorie content, which is actually kilocalories, is the energy that would be obtained in an experiment were that food to be burned in an excess of oxygen.

That's to do with an enzyme called alcohol dehydrogenase which contains a zinc atom. Different amounts of this enzyme would be expressed in people who have different genetic make up. This is one part of the answer. If you are a regular user you boost the enzymes in the liver to increase the numbers so you break these things down a little bit more.