It may shock some people, but your feet actually squirt about half a litre of sweat into your socks and shoes every single day. You also shed in the order of about 40 000 skin cells every minute or so from your body. Over a lifetime that adds up to a few stones in weight of dead skin. Now this is perfect bacterial food, so you have a combination of a warm, damp place with lots of food. This makes your feet a thriving emporium of bacteria and fungi. When these eat the skin in your shoes, they produce volatile substances that smell. It's these substances that come whiffing up to your nose. People who wear trainers a lot end up locking their feet in and let them stew. The way around it is either to use odour eaters or wear sandals, as this lets your feet ventilate. Alternatively, you can wear leather shoes, as this helps your feet breathe more naturally.

The reality is that if you take a deep breath, the only things it's going to do is affect the volume of your lungs, and affect your blood pressure and heart rate. When you take a deep breath in, it triggers a reflex that makes your heart rate go up a little bit, but that's about all. It won't affect anything to do with your bones and it certainly won't affect whether you can tolerate being electrocuted. If you put your fingers anywhere near mains electricity, you have a very real chance of being killed. You must tell this person to stop spreading silly rumours, because he's going to get someone killed at some point.

The shape of the plug has something to do with it, because you get a kind of whirlpool effect. The size of the whirlpool is affected by the size of the the plug hole. Some people believe that the direction of the whirlpool is down to the Coriolis Effect, the conservation of angular momentum which applies to moving things - like air and fluids - as the Earth turns in space. But simple calculations show that actually the Coriolis force is too small to account for the direction that water goes down the plughole, so the whirlpool produced when the plug comes out must be a product of the shape of the sink and the drain hole.

We really shouldn't be using the word pandemic. It basically means a global outbreak. Really, flu is the only one that is pandemic. It can start anywhere and can sweep around the world. An epidemic can mean an outbreak in Norfolk and then maybe spreading to London but not going too far into Europe. So an epidemic is usually restricted, but a pandemic sweeps the whole world.

Actually, not a lot of people do. Most of the phlegm that you produce ends up in your stomach. On the way to your lungs, all of your airways are lined with a sticky substance called mucus. It's there to mop up things like bacteria, viruses and particles of dust and dirt from the air. The linings of your lungs have tiny thread-like projections on their that beat. They all beat in the same direction which creates a current which pushes the mucus out of your lungs and up to your throat. Now if you get a lot of mucus, sometimes you cough and it can come flying out of your mouth. But most of it goes down into your stomach. That's very important, because as it has all the nasty things you've breathed in locked up in it. These are carried down into your stomach where stomach acid kills all the bugs. What's left then goes into your intestines. In the walls of your intestines the dead bugs and dirt meet special patches called Peyer's patches, and that's where your immune system learns what's doing the rounds in the air around you, what sorts of things it has to mount an attack against, and what sorts of things it has to ignore. So normally you swallow most of your phlegm, but if you have excess production, coughing it up helps to get rid of it.

It's something like three or four days. In someone your age Lydia, it would probably be four or five days. But we've known people who've had it much longer, maybe even eight, nine or ten days. That's really bad luck though!

It's called the photic sneeze reflex. It's a defined entity and about 20% of the population have this, when you look at a bright light after coming out of a dark room and you have this irresistible urge to start sneezing. This has been investigated by the US military because they were a bit worried about their fighter pilots flying towards the sun and going into a sneezing fit. They don't know exactly what's happening at the nerve level, but what we think is happening is that there's a bit of cross-wiring going on. When you look at the sun, your pupil closes up and it gets much much smaller in order to stop as much light getting into your eye. But sometimes this can get a bit muddled up with the bit of the brain that thinks that your nose must be irritating. This triggers a sneeze instead. In the old days, people used to think that when you look at the sun, it made your eyes water and the tears trickled down your nose, making you sneeze. They did some experiments to test this and found that the tears would trickle too slowly to make you sneeze, so we think at the moment that it must be cross-wiring.

I think that answer is that the fewer virus particles you have in your nose at one time, the longer the incubation period is likely to be. So it will be the same severity, but it will take longer to get to that point.

Standing on Jupiter would be like having a bus standing on your head, as you'd weigh so much. So the bones in your feet which are set up to withstand 50 kg of weight pushing through them, would now have to withstand 13 tonnes. I don't think even the nest hip replacement would be able to withstand that kind of load. So you would be as flat as a pancake.

This is because the flu vaccine is grown in eggs, so there will be a smidgen of contaminating egg in the final vaccine. If she's allergic, she might get a reaction so it's best not to go along.