Barbara Ana Boothroyd, age 8, of Asheville, North Carolina, for her question:

Why does the cold make me shiver?

A snappy cold winter spell brings a person a few problems. It calls for you to decide what to do about it. For example, you may stay indoors. Or you may find those warm mittens, get into those cozy boots, bundle up and go outdoors to master the cold and have some frisky fun. This, naturally, is the best way to cope with a frosty day    especially the part about frisky fun.

Your body does a million clever things that you don't even know about. Not even the cleverest scientists understand all the miraculous things it does to keep going. One of those things is shivering in the cold    and the body does it for a very good reason. Actually, shivering is just one part in a team operation. Several other clever tricks work together to keep the body's temperature comfortable    not too hot or too cold. In hot weather, sweaty moisture pours out and cools off the skin as it dries. In cold weather, the body starts shivering and shaking to make itself warmer.

This secret is easy to understand when you remember what happens when you race and chase around for a while. True, you get out of breath    but you also get warmer. This is because exercise makes the body's muscles create heat. To them, moving around is work. When they work, they burn up secret stores of food to get the energy they need. This special kind of slow slow burning gives off the gentle heat that makes you warm.

In its own mysterious way, the body uses this trick when it feels that things are getting too cold for comfort. Tiny nerves in the skin flash chilly messages to the brain. The brain knows what to do without asking you. It sends a lot of emergency messages all through the body. First, it tries to stop any more inside heat from escaping outside. So the tiny blood vessels in the skin are ordered to shrink. True, this makes a person look pale. But it keeps the circulating blood deeper inside, away from the skin where the cold air waits to steal its warmth.

Next the brain orders the body to stoke up its billions of tiny furnaces to make some more heat. The bast way to do this is to exercise the muscles. But the body cannot run or skip around unless it has your permission. All it can do is make the muscles shiver and shake. This is work, and in working they produce energy. Some of this is heat energy. So when the body feels cold, it starts shivering without your permission. Its shaking muscles are exercising to give you some extra warmth.

But even if you shiver and shake like jelly, it does not make you very much warmer. Naturally this gives you an idea. If exercise helps, why not give your body permission to exercise in a big way. Wrap up well, go outdoors to face the frost and enjoy a lot of frisky fun. That should keep you warm without shivering. It's far better than moping around in the house, griping about the weather outside.