Dear Alice

You may know that everything is made up of tiny little things called atoms. Atoms are usually joined together in little clumps called molecules. (You could fit trillions of them in the sharp end of a pin!)

When some atoms and molecules get moved around the little electrons on their outside get rubbed off (or extra get rubbed on). When that happens the molecules have an electrical charge. They go around all charged up, wanting to discharge and get back to normal.

Well, it's a bit like that with clouds--especially big, moist clouds that are moving quickly in the atmosphere. They 'rub' against the air and get a massive electrical charge.

When they get close enough to another cloud with an 'opposite' charge they can share electrons to restore the balance and get back to normal. There's a big flash as the electricity goes from one cloud to another (or from one part of a cloud to another part of a cloud). That's called sheet lightning.

If there isn't another cloud nearby with the right charge then electrons can come up from the ground to give the cloud the right number of electrons again. At first a little trickle of electrons goes from a point on the earth to the cloud. This happens a few times very quickly, in a fraction of a second.

By then a pathway is made that a huge bolt of electricity can run up--from the ground to the cloud. (I know it looks as though the lightning comes down from the cloud, but, no, it's really the other way around.) That's called forked lightning--because often the electrons come along lots of paths from the ground and the paths keep joining together until one mighty bolt makes the final connection with the cloud.

There is enough energy in one lightning flash to power a small city for a day&emdash;as well as make a noise bigger than any rock concert!

There are other kinds of lightning. But I must explain that the electricity doesn't always jump so fast that it causes lightning. Sometimes there is a process of induction where the balancing-out effect happens without lightning. If that happens in power lines then a sudden surge of electricity can run along the lines. This surge of electricity can cause problems for electronic equipment like TVs, hifis, videos and computers. That's why you should turn them off and unplug them if a severe electrical storm is threatening.

Yours sincerely 

Virginia R. Claire


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