Laucra Tarr, age 10, of Muncie, Indiana, for her question:

How big is an atom?

No atom is big enough for human eyes to see and only a few super microscopes can reveal a dim portriat of its shape. Atoms, of course, come in different sizes. Scientists estimate that a row of 100 million average sized ones measures about one inch. It is possible to form an idea of the average atom's infinitesimal size by using the imagination. This trick is done by comparing it with objects that are large enough to be seen.

You can see the size of a pinprick in a piece of paper and you can picture the distance of a mile. Now let's compare those two thins with a tiny atom. Let's just suppose a tiny atom puffs itself up to the size of a pinprick  and the pinprick does the same amount of puffing. The atom would fill the old pinprick and the old pinprick would be a mile wide. Of course this trick is impossible. But it helps to know that if an atom were the size of a pinprick, then a pinprick would be as big as that huge famous crater in Arizona.