Michael Huff, age 10, of Bountiful, Utah, for his question:

Is anything smaller than an atom?

This problem bothers every future scientists. In order to grasp a sensible answer, a young person has to strain the brain somewhat. This is because even an atom is too small for human eyes to see. It takes 100 million average sized ones to measure an inch. The notion that anything is smaller than this is hard to believe. But it is true. So get set to stretch the old imagination to the limit.

One way to tackle this problem is to trace back fn history to learn how people figured out that atoms exist. The story began more than 2,000 years ago in ancient Greece. The thinkers in those days were very bright, even though they had no microscopes and such to test their ideas. They noticed that leaves grow and decay with the seasons, that boiling water becomes steamy gas, that iron rusts to dust. They wondered a lot about why things keep changing into other things.

The thinkers of ancient Greece figured out an answer to this problem. They reasoned that all solids, liquids and gases must be made of tiny, invisible particles of matter. They called them atoms. It seemed logical that atoms were building things, breaking apart and building other things. Modern scientists proved this brilliant idea as correct. However, the Greeks thought that their atom was the smallest possible particle of matter    that it could not be broken into smaller pieces.

Nobody questioned this idea until the age of modern science. Then researchers used new skills and instruments to probe inside the tiny atom. They found that it reminded them of the solar system    and most of it was empty space. Its miniature sun was a tight fisted nucleus, its planets were swarming electron particles. Naturally, the electrons were much smaller than a whole atom    so was the nucleus.

This exciting news sent scientists probing for more details. At  last, they knew that the atom is built from even smaller particles. One by one, they discovered what these different particles of matter are like. For a long time, the smallest of them seemed to be the electron, swarming around with other electrons dust like it. They broke apart the nucleus and found it is a wad of proton and neutron particles. But these are 1836 times more massive than a midget electron.

Radioactivity revealed a lot more, because the nucleus breaks apart with a shower of energy and smaller particles. Several new ones were much smaller than protons and neutrons. One by one the list of smaller than atom particles grew to more than 20. Meantime researchers were finding others that did not belong to atoms.

The search still goes on. Modern scientists reason out their problems, somewhat as the Greek thinkers did. They study what they know about the atom and figure that a certain unknown particle must be there to make things work. Then they use their skills to search for it. Not so long ago, they discovered the neutrino, which weighs less than an electron. In fact, this peppy little particle weighs nothing at all.