Roseanne Lisuzzo, age 11, of Rochester, New York, for her question:

What are dust particles made of?

Everything in the world is wearing out    and the dust drifts around to prove it. Solid substances are made from tiny particles. The surfaces are exposed to wear and tear and small fragments of matter break away. Many of these fragments are small and light enough to float in the air, at least for a while. They form the drifting dust that sooner or later comes down and settles on such things as the furniture.

The wind and rain brush particles of dust from all the earth's rocks, from deserts and prairies, from dry meadows and fields. A large percentage of dust is mineral particles of this sort. Other particles come from industrial furnaces and smokey fires. Some of the household dust blows in from outdoors. But a lot of it is the particles that rub off when chairs brush the rug, when forks touch the table, when anything hard rubs against something softer. Everything, everything is wearing away, though most of the dusty debris is too fine to be seen.