Dorothy Foote, age 11, of Willowdale, Ontario, Canada, for her question:

Do falling stars ever reach the ground?

Sometimes one of them plonks on the ground or splashes into the sea. But the event is so rare that nobody is likely to be there when it happens. After all, most of the land area still is unpopulated and four fifths of the globe is covered by water. Almost all the so called falling stars swoop down like bright sparks and disappear long before they reach the ground. Or so it seems. Actually they burn to ashes and gradually the dust filters down to the earth.

Most and perhaps all meteor showers are dust trails left when long gone comets crossed the earth's orbit. We pass through them on certain dates as we circle the sun, There the massive earth pulls down swarms of the dusty fragments and they burn up as they dash down through the atmosphere. Most of them catch fire about 100 miles up and die about 30 miles above the ground.

But not all meteors come from comets and not all of them are tiny fragments. Some axe chunks of rock, minerals and even clay that come from who knows where in the Solar System. Most of these space travelers are no bigger than grains of sand. Like the dust from old comets, they, too, burn to dead ashes long before they reach the ground.

However, some of the meteors straying through the solar system are as big as pebbles and a few are mighty big boulders. The smallish pebbles may have time to burn to dead ashes long before they reach the ground.

However, some of the meteors straying through the solar system are as big as pebbles and a few are mighty big boulders. The smallish pebbles may have time to burn to ashes before they reach the ground. But most meteors that weigh ten pounds or more merely scorch their skins. Some crack apart and land in pieces. Once in a while a whopping meteor lands with a walloping thump. All the meteors that land on the earth are called meteorites.

A few giant meteorites weigh many tons, but they are very rare. Every day, hundreds of scorched meteors land somewhere on earth and become pebble sized meteorites. And all the dusty ashes from tiny falling stars eventually filters down through the air. Astronomers tell us that meteorites and meteor dust add tons and tons to the weight of the world every year.