David Krohn, age 11 of Sioux City, Iowa, for his question:

How much does the world weigh?

Naturally nobody can give the exact weight of the planet earth right down to the last precise ounce. The best we can do is estimate its total weight. The usually accepted estimate is 6.6 sextillion tons  give or take a few thousand tons or so. In round numbers, this stupendous figure is wirtten as 6.6 plus a string of 20 zeros. So far as we know, the earth is not losing any weight. But astronomers report that tons of dust are added as countless falling meteros burn to dusty ashes and sink down to the surface.