James Martin, age 12, of Utica, New York, for his question:

Does decayed vegetation add to the weight of the earth?

The plant world takes its nourishment from natural substances of the earth. It uses hater and a large assortment of chemicals from the soil. It exchanges gases with the air. it uses the energy of the sunlight that falls upon the earth to manufacture molecules for building solid plant substances. It uses the sunlight energy to create simple sugar from grater and gaseous carbon dioxide and remakes these molecules of basic food into a wide assortment of complex chemicals.

None of the atoms or molecules in these building processes comes from outside the earth. The energy of the sun is used to lock assorted atoms into molecule packages. The cellulose molecules in wood are assorted atoms tied together with the energy of sunlight. When these molecules burn, they break apart and this store of solar energy is released as heat. When plants decay, their molecules are broken up again into simpler chemicals, some of which are reused to feed the next generations of plants. The plant world merely uses and reuses the chemicals that belong to the earth. And the plant world is included in the weight of the world. As it grows, it steals none of the earth's weight. As it decays, it adds no extra weight.