Susan Meyer, age 11, of St. Louis, Missouri, for her question:

Where does the rain really come from?

It is hard to say where the rain really comes from, because the water it uses circles around and around in a cycle. We can trace the stages of the cycle but nobody can say where it begins and ends. Obviously the rain falls out of the clouds but this is only one stage of the water cycle. How it gets into the clouds is hard to believe because it happens invisibly.

The beaming sun causes water on the earth to evaporate. The liquid molecules change to separate molecules of gaseous vapor and zoom off to mingle with the other gases of the air. This part of the water cycle is invisible. But when the air grows chilly, some of its invisible vapor is changed back into mini droplets of water. This usually happens high above the ground, where the air is always cooler. The misty droplets form puffs of misty clouds which become visible. When conditions up there are just right, the minidroplets team together to form sizeable drops.. When the drops grow too heavy to float aloft, down comes the rain.