Trudy Kay Hoge, age 8, of Salt Lake City, Utah, for her question:

WHAT MAKES RAIN CLOUDS TURN DARK?

A fluffy white cloud is made of misty moisture, with mini minidroplets of water hanging in the air. Its droplets play tricks with the sunbeams—but they are too tiny to make shadows. As a cloud gets ready to rain, its minidroplets clog together to make sizable raindrops. These raindrops are big enough to cast gloomy shadows. There are so many of them up there that their shadows merge to add a gloomy darkness to the whole cloud.