Leslie McLenon, age 9, of Sarasota, Fla., for her question:

HOW CAN CLOUDS FLOAT IN THE AIR?

The clouds are made of mini minidroplets of moisture. They are so tiny that they mix and mingle with the air—and the air itself helps to hold them up. In fact, the average cloud is a misty mixture of air and moisture. Sometimes a current of warmer air near the ground also helps to hold it aloft. But even the lightest cloud cannot stay up there forever. As it drifts along, it slowly sinks lower and lower.