Beth Sotterfield, age 10, of South Boston, Va., for her question:

DOES THE DEW COME FROM THE AIR OR THE GROUND?

Some folks say that the dew rises; others say that it falls. Actually it forms in the air and lands on the ground, the grass and other low lying objects. It forms from invisible molecules of gaseous water vapor that were mixed with the other gasses of the air. It so happens that warm air can hold more vapor than cool air. So when warm air chills, some of its vapor must be changed into droplets of liquid water. This happens when the air cools during the night ¬and its surplus moisture forms those pearly dewdrops on the ground.