Dawn Rudka, age 7, of Utica, New York, for her question:

Where does fog come from?

The story of fog is one about something we can't see that turns into something we can see. The something we can't see is water vapor, which is an invisible gas mixed with the air. It may be hard to believe, but this gaseous vapor is made of the same molecules in wet water and solid ice. All it needs is a drop in the temperature to change into water and another drop to change into ice    both of which we can see.

A fog, believe it or not, is made of miniature droplets of water floating in the air just above the ground. The same sort of misty moisture is used to make the clouds. They forth on high because things up there tend to be cooler. Fogs form when the earth cools the air just above the ground. If the air happens to have a lot of invisible vapor mixed with its gases, some of it changes to misty droplets of liquid moisture. Fogs are formed when moist warmish air turns cooler.