Francine Blanchard, age 12, of Newport News, Va., for her question:

WHY DOES THE TEMPERATURE DROP WITH ALTITUDE?

It seems strange that mountaintops are cooler than the valleys because they are somewhat closer to the sun. However, the beaming sun saves its warmth to shed on the seas and the surface of the land. The air takes very little warmth from the sunbeams on the way down. It is warmed by the warm surface of the land and sea below. This means that the lower levels of the atmosphere that touch the earth get the warmth and the upper levels often are left out in the cold.

Usually the warmest air is at ground level and often the air upstairs is freezing cold. On the average, the temperature drops two or three degrees Fahrenheit with each 1,000 feet of altitude above the surface. Hence we have snowcapped peaks in the torrid tropics  even right on the equator.