Steve Davison, age 13, of Boise, Ida., for his question:

Why are mountain peaks cooler than valleys?

This old problem has tormented many thoughtful people. The Earth gets its warmth from the sun, and the mountain peaks are sometimes miles closer than the valleys and plains are to the sun. They should, you might think, be warmer. But they are cooler, and peaks at the very Equator are cold enough to wear crowns of snow throughout the year.

Sunlight is part of the sun's radiant energy, and on its way down it must come through our filmy atmosphere. It does not, however, give up much of its warmth to the gaseous air. This happens when it strikes the surface of the globe and some of its wavelengths are converted into heat. The land and sea become warm and in turn they warm the air above them. This heat is transferred only to the lower levels of air and the upper atmosphere remains cool. The valleys may be scorching hot, but little or none of this heat reaches up to warm the lofty peaks.