Irwin Zucker, age 13, of Compton CA:

What causes atmospheric pressure?

It is hard to believe that gases have weight. The air in a sizable room weighs maybe two pounds. And this is a minute fraction of the weight of the whole atmosphere. It is estimated that the total weight of the atmosphere is around 5,500 million, million tons. This terrific weight is the atmospheric pressure pressing down upon the earth.

The gaseous air, however, is far more fickle than the solid earth and the watery sea. It is a burly burly of dense, heavy patches and thinner, light patches. Dense air weigh3 more than thin air. The air on top of a mountain weighs less than the air above the beaches at sea level. All these variations make differences in the atmospheric pressure. At sea level, the. atmospheric pressure above one square inch is about 14 1/2 pounds. This sea level pressure varies with height, temperature and weather conditions,