Peggy Sue Honer, Age 11, Of  Bede Vernon, Pa., for her question:

What causes air pressure?

We live on the floor of a vast ocean of air. It fills every empty corner. Pockets of air are trapped in the pores of rocks and down in the crumbly soil. We Cannot see it because it is made of invisible gases, and as a rule we move through The air without noticing it. This filmy sea of gases is the atmosphere which enfolds the entire globe.     Pressure is weight, and it is surprising to learn that the air around us has weight. The air in a room weighs several pounds. The weight of the entire atmosphere is estimated to be about 5.5 quadrillion tons. In round figures., you can write this down as 55 followed by 14 zeros. The total weight of the globe is about a million times greater than the atmosphere above it.     The invisible gases of the atmosphere reach up to about 1000 miles above our heads. When we measure air pressure, we take into account the total depth of the atmosphere from the ground up to about 1000 miles. This is the weight of all the air pressing down upon the surface of the globe. For this reason, air pressure is Properly called atmospheric pressure to measure atmospheric pressure, we need a sample or unit. We take the weight of the tall column of atmosphere pressing down upon one square inch of land. The p1ace for this standard unit of air pressure is at sea level. This is because air pressure varies. The higher we go, the lighter it becomes  the heaviest air is the layer of atmosphere closest to the ground. Near the top of the atmosphere, the weight of the air dwindles to almost nothing.     A corn of air pressing down on one square inch at sea level weighs 14.7 pounds. At the top of a mountain three and a half miles above sea level, air pressure is 7.35 pounds. Seven miles above the earth, the air pressure dwindles to about three and a half pounds. The gases of the air are made of molecules. All atoms and molecules are particles of matter, and matter has weight. 5017.4 iron is heavy because it is dense with crowded atoms. Gases are light because their particles of matter are widely separated by empty spaces. But there are enough gas molecules in a cup to equal the weight of a small feather.

We do not notice the weight of the air, because the pressure 18 exerted on all sides. What's more, our bodies are stuffed with solids and liquids which resist the Pressure of air around us. A column of air reaching to the very top of the Atmosphere presses down on your body day and night. The weight of this air equals about one ton  but you are so used to the load of air pressure that you do not notice it.