Judith Ann Zellers, age 14, of Allentown, Pa., for her question;
Why don't we use up the breatheable air?
The gas we breathe from the air is oxygen and we breathe it day and night. The animals of the world also breathe up oxygen day and night. This includes tho fishes. The countless trees and plants also breathe oxygen day and night. Next we learn that fires use oxygen from the air. Every furnace and campfire is busy taking oxygen out of the air, We begin to worry, Will the breatheable air become all used up with this extravagance?
Andy says there is no need to worry about the supply of breatheable air at all. In fact, the right blend of air has been waiting here for us for half a billion years. In all that time, it has always had the right proportion of oxygen and nitrogen for breathing. The right amount of nitrogen is necessary to slow down the busy oxygen. Most of this long time, the earth has teemed with living things, using up the oxygen, Yet there has always been enough to go around, and there always will be.
For every day, though tons of oxygen are taken from the air, tons of fresh oxygen are returned. Mother Nature is a great one for give and take. She orders her creatures to give and take among themselves. The ever‑new oxygen supply is part of the give‑and‑take between the huge animal kingdom and the huge vegetable kingdom. The plants trade oxygen for carbon dioxide, the waste gas breathed out by ourselves and the animals. The animal kingdom trades its waste carbon dioxide for fresh oxygen. And all this marketing goes on with no trouble to either side.
But, you say, the plants themselves breathe up oxygen. And so they do. And day and night they also return waste carbon dioxide to the air, However, during the daylight, green plants carry on another business. This process needs carbon dioxide ‑ far more carbon dioxide than they give off themselves. They need extra supplies from the carbon dioxide breathed out by the animal kingdom. And they are eager to exchange it for fresh oxygen.
This magic plant process is photosynthesis ‑ the sunlight recipe. It is carried out by the chlorophyll in green stems and leaves. Tiny green bodies use the energy of sunlight to turn gases and water into plant sugar. The carbon from carbon dioxide is used and the oxygen from that gas is returned to the air. A11 during the daylight hours, green plants are busy sifting our waste carbon dioxide from the air and returning oxygen. Some of the oxygen they breathe themselves. But most of it is poured out to replenish the breatheable air. Even a small house plant sends a little oxygen into the room, A vast forest pours out tons and tons of oxygen through every summer’s day, This oxygen blends with the other gases in the air and the winds and breezes waft it around the world.
Meantime we and the animals take it from the air in exchange for more carbon dioxide for the plants to use in their magic recipe. The trading goes back and forth, new air for old. And this wonderful cycle of giveand‑take will go on so long as there are plants and animals in the world. So there is no need to worry lest we run short of breatheable air. New supplies are always on the way,