Jimmy Hopinstall age 12 of Albany N. Y.

Does the air weigh anything?

We cannot see the airs feel it or smell it ‑ unless someone happens to be frying onions. We tend to take this invisible air around us for granted.  We breathe in its oxygen and return carbon dioxide without giving it a thought. We see birds beat it into cushions to use as stairways aloft. Even so we forget it has density, substance and weight,

Air is a mixture of gases. And with enough heats anything can be turned into a gaseous state. Fumes from volcanoes add sulphur gases to the air, steel foundries add small amounts of vaporized iron.  As things wear away, they add fine particles of dust to the air. And there is always water vapor floating in the air,

Most of the air, however! is a mixture of nitrogen,  oxygen and a speck of carbon dioxide. Even without the dust vapor and other substances these permanent gases have weight, Imagine a ten‑foot cube box, The air in it weighs 75 pounds, The air in a fair‑sized living room weighs 200 to 300 pounds.

Earth’s blanket of air reaches high above our heads. But the thickest density heaviest layer is near the ground, As we go up the air around us is thinner,  It gets thinner and thinner until it finally peters out.  There are still a few particles of air 600 miles above our heads,

Imagine this great load of air pressing down upon the face of the earth, At sea levels 14,697 pounds of air press down on every square inch. The barometer is an instrument for measuring this air pressure, At sea level, the barometer reads 29.92 inches. It is measuring a column of air over one square inch reaching right up to the top of the atmosphere, The weight is over 142 pounds.

Now let’s take that barometer to the top of Mount Orizaba in the Sierra Madre of Mexico. We chose this mountain because its top is just about three and one half miles above sea level, The barometer there reads 14.96 inches  just half what it did on the beach, The column of air pressing down on each square inch weighs only 7035 pounds,

We cannot find a mountain top seven miles above the ground, So we will take our next hop in a plane, Seven miles above sea level the pressure has dropped in half again, The weight of the air over every square inch is a little over three and one half pounds. It seems that this weight is cut in half every three and one half miles up. Half the weight of the air is in the three and one half mile layer next to the ground,

We don’t notice the weight of the air because we are used to it and our bodies are built to keep it from crushing us. It presses in on us from all directions. In square inches this tots up to a lot of weight.  A man on a beach is under air pressure of 14 tons