Weight of air - ???

What is the mass of air? Ancient scientists did not know the answer to this question. At the time of the infancy of science, many believed that air does not have mass. In the ancient world and even in the early Middle Ages , numerous misconceptions were associated with the lack of knowledge and the lack of accurate instruments. Not only such a physical quantity, as the mass of air, fell into the list of amusing errors. Medieval scientists (it would be more correct to call them curious monks), unable to measure non-obvious quantities, quite seriously believed that light propagates in space infinitely fast. However, this is not surprising. Science was then interested in very, very few. Where more people at that time collected theological discussions on the topic "how many angels fit on the tip of a needle."

But time passed, knowledge about the world became more and more extensive. Scientists already knew that everything in the world has weight, but to calculate what the mass of air, until they could. And, finally, in the eighteenth century, it was possible to calculate the density of air, and with it the mass of the entire terrestrial atmosphere. The total mass of air of our planet turned out to be equal to the number with seventeen zeros - 53x10 ¹⁷ kilograms. True, this figure includes the mass of water vapor, also part of the atmosphere.

Today it is considered that the thickness of the Earth's atmosphere is about one hundred and twenty kilometers, and the air is distributed unevenly in it. The lower layers are denser, but gradually the number of molecules of gases that make up the atmosphere per unit volume decreases and vanishes. The specific weight of air (density) at the surface of the Earth under normal conditions is about one thousand three hundred grams per cubic meter. At an altitude of twelve kilometers, the air density decreases more than four times and already has a value of three hundred and nineteen grams per cubic meter.

The atmosphere consists of several gases. Ninety-eight to ninety-nine percent is nitrogen and oxygen. In minor quantities, there are others - carbon dioxide, argon, neon, helium, methane, carbon. The first to determine that the air is not gas, but a mixture, the Scottish scientist Joseph Black in the middle of the eighteenth century.

At altitudes of more than two thousand meters, both atmospheric pressure and the percentage of oxygen in it decrease. This circumstance caused the so-called "altitude sickness". Physicians distinguish several stages of this disease. In the most severe case, it is haemoptysis, pulmonary edema and death. The internal pressure of the human body at a great height becomes much more atmospheric, and the circulatory system begins to fail. The first to break the capillaries.

It is established that the height limit that people can withstand without an oxygen device is eight thousand meters. And up to eight thousand can only reach a well-trained person. Long-term living in high mountains adversely affects health. Physicians observed a group of Peruvians, who lived for generations at an altitude of 3,500-4,000 meters above sea level. They have a decrease in mental and physical performance, there are changes in the central nervous system. That is, the highlands for people's lives are not adapted. And man can not adapt to life there. And is it necessary?