Air density varies. Where it is smaller, the air is rarefied. Let's find out what rarefied air means and what features it is characterized by.
Earth's gas shell
Air is an intangible, but extremely important component of our planet. It participates in the process of energy exchange, supporting all the vital functions of organisms. It promotes the transmission of sounds, prevents the Earth from hypothermia and protects it from excessive solar radiation.
Air is the outer shell of the planet, called the atmosphere. It consists of many gases: neon, argon, hydrogen, methane, helium, krypton, etc. The main share is oxygen and nitrogen, which make up from 98% to 99% of air.
The ratio of gases and their quantity may vary. So, because of exhausts of cars and emissions of factories, urban air is more saturated with carbon dioxide. In forests, in areas where there are no industries, the amount of oxygen increases. But in the pasture area, the proportion of methane that cows emit during digestion is growing.
Air density
The density of the gas envelope is influenced by many factors, in different parts of the world and in differentit differs in height. Air with a low density is rarefied air (from the word "rare"). The rarer it is, the farther its molecules are from each other.
Density shows how much air is in one cubic meter of volume. The standard for this value is 1.293 kilograms per cubic meter under normal conditions and dry air.
In physical science, it is customary to distinguish between specific and mass density. Specific determines how much air weighs in one cubic meter. It depends on the geographic latitude and inertia from the rotation of the planet. Mass is determined based on barometric pressure, absolute temperature and specific gas constant.
The main patterns of occurrence and principles of rarefied air are described by the law of Gay-Lussac and Boyle-Mariotte. According to them, the higher the temperature and the lower the pressure, the rarer the air. At the same time, its humidity is also important: with its increase, the density decreases.
Rarified air and altitude
The force of attraction of the Earth, like a magnet, attracts all the bodies available to it to itself. Therefore, we walk, and not chaotically hover in space. Therefore, more molecules of matter are collected at the bottom, which means that its density and pressure are also higher at the earth's surface. The farther from it, the less these indicators are.
Have you noticed that as you climb to great heights, such as in the mountains, it becomes harder to breathe? All because of the rarefied air. With altitude, the total oxygen content in one literthere is less air. It does not saturate the blood properly and we have difficulty breathing.
The height of Mount Everest is 8488 meters. At its summit, the air density is one third of the standard density at sea level. A person can notice changes already at an altitude of 1500 to 2500 meters. Further, the change in density and pressure is felt more acutely and already poses a potential he alth risk.
The most rarefied air is characteristic of the exosphere - the outer layer of the atmosphere. It starts from a height of 500-1000 kilometers above the earth's surface. It smoothly passes into open space, where the space is close to the state of vacuum. The pressure and density of gas in space is very low.
Helicopter and rarefied air
A lot depends on air density. For example, it defines a "ceiling" for lifting above the earth's surface. For a person, it is ten thousand meters. But to climb this high, a long preparation is needed.
Aircraft also have their limits. For helicopters, it is about 6 thousand meters. Much less than airplanes. Everything is explained by the design features and principles of operation of this "bird".
Helicopter gains lift with propellers. They spin, dividing the air into two streams: above them and below them. In the upper part, the air moves in the direction of the screws, in the lower part - against. Thus, the density under the wing of the apparatus becomes greater than above it. The helicopter seems to be leaning on the air underand takes off.
Rarefied air does not allow you to create the desired pressure. Under such conditions, it will be necessary to greatly increase the engine power and the speed of the propellers, which the materials themselves will not withstand. As a rule, helicopters fly in denser air at altitudes of 3-4 thousand meters. Only once did the pilot Jean Boulet raise his car to 12,5 thousand meters, however, the engine caught fire.
