The density of air is not the same. Where it is smaller, rarefied air. 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. He participates in the process of energy exchange, supporting all the vital functions of organisms. It contributes to the transmission of sounds, prevents the Earth from overcooling and protects it from the excessive influence of 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 falls on oxygen and nitrogen, which make up from 98% to 99% of air.
The ratio of gases and their amount may vary. So, because of car exhausts and plant emissions, urban air is more saturated with carbon dioxide. In forests, in areas where there is no production, 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 shell is influenced by many factors, in different corners of the planet and at different heights it differs. Low density air is rarefied air (from the word "rare"). The less often it is, the farther its molecules are from each other.
Density shows how much air is in one cubic meter of volume. The value of 1.293 kilograms per cubic meter under normal conditions and dry air was chosen as the standard of this value.
In physical science, it is customary to distinguish between specific gravity and mass. Specific determines how much air weighs in one cubic meter. It depends on the latitude and inertia of the rotation of the planet. Mass is determined on the basis of barometric pressure, absolute temperature and specific gas constant.
The main laws of occurrence and the principles of rarefied air are described by the law of Gay-Lussac and Boyle-Marriott. According to them, the higher the temperature and lower the pressure, the rarer the air. Along with this, its humidity is also important: with its increase, the density decreases.
Rarefied air and height
The force of gravity of the Earth, like a magnet, attracts all the bodies accessible to it to itself. Therefore, we walk, and not randomly soar in space. Therefore, the molecules of matter gather more precisely 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.
Have you noticed that with the rise to high altitudes, for example in the mountains, it becomes harder to breathe? All due to the fact that there is rarefied air. With height, the total oxygen content in one liter of air becomes less. It does not saturate the blood properly, and we experience difficulty in breathing.
Heights of Mount Everest - 8488 meters. At its peak, air density is one third of the standard density at sea level. A person can notice changes already at an altitude of 1,500 to 2,500 meters. Further, the change in density and pressure is felt more acutely and already poses a potential health risk.
The most discharged air is characteristic of the exosphere - the outer layer of the atmosphere. It begins with a height of 500-1000 kilometers above the earth's surface. It smoothly passes into outer space, where space is close to a state of vacuum. The pressure and density of gas in space is very low.
Helicopter and rarefied air
A lot depends on the density of air. For example, it defines a "ceiling" for rising above the earth's surface. For a man, it is ten thousand meters. But to rise so high, lengthy preparation is necessary.
Aircraft also have their limits. In helicopters, it is about 6 thousand meters. Much less than aircraft. Everything is explained by the design features and principles of operation of this "bird".
The helicopter gains lift by means of screws. They spin, dividing the air into two streams: above 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 lean on the air beneath it and takes off.
Thin air does not allow to create the desired pressure. Under such conditions, it will be necessary to greatly increase engine power and propeller speed, which the materials themselves will not withstand. As a rule, helicopters fly in denser air at heights of 3-4 thousand meters. Only once did the pilot Jean Boule raise his car by 12.5 thousand meters, although the engine caught fire.