What is rarefied air? Its properties and principles

Air density is not the same. Where it is smaller, the air is sparse. Let's find out what the rarefied air means and what features it features.

Earth's gas shell

Air is an intangible, but extremely important part of our planet. He participates in the process of energy exchange, supporting all vital functions of organisms. It facilitates the transmission of sounds, prevents the supercooling of the Earth 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 major part is oxygen and nitrogen, which range from 98% to 99% of air.

The ratio of gases and their quantity can vary. So, because of exhausts of cars and emissions of factories, urban air is more saturated with carbon dioxide. In forests, in a locality where there are no industries, the amount of oxygen increases. But in the area of pastures, the share of methane that cows secrete during digestion grows.

Air density

The density of the gas shell is affected by many factors, it differs in different parts of the planet and at different altitudes. Air with a low density is a rarefied air (from the word "rare"). Than it is rarer, the further its molecules are from each other.

Density shows how much air is in one cubic meter of volume. As a standard of this value, the value of 1.293 kg per cubic meter is chosen under normal conditions and dry air.

In physical science it is customary to distinguish specific and mass densities. Specific determines how much air weighs in one cubic meter. It depends on the geographical latitude and the innervation from the rotation of the planet. Mass is determined based on barometric pressure, absolute temperature and specific gas constant.

The main regularities of origin and the principles of rarefied air are described by the law of Gay-Lussac and Boyle-Mariott. According to them, the higher the temperature and the lower the pressure, the air is rarer. At the same time, its humidity is also important: with its increase, the density decreases.

Dilute 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 do not chaotically wander in space. Therefore, molecules of matter are collected more precisely at the bottom, which means that its density and pressure are also higher near the earth's surface. The farther away from her, the less these indicators are.

Did you notice that it's getting harder to breathe with ascent to higher altitudes, for example in the mountains? All because of the rarefied air. With altitude, the total oxygen content in one liter of air becomes smaller. It does not saturate the blood properly, and we experience difficulty in breathing.

The heights of Mount Everest are 8,488 meters. At its top, the density of air is one third of the standard density at sea level. To notice changes a person can already at an altitude of 1500 to 2500 meters. Further, the change in density and pressure is felt more sharply and already represents a potential health risk.

The most discharged air is typical for the exosphere - the outer layer of the atmosphere. It starts from a height of 500-1000 kilometers above the earth's surface. It smoothly goes into open space, where space is close to the state of vacuum. The pressure and density of gas in space are very low.

Helicopter and rarefied air

A lot depends on the density of air. For example, it defines a "ceiling" for lifting above the earth's surface. For a man, it is ten thousand meters. But in order to rise so high, long preparation is necessary.

The aircraft also have their own limit. At helicopters it is about 6 thousand meters. Much less than aircraft. Everything is explained by the features of the design and the principles of the work of this "bird".

Lifting power helicopter acquires with screws. They spin, dividing the air into two streams: above and below them. At the top, air moves in the direction of the screws, in the lower part - against. Thus, the density under the wing of the apparatus becomes larger than above it. The helicopter seems to lean on the air under it and soars.

Dilute air does not allow you to create the right pressure. In such conditions, it will be necessary to greatly increase the engine power and the speed of the propellers, that the materials themselves can not stand. As a rule, helicopters fly in denser air at altitudes of 3-4 thousand meters. Only once the pilot Jean Bule raised his car to 12.5 thousand meters, however, while the engine caught fire.