Since ancient times, people noticed that the air, as a substance "disembodied", nevertheless affect the status of the various bodies.Flying arrows or darts, soaring birds, movement of objects during strong winds and storms caused unconcealed interest.But also from time immemorial, probably not understanding the nature of the phenomenon, and people have learned to enjoy the benefits that are created atmospheric pressure.
Initially, scientists who were interested in this issue, formulate it in such a way that air has weight, under the influence of which happen all the atmospheric phenomena.
prove the weight of air is quite difficult, it took a long time before scientists were able to establish experimentally the physical fact.And the proof of this case is favored.In the middle of the 17th century in European cities it was distributed fashion on the fountains.It is a symbol of wealth and respectability of a city, castle or manor.Guided by these considerations, the decision to build a fountain in his palace took Duke of Tuscany, in Italy.The design of the fountain called for withdrawal of water from the reservoir, which was not far from the fountain, but water at the start and could not rise above 10 meters.This phenomenon could not immediately explain even the great Galileo.It was only his student - Torricelli - could not only prove the existence of the "weight" in the air, but was able to measure the value of what is normal atmospheric pressure.He invented a special instrument for these measurements - the barometer.And then use this instrument to measure the optimal air pressure - is one in which it can be offset by some volume of water 32 feet high.Then, it was found that 1 square centimeter earth air presses weighing 1.033 kg.
This applies to all objects that are on the earth's surface, including the human body itself.If measure its area, we obtain a value equal to about 15000 cm², which means that the body is subjected to an air pressure of approximately 15500 kg.Since this pressure is distributed evenly over the entire surface, a person does not experience any discomfort from a "burden."
Atmospheric pressure is measured in such quantities as millimeters of mercury.Used and unit millibars (mb), but in recent years the most common is the use of Pascal (or hectopascals, hPa), which is equal to one millibar.If we compare all three units, the ratio between them is as follows: 760 mm Hg= 1013 hPa = 1013.25 mbar.All of these values are accepted as the norm for human atmospheric pressure.The human body is able to re-tune, adapting to changes in atmospheric pressure.In addition, the ability to feel fine at other pressures can shape a person at using training.
However, it should be understood that such a rule atmospheric pressure for a man does not mean that it will be the climate norm, because in different points of the Earth are a variety of factors that significantly affect the rate.For example, in Vladivostok climatic pressures in an average dimension of 761 mm Hg, and it is almost the norm for human atmospheric pressure.At the same time, in some places in Tibet, where the height of the settlements higher than 5,000 meters, the pressure is only 413 mmHgThis value is easy to calculate, 1.8 times less than the rate of atmospheric pressure in humans.
But the fact that the value of the atmospheric pressure is very much dependent on the altitude.That is why harmonization of the readings and statistics received by reflection pressure indicates the value at a certain level - the level of the sea.
