Everyone knows that the Earth’s surface is surrounded by a layer of air. It is located from the surface of the planet tens and hundreds of kilometers up. But the amazing properties of air near the surface of the Earth are extremely interesting. The air surrounding us is so weightless, transparent and invisible that people did not even immediately realize that it has a constant effect on everything living.
This was first noticed in 1640. The reason was an idle fountain on the terrace of the palace of the Duke of Tuscany. Water could not be raised to a considerable height. An explanation for this phenomenon was suggested by Torricelli. He suggested that there is air pressure that affects everything on the surface of the Earth. To confirm his thought, he took a glass tube, one end of which was sealed, and filled it with mercury. Then Torricelli placed the free end of the tube in a flat vessel with mercury.
Mercury in the tank dropped, its height above the surface of the bowl was 760 millimeters. So for the first time it was proved that there is atmospheric pressure, and barometric pressure was measured. It is measured in millimeters of mercury. Because the mercury column was the first device of this type, the pressure measured in this way is called barometric. The result obtained is simply explained - air presses on the surface with a force equal to the weight of a mercury column 760 millimeters high.
These findings were confirmed by the French scientist Pascal. He suggested that air pressure depends on the height above the surface of the earth. The higher the pressure should be less. He took his measurements with tubes filled with water. They were delivered to the mountain, and an experiment was conducted there. The result fully confirmed Pascal's assumption - the level of water rise in the tube on the top of the mountain was less than on the surface.
If one plunges so deeply into the history of the discovery of atmospheric pressure, then it is necessary to recall the experience conducted in 1654 in the city of Magdeburg by the German scientist Otto von Guericke. He took two hemispheres, connected them together and pumped air out of the internal volume. Two teams of horses, each of which pulled in its own direction, could not tear the hemispheres from each other. That's the force with which air pressure squeezed them.
This experience can be considered decisive confirmation of the assumption of atmospheric pressure. Later, scientists were engaged in the study of the atmosphere directly and the influence of barometric pressure on the body of humans and animals. They did not forget about the study of weather and its connection with atmospheric pressure. Pressure measurements were taken at different heights, in different territories, patterns and relationships of air pressure with natural phenomena were revealed
Now, for measuring pressure, they do not use a tube with mercury, but a special aneroid barometer. Its base, the air pressure sensor, is a metal box with a corrugated surface, to which an arrow is attached, indicating the air pressure on the scale of the device. Such a device in itself is much more compact than a mercury barometer and can be used in harsh expeditionary conditions.
It must be said that the discovery and further investigation of atmospheric pressure played a huge role in the study and understanding of many processes taking place on Earth. Weather changes, cyclones and anticyclones, the effect of weather on the human body is largely associated with changes in atmospheric pressure. So our current knowledge about the world and health are based on the discoveries of brilliant medieval scientists.
Here, the history of the emergence and study of such a concept as air pressure was considered. Descriptions of experiments performed to confirm a new theory for that time were given, and how air pressure was measured was described.