Atmospheric pressure — the pressure of the atmosphere on all objects and the Earth's surface. Atmospheric pressure is created by the gravitational attraction of the air to the Ground.
The presence of atmospheric pressure led people to confusion in 1638, when the failed idea of the Duke of Tuscany to decorate the gardens of Florence fountains — the water did not rise above of 10.3 meters. The search for the causes of this and experiences with more severe substance — mercury, taken by Evangelista Torricelli led to the fact that in 1643 he proved that air has weight. Together with V. Viviani, Torricelli held the first experience in pressure measurement, invented the Torricelli tube (the first mercury barometer) — the glass tube in which there is no air. In such a tube the mercury rises to a height of about 760 mm