The severity of the ocean air

Up to the seventeenth century AD, even the scientists did not come up with the idea that air has weight. In 1664, in Italy the Duke Goskonsky decided to build a fountain on the terrace of his palace. To supply water from the lake was built by a large pump. But it turned out that the pump is not working. Water in it 'rose to 10.3 meters above the reservoir. Everyone was puzzled, until a student of Galileo - Torricelli did not express an interesting thought. He suggested that the water pump is experiencing the action of gravity atmosphere. Water column height of 10.3 meters exactly balances the pressure. Torricelli has done such an experience. He took a long, about one meter glass tube, sealed at one end. Then filled the tube with mercury and, turning, down the other end into another container of mercury. Mercury is not poured, but only slightly lowered. Something prevented the mercury leak from the tube into the vessel. Torricelli correctly suggested that the reason is the air pressure at the surface of the mercury poured into the vessel. Now it is calculated that an adult human palm is under pressure of the atmosphere is about 150 pounds. A body of an adult person experiencing weight equal to 12 ... 15 tons. But this person does not feel gravity, because the pressure inside his body is balanced with external pressure. The first device, measuring the air pressure tube was Torricelli. In modern times the atmospheric pressure is measured by a barometer of the device. At the surface of the Earth's highest density of air. The air, too, has weight. We do not see it just for the reason that the air molecules is almost completely transparent. And all that at least some weight of the earth attracts. With a show at the height of the air becomes less likely, its pressure decreases. Gak, for example, at 5.5 kilometers, the air is twice less than the Earth's surface. No oxygen a person can only rise to a height of 5 kilometers. If the rise rapidly, for example on an airplane, above this level, a person can die from that internal pressure of his body burst lungs and damage the blood vessels.