What is a vacuum?

In fact, vacuum is not really empty, refers to the gas state below an atmospheric pressure in a given space, is a physical phenomenon. The interaction between the vacuum environment and various substances will produce different effects, such as vacuum suction, vacuum heat insulation and heat dissipation, vacuum distillation, true air oxidation prevention, vacuum drying, vacuum insulation, vacuum degassing, preservation, cleaning, sterilization, leak detection, rarefied gas discharge, cosmic vacuum effect, etc. The vacuum science and technology formed accordingly is now widely used in semiconductor, integrated circuit, metallurgy, food, medicine, transportation, heat treatment, welding, casting, coating, testing, ion beam, controlled thermonuclear reaction and aerospace and other fields, which has promoted the progress of modern science and technology and the development of industry and agriculture.

The Torricelli experiment

In 1643, the Italian physicist Torricelli experimented with atmospheric pressure. He used a thin glass tube closed at one end and a tank containing mercury, and first poured the mercury through the open end of the glass tube until the tube was full. Then press the opening with the finger, the glass tube upside down in the mercury tank, and then let go of the finger, at this time the height of the mercury in the glass tube gradually decreased until the distance from the liquid level of the small tank 760mm, it no longer fell. Torricelli believed that the void at the top of the glass tube was a vacuum, which opened the way for human exploration of vacuum.

The Magdeburg Hemisphere experiment

In 1654, Otto von Guerick, mayor of the city of Madburg, Germany, invented the piston vacuum pump and conducted a public scientific experiment. He and his assistant docking the two copper hemispheres together, with a vacuum pump to remove the air in the ball, so the surface of the ball by the atmospheric pressure is very large, each hemisphere of its lateral force, with 16 horses to the two hemispheres successfully pulled apart. Through this large-scale experiment, people finally believe that there is atmospheric pressure and atmospheric pressure is very amazing, and at the same time realize the vacuum, so the concept of vacuum in the true scientific sense was born.

In the natural environment, only outer space can be called the space closest to vacuum, the solar system space beyond the tens of kilometers high atmosphere, the Milky Way outside the solar system and the entire visible universe are all vacuum. Although vacuum sounds far away from us, it is actually all around us. Many modern high-precision products must be manufactured in different degrees of vacuum environment in the manufacturing process, such as semiconductors, vacuum glass, hard disks, scanning electron microscopy and so on.

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