What does vacuum mean?

The meaning of vacuum refers to the state of gas below one atmosphere in a given space, which is a physical phenomenon. In the "void", because there is no medium, sound cannot spread, but the propagation of electromagnetic waves is not affected by vacuum.

In fact, in vacuum technology, vacuum refers to the atmosphere, and some substances in a specific space are discharged to make its pressure less than a standard atmospheric pressure, so we generally call this space vacuum or vacuum state. Vacuum usually uses Pascal or Torr as the unit of pressure. In the natural environment, only outer space can be called the space closest to vacuum.

Extended data

Human understanding of vacuum has undergone several fundamental changes and repetitions. Democritus's atomism in ancient Greece believed that everything was made up of atoms, and there was nothing outside the atoms. /kloc-in the 0/7th century, R Descartes put forward the theory of etheric vortex, arguing that space is full of ether and used it to explain the motion of planets.

Newton quickly established Newtonian mechanics based on the three laws of motion and the law of universal gravitation, and successfully solved the problem of planets moving around the sun. Gravity is considered as a long-distance action, and the sun is not needed as a transmission medium, thus denying the etherism.

The fluctuation of light was discovered in the19th century, and it is believed that the wave propagation must depend on the medium, especially the fluctuation of electromagnetic field was discovered later. Etherism rises again, thinking that no matter when and where the universe is, any object is full of ether, and light and electromagnetic waves are interpreted as mechanical vibration of ether.

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