What is a vacuum?
vacuum - a concept widely used in physics and engineering.This word comes from the Latin vacuus, which means "empty".This sense of the word "vacuum" is stored in a general sense the vacuum space is free of substances.In physics and engineering sciences is considered vacuum environment in which the contained gas at a pressure lower than atmospheric pressure.Let us consider what is a vacuum in physics, technical vacuum and the vacuum in space.
vacuum in quantum physics
physical vacuum is the lowest energy state of a quantum field, which has an angular momentum, zero momentum, as well as other quantum indices.The vacuum in physics is not always equivalent to the void.Thus, it can be a field of quasi-particles in a dense nucleus of an atom, or a solid.
In addition, the physical vacuum - the space, completely devoid of substance, but it filled the field, however, and it can not be considered a complete vacuum.The reason is that in the physical vacuum all the time appear and disappear particles minor fluctuations occur in the field.
technical vacuum in practice is highly rarefied gas.It can be obtained in a small amount.To achieve a perfect technical vacuum in large amounts, in practice, it is impossible, because in the final temperature of the materials will have a non-zero density of the saturated vapor.Also, many materials that are used in practice, the gases are passed.
vacuum in space
space itself has a low density and pressure, so it is closest to the physical vacuum.But even the vacuum of space can not be considered a perfect vacuum environment, as in space can detect hydrogen atoms per cubic centimeter.
vacuum can be divided into several levels, depending on the amount of material that has been left.So, there are the following degree of vacuum (range from less represented in greater):
- atmospheric pressure - 760 mm.Hg.Art.
- Low vacuum - from 760 to 25 pm.Art.
- average pressure - from 25 to 1 × 10-3 mm.Hg.Art.
- High vacuum - from 1 × 10-3 to 1 × 10-9 mm.Hg.Art.
- UHV - from 1 × 10-9 to 1 × 10-12 mm.Hg.Art.
- Extreme vacuum - & lt; 1 × 10-12 mm.Hg.Art.
- Space - from 1 × 10-6 to & lt; 3 × 10-17 mm.Hg.Art.
- absolute vacuum - 0 mm.Hg.Art.
Learn the value of other physical terms, you can in the articles section of physical concepts.