The original meaning of its etymology is void, that is, nothing of space; in accordance with the views of modern physics, a vacuum is not empty, which contains an extremely rich physical content. Is a saying that when the pressure vessel below atmospheric pressure when the atmospheric pressure is lower than some called a vacuum, and the pressure inside the container is called absolute pressure. Another argument is that where a low pressure than atmospheric pressure containers are known as the vacuum of space. Vacuum degree difference: When the container is not the pressure that is equal to zero when the absolute pressure, called the complete vacuum; remaining vacuum called incomplete.
 
       The meaning and characteristics of vacuum
Science in a vacuum, vacuum meant that in a given space than an atmospheric pressure of the gas state. It is generally thin gases such as the vacuum state. This particular vacuum and human survival, compared to the atmosphere in the state, there are a few basic characteristics are as follows:
       (1) vacuum gas pressure less than an atmospheric pressure, therefore, in the Earth's surface on a variety of vacuum container, will be the role of atmospheric pressure, the pressure difference the size of the containers inside and outside of the pressure value. Because of the role of the Earth's surface in an atmospheric pressure of about 101325N/m2, so when the pressure of container very hour, then containers are subject to atmospheric pressure to reach an atmospheric pressure.
       (2) vacuum thin as a result of gas, per unit volume of gas molecules, which is the molecular gas density is less than atmospheric pressure density of gas molecules. Thus, molecules, molecular and other particles (such as electronics, plasma, etc.) as well as between molecules and a variety of surfaces (such as the wall) between the relative reduction in the number of collisions, so that gas molecules free path increases.
 
       Physical vacuum
       The particles do not have any kind of space there, but nothing of the space does not exist. To assume that you put a space of gas are off, you will find that there are elementary particles or from time to time occur in a vacuum also disappeared, something out of nothing. Physical vacuum is actually a non-stop energy fluctuations in the sea. When the energy to reach the peak, energy into positive and negative pairs of elementary particles, when the energy to reach trough, pairs of positive and negative particles annihilate each other, into energy.
 
       Industrial vacuum
       Industrial vacuum refers to a standard atmospheric pressure than the smaller gas space, is the rarefied gas state, can be divided into high vacuum, vacuum and low vacuum, the Earth, as well as the broad masses of the planet Central is the vacuum of space. The general is a special machine to be vacuum exhaust. The extent of its rarefied gas measured using a vacuum, it is now can exhaust and the proliferation of molecular machines to be .0000000001 exhaust atmospheric pressure of high vacuum. Vacuum in science and technology, electric vacuum apparatus, tubes and other electronic equipment, there has been substantial use.
 
       Mankind's understanding of the historical development of vacuum
       On the understanding of human vacuum has undergone several fundamental changes and repeatedly. Atomism Democritus of ancient Greece believed that all the material from atoms, atomic outside is void. R. Descartes the 17th century made Ethernet whirlpool said that the space filled with ether, and to illustrate the planet's movement. I. Newton shortly establish a three-movement law and the law of universal gravitation as the cornerstone of Newton's mechanics, successfully resolved the issue of planets around the Japanese movement, gravity is considered the role of super-distance without Ethernet as the transmission media, thus negating the ether theory . The 19th century found that the volatility of light that the wave propagation must rely on the media, especially the later discovery of electromagnetic field fluctuations, and Ethernet on the rise again, that the universe anywhere, any object inside all filled with Ethernet, light and electromagnetic waves Ethernet be interpreted as the mechanical vibration. Later, although the change in concept, the electromagnetic fields as light and electromagnetic vibration, but still retains some Ethernet absolute nature, it can be described as a movement absolutely everything static reference system. The end of the 19th century and early 20th century various attempts to detect the Earth's velocity relative to Ethernet experiment failed, A. Einstein's special theory of relativity to establish once again that as an absolute denial of the existence of static Ethernet. Later, in the use of Einstein's gravitational phenomena perspective, it is already recognized the empty vacuum there is a problem with the concept that he had raised a vacuum is the gravitational field of a particular state of mind.
       First of all, given the physical contents of the new vacuum is PAM Dirac. Dirac in 1930 in order to shake off negative energy solutions of Dirac equation plight, the vacuum is full of negative energy state electronic sea. When the negative energy state electronic absorbed enough energy to positive energy state transitions become ordinary electronic, the electronic sea can be observed in order to leave a hole that is electronic. The energy from the system point of view to examine the situation more than just an electronic vacuum to high vacuum is the lowest energy state. From the modern quantum field theory point of view, each corresponding to a particle of a quantum field, particle is the corresponding quantum field of quantum field. When the space when there is some kind of particle, indicating that the kind of quantum field in the excited state; Instead particles do not exist, it means that the market is in the ground state. Therefore, the vacuum is no field has been inspired by quantum state, or a vacuum is a quantum field system, the ground state.
       With regard to the modern understanding of the vacuum is no longer a philosophical argument, but can be tested through experiments. There are many phenomena of modern times need to use a vacuum to explain the concept. For example, hydrogen atomic energy level shift and electronic Lamb anomalous magnetic moment, the experiment has a very high precision to confirm the effect of vacuum polarization; high-energy electron-positron annihilation collision for high-energy photons, instead, to stimulate high-energy photons can vacuum a large number of particles, is also a very good proof. For vacuum awareness is the primary exploration phase, physicists also exploring spontaneous symmetry breaking vacuum and vacuum phase-change and other issues, will surely promote the further development of physics.
 
       The nature of vacuum
       Vacuum has the following properties:
       1, empty of non-free, is not nothing, it is common to all particles of the ground state, can be said that particles had been inspired by a vacuum, a vacuum is not excited particles, the existence of particles can be reflected in the role, or more precisely, the role is a kind of particle, if the particles can not be the role, you can say it is a vacuum, any vacuum from the so-called absolute isolation of the particles did not exist, vacuum all the time in a dynamic equilibrium, the Each particle can not be separated from changes in the interaction with the vacuum, the interaction between particles and the vacuum is the place every day, and any absolute static material does not exist, the nature of particles is its own emptiness.
       2, the existence of polar vacuum, so that the vacuum is asymmetrical. However, this asymmetry is relatively localized, in the relative overall is symmetrical, so the cycle of nested constitute the nature of the vacuum.
       3, each partial vacuum with a vacuum of all nature. Large and small are relative terms. Time is relative to space in terms of time can not be divorced from a specific space and a separate existence.
 
       Vacuum and microgravity environment for the use of technology
       Spacecraft orbit to provide the vacuum and microgravity environment, is a treasure trove, providing people with access to the ground on the scientific experiments and production process conditions, to carry out the ground difficult to carry out scientific experiments, production ground difficult to produce materials, industrial products and medicines.
       Vacuum and microgravity environment is a valuable resource. High vacuum or ultra-high vacuum to provide an ultra-clean conditions. Microgravity provides a very weak influence of gravity of the extreme physical conditions. Gravity caused by the basic elimination of natural convection, diffusion process to become a major factor; fluid disappeared buoyancy, the density of different liquids and separation caused by the phenomenon of the disappearance of ups and downs, liquid bound only by the surface tension; wetting and capillarity and the poor; hydrostatic pressure disappeared. In short, gravity caused by the almost elimination of negative factors. The use of these very ideal environment, they can conduct microgravity technology physics, biology and microgravity microgravity life science research, testing and processing technology for manufacturing, as well as other micro-gravity applications studied.
       In the high vacuum and microgravity environment for the conduct of life and biological science experiments, there will be no organic pollution, the occurrence of mixed or measured error, bacteria and other micro-organisms used in the experiment will not be everywhere proliferation, very safe. In zero gravity, or microgravity conditions, can be no container smelting, this will not have any impurities mixed to obtain high-quality alloys; may be a different proportion of metallic or non-metallic evenly mixed to obtain a new type alloy materials; can be overcome the existence of the ground processing component cooling and density fluctuations, such as defects in the growth of high-quality, large diameter single crystal of gallium arsenide semiconductor material; can produce 100 percent of roundness sphere of industrial products such as ball bearings, and in the ground, Due to the effects of gravity, ball bearings, etc. is not truly spherical.
       Pharmaceutical space is a vacuum and microgravity environment an important aspect of use. Pharmaceuticals in the ground, due to the Earth's gravity, culture precipitation will occur, in the precipitation of micro-organisms due to lack of oxygen to death; such as oxygen mixing, the formation of low pressure will also damage cells in the small bubble; such as an increased anti-foam agent will reduce the solubility of oxygen that is not conducive to the propagation of micro-organisms, forming a vicious circle. And in micro-gravity environment, the culture fluid contains a lot of bubbles, it would not precipitation, micro-organisms readily available oxygen, the ground faster than the growth rate more than doubled. Can be highly efficient, high-purity to create a lot of drugs, such as epidermal growth factor treatment of burns, the red blood cell growth hormone treatment of anemia, infection prevention and control of the serum, the treatment of emphysema trypsin inhibitor, treatment of thrombosis of urokinase, treatment hemolytic anti-hemophilia factor 8, β-cells to treat diabetes, cancer, etc. more than 40 kinds of interferon. The main pharmaceutical approach is electrophoresis, will be a mixture of different components in the DC Field accurately separated into different components. Their equipment, took the first static electrophoresis instrument, second generation continuous flow electrophoresis.