The vacuum is the absence of matter.

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In direction common, when it is said that a container is empty, he is in fact filled of air. Glass empties, an empty bottle, a paperboard empties… contain in fact approximately 2·10¹⁵ Molécule S by millimetre cubes, two billions of molecules.

In philosophy

The concept of vacuum is closely related to the concept of to be. The vacuum is the absence of Matière, the absence to be. But can one speak about the vacuum like entity in oneself, or only like one absence. Parménide said “the being is, the non-being is not”; is the vacuum to be it or of the non-being?

The statute of the vacuum varies much according to the cultures. Leucippe, when he imagined the division of the matter, concluded that one arrived at an indivisible particle ( a-tomos , the Atome), if not one would arrive at the vacuum; it was inconceivable for him that the matter could be made of vacuum.

Descartes denied the existence of the atom like that of the vacuum, concepts to which he opposed the geometrical theories, reducing space to pure and simple extent, matter being only one formal amendment. Gassendi heavily contradicted it on this point (5th objection of the Méditations metaphysics ). Indeed, the vacuum and the atom compose the matter indeed, and these characteristics confer to him a nature intrinsically different from the extent.

The discovery, or rather the admission of the vacuum in nature is a decisive stage of the history of sciences, the polemic strongly agitated the erudite mediums during the scientific revolution of the XVIIè century.

Thus, when an European sees glass, he sees initially the matter, his form; a taoist would see there initially the vacuum which makes it useful (which makes it possible to be filled).

The vacuum taoist is conceived like a potential, something which waits to be filled, and by extension to be carried out: it is the empty spirit of thought in which can be born the ideas, it is the white of the sheet which waits to be drawn (see Taoïsme: Plenitude of the vacuum and other paradoxes ).

In the Buddhism, the vacuum indicates the clean absence of nature of any thing, the Vacuité.

In physics

In physics, the vacuum is a concept which conceals properties completely surprising and nevertheless fundamental.

It is not the nothing (the absence of all). Modern physics states to us besides that it is completely relevant to discuss the energy of the vacuum. It is not either a ether , a material medium, according to the times, moving or fixed and independent of any reference frame, imagined, for example, like support of the electromagnetic waves. It was proven that this last does not exist (by Michelson and Morley), one thus gave up the idea of it.

One can in a first approach say that the vacuum is a space in which the molecules are strongly rarefied. Thus, “to make the vacuum”, a tight enclosure is taken and one pumps the air with a Vacuum pump; one defines the quality of the vacuum by the residual air pressure, expressed in Pascal (Pa, unit of the international system), or more often in industrial environment in millibar (mbar) or Torr (mm of mercury). One cannot reach as well as a partial vacuum, whatever the Température.

A vacuum considered as very thorough, “ultra-high vacuum”, correspond to a pressure about 10^-8 Pa; one counts there 2 more million molecules per cubic centimeter. By comparison, the density within the interstellar Gaz is about 1 atom per cubic centimeter.

But which says absence of matter does not say absence of event. Thus, the electromagnetic waves cross the vacuum, and it is the medium which is opposed less to their advance (the Speed of light about which one usually speaks, limit with any transmission of information, is that in the vacuum); there is in the vacuum of the variations of the electric field and the magnetic field, but these fields do not require any material support. The total vacuum thus requires the absence at the same time matter but also of radiation.

The definite absolute vacuum above is thus a medium statistically without elementary particles. The Quantum physics, which defines the vacuum as the state of minimal energy of the theory, shows that there remains nevertheless the seat of spontaneous and fugacious matérialisations of particles and their associated antiparticles, one speaks about virtual particles, which are destroyed almost immediately after their creation. These quantum fluctuations are a direct consequence of the Principe of uncertainty which affirms that it is never possible to know with an absolute certainty the precise value of energy. One calls this phenomenon the quantum fluctuations of the vacuum.

Einstein devotes appendix 5 of its book Relativité - Theories special and general ( Relativity - The Special and the General Theory , translation of Robert Lawson, 1961) with the relativity and problem of space . It there quotes Descartes and Kant and gives reason to the first against the second, by denying the existence of the vacuum, i.e., specifies it, the existence of a space vacuum of field . It notes in its foreword with the 9th edition of the book: “the physical objects are not in space , but these objects have a space extent . This way, the concept of “empty space” loses its direction. ”

Pressure of the vacuum

See also: Effect Casimir

One of the properties most curious about the quantum vacuum is highlighted by the Effet Casimir: when the vacuum is carried out between two conducting plates, and in the absence of very forced mechanical external, a pressure is exerted on the plates whose value depends on the particular geometry of the system. This effect is explained within the framework of the Quantum theory of the fields which affirms that the concept of vacuum depends on the geometry. Thus the vacuum locked up between the two conducting plates has a density of energy different from the vacuum external with the enclosure. This difference in density of energy has as a direct consequence the appearance of a mechanical force exerted on the interface separating both mediums.

Physical properties of the vacuum

magnetic Permeability of the vacuum μ₀ ≡ 4π×10-7 kg·m/A ² S ² (or H/m)

Conductance of the vacuum = 1/119,916 983 2·π S ≈ 2,654 418.729.438 07×10-3 has ² S ³ /kg·m ² ≡ 1/μ₀c

permittivity of the vacuum ε₀

= 1/35 950.207.149·π F/m ≈ 8,854 187.817.620 39×10-12 has ² S ⁴ /kg·m ³ ≡ 1/μ₀c ²

Impedance characteristic of the vacuum Z₀ = 119,916 983 2·π Ω ≈ 376,730 313.461.770 68 kg·m ² /A ² S ³ ≡ μ₀c

In mathematics

See also: Empty set

In art

August 1st Vacuum is the acronym commonly used to designate a Canadian of the time Contemporaine called Alexandre Simard which, after having finished its studies in engineering civil at the University of Sherbrooke, built multiple public edifices, bridges, exchangers.

Little story of the vacuum

• 1644 : Discovered physical notion of the vacuum by Torricelli

• 1646: Pascal confirms and refines this theory
• 1654: Otto von Guericke manufactures the first vacuum pump
• 1855: Geissler manufactures the first vacuum pump with displacement of mercury. The vacuum obtained is close to 1/10 of Torr (= 0,1 mm Hg or 0,133 mbar)
• 1865: Sprengel invents the mercury pump
• 1905: Gaede creates the rotary vacuum pump with mercury
• 1910: Gaede invents the vane pump (unchanged principle at our days!)
• 1913: Gaede invents the pump turbomoléculaire, then, in the tread, the pump diffusion, which will be thereafter sophisticated by Langmuir.

See too

Related articles

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• Vacuum
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