| Vacuum How1 #722798 In physics, there is no such thing as absolute vacuum: a given volume, whatever its conditions, always contains molecules. The pressure of the residual gas is expressed in pascals (Pa) or in millibars (mbar). The atmosphere has a pressure of approx. 100,000 pascals (1 bar). In the LHC the "Ultra-vacuum", corresponds to a pressure of 10-8 Pa; there remain 2 million molecules par cubic centimetre. By comparison, interstellar gases contain a few atoms per cubic centimetre. |
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