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Otto von Guericke's air-pump.
Otto von Guericke, Experimenta Nova (ut vocantur) Magdeburgica
De Vacuo Spatio, Amsterdam 1672
Otto von Guericke's air-pump.
Otto von Guericke, Experimenta Nova (ut vocantur) Magdeburgica
De Vacuo Spatio, Amsterdam 1672
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The
torricellian experiment of 1644
highlighted atmospheric pressure and demonstrated the existence of
the vacuum.
Torricelli
was convinced that the upper, closed part of the tube had to be empty.
This was the first time that the existence of the vacuum had been
claimed not at the level of pure speculation, but with the back-up
of convincing experimental evidence.
Naturally, the torricellian vacuum was not a perfect vacuum, because
mercury vapours stayed in the space created by the liquid metal's
descent. It took only another ten years and the invention of the air-pump
to succeed in making better and better vacuums, which encouraged experimentation.
Today we distinguish between various types of vacuum: the industrial
vacuum, corresponding to 0.1 mmHg (1 mmHg=1 millimetre of mercury);
the medium vacuum, up to 10-1 mmHg; the high vacuum, up
to a 10-7; and lastly, the ultra vacuum, at less than 10-7
mmHg.
The procedures for producing the ultra vacuums up to 10-15
mmHg, needed for high speed particle colliders, are particularly complex.
Even these vacuums are vastly inferior to the interstellar vacuum,
which contains less than one atom every cm3.
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