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Experiment with a glass bell-jar in which
a vacuum has been created.
Robert Boyle, New Experiments Physico-Mechanicall, Touching the
Spring of the Air and its Effects, Oxford 1660
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At every moment of the day the
atmosphere weighs down on us, at 10 tons on every square metre of
the earth's surface. Describing the implications of his discovery,
Evangelista
Torricelli rightly stated that we live
at the bottom of an "ocean of air".
Indeed, the force of gravity, which nothing and no-one can escape,
also works on the molecules of air. This is how they get weight, exerting
a pressure of 1 kg
per cm² on
the surface of the Earth.
The process which arrived at the discovery of atmospheric pressure
and its many consequences makes for a fascinating adventure which
takes place in the span of a few decades, starting with the experiment
of Torricelli in 1644. In these decades,
some of the most extraordinary figures of the Scientific Revolution
entered the fray to demonstrate that the air had weight and that the
vacuum existed.
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