Institute and Museum of History of Science, Florence, ITALY

      "At the bottom of an ocean of air"        
Much ado about nothing The unbearable lightness of air Relative pressures

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



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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