PASCAL, Traité de l'équilibre des liqueurs et de la pesanteur, 1663 EO

First edition.
Milestone in the history of science in which Pascal discovers atmospheric pressure.

The famous experiment, carried out by his brother-in-law in Auvergne, consisted of comparing the height of a column of mercury in Clermont-Ferrand and then at the top of Puy-de-Dôme.
The question of the weight of the air was already under discussion in Descartes and Galileo, but it is Pascal with this experience who provides the proof. He thus broke with nearly 2000 years of Aristotelian physics: "Nature abhors a vacuum", more than a popular maxim then took the place of the only physical principle of hydrostatics.

"Nature has no repugnance for emptiness; she makes no effort to avoid it; all the effects that have been attributed to this horror proceed from the gravity and pressure of the air; she is the only one. real cause, and, lack of knowing it, we had invented this imaginary horror of emptiness on purpose, to make it right." (extract from chapter II)

Then pascal (Pa) will be adopted as the international unit of measurement of pressure.