Today is the birthday of Henri Poincaré (29 April 1854 – 17 July 1912), French philosopher of science, engineer, mathematician, and theoretical physicist. Among his many contributions, Poincaré was the first to propose that nothing could travel faster than the speed of light in a vacuum. He also wrote a short paper on relativity that predated Einstein’s by several months-although Poincaré is rarely credited popularly with contributions to relativity, Einstein himself acknowledged his debt. Poincaré’s assertion that nothing is faster than light in a vacuum came at time when science was trying to establish what a vacuum meant at all-whether or not there was a measurable ether.
The word vacuum came into English in the 1540s from the neuter noun use of the Latin vacuus meaning empty.
Another shout out needed here: Poincaré taught at L’Université de Caen, in Lower Normandy, an institution I am proud to call one of my alma maters! Allez Phénix!