January 7, 1851 –
Jean Bernard Léon Foucault first used a pendulum to demonstrate that the Earth rotated on this date. This initial experiment, which was conducted in the cellar of his home using a five kilogram pendulum suspended from a two meter cable, represents the first time the Earth’s rotation has been proven experimentally, rather than through observation.
Foucault went on to give a public demonstration for scientists using an eleven meter wire at the Paris observatory on February 3 and again at the Pantheon in Paris on March 31.
Now you know.
The Haus of Dcaligari 