Summary : In January 1851, Léon Foucault hung a five kilogram sphere from the ceiling of the basement in his house in Paris, using a 2 metre long steel wire. With this simple artefact, Foucault shows the Earth’s rotation movement. During the session, we will outline the life of this great experimental physicist and his experiments, and we will explain the relationship between the movement of the pendulum and the rotation of the Earth.