Pendulum plane of oscillation of a pendulum, like a gyroscope, tends to stay constant regardless of the motion of the pivot, and that this could be used to demonstrate the rotation of the Earth. He suspended a pendulum free to swing in two dimensions (later named the Foucault pendulum) from the dome of the Panthéon in Paris. The length of the cord was . Once the pendulum was set in motion, the plane of swing was observed to precess or rotate 360° clockwise in about 32 hours. This was the first demonstration of the Earth's rotation that didn't depend on celestial
Pierre-François-Victor Foucault Société d'encouragement pour l'industrie nationale, then he showed it at The Great Exhibition (1851) in London. Pierre-François-Victor Foucault Pierre-François-Victor Foucault (1797-1871) was the inventor in 1843 of the first printing machine for braille, the . A pupil of the Institut National des Jeunes Aveugles, Foucault married Thérèse-Adèle Husson, a blind author, in 1826. This marriage gave birth to two daughters. After his wife's death in 1831, following a fire, he married a seamstress (non blind) in 1832, Adélaïde Louise Juteau. This allowed him to become a resident of the Quinze-Vingts (marriages between blind people were prohibited), which gave him the