Fizeau–Foucault apparatus unit. At the time, Foucault was working at the Paris Observatory under Urbain le Verrier. It was le Verrier's belief, based on extensive celestial mechanics calculations, that the consensus value for the speed of light was perhaps 4% too high. Technical limitations prevented Foucault from separating mirrors R and M by more than about 20 meters. Despite this limited path length, Foucault was able to measure the displacement of the slit image (less than 1 mm) with considerable accuracy. In addition, unlike the case with Fizeau's experiment (which required gauging the rotation rate of an adjustable-speed toothed wheel), he could
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