Jean-Bernard-Léon Foucault (born September 18, 1819, Paris, France—died February 11, 1868, Paris), was a French physicist. He introduced and helped develop a way of measuring the absolute velocity of light with extreme accuracy. He provided experimental proof that the Earth rotates on its axis.
Foucault was educated for the medical profession, but his interests turned to experimental physics. With Armand Fizeau, he began a series of investigations of light and heat.