of rotation, Fizeau was able to calculate the speed of light as .

Léon Foucault carried out an experiment which used rotating mirrors to obtain a value of in 1862. Albert A. Michelson conducted experiments on the speed of light from 1877 until his death in 1931. He refined Foucault's methods in 1926 using improved rotating mirrors to measure the time it took light to make a round trip from Mount Wilson