Armand-Hippolyte-Louis Fizeau died #OTD in 1896.
In 1849, Fizeau calculated a value for the speed of light to a better precision than the previous value determined by Ole Rømer in 1676. In 1850 he measured the relative speeds of light in air and water, using a rotating mirror, however Foucault independently achieved the same result seven weeks earlier.
Fizeau was involved in the discovery of the Doppler effect, which is known in French as the Doppler–Fizeau effect.