Hippolyte Fizeau

Hippolyte Fizeau (1819 to 1896) was a French physicist who in 1849 measured the speed of light to within 5 percent of the modern value, sending a beam to a mirror 8633 metres away through the gaps of a rapidly turning toothed wheel with 720 teeth. In 1850 he compared the speed of light in air and in water with a rotating mirror, an arrangement Foucault independently achieved seven weeks earlier, and in 1851 he measured light in moving water in the experiment that carries his name. His earliest work improved photographic processes, and with Leon Foucault he investigated the interference of light and heat. In 1853 he described using a capacitor to make the induction coil more efficient, and later he studied the thermal expansion of solids by light interference. He became a member of the Academie des Sciences in 1860, the Doppler-Fizeau effect carries his name, and a lunar crater honours him.