H. (Hippolyte) Fizeau

Born in Paris in 1819, Hippolyte Fizeau became one of the important experimental physicists of his century. Early in his career he worked on photographic methods, and he also collaborated with Léon Foucault on investigations involving light and heat.

Fizeau is especially remembered for his 1849 experiment measuring the speed of light with a rotating toothed wheel, a landmark result in physics. He also studied the way light behaves in moving media, and the effect now known as the Doppler shift was independently described by him in connection with light.

His achievements were widely recognized in France and beyond: he became a member of the French Academy of Sciences and later received the Royal Society’s Rumford Medal. He died in 1896, leaving behind a body of work that helped make precision optical measurement central to modern physics.