Chasing Apollo — Armand Hippolyte Louis Fizeau
Armand Hippolyte Louis Fizeau devoted his career on a quest into the realm of Apollo, the Greek god of light and truth.
Augustin-Jean Fresnel upended physics in 1818 when he demonstrated that light exhibited wave-like properties. Previously, it had been widely assumed that light was transmitted as a stream of particles. Suddenly, the true nature of light was a topic of intense interest.
The challenge was in devising new ways of investigating light’s properties and with the technologies at hand. This is where Fizeau excelled. Working at times with Francois Arago and Leon Foucault, Fizeau conducted detailed studies of phenomena related to diffraction. Fizeau collaborated with Foucault to explore the application of the brand-new technology of photography in astronomy, capturing the first photograph of the sun. But, Fizeau is perhaps best known for his experiments to measure the speed of light through air and other denser media.
Fizeau was the first to measure the speed of light experimentally, which he did in 1849. Fizeau constructed an apparatus to transmit a beam of light from his father’s home in the town of Suresnes, northwest of Paris, to a church steeple on Montmartre. There, a mirror reflected the light back along the same path, a round trip of about 17 kilometres. At the source, the light beam was broken into a series of pulses by directing it through slots cut into a rotating wheel. By varying the speed of the wheel’s rotation, Fizeau was able to synchronize the transmission of a pulse of light with the return of the previous pulse and thus calculate the speed of light.
Armand Hippolyte Louis Fizeau is one of the 72 scientists and engineers named on the Eiffel Tower.
