Armand Hippolyte Louis Fizeau (French:[ipɔlitfizo]; 23 September 1819 – 18 September 1896) was a Frenchphysicist who, in 1849,measured the speed of light to within 5% accuracy. In 1851, he measured the speed of light in moving water in an experiment known as theFizeau experiment.
Fizeau was born in Paris to Louis and Beatrice Fizeau.[1] He married into thede Jussieu botanical family. His earliest work was concerned with improvements in photographic processes.[2] Following suggestions byFrançois Arago,Léon Foucault and Fizeau collaborated in a series of investigations on theinterference of light and heat.[3] In 1848, he predicted theredshifting ofelectromagnetic waves.[4]
In 1849, Fizeau calculated a value for the speed of light to a better precision than the previous value determined byOle Rømer in 1676. He used a beam of light reflected from a mirror 8633 meters away. The beam passed through the gaps between the teeth of a rapidly rotating wheel with 720 teeth. The speed of the wheel was increased until, at 12.6 rotations per second, the returning light hit the next tooth and could not be seen. At 25.2 rotations per second, the light was again visible.[5] This gives a result of2 x 8633m x 25.2 x 720/s = 313,274,304 m/s, which is within 5% of the correct value (299,792,458 meters per second). (SeeFizeau's measurement of the speed of light in air.)[6] Fizeau made the first suggestion in 1864 that the "speed of a light wave be used as a length standard".[7]
Fizeau was involved in the discovery of theDoppler effect,[9] which is known in French as the Doppler–Fizeau effect.
In 1853, Fizeau described the use of acapacitor (sometimes termed a "condenser") as a means to increase the efficiency of theinduction coil. Later, he studied thethermal expansion of solids and applied the phenomenon of interference of light to the measurement of the dilatations ofcrystals. He became a member of theAcadémie des Sciences in 1860 and a member of theBureau des Longitudes in 1878. He died in France atVenteuil on 18 September 1896.[3]
"Fizeau" is one of the72 names inscribed on the frieze below the first platform of the Eiffel Tower, all of whom were French scientists, mathematicians, engineers, or industrialists from the hundred years before the tower's public opening for the1889 World's Fair. Of the 72, Fizeau is the only one who was still alive when the tower was opened.[10]
^Solbert, Oscar N.; Newhall, Beaumont; Card, James g., eds. (May 1952)."Hippolyte-Louis Fizeau (1819–1896)"(PDF).Image, Journal of Photography of George Eastman House.1 (5). Rochester, N.Y.: International Museum of Photography at George Eastman House Inc.:3–4. Archived fromthe original(PDF) on 14 July 2014. Retrieved22 June 2014.
^Houdas, Y. (April 1991). "Doppler, Buys-Ballot, Fizeau. Historical note on the discovery of the Doppler's effect".Annales de cardiologie et d'angéiologie (in French).40 (4):209–13.PMID2053764.
