Hippolyte Fizeau
Hippolyte Fizeau in 1883 by Eugène Pirou.
Born23 September 1819
Died18 September 1896
(aged 76)
Known forFizeau experiment
Fizeau interferometer
Fizeau wheel
Fizeau's measurement of the speed of light in air
Doppler–Fizeau effect
Astronomical interferometry
Optical dilatometer
AwardsRumford Medal (1866)
FRS (1875)
Scientific career

Armand Hippolyte Louis Fizeau FRS FRSE MIF[clarification needed] (French pronunciation: [aʁmɑ̃ ipɔlit lwi fizo]; 23 September 1819 – 18 September 1896) was a French physicist, 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 the Fizeau experiment.


Fizeau was born in Paris to Louis and Beatrice Fizeau.[1] He married into the de Jussieu botanical family. His earliest work was concerned with improvements in photographic processes.[2] Following suggestions by François Arago, Léon Foucault and Fizeau collaborated in a series of investigations on the interference of light and heat.[3] In 1848, he predicted the redshifting of electromagnetic waves.[4]

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. 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 of 2 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). (See Fizeau'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]

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.[8]: 129 

Fizeau was involved in the discovery of the Doppler effect,[9] which is known in French as the Doppler–Fizeau effect.

In 1853, Fizeau described the use of a capacitor (sometimes termed a "condenser") as a means to increase the efficiency of the induction coil. Later, he studied the thermal expansion of solids and applied the phenomenon of interference of light to the measurement of the dilatations of crystals. He became a member of the Académie des Sciences in 1860 and a member of the Bureau des Longitudes in 1878. He died in France at Venteuil on 18 September 1896.[3]

"Fizeau" is one of the 72 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 the 1889 World's Fair. Of the 72, Fizeau is the only one who was still alive when the tower was opened.[10]

The crater Fizeau on the far side of the Moon is named after him.[11]

See also


  1. ^ Hockey, Thomas (2009). The Biographical Encyclopedia of Astronomers. Springer Publishing. ISBN 978-0-387-31022-0. Retrieved August 22, 2012.
  2. ^ 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 from the original (PDF) on 14 July 2014. Retrieved 22 June 2014.
  3. ^ a b  One or more of the preceding sentences incorporates text from a publication now in the public domainChisholm, Hugh, ed. (1911). "Fizeau, Armand Hippolyte Louis". Encyclopædia Britannica. Vol. 10 (11th ed.). Cambridge University Press. p. 452.
  4. ^ Hellemans, Alexander; Bryan Bunch (1988). The Timetables of Science. New York City: Simon and Schuster. pp. 317. ISBN 0-671-62130-0.
  5. ^ "Fizeau's experiment: The original paper". Skulls in the Stars. 1 April 2008. Retrieved 9 March 2023.
  6. ^ Poincaré, H. (1904). "Experiments of MM. Fizeau and Gounelle". Maxwell's Theory and Wireless Telegraphy: Part 1. New York: McGraw Publishing Co. pp. 52–55.
  7. ^ Physics part 1 Resnick/Halliday p. 5.
  8. ^ Tobin, William John (2003). The Life and Science of Leon Foucault: The Man Who Proved the Earth Rotates. Cambridge University Press. ISBN 9780521808552. Retrieved 10 March 2023.
  9. ^ 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. PMID 2053764.
  10. ^ Lemoine, Bertrand (2020-06-18). "Whose are the 72 names inscribed on the Eiffel Tower and why are they there". Archived from the original on 2023-01-29. Retrieved 2023-05-10.
  11. ^ "Fizeau on Moon". Gazetteer of Planetary Nomenclature. United States Geological Survey. Retrieved 21 September 2018.