name = Léon Foucault|
image_width = 225px
caption = Léon Foucault (1819-1868)
September 18 1819
death_date = dda|1868|2|11|1819|9|18|
nationality = French
Jean Bernard Léon Foucault (IPA2|ʒɑ̃ bɛʁnaʁ leɔ̃ fu'ko) (
18 September 1819– 11 February 1868) was a French physicist best known for the invention of the Foucault pendulum, a device demonstrating the effect of the Earth's rotation. He also made an early measurement of the speed of light, discovered eddy currents, and although he didn't invent it, is credited with naming the gyroscope. The Foucault crater on the Moonis named after him.
Foucault was the son of a publisher at
Paris, where he was born on September 18, 1819. After an education received chiefly at home, he studied medicine, which, however, he speedily abandoned for physical science due to a fear of blood. [CathEncy|url=http://www.newadvent.org/cathen/06156c.htm|title=Jean-Bertrand-Léon Foucault] He first directed his attention to the improvement of L. J. M. Daguerre's photographic processes. For three years he was experimental assistant to Alfred Donné(1801–1878) in his course of lectures on microscopic anatomy.
With A. H. L. Fizeau he carried on a series of investigations on the intensity of the
lightof the sun, as compared with that of carbonin the arc lamp, and of lime in the flame of the oxyhydrogen blowpipe; on the interference of infrared radiation, and of light rays differing greatly in lengths of path; and on the chromatic polarizationof light.
His demonstration in 1851 of the diurnal motion of the Earth by the rotation of the plane of oscillation of a freely suspended, long and heavy pendulum in
the Panthéonin Paris, caused a sensation in both the learned and popular worlds, for it was the first dynamical proof of the Earth's rotation. In the following year he used (and named) the gyroscopeas a conceptually simpler experimental proof. In 1855 he received the Copley Medalof the Royal Societyfor his 'very remarkable experimental researches'. Earlier in the same year he was made "physicien" (physicist) at the imperial observatory at Paris.
In September 1855 he discovered that the force required for the rotation of a
copperdisc becomes greater when it is made to rotate with its rim between the poles of a magnet, the disc at the same time becoming heated by the eddy currentor "Foucault currents" induced in the metal.
In 1857, Foucault invented the polarizer which bears his name, and in the succeeding year devised a method of testing the mirror of a reflecting telescope to determine its shape. The so-called "Foucault Test" allows the worker to tell if the mirror is perfectly spherical, or if it deviates from a sphere. Prior to Foucault's invention, testing reflecting telescope mirrors was a "hit or miss" proposition. With
Charles Wheatstone’s revolving mirror he in 1862 determined the speed of light to be 298,000 km/s (about 185,000 mi./s) —10,000 km/s less than that obtained by previous experimenters and only 0.6% off the currently accepted value.
In that year, he was made a member of the
Bureau des Longitudesand an officer of the Légion d'Honneur. In 1864 he was made a member of the Royal Societyof London, and the next year a member of the mechanical section of the Institute. In 1865 his papers on a modification of Watt's governor appeared, upon which he had for some time been experimenting with a view to making its period of revolution constant, and on a new apparatus for regulating the electric light; and in the year (Compt. Rend. lxiii.) he showed how, by the deposition of a transparently thin film of silveron the outer side of the object glass of a telescope, the sun could be viewed without injuring the eye. His chief scientific papers are to be found in the "Comptes Rendus", 1847—1869.
Death and afterwards
Foucault died of what was probably a rapidly-developing case of
multiple sclerosis[W. Tobin, The Life and Science of Léon Foucault, Cambridge University Press (2003).] on February 11, 1868in Paris and was buried in the Cimetière de Montmartre.
William Tobin, "Perfecting the Modern Reflector". Sky & Telescope, October 1987.
William Tobin, "Léon Foucault". Scientific American, July 1998.
Amir D. Aczel, "Pendulum: Léon Foucault and the Triumph of Science", Washington Square Press, 2003, ISBN 0-7434-6478-8
William Tobin, "The Life and Science of Léon Foucault: The Man who Proved the Earth Rotates". Cambridge University Press, 2003. ISBN 0-521-80855-3
* [http://num-scd-ulp.u-strasbg.fr:8080/513/ Volume One - "Recueil des travaux scientifiques de Léon Foucault"] 1878.
* [http://num-scd-ulp.u-strasbg.fr:8080/527/ Volume Two - "Recueil des travaux scientifiques de Léon Foucault"] 1878.
* [http://www.magnet.fsu.edu/education/tutorials/java/foucaultdisk/index.html Foucault Disk - Interactive Java Tutorial] Foucault created this device showing how eddy currents work (National High Magnetic Field Laboratory)
* [http://web2.bium.univ-paris5.fr/livanc/?cote=00576&do=livre Donné & Foucault Atlas of medical micrographs] 1845
Wikimedia Foundation. 2010.
Look at other dictionaries:
Léon Foucault — León Foucault (1819 1868) Nacimiento 18 de septiembre 1819 París, Francia … Wikipedia Español
Léon Foucault — Pour les articles homonymes, voir Foucault. Léon Foucault Léon Foucault, pionnier de l optique ondulatoire Naissance 18 … Wikipédia en Français
Leon Foucault — Jean Bernard Léon Foucault (* 18. September 1819 in Paris; † 11. Februar 1868 ebenda) war ein französischer Physiker. Inhaltsverzeichnis 1 Leben 2 Wirkung 3 Weblinks 4 Quellen … Deutsch Wikipedia
Léon Foucault — Jean Bernard Léon Foucault (18 de septiembre, 1819 11 de febrero, 1868) Físico francés. Demostró experimentalmente la rotación terrestre en 1851 mediante un enorme péndulo (el péndulo de Foucault) que se balanceaba en el Observatorio de París.… … Enciclopedia Universal
Jean Bernard Leon Foucault — Léon Foucault Pour les articles homonymes, voir Foucault. Jean Bernard Léon Foucault, né à Paris le 18 septembre 1819 et mort à Paris le 11 février 1868, était un physicien et astronome français. Connu principalement pour son… … Wikipédia en Français
Jean Bernard Leon Foucault — Jean Bernard Léon Foucault (* 18. September 1819 in Paris; † 11. Februar 1868 ebenda) war ein französischer Physiker. Inhaltsverzeichnis 1 Leben 2 Wirkung 3 Weblinks 4 Quellen … Deutsch Wikipedia
Jean Bernard Léon Foucault — (* 18. September 1819 in Paris; † 11. Februar 1868 ebenda) war ein französischer Physiker. Inhaltsverzeichnis 1 Leben 2 Wirkung 3 Weblinks … Deutsch Wikipedia
Jean-Bertrand-Leon Foucault — Jean Bertrand Léon Foucault † Catholic Encyclopedia ► Jean Bertrand Léon Foucault A physicist and mechanician, b. at Paris, 19 Sept., 1819; d. there 11 Feb., 1868. He received his early schooling at home and showed his mechanical… … Catholic encyclopedia
Jean Bernard Leon Foucault — noun French physicist who determined the speed of light and showed that it travels slower in water than in air; invented the Foucault pendulum and the gyroscope (1819 1868) • Syn: ↑Foucault • Instance Hypernyms: ↑physicist … Useful english dictionary
Jean Bernard Leon Foucault — gyroscope … Inventors, Inventions