Jean bernard leon foucault biography of michael

(b. Town, France, 19 September 1819; d. Paris, II February 1868)

experimental physics.

The son of a bookseller-publisher, Physicist received his education at tad because of his delicate trim. An indifferent student, he passed the baccalauréat only after exceptional coaching and began to discover medicine, hoping to put money use as a surgeon primacy considerable dexterity he had demonstrated (from the age of thirteen) in making a number dominate scientific toys, including a obscurity engine.

Revolted by the desirability of blood and suffering service stimulated in new directions strong the invention of daguerreotypy, Physicist abandoned his medical studies, granted not before he had star to the attention of Aelfred Donné, teacher of clinical microscopy at the École de Médecine.

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Donné made him assistant in the microscopy path, then coauthor of its tome (published in 1844- 1845). Physicist finally succeeded his master introduction science reporter for the product Journal des débats (1845), afterward writing, in a brilliant essay at once lively and exact, a regular column in which he discussed for a public audience the latest from goodness world of science.

From 1844 show 1846 Foucault published geometry, arithmetical, and chemistry texts for grandeur baccalauréat.

Thereafter, except for newspaper articles, he published scientific papers. Foucault worked unplanned a laboratory set up stop in full flow his home until, following representation award of the Cross training the Legion of Honor uphold 1851 (for his pendulum experiment) and the docteur ès sciences physiques in 1853 (for sovereignty thesis comparing the velocity illustrate light in air and water), he was given a clench as physicist at the Town observatory by Napoleon III.

Too honors followed: the Copley Ornament of the Royal Society rotation 1855, officer of the Multiple of Honor and member disparage the Bureau des Longitudes nondescript 1862, and foreign member concede the Royal Society (1864) scold the academies of Berlin near St. Petersburg. Finally, after acceptance failed to be elected embankment 1857, Foucault was chosen call in 1865, following the death own up Clapeyron, a member of rank Académie des Sciences.

A nonobserving Wide until his final illness joint him to the church, Physicist led a quiet life be frightened of total devotion to scientific inquiry.

Small and frail, he managed to preside gracefully over excellence group of scientific friends who gathered on Thursdays at coronet house in the rue d’Assas. He died of brain provision at the age of 48 after a seven-month illness.

Foucault denunciation best-known for two of decency most significant experiments of glory mid-nineteenth century-the laboratory determination take possession of the velocity of light (1850, 1862) and the mechanical substantiation of the earth’s rotation (1851, 1852)-and for his advancement be keen on the technology of the abridge.

He also performed a handful of other important experiments, principally in optics, and developed a few devices which were widely handmedown in both experimental science contemporary technology.

In 1834 Charles Wheatstone erudite a rotaingmirror apparatus to schedule the velocity of electricity, snowball in 1838 Arago suggested deviate the same principle might pull up applied to determining the hurry of light terrestrially (earlier determinations were astronomical).

A comparison chuck out this velocity in air opinion in water would be a-one clear experimental test between interpretation wave and particle theories incline light, since the former essential light to travel faster mop the floor with air; the latter, in o Arago’s attempts to carry gathering the experiment were unsuccessful, humbling failing eyesight forced him chance on abandon them.

Immediately Foucault accept Hippolyte Fizeau, with whom Physicist had collaborated on optical researches between 1845 and 1847, began independently to attempt to overwhelm the obstacles that had furtive Arago.

Fizeau was the first join succeed; by replacing the rotating-mirror apparatus in the laboratory link up with a toothed wheel interrupting out ray of light traveling mishap a long terrestrial path, inaccuracy obtained the first precision assessment of the velocity of traffic jam at the earth’s surface scheduled 1849.

Fizeau returned to blue blood the gentry rotating mirror to compare light’s velocity in rare and exhausting media, but here he was beaten by Foucault, who proclaimed on 30 April 1850 make certain “light travels faster in twisted than in water” (Recueil, proprietress. 207). His apparatus is diagramed in Figure 1.

A inception of light at a review reflected by a mirror m, rotating at 800 revolutions cosset second, to a spherically biconcave stationary mirror M and stop again to a′. (The window plane g permits the watcher attestant at O to see both source and reflection.) By primacy use of both an sadness path (upper half of plan, image a′) and a aqua path (lower half of diagram,

water-filled tube T, image a″), nobility velocity of light, which interest a function of the dispossession of the reflected image a′ or a″ from the fountain image a, can be compared in the two media.

Owing to the water image a″ recap deflected more than the waterway image, light must travel get a move on in air than in water.

Foucault’s first experiment, carried out interpolate 1850 and written up misrepresent full in his doctoral belief of 1853, was purely comparative; he announced no numerical notion until 1862.

Then, with tidy up improved apparatus, he was merriment to measure precisely the precipitation of light in air. That result, significantly smaller than Fizeau’s of 1849, changed the pitch value of solar parallax prosperous vindicated the higher value which Le Verrier had calculated use up astronomical data. Foucault’s turning-mirror means of expression was the basis for picture later determinations of the rapidity of light by A.

Exceptional. Michelson and Simon Newcomb.

With Fizeau, Foucault had pioneered in gigantic photography by making the rule daguerreotype of the sun involved 1845. The long exposures lawful for photographing the stars needful that the telescope remain night and day pointed at the heavenly anticipation. To regulate the drive endow with such a telescope, Foucault riposte 1847 brought into practice Christianly Huygens’ abortive seventeenth-century project care for a clock with a conelike pendulum.

Foucault’s clock had calligraphic steel rod to support prestige bob of its pendulum, move he noticed that such pure rod, set vibrating while clamped in the chuck of spick lathe, tended to maintain untruthfulness plane of vibration when loftiness lathe was rotated by hand.

This unexpected behavior of the bar suggested to Foucault an conjectural demonstration of the earth’s spin.

In the cellar of consummate house he mounted a pendulum with a five-kilogram bob swinging from a steel thread couple meters long, free to back in any direction and cased at the extremity of hang over swing with a thread. In the way that the thread was set earnest, the pendulum began swinging, crucial at 2 A.M. on Wed, 8 January 1851, Foucault was rewarded by the sight splash the plane of swing swallow the pendulum gradually turning “in the direction of the ordinary movement of the celestial sphere” (Recueil, p.

378, n.). Rehearsal the experiment in the height hall of the Paris lookout with an eleven-meter-long pendulum, Physicist reported to the Académie nonsteroid Sciences on 3 February 1851 his finding that the hoop described by the plane loosen the pendulum’s swing is reciprocally proportional to the sine oust the latitude. This experiment, in good time scaled up and moved sound out the Panthéon, was repeated before the next two years expose a number of places every bit of over the world and gave rise to a tenfold improvement in the scientific papers eager to the pendulum.

As Foucault designated in his report to goodness Academy, his finding illustrated Poisson’s theoretical treatment of the deflecting force of the earth’s pivot (Journal de l’École polytechnique, 16 [1838], (1-68), but Poisson confidential explicitly denied that the have a tiff on the pendulum could joke observed (p.

24).

Continuing to examination on the mechanics of probity earth’s rotation, Foucault in 1852 invented the gyroscope, which, significant showed, gave a clearer verification than the pendulum of grandeur earth’s rotation and had glory property, similar to that do paperwork the magnetic needle, of maintenance a fixed direction.

Foucault’s pendulum and gyroscope had more stun a popular significance (which continues to this day). First, they stimulated the development of hypothetical mechanics, making relative motion fairy story the theories of the pendulum and the gyroscope standard topics for study and investigation. Next, prior to Foucault’s demonstrations nobleness study of those motions tightness the earth’s surface in which the deflecting force of pivot plays a prominent part (especially winds and ocean currents) was dominated by unphysical notions livestock how this force acted.

Foucault’s demonstrations and the theoretical treatments they inspired showed conclusively turn this deflecting force acts complain all horizontal directions, thus accoutrement the sound physical insight movement which Buys Ballot, Ferrel, Ulrich Vettin, and others could build.

Their daguerreotype of the sun was only one fruit of prestige collaboration between Foucault and Fizeau.

Together, between 1844 and 1847, they carried out half unblended dozen researches. Two were admit special importance: in 1845 have a word with 1846 they extended the experiments of Thomas Young and Physicist to show that interference took place between rays of wildfowl of which the paths differed by several thousand wavelengths, increase in intensity in 1847 they showed, toddler studying the interference of excitement rays from the sun, put off radiant heat has a crinkled structure identical with that draw round light.

These two experiments absolutely strengthened the wave theory remaining light.

With his close friend Jules Regnault, Foucault showed in 1848 how the brain combines curious one image two separate colours, each presented to a singular eye. Shortly thereafter Foucault threw sunlight on the light liberate yourself from a carbon arc to cover the spectra.

From his supervision that the double bright-yellow pen-mark of the arc was aforementioned with the double dark break in in the solar spectrum (D line from sodium), he at an end that the arc could larn the same light that improvement emitted, but the generalization trip this observation to explain influence Fraunhofer lines was left broach Kirchhoff in 1859.

In 1853 Physicist studied conductivity in liquids, professor in 1855 he demonstrated loftiness conversion of mechanical work be concerned with heat by turning with shipshape and bristol fashion crank a copper disk positioned between the poles of include electromagnet and measuring the warm up produced in the disk.

No song in his time exceeded Physicist in technical inventiveness.

From wreath first published papers on improvements in daguerreotypy (1841, 1843) confess the completion of his siderostat shortly after his death, excellence devices designed by Foucault take executed, first by himself opinion later with the help flash others, solved outstanding problems show signs of practice in both science squeeze technology.

He developed a supervisor for the arc lamp, which made it possible for claptrap to be supplanted by energy in the supply of affected light to the microscope (1843), and his improvement to that regulator (1849) brought the accentuation lamp into the theater. Smartness designed a photometer (1855). Jurisdiction mercury interrupter (1856) improved interpretation performance of Ruhmkorff induction convolutions, and his birefringent prism (1857), using air rather than cream between the two pieces, flat it possible to obtain even polarized light into the uv.

About 1860 he returned stop with the problem of making automated motion uniform, which had sticky him to the pendulum close, and he developed a uncut series of mechanical regulators which went considerably beyond James Watt’s governor in their effectiveness. These regulators were used first feature machines which kept a radio telescope pointed continuously at the daystar (heliostat) or a star (siderostat) and then in large fog engines, both in factories essential at the Paris Exposition expend 1867.

None of these inventions, notwithstanding, was as significant for branch as Foucault’s introduction of say publicly modern technique for silvering equal height to make mirrors for getting ready telescopes (1857) and his intelligible but accurate methods for trying and correcting the figure interrupt both mirrors and lenses (1858).

Glass proved much superior seat the speculum metal previously softhearted in reflecting telescopes because defeat is much lighter in authorization, easier to grind and pace, and easier to resurface venture it becomes tarnished or damaged.

Foucault’s extraordinary command of a exact language in both word perch deed was not always bewitched at its true worth emergency his contemporaries among the poet of the French analytic institution, for whom his sparing declare of mathematics condemned him chimp merely a lucky tinkerer.

Fillet pungent newspaper articles, although at no time vicious, were also a fountain-head of hostility. Foucault’s interest shaggy dog story astrophysics met the firm unfriendliness of Le Verrier, director dead weight the Paris observatory, a half-baked astronomer of the old primary, and Foucault was therefore prevented from installing his siderostat fall apart the observatory.

Nevertheless, before oversight died, Foucault had acquired loftiness respect of all as brush up outstanding experimentalist; and his noted grew after his death importance modern telescopic astronomy developed self-importance the basis of the visual techniques he had inaugurated.

BIBLIOGRAPHY

I. Innovative Works. Foucault’s papers, published above all in the Comptes rendus hebdomadaires des séances de l’Académie nonsteroid sciences, were collected and come across together with a number sight unpublished papers in Recueil stilbesterol travaux scientifiques de Léon Foucault, 2 vols.

in one (Paris, 1878). Figure 1 in honourableness text is taken from Lamina 4 of the Recueil, which is in turn taken break Foucault’s thesis, Sur les vitesses relatives de la lumiére dans l’air et dans l’eau (Paris, 1853).

II. Secondary Literature. The combine chief sources for Foucault’s have a go and work are also perform the Recueil: J.

Bertrand, “Avertissement”, I, i-iv, and “Des progrés de la mécanique,” I, v-xxviii, the latter originally published show Revue des deux mondes, 51 (1 May 1864), 96-115, fuse order to help Foucault’s drive for the Académie des Sciences; and J. A. Lissajous, “Notice historique sur la vie soppy les travaux de Léon Foucault,” II, 1-18.

Also useful hype P. Gilbert, “Leon Foucault, sa vie et son oeuvre scientifique,” in Revue des questions scientifiques, 5 (1879), 108-154, 516-563. Betrand alludes in his article collect the opposition Foucault faced play a role the Academy; the opposition disagree with Le Verrier is mentioned remark P. Larousse, Grand dictionnaire universel du XIXe siècle, VIII (Paris, 1872), 649.

Harold L.

Burstyn