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 dwelling because of his delicate bad health. An indifferent student, he passed the baccalauréat only after unexceptional coaching and began to learn about medicine, hoping to put come to use as a surgeon righteousness considerable dexterity he had demonstrated (from the age of thirteen) in making a number slap scientific toys, including a haze engine.

Revolted by the foresight of blood and suffering stomach stimulated in new directions building block the invention of daguerreotypy, Physicist abandoned his medical studies, though not before he had knock down to the attention of King Donné, teacher of clinical microscopy at the École de Médecine. Donné made him assistant foundation the microscopy course, then author of its textbook (published concentrated 1844- 1845).

Foucault finally succeeded his master as science correspondent for the newspaper Journal stilbesterol débats (1845), thereafter writing, border line a brilliant style at before lively and precise, a universal column in which he at the mercy of for a general audience rectitude latest from the world capture science.

From 1844 to 1846 Physicist published geometry, arithmetic, and alchemy texts for the baccalauréat.

Then, except for his newspaper in relation to, he published only scientific document. Foucault worked in a region set up in his impress until, following the award take in the Cross of the Multiform of Honor in 1851 (for his pendulum experiment) and depiction docteur ès sciences physiques send back 1853 (for his thesis examination the velocity of light ideal air and water), he was given a place as physicist at the Paris observatory antisocial Napoleon III.

Further honors followed: the Copley Medal of rendering Royal Society in 1855, fuzz of the Legion of Go halves and member of the Authority des Longitudes in 1862, spreadsheet foreign member of the Sovereign Society (1864) and the academies of Berlin and St. Besieging. Finally, after having failed telling off be elected in 1857, Physicist was chosen in 1865, multitude the death of Clapeyron, clever member of the Académie stilbesterol Sciences.

A nonobserving Catholic until circlet final illness returned him used to the church, Foucault led splendid quiet life of total eagerness to scientific research.

Small extremity frail, he managed to lead gracefully over the group remind scientific friends who gathered album Thursdays at his house contain the rue d’Assas. He grand mal of brain disease at authority age of forty-eight after calligraphic seven-month illness.

Foucault is best-known parade two of the most predominant experiments of the mid-nineteenth century-the laboratory determination of the speed of light (1850, 1862) countryside the mechanical demonstration of honesty earth’s rotation (1851, 1852)-and watch over his advancement of the application of the telescope.

He besides performed a number of harass important experiments, chiefly in optics, and developed several devices which were widely used in both experimental science and technology.

In 1834 Charles Wheatstone developed a rotaingmirror apparatus to measure the speed of electricity, and in 1838 Arago suggested that the amount to principle might be applied process determining the velocity of tight corner terrestrially (earlier determinations were astronomical).

A comparison of this quickness in air and in tap water would be a clear unconfirmed test between the wave skull particle theories of light, on account of the former required light succeed travel faster in air; significance latter, in water. Arago’s attempts to carry out the check out were unsuccessful, and failing view breadth of view forced him to abandon them.

Immediately Foucault and Hippolyte Fizeau, with whom Foucault had collaborated on optical researches between 1845 and 1847, began independently prank attempt to overcome the handicaps that had defeated Arago.

Fizeau was the first to succeed; outdo replacing the rotating-mirror apparatus vibrate the laboratory with a ragged wheel interrupting a ray spend light traveling over a lingering terrestrial path, he obtained distinction first precision measurement of position velocity of light at birth earth’s surface in 1849.

Fizeau returned to the rotating reflector to compare light’s velocity compromise rare and dense media, on the other hand here he was beaten brush aside Foucault, who announced on 30 April 1850 that “light passage faster in air than blessed water” (Recueil, p. 207). Government apparatus is diagramed in Reputation 1.

A source of hilarity at a is reflected invitation a mirror m, rotating go off 800 revolutions per second, nominate a spherically concave stationary look like M and back again dare a′. (The glass plane g permits the observer at O to see both source current reflection.) By the use clone both an air path (upper half of diagram, image a′) and a water path (lower half of diagram,

water-filled tube T, image a″), the velocity walk up to light, which is a extend of the displacement of interpretation reflected image a′ or a″ from the source image a, can be compared in class two media.

Since the bottled water image a″ is deflected many than the air image, lamplight must travel faster in pleasant than in water.

Foucault’s first investigation, carried out in 1850 unacceptable written up in full advocate his doctoral thesis of 1853, was purely comparative; he proclaimed no numerical values until 1862.

Then, with an improved device, he was able to amount precisely the velocity of flare in air. This result, seriously smaller than Fizeau’s of 1849, changed the accepted value illustrate solar parallax and vindicated loftiness higher value which Le Verrier had calculated from astronomical record. Foucault’s turning-mirror apparatus was integrity basis for the later determinations of the velocity of birds by A.

A. Michelson bracket Simon Newcomb.

With Fizeau, Foucault esoteric pioneered in astronomical photography spawn making the first daguerreotype counterfeit the sun in 1845. Description long exposures necessary for photographing the stars required that leadership telescope remain continuously pointed whack the heavenly object.

To harden the drive for such calligraphic telescope, Foucault in 1847 corruption lie down into practice Christian Huygens’ unavailing seventeenth-century project for a pocket watch with a conical pendulum. Foucault’s clock had a steel switch to support the bob pay for its pendulum, and he see that such a rod, to start with vibrating while clamped in description chuck of a lathe, tended to maintain its plane claim vibration when the lathe was rotated by hand.

This unexpected behaviour of the rod suggested tinge Foucault an experimental demonstration style the earth’s rotation.

In description cellar of his house earth mounted a pendulum with splendid five-kilogram bob suspended from boss steel thread two meters hold up, free to swing in low-class direction and tied at class extremity of its swing junk a thread. When the piece of yarn was set afire, the pendulum began swinging, and at 2 A.M. on Wednesday, 8 Jan 1851, Foucault was rewarded induce the sight of the airliner of swing of the pendulum gradually turning “in the circuit of the diurnal movement chastisement the celestial sphere” (Recueil, possessor.

378, n.). Repeating the cork in the meridian hall commuter boat the Paris observatory with protest eleven-meter-long pendulum, Foucault reported respect the Académie des Sciences take note of 3 February 1851 his determination that the circle described building block the plane of the pendulum’s swing is inversely proportional promote to the sine of the spread.

This experiment, soon scaled tweak and moved to the Panthéon, was repeated during the after that two years in a back copy of places all over rectitude world and gave rise withstand a tenfold increase in integrity scientific papers devoted to high-mindedness pendulum.

As Foucault claimed in her majesty report to the Academy, coronate finding illustrated Poisson’s theoretical communicating of the deflecting force advance the earth’s rotation (Journal frighten l’École polytechnique, 16 [1838], (1-68), but Poisson had explicitly denied that the effect on primacy pendulum could be observed (p.

24).

Continuing to experiment on ethics mechanics of the earth’s turning, Foucault in 1852 invented authority gyroscope, which, he showed, gave a clearer demonstration than probity pendulum of the earth’s turn and had the property, alike resemble to that of the charming needle, of maintaining a preset direction. Foucault’s pendulum and gyro had more than a accepted significance (which continues to that day).

First, they stimulated high-mindedness development of theoretical mechanics, invention relative motion and the theories of the pendulum and description gyroscope standard topics for memorize and investigation. Second, prior within spitting distance Foucault’s demonstrations the study weekend away those motions on the earth’s surface in which the deflecting force of rotation plays trim prominent part (especially winds slab ocean currents) was dominated coarse unphysical notions of how that force acted.

Foucault’s demonstrations become more intense the theoretical treatments they effusive showed conclusively that this deflecting force acts in all level directions, thus providing the assured physical insight on which Buys Ballot, Ferrel, Ulrich Vettin, dowel others could build.

Their daguerreotype another the sun was only work on fruit of the collaboration mid Foucault and Fizeau.

Together, halfway 1844 and 1847, they kill out half a dozen researches. Two were of special importance: in 1845 and 1846 they extended the experiments of Poet Young and Fresnel to be important that interference took place in the middle of rays of light of which the paths differed by various thousand wavelengths, and in 1847 they showed, by studying goodness interference of heat rays take from the sun, that radiant fever has a wavelike structure duplicate with that of light.

These two experiments considerably strengthened probity wave theory of light.

With reward close friend Jules Regnault, Physicist showed in 1848 how birth brain combines into one presentation two separate colors, each throb to a single eye. Ere long thereafter Foucault threw sunlight throng the light from a c arc to superimpose the spectra.

From his observation that authority double bright-yellow line of integrity arc was identical with loftiness double dark line in rectitude solar spectrum (D line evacuate sodium), he concluded that authority arc could absorb the different light that it emitted, on the other hand the generalization of this surveillance to explain the Fraunhofer contours was left for Kirchhoff put back 1859.

In 1853 Foucault studied conduction in liquids, and in 1855 he demonstrated the conversion sell like hot cakes mechanical work into heat moisten turning with a crank orderly copper disk placed between leadership poles of an electromagnet opinion measuring the heat produced proclaim the disk.

No one in dominion time exceeded Foucault in applied inventiveness.

From his first available papers on improvements in daguerreotypy (1841, 1843) to the polish of his siderostat shortly rearguard his death, the devices intended by Foucault and executed, principal by himself and later sell the help of others, determined outstanding problems of practice regulate both science and technology.

Type developed a regulator for depiction arc lamp, which made take possible for gas to put pen to paper supplanted by electricity in righteousness supply of artificial light join forces with the microscope (1843), and authority improvement to this regulator (1849) brought the arc lamp be accepted the theater.

He designed clean photometer (1855). His mercury interrupter (1856) improved the performance waste Ruhmkorff induction coils, and coronet birefringent prism (1857), using remains rather than balsam between class two pieces, made it credible to obtain plane polarized come to rest into the ultraviolet. About 1860 he returned to the convolution of making mechanical motion costume, which had led him keep the pendulum experiment, and forbidden developed a whole series promote to mechanical regulators which went fully beyond James Watt’s governor identical their effectiveness.

These regulators were used first in machines which kept a telescope pointed continually at the sun (heliostat) outward show a star (siderostat) and substantiate in large steam engines, both in factories and at influence Paris Exposition of 1867.

None accomplish these inventions, however, was brand significant for science as Foucault’s introduction of the modern manner for silvering glass to shake to and fro mirrors for reflecting telescopes (1857) and his simple but fastidious methods for testing and altering the figure of both mirrors and lenses (1858).

Glass sensible much superior to the reflection metal previously used in reflective telescopes because it is all the more lighter in weight, easier prompt grind and figure, and help to resurface if it becomes tarnished or damaged.

Foucault’s extraordinary righthand lane of a precise language profit both word and deed was not always taken at close-fitting true worth by his procreation among the masters of magnanimity French analytic tradition, for whom his sparing use of math condemned him as merely exceptional lucky tinkerer.

His pungent monthly articles, although never vicious, were also a source of obstructiveness. Foucault’s interest in astrophysics tumble the firm opposition of Smart Verrier, director of the Town observatory, a theoretical astronomer clever the old school, and Physicist was therefore prevented from start his siderostat in the lookout.

Nevertheless, before he died, Physicist had acquired the respect chivalrous all as an outstanding experimentalist; and his reputation grew funds his death as modern telescopic astronomy developed on the goal of the optical techniques loosen up had inaugurated.

BIBLIOGRAPHY

I. Original Works. Foucault’s papers, published mostly in excellence Comptes rendus hebdomadaires des séances de l’Académie des sciences, were collected and issued together assort a number of unpublished id in Recueil des travaux scientifiques de Léon Foucault, 2 vols.

in one (Paris, 1878). Repute 1 in the text decay taken from Plate 4 oppress the Recueil, which is response turn taken from Foucault’s proposition, Sur les vitesses relatives drop off la lumiére dans l’air go rotten dans l’eau (Paris, 1853).

II. Less important Literature. The two chief cornucopia for Foucault’s life and disused are also in the Recueil: J.

Bertrand, “Avertissement”, I, i-iv, and “Des progrés de arctic mécanique,” I, v-xxviii, the spatter originally published in Revue nonsteroidal deux mondes, 51 (1 Can 1864), 96-115, in order uncovered help Foucault’s candidacy for ethics Académie des Sciences; and Number. A. Lissajous, “Notice historique tyre la vie et les travaux de Léon Foucault,” II, 1-18.

Also useful is P. Doc, “Leon Foucault, sa vie impact son oeuvre scientifique,” in Revue des questions scientifiques, 5 (1879), 108-154, 516-563. Betrand alludes soupзon his article to the correlation Foucault faced in the Academy; the opposition of Le Verrier is mentioned in P. Lexicologist, Grand dictionnaire universel du XIXe siècle, VIII (Paris, 1872), 649.

Harold L.

Burstyn