Urbain Jean Joseph Leverrier

Source

• Born: 1811
• Birthplace: Saint-Lô, France
• Died: 1877
• Best Known As: The mathematician who predicted the existence of Neptune

Urbain Jean Joseph Leverrier was a French astronomer and mathematician who analyzed the orbit of Uranus and accurately predicted the existence of another planet nearby. His prediction led directly to the discovery of Neptune in 1846. An English astronomer, John Couch Adams, calculated the same thing independently and earlier, but Leverrier's work was published first. Leverrier is credited with coming up with the idea of daily weather reporting, and he also tried to prove the existence of another planet, Vulcan, near Mercury.

French astronomer (1811–1877)

Born the son of a local government official in St. Lô, northern France, Le Verrier was educated at the Ecole Polytechnique and worked afterward on chemical problems with Joseph Gay-Lussac. He became a lecturer in astronomy at the Ecole Polytechnique in 1836 and succeeded Dominique Arago as director of the Paris Observatory in 1854.

Le Verrier worked on celestial mechanics, and in particular considered the problems associated with the motion of Uranus. In 1821 Alexis Bouvard, of the Paris Observatory, had published a set of tables of the motion of Uranus. Within a few years there was a noticeable discrepancy between the predicted and the observed position of Uranus. Assuming the correctness of Bouvard's work there were only two possibilities: either Newton's gravitational theory was not as universal as had been supposed, or there was an undetected body further out than Uranus but exerting a significant gravitational influence over its orbit. After much effort Le Verrier managed to deduce the mass and position that such a body would have to have to cause such disturbances in the orbit. (Le Verrier was unaware – as were most astronomers – that John Couch Adams had made these calculations in the previous year.) He asked Johann Galle in Berlin to search for the proposed planet. Galle was immediately successful, sighting Neptune on his first night of observation, 23 September 1846. The new planet was named Neptune and Le Verrier immediately became famous. He went into politics for a short time but wisely returned to astronomy in 1851.

Continuing with problems of celestial mechanics, Le Verrier reworked and revised much of the work of Pierre Simon Laplace. He discovered the advance of the perihelion (the point of the orbit nearest the Sun) of Mercury and was convinced that this anomaly was caused by an undiscovered planet between Mercury and the Sun. So confident was he of its existence that he named it Vulcan, but despite much searching Vulcan still remained undetected. (The discrepancies in the position of Uranus could be seen as an impressive vindication of Newtonian mechanics, but the true explanation of the anomalous motion of Mercury was to play a vital role in confirming Einstein's general theory of relativity.)

Camille Flammarion claimed that Le Verrier had never taken the trouble to look through a telescope at Neptune, being satisfied with his equations and the words of others.

The French mathematical astronomer Urbain Jean Joseph Leverrier (1811-1877) made theoretical investigations which led to the discovery of the planet Neptune.

Born at Saint-Lô in Normandy on March 11, 1811, U. J. J. Leverrier entered the highly competitive école Polytechnique to prepare for a career as a professional scientist. His early interest was in chemistry; but when the teaching post in astronomy fell vacant at the Polytechnique in 1837, Leverrier took it and thereby entered the discipline in which he was to spend the rest of his life.

The aspect of astronomy with which Leverrier was primarily concerned was celestial mechanics, the mathematical analysis of the planetary motions. According to the principles of celestial mechanics, each planet was supposed to move around the sun in an essentially elliptical orbit with minor deviations due to attractions by the rest of the planets. The computations involved were very complicated, but the results were generally sufficient to provide predictions of considerable accuracy. There was, however, one prominent exception - the planet Uranus. Although it had been the subject of a great deal of study since its discovery in 1781, attempts to reduce its motion to rule had yet to meet with complete success. The remaining error was small by ordinary standards (1 minute of arc, or the angle subtended by a nickel at a distance of 100 yards), but it was a scandal in a profession accustomed to accounting for angles less than one-tenth that size.

In 1845 Leverrier decided to look into the question. After concluding that the difficulty was probably due to the action of an unknown planet whose effects were not being taken into account, he undertook a series of detailed calculations which culminated in an estimation of the location of the unknown planet. On Sept. 23, 1846, the planet, later named Neptune at Leverrier's suggestion, was discovered by J. G. Galle, the director of the Berlin Observatory, less than a degree from the spot indicated by Leverrier.

Leverrier's work was universally acclaimed as one of the outstanding scientific achievements of all time, and he received honors from virtually every country and scientific society in Europe. He embarked on similar but less successful investigations of a slight anomaly in the motion of Mercury which was resolved only in the 20th century through the work of Albert Einstein. Leverrier continued with exhaustive examinations and revisions of all the existing planetary theories. In addition, he served with distinction as director of the Paris Observatory, organized the French meteorological service, and worked for the inclusion of scientific instruction in the French educational system. He died in Paris on Sept. 23, 1877.

Further Reading

There is no biography of Leverrier, nor is there any thorough discussion of his technical contributions. Most of what has been written about him is in French; but Morton Grosser, TheDiscovery of Neptune (1962), presents a good account of Leverrier and one aspect of his work.

Urbain Le Verrier

Urbain Jean Joseph Le Verrier (11 March 1811 – 23 September 1877) was a French mathematician who specialized in celestial mechanics and is best known for his part in the discovery of Neptune.

Contents 1 Early life and career 2 Discovery of Neptune 3 Anomalous precession of Mercury's perihelion 4 Later life 5 Honours 6 See also 7 References 8 Further reading 9 External links

Early life and career

Le Verrier was born in Saint-Lô, France, and studied at the Ecole Polytechnique. Following a brief period studying chemistry under Gay-Lussac, Le Verrier switched to astronomy, particularly celestial mechanics. He accepted a job at the Paris Observatory, where he spent most of his professional life, and eventually became that institution's Director.^[1] In 1855, he was elected a foreign member of the Royal Swedish Academy of Sciences.

Discovery of Neptune

Le Verrier's most famous achievement is his prediction of the existence of the then unknown planet Neptune, using only mathematics and astronomical observations of the known planet Uranus. Encouraged by physicist Arago,^[2], Director of the Paris Observatory, Le Verrier was intensely engaged for months in complex calculations to explain small but systematic discrepancies between Uranus's observed orbit and the one predicted from the laws of gravity of Newton. At the same time, but unknown to Le Verrier, similar calculations were made by John Couch Adams in England. Le Verrier announced his final predicted position for Uranus's unseen perturbing planet publicly to the French Academy on 31 August 1846, two days before Adams's final solution, which turned out to be 12° off the mark, was privately mailed to the Royal Greenwich Observatory. Le Verrier transmitted his own prediction by 18 September letter to Johann Galle of the Berlin Observatory. The letter arrived five days later, and the planet was found with the Berlin Fraunhofer refractor that same evening, 23 September 1846, by Galle and Heinrich d'Arrest within 1° of the predicted location near the boundary between Capricorn and Aquarius.

There was, and to an extent still is, controversy over the apportionment of credit for the discovery. There is no ambiguity to the discovery claims of Le Verrier, Galle, and d'Arrest. Adams's work was begun earlier than Le Verrier's but was finished later and was unrelated to the actual discovery. Not even the briefest account of Adams's predicted orbital elements was published until more than a month after Berlin's visual confirmation. But Adams himself made full public acknowledgement of Le Verrier's priority and credit (not forgetting to mention the role of Galle) when he gave his paper to the Royal Astronomical Society in November 1846:^[3]

I mention these dates merely to show that my results were arrived at independently, and previously to the publication of those of M. Le Verrier, and not with the intention of interfering with his just claims to the honours of the discovery ; for there is no doubt that his researches were first published to the world, and led to the actual discovery of the planet by Dr. Galle, so that the facts stated above cannot detract, in the slightest degree, from the credit due to M. Le Verrier.

Anomalous precession of Mercury's perihelion

In 1859, Le Verrier was the first to report that the slow precession of Mercury’s orbit around the Sun could not be completely explained by Newtonian mechanics and perturbations by the known planets. He suggested, among possible explanations, that another planet (or perhaps, instead, a series of smaller 'corpuscules') might exist in an orbit even closer to the Sun than that of Mercury, to account for this perturbation.^[4] (Other explanations considered included a slight oblateness of the Sun.) The success of the search for Neptune based on its perturbations of the orbit of Uranus led astronomers to place some faith in this possible explanation, and the hypothetical planet was even named Vulcan. However, no such planet was ever found,^[5] and the anomalous precession was eventually explained by general relativity theory.

Later life

Le Verrier had a wife and children.^[6] He died in Paris, France and was buried in the Cimetière Montparnasse. A large stone celestial globe sits over his grave. He will be remembered by the phrase attributed to Arago: "the man who discovered a planet with the point of his pen."

Honours

• Gold Medal of the Royal Astronomical Society - 1868 and 1876

• Namesake of craters on the Moon and Mars, a ring of Neptune, and the asteroid 1997 Leverrier

• One of the 72 names engraved on the Eiffel Tower

See also

• Discovery of Neptune

References

1. ^  "Urbain-Jean-Joseph Le Verrier". Catholic Encyclopedia. New York: Robert Appleton Company. 1913. http://en.wikisource.org/wiki/Catholic_Encyclopedia_(1913)/Urbain-Jean-Joseph_Le_Verrier. 
2. ^ Arago summary
3. ^ Adams, J.C., MA, FRAS, Fellow of St Johns College, Cambridge (1846). "On the Perturbations of Uranus (p.265)". Appendices to various nautical almanacs between the years 1834 and 1854 (reprints published 1851) (note that this is a 50Mb download of the pdf scan of the nineteenth-century printed book). UK Nautical Almanac Office, 1851. http://www.archive.org/details/appendicestovari00grearich. Retrieved 2008-01-23. 
4. ^ U. Le Verrier (1859), (in French), "Lettre de M. Le Verrier à M. Faye sur la théorie de Mercure et sur le mouvement du périhélie de cette planète", Comptes rendus hebdomadaires des séances de l'Académie des sciences (Paris), vol. 49 (1859), pp.379-383. (At p.383 in the same volume Le Verrier's report is followed by another, from Faye, enthusiastically recommending to astronomers to search for a previously undetected intra-mercurial object.)
5. ^ Baum, Richard; Sheehan, William (1997). In Search of Planet Vulcan, The Ghost in Newton's Clockwork Machine. New York: Plenum Press. ISBN 0-306-45567-6. 
6. ^ "Urbain Jean Joseph Leverrier". Encyclopaedia Britannica. LoveToKnow Classic Encyclopedia. 1911. http://www.1911encyclopedia.org/Urbain_Jean_Joseph_Leverrier. Retrieved 23 November 2008. 

Further reading

• David Aubin, The Fading Star of the Paris Observatory in the Nineteenth Century: Astronomers' Urban Culture of Circulation and Observation. Osiris 18 (2003), 79-100. [1]
• Grosser, M. (1962). The Discovery of Neptune. Harvard University Press. ISBN 0674212258. 
• Le Verrier, Urbain (1835). Annales de Chimie et de Physique (Paris) 60: 174 - Chemical research of Le Verrier
• Fabien Locher, Le Savant et la Tempête. Étudier l’atmosphère et prévoir le temps au XIXe siècle, Rennes, Presses Universitaires de Rennes, Collection « Carnot », 2008.
• Dennis Rawlins (1999). Recovery of the RGO Neptune Papers. Adams' Final Prediction Missed by Over Ten Degrees. DIO, volume 9, number 1, pages 3–25.
• See, T. J. J. (1910). "Leverrier's Letter to Galle and the Discovery of Neptune". Popular Astronomy 18: 475 – 476. http://articles.adsabs.harvard.edu//full/1910PA.....18..475S/0000475.000.html?high=47333308e521469. Retrieved 2007-11-09. 

External links

• Le Verrier on the French 50 Franc banknote
• "Theorie du Mouvement de Mercure" (195 pages, 17.6 MB)
• Obituary - Nature, 1877, vol. 16, page 453

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