Editing Henri Poincaré (section)

==Life==
Poincaré was born on 29 April 1854 in Cité Ducale neighborhood, [[Nancy, Meurthe-et-Moselle]], into an influential French family.<ref>Belliver, 1956</ref> His father {{ill|Léon Poincaré|fr}} (1828–1892) was a professor of medicine at the [[University of Nancy]].<ref>Sagaret, 1911</ref> His younger sister Aline married the spiritual philosopher [[Émile Boutroux]]. Another notable member of Henri's family was his cousin, [[Raymond Poincaré]], a fellow member of the [[Académie française]], who was [[President of France]] from 1913 to 1920, and three-time [[Prime Minister of France]] between 1913 and 1929.<ref name="IEP">[http://www.utm.edu/research/iep/p/poincare.htm The Internet Encyclopedia of Philosophy] {{Webarchive|url=https://web.archive.org/web/20040202060803/http://www.utm.edu/research/iep/p/poincare.htm |date=2 February 2004 }} Jules Henri Poincaré article by Mauro Murzi&nbsp;– Retrieved November 2006.</ref>

===Education===
[[File:Henri Poincaré maison natale Nancy plaque.jpg|thumb|right|200px| Plaque on the birthplace of Henri Poincaré at house number 117 on the Grande Rue in the city of Nancy]]

During his childhood he was seriously ill for a time with [[diphtheria]] and received special instruction from his mother, Eugénie Launois (1830–1897).

In 1862, Henri entered the Lycée in [[Nancy, Meurthe-et-Moselle|Nancy]] (now renamed the {{ill|Lycée Henri-Poincaré|fr}} in his honour, along with [[Henri Poincaré University]], also in Nancy). He spent eleven years at the Lycée and during this time he proved to be one of the top students in every topic he studied. He excelled in written composition. His mathematics teacher described him as a "monster of mathematics" and he won first prizes in the [[concours général]], a competition between the top pupils from all the Lycées across France. His poorest subjects were music and physical education, where he was described as "average at best".<ref>O'Connor et al., 2002</ref> Poor eyesight and a tendency towards absentmindedness may explain these difficulties.<ref>Carl, 1968</ref> He graduated from the Lycée in 1871 with a [[baccalauréat]] in both letters and sciences.

During the [[Franco-Prussian War]] of 1870, he served alongside his father in the [[Ambulance Corps]].

Poincaré entered the [[École Polytechnique]] as the top qualifier in 1873 and graduated in 1875. There he studied mathematics as a student of [[Charles Hermite]], continuing to excel and publishing his first paper (''Démonstration nouvelle des propriétés de l'indicatrice d'une surface'') in 1874. From November 1875 to June 1878 he studied at the [[École des Mines]], while continuing the study of mathematics in addition to the [[mining engineering]] syllabus, and received the degree of ordinary mining engineer in March 1879.<ref>F. Verhulst</ref>

As a graduate of the École des Mines, he joined the [[Corps des Mines]] as an inspector for the [[Vesoul]] region in northeast France. He was on the scene of a mining disaster at [[Magny-lès-Jussey|Magny]] in August 1879 in which 18 miners died. He carried out the official investigation into the accident.

At the same time, Poincaré was preparing for his [[Doctorate in Science]] in mathematics under the supervision of Charles Hermite. His doctoral thesis was in the field of [[differential equations]]. It was named ''Sur les propriétés des fonctions définies par les équations aux différences partielles''. Poincaré devised a new way of studying the properties of these equations. He not only faced the question of determining the integral of such equations, but also was the first person to study their general geometric properties. He realised that they could be used to model the behaviour of multiple bodies in free motion within the [[Solar System]]. He graduated from the [[University of Paris]] in 1879.

[[Image:Young Poincare.jpg|left|upright|thumb|The young Henri Poincaré in 1887 at the age of 33]]

===First scientific achievements===
After receiving his degree, Poincaré began teaching as junior [[lecturer]] in mathematics at the [[Caen University|University of Caen]] in Normandy (in December 1879). At the same time he published his first major article concerning the treatment of a class of [[automorphic function]]s.

There, in [[Caen]], he met his future wife, Louise Poulain d'Andecy (1857–1934), granddaughter of [[Isidore Geoffroy Saint-Hilaire]] and great-granddaughter of [[Étienne Geoffroy Saint-Hilaire]] and on 20 April 1881, they married.<ref>{{Cite journal |last=Rollet |first=Laurent |date=2012-11-15 |title=Jeanne Louise Poulain d'Andecy, épouse Poincaré (1857–1934) |url=https://journals.openedition.org/sabix/1131 |journal=Bulletin de la Sabix. Société des amis de la Bibliothèque et de l'Histoire de l'École polytechnique |language=Fr |issue=51 |pages=18–27 |doi=10.4000/sabix.1131 |s2cid=190028919 |issn=0989-3059}}</ref> Together they had four children: Jeanne (born 1887), Yvonne (born 1889), Henriette (born 1891), and Léon (born 1893).

Poincaré immediately established himself among the greatest mathematicians of Europe, attracting the attention of many prominent mathematicians. In 1881 Poincaré was invited to take a teaching position at the Faculty of Sciences of the [[University of Paris]]; he accepted the invitation. During the years 1883 to 1897, he taught [[mathematical analysis]] in the [[École Polytechnique]].

In 1881–1882, Poincaré created a new branch of mathematics: [[qualitative theory of differential equations]]. He showed how it is possible to derive the most important information about the behavior of a family of solutions without having to solve the equation (since this may not always be possible). He successfully used this approach to problems in [[celestial mechanics]] and [[mathematical physics]].

===Career===
He never fully abandoned his career in the mining administration to mathematics. He worked at the [[Ministry of Public Services]] as an engineer in charge of northern railway development from 1881 to 1885. He eventually became chief engineer of the [[Corps des Mines]] in 1893 and inspector general in 1910.

Beginning in 1881 and for the rest of his career, he taught at the [[University of Paris]] (the [[University of Paris|Sorbonne]]). He was initially appointed as the ''maître de conférences d'analyse'' (associate professor of analysis).<ref>Sageret, 1911</ref> Eventually, he held the chairs of Physical and Experimental Mechanics, Mathematical Physics and Theory of Probability,<ref>{{cite book|first =Laurent|last= Mazliak|chapter= Poincaré’s Odds |title = Poincaré 1912–2012 : Poincaré Seminar 2012|editor1-first= B.|editor1-last= Duplantier |editor2-first= V.|editor2-last= Rivasseau|volume = 67 |series = Progress in Mathematical Physics|publisher = Springer|isbn = 9783034808347|location = Basel|page = 150|url = https://books.google.com/books?id=njNpBQAAQBAJ|date= 14 November 2014}}</ref> and Celestial Mechanics and Astronomy.

In 1887, at the young age of 32, Poincaré was elected to the [[French Academy of Sciences]]. He became its president in 1906, and was elected to the [[Académie française]] on 5 March 1908.

In 1887, he won [[Oscar II of Sweden|Oscar II, King of Sweden]]'s mathematical competition for a resolution of the [[three-body problem]] concerning the free motion of multiple orbiting bodies. (See [[#Three-body problem|three-body problem]] section below.)

In 1893, Poincaré joined the French [[Bureau des Longitudes]], which engaged him in the [[Clock synchronization|synchronisation of time]] around the world. In 1897 Poincaré backed an unsuccessful proposal for the [[Decimal degrees|decimalisation of circular measure]], and hence time and [[longitude]].<ref>see Galison 2003</ref> It was this post which led him to consider the question of establishing international time zones and the synchronisation of time between bodies in relative motion. (See [[#Work on relativity|work on relativity]] section below.)

In 1904, he intervened in the [[Dreyfus affair|trials]] of [[Alfred Dreyfus]], attacking the spurious scientific claims regarding evidence brought against Dreyfus.

Poincaré was the President of the [[Société astronomique de France|Société Astronomique de France (SAF)]], the French astronomical society, from 1901 to 1903.<ref name=BSAF1911>{{cite web| url = http://gallica.bnf.fr/ark:/12148/bpt6k9626551q/f616.item| title = ''Bulletin de la Société astronomique de France'', 1911, vol. 25, pp. 581–586| year = 1911}}</ref>

====Students====
Poincaré had two notable doctoral students at the University of Paris, [[Louis Bachelier]] (1900) and [[Dimitrie Pompeiu]] (1905).<ref>[http://www.genealogy.ams.org/id.php?id=34227 Mathematics Genealogy Project] {{Webarchive|url=https://web.archive.org/web/20071005011853/http://www.genealogy.ams.org/id.php?id=34227 |date=5 October 2007 }} North Dakota State University. Retrieved April 2008.</ref>

=== Death ===

In 1912, Poincaré underwent surgery for a [[prostate]] problem and subsequently died from an [[embolism]] on 17 July 1912, in Paris. He was 58 years of age. He is buried in the Poincaré family vault in the [[Cimetière du Montparnasse|Cemetery of Montparnasse]], Paris, in section 16 close to the gate Rue Émile-Richard.

A former French Minister of Education, [[Claude Allègre]], proposed in 2004 that Poincaré be reburied in the [[Panthéon, Paris|Panthéon]] in Paris, which is reserved for French citizens of the highest honour.<ref>{{cite web |url = http://www.lexpress.fr/idees/tribunes/dossier/allegre/dossier.asp?ida=430274 |title = Lorentz, Poincaré et Einstein |archive-url=https://web.archive.org/web/20041127160356/http://www.lexpress.fr/idees/tribunes/dossier/allegre/dossier.asp?ida=430274 |archive-date=27 November 2004 |url-status=dead}}</ref>[[File:Poincaré gravestone.jpg|upright|thumb|The Poincaré family grave at the [[Cimetière du Montparnasse]]]]