# Henri Poincaré

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Henri Poincaré

Infobox Scientist
box_width = 300px
name = Henri Poincaré

image_size = 250px
caption = Jules Henri Poincaré (1854-1912). Photograph from the frontispiece of the 1913 edition of "Last Thoughts."
birth_date = birth date|df=yes|1854|4|29
birth_place = Nancy, Lorraine, France
death_date = death date and age|df=yes|1912|7|17|1854|4|29
death_place = Paris, France
residence = France
citizenship =
nationality = French
ethnicity =
fields = Mathematician and physicist
workplaces = Corps des Mines
Caen University
La Sorbonne
Bureau des Longitudes
alma_mater = Lycée Nancy
École Polytechnique
École des Mines
doctoral_students = Louis Bachelier
Dimitrie Pompeiu
Mihailo Petrović
notable_students = Tobias Dantzig
known_for = Poincaré conjecture
Three-body problem
Topology
Special relativity
Poincaré–Hopf theorem
Poincaré duality
nowrap|Poincaré–Birkhoff–Witt theorem
Poincaré inequality
Hilbert–Poincaré series
Poincaré metric
Rotation number
Coining term 'Betti number'
Chaos theory
Sphere-world
Poincaré-Bendixson theorem
author_abbrev_bot =
author_abbrev_zoo =
influences = Lazarus Fuchs
influenced = Louis Rougier
George David Birkhoff
awards = nowrap|RAS Gold Medal (1900)
Sylvester Medal (1901)
Matteucci Medal (1905)
Bruce Medal (1911)
religion = Roman Catholic (until 1872)

footnotes = He was a cousin of Pierre Boutroux.

Jules Henri Poincaré (29 April 1854 &ndash; 17 July 1912) (IPA2|ˈʒyl ɑ̃ˈʁi pwɛ̃kaˈʁe [ [http://www.bartleby.com/61/wavs/3/P0400300.wav] Poincaré pronunciation example at Bartleby.com ] ) was a French mathematician and theoretical physicist, and a philosopher of science. Poincaré is often described as a polymath, and in mathematics as "The Last Universalist", since he excelled in all fields of the discipline as it existed during his lifetime.

As a mathematician and physicist, he made many original fundamental contributions to pure and applied mathematics, mathematical physics, and celestial mechanics. He was responsible for formulating the Poincaré conjecture, one of the most famous problems in mathematics. In his research on the three-body problem, Poincaré became the first person to discover a chaotic deterministic system which laid the foundations of modern chaos theory. He is considered to be one of the founders of the field of topology.

Poincaré introduced the modern principle of relativity and was the first to present the Lorentz transformations in their modern symmetrical form. Poincaré discovered the remaining relativistic velocity transformations and recorded them in a letter to Lorentz in 1905. Thus he obtained perfect invariance of all of Maxwell's equations, an important step in the formulation of the theory of special relativity.

The Poincaré group used in physics and mathematics was named after him.

Life

Poincaré was born on 29 April 1854 in Cité Ducale neighborhood, Nancy, France into an influential family (Belliver, 1956). His father Leon Poincaré (1828-1892) was a professor of medicine at the University of Nancy (Sagaret, 1911). His adored younger sister Aline married the spiritual philosopher Emile Boutroux. Another notable member of Jules' family was his cousin, Raymond Poincaré, who would become the President of France, 1913 to 1920, and a fellow member of the Académie française. [http://www.utm.edu/research/iep/p/poincare.htm The Internet Encyclopedia of Philosophy] Jules Henri Poincaré article by Mauro Murzi - accessed November 2006. ]

Education

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 (now renamed the Lycée Henri Poincaré in his honour, along with the University of 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" (O'Connor et al., 2002). However, poor eyesight and a tendency towards absentmindedness may explain these difficulties (Carl, 1968). He graduated from the Lycée in 1871 with a Bachelor's degree in letters and sciences.

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

Poincaré entered the École Polytechnique in 1873. 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. He graduated in 1875 or 1876. He went on to study at the École des Mines, continuing to study mathematics in addition to the mining engineering syllabus and received the degree of ordinary engineer in March 1879.

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 in August 1879 in which 18 miners died. He carried out the official investigation into the accident in a characteristically thorough and humane way.

At the same time, Poincaré was preparing for his doctorate in sciences 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 différences". 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. Poincaré graduated from the University of Paris in 1879.

Career

Soon after, he was offered a post as junior lecturer in mathematics at Caen University, but he never fully abandoned his mining career 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 de 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 Sorbonne). He was initially appointed as the "maître de conférences d'analyse" (associate professor of analysis) (Sageret, 1911). Eventually, he held the chairs of Physical and Experimental Mechanics, Mathematical Physics and Theory of Probability, and Celestial Mechanics and Astronomy.

Also in that same year, Poincaré married Miss Poulain d'Andecy. Together they had four children: Jeanne (born 1887), Yvonne (born 1889), Henriette (born 1891), and Léon (born 1893).

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 in 1909.

In 1887 he won 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 #The three-body problem section below)

In 1893 Poincaré joined the French Bureau des Longitudes, which engaged him in the synchronisation of time around the world. In 1897 Poincaré backed an unsuccessful proposal for the decimalisation of circular measure, and hence time and longitude (see Galison 2003). 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 section below)

In 1899, and again more successfully in 1904, he intervened in the trials of Alfred Dreyfus. He attacked the spurious scientific claims of some of the evidence brought against Dreyfus, who was a Jewish officer in the French army charged with treason by anti-Semitic colleagues.

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 Cemetery of Montparnasse, Paris.

The French Minister of Education, Claude Allegre, has recently (2004) proposed that Poincaré be reburied in the Panthéon in Paris, which is reserved for French citizens only of the highest honour. [ [http://www.lexpress.fr/idees/tribunes/dossier/allegre/dossier.asp?ida=430274 Lorentz, Poincaré et Einstein - L'Express ] ]

tudents

Poincaré had two notable doctoral students at the University of Paris, Louis Bachelier (1900) and Dimitrie Pompeiu (1905). [ [http://www.genealogy.ams.org/id.php?id=34227 Mathematics Genealogy Project] North Dakota State University, Accessed April 2008]

Work

ummary

Poincaré made many contributions to different fields of pure and applied mathematics such as: celestial mechanics, fluid mechanics, optics, electricity, telegraphy, capillarity, elasticity, thermodynamics, potential theory, quantum theory, theory of relativity and physical cosmology.

He was also a populariser of mathematics and physics and wrote several books for the lay public.

Among the specific topics he contributed to are the following:
*algebraic topology
*the theory of analytic functions of several complex variables
*the theory of abelian functions
*algebraic geometry
*Poincaré was responsible for formulating one of the most famous problems in mathematics. Known as the Poincaré conjecture, it is a problem in topology.
*Poincaré recurrence theorem
*Hyperbolic geometry
*number theory
*the three-body problem
*the theory of diophantine equations
*the theory of electromagnetism
*the special theory of relativity
*In an 1894 paper, he introduced the concept of the fundamental group.
*In the field of differential equations Poincaré has given many results that are critical for the qualitative theory of differential equations, for example the Poincaré sphere and the Poincaré map.
*Poincaré on "everybody's belief" in the [http://en.wikiquote.org/wiki/Henri_Poincaré "Normal Law of Errors"] (see normal distribution for an account of that "law")
*Published an influential paper providing a novel mathematical argument in support of quantum mechanics.Citation
last =McCormmach
first =Russell
title = Henri Poincaré and the Quantum Theory
journal = Isis
volume = 58
issue = 1
pages = 37–55
date = Spring, 1967
doi =10.1086/350182
] Citation
last =Irons
first =F. E.
title = Poincaré's 1911–12 proof of quantum discontinuity interpreted as applying to atoms
journal = American Journal of Physics
volume = 69
issue = 8
pages = 879–884
date = August, 2001
doi =10.1119/1.1356056
]

The three-body problem

The problem of finding the general solution to the motion of more than two orbiting bodies in the solar system had eluded mathematicians since Newton's time. This was known originally as the three-body problem and later the "n"-body problem, where "n" is any number of more than two orbiting bodies. The "n"-body solution was considered very important and challenging at the close of the nineteenth century. Indeed in 1887, in honour of his 60th birthday, Oscar II, King of Sweden, advised by Gösta Mittag-Leffler, established a prize for anyone who could find the solution to the problem. The announcement was quite specific:

In case the problem could not be solved, any other important contribution to classical mechanics would then be considered to be prizeworthy. The prize was finally awarded to Poincaré, even though he did not solve the original problem. One of the judges, the distinguished Karl Weierstrass, said, "This work cannot indeed be considered as furnishing the complete solution of the question proposed, but that it is nevertheless of such importance that its publication will inaugurate a new era in the history of celestial mechanics."(The first version of his contribution even contained a serious error; for details see the article by Diacu). The version finally printed contained many important ideas which lead to the theory of chaos. The problem as stated originally was finally solved by Karl F. Sundman for "n" = 3 in 1912 and was generalised to the case of "n" > 3 bodies by Qiudong Wang in the 1990s.

Work on relativity

Local time

Poincaré's work at the Bureau des Longitudes on establishing international time zones led him to consider how clocks at rest on the Earth, which would be moving at different speeds relative to absolute space (or the "luminiferous aether"), could be synchronised. At the same time Dutch theorist Hendrik Lorentz was developing Maxwell's theory into a theory of the motion of charged particles ("electrons" or "ions"), and their interaction with radiation. He had introduced in 1895 an auxiliary quantity (without physical interpretation) called "local time" $t^prime = t-vx^prime/c^2$, where $x^prime = x - vt$ and introduced the hypothesis of length contraction to explain the failure of optical and electrical experiments to detect motion relative to the aether (see Michelson-Morley experiment). [Citation
author=Lorentz, H.A. | year=1895 | title= [http://www.historyofscience.nl/search/detail.cfm?pubid=2690&view=image&startrow=1 Versuch einer theorie der electrischen und optischen erscheinungen in bewegten Kõrpern] | place =Leiden| publisher=E.J. Brill
] Poincaré was a constant interpreter (and sometimes friendly critic) of Lorentz's theory. Poincaré as a philosopher, was interested in the "deeper meaning". Thus he interpreted Lorentz's theory and in so doing he came up with many insights that are now associated with special relativity. In (1898), Poincaré discussed the difficulty of establishing simultaneity at a distance and concluded it can be established by convention. He also argued, that scientists have to set the constancy of the speed of light as a postulate to give physical theories the simplest form. [Citation
author=Poincaré, H. | year=1898 | title= [http://www.univ-nancy2.fr/poincare/bhp/ La mesure du temps] | journal=Revue de métaphysique et de morale | volume =6 | pages =1–13
Reprinted as in "The Value of Science", Ch. 2.
] Based on these assumptions he discussed in 1900 Lorentz's "wonderful invention" of local time and remarked that it arose when moving clocks are synchronised by exchanging light signals assumed to travel with the same speed in both directions in a moving frame.Citation
author=Poincaré, H. | year=1900 | title= [http://www.soso.ch/wissen/hist/SRT/P-1900.pdf La théorie de Lorentz et le principe de réaction] | journal=Archives néerlandaises des sciences exactes et naturelles | volume =5 | pages =252–278
. Reprinted in Poincaré, Oeuvres, tome IX, pp. 464-488. See also the [http://www.physicsinsights.org/poincare-1900.pdf English translation] ]

Principle of relativity and Lorentz transformations

He discussed the "principle of relative motion" in two papers in 1900 [Citation
author=Poincaré, H. | year=1900 | title= [http://gallica.bnf.fr/ark:/12148/bpt6k17075r/f1167.table Les relations entre la physique expérimentale et la physique mathématique] | journal=Revue générale des sciences pures et appliquées | volume =11 | pages =1163–1175
. Reprinted in "Science and Hypothesis", Ch. 9-10.
] and named it the principle of relativity in 1904, according to which no mechanical or electromagnetic experiment can discriminate between a state of uniform motion and a state of rest. Citation
author=Poincaré, Henri
year=1904
title=L'état actuel et l'avenir de la physique mathématique
journal=Bulletin des sciences mathématiques
volume=28
issue=2
pages=302-324
. English translation in Citation
author=Poincaré, Henri
year=1905
chapter=The Principles of Mathematical Physics
editor=Rogers, Howard J.
title=Congress of arts and science, universal exposition, St. Louis, 1904
volume=1
pages=604-622
publisher=Houghton, Mifflin and Company
place=Boston and New York
chapterurl=http://en.wikisource.org/wiki/The_Principles_of_Mathematical_Physics
Reprinted in "The value of science", Ch. 7-9.] In 1905 Poincaré wrote to Lorentz about Lorentz's paper of 1904, which Poincaré described as a "paper of supreme importance." In this letter he pointed out an error Lorentz had made when he had applied his transformation to one of Maxwell's equations, that for charge-occupied space, and also questioned the time dilation factor given by Lorentz. [ [http://www.univ-nancy2.fr/poincare/chp/text/lorentz3.xml Letter from Poincaré to Lorentz, Mai 1905] ] In a second letter to Lorentz, Poincaré gave his own reason why Lorentz's time dilation factor was indeed correct after all: it was necessary to make the Lorentz transformation form a group and gave what is now known as the relativistic velocity-addition law. [ [http://www.univ-nancy2.fr/poincare/chp/text/lorentz4.xml Letter from Poincaré to Lorentz, Mai 1905] ] Poincaré later delivered a paper at the meeting of the Academy of Sciences in Paris on 5 June 1905 in which these issues were addressed. In the published version of that he wroteCitation | author=Poincaré, H. | year=1905b | title= [http://www.univ-nancy2.fr/poincare/bhp/ Sur la dynamique de l'électron] | journal=Comptes Rendus | volume =140 | pages =1504–1508 Reprinted in Poincaré, Oeuvres, tome IX, S. 489-493.] :

cquote|1=The essential point, established by Lorentz, is that the equations of the electromagnetic field are not altered by a certain transformation (which I will call by the name of Lorentz) of the form:::$x^prime = kellleft\left(x + varepsilon t ight\right),~$$t^prime = kellleft\left(t + varepsilon x ight\right),~$$y^prime = ell y,~$ $z^prime = ell z,~$$k = 1/sqrt\left\{1-varepsilon^2\right\}.$

and showed that the arbitrary function $ellleft\left(varepsilon ight\right)$ must be unity for all $varepsilon$ (Lorentz had set $ell = 1$ by a different argument) to make the transformations form a group. In an enlarged version of the paper that appeared in 1906 Poincaré pointed out that the combination $x^2+ y^2+ z^2- c^2t^2$ is invariant. He noted Lorentz transformation is merely a rotation in four-dimensional space about the origin by introducing $ctsqrt\left\{-1\right\}$ as a fourth imaginary coordinate, and he used an early form of four-vectors.Citation
author=Poincaré, H. | year=1906 | title= [http://www.soso.ch/wissen/hist/SRT/P-1905.pdf Sur la dynamique de l'électron] | journal=Rendiconti del Circolo matematico Rendiconti del Circolo di Palermo | volume =21 | pages =129–176
Reprinted in Poincaré, Oeuvres, tome IX, pages 494-550. Partial English translation in [http://www.univ-nancy2.fr/poincare/bhp/ Dynamics of the electron] .] Poincaré’s attempt of a four-dimensional reformulation of the new mechanics was rejected by himself in 1907, because in his opinion the translation of physics into the language of four-dimensional metry would entail too much effort for limited profit. [Walter (2007), Secondary sources on relativity] So it was Hermann Minkowski, who worked out the consequences of this notion in 1907.

Mass-energy relation

Like others before, Poincaré (1900) discovered a relation between mass and electromagnetic energy. While studying the conflict between the action/reaction principle and Lorentz ether theory, he tried to determine whether the center of gravity still moves with a uniform velocity when electromagnetic fields are included. He noticed that the action/reaction principle does not hold for matter alone, but that the electromagnetic field has its own momentum. Poincaré concluded that the electromagnetic field energy of an electromagnetic wave behaves like a fictitious fluid ("fluide fictif") with a mass density of "E/c²". If the center of mass frame is defined by both the mass of matter "and" the mass of the fictitious fluid, and if the fictitious fluid is indestructible — it's neither created or destroyed — then the motion of the center of mass frame remains uniform. But electromagnetic energy can be converted into other forms of energy. So Poincaré assumed that there exists a non-electric energy fluid at each point of space, into which electromagnetic energy can be transformed and which also carries a mass proportional to the energy. In this way, the motion of the center of mass remains uniform. Poincaré said that one should not be too surprised by these assumptions, since they are only mathematical fictions.

However, Poincaré's resolution led to a paradox when changing frames: if a Hertzian oscillator radiates in a certain direction, it will suffer a recoil from the inertia of the fictitious fluid. Poincaré performed a Lorentz boost (to order v/c) to the frame of the moving source. He noted that energy conservation holds in both frames, but that the law of conservation of momentum is violated. This would allow perpetual motion, a notion which he abhorred. The laws of nature would have to be different in the frames of reference, and the relativity principle would not hold. Therefore he argued that also in this case there has to be another compensating mechanism in the ether.

Poincaré himself came back to this topic in his St. Louis lecture (1904). This time (and later also in 1908) he rejected [Miller 1981, Secondary sources on relativity] the possibility that energy carries mass and also the possibility, that motions in the ether can compensate the above mentioned problems:

He also discussed two other unexplained effects: (1) non-conservation of mass implied by Lorentz's variable mass $gamma m$, Abraham's theory of variable mass and Kaufmann's experiments on the mass of fast moving electrons and (2) the non-conservation of energy in the radium experiments of Madame Curie.

It was Albert Einstein's concept of mass–energy equivalence (1905) that a body losing energy as radiation or heat was losing mass of amount $m = E/c^2$ that resolvedDarrigol 2005, Secondary sources on relativity] Poincare's paradox, without using any compensating mechanism within the ether. [Citation | author=Einstein, A. | year=1905b | title= [http://www.physik.uni-augsburg.de/annalen/history/papers/1905_18_639-641.pdf Ist die Trägheit eines Körpers von dessen Energieinhalt abhängig?] | journal=Annalen der Physik | volume =18 | pages =639–643. See also [http://www.fourmilab.ch/etexts/einstein/specrel/www English translation] .] The Hertzian oscillator loses mass in the emission process, and momentum is conserved in any frame. However, concerning Poincaré's solution of the Center of Gravity problem, Einstein noted that Poincaré's formulation and his own from 1906 were mathematically equivalent. [Citation | author=Einstein, A. | year=1906 | title= [http://www.physik.uni-augsburg.de/annalen/history/papers/1906_20_627-633.pdf Das Prinzip von der Erhaltung der Schwerpunktsbewegung und die Trägheit der Energie] | journal=Annalen der Physik | volume =20 | pages =627–633 | doi=10.1002/andp.19063250814]

Poincaré and Einstein

Einstein's first paper on relativity was published three months after Poincaré's short paper, but before Poincaré's longer version. It relied on the principle of relativity to derive the Lorentz transformations and used a similar clock synchronisation procedure (Einstein synchronisation) that Poincaré (1900) had described, but was remarkable in that it contained no references at all. Poincaré never acknowledged Einstein's work on Special Relativity. Einstein acknowledged Poincaré in the text of a lecture in 1921 called "Geometrie und Erfahrung" in connection with Non-Euclidean geometry, but not in connection with special relativity. A few years before his death Einstein commented on Poincaré as being one of the pioneers of relativity, saying "Lorentz had already recognised that the transformation named after him is essential for the analysis of Maxwell's equations, and Poincaré deepened this insight still further ..." [Darrigol 2004, Secondary sources on relativity]

Assessments

Poincaré's work in the development of special relativity is well recognised, though most historians stress that despite many similarities with Einstein's work, the two had very different research agendas and interpretations of the work. [Galison 2003 and Kragh 1999, Secondary sources on relativity] Poincaré developed a similar physical interpretation of local time and noticed the connection to signal velocity, but contrary to Einstein he continued to use the ether-concept in his papers and argued that clocks in the ether show the "true" time, and moving clocks show the "apparent" time. A minority go much further, such as E.T. Whittaker, who held that Poincaré and Lorentz were the true discoverers of Relativity. [Whittaker 1953, Secondary sources on relativity] . See → Relativity priority dispute.

Poincaré consistently credited Lorentz's achievements, ranking his own contributions as minor. Thus, he wrote:

In an address in 1909 on "The New Mechanics", Poincaré discussed the demolition of Newton's mechanics brought about by Max Abraham and Lorentz, without mentioning Einstein. In one of his last essays entitled "The Quantum Theory" (1913), when referring to the Solvay Conference, Poincaré again described special relativity as the "mechanics of Lorentz" [See Poincaré, Last Essays (1913)] :

On the other hand, in a memoir written as a tribute after Poincaré's death, Lorentz readily admitted the mistake he had made and credited Poincaré's achievements [Citation | author=Lorentz, H.A. | year=1921 | title= [http://www.new.dli.ernet.in/scripts/FullindexDefault.htm?path1=/data/upload/0050/246&first=702&last=724&barcode=1990050050241 Deux Memoirs de Henri Poincaré sur la Physique Mathematique] |journal=Acta Mathematica | volume=38 | pages =293–308 | doi=10.1007/BF02392073 Reprinted in Poincaré, [http://www.archive.org/details/ceuvresdeehenrip027739mbp Oeuvres tome XI] , S. 247-261.] :

In summary, Poincaré regarded the mechanics as developed by Lorentz in order to obey the principle of relativity as the essence of the theory, while Lorentz stressed that perfect invariance was first obtained by Poincaré. The modern view is inclined to say that the group property and the invariance are the essential points.

Character

Poincaré's work habits have been compared to a bee flying from flower to flower. Poincaré was interested in the way his mind worked; he studied his habits and gave a talk about his observations in 1908 at the Institute of General Psychology in Paris. He linked his way of thinking to how he made several discoveries.

The mathematician Darboux claimed he was "un intuitif" (intuitive), arguing that this is demonstrated by the fact that he worked so often by visual representation. He did not care about being rigorous and disliked logic. He believed that logic was not a way to invent but a way to structure ideas and that logic limits ideas.

Toulouse' characterisation

Poincaré's mental organisation was not only interesting to Poincaré himself but also to Toulouse, a psychologist of the Psychology Laboratory of the School of Higher Studies in Paris. Toulouse wrote a book entitled "Henri Poincaré" (1910). In it, he discussed Poincaré's regular schedule:

* He worked during the same times each day in short periods of time. He undertook mathematical research for four hours a day, between 10 a.m. and noon then again from 5 p.m. to 7 p.m.. He would read articles in journals later in the evening.

* His normal work habit was to solve a problem completely in his head, then commit the completed problem to paper.

* He was ambidextrous and nearsighted.

* His ability to visualise what he heard proved particularly useful when he attended lectures, since his eyesight was so poor that he could not see properly what the lecturer wrote on the blackboard.

These abilities were offset to some extent by his shortcomings:

* He was physically clumsy and artistically inept.

* He was always in a rush and disliked going back for changes or corrections.

* He never spent a long time on a problem since he believed that the subconscious would continue working on the problem while he consciously worked on another problem.

In addition, Toulouse stated that most mathematicians worked from principles already established while Poincaré started from basic principles each time (O'Connor et al., 2002).

His method of thinking is well summarised as:

:"Habitué à négliger les détails et à ne regarder que les cimes, il passait de l'une à l'autre avec une promptitude surprenante et les faits qu'il découvrait se groupant d'eux-mêmes autour de leur centre étaient instantanément et automatiquement classés dans sa mémoire."("Accustomed to neglecting details and to looking only at mountain tops, he went from one peak to another with surprising rapidity, and the facts he discovered, clustering around their center, were instantly and automatically pigeonholed in his memory.") Belliver (1956)

hortcomings

Despite his great genius, Poincaré was resistant to contributions from mathematicians like Georg Cantor and saw mathematical work in economics and finance as peripheral. In 1900 Poincaré commented on Louis Bachelier's thesis "The Theory of Speculation", saying: "M. Bachelier has evidenced an original and precise mind [but] the subject is somewhat remote from those our other candidates are in the habit of treating." (Bernstein, 1996, p.199-200) However, Bachelier's work explained what was then the French government's pricing options on French Bonds and anticipated many of the pricing theories in financial markets used even today. [cite book |title= INVENTING MONEY |last= Dunbar|first= Nicholas|authorlink= Nicholas Dunbar|publisher= JOHN WILEY & SONS, LTD|isbn= 0-471-49811-4]

Honours

Awards
* Oscar II, King of Sweden's mathematical competition (1887)
* American Philosophical Society 1899
*Gold Medal of the Royal Astronomical Society of London (1900)
*Bolyai prize in 1905
* Matteucci Medal 1905
*Bruce Medal (1911)

Named after him
*Poincaré Prize (Mathematical Physics International Prize)
*Annales Henri Poincaré (Scientific Journal)
*Poincaré Seminar (nicknamed "Bourbaphy")
*Poincaré crater (on the Moon)
*Asteroid 2021 Poincaré

Philosophy

Poincaré had philosophical views opposite to those of Bertrand Russell and Gottlob Frege, who believed that mathematics was a branch of logic. Poincaré strongly disagreed, claiming that intuition was the life of mathematics. Poincaré gives an interesting point of view in his book "Science and Hypothesis":

:"For a superficial observer, scientific truth is beyond the possibility of doubt; the logic of science is infallible, and if the scientists are sometimes mistaken, this is only from their mistaking its rule."

Poincaré believed that arithmetic is a synthetic science. He argued that Peano's axioms cannot be proven non-circularly with the principle of induction (Murzi, 1998), therefore concluding that arithmetic is "a priori" synthetic and not analytic. Poincaré then went on to say that mathematics cannot be deduced from logic since it is not analytic. His views were similar to those of Immanuel Kant (Kolak, 2001, Folina 1992). He strongly opposed Cantorian set theory, objecting to its use of impredicative definitions.

However Poincaré did not share Kantian views in all branches of philosophy and mathematics. For example, in geometry, Poincaré believed that the structure of non-Euclidean space can be known analytically. Poincaré held that convention plays an important role in physics. His view (and some later, more extreme versions of it) came to be known as "conventionalism". Poincaré believed that Newton's first law was not empirical but is a conventional framework assumption for mechanics. He also believed that the geometry of physical space is conventional. He considered examples in which either the geometry of the physical fields or gradients of temperature can be changed, either describing a space as non-Euclidean measured by rigid rulers, or as a Euclidean space where the rulers are expanded or shrunk by a variable heat distribution. However, Poincaré thought that we were so accustomed to Euclidean geometry that we would prefer to change the physical laws to save Euclidean geometry rather than shift to a non-Euclidean physical geometry. Fact|date=February 2008

ee also

*Poincaré–Bendixson theorem
*Poincaré–Birkhoff–Witt theorem
*Poincaré half-plane model
*Poincaré symmetry
*Poincaré–Hopf theorem
*Poincaré metric
*Poincaré duality
*Poincaré group
*Poincaré map
*Institut Henri Poincaré, Paris
*History of special relativity
*Relativity priority dispute
*Poincaré Conjecture

References

Footnotes and primary sources

Poincaré's Writings in English translation

Popular writings on the philosophy of science:
*1902. Citation | title= [http://www.archive.org/details/scienceandhypoth00poinuoft Science and hypothesis.] |place=London and Newcastle-on-Cyne |publisher=The Walter Scott publishing Co.
*1905. Citation | title= [http://hdl.handle.net/2027/mdp.39015002454455 The value of science.] | place=New York | publisher=Dover reprint, 1958
*1908. Citation | title= [http://www.ac-nancy-metz.fr/enseign/philo/textesph/Scienceetmethode.pdf Science et Methode (in French).]
*1913. Citation | title= [http://www.archive.org/details/mathematicsandsc001861mbp Last Essays.] |place=New York |publisher=Dover reprint, 1963

On algebraic topology:
* 1895. "Analysis situs". The first systematic study of topology.

On celestial mechanics:
* 1892-99. "New Methods of Celestial Mechanics", 3 vols. English trans., 1967. ISBN 1563961172.
* 1905-10. "Lessons of Celestial Mechanics".

On the philosophy of mathematics:
** Ewald, William B., ed., 1996. "From Kant to Hilbert: A Source Book in the Foundations of Mathematics", 2 vols. Oxford Univ. Press. Contains the following works by Poincaré:
**1894, "On the nature of mathematical reasoning," 972-81.
**1898, "On the foundations of geometry," 982-1011.
**1900, "Intuition and Logic in mathematics," 1012-20.
**1905-06, "Mathematics and Logic, I-III," 1021-70.
**1910, "On transfinite numbers," 1071-74.

General references

* Bell, Eric Temple, 1986. "Men of Mathematics" (reissue edition). Touchstone Books. ISBN 0671628186.
* Belliver, André, 1956. "Henri Poincaré ou la vocation souveraine". Paris: Gallimard.
*Bernstein, Peter L, 1996. "Against the Gods: A Remarkable Story of Risk". (p. 199-200). John Wiley & Sons.
* Boyer, B. Carl, 1968. "A History of Mathematics: Henri Poincaré", John Wiley & Sons.
* Grattan-Guinness, Ivor, 2000. "The Search for Mathematical Roots 1870-1940." Princeton Uni. Press.
* Folina, Janet, 1992. "Poincare and the Philosophy of Mathematics." Macmillan, New York.
* Gray, Jeremy, 1986. "Linear differential equations and group theory from Riemann to Poincaré", Birkhauser
* Kolak, Daniel, 2001. "Lovers of Wisdom", 2nd ed. Wadsworth.
* Murzi, 1998. [http://www.iep.utm.edu/p/poincare.htm "Henri Poincaré"] .
* O'Connor, J. John, and Robertson, F. Edmund, 2002, [http://www-history.mcs.st-andrews.ac.uk/Mathematicians/Poincare.html "Jules Henri Poincaré"] . University of St. Andrews, Scotland.
* Peterson, Ivars, 1995. "Newton's Clock: Chaos in the Solar System" (reissue edition). W H Freeman & Co. ISBN 0716727242.
* Sageret, Jules, 1911. "Henri Poincaré". Paris: Mercure de France.
* Toulouse, E.,1910. "Henri Poincaré". - (Source biography in French)

econdary sources to work on relativity

*

*

*

*

*

*

*Citation | author=Holton, G. | year=1973/1988 | chapter=Poincaré and Relativity| title= Thematic Origins of Scientific Thought: Kepler to Einstein | publisher=Harvard University Press|isbn=0674877470

*

*

*

*

*Citation|author=Miller, A.I. |title=A study of Henri Poincaré's "Sur la Dynamique de l'Electron |year=1973 |journal=Arch. Hist. Exact. Scis.|volume=10|pages=207–328|doi=10.1007/BF00412332

*

*Citation| author=Miller, A.I. |contribution= Why did Poincaré not formulate special relativity in 1905? |year=1996 |editor=Jean-Louis Greffe, Gerhard Heinzmann, Kuno Lorenz| title=Henri Poincaré : science et philosophie| pages=69–100|place=Berlin

*

*

*

*

*Citation| author=Zahar, E. |year=2001 |title=Poincare's Philosophy: From Conventionalism to Phenomenology| |publisher=Open Court Pub Co|place=Chicago|isbn=081269435X

;Non-mainstream

*

*

*

*

*

*Online English translations of whole works by Poincaré:
**" [http://www.carlmanchester.net/poincare The Sciences and the Humanities.] "
**" [http://www.brocku.ca/MeadProject/Poincare/Poincare_1905_toc.html Science and Hypothesis.] "
*gutenberg author| id=Henri+Poincaré | name=Henri Poincaré
* [http://librivox.org/science-and-hypothesis-by-henri-poincare/ Free audio download of Poincaré's "Science and Hypothesis"] , from LibriVox.
*Internet Encyclopedia of Philosophy: " [http://www.utm.edu/research/iep/p/poincare.htm Henri Poincare] "--by Mauro Murzi.
*
*
* [http://www.univ-nancy2.fr/ACERHP/documents/kronowww.html A timeline of Poincaré's life] University of Nancy (in French).
* [http://phys-astro.sonoma.edu/brucemedalists/Poincare/index.html Bruce Medal page]
*Collins, Graham P., " [http://www.sciam.com/print_version.cfm?articleID=0003848D-1C61-10C7-9C6183414B7F0000 Henri Poincaré, His Conjecture, Copacabana and Higher Dimensions,] " "Scientific American", 9 June 2004.
*BBC In Our Time, " [http://www.bbc.co.uk/radio4/history/inourtime/inourtime.shtml Discussion of the Poincaré conjecture,] " 2 November 2006, hosted by Melvynn Bragg. [http://web.archive.org/web/*/http://www.bbc.co.uk/radio4/history/inourtime/inourtime.shtml See Internet Archive]
* [http://www.mathpages.com/home/kmath305/kmath305.htm Poincare Contemplates Copernicus] at MathPages

Persondata
NAME= Poincaré, Henri
ALTERNATIVE NAMES= Poincaré, Jules
SHORT DESCRIPTION= Mathematician and physicist
DATE OF BIRTH= 29 April 1854
PLACE OF BIRTH= Nancy, Lorraine, France
DATE OF DEATH= 17 July 1912
PLACE OF DEATH= Paris, France

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