**Henri Poincaré** (April 29, 1854 - July 17, 1912) full name **Jules Henri Poincaré ** was one of France's greatest theoretical scientists.. He made many original fundamental contributions to 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 and laid the foundations of modern Chaos theory. Poincaré anticipated Albert Einstein’s work and sketched a preliminary version of the special theory of relativity.

Table of contents |

2 Life 3 Character 4 Quotations 5 Related articles 6 Publications 7 References 8 External Links |

- algebraic topology
- the theory of analytic functions of several complex variables
- the theory of abelian functions
- algebraic geometry
- number theory
- the three-body problem
- the theory of diophantine equations
- the theory of electromagnetism
- the special theory of relativity

Poincaré studied mathematics at the École Polytechnique where he was a student of Charles Hermite, graduating in 1875. He went on to study at the École des Mines , continuing to study mathematics in addition to the mining engineering syllabus and received he degree of ordinary engineer in March 1879 .

As a graduate of the École des Mines he joined the Corps de Mines as an inspector for the Vesoul region in north east 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.

Soon after he was offered a post as junior lecturer in mathematics at Caen University. He never fully abandoned his mining career to mathematics however and became chief engineer of the Corps de Mines in 1893 and inspector general in 1910.

He began work on his doctoral thesis, which was in the field of differential equations. Poincaré devised a new way of studying the properties of these functions. 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.

Beginning in 1881 and for the rest of his career, he taught at the University of Paris, (the Sorbonne). There he held the chairs of Physical and Experimental Mechanics, Mathematical Physics and Theory of Probability, and Celestial Mechanics and Astronomy.

In 1885 Oscar II , King of Sweden sponsored a mathematical competition with a cash prize for a resolution of the question of how stable is the solar system, a variation of the three-body problem. While Poincaré did not succeed in giving a complete solution, his work was so impressive that in 1888 he was awarded the prize anyway. Poincaré found that the evolution of such a system is often chaotic in the sense that a small perturbation in the initial state such as a slight change in one body's initial position might lead to a radically different later state. If the slight change isn't detectable by our measuring instruments, then we won't be able to predict which final state will occur. 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."

At the young age of 32 in 1887 Poincaré was elected to the French Academy of Sciences, became its president in 1906, and was elected to the Académie française in 1909.

In 1893 he joined the French Bureau of Longitude which engaged him in the synchronisation of time around the world. In 1897 he backed an unsuccessful proposal for the decimalisation of circular measure and hence time and longitude. This work led him to consider how clocks moving at high speed with respect to each other could be synchronised. In 1898 in “ The Measure of Time” he formulated the principle of relativity, according to which no mechanical or electromagnetic experiment can discriminate between a state of uniform motion and a state of rest. In collaboration with the Dutch theorist Hendrik Lorenz he went on to push the physics of the time to the limit to explain the behaviour of fast moving electrons. It was Albert Einstein however, who was prepared to reconstruct the entire edifice of physics, who produced the successful new relativity model.

He was responsible for formulating one of the most famous problems in mathematics. Known as the Poincaré Conjecture it is a problem in topology and is still not fully resolved today.

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 Poincare underwent surgery for a prostate problem and subsequently died from an embolism on 17 July 1912.

He had an amazing memory and could state the page and line of any item in a text he had read. He was also able to remember verbatim by ear. He retained these abilities throughout his life.

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

He was however physically clumsy and artistically inept. He was always in a rush and disliked going back for changes or corrections.

- "It is the simple hypotheses of which one must be most wary; because these are the ones that have the most chances of passing unnoticed"
- Wikiquote - Quotes by Henri Poincaré in Wikiquotes

- "
*New Methods of Celestial Mechanics*" ISBN 1563961172 (3 vols., 1892-99; Eng. trans., 1967) - "
*Lessons of Celestial Mechanics*". (1905-10).

*Science and Hypothesis*, 1901.*The Value of Science*, 1904.*Science and Method*, 1908.

- Bell, E. T.;
*Men of Mathematics*, Simon & Schuster; ISBN 0671628186 (1986). - Peterson, Ivars;
*Newton's Clock: Chaos in the Solar System*; pub W. H. Freeman ; ISBN 0716727242 (1993). - Galison , Peter;
*Einstein’s Clocks, Poincare’s Maps*; Hodder & Stoughton; ISBN 034079447X (2003)

Review of Poincare’s mathematical achievements from the University of Tennessee at Martin, USA]

Henri Poincaré's student notebooks, 1870-1878at the University of Nancy, France

Time line of Poincare’s life from the University of Nancy, France (in French)

Poincare’s 1897 article "The Relativity of Space" in English translation