Jean François Chazy (15 August 1882,

Villefranche-sur-Saône Villefranche-sur-Saône (, ; frp, Velafranche) is a commune in the Rhône department in eastern France. It lies 1 mile (1.6 km) west of the river Saône, and is around north of Lyon. The inhabitants of the town are called ''Caladois''. Hi ...

– 9 March 1955,

Paris Paris () is the capital and most populous city of France, with an estimated population of 2,165,423 residents in 2019 in an area of more than 105 km² (41 sq mi), making it the 30th most densely populated city in the world in 2020. S ...

) was a French

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, structure, space, models, and change. History On ...

and

astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, natural satellite, moons, comets and galaxy, g ...

Life

Chazy was the son of a small provincial manufacturer and studied mathematics at the

École Normale Supérieure École may refer to: * an elementary school in the French educational stages normally followed by secondary education establishments (collège and lycée) * École (river), a tributary of the Seine flowing in région Île-de-France * École, Savoi ...

with completion of the

agrégation In France, the ''agrégation'' () is a competitive examination for civil service in the French public education system. Candidates for the examination, or ''agrégatifs'', become ''agrégés'' once they are admitted to the position of ''professe ...

in 1905. He received his doctorate in 1910 with thesis ''Équations différentielles du troisième ordre et d’ordre supérieur dont l’intégrale générale a ses points critiques fixes''. In 1911 he was ''

maître de conférences ''Maître'' (spelled ''Maitre'' according to post-1990 spelling rules) is a commonly used honorific for lawyers, judicial officers and notaries in France, Belgium, Switzerland and French-speaking parts of Canada. It is often written in its abbrev ...

'' for mechanics in

Grenoble lat, Gratianopolis , commune status = Prefecture and commune , image = Panorama grenoble.png , image size = , caption = From upper left: Panorama of the city, Grenoble’s cable cars, place Saint- ...

and then in

Lille Lille ( , ; nl, Rijsel ; pcd, Lile; vls, Rysel) is a city in the northern part of France, in French Flanders. On the river Deûle, near France's border with Belgium, it is the capital of the Hauts-de-France Regions of France, region, the Pref ...

. In World War I he served in the artillery and became famous for accurately predicting the location of the German siege gun which bombarded Paris. After the war he was again professor in the ''Faculté des Sciences de Lille'' (which later became the

Lille University of Science and Technology , image_name = Lilliad Learning Center Innovation.jpg , image_size = , caption = Université de Lille I , established = 1559, 1854, 1970 , type = Public: science and technology , president ...

). Simultaneously he taught at the ''Institut industriel du Nord'' (

École Centrale de Lille Located in the campus of Science and Technology (Cité Scientifique) of the University of Lille in Villeneuve-d'Ascq ( European Metropolis of Lille - Hauts-de-France); École Centrale de Lille is a renowned graduate engineering school, with roots ...

). In 1923 he was ''maître de conférences'' at the ''

École centrale des arts et manufactures École may refer to: * an elementary school in the French educational stages normally followed by secondary education establishments (collège and lycée) * École (river), a tributary of the Seine flowing in région Île-de-France * École, Savoi ...

'' in Paris (as well as examiner at the ''École polytechnique''). In 1924 he became professor for mechanics and later for celestial mechanics at the

Sorbonne Sorbonne may refer to: * Sorbonne (building), historic building in Paris, which housed the University of Paris and is now shared among multiple universities. *the University of Paris (c. 1150 – 1970) *one of its components or linked institution, ...

, where he retired in 1953 as professor emeritus.

Work

He worked on celestial mechanics and especially on the

three-body problem In physics and classical mechanics, the three-body problem is the problem of taking the initial positions and velocities (or momenta) of three point masses and solving for their subsequent motion according to Newton's laws of motion and Newton's ...

and the

perihelion precession In celestial mechanics, apsidal precession (or apsidal advance) is the precession (gradual rotation) of the line connecting the apsides (line of apsides) of an astronomical body's orbit. The apsides are the orbital points closest (periapsi ...

Mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...

's orbit. The problem of explaining Mercury's orbit was solved by

Albert Einstein Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theory ...

general relativity theory General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics. G ...

Honors

In 1922 Chazy was awarded the

Valz Prize The Valz Prize ''(Prix Valz)'' was awarded by the French Academy of Sciences, from 1877 through 1970, to honor advances in astronomy. History The Valz Prize was established in June 1874 when the widow of astronomer Benjamin Valz, Marie Madeleine J ...

from the

French Academy of Sciences The French Academy of Sciences (French: ''Académie des sciences'') is a learned society, founded in 1666 by Louis XIV of France, Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French Scientific me ...

for his papers on the

. He was an Invited Speaker of the ICM in 1924 at Toronto and in 1928 at Bologna. In 1937 he was elected to the ''

Académie des Sciences The French Academy of Sciences (French: ''Académie des sciences'') is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research. It was at the ...

'' in the ''Astronomie'' section. He was also a member of the Romanian Academy of Sciences and a member of the Belgian Academy of Sciences. In 1934 he was president of the ''

Société Mathématique de France Lactalis is a French multinational dairy products corporation, owned by the Besnier family and based in Laval, Mayenne, France. The company's former name was Besnier SA. Lactalis is the largest dairy products group in the world, and is the sec ...

''. Since 1952 he was an official member of the ''

Bureau des Longitudes Bureau ( ) may refer to: Agencies and organizations *Government agency *Public administration * News bureau, an office for gathering or distributing news, generally for a given geographical location * Bureau (European Parliament), the administrat ...

''. He was made a commander of the ''

Légion d'honneur The National Order of the Legion of Honour (french: Ordre national de la Légion d'honneur), formerly the Royal Order of the Legion of Honour ('), is the highest French order of merit, both military and civil. Established in 1802 by Napoleon ...

''.

Selected works

*''La théorie de la relativité et la mécanique céleste'', vol. 1, 1928, vol. 2, 1930, Gauthier-Villars, Paris *''Cours de mécanique rationnelle'', 2 vols., Gauthier-Villars 1933, new edns, 1941/42, 1948, 1952 *''Mécanique céleste: équations canoniques et variation des constantes'', Presses Universitaires de France, Coll. Euclide, Paris 1953

References

External links

Darmois ''Notice sur la travaux de Jean Chazy'', pdf
{{DEFAULTSORT:Chazy, Jean 20th-century French mathematicians 1882 births 1955 deaths 20th-century French astronomers People from Villefranche-sur-Saône École Normale Supérieure alumni French military personnel of World War I Academic staff of the University of Paris Members of the French Academy of Sciences Commandeurs of the Légion d'honneur