Gérard Desargues
Encyclopedia
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
mathematician
Mathematician
A mathematician is a person whose primary area of study is the field of mathematics. Mathematicians are concerned with quantity, structure, space, and change....
and engineer, who is considered one of the founders of projective geometry
Projective geometry
In mathematics, projective geometry is the study of geometric properties that are invariant under projective transformations. This means that, compared to elementary geometry, projective geometry has a different setting, projective space, and a selective set of basic geometric concepts...
. Desargues' theorem
Desargues' theorem
In projective geometry, Desargues' theorem, named in honor of Gérard Desargues, states:Denote the three vertices of one triangle by a, b, and c, and those of the other by A, B, and C...
, the Desargues graph
Desargues graph
In the mathematical field of graph theory, the Desargues graph is a distance-transitive cubic graph with 20 vertices and 30 edges. It is named after Gérard Desargues, arises from several different combinatorial constructions, has a high level of symmetry, is the only known non-planar cubic partial...
, and the crater Desargues
Desargues (crater)
Desargues is an ancient lunar crater that is located near the northern limb of the Moon, on the western hemisphere. It lies nearly due south of the crater Pascal, and southeast of Brianchon...
on the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
are named in his honour.
Born in Lyon
Lyon
Lyon , is a city in east-central France in the Rhône-Alpes region, situated between Paris and Marseille. Lyon is located at from Paris, from Marseille, from Geneva, from Turin, and from Barcelona. The residents of the city are called Lyonnais....
, Desargues came from a family devoted to service to the French crown. His father was a royal notary
Civil law notary
Civil-law notaries, or Latin notaries, are lawyers of noncontentious private civil law who draft, take, and record legal instruments for private parties, provide legal advice and give attendance in person, and are vested as public officers with the authentication power of the State...
, an investigating commissioner of the Seneschal's
Seneschal
A seneschal was an officer in the houses of important nobles in the Middle Ages. In the French administrative system of the Middle Ages, the sénéchal was also a royal officer in charge of justice and control of the administration in southern provinces, equivalent to the northern French bailli...
court in Lyon (1574), the collector of the tithe
Tithe
A tithe is a one-tenth part of something, paid as a contribution to a religious organization or compulsory tax to government. Today, tithes are normally voluntary and paid in cash, cheques, or stocks, whereas historically tithes were required and paid in kind, such as agricultural products...
s on ecclesiastical revenues for the city of Lyon (1583) and for the diocese of Lyon.
Girard Desargues worked as an architect
Architecture
Architecture is both the process and product of planning, designing and construction. Architectural works, in the material form of buildings, are often perceived as cultural and political symbols and as works of art...
from 1645. Prior to that, he had worked as a tutor and may have served as an engineer and technical consultant in the entourage of Richelieu.
As an architect, Desargues planned several private and public buildings in Paris and Lyon. As an engineer, he designed a system for raising water that he installed near Paris. It was based on the use of the at the time unrecognized principle of the epicycloid
Epicycloid
In geometry, an epicycloid is a plane curve produced by tracing the path of a chosen point of a circle — called an epicycle — which rolls without slipping around a fixed circle...
al wheel.
His work was rediscovered and republished in 1864. His works were subsequently collected in L'oeuvre mathématique de Desargues (ed. by René Taton; Paris, 1951). The 1864 version of his work is shortly to be republished (2011) by Cambridge University Press as part of the Cambridge Library Collection.
Late in his life, Desargues published a paper with the cryptic title of DALG. The most common theory about what this stands for is Des Argues, Lyonnais, Géometre, proposed by Henri Brocard
Henri Brocard
Pierre René Jean Baptiste Henri Brocard was a French meteorologist and mathematician, in particular a geometer...
.