Background
Ernest Benjamin Esclangon was born on March 17, 1876, in Mison, France, in a family of landed proprietors François-Honoré Esclangon and Marie-Caroline Maigre.
École Normale Supérieure, 45 Rue d'Ulm, 75005 Paris, France
As a student at the École Normale Supérieure (1895-1898) and an agrégé in mathematics (1898), Esclangon took up the problem of quasi-periodic functions. Esclangon elaborated a theory for these functions, studied their differentiation and integration, and examined the differential equations which allow them as coefficients. His doctoral thesis established a basis for their employment at a time when their role in mathematical physics was only beginning to be developed.
1939
Académie des Sciences, 23 Quai de Conti, 75006 Paris, France
Esclangon was a member of the Académie des Sciences (1939).
École Normale Supérieure, 45 Rue d'Ulm, 75005 Paris, France
As a student at the École Normale Supérieure (1895-1898) and an agrégé in mathematics (1898), Esclangon took up the problem of quasi-periodic functions. Esclangon elaborated a theory for these functions, studied their differentiation and integration, and examined the differential equations which allow them as coefficients. His doctoral thesis established a basis for their employment at a time when their role in mathematical physics was only beginning to be developed.
A drawing of Esclangon.
Esclangon in front of the talking clock of the Observatoire de Paris (1933).
The lunar crater Esclangon was named after Ernest Esclangon.
Esclangon was promoted to the rank of officer of the Legion of Honor in 1930.
Astronomer mathematician physicist scientist
Ernest Benjamin Esclangon was born on March 17, 1876, in Mison, France, in a family of landed proprietors François-Honoré Esclangon and Marie-Caroline Maigre.
Esclangon’s first training was as a mathematician. As a student at the École Normale Supérieure (1895-1898) and an agrégé in mathematics (1898), he took up the problem of quasi-periodic functions. Esclangon elaborated a theory for these functions, studied their differentiation and integration, and examined the differential equations which allow them as coefficients. His doctoral thesis established a basis for their employment at a time when their role in mathematical physics was only beginning to be developed.
Esclangon’s subsequent career as an astronomer and teacher was the result of chance - in the form of a vacant position - and of his own curiosity that led him to accept it. He was an astronomer at Bordeaux, beginning in 1899, then director of the observatories of Strasbourg (1918) and Paris (1929-1944). In addition, he taught mathematics at the Bordeaux Faculty of Science (from 1902), then became a professor of astronomy at Strasbourg (in 1919) and then at Paris (1930-1946).
For fifty years Esclangon explored all the branches of fundamental astronomy. He devoted special attention to perfecting instruments, with a view to increasing the precision of observations. Of particular interest is his solution to a critical problem in positional astronomy, the rigorous definition of the axis of rotation of a transit instrument. Esclangon demonstrated that by fitting an objective in one of the extremities of this axis, which is hollow, and fitting a reticle to the other, the observer is permitted to measure the displacement of the instantaneous axis of rotation continuously throughout the course of the observation.
Esclangon’s work in ballistics began in 1914 when, at the beginning of World War I, he proposed to French military authorities that they employ soundranging techniques to localize enemy artillery. He was charged with organizing the experimental study of this method; he was thus able to analyze the two components of the wave emitted by the projectile, the conical shock wave and the spherical wave centered on the point of emission. Esclangon then succeeded in 1916 in eliminating the registration of the shock wave and thereby assured a great precision in pinpointing enemy gun locations.
As director of the Bureau International de l’Heure (1929-1944), Esclangon was led to devote himself to problems of time. In addition to making studies on the astronomical determination of time and on its conservation and diffusion, he devised the “talking clock” (employing time signals from an observatory clock) that has made telephonic announcements of the exact time available to the Paris public since 1933.
Esclangon’s practical bias and his inclination toward solid demonstrations (whether mathematical or experimental) caused him to be critical or the general theory of relativity. In a memoir of 1937, "La notion de temps. Temps physique et relativité" he discusses the restrictions necessary to certain conclusions that have been stated too absolutely and states how, for example, it is possible to conceive of phenomena faster than light and why the ordinary formulas are not strictly applicable to the motion of masses at great speeds.
Esclangon was a member of the Académie des Sciences (1939) and the Bureau des Longitudes (1932). He also served as president of the Union Astronomique Internationale from 1935 to 1938.
Esclangon assumed his official functions with simplicity and amiability; he was affable and loved to joke, and did not deny himself leisure time. It would almost seem that he accomplished his body of important work without effort.
In 1909 Esclangon married Marie-Léa Cambérou with whom he had a daughter, Germaine, who was born on October 6, 1911.