Jean-Baptiste Delambre
| Jean Baptiste Joseph Delambre | |
|---|---|
 |
|
| Born |
19 September 1749 Amiens |
| Died | 19 August 1822 (aged 72) Paris |
| Nationality | French |
| Scientific career | |
| Fields | Astronomy |
| Doctoral advisor | Jérôme Lalande |
| Doctoral students | Gerard Moll |
Jean Baptiste Joseph, chevalier Delambre (19 September 1749 – 19 August 1822) was a French mathematician and astronomer. He was also director of the Paris Observatory, and author of well-known books on the history of astronomy from ancient times to the 18th century.
After a childhood fever, he suffered from very sensitive eyes, and believed that he would soon go blind. For fear of losing his ability to read, he devoured any book available and trained his memory. He thus immersed himself in Greek and Latin literature, acquired the ability to recall entire pages verbatim weeks after reading them, became fluent in Italian, English and German and even published Règles et méthodes faciles pour apprendre la langue anglaise (Easy rules and methods for learning English).
Delambre's quickly achieved success in his career in astronomy, such that in 1788, he was elected a foreign member of the Royal Swedish Academy of Sciences. In 1790, to establish a universally accepted foundation for the definition of measures, the National Constituent Assembly asked the French Academy of Sciences to introduce a new unit of measurement. The academics decided on the metre, defined as 1 / 10,000,000 of the distance from the North Pole to the equator, and prepared to organise an expedition to measure the length of the meridian arc between Dunkirk and Barcelona. This portion of the meridian, which also passes through Paris, was to serve as the basis for the length of the quarter meridian, connecting the North Pole with the Equator. In April 1791, the academy's Metric Commission confided this mission to Jean-Dominique de Cassini, Adrien-Marie Legendre and Pierre Méchain. Cassini was chosen to head the northern expedition but, as a royalist, he refused to serve under the revolutionary government after the arrest of King Louis XVI on his Flight to Varennes. On 15 February 1792, Delambre was elected unanimously a member of the French Academy of Sciences and in May 1792, after Cassini's final refusal, was placed in charge of the northern expedition, measuring the meridian from Dunkirk to Rodez in the south of France. Pierre Méchain headed the southern expedition, measuring from Barcelona to Rodez. The measurements were finished in 1798. The gathered data were presented to an international conference of savants in Paris the following year.
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