Monday, September 20, 2010

Jean Baptiste Joseph Delambre

Jean Baptiste Joseph Delambre was born near Amiens, France on September 19, 1749. The eldest child in his family, he suffered from a bout of smallpox at the age of 15 months. His parents feared he would loose his eyesight, and he did loose his eyelashes, which never grew back in, but although his sight was limited he did not go blind. Fear of loosing his eyesight made him a voracious reader, and he was able to memorize all that he read, becoming fluent in English, German and Italian.

He attended the Jesuit college in Amiens until 1764 when Jesuits were banned from France and he continued his education under teachers brought from Paris. Originally his intent was to become a parish priest, but with the encouragement of his teachers he went to Paris to continue his studies. He won a scholarship at the College du Plessis where he studied classical languages and prepared himself for university study. He sat for the university entrance exam, but with his poor eyesight he had difficulty reading the exam and he failed to gain a scholarship. His parents, unable to afford a university education, urged him to return to Amiens, instead he began studying mathematics in order that he could become a tutor and he took a position as the tutor of the son of a nobleman in Compiegne. Studying mathematics he soon became an expert, developing exceptional calculating skills.

In 1771 Delambre returned to Paris to take a position tutoring the son of Jean-Claude Geoffroy d'Assy, the Receiver General of Finances. He took this position for less than d'Assy offered in exchange for housing. Once again in Paris he began studying Greek and Greek sciences, including astronomy. He continued his study of astronomy, studying the works of current astronomers, including Jerome Lelande. He began attending lectures given by Lelande and soon impressed the teacher with his knowledge, so much so that Lelande offered him a position as his assistant. In 1786 Delambre observed the transit of Mercury across the sun and found that the tables of its transit, prepared by Lelande, were inaccurate, and Delambre would expend much effort to correct them. He also completed tables of the orbits of Jupiter and Saturn. In 1789 Delambre won a prize from the Academie des Sciences for correctly determining the orbit of Uranus. At the time of the French Revolution Delambre changed his name, which had originally been D'Lambre in order that he would not be arrested.

Delambre was elected associate member of the mathematical section of the Academie des Sciences in 1792 and was given a commission by the Academie to measure the arc distance between Dunkerque to Rodez. This was part of the Commission of Weights and Measures attempt to define the meter. It had been decided to define the meter, the unit of length measurement in the newly created metric system, as one ten millionth of a quarter of the distance between the North Pole and the equator. Delambre reported his results in 1799, having twice been detained by revolutionary forces, and accused of espionage. Delambre finished the report, establishing the length of the meter, in 1806.

Delambre devoted the remainder of his career to the study of the history of mathematics and astronomy. His major work was a six volume history of astronomy, the first two volumes covering ancient astronomy and the remaining four on astronomy of the middle ages, the Renaissance, the seventeenth and eighteenth centuries receptively. The final two volumes were published posthumously. This work has been haled by science historian I. Bernard Cohen as "the greatest full-scale technical history of a single branch of science written by a single individual". Delambre also has a crater on the moon named after him.

Delambre died on August 19, 1882.


O'Connor, JJ and Robertson, EF; "Jean Baptiste Joseph Delambre"; at

Jarrell, Richard A.; "Delambre, Jean-Baptiste Joseph (1749-1822)" in History of Astronomy: An Encyclopedia; John Lankford ed.; Taylor and Francis; 1997

Jean Baptiste Joseph Delamber wikipedia entry

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