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Pierre François André Méchain (16 August 1744 – 20 September 1804) was a French astronomer and surveyor who, with Charles Messier, was a major contributor to the early study of deep sky objects and comets. ==Life== Pierre Méchain was born in Laon, the son of the ceiling designer and plasterer Pierre François Méchain and Marie-Marguerite Roze. He displayed mental gifts in mathematics and physics but had to give up his studies for lack of money. However, his talents in astronomy were noticed by Joseph Jérôme Lalande, for whom he became a friend and proof-reader of the second edition of his book "L'Astronomie". Lalande then secured a position for him as assistant hydrographer with the Naval Depot of Maps and Charts at Versailles, where he worked through the 1770s engaged in hydrographic work and coastline surveying. It was during this time—approximately 1774—that he met Charles Messier, and apparently, they became friends. In the same year, he also produced his first astronomical work, a paper on an occultation of Aldebaran by the Moon and presented it as a memoir to the Academy of Sciences. In 1777, he married Barbe-Thérèse Marjou whom he knew from his work in Versailles. They had two sons: Jérôme, born 1780, and Augustin, born 1784, and one daughter. He was admitted to the French Académie des sciences in 1782, and was the editor of ''Connaissance des Temps'' from 1785 to 1792; this was the journal which, among other things, first published the list of Messier objects. In 1789 he was elected a Fellow of the Royal Society.〔(【引用サイトリンク】Library and Archive )〕 He participated in the Anglo-French Survey (1784–1790) to measure by trigonometry the precise distance between the Paris Observatory and the Royal Greenwich Observatory. This project was initiated by Dominique, comte de Cassini, and in 1787 Méchain visited Dover and London with Cassini and Adrien-Marie Legendre to facilitate its progress. The three men also visited the astronomer William Herschel at Slough. With his surveying skills, he worked on maps of Northern Italy and Germany after this, but his most important mapping work was geodetic: the determination of the southern part of the meridian arc of the Earth's surface between Dunkirk and Barcelona beginning in 1791. This measurement would become the basis of the metric system's unit of length, the meter. He encountered numerous difficulties on this project, largely stemming from the effects of the French Revolution. He was arrested after it was suspected his instruments were weapons, he was interned in Barcelona after war broke out between France and Spain, and his property in Paris was confiscated during The Terror. He was released from Spain to live in Italy, then returned home in 1795. A particularly intriguing fact about this project was that Méchain was uncertain of the precision of his measurements owing to anomalous results in verifying his latitude by astronomical observation. Ultimately, the distance from the pole to the equator, which Méchain and his associate Jean Baptiste Joseph Delambre had intended to be exactly ten million meters (or ten thousand kilometers), was determined in the late 20th century by space satellites to be 10,002,290 meters.〔Alder, Ken, ''The Measure of All Things: The Seven-Year Odyssey and Hidden Error that Transformed the World'' (2002, NY, The Free Press) page 7; the book is a detailed account of Méchain's arduous adventures with this project and his efforts to correct or conceal any miscalculations. The reason for his anomalous latitude calculations is not certain, but possibly the problem lay with astronomical observations of stars so near the southern horizon that there may have been atmospheric distortion.〕 This small error of 2,290 meters equals 1.423 statute miles; the error in such a large measurement amounts to 14½ inches per statute mile. It represents in each meter an error of approximately 0.16 millimeter - slightly more than the width of a single strand of human hair. This discrepancy is sometimes mentioned as "Mechain's error", with the suggestion that the tiny variation in the length of the meridian (not detected for nearly two hundred years) can be attributed to Mechain's calculations. But analysis of Mechain's figures reveals that Mechain consistently kept the discrepancy very tiny, essentially forcing his individual reported measurements to appear more precise and consistent than would be reasonably expected of a survey involving more than a hundred measurements of mostly rough country using 18th century equipment; Mechain's putative error did not effect the final value of the length of the meter nor the measurement of the meridian.〔Alder, Ken, ''The Measure of All Things: The Seven-Year Odyssey and Hidden Error that Transformed the World'' (2002, NY, The Free Press) chapter 11, pages 291-324.〕 From 1799, he was the director of the Paris Observatory. Continuing doubts about his measurements of the Dunkirk-Barcelona arc led him to return to that work. This took him back to Spain in 1804, where he caught yellow fever and died in Castellon de la Plana. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pierre Méchain」の詳細全文を読む スポンサード リンク
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