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In 1791, the French Academy of Sciences chose to define the metre as one ten-millionth of the distance from the equator to the North or South Pole. This replaced the earlier definition based on the period of a pendulum, because the force of Earth's gravityvaries slightly over the surface of the Earth, which affects the period of a pendulum.[1] To establish a universally accepted foundation for the definition of the metre, more accurate measurements of a meridian were needed. The French Academy of Sciences commissioned an expedition led by Jean Baptiste Joseph Delambre and Pierre Méchain, lasting from 1792 to 1799, which attempted to accurately measure the distance between a belfry in Dunkerque and Montjuïc castle in Barcelona to estimate the length of the meridian arc through Dunkerque. This portion of the meridian, assumed to be the same length as the Paris meridian, was to serve as the basis for the length of the quarter meridian connecting the North Pole with the Equator. The problem with this approach is that the exact shape of the Earth is not a simple mathematical shape, such as a sphere or oblate spheroid, at the level of precision required for defining a standard of length. The irregular and particular shape of the Earth smoothed to sea level is represented by a mathematical model called a geoid, which literally means "Earth-shaped". Despite these issues, in 1793 France adopted this definition of the metre as its official unit of length based on provisional results from this expedition. However, it was later determined that the first prototype metre bar was short by about 200 micrometres because of miscalculation of the flattening of the Earth, making the prototype about 0.02% shorter than the original proposed definition of the metre. Regardless, this length became the French standard and was progressively adopted by other countries in Europe. This is why the polar circumference of the Earth is 40,008 km, instead of 40,000.[1]
^ abcAlder, K. (2002). The Measure of All Things: The Seven-year Odyssey and Hidden Error that Transformed the World. Free Press. ISBN978-0-7432-1675-3. Retrieved 2020-08-02.
October 21, 2023
measurement, delambre, méchain, this, article, multiple, issues, please, help, improve, discuss, these, issues, talk, page, learn, when, remove, these, template, messages, this, article, relies, largely, entirely, single, source, relevant, discussion, found, t. This article has multiple issues Please help improve it or discuss these issues on the talk page Learn how and when to remove these template messages This article relies largely or entirely on a single source Relevant discussion may be found on the talk page Please help improve this article by introducing citations to additional sources Find sources Arc measurement of Delambre and Mechain news newspapers books scholar JSTOR October 2020 You can help expand this article with text translated from the corresponding article in French October 2020 Click show for important translation instructions View a machine translated version of the French article Machine translation like DeepL or Google Translate is a useful starting point for translations but translators must revise errors as necessary and confirm that the translation is accurate rather than simply copy pasting machine translated text into the English Wikipedia Do not translate text that appears unreliable or low quality If possible verify the text with references provided in the foreign language article You must provide copyright attribution in the edit summary accompanying your translation by providing an interlanguage link to the source of your translation A model attribution edit summary is Content in this edit is translated from the existing French Wikipedia article at fr Figure de la Terre et meridienne de Delambre et Mechain see its history for attribution You should also add the template Translated fr Figure de la Terre et meridienne de Delambre et Mechain to the talk page For more guidance see Wikipedia Translation Learn how and when to remove this template message The arc measurement of Delambre and Mechain was a geodetic survey carried out by Jean Baptiste Delambre and Pierre Mechain in 1792 1798 to measure an arc section of the Paris meridian between Dunkirk and Barcelona This arc measurement served as the basis for the original definition of the metre 1 In 1791 the French Academy of Sciences chose to define the metre as one ten millionth of the distance from the equator to the North or South Pole This replaced the earlier definition based on the period of a pendulum because the force of Earth s gravity varies slightly over the surface of the Earth which affects the period of a pendulum 1 To establish a universally accepted foundation for the definition of the metre more accurate measurements of a meridian were needed The French Academy of Sciences commissioned an expedition led by Jean Baptiste Joseph Delambre and Pierre Mechain lasting from 1792 to 1799 which attempted to accurately measure the distance between a belfry in Dunkerque and Montjuic castle in Barcelona to estimate the length of the meridian arc through Dunkerque This portion of the meridian assumed to be the same length as the Paris meridian was to serve as the basis for the length of the quarter meridian connecting the North Pole with the Equator The problem with this approach is that the exact shape of the Earth is not a simple mathematical shape such as a sphere or oblate spheroid at the level of precision required for defining a standard of length The irregular and particular shape of the Earth smoothed to sea level is represented by a mathematical model called a geoid which literally means Earth shaped Despite these issues in 1793 France adopted this definition of the metre as its official unit of length based on provisional results from this expedition However it was later determined that the first prototype metre bar was short by about 200 micrometres because of miscalculation of the flattening of the Earth making the prototype about 0 02 shorter than the original proposed definition of the metre Regardless this length became the French standard and was progressively adopted by other countries in Europe This is why the polar circumference of the Earth is 40 008 km instead of 40 000 1 See also EditCartography of France Earth s circumference Historical use in the definition of units of measurement Earth radius History History of geodesy Prime meridian and standard of length History of the metre Meridional definition Meridian arc 17th and 18th centuries Metre Early adoption of the metre as a scientific unit of length the forerunners Paris meridian The West Europe Africa Meridian arcReferences Edit a b c Alder K 2002 The Measure of All Things The Seven year Odyssey and Hidden Error that Transformed the World Free Press ISBN 978 0 7432 1675 3 Retrieved 2020 08 02 Retrieved from https en wikipedia org w index php title Arc measurement of Delambre and Mechain amp oldid 1178715410, wikipedia, wiki, book, books, library,
