Metre Wikipedia. The metre British spelling or meter American spelling from the Greek noun, measure is the base unit of length in the International System of Units SI.The SI unit symbol is m.The metre is defined as the length of the path travelled by light in a vacuum in 12.The metre was originally defined in 1.Mnemonic Device For Activity Series Of Metal' title='Mnemonic Device For Activity Series Of Metal' />A description of tropes appearing in Office US.Based upon the British version, the American adaption of The Office ran on NBC from 2005 to 2013.Set at. Ancient Aliens Debunked Mystery 7.Chris White hopes to demonstrate to you that Ancient Aliens.In Search of Ancient Astronauts Mystery 52 min 6.I succesfully build the device, works like a charm.I tried the more simple one before, just a 9V battery with a resisitor but I experienced flashes, phosphane I.Welcome back to school, kids In just a few short weeksmaybe sooneryoull have to get back to your favorite latenight hobby writing papers.I struggled with.CrRGYAPHo/VotHR4fSIpI/AAAAAAAACjY/P2pSz_FrOYY/s1600/kingdomphylum.jpg' alt='Mnemonic Device For Activity Series Of Metal' title='Mnemonic Device For Activity Series Of Metal' />North Pole.In 1. In 1. 96. 0, the metre was redefined in terms of a certain number of wavelengths of a certain emission line of krypton 8.In 1. 98. 3, the current definition was adopted.The imperial inch is defined as 0.One metre is about 3 38 inches longer than a yard, i.SpellingeditMetre is the standard spelling of the metric unit for length in nearly all English speaking nations except the United States345, Sweden6 and the Philippines,7 which use meter.Measuring devices such as ammeter, speedometer are spelled meter in all variants of English.The suffix meter has the same Greek origin as the unit of length.EtymologyeditThe etymological roots of metre can be traced to the Greek verb metreo to measure, count or compare and noun metron a measure, which were used for physical measurement, for poetic metre and by extension for moderation or avoiding extremism as in be measured in your response.This range of uses is also found in Latin metior, mensura, French mtre, mesure, English and other languages.The motto metro chro in the seal of the International Bureau of Weights and Measures BIPM, which was a saying of the Greek statesman and philosopher Pittacus of Mytilene and may be translated as Use measure, thus calls for both measurement and moderation.History of definitioneditIn 1.English cleric and philosopher John Wilkins proposed in an essay a decimal based unit of length, the universal measure or standard based on a pendulum with a one second period.Christiaan Huygens had observed that length to be 3.Rijnland inches or 3.English inches. This is the equivalent of what is now known to be 9.No official action was taken regarding this suggestion.In 1. 67. 0 Gabriel Mouton, Bishop of Lyon, also suggested a universal length standard with decimal multiples and divisions, to be based on a one minute angle of the Earths meridian arc or as the Earths circumference was not easy to measure on a pendulum with a one second period.In 1. 67. 5, the Italian scientist Tito Livio Burattini, in his work Misura Universale, used the phrase metro cattolico universal measure, derived from the Greek mtron katholikn, to denote the standard unit of length derived from a pendulum.As a result of the French Revolution, the French Academy of Sciences charged a commission with determining a single scale for all measures.On 7 October 1. 79.March 1. 79. 1 advised the adoption of the term mtre measure, a basic unit of length, which they defined as equal to one ten millionth of the distance between the North Pole and the Equator,1.In 1. 79. 3, the French National Convention adopted the proposal this use of metre in English began at least as early as 1.Creating the metre alloy in 1.Conservatoire des Arts et Mtiers.Present Henri Tresca, George Matthey, Saint Claire Deville and Debray.Meridional definitioneditIn 1.French Academy of Sciences selected the meridional definition over the pendular definition because the force of gravityvaries slightly over the surface of the Earth, which affects the period of a pendulum.To establish a universally accepted foundation for the definition of the metre, more accurate measurements of this meridian were needed.The French Academy of Sciences commissioned an expedition led by Jean Baptiste Joseph Delambre and Pierre Mchain, lasting from 1.Dunkerque and Montjuc 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 half 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 1.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 2.Earth, making the prototype about 0.Regardless, this length became the French standard and was progressively adopted by other countries in Europe.The expedition was fictionalised in Denis Guedj, La Mesure du Monde.Ken Alder wrote factually about the expedition in The Measure of All Things the seven year odyssey and hidden error that transformed the world.International prototype metre bareditIn 1.International Association of Geodesy held in Berlin, the question of an international standard unit of length was discussed in order to combine the measurements made in different countries to determine the size and shape of the Earth.The conference recommended the adoption of the metre and the creation of an international metre commission, according to the proposal of Johann Jacob Baeyer, Adolphe Hirsch and Carlos Ibez e Ibez de Ibero.In the 1. 87. 0s and in light of modern precision, a series of international conferences was held to devise new metric standards.The Metre Convention Convention du Mtre of 1.International Bureau of Weights and Measures BIPM Bureau International des Poids et Mesures to be located in Svres, France.This new organisation was to construct and preserve a prototype metre bar, distribute national metric prototypes, and maintain comparisons between them and non metric measurement standards.The organisation created such a bar in 1.General Conference on Weights and Measures CGPM Confrence Gnrale des Poids et Mesures, establishing the International Prototype Metre as the distance between two lines on a standard bar composed of an alloy of 9.The original international prototype of the metre is still kept at the BIPM under the conditions specified in 1.Wavelength definitioneditIn 1.Albert A. Michelson, the inventor of the device and an advocate of using some particular wavelength of light as a standard of length.By 1. 92. 5, interferometry was in regular use at the BIPM.However, the International Prototype Metre remained the standard until 1.CGPM defined the metre in the new International System of Units SI as equal to 1 6.Speed of light definitioneditTo further reduce uncertainty, the 1.CGPM in 1. 98. 3 replaced the definition of the metre with its current definition, thus fixing the length of the metre in terms of the second and the speed of light 2The metre is the length of the path travelled by light in vacuum during a time interval of 17.This definition fixed the speed of light in vacuum at exactly 7.An intended by product of the 1.CGPMs definition was that it enabled scientists to compare lasers accurately using frequency, resulting in wavelengths with one fifth the uncertainty involved in the direct comparison of wavelengths, because interferometer errors were eliminated.To further facilitate reproducibility from lab to lab, the 1.CGPM also made the iodine stabilised heliumneon laser a recommended radiation for realising the metre.For the purpose of delineating the metre, the BIPM currently considers the He.Ne laser wavelength, He. Microsoft Word Avery Template 5162 Christmas . Ne, to be 6. 99. 36.U of 6. 98. 92. 10.This uncertainty is currently one limiting factor in laboratory realisations of the metre, and it is several orders of magnitude poorer than that of the second, based upon the caesium fountain atomic clock U 6.Consequently, a realisation of the metre is usually delineated not defined today in labs as 7.This bracket notation expressing the error is explained in the article on measurement uncertainty.Practical realisation of the metre is subject to uncertainties in characterising the medium, to various uncertainties of interferometry, and to uncertainties in measuring the frequency of the source.
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