Metre
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The metre is the base unit of length in the International System of Units. Since 2019, the metre has been defined as the length of the path travelled by light in vacuum during a time interval of 1/299
Replicas of historical metric standards, including a copy of the Mètre des Archives
History of the metre
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During the French Revolution, the traditional units of measure were to be replaced by consistent measures based on natural phenomena. As a base unit of length, scientists had favoured the seconds pend
Metre
…1/334. Following the arc measurement of Delambre and Méchain, the historical French official standard of the metre was made available in the form of the Mètre des Archives, a platinum bar held in Paris. It was originally also planned to dematerialise the definition of the metre by counting the number of swings of a…
A copy of the "provisional" metre located in the wall of a building, 15 rue de Vaugirard, Paris.
Closeup of National Prototype Metre Bar No. 27, made in 1889 by the International Bureau of Weights and Measures (BIPM) in collaboration with Johnson Mattey and given to the United States, which served as the standard for American cartography from 1890 replacing the Committee Meter, an authentic copy of the Mètre des Archives produced in 1799 in Paris, which Ferdinand Rudolph Hassler had brought to the United States in 1805.
A Krypton-86 lamp used to define the metre between 1960 and 1983