Metre  

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The metre or meter (American spelling), (SI unit symbol: m), is the fundamental unit of length (SI dimension symbol: L) in the International System of Units (SI), which is maintained by the BIPM. Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole (at sea level), its definition has been periodically refined to reflect growing knowledge of metrology. Since 1983, it has been defined as "the length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second."

History

A decimal-based unit of length, the universal measure or standard was proposed in an essay of 1668 by the English cleric and philosopher John Wilkins. In 1670 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 Earth's meridian arc or (as the Earth's circumference was not easy to measure) on a pendulum with a one-second period. In 1675, the Italian scientist Tito Livio Burattini, in his work Misura Universale, used the phrase Template:Lang (lit. "catholic [i.e., universal] measure"), derived from the Greek Template:Lang (métron katholikón), to denote the standard unit of length derived from a pendulum. In the wake of the French Revolution, a commission organised by the French Academy of Sciences and charged with determining a single scale for all measures, advised the adoption of a decimal system (27 October 1790) and suggested a basic unit of length equal to one ten-millionth of the distance between the North Pole and the Equator, to be called mètre ("measure") (19 March 1791). The National Convention adopted the proposal in 1793. The first occurrence of metre in this sense in English dates to 1797.

See also

• Conversion of units for comparisons with other units
• International System of Units
• Introduction to the metric system
• ISO 1Template:Spaced ndashstandard reference temperature for length measurements
• Length measurement
• Metre Convention
• Metric system
• Metric prefix
• Metrication
• Orders of magnitude (length)
• SI prefix
• Speed of light