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Page 453 SI unit definitions

  • Welcome – BIPM – the International Bureau of Weights and Measures (Bureau International des Poids et Mesures)
  • SI units – NPL – National Measurement Institute (UK)
  • SI Units | NIST – National Institute of Standards and Technology (U.S Department of Commerce)
  • The metre: In 1791, the French Academy of Sciences defined the metre as1/10,000,000 of the distance from the Earth’s equator to the North Pole, measured on a meridian line through the Paris Observatory in Paris, France. A standard bar representing one metre was constructed, first in brass (in 1795), then in platinum (1799) and then in platinum-iridium (1889). Whilst the bars provided a consistent reference for calibration purposes. The 1791 definition of the metre was problematic for reasons such as the Earth constantly changes shape due to gravitational forces, and the original equator to North Pole measurement was slightly wrong. This website provides some additional historical context Measurements: History of the Metre — Steemit
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