The meter was initially defined as $10^{-7}$ times the distance of the north pole to the equator. How exactly was this definition used to fabricate the actual meter sticks from which the standard meter bar -which subsequently actually determined how long one meter was- was selected?


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Once the definition in terms of the length of the meridian was accepted, the French sent several expeditions to measure the meridian. On the basis of these expeditions, the reference meter (a stick of a special alloy, which has very little thermal expansion) was made and kept under controlled conditions. Later, when more precise measurements of Earth were made, it was decided to change the definition, and use the standard reference stick instead of the length of the meridian.

See, for example this article

  • $\begingroup$ Given this numerical value of the length of the meridian, how did they actually fabricate a stick with the length of a ten-millionth? $\endgroup$
    – Marc
    Dec 1, 2018 at 15:55
  • 1
    $\begingroup$ @Marc: That's a purely technical problem. Some stick was necessary in the process of measuring the meridian, to set a unit of length in the triangulation process. After the measuring, from this stick a new one can be manufactued to match the given part of the meridian. $\endgroup$ Dec 1, 2018 at 20:25
  • $\begingroup$ Copypaste from Wikipedia entry 'Toise': In 1735 two geodetic standards were calibrated against the Toise of Châtelet. One of them, the Toise of Peru was used for the Spanish-French Geodesic Mission. In 1766 the Toise of Peru became the official standard of length in France and was renamed Toise of the Academy (French: Toise de l'Académie). In 1799, after the remeasurement of the Paris meridian arc (French: Méridienne de France) between Dunkirk and Barcelona by Delambre and Mechain, the metre was defined as 3 pieds (feet) and 11.296 lignes (lines) of the Toise of the Academy.[2] $\endgroup$
    – xxavier
    Dec 2, 2018 at 9:19

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