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The Mètre Etalon

Etched into marble, on the side of the Ministry of Justice building in Paris, lies the mètre étalon - one of the first metre sticks ever created. But how did it get there? Well, in the late 1700s, Europe was riddled with different measurement systems, which made marketplace conversions an exhausting task. After the French Revolution, the new republican government set out to unify the country - and Europe - by creating one methodology. On April 7th, 1795, the metric system was born. An important part of the government's mission was to base the system on natural calculations. Therefore, officials decided to make the metre one 10-millionth of the distance from the North Pole to the equator. Not exactly an easy calculation - we’ll just assume they got it right. Once they had the measurement, they needed to share it. But the accuracy and replication of a measurement is key to its success. So, to help Parisians make and verify their own calculations, mètre étalon replicas were placed around the city. The idea being that you could simply walk up, hold up your item and measure it.

A solid platinum rod was used as the original reference - stored safely away - until a more accurate platinum-iridium model was constructed in 1889. In order to avoid errors caused by heat expansion, officials would cool the rod to the melting point of ice before taking a measurement. The length of the metre has since been updated to allow for more accurate calculations. For example, in 1960, the metre was set to a specific wavelength of light. These updates make it easier to replicate the metre without using clumsy, manual processes - like holding up a piece of fabric to a block of marble in the town square… (And yes, this newsletter is created by British/Norwegian ladies, so this is our subtle push to convert you to the metric system)

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Photo credit: PjrTravel/Alamy


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