How did units of measurement originate?

Who decided the length of our units of measurement? And how is a length of one metre actually defined?

The metric system – with the basic elements of metres, litres and kilograms – was developed by scientists in Paris in the late 1700s. Before then, length was measured by variable units, such as a foot, which corresponded to the length of an adult man’s foot, too variable as a standard.

The French scientists based the new system on the distance between the North Pole and the Equator measured along the degree of longitude that passes through Paris. The length of one metre was defined as being one 10-millionth of this distance.

The kilogram unit was linked directly with the metre, defined as the mass of water that – at four degrees – could be poured into a container of 1/1000m3 . A platinum-based 1kg ingot was created as a reference, ‘Le Grand K’, which was kept locked away in a safe in Paris. But variations in the reference and its successors led the world’s top measuring scientists to vote in 2018 to redefine the kilogram in relation to the unchanging Planck constant. The change took effect from 20 May 2019.

One metre was defined as one 10-millionth of the distance between the North Pole and the Equator. The metric system was introduced by statute in France in 1799, when scientists made a prototype known as the ‘Archive metre’. Marble blocks engraved with metres were installed in Paris, so people could get used to the measure. THE FRENCH DEFINED THE METRE