What is the basis of a kilometer?

Answer 1

The world official standard of length is the Metre. (In USA they spell it - Meter. They like to be different to the rest of the world.) A French scientist Charles Marie de La Condamine, went on an expedition and measured the distance from the Equator to the North Pole. This distance was multiplied by 4 to assess the perimeter of a line of Longitude around the Earth. This distance was divided by 10 Million and given the name Metre (not meter) The French government used this length as a standard, but actually Condamines measurements were found about 50 years later, to be inaccurate by an amount of 1/5th of a millimetre. (believe it or not) In 1791 on 30th March . The French Government made a brass bar in 1795 , having a cross sectional shape of an X . Since 1795 there have been very minor changes to the 'Metre Bar' but they are only very minor changes. The name Kilometre was adopted as being 1000 Metre, and used for measuring large lengths, and the name Millimetre , for small lengths ( 1Metre = 1000 millimetre).