Earth's circumference mile in the seventeenth century and the metre in the eighteenth. Earth's polar circumference is almost exactly 40,000 km because the metre was originally calibrated on this measurement (1/10-millionth of the distance between the poles and the equator), which is almost exactly 21,600 nautical miles (being defined as one minute of a degree – i.e. 360 multiplied by 60). It has been described as "the single most important measurement" of the Earth, assuming the Earth to be a sphere (the Earth is an technically an ellipsoid, albeit with just 0.3% flattening). Earth's circumference lines are the foundation of the coordinate
History of measurement to use their customary units. Among the numerous customary systems, many have been adapted to become an integer multiple of a related metric unit: The Scandinavian mile is now defined as 10 km, the Chinese jin is now defined as 0.5 kg, and the Dutch ons is now defined as 100 g. The American system is unusual in that its units have not been adapted in such a manner. History of measurement The earliest recorded systems of weights and measures originate in the 3rd or 4th millennium BC. Even the very earliest civilizations needed measurement for purposes of agriculture, construction,