The polar circumference is also close to 40,000 kilometres because the metre was originally defined to be one ten millionth (i.e., a kilometre is one ten thousandth) of the arc from pole to equator ( quarter meridian). Earth's polar circumference is very near to 21,600 nautical miles because the nautical mile was intended to express one minute of latitude (see meridian arc), which is 21,600 partitions of the polar circumference (that is 60 minutes × 360 degrees). In modern times, Earth's circumference has been used to define fundamental units of measurement of length: the nautical mile in the seventeenth century and the metre in the eighteenth. Earth deviates from spherical by about 0.3%, as characterized by flattening. Treating the Earth as a sphere, its circumference would be its single most important measurement. ![]() The first known scientific measurement and calculation was done by Eratosthenes, who achieved a great degree of precision in his computation. ![]() Measurement of Earth's circumference has been important to navigation since ancient times. For modern definitions and measurements, see Earth radius.Įarth's circumference is the distance around Earth.
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