The meridional circumference (polar circumference) of the Earth is 40007 km, 40008 km, or 40009 km, depending on the source. (Why is there a discrepancy?) The fact that it is so close to 40000 is not a coincidence: the kilometer used to be defined as 1/10000 the distance from north pole to equator.
What is the reason for the roughly 8 km difference from 40000? Was it lack of precision in measuring the Earth back in the day? Or more intriguingly, is it caused by the Earth not being a perfect oblate ellipsoid? Perhaps going the rest of the way around is a bit longer than symmetry predicts (pear-shaped), or it depends on what meridian you measure along (triaxiality).
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