The meridian is 40,000 km, by original definition. Trace any great circle through both poles (any pair of antipodal meridians, such as 0° and 180°) and that is 40k km.
The equator is more than that because of the oblateness of the spheroid.
And nowadays, the meter is defined in terms of natural units (time and the speed of light) in a way to be compatible with the original definition by the meridian.
The equator is more than that because of the oblateness of the spheroid.
And nowadays, the meter is defined in terms of natural units (time and the speed of light) in a way to be compatible with the original definition by the meridian.