Earth is an oblate spheroid, not a sphere, since it's rotation around the axis causes it to bulge along the equator.
Is it teally a symetric oblate spheroid though, or also not even that?
To explain: If we combine the effect due to the rotation around the axis, with the precession of the axis itself, is it correct to assume that there should also be some asymmetry between the geographic north and south poles?
Namely that there is at least a small difference between the diameter of the two? If so, how large is it?
Part two: If there is such asymetry, does it change in the duration of a milankovitch cycle?