(a) What, if anything, is the difference between Earths geographic center, i.e. mid-point of the spin axis, and the gravitational center?

(b) What is the average distance between the Earth's center of gravity, and the Earth-Moon system's center of gravity?

(c) The recent 'super-moon' is a reminder that the moon's distance has an orbital wobble. So, by how much does this vary the distance between the Earth vs Earth-Moon gravitational centres, and

(d) Is the moon's varying distance from the Earth sufficient to create any noticeable effect upon sea/ocean tidal amplitudes?

  • $\begingroup$ PS: By 'noticeable', I mean more than a few millimeters. $\endgroup$ Nov 25 '16 at 1:01
  • 2
    $\begingroup$ en.wikipedia.org/wiki/Barycenter $\endgroup$
    – Spencer
    Nov 25 '16 at 1:36
  • $\begingroup$ I think there's more than one question here. (c) and (d) are easy to relate and fit together (and FWIW, I'm pretty sure the answer to (d) is "yes"), but I think the others need asking separately. Might I suggest seperating them out? $\endgroup$ Nov 25 '16 at 14:06
  • $\begingroup$ Information on (d): earthscience.stackexchange.com/questions/8917/… $\endgroup$
    – arkaia
    Nov 25 '16 at 16:23
  • $\begingroup$ What exactly is the "mid-point of the spin axis"? The axis is infinitely long, it doesn't have a mid-point. $\endgroup$ Nov 25 '16 at 23:44

For (a) through (c), consider the differences between the geoid and the reference ellipsoid, in addition to the barycentre.

For (d): A slightly higher perigean spring tide than usual, meaning in some geographical locations perhaps an amplitude difference of inches rather than millimetres.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.