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When talking about the Seasons, I said the orientation of the Earth's tilt stays more or less fixed with respect to the stars.  Because of the pull of the moon, the Earth's axis wobbles, or precesses:

As a result, the celestial pole moves in the sky:

It takes 26,000 years for the wobble to make one complete circle.  Because the pole moves, the position of the Equinoxes changes (see ecliptic figure).  This really messes up the whole astrology thing and keeps astronomers (or their computers) busy recalculating the positions of stars.
 

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