This Ages of Pisces and Aquarius page and the entire website are excerpted from You and the Universe, a handmade, individualized fine art book on astrology, mythology and astronomy through which the recipient's complete astrological reading is woven.

Since the Earth is not a perfect sphere (see "oblateness" in glossary), the Sun and Moon pull on it unevenly. This non-uniform pull or force causes the Earth’s spin axis to wobble or "precess" in space, the way a top’s axis pulled on by gravity circles the vertical as it slows down.  Thus the Earth’s equator -- and in turn the line formed by the intersection of the equatorial and ecliptic planes -- precesses as well. As this line of intersection is the line of the equinoxes, we get the "precession of the equinoxes."  This is illustrated in You and the Universe on pages 91 and 92.