Earth is no exception to this general rule, although it does exhibit several tottering motions, the two most prominent being the so-called Chandler wobble and the precession of the equinoxes
As has often been pointed out, the movement that Spenser describes was the result of the precession of the equinoxes
, which had caused the constellations to shift from the sign of the zodiac they had occupied in Ptolemaic astronomy into the adjacent sign.
One of his examples of the consilience of inductions was Newton's use of Kepler's laws in explaining the central force of the sun and the precession of the equinoxes
He also believed, in particular, in the importance to human affairs of the Precession of the Equinoxes
(a new zodiacal `Age' every 2,160 years).
Because of the precession of the equinoxes
, in the course of approximately 26,000 years, the constellations including the signs of the zodiac, will re-assume their original positions in relation to the earth.
Because it meant that the vernal equinox came a bit ahead of its previous mark each year, this motion was called the precession of the equinoxes
His greatest discovery was the precession of the equinoxes
, the gradual creep of a star's celestial coordinates over the centuries (in a direction parallel to the ecliptic) due to a drift in the orientation of the Earth's axis.
These originally corresponded to the zodiacal constellations bearing the same names, but now, through the precession of the equinoxes
, they coincide with the constellations bearing the names next in order.