Message #26599

[Bianca]

A lesson in precession



Earth wobbles as she spins and is also inclined on her axis of rotation. This tilt creates the seasons, and the wobble creates the phenomenon astronomers and astrologers alike call precession. Like a slowly spinning top, earth's wobble causes the axis to trace an imaginary circle in the heavens.

This imaginary stylus moves at the rate of roughly one degree of arc in seventy-two years. An additional byproduct of this wobble causes the spring equinox sun (in the northern hemisphere) to rise due east against a backdrop of stars which slowly shifts. Because this event occurs on the ecliptic, (the apparent path of the sun through the year), the stellar backdrop is formed by the slowly moving starry curtain of the twelve zodiacal constellations.

The zodiacal constellations are divisions of space which contain stars and deep sky objects within borders outlined by astronomers. Zodiacal constellations are twelve of eighty-eight divisions of space recognized by astronomers since 1930. The zodiacal "signs," on the other hand, are divisions of time, beginning with the spring equinox.

The astrological sign of Aries is the symbolic birth of the new year. In the northern hemisphere spring, and zero degrees Aries, begins at the vernal equinox when the balance of light and dark achieves momentary equilibrium, before tilting toward increasing light. Down under the seasons march in the opposite direction.