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The Precession of the Equinoxes

Earth's equatorial and orbital planes


In this discussion and in the diagram above , , and refer not to the entire 30° astrological signs : Aries, : Libra, : Cancer and : Capricorn, but rather just to their beginning points. These four points are known as the equinoxes ( and ) and the solstices ( and ), and collectively are called the "cardinal points" of the zodiac.

Twice a year (at the vernal equinox and the autumnal equinox ) an imaginary line drawn from the Sun to the Earth would fall on the Earth’s equator. In the diagram above these lines connect the turquoise and orange arrows, the line of the equinoxes. Experienced on Earth as the moment the Sun crosses the equator, on that day all over the Earth day and night are of equal length. Hence the Latin name equinox meaning "equal night."

This moment in spring, about March 21st, is called the vernal equinox. Its symbol in astronomy, , defines 0° of the sign Aries, but in astrology it more popularly symbolizes the entire 30° of the sign of Aries beginning at the vernal equinox . Both uses of the symbol , however, mark the beginning of the annual cycle of light and dark that we experience here on the Earth.

From its low point at the winter solstice , the light force waxes through the vernal equinox to its maximum at the summer solstice . From there it wanes back through its balance point at the autumnal equinox to its nadir at the winter solstice . The astrological signs are 12 equal divisions of the interval between successive vernal equinoxes that slowly move* relative to the fixed stars. "Tropical" astrologers believe that these 12 signs are interpretively significant. "Sidereal" (meaning "of the stars") astrologers believe rather that it is the fixed groups of stars or constellations from which the signs originally took their names that are interpretively significant.

*Please refer to the diagrams above and below during this discourse. Since the Earth is not a perfect sphere, the Sun and Moon pull on it unevenly. This non-uniform pull causes the Earth’s 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 equatorial plane (the blue plane above and the blue circle in the diagram below) and its intersection line with the ecliptic plane (the red plane in the diagram above and red circle in the diagram below) also precess.


diagram: ecliptic plane, precessional circle


And as this intersection line is the line of the equinoxes, we get the "precession of the equinoxes." This precessional wobble takes 25,788 years to complete one cycle (above diagram), or about 2150 (25,788÷12) years per zodiacal constellation. But not only are all of the zodiacal constellations different sizes, but we cannot know exactly where one of them ends and the next begins for their boundaries can only be arbitrarily drawn around the groups of stars forming them. 2150 years is just an average; the exact time an age ends or begins is open to interpretation.

A "great age" takes its name from that constellation through which the vernal equinox is precessing. Thus the Age of Pisces lasted from about the birth of Christ to the mid-20th century, and the Age of Aquarius from then until about 4100 AD. The advent of the Aquarian Age can be correlated with that of radio, TV, the Internet and mass-communication. The Aquarian water-bearer is pouring mankind’s consciousness and awareness of itself from his vessel into our souls. See my essay on "Surfing the Tsunami on the cusp of the Age of Aquarius" for more about this immense transition in which humanity is currently embedded.


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© Carl Woebcke: Precession of the Equinoxes, 1991-2014. All rights reserved.