The Precession of the Equinoxes

This Precession-of-the-Equinoxes 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. Precession of the equinoxes: The spin of a planet or a star increases as it condenses from a cloud of gas and debris, just as a skater increases her spin by pulling in her arms. And since all spinning bodies have rotational inertia, the Earth’s spin axis always points in the same direction in space,*(continuation of this page) the North star as it orbits the Sun. Now the Earth’s equator is perpendicular to its axis, so the Earth’s equatorial plane also points in the same direction* in space as the Earth orbits the Sun. And since the Earth’s orbital plane (the ecliptic) is also directionally fixed in space, these two fixed planes (in red and blue below) intersect in a line that is also directionally fixed* in space, the orange-turquoise line of the equinoxes pointing to ‘ and — below.

Please note that on this page the symbols ‘, —, " and š refer not to the entire sign, but rather just to their beginning points, known respectively as the equinoxes and the solstices; together, these four points are called the "cardinal" points of the zodiac.

Twice a year (at ‘ and —) an imaginary line drawn from the Sun to the Earth would fall on the Earth’s equator. In the diagram these lines fall on the line connecting 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, around March 21st, is called the vernal equinox, and its symbol ‘ in astronomy is the same as the symbol used in astrology for the whole 30° sign of Aries beginning at the vernal equinox. Thus ‘ defines 0° of the sign Aries, symbolizes the whole sign of Aries, and marks the beginning of the astrological year's cycle of light and dark.

From its low point at the winter solstice š, 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 š. 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.

"rotational inertia" is the tendency of a spinning body’s spin axis to remain pointed in the same direction in space. As long as a spinning body is not acted upon by an outside force its spin axis will remain forever pointed in the same direction in space relative to the stars! This is how gyroscopes form inertial guidance systems for planes, submarines and spacecraft. These vehicles constantly refer to a gyroscope’s fixed and rigid orientation in space in order to navigate and maintain their bearings (for more on this, click here).  otherwise, return to the above story