Zodiac

The zodiac, literally the circle of animals, is constituted by the 12 stellar constellations through which the Sun appears to pass in its annual movement through the heavens. The 12 constellations form a belt across the night sky some 8 to 9 degrees on either side of the solar orbit. The Moon and the planets of this solar system also move within that belt. The path of the Sun is called the ecliptic as eclipses occur when the Moon's orbit crosses the Sun's path.

The idea of a zodiac is relatively complex, and long-term observation of planetary motion is quite possible without it. The idea of naming the various constellations in the sky for gods and animals is ancient; the singling out of the 12 constellations that constitute the zodiac goes back at least to the second millennium B.C.E. in ancient Mesopotamia. The zodiac as it appears in modern astrology was certainly in use by the sixth century B.C.E. Each culture gave the constellations of the zodiac different names, the modern Western zodiac being derived from the Greeks. The designation of 12 constellations, a worldwide phenomenon, relates to the division of the year by the Moon's 12 complete orbits through the zodiac in each solar year.

In modern astrology, two different zodiacs are popularly recognized. The sidereal zodiac reflects the actual location of the constellations in the night sky. Practitioners of Vedic astrology use this zodiac. The position of the constellations relative to the beginning of the years shifts slightly each year due to the phenomenon known as the procession of the equinoxes. Most Western astrologers use the tropical zodiac as defined by Ptolemy in the second century C.E. According to Ptolemy, the astrological year would begin each spring equinox and it would assume that the sun was at 0 degrees Aries. Due to the progression of the equinoxes, the sun at the spring equinox is close to 0 degrees Pisces. Much of the symbolism of the signs of the zodiac in Western astrology is tied to the seasons of the year. That symbolism would be lost with the acceptance of the sidereal zodiac.

The 12 signs of the zodiac are: Aries, Taurus, Gemini, Cancer, Leo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces.

Sources:

Brau, Jean Louis, Helen Weaver, and Allen Edwards. Lau-rouse Encyclopedia of Astrology. New York: New American Library, 1980.

Cirlot, J. E. A Dictionary of Symbols. New York: Philosophical Library, 1971.

McCaffery, Ellen. Astrology: Its History and Influence in the Western World. New York: Charles Scribner's Sons, 1942.