The Zodiac (literally the “circle of animals” or, in its more primary meaning, the “circle of life” or “circle of living beings”) is the belt constituted by the 12 signs—Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces. This “belt” is said to extend 8° or 9° on either side of the ecliptic (the imaginary line drawn against the backdrop of the stars by the orbit of the Earth). The orbits of the various planets in the solar system all lie within approximately the same geometric plane, so that, from a position within the system, all of the heavenly bodies appear to move across the face of the same set of constellations. Several thousand years ago, these constellations gave their names to the Zodiac.
The notion of the Zodiac is very ancient, with roots in the early cited cultures of Mesopotamia. The first 12-sign zodiacs were named after the gods of these cultures. The Greeks adopted astrology from the Babylonians, and the Romans, in turn, adopted astrology from the Greeks. These peoples renamed the signs of the Mesopotamian Zodiac in terms of their own mythologies, which is why the familiar Zodiac of the contemporary West bears names out of Mediterranean mythology. The notion of a 12-fold division derives from the lunar cycle (the orbital cycle of the Moon around the Earth), which the Moon completes 12 times per year. From a broad historical perspective, zodiacal symbolism can be found everywhere, and zodiacal expressions are still in use in modern English—e.g., “bull-headed” (an allusion to Taurus), “crabby” (an allusion to Cancer), etc.
The popularity of Sun-sign astrology (the kind found in the daily newspaper) has kept these ancient symbols alive in modern society, so that even such prominent artifacts as automobiles have been named after some of the signs (e.g., the Taurus and the Scorpio). The sign of the Zodiac the Sun is in at the time of a person’s birth is his or her Sun sign (sometimes also called the birth sign). The Sun, as the most important celestial body for Earth-dwellers, is the most important influence in a horoscope (an astrological chart). Consequently, the sign that the Sun is in at birth will usually be the single most important influence on an individual’s personality. Thus when people say that they are a certain sign, they are almost always referring to their Sun sign. Sun-sign astrology, which is the kind of astrology one finds in newspapers and magazines, has the advantage of simplicity—all one needs to know is one’s birthday to be able to figure out one’s sign—but this simplicity is purchased at the price of ignoring all other astrological influences.
The other important celestial bodies, for example, were all located in signs at the moment of birth. Thus, someone with a Scorpio Sun sign might also have a Sagittarius Moon sign, a Virgo Venus sign, a Libra Mercury sign, etc. Each of these other signs has an influence, which is why everyone with the same Sun sign does not have the same personality. The subsidiary influences of the sign positions of the planets is further modified by the angles between them (referred to as aspects), as well as by their house positions (another set of 12 divisions).
These other influences make Sun-sign astrology a hit-or-miss system that works sometimes but fails miserably at others. Professional astrologers tend to dislike Sun-sign astrology because it creates a misconception of the science of the stars (i.e., that astrology is entirely about Sun signs), and because its inaccuracy leads non-astrologers to reject astrology as untrue. Similar remarks apply to predictions of the future by the 12 signs. Sun sign prediction, in other words, is also a hit-or-miss system that sometimes works and sometimes misses the mark entirely. The columns found in popular periodicals also tend to create misperceptions about the nature of astrological prediction. In particular, readers can come away with the impression that astrological prediction is a kind of astrological fortune-telling that portrays the stars as if they foretold an irrevocable destiny for the person having her or his fortune told. Modern astrologers, however, tend to distance themselves from this tradition of predicting specific events. Instead of predicting events, most contemporary astrologers describe upcoming planetary conditions, with the understanding that clients have the free will to respond to planetary influences in different ways. Like a meteorologist, an astrologer can only predict trends and probabilities—not details.
THE ASTROLOGY BOOK - The Encyclopedia of Heavenly Influences