Astrology is a divination consisting of the interpretation of the influence of heavenly bodies (see other stars and planets) on Earthly affairs and human destinies. Originating in 3rd century BC Mesopotamia, it quickly spread to India and China in the East, and to Greece and the Mediterranean world in the West. Entering the Islamic culture due to early Greek influence, these beliefs found their way back into European society during the early Middle Ages. Astrology was also important in ancient China, and in imperial times it became standard practice to have a horoscope cast for each newborn child and at all decisive junctures of life. Though the Copernican system shattered the geocentric worldview that astrology requires, interest in astrology has continued into modern times and astrological signs are still widely believed to influence personality.
According to tradition, the Heavens are divided according to the 12 constellations of the zodiac, and the bright stars that rise at intervals cast a spiritual influence over human affairs. In this belief system, a belt around the heavens extending 9° on either side of the ecliptic, the plane of the Earth's orbit and of the Sun's annual path. The orbits of the Moon and of the planets also lie entirely within the zodiac. The 12 astrological signs of the zodiac are each considered to occupy 1/12 (or 30°) of its great circle. Because most of the constellations through which the ecliptic passes represent animals, the ancient Greeks called its zone zōdiakos kyklos, “circle of animals,” or ta zōdia, “the little animals.” The size and number of zodiacal constellations varied in antiquity and became fixed only with the development of mathematical astronomy. The list below gives the constellations of the zodiac, with the dates of the Sun’s passage through them in the era when their boundaries were fixed. These dates are still used for the astrological signs, though precession of the equinoxes has shifted the constellations eastward; e.g., on January 1 the direction of the sun is now in Sagittarius instead of Capricornus. The history of the symbols is unknown; they seem to appear first in Greek manuscripts of the late Middle Ages.
Planetary rulership reserves a big spot in astrological analysis as it indicates how the planets influence the energy of each of the zodiac signs. Each sign has a specific ruling planet, which provides a bonus layer into the bigger picture of the birth chart.
Zodiac sign qualities (also called modalities or triplicities) refer to the different stages in the year's seasonal cycle, grouped into the following three: Cardinal zodiac signs start a season. Fixed zodiac signs embody each season fully. Mutable zodiac signs conclude each season and help to transition us into the next one.
