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[[File:Zodiac-Signs.png|300px|thumb|Signs of the Western Zodiac]] | [[File:Zodiac-Signs.png|300px|thumb|Signs of the Western Zodiac]] | ||
The '''zodiac''' is a belt-shaped region of the sky that extends approximately 8° north or south (as measured in celestial latitude) of the ecliptic, the apparent path of the [[Sun]] across the celestial sphere over the course of the year. The paths of the [[Moon]] and visible planets are within the belt of the zodiac. | The '''zodiac''' is a belt-shaped region of the sky that extends approximately 8° north or south (as measured in celestial latitude) of the ecliptic, the apparent path of the [[Sun]] across the celestial sphere over the course of the year. The paths of the [[Moon]] and visible planets are within the belt of the zodiac. | ||
The zodiac is a fundamental aspect of [[astrology]] and the casting of [[horoscope]]s. | |||
==Name== | ==Name== | ||
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==Composition== | ==Composition== | ||
As each sign takes up exactly 30 degrees of the zodiac, the average duration of the solar stay in each sign is one twelfth of a sidereal year, or 30.43 standard days. Due to Earth's slight orbital eccentricity, the duration of each sign varies appreciably, between about 29.4 days for Capricorn and about 31.4 days for Cancer. In addition, because the Earth's axis is at an angle, some signs take longer to rise than others, and the farther away from the equator the observer is situated, the greater the difference. Thus, signs are spoken of as "long" or "short" ascension. | As each sign takes up exactly 30 degrees of the zodiac, the average duration of the solar stay in each sign is one twelfth of a sidereal year, or 30.43 standard days. Due to [[Earth]]'s slight orbital eccentricity, the duration of each sign varies appreciably, between about 29.4 days for Capricorn and about 31.4 days for Cancer. In addition, because the Earth's axis is at an angle, some signs take longer to rise than others, and the farther away from the equator the observer is situated, the greater the difference. Thus, signs are spoken of as "long" or "short" ascension. | ||
In Western [[astrology]], and formerly astronomy, the zodiac is divided into twelve signs, each occupying 30° of celestial longitude and roughly corresponding to the star constellations: | In Western [[astrology]], and formerly astronomy, the zodiac is divided into twelve signs, each occupying 30° of celestial longitude and roughly corresponding to the star constellations: | ||
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The zodiac and system of astrology currently in use in the Western world today has no real connection to the astrology used by the ancient [[Egyptian religion|Egyptians]], although they do sometimes utilize the same stars. The Egyptian system was based on the fixed stars, specifically [[Sirius]] and the movement of the [[Egyptian decans|decanal stars]] across the night sky. Although the Egyptians did organize the decans into groups, these were not in any way similar to the "connect the dots" constellations of Hellenistic and Persian astrology. | The zodiac and system of astrology currently in use in the Western world today has no real connection to the astrology used by the ancient [[Egyptian religion|Egyptians]], although they do sometimes utilize the same stars. The Egyptian system was based on the fixed stars, specifically [[Sirius]] and the movement of the [[Egyptian decans|decanal stars]] across the night sky. Although the Egyptians did organize the decans into groups, these were not in any way similar to the "connect the dots" constellations of Hellenistic and Persian astrology. | ||
The division of the ecliptic into the zodiacal signs originates in Babylonian astronomy during the first half of the 1st millennium BC. The zodiac draws on stars in earlier Babylonian star catalogues, such as the MUL.APIN catalogue, which was compiled around 1000 BC. Some constellations can be traced even further back, to Bronze Age (First Babylonian dynasty) sources, including Gemini "The Twins," from MAŠ.TAB.BA.GAL.GAL "The Great Twins," and Cancer "The Crab," from AL.LUL "The Crayfish," among others. | The division of the ecliptic into the zodiacal signs originates in Babylonian astronomy during the first half of the 1st millennium BC. The zodiac draws on stars in earlier Babylonian star catalogues, such as the MUL.APIN catalogue, which was compiled around 1000 BC. Some constellations can be traced even further back, to Bronze Age (First Babylonian dynasty) sources, including [[Gemini]] "The Twins," from MAŠ.TAB.BA.GAL.GAL "The Great Twins," and [[Cancer]] "The Crab," from AL.LUL "The Crayfish," among others. | ||
Around the end of the 5th century BC, Babylonian astronomers divided the ecliptic into 12 equal "signs", by analogy to 12 schematic months of 30 days each. Each sign contained 30° of celestial longitude, thus creating the first known celestial coordinate system. According to calculations by modern astrophysics, the zodiac was introduced between 409 and 398 BC, during Persian rule, and probably within a very few years of 401 BC. Unlike modern astrologers, who place the beginning of the sign of Aries at the position of the Sun at the vernal equinox in the Northern Hemisphere (March equinox), Babylonian astronomers fixed the zodiac in relation to stars, placing the beginning of Cancer at the "Rear Twin Star" (β Geminorum) and the beginning of Aquarius at the "Rear Star of the Goat-Fish" (δ Capricorni). | Around the end of the 5th century BC, Babylonian astronomers divided the ecliptic into 12 equal "signs", by analogy to 12 schematic months of 30 days each. Each sign contained 30° of celestial longitude, thus creating the first known celestial coordinate system. According to calculations by modern astrophysics, the zodiac was introduced between 409 and 398 BC, during Persian rule, and probably within a very few years of 401 BC. Unlike modern astrologers, who place the beginning of the sign of Aries at the position of the Sun at the vernal equinox in the Northern Hemisphere (March equinox), Babylonian astronomers fixed the zodiac in relation to stars, placing the beginning of Cancer at the "Rear Twin Star" (β Geminorum) and the beginning of Aquarius at the "Rear Star of the Goat-Fish" (δ Capricorni). | ||
Due to the precession of the equinoxes, the time of year the Sun is in a given constellation has changed since Babylonian times, the point of March equinox has moved from Aries into Pisces. | Due to the precession of the equinoxes, the time of year the Sun is in a given constellation has changed since Babylonian times, the point of March equinox has moved from [[Aries]] into [[Pisces]]. | ||
Because the division was made into equal arcs, 30° each, they constituted an ideal system of reference for making predictions about a planet's longitude. However, Babylonian techniques of observational measurements were in a rudimentary stage of evolution. They measured the position of a planet in reference to a set of "normal stars" close to the ecliptic (±9° of latitude) as observational reference points to help positioning a planet within this ecliptic coordinate system. | Because the division was made into equal arcs, 30° each, they constituted an ideal system of reference for making predictions about a planet's longitude. However, Babylonian techniques of observational measurements were in a rudimentary stage of evolution. They measured the position of a planet in reference to a set of "normal stars" close to the ecliptic (±9° of latitude) as observational reference points to help positioning a planet within this ecliptic coordinate system. | ||
In Babylonian astronomical diaries, a planet position was generally given with respect to a zodiacal sign alone, less often in specific degrees within a sign. When the degrees of longitude were given, they were expressed with reference to the 30° of the zodiacal sign, i.e., not with a reference to the continuous 360° ecliptic | In Babylonian astronomical diaries, a planet position was generally given with respect to a zodiacal sign alone, less often in specific degrees within a sign. When the degrees of longitude were given, they were expressed with reference to the 30° of the zodiacal sign, i.e., not with a reference to the continuous 360° ecliptic. | ||
===Hebrew astronomy and astrology=== | ===Hebrew astronomy and astrology=== | ||
[[File:ZodiacCircle.png|350px|thumb|A modern zodiac wheel]] | [[File:ZodiacCircle.png|350px|thumb|A modern zodiac wheel]] | ||
Knowledge of the Babylonian zodiac is said to be reflected in the Hebrew [[Bible]]; E. W. Bullinger interpreted the creatures appearing in the book of Ezekiel as the middle signs of the four quarters of the zodiac, with the Lion as Leo, the Bull is Taurus, the Man representing Aquarius and the Eagle representing Scorpio. Some authors have linked the twelve tribes of Israel with the same signs or the lunar Hebrew calendar having twelve lunar months in a lunar year. Martin and others have argued that the arrangement of the tribes around the Tabernacle (reported in the Book of Numbers) corresponded to the order of the zodiac, with Judah, Reuben, Ephraim, and Dan representing the middle signs of Leo, Aquarius, Taurus, and Scorpio, respectively. | Knowledge of the Babylonian zodiac is said to be reflected in the Hebrew [[Bible]]; E. W. Bullinger interpreted the creatures appearing in the book of Ezekiel as the middle signs of the four quarters of the zodiac, with the Lion as [[Leo]], the Bull is [[Taurus]], the Man representing [[Aquarius]] and the Eagle representing [[Scorpio]]. Some authors have linked the twelve tribes of Israel with the same signs or the lunar Hebrew calendar having twelve lunar months in a lunar year. Martin and others have argued that the arrangement of the tribes around the Tabernacle (reported in the Book of Numbers) corresponded to the order of the zodiac, with Judah, Reuben, Ephraim, and Dan representing the middle signs of Leo, Aquarius, Taurus, and Scorpio, respectively. | ||
==Use in astronomy== | ==Use in astronomy== | ||