Zodiac

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Name given to the twelve constellations that the ecliptic crosses - actually it crosses a thirteenth, Ophiuchus, but this is traditionally excluded from the list. Because the ecliptic lies in the general plane of the solar system, the Sun and planets seem to move through the Zodiacal constellations.

A traditional mnemonic:

The Ram, the Bull, the Heavenly Twins,
And next' the Crab, the Lion shines,
The Virgin and the Scales.
The Scorpion, Archer, and the Goat,
The Man who holds the Watering Pot,
And Fish with glittering scales.
SignSymbol Birthdates
TropicalSiderealActual Astronomical Dates
(as of 2000 AD)
Aries March 21 - April 19 April 14 - May 14 April 19 - May 13
Taurus April 20 - May 20 May 15 - June 14 May 14 - June 19
Gemini May 21 - June 20 June 15 - July 16 June 20 - July 20
Cancer June 21 - July 22 July 17 - August 16 July 21 - August 9
Leo July 23 - August 22 August 17 - September 16 August 10 - September 15
Virgo August 23 - September 22 September 17 - October 17 September 16 - October 30
Libra September 23 - October 22 October 18 - November 16 October 31 - November 22
Scorpius October 23 - November 21 November 17 - December 15 November 23 - November 29
Ophiuchus November 30 - December 17
Sagittarius November 22 - December 21 December 16 - January 14 December 18 - January 18
Capricornus December 22 - January 19 January 15 - February 12 January 19 - February 15
Aquarius January 20 - February 18 February 13 - March 14 February 16 - March 11
Pisces February 19 - March 20 March 15 - April 13 March 12 - April 18

The "tropical" zodiacal dates (those that divide the zodiac starting with the vernal equinox) are used primarily in the United States and western Europe. The "sidereal" dates (those that divide the zodiac starting with the alignment of the Sun with a distant star in Aries) are used everywhere else.

Even people who don't know anything about constellations have heard about the constellations (signs) of the Zodiac in an astrological context.

The astronomers/astrologers (originally the observations and magic/religious applications were made by the same people), tried to use the movements of the night sky with divinatory purposes. Some of these applications where founded on correspondence between practical knowledge and celestial observations (for example, the relationship between solar position and stellar positions depends on the season, which has practical implications for agriculture), some others completely unfounded.

The "sign" under which a person is born, used to depend on the apparent position of the sun relative to the position of the houses of the Zodiac, the constellations on the ecliptic, on his/her birthdate. But because of the precession of the Equinox over the last three thousand years or so, the "signs" are out of phase with the real position of the sun by about a month. Some modern astrologers attempt to take this into account in drawing astrological charts.

The idea of astrological birth sign is that the person would have some characteristics of the arbitrary shape that the ancients identified with a group of stars; so, for example, a "Libra" (the scales) will be balanced and stable. Also, as mentioned in the main article, the planets are found near the ecliptic, and by consequence, in the zodiac. The position of a planet relative to a particular constellation would have a consequence on the life of a person born under not only under that "sign", but also on one with a different birth sign. For example: A person may be born on, say, June 1st. This is near the center of the sign of Gemini, and so Gemini would be his birth sign. Any planets also observed to be within the 30 degrees of sky occupied at its center by Gemini, would be said to have a particularly strong effect on the destiny and personality of the person. If, at the same time, other planets are seen to be within other signs of the zodiac, then their effects would be felt on the portions of a person's life "ruled" by that sign. Significance is also imputed to the angular positions of planets and signs relative to each other at the moment of a birth or other significant event.

One of the first great modern astronomers, Kepler, was also an astrologer. Whether he was both from conviction or simply to have a supplementary income, is still debated.

Modern astrology tries to dress itself with the garments of real science, using computers and in some cases adding more recently found planets and other objects to make its evaluations and predictions. However, astrology should be regarded as an entertainment (or in the best of cases an art) - one that is followed by millions of people worldwide.