What is the zodiac?

The word 'zodiac' has roots in ancient Greek and basically means 'circle of little animals'. It was the Europeans that attached this term to a yearly cycle they developed associated with the passage of the Sun through twelve constellations in the sky. This cycle is the basis for the 'if you were born between this date and that date you're this sign' thing that the newspaper horoscopes are rooted in. At this point in history (this is still well before Christ), people still thought the solar system revolved around the Earth - this is called the 'geocentric' ('Earth-centred') model . This theory would have encompassed the rest of the universe too, had they known more existed.

Anyway, the constellations of the zodiac are all contained within a band of sky that extends 8° above and below the path of the Sun across the heavens (called the ecliptic). This band encompasses all the movements of the Moon, the Sun and the 5 'classical' planets (Mercury, Venus, Mars, Jupiter and Saturn - the only ones that can be seen with the naked eye). This division of the sky into equal sections using these twelve constellations was the first attempt (at some point in the 1st millennium B.C.E) to assign a latitude/longitude system to the celestial sphere like the one we have now for the Earth. There are some differences between Earth and Zodiac latitude/longitude, though - the main one is that the equator of the zodiac latitude is the path of the Sun, not the actual equator of the Earth - the Zodiac and Earth equators are different by 23°, due to the tilt of the Earth on its axis. So the zodiac, originally, was meant to be a scientific way to map out the sky and the positions of the stars and planets.


Tropical zodiac or sidereal zodiac?

To be included in the zodiac, a constellation must lie within that 16° band of sky we call the ecliptic. Traditionally, there are 12 constellations contained within this band - Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius, Sagittarius, Capricornus, Aquarius and Pisces (these are obviously where we get the names for our star signs). But from an astronomical point of view, there are actually 13 constellations within the ecliptic - the 12 I've just mentioned plus another one called Ophiuchus. Ophiuchus doesn't appear in the traditional, 12-constellation zodiac because when it was first devised (in the 1st millennium B.C.E), Ophiuchus wasn't actually in the ecliptic - the changing positions of the Sun and Earth and everything else in the universe over the millennia have changed the positions of things in the celestial sphere, and today the Sun passes through Ophiuchus as well as the 12 classical constellations. This poses a question - do we continue on in the 'spirit' of the ancient zodiac and ignore the changes in the sky, or do we follow the stars around the celestial sphere? Fortunately, there's a variety of astrology for both situations - tropical and sidereal.

Tropical astrology is the type we all read in the paper every morning. It includes the 12 classical constellations in its calculations and uses their positions in the sky at the time the zodiac was devised. 3000 years ago, when the sky was first divided into its 12 neat sections by the Babylonians, the Earth and the Sun were in a vastly different position relative to the zodiac constellations. So, basically, tropical astrology is still casting horoscopes against the positions of the constellations in a 3000-year-old sky. It ignores the fact the Earth and Sun have moved in relation to the stars, and has not changed with the sky - as such, the sign dates are astronomically now out by about a month. This type of astrology applies the symbolic meanings of the zodiac.

Sidereal astrology is much less commonly used than the tropical variety. It includes whatever constellations are present in the ecliptic at that point in time and horoscopes are cast against the position of the Sun in the current sky. Consequently, the sign dates are somewhat different to those of tropical astrology and reflect the true progress of the Sun across the sky. Personally, I like this type of astrology better - it applies the real-time physical energies of the solar system!


Constellation Sign Symbol Identity Tropical Dates Sidereal Dates
Aries Aries Symbol for Aries The Ram March 21 - April 20 April 19 - May 13
Taurus Taurus Symbol for Taurus The Bull April 20 - May 21 May 14 - June 19
Gemini Gemini Symbol for Gemini The Twins May 21 - June 22 June 20 - July 20
Cancer Cancer Symbol for Cancer The Crab June 22 - July 23 July 21 - August 9
Leo Leo Symbol for Leo The Lion July 23 - August 22 August 10 - September 15
Virgo Virgo Symbol for Virgo The Virgin August 22 - September 22 September 16 - October 30
Libra Libra Symbol for Libra The Scales September 22 - October 23 October 31 - November 22
Scorpius Scorpio Symbol for Scorpio The Scorpion October 23 - November 22 November 23 - November 29
Ophiuchus ~ Symbol for Ophiuchus The Serpent Holder ~ November 30 - December 17
Sagittarius Sagittarius Symbol for Sagittarius The Archer November 22 - December 22 December 18 - January 18
Capricornus Capricorn Symbol for Capricorn The Goat December 22 - January 21 January 19 - February 15
Aquarius Aquarius Symbol for Aquarius The Water Bearer January 21 - February 19 February 16 - March 11
Pisces Pisces Symbol for Pisces The Fish February 19 - March 21 March 12 - April 18


Where did the zodiac sign symbols come from?

Each of the 12 constellations represented a certain animal to ancient astronomers, and they had appropriate corresponding symbols. The symbols we know today are not all animal forms, and have existed as we know them since about 200BC - our modern symbols are a simplification of older, more complicated ones.


What does the zodiac have to do with astrology?

Although the zodiac was not originally designed for divination, that's what astrologers use it for. They profess that the position of the planets in the zodiac constellations at someone's birth can be used to determine some traits that person will have and also what their future might hold - for example, people born between May 21 and June 22 are attributed the sign of Gemini in tropical astrology and are said to possess the traits of that sign, such as being patient and consistent people. Astrologers also believe that as different planets move through the sign (that is, the constellation) under which you were born, they have an effect on your immediate fortunes - this is the basis of the horoscopes we see in newspapers every day.


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