There's another problem with the zodiac as astrologers see it and the position of the sun along the elliptic. That means if the founders of the zodiac had been aware of precession, she'd have been an Aries rather than going through her whole life as a Taurus. So taking 2010 as an example - an 'average year' slotted between two leap years - a child born on April 26, 2010, will be a Taurus despite the fact the sun was actually in the constellation Aries on that day and wouldn't move into Taurus until May 14. As result zodiac signs no longer align with the position of the sun.įor example, the astrological sign Taurus is said to govern the period between April 20 and May 20, as that's the constellation that the sun once appeared to be in during this period. That means that each period now occurs about one-tenth of a year - roughly a month - later than it did when astrology was being devised.īut horoscopes published in papers and magazines don't follow this astronomical system. For this reason, it is often called the precession of the equinoxes.Īs a result, the astrological signs have also shifted one-tenth around the elliptic to the west in relation to the background stars. Precession has also had the effect of shifting the equinoxes of Earth - the two points of the year at which day and night have equal lengths - along the ecliptic. Over the last 2,500 years, the intersection of the celestial equator and the ecliptic has drifted west along the ecliptic by 36 degrees - about one-tenth of its length.Īn illustration showing Earth's wobble along its rotational axis. This means that the North Pole isn't always pointing in the same direction as the background stars of the celestial sphere, and this effect accumulates. Watching this pole over the course of 25,800 years, we would see it trace out a circle over the Earth. To picture this precession, imagine a literal pole extending out of Earth at the North Pole. Known as precession this 'wobble' has a 25,800-year cycle. The gravity of the moon and the sun, and to a lesser extent the planets, acts on Earth's equatorial bulge - caused by the planet's rotation - to shift its axis of rotation.

The cause of the shifting in zodiac signs is precession, the slight 'wobble' Earth experiences as it orbits the sun. The problem was, that these ancient astrologers weren't aware of a ' wobble' in Earth's motion that would seriously disrupt their system as time progressed. The other astrological signs of the zodiac were categorized in a similar way, each grabbing its own 30-degree slice of the ecliptic. This intersection is also known as the vernal equinox and the spring equinox in the Northern Hemisphere because it is considered the first day of spring.Ģ,200 years ago this zero point occurred in Aries, hence its name the 'first point of Aries.' As a result, Aries the constellation occupied the first 30 degrees of the ecliptic from 30 to 60 degrees was taken by Taurus, and Gemini was positioned from 60 to 90 degrees. The zodiac was initially developed around 600 BCE and its zero point was defined as the point that the ecliptic intersected with the celestial equator - the great circle of the terrestrial equator on the celestial sphere. (Image credit: Wikimedia commons/Tauʻolunga) The inclusion of Ophiuchus and Cetus alters the dates of the 12 zodiac signs already known, so some people could change their sign.An illustration of the sun's motion relative to Earth throughout the year as it crosses in front of constellations representing the astrological signs of the zodiac. Ophiuchus is located between Scorpio and Sagittarius, and its origin dates back to Greek mythology as being related to Apollo's son, Asclepius, a physician with gifts of healing.Ĭetus is represented by a sea monster that, according to Greek mythology, Perseus kills when Andromeda was about to feed him, and is located between Aries and Pisces. What is the origin of Ophiuchus and Cetus and what are their dates?

Ophiuchus and Cetus are the two new signs proposed by astrology.īoth interact very little time with the Earth's orbit and their inclusion affects the distribution, elements and dates of the other signs. Like the months of years, there have been 12 igns: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius and Pisces, but astrology proposes the inclusion of two more signs.

The zodiac signs apparently reflect human behavior and activities in relation to their date of birth and the alignment of the stars. Astrology has considered the inclusion of two more signs: Ophiuchus and Cetus. Astrology has always worked with 12 zodiac signs, but everything can change at once.