Monday, June 28, 2010

Zodiac Signs and Their Dates Called Into Question

Zodiac Signs and Their Dates Called Into Question
Most people know their Zodiac signs, and their dates, but it turns out those Zodiac signs might not be correct when an astronomical phenomenon called "precession" is taken into account. This might need a little explaining.
Taurus is traditionally observed from April 20 to May 21, but it may be more accurate to observe it from May 13 - June 21. (Getty Images)
First, a Zodiac is broken up into 12 parts that measure, roughly, where the Earth is at on its year-long ellipse-shaped journey around the sun. Each of the 12 Zodiac signs is represented by a constellation. Whenever the sun appears to be in that constellation (based on where the Earth is at in its yearly ellipse), that's the current sign which we're under.

It can seem confusing, which is why each of the 12 phases have been conveniently broken up into the Zodiac we know, love and read about in horoscopes. Those dates are based on the premise that the vernal equinox takes place every year on March 20, which as enthusiasts will know is the beginning of the first Zodiac phase: Aries.

But here's where it gets messy. The vernal equinox is in a slow, continual flux thanks to a process called "precession" which basically makes the Earth wobble like a top. If you take precession into account, it actually changes many people's Zodiac signs.

Below I've included the original Zodiac dates with which many of us are familiar along with the Zodiac dates modified to reflect the effects of precession.

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