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the three zodiacs

Repeat after me three times:

“The signs in the astrological zodiac are NOT the same as the astronomical constellations.”

What does this mean for you?

That, no matter what the astronomers say, your astrological Sun sign never changes.

The Three Zodiacs

So, why does this story about changes to Zodiac signs (or its cousin about the 13th sign) keep popping up? (Like this recent version on Spirit Science.)

The word Zodiac refers to the circular band of the sky through which the Sun appears to travel through the course of the year as the Earth revolves around it.  It’s from a Greek word that means “life” or “way of life.”

But there are different ways to measure along this band, with different starting points or divisions.

And today, we have actually use three ways of describing the Zodiac: the Zodiac constellations, and the tropical and sidereal zodiacs.

Zodiac Constellations

In this case, the astronomers are referring to the constellations that fall across the zodiacal band, also called the ecliptic.  These constellation boundaries are uneven, and defined by the International Astronomical Union (the same folks who demoted Pluto to dwarf planet).

Beginning in 2011, astronomers — scientists who study the stars — started referring to 13 zodiac constellations, including Ophiuchus, in this zodiac. (Some systems also include the constellation Cetus as a 14th sign.)

Astrological Zodiacs

There are two astrological zodiacs: the tropical and the sidereal.

Both of these Zodiacs measure the ecliptic with 12 equal 30-degree divisions of the 360 degree circle. That’s why there have always been – and will always be – only 12 astrological zodiac signs. It’s just very convenient math.

These two zodiacs are actually identical, except for their starting points:

  • The tropical zodiac based on the seasons. This is the zodiac used in Sun sign columns and by most modern Western astrologers. Zero degrees Aries marks the first day of Spring and the beginning of this zodiac.
  • The sidereal zodiac, used primarily in Indian astrology (called Vedic or Jyotish), starts its 12-sign zodiac from the point against the backgournd of fixed stars where the Sun appears to be at the spring equinox.

Currently this means the tropical zodiac starts 24 degrees later than the sidereal zodiac.

Or, to put it another way, this means all tropical zodiac signs must be “backed up” 24 degrees to get a sidereal equivalent. For example, 0 degrees of Aries in the tropical zodiac would become 6 degrees Pisces in the sidereal Zodiac.

The Earth Zodiac

Western astrologers calculate zodiac signs using what’s called the Tropical Zodiac. The Tropical Zodiac is based on the Earth’s seasons, not the constellations.

Now, the word “tropical” may evoke images of beautiful blue water and sandy beaches. But the the word actually comes from ancient Greek words that mean "to turn" or a "turning point."

three zodiacsIn essence, your Western astrology sign measures how long after the Spring Equinox you were born.

A little background: our Earth tilts 23 1/2 degrees on its axis. So, as our planet orbits the Sun, the latitude where the Sun's appears directly overhead changes throughout the year. These changes mark our four seasons.

And the tropical zodiac measures the seasons from the point of view of the northern hemisphere:

• 0 degrees Aries is the Vernal Equinox, the beginning of Spring. The Sun appears over the equator.

• 0 degrees Cancer is the Summer Solstice. On this day, the Sun is at its highest point in the sky (and there’s 24 hours of daylight at the north pole).

• 0 degrees Libra is the Autumnal Equinox, the beginning of Fall. Once again the Sun is now over the equator.

• 0 degrees Capricorn is the Winter Solstice. On this day, the Sun appears at its lowest in the sky (and from the north pole, you can’t see it at all).

Each of the 12 tropical zodiac signs stretches 30 degrees, or 1/12 of a 360 degree circle. It takes exactly 1 year for the Sun to appear to travel through all 360 degrees.

So, if you were born in the 4th Zodiac sign (which happens to be called Cancer), you were born 4/12 (or ¼, or 90 degrees) past the spring equinox.

Why the difference in the Zodiacs?

So why is there a 24 degree difference in these two astrological zodiacs?

Well, the Earth wobbles on its axis. Over time, the location of the Sun at the spring equinox precesses (moves clockwise) agains the background stars about 1 degree every 72 years.

This “precession of the equinoxes” is what astronomers are attempting to adjust for when they “redefine” the zodiac. They are confusing the zodiacal constellations, with the astrological signs named after them.

You see, arround 2,500 years ago when our practice of astrology was being “invented” by the Hellenistic Greeks, the Sun could be found within the constellation Aries when Spring began.

An early Greek astrologer, Hipparchus of Nicea (190-120 BCE), coined the phrase “The First Point of Aries” to mark this starting point for the spring season.

(Ironically, it was less than 100 years after his death before the “First Point of Aries” had moved to Pisces.)

But the name “The Aries Point” was never changed. Even astronomers still use the term Aries Point to describe the starting place of their own measurement system around the celestial equator (called right ascension) where the Sun is located on the first day of spring.

Western tropical astrologers will still be using the term Aries Point in 2597 when the Sun will be found in the astronomical constellation of Aquarius on the first day of Spring.

Astrological signs are named after constellations, but are not the constellations themselves.

Why are the Astronomers so Confused?

So, why do astronomers keep trying to redefine the astrological zodiac?

Well, astronomers are’t stupid. They are aware of the differences between the constellations and meaurements along the ecliptic. In fact, they’re quite good at measuring things.

But, unfortunately, most astronomers have never taken the time to actually research what astrologers are doing, or why. (And they seem to forget that astrologers invented astronomy, just like the alchemists invented chemistry.)

Alas criticizing something you know little about doesn’t usually work well. There are, of course, plenty of things science could criticize about astrology, but this subject isn’t really one of them. It just makes astronomers sound ignorant.

And some of the astronomers probably do it because it’s a chance to get some press for astronomy. But, in a way, astrologers should be grateful – each time the topic gets brought up, it gives astrologers a chance to set the record straight!

About the author

Enid Newberg

Enid Newberg

Since 2006, Enid Newberg has served as president of Kepler College, one of the world’s largest online schools of astrology. An astrologer since 1973, Enid has an extensive background both in information systems and online learning. She holds a Master’s degree from Antioch University in Whole Systems Design.

1 Comment

  • Great explanation! I was just explain G the difference between astronomy and astrology to a friend who didn’t know that I am studying to be an astrologer. This explanation of the tropical and sidereal zodiacs was clear as a bell

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