Why Your Zodiac Sign Hasn’t and Won’t Change

NASA has caused quite a stir with its mention of a thirteenth constellation, Ophiuchus, inferring that there is a thirteenth zodiac sign and that the dates of the existing 12 signs have moved. This is based on a wrong interpretation of the origins of astrology from not only NASA, but the slew of journalist writing about this topic recently. In this article, we are going to clear up the confusion and show you why your zodiac sign has not changed…


Three Zodiac Systems

The misinterpretation by NASA has to do with confusion of the three types of zodiac, which are as follows:

– Tropical Zodiac: a zodiac system which is based on seasons and which Western astrology adheres to.

– Sidereal Zodiac: which is based on constellations and is what Eastern astrology adheres to.

– Astronomical Constellations: which is based on a system defined in 1930 by the International Astronomical Union and defined the boundaries of 88 constellations.

These systems all use similar names and origins, but it does not infer that only one system is correct. Therefore, you should take NASA’s statements about the number of zodiac signs and date ranges with a grain of salt.

Origin of the 12 Sign Zodiac

Around 500 BC in Mesopotamia, the 12 sign zodiac used chosen constellations along the annual path of the sun.

Babylonians used zones based on equinoxes and solstices. They divided the sky into 12 zones, roughly 30° apart. The autumnal equinox starts with the sign of Aries at the northern hemisphere vernal equinox which is on or around March 21 of each year – and always will.

300 years later, the Ptolemy refined and defined the Western Tropical Zodiac system that we use today.

The Father of Western Zodiac: Ptolemy

The Ptolemy established what is known as Tropical Zodiac in the second century in Alexandria. He established a stable measuring system based on the position of the planets. The planets are measured within zones which are defined by the path of the Sun as seen by Earth.

The Tropical Zodiac system starts with Aries at the position of the Sun at the optimal equinox. Therefore, shifts in the Earth’s axis do not affect this zodiac system. Ptolemy based the system on equinoxes and solstices. Fixing it in this way prevents it from slipping out of alignment for centuries to come.

Any confusion, comes from the fact that the Ptolemy used similar or the same names for the signs as the names of the constellations when developing the system. This is further confused by the names being based upon scientifically artificial constellations.

The Ptolemy and Ophiuchus

Ptolemy mentioned Ophiuchus too. He recognized it among 48 other constellations listed in Almagest and Tetrabiblos. However, he only allocated 12 constellations to the Tropical Zodiac.

The Tropical Zodiac system is not based on constellations, therefore, the thirteenth constellation Ophiuchus has no effect on the system. The Tropical Zodiac system is solely based on the motion of the planets relative to our year; it is based on the annual orbit of earth around the sun, not on the stars.

Initially when astrologers did not yet have charts of planetary tables, it was simply more convenient and accurate to use the “distant stars” that were visible and had the appearance of being “fixed.,” At the time, this was more consistent for measuring the positions of “wandering stars,” otherwise known as the planets of our solar system.

Moon Cycles

There are some that present the case for thirteenth sign based on the fact that the moon performs 13 rotations per year around the earth. That’s all fine and dandy but, astrology is more concerned with lunar cycles. Lunations start at a new moon and there are only 12 per year. Lunations are based on the cycle of the sun and moon.

Why 13 Signs Do Not Work

The method in which astrology works is based on three qualities (Cardinal, fixed and mutable) and four elements (fire, Earth, air and water) coming together to form the 12 signs.

The Planets

The planets considered in Western astrology are better termed astrological planets. Rather than the known planets we observe in our solar system, astrology is based on the seven heavenly bodies that were known to the ancients. The Sun and the Moon are also included. They are known as “the lights” because they were thought to act like astronomical planets. The seven “astrological planets” are: Mercury, Venus, Mars, Jupiter, Saturn, the Sun, and the Moon.

How Astrology Is Interpreted

Five key factors are considered when interpreting a horoscope in the western tropical system. They are:

– The position of the astrological planets in the astrological signs of the zodiac.
– The position of the astrological planets in the “houses” of the horoscope.
– The position of the “primary angles” of the horoscope, or “horizon line” also called the “ascendant/descendant axis”; in addition to considering the “prime vertical line” also called the “Zenith/Mid-heaven axis.”
– The angles formed by the astrological planets in relation to one another and their primary angles called aspects.
– The position of produced astronomical entities, such as the “lunar nodes.”

A full explanation and definition of the above factors in interpreting astrology is beyond the scope of this article. There mention goes to show how well the current Western Tropical Zodiac System is established.

Your Zodiac Sign Will Not Change

As you have read, the factors and practices of interpretation that make up Western Tropical Astrology, as we all know it, is well established. It is not based on constellations as NASA in their uninformed manner would lead you to believe. Astrology as we all know and love it in the West is not based on astronomical constellations.Western astrology is based on seasons.The occurrences of equinoxes and solstices has not changed. The interactions of the sun and moon have not changed. Everything we know about Western astrology has not changed. No matter what the TV news, Internet, or newspapers say… Your sign is still the same– It will not change!


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If you’d like to learn more about Astrology in general, then check out our Astrological Articles, watch these Zodiac Videos, or head on over to Zodiac 101 to learn more about each individual sign, and the meaning of it all.

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did you know

If you need a hard worker who won’t get distracted from the task at hand, choose a Capricorn!

In case you’re curious – if your sign was Ophiuchus, your birth date would fall between Nov 30 and Dec 10.