Q&A Friday: What Is the Zodiac, Anyway?

Astrology's astronomy

“So, what is the Zodiac, anyway?” I’m always happy to answer this question because there are so many misunderstandings surrounding it. Even astronomers and scientists like Neil deGrasse Tyson and Bill Nye clearly don’t understand the astrological Zodiac, or they’d stop trying to shoehorn Ophiuchus in where it doesn’t belong.

Essentially, the Zodiac is a way to locate planets (and other objects) in space in their relationship to Earth and to each other. The astrologer draws a chart of those locations, putting the three-dimensional reality of the solar system into a two-dimensional map centered on Earth, and interprets that map based on the symbolism of the Zodiac. The map is astronomically accurate; the Zodiac is a metaphysical template laid over it.

When astronomers map the sky, they use celestial coordinate systems, which are ways of placing objects within a specific frame of reference. The Zodiac is a 12-fold division of the ecliptic based on a geocentric ecliptic coordinate system.

Let’s start with some definitions. Geocentric means it is centered on the Earth. The ecliptic is the apparent path of the Sun along the celestial sphere, which tracks our yearly journey around the Sun. The celestial sphere is an imaginary sphere projected into space, centered on the Earth, that astronomers use to map the sky, using coordinate points similar to the latitude and longitude of Earth. (You can read more about that here.)

The Celestial Sphere

Since the ecliptic is a circle, and a circle is always 360°, it can be divided equally into twelve 30° sections. These sections are the signs, each of which designates a certain sector of the sky relative to the ecliptic.

Now, this is where it can get a bit complex because there are two separate branches of astronomy used in astrology. (But stick with me. It gets easier.)

Millennia ago, the signs were assigned their names according to the constellation that occupied that sector of the sky as the Sun moved through it from Earth’s perspective, beginning at the March equinox. However, because of something called axial precession or precession of the equinoxes, the background constellation at the March equinox slowly changed by about 1 degree every 72 years.

One type of astrology, sidereal astrology, jumps through some complex and varied mathematical hoops to keep the signs in alignment with their original constellations as the background constellation at the March equinox changed over the centuries. Vedic or Jyotish astrology is one example of this method.

Tropical astrology — which encompasses the branches known as Hellenistic and Western — puts the starting point of the zodiac on the ecliptic at the point where the ecliptic crosses the celestial equator (that’s just the equator projected onto the celestial sphere) at the March equinox. This point is zero degrees on the circle of the ecliptic.

Why is it called “tropical”? Because there are two circles of latitude, the Tropic of Cancer and the Tropic of Capricorn, that mark the points of the March and December solstices, the furthest points north or south Sun will reach in our sky, and tropical astrology is based on the relationship between Sun and Earth.

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Let me repeat that so it’s very clear: The background constellations do not matter to the tropical Western Zodiac because it is based on the relationship between Earth and the Sun, not on the relationship between Earth and the constellations.

It should be noted that branches of astrology that are based on the relationship between Earth and the constellations correct for axial precession in their calculations. Mostly, they use the same zodiac, but the dates differ.

Astrology is based on accurate astronomy. The difference between astrology and astronomy is that astronomers map the sky and draw conclusions about the physical nature of space and its objects. Astrologers use those maps but overlay them with the template of the Zodiac, an esoteric division of the ecliptic, and then draw conclusions about life on Earth based on the patterns they see there.

Having two such varied branches of astrology inevitably leads to the question of which one is “right”, which one is more accurate. I don’t know. (Though I wouldn’t have been practicing tropical Western astrology for over half a century if I didn’t think it worked well.) But here is my best guess.

I believe that, as we come to understand more about how the Universe is created and structured, we will find that it is a weaving of many different types of energy, some of which we know and can measure, some of which we have yet to discover. That weaving forms patterns of energy, which, in turn, form our physical reality. Astrologers read these patterns and interpret them in relation to the world we experience.

I don’t believe the planets give off some kind of rays that affect life on our planet (so don’t @ me with stats about gravitational influences). I’m open to the possibility that I’m wrong, but I’ve read those stats on gravitational influences too.

However, if the Universe is a weaving of energy and we are reading patterns as threads within that weaving, then it’s not surprising that different cultures have come up with different ways of identifying and interpreting those patterns. The Universe is unimaginably large and varied.

But we all live in the same solar system and look at the same sky. And both tropical and sidereal astrology use accurate celestial coordinate systems to cast their charts. The mystery of the Zodiac is how very well it allows us to interpret and even predict life here on our little blue marble. (Prediction is another mystery, but I’ll save that for another essay.)

Now, if astronomers and other scientists would stop fussing endlessly about the fact that astrologers lay a metaphysical template over their calculations, then they’d have a lot more time to do their work of discovering the secrets of the Universe. May it be so.

Do you have a question about astrology? Feel free to leave it in the comments or email me here.