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Why do we have 12 zodiac signs? Why not 4, 9, 15, 27 or any other random number?

What is the relationship between signs and the zodiac constellations? Does the procession of the equinoxes ‘change’ the signs?

In the next 3 days, I will write a 3-email series to answer 3 of the most frequently asked questions from readers and students.

This is the 1st email in the series:

Q: Why do we have 12 signs?

A: We have 12 signs because we have 12 months, or 12 lunar cycles in a year. Each sign corresponds to one lunar cycle, which is why there are 12 signs.

The complete answer can be traced back to the origins of tropical astrology, which aligns with the 12-month solar calendar.

Topical astrology means “derived from the tropics” or seasons and cycles. When the Sun reaches the maximum distance from the equator at 23° North (also called the Tropic of Cancer) we have the solstice, and the sign of Cancer.

When the Sun reaches the maximum distance downwards from the celestial equator at 23° South (also called the Tropic of Capricorn) we have the other solstice, and the Capricorn season starts.

You may think that the 12 tropical signs are the same thing as the 12 zodiac constellations… they are not.

The 12 tropical signs were indeed named after the constellations for easy reference (the Greeks ‘borrowed’ the zodiac constellations from the Mesopotamians) – but that’s pretty much as far as this relationship goes.

Coming back to our initial question – why 12, and not any other random number?

We have 12 signs (and not 10, or 15) because we have 12 lunar cycles in a year.

Put simply – we have 12 signs because there are 12 months. The word “month” comes from the Old English word “mōnaþ,” which means “Moon”. In a 365-day interval (a year) we have 12 lunar cycles (12 months).

We start the astrological year at the Equinox. So, the beginning of the astrological year is based on the position of the Sun relative to the Earth.

The entire tropical system is based on the relationship between the Sun, the Moon and the Earth. We have 12 lunar cycles (Moon) in 1 solar year (Sun), from the reference point of the Earth.

TO RECAP: Signs are cycles. They are NOT areas of the sky. They are NOT constellations.

This is a difficult concept to grasp even for seasoned astrologers. When we look at our mobile apps, we see the Moon in the constellation of Aquarius, but astrologers say we have the Moon in Pisces. Confusing, right?

Not if we understand that the signs are not the same thing as constellations. Just because you and someone else share the same name, it doesn’t mean you are the same person.

Just because the tropical signs and the 12 constellations on the ecliptic are called the same, it doesn’t mean they are the same thing. Of course, there is a relationship there, and we will get to that.

But first, let’s get this sink in. Signs are not something we can observe. Sings are cycles. We cannot “see” them, in the same way we cannot “see” time. If you think of time, you can’t localize it in the physical space; time is not a rock, or a tree. It is an abstract concept. So are the signs.

And it’s precisely due to the difficulty of conceptualizing these 12 cycles, aka the 12 signs, that our first tropical astrologers used the backdrop of the sky and the constellations to name them.

And this takes us to our 2nd important question:

Why do signs have constellation names?

In theory, they don’t have to. We could call them Sign 1 (or cycle 1), Sign 2, etc, or give them other names – many other cultures and traditions have other names for cycles of nature.

The reason Hellenistic astrologers used the constellations on the ecliptic (which preceded the 12 tropical signs) is because these constellations made it easier to track the positions of the Sun, Moon and planets in the sky.

Remember – we cannot see the signs, so these early astrologers needed some sort of system to figure out when the Moon, Venus or Jupiter were in the 1st sign (aka the first 30 days from the Equinox), in the 2nd sign (aka day 30 to 60 from the Equinox) and so on.

The first sign, or the first 30-day cycle from the Equinox was called Aries, because back in the day (approx 2.000 years ago, when Tropical astrology as we know it was conceptualized) it was the Aries constellation that was rising at the Equinox.

The next sign, aka the 30-day cycle following Aries, was called Taurus, because the constellation following Aries was Taurus.

In the tropical model, Aries, Cancer, Libra, and Capricorn are called “cardinal” signs because they mark the beginning of the seasons (i.e. when the Sun changes direction in the sky); so they have an initiating quality.

The signs in the middle of the seasons (Taurus, Leo, Scorpio, Aquarius) are “fixed” because in the middle of the season is when the weather is most stable.

And the signs at the end of the seasons (Gemini, Virgo, Sagittarius and Pisces) are called “mutable” because this is when the weather begins to change, as we are slowly moving into the next season.

In the tropical sign system, we also have the elements. The first sign (Aries) is a fire element, because fire is the primordial element. Next comes the element of earth (Taurus). We then have air, to allow movement (Gemini) and then finally the life-giving water (Cancer). Then the elements repeat.

When we combine “cardinal” and “fire” we get Aries, or the qualities of initiative, enthusiasm, and impulsiveness. When we combine “fixed” and “earth” we get Taurus – or the qualities of stability, persistence and practicality.

When we apply the modality/element matrix to the 12 lunar cycles we get the 12 tropical signs as we know them.

This tropical model is reliable and works well in both Hemispheres. Aries is “cardinal fire” in both the Northern and Southern hemispheres.

Of course, tropical astrology, where the astrological year starts with Aries, was created in the Northern Hemisphere; if astrology had been designed in the Southern Hemisphere probably the model would have looked a bit differently, but it would have still worked, if it was methodologically sound.

Next question:

How did the zodiac constellation influence the 12 tropical signs?

The zodiac constellations preceded the 12 signs. These constellations were already named by Babylonians by the time tropical astrology was born (approx. 2.000 years ago).

Some of the zodiac constellations were named as early as 16-18th centuries BC. Back then, Babylonians named around 18-22 constellations around the Ecliptic plus other constellations that were not on the zodiac belt (i.e. ecliptic).

These initial constellations had different sizes, because they were based on the actual star configurations, not on mathematical calculations.

Then, when tropical astrology was conceptualized approx. 2.000 years ago, the 18-22 constellations on the Ecliptic were resized (and some of them dropped) to fit the 12-cycle tropical model.

The fact that only the ecliptic constellations were used to name the signs (and not other non-ecliptic constellations like Orion, etc.) speaks about the solar system-centered, tropical origin of the 12 signs.

Now, we have the phenomenon called the procession of the Equinoxes, which means that constellations move with approx. 1 degree every 72 years as seen from Earth. The sky in 2023 looks quite different from how it looked 1.800 years ago, when Ptolemy wrote Tetrabiblos, the tropical astrology “bible”.

But this phenomenon doesn’t affect in any way our tropical, seasonal 12-sign system, because – again – the 12 signs are not based on constellations.

The tropical signs are solar system centered. The constellations and the stars are not in our solar system, so they are out of the scope of tropical astrology. (this does not mean that constellations and fixed stars don’t influence us, but that’s a different topic).

The Equinox happens on March 20-21 every.single.year everywhere on Earth. In 1.000 years from now, the Equinox (and the tropical sign of Aries) will still happen on March 20-21st. In 5.000 years, 10.000 years still on March 21st.

Tropical signs never shift – they cannot, because they are based on the Equinox and the seasons.

Did the Babylonian constellations influence the Hellenistic, 12-sign tropical model we are using today? Very likely. The astrological ages – which seem to correlate with the qualities of the zodiac constellations are a testament to that.

So, most likely, back in the day, there was some sort of conceptual transfer from the Babylonian sidereal model to the tropical model.

But again, this doesn’t change in any way our understanding of the 12 tropical signs, because they are based on a completely different framework – seasons, modalities, elements etc.

RECAP – Let’s summarize the answers to the initial questions

Q: Why do we have 12 signs?

A: Because we have 12 lunar cycles in a year.

Q: What is the relationship between signs and zodiac constellations?

A: The 12 tropical signs got their names from the zodiac constellations because 2.000 years ago, the constellations made it easier for our ancestors to track the position of the Sun, Moon and planets.

Since then, the backdrop of the sky has changed and is no longer a reliable way to track the tropical signs. Thankfully, we have astrology software that does it for us.

Q: Does the procession of the equinoxes ‘change’ the signs?

A: No, because tropical astrology is based on seasons and synodical cycles, NOT on the sidereal sky (constellations). So next time your ‘scientist’ friend says the procession of the equinoxes refutes astrology, tell them to do their research properly 😉

The origin of the 12 signs is a very important topic because understanding the tropical system is the very base of understanding western astrology. When we understand the origin and the nature of the tropical signs – everything else – planetary cycles, aspects, houses – falls into place.

Talking about houses – in the next email [2/3] I will talk about another frequently asked question: which house system to use?