The Zodiac

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Podcast Transcript

Several thousand years ago, astronomers in the Middle East studying the night sky divided it into 12 equal regions. Each region was given a name, was associated with an animal and a constellation.  

These divisions became the basis for the nascent disciplines of astronomy and astrology.

Today, the system created by those ancient astronomers can still be found in the pseudoscience of horoscopes and the very much science of astronomy. 

Learn more about the zodiac and the signs of the zodiac, where they came from, and how they spread around the world on this episode of Everything Everywhere Daily.


I’ll start this discussion by noting that the zodiac is technically different from the collection of constellations found in the zodiac.

The zodiac is the region of the sky that is approximately 8 degrees north or south of the ecliptic. 

If you recall from past episodes, the ecliptic is the plane in which the Earth orbits the Sun. From the Earth’s vantage point, it is the path that the Sun makes in the sky.  The Moon and all other visible planets can be found in this same region of the sky because they all have orbits on the ecliptic plane. 

So the Zodiac is just the belt in the night sky that surrounds the ecliptic. 

This is an actual astronomical concept, not an astrological one. 

Before I get much further, I should point out that thousands of years ago, even hundreds of years ago for that matter, there wasn’t really a difference between astrology and astronomy. 

The main reason anyone cared about tracking the stars in the sky was for purposes of divination and religion. Even if the way the observations were used weren’t scientific, the observations themselves were. 

So, within this belt in the sky which we call the zodiac, are 12 constellations that you are probably familiar with. What is the deal with those, and where did they come from?

The signs of the zodiac were given to us by ancient Babylonian astronomers. 

For certain, humans had been looking up at the night sky for hundreds of thousands of years, and during that time, every group of humans probably gave names to the collection of stars they found interesting. 

The Babylonians really took sky observations to another level. If you remember from several previous episodes, the Babylonians had a system of numbers that was base-60 as opposed to our system, which is base-10.

The Babylonians gave us a circle with 360 degrees, which makes perfect sense if you have a base-60 numbering system. 

They then took the zodiac band of the night sky and divided it up into 12 different sections to correspond to the number of months in a year. 

Over 4000 years ago, the Egyptians had their own system where they divided the night sky into 36 different zones, called a decan. It isn’t known if the Babylonian system came from the Egyptian system or if it was developed independently. 

Each of the 12 zones had a primary constellation that defined the zone and after which it was named after. Their divisions of the sky were more approximate than precise because they didn’t have the ability to measure down to a level of detail beyond that.

When they saw a new constellation start to rise over the horizon, then they would know that they were entering in a new part of the zodiac. I should note that while each zodiac constellation is set within a region of the sky, they are all different sizes. Virgo is five times larger than Scorpio.  

Unlike modern astrologers, each part of the zodiac was set again the stars, not the sun, for the Babylonians. It is common today to define Aires as beginning with the vernal equinox in March. However, in reality, the vernal equinox now is actually in Pisces. 

This change zodiac constellation that the vernal equinox appears in is due to precession. As I mentioned in a previous episode on Milankovitch Cycles, we measure our years as solar years, so equinoxes and solstices are around the same date. 

However, there is a sidereal year which is slightly different from a solar year. This measures where this Earth is with respect to the stars. The difference over a whole year is only 20 minutes, 24.5 seconds.

It isn’t much, but it adds up over the years. In fact, every 2,160 years, the difference between solar and sidereal years will be big enough that the vernal equinox will be in a new zodiac sign. This period of time is known as an astrological age. 

When the Babylonians first figured it out, it was the Age of Aires. Currently, it is the Age of Pisces, which is coming to a close. The next age will be the Age of Aquarius, which is a phrase you’ve probably heard before, from the hit song from the 1969 musical “Hair”. 

The problem is there is no set dividing line for when these ages begin or end. Some say we are in the Age of Aquarius now, some say we are still centuries away. 

The time it takes to go through all 12 of these ages is known as a Great Year, and it takes ??25,920 to go through a complete precision cycle. 

While it is generally agreed upon that the Babylonians were the inventors of the zodiac and the 12 constellation system, most of what you might know of it isn’t Babylonian. It’s Greek. 

The Babylonian system became the basis for the astronomical and astrological systems of many different cultures. 

Hebrew astrology was based on the Babylonian system, and there are some who argue that the 12 signs of the zodiac are reflected in the 12 tribes of Israel

The Indian system of astrology was based on the Babylonian system, but it most probably arrived in India from Greece via Alexander the Great’s invasion. The words for the signs are different, but the symbols and what they represent are similar. 

The Indian system has stuck with the original sidereal signs, whereas the modern western system has gone with a solar or tropical system of zodiac signs. The western system, which astrologers still use today, was developed by the Greco-Egyptian astronomer Ptolemy in the first century.

Likewise, most Chinese researchers agree that the system of dividing the sky into 12 sections probably came into China from Babylon. However, China took it in a totally different direction and created a totally different zodiac which will be the subject of a different episode. 

It was the Greeks who also took the Babylonian symbols and expanded upon it. The names of the zodiac signs that we know today came from Greek or Latin, and I’m lumping them together because it was yet another thing the Romans just ripped off from the Greeks. 

The word “zodiac,” in fact, is a Greek word. It comes from z?diakòs kýklos, which means “circle of small animals.” 

Just to go through them briefly, even though I’m sure most of you have heard them, these are the 12 signs of the western zodiac and what they represent:

Aries, the ram

Taurus, the bull

Gemini, the twins

Cancer, the crab

Leo, the lion

Virgo, the maiden

Libra, the scales

Scorpio, the scorpion

Sagittarius, the archer

Capricorn, the goat

Aquarius, the water bearer

and Pisces, the fish

The use of the zodiac signs for western astrology, horoscopes, and other mystical divinations all comes from the aforementioned Ptolemy’s Tetrabiblos or four books. 

The Tetrabiblos laid the foundation for western astrology for 2,000 years, including by pagans, Christians, and Muslims. 

Astrology was considered to be very compatible with both Christianity and Islam for centuries and was practiced at the highest levels. Centuries ago, there were court astrologers for both Christian popes and Islamic caliphs. 

While astrological predictions eventually fell out of favor in religious circles, although it has never gone away completely, the use of the zodiac for astronomy lasted through the Renaissance. 

If you visit some older cities in Europe, you can still find references to the signs of the zodiac used as a reference for astronomy. The most famous example of this would be the Prague Astronomical Clock. One of its rings shows the signs of the zodiac as one of the clock’s complications. 

It was built in the early 15th century to display just how advanced and progressive Prague was. 

Likewise, astronomers used the zodiac as a reference point when describing features in the night sky, as there really wasn’t any other reference system. 

This system eventually fell out of favor for the far more accurate system of right ascension and declination. 

Despite the scientific revolution, some people have never stopped believing in astrology, even though western astrology is actually not even based on the location of the constellations that the astrological signs are named after.

Today when you hear the word “zodiac,” your mind immediately jumps to horoscopes or serial killers. However, there was a time when the zodiac was actually the most advanced system of astronomical categorization.  

The system which gave us a pseudoscience was also responsible for laying the foundations of the very real science of astronomy.


Everything Everywhere Daily is an Airwave Media Podcast. 

The executive producer is Darcy Adams.

The associate producers are Thor Thomsen and Peter Bennett.

Today’s review comes from listener c-crash, over at Apple Podcasts in the United States. They write, 

84 to go

Gary is amazing. how do you do it? I believe I better start supporting you . it’s only fair actually let me do that right now.

Thanks, c-crash!  If you’d like to support the show over at Patreon, well, don’t let me stop you. 

Actually, I figured I’d let everyone know that starting this month I’m going to begin doing some shorter, more off the cuff audio updates for patrons. These will not be full blown episodes, as I don’t have time to do more than what I’m doing now.

However, I do come across things which I don’t think I can make into full podcast episodes which I still think are of interest.  And there are always updates in the news to previous episodes that would probably be worth mentioning…..like the Artemis Program missions.

So, think of them as shorter episodes without a script. My first one is going to be on some of the ways you might not realize Buggs Bunny has impacted popular culture. 

So, if you’d like more Gary in your media diet, as well as support the show, head over to Patreon.com/EverythingEverywhere, or click on the link in the show notes.