PBP: Zōidiakos, or the zodiac

'Z' is not the easiest word to make a post around when it comes to Hellenism or ancient Hellas, and it says something special about me that my first thought for two years in a row is 'zombies'. No matter how much I love my zombie genre as well as Hellenism, there is no way I am going to be able to merge these without confusing a heck of a lot of people, so I'm settling on something else: the zodiac. The other option was 'zygote', so, you know, you got off easy today because I doubt anyone wants to hear me go on about the wonders of reproduction.


Anyway, the zodiac. To borrow heavily from Wikipdia, because I never really had much interest in the zodiac, the zodiac is a circle of twelve 30° divisions of celestial longitude that are centred upon the ecliptic: the apparent path of the Sun across the celestial sphere over the course of the year. The paths of the Moon and visible planets also remain close to the ecliptic, within the belt of the zodiac, which extends 8-9° north or south of the ecliptic, as measured in celestial latitude. Historically, these twelve divisions are called signs. Essentially, the zodiac is a celestial coordinate system, or more specifically an ecliptic coordinate system, which takes the ecliptic as the origin of latitude, and the position of the sun at vernal equinox as the origin of longitude.

The ancient Hellenes were already aware of celestial movements and the bodies in the sky, but it were the Romans who put everything together to form the zodiac we know today. The Hellenic name for constellations was 'katasterismoi', and of the katasterismoi, only twelve signs whose risings intersected the sun's at dawn were known as the 'zōidiakos' (ζῳδιακός) or 'zōdiakos kyklos' (ζῳδιακὸς κύκλος): 'circle of little animals'.

The modern zodiac is a mix between Babylonian astronomy, Hellenic thinking, Egyptian horoscopes, and good old Roman ingenuity. The division of the ecliptic into the zodiacal signs originates in Babylonian ("Chaldean") astronomy during the first half of the 1st millennium BC; the ancient Babylonians made the division into twelve equal 30º arcs, assigned each month to a sign, and set the starting point of the zodiac at the position fixed stars in the sky. They were the ones who set Aries as the starting point of the zodiac.

Astrologer and astronomer Ptolemy, whose work I am basing my constellation series off of, had a huge impact on the zodiac. Under the Hellenes, and Ptolemy in particular, the planets, Houses, and signs of the zodiac were rationalized and their function set down in a way that has changed little to the present day. Ptolemy forever cemented the stories behind the signs, and he also un-fixed them from the sky: instead of the Babylonian ecliptic system, he adopted what we now call the 'tropical' system.

The classical zodiac was introduced around the seventh to the sixth century BCE. At the time, the precession of the equinoxes had not been discovered. Classical Hellenistic astrology consequently developed without consideration of the effects of precession. The discovery of the precession of the equinoxes, is attributed to Hipparchus, a Hellenic astronomer active around 130 BC. Ptolemy, writing some 250 years after Hipparchus, was thus aware of the effects of precession. He opted for a definition of the zodiac based on the point of the vernal equinox, i.e., the tropical system. This shift means that the start of the zodiac is now always at the same time, even if the constellation associated with the zodiac sign is not yet showing. Currently, this means that the tropical sign of Aries lies somewhere within the constellation Pisces. Fun, right?

It is important to distinguish the zodiacal signs from the constellations associated with them, not only because of their drifting apart due to the precession of equinoxes but also because the physical constellations by nature of their varying shapes and forms take up varying widths of the ecliptic, and so the Sun is not in each constellation for the same amount of time. The zodiacal signs are an abstraction from the physical constellations designed to represent exactly one twelfth of the full circle each, or the longitude traversed by the Sun in about 30.4 days. The zodiac signs take their name from the constellations they are named after, but they are not synonymous.

The twelve zodiac signs are as follows: Aries, The Ram (Κριός - Krios); Taurus, The Bull (Ταῦρος -Tavros); Gemini, The Twins (Δίδυμοι - Didymoi); Cancer, The Crab (Καρκῖνος - Karkinos); Leo, The Lion (Λέων - Leōn); Virgo, The Maiden (Παρθένος - Parthenos); Libra, The Scales (Ζυγός - Zygos); Scorpio, The Scorpion (Σκoρπιός - Skorpios); Sagittarius, The Centaur (Τοξότης - Toxotēs); Capricorn, The Sea-Goat (Αἰγόκερως - Aigokerōs); Aquarius, The Water Carrier (Ὑδροχόος - Hydrokhoos), and Pisces, The Fishes (Ἰχθύες - Ikhthyes).

The zodiac can be used as the foundation of many things, including divination--something done by the ancient Hellenes. I doubt the ancient Hellenes drew horoscopes or the intricate maps we do to describe a person based on their date and time of birth, but the ancient Hellenes realized that this ever-turning wheel in the sky had an impact on them--or could perhaps explain a bit about them. Elements were already assigned to the signs at that time, of this we can be relatively sure. Ptolemy used them, at least. He also laid the groundwork for character traits associated with the signs today. So, the next time you are looking through the newspaper and find your horoscope, think of the ancient Hellenes, and Ptolemy in particular, because your prediction of (future) love was made possible by their hard work.

Image source: here.