How it began
The zodiac was invented in ancient Babylon, in present-day Iraq, around 500 BCE. Britannica states that the Babylonians divided the zodiac into 12 signs, each occupying one twelfth, or 30 degrees, of its great circle, about 500 BCE. Mathieu Ossendrijver, a historian of science at Freie Universitat Berlin, calls this change the zodiacal turn and places it in Babylon about 2,500 years ago.
Before it existed
Before the zodiac existed, the Babylonians had already observed and recorded the movements of the stars and planets and had recognized regularities and patterns in them. They then went beyond observation and developed mathematical techniques to calculate and predict the motions of the planets. Ossendrijver describes this as a mathematical turn that formed part of the zodiacal turn.
How it works
The zodiac is a band of sky a few degrees above and below the apparent path of the Sun, within which the Moon and planets also appear to move. It is not a set of natural constellations but a mathematical construction, divided into twelve parts of 30 degrees each. Each part was given a figure and a name, such as Aries, Gemini, Leo or Virgo, taken from a constellation prominent in it. Positions of planets could then be calculated within the signs.
How it spread
From Babylon the zodiac and the horoscope spread through the ancient world and into the Roman Empire, and later into Jewish, Christian and Islamic cultures. Greek astrologers of the Hellenistic period divided the ecliptic into 12 equal signs of 30 degrees, and in this, Britannica notes, they followed the Babylonians. The ancient Greeks also gave the zodiac its name.
Where it stands today
The Babylonian division still serves as the basis for horoscopes printed in magazines. Researchers attribute its persistence to the human wish to know the future and to an abstract system of numbers and constellations that translates easily across languages and scripts. In 2022 Freie Universitat Berlin opened an institute whose ZODIAC project studies the invention and its transmission.
