Zodiac (Babylonian)

Definition

The Babylonian zodiac is the division of the ecliptic — the Sun's yearly path through the sky — into twelve equal slices of 30° each. It replaced an older, uneven frame built from constellations of differing sizes. The earliest cuneiform text that uses zodiac signs (rather than constellations or the reference stars called Normal Stars) is the Diary VAT 4924, for the year -418, in the Persian-Achaemenid period; in that month-VIII record the planets are placed in the order Jupiter, Venus, Mars, Saturn, Mercury against what look like 30° signs.

In Tradition

In Babylonian mathematical astronomy, as Hunger and Pingree describe it, the twelve 30° signs are the standard frame for the System A and System B planetary ephemerides and for the Diary records of the Late Babylonian period. The Babylonian zodiac is sidereal — anchored to the fixed stars — rather than tropical, which would anchor it to the equinox. It is the line of descent from which the Greek tropical zodiac was later adapted, by way of Hipparchus and Ptolemy.

In Practice

Babylonian astronomers used the twelve-sign zodiac in two ways. As a measuring frame, it let them record planetary positions in the Astronomical Diaries (-652 to -61 BCE) and the Normal Star Almanacs. As a computing frame, it let them predict planetary events through the System A ephemerides (a zone-function method) and System B (a linear zigzag method). Each sign also carries a planet that does especially well there — the Babylonian "exaltation" assignments: Sun in Aries, Moon in Taurus, Jupiter in Cancer, Mercury in Virgo, Saturn in Libra, Mars in Capricorn, Venus in Pisces. These passed into Hellenistic astrology as the doctrine of exaltations.

Historical Origin

The earliest surviving zodiac-sign reference is VAT 4924 (the Diary for -418, month VIII; published in Sachs & Hunger, *Astronomical Diaries* Volume I, 1988). The zodiac is treated systematically in Hunger & Pingree, *Astral Sciences in Mesopotamia* (in the chapters on the Diaries and the Normal-Star Almanacs), and in Rochberg, *The Heavenly Writing* (chapter 4, on the Babylonian horoscope corpus).

Further Reading

  • Francesca Rochberg, The Heavenly Writing
  • Hermann Hunger & David Pingree, Astral Sciences in Mesopotamia
  • Otto Neugebauer, A History of Ancient Mathematical Astronomy