Lunar Six

LOO-nar SIX

babylonian: NA + ŠÚ + NA + ME + GE₆ + KUR

Definition

The Lunar Six are six short time-intervals between sunset or sunrise and moonset or moonrise that Babylonian observers measured around the new moon, the full moon, and the quarter moons. They are: NA (sunset to moonset on the first crescent), ŠÚ (moonset to sunrise near full moon), a second NA (sunrise to moonset near full moon), ME (moonrise to sunset near full moon), GE₆ (sunset to moonrise near full moon), and KUR (moonrise to sunrise on the last crescent). Each interval was recorded in time-degrees — the UŠ, where 1 UŠ equals 4 minutes.

In Tradition

The name "Lunar Six" is conventionally credited to A. J. Sachs ("A Classification of the Babylonian Astronomical Tablets," JCS 2, 1948). Rochberg, Hunger-Pingree, and Steele all treat the Lunar Six as the foundational class of observations behind the Babylonian Astronomical Diaries — the raw, real-world readings that the System A and System B mathematical tables were built to predict.

In Practice

From at least the diary for 372 BCE onward, Babylonian observers recorded the Lunar Six on the relevant nights of every month. The values flowed into the Astronomical Diaries, the Normal Star Almanacs, and the Goal-Year Texts as the empirical raw material for lunar theory. A smaller subset, the Lunar Three — month-length indicator NA, mid-month NA, and end-of-month KUR — appears in the Almanacs and in the horoscopes from Babylon, though the Uruk horoscopes leave lunar data out altogether. In Hunger-Pingree's reconstruction, the System B tables compute the Lunar Six from four columns: N (the time between a syzygy and sunrise or sunset), O (the Moon-Sun elongation), Q (the oblique ascensional difference), and R (the Moon's latitude). Modern historians of astronomy count this centuries-long Lunar Six observation programme among the most sustained efforts of scientific data-collection in human history.

Historical Origin

The Lunar Six were recorded systematically in the Babylonian Astronomical Diaries from roughly 372 BCE onward — with reconstructed antecedents reaching into the seventh century BCE — and continuing into the first century BCE; they were then processed in the System A and System B lunar-theory ACT corpus. Modern critical treatments: Sachs and Hunger, *Astronomical Diaries and Related Texts from Babylonia* (1988-1996); Hunger-Pingree, *Astral Sciences in Mesopotamia* (1999); Rochberg, *In the Path of the Moon* (2010); and various studies by Steele in the 2000s.

Definition

In Tradition

In Practice

Historical Origin

Further Reading