Mesopotamian lunar table

by Martin Bush
Publish date
25 May 2012
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Martin is the programmer at the Planetarium at Scienceworks.

A personal highlight for me in The Wonders of Ancient Mesopotamia exhibition is the Babylonian lunar table. I love this artefact not just because of the antiquity of its writing or how long it lay preserved in the ground, and certainly not just because of the skill needed to make the rows of tiny cuneiform script. (How did they do it? I could never have managed.)

Babylonian lunar table Lunar table K.90 from the British Museum on display in The Wonders of Ancient Mesopotamia.
Source: © The Trustees of the British Museum

This tablet is exciting because shows just how seriously Mesopotamian cultures took astronomy. Observers recorded the appearance of the Moon – and also the stars and planets – every single night of the year. (Ok, unless it was cloudy.) They sent reports of these observations to the king. Babylonian astronomers had centuries of astronomical observations to work with. Unfortunately we don’t as not so many of these reports have survived.

Some concerns of these ancient astronomers – like making horoscopes to advise the king – are no longer of much interest to modern astronomers. But many ancient achievements live on to this day. Astronomers still number lunar eclipse using a system known as the Saros Cycle. This cycle was discovered by Babylonian astronomers around the 5th century BCE.

The work of these Babylonian astronomers can also be seen in the Jewish calendar. Sometime around the 4th Century BCE Mesopotamian astronomers calculated the average length of the lunar month. The extensive observations they had to work with meant that they came up with a remarkably accurate figure, different to the modern value by only a fraction of a second. This value was taken up by Greek astronomers such as Ptolemy and from there it was incorporated into the Jewish calendar when it was codified in the first millennium CE. The value determined by Babylonian astronomers is still used today to determine the date of the Jewish New Year.

This lunar table survived for centuries in the ground while the influence of Mesopotamian astronomy on our study of the skies has lasted even longer.

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