Astronomy in Ancient Babylon

The observations of the astrologers, which were meticulously recorded on a nightly basis over many centuries, led to accurate predictions of various astronomical phenomena and the correct calculation of the solar and lunar year. The Babylonian calendar was based upon the lunar year but, thanks to the astrologer's knowledge, could be reconciled with the solar year by means of intermediary months.

We owe much of our calendar system to the Babylonians. They were probably the first people after the Sumerians to have a calendar. This calendar was very important because without it agriculture could not be planned properly.

There were twelve lunar months in the year but as the months were shorter than our months often an extra month would have to be added. This was called the second Elul. Each week was divided into seven days. The day was divided into six parts each of two hours duration and containing thirty parts. The Babylonians measured time with a water or sun clock.

One can see from this that the Babylonian calendar has marked similarities with our own: for instance the twelve months in the year and seven days in a week.

Babylonian clay tablets (such as the one to the left listing eclipses between 518 and 465 BC) record the earliest total solar eclipse seen in Ugarit on May 3, 1375 BC. Babylonian astrologers kept careful records about celestial happenings including the motions of Mercury, Venus, the Sun, and the Moon on tablets dating from 1700 to 1681 BC. Later records identified a total solar eclipse on July 31, 1063 BC, that "turned day into night," and the famous eclipse of June 15, 763 BC, recorded by Assyrian observers in Nineveh. By carefully noting local lunar and solar eclipses, Babylonian astronomers were eventually able to predict lunar eclipses and -later- solar eclipses with a fair accuracy. Their tool was the so-called Saros-cycle: this is the period of 223 synodic months (or 18 years and 11.3 days) after which lunar and solar eclipses repeat themselves.

Ancient eclipse forecasts, when successful, were a powerful means of divining omens for anxious Kings. Lunar eclipses were considered to be particularly evil omens that involved their kings. Since these eclipses could now be predicted in advance, substitute kings could be appointed who would bear the brunt of the gods' wrath. The real king would remain unharmed and the continuity of the state's policy was guaranteed. (The poor man who was appointed as substitute king was killed. In this way, the omen was always right.)