Lunar eclipses were more than just entertainment for the ancient Babylonians, who saw these celestial events as harbingers of doom. Reading the signals lurking in the shadows that devoured the Moon was therefore an important science, and resulted in the production of a series of texts documenting the various omens to be found in an eclipse.

Written in cuneiform in the early second millennium BCE, these 4,000-year-old Mesopotamian warnings have finally been interpreted from four tablets that have been sitting in the British Museum for well over a century. Presenting their translations in a new study, the researchers reveal how various features of an eclipse could be used to foresee future events.

By observing the time and date of a lunar eclipse, as well as the movement of the Earth’s shadow across the Moon, royal advisers could predict grave misfortunes that destiny had in store for a king. For instance, the tablets reveal that “an eclipse in the morning watch” signaled “the end of a dynasty” in the Mesopotamian city of Akkad. 

“Babylonian astrology was an academic branch of divination founded on the belief that events in the sky were coded signs placed there by the gods as warnings about the future prospects of those on Earth,” write the study authors. Accordingly, “astrological observation was part of an elaborate method of protecting the king and regulating his behavior in conformity with the wishes of the gods.”

By cross-referencing the various features of an eclipse against an “academic corpus of celestial-omen texts,” royal advisors were able to decipher the intentions of the heavens and assist the king in avoiding a nasty outcome. The texts analyzed by the study authors are believed to have originated in the ancient Babylonian city of Sippar, located in modern-day Iraq.

Another of the omens inscribed on the tablets explains that “an eclipse in the evening watch… signifies pestilence,” while a particularly threatening entry states that “[if] an eclipse is the wrong way around… nothing will be spared, the Deluge will occur everywhere.” Exactly what the ancient astronomers mean by “the wrong way round” is unclear, though the researchers say this probably relates to a scenario in which the lunar disk is “somehow judged to be facing the opposite direction from that expected.”

Fortunately, however, kings didn’t have to accept their fate lying down, as protective rituals could be employed to counteract unfavorable omens. Citing a letter from a diviner to King Zimri-Lim of Mari (a region in Mesopotamia), the researchers say that the portents of ill-boding eclipses could be double-checked by extispicy – which involves examining animals’ entrails – “to determine whether the king was in real danger.”

“First-millennium texts show that if, after such enquiry, the king’s advisers felt the threat still to be present, action could be taken to annul it, by identifying the forces of evil that lay behind it and countering them with apotropaic rituals,” explain the study authors.

Highlighting the overall importance of these somewhat paranoid engravings, the researchers say they “represent the oldest examples of compendia of lunar-eclipse omens yet discovered and thus provide important new information about celestial divination among the peoples of southern Mesopotamia in the early second millennium BCE.”

The study is published in the Journal of Cuneiform Studies.