Codex Climaci Rescriptus

Flick through these three images, dear readers, and you will observe something that scholars have been looking for for over 2,000 years — finally brought to light via a student class project, the COVID lockdowns, and state-of-the-art multispectral imaging. It is the oldest star map of the universe.

The manuscript you see is the _Codex Climaci Rescriptus_, a Medieval collection of several documents dating across the ages and stored for most of its history in the Egyptian Monastery of Saint Catherine’s, one of the most important treasure-houses of ancient knowledge. But the Codex is a palimpsest, a text whose parchment has been scraped to make room for later writings.

And what recent scholars have discovered, just published in the _Journal for the History of Astronomy_, is part of a long-lost star map by the ancient Greek astronomer Hipparchus. One of the deciphered passages has the length and breadth in degrees of the constellation Corona Borealis. The precision of the coordinates was so accurate that scientists were able to note the Earth’s particular precession when they were made (every 72 years the Earth wobbles a bit on its axis by one degree, changing what we observe about stars’ location). This allowed the dating of the star observations to about 129 BCE, which is when Hipparchus was writing.

The Greek also recorded other star coordinates for the constellations Draco and Ursa Major and Ursa Minor.

This discovery is really astounding. Historians had known about Hipparchus but until this discovery the earliest extant star maps dated to the second-century CE astronomer Ptolemy. The astronomical nature of the palimpsest’s hidden writings (much of the overwriting is in Christian Palestinian Aramaic) started to come clear in 2012 when Professor Peter Williams assigned the manuscript to his students as a class project and one of them spotted some Greek work by the astronomer Eratosthenes. Eventually the pages were photographed in 42 different wavelengths of light, and during the COVID lockdowns the true nature of the Hipparchus’ writings was discovered, their findings just published this week.