In a conservation lab in Washington DC, there is a small book made of goatskin. It measures roughly 18 by 21 centimetres - paperback sized, worn and brown with age. It is called the Codex Climaci Rescriptus, and it has been written on at least twice. The top layer is Syriac: monastic text, the devotional writings of John Climacus, Abbot of Saint Catherine's Monastery in Egypt's Sinai desert, transcribed by a medieval scribe sometime in the 9th or 10th century. Beneath that, nearly invisible, is something else entirely.
THE ERASED WORLD
A palimpsest is a document that has been scraped clean and written over again. The word comes from the Greek - palin, meaning again, and psaō, meaning to rub away. In the first millennium, parchment was scarce. Papyrus had been overfarmed in Egypt; paper from China had not yet reached the West. So monks scraped the old ink from goatskin and started again. The past was not destroyed so much as buried under the present, which in turn would be buried under whatever came next.
The Codex Climaci Rescriptus held nine folios that scholars had suspected contained Greek writing. For decades, no one could read them. The traces were too faint, the erasure too thorough.
In 2012, a Cambridge undergraduate named Jamie Klair was examining one of those folios when he noticed something: astronomical content. Not theological commentary, not scripture. Star material. He flagged it, and the slow work of identification began. Years passed. In 2021, Peter Williams first recognised the presence of actual astronomical measurements in the undertext. By 2022, a research team led by Victor Gysembergh at CNRS in Paris had confirmed what those measurements were: fragments from the lost star catalogue of Hipparchus of Nicaea, compiled around 150 BC - the oldest such catalogue in Western history. The text that had been scraped away to make room for a monk's prayers turned out to contain some of the foundational data of astronomy.
THE ASTRONOMER WHO DISAPPEARED
Hipparchus is a figure of peculiar historical tragedy. He is considered the founder of trigonometry and the first in the Western world to attempt a systematic catalogue of the night sky. By Roman accounts, he documented the positions of at least 850 stars. He discovered the precession of the equinoxes. He developed the magnitude scale used to classify stellar brightness that scientists still use today. He was, by any measure, one of the most accomplished observers who ever lived.
Almost none of his work survived.
What survived instead was the work of Claudius Ptolemy, who came four centuries later and who produced a star catalogue far larger and more famous. For years, scholars had suspected that Ptolemy's catalogue was not original - that it drew heavily, perhaps dishonestly, on Hipparchus. The palimpsest helped settle the debate. When Gysembergh's team compared the newly recovered Hipparchus coordinates with Ptolemy's, they found both agreement and genuine divergence. Ptolemy had used Hipparchus as a source, yes, but also drew on other scholars.
"That's not plagiarism, that's science," Gysembergh said. "We still do that today, combining sources to get the best data possible."
The deeper point: Hipparchus was not erased by fraud. He was erased by time, by scarcity, by the ordinary processes of knowledge being written over and consolidated. His coordinates survived in Ptolemy's synthesis, unnamed. His work lived on, but his authorship did not.
HOW LIGHT READS THE PAST
The 2022 discovery used multispectral imaging. The 2026 continuation at the Stanford Synchrotron Radiation Lightsource at SLAC went further. The X-ray beams used there are a million times stronger than those in a dentist's office. They do not read ink - they read elements. The scribe who wrote the Syriac overtext used iron-rich ink. The original Greek text beneath used a calcium-based ink. When the X-rays hit the parchment, the calcium signals from the older layer were actually more prominent than the newer writing above it. The erased text was, in a sense, louder than the text that replaced it.
The distinction matters: this is physics, not metaphor. The right kind of attention, applied with sufficient precision, can recover what was deliberately removed.
The manuscript is now yielding descriptions of constellations, star coordinates, the word for Aquarius. Researchers believe more remains hidden in the folios not yet scanned. The catalogue of Hipparchus - absent from scholarship for two millennia - is being reconstructed, star by star, from the calcium ghosts of a text someone thought they had erased.
THE DEVELOPER'S PALIMPSEST
Every codebase is a palimpsest. New code is written over old code. Refactors bury the original architecture. Libraries replace libraries. The file you are editing today has been rewritten by a dozen hands before yours, and the logic that existed two years ago - the decisions that shaped what you are now changing - is gone from view unless you know where to look.
Git preserves commits, yes. But the contribution graph on GitHub shows only the last year by default. Everything before it is buried. The developer who spent three years on the foundation of a system may show up as a thin line in the history, or may not show up at all after the code was migrated, the repo was recreated, the organisation was renamed. Most developers have years of work that has been scraped away and overwritten, invisible unless someone shines the right light on it.
The cognitive effect of this is real. When new engineers join a team, they read the current code as if it always existed in this form. They do not see the calcium signature of the original architecture. They do not see the three rewrites, the abandoned patterns, the decisions that were made and reversed. The code they inherit is a surface. The history beneath it is the thing that would actually tell them what they are working with.
There is also something more personal in this. A career is not the sum of what is currently deployed. It is the sum of everything ever built - including the things that were replaced, deprecated, migrated away from, or simply forgotten when the company was acquired and the old repos were archived. The palimpsest of a developer's working life is rarely visible to anyone, including the developer.
WHAT THE X-RAYS DO
This is what Codex Stellarum does. Not X-rays - but the same essential act. It takes the full contribution history, not just the last year, and renders it as a permanent record. A star atlas, built from the complete signal of the work, not just the surface that happens to be visible today.
The irony is not lost on us that the product shares its name with the artefact. The Codex Climaci Rescriptus is, literally, a codex - a bound manuscript. Codex Stellarum is named for the same idea: a book of stars, a catalogue, a record that survives. What the researchers at SLAC are doing for Hipparchus - recovering authorship from beneath layers of institutional and historical erasure - is precisely the problem that any serious record of a developer's work has to solve.
Hipparchus spent decades making careful observations. He was accurate to within a degree, using no instruments more sophisticated than his own eyes and the geometry he had partly invented. He wrote it all down. Then it was scraped away.
The light still carries the signal. It just needed someone willing to look.
If you have years of work buried beneath the default view, Codex Stellarum renders the full record - every contribution, every layer, as a permanent star atlas.