It is difficult to know when to accept history on its own terms. We tend to not condemn the ancient Greeks, Romans, or Jews for having slaves, though we hold the ante-bellum South culpable. I was not surprised by Seb Falk’s story about Brother John Westwyk’s productive labors in mathematical astronomy and the consequential instrumentation of measurement for those works. But I was enlightened by the search for and discovery of the man who wrote an astronomy text commonly credited to Geoffrey Chaucer.
Chaucer did author A Treatise on the Astrolabe. It was Dompnus Johannes de Westwyke (Brother John of Westwick) who created Equatorie of the Planetis, a book that had been credited to Chaucer. So, Seb Falk interleaves two stories here: the life of Brother John as best it can be built from scant records; and the development of astronomy (and, generally, science) in the Middle Ages.
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Reading this book the first time through, I knew that I would annotate post-its to bookmark passages. The second time through the book, it soon became clear that I should just copy the whole thing here—which, of course, is not allowed.
“Far from the stereotype of a stagnant scientific environment which did no more than preserve the ideas of the ancients, computists in the twelfth and thirteenth centuries continued to refine their astronomical models, with ever more accurate estimates of the solar and lunar cycles. Scholars became more outspoken in their criticism of the increasingly unrealistic ecclesiastical calendar. In the 1260s Franciscan friar and proponent of empirical science Roger Bacon wrote, at the Pope’s request, a series of tracts on educational reform.” (page 74)
To compute, you must have a computer. God gave you ten fingers, each with two knuckles. Supported and enhanced with recipes for rapid mental arithmetic, you could calculate the rising and setting of the Sun for your locale—and you could measure musical harmonies, also. If you were enrolled at a university in 1325, to complete a bachelor’s degree required completing the Trivium of Logic, Rhetoric, and Grammar; the master’s degree required the Quadrivium of Geometry, Arithmetic, Music, and Astronomy. But attending one of the newly founded universities was expensive. So, monasteries most often paid for a limited education after which the motivated monk studied (and wrote) on his own—and sometimes her own (page 73).
One result of that was that no two books are exactly the same. Copyists used the intentionally available spaces to add their own amendments and emendations, expanding, explaining, and correcting. Books lived. (ref. esp. pages 77 and 124). Knowing this, and expecting that copies will be carried to other places, Brother John Westwick cautioned the next one building an equatorie from his plans: “Nota I conseile the ne write no names of signes til that thow hast proved this commune centre defferent is trewli and justli set.” (Illustration 7.9).
The Light Ages: The Surprising Story of Medieval Science by Seb Falk; W. W. Norton & Company, New York, 2020. (Published in the UK as The Light Ages: A Medieval Journey of Discovery; W. W. Norton & Company, London, 2019.) W. W. Norton's webpage mentions the Best Book awards from The Times, The Telegraph, and BBC History Magazine. I learned of it because it garnered the AAS Historical Astronomy Division Osterbrock Book Award for 2024.
One thread not followed here, which I considered important, is that the manuscript under discussion was first rediscovered by Derek Price deSolla. Price deSolla is also credited with the first rigorous examination of the Antikythera Mechanism (NecessaryFacts here.) No mention of that appears in this book.
Previously on Necessary Facts
Astronomical Symbols on Ancient and Medieval Coins
Rescuing Aristotle and the Church
Copernicus On the Revolution of Heavenly Bodies
