The fault in our stars
why we check our work
I’ve tried to stick to a weekly schedule of substack posts, and doing that has helped me find discipline in other areas of writing. The post I planned to write this week has been delayed. As it happens, the reasons for the delay are interesting in their own right, and so I’m sharing them here. Consider this a holding piece, a glimpse into history and into how I spend my time, while we wait for the second installment of my description of the horizon line for the Prague astronomical clock and for horologies in general.
checking the math
Most of my work time is spent comparing medieval Persian and Arabic manuscripts to try to figure out what was copied where, by whom, and from what source material. Occasionally I encounter something confusing and have to figure out what happened to introduce the confusion. Usually this means the scribe who made the manuscript copy just skipped a line of text, or a whole page of text, or the source manuscript was out of order or damaged and the scribe was doing their best to make sense of imperfect material. Sometimes the way a word is written means it can be read in different ways. This is especially true with the Perso-Arabic alphabet, where a missing or misplaced dot can change the reading of a word. Occasionally, a scribe doesn’t like what is written, or thinks they know a better version of events in intervenes in the text. It’s a rewarding feeling to recreate the process of another scholar working six or seven centuries ago, even if that process was faulty.
In the case of the Prague astronomical clock, I think the designers made a mistake in drawing the horizon line on the clock face. I identified the mistake by making it myself when I first tried creating visuals to help explain the layout of the clock face. In fact, my last post contains the error, but in the context of that post, which introduces the concept of the horizon line on the clock but not the maths of it, the specifics of the mistake don’t matter and so I am leaving the error in place. For the next post, I’m faced with the double task of simultaneously explaining how the horizon line works in theory and how it came to exist in history in a slightly incorrect form.
Of course, it is hard for me to believe that the clockmakers actually got it wrong, and I am open to any argument that shows the error of my ways. However, when I do the math wrong, I consistently get a line that matches the clock face. When I do the math correctly—using two different methods—I consistently get a different outcome. Of course, I don’t know if the error was in the original clock design of 1410, or if it was introduced in a subsequent renovation (there have been at least two just in the last century). Also, I have to acknowledge that I am working with images of the clock, and not its precise measurements but the difference is significant enough to suggest that this is not the issue. I will check everything at least once more and send the post out once I am comfortable with it. If you are anxious to see “The horizon line, part 2,” please be patient.
when life intervenes
This is all further complicated by the fact that I am currently in Oxford looking at manuscripts made in Iran, Central Asia, and Anatolia between 1200 and 1430 as part of a large research project I joined two years ago. By my last count, I have looked at over 270 manuscripts in the past week, and I have more to see in the week ahead. For this work, I am searching for the names and dates of the manuscripts’ copyists, patrons, and owners. Among the dozens of fairly unremarkable books are a few absolute beauties that I want to share with you here but don’t have permission to. One of them is a copy of two important astronomical texts copied in 1419 for Ulugh Beg, a grandson of Tamerlane, when he was just 25 years old. Before he was crowned Sultan of the Timurid Empire in March 1447, Ulugh Beg had become one of the most accomplished astronomers of the pre-modern world. I like to imagine him wandering around Samarqand with this beautiful little book in his pocket, learning the science of the stars.
One of the texts in the manuscript is a treatise on various possible designs for an astrolabe, first written four centuries earlier by Abu Rayhon Biruni (d. 1048). The work includes numerous finely-drawn diagrams, including some that bear a striking resemblance to the Prague astronomical clock. While I am not allowed to share my images from Ulugh Beg’s pocketbook, here is one from an even earlier, if messier, copy in public domain:
The visual similarity between Biruni’s design for an astrolabe and the Prague astronomical clock is no accident, because both are based on a set of mathematical principles for depicting the circular motions of the heavens on a flat plane. These mathematics had been worked out as early as the Hellenistic period. At almost exactly the same time as when Biruni wrote his treatise in Central Asia, where Ulugh Beg would one day rule, another Arabic scholar (who will feature in my next post) described the same mathematics in a work he wrote in Spain. From there, it was translated into Latin and introduced into Catholic Europe. In Prague, the clock maker Mikuláš of Kadaň and the mathematician and astronomer Jan Šindel used the translation of that work to design their astronomical clock, just nine years before `Abd al-Mu`min bin Nasrallah al-Munshi copied Biruni’s text for a young Timurid prince.
why studying old stuff matters
The fact that the same mathematical processes were to be found simultaneously in the workshops of Bohemia and the palaces of Samarqand speaks to the significant promise of comparative research in astral science, and to a deep shared intellectual legacy of Europe and Southwest and Central Asia. This so often gets ignored in favour of reductionist ideas about irredeemable differences between the Islamic and Christian worlds, exemplified by a modern fascination with the Crusades as the defining moment of pre-modern contact between the two civilizations.
Richard the Lionhearted, most famous of Crusaders, was born in Oxford, in a small palace about 500 metres from where Ulugh Beg’s pocket copy of Biruni now lives. That palace, called Beaumont, was granted to the Carmelite order in the early fourteenth century, and two centuries later it was dismantled, its stones reused to build colleges for the expanding university. Its location is now Beaumont Street, part of the A4144 that runs through the length of Oxford. In January 1188, news arrived in England that Crusader Jerusalem had fallen to Saladin. Those around Richard interpreted this calamity as the result of a massive astrological conjunction of all seven visible planets in the fall of 1186. In March of 1193, as Richard sat in captivity in a castle outside Vienna, Saladin died. For the Muslim population of Syria and Palestine, this was the great catastrophe foretold by the massive conjunction of 1186.
The exploits of Richard and Saladin have been told many times, and I have no interest in revisiting them here. It is worth remembering, though, that in the late twelfth century, the astrologers of Syria and those of England looked up at the same sky, saw the same arrangement of planets, and understood it as an omen of great disaster. In doing this, they drew on the same texts and traditions of celestial observation and interpretation, rooted in Hellenistic Egypt, synthesized in Persian Gundishapur and Arab Baghdad, developed in Muslim Spain and Central Asia, and applied to horoscopes and horologies in Samarqand and Prague.
I love the mystical quality of these mathematical equations. The likeness between the Persian clock and the Prague clock is uncanny. I'd love to see a photo of the cover of that pocketbook. I work with archives too, so I found the description of the detective work you are doing very satisfying.