The Light Ages

Cover of The Light Ages.

Seb Falk follows the reconstructed life story of one particular English monk, John Westwyk, to show off how life and particularly science and research worked in the High Middle Ages. This means a lot of tangents, naturally, but it also means a lot of math and astronomy and nitty gritty details. While I didn’t manage to appreciate all details about astronomy calculations, those were not hard to skip, and generally the book was very valuable, and approachable through its dedication to actual humans instead of anonymous groups.

Before reading this book, I was not aware of the role and sophistication of astronomy during the High Middle Ages, and even earlier. Falk starts with a mysterious manuscript about the construction of an unknown astrolabe-like instrument, which got a lot of attention because it could have plausibly been written by Geoffrey Chaucer – I really enjoyed getting insights into not only medieval life, but also how historians debate and improve their understanding of their findings. But I’m also just extremely impressed with some of the contents, and I very much share the author’s need to tell everybody just how cool medieval clocks are.

This book’s bibliography is also amazing and I’m going to follow up on it.

As is tradition, here are my detailed notes. Order of topics: The science, the monasteries, the universities.


Yada yada the medieval period was not Dark, that’s a concept spread by many people aiming to feel better about themselves, not least of which the Protestant Reformation, and then later fans like Gibbon. Falk notably also wants to side-step a second danger: lauding medieval people for being “like us” (because they weren’t, and constructing them to be like us is misleading at best).

Instead of standing for backwardness, ‘medieval’ should be a synonym for a rounded university education, critical engagement with all kinds of text, openness to ideas from all over the world, modesty, and a respect for the unknown.

The Science

Astronomy was the main reason for mathematics to get pushed for a long time, though I suspect that surveying was a close second. Farming was inseparable from astronomy, as the regionally different choice of calendars highlights: Nomadic peoples in Arabia, with less seasonal changes and lower latitudes, chose the lunar calendar, and the agricultural pre-modern societies of Europe, with their higher, more seasonal latitudes, gravitated to using the solar calendar. Written agricultural advice, for example the handbook by Palladius (5th century) list normal things like times for planting and harvesting, soil assessment methods, the advantages of ceramic piping over lead, and then include for each month the length of shadows for each hour of the day, pointing out symmetries and so on. During this time, as for most of the Middle Ages, unequal hours were in use, as they had been since they were invented in ancient Egypt – 12 hours between sunrise and sunset, no matter the duration. Equal hours started slowly to be widely used in the twelfth century, though astronomers had preferred their use for centuries. Similarly, the starting point of the day was not agreed on: the Romans started from sunrise, others roughly at dawn, astronomers at noon, Chaldeans at midnight, Jews at sunset.

Literacy is often assumed to be terribly low in the ‘Dark Ages’, and while it was of course much lower than today, the estimate of 50% basic literacy (enough to read an easy text, like a prayer or general information) doesn’t sound terrible, especially considering the tighter communal structures. Basic literacy in combination with little to no schooling was the main reason that Roman numerals stuck around despite Hindu-Arabic numerals being popular among scholars and merchants starting in the twelfth century. Similarly to literacy, mental maths were common and taught with plenty of useful techniques at a basic level, including multiplication by doubling, finger counting (using the phalanxes, reaching numbers of 10000 if need be).

Knowledge also relied heavily on memorisation, even among monks. Memorisation is not just “rote learning” – it was creative and active, and central to the production of new ideas. There were mnemonics for absolutely everything, like a nonsense poem called Cisiojanus from the late twelfth century that helped people memorise the many many holidays of the Church, by incorporating their names – one syllable per day, and when a day had no special meaning, the preceding day got its syllables. It’s pretty cool, and exists in dozens of slightly different versions – the start is the same, as are the big holidays, but every country, region and church had their own saints to include. Interestingly enough, it does start with January 1st, not the beginning of the liturgical year – because that would be a movable feast, which is also why all Easter related holidays are not included.

Side note from additional research): The Cisiojanus was even used to provide actual dates in paperwork, by saying things like “the day in May on the syllable In”. Even Luther released a calendar („Ein betbuchlin mit eym Calender vnd Passional“) that included a Cisiojanus with all those saints. Later Protestant versions of course reduce the number of saints drastically – though they usually printed both a “novum correctum” version and a “vetus” one with the traditional medieval form, which kept being popular. The beginning of the year was highly contested for a long time. January 1st was popular, but alternatives incldued Christmas, March 1st (Roman style), March 25th (Annunciation), Easter (terrible, terrible idea), or September 1st (Byzantian). Localised versions of the Cisiojanus typically didn’t use Latin hexameters but instead rhymed local language. Some switched to having one word per day – longer, harder to count off your fingers, but much easier to remember (and often hilarious). End side note.

We naturally know more about knowledge and technique used in monasteries, both because they were for a long time at the cutting edge of knowledge, and because their knowledge was written down and preserved. For example, we see calendars in prayer books that next to the enumeration of days hava a repeating sequence of letters A to G. As long as you remember which letter stands for Sunday in the current year, you’ll know all the weekdays at a glance. And of course, you don’t really need a full book: You only need to know the starting weekday of each month, and of course there was a mnemonic for the order of Weekdays: Altitonans Dominus Divina Gerens Bonus Extat Gratuito Coeli Fert Aurea Dona Fideli (‘The good Lord is ruling, thundering on high; He freely brings divine golden gifts of heaven for the faithful’, though with word ordering straight out of hell). Mathematical advancements was not restricted to monks, either: the Abbess Herrad of Landsberg not only wrote an encyclopedia, she also developed a complex code to compile tables that encoded the full 532 year Easter cycle.

Written tables were not uncommon: The astrolabe could find the exact time, provided you knew your latitude (or the other way around, at sea). To use it, you would have to read lengthy manuals, and to really understand it, people figured out tricky fractions and wrote down handy tables (and you can tell which scribes understood them, and who just copied them mindlessly by checking for mistakes. Provided you, the historian, understand all the maths!). People also compiled astronomical calendars for decades into the future, including star positions, sunrise and sunset times, moon phases, even shadow lengths at different hours.

Written helps were not uncontested, though: As church music grew more complicated than the traditional plainchant and started including harmonies (a mathematical concept), monks were allowed to bring candles into the choir. Older monks predicted that this innovation would rot the novices’ memories.

Another useful primary source for memorisation practices are the instructions for the cellarers in monasteries, who were responsible to wake the monks in the extremely early morning - the canoncial hours had to line up with dawn and sunrise, respectively. So we see, for example instructions on how to tell the time at night by the stars on specific days and from specific places in the monastery (“on the feast of St Vincent […] you must move back a little from the usual place towards the juniper bush”). Monasteries also had alarm clocks, the first of which were water-driven – but of course, even with an alarm clock, you had to know how long the night was going to be.

The first big clocks, towards the end of the thirteenth century, were as much astronomical instruments as anything else. They didn’t have clockfaces, and marked the hours by ringing a bell (lat. clocca). But they could still be extremely involved – take the clock of Richard of Wallingford, abbot of St Albans. This one did have visual marks to tell the time, but not on a traditional watchface – the plate they used had both straight and curved lines, to be able to tell equal and unequal hours – which needed to rely on the date, of course, so the “clock” was a full running calendar. It also indicated the phases of the moon (with a partially-to-fully lighted ball), eclipses, and regional high tide times at London Bridge. And even rarer and more complex: the clock had an additional pointer that showed the true solar time. Our watches and phones show us the mean time (the M in GMT) – but days aren’t really consistent 24 hours long (cf “equation of time”), and this masterpiece of medieval technology could reflect the up to 30 seconds of difference per day (which, of course, accumulate to up to 15 minutes at some points of the year). To put this into perspective: that part of the clock required an oval gear with 331 precisely spaced teeth – plus the knowledge and calculations to come up with the right curvature and teeth numbers. (Much more impressive than the already non-trivial calculation of assuming 235 lunar months in 19 solar years, a fact cribbed from ancient Greece).

The craft spread fast (though not at this level!), and soon, cathedrals and cities would employ clockmakers, who would take several years as a team to build a clock – which could easily cost 10% of the cathedral’s large income. It’s impressive to see how readily the Church invested large amounts of money in new and emerging technology.

There was of course a lot of superstition along with the science, though astrology and astronomy separated very early into related but separate sciences. Astrology assigned plantes and stars to absolutely everything: to week days, to months, to seasons, to hours of the day, and claimed to draw insights from all this – which were also commonly used in medicine. But even Ptolomy already acknowledged that astrology was much less useful and applicable, and thought it could never compare to the sureness and precision of astronomy – the difference in quality was known. A later astronomer, Heinrich Selder, wrote strong attacks against astrology as a concept, closing with the excellent remark that the only thing the heavens really affected was the weather.

And the practitioners of this exact science were very capable. I’ll not go into detail regarding the reform of the Gregorian Calendar (but please read or watch my talk on the topic here, for the full story of the debacle), but it happened in the sixteenth century, so I had always assumed that medieval people just didn’t notice their calendar rotating off the solar year. Ha! Roger Bacon, of Name of the Rose fame if you’re a nerd and read the boring historical side notes hidden next to the very boring theology passages, wrote a scathing commentary in the 1260s (at the request of the Pope!) on the ‘corruption of the calendar, […] intolerable to any wise person, horrible to any astronomer, and ridiculous to any computist’. The above mentioned calendars and tables also sometimes included columns for the accumulated divergence of the calendar from the solar year, which was off by about 11 minutes per year ever since the introduction of the Julian calendar.

The book spends a lot of time on the astrolabe, including explaining its use. I followed, uh, some of that – not the parts about the sun’s ecliptic and weird axes and stuff. There’s a neat manual by Chaucer written for his son, and it’s kinda cute. (And the astrolabe is not the only interesting device, the book goes into many more, both predecessors and completely alternate inventions). Interesting things stood out to me, though: An astrolabe is made for a certain latitude, and if you move away from it, you limit its usefulness – so people started carrying multiple plates, engraved on both sides for different latitudes. It also required a lot of skill to produce in the first place: the scales have to be engraved in perfect spacing and consistency.

Perfect spacing and consistency, on the other hand, was not a feature of maps at the time. But then, it wasn’t supposed to be – maps were meant to depict routes and function as a kind of travel guide. The Hereford world map was almost as large as a double bedsheet, and was densely packed with letters around 3mm tall – and while distorted to our eyes, the information was useful, just structured differently. But hard geography facts were known despite that – we have tables of latitudes and longitudes of notable towns and cities in plenty of medieval manuscripts. Maps more interested in geographical accuracy arise together with the spread of the compass, probably also around the end of the twelfth century.


This was the time of the beginning of universities, and for our purposes that means Oxford. Universities were very soon international affairs, but even a development that early led to protests: After a large influx of students from Paris, the existing students protested against Oxford landlords raising their rents to take advantage of the newcomers. Sound familiar?

Universities took formats established in monasteries and developed and formalised them. Reports of discussions were refined for publication, usually in a structure of argument-counterargument-decision. These had the advantage that you could present radical theories without making yourself vulnerable to accusations of heresy. And these books were not static objects – later users would add commentary in the margins, fill in diagrams, and reproduced these versions further and further. There was no real boundary between reading, copying and editing, which feels more modern than the book culture of printed works.

Lots of students were monks, though not all finished studying, since all but the richest monasteries had serious problems financing them. In their efforts, they placed levies on senior monks, and often supplied goods like candles and paper directly instead of sending money. In some ways, not much has changed since then: similar curricula plus widespread monastic networks meant that a monk could easily transfer from one university to another, just like people do today, either with universities or international corporations where you move to a different office.

And with them, books travelled. Sometimes frivolous books like fortune-telling manuals with included roulette wheels to obtain a random number – but also all kinds of other, scholarly texts, that were then copied and spread even further. And as monks (against the angry judgement of their superiors), could even join in on crusades, the spread was not even limited to the traditional monastic routes. (The book goes on an entertaining, but ultimately not all that relevant tangent about minor crusades that was extremely funny).

Then as now, there were some star professors who had their own fan base, and not always with good reason. Albert was called ‘the Great’ in his lifetime, but had an unrelenting critic in Roger Bacon. Jean Buridan was no less impressive than either of them, solving the puzzle of how a ball keeps moving after having been thrown (aka relative motion), and his student Oresme applied this theory to explain the Earth’s rotational movement, and how it doesn’t impact for example an arrow shot straight up.

Extremely niche fun fact: In London, pigs were not allowed to roam freely (because dangerous animals, capable of killing children and causing general havoc), except the ones belonging to St Anthony’s hospital. The hospital was gifted the smallest runts as support, who then had to wear bells to mark them as hospital property, and were fed by civic charity (aka anything they could find anywhere). Probably made for great acoustics.


Monastic orders underwent constant, constant efforts of reformation. An order would start in an effort to live a good, honest, poor, devoted life, and within decades of the founder’s death would turn into a rich, heavy, corrupted institution of power and authority. St Albans, a particularly rich and far-reaching Benedictine abbey, is a great example. Rich, and with many daughter houses, there are many stories to underscore just how far from ideal it was. For example, when Queen Isabella visited the town, the women of the town staged a protest with their babies, telling the queen they had been raped by the monks – but the queen did not speak English, so nothing changed. St Albans was also the abbey that, when the townspeople refused to use their expensive watermill and resorted to using hand-mills at home, forcefully collected the millstones, and used them to pave the floor in the abbey as a hideous show of authority. Little wonder that the Peasants’ Revolt was particularly fierce at St Albans, and resulted not only in a new charter of rights, but also in the smashing of the (over a century old!) millstones, distributing the shards as symbol of their victory.

A thing that stood out to me was just how good the primary source situation is, particularly in England. In Germany, most church registers from before the 30 years war have been lost, and you can often trace the war’s progress along the years the registers start (this goes especially for small villages). Whereas in England, you can say stuff like “He was probably ordained in this year, but we can’t know for sure, because the ordinations from the years 1368-79 are lost”.

77/ The Light Ages by Seb Falk. Explains medieval astronomy and all the related science and things by following one specific monk. Very down to earth and interesting as long as you skip the technical astronomy parts. https://books.rixx.de/seb-falk/the-light-ages/
77/ The Light Ages by Seb Falk. Explains medieval astronomy and all the related science and things by following one specific monk. Very down to earth and interesting as long as you skip the technical astronomy parts. https://books.rixx.de/seb-falk/the-light-ages/ #rixxReads

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