The Light Ages

A Mediæval Journey of Discovery

Seb Falk

Penguin 2021

Pb, 416pp, £10.99, ISBN 9780141989679

The myth of the “darkness of the Middle Ages” descending after the fall of Rome is dispelled in The Light Ages.

Here historian, science historian and broadcaster Seb Falk demonstrates that “mediæval science” is no contradiction in terms, while religion and science weren’t antagonists in the mediæval world.

Falk illustrates this through a fascinating biography of John Westwyk, a 13thcentury Benedictine monk based at St Albans

Abbey who wrote important treatises on astronomy, accidentally rediscovered in the 1950s.

The astrolabe was a flattened, portable model of the Solar System made from brass discs slotted on top of each other, through which you could measure the “ascensions” of moving celestial bodies.

Functioning regardless of whether the Universe was geocentric or heliocentric, astrolabes calculated the number of daylight hours in each day, reckoned the dates of Easter, predicted when the heavens were moving into zodiacal “houses” whose influence might affect us and forewarned of planting seasons heralded by the appearance of certain stars visible just before dawn. Such calculations may have been a form of meditation for monks. Physicians’ astrolabes chose auspicious times to administer bleedings.

Previous inmates at St Albans had produced new discs to add to the astrolabe “for all altitudes”. Westwyk added a guide to these, demystifying earlier manuals and correcting their errors.

Astrolabes dominate The Light Ages, and while the astrolabe was a “simplified” instrument compared to its predecessors, after a 39page digression on them I was struggling with the azimuth and the obliquity of the elliptic.

This was an exciting time for astronomy. A standardised 24hour day with 60minute hours was proliferating, along with clocks. The long transition to Arabic numerals was apace. There was a flood of philosophical works emerging in Arabic, Greek and Hebrew – pagan sciences could now become “the handmaiden of religion”.

My favourite section of The Light Ages describes the rise of the universities. In 1336 the pope called on monastic orders to send one in 20 monks to university. Today’s Worcester College, Oxford, began life as a Benedictine institution. As a graduate returning to the monastery, Westwyk’s privileges included being excused midday Mass.

The new universities were particularly awestruck by the recent rediscovery of Aristotle; his works quickly dominated the curriculum. Periodic ecclesiastical bans on the study of Aristotle were largely ignored.

Around 1370 Westwyk left for the bleak clifftop subsidiary monastery at Tynemouth, taking with him some astronomy works to copy. Tynemouth was three degrees further north than Classical philosophers had ever been, so Westwyk wrote a treatise with instructions on engraving an astrolabe dial for “ascensions” at a new latitude, 55 degrees North.

Like many clerics, Westwyk joined the debacle that was the 1382 Despenser’s Crusade – fighting not in the Holy Land, but in Belgium. Led by an incompetent warrior bishop of Norwich, the crusaders – outnumbered by FrancoFlemish forces loyal to antipope Clement – fought with extraordinary courage, the clerics in particular. They withdrew to England in disgrace within six months. Westwyk kept his head down for the next decade.

He next pops up at London’s Benedictine inn, where he wrote a manual – in English, daring and innovative at the time – with instructions for building an enormous astrolabe six feet in diameter. This manual, Equatorie,

is a computer and equation solver. Its 140 pages of tables allow the user to calculate the motion of the planets back to the birth of Christ and to any point in the future, adjusting for leap years, aided by charts for roots and “sexagesimal ninths”. Nothing equalled the Equatorie

until the first printed astronomy textbooks appeared nearly a century later.

Matt Salusbury

★★★★