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Surprising facts and beliefs about eclipses during medieval and Renaissance times

STARRY-EYED: Ancient and medieval astronomers 糖心传媒渒new quite well how to predict when conjunctions and eclipses were going to happen,糖心传媒� says historian Laura Smoller. (糖心传媒 illustration based on the miniature of Christine and Sybil from Christine de Pizan糖心传媒檚 / Michael Osadciw)

糖心传媒 experts offer historical insights into medieval society糖心传媒檚 fascination with astronomical and astrological phenomena.

In medieval and Renaissance society and culture, celestial events were not mere spectacles in the sky. Rather, they were omens, predictors of the future, and windows into the workings of the universe. 糖心传媒 historian and librarian Anna Siebach-Larsen, director of the , shed light on how the people of the (falsely labeled) 糖心传媒淒ark Ages糖心传媒� actually understood, interpreted, and experienced eclipses, planetary conjunctions, and other astronomical phenomena.

Eclipses were well understood in medieval Europe糖心传媒攁t least mathematically.

Forget the idea of flat earthers and the notion that medieval people 糖心传媒渨ere generally stupid, ignorant, and superstitious,糖心传媒� says Smoller, a professor of history at Rochester and a fellow of the Medieval Academy of America. Ancient and medieval astronomers 糖心传媒渒new quite well how to predict when conjunctions and eclipses were going to happen,糖心传媒� she says.

Close-up of a page from "De revolutionibus orbium coelestium" (English translation: On the Revolutions of the Heavenly Spheres) by Copernicus showing mathematical schematics of the relationship between the sun and the moon.
OFF-CENTER: First printed in 1543, De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres) by Renaissance astronomer and mathematician Nicolaus Copernicus posited a heliocentric model of the universe as an alternative to the then-widely accepted Earth-centric one. The University糖心传媒檚 copy of the book dates to 1566. (糖心传媒 photo / J. Adam Fenster)

They understood that if the moon was either new or full, and when its path crossed the ecliptic糖心传媒攖he sun糖心传媒檚 path糖心传媒攜ou had an eclipse (a solar eclipse with the new moon and a lunar eclipse with the full moon). During an eclipse, the sun and moon are either in opposition (180 degrees opposite each other) or in conjunction in the exact same degree. But their paths have to be on the exact same plane and need to have crossed, explains Smoller. 糖心传媒淭hat糖心传媒檚 mathematically pretty sophisticated to conceive,糖心传媒� she says.

That said, medieval Europe still held a strictly Earth-centric view that considered the sun and the moon to be planets that orbit Earth糖心传媒攁long with the five then-known planets Venus, Mercury, Mars, Jupiter, and Saturn. This geocentric model was not just specific to the Middle Ages糖心传媒攊ndeed, it was the predominant model in several classical civilizations, including ancient Greece and Rome.

In 1543, the publication of De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres) by Renaissance astronomer and mathematician Nicolaus Copernicus would kick off the Copernican Revolution. His work ultimately led to the long-held Earth-centric model糖心传媒檚 being replaced with a heliocentric one that has the sun at the center of our solar system.

Celestial events like eclipses were used to predict the future, including the weather.

Scan of yellowed page from "Opusculum repertorii prognosticon in mutationes aeris" by Firmin de Beauval.
THE FINE PRINT: According to the text, when a solar eclipse is combined with the planetary conjunction of Saturn and Jupiter in the head of Aries, 糖心传媒渢he effects will last 12,000 years.糖心传媒� Note the faded marks near that passage in the lower right-hand margins糖心传媒攍ikely supplied by an early reader noting the super-booster effect. (Photo by Laura Ackerman Smoller)

Medieval Europeans saw alignments of planets, like conjunctions of Jupiter and Saturn, as signs of things to come糖心传媒攆rom famines, earthquakes, and floods, to the birth of Christ, and even the collapse of empires. They believed that eclipses, especially solar eclipses, could amplify and strengthen the effects of these planetary conjunctions.

The University糖心传媒檚 (RBSCP) is home to an early printed book from 1485 by Firmin de Beauval titled (On Predicting Changes in the Weather), published by Erhard Ratdolt, who specialized in printing works of geometry, astrology, and astronomy.

A compilation of ancient medieval sources, the treatise deals with the influence of planets on meteorological phenomena and weather forecasting. But it also covers solstices and equinoxes, planetary conjunctions, and eclipses糖心传媒攁nd their reported ability to prognosticate the future.

Reading the original imprint (or incunable) in Latin, Smoller notes that eclipses were considered to boost the effects of planetary conjunctions. According to the text, when a solar eclipse is combined with the planetary conjunction of Saturn and Jupiter in the head of Aries, 糖心传媒渢he effects will last 12,000 years.糖心传媒� That staggering number is not a typo. Smoller points to faded marks in the right margins that an early reader, likewise astonished at the described super-booster effect, made in the same passage.

Smoller pushes back against the conventional notion of the superstitious Middle Ages. 糖心传媒淚 don糖心传媒檛 think it糖心传媒檚 superstitious on their part to believe that things that happen in the heavens have an effect on Earth,糖心传媒� she says, pointing to the example of tidal changes that are synched with the moon cycle. 糖心传媒淭hat is the nature of medieval, ancient, and a lot of early modern natural philosophy, including beliefs held by Galileo and Kepler.糖心传媒�

Medieval theologians pondered the meaning of the 糖心传媒渕iraculous eclipse糖心传媒� that apparently occurred during Jesus糖心传媒檚 Crucifixion.

William of Auvergne's "De universo" medieval manuscript opened to the first page, showing an intricate and colorful illumination.
TIME CHECK: The University糖心传媒檚 copy of De universo by William of Auvergne, a 13th-century theologian. Among other Christian writers, William insisted that the eclipse at the time of the Crucifixion had to be miraculous since such an event was not naturally possible given the timing. (糖心传媒 photo / J. Adam Fenster)

The study of eclipses was, unsurprisingly, essential for specialized astronomers. But it also formed part of a general university education during the Middle Ages, including for theologians.

Take the example of William of Auvergne, the bishop of Paris from 1228 to 1249 and a prominent theology professor at the University of Paris. William is one of many writers to discuss the purported 糖心传媒渕iraculous eclipse糖心传媒� that occurred at the time of Jesus糖心传媒檚 Crucifixion. With the 600-folio De universo, which translates to On the Universe, William provides 糖心传媒渁n extraordinary look at the culture of scientific thought and the ways in which it was transmitted,糖心传媒� explained Siebach-Larsen . The manuscript boasts an unusual illumination that is broken into the four elements: earth (complete with mountains and trees), water (with fish), air (with flies), and fire. (Want to take a deeper dive into the De universo manuscript? Take a .)

Close-up of the illumination on the first page of the medieval text "De universo" depicting the elements of earth, water, wind, and fire.
SPHERES OF INFLUENCE: The first page of De universo features a remarkably detailed illumination depicting the four elements of nature (from right): earth, water (note the pair of fish), air (complete with flies), and fire. (糖心传媒 photo / J. Adam Fenster)

An early witness to the idea of 糖心传媒渘atural magic糖心传媒� among medieval thinkers, William covers the topic of eclipses in De universo. He counts among the many Christian writers, beginning with the earliest Church fathers, to insist that the eclipse at the time of the Crucifixion had to have been miraculous, as it was not naturally possible, says Smoller. Why? Timing is everything: The Crucifixion reportedly took place during Passover, which begins on the first or second full moon after the spring equinox. But you聽need a new moon糖心传媒攏ot a full moon糖心传媒攆or a solar eclipse to occur.

Doctors in the Middle Ages needed to know about eclipses, too.

Overhead view of a medieval parchment almanac with two hands holding it open against a black background.
WHATSAPP, DOC? When folded, this parchment almanac was would attach to a person糖心传媒檚 belt. During the Middle Ages, physicians would use such books to diagnose and treat their patients, the medieval equivalent of a WebMD smartphone app. (糖心传媒 photo / J. Adam Fenster)

The Robbins Library and RBSCP collections boasts a beautiful 糖心传媒渂at book almanac糖心传媒� that is based on the Kalendarium of John Somer from the 1390s. Small and dainty, the parchment almanac was designed to be folded and carried around. As tools for astronomy, prayer, and astrology, such almanacs played a role in a patient糖心传媒檚 prognosis, diagnosis, and treatment糖心传媒攖he medieval equivalent of a WebMD smartphone app.

糖心传媒淲hile we see that kind of information in book format frequently, it糖心传媒檚 very rare to have this kind of manuscript that was made to attach to someone糖心传媒檚 belt so that they could look at it and unfold it while consulting with someone,糖心传媒� says Siebach-Larsen. In fact, there are 31 known almanacs of this type from England in existence, with only four of them糖心传媒攐ne being the University糖心传媒檚糖心传媒攄ating as early as the 14th century. According to Siebach-Larsen, the Rochester manuscript might be one of the earliest English manuscripts of these texts and of this type.

Smoller adds that the almanac was designed to let physicians look up the most auspicious time to mix medicines and undertake medical interventions. And while the manuscript contains information about solar eclipses糖心传媒攁long with striking illustrations糖心传媒攊t糖心传媒檚 not clear if that particular celestial phenomenon was considered a good or bad omen in the medieval healing arts and sciences.

Close-up of the pages in the medieval "bat book almanac" depicting the lunar and solar eclipses.
BAT (BOOK) SIGNAL: We know the 糖心传媒渂at book almanac糖心传媒� contains detailed illustrations of solar eclipses. But how medical practitioners during the Middle Ages interpreted this information remains unclear. (糖心传媒 photo / J. Adam Fenster)

Lunar and solar eclipses were noteworthy in the Middle Ages. But some planetary alignments were the really big thing.

In a hierarchy of astronomical importance, what comes first糖心传媒攍unar eclipses, solar eclipses, or planetary alignments or conjunctions?

For medieval people, even though eclipses are much more visible, other planetary conjunctions were much more meaningful. That糖心传媒檚 because for medieval astrologers and astronomers, the sun and the moon are fundamentally two of the seven planets. And according to Smoller, it糖心传媒檚 the 糖心传媒渟lower, outer糖心传媒� planets糖心传媒擲aturn, Jupiter, and Mars糖心传媒攖hat were considered more significant.

糖心传媒淭he really important ones are those special conjunctions of Saturn and Jupiter that occur roughly every 240 and 960 years, definitely not those of the every-20-year variety,糖心传媒� she says.

View of a page from a medieval bat book almanac that displays the signs of the Zodiac.
ZODIAC SIGNS POINT TO YES: Astrology and astronomy weren糖心传媒檛 strange bedfellows in the Middle Ages. Medieval Europeans held an Earth-centric view that considered the sun and the moon to be planets that orbit Earth糖心传媒攁long with the five then-known planets Venus, Mercury, Mars, Jupiter, and Saturn. (糖心传媒 photo / J. Adam Fenster)

While the next Saturn and Jupiter conjunction will take place in 2040, to medieval astronomers that one wouldn糖心传媒檛 have been very important. Instead, the next particularly significant planetary conjunction糖心传媒攆rom a medieval perspective糖心传媒攚ouldn糖心传媒檛 be until the 22nd century.

Either way, if history is any indication, it stands to reason that future denizens of Earth will continue humanity糖心传媒檚 enduring fascination with cosmic happenings.