Gervase and the Moon

Yesterday I mentioned Gervase of Canterbury and his fairly unremarkable life. What follows is the reason he makes an appearance in footnotes in astronomical texts.

Among his other writing duties and pleasures, Gervase also kept the monastery's chronicles, and in 1178 he recorded something interesting:

This year on the 18th of June,[*] when the Moon, a slim crescent, first became visible, a marvelous phenomenon was seen by several men who were watching it. Suddenly, the upper horn of the crescent was split in two. From the mid point of the division, a flaming torch sprang up, spewing out over a considerable distance fire, hot coals and sparks. The body of the Moon which was below, writhed like a wounded snake. This happened a dozen times or more, and when the Moon returned to normal, the whole crescent took on a blackish appearance.

Scholars and astronomers have puzzled over this. Astronomer Jack Hartung in the September 1976 issue of the journal Meteoritics proposed that they had witnessed a meteor strike that created the lunar crater "Giordano Bruno." Recent photos by Apollo made it, in his opinion, a candidate for a young crater only 800 years old. Hartung had his critics, but without new data on the crater, the verdict could rightly claim to be "up in the air." Until years later a student named Paul Withers in Weekly Scientist pointed out an obvious flaw. An impact great enough to create the 14-mile wide Giordano Bruno would have thrown "10 million tons" of debris off the lunar surface; the ejecta in short order would have created unbelievably spectacular meteor showers in Earth's atmosphere. These meteor showers were not noted by monks in England or any other of the sky-gazing cultures that dotted the globe at the time.

So what did the monks see? His guess is that they were looking in the right place at the right time to observe a meteor entering Earth's upper atmosphere between their line of sight and the horns of the crescent moon.

For a modern astrophysicist's view on Gervase' chronicle, see Brian Koberlein's Google + post for today, June 25th, called "Mining for Science."


*N.B. The Proleptic Gregorian Calendar (used for dates prior to 1582 because of a necessary correction) turns this date into June 25th, meaning today is the 834th anniversary of the monks' observation.

Gervase of Canterbury

Gervase of Canterbury (c.1141-c.1210) was a monk of Christ Church in Canterbury. He was ordained on February 16, 1163 by Archbishop of Canterbury Thomas Becket (who would be assassinated in 1170, canonized by Alexander III a few years later, and become the focus of the most famous shrine in England).

Gervase had a fairly undistinguished career as a monk, and his "importance" for us is in his connection to other people and events. He was involved in the dispute between the monks of Christ Church and Archbishop of Canterbury Baldwin of Forde. Baldwin disapproved of the luxury in which the monks of Christ Church lived, derived from the donations made by pilgrims to the shrine of St. Thomas Becket. At one point, Baldwin had the entire monastery confined under house arrest for a year and a half. Gervase was one of the monks sent to inform Baldwin that they were making an appeal to the pope. Ultimately, the monks were given their freedom and normalcy restored (except that Baldwin appointed Roger Norris, a pretty ineffective administrator, as their prior).

For a brief time Gervase held the position of sacristan (the person who takes care of the church and its contents), working for the Archbishop Hubert Walter.

...and that's about it for Gervase, except for one little thing that has intrigued historians and astronomers for centuries. Gervase kept records and wrote books, such as a history of the Archbishops of Canterbury and his Mappa Mundi, which lists bishoprics and ecclesiastical houses in England, Wales and Scotland. He was also the chronicler of his monastery, and on the night of June 18th, 1178,* he recorded something curious and previously unseen.

...but what the event was, and how June the 25th is actually the anniversary of the event on the 18th, I'll save for tomorrow.

*The same year this was happening in Italy, as mentioned on the June 20th post.