What the Monks Saw: A Medieval Mystery

Just to show that life is full of unexpected turns, on June 18, 1178, a group of medieval English monks threw a fine puzzle in the laps of astronomers that lingers to this day.On that day, shortly after sunset, five monks at the abbey of the Christ Church of Canterbury (on the site of Canterbury Cathedral,) noticed that something very odd was happening in the sky. Gervase, who was Canterbury’s chronicler, provided the eyewitness record:“The upper horn of the Moon split in two. From the midpoint of the division a flaming torch sprang up, spewing out, over a considerable distance, fire, hot coals and sparks. Meanwhile the body of the Moon which was below writhed, as it were in anxiety, and to put it in the words of those who reported it to me and saw it with their own eyes, the Moon throbbed like a wounded snake. Afterwards it resumed its proper state. This phenomenon was repeated a dozen times or more, the flame assuming various twisting shapes at random and then returning to normal.…