The Canterbury Moon sighting

Five witnesses from Canterbury told the chronicler Gervase that on 18 June 1178 the Moon's upper horn split and threw out fire. A later geophysicist proposed an impact on the Moon.

On 18 June 1178, soon after sunset, five witnesses from Canterbury reported to Gervase, the abbey's chronicler, what they had seen: the Moon's upper horn splitting in two. Gervase wrote that from the middle of the split a flaming torch leapt up and sent out fire, glowing coals and sparks. The lower body of the Moon writhed, and the witnesses compared its motion to a wounded snake. Then the Moon returned to its usual state. Gervase recorded that this happened twelve times or more, with the flame taking twisting shapes before returning to normal.

Gervase's account lay forgotten for centuries. Jack Hartung, who held a geophysics post at Stony Brook University in New York State, rediscovered it. Hartung suggested the monks saw a meteor, or else an asteroid striking the Moon. He pointed to the 22-kilometre crater Giordano Bruno as the likely result, because the period of its formation matches the date of the sighting. The monks' report and Hartung's explanation are separate things: the first is the 1178 testimony, the second a proposal made centuries afterwards.