The moon disappeared from view in May 1110. The unusual phenomenon greatly puzzled eyewitnesses and continued to baffle astronomers for centuries.
It was believed that the disappearance of the moon was the result of an eclipse. The British astronomer George Frederick Chambers wrote about this mystery in his 1899 book The History of Eclipses. About 800 years after this happened, Chambers set the date for the eclipse as May 5, during the reign of Henry I.
“It all happened before midnight,” Chambers wrote, “and it was obvious that this was a case of a “black” eclipse, when the moon becomes completely invisible.”
But was it really so?
A more likely version was that the cause of the phenomenon was the eruption of the Hekla volcano in Iceland.
When Hekla erupted around October 15, 1104, sulfur-rich particles were released into the stratosphere. For many years this event was thought to be the catalyst for the apparent disappearance of the Moon.
A Scientific Reports study by a team from the University of Geneva in Switzerland has uncovered new information about the moon’s “location”. To find out if the Hekla eruption was the sole cause of the disappearance, the researchers analyzed ice cores from Iceland and Antarctica and eventually determined that the date of the eruption did not coincide with the schedule for the absence of the moon in 1110.
To find the true source, researchers combed medieval records for any mention of a “dark lunar eclipse”. And then they came across an entry in 1110 from the Peterborough Chronicles: “The moon was so extinguished that no light, no disk, or anything at all could be seen.”
The team suggests that the main cause was most likely a cluster of volcanic eruptions between 1108 and 1110, rather than the 1104 Hekla eruption.
One of these eruptions occurred in 1108 in Honshu, Japan. A diary entry by a Japanese statesman, discovered by researchers and cited in Scientific Reports, states that the eruption of the Asama volcano on the island of Honshu began in late August 1108 and continued until October.
In addition to the “eclipse”, the eruptions of 1108–1110 led to a number of social consequences in Europe, especially in agriculture. The researchers’ work revealed many descriptions of severe weather, crop failure and famine compared to other years with similar volcanic events.
