Did a medieval flying monk spot Halley’s comet, twice? It’s complicated

In the early 11th century, a young Benedictine monk named Eilmer took a daring leap from the towering structure of his abbey in Malmesbury, England. Equipped with a set of rudimentary wings crafted from willow and cloth, Eilmer managed to glide an impressive 600 feet before crashing into a nearby valley, resulting in severe injuries to both of his legs. This bold experiment in early aviation is immortalized by a stained-glass window at Malmesbury Abbey, dedicated to Brother Eilmer. The tale of Eilmer’s flight is recounted by 12th-century historian William of Malmesbury in an account from around 1125. However, William left out specific details regarding the date of Eilmer’s audacious leap. He did, however, reference another significant moment in Eilmer's life that took place when he was older: witnessing Halley’s comet in 1066. Eilmer reportedly remarked, “It is long since I saw you,” prompting some historians to speculate that he could have also seen Halley’s comet during its previous appearance in 989 when he was likely just a child. Assuming Eilmer was born no later than 984, he would have been in his 80s during the 1066 sighting, with his flight attempt occurring in his youth, potentially between 1000 and 1010. However, this estimation relies heavily on assumptions. James Aitcheson from the University of Leicester suggests in a paper published in the journal Notes and Queries that Eilmer may have actually witnessed a different comet in his youth, specifically the comet of 1018. If this is the case, it would imply a later birth date for Eilmer, pushing his flight attempt into the 1020s or 1040s.