June 18

Gervase Views the Moon Throbbing Like a Wounded Snake

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One day, he would witness balls of lightning ... but first, the moon the moon danced...

Shortly after sunset on June 18, 1178, five monks of the Christ Church Priory in Canterbury stepped outside into the long English twilight and looked up at the crescent new moon hanging in the western sky. What they saw next, and later reported to Gervase of Canterbury, the monastery’s meticulous chronicler, has been debated by astronomers, medievalists, and occultists ever since…

In Gervase’s own words, translated from his Latin Chronicle: “The upper horn of the Moon split in two. From the midst of this division sprang a burning torch, throwing forth flame, hot coals, and sparks over a considerable distance. Meanwhile the body of the Moon, which was below, writhed as if 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.”

According to Gervase, the phenomenon recurred a dozen times or more before the moon settled back into its ordinary appearance. The monks were terrified, and Gervase recorded their account. And then, for eight centuries, the event slept quietly in an old manuscript in Canterbury—waiting.

Gervase of Canterbury: An Unlikely Witness

Gervase of Canterbury was born around 1145 and acted as a Benedictine monk at Christ Church from 1163 until his death in the early thirteenth century. He was known as one of the finest chroniclers of his age and, as proof, his writings remain a major source for what we know of twelfth-century England; he even documented the martyrdom of Thomas Becket, who murdered in that same Christ Church eight years before the lunar event, in 1170, since he was witness to the very event. And like many scholars of his age, Gervase had a particular interest in astronomical phenomena: his Chronicle contains careful records of lunar and solar eclipses, comets, and unusual atmospheric events—and modern researchers have been able to verify many of these against independent records from European, Chinese, Arabic, Japanese, and Korean astronomical archives. As such, he was also regarded as a careful and accurate documentarian.

The lunar “event: of June 18, 1178 was recorded by Gervase without embellishment or (most surprisingly) theological interpretation—which is quite significant. Medieval chroniclers were generally expert at finding providential meaning in celestial events, and the fact that Gervase records this one as a curiosity rather than an omen suggests it did not fit neatly into the available interpretive frameworks. Something happened that the tradition of signs and wonders could not readily contain.

Gervase’s objectivity is, in itself, a wonder; at the time, the Aristotelian model of the universe—which dominated European thought in 1178 and was accepted as fact for another four centuries—divided reality into two fundamentally different realms: below the moon was the sublunary world, impermanent, changeable, and subject to decay (in essence, the domain of the four elements and the suffering of mortal life); above the moon was the superlunary realm, which was viewed as perfect, eternal, crystalline, and unchanging. Here, the heavens did not burn, crack, writhe, or explode, because only the earth (the material world) did that.

What those five monks witnessed was therefore not merely a surprising event but a cosmological impossibility. The upper horn of the crescent moon splitting in two, fire and hot coals erupting from the division, and—most startlingly—the moon throbbing “like a wounded snake.” This was the perfect, eternal heavens behaving like corrupt, mortal matter, and could easily have been interpreted as a divine sign. It’s no small wonder the five men were frightened; in their shared view, they were watching the architecture of the universe crack.

“Giordano Bruno” Weighs In

For eight hundred years, the Canterbury monks’ report was an historical curiosity with no scientific repercussions. Then, in 1976, geologist Jack Hartung published a paper in the journal Meteoritics proposing a remarkable explanation: what the monks had actually witnessed was a large asteroid or comet impacting the near-far edge of the moon, causing a plume of molten matter to erupt from the lunar surface precisely as Gervase described. The candidate crater, Hartung argued, was Giordano Bruno—named, with magnificent irony, after the philosopher burned at the stake in 1600 for proposing, among other heresies, that the universe was infinite and contained countless worlds like our own.

When it comes to timing, Hartung’s theory fits perfectly: the “Giordano Bruno crater” is the youngest crater of its size on the near side of the moon—fresh enough, in geological terms, that its ejecta rays are still clearly visible from Earth, while its location places it at the boundary between the near and far sides of the lunar surface, which would explain why the explosion appeared to erupt from the upper horn of the crescent as seen from Canterbury. The plume would have been visible; the writhing and throbbing of the moon’s apparent surface could be explained by atmospheric turbulence and the distortion of the newly ejected gases still surrounding the impact site.

For a time, Hartung’s hypothesis was widely circulated as the probable explanation. (It had the great virtue of making a medieval monk’s bewildered description do real scientific work—of using a twelfth-century account to pinpoint the date of a lunar event that left a crater still visible today). However, the difficulty was identified in a 2001 paper by Paul Withers, a graduate student at the University of Arizona. Wither’s own theory received considerable attention from NASA, especially his fundamental problem with the Hartung hypothesis: an impact large enough to create a crater of Giordano Bruno’s size would have produced a debris field of staggering proportions. He argued that the ejecta from such an impact would have reached Earth within days, creating a meteor storm of extraordinary intensity—blinding, blizzard-like, and most-likely visible for a week or more across the entire sky.

Withers’s conclusion was that the monks almost certainly did not witness a large lunar impact. The more probable explanation, he suggested, was a much smaller event—a meteor entering Earth’s atmosphere at the precise line of sight between Canterbury and the crescent moon, so that the fireball appeared to originate from the lunar surface. This would explain the fire, the sparks, the apparent splitting—all without requiring any impact on the moon itself. The crater that bears Giordano Bruno’s name may be considerably older than 1178, and its apparent youth could have been a function of the particular nature of its surface material, rather than its actual age.

The debate between Hartung and Withers has never been conclusively resolved. What we are left with is the original mystery in its full, undiminished strangeness is that five men in Canterbury, shortly after sunset on June 18, 1178, watched the moon split apart and breathe fire, and their account was recorded by one of the most reliable chroniclers of the medieval age. For the esoteric tradition, the event carries a significance that neither the impact hypothesis nor the meteor explanation fully captures:

Medieval Hermetic and astrological thought attributed profound importance to the moon as the lowest sphere of the celestial realm—the boundary between the eternal and the temporal, the interface through which spiritual influences descended into the material world and through which the soul ascended at death. The moon was not merely a rock; it was nothing less than a threshold. And what the Canterbury monks witnessed, in their own cosmological framework, was the threshold catching fire … the wound appearing in the membrane between worlds. But whatever the scientific explanation—meteor, impact, atmospheric anomaly—the symbolic resonance of a burning, writhing, snake-like moon remains one of the more vivid images in the history of celestial observation. It belongs to that category of events that refuse to be fully domesticated by explanation, that retain their strangeness regardless of what mechanism is eventually assigned to them.

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