(meteorobs) Re: An Explosion on the Moon

YoungBob2 at aol.com YoungBob2 at aol.com
Sat Dec 24 16:38:59 EST 2005

In a message dated 12/24/2005 9:48:50 AM Eastern Standard Time, 
drobnock at penn.com writes:

<< Wasn't there an Irish monk
 claiming to see  something strike the moon during the middle ages? It
 was a dragon or an angel falling?

That was probably a meteorological optical phenomenon, 
a mirage effect at the "zone of avoidance", similar to the dark
band seen at the Sun near sunset.  There have been several
published accounts of this very similar to the Gervase of
Canterbury report.

The Giordano Bruno idea was published in the "News Notes" section 
of the October 1984, Sky & Telescope, page 313.  I sent the following
letter proposing a meteorological optical explanation.  It was published
in the Letters section of the April 1985 Sky & Telescope, page 292:

"Kenneth Brecher of Boston University has proposed the name 
'Canterbury Swarm' for a group of possibly related bodies in the orbit of 
Comet Encke, as reported in your "News Notes" recently (S&T: Ocober, 
1984, page 313).  The name comes from a curious June 25, 1178, 
observation of the moon reported by a monk, Gervase, in the annals of
Canterbury Cathedral.  In 1976 Jack B. Hartung suggested this was a 
naked-eye observation of the formation of the far-side lunar crater 
Giordano Bruno.

Gervase wrote, "...after sunset when the moon had first become visible
a marvelous phenomenon was witnessed ... Now there was a bright new
moon ... suddenly the upper horn split in two.  From the midpoint of this
division a flaming torch sprang up, spewing out, over a considerable 
distance, fire, hot coals, and sparks ... the body of the moon which was
below 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
... after these transformations the moon ... along its whole length, took on
a blackish apperance." (emphasis mine)

Hartung claimed this observion, "appears to be unique", because, "to
my knowledge no similar event of the magnitude and complexity observed
has ever been described."

I have recently found five similar observations of the moon and one of 
the Sun which have been published in the meteorological literature or old

In a letter in the May 31, 1988, issue of Nature, p. 102, T. Mellard
Reade reports his daughter at Maryborough, Queensland, Australia, saw
moon "apparently dancing up and down ... visible only when she was 
behind a narrow stratum of cloud and continued at intervals for 30
minutes ..." He added that the observers said they became "seasick"

In the Marine Observer (30: 135, 1960) observers on the S.S. Devon
described the lower edge of the mon scintillating with a brilliant scarlet
color when the moon was about 15 seconds of arc above a horizon cloud
bank, in conditions of strong scintillation of stars and an apparent looming
mirage.  The editor notes similar reports by aircraft crews, usually at
sunrise, and associated with "low level temperature inversions, probably at
about 1,000 ft."

Also in the Marine Observer (31: 68, 1961) the rising moon was
described as being distorted and exhibiting a brilliant red flash which lasted
for 1-1/2 seconds.  This phenoomenon is similar to the green flash seen at
sunset.  Another Marine Observer report (27: 83-4, 1957) notes the crew of
the Motor Vessel Tyrone reported on June 28, 1956, seeing, just prior to 
moonrise, a bright red glow on the bearing on which the moon was expected
to rise, "A red light suddenly appeared and at first was taken to be a 
hurricane lamp, lit  by a small boat about 2 miles away ... The light spread
to 2 degrees in width and was obviously in, not on, the water (an inferior
mirage?) as it did not lift with swell; it had the appearance of a flaming
log, but the 'flame' was motionless.  hree minutes later a line of white
appeared over an arc of 10 degrees ... the moon then rose and the red,
flame-like light disappeared, to be replaced by two half-moon glows in the
water.  As the moon rose, the irregularities on its upper limb were plainly
visible to the naked eye, and when just clear of the horizion the lower limb
appeared to have a Dent in the edge at about five o'clock."  Another report
from the Marine Observer from 1958 mentions several distinctly separate
lunar crescents visible close together.

Meteorological Magazine (58: 10-11, 1923) has a report by Joseph
Mintern of the sun seen on January 9, 1923. The sun was described as,
"Surrounded by bright red, flashing rays in all directions, then changing 
to yellow ... the body of the sun ... appeared to dance and shift about 
there in a radius of about 5 degrees ... changing to green ... no 
description is able to convey whatwas seen in these ten or twelve 

It seems evident that meteoroloical optical phenomena related to a 
superior mirage with its "zone of avoidance", such as that which create
distortions of the rising or setting sun, the "red and green flash" and
scintillation of stars could quite possible have been the origin of the 
1178 observation. An atmospheric origin was mentioned by Hartung in
his original 1976 paper but quickly set aside.

Since there is no naked  eye observation of an object striking 
the moon in recorded history, other than the Gervase record, which
seems not to be unique, applying Occam's Razor suggests that a 
meteorological explanation of the 1178 puzzle is far more likely than
either of the two other published explanations, the formation of
Geordano Bruno or an atmospheric meteor (Nininger and Huss, 1977).

Use of the name "Canterbury Swarm" as anything other than a literary
convention does not seem to be warrented by the evidence provided in the
medieval record of the good brother.  "Encke Swarm", though less flashy,
seems more logical.


1. Hartung, Meteoritics 11: 187-194, 1976.
2. Nininger and Huss, Meteoritics 12: 21-25, 1977.
3. Calame and Mulholland, Science 199: 875-877, 1978.
4. "News Notes", Sky & Telescope, 68: 313, 1984.
5. Reade, Nature, 38: 102, 1888.
6. Brittain, Marine Observer 30: 135, 1960.
7. Thomas, Marine Observer 31: 68, 1961.
8. Fraser, Marine Observer 27: 83-84, 1957.
9. Townshend, Marine Observer, 29: 178, 1959.
10. Minern, Meteorological Magazine, 58: 10-11, 1923.
11. Minnaert, Nature of Light and Colour in the Open Air, Dover.
12. Corliss, Handbook of Unusual Natural Phenomena, Sourcebook
      Project, 1977.

Bob Young

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