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Re: (meteorobs) Dec 22nd

This is about the umpteenth time I've seen the Full Moon of December 1999 
e-mail circulating through the internet and quite frankly I am getting weary 
of it.  
Indeed . . . it is an artifact of an article that originally appeared in the 
1999 Old Farmer's Almanac by an unnamed author.  I honestly believe that they 
needed to fill a couple of pages and decided to latch-on to writing about a 
perigean full Moon occurring on a winter solstice.

Is this an extraordinary event?  No.  Every year, we have a full Moon that in 
most cases will coincide with the most extreme perigee of the year 
(occasionally in some years, the most extreme perigee will coincide with new 
Moon). 

Will the Moon appear extraordinarily brilliant because it is the largest (in 
apparent size) and closest full Moon of the year?  Not really.  Read what Dr. 
Jean Meeus, a Belgium meteorologist and renowned celestial mechanic recently 
wrote of the closest/largest full Moon of the 20th century (which occurred in 
1912):

"The most extreme perigee, of January 4, 1912, coincided almost exactly with 
the full moon.  Moreover, the Earth was very close to its perihelion, so that 
the Moon received more sunlight than under average circumstances.  Was that 
full moon exceptionally bright?

"The perigee distance on that date was 356,375 km.  Let us also suppose than 
an observer saw the Moon directly overhead, yielding a distance to its center 
of only 349,997 km.  The Earth's distance to the Sun was 0.9832 astronomical 
unit.

"Now, remembering that the mean distance of the Earth-Moon is 384,400 km. and 
the Earth-Sun 1.0 a.u., and that the apparent brightness of a body varies 
inversely as the square of its distance, we find that the full moon was 
(384,400/349,997)2 x (1.0/0.9832)2 = 1.2478 times as bright as the "mean" 
full moon.  This corresponds to an increase of only 0.24 magnitude; thus the 
moonlight was not exceptionally bright."

The Old Farmer's Almanac article also notes that in areas with a snow cover:  
"...your car's headlights -- may seem superfluous," and "on the night of 
December 21, 1866, the Lakota Sioux staged a devastating retaliatory ambush 
of soldiers in the Wyoming Territory -- perhaps planning the attack for that 
bright night, whose lunar confluence was identical to this year's."

The first encourages reckless driving, with many people wanting to "try" the 
strategy of turning off headlights, and the second, well I believe Dakota 
Indians might have timed attacks for full moons, but I do not at the moment 
believe they kept track of the exact brightness of full moons or knew of the 
pattern associated with perigee cycles. 

Truth be told, the only thing that makes this upcoming perigee Moon "unusual" 
is its coincidence with the winter solstice.  But aside from the fact that 
this is the first time this has happened since 1866 . . . there is nothing 
else really noteworthy about this.   I'm sure, however, that come December 
22nd, this will be at the top of the "Millennium Madness Headlines," and 
everybody will be rushing outside to gawk at the "Astonishing Lunar 
Coincidence" (as the Old Farmer's Almanac billed it).  We can only hope that 
the media coverage will be just as enthusiastic next month when next month's 
full Moon will provide North Americans and Europeans with something really 
interesting to look at:  A Total Eclipse of the Moon!     

By the way . . . the original article appeared in the "Old" Farmer's Almanac 
(published in Dublin, New Hampshire) and not "The" Farmers' Almanac 
(published in Lewiston, Maine).  Let's give dis-credit, where dis-credit is 
due!

-- joe rao 
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