Something for which to look forward?
Mime-Version: 1.0 (NeXT Mail 3.3 v118.2)
From: Peter Langston <psl>
Date: Mon, 20 Dec 99 13:57:45 -0800
Subject: Something for which to look forward?
X-Lib-of-Cong-ISSN: 1098-7649 -=[ Fun_People ]=-
[In the last three weeks Fun_People have (no doubt) been inundated with
articles like the one below. Unfortunately, the science in these articles
isn't quite kosher. Apparently all these articles came from an article
in the farmer's almanac (see http://tbtf.com/blog/1999-12-12.html#6 for
I've appended the text of an article from Sky and Telescope that gives
a slightly different view...
Forwarded-by: Cal Herrmann <firstname.lastname@example.org>
Subject: Something for which to look forward
Forwarded-by: "Michael Cooney" <email@example.com>
Watch for this full moon...
Something to look forward to on December 22, 1999:
This year will be the first full moon to occur on the winter solstice,
Dec. 22nd, commonly called the first day of winter. Since a full moon
on the winter solstice occurs in conjunction with a lunar perigee (point
in the moon's orbit that is closest to Earth), the moon will appear about
14% larger than it does at apogee (the point in it's elliptical orbit that
is farthest from the Earth). Since the Earth is also several million
miles closer to the sun at this time of the year than in the summer,
sunlight striking the moon is about 7% stronger making it brighter.
Also, this will be the closest perigee of the Moon of the year since the
moon's orbit is constantly deforming. If the weather is clear and there
is a snow cover where you live, it is believed that even car headlights
will be superfluous.
On December 21st. 1866 the Dakota Sioux took advantage of this combination
of occurrences and staged a devastating retaliatory ambush on soldiers in
the Wyoming Territory.
In laymen's terms it will be a super bright full moon, much more than
the usual AND it hasn't happened this way for 133 years!
Our ancestors 133 years ago saw this. Our descendants 100 or so years
from now will see this again.
Wednesday, December 15
Brightest Moon in 133 Years?
[IMAGE] Left: Portuguese amateur astronomer Antsnio Cidadco
captured these images of the full Moon on two different dates using a
black-and-white QuickCam on a 4-inch f/6.3 Schmidt-Cassegrain telescope.
In the left-hand image the Moon was at perigee, i.e., closest to Earth.
In the right-hand image it was at apogee, i.e., farthest from Earth. the
difference in the Moon's apparent size is quite...apparent! Click on
image for larger view.
Suddenly a lot of people are asking this question: Will the full Moon of
December 22, 1999, be the brightest full Moon in 133 years?
According to Roger W. Sinnott, associate editor of Sky & Telescope
magazine, the answer is unequivocal: No!
It is true that there is a most unusual coincidence of events this year.
As S&T contributing editor Fred Schaaf points out in the December
1999 issue of Sky & Telescope, "The Moon reaches its very closest point
all year on the morning of December 22nd. That's only a few hours after
the December solstice and a few hours before full Moon. Ocean tides will
be exceptionally high and low that day."
But to have these three events -- lunar perigee, solstice, and full Moon
-- occur on nearly the same day is not especially rare. The situation
was rather similar in December 1991 and December 1980, as the following
dates and Universal Times show:
Event | Dec. 1999 | Dec. 1991 | Dec. 1980
Full Moon | 22, 18h | 21, 10h | 21, 18h
Perigee | 22, 11h | 22, 9h | 19, 5h
Solstice | 22, 8h | 22, 9h | 21, 17h
So is it really true, as numerous faxes and e-mails to Sky & Telescope
have claimed, that the Moon will be brighter this December 22nd than at
any time in the last 133 years? We have researched the actual perigee
distances of the Moon throughout the years 1800-2100, and here are some
perigees of "record closeness" that also occurred at the time of full
Date | Distance (km)
1866 Dec. 21 | 357,289
1893 Dec. 23 | 356,396
1912 Jan. 4 | 356,375
1930 Jan. 15 | 356,397
1999 Dec. 22 | 356,654
2052 Dec. 6 | 356,421
So it turns out that the Moon comes closer to Earth in the years 1893,
1912, 1930, and 2052 than it does in either 1866 or 1999. The difference
in brightness will be exceedingly slight. But if you want to get
technical about it, the full Moon must have been a little brighter in
1893, 1912, and 1930 than in either 1866 or 1999 (based on the calculated
The 1912 event is undoubtedly the real winner, because it happened on
the very day the Earth was closest to the Sun that year. However,
according to a calculation by Belgian astronomer Jean Meeus, the full
Moon on January 4, 1912, was only 0.24 magnitude (about 25 percent)
brighter than an "average" full Moon.
Our data are from the U.S. Naval Observatory's ICE computer program,
Jean Meeus's Astronomical Algorithms, page 332, and the August 1981
issue of Sky & Telescope, page 110.
(c) 1999 Sky Publishing Corp. All rights reserved.
© 1999 Peter Langston