A fun fact to end the year with: "Uh-Oh! A 'Blue Moon' Ends the '00s"
Uh-Oh! A "Blue Moon" Ends the 00s
As twilight descends on New Year's Eve of 2009, a full Moon will rise in the
eastern sky for the second time this month (the first time came on December
2nd). Many people use the expression "once in a blue Moon" to mean something
that occurs rarely, and you might be tempted to call December 31st's big,
bright orb a "Blue Moon" too. While the former meaning can be traced back
centuries, the latter definition is much newer -- and it's wrong! At least
if you're a stickler about these things.
"In modern usage, the second full Moon in a month has come to be called a
'Blue Moon.' But it's not!" says Kelly Beatty, Senior Contributing Editor
for Sky & Telescope magazine. "This colorful term is actually a calendrical
goof that worked its way into the pages of Sky & Telescope back in March
1946, and it spread to the world from there."
Sky & Telescope admitted to its "Blue Moon blooper" in its May 1999 issue.
Canadian folklorist Philip Hiscock and Texas astronomer Donald W. Olson had
helped the magazine's editors figure out how the mistake was made, and how
the two-full-Moons-in-a-month meaning spread into the English language.
Before 1946, a Blue Moon always meant something else. For example, says
Hiscock, sometimes it referred to an obvious absurdity. Quite a few old
songs use it as a symbol of sadness and loneliness. There's even a cocktail
called a Blue Moon; it's a mix of curacao, gin, and perhaps a twist of
lemon. And, exceedingly rarely, the Moon actually does turn blue in our sky
-- when a volcanic eruption, forest fires or dust storms send lots of fine
dust into the atmosphere.
Our 1946 writer, amateur astronomer James Hugh Pruett (18861955), made an
incorrect assumption about how the term had been used in the Maine Farmers'
Almanac -- which consistently used "Blue Moon" to mean to the third full
Moon in a season containing four of them (rather than the usual three).
By this definition, there is no Blue Moon in December 2009; instead, the
last one was in May 2008, and the next happens in November 2010.
But there's no turning back now. The concept of a Blue Moon as the second
full Moon in a month with two, as well as the third full Moon in a season
with four, are now both listed as official definitions in the 4th edition of
the American Heritage Dictionary (Houghton Mifflin, 2000).
By either definition, Blue Moons happen about once every 2.7 years on
average. The last occurrence of two full Moons in a calendar month was in
May 2007 (in North American time zones; the clock had already turned over to
June 1st in Europe and Asia.) The next will be in August 2012.
The last time a second full Moon last fell on New Year's Eve was in 1990.
If you want to tell your readers, listeners, or viewers that this Thursday's
full Moon is a Blue Moon, go right ahead. Pretty much everyone else will
too. The newer, "wrong" definition is simpler and handier for most people to
grasp and use. "That's how the English language shifts. You can't beat back
the tide," quips Sky & Telescope Senior Editor Alan MacRobert. "Not when the Moon is pulling the tide."
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