A Moon for the Misinformed
Published: April 2, 1999
So now it turns out that the ''blue moon'' that appeared on Wednesday -- supposedly the second blue moon of the year -- really wasn't. In fact, the first blue moon of the year, spotted back in January, really wasn't, either. What started out as one of those remarkable years in which two blue moons were to lighten the skies will actually end up as a year in which not a single blue moon emerges.
We know all this thanks to a timely confession by Sky & Telescope magazine, which made a careless error half a century ago that has reverberated ever after among astronomy buffs. The term ''blue moon'' to these people has come to mean the second full moon to appear in any calendar month. But when a Canadian folklorist tried to trace the origins of this meaning, he had a horrendous time. He tracked it back through a 1986 Trivial Pursuit question, which was based on a 1985 children's almanac, which may have gotten it from a 1980 radio broadcast, which was based on a 1946 article in Sky & Telescope, which cited the 1937 Maine Farmers' Almanac. The only trouble was, Sky & Telescope now acknowledges, the original almanac never said a blue moon was the second full moon in a month. That interpretation was mistakenly inferred by a contributor to the magazine. The almanac itself apparently decided that if there were four full moons in a three-month season, the third should be called a blue moon. By that reckoning, there will be no blue moons this year.
The only cause for joy is that we can now get back to the deeper meanings of ''blue moon,'' which never quite fit with the two-in-a-month definition anyway. The common expression ''once in a blue moon'' has always meant ''once in a very long time.'' Yet the appearance of two full moons in the same calendar month is not all that rare, occurring about once every two and a half years or so on average.
Lyricists think that blue moons are sad moons that see us ''standing alone . . . without a love of my own.'' But the term ''blue moon'' goes back more than 400 years, with meanings that range from absurdity (much like saying the moon is made of ''green cheese'') to actual visual descriptions of moons that looked blue when viewed through the dust kicked up by huge volcanic explosions or forest fires. Such cataclysmic events really do occur rarely, or ''once in a blue moon.''