Heavens: Every 2 1/2 to three years, a rare lunar event occurs -- a second full moon in a month's time. Gaze skyward tonight and see for yourself.


June 30, 1996|By Richard O'Mara | Richard O'Mara,SUN STAFF

Look to the sky! For one moment tonight near midnight the moon will be "blue." If the sky is clear and you see it, don't expect strange happenings. Don't expect it to actually be the color blue, though that has been known to happen now and then.

The blue moon does not provoke weird behavior in man or beast, any more than any other full moon. Astronomically, it is as predictable as the rising of the sun. Meteorologically, it can signal disaster. As a metaphor, it describes two conditions: absurdity and rarity.

For the latter reason, thousands of people will be out tonight all across the country, camping on high places and on desert plains far removed from city lights, adjusting telescopes at oblique attitudes on rooftops, to regard its unfolding.

For rare things are often thought important just for being rare. They excite the mind for reasons that are unclear, the way certain round numbers do, such as those which mark the birth of new centuries. They are ticklish curiosities.

So what is a blue moon?

Astronomers call the second full moon to appear in a single month the blue moon. It occurs every 2 1/2 to three years. It is a byproduct of the irregularity of our calendar. Calendar months are 28 to 31 days long. The lunar month is about 29 1/2 days long. So in those months when the new moon appears early on the first day of the month -- as it did earlier this month -- a second new moon is bound to appear before the calendar month is out. A blue moon.

But never in February, which is too short ever to have a second full moon. February comes and goes, year in, year out, blue moon-less. February is doubly bereft on that far more uncommon occasion when two blue moons appear in the same year. This occurs every 19 years, and when it does February does not even have one full moon to light its winter darkness.

Two blue moons will rise next in 1999. February is not enthused.

Astronomers did not always call this second full moon in a calendar month a blue moon. They had no particular name for it until a couple of decades ago, when a Texas star-gazer named Debbie Byrd rediscovered and popularized the expression. She gleaned her reference to the double moon from a 1946 article written in Sky and Telescope magazine.

Byrd, who has a show on National Public Radio called "Earth and Sky," founded the Texas Star Party about 20 years ago. It is not what you might think. "A star party is an occasion when lots of people get together with their telescopes and look at the stars." It's all about fun, she says.

The article in Sky and Telescope was written by J. Hugh Pruett. Pruett searched the many books on astronomy and meteorology at the library at the University of Oregon, all copies of Monthly Weather Review published by the U.S. Weather Bureau from 1898 to 1942. He found not a single reference to blue moon.

He finally found one in the 1937 edition of the "Maine Farmers' Almanac."

It told him that in earlier times names had been given to each of the full moons as they appeared through the year. There was Moon after Yule, Wolf Moon, Lenten Moon, Egg Moon, Milk Moon, Flower Moon, Hay Moon, Grain Moon, Fruit Moon, Harvest Moon, Hunters' Moon and Moon Before Yule.

The second moon in a single month, Pruett wrote, "was called Blue Moon, and was considered unlucky and a real nuisance as it occurred at various times of the year and upset scheduling of church festivals."

Maybe it should have been called Nuisance Moon.

Heavenly absurdity

Since most Americans are not astronomy buffs, their understanding of the blue moon derives from the expression "once in a blue moon." It is proverbial, and means something "never or rarely seen."

The words "blue moon" were also used another way, said Anthony Curtis, a science writer on the faculty of Salisbury State University. "In the 19th century [and long before] people used the phrase blue moon the way we used to refer to someone who would argue, say, that black is white. It was a way of expressing an absurdity. An obvious absurdity."

Harry Augensen, an astronomer at Widener University in Pennsylvania, says that in the 14th century "once in a blue moon" meant something that never happened. "Today it's come to mean very rarely, or hardly ever."

There is no report as to who said it first, but probably it wasn't the person who said the moon is made of green cheese. That is a metaphorical allusion to the full moon -- which is round like an uncut cheese; and new, hence green.

The blue moon the proverb refers to is probably the real thing. For there have been occasions when the hue of the moon actually appeared blue to the human eye. It is a much rarer event than the rising of a second full moon in a single month.

Nobody can predict when it will happen. Entire generations pass without anyone seeing one. But the testimony of those who have goes way back.

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