Friday, August 31, 2012
Tonight, if the sky is clear, you'll be able to look up and see a Blue Moon.
No, not a Smurf-blue moon…in spite of my header photo. That's a fake. Well, the moon image is real, but it's an ordinary warm silvery full moon, identical in color to all those other full moons we see hanging up there every 29.5 days…er, nights. I just borrowed a bottle of hair-color from an octogenarian up the road and gave it a snazzy tint job.
The term "Blue Moon" has been around for upwards of 500 years. Each of our seasons—spring, summer, autumn, winter—typically host only three full moons. But sometimes, because the lunar cycle is a tad shorter than the average number of days per month—and since we start and end our seasons on equinoxes and solstices, not months—there's sometimes an extra moon full moon in a given season; making thirteen full moons in a year instead of the expected twelve. Historically, the term "Blue Moon" was applied to the third moon of a four moon season.
Because this extra third-out-of-four moon didn't happen all that often, the term "Blue Moon" became synonymous with rarity. And after awhile "Blue Moon" stepped outside of astronomy folklore and came to mean any sort of rare event. For example, someone might say: "A politician speaking for more than ten minutes without skewing the facts or outright lying happens once in a blue moon."
Country folks, while often poorly-educated were nevertheless quite nature-cognizant, and naturally had no trouble understanding and employing the original and correct definition of a Blue Moon. For a couple hundred years your average hay-gnawing rube could have told told you it meant the third moon out of four in a particular season.
However, as you might also guess, once it reached our Twentieth Century nature-oblivious, city-atrophied hands, we promptly managed to mess it up.
Apparently an amateur astronomer, James Hugh Pruett, writing for Sky & Telescope magazine back in 1946, got confused by the historic simplicity and thought the term meant the second of two full moons occurring within the same month. An event not all that uncommon. If left there, the mistake might have eventually sank beneath the ignominy of ignorance. But, unfortunately, it received a major 1980s technological boost when Deborah Byrd failed to research the matter and simply parroted Pruett's old mistake on her popular SkyWatch radio broadcast…and from then on, the error became embedded.
So tonight's Blue Moon won't be blue and won't be a genuine Blue Moon as originally defined. There will only be the usual three full moons this season: one full moon back in July, plus two in August. No full moon occurred in June after summer's solstice start, and no full moon will arise in September before summer ends with the equinox. We're therefore a full moon short of being able to claim true Blue Moon status…unless you're willing to concede to our modern mangled misinterpretation.
Still, that big ol' silver dollar moon will be up there tonight, shining bright and rolling across the star-spattered heavens. Pretty enough to please anyone except a Smurf.