It's a good thing Shakespeare's Romeo didn't swear his love for Juliet by a blue moon. After all, his choice of a regular moon didn't sit well with her. "O! swear not by the moon," she said, "the inconstant moon,/That monthly changes in her circled orb,/Lest that thy love prove likewise variable."
Even more inconstant is a "blue moon," the phenomenon in which two full moons appear in the same month. Hence the old folk saying "Once in a blue moon," which to Juliet would have meant "never." Or close to it.
Blue moons show up, on average, once every 33 months. This year, however, we'll see two blue moons -- an exceptionally rare occurrence, according to Dr. David H. Menke, director of the Buehler Planetarium at Broward Community College in Davie. The first one took place in January, and the second will occur next week. Menke says that not since 1961 have we seen two blue moons in one year, and it won't happen again until 2018.
To mark the occasion, Menke will present the program Once in a Blue Moon: Myths and Mysteries March 31. His program will deal with more than just science, however. Menke teaches astronomy to students of all ages, from prekindergarten to college, and conducts a monthly lecture series at the planetarium. During all of his presentations, the witty and knowledgeable moon-gazer combines astronomy with history, literature, folklore, and linguistics.
The earliest-known written reference to the blue moon, he relates, is Roy and Barlowe's 1526 book Rede Me and Be Not Wroth. In it the authors write (in Old English, mind you), "Yf they say the mone is blewe/We must believe that it is true." What the English chaps were pointing out is that the moon, of course, is not blue. A "blewe" moon, to them, signified something that's not possible.
But since Rede Me was published, some natural disasters have given the moon a bluish tint. Following the eruption of the Indonesian volcano Krakatoa in 1883, the ash made the moon look blue for nearly two years. A monsoon in India in 1927 and forest fires in Newfoundland in 1951 had similar effects, so a blue-colored moon is now considered rare, not impossible.
During Menke's show, he'll relate many a blue-moon myth, and a re-creation of the night sky will be viewed inside the planetarium. Afterward viewers will move outside to check out the big-screen version.
Once in a Blue Moon: Myths and Mysteries will be presented Wednesday, March 31, at 7:30 p.m. in the Buehler Planetarium, 3501 SW Davie Rd., Davie. Admission is $6. Reservations are required, and kids younger than age 5 will not be admitted. Call 954-475-6681.