Blue Moon Goes Viral
Pruett's 1946 explanation was, of course, the wrong interpretation and it might have been completely forgotten were it not for Deborah Byrd who used it on her popular National Public Radio program, StarDate on Jan. 31, 1980. We could almost say that in the aftermath of her radio show, the incorrect Blue Moon rule "went viral." Over the next decade, this new Blue Moon definition started appearing in such diverse places such as the Kids edition of the World Almanac, and the board game Trivial Pursuit.
I must confess that even I was involved in helping to perpetuate the new Blue Moon phenomenon. More than 30 years ago, in the Dec. 1, 1982 edition of The New York Times, I made reference to it in the "New York Day by Day" column.
And by 1988 the new definition started receiving international press coverage.
Today, Pruett's misinterpreted "two full moons in a month rule" is recognized worldwide. Indeed, Sky & Telescope turned a literary lemon into lemonade, proclaiming later that — however unintentional — it changed pop culture and the English language in unexpected ways.
Meanwhile, the original Maine Farmers' Almanac rule had been all but forgotten.
Playing by the (Old) Rules
Now, let's come back to this August's full moon. Under the "old" Almanac rule, Tuesday's lunar event will be a "Blue Moon."
In northern summer of 2013, there are four full moons: They occur on June 23, July 22, Aug. 20 and Sept. 19.
This means that under the original Maine Almanac rule — the one promoted by Lafleur and later misinterpreted by Pruett — the third full moon of the 2013 summer season on Aug. 20 would be a Blue Moon.
Final Full Moon Thoughts
So what blue moon definition tickles your fancy? Is it the second full moon in a calendar month, or (as is the case on Tuesday) the third full moon in a season with four? Maybe it's both. The final decision is solely up to you.
Tuesday's full moon will look no different than any other full moon. But the moon can change color in certain conditions. After forest fires or volcanic eruptions, the moon can appear to take on a bluish or even lavender hue.
Soot and ash particles, deposited high in the Earth's atmosphere, can sometimes make the moon appear bluish. In the aftermath of the massive eruption of Mount Pinatubo in the Philippines in June 1991 there were reports of blue moons (and even blue suns) worldwide.
And in case you're wondering when the next time we'll have two full moons in a calendar month — call it "Pruett's Blue Moon Rule" — that will happen in July 2015. The second full moon in that month, the Blue Moon, will come on July 31 of that year.