Today, August 20th is a full moon and it is also a blue moon. But the meaning of a blue moon has apparently been misinterpreted over the years, not meaning what you thought it did. If you are like me, I understood a blue moon to be the second full moon in any given month, but that is not true of the moon today. This untrue tale has been passed around for years now and it’s time to break the rumor and spell out what a blue moon is really all about.
According to the old Maine Farmer’s Almanac, an article including a question and answer series, published way back in the 1943 edition of Sky & Telescope Magazine explained the original definition of the ‘blue moon’ as occasionally “one of the four seasons would contain four full moons instead of the usual three.” In the case of the unusual fourth full moon in a calendar season, the third would be called the ‘blue moon’, as is true with the full moon today.
The Maine 1937 Farmer’s Almanac continued to explain that in nineteen years there would be roughly only seven blue moons, and since it used to be difficult to predict and calculate such a rare event the saying ‘once in a blue moon’ came about. At that time, names were given to each full moon in a season, for example in summer you would have — the early full moon, the midsummer moon and the late summer moon. If there were four full moons in a season, the third would be called the ‘blue’ moon, so the fourth could take the ‘late’ moon position. Which is what happened in August of 1937, the year of the Maine Farmer’s Almanac.
Going back to Sky & Telescope Magazine in 1943, the author of the article to which we are referring was James Hugh Pruett and he did not have the Almanac to reference when he was explaining the process of naming full moons and such. So, an error occurred when he made the following statement: “Seven times in 19 years there were — and still are — 13 full moons in a year. This gives 11 months with one full moon each and one with two. This second in a month, so I interpret it, was called Blue Moon.” However, that year the full moon to which he was referring, on August 21st of 1943, was not the second in the month — it was just like the one we are having today — the third of four full moon of the summer season. The season runs all the way through the Fall equinox, according to astronomical references, and since we have another month to go until that fated date — we will also see another full moon.
All of the mis-referencing and mis-understanding of Pruett would have been possibly overlooked if it weren’t for radio host Deborah Byrd who used Pruett’s article on StarDate, her National Public Radio program, on Jan. 31, 1980. It was all over after that, the message of the ‘blue moon’ being the second full moon of a calendar month went viral and the rest is history — or ‘her’ story as the case may be.
This summer, in 2013, the full moons fall on June 23, July 22, Aug. 20 and Sept. 19. So, according to the original definition of the blue moon, we would be experiencing one today. In case you liked the newer definition of two full moons in one month, well, apparently that won’t happen again until July of 2015. Until then, enjoy this full moon no matter what you want to call it.
Will this blue moon be blue? Well, now we know that a blue moon isn’t necessarily what you thought, but it will surely still be beautiful. If there is any pollution in the air, especially from the aftermath of forest fires or volcanic eruptions, you may actually see the moon as blue tonight, as ash in the sky can color the moon as such. In any event — get out under the moon tonight and find joy in basking in its silvery rays — whether blue or not.
Written by: Stasia Bliss