|Moon Over HNWR, by Mary Karam|
July 2015 has two full moons. That’s somewhat unusual, according to the website, earthsky.org. Most months only have one. But in cycles of 19 years, or 228 calendar months, seven to eight calendar months will always have two full moons. In other words, there’s a month with two full moons every two to three years. When it happens, the second one is popularly called a Blue Moon.
The first of the two full moons for this month occurred on July 1. The second, or Blue Moon, will occur on July 31.
By recent popular acclaim, the second of two full moons in a single calendar month goes by the name of Blue Moon. A Blue Moon can also be the third of four full moons in a season. But the second-full-moon-in-a-month definition is the easier to remember, and it’s probably what most people think of when they hear Blue Moon. (earthsky.org)
According to Wikipedia, "The phrase has nothing to do with the actual color of the moon, although a literal "blue moon" (the moon appearing with a tinge of blue) may occur in certain atmospheric conditions; e.g., when there are volcanic eruptions or when exceptionally large fires leave particles in the atmosphere. This phenomenon is specific to calendars." A Google search revealed that actual blue-colored moons may be seen following volcanic eruptions or sometimes forest fires, due to ash in the atmosphere.
The contemporary definition of "blue moon" is more technical than some historical usages, according to an article on the International Planetarium Society website, in which we find that the phrase is well over 400 years old, but with the meaning changing through the years. Earliest folklore references use the term to signify something "absurd" or that would never happen. Since actual "blue moons" were sighted during volcanic eruptions the term changed to "once in a blue moon"/infrequent. "Blue Moon" is also found as a symbol of sadness and loneliness in popular songs.
With the supposedly 100 year flooding of Lake Texoma and Hagerman National Wildlife Refuge occurring in 1957, 1990, 2007 and 2015, we would hope that the future occurrences are even less frequent than "once in a blue moon".