This coming Friday we’ll have a Blue Moon, so what does that mean? It’s was memorialized in song by the Macels back in 1961 and I’m sure you’ve heard the old saying, “Once in a blue moon”, but what exactly is a blue moon? If the moon isn’t actually blue, how did it get that name?
There are two types of Blue Moons, well, three really if you count the beer but astronomically speaking there are two. One is when the moon actually does appear blue which is caused by dust in the atmosphere. That type of Blue Moon is very rare. The other Blue Moon is a full moon that doesn’t quite fit in with the months in our calendar. Let me try to explain, emphasis on “try”…
There are two different ways of determining which moon is a Blue Moon. If it’s the third full moon in an astronomical season with 4 full moons (normally there are three) it’s called a Blue Moon, or if it’s the second full moon in a month with two full moons. Confused? Yeah, so am I.
With that being said, the correct, original definition is that a “Blue Moon” is the third full moon in an astronomical season with four full moons.
A normal year has four astronomical seasons, spring, summer, fall and winter, each are three months long with three full moons in each. When one of the seasons has four full moons, instead of the normal three, the third full moon is called a Blue Moon. Why the third? I don’t know, I’m a disc jockey not an astronomer. All I know is it’s fairly rare which is why you will hear people say “Once in a blue moon” when talking about something rare.
All this of course still doesn’t answer the question, why is it called a blue moon? Here’s what Wikipedia has to say “The suggestion has been made that the term “blue moon” for “intercalary month” arose by folk etymology, the “blue” replacing the no-longer-understood belewe, ‘to betray’. The original meaning would then have been “betrayer moon”, referring to a full moon that would “normally” (in years without an intercalary month) be the full moon of spring, while in an intercalary year, it was “traitorous” in the sense that people would have had to continue fasting for another month in accordance with the season of Lent.”
Well, that certainly cleared things up, didn’t it? If all this is far to confusing you can always pop open a Blue Moon or two, they’re great with a slice of orange or have one of these. As for me, I’ll stick to music and leave this sort of thing to smarter folks…