Yesterday I was at the Observatory picking up a calendar for 2010. I noticed that Australia and New Zealand get two full moons in both January and March next year, but no full moon in February. This got me wondering whether a calendar month without a full moon has its own special descriptive term.
I think there are fewer days in the moon’s rotational period than in even the shortest month. At least for now. Might have been different in the past, and might be different in the future, but I think it would be pretty hard to miss a full moon in a month nowadays.
According to Wikipedia, this is sometimes called a Black Moon
From the page: “In astronomy, the term black moon is neither well-known nor frequently used. As a consequence it has no accepted definition, but seems to have occasionally been applied to at least four different situations:
3. The absence of a full moon in a calendar month.”
Not sure how accurate that article is. I saw no references, so, being curious, went Here and see I was not alone:
“Lack of references
References for this phrase and its referent? It sounds invented, and for all I know may have been invented by the anonymous wikipedian who made the page. I’ve never called for a VfD before, but this might be my first.”
Heh. Not a terribly accurate term - this will only happen in February, yes, but most of the time February does get a full moon.
I like ‘Black Moon’.
ETA - even if it was invented by a Wikipedian.
Every month but February is longer than the synodic lunar period, and therefore will automatically include at least one instance of every phase of the moon. A ‘normal’ February’s 28 days will not include evey phase, and may or may not include any single given phase. Even a leap year February is still a few hours short of a full synodic period, and the same can hold true. So, while most Februaries will include a full moon, or a new moon or first quarter or any other phase, ithere will occasionally occur a February in which some given phase, full moon or any other, will fail to occur, being in the last days of January and/or the first days of March (which will likely have two of that phase).
If February has no full moon, then January and March both are not only likely but guaranteed to have two each.