Tuesday, June 01, 1999

Blue Moon, or Risqué Moon?


Breaking News! 

This just in to Dancing Trail News Center:  Here is the latest on the REAL Blue Moon story!  The magazine, Sky & Telescope, has just had their, probably, first ever exposé in the May issue of 1999.  

It turns out that the Real Blue Moon may not necessarily be the second full moon when two full moons occur in one month!  Now, what follows in this bulletin contains graphic material and may not be suitable for all ages –  please use suitable discretion: It turns out,  according to Sky and Telescope, that the length of time from full moon to full moon is 29.5 days, and since the solar year has 365.25 days, then each year contains enough days for 12 full moons plus 11 days left over, so therefore 7 years out of every 19 there will actually be 13 full moons.  Also the Astronomical Calendar  Year, called a “tropical year”, does not run from January 1 to December 31, but from “Yule” ( December 21, or winter solstice) to “Yule”; this places three full moons in each season except for those 7/19 years (told you it would get graphic) which will contain one season which will have four full moons.   Therein lies the scientific part of the problem; the REAL problem, however is religious, and that mix-match goes something like this:   The Roman Catholic Church has decided that Easter is apparently more important than the sun, and therefore the vernal equinox will always fall on March 21, regardless of whether the sun actually crosses the equator on that day or not (people more familiar with the Roman Catholic Church than I am usually close their eyes and nod their head when we get to this part), and also that Easter MUST fall within one week after the Paschal Moon which, they say, is that first full moon after March 21.   So, ALL the moons of the year are determined by the “tropical” year (yule-yule rule) EXCEPT for the two near Easter, the Paschal Moon (the first full moon of spring) and the one before it, called (by the Church) the Lenten Moon, (and which therefore must be the last full moon of winter). These are determined by ecclesiastical, not not tropical or astronomical rules.  And, in order to keep the other main moons still corresponding to the activity suitable to them (harvest, mid-summer, long-night) whenever a season, as measured from Yule to  Yule has four full moons in it, the THIRD (not the fourth) full moon is designated as the Blue Moon.  So, now you know.  

The Jewish faith handle this problem by adding to seven out of every nineteen years, basically a “blue month”, which they call Adar.  The Islamic faith, not being especially concerned with Passover,  Easter or Christmas, ignores the whole thing, letting their calendar years rotate backwards so any given month begins 11 days earlier each year.  So, if you want to refer to a really, really, really long time, you might try the term “Islamic Blue Moon”!  

Sky & Telescope apologies for their “error”, committed 53 years ago in the March, 1946 issue, and suggests that both methods be retained, since “theirs” is certainly much simpler!  How does all this affect our current Blue Moon status? Hmmm.   That would mean no Blue Moons at all in 1999!  Next one would be February 19, 2000.  February, of course is the only month which could NEVER have a Blue Moon under the second full moon in a month rule, but under the four in a season rule, one out of every four blue moons MUST occur in February!  The others will have to be in May, August, & November.  

The official Dancing Trail policy toward this new development will be to try to celebrate all Blue Moons, whether “tropical”, "astronomical" or “ecclesiastical”. And perhaps we might call the now unauthorized, two in a month occurrence a Risqué Moon, and the new, but really older, four in a season occurrence an Out-of-the-Blue Moon.

© John Womack, 1999.  All rights reserved