Among the many irritating oversimplifications of our age is the repeated-till-it’s-true naming of any second Full Moon in a calendar month as a “Blue Moon.”

Historically and astronomically speaking, that is not the origin of the term “Blue Moon.” 

Besides, a second Full Moon within a calendar month happens much too frequently to give any meaning to the old adage, “Once in a Blue Moon.”

It is a human trait to notice things that move.  Our ancient ancestors kept an eye on the movement of the things that move in the sky:  the sun, the moon, the planets.  That is, they noticed that these celestial lights have movement with respect to the fixed stars. 

The sunrise changes position through the course of the year.  When the sun completes one cycle of movement, we say a year has passed.  The moon is arguably easier to observe as it changes from full to new and back.  When the moon completes one cycle, the ancients would say a month had passed. 

Nowadays most of us accept the calendar that fudges the months to fit the solar year and let the Full Moons fall as they may. 

But back in the old days, my children, the lunar calendar was the going thing.  All the really hip  cultures were doing it.  (Some still are.)  The problem is that after a few years of twelve lunar months, the seasons start to get out of whack from the holidays that were supposed to celebrate them.  So it was that the ancients instituted “leap months” every once in a while to get things back into synch. 

In the early centuries of the Common Era, sky-watcher theologian types faced the problem of figuring out when Lent and Easter would occur.  “Why not just use the Jewish calendar?,” you ask.  I don’t know (I blame lack of internet access). 

This salient passage from the Wikipedia page on Blue Moon: 

“In calculating the dates for Lent and Easter, the Clergy identify the Lent Moon. It is thought that historically when the moon’s timing was too early, they named an earlier moon as a “betrayer moon” (belewe moon), thus the Lent moon came at its expected time.” 

The Old English Dictionary says “lǽwan… to betray [Goth léwjan].”

So a real  Blue Moon would happen seven times every 19 years.  Clear?    

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- Autoposted from http://www.crowndot.com/once-in-a-blue-moon