Herbdoc has some “moon musings:”
I have always been fascinated with the moon, its phases and the myths associated with it. This month we have a “blue moon” to look forward to on New Year’s Eve.
There are actually two definitions for a blue moon, and the most recent definition is two full moons in the same month. For this to occur, the first full moon must fall early in the month since the average span between full moons is 29.5 days. Our last full moon was December 2nd.
The other definition of blue moon was published in early editions of the Maine Farmer’s Almanac. According to this source, a blue moon is the third full moon in a season that has four full moons. Since moons were named, a fourth moon would upset the balance. For instance the first full moon of summer is called the early summer moon, the second is the midsummer moon and the last is the late summer moon. By naming the third full moon in that season, the blue moon, the last moon could continue to be the late summer moon. Because some years have 13 moons instead of 12, an extra moon would also upset the Christian Ecclesiastical calendar since there were only names for 12. By naming the 13th moon as the blue moon, the calendar stayed on track.
In folklore, full moons were given names so that people could prepare for weather conditions and crop needs. Names vary with locale and culture, but most gardeners are familiar with the Harvest Moon in October which warns us to get our crops in prior to damaging frost. December was called the Full Cold Moon or Full Long Nights Moon because nights are at their longest and darkest. Next month is the Full Wolf Moon which was named by Indian tribes who would see and hear hungry wolf packs prowling in the snow around their villages.
There will be about 15 blue moons in the next 20 years, but no blue moons of any kind will occur in the years 2011, 2014, and 2017. Using the Farmer’s Almanac definition, that type of blue moon will next occur on November 21, 2010.