A Special Kind of Moon

There is something about a full moon that affects us (sometimes literally!) and our admiration of it can be found in art, literature, music, and poetry.  The full moon is revered in many cultures across the globe.  In North America, tribes of Native Americans gave varying names to the full moons according to the season, such as Wolf Moon in January, Hunger or Snow Moon in February, and Strawberry Moon in June.  Traditionally, the full moon that occurs closest to the autumnal equinox is called the Harvest Moon.  It occurs mostly in September, but can occur in October.  Full moons are also given names as they relate to religious events, such as the Lenten Moon, which is the last full moon of winter, and the Paschal or Easter Moon, which is the first full moon of spring.

One of the more popular full moons might be the Blue Moon. There are two definitions of a Blue Moon – what I like to call the traditional and the modern.

The modern definition of Blue Moon is the second full moon of the month (by the way, the word month is connected to the Old English word ‘mona’ or moon), and we will have one on Friday August 31, 2012. This type of Blue Moon happens every 2 ½ years or so, with the last one being December 31, 2009. There were about 40 of these moons in the twentieth century.

The traditional definition of a Blue Moon is based on the tropical year (winter solstice to winter solstice), which contains 12 full moons (3 each season). However, some tropical years have 13 full moons and thus one season will have four full moons. When this occurs, the third full moon of the four full moon season is called a Blue Moon. The next Blue Moon of this definition will occur August 21, 2013.

The expression “blue moon” has been around for a very long time, and it almost always refers to a full moon of a very special kind, but sometimes it actually describes the moon, which for different reasons, turns blue.  Today’s modern expression of a Blue Moon, that is the second full moon in a month, started from a misinterpretation published in a magazine article, and thanks to the perseverance of librarians from Southwest Texas State University, we now know when this new definition originated. For the details, check out our Everyday Mystery What is a blue moon?