August 2021's full moon is a Blue Moon. Here's why

The American Astronomical Society has just indicated that if the skies would be clear this weekend, then the full moon of Sunday, August 22, will be a 'Blue Moon'. A blue moon is an additional full moon that appears in a subdivision of a year: the third of four full moons in a season. In modern usage, 'Blue Moon' has come to refer to the second full moon in a month (the last of these occurred on October 31, 2020) - but that has not always been the case. Also Read | Afghanistan: People hang on flying aircraft in hurry to leave the country, two of them fall This colorful term is actually a calendar goof that worked its way into the pages of Sky & Telescope in March 1946 and spread around the world from there. Also Read | Afghanistan-Taliban News: Taliban leader Mullah Baradar says ‘victory was unexpectedly swift’ Editors and contributors to Sky & Telescope have traced the traditional astronomical definition to the Maine Farmers' Almanac in the late 1930s. The Almanac consistently used the term to refer to the third full Moon in a season containing four (rather than the usual three). "Introducing the 'Blue' Moon meant that the traditional full Moon names, such as the Wolf Moon and Harvest Moon, stayed in synch with their season," said Diana Hannikainen (pronounced HUHN-ih-KY-nen), Sky & Telescope's Observing Editor. But in 1946, amateur astronomer and frequent contributor to Sky & Telescope James Hugh Pruett (1886-1955) incorrectly interpreted the Almanac's description, and the second-full-Moon-in-a-month usage was born. Sky & Telescope admitted to its 'Blue Moon blooper' in the March 1999 issue ("What Is a Blue Moon in Astronomy?"). Canadian folklorist Philip Hiscock and Texas astronomer-historian Donald W. Olson worked with the magazine's editors at the time to figure out the origin of the mistake, and how the two-full-Moons-in-a-month meaning spread into the English language. Historically, the term 'Blue Moon' was more often not an astronomical term: In older songs, it's used as a symbol of sadness or loneliness, while "once in a blue Moon" means a rare event. Only exceedingly rarely does the Moon actually turn blue in our sky -- when volcanic eruptions or forest fires send lots of smoke and fine dust into the atmosphere. Popular culture has also enthusiastically adopted the phrase "Blue Moon" and applied it to many different things. As you wait for the Blue Moon to rise on August 22nd, you could treat yourself to a Blue Moon cocktail: In a tall glass filled with ice, mix four parts of gin to one part of the blue mocktail and add a twist of lemon. Enjoy! -PTC News