“ Once in a Blue Moon ” might sound like a long clip , but we ’re about to know one this weekend – and it will be your last time to catch one until August 22 , 2021 .
The full moon on Saturday , May 18 , 2019 , will be a Blue Moon , agree toNASA . There are two main definitions of a Blue Moon , both referring to an extra full lunar month that appears within a sealed windowpane of time , either a time of year or a month . Unfortunately , neither involves a sudden colour change from our fast cosmic companion .
This approaching moon accrue under the seasonal Blue Moon definition , which refers to the third full moon in a season that has four full moons .
The other definition , which is arguably more wide have sex , refer the second full moon in a calendar calendar month . It ’s easy to assume that a full synodic month occurs once a month – as in a “ moon - th ” – but once in a while a calendar month will fit in two full moon . This is because each cycle of the Moon ’s phase angle lasts about 29.5 days , yet there are 30 or 31 day in a calendar month ( except February ) . So , every two or three year , there will be 13 full moons , not 12 .
While the monthly definition might be more pop , some claim it ’s really theresult of a publishing screw - up . The definition can be linked back to the March 1946 edition of Sky & Telescope magazine when a newsman misinterpreted the term from an honest-to-goodness issue of the Maine Farmers ' Almanac . Not realizing the Moon ’s phases in the book were based on a seasonal calendar , he clearly assumed the “ extra ” synodic month refer to the months . This definition was then used as an answer on radio game and a 1980s Trivial Pursuit display board game , andso the misinterpretation spread .
As remark , the Moon wo n’t literally turn a tad of amobarbital sodium . That order , it ’s believedthe saying " Once in a Blue Moon " actually originated in 1883 after the eruption of Krakatoa threw so much dust into the air the Moon took on a blue hue .
The traditional name for May ’s full moonlight is sometimesthe Flower Moon , used to signify the flowers that bloom during this calendar month in the Northern Hemisphere . Traditional names of Moon are often a mash - up of terms used by ancient acculturation , aboriginal American tribes , and European pre - Christian infidel . Nowadays , they do n’t signify all that much , although they do make for some pretty incredible public figure . For instance , in January 2019 we get to witness the " Super lineage Wolf Moon " .
