Once in a blue moon: rare phenomenon expected in Saturday night sky
by Victoria Bekiempis from Science | The Guardian on (#59S64)
Blue moons - the second full moon in a month - occur only every few years, and the name is misleading
On Saturday night, Democrats yearning for a blue wave on election day may choose to look to the skies for an omen: a blue moon.
Blue moons, typically defined as the second full moon in one month, are rare, arriving every two to three years. According to Earthsky.org, the last was on 31 March 2018.
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