At one time or another most of us will have referred to a rare event as being something that happens “once in a blue moon” but how many people I wonder know what it means?
A blue moon is the appearance of a third full moon in a season that has four full moons instead of the usual three, though of course it is never visually blue. A blue moon occurs only every two or three years and so hence the phrase “once in a blue moon”. Each calendar year contains roughly 11 days more than the number of days in 12 lunar cycles. The extra days accumulate, so every two or three years there is an extra full moon. The extra moon necessarily falls in one of the four seasons, giving that season four full moons instead of the usual three and this is known as the blue moon.
On 31 August 2012 we were lucky enough to witness a blue moon and it was stunningly beautiful… as all full moons are 🙂