When a month has two full Moons the second is called a “Blue Moon”. It’s fascinating to think how important a blue moon is in popular culture. We talk about something happening “once in a Blue Moon", meaning very infrequently and the wonderful 1934 song Blue Moon was inspired by the phenomenon.
In the 1500s, the phrase "the Moon is blue" was the Renaissance equivalent of "pigs may fly"—a sarcastic way to describe an obvious absurdity or something impossible. Cardinal Wolsey, Henry VIII’s advisor, to comment that they “would have you believe the Moon is blue”, an excellent way in which to criticise the intelligence of his opponents. This first appears in Rede Me and Be Nott Wrothe, a poem by Cardinal Wolsey.
