Most people must have heard of an English expression "once in a blue moon", but have you wondered why a blue moon? Also, is there really a blue moon? 大家都聽過英文諺語"once in a blue moon" (千載難逢)? 可是你們想過為何是藍色月亮嗎? 還有，真的有藍色月亮嗎?
I think that I've heard of what "a blue moon" refers to, but I could't recall it until I read news today. 其實我應該很久以前，約莫大學時代就聽過所謂的藍色月亮，只是歲月增長，我的記憶力也不復，直到今天看到新聞，我才隱約想起很久以前我曾在網路上看過藍色月亮的報導。