20101117
once in a blue moon
中文解释:千载难逢地
英文解释:very seldom
来源:Ask the man on the Clapham omnibus the question 'What is a blue moon exactly?' and you are likely to get one of three answers: 1. Duh.
2. It's the second full moon in a calendar month.
3. It's when the moon looks blue.
Let's start with 3. Very occasionally, the moon actually does appear to be blue. This sometimes occurs after a volcanic eruption, like that of Krakatao in 1883. Dust particles in the atmosphere are normally of a size to diffract blue light, making the moon appear reddish at sunset. Larger volcanic dust particles diffract red light, making the moon appear bluish. Tempting as it is to suppose that something that happens very rarely, and which is mentioned by name in a phrase that means 'very rarely', is the source of the phrase, it probably isn't.
eg:Jill: Does your husband ever bring you flowers? Ellen: Once in a blue moon. |