Once in a Blue Moon Transcript

Hey everyone! It’s Anne from Elevate English.

00:08 Today I’m going to explain a pretty common expression we have in English, “once in a blue moon”. To quote a great old song that I can’t actually play here for copyright reasons, “once in a blue moon something good comes along”.

00:21 The meaning of this expression is something that happens very rarely. Something that almost never happens. Something unlikely. So the lyric “once in a blue moon something good comes along” means good things happen rarely, or don’t happen very often. Another example could be, “In my country, earthquakes happen only once in a blue moon”. You’re saying that earthquakes aren’t very common where you live.

00:46 This expression is quite old. Most sources I found online say it’s been in use since the 1800’s. Historically, there are some very rare examples of the moon actually appearing blue, caused by unusual weather or a volcanic eruption. But that’s probably not where this expression comes from. It doesn’t actually have to do with the color of the moon. “Blue moon” is what it’s called when a full moon happens a second time in the same month of the year. The average time between full moons is about 29.53 days, while the average length of a month is 30.4 days. This means that although it’s pretty uncommon for one month to have two full moons, every so often it does happen.

01:31 Some people calculated that the mathematical probability of a second full moon occurring is 8 chances out of 228. So that means technically if you say something happens once in a blue moon, you’re saying there is a 3.5% chance of that thing happening! Unlikely, but not impossible.

01:52 If listening to music helps you in your language learning, I definitely recommend looking up Van Morrison’s song called “Once in a Blue Moon” to help remember this expression. I put a link to the song in the description. Thanks for listening! Have a great day guys.