The second blue moon of 2018 is about to arrive — here's what that means and how rare they really are

March 31, 2018

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On March 31, much of the world will get to see the second blue moon of the year, making this a rare double-blue moon year.
That's according to a newer definition of the term "blue moon" — it would be impossible under an older definition.
But both definitions allow for "blue moons" every two to three years. There's another rarer kind of blue moon, however — but that one has to do with volcanoes and fires.

On March 31, much of the world will get to see a rare event: A second blue moon in one year. It'll be the second blue moon of 2018 — at least, according to one definition of the term.

Despite the name, as many of us have learned at some point (often in a disappointing fashion, if we learned this as a kid) a blue moon doesn't mean the moon turns blue. The term refers to frequency, not color.

See the rest of the story at Business Insider

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