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Have you ever told someone that “it only happens once in a blue moon?”
Well, that blue moon is about to happen! Look for it on Friday, July 31.
The moon won't actually be blue. So what is it?
There are two definitions of a Blue Moon in astronomy; both are a type of full moon. (If the moon does look blue, it’s caused by a rare type of dust in the atmosphere.)
In astronomy, a Blue Moon is a full moon that doesn’t quite fit in with the months in our calendar.
There are two different ways of calculating which full moon is a Blue Moon.
That being said, the correct, original definition is that a “Blue Moon” is the third full moon in an astronomical season with four full moons.
A normal year has four astronomical seasons — spring, summer, fall and winter — with three months and normally three full moons each. When one of the astronomical seasons has four full moons, instead of the normal three, the third full moon is called a Blue Moon.
So now you know! (Or are you more confused?)
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