If anything unusual happens to you Friday, you’ll be right to say it was “once in a blue moon.”
The July 31 appearance of the month’s second full moon will be the first such occurrence in the Americas since August 2012. Every month has a full moon, but because the lunar cycle and the calendar year aren’t perfectly synched, about every three years we wind up with two in the same calendar month.
But Earth’s satellite will most likely not appear blue at all.
Here are some additional resources on Friday’s event:
You might also be interested in these other moon-related “Best” lists: