Physics Question #332

Gary John Walsh, a 40 year old male from the Internet asks on February 9, 1998,

What is a blue moon? When will the next one be? Are there ever two in the same year?

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The answer

Barry Shell answered on February 9, 1998

Depending on your source, a blue moon means either when a second full moon comes in one calendar month OR (according the Maine Almanac), when a season (Spring, Summer, Fall, Winter) has four full moons, rather than the usual three. For more information, including a calendar of upcoming blue moons, check out the Sky & Telescope website.

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