What’s a Supermoon?

The biggest supermoon, as seen from Earth, is compared to the smallest it appears when farthest from us.

Supermoons have been around for, oh, I don’t know, roughly 4.5 billion years. They just didn’t used to be called that. In fact the origin of the term is really, really recent and, shall we say, unconventional by normal scientific conventions (as you’ll learn below, the word has nothing to do with science).

And even by the overused definition, they’re not very rare. In fact, there will be three of them this year: Jan. 21, Feb…