Ah crap, we meant to post this yesterday but better late than never. So tonight is a blue moon, that once in a great while occurrence when there are two full moons within a calendar month. Full moons are separated by 29 1/2 days, so on average, every two and half years or so, two will occur during the same month. The second one is the blue one. Of course, the moon isn't actually blue. The phrase goes back at least 150 years and has evolved through 5 or 6 different meanings. However, the Oxford English Dictionary sites that the first reference to a blue moon comes from a proverb recorded in 1528:
If they say the moon is blue, We must believe that it is true.
Stating that the moon was blue was a pure absurdity. In the 19th century, the phrase until a blue moon developed, meaning "never."
According to NASA, in 1883, an Indonesian volcano named Krakatoa exploded sending an enormous amount of ash into the atmosphere. Some of the ash-clouds were filled with particles about 1 micron (one millionth of a meter) wide--the right size to strongly scatter red light, while allowing other colors to pass. White moonbeams shining through the clouds emerged blue, and sometimes green. The blue moons persisted for years after the enormous volcanic eruption.
Incidentally, there are two definitions of a blue moon. The modern one as described previously, and an older one from the 19th Century Farmer's Almanac, which defines a blue moon as a true blue moon as the third full moon in a season that has four full moons. That would mean, according to the older definition, tonight is just a full moon, no blue. Too complicated for us. We like to keep it simple. According to the interactive blue moon calendar the next one is June 30th, 2007.
So today we are trying to think what things we have described as happening once in a blue moon. Once in a blue moon well have 3 slices of pizza (lie, try almost every time). Once in a blue moon we'll stay home and watch 3 Netflix movies back to back to back. Gothamist will be up in the Adirondacks tonight to enjoy it because once in a blue moon, we get some time to relax.