What Is A Blue Moon, Anyway?

by Kendyl Kearly

Summer is pretty much the perfect time to stop your busy schedule and look at some cool stuff in the sky. It's finally warm enough to spread out a blanket in the grass and look to the heavens for a show. On the evening of July 31, a blue moon will be visible for everyone who takes the time to look up. So, here's a good question: what is a blue moon?

A blue moon is either the third full moon of an astronomical season with four full moons or the second full moon in a calendar month. July's blue moon will be the latter. It's also not actually blue. They aren't exactly rare, but the last blue moon we saw was three years ago.

Blue moons give astronomers the opportunity to track the moon. It also means that you have two opportunities to see a full moon in case your missed your romantic — or loony, depending on your opinion — night earlier in the month.

On Wednesday, the first full moon will be visible at 10:20 p.m., according to the Old Farmer's Almanac. The moon will rise and turn from red-orange to copper to black to white, according to the Columbia Missourian. You can track the moon as it waxes and wanes throughout the month. It will reach its last quarter on July 8 at 4:24 p.m. Then, it will be a new moon (meaning you will be able to see nothing at all) on July 15. The last quarter will appear again on July 24 at 12:04 a.m.


The grand spectacle won't appear until July 31, though. That's when the blue moon will show up. It will rise as the sun sets but will be in its full brightness at 6:43 a.m. The moon will do the same color trick that it did the first time in July.

The phrase "blue moon" has been around for 400 years, according to Sky and Telescope. However, its calendar meaning only came into use about 25 years ago, so the phrase "once in a blue moon" did not come from this astronomical marvel.

When it came into use, the term really just meant that something was absurd, as in, "The idiot probably thinks the moon is blue," or will never happen, as in, "I will date him when the moon is blue." However, "never" isn't really true. The moon has been blue before. Certain volcano eruptions and monsoons have been known to make the moon appear blue.

So to celebrate, grab a Blue Moon beer or a blue moon cocktail (blue curaçao, gin, and lemon), stretch out on your balcony, and maybe do something you'd only consider once in a blue moon. Geddit?

Images: Getty Images