Aug. 28, 2012 — When two full moons occur in the same month, it’s called a blue moon, and according to the NASA website, if the wildfires continue to rage throughout the western U.S., the blue moon, occurring Aug. 31, could actually appear blue in color.

The website stated, “The key to a blue moon is having in the air lots of particles slightly wider than the wavelength of red light (0.7 micron)---and no other sizes present. This is rare, but volcanoes sometimes spit out such clouds, as do forest fires.”

If the fires produce oily smoke with lots of one-micron particles, then we could have a literal blue moon.

Red moons are more common, however, in these conditions, and with the ash and dust hovering in the atmosphere, we are more likely to see an amber, rather than blue, orb in the sky this Friday.

Blue moons happen, on average, once every two and a half years, and some people claim this is where the popular phrase once in a blue moon came from; however, folklorist Philip Hiscock claims this isn’t true.

In his article “Once in a blue moon: fact and fantasy about blue moons,” from Sky and Telescope Magazine, he claims the term has been around well over 400 years.

He writes, “The concept that a blue moon was absurd led eventually to a second meaning, that of never”

Hiscock, like NASA, also notes historical examples of the moon actually looking blue.

One example is the Indonesian volcano, Krakatoa, which exploded in 1883. For nearly two years, all around the world, the particles of dust in the atmosphere made the sunsets green and the moon appear blue.

Another occurrence was in 1927 when Indian monsoons were late and the dry season blewenough dust into the air to create a blue moon.

In 1951, major forest fires in western Canada produced the same effect.

But our modern phrase, once in a blue moon, meaning something that happens infrequently, has not been around all that long, according to Hiscock.

To search out the more modern and widespread use of the phrase, Hiscock searched through archives of regional folklore, the Oxford English Dictionary, a children’s almanac, a 1946 edition of Sky and Telescope and an old Trivial Pursuit game.

He concluded it was the 1946 Sky and Telescope edition, which broadcaster Deborah Byrd had read in 1980 for her National Public Radio program, Star Date, which started the current usage of once in a blue moon.

He wrote, “Clearly, Byrd's radio broadcast got the recent ‘blue Moon’ ball rolling.”

Whatever the case, the blue moon has made its way into the annals of contemporary folklore and urban legends, and has been the subject of at least one popular song.

Hiscock wrote, “Our new blue Moon has something of the modern times in it, a technical aspect that most of the earlier meanings lacked. Perhaps that's why it caught on so quickly. It appeals to our modern sensibilities, including our desire to have plausible origins. But any folklorist will tell you plausibility is the mantle folklore wears to sneak through history's lines. "Old folklore" it is not, but real folklore it is. Given its present popularity, it may last a long time.”

Sources: skyandtelescope.com/observing/objects/moon nasa.gov/vision/universe/watchtheskies