31/08/2012 08:49 BST | Updated 30/10/2012 05:12 GMT

Once in a Blue Moon

The blue moon appears on Friday 31 August 2012. "The moon will turn full Friday, the second time since its first full appearance Aug 2 this year. The next blue moon will only be seen three years from now, July 2015" said Science Popularization Association Communicators and Educators (SPACE) in a statement.

The average interval between full moons is about 29.5 days, while the length of an average month is roughly 30.5 days. NASA Science News had this to say: "According to modern folklore, whenever there are two full Moons in a calendar month, the second one is "blue " while the Harvard University astronomer Avi Loeb was a little less excited. He told Fox News that the moon is far more important to lovers, literature and folklore than to science.

In a single month, two full moons exist as the calendar months are not synchronised with the lunar months. Blue moons are not always blue in colour but there is a small probability of a hint of blue. Moons are usually white or yellow. So will the moon turn blue this time? Well, a blue moon requires a volcanic eruption. In the past, blue moons have indeed been seen.

In 1883, a blue moon was seen after the eruption of the Indonesian volcano Krakatoa. The plume rose above the Earth's atmosphere and caused the moon to turn blue. The blue moon effect can also occur following smoke from volcanoes and forest fires [e.g. the muskeg fire in September 1953 in Alberta, Canada]. Again, in 1983, blue moons were seen in El Chichon volcano [ Mexico], in 1980 [Mount St Helens] and in 1991 [Mount Pinatubo].

NASA Science News writes

"There are plenty of wildfires burning in the hot, dry USA this month. If any of them produce smoke with an extra dose of micron-sized particles, the full Moon might really turn blue. On the other hand, maybe it will turn red. Often, when the moon is hanging low, it looks red for the same reason that sunsets are red. The atmosphere is full of aerosols much smaller than the ones injected by volcanoes. Measuring less than a micron in diameter, these aerosols scatter blue light, while leaving the red behind. For this reason, red Blue Moons are far more common than blue Blue Moons."

Travelling back in time to discover the origin of the phrase "blue moon" is fascinating. Philip Hiscock, a professor of Memorial University in Newfoundland states that it first appeared in writing during the 16th Century. Cardinal Wolsey advisor to Henry VIII writes about his opponents "who would have you believe the moon is blue" leading us to infer that the term meant "an impossibility". A 1524 pamphlet criticising the English clergy was entitled " Rede Me and Be Not Wrothe [ Read me and be not angry] had the phrase "If they say the moon is belewe/we must believe that is true" [ If they say the moon is blue, we must believe that it is true]. By the 1700s, meaning shifted to "never" . In the 19th Century, it was used on the London streets and meant" a long time". By 1869, an autobiography of a shipwreck survivor referred to "that indefinite period known as a blue moon". By 1871, a discussion of a diet in a book had the phrase " A fruit pastry once in a blue moon"

In 1946, an amateur astronomer writing for the Sky and Telescope magazine "made an incorrect assumption about how the term had been used in the Maine Farmers' Almanac. He used "blue moon" while referring to the third full moon in season of four [not three]. The error repeated itself on radio in 1989. The phrase seems to have stuck. The rumour is that the third moon is referred to as "blue" in Czechoslovakia.

Professor Hiscock said

"It seems to be absolutely possible that someone took the English meaning," now and again" and assigned this astronomical meaning" . So in conclusion the current meaning is " Rare, seldom, even absurd".

Blue moon was also a song sung by lovely Ella Fitgerald and the devilishly handsome Elvis Presley. Sporting the words " Blue Moon..... You saw me standing alone, without a dream in my heart, without a love of my own" the term was madeworld famous. The 1934 song relates the tale of a man who finally found the love of his life - something that was so unexpected for him that it must have happened under a blue moon. In music and through literary use, it has described lost love and sadness. In popular culture, it has been in The Smurfs - the blue moon was used as the period of time in the medieval world. Those who remember Bruce Willis will know that he started off in a television series called Moonlighting working at a detective agency called Blue Moon Detective Agency. In the popular TV series, Charmed, the blue moon was used as a period where the girls were transformed into monsters. The rare appearance of the blue moon gives it a magical if not mysterious quality driving the public to be fascinated by its appearance.

This year the blue moon coincides with the memorial service held for the astronaut Neil Armstrong, the first man to set foot on the moon. He died last Saturday aged 82. This serendipitous timing has led his family to suggest that everyone should pay a tribute to him by looking at the moon and giving him a wink.

Many of us can try and watch the moon ourselves. An alternative is the web-based Slooh Space Camera , which showcases live views from various telescopes around the world. It is hosting a special broadcast of the blue moon on Friday, beginning at 6 p.m. EDT (2200 GMT). . Let us all hope for a magical blue moon.