Blue Moon On New Year�s Eve

If people thought once in a blue moon was rare, then they better consider the idea of once in a blue moon on New Year�s Eve. In reality, blue moons aren�t actually all that rare. According to the Farmer�s Almanac definition, a blue moon is termed for an extra full moon that occurs in a season. Generally, there are 12 full moons in a year, with one appearing each month. However, every three years or so there are 13 full moons in a year. The lunar month, or the time that it takes for the moon to circle around the Earth is approximately the same as the calendar month. The calendar year though is based off of the solar calendar, or the time it takes the Earth to travel around the sun, so it does not perfectly correspond to the lunar calendar. Thus, an extra full moon slips into the calendar year, and a blue moon occurs.

A blue moon on New Year�s Eve only happens about once every 20 years. The last time it happened was 2009, and it is not scheduled to coincide again until 2028. Astronomers do not place much importance on this rare occurrence. The moon does not actually turn blue, as some celebrators hope, because it is actually just like any other full moon throughout the year. One special, striking quality of the 2009 New Year�s blue moon was its ability to be seen almost everywhere. Full moons that take place around the winter solstice rise the highest than the rest of the year. The 2009 blue moon reached its highest point at midnight, so even viewers downtown in a large city could look up through the skyscrapers and see the full moon at the stroke of midnight.

This is not to say that the moon cannot ever turn blue though. Under certain atmospheric conditions, such as a forest fire or a volcanic eruption, particles in the air can sometimes cast a bluish hue on the moon. In 1883, the Indonesian volcano Krakatoa erupted and put so much volcanic dust in the atmosphere that the moon supposedly looked blue for almost two years. This event was so unusual that it coined the original meaning of the idiom �once in a blue moon.�

However, the term blue moon didn�t originate with either of these definitions. Hundreds of years ago, a blue moon was synonymous with something that was absurd or would never happen. At one point, each full moon of a year was referred to by a unique name. January�s full moon was the Old Moon, and so on. The extra full moon of a year was therefore called a blue moon. These varying definitions spiraled to a point where professional astronomers couldn�t even pick through the convoluted meanings. In the 1940s, a writer for the Farmer�s Almanac in Maine defined a blue moon by its current, modern meaning. It wasn�t the correct historical definition, but it has since stuck.

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