Posted by ESC on July 30, 2004
Once in a blue moon
By Joe Rao
Friday, July 30, 2004 Posted: 1:59 PM EDT (1759 GMT)
(SPACE.com) -- Some almanacs and calendars assert when two full moons occur within a calendar month, that the second full moon is called the "Blue Moon."
That second full moon this month will come on Saturday, July 31st, and will look no different than any other full moon.
On past occasions, usually after forest fires or volcanic eruptions, the moon can indeed take on a bluish or lavender hue. Soot and ash particles, deposited high in the Earth's atmosphere can sometimes make the moon appear bluish. Such a situation was noted across eastern North America in late September 1950, due to smoke from widespread forest fire activity in western Canada. Also, in the aftermath of the massive eruption of Mount Pinatubo in the Philippines in June 1991 there were reports of blue moons worldwide.
The phrase "Once in a blue moon" was first noted in 1824 and refers to occurrences that are uncommon, perhaps even rare. Yet, to have two full Moons in the same month is not as uncommon as one might think. In fact, it occurs, on average, about every 32 months. And in the year 1999 it actually occurred twice in three months...
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