Green
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Written by Steve Glennie-Smith
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Thursday, 31 December 2009 15:55 |
If we see it tonight, there will be a Blue Moon - which is a second full moon in the same calendar month. Hence the phrase 'Once in a Blue Moon'. They're not as infrequent as you might think - the last Blue Moon was on 30th June 2007, and the next will be on 31st August 2012. Even Blue Moons on New Years Eve are not exceptionally rare - the last was on 31st December 1990, and the next will be on 31st December 2028. This 19 year interval is known as a Metonic Cycle.
However, two other things will make this one special. There will be a partial eclipse of the moon, which should be at its best at 19:11 - though the viewing prognosis is not good.
The other is that this week is Week 53 in the ISO 8601 date standard. Most years only get up to Week 52 - it depends when the first Thursday of the year occurs - which in practice means it must be 1st January, as it was in 2009. If 2nd January in a leap year is a Thursday, that year will also have 53 weeks. There will be no more Blue Moons in Week 53 in this century or the next.
By the way, the converse - known as a Black Moon, is when there are two new moons in the same calendar month.
Having furnished you with the last bits of useless information for 2009 - have a good 2010!
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Last Updated on Saturday, 09 January 2010 11:02 |