Wednesday, July 22, 2009

Painting the map blue

Today, the 22nd of July, is eclipse day. Or is it? Depends on where you are. In New England, mid-eclipse (visible over the western Pacific Ocean) occurred at 10:34 PM EDT on the 21st. Here in Ireland, it happened in the wee morning hours of the 22nd. The eclipse began in India on the 22nd, local time, and ended about four hours later in mid-Pacific on the 21st. Got that?

If you were watching the eclipse from the Moon, you'd have seen a dark spot about 150 miles wide sweep across the sunlit face of the Earth, including in its path four of China's ten largest cities. You can see the path on the map above, showing in blue the paths of totality 2001-2020 (click to enlarge). During this period, Argentina is apparently the place to be, although two of their three eclipses will be near horizon events. Europe is out of luck; it will not have a total solar eclipse until 2027, and then only Gibraltar will be touched (the rock may sink under the weight of the people who pile in). The United States will be graced from west to east in 2017. I caught the 2006 eclipse in Turkey, under cloudless skies. Here is grandson Dan with partial eclipses on his chest (click to see crescents); as we waited for totality, I pricked his name in pinholes in a piece of paper. I wonder will he ever see another?

Notice how unlikely it is that a total solar eclipse will come to you. If you sit tight, the longest you will have to wait is 4,500 years. That is to say, every 4,500 years the dot of the Moon's shadow paints the entire map blue!