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Solar Eclipse

July 10, 2010

If you need an excuse to cruise the South Pacific, here's a doozy: a total solar eclipse. It'll darken the skies around midday tomorrow as measured from here in the Lower 48 States. Unfortunately, though, we won't get to see any of it -- the Moon will pass too far south to create an eclipse from northern latitudes.

A total solar eclipse occurs when the Moon passes directly between Earth and the Sun and completely covers the Sun. That turns the skies dark. But some sunlight still makes it through -- the glow of the Sun's hot but thin outer atmosphere, known as the corona. It surrounds the lunar disk with tendrils of fire.

The eclipses are part of a nice astronomical coincidence: The Sun is 400 times wider than the Moon, but it's also 400 times farther. So when the Moon passes in front of the Sun, it just covers the Sun.

But the Moon is moving farther from Earth -- by about an inch and a half a year. That's not much, but over cosmic time, it adds up. Tens of millions of years from now, the Moon will have moved far enough that it will no longer completely cover the Sun, and total solar eclipses will pass into legend.

This eclipse will curve across the South Pacific from near New Zealand to the southern tip of South America -- a narrow path that crosses only a few tiny islands and the remote mountains of Chile. A partial eclipse will cover a wide swath of the South Pacific and South America.

Tomorrow: red rivals.

Script by Damond Benningfield, Copyright 2010

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