The celestial spectacle on Wednesday, 22 July 2009, will darken major cities, densely populated countryside, and a vast expanse of tropical ocean. The eclipse itself will be a monster, with totality – when the sun is completely covered by the moon – lasting more than 6.6 minutes at maximum. That makes this the longest totality until 2132.
A total solar eclipse occurs once every year or two on average, but each is visible only from a narrow track covering less than 1 per cent of Earth's surface. The eclipse of 1 August 2008, was visible only from parts of the Arctic, Siberia, and central Asia.
The main reason why this year's totality lasts so long is because the eclipse starts just a few hours after the moon reaches perigee, the point at which it is closest to Earth in its orbit . At such a close distance, the moon appears fully 8 per cent larger than the sun and casts a broader than usual shadow. At the point of greatest eclipse in the western Pacific, the path of totality is 258 km wide.
Gravity anomaly:
The Chinese researchers are poised to conduct an audacious once-in-a-century experiment, covering remote observatories on the Tibetan plateau to a cave in a Shanghai suburb. The plan is to test a controversial theory: the possibility that gravity drops slightly during a total eclipse.
NASA's eclipse website
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