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Earth gravity may drop slightly on July 22!

Does Earth's gravity drop slightly during a total eclipse? A team of Chinese scientists is planning to conduct a once-in-a-century experiment on this controversial theory on July 22, the day of the total solar eclipse.

india Updated: Jul 21, 2009 01:29 IST

A team of Chinese scientists is planning to conduct a once-in-a-century experiment on July 22, the day of the total solar eclipse, which would test the controversial theory that gravity drops slightly during a total eclipse.

According to a report in New Scientist, geophysicists from the Chinese Academy of Sciences are preparing an unprecedented array of highly sensitive instruments at six sites across the country to take gravity readings during the total eclipse due to pass over southern China on July 22.

The results, which will be analysed in the coming months, could confirm once and for all that anomalous fluctuations observed during past eclipses are real.

"It sounds like what is really necessary to break the uncertainty," said Chris Duif of Delft University of Technology in The Netherlands.

"I'm not really convinced the anomaly exists, but it would be revolutionary if it turned out to be true," he said.

The first sign that gravity fluctuates during an eclipse was in 1954, when French economist and physicist Maurice Allais noticed erratic behaviour in a swinging pendulum when an eclipse passed over Paris.

Pendulums typically swing back and forth as a result of gravity and the rotation of the Earth.

At the start of the eclipse, however, the pendulum's swing direction shifted violently, suggesting a sudden change in gravitational pull.

Fluctuations have since been measured during around 20 total solar eclipses, but the results still remain inconclusive.

In the run up to July's eclipse, Chinese researchers have prepared eight gravimeters and two pendulums spread across six monitoring sites.

The team hopes that the vast distance between the sites (roughly 3000 kilometers between the most easterly and westerly stations), as well as the number and diversity of instruments used, will eliminate the chance of instrument error or local atmospheric disturbances.

"If our equipment operates correctly, I believe we have a chance to say the anomaly is true beyond all doubt," said Tang Keyun, a geophysicist at the Chinese Academy of Sciences.

The opportunity won't come again soon. At over five minutes, the event will be the longest total solar eclipse predicted for this century.

What's more, the event will occur when the sun is high in the sky; a time when, according to Tang, any potential gravitational anomaly should be greatest.