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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 analyzed in the coming months, could confirm once and for all that anomalous fluctuations observed during past eclipses are real.

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.

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

At over five minutes, the event will be the longest total solar eclipse predicted for this century.