Tomorrow, Chinese scientists will get a once-in-a-century opportunity to try out a particularly controversial theory that, if proven, will change our idea of the way that the world works. The theory? That gravity will lessen during a total eclipse.

The idea that gravity will drop during an eclipse originated with French physicist Maurice Allais in 1954, when he noticed a pendulum's swing suddenly change direction during an eclipse but, despite similar fluctuations in gravitational pull being registered during 20 total solar eclipses, no conclusive proof has been found to support or disprove the theory once and for all. Tomorrow's eclipse offers the longest opportunity this century for the scientists (working at six separate sites almost 3000 kilometers apart) to investigate further, but even so, they'll have to act fast — the eclipse is only expected to last five minutes. Final results won't be known for months, but could be worth the wait, according to Dutch researcher Chris Duif, of Delft University of Technology:

It sounds like what is really necessary to break the uncertainty... I'm not really convinced the anomaly exists, but it would be revolutionary if it turned out to be true.

July eclipse is best chance to look for gravity anomaly [New Scientist]