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The weight of the Earth has fallen by a trillion tonnes, thanks to a
recalculation of the gravitational constant. 鈥淏ig G鈥� is incredibly difficult to
measure and its official value is the most uncertain of all the physical
constants. At last week鈥檚 meeting of the American Physical Society in Long
Beach, California, researchers from the University of Washington unveiled
preliminary results for a measurement of G 10 to 100 times more accurate than
earlier values. The team used a version of the instrument employed to measure
the constant since the 1700s.