G Whiz

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Science  18 Dec 1998:
Vol. 282, Issue 5397, pp. 2149
DOI: 10.1126/science.282.5397.2149a

Although it has been about 200 years since Cavendish first determined the gravitational constant G, most experiments have used a similar technique: A torsion balance measurement of the restoring force in a fiber between two large masses. In recent experiments by various groups, the systematic errors inherent in these measurements have resulted in scatter in the value for G varying by up to 40 times their individual errors. Schwarz et al. (p. 2230; see the news story by Kastenbaum) have been able to reduce or remove these systematic errors by using a different experimental setup: Laser interferometry is used to track a free-falling body under the influence of a nearby mass.

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