A free-fall determination of the Newtonian constant of gravity

Recent determinations of the Newtonian constant of gravity have produced va lues that differ by nearly 40 times their individual error estimates (more than 0.5%). In an attempt to help resolve this situation, an experiment tha t uses the gravity field of a one-half metric ton source mass to perturb th e trajectory of a free-falling mass and laser interferometry to track the f alling object was performed. This experiment does not suspend the test mass from a support system. It is therefore free of many systematic errors asso ciated with supports. The measured value was G = (6.6873 +/- 0.0094) x 10(- 11) m(3) kg(-1) sec(-2).