The rise and fall of a non-Newtonian gravity experiment

An experiment was conducted in 1987 in search for a possible non-Newtonian component to gravity. The test compared accurately measured gravity values on a 600 m tower with upward continued surface gravity. The results indicated a dominant attractive non-Newtonian force that asymptotically approached -540 µGal at the top of the tower. An exhaustive search of possible error sources led to the discovery that our surface data did not accurately represent some of the local topographic features. The surface survey was supplemented by gravity data to remove some of the biases that were caused by the misrepresentation. In addition, a rigorous terrain correction was applied to the surface data resulting in terrain-corrected Bouguer anomalies. These anomalies were then upward continued using two independent techniques. The terrain effect was added back to the predicted values at altitude. With this procedure almost the entire non-Newtonian effect was explained. Currently we find no conclusive evidence for a non-Newtonian force over the range of several hundred meters.