Laboratory test of Newtonʼs law of gravity for small accelerations

The rotation curves of spiral galaxies suggest that either a considerable fraction of the galactic mass must be dark matter, or that one of Newtonʼs laws needs revision at accelerations less than . We have endeavored to search for evidence of the latter in a terrestrial laboratory. A sensitive torsion balance was employed to measure small accelerations due to gravity. No deviations from the predictions of Newtonʼs law were found down to 1 × 10−12 m s−2.