Laboratory test of Newton\u27s second law for small accelerations

We have tested the proportionality of force and acceleration in Newton\u27s second law, F = ma, in the limit of small forces and accelerations. Our tests reach well below the acceleration scales relevant to understanding several current astrophysical puzzles such as the flatness of galactic rotation curves, the Pioneer anomaly, and the Hubble acceleration. We find good agreement with Newton\u27s second law at accelerations as small as 5 x 10(-14) m/s(2)