DYNAMICS - Gravitational Forces A Cavendish balance apparatus is used for the experimental verification of Newton's law of universal gravitation. This video shows a time lapse of the position of a laser beam which is reflected off of a mirror attached to a torsional balance which is set to oscillating by a change in position of two lead balls from equilibrium. The apparatus is arranged to ensure that the gravitational force of the lead balls dominates. http://18.74.1.138/~bil/DemoPage/B/B5/B5.htm http://books.google.com/books?id=O58mAAAAMAAJ&pg=PA59 http://en.wikipedia.org/wiki/Cavendish_experiment