© Blayne Heckel.
The gravitational attraction between two suspended masses will cause the suspension fibers to be tilted away from local vertical. For two 1 kg spheres whose centers are 10 cm apart, the tilt angle will be 4 x 10-8 degrees, far too small to be noticeable. Trying to see such a small change is equivalent to trying to watch something on the Moon move a few inches. To detect the gravitational force between small objects in the laboratory, physicists turn to sensitive instruments such as torsion balances. (Unit: 3)