  The presence of finite energy in quantum vacuum has profound implications to
physics at the microscopic and macroscopic levels. One of the direct
consequences of vacuum energy is the Casimir Force, which is a force of
attraction experienced by a pair of infinite planar conductive plates placed in
vacuum. Experiments to measure Casimir force have been carried out since the
1950s. This thesis presents a measurement of Casimir force between a flat and a
spherical conducting surface using a torsion balance for separations in the
range of 1 micron to 8 micron. The details of the construction of the torsion
balance apparatus, the experimental procedure and the analysis to obtain the
Casimir force as a function of separation are described. There are indications
of the finite temperature effects which become important for separations
greater than ~ 3microns. The combined import of this experiment with others at
shorter distances is to favor the finite temperature theory of Casimir forces.
The contributions of this experiment towards bounding the strength of inverse
square law short-range violating interactions are presented.
