Exploring Fifth Force Interactions with 18th Century Technology

Many theories which unify gravity with the other known forces of nature predict the existence of an intermediate-range ``fifth force'' similar to gravity. Such a force could be manifest as a deviation from the gravitational inverse-square law. Currently, at distances near $10^{-1}$m, the inverse-square law is known to be correct to about one part per thousand. I present the design of an experiment that will improve this limit by two orders of magnitude. This is accomplished by constructing a torsion pendulum and source mass apparatus that are particularly insensitive to Newtonian gravity and, simultaneously, maximally sensitive to violations of the same.