Journal article Open Access
Niebauer, T. M.; McHugh, M. P.; Faller, J. E.
We have carried out a direct free-fall experiment to measure the differential acceleration between two different materials (copper and uranium) falling in the Earth's gravitational field. The differential acceleration was measured to be less than 5 parts in 1010 of the normal gravitational acceleration. This null result puts new limits on the strength and range of the proposed fifth force.