Fifth force

In physics, the fifth force is indicative of a hypothetical fifth interaction in addition to gravitational, weak, electromagnetic and strong interactions.

Often thus forces are referred to the (more precisely coupled to the energy -momentum tensor ) as the gravitational mass are proportional to, but with increasing distance fall faster than according to the Newtonian law of gravitation, that is faster than

This hypothesis attracted some interest from 1986, as a summary evaluation of old experiments of the type of the Eötvös experiment, an effect suggesting ( Ephraim Fischbach and others). Initial attempts to reproduce the experimental reach apparently, but with more sensitive tests, it was clear in the next few years, that the effect, if any, had to be very small.

The experiments revealed four size scales from:

An active research area is still the millimeter range and below. Here deviations would be expected from the behavior when some of the predicted by string theory higher dimensions are not limited to the Planck length, the so-called theory of large extra dimensions.