Millimetre-Range Forces in Superstring Theories with Weak-Scale Compactification

We show that theories in which supersymmetry is broken via Scherk-Schwarz compactification at the weak scale, possess at least one scalar particle with Compton wavelength in the millimetre range, which mediates a force with strength 1/3 of gravity. Such forces are going to be explored in upcoming experiments using micro-electromechanical systems or cantilever technology. We also present a simple way of understanding some decoupling aspects of these theories by analogy with finite-temperature field theory.