Unification of Couplings

Ambitious attempts to obtain a unified description of all the interactions of nature have so far been more notable for their ingenuity, beauty and chutzpah than for any help they have afforded toward understanding concrete facts about the physical world. In this article we wish to describe one shining exception: how ideas about the unification of the strong, weak and electromagnetic interactions lead to concrete, quantitative predictions about the relative strengths of these interactions.