Number 86 (Story #4), June 26, 1992 by Phillip F. Schewe and Ben Stein SUPERSTRING THEORY has hit some snags. The notion that the universe consists of tiny one-dimensional strings vibrating and interacting to produce particles and forces was an attractive one, because, when combined with several mathematical postulates such as "supersymmetry," it showed promise of combining the laws of quantum mechanics and those of general relativity within a single framework, a feat that would unify all four known forces in physics. However, theorists now believe a more fundamental understanding of the nature of particles and forces--and a better grasp of the mathematical implications of superstrings--will be necessary before a successful theory can be constructed. One troubling aspect of the theory is that it tolerates many solutions, some of which are nonsensical, and others which, although approximating the real world, require the existence of extra dimensions and exotic particles presently unsubstantiated by experiment. Nevertheless, theorists are not abandoning the concept of superstrings because, for example, the theory can directly produce the equations of general relativity and more recently has yielded simplified sets of equations describing black holes. (Science, 12 June 1992)