Flavor tests of grand unification

How will we ever be convinced that grand unification, or string theory, or some other physics at very high energies, is correct? Two ways in which this could happen are: The structure of the theory is itself so compelling and tightly constrained, and the links to observed particle interactions are sufficiently strong, that the theory is convincing and is accepted as the standard viewpoint. String theory is a candidate for such a theory, but connections to known physics will require much further understanding of the breaking of its many symmetries. The theory predicts new physics beyond the standard model, which is discovered. If the structure of the theory is not very tightly constrained, several such predictions will be necessary for it to become convincing. Grand unification is a candidate for such a theory, but as yet there have been no discoveries beyond the standard model. Supersymmetric grand unified theories do have a constrained gauge structure, and this has led to the successful prediction of the weak mixing angle at the percent level of accuracy While significant, this is hardly convincing. Never-the-less, supersymmetric grand unified theories offer the prospect of many further tests. In this talk I make the case that experiments of this decade, and the next, allow for the possibility that we might become convinced that grand unification is correct