Faster Than Light?

Robert Geroch

University of Chicago

It is widely believed that relativity -- both special and general -- requires that no physical signal travel at a speed faster than that of light.  For instance, the assumption that there could be superluminal signals in relativity gives rise to well-known paradoxes.  We suggest that this situation is not nearly as dire as it appears at first sight.  Indeed, we shall argue that relativity is virtually as viable and self-consistent as a physical theory in the presence of superluminal signals as it is with such signals excluded.