An Assessment of Faster-Than-Light Spacetimes: Make or Break Issues

Implementation of faster-than-light (FTL) interstellar travel via traversable wormholes, warp drives, or other spacetime modification schemes generally requires the engineering of spacetime into very specialized local geometries. The analysis of these via Einstein’s General Theory of Relativity plus the resultant equations of state demonstrates that such geometries require the use of “exotic” matter. It has been claimed that since such matter violates the energy conditions FTL spacetimes are not plausible. However, it has been shown that this is a spurious issue. The identification, magnitude, and production of exotic matter is seen to be a key technical challenge, however. FTL spacetimes also possess features that challenge the notions of causality, and there are alleged constraints placed upon them by quantum effects. These issues are reviewed and summarized, and an assessment on the present state of their resolution is provided.