Abstract

I have written a number of columns in this magazine about wormholes, warp drives, and other constructs of Einstein’s general relativity (GR) that appear to offer a good physics foundation for faster-than-light travel and even for travel back in time. All of these GR constructs come from a particular non-standard way of using Einstein’s theory, an approach that might be described as "metric engineering." Instead of considering a particular arrangement of mass and energy and asking how space would be warped and what effects would be produced by such an arrangement, in metric engineering we specify how we want space to be warped in order to produce these effects, and then ask what arrangement of mass and energy would be required to accomplish this. The usual outcome of this kind of GR calculation is that a certain quantity of negative mass-energy would be needed. For example, to stabilize a wormhole, a significant quantity of negative mass-energy is needed near the wormhole’s throat.