  This essay reviews some of the recent progress in the area of energy
conditions and wormholes. Most of the discussion centers on the subject of
``quantum inequality'' restrictions on negative energy. These are bounds on the
magnitude and duration of negative energy which put rather severe constraints
on its possible macroscopic effects. Such effects might include the
construction of wormholes and warp drives for faster-than-light travel, and
violations of the second law of thermodynamics. Open problems and future
directions are also discussed.
