Alcubierre Drive

The Alcubierre drive (or Alcubierre metric see: Metric tensor) is a speculative idea based on a valid solution of Einstein's field equations as proposed by Miguel Alcubierre, by which a spacecraft may achieve faster-than-light travel, making travel to other stars more feasible. It is impossible for objects to actually accelerate to the speed of light within normal spacetime. However, rather than exceeding the speed of light within its local frame of reference, the ship would traverse distances by contracting space in front of it and expanding space behind it, allowing it to effectively move faster than light. The proposed mechanism implies a negative density of energy and thus requires exotic matter.