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No object can travel faster than light, according to Einstein's theory of relativity. The theory prohibits material objects as well as energy or information from moving at any velocity greater than the speed of light.

Many works of science fiction propose that future advances in science will discover some (as yet unknown) new theory to allow a loophole in the theory, allowing faster-than-light travel to be possible. It has been proposed that such a theory might involve an as-yet undiscovered type of particle that moves faster than light ("tachyon"), "warping" of the geometry of space (tagged a "warp drive"), use of a fourth (or higher) spatial dimension (often called hyperspace), use of quantum mechanical effects such as entanglement, or travel through a wormhole.

Faster-than-light travel is often abbreviated in science fiction as "FTL." Many other terms have been used, including "warp engines" (Star Trek), "folding space," (Dune), "jump to lightspeed" (Star Wars), "overdrive," "hyperdrive," and others. A device that allows communication but not travel faster than light has been tagged an "ansible" (the word was coined by Ursula K. Le Guin).

It is notable that while Einstein's Special Theory of Relativity prohibits speeds faster than light, his later and more comprehensive General Theory of Relativity does not prohibit arriving at a place in a time shorter than the time a light beam would take to travel the same distance, as long as your actual speed at any given place never exceeds that of light. (See wormhole.)

The rule of thumb is: "Causality, Relativity, FTL travel: chose any two." You cannot have all three existing in the universe. Relativity forces FTL travel to be functionally equivalent to time travel, which is incompatible with causality. So if you postulate the existence of FTL travel, either causality or relativity are not true.

Controversy to this article can be viewed at this page if you are not satisfied by the status quo: http://scifipedia.scifi.com/index.php/Talk:Faster_than_Light

External Links

Lab Notes by Wil McCarthy "Faster Than Light, Part I"

Lab Notes by Wil McCarthy "Faster Than Light, Part II"

Atomic Rockets "Faster Than Light"

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