Faster-than-light

Faster-than-light (also superluminal or FTL) communications and travel are staples of the science fiction genre. However, according to currently understood physics, these concepts require exotic conditions that current technology can't establish, and that may be directly forbidden by more complete models of the universe's physical laws. Current theories of physics suggest that FTL travel or communication would necessarily involve time travel and thus would almost certainly cause problems with causality.

External links

• Encyclopedia of laser physics and technology on "superluminal transmission", with more details on phase and group velocity, and on causality
• July 22, 1997, The New York Times Company: Signal Travels Farther and Faster Than Light Quote: "..."We find," Chiao said, "that a barrier placed in the path of a tunneling particle does not slow it down. In fact, we detect particles on the other side of the barrier that have made the trip in less time than it would take the particle to traverse an equal distance without a barrier -- in other words, the tunneling speed apparently greatly exceeds the speed of light. Moreover, if you increase the thickness of the barrier the tunneling speed increases, as high as you please..."
• Markus Pössel: Faster-than-light (FTL) speeds in tunneling experiments: an annotated bibliography Quote: "...An experiment of theirs, where a single photon tunnelled through a barrier and its tunneling speed (not a signal speed!) was 1.7 times light speed, is described in Steinberg, A.M., Kwiat, P.G. & R.Y. Chiao 1993: "Measurement of the Single-Photon Tunneling Time" in Physical Review Letter 71, S. 708--711..."
• Relativity and FTL (=Superluminal motion) Travel Homepage
• The Warp Drive: Hyper-Fast Travel Within General Relativity, Miguel Alcubierre Class. Quantum Grav. 11 (1994), L73-L77 Quote: "...It is shown how, within the framework of general relativity and without the introduction of wormholes, it is possible to modify a spacetime in a way that allows a spaceship to travel with an arbitrarily large speed..."
• NASA: Status of "Warp Drive" Maturity - speculation
• Usenet Physics FAQ: is FTL travel or communication Possible?
• Critique of Geometro-Stochastic Theory
• Superluminal
• The Speed of Light: How Fast Can We Go?
• Smarandache Hypothesis that there is no speed barrier and one can construct arbitrary speeds
• Light Speed