Faster-than-light (FTL) communications and travel are the propagation of information or matter faster than the speed of light. Superluminal is an adjective used for a speed or velocity exceeding the speed of light.
With the old laws of physics, Einstein's special theory of relativity says that only particles with zero rest mass (like photons) may travel at the speed of light. Mass gains weight as it accelerates and as it approaches the speed of light, it becomes infinitely heavy. There is also increasingly severe time dilation experienced by the traveler approaching the speed of light, and everything else ages as you travel. Ways around these problems had to found via technology to effectively travel "faster than light" using spacetime warp displacement, hyperspace lanes, or natural cosmological structures like wormholes.
Tachyons, particles whose speed have to be faster than light, are used once the new laws of physics are discovered.
Cherenkov radiation is emitted when a charged particle, such as an electron, passes through a transparent medium, such as glass or water, at a speed greater than the speed of light in that medium. In glass or water, light typically travels around 70% of its speed in a vacuum, and it is possible for charged particles to travel faster than light in this medium. The displaced atomic electrons emit radiation to form a strong electromagnetic wave reminiscent of the sonic boom produced by an airplane traveling faster than the speed of sound in air. The emitted radiation is conical in shape, with a cone angle that depends on particle velocity and speed of light in the medium.
Because of the Big Bang and the fabric of space itself expanding, it seems that galaxies themselves move faster than light.
FTL drives are significant for Type II civilizations. Beyond that, instantaneous methods of travel are used unless traversable wormholes are discovered first.
| Hyperspace | extremely fast; galactic and intergalactic |  |
| Krasnikov tube | extremely fast |  |
| Mass Relay | instantaneous from relay to relay |   |
| Planeswalking | Instantaneous |   |
| Portal | A general term used to denote a gate/window/door that connects or bridges two dimensions or points in spacetime. It can be a stargate or wormhole. Travel is instantaneous. An example is the portal that connects Xen and Earth in the Half-Life Universe. |   |
| Quantum tunneling | fast enough to traverse a galaxy |   |
| Slipstream | extremely fast; intergalactic |   |
| Stargate | instantaneous |   |
| Tachyon | instantaneous |   |
| Warp drive | fast; interstellar |   |
| Webway | very fast to instantaneous, depending on the lines of the web that are used |   |
| Artificial wormholes | instantaneous; able to travel to any place in the universe. |   |
| Natural wormholes | instantaneous; able to travel to any place in the universe. |   |
