Faster than light

Faster-than-light (FTL) communications and travel are the propagation of information or matter faster than the speed of light.

The special theory of relativity implied that only particles with zero rest mass may travel at the speed of light. Tachyons, particles whose speed exceeds that of light, have been hypothesized, but their existence would violate causality. Mass gains weight as it accelerates so ways around this burden had to found. Technology was invented to travel "faster" than light, or natural cosmological structures were used.

FTL drives are significant for Type II civilizations. Beyond that, instantaneous methods of travel are used unless traversable wormholes are discovered first.