A warp drive is a fictional superluminal spacecraft propulsion system in many science fiction works, most notably Star Trek, and a subject of ongoing physics research. A spacecraft equipped with a warp drive may travel at speeds greater than that of light by many orders of magnitude. In contrast to some other fictitious faster-than-light technologies such as a jump drive, the warp drive does not permit instantaneous travel and transfers between two points, but rather involves a measurable passage of time which is pertinent to the concept. In contrast to hyperspace, spacecraft at warp velocity would continue to interact with objects in "normal space". The general concept of "warp drive" was introduced by John W. Campbell in his 1957 novel Islands of Space.Einstein's theory of special relativity states that speed of light travel is impossible for material objects that, unlike photons, have a non-zero rest mass. The problem of a material object exceeding light speed is that an infinite amount of kinetic energy would be required to travel at exactly the speed of light. Warp drives serve to circumvent this limitation in fiction to facilitate stories set at galactic scales.