An Einstein–Rosen bridge, or wormhole, is a postulated method, within the general theory of relativity, of moving from one point in space to another without crossing the space between. Wormholes are a popular feature of science fiction as they allow faster-than-light interstellar travel within human timescales. A related concept in various fictional genres is the portable hole. While there's no clear demarcation between the two, this article deals with fictional, but pseudo-scientific, treatments of faster-than-light travel through space.