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. A jumpgate is a fictional device able to create an Einstein–Rosen bridge portal (or wormhole), allowing fast travel between two points in space. In franchises Stargate franchise Wormholes are the principal means of space travel in the Stargate movie and the spin-off television series, Stargate SG-1, Stargate Atlantis and Stargate Universe, to the point where it was called the franchise that is "far and away most identified with wormholes". The central plot device of the programs is an ancient transportation network consisting of the ring-shaped devices known as Stargates, which generate artificial wormholes that allow one-way matter transmission and two-way radio communication between gates when the correct spatial coordinates are "dialed". However, for some reason not yet explained, the water-like event horizon breaks down the matter and converts it into energy for transport through the wormhole, restoring it into its original state at the destination. This would explain why electromagnetic energy can travel both ways — it doesn't have to be converted. The one-way rule may be caused by the Stargates themselves: as a Gate may only be capable of creating an event-horizon that either breaks down or reconstitutes matter, but not both. It does serve as a very useful plot device: when one wants to return to the other end one must close the original wormhole and "redial", which means one needs access to the dialing device. The one-way nature of the Stargates helps to defend the gate from unwanted incursions. Also, Stargates can sustain an artificial wormhole for only 38 minutes. It's possible to keep it active for a longer period, but it would take immense amounts of energy. The wormholes generated by the Stargates are based on the misconception that wormholes in 3D space have 2D (circular) event horizons, but a proper visualization of a wormhole in 3D space would be a spherical event horizon. Babylon 5 and Crusade In television series Babylon 5 and its spin-off series Crusade,