The wormhole idea comes from Einstein's theory of general relativity itself using "Schwartzschild geometry", a way of inscribing a space-time coordinate system on the highly curved space in the vicinity of a black hole. A wormhole is a funnel-shaped tunnel that can connect one complete universe with another or can connect two separated regions of the same universe. In the latter case it is a short path connecting two distant locations in space. Thus it the SF writer's dream, a spatial shortcut that a space traveler might use to bypass the speed-of-light barrier and travel almost instantaneously from one place to another within our universe.