Einstein’s general theory of relativity can be used to construct model universes in which shortcuts in space exist. For certain regions of space one has two possibilities to travel from one to the other – one conventionally through space, the other by entering a spherical region, a “mouth” of the wormhole, to come out near the target in a similar region, the other mouth – without having to travel a long distance on the way from one mouth to the other. If the two wormhole mouths could be set in motion relative to each other, it would even be possible to create a time shift: anyone who dives into one mouth of the wormhole and comes out at the other end would have travelled a little into the future or the past.

According to all we know, wormholes are certainly very unrealistic and speculative model universes. In order to stabilize a wormhole to such an extent that it would be traversable, one would need matter with highly exotic properties – it is quite possible that for this reason alone, there are no wormhole shortcuts in the real universes.