Einstein–Rosen bridge

Schwarzschild wormholes, also known as Einstein–Rosen bridges (first proposed by Albert Einstein and Nathan Rosen in 1935), are connections between areas of space that can be modeled as vacuum solutions to the Einstein field equations, and that are now understood to be intrinsic parts of the maximally extended version of the Schwarzschild metric describing an eternal black hole with no charge and no rotation. Here, "maximally extended" refers to the idea that the spacetime should not have any "edges": it should be possible to continue this path arbitrarily far into the particle's future or past for any possible trajectory of a free-falling particle (following a geodesic in the spacetime). Thus they could potentially be used for faster-than-light travel or as a shortcut through space.