Concept
Einstein–Rosen bridge
A 1935 mathematical solution in general relativity: two sheets of space joined by a bridge. Later nicknamed a wormhole. The paper was about representing particles without singularities, not about travel.
Illustration made for this site. Not a photograph of the claim.
Traversable bridges have not been observed. In 2013 Maldacena and Susskind conjectured that some such bridges are related to quantum entanglement (ER = EPR). That is active theory. It is not a method for changing timelines, navigating dimensions, or sending messages faster than light.