EinsteinRosen

The Einstein–Rosen bridge, commonly referred to as an Einstein–Rosen wormhole, is a theoretical construct in the theory of general relativity describing a tunnel-like connection between separate points in spacetime. It was proposed by Albert Einstein and Nathan Rosen in 1935 as a continuation of the Schwarzschild solution.

In the mathematical model, the bridge arises from the maximally extended Schwarzschild solution, described using Kruskal–Szekeres coordinates, which reveals two distant asymptotically flat regions connected by a throat. The original interpretation depicted a non-traversable bridge: the throat would pinch off before any object could cross from one side to the other.

The concept illustrates how spacetime geometry can, in principle, provide shortcuts between distant regions. However, creating a traversable wormhole within general relativity generally requires exotic matter with negative energy density to stabilize the throat, a condition not known to exist in macroscopic quantities. The classic traversable-wormhole models were proposed by Morris and Thorne in 1988, highlighting the speculative status of such constructs.

In contemporary physics, Einstein–Rosen bridges remain a theoretical tool rather than an empirical phenomenon. They appear in discussions of quantum gravity and in conjectures linking spacetime geometry to quantum entanglement, such as the ER=EPR idea, though these ideas are speculative and debated.