What is a wormhole?

Albert Einstein and Nathan Rosen described such connections in 1935, giving the name Einstein–Rosen bridges, and physicist John Wheeler coined the word wormhole in 1957. General relativity allows wormholes mathematically, but no one has ever detected one. Calculations suggest they would collapse too quickly for anything to pass through unless held open by exotic matter with negative energy, which may not exist in usable amounts. Physicist Kip Thorne studied traversable wormholes and advised on the 2014 film Interstellar, which depicts one near Saturn. For now, wormholes remain firmly in theory and science fiction.