Idea on the edgeSpeculative · Universe

Wormholes

A tunnel through space-time that could link two distant places, or two different universes. They appear in the equations; whether they can exist in reality is open.

Speculative · never observed

Idea: A bridge or tunnel through space-time
Origin: Einstein-Rosen bridges in general relativity
Issue: Requires exotic matter to stay open
Status: Theoretical, none observed

A tunnel through space-time

Les Bossinas / NASA

Wormhole travel as envisioned by Les Bossinas for NASA — Wormhole travel as envisioned for NASA by Les Bossinas. Image: Les Bossinas / NASA.

Shortcuts through space-time

A wormhole has two mouths joined by a throat. In principle it connects two regions of the same universe, or two different universes, with a path shorter than the ordinary one. The Einstein-Rosen bridge is the classic example, found in the mathematics of black holes.

Keeping one open

A plain wormhole pinches shut too quickly for anything to cross. Holding it open would take matter with negative energy, sometimes called exotic matter. Whether such matter exists in the needed amounts is unknown.

Could we use one

Traversable wormholes remain a thought experiment. There is no known way to build one, keep it stable, or survive the trip. They are useful for testing ideas about causality and quantum gravity, less so as a travel plan.

Key publications

Year	Paper	Venue	Link
1935	Einstein & Rosen, The Particle Problem in the General Theory of Relativity	Physical Review 48, 73	DOI
1988	Morris & Thorne, Wormholes in spacetime and their use for interstellar travel	Am. J. Phys. 56, 395	DOI
2013	Maldacena & Susskind, Cool horizons for entangled black holes	Fortschr. Phys. 61, 781	DOI

Selected papers for further reading. DOI links open the publisher's record; preprints are linked on arXiv.

Worth knowing

Wormholes can link two places in one universe or two universes.
A traversable one would need exotic matter.
They remain a staple of physics thought experiments.