A shortcut through spacetime
In general relativity, mass and energy curve spacetime. Mark two dots at opposite ends of a sheet of paper, fold the paper so the dots touch and punch a hole through: the hole is far shorter than the route across the paper. A wormhole is a structure with a "throat" that links two distant regions of curved spacetime in a similar way. In 1935 Albert Einstein and Nathan Rosen, studying black hole solutions, found a bridge connecting two regions, now called the Einstein–Rosen bridge. The name wormhole was coined in 1957 by the American physicist John Wheeler, after a worm that bores through an apple instead of crawling around its surface. In the 1960s it was shown that this original bridge pinches off so quickly that not even light can cross it.
Traversable wormholes and time travel
In 1988 Kip Thorne and Michael Morris at Caltech worked out what a wormhole people could travel through would require. The answer was "exotic matter" with negative energy density to hold the throat open. Tiny amounts of negative energy do appear in quantum effects such as the Casimir effect, but no one knows how to gather enough to support a wormhole. Calculations also showed that moving one mouth of a wormhole at nearly the speed of light and bringing it back would create a time difference between the mouths, turning it into a time machine. In 1992 Stephen Hawking proposed the chronology protection conjecture, that the laws of physics prevent such time travel. Thorne later served as science adviser on the 2014 film Interstellar, whose wormhole and black hole visuals were based on his calculations.
ER=EPR and the quantum-processor experiment
In 2013 Juan Maldacena and Leonard Susskind proposed ER=EPR: the idea that Einstein–Rosen bridges (ER) and quantum entanglement (EPR, after Einstein, Podolsky and Rosen) may be two faces of the same phenomenon, so that entangled black holes could be connected by wormholes. It is seen as an important clue in efforts to unite quantum mechanics and gravity. In 2022 a Nature paper describing a simulation of traversable-wormhole dynamics on Google's quantum processor drew headlines, but it reproduced a mathematical model based on holography in a quantum circuit; it did not create a wormhole in real spacetime. No wormhole has ever been observed, and whether the laws of physics truly allow them remains an open question.
FAQ
- Are wormholes and black holes the same thing?
- No. Black holes are observed objects, whereas wormholes are hypothetical structures that exist only as solutions to equations. They are often mentioned together because early wormhole theory grew out of black hole solutions.
- Could a wormhole be used for time travel?
- Some solutions allow it in theory, but nobody knows whether the exotic matter needed for a traversable wormhole exists, and many physicists think nature forbids travel into the past. For now it belongs to science fiction.
Sources reviewed: 2026-10-26
References
- Einstein, A., & Rosen, N. (1935). The particle problem in the general theory of relativity. Physical Review, 48(1), 73–77.
- Morris, M. S., & Thorne, K. S. (1988). Wormholes in spacetime and their use for interstellar travel: A tool for teaching general relativity. American Journal of Physics, 56(5), 395–412.
- Hawking, S. W. (1992). Chronology protection conjecture. Physical Review D, 46(2), 603–611.
- Maldacena, J., & Susskind, L. (2013). Cool horizons for entangled black holes. Fortschritte der Physik, 61(9), 781–811.
- Jafferis, D., et al. (2022). Traversable wormhole dynamics on a quantum processor. Nature, 612(7938), 51–55.