Wormholes are theoretical tunnels through spacetime that connect distant points in the universe, and despite decades of serious theoretical work, none has ever been observed or created. They emerge naturally from the mathematics of general relativity, but every version that would allow something to pass through demands conditions so extreme that physicists remain deeply divided on whether they could exist outside of equations. The science around wormholes has grown far richer than the simple “shortcut through space” image from science fiction, touching quantum information theory, alternative models of gravity, and even laboratory experiments on quantum processors.
How Wormholes Emerged from Einstein’s Equations
The idea traces back to 1935, when Albert Einstein and Nathan Rosen noticed that certain solutions to the equations of general relativity described a bridge connecting two separate regions of spacetime. This “Einstein-Rosen bridge” wasn’t designed as a travel concept. It arose from the mathematics of black holes: if you extended the geometry of a black hole solution fully, the math produced a second exterior region linked to the first by a narrow throat. In the simplest case, a non-rotating, uncharged black hole described by the Schwarzschild solution, this bridge collapses so quickly that nothing can cross it. Even light wouldn’t make it through before the throat pinches shut.
The situation changes for more complicated black holes. A traversable Einstein-Rosen bridge exists inside both rotating black holes and electrically charged black holes, but it is entirely absent inside a non-rotating, uncharged Schwarzschild black hole.1arXiv. Generalized Einstein–Rosen bridge inside black holes In plain terms, adding spin or charge to a black hole restructures its interior geometry enough to prevent the throat from collapsing instantly. Even so, these bridges are “one-way” in a practical sense and sit deep inside a black hole’s event horizon, making them irrelevant for any kind of journey.
The physicist John Wheeler, who coined the term “wormhole” in the 1950s, imagined something even stranger: at the tiniest conceivable scales, the fabric of spacetime itself might be riddled with tiny wormholes, constantly appearing and disappearing. Wheeler suggested more than 65 years ago that quantum uncertainties in the metric of spacetime would become enormous at the Planck scale, producing what he called “spacetime foam.”2Reports on Progress in Physics. Spacetime foam: a review Whether this foam actually exists remains an open question. The scales involved are roughly twenty orders of magnitude smaller than an atomic nucleus, far beyond anything current instruments can probe.
Why Holding One Open Requires Something Strange
The wormholes that capture the public imagination aren’t the Einstein-Rosen bridges buried inside black holes. They’re the traversable kind: stable tunnels you could, in principle, send a spacecraft through. In 1988, Kip Thorne and Michael Morris published the foundational paper on these, showing that general relativity permits a traversable wormhole geometry if you fill its throat with material that has a property physicists call negative energy density. In everyday terms, normal matter and energy create gravity that pulls inward, which would crush a wormhole’s throat shut. To keep the throat open, you need material that pushes outward, exerting a kind of anti-gravity. This material violates what’s called the null energy condition, a basic rule that all known classical forms of matter obey.
Physicists sometimes call this hypothetical stuff “exotic matter,” and the name is apt. Nothing in the everyday world behaves this way. However, quantum physics does offer one tantalizing loophole: the Casimir effect. When two uncharged metal plates are placed extremely close together in a vacuum, quantum field fluctuations create a measurable attractive force between them. This effect, confirmed in the lab, produces a region of negative energy density between the plates.3The European Physical Journal C. Casimir wormholes in modified symmetric teleparallel gravity Some researchers have explored whether the Casimir effect could serve as a source for the exotic matter a wormhole needs. The energy densities involved are fantastically tiny compared to what would be required to hold open a human-scale wormhole, so this remains a mathematical exercise for now rather than an engineering plan.
Modified Gravity as a Way Around Exotic Matter
One of the most active areas in wormhole research asks a simple question: what if the problem isn’t that wormholes need impossible matter, but that our theory of gravity is slightly wrong? General relativity is extraordinarily well tested, but physicists know it breaks down at extreme scales, specifically at singularities and at quantum scales where it conflicts with quantum mechanics. Several alternative theories of gravity have been proposed that agree with general relativity in everyday conditions but diverge in extreme regimes. Researchers have found that some of these alternatives allow wormhole solutions without violating the null energy condition.
In one approach, working within a framework called f(R,T) gravity, which modifies how spacetime curvature relates to the energy content of matter, researchers have found novel wormhole geometries with ordinary, non-exotic matter that respects the null energy condition.4Annals of Physics. Wormholes in f(R,T) gravity satisfying the null energy condition with isotropic pressure Similar work has examined Morris-Thorne-type wormholes carrying a topological defect known as a global monopole charge, finding configurations where energy conditions can be satisfied depending on the shape of the wormhole’s throat.5The European Physical Journal C. Morris–Thorne-type wormholes with global monopole charge and the energy conditions Other groups have explored extended teleparallel gravity theories and found wormhole solutions where the exotic matter violation persists near the throat but thermodynamic analysis suggests the structures could be stable.6Physics of the Dark Universe. Possible formation of traversable wormholes and their thermodynamic analysis in F(Q,Lm,T) gravity
The catch is that none of these alternative gravity theories has been experimentally confirmed. They’re consistent with current observations, but so is standard general relativity. Until an experiment or observation distinguishes one from the other, these wormhole-friendly solutions remain mathematical possibilities, not predictions about the real universe. Still, the sheer number of viable wormhole solutions across different modified gravity frameworks has shifted the conversation. Two decades ago, most physicists would have flatly called traversable wormholes impossible. Today, the consensus is more cautious: they require exotic physics, but the definition of “exotic” keeps getting broader.
The ER=EPR Conjecture
In 2013, Juan Maldacena and Leonard Susskind proposed one of the most provocative ideas in modern theoretical physics. They suggested that every pair of entangled particles, the kind used in quantum information experiments all the time, is connected by a tiny, non-traversable wormhole. They named the idea ER=EPR, linking Einstein-Rosen bridges (wormholes) to Einstein-Podolsky-Rosen pairs (entangled particles). The implication is stunning: the spooky connection between entangled particles isn’t just a metaphor for a bridge through spacetime. It literally is one.
This remained a conceptual conjecture for years, but researchers have since built a concrete quantitative model for it. A 2023 paper presented a framework in which two entangled particles with spin are connected by a non-traversable wormhole in standard general relativity, providing mathematical substance to the ER=EPR idea.7PubMed. Probing the Connection between Entangled Particles and Wormholes in General Relativity If ER=EPR is correct, wormholes aren’t rare exotic objects. They’re everywhere, at the quantum scale, woven into the fabric of reality wherever entanglement exists. They just happen to be non-traversable and far too small to serve as shortcuts.
The conjecture has deep implications for the black hole information paradox, one of the central unsolved problems in physics. If the interior of a black hole is connected via wormholes to the radiation it emits, that could provide a mechanism for information to escape, resolving the paradox that Stephen Hawking first raised in the 1970s. Whether the math ultimately validates this picture remains an active research question.
Wormholes Simulated on a Quantum Processor
In late 2022, headlines announced that Google’s Sycamore quantum processor had “created” a wormhole. The reality was more subtle but still genuinely interesting. The experiment used a mathematical model called the Sachdev-Ye-Kitaev (SYK) model, a system of interacting quantum particles that, under certain theoretical frameworks, behaves like a wormhole in a lower-dimensional universe. Using learning techniques to simplify the model, the team implemented it as a nine-qubit quantum circuit with 164 two-qubit gates and observed dynamics consistent with what a traversable wormhole would produce in that mathematical framework.8Nature. Traversable wormhole dynamics on a quantum processor
What the experiment actually showed was quantum teleportation, the transfer of quantum information from one part of the circuit to another, behaving in a way that mirrors how information would travel through a traversable wormhole in the SYK model. The underlying theory had predicted that the teleportation protocol based on this model could achieve almost perfect fidelity.9Journal of High Energy Physics. A traversable wormhole teleportation protocol in the SYK model Subsequent analysis, however, showed that the teleportation signal diminishes rapidly as the system size shrinks, meaning that observing a sharp signature of emergent wormhole-like geometry requires a much larger number of qubits than the nine used in the experiment.10Journal of High Energy Physics. Fidelity of wormhole teleportation in finite-qubit systems
No actual tunnel through space was opened. The experiment operated entirely within quantum circuitry and explored a mathematical correspondence, not physical spacetime geometry. But the result is meaningful because it showed that quantum systems can reproduce the information-theoretic signatures of wormhole traversal, lending support to the deep conjectured relationship between quantum entanglement and geometry.
Could We Spot a Wormhole Through a Telescope?
If a wormhole exists in the wild, it would look a lot like a black hole to our current instruments. Both would bend light around them, cast shadows, and potentially host swirling accretion disks of gas. The images captured by the Event Horizon Telescope of the supermassive objects in M87 and at the center of the Milky Way are consistent with black holes, but could a wormhole hide in plain sight as one?
Researchers have studied the differences in detail. One analysis of a rotating wormhole model known as the Damour-Solodukhin wormhole found that for most physically plausible parameter values, its accretion disk properties are “experimentally indistinguishable” from those of a standard rotating black hole.11The European Physical Journal C. Accretion disk around the rotating Damour–Solodukhin wormhole Differences in the luminosity profile do appear at extreme spin values, but the deviations are too tiny to observe with current technology for the parameter ranges allowed by existing observational constraints. In other words, if one of the objects we’ve been calling a supermassive black hole is actually a wormhole of this type, we probably wouldn’t know yet.
Other approaches look at the image itself rather than the accretion disk. A recent study of traversable wormhole images found that unlike black holes, whose images can extend beyond a certain critical boundary, wormhole images are confined within that boundary, producing smaller variations in the apparent position of the light centroid.12arXiv. Observational Signatures of Traversable Wormholes This is a potentially testable difference, but it requires the kind of angular resolution and image fidelity that pushes beyond what the Event Horizon Telescope currently delivers. Future upgrades and space-based extensions of the array may eventually reach the sensitivity needed to distinguish between these scenarios.
Wormholes and the Time Travel Problem
Almost as soon as traversable wormholes were proposed, physicists noticed a disturbing implication. If you could move one mouth of a wormhole at high speed relative to the other, time dilation from special relativity would cause the two mouths to age at different rates. Enter one mouth, and you’d emerge from the other not just at a different location but at a different time. In principle, you could arrange the geometry so that your exit precedes your entrance, creating a closed timelike curve: a path through spacetime that loops back on itself, allowing time travel into the past.
Recent theoretical work has extended this idea. A 2025 paper modeled a system of two coupled wormholes in a framework with opposing causal orientations, one bridge with ingoing causal flow and one with outgoing flow. By composing a traveler’s path through both bridges, the authors constructed a complete closed timelike curve where the traveler returns to their starting event, with the entire worldline remaining physical throughout.13arXiv. Closed timelike curves in 𝒫𝒯-symmetric wormholes The model adheres to Novikov’s self-consistency principle, which demands that any time-travel scenario must be internally consistent: you can’t go back and prevent the trip from happening in the first place.
Stephen Hawking famously proposed the “chronology protection conjecture,” suggesting that the laws of physics conspire to prevent time travel. Analysis of the specific case of wormhole-based time machines supports this intuition. As a wormhole approaches the conditions needed to create a time loop, quantum effects like the Casimir effect and gravitational back-reaction grow rapidly. A detailed study showed that in the class of wormhole models examined, the gravitational back-reaction becomes large enough to disrupt the wormhole before the relevant quantum gravity scale is reached, supporting Hawking’s conjecture.14Physical Review D. From wormhole to time machine: Comments on Hawking’s Chronology Protection Conjecture In short, general relativity’s equations permit time loops involving wormholes, but quantum effects may act as a kind of cosmic censor, destroying the wormhole before paradoxes can arise.
Wormholes in Cosmology
Most wormhole discussions focus on objects you might encounter or create. But some researchers have asked whether wormholes could have formed naturally in the early universe, when conditions were far more extreme than anything found today. In the first fractions of a second after the Big Bang, energy densities and spacetime curvatures were enormous, and quantum gravitational effects that are negligible today may have been dominant.
One line of theoretical work has explored whether a primordial wormhole embedded in an expanding universe could grow along with the cosmic expansion. Analysis has shown that above a certain threshold, solutions exist for self-similar cosmological wormholes connecting two large-scale regions: one with a standard expanding cosmology and one with an approximately similar expansion.15IOP Publishing (Classical and Quantum Gravity). Can a primordial black hole or wormhole grow as fast as the universe? If such objects formed and survived to the present day, they could potentially link regions of the universe that are otherwise causally disconnected, separated by distances that light hasn’t had time to cross since the Big Bang.
Primordial wormholes remain entirely hypothetical, with no observational evidence for them. But the theoretical possibility matters because it connects wormhole physics to cosmology and to questions about the large-scale structure of the universe. If wormholes can form naturally, they wouldn’t require an advanced civilization to build them. They’d be features of the landscape, like mountains or rivers, waiting to be discovered.
What Would Traveling Through One Actually Involve?
Science fiction typically shows wormhole travel as a brief, dramatic visual experience: a swirling tunnel, some turbulence, and then you’re at your destination. The physics is more sobering. Even setting aside the question of whether a traversable wormhole can exist, the conditions a traveler would experience depend enormously on the wormhole’s size and geometry.
Tidal forces are the primary concern. Just as the difference in gravitational pull between your head and feet becomes devastating near a stellar-mass black hole, a small wormhole would stretch or compress a traveler beyond any survivable limit. For a human to pass through comfortably, the wormhole’s throat would need to be large enough that the curvature of spacetime across the span of a human body remains gentle. Researchers have worked out the parameters needed for what they call “humanly traversable” wormholes. The throat radius would typically need to be on the order of astronomical units, not meters, and the exotic matter requirements would scale accordingly. The energy needed to maintain such a structure would be negative and comparable in magnitude to stellar masses, a quantity far beyond anything even conceptually within reach of current or foreseeable technology.
Transit time is another consideration. In many traversable wormhole geometries, the trip through the throat could be nearly instantaneous from the traveler’s perspective, but the clocks of distant observers might register a much longer interval. In some configurations, the time experienced by the traveler and by an external observer are both short, making the wormhole genuinely useful as a shortcut. In others, the external time penalty is large enough that the shortcut advantage vanishes. The specific answer depends on the geometry chosen, and there’s no single “wormhole travel time” any more than there’s a single “airplane travel time” without specifying the route.
Radiation is a further hazard. Any light, particles, or cosmic rays that happen to be funneled into the wormhole throat from the other side would be encountered by the traveler. Depending on the wormhole’s environment, this could range from harmless to lethal. A wormhole mouth near an active galactic nucleus would channel vastly more energy through its throat than one floating in the void between galaxies.
Why Physicists Keep Working on Something That Might Not Exist
Given all the obstacles, why do hundreds of papers on wormholes appear in serious physics journals every year? The answer is that wormholes have become indispensable tools for understanding the structure of physical theories themselves, regardless of whether they turn out to be real objects. The exotic matter requirement revealed deep truths about energy conditions in general relativity. The ER=EPR conjecture is reshaping how physicists think about the relationship between quantum mechanics and gravity. The quantum processor experiments are testing ideas about holography and emergent spacetime that would be inaccessible through any other approach.
Wormholes also serve as stress tests. When a theory of gravity allows traversable wormhole solutions, physicists can examine whether those solutions lead to paradoxes, instabilities, or violations of fundamental principles. The chronology protection conjecture, for instance, only emerged because traversable wormholes raised the question of time travel in a precise, calculable way. Each new modified gravity theory that permits wormhole solutions gets pressure-tested: does it also permit nonsensical results, like perpetual motion or faster-than-light communication? If so, the wormhole solution acts as a warning flag about the theory itself, pointing to where it might break down. In this way, studying wormholes is less about building one and more about mapping the boundaries of what physics allows.