Traversable Wormholes
A hypothetical tunnel through spacetime connecting two distant points. The ultimate shortcut — if they can exist. Current verdict: theoretically richer than ever, practically as far away as in 1988.
The Basics (Morris-Thorne, 1988)
Kip Thorne and Michael Morris asked: what would a wormhole need to be if a human could pass through it?
- A “throat” connecting two regions of spacetime — no event horizon (unlike a black hole)
- Held open by exotic matter — material with negative energy density, violating the Null Energy Condition (NEC)
- Throat size, tidal forces, and travel time are all tunable in theory
- The problem is always the same: where do you get the exotic matter?
The Exotic Matter Problem
For a human-traversable wormhole (throat ~1 meter), you need roughly a Jupiter-mass of negative energy. Known quantum effects that produce negative energy:
| Mechanism | Scale | Gap to Useful |
|---|---|---|
| Casimir effect | ~10^-32 meters | ~50+ orders of magnitude |
| Squeezed vacuum states | Transient, microscopic | ~50+ orders of magnitude |
| Ford-Roman quantum inequalities | More energy = shorter duration | Fundamental constraint |
The gap is not “hard engineering” — it’s ~10^50 times beyond anything achievable. This isn’t like building a bigger rocket; it may be a fundamental limit of nature.
Recent Theoretical Progress (2019-2026)
Gao-Jafferis-Wall (GJW) Mechanism (2016+)
In AdS/CFT holographic framework, coupling two boundary systems introduces a negative-energy shock that briefly makes a wormhole traversable. No bulk exotic matter needed — the effect arises from quantum entanglement between the two sides. Refined extensively through 2023-2025.
Maldacena, Milekhin & Popov (2020-2021)
Proposed a 4D traversable wormhole supported by Casimir-like energy from massless fermion fields threading the throat. Requires ~10^20 fermion species (not physically realistic), but proved solutions exist without hand-placing exotic matter.
The 2022 “Wormhole on a Quantum Computer” (Jafferis et al., Nature 2022)
What they did: Simulated a simplified SYK model (holographically dual to 1+1D gravity) on Google’s 9-qubit Sycamore processor. Sent a qubit through and observed dynamics matching the GJW traversable wormhole protocol.
What it actually means:
- Demonstrated quantum teleportation through a holographic wormhole dual
- It’s a simulation of quantum mechanics that maps to a gravitational wormhole via AdS/CFT
- No actual spacetime wormhole was created. No exotic matter involved.
The controversy: Kobrin et al. (2023) argued the simplified model lost its gravitational features — the observed dynamics were mundane quantum scrambling, not holographic traversal. By 2024-2025, consensus is cautious: interesting proof-of-concept, but the “created a wormhole” framing was overstated.
Stability Problems (Emparan et al., 2024)
Higher-dimensional wormhole solutions appear unstable to perturbations — they collapse into black holes when anything passes through. A serious additional barrier.
ER=EPR: Entanglement IS Geometry?
Maldacena & Susskind (2013) conjectured: every entangled particle pair (EPR) is connected by a non-traversable Einstein-Rosen bridge (wormhole). Entanglement is spacetime geometry at the quantum level.
Critical caveat: These wormholes are:
- Non-traversable by default (no-signaling theorem)
- Planck-scale — not macroscopic tunnels
- Making them traversable (GJW) requires classical interaction between both sides — which itself is limited to light speed
ER=EPR doesn’t provide a shortcut. If anything, it clarifies why wormholes are non-traversable by default.
What If They Worked?
| Destination | Through Space (0.9c) | Through Wormhole |
|---|---|---|
| dest-proxima-centauri | 4.7 years | Instantaneous |
| dest-trappist-1 | 44 years | Instantaneous |
| dest-andromeda | 2.82 million years | Instantaneous |
A working wormhole network would make every destination in the index equally accessible. It would also potentially enable time travel (closed timelike curves), which may be why physics forbids it.
Honest Assessment (2026)
Traversable wormholes are no closer to physical realization than in 1988. Our theoretical understanding is vastly richer — we know much more about how wormholes relate to quantum information, entanglement, and holography. But every advance has clarified how far we are from building one. The exotic matter problem is not a minor engineering challenge; it appears to be a fundamental constraint.
We don’t live in Anti-de Sitter space. Nearly all concrete wormhole constructions work in AdS. Our universe has a positive cosmological constant (de Sitter-like). Traversable wormholes in dS space are far less understood and may not exist.
See Also
- tech-alcubierre-drive — also requires exotic matter
- concept-relativistic-travel
- concept-time-dilation
- overview-distance-scales