LOR-4: The Scharnhorst effect and OPERA

The one reported superluminal velocity in the literature was an instrument error, and the one calculated is unmeasurable and causally harmless.

Kind: constraint · Family: LOR (Kinematics) · Last reviewed: 2026-09-12

The result

The Scharnhorst effect: light propagating perpendicular to Casimir plates has a phase velocity exceeding c by a fraction of order 10^-32 for micron plates, falling as the fourth power of the gap, and too small by many orders of magnitude to measure. Liberati, Sonego and Visser show the effect is benign and constrained so as not to lead to causality violation. The OPERA superluminal-neutrino anomaly of 2011 was traced to a mis-seated optical fibre connection and an oscillator frequency offset; the corrected result, consistent with c, is the published paper. Nothing was retracted

What it forbids or costs

The one reported superluminal velocity in the literature was an instrument error, and the one calculated is unmeasurable and causally harmless

Escape hatches

None

Who it bites

Physics proposals

• SATISFIES: Lorentz-violating frameworks (the Standard-Model Extension and Hořava-Lifshitz gravity). The frameworks contain the Scharnhorst shift as a coefficient and absorbed the OPERA episode as a bound; every measured coefficient in the Kostelecký and Russell tables is consistent with zero, which is what the entry's two cases say.
• SATISFIES: The OPERA superluminal neutrino (2011). This is the entry carrying the verified account: fibre connection plus oscillator offset, corrected not retracted, consistent with c; its other half, the Scharnhorst effect, is the calculated superluminal velocity that nobody can measure.
• SATISFIES: The Scharnhorst effect. This is the entry: magnitude of order $10^{-32}$ for micron plates, unmeasurable, causally harmless. The entry's other half, the OPERA neutrinos, was an instrument; this was a calculation
• SILENT: White et al. 2021: the worldline-numerics Casimir pattern. Light between Casimir plates is the Scharnhorst case, a phase velocity above $c$ by a part in $10^{32}$, unmeasurable and benign; the paper proposes to time photons through a Casimir structure and never mentions it

Fictional drives

• SILENT: Mass Effect: element zero and the FTL drive (BioWare, 2007). The claim that the field raises the speed of light within it is a Scharnhorst-type claim made without a mechanism; the setting never says how a vacuum's light speed is changed.
• ENGAGES: Death's End: curvature propulsion (Liu Cixin, 2010). The trails are the Scharnhorst effect reversed: a vacuum whose light speed is set by its state. The novel engages the idea on the page, with death lines at zero lightspeed and the black domain at 16.7 km/s, without naming the physics.
• ENGAGES: EVE Online: the warp drive (CCP Games, 2003). A vacuum emptied of energy in which things move faster than light is the Scharnhorst effect by description; the lore does not name it and the register puts the real effect at one part in $10^{32}$. Engaged in substance, not by name.
• ENGAGES: Futurama: the Planet Express ship's dark matter engines (1999 onward). "Scientists increased the speed of light in 2208" is a Scharnhorst-shaped claim made as a punchline: c as a number that can be changed. Engaged on screen, in one line, never again.

Sources

• Scharnhorst, Phys. Lett. B 236, 354 (1990), erratum 787, 204 (2018); Barton, Phys. Lett. B 237, 559 (1990); Liberati, Sonego and Visser, Ann. Phys. 298, 167 (2002), arXiv:gr-qc/0107091, and arXiv:quant-ph/0010055 eq. 65 for the magnitude; OPERA collaboration, JHEP 10, 093 (2012), arXiv:1109.4897, §6.1 ✓