ENE-6: The Casimir floor

The only negative energy anyone has ever made, and the only one anyone can point to, and it is tens of orders of magnitude short of any….

Kind: constraint · Family: ENE (Energy) · Last reviewed: 2026-09-12

The result

The Casimir effect is real negative energy density between conducting plates, measured to about 5%. Its magnitude is tiny: energy density −π²ħc/720d⁴, about −4 × 10^-4 J per cubic metre at one micron, falling as the fourth power of the gap

What it forbids or costs

The only negative energy anyone has ever made, and the only one anyone can point to, and it is tens of orders of magnitude short of any bill on this page

Escape hatches

None; this is a floor, not a ceiling

Who it bites

Physics proposals

• VIOLATES: Morris, Thorne and Yurtsever: the wormhole time machine (1988). The paper points to Casimir-type effects as the only known negative energy; the register's measured Casimir density is tens of orders of magnitude below the throat's requirement.
• VIOLATES: Morris–Thorne traversable wormhole (1988). The paper invokes Casimir-type quantum effects as the hint that exotic matter may exist; the register's measured Casimir density is some 35 orders of magnitude below the throat's $c^4/(8\pi G r_0^2)$ scale at 500 km.
• VIOLATES: Visser's thin-shell wormholes (1989). Visser tried to source the edge stress-energy from a Casimir energy and could not; the measured Casimir density is tens of orders of magnitude below the requirement.
• VIOLATES: White et al. 2021: the worldline-numerics Casimir pattern. The proposal is precisely to use Casimir energy as the bubble's source; the entry records the floor as tens of orders short of any bill, and the pillar's factor of 3 to 5 over $-1.7 \times 10^{-6}$ J m$^{-3}$ does not change that
• SATISFIES: Gao, Jafferis and Wall: traversable wormholes via a double-trace deformation (2017). The negative energy is Casimir-like in origin and magnitude, and the opening it buys is Planck-suppressed, consistent with the register's point that Casimir-scale negative energy buys nothing usable.
• SATISFIES: Maldacena, Milekhin and Popov: traversable wormholes in four dimensions (2018), and the humanly traversable sequel (2021). The negative energy is Casimir energy of massless two-dimensional fields on a circle, $-q/8\ell$; the construction lives entirely within the Casimir-scale negative energy the register says is the only kind anyone has, and pays for it with a throat of length $q^2 l_p$ and a large flux $q$.
• SATISFIES: The Scharnhorst effect. The effect is driven by exactly the energy density ENE-6 records, about $-4\times10^{-4}$ J per cubic metre at one micron, and inherits its fourth-power falloff with gap
• SILENT: Alcubierre 1994: the warp drive metric. The letter names the Casimir effect as the reason negative energy is not forbidden outright, and never prices it. ENE-6 puts the only negative energy ever produced at about $-4 \times 10^{-4}$ J per cubic metre at a micron gap, against wall densities that the inequalities push to Planck scale; the gap is tens of orders of magnitude and the proposal does not address it.
• SILENT: Bobrick and Martire 2021: physical warp drives. Mentions zero-point fluctuations only to say Alcubierre walls would need Planck thickness; never names a source for the negative density its axisymmetric members need
• SILENT: Everett and Roman 1997: the superluminal subway. The negative energy is assumed to come from a quantum field in some state (footnote 21 says the conclusion is unchanged for massive scalar or electromagnetic fields); no source at Casimir scale is proposed and the gap is not addressed.
• SILENT: Fell and Heisenberg 2021: positive energy from hidden geometric structure. No source is named for the negative pressures the paper admits it needs
• SILENT: Krasnikov 1998: the tube laid on the way out. No source is proposed for the negative energy; the Casimir floor is tens of orders of magnitude below any wall density and the paper does not address it.
• SILENT: Lentz 2021: hyper-fast positive-energy solitons. The paper's purpose was not to need a negative-energy source; with negative regions restored it names none, and the Casimir floor is the only one there is
• SILENT: NASA Eagleworks warp field interferometer. The only negative energy on offer, the Casimir floor, is not invoked; the documents speak of "negative vacuum energy" from q-thruster physics without a formula that general relativity recognises
• SILENT: Natário 2002: warp drive with zero expansion. The paper does not invoke a source at all; the only negative energy ever made (Casimir) is tens of orders of magnitude short of any wall density, and the gap is not addressed.
• SILENT: Van Den Broeck 1999: the pocket geometry. The Casimir effect is named as the reason the WEC may be violated quantum mechanically and never priced; the neck density of $10^{93}$ kg per cubic metre is about a hundred orders of magnitude above the Casimir floor and the paper does not address the gap beyond saying that generating enough negative energy remains a question.

Fictional drives

• SILENT: 2001: A Space Odyssey (1968): the Star Gate. No source of negative energy is named; the Casimir floor is not approached.
• SILENT: Battlestar Galactica: the FTL jump (2004 series). No source of negative energy is named.
• SILENT: Commonwealth: CST wormholes with trains through them (Hamilton 2004). No source of negative energy is named.
• SILENT: Contact: the Machine and the tunnel system (Sagan 1985, Zemeckis 1997). The Casimir effect is the only negative energy ever produced and it is tens of orders of magnitude short of any throat; the work never names a source for its exotic material beyond "somebody older built it".
• SILENT: Cowboy Bebop (1998): the astral gates. No source of negative energy is named; the Casimir floor is not approached.
• SILENT: Death's End: curvature propulsion (Liu Cixin, 2010). The trail is a vacuum with a changed light speed, which is what the Casimir vacuum is on a scale of one part in $10^{32}$; the novel never connects the two or prices the change.
• SILENT: Dune: the Guild navigators and folding space (Herbert 1965). No source of negative energy is named; the Casimir effect does not appear.
• SILENT: Event Horizon (1997): the gravity drive. The only real negative energy is Casimir's, and the film neither invokes it nor names any source for holding a gateway open.
• SILENT: Farscape (1999): wormholes, and starburst as a separate thing. No source of negative energy is named; the Casimir floor is not approached.
• SILENT: Guardians of the Galaxy Vol. 2 (2017): jump points. No source of negative energy is named; the Casimir floor is not approached.
• SILENT: Hyperion: the farcasters (Simmons 1989). No source of negative energy is named.
• SILENT: Interstellar: the wormhole near Saturn (2014). The Casimir effect is never mentioned; the film has no candidate source for negative energy beyond "they".
• SILENT: Mass Effect: the mass relays (BioWare 2007 onward). No source of negative energy is named.
• SILENT: Outer Wilds (2019): Nomai warp cores. No source of negative energy is named; the supernova is positive energy, and the Casimir floor is not approached.
• SILENT: Star Citizen: quantum drive and jump points. No source of negative energy beyond "quantum fuel" is named; the Casimir floor is not approached.
• SILENT: Starfield (2023): the grav drive. No source of negative energy is named; the Casimir floor is not approached.
• SILENT: Stargate: the gate network (1994 film, SG-1 1997 onward). No source of negative energy is named.
• SILENT: Stargate: the ships' hyperdrives. The ZPM's "vacuum energy" is the one place the series reaches toward the Casimir vacuum, and it never states a magnitude or a mechanism; the row applies to the claim and is never addressed.
• SILENT: Starman Jones: the congruencies (Heinlein 1953). No source of negative energy is named.
• SILENT: Super Dimension Fortress Macross (1982): the space fold. No source of negative energy is named; the Casimir floor is not approached.
• SILENT: The Alderson drive (Niven and Pournelle 1974). No source of negative energy is named.
• SILENT: The Expanse: the ring gates and the slow zone (Corey 2013 onward). No source of negative energy is named.
• SILENT: The Forever War: collapsar jumps (Haldeman 1974). No source of negative energy is named.
• SILENT: Thor (2011): the Bifrost. No source of negative energy is named; the Casimir floor is not approached by anything on screen.
• SILENT: Wing Commander (1990) and the 1999 film: jump points. No source of negative energy is named; the Casimir floor is not approached.
• ENGAGES: EVE Online: the warp drive (CCP Games, 2003). The depleted vacuum between two polar discs is the Casimir geometry described in the lore's own words: vacuum with its energy drawn out between two plates. The lore does not name Casimir and does not price the effect, which the register puts at $-4 \times 10^{-4}$ joules per cubic metre.

Sources

• Casimir, Proc. K. Ned. Akad. Wet. 51, 793 (1948); Lamoreaux, Phys. Rev. Lett. 78, 5 (1997), erratum 81, 5475 (1998) ✓