Extracting electrical energy from the vacuum by cohesion of charged foliated conductors
Robert L. Forward
Abstract and summary · read the original at the source · none found
In one page
Casimir predicted in 1948 that two conducting plates a whisker apart are pushed together by the zero-point fluctuations of the vacuum. Robert Forward, writing from Hughes Research Laboratories and the Air Force Rocket Propulsion Laboratory, asks the engineer’s question: can that pull be made to do useful work? His answer is a device he calls a vacuum-fluctuation battery. Stack ultrathin aluminium leaves a few micrometres apart, put the same positive charge on every leaf so that they repel each other, then trim the voltage until the electrostatic push is a shade weaker than the Casimir pull. The leaves drift together, the Casimir force does work against the electric field between them, and an active power supply takes that work out as electricity. Raise the voltage again and the stack re-expands, so the battery recharges. Forward’s own analogy is a hydroelectric dam: the foliated conductor is water held high, the vacuum field is the catalyst, and the servo-controlled leaves are the turbines.
Why it matters hereThis is the founding engineering proposal of chapter 6 — the first time the Casimir force was written down as a power-cycle component rather than a curiosity, by a working propulsion physicist with a contract number on the paper. Chapter 2 gains from it the precise boundary Forward himself drew: the vacuum field is almost certainly conservative, so what he designs is a battery that stores and returns energy, and the open question is what happens at plate separations nobody had yet measured.
What it claims
01The Casimir attraction is treated as a fundamental force of the vacuum rather than a material effect: it exists between any pair of conductors, it is independent of the metal the plates are made of, it is purely attractive, and it falls off as an inverse power of the separation — properties the paper explicitly compares with gravity. Forward quotes the standard reading of it as a zero-point pressure of electromagnetic waves, and notes that Lifshitz later extended the calculation to dielectrics.Section I, Casimir force, page 1700
Settled physics02The architecture is stated as an analogy that keeps the thermodynamics honest. A conductor prepared in a foliated state sits in a high vacuum-fluctuation potential-energy state because of its large surface energy; the Casimir force then converts that potential energy into kinetic energy as the leaves cohere into a solid block in a low state. Forward’s comparison is a hydroelectric dam, where gravity is the catalyst and the water’s starting height is the stored quantity — and where the dam is also used to store energy by pumping the water back up.Section on the vacuum-fluctuation battery, page 1701, the hydroelectric-dam passage
Designed, not yet built03The device itself is specified. A large number of leaves of ultrathin aluminium foil are stacked a few micrometres apart; each leaf is wired to an active bidirectional power supply and its shape and position are watched by sensors; the supply puts a small positive charge on every leaf so that electrostatic repulsion holds the stack open against the Casimir pull. That suspension is unstable, so each leaf is stabilised electronically by feedback from the position sensors, with the option of insulating frames of a material such as aluminium oxide giving partial mechanical support.Section on the vacuum-fluctuation battery, page 1701
Designed, not yet built04The cycle is run one leaf pair at a time, or all at once. Lower the voltage between the end leaf and its neighbour until the electrostatic repulsion is slightly less than the Casimir force at that distance; the two leaves are drawn together and do work against the repulsive field; by keeping the electric field always slightly below the Casimir force the bidirectional supply extracts electrical energy as the pair moves from wide separation to minimum separation. Repeat leaf by leaf until the foliated conductor is condensed into a solid block, or bring all the leaves together at once like compressing an accordion.Section on the vacuum-fluctuation battery, page 1701 to 1702
Designed, not yet built05It is a battery, and Forward says so in the paper’s own terms. If the collapse is halted before the aluminium films cohere, the device is recharged by making the applied electrostatic force slightly larger than the Casimir force, pushing the leaves apart at the cost of energy supplied from the bidirectional power supply. He also gives a second geometry that would be easier to fabricate and more stable — a wide flat spiral of foil built along the lines of a Slinky toy, where each turn acts against its neighbours so that only one conductor has to be contacted, and the spacing stays uniform through a large compaction.Page 1702 and Figure 1
Designed, not yet built06Two open questions are named, and both are experimental. First, no rigorous proof is known that the vacuum-fluctuation field is conservative like the gravity field; Forward judges it highly probable that it is, on the ground that otherwise one could design Casimir machines from which an infinite amount of energy could be extracted. Second, there were then no good measurements on metal plates in the one-to-twenty-nanometre range where theory predicts the crossover from the retarded law to the much stronger nonretarded van der Waals law — and he argues that molecular-beam-epitaxy monolayer deposition had just made plates flat enough to run that experiment below eight nanometres, where, if the very strong predicted forces appear, they may be a new source of energy.Section II, Experimental verification of the Casimir force, pages 1700 to 1701, and the conservative-field paragraph
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Read it · abstract
Abstract
Any pair of conducting plates at close distances (of the order of one micrometre) experience an attractive Casimir force that is due to the electromagnetic zero-point fluctuations of the vacuum. A “vacuum-fluctuation battery” can be constructed by using the Casimir force to do work on a stack of charged conducting plates. By applying a charge of the same polarity to each conducting plate, a repulsive electrostatic force will be produced that opposes the Casimir force. If the applied electrostatic force is adjusted to be always slightly less than the Casimir force, the plates will move toward each other and the Casimir force will add energy to the electric field between the plates. The battery can be recharged by making the electrical forces slightly stronger than the Casimir force to reexpand the foliated conductor.
Robert L. Forward, Hughes Research Laboratories, Malibu, California, and Air Force Rocket Propulsion Laboratory, Edwards Air Force Base, California. Physical Review B 30, number 4, pages 1700 to 1702, 15 August 1984. The article’s own printed abstract, with two scanning errors repaired and the micrometre symbol written out.
(Abstract only — see the rights note above. The three pages of derivation, the experimental review and the Slinky-spiral figure are at the source.)
Where this sits on the site. Cole and Puthoff’s 1993 Brief Report, the paper that took up Forward’s proposal and asked whether thermodynamics permits it at all, is at /library/stm-e61f12f673; their verdict was that in principle it is correct. Cole’s longer 1999 treatment of the same energy and entropy accounting is at /library/stm-b0a4676561. The measurement history Forward said was missing has since been made: Sparnaay’s first parallel-plate attempt of 1958, which he cites, is at /library/stm-2aa45438b3; Brown and Maclay’s 1969 image solution for the vacuum stress between plates is at /library/stm-726dc09a74; Bressi, Carugno, Onofrio and Ruoso’s 2002 return to the parallel-plate geometry is at /library/stm-208d347532; and Lamoreaux’s review of the whole experimental record is at /library/stm-4c6743a6b7. The line from this design to hardware runs through the Haisch and Moddel patent Quantum vacuum energy extraction, which cites this paper directly, and the survey Zero-Point Energy: Capturing Evanescence.
The way in
https://doi.org/10.1103/physrevb.30.1700PUBLICATION. Physical Review B, volume 30, number 4, pages 1700 to 1702, issue dated 15 August 1984; received 23 November 1983, revised manuscript received 16 April 1984. The author is printed as Robert L. Forward, Hughes Research Laboratories, Malibu, California 90265, permanent address, and Air Force Rocket Propulsion Laboratory, Edwards Air Force Base, California 93523. The paper’s own acknowledgment records support by Air Force Rocket Propulsion Laboratory contract F04611-83-C-0013 and by the Hughes Aircraft Company. YEAR. The library registry reached this sheet with a null year and the author’s name carrying a date; the year is 1984, confirmed on the Crossref record for this DOI, and both have been corrected here. LICENCE. Crossref registers only the APS default licence for the version of record, which is a publisher copyright and not a licence to readers, and Unpaywall and OpenAlex both report the article closed with no repository copy — so nothing beyond the article’s own abstract is reproduced on this page. WHAT WAS READ. The complete three-page article was retrieved on 2026-09-08 from the APS harvest full-text endpoint for this DOI, https://harvest.aps.org/v2/journals/articles/10.1103/physrevb.30.1700/fulltext, and read in full; every claim below cites the article’s own numbered section or named passage. The scan is an optical-character reading of the 1984 typesetting and its mathematics is damaged, so the equations are described in words here rather than transcribed, and the abstract below is the article’s printed abstract with two scanning errors repaired and the micrometre symbol written out in words — noted so that a reader comparing it with the source knows exactly what changed. RELATED PAGES: see the cross-links at the foot of this page.
How to cite it
Robert L. Forward (1984) Extracting electrical energy from the vacuum by cohesion of charged foliated conductors. doi:10.1103/physrevb.30.1700
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