Quantum theory tells us that empty space is not truly empty, but rather contains an enormous amount of untapped electromagnetic energy known as zero point energy, or ZPE. Such energy can be traced to radiation from the fluctuating quantum motion of charged particles distributed throughout the universe. The ZPE is responsible for such diverse phenomena as the van der Waals forces of chemical attraction at absolute zero, the perturbation of atomic spectral lines known as the Lamb Shift, and the "Casimir Effect," a unique attractive quantum force between closely-spaced metal plates. Tests at the Los Alamos National Laboratory (LANAL) ) have verified the Casimir effect.

The energy associated with the ZPE is known to be essentially inexhaustible and ubiquitous, so a question that arises in the mind of the technologist is whether such energy can be "mined" for practical use and thereby constitute the "Holy Grail" of energy research. Although deferring for the present any technological considerations for actual application and use, Daniel Cole of IBM in Essex Junction, Vermont, and Harold Puthoff of the Institute for Advanced Studies in Austin Texas, have addressed this issue in a recent article entitled, "Extracting energy and heat from the vacuum" (Physical Review E. Vol. 48, p 1562). These researchers critically examined the underlying energetic and thermodynamic processes involved in such a concept and concluded that. in principle, proposals to extract energy from vacuum fluctuations do not violate any fundamental precepts and that the basic concept of the conversion of vacuum energy to other potentially useful forms of energy is a legitimate and viable principle. However, the remaining work will requires the demonstration that vacuum energy conversion can be developed as an energy source.

What is the Casimir Effect?

The Casimir effect is a small attractive force which acts between two close parallel uncharged conducting plates. It is due to quantum vacuum fluctuations of the electromagnetic field.

The effect was predicted by the Dutch physicist Hendrick Casimir in 1948. According to the quantum theory, the vacuum contains virtual particles which are in a continuous state of fluctuation (see physics FAQ article on virtual particles). Casimir realized that between two plates, only those virtual photons whose wavelengths fit a whole number of times into the gap should be counted when calculating the vacuum energy. The energy density decreases as the plates are moved closer which implies there is a small force. drawing them together.

The Casimir force between two plates of area A separated by a distance a can be calculated to be:

     pix pi h-bar c
  F = ----------- A
        240 a4

where h-bar is Planck's constant over two pi and c is the speed of light.

The tiny force was measured in 1996 by Steven Lamoreaux. His results were in agreement with the theory to within the experimental uncertainty of 5%

Particles other than the photon also contribute a small effect but only the photon force is measurable. All Bosons such as photons produce an attractive Casimir force while Fermions make a repulsive contribution. If electromagnetism was supersymmetric there would be fermionic photons whose contribution would exactly cancel that of the photons and there would be no Casimir effect. The fact that the Casimir effect exists shows that if supersymmetry exists in nature it must be a broken symmetry

According to the theory the total zero point energy in the vacuum is infinite when summed over all the possible photon modes. The Casimir effect comes from a difference of energies in which the infinities cancel. The energy of the vacuum is a puzzle in theories of quantum gravity since it should act gravitational and produce a large cosmological constant which would cause space-time to curl up. The solution to the inconsistency is expected to be found in a theory of quantum gravity.

References

H.B.G. Casimir, Proc. Kon. Ned. Akad. Wetensch. B51, 793 ( 1948)

S. Lamoreaux, Phys Rev Lett, 78, p5 (1996).