The Aharonov-Bohm effect, sometimes called the Ehrenberg - Siday - Aharonov-Bohm effect, is a quantum mechanical phenomenon in which an electrically charged particle shows a measurable interaction with an electromagnetic field despite being confined to a region in which both the magnetic field B and electric field E are zero.
The Aharonov-Bohm effect shows that the local E and B fields do not contain full information about the electromagnetic field, and the electromagnetic four-potential, A, must be used instead. By Stokes' theorem, the magnitude of the Aharonov-Bohm effect can be calculated using A alone or using E and B alone. But when using E and B, however, the effect depends on the field values in a region from which the test particle is excluded, not only classically but also quantum mechanically. In contrast, the effect depends on A only in the region where the test particle is allowed. Therefore we can either abandon the principle of locality (which most physicists are reluctant to do) or we are forced to accept the realisation that the electromagnetic potential offers a more complete description of electromagnetism than the electric and magnetic fields can. In classical electromagnetism the two descriptions were equivalent. With the addition of quantum theory, though, the electromagnetic potential A is seen as being more fundamental or "real"; the E and B fields can be derived from the potential A, but the potential can not be derived from the E and B fields.
Werner Ehrenberg and Raymond E. Siday first predicted the effect in 1949, and similar effects were later rediscovered by Yakir Aharonov and David Bohm in 1959. (After publication of the 1959 paper, Bohm was informed of Ehrenberg and Siday's work, which was acknowledged and credited in Bohm and Aharanov's subsequent 1961 paper.) (WikiPedia)
See Also
2.22 - Voiding - an Effect of Desire and Will Force
15.24 - Water is Sensitive to Biometeorological Effects
Bohm Aharonov Effect
David Bohm
Etheric Elements
Neutral Center
Table of Cause and Effect Dualities