| Introduction |
| Casimir's Biography |
| Measurements |
| Zero Point Energy |
| Calculations |
| Fundamental Physics Links |
| ESA Programme |
| MEMS and NEMS |
Quantum mechanics was one of the most outstanding physical theories of the twentieth century. It revealed Nature at the microscopic scale as a strange and fascinating scientific object which seems to defy natural human intuition developed through our every day experience. Though this quantum character is present everywhere as the building block of the physical world, it seldom revels itself at a macroscopic level. The Casimir effect is one of those rare exceptions where a quantum effect can have significant consequences beyond the atomic level.
The simplest form of the Casimir effect was predicted in 1948 by
H.B.G. Casimir
and consists in the attraction between a pair of neutral, parallel conducting
plates placed in the vacuum. This attractive force has a purely quantum origin
and cannot be obtained using the classical description of electromagnetic field
since it is a direct consequence of the existence of
Zero-Point Fluctuations:
a turmoil of virtual particles that come in and out of existence and that can
violate the energy-momentum conservation of the system for very short periods
of time, as described by Heisenberg's uncertainty principle. The fluctuating virtual particles
exert a "radiation pressure" on the plates which on average is greater outside
the plates than between them - as shown in the diagram.
Though the Casimir effect is expected to exist for any type of quantum field, in most cases this phenomena is considered for the electromagnetic field in view of the fact that this is the strongest fundamental interaction and it is the most likely to generate measurable effects.
It should be noticed that the prefix Casimir is now often used in wide range of effects related to Zero-Point Fluctuations, which extend far beyond the Casimir force and the initial Casimir effect. In fact, Zero-Point Fluctuations exist everywhere and are responsible for an infinite amount of energy in the universe, hence they may be expected to have vast bearing in many scientific problems.
An important characteristic of the Casimir effect is that it is a macroscopic quantum effect. For two plane parallel metallic plates of area of 1cm2 separated by a large distance (on the atomic scale) of 1 micron, the value of the attractive force is approximately 10-7N. This force is quite small but is now within the range of modern laboratory force measurement techniques.
The main feature of the Casimir force is its strong dependence on shape, switching from attractive to repulsive as a function of the geometry and of the coupling with the constraining objects. This makes the Casimir a strong candidate for applications in nano-technologies and micro or nanoelectromechanical devices (MEMS and NEMS).