The Casimir effect

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Keywords: Casimir effect, quantum mechanics, physics, non-energy conservation, plate, vacuum energy, zero point energy.

More: forum sciences et technologie

The Casimir effect is manifested in the form of a very small attractive force between two parallel metal plates immersed in a resonant cavity (sealed metal box) in the absence of electromagnetic field.

According to the classical theory of electromagnetism and classical mechanics, the two plates should remain immobile because reign in the cavity an absolute vacuum of any field. To move, the metal plates need energy they can not draw anywhere.

The Casimir effect is a pure result of quantum field theory. It was designed and calculated by the Dutch physicist Hendrik Casimir in 1948.

according to quantum field theoryThe electromagnetic field (and this is also applicable to all quantum fields) has different energy states. The state of lowest energy - the ground state - is the absence of energy quanta (photons in the case of the electromagnetic field) or in other words, the void. The first "excited" state is the state with an energy quantum or a photon. The second excited state is the two photons, and so on.

However, the representation given by the quantum theory of the empty fields is somewhat paradoxical. This vacuum is actually full of energy that is not "materialized" in the form of particles. However, for short periods, this energy can materialize in particles or quanta whose life span is very short. They are called virtual particles. Although still standing termed virtual, the effects of these quanta (photons in our case) are indeed real.

In the cavity, virtual quanta (virtual photons) therefore will spontaneously "emerge" of vacuum. The spectrum of wavelengths of these photons is continuous but the fact that the cavity is closed, most of the frequencies will be destructive and eventually only a few specific frequencies (called resonance modes) Will remain in the cavity. This is the classic phenomenon of resonance in a resonant cavity. The resonance modes are characterized in that the guide wavelength is an integer sub-multiple of the distance between the faces of the cavity. The number of allowed modes is thus proportional to the distance between the faces of the cavity.

In the configuration that interests us, he settled resonances between the faces of the cavity and the plates and between the plates themselves. If the distance between the plates is less than their distance from the faces of the cavity, then there will be more resonant modes between the faces of the cavity and the plates, between the plates themselves. Radiation pressure exerted on the faces "internal" plates is lower than that which applies to their "external" surfaces. This results in a very low force which brings the plates towards each other.

Although predicted for 1948, this effect has been observed experimentally for the first time only 1997.

To be rigorous, it would involve the quanta of all existing quantum fields. But these fields require a lot of energy to materialize out of the vacuum which results in a low probability of materializing associated quanta compared to the electromagnetic field. Therefore, their contribution to the Casimir effect is largely negligible.

The Casimir effect shows thatwith vacuum, it is possible to generate the movement. In this he is a major violation of conventional energy conservation principle and to measure how quantum physics can be confusing!


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