The Casimir effectgives rise to a force between close parallel uncharged conducting plates and arises from quantum vacuum fluctuations of the electromagnetic field.

According to the quantum theory, the vacuum contains virtual particles which are in a continuous state of fluctuation. Casimir realised 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 that there is a small force drawing them together.

The attractive Casimir force between two plates of areaseparated by a distancecan be calculated to be,

whereis Planck's constant andis the speed of light.

Sinceis in the denominator, the biggergets, the smaller the force will be; and because the force goes as the fourth power ofthe force decreases rapidly with increasingSupposeand