In physics, the Casimir effect and the Casimir-Polder force are physical forces

arising from a quantized field. The typical example is of two uncharged metallic plates in a vacuum,

placed a few micrometers apart, without any external electromagnetic field.

In a classical description, the lack of an external field also means that there is no field between the plates,

and no force would be measured between them.

When this field is instead studied using quantum mechanics,

it is seen that the plates do affect the virtual photons which constitute the field, and generate a net force

—either an attraction or a repulsion depending on the specific arrangement of the two plates.

This force has been measured, and is a striking example of an effect purely due to second quantization.

Although the Casimir effect can be expressed in terms of virtual particles interacting with the objects,

it is best described and more easily calculated in terms of the zero-point energy

of a quantized field in the intervening space between the objects.

In modern theoretical physics, the Casimir effect plays an important role in the chiral bag model of the nucleon;

and in applied physics, it is becoming increasingly important in the development of the ever-smaller,

miniaturised components of emerging microtechnologies and nanotechnologies.

The Casimir effect is an outcome of quantum field theory,

which states that all of the various fundamental fields, such as the electromagnetic field,

must be quantized at each and every point in space.

Casimir effect and wormholes

Exotic matter with negative energy density is required to stabilize a wormhole.

Morris, Thorne and Yurtsever pointed out that the quantum mechanics of the Casimir effect

can be used to produce a locally mass-negative region of space-time,

and suggested that negative effect could be used to stabilize a wormhole to allow faster than light travel.

This was used in the novel Warp Speed by Travis S. Taylor.

Analogies

A similar analysis can be used to explain Hawking radiation

that causes the slow "evaporation" of black holes

(although this is generally visualised as the escape of one particle from a virtual particle-antiparticle pair,

the other particle having been captured by the black hole).

Reversal

Through the use of a perfect lens

(one with the ability to focus an image with resolution unrestricted by the wavelength of light)

with a negative refractive index,

the effect can be reversed, causing small objects to be repelled rather than attracted.

However, because of the scale at which the effect applies,

its applications are most likely to be found in nanotechnology.

According to Professor Ulf Leonhardt and Dr Thomas Philbin of the University's School of Physics & Astronomy,

it is theoretically possible to levitate objects as big as humans,

but scientists are a long way from developing the technology for such feats.