Casimir effect

The notion of Casimir interaction often conjures images of metallic plates in a vacuum, at absolute zero temperature. However, its origins trace back to an unexpected source: the study of colloid stability within the laboratories of Philips during the 1930s. Physicists Verwey and Overbeek found experimental evidence that, for long distances, the interaction energy seemed to deviate from the usual Van der Walls theory, from  r^-6 dependency, shifting to r^-7.

In response, physicist H. Casimir was invited to lend his expertise to untangle this enigma. Within the realm of colloidal systems, electromagnetic interactions, manifested as the well-known Van der Waals force, play a pivotal role in stability. Casimir's pivotal breakthrough lay in his incorporation of the finite speed of light into the problem formulation.

Within a year, Casimir revisited the problem, this time using the unexpected quantum vacuum fluctuations to reassert the same conclusion. From standard fourth-order perturbation theory, using quantum electrodynamics to vacuum fluctuation, thus giving rise to what is now known as the Casimir effect.