Does the Casimir effect prove that vacuum fluctuations really exist ?
The Casimir effect seems to result from a change in the energy of vacuum fluctuations due to boundary conditions as if the structure of vacuum were “polarized” by the external perturbations represented by these boundary conditions. However, it is, in principle, possible to obtain the Casimir force without assuming the existence of vacuum fluctuations. For this purpose, let us consider the Casimir effect for two parallel dielectric slabs (the case of metallic plates would be the limiting case of dielectrics with infinite conductivity). There are Casimir-Polder forces among the atoms constituting the two slabs and these forces, as we have seen above, can be obtained by the use of the reaction or source field. Clearly, the sum of the Casimir-Polder forces between the slabs’ individual atoms should result in a nonvanishing force between the slabs. Unfortunately, this sum has not been calculated yet. The calculation is highly complicated because these long-range forces are non-additive. In
