  The zero-point radiation is an electromagnetic form of energy pervading the
universe. Its existence is granted by standard quantum theories. We provide
here an explanation based on deterministic classical electrodynamics, by
associating to particles and nuclei a series of shells, made of constrained
photons, with frequencies decaying with the distance. Such photons are part of
a pre-existing background, evolving in vacuum even at zero temperature, and are
captured by stable subatomic particles to form very distinctive quantized
patterns. The evolving shells bring, for instance, to the creation of a
fractal-type structure of electromagnetic layers around a conductive body. This
property is then used to justify, both qualitatively and quantitatively, the
attractive Casimir force of two metal plates. The analysis is carried out by
standard arguments, except that here the surrounding zero-point energy is
finite and, albeit with a very complicated appearance, very well-organized.
