  General formalism of quantum field theory and addition theorem for Bessel
functions are applied to derive formula for Casimir-Polder energy of
interaction between a polarizable particle and a dilute dielectric ball. The
equivalence of dipole-dipole interaction and Casimir energy for dilute
homogeneous dielectrics is shown. A novel method is used to derive Casimir
energy of a dilute dielectric ball without divergences in calculations.
Physically realistic model of a dilute ball is discussed. Different approaches
to the calculation of Casimir energy of a dielectric ball are reviewed.
