We simplify the formalism of Polder and Van Hove [Phys.Rev.B {\bf 4},
3303(1971)], which was developed to calculate the heat transfer between
macroscopic and nanoscale bodies of arbitrary shape, dispersive and adsorptive
dielectric properties. In the non-retarded limit, at small distances between
the bodies, the problem is reduced to the solution of an electrostatic problem.
We apply the formalism to the study of the heat transfer between: (a) two
parallel semi-infinite bodies, (b) a semi-infinite body and a spherical body,
and (c) that two spherical bodies. We consider the dependence of the heat
transfer on the temperature T, the shape and the separation d. We determine
when retardation effects become important.Comment: 11 pages, 5 figure