  Action at distance in Newtonian physics is replaced by finite propagation
speeds in classical post--Newtonian physics. As a result, the differential
equations of motion in Newtonian physics are replaced by functional
differential equations, where the delay associated with the finite propagation
speed is taken into account. Newtonian equations of motion, with
post--Newtonian corrections, are often used to approximate the functional
differential equations. Are the finite propagation speeds the origin of the
quantum mechanics? In this work a simple atomic model based on a functional
differential equation which reproduces the quantized Bohr atomic model is
presented. As straightforward application of the result the fine structure of
the hydrogen atom is approached.
