  The magnitude of the strong interaction is characterized by $\alpha_s$, the
coupling parameter in Quantum Chromodynamics (QCD), a parameter with an
unexplained value in the Standard Model. In this paper, a candidate explanation
for $\alpha_s$ is derived from (1) the lifetime of quark-antiquark pairs in
vacuum fluctuations given by the Uncertainty Principle, (2) the variation of
$\alpha_s$ as a function of energy in QCD, and (3) classical relativistic
dynamics of the quarks and antiquarks. A semiclassical model for heavy
quark-antiquark vacuum fluctuations is described herein, based on (2) and (3).
The model in this paper predicts the measured value of $\alpha_s(M_{Z^0})$ to
be 0.121, which is in agreement with recent measurements within statistical
uncertainties.
