  We consider the classical and relativistic Vlasov-Poisson systems with
spherically-symmetric initial data and prove the optimal decay rates for all
suitable $L^p$ norms of the charge density and electric field, as well as, the
optimal growth rates for the largest particle position and momentum on the
support of the distribution function. Though a previous work \cite{Horst}
established upper bounds on the decay of the supremum of the charge density and
electric field, we provide a slightly different proof, attain optimal rates,
and extend this result to include all other norms. Additionally, we prove sharp
lower bounds on each of the aforementioned quantities and establish the
time-asymptotic behavior of all spatial and momentum characteristics. Finally,
we investigate the limiting behavior of the spatial average of the particle
distribution as $t \to \infty$. In particular, we show that it converges
uniformly to a smooth, compactly-supported function that preserves the mass,
angular momentum, and energy of the system and depends only upon limiting
particle momenta.
