  We introduce a new asymptotic ansatz for spherical perturbations of the
Standard Model of Cosmology (SM) which applies during the $p=0$ epoch, and
prove that these perturbations trigger instabilities in the SM on the scale of
the supernova data. These instabilities create a large, central region of
uniform under-density which expands faster than the SM, and this central region
of accelerated uniform expansion introduces into the SM {\it precisely} the
same range of corrections to redshift vs luminosity as are produced by the
cosmological constant in the theory of Dark Energy. A universal behavior is
exhibited because all sufficiently small perturbations evolve to a single
stable rest point. Moreover, we prove that these perturbations are consistent
with, and the instability is triggered by, the one parameter family of
self-similar waves which the authors previously proposed as possible
time-asymptotic wave patterns for perturbations of the SM at the end of the
radiation epoch. Using numerical simulations, we calculate the unique wave in
the family that accounts for the same values of the Hubble constant and
quadratic correction to redshift vs luminosity as in a universe with seventy
percent Dark Energy, $\Omega_{\Lambda}\approx.7$. A numerical simulation of the
third order correction associated with that unique wave establishes a testable
prediction that distinguishes this theory from the theory of Dark Energy. This
explanation for the anomalous acceleration, based on instabilities in the SM
together with simple wave perturbations from the radiation epoch that trigger
them, provides perhaps the simplest mathematical explanation for the anomalous
acceleration of the galaxies that does not invoke Dark Energy.
