  Current cosmological data indicate that our universe contains a substantial
component of dark vacuum energy that is driving the cosmos to accelerate. We
examine the immediate and longer term consequences of this dark energy (assumed
here to have a constant density). Using analytic calculations and supporting
numerical simulations, we present criteria for test bodies to remain bound to
existing structures. We show that collapsed halos become spatially isolated and
dynamically relax to a particular density profile with logarithmic slope
steeper than -3 at radii beyond r_200. The asymptotic form of the space-time
metric is then specified. We develop this scenario further by determining the
effects of the accelerating expansion on the background radiation fields and
individual particles. In an appendix, we generalize these results to include
quintessence.
