  We discuss several observables measured by PHOBOS that show common scaling
features in Cu+Cu and Au+Au collisions at RHIC energies. In particular, we
examine the centrality and energy dependence of the charged particle
multiplicity, as well as the centrality dependence of the elliptic flow at
mid-rapidity. The discrepancy between Cu+Cu and Au+Au of the final state
azimuthal asymmetry (elliptic flow), relative to the initial state geometry of
the collision, can be resolved by accounting for fluctuations in the
description of the initial geometry.
