  PHOBOS measurements of elliptic flow are presented as a function of
pseudorapidity, centrality, transverse momentum, energy and nuclear species.
The elliptic flow in Cu-Cu is surprisingly large, particularly for the most
central events. After scaling out the geometry through the use of an
alternative form of eccentricity, called the participant eccentricity, which
accounts for nucleon position fluctuations in the colliding nuclei, the
relative magnitude of the elliptic flow in the Cu-Cu system is qualitatively
similar to that measured in the Au-Au system.
