  The first three measurements from the RHIC program were results on global
observables: charged particle multiplicity (N_ch), transverse energy (E_T) and
elliptic flow (v_2). They offer a look at the large-scale features of particle
production in high-energy nuclear collisions, with particular insight into
entropy production and collective behavior. Results from all of the RHIC
experiments are discussed in light of data from lower energy nuclear collisions
as well as from high-energy hadronic collisions to test our current
understanding of the collision dynamics.
