WHAT ARE WE LEARNING FROM RHIC?

Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory on Long Island, New York, began operation in 2000 culminating over ten years of development and construction, and a much longer period of theoretical speculations about the properties of hot QCD matter produced in nuclear collisions in the collider regime. RHIC's 2.4mile rings contain superconducting magnets, which operate at minus 451.6 degrees Fahrenheit, 4.5 degrees above the absolute zero. RHIC collides two intersecting heavy ion beams at center-of-mass energy of up to 200 GeV/A (at luminosity of up to 1026sec-1cm2, which can be further increased in the future), and polarized proton beams at c.m.s. energy of up to 500 GeV. The total energy in the gold-gold collision thus reaches 40 TeV, which is at present the World's record collision energy. In the pp mode, the unique possibility offered by RHIC for the first time is the study of double spin asymmetries and other spin observables. This talk is an attempt to summarize some of the first results obtained at RHIC. The author discusses the significance of these measurements for establishing the properties of hot and dense QCD matter and for understanding the dynamics of the theory at the high parton density, strong color field frontier