Type IA Supernovae & the Accelerating Universe

Work by two independent research teams -- the Supernova Cosmology Project and the High-Z Team -- has shown evidence using Type Ia supernovae at <z> ~ 0.5 that the expansion of the universe is accelerating. Observations of the CMB and cluster abundances confirm these findings, while new tests have strengthen the case for Type Ia supernovae as reliable distance indicators. In addition to reviewing these findings, this talk will discuss programs which are now being developed to obtain much tighter cosmological constraints using Type Ia supernovae, and which should also lead to a much better understanding of their behavior.