Supernovae, Dark Energy, & the Accelerating Universe - What Next?
The Supernova Cosmology Project was surprised to discover that the expansion of the universe is not decelerating (as expected due to gravity), but accelerating. Apparently, some new, unidentified "dark energy" that pervades all space is accelerating the expansion. This is the first decade in which we can begin to address such fundamental physics questions with a variety of measurement techniques. We have been using Type Ia supernovae to track the past expansion of the universe and extrapolate its fate. We have now embarked on new studies using this approach to constrain possible theories of this dark energy, by improving both the statistical and systematic uncertainties of the supernova measurements. In particular, I will discuss the proposed new satellite, the Supernova / Acceleration Probe (SNAP), a 2-meter class telescope with a wide-field imager and optical-to-near-IR spectrograph system.