The Cosmic Microwave Background as a cosmological probe

Observations of the Cosmic Microwave Background (CMB) have already proven to be a powerful probe of physical conditions in tile early universe (z similar to 10(3)). These observations have made precision tests of tile standard cosmological model and appear to confirm that we live in a bizarre universe mostly composed of dark matter and dark energy. Over the next several Years, new experiments will make high resolution measurements of the microwave background. These measurements use the microwave background as a "backlight" for studying the universe at low redshift. The scientific value of these high resolution CMB observations will be significantly enhanced by cross-correlating these observations with optical, radio and X-ray observations.