Remarkable progress has been made in the characterization of the cosmic microwave background radiation (CMB) over the last several years. It was nearly 30 years after the initial discovery of the CMB by Penzias and Wilson in 1965 before small differences in its intensity were measured by COBE and its spectrum was shown to be a blackbody to high precision. The finding helped motivate the inflation theory for the origin of the universe.
In the past few years, scientists have pursued a full accounting of the matter-energy densities of the universe, finding in agreement with the analysis of Type 1a supernovae observations that the universe is now dominated by some sort of “dark energy” that apparently is causing the expansion of the universe to accelerate.
While these measurements have led to rapid progress in our understanding of the universe, they have raised even more profound questions about the nature of dark energy and of the possibility of directly testing inflation and determining its energy scale. Remarkably, these questions can be addressed through future measurements of the CMB temperature anisotropy on fine angular scales and of the CMB polarization anisotropy on all angular scales; they form the basis of the scientific case for the South Pole Telescope (SPT) program.