The Big Bang theory proposes that the universe we know emerged from a uniformly hot and impenetrable mass of protons, electrons and radiation. But until recently, we knew very little of the first stages of the 13 billion year process in which our cosmos took shape. In 1974, a young astrophysicist, John Mather of Columbia University's Goddard Center for Space Studies, devised a proposal for a satellite, the Cosmic Background Explorer (COBE), to measure the microwave background radiation in space. From temperature variations in the radiation emanating from different points in the universe, he hoped to trace the paths of the infant galaxies from their starting point. Mather persuaded NASA to undertake the mission, and was hired by NASA's Goddard Space Flight Center to guide the project. For the next decade and a half, Mather led a team of over 1,000 scientists and engineers, designing and building the exquisitely calibrated instruments such an experiment required. In 1989, COBE was launched into space. By 1992, Mather had found what he was looking for: cool trails etched in the otherwise uniform background, precisely the 'blackbody' patterns predicted by the Big Bang theory. Mather's discovery has been hailed as 'the missing link in cosmology.' The Royal Swedish Academy of Sciences praised Mather for elevating cosmology to a precision science, and honored his achievement with the Nobel Prize. Adam Riess was a doctoral candidate in astrophysics at Harvard when he devised a more accurate method for measuring the position of the exploding 'white dwarf' stars known as Type 1a supernovae. In 1998, he joined the High-Z Supernova Search Team, an international effort monitoring Type 1a supernovae to measure the expansion rate of the universe. Physicists long believed that the expansion of the universe was gradually slowing. Riess and his colleagues determined that the stars are, in fact, moving outward at an ever more rapid rate. The expansion of the universe is not slowing, but accelerating. This momentous discovery has spurred a massive surge of research in the 'dark energy' that propels this expansion. In honoring 41-year-old Adam Riess with the 2011 Nobel Prize in Physics, the Swedish Academy noted that the field of cosmology had been 'shaken at its foundation' by his discoveries. In this podcast, John Mather and Adam Riess, discuss the past and future of the universe and the theory of dark energy. It was recorded at the Top of the Hay in the Hay-Adams Hotel, during the 2012 International Achievement Summit in Washington D.C.