Wilkinson Microwave Anisotropy Probe

The Wilkinson Microwave Anisotropy Probe (WMAP) is a NASA Explorer mission. It has produced a wealth of precise and accurate cosmological information. WMAP produced the first full-sky map of the microwave sky with a resolution of under a degree, about the angular size of the moon. The patterns in the map result from well-understood physical processes that happened when the universe was young. By matching the patterns in the map to the physics we know, WMAP has produced a convincing consensus on the contents of the universe, erasing lingering doubts about the existence of dark energy, and severely limiting the density of hot dark matter. WMAP has determined the age of the universe, the epochs of the key transitions of the universe, and the geometry of the universe, while providing the most stringent data yet on events in the first fraction of a second of the universe.

The Cosmic Microwave Background (CMB) radiation is the light left over from the Big Bang, shifted to microwave wavelengths due to the expansion of the universe. The whole universe is bathed in this afterglow light. This is the oldest light in the universe and has been traveling across the Universe for about 13.7 billion years. The light patterns across the sky encode a wealth of details about the history, shape, content, and ultimate fate of the Universe.