© NASA, WMAP Science Team.
This map shows the pattern of temperature variations in the cosmic microwave background (CMB) measured with the WMAP satellite. WMAP made a differential measurement of the CMB temperature with two sensitive radio antennae mounted with a fixed displacement between them. As the satellite rotated, the radio antennae traced out temperature variations in the entire sky. The largest temperature differences (between red and dark blue regions) are about 0.0004 K, and the characteristic angular size of the temperature variations is around 1 degree. The 1-degree scale of the temperature variations tells scientists that the geometry of the universe is flat, so = 1, and the overall pattern reveals that is 0.27. If = + , then , = 0.73 and dark energy makes up the bulk of the universe. (Unit: 11)