Cover Pictures

Front Cover:The anisotropy of the temperature of the cosmic microwave background radiation, as mapped by the Differential Microwave Radiometer on NASA's Cosmic Background Explorer Satellite. Red shades represent hotter fluctuations, and blue and black shades represent cooler fluctuations. (Courtesy of the COBE team and NASA.)

Back Cover: Looking back in time with NASA's Hubble Space Telescope (HST). The HST's Wide-Field Planetary Camera (WFPC2) captured this image of galaxies as they were billions of years ago. Many oblects are irregular and ill-formed compared to nearby galaxies, showing the evolution of forms of galaxies between the distant past and times closer to the present. The size of the image is 75 arc seconds, and the total exposure time is 15 hours. (Courtesy of Edward Groth, Jerome Kristian, and members of the WFPC2 team.) Click on the image to view the full size version 10 in. x 10 in. (301 K)