English: Map of the cosmic microwave background showing dipole anisotropy caused by the motion of the Sun and galaxy, produced using data from the WMAP satellite. The Doppler effect causes the measured temperature of the cosmic microwave background to be slightly higher in the direction of motion and lower in the opposite direction. On the map, blue corresponds to 2,721 K (2,448 °C; 4,438 °F) and red is 2,729 K (2,456 °C; 4,453 °F). The galactic plane corresponds to the central horizontal line, where the interference of the Milky Way can be observed.