Map of the universe. Computer-generated map of the universe showing galactic superclusters (yellow) separated by voids (black). This huge map, centred on the Earth, covers a sphere with a diameter of 1.4 billion light years, around a five thousandth of the observable universe. The positions of over 15,000 galaxies were measured by the satellite IRAS at infrared wavelengths. Galaxies are not scattered randomly through space, but are found in huge groups known as superclusters. Study of the sizes and shapes of the voids, in which galaxies are far more scarce, will give insight into the history, and the future, of the universe.