Data courtesy Marc Imhoff of NASA GSFC and
Christopher Elvidge of NOAA NGDC.
Image by Craig Mayhew and Robert Simmon, NASA GSFC

When the lights go on it is easy to see
the world's cities - the brightest areas are the
most urbanized. At night their lights outline most
of the continents when viewed from space.
These images are composites of hundreds of pictures
made by orbiting satellites.