City Lights : This image of Earth’s city
lights was created with data from the Defense Meteorological
Satellite Program (DMSP) Operational Linescan System (OLS).
Originally designed to view clouds by moonlight, the OLS is also
used to map the locations of permanent lights on the Earth’s
surface. The brightest areas of the Earth are the most urbanized,
but not necessarily the most populated. Cities tend to grow along
coastlines and transportation networks; even without the
underlying map, the outlines of many continents would still be
visible. The Nile River, from the Aswan Dam to the Mediterranean
Sea, is another bright thread through an otherwise dark region.