Street lamps, house lights and neon signs; lights in stores and office blocks; floodlights at sporting venues and on historic buildings. If the entire world were in darkness at the same time this is how the villages, towns and cities of Planet Earth would light up the night sky.
This striking image (click to enlarge) comes courtesy of NASA and was created with data from the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS).
Originally the OLS was designed in order to be able to view clouds by moonlight, but it is also used to map the locations of permanent lights on the Earth’s surface.
The earliest cities sprang up along coastlines and, across the millennia, their growth followed transportation networks of rivers, canals, roads and railways. Even if the underlying map were missing from this image, it would still be possible to trace the outlines of most of the world’s continents.
The interstate highways of the USA form an intersecting maze joining one city centre to another; while in Russia, the Trans-Siberian railroad is a brilliant dot-to-dot line that runs from Moscow through the centre of Asia to Vladivostok.
And yet there are still whole swathes of land where electricity has yet to shed any illumination: the Arctic and Antarctica; the jungles of Africa and South America; the forests of Canada and Russia; the towering mountain ranges of the Himalaya and the desert lands of Africa, Arabia, Australia, Mongolia, and the United States.
The result is a complex portrait of both the reach and the limit of man's presence on the blue planet...
You can read more about this photograph in a three-page NASA article Bright Lights Big City and download your own copy (it makes an impressive desktop picture) at Visible Earth.
[Image credits: Data courtesy Marc Imhoff of NASA GSFC and Christopher Elvidge of NOAA NGDC. Image by Craig Mayhew and Robert Simmon, NASA GSFC.]