You only have to walk outside at night, look up and not see the Milky Way to know that light pollution is a problem. And seen from space at night, the Earth’s surface glows with the light of millions of homes, buildings, cars and streetlights. Seen at night, our impact on the Earth is immediate and obvious.
A few years ago, NASA and NOAA compiled a complete world map of the nighttime Earth, using 9 months of data collected by satellites. This “Night Lights” image is pretty famous, and widely circulated around the Internet.
There’s a great article at NASA’s Earth Observatory that describes how they capture these night images of the Earth’s surface. You can also see many of the best images taken so far.