Cities at Night

Chicago at night

Chicago during day


To an observer in space, humanity’s footprints on the surface of the Earth are large and varied. They include the regular patterns of irrigated cropland, straight lines of roads and railways running across continents, reservoirs on river systems, and the cement rectangles of ports and seawalls along coastlines. But what about humanity’s signature footprint—cities? By day, cities viewed from space can blend into the countryside, or appear as gray smudges, depending on the style of development and size of the urban area.At night however, city lights present the space observer spectacular evidence of our existence, our distribution, and our ability to change our environment.
A few years ago, NASA and NOAA joined forces to present the first world map of the nighttime Earth using 9 months of data collected by the DMSP (Defense Meteorological Satellite Program) satellite from an altitude of 830 kilometers (1 kilometer is 0.62 miles) above Earth. That “Night Lights” map, widely distributed on the Internet, helped many people visualize the world’s distribution of people and cities.
http://earthobservatory.nasa.gov/Study/CitiesAtNight/ and many other cities at night. Earth never sleeps...

Orange sodium vapor lights illuminate the port facilities of Long Beach, California, supporting the round-the-clock operations of one of the world’s busiest commercial cargo ports.