A favorite activity of astronauts and cosmonauts aboard the International Space Station is looking at the city lights below when the Station crosses the Earth’s dark side. The lights outline the densest population centers and coastlines, and suggest cultural patterns.
From a geographic perspective, cities at night tell different stories about a region.
Tokyo, Japan
Cities from different regions of the Earth are also identified by differences in their nighttime lights. Japanese cities glow a cooler blue-green than other regions of the world. Newer developments along the shore of Tokyo Bay are characterized by orange sodium vapor lamps, while the majority of the urban area has light green mercury vapor lamps.
This astronaut photograph illustrates the Seoul urban area at night. Major roadways and river courses (such as the Han River) are clearly outlined by street lights, while the brightest lights indicate the downtown urban core (center of image) and large industrial complexes. One such complex is located at the far left of the image and occupies an island in the Yellow Sea. Very dark regions in the image are mountains or large bodies of water. Nighttime images have been used extensively in urban climate and urban growth research to map the extent of urban (bright) versus rural (dark) regions.
This nighttime view of the British capital offers unique insight into the city’s urban density and infrastructure as highlighted by electrical lighting. Interpreting the brightest areas as the most populated, the population density drops off rapidly from the bright urban center until it reaches the vicinity of the Orbital, an encircling roadway. Beyond lie isolated bright areas marking the numerous smaller cities and towns of the region and as far southeast as Hastings on the coast. Note London’s two major airports, Heathrow and Gatwick, and the particularly bright, sinuous stretch of the Orbital to the south of the city.
Chicago, Illinois, is home to roughly three million people, but the wider metropolitan area includes nearly 10 million. By night , the region’s ten million people cannot be missed. This picture was taken on October 7, 2003, with a 50 mm lens.
US / Mexico Border
Border cities like Ciudad Juaréz, Mexico, and El Paso, Texas, illustrate different city patterns side-by-side, suggesting cultural influences on the development and growth of cities and infrastructure. Ciudad Juaréz, supports at least 1,300,000 people. On the U.S. side of the Rio Grande, El Paso is marked by the brightly-lit Interstate Highway I-10 that cuts across the city. Although the area of El Paso, with an estimated population of slightly more than 600,000 is roughly on the order of the area of built-up Ciudad Juaréz, the density of settlement evidenced by the distribution of lights, is much less.
The rapid growth in Jiddah and Mecca in Saudi Arabia can be mapped from the lighting patterns, and the road connecting them stands out as a bright string in the surrounding dark desert.
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. This picture was taken on February 4, 2008, using the 400 mm lens, providing superior resolution.
From a geographic perspective, cities at night tell different stories about a region. City lights provide sharp boundaries that delineate the densest concentrations of people, a characteristic that has been used to assess the effect of urbanization on Earth’s ecosystems. The increased detail of city lights available from astronaut photography can help refine urban boundaries defined from satellite data. Transportation corridors and major commercial development, such as ports, shopping centers, and cultural icons—like the Las Vegas strip—jump out of the landscape.
This image shows the sprawling urban footprint of São Paulo, Brazil, South America’s largest city with roughly 17 million people. The different colors (pink, white, and gray) define different types and generations of streetlights. The port of Santos, on the right side of the photograph, is also well defined by lights.
Earth is becoming an urban planet. As more and more people move to cities, and the surrounding rural and suburban areas are increasingly developed, the pattern of lights in cities around the world will change. Individual city footprints will coalesce into ever larger bright blobs. More roads will connect those cities to form an illuminated, lace-like web on the habitable parts of the continents. Nighttime photographs from astronauts on upcoming missions will document these changes, providing dramatic illustrations for the continuing story of humanity’s footprints on the Earth.
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