Throughout its 50-year history, NASA has studied our home planet
as much as outer space. Over the decades, Earth-observing
satellites have recorded the effects of seasonal changes,
storms, droughts, tsunamis, volcanic eruptions, and earthquakes.
Satellites have also shown us remote evidence of human activity,
such as agriculture, urbanization, and other land-use changes.
One of the most revealing aspects of human activity on Earth,
however, is not apparent under the bright light of the Sun; it
appears best in the dark of night. This image shows Earth’s
human-generated nighttime lights for the calendar year 2003,
based on observations by the Defense Meteorological Satellite
Program Operational Line Scanner. In this image, oceans appear
black, landmasses appear in varying shades of blue, and lights
appear yellow-white. Because these images focus on human impact,
they do not include other (natural) light sources. Besides
assembling cloud-free images, data visualizers carefully
excluded sunlight, moonlight, and l