In satellite imagery, Earth has sometimes been called a “blue marble.” When lit by sunlight, our planet’s watery surface shines blue. On the nightside of Earth, things look different. Using satellite imagery and computer algorithms, NASA’s Black Marble lets us see Earth as illuminated by the lights of humanity.
These images of Earth at Night are beautiful, but studying electric lights from space also has some important applications. We can watch cities grow, see populations change, and, during natural disasters, track where power has been lost.
After Hurricane Maria, lights in Puerto Rico went out, making it possible to identify where the power grid was still functioning and determine which regions were affected the most. NASA researchers were able to use this data to literally watch the lights switch back on, highlighting areas where resources were being restored and areas that still needed help.