From the Atlantic earlier this year:
“Nothing tells us more about the spread of humans across the Earth than city lights.”
For three weeks spread out over April and October of this year, the Suomi NPP satellite (jointly of NASA and NOAA) scanned all the Earth’s land as it appeared at night. Scientists then mapped the satellite’s data — 2.5 terabytes of it — over an earlier Blue Marble image, transforming that picture’s daytime blues, browns, and greens into a nightime palette of blues, blacks, and gold.
The Suomi NPP’s Visible Infrared Imaging Radiometer Suite can detect lights as faint as a lone highway lamp — meaning pretty much any human outcropping where electricity runs. “Nothing tells us more about the spread of humans across the Earth than city lights,” says NOAA scientist Chris Elvidge. When you watch the video above (and do expand to full screen), you can see the at the horizon how the daylight masks human development, but as the land falls dark, the signals of our settlements glow bright, giving us, as NASA calls it, “a global view of the human footprint on the Earth.”