Because of light pollution, when clouds roll in at night, city skies brighten instead of growing darker, researchers find. Here are photos of the artificial nighttime glow. [Read the full story about light pollution and cloudy nights. ]

Lighting the night

The Sony Center at Potsdamer Platz in Berlin. This is the brightest area (in terms of skyglow) in the entire city, according to Christopher Kyba, a light pollution researcher at the GFZ Center for Geoscience in Potsdam, Germany. (Photo credit: Christopher Kyba)

Berlin's nightlife

Clouds above Berlin glow orange and brighten the night sky because they are reflecting artificial light. (Photo credit: Christopher Kyba)

Natural glow

Nighttime clouds in Glacier National Park darken the sky. (Photo credit: Ray Stinson)

Dark stars

The darkest night sky measured in the study was at Kitt Peak National Observatory in Arizona. (Photo credit: Megan Gannon)

Night lights

A global map of night light sources assembled from data acquired by the Suomi NPP satellite. (Image credit: NASA Earth Observatory)

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