Vegetation, clouds, aerosols, snow and ice cover, and even faint atmospheric emissions (such as airglow and auroras) change the way light is observed in different parts of the world.

Satellite images of Earth at night -- often referred to as “night lights” -- have captured the curiosity of the public and have been a tool for fundamental research for nearly 25 years.

By studying Earth at night, researchers can investigate how cities expand, monitor light intensity to estimate energy use and economic activity, and aid in disaster response.

The East Coast is super bright from being heavily populated.

The most noticeable difference in the nighttime composite view of Chicago and surrounding areas in 2016 is lighting along a recently expanded section of Interstate 90. This part of the highway, the Jane Addams Memorial Tollway, links Chicago with Rockford, Ill., to the northwest.

In the years since the 2011 launch of the NASA-NOAA Suomi National Polar-orbiting Partnership (NPP) satellite, researchers have been analyzing night lights data and developing new software and algorithms to make night lights imagery clearer, more accurate and readily available.

Heavily populated areas are along the coast as seen in this image.