The International Dark-Sky Association works to protect the night skies for present and future generations.

Light pollution is the presence of artificial light in the night environment

Light pollution can be detrimental to the health of people and animals in the area. 

Light pollution is excessive, misdirected, or obtrusive artificial (usually outdoor) light.

A video by National Geographic about light pollution.

Interactive world light pollution map. See what it looks like in your neighborhood.