The ability of humans to produce light changed society. It allowed people to control the amount of light available to them independent of time of day, which lengthened the workday, created a new industry, and made way for other machines to enter homes as electric wiring became more available. However, humanity’s ability to light the night has had some consequences.

Light pollution, or artificial light at night, is the excessive or poor use of artificial outdoor light, and it has several forms: glare or overillumination, which is direct light from the fixture; sky glow or the human-created brightening of the night sky; light trespass that occurs when light hits areas not intended to be lit; and clutter, which occurs when lights are grouped in an excessive or confusing pattern. Largely a result of poor design where the light shines out or up in addition to its desired direction, light pollution disrupts the natural patterns of wildlife, contributes to the increase in carbon dioxide (CO2) in the atmosphere, disrupts human sleep, and obscures the stars in the night sky.

Light pollution impacts urban and suburban areas most severely and more than half of humanity lives in cities, a percentage the United Nations expects to increase. No matter where you live you can help lessen light pollution in your community by:

• Assessing the outdoor lights on your home or school, then change the design or advocate for a design update by talking to your guardian, property manager, or principal about eliminating some fixtures or replacing them with dark sky-friendly lighting.
• Spreading the word! Talk to your family, friends, neighbors, or share the word online to help raise awareness about the impacts light pollution has on the environment.
• Advocating for updated lights in your community. Do your research on areas where lighting can be improved and present your work to your local government officials.
• Becoming a citizen scientist and submitting measurements of the night sky brightness where you live to the Globe at Night project.

This map layer was created by the U.S. National Aeronautics and Space Administration (NASA) with data collected by satellites then corrected for factors such as cloud cover, vegetation, and land cover type. The data has been validated with measurements taken on the ground.