The Value of Night SkiesThe night skies in national parks are a protected park resource just like plants and animals. They are a natural resource; many natural processes rely on the cycle of light and dark. They are also a cultural resource. People have been viewing the skies for thousands of years and shaping beliefs, traditions, navigation, and wayfinding. Effects of Light PollutionLight pollution, defined as the excessive use of artificial light, obstructs the view of the Milky Way for 80 percent of Americans. Millions of people worldwide never experience the Milky Way, or even stars, from where they live.Light pollution affects more than just astronomers and night sky enthusiasts. It is a widespread challenge across the globe. Sky glow is the increase in the brightness of the night sky that can reduce visibility. Natural sources of sky glow exist, like a bright full moon, but human-made sources are the largest concern. Lights from homes, buildings, parking lots, stadiums, and businesses can increase sky glow and create the "dome" of light seen above populated areas. Nocturnal animals need darkness for survival. Light pollution can disturb natural behaviors such as hunting and migration. Circadian rhythms of humans and plants also rely on an unaltered night sky. Protecting Night SkiesThough light pollution is created by a multitude of lights, these problems can be resolved one light at a time. Measuring DarknessDark Sky designated locations typically use sky quality meters (SQMs) to measure the darkness of their sky. Readings are usually taken at zenith (the point in the sky directly overhead) and at four other slightly lower points in the sky. SQMs read sky brightness in magnitude per square arcsecond - the higher the number, the darker the sky. The highest possible reading is 23. Your Night SkiesWondering how you can help? Be an advocate for your night skies at home. Here are simple ways you can protect the night. Stargazing
Stargaze in an International Dark Sky Park! Learn about the best spots to view the stars and summer program offerings. NPS Night Skies
Learn more about ways the National Park Service protects night skies across the country. |
Last updated: September 23, 2024