Chicago Skyglow in 2012. Credit: Bob Trembley

The Night Sky
A hundred years ago, you could go out on a clear night in the country and see two thousand stars with the unaided eye. Other objects like the Milky Way, planets, nebulae and star clusters were often visible. With binoculars or telescopes, more objects became visible.

In many locations, the number of visible stars has been reduced by half or more. Only the brightest objects are easy to see, the Milky Way and other dimmer objects are invisible.

Why Has This Happened?
These changes have occurred because of light pollution. The accumulated effect of countless lights in large cities (streetlights, car lights, lights from homes and businesses, etc.) drown out all but the brightest astronomical objects. Even hundreds of miles/kilometers from a big city or near smaller cities prominent glows appear near the horizon that block out the sky. Less obvious is a fainter glow over the entire sky that reduces the number of stars visible.

It is harder and harder to find isolated locations where dark skies still exist.

Light Pollution in lower Michigan in 2016. Credit: NASA/JPL-Caltech

What Can You Do About It?
Some lights at night are essential; lights allow us to live and work when the sky is dark; appropriate lighting may reduce crime. However lights are often brighter than they need to be. Inefficient lighting results in high electric bills and contributes to air pollution and similar problems. While lights can help people see at night, glare from lights that are too bright make it difficult to see.

The trick is to use just enough light to serve a particular need and send that light in the direction needed. Anything more is wasteful. If you are considering installing lighting, consider using the most efficient kind.

Many communities (such as Tucson, Arizona) have set up light pollution ordinances that allow lighting at night, but have guidelines that prevent wasteful lighting. Find out if your community has a light pollution ordinance. If not, bring this to the attention of your city government. The best approach is to mention the costs of electricity to city officials, you may be surprised the effect a single persistent individual can have.

Earth at Night

Earth at Night 2016 – Flat Map. Credit: NASA/JPL-Caltech.

To learn more, visit the International Dark-Sky Association.

Join the fight for sensible light in Washtenaw County

Share via Social Media! Use #AstronomyattheBeach


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