WHAT IS LIGHT POLLUTION?

Light pollution is wasted artificial outdoor lighting in the natural environment. This is a manmade problem, caused by overly bright, outdoor lighting that shines when or where it is not needed. Light pollution alters the color and contrast of the nighttime sky, making it difficult or impossible to see natural starlight and impacting wildife. 

Light pollution generally falls into four categories: skyglow, light trespass, glare, and light clutter. It is a completely solvable problem, and you can avoid the following negative effects of light pollution by choosing the correct night sky friendly lighting when installing lighting features in your own backyard and within your community.

Credit: Gil Goldstein

Types of Light Pollution

Skyglow

Do you notice the hazy sky to the left in the “Before” image? When light shines upward into the night sky, it reflects off of particles in the atmosphere and creates a visible haze. This effect is called skyglow. Skyglow impedes the view of stars in the night sky for both humans and the many nocturnal animals that navigate by the stars.

Image: Todd Carleson

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Light Tresspass

When light shines across property lines, it is called light trespass. Shielding and aiming a light so that its throw ends at the property line is the best solution. 
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Image: ivinsnightsky.org

Light Clutter

Just as a countertop can become overwhelmed with clutter when things get busy, communities can also suffer from clutter. When big cities – or in some cases, small towns – are flooded with excessive amounts of artificial light, they develop light clutter. These sources of light are often confusing, cause unsafe glare, and lead to an inability to see far beyond the light sources.​

Image: Walton-Gray Marton

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Glare

Glare is caused by light shining directly from the source into the eye. It constricts our pupils and makes it harder to see into the shadows, decreasing visibility, often having the opposite of its intended effect.

Photo: Ken Walczak