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Light Pollution

The sun, the moon and the stars would have disappeared long ago . . . had they happened to be within the reach of predatory human hands.
— Havelock Ellis, The Dance of Life, 1923

Less than 100 years ago, everyone could look up and see a spectacular starry night sky. Now, millions of children across the globe will never experience the Milky Way where they live. The increased and widespread use of artificial light at night is not only impairing our view of the universe, it is adversely affecting our environment, our safety, our energy consumption and our health.

What is Light Pollution?

Most of us are familiar with air, water, and land pollution, but did you know that light can also be a pollutant?

The inappropriate or excessive use of artificial light – known as light pollution – can have serious environmental consequences for humans, wildlife, and our climate. Components of light pollution include:

  • Glare – excessive brightness that causes visual discomfort
  • Skyglow – brightening of the night sky over inhabited areas
  • Light trespass – light falling where it is not intended or needed
  • Clutter – bright, confusing and excessive groupings of light sources
Light Pollution Diagram

The infographic above illustrates the different components of light pollution and what “good” lighting looks like. (Image by Anezka Gocova, in “The Night Issue”, Alternatives Journal 39:5 (2013). Click to enlarge.

Light pollution is a side effect of industrial civilization. Its sources include building exterior and interior lighting, advertising, commercial properties, offices, factories, streetlights, and illuminated sporting venues.

The fact is that much outdoor lighting used at night is inefficient, overly bright, poorly targeted, improperly shielded, and, in many cases, completely unnecessary. This light, and the electricity used to create it, is being wasted by spilling it into the sky, rather than focusing it on to the actual objects and areas that people want illuminated.

Glossary of Lighting Terms

How Bad is Light Pollution?

With much of the Earth’s population living under light-polluted skies, over lighting is an international concern. If you live in an urban or suburban area all you have to do to see this type of pollution is go outside at night and look up at the sky.

Before and during the 2003 Northeast blackout, a massive power outage affecting 55 million people. Courtesy of Todd Carlson

Before and during the 2003 Northeast blackout, a massive power outage that affected 55 million people. Photo by of Todd Carlson

If you want to find out how bad light pollution is where you live use the NASA Blue Marble Navigator for a bird’s eye view of the lights in your town or check out the Globe at Night interactive light pollution map data created with 8 years of data collected by citizen scientists.

NASA Blue Marble Navigator

NASA Blue Marble Navigator

Globe at Night light pollution map

Globe at Night light pollution map

Effects of Light Pollution

For three billion years, life on Earth existed in a rhythm of light and dark that was created solely by the illumination of the Sun, Moon and stars. Now, artificial lights overpower the darkness and our cities glow at night, disrupting the natural day-night pattern and shifting the delicate balance of our environment. The negative effects of the loss of this inspirational natural resource might seem intangible. But a growing body of evidence links the brightening night sky directly to measurable negative impacts including

Light pollution affects every citizen. Fortunately, concern about light pollution is rising dramatically. A growing number of scientists, homeowners, environmental groups and civic leaders are taking action to restore the natural night. Each of us can implement practical solutions to combat light pollution locally, nationally and internationally.

You Can Help!

The good news is that light pollution, unlike many other forms of pollution, is reversible and each one of us can make a difference! Just being aware that light pollution is a problem is not enough; the need is for action. You can start by minimizing the light from your own home at night. You can do this by:

  • Only using lighting that is needed
  • Using energy efficient bulbs
  • Installing motion detector lights and timers
  • Properly shielding outdoor lights
  • Keeping your blinds drawn to keep light glow inside
  • Becoming a citizen scientist and helping to measure light pollution

Learn more about Outdoor Lighting Basics

Then spread the word to your family and friends and tell them to pass it on. Many people either don’t know or don’t understand a lot about light pollution and the negative impacts of artificial light at night. By being an ambassador and explaining the issues to others you will help bring awareness to this growing problem and inspire more people to take the necessary steps to protect our natural night sky. IDA has many valuable resources to help you including: Public Outreach Materials, How to Talk to Your Neighbor, Lighting Ordinances and Residential and Business Lighting.

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