Dark Skies

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Why Dark Skies are Important

You don't need to be an astronomer for dark skies to be important.

Dark night skies are a vanishing natural resource. A generation ago, most Americans could still see the Milky Way from their own backyard. Now that is true for less than half of all Americans. If present trends continue, our grandchildren may be able to see few if any stars at all!

Loss of dark night skies is caused by light pollution. Light pollution is artificial light (streetlights, signs, outdoor residential lighting, etc) that shines upward. Any light that shines upward is wasted energy. In the United States, we pay over $1.5 billion (yes, billion) per year for electric energy on light that is wasted by shining into outer space. Much of this wasted light is reflected within the earth's atmosphere, causing the night sky to become brighter and brighter. This, in turn, washes out our view of the stars and our home galaxy, the Milky Way. There are now only a very few spots east of the Mississippi River in the U.S. that are still truly dark, and these spots are endangered. Dark skies are more common in the western U.S., but are also dwindling.

The wasted electric energy that powers lights that shine upwards must be generated by electric generating power plants. These plants often use non-renewable energy sources such as nuclear fuels, oil, natural gas, or coal. In the case of fossil-fueled plants, burning these fuels causes additional air pollution. All this to power lights that shine upwards into the atmosphere and into outer space.

This waste is unnecessary. Properly designed and appropriate outdoor lighting shines downwards, putting the light where it is needed, and often uses less energy than poorly designed outdoor lighting. In addition, poorly designed outdoor lighting creates a safety hazard by causing glare. Glare is light that shines directly from the source (the bulb) into one's eyes. A common example is an unshielded streetlight. When the human eye is exposed to an unshielded streetlight, the iris automatically contracts. This means that the areas that are intended to be lit (the area under the streetlight) appear to be darker, since the smaller pupil size allows less light to enter the eye. A properly shielded streetlight prevents glare, allowing the eye to see better the area that is intended to be lit.

Likewise, residential lighting is most effective when it shines only where it is intended. All-night backyard lighting is rarely needed. Where lighting is needed for security, a motion-sensor activated light is much more effective. Continuous lighting lights the scene for the criminal. Absent continuous lighting, the criminal can not see, and must provide his own lighting, usually in the form of a flashlight, which draws attention to him from neighbors and the police. A motion-sensor activated light also acts as an alert to suspicious activity versus the continuous light which burns all night. The glare from poorly designed security lighting causes dark shadows that provide easy cover for the criminal. Well designed (shielded) security lighting lights the scene, rather than causing glare that easily masks criminal activity.

Good lighting provides for energy conservation and lower operating costs, a more aesthetic appearance, improved security and safety, and darker skies from less light that escapes upward. Good lighting can be installed at an initial cost that is only slightly greater than "bad" lighting, and its lower operating costs more than make up for its slightly higher initial costs.

Even if you don't care a lick about seeing the stars or the Milky Way, there is still good reason to push for better outdoor lighting. Each year, hundreds of millions of taxpayer dollars are spent on spewing light into outer space. Yes, your taxes pay for the electricity to power the streetlights and lights on government buildings that shine out and up (instead of down). Unless you think that spending tax dollars to shine light into outer space is a good way to spend your money, you should be in favor of good outdoor lighting practices.

There is much each person can do to fight light pollution. Ask your community representative to work for full cut off (FCO) streetlights. FCO streetlights put the light on the ground, where it is needed, rather than upward into the sky or sideways (into drivers' eyes). Don't leave your outside lights on all night. Where security lighting is needed outdoors, use properly shielded lights that light the scene and don't blind neighbors and the police, and use motion-sensor activated lighting rather than continuous lighting. Remember - when it is dark, the criminal can't see either without a flashlight. And when the criminal must use a flashlight, it is a like a an arrow pointing right to him that says "something suspicious is going on here".

Here is a link to a handout on good and bad lighting fixtures: Good lighting practices

Support the International Dark-Sky Association (IDA), which works for quality outdoor lighting and preserving the view of the nighttime heavens for our children and their children.

Link to photos of really bad lighting in my home town

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