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Information Si�eet 139 (July 1998) D?198 Page 1 of 4 International Dark Sky Association -- Information Sheet �39 Why Shoufd a City Government Be Concerned About Light Pol�ution? The public's loss of �he stars from �he nighttime sky is a real tragedy that eve�y city gavernment s�ould be aware of and not allow. This loss is a testament to our myopia and to our growing insulation from the natural world. Like the canary in the mineshafts of old, astronomers are warning us of the unnecessary loss of a dark n�ghttime sky in almost every urban area. Their warnings point to the probiem as well as revea�ing a missed opportuni�y. We have only b�en pitch�ng our tents for a little while in the land of power stations and industry, so it is no surprise that we are somet�mes blinded by its promise. Part of the advance of ou�c technological society has been a steady if sometimes intermittent advance in �he efficient uses of ene�rgy. However, when energy appears cheap, w� tend to waste energy rather than use less of i�. Light pollution represents a waste of a magnitude that almost no hoameowner would allow inside their homes. Interior ligh�s bounce off of a�l the room's suarfaces, providing for good general illum�na�ion. �nly small amoun�s of light will escape out of the windows. How strange it is, then, that when we attempt to light the outdoors, we often earelessly a1�ow a large percentage of light to escape unused. With our older outdoor lighting, we often see up �0 5�% or more of the �ight going directly up inCo the sky or at such shallow angles that it is not useful. Like a driver driving toward the light of the ,s�tting sun, such unshi�ided Iighting creates glare and diminishes visibility. In engineering terms, this is known as a poor "coeff cient of utilization". 4ur tole�rance of wasted light means most lighting fixtures are oversized by ai least a third in watiage. Many light sources are of an older, less efficient type, whieh means ihat oppoz-tunities ofien exist io significan�ly reduee energy consumption by switching to a newer, more efficient �ype of light source in a f xture with good cantrol of the light output and proper shielding. Using $10 a year as the ave�age cost for ou�door ligh�ing per person, from $3 to $5 is being http://www.darksky.org/in�oshts/is 139.�izn1 6/20/2005