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<br />Information Sheet 139 (July 1998) <br />07/98 <br /> <br />Page 1 of 4 <br /> <br />International Dark-Sky Association -- Information Sheet 139 <br /> <br />Why Should a City Government Be Concerned <br />About Light Pollution? <br /> <br />The public's loss of the stars from the nighttime sky is a real tragedy that every <br />city government should be aware of and not allow. This loss is a testament to our <br />myopia and to our growing insulation from the natural world. Like the canary in <br />the mineshafts of old, astronomers are warning us of the unnecessary loss of a <br />dark nighttime sky in almost every urban area. Their warnings point to the <br />problem as well as revealing a missed opportunity. <br /> <br />We have only been pitching our tents for a little while in the land of power <br />stations and industry, so it is no surprise that we are sometimes blinded by its <br />promise. Part ofthe advance of our technological society has been a steady if <br />sometimes intermittent advance in the efficient uses of energy. However, when <br />energy appears cheap, we tend to waste energy rather than use less of it. <br /> <br />Light pollution represents a waste of a magnitude that almost no homeowner <br />would allow inside their homes. Interior lights bounce off of all the room's <br />surfaces, providing for good general illumination. Only small amounts of light <br />will escape out of the windows. How strange it is, then, that when we attempt to <br />light the outdoors, we often carelessly allow a large percentage of light to escape <br />unused. <br /> <br />With our older outdoor lighting, we often see up to 50% or more of the light going <br />directly up into the sky or at such shallow angles that it is not useful. Like a driver <br />driving toward the light of the setting sun, such unshielded lighting creates glare <br />and diminishes visibility. In engineering terms, this is known as a poor <br />"coefficient of utilization". <br /> <br />Our tolerance of wasted light means most lighting fixtures are oversized by at <br />least a third in wattage. Many light sources are of an older, less efficient type, <br />which means that opportunities often exist to significantly reduce energy <br />consumption by switching to a newer, more efficient type of light source in a <br />fixture with good control of the light output and proper shielding. Using $10 a <br />year as the average cost for outdoor lighting per person, from $3 to $5 is being <br />http://www.darksky.org/infoshts/isI39.htmI6/20/2005 <br />