"Twinkle, twinkle, little star, How I wonder where you are. I know you're up there in the sky, But I've got these streetlights in my eye!"
For the first time in human history, the majority of people in the world are unable to see the splendour of the night time sky. This human inheritance is being taken from us by urban sky glow produced by the lights of cities and towns across the world. Instead of the 3,000 or so stars visible to an unaided eye in good conditions, most city dwellers can see fewer than a couple of dozen. The majority of people living in North America have never seen the Milky Way!
The blaze of light escaping from human night time activity cuts us off from our heritage as thinking beings. Much of philosophy, religion and science originated as men gazed skyward and tried to make sense of the patterns and movements of the stars and planets overhead.
Until recently only the concern of astronomers, light pollution is increasingly being viewed as an environmental problem akin to the destruction of our forests and the pollution of our water and air. Scientists are turning their attention to studying the possible adverse effects of light pollution on human health and on animal populations. (See for instance "Blinded by the Light," in the Globe and Mail, Jan. 12.)
Solutions to this problem are surprisingly simple and inexpensive. Better-designed and better-installed light sources can dramatically reduce light pollution, often while actually providing more effective illumination. How? First, let’s identify the types of and sources of light pollution:
Sky glow is the dome of light seen over cities and towns resulting from stray light reflecting off dust and water vapour in the air. A large percentage of sky glow is caused by poorly designed or installed lights that misdirect light into the sky. For instance, the ubiquitous cobra-head-style streetlight spews about 20 per cent of its light output upwards. (The next time you are in an airplane, notice how many streetlights you can see from 30,000 feet!) In addition to the light pollution this causes, it is a tremendous waste of energy.
Glare is created when the light source is within our field of view due to incorrect aiming or insufficient shielding of the light. Glare hinders our ability to see the area illuminated by the light source and can create safety hazards for pedestrians, cyclists and motorists as well as simply being an annoyance. If light sources are designed to eliminate glare, it is often possible to reduce overall illumination levels (thus reducing energy use) while increasing one’s ability to see detail in the lit area. "Security" floodlights on homes are notorious glare producers and thus can actually reduce security.
Light trespass refers to misdirected light that unintentionally invades neighbouring property. While the most obvious example is the neighbour’s security light that shines in your bedroom window, it includes any light that spills, unwanted, beyond the area that is intended to be lit.
Clutter refers to the combination of light sources, glare and light trespass that can create confusion, for instance for a motorist or pilot, or is simply unpleasant.
Next week we’ll look at ways to reduce these forms of light pollution and see how well we are doing in Whistler at this task.
Web site of the Week : There’s no shortage of Web sites devoted to reclaiming the night sky. Type "light pollution" in your search engine, or try the International Dark-Sky Association (www.darksky.org) for a great introduction to the subject.
Saturday, February 2nd — Monthly Bird Walk .Meet at the base of Lorimer Road at 8 a.m. Contact Michael Thompson for details.
Written by: Don Brett