Published On: Sat, Jan 30th, 2010

Earth Matters by Jacqueline Milner – Light Pollution….What is that? – January 30, 2010

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Light Pollution…What is that?

Have you ever noticed the glow in the night sky as you approach a city or subdivision?  If you are a city dweller have you wondered where the stars have gone or why you cannot see the stars at night?  The answer to these questions is light trespass or light pollution. This is wasted light; wasted energy that obstructs our night sky, confuses birds and other wildlife, and can even harm the development of your eyes.

Take a good look at the light fixtures being used to light your driveway entrance, the street, the parking lots and the front walkway of City Hall.  Chances are that what is being used for this task is an unshielded light which lights not only the ground it was intended to illuminate but also the neighbours property and part of the night sky.  Light pollution and light trespass represents needless greenhouse gas production.

Unshielded lights often produce glare which hinders the eyes ability to see what is in the darker areas of the scenery that is directly ahead.  Shielded lights will direct light only to where the light is wanted and needed and produce energy and operating cost savings. I have heard for sometime that significant energy savings can be achieved by incorporating a light shield with a lower watt bulb to effectively light an area which was previously lit by a higher wattage bulb.


So I did a little experiment.  I have an area in my Studio that I use specifically for painting.  There is a bare compact florescent bulb in an overhead socket not far from my work table.  I make daily use of a light meter in my occupation so this indispensable tool was now going to help me with this light shield experiment.   I took a light meter reading at four feet directly under the bare bulb light in the ceiling receptacle close to my work table.  I then fashioned a rough shield around the bulb with aluminum foil, directing all of the light to the ground.  I then took another light meter reading at the same four foot spot under the light.

The reading was four times brighter than the first reading.  Wow!  Conclusion; I could light or dare I say better light a work area with a lower watt bulb, save money and eliminate light trespass in a neighbouring area by utilizing a light shield.  The above drawings of an outside floodlight visually demonstrate these conclusions.

Here are some simple considerations when shopping for your next outdoor fixtures.  Ask for ‘neighbor-friendly or ‘glare free’ lights. Your fixture light should not trespass on your neighbour’s property.  Look for fixtures that direct the light towards the ground.  They will have an opaque cover that hides the bare bulb from view at the side.  Note that ‘Energy Star’ fixtures do not mean that they are neighbour friendly.  Insure that their light is directed to the ground and does not trespass on the night sky. Glare should be kept to a minimum.

Our bodies and those of all the other creatures that we share this planet with depend on a regular cycle of light and darkness for their health and well being.  Please help to eliminate light trespass so that we can continue to enjoy the simple pleasure of a star filled night sky and save precious resources in the process.   Twinkle, twinkle little star…


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  1. Joe says:

    Great insights and well illustrated. I will fix my outdoor lights … when the weather gets warmer..

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