Astronomers rely on dark skies to see dim stars, galaxies and nebulae. Glare from neighbours' lights can prevent our eyes from adapting to the dark. But light from many street lamps is even worse. The upward light reflects off the air, making the sky glow.

According to this National Geographic Magazine article on light pollution "of all the pollutions we face, light pollution is perhaps the most easily remedied." Like other forms of pollution,   the basic problem is that people have considered the sky to be a free place to dump excess photons of light.

Sky glow is caused by thousands of lights which either let light escape upward,  or illuminate large areas beyond the sidewalk,  road or parking lot they are designed for. Better types of lamps are available which direct light downward and only to the area needing light. These lights also use less energy and create less glare. This is where organized groups who have researched light pollution can, over time, make a huge difference.

Light trespass comes from lights which shine unwanted into your yard or house. The answer is proper complaints. When a neighbour is asked politely, a lamp shining into a backyard might be turned off or replaced with one that shines down. The engineering departments of many towns will respond to complaints from individuals or groups. Politicians  usually try to keep their voters happy. There is tentative evidence also that darkness is important for human health.

Glare from bright lights can make it harder to see things, especially for older people. Often, it is assumed that over-bright lights make people safer, when, in some instances over-bright lighting which shines outward can actually make an area less safe. Again, complain, especially after reading information on glare. 

Astronomers in Richmond Hill, Ontario approached politicians about light pollution in that growing town. Eventually a light pollution control bylaw was passed.  Other Canadian towns with bylaws include Ottawa,  Mississippi Mills and Saanich.

Bylaws vary, but many include: 

• requirements that new light fixtures must be shielded, that is only shine down
• limits to the maximum brightness of lights
• requirements that some lights (such as parking lots) be turned down after certain hours

There are several organizations working to reduce light pollution. All welcome assistance from people who want to make a difference.