Light pollution is a type of pollution. It is defined as “any adverse (or bad) effect as a result of man-made lights.” Usually, this means too much light. Several species, including plants and humans, are badly affected by light pollution. Most people have never heard of light pollution, and those who have usually don’t care, or do anything about it. Light pollution costs Americans billions of dollars every year.

There are five kinds of light pollution:

• Sky glow
• Light trespass
• Over-illumination
• Clutter
• Glare

Sky glow usually has more of an effect on the environment than light trespass and glare, but all of them are a major problem to people today.

Sky glow is the kind of light pollution that prevents people from seeing the moon and the stars. This causes birds to not be able to migrate to the right place because they can't follow the moon and stars. Sky glow also prevents astronomers from making discoveries.

Light trespass is when light being used by a person goes into the property of another. Though light trespass is not an environmental issue, it is still light pollution.

The third kind of light pollution, glare, has different kinds. The first, disability glare, is the loss of visibility because of too many lights. Discomfort glare is when the lights cause pain.

Light pollution stops migrating birds of having any way of seeing the moon and stars, which they use to navigate, therefore not being able to migrate to the correct place. Also, sea turtles do not come to shore and nest as often, because they are afraid of the lights.

Glare causes sleep problems in humans. Too much light in an apartment shinning in from a nearby billboard will disturb their sleep. Also science is being affected by light pollution. Astronomers have no way of observing, or making discoveries with too much light to block the night sky.

There are now several groups that are trying to prevent light pollution. Light pollution first made news in 1964, when an observatory was specially placed just to avoid light pollution. However, it wasn’t brought the attention of most people until June 6th, 2002, when the Czech Republic passed the world’s first light pollution law. Since then, light pollution is slowly being recognized by the general public as a major problem.

You can lower the amount of light pollution by having lights off when they are not needed. You can also shield yourself from this pollution by putting curtains on a window facing the street or any other disturbing light source.

Source: Wikipedia (All text is available under the terms of the GNU Free Documentation License)

For more information (background, pictures, experiments and references): Light Pollution