Light pollution is a term that is often used to describe excess light in an area or location. Its effects and causes are continuously under debate, but there are certain effects of light pollution that can be irritating, and according to some, even harmful to health and the environment.

The term itself is subjective, and not everyone agrees that light pollution is a problem. Often, one person’s “light pollution" could be another person’s enjoyment, and vice versa. If a car’s headlights shine into your room, causing you to wake up and sleep poorly, it is considered light trespass, a milder form of ‘light pollution."

If an area is so filled with light you cannot see the night sky, the phenomenon is considered light pollution. A night-time sporting event is considered light pollution, as is over-illumination or the excess use of lights.

Light pollution is also the cause of the moving of several observatories away from brightly lit areas. An excess of light results in the inability to study the sky, and this is detrimental to an institution that relies on the sky for information.

There are several common types of ‘light pollution’ that are typically quoted by those adhering to the belief that lighting adversely affects the environment around us. Three of the main culprits include: light trespass, over-illumination, and sky-glow.

Light trespass is usually the effect of an accident and is simply a small annoyance. A common example of light trespass is light that shines into a dark room, which many say creates sleep problems and the inability to see outside. This can include headlights from a car, a flashlight, etc.

Over-illumination simply refers to the extreme over-use of light, which can cause waste most people aren’t even aware of. For example, the use of light in excess, common in both residential and industrial areas, can cost the nation the equivalent of 5 million barrels of oil (equivalent) per day. Over-illumination is easy to fix: simply turn off the lights in your home and at work when they’re not in use, employ energy saving lights, implement timer systems, choose the correct fixtures; basically, train your household or employees to use light effectively and without waste.

The term “sky glow" is referred to when the all the lights of a city create a hazy, glowing effect in the sky. “Sky glow" is the result of all the lights combined into a mess of directions and released into the surrounding atmosphere. For example, if you go a few miles outside of a big city at night, you can see the glow, sometimes faint, other times strong, of light being refracted into the sky. It is a special annoyance to astronomers, who cannot accurately study a washed-out sky.