Light pollution essentially amounts too excessive and obtrusive light created by humanity. Our cities produce an enormous amount of light at night, which fills the night sky and is reflected back toward the ground by the Earth's atmosphere. But, what's the big deal with light pollution, how could be that bad? Unlike other forms of pollution, light doesn't cause any chemical damage to ecosystems or the atmosphere. Instead its effects are much more subtle. Artificial light during the dark hours of the night are something we as a civilization are quite accustomed to. Since the days of candlelight, humanity has made an effort to bring some illumination to the darkness of the night. The advent of modern lighting has made mankind's small battle against the darkness much easier. However, the world has gone a little overboard. Densely populated areas produce light well in excess of what is needed to be illuminated. Outdoor lighting on houses, public buildings and even parking lots, tends to be used rather inefficiently. Light fixtures and bulbs commonly project light outward in all directions, rather than toward the area the light is needed. This extra light shines upward into the sky, where its reflected back onto the ground by certain characteristics of the atmosphere. Almost everyone on Earth is familiar with the glow in the sky over urban areas. Research in recent decades has determined that this excessive light is having negative effects on the health of humans and ecosystems. Aside from the simple nuisance of blocking out the stars, the effects of over illumination of the night sky are more pervasive than previously thought. There are several forms of light pollution, and depending upon the source, these forms will have different names. The most common form is over illumination, this simply amounts to providing more light than is actually necessary for a given area. Over illumination is rather obvious, especially if a given outdoor light makes night seem like day. Flood lights are the most common culprit of this form of light pollution, as theyÎêre design to fill large open areas with bright light. A simple solution is to equip these lights with motion sensors, which will give the flood light a dual purpose as serving the original function for the homeowner and providing an added element of security. When light ventures from one property to another it is known as light trespass. This is more impolite than detrimental, and can cause conflicts amongst neighbors. The most obvious form of light pollution is sky glow, where the excess light causes the sky to become ominously bright at night. This is the most detrimental form of light pollution for both humans and the natural world. Biological adaptation of mankind and the natural world before the rise of civilization has resulted in a natural need for darkness at night. Innumerable plant and animal species rely on the darkness for various biological needs. Humans too need the darkness. Excessive artificial light has been found to cause sleeping disorders and can contribute to the light-related causes of depression. In recent decades the dark sky movement has spearheaded efforts to reduce excessive light. State governments have made steps to help mitigate light pollution and manufacturers now produce lighting solutions that help reduce excess light.