Light pollution is a relatively unknown form of pollution that refers to excessive or obtrusive artificial light.
Light pollution is usually divided into the two main categories: annoying light and excessive light. Light pollution can be also divided to indoor and outdoor light pollution.
The official light pollution definition comes from the International Dark-Sky Association and states that the light pollution is "any adverse effect of artificial light including sky glow, glare, light trespass, light clutter, decreased visibility at night, and energy waste."
Light pollution is usually occurring in large urban areas (large cities) and has been shown to reduce the visibility of stars.
Light pollution also disrupts ecosystems and can even have negative health effects.
Some scientists even argue that the ever-increasing light pollution could lead to disruption of food webs and affect entire ecosystems. This is because the light pollution causes screening of the celestial compass for many nocturnal animals such as beetles, moths, crickets, and spiders which can totally disrupt their navigation ability.
Light pollution can be decreased with the more efficient use of lightning. The more efficient use of lightning would require changing the habit of much of our society.
Skyglow over the large cities is a major issue for many astronomers across the globe because it obscures stars, even in perfectly clear nights.
The scientists have calculated that the sky brightness is at least 2 to 4 times above normal in large parts of urban areas in Europe and North America.
Light pollution can have adverse health effects such as frequent headaches, fatigue, increased stress, decrease of libido and increased anxiety.
There were also several studies which claimed that there is a link between light pollution and breast cancer because of the suppression of the normal nocturnal production of melatonin.
The light pollution is also believed to contribute to smog. According to the study by the American Geophysical Union light pollution destroys nitrate radicals thus preventing the normal night time decrease of atmospheric smog.
Measuring the total amount of light pollution in certain area is very difficult and complex procedure because the natural atmosphere is not completely dark.