Light Pollution 101 | National Geographic

• [Narrator] The invention of the electric light bulb, 150 years ago, was one of the most transformative milestones in history. This new form of light, artificial light, brightened and made safe once-dark streets, prolonged waking hours into the evening, and brought electricity into homes for the very first time.

Today, this glow has grown, but at a cost. Light pollution is the over-illumination of cities and night skies by artificial lighting. It's caused by the abundance of light sources emitting light outside of an intended direction. Several types of light pollution exist, including glare, which is a disruptive light that shines horizontally, light trespass, the unwanted shining of light onto nearby areas, and sky glow, a halo over inhabited areas caused by the scattering of light particles.

No matter what form light pollution takes, each can have unintended, yet harmful impacts. Wildlife, particularly sea turtles, have had their nocturnal patterns disrupted. The turtle hatchling's instinct to follow the light of the moon in order to reach the sea is intercepted by the light of inland cities. Because of this, many never find their way to the ocean.

Human's well being is also compromised by light pollution. The excess light can overwhelm photoreceptor cells in the retina, damaging one's eyesight. Plus, it disrupts natural sleep cycles, and causes sleep deprivation, leading to a number of health problems, possibly including cancer.

Light pollution also results in the production of additional carbon emissions. Each year, potentially billions of dollars worth of coal or oil, which are burned to produce electricity, are wasted on unnecessary light. Over the past several decades, light pollution in North America has increased an estimated 6 to 10% each year. A rise fueled by growing populations, greater access to electricity, and increased urban development.

Efforts have been made to help counter this rise in excess light, including the development of alternative energy-efficient light bulbs and smarter directional lighting designs. These and other innovations will continue to refine this 150-year-old technology, artificial light, and optimize it for a brighter future.

(light switch clicks)