Even though much of globe is dark at night, great swaths of the planet are illuminated by human development. In most large cities of the world, it is no longer possible to appreciate the beauty of the night sky. Inefficient public lighting both wastes energy and causes "light pollution" that hides our Universe from us. Light pollution is a form of environmental degradation in which excessive artificial outdoor lights—such as street lamps, neon signs, and illuminated billboards—affect the natural environment and ecosystem.

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La Tierra en la Noche
Aunque gran parte del globe est‡ oscuro en la noche, grandes franjas del planeta est‡n iluminadas por el desarrollo humano. En la mayor’a de las grandes ciudades de la Tierra, ya no es posible apreciar la belleza del cielo nocturno. La iluminaci—n pœblica ineficiente gasta energ’a y causa contaminaci—n lum’nica que nos esconde el Universo. La contaminaci—n lum’nica es una forma de degradaci—n ambiental en la cual la iluminaci—n artificial exterior excesiva - como los postes de luz, los letreros con luces de ne—n y los letreros iluminados - afectan el ambiente natural y el ecosistema.

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