November 29, 2006

Five Forms of Light Pollution

Having trouble sleeping at night? It could be the light from a streetlight (or a neighbor’s floodlights) streaming through your bedroom window and interrupting your circadian rhythms. Intrusive artificial light at night can take several forms, and each causes its own set of problems. Here are five examples, taken from Interesting Thing of the Day and the Wikipedia:

  • Light trespass: When someone else’s light shines onto your property (and, especially, through your windows), that’s known as light trespass. If curtains can keep it out, it’s not serious, but in many cases there’s no way to get away from your neighbor’s light.
  • Over-illumination: Artificial lighting in excess of what is needed for its intended purpose (e.g., safety) is known as over-illumination. Excess nighttime lighting wastes an astonishing amount of electricity (and, therefore, money—not to mention natural resources).
  • Glare: Any light that impairs your vision at night is known as glare; it’s especially dangerous for drivers but can cause problems for anyone whose eyes need to be adapted to low light levels.
  • Clutter: Put too many lights too close together, and they can create a distraction for motorists and pilots.
  • Skyglow: When lights—especially those pointing upwards—hit a layer of cloud, fog, dust, or pollution in the atmosphere, it creates a glowing layer of light above a city that makes it impossible to see the stars. Skyglow is the bane of astronomers, both amateur and professional, around the world. (Sometimes written as two words: sky glow.)

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