Polarized light pollution



Polarization is a property of light waves that describes the orientation of their oscillations. Polarized light pollution is a subset of the various forms of light pollution referring specifically to polarized light.

In nature, water and water vapor polarize the sunlight (which itself is slightly polarized). By receiving the direction of polarized photons, some species can correct their course during migration. Artificial polarization of natural or artificial light can disrupt the behavior of these species and the ecosystems in which these species play an important role. Pollination is one example of this.

History of this notion
Jean-Baptiste Biot and his successors have shown that solutions of organic products, such as fructose or sucrose, can polarize light. However, only in recent decades has it been realised that the polarized light may play an important role in ecosystems, especially in the insect world.

More recently, when the concept of light pollution emerged, the question of the possible impacts of the artificial polarization of light has arisen.

Gábor Horváth and his team have proposed that this new term needs to be better described and understood in order to better address the specific ecological consequences (direct or delayed in space and time) of light that was polarized (at source or by interacting with objects made or modified by humans).

Impact on insects
A representative example is the ecological trap caused by asphalt surfaces polarizing light in a similar way as ponds do. Research has shown swarms of mayflies are laying their eggs on roads rather than rivers or ponds. Many insects have aquatic larval stage, and they largely depend on visual cues such as the light reflection of ponds or rivers to find egg-laying places. They therefore often mistake asphalt surface for water and lay eggs directly on the road, leaving the eggs to dehydrate and die under the sun.

Related organizations

 * International Dark-Sky Association
 * Links and Web Resources

Research about light pollution

 * The Challenge article "Is Light Pollution Killing Our Birds"
 * The Discover article relating light pollution to insects, birds, and breast cancer (requires paid registration)
 * Ecology of the night symposium (2003 conference)
 * "Ecological Consequences of Artificial Night Lighting" (2002 conference, by the Urban Wildlands Group)
 * Light pollution and the protection of the night environment, UNESCO, IDA Regional Meeting, 360 pages,(2002) English — Italian. Proceedings are available as a downloadable PDF.
 * Sherbrooke College Light pollution research activities
 * Examples of the good, bad and ugly lighting
 * "Our Vanishing Night", Verlyn Klinkenborg. [[National Geographic (magazine)|National Geographic], November 2008, pp102–23.]
 * "Blinded by the Light?", CfDS 2009, Various authors discussing the "hidden" environmental harm, the human health harm, the money waste, lighting failing to prevent crime and even astronomy.

Collections of links related to light pollution

 * Dark Sky Awareness global project
 * BAA CfDS Discussion Forum
 * Dark Sky Importance gallery at The World at Night
 * The Dark Side: an article in The New Yorker magazine about light pollution
 * Reclaiming the Night Sky, article by Judith Dobrzynski from The New Republic on light pollution
 * Astronomical Society of South Australia article on Light Pollution in Adelaide, South Australia
 * Good Bad and Ugly Outdoor Lighting and update Adelaide South Australia
 * Turn Out the Lights!
 * ALI - the Alliance for Lighting Information - website contains information about light, lighting and related topics.
 * Verlyn Klinkenborg: "Our vanishing night" National Geographic November 2008 link
 * Verlyn Klinkenborg: "Our vanishing night" National Geographic November 2008 link

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