LIGHT POLLUTION Definition by IDA(International Dark-Sky Association): Any adverse effect of artificial light including sky glow, glare, light trespass, light clutter, decreased visibility at night, and energy waste.
REAL MEANING: Lightpollution is the alteration of lightlevels in the outdoor environment (fromthose present naturally) due to man-madesources of light. Lightpollution is the introduction byhumans, directly or indirectly, of artificiallight into the environment.
INTRODUCTION TO TERMS Urbansky glow: the brightening of the nightsky over inhabited areas Light trespass: light falling where it ‘s notintended, wanted or needed Glare:excessive brightness which causesvisual discomfort. High levels of glare candecrease visibility Clutter:bright, confusing and excessivegroupings of light sources, commonly found inover-lit urban areas. The proliferation ofclutter contributes to urban sky glow, trespassand glare.
Glaring lights can actually reduce visibility. Here the brightest most visible objects in the area are the lighting fixtures, not the roadways, walkways or parking areas which a driver or pedestrian would expect to be lighted. Atlanta, Georgia.
Source: World Atlas of Artificial Night Sky Brightness
Light pollution in Europe (left) and Greece (right)
CAUSES OF LIGHT POLLUTION Starlight Totally controllable: Water vapors, Cosmichumidity dust , clouds Within the Environmental and fog atmosphere pollution and uncontrollable Excessive Atmosph Particles outdoor eric dust in the air lighting
EXCESSIVE OUTDOOR LIGHTING Over-lighted Parking Areas Commercial Establishments – Advertisements. Bad street lighting Lamps send light upwards and not downwards, where it’s needed. 35% to 50% of all Light Pollution comes from Streetlights
EFFECTS OF LIGHT POLLUTION Ecological Disorientation of nocturnal animals and sea turtles from additional illumination which affects foraging, reproduction, communication, and other critical behaviors Both bright days and dark nights are necessary to maintain healthy hormone production, cell function, and brain activity, as well as normal feeding, mating, and migratory behavior for many species, including humans. The photosynthetic cycles of deciduous trees have been shown to be disrupted due to the predominance of artificial nighttime lights.
EFFECTS OF LIGHT POLLUTION Financial-Social 30% of produced light goes to waste. Waste of light=energy waste unnecessary nighttime lighting wastes upwards of $1.5 billion in electricity costs around the world per year. Well-planned lighting can save money, decrease crime and improve night-time ambiance. Contribution to the Greenhouse Effect Accounts for the release of more than 12 million tons of carbon dioxide, the leading greenhouse gas, into the atmosphere.
EFFECTS OF LIGHT POLLUTION Obstruction of Night Sky Watch Increased urban sky glow reduces the contrast between stars and galaxies, making it difficult to detect fainter objects. The visibility of diffuse sky objects such as nebulae and galaxies is affected by light pollution more than are stars. Light trespass can impact observations when stray light enters the tube of the telescope, causing a glow across the field of view.
In astronomy, limiting magnitude is the faintest apparent magnitude of a celestial body that is detectable or detected by a given instrument. Amateur astronomers usually judge their skies by noting the magnitude of the faintest star visible to the naked eye. However, depends too much on a persons visual ability. One persons "5.5- magnitude sky" is anothers "6.3-magnitude sky“.
HOW DO WE MEASURE LIGHT POLLUTION John Bortle‘s Light Pollution Scale Class 1: Excellent dark-sky site - Black Class 2: Typical truly dark site - Gray Class 3: Rural sky - Blue Class 5: Suburban sky Class 6: Bright suburban sky Class 7: Suburban/urban transition. Class 8: City sky - white Class 9: Inner-city sky - White
JOHN BORTLE‘S LIGHT POLLUTION SCALE Class 1: The zodiacal light and Class 5: Only hints of the zodiacal zodiacal band are all very visible. To light are seen. The Milky Way is the unaided eye the limiting very weak/invisible. The naked-eye magnitude is 7.6-8.0. limit is 5.6-6.0. Class 2: Airglow may be weakly Class 6: No trace of the zodiacal apparent. The zodiacal light is still light. Only few indications of the bright. The limiting naked-eye Milky Way. The naked-eye limit is magnitude is 7.1-7.5. about 5.5. Class 3: Some indication of light Class 7: The entire sky has a vague, pollution is evident. The Milky Way grayish white color. The Milky Way still appears complex. The naked-eye is totally invisible. The naked-eye limiting magnitude is 6.6-7.0. limiting magnitude is 5.0. Class 4: Obvious light-pollution. The Class 8: The sky glows whitish gray zodiacal light is clearly visible. The or orangish. The naked eye can pick Milky Way has only the most out stars down to magnitude 4.5 at obvious structure. The maximum best. naked-eye limiting magnitude is Class 9: The entire sky is brightly 6.1-6.5. lit. Many stars are invisible The naked-eye limiting magnitude is 4.0 or less.
PHOTO/79297308@N00/3180280752 ORION, 8 JANUARY 2009, 10:29:34, FROM HTTP://FLICKR.COM/ The constellation Orion, imaged at left from dark skies, and at right from the teeming metropolis of Orem
NIGHT SKY WITH LIGHT POLLUTION (LEFT) ANDNIGHT SKY WITHOUT LIGHT POLLUTION (RIGHT)
Picture ofSaturn’ssatellite, Titan,with high light PHOTOS TAKENpollution levels BY THE STUDENTS OF 2 GE.L. OF ND EHEDOROS, FOR THE DETERMINATION OF SATURN AND TITAN’S DISTANCE AND OF THEPicture of ORBITAL PERIODSaturn’ssatellite, Titan, OF TITAN.with low lightpollution levels
WHAT CAN WE DO? Learn the facts about light Use light only when and pollution where it’s needed.Educate others Use only as much light as needed. Get involved Shine lights down, not up. Use efficient light sources for outdoor lighting around homes and businesses.
REFERENCES http://en.wikipedia.org/wiki/Light_pollution http://www.astrovox.gr/lightpollution.html http://www.darksky.org/ http://skytonight.com/resources/darksky/3304011.html http://www.novac.com/lp/def.php U.S. Lighting Market Characterization, Volume I: National Lighting Inventory and Energy Consumption Estimate - Received by Building Technologies Program; Office of Energy Efficiency and Renewable Energy; U.S. Department of Energy; Prepared by Navigant Consulting Inc. 1801 K Street, NW Suite 500 Washington DC, 20006 with XENERGY, Inc. Burlington, MA; September 2002.