Past generations were able to see the stars at night set against a black sky.
In 1889, during his stay at the asylum of Saint-Paul-de-Mausole near Saint-Rémy-de-Provence, Vincent van Gogh painted the night sky filled with stars in his famous painting, "The Starry Night".
Today, with modern street lighting, seeing stars at night is a thing of the past. Indeed, it has become very difficult to find a place on the planet where the skies are dark at night, and millions of people have never seen the Milky Way.
In June 2016, it was estimated that one third of the world's population could no longer see the Milky Way. This included 80% of Americans, and 60% of Europeans. Singapore was found to be the most light-polluted country in the world.
Light pollution is a by-product of industrial society, and its sources include building exterior and interior lighting, advertising, area lighting such as parking lots, streetlights, and illuminated sports venues.
Cities in some countries emit more light than others; for example, U.S. cities emit 3 to 5 times more light than their German counterparts.
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Exposure to light suppresses the secretion of melatonin, a hormone that influences circadian rhythms, and experimental evidence has shown that lower melatonin levels are associated with cancer.
The effects of light pollution also include an increased incidence of headache, fatigue, stress, anxiety, and a decrease in sexual function.
The spectral composition of that light is an issue, with blue light being more disruptive than red light, especially at night. Both compact fluorescent light bulbs and LED lights produce more blue light than do incandescent lights.
The International Dark-Sky Association
In 1988, professional astronomer David Crawford, and physician/amateur astronomer Tim Hunter started the International Dark-Sky Association (IDA) to combat light polution.
Light that shines into people's eyes is called glare, and light that shines into the night sky is called skyglow. Light can even "trespass" when it shines into an area where it is not wanted, for example, your neighbor's outdoor lights can shine into your yard or bedroom windows.
IDA is part of the larger dark-sky movement, which is a campaign to reduce light pollution. IDA educates lighting designers, manufacturers and the public about ways to control light pollution.
Lights should be shielded on the top and sides so that light doesn't go up to the sky. IDA provides a Fixture Seal of Approval for lighting that minimizes glare, reduces light trespass, and doesn’t pollute the night sky.
The IDA website provides a list of retailers selling Dark Sky-Approved products, and one of the cooperating retailers is The Home Depot.
IDA has lists of properly-shielded types of lighting that won't create light pollution. These include security lighting, deck and stair lighting, pathway lighting and even flag pole lighting.
IDA creates a series of public outreach materials that include a postcard that explains how to eliminate light pollution:
Their short film, "Losing the Dark" explains the effect of light pollution on our cities and what we can do to combat it:
The IDA website even includes a sample letter that you can send to a neighbor whose outdoor lighting "trespasses" on your property.
IDA's Public Policy
IDA gets involved in state and local lighting public policy. Recently, they sent a letter to the state of Massachusetts supporting a pending bill that would improve outdoor lighting and increase dark-sky visibility. They've sent letters to members of the New Jersey Legislature regarding the use of energy-efficient outdoor lighting fixtures, and IDA weighed in on a proposal by the City of Reno, Nevada, to set luminance limits for electronic signs.
In May 2019, IDA issued a position statement concerning the SpaceX "Starlink" communications satellites.
"The number of low Earth orbit satellites planned to launch in the next half-decade has the potential to fundamentally shift the nature of our experience of the night sky. IDA is concerned about the impacts of further development and regulatory launch approval of these satellites. We therefore urge all parties to take precautionary efforts to protect the unaltered nighttime environment before deployment of new, large-scale satellite groups."
IDA'S International Dark Sky Places Program
The International Dark Sky Places Program(IDSP) was founded in 2001 to encourage communities, parks and protected areas around the world to preserve and protect dark sites through responsible lighting polices and public education.
The program has six types of designations:
* International Dark Sky Communities - legally organized cities and towns that adopt outdoor lighting ordinances and educate their residents about the importance of dark skies.
* International Dark Sky Parks - public or private spaces protected for natural conservation that implement good outdoor lighting and provide dark sky programs for visitors.
* International Dark Sky Reserves - a dark "core" zone surrounded by a populated periphery where policy controls are enacted to protect the darkness of the core.
* International Dark Sky Sanctuaries - the most remote and often darkest places on the planet, and whose conservation is most fragile.
* Urban Night Sky Places - large urban sites whose planning and design actively promote dark skies even in the midst of significant artificial light.
* Dark Sky Friendly Developments of Distinction - subdivisions, master planned communities, and unincorporated neighborhoods and townships whose planning actively promotes a more natural night sky but does not qualify them for IDS Community designation.
Below is a list of the Dark Sky Places program's locations and the year in which they were designated by IDA:
International Dark Sky Parks:
*Natural Bridges National Monument, Utah, United States, 2006
*Cherry Springs State Park, Pennsylvania, United States, 2008
*Galloway Forest Park, Scotland, United Kingdom, 2009
*Zselic National Landscape Protection Area, Hungary, 2009
*Clayton Lake State Park, New Mexico, United States, 2010
*Goldendale Observatory State Park, Washington, United States, 2010, suspended 2016, revoked 2017
*Hortobágy National Park, Hungary, 2011
*The Headlands, Michigan, United States, 2011
*Observatory Park, Ohio, United States, 2011
*Big Bend National Park, Texas, United States, 2012
*Death Valley National Park, California, United States, 2013
*Chaco Culture National Historical Park, New Mexico, United States, 2013
*Northumberland National Park, England, United Kingdom, 2013
*Eifel National Park, Germany, 2014
*Mayland Community College Blue Ridge Observatory and Star Park, North Carolina, United States, 2014
*Grand Canyon-Parashant National Monument, Arizona, United States, 2014
*Hovenweep National Monument, Utah and Colorado, United States, 2014
*Copper Breaks State Park, Texas, United States, 2014
*Enchanted Rock State Natural Area, Texas, United States, 2014
*Elan Valley Estate, Wales, United Kingdom, 2015
*Yeongyang Firefly Eco Park, Yeongyang, South Korea, 2015
*Mayo International Dark Sky Park, County Mayo, Republic of Ireland, 2016
*Warrumbungle National Park, New South Wales, Australia, 2016
*Waterton-Glacier International Peace Park, Alberta, Canada and Montana, United States, 2017
*Ramon Crater, Negev Desert, Israel designated 2017
*Kartchner Caverns State Park, Arizona, United States, 2017
* Joshua Tree National Park, California, United States, 2017
*Obed Wild and Scenic River, Tennessee, United States, 2017
*Anza-Borrego Desert State Park, California, United States, January 2018
*Iriomote-Ishigaki National Park, Okinawa Prefecture, Japan, 2018
*Steinaker State Park, Utah, United States, 2018
International Dark Sky Reserves:
*Aoraki Mackenzie International Dark Sky Reserve, South Island, New Zealand, 2012
*Brecon Beacons National Park, Wales, United Kingdom, 2013
* Central Idaho Dark Sky Reserve, Idaho, United States, 2017
*Exmoor National Park, England, United Kingdom, 2011
*Kerry International Dark-Sky Reserve, County Kerry, Ireland, 2014
*The Reserve at Mont-Mégantic, Quebec, Canada, 2008
*Moore's Reserve (South Downs), England, 2016
*NamibRand Nature Reserve, Namibia, Africa, 2012
*Pic du Midi, France, 2013
*Rhön Biosphere Reserve, Germany, 2014
*Snowdonia National Park, Wales, 2015
*Westhavelland Nature Park, Germany, 2014
International Dark Sky Communities:
*Flagstaff, Arizona, United States, 2001
*Borrego Springs, California, United States, 2009
*Sark, Channel Islands, 2011
*Homer Glen, Illinois, United States, 2011
*Coll in the Inner Hebrides of Scotland, 2013
*Dripping Springs, Texas, United States, 2014
*Beverly Shores, Indiana, United States, 2014
*Sedona, Arizona, United States, 2016
*Westcliffe and Silver Cliff, Colorado, United States, 2015
*Thunder Mountain Pootsee Nightsky, Arizona, United States, 2015
*Bon Accord, Alberta, Canada, August 2015
*Big Park/Village of Oak Creek, Arizona, 2014
*Horseshoe Bay, Texas, 2015
*Moffat, Scotland, 2016
*River Oaks, Texas, Dark Sky Friendly Development of Distinction, 2017
*Ketchum, Idaho, 2017
*Møn, Denmark and Nyord, Denmark, 2017
*Fountain Hills, Arizona, 2018
*Torrey, Utah, 2018
*Camp Verde, Arizona, 2018
Other Dark-Sky Initiatives
Besides IDA, other dark-sky initiatives include Earth Hour which is organized by the World Wide Fund for Nature (WWF).
Held annually, it encourages individuals, communities, and businesses to turn off non-essential electric lights for one hour, from 8:30 to 9:30 p.m. on a day at the end of March.
Earth Hour started in 2007 as a lights-off event in Sydney, Australia, and has since grown to include more than 7,000 cities and towns across 187 countries and territories.
In 2020, Earth Hour is scheduled for March 28th, from 8:30 pm to 9:30 p.m.
National Dark-Sky Week (NDSW) is held during the week of the new moon in April, and people worldwide are encouraged to turn out their lights in order to observe the beauty of the night sky. It began in 2003 by a Virginia high school student, Jennifer Barlow and the event is endorsed by IDA, the American Astronomical Society (AAS), the Astronomical League, and Sky & Telescope magazine.