Dark-sky movement

Dark-sky lighting is a concept very important to the dark-sky movement, as it greatly minimizes light pollution. The concept was started in the 1950s by the city of Flagstaff, Arizona.[10] Flagstaff is a city of over 70,000, but because of their lighting, their skies are dark enough to see the Milky Way.[11] Lights should be shielded on the top and sides so light doesn't go up to the sky and only used when needed (use motion detectors and only the wattage necessary).[12] The International Dark-Sky Association certifies fixtures as dark sky friendly, and these will have the IDA Fixture Seal of Approval. Opinions vary on what color the light should be, but most agree on the description of "warm", which is considered more yellow or orange/amber than white.

Mexico City at night, showing skyglow bright enough to read a book outside

Skyglow is the illumination of the night sky or parts of it, resembling an orange "smog". It occurs from both natural and human-made sources.[13] Artificial skyglow is caused by the over-illumination of the sky from large city centres, shopping centres, or stadiums. It consists of light that is either emitted directly upward or reflected from the ground that is then scattered by dust and gas molecules in the atmosphere, producing a luminous background or light dome. These artificial skyglows cause the sky to be 5–10 times brighter in urban areas than a naturally dark sky that is unaffected by artificial light. Natural skyglow can come from natural light sources, such as the Sun, the Moon, the stars, or auroras.

Some communities are becoming aware of this problem and are putting forth efforts to minimize the hazy, orange skyglow. A community in particular is the city of Merritt, British Columbia. An article published July 8, 2010 states that they are making minor changes to lighting in and around Merritt, such as the installment of down-cast lighting to commercial buildings, as part of their light pollution abatement program.[14] The benefits of this technological change include "saving energy through better focused lights, preserving the environment by reducing excess light that may affect flora and fauna, reducing crime and increasing safety by more adequately illuminating areas, and reducing health risks."[14]

Scotobiology is the study of the role darkness plays in living organisms and shows that interrupting darkness by light pollution creates drastic effects for most organisms; changing their food gathering and feeding habits, their mating and reproduction behavior, migration behaviour (birds and insects) and social behavior.[15] Approximately 30% of vertebrates and 60% of invertebrates are nocturnal, meaning that they depend on darkness. Their everyday behaviors are biologically evolved to adapt in uninterrupted darkness.[16]

Human health is also adversely affected by the effects of light pollution. Light during night time hours has been linked to human cancers and psychological disorders.[15]

Dark-sky preserves are the main contributors to the dark-sky movement. They are protected areas found mostly in national parks that have a zero light pollution policy set in by the government and controlled by the National Dark Sky Association.

As of February 6, 2012, there were 35 formally recognized dark-sky preserves in the world with Canada in the lead containing 15 preserves. These preserves are located in Nova Scotia, New Brunswick, Quebec, Ontario, Saskatchewan, Alberta, and British Columbia. Other countries that have dark-sky preserves are the Czech Republic, Hungary, Poland, Slovakia, Spain, United Kingdom, and the United States. A current list of designated parks is maintained by the Dark Skies Advisory Group [17] of the International Union for Conservation of Nature (IUCN).

The parks are put in place by the Dark Sky Places program with the intention to remind us that the night sky serves just as much importance to our culture and history as our day-time sky.[18]

The International Dark-Sky Association (IDA) began in 1988. A non-profit, it manages the Fixture Seal of Approval program, which offers a third-party rating system judging the "sky-friendliness" of lighting fixtures. In 2009, the IDA opened an office for public policy and government affairs in Washington, D.C. to inform lawmakers and lobbyists about the energy efficiency of outdoor lighting and to promote the adoption of energy-saving measures.[19] The IDA has implemented several simple guidelines to responsible outdoor lighting along with some practical considerations.

• In regard to safety, one needs only the right amount of light, in the right place, at the right time. More light often means wasted light and energy.
• Use the lowest wattage of lamp that is feasible. The maximum wattage for most commercial applications should be 250 watts of high intensity discharge lighting, but less is usually sufficient.
• Incorporate curfews (i.e., turn lights off automatically after a certain hour when businesses close or traffic is minimal).[20]

• International Dark-Sky Association
• MyDarkSky – dark sky survey maps
• Outdoor Lighting Regulations and Ordinances on Google Earth Archived 2007-09-30 at the Wayback Machine
• Interactive map comparing U.S. dark sky laws
• The dark sky movement – yahoo
• Jasper National Park Archived 2012-05-12 at the Wayback Machine
• Dark-sky parks of the world
• Flagstaff Dark Skies Coalition
• Globe at Night
• Cities at Night
• Dark Skies Awareness Archived 2011-04-10 at the Wayback Machine
• The Consortium for Dark Sky Studies