The dark-sky movement is a campaign to reduce light pollution. The advantages of reducing light pollution include an increased number of stars visible at night, reducing the effects of electric lighting on the environment, improving the well-being, health and safety of both people and wildlife, and cutting down on energy usage. Earth Hour and National Dark-Sky Week are two examples of such efforts. The movement started with professional and amateur astronomers alarmed that nocturnal skyglow from urban areas was blotting out the sight of stars. For example, the world-famous Palomar Observatory in California is threatened by sky-glow from the nearby city of Escondido and local businesses. For similar reasons, astronomers in Arizona helped push the governor there to veto a bill in 2012 which would have lifted a ban on illuminated billboards. Nocturnal animals can be harmed by light pollution because they are biologically evolved to be dependent on an environment with a certain number of hours of uninterrupted daytime and nighttime. The over-illumination of the night sky is affecting these organisms (especially birds). This biological study of darkness is called scotobiology. Light pollution has also been found to affect human circadian rhythms. The dark-sky movement encourages the use of full-cutoff fixtures that cast little or no light upward in public areas and generally to encourage communities to adopt lighting regulations. A 2011 project is to establish "dark sky oasis" in suburban areas. Dark-sky lighting 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. Flagstaff is a city of over 70,000, but because of their lighting, their skies are dark enough to see the Milky Way. 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). 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. Skyglow 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. Artificial skyglow is caused by the over-illumination of the sky from large