Earth Hour is a worldwide movement organized by the World Wildlife Fund (WWF). The event is held annually, encouraging the individuals, communities, and businesses to give an hour for Earth, and additionally marked by landmarks and businesses switching off non-essential electric lights, for one hour from 8:30 to 9:30 p.m., usually on the last Saturday of March, as a symbol of commitment to the planet. It was started as a lights-off event in Sydney, Australia, in 2007.

Light pollution is the presence of any unwanted, inappropriate, or excessive artificial lighting. In a descriptive sense, the term light pollution refers to the effects of any poorly implemented lighting sources, during the day or night. Light pollution can be understood not only as a phenomenon resulting from a specific source or kind of pollution, but also as a contributor to the wider, collective impact of various sources of pollution.