Dark-sky preservation

Dark-sky preservation is the reduction and careful management of artificial light to protect natural nighttime darkness, astronomical observation, ecosystems, and human health.

Light pollution: The excessive or misdirected use of artificial light at night. It is the broad problem that dark-sky preservation seeks to reduce.
International Dark-Sky Places: Protected areas and communities recognized for exceptional night skies and programs to limit light pollution. The designation links local protection measures with recognized dark-sky conservation.
Circadian rhythm: An approximately 24-hour cycle in biological processes, regulated by internal clocks and environmental cues. Nighttime light can shift or suppress biological timing in people and other organisms.
Street lighting: Fixed outdoor lighting used to illuminate streets, sidewalks, and public spaces. Its safety and visibility goals must be balanced against unnecessary brightness and spill.
Skyglow: The brightening of the night sky caused when artificial light scatters through the atmosphere. It directly obscures stars and other features of a naturally dark sky.
Dark-sky reserve: A protected area with dark-sky policies and a surrounding community committed to limiting light pollution. Reserves coordinate protection across both a core area and its neighboring settlements.
Melatonin: A hormone involved in regulating sleep and circadian timing, whose secretion is affected by light. Exposure to light at night can suppress its normal nighttime production.
Light trespass: Unwanted artificial light that falls beyond the area it is intended to illuminate. It identifies a local nuisance that shielding and careful placement can prevent.
Full-cutoff lighting: Outdoor lighting designed to emit no light above the horizontal plane. Shielding luminaires limits upward light that contributes to skyglow.
Outdoor lighting ordinance: A local law regulating outdoor lighting, often through limits on brightness, direction, or operating hours. Municipal rules can turn dark-sky goals into enforceable lighting requirements.

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