Light pollution is the unwanted effects of artificial lighting in the night environment.
It can take various forms, and may originate from both diffuse and point sources:
Glare: The excessive contrast between bright and dark areas in the field of view.
Light trespass: Unwanted light (spill light), for example from adjacent properties and activities.
Light clutter: The excessive grouping of lights, for example in roadside advertising which can prove a dangerous distraction to motorists.
Excessive lighting: Excessive lighting wastes energy and money.
Sky glow: A combination of reflected and refracted light within the atmosphere. A major effect of sky glow at night is to reduce contrast in the sky. This is the most pervasive form of light pollution and can affect areas many kilometres from the original light source.
An absence of darkness: Artificial light makes experiencing natural night-time lighting conditions impossible in many parts of the country.
Light spectrum: Inappropriate colour temperature for ecological and human health and astronomy.