Knowra Light pillar Light pillar A light pillar is a vertical column of light appearing above or below a bright source when light reflects from horizontally oriented ice crystals in the atmosphere.
Ice crystal : A crystalline particle of ice with an ordered molecular structure and characteristic faces. Flat crystal faces provide the surfaces that reflect light into vertical columns.
Moon pillar : A vertical column of light extending above or below the Moon through reflection from atmospheric ice crystals. It is the lunar counterpart to pillars seen around the Sun or artificial lights.
Ice crystal habit : The characteristic external shape of a crystal, shaped by its growth conditions. Crystal habit determines whether atmospheric ice particles present broad, flat faces to incoming light.
Crepuscular rays : Beams of sunlight made visible by scattering from dust, haze, or clouds. They look like shafts of light but arise from scattering and perspective, not ice-crystal reflection.
Plate crystal : A flat, hexagonal ice crystal whose broad faces are parallel to its base. Its broad faces tend to align horizontally as it falls, creating pillars from ground lights.
Artificial light pillar : A light pillar produced when artificial ground lights reflect from ice crystals in the atmosphere. Streetlights and other bright sources can produce pillars, often visible in cold weather.
Crystal orientation : The direction of a crystal’s internal axes or faces relative to an external reference frame. Pillars require many crystals to present suitably oriented reflecting faces.
Aurora : A natural display of light in the upper atmosphere caused by energetic charged particles. Auroral curtains can appear vertical, but their light is emitted by atmospheric gases rather than reflected.
Specular reflection : Reflection in which light leaves a surface in a single direction determined by the angle of incidence. Reflected rays from ice crystals form the apparent column when they reach an observer.
Antisolar pillar : A vertical luminous column centered on the antisolar point, opposite the Sun in the sky. It is a related ice-crystal column formed opposite the Sun rather than directly above or below it.
Show all 21