Light pillar
Encyclopedia
A light pillar is a visual phenomenon created by the reflection
of light
from ice
crystals with near horizontal parallel
planar surfaces. The light can come from the Sun
(usually at or low to the horizon) in which case the phenomenon is called a sun pillar or solar pillar. It can also come from the Moon
or from terrestrial sources such as streetlights.
The light pillar looks like a thin column that extends vertically above and/or below the source of light. The light pillar is prominently visible when the Sun is low or lies below the horizon. It normally forms an arc that extends from five to ten degrees beyond the solar disc. Light pillars can sometimes also be seen arising from the Moon.
Light pillars are formed by reflection from ice crystals with roughly horizontal faces.
Reflection (physics)
Reflection is the change in direction of a wavefront at an interface between two differentmedia so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves...
of light
Light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
from ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...
crystals with near horizontal parallel
Parallel (geometry)
Parallelism is a term in geometry and in everyday life that refers to a property in Euclidean space of two or more lines or planes, or a combination of these. The assumed existence and properties of parallel lines are the basis of Euclid's parallel postulate. Two lines in a plane that do not...
planar surfaces. The light can come from the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
(usually at or low to the horizon) in which case the phenomenon is called a sun pillar or solar pillar. It can also come from the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
or from terrestrial sources such as streetlights.
Images
Light pillars are a kind of optical phenomenon which is formed by the reflection of sunlight or moonlight by ice crystals that are present in the Earth's atmosphere.The light pillar looks like a thin column that extends vertically above and/or below the source of light. The light pillar is prominently visible when the Sun is low or lies below the horizon. It normally forms an arc that extends from five to ten degrees beyond the solar disc. Light pillars can sometimes also be seen arising from the Moon.
Light pillars are formed by reflection from ice crystals with roughly horizontal faces.
See also
- HaloHalo (optical phenomenon)A halo from Greek ἅλως; also known as a nimbus, icebow or gloriole) is an optical phenomenon produced by ice crystals creating colored or white arcs and spots in the sky. Many are near the sun or moon but others are elsewhere and even in the opposite part of the sky...
- Light beamLight beamA light beam or beam of light is a narrow projection of light energy radiating from a source into a beam. Sunlight is a natural example of a light beam when filtered through various mediums...
- Sun DogSun dogA sun dog or sundog, scientific name parhelion ; , also called a mock sun or a phantom sun, is an atmospheric phenomenon that creates bright spots of light in the sky, often on a luminous ring or halo on either side of the sun.Sundogs may appear as a colored patch of light to the left or right of...
- False sunriseFalse sunriseA false sunrise or dawn sundog is a very particular kind of parhelion, belonging to the optical phenomenon family of halos.It is an atmospheric optical phenomenon associated with the reflection or refraction of sunlight by small ice crystals making up cirrus or cirrostratus clouds in the very...
- False sunsetFalse sunsetA false sunset or sunset sundog is a very particular kind of parhelion, belonging to the optical phenomenon family of halos.It is an atmospheric optical phenomenon associated with the reflection and refraction of sunlight by small ice crystals making up cirrus or cirrostratus clouds in the very...
External links
- Pillars. Atmospheric Optics. Explanations (10 pages) and many images.
- Light Pillars: An Introduction to Sun Pillars and Related Phenomena. The Weather Doctor's Weather Eyes. Another nice explanation, all on one page
- Fabulous frozen frames - Sydney Morning Herald. November 1, 2006
- A Sun Pillar Over North Carolina. NASA Astronomy Picture of the DayAstronomy Picture of the DayAstronomy Picture of the Day is a website provided by NASA and Michigan Technological University . According to the website, "Each day a different image or photograph of our universe is featured, along with a brief explanation written by a professional astronomer."The photograph is not necessarily...
, 15 December 2008 - Interactive view of sky-wide artificial light pillar show photographed in Finland, November 2010.