Glory (optical phenomenon)

A glory is an optical phenomenon appearing much like an iconic Saint's halo about the head of the observer which is produced by light backscattered (a combination of diffraction, reflection and refraction) towards its source by a cloud of uniformly-sized water droplets. The association with a halo is not coincidental, but derivative, though a real glory has multiple colored rings. Most people see only one ring. The glory, however, can show many rings when the cloud is made of uniform water droplets. Sometimes the rings fluctuate wildly in size. This happens when a plane, for instance, skirts a canyon of clouds and its glory shadow comes and goes. [ [http://www.weatherquesting.com/glory.htm Glories!] ]

The angular size is much smaller than a rainbow, about 5° to 20°, depending on the size of the droplets. Since it is seen in the direction opposite the sun, it is most commonly observed while airborne, with the glory surrounding the airplane's shadow on clouds (this is often called "The Glory of the Pilot"). The phenomenon is also known as an anthelion.

Theory

In 1947, the Dutch astronomer Hendrik van de Hulst suggested that surface waves were involved in the formation of glories. The colored rings of the glory are caused by two-ray interference between "short" and "long" path surface waves – which are generated by light rays entering the droplets at diametrically opposite points (both rays suffer one internal reflection). For a more complete description, see the external link to "How are glories formed?"

Glories are often seen in association with a Brocken spectre, the apparently enormously magnified shadow of an observer, cast (when the Sun is low) upon the upper surfaces of clouds that are below the mountain upon which he or she stands. The name derives from the Brocken, the tallest peak of the Harz mountain range in Germany. Because the peak is above the cloud level, and the area is frequently misty, the condition of a shadow cast onto a cloud layer is relatively favored. The appearance of giant shadows that seemed to move by themselves due to the movement of the cloud layer (this movement is another part of the definition of the Brocken Spectre), and which were surrounded by optical glory halos, may have contributed to the reputation the Harz mountains hold as a refuge for witches and evil spirits. In Goethe's Faust, the Brocken is called the "Blocksberg" and is the site of the Witches' Sabbath on Walpurgis Night.

Glories in culture

C. T. R. Wilson saw a glory while working as a temporary observer at the Ben Nevis weather station. Inspired by the impressive sight, he decided to build a device for creating clouds in the laboratory, so that he could make a synthetic, small-scale glory. His work led directly to the cloud chamber, a device for detecting ionizing radiation for which he and Arthur Compton received the Nobel Prize for Physics in 1927.

In China, this phenomenon is called Buddha's light. It was often observed on cloud-shrouded high mountains, such as Huangshan Mountains and Mount Emei. Records of the phenomenon at Mount Emei date back to A.D. 63. The colorful halo always surrounds the observer's own shadow, and thus was often taken to show the observer's personal enlightenment (associated with Buddha or divinity).

Glories in literature

Engineer and science-fiction Leo Frankowski made glories a key plot element in his Conrad Stargard saga, where the protagonist and title character, a Polish engineer named Conrad Schwartz is sent back in time to the 13th Century where he has to establish himself and cope with various crises including planning for the eventual Mongol invasion of Eastern Europe in 1241, nine years after his arrival. After establishing himself as gentry in the first two works, in the third book "The Radiant Warrior" Stargard begins building a modern army and uses the reliable glories along one stretch of his boot camp to invoke religious faith backed "esprit de corps" and feelings of elite invincibility in his newly forming cadre. The same phenomena dupes the highly pious heir apparent of the Polish duchy into strongly supporting the new model armies pragmatic departures from the days chivalristic practices and allows him to proceed with building a large well trained standing army centuries ahead of the Napoleonic wars that in the end protects the west from the Mongols.

See also

* Rainbow
* Antisolar point
* Subparhelic circle
* Gegenschein
* Heiligenschein
* Sylvanshine
* Aureola

Notes, links and references

External links

* [http://www.atoptics.co.uk/droplets/glory.htm Glories - Explanation and image gallery]
* [http://freespace.virgin.net/ljmayes.mal/var/glorytxt.htm Glories - an Atmospheric Phenomenon]
* [http://www.philiplaven.com/p2c1a.html How are glories formed?]

References

Citation
last = Mayes
first = Lawrence
title = Glories - an Atmospheric Phenomenon
date = 01/09/2003
year = 2003
url = http://freespace.virgin.net/ljmayes.mal/var/glorytxt.htm
accessdate = 09/04/2007

Citation
last = Nave
first = R
title = Coronas
date = Undated
url = http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/corona.html#c2
accessdate = 09/04/2007

Footnotes