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A Brocken spectre (German: Brockengespenst), also called Brocken bow, mountain spectre, or spectre of the Brocken is the magnified (and apparently enormous) shadow of an observer cast in mid air upon any type of cloud opposite to a strong light source. Additionally if the cloud consists of water droplets backscattered a bright area called heiligenschein and halo-like rings of rainbow coloured light called a glory can be seen around the head or apperature silhouette of the spectre. Typically the spectre appears in sunlight opposite to the Sun's direction at the antisolar point.
The phenomenon can appear on any misty mountainside, cloud bank, or from an aeroplane, but the frequent fogs and low-altitude accessibility of the Brocken, a peak in the Harz Mountains in Germany, have created a local legend from which the phenomenon draws its name. The Brocken spectre was observed and described by Johann Silberschlag in 1780, and has since been recorded often in literature about the region.
The "spectre" appears when the sun shines from behind the observer, who is looking down from a ridge or peak into mist or fog. The light projects their shadow through the mist, often in a triangular shape due to perspective. The apparent magnification of size of the shadow is an optical illusion that occurs when the observer judges their shadow on relatively nearby clouds to be at the same distance as faraway land objects seen through gaps in the clouds, or when there are no reference points by which to judge its size. The shadow also falls on water droplets of varying distances from the eye, confusing depth perception. The ghost can appear to move (sometimes suddenly) because of the movement of the cloud layer and variations in density within the cloud.
References in popular culture and the arts
Samuel Taylor Coleridge's poem "Constancy to an Ideal Object" concludes with an image of the Brocken spectre:
And art thou nothing? Such thou art, as when
The woodman winding westward up the glen
At wintry dawn, where o'er the sheep-track's maze
The viewless snow-mist weaves a glist'ning haze,
Sees full before him, gliding without tread,
An image with a glory round its head;
The enamoured rustic worships its fair hues,
Nor knows he makes the shadow he pursues!
Lewis Carroll's "Phantasmagoria" includes a line about a Spectre who "...tried the Brocken business first/but caught a sort of chill/so came to England to be nursed/and here it took the form of thirst/which he complains of still."
Stanisław Lem's Fiasco (1986) has a reference to the "Brocken Specter" (sic): "He was alone. He had been chasing himself. Not a common phenomenon, but known even on Earth. The Brocken Specter in the Alps, for example." The situation, of pursuing one's self, via a natural illusion is a repeated theme in Lem. A scene of significance in his book The Investigation (1975) depicts a detective who, within the confines of a snowy, dead-end alley, confronts a man who turns out to be the detective's own reflection, "The stranger... was himself. He was standing in front of a huge mirrored wall marking the end of the arcade."
In The Radiant Warrior (1989), part of Leo Frankowski's Conrad Stargard series, the protagonist uses the Brocken Spectre to instill confidence in his recruits.
The Brocken spectre is a key trope in Paul Beatty's The White Boy Shuffle (1996), in which a character, Nicholas Scoby, declares that his dream (he specifically calls it a "Dream and a half, really") is to see his glory through a Brocken spectre (69).
In James Hogg's novel The Private Memoirs and Confessions of a Justified Sinner (1824) the Brocken spectre is used to suggest psychological horror.
... I had a dream which both frightened and encouraged me. It was night in some unknown place, and I was making slow and painful headway against a mighty wind. Dense fog was flying along everywhere. I had my hands cupped around a tiny light which threatened to go out at any moment... Suddenly I had the feeling that something was coming up behind me. I looked back, and saw a gigantic black figure following me... When I awoke I realized at once that the figure was a "specter of the Brocken," my own shadow on the swirling mists, brought into being by the little light I was carrying.
In Gravity's Rainbow, Geli Tripping and Slothrop make "god-shadows" from a Harz precipice, as Walpurgisnacht wanes to dawn. Additionally, the French–Canadian quadruple agent Rémy Marathe muses episodically about the possibility of witnessing the fabled spectre on the mountains of Tucson in David Foster Wallace's novel Infinite Jest.
Then the towering buttresses of Batian and Nelion appeared; the rays of the setting sun broke through and, in the east, sharply defined, a great circle of rainbow colours framed our own silhouettes. It was the only perfect Brocken Spectre I have ever seen.
The progressive metal band Fates Warning makes numerous references to the Brocken Spectre in both their debut album title Night on Bröcken and in lyrics on a subsequent song called "The Sorceress" from the album Awaken the Guardian that read "Through the Brocken Spectre rose a luring Angel."
In Charles Dickens's Little Dorrit, Book II Chapter 23, Flora Finching, in the course of one of her typically free-associative babbles to Mr Clennam, says " ... ere yet Mr F appeared a misty shadow on the horizon paying attentions like the well-known spectre of some place in Germany beginning with a B ... "
In the manga and anime Tensou Sentai Goseiger, Brocken Spectres were one of the enemies that Gosei Angels must face.
In the manga One Piece, Brocken spectres make an appearance in the Skypiea story arc.
In the anime Detective Conan, Brocken spectres are mentioned in episode 348 and episode 546 as well.
- Earth's shadow, the shadow that the Earth itself casts on its atmosphere
- Am Fear Liath Mòr, "Big Grey Man" in Scots Gaelic, a supposed supernatural being found on Scotland's second-highest peak, Ben Macdhui
- Dark Watchers, supposed supernatural beings seen along the crest of the Santa Lucia Mountains, in California
- Heiligenschein, an optical phenomenon which creates a bright spot around the shadow of the viewer's head
- Opposition surge, the brightening of a rough surface, or an object with many particles, when illuminated from directly behind the observer
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- Greenler, R (1980). Rainbows, Halos, and Glories. Cambridge University Press.
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- "What are Brocken Spectres and How Do They Form?", an article on the Online Fellwalking Club page (dead link, 2012 archived version)
- A Cairngorm example, from the Universities Space Research Association
- See a picture and a YouTube videoclip taken by Michael Elcock here 
- Snowdon walker captures rare Brocken spectre, BBC News Online, 3 January 2020
- Brocken Spectre panorama
- "Time-lapse video of Brocken specter cast by Mt. Tamalpais fire lookout in Marin County California."