Akademik

   Also known as Spectre of the Brocken and mountain spectre. The name Brocken spectre, or Brockengespenst in German, refers to the Brocken, a peak in the Harz mountains in Germany. It is used to denote a * physical illusion consisting of the observer's disproportionally large shadow projected upon the surfaces of clouds at the horizon facing the rising or setting Sun. The person credited with documenting the phenomenon for the first time, in 1780, is the German theologist and natural scientist Johann Esaias Silberschlag (1721-1791). As noted by Silberschlag and numerous observers after him, both near the Brocken peak and in other mountainous regions. Brocken spectres typically arise when a low-lying Sun projects a large shadow into a bank of mist or fog in the distance. The resulting shadow figure may appear to be moving. and strike one as being three-dimensional in shape because of the extent to which the shadow is projected into the fog. and because of the relative movements of separate fog banks. Lending the phenomenon an even more impressive appearance. Brocken spectres can be accompanied by coloured concentric arches or circles, called glories or * Brocken bows, and a pale outer arch or circle which is called a white rainbow or *Ulloa circle. These * halo figures are explained by reference to the interaction of sunlight and droplets of water suspended in the air.

   References

   Flammarion, C. (1873). The atmosphere.Trans-lated by Pitman, C.B. Edited by Glaisher, J. London: Sampson Low, Marston, Low, & Searle.

   Lynch, D.K., Livingston, W. (1995). Color and light in nature. Cambridge: Cambridge University Press.