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Glory and Brocken Spectre – optical phenomena at fog margins

The Glory is a light phenomenon that can be observed from an aeroplane, hot air balloon or other aircraft. It consists of coloured rings, usually circular, around the shadow cast by an aircraft on the cloud or layer of fog.


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Glories can also be observed from the ground. The chances of seeing this phenomenon, especially on hills or mountain tops, are quite high in suitable weather situations, as it occurs relatively frequently. The observer only has to stand with his or her back to the sun as the sun's rays fall on a layer of fog or cloud in front of or below the observer.

The theoretical explanation for the formation of Glories is relatively complex, and for a long time the phenomenon was not fully understood. Simply put, the incident light is scattered in all directions by the fog droplets, with some of it going in the direction of the observer. Due to its wave-like properties the light is diffracted (in physics, this is referred to as Mie scattering, diffraction and interference).

It is not only the coloured rings that are impressive. To someone standing close to the fog layer, as in the picture above, the movement and vastness of their own shadow can be quite disconcerting. With the sun at the person's back, the shadow is projected onto the screen of fog and can look outlandishly large. This eerie phenomenon is known as the Brocken Spectre.

The name comes from the Brocken in the Harz mountains, the highest mountain in northern Germany at 1,141 metres. Because the Brocken's location is very open and also prone to fog (for more than 300 days a year), the Brocken Spectre is a frequent and very impressive visitor here.