Brocken Spectres, optical phenomena, area combination of projected shadow and an iridescent glory. They are usually, but not exclusively, seen in misty conditions in the mountains and sighting a Brocken Spectre is particularly prized by walkers and climbers. As an origin of the halo, they are found in sacred art of many cultures.
Early accounts of Brocken Spectres described the spectre as 'looming', a shadowy form, large, threatening or approaching. I certainly felt this as my shadow on the vapour moved forward and back, larger and smaller in the breeze. Twice I involuntarily moved backward as the wind suddenly carried the spectre towards me.
Rainbow and glories have much in common but their differences are telling. The optics of the spectrum with light refracted, reflected and diffracted within water droplets, can be explained by post Newtonian physics. The Brocken Spectre is similar but, with the size of water droplets of mist approaching the wave length of light, there is a curious shifting of the light around the edge to make the mathematics work. The theories of Mie Scattering can predict the scale and patterns of the glory. But this is short of a full explanation. Some mystery still surrounds the Brocken Spectre.
Part of a Bend In The River project to be shown this autumn at the old St John the Divine in Gainsborough under the title of Seeing the Light.