Fear not, this isn’t an early Halloween posting though the word ‘Spectre’ is accurate in the spooky image that it relates to.
In my last post on climbing Skiddaw, I neglected to mention that I was lucky enough to see a Brocken Spectre. These are rather rare natural occurrences though I am fortunate to have seen another, one many years ago, I must add.
Though it is not a ghostly apparition, it is easy to see why some in times past might have thought a Brocken Spectre to be a close encounter with a visit from the spirit world.
The Brocken Spectre is a rare thing because it is in some ways rather like a rainbow and so it’s appearance is only fleeting. Most of us see Rainbows from time to time as an arch that rises from the horizon and peaks in the sky before dropping away again in the opposite direction.
If you travel in mountains or even aeroplanes, if you are very lucky then you will see what is known as a Glory. It looks like a circular rainbow, rather like a target on an archery or shooting range. It has a much smaller appearance than a rainbow and to the viewer seems to be only a few feet or metres across when it becomes visible on a mountainside.
The rarest of all is a Brockenspectre which is what I was lucky enough to observe for about 30 seconds last Sunday. In addition to the unusual conditions needed for a glory or a rainbow, a Brockenspectre is the apparently enormous and magnified shadow of an observer, cast upon the upper surfaces of clouds opposite the sun. The head of the figure is often surrounded by the glowing halo-like rings of a glory—rings of coloured light that appear directly opposite the sun when sunlight meets a cloud of uniformly-sized water droplets.
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 his or her 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.
In my case, I saw it because the sun was behind me and at the same level or below the mountain ridge I was on top off. Between myself and the sun was a bank of fog or cloud which was quite thick behind me but in front of me quickly wafted away. Due to a long run of coincidences, my shadow was stretched out by the sun and fog with the shadow of my head, centred in the Glory to give the appearance of a scary monster or Brockenspectre.
Even when I saw the Brockenspectre, it was fading so rather than fumble for a photo, I stood and watched this very rare phenomenon. In fact, I was standing near an elderly climber who has climbed thousands of peaks, and this was only the 4th spectre which he had seen so I was very lucky indeed.
The term Brocken Spectre originated in 1780 when it was observed and described by Johann Silberschlag in 1780 in the Harz Mountains of Germany. An 18th-century writer who spent much of his time in the Lake District, Samuel Taylor Coleridge, penned a verse after his encounter with one not too far away from mine.
Constancy to an Ideal Object
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!