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The Block Inspector, a term used whilst I was
on the Stafford team for a Brocken Spectre, hehehe! But be warned I spent
12 years on MR and only saw four in all that time. I would sometimes go
miles off route to find the best position to view, this phenomenon. I was
once on the summit of Helvellyn and realised that I would be able to view
the Spectre from the Col between 863(White Side) and Raise, looking down
into Keppel Cove. This meant we had to go back down the mountain, climb
two hills we had already done and drop into the Col the troops were initially
pi**ed off because they had no idea what I was up to. They were however
amazed at the sight of the Brocken Spectre, which made the extra couple
of miles well worth while. |
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So what is a Brocken Spectre? Below is an explanation of what is happening
when this phenomenon occurs, if you understand the bit below about the
polarisation of the glory, please let me know exactly what it means (In
simple MR troop terms), as I haven’t got a clue.
The Brocken Spectre or Spectre of the Brocken is a rather mysterious |
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phenomenon. If you are on the hill occasionally
you may break through the clouds into the bright sunlight. When they turn
around they are confronted by a giant with multi-coloured rings around his
head. The spectacle was named the Spectre of the Brocken after the peak
in the Harz Mountains of Germany, where it is often seen. The giant figure
is your shadow cast over the cloud, which is often exaggerated in size depending
how close or far away; you are from the clouds. But the coloured rings around
the head, the Glory, proved much more difficult to explain. |
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The physical origin of the glory was an optical
riddle until the seventies, when it was calculated correctly by scattering
theory. The small water drops of clouds and fog produce it; however, no
intuitive physical explanation is available. In part the glories come from
light guided by the interface of water and air and in part from light that
undergoes ten internal reflections.
The polarisation of the glory is extremely unusual. The coloured rings are
radially polarised, contrary to a rainbow. On the other hand, the white
region close to the centre is |
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tangentially polarised. With a linear polarizer
a distinctive pattern appears, formed by sections of the coloured rings
plus dark triangles in the centre region pointing towards the centre. |
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So that was the explanation! Below are a few interesting facts about the
Brocken Spectre: - If you see such an effect on the hill, you may be
perplexed by the fact that the coloured rings appear only around the shadow
of your own head - and not around the shadows of your companions. Of course,
each of your companions sees rings around their own shadows - but not
around yours! Even more strangely, if you take a picture with a camera
at the end of your outstretched arm, the picture will show rings around
the shadow of the camera. |
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In a more superstitious era, it is easy to understand why such people might
interpret these coloured rings as a sign that they were "special"
or, even, that, they had been anointed, by God. Perhaps, the idea that saints
have halos around their heads originated from reports of glories. Many classical
paintings show halos as vertical discs centred on the eyes of saints.
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It is worth to look for the glory when travelling
by plane as it is quite common. In fact, at one time some pilots used it
to find the position of the sun when it was behind them and there was no
visible shadow ("shooting the glory"). Interestingly, the pilot
will see the glory centred on the front of the aircraft shadow (if visible),
while a passenger on the last seat will see it centred towards the tail
of the shadow. |
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Glories vary considerably in size, depending
on the radius of the water droplets of the cloud in which they have their
origin. The smaller the water droplets in the cloud, the larger the diameter
of the Glory. Now you know everything about the Brocken Specter, get
on the hill and find one! And don’t forget your camera! |
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Jim 'Dip' Thomas |
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