A ghostly figure haunting the mountain mists

A tradition has grown up in the Footler household that we take to the hills for a walk on New Year’s day. The weather can be unreliable and one has to take extra care but even on a grim winter day there will be something to look out for.

However, there is one strange phenomenon that we have yet to witness. The Brocken spectre was named after a peak called the Brocken among the Harz Mountains in Germany where conditions are particularly favourable for this optical illusion. The spectre has often been seen in the Haleakala National Park in Hawaii and was also recorded in ancient China where it was known as “Buddha’s light”.

A Brocken spectre is in fact one’s own shadow cast onto mist or cloud. It appears when the sun is shining from behind someone who is looking down from a ridge or peak into the mist. The apparition can appear to move as the density of the mist varies and the clouds swirl around the mountain.

The image is often accompanied by another optical effect known as “the glory”. In this instance the head of the figure is surrounded by rings of coloured light like a halo of rainbows. This occurs as the sunlight is reflected by uniformly sized water droplets in the mist. Monks and pilgrims who witnessed this effect thought themselves particularly enlightened.

Brocken spectres have also been seen from aircraft when the plane’s shadow is cast on underlying clouds. In the early years of aviation pilots occasionally reported these illusions, which came to be known as “pilot’s glory”, as other aircraft flying too close for safety.

It must still be a terrifying sight for an inexperienced pilot, who might then execute a panic-stricken manoeuvre.