Extraordinary weather phenomenon: the Brocken spectrum

This optical phenomenon has indeed long been considered a divine apparition. It can be seen in all mountains and every winter, new videos of “specters” appear: they are often filmed in the Alps, but also in the United States, Japan or Germany. This phenomenon takes its name from a German peak, the Brocken, the highest point in the Harz range, where it is seen every winter. It was when he saw it in these mountains that the naturalist Johann Silberschlag gave it this name with a paranormal tone, in 1780.

A question of shade, altitude and drops of water

This spectrumwhich can give the impression of being followed by a strange character during a rhiking in the mountains, is actually your shadow, or that of someone next to you! It is a shadow cast on water droplets, which form a mist or a cloud: in this case, the cloud or mist ultimately serves as a screen. The shadow is usually enlarged, stretched, distorted with large limbs.

Around this lugubrious projection, it happens that the light from Sun be diffracted. A luminous circle is then formed which looks like a small haloto colors of the rainbow is called Glory. This luminous circle is not necessarily always visible: this Glory is formed by retro-diffusion, that is to say the diffusion in the direction opposite to the radiation of sunlight by the water droplets.

The phenomenon is observed at altitude, whether in the mountains or even by plane. To see it, it is necessary to have a fairly dense fog or cloud in front of you, as well as the sun in the back. In the case of an observation seen from an airplane, paraglider, ULM orhelicopter, it is the shadow of the device that is cast in the clouds below, the clouds must be lower than the real object. It is therefore necessary that the sky is clear on one side, that a cloud is present on the other side and that an object or a person is present in the middle. The dimensions of the Spectrum are then proportional to the distance between the object or person, and the cloud or fog.

A Ghost that seems very much alive

If you are in movement and the specter is your shadow, it obviously walks with you. But, even while being motionless, one can have the impression that this shadow is moving, which makes this appearance “alive” to eyes of the observer. This movement is very real and is simply explained by the fact that this shadow is projected on droplets in suspension which themselves move (they are the ones which constitute the cloud), hence this Specter which seems to move or vary in size .

The Brocken spectrum does not only occur in the mountains or in an airplane, it can sometimes appear in front of the headlights of a car ! It is enough for an object or a person to be illuminated from behind, with clouds below, to give rise to this appearance.