Glory (optical Phenomenon) - Theory

Theory

The explanation of Glories is still subject of debates and research. In 1947, the Dutch astronomer Hendrik van de Hulst suggested that surface waves are involved. He speculated that the colored rings of the glory are caused by two-ray interference between "short" and "long" path surface waves—which are generated by light rays entering the droplets at diametrically opposite points (both rays suffer one internal reflection). A new theory by Brazilian physicist Herch Moysés Nussenzveig, however, suggests that the light energy beamed back by a glory originates mostly from classical wave tunneling, which is when light rays that missed a droplet can still transfer energy into it.

Glories are often seen in association with a Brocken spectre, the apparently enormously magnified shadow of an observer, cast (when the Sun is low) on clouds below the mountain the viewer is standing on. The name derives from the Brocken, the tallest peak of the Harz mountain range in Germany. Because the peak is above the cloud level and the area frequently misty, conditions conducive to casting a shadow on a cloud layer are common. Giant shadows that seemed to move by themselves due to movement of the cloud layer (this movement is another part of the definition of the Brocken Spectre), and that were surrounded by optical glory halos, may have contributed to the reputation the Harz mountains hold as a refuge for witches and evil spirits. In Goethe's Faust, the Brocken is called the Blocksberg and is the site of the Witches' Sabbath on Walpurgis Night.