A glory is an optical phenomenon, resembling an iconic saint's halo around the shadow of the observer's head, caused by sunlight or (more rarely) moonlight interacting with the tiny water droplets that comprise mist or clouds. The glory consists of one or more concentric, successively dimmer rings, each of which is red on the outside and bluish towards the centre. Due to its appearance, the phenomenon is sometimes mistaken for a circular rainbow, but the latter has a much larger diameter and is caused by different physical processes. Glories arise due to wave interference of light internally refracted within small droplets. Appearance and observation Depending on circumstances (such as the uniformity of droplet size in the clouds), one or more of the glory's rings can be visible. The angular size of the inner and brightest ring is much smaller than that of a rainbow, about 5° to 20°, depending on the size of the droplets. In the right conditions, a glory and a rainbow can occur simultaneously. Like a rainbow, a glory is centred on the antisolar (or, in case of the moon, antilunar) point, which coincides with the shadow of the observer's head. Since this point is by definition diametrically opposed to the sun's (or moon's) position in the sky, it always lies below the observer's horizon when the sun (or moon) is up. In order to see a glory, therefore, the clouds or fog causing it must be located below the observer, in a straight line with the Sun/Moon and the observer's eye. Hence, the glory is commonly observed from a high viewpoint such as a mountain, tall building or from an aircraft. In the latter case, if the plane is flying sufficiently low for its shadow to be visible on the clouds, the glory always surrounds it. This is sometimes called The Glory of the Pilot. Brocken spectre When viewed from a mountain or tall building, glories are often seen in association with a Brocken spectre, also called Mountain spectre, the apparently enormously magnified shadow of an observer, cast (when the sun is low) on clouds below the mountain on which the viewer is standing. 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 is frequently misty, conditions conducive to casting a shadow on a cloud layer are common.