glory

A glory is a set of concentric colored rings that appear around the antisolar point, the spot directly opposite the sun in the sky. You see it most clearly when you stand on a mountain or aircraft above a cloud layer with the sun behind you, looking down at your shadow cast onto the clouds below. The rings form because sunlight enters water droplets in the cloud, bounces internally, and exits back toward your eye, creating interference patterns that reinforce certain wavelengths of light while canceling others out.

The phenomenon differs fundamentally from a rainbow, which appears 40 to 42 degrees away from the antisolar point and forms from a single internal reflection. A glory sits at the antisolar point itself and involves multiple internal reflections, usually two or three, plus diffraction at the droplet surface. The inner rings are typically violet or blue, with red on the outer edge, though the colors are often pale or washed out because each color appears at slightly different angles.

Glory size and intensity depend on droplet diameter. Water droplets around 10 to 20 micrometers produce bright, tightly spaced rings; smaller droplets in fog create less distinct glorys with wider spacing. Aircraft passengers see glories most reliably when flying at altitude with fair-weather cumulus clouds below, especially over mountains or water where clouds are common and stable. The antisolar point moves across the cloud as your viewing angle changes, so the glory appears to drift across the cloud surface as the aircraft maneuvers.

Confusion and historical naming

Glories are often confused with coronas, which are much smaller rings around the sun or moon itself caused by diffraction around cloud droplets near the light source. Coronas appear close to the solar disk and have a radius of only a few degrees; glories appear far from the sun and are centered on the antisolar point. The term glory, possibly from the halo-like appearance, has stuck in optical literature since at least the 19th century, though the phenomenon was observed and sketched by mountaineers centuries earlier.

In imaging systems and surveillance, glories can degrade contrast and introduce false detail when aircraft or high-altitude platforms collect imagery with the sun near nadir. Computational approaches to remove glories from aerial photographs exist, but are complex because the effect depends on unknown cloud droplet size distributions. Understanding glory formation helps optical engineers predict where halos and artifacts will appear in systems observing from above clouds.