Ice Crystals Can Create Extraordinary Shapes
Tiny ice crystals in the atmosphere can act almost like microscopic optical instruments.
Their shapes and orientations influence the way sunlight travels through them.
When sunlight encounters appropriately shaped ice crystals, the light can be refracted or reflected, producing luminous structures in the sky.
This is part of the physics behind several atmospheric optical phenomena.
A particularly striking example is a sun pillar, in which vertically aligned or plate-like ice crystals can create an elongated column of light appearing above or below the Sun.
Depending on the atmospheric conditions and the observer’s position, such effects can look remarkably dramatic.
The light does not necessarily represent a physical object occupying the space where it appears to be.
It is an optical pattern created by the interaction between sunlight and crystals suspended in the atmosphere.
The Atmosphere Is Never Completely Uniform
Another important factor is that Earth’s atmosphere is constantly changing.
