Mirages

Looming

The looming effect is the result of a superior mirage. A typical example is a mirage of a ship formed over cool water in an area where the temperature increases with height. Refraction bends light down toward the water in this case.

Twinkling

Star twinkling is caused by nonuniformity in the index of refraction caused by turbulence of the air through which the light from the stars travel. Stars are so distant that they appear as points of light, so that point of light will appear to dance about as it encounters different "cells" of the atmosphere which have different temperatures and/or densities. Planets are close enough that they appear as disks of light which tend to average the light over multiple cells of the atmosphere and they appear as steadier, even though they are not perceived to be larger than stars by the unaided eye.

Pillars

Sun pillars are caused by reflection from falling ice crystals, unlike the 22° halo and sun dogs which are refraction phenomena.

Crepuscular Rays

Rays or beams of light may appear to fan out radially from a low sun when the cloud structure is right. The rays from the sun, 93 million miles away, are parallel - but in the setting of the crepuscular rays they appear to diverge because of perspective narrowing over the long path on which they are visible (like the apparent converging of railroad tracks when you look down a long straight track.) Under rare conditions the crepuscular rays extend all the way across the sky and appear to converge back together on the horizon opposite the sun.