Atmospheric Optical Phenomena

Perhaps the most common example of an atmospheric effect created by refraction is the displacement of astronomical bodies. When the sun is directly overhead, the light rays it emits pass straight through Earth's atmosphere. No refraction occurs, and no change in the sun's apparent position takes place.

As the sun approaches the horizon, that situation changes. Light from the sun now enters Earth's atmosphere at an angle and is refracted. The eye sees the path of the light as it is bent and assumes that it has come from a position in the sky somewhat higher than it really is. That is, the sun's apparent location is displaced by some angle from its true location. The same situation is true for any astronomical object. The closer a star is to the horizon, for example, the more its apparent position is displaced from its true position.