Due to earth’s rotation, everyday we can the sun disappearing below the horizon or the sun beginning to fall below the horizon. This is commonly termed as sunset. This is an atmospheric condition which usually occurs after or before the sun disappears below the horizon. In astronomy sunset is defined as the trailing edge of the sun's disk disappearing in the west below the horizon. While the sun is setting the ray path is highly distorted near the horizon due to refraction of the light in the atmosphere. Due to atmospheric refraction, the light of the sun is bent and this makes the sun visible when it is below the horizon also.
