Sunset

Sundown or sunset is the daily disappearance of the sun below the horizon in the west as a result of rotation of the Earth. 

The time of sunset is defined in astronomy as the time when the trailing edge of the disk of the sun disappears below the horizon in the west. The beam of light from the sunset is very distorted near the horizon due to atmospheric refraction, with fantastic astronomical occur when the Sun's disk and is close to a diameter below the horizon. Sunset is different from the dusk, when night falls, which occurs when the Sun is about eighteen degrees below the horizon. The period between sunset and astronomical twilight is called penumbra. 

Places north of the Arctic Circle and south of the Antarctic Circle experience no sunset or sunrise at least one day each year when day and night polar fleece persists continuously for 24 hours. 

Sunset creates the unique atmospheric conditions such as orange and red often intense sun and the surrounding sky.