Xavier-heights-sunset
The time of sunset is defined in +astronomy as the moment when the trailing edge of the Sun's disk disappears below the horizon. The ray path of light from the setting Sun is highly distorted near the horizon because of atmospheric refraction, making the sunset appear to occur when the Sun’s disk is already about one diameter below the horizon.
Sunset is distinct from dusk, which is the time at which the sky becomes completely dark, which occurs when the Sun is approximately eighteen degrees below the horizon. The period between sunset and dusk is called +twilight.The time of sunset is defined in astronomy as the moment when the trailing edge of the Sun's disk disappears below the horizon. However, it takes over 8 minutes for the light from the Sun to reach the Earth. During that time, the Sun's position in the sky changes by approximately 2 degrees. Near to the horizon, atmospheric refraction causes the ray path of light from the Sun to be distorted to such an extent that geometrically the Sun's disk is already about one diameter below the horizon when sunset is observed
