One Light Year

from the given of time that is restored to light or given to know light from appearing 4 seconds in or out the closing or opening of the eye. for example someone who goes inside a house will experience 4 seconds of darkness before they see light. or vise versa someone going out side in the dark will experience the speed of light that casted from the eye and given to be understood that if a star appears in 4 seconds then that star would be a light year away.