Twilight has long been popular with photographers and painters, who often refer to it as the blue hour. When the Sun reaches 18° below the horizon, the twilight's brightness is nearly zero, and evening twilight becomes nighttime. The lower the Sun is beneath the horizon and the dimmer the twilight.
See also: The Twilight Saga (film series), List of Twilight characters, Twilight (2008 film), The Twilight Zone, The Twilight Zone (1959 TV series), and Twilight Zone accident.