 The episode presented an in-depth treatment of black holes, beginning with John Michell's suggestion of the existence of an "invisible star" to the first discovery of a black hole, Cygnus X-1.The episode's title is an allusion to how light from stars and other cosmic objects takes eons to travel to Earth, giving rise to the possibility that we might be viewing objects that no longer exist.The episode received positive reviews, with one critic remarking on how the "high level of production value is consistently entertaining and informative."