. . "A Sky Full of Ghosts"@en . "4"^^ . . "2014-03-30Z"^^ . . . . . "\"A Sky Full of Ghosts\" is the fourth episode of the American documentary television series Cosmos: A Spacetime Odyssey. It premiered on March 30, 2014 on Fox and on March 31, 2014 on National Geographic Channel. 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."@en . .