 Erle Cox's 1925 novel "Out of the Silence" has also been cited as a possible influence on Barjavel.Cox's story also deals with the discovery of a sphere preserving the knowledge of a vanished, prehistoric civilization with advanced technology, one man and one woman being preserved in suspended animation; the woman alone is awakened, but dies at the end of the story; the knowledge of the ancient civilization is lost.Barjavel was also writing in the context of political unrest, especially among the youth of France, that led to mass protests that year similar to those depicted in the novel, see Protests of 1968 and May 1968 in France.