Erich Von Daniken, Chariots of the Gods: Unsolved Mysteries of the Past

Professor Dr Willy Ley, the well-known scientific writer and friend of Wernher von Braun, told me in New York: 'The estimated number of stars in our Milky Way alone amounts to 30 milliards. The assumption that our Milky Way contains at least 18 milliard planetary systems is considered admissible by present-day astronomers. If we now try to reduce the figures in question as much aspossible and assume that the distances between planetary systems are so regulated that only in one case in a hundred does a planet orbit in the ecosphere of its own sun, that still leaves 180 million planets capable of supporting life. If we further assume that only one planet in a hundred that might support life actually does so, we should still have the figure of 1-8 million planets with life. Let us further suppose that out of every hundred planets with life there is one on which creatures with the same level of intelligence as homo sapiens live. Then even this last supposition gives our 'Milky Way the vast number of 18,000 inhabited planets.'