"What one needs is a self-reproducing universal constructor... a machine capable of making any device... capable of making a copy of itself. Von Neumann has shown... that such... is theoretically possible, and... a human being is a universal constructor specialized to perform on the surface of the Earth."
Frank Jennings Tipler is an American mathematical physicist and cosmologist, holding a joint appointment in the Departments of Mathematics and Physics at Tulane University. Tipler has written books and papers on the Omega Point based on Pierre Teilhard de Chardin's religious ideas, which he claims is a mechanism for the resurrection of the dead. He is also known for his theories on the Tipler cyli
"The basic idea... is straightforward and... has led other authors, such as Fermi... Dyson... Hart... Simpson... and Kuiper & Morris... to conclude that extraterrestrial beings do not exist: if they did exist and possessed the technology for interstellar communication, they would also have developed interstellar travel and thus would already be present in our solar system."
"[T]hat any intelligent species which develops... interstellar communication will also have... rocketry... is... a consequence of the principle of mediocrity... (that our own evolution is typical)... [T]he human species developed rockets 600 years before... radio waves..."
"[I]t seems likely that a species engaging in interstellar communication would possess a fairly sophisticated computer technology. ...Sagan has asserted that Communication with extraterrestrial intelligence... will require... computer actuated machines with abilities approaching... intelligence."
"I shall assume that such a species will... develop a self-replicating universal constructor with intelligence comparable to the human level—such a machine should be developed within a century, according to the experts...—and... combined with present-day rocket technology would make it possible to explore and/or colonize the Galaxy in less than 300 million years, for an initial investment less than the cost of operating a 10 MW microwave beacon for several hundred years, as proposed by SETI..."
"As the copies of the space probe were made, they would be launched at the stars nearest the target star. When these probes reached these stars, the process would be repeated... until the probes covered all the stars of the Galaxy."
"It is argued that if extraterrestrial intelligent beings exist, then their spaceships must already be present in our solar system."