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No. 21: May-Jun 1982

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Don't build von neumann machines

Back in April 1981, Frank J. Tipler published a comment in Physics Today entitled, "Extraterrestrial Beings Do Not Exist." A key element of his argument was that the first intelligent civilization would inevitably colonize the entire universe with themselves or their self-reproducing (von Neumann) machines. Since we can detect neither kind of colonist, we must be the first and only intelligent civilization. Essentially Tipler was criticizing the prevailing notion that, from a statistical point of view, there must be many other civilizations among the numberless stars and galaxies. Tipler's thoughts evoked a richly provocative group of letters, some of which were published in the March 1982 issue of Physics Today along with a closely related article by Ornstein.

Ornstein tackled the problem of estimating the probability that intelligent life would evolve on other planets from a biologist's perspective. Whereas some physical scientists have set this probability at about 1.0, Ornstein inclines toward 10-9 , believing that intelligent life is probably unique to the earth. But concludes Ornstein, the 15 separate developments of eyes among disparate terrestrial organisms may infer some unrecognized directing factor in evolution that would force him to revise his estimate upwards drastically.

On the other hand, those 15 eyes might indicate a common, but still undiscovered, eye-possessing ancestor far back along evolution's track. The fossil record might be mute on this matter because eyes are soft tissues that are rarely preserved or perhaps because many eyes were jettisoned because the organisms didn't need them, as cave dwellers are wont to do with surprising rapidity.

Some of the letters responding to Tipler questioned whether an intelligent civilization would be stupid enough to build self-reproducing von Neumann machines for galactic exploration. Wouldn't it be far more fun to go in person rather than by proxy? And, some pointed out, von Neumann machines would be ravenous consumers of energy and materials and might turn on man as an unnecessary competitor. Machines are not immutable. Space radiation and other environmental factors might alter computer programs and memories to drastically affect the behavior and objectives of such machines. Actually, as one letter writer observed, the earth has already been invaded by a self-reproducing, energy-hungry machine with exploratory tendencies -- man!

(Anonymous; "Extraterrestrial Intelligence: The Debate Continues," Physics Today, 35:26, March 1982. Also: Ornstein, Leonard; "A Biologist Looks at the Numbers," Physics Today, 35:27, March 1982.)

From Science Frontiers #21, MAY-JUN 1982. 1982-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:


  • "A sourcebook of unexplained phenomena is therefore a valuable addition to a collection of scientific literature. William R. Corliss has provided this in the past with his source books of scientific anomalies in several subjects, and now he has provided it for astronomy. He has done an excellent job of collecting and editing a large amount of material, taken in part from scientific journals and in part from scientific reporting in the popular or semi-scientific press." -- "The Mysterious Universe: A Handbook of Astronomical Anomalies", reviwed by Thomas Gold, Cornell University, in Icarus, vol.41, 1980

  • "An interesting, systematic presentation of unusual weather [..] This book is recommended for a general audience" --"Corliss, William R., Tornados, Dark Days, Anomalous Precipitation, and Related Weather Phenomena, Sourcebook Project, 1983.", revieweed in Choice, September 1983
  • "..the science is necessarily somewhat speculative, but Corliss's symthesis is based on reputable sources." -- "Corliss, William R. (Compiler). Lightning, Auroras, Nocturnal Lights, and Related Luminous Phenomena" reviwed by Joseph M. Moran, Univ. of Wisconsin in Science Books and Films, Sep/Oct 1983

  • "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 (1987), p. 24., 02/1987