Extraterrestrial intelligence: an international petition.

  title={Extraterrestrial intelligence: an international petition.},
  author={Carl E. Sagan},
  volume={218 4571},
  • C. Sagan
  • Published 29 October 1982
  • Physics
  • Science
The human species is now able to communicate with other civilizations in space, if such exist. Using current radioastronomical technology, it is possible for us to receive signals from civilizations no more advanced than we are over a distance of at least many thousands of light years. The cost of a systematic international research effort, using existing radio telescopes, is as low as a few million dollars per year for one or two decades. The program would be more than a million times more… 

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