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The search for extraterrestrial intelligence

Abstract

As far as we know, humanity is alone in the Universe: there is no definite evidence for the existence of extraterrestrial life, let alone extraterrestrial civilizations (ETCs) capable of communicating or travelling over interstellar distances. Yet popular speculation about the existence of ETCs abounds, including reports of alien visitations either now or in the past. But there is a middle way. It is now possible to put limits on the existence of ETCs of varying capabilities, within arbitrary distances from the Solar System, and conceive of real-world strategies whereby we might communicate with ETCs, or they with us.

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Figure 1: Noise from the Earth's atmosphere and the minimum noise from our Galaxy, versus wavelength.
Figure 2: How increases in effective radiated power (ERP) of a transmitting radio dish are related to wavelength and the size and distance of the target.
Figure 3: An example of a possible message from an ETC.

References

  1. Hart, M. H. An explanation for the absence of extraterrestrials on Earth. Q. J. R. Astron. Soc. 16, 128–135 (1975).

    ADS  Google Scholar 

  2. Sagan, C. & Drake, F. D. The search for extraterrestrial intelligence. Sci. Am. 232, 80–89 (May 1975).

    ADS  Article  Google Scholar 

  3. Vogt, S. S., Marcy, G. W., Butler, P. R. & Apps, K. Six new planets from the Keck Precision Velocity Survey. Astrophys. J. 536, 902–914 (2000).

    ADS  CAS  Article  Google Scholar 

  4. McKay, D. S. et al. Search for past life on Mars: possible relic biogenic activity in martian meteorite ALH84001. Science 273, 924–930 (1996).

    ADS  CAS  Article  Google Scholar 

  5. Ward, P. D. & Brownlee, D. Rare Earth: Why Complex Life is Uncommon in the Universe (Copernicus Books, New York, 2000).

    Google Scholar 

  6. Cocconi, G. & Morrison, P. Searching for interstellar communications. Nature 184, 844–846 (1959).

    ADS  Article  Google Scholar 

  7. Drake, F. D. in Current Aspects of Exobiology (eds Mamikunian, G. & Briggs, M. H.) 323–345 (Pergamon, New York, 1965).

    Book  Google Scholar 

  8. Baum, L. F. The Wizard of Oz (Bobbs-Merrill, New York, 1900).

    Google Scholar 

  9. Tarter, J. in The Search for Extraterrestrial Intelligence (eds Kellermann, K. I. & Seilstad, G. A.) 79–98 (National Radio Astronomy Observatory, Greenbank, 1986).

    Google Scholar 

  10. Tarter, J. & Klein, M. in Progress in the Search for Extraterrestrial Life (ed. Shostak, G. S.) ASP Conf. Ser. 74, 457–469 (The Astronomical Society of the Pacific, 1995).

    Google Scholar 

  11. McDonough, T. in Progress in the Search for Extraterrestrial Life (ed. Shostak, G. S.) ASP Conf. Ser. 74, 419–422 (The Astronomical Society of the Pacific, 1995).

    Google Scholar 

  12. Pierson, T. in Progress in the Search for Extraterrestrial Life (ed. Shostak, G. S.) ASP Conf. Ser. 74, 443–444 (The Astronomical Society of the Pacific, 1995).

    Google Scholar 

  13. Werthimer, D., Ng, D., Bowyer, S. & Donnelly, C. in Progress in the Search for Extraterrestrial Life (ed. Shostak, G. S.) ASP Conf. Ser. 74, 293–301 (The Astronomical Society of the Pacific, 1995).

    Google Scholar 

  14. Rohlfs, K. & Wilson, T. L. Tools of Radio Astronomy 3rd edn (Springer, Heidelberg, 1999).

    Google Scholar 

  15. Leigh, D. & Horowitz, P. in Bioastronomy '99—A New Era in Bioastronomy (eds Lemarchand, G. & Meech, K.) ASP Conf. Ser. 213, 459–465 (The Astronomical Society of the Pacific, 2000).

    Google Scholar 

  16. Welch, W. J. & Dreher, J. in Radio Telescopes (ed. Butcher, H. R.) Proc. SPIE 4015, 8–18 (2000).

    Book  Google Scholar 

  17. Oliver, B. M. & Billingham, J. (eds) Project Cyclops. NASA CR-114445 (1973).

  18. Kuiper, T. B. H. & Morris, M. Searching for extraterrestrial civilizations. Science 196, 616–621 (1977).

    ADS  CAS  Article  Google Scholar 

  19. Mauersberger, R. et al. SETI at the spin-flip line frequency of positronium. Astron. Astrophys. 306, 141–144 (1996).

    ADS  CAS  Google Scholar 

  20. Kardashev, N. S. Optimal wavelength region for communication with extraterrestrial intelligence—λ=1.5 mm. Nature 278, 28–30 (1979).

    ADS  Article  Google Scholar 

  21. Kardashev, N. S. Transmission of information by extraterrestrial civilizations Sov. Astron. 8, 217–221 (1964).

    ADS  Google Scholar 

  22. LePage, A. J. Where they could hide. Sci. Am. 283, 40 (2000).

    ADS  CAS  Article  Google Scholar 

  23. Cordes, J. M. & Sullivan, W. T. III in Progress in the Search for Extraterrestrial Life (ed. Shostak, G. S.) ASP Conf. Ser. 74, 325–334 (The Astronomical Society of the Pacific, 1995).

    Google Scholar 

  24. Cohen, C. & Charlton, D. in Progress in the Search for Extraterrestrial Life, (ed. Shostak, G. S.) ASP Conf. Ser. 74, 313–322 (The Astronomical Society of the Pacific, 1995).

    Google Scholar 

  25. Townes, C. H. At what wavelength should we search for signals from extraterrestrial intelligence? Proc. Natl Acad. Sci. USA 80, 1147–1151 (1983).

    ADS  CAS  Article  Google Scholar 

  26. Kingsley, S. A. in The Search for Exterrestrial Intelligence in the Optical Spectrum Vol. II (ed. Kingsley, S. A. & Lemarchand, G. A.) Proc. SPIE 2704, 102–116 (1996).

    Google Scholar 

  27. Howard, A. et al. in Bioastronomy '99—A New Era in Bioastronomy (eds Lemarchand, G. & Meech, K.) ASP Conf. Ser. 213, 545–552 (The Astronomical Society of the Pacific, 2000).

  28. Dyson, F. J. in Perspectives in Modern Physics (ed. Marshak, R. E.) 641 (Wiley, New York, 1966).

    Google Scholar 

  29. Brin, G. D. The 'great silence': the controversy concerning extraterrestrial intelligent life. Q. J. R. Astron. Soc. 24, 283–309 (1983).

    ADS  Google Scholar 

  30. Morrison, P. M. in Interstellar Communication: Scientific Perspectives 168–186 (ed. Ponnamperuma, C. & Cameron, A. G. W. (Houghton-Mifflin, Boston, 1974).

    Google Scholar 

  31. Oliver, B. M. Efficient interstellar rocketry. International Astronautical Federation IAA-87-606, 1–6 (1987).

  32. Bracewell, R. N. The Galactic Club (Freeman, San Francisco, 1974).

    Google Scholar 

  33. Sullivan, W. T. III, Brown, S. & Wetherill C. Eavesdropping: the radio signature of the Earth. Science 199, 377–388 (1978).

    ADS  Article  Google Scholar 

  34. Glaser, P. E. Power from the Sun: its future Science 162, 857–861 (1968).

    ADS  CAS  Article  Google Scholar 

  35. Wilson, T. L. & Huettemeister, S. Tools of Radio Astronomy: Problems and Solutions p. 15 (Springer, Heidelberg, 2000).

    Book  Google Scholar 

Download references

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Correspondence to T. L. Wilson.

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Wilson, T. The search for extraterrestrial intelligence. Nature 409, 1110–1114 (2001). https://doi.org/10.1038/35059235

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