A Caltech Library Service

Searching for Extraterrestrial Civilizations

Kuiper, T. B. H. and Morris, M. (1977) Searching for Extraterrestrial Civilizations. Science, 196 (4290). pp. 616-621. ISSN 0036-8075. doi:10.1126/science.196.4290.616.

Full text is not posted in this repository. Consult Related URLs below.

Use this Persistent URL to link to this item:


We have argued that planning for a search for extraterrestrial intelligence should involve a minimum number of assumptions. In view of the feasibility (at our present level of understanding) of using nuclear fusion to effect interstellar travel at a speed of 0.1c, it appears unwarranted (at this time) to assume that it would not occur for at least some technologically advanced civilizations. One cannot even conclude that humans would not attempt this within the next few centuries. On the contrary, the most likely future situation, given the maintenance of technological growth and the absence of extraterrestrial interference, is that our civilization will explore and colonize our galactic neighborhood. A comparison of the time scales of galactic evolution and interstellar travel leads to the conclusion that the galaxy is either essentially empty with respect to technological civilizations or extensively colonized. In the former instance, a SETI would be unproductive. In the latter, a SETI could be fruitful if a signal has been deliberately directed at the earth or at an alien outpost, probe, or communication relay station in our solar system. In the former case, an existing antenna would probably be sufficient to detect the signal. In the latter case, success would depend on the way in which the communications were coded. Failure to detect a signal could permit any of the following conclusions: (i) the galaxy is devoid of technological civilizations, advanced beyond our own, (ii) such civilizations exist, but cannot (for some reason which is presently beyond our ken) engage in interstellar colonization, or (iii) such civilizations are not attempting overt contact with terrestrial civilizations and their intercommunications, if present, are not coded in a simple way. To plan at this time for a high-cost, large-array SETI based on the last two possibilities appears to be rather premature.

Item Type:Article
Related URLs:
URLURL TypeDescription
Kuiper, T. B. H.0000-0003-1798-4918
Morris, M.0000-0002-6753-2066
Additional Information:© 1977 American Association for the Advancement of Science. We gratefully acknowledge helpful criticisms from R. Carpenter, R. Edelson, B. Gary, S. Gulkis, M. Janssen, M. Jura, G. and S. Knapp, D. Kunth, R. McEliece, B. C. Murray, J. Rather, E. Rodriguez Kuiper, P. Swanson, and B. Zuckerman. This work has been carried out at the Jet Propulsion Laboratory (JPL) and the Owens Valley Radio Observatory, partially supported by a grant from the JPL Director's Discretionary Fund. Jet Propulsion Laboratory is operated by the California Institute of Technology under NASA contract NAS 7-100. Research at Owens Valley Radio Observatory is sponsored by the National Science Foundation under grant AST 73-04677AO3.
Funding AgencyGrant Number
Owens Valley Radio ObservatoryUNSPECIFIED
NSFAST 73-04677AO3
Issue or Number:4290
Record Number:CaltechAUTHORS:20151117-080411529
Persistent URL:
Official Citation:Searching for Extraterrestrial Civilizations T. B. H. Kuiper and M. Morris Science 6 May 1977: 196 (4290), 616-621. [DOI:10.1126/science.196.4290.616]
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:62148
Deposited By: Ruth Sustaita
Deposited On:17 Nov 2015 18:33
Last Modified:10 Nov 2021 22:58

Repository Staff Only: item control page