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Record Details

Record 18 of 12760
Galactic civilizations - Population dynamics and interstellar diffusion
External Online Source: doi:10.1016/0019-1035(81)90135-4
Author and Affiliation:
Newman, W. I.(Institute for Advanced Study, Princeton, NJ, United States)
Sagan, C.(Cornell University, Ithaca, NY, United States)
Abstract: A model is developed of the interstellar diffusion of galactic civilizations which takes into account the population dynamics of such civilizations. The problem is formulated in terms of potential theory, with a family of nonlinear partial differential and difference equations specifying population growth and diffusion for an organism with advantageous genes that undergoes random dispersal while increasing in population locally, and a population at zero population growth. In the case of nonlinear diffusion with growth and saturation, it is found that the colonization wavefront from the nearest independently arisen galactic civilization can have reached the earth only if its lifetime exceeds 2.6 million years, or 20 million years if discretization can be neglected. For zero population growth, the corresponding lifetime is 13 billion years. It is concluded that the earth is uncolonized not because interstellar spacefaring civilizations are rare, but because there are too many worlds to be colonized in the plausible colonization lifetime of nearby civilizations, and that there exist no very old galactic civilizations with a consistent policy of the conquest of inhabited worlds.
Publication Date: Jun 01, 1981
Document ID:
19810061288
(Acquired Nov 30, 1995)
Accession Number: 81A45692
Subject Category: SPACE SCIENCES (GENERAL)
Document Type: Journal Article
Publication Information: Icarus; p. June 198; 46
Publisher Information: United States
Contract/Grant/Task Num: NSF AST-75-21153; NSF PHY-77-20612; NGR-33-010-101
Financial Sponsor: NASA; United States
Organization Source: Institute for Advanced Study; Princeton, NJ, United States
Cornell Univ.; Ithaca, NY, United States
Description: 35p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright
NASA Terms: DIFFUSION; EXTRATERRESTRIAL INTELLIGENCE; EXTRATERRESTRIAL LIFE; INTERSTELLAR TRAVEL; POPULATION THEORY; DIFFERENCE EQUATIONS; DIFFERENTIAL EQUATIONS; DISCRETE FUNCTIONS; GENES; NONLINEAR EQUATIONS; POTENTIAL THEORY
Imprint And Other Notes: Icarus, vol. 46, June 1981, p. 293-327.
Miscellaneous Notes: p. 293-327
Availability Source: Other Sources
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