N is neither very small nor very large
Abstract
A number of estimates of N (the number of advanced civilizations in the Galaxy) are based on minimum assumptions, and lead to 'moderate' values of about 100,000. The suggestion that N may be very much larger is not supported observationally. The suggestion that the lack of extraterrestrial colonists on the earth means that N is very small is examined in detail. It is shown that the interstellar colonization scenario is, in fact, not plausible because even one colony calls for expenditures of energy sufficient to support hundreds of millions of individuals for hundreds of years. The laws of physics, biology, and interstellar distances thus make interstellar colonization unreasonable, and moderate values of N continue to be most plausible.
- Publication:
-
Strategies for the Search for Life in the Universe
- Pub Date:
- 1980
- DOI:
- 10.1007/978-94-009-9115-6_4
- Bibcode:
- 1980ASSL...83...27D
- Keywords:
-
- Exobiology;
- Extraterrestrial Intelligence;
- Biochemistry;
- Biological Evolution;
- Cosmology;
- Interstellar Space;
- Populations;
- Space Sciences (General)