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Title: DIRECT CONTACT AMONG GALACTIC CIVILIZATIONS BY RELATIVISTIC INTERSTELLAR SPACE-FLIGHT

Abstract

An estimate of the number of advanced technical civilizations on planets of other stars depends on our knowledge of the rate of star formation; the frequency of favorably situated planets, the probabilities of the origins of life, of intelligence, and of technical civilization, and the lifetimes of technical civilizations. These parameters are poorly known. The estimates lead to approximates 10/sup 6/ extant advanced technical civilizations in our galaxy. The most probable distance to the nearest such community is then several hundred light years. Interstellar spaceflight at relativistic velocities has several obvious advantages over eiectromagnetic communication among these civilizations. One striking feature is that with uniform acceleration of 1 g to the midpoint of the journey, and uniform deceleration thereafter, all points in the galaxy are accessible within the lifetime of a human crew, due to relativistic time dilation. Some of the technical problems in the construction of starships capable of relativistic velocities are discussed. It is concluded that with nuclear staging, fusion reactors, and the Bussard interstellar ramjet, no fundamental energetic problems exist for relativistic interstellar spaceflight. It is assumed that there exists in the galaxy a loosely integrated community of diverse civilizations, cooperating in the exploration and sampling ofmore » astronomical objects and their inhabitants. If each such advanced civilization launches one instellar vehicle per year, the mean time interval between samplings of an average star would be 10/sup 5/ years, that between samplings of a planetary system with intelligent life would be 10/sup 4/ years, and that between sampling of another advanced civilization would be 10/sup 3/ years. It follows that there is the statistical likelihood that Earth was visited by an advanced extraterrestrial civilization at least once during historical times. There are serious difficulties in demonstrating such a contact by ancient writings and iconography alone. Nevertheless, there are legends that might profitably be studied in this context. Bases or other artifacts of interstellar spacefaring civilizations might also exist elsewhere in the solar system. The conclusions are clearly provisional. (auth)« less

Authors:
Publication Date:
Research Org.:
Stanford Univ., Palo Alto, Calif.
OSTI Identifier:
4663688
NSA Number:
NSA-17-026959
Resource Type:
Journal Article
Journal Name:
Planetary Space Sci.
Additional Journal Information:
Journal Volume: Vol: 11; Other Information: Orig. Receipt Date: 31-DEC-63
Country of Publication:
Country unknown/Code not available
Language:
English
Subject:
GENERAL AND MISCELLANEOUS; ASTROPHYSICS; COMMUNICATIONS; DISTANCE; EARTH; ELECTROMAGNETIC WAVES; FREQUENCY; LIFETIME; MAN; PLANETS; POPULATIONS; RELATIVITY THEORY; SAMPLING; SPACE FLIGHT; STARS; SUN; THERMONUCLEAR REACTIONS; VELOCITY

Citation Formats

Sagan, C. DIRECT CONTACT AMONG GALACTIC CIVILIZATIONS BY RELATIVISTIC INTERSTELLAR SPACE-FLIGHT. Country unknown/Code not available: N. p., 1963. Web. doi:10.1016/0032-0633(63)90072-2.
Sagan, C. DIRECT CONTACT AMONG GALACTIC CIVILIZATIONS BY RELATIVISTIC INTERSTELLAR SPACE-FLIGHT. Country unknown/Code not available. doi:10.1016/0032-0633(63)90072-2.
Sagan, C. Wed . "DIRECT CONTACT AMONG GALACTIC CIVILIZATIONS BY RELATIVISTIC INTERSTELLAR SPACE-FLIGHT". Country unknown/Code not available. doi:10.1016/0032-0633(63)90072-2.
@article{osti_4663688,
title = {DIRECT CONTACT AMONG GALACTIC CIVILIZATIONS BY RELATIVISTIC INTERSTELLAR SPACE-FLIGHT},
author = {Sagan, C.},
abstractNote = {An estimate of the number of advanced technical civilizations on planets of other stars depends on our knowledge of the rate of star formation; the frequency of favorably situated planets, the probabilities of the origins of life, of intelligence, and of technical civilization, and the lifetimes of technical civilizations. These parameters are poorly known. The estimates lead to approximates 10/sup 6/ extant advanced technical civilizations in our galaxy. The most probable distance to the nearest such community is then several hundred light years. Interstellar spaceflight at relativistic velocities has several obvious advantages over eiectromagnetic communication among these civilizations. One striking feature is that with uniform acceleration of 1 g to the midpoint of the journey, and uniform deceleration thereafter, all points in the galaxy are accessible within the lifetime of a human crew, due to relativistic time dilation. Some of the technical problems in the construction of starships capable of relativistic velocities are discussed. It is concluded that with nuclear staging, fusion reactors, and the Bussard interstellar ramjet, no fundamental energetic problems exist for relativistic interstellar spaceflight. It is assumed that there exists in the galaxy a loosely integrated community of diverse civilizations, cooperating in the exploration and sampling of astronomical objects and their inhabitants. If each such advanced civilization launches one instellar vehicle per year, the mean time interval between samplings of an average star would be 10/sup 5/ years, that between samplings of a planetary system with intelligent life would be 10/sup 4/ years, and that between sampling of another advanced civilization would be 10/sup 3/ years. It follows that there is the statistical likelihood that Earth was visited by an advanced extraterrestrial civilization at least once during historical times. There are serious difficulties in demonstrating such a contact by ancient writings and iconography alone. Nevertheless, there are legends that might profitably be studied in this context. Bases or other artifacts of interstellar spacefaring civilizations might also exist elsewhere in the solar system. The conclusions are clearly provisional. (auth)},
doi = {10.1016/0032-0633(63)90072-2},
journal = {Planetary Space Sci.},
number = ,
volume = Vol: 11,
place = {Country unknown/Code not available},
year = {1963},
month = {5}
}