コペルニクス原理(Copernican principle)

In physical cosmology, the Copernican principle, named after Nicolaus Copernicus, is a working assumption that arises from a modified cosmological extension of Copernicus' Sun centered Heliocentric Universe. The Copernican principle assumes that neither the Sun nor the Earth are in a central, specially favored position in the universe.[1] More recently, the principle has been generalized to the relativistic concept that humans are not privileged observers of the universe.[2] In this sense, it is equivalent to the mediocrity principle, with important implications for the philosophy of science.


[1] Bondi, Hermann (1952). Cosmology. Cambridge University Press. p. 13.
[2] Peacock, John A. (1998). Cosmological Physics. Cambridge University Press. p. 66. ISBN 0-521-42270-1.

[ wikipedia:Coperinican Principle ]

動物園仮説(Zoo Hypothesis)


The zoo hypothesis is one of many theoretical explanations for the Fermi Paradox. The hypothesis speculates as to the assumed behavior and existence of technically advanced extraterrestrial life and the reasons they refrain from contacting Earth. One interpretation of the hypothesis argues that intelligent alien life intentionally ignores Earth to allow for natural evolution and sociocultural development. The hypothesis seeks to explain the apparent absence of extraterrestrial life despite its generally accepted plausibility and hence the reasonable expectation of its existence.[1]

Aliens might, for example, choose to allow contact once the human race has passed certain technological, political, or ethical standards. They might withhold contact until humans force contact upon them, possibly by sending a spacecraft to planets they inhabit. Alternatively, a reluctance to initiate contact could reflect a sensible desire to minimize risk. An alien society with advanced remote-sensing technologies may conclude that direct contact with neighbors confers added risks to oneself without an added benefit.



[1] Ball, John A. (Jul 1973). "The Zoo Hypothesis". Icarus 19 (3): 347–349. Bibcode:1973Icar...19..347B. doi:10.1016/0019-1035(73)90111-5.
[2] Jump up ^ A. D. Wissner-Gross, "Causal entropic forces", Physical Review Letters 110, 168702 (2013).

[ wikipedia:Zoo hypothesis ]

Hart's (1975) paper is based on Fact A: we have not been previously colonized by extraterrestrials. Part of my paper( Gott. 1993) is about what I would call Fact B; we have thus far not colonized the Galaxy. As I argue there, Fact B together with the Coeprnican Principle is sufficient by itself to explain Fact A. Since we observe Fact B, by Occam's Razoer, that is enough.

ファクトA: 我々はこれまでに、地球外生命によって植民地化されていない。
ファクトB: 我々は銀河を植民地化していない。
Thus, with Fact B alone and anthropic and Copernican Principle arguments, we can show that it is unlikely that the Earth would have been colonized by extraterrestrials (see also Leslie, 1989, 1990, 1992, who, using similar arguments (discussed by B. Carter in a 1983 talk although never in print, as well as Nielsen 1989), also argues that we are unlikely to colonize the Galaxy). Of cource, my arguments show that the zoo hypothesis (Ball, 1973) is unlikely as well. If there is a big galactic club, it is improbable for you to belong to one of the few intelligent species that do not belong to it.


[ J. Richard Gott, III: "Cosmological SETI frequency standards", in "Extraterrestrials: Where Are They?" edited by Ben Zuckerman, Michael H. Hart (1955) ]








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