|
The Fermi paradox — or Fermi's paradox — is the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilizations, such as in the Drake equation, and the lack of evidence for such civilizations. The basic points of the argument, made by physicists Enrico Fermi (1901–1954) and Michael H. Hart (born 1932), are: * The Sun is a typical star, and there are billions of stars in the galaxy that are billions of years older.〔, page 282.〕〔 Accepted for publication in MNRAS. See Figure 15 in particular.〕 * With high probability, some of these stars will have Earth-like planets, and if the earth is typical, some might develop intelligent life. * Some of these civilizations might develop interstellar travel, a step the Earth is investigating now. * Even at the slow pace of currently envisioned interstellar travel, the Milky Way galaxy could be completely traversed in about a million years. According to this line of thinking, the Earth should already have been visited by extraterrestrial aliens though Fermi saw no convincing evidence of this, nor any signs of alien intelligence anywhere in the observable universe, leading him to ask, "Where is everybody?" == Overview == The age of the universe and its vast number of stars has led some to suggest that unless the rare Earth hypothesis holds true, extraterrestrial life should be common.〔Sagan, Carl ''Cosmos,'' Random House 2002 ISBN 0-375-50832-5〕 In an informal discussion in 1950, the physicist Enrico Fermi questioned why, if a multitude of advanced extraterrestrial civilizations exist in the Milky Way galaxy, evidence such as a flying saucer or Von Neumann probe have not yet been seen. Counterarguments suggest that intelligent extraterrestrial life does not exist or occurs so rarely or briefly that humans will never make contact with it. Other common names for the ''Fermi's question'' ("Where are they?") include: the ''Great Silence'',〔 and ''silentium universi'' (Latin for "silence of the universe"). Michael H. Hart published in 1975 a detailed examination of the paradox,〔 which has since become a theoretical reference point for much of the research into what is now sometimes known as the Fermi-Hart paradox. Interest in the paradox has spawned numerous scholarly works addressing it directly, while questions that relate to it have been addressed in fields as diverse as astronomy, biology, ecology, and philosophy. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Fermi paradox」の詳細全文を読む スポンサード リンク
|