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This is an accepted version of this page This is the latest accepted revision, reviewed on 17 January 2025. Problem of the lack of evidence for alien life despite its apparent likelihood This article is about the absence of clear evidence of extraterrestrial life. For a type of estimation problem, see Fermi problem. Enrico Fermi (Los Alamos 1945) The Fermi paradox is the discrepancy between ...
The "dark forest" hypothesis presumes that any space-faring civilization would view any other intelligent life as an inevitable threat and thus destroy any nascent life that makes itself known. As a result, the electromagnetic spectrum would be relatively quiet, without evidence of any intelligent alien life. [8] [9]
Extraterrestrial life forms might, for example, choose to allow contact once the human species has passed certain technological, political, and/or ethical standards. Alternatively, they may withhold contact until humans force contact upon them, possibly by sending a spacecraft to an extraterrestrial-inhabited planet. In this regard, reluctance ...
The extraterrestrial hypothesis is the idea that some UFOs are vehicles containing or sent by extraterrestrial beings (usually called aliens in this context). [13] As an explanation for UFOs, ETI is sometimes contrasted with EDI (extradimensional intelligence) , for example by J. Allen Hynek . [ 24 ]
The Great Filter is the idea that, in the development of life from the earliest stages of abiogenesis to reaching the highest levels of development on the Kardashev scale, there is a barrier to development that makes detectable extraterrestrial life exceedingly rare. [1] [2] The Great Filter is one possible resolution of the Fermi paradox.
The scientific search for extraterrestrial life is being carried out both directly and indirectly. As of September 2017 [update] , 3,667 exoplanets in 2,747 systems have been identified , and other planets and moons in the Solar System hold the potential for hosting primitive life such as microorganisms .
Life typically expands until it fills all available niches. [5] These contradictory facts form the basis for the Fermi paradox , of which the firstborn hypothesis is one proposed solution. Avi Loeb , an astrophysicist and cosmologist, has suggested that Earth may be a very early example of a life-bearing planet and that life-bearing planets may ...
Although no actual extraterrestrial life has been found, either in the Solar System or elsewhere, science currently has a far greater understanding of the context of such life or lack thereof. Biology studies the nature of life, and chemistry and biochemistry the way it works.