In planetary astronomy and astrobiology, the Rare Earth hypothesis argues that the emergence of complex multicellular life (metazoa) on Earth (and, as follows, intelligence) required an improbable combination of astrophysical and geological events and circumstances. The hypothesis argues that complex extraterrestrial life requires an Earth-like planet with the right conditions and that few if any such planets exist. The term "Rare Earth" comes from Rare Earth: Why Complex Life Is Uncommon in the Universe (2000), a book by Peter Ward, a geologist and paleontologist, and Donald E. Brownlee, an astronomer and astrobiologist.
The rare earth hypothesis is the contrary of the widely accepted principle of mediocrity (also called the Copernican principle), advocated by Carl Sagan and Frank Drake, among others. The principle of mediocrity concludes that the Earth is a typical rocky planet in a typical planetary system, located in a non-exceptional region of a common barred-spiral galaxy. Hence it is probable that the universe teems with complex life. Ward and Brownlee argue to the contrary: planets, planetary systems, and galactic regions that are as friendly to complex life as are the Earth, the solar system, and our region of the Milky Way are very rare.
By concluding that complex life is uncommon, the Rare Earth hypothesis is a possible solution to the Fermi paradox: "If extraterrestrial aliens are common, why aren't they obvious?"
Other articles related to "rare earth hypothesis, earth, hypothesis":
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... See also Rare Earth hypothesis Those who believe that extraterrestrial intelligent life does not exist argue that the conditions needed for life—or at least complex life—to ... This is known as the Rare Earth hypothesis, which attempts to resolve the Fermi paradox by rejecting the mediocrity principle, and asserting that Earth is not typical, but unusual or even unique ... While a unique Earth has historically been assumed on philosophical or religious grounds, the Rare Earth Hypothesis uses quantifiable and statistical arguments to argue that multicellular life is ...
... This hypothesis states that based on astrobiological findings, multi-cellular life forms found on Earth may actually be more of a rarity than scientists initially assumed ... The Principle of Mediocrity suggests that life on Earth is not exceptional, but rather that life is more than likely to be found on innumerable other worlds ... The anthropic principle supports the Rare Earth Hypothesis by arguing the overall elements that are needed to support life on Earth are so fine-tuned that it is nearly impossible for ...
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