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The Gaia hypothesis (/ ˈ ɡ aɪ. ə /), also known as the Gaia theory, Gaia paradigm, or the Gaia principle, proposes that living organisms interact with their inorganic surroundings on Earth to form a synergistic and self-regulating complex system that helps to maintain and perpetuate the conditions for life on the planet.
It took 4.5 billion years before humanity appeared on Earth, and life as we know it will see suitable conditions for 1 [95] to 2.3 [96] billion years more. Red dwarfs, by contrast, could live for trillions of years because their nuclear reactions are far slower than those of larger stars, meaning that life would have longer to evolve and survive.
An artist's conception shows a terraformed Mars in four stages of development.. Terraforming or terraformation ("Earth-shaping") is the hypothetical process of deliberately modifying the atmosphere, temperature, surface topography or ecology of a planet, moon, or other body to be similar to the environment of Earth to make it habitable for humans to live on.
A superhabitable world is a hypothetical type of planet or moon that is better suited than Earth for the emergence and evolution of life. The concept was introduced in a 2014 paper by René Heller and John Armstrong, in which they criticized the language used in the search for habitable exoplanets and proposed clarifications. [ 2 ]
Earth is the only known place that has ever been habitable for life. Earth's life developed in Earth's early bodies of water some hundred million years after Earth formed. Earth's life has been shaping and inhabiting many particular ecosystems on Earth and has eventually expanded globally forming an overarching biosphere. [242]
Evidence suggests that life on Earth has existed for about 3.7 billion years. [30] All known life forms share fundamental molecular mechanisms, and based on these observations, theories on the origin of life attempt to find a mechanism explaining the formation of a primordial single cell organism from which all life originates.
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This is an accepted version of this page This is the latest accepted revision, reviewed on 27 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 ...