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The Big Bang took place 13.8 billion years ago, the Solar System was formed 4.6 billion years ago, and the first hominids appeared 6 million years ago. Life on other planets may have started, evolved, given birth to extraterrestrial intelligences, and perhaps even faced a planetary extinction event millions or even billions of years ago.
The Rare Earth hypothesis argues that planets with complex life, like Earth, are exceptionally rare.. In planetary astronomy and astrobiology, the Rare Earth hypothesis argues that the origin of life and the evolution of biological complexity, such as sexually reproducing, multicellular organisms on Earth, and subsequently human intelligence, required an improbable combination of astrophysical ...
On the other side of this are those scientists of the time who rejected Pasteur's results and instead supported the idea that life on Earth came from existing life. This necessarily requires that life has always existed somewhere on some planet, and that it has a mechanism of transferring between planets.
Life in the atmosphere brown dwarfs was also discussed by Yates et al. in 2017, and in 2019 Manasvi Lingam and Abraham Loeb extended the discussion of Yates et al.. Both articles extend the viability of Earth-like biological life beyond planets. [8] [9] Their ideas were criticized by experts in brown dwarfs. [10]
While Earth is the only place in the Universe known to harbor life, [10] [11] estimates of habitable zones around other stars, [12] [13] along with the discovery of thousands of exoplanets and new insights into the extreme habitats on Earth where organisms known as extremophiles live, suggest that there may be many more habitable places in the ...
This is also called the habitable zone, when a planet is the right distance from its star to have a comfortable temperature and liquid water pooling on its surface. For possible life on other ...
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 ...
It does not attempt to explain how life originated, but shifts the origin of life to another heavenly body. The advantage is that life is not required to have formed on each planet it occurs on, but rather in a more limited set of locations, or even a single location, and then spread about the galaxy to other star systems via cometary or ...