Extraterrestrial life is
life originating outside of the
Earth. It is the subject of
astrobiology, and its existence remains theoretical. There is no evidence of extraterrestrial life that has been widely accepted by the
scientific community. Many scientists believe that if extraterrestrial life exists, its emergence occurred independently, in different places in the universe. An alternative hypothesis is
panspermia, which suggests that life might emerge in one location and then spread between
habitable planets. These two hypotheses are not
mutually exclusive. The study and theorization of extraterrestrial life is known as
astrobiology, exobiology or xenobiology. Speculative forms of extraterrestrial life range from
sapient beings to life at the scale of
bacteria.
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