Extraterrestrial life

Extraterrestrial life is life that is not from the planet Earth. It is also called alien life or just extraterrestrials or aliens. The word 'Terra' in Latin refers to our planet - Earth. Thus, extraterrestrial life refers to the life forms not originating on or from the planet Earth.

It is reasonable to say that planets rather like ours exist, and that life might evolve there also. So far, none has been found, though it is possible that life once existed on Mars.^[1] It is not a new idea. Some philosophers have speculated on the existence of other planets like ours, with the idea that what happened here could also happen there.^[2][3] One thing we do know is that many other star systems have exoplanets.

Searches like SETI have been made for signals from extraterrestrial life-forms.^[4] No clear signals from outer space have been detected yet.

1. ↑ Sagan, Carl & Shklovskii I.S. 1966. Intelligent life in the Universe. Random House.
2. ↑ Crowe, Michael J. 1986. The Extraterrestrial life debate, 1750–1900. Cambridge. ISBN 0-521-26305-0
3. ↑ Crowe, Michael J. 2008. The extraterrestrial life debate Antiquity to 1915: a source book. University of Notre Dame Press. ISBN 0-268-02368-9
4. ↑ Sagan, Carl 1973. Communication with extraterrestrial intelligence. MIT Press. ISBN 0-262-19106-7