Extraterrestrial life

Distant galaxies

Extraterrestrial life

Aliens, UFOs, little green men: Whatever you call it, life that did not start on the Earth has yet to be found, but a number of respected scientists speculate that extraterrestrial life exists. Some such as Frank Drake have even attempted to estimate the number of civilisations in our galaxy based on what we know about the Universe and life on Earth.

Scientists have also identified places in the Solar System such as Jupiter's moon Europa that have the potential to support life. Future missions to these places may find some form of life.

Image: Could an advanced civilisation exist in one of the thousands of galaxies shown in this Hubble image? (credit: NASA, ESA, S. Beckwith/STScI, HUDF Team)

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Distant galaxies


Is life out there?

About Extraterrestrial life

Extraterrestrial life[n 1] is life that does not originate from Earth. It is also called alien life, or, if it is a sentient and/or relatively complex individual, an "extraterrestrial" or "alien" (or, to avoid confusion with the legal sense of "alien," a "space alien"). These as yet hypothetical forms of life range from simple bacteria-like organisms to beings far more complex than humans. The possibility that viruses might exist extraterrestrially has also been proposed.

The development and testing of hypotheses on extraterrestrial life is known as "exobiology" or "astrobiology," although astrobiology also considers Earth-based life in its astronomical context. Scientists at the National Institutes of Health reported studies that life in the universe may have begun "9.7±2.5 billion years ago", billions of years before the Earth was formed, based on extrapolating the "genetic complexity of organisms" [from "major phylogenetic lineages"] to earlier times. Many scientists consider extraterrestrial life to be plausible, but there is no direct evidence of its existence. Since the mid-20th century, there has been an ongoing search for signs of extraterrestrial life, from radios used to detect possible extraterrestrial signals, to telescopes used to search for potentially habitable extrasolar planets. It has also played a major role in works of science fiction.

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