Extraterrestrial life

:This article is about the scientific study of extraterrestrial life; for treatment in popular culture, see Extraterrestrial life in popular culture.

Beliefs in extraterrestrial life

Ancient and Early Modern ideas

See also Cosmic pluralism

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Belief in extraterrestrial life may have been present in ancient Egypt, Babylon, and Sumer, although in these societies, cosmology was fundamentally supernatural and the notion of aliens is difficult to distinguish from that of gods, demons, and such. The first important Western thinkers to argue systematically for a universe full of other planets and, vicariously, possible extraterrestrial life were the ancient Greek writers Thales and his student Anaximander in the 7th and 6th centuries B.C.E. The atomists of Greece took up the idea, arguing that an infinite universe ought to have an infinity of populated worlds. Ancient Greek cosmology worked against the idea of extraterrestrial life in one critical respect, however: the geocentric universe, championed by Aristotle and codified by Ptolemy, privileged the Earth and Earth-life (Aristotle denied there could be a plurality of worlds) and seemingly rendered extraterrestrial life impossible.

Related Topics:
Egypt - Babylon - Sumer - Cosmology - Thales - Anaximander - Atomists - Geocentric - Aristotle - Ptolemy

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When Christianity spread through the West the Ptolemaic system became dogma and although the Church never issued any formal pronouncement on the question of alien life http://www.crisismagazine.com/november2002/feature7.htm, at least tacitly the idea was heretical. In 1277 the Bishop of Paris, Etienne Tempier did overturn Aristotle on one point: God could have created more than one world (given His omnipotence) yet we know by revelation he only made one. To take a further step and argue that aliens actually existed remained dangerous. The best known early-modern proponent of extra-solar planets and widespread life off Earth was Giordano Bruno, who was burned at the stake for this and other unorthodox ideas in 1600.

Related Topics:
Christianity - Bishop of Paris - Etienne Tempier - Giordano Bruno - 1600

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The Church, however, could not contain the storm that accompanied the invention of the telescope and the Copernican assault on geocentric cosmology. Once it became clear that the Earth was merely one planet amongst countless bodies in the universe the extraterrestrial idea moved towards the scientific mainstream. In the early 17th century the Czech astronomer Anton Maria Schyrleus of Rheita mused that "if Jupiter has?inhabitants?they must be larger and more beautiful than the inhabitants of the Earth, in proportion to the of the two spheres;" he did not dare to confirm the existence of Jovian beings due to potential theological difficulties. Later, this bold step would be taken. William Herschel, the discoverer of Uranus, was one of many 18th-19th century astronomers convinced that our Solar System, and perhaps others, would be well populated by alien life. Other luminaries of the period who championed "cosmic pluralism" included Immanuel Kant and Benjamin Franklin. At the height of the Enlightenment even the Sun and Moon were considered candidates for hosting aliens. The Christian attitude towards extraterrestrials turned from denial to ambivalence. Theological criticisms had been partially stalemated by a critical counter-argument that had remained in the background since the pronouncements of 1277: God's omnipotence not only allowed for other worlds and other life, on some level it necessitated them.

Related Topics:
Telescope - Copernican - Anton Maria Schyrleus of Rheita - William Herschel - Uranus - Immanuel Kant - Benjamin Franklin - Enlightenment - Sun - Moon

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Extraterrestrials and the Modern era

This enthusiasm towards the possibility of alien life continued well into the 20th century. Indeed, the roughly three centuries from the Scientific Revolution through the beginning of the modern era of solar system probes were essentially the highpoint for belief in extraterrestrials in the West: many astronomers and other secular thinkers, at least some religious thinkers, and much of the general public were largely satisfied that aliens were a reality. This trend was finally tempered as actual probes visited potential alien abodes in the solar system. The moon was decisively ruled out as a possibility, while Venus and Mars?long the two main candidates for extraterrestrials?showed no obvious evidence of current life. The other large moons of our system which have been visited appear similarly lifeless, though interesting geothermic forces observed (Io's volcanism, Europa's ocean, Titan's thick atmosphere) has underscored how broad the range of potentially habitable environments may be. Finally, the failure of NASA's SETI program to detect anything resembling an intelligent radio signal after four decades of effort has partially dimmed the optimism that prevailed at the beginning of the space age and emboldened critics who view the search for extraterrestrials as unscientific. http://www.crichton-official.com/speeches/speeches_quote04.html

Related Topics:
20th century - Scientific Revolution - Venus - Mars - Io - Europa - Titan - NASA - SETI

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Thus, the three decades preceding the turn of the second millenium saw a crossroads reached in beliefs in alien life. The prospect of ubiquitous, intelligent, space-faring civilizations in our solar system appears increasingly dubious to many scientists ("All we know for sure is that the sky is not littered with powerful microwave transmitters" in the words of SETI's Frank Drake). At the same time, the data returned by space probes and giant strides in detection methods have allowed science to begin delineating habitability criteria on other worlds and to confirm that, at least, other planets are plentiful though aliens remain a question mark.

Related Topics:
Frank Drake - Other planets

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Amongst the general public belief and interest in extraterrestrials remains high and skepticism towards galaxy-exploring alien civilizations is not shared by many individuals. At present, some enthusiasts in the topic believe that extraterrestrial beings regularly visit or have visited the Earth. Some think that unidentified flying objects observed in the skies are in fact sightings of the spacecraft of intelligent extraterrestrials, and even claim to have met such beings. Crop circle patterns have also been attributed to the actions of extraterrestrials, although many were later found to be hoaxes. While at least one recent scientific paper published in a respected, peer-reviewed, journal has urged a re-evaluation of the UFO phenomenon (Deardorff et al., 2005) http://www.ufoskeptic.org/JBIS.pdf, as of this time mainstream scientific opinion holds that such claims are unsupportable by the evidence currently available and unlikely to be true.

Related Topics:
Unidentified flying objects - Crop circle

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The possible existence of primitive (microbial) life outside of Earth is much less controversial to mainstream scientists although at present no direct evidence of such life has been found. Indirect evidence has been offered for the current existence of primitive life on the planet Mars; however, the conclusions that should be drawn from such evidence remain in debate.

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