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'''Extraterrestrial life''' is [[Life science|life]], whether demonstrated, hypothesized, or merely imagined, that did not obviously originate on the [[earth]]. It has been a staple of [[science fiction]] since the [[Edward VII|Edwardian]] era, but has also lately become the subject of intense speculation, scientific debate, and even theological debate.

'''Extraterrestrial life''' is [[Life science|life]], whether demonstrated, hypothesized, or merely imagined, that did not obviously originate on the [[earth]]. It has been a staple of [[science fiction]] since the [[Edward VII|Edwardian]] era, and has more recently become the subject of scientific debate and even theological debate.

The term ''life'' is here used in its usual manner to connote living things, regardless of complexity or condition of sentience.  However, in [[science fiction]] especially, extraterrestrial life may take unconventional form, such as non-carbon-based life forms or even disembodied intelligence.

The term ''life'' is here used in its usual manner to connote living things, regardless of complexity or condition of sentience.  However, in [[science fiction]] especially, extraterrestrial life may take unconventional form, such as non-carbon-based life forms or even disembodied intelligence.

Vigorous scientific research on the subject is fairly limited, and has focused on both the "micro" and "macro" aspects of the problem:

Vigorous scientific research on the subject is fairly limited, and has focused on both the "micro" and "macro" aspects of the problem:

# The [[exogenesis]], nature, survival, and movement of primitive life forms, including the hazard that such microbes might pose to [[astronaut]]s or to the earth itself.

# The genesis, nature, survival, and movement of primitive life forms, including the hazard that spaceborne microbes might pose to [[astronaut]]s or to the earth itself.

# The possibility of prior or future detection, contact, trade, or war with an extraterrestrial [[civilization]].

# The possibility of prior or future detection, contact, trade, or war with an extraterrestrial [[civilization]].

=== Extraterrestrial Civilizations ===

=== Extraterrestrial Civilizations ===

Do one or more extraterrestrial civilizations exist? Until recently, speculation about extraterrestrial races was confined either to [[science fiction]] or to innumerable anecdotal reports of "[[UFO|unidentified flying objects]]." These latter reports were once the subject of an investigation, known as [[Project Blue Book]], by the [[United States Air Force]].<ref>Anonymous, "[http://www.ufoevidence.org/topics/ProjectBlueBook.htm Project Blue Book]", ''[http://www.ufoevidence.org/ UFO Evidence.org]'', retrieved April 16, 2007</ref><ref>Anonymous, ''[http://www.bluebookarchive.org/ The Project Blue Book Archive]'', retrieved April 16, 2007</ref><ref>Fund for Unidentified Flying Object Research (FUFOR), ''[http://www.nicap.org/index.htm Official Site of the National Investigative Committee for Aerial Phenomena]'', Francis L. Ridge, editor and Webmaster, December 15, 1997 to present. Retrieved April 16, 2007.</ref><ref>Presumably the [[Union of Soviet Socialist Republics|Soviet]] Army Air Forces had their own version of Blue Book as well.</ref> But years after Blue Book wound down, a large cadre of scientists began to entertain seriously the notion that extraterrestrial civilizations might exist.

Do one or more extraterrestrial civilizations exist? Until recently, speculation about extraterrestrial races was confined either to [[science fiction]] or to innumerable anecdotal reports of "[[UFO|unidentified flying objects]]." These latter reports were once the subject of an investigation, known as Project Blue Book, by the [[United States Air Force]].<ref>Anonymous, "[http://www.ufoevidence.org/topics/ProjectBlueBook.htm Project Blue Book]", ''[http://www.ufoevidence.org/ UFO Evidence.org]'', retrieved April 16, 2007</ref><ref>Anonymous, ''[http://www.bluebookarchive.org/ The Project Blue Book Archive]'', retrieved April 16, 2007</ref><ref>Fund for Unidentified Flying Object Research (FUFOR), ''[http://www.nicap.org/index.htm Official Site of the National Investigative Committee for Aerial Phenomena]'', Francis L. Ridge, editor and Webmaster, December 15, 1997 to present. Retrieved April 16, 2007.</ref><ref>Presumably the [[Union of Soviet Socialist Republics|Soviet]] Army Air Forces had their own version of Blue Book as well.</ref> But years after Blue Book wound down, a large cadre of scientists began to entertain seriously the notion that extraterrestrial civilizations might exist.

SETI ('''S'''earch for '''E'''xtra'''t'''errestrial '''I'''ntelligence)<ref>[http://www.seti.org/site/pp.asp?c=ktJ2J9MMIsE&b=178025 Home of the SETI Institute]</ref> is the name given to several government and privately-funded projects that over the years have searched for evidence of extraterrestrial civilizations.  This is done by listening via [[radiotelescope]] on a defined frequency band for any transmission having any semblance of order. The frequency band is one that, they believe, is the likeliest region in the [[electromagnetic spectrum]] for anyone to be sending a signal intended to cross interstellar, or even intergalactic, space.

[[Search for Extra-Terrestrial Intelligence|SETI]] ('''S'''earch for '''E'''xtra'''t'''errestrial '''I'''ntelligence)<ref>[http://www.seti.org/site/pp.asp?c=ktJ2J9MMIsE&b=178025 Home of the SETI Institute]</ref> is the name given to several government and privately-funded projects that over the years have searched for evidence of extraterrestrial civilizations.  This is done by listening via radio [[telescope]] on a defined frequency band for any transmission having any semblance of order. The frequency band is one that, they believe, is the likeliest region in the [[electromagnetic spectrum]] for anyone to be sending a signal intended to cross interstellar, or even intergalactic, space.

No definitive evidence exists for any form of extraterrestrial civilization. While the [[Project Blue Book]] investigators found a number of cases that they had to classify as "unknown," they were able to classify the bulk of the anecdotes as anything from outright hoaxes to misinterpretations of common weather features to misinterpretation of the sightings of ordinary aircraft.<ref>The Air Force might also have acted in a deceptive manner in certain isolated cases in which what the witnesses took for [[UFO]]s were actually secret experimental prototypes. Perhaps some of these prototypes exist today as the [[B-2]], [[F-117]], and other [[Stealth aircraft]].</ref> Neither has any [[Astronomy|astronomer]] or [[astronaut]] reported a definite sighting of, much less contact with, any carrier-like vessel that would have been capable of launching any of the alleged two-seater or similar small-crewed craft that various "witnesses" report having encountered. Nor has any [[physics|physicist]] yet suggested a method by which such a craft could have visited our [[solar system]], given the fixed speed limit set by the [[Special Theory of Relativity]]. Finally, the SETI project, for all their searching for a signal (even to recruiting civilians to participate in a "distributed computing" project to process the noise they have received from their radiotelescopes), have never isolated anything like a definite signal.

No definitive evidence exists for any form of extraterrestrial civilization. While the Project Blue Book investigators found a number of cases that they had to classify as "unknown," they were able to classify the bulk of the anecdotes as outright hoaxes, misinterpretations of common weather features, or misinterpretations of sightings of ordinary aircraft.<ref>The Air Force might also have acted in a deceptive manner in certain isolated cases in which what the witnesses took for [[UFO]]s were actually secret experimental prototypes. Perhaps some of these prototypes exist today as the [[B-2]], [[F-117]], and other [[Stealth aircraft]].</ref> Neither has any [[Astronomy|astronomer]] or [[astronaut]] reported a definite sighting of a vessel that could have launched any of the craft that witnesses report having encountered. And the SETI projects, despite years of searching for a signal (at one point recruiting civilians to participate in a "distributed computing" project to process the noise they have received from their radiotelescopes), have never isolated anything like a definite signal.

====The Drake Equation====

====Theoretical approaches====

In 1961, astronomer Frank Drake developed a method for estimating of the number of extraterrestrial civilizations in the galaxy.  The Drake Equation simply begins with the number of stars, then multiplies that number by a series of probabilities (probability that a star has planets, that a planet can support life, etc.) to obtain the quantity desired (number of populated planets, number of civilizations whose existence is detectable, etc.).

In 1961, astronomer Frank Drake developed a method for estimating of the number of extraterrestrial civilizations in the galaxy.  The Drake Equation simply begins with the number of stars, then multiplies that number by a series of probabilities (probability that a star has planets, that a planet can support life, etc.) to obtain the quantity desired (number of populated planets, number of civilizations whose existence is detectable, etc.).

In principle, the Drake Equation can provide an upper and lower bound for the number of extraterrestrial civilizations by setting upper and lower bounds for each probability factor, which can then be improved upon as better information becomes available.  Because the number of stars in so huge, even the lower bound is often calculated to be a respectable number.  However, a serious problem is that some of the probabilities are completely unknown, or even unknowable.  For example, the probability of life emerging on a planet is a meaningless concept if life is created directly by God and not by some naturalistic process.

In principle, the Drake Equation can provide an upper and lower bound for the number of extraterrestrial civilizations by setting upper and lower bounds for each probability factor, which can then be improved upon as better information becomes available.  Because the number of stars in so huge, even the lower bound is often calculated to be a respectable number.  However, a serious problem is that some of the probabilities are completely unknown, or even unknowable.  For example, the probability of life emerging on a planet is a meaningless concept if life is created directly by God and not by some naturalistic process. If any of the probabilities appearing in the equation is zero, then the number of extraterrestrial civilizations of course goes to zero.

 

If any of the probabilities appearing in the equation is zero, then the number of extraterrestrial civilizations of course goes to zero. This is a serious problem if one relies only on naturalistic explanations of the genesis of life.  One of the most well-accepted scientific laws, the [[law of biogenesis]], says that life only comes from life, which means that it cannot come from non-life.  Furthermore, scientific observations are that evolution itself is impossible, as evolution requires ''increasing'' genetic [[information]], whereas observations show that living things ''lose'' genetic information.<ref>Wieland, Carl, [http://www.creationontheweb.com/content/view/431/ The evolution train’s a-comin’], ''Creation'' 24(2):16–19, March 2002.</ref>

== Extraterrestrial Life in Science Fiction ==

== Extraterrestrial Life in Science Fiction ==

Extraterrestrial nation-states and, almost as often, extraterrestrial microbes, have been a staple of [[science fiction]] since soon after science-fiction writers first began speculating on what sort of inventions might carry men into outer space, and what they might discover there. [[H. G. Wells]] even speculated on an extraterrestrial civilization on the [[moon]], populated by man-sized insects (''The First Men in the Moon''). Wells also speculated that the Martian nation-state would launch an invasion of earth (''The War of the Worlds''), an invasion that would fail when the Martian soldiers and pilots fell terminally ill with earthly microbes against which their immune systems would have no defense. [[Edgar Rice Burroughs]] indulged in far richer speculation on an entire civilization on Mars, and on semi-regular commerce between his Martians and a select few visitors from earth.

Extraterrestrial life, from nation-states to microbes, has been a staple of [[science fiction]] since the early days of the genre.  Novelist [[H. G. Wells]] speculated on what sort of inventions might carry men into outer space, and what they might discover there. In ''The First Men in the Moon'', he describes a fictional extraterrestrial civilization on the [[moon]], populated by man-sized insects. Wells also wrote about a Martian nation-state that launched an invasion of Earth (''The War of the Worlds''), only to fail when the invaders fell terminally ill from earthly microbes against which their immune systems had no defense. [[Edgar Rice Burroughs]] indulged in far richer speculation on an entire civilization on Mars, and on semi-regular commerce between his Martians and a select few visitors from earth.

 

 

 

 

# The alleged crash of an extraterrestrial scout craft near [[Roswell]], [[New Mexico]], [[United States]].

The middle twentieth century introduced other now-familiar themes, often through the media of comic books, novels, low-budget films, and [[television]]: humans caught up in events on other inhabited worlds, spacefaring starship crews, and extraterrestrial "prophets" appearing on earth with either good intentions or bad.  By the late twentieth century, big-budget films repeated these thems and introduced new ones, sometimes (as in ''[[Star Wars]]'') bypassing Earth altogether in favor of mythlike tales of ancient civilizations.

# The synthetic religion, called [[Scientology]], developed by the late [[L. Ron Hubbard]]. This movement informed many of Hubbard's works, including [[Battlefield Earth]] (which the actor [[John Travolta]], an adherent of Scientology, has lately adapted for the [[motion picture]]s), and [[Mission Earth]], a ten-volume series completed shortly before Hubbard's death and published posthumously.

The [[Star Trek]] [[television]] franchise that [[Gene Roddenberry]] created, with its myriad of extraterrestrial and often trans-galactic nation-states and empires hardly needs introduction. But in addition, producer [[Quinn Martin]] created a series that centered on one man's attempt to warn his government that certain people were not what they appeared, but were instead extraterrestrial spies. More recently, [[Kenneth Johnston]] created a concept (''V'') of a space-borne force whose commanding admiral and officers at first puts on a friendly appearance similar to that of [[Matthew Perry]] (the American [[commodore]] who first visited [[Japan]]) but, soon afterward, subvert human governmental and media institutions in order to further their true purpose, which is to steal earth's water and carry away earth's population for food.

The [[Star Trek]] television franchise created by [[Gene Roddenberry]], with its myriad of extraterrestrial and often trans-galactic nation-states and empires, hardly needs introduction. Producer Quinn Martin created a series that centered on one man's attempt to warn his government that certain people were not what they appeared, but were instead extraterrestrial spies. More recently, Kenneth Johnston created a concept (''V'') of a spaceborne force whose commanding admiral and officers at first puts on a friendly appearance similar to that of [[Matthew Perry]] (the American commodore who first visited [[Japan]]) but, soon afterward, subvert human governmental and media institutions in order to further their true purpose, which is to steal earth's water and carry away earth's population for food.

Nor have science fiction writers ignored speculation on the finding of extraterrestrial microbes. Usually they have portrayed such microbes as capable of producing deadly extinction-level pandemics. (See, for example, ''The Andromeda Strain'' by Michael Crichton.) John B. Olson and Randall S. Ingermanson, however, speculated that the first crew to fly to Mars might discover incontrovertible evidence of microbial life--including a culturable microbe. This would engender excitement in the hearts of their launch authorites, but would also inspire such fear in the mind of a [[National Aeronautics and Space Administration|NASA]] engineer that she would actually attempt to strand or murder the crew to stop them from [[back-contamination|back-contaminating]] the earth with their culture.

Nor have science fiction writers ignored speculation on the finding of extraterrestrial microbes. Usually they have portrayed such microbes as capable of producing deadly extinction-level pandemics. (See, for example, ''The Andromeda Strain'' by Michael Crichton.) John B. Olson and Randall S. Ingermanson, however, speculated that the first crew to fly to Mars might discover incontrovertible evidence of microbial life--including a culturable microbe. This would engender excitement in the hearts of their launch authorites, but would also inspire such fear in the mind of a [[National Aeronautics and Space Administration|NASA]] engineer that she would actually attempt to strand or murder the crew to stop them from back-contaminating the earth with their culture.

== Christian Views on Extraterrestrial Life ==

== Christian Views on Extraterrestrial Life ==