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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.

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 multplies 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 existance 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 unkown, or even unknowable. For example, the probability of life emerging on a planet is a meaningless concept if that 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.

However, 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>

The two questions that most speculators raise regarding extraterrestrial civilizations are mainly whether:

The two questions that most speculators raise regarding extraterrestrial civilizations are mainly whether: