<div style="margin: 12px 0px; font-family: arial; color: #333333; background: #ffffff; border: solid 4px #e5e5e5; width: 100%; clear: left;"><div class="CM_CTB_Content_Wrap" style="margin: 0px; padding: 0px;background-color: #ffffff;"><div style="border-bottom: solid 1px #dcdcdc; white-space: nowrap; margin-bottom: 8px; background-color: #eeeeee ;background-image: url(http://clipmarks.com/images/source-bg.gif); background-repeat: repeat-x; height: 24px; line-height: 24px; vertical-align: middle; padding-bottom: 4px; color: #666666; font-size: 10px;" ><a href="http://clipmarks.com/clip-to-blog/" title="see clips that are hot right now"><img src="http://content.clipmarks.com/blog_embed/4f97eaa2-e17a-4cb4-9326-1fcc4381f310/0CF21FA2-A970-430B-ADDC-E033DB1B0E52/" alt="" width="19" height="19" border="0" style="vertical-align: middle; margin: 0px 4px; display: inline; border: none; float:none;" /></a>clipped from <a title="http://en.wikipedia.org/w/index.php?title=Rare_Earth_hypothesis&oldid=310577591" href="http://en.wikipedia.org/w/index.php?title=Rare_Earth_hypothesis&oldid=310577591" style="font-size: 11px;">en.wikipedia.org</a></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://en.wikipedia.org/w/index.php?title=Rare_Earth_hypothesis&oldid=310577591"><div align="center"><img src="http://content7.clipmarks.com/blog_cache/en.wikipedia.org/img/24359F4A-E095-4460-9F88-B260CB22E1A2" alt="" /></div></blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://en.wikipedia.org/w/index.php?title=Rare_Earth_hypothesis&oldid=310577591"><DIV class="thumbcaption"> <DIV class="magnify"><A title="Enlarge" class="internal" href="http://en.wikipedia.org/wiki/File:The_Earth_seen_from_Apollo_17.jpg" linkindex="6"><IMG width="15" height="11" alt="" src="http://en.wikipedia.org/skins-1.5/common/images/magnify-clip.png" /></A></DIV> Are planets that support life, such as <A title="Earth" href="http://en.wikipedia.org/wiki/Earth" linkindex="7">Earth</A>, rare?</DIV></blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://en.wikipedia.org/w/index.php?title=Rare_Earth_hypothesis&oldid=310577591"><P>In <A class="mw-redirect" title="Planetary astronomy" href="http://en.wikipedia.org/wiki/Planetary_astronomy" linkindex="8">planetary astronomy</A> and <A title="Astrobiology" href="http://en.wikipedia.org/wiki/Astrobiology" linkindex="9">astrobiology</A>, the <B>Rare Earth hypothesis</B> argues that the <A class="mw-redirect" title="Origin of life" href="http://en.wikipedia.org/wiki/Origin_of_life" linkindex="10">emergence</A> of complex <A class="mw-redirect" title="Multicellular life" href="http://en.wikipedia.org/wiki/Multicellular_life" linkindex="11">multicellular life</A> (<A class="mw-redirect" title="Metazoa" href="http://en.wikipedia.org/wiki/Metazoa" linkindex="12">metazoa</A>) on <A title="Earth" href="http://en.wikipedia.org/wiki/Earth" linkindex="13">Earth</A> required an improbable combination of <A title="Astrophysics" href="http://en.wikipedia.org/wiki/Astrophysics" linkindex="14">astrophysical</A> and <A title="Geology" href="http://en.wikipedia.org/wiki/Geology" linkindex="15">geological</A> events and circumstances. The term "Rare Earth" comes from <I>Rare Earth: Why Complex Life Is Uncommon in the Universe</I> (2000), a book by <A title="Peter Ward (paleontologist)" href="http://en.wikipedia.org/wiki/Peter_Ward_(paleontologist)" linkindex="16">Peter Ward</A>, a <A title="Geologist" href="http://en.wikipedia.org/wiki/Geologist" linkindex="17">geologist</A> and <A class="mw-redirect" title="Paleontologist" href="http://en.wikipedia.org/wiki/Paleontologist" linkindex="18">paleontologist</A>, and <A title="Donald E. Brownlee" href="http://en.wikipedia.org/wiki/Donald_E._Brownlee" linkindex="19">Donald E. Brownlee</A>, an <A title="Astronomer" href="http://en.wikipedia.org/wiki/Astronomer" linkindex="20">astronomer</A> and <A title="Astrobiology" href="http://en.wikipedia.org/wiki/Astrobiology" linkindex="21">astrobiologist</A>. Their book is the source for much of this article.</P></blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://en.wikipedia.org/w/index.php?title=Rare_Earth_hypothesis&oldid=310577591"><P>By concluding that complex life is uncommon, the Rare Earth hypothesis is a possible solution to the <A title="Fermi paradox" href="http://en.wikipedia.org/wiki/Fermi_paradox" linkindex="32">Fermi paradox</A>: "If extraterrestrial aliens are common, why aren't they obvious?"<SUP class="reference" id="cite_ref-Webb.2C_Stephen_2002_1-0"><A href="#cite_note-Webb.2C_Stephen_2002-1" linkindex="33"><SPAN>[</SPAN>2<SPAN>]</SPAN></A></SUP></P></blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://en.wikipedia.org/w/index.php?title=Rare_Earth_hypothesis&oldid=310577591"><SPAN class="mw-headline">The galactic habitable zone</SPAN></blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://en.wikipedia.org/w/index.php?title=Rare_Earth_hypothesis&oldid=310577591"><div align="center"><img src="http://content9.clipmarks.com/blog_cache/en.wikipedia.org/img/1ADAF48A-F180-4C0A-9C17-F1CBA3FA7255" alt="" /></div></blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://en.wikipedia.org/w/index.php?title=Rare_Earth_hypothesis&oldid=310577591"><div align="center"><img src="http://content6.clipmarks.com/blog_cache/en.wikipedia.org/img/8E0B8E21-F503-49CA-8159-897AB92FD2D6" alt="" /></div></blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://en.wikipedia.org/w/index.php?title=Rare_Earth_hypothesis&oldid=310577591"><div align="center"><img src="http://content7.clipmarks.com/blog_cache/en.wikipedia.org/img/0F25F1D6-F235-4323-82E8-FEB041D796A9" alt="" /></div></blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://en.wikipedia.org/w/index.php?title=Rare_Earth_hypothesis&oldid=310577591"><div align="center"><img src="http://content8.clipmarks.com/blog_cache/en.wikipedia.org/img/86F0E3D9-7B94-4601-8FFE-C1215C60350E" alt="" /></div></blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://en.wikipedia.org/w/index.php?title=Rare_Earth_hypothesis&oldid=310577591"><SPAN class="mw-headline">Many-Worlds quantum mechanics</SPAN></blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://en.wikipedia.org/w/index.php?title=Rare_Earth_hypothesis&oldid=310577591"><li style="margin-left:16px;padding-left: 0px;"><A rel="nofollow" title="http://news.bbc.co.uk/1/hi/sci/tech/7249884.stm" class="external text" href="http://news.bbc.co.uk/1/hi/sci/tech/7249884.stm" linkindex="426">'Hundreds of worlds' in Milky Way</A></LI></blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://en.wikipedia.org/w/index.php?title=Rare_Earth_hypothesis&oldid=310577591"><li style="margin-left:16px;padding-left: 0px;"><A title="John D. Barrow" href="http://en.wikipedia.org/wiki/John_D._Barrow" linkindex="427">John D. Barrow</A> and <A title="Frank J. Tipler" href="http://en.wikipedia.org/wiki/Frank_J._Tipler" linkindex="428">Frank J. Tipler</A>, 1986. <I><A title="Anthropic principle" href="http://en.wikipedia.org/wiki/Anthropic_principle" linkindex="429">The Anthropic Cosmological Principle</A></I>. Oxford Univ. Press.</LI></blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://en.wikipedia.org/w/index.php?title=Rare_Earth_hypothesis&oldid=310577591"><li style="margin-left:16px;padding-left: 0px;"><A rel="nofollow" title="http://www.astro.washington.edu/rareearth/" class="external text" href="http://www.astro.washington.edu/rareearth/" linkindex="445">Home page</A> of <I>Rare Earth</I>.</LI></blockquote></div><div style="margin: 0px 6px 6px 4px;"><table style="font-size: 11px;border-spacing: 0px;padding: 0px;" cellpadding="0" cellspacing="0" width="100%"><tr><td style="background:transparent;border-width:0px;padding:0px;">&nbsp;</td><td align="right" style="background:transparent;border-width:0px;padding:0px;width:107px" width="107"><a href="http://clipmarks.com/share/0CF21FA2-A970-430B-ADDC-E033DB1B0E52/blog/" title="blog or email this clip"><img src="http://content9.clipmarks.com/images/c2b-foot.png" border="0" alt="blog it" width="107" height="17" style="border-width:0px;padding:0px;margin:0px;" /></a></td></tr></table></div></div>

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