Editing Life (section)

=== Challenge ===

The definition of life has long been a challenge for scientists and philosophers.<ref name="Definitions 2009">{{cite journal |title=Why Is the Definition of Life So Elusive? Epistemological Considerations |journal=Astrobiology |date=May 2009 |last=Tsokolov |first=Serhiy A. |volume=9 |issue=4 |doi=10.1089/ast.2007.0201 |bibcode=2009AsBio...9..401T |pages=401–412 |pmid=19519215}}</ref><ref name=Emmeche1997>{{cite web |first1=Claus |last1=Emmeche |year=1997 |title=Defining Life, Explaining Emergence |publisher=Niels Bohr Institute |url=http://www.nbi.dk/~emmeche/cePubl/97e.defLife.v3f.html |access-date=25 May 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120314095044/http://www.nbi.dk/~emmeche/cePubl/97e.defLife.v3f.html |archive-date=14 March 2012 }}</ref><ref name=McKay>{{Cite journal |title=What Is Life—and How Do We Search for It in Other Worlds? |journal=PLOS Biology |date=14 September 2004 |first=Chris P. |last=McKay |pmid=15367939 |volume=2 |issue=9 |pmc=516796 |page=302 |doi=10.1371/journal.pbio.0020302 |doi-access=free }}</ref> This is partially because life is a process, not a substance.<ref name="DefinitionMotivation">{{Cite journal |last=Mautner |first=Michael N. |title=Directed panspermia. 3. Strategies and motivation for seeding star-forming clouds |journal=Journal of the British Interplanetary Society |year=1997 |volume=50 |pages=93–102 |url=http://www.astro-ecology.com/PDFDirectedPanspermia3JBIS1997Paper.pdf |bibcode=1997JBIS...50...93M |url-status=live |archive-url=https://web.archive.org/web/20121102064738/http://www.astro-ecology.com/PDFDirectedPanspermia3JBIS1997Paper.pdf |archive-date=2 November 2012 }}</ref><ref name="SeedingBook">{{Cite book |last=Mautner |first=Michael N. |title=Seeding the Universe with Life: Securing Our Cosmological Future |date=2000 |publisher=Michael Mautner |isbn=978-0-476-00330-9 |url=http://www.astro-ecology.com/PDFSeedingtheUniverse2005Book.pdf |url-status=live |archive-url=https://web.archive.org/web/20121102064713/http://www.astro-ecology.com/PDFSeedingtheUniverse2005Book.pdf |archive-date=2 November 2012 }}</ref><ref>{{cite journal |title=What is life? It's a Tricky, Often Confusing Question |journal=Astrobiology Magazine |date=18 September 2014 |last=McKay |first=Chris}}</ref> This is complicated by a lack of knowledge of the characteristics of living entities, if any, that may have developed outside Earth.<ref>{{Cite journal |last1=Nealson |first1=K.H. |last2=Conrad |first2=P.G. |title=Life: past, present and future |journal=[[Philosophical Transactions of the Royal Society of London B]] |volume=354 |issue=1392 |pages=1923–1939 |date=December 1999 |pmid=10670014 |pmc=1692713 |doi=10.1098/rstb.1999.0532 |url=https://royalsociety.org/journals/|archive-date=3 January 2016 |archive-url=https://wayback.archive-it.org/all/20160103000925/https://royalsociety.org/journals/ |url-status=live }}</ref><ref name="Bioethics">{{Cite journal |last=Mautner |first=Michael N. |title=Life-centered ethics, and the human future in space |journal=Bioethics |volume=23 |pages=433–440 |year=2009 |doi=10.1111/j.1467-8519.2008.00688.x |pmid=19077128 |url=http://www.astro-ecology.com/PDFLifeCenteredBioethics2009Paper.pdf |issue=8 |s2cid=25203457 |url-status=live |archive-url=https://web.archive.org/web/20121102064743/http://www.astro-ecology.com/PDFLifeCenteredBioethics2009Paper.pdf |archive-date=2 November 2012 }}</ref> Philosophical definitions of life have also been put forward, with similar difficulties on how to distinguish living things from the non-living.<ref name=Jeuken1975>{{cite journal|title=The biological and philosophical defitions of life |author=Jeuken M |journal=Acta Biotheoretica |volume=24 |issue=1–2 |pages=14–21 |year=1975 |doi=10.1007/BF01556737|pmid=811024 |s2cid=44573374 }}</ref> [[Legal death|Legal definitions]] of life have been debated, though these generally focus on the decision to declare a human dead, and the legal ramifications of this decision.<ref name=Capron1978>{{cite journal|title=Legal definition of death |author=Capron AM |journal=Annals of the New York Academy of Sciences |year=1978 |doi=10.1111/j.1749-6632.1978.tb50352.x |pmid=284746 |volume=315 |issue=1 |pages=349–362 |bibcode=1978NYASA.315..349C |s2cid=36535062 }}</ref> At least 123 definitions of life have been compiled.<ref name="JBSD-20110317">{{cite journal |last=Trifonov |first=Edward N. |title=Vocabulary of Definitions of Life Suggests a Definition |date=17 March 2011 |journal=Journal of Biomolecular Structure and Dynamics |volume=29 |issue=2 |pages=259–266 |doi=10.1080/073911011010524992 |pmid=21875147 |doi-access=free }}</ref>