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Do not fill this in! === Physics === {{further|Entropy and life}} From a [[physics]] perspective, an organism is a [[thermodynamic system]] with an organised molecular structure that can reproduce itself and evolve as survival dictates.<ref name="Luttermoser-1">{{cite web |last1=Luttermoser |first1=Donald G. |title=ASTR-1020: Astronomy II Course Lecture Notes Section XII |url=http://www.etsu.edu/physics/lutter/courses/astr1020/a1020chap12.pdf |publisher=[[East Tennessee State University]] |access-date=28 August 2011 |url-status=dead |archive-url=https://web.archive.org/web/20120322185054/http://www.etsu.edu/physics/lutter/courses/astr1020/a1020chap12.pdf |archive-date=22 March 2012 }}</ref><ref name="Luttermoser-2">{{cite web |last1=Luttermoser |first1=Donald G. |title=Physics 2028: Great Ideas in Science: The Exobiology Module |url=http://www.etsu.edu/physics/lutter/courses/phys2028/p2028exobnotes.pdf |date=Spring 2008 |publisher=[[East Tennessee State University]] |access-date=28 August 2011 |url-status=dead |archive-url=https://web.archive.org/web/20120322185041/http://www.etsu.edu/physics/lutter/courses/phys2028/p2028exobnotes.pdf |archive-date=22 March 2012 }}</ref> Thermodynamically, life has been described as an open system which makes use of gradients in its surroundings to create imperfect copies of itself.<ref name="Review 2009">{{cite journal |title=What makes a planet habitable? |journal=The Astronomy and Astrophysics Review |year=2009 |last1=Lammer |first1=H. |last2=Bredehöft |first2=J.H. |last3=Coustenis |first3=A. |author3-link=Athena Coustenis |last4=Khodachenko |first4=M.L. |volume=17 |issue=2 |pages=181–249 |doi=10.1007/s00159-009-0019-z |url=http://veilnebula.jorgejohnson.me/uploads/3/5/8/7/3587678/lammer_et_al_2009_astron_astro_rev-4.pdf |access-date=3 May 2016 |quote=Life as we know it has been described as a (thermodynamically) open system (Prigogine et al. 1972), which makes use of gradients in its surroundings to create imperfect copies of itself. |url-status=dead |archive-url=https://web.archive.org/web/20160602235333/http://veilnebula.jorgejohnson.me/uploads/3/5/8/7/3587678/lammer_et_al_2009_astron_astro_rev-4.pdf |archive-date=2 June 2016 |bibcode=2009A&ARv..17..181L|s2cid=123220355 }}</ref> Another way of putting this is to define life as "a self-sustained chemical system capable of undergoing [[Darwinian evolution]]", a definition adopted by a [[NASA]] committee attempting to define life for the purposes of [[exobiology]], based on a suggestion by [[Carl Sagan]].<ref>{{Cite journal |last=Benner |first=Steven A. |date=December 2010 |title=Defining Life |journal=Astrobiology |volume=10 |issue=10 |pages=1021–1030 |doi=10.1089/ast.2010.0524 |pmc=3005285 |pmid=21162682 |bibcode=2010AsBio..10.1021B}}</ref><ref>{{cite book |first1=Gerald F. |title=Extraterrestrials |last1=Joyce |author-link=Gerald Joyce |pages=139–151 |publisher=Cambridge University Press |date=1995 |doi=10.1017/CBO9780511564970.017 |isbn=978-0-511-56497-0 |chapter=The RNA World: Life before DNA and Protein |hdl=2060/19980211165 |s2cid=83282463 }}</ref> This definition, however, has been widely criticized because according to it, a single sexually reproducing individual is not alive as it is incapable of evolving on its own.<ref>{{Cite journal |last=Benner |first=Steven A. |date=December 2010 |title=Defining Life |journal=Astrobiology |volume=10 |issue=10 |pages=1021–1030 |doi=10.1089/ast.2010.0524 |pmc=3005285 |pmid=21162682|bibcode=2010AsBio..10.1021B }}</ref> The reason for this potential flaw is that "NASA's definition" refers to life as a phenomenon, not a living individual, which makes it incomplete.<ref name="Piast-2019">{{Cite journal |last=Piast |first=Radosław W. |date=June 2019 |title=Shannon's information, Bernal's biopoiesis and Bernoulli distribution as pillars for building a definition of life |journal=Journal of Theoretical Biology |volume=470 |pages=101–107 |doi=10.1016/j.jtbi.2019.03.009 |pmid=30876803 |bibcode=2019JThBi.470..101P |s2cid=80625250 }}</ref> Alternative definitions based on the notion of life as a phenomenon and a living individual have been proposed as [[Continuum mechanics|continuum]] of a self-maintainable information, and a distinct element of this continuum, respectively. A major strength of this approach is that it defines life in terms of mathematics and physics, avoiding biological vocabulary.<ref name="Piast-2019" /> Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. If you do not want your writing to be edited mercilessly, then do not submit it here. You are also promising us that you wrote this yourself, or copied it from a public domain or similar free resource (see Christianpedia:Copyrights for details). Do not submit copyrighted work without permission! Cancel Editing help (opens in new window) Discuss this page