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Isolated system
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<h2 id="radiative-isolation">Radiative isolation</h2> <p>For radiative isolation, the walls should be perfectly conductive, so as to perfectly reflect the radiation within the cavity, as for example imagined by <a href="/facts/Max_Planck/KKk0698y">Planck</a>. </p><p>He was considering the internal thermal radiative equilibrium of a thermodynamic system in a cavity initially devoid of substance. He did not mention what he imagined to surround his perfectly reflective and thus perfectly conductive walls. Presumably, since they are perfectly reflective, they isolate the cavity from any external electromagnetic effect. Planck held that for radiative equilibrium within the isolated cavity, it needed to have added to its interior a speck of carbon.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a><a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a><a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p><p>If the cavity with perfectly reflective walls contains enough radiative energy to sustain a temperature of cosmological magnitude, then the speck of carbon is not needed because the radiation generates particles of substance, such as for example electron-positron pairs, and thereby reaches thermodynamic equilibrium. </p><p>A different approach is taken by <a href="/facts/Roger_Balian/4Y0knxtK">Roger Balian</a>. For quantizing the radiation in the cavity, he imagines his radiatively isolating walls to be perfectly conductive. Though he does not mention mass outside, and it seems from his context that he intends the reader to suppose the interior of the cavity to be devoid of mass, he does imagine that some factor causes currents in the walls. If that factor is internal to the cavity, it can be only the radiation, which would thereby be perfectly reflected. For the thermal equilibrium problem, however, he considers walls that contain charged particles that interact with the radiation inside the cavity; such cavities are of course not isolated, but may be regarded as in a heat bath.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Closed_system/8KEjjgQE">Closed system</a></li> <li><a href="/facts/Dynamical_system/782gREl5">Dynamical system</a></li> <li><a href="/facts/Open_system_(systems_theory)/V9KwQ0dS">Open system</a></li> <li><a href="/facts/Thermodynamic_system/VUr0kpWu">Thermodynamic system</a></li> <li><a href="/facts/Open_system_(thermodynamics)/VUr0kpWu">Open system (thermodynamics)</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Kolesnikov, I. M. (2001). Thermodynamics of Spontaneous and Non-spontaneous Processes. Nova Publishers. ISBN 978-1-56072-904-4. <a href="978-1-56072-904-4" target="_blank">978-1-56072-904-4</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>A System and Its Surroundings; UC Davis ChemWiki, by University of California - Davis, at http://chemwiki.ucdavis.edu/Physical_Chemistry/Thermodynamics/A_System_And_Its_Surroundings#Isolated_System Archived February 3, 2016, at the Wayback Machine <a href="http://chemwiki.ucdavis.edu/Physical_Chemistry/Thermodynamics/A_System_And_Its_Surroundings#Isolated_System" target="_blank">http://chemwiki.ucdavis.edu/Physical_Chemistry/Thermodynamics/A_System_And_Its_Surroundings#Isolated_System</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Hyperphysics, by the Department of Physics and Astronomy of Georgia State University; at http://hyperphysics.phy-astr.gsu.edu/hbase/conser.html#isosys <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/conser.html#isosys" target="_blank">http://hyperphysics.phy-astr.gsu.edu/hbase/conser.html#isosys</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Planck, M. (1914). The Theory of Heat Radiation, second edition translated by Masius, P. Blakiston's Son & Co., Philadelphia, p. 43. <a href="/wiki/Max_Planck" target="_blank">/wiki/Max_Planck</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Fowler, R.H. (1929). Statistical Mechanics: the Theory of the Properties of Matter in Equilibrium, Cambridge University Press, London, p. 74. <a href="/wiki/Ralph_Fowler" target="_blank">/wiki/Ralph_Fowler</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Landsberg, P.T. (1978). Thermodynamics and Statistical Mechanics, Oxford University Press, Oxford UK, ISBN 0-19-851142-6, pp. 208–209. <a href="/wiki/ISBN_(identifier)" target="_blank">/wiki/ISBN_(identifier)</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Balian, R., (1982). From Microphysics to Macrophysics: Methods and Applications of Statistical Physics, translated by D. ter Haar, volume 2, Springer, ISBN 978-3-540-45478-6, pp. 203, 215. <a href="/wiki/Roger_Balian" target="_blank">/wiki/Roger_Balian</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> </ol>