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I deleted the paragraph dealing with background microwave radiation. I think the statement that it permeates every object is mistaken. While the radiation may be ubiquitous, it's still just microwave radiation, and not at all difficult to shield against with any conductive barrier. It might be difficult to build an isolated system without an initial contribution of energy from this background radiation, but that is also not a requirement for an isolated system. As long as it's isolated now, it doesn't matter if some of the energy originally came from an outside source.
I also realize a metal barrier would eventually heat up to 2.7K from the background radiation and emit its own blackbody radiation. In that sense, one could argue that the background radiation has "permeated through the barrier" once equilibrium is achieved, but that time can be made arbitrarily long by using thicker or successive insulating layers. So I agree it's impossible to build a permanently isolated system, but that point has already been addressed in the previous paragraph. It seems pretty clear that like many concepts in science, the isolated system is just a model of an ideal limiting case, and the bulk of the article need not be spent on reasons why the limit can never trully be attained in real life.
The final paragraph is just one opinion in a hotly debated philosophical area, and is probably not the right way to look at it. See the book "Time's Arrow and Archimedies' Point" by Huw Price. 139.184.30.18 15:50, 31 July 2007 (UTC)
No sources are cited and the page should differentiate between the use of the term in mathematics/physics from the uses in other areas. This is important to prevent misleading analogies and metaphors, and hence the misinterpretation of science. -- Kenneth M Burke 01:28, 25 August 2007 (UTC)
The statement claiming an isolated system is not affected by gravity is simply incorrect. There is significant gravity everywhere in the Solar System and of course it applies a force to the mass of molecules in any isolated system. The force of gravity must be taken into account, for example, when determining the state of maximum entropy that the Second Law of Thermodynamics tells us will evolve in an isolated system. That law in fact only applies to an isolated system. This is where Clausius was in error because he ignored the effect on entropy of gravity acting on molecules at different heights. As a consequence, the Clausius statement (when applied to heat transfer that is other than by radiation) is not correct in a vertical plane in a gravitational field. So the statement made in the article is false and prone to lead to incorrect conclusions if applied in any vertically oriented isolated system.
Is it clear that the universe is an isolated system? Of course, one could define it as such, but that misses the point. The observable universe certainly is not isolated since the boundary of the observable universe is expanding at the speed of light. Our four dimensional universe may not be closed to collisions with other four dimensional branes in a higher dimensional universe. We have recently learned that space can be created by dark energy. Is it unthinkable that energy, fields and particles might be as well. This was a part of Hoyle's Steady State theory that was largely defeated by evidence of the Big Bang. However, it is not clear that Big Bang and aspects of Steady State might not both be true. I cannot accept the notion of an isolated universe as an axiomatic definition without clarification of what we mean by the universe. And that, it seems to me, is part of the yet unfinished job of physics. Lou ( talk) 21:07, 15 January 2008 (UTC)
Added a line that says that the universe is often considered to be an isolated system, which seems to agree with literature. Left intentionally vague, as there is clearly some disagreement about this statement. -- Tim Alphabeaver ( talk) 00:09, 30 January 2020 (UTC)
The connection between all the (functioning) external links and this topic seem weak, so I have removed them. They are:
They do mention the term "isolated system" but not in much detail. Based on my reading of Wikipedia:External links these links are too indirect to be included. Others may have different interpretations however, hence posting here. David Hollman ( Talk) 21:28, 2 September 2010 (UTC)
Hi all,
Maurice Carbonaro ( talk) 19:31, 7 November 2012 (UTC)
Shouldn't this just be merged into, or deleted in favor of, "Closed System"? They're essentially synonyms. The main differences are that this article is a very miscellaneous stub, and that it contains this sort of weakly-supported distinction between "closed" and "isolated" (which is used in a few physical chemistry texts, I guess, but hardly a generally-accepted distinction, is it?). In contrast, Closed Systems says, more plausibly, "The specification of what types of transfers are excluded, is different in different contexts." Orbst ( talk) 19:13, 30 April 2014 (UTC)
In the article " walls" is used 11 times... maybe " boundaries" would be more appropriate? M aurice Carbonaro 10:00, 29 October 2015 (UTC)
![]() | This article is rated C-class on Wikipedia's
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I deleted the paragraph dealing with background microwave radiation. I think the statement that it permeates every object is mistaken. While the radiation may be ubiquitous, it's still just microwave radiation, and not at all difficult to shield against with any conductive barrier. It might be difficult to build an isolated system without an initial contribution of energy from this background radiation, but that is also not a requirement for an isolated system. As long as it's isolated now, it doesn't matter if some of the energy originally came from an outside source.
I also realize a metal barrier would eventually heat up to 2.7K from the background radiation and emit its own blackbody radiation. In that sense, one could argue that the background radiation has "permeated through the barrier" once equilibrium is achieved, but that time can be made arbitrarily long by using thicker or successive insulating layers. So I agree it's impossible to build a permanently isolated system, but that point has already been addressed in the previous paragraph. It seems pretty clear that like many concepts in science, the isolated system is just a model of an ideal limiting case, and the bulk of the article need not be spent on reasons why the limit can never trully be attained in real life.
The final paragraph is just one opinion in a hotly debated philosophical area, and is probably not the right way to look at it. See the book "Time's Arrow and Archimedies' Point" by Huw Price. 139.184.30.18 15:50, 31 July 2007 (UTC)
No sources are cited and the page should differentiate between the use of the term in mathematics/physics from the uses in other areas. This is important to prevent misleading analogies and metaphors, and hence the misinterpretation of science. -- Kenneth M Burke 01:28, 25 August 2007 (UTC)
The statement claiming an isolated system is not affected by gravity is simply incorrect. There is significant gravity everywhere in the Solar System and of course it applies a force to the mass of molecules in any isolated system. The force of gravity must be taken into account, for example, when determining the state of maximum entropy that the Second Law of Thermodynamics tells us will evolve in an isolated system. That law in fact only applies to an isolated system. This is where Clausius was in error because he ignored the effect on entropy of gravity acting on molecules at different heights. As a consequence, the Clausius statement (when applied to heat transfer that is other than by radiation) is not correct in a vertical plane in a gravitational field. So the statement made in the article is false and prone to lead to incorrect conclusions if applied in any vertically oriented isolated system.
Is it clear that the universe is an isolated system? Of course, one could define it as such, but that misses the point. The observable universe certainly is not isolated since the boundary of the observable universe is expanding at the speed of light. Our four dimensional universe may not be closed to collisions with other four dimensional branes in a higher dimensional universe. We have recently learned that space can be created by dark energy. Is it unthinkable that energy, fields and particles might be as well. This was a part of Hoyle's Steady State theory that was largely defeated by evidence of the Big Bang. However, it is not clear that Big Bang and aspects of Steady State might not both be true. I cannot accept the notion of an isolated universe as an axiomatic definition without clarification of what we mean by the universe. And that, it seems to me, is part of the yet unfinished job of physics. Lou ( talk) 21:07, 15 January 2008 (UTC)
Added a line that says that the universe is often considered to be an isolated system, which seems to agree with literature. Left intentionally vague, as there is clearly some disagreement about this statement. -- Tim Alphabeaver ( talk) 00:09, 30 January 2020 (UTC)
The connection between all the (functioning) external links and this topic seem weak, so I have removed them. They are:
They do mention the term "isolated system" but not in much detail. Based on my reading of Wikipedia:External links these links are too indirect to be included. Others may have different interpretations however, hence posting here. David Hollman ( Talk) 21:28, 2 September 2010 (UTC)
Hi all,
Maurice Carbonaro ( talk) 19:31, 7 November 2012 (UTC)
Shouldn't this just be merged into, or deleted in favor of, "Closed System"? They're essentially synonyms. The main differences are that this article is a very miscellaneous stub, and that it contains this sort of weakly-supported distinction between "closed" and "isolated" (which is used in a few physical chemistry texts, I guess, but hardly a generally-accepted distinction, is it?). In contrast, Closed Systems says, more plausibly, "The specification of what types of transfers are excluded, is different in different contexts." Orbst ( talk) 19:13, 30 April 2014 (UTC)
In the article " walls" is used 11 times... maybe " boundaries" would be more appropriate? M aurice Carbonaro 10:00, 29 October 2015 (UTC)