# Thermodynamic Entropy **URL:** \ **Category:** Factual Questions\ **Created:** [February 12, 2018, 2:14am UTC](https://boards.straightdope.com/t/thermodynamic-entropy/808665 "2018-02-12T02:14:29Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [February 12, 2018, 2:14am UTC](https://boards.straightdope.com/t/thermodynamic-entropy/808665/1 "2018-02-12T02:14:29Z")
Entropy…the process where order decays into chaos. The universe, as a whole, goes from a state of higher order to a state of higher entropy. Now, some small section of the universe for a time can assemble some order, but that comes at a price…the rest of the universe has it’s entropy proportionally increased. Does the Rate of Universal Entropy have a constant value? A Universal Constant? ---
**Author:** ![Ruken](https://avatars.discourse-cdn.com/v4/letter/r/f475e1/32.png) [@Ruken](https://boards.straightdope.com/u/Ruken)\ **Post date:** [February 12, 2018, 1:06pm UTC](https://boards.straightdope.com/t/thermodynamic-entropy/808665/2 "2018-02-12T13:06:19Z")
Since it’s been nearly half a day with no answer, you’re stuck with my nitpicky not-answer. Entropy is more of a measure of disorder than a process. You may be equating the second law of thermodynamics with entropy. This may be a good starting point but probably doesn’t fully answer you. > **[Introduction to entropy](https://en.m.wikipedia.org/wiki/Introduction_to_entropy)** > > In thermodynamics, entropy is a numerical quantity that shows that many physical processes can go in only one direction in time. For example, you can pour cream into coffee and mix it, but you cannot "unmix" it; you can burn a piece of wood, but you cannot "unburn" it. The word 'entropy' has entered popular usage to refer a lack of order or predictability, or of a gradual decline into disorder. A more physical interpretation of thermodynamic entropy refers to spread of energy or matter, or to If... ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [February 12, 2018, 3:13pm UTC](https://boards.straightdope.com/t/thermodynamic-entropy/808665/3 "2018-02-12T15:13:04Z")
Thank you for that link, **Ruken** , that does provide the terms we can discuss this matter further with … and so I’d like to change the OP’s question a bit “Does the Rate of Universal Entropy _change_ have a constant value? A Universal Constant?” I believe the answer is NO … the rate of change is strictly dependent on the material in question … but others more knowledgeable may come by to correct this … If we use the most common demonstration of the 2nd Law: take a kg of iron at -100ºC and another kg of iron at +100ºC and out them together, after some amount of time both kg’s will be 0ºC … the exact same thing happens if we substitute the iron for copper _except_ the amount of time is different … the rate of entropy change is different … so there’s no rate of change common to all materials … ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [February 12, 2018, 3:36pm UTC](https://boards.straightdope.com/t/thermodynamic-entropy/808665/4 "2018-02-12T15:36:31Z")
> [@watchwolf49](#): > > Thank you for that link, **Ruken** , that does provide the terms we can discuss this matter further with … and so I’d like to change the OP’s question a bit “Does the Rate of Universal Entropy _change_ have a constant value? A Universal Constant?” > > I believe the answer is NO … the rate of change is strictly dependent on the material in question … but others more knowledgeable may come by to correct this … > > If we use the most common demonstration of the 2nd Law: take a kg of iron at -100ºC and another kg of iron at +100ºC and out them together, after some amount of time both kg’s will be 0ºC … the exact same thing happens if we substitute the iron for copper _except_ the amount of time is different … the rate of entropy change is different … so there’s no rate of change common to all materials … It’s not just a question of materials, it’s also what happens to those materials. Entropy isn’t just about heat transfer - it’s also created by things falling/flowing downhill, and by chemical/nuclear reactions happening. It should be plenty obvious that the entropy of the universe does not increase at a constant rate. For example, if I set off a nuclear bomb, I can create a whole lot of entropy in a very short period of time; regardless of whatever else might have been happening (entropy-wise) in the rest of the universe, this bomb - which had, until now, been existing in a nice low-entropy state - suddenly transitioned to a state of high entropy. In the theorized [heat death of the universe,](https://en.wikipedia.org/wiki/Heat_death_of_the_universe) entropy is at its maximum and cannot increase any further: the stars are all burned out, the water has all run downhill, the iron has all oxidized, everything in the universe is at the same temperature. If a day will come when entropy can increase no more, then the rate of entropy change cannot possibly be constant. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [February 12, 2018, 10:06pm UTC](https://boards.straightdope.com/t/thermodynamic-entropy/808665/5 "2018-02-12T22:06:40Z")
Yeah, entropy can never decrease, but it can increase quickly or slowly, sometimes so slowly that it’s, in effect, not changing at all. There’s no fundamental law that says that it must increase at some specific rate. ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [February 13, 2018, 1:17am UTC](https://boards.straightdope.com/t/thermodynamic-entropy/808665/6 "2018-02-13T01:17:08Z")
I was thinking of, say, a sphere that is shedding heat, or, due to having X amount of mass, radiates Y amount of gravity. If the Universe is a (hyper)sphere of 3+N dimensions, so-and-so wide expanding at the speed of light, such-and-such mass, this amount of temperature, that amount of charge, etc., could an estimate of the rate be had…and if non-constant over cosmic time, give a rate-trend? ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [February 13, 2018, 1:49am UTC](https://boards.straightdope.com/t/thermodynamic-entropy/808665/7 "2018-02-13T01:49:30Z")
The posited heat death of the universe is probably about the nearest you will get. That makes a lot of assumptions about stellar processes, the cosmological constant, unknowns in quantum mechanics and the like. Reaching equilibrium isn’t a straight line of entropy increase here either. But you can hand wave a point say 10[sup]100[/sup] years hence where things are pretty slow. But stellar processes will have long since stopped, and we have been waiting for the black holes to evaporate for a _very_ long time. During the time of stars things were moving along much faster. You might make an estimate for a given epoch in the universe’s history and its future, but there isn’t a constant number. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [February 13, 2018, 2:29am UTC](https://boards.straightdope.com/t/thermodynamic-entropy/808665/8 "2018-02-13T02:29:37Z")
You can also make a pretty good case that the heat death of the Universe happened in the first fraction of a second. Sure, entropy isn’t quite completely maximized, but it’s 99 point a lot of 9s percent of the way there. ---
**Author:** ![harmonicamoon](https://avatars.discourse-cdn.com/v4/letter/h/65b543/32.png) [@harmonicamoon](https://boards.straightdope.com/u/harmonicamoon)\ **Post date:** [February 13, 2018, 5:03am UTC](https://boards.straightdope.com/t/thermodynamic-entropy/808665/9 "2018-02-13T05:03:55Z")
Doesn’t laws of thermodynamics require a closed system? Do we have one? ---
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [February 13, 2018, 5:26am UTC](https://boards.straightdope.com/t/thermodynamic-entropy/808665/10 "2018-02-13T05:26:29Z")
It helps if you ignore the older “disorder” analogy and think entropy increase as the result of the dispersal of energy in a general way and the increase in microstates in specific. entropy = thermal flow / temperature Ignore the ‘disorder’ explanation and consider how much energy is freed when a silicon crystal is formed. Despite that easy to describe structure in the crystal the free energy is far more difficult to fully describe. The released energy results in a greater number of microstates. This paper may be useful in clarifying the typical flawed analogy (better than my alt flawed ones) [http://khimiya.org/volume15/Entropia.pdf](http://khimiya.org/volume15/Entropia.pdf) ---
**Author:** ![octopus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/octopus/32/3716_2.png) [@octopus](https://boards.straightdope.com/u/octopus)\ **Post date:** [February 13, 2018, 5:44am UTC](https://boards.straightdope.com/t/thermodynamic-entropy/808665/11 "2018-02-13T05:44:28Z")
Maximum entropy is basically homogeneity and increasing entropy is the decreasing of gradients. ---
**Author:** ![PlaceboTarget](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/placebotarget/32/1073_2.png) [@PlaceboTarget](https://boards.straightdope.com/u/PlaceboTarget)\ **Post date:** [February 13, 2018, 7:03am UTC](https://boards.straightdope.com/t/thermodynamic-entropy/808665/12 "2018-02-13T07:03:07Z")
> [@harmonicamoon](#): > > Doesn’t laws of thermodynamics require a closed system? > > Do we have one? Yes, we do. A closed system is one that has no interaction with the environment. Since the universe is defined as the entire matter and energy as well as the space (and time) containing them, it appears to be a closed system par excellence because there simply is no environment for the universe to interact with. ---
**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\ **Post date:** [February 13, 2018, 3:47pm UTC](https://boards.straightdope.com/t/thermodynamic-entropy/808665/13 "2018-02-13T15:47:53Z")
Your initial premise is flawed. There’s no “Law of the Conservation of Entropy”. Remember you have to define the boundaries of your system, first. Within that system, you will not find a decrease of entropy at point “X” resulting in an increase of entropy at point “Y”. (Assume points “X” and “Y” are two distinct points within the system whose boundaries you have defined.) ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [February 13, 2018, 7:32pm UTC](https://boards.straightdope.com/t/thermodynamic-entropy/808665/14 "2018-02-13T19:32:02Z")
> [@PlaceboTarget](#): > > Yes, we do. A closed system is one that has no interaction with the environment. Since the universe is defined as the entire matter and energy as well as the space (and time) containing them, it appears to be a closed system par excellence because there simply is no environment for the universe to interact with. That the second law applies to the universe seems like it should be true, but i[t isn’t](https://www.scientificamerican.com/article/does-the-universe-violate-the-laws-of-thermodynamics/). > [@](#): > > Does the Universe Violate the Laws of Thermodynamics? > > Total energy must be conserved. Every student of physics learns this fundamental law. The trouble is, it does not apply to the universe as a whole. More directly to harmonicamoon’s question is not whether the universe is open or closed, but whether it is an _isolated_ system, i.e. one that that cannot exchange either matter or energy with its surroundings. (Open systems can exchange both; closed systems can only exchange energy.) This causes those who require God as a creator quite a bit of [anguish](http://www.apologeticspress.org/apcontent.aspx?category=9&article=3704): > [@](#): > > A common assertion being raised today by some is that the laws of thermodynamics do not apply to the Universe as a whole, and therefore cannot be used to prove that God played a role in the origin of the Universe. More specifically, some question whether our Universe can be considered an “isolated system” (i.e., a system in which mass and energy are not allowed to cross the system boundary; Cengel and Boles, 2002, p. 9). In their well-known thermodynamics textbook, Fundamentals of Classical Thermodynamics, Van Wylen and Sonntag note concerning the Second Law of Thermodynamics: “[W]e of course do not know if the universe can be considered as an isolated system” (1985, p. 233). Dr. Robert Alberty, author of Thermodynamics of Biochemical Reactions, is quoted as saying, “I do not agree that the universe is an isolated system in the thermodynamic sense” (as quoted in Holloway, 2010). I cite that because it comes up very high on Google and because it shows that the understanding of a non-isolated universe is so deep and widespread in physics that it must be addressed by those who want an alternative. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [February 13, 2018, 9:42pm UTC](https://boards.straightdope.com/t/thermodynamic-entropy/808665/15 "2018-02-13T21:42:26Z")
> [@Exapno\_Mapcase](#): > > That the second law applies to the universe seems like it should be true, but i[t isn’t](https://www.scientificamerican.com/article/does-the-universe-violate-the-laws-of-thermodynamics/). From the little I remember from “A brief history of time”, Stephen Hawking argued that a perfectly “black” black hole will not be consistent with thermodynamic entropy laws. And it was this line of thought in part that led to the discovery of Hawking Radiation. I thought, that a Black hole came the closest to an Isolated system, and even then it was not and the laws of thermodynamics applied to it. Why not the Universe at large ? Please explain ---
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [February 14, 2018, 4:18am UTC](https://boards.straightdope.com/t/thermodynamic-entropy/808665/16 "2018-02-14T04:18:01Z")
> [@am77494](#): > > From the little I remember from “A brief history of time”, Stephen Hawking argued that a perfectly “black” black hole will not be consistent with thermodynamic entropy laws. And it was this line of thought in part that led to the discovery of Hawking Radiation. > > I thought, that a Black hole came the closest to an Isolated system, and even then it was not and the laws of thermodynamics applied to it. Why not the Universe at large ? Please explain Trying to try a novel way to explain this without math. But note it is not meant to be taken as fact, just another way to approach the subject. First realize how warm the Universe is compared to black holes, hawking radiation will take a very long time to evaporate a black hole. ~0.00036 Kelvin – Recent laser cooling ~0.00000006 Kelvin – 1 solar mass black hole. ~0.000000000000014 Kelvin – super massive black hole. ~2.725 Kelvin – CMB today. As for the universe, if it is flat or open, or if dark energy is proven it will expand until temperature differences etc… can no longer be exploited to perform work. This is the common use of _heat death_ mentioned above but most modern data tends to point to a positive, non-zero cosmological constant that will result in a slowing approach to a limit that is not zero. If the current data holds and the cosmological constant is positive what may happen is that as the Universe approaches zero the arrow of time will slowly disappear and possibly stop. #1 Without the ability to do work initial conditions required for the 2nd don’t hold. #2 Without time the 2nd law doesn’t hold. There are other issues and possibilities like the max life of a proton, wave function collapse etc… There are also other ways to conceptualize these concepts.