Talk:Entropy

economics

The final section on applications to economics feels like an advertising piece. 2600:4041:2D9:CC00:F8DC:AB0:B403:4880 (talk) 19:44, 25 July 2025 (UTC)

It does, but I do not know enough about the subject to edit it. Richard-of-Earth (talk) 06:31, 29 July 2025 (UTC)

I did my best to remove the MOS:Puffery from that section. Gfox88 (talk) 20:28, 25 June 2026 (UTC)

Much better. Richard-of-Earth (talk) 01:09, 4 July 2026 (UTC)

Suggestion to Add and Discuss this More Practical Understanding of Entropy

I copy herewith a comment I posted in the Talk page for Second Law of Thermodynamics which references entropy:

The article currently presents the Second Law primarily through corollaries involving heat flow and temperature differences. However, the general statement of the Second Law — as correctly given in Laws of thermodynamics — is not included here, even though it is the foundational formulation from which those corollaries follow.

The concept of “heat transfer from hot to cold” is only one special case. The Second Law is fundamentally about entropy, and entropy is affected by changes in any form of internal energy — not only kinetic energy (which determines temperature), but also potential energy in a force field, phase‑change energy, chemical energy, and other internal energy components such as those in a compressed gas or a wound spring.

The Law applies to any natural thermodynamic process, or to a set of interacting processes considered together. “Net effects” are meaningful only when processes interact; they are not the basis of the Law itself.

The general statement — “in a natural thermodynamic process, the sum of the entropies of the interacting thermodynamic systems never decreases” — should be quoted in this article. In practice, this means entropy increases in any irreversible process, and when entropy reaches a maximum the system is in thermodynamic equilibrium, which is not necessarily the same as thermal equilibrium. This distinction is important and is one reason the general formulation refers to entropy rather than simply to heat flow.

Entropy is often described informally as “disorder,” but this is not the most accurate or useful interpretation. More precisely, entropy increases because unbalanced energy potentials tend to diminish: the system evolves toward a state in which the difference between initial and final internal energies is reducing towards zero. In a force field such as gravity, this includes changes in mean molecular gravitational potential energy as well as kinetic energy. For example, when an object falls onto a table, the gravitational potential energy difference between its initial height and the height of the table surface is eliminated — an irreversible process in which entropy increases. Likewise, when ice at 0°C melts in warmer water, the incoming internal energy from the warm water does not raise the ice’s temperature; it drives an irreversible phase change, and the entropy increases accordingly.

Given these considerations, the article would benefit from beginning with the general statement of the Second Law as presented in Laws of thermodynamics and then treating heat‑flow descriptions as corollaries that apply only when the relevant internal‑energy changes are limited to mean molecular kinetic energy. Retired Physicist (talk) 01:31, 14 August 2026 (UTC)

Image of paper offcuts ("material entropy")

I propose removing [[:File paper offcuts illustrating material entropy02.jpg]] from its current position. The caption presents the fragmentation of paper as illustrating increased entropy, but it does not explain the connection to thermodynamic entropy.

* The photograph shows macroscopic fragments. Their visible arrangement does not, by itself, establish an entropy difference between specified thermodynamic states. (Presumably, the states are uncut and cut paper?)

* Sure, industrial cutting will produce entropy through dissipation. However, that entropy production should not be identified with the untidy appearance of the resulting scraps. I would guess that more entropy is produced in the motor driving the machine doing the cutting.

* Counting possible arrangements of the scraps could be possible in theory, given a defined statistical model and a justification for relating that count to thermodynamic entropy. That is not clear how it is supposed to be done from the caption (or if that is what is intended with the image).

* The image risks reinforcing the identification of entropy with everyday “disorder.” The article itself discusses the limitations of this interpretation and cites Lambert’s "Disorder—A Cracked Crutch for Supporting Entropy Discussions" (J. Chem. Educ. 2002, 79, 187–192; doi:10.1021/ed079p187), which specifically criticizes using the rearrangement of macroscopic objects (including sheets of paper) as an illustration of thermodynamic entropy increase. Although cutting paper is a different process (and there is some entropy produced in the process, as it must be according to non-equilibrium thermodynamics), the same caution would apply to inferring entropy from the visible disorder of the resulting scraps.

Also, the file description uses "material entropy". This is a specialised concept, perhaps from ecological economics which is mentioned at the end of the page (I see that there are some previous discussion about this part). It is not clear what its relationship to the thermodynamic entropy is.

In its current form, I find the image misleading (and it is not clear how it connects to the macroscopic or microscopic description).

~2026-50914-55 (talk) 05:25, 21 September 2026 (UTC)

I agree and will remove the image. While entropy will increase in a paper mill when paper is cut into smaller sheets, it also increases when the many small logs used in paper production are converted to a single large roll of paper. It is better to keep the article focused on thermodynamic entropy. StarryGrandma (talk) 14:48, 21 September 2026 (UTC)

Upon further thought the illustration is not of "material entropy" as used in materials science. There is no change in the internal structure of the paper when it is cut into sheets and packaged. We just have smaller samples of it. StarryGrandma (talk) 21:00, 21 September 2026 (UTC)

Where does this article fit in the schema of entropy articles here?

In trying to respond to the above, I was trying to find what the scope of this article was compared to the various other closely related concepts of entropy. The result was I could not find what the scope of this article is. The lead of this article is ambiguous and there are a plethora of similar pages that cover similar topics. Even with Introduction to entropy as different, there is still Entropy (thermodynamics), Entropy (statistical thermodynamics), Entropy (order and disorder), and Entropy (energy dispersal).

My question is where does this article fit relative to the other articles on entropy? TStein (talk) 18:25, 21 September 2026 (UTC)

Entropy (thermodynamics) is a redirect to this article. This article is a very long one, so some topics have much of the material covered in "child articles". See Entropy#Statistical mechanics, Entropy#Order and disorder. Entropy#Energy dispersal and Wikipedia:Summary style. StarryGrandma (talk) 21:07, 21 September 2026 (UTC)

Thanks. Somehow I missed the redirect, even though I was looking for it. TStein (talk) 21:21, 21 September 2026 (UTC)