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)

Changed introduction

while the new introduction is an improvement, it is still not right.

There is (classical) thermodynamic entropy, which makes no use of microstates or probabilities. These are concepts of statistical mechanics. Statistical mechanics is a very successful theory which was developed to provide an explanation of classical thermodynamics. Ultimately, that explanation includes the relationship between thermodynamic entropy and information entropy.

I wonder if there is an easily accessible way to write the introduction without confusing thermodynamic entropy (a state variable) and information entropy (a statistical mechanical variable, involving probabilities, etc.) PAR (talk) 22:16, 29 April 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)