## Comments about "Entropy" in Wikipedia

This document contains comments about the article Entropy in Wikipedia
• The text in italics is copied from that url
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In the last paragraph I explain my own opinion.

### Introduction

The article starts with the following sentence.
Entropy is a scientific concept, as well as a measurable physical property, that is most commonly associated with a state of disorder, randomness, or uncertainty.
All these three 'states' can not be measured.
In 1865, German physicist Rudolf Clausius, one of the leading founders of the field of thermodynamics, defined it as the quotient of an infinitesimal amount of heat to the instantaneous temperature.
It is important to know how the total entropy of a system is measured.
For example: The entropy of melting ice and boiling water.
Entropy is central to the second law of thermodynamics, which states that the entropy of isolated systems left to spontaneous evolution cannot decrease with time, as they always arrive at a state of thermodynamic equilibrium, where the entropy is highest.
A consequence of entropy is that certain processes are irreversible or impossible, aside from the requirement of not violating the conservation of energy, the latter being expressed in the first law of thermodynamics.
This sentence is tricky. How can an actual process be impossible?
Processes in general are irreversible, but that does not mean that certain parts in a process can not be reversible.
My impression is that these parts

### 3. Definitions and descriptions

The concept of entropy is described by two principal approaches, the macroscopic perspective of classical thermodynamics, and the microscopic description central to statistical mechanics.
Both approaches are important.
The classical approach defines entropy in terms of macroscopically measurable physical properties, such as bulk mass, volume, pressure, and temperature.
Okay.
The statistical definition of entropy defines it in terms of the statistics of the motions of the microscopic constituents of a system – modeled at first classically, e.g. Newtonian particles constituting a gas, and later quantum-mechanically (photons, phonons, spins, etc.).
Okay.
The two approaches form a consistent, unified view of the same phenomenon as expressed in the second law of thermodynamics, which has found universal applicability to physical processes.

### 8.3 Cosmology

Assuming that a finite universe is an isolated system, the second law of thermodynamics states that its total entropy is continually increasing.
The second law of thermodynamics can not make any claim about the evolution of the universe.
It has been speculated, since the 19th century, that the universe is fated to a heat death in which all the energy ends up as a homogeneous distribution of thermal energy so that no more work can be extracted from any source.
Correct. This is pure speculation.

### 8.4 Economics

Romanian American economist Nicholas Georgescu-Roegen, a progenitor in economics and a paradigm founder of ecological economics, made extensive use of the entropy concept in his magnum opus on The Entropy Law and the Economic Process.
The entropy law of thermodynamics, based on the parameters dQ and T, has nothing to do with any economic process.

### 9. See also

Following is a list with "Comments in Wikipedia" about related subjects

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Created: 1 November 2022

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