## 1. Introduction

## 2. The Essence of “Mass-Energy, Entropy and the Second Law Fundamentals”

**Box 1.**Natural Processes and Laws.

**Box 2.**It Is Hard to Believe Nowadays.

## 3. The Three Essential “Entropy and Second Law Misconceptions”

#### 3.1. Is Entropy a Measure of Any Disorder?

**Box 3.**Entropy Is Thermal Randomness, Not Any Randomness.

#### 3.2. Can the Second Law Be Valid and Entropy Always Increasing in Isolated Systems and the Universe, but (Maybe) Not Necessarily in All Processes and All Space and Time Scales?

**Box 4.**Entropy Is Always Generated at Any Space and Time Scales and Cannot Be Destroyed by Any Means.

#### 3.3. Can Self-Sustained Non-equilibrium, i.e., Structural Quasi-Equilibrium, Violates the Second Law?

**Box 5.**A Quasi-Equilibrium with Non-Uniform Properties Does Not Violate the Second Law.

## 4. Other Typical “Entropy and Second Law Misconceptions”

#### 4.1. Does Maxwell’s Demon Violate the Second Law?

**Box 6.**Maxwell’s Demon Requires More Effort Than Just to Operate a Gate [15].

#### 4.2. Can a Vortex Tube and Similar Cooling Devices Violate the Second Law?

#### 4.3. Could the Second Law Be Violated during Animated Life and Intelligent Processes?

**Box 7.**Creation of Ordered Structures or Live Species Always Generate Thermal Disorder, i.e., Always Generate Entropy.

#### 4.4. Could the Second Law Be Violated during Micro-Fluctuations?

**Box 8.**Near-Reversible Micro-Fluctuations Make Up Macro-Equilibrium and Cannot Be Demonized to Destroy Entropy.

#### 4.5. Could the Second Law Be Violated Locally and Temporarily and “Compensated” Elsewhere Later?

**Box 9.**Entropy Cannot Be Destroyed, Locally or at a Time, and “Compensated” by Generation Elsewhere or Later.

#### 4.6. Thermodynamic “Arrow of Time”

**Box 10.**The “Thermodynamic Arrow of Time” May Be the Answer to “Where Does Our Arrow of Time Come From?”

## 5. Further Comments

**Box 11.**Hypotheses of Second Law Violation Are Still to Be Proven.

## Funding

## Conflicts of Interest

## References and Note

- Carnot, S. Reflections on the Motive Power of Heat; Chapman & Hall, Ltd.: London, UK, 1897; Available online: https://sites.google.com/site/professorkostic/energy-environment/sadi-carnot (accessed on 15 May 2020).
- Clausius, R. The Mechanical Theory of Heat; McMillan and Co.: London, UK, 1879; Available online: http://www.archive.org/details/londonedinburghd02lond (accessed on 15 May 2020).
- Bridgman, P.W. The Nature of Thermodynamics; Harvard University press: Cambridge, MA, USA, 1941. [Google Scholar]
- Kostic, M. Irreversibility and Reversible Heat Transfer: The Quest and Nature of Energy and Entropy. In Proceedings of the Innovations in Engineering Education: Mechanical Engineering Education, Mechanical Engineering/Mechanical Engineering Technology Department Heads; ASME International: New York, NY, USA, 2004; pp. 101–106. [Google Scholar]
- Kostic, M. Revisiting the Second Law of Energy Degradation and Entropy Generation: From Sadi Carnot’s Ingenious Reasoning to Holistic Generalization. AIP Conf. Proc.
**2011**, 327, 1411. [Google Scholar] [CrossRef] - Kostic, M. The Elusive Nature of Entropy and Its Physical Meaning. Entropy
**2014**, 16, 953–967. [Google Scholar] [CrossRef] - Kostic, M. Nature of Heat and Thermal Energy: From Caloric to Carnot’s Reflections, to Entropy, Exergy, Entransy and Beyond. Entropy
**2018**, 20, 584. [Google Scholar] [CrossRef] - Kostic, M. Comments on “Removing the Mystery of Entropy and Thermodynamics,” Northern Illinois University. Available online: https://www.kostic.niu.edu/kostic/_pdfs/Comments-Key-Pointsf-Mystery-Entropy-Leff (accessed on 15 May 2020).
- Eddington, A.S. The Nature of the Physical World; Cambridge University Press: Cambridge, MA, USA, 1929. [Google Scholar]
- Lavoisier, A. Réflexions Sur Le Phlogistique. 1783. Available online: http://www.lavoisier.cnrs.fr/ (accessed on 15 May 2020).
- Maxwell, J.C. Theory of Heat; Longmans, Green, and Co.: London, UK, 1871; Chapter 12. [Google Scholar]
- Leggett, A.J. Reflections on the past, present and future of condensed matter physics. Sci. Bull.
**2018**, 63, 1019–1022. [Google Scholar] [CrossRef] - Leff, H.S.; Rex, A.F. Maxwell’s Demon 2: Entropy, Classical and Quantum Information, Computing; CRC Press: Boca Raton, FL, USA, 2002; ISBN 0-7503-0759-5. [Google Scholar]
- Knott, C.G. Life and Scientific Work of Peter Guthrie Tait; Cambridge University Press: London, UK, 1991; pp. 213–215. [Google Scholar]
- Kostic, M. Maxwell’s Demon and Its Fallacies Demystified. arXiv
**2020**, arXiv:2001.10083. [Google Scholar] - Kostic, M.M. “Heat Flowing from Cold to Hot Without External Intervention” Demystified: Thermal-Transformer and Temperature Oscillator. arXiv
**2020**, arXiv:2001.05991. [Google Scholar] - Only list of selected and this author’s related publications is provided, since intention of this treatise is not to review the vast entropy and Second Law literature, but to present this author’s long-contemplated reflections on the essence of the Second Law of thermodynamics and physical meaning of entropy, and to put certain physical and philosophical concepts in historical and contemporary perspective.

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