Uploaded January 2020 | Updated September 2026, 1 week ago
We consider in more detail how the fundamental laws of mechanics cannot account for the irreversibility of a system. Yet we find evidence that "special" states are easily transformed into "non-special" states while transforming a non-special state into a special state requires "fine-tuning" of initial conditions. We end with the conventional statement of the 2nd Law of Thermodynamics and the historic definition of entropy.
Note on the definition of a "closed system." I am using the term "closed system" in the sense of the following definition from Thermal Physics by Charles Kittel: "A closed system is defined as a system with constant energy, constant number of particles, and constant volume." Another term for such a system is "isolated system," in which case "closed system" may refer to a system that has a constant number of particles but can exchange energy with its surroundings.
We consider in more detail how the fundamental laws of mechanics cannot account for the irreversibility of a system. Yet we find evidence that "special" states are easily transformed into "non-special" states while transforming a non-special state into a special state requires "fine-tuning" of initial conditions. We end with the conventional statement of the 2nd Law of Thermodynamics and the historic definition of entropy.
Note on the definition of a "closed system." I am using the term "closed system" in the sense of the following definition from Thermal Physics by Charles Kittel: "A closed system is defined as a system with constant energy, constant number of particles, and constant volume." Another term for such a system is "isolated system," in which case "closed system" may refer to a system that has a constant number of particles but can exchange energy with its surroundings.
