Philosophy of Thermal and Statistical Physics: Arrow of Time, Boltzmann Brain, Brownian Ratchet, Configuration Entropy, Entropy in Thermodynamics and

Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Pages: 42. Chapters: Arrow of time, Boltzmann brain, Brownian ratchet, Configuration entropy, Entropy in thermodynamics and information theory, Ergodic hypothesis, H-theorem, Kelvin-Planck statement, Landauer's principle, Loschmidt's paradox, Maximum entropy thermodynamics, Maxwell's demon, Molecular chaos, Second law of thermodynamics, Statistical ensemble (mathematical physics), T-symmetry. Excerpt: Entropy in statistical mechanics is a measure of the number of specific ways in which a system may be arranged, often taken to be a measure of "disorder"; the higher the entropy, the higher the disorder. The entropy of an isolated system never decreases, because isolated systems spontaneously evolve towards thermodynamic equilibrium - the state of maximum entropy. (see Second law of thermodynamics) Entropy is a mathematically-defined thermodynamic quantity that helps to account for the flow of energy through a thermodynamic process. Entropy was originally defined for a thermodynamically reversible process as where the uniform temperature () of a closed system is divided into an incremental reversible transfer of heat energy into that system (). The above definition is sometimes called the macroscopic definition of entropy because it can be used without regard to any microscopic picture of the contents of a system. In thermodynamics, entropy has been found to be more generally useful and it has several other reformulations. Entropy was discovered when it was noticed via mathematics to be a quantity that behaves as a function of state. Entropy is an extensive property, but it is often given as an intensive property of specific entropy as entropy per unit mass or entropy per mole. In statistical mechanics, entropy is often related to the notions of order and disorder. In the modern microscopic interpretation of entropy in statistical mechanics, entropy is the amount of additional information needed to specify the exact physical state of a system, given its thermodynamic specification. Various thermodynamic processes thus can be reduced to a description of how that information changes as the system evolves from its initial condition. It is often said that entropy is an expression of disorder or randomness, although those concepts lack clear definitions except in terms of entropy itself. The second law is now often seen as an expression of the fundamental postulate of st