Philosophy of thermal and statistical physics Philosophy of thermal and statistical physics Physical processes at the microscopic level are either entirely or mostly (see below) time symmetric, meaning that the theoretical statements that describe them remain true if the direction of time is reversed; yet when we describe things at the macroscopic level it often appears that this is not the case: there is an obvious direction (or flow) of time. An arrow of time is anything that exhibits such time-asymmetry. ...more on Wikipedia about "Arrow of time"
In thermodynamics and statistical mechanics, the thermodynamic entropy (or simply the entropy) S is a key physical variable in describing a thermodynamic system. ...more on Wikipedia about "Entropy"
In physics and thermodynamics, the ergodic hypothesis says that, over long periods of time, the time spent in some region of the phase space of microstates with the same energy is proportional to the volume of this region, i.e., that all accessible microstates are equally probable over long period of time. Equivalently, it says that time average and average over the statistical ensemble are the same. ...more on Wikipedia about "Ergodic hypothesis"
In thermodynamics, the H-theorem, introduced by Boltzmann in 1872, describes the increase in the entropy of an ideal gas in an irreversible process, by considering the Boltzmann equation. ...more on Wikipedia about "H-theorem"
Landauer's Principle, first argued in 1961 by Rolf Landauer of IBM, holds that "any logically irreversible manipulation of information, such as the erasure of a bit or the merging of two computation paths, must be accompanied by a corresponding entropy increase in non-information bearing degrees of freedom of the information processing apparatus or its environment". (Bennett 2003) . ...more on Wikipedia about "Landauer's Principle"
Loschmidt's paradox, also known as the reversibility paradox, is the objection that it should not be possible to deduce an irreversible process from time-symmetric dynamics and a time-symmetric formalism. This puts the time reversal symmetry of (almost) all known low-level fundamental physical processes at odds with any attempt to infer from them the second law of thermodynamics which describes the behaviour of macroscopic systems. Both of these are well-accepted principles in physics, with sound observational and theoretical support, yet they seem to be in conflict; hence the paradox. ...more on Wikipedia about "Loschmidt's paradox"
In physics the MaxEnt school of thermodynamics, initiated with two papers published in the Physical Review by Edwin T. Jaynes in 1957, views statistical mechanics as an inference process: a specific application of inference techniques rooted in information theory, which relate not just to equilibrium thermodynamics, but are general to all problems requiring prediction from incomplete or insufficient data (such as for example image reconstruction, spectral analysis, or inverse problems). ...more on Wikipedia about "MaxEnt thermodynamics"
Maxwell's demon is a character in an 1867 thought experiment by the Scottish physicist James Clerk Maxwell, meant to raise questions about the second law of thermodynamics. This law forbids (among other things) two bodies of equal temperature, brought in contact with each other and isolated from the rest of the Universe, from evolving to a state in which one of the two has a significantly higher temperature than the other. The second law is also expressed as the assertion that entropy never decreases. ...more on Wikipedia about "Maxwell's demon"
In kinetic theory in physics, molecular chaos is the assumption that the velocities of colliding particles are uncorrelated, and independent of position. This assumption, also called in the writings of Boltzmann the Stosszahlansatz (collision number hypothesis), makes many calculations tractable. ...more on Wikipedia about "Molecular chaos"
The philosophy of thermal and statistical physics is one of the major subdisciplines of the philosophy of physics. Its subject matter is classical thermodynamics, statistical mechanics, and related theories. Its central questions include: What is entropy, and what does the second law of thermodynamics say about it? Does either thermodynamics or statistical mechanics contain an element of time-irreversibility? If so, what is its connection with the arrow of time? ...more on Wikipedia about "Philosophy of thermal and statistical physics"
The second law of thermodynamics, in a concise form, states that "the total entropy of any thermodynamically isolated system tends to increase over time, approaching a maximum value." ...more on Wikipedia about "Second law of thermodynamics"
In mathematical physics, especially as introduced into statistical mechanics and thermodynamics by J. Willard Gibbs in 1878, an ensemble (also statistical ensemble or thermodynamic ensemble) is an idealization consisting of a large number of mental copies (possibly infinitely many) of a system, considered all at once, each of which represents a possible state that the real system might be in. ...more on Wikipedia about "Statistical ensemble (mathematical physics)"
T-symmetry is the symmetry of physical laws under a time-reversal transformation— ...more on Wikipedia about "T-symmetry"
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