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In theoretical physics, T-symmetry is the theoretical symmetry of physical laws under a time reversal transformation: : Although in restricted contexts one may find this symmetry, the observable universe itself does not show symmetry under time reversal, primarily due to the second law of thermodynamics. Hence time is said to be non-symmetric, or asymmetric, except for equilibrium states when the second law of thermodynamics predicts the time symmetry to hold. However, quantum noninvasive measurements are predicted to violate time symmetry even in equilibrium, contrary to their classical counterparts, although it has not yet been experimentally confirmed. Time ''asymmetries'' are generally distinguished as between those intrinsic to the dynamic physical laws, those due to the initial conditions of our universe, and due to measurements # The T-asymmetry of the weak force is of the first kind, # The T-asymmetry of the second law of thermodynamics is of the second kind, while # The T-asymmetry of the noninvasive measurements is of the third kind. == Invariance == Physicists also discuss the time-reversal invariance of local and/or macroscopic descriptions of physical systems, independent of the invariance of the underlying microscopic physical laws. For example, Maxwell's equations with material absorption or Newtonian mechanics with friction are not time-reversal invariant at the macroscopic level where they are normally applied, even if they are invariant at the microscopic level; when one includes the atomic motions, the "lost" energy is translated into heat. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「T-symmetry」の詳細全文を読む スポンサード リンク
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