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→Ponderable matter
===Ponderable matter===
===Ponderable matter===
有重量物质
''Local thermodynamic equilibrium of matter''<ref name="Gyarmati 1970"/><ref name="G&P 1971"/><ref name="Balescu 1975"/><ref name="Mihalas Mihalas 1984"/><ref name="Schloegl 1989"/> (see also Keizer (1987)<ref name="Keizer 1987"/> means that conceptually, for study and analysis, the system can be spatially and temporally divided into 'cells' or 'micro-phases' of small (infinitesimal) size, in which classical thermodynamical equilibrium conditions for matter are fulfilled to good approximation. These conditions are unfulfilled, for example, in very rarefied gases, in which molecular collisions are infrequent; and in the boundary layers of a star, where radiation is passing energy to space; and for interacting fermions at very low temperature, where dissipative processes become ineffective. When these 'cells' are defined, one admits that matter and energy may pass freely between contiguous 'cells', slowly enough to leave the 'cells' in their respective individual local thermodynamic equilibria with respect to intensive variables.
''Local thermodynamic equilibrium of matter''<ref name="Gyarmati 1970"/><ref name="G&P 1971"/><ref name="Balescu 1975"/><ref name="Mihalas Mihalas 1984"/><ref name="Schloegl 1989"/> (see also Keizer (1987)<ref name="Keizer 1987"/> means that conceptually, for study and analysis, the system can be spatially and temporally divided into 'cells' or 'micro-phases' of small (infinitesimal) size, in which classical thermodynamical equilibrium conditions for matter are fulfilled to good approximation. These conditions are unfulfilled, for example, in very rarefied gases, in which molecular collisions are infrequent; and in the boundary layers of a star, where radiation is passing energy to space; and for interacting fermions at very low temperature, where dissipative processes become ineffective. When these 'cells' are defined, one admits that matter and energy may pass freely between contiguous 'cells', slowly enough to leave the 'cells' in their respective individual local thermodynamic equilibria with respect to intensive variables.
你可以在这里想象一下两个被数量级分开的“弛豫时间”。较长的弛豫时间是系统宏观动力学结构改变所需时间的数量级。较短的一个数量级是单个“单元”到达局部热力学平衡所需的时间。如果这两个弛豫时间没有很好地分开，那么局部热力学平衡的经典非平衡热力学概念就失去了意义，必须提出其他方法，例如扩展的不可逆热力学。例如，在大气中，声速远远大于风速；这就支持在60公里以下高度的大气热传导研究中局部物质热力学平衡的想法，在这个高度范围内声音可以传播，但不能超过100公里，在那里由于分子间的碰撞，声音不能传播。
你可以在这里想象一下两个被数量级分开的“弛豫时间”。较长的弛豫时间是系统宏观动力学结构改变所需时间的数量级。较短的一个数量级是单个“单元”到达局部热力学平衡所需的时间。如果这两个弛豫时间没有很好地分开，那么局部热力学平衡的经典非平衡热力学概念就失去了意义，必须提出其他方法，例如扩展的不可逆热力学。例如，在大气中，声速远远大于风速；这就支持在60公里以下高度的大气热传导研究中局部物质热力学平衡的想法，在这个高度范围内声音可以传播，但不能超过100公里，在那里由于分子间的碰撞，声音不能传播。
===Milne's definition in terms of radiative equilibrium===
===Milne's definition in terms of radiative equilibrium===