Almost all of the entropy in the universe is in the form of Bekenstein–Hawking (BH) entropy of super-massive black holes. This entropy, if it satisfies Boltzmann’s equation \(S=\log \mathcal{N}\), hence represents almost all the accessible phase space of the Universe, somehow associated to objects which themselves fill out a very small fraction of ordinary three-dimensional space. Although time scales are very long, it is believed that black holes will eventually evaporate by emitting Hawking radiation, which is thermal when counted mode by mode. A pure quantum state collapsing to a black hole will hence eventually re-emerge as a state with strictly positive entropy, which constitutes the famous black hole information paradox. Expanding on a remark by Hawking we posit that BH entropy is a thermodynamic entropy, which must be distinguished from information-theoretic entropy. The paradox can then be explained by information return in Hawking radiation. The novel perspective advanced here is that if BH entropy counts the number of accessible physical states in a quantum black hole, then the paradox can be seen as an instance of the fundamental problem of statistical mechanics. We suggest a specific analogy to the increase of the entropy in a solvation process. We further show that the huge phase volume (\(\mathcal{N}\)), which must be made available to the universe in a gravitational collapse, cannot originate from the entanglement between ordinary matter and/or radiation inside and outside the black hole. We argue that, instead, the quantum degrees of freedom of the gravitational field must get activated near the singularity, resulting in a final state of the ‘entangled entanglement’ form involving both matter and gravity.

宇宙中几乎所有的熵都以超大质量黑洞的Bekenstein-Hawking（BH）熵的形式出现。如果满足玻尔兹曼方程\（S = \ log \ mathcal {N} \），则此熵因此，表示宇宙的几乎所有可访问相空间，它们以某种方式与对象相关联，这些对象本身仅填充了普通三维空间的一小部分。尽管时间尺度很长，但据信黑洞最终会通过发射霍金辐射而蒸发，该霍金辐射在逐个模式计数时是热的。崩溃到黑洞的纯量子态将最终最终重新出现为具有严格正熵的状态，这构成了著名的黑洞信息悖论。在霍金的评论中，我们假设BH熵是一种热力学熵，必须将其与信息理论熵区分开来。矛盾可以通过霍金辐射中的信息返回来解释。这里提出的新颖观点是，如果BH熵计算出量子黑洞中可访问的物理状态的数量，那么这种悖论就可以看作是统计力学基本问题的一个实例。我们建议一个特定的类比，以增加溶剂化过程中的熵。我们进一步表明，巨大的相体积（\（\ mathcal {N} \））必须在重力崩溃中提供给宇宙，它不能源自黑洞内外的普通物质和/或辐射之间的纠缠。我们认为，相反，引力场的量子自由度必须在奇点附近被激活，从而导致涉及物质和引力的“纠缠纠缠”形式的最终状态。