7. Disorder increases as time passes.
随着时间的流逝，宇宙的无序程度会上升。

At the heart of every difference between the past and future — memory, aging, causality, free will — is the fact that the universe is evolving from order to disorder. Entropy is increasing, as we physicists say. There are more ways to be disorderly (high entropy) than orderly (low entropy), so the increase of entropy seems natural. But to explain the lower entropy of past times we need to go all the way back to the Big Bang. We still haven't answered the hard questions: why was entropy low near the Big Bang, and how does increasing entropy account for memory and causality and all the rest?
在过去与未来的所有差别——记忆、衰老、因果、自由意志——背后，隐藏着一个核心事实，那就是宇宙是从有序逐渐走向无序的。或者如物理学家所说：“熵（动力学方面不能做功的能量总数）在不断增加。”达到无序状态（高熵）比达到有序状态（低熵）的途径要多，因此熵的增加看起来再正常不过。但要解释宇宙曾有过的低熵状态，就必须回溯至最初的宇宙大爆炸。我们仍然不能回答如下问题：为何在大爆炸之时熵如此低，以及熵增如何导致了记忆、因果以及其他一切。