《关于时间》阅读笔记About Time: Einstein’s Unfinished Revolution

这本书是在今年二月份的书市上买的二手书，1995年出版。虽然担心它的内容有点过时了，但是经不住这个标题的诱惑，买下来一口气读完。

我很小就对时间感兴趣。

小时候父母白天去上班，就把我和姐姐锁家里，那时候妹妹还没有出生。其实父母刚去上班不久，我们就开始盯着闹钟，盼望着他们下班。时间过得非常慢，那时候的一分钟，好像现在的一小时。我经常把时针往前转动，然后再调回来。调来调去，结果闹钟就不准了。

还差5分钟就下班了，那种等待父母回家的急迫的心情，与父母刚离开家时我们的急迫的心情，其实没有多少区别。我那个时候就有一个非常奇怪的感受，就是时间可能是不均匀的。虽然那时候不知道时间的非均匀性这个概念，很多年之后学习了相对论，我才发现相对论并不是非常深奥难懂的理论。就像爱因斯坦自己所说的，他能够对一个五六岁的小孩讲解相对论。他的传记里边也确实描述了这样一段情节。

很多年后，我看过一部电影《时光倒流七十年》，其中的主题曲至今仍然是我的最爱之一。我甚至专门做了一个网站叫做“时光倒流“，timebk.com。这个域名注册得非常早，估值不低，可惜后来疏于维护，域名被别人抢注了，而且别人用它做了一个不太雅的网站，也许有的老网友还会对此有误解，其实新网站早已和我无关了。下面这个图是著名的互联网档案网站收藏的历史截屏（2000年至2007年左右）。

我真正对时间问题进行认真的研究是从相对论开始的。学习了狭义相对论和广义相对论，很自然的就会延伸到量子力学、宇宙学。这样一路顺藤摸瓜，一发不可收。阅读和研究的内容在旁人看来越来越专业，甚至有点不可思议。最近又读了一本《关于时间》，这本书进一步扩展了我对时间的理解。

在这之前，很多年前就读过霍金的《时间简史》。坦率地说，我当时并没有看懂。时间问题比我们想象的要复杂得多。比如，当我们说时间有起点的时候，很自然地就会问到：这个起点之前是什么时间呢？很多物理学概念都涉及到哲学问题，没有深厚的哲学功底就很难理解这些问题。时间问题一直困扰着我，也持续不断地激发着我的好奇心。终于有一天我读到了《关于时间》这本书。

作者保罗·戴维斯是澳大利亚物理学家和科普作家，他在这本书里深入浅出地引导读者重新思考我们每天都在经历、却从未真正理解的“时间”究竟是什么。

戴维斯首先回顾了物理学史上对时间的理解演变。在牛顿的时代，人们普遍相信时间是绝对的，像钟表一样均匀流动，跟空间和物体的运动无关。但爱因斯坦的相对论颠覆了这个观点，指出时间其实是可以伸缩的，它会因速度或引力而变慢或者变快。比如，在靠近黑洞的地方，时间会变得非常缓慢。更重要的是，爱因斯坦让人们明白，时间和空间是一体的，构成了一个叫“时空”的整体。

接着，戴维斯带我们进入量子力学的世界。在这个微观世界里，事件不是确定的，而是充满不确定性和概率性。波函数的演化虽然是连续的，但一旦进行观测，结果就会“塌缩”到某个确定值。这种“测量”的不确定性，引发了人们对时间本质的新一轮疑问：时间是连续流动的，还是只在观测中才“显现”出来？

书中另一个引人深思的内容是“时间的箭头”问题。虽然物理学的基本定律通常不区分过去与未来（例如牛顿定律或量子方程都是可逆的），但我们日常经验中时间总是向前流动的。一个玻璃杯掉地上会碎掉，但碎片不会自己跳起来复原。这种“时间有方向”的体验其实来自热力学中的熵——宇宙的混乱度总是在增加。戴维斯探讨了为什么宇宙一开始会处在一个极其有序的状态，从而让时间表现出“从过去到未来”的方向感。

此外，他还讨论了许多大胆的问题，比如宇宙有没有一个真正意义上的“现在”？我们对“现在”的感觉是不是只是人的主观感受？在不同的宇宙模型中（如多重宇宙理论或量子引力理论），时间甚至可能不是基本的存在，而是一种衍生现象。他也探讨了黑洞、宇宙大爆炸、以及时间是否有终点这些看似天方夜谭但其实在物理前沿非常严肃的问题。

总的来说，这本书不仅仅是在介绍科学理论，它更像是一场对我们世界观的挑战。戴维斯用清晰的语言解释复杂的科学问题面，让人意识到我们最熟悉的“时间”，其实是宇宙中最神秘、最难解的谜题之一。这场由爱因斯坦开启的关于时间的“革命”，其实还远远没有结束。

时间的本质不仅是一个物理问题，更是一个哲学问题。康德认为时间和空间是人类认识世界的先验条件，是感官经验得以产生的基础。所以时间和空间是人类理性能够存在的前提条件。这本书的观点，显然对康德哲学提出了某种挑战。

人的时空观念是很顽固的，难以在突然之间改变。读这本书或许只是一个改变的起点，我们只能在漫长的岁月中逐渐地建立起更加科学的时间概念。这种书应该早一点读，越早越好。就好像一个人外出旅行看世界应该尽早进行，因为早期的经历会影响后续的人生。

我没有找到这本书的中文版，喜欢读英文的朋友可以很容易在网上找到电子版（在不涉及版权的条件下）。

My Lifelong Fascination with Time

I’ve been interested in time ever since I was a child.

When I was young, my parents would lock my sister and me at home during the day while they went to work—my younger sister hadn’t been born yet. Not long after they left, we would start staring at the clock, eagerly awaiting their return. Time passed excruciatingly slowly. One minute back then felt like an hour today. I would often try to turn the clock hands forward and then back again. After doing this many times, the clock became inaccurate.

The feeling of urgency we had when it was five minutes before they were due home was not so different from the moment they first left. Even then, I had a strange sense that time might not be uniform. Although I didn’t understand the concept of temporal non-uniformity at the time, years later when I studied relativity, I realized that the theory wasn’t as hard to grasp as people make it out to be. As Einstein himself claimed, he could explain relativity to a five- or six-year-old child. One of his biographies even records such an episode.

Many years later, I watched the film Somewhere in Time, and its theme song has remained one of my favorites ever since. I even created a website called “Time Back,” with the domain timebk.com. I registered the domain very early—it was probably quite valuable. Unfortunately, due to neglect, I lost it. Someone else took over the domain and used it for a rather unsavory site. Some old visitors might still associate it with me, but in fact, it has long had nothing to do with me. The screenshot below is an archive from the Internet Archive, showing what it looked like around 2000–2007.

My serious study of time began with relativity. Learning special and general relativity naturally led me to quantum mechanics and cosmology. One thing led to another, and I found myself on an unstoppable intellectual journey. To outsiders, my reading and research became increasingly technical—maybe even a bit unbelievable. Most recently, I read a book titled About Time, which further expanded my understanding of time.

Before that, I had read Hawking’s A Brief History of Time many years ago. To be honest, I didn’t really understand it back then. Time is far more complicated than we tend to assume. For instance, when we say that time has a beginning, it naturally raises the question: what was before that beginning? Many concepts in physics touch on deep philosophical issues. Without a solid philosophical foundation, these questions are hard to grasp. Time has always puzzled me—and continuously stirred my curiosity—until one day, I came across About Time.

The author, Paul Davies, is an Australian physicist and science writer. In this book, he guides readers to reconsider what “time” truly is—something we all experience but rarely understand.

Davies starts by reviewing how the concept of time has evolved in physics. In Newton’s era, people believed time was absolute, flowing uniformly like a clock, unaffected by space or motion. Einstein’s relativity overturned this view, showing that time is flexible—it can slow down or speed up depending on speed or gravity. For instance, time near a black hole passes extremely slowly. More importantly, Einstein helped us realize that time and space are not separate—they form a unified fabric called spacetime.

Davies then takes us into the quantum world. In this microscopic realm, events aren’t deterministic but are governed by uncertainty and probability. While the wave function evolves continuously, the moment we measure it, the outcome “collapses” into a definite state. This uncertainty of measurement brings fresh questions about the nature of time: is time flowing continuously, or does it only “appear” when we observe it?

One of the most thought-provoking topics in the book is the question of the “arrow of time.” Most physical laws—like Newton’s laws or quantum equations—are time-symmetric; they don’t distinguish between past and future. Yet, in daily life, time always seems to flow forward. A glass falling and shattering won’t reassemble itself. This sense of direction in time comes from the concept of entropy in thermodynamics—the universe tends toward increasing disorder. Davies explores why the universe began in such an extremely ordered state, which allows us to experience time as flowing from past to future.

He also ventures into bold questions like: is there really a universal “now” in the universe? Is our sense of “the present” just a human illusion? In certain cosmic models—like the multiverse or quantum gravity theories—time may not even be fundamental. It might just be an emergent property. Davies also addresses seemingly fantastical but scientifically serious issues like black holes, the Big Bang, and whether time has an endpoint.

Overall, this book is not just a presentation of scientific theories; it’s a challenge to our worldview. Davies brings complex ideas down to earth with clear language, helping readers realize that time—something we think we understand so well—is perhaps the most mysterious and elusive puzzle in the universe. The revolution Einstein started in our understanding of time is far from over.

The nature of time is not only a question of physics but also a fundamental issue in philosophy. Kant argued that time and space are a priori conditions for human cognition and form the foundation upon which sensory experience arises. In this sense, they are prerequisites for the existence of reason. The perspective presented in this book clearly poses a certain challenge to Kant’s philosophy.

Human conceptions of time and space are often deeply ingrained and cannot be altered overnight. Reading this book may serve only as a starting point. It is through the passage of time that we gradually develop a more scientific understanding of time itself. Books like this are best read as early as possible—just as one should embark on a journey early in life, because early experiences can profoundly shape the path that follows.

I haven’t found a Chinese version of this book, but English readers can easily find a digital copy online(as long as it’s within the bounds of copyright).