关于时间你不可不知的十件事

“Time” is the most used noun in the English language, yet it remains a mystery. We’ve just completed an amazingly intense and rewarding multidisciplinary conference on the nature of time, and here’s my stab at a top ten list partly inspired by our discussions: the things everyone should know about time.

“时间”是英语中使用最频繁的一个词，但人们对它依然所知甚少。我们刚刚进行了一场关于时间本质的、激烈而有意义的跨学科讨论会。受到这场讨论的启发，我将试图开列如下这个“十大清单”：关于时间，每个人都该知道的十件事。

1. Time exists.

1.时间确实存在。

Might as well get this common question out of the way. Of course time exists — otherwise how would we set our alarm clocks? Time organizes the universe into an ordered series of moments, and thank goodness; what a mess it would be if reality were complete different from moment to moment. The real question is whether or not time is fundamental, or perhaps emergent. We used to think that “temperature” was a basic category of nature, but now we know it emerges from the motion of atoms. When it comes to whether time is fundamental, the answer is: nobody knows. My bet is “yes,” but we’ll need to understand quantum gravity much better before we can say for sure.

如果你觉得这个问题太过普通，大可以跳过它。时间当然存在——否则我们怎么上闹钟呢？时间将宇宙有序地组织起来——谢天谢地，否则我们的世界就会乱成一锅粥了。真正的问题其实是：时间究竟是我们这个宇宙的基本组成要素，还是只是偶然出现的。我们曾以为“温度”是自然的基本要素之一，但现在我们知道它其实是原子运动的附加产物。而对于“时间是否是宇宙的基本要素”，回答是：没人知道。我认为它是，但要确认这一点，我们得先对量子引力有更好的理解。

2. The past and future are equally real.

2.过去与未来都是真实的。

This isn’t completely accepted, but it should be. Intuitively we think that the “now” is real, while the past is fixed and in the books, and the future hasn’t yet occurred. But physics teaches us something remarkable: every event in the past and future is implicit in the current moment. This is hard to see in our everyday lives, since we’re nowhere close to knowing everything about the universe at any moment, nor will we ever be — but the equations don’t lie. As Einstein put it, “It appears therefore more natural to think of physical reality as a four dimensional existence, instead of, as hitherto, the evolution of a three dimensional existence.”

并不是所有人都接受这个观点，但是大家应该接受。凭直觉，我们认为“现在”是真实的，“过去”只存在于书中，而“未来”尚未发生。但物理学告诉我们一个惊人的事实：过去与未来的每一刻都存在于当下。在我们的日常生活中要理解这一点很难，因为我们无从知晓宇宙中每一刻所发生的全部事件——但是数学方程可不会说谎。就像爱因斯坦说的：“长久以来，我们都把物质世界看成是一个不断发展的三维存在，但将它看成一个四维存在似乎更为自然一些。”

3. Everyone experiences time differently.

3.每个人对时间的体验是不同的。

This is true at the level of both physics and biology. Within physics, we used to have Sir Isaac Newton’s view of time, which was universal and shared by everyone. But then Einstein came along and explained that how much time elapses for a person depends on how they travel through space (especially near the speed of light) as well as the gravitational field (especially if its near a black hole). From a biological or psychological perspective, the time measured by atomic clocks isn’t as important as the time measured by our internal rhythms and the accumulation of memories. That happens differently depending on who we are and what we are experiencing; there’s a real sense in which time moves more quickly when we’re older.

从生物学和物理学角度来说都确有其事。物理学上，牛顿曾提出过经典的、普适的时空观，但后来爱因斯坦提出，人们身上时间的流逝跟他们在空间中的运动方式（尤其是当运动速度接近光速时）和引力场（尤其是靠近黑洞时）紧密相关。从生物学或心理学的角度来看，由原子钟计量的精确时间并不如人体内在节律和记忆所计量的时间那样重要。而受到个人身份和经历的影响，每个人的生物节律都是不同的。随着年龄的增长，我们确实会有“时间过得更快”的感觉。

4. You live in the past.

4.我们活在过去。

About 80 milliseconds in the past, to be precise. Use one hand to touch your nose, and the other to touch one of your feet, at exactly the same time. You will experience them as simultaneous acts. But that’s mysterious — clearly it takes more time for the signal to travel up your nerves from your feet to your brain than from your nose. The reconciliation is simple: our conscious experience takes time to assemble, and your brain waits for all the relevant input before it experiences the “now.” Experiments have shown that the lag between things happening and us experiencing them is about 80 milliseconds.

准确地说，是活在80毫秒前。用一只手碰碰你的鼻子，同时用另一只手去碰你的脚，你会觉得这两件事是同时发生的。但这正是不可思议之处——显然，信号从你的脚传到你的大脑应该要比从你的鼻子到大脑花费更多时间。不过这一点很容易弄明白：我们的意识需要时间来收集信息，而大脑要等收集到所有相关信息之后才能体验到“现在”。实验表明，从事件真正发生到我们的大脑体验到事件的发生，中间大约有80毫秒的时滞。

5. Your memory isn’t as good as you think.

5.你的记忆力并不像你想的那么好

When you remember an event in the past, your brain uses a very similar technique to imagining the future. The process is less like “replaying a video” than “putting on a play from a script.” If the script is wrong for whatever reason, you can have a false memory that is just as vivid as a true one. Eyewitness testimony, it turns out, is one of the least reliable forms of evidence allowed into courtrooms.

我们的大脑记忆过去的机制和想像未来的机制是非常相似的。这个过程更像是“照着剧本演戏”而不是“重放录像带”，如果剧本出错了（不管是什么原因引起的），你就会得到一段虚假的记忆，而它和真实的记忆一样生动清晰。因此，目击者的证词其实是法庭上出示的所有证据中最不靠谱的一种。