第四章 Is time travel possible

Is Time Travel Possible? 1257 words

Hello. My name is Stephen Hawking. Physicist, cosmologist and something of a dreamer. Although I cannot move and I have to speak through a computer, in my mind I am free. Free to explore the universe and ask the big questions, such as: is time travel possible? Can we open a portal to the past or find a shortcut to the future? Can we ultimately use the laws of nature to become masters of time itself?

大家好，我是斯蒂芬·霍金，我是一个物理学家，宇宙论者，也是一个梦想家。尽管我无法行走，只能通过电脑沟通，但我的内心是自由的。自由的探索整个宇宙，提出大胆的问题：比如：时间旅行时可能的吗？我们能够打开通向过去的入口或发现通向未来的捷径吗？我们最终能够利用自然法则成为时间的主人吗？

To see how this might be possible, we need to look at time as physicists do - at the fourth dimension. It's not as hard as it sounds. Every attentive schoolchild knows that all physical objects, even me in my chair, exist in three dimensions. Everything has a width and a height and a length.

了解这一切是可能的，我们需要从物理学家的角度看待时间- 那就是四维空间。这听起来并不难。每个学生都知道，所有的物理对象都存在于三维空间中，甚至我坐在椅子上也是。每个物体都有长宽高。

But there is another kind of length, a length in time. While a human may survive for 80 years, the stones at Stonehenge, for instance, have stood around for thousands of years. And the solar system will last for billions of years. Everything has a length in time as well as space. Travelling in time means travelling through this fourth dimension.

但是时间的长度是另外一种长度。比如：人类可能生存80年，巨石阵的石头已经矗立了大约上千年，太阳系将持续几十亿年，一切都有时间长度和空间。时间旅行也就意味着在第四空间旅行。

To see what that means, let's imagine we're doing a bit of normal, everyday car travel. Drive in a straight line and you're travelling in one dimension. Turn right or left and you add the second dimension. Drive up or down a twisty mountain road and that adds height, so that's travelling in all three dimensions. But how on Earth do we travel in time? How do we find a path through the fourth dimension?

为了更加清楚的了解这些，我们设想一下我们每天做的平常的事情，开车。在一条直路上行驶就相当于在一维空间旅行，向左向右转意味着进入了二位空间，在一条崎岖不平的山路上上上下下，增加了高度，也就是在三维空间中旅行。但究竟我们如何在时间中旅行呢？我们如何发现一条通往四维空间的道路呢？

Let's indulge in a little science fiction for a moment. Time travel movies often feature a vast, energy-hungry machine. The machine creates a path through the fourth dimension, a tunnel through time. A time traveller, a brave, perhaps foolhardy individual, prepared for who knows what, steps into the time tunnel and emerges who

knows when. The concept may be far-fetched, and the reality may be very different from this, but the idea itself is not so crazy.

我们片刻回顾一下科幻片中的情节，有关时间旅行的电影通常由一个巨大的，高能耗的机器，这个机器能够开辟一条通往四维空间的道路，一条时间隧道。一个勇敢，但也许莽撞的时间旅行者，谁也不知道他准备什么，进入时间隧道并出现在谁也不知道的时候。电影中的情节也许太过牵强，现实也许完全不同，但这个想法其实也并不是那么疯狂。

Physicists have been thinking about tunnels in time too, but we come at it from a different angle. We wonder if portals to the past or the future could ever be possible within the laws of nature. As it turns out, we think they are. What's more, we've even given them a name: wormholes. The truth is that wormholes are all around us, only they're too small to see. Wormholes are very tiny. They occur in nooks and crannies in space and time. You might find it a tough concept, but stay with me.

物理学家们也一直在思考关于时间隧道，但出发角度不同。我们想知道过去和未来的入口在自然法则中是否可能存在。我们的结果是，它是存在的。它是什么呢？我们给了它一个名字：虫洞。事实上，虫洞就在我们身边，只是它太小了肉眼看不见。虫洞是非常微小的，他们存在于时间和空间的每个角落和缝隙。你可能认为这是很难理解，但它确实就在我们身边。

Nothing is flat or solid. If you look closely enough at anything you'll find holes and wrinkles in it. It's a basic physical principle, and it even applies to time. Even something as smooth as a pool ball has tiny crevices,wrinkles and voids.Now it's easy to show that this is true in the first three dimensions. But trust me, it's also true of the fourth dimension. There are tiny crevices, wrinkles and voids in time. Down at the smallest of scales, smaller even than molecules, smaller than atoms, we get to a place called the quantum foam. This is where wormholes exist. Tiny tunnels or shortcuts through space and time constantly form, disappear, and reform within this quantum world. And they actually link two separate places and two different times.

所有物质都不是完全平滑实心的。如果你仔细观察你将发现上面有空洞和裂缝。从物理的原则上讲，这也适用于时间。即使是和撞球一样平滑的物体，也会有细微的缺口，缝隙和空洞。目前，这些在三维空间中是显而易见的。但我认为，在四维空间中这也是存在的。时间也存在微小的缺口，裂缝和空洞。从最小的缝隙向下，这个缝隙甚至比分子小，比原子小，可以到达一个叫量子泡沫的地方。虫洞就存在其中。通向空间和时间微小的隧道和捷径在量子的世界里不断形成，消失和改变。它们实际上连接着不同时间段的两个分开的地方。

Unfortunately, these real-life time tunnels are just a billion-trillion-trillionths of a centimetre across. Way too small for a human to pass through - but here's where the notion of wormhole time machines is leading. Some scientists think it may be possible to capture a wormhole and enlarge it many trillions of times to make it big enough for a human or even a spaceship to enter.