人们想实现时空旅行从技术上来说也不是完全不可能的。这需要都跑得非常非意快。具体地说。速度需要接近3*108米/秒。这个速度能够使你在眨眼问绕着地球跑好几圈。

Time travel is not technically impossible. It needs to be very fast. Specifically, it needs to be close to 3*108 m/s, a speed that would allow you to run around the world several times in the blink of an eye.

3*108米/秒是光运动的速度。 这几乎是宇宙的速度极限。有趣的是。当物体加速到接近光速。时间就会变慢。

3*108 m/s is the speed of light, which is almost the speed limit of the universe. Interestingly, time slows down when objects accelerate close to the speed of light.

时空旅行
出于对这个现象的好奇。物理学家曾经设想。如果让双胞胎兄弟或姐妹中的一人乘上星际飞船作太空遨游而另一个则留在地球上生活。结果会是怎样。那就让我们设想一下这个也许会发生在遥远的未来的故事吧。

Curious about this phenomenon, physicists have wondered what it would be like to have one twin or sister travel in a starship while the other stays on earth. So let's imagine a story that might happen in the distant future.

假设贝丝和芭比是双胞胎。都是30岁。贝丝是一位宇航员。而芭比则是一个新闻记者。贝丝刚接到一项飞行任务。这可能会成为她一生的使命：乘坐宇宙飞船到邻近的一个恒星系统去考察。芭比会为她工作的报社全程报道这次字宙旅行。

Let's say beth and barbie are twins, both 30 years old. Beth is an astronaut and barbie is a journalist. Beth has just been sent on what could be her mission of a lifetime: a spacecraft to investigate a nearby star system. Barbie will cover the entire trip for the newspaper she works for.

目的地距离地球96万亿千米。大约10光年的距离。贝丝乘坐的宇宙飞船以光速的90%的速度运行。照此推算。从地球上出发到回到地球需要22年的时间。在这段时间里。芭比结了婚。生了两个孩子。而且头发都变花白了。

The destination is 96 trillion kilometers from earth, about 10 light years away. At 90 percent of the speed of light, beth's spacecraft would take 22 years to get back to earth. During that time, barbie got married, had two children, and her hair turned gray.

但这段时间对于宇航员贝丝来说却是另外番情景。 当宇南飞船以极快的速度穿梭于星际时。船舱内的钟表悄悄地放慢了脚步。并不是表没电了或是坏掉了。而是时间本身为飞船和飞船上的成员放慢了节奏。然而飞行员们自己却感觉不到丝毫的变化。对于他们来说。1分钟仍然是分钟。井没有多出1秒钟。但在贝丝出发之后。飞船上的时间和地球上的相差越来越多了。

But it was a different story for astronaut beth. When the yonan spacecraft with a very fast speed through the stars, the cabin clock quietly slowed down the pace. It wasn't that the watch had run out of power or that it was broken, but that time itself had slowed the ship and its crew down. But the pilots themselves felt no change. For them, a minute was still a minute. But after beth's departure, the difference in time between the spacecraft and earth grew larger and larger.

《星际穿越》剧照
成功完成任务之后。宇航员们返回了地球。当飞船进人太阳系时。船舱里的电子钟显示这次太空旅行花了10年时间。当飞船途经冥王星时。贝丝刚好庆祝自己40岁的生日。

After the successful completion of the mission, the astronauts returned to earth. As the spacecraft entered the solar system, an electronic clock in the cabin indicated that the journey took 10 years. As the spacecraft passed by Pluto, beth celebrated her 40th birthday.

贝丝和芭比都知道这种时间变慢的效应会发生。但当两姐妹重逢时。她们仍然很震惊。贝丝是-位40岁的中年女子。而芭比已是52岁的妇人了。两姐妹不再像是双胞胎了。芭比如今已不再年轻。她把这次太空旅行看作是年轻时的回忆。而贝丝则有些茫然：22年过去了。这个世界发生了很大的变化。对于她来说。相当于经过了10年的长途旅行来到了12年后的未来。

Both beth and barbie knew the slower time effect could happen, but they were still in shock when the sisters were reunited. Beth is a 40-year-old woman and barbie is a 52-year-old woman. The two sisters are no longer twins. Barbie, who is no longer young, sees the space trip as a memory of her youth. Beth, on the other hand, was at a loss: 22 years had passed and the world had changed so much that, for her, it was the equivalent of a long journey of 10 years to the future in 12 years.

广义相对论
这种时空旅行的创意灵感来自于阿尔伯特.爱因斯坦的狭义相对论。该理论描述了运动给时间、距离和质量带来的影响。更接近光速的旅行将把宇航员们送到更遥远的未来。比如说1个世纪之后。虽然我们现在仍不能制造出可以如此高速运行的飞行器。但我们仍然能从相对低速的运动物体身上观察到这种效应。科学家们曾在超音速飞机上装上非常精确的时钟。在飞行结束后。他们发现时钟整整慢了1秒钟。

The idea for time travel was inspired by Albert Einstein's special theory of relativity, which describes the effects of motion on time, distance and mass. Travel closer to the speed of light would send astronauts into the far future, say, a century later. Although we still can't build an aircraft that can travel that fast, we can still observe this effect in relatively low-speed moving objects. Scientists used to put very precise clocks on supersonic planes. At the end of the flight, they found that the clocks were a full second slower.

在爱因斯坦的广义相对论中。他预言。随着引力的增加。时间也会变慢。依据这个语言。有人提出这样的设想。也许我们可以利用宇宙中最具有极大吸引力的天体结构。比如黑洞。帮助年迈的老人重返童年。

In Einstein's general theory of relativity, he predicted that time would slow down as gravity increased. Based on this language, it has been suggested that perhaps we could use some of the most attractive celestial structures in the universe, such as black holes, to help old people return to their childhood.