時空旅行可以實現? 科學家們來告訴你!

Time travel is a familiar subject of science fiction and fantasy stories, from H.G. Wells to Rod Serling to Hot Tub Time Machine. But could time travel ever be possible in real life? And, if so, how would humans even handle a technology with such great capacity for destruction?

從科幻作家赫伯特·喬治·威爾斯到編劇羅德·瑟林再到科幻喜劇《熱浴盆時光機》，時空旅行一直是科幻小說和奇幻故事中熟悉的主題。但時空旅行究竟能否在現實生活中真正實現？如果真的可以實現，那麼人類將如何處理一項擁有如此巨大破壞力的技術呢？

Some scientists say time travel is theoretically possible, at least if you want to jump ahead to the future, but don't start saving up for a time machine just yet. As physicist Paul Davies explained for CNN in 2013, "Over a century ago, Albert Einstein showed that time is intrinsically elastic, capable of being stretched or shrunk by motion."

一些科學家認爲，時空旅行從理論上是可以實現的，起碼如果你想去往將來還是可以的。但是也不要從現在開始就攢錢買一臺時光機。正如物理學家保羅·戴維斯於2013年在CNN中所解釋的那樣：“一百年以前，埃爾伯特·愛因斯坦證明：時間從本質上來講是具有彈性的，能夠受運動影響而擴展或收縮。”

Essentially the closer you're going to the speed of light, the slower time moves. "Fly to the star Vega, 25 light years away, and back again at 99% of the speed of light, and when you return to Earth in 2062, you will have experienced only seven years' travel time in the spacecraft. In effect, you will have leaped 42 years into Earth's future," Davies wrote.

從本質上來講，你的速度越是接近光速，時間移動地相對也就越慢。戴維斯寫道：“假如你想要飛到二十五光年之外的織女星，然後再以99%光速的速度回到地球。那麼當你回到地球時，大約已經是2062年了，這僅僅相當於你在宇宙飛船內停留7年的時間。換句話說，你將跨越了42年的時間，來到了地球的未來時空。”

So if you were to, theoretically, take a trip in a super-fast spaceship, you might feel (and look) as though only a few years had passed, but when you arrived back on Earth, decades would have passed and all your friends and family would be dead and gone. Time travel!

從理論上來講，如果你乘着超快速宇宙飛船去太空旅行，你可能會感覺到時間僅僅過了幾年。不過當你回到地球之後，實際上幾十年已經過去了，你的家人或朋友很可能已經不在人世了。這就是所謂的時空旅行！

But what about going backwards? Could it ever be possible to pop back in time and stop bad things from happening and good people from dying? Theoretically, if you were to travel faster than the speed of light, you would be moving backwards in time, according to one hypothesis LiveScience reported.

那麼如果想要回到過去呢？有沒有可能使人類回到過去，從而阻止那些不好的事情發生，使那些善良的人們免於死亡？根據《生活科學》中曾提出的一個假說，從理論上來講，只有當你運動的速度能夠超越光速，你纔有可能引起時光倒流，回到過去。

But most scientists believe that nothing can actually travel faster than light, and, if you could go back in time, messing with the past would create all kinds of unsolvable paradoxes, like the Grandfather Paradox.

但大多數科學家都認爲，沒有任何物體的運動速度可以超越光速。並且，如果人類能夠回到過去，和過去糾纏不清，就可能引發一系列不易解決的問題和矛盾。比如“祖父悖論”。

Although some theories have attempted to propose workarounds for these inconvenient time-travel problems, it remains a pretty widely held belief that traveling backwards in time isn't possible for us humans. After all, as physicist Stephen Hawking said in his book A Brief History of Time, "If time travel is possible, where are the tourists from the future?"

儘管一些理論已經嘗試着爲這些複雜的時空旅行問題提供了一些替代解決辦法，但大多數意見還是認爲回到過去是人類不可能實現的一個夢想。畢竟，正如著名物理學家斯蒂芬·霍金在他的《時間簡史》中提到的那樣：“如果時空旅行可能實現，那些從未來穿梭到現今世界的旅行者們又在哪裏呢？”