Two of the most popular themes in science fiction movies are space travel and time travel, and a 2014 film called Interstellar makes use of both ideas. It is about a scientist who travels to a distant place in outer space, leaving his young daughter behind on Earth. When he next meets her, on a space station orbiting Saturn, she is a very old woman. The scientist, on the other hand, is only a few months older. This phenomenon is explained by Albert Einstein's theories of relativity. Thanks to Einstein, scientists know that time slows as moving objects approach the speed of light. Moving at such speeds would make time travel theoretically possible.
科幻電影最受歡迎的兩個主題是太空旅行和時光旅行，而 2014 年一部叫做《星際效應》的電影同時採用了這兩個概念。電影是關於一位科學家去了遙遠的外太空，獨留他的小女兒在地球。當他在繞著土星運行的太空站上再次見到她時，她已成了一個老婦人。另一方面，科學家只老了幾個月而已。這種現象可以用愛因斯坦的相對論來解釋。多虧了愛因斯坦，科學家瞭解當物體以接近光速移動時，時間會變慢。用這樣的速度移動，會讓時光旅行在理論上成為可能。
As countless movies and novels have demonstrated, people love the idea of traveling through time. They like to imagine themselves seeing what the world is like in the years to come, and then coming back to the present with knowledge that nobody yet possesses. Likewise, the possibility of going to the past is equally attractive. We could prevent disasters from happening in our lives, or stop terrible events from taking place. Returning to the present, however, we would undoubtedly find things changed.
如同無數電影和小說所呈現的，人們喜愛穿越時空的概念。他們喜歡想像自己看見未來世界的模樣，並且掌握著尚未有人知道的知識回到現在。同樣地，回到過去的可能性也同樣吸引人。我們能夠預防災害在生活中發生，或是阻止可怕的事件發生。然而，回到現在之後，我們肯定也會發現一切都被改變了。
Imagine you could travel to the past. You would discover what really happened in events that historians can only theorize about. Think how amazing it would be to witness Cao Cao's fleet set ablaze by the fire ships in the Battle of Red Cliffs in AD 208. You could also meet important historical figures, like Christopher Columbus. You might join his great voyages across the Atlantic Ocean to the New World. You would have to be careful, though. Getting involved in past events and changing them would in turn affect the present, and maybe not in a good way.
想像你能回到過去。你就能一窺那些歷史學家僅能以理論推測出的事件的真實面貌。試想若能目睹曹操的艦隊在西元 208 年的赤壁之戰中被火船燒成烈焰，那該有多麼驚人。你也可以和重要的歷史人物見面，像是哥倫布。你或許可以加入他橫越大西洋到新世界的偉大航程。不過，你得小心。捲入過去的事件，然後改變它們，可能會反過來影響現在，而且可能是不好的影響。
In that case, you might prefer to go forward in time. You could observe the long-term effects of climate change, for instance. Then you could come back and advise the rest of us what to do and what to avoid doing. What's more, you could find out whether humans or machines rule the world, or whether humans even exist anymore. Perhaps people would have made contact with intelligent alien life. You could tell everyone what aliens look like on your return. Or, you could just take a look at your future self, as well as your wife or husband and kids.
既然如此，你可能比較偏好前往未來。舉例來說，你可以觀察氣候變遷的長遠影響。然後你可以回來建議我們其他人什麼該做，什麼不該做。此外，你也可以知道是人類還是機器在統治世界，或是否人類仍然存在。也許人類已經和有智慧的外星生物接觸了。你可以在回來後告訴大家外星人的樣子。或者，你可以只看看未來的自己，還有你未來的老婆或是老公以及孩子。
It's fun to speculate about time travel. If it really were possible, however, the effects could be chaotic. The fact that we could travel without restriction to the past or the future would change life beyond our imagination or even threaten our existence. For the time being, we can only make movies that guess at the consequences.
臆測時光旅行很有趣。然而，如果時光旅行成真了，結果將可能很混亂。若是我們能毫不受限地穿越到過去或是未來，那將會對我們的生活造成難以想像的改變，或甚至威脅到我們的生存。目前我們就只能拍電影來揣測後果。
