If you could time travel, would you visit the past or the future?
如果你可以时间旅行，你会去过去还是未来？
You could find your ancestors, descendants, or experience life when dinosaurs roamed your back garden.
你可以找到你的祖先、后代，或者体验恐龙在你后院漫步时的生活。
It sounds otherworldly, but scientists have looked into whether time travel is actually possible.
这听起来像是天方夜谭，但科学家们已经研究过时间旅行是否真的可能。
Albert Einstein's theory of relativity revolutionised understanding of space, time, mass and gravity.
阿尔伯特·爱因斯坦的相对论彻底改变了人们对空间、时间、质量和引力的理解。
The key element of this theory is that time and space are linked together, and time doesn't flow at a constant rate, meaning it speeds up or slows down, depending on where you are.
这个理论的关键要素是时间和空间是相互关联的，时间不以恒定的速率流动，这意味着它会加速或减慢，取决于你所在的位置。
For example, when you travel at high speeds, time decreases, which means, according to NASA, astronauts in space age more slowly than those on Earth!
例如，当你高速旅行时，时间会变慢，这意味着，根据美国宇航局的说法，太空中的宇航员比地球上的宇航员衰老得更慢！
So, if you wanted to travel to the future, you would need to move close to the speed of light.
所以，如果你想去未来旅行，你需要以接近光速移动。
Then, while centuries pass on Earth, you'd experience a relatively short amount of time and could hypothetically return home, where it would be the future!
然后，在地球上过去几个世纪的时间里，你会体验到相对较短的时间，并且可以假设返回家园，那里将是未来！
Travelling backwards in time seems much more difficult.
回到过去旅行似乎要困难得多。
Theoretically, one way of going back is via a wormhole.
理论上，回到过去的一种方式是通过虫洞。
That means, if space and time can be folded like paper, we could create a tunnel – a shortcut between points in time.
这意味着，如果空间和时间可以像纸一样折叠，我们可以创建一个隧道——时间点之间的捷径。
The problem is that there is no evidence that wormholes exist.
问题是没有证据表明虫洞存在。
It's been shown mathematically that they can exist, but whether they exist physically is something else, says Emma Osborne, an astrophysicist at the University of York.
约克大学的天体物理学家艾玛·奥斯本说，数学上已经证明它们可以存在，但它们是否在物理上存在是另一回事。
Also, theories show that wormholes would be so small that a person definitely couldn't fit through one, and they would have such an intense gravitational field that they would collapse very quickly.
此外，理论表明虫洞会非常小，以至于一个人肯定无法通过，并且它们会有如此强烈的引力场，以至于会迅速坍塌。
For now, it seems we'll have to be content with science fiction and using telescopes to look back in time rather than travelling through it.
目前看来，我们似乎只能满足于科幻小说和使用望远镜回顾过去，而不是穿越时间旅行。
