Is time travel possible?

If you could time travel, would you visit the past or the future? You could find your ancestors, descendants, or experience life when dinosaurs roamed your back garden. It sounds otherworldly, but scientists have looked into whether time travel is actually possible.
如果你能进行时间旅行，你会去过去还是未来？你可以找到自己的祖先和后代，或者体验恐龙在你家后花园漫步时的生活。这听起来很不可思议，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. 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. 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! So, if you wanted to travel to the future, you would need to move close to the speed of light. 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!
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。这个理论的关键要素是时间和空间是联系在一起的，时间不会以恒定的速度流动，这意味着它会加速或减速，这取决于你在哪里。例如，当你高速旅行时，时间会减少，这意味着，根据美国国家航空航天局的说法，太空中的宇航员比地球上的宇航员衰老得慢！因此，如果你想穿越到未来，你需要以接近光速的速度移动。这样，虽然地球上的时间已经过去了几个世纪，但你所经历的时间却相对较短，假设你可以返回家园，那里就是未来！

Travelling backwards in time seems much more difficult. Theoretically, one way of going back is via a wormhole. That means, if space and time can be folded like paper, we could create a tunnel – a shortcut between points in time. The problem is that there is no evidence that wormholes exist. "It's been shown mathematically that they can exist, but whether they exist physically is something else," says Emma Osborne, anastrophysicist at the University of York. 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.
时光倒流似乎要困难得多。从理论上讲，回到过去的一种方法是通过虫洞。也就是说，如果空间和时间可以像纸一样折叠起来，我们就可以创造出一条隧道--一条时间点之间的捷径。问题是，没有证据表明虫洞存在。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，但物理上是否存在却是另一回事。另外，理论显示，虫洞会非常小，一个人肯定穿不过去，而且虫洞的引力场非常强，会很快坍塌。

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.
现在看来，我们只能满足于科幻小说，用望远镜回望过去，而不是穿越时空。

词汇表
ancestor 祖先
descendant 后代
otherworldly 超脱尘俗的，非现实世界的
theory of relativity 相对论
mass 质量
gravity 重力，引力
flow （时间）流动，流逝
speed up 加速
slow down 减速
age 变老
the speed of light 光速
century 一百年，世纪
wormhole 蠕虫洞
shortcut 捷径，近路
astrophysicist 天体物理学家
gravitational field 引力场
collapse 崩塌，坍塌
science fiction 科幻小说
telescope 望远镜

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