Time travel can be complicated,and complicating.So let's ignore all the paradoxical stuffs and talk about a few simple ways that you can time travel without leaving your home.
First,do nothing,You are already traveling through time.I mean,here you are,fifteen seconds into the future since the start of this video.Easy,right? The point is,we are all always traveling forwards through time.But that's boring time travel.What's interesting is time travel relative to other people.
To do that,start walking,and you'll travel through time relative to someone standing still.We've know for over a century that time and space are really just two components of a single space-time,and the faster you move,the slower time will pass for you.If you take a walk around the block,you'll be 3 femtoseconds younger than your friend who stayed home.
想要成功 走走路 相对那些站着不动的人你就是在做时空穿梭。一个世纪以来 我们都知道时间和空间都是单个时空中的两个组成元素，你动得越快对你而言时间过得就越慢。如果你绕着楼走，你会比房间中的朋友年轻3飞秒。
Except,in order to walk around the block,you had to stand up.You're now further from the earth,and so gravity is a tiny bit weaker for you.Which menas you are traveling through time relative to your friend who's sitting down.That's right,more gravity makes time slow down,too.If you stand up for a minute,your feet will age 10 femtoseconds less than your head.
不过你得站起来才能在房子周围走动。现在你离地球更远对你而言引力弱了一点点。也就是说 相对于那个坐着的朋友你就已经在做时间穿梭了。的确 引力更大 时间也更慢。如果你站1分钟 你的头部会比足部小10飞秒。
On the other hand,GPS satellites high in orbit experience less of earth's gravity and this travel noticeably faster through time than we do.which is why their clocks are calibrated to run slow.Maybe you wanna time travel more than a few femtoseconds.Get ready for your head to start spinning.I mean,the Universe.Because if the whole universe was spinning really fast,General relativity predicts there will be time loops all over the place.
另外 高空轨道上的GPS卫星受到地球引力更小 穿梭的速度也就比我们更快。这也是为什么卫星时钟被调慢了。或许 你不只想穿梭这几飞秒。准备着让大脑转起来吧。我要说的 是宇宙。因为如果整个宇宙飞速旋转，广义相对论预测 空间将内处处都是时间循环。
Moving along one of these loops,you'd always feel like you were moving forwards in time.But overall,you'd loop around and travel back to a time and place in your own past.It's a little like how you can keep moving forwards on the earth,but earth's curvature brings you back to where you started.Unfortunately,our universe isn't spinning.Maybe it would be easier to build an infinite long,super dense spinning cylinder.which would also curse spacetime enough to create a Time Loop.
穿梭于这些循环内时 你总会觉得自己在走向未来。而整体上 你将穿梭到自己过去一个时间和地点。这有点像是你在地球上不停地向前走，但地球的曲率把你带回了起点。不幸的是 宇宙并不在自旋。可能做一个无限长 密度无限大的转筒更简单点。这也会让时空弯曲 制造出时间循环。
The problem,of course,is how do you build something that's infinite in size.Maybe you could just make it really really big?Nnnnn,no.If you try to squeeze this time machine into finite space,you'd need negative energy,something nobody knows how to create,to make it work.Otherwise,you'd end up with a black hole.Wait,but what if instead of a black hole,we built a worm hole?Worms holes are hypothetical,but not physically impossible bridges through spacetime,shortcuts that can instantaneously connect to different places and time in our uneiverse.
当然 问题在于如何造出无限大的物体。那造一个很大很大的呢？呐不行。如果你把这个时间机器塞到有限空间内，想要让它动起来 得用到没人能制造出的负能量才行。要么 结果就是一个黑 洞。等等 如果我们造出的不是黑洞 而是虫洞呢？虫洞是假想之物 但并非物理上不可能的 穿越时空的桥梁，它是能瞬间连接宇宙内两个不同时间地点的捷径。
If you had a worm hole,you might be able to use it to travel into the past or the future.Problem is,no one knows how to build a worm hole.Or once you've build it,how to keep it from collapsing.As Shawn Carol has eloquently written:Keeping worm holes open requires a form of negative energies.Nobody knows how to make negative energies,although they occasionally slap the name Exotic Matter on the concept and pretend it might exist.
如果你有虫洞 兴许能用它穿梭到过去或未来。只是 问题是没人知道怎么造虫洞。造出虫洞后 又如何阻止它塌缩。正如Shawn Carol所说：让虫洞保持打开要用到一种负能量。让虫洞保持打开要用到一种负能量。没有人知道如何制造负能量，尽管人们经常就这个概念甩出“异物质”并且假装它存在。
Well,that's to bad,but as a conciliation,welcome to the future.Almost 3 minutes have past since the beginning of this video.And we now have personal jet packs.