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3 Simple Ways to Time Travel (& 3 Complicated Ones)

时间旅行很复杂也让人感到复杂 所以 让我们忽略所有的诡谲因素
Time travel can be complicated – and complicating, so let’s ignore all the paradoxical stuff
and talk about a few simple ways that you can time travel without leaving your home.
什么都不做 你已经在时间穿梭 我的意思是 你正位于视频的第十五秒
1) Do nothing – you’re already traveling through time! I mean, here you are – fifteen seconds
从视频伊始已经进入未来 很简单 是吗 关键在于
into the future since the start of this video! Easy, huh? The point is, we’re all always
我们一直在时间旅行 但是无趣的一种
traveling forwards through time. But that’s boring time travel. What’s interesting is
什么是与人相对的有趣时间旅行呢 为此
time travel relative to other people. To do that…
开始步行 相对于站着的人你就正在时间旅行!
2) Start walking, and you’ll travel through time relative to someone standing still! We’ve
known for over a century that time and space are really just two components of a single
并且 你移动得越快 你的时间就过得越慢 如果你
“spacetime”, and the faster you move, the slower time will pass for you. If you take
绕街走 你会比你待在家里的朋友年轻3飞秒
a walk around the block, you’ll be 3 femtoseconds younger than your friend who stayed home.
另外 为了能绕着这条街走 你必须
Except, in order to walk around the block, you had to…
站起来 你现在远离了地球 地心引力对你的作用力小了一些
3) Stand up. You’re now further from the Earth, and so gravity is a tiny bit weaker for you.
Which means you’ve traveled through time relative to your friend who’s sitting down. That’s
对了 地心引力越大时间越慢 如果你站起来一分钟
right, more gravity makes time slow down, too. If you stand up for a minute your feet
你的脚会比你的头老10飞秒 另一方面
will have aged 10 femtoseconds less than your head. On the other hand, GPS satellites high
绕轨的GPS卫星受的重力很少 因此移动得比我们快
in orbit experience less of earth’s gravity and thus travel noticeably faster through
time than we do, which is why their clocks are calibrated to run slow.
也许你想要超过几飞秒的时间旅行 准备好
But maybe you want to time travel more than a few femtoseconds. Get ready for your head
转动你的头 我的意思是 宇宙
to start spinning – I mean, the universe.
因为如果整个宇宙都在极速转动 据广义相对论
4) Because if the whole universe were spinning really fast, general relativity predicts there
所有的地点都会进入时间循环 依循其中一个循环 你会感觉
would be time-loops all over the place.Moving along one of these loops, you’d always feel
你一直在朝时间前端行进 但是总体来说你循环一圈
like you were moving forwards in time, but overall you’d loop around and travel back
然后回到了你曾经的时间和地点 这就有点像你在地球上
to a time and place in your own past. It’s a little like how you can keep moving forwards
直线前行 但是地球的弧度让你回到了原点
on the Earth, but Earth’s curvature brings you back to where you started.
不幸的是 我们的宇宙并没有旋转 或许下个方法简单一点
Unfortunately, our universe isn’t spinning. Maybe it would be easier to build…
一个超级大且转速极快的圆柱 也能使时空弯曲到
5) An infinitely long, super-dense spinning cylinder, which would also curve space-time
足够创造时间循环 问题是 如何建造符合尺寸的东西
enough to create a time-loop. The problem, of course, is how do you build something that’s
也许可以让它非常非常大?不 如果你
infinite in size? Maybe you could just make it really really really big? MmmNo. If you
试图将这时间机器压榨到有限的空间 你需要能量让它运转
tried to squeeze this time machine into finite space, you’d need negative energy – something
而 这种能量无法制作 而你已经消失在黑洞
nobody knows how to create – to make it work. Otherwise you’d end up with a black hole.
等等 用黑洞代替怎么样
Wait, but what if instead of a black hole, we…
6) Built a wormhole? Wormholes are hypothetical (but not physically impossible) bridges through
在时间中架桥 可在宇宙中连接两方与时间并促成捷径
space-time, shortcuts that can instantaneously connect two different places and times in
若你有虫洞 你或许可以利用它穿梭过去
our universe. If you had a wormhole you might be able to use it to travel into the past
or the future.
问题在于没人知道如何建立虫洞 或 一旦建立
The problem is that no-one knows how to build a wormhole. Or, once you’ve built it, how
如何防崩溃 就像肖恩·卡罗尔 曾写的
to keep it from collapsing: as Sean Carroll has eloquently written, “keeping wormholes
保持虫洞张开需要特殊的能量 但无人知晓如何获得
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
这不是什么好事 但作为安慰 欢迎来到未来
Well that’s too bad… but as consolation, welcome to the future! Almost three minutes
从视频开始已经差不多三分钟了 现在我们已经有了喷气式背包
have passed since the beginning of this video, and we have personal jet-packs.