了解宇宙是如何运行的（2010）

How the Universe Works S08E05

Part 6 Jan. 30, 2022, 2:58 p.m.

most likely to harbor
像时间旅行这样疯狂事件的区域
the greatest possibility for
something crazy like time travel
是在时空曲率最极端的区域
is in the most extreme regions
of spacetime curvature.
你可以想象一个非常复杂的情况
You can imagine a very
complicated situation
你有足够的质量，它以这样一种方式运动
where you had enough mass
and it was moving in such a way
你可以把空间扭曲起来
that you could twist space
up on itself.
理论上的物体叫做裸线奇点
Narrator: Theoretical objects
called naked line singularities
可以做到这一点
could do just that.
就像两个黑洞的心脏
Like the hearts of two
black holes
但是无限延伸
but stretched out infinitely.
对于裸奇点来说，相互靠近可以在时空中
To naked singularities
moving close to each other
创造出一种环形路径
could create a looped path
through spacetime
称为封闭的类时曲线
called a closed time-like curve.
封闭的类时曲线是一种非常特殊的
A closed time-like curve
is a very special
穿越时空的路径，你有一个起点
kind of path through spacetime
where you have some
你开始穿越时空
starting point, and you start
moving through spacetime
就像你在影片中前进的帧一样
just like you'd advance
in frames in this piece of film.
在封闭的时间型曲线中
And it just so happens
in a closed time-like curve
结束坐标系和开始坐标系
that your ending frame
is exactly the same
完全相同
as your beginning frame.
所以当你穿越空间，你开始进入你的未来
So as you move through space,
you start moving into
但你也进入你自己的过去
your future, but you also move
into your own past
你最终在空间和时间上
and you end up
at exactly the same point
完全相同的点上开始
where you started both in space
and in time,
你已经结束了这个循环
and you've closed the loop.
有了封闭的时间曲线
Narrator: With closed
time-like curves,
你也许可以通过时空循环来回顾你自己的过去
you may be able to visit your
own past by looping spacetime.
但在大块宇宙中旅行有一个很大的缺点
But travelling in the block
universe has a big drawback.
你永远无法改变过去
You can never alter the past.
如果这个大块宇宙的想法是正确的
If this block universe idea
is correct,
这个电影胶卷宇宙所有的时间都同时存在
this movie reel universe
that all of time exists
那就解决了祖父悖论
all at once, that solves
the grandfather paradox.
你不能回到过去
You can't go back in time
杀死你的祖父，因为还没有你
to kill your grandfather
because you haven't.
你永远不会也永远做不到
You never will.
You never will have done it.
你做不到，因为根本没发生过
You can't do it
because it didn't happen.
时空旅行者
Narrator: Time travelers
in a block universe
无法改变历史
can't change history.
既然我们知道没人参加霍金的派对
So since we know
that no one attended
以后也不会有人参加了
stephen hawking's party,
no one ever will.
通过研究时间旅行，科学家们
By investigating time travel,
scientists are unraveling
正在解开宇宙之谜
mysteries of our universe.
但有一个问题仍然没有答案
But one question
remains unanswered.
为什么时间似乎只朝着一个方向跑？
Why does time seem to only run
in one direction?
那为什么我们记得过去
How is it then
that we remember the past,
却不知道未来呢？
but we don't know the future?
泰格马克:令人震惊的是，这个看似显而易见的问题
Tegmark: This seemingly
obvious question turns out
竟然在我们的
to have its explanation
宇宙起源中得到了解释
in the origin of
our universe shockingly.
♪
时间的流逝并不是一成不变的
narrator: The passage of time
isn't set in stone.
时间可以弯曲，可以放慢，甚至可以冻结
Time can be bent, slowed,
even frozen.
但我们的时间经验似乎是固定的
But our experience of time
seems fixed.
时间只朝一个方向流动
Time only flows
in one direction.
卡罗尔:只有时间的方向
Carroll: There just
is a direction to time
而没有空间的方向
in a way that there's not
a direction to space.
上，下，左，右，前，后
There's no difference between
up, down, left, right,
都没有区别，但昨天和明天
forward backward,
but there's still a difference
仍然有区别
between yesterday and tomorrow.
为什么时间似乎向前跑
Narrator: Why does time
seem to run forwards
而不是向后跑？
and not backwards?
在我们的日常生活中
So many things
in our everyday life
很多事情只能在一个时间方向上有意义
only make sense
in one direction of time.
你打破一个鸡蛋，它不会突然又变成一个鸡蛋
You break an egg, it doesn't
suddenly become an egg again.
你炒一个鸡蛋，它不会变成原来完整的样子
You scramble an egg,
it doesn't become whole.
你知道，事情是有方向的
You know, there's
sort of directions of things.
这个时间之箭似乎与我们在日常生活中
Narrator: This arrow of time
seems to be linked to the chaos
看到的混乱和无序有关
and disorder
we see in our day to day lives.
最好的解释也许是边喝咖啡边说
Best explain perhaps
over a coffee.
如果我有一杯咖啡，只有一种方法
If I have a mug of coffee,
there's only one way
可以让杯子的所有小块
for all the little bits
and pieces of the mug
液体和咖啡都变成这个形状
and the liquid and the coffee
to be in this shape,
就在我面前
and it's right here
in front of me.
这个杯子处于所谓的高度有序状态
Narrator: The mug is in what's
called a highly ordered state.
萨特:但如果我把它从桌子上推下去
Sutter: But if I shove it
off the table
它就摔得粉碎
and it smashes into
a million pieces,
我们就再也看不到这些小块和液体
we'll never see all those pieces
and the bits of liquid
重新组合成杯子的形状了
reassemble into the shape
of the mug again.
我们知道破碎的杯子不会自己组装起来
Narrator: We know the shattered
mug won't reassemble itself.
用科学术语来说，咖啡杯的无序程度
In scientific terms,
the disorder or entropy
或熵值会增加，但不会减少
of the coffee mug increases
but never decreases.
穿越宇宙，熵总是在增加
And across the universe,
entropy always increases,
就像穿越宇宙一样，时间从过去流向未来一样
just like across the universe,
time flows from past to future.
宇宙中的一切
Narrator:
Everything in the universe
逐渐变得越来越混乱
is gradually becoming more
and more disordered.
但为什么呢？
But why?
我们从来没有想过破碎的鸡蛋会自行重组
We never really think about
broken eggs reassembling
这实际上可能要追溯到
themselves, and that actually
may go all the way back
大爆♥炸♥时的情况
to what the conditions
of the big bang were like.
138亿年前，时空从一个小点
Narrator: 13.8 billion
years ago, spacetime rapidly
迅速膨胀
expanded from a tiny point.
一眨眼的功夫，宇宙诞生了
In the blink of an eye,
the universe was born.
这标志着时间的第一个时刻
This marked the first moment
of time.