了解宇宙是如何运行的（2010）

How the Universe Works S08E05

Part 4 Jan. 30, 2022, 2:58 p.m.

穿越时间的入口
is a portal through time.
我们所知道的是，穿越黑洞的视界
What we do know is crossing
a black hole's event horizon
是一种单向旅行
is a one way trip.
这就是黑洞的特点
That's the thing
about black holes.
你不能出来了
You ain't coming out.
在拜访霍金教授的派对后
To return to the present
after visiting
必须回到现在
professor hawking's party,
所以我们需要一种不同的时间机器
we'll need a different
kind of time machine,
一种能让我们回到过去的机器
one that lets us come back.
它们可能存在，但它们也可能摧毁任何进入的东西
They might exist, but they might
also crush anything that enters.
♪
在电影中，时间旅行很简单
in the movies, time travel
is as easy as hitting
时速88英里（约142公里）
88 miles an hour
或跳进黑洞
or diving into a black hole.
斯特里克:我们经常在电影和电视中
Stricker: We've seen the concept
of time travel into the past
看到穿越到过去的概念
very often in movies and in tv.
他们做对了吗？他们做错了吗？
Do they get it right?
Do they get it wrong?
这很难说
It's hard to tell.
明加雷利:我们现在真正理解
Mingarelli: The way that we
currently understand time travel
时间旅行的方式是
in a real sense
is through either
要么非常快地旅行，要么穿过一个引力场
travelling very quickly or
through a gravitational field.
所有这些都会把你带到未来
All of these things will
bring you into the future
而不是过去
but not into the past.
物理学能不能提供一条不同的路径回到过去？
Narrator: Could physics offer
a different route to the past?
恒星和行星使时空弯曲
Stars and planets
curve spacetime.
黑洞是无限地弯曲它
Black holes bend it infinitely.
但被称为虫洞的奇特理论
But strange theoretical objects
called wormholes
可以使物体穿透时空
could punch right
through spacetime,
用隧♥道♥将两个不同的时间点连接起来
connecting two different
points in time with a tunnel.
所以如果你考虑时空的结构
So if you think about
the fabric of spacetime,
它是一个巨大的薄片
it's this giant sheet,
你想从一点到另一点
and you want to get
from one point to the other.
虫洞要做的是它将提供一个
What a wormhole will do
was it will provide a bridge
两个点之间的桥梁，使他们彼此相邻
between the two points,
making them next to each other.
♪
旅行者会进入虫洞的一端……
travelers would enter
one end of the wormhole...
♪
……并在不同的时间出来
...And exit in a different time,
然后直接进入遥远的地方
allowing direct access
to far away places.
由于虫洞连接了时间和空间
And since wormholes connect
points in space and time,
它们可以开启现实生活中的时间旅行
they could unlock
real life time travel.
有一些广义相对论的解决方案
There are some solutions
to general relativity
允许虫洞的概念
that allow for a concept
of wormholes
如果你进入虫洞，并以某种方式穿越它
where if you entered it
and could somehow survive
你会在真正进入虫洞之前的
travelling through it, you would
exit the wormhole at a time
某个时间点离开虫洞，对吧？
before you actually
entered it, right?
所以这就是时间旅行
So this would quite literally
be time travel.
旅行者需要确保虫洞的入口
Narrator: Travelers would need
to ensure the wormholes
被锁定在现在
entry point is anchored
in the present,
而出口被锁定在过去
while the exit is locked
in the past.
事实证明是有办法做到这一点的
Turns out there's
a way to do that.
你拿一个虫洞的两端
You take two ends
of a single wormhole,
它们之间有一条穿越时空的隧♥道♥
a tunnel through spacetime
between them.
现在，你拿其中的一个
Now, you take one of those,
and you speed it up
把它加速到接近光速
to near the speed of light.
它会因时间膨胀而冻结
It will freeze in time
by time dilation.
另一方面，虫洞的这一端
On the other hand,
this end of the wormhole
会继续穿越时间
will continue to travel
through time.
假设在遥远的未来，你想回到
Let's say in the far future,
you want to travel back
那些虫洞被创造出来的地方
to the point where
those wormholes are created.
你只需要进入虫洞的这一端
You just enter this end
of the wormhole,
在时间上一直向前走的那一端
the one that's been
ticking forward in time,
然后你就会从冻结的虫洞里出来
and you'll emerge from
the frozen wormhole
回到你开始的地方
back where you started from.
但是最远的距离是有限的
Narrator: But the furthest back
you could travel is limited.
你无法回到创造它的
You wouldn't be able
to go back before the moment
那一刻，对吧？
you created it, right?
所以你可以在此时此地创造这个时间机器
So you could create
this time machine here and now,
然后未来的人可以回到
and then people in the future
could come back
你创造它的那一刻
to the moment you created it.
虫洞时间机器不会让我们回到
Narrator: A wormhole time
machine won't let us go back
霍金的派对除非它是在派对之前
to hawking's party
unless it was created
被创造出来的
before the party took place.
[时钟滴答作响]
[ clock ticking ]
使用虫洞进行时间旅行还有一个更大的问题
and there's a bigger problem
using wormholes for time travel.
如果我们发现了一个虫洞并试图利用它
If we found a wormhole
and tried to use it
来穿越回过去
to travel backward in time,
引力场真的会非常强大
really the gravitational field
would be so strong
以至于它都会坍缩成一个黑洞
that it would all just collapse
into a black hole.
奥多德:当然，你需要在通过虫洞过程中存活下来
O'dowd: Of course you need
to survive passage through
要做到这一点，你需要保持
a wormhole, and to do that,
you need to essentially
打开虫洞的喉咙
hold open the throat
of the wormhole.
只有一种方法做到这点
There's only one way
to do that.
卡罗尔:要保持虫洞的开放需要负能量
Carroll: To keep the wormhole
open requires negative energies.
这听起来很糟糕，而且的确很糟糕
That sounds bad,
and it should sound bad.
我们不知道你是否能制♥造♥出
We don't know whether
you can make these kinds
这种负能量
of negative energies.
菲利平科:人们谈论的是可以将这些虫洞打开的
Filippenko: People talk about
exotic forms of energy
一种奇异能量形式
that could push apart
these wormholes.
但我们对这类事情一无所知
But we don't know of anything
of that sort.
据我们所知，与之最接近的是暗能量
The closest we know of
is the dark energy
据说它正在加速宇宙的膨胀
that is supposedly accelerating
the expansion of the universe.
暗能量能将宇宙推开
Narrator: Dark energy pushes
the universe apart
但还不足以打开一个虫洞
but isn't exotic enough
to hold open a wormhole.
它没有负能量
It doesn't have negative energy.
但一些科学家希望我们能找到这样的东西
But some scientists hope
we'll find something that does.