了解宇宙是如何运行的（2010）

How the Universe Works S08E05

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

——准备发射
——起飞
-Ramping up.
-Liftoff.
2015年3月27日，宇航员斯科特·凯利
March 27, 2015,
astronaut scott kelly
前往国际空间站
traveled to
the international space station.
♪
他长达一年的任务是研究
his yearlong mission
was to study
太空飞行对人体的影响
the effects of space flight
on the human body.
斯科特是最佳人选
Scott was the perfect candidate
因为在地球上，他有个同卵双胞胎，马克
because back on earth,
he had an identical twin, mark.
萨特:他们这样做是出于各种各样的原因
Sutter: They did this for
a variety of reasons
尽可能使用完整的控制条件环境
to explore the effects
of space travel
来研究太空旅行
and weightlessness
on the human body
和失重对人体的影响
using as controlled
an experiment as possible.
失重并不是这对双胞胎
Narrator: Lack of gravity wasn't
the only difference
唯一的区别
between the twins.
斯科特以每小时17000英里（约11300公里）的速度绕地球飞行
Scott was orbiting earth
at 17,000 miles an hour.
所以和他在地球上的双胞胎相比
So compared
to his earthbound twin,
斯科特穿越了时间
scott moved forwards
through time.
穿越到未来并不只是一个
This time travel into
the future isn't just
抽象的物理概念
an abstract physics concept.
斯科特，这个绕轨道飞行的孪生兄弟实际上是在
Scott the orbiting twin
literally jumped into the future
几分之一秒的时间里跳进了未来
by a fraction of a second.
当斯科特最终回到地球
When scott finally returned
back to earth,
由于他的速度很快
because of his rapid speed,
他衰老的速度比他哥哥慢了一点点
he aged just a little bit slower
than his brother
实际上他比哥哥年轻了一点点
and he was actually younger
by a tiny fraction of a second.
17000英里（约11300公里）的时速是很快，但是要想
Narrator: 17,000 miles an hour
as fast, but to jump more than
跳跃到未来超过几分之一秒
a fraction of a second
into the future,
斯科特需要跑得更快
scott needed to go way faster.
如果斯科特·凯利想在轨道上呆一年
What if scott kelly
had wanted to let the earth age
而让地球比他老1000年呢？
1,000 years while he was
in orbit for one year?
要绕地球转多快才能做到这一点？
How fast would he have had
to orbit the earth to do that?
结果是他必须以
And it turns out
he'd have to orbit
接近光速的速度飞行
at almost the speed of light.
让我们来看看它到底有多快
To put it in perspective
just how fast that is,
历史上最快的人类驾驶飞行器
the fastest human piloted
vehicle in history
是阿波罗10号♥
was apollo 10.
它的速度是每小时两万五千英里（约40000公里）
That went at 25,000
miles per hour.
你需要比这个速度
You would need to go more
than 25,000 times
快25000倍以上
faster than that.
这是非常快的速度
That's pretty fast.
在未来，我们可能会尝试
Narrator: In the future,
we might try to build
建造一艘具有先进推进力
a spaceship with
advanced propulsion
能够达到光速的宇宙飞船
capable of light speed.
但物理定律不会让这变得容易
But the laws of physics
won't make it easy.
要将某物加速到光速
It would take an infinite
amount of energy
比如一辆车、一颗弹珠或一个星系，无论什么
to accelerate something,
a car, a marble, a galaxy,
都需要无穷无尽的能量
whatever to the speed of light.
因此，我们认为光速本身
And so for that reason,
we think that the speed of light
是一个真正牢不可破的速度
is itself
a truly unbreakable speed.
萨特:如果你想要一个人类大小的飞船
Sutter: If you want to take
a human sized spacecraft
仅仅加速到光速的10%
and accelerate it to
10% of the speed of light,
更别说90%或99%光速
let alone 90% or 99%
the speed of light,
它需要的能量比人类有史以来
it requires more energy
than humanity has ever used
在其整个历史中使用过的
in its entire existence
以及还未曾使用过的能量的总合还要多
and probably will ever use
in its entire existence.
在时间中跳跃并不简单
Narrator: Jumping forward
in time isn't simple,
但是宇宙的物理原理使它成为可能
but the physics of the universe
make it possible.
接近光速会让你
Going close to
the speed of light slingshots
更快地进入未来
you into the future faster,
但它不会以任何方式带你回到过去
but it does not take you
to the past in any way.
这不是一种回到过去
It's not a way to go
backwards in time
去参加任何派对的方式
and visit anyone's party.
[时钟嘀嗒作响]
[ clock ticking ]
一艘超快时间旅行的宇宙飞船
narrator: A super fast
time travelling spaceship
不能把我们带回霍金的派对
can't take us back
to hawking's party.
但是宇宙中存在的时间机器呢？
But what about a time machine
that exists out in the cosmos?
[拔出软木塞]
[ cork pops ]
2009年，斯蒂芬·霍金为时间旅行者
narrator: In 2009,
stephen hawking held a party
举办了一场派对
for time travelers.
没有人来
No one showed up.
这种情况会改变吗？
Could that situation
ever change?
现在我们来到了未来
So here we are in the future,
我们真的很想去参加那个派对
and we'd really love
to go to that party.
我听说那里的小吃很好吃
I heard there's great snacks.
我们怎么回去？
How do we get back there?
我们知道极端的速度可以把我们送到未来
Narrator: We know extreme speeds
can send us into the future.
但宇宙中还有另一种力与时间有关，那就是——
But the universe has another
force that messes with time --
引力
gravity.
记住，只有一种东西叫做时空
Remember that there is
only something called spacetime,
时空不是分离的
not separate space and time.
引力实际上是时空本身的弯曲
And what gravity really is is
a bending of spacetime itself.
把时空想象成一块橡皮
Narrator: Think of spacetime
like a rubber sheet.
像行星和恒星这样的大质量物体会拉伸它
Massive objects like planets
and stars stretch it,
使空间和时间弯曲
bending space
and passages of time.
当你接近一个有很大引力的物体时
As you get closer to something
with a lot of gravity,
时间和空间就会被拉长
time and space are stretched.
这确实意味着时间过得更慢
And that really does mean
that time goes more slowly.
这甚至发生在地球上
Narrator:
It even happens on earth.
在这里，接近地面的时间运行得更慢
Here, time runs more
slowly close to the ground.
布洛克:所以这意味着，如果你住在
Bullock: So what this means is
if you live high up in
公♥寓♥大楼的高层，你的时钟滴答作响的速度
an apartment building,
your clock is ticking by
比住在公♥寓♥大楼底层的人
slightly more quickly than
people living at the bottom
略快一些
of the apartment building.
你对地球引力的感觉和他们的
You feel the earth's gravity
slightly differently
略有不同
than they do.
如果你住在豪华高层的顶层公♥寓♥
If you live in the top floor
of a luxury high rise