宇宙（2007）

In other words, it can't be done.
换句话说 悖论不可能发生
A different alternative is the strange idea of multiple universes.
另一种选择是 多重时空的奇妙想法
One way of dealing with travel back in time
应对回到过去的一种理论就是
is to say that you actually enter a different parallel universe
在你进行时间旅行回到过去时
after having made the journey back in time.
其实是进入了另一个宇宙
So you don't affect the history of the universe from which you came.
所以你不会对你原本的宇宙历史造成影响
In effect, anything that can happen will happen.
实际上 任何会发生的事情都将会发生
But the way it happens is by entering a parallel universe.
但发生的方式便是进入到一个平行的宇宙
Pretty bizarre thought.
相当奇怪的想法
A third solution to the paradox problem
第三种解决悖论的理论是
is the notion that if time travel is possible,
如果时间旅行是可能的
You just won't be able to change the past when you get there.
当你回到过去时 你不能改变历史
The science behind this can be illustrated by reducing the problem
隐藏其后的科学可以通过将问题
to the simplest situation you can think of.
减化到你可以想象的最简单程度来进行说明
For example, balls on a pool table.
就用台球桌上的球来举例
Let's set up a pool table that's like a time machine.
我们把台球桌假设成一台时光机
If a ball enters one pocket,
如果一个桌球进入到一个球袋中
it travels through a wormhole and can exit another pocket
然后通过虫洞 回到进入第一个球袋之前
before it entered the first pocket.
从另一个球袋出来
So it's a time machine.
所以这就是一台时间机器
So now suppose the ball really does go through the first pocket,
现在假设桌球的确会进入第一个球袋
emerges before it entered,
并在它进入第一个球袋之前便出现的话
and then hits itself before
那么在进入第一个球袋之前
it entered the first pocket.
桌球便会击中自己
That would deflect it,
使自己偏离方向
preventing it from entering the first pocket,
而无法进入第一个球袋
and thus preventing it from having exited the second pocket
如此一来 就不可能从第二个球袋出现
and done the deflection in the first place.
也就不可能使自己发生偏离
So, it's a paradox.
所以 这是一个悖论
However, the idea of self-consistent solutions
然而 自洽性的想法
gives us a way out of this paradox.
使得我们从矛盾中摆脱
Suppose that the ball exiting the second pocket
假设桌球从第二个球袋中出现
can only hit itself in such a way
能且只能击中自己
as to deflect it into the first pocket.
并使其进入第一个球袋
Then the whole loop is self-consistent.
那么整个循环过程就符合自洽性
There's no paradox.
就没有悖论
We think that nature always somehow manages
我们认为大自然总能
to choose the solution that provides self-consistency.
提供自洽的解决方案
In other words, you always get a solution
换句话说 你会得到
that does not produce a paradox.
不会产生矛盾的方案
If that's the case and Clifford Johnson were able
如果那样的话 克里福德·约翰逊就能够
to travel to the year 1937,
回到1937年
he might be able to meet his grandfather.
他也许能够见到他的祖父
But despite his best efforts,
但是 尽管他尽了最大的努力
nothing he does would alter the fact
他的举动也不会
that somehow his grandfather will meet his grandmother
改变他祖父祖母的相遇
to allow Clifford to be born.
因此允许克里福德的出生
Hi. How are you? How you doing?
你好 你好
One way or another, the universe will prevent him from changing history.
以某种方式 宇宙会阻止他去改变历史
But we don't have to worry about paradoxes when we travel forward,
当我们跃向未来时则不必担心悖论发生
Taking the arrow of time into the future.
时间箭头永远指向未来
Traveling forward in time is the easiest thing in the world.
向未来行进是世界上最容易的事情
Every minute, you move one minute forward in time.
每一分钟 你都在往下一分钟移♥动♥
One thing we can do to change how we move forward in time
与其他人相比
relative to each other is to actually move
我们唯一可以做出改变的
at different velocities compared to each other.
是以不同速度向前移♥动♥
A time machine that takes us into the future
时光机将我们送到未来
is based on Einstein's discovery about time and speed.
是根据爱因斯坦关于时间和速度的发现
The faster you move in space,
你在空间上移♥动♥得越快
time, for you, slows down as compared to people standing still.
跟其他人相比 时间对你就相对慢了下来
And as mind-bending as this seems,
这种想法似乎很疯狂
It's actually been proven by experiments.
事实上 这是通过实验得到了证明的
Clocks have been placed on rapidly moving airplanes and rocket ships,
时钟被安置在快速移♥动♥的飞机或者火箭上
and they've moved over some distance at a very rapid speed.
它们以高速飞行一段距离
And when the atomic clocks were measured after the end of the journey,
旅行结束后 来测量原子钟
they had progressed forward in time a little bit less
它们已经比安置在地面同样的钟
than similar clocks which had remained at rest on earth.
慢了一些
The effect is called time dilation,
这被称作时间膨胀
and we can use it to travel into the future.
我们可以利用它去到未来
In fact, it's already been done.
事实上 已经有人这么做了
Russian cosmonaut, Sergei Krikalev
俄♥罗♥斯♥宇航员谢尔盖·克里卡列夫
has logged more than 803 days in orbit,
已经在绕地轨道中
traveling 17,000 miles an hour,
以每小时17,000英里的速度旅行了803天
making him the world's record holder in time travel,
这使得他成为间旅行最长时间的纪录保持者
though you'd hardly know it to look at him.
虽然从表面上来几乎看不出来
What's actually happened is that he's about a 50th of a second slower
实际发生的情况是 他所经历的时间中
in the amount of time that has passed for him
跟在地球上的每个人相比
compared to everyone else who's stayed on earth.
每50秒就会慢上一秒钟
But dilation really begins to pay off as a time machine
当你的速度接近光速的时候
when you pump your speed to just under the speed of light.
时间膨胀产生的作用就等同于时间机器
The idea is to let clocks on earth move at their normal speed,
地球上的时间以正常速度向前移♥动♥
while you're off in space and your clock is moving more slowly.
与此同时 在太空中时间向前移♥动♥要慢一些
When you get back, you're in the future.
当你回到地球 你就来到了未来世界
Suppose, for example, you wanted to go 500 years into the future.
假设说 你想去到500年后的世界
To move 500 years into the future,
要去到500年后的世界
you'd have to move at 99.99% of the speed of light for 7 years.
你要以接近光速99.99%速度飞行7年
When you get back, you will have aged only 7 years,
当你回到地球时 你的时间只前进了7年
but everything on earth will have aged 500.
但是地球上已经过去了500年
But one of the biggest problems with building a time machine
但是要打造一个飞往未来的时光机
for travel into the future is finding enough fuel
最大的问题就是要有充足的燃料
to boost a spaceship to speeds that high.
以便让飞船能够以如此高的速度飞行
There's no law of physics that says you can't
没有物理法则指出
go close to the speed of light,
我们不能如此接近光速
But your rocket ship becomes heavier and heavier
但是 随着越来越接近光速
as you go closer and closer to light speed.
你的飞船也会变得越来越沉重
So you require more and more fuel to accelerate
如此一来 就会需要更多的燃料来加速
you smaller and smaller amounts,
但加速的速度却越来越慢
And you need more than an infinite amount of energy
你需要超过无限多的能源
to actually break the light-speed barrier.
来打破光速障碍
But high speed isn't the only way to zip into the future.
但是高速并不是去到未来世界的唯一办法
Einstein's theory of relativity says high gravity
爱因斯坦的相对论中也阐释了
also slows down your clock,
强引力也可以减慢时间的移♥动♥
The kind of gravity you might find near a black hole.
这种引力你能在黑洞附近发现
Let's say you're in a spaceship,
假如说 你在一架宇宙飞船中
and you go and you park yourself just outside a black hole for a while.
你飞往黑洞附近 并且停留一会
Once you return to earth,
然后立刻回到地球
you will notice that many, many years may have passed on earth,
你就会发现你来到了许多年以后的地球
but only a few weeks or months will have passed in your own frame of reference.
事实上你的时间只过去了几周或几月而已
You will have jumped into the future while aging very little.
这样就可以花很短的时间就去到未来
That's really cool.
真酷
But spending years at high speed
但是高速飞行几年时间
or near a black hole is a slow kind of time travel.
或利用黑洞重力仍是很缓慢的时间旅行
For more impatient voyagers,
对于很多没有耐心的旅行者
there may be an instantaneous version
最好是有一种瞬间的办法
by way of a shortcut through space called a wormhole
那就是通过叫虫洞的捷径
that could also become a corridor through time.
虫洞就宛如一个时间走廊一样
To conquer time travel,
为了攻克时间旅行
we have to tread a long path that takes us through bizarre theories
我们还有漫漫长路要走 验证各种奇特理论
and incredibly complex technology toward a goal
以及异常复杂的技术
that will one day make starships into time machines.
以便达到某日能造出时光机的目标
Starships, in fact, may be our best bet.
飞船也许是我们最好的选择
Shoot off in a rocket ship at super speed and let our own time slow down
发射超高速火箭 让我们的时间慢下来
while the rest of the world moves on.
而其他一切照常运行
We have a vested interest in these kinds of adventures.
对于这种冒险我们有着既得的利益
The high speeds that result in time travel
能够支持时间旅行的高速度
are also our only way of smashing a time barrier
同时也是打破阻止我们
that keeps us from traveling to the stars.
进行星际旅行的障碍的唯一方法
Because the distances are so huge.
因为距离是如此的远
We would really like to be able to traverse giant distances in a short
我们当然希望能够以人类的时间量程
amount of time in order to explore the universe on a human time scale.
短时间内横越很遥远的距离去探索宇宙