Is time travel possible? - Colin Stuart

穿越时空有能成为现实吗? - 科林.斯图尔特

翻译人员: Alice Yu 校对人员: Hada Fong Ha Ieong

Have you ever daydreamed about traveling through time,

你曾白日梦过

穿越时空吗？

perhaps fast forward in the centuries and seeing the distant future?

或者穿越到几百年之后

及看到遥远未来？

Well, time travel is possible,

让我告诉你，穿越时空是有可能的。

and what's more, it's already been done.

而且，还有的是

它已经被实现了。

Meet Sergei Krikalev,

谢尔盖.克里卡列夫

the greatest time traveler in human history.

是人类历史上最伟大的穿越时空者。

This Russian cosmonaut holds the record

这位俄罗斯宇航员创了记录。

for the most amount of time spent orbiting our planet,

他是环绕地球

时间最久的人，

a total of 803 days, 9 hours, and 39 minutes.

总共803天9小时39分钟。

当他在太空的时候，

During his stay in space,

he time traveled into his own future

他时空穿越到自己的未来，

by 0.02 seconds.

且用了0.02秒。

Traveling at 17,500 miles an hour,

当时，他在太空时的行驶速度为每小时17500英里。

he experienced an effect known as time dilation,

他体验了一种

名为"时间膨胀"的效应。

and one day the same effect

而且，終一天 这种效应

将会让穿越时空之时间更持久

might make significant time travel to the future commonplace.

也变以家常便饭的事。

To see why moving faster through space affects passage of time,

如果想了解为什么加快在空间里的行驶速度

会影响时间流逝的速度,

we need to go back to the 1880s,

我们得回到1880年,

when two American scientists,

当时 两个美国科学家

Albert Michelson and Edward Morley,

阿尔伯特·迈克尔逊 和 爱德华·莫雷

were trying to measure the effect of the Earth's movement around the Sun

尝试衡量

地球绕太阳

on the speed of light.

对光速有什么影响。

When a beam of light was moving in the same direction as the Earth,

他们以为， 当一束光

和地球往同一个方向移动时,

光的速度会更快。

they expected the light to travel faster.

And when the Earth was moving in the opposite direction,

而且，当地球与光束作反方向移动时，

they expected it to go slower.

光的速度会减慢。

But they found something very curious.

但是结果并非如此，有趣的是

The speed of light remained the same no matter what the Earth was doing.

不管地球往哪个方向移动

光的速度并没有改变。

Two decades later, Albert Einstein was thinking

20年之后，爱因斯坦回到

about the consequences of that never-changing speed of light.

这个问题的結果上：

光速不变。

And it was his conclusions,

他的结论是：

formulated in the theory of special relativity,

他所創的“相对论”

that opened the door into the world of time travel.

开启了

穿越时空的大门。

Imagine a man named Jack,

试想 一個名為杰克的人

standing in the middle of a train carriage,

站在一辆火车卡中間

traveling at a steady speed.

在稳定状态下移动，

杰克覺无聊

Jack's bored and starts bouncing a ball up and down.

开始在地上上下拍球

What would Jill, standing on the platform, see through the window

這个时候站在月台上的吉尔

会透过窗口所看到

是什么？

as the train whistles through?

Well, between Jack dropping the ball and catching it again,

在杰克扔下球

和接著球之间

Jill would have seen him move slightly further down the track,

吉尔会看到杰克

和火车一起向前移动，

resulting in her seeing the ball follow a triangular path.

結果她看到的球

是以三角形的路线移动的。

This means Jill sees the ball travel further than Jack does

意思是，吉尔看到的球

比杰克所看到的 移动得更远

在同一个时间段里。

in the same time period.

And because speed is distance divided by time,

因为速度等于距离除以时间，

事實上 吉尔所看到球比杰克所看到的移动得更快。

Jill actually sees the ball move faster.

But what if Jack's bouncing ball is replaced with two mirrors

但是，如果我们把杰克的球

用两面镜子作代替

which bounce a beam of light between them?

而在镜子之间有一束光來回反弹。

Jack still sees the beam dropping down

杰克依然会看到光束反弹

and Jill still sees the light beam travel a longer distance,

吉尔还是会看到该光束

移动得更远，

except this time Jack and Jill cannot disagree on the speed

例外的是，这次杰克和吉尔

却会对光的速度有分歧。

because the speed of light remains the same no matter what.

這是因为光的速度

无论如何 還是 保留不变。

And if the speed is the same while the distance is different,

如果速度是一样的话，

而距离却不一样，

this means the time taken will be different as well.

那花的时间将也不一样。

Thus, time must tick at different rates for people moving relative to each other.

所以 当人们对他人相对地移动时，

时间一定以不一样的速率流逝。

Imagine that Jack and Jill have highly accurate watches

试想如果杰克和吉尔都有非常精确的手表。

that they synchronize before Jack boards the train.

他们在杰克上火车前校对好时间。

当这个实验中，杰克和吉尔会看到

During the experiment, Jack and Jill would each see

their own watch ticking normally.

自己的手表正常的走。

但是如果他们在实验结束后相遇

But if they meet up again later to compare watches,

比对彼此手表时，

less time would have elapsed on Jack's watch,

他们会发现杰克的手表会走慢一些，

balancing the fact that Jill saw the light move further.

因此解释了这事实：

吉尔看到的光移动得更远。

This idea may sound crazy,

这听上去很诡异，

but like any good scientific theory,

但是，像任何一个完好的科学理论，

it can be tested.

它是可以被测试的。

在1970年左右，

In the 1970s, scientists boarded a plane

with some super-accurate atomic clocks

科学家们 校对了一些超级准确的原子钟

that were synchronized with some others left on the ground.

一起带到飞机上去，

而数个原子钟则留在陆地上，

当飞机环球飞行之后，

After the plane had flown around the world,

他们发现飞机上的原子钟

the clocks on board showed a different time

和地球上的原子钟上显示的时间是不一样的。

from those left behind.

Of course, at the speed of trains and planes,

当然，以火车与飞机的速度，

the effect is minuscule.

对时间膨胀的影响是很微小的。

But the faster you go, the more time dilates.

但是行驶的速度越快，

时间的膨胀越多。

For astronauts orbiting the Earth for 800 days,

如果宇航员们环绕地球800天，

it starts to add up.

其影响就会明显。

But what affects humans also affects machines.

言而，影响人类的也会影响机器。

Satellites of the global positioning system

GPS的卫星

are also hurdling around the Earth

同時也环绕著地球行驶，

at thousands of miles an hour.

且速度为每小时数千英里。

So, time dilation kicks in here, too.

因此，时间在这情況也显见膨胀的。

In fact, their speed causes the atomic clocks on board

事實上，GPS卫星的行驶速度导致

飞行著的原子钟

to disagree with clocks on the ground

与地上的原子钟之間

by seven millionths of a second daily.

产生每天7百万分之一秒之差。

Left uncorrected,

如果再不做校对的话，

this would cause GPS to lose accuracy

这将会令GPS失去准确性

by a few kilometers each day.

且产生每天几公里差異 。

So, what does all this have to do with time travel

那么，这些和穿越时空

to the far, distant future?

和去遥远的未来有什么关系呢？

Well, the faster you go, the greater the effect of time dilation.

当行驶的速度越快，

时间膨胀的效应越大。

If you could travel really close

如果你行驶的速度真的能夠接近

to the speed of light, say 99.9999%,

光速的話，比方说，百分之99.9999,

on a round-trip through space

绕太空來回一圈，

for what seemed to you like ten years,

对你来说可能像过了10年，

you'd actually return to Earth

但是当你回到地球时，

around the year 9000.

将会是9000那年左右。

Who knows what you'd see when you returned?!

到那时候，谁知道你回来后会看到什么？

Humanity merged with machines,

人类与机器分不开，

extinct due to climate change or asteroid impact,

灭绝原於全球暖化

或行星之間撞击，

or inhabiting a permanent colony on Mars.

又或是人类在火星定居了。

But the trouble is,

但问题是，

要把像人一样那么重的东西，

getting heavy things like people, not to mention space ships,

莫说太空飞船了，

up to such speeds requires unimaginable amounts of energy.

移动到达接近光速般，

是需要不能想象的巨大能量。

It already takes enormous particle accelerators

龐大量的粒子加速器

like the Large Hadron Collider

如大型粒子对撞机

to accelerate tiny subatomic particles to close to light speed.

已被需要来把微小的亚原子粒子加速

到达接近光速了。

But one day, if we can develop the tools to accelerate ourselves to similar speeds,

但是终有一天，如果我们能够发明一些工具

可以让我们加速到如光速度般，

then we may regularly send time travelers

到那时候，我们可能隨時可以把穿越时空者

into the future,

送到遥远的未来，

bringing with them tales of a long, forgotten past.

还有带著我们 古老，被遺忘的故事去。