宇宙的奇迹（2011）

are messengers from the distant past,
是遥远过去的信使
and they carry with them a story,
它们带来了一个故事
the story of the origin of the universe.
宇宙起源的故事
In order to read this story,
为了品读这个故事
to see how light can transport us to the past,
为了明白光如何能把我们带回过去
we must first understand one of its fundamental properties-
首先 我们必须理解它的一条基本性质
its speed.
它的速度
Everything in our universe has a speed limit,
宇宙中万物都有速度限制
even intangible phenomena like waves of sound and light.
即使是无形的声波和光波
These speed limits are very real physical barriers,
这些速度限制是真正的物理障碍
and they have profound consequences
它们对我们理解宇宙
for our understanding of the universe.
造成了深远的影响
Today, I'm going to try and break one of those barriers.
今天 我将尝试打破其中的一个障碍
This is a Hawker Hunter.
这是一架猎人战斗机
It was built in the 1950s.
于二十世纪五十年代制♥造♥
When breaking the sound barrier
当时打破声障
was at the very limit of our technical abilities.
是人类技术能力的极限
A sound barrier's an incredibly evocative term, you know,
声障是个非常有趣的课题
it has an almost legendary status in the history of aviation,
它在航♥空♥史上有着近乎传奇般的地位
but there's nothing fundamental about it -
但是关于它并没有什么基本原则可言
it's something that you can
用一些极聪明的工程设计
overcome with some extremely clever engineering,
便可以克服声障
and in the early days, quite a lot of courage.
在早期 这还需要很大的勇气
The reason we don't usually think
通常认为
about sound as having some kind of speed limit, a limit in speed,
声音并没有速度限制
is because it is incredibly fast
因为与我们在日常生活中习惯的事物相比
compared to the things we're used to in everyday life.
声音的速度非常之快
But today, we're going to try and break it.
但是今天 我们要尝试打破它
I'm going to try and break it,
我将坐上这台不可思议的机器
sat in this marvellous machine.
尝试打破它
On Earth, the speed of sound, depending on altitude
在地球上 根据海拔高度 声速
is around 1,200 kilometres per hour, known as Mach 1.
大约是每小时1200公里 也就是1马赫
This jet isn't designed to fly that fast in normal flight,
这架喷气式飞机在普通飞行时速度并不会这么快
but there is a way to make it travel faster than sound,
但是有种方法可以让它超过声速
and for that, we need to fly high.
为此 我们必须飞得很高
As the plane flies faster,
飞机越飞越快
it begins to catch up with its own sound.
它开始追上自己的声音
The sound waves simply can't get out of the way fast enough,
声波的速度只是不足以快到甩开飞机
so they begin to pile up at the front of the jet.
所以开始在飞机前面堆积起来
But to outrun our sound waves,
但是为了超过声波
we need to push this jet to its absolute limit.
我们得努力使这架飞机达到它的绝对极限
In just seconds, the jet smashes through the sound barrier.
数秒之内 飞机便冲破了声障
This can be heard from the ground as a sonic boom.
在地面上听起来就是一次声爆
It was a doddle, actually.
简直不费吹灰之力
Well, you know, having said that, it was inverted full throttle
在12.80公里的高空
at 42,000 feet, but it's a different definition of "Doddle".
倒挂金钩 "小菜一碟"可不是这么定义的
So this magnificent piece of engineering
这架宏伟的机械大作
is fast enough, if you just push it a little bit,
马力十足 只要稍作努力
to outrun its own sound,
它就能超过自身声音
so the sound barrier is negotiable.
所以突破声障不再遥不可及
You can smash your way through it.
你可以轻易通过
But the speed of light, the light barrier,
但光速 也就是光障
that's a very different story.
情况就截然不同了
Sound has a definite speed that we can measure,
我们能够确切测量声音的速度
but for thousands of years, the world's greatest minds
但千百年来 世上的智者们
thought that light was different,
认为光完全是另一回事
that it travelled instantaneously from object to eye.
它的传播是瞬时性的
Then, around 350 years ago,
直到大约350年前
the truth about light was revealed through a combination
凭借一人的聪明才智结合天体有规律的运行
of one man's genius and the clockwork orbits of the heavens.
光传播的真谛才得以被揭示
Ever since Galileo discovered that Jupiter had moons,
自从伽利略发现了木星的卫星
astronomers realised that you could use Jupiter and its moons
天文学家就意识到可以把木星及其卫星
as a very precise clock in the sky.
当做天空中一轮精准的时钟
So here's the Solar System, there's the Sun, there's the Earth,
假设这是太阳系 太阳在这 地球在这
here's Jupiter, and here is Jupiter's innermost moon, IO.
而那是木星 这是木星最内环的卫星IO
It was known that IO takes precisely
众所周知 IO围绕木星
42.5 hours to orbit around Jupiter,
公转一圈的时间正好是42.5小时
so if, from the Earth,
所以 从地球上看来
you see IO emerge from behind Jupiter at say,
如果IO在周二的午夜
midnight on a Tuesday,
绕过木星进入视野
then you know that it should re-emerge again
那么它应该在周四下午六点三十
at 6:30 on Thursday afternoon.
再次出现在天际
Beautiful.
精确
Now one of the men charged with making precise tables
有位天文学家致力于建立IO环绕木星
of exactly when IO should be seen to emerge from behind Jupiter
公转的准确时间表
was the Danish astronomer Ole Romer,
他是丹麦的奥尔·罗默
but he noticed something surprising.
但他发现了一丝蹊跷
See, depending on the time of year,
在一年中
IO emerged later than expected,
IO的出现时间
or earlier than expected.
总是与预期有或早或晚的偏差
Now, Romer's genius was to realise
睿智的罗默
that had nothing to do
意识到
at all with the orbit of IO around Jupiter.
这与IO环绕木星运行的轨道没有任何关系
It was to do with the orbit of the Earth around the Sun.
产生差距的原因是地球的公转
See, what Romer noticed was that
罗默注意到
when the Earth was in a position
如果地球处于
in its orbit so that it was close to Jupiter,
靠近木星的公转位置上
then IO emerged earlier than it was expected to.
IO出现的时间就比预期的早
Then, as the year passed and Earth moved around the Sun
随着四季更替 地球公转到
and got further away from Jupiter,
远离木星的位置时
Roma noticed that IO then emerged later than it was expected to.
IO出现的时间就比预期的晚
Roma realised that it takes time for light to travel from Jupiter
罗默这才发现 光从木星传至地球
to the Earth, so when the Earth is far away from Jupiter,
需要花费一定时间 所以当地球远离木星时
it takes longer for the light to travel, and therefore
传播距离大大增长
you see IO emerge from behind Jupiter later than you'd expect.
因此IO出现的时间比预期的要晚
Then, when the distance is small,
然而 当距离较短时
it takes less time for the
光传至地球
light to travel and you see IO emerge earlier
所用的时间就短
than you might expect.
IO出现的时间就会早于预期
So Romer had discovered
罗默发现
that light doesn't travel instantaneously.
光的传播不是瞬时性的
It moves through space with a finite speed.
它的速度也是有限的
This remarkable insight
拜他卓越的洞察力所赐
led to a measurement of the speed of light.
我们开始了对光速的测量
We now know that light travels
现在我们精确地知道
at precisely 299,792,458 metres per second.
光每秒传播299792458米
That means in the time that it takes for me to click my fingers,
这意味着在我打个响指的瞬间
light has travelled around the Earth seven times,
光已经绕地球七周
or that it travels ten million,
它在一年中的传播距离
million kilometres in one year,
是十万亿公里
and that's the yardstick that we use to measure the universe,
这通常被用作衡量宇宙的尺度
as ten million, because
因为一光年也就约等于
million kilometres is approximately one light year.
十万亿公里
The speed of light is the speed limit of the universe
光速是宇宙的极限速度
built into the very fabric of space and time itself.
正是它将时间和空间编织成一个整体
But because light travels at a finite speed, a light year
但因为光的传播速度有限
isn't just a measure of distance,
所以光年不只是距离尺度
it's also a measure of time.
还是一个时间尺度
The further away an object is,
天体的距离越远
the further back in time we see it.
我们所见之景就越久远
The distances that light travels on Earth are relatively short,
地球上光传播的距离相对较短
so the time it takes light to travel to our eye is imperceptible.
所以它射入人眼的时间几乎难以察觉
But when we look out to space,
但当我们放眼太空
over astronomical distances,
跨越天文距离
to the stars, planets and galaxies beyond,
瞭望遥远的恒星 行星和星系
then light's finite speed has profound consequences.
有限的光速就会产生深远的影响
This is Tanzania in eastern Africa,
这里是位于东非的坦桑尼亚
the cradle of humankind.
孕育人类的摇篮
It's here that some of our
二百五十万年前 就在此地
earliest ancestors walked 2.5 million years ago.
我们最早的祖先开始直立行走