BBC.地平线.2012.宇宙何其大

Where gravity pulls -
而暗能量则全部推开
dark energy pushes.
你无法看到这种东西
You don't see this stuff.
也不能直接看到它是怎样起作用
You don't see it doing anything, directly.
基本上这有点像只会做一件事
Basically, it's sort of this one hit wonder,
它只有一种作用 就是造成反引力
that just does one thing, it causes an anti-gravity force.
我们对其没有其他的感觉
We don't have any other handle on it.
暗能量是暗物质的对立面
Dark energy is dark matter's dark adversary.
是整个宇宙的阴影
A shadow on the entire universe.
星系里面存在暗能量
There's dark energy in the galaxy.
地球上也存在暗能量
There's dark energy, here on Earth.
现在就有暗能量正穿过我们
There's dark energy passing through us right now.
我们体内充满了这种暗能量
We're filled with this dark energy.
我们看不见它 也感觉不到它
We don't see it - we don't feel it.
但是它无处不在
But it's everywhere.
在宇宙之图上 这是必然存在的一部分
It's kind of just a uniform colouration to our map.
宇宙的73%都是暗能量
73% of the universe is dark energy,
但是你永远不会知道
but you'd never know.
在日常生活中 这种东西很难发现
In everyday life, this stuff is just hard to detect.
现在 在我的两根手指之间
Now, it's true that between my two fingers,
此刻就存在着一种反引力
there's an anti-gravity force, right now.
但是这种反引力非常小
But that anti-gravity force is so incredibly minuscule,
小到我注意不到
that I'll never ever notice it.
只有在尺度很大的时候
It's only when you get to really large scales,
你才能意识到这种力的作用
that you really see the affect of this stuff.
如果我将自己的手指 放在宇宙的两端
If I could move my fingers, all the way across the universe,
那它们就能感受到这种暗能量的作用
then they'd feel this tremendous push apart,
这种巨大的推力
due to this dark energy.
站在整个宇宙的角度来看
In the really big scheme of things,
暗物质的抵抗毫无作用
dark matter is fighting a losing battle...
因为它们的量有限
because there's only so much of it to go round.
如果空间继续膨胀
If you add more space,
如果给这些暗物质更多的地方
if you give more place for those little pieces of matter to be,
它们的密度就会降低
then, the density of them goes down.
这样它们就会因为被稀释而显得更少
You just see less of it - it gets diluted.
随着宇宙的膨胀 暗物质密度降低
As the universe expands, dark matter thins out
逐渐无法再与暗能量抗衡
until it can no longer compete with dark energy.
这种暗能量有一个重要特性
The really crucial thing about how this dark energy behaves,
它不会被稀释
is that it doesn't dilute.
当宇宙变得像现在的两倍大时
When the universe doubles in size,
暗能量也会变成现在的两倍
you've got twice as much dark energy.
宇宙变大四倍时
You make it four times as big,
暗能量也会变大四倍
you've just got four times as much dark energy.
以宇宙这等规模
Once you get to this cosmological scale,
即可能达到的最大尺度来看
the biggest possible scale,
这就成了世间最大的竞技
it becomes the biggest game in town.
暗能量成为了头号♥选手
It becomes the prime player.
暗能量相当重要
Dark energy is on the map.
但是宇宙学家们却一直无法作出解释
But cosmologists can't explain it.
这令人失望还是兴奋 我认为是兴奋
Depressing, or exciting? I think it's exciting.
作为一名制图师 这事很奇怪
As a map maker, this is a strange thing.
我们绘制了星图 发现了这块新大♥陆♥
We go out, we make this map, we discover this land,
虽然已经绘制成功 但我们还不知道它是什么
we've mapped it out, and we still don't know what it is.
我很喜欢这样
I love that.
整个可观测宇宙都充满了暗能量
The entire observable universe is saturated in dark energy.
但是宇宙最远的边缘还有最后一组线索
But there's one final set of clues to be found
有待发现
on its furthest edge.
而且还可能包含了宇宙之外的秘密
And it may contain the secrets to the universe beyond.
我们正在开拓不可能涉足的领域
We're heading off the map into impossible territory.
可观测宇宙的边缘
The edge of the observable universe
是我们的望远镜能看到的最远距离
is the furthest horizon our telescopes can see.
但是对于像肖恩·卡罗尔这样的宇宙学家
But for cosmologists like Sean Carroll,
这是远远不够的
that's not enough.
他想知道整个宇宙的大小
He wants to know the size of the whole universe.
我认为可以考虑我们目前不能
I definitely think it's OK to think about parts of the universe
或者永远不能观察到的那部分宇宙
that we can't observe and can never observe.
对于理解宇宙的可见部分
We've done a very good job at understanding
我们已经取得了很好的成绩
what the universe looks like in that visible portion.
所以现在我们的想象力更为发散
So now when our imaginations roam,
肖恩·卡罗尔博士
加州理工学院
常常会思考可见区域以外的宇宙
they often sneak outside the visible portion to ask
在我们视线范围外宇宙会是什么样的
what might the universe look like beyond our visible horizon.
我们看不见的宇宙
The universe that we can't see -
现在正是理论学家的研究领域
that's the playground for theorists now.
但是如果我们看不到余下的宇宙
But if we can't see the rest of the universe,
我们又怎么能知道它有多大呢
how can we figure out how big it is?
对扬娜·莱文来说
For Janna Levin,
这和计算地球的大小
it's a similar task to working out the shape
是相似的
and size of the earth.
但是有一点不同
But there's a catch.
我们知道自己能离开地球
We know we could step far from the Earth,
就像宇航员那样
as an astronaut has.
我们从外部俯瞰得知
We can look down on it
地球是一个球体 表面是曲面
and see from the outside that it was a sphere and it was curved.
但你无法置身宇宙之外
You can't step outside of the universe.
你得在宇宙内部完成所有研究
You have to do everything from inside of space.
怎样才能在不离开地球的前提下
Without leaving the earth, how do you know it's round,
知道地球是圆的 因而面♥积♥有限
and therefore has finite size?
它也可能是个平面
It could be completely flat,
向四面八方无限延展
and stretch to infinity in all directions.
用简单的数学知识就能得出结论
One way is to use a simple piece of mathematics.
你只需画一个三角形
All you have to do is draw a triangle.
如果只是在海滩上画一个很小的三角
If you're drawing a small enough triangle on the beach,
你就不会注意到地球表面的曲率
you won't notice the curvature of the earth.
看上去就是个正常的三角形
It will look like a normal triangle,
你画出的线条会很直
you'll be able to draw the lines pretty straight
三个内角之和
and the interior angles
似乎是180度没错
will look like they add up to 180 degrees,
就像你在平面上画出的三角形一样
it will look like the triangle you draw on a flat sheet of paper.
但这并不是一个正常的三角形
But this isn't a normal triangle,
因为地球表面呈曲面
because the earth's surface is curved.
只是弯曲弧度太细微
It's just so subtle,
三角形的边看上去还是直的
that the sides of the triangles still look straight.
要在海滩上画出一个
It would probably be a challenge
大到足够体现地球曲率的三角形
on the beach to draw it big enough
可能的确是个挑战
that you would be able to notice the curvature of the earth.
让曲率显而易见的关键在于
The key is to make the curvature more obvious -
三角形要足够大
by drawing the biggest triangle you can.
如果我画一个大三角形 始于北极
If I draw a triangle big enough that it comes from the North Pole
南下一路横贯北美洲
and it wraps all the way around North America,
这样就能明显看出
now it's very obvious
三内角之和大于180度
that those angles are bigger than 180 degrees
而且三角形的边并不是直线
and that the sides of the triangle are not straight lines.
这样 不用离开地球
So, we can show the earth is curved
我们也能证明地球是球体 因而面♥积♥有限
and therefore has finite size without leaving it.
要探究宇宙的形状和大小
And we can find out the shape and size of the universe
此方法同样适用
in exactly the same way -
我们要寻找光线三角
by looking for triangles of light.
如果空间是平的 光线沿直线传播
Light will travel in a straight line if the space is flat,
如果空间弯曲 光传播时也会跟着呈弧线
and light itself will travel in an arc if the space is curved.
这种弯曲微乎其微
These curves are going to be so subtle,
甚至小于地球本身的曲率
more subtle than the curvature of the earth.
我们要尽最大的可能回溯历史
We really have to look back as far as we possibly can.
探究宇宙中最古老的痕迹
And that means the oldest relic we have in the universe.
也就是说要寻找诸如
So that means looking at things
宇宙大爆♥炸♥残留光线之类的东西
like the light left over from the Big Bang.
早期宇宙是一颗高密度的火球
The early universe was a hot, dense fireball.
冷却过程中 可观测宇宙的边缘
When it cooled, a pattern of light emerged
某种模式的光出现了
at what is now the edge of the observable universe.
宇宙微波背景简称CMB 是散布于宇宙空间的微波辐射
其存在证实了自大爆♥炸♥之后 宇宙在不断冷却
这就是宇宙微波背景