与摩根·弗里曼一起穿越虫洞（2010）

Through The Wormhole With Morgan Freeman S01E08

Part 4 April 19, 2021, 2:25 p.m.

所有我们已知的普通粒子
that all the ordinary particles that we know about
都有这种类型的镜像
have this sort of a mirror image,
宇宙中存在这类粒子
that there's this extra set of particles
藏身于黑暗之中
that is in the dark sector
与普通物质毫无干涉
that don't interact in any way with the ordinary material
只是发生很微弱的引力作用
except through the force of gravity, which is very weak.
科学家们给这些
Scientists have another name
暗物质粒子另起了个名字
for these dark-matter particles --
微交互作用质粒子
weakly interacting massive particles,
缩写为“wimps”（字面意思“懦弱者”）
"wimps" for short.
懦弱者们几乎不与普通物质发生作用
Wimps hardly ever interact with atoms of normal matter,
所以，俘获和研究它们是一项很难的工作
so capturing and studying them is really hard.
由于这个世界到处是普通物质粒子
And since the world is full of particles of regular matter,
很容易误捕到普通粒子
it's all too easy to end up snagging them by mistake
而让懦弱者们溜之大吉
and letting the wimps get away.
丹·鲍尔发现了寻找懦弱者的完美场所
Dan Bauer has found the perfect place to hunt for wimps --
在明尼苏达一个半英里深的废弃铁矿中
down an abandoned Minnesota iron mine half a mile underground.
我们现在在地下前进
We're now heading down underground
进入苏丹地下实验室
into the Soudan Underground Laboratory.
大概需要3分钟的旅程
It'll be about a 3-minute trip down.
1960年之前
This is the same way the miners used to go down before 1960
矿工们也是这样下井的
to do the iron mining.
大概有2341英尺深
It's about 2,341 feet underground,
也就是大概半英里
or about half a mile.
你恐怕不会想到在这里研究物理学
It's not the first place you'd think of to do physics,
但是，另一方面我们来这儿是有原因的
but, on the other hand, we're down here for a reason.
在这里能够避免来自空间的粒子干扰
We're down here to avoid the particles coming from space --
也就是那些宇宙射线粒子
the so-called cosmic-ray particles.
我们到了27层
We've arrived at level 27.
你也许认为半英里厚的岩床
You'd think half a mile of bedrock
也许会足够深能够阻挡住背景噪声
would be enough of a shield from background noise
寻找懦弱者的工作就会是小事一桩了
to make wimp-hunting a cinch...
但是，非也
But it's not.
懦弱者探测器
The wimp detectors are buried
埋设在几英尺厚的
inside several more feet of solid metal
金属和重塑料护盾
and heavy plastic shielding.
穿过岩石的洞穴
Throughout the rock of the cavern,
穿过我们周围的材料甚至我们本身
the materials around us, even in us,
仍有少量的辐射粒子
there are small amounts of radioactivity.
这些粒子如果它们进入我们的检测器
Those particles, if they got to our detectors,
那就是巨大的背景
would be a huge background
这样我们就无法看到懦弱者了
such that we would never be able to see wimps.
而且，这个护盾
And this shield
也在阻挡这些粒子使之无法到达探测器
prevents those particles from reaching the detectors
因为我们要找的是懦弱者
because we're trying to find wimps, not background particles.
在护盾内部
Inside the shield
是一堆18个冰球大小的
is a stack of 18 hockey-puck-sized crystals
实心锗晶体管
of solid germanium.
它们被设计用来检测如果有懦弱者进入
They're designed to pick up the faintest of vibrations
这些锗原子时产生的最微弱变化
if and when a wimp bumps into one of the germanium atoms.
为了达到此目的
To have a chance of doing that,
它们必须非常纯净，非常冷
they have to be ultrapure and ultracold.
这是我们锗晶体的模型
This is our model of a germanium crystal.
这些网球代表了晶体里的锗原子
These tennis balls represent the germanium atoms in the crystal.
在室温条件下
And at room temperature,
这些原子彼此之间
what's happening is that all of these atoms are moving
相对运动
relative to one another.
这就是我们所知的热运动
This is what we know as heat.
如果你将一个懦弱者放入晶体，会发生什么？
What would happen if you tossed a wimp into this crystal?
你几乎不会注意到变化
You wouldn't even notice the difference,
因为晶体本身变化就很剧烈
because the crystal is vibrating so much.
然而，如果将晶体冷却到很接近绝对零度的程度
However, if I cool this crystal down to very near absolute zero
原子的热运动就几乎停止了
so that the motion of the atoms stops,
那么，如果有懦弱者进来
then if I toss our wimp into the crystal,
我就看到晶体的变化
I see the vibration of the crystal,
这就是我们要找的信♥号♥♥
and that's the signal we're looking for.
寻找这些
Looking for particles
几乎不与普通物质发生作用的粒子
that hardly ever interact with normal matter
没有耐心的人可干不了这个活儿
is not a job for the impatient.
每秒钟，都有几千万的懦弱者穿过我们
There are millions of wimps passing through us every second.
由于他们交互作用很微弱
And because they're weakly interacting,
它们仅仅是
they do exactly that --
穿过我们，继续赶路
they pass right through us and just go on their way.
它们穿过整个地球
They pass through the entire Earth and go on their way.
我们希望每年有那么一两个粒子
We maybe expect one or two of these
进入我们的探测器产生作用
to interact in our detectors per year.
难以置信的低概率
So, incredibly low rate.
为了避免错误
To help prevent false positives,
数据记录在一个上了封条的
the data is blindly collected in a sealed box
盒子中的计算机硬盘上
on the hard drive of a computer.
一年之中，研究组中的任何人都
No one on the team is allowed to search it for wimp signals
不能搜索计算机上的信♥号♥♥
for an entire year.
他们就只能干瞪眼祈求好运
And then they look and hope.
2007年，我们最后一次打开盒子，啥子都没有
In 2007, when we last opened the box and found nothing,
当然会有一点失望
it was certainly a bit disappointing
因为我们的实验已经搞了一年了
because we had been running the experiment for a year.
但是，为了建立这个实验我们花了大概7年
But it had taken us almost seven years to build the experiment,
所以如果在这点上发现什么东西，那就太棒了
and so it would have been nice to find something at that point.
但是，花了7年时光和几千万美元
But after seven years and tens of millions of dollars,
丹和他的研究团队懦弱者抓捕队
Dan and his team of wimp catchers
不会放弃
were not about to give up.
在2009年底
And in late 2009,
他们打开盒子取出另外一整年的数据
they opened the box on another entire year's worth of data.
你在这个区域看到的
What you see in this region
应该是背景辐射
is where the background radiation would be.
有一些我们不感兴趣的事件
These are events we're not interested in.
我们知道那不是懦弱者
We know that they're not wimps.
在这个区域
In this area,
在红色边缘，绿线之上
bordered by the magenta and above this green line,
是我们应该发现懦弱者的地方
is where we should see wimps.
如果这些是懦弱者候选人
If any of these are wimp candidates,
它们会在我们打开盒子时变红
then they will turn red when we open the box.
所以，我们仅仅点击过去
So, let's just click through.
探测器上这个区域没有任何红点
This detector doesn't have any red dots in that area,
所以没有懦弱者候选人
so there are no wimp candidates.
这个和这个都是如此
Same with this one and this one.
啊，瞧瞧这儿
Ah, but look here --
这里真的显示了一个
we do have one that appears right here
就在我们希望懦弱者显示的区域
in the region that we would expect a wimp to appear.
这儿没有，这儿没有
Nothing here. Nothing here.
嗷！但是看看这里
Oh! But look right down here.
在这个区域里，有一点
We have one that just made it into the region
就在我们认为的懦弱者区域
that we think is the wimp region.
两个事件一年每天24小时的监测
Two events, two possible wimp impacts
两个可能的懦弱者碰撞结果
in one year of 24-hour-a-day detecting.
史上首次我们可能抓到了
For the first time, we may have actually trapped
神秘暗物质的尾巴
pieces of this elusive Dark Matter.
这可能是在了解暗物质本质路上的
This could be a giant leap
巨大飞跃
toward understanding what Dark Matter really is.
但是丹并不是100%确定
But Dan's not 100% sure
他看到的是不是懦弱者
that what he has are even wimps at all.
搜寻还要继续
So the search must go on.
很令人激动
It's exciting,
但作为科学家激动之余必须保持淡定
but you have to temper that excitement as a scientist
要意识到你还没有证明它
and realize that you haven't proven it yet.
如果我们下一步能看到好几个懦弱者
If we see half a dozen wimps, say, in this next run,
我们就能决定性的说
what we will be able to say is, definitively,
有暗物质跑到了苏丹下面来
there is Dark Matter getting down to this level of Soudan,
这意味着地球被暗物质包围
which means that Earth is surrounded by Dark Matter
银河系中存在暗物质
and the Milky Way has Dark Matter.