了解宇宙是如何运行的（2010）

How the Universe Works S09E08

Part 4 March 16, 2022, 8:55 a.m.

a single neutrino
一些非常令人不安的事情
told us about something
very troubling,
宇宙中最强烈的辐射源之一
one of the most intense
sources of radiation
它正指向我们
in the universe, and it was
pointing right at us.
2017年春季
Spring 2017.
南极的科学家们正在寻找
Scientists at the South Pole
are on the lookout
中微子
for neutrinos.
这些幽灵粒子非常难以探测
These ghostly particles are
extremely hard to detect.
中微子是宇宙中最大的“内向者”
Neutrinos are the biggest
introverts in the universe.
它们只是不喜欢与任何东西互动
They just don't like
interacting with anything, so if
所以如果你想探测这些东西
you want to detect
one of these things,
你需要很多东西
you need a lot of stuff.
你需要在一个点上有很多原子
You need a lot of atoms
in one spot.
因此，科学家们用大量可用的原子
So scientists built a facility
建造了一个设施
with lots of available atoms.
它被称为冰立方
It's called IceCube,
with neutrino
中微子探测器深埋在冰层下面
detectors buried deep beneath
sheets of ice.
事实证明，水是一个非常非常好的
It turns out
that water is a very,
中微子探测器
very good detector of neutrinos.
为了捕获中微子，你需要以合理的成本
To catch neutrinos,
you need to build
建立一个非常大的目标
a very large target for
a reasonable cost.
两个盒子都有大面♥积♥的冰块
Large areas of ice
checks both boxes.
所以你需要大量非常非常干净的水
So you need a lot of water
that's very, very clean.
地球上最干净的水源是什么？
What's the cleanest source
of water on the planet?
南极冰盖
The Antarctic Ice Sheet.
南极探测器“冰立方”
The Antarctic detector IceCube
直径为3280英尺（1000米）
measures 3,280 feet across.
这大约是九个足球场的长度
That's about the length of
nine football fields.
它有5000个传感器。周围的水原子
It contains 5,000 sensors,
surrounded by more water
比宇宙中恒星的数量还多
atoms than there are
stars in the universe.
2017年9月22日
September 22nd, 2017.
冰立方探测到中微子与水原子碰撞
IceCube detects a neutrino
colliding with a water atom.
当中微子撞击冰立方内部的冰原子时
When a neutrino hits an ice
atom inside of IceCube,
一个带电粒子会飞出来
a charged particle flies out,
正是这个带电粒子发出了我们可以探测到的
and it's this charged particle
that makes a signal
信♥号♥♥
we can detect.
喷射出的粒子似乎
The ejected particle
appears to fly out
飞得比光速还快
faster than the speed of light.
乍一看，这似乎违反了物理学中
At first glance, this
looks like it violates
非常非常重要的一点
something very, very important
即没有任何物体的速度能超过光速
about physics, that nothing
can travel faster than light.
但是光在穿过像空气或水这样的介质时速度会变慢
But light slows down when
traveling through a medium like
但穿过其他东西
air or water, and it is possible
或其他粒子时，也有可能在介质中
for other things,
other particles, to outrun light
跑得比光快
in a medium.
当粒子穿过冰层时
As it hurtles through the ice,
会产生一束蓝♥光♥
the particle generates a burst
of blue light called
称为切伦科夫辐射
Cherenkov radiation.
就像音爆一样
It's almost like a sonic boom.
如果你的速度超过声速
If you travel faster than
the speed of sound,
就会发生声爆，对吧？当你听到轰鸣声时
there's a boom, right?
- When you hear that boom,
你也会看到这个风锥
you also see this cone of wind.
切伦科夫辐射也是如此
It's the same thing
with Cherenkov radiation.
你会看到这个光锥
You get this cone of light.
中微子携带不同的能量
Neutrinos carry
different amounts of energy.
有些中微子，比如2017年的中微子
Some, like the 2017 neutrino,
具有相当大的冲击力
carry quite a punch,
而中微子的能量取决于它的来源
and the energy of the neutrino
depends on its source.
高能中微子来自高能事件
High-energy neutrinos come
from high-energy events,
所以我们在寻找爆♥炸♥的物质
so we're looking for stuff
blowing up.
于是我们开始寻找正在碰撞的物体
We're looking for
stuff colliding.
寻找碰撞和爆♥炸♥的物体
We're looking for stuff
colliding and blowing up.
寻找那些令人惊叹的事件
We're looking for
awesome things.
切伦科夫辐射的蓝色爆发
The blue burst
of Cherenkov radiation
给了我们一条关于中微子
gives us a clue about
the fearsome origin of
可怕源头的线索
the neutrino.
我们可以沿着蓝♥光♥的路径
We can follow the path
of that blue light,
回头看看中微子是从哪里来的
and we can look backwards to see
where the neutrino came from.
我们追踪中微子到一个
We track the neutrino to
60亿光年之外的星系
a galaxy nearly six billion
light-years away.
它的中心是宇宙中
At its heart sits one of
最强大的物体之一
the most powerful objects in
the universe,
耀变体
<即从超大质量黑洞喷射出来的喷流>
a blazar.
这个耀变体是最大的，来自一个
A blazar is the biggest,
baddest form of feeding
最糟糕的正在积极进食的超大质量黑洞
active, supermassive
black hole out there,
物质不仅仅是落入黑洞
where material isn't just
falling into the black hole,
还在其周围旋转，形成一个
it's swirling around,
creating a high-energy
高能量的吸积盘
accretion disk.
这个耀变体吸积盘正以每小时
The blazar's
accretion disk spins at millions
数百万英里的速度旋转
of miles an hour,
给气体和尘埃粒子充电
charging particles of gas
and dust.
当圆盘在黑洞周围旋转时
The disk also generates
magnetic fields
也会产生扭曲和缠绕的磁场
that twist and tangle as they
swirl around the black hole.
因为在周围有了扭曲的
Because you have
magnetic fields that are
磁场
twisted around,
它们也会产生电场
they also generate
electric fields.
电场可以使带电粒子
The electric fields can then
accelerate the charged
沿着磁场加速
particles along
the magnetic fields
从而产生大量的粒子
and thus produce
a lot of both particles
和辐射沿喷流喷射而出
and radiation
coming out along jets.
喷射流
The jets blast out
从黑洞的两极喷射而出
of the poles of the black hole.
这是宇宙所能产生的
These are the most
intense sources of radiation
最强烈的辐射源
that the cosmos can
ever produce,
它们从数十亿光年外
and they are pointed right at
us from billions of
正对着我们
light-years away.
喷射能产生强大的中微子吗？
Do the jets create
the powerful neutrinos?
这有点神秘
It's a bit of a mystery.
有一段时间，人们认为