宇宙时空之旅（2014）

Cosmos: A SpaceTime Odyssey S01E06

Part 5 April 25, 2021, 12:40 p.m.

多是从天而降的质子和电子
mostly protons and electrons that rain down from space...
穿不过探测器上面的岩石
cannot get through all that rock above us.
但物质不能拦截中微子
But matter poses no obstacle to a neutrino.
一个中微子可以穿过一百光年的钢
A neutrino could pass through 100 light-years of steel
而速度不减
without even slowing down.
中微子几乎不与物质发生作用
Neutrinos hardly interact with matter at all.
正因如此要想捕捉到一个中微子
That's why you need so much of it
需要如此多的光电倍增管
to catch even one of them.
极个别情况下
On those rare occasions when a neutrino
中微子会与普通物质碰撞
actually does collide with a particle of ordinary matter,
产生鬼魅般的环形闪光
it produces a ghostly, ring-shaped flash of light.
我们静候
We're lying in wait
一个质量几乎为零的粒子
for a particle that weighs next to nothing.
即便是微不足道的电子
Even the miniscule electron
都比中微子重百万倍
has more than a million times its mass...
来了
There!
当大麦哲伦星云的一个超新星
When the supernova in the large magellanic cloud
于1987年爆♥炸♥时
blew its top in 1987,
这里会出现这样的景象
this is what it would have looked like in here.
记住大麦哲伦星云
Now remember, the large magellanic cloud
在南半球那侧
is in our Southern hemisphere,
这些中微子不是穿过上边一公里岩石
so the neutrinos didn't come through that half-mile of rock above us,
而是穿过我们下边几千公里岩石和铁
they had to pass through the thousands of miles of rock and iron
才到达这个探测器
below us to reach this detector.
最奇妙的是这些中微子
But the coolest thing was that those neutrinos
比超新星发出的光
hit Earth three hours before
早三个小时到达地球
the light from the supernova did.
如果光速是宇宙中最快的速度
If nothing can travel faster than light,
这是怎么回事呢
how could that possibly be?
面前这颗死亡恒星在移♥动♥
This is a dead star walking.
它看似正常然而在它的深处
It may look normal, but deep within it
灾难正在蓄势
something cataclysmic is happening.
这颗蓝巨星
This blue super giant star
已从内部开始爆♥炸♥
has already begun to explode inside.
如同跳离沉船的老鼠
Like rats deserting a sinking ship,
在即将爆发的恒星中心产生的中微子
the neutrinos produced in the heart of the exploding star
在短短几秒内穿透质量巨大的恒星
race outward at near the speed of light,
以接近光速的速度向外逃散
through overlying mass in only a few seconds.
然而爆♥炸♥气体产生的冲击波
But the shock wave of the exploding gas
从恒星中心以千分之一光速
plods along from the center of the star
缓慢向外移♥动♥
at 1/1000 of the spead of light
最终到达恒星表面
until it finally reaches the star's surface,
恒星转化为1987a超新星
turning it into supernova 1987a.
爆♥炸♥传播到恒星表面
It took hours for the explosion to reach
将其彻底炸碎露出超高温核心
the surface of the star and blow it wide open
需要几个小时的时间
exposing the super hot core.
中微子在这场跑赛中占尽先机
The neutrinos had an insurmountable head start.
因此闪光比那阵中微子雨
That's why the flash of light arrived on Earth
到达地球要晚很多
so much later than the shower of neutrinos.
在任何人捕捉到宇宙中的中微子之前
Before anyone had ever snared the wild neutrino,
一位理论物理学家早就知道它的存在
it existed in the mind of a theoretical physicist.
正如查尔斯·达尔文坚信
Just as Charles Darwin knew
在马达加斯加某处
there must be an extremely long-nosed creature
一定有某种长鼻子生物在飞
flying around somewhere in Madagascar,
沃尔夫冈·泡利一位二十世纪物理学家
a 20th-century physicist named Wolfgang Pauli
迫切地寻找一种粒子
was desperately seeking a particle
用来拯救现代物理的重要基石
to rescue one of the pillars of modern physics,
即能量守恒定律
the law of the conservation of energy.
我为什么没有退缩
So why didn't I flinch?
因为物理定律
Because the laws of science differ fundamentally
与人类研究的其他领域有本质不同
from those of other human endeavors.
一个想法要想成为科学定律
In order for an idea to become a scientific law,
它必须是不可打破的
it has to unbreakable.
所以我才敢用自己这张脸
That's why I was willing to bet this face
为能量守恒定律下注
on the laws of conservation of energy.
如果你想在家模仿
Now, if you try this at home,
注意不要推这个红球
take care not to give the cannonball a push.
会增加它的能量
That's adding energy,
不然球一定会摆回来伤到你
and the ball will surely come back and do some damage.
你只需松手像这样
You just have to let it go, like this.
抬起球
By lifting the ball,
你将给它重力势能
you give it gravitational energy,
即加速下落的趋势
which is the potential to fall and accelerate.
当红球摆到最低点时
The cannonball is going fastest
它的速度最大
when it's at the bottom of its arc,
在这一刻
and at that moment,
它的所有重力势能
it's converted all of its gravitational energy
都转化成动能
to the energy of motion.
随着摆动红球将两种能量
As it swings, the cannonball is constantly exchanging
不停地相互转化
one of these two kinds of energy for the other,
但总能量不变
but the total amount of energy remains constant.
这是能量守恒定律的一个例子
That's an example of the law of conservation of energy.
一旦松手放开红球
Once the cannonball is released,
它不可能获得比初始时更多能量
it can never gain more energy than it had to begin with.
它不可能飞过来砸我的鼻梁
It has no way to fly up and break my nose.
能量的会计账簿永远收支平衡
The energy accounting books are always strictly balanced.
不存在作弊这一说
There's no such thing as cheating.
在二十世纪
So in the 20th century,
当物理学家首次精确计算出原子的能量
when physicists first calculated the energy of atoms precisely,
它们很震惊地发现
they were startled to discover
这个定律显然被打破了
an apparent violation of this law.
他们发现在一些放射性原子中
They found that in some radioactive atoms,
原子核可以自发释放电子
the nucleus can spontaneously eject an electron.
原子本身也变成了另一种元素
This transforms the atom into a different element.
物理学家们很不解
The physicists were mystified.
被释放的电子的能量
The energy of the escaped electron
加上新元素的原子能量
plus that of the new element
比之前的原子核的能量小
adds up to less than the energy in the original nucleus.
但是根据定律
But the law says,
能量不会凭空消失或产生
"Thou shall not destroy or create energy."
缺失的那部分能量去哪儿了呢
So where did the missing energy go?
在1930年
In 1930...
沃尔夫冈·泡利预测存在一种未知的粒子
Wolfgang Pauli predicted there must be an undiscovered particle,
可以补偿丢失的能量
one that makes off with the missing energy.
在那时泡利悲叹
At the time, Pauli lamented
这种幽灵般的粒子可能太小太快
that such a phantom particle might be so minute,
太善于躲藏永远无法探测
swift and evasive as to forever defy detection.
但这次他罕见地想错了
But that was a rare failure of his imagination
因为科学永远有办法更深入探究
because science is always searching for a way to go deeper still.
一代人之后
A generation later,
泡利所说的中微子首次
Pauli's neutrinos were actually detected for the first time
在核反应器的辐射中被探测到
in radiation from a nuclear reactor.
尽管艰辛自此一直能找到它们的身影
And we've been finding them, with difficulty, ever since.
如今有一些科学家
There are scientists today
想要通过研究中微子
who are trying to find a way to ride those neutrinos
探秘宇宙的诞生
all the way back to the beginning of time.
我们去看看他们追溯到多远
We'll go as far as they have gone
我们面对的是永恒之墙
to come up against the wall of forever.
我们对永恒之墙并不陌生
The wall of forever is nothing new.
我们的祖先开始想象
Our ancestors came up against it
时间的起点时就碰到了它
almost as soon as they first started imagining it.
一百万个日出前公元前十三世纪
A million dawns ago, in the 13th century BC,
埃及人为了纪念法老拉美西斯二世
the Egyptian built this temple at Abu Simbel
在阿布辛贝建造了这座神庙
to honor the Pharaoh Ramses II,
这四尊巨大雕塑都刻画了这位法老
depicted here in four colossal statues.
比强大的法老更位高权重的是
Reigning even above even this mighty king
隼头神瑞·哈拉胡提
is the falcon-headed Ra-Harakhti,
即太阳神
God of the Sun.
神庙的特殊设计
The temple was designed
限制一年中只有两天
so that the light from the rising Sun