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Neutrinos are tiny, almost weightless particles
微中子是个很小、几乎无质量的粒子
that only interact via gravity and nuclear decay.
而且只会与重力和核衰变产生反应
Because they don't interact electromagnetically, that is, with light,
因为他们不和电磁产生作用 也就是光
they literally can't be seen!
所以它们没办法被看见
In fact, detecting a neutrino is kind of like trying to catch a bullet with a butterfly net
事实上，要侦测到微中子和试着用蝴蝶网网到子弹一样困难
– a beam of neutrinos will travel through lead for two years before it stops.
一束中微子将在铅中穿行两年，然后停止。
(in comparison, radiation from nuclear fallout can be blocked by about ten cm of lead)
相较之下，核辐射微尘只能在铅里面行进10厘米
So how do you detect a neutrino?
所以要如何侦测到微中子呢？
One common way is to fill a big tank with water:
一个普遍的方法就是 需要一个装满水的巨无霸水缸：
we know light slows down through water,
我们知道光在水中会减速
and if a neutrino with enough energy happens to knock into an electron,
所以一个有能量的微中子碰巧地撞到了一个电子
the electron will zip through the water faster than the light does!
那个电子会以比光快的速度下在水中电过去
When this happens, the electron gives off a weak glow called Cherenkov Radiation
当这发生时，电子会产生一个很弱的光辉叫做“契忍可夫辐射”
- it's kind of like a sonic boom for light,
它像是个用光产生出来的音爆，
and it allows us to detect the neutrino.
所以我们就用这个来侦测微中子
The biggest neutrino detector in the world is a balloon over the south pole
世界上最大的微中子侦测器是一个在南极的气球
that actually uses the whole antarctic ice sheet as its tank of water!
而且它是用整个南极冰山来当大水缸来用的
Neutrinos also tell us that the universe is not the same as its mirror image.
微中子也告诉我们宇宙中不是所有东西都有对称的。
If you switch left with right, clockwise with counterclockwise,
如果你把左换成右、顺时针换成逆时针、
almost all of physics, like gravity, electromagnetism, and the strong nuclear force, is unchanged.
在物理里面，像重力、电磁力、以及强核力，都不会改变。
However, the weird thing about neutrinos is that
微中子有个很怪的地方是
in physics terms, they're all left-handed
在物理里，它们都是“左撇子”
- their mirror image doesn't exist!
它们的对称不存在！
So neutrinos are the vampires of physics.
所以微中子是物理界里的吸血鬼
