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寻找反物质

The Search for Antimatter

反物质!你应该听说过它
Antimatter! You’ve probably heard of it.
你可能还不知道它是什么
You probably have no idea what it is.
但是不要着急!世界上最聪明的人
But don’t worry! The brightest minds in the world
刚开始理解
On the beginning to understand
它是什么 世界怎么运作
what it is and how world works
它们做了什么时 只要“哇”就够了
what they do. Just wow!
反物质很大程度上听起来像
Antimatter is pretty much what it sounds like
物质的反面
Matter’s alter ego.
正如我们所知道的 每个组成物质的粒子
Every particle that makes up matter
比如电子和质子 有对应的“双胞胎”粒子
as we know like electrons and protons has a twin.
它们恰好有相同的质量 但是带有相反的电荷
with exactly the same mass but the opposite electric charge.
这些就是反物质
these are antiparticles.
比如一个正电子 就如同一个电子一样
A positron, for example, is just like a electron
但是带有一个单位正电荷
but has a positive charge;
一个反质子就如同一个质子一样
and an antiproton is just like a protron
但是带有一个单位负电荷
but has a negative charge.
当一个电子与正电子相遇 或者一个质子与反质子相遇
And when an electron and a positron or a proton and an antiproton meet
它们将会湮灭
they annihilate.
这并不是意味着它们仅仅只是消失
That doesn’t mean that they just disappear.
宇宙中没有任何物质会永远消失
Nothing in the universe ever disappears.
这就是质量守恒定律
That’s the law of conservation of mass.
它们只是转变成了其它物质
They just turned into something else.
在这种情况下 比如电子和正电子相遇
In the case, the electron and positron, for example
它们湮灭成两个光子
they formed two photons
光子是静止质量为零的粒子 是电磁辐射的载体
massless virtual particles that can radiate electromagnetic force.
因此你可以想到为什么物理学家如此着迷于反物质了
So you can see maybe why physicists are so fascinating with antimatter.
因为物理法则对于反物质同样适用
Because the laws of physics are exactly the same for antimatter
就像它们适用于物质一样
as they are for matter.
你知道的有关宇宙起源的理论
And theories about the original universe you know
大爆炸学说预言了物质与反物质
BigBang stuff predicted that matter and antimatter
应该是等量产生的
should have been produced in euqual quantities.
这就导致了一些严重问题如:
So that leads to some big questions like:
为什么我们看见的每一样东西都是由物质组成?
Why is everything we see only made of matter?
等量的物质
Wouldn’t equal amount of matter
与反物质不是应该互相湮灭么?
and antimatter just annihilate each other?
为什么我们竟然还存在?
And why do we even exist?
为了得到答案 物理学家瞄向了中微子——
To get some answers, physicists look at neutrinos,
在原子核反应中射出的基础粒子
fundamental particles emitted during nuclear reactions.
它们很小 比电子还小
They are tiny, way tinier than electrons
没有质量和电荷
with barely any mass and no electromagnetic charge.
所以它们很难和其它东西相互作用
So they hardly interact with anything,
但是虽然时间很短暂 它们依然能被检测到
but they can be observed even if very briefly.
可以观测到它们与对应反物质的异同
And observing how they are like and unlike their antiparticles
这可以帮助我们了解宇宙的本质
could help us understand the very nature of the universe.
看!有三味中微子:
See! there are three different kinds of flavors of neutrinos:
电子中微子 τ中微子 μ中微子
electron neutrinos, tau neutrinos and muon neutrinos.
它们都是电中性的
They’re all electrically neutral
也有各自的反中微子
and have their own antineutrino alter egos.
如果你曾经看过我讲物理的四种基本相互作用力 应该知道
Now if you’ve seen me talk about the 4 fundamental forces of physics and you should.
味是物理学家
You know that flavors are just cute ways
用来描述粒子存在于各种状态的有趣方式
for physicists to have a describing the various states that a particle can exist in
在此例中 味是振荡不同的基本状态
In this case, flavors are basically different states of oscillation.
但是这些状态是不稳定的
But these states are not stable?
对 它并不是 当它们一次又一次飞过宇宙的时候
No no. Neutrinos can oscillate into different flavors
中微子可以在不同味之间振荡
over and over again as they fly through the universe.
所以物理学家设法了解的是
So physicists are trying to learn is
中微子和反中微子改变味有多快
how fast neutrinos and their antineutrinos change flavor.
这仅是从一方面来了解粒子和物质
It’s just one way of understanding how particles and matter
与它们的反物质的异同
may be similar to and different from their antiparticles.
如果证实它们不仅是彼此的镜像
If it turns out that they are not just mirror-images of each other
而且在一些基础的特征上有不同
but instead differing in some fundamental properties,
那就可以解释为什么宏观宇宙
that could explain why the observable universe
似乎是如此的不对称
seems so weirdly asymmetrical,
为什么物质是占绝对优势
why matter is so totally dominant
而反物质几乎不存在
while antimatter is almost non-existent.
我们在哪儿可以找到中微子和它们的反中微子呢?
So where we find these neutrinos and their antineutrinos?
当然 得出现一个原子核反应
Streaming out of a nuclear reactor of course.
在中国广东省的大亚湾核反应堆中
At the Daya Bay nuclear reactor in China’s GuangDong province,
物理学家正在追踪电子中微子
physicists are tracking electron flavor neutrinos
研究它们改变味有多快
to see how quickly they change flavors.
由于反中微子没有电荷
Since antineutrinos have no charge
只有很小的质量
and only a miniscule mass,
它们一般就像光速幽灵一样穿透任何事物
they normally pass right through everything like light-speed ghosts.
因此为了能与一种物质相互作用
So to have any hope of interacting with one,
物理学家使用了大量的
physicists put enormous tanks of mineral oils
与重金属元素钆相结合的矿物油
combined with the heavy element gold gadolinoum,
置于大亚湾附近的山下的窑洞中
in the cave under a mountain near Daya Bay.
成千上万不同味的反中微子
Thousands of antineutrinos of different flavors
每天通过窑洞
pass through the cave everyday.
偶尔 一个反电子中微子
And every so often, an electron antineutrino
通过并且击打油中的质子
passes through and hits a proton in the oil
开始一个反应链
which starts a chain reaction.
碰撞首先生成一个中子然后生成一个正电子
The collision first forms a neutron and then a positron.
正电子马上找到一个电子
The positron then immediately finds a electron,
这两个湮灭时产生光子的微小闪光
the two annihilate making a tiny flash light of photon.
矿物油放大了闪光
The mineral oil magnifies the flash
使之能被光子探测器获得
which is picked up by photon detectors.
与此同时 几公里之外的物理学家
At the same time, physicists a couple of kilometers away
在测量通过他们检测器的反电子中微子的数量
are measuring the amount of electron flavor antineutrino that are passing through their detectors.
他们发现被检测到的较远的反中微子少于
What they’ve found is that fewer of these antineutrinos are being detected
刚好在反应堆下方发现的反中微子
farther away than our found right beneath the reactor.
这两种数量之间的不同恰好告诉我们
The difference between these two amounts tells us that exactly
反中微子振成不同的味有多快
how fast the antineutrinos are oscillating into different flavors.
所以保罗狄拉克关于这方面的理论与为什么我们存在有关
So what in the name of Paul Dirac goes to this have to do with why we exist.
物理学家只能获得很少的数据
While with the little more data physicist will be able to
来比较各种中微子与反中微子
compare how fast all kinds of neutrinos and antineutrinos
在不同味间振荡有多快
are oscillating between flavors.
如果那些比率不同
And if those rates are different,
就会说明中微子与反中微子
it’ll show the neutrinos and the antineutrinos
不是彼此的精确镜像
aren’t exact mirror-images of each other.
了解它们的差异将会给我们一个关于宇宙为何更喜欢物质
And our understanding how they differ will give us a clue
而非反物质 以及我们为何存在
as to why the universe seems to favor matter over antimatter
的线索
and why we exist.
感谢观看这期的《科普脱口秀》
Thank you for watching this episode of SciShow.
如果你对我们有什么建议 评论 想法 问题
If you have any suggestions or comments or ideas or questions for us
可以在脸书和推特的评论区下留言
please leave them in the comments blow on Facebook or Twitter.
如果你想和我们一起了解世界
And if you wanna keep things smarter with us,
你可以访问和订阅Youtube网站的科普脱口秀
you can go to youtube.com/scishow, and subscribe.

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译制信息
视频概述

在量子力学的基础上对反物质能有一个初步了解,科普文

听录译者

Zero

翻译译者

【MED】Star

审核员

审核团EM

视频来源

https://www.youtube.com/watch?v=lFnsEHSz5bs

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