未登录,请登录后再发表信息
最新评论 (0)
播放视频

如何区分物质与反物质

How to Tell Matter From Antimatter | CP Violation & The Ozma Problem

Most everyday phenomena happen equivalently in a mirror as they do normally.
大多数日常现象的镜像与实际是相同的
at least, from a physics perspective.
至少在物理学上如此
Unlike when you play a video backwards in time
不同于倒着播放视频
(where it’s pretty obvious that something weird’s going on)
虽然倒着放 看着就很奇怪
when compared with a normal video,
与正常的视频相比
motion in a mirrored video still looks totally physically normal
镜像视频中的运动看起来完全正常
–just mirrored.
——只是镜像的而已
In fact, without outside context,
实际上 要是没有参照
there’s no way to tell which was the original
根本无法分辨哪个是原视频
and which was mirrored.
哪个是镜像视频
Which’s why horizontally flopped shots are used in movies all the time.
所以电影里经常用到水平翻转镜头
In fact, as far as we know,
事实上 就我们所知
everything in the universe governed by electromagnetism
宇宙中由电磁力
and gravity and the strong nuclear force
引力和强互作用力掌控的一切
behaves this way
都是如此
if you set up two experiments that are mirror images one another,
如果你以互为镜像的方式做两个实验
they’ll produce results that look like the mirror images of each other.
就会出现两个互为镜像的结果
Which presents a problem
那就会有个问题
if we ever need to communicate with aliens from afar:
如果我们需要和遥远的外星人交流:
if all physics is mirror-symmetric,
要是所有物理现象都镜像对称
that would mean left handed and right handed are relative
那就说明左边和右边是相对的
just like up and down and forward and back
就像上下和前后一样
so if we were communicating with aliens
所以如果我们和外星人交流
and didn’t have any shared reference objects,
且没有共同参照物时
we’d we have no way of explaining
就不能用物理解释
what we mean by left-handed and right-handed using physics.
我们所谓的左边和右边是什么
This Left/Right ambiguity is called “the Ozma Problem”.
这种左右不确定性被称为“奥兹玛问题”
And the distinction between left and right is important,
区分左和右非常重要
because earth-based life
因为地球上的生命
mostly relies on sugars with right-handed symmetry
大多都需要右旋对称的糖
and amino acids with left-handed symmetry
和左旋对称的氨基酸
This isn’t a physics constraint-
这并不是物理约束
– it’s easily been the other way around –
反过来也有可能
– but the point is, the molecules in our food and our bodies
但问题在于 食物以及身体中的分子
do have a specific orientation,
存在一个特定的方向
so not knowing left from right could impair intergalactic culinary relations.
无法区分左右可能会影响到跨星系的饮食
However, there is a solution:
但是存在一种解决办法:
the weak nuclear force which governs the decay of subatomic particles
弱核力能控制亚原子衰变
doesn’t always play nicely when mirrored.
但它在镜像时并不规矩
For example, when uranium nuclei beta decay
例如 当铀原子核β衰变时
they emit mostly electrons spinning like left-handed corkscrews,
放射出的电子大多向左螺旋
but if you perform the mirror-image experiment ,using a mirror-image uranium nucleus,
但如果用镜像的铀核做镜像实验
the nucleus still emits electrons spinning like left-handed corkscrews,
原子核放射的电子依然向左螺旋
rather than right-handed, as they would in a mirror.
而不会像在镜子里那样向右旋
It turns out that in our universe,
这说明在宇宙中
the mirror-image of a physical process
镜像的物理过程
doesn’t always result in the mirror image of the outcome-
不一定会产生镜像的结果
– uranium always decays more into
——不管你怎么观察
left-handed electrons, no matter how you look at it.
铀都更倾向于衰变成左旋电子
So we’d tell the aliens
所以我们跟外星人说
“you know how electrons spin when uranium decays?
“你知道铀衰变时电子怎么旋转吗?
That direction is what we call ‘left’”.
那个方向我们称为左”
Which would solve the Ozma problem –
这样就能解决奥兹玛问题
except, our universe has a next level Ozma Problem of it’s sleeve.
此外 宇宙还有一个更深层的奥兹玛问题
Because what if the distant aliens were made entirely of antimatter?
如果遥远的外星人由反物质构成呢?
I mean, in principle they could be and we wouldn’t know.
理论上确实有可能 但我们不知道
Antimatter interacting with itself
反物质与自身相互作用
behaves exactly like matter interacting with itself:
跟物质与自身相互作用是一样的:
antihydrogen has the same atomic spectrum as hydrogen,
反氢原子与氢原子的原子光谱相同
and antimatter–you looks and exactly like matter-you –
反物质的你和正物质的你也一样
-until it interacts with matter.
直到正反物质相互作用
And here’s the problem: while the matter version of a uranium nucleus,
那么问题来了:无论是不是镜像
always decays into left-handed electrons whether it’s in a mirror or not,
正物质的铀核总是衰变为左旋电子
the anti-matter version always decays into right-handed anti-electrons,
而反物质的铀核总是衰变为右旋的反电子
whether it’s in a mirror or not.
不管是不是镜像
So if we told the aliens
所以如果对外星人说
“look at the beta decay of the nucleus with atomic weight 239
“看原子量239的原子核的β衰变
– that’s always the orientation we call left-handed”,
那就是我们所说的左边”
that would be wrong:
那就错了:
for aliens made of antimatter, it’d in fact be the right handed.
对反物质外星人来说 这其实是右边
And you definitely don’t wanna shake either hand of aliens made of antimatter.
你最好也不要和反物质外星人握手
So how can you figure out, from far,
那么如何才能知道
whether or not a distant alien is made of antimatter?
遥远的外星人是否由反物质构成?
This is the Ozma problem, level 2.
这就是第二层的奥兹玛问题
Essentially, antimatter’s another kind of mirror we can hold up the universe,
本质上 反物质是反映宇宙的另一面镜子
which combined with the possibility of regular mirroring
加上普通镜像效应的可能
means we can’t use beta decay to define left vs right.
导致我们不再能用β衰变来定义左和右
But luckily, there’s a next level solution,
所幸 还有一个绝妙的方法
again thanks to the weak nuclear force.
又一次 多亏了弱核力
Enter the Kaon, a fast-decaying subatomic particle.
K介子 一种快速衰变亚原子粒子
Whether they’re mirrored or not,
无论它们是否是镜像
around 20.3% of the time Kaons decay into right-handed anti-electrons,
都会有约20.3%的k介子衰变为右旋反电子
while around 20.1% of the time – slightly less often –
而约20.1%的k介子(略少)
– they decay into left-handed electrons.
衰变为左旋电子
And the key’s this : if you instead take antimatter Kaons,
关键是 如果转而用反物质的k介子
whether mirrored or not,
无论是否镜像
they still decay slightly less often into left-handed electrons,
它们衰变成的左旋电子仍然略少
rather than right-handed anti-electrons as you might have expected.
而不是如你所想的右旋反电子会更少
That is, normal kaons – whether mirrored or not – and anti-kaons
也就是说无论是否镜像 正常k介子和反k介子
both decay less often into left-handed electrons.
都会衰变出较少的左旋电子
And this is how distant aliens could figure out
于是遥远的外星人就能知道
if they’re made of matter or antimatter
他们是由物质还是反物质构成的
and whether or not they’re using the same concept of “left” or”right” as we are:
无论他们左右的概念与我们是否相同
simply build a particle accelerator
只要建一个粒子加速器
and look at the decays of neutral kaon particles;
并观察中性K介子的衰变
electron-like thing that they decay into slightly less frequently
衰变出来的电子类粒子相对较少的
is made of what we call matter,
是由我们认为的正物质构成的
and it’ll be moving in what we call a left-handed way.
它会以我们所说的左旋方式运动
The universe doesn’t distinguish between left and right or matter and antimatter
宇宙无法区分左右或正反物质
for electromagnetism, for gravity, and for the strong nuclear force.
电磁力 重力和强核力也不行
But for some reason, the weak force allows us to tell difference.
但出于某种原因 弱力能帮我们区分
This video’s made with the generous support of the Heising Simons foundation
本视频由海辛·西蒙斯基金会大力支持
which also supports research into the
它也支持关于宇宙中
violation of antimatter-mirror symmetry in universe.
破坏反物质镜像对称性的研究
Processes that violate antimatter-mirror symmetry
破坏反物质镜像对称性的过程
(which is called “CP Violation”) are necessary to explain
(称为“宇称破环”)可以解释
why there’s so much more matter in universe than antimatter,
为什么宇宙中物质比反物质多得多
and while the weak nuclear force does violate that symmetry,
虽然弱核力破坏了这种对称性
it doesn’t come anywhere close to accounting for
但它并不能解释
the observed imbalance between matter and antimatter in the universe.
宇宙中观测到的物质与反物质的不平衡
So physicists around the world
所以全球的物理学家
(among them researchers supported by the Heising Simons foundation)
其中也有海辛·西蒙斯基金的赞助者
are searching for other possible processes that might break antimatter-mirror symmetry
正在寻找其他破坏反物质镜像对称性的过程
to help explain how the universe ended up made mostly of matter,
来帮助解释为什么宇宙主要由物质构成
and thus, why it was possible for us to exist.
以及我们得以存在的原因
Thanks Heising Simons!
感谢海辛•西蒙斯!

发表评论

译制信息
视频概述

通过举如何与可能是由反物质构成的外星人进行交流的例子,告诉我们区分物质反物质的方案。

听录译者

收集自网络

翻译译者

Syllab

审核员

审核员 AF

视频来源

https://www.youtube.com/watch?v=Elt0Gt9Cb6Q

相关推荐