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上帝粒子发现很久之前
Long before the God particle,
这里有类“Oh-My-God”粒子
there is the Oh-My-God particle,
作为一种宇宙射线
a cosmic ray
与曾经已知 甚至 与认为可能的粒子 比较起来 其能量要大上很多
vastly more energetic than had ever been seen or was even thought possible.
这种超大能量的宇宙射线 依旧让科学家们困惑不解
These ultra-high energy cosmic rays still perplex scientists.
这种特别的星系死亡射线 源自于何处?
Where are these extra galactic death rays coming from?
1991年10月15日 一个原子核以 99.99999999999999999999951%光速行进
On October 15th, 1991, a single atomic nucleus travelling at 99.99999999999999999999951%
of the speed of light
撞击并穿过地球大气层
crashed through our atmosphere
在犹他州上空 一掠而过
and streaked across the Utah sky.
这个原子核快速地分解成
The nucleus quickly disintegrated
大量亚原子粒子和光线 撒向大地
into a shower of subatomic particles and lights.
这些光能够被蝇眼观测站观察到
That light was seen by the Fly’s Eye Observatory, a collection
蝇眼是一个拥有许多巨大桶罐的收集器
of oversized tin cans that was an early experiment
是犹他州大学早期的一项实验用于观测
by the University of Utah to spot the highest energy
宇宙中的高能宇宙射线
cosmic rays in the universe.
科学家分析蝇眼观测的数据
Scientists analyzing the Fly’s Eye data
计算得出 宇宙射线对应其独特的闪光
calculated that the cosmic ray responsible for this particular
至少拥有300千兆兆电子伏特的
flash must have had a kinetic energy of 300 exa electron
能量
volts.
那是相当于48焦耳的能量
That’s 48 joules, an amount of energy
我们可以用肉眼观测到的非亚原子物质
we associate with macroscopic, not subatomic objects.
这个原子核携带着如此高的能量
That single atomic nucleus carried as much kinetic energy
就像一颗石子以每小时50英里的速度撞击在你的头上
as a good sized stone thrown at your head at 50 miles an hour.
这种粒子被成为上帝粒子
The particle was dubbed the Oh-My-God particle.
在此之前没有发现类似的物质
Nothing like it had ever been seen before.
事实上 拥有如此能量的宇宙射线
In fact, cosmic rays of that energy
本应该是不存在的
was supposed to be impossible.
让我们来讨论一下宇宙射线
Let’s talk about cosmic rays for a second.
放射能力是由居里夫人和亨利贝克在十八世纪末
Radioactivity was discovered by Mary Curie and Henri Bacquerel
发现的
at the end of the 1800s.
高能粒子 电子
High energy particles, electrons,
微小的原子核 和伽马射线一样
and small atomic nuclei, as well as gamma rays,
当较重的放射性元素衰变时被释放出来
are ejected when heavier radioactive elements decay.
我们一直沐浴在很低等级的辐射中
We’re bathed in a very low level of this radiation
这归结于地球上自然产生的
due to naturally occurring radioactive elements
放射性元素
in the Earth.
这项发现不久之后 人们发现周围的辐射流
Soon after its discovery, this ambient radioactive flux
随着离地面的高度增加而减弱
was found to weaken with height above the ground,
这是因为辐射能量在空气分子中不断消散
because the radiation loses energy to air molecules.
但是令人不解的是 到达一定高度
But weirdly, above a certain height,
辐射开始再次增加
this radiation starts to increase again.
希欧多尔 伍尔夫在1909年首先发现这个现象
Theodore Wulf first noticed this in 1909
当时他携带探测器来到埃菲尔铁塔顶端
when he took a detector to the top of the Eiffel Tower.
但是真正的证据是在几年之后的1912年
But the real proof came a few years later in 1912
维克多 赫斯携带着一些伍尔夫的探测器
when Victor Hess took some of Wulf’s detectors
乘坐热气球
on a hot air balloon ride.
辐射水平随着高度的增加而增加
Radiation levels increased with height.
那就意味着上面一定有着
And that meant there had to be a source
这些高能粒子的源头
of these high-energy particles somewhere above.
最终结果是他们来自太空
It turns out they were coming from space.
宇宙射线被发现
Cosmic rays had been discovered.
随着赫斯的热气球之旅
In the years following Hess’s balloon ride,
和蝇眼探测上帝粒子事件之后的几年
and even following the Fly’s Eye detection
我们走过了很长道路
of the Oh-My-God particle, we’ve come a long way
去捕捉宇宙射线
in the art of catching cosmic rays.
这些小家伙令人难以琢磨
They are elusive little critters.
你无法通过相机拍摄光线那样聚焦他们
You can’t focus them into a camera like you can with light.
而且 如赫斯的发现那样 无论如何 大部分都无法在地面上
Also, as Hess discovered, most don’t make it to the ground
实现
anyway.
对于能量较低的宇宙射线 一个途径
For lower energy cosmic rays, one approach
就是寻找它们的切伦科夫辐射
is to look for their Cherenkov radiation.
所有的宇宙射线都以接近
All cosmic rays are traveling at pretty close
光速前进 但是
to the speed of light, but that’s
那是在真空中的光速
the speed of light in a vacuum.
光在类似空气的媒介中速度会稍慢
Light travels slower in a medium like air.
所以当宇宙射线进入大气层时
So when cosmic rays enter the atmosphere,
它们的速度实际上要比在大气层中有所减慢
they’re actually traveling faster than the new, lower
的光速更快
speed of light.
结果就是伽马射线和切伦科夫辐射的爆发
This results in a burst of gamma rays, Cherenkov radiation,
实际上在地面是可探测到的
that is actually detectable from the ground.
高能宇宙射线通常会在地面上方几公里的地方
Higher energy cosmic rays tend to obliterate themselves
空气分子的原子核
several kilometers above the ground in massive collisions
大规模碰撞后趋于消散
with nuclei of air molecules.
其结果就是形成亚原子粒子
The result is a cascade of subatomic particles, the debris
和由碰撞产生的碎片构成的瀑布
of the collision, that can spread itself out
可以扩散到几公里的范围
over several kilometers.
这种倾泻叫做空气浴
These cascades are called air showers,
带电粒子束引起
streams of charged particles cause the air
空气发出荧光 这种荧光可以被专业望远镜观测到
to fluoresce, a glow that can be seen by specialized telescopes.
很多碎片离子也到达了地面
Many of the debris particles also reach the ground
并且被探测到
and can be detected there.
通过分析能量和碎片的抛射轨迹
By analyzing the energies and trajectories of the debris,
产生它们的碰撞和最初宇宙射线的性质
the collision that produced them and the nature
都能被重建出来
of the original cosmic ray can be reconstructed.
全球有几家机构
Several facilities around the world
正在致力于捕捉宇宙射线
are devoted to catching cosmic rays.
例如 在阿根廷的Pierre Auger观测站
For example, the Pierre Auger Observatory in Argentina
监视着3000平方公里的区域中的
monitors a region around 3,000 square kilometers
高能宇宙射线
for high-energy cosmic rays.
它包括1660个巨大的水罐用于
It includes 1,660 giant tanks of water designed
在空气浴经过这些水罐时观测切伦科夫辐射
to see Cherenkov radiation when air shower particles pass
并有望远镜
through them, as well as telescopes
观测空气上方的荧光
to spot fluorescence in the air above,
如老式的蝇眼观测站
just like the old Fly’s Eye.
蝇眼观测站已经进入到望远镜阵列
The Fly’s Eye itself has evolved into the Telescope Array
项目中
Project.
它任然使用升级版的荧光望远镜
It still uses upgraded fluorescence telescopes
并且在地面上增加了闪烁探测器
and has added scintillation detectors on the ground.
那是一些简单的夹在金属板中的丙烯酸薄片
These are simple slabs of acrylic
用于阻止空气浴中的粒子
between metal plates designed to stop air shower particles
和探测粒子撞击那些
and detect the light produced as they smack
薄片中的原子核所产生的光
into nuclei within the slab.
目前为止 我们已经对那些趋于撞向地球的宇宙射线进行了
By now, we have a pretty good census
相当成功的统计研究
of the types of cosmic rays that tend to hit the Earth.
他们之中大部分是单个的质子 氢原子核
Most of them are single protons, the nuclei of hydrogen atoms.
和相当数量的氦原子核
And a fair number are helium nuclei.
但是宇宙射线中大约1%的部分是像铁一样的
But about 1% of cosmic rays are heavier nuclei,
较重的原子核
as heavier as iron.
我们也可以看到伽马射线 甚至反物质粒子
We also see gamma rays and even anti-matter particles.
他们形成了所有能量 从令人难以置信的百万电子伏
They come in at all energies, from a sickly billion electron
的最低点到令人疯狂的10的20次方
volts at the low end to the crazy 10 to the power of 20
电子伏或者更高 就像上帝粒子
electron volts or higher, like the Oh-My-God particle.
蕴含的能量越高越稀有
The higher the energy, the rarer they are.
像最低能量的粒子 地球
At the lowest energies, the cosmos
表面每平方米每秒钟能接收到
flings one particle every second per square meter
一个粒子
of the Earth’s surface.
如果能量接近上帝粒子
At energies up near that of the OMG particle,
他们稀少的令人难以置信
they are incredibly rare.
从第一次到现在也只有少数被发现
Only a handful have been spotted since the first,
估计每隔几个世纪每平方公里
giving a rare estimate of 1 per square kilometer
能发现一个
every couple of centuries.
那么这些物质究竟来自何方？
So where do these things come from anyway?
加速一个粒子使其拥有宇宙射线的能量
To accelerate a particle to the energies of cosmic rays,
你需要一个粒子加速器
you need a particle accelerator.
我们在地球上利用巨大的圆环和
We build artificial ones on Earth using giant rings
强力的磁场人工建造了一个
and powerful magnetic fields.
原来宇宙充满了自然形成的粒子
It turns out that the universe is full of natural particle
加速器
accelerators.
对于能量较低的宇宙射线
For lower energy cosmic rays, it’s
被认为很多 可能大多数来我们银河系的超新星
believed that many, and perhaps most, come from supernova
的爆炸
explosions within our galaxy.
当一颗恒星爆炸 四散的冲击波
When a star explodes, the expanding shock wave
携带着强大的磁场
carries a strong magnetic field.
它能捕获粒子并进行加速
It can trap particles and accelerate them
直到这些离子拥有足够的能量脱离冲击波
until they’re energetic enough to escape the shock.
然而越是拥有较高能量的宇宙射线
The higher the energy of the cosmic ray, though,
越是可能是来源于
the more likely it is to have originated
我们银河系之外
from outside our galaxy.
这些被称作银河系外
The exact sources of these so-called extra galactic
的宇宙射线的准确来源是十分神秘的
cosmic rays are more mysterious.
但是他们也可能来自恒星内的磁场加速
But they may come from magnetic acceleration in quasars,
或者可能是从伽马射线爆发中被喷发出来的
or perhaps they’re blasted out in gamma ray bursts.
那些最难以置信的宇宙射线 像上帝粒子
The most ridiculous cosmic rays, like the Oh-My-God particle,
根本就不应该存在
shouldn’t exist at all.
瞧 宇宙基本上来说对于拥有如此高能量的粒子
See, the universe is basically opaque to particles
是不透明的
with such high energies.
空空荡荡的太空实际上并不是真空的
Empty space isn’t really empty, it’s
他充满了低能量的微波光子是最初几次
full of low-energy microwave photons leftover
绚丽光彩的剩余
from the heat glow of the very earliest of times.
这就是宇宙微波背景辐射
This is the cosmic microwave background radiation.
我们在这一期讨论这个话题
We talk about it in this episode.
蕴含超过5乘10的19次方电子伏特
Cosmic rays with energies over 5 times 10
约为8焦耳能量的宇宙射线
to the power of 19 electron volts, about 8 joules,
跑不了多远的距离 因为它们很快就要撞入质子
can’t travel far before smacking into these photons
损失一部分能量
and giving up some of their energy.
我们把这种现象叫做格雷森-扎采品-库兹民
This is the so-called Greisen-Zatsenpin-Kuzmin,
或者GZK界限
or GZK, limit.
很多年来 人们认为没有宇宙射线能够超过它
For years, it was thought that no cosmic ray could exceed it,
只是上帝粒子拥有六倍以上的能量
except that the OMG particle was six times more energetic.
在上帝粒子被发现后 只有极少数的拥有这样极端能量的
Only a very small number of these extreme energy
宇宙射线被发现
cosmic rays have been seen since the OMG particle.
但是那些射线使人困惑
But those are perplexing.
瞧 他们必须来自附近
See, they must have come from nearby,
必须足够近才能不被宇宙微波所抹除
from close enough to our galaxy to not be wiped out by the CMB.
不过 我说的“足够近”是相对于宇宙级规模而言的
In Now I’m talking close by on cosmic scales, so within 1
即一百万至二亿光年之内
to 200 million light years.
但是在这种距离上 来源类似于类星体和伽马射线
But at that distance, sources like quasars and gamma ray
的爆发应该十分明显
bursts should be very obvious.
当然 它们似乎是来自四面八方
Yet they seem to come from nowhere in particular.
我们看到的的确要远比来自
We do see more than the average number coming
大熊星云方向的平均值高得多
from the direction of the Ursa Major cluster,
但是在那里并没有明显的源头
but there’s no obvious source there.
是什么产生了
It’s still a mystery exactly what
这些超级宇宙射线 源头离我们到底有多近
produces these extreme cosmic rays and how close to us
这仍然是个迷
the sources are.
对于宇宙射线天体物理学家们来说
For cosmic ray astrophysicists, there’s
有一个巨大的不可见的粒子加速器
a giant invisible particle accelerating
就像房间里有一头大象一样明显
elephant in the room.
理解宇宙射线的部分挑战在于
Part of the challenge in understanding cosmic rays
我们的大气层和磁场
is that our atmosphere and magnetic field
完美地保护了地球表面
shield the surface of the earth so well.
但我们应该把它当做是一次幸运
But we should count that as a blessing.
阿波罗宇航员在地球磁层外旅行
Apollo astronauts traveling outside Earth’s magnetosphere
报告说有奇怪的闪光
reported strange flashes of light,
这可能归咎于宇宙射线传过
which may be due to Cherenkov radiation
他们眼睛中的玻璃体
from cosmic rays passing through their eye’s vitreous humor,
或者是粒子撞击他们的视觉神经多产生的切伦科夫辐射
or from the particles hitting their optic nerves.
甚至是国际空间站的宇航员都曾遭遇
Even ISS astronauts are subjected
巨大的辐射风险
to a significant radiation risk.
随着太阳的爆发 宇宙射线
Along with solar outbursts, cosmic rays
是星际旅行中最严重的
are one of the most serious obstacles
阻碍之一
to manned interplanetary travel.
当我们思考这些粒子的起源时
As we figure out the origins of these particles,
宇宙射线天文学正在日益成为探索神秘宇宙
cosmic ray astronomy is becoming an increasingly powerful tool
的强大工具
for investigating our amazing universe.
但是 即使是现在这些粒子也是非常有用的
But even now, these particles are extremely useful.
超能宇宙射线 像上帝粒子
The highest energy cosmic rays, like the Oh-My-God particle,
产生的碰撞远比
generate collisions far more energetic
我们最大的粒子加速器 Large Hadron 对撞机
than our largest particle accelerator, the Large Hadron
强有力的多
Collider.
研究宇宙射线能够揭开
Studying cosmic rays may crack open
最大和最小规模时空的
the mysteries of both the largest and the smallest scales
神秘面纱
of space time.
本期由CuriosityStream提供
This episode is brought to you by CuriosityStream,
一个从世界上最好的制片人中提供记录片
a subscription-streaming service that offers documentaries
和非虚构主题的订阅流体服务商
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CuriosityStream的宇宙之前系列是我的最爱之一
CuriosityStream’s cosmic front series is one of my favorites.
它挖掘出了一些最大的秘密
It delves into some of the biggest mysteries
和天文学和太空探索面临的挑战
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每个月2.99美元就可以无限制访问
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观众将获得头两个月的免费
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上一周我们探讨了关于在月球上建造
Last week, we talked about the prospects of building
望远镜的前景
telescopes on the moon.
我们来看看你会说什么
Let’s see what you had to say.
Acousticpsychosis想知道
Acousticpsychosis wonders why we’re
当月球上建立一个如此完美毗邻的站点时我们为什么这么着迷
so obsessed with going to Mars when the moon makes
要去火星
such a perfect nearer station.
好吧 我绝对同意这个观点
Well, I absolutely agree with this.
月球是一个不可思议的礼物
The moon is an incredible gift and we should make
我们应该好好的 和平的使用
good and peaceful use of it.
Ragdala问 谁允许的月球登陆
Ragdala asks, who gives permission for moon landings.
对于月球快递计划来说
In the case of the Moon Express program,
是得到美国政府同意的
the approval was from the US government.
但是 你是对的 没有人拥有月球
But you’re right, no one owns the moon.
所以理论上 没有人可以按规定登陆月球
So in principle, no one can regulate landing on it.
然而 一个国家可以规定一个公司
However, a country can regulate the activities
在他国的行为
of companies based in that country,
即使那些行为没有发生在国境线内
even if those activities don’t happen within national borders.
然而 确实有具有法律约束的条例
However, there are real legally binding regulations.
联合国形成了一个关于管理在开发勘探和利用外太空
The United Nations developed the Treaty on Principles
中的各种行为的基本原则的条约
Governing the Activities of States in the Exploration
包括
and Use of Outer Space, including
月球和其他星体
the Moon and Other Celestial Bodies,
或者称为外太空条约
or, the Outer Space Treaty, which
美国已经批准
the United States has ratified.
该条约限定太空的利用是出于和平目的
It restricts the use of space for peaceful purposes,
但是另外也允许各国自由参与
but otherwise grants free access to nation states.
这并不是说一个国家不能对其国民进行
That doesn’t mean a nation state can’t impose legal restrictions
合法的限制
on its own citizens.
David Connolly 发送电邮提醒我们
David Connolly emailed to remind us
为了太空发射系统的顺利进行
that the Constellation Program and its Ares rockets
星座计划和阿瑞斯火箭将在2009年终止
was discontinued in 2009 in favor of the Space Launch System.
当时得知此事时我向我的火箭科学家朋友们
Yet, and I even commiserated with rocket scientist friends
表达了我的同情
when that happened.
当你明明知道这件事很重要
Don’t you hate it when knowing something
而你却忘了自己知道它时
doesn’t translate to remembering you know it
难道你不生气吗？
when it really matters?
好吧 有几个人想知道
Oh well, a few people wondered if I
我是否在上一期回复评论时生病了
was sick during the comment responses of the last episode
并且祝愿我早日康复
and wished me a speedy recovery.
好的 谢谢大家
Well, thanks guys.
我感觉好多了
I am feeling a lot better.
你刚看过的那一期节目是我在同一天拍摄的
I shot the episode you just watched that same day, so
所以我对我的嗓音感到抱歉
apologies for the voice.
并且亚历山大 谢多夫和其他人想知道
And Alexander Sedov and others wondered
我为什么在那一期要穿牛仔内衣
why I was wearing cowboy underwear in that episode.
兄弟 我生病了
Dude, I was sick.
你很幸运 我毕竟从病床上爬了起来
You’re lucky I got out of bed at all.
能穿上内衣就已经是巨大胜利了
Having any type of underwear on was a major victory.