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如何看到原子 – 译学馆
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如何看到原子

How Can You See an Atom?

It’s hard to imagine just how tiny atoms are.
很难想象原子有多微小
One sheet of paper is roughly half a million atoms thick.
一层纸大约有五十万个原子层
Volume-wise, one atom is as small compared to an apple
从体积来看 一个原子相对于一个苹果
is as apple to entire earth
就像苹果相对于整个地球
So you might be surprised to learn that
所以你可能会怀疑
chemists can actually see atoms.
化学家是否能真的看到原子
Not with their eyes.
不是用眼睛
With incredibly precise tools.
而是用那些精密的仪器
[Legends of Chemistry intro]
[化学的传奇]
The idea of atoms stretches back to ancient Greece,
原子的概念要追溯到古希腊
when the philosopher Democritus declared that
那时哲学家德谟克利特宣称
all matter is made of tiny particles.
所有物体都是由微小的粒子构成
The philosopher Plato even decided wrongly
哲学家柏拉图甚至错误地判定
that different substances had different shaped atoms,
不同物体有不同形状的原子
like pyramids or cubes.
有锥形还有方形的
The first modern evidence for atoms appeared in the early 1800s,
关于原子的第一个现代证据出现在19世纪初期
when British chemist John Dalton discovered
当时英国化学家 约翰·道尔顿发现
that chemicals always contain whole-number ratios of elements.
化合物的元素之间总成整数比
That’s why it’s H₂O and not H₂.₄ O or H√₁ ₇O.
这就是为什么是H₂O而不是H₂.₄O或H√₁₇O
The reason for these whole numbers, Dalton suggested,
对于这些是整数的原因 道尔顿认为
was because you can’t have a half of an atom or 0.2 atoms
是因为没有半个原子或0.2个原子
only whole atoms.
只有整数个原子
It’s actually kind of hard to imagine chemistry today without Dalton’s insight.
现在很难想象没有道尔顿的这个概念 今天的化学将会是怎样
But it was controversial during its day.
但在当时这个说法颇受争议
Why?
为什么?
Because chemists couldn’t see atoms.
因为化学家们看不到原子
Many considered them like negative numbers
许多人认为它们像负数一样
useful for calculating things,
对计算有用
but not existing in the real world.
但在现实世界不存在
Even Dmitri Mendeleev, father of the periodic table,
甚至是门捷列夫⸺元素周期表之父
refused to believe in atoms for many years.
在很多年里也不相信原子的存在
So why didn’t chemists just look for atoms under microscopes?
那么为什么化学家不在显微镜下找找原子呢?
To see something under a microscope,
要在显微镜下看见什么东西
the wavelength of light you’re shining through the microscope
透过显微镜的光的波长
can’t be larger than whatever you’re looking at.
不能比待观测的物体的大
Unfortunately, visible light is thousands of times bigger than atoms.
很不幸 可视光的波长是原子的几千倍
So chemists had to wait for light with shorter wavelengths,
所以化学家不得不等待一种波长更短的光
like x-rays.
像是X射线
X-rays were discovered in the 1890s by German scientist Wilhelm Röntgen,
X射线在19世纪80年代由德国科学家伦琴发现
who realized that photographs taken with x-rays
他发现用X射线拍照
allowed him to see through objects.
可以透视物体
Roentgen thought he’d gone insane when he saw this,
当伦琴看到这个现象时他觉得自己疯了
but today we’re all familiar with x-rays
而今我们都已经从牙医和医生那儿
from trips to the dentist and doctor.
熟悉了X射线
Chemists don’t use x-rays to see through things,
化学家们不用X射线透视物体
however Instead, they bounce x-rays off things like crystals,
而是让X射线从像水晶一样的物体上反弹
which are solids with layers of atoms.
它们是原子排列成层状的固体
When x-rays hit an atom in a crystal, they bounce back.
当X射线撞到水晶里的原子 他们会回弹
Others slip through and bounce off the second layer down.
其他的会划过这层并被下面第二层弹回
Or the third layer, or deeper.
或者第三层甚至更深
After being reflected, these x-rays strike a detector screen,
被反射之后,这些X射线撞击到检测屏上
like the ball bouncing back in Pong.
像弹球里球被弹回一样
And based on the pattern of where they striked the wall
根据它们在显示屏上留下的痕迹
scientists can work backward and figure out
科学家们可以反推算出
the 3D arrangement of atoms in the crystal.
水晶里原子的立体排列方式
This reflection and interaction of light rays is called diffraction.
这种反射和光的相互影响被称为衍射
X-ray diffraction, sometimes called x-ray crystallography,
X射线的衍射有时被称为X射线晶体学
has led to dozens of Nobel Prizes for chemists since the 1920s.
20世纪20年代以来为化学家们带来了几十个诺奖
It also led to one of the biggest discoveries in science history,
它也引出了科学史上最大的发现之一
the structure of DNA
DNA的结构
James Watson and Francis Crick get credit nowadays,
沃森和克里克如今获得了很高的评价
but they based their work on the work of Rosalind Franklin,
但他们的研究却是基于富兰克林的工研究成果
a crystallographer in England.
富兰克林是一个英国的晶体学家
She began taking x-ray pictures of DNA in 1952,
她从1952年开始拍摄DNA的X光片
and Watson’s glimpse of one picture — photograph 51.
沃森对照片51的一瞥
— was the vital clue in determining that DNA was a double helix.
是确认DNA双螺旋结构至关重要的线索
This incident remains controversial today
这个小插曲至今仍具有争议
Because Franklin never gave Watson permission to view photograph 51.
因为富兰克林从未允许沃森看过照片51
If x-rays let chemists peer at the structure of atoms,
如果说X光让化学家们得以窥视原子结构
scanning tunneling microscopes finally revealed atoms themselves.
那扫描隧道显微镜(STM)就是揭示了原子的本貌
Rather than bounce light off something,
比起让光从物体上弹回
an STM runs a sharp needle over the surface.
STM在物体表面移动一根尖锐的针
It’s like chemical Braille,
就像化学上的盲人点字法
except the tip never quite touches.
但针的顶端并不会完全接触
As the tip moves along the surface,
当顶端沿表面移动时
scientists can reconstruct the atomic landscape
科学家们可以重现原子层面的景致
-making individual atoms visible at last in the early 1980s.
而单原子可视在20世纪80年代初实现
Lo and behold, the atoms weren’t Plato’s cubes and pyramids,
看吧 原子不是柏拉图的方形和锥形
but spheres of different sizes.
而是不同大小的球体
By 1989 a few scientists had even adapted STM technology
到1989年 科学家甚至可以用STM技术
to manipulate xenon atoms and spell out words.
操纵氙原子拼写单词
We’ll let you guess what company they worked for.
你可以猜一下他们在为哪家公司工作
Also in 1989, the chemist Ahmed Zewail
1989年 化学家艾哈迈德·泽韦尔
moved beyond looking at stationary atoms
不甘心仅仅观察固定的原子
and developed tools to see atoms in action
并开发出工具观测化学反应中的原子
Zewail wanted to study how atoms break bonds
泽韦尔想要了解原子键是怎么断裂的
and swap partners during reactions.
在化学反应中是怎么交换伙伴的
So he developed the world’s fastest camera,
所以他开发出了世界上最快的摄像机
which shoots pulses of laser light a few femtoseconds long
可以用几飞秒的时间发射镭射脉冲
—a few billionths of a microsecond.
也就是十亿分之几微秒
While Zewail’s laser flashed like a strobe,
泽韦尔的镭射光闪得像频闪记录器
his camera snapped pictures.
照相机啪啪地拍照
Zewail then ran the pictures together
之后泽韦尔把照片放在一起
like a slow-motion replay.
就像慢动作重播一样
Since then femtochemistry had provided insight into
从那时起 飞秒化学为我们提供了深入的了解
everything from ozone depletion to the workings of the human retina.
覆盖了从臭氧消耗到人类视网膜研究的各个方面
Zewail won a Nobel Prize for his work in chemistry in 1999.
泽韦尔在1999年因此获得了诺贝尔化学奖
The ancient Greeks dreamed up fanciful shapes for atoms.
古希腊人想象原子有稀奇古怪的形状
But it took 2,400 years before scientists could see
但是经过2400年 科学家们
them for real and study their behavior.
才真正看到它们和研究它们的行为
Seeing truly is believing for human beings,
眼见为实是人类的信仰
and it was chemist and other scientists who fulfilled this need
而正是化学家和其他科学家完成了这个任务
and finally revealed what our universe is made of.
最终揭示了我们的宇宙是由什么组成的
Thanks for watching chemheads.
感谢观看chemheads
Be sure to check out other videos in the Legends of Chemistry series,
一定去看[化学的传奇]系列的其他视频哦
Like the Woman Who Saved the U.S. Space Program, and
像是 拯救美国太空计划的女性
the crafty scientists who tricked the Nazis.
追踪纳粹的狡猾科学家
Don’t forget to hit the subscribe button
别忘了按订阅
for weekly chemistry awesomeness.
这里每周更新关于化学的趣事

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视频概述

从两千多年前对原子奇妙的猜想,到一步步确认原子的存在,检测到原子,拍摄到原子的照片,人类为揭示原子的真实面目做了不懈努力。

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视频来源

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

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