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放射性:意料之外 – 译学馆
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放射性:意料之外

Radioactivity: Expect the unexpected - Steve Weatherall

在最近100年或者更近的这些年,人类才明白
It is only in the last 100 or so years that human kind has understood
那些化学元素的原子核并不全部都是固定的。
that the nucleus of the chemical elements is not always fixed.
那可以自然地从一个元素改变成另一个。
It can change spontaneously from one element to another.
这个过程叫做放射性衰变。
The name for this process is radioactivity.
你可能已经知道一些关于原子核的事情:
You probably already know something about the nucleus:
它比起原子来说更小一些
it’s much tinier than the atom,
它由叫做质子和中子的微粒组成
it’s made of particles called protons and neutrons,
在它周围,有电子围绕着运行
there are electrons orbiting around it.
并且尽管原子可以在结合在一起的时候分离或交换电子
And though the atoms can share or swap electrons when they bond together,
核的本身并没有改变。
the nuclei themselves never change.
对吗?
Right?
额,并不是这样
Well, no.
某些原子核并不稳定
Certain nuclei are not stable in that way.
这意味着它们可能会突然发生变化
This means they may change suddenly,
自发地
spontaneously.
具有放射性的核会抛出一个小微粒
The radioactive nucleus flings out a small particle
并且变换成另一种元素 就像这样
and transforms into another element, just like that.
例如
For example,
碳核可以喷射出一种快速移动的电子
the carbon nucleus can eject a fast-moving electron
并且转换成氮核
and turn into a nitrogen nucleus.
从放射性核中抛射出的有两种粒子
There are two different particles that can be emitted from radioactive nuclei,
但不会同时抛出
but never together.
非常快的电子被称为贝塔微粒
The very fast electron is known as a beta particle.
如果你知道一些关于电子的知识,你可能会想,
If you know a little bit about electrons, you may be thinking,
“在原子核中与电子相对应的是什么呢?”
‘What was the electron doing in the nucleus in the first place?’
答案就是原子核中的中子
The answer is there is a neutron in nucleus
然后自行转变成质子
spontaneously changed into a proton,
会留下来
which stayed behind,
然后电子作为贝塔粒子流出
and the electron flew out as a beta particle.
这并不是化学课所教我们的
This is not what chemistry has taught us to expect.
课上说的会是 核应该是稳定的
The nucleus is supposed to be stable.
中子不会改变成质子
Neutrons don’t change into protons.
但是 某些时候它们会这样!
Except, sometimes they do!
另一个从
The other particle it emits spontaneously
不稳定的原子核中发射出的是阿尔法粒子
from an unstable nucleus is alpha.
阿尔法粒子比贝塔粒子大了8000倍
An alpha particle is 8,000 times more massive than beta,
并且慢了许多
and it’s a bit slower.
阿尔法粒子是由两个质子和两个中子结合而成
Alpha is made from two protons and two neutrons.
如果我们能捕获所有的阿尔法粒子
If we trap all those alpha particles together,
就能得到氦气
we get helium gas.
阿尔法粒子就是氦原子核
Alpha is a helium nucleus.
如果贝塔粒子一样 你不会指望
Like the beta particle, you would not have expected
一个较重的原子核能把阿尔法粒子抛射出来
a heavier nucleus to throw out helium.
但是再一次 它发生了
But again, it happens,
然后原子核变成了一种新的元素
and the nucleus becomes a new element.
那么 放射性是有意义的还只是危险的呢?
So, is radioactivity useful or just dangerous?
无论你正坐在哪里
Wherever you are sitting,
附近很可能有一个设备
it is quite likely that there is a device nearby
包含了一种阿尔法粒子来源:
which contains a source of alpha particles:
那就是烟雾报警器
a smoke detector.
来源是放射镅
The source is radioactive Americium.
在阿尔法粒子面前你完全是安全的
You are totally safe from these alpha particles,
这些粒子只能在空气中飞行几厘米
which cannot travel more than a few centimeters in air.
贝塔粒子比阿尔法粒子传播的要远
Beta particles penetrate much farther
也更具有穿透性
through materials than alpha can.
放射性原子被用于医疗做为一种探测工具
Radioactive atoms are used in medicine as traces,
可以显示出化学物质在病人身体中的运动痕迹
to show where chemicals travel in the patient.
放射出的贝塔粒子有足够的能量
Beta particles are emitted and have enough energy
能从身体中浮现并能被探测到
to emerge from the body and be detected.
以下是核放射的三种类型:
There is a third type of nuclear radiation:
伽玛射线,这不是粒子。
gamma, which is not a particle at all.
它是一种电磁波
It is an electromagnetic wave,
像微波 或是光
like microwaves, or light,
但是它的能量是可见光能量的1000倍
but it is actually 1,000 times more energentic than visible light.
伽马射线可能能够穿透你的身体
Gamma rays may pass right through your body.
可以杀死细菌以延长水果的保质期
Gamma is used to zap the bacteria in fruit to increase its shelf life,
或者可以通过放疗杀死癌细胞
or in radiotherapy to kill cancer cells.
放射性物质可以放出热量
Radioactive substances get hot,
这种热量可以用来发电
and this heat can be used to generate power.
这种热量已经被用于太空探测任务
This heat has been brought to you since space probes,
以及 在过去应用于心脏起搏器
and, in the past, in pacemakers for hearts.
核辐射减慢得越突然
The more abruptly nuclear radiation is slowed down,
对于原子的伤害就越多
the more damage it does to the atoms it hits.
这叫做离子化
This is called ionization.
当阿尔法粒子冲击其它原子时能引起最大程度的电离
Alpha causes the most ionization as it crashes into other atoms
并且伽玛粒子引起得最少
and gamma the least.
辐射给人类带来的最严重的影响是
For humans, the most serious effect of radiation
它会导致我们DNA的损伤
is the damage that it can cause to our DNA.
尽管α粒子不能穿透你的皮肤
Although alpha cannot penetrate your skin,
如果你吸入或者摄取了一个放射性核
if you inhale or ingest a radioactive nucleus,
会对健康造成严重的后果
the health consequences can be severe.
放射性物质有两面性
Radioactivity is both useful and deadly,
但是我们就生活在它所围绕的自然环境里
but it is all around us as a background to the natural world.

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