When we hear the word radiation,
当我们听到辐射这个词，
it's tempting to picture huge explosions and frightening mutations, but that's not the full story.
我们会不禁想起大爆炸和可怕的变异，但那并不完整。
Radiation also applies to rainbows and a doctor examining an x-ray.
辐射同适用于彩虹和医生检测用的X射线。
So what is radiation really, and how much should we worry about its effects?
那么辐射到底是什么，对于它的影响我们又应该担心多少呢？
The answer begins with understanding that the word radiation describes two very different scientific phenomena:
答案从理解辐射这个描述两种完全不同的科学现象开始：
electromagnetic radiation and nuclear radiation.
电磁辐射和核辐射。
Electromagnetic radiation is pure energy consisting of interacting electrical and magnetic waves oscillating through space.
电磁辐射是纯能量，由相互作用的电磁波在空间中振动形成。
As these waves oscillate faster, they scale up in energy.
这些波振动越快，能量也就成比例增加。
At the lower end of the spectrum, there's radio, infrared, and visible light.
在光谱的低频端的是无线电，红外线和可见光。
At the higher end are ultraviolet, X-ray, and gamma rays.
位于高频端的有紫外线，X射线和伽马射线。
Modern society is shaped by sending and detecting electromagnetic radiation.
发射和检测电磁辐射构成了现代社会。
We might download an email to our phone via radio waves to open an image of an X-ray print,
我们可以通过无线电波下载一封邮件到手机上，以打开X射线印出的一张图，
which we can see because our screen emits visible light.
我们可以看见这些是由于屏幕发出可见光。
Nuclear radiation, on the other hand, originates in the atomic nucleus,
另一边呢，核辐射源于原子核，
where protons repel each other due to their mutually positive charges.
带有正电荷的质子正正相斥。
A phenomenon known as the strong nuclear force struggles to overcome this repulsion and keep the nucleus intact.
一种叫做强核力的现象，艰难地克服这种排斥并保持原子核完整。
However, some combinations of protons and neutrons, known as isotopes, remain unstable, or radioactive.
然而，一些质子和原子的组合，同位素，依然不稳定，换句话说有放射性。
They will randomly eject matter and/or energy, known as nuclear radiation, to achieve greater stability.
它们会随机释放出物质和(或)能量，也就是核辐射，来使自己更稳定。
Nuclear radiation comes from natural sources, like radon, a gas which seeps up from the ground.
核辐射来源于自然物质，例如氡，一种从地下渗出的气体。
We also refine naturally occurring radioactive ores to fuel nuclear power plants.
我们也提纯自然出现的放射性矿石来为核能工厂提供燃料。
Even bananas contain trace amounts of a radioactive potassium isotope.
即使是香蕉都含有微量钾的放射性同位素。
So if we live in a world of radiation, how can we escape its dangerous effects?
因此如果我们住在充满辐射的世界，我们怎么能躲开它的危害呢？
To start, not all radiation is hazardous.
首先，不是所有的辐射都有危险。
Radiation becomes risky when it rips atoms' electrons away upon impact, a process that can damage DNA.
当撞击将原子的电子分开时核辐射才有危险，这是一个可以损坏DNA的过程。
This is known as ionizing radiation because an atom that has lost or gained electrons is called an ion.
这个叫做电离辐射，因为一个已经失去或得到电子的原子叫做离子。
All nuclear radiation is ionizing, while only the highest energy electromagnetic radiation is.
所有的核辐射都是电离，然而电磁辐射只有最高能量的才是。

That includes gamma rays, X-rays, and the high-energy end of ultraviolet.
那包括γ射线，X射线和紫外线的高能末端。
That's why as an extra precaution during X-rays,
那就是为什么要在X射线时额外警惕，
doctors shield body parts they don't need to examine, and why beach-goers use sunscreen.
医生们把不需要检测的身体部分保护住，以及为什么常去海滩的人要用防晒霜。
In comparison, cell phones and microwaves operate at the lower end of the spectrum,
对比来看，手机和微波在光谱的低频端，
so there is no risk of ionizing radiation from their use.
因此使用它们没有电离辐射的危险。
The biggest health risk occurs when lots of ionizing radiation hits us in a short time period, also known as an acute exposure.
最大的健康危害发生在大量的电离辐射在短时间内击中我们时，或急性暴露。
Acute exposures overwhelm the body's natural ability to repair the damage.
急性暴露压垮人体自然修复损害的能力。
This can trigger cancers, cellular dysfunction, and potentially even death.
这可能引发癌症，细胞功能紊乱，甚至死亡。
Fortunately, acute exposures are rare,
幸运的是，急性暴露很少见，
but we are exposed daily to lower levels of ionizing radiation from both natural and man-made sources.
但我们每天都暴露在较低级的电离辐射下，既来自于自然，也来自于人造物质。
Scientists have a harder time quantifying these risks.
科学家们很难给这些危害定量。
Your body often repairs damage from small amounts ionizing radiation,
你的身体经常修复小量电离辐射造成的损害，
and if it can't, the results of damage may not manifest for a decade or more.
如果无法修复，损害带来的结果十年或更久都不会显现。
One way scientists compare ionizing radiation exposure is a unit called the sievert.
科学家们区别电离辐射暴露的一个方法是一种叫西韦特的单位。
An acute exposure to one sievert will probably cause nausea within hours, and four sieverts could be fatal.
一西韦特的急性暴露下可能会造成几个小时的恶心，四西韦特可以致命。
However, our normal daily exposures are far lower.
不过，我们正常生活的暴露度要低好多。
The average person receives 6.2 millisieverts of radiation from all sources annually, around a third due to radon.
平均每个人每年累计接收6.2毫西韦特辐射，大约三分之一是氡。
At only five microsieverts each, you'd need to get more than 1200 dental X-rays to rack up your annual dosage.
口腔X光一次仅5微西韦特，你需要1200次以上的口腔X光才抵得上每年的量。
And remember that banana?
还记得那个香蕉吗？
If you could absorb all the banana's radiation, you'd need around 170 a day to hit your annual dosage.
如果你把香蕉所有的辐射都吸收了，你每天吃大约170根香蕉才能达到你一年的量。
We live in a world of radiation. However, much of that radiation is non-ionizing.
我们住在一个充满辐射的世界。然而，大多的辐射是非电离的。
For the remainder that is ionizing, our exposures are usually low,
余下那些电离的，我们暴露度基本很低，
and choices like getting your home tested for radon and wearing sunscreen can help reduce the associated health risks.
而且像检测你家的氡含量和抹防晒霜这样的决策，能够帮助减少相关的健康危害。
Marie Curie, one of the early radiation pioneers, summed up the challenge as follows:
玛丽·居里，早期的辐射研究先驱之一，将挑战总结如下：
'Nothing in life is to be feared, it is only to be understood.
“世上无可畏惧，只是有待理解。
Now is the time to understand more, so that we may fear less.'
现应当理解更多，我们才可越无惧。”