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机场安检的科学 – 译学馆
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机场安检的科学

The Science of Airport Security

机场安检是每段旅行中最尴尬 困惑 无聊的时刻
Airport security is the most awkward, confusing, and tedious part of every trip!
在花费了1小时左右时间排队后
After spending an hour or so marinating in a long line, you and your bags are scanned
你和你的包裹被不知道什么科技查看 不知道吸收了多少辐射
with who-knows-what kind of technology, zapped with who-knows-how much radiation, and possibly
甚至可能因为一些莫名的理由而被用小棉签擦拭
wiped down with a little swab for who-knows-what reason.
好了 我们不能再让机场安检这么糟下去
Well, we can’t make airport security suck any less.
我们正好来说一下你和你的包裹经历了什么…
But we can explain exactly what’s being done to you and your bags … what you’re
你被什么扫射…还有目前安检是怎么做的
being exposed to … and how the science of security works these days.
当你站在安检线内时 你所看见的第一样东西应该就是安检机了
When you get to the security line, one of the first things you see is probably the bag scanner.
安检机使用X光射线去探测你包里的东西 以及它们的密度
The scanner uses X-rays to detect objects inside your bag, as well as how dense they are.
安检机的一侧发射不同波长的x线
One side of the machine emits both low- and high-energy X-rays, which pass through your
这些射线会穿过你的包 碰撞上另一边的探测器
bag and hit detectors on the other side.
当x线穿过你的包和包里的东西时 一些射线被吸收
When the X-rays pass through your bag and its contents, some of them get absorbed.
低密度的东西 像有机材质的东西
Objects with lower density, like stuff that’s made of organic materials, will allow more
会让低能级的X射线穿过
of the lower-energy X-rays to pass through.
而那些高密度的东西则会吸收大部分的低能级X射线
And things with higher density will absorb most of the low-energy X-rays, and allow some
允许高能级的射线穿过
of the higher-energy rays to pass through.
通过那些碰撞到探测器的射线
Based on the X-rays that reach the detector, the machine generates an image that shows
机器生成不同东西的图像 根据它们的密度着色
all the different objects in your bag, colored based on their density.
例如 如果某个东西上了橙色 那意味着它可能是由有机材料构成的
If something is colored orange, for example, that means it’s probably made of organic
也就是说 它含有碳
material — that is, something that contains carbon.
这对于安检来说十分重要 因为爆炸物一般都含有这样的有机混合物
That’s important for security to know, because explosives tend to involve organic compounds.
安检团队分析任何可疑东西的图像
The security team analyzes the image for anything suspicious, like the outline of a gun or a
如轮廓像枪的东西 或者藏在鞋子里的一串有机材质的东西
bunch of organic material hidden inside a shoe.
每天都有数以千计的物品被X射线扫描
With all those X-rays scanning thousands of bags every day, you might think that security
你可能会认为安检人员会置身于太多的辐射之中
personnel would be exposed to a lot of radiation.
但是X射线仅被限于安检机中 所以安检人员能接触到的辐射少之又少
But the X-rays are confined to the machine, so the amount of radiation that workers are
他们甚至都不用带徽章,来表示他们暴露于屏幕辐射
exposed to is so low that they aren’t even required to wear badges that monitor radiation exposure.
当你的包通过X射线安检机时
While your bag goes through the X-ray machine, you’ve probably been asked to step through
你也会被要求通过某些安检机器
some kind of scanner yourself.
知道几年前 扫描仪还大多都是金属探测器
Until a few years ago, that scanner was usually a metal detector.
金属探测器是通过线圈产生脉冲电流工作的
Metal detectors work by generating a current in a coil of wire in short pulses, each of
每一个脉冲电流会在探测器中形成一个磁场
which briefly creates a magnetic field within the detector.
当某一金属物体通过探测器时 这个磁场会在金属中产生另一个电流
When a metal object passes through the detector, this magnetic field creates another current
这个电流会在金属周围产生另一个磁场
in the metal, which in turn generates another magnetic field around the object.
两个磁场的相互干扰产生警报
The interference caused by this magnetic field is what sounds the alarm.
但现在 你也许不会再被要求通过金属探测器了
But these days, you’re probably not asked to step through a metal detector.
反而 安检员会让你走进一些大机器中并且举起手
Instead, you walk into some big machine and raise your hands.
这类机器是反向散射扫描仪 或是毫米段波扫描仪
This machine is either a backscatter X-ray or millimeter wave scanner.
如果这个机器看起来像一堵墙 它可能就是反向散射扫描仪
If the machine just looks like a flat wall, it’s probably a backscatter X-ray scanner.
它运用少量的弱x线 这种x线只能穿透你的衣服
These use very small amounts of weak X-rays that only penetrate your clothes, and don’t
并不会穿过你的皮肤
go through your skin.
这种机器探测你皮肤或衣服下的其他东西反射的辐射
The machine detects the radiation reflected by your skin and anything else under your
然后轻而易举的把任何你想隐藏的东西展现出来
clothes, and generates an image that easily shows anything you’re trying to conceal.
反向散射器扫描辐射非常小
The amount of X-ray radiation you’re exposed to in a backscatter scan is extremely low,
比在飞机上接受的辐射少得多
a tiny fraction of the amount you’re about to be exposed to by flying on a plane.
但是直到现在 这个技术应用仍并不广泛 并且它在许多国家被禁止使用
But still, this technology isn’t used very often, and it’s banned in many countries.
反之 毫米段波扫描仪要普遍的多
Instead, millimeter wave scanners are much more common.
它们呈圆柱形状 看起来像电话亭
They’re the cylindrical machines that look like futuristic phone booths, and they use
它们的工作原理和反向散射扫描一样
the same basic principles as backscatter scanners.
但它们发出的并不是X射线 而是不电离的微波
But instead of X-rays, they emit microwaves, which are non-ionizing, meaning that they
这意味着它们并不会损伤你的DNA 你也不必担心有辐射
can’t damage your DNA, and you don’t need to worry about exposure.
因为毫米段波扫描仪也能穿透衣服
Since millimeter waves can penetrate through clothing, they can still show if you’re
所以它们也能发现任何你想藏却违禁的物品
hiding something that you shouldn’t be.
一旦扫描到违禁物品 你就要进行一系列的检查啦
Once you make it through the scanner though, you might still be in for some follow-up tests.
如果安检人员在你的包里发现任何可疑物
If security finds anything in your bag that looks suspicious, they’ll probably
他们就会用棉签擦拭你判断来追踪爆炸物的痕迹
swab you for traces of explosives.
安检人员可能会擦在你的手 鞋子或者包
A security officer might swab your hands, your shoes, or your bag, then place the swab
那些被擦过的地方还要经过其他器械的分析
in yet another machine for analysis.
这就是炸药跟踪检测机 简称ETD
This is the Explosives Trace Detection machine, or ETD.
它的工作原理是 要是你拿了爆炸物 或者你的包里藏了
The idea here is that, if you’ve been handling explosives, or if there were any inside your
这个棉签就获得可疑化合物
bag, the swab will pick up traces of suspicious compounds.
为了分析棉签中可疑化学物的成分 将使用淌度普法
To analyze the swab, the ETD uses a process called ion mobility spectrometry.
ETD会给棉签上的微粒带上电荷 使它们变成离子
The machine gives the molecules on the swab an electric charge, turning them into ions.
然后 使得气体带有这种离子通过电子管
Then, a gas carries the ions through a tube.
不同的离子通过电子管时花费不同的时间
Different ions will take different amounts of time to pass through the tube, depending
这取决于离子的大小和电荷
on things like their mass and charge.
ETD根据它通过电子管的时间
The machine then identifies different compounds based on how long it took them to move through
来辨别不同的化合物
the tube.
所以 机场安检既费时又无聊
So, airport security might be tedious and annoying.
但至少现在你知道机场安检具体是干些什么了吧
But at least now you know what’s happening to you and your carry-on.
感谢观看科学秀 感谢我们在Patreon的赞助商
Thanks for watching this episode of SciShow, which was brought to you by our patrons on Patreon.
如果你想继续关注我们的话 直接搜索patreon.com或者scishow
If you want to help support this show, just go to patreon.com/scishow.
并且不要忘了去youtube.com或者scishow上评论我们哦
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