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路标中的小学问

The shape that changed our world forever

Did you know that stop signs used to be yellow?
你知道停车标志以前是黄色的吗?
Back in the 1920s,
上溯到二十世纪二十年代
even though red had already become known for stop in traffic lights,
尽管人们早已知道红色在交通灯中表示停止
the convention in science wasn’t yet established.
但这还没有成为科学界的惯例
And there were two major problems with red.
而且红色主要有两个问题
One: there wasn’t yet a way to make red pigment that wouldn’t fade.
第一:当时还无法制造出不褪色的红色颜料
And two: red is way harder to see at night.
第二:人们在夜晚更难看清红色
You see, your eye has three types of cones that detect color:
你看 眼睛有三种识别颜色的视锥细胞
red, green and blue cones.
它们分别可以识别出红色 绿色和蓝色
But at night, there isn’t enough light to activate these cones in your retina.
但夜晚 没有足够的光线激活视网膜的视锥细胞
And so, your eyes rely on rods
因此 我们的眼睛得依赖视杆细胞
which are much better at perceiving low light.
因为它更擅长感知弱光
And if we look at the wavelength sensitivity of rods,
如果我们看到视杆细胞的波长敏感区
you’ll notice they actually don’t even pick up red wavelengths.
我们会知道 实际上它们甚至不接收红色波长
When we see red at night,
当我们在晚上去看红色时
it can only be picked up by cones.
只有视锥细胞会接收红光
And as a result,
因此
red is the hardest color to see in low light.
在弱光条件下 红色是最难被看到的颜色
So while a traffic light shining red is one thing
所以尽管交通灯闪红光
a lowly lit red sign is completely different.
但微光照射的红色标志是完全不同的
On top of this, even in daylight,
除此之外 即使是在白天
our eyes are actually most sensitive to a yellow greenish color.
我们的眼睛一般对黄绿色是最敏感的
This is because it’s right in the overlap
这是因为它正好位于
between our red and green cone sensitivity,
我们红色和绿色视锥敏感区的重叠处
peaking at about 550 nanometres,
峰值约为550纳米
making it a perfect option for visibility.
因此从可见度考虑它是最优选择
But not exactly one for consistency with red meaning stop.
但它又与红色表示停止的理念不一致
So when did this switch to red signs happen
那么标志什么时候换成了红色
and how did we overcome this hurdle?
我们又是怎么克服这个障碍的呢?
It’s actually one of the most ingenious and coolest inventions to ever come about.
这其实是有史以来最巧妙的最酷的发明之一
Retroreflection.
回射
I’m here at 3M’s Innovation Theater,
我现在在3M的创新剧院里
the home of the retroreflector
这里是回射器的发源之地
where it was invented, created and first implemented.
是发明 创造 并首次应用它的地方
And we’re going to talk about what they are and how they work.
我们会介绍回射器及其原理
I have a little laser light here,
我这里有一个小激光灯
but to not blind you,
但为了不晃瞎你
we understand if a light comes into the mirror,
我们知道如果有光线射进镜子里
it’s going to reflect back into this lens or your eye.
它会反射回这个镜头或者你的眼睛
But if you point a laser at an angle to a mirror,
但如果你将激光以一个角度射入镜子
it exits at the equal angle the other way.
它会以同样的角度从另一个方向射出
So you can see over there, I have that laser pointer on the shelf.
你看那儿 那个架子上有个激光点
And that’s not very useful
如果想让射到标志上的光
if you’re trying to get light reflecting back to someone on a sign.
再射回给某人 这样的反射就意义不大
So we need a better solution.
那么我们需要一个更好的解决方案
And 3M came up with that many decades ago.
3M在很多年前就提出了这个问题
They first used these glass beads.
他们首先使用了这些玻璃珠
Now when light enters glass,
现在 当光线射入玻璃时
it’s a different refractive index,
它的折射率不同
so it actually bends the light.
所以实际上它会使光线弯曲
If we put this down here,
如果我们把它放在这里
the white surface that’s reflective behind it,
它后面的白色表面是可折射的
and I shine this laser through it,
我点亮激光穿过它
you can see that laser comes back to me now.
你会看到激光现在射回到我身上
Instead of bouncing out the other direction,
而不是从另一个方向射出
it’s actually shooting back at my stomach.
它实际射到了我肚子上
A little faint, but still there.
有点弱 但还是回来了
But 3M took that principle even further with a full cube retroreflector.
但3M公司在全立方体回射器上进一步运用了这个原理
If we take this and just talk about these first two mirrors here,
如果我们拿着这个 只讨论这里的前两个镜子
if I shine a laser in one side of that mirror,
如果我用激光照射镜子的一侧
it will bounce out at the equal and opposite angle.
它会以相同的角度从相反方向射出
And then do it again, and you can see on me,
然后再反射一次 你可以在我身上看到
this laser looks basically just as strong as it did go again as it does on me.
这个激光和照在我身上的激光强度基本一致
So that’s really useful
所以这很有用
that it’s reflecting back to the source where it’s coming from.
它能够反射回它的源头
And when you think about signage,
当我们想到标牌时
you want the light to hit it,
我们想要灯光
even if it’s at a weird angle
无论以多奇怪的角度照向它
and come back to you, so you can see the thing.
都能射回我们身边 那样我们就可以看到它
By adding a third mirror down here,
在这儿加上第三面镜子
we can now basically point anywhere on here.
我们现在基本上可以指向这里的任何地方
And we’re gonna have reflection that ends up back towards me.
最终光都会射回给我们
You can see it here as well,
你也可以在这里看到
even though I’m pointing on the bottom.
即使我指向底部
And that is a basic 101 of how a retroreflector works.
这就是回射器工作的基本原理
Now the question is:
现在的问题是
how do we go from the principle of retroreflection
我们该怎样把回射原理应用到
to getting it on a huge variety of surfaces,
各种各样的表面上
like not only signs but multiple plastics,
比如 不仅是标志 还包括多重塑料
the lines on the road and even clothing?
道路上的线条甚至 衣服?
– Walk me through what the heck you are moving around here.
-告诉我 你在这儿移动什么东西
– These are our reflective sheeting,
-这是我们的反光膜
what we have here are different type of reflective sheeting.
我们这里有不同类型的反光膜
– So these are all basically full of retroreflectors, right? – Correct.
-所以这些基本上都布满了回射器吗? -对的
– This is full of retroreflectors.
-这里都布满了回射器
– Basically, each of these little squares
-基本上 每个小方块
has 6000 retroflectors per square centimeter.
每一平方厘米有6000个回射器
– Yes, you did your homework. That’s pretty good, you got it.
-是的 你做了功课 很好 你答对了
– This, though, is like a metal backing
-这好像是一个用来
of which these retroreflective sheets are put onto.
放反光膜的金属背衬
– Totally correct. The most important sign of the role,
-完全正确 这是最重要的标志
the stop signs with our materials.
用我们材料做成的“停止”标志
I wasn’t about to leave 3M without a sign of my own.
不给我做个标志 我是不会离开3M公司的
So I made sure to ask specifically
所以我特意问了一下
how the signs get put together.
这些标志是怎么样组合在一起的
– We’re gonna start with the retroreflective sheeting.
我们会从反光膜开始
So I’ll cut its size.
所以我得裁剪它
And our retroreflective sheeting is basically a big sticker,
我们的反光膜基本上就是一张大贴纸
so there’s a liner and adhesive on the back.
所以背面有衬垫和粘合剂
So once you apply it on here,
所以一旦你把它贴在这里
you get kind of this lip, this overhang.
你就会得到这样凹凸不平的边
So we have to trim that off.
所以我们得把它剪掉
And then separately, we’ll take the Electro Cut Overlay Film,
然后我们将单独采取电切覆盖膜
or E-conf, as some people call it,
或者 有些人会叫它 E-conf
And we’ll put it through a friction-fed platter.
我们会把它放在一个摩擦送料的平板上
We wrote Asap SCIENCE.
我们写下Asap SCIENCE
– Yes, I hope I got to keep this.
-是的 我希望我能留下这个
– You kind of grab the edge and just push it,
-你可以抓住边缘 推它
and then you can just lift the letter off.
然后你就可以把字拿走了
– Whoa, ok, there we go, all right.
-哇哦 好 好了 可以的
– Some letters like the A
-有些字母比如A
will actually have a little floating piece, right? Like the middle.
实际上会有一个小的浮动块 对吗?就像这中间
And so applying this pre-space
所以使用这个预置膜
allows you to keep everything in place and remove the liner.
让你可以保持一切原样并去除衬垫
And essentially, you end up with something like this.
基本上你会得到这样的结果
So you remove the liner,
所以你移除衬垫后
the green is stuck to the white retroreflective sheeting, it’s on aluminum.
绿色粘在白色反光板上 在铝上
And the last thing to do is to remove this pre-space.
最后要做的就是移除这个预置膜
Which you want to give it a try?
你想来试试吗?
– I would love to.
-我很乐意
Are we ready?
我们准备好了吗?
– Wow, look at that. Asap SCIENCE.
-哇哦 看它 Asap SCIENCE
– Almost every street name sign is made like this, before digital printing.
-在数字印刷之前 几乎每一条街道名称标志都是这么做出来的
-That’s crazy.
-太神奇了!
– Another way to manufacture signs is using digital printing.
-另一种制作标志的方法就是数字印刷
So digital printing is been around for about 10-15 years probably, at 3M.
3M公司使用数字印刷已经有大约10到15年
– So this is printing on retroreflective sheeting.
-所以现在是在回射膜上打印
– Exactly! This specific printer uses HP latex inks.
-对的!这台特殊的打印机用的是惠普乳胶墨水
So it’s water-based.
所以它是水性的
So it’s similar to, like your printer at home. We’re just laying down ink.
所以这和你在家打印类似 我们只需要把墨水倒进去
– All right, can we see a little some…some…?
-好 我们可以看一点点 一点点……吗?
– Absolutely, yeah.
-当然 是的
– Aah, it’s Mory’s Asap Science signs!
-啊 这是莫瑞的Asap Science标志!
That’s so cool.
它好酷
Boom! Ok, we’re outside in the dark.
嘣!好了 我们在漆黑的室外
And we’re gonna do a little experiment with the sign now to see it in action.
我们现在要对这个标志做一个小实验 看看它是如何工作的
So if I shine this flashlight on the ground,
所以如果我把手电筒照在地上
my immediate surroundings are pretty visible,
我近身的环境清晰可见
but become increasingly less visible as you go further out.
但手电筒的光照得越远就越难以看清
That’s because light scatters in all directions,
那是因为光向四面八方散射
and less photons are actually making it back to the camera lens.
实际回到相机镜头的光子就越来越少
But, if I shine this light now over towards Greg,
但是如果我把这个光照向格雷格
holding our fancy retroreflectoring sign,
他现在正拿着我们精美的反光标志
and put the light right beside the camera lens,
然后把灯放在相机镜头旁边
you’ll see just how much brighter the sign is
你就会看到这个标志比
than almost anything else the light is touching,
光线接触到的所有其它的东西都要亮很多
even though it’s all the way over there.
尽管它远在那边
Now of course, if I move the light away from the lens,
当然 现在如果我把光源从镜头前挪开
the sign becomes less bright.
标志就没那么亮了
Even here I’m about six inches,
即使在这里 我也只隔了6英寸
go a little further about a foot,
再往前走大约1英尺
you can see how much darker the sign is.
你可以看到这个标志有多暗
And that’s because the camera lens or you are no longer the source.
那是因为摄像机或你不再是光源
And instead, the majority of the light is bouncing back over here.
反之 大部分的光被反射到这里
Over here where I’m holding the light,
在我举着灯的地方
I see the sign just as bright, but you don’t.
我看到了同样明亮的标志 但你没有
And that’s because the light is always reflecting back to the source.
这是因为光线总是会被反射回光源
You’ve likely seen this while driving at night.
你可能在晚上开车时见过这种情况
When there are minimal overhead lights,
当头顶没什么光线时
signs super far in the distance are extremely bright,
远处的标志非常明亮
while things closer are completely dark,
而近处的东西则完全是黑暗的
even the metal post seems invisible here.
这里甚至连金属柱子都看不见
Now what about when it’s raining outside?
现在外面下雨了怎么办?
Sure in the broad daylight, you can still see the lines on the road,
当然 在大白天 你仍然可以看到路上的线条
but I think we’re all familiar with
但是我想我们都熟知
that scary problem of lines disappearing at night.
一个恐怖的问题 晚上标线会消失
The problem here is that the water actually changes the refraction of light.
这里的问题是 水实际上改变了光的折射
So where the retroreflectors act ideally under dry conditions
因此 当回射器在干燥条件下能理想地工作时
as soon as water is on top of them,
只要有水覆盖在上面
their refractive index is lowered by a ratio of 1.33,
它们的折射率就会降低1.33的因子
and so the light leaves at a different angle,
也因此光线会以不同的角度离开
sending less back to the source.
能回到源头的光线也就更少
And this is incredibly important,
这非常重要
because while only 25 percent of driving occurs at night,
因为人们只有25%的概率会夜晚行驶
55 percent of deaths from car accidents happen when it’s dark,
但车祸造成的死亡却有55%发生在黑暗中
with rain being disproportionately dangerous at low light conditions compared to the day.
与白天相比 在弱光条件下下雨是极度危险的
To combat this rain visibility problem,
为了解决这种雨中能见度的问题
3M actually developed these elements
实际上3M公司开发出了这些元件
which are retroreflectors that have different refractive indices.
有着不同折射率的回射器
So on this side, we have elements to have a refractive index of 1.9,
所以在这一边 我们有折射率为1.9的元件
and they work well in dry conditions.
它们在干燥条件下性能良好
And on this side, we have elements that have a 2.4 refractive index,
在这边 我们有折射率为2.4的元件
and work better in wet conditions.
它们在潮湿条件下表现更好
And on top, they’re both in air.
上面的这两块都在空气中
And on the bottom, they’re both submerged in water.
下面的这两块都沉在水里
Then I’m going to show you what happens when we’re in the dark,
然后我会给你展示 当我们在黑暗中
and shine a light on both of these.
把灯照在这些上面会发生什么
You can see that, the one on the left at the top
你可以看到 左边上面那个
is optimized for dry conditions,
在干燥环境下状态最佳
because it’s flashing back more light.
因为它反射回了更多光线
And then the one at the bottom on the right
然后右边下面那个
is optimized for water,
在水里表现最佳
and is sending more light back to us,
即使它沉在水里
even though it’s submerged in water.
它也反射给我们更多的光线
Now of course, the best solution is
当然现在最好的解决方案是
to include a mix of these elements in the product
在产品中混合这些元件
whether it’s the layer put on top of painted lines,
无论是混进油漆标线上的添加层里
or directly into taped lines,
还是直接混进标线胶带里
so that people can see them in either weather condition.
都能让人们在任一天气状况下看到它们
If it’s dry, the 1.9 will send the light back
如果处于干燥条件 1.9的那个会把光线反射回来
while the 2.4 won’t.
2.4的不会
And when it’s wet, the opposite occurs.
当处于潮湿条件下 情况相反
So behind me, we have a variety of painted lines,
所以我身后有大量的油漆线
some have the regular glass beads on them,
一些上面是普通的玻璃珠
and other ones have the 3M elements on them,
另一些上面是3M公司的元件
with the 1.9 refractive index,
有折射率为1.9的
or the 2.4 refractive index,
折射率为2.4的
or a combination of those.
或者它们的混合体
And we’re gonna see what happens in the dark when they get rained on
我们来看看 当它们在黑暗中被淋湿会发生什么
Here’s the setup in the dark
这是在降雨设备开启之前的
before the rain machine has been turned on.
处于黑暗中的装置
And you can see all the lines are equally visible.
你可以看到所有线都是可见的
But as the rain begins to run,
但是一旦开始降雨
some of the lines slowly start to become obscured,
一些线就逐渐看不清了
and harder and harder to see.
越来越难以看到
It’s only the few stripes on this right-hand side that remain visible
只有右手边少数几条线可以被看到
as they have varying amounts of the water reflective elements.
因为它们具有不同数量的水反射元件
And here’s the difference in the real world,
这是现实场景中的对比
on the left is a wet line without water reflective elements,
左边是没有水反射元件的湿线
and on the right, you can see it with these elements.
在右边 你可以看到添加了那些元件的线
And as a result, you can actually see that line even in the rain.
结果就算在雨里 你实际是可以看到那条线的
So there you have it.
所以你知道了
Road signs are officially way cooler than you probably thought,
路标比你想象的要酷得多
or at least, are a lot cooler than I ever realized they were
或者至少 比我在做这期视频之前以为的
before making this video.
要酷得多
And hopefully, I’ve convinced you of that too.
希望我也说服了你
I want to send a huge thank you to 3M for having me at the facility,
我要狠狠感谢3M公司让我参观了工厂
and to JC and Gus for showing me around and teaching me,
也同样感谢JC和Gus带我参观 给我解说
and especially making me multiple signs that I could bring home,
特别是给我做了很多标牌让我能带回来
back here to the Asap SCIENCE headquarters.
带回Asap SCIENCE的总部
I will cherish it forever.
我会永远珍惜它的
Thank you so much for watching.
非常感谢您的观看
Make sure you like the video.
一定要点个赞哦
Subscribe if you haven’t already.
如果您还没有订阅 请订阅
And we’ll see you next time for some more science. Peace.
下次我们再学习更多的科学知识 拜拜

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视频概述

本期的Asap SCIENCE与我们日常生活中随处可见的路标有关,让我们来看看这些常见的路标里有什么学问吧~

听录译者

panda

翻译译者

广君

审核员

审核员AL

视频来源

https://www.youtube.com/watch?v=4iY8JqHN-kI

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