Science and Technology Military camouflage That old razzle dazzle
科技 军事伪装 旧式迷魂战术
How to confuse the enemy about how quickly you are travelling
如何让敌方无法判断己方的前行速度
IN THE second world war, many Allied ships were painted with dark and light stripes, and other contrasting shapes, making them look a bit like zebra.
二战期间，许多盟军军舰船身都被喷涂了黑白条纹及其它迷彩图案，这让它们看上去有些象斑马。
The idea was to distort an enemy submarine commander's perception of the ship's size, shape, range, heading and speed, so as to make it harder to hit with the non-homing torpedoes of the period.
这样做的目的是为了迷惑敌军潜水艇指挥官，使其无法判断盟军船舰的尺寸，形状，距离，航向和速度。由于当时的鱼雷还不具备制导系统，因此想要击中目标愈加困难。
These had to be pointed not at the target directly but, rather, at the place where the commander thought the target would be when the torpedo arrived.
因此敌军指挥官不再让鱼雷直接对准目标发射，而是将它们发射到他认为盟军军舰可能会驶向的位置。
At the time, though, it was only an educated guess that this so-called dazzle camouflage would work.
当时, 对于这种所谓的迷彩伪装术的有效性判断还只是基于经验上的考量。
Now someone has actually tested it and the short answer is that it does work—but not in the way that Allied navies thought it did. Ships move too slowly for dazzle camouflage to be effective.
而如今已经有人对此进行了真实测试，结果验证这种迷彩伪装的确有效——但并不是按照盟军海军所设想的那种方式发挥作用。
However, it might well have a role in protecting faster-moving vehicles, such as military Land Rovers.
迷彩伪装无法保护航行速度过慢的船艇。但它对于军用路虎这样快速行驶的车辆却能起到很好的保护作用。
Nicholas Scott-Samuel, of the University of Bristol, and his colleagues, came to this conclusion by asking volunteers to watch patterned rectangles cross a computer screen.
以上结论是由布里斯托尔大学的Nicholas Scott-Samuel和他的同事通过实验得出的。
Some of the rectangles had horizontal stripes inside them. Some had vertical stripes. Some had zigzags. And some had checks.
他们让志愿者观察在电脑屏幕内横向移动的长方形物体，这些物体内部被喷涂了不同图案，图案形式有横纹，竖纹，锯齿纹和方格纹。
Others, acting as controls, had no internal patterns.
而作为参照的物体则未喷涂任何图案。
Each test involved a jazzy rectangle crossing the screen either before or after a plain one. Volunteers had to estimate which of the two was travelling faster.
每次实验志愿者在观看了迷彩图案的长方形横过电脑屏幕之前或之后,还被要求观看一个没有条纹图案的物体横过屏幕，之后志愿者需要估计这两个物体哪个移动速度较快。
In fact, in all cases, the two rectangles travelled at the same speed.
实际上，在所有实验中，这两个长方形物体移动的速度都相同。
But the researchers varied the conditions in other ways, without telling the participants.
但研究人员通过其它方式改变了实验条件，志愿者对此却一无所知。
Sometimes both rectangles travelled slowly, at just over 3o of arc a second from the observer's point of view, as a ship might. Sometimes they travelled much faster, at 20o a second, mimicking the way a land vehicle moves.
有时两个长方形物体移动速度都很慢，从志愿者的观察角度看，就象一艘船以每秒驶过3度的距离在航行，有时它们都模仿陆地车辆行驶方式以每秒走过20度的距离快速移动。
The jazzy rectangles also came in different flavours. Some were low-contrast (ie, not very jazzy at all) and some high-contrast.
长方形物体的迷彩图案也不尽相同，有些图案对比度不强烈（看起来不那么花哨），有些图案的对比度则很强。
The upshot, as Dr Scott-Samuel reports in the Public Library of Science, was that participants were not fooled by slow-moving rectangles, nor by low-contrast ones.
实验结果如同Scott-Samuel 博士在公共科学图书馆报告所说，志愿者对慢速移动或图案对比度不强的物体移动速度判断较准确。
Fast-moving, high-contrast shapes, however, did befuddle them.
而对于快速移动和图案对比度强烈的物体,他们的判断常常出错。
On average, an observer reckoned that such a fast, jazzy rectangle was going 7% slower than was actually the case.
志愿者对于有迷彩图案和快速移动的正方形物体的速度估计要比它们的实际速度平均低了7%。
Ships, therefore, travel too slowly for dazzle camouflage to work.
因此喷涂迷彩伪装的军舰航行速度过于缓慢是起不到迷惑敌军作用的。
In any case, modern torpedoes and missiles are guided to their target electronically.
在任何情况下,现代的鱼雷和导弹都采用了电子制导来跟踪目标。
But 20o a second corresponds to the perceived movement of a vehicle 70 metres away that is travelling at 90kph.
但是从视觉角度看,每秒20度的移动速度相当于在70米外看到一部车辆在以90公里/小时行驶。
That is precisely the sort of distance from which an unguided rocket-propelled grenade might be fired at a lightly armoured military vehicle, and just the sort of speed such a vehicle might be travelling at.
在与此相同的距离和速度条件下,一个非制导火箭推进榴弹能够击中一辆轻型装甲军车。
Perhaps the answer, then, is for modern armies to buy their Land Rovers second-hand from game parks, which often paint them in zebra stripes for effect.
如果果真如此,那么现代军队可以考虑在狩猎公园买个涂有斑马条纹的二手路虎车了。
Whether real zebra got their own jazzy stripes to confuse predators has yet to be determined.
至于斑马身上的条纹能否让其躲过掠食动物的捕杀则还有待证实。