评论
打印
This is the first live cat recorded on film,
这是电影记录的第一个活猫的镜头，
and it’s being dropped to solve a physics problem:
扔猫这个动作则是为了解决一个物理问题：
Why do cats always land on their feet?
为什么猫（落下时）总是脚先着地?
It’s a question that was driving 19th-century scientists nuts.
这个问题曾让19世纪的科学家们十分抓狂。
Until one of them used an unexpected tool to solve the mystery: a camera.
直到其中一人用一种意想不到的工具——相机——解开了谜团。
Etienne-Jules Marey was an obsessive scientist and inventor who analyzed how things moved.
艾蒂尼·朱尔斯·马莱是一位痴迷于分析事物运动原理的科学家和发明家。
And he started experimenting with photography at a time when the medium was mostly used to document static subjects.
而且，在摄影的主要用途还是记录静态对象时，他就已经开始用摄影辅助实验了。
But his goal was to capture motion.
而他这么做的目标却是捕捉运动。
And he did that by building on a basic principle of photography:
具体操作的基础则是摄影的一个基本原理：
exposing a photosensitive material to light and then covering it in darkness.
先将感光材料暴露在光线下，再将其置于黑暗之中。
So his way of creating this darkness and light was to have a disc with slots in it.
这样交替制造黑暗和光明，是为了在相机里面放一个有缝隙的圆盘。
By controlling the light as the subject moved across the frame,
通过控制主体在画面上移动时的光线，
Marey was able to record movement onto a single glass plate.
马莱只用一块玻璃板就记录下了主体的运动轨迹。
Essentially, all he does is block that light intermittently.
说白了，他所做的就是间歇性地挡住光线。
A slot from the disc opens, and then there’s darkness as the man moves, opens, darkness.
打开圆盘上的一个缝隙，然后在这个人移动的时候，遮住光线，再打开，再遮住。
This technique is called chronophotography,
这种技术就是“定（延）时摄影”，
and the results show something human eyes will never see on their own: individual stages of motion.
得到的结果是人眼永远无法自己看到的东西：运动的各个阶段。
A couple of years later, Kodak introduced celluloid film and Marey updated his slot camera in a crucial way.
几年后，柯达推出了赛璐珞胶片，马雷对他的插槽照相机进行了关键性的升级处理。
He swapped the single glass plate with a roll of film that moved in between exposures.
他把玻璃板换成了胶卷，这样就可以在两次曝光之间移动胶卷了。
So, light: an image is made. Darkness, the film moves on.
这样一来，进光：产生一个图像。遮光，移动胶卷。
Light, an image — so it’s a movie camera, is what it is.
进光：产生一个图像——照相机就这样变成了一个电影摄影机。
Marey made a lot of films for research purposes,
马莱拍了很多研究用途的电影，
and even tried dropping other animals to see if they’d land on their feet, specifically this rabbit and this chicken.
甚至还尝试过扔其他动物，尤其是这只兔子和这只鸡，看它们是否是脚先着地。
Which brings us back to the cat.
这样一来，我们就又回到了猫的话题上。
It seems to be able to right itself by flipping in the air without pushing off anything first,
猫似乎不用先推一下其他物体就能在下落的时候翻个儿，从而调整自己的落姿，
which would contradict the law of conservation of angular momentum.
这样一来就和角动量守恒定律矛盾了。
Sounds scary, but stick with me here.
听起来很吓人是吧，但还是请您继续听下去。
One of Newton’s laws of motion says that something in motion can’t just stop itself unless an opposing force acts upon it.
牛顿三大（运动）定律中有一条规定，运动中的物体是不会停止运动的，除非有相反的力作用于它。
Basically, you can’t just change direction mid-air, Wile E. Coyote style.
换句话说，你无法像歪心狼一样在半空中改变方向。
But to the naked eye, it looks like a cat can.
但是对肉眼来说，猫似乎就能做到这一点。
Most people assumed the cat was “cheating” by kicking off the hands of the person dropping it,
大多数人都以为猫在“作弊”，因为它踢了扔它的那个人的手，
but Marey’s film showed what’s actually happening.
但马莱的电影告诉了我们其中的真正原委。
The first few frames prove right away that the cat doesn’t start its rotation from a kick.
刚开始的几帧画面就证明了猫不是从“踢”开始旋转的。
But what it does do is arch its back.
那个时候猫真正的举动是拱起它的背部。
And by arching its back, it’s divided its body into a front part and a back part, and the two parts can work independently.
通过拱起背部，猫就将身体分成了前后两个部分，而这两个部分是可以独立运动的。
You know how a figure skater pulls their arms into rotate faster?
见过花样滑冰运动员把手臂收起来以便加快旋转速度吧?
That’s what’s happening here too.
猫拱起背部也是一个道理。
Early in the rotation, the cat pulls its front legs in and leaves the back splayed out
在旋转的早期，猫把前腿收进去的同时把后腿张开，
so the front half can rotate quickly while the back half stays relatively still.
这样一来，它的前半身就可以快速旋转，同时保持后半身相对静止。
Then halfway through, it does the opposite.
落到一半的时候，再反过来做一遍。
Front legs stretched out, back ones tucked in to flip the other half of its body around.
前腿张开，后腿收起来，翻转身体的后半部分。
And you notice by the time the cat is landing, all four legs are stretched out as far as they can be, which means slow rotation.
你会注意到，着地的时候，它的四条腿都是尽可能地伸展开来的状态，这就意味着那个时候旋转的速度是很慢的。
So the cat has rotated itself, but not overall; the two halves are working in opposite ways.
所以，猫是发生了旋转，但不是整个同步地在旋转；而是两部分朝着相反的方向在旋转
It uses the inertia of its own bodyweight to spin each side.
每次旋转的时候，它都利用了自身体重的惯性。
And because the two spins operate separately in opposing directions, they cancel each other out.
因为两次旋转时间上是分开的，而且方向也是相反的，所以它们能够相互抵消。
So Newton’s law isn’t broken.
牛顿定律也没有被打破。
Marey published his findings in Nature in 1894, breaking down the falling cat problem for the first time.
1894年，马雷在《自然》杂志上发表了他的研究成果，首次揭示了猫的下落问题。
His work remains an early example of using photography for scientific discovery.
他的作品仍然是用摄影辅助科学发现的一个早期例子。
What does photography do for science?
摄影对科学到底能有什么帮助呢?
It records something and it makes it permanent so you can analyze it later, or so you can share it.
它能记录并且能够永远地记录东西，从而方便我们日后对其进行分析、分享。
But what Marey did was show something that the eye could not possibly see — ever.
马莱却记录下了我们肉眼无法看到而且是永远都无法看到的东西。
You might have seen another famous early example of motion photography:
你可能已经看过另一个著名的早期运动摄影的例子：
In 1878, Eadweard Muybridge used 12 cameras connected to tripwires to prove that a horse lifts all four feet off the ground at some point in a gallop.
1878年，埃德沃德·迈布里奇用12台连接在绊索上的摄像机证明了，一匹马在奔跑的某个时刻是会四脚全部离地的。
