科学美国人60秒 打响指的惊人物理现象

The Surprising Physics of Finger Snapping

打响指的惊人物理现象

Karen Hopkin: This is Scientific American’s 60-Second Science. I’m Karen Hopkin.

Doing science isn’t easy. It takes an enormous amount of time and energy to collect and analyze¹ data. At least, that’s the way it usually works.

凯伦·霍普金：这是《科学美国人》的60秒科学。我是凯伦·霍普金。

做科学并不容易。收集和分析数据需要花费大量的时间和精力。至少，这是它通常的工作方式。

Saad Bhamla: This is one of those examples that we joke that we can snap our fingers and get data.

萨阿德·巴姆拉：这是我们开玩笑说我们可以折断手指获取数据的例子之一。

Hopkin: That’s because Saad Bhamla and his students just wrapped up a study of the physics of finger snapping. They found that the right amount of friction² is key to a successful snap. Their work appears in the Journal of the Royal Society Interface³. [Raghav Acharya et al., The ultrafast snap of a finger is mediated⁴ by skin friction]

霍普金：那是因为萨阿德·巴姆拉和他的学生刚刚完成了一项关于手指折断的物理研究。他们发现适当的摩擦力是成功抓拍的关键。他们的研究成果发表在《皇家学会杂志》上。

Bhamla’s lab at Georgia Tech focuses on ultrafast motion in nature.

Bhamla: Organisms can achieve really, really fast motions, and we are curious about how they’re able to do this and how we may extract those principles for perhaps synthetic⁵ systems.

巴姆拉在佐治亚理工学院的实验室专注于自然界的超快运动。

巴姆拉：生物体可以实现非常非常快的运动，我们很好奇它们是如何做到这一点的，以及我们如何为可能的合成系统提取这些原理。

Hopkin: Their science may be hard-core. But their lab meetings include time to be a bit more playful.

霍普金：他们的科学可能是核心。但是他们的实验室会议包括时间变得更有趣一点。

Bhamla: We have something called Super Happy Fun Time. And in this, we’ll talk about something typically nonscientific just to kind of defuse the situation after a typically intense scientific discussion that a student presents.

巴姆拉：我们有一种叫做“超级快乐时光”的活动。在这篇文章中，我们将讨论一些典型的非科学的东西，只是为了在一个学生典型的激烈的科学讨论之后缓解这种情况。

Hopkin: A couple years back, their talk turned to the movie Infinity⁶ Wars. In the climax⁷ of this Avengers flick⁸, supervillain Thanos forever alters the Marvel⁹ Cinematic Universe with a snap of his massive, metal-clad fingers. But something about the scene left Bhamla scratching his head.

霍普金：几年前，他们的话题转到电影《无限战争》。在这部《复仇者》电影的高潮中，超级反派塔诺斯用他那硕大的金属手指的一瞬间永远改变了奇迹般的电影世界。但现场的一些情况让巴姆拉抓挠着头。

Bhamla: And I said, “You know what? I’m willing to make a bet that if you had metallic¹⁰ gauntlets like Thanos has, I would suspect that it’s actually very difficult to store energy in a controllable way.”

巴姆拉：我说，“你知道吗？我愿意打赌，如果你有像塔诺斯那样的金属护手，我会怀疑以可控的方式储存能量是非常困难的。”

Hopkin: Energy that then has to get quickly released if you really want to snap. So Raghav Acharya, a student in Bhamla’s lab, set up an experiment.

霍普金：如果你真的想抓拍的话，能量必须很快释放出来。因此，Bhamla实验室的学生Raghav Acharya进行了一项实验。

Bhamla: He put some reflective dots on his fingers so he could automatically track the finger movement when you take a side view video with a high-speed camera—just to be able to extract out the velocities¹¹ and accelerations¹³.

巴姆拉：他在手指上放了一些反射点，这样当你用高速摄像机拍摄侧视视频时，他就可以自动跟踪手指的运动，以便提取速度和加速度。

Hopkin: Because the first thing they wanted to know was: Just how fast is this jazzy hepcat gesture?

霍普金：因为他们想知道的第一件事是：这个爵士赫普卡特手势有多快？

Bhamla: We discovered that the finger snap takes about seven milliseconds. To put that into context, that’s 20 times faster than the blink of an eye. A blink of an eye is glacially slow: it’s like about 150 milliseconds.

巴姆拉：我们发现手指抓拍大约需要7毫秒。把它放在上下文中，比眨眼快20倍。眨眼的速度非常慢：大约150毫秒。

Hopkin: Even more impressive than its speed was its acceleration¹², which was three times faster than the throwing arm of a big-league baseball pitcher¹⁴.

霍普金：比它的速度更令人印象深刻的是它的加速度，它比大联盟棒球投手的投球臂快三倍。

Bhamla: So here we have a snap done by scientists. So we’re no professional athletes; we barely go to the gym. And we’re about almost three times in acceleration faster. So that kind of led to this question: How are we able to perform this seemingly extraordinary feat¹⁵ of acrobatics¹⁶ and human dexterity¹⁷?

巴姆拉：这里我们有一个由科学家拍摄的快照。所以我们不是职业运动员；我们几乎不去健身房。我们的加速度快了将近三倍。这就引出了一个问题：我们如何才能完成这个看似非凡的杂技和人类灵巧的壮举？

Hopkin: To find out, they started to fiddle¹⁸ with friction. First, Raghav and his grad student mentor¹⁹ Elio Challita used some moisturizer to make their fingers a little more slippery. And they found the resulting snaps were not so snappy. So then they went the other way.

霍普金：为了找到答案，他们开始玩弄摩擦。首先，Raghav和他的研究生导师Elio Challita使用了一些润肤霜，使他们的手指更加光滑。他们发现结果的快照并不那么快。于是他们走了另一条路。

Bhamla: Counterintuitively, we thought, “Oh, friction is great. Let’s put some high-friction rubber pads”—thinking, “If I increase the friction, I’m going to get a louder snap perhaps.”

巴姆拉：与直觉相反，我们认为，“哦，摩擦很好。让我们放一些高摩擦橡胶垫”——想，“如果我增加摩擦，我可能会得到更大的响声。”

Hopkin: But that also squelched²⁰ the snap because you waste too much of the stored energy trying to get your fingers to slide past each other.

霍普金：但这也压制了这一瞬间，因为你浪费了太多储存的能量试图让你的手指滑过彼此。

Bhamla: And so it turns out that, in our experiments, we find that the skin friction is kind of this optimal²¹ sweet spot in this Goldilocks zone that gives you enough energy but also detaches quickly to give you the snap [snaps].

Bhamla：所以，在我们的实验中，我们发现表面摩擦力是这个金发区的一个最佳最佳最佳点，它能给你足够的能量，但也能很快分离，让你抓紧

Hopkin: And as for Thanos?

霍普金：至于塔诺斯呢？

Bhamla: If you put copper²² thimbles, which we did to test the Thanos hypothesis, turns out that the compressibility of the finger pads is important as well. If you have these rigid²³ surfaces, although the friction is the same as the skin, not being able to compress affects the grip and storage of energy, so you get a very weak, or not really a satisfactory, snap.

巴姆拉：如果你放上铜套管，我们就是为了验证萨诺斯假说而做的，结果证明手指垫的可压缩性也很重要。如果你有这些刚性表面，尽管摩擦力与皮肤相同，但不能压缩会影响抓地力和能量储存，因此你会得到非常弱的，或者不是很令人满意的抓拍。

Hopkin: Bhamla wonders whether there’s also something special about the shape of our hands that gives us this ability. Or can other primates²⁴ do it, too?

霍普金：巴姆拉想知道我们的手的形状是否也有特殊的东西赋予我们这种能力。或者其他灵长类动物也能这样做？

Bhamla: I have written so many e-mails to so many anthropologists, zookeepers.

巴姆拉：我给这么多人类学家、动物园管理员写了这么多电子邮件。

Hopkin: He’s even gone back to the movies.

霍普金：他甚至还回去看电影了。

Bhamla: What if I saw, in Planet of the Apes, these apes sitting on top of a horse and snapping? Well that would be okay for me because somebody at least imagined it, right? Maybe they did their homework. Maybe it was described in some journal somewhere by a naturalist²⁵.

巴姆拉：若我在《类人猿星球》中看到，这些类人猿坐在马背上偷吃呢？那对我来说没关系，因为至少有人想象出来了，对吧？也许他们做了家庭作业。也许是某个博物学家在某个杂志上描述的。

Hopkin: If you’ve ever seen a chimp²⁶ snap, please let Bhamla know. In the meantime, he’ll continue to pursue projects that captivate his curiosity.

霍普金：如果你见过黑猩猩咬人，请告诉巴姆拉。与此同时，他将继续从事吸引他好奇心的项目。

Bhamla: Life is too short to do boring stuff. I think it’s more enjoyable for me and the students to say, “Oh my god, like, how cool is that?” And when nature pushes the limits of physics and engineering, there are interesting things to be gleaned²⁷ out of it.

巴姆拉：生命太短暂，不能做无聊的事情。我认为对我和学生来说，说“哦，天哪，那有多酷？”更令人愉快当大自然突破物理学和工程学的极限时，我们可以从中收集到一些有趣的东西。

Hopkin: Plus, you can explain your findings like [snaps].

霍普金：另外，你可以这样解释你的发现

Bhamla: My parents now get it [laughs]. Well, I think they do.

巴姆拉：我父母现在明白了[笑]。嗯，我想是的。

Hopkin: For Scientific American’s 60-Second Science, I’m Karen Hopkin.

霍普金：《科学美国人》的《60秒科学》，我是凯伦·霍普金。

1 analyze   

vt.分析，解析 (=analyse)

参考例句：

• We should analyze the cause and effect of this event.我们应该分析这场事变的因果。
• The teacher tried to analyze the cause of our failure.老师设法分析我们失败的原因。

2 friction   

n.摩擦，摩擦力

参考例句：

• When Joan returned to work,the friction between them increased.琼回来工作后，他们之间的摩擦加剧了。
• Friction acts on moving bodies and brings them to a stop.摩擦力作用于运动着的物体，并使其停止。

3 interface   

n.接合部位，分界面；v.(使)互相联系

参考例句：

• My computer has a network interface,which allows me to get to other computers.我的计算机有网络接口可以与其它计算机连在一起。
• This program has perspicuous interface and extensive application. 该程序界面明了，适用范围广。

4 mediated   

调停，调解，斡旋( mediate的过去式和过去分词 )； 居间促成； 影响…的发生； 使…可能发生

参考例句：

• He mediated in the quarrel between the two boys. 他调解两个孩子之间的争吵。
• The government mediated between the workers and the employers. 政府在工人与雇主间搞调和。

5 synthetic   

adj.合成的，人工的；综合的；n.人工制品

参考例句：

• We felt the salesman's synthetic friendliness.我们感觉到那位销售员的虚情假意。
• It's a synthetic diamond.这是人造钻石。

6 infinity   

n.无限，无穷，大量

参考例句：

• It is impossible to count up to infinity.不可能数到无穷大。
• Theoretically,a line can extend into infinity.从理论上来说直线可以无限地延伸。

7 climax   

n.顶点；高潮；v.(使)达到顶点

参考例句：

• The fifth scene was the climax of the play.第五场是全剧的高潮。
• His quarrel with his father brought matters to a climax.他与他父亲的争吵使得事态发展到了顶点。

8 flick   

n.快速的轻打，轻打声，弹开；v.轻弹，轻轻拂去，忽然摇动

参考例句：

• He gave a flick of the whip.他轻抽一下鞭子。
• By a flick of his whip,he drove the fly from the horse's head.他用鞭子轻抽了一下，将马头上的苍蝇驱走。

9 marvel   

vi.(at)惊叹vt.感到惊异；n.令人惊异的事

参考例句：

• The robot is a marvel of modern engineering.机器人是现代工程技术的奇迹。
• The operation was a marvel of medical skill.这次手术是医术上的一个奇迹。

10 metallic   

adj.金属的；金属制的；含金属的；产金属的；像金属的

参考例句：

• A sharp metallic note coming from the outside frightened me.外面传来尖锐铿锵的声音吓了我一跳。
• He picked up a metallic ring last night.昨夜他捡了一个金属戒指。

11 velocities   

n.速度( velocity的名词复数 )；高速，快速

参考例句：

• In experimenting we find out that sound travels with different velocities through different substances. 在实验中，我们发现声音以不同的速度通过不同的物质而传播。 来自《现代汉英综合大词典》
• A gas in thermal equilibrium has particles of all velocities. 处于热平衡的气体，其粒子有一切速度。 来自辞典例句

12 acceleration   

n.加速，加速度

参考例句：

• All spacemen must be able to bear acceleration.所有太空人都应能承受加速度。
• He has also called for an acceleration of political reforms.他同时呼吁加快政治改革的步伐。

13 accelerations   

n.加速( acceleration的名词复数 )；加速度；（车辆）加速能力；（优秀学生的）跳级

参考例句：

• The two particles will undergo accelerations as a result of their interaction. 这两个粒子由于相互作用将获得加速度。 来自辞典例句
• Since the cord connecting the two blocks is inextensible, the accelerations are the same. 由于连接两物块的绳子无伸缩性，因此它们的加速度相同。 来自辞典例句

14 pitcher   

n.(有嘴和柄的)大水罐；(棒球)投手

参考例句：

• He poured the milk out of the pitcher.他从大罐中倒出牛奶。
• Any pitcher is liable to crack during a tight game.任何投手在紧张的比赛中都可能会失常。

15 feat   

n.功绩；武艺，技艺；adj.灵巧的，漂亮的，合适的

参考例句：

• Man's first landing on the moon was a feat of great daring.人类首次登月是一个勇敢的壮举。
• He received a medal for his heroic feat.他因其英雄业绩而获得一枚勋章。

16 acrobatics   

n.杂技

参考例句：

• Acrobatics is hard to learn but beautiful to watch.杂技不好学，但很好看。
• We watched a performance which included a puppet show and acrobatics.我们观看了一场演出，内容有木偶和杂技。

17 dexterity   

n.(手的)灵巧，灵活

参考例句：

• You need manual dexterity to be good at video games.玩好电子游戏手要灵巧。
• I'm your inferior in manual dexterity.论手巧，我不如你。

18 fiddle   

n.小提琴；vi.拉提琴；不停拨弄，乱动

参考例句：

• She plays the fiddle well.她小提琴拉得好。
• Don't fiddle with the typewriter.不要摆弄那架打字机了。

19 mentor   

n.指导者，良师益友；v.指导

参考例句：

• He fed on the great ideas of his mentor.他以他导师的伟大思想为支撑。
• He had mentored scores of younger doctors.他指导过许多更年轻的医生。

20 squelched   

v.发吧唧声，发扑哧声( squelch的过去式和过去分词 )；制止；压制；遏制

参考例句：

• We squelched over the soggy ground. 我们咕唧咕唧地走过泥泞的土地。
• The mud squelched as I walked through it. 我扑哧扑哧地穿过泥泞。

21 optimal   

adj.最适宜的；最理想的；最令人满意的

参考例句：

• What is the optimal mix of private and public property rights in natural resources?私人和国家的自然资源产权的最适宜的组合是什么？
• Optimal path planning is a key link for the sailing contest.帆船最优行驶路径规划是帆船比赛取胜的关键环节。

22 copper   

n.铜；铜币；铜器；adj.铜(制)的；(紫)铜色的

参考例句：

• The students are asked to prove the purity of copper.要求学生们检验铜的纯度。
• Copper is a good medium for the conduction of heat and electricity.铜是热和电的良导体。

23 rigid   

adj.严格的，死板的；刚硬的，僵硬的

参考例句：

• She became as rigid as adamant.她变得如顽石般的固执。
• The examination was so rigid that nearly all aspirants were ruled out.考试很严，几乎所有的考生都被淘汰了。

24 primates   

primate的复数

参考例句：

• Primates are alert, inquisitive animals. 灵长目动物是机灵、好奇的动物。
• Consciousness or cerebration has been said to have emerged in the evolution of higher primates. 据说意识或思考在较高级灵长类的进化中已出现。

25 naturalist   

n.博物学家(尤指直接观察动植物者)

参考例句：

• He was a printer by trade and naturalist by avocation.他从事印刷业，同时是个博物学爱好者。
• The naturalist told us many stories about birds.博物学家给我们讲述了许多有关鸟儿的故事。

26 chimp   

n.黑猩猩

参考例句：

• In fact,the color of gorilla and chimp are light-color.其实大猩猩和黑猩猩的肤色是较为浅的。
• The chimp is the champ.猩猩是冠军。

27 gleaned   

v.一点点地收集（资料、事实）( glean的过去式和过去分词 )；（收割后）拾穗

参考例句：

• These figures have been gleaned from a number of studies. 这些数据是通过多次研究收集得来的。
• A valuable lesson may be gleaned from it by those who have eyes to see. 明眼人可从中记取宝贵的教训。 来自《现代汉英综合大词典》