我们为什么造不出永动机
Why don't perpetual motion machines ever work
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Around 1159 A.D., a mathematician called Bhaskara the Learned sketched a design for a wheel containing curved reservoirs of mercury. He reasoned that as the wheels spun, the mercury would flow to the bottom of each reservoir, leaving one side of the wheel perpetually heavier than the other. The imbalance would keep the wheel turning forever. Bhaskara's drawing was one of the earliest designs for a perpetual motion machine, a device that can do work indefinitely without any external energy source.
Imagine a windmill that produced the breeze it needed to keep rotating. Or a lightbulb whose glow provided its own electricity. These devices have captured many inventors' imaginations, because they could transform our relationship with energy.
For example, if you could build a perpetual motion machine that included humans as part of its perfectly efficient system, it could sustain life indefinitely. There's just one problem. They don't work.
Ideas for perpetual motion machines all violate one or more fundamental laws of thermodynamics, the branch of physics that describes the relationship between different forms of energy.
The first law of thermodynamics says that energy can't be created or destroyed. You can't get out more energy than you put in. That rules out a useful perpetual motion machine right away, because a machine could only ever produce as much energy as it consumed. There wouldn't be any left over to power a car or charge a phone.
But what if you just wanted the machine to keep itself moving? Inventors have proposed plenty of ideas. Several of these have been variations on Bhashara's over-balanced wheel, with rolling balls or weights on swinging arms. None of them work. The moving parts that make one side of the wheel heavier also shift its center of mass downward below the axle. With a low center of mass, the wheel just swings back and forth like a pendulum, then stops.
What about a different approach? In the 17th century, Robert Boyle came up with an idea for a self-watering pot. He theorized that capillary action, the attraction between liquids and surfaces that pulls water through thin tubes, might keep the water cycling around the bowl. But if the capillary action is strong enough to overcome gravity, and draw the water up, it would also prevent it from falling back into the bowl.
Then there are versions with magnets, like this set of ramps. The ball is supposed to be pulled upwards by the magnet at the top, fall back down through the hole, and repeat the cycle. This one fails because like the self-watering pot, the magnet would simply hold the ball at the top. Even if it somehow did keep moving, the magnet's strength would degrade over time, and eventually stop working.
For each of these machines to keep moving, they'd have to create some extra energy to nudge the system past its stopping point, breaking the first law of thermodynamics. There are ones that seem to keep going, but in reality, they invariably turn out to the drawing energy from some external source.
Even if engineers could somehow design a machine that didn't violate the first law of thermodynamics, it still wouldn't work in the real world because of the second law.
The second law of thermodynamics tells us that energy tends to spread out through processes like friction. Any real machine would have moving parts or interactions with air or liquid molecules, that would generate tiny amounts of friction and heat, even in a vacuum. That heat is energy escaping, and it would keep leaching out, reducing the energy avalible to move the system itself, until the machine inevitably stopped.
So far, these two laws of thermodynamics have stymied every idea for perpetual motion, and the dreams of perfectly efficient energy generation they imply. Yet it's hard to conclusively say we'll never discover a perpetual motion machine, because there's still so much we don't understand about the universe. Perhaps we'll find new exotic forms of matter that'll force us to revisit the laws of thermodynamics. Or maybe there's perpetual motion on tiny quantum scales.
What we can be reasonably sure about is that we'll never stop looking. For now, the one thing that seems truly perpetual is our search.
生词统计
| 单词 | 音标 | 翻译 |
|---|---|---|
| A.D. | Anno Domini | 公元后、耶稣纪元后 |
| reservoir | ˈrezərvwɑːr | n. 水库、蓄水池 |
| spun | spʌn | v. 旋转、急转弯 |
| indefinite | ɪnˈdefɪnət | adj. 不确定的、无限的、模糊的 |
| thermodynamic | ˌθɜːrmoʊdaɪˈnæmɪk | adj. 热力学的、使用热动力的 |
| variation | ˌveriˈeɪʃn | n. 变化、变更、变动、变异 |
| axle | ˈæksl | n. 车轴、轮轴 |
| pendulum | ˈpendʒələm | n. 摆钟、摇摆、摇摆不定的事态 |
| ramp | ræmp | n. 斜坡、坡道 、敲诈 |
| nudge | nʌdʒ | n. 推动、轻推、触发； v. 轻推、轻撞、推开 |
| molecule | ˈmɑːlɪkjuːl | n. 分子、微小颗粒、微粒 |
| vacuum | ˈvækjuːm | n. 真空、空间 |
| inevitable | ɪnˈevɪtəbl | adj. 必然的、不可避免的 |
| stymie | ˈstaɪmi | v. 从中作梗、阻挠、妨碍 |
| exotic | ɪɡˈzɑːtɪk | adj. 异国的、外来的、异国情调的 |
| quantum | ˈkwɑːntəm | n. 量子论 |
翻译
Around 1159 A.D., a mathematician called Bhaskara the Learned sketched a design for a wheel containing curved reservoirs of mercury. He reasoned that as the wheels spun, the mercury would flow to the bottom of each reservoir, leaving one side of the wheel perpetually behavier than the other. The imbalance would keep the wheel turning forever. Bhaskara's drawing was one of the earliest designs for a perpetual motion machine, a device that can do work indefinitely without any external energy source.
大约在公元1159年，一位数学家Bhaskara绘制了一个轮子的草图，是一个弯曲的水银容器。他推断，当轮子旋转时，水银会流到每个水池的底部，使轮子的一侧永远比另一侧重。这种不平衡会让轮子永久转动。Bhaskara这幅画是永动机的最早设计之一，一种不需要任何外界能源就可以无限期运行的装置。
Imagine a windmill that produced the breeze it needed to keep rotating. Or a lightbulb whose glow provided its own electricity. These devices have captured many inventors' imaginations, because they could transform our relationship with energy.
想象一下，风车制造使其不停转动的微风，电灯泡自给自足发光的电力，这些装置激发了许多发明家的想象，因为这能改变人与能源的关系。
For example, if you could build a perpetual motion machine that included humans as part of its perfectly efficient system, it could sustain life indefinitely. There's just one problem. They don't work.
例如，如果你能创造出一个永动机，并且把人类作为整个系统中的一部分，生命可能因此永存。但是又一个问题，就是这种机器行不通。
Ideas for perpetual motion machines all violate one or more fundamental laws of thermodynamics, the branch of physics that describes the relationship between different forms of evergy.
永动机的想法都至少违背一项热力学基本定律，这是物理学的一个分支，用来解释不同能量形态之间的关系。
The first law of thermodynamics says that energy can't be created or destroyed. You can't get out more energy than you put in. That rules out a useful perpetual motion machine right away, because a machine could only ever produce as much energy as it consumed. There wouldn't be any left over to power a car or charge a phone.
热力学第一定律提到，能源无法被创造或毁灭。输出的能量必定不多于输入的能量，此定律立即排除了永动机的制造可能。因为一台机器最多能产出它消耗的能量，没有一丝多余的能量给车或者手机充电。
But what if you just wanted the machine to keep itself moving? Inventors have proposed plenty of ideas. Several of these have been variations on Bhashara's over-balanced wheel, with rolling balls or weights on swinging arms. None of them work. The moving parts that make on side of the wheel heavier also shift its center of mass downward below the axle. With a low center of mass, the wheel just swings back and forth like a pendulum, then stops.
若只是想让机器自己不停的运转呢？发明家们提出了很多想法，其中有几个是Bhaskara不平衡轮子的变体，把水银换成滚动的球体或摆动的重力臂，都不行。移动的部分加重轮子的一端，也使轮子的重心下坠至低于轮轴中心，最后轮子会像摆钟一样来回摆动，直至停止。
What about a different approach? In the 17th century, Robert Boyle came up with an idea for a self-watering pot. He theorized that capillary action, the attraction between liquids and surfaces that pulls water through thin tubes, might keep the water cycling around the bowl. But if the capillary action is strong enough to overcome gravity, and draw the water up, it would also prevent it from falling back into the bowl.
如果采用其他方式呢？17世纪，Robert Boyle提出了一个自给水壶的想法，他解释毛细管的作用，即液体于管子表面的吸力，把水戏进管子，或许可以让水在容器中循环流动。但若毛细管吸力大到足以克服引力把水吸上来，同样能阻止水流入到容器中。
Then there are versions with magnets, like this set of ramps. The ball is supposed to be pulled upwards by the magnet at the top, fall back down through the hole, and repeat the cycle. This one fails because like the self-watering pot, the magnet would simply hold the ball at the top. Even if it somehow did keep moving, the magnet's strength would degrade over time, and eventually stop working.
其他情况是利用磁铁，就像斜坡。顶端的磁铁把球吸上来，然后球掉进洞里，重复循环。这种想法也不行，原因如同自给水壶，球会被磁铁吸附在上面。就算球真的循环运动，磁铁的磁力也会逐渐减弱，最后停止运作。
For each of these machines to keep moving, they'd have to create some extra energy to nudge the system past its stopping point, breaking the first law of thermodynamics. There are ones that seem to keep going, but in reality, they invariably turn out to the drawing energy from some external source.
想让这类机器持续运作，则必须制造额外的力量，促使整个系统超越停止点，打破热力学第一定律。有些能量看似持续运作，但实际上它们总是从外部获取能量。
Even if engineers could somehow design a machine that didn't violate the first law of thermodynamics, it still wouldn't work in the real world because of the second law.
就算工程师能设计一个机器不违背热力学第一定律，因为有第二定律存在，这也是行不通的。
The second law of thermodynamics tells us that energy tends to spread out through processes like friction. Any real machine would have moving parts or interactions with air or liquid molecules, that would generate tiny amounts of friction and heat, even in a vacuum. That heat is energy escaping, and it would keep leaching out, reducing the energy avalible to move the system itself, until the machine inevitably stopped.
热力学第二定律是说能量往往会在摩擦过程中消散。任何现实中存在的机器都会有移动的部件或于空气和水分子产生交互作用。这回产生少量的摩擦于热能，即使在真空亦是如此。这就是能量散逸，且持续散逸。这回降低可供系统运作的能量，直至机器不可避免的停下来。
So far, these two laws of thermodynamics have stymied every idea for perpetual motion, and the dreams of perfectly efficient energy generation they imply. Yet it's hard to conclusively say we'll never discover a perpetual motion machine, because there's still so much we don't understand about the universe. Perhaps we'll find new exotic forms of matter that'll force us to revisit the laws of thermodynamics. Or maybe there's perpetual motion on tiny quantum scales.
截至目前，这两项热力学定律阻碍了与永动机相关的所有想法及其他完美节能的美梦。是否永远无法产生永动机这个无法定论，认为人类对宇宙的了解仍极为有限。或许人们会发现全新的运动规则，迫使我们重新审视热力学定律。又或许永动机存在于渺小的量子领域。
What we can be reasonably sure about is that we'll never stop looking. For now, the one thing that seems truly perpetual is our search.
唯一能确定的是人类会不停的探索，现在，唯一看似永动机的就是人类的探索。