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永动机的问题

Why don't perpetual motion machines ever work? - Netta Schramm

公元1159年左右
Around 1159 A.D.,
一位被称为 渊博的婆什迦罗 的数学家
a mathematician called Bhaskara the Learned
设计了一个转轮
sketched a design for a wheel
轮内由曲线构成的容器内放着水银
containing curved reservoirs of mercury.
跟据他的推测 轮子旋转时
He reasoned that as the wheels spun,
水银会流向各个容器的底部
the mercury would flow to the bottomof each reservoir,
使轮子的一侧永远比另一侧沉
leaving one side of the wheelperpetually heavier than the other.
这种失衡状态会使轮子一直转下去
The imbalance would keep the wheel turning forever.
婆什迦罗的设计方案
Bhaskara’s drawing
是永动机初始设计方案中的一种
was one of the earliest designs for a perpetual motion machine,
即指可以不靠外部能源
a device that can do work indefinitely
而不停做功的装置
without any external energy source.
设想一下 一架风车
Imagine a windmill
可以靠自身产出的风力供自己旋转
that produced the breeze it needed to keep rotating.
或者一个灯泡
Or a lightbulb
可以靠自身发光来给自己供电
whose glow provided its own electricity.
这些装置在许多发明家的脑海中萦绕不去
These devices have captured many inventors’ imaginations
因为它们能改变我们和能源间的关系
because they could transformour relationship with energy.
例如 假使你能建造一个永动机
For example, if you could builda perpetual motion machine
使人类成为这个完美 高效的系统中的一环
that included humans as part of itsperfectly efficient system,
那它就可以永远的供给生命生存所需
it could sustain life indefinitely.
只有一个问题
There’s just one problem.
做不出来永动机
They don’t work.
所有永动机的设想
Ideas for perpetual motion machines
都至少违背了一条热力学基础定律
all violate one or morefundamental laws of thermodynamics,
热力学是物理学中
the branch of physics that describesthe relationship
描述不同类型能量间关系的分支学科
between different forms of energy.
热力学第一定律表明
The first law of thermodynamics says
能量不能被创造也不能被消灭
that energy can’t be created or destroyed.
你输出的能量不能比摄入的能量多
You can’t get out more energythan you put in.
这一下子就宣判了永动机的死刑
That rules out a usefulperpetual motion machine right away
因为一台机器产出的能量
because a machine could only ever produce
永远等于自身消耗的
as much energy as it consumed.
没有多余的能量
There wouldn’t be any left
去供给汽车或是给电话充电
over to power a car or charge a phone.
但要是只让机器维持自身运动呢?
But what if you just wanted the machine to keep itself moving?
发明者们提出了许多点子
Inventors have proposed plenty of ideas.
其中一些是婆什迦罗过平衡轮的变种
Several of these have been variationson Bhaskara’s over-balanced wheel
在旋臂上装有滚动的小球或者重物
with rolling ballsor weights on swinging arms.
不过它们都失败了
None of them work.
运动部件不光使转轮的一侧变重
The moving parts that make oneside of the wheel heavier
还使转轮的质心移到轮轴下方
also shift its center of mass downwardbelow the axle.
随着质心降低
With a low center of mass,
转轮只能像钟摆一样前后摇摆
the wheel just swings back and forth like a pendulum,
然后停止不动
then stops.
那换一种方式呢?
What about a different approach?
17世纪时
In the 17th century,
罗伯特•玻义耳想到了一个点子
Robert Boyle came up with an idea
自注水容器
for a self-watering pot.
他的理论依据来源于毛细现象
He theorized that capillary action,
作用于液体和容器壁间的张力
the attraction between liquids and surfaces
会使水流过细管
that pulls water through thin tubes,
这或许能使水在容器中循环流动
might keep the water cycling around the bowl.
但是 如果毛细现象能大到克服重力
But if the capillary action is strongenough to overcome gravity
把水吸上来
and draw the water up,
那它也能让水不落回到碗里
it would also prevent it from falling back into the bowl.
然后 是类似这架斜坡装置的磁石版本
Then there are versions with magnets,like this set of ramps.
小球会被顶端的磁石
The ball is supposed to be pulled upwards
吸上去
by the magnet at the top,
在孔洞处掉下滚回
fall back down through the hole,
然后重复这个周期运动
and repeat the cycle.
这个装置失败的原因和自注水容器的一样
This one fails because like the self-watering pot,
磁石只会把小球吸上去
the magnet would simply hold the ball at the top.
即使它确实一直在运动
Even if it somehow did keep moving,
磁石的引力会随时间而减弱
the magnet’s strength would degrade over time
它最终也会停下来
and eventually stop working.
为了能一直运行下去
For each of these machines to keep moving,
这些机器需要产出额外的能量
they’d have to create some extra energy
来推动自身 维持自身运动
to nudge the system past its stopping point,
这违背了热力学第一定律
breaking the first law of thermodynamics.
有那么一些机器貌似能永不停歇
There are ones that seem to keep going,
但事实上 它们都被证实有外部能源
but in reality, they invariably turn out to be
可汲取能量
drawing energy from some external source.
即使工程师们能设法设计出
Even if engineers could somehow design a machine
一台不违背热力学第一定律的机器
that didn’t violate the first law of thermodynamics,
在现实中
it still wouldn’t work in the real world
它还是会因为热力学第二定律而失败
because of the second law.
热力学第二定律告诉我们
The second law of thermodynamics tells us
能量会在诸如摩擦的过程中耗散掉
that energy tends to spread out through processes like friction.
现实中任意一款机器都有运动部件
Any real machine would have moving parts
或与空气分子 液体分子相互作用
or interactions with air or liquid molecules
这就会产生细微的摩擦和热量
that would generate tiny amountsof friction and heat,
即使在真空环境中也一样
even in a vacuum.
这部分热量就是散失的能量
That heat is energy escaping,
它会不停的耗散
and it would keep leeching out,
使得用来做功的能量越来越少
reducing the energy available to move the system itself
直到机器最终停下来为止
until the machine inevitably stopped.
时至今日 这两条热力学定律
So far, these two laws of thermodynamics
已经截断了所有关于永动机的设想
have stymied every idea for perpetual motion
并破灭了百分百效率的能源发电的美梦
and the dreams of perfectly efficientenergy generation they imply.
但是 也无法断言
Yet it’s hard to conclusively
我们永远都做不出永动机
say we’ll never discover a perpetual motion machine
因为宇宙中还有许多不为人知的东西
because there’s still so much we don’tunderstand about the universe.
或许我们会发现新型的系外物质
Perhaps we’ll findnew exotic forms of matter
迫使我们重新审视热力学定律
that’ll force us to revisit the lawsof thermodynamics.
又或者在量子级别中有永动存在的可能性
Or maybe there’s perpetual motionon tiny quantum scales.
我们唯一能确定的是
What we can be reasonably sure about
我们的探索会永不止步
is that we’ll never stop looking.
眼下 这也是唯一可以称为永动的了
For now, the one thing that seems truly perpetual is our search.

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视频概述

历史上,有无数的仁人智士投身于永动机的制做中。然而它却似乎只是一个美好的幻想?

听录译者

收集自网络

翻译译者

🔥云四

审核员

审核员 V

视频来源

https://www.youtube.com/watch?v=A-QgGXbDyR0

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