中国的三峡大坝太大了，把地球的旋转都拖慢了 [美国媒体]

TIL the Three Gorges Dam in China is so massive it has slowed the rotation of the Earth

中国的三峡大坝太大了，把地球的旋转都拖慢了





MajorNoodles
Tl:DR it's not the size of the dam itself that slowed the rotation of the Earth, it's the sheer volume of water mass that has shifted because of the dam.

不是大坝本身的体积拖慢了地球旋转，而是大坝造成的垂直的水的体积。

812many
Just like how an ice skater will slow their rotation by moving their arms away from their body, by lifting an amount of water away from the axis of spin of the planet it will slow the planets spin by that much. At least, that's what I'm guessing is the reason.

就像滑冰的人通过伸展手臂来减慢自己的转动速度，将一定量的水推离地球的旋转轴可以相应降低地球的转速。至少这是我猜测的原因。

pulse14
Moment of inertia

转动惯量。

BIOHAZARDB10
I understand perfectly now. Thank you

完全理解了，谢谢你。

devilslaughters
Gotta thank skaters, how else will we phrase complex physics and be understood easily?

我们应该感谢溜冰的人，要不然我们怎么能把复杂的物理表达的容易理解？

ARN_01D 
Even standing up out of bed in the morning slows down the rotation of the earth. The rpms may be indistinguishable from zero, but it does slow down

甚至早上从床上站起来都能减慢地球的自传。虽然减慢的速度接近于零，但确实是减慢了。

Zappke
So when I lay on my back, my morning wood...

所以当我躺在床上，我的早上就会……

MissFix8ed
It's not you pushing off the ground that makes you jump, it's the earth pushing you away. (I ? physics)

让你跳起来的并不是你把地面推开，而是地球把你推开。（我爱物理。）

pizzabyAlfredo 
I was going to say, the materials the dam has been constructed with are already on earth...but pooling massive amounts of water would do the trick.
Edit: since users want to blast me for this...I was basing this off of a ballast effect. I know the water was already there. Having a large amount of water pooled to one side of the earth could be enough to slightly shift the center of gravity making the rotation just that much slower.

我要说的是，建造大坝的物质已经在地球上……但集中大量的水能够产生效果。
编辑：因为有人想因为这句话炸了我，我把这种情况归结为一种压载效应。我知道水也在那里。但是把水集种到地球的一边足够轻微的改变其重心，让地球转动速度变慢。

CoopertheFluffy
So was the water though. It's all about the placement.

水也是这样。只不过是位置问题。

gwopy 
Elevation was the word you wanted...more specific than placement.

你想说的应该是海拔，这个词更合适。

greendestinyster
Even more specific... conservation of angular momentum!

更合适的是角动量守恒！

Utis_Khan
wow this is exactly what is going on.

就是这么个道理。

Erares
So in theory... If one could shift massive amounts of water up in elevation and in turn affecting how storms work and potentially using them as a weapon?

所以理论上，如果有人能把大量的水抬高到一定海拔，转而影响风暴的形成，有潜力当做武器使用？

wbotis
Can’t you explain just about anything by reducing it to “conservation laws?”

难道不能把它解释成守恒定律？

greendestinyster
Tide goes in, tide goes out. You can't explain that!

潮来潮去。你不能那么解释！

Athildur
That's just Poseidon and his shenanigans, trying to keep the ancient Greeks guessing.

只不过是波塞冬为了让古希腊人胡思乱想而搞的恶作剧。

NimChimspky
That quote is so amazing.
I might watch it again.

引用的那句话很赞。我想再看一遍。

wbotis
Fuck it! We’ll do it live!

其他的！我们要现场直播！

RMCPhoto
To the top plz

顶上首页。

Jericho85
I've heard about this numerous times, never understood why until this comment thread.

这件事我听了好多次了，从来没搞懂，直到这个看到这个讨论串。

rising3d
Even more specific... gravity

更合适的是重力。

toasters_are_great
Elevation, yes, but far and away the most important consideration is latitude. If this were at the Arctic Circle, say, then the reservoir water (that ultimately is transferred from the world ocean) would wind up closer to the Earth's rotation axis than it was before for a smaller moment of inertia. The Earth would spin slightly faster than before and the day shorten. Exact breakeven latitude depends on the distribution of the world ocean and the integral of the square of the cosine of the latitude of its parts.

海拔，是的，但最重要的考虑因素是纬度。如果三峡大坝建在北极圈，那么水库里的水（最终从世界各大洋转移而来）将比转动惯量较小之前更加靠近地球的自转轴。地球将会比之前转的快一点，一天的时间会变短。精确的盈亏平衡纬度取决于世界海洋的分布和其纬度纬度余弦的平方积分。

gwopy
I'll just catch your mic for you there, sir. Wouldn't want it to get damaged.

我会在那里帮你接住麦克风的，老大。不想把它摔坏。

bandanagirl95
As a sound designer, I thank you for not letting the dropped mic hit the floor.
Edit: fixed autocorrect

作为一个音响设计师，我谢谢你没让那个麦克风掉到地上。

JCMcFancypants
Could you accurately say that you've slowed the rotation of the earth by increasing the elevation of any mass...just by an insignificantly minute amount?

你难道不能准确的说你通过增加任何物质的海拔来降低地球的自转速度？只不过减小的量微不足道。

Theurv
That's why time goes so fast when you sleep. When you get up in the morning the world slows back down

这就是为什么你睡觉的时候时间过得这么快。当你早上醒来世界的速度又降回去了。

Heslay_Cashlion
I hope...... the rise of my morning wood would make the world spin slower.
Someone please confirm or lie to me so I can show my wife!

我希望，我早上起来能让地球转慢一点。
来个人给我确认一下，或者骗我一把，我好跟我老婆显摆一下！

herrybaws
It's true but only if you're on your back

是这样的，但除非你躺在床上。

gwopy
...or if you're really good at balancing.

……或者如果你的平衡性非常好。

willbear10 1分 
ow ooh ouch

哎呦，喔，哎呦

simonlorax
Kinda like how because time slows down as you approach the speed of light and within a gravitational field, does time go slower on your run or with any movement???

有点像当你接近光速和处于重力场之中的时候，速度会减慢，你跑步或者做任何运动的时候时间会变慢吗？

Pandarandrist
Eh, distance from earth's rotational axis is not equal to elevation. Latitude is far more critical, here

到地球自转轴的距离不等于海拔。纬度在这里更为关键。

dubBAU5 5分 
Or displacement

或者吨位。

memesplaining
ikr, in both cases, not sure what their point was

两种情况，不太肯定他们是什么观点

anoleiam
Pooling massive amounts of water is basically the same concept as pooling together the materials to build the dam that were already on Earth. All that water was also already on Earth, save for the water periodically suspended in the air. I think it would be the same to say building a dam using every rock on Earth would have the same effect as pooling all the water, it's just a difference in the resource you are pooling in one location.
Edit: just realized every other person in this thread has hammered you on the same point. I rest my case, and humbly apologize

把大量的水汇集在一起跟把原本在地上的物质堆积在一起形成大坝基本上是同样的原理。所有那些水原本在地上，除了周期性悬浮在空气中的水。我认为用地上的每块石头建造一座大坝跟汇聚所有的水是同一个效果，区别在于你汇集在那个地方的物质不一样。
编辑：刚刚看到这个串里的每个人都在因为同一个观点喷你。我休息一下，向你道歉。

CryTheSly
As opposed to the water not being on Earth? Building a dam is pooling a lot of concrete in one spot

难道水不在地球上吗？建造大坝也不过是把很多水泥聚集在一个地方，

IsABot
The amount of concrete is nothing compared to the amount of water being held back by that concrete. And how that changes earth's moment of inertia.
When the water level is maximum at 175 meters (574 ft) over sea level (91 meters (299 ft) above river level), the reservoir created by the dam is about 660 kilometers (410 mi) in length and 1.12 kilometers (0.70 mi) in width on average. The total surface area of the reservoir is 1045 square kilometers, and it will will flood a total area of 632 square kilometers, of land. The reservoir will contain about 39.3 cu km (9.43 cubic miles) of water. That water will weigh more than 39 trillion kilograms (42 billion tons).
A shift in a mass of that size would affect the rotation of the Earth due to a phenomena known as the moment of inertia, which is the inertia of a rigid rotating body with respect to its rotation. The moment of inertia of an object about a given axis describes how difficult it is to change its angular motion about that axis. The longer the distance of a mass to its axis of rotation, the slower it will spin. You may not know it, but you see examples of this in everyday life. For example, a figure skater attempting to spin faster will draw her arms tight to her bodies, and thereby reduce her moment of inertia. Similarly, a diver attempting to somersault faster will bring his body into a tucked position.
Raising 39 trillion kilograms of water 175 meters above sea level will increase the Earth’s moment of inertia and thus slow its rotation.
http://www.businessinsider.com/chinas-three-gorges-dam-really-will-slow-the-earths-rotation-2010-6

水泥的量远不能跟被水泥拦截的水量相比。那是怎样改变地球转动惯量的呢？
当水位最高到达175m（574英尺），超过海平面（91m-299英尺）的时候，大坝造成的蓄水池长度大约为660km（410英里），平均宽度为1.12km（0.70英里）。蓄水池的表面积总共为1045平方千米，它可以淹没总计632平方千米的土地。这个蓄水池可以积蓄大约39.3立方千米（6.43立方英里）的水。这些水的重量超过39万亿kg（420亿吨）。
那么大体积的物质的位移由于一种称为转动惯量的现象，将会影响到地球的自转，这个惯量是刚性旋转体由于旋转造成的。物体对于给定轴的转动惯量描述了改变它相对于那个轴的角运动的困难程度。物体与旋转轴的距离越长，它旋转的速度就越慢。你可能不知道它，但你可以在日常生活中看到这样的例子。例如，花样滑冰运动员试图快速旋转时会用手臂紧紧地抱住身体，从而减少了她的转动惯量。同样的，一个试图快速翻腾的跳水运动员会使他的身体进入翻折的位置。
在海拔175米处增加39万亿kg的水，将增加地球的惯性力矩，从而减慢自转速度。