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How Infamous Hydroelectric Dam Changed Earth’s Rotation

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How Infamous Hydroelectric Dam Changed Earth’s Rotation
Umer Abrar


As the $30 billion plan was declared, Chinese administrators have encountered heavy inspection from both environmental activists like and scientists. Many consider that the dam will eventually result in disaster. Some worries include the dam trapping pollution, producing earthquakes and mudslides, displacing citizens and according to a report more than 1.3 million people have already been enforced to relocate, and terminating historical locations – alongside with the habitats of rare animals. (The government finally approved that the project was ill conceived – after years of labelling the dam one of the most remarkable pieces of engineering in Chinese history – but the loss is already done.) The last 32 generators went into action in July last year. The flowing water produced by the dam has sufficient power to produce about 22.5 million kilowatts of energy, which is equal to around FIFTEEN nuclear reactors and, obviously, it doesn’t cause worries about radioactive materials being released, which is a very good thing, the terrible effects can be cancelled by most, mostly due to the fact that it’s a clean, effective way of rendering energy for a growing population.


Credit: STR/AFP/Getty Images

Speculating how this could possibly have an influence on the Earth’s rotation? Here’s a perfect source that breaks it down further:


“Three Gorges Dam crosses the Yangtze River in Hubei province, China. It is the world’s largest hydroelectric power station by total capacity, which will be 22,500 MW when completed. When the water level is at maximum….it will flood a total area of 632 km2 of land. The reservoir will contain about 39.3 cubic 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 will impact 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 body, 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. However, the impact will be extremely small. NASA scientists calculated the shift of such a mass will increase the length of day by only 0.06 microseconds, and make the Earth only very slightly more round in the middle and more flat on the top. It will also shift the pole position by about two centimeters (0.8 inch). Note that a shift in any object’s mass on the Earth relative to its axis of rotation will change its moment of inertia, although most shifts are too small to be measured (but they can be calculated).” Source


Earth’s rotation changes regularly, with many changed variables added into the equation. First, we have the moon gradually receding from the Earth changing Earth’s rotation ever-so-slightly. Earthquakes also help along the process (the mega quake in Japan back in 2011changed Earth’s spin by 2.68 microseconds). Also, every 5 years the length of the day increases and decreases by approximately a millisecond, or roughly 550 times greater than the change produced by the Japanese earthquake.

How Infamous Hydroelectric Dam Changed Earth’s Rotation | Physics-Astronomy

@Levina @thesolar65 :what:
 
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It is certainly a ecological disaster. Now a days it is accepted that smaller earthen dams are better than huge concrete ones. It seems china wants to impress the world about its achievement so they blindly end up racing to build fastest,tallest,highest......etc without any concern for future consequences.
 
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Hmmmmm

I have my doubts ...nary that I consider myself smarter than the NASAns(inhabitants of NASA in my language).
One, earth has a diameter of about 12000kms(approx) and a mass of 6x10^24kgs. So whatever effect is caused is minuscule to be noticed- nothing that will effect us.
Two, shift of poles is a magnetic phenomenon. I am not sure, how's it related to the Dam.
Nonetheless, dam of this size, if not maintained well, can jeopardise lives of millions.
 
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Hmmmmm

I have my doubts ...nary that I consider myself smarter than the NASAns(inhabitants of NASA in my language).
One, earth has a diameter of about 12000kms(approx) and a mass of 6x10^24kgs. So whatever effect is caused is minuscule to be noticed- nothing that will effect us.
Two, shift of poles is a magnetic phenomenon. I am not sure, how's it related to the Dam.
Nonetheless, dam of this size, if not maintained well, can jeopardise lives of millions.

When I was in 11th std- we solved a similar problem- The question was does High rise buildings affect earth's rotation- and the answer came in yes but in nano scale of seconds- It was in rotational dynamics chapter of Physics book written by KC Shina- It is simple when we change the moment of inertial the omega which is angular velocity also changes as the Torque is constant-

Shifting of pole here would be the actual physical North and South poles and not magnetic poles which are opposite of physical poles and at a fair distance from them-
 
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It is certainly a ecological disaster. Now a days it is accepted that smaller earthen dams are better than huge concrete ones. It seems china wants to impress the world about its achievement so they blindly end up racing to build fastest,tallest,highest......etc without any concern for future consequences.

Yup! Smaller dams and checkdams are the way to go! The benefits are immense, of course with less hydro-electric potential. Not only are the checkdams environmentally less damaging, they prevent soil erosion far better and increase underground water-tables much more uniformly than a single large dam can.

A very good documentary on dam demolition in the US which also hastily built literally hundreds of thousands of dams at the turn of the last century at an enormous cost to the local flora and fauna, not to mention resettlement of thousands of communities/industries!

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