How Infamous Hydroelectric Dam Changed Earth’s Rotation

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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.

So readers, what are your thoughts?
This post was written by Umer Abrar. To contact the author of this post, write to or add/follow him on facebook :

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