Wednesday 2 April 2014

"Three Gorges Dam" ( China) has slowed down the rotation of Earth!

Here I AM telling you an INTERESTING fact about our Earth's Rotation.
 Do you Know "Three Gorges Dam" ( China) has slowed down the rotation of the Earth!!!


China’s Three Gorges Dam is the world’s largest hydroelectric station.  It is a structure that stands as a testament to the tenacity of human ingenuity.  First envisioned in 1919 and finally completed in 2012, the dam spans the Yangtze River and measures 2.3 kilometers (1.4 miles) long and 185 meters (607 feet) tall.  Almost 30 million cubic meters (just over 35 million cubic yards) of concrete and 463,000 tons of steel were used to erect the massive structure.


With a ridiculous reservoir that runs for 660 kilometers (410 miles), the dam raises water to 175 meters (574 feet) above sea level.  The amount of water displaced when the dam is full weighs about 39.3 TRILLION kilograms (or around 86 TRILLION pounds).  Yeah, it’s huge.  


What does a dam have to do with the Earth’s rotation?

What it comes down to is something called moment of inertia.  Essentially, this is a property of rotating bodies that can tell us how easy (or difficult) it is to spin something.The moment of inertia of an object depends on a few things.One,it depends on an object’s shape and the point about which it’s rotating.It also depends on an object’s mass and how it’s distributed.

 
For our purposes, let’s focus on the mass distribution property of moment of inertia. If two balls are the same size but different masses, the lighter ball rotates more easily than the heavier one.  What happens, though, if we displace some of the mass?



Imagine a figure skater. They displace their mass by bringing in or extending their arms upon rotation to speed up or slow down.If you’ve got a good visual, you can see “arms in” is fast and “arms out” is slow.  If the weight moves away from the axis of rotation, the rotation is slowed.  This is pretty much what the Three Gorges Dam has accomplished by displacing all that water!.

Mass is displaced on the Earth every day but only when it is done on such a colossally large scale does it have the power to effect a measurable change. 
            NASA scientists calculated that shift of such as mass would increase the length of day by only 0.06 microseconds and make the Earth only slightly more round in the middle and flat on the top. It would shift the pole position by about two centimeters (0.8 inch).



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