The Dam From China That Slowed The Rotation Of The Earth

But how did this man-made structure manage to do so?


Spreeha Dutta

2 years ago | 2 min read

The Three Gorges Dam built across the Yangtze River in Hubei province was first proposed in 1919 by the provisional first president of the Republic of China, Sun Yat-sen as a measure to control the flooding of the Yangtze River. It was also to be symbolic of China’s might.

Other than the fact that it took decades to build the dam, what is more striking is that the dam slowed the rotation of the earth.

But damn! How is this dam slowing the rotation of the Earth?

The dam holds water at a level that is 175 meters above sea level. The weight of the water it holds is more than 39 trillion kilograms. Because of its huge mass, it has the capacity to affect the rotation of the earth through moment of inertia.

What is moment of inertia?
“A quantity expressing a body’s tendency to resist angular acceleration, which is the sum of the products of the mass of each particle in the body with the square of its distance from the axis of rotation.”

But to put it simply, the longer the distance of a body from its axis, higher will be its moment of inertia or slower will be its speed of rotation.

To give you an example of moment of inertia that we see in everyday life -

A diver brings his body into a tucked position before diving in order to reduce his moment of inertia.

News Source: The Guardian
News Source: The Guardian

So yes, the huge mass of the water above sea level in the Three Gorges Dam does increase the moment of inertia of our Earth but the change in its rotation is as little as 0.06 microseconds. That is to say we have days that are only 0.06 microseconds longer now.

But is that the only reason why the dam is so controversial?

That is not the only reason why the dam continues to be in controversy.

  1. The dam did have some positive effects where it controlled flooding and helped generate massive amounts of power.
  2. But 1.2 million people were forced to relocate for the construction of the dam.
  3. Erosion of the reservoir affect the thousands of insect and fish species living in its water.
  4. In addition to that, the cost of building the dam is estimated to be a whopping $25 billion with some counts saying that it could go as high as $37 billion.
News Source: BBC
News Source: BBC

To Conclude…

As far as the rotation of the earth is concerned, NASA scientists have said that the Earth’s rotation fluctuates occasionally due to events like natural disasters and also due to the moon.

Thus the change caused by the dam is fairly insignificant in the larger scheme of things. But we cannot ignore the fact that the Three Gorges Dam is the only man-made object till date that has the capacity to singularly affect the Earth’s rotation.


Created by

Spreeha Dutta

Navigating my way through life's beautiful stories!







Related Articles