This may sound to you like the plot of the next Austin Powers movie, whereby Dr. Evil seeks to steal time and then sell it back to the world for ONE HUNDRED BILLION DOLLARS!
Alas, this is no such story, much as I might like to watch it. This is the story of how the Chinese government is trying to steal time and then sell it back to the world for…OK no, it isn’t that either.
This is the story of a hydroelectric dam in China that has effectively stolen time, though no word yet on its demands for the return of that time. You see, the Three Gorges Dam that currently spans the Yangtze River in the Hubei province of China is…well, it’s stealing time.
The Three Gorges Dam is one of the most ambitious renewable energy projects that’s ever been attempted anywhere, and is currently the largest hydroelectric power station in the world. It’s a project that’s a hundred years in the making, having been conceived in 1919 by Sun Yat-sen, the first president and founding father of the Republic of China. The dam was officially completed on July 4, 2012 (which eerily mirrors the narrative of the semi-flaccid blockbuster movie 2012). It now generates roughly 22.5 million kilowatts of energy, which is equivalent to fifteen nuclear reactors. So, you know, it won’t cause any Godzilla-like mutation – that’s Japan’s territory anyway.
Three Gorges provides electricity for nine provinces and two major cities, accounting for roughly 15 percent of China’s total hydroelectric consumption. It has also made the Yangtze River (up-stream) considerably wider and deeper, though this was actually by design. Officials hoped it would augment river shipping traffic, allowing for easier exchange of goods between provinces, thus stimulating their economy.
Of course, you can’t change the size and flow of a major river to that extent without some environmental consequences. The dam has displaced nearly 1.3 million people as their former homes are now under water. It has also, obviously, destroyed many riverside habitats, both through flooding up-river and drought down-river, and has increased the risk of landslides in certain locations drastically. Not to mention the disruption to fishing communities and those who rely on regional fisheries for work and sustenance.
Even though it’s been quite controversial both in China and elsewhere, most have accepted that you have to take the good with the bad. This new information though, may bring the whole thing back into the spotlight.
Right, the dam is stealing time.
That is, of course, not a completely accurate statement. It’s not stealing anything, what it is doing is slowing the rotation of the earth. That doesn’t seem much better, actually.
Scientists at NASA have calculated that the mass of the dam, and the shift in flow and capacity of the river have resulted in a change to Earth’s moment of inertia. According to NASA, as was reported back in 2010, the dam effectively raised 39 trillion kilograms of water nearly 175 meters above sea level. While certainly a marvel of modern engineering, you may not see the connection.
The moment of inertia is the mass property of a rigid body that determines the torque needed for a desired angular acceleration about an axis of rotation. Simple, right?
In more common terms, think of a figure skater spinning dizzily on the ice. As the skater pulls their limbs in toward their body, they begin to spin faster and faster, and vice versa; as they spread their arms and legs out, they slow down. It all depends on the distribution of mass, the more evenly distributed, the faster the rotation.
What this means for Three Gorges is that they’re essentially sticking their giant cement and water filled arm out and causing us to slow down (not to mention ruining our chances of making gold in figure skating). There’s no need to panic, mind you. This happens all the time.
Earthquakes regularly cause changes to our moment of inertia, as do changes to the polar ice caps. The Moon also affects our rate of spin – and incidentally, as the Moon’s orbit continues to recede away from Earth, it’s causing us to spin slower and slower. Though at some point it will no longer affect our mass (but don’t worry, we’ll probably be long gone when it does).
Three Gorges however, will only have a very small effect on our moment of inertia. It results in an increase of .06 microseconds for our daily rotation, and shifts the poles a mere 0.8 inches. The earthquake in April of 2011, which resulted in the Fukushima Nuclear Disaster, shifted the poles by four inches. What makes Three Gorges special is that it’s the first time a man-made process or structure has had such an effect.
In any event, there’s little that could be done to reverse it now anyway. Destruction of the dam would cause tenfold the amount of damage that was caused during its construction. Plus, the project used 27.2 million cubic metres (35.6×106 cu yd) of concrete, and 463,000 tonnes of steel (enough to build 63 Eiffel Towers), so that would be one hell of a demolition project.
