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Introducing the Three Gorges Dam -

Located along the Yangtze River in Hubei province, China, the Three Gorges Dam is the largest hydroelectric project in the world.

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Construction -

It was no mean feat to build: standing at 2,335 meters (7,660 feet) long and 185 meters (607 feet) high, it was completed in 2012 after nearly two decades of construction.

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Providing electricity - The Three Gorges Dam is useful for a number of reasons. Firstly, it produces enough electricity to meet the needs of millions, thanks to reservoirs that can hold around 10 trillion gallons of water.

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Other benefits -

It was also designed to increase shipping capacity on the Yangtze River and to provide flood storage space, thereby reducing the potential for flooding downstream.

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The problem with flooding -

Historically, the Yangtze Plain has struggled with flooding. In 1931, for example, floods on the river caused the deaths of four million people.

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Overall success -

In general, China considers this major hydroelectric project to be a success. Indeed, it has state-of-the-art turbines and is moving towards limiting greenhouse gas emissions.

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Controversy -

However, it has also caused significant environmental, social, and ecological changes, some of which have sparked controversy both in China and worldwide.

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Displacement of residents -

On the one hand, the building of the Three Gorges Dam required huge numbers (roughly 1.5% of the Hubei population) to be displaced.

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Landslides and risk to wildlife -

On the other hand, experts have also expressed concerns about an increased risk of landslides and interruptions to surrounding wildlife, in particular endangered species.

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Terrestrial impact -

Perhaps the most curious impact of the Three Gorges Dam, however, lies in its potential power to alter the Earth's rotation.

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Broaching the subject -

This topic was first raised in a 2005 NASA post, where geophysicist Benjamin Fong Chao drew attention to the fact that the dam holds enough water to shift the distribution of the Earth's mass.

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The scientific principle -

When you consider that the distribution of an object's mass impacts its rotational speed (the principle of moment of inertia), this suggests that the dam could also impact the Earth's rotational speed.

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Increasing day length -

Indeed, Chao calculated that due to its size, the reservoir of the Three Gorges Dam could increase the length of a day by approximately 0.06 microseconds.

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Other effects -

In addition, it could also make the Earth slightly more round in the middle, and slightly flatter on the poles.

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Planet-scale impact -

While these changes may seem tiny and insignificant, they do serve as a reminder, as Chao mentioned, that human engineering can have a planet-scale impact.

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The role of natural disasters -

However, human engineering is not the only factor that can influence the Earth's spin. For years now, NASA scientists have been looking at how natural disasters can impact the Earth's rotation.

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Example: 2004 tsunami - One particularly interesting example of this was in 2004, when a huge tsunami and earthquake hit across the Indian Ocean.

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Tectonic plate movements - This event had catastrophic social and environmental consequences, but it also caused large-scale tectonic plate movements.

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NASA findings -

In fact, according to NASA research, this single extreme weather event shortened the length of a day by 2.68 microseconds. That's considerably more than the Chinese dam would lengthen a day by.

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The role of climate change -

Climate change is another factor that influences the Earth's rotation by serving to redistribute its mass.

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More water near the equator -

As global temperatures increase, polar ice caps melt and sea levels rise. As a result, an increasing volume of water is accumulating near the equator.

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Changing distribution of mass -

This results in a changing distribution of mass, which could, in theory, slow down the Earth's rotation.

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Imperceptible and irrelevant -

Until now, these changes to the Earth's rotation have been so tiny that they are imperceptible and irrelevant to daily life. However, that may not always be the case.

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Recalibration of time-keeping mechanisms -

Already, experts are talking about a need to recalibrate time-keeping mechanisms that are used for ultra-precise measurements, such as atomic clocks.

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Impacting technology -

Indeed, although it may seem trivial, the cumulative effect of timekeeping errors could impact modern technologies, such as GPS systems and satellite communications.

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The negative leap second -

Some scientists have even called for a "negative leap second" (i.e. a minute with 59 rather than 60 seconds) to be introduced in the next few decades.

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The concept -

The idea is that the extra second would compensate for the gradual and cumulative changes in day length as a result of natural disasters or man-made structures.

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Final thoughts -

For now, it seems clear that the Three Gorges Dam is not impacting our day length in any meaningful way. It does serve as a reminder, however, of the way in which human engineering impacts the Earth.

Sources: (Firstpost) (Business Today)

See also: China's magnificent city of ice

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