The scientific explanation of how a mega-project in China is affecting the Earth’s rotation

One of the most ambitious feats of modern engineering is now raising concerns that go far beyond the realm of energy. The Three Gorges Dam, located on China’s Yangtze River, is known as the world’s largest hydroelectric power station. But recently, scientists have warned that this colossal structure may be imperceptibly altering Earth’s rotation.

The explanation behind this startling claim lies in a principle of physics known as the moment of inertia. When a massive volume of matter is relocated on Earth’s surface – such as the water stored in a dam of this scale – it can shift the planet’s weight distribution relative to its rotational axis. As a result, Earth subtly adjusts its rotational speed to maintain dynamic balance.

How can a dam affect the planet’s spin?

According to NASA geophysicist Benjamin Fong Chao, the dam’s reservoir holds approximately 40 cubic kilometers of water. This mass, he says, may have caused an almost immeasurable change in Earth’s daily rhythm – lengthening the day by 0.06 microseconds and shifting the planet’s axis by roughly two centimeters.

While those numbers seem negligible, they offer compelling proof that human interventions can have physical consequences on a planetary scale.

This isn’t the first time scientists have observed such an effect. In 2004, the massive Indian Ocean earthquake redistributed Earth’s mass so violently it shortened the day by 2.68 microseconds. But unlike that natural disaster, the Chinese dam is the result of a deliberate and sustained human project.

Although these shifts don’t affect our daily lives, they carry important implications for science. Minuscule changes like these can disrupt the calibration of atomic clocks, satellite navigation systems, and other technologies that rely on extremely precise timing. For this reason, phenomena like this are closely monitored by agencies such as NASA.

A warning for the future

Beyond the technical debate, this situation raises a deeper, more unsettling question: to what extent can human infrastructure reshape the physical balance of our planet?

China is already planning an even bigger dam in Tibet, on the Yarlung Tsangpo River. If built, it could triple the energy capacity of the Three Gorges Dam – and potentially have a much greater impact on Earth’s dynamics.

At the same time, global phenomena like the accelerated melting of polar ice – driven by climate change – are also redistributing Earth’s mass. Numerous scientific studies have warned that these processes are gradually slowing the planet’s rotation and causing slight shifts in its axis.

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