Throughout history, humanity has achieved remarkable engineering milestones, particularly in China. The Great Wall stretches approximately 13,166 miles, constructed over 2,300 years from the 3rd century BC to the 17th century AD. Despite myths about its visibility from space, its extraordinary scale remains undeniable.
Across the world, numerous dams have stored vast amounts of water, which has had a noticeable impact on the Earth’s pole positions. The Three Gorges Dam on the Yangtze River in Hubei province, however, is said to be causing a significant change in Earth’s rotation independently.
This monumental hydroelectric project, which commenced in 1994 and was completed in 2006, holds about 44 billion tons of water, a weight significant enough to reduce Earth’s rotation time by 0.06 microseconds, as reported by NASA scientists. Standing at 607 feet tall and spanning nearly 1.5 miles across the river, it generates 22,500 megawatts of electricity—three times the output of the largest dam in the U.S., the Grand Coulee. The project resulted in the relocation of approximately 3.67 million people and affected around 55 million, as it led to the submersion of 13 cities, over 1,300 villages, countless archaeological sites, and hazardous waste locations.
Earth Will Continue to Spin
The Earth completes a full rotation every 24 hours, but its rotation length varies from day to day. The 0.06 microseconds adjusted by the Three Gorges Dam is relatively minor when compared to other significant natural phenomena. For example, the 2011 Tōhoku earthquake off Japan, which caused the Fukushima disaster, accelerated Earth’s rotation by 1.8 millionths of a second, while the 2004 Sumatran earthquake shortened the day by 2.68 microseconds by shifting mass around.
The largest dam in the world, the Three Gorges Dam, will continue to influence the geophysical characteristics of the planet. Concentrating water in a single region alters Earth’s inertia and results in an extremely slight, yet measurable, slowdown of its rotation—similar to how a figure skater manages their spin speed by adjusting their arms.
The substantial displacement of water affects the planet’s shape, leading to what is termed “true polar wander.” This refers to the Earth’s adjustment as it rotates to redistribute mass and maintain its rotational balance. A study in Geophysical Research Letters notes that the accumulation of water at the dam has, over recent decades, shifted the planet’s rotational axis by nearly one meter. While there’s no immediate need for concern regarding the Earth’s slowing rotation, it is a phenomenon warranting observation in the long run.
