One of humanity's largest ever projects that worried NASA scientists is slowing down Earth's spin

One of the largest ever projects created by humanity has slowed down the rotation of the Earth.

It happened as a result of engineering work over in China to create of its Three Gorges Dam; the world's largest power station.

Situated 175 metres above sea level, the dam saw 1.5 million people in China forced to leave their homes as 13 cities and 140 towns in the country were flooded for the project to become a reality.

A hydroelectric dam on the Yangtze River, it lies to the far west of Wuhan.

Deemed essential by the Chinese government to stop continuous devastating floods across lower lying lands, it was also seen as a way of powering towns and cities.

The Three Gorges Dam is immense (VCG/VCG via Getty Images)

NASA concern over the project

We're talking worries of landslides, pollution, disease, and seismic activity issues.

"The epic scale of the dam project is matched by the level of controversy it continues to generate," NASA wrote on its Earth Observatory website.

"Concerns about major environmental impacts, the relocation of 1.2 million people, and the flooding of 13 cities, more than 1300 villages, archeological locations, and hazardous waste dumps were raised throughout the planning and implementation.

"Environmental concerns include increased seismicity from the loading of the water, landslides, changed ecosystems, accumulated pollution, increased chances for waterborne diseases, and salinity changes in the Yangtze estuary."

Water being released from the Three Gorges Dam (STR/AFP via Getty Images)

And on top of this, it was deemed that the dam - which was completed in 2012 - has impacted the spinning motion of planet Earth as it travels through the universe.

NASA has explained that massive changes to where mass lies on Earth can have small influences on Earth's inertia (posh word for how it rotates).

How the dam slowed Earth's rotation

Dr Benjamin Fong Chao, a geophysicist at NASA's Goddard Space Flight Center, explained that the giant dam has a capacity of 40 cubic kilometres.

That is equal to a staggering 10 trillion gallons of water. In an eye-opening comparison to show the scale of the project, Dr Chao said this volume was similar to the amount of mass that was shifted in the 2004 Indian Ocean earthquake and tsunami, which registered at 9.1 on the Richter scale.

NASA said that that earthquake decreased the length of day by 2.68 microseconds. In contrast to that, the space agency states that when the Chinese dam is at its fullest point, it actually creates a really small resistance to Earth's spin - making the day longer.

The dam and river from above (NASA)

Dr Chao's own calculations say it would increase the length of a day by 0.06 microseconds as well as move the pole position of Earth by roughly two centimetres.

So there is change, albeit it is marginal. And it is something we also experience during natural disasters such as earthquakes.

But given that those are huge geographical events, for humanity to do the same through its own inventions shows the scale of potential. And maybe why we should also be cautious of what we're doing.