NASA Has Done the Math: China Can Slow Earth's Rotation by Filling the Three Gorges

China’s Three Gorges Dam, the world’s largest hydroelectric project, could minutely slow Earth’s rotation as its reservoir fills.

According to NASA calculations, the shifted water mass slightly changes Earth’s moment of inertia and lengthens the day by a tiny fraction of a microsecond.

The effect is extremely small, but it shows that major human engineering projects can measurably alter planetary physics.