The Three Gorges Dam in China is the largest hydroelectric dam on Earth, holding back a massive reservoir along the Yangtze River. Due to the sheer volume of water it displaces—tens of billions of tons—it has a small but measurable effect on the planet itself. When the reservoir fills, the water spreads over land at a higher elevation, slightly increasing Earth’s moment of inertia—its resistance to rotational movement. Similar to how a figure skater slows down when extending their arms, this red