Earth's Rotation Is Slowing Down

Our planet's daily rhythm is locked in a slow-motion gravitational dance with the Moon. The Moon’s pull creates tidal bulges in Earth's oceans, and because our planet spins faster than the Moon orbits, it drags these bulges slightly ahead. The Moon, in turn, pulls back on this displaced water, creating a subtle but constant friction. This "tidal braking" has been acting on our planet for billions of years, steadily stealing a tiny amount of rotational energy and causing its spin to gradually decrease.

While the change is imperceptible in a human lifetime, the cumulative effect over geological time is profound. Back in the Ediacaran Period, around 600 million years ago, when the first complex multicellular life was emerging, a day on Earth was a brisk 21 hours long. This cosmic exchange of energy is a two-way street; as Earth’s spin slows, that lost angular momentum is transferred to the Moon, pushing it into a slightly higher orbit and causing it to drift away from us by about 3.8 centimeters each year.

This ancient astronomical process has a direct impact on our modern, high-tech world. Our ultra-precise atomic clocks, which define Coordinated Universal Time (UTC), do not slow down. To keep this standardized time in sync with Earth's slightly longer, slowing day, international timekeepers must occasionally insert a "leap second." This small adjustment bridges the growing gap between our perfect clocks and our imperfectly spinning planet.