Earth’s day isn’t exactly 24 hours. The reason may lie deep inside the planet

Scientists may have solved why the length of Earth’s day changes by a few milliseconds over decades. Subtle shifts in the inner core appear to tug on the mantle, revealing a surprisingly dynamic world thousands of kilometers beneath our feet. Earth’s day isn’t exactly 24 hours. The reason may lie deep inside the planet.

The reason may lie deep inside the planet Date: September 29, 2026. Most of us think of a day as a fixed 24 hours. In reality, Earth’s rotation is not perfectly constant.

The difference is tiny, measured in milliseconds, but physicists can detect it. Over time, some days become slightly shorter or longer depending on subtle changes deep inside the planet. Earth’s Core and Mantle Trade Momentum For roughly three decades, scientists have known that Earth’s liquid core does not always rotate at the same rate.