Overview
- NASA-supported analyses of more than a century of records show that melting ice, falling groundwater, and rising seas shift Earth’s mass, nudge the spin axis, and add tiny fractions of a millisecond to the day.
- The dominant brake remains lunar tidal friction, which saps a bit of Earth’s rotational energy and sends the Moon gradually farther away.
- Since about 2000, rapid ice loss in Greenland and Antarctica and other climate-driven changes have quickened the long-term tendency for days to grow longer.
- Modern geodesy tracks these shifts using radio observations of distant quasars, satellite laser ranging, and machine-learning tools that separate drivers and reveal smaller deep-Earth contributions and roughly 25-year patterns.
- Turning a 24-hour day into a 25-hour one would take on the order of 200 million years, and the present changes are too small to affect clocks or calendars.