Earth’s centre of mass wanders several millimetres relative to the solid planet over the course of each year, as monsoon rains, snowpack, ocean water and shifting air masses redistribute weight around

A new geodetic analysis combines satellite ranging, GPS and orbital data to trace the millimetre-scale annual offset between Earth's mass centre and its solid surface.

Published September 20, 2026 · How we edit

Earth has a centre of mass, but it is not a point permanently fixed inside the rock. Water, air and snow move across the planet through the seasons. Because they have mass, those migrations move the balance point of the complete Earth system by several millimetres relative to the solid surface.

A study published in Geophysical Journal International has produced two new estimates of that annual movement by combining satellite laser ranging, GPS measurements and the tracked orbits of low-Earth satellites. This is one study, not settled consensus. Its main contribution is a cleaner way to separate movement of the mass centre from deformation of the ground stations used to measure it.