Geodetic precession is a relativistic effect that occurs when a spinning object, like a gyroscope, moves through curved spacetime. As it orbits a massive body (such as Earth), the curvature of spacetime causes the axis of the gyroscope’s spin to slowly shift over time.
This happens because, in general relativity, spacetime itself is not flat near massive objects. As a gyroscope moves through this curved geometry, the direction of its spin—which would stay constant in flat space—gradually precesses due to the warping of spacetime along its path.
Geodetic precession was precisely measured by Gravity Probe B, a satellite mission that confirmed Einstein’s prediction by observing tiny shifts in the orientation of ultra-sensitive gyroscopes orbiting Earth.
This effect is distinct from the Lense–Thirring effect (frame dragging), which involves spacetime being twisted by a rotating mass. Geodetic precession, in contrast, is caused purely by spacetime curvature from the mass, even if that mass is not rotating.
It provides yet another powerful confirmation of general relativity and deepens our understanding of how motion, mass, and geometry are intertwined in the fabric of the universe.