Relativitaet auf dem Pruefstand
According to classical newtonian mechanics the rotation axis of a spinning top - physicists call them gyroscopes - always shows in one an the same direction as long as there are no external forces.
However, in Einsteins General Relativity with curved space-time changes in the direction may arise, as compared with a fixed reference point. On the one hand side these are due to the curvature effect near a mass (de Sitter precession), and on the other hand due to a dragging effect caused by the rotation of the mass (Lense-Thirring effect).
In analogy to electrodynamics one subsumes these effects to gravitomagnetism.