Precession

Precession is the turning of a rotating body's spin axis around another direction. A torque changes its angular momentum according to $d\mathbf{L}/dt=\mathbf{\tau }$. If the torque is mainly perpendicular to a large spin angular momentum, it changes the direction of $\mathbf{L}$ more rapidly than its magnitude, producing a turning motion rather than an immediate large fall.

For a rapidly spinning supported top with centre of mass a distance $l$ from the pivot, the slow steady-precession approximation gives ${\Omega }_p\simeq Mgl/L$ when the tilt is fixed and the spin angular momentum dominates. Holding the same top at the same tilt while changing its spin tests the inverse dependence on $L$.

A general top can also exhibit nutation, so its axis need not trace a uniform cone. The approximate expression requires the fast-spin regime and does not describe every released-top transient.

Precession refers to the gradual change or movement in the orientation of an astronomical body's rotational axis or orbital path. It occurs in various contexts in astronomy and physics, but one of the most commonly discussed forms is axial precession. ### Axial Precession (Precession of the Equinoxes) This is the phenomenon where the rotation axis of a planet (like Earth) wobbles over time.