# How do you calculate the angular velocity of precession?

##### 1 Answer

The angular velocity vector of precession is normal to the Earth's orbital plane and its magnitude is the angular speed 50.2"/year, nearly.

#### Explanation:

Relative to the Earth's center, the poles move along parallel circles, parallel to (orbital plane of the Earth) the ecliptic, taking about a Great Year of 25800 Earth years, to complete the circle.

The radius of this circle = (polar radius of the Earth) X

The angular speed of precession =

Importantly, the inclination of the polar axis to the normal to the ecliptic (tilt angle) remains the same