Museo Galileo
Virtual Museum

There is a distinction between geographic north and magnetic north:

Geographic north

The cardinal point materialized on the celestial sphere by the right-angle intersection of the plane of the local horizon and the meridian plane passing through the zenith of the observation locality. Since antiquity, the most practical way to find the north direction was to observe the direction of the shortest shadow of a vertical gnomon by day, and the position of the Pole Star (North Star) at night.

Magnetic north

Small sector of the Earth's surface at the top of the northern hemisphere in which the lines of force in the magnetic field are vertical. The magnetic needle of the compass points to this area.