Magnetic compasses work as they do because the Earth itself is a magnet with a north-south field that causes freely moving magnets to align themselves with the field.

• 磁罗盘之所以能如此,原因在于地球本身为一大磁棒,有南北向磁场,可使能够自由移动的磁铁也指向与之相同的方向。