We are introduced to the magnetic field as a way to keep track
of the force that arises from lenght contraction in special
relativity. A moving distribution of charge becomes more dense in
the right frame. So in a way, the magnetic field is just the
E-field. However, when I glance over the physics of permanent
magnets, it is said that their magnetic field arises from the
integral sum of their electrons with aligned spin(which generates a
magnetic moment).Spin is...