““Einstein solved the puzzle by playing the same great trick that Newton and Galileo had originally played to establish the relativity of motion. He realized that the distinction between electrical and magnetic effects depends on the motion of the observer. So Maxwell's unification was deeper than even Maxwell had suspected. Not only were the electric and magnetic fields different aspects of a single phenomenon, but different observers would draw the distinction differently; that is, one observer might explain a particular phenomenon in terms of electricity, while another observer, moving relative to the first, would explain the same phenomenon in terms of magnetism. But the two would agree about what was happening. And so Einstein's special theory of relativity was born, as a joining of Galileo's unification of rest and motion with Maxwell's unification of electricity and magnetism.””
