TABLE OF CONTENTS In the following we consider first transformations from one frame of reference to another which moves with uniform velocity relative to the first; this is the topic of the Special Theory of Relativity. The significance and necessity of such considerations is immediately apparent if one recalls the field of an electric charge in its rest frame and then visualises this from a moving frame: In the first case one has only the static electric field, but in the second ? in view of the motion of the charge ? one observes also a magnetic field. It therefore becomes necessary to formulate Maxwell's equations, and more generally all laws of physics, independent of the respective reference frame, and this means in covariant formulation.
We recapitulate first some aspects of the Special Theory of Relativity, which unifies Maxwell's electrodynamics with mechanics. The Special Theory of Relativity is based on the following two important principles or postulates of Einstein:
Einstein's principle of relativity (1905). This principle says: The laws which describe the change of the state of a physical system are not affected by choosing one or another frame of reference which are related to each other by uniform translational motion (i.e. with constant relative velocity; systems which are accelerated to each other are treated in the General Theory of Relativity).
Reference frames in uniform translational motion to each other (uniform motion meaning moving with constant velocity)...
