Einstein Takes the Simple Approach

At this time, Albert Einstein was working as a clerk in the patent office in Zürich, a position which afforded him lots of free time to toy with crazy ideas. Aware of this dilemma, he suggested the following approach to the problem: since we have to give up some part of our common sense, why not simply take both the experiments and the Maxwell equations at face value and see what the consequences are? No matter how crazy the implications, at least we will be able to remember our starting assumptions without much effort. They are:

• The ``Laws of Physics'' are the same in one inertial reference frame as in another, regardless of their relative motion.

• All observers will inevitable measure the same velocity of propagation for light in their own reference frame, namely c.

These two postulates are the starting points for Einstein's celebrated Special Theory of Relativity (STR), for which this handout is named. The adjective ``Special'' is there mainly to distinguish the from the General Theory of Relativity, which deals with gravity and accelerated reference frames, to be covered later.