The Principle of Relativity and its Application to some Special Physical Phenomena.
By H. A. Lorentz.
To discuss Einstein's principle of relativity here in Göttingen, where Minkowski has worked, appears to me as a particular welcomed task.
One can highlight the importance of this principle from different points of views. About the mathematical side of the question, which has found such a gleaming representation by Minkowski and which was further developed by Abraham, Sommerfeld etc., shall not be spoken here. Rather (after some epistemological considerations concerning the concepts of space and time) those physical phenomena shall be discussed, which could contribute to an experimental test of this principle.
The relativity principle asserts the following: When a physical phenomenon is described in reference system by certain equations, then a phenomenon which can be described in another reference system by the same equations, will exist as well. There, both reference systems are connected by relations in which the speed of light occurs, and which express that a system is moving with uniform velocity relative to the other one.
If observer is in the first, in the second reference system, and if any of them is equipped with measuring rods and clocks at rest in his respective system, then will measure the values of , while measure the values of , where it is to be remarked, that and can use the same measuring rods and the same clocks as well. We have to assume, that when measuring rods and clocks are somehow transfered from the first observer to the second one, then they take over the correct length and the correct rate by themselves, so that obtains the values of form his measurements. Both will now obtain the same value for the speed of light, and generally can make the same observations.
