Page:Zur Theorie der Strahlung in bewegten Körpern.djvu/3

 of which one is stemming from the heat reservoir of the boundary of the cavity, while the other one is the equivalent of the work required to set such a system into motion.

Up to now, only the existence of radiation pressure was presupposed. Since we also have to know the amount of it, we have to take (in § 4) the value of the radiation pressure from the works of, and also another derivation of the value (as mentioned before) is given.

In § 5 the work is calculated, which must be performed to change the velocity of a cavity filled with radiation. The work that must be performed to increase the velocity, is gained again when it is decreased by the same quantity, in case the velocity change is carried out infinitively slow. Then this process is thus reversible: namely both at "isothermic" as well as at "adiabatic" change of velocity. These relations give rise to the formation of the concept of an apparent mass caused by radiation, which is quite analogous to the so-called electromagnetic mass.

In § 6 we concern ourselves with the quantity of heat, given off by a moving black body to a cavity rigidly connected with it, when the velocity of this system is changed. There, we come to a contradiction with the second law of thermodynamics, which can be solved by assuming, that the dimensions of matter are depending on the velocity of their translatory motion through the aether. Namely, exactly the amount for this dependency is given, which according to and  is necessary for the explanation of the negative result of the experiment of  and.

§ 1.

It's known that it is convenient in the optics of moving bodies to use two reference systems, of which one