The relationships between frequency, wavelength and speed of waves is considered for both sound and light waves. Einstein's prediction of the gravitational red shift was based on an important observation about the dependence of measured frequencies of light waves on gravitational potential. He pointed out that the only reason observers located on the earth's surface and the lower potential of the sun could differ on their value of a given light frequency is because their respective timing devices do not run at the same rate, even though they are otherwise completely equivalent ("gleich beschaffen"). This amounts to assuming that the unit if time varies with gravitational potential. The analogous conclusion holds for all other physical properties. In effect, this means that there is a conversion factor between the units of each quantity for any pair of rest frames that the respective stationary observers located there can use to quantitatively relate the measurements of one another. How this factor, referred to as S, can be determined in general is discussed. Furthermore, it is argued on the basis of experiments with 
atomic clocks that an analogous conversion factor (Q) can also be determined for each pair of rest frames. On basis of the Law of Causality it can be assumed that the rate of an inertial clock cannot change spontaneously. This conclusion (Newtonian Simultaneity) rules out any occurrence of remote non-simultaneity, contrary to what is predicted on the basis of the Lorentz transformation.