First and second order electromagnetic equivalency of inertial systems,   based on the wavelength and the period as speed-dependant units of length and   time
  The cause for first and second order electromagnetic equivalency of inertial systems is approached from a different point of view than that of special relativity. While special relativity applies dilatation to time and contraction to space itself, the proposed framework applies restrictively these effects to the units of space and time, embodied in the beam wavelength and period, as perceived on the inertial system due to the Doppler effect. It is not space and time themselves that would actually vary but the electromagnetic units of space and time constituted by the wavelength and period. Mathematical constructs accept indifferently both setting out, which provide identical results, so their valuation must be made on physical grounds. The reader is invited to ponder on interpreting physical reality through the contraction of space and dilatation of time or through the variation of the natural units of space and time provided by the wavelength and the period. These two issues, mathematically equivalent, lead however to drastically different conceptions of the physical world. 
G. Sardin