In this paper, I try to combine Electromagnetic and Gravitation into one theory, using hidden parameters of Special Relativity. Assumption The electron charge cannot be separated from the electron mass. Both are "connected "to the same particle. This is true for all other "elementary particles". In electricity and electronic we can accumulate charge only on capacitors, so I assume that particle mass is the capacitor mass that hold the particle charge. Of course, such an assumption must agree with all other theories like Relativity Gravitation Electromagnetic etc I paid attention that "Transmission lines" behave mathematically according to Special Relativity, (3D electromagnetic cavity also) , hence I used the Transmission line to explain why "Space Time" is the "capacitor" of particle charge. The final conclusion was that the entire universe is an electromagnetic cavity. The electromagnetic waves create AC currents in the "mass capacitance" and the mass move according to professor Einstein equations. But Gravitation waves does not exists.