The sine wave is a solution and carries the characteristics of the normal wave equation which is symmetric in space and time and represents the oscillating transformation between kinetic and potential energy stores. It is also the wave-function of QM that is supposed to represent anything in the world. Further, one ‘sine’ cycle of E=hf=f, gives Einstein quanta which has a constant energy h and behaves like independent gas molecules. The quanta (sine wave) can thus stand for radiation, matter as condensed radiation via E=mc^2, and also for the all-important and universal radiation matter interactions.