We recognize that the spreading of light at large distances (the whole space) is the only property which can decide by yes or no if light really behaves physically like waves, while the fit of the waves for describing the diffraction fringes is insufficient for this purpose. Indeed, the fringe space is too limited and hence, brings the possibility of misinterpretation. Hence, the experiment for the verification if light is spreading like waves at large distances is necessary in principle. However, very surprisingly and tragically, this experiment was totally missing in history. We describe in detail the complex analytical and experimental design, and our attempt for many years for this experiment. Practically, this experiment verifies if there is a dependence of the diffracted light at large distances in the geometrical shadow on the beam thickness traversal to a straight edge, as the wave theory for light predicts. We could not finish the experiment because of the lack of resources to measure at 100 – 500 m, but this article will empower bigger labs to perform this experiment, especially the laser laboratory in Magurele, Romania But we show that the answer for how light spreads also comes alternatively from comparing the well known data for the diffraction on macroscopic holes with already existing data for the diffraction on nanoscopic holes. This comparison shows that light does not spread like waves, which makes necessary a new, non-wave but periodic structure for light. This answer makes absolutely necessary to perform the above missing experiment, as a double check and a direct way that convinces anybody how light is spreading.