The Constancy of the Speed of Light as a Consequence of the Uniqueness of the Elementary Quantum of Energy Transfer

The speed of light in free space is the same for every radiation of the electromagnetic spectrum, across more than thirty orders of magnitude in energy, and is independent of the motion of source and observer. Special relativity assumes this invariance as a postulate. The present work shows that it follows from the uniqueness of the elementary unit of energy transfer, E_min, identified in [1] and verified in [2] across seven physical contexts unrelated to radiation. Energy differences between radiations translate into the number of transmission acts, and not into the amount of energy each act transfers, which is E_min for all of them: the observed speed therefore remains that of the single act, identical throughout the spectrum. The photon, as understood in current physics, remains the complete process identified by the energy it carries: what is set out here concerns the way in which that energy is transferred, not the object. Independence of motion follows from the isotropy and homogeneity of the energetic structure of space, here termed the Reticular Energetic Structure of Space and denoted by the acronym RES. The work reports the calculation of the propagation speed from measured quantities and from the energy density of the RES. Performed across seven mutually unrelated physical contexts, the calculation returns the observed value with a mean deviation of 0.013 per cent, and shows that the result depends on the uniqueness of the transfer unit and not on its magnitude.