Kassir, Radwan M.
February 18, 2018
In its basic form, the Special Relativity’s famous mass-energy equivalence equation doesn’t seem to hold for massless particles. To get around this deficiency, another form (energy-momentum relation) of the same equation incorporating a momentum term has been introduced by the physics mainstream. The adopted mainstream derivation of the energy-momentum relation is based on certain assumptions using Minkowski spacetime four-momentum, forcing a solution towards the energy-momentum relation. This form of the mass-energy equivalence equation appears to hold for massless particles. However, in this paper, an analysis of the mainstream derivation of the energy-momentum relation is carried out, highlighting the made assumptions, and revealing a resulting contradiction. It is clearly shown, through a straight forward derivation, that the energy-momentum relation still doesn’t hold for massless particles. Consequently, the energy-momentum relation requires that a photon must have an infinitesimal rest mass, for which its speed only approaches Thus, the speed of light will no longer be invariant with respect to all inertial reference frames, as postulated by Einstein in his formulation of the Special Relativity!