Classical physics predicts fundamental particle masses from the same analytical equations comprising fundamentals constants only that correctly predicted the fundamental cosmological parameters such as the acceleration of the expansion of the cosmos, the Hubble constant, and the curvature (See Closed Universe… post). The mass of the X17 particle which decays into a positron-electron pair is given by the equation that correctly predicts the masses of all leptons, the electron, muon, and tau. The predicted mass of X17 is 17.11 MeV in agreement with observations GUTCP Chp. 36.