In this paper, a review of the experiments, developments and ideas which have been presented on this topic together with its natural extension to the description of gravity, the ultimate dominating mystery of the universe, was taken out. A parallel mechanism was proposed between the emission of light and of neutrino by quantum leaps of electrons between the fixed energy levels of atomic orbits. The analysis of the neutron-proton mix of existing nuclides provides a rule for the calculation of

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... neutrino flux from matter and suggests both a medium for the transmission of light and a solution to the problem of gravitation.