Engineering Physics Annotation << Back Annihilation of Photons in the Upper Layers of the Atmosphere and the Blue Color of the Sky Before the Sunrise Ogluzdin V.E. In the process of interaction of solar radiation with gas atoms in the upper layers of the earth's atmosphere, axions take part along with photons. The resonant absorption of hard ultraviolet photons by oxygen atoms, as well as the annihilation of hard ultraviolet photons, the energy of which is not equal to the energy of electronic transitions in oxygen atoms, ensures the safe blue color of the morning sky. Indeed, during the annihilation of a pair of photons in the fi eld of an atomic nucleus and the subsequent decay of an axion, of the two newly appeared photons, the atom, as a rule, absorbs the harder photon. As solar radiation moves towards the earth's surface, multiple cascade annihilation reduces the hardness of ultraviolet radiation. The issues of coloring the sky in the morning, afternoon and evening are considered. Keywords: photon, axion, blue sky, ultraviolet radiation. Pp. 43-48.