Theory of chemical evolution of molecule compositions in the universe, in the Miller–Urey experiment and the mass distribution of interstellar and intergalactic molecules

•Derivation of the equations governing the distribution of existing mass composition of molecules.•Explaining the distribution of observable molecule compositions today and in the past.•Estimates for the number of different extragalactic compounds.•Estimation for the time of emergence of first amino acids in the Universe.•Explaining the timescale of the Miller–Urey experiment.