he began working on it in 1912, after he had realized that "most of meteorology is nothing but a collection of innumerable empirical findings, mainly numerical data, with traces of physics used to explain some of them... mathematics was even less applied, nothing more than elementary calculus... advanced mathematics had no role in that science..." his first work described the present climate on earth and how the sun's rays determine the temperature on earth's surface after passing through the atmosphere. he published the first paper on the subject entitled ""contribution to the mathematical theory of climate"" in belgrade on 5 april 1912. his next paper was entitled ""distribution of the sun radiation on the earth's surface"" and was published on 5 june 1913. he correctly calculates the intensity of insolation and developed a mathematical theory describing earth's climate zones. his aim was an integral, mathematically accurate theory which connects thermal regimes of the planets to their movement around the sun. he wrote: "...such a theory would enable us to go beyond the range of direct observations, not only in space, but also in time... it would allow reconstruction of the earth's climate, and also its predictions, as well as give us the first reliable data about the climate conditions on other planets." then he tried to find a mathematical model of a cosmic mechanism to describe the earth's climatic and geological history. he published a paper on the subject entitled ""about the issue of the astronomical theory of ice ages"" in 1914. but the cosmic mechanism was not an easy problem, and milanković took three decades to develop an astronomical theory.