ABSTRACT
However, long before Plato, as well as much later, several Greek philosophers had developed correct explanations of hydrologic cycle, revealing good understanding of the related phenomena. In fact, as Koutsoyiannis and Xanthopoulos[2] note, the first civilization in which these phenomena were approached in an organized theoretical manner, through reasoning combined with observation, and without involving divine and other hyperphysical interventions, was the Greek civilization. The same authors catalog a number of ancient Greek contributions revealing correct understanding of water related phenomena. Thus, the Ionic philosopher, Anaximenes (585-525 B.C.) studied the meteorological phenomena and presented reasonable explanations for the formation of clouds, hail and snow, and the cause of winds and rainbow. The Pythagorean philosopher Hippon (5th century B.C.) recognizes that all waters originate from sea. Anaxagoras, who lived in Athens (500-428 B.C.) to Empedocles (ca. 493-433 B.C.) and is recognized equally as the founder of experimental research, clarified the concept of hydrologic cycle: the sun raises water from the sea into the atmosphere, from where it falls as rain; then it is collected underground and feeds the flow of rivers. He also studied several meteorological phenomena, generally supporting and complementing Anaximenes’ theories; his theory about thunders, which was against the belief that they are thrown by Zeus, probably cost him imprisonment (ca. 430 B.C.). In particular, he correctly assumed that winds are caused by differences in the air density: the air, heated by the sun, moves towards the North pole leaving gaps that cause air currents. He also studied Nile’s floods and attributed them to snowmelt in Ethiopia. The ‘‘enigma’’ of Nile’s floods (which, contrary to the regime of Mediterranean rivers, occur in summer) was also thoroughly studied by Herodotus (480-430 B.C.), who seemed to have clear knowledge of hydrologic cycle and its mechanisms.
