When did men first suspect that the earth was round, not flat? In the days of Christopher Columbus? No. Earlier than that! Irving Robbin wrote: “To believe that one could sail to the East by sailing west, one must also believe that the earth is a sphere. A Genoese sea captain named Christopher Columbus believed this, but he was not alone. He was not alone by many centuries, for as far back as 500 B.C., a Greek scholar, Pythagoras, asserted that the earth was round. A Norwegian textbook written in 1250 not only said the same thing, but also gave the reasons for the varying climates of the earth, the angle of the sun at different times of the year and the prevailing winds. Not all the ancient knowledge had been lost it— was just out of favor for a while.”—The How and Why Wonder Book of Explorations and Discoveries.
Pythagoras lived about 540 to 500 B.C.E. Much earlier, however, the Hebrew prophet Isaiah, of the eighth century B.C.E., indicated that the earth was spherical. He wrote: “There is One [God] who is dwelling above the circle of the earth, the dwellers in which are as grasshoppers.(Isa. 40:22)