It was common knowledge by many men of science back during biblical times that the Earth was a sphere, and NOT flat. So...your bible prophets needed no god to know this--they could have simply listened to science guys.
Like religious folks should do nowadays.
The Hebrew record is the oldest, because
Job is one of the oldest books in the Bible. Historians generally [wrongly] credit the Greeks with being the first to suggest a spherical earth. In the sixth century B.C., Pythagoras suggested a spherical earth. [JSM]
Eratosthenes of
Alexandria (circa 276 to 194 or 192 B.C.) calcuated the circumference of the earth “within 50 miles of the present estimate.” [
Encyclopedia Brittanica]
The
Greeks also drew meridians and parallels. They identified such areas as the poles, equator, and tropics. This spherical earth concept did not prevail; the Romans drew the earth as a flat disk with oceans around it. [JSM]
The round shape of our planet was a conclusion easily drawn by watching ships disappear over the horizon and also by observing
eclipseshadows, and we can assume that such information was well known to New Testament writers. Earth's spherical shape was, of course, also understood by
Christopher Columbus. [DD]
The implication of a round earth is seen in the
book of Luke, where
Jesus described his return,
Luke 17:31. Jesus said, “In that day,” then in verse
34, “In that night.” This is an allusion to light on one side of the globe and darkness on the other simultaneously. [JSM]