If we examine our universe there are a number of observations that must be consistently explained:
1. tidal effects on earth
2. moon's near side "locked' to earth
3. phases of the moon
4. retardation of the moon's 'rising'
5. seasons of the earth
6. seasonal 24 hour days and nights in the arctic and antarctic
7. coreolis effects on earth
8. Foucault's pendulum
9. precession of the earth's axis
10. apparent daily rotation of the "fixed stars" about the pole star
11. motion of the "wandering stars" (planets) including retrograde motion
12. earth-moon centre of gravity orbits
13. eclipses of the sun, moon and planets
14. northern and southern lights
15. meteors, asteroids and comets
16. moons and/or rings around other planets
17. there are certainly other effects that I have missed
There is only one self consistent model that explains all of these observations and that is the present cosmology of our solar system. This does not explain why these objects behave as they do, it only provides a very refined model that accounts for all the observed effects.
Now add into this the experimentally verified non-relativistic laws of motion and of gravity, known as Newtonian or classical mechanics, and we now have the why that explains the model in a near perfect manner. It is so successful that it has enabled us to send people into earth and moon orbits, to the moon itself and even return to earth. We have been able to navigate probes to all the planets and beyond. People have stood on our moon and observed our planet rotating in front of them in real time. Any other cosmology finds it necessary to suspend known laws of science, hypothesize supernatural intervention and invoke a conspiracy theory extending over centuries involving tens of millions of people a great many of whom are Christian.
In Old Testament times it is certainly true that they regarded the earth as flat in a three tiered universe --- flat with a sky-dome (the firmament) overhead. Just like the rapture theory and the trinity theory, the flat earth worldview is nowhere stated explicitly but it is alluded to in many places. There are also many old testament and even a few new testament stories that are only to be understood in a flat earth context. Generally this flat earth was regarded as circular but we are in places told that it has four corners and is supported by pillars and that there are storehouses for the snow and hail. Of course this seems very primitive to us today but we must remember that these scriptures come out of a far less sophisticated culture. A culture that was deeply suspicious of anything Gentile. It may well be that some of the educated elite were aware of the Greek notion of a spherical world but with an illiteracy rate of about 90% the common people certainly were not. The scriptures were most likely written with the naivety of the common people in mind and used language that would not stretch their credulity too far.
In New Testament times, the young Christian church had a similar suspicion of paganism. Over a period of several centuries it systematically destroyed all things pagan. Temples, shrines, academies, libraries and universities were pulled down and burned. Their priests, teachers and professors were tortured and executed often in front of bloodthirsty Christian mobs. They destroyed not just spiritual works but any book even the slightest bit tainted by paganism even if it was on astronomy, medicine, engineering, technology, mathematics, geography, history or architecture. This massive loss of the underpinnings of civilization contributed in part to the decline and fall of the Roman Empire and the subsequent thousand years of the Dark Ages. In AD380 after a yet another wave of persecution, the 95 year-old hierophant Nestorius, ended the Eleusinian Mysteries and announced the predominance of mental darkness over the human race. How very ironic and prophetic!
It is little wonder then that the flat earth notion persisted so long and that the bible was used to support it. After all the flat earth was the biblical worldview. Should it concern us that the bible supported this notion? Not at all! We do not need to rush to its defense and use weasel words to somehow prove to ourselves that the bible authors had the same worldview that we do. We must realize that these authors lived in a historical context and that the language and ideas that they used fit that context as well.