It is of course a myth that most Christians believed the earth was flat before Columbus. But contrary to a ‘counter-myth’. Some, especially in the Eastern Church (beyond Cosmas), ‘did’. Not to mention, a flat earth was the consensus view among early Rabbis, who discussed where the sun went at night without any suggestion that it stayed in the sky somewhere on earth.
Here’s a thread I wrote on the subject. In the future I’ll be doing a thread on what the Old Testament says. (I’ll also be discussing a possible exception in the New Testament)
And some on the Raqia: