The Medieval Flat Earth Myth

Despite it having been repeatedly debunked by historians, some atheist activists continue to peddle the myth that the Medieval Church taught the earth was flat. But how did this myth arise and what did medieval people really know about the shape of the earth?

See also:
https://historyforatheists.com/2016/06/the-great-myths-1-the-medieval-flat-earth/​
https://historyforatheists.com/the-great-myths/​

And my detailed critique of the claims of "Aron Ra":
https://historyforatheists.com/2019/08/aron-ra-gets-everything-wrong/