Mappa Mundi (Map of the World), meant to portray the part of the world believed to be habitable, does make the world look flat and finite. Way back in he 3rd century BCE, however, Eratosthenes had coined the term "geography" and measured the circumference of the clearly round Earth by noting the difference in shadows of a stick at noon on two points many miles apart; the angles and length of the shadows told him that the sun was shining down on the surface at different angles, and the surface was therefore curved.
As revered an early christian as Boethius (480-524, mentioned here) in De consolatione philosophiæ (The Consolation of Philosophy) reminds us of how small we are in the grand scheme of things with this:
It is well known and you have seen it demonstrated by astronomers, that beside the extent of the heavens, the circumference of the earth has the size of a point; that is to say, compared to the magnitude of the celestial sphere, it may be thought of as having no extent at all.Medieval sources even quote Pliny the Elder's figure of 29,000 miles for the circumference, a remarkably accurate figure.*
So was there a conflict between science and Christianity? Depends who you talk to, I suppose. William of Conches (1085-1154), who may have been a tutor to the young man who became King Henry II of England, wrote extensively on reconciling the origin of the cosmos in Plato's Timaeus with Genesis. The Bible may have described the earth as flat, but William knew this should not be taken literally, explaining:
The authors of Truth are silent on matters of natural philosophy, not because these matters are against the faith, but because they have little to do with the upholding of such faith, which is what those authors were concerned with.As learning spread—specially with the advent of mass printing—perceptions of the Earth's shape would have spread thanks to re-printed classical works. Columbus' idea to go west to arrive at an eastward point was not a risky gamble or a brilliant insight. Other "facts" in the Bible were also understood to be not literal: Pope Innocent III, for instance, knew that the Moon shone with reflected light, even though the Bible refers to the Sun and Moon as "two lights."
So what account for the learned Bacon's statement? It may have something to do with the conflict between Galileo and the Church. Although the famous trial would not take place until 1633, Galileo had received a formal Admonition in 1616, warning him:
to relinquish altogether the said opinion that the Sun is the center of the world and immovable and that the Earth moves; nor further to hold, teach, or defend it in any way whatsoever, verbally or in writing; otherwise proceedings would be taken against him by the Holy Office; which injunction the said Galileo acquiesced in and promised to obey. [link]It is very likely that Bacon and the rest of Europe's scientific community was aware of this growing conflict. In this historical context, Bacon's statement can be seen as a condemnation of the Church because of a recent action—even though for centuries the knowledge of a round Earth was common.
*In fact, the original figure might have been more accurate than we suspect: it was given in Greek stadia, a measurement which meant different things to different users. Our best interpretation is 29,000 miles, but if Pliny were using stadia of a slightly shorter length... .