Bill Dembski blogged about this at Uncommon Descent a while back and I posted on this at Overwhelming Evidence previously as well. But because this issue keeps coming back, I will post on it again. Here is the truth about the "Flat Earth" story:
THE FLAT EARTH MYTH
“The earth isn’t flat - end of story.” So says Case Western Reserve University physicist Lawrence Krauss, according to the Cleveland Plain Dealer. “We don’t have to have classes or be sensitive to the issues of those who believe that, because they’re wrong.”
Defenders of Darwinian evolution sometimes compare their critics to believers in a flat earth. According to the standard story, Christians used to believe for theological reasons that the earth is flat. When modern science demonstrated that the earth is actually a sphere, most Christians acknowledged their mistake, but a few continue to persist in their outmoded belief. Since modern science has likewise demonstrated the truth of Darwinian evolution (so the story goes), its critics are like people who still believe in a flat earth.
But the story is false. It began as fiction, and it was elevated to a historical claim by late-19th century Darwinists who used it as a weapon to ridicule Christians.
The spherical shape of the earth was known to the ancient Greeks, who even made some decent estimates of its circumference. Christian theologians likewise knew that the earth was a sphere. The only two who are known to have advocated a flat earth were a 4th-century heretic, Lactantius, and an obscure 6th-century writer, Cosmas Indicopleustes. [These were really second stringers. The leading theological lights of that period were Origen, Athanasius, the Cappadocian Fathers, and Augustine — none of these thought the earth was flat.]
A major promulgator of the flat earth myth was the 19th-century American writer Washington Irving. In his fictional History of the Life and Voyages of Christopher Columbus (1828), Irving wrote that flat-earth churchmen had opposed Columbus on the grounds that he would fall off the edge of the earth if he tried to sail across the Atlantic. In actuality, Columbus had been opposed by people who not only knew the earth was a sphere, but also had a pretty good idea of how big it was - but who knew nothing of the Americas and thus thought a voyage to the Far East would take too long and cost too much.
The flat earth remained clearly in the realm of fiction until after Darwin published his Origin of Species in 1859. Two of Darwin’s followers then elevated it to a historical claim in books defending Darwinism and attacking Christianity: John Draper’s The History of the Conflict Between Religion and Science (1874), and Andrew Dickson White’s A History of the Warfare of Science with Theology in Christendom (1896).
So defenders of Darwinism who ridicule their critics for being like believers in a flat earth are being misled by a myth that Darwinists themselves helped to create.
For an objective and very readable account of the flat earth myth, see Jeffrey Burton Russell (Professor of History, University of California at Santa Barbara), Inventing the Flat Earth (New York: Praeger, 1991).