"BTW who said columbus was told he could sail off the edge of the world?."

The American writer Washington Irving came up with that silly idea in a book he wrote about Columbus in the early 1800s.

Quote from Wicki:

"Irving's writings on Columbus are a mixture of history and fiction, a genre now called romantic history/historical fiction. Irving based them on extensive research in the Spanish archives, but also added imaginative elements aimed at sharpening the story. The first of these works is the source of the durable myth that medieval Europeans believed the Earth was flat."

This was an idea that gained popularity precisely because of Irving's popular writing, but it had no basis in fact. Mariners all over Europe in the medieval period were well aware that the Earth was round, and that same knowledge had been common since classical times when the Greeks, Romans, and Egyptians were also well aware of it.

The reason Columbus' sailors got scared and almost mutinied was not that they thought they would fall off the edge of the world! It was because they were afraid they would run out of drinking water before they ever reached landfall in Asia...which is where Columbus thought he was going. Columbus was under the impression that the globe was significantly smaller than it is. Some other authorities at the time thought he was wrong about that, and he was, of course. If there had been no American continent and no Caribbean islands for Columbus to run into on his way west to Asia, he would have indeed run out of fresh water supplies less than halfway there, and he and all his men would have died.