Was America truly unknown to the outside world until Christopher Columbus "discovered" it in 1492? Could a people gifted enough to raise the Great Pyramid more than 4,000 years ago have lacked the skills necessary to build a ship capable of crossing the Atlantic? Did the Phoenicians, who circumnavigated the African continent in 600 bc, never consider sailing farther? Were the Vikings, the most fearless warriors and seafarers of all time, terrified...