Five hundred years before Columbus, a Viking woman named Gudrid sailed past the edge of the known world. She landed in the New World and lived there for three years, giving birth to a baby before sailing home. Or so the Icelandic sagas say. Even after archaeologists found a Viking longhouse in Newfoundland, few believed that the details of Gudrid's story were true. Then, in 2001, a team of scientists discovered what may have been this pioneering woman's...