What gave Christopher Columbus the confidence in 1492 to set out across the Atlantic Ocean? Fish on Friday tells the story of the discovery of America as a product of the long sweep of history: the spread of Christianity and the radical cultural changes it brought to Europe, the interaction of economic necessity with a changing climate, and generations of unknown fishermen who explored the North Atlantic in the centuries before Columbus. A fascinating and multifaceted book, Fish on Friday will intrigue everyone who wonders how the vast forces of climate, culture, and technology conspire to create the history we know.