What happens to a human being at the edge of the world? The temperature can drop to minus eighty-nine degrees. The sun disappears for four months. The nearest help is unreachable. And yet people keep going south. In The Edge of the Ice, David Ashby explores the science and psychology of the polar regions - what extreme cold does to the human body, what months of darkness do to the human mind, and what the ice reveals about the deepest limits of human endurance. Drawing on polar physiology, neuroscience, and the real experiences of the scientists and field workers who winter over at the world's most remote research stations, Ashby examines the cascade of physiological deterioration that cold and isolation drive, the decision-making failures that the Antarctic environment produces, and the surprising cognitive and psychological transformations that the long winter-over delivers to the people who survive it. He travels across the East Antarctic plateau with a logistics traverse, explores the Arctic through the lens of Inuit cold-adaptation - the most sophisticated survival culture ever developed - and investigates what the Emperor penguin, the Weddell seal, and the icefish reveal about the biological possibilities of life in the cold. The Edge of the Ice is also a book about the science the polar regions make possible: the ice cores that contain eight hundred thousand years of climate history, the telescope at the South Pole pointed at the birth of the universe, and the atmospheric instruments that have been watching the carbon dioxide rise since 1958. The fourth book in the Science of Extremes series, The Edge of the Ice follows One-Way Ticket, Eight Thousand Metres, and The Hadal Zone in taking readers to the places where human limits are most honestly tested - and most completely revealed.