The Earth's magnetic field is vital to the survival of life on this planet we call home - not only does it shield us form a constant barrage of solar winds and cosmic radiation, it has also been the main method of navigation not only for sailors and other travellers, but for birds, fish, whales, insects and even butterflies undertaking astonishing migrations across the globe. But what is the source of this magnetic field? What mysterious force makes compass needles point North, and dangerous particles from the sun veer back into space? For centuries this question has absorbed and often obsessed the world's greatest scientific minds, Albert Einstein even called it the last great unsolved mystery of science. This engrossing book tells, for the first time, the complete story of the quest to understand Earth's magnetism from the fascination of ancient Greeks with magnetised rocks to the astonishing modern discoveries that finally allowed two scientists to unravel the mystery. North Pole, South Pole gives us an extraordinary window into science, passion and the brilliance of the human mind.