Shortlisted for the Royal Society Winton Prize for Science Books Albert Einstein's General Theory of Relativity is possibly the most perfect intellectual achievement in modern physics. Anything that involves gravity, the force that powers everything on the largest, hottest or densest of scales, can be explained by it. From the moment Einstein first proposed the theory in 1915, it was received with enthusiasm yet also with tremendous resistance, and for the following ninety years was the source of a series of feuds, vendettas, ideological battles and international collaborations featuring a colourful cast of characters. A gripping, colourfully told story, A Perfect Theory entangles itself with the flashpoints of modern history. In this first complete popular history of the theory, Pedro G. Ferreira shows how the theory has informed our understanding of exactly what the universe is made of and how much is still undiscovered: from the work of the giant telescopes in the deserts of Chile to the way in which the latest work on black holes is providing a fresh, new perspective on what space and time are truly made of. As we near the first centenary of Einstein's iconic theory, scientists the world over are wondering once again if we have reached the limits of the theory and just how much of the universe's future it can explain.