Albert Einstein - the century’s greatest physicist - was never able to come to terms with quantum mechanics, the century’s greatest theoretical achievement. For physicists who routinely use both quantum laws and Einstein’s ideas, this contradiction can be almost too embarrassing to dwell on. Yet Einstein was one of the founders of quantum physics and he spent many years preaching the quantum’s importance and its revolutionary nature. The Danish genius Neils Bohr was another founder of quantum physics. He had managed to solve one of the few physics problems that Einstein ever shied away from, linking quantum mathematics with a new model of the atom. This leap immediately yielded results that explained electron behaviour and the periodic table of the elements. Despite their mutual appreciation of the quantum’s importance, these two giants of modern physics never agreed on the fundamentals of their work. In fact, they clashed repeatedly throughout the 1920s. Powerful and illuminating, Einstein Defiant is the first book to capture the soul and the science that inspired this dramatic duel, revealing the personalities and the passions - and, in the end, what was at stake for the world.