A scandal hovers over the history of modern physics. Albert Einstein--the century's greatest physicist--was never able to come to terms with quantum mechanics, the century's single greatest theoretical achievement. For physicists who routinely use both quantum laws and Einstein's ideas, this contradiction can be almost embarrassing to dwell on. Yet Einstein was one of the founders of quantum physics and he spent many years preaching the quantum's revolutionary importance. The Danish genius Neils Bohr was another founder of quantum physics. He had managed to solve one of the few physics problems from which Einstein ever shied away, linking quantum mathematics with a new model of the atom. This leap immediately yielded results that explained electron behavior 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, arguing first about Einstein's theory of "light quanta" (photons), then about Niels Bohr's short-lived theory that denied the conservation of energy at the quantum level, and climactically about the new quantum mechanics that Bohr enthusiastically embraced--and Einstein stubbornly defied. This contest of visions stripped the scientific imagination naked. Einstein was a staunch realist, demanding to know the physical reasons behind physical events. At odds with this approach was Bohr's more pragmatic perspective that favored theories that worked, even if he might not have a corresponding explanation of the underlying reality. Powerful and illuminating. "Einstein Defiant is the first book to capturethe soul and the science that inspired this dramatic duel, revealing the personalities and the passions--and, in the end, what was at stake for mankind's fundamental understanding of the physical world.