he most skeptical of physicists were forced to accept atoms, which until then had been mere conjecture as real material objects. For four years, from 1914 to 1918, World War I engulfed the world and overshadowed scientific pursuits. When it was over, and scientists could resume their research, they immediately began applying the conceptual tools perfected before the war to push the frontiers of physics both outward, and inward. In the cosmic realm, General Relativity provided the theoretical framework, and the giant telescopes built in the clear air of California the observational foundation, for the emergence of physical cosmology-- the science of the structure and history of the universe. An essential preliminary step was a test of General Relativity. In 1919, when the bending of starlight by the sun, as predicted by Einstein, was observed, he instantly became an international media star. The curvature of of space time, while not fully comprehensible to most people, nevertheless seemed to be such a profound insight into the structure of the universe that it caught the imagination of a wide public. Since then, General Relativity has been confirmed by numerous observations, and remains in place as the correct theory of gravity. But the study of cosmology itself would turn up wonderful surprises in the coming decades. In the atomic realm. confusion reigned. Despite heroic efforts by physicists throughout the world, Bohr's theory had only very limited success in accounting for the properties of the light, and X rays emitted by atoms. Quantum theory seemed headed for failure, or a revolution. The vital clue was found more by guessing than by deduction. in 1923 the French physicist Louis de Brogile was writing his doctoral dissertation at the age of 31. Deeply impressed with Einstein's interpretation of light as both wave-like and particle-like, he wondered whether this strange wave-particle duality could apply to particles of...
