As the 19th century drew to a close, the age-old quest to understand the physical world appeared to be complete except for a few minor details. "It seems probable that most of the grand underlying principles have been firmly established," said Albert Michelson, the first American scientist to win a Nobel Prize in physics.
But when Michelson made that prediction, he never dreamed that one of the "details"—his own curious discovery that the speed of light is constant no matter how fast an observer is moving—would soon be explained by a revolutionary theory that redefined the very concepts of space, time, matter, and energy.
The author of that theory, called relativity, was Albert Einstein. He would also lay the foundation for a strange new picture of the atom, which would eventually lead to quantum mechanics and a succession of startling discoveries driving physicists to ever more bizarre theories of the ultimate nature of the universe.