By 1927, the date of an important meeting of physicists in Belgium to discuss the theory, they had largely staked its basic principles. What they produced was the equivalent of rock and roll, a radically new way of looking at matter and energy. And like rock and roll, there wasn't room for any of the old-timers like Isaac Newton, whose classical laws so elegantly described the world of tangible objects, but failed miserably at the atomic level. Consider what quantum mechanics says about the atomic world. At this level, all the familiar stability of tangible objects vanishes.
Matter twitches with unpredictable palpitations.
Observed on the smallest scales, it exhibits a schizophrenic shift between wave and particle-like behavior. An electron, for example will act like a wave or a particle depending on the circumstances. That said, quantum mechanics has produced some of the most precise scientific measurements in history. Few would argue the theory stands as one of humankind's greatest intellectual achievements. But for all the questions it has answered about the fundamental workings of the universe, it has also revealed unsolvable paradoxes.