In a 1905 paper, Albert Einstein proposed that light could travel in the form of particles later called photons. It was one of the pioneering papers in the research that led to quantum mechanics, the mathema­tical framework for describing matter and energy on a fundamental level. But in his later years, Einstein expressed grave dissatisfaction with quantum mechanics. He was especially unhappy with its description of reality in terms of probabilities, a view developed by the German physicist Max Born. Einstein preferred the deterministic cause-and-effect rigor of classical physics, expressing ... (p. 36)