Otto Stern.

Otto Stern (in German, pronounced "shtehrn") was born in 1888, the first of five children who would be born to Oskar Stern and Eugenie Rosenthal. Oskar came from a prosperous Jewish family of grain merchants and flour millers. As a college student, the family prosperity allowed Otto to wander among the universities of Germany, pursuing whatever interested him. Stern attended lectures on theoretical physics by Arnold Sommerfeld, a premier physicist of the day. He was fascinated by Ludwig Boltzmann's works on molecular theory and statistical mechanics and by the works on thermodynamics of Rudolf J. E. Clausius and Walther Hermann Nernst. Eventually, Stern returned to the University of Breslau to pursue his interests in thermodynamics and to earn a doctorate in physical chemistry. From 1912 to 1919, Stem's scientific activity was as a theorist. For the first two years, he worked as a postdoctoral assistant to Albert Einstein, who became a lifelong friend. Although Einstein was a theorist, perhaps the most important lessons that Stern learned from Einstein were which questions to ask and what experiments to attempt in order to find the answers. Stern and Einstein coauthored a paper showing that molecular motion need not cease at a temperature of absolute zero. Stern also published a paper in which he calculated the absolute entropy (disorder) of a monatomic gas. INSET: Otto Stern.