Otto Stern

Otto Stern was born in 1888 in Sohrau, Upper Silesia (now Żory, Poland), into a prosperous Jewish family, and took his doctorate in physical chemistry at Breslau in 1912. He spent a formative period as Einstein's first assistant in Prague and Zurich before turning to experimental physics, where his gift lay in coaxing fundamental answers out of beams of atoms and molecules travelling through vacuum.

In the early 1920s Stern developed the molecular-beam method into a precision tool. Using a rotating apparatus he measured the distribution of molecular speeds in a gas directly, confirming Maxwell's predicted distribution. With Walther Gerlach he performed the celebrated Stern–Gerlach experiment of 1922, showing that a beam of silver atoms splits into two discrete deflections in a magnetic field — direct evidence of space quantisation and, later understood, of electron spin.

Stern continued to refine molecular beams in Hamburg through the 1920s and early 1930s, measuring the magnetic moment of the proton and finding it anomalously large, a surprise that later proved important for understanding nuclear structure. When the Nazis came to power in 1933 Stern, as a Jew, was forced from his post; he emigrated to the United States and joined the Carnegie Institute of Technology in Pittsburgh.

Stern received the Nobel Prize in Physics for 1943 for the molecular-beam method and the discovery of the proton's magnetic moment. He retired to Berkeley, California, and died there in 1969.